Direct Lateral or Minimally Invasive Surgical Approach for Hemiarthroplasty in Hip Fracture

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Direct Lateral or Minimally Invasive Surgical Approach for

Hemiarthroplasty in Hip Fracture

Department of Orthopaedic Surgery

University of Oslo Faculty of medicine

2020

Doctoral thesis by Terje Osmund Ugland

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© Terje Osmund Ugland, 2021

Series of dissertations submitted to the Faculty of Medicine, University of Oslo

ISBN 978-82-8377-846-5

reproduced or transmitted, in any form or by any means, without permission.

Cover: Hanne Baadsgaard Utigard.

Print production: Reprosentralen, University of Oslo.

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“The price of success is hard work, dedication to the job at hand, and the determination that whether we win or lose, we have applied the best of ourselves to the task at hand”

-Vince Lombardi

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Preface

The work presented in this thesis was carried out at the Department of Orthopaedics, Sorlandet Hospital Kristiansand from 2013 to 2020.

I thank the Medical Faculty of the University of Oslo for admission to the PhD program. I thank Helse Sør-Øst and the local SSHF research unit for funding my PhD.

My interest in science has grown steadily over the course of my career. From the very small beginning as a humble resident in Ullevål Hospital, privileged amidst renowned capacities in orthopedic research, until this day battling the scourge of self-doubt writing my thesis.

In the beginning of this centennial, the concept of different surgical approaches to the hip slowly became the focus of my attention. Patients admitted to Ullevål Hospital and

Diakonhjemmet Hospital during my residency were operated through a direct lateral (DL) approach when receiving their total hip arthroplasty (THA). Later, as a consultant in Sorlandet Hospital and working at the Sahlgrenska University Hospital, Mölndal, the same procedure took place. Then gradually a paradigm shift in the surgical approach to the hip come to pass.

Total hip surgeons shifted from the DL approach to the posterior and anterior approaches. We all knew why this was taking place, having had the depressing experiences of patients treated with a THA complaining of limping and a painful hip. They were Trendelenburg positive. At the same time, I always had an interest in the fragile elderly with an acute fracture of the femoral neck. Many of them frail with a multitude of illnesses referred to surgery performed by a junior resident. These patients were treated mostly with a hemiarthroplasty (HA) inserted in the DL approach, and still are. It gradually struck me; the ongoing fundamental shift in surgical approach to the hip in THA was not the case for patients treated with a HA for a femoral neck fracture. These patients had surgery mainly in the DL approach. Why was this?

Are femoral neck fracture patients not prone to adverse events in the DL approach? Is the

Trendelenburg gait not reckoned by a FNF patient, often sick, fragile and exhausted? The idea

of my thesis was gradually evolving.

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Acknowledgements

Above all, I want to thank my main supervisor Professor Lars Nordsletten for his endless patience mentoring my dissertation. Always available to answer my questions, offer academic advice and tutor me when necessary. Thank you Lars for your friendly support and last but not least enjoyable deep dives into the world of soccer. Forever grateful!

I am very thankful to Svein Svenningsen. At my very beginning as a newly graduated

resident, he was my head senior Orthopaedic consultant at Arendal Hospital. He has been my role model and good example since.

Thank you Professor Glenn Haugeberg for support and academic advice. Always a smile and words of encouragement.

Thank you to my co-authors Stein Ugland and Øystein Berg for performing surgery. Further thanks to Øystein for allowing me to concentrate on my PhD in the midst of a busy day to day routine as an orthopaedic surgeon. I thank all my colleagues at the department of orthopaedics Kristiansand.

I thank Professor Are Hugo Pripp for statistical advice and kind guidance both in methodological issues and statistical calculations.

I am so grateful to Isabel Priscilla Nunez for her invaluable assistance in keeping track of the patients and managing the database. I consider her contribution to my PhD as indispensable.

I am so thankful to our physiotherapists Linda Hansen and Arild Ege. This RCT would not have been possible without you.

I especially would like to thank the nursing staff and head of nursing Linda S. Johansen.

The authors thank the staff at the Osteoporosis Clinic, Sorlandet Hospital, for performing the DXA examinations

I am grateful to Marianne Nesdal Jonassen for her help on all matters of urgency and establishing perfect working conditions. Thanks to Jørn Hjørungnes at the library for his technical assistance in Endnote.

Thanks to Frede Frihagen and Johan Kärrholm in giving advice in the early stages of the trial.

I really appreciate the guidance by Ludvig A. Munthe in his compendium “Advice on writing the PhD Thesis”.

I thank my parents Laila and Ole Kurt for their endless support and motivation. Also thank you to my parents-in-law Erna and Johnny for support and encouragement.

I do have to mention our English springer spaniel Luna for accompanying me in the woods

trying to clear my head. Great company!

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Finally I would like to thank my beautiful wife Mia and our 3 beloved children Hannah, Jakob

and William.

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Abbreviations

ASA American Society of Anesthesiologists

BMD Bone mineral density

BMI Body mass index

CV Coefficient of variation

DXA Dual-energy X-ray absorptiometry

FNF Femoral neck fracture

ROI Region of interest

THA Total hip arthroplasty HA Hemiarthroplasty

TUG Timed Up and Go test

PROMs Patient reported outcome measures MCID Minimal clinically important difference DAA Direct Anterior Approach

DL Direct Lateral Approach

AL Anterolateral Approach

HOOS Hip disability and Osteoarthritis Outcome Score

HHS Harris Hip Score

PJI Periprosthetic Joint Infection

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Thesis summary

Paper I

Less periprosthetic bone loss following the anterolateral approach to the hip compared with the direct lateral approach.

Acta Orthop. 2018 Feb;89(1):23-28. doi: 10.1080/17453674.2017.1387730. Epub 2017 Oct 17. PMID: 29037093

Bone loss seems to be an unavoidable event when inserting a hip implant. This subgroup analysis of the main study examined a possible impact of the surgical approach on

periprosthetic bone remodeling. Dual-energy X-ray absorptiometry (DXA) was performed in 51 patients included in the RCT. The results at three months showed significant higher BMD loss in the proximal Gruen zones in the DL compared to the anterolateral (AL) approach, suggesting that surgical approach may influences perisprosthetic BMD remodeling. The results and conclusion from this subgroup analysis should be interpreted with caution.

Paper II

Biomarkers of muscle damage increased in anterolateral compared to direct lateral approach to the hip in hemiarthroplasty: no correlation with clinical outcome: Short- term analysis of secondary outcomes from a randomized clinical trial in patients with a displaced femoral neck fracture.

Osteoporos Int. 2018 Aug;29(8):1853-1860. doi: 10.1007/s00198-018-4557-y. Epub 2018 May 22. PMID: 29789919

Serum levels of Biomarkers such as Creatine Kinase may act as a marker of invasiveness of

muscle sparing approaches to the hip. In this trial we monitored this enzyme after inserting a

hemiartrhroplasty in FNF patients through two different surgical approaches. To assess the

association between CK and PROMs we performed statistical correlation tests. At 24 and 48

hours there was higher levels of serum CK in the AL muscle sparing approach. No correlation

was detected between levels of CK and functional assessments.

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11 Paper III

High risk of positive Trendelenburg test after using the direct lateral approach to the hip compared with the anterolateral approach: a single-centre, randomized trial in patients with femoral neck fracture.

Bone Joint J. 2019 Jul;101-B(7):793-799. doi: 10.1302/0301-620X.101B7.BJJ-2019-0035.R1.

PMID: 31256660

Randomized trials investigating the role of muscle-sparing approaches to the hip in patients

with femoral neck fractures are sparse. The aim of this randomized clinical study was to

compare functional outcomes between a muscle sparing AL approach and a DL approach

when inserting a hip HA in elderly with a femoral neck fracture. At twelve months, results

showed few differences in the primary outcome between the groups. Among secondary

outcomes, the DL group had more patients with positive Trendelenburg tests, suggesting a

poorer clinical outcome.

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Sammendrag på norsk

Lårhalsbrudd er en konsekvens av fall hos eldre. Dette er gamle pasienter som ofte er syke og derangerte. To tredjedeler er kvinner som har passert 80 år, ofte med underliggende

beinskjørhet. Tidligere var det vanlig å fiksere et lårhalsbrudd med 2 eller 3 skruer etter at selve bruddet var reponert. I dag behandles de fleste med en halvprotese. Selve inngrepet tar som regel mindre en 60 minutter å utføre og pasienten kan mobiliseres ut av senga dagen derpå. Inngrepet gir gode resultater og risikoen for operative komplikasjoner er relativt liten.

Til tross for dette dør mellom 20% og 25% av lårhalsbrudd pasientene innen et år. I noen institusjoner er det vanlig å bruke en totalprotese og mange ortopeder vil velge denne løsningen på pasienter under 60 år. Resultatene ved totalprotese er sammenliknbare med halvprotese. De vanligste tilgangene til hofteleddet når man setter inn en protese er bakre tilgang, direkte lateral tilgang og de fremre tilgangene. Den bakre tilgangen og den direkte laterale tilgangen dominerer. Alle kirurgiske tilganger til hofteleddet har sine fordeler og ulemper. Hovedinnvendingen mot den bakre tilgangen er at den gir økt risiko for dislokasjon av protesen. Den lateral tilgangen (tilgang fra siden av låret) er assosiert med smerter over den store lårbensknuten og halting. Dette skyldes sannsynligvis at man skjærer over muskler som fester på lårbensknuten. En av oppgavene til disse musklene er å holde bekkenet i vater og bortfall av denne funksjonen medfører derfor halting. På grunn av disse forhold synes den laterale tilgangen ved innsetting av totalprotese på artrosepasienter å avta i popularitet. De fleste ortopeder har valgt å forflytte seg bakover til den bakre tilgangen. Et mindretall har valgt de fremre tilgangene. Disse er kjennetegnet ved at man velger en vei inn til hofteleddet som går mellom musklene, dvs at disse ikke skjæres over. De siste årene har det vært økt fokus på disse muskelsparende tilgangene, spesielt ved innsetting av totalprotese på artrose pasienter. Paradoksalt nok velger vi fremdeles å sette inn halvproteser på lårhalsbrudd pasienter i den direkte lateral tilgangen. Med bakgrunn i dette må man spørre seg om det forholder seg slik at pasienter med lårhalsbrudd som opereres med halvprotese i lateral tilgang ikke har smerter over den store lårbensknuten eller opplever halting? Dette er bakgrunnen for at vi i dette doktorgradsarbeidet valgte å sammenlikne den laterale tilgangen med den fremre tilgangen hos pasienter over 70 år operert med halvprotese for et dislokert lårhalsbrudd.

Artikkel 1: Det er vist at man taper ben rundt hofte implantatet når man setter inn en protese.

Vi ville undersøke om den kirurgiske tilgangen til hofteledd påvirker remodelleringen av ben

rundt hemiprotesens stamme. I denne artikkelen foretok vi en subgruppe analyse av 51

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pasienter randomisert til enten den fremre tilgangen eller den laterale tilgangen og skannet disse med DXA umiddelbart etter operasjonen, tre og tolv måneder. Resultatene viste et økt bentap etter tre måneder i de øvre sonene rundt protesestammen i den laterale tilgangen. Dette bentapet kan være en medvirkende årsak til den økte risikoen for brudd rundt usementerte protesestammer.

Artikkel 2: Enkelte biomarkører i blodet kan muligens benyttes som en markør for å måle invasiviteten til et kirurgisk inngrep. Kreatin kinase er et slikt enzym. Økt forekomst av kreatin kinase i blodet er et uttrykk for graden av muskelskade. I artikkel nr. 2 målte vi serumnivåer av dette enzymet hos alle pasientene som ble inkludert i studien. Vi fant at det var høyere serum nivåer av kreatin kinase i den fremre muskelsparende tilgangen. Vi utførte korrelasjons analyser som ikke viste noen sammenheng mellom nivåer av kreatin kinase i blodet og funksjonstester hos pasientene.

Artikkel 3: Dette var hovedartikkelen hvor vi så på om det var forskjeller i de to gruppene med hensyn til smerter og pasienttilfredshet. Vi registrerte de pasient rapporterte

utfallsmålene og så på andelen pasienter som rapporterte halting. Vi fant ingen forskjeller av

statistisk betydning i rapportert smerte og pasient tilfredshet mellom de to tilgangene. Vi fant

en klar overvekt av pasienter som rapporterte halting og muskelsvikt i den direkte laterale

gruppen. Disse pasientene scoret dårligere i enkelte av spørreundersøkelsene og var mindre

tilfredse med hoften sin.

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Articles in the thesis

Ugland TO, Haugeberg G, Svenningsen S, Ugland SH, Berg OH, Hugo Pripp A, et al. Less periprosthetic bone loss following the anterolateral approach to the hip compared with the direct lateral approach. Acta Orthopaedica. 2018;89(1):23-8. (1)

Ugland TO, Haugeberg G, Svenningsen S, Ugland SH, Berg OH, Pripp AH, et al. Biomarkers of muscle damage increased in anterolateral compared to direct lateral approach to the hip in hemiarthroplasty: no correlation with clinical outcome : Short-term analysis of secondary outcomes from a randomized clinical trial in patients with a displaced femoral neck fracture.

Osteoporosis International. 2018;29(8):1853-60. (2)

Ugland TO, Haugeberg G, Svenningsen S, Ugland SH, Berg OH, Pripp AH, et al. High risk

of positive Trendelenburg test after using the direct lateral approach to the hip compared with

the anterolateral approach: a single-centre, randomized trial in patients with femoral neck

fracture. The Bone & Joint Journal. 2019;101-b(7):793-9.(3)

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Introduction

What is this doctoral thesis all about?

This thesis is about the surgical approach to the hip in patients with a femoral neck fracture. It is about the interpretation of the results of two very different surgical approaches and how these are experienced by the patients. It is an attempt to clarify to what extend the surgical approach matters to the patient in terms of patient reported outcome measures (PROM) and other instruments used to appraise patient outcome.

This thesis is also about an expected influence of the surgical approach on the process of bone loss around a femoral hip implant. Finally the thesis attempts to elucidate the meaning of invasiveness of the two approaches in terms of measuring serum levels of biomarkers and a possible association to functional outcome.

Figure 1. Blue: Anterolateral approach. Red: Direct lateral. Illustration by Alf Inge Hellevik.

Our society and health care system experiences an increasing challenge to hospital capacity and nursing care due to fragility fractures in an ageing population (4, 5).

These fractures causes a substantial burden to the economy and to the national fracture

services (6-8), and to the patient who was unlucky and fractured her hip. Despite a

recent decline in the incidence of FNF numbers are likely to increase quite

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substantially due to the increasing population in high age (9, 10). The British

Orthopaedic Association and the British Geriatrics Society in its Blue Book predicts an epidemic increase in the number of fragility fractures, and that hip fractures likely may double by 2050 (11). Estimates of future hip fracture incidence predicts a number of 4.5 million cases worldwide in 2050 (12).

Fragility fracture typically results from a fall in an older and frail person, with often devastating results. Elderly with FNF admitted from nursing homes and residential

establishments are at high risk of complications (13). The geriatric patient with a hip fracture offers a complex mixture of medical challenges (14). The one year mortality is reported to be as high as 30% (15, 16) and 10-30 % will move on to residential or nursing care after hip fracture (17-19). There is a substantial risk of decreased mobility and increased need for assistance with temporary and often lasting impairment to quality of life (20, 21). This poses a challenge to how we treat these patients. Emphasis should be on evidence-based care such as prevention of osteoporosis (22), drugs to improve bone quality (23, 24), fall prevention and fracture risk assessment tools (25, 26). Special consideration should be given to improving surgery when dealing with poor mechanical properties in osteoporotic bone. A variety of orthopaedic implants are on the market and surgical procedures and techniques differs. Multiple RCTs now show that the clinical outcome is better for operations with HA on displaced fractures than screw osteosynthesis (27, 28). Tseng et al in a meta-analysis found HA and THA to have statistically lower revisions rates compared to internal fixation (29). Advocates of HA are increasing rapidly, aside from devotees of THA for displaced femoral neck fractures. Implantation of hip arthroplasties are performed with cement and sometimes without cement. Although cementing increasingly seem to capture the headlines and gather in popularity (30), some controversy still exists whether cemented or uncemented fixation of the implant is preferable in this patient population. Intraoperative, fatal

pulmonary complications and morbidity due to cement implantation syndrome may be of concern (31-33). Cemented HA is believed to be associated with lower numbers of reoperation, and possibly reduced pain in the short term (34-38). National guidelines in Norway and Great Britain recommend cemented HA (39-41). Uncemented

hemiarthroplasties are associated with periprosthetic fractures and reoperations with increased morbidity and mortality (42-47).

The influence of the surgical approach in patients with a hip fracture has not received the

same attention, although it may be of more importance. Randomized controlled trials

examining patients with arthritis receiving a total hip arthroplasty in a minimally invasive

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approach show short-term benefits regarding less pain, improvement in walking functions and weakening of the hip abductors (48-50). This brings up the question if this could be the case for femoral neck fracture patients treated with a HA, and consequently affect the outcome of the surgery. Literature dealing with this conundrum is truly sparse. Clearly, an improvement in short term mobility would be desirable in the geriatric patient with a hip fracture. Complication rates would potentially be reduced and improve the quality and cost- effectiveness of the surgical treatment thus reducing the burden on our community services.

The anticipated length of hospital stay would possibly come down leading to reduced financial strain on our public health system. National Hip registries in Norway and Sweden call for randomized controlled trials examining the influence of the surgical approach in geriatric hip fracture patients. Conducting trials with emphasis on surgical approach in femoral neck fracture could lead to a better understanding of the matter and hence benefit elderly patients requiring surgery due to hip fracture.

A multitude of surgical approaches, and modalities to these, are available when performing hip arthroplasty. There are, roughly speaking, three major anatomic pathways to the hip joint.

The posterior approach, the DL approach and the anterior approaches. The different surgical approaches have been developed and matured over the past two hundred years. They all come along with pros and cons and are utilized based on institutional historic affiliation and

surgeon’s temper and choice. Before we probe into the different surgical approaches a short historical overview to the development of modern hip arthroplasty is required.

Figure 2. Surgeon having a difficult time making a decision when faced with multiple options.

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Historical overview

Over the last 2 decades, we have observed a significant shift in the treatment of femoral neck fractures. Gradually closed reduction and screw osteosynthesis was replaced by arthroplasty yielding favorable results in terms of reoperations and patient satisfaction. Most surgeons prefer to insert a HA for a femoral neck fracture, although THA for this reason is increasing.

In THA, to avoid instability and implant dislocation, femoral head sizes are increasing from 22 and 28 mm to 32 and 36 mm and a clear shift has taken place regarding the preferred surgical approach to the hip.

The posterior approach to the hip

Bernhard Rudolf Konrad von Langenbeck was born in Padingbüttel at the North Sea coast of Germany in 1810. He studied medicine in Göttingen in Lower Saxony and in 1842

Langenbeck was appointed Professor of Surgery and Director of the Hospital in Kiel,

Schleswig-Holstein. Following his appointment in Kiel he was engaged as the Director of the Clinical Institute for Surgery and Ophthalmology at the Charité in Berlin. I guess this is a coincidence but both Berlin and Kiel are homes to the institutions were my education as a physiotherapist and medical doctor took place. Langenbeck was trained as a war surgeon and served as such in the First Scleswig war (1874-1852). In 1874 Langenbeck described a longitudinal surgical approach to treat hip infections and war wounds, thus often credited to be the founder of the posterior approach (51). The posterior approach was since popularized by Austin Moore and is often referred to as the Austin Moore or Southern approach (52). The posterior approach enters the hip joint through a slightly curved incision posterior to the greater trochanter. Gluteal fibers are split and stay sutures placed on the small external rotators, piriformis and obturator internus tendon.

The anterior approach to the hip

Carl Hueter was born in Marburg, Germany, in 1838. He studied medicine and became a

professor at the Greifswald University where he published his major work “Grundriss der

Chirurgie” in 1881. This classic work was published in several editions. The muscle sparing

approach to the hip which takes advantage of the interval between the Tensor fascia lata

muscle and the Sartorius muscle was described in the second edition in 1883 and is later

referred to as the Hueter approach (53). The Hueter approach was popularized in the English

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speaking world by Marius Nygaard Smith-Petersen (54). Marius was born in Grimstad, Norway in 1886. His father died of pneumonia in 1888, Marius being only two years old. At the age of 16 Marius and his mother immigrated to the US settling down in the town of Milwaukee, Wisconsin. He went on to study medicine and later served as Clinical Professor of Orthopaedic Surgery at Harvard Medical School, Boston. In the late 1920s Marius Smith- Petersen was appointed Chief of Orthopaedic Surgery at the Massachusetts General Hospital in Boston. Interestingly the first hip arthroplasty inserted in the Hueter interval was a HA done by Jean and Robert Judet (55). The French brothers Jean and Robert Judet developed a short metal stemmed acrylic head HA in the late 1940s. The stem was anchored in the femoral neck and was inserted through a modified Smith-Petersen approach (56). The Judet brothers would later in the 1980s describe the insertion of a THA through an anterior approach with the use of an orthopaedic traction table later gaining popularity by the works of Joel Matta (57, 58). Today the anterior approaches are more than anything used when performing total hip arthroplasty (59-61). Several modifications of the original Hueter or Smith-Petersen approach evolved in the 1960s (62). The Smith- Petersen approach is equivalent to the direct anterior approach (DAA).

The direct lateral approach to the hip

As THA gradually became a routine intervention the anterior approaches were by far being outnumbered by the implants inserted in the DL approach and the posterior approach. The pioneering of modern hip arthroplasty is to a great deal due to the contributions of the English orthopaedic surgeon, Sir John Charnley. Charnley established a hip center at Wrightington Hospital outside the city of Manchester and from the late 1950s and over the next decades major developments were achieved laying the foundation of today’s total hip implants (63).

Charnley preferred a transtrochanteric approach. After insertion of the total hip the osteotomy was fixed with tension band wiring. Opponents of this approach worried about the risk of non-union of the greater trochanter fragments and different variations of the direct lateral approach came to use. In 1982, Kevin Hardinge at the Centre for Hip Surgery, Wrightington Hospital, Lancashire, published a paper describing the Hardinge approach to the hip (64).

This was partly based on the works of McFarland and Osborne moving the gluteus medius

and vastus lateralis forward after detaching them from their posterior insertion (65). Professor

Hardinge would incise the gluteus medius a bit more anteriorly creating a tendon split and at

the proximal part of the trochanter he would extend the incision parallel to the gluteal fibers.

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Some surgeons will refer to this surgical approach as a Gammer approach or a modified lateroanterior approach (66). Concerns exists regarding gluteal insufficiency and post- operative limping linked to the Hardinge approach and its offshoots.

The anterolateral approach to the hip

The AL approach to the hip, also referred to as a modified Watson-Jones procedure or the Röttinger approach is a muscle sparing approach in which the pathway to the hip make use of the interval between the tensor muscle and the medial gluteal muscle (67). The original approach was popularized and described by Sir Watson Jones in “ Fractures of the neck of the femur” in 1936 (68). This approach was used in our RCT.

Anatomical considerations

The human hip joint, articulatio coxae, is a ball and socket joint. The socket is the acetabulum of the pelvis and the ball is the head of femur, the capitis femoris. The femoral head is

contained within the acetabulum with a centrally located ligamentum capitis femoris. The labrum runs along the acetabular rim with a transversal ligament caudally. Strong ligaments surrounding the joint forms the joint capsule. These are the ischiofemoral, pubofemoral and iliofemoral ligaments. This is all beautiful outlined with impressive anatomical illustrations in Rauber-Kopsch Lehrbuch und Atlas Der Anatomie Des Menschen (69). One of the publishers of this great book was Prof. Bernhard Tillmann. As a young medical student in Germany I had the great privilege of attending his famous anatomical lectures. Memories from his joyful lessons will for sure accompany me for the rest of my surgical career.

The hip joint is surrounded by a number of muscles. The exact number and classification of

these muscles vary. Some prefer to label them in 4 anatomical groups based on their location

(70). The number of muscles surrounding the hip joint depends on inclusion of the small

external rotators of the hip or to choose to classify these as one group per se. Now, to insert an

implant into the hip one may choose to find intermuscular pathways with minor injury to

these muscles or deprive a muscle of its insertion or simply pass right through it. As already

mentioned, the three commonly used surgical approaches worldwide for total hip arthroplasty

are the posterior, the DL and the anterior approaches (71, 72). Let’s take a look at the pros and

cons of the three main surgical approaches to the hip joint.

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Pros and cons of the major surgical approaches

The direct lateral approach; Pros and Cons

The DL approach and its modifications require a repair of the traumatized gluteal muscles or their insertion to the greater trochanter. The DL approach provides a nice overview of the acetabulum (73). The main advantage of this approach is the reduced risk of dislocation of the hip implant (74, 75). Demerits of the DL approach is the risk of abductor insufficiency, postoperative walking problems and perioperative damage to the superior gluteal nerve (76- 80). The presence of a Trendelenburg sign is commonly interpreted as an insufficient gluteal muscle. In 2003 Michael S. Madsen et al published a paper comparing a gluteal splitting approach to a posterior approach and found that 6 months after receiving a THA almost all of the patients in the gluteal splitting group deviated from normal gait patterns (81). The

appraisal of gait speed is shown in the short term to be lower in the DL approach to the hip compared to the direct anterior approach (82). In an MRI study of THA inserted in the direct anterior approach no fatty degeneration or damage to the medial gluteal muscle was found (83). Some authors report on heterotopic ossification in the DL approach (84, 85).

The posterior approach; Pros and Cons

The posterior approach and the DL approach are the most commonly used approaches

worldwide for THA (71). These two approaches also dominate for insertion of HA in patients with FNF. The posterior approach offers a good view over the acetabulum and the proximal parts of the femur and spares the gluteal muscles thus avoiding the worries of trochanter pain and Trendelenburg gait associated with the DL approach. The risk of dislocation is the major counterargument against the posterior approach. A meta-analysis from van der Sijp et al showed the posterior approach for HA for FNF to be associated with a higher risk of

dislocation and reoperation (86). This very much resembles the findings from the Norwegian Hip Fracture Register and the Swedish Hip Arthroplasty Register published by Rogmark et al (87). Enocson et al in a retrospective study found the posterior approach to be associated with a higher risk of dislocation although a posterior repair did yield somewhat better results (88).

Better results regarding posterior dislocation may be obtained when sparing the piriformis and internus tendon and repairing the externus tendon. This technique is referred to as the

SPAIRE technique (89). Khan et al described a technique allowing the piriformis and most of

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the quadratus femoris to remain intact (90). These techniques, including the reattachment of the rotators is believed to reduce the incidence of dislocation.

The minimal invasive approaches; Pros and Cons

In a prospective randomized trial comparing the Smith-Petersen approach to the DL approach for total hip arthroplasty the direct anterior approach showed significantly better results in terms of physical and mental health dimensions up to 12 months of follow up (59). Numerous publications addressing the anterior approaches demonstrate functional improvements

compared to the DL or the posterior approach (48-50, 91). The anterior approach is also shown to reduce blood loss (92). These are mainly short term results in trials investigating THA and the differences seem to level out over time. Higgins et al in a systematic review and meta-analysis could not draw a firm conclusion when looking at functional outcome for THA in the DAA compared to the posterior approach (93). Kunkel et al published a systematic review and meta-analysis on the DAA when treating FNF with a HA suggesting better early functional mobility with the DAA. They did not find a significant difference in overall complications between the DAA and other approaches (94). The use of the term “Minimal invasive approaches” sometimes refers to the length of the surgical incision. Benefits related to the length of incision may be decreased blood loss and reduced surgery time (95, 96). This could not be confirmed in a systematic review by Meermans et al reporting conflicting results regarding incision length comparing the direct anterior approach to other conventional

approaches (97). They also reported a considerable learning curve for the anterior approach and mean surgery time to be longer. The direct anterior approach may increase the risk of nerve injury and possible damage to nearby blood vessels (98). The increased risk of nerve injury in the anterior approach was confirmed in the systematic review by Miller et al comparing the anterior approach to the posterior approach in THA (99).

Trends in surgical approach for FNF

In the Scandinavian countries the DL approach for THA has gradually been replaced by the

posterior approach or the anterior approaches. This observed shift is probably due to the

increased risk of a gluteal insufficiency or a postoperative limp usually resulting in reduced

patient satisfaction (100). Data from the Norwegian Arthroplasty register show a major shift

in the surgical approach when performing THA (Figure 3).

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Figure 3. Surgical approach for insertion of THA. Dark green; Direct lateral. Bright green; Posterior. The Norwegian Arthroplasty Register. Annual Report 2018.

This trend is not obvious in the field of HA for FFN (Figure 4), although reported PROMs after the DL approach in FNF treated with a HA are troublesome.

Figure 4. Surgical approach for insertion of HA. Bright green; Direct lateral. Red; Posterior. The Norwegian Arthroplasty Register. Annual Report 2018.

In Sweden, between 2005 and 2013, a steady increase in the use of the DL approach for

fracture related arthroplasty (HA) was observed (Figure 5), although leveling out in recent

years.

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Figure 5. Surgical approach for fracture related prosthesis. Blue; Direct lateral. Red; Posterior.

The Swedish Hip Arthroplasty Register. Annual Report 2017.

Tools of evaluation DXA

The principal of Dual-energy X-ray absorptiometry (DXA) is the transmission of two X-ray beams with different energy through the body. The intensity of these X-ray beams are then recorded after transmission through the patient. In this trial we measured BMD around an uncemented femoral stem at two follow-up times (Figure 6). We used software from

Orthopedic Hip for GE Lunar Prodigy (GE Healthcare, Chicago, IL, USA). Changes in BMD for each Gruen zone was recorded and expressed as percentage change.

Figure 6. Illustration by Alf Inge Hellevik.

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Creatine Kinase

What is a minimal invasive approach? Is it the sparing of the muscles when inserting the implant or is it defined by the length of the surgical wound? How can one define how invasive the surgical approach is? Goutallier et al. performed a CT evaluation of cuff tears and

proposed a classification system grading fatty degeneration of the muscle in 5 stages (101).

Based on Goutalliers classification others have performed MRI evaluation of muscles to grade the different stages of fatty degeneration and infiltration after the insertion of hip

arthroplasties (102, 103). The evaluation of biomarkers such as CK as an objective marker of muscle damage has been put forward in the literature (104). Creatine kinase (CK) is an enzyme in cellular lysosomes and mitochondria which catalyzes the re- phosphorylation of ADP to ATP. It plays an important role in the cellular energy homeostasis. CK exists as three isoenzymes. CK-MM in striated muscle, CK-MB in heart tissue and CK-BB in brain tissue (105). The CK-MM isoenzyme predominates in serum. Ultraviolet kinetic method was used to analyze the levels of CK in serum. Raised levels of CK in blood has typically been associated with muscle damage, although one may question the reliability of CK as a

biomarker of muscle damage (106). Others have published data on how the surgical approach to the hip affects levels of serum CK, some of which anticipating low levels of CK in muscle sparing approaches (60, 107, 108). Gait analysis has also been put forward as a tool to assess the invasiveness of a surgical approach (109).

PROMS, VAS, HHS and the Trendelenburg Test

The visual analog scale (VAS) was used to measure the primary outcome pain and patient satisfaction. The VAS is an instrument that measures a characteristic feature along a

horizontal or vertical continuous scale, usually 100 mm long rooted by 2 verbal descriptors in

both ends (110). The Harris Hip Score (HHS) is a clinician- based outcome score assessed to

evaluate the functional status of a patient , in this RCT after hip surgery for FNF (111). As to

PROMs we used the Hip Disability Osteoarthritis Outcome Score (HOOS) (112). The HOOS

is made up of 40 questions divided in to 5 subscales assessing the function of the patient’s hip

during the last week. The subscales are; Symptoms; Pain; Activity limitations of daily living

(ADL); Function in sport and recreation and hip related quality of life (QOL). Each subscale

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runs from 0 (worst) to 100 (best). Blinded physiotherapists performed the Trendelenburg test

as described by Hardcastle and Nade (113).

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Aims of the studies

The aim of this thesis was to investigate the role of the surgical approach to the hip in patients with femoral neck fracture.

Study I

The objective of this study was to examine whether peri-prosthetic BMD, measured by DXA, differed according to surgical approach in patients with femoral neck fracture.

Study II

The objective of this study was to compare increase in serum creatine kinase as a marker of surgical invasiveness and its association to functional outcome between the muscle sparing AL approach and the DL approach to the hip in patients with displaced femoral neck fracture.

Study III

The primary objective of this study was to test the following hypothesis. Patients 70 to 90 years of age with a displaced femoral neck fracture, operated with a HA using an AL

approach, have less pain and better patient satisfaction as measured by PROMs and VAS than

patients operated through the lateral approach. Among secondary objectives we sought to

address the presence of a Trendelenburg sign.

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Material and methods Patients

150 patients were included in this RCT between February 2014 and July 2017. Study

participants were allocated to an uncemented HA inserted in a DL or AL approach (Figure 7).

Figure 7. Flowchart of patients during the RCT.

Randomized (n=150)

Allocated to Anterolateral approach (n=75) Received allocated intervention (n=75)

Allocated to Direct lateral approach (n=75) Received allocated intervention (n=75)

Anterolateral approach (n=62) Lost to follow-up (n=13) - Deceased (n=7)

- Too sick to attend (n=4) - Withdrawn (n=2)

Direct lateral approach (n=65) Lost to follow-up (n=10) - Deceased (n=6)

- Too sick to attend (n=1) - Withdrawn (n=1) - Did not attend (n=2)

Anterolateral approach (n=54) Lost to follow-up (n=8) - Deceased (n=6)

- Too sick to attend (n=1) - Did not attend (n=1)

Direct lateral approach (n=56) Lost to follow-up (n=9) - Deceased (n=5)

- Too sick to attend (n=3) - Did not attend (n=1) 3 months

12 months Allocation

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The BMD study was a pre-specified subgroup analysis consisting of 51 patients included in the RCT. Fifty-one of the first 56 patients included in the main study (n=120) were screened for inclusion.

All patients were recruited from one hospital, SSHF Kristiansand. There were no significant baseline differences in the two groups (Table 1).

Variable Direct lateral approach (n = 75)

Anterolateral approach (n = 75)

All (n = 150)

Mean age, yrs (

SD

)

81.3 (6.3) 81.4 (5.9) 81.3 (6.1)

Male

18 (24) 23 (31) 41 (27)

Female

57 (76) 52 (69) 109 (73)

Dorr types

^*

, A (B/C)

20 (5) 22 (4) 42 (9)

ASA, groups I - II

^{25 (33)} ^{24 (32)} ^{49 (33)}

ASA, groups III - IV

^{50 (67)} ^{51 (68)} ^{101 (67)}

BMI, (SD)

22.5 (3.2) 23.2 (3.99) 22.8 (3.6)

Median stem size

12 (10 to 16) 12 (9 to 18) 12 (9 to 18)

Mean HHS, (

SD

)†

85.4 (16.3) 82.6 (15.4) 84 (15.8)

Mean incision length,

mm (

SD

)

104 (13) 101 (15) 102 (14)

Mean operating time, mins (

SD

)

41 (11) 46 (10) 44 (11)

*Dorr Classification, recorded in 51 patients

†HHS, Harris Hip Score; estimated prior to fall

ASA, American Society of Anesthesiologists; BMI, body mass index (kg/m²)

Table 1. Baseline and perioperative characteristics of included patients and Harris hip scores according to allocated surgical approach. Figures are numbers (percentages) unless stated otherwise.

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Outcome measures

In this RCT we monitored the primary outcome measures pain and patient satisfaction by a visual analogue scale (VAS). Secondary outcome measures specified in the study protocol were the HHS, presence of a gluteal insufficiency and limping evaluated by the

Trendelenburg test and the degree of muscle injury assessed by serum levels of CK.

Secondary outcome measures included the HOOS, the timed `Up and Go` (TUG) test (114), the Barthel Index (115) and the EuroQol (EQ-5D)(116). Primary and secondary outcome measures were in general recorded at the time of inclusion of study participant, immediate post operatively, and at 3 and 12 months.

Adverse events

Study personnel collected and reported adverse events after enrollment in the trial. The follow-up form contained a check box on infection and a comment box on other adverse events. We recorded infections (PJI) demanding surgery, early and late occurring

periprosthetic fractures, nerve injuries, and mortality at 30 days and 12 months. Adverse events such as infection were recorded according to the definition of periprosthetic joint infection (PJI) by Parvizi J. and the Musculoskeletal Infection Society (117). Dislocations contains both dislocation solved by closed reduction and dislocation needing revision surgery.

All periprosthetic fractures were recorded and treated according to the Vancouver

classification. The monitoring and recording of adverse advents was performed from the time the patients enrolled in the study until final follow up at 12 months. All medical charts were examined by a research assistant for adverse events. When problems collecting adequate information due to patients health, data would be collected from relatives, friends or health personnel accompanying the patient to the follow up. On a few occasions patient data were collected through telephone interview.

DXA

We measured changes in BMD using DXA. This was performed in study I. The DXA scans took place at the osteoporosis clinic by DXA technicians blinded to the allocated treatment.

The DXA scanning was performed with patients positioned in the supine position. As

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rotational differences are known to influence the BMD (118, 119) a triangle was placed between the patient’s feet to obtain a standard rotation of the hip. We included both hips and standard scanning protocol was used (120). The scanning started 2 centimeters proximal to the tip of the greater trochanter and readings distally to just below the femoral arthroplasty stem. We performed the baseline scan twice. Between the 2 baseline scans the patient was moved or repositioned in order to estimate the precision expressed as coefficient of variation for the measurement procedure. The difference between these 2 scans were used to calculate the in-vivo precision error for the BMD procedures. The coefficient of variation (CV) for every ROI was calculated using the formula: CV% = 100 X [(δ/√2)/μ]. The standard deviation (SD) of the differences between the paired BMD measurements is represented by δ. The overall mean of all the measurements for that region of interest (ROI) is represented by μ (121). The overall precision error in our study was 3,2%, considered to be acceptable (122, 123).

The scans were performed postoperatively, at three and twelve months. Baseline values were equal to mean bone mineral density (g/cm

²

) postoperatively. Postoperative BMD both for the affected hip as well as the contralateral hip was not different between groups. Changes in BMD were recorded for the different Gruen Zones. In a radiographic study Gruen, McNeice and Amstutz attempted to assess loosening around the femoral component in patients with total hip arthroplasties. They delineated the proximal femur into 7 zones in the AP

radiographic view of the cemented femoral stem (Figure 8). Each zone being macroscopically examined for radiographic signs of loosening (124).

Figure 8. Gruen zones 1-7. 7 delineated areas around the femoral stem. Illustration by Terje O. Ugland

.

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CK

We used the cobas® 6000 analyzer (Roche Diagnostics International Ltd., Switzerland) in study 2. The Cobas 6000 uses Ultraviolet kinetic method to measure total CK. A laboratory technician performed a blood test preoperatively, postoperatively and at day 1 and 2 post surgery.

Statistics

Statistical analysis was conducted using IBM SPSS statistics 21 for Windows (SPSS Inc., Chicago, Illinois).

Statistical tests

All patients were analyzed according to the intention to treat principle. Q-Q plots, histograms and the Shapiro–Wilks test were used to assess data for normal distribution. When continuous dependent variables were normally distributed we performed an Independent-t-test, also referred to as Student`s t-test, to test if there were statistically significant differences in means between the two groups. Pearson’s chi-square test was used to analyze categorical data. When the normal distribution- assumptions of the Student's t-test were not met we performed non parametric testing. Binary outcomes were assessed using Pearson Chi-Square test or logistic regression. Further details of the statistical plan is outlined in the methods section in paper 3 (3).

Study design

This study was designed as a randomized trial. The trial was reported based on the

Consolidated Standards of Reporting Trials , the CONSORT statement (125). The CONSORT statement consists of a flow diagram and a 25-item checklist. Power calculations was

performed based on an estimated difference in HHS of 10 points (27), standard deviation (SD) of 15, statistical power of 95 % and a significance level of 5%. A power of 0.95 was chosen to increase the probability of detecting a difference in HHS of 10 points between the population means. The sample size estimated in our study would also be enough to detect a mean

difference between two groups of approximately half of their SD, with 80% statistical power.

Thus, the sample size was sufficient at 80% power to detect an assessed minimal clinical

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important difference in other continuous and normally distributed outcome variables,

including VAS. The total sample size was estimated to 120 patients, i.e. 60 in each group. To allow for loss to follow up we planned to include 150 patients between 70 and 90 years with a dislocated FNF (3). “Simple randomization” was performed with a pre specified sample size of each arm, applying the random allocation rule, the simplest form of permuted block randomization (126). As to allocation concealment and steps in performing simple

randomization, we followed the practical guide for researchers by Doig and Simpson (127).

The physiotherapists that reported and monitored the outcome measures were blinded to allocated treatment. Patients were attempted masked to the surgical approach. In the CK paper an a priori sample size was calculated based on the values obtained in former published trials by Cohen et al (128) and Suzuki et al (96). Here we estimated that a sample size of total 82 patients, i.e. 41 in each treatment group would be sufficient. This was based on the

assumption that a difference of 75 U/L in CK would be clinically relevant. Statistical power was set to 80%, 5% significance level and an expected standard deviation (SD) of 75 U/L in each treatment group. To assess the strength of the association between CK values and functional assessments a correlation coefficient of 0.3 was understood as a minimum clinical relevant positive (or negative) association (129) . To detect an assumed correlation coefficient of 0.3 we would need a sample size of 85 patients. The level of significance was set to 5% and a power of 80% (2). The subgroup analysis was pre specified in the study protocol seeking to clarify if the surgical approach to the hip influences changes in periprosthetic bone mineral as measured by DXA. The authors consider the study to be confirmatory. The trial consisted of two treatment groups with a primary outcome variable (Mean reduction in BMD) and a pre specified hypothesis in the study protocol related to this variable. An a priori sample size calculation was performed and no interim analysis was conducted. We estimated that we would need a sample size of 34 patients, i.e. 17 in each treatment group. We assumed a 10%

difference to be clinically important (SD 10), statistical power of 80% and a significance level

of 5%. Calculations were based on previous studies on bone remodeling around the femoral

stem (123, 130, 131). A total of 50 patients were planned included to allow for loss to follow-

up (1). At the time of the DXA measurements the protocol as whole was planned for 120

study participants. This was later increased to 150 patients (2013/1853/REK sør-øst). We did

not protect the type I error rate against effects of the multiplicity issues through statistical

adjustments for multiple tests. As too the multiplicity concern this will be discussed later.

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We do believe that the statistical and methodological tools in this RCT were conducted

according to recommendations (132). Guidelines from the Consort group was respected and

statistical issues thoroughly evaluated by a statistical expert. Professional peer review was

performed prior to publication and ethical review by an independent institution (REK).

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Results

Results DXA study

In the immediate postoperative DXA measurement both the AL approach and the DL approach had similar BMD in both hips. The precision of the DXA measurements (CV %) were considered acceptable and differed from 1.2% in Gruen zone 4 to 5.5% in Gruen zone 6 (Table 2).

Gruen zone 1 2 3 4 5 6 7

Coefficients of variation

3.2 2.4 2.1 1.2 3.8 5.5 4.7

Table 2. Precision of DXA measurements for every Gruen zone. Coefficients of variation (CV %).

The DXA subgroup analyses showed a higher amount of bone loss in the proximal zones in the DL approach compared to the AL approach (Figure 9).

Figure 9. Mean BMD (g/cm2) postoperative, 3 and 12 months for AL and DL approach.

There was a mean reduction in total periprosthetic bone from baseline to 3 months (4.2%, 95% confidence interval 2.4-6.1) and to twelve months (5.8%, 95% confidence interval 3.3 to 8.3) all p<0.001. Measurements at 3 months showed a mean reduction in total periprosthetic

1,121,14 1,161,181,2 1,221,24 1,261,281,3 1,32

BMD Postop BMD 3 Months BMD 12 Months

Mean BMD (g/cm2)

Periprosthetic changes Proximal Gruen Zones

Anterolateral Direct lateral

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bone of 6.5% in the DL group versus 1.6% in the AL group. At twelve months the associated numbers were 8.1% in the DL group compared to 3.3% reduction in the AL group. DXA at three months displayed BMD loss in the proximal Gruen zones in the DL group compared to the AL group. Zone 1 (-5.0% vs. 2.7%), zone 2 (-4.3% vs. 4.1%), zone 6 (-6.5% vs. 0.0%) and zone 7 (-11.2% vs. -2.4%, all p<0.05) (Figure 10). There was a difference between groups at three months in mean change in total BMD in favor of the AL group (4.8%, 95%

confidence interval 1.6 to , p=0.04). The corresponding numbers at twelve months (4.8%, 95% confidence interval 0.0 to 9.6; P=0.05). These results are in conformity with our aim. We did expect a difference in BMD between the two groups as anticipated in the subsidiary objectives of the study protocol. I quote, “A hemiarthroplasty inserted through an

anterolateral approach gives less bone resorption, as measured by DXA around the stem, than a hemiarthroplasty inserted via a direct lateral approach”. The DXA measurements in this study indicate that periprosthetic BMD is influenced by the choice of surgical approach to the hip.

Figure 10. Periprosthetic changes (Gruen zones) in bone mineral density (BMD) around the

hydroxyapatite coated Corail stem measured by dual-energy X-ray absorptiometry (DXA) at 3 months.

The mean bone mineral density (g/cm2) postoperatively serves as baseline. Mean percentage change in BMD.

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Results Biomarker study

For all included study participants the increase in total CK from baseline to 24 h was mean 228 U/L (95% CI 187 to 269; P < 0.001). At 48 h the increase for all patients from baseline was mean 202 U/L (95% CI 154 to 251; P < 0.001) (Figure 11). As to change in CK, we found a difference between groups at both 24 h and 48 h compared to baseline. CK levels were higher in the AL group at 24 h (mean difference 80 U/L; 95% CI − 0.5 to 162; P = 0.05) and at 48 h (mean difference 117 U/L; 95% CI 22 to 212; P = 0.01).

Figure 11. Serum levels of CK (U/L) at 24h and 48h for AL (blue) and DL (red) approach to the hip.

Illustration by Alf Inge Hellevik.

Correlation analyses did not show any association between postoperative levels of serum marker CK and recorded continuous outcomes, except for CRP levels at 24 h and surgery time and CRP levels at 24 h and HHS at 3 months. As mentioned in the results section of the RCT main finding, a group difference was measured in surgery time (mean difference 4.5 minutes, 95% confidence interval (CI) 1.1 to 8.0; p = 0.009). Despite this difference no correlation was found with levels of CK. A correlation between surgical approach and the rise in CK values was found which was statistically significant (r = − 0.208; 95% CI − 0.36 to

−0.04; P =0.01).

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Results main RCT

There were no statistical significant differences in primary outcome measures VAS pain and VAS patient satisfaction between the DL and the AL group at all points of follow-up. No difference were found in HHS between the DL and the AL group at final follow-up at 12 months (mean HHS: AL, 84.4 (sd 15.4); DL, 85.3 (sd 11.2); mean difference in HHS 0.89, 95% confidence interval -6.0 to 4.1; p = 0.70). The differences measured failed to reach clinically improved thresholds. Only minor differences were detected in additional assessment scores such as the Timed Up and Go test and the Bartel Index Score. The AL approach was slightly more time-consuming compared to the DL approach; mean operating time was 41 minutes (27 to 104) in the DL approach versus 46 minutes (29 to 78) in the AL group (mean difference 4.5 minutes, 95% CI 1.1 to 8.0; p = 0.009). Length of stay in hospital was slightly shorter in the DL group compared to the AL group (4.6 days vs 5.5 days, p >0.05). The overall 30-day mortality rate was 6%. The mortality at 12 months was 16%. There was a higher number of patients with a positive Trendelenburg test in the DL group (11/55 (20%) vs 1/55 (1.8%), relative risk (RR) 11.1; p = 0.004) (Figure 12). Cramer’s V was 0.293. This indicates a low to moderate correlation between the surgical approach and the presence of a positive Trendelenburg sign

Figure 12. Number of patients with a positive Trendelenburg test in the AL (blue) and DL (red) group.

Illustration by Alf Inge Hellevik.

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We found a difference in mean HHS score at 12 months with lower scores in the

Trendelenburg positive group compared to the Trendelenburg negative group (78.5 vs 85.6).

The Trendelenburg positive group reported significantly lower HOOS sub scores in:

symptoms (mean difference 14.1, 95% confidence interval -27.5 to; p = 0.04); ADL (mean difference 23.0, 95% confidence interval -26.6 to -9.5; p = 0.001); and QOL (mean difference 19.6, 95% confidence interval -38.2 to -1.0; p = 0.03), (Figure 13).

Figure 13. HOOS subscale scores at 12 months inTrendelenburg positive and Trendelenburg negative patients. *P<0.05.

0 20 40 60 80 100 120

Symptoms * Pain ADL * Sport/Rec QOL *

Mean HOOS Score 12 months

Trendelenburg Positiv Trendelenburg Negative

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Adverse events

Adverse events included surgical complications such as, PJI, dislocation, nerve injury early and late occurring fractures and mortality (Table 3).

Adverse event Direct lateral approach (n = 75), n (%)

Anterolateral approach (n = 75),

n (%)

Total (n = 150), n (%)

Infection (PJI) 2 (2.6) 1 (1.3) 3 (2.0)

Dislocation 0 (0.0) 0 (0.0) 0 (0.0)

Nerve injury 0 (0.0) 1 (1.3) 1 (0.6)

Intraoperative fracture

2 (2.6) 1 (1.3) 3 (2.0)

Late occurring fracture

3 (4.0) 1 (1.3) 4 (2.6)

Mortality within 30 days

6 (8.0) 3 (4.0) 9 (6.0)

Mortality within 12 months

11 (14.6) 13 (17.3) 24 (16.0)

Table 3. Adverse advents. PJI (Prosthetic joint infection). Figures are numbers (percentages) unless stated otherwise.

There were no dislocations reported. Three patients (2%) acquired an infection needing revision surgery. Two in the DL group and one in the AL group. They were successfully revised without implant removal. Three patients had an intraoperative fracture. Two in the DL group and one in the AL group. They were minor calcar fractures that healed without surgery.

Four patients had a late occurring periprosthetic fracture. Two of them (one in each group)

needed surgery with revision stems. Both healed without further intervention. A temporary

footdrop was found in one patient in the AL group. This adverse advent was probably not due

to surgery. MRI scan showed a spinal meningioma, probably the cause of the foot drop. As

previous mentioned the overall 30-day mortality rate was 6%. The mortality at 12 months was

16%.

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Discussion

There were no differences in the primary outcome measure VAS for pain and patient

satisfaction between the DL and the AL approach. We found a higher number of patients with a positive Trendelenburg sign in the DL group compared to the AL group at 12 months.

Patients with a positive Trendelenburg sign reported HOOS levels inferior to those that were not Trendelenburg positive. In the biomarker study CK values were higher in the AL group, although no correlation was found between CK values and functional outcome measures. In the BMD study we found the loss of bone mineral around the femoral stem to be more pronounced in the proximal Gruen zones in the DL group compared to the AL group.

As mentioned earlier the aim or overall objective of this thesis is to investigate the role of the surgical approach when treating patients with a femoral neck fracture. The thesis is built on three papers attempting to elucidate key factors of the overall objective, striving for a coherent whole. This is; the evaluation of changes in bone mineral around the stem (paper I), the

invasiveness of the surgical intervention in terms of CK measurements (paper II), and finally the appraisal of functional outcome after one year (paper III).

Current scientific literature on the benefits of the muscle sparing approaches are confusing for FNFs. Published papers are often prone to noisy data sets and the lack of high quality papers dealing with FNF and surgical approach are inconspicuous. Trials of good quality,

investigating surgical approach to the hip in THA, are more frequent. In a recent systematic

review with meta-analysis Miller et al found the anterior approach in THA to be associated

with less pain, less consumption of analgetics and better hip function at 90 days compared to

the posterior approach (133). No statistical difference was found in the rates of complications

between different surgical approaches. The systematic review by Meermans et al, who found

little evidence of superiority for the direct anterior approach in THA, was included in Millers

review (97). As to complication rates this is in contrast to numbers reported when inserting

HA in FNF patients. An editorial review by Robertson and Wood identifies two meta-

analyses and one Cochrane review regarding the superior surgical approach for HA in FNF

(134). The first systematic review and meta-analysis mentioned, by Kunkel et al, reports on

results of the direct anterior approach compared to other surgical approaches when inserting

HA in patients with FFN. They did have difficulties assessing secondary outcomes such as

pain due to diversity in assessment tools and when these were measured. Analysis of these

assessments showed no clear favor of one surgical approach over another. This also applies

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for surgery time and blood loss. Their primary outcome measure, postoperative functional mobility, was in favor of the direct anterior approach (94). In the second meta-analysis van der Sijp et al concluded that there is a higher risk of dislocation in the posterior approach. No conclusions could be drawn by the authors as to functional outcome (86). The Cochrane Review by Parker et al consisting of only one RCT could not come to an conclusion (135).

Verzellotti et al in a recent RCT published in Hip International investigating hip HA for FNF found the direct anterior approach to cause less pain in the immediate postoperative period compared to the posterolateral approach (136). Renken and Co-workers found that

mobilization was improved for the direct anterior group compared with the Watson Jones group in patients with femoral neck fractures operated with a HA. Both groups (n=30) received a muscle sparing approach (137). Preininger and co-workers found in their retrospective material that patients with femoral neck fractures operated with an anterior minimally invasive approach were mobilized quicker than those with a trans gluteal approach (138). Others have found the direct anterior approach for HA in FNF patients to be associated with good functional results (139). Despite conflicting reports on the merits of the anterior approaches in hip arthroplasty the anterior approaches are often considered more technically demanding. There is clearly a learning curve to this procedure. In a study from Australia they found the surgeons individual learning curve for THA in the anterior approach to be 50 or more procedures in order to reach the same revision rate numbers as surgeons having performed more than 100 procedures (140). A learning curve for the anterior approach in THA has also been shown on a departmental level (141). Schwartz et al came to the opposite conclusion stating that the transition to a DAA approach was safe. This was a high volume single surgeon study and they cautioned about translation of these results to low volume hip surgeons (142). To my knowledge quality papers on learning curves for HA in the anterior approach for FNF are absent. Probably the same learning curve applies for HA in the anterior approach. The numbers of patients with an FNF are in most hospitals high. Surgery is

Direct Lateral or Minimally Invasive Surgical Approach for Hemiarthroplasty in Hip Fracture