Results and complications of large diameter head cementless metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty

(1)

DISSERTATIONS | SIMO MIETTINEN | RESULTS AND COMPLICATIONS OF LARGE DIAMETER HEAD... | No 462

uef.fi

PUBLICATIONS OF

THE UNIVERSITY OF EASTERN FINLAND Dissertations in Health Sciences

ISBN 978-952-61-2768-2 ISSN 1798-5706

Dissertations in Health Sciences

THE UNIVERSITY OF EASTERN FINLAND

SIMO MIETTINEN

RESULTS AND COMPLICATIONS OF LARGE DIAMETER HEAD CEMENTLESS METAL-ON-METAL TOTAL HIP ARTHROPLASTY AND HIP RESURFACING ARTHROPLASTY

The main objective of total hip replacement is to relieve pain and improve function. Many challenges have been encountered in the field of hip arthroplasty during last decades while developing implant materials and surgical techniques. Solving of these challenges have led to a current modern type of total hip arthroplasty.

Aims of this dissertation were to study some of the most common problems related to total hip arthroplasty. The conclusion of this dissertation

is that the orthopaedic surgeon must be aware of the possible complications related to hip arthroplasty and also know how to avoid them.

SIMO MIETTINEN

(2)

(3)

SIMO MIETTINEN

Results and complications of large diameter head cementless metal-on-metal total hip

arthroplasty and hip resurfacing arthroplasty

To be presented by permission of the Faculty of Health Sciences, University of Eastern Finland for public examination in Auditorium 2, Kuopio University Hospital, Kuopio, on Friday, May 4^th 2018,

at 12 noon

Publications of the University of Eastern Finland Dissertations in Health Sciences

Number 462

Department of Orthopaedics, Traumatology and Hand Surgery of Kuopio University Hospital, Institute of Clinical Medicine, School of Medicine, Faculty of Health Sciences,

University of Eastern Finland Kuopio

2018

(4)

Jyväskylä, 2018 Series Editors:

Professor Tomi Laitinen, M.D., Ph.D.

Institute of Clinical Medicine, Clinical Physiology and Nuclear Medicine Faculty of Health Sciences

Professor Hannele Turunen, Ph.D.

Department of Nursing Science Faculty of Health Sciences Professor Kai Kaarniranta, M.D., Ph.D.

Institute of Clinical Medicine, Ophthalmology Faculty of Health Sciences

Associate Professor (Tenure Track) Tarja Malm, Ph.D.

A.I. Virtanen Institute for Molecular Sciences Faculty of Health Sciences

Lecturer Veli-Pekka Ranta, Ph.D. (pharmacy) School of Pharmacy

Faculty of Health Sciences Distributor:

University of Eastern Finland Kuopio Campus Library

P.O.Box 1627 FI-70211 Kuopio, Finland http://www.uef.fi/kirjasto ISBN (print): 978-952-61-2768-2

ISBN (pdf): 978-952-61-2769-9 ISSN (print): 1798-5706

ISSN (pdf): 1798-5714 ISSN-L: 1798-5706

(5)

Author’s address: Department of Orthopaedics, Traumatology and Hand Surgery Kuopio University Hospital

KUOPIO FINLAND

Supervisors: Docent Jukka Kettunen, M.D., Ph.D.

Department of Orthopaedics, Traumatology and Hand Surgery Kuopio University Hospital

KUOPIO FINLAND

Docent Tatu Mäkinen, M.D., Ph.D.

Department of Orthopaedics and Traumatology Helsinki University Hospital

HELSINKI FINLAND

Docent Ville Remes, M.D., Ph.D.

Department of Orthopaedics and Traumatology Helsinki University Hospital

HELSINKI FINLAND

Reviewers: Docent Teemu Moilanen, M.D., Ph.D.

Department of Orthopaedics and Traumatology Tampere University Hospital

TAMPERE FINLAND

Docent Jorma Pajamäki, M.D., Ph.D.

Department of Orthopaedics and Traumatology Tampere University Hospital

TAMPERE FINLAND

Opponent: Professor Juhana Leppilahti, M.D., Ph.D.

Department of Orthopaedics and Traumatology Oulu University Hospital

OULU FINLAND

(6)

(7)

Miettinen, Simo

Results and complications of large diameter head cementless metal-on-metal total hip arthroplasty University of Eastern Finland, Faculty of Health Sciences

Publications of the University of Eastern Finland. Dissertations in Health Sciences 462. 2018. 78 p.

ISBN (print): 978-952-61-2768-2 ISBN (pdf): 978-952-61-2769-9 ISSN (print): 1798-5706 ISSN (pdf): 1798-5714 ISSN-L: 1798-5706

ABSTRACT

Total hip arthroplasty is a surgery in which the hip joint is replaced by a prosthetic implant.

The current concept of total hip arthroplasty has constantly evolved since the introduction of the first implants in early 1960s. Different materials and implant designs have been developed and a large amount of research has been performed during the last few decades.

Successes and failures have been encountered and the adoption of this knowledge has led to the current treatment methods for hip osteoarthritis.

The main aims of this doctoral thesis were to examine the five-year survival rate of cementless large diameter head total hip arthroplasties s and hip resurfacing arthroplasties, and to compare complications and revision rates between these devices (I-IV). In more detail, the aims were to investigate the incidence and risk factors of intraoperative calcar fractures of cementless femur components (II), evaluation of the incidence and denominators related to the early aseptic loosening of the cementless acetabular components (III) and examination of the incidence and factors for the dislocation of large diameter head total hip arthroplasties and hip resurfacing arthroplasties (IV).

This study showed that total hip arthroplasties encounter more intraoperative complications and have a marginally lower cumulative survival rate than hip resurfacing arthroplasties (I). The study dealing with intraoperative complications showed that patients with osteoporosis, hip dysplasia, and/or a history of previous hip surgery, fracture or small proximal femurs and wide proximal femur canals with thin cortices were at a higher risk of intraoperative calcar fracture (II). Another study dealing with complications showed that one percent of patients will not achieve adequate component stabilisation and osseointegration will fail, leading to acetabular component revision (III). Dislocation of large diameter head total hip arthroplasty is a rare complication; placing the acetabulum component in the correct inclination and anteversion angles and restoring the hip anatomical rotation centre will reduce the risk of dislocation (IV).

Problems related to metal-on-metal bearings have been recognised in recent years, so the use of these bearings is no longer recommended.

National Library of Medicine Classification: WE 860, WE 862, WE 865, WO 181

Medical Subject Headings: Arthroplasty, Replacement, Hip; Metal-on-Metal Joint Prostheses; Intraoperative Complications; Incidence; Femoral Fractures; Survival Rate; Hip Dislocation; Risk Factors; Osseointegration;

Patients; Osteoarthritis, Hip; Follow-Up Studies

(8)

(9)

Miettinen, Simo

Sementittömien suurinuppisten lonkan metalli-metalli liukupintaisien varrellisten- ja pinnoitetekonivel- leikkausten tulokset ja komplikaatiot

Itä-Suomen yliopisto, terveystieteiden tiedekunta

Publications of the University of Eastern Finland. Dissertations in Health Sciences 462. 2018. 78 s.

ISBN (print): 978-952-61-2768-2 ISBN (pdf): 978-952-61-2769-9 ISSN (print): 1798-5706 ISSN (pdf): 1798-5714 ISSN-L: 1798-5706

TIIVISTELMÄ

Lonkan kokotekonivelleikkaus on toimenpide, jossa lonkkanivel korvataan implantilla.

Ensimmäinen moderni lonkan kokotekonivelleikkaus tehtiin 1960-luvun alkupuolella ja sen jälkeisen tutkimustyön tuloksena ovat syntyneet nykyiset hoitosuositukset lonkan tekonivelleikkauksista. Monenlaisia materiaaleja sekä implantteja on viime vuosikymmenten aikana tutkittu ja samalla on saatu runsaasti tutkimustietoa aiheesta.

Onnistumiset ja epäonnistumiset kehitystyössä ovat ohjanneet kohti nykyisin käytössä olevia hoitosuosituksia lonkan nivelrikon hoidosta.

Tämän väitöskirjan tutkimusaiheena oli selvittää suurinuppisten lonkan sementittömien metalli-metalli liukupintaisten varrellisten- ja pinnoitetekonivelien keskipitkän seuranta- ajan tulokset (I). Lisäksi tutkittiin erilaisten leikkauskomplikaatioiden esiintyvyyttä ja syitä sekä selvitettiin uusintaleikkauksiin johtaneet tekijät (I-IV). Tarkemmin tutkittuja komplikaatiota olivat toimenpiteenaikaiset reisiluun yläosan murtumat varrellisilla kokotekonivelillä (II), lonkkamaljakon kuppikomponentin varhaiset irtoamiset (III) ja tekonivelten sijoiltaanmenot (IV). Näistä komplikaatioista selvitettiin esiintyvyys ja riskitekijät (II-IV).

Tutkimuksessa todettiin lonkan varrellisilla kokotekonivelillä olevan enemmän toimenpiteenaikaisia komplikaatioita kuin pinnoitetekonivelillä ja lisäksi varrellisten tekonivelten kumulatiivisen uusintaleikkausriskin todettiin olevan marginaalisesti suurempi (I). Toimenpiteenaikaisten reisiluun yläosan murtumien riskitekijöitä olivat osteoporoosi, lonkan dysplasia sekä aiemmat lonkkaleikkaukset ja –murtumat (II).

Radiologisissa tutkimuksissa todettiin reisiluun poikkeavan yläosan ja ohuen kortikaalisen luun olevan riskitekijöitä murtumalle (II). Lonkkamaljan kuppikomponentin irtoamisen esiintyvyys tutkimusaineistossa oli yksi prosentti ja syynä siihen olivat puutteellinen komponentin kiinnitys sekä riittämätön luun integroituminen (III). Lonkan tekonivelen sijoiltaanmeno suurinuppisilla kokotekonivelillä on erittäin harvinaista ja syy sijoiltaanmenoon johtuu luultavimmin lonkkamaljan kuppikomponentin virheellisestä asemoinnista (IV).

Metalli-metalli liukupintaisia tekoniveliä ei nykyisin suositella käytettäväksi niihin liittyvien ongelmien vuoksi.

Luokitus: WE 860, WE 862, WE 865, WO 181

Yleinen Suomalainen asiasanasto: lonkka; tekonivelet; implantit; leikkaushoito; hoitotulokset; komplikaatiot;

esiintyvyys; luunmurtumat; sijoiltaanmeno; riskitekijät; potilaat; nivelrikko; seurantatutkimus

(10)

(11)

To Outi, Selma and Armi

(12)

(13)

Acknowledgements

“A man who dares to waste one hour of time has not discovered the value of life.”

― Charles Darwin (1809 - 1882)

This study was carried out in the Department of Orthopaedics, Traumatology and Hand Surgery of Kuopio University Hospital during the years 2012 - 2018. This was a multicenter study and other participating hospitals were Helsinki University Central Hospital and Turku University Hospital. I wish to express my thanks for all the people who in some way have participated in the present study.

I want to express my gratitude to Professor Heikki Kröger, M.D., Ph.D., Head of Department of Orthopedics, Traumatology and Hand Surgery for his support and providing me good facilities to do this study. He introduced the field of research to me by guiding my advanced studies in medical school and encouraged me to begin a scientific career. Heikki also provided me a position of a clinical teacher in year 2017, and in this position I have had time to complete these studies and this doctoral dissertation.

I am deeply grateful to my supervisors Docent Jukka Kettunen, M.D., Ph.D., Docent Tatu Mäkinen, M.D., Ph.D. and Docent Ville Remes, M.D., Ph.D. for their support and guidance and finally making these studies possible. Jukka has given a lot of valuable comments, support and excellent guidance throughout this research project. My deepest respect to Tatu and Ville for their inspiration and knowledge on the field of arthroplasty, it has been essential to this thesis.

I express my sincere thanks to my co-authors Inari Laaksonen M.D., Ph.D. and Docent Keijo Mäkelä M.D., Ph.D. for their help in collecting data and for their valuable comments and important proposals.

I am grateful to Heini Huhtala, M.Sc. for her kind, fast and fully reliable guidance in statistical problems during many phases of the research.

I am grateful to the official reviewers of the dissertation, Docent Jorma Pajamäki, M.D., Ph.D. and Docent Teemu Moilanen, M.D., Ph.D. for the time they spent reviewing the manuscript, and for their valuable criticism and suggestions, which greatly improved this work.

I express my thanks to all my current and former colleagues in the Department of Orthopaedics, Traumatology and Hand Surgery of Kuopio University Hospital. Special thanks belongs to my closest colleagues Jussi Jalkanen, M.D. and Samuli Törmä, M.D. in the Division of Traumatology for sharing work and constructive discussions. I would also like to thank my colleagues Antti Joukainen, M.D., Ph.D. and Tommi Kääriäinen, M.D. for guiding me into the world of arthroscopy. I also thank Antti and Jussi for relaxing sport events during these years.

I would like to thank my friends Atte Moilanen, Erno Voutilainen, Juuso Heinonen and Juuso Väistö for relaxing moments and discussions from childhood to present. My warmest thanks to family friends Eeva Kurkirinne and Teemu Merinen, Sara and Antti Stenroos, Anna Govenius and Jussa Nieminen, Sari and Lasse Nieminen, and their families for sharing happy moments throughout these years. I also thank my friends and colleagues Elina Ekman and Tero Kortekangas for long-lasting and entertaining discussions related to work and off-work.

I express my warmest thanks to my parents-in-law Ulla Kuikka and Arto Piisilä for taking care of my children. Without your incredible help this thesis would still be incomplete.

(14)

I am grateful to my brother Henri for friendship and brotherliness, and also for his help in this research by collecting data. I am also very thankful for my loving sisters Saara and Nelli for being part of my life.

Above all, I want to thank my parents Hilkka and Hannu for all of their warm support I have had throughout my life. Warm thanks to you Mom for all love and care you have given to grandchildren. Besides being my dad, Hannu has also been an orthopaedic surgeon role model to me. His encouraging support and skillful guidance in the field of science as well as in clinical work have been exceptional good, and he has always been a rearmost backup to me.

Finally, I wish to sincerely thank my wife Outi for her love, support and tolerance to me during these years. I am deeply grateful to Outi for her understanding towards me while I have tried my best in compounding my work, sports activities and research into the family life. This thesis would not ever have finished without your help and tremendous Word™

and Excel™ processing skills. I am very fortunate to have a person like you beside me, loving thanks to you Outi!

Selma and Armi, my beloved daughters, you are the light of my life! You have given me so much joy and fun to everyday life! You keep me happy and smiling all the time!

This study was made possible by support from the Finnish Arthroplasty Society, Finnish Research Foundation for Orthopedics and Traumatology, Research Foundation of Kuopio University Hospital, EVO-Funding of Kuopio University Hospital, Finnish Cultural Foundation North Savo Regional fund, The Finnish Medical Foundation Duodecim and Research Foundation of Vappu Uuspää.

Kuopio, March 2018

Simo Miettinen

(15)

List of the original publications

This dissertation is based on the following original publications, which are referred to in the text by their Roman numerals:

I Miettinen SS, Mäkinen TJ, Mäkelä K, Huhtala H, Kettunen JS, Remes V.

Intraoperative complications and mid-term follow up of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty.

Manuscript is accepted for publication on 22th August 2017 in Scandinavian Journal of Surgery.

II Miettinen SS, Mäkinen TJ, Kostensalo I, Mäkelä K, Huhtala H, Kettunen JS, Remes V. Risk factors for intraoperative calcar fracture in cementless total hip arthroplasty. Acta Orthop. 2016; 87: 113-9.

III Miettinen SS, Mäkinen TJ, Laaksonen I, Mäkelä K, Huhtala H, Kettunen J, Remes V. Early aseptic loosening of cementless monoblock acetabular components. Int Orthop. 2017; 41: 715-722.

IV Miettinen SS, Mäkinen TJ, Laaksonen I, Mäkelä K, Huhtala H, Kettunen J, Remes V. Dislocation of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty. Manuscript in press.

The publications were adapted with the permission of the copyright owners.

(16)

(17)

Abbreviations

ADR Acetabular depth-width ratio aHR Adjusted hazard ratio AP Antero-posterior

ARMD Adverse reaction to metal debris

AVN Avascular necrosis CE Centre-edge angle CFI Canal flare index CoCr Cobalt-Chromium

DDH Developmental dysplastic hip DVT Deep vein thrombosis

ESR Erythrocyte sedimentation rate

FHEI Femoral head extrusion index HR Hazard ratio

HRA Hip resurfacing arthroplasty LDH Large diameter head

LLD Leg length discrepancy MoM Metal-on-Metal

MoP Metal-on-Polyethylene M/L Medio-lateral

OA Osteoarthritis

PACS Picture archiving and communication systems PE Pulmonary embolism PJI Periprosthetic joint infection RA Rheumatoid arthritis SD Standard deviation THA Total hip arthroplasty THR Total hip replacement VTE Venous thromboembolism

(20)

(21)

1 Introduction

Total hip arthroplasty (THA) is a surgery in which the hip joint is replaced by a prosthetic implant. THA is the treatment of choice when the conservative treatment of hip osteoarthritis (OA) has failed. The present state of THA was first introduced by Sir John Charnley in early 1960s (Charnley 1961). Since Charnley’s innovations, a large amount of research has been undertaken to improve the survival associated with THA. Innovations in component materials, surgical techniques, methods of fixation, and the sterilisation of implants have resulted in a breakthrough in hip surgery (Derar et al. 2015). Rehabilitation programs and medical innovations have also improved the results of THA. One of these innovations in implant design is hip resurfacing arthroplasty (HRA) with Metal-on-Metal (MoM) articulation in the early 1990s (McMinn et al. 1996).

THA has become a routine surgery which offers patients pain relief and improves functioning and quality of life with a low rate of complications. Today, there are approximately one million THA performed worldwide annually and hip replacements are performed for more active and younger patients than ever before, while at the same time, the life expectancy of patients is increasing. This combination means that the total number of THAs is increasing yearly worldwide (Pivec et al. 2012).

Although the risks of THA surgery are quite low, there are short- and long-term complications and the current burden of these devices is that approximately ten percent of the implanted hip prostheses will require a revision surgery within ten years (Sargeant et al. 2006).

Complications can be divided into intraoperative and post-operative and also into technical, medical and infection complications. The most common intraoperative complications are fractures, nerve damage and medical problems. The complication profile of each type of THA (e.g. conventional THA or HRA and cementless, cemented or hybrid) is similar, but there are also some unique complications of different devices. Some of the complications are related to differences in surgical technique.

Problems related to Metal-on-Polyethylene (MoP) bearings, which were used widely in the 1980s, led to a rapid increase in the use of MoM bearing THAs in the late 1990s and early 2000s. These implants had excellent functional results and the first short-term results were astonishing (Amstutz et al. 2004, Shimmin et al. 2005). In particular, dislocation, which is a frustrating problem of smaller head size THA, was rare or even non-existent with large diameter head (LDH) THAs and HRAs (Jameson et al. 2011). However, in the late 2000s, problems were encountered and the first cases of MoM-related periarticular fluid collections, soft tissue masses and gluteal muscle necrosis were diagnosed (Ollivere et al. 2009, Langton et al. 2011). These findings are called adverse reactions to metal debris (ARMD); due to these serious problems, national and international orthopaedic organisations announced guidelines stating that LDH MoM THA and HRA device use should be discontinued (MHRA 2010, AOANJRR 2014, SAY 2015).

The aim of this thesis was to examine midterm survival rates of LDH MoM THAs and HRAs and compare in detail the complications and revision rates between these devices.

(22)

(23)

2 Review of the literature

2.1 HIP JOINT OSTEOARTHRITIS

Hip osteoarthritis (OA) is not a disease of the modern era, since it was a problem for our ancestors in ancient eras (Entezami et al. 2011). OA has been diagnosed by palaeopathologists in ancient skeletons around the world, e.g. from the ruins of Pompeii and ancient Egypt and from the remains of Norse Viking warships (Entezami et al. 2011). In ancient literature, OA and rheumatoid arthritis (RA) are often confused; they were first described by Hippocrates and other physicians of his era (Entezami et al. 2011).

There is a consensus that OA is not a single disease affecting joints but rather a number of distinct conditions with unique aetiological factors which share a common final endpoint (Brandt et al. 2008). Hip OA is a disabling condition, primarily affecting elderly people. It is estimated that there is a 25% lifetime risk of having a symptomatic hip OA in people who live to the age of 85 years (Murphy et al. 2010). The age-standardized prevalence of radiographic hip OA varies form 1–10% (Nevitt et al. 2002, Jordan et al. 2009, Kim et al. 2014). The age- adjusted prevalence of clinically diagnosed hip OA in the Finnish population aged over 30 years was 5.7% in men and 4.6% in women (Kaila-Kangas 2007).

The American College of Rheumatology has established criteria for the diagnosis of hip OA in clinical practice. Clinical criteria A are: 1) hip pain; 2) hip internal rotation <15°; and 3) erythrocyte sedimentation rate (ESR) ≤45mm/h or hip flexion ≤115° if ESR unavailable. Clinical criteria B are: 1) hip pain; 2) pain with hip internal rotation; 3) morning stiffness of the hip ≤ 60min; and 4) age over 50 years. Clinical plus radiographic criteria are hip pain and any of the following: ESR <20mm/h or radiographic femoral and/or acetabular osteophytes or radiographic joint space narrowing (Altman et al. 1991). Commonly used radiographic classification for OA is the Kellgren and Lawrence grading, which uses a five-point scale between 0 and 4; grades 2 and higher indicate radiographic OA (Kellgren et al. 1957) (Figure 1). Both clinical and radiographic grading of hip OA are relevant for use in clinical practice.

(24)

Figure 1. Hip joint osteoarthritis in a native pelvic radiograph. On the right hip joint (R) there is Kellgren-Lawrence grade 3/4 osteoarthritis and on the left Kellgren-Lawrence grade 2/4 osteoarthritis.

Risk factors for hip OA can be split into person level and joint level risk factors. Person level risk factors are age, gender, weight, genetics, ethnicity, occupation and diet (Felson et al. 2000, Nevitt et al. 2002, Peterson et al. 2010, Jiang et al. 2011, Kim et al. 2014, Harris et al. 2015). The prevalence of hip OA increases with age in both men and women and it is higher in men overall (Kaila-Kangas 2007). Genetics and ethnicity are known risk factors for OA and in a recent study hip OA prevalences were lower in Blacks and Asians than Whites, respectively (Smith et al. 2017). Hip joint level risk factors are joint morphology, muscular function and joint shape (Weinstein et al. 1987, Sandell et al. 2012). Hip joint morphology might be congenitally faulty or acquired during life; for example, OA might be caused by arthritis or post-traumatic conditions.

2.1.1 Pathogenesis of the hip joint osteoarthritis

Hip joint OA is a common final pathway to a number of distinct aetiological factors and there is common pathogenesis of OA-affected hip joints, regardless of the cause of OA. Hip joints undergo pathological biomechanical stress caused by the risk factors and this cascade further leads to the pathogenesis of OA (Guilak 2011). Biomechanical stress and altered joint loading

(25)

cause cellular and molecular changes at the articular surface which further initiate apoptotic cellular changes and cartilage damage, leading to OA (Smith et al. 2004, Li et al. 2013).

2.2 CONSERVATIVE TREATMENT OF THE HIP JOINT OSTEOARTHRITIS Hip joint OA treatment is initially conservative, including non-pharmacological and pharmacological treatments (Duodecim 2014). Non-pharmacological treatments include patient education, weight management and physical exercise (Bennel et al. 2013, Nguyen et al.

2016). Pharmacological managements include topically- and orally-administered non-steroidal anti-inflammatory drugs (da Costa et al. 2017). Also, paracetamol and opioids can be used for pain management (da Costa et al. 2017), while intra-articular injection of cortisone offers symptomatic pain relief (McCabe et al. 2016). Is has been claimed that the concentration of hyaluronic acid is decreased in OA so it can be administered via intra-articular injection to the hip joint; however, the efficacy of it with regard to pain relief is unclear (Qvistgaard et al.

2006).

2.3 HIP JOINT ARTHROPLASTY

Hip joint arthroplasty is the drug of choice when conservative treatment of hip OA fails. Total joint replacement as a treatment of OA of the hip joint is considered the operation of the century (Learmonth et al. 2007). There is an estimated lifetime risk of undergoing THA of almost 10% (Culliford et al. 2012).

Inter-positional arthroplasty was the first known surgical attempt to treat hip arthrosis in the late 19^th and early 20^th centuries (Smith-Petersen 1948, Learmonth et al. 2007). A wide range of inter-positional material, e.g. fascia lata autograft and skin and pig bladder, were used between articular surfaces (Learmonth et al. 2007). The first hip arthroplasty (a hemiarthroplasty) was performed by Themistocles Gluck in 1891 using an ivory femoral head (Gluck 1891). The history of total hip replacement (THR) begins in 1938, when the first THR was implanted (Wiles 1958). The vitallium mould design of Smith-Petersen was the first attempt to use artificial materials as a bearing surface in THA and this device was also the first THA with MoM bearings (Smith-Petersen 1948). Before Smith-Peterson, there were many ingenious surgeons whose attempts at reconstruction of the hip joint failed largely due to poor implant design, inferior materials and mechanical failure (Wiles 1958, Grigoris et al. 2006).

The present state of THR was introduced by Sir John Charnley in the early 1960s when he presented a modern type THA with a cemented stem (Thompson) and a cemented acetabulum component (Charnley 1961). Before presenting modern type THR, Charnley did a lot of research with different materials and surgical techniques in the 1950s (Charnley 1961). For example Charnley performed the first hip resurfacing in the early 1950s by using thin cups of Teflon but results were poor because of rapid wear of Teflon occurred (Charnley 1961).

Charnley studied also many other materials by that time and finally he figured out to use low friction metal and high-density polyethylene-bearing surfaces (Charnley 1961). Charnley’s contribution to the evolution of modern THR can be divided into three major points of knowledge: 1) the idea of low friction torque arthroplasty; 2) the use of acrylic cement to fix components to living bone; and 3) the introduction of high-density polyethylene as a bearing material (Charnley 1961, Learmonth et al. 2007). The long-term results of these first generation low friction arthroplasties were good; in a 25-year follow-up, survivorship has been reported to be 77–81% (Callaghan et al. 2000, Berry et al. 2002). However, the outcomes of other types of

(26)

cemented THRs were poor, with revision rates as high as 40% at the 10-year follow-up due to acetabulum component loosening (Olsson et al. 1981, Sutherland et al. 1982). These poor outcomes of early cemented THRs were mostly related to implant design and cementing technique. At the time, loosening of the implant due to cementing failure was called “cement disease”; as a result, the cementless THR was developed (Yamada et al. 2009). Nevertheless, the outcomes of the first models of cementless implants in the 1970s were also poor (Grigoris et al. 2006, Yamada et al. 2009). The main reason for the poor survival of the first cementless devices was that the surface of the implants was smooth and adherence to bone did not occur, which soon led to early aseptic loosening of the implant. In the early 1960s cemented THAs with metal-on-metal articulations were introduced as a solution to aseptic loosening which was thought to be caused by polyethylene debris reliased from the MoP surfaces (McKee et al.

1966). A long-term results of these first modern type MoM THAs at average follow-up of 13.9 years were moderate with a survivorship of 81% (August et al. 1986).

Implant design improved in the 1980s, when more adherent materials were introduced.

Implant materials like titanium and cobalt-chromium allowed bone ingrowth to the implant, which further led to stable biological implant fixation with good survival rates (Yamada et al.

2009). However, in the late 1980s and early 1990s, stable implant fixation was noticed to cause changes in the proximal femur in a phenomenon known as stress-shielding (Huiskes et al.

1992). There were also problems related to cementless acetabulum components, including failures of the locking system of the polyethylene liner, insufficient polyethylene thickness and their application in patients with developmental dysplastic hip (DDH) with poor results (Yamada et al. 2009). Another major problem was polyethylene wear particle production from poor quality polyethylene liners as it was found to be as a triggering mechanism of osteolysis and aseptic loosening (Gomez-Barrena et al. 1998).

The longevity of THR is the greatest concern among orthopaedic surgeons. Although the long-term survival of THR implants is affected by multiple factors, an effect called tribology is considered the most important. Tribology is defined as “the branch of science and technology that deals with the study of friction, wear and lubrication” (Chambers 21^st Century Dictionary). Tribology in THR means a combination of friction, lubrication and wear of articulation surfaces (Rieker 2017). In natural hip joints, this coefficient is achieved by three lubrication mechanisms: 1) elastohydrodynamic lubrication, 2) micro-elastohydrodynamic lubrication, and 3) squeeze-film lubrication (Scholes 2006).

2.3.1 Total hip arthroplasty

Indications for THA are guided by pain, functional impairment and radiographic findings (NIH 1995). However, no international consensus exists for surgical indications. Optimum surgical results are obtained through careful patient selection. Risk factors for complications should be evaluated, along with the benefits of THA, and patient expectations of the procedure should also be evaluated. Hip replacements are being performed in more active and younger patients than ever before, while life expectancy of patients is increasing at the same time. This combination means that the total number of THAs is raising worldwide on a yearly basis (Pivec et al. 2012).

There are four different fixation options for THA: 1) fully cementless design of both the femur and acetabulum components, 2) fully cemented design of both components, 3) hybrid design with a cemented stem and cementless acetabulum component, and 4) reverse hybrid design with a cemented cup and cementless stem. Bearing surface options for the THA components are MoP, ceramic-on-ceramic, metal-on-ceramic and MoM while bearing surfaces of the HRA are MoM (Figures 2 and 3).

(27)

Figure 2. Cementless metal-on-metal total hip arthroplasty components (Biomet M2a38 acetabulum component and Biomet BiMetric stem; Biomet, Warsaw, IN, USA).

Figure 3. Hip resurfacing arthroplasty components (Acetabulum component: Biomet ReCap;

Biomet, Warsaw, IN, USA and femoral stem: BioPro Resurfacing, Port Huron, MI, USA).

(28)

THA has shown good and excellent long-term outcomes, but the revision surgery burden has remained unchanged over the last several decades (Callaghan et al. 2000, Berry et al. 2002, SHAR 2015, AOANJRR 2016). The Charnley low-friction THA was the first device distributed worldwide and had excellent survivorship (78%) at the 35-year follow-up (Callaghan et al.

2000). Cemented THA survivorship has reached 83% at the 20 to 25-year follow-up (Petheram et al. 2016). Cementless THA have been used most often, with favourable survival results of 60–95% depending on the component used and the bearing surfaces and follow-up times (SHAR 2011, AOANJRR 2016). Some cementless stem designs have survivorship as high as 95% at the 20-year follow-up (Khanuja et al. 2011). The 10-year hybrid implant survival has been reported to be 91.6% in patients aged 65 to 74 and 93.9% in patients 75 and older at the 10-year follow-up (Mäkelä et al. 2014). Reverse hybrid survival rates have been reported to be 94% at the 10-year follow-up (Wangen et al. 2017).

Restoration of the normal anatomy of the hip at the THA provides better clinical function and abductor strength and reduces wear debris (Sakalkale et al. 2001, Yamaguchi et al. 2004).

Failure to restore the normal anatomy following THA is a risk for complications. Typical complications associated with the failure of restoration are dislocation, muscle weakness, leg- length discrepancy, impingement and early loosening of the implant (Kelley 1994, Asayama et al. 2005, Konyves et al. 2005). To improve the precision of the anatomical reconstruction, the size of the femoral head was increased and modularity of the components was introduced in the late 1990s.

2.3.1.1 Large diameter head metal-on-metal total hip arthroplasty

The first MoM articulation in THA was used in 1938 by Wiles (Wiles 1958). The McKee-Farrar prosthesis was the first cemented MoM THA in the early 1960s with acceptable results (McKee et al. 1966). The McKee-Farrar MoM THA had a higher early failure rate than Charnley MoP articulation THA, however at 20 years follow-up the survival rates were almost similar, with 77% (MoM) and 73% (MoP), respectively (Jacobsson et al. 1996). MoM THAs were widely used in the 1960s, but were later phased out in the mid-1970s and replaced by MoP bearings. The reason for this change was the higher loosening rates for MoM bearings compared to MoP bearings. There were also concerns about biological reactions related to alloy constituents (Benson et al. 1975, Dumpleton et al. 2005). Large diameter head hip resurfacing arthroplasty THA using Cobalt-Chromium (CoCr) articulation was re-introduced in early 1990s and became popularised in the late 1990s (McMinn et al. 1996, Mont et al. 2008, Malviya et al. 2010) (Figures 2 and 4). One reason for the increased use of LDH HRA and later also THA MoM bearings was the modest long-term results associated with the MoP bearings due to wear and osteolysis, especially among young and active individuals. Other reasons for the popularity of LDH THA and HRA were based on the proposed increased functional ability as a consequence of the larger head size and reduced risk of dislocation.

(29)

Figure 4. Large head MoM total hip arthroplasty in postoperative antero-posterior (1) and medio- lateral (2) native radiographs.

Problems related to MoM bearings include peri-articular fluid collections, soft tissue masses and gluteal muscle necrosis (Ollivere et al. 2009, Langton et al. 2011); these findings are called ARMD. The factors affecting the amount of wear debris are component size and positioning, diameter clearance, which allows fluid to lubricate between bearing surfaces, and the roughness of the surfaces (Mont et al. 2007). Metal ions and wear debris are potentially mutagenic, but because of the long latency period of cancers it is not possible to draw robust conclusions (Malviya et al. 2010). There is some evidence that the high levels of CoCr could cause hematopoietic malignancy (Wagner et al. 2012). Patients exposed to high circulating concentrations of cobalt may rarely develop neurological damage, hypothyroidism and cardiomyopathy which may not resolve even after removal of the implant (Bradberry et al.

2014). Large amounts of metallic wear debris lead to synovitis and osteolysis (Shimmin et al.

2008, Malviya et al. 2010). Further on, soft tissue reactions like ARMD may cause a failure of the implant due to the formation of peri-articular masses called pseudotumours (Langton et al.

2010, Bosker et al. 2012). This wear process of MoM prostheses can be monitored by following

(30)

systemic cobalt and chromium ion levels in serum and whole blood because elevated ion levels are associated to local ARMD and pseudotumours (De Pasquale et al. 2014). It is recommended to follow cobalt and chromium ion whole blood levels in every second year and if they raise over 5 µg/l, a metal artefact-reducing sequences magnetic resonance imaging (MARS-MRI) should be utilized to detect pseudotumours and ARMD (Lainiala et al. 2014, SAY 2015, Kwon et al. 2016). There are common indications for revision surgery following MoM THA including periprosthetic fracture, implant loosening, pseudotumour and pain, however threshold for revision surgery due ARMD and elevated whole blood metal ion levels is to some extent unclear (Haddad et al. 2011, Matharu 2017). Guidelines for MoM follow-up are evolving continually, however economical aspects should be also considered when choosing the screening level (Reito et al. 2016).

The number of LDH THAs and HRAs increased rapidly in the late 2000s. In 2008 approximately 35% of all hip replacements in the United States had MoM articulation while in the United Kingom HRA represented approximately 10% of all implanted hip devices (Bozic et al. 2009, NJR 2012). The use of MoM bearings decreased sharply in the early 2010s due to serious complications noted by national and international arthroplasty registers (MHRA 2010, Smith et al. 2012, AOANJRR 2014). National and international orthopaedic organisations announced guidelines stating that LDH MoM THA and HRA device use should be discontinued (MHRA 2010, AOANJRR 2014, SAY 2015).

2.3.2 Hip resurfacing arthroplasty

The ideal treatment of hip OA of the hip would preserve large femoral head, provide complete pain relief, have minimal morbidity and allow full range of motion and activity without restrictions related to small head size THA. HRA is the closest option for the ideal treatment of hip OA and is kept as an alternative to traditional THA (Figures 3 and 5). Femoral resurfacing has spanned four technologic phases during the past eighty years. In the 1920s, pioneering orthopaedic surgeries used various techniques and materials for resurfacing of the femoral head (Amstutz et al. 1996, Clarke et al. 2005, Grigoris et al. 2006). The earliest form of hip resurfacing was introduced by Smith-Petersen who used a moulded glass acetabulum component; however, it resulted in broken glass (Smith-Petersen 1948, Grigoris et al. 2006).

Surface replacement arthroplasty was first introduced by Charnley in the 1950s prior to low- friction arthroplasty. In this procedure, Charnley covered the femoral head and also the acetabulum with Teflon (Charnley 1961). The results of these first resurfacing arthroplasties were unsatisfactory. Next generation HRAs were introduced in the late 1970s, with improved surgical techniques and implants. Most of these implants had a plastic acetabulum component and large metal bearing femoral head fixed with cement. However, the results of these devices were also poor due implant loosening and osteolysis. Technical improvements in metallurgy and manufacturing led to MoM bearing re-introduction in early 1990s; the initial short-time results were promising (McMinn et al. 1996, Mont et al. 2006).

(31)

Figure 5. Hip resurfacing arthroplasty in postoperative antero-posterior (1) and medio-lateral (2) native radiographs.

THA is a very effective treatment for late middle-aged and elderly patients for hip OA, with a survival rate in excess of 90% at the 10-year follow-up (AOANJRR 2014, SHAR 2015).

However, younger and more active patients have poor THA survival rates, of 80% at the 10- year follow-up (AOANJRR 2014, SHAR 2015). The answer to this poor survival of traditional THA was large diameter HRA, which allowed a better range of motion with a very low risk of dislocation. Restoration of the normal proximal femoral anatomy provides better clinical function and restoration has been most precise with HRA (Girard et al. 2006).

The benefits of HRA over THA include preservation of the femoral neck and the ability to perform arthroplasty in patients with proximal femoral deformities or existing hardware.

However, resurfacing requires a more difficult surgical exposure to prepare the acetabulum without excising the femoral head and neck. Another advantage of HRA over THA is claimed to be the better stress transfer to the proximal femur, which may further avoid problems related to stress shielding caused by conventional femoral stems (Watanabe et al. 2000, Mont et al. 2006). Revision surgeries were stated easier in HRA than in THA because the conversion of HRA to THA was claimed simple. Dislocation of THA is an annoying complication, while no dislocations have been reported in two large HRA series (Amstutz et al. 2004, Daniel et al.

2005).

Despite many theoretical advantages compared to conventional THA, HRAs have some unique complications. Avascular necrosis (AVN) of the remaining proximal femur may lead to loosening of the femoral component or to femoral neck fracture in HRA (Campbell et al. 2000).

(32)

The risk of AVN has varied from 6.5% to 12% and this effect was linked to a phenomenon called neck melting (Campbell et al. 2000). Other common complications of both HRA and THA include aseptic loosening of the implant, joint infection, ARMD and medical complications [e.g. deep vein thrombosis (DVT), pulmonary embolism (PE)].

The first results of HRA with a follow-up of 2–8 years were promising, with survival rates over 97% (Amstutz et al. 2004, Daniel et al. 2004, Shimmin et al. 2005). In even longer follow- up studies, the overall survival rate of HRAs varied from 91–96% in selected populations (Hunter et al. 2017, Moroni et al. 2017). The criteria for such a success in survival are male gender, good bone quality, head component size greater than 48mm and cup inclination less than 45 degrees (Girard 2006).

2.4 COMPLICATIONS IN TOTAL HIP REPLACEMENT

The complication profile of each type of THA (e.g. conventional THA or HRA and cementless, cemented or hybrid) is unique and related to the surgical technique used for each type of implant. Complications can be divided to intraoperative and post-operative and further into technical, medical and infection complications. Common intraoperative complications are fractures, nerve damage and medical problems. Post-operative complications are more heterogeneous and more common than intraoperative complications and may occur years or even decades after the index surgery (Table 1).

Table 1. Incidences of common complications in primary total hip replacement.

Incidence (%) References

Periprosthetic joint infection 0.76 - 1.24 AOANJRR 2016, Springer et al. 2017 Conventional total hip arthroplasty

Intraoperative calcar fracture 0.4 - 5.4 Berry 1999, Berend et al. 2010 Neurologic injury 0.09 - 3.7 Brown et al. 2008

Aseptic loosening 1.9 Varnum et al. 2015

Dislocation <2.5% Kostensalo et al. 2013

Hip resurfacing arthroplasty

Femoral neck fracture 0.96 - 1.98 Berry 2002, Langton et al. 2011

Neurologic injury 0.95 Kohan et al. 2012

Dislocation 0 - 0.6 Leclercq et al. 2013, Girard et al. 2017

In the United States, five main sources for litigation after THA are infection and leg length discrepancy (LLD), as well as dislocation and nerve damage and embolic events (Hofmann et al. 2000, Upadhayay et al. 2007). In a Finnish register study, Järvelin et al. found that predisposing factors for not experiencing claims after THA are male gender and elderly patients receiving a cemented THA (Järvelin et al. 2012). In a large study from the Netherlands, Zengerink et al. found that most claimants were female, with a mean age of 63 years; furthermore, most of the claims concerned cementless THAs and the posterolateral approach (Zengerink et al. 2016). In general, complications are more common in THR following acute hip fracture than in elective hip surgery (Chammout et al. 2017, Hailer et al.

2017).

Implant related complications are mostly related to polyethylene or metal debris released from the implant, which leads to osteolysis in MoP bearings and ARMD in MoM bearings.

(33)

High volumetric wear of polyethylene plays an important role in peri-prosthetic loosening and bone loss and further failure of the implant. Clinical experience and histopathological analysis have shown that aseptic acetabular component loosening is the result of a progressive disruption of the acetabular component–bone interface, which is driven by an inflammatory response to polyethylene wear (Schmazried et al. 1992, Cates et al. 1993). Technical complication leads typically to fracture, nerve damage or dislocation

Complications related to surgical approaches are technical and each type of approach has its own type of complication. Typical complications to each approach are nerve damage and peri-prosthetic fractures. Commonly used approaches are the anterior approach, anterolateral approach, direct lateral approach (Hardinge) and posterior approach. In the anterior approach, also known as the Smith-Petersen approach, the interval between the musculus sartorius and rectus femoris is dissected. In this opening, the superior gluteal nerve and lateral cutaneous nerve can be violated (Callaghan et al. 2007). The direct lateral opening to the hip was described by Hardinge, where the tendon and muscle fibres of the gluteus medius are split at the midway point between the most anterior and posterior extent of the muscle (Hardinge 1982). Typical complications related to the Hardinge approach include the insufficient function of the gluteus medius muscle after the operation. Improper muscle function causes hip pain and patients are unable to stand steadily on the operated leg. The posterior approach was popularised by Moore in the 1950s (Callaghan et al. 2007, Hoppenfeld et al. 2009). In the posterior approach, a typical complication is sciatic nerve damage. Besides nerve complications, fracture complications also occur, with the most being a calcar fracture related to cementless stems (Berry 1999, Berry 2002, Cameron 2004, Berend et al. 2010, Ponzio et al.

2015).

2.4.1 Intraoperative complications in hip arthroplasty

Cementless THAs have some similar technical complications than cemented THAs, but also some different complications. Similar complications are peri-prosthetic intraoperative acetabulum and femur fractures which may occur during trialing of the acetabulum and femur components. Similar complications include nerve damage, bleeding and medical complications related to hip surgery. Different complications are related to the cementing technique. Cement or fat embolism related to cementing may cause devastating pulmonary embolism and sudden death. A rare cement-related complication is protrusion of cement to the foramen obturator in the acetabulum and causes obturator nerve irritation. Also, the sciatic nerve can be damaged by cement-induced thermal reaction (Brown et al. 2008).

The spectrum of intraoperative complications is different in HRAs compared to cementless THAs. The main reason for this is the difference in surgical technique. When implanting the HRA, the femoral component is cemented onto the femoral head. When implanting cementless THA, the femoral canal is broached and the stem is implanted using impaction force to achieve the press-fit stability. Technical error in cementless THA femoral component impaction may cause femur fracture which does not occur in HRA. Another problem in HRA implanting is restricted vision to the acetabulum, which may cause problems in acetabulum reaming and component implantation. Technical failure in acetabulum component placing raise the risk of dislocation in both HRA and THA. Failures during implantion and hip joint reposition manouvers in both HRA and THA may cause nerve damage.

2.4.1.1 Intraoperative fracture complications

Intraoperative fractures are known complication of cementless THA (Lindahl 2007). Fractures may occur in the acetabulum or in the proximal femur or the femur diaphysis. The most common intraoperative fracture is the calcar fracture, with an incidence varying from 0.4–5.4%

(Berry 1999, Cameron 2004, Berend et al. 2010) (Figure 6). In a large series of 32,644 THAs,

(34)

there was a 3.0% risk of intraoperative fracture when a cementless stem was used and a 0.23%

risk with cemented stems, respectively (Abdel et al. 2016). In the same study, Abdel et al.

showed that intraoperative fractures are more common in females and patients over 65 years and most of the fractures occurred during the placement of the femoral component (60%) and the calcar area was involved in 69% of the cases (Abdel et al. 2016). In HRAs osteonecrosis of femoral neck has been reported to be a risk factor for periprosthetic fracture with incidence of 1.8% (Steffen et al. 2009, Zustin et al. 2010).

Figure 6. Hip plain radiograph picture series where there is OA in the preoperative picture (1). The second picture was taken postoperatively and shows a dislocated calcar fracture (2). In the third picture, the calcar fracture has been stabilised with wires (3).

The calcar area is defined as a thickened, dense cortical bone of the inferomedial femoral neck at the junction of the neck and shaft of the femur (Noble 1988). A press-fit stem in cementless THA aims to tightly fill the proximal femur and provide better stability. The geometry of the proximal femur is critical for press-fitting the femoral stem and the subsequent survival of the THA (Rubin et al. 1992). Risk factors for intra-operative femur fracture are reported to be female gender, older age, and thin cortical bones (Newell 1997).

In general, when intraoperative fracture is noticed and treated, the implant and fracture must be stable both intraoperatively and postoperatively (Berry 2002). Various methods have been used to stabilise intraoperative femur fractures. Cerclage wiring and cables are the currently recommended treatment for stable and non-displaced calcar fracture (Kyle et al.

1998, Berry 2002). Other methods to treat periprosthetic femoral fractures are longer cementless stems or plates and wires. Intraoperative acetabulum fractures often need modular cementless acetabulum components with additional screws, as well as plates around the bone acetabulum.

2.4.1.2 Intra-operative nerve complications

Neurologic injuries are devastating complications of THR with an incidence varying from 0.09–3.7% in primary THA and 0.08–7.6% in revision THA, respectively (Brown et al. 2008).

The incidence of nerve injury in HRA has been reported to be 0.5% (Shimmin et al. 2005).

Aetiological factors for nerve injuries include intraoperative direct nerve injury, significant leg lengthening, improper retractor placement, patient positioning, nerve manipulation and

(35)

postoperative haematoma (Brown et al. 2008). Risk factors for nerve damage are acetabulum dysplasia and revision THA, but most of the injuries occur in patients without any risk factors (DeHart et al. 1999, Brown et al. 2008). Nerve injuries can be classified as neuropraxia, axonotmesis or neurotmesis, with the worst prognosis seen in patients with complete motor and sensory deficits and in patients with causalgic pain (DeHart et al. 1999).

Injury to the sciatic nerve is the most common type of injury, but the superior gluteal, femoral and obturator nerves can also be injured (DeHart et al. 1999). Sciatic nerve injury is the most common peripheral nerve damage, representing of 79% of all cases (Yang 2014). Sciatic nerve injury causes an inability or impaired ability to raise the great toe or foot and paraesthesia in the medial side of the foot. The prognosis of sciatic nerve injury after THA varies, and some recovery is noted in 70–80% of cases (Yang 2014). Femoral nerve injury is the second most common nerve injury after THA, representing 13% of the cases (Simmons et al.

1991). Femoral nerve damage symptoms are paraesthesia in the medial aspect of the pelvis and pain in the femoral area and weakness of the quadriceps muscle. Obturator nerve injury prevalence is very low and is often overlooked since it is difficult to diagnose and does not cause serious functional disorders. Symptoms of obturator nerve injury are groin pain and weakness of the adductor muscles. Gluteal nerve damage may occur in the Hardinge approach if the musculus gluteus medius is opened too proximally. Gluteal nerve damage symptoms include weakness of the gluteus medius muscle, which causes limping and pain in the hip; also, dislocation may occur due to weak abductor muscles (Ramesh et al. 1996).

Lateral femoral cutaneous nerve injury is very common when the anterior approach is used.

Neurpraxia prevalence in HRA was as high as 91% and in THA was 67% (Goulding et al.

2010). In general, nerve injury in HRA is most likely related to the more demanding acetabular exposure as the femoral neck is not osteotomised, thus increasing the susceptibility of stretching of the sciatic nerve when the posterior approach is used and stretching of the lateral femoral cutaneous nerve in the anterior approach.

2.4.2 Postoperative complications of hip arthroplasty

Complications following THA have been investigated extensively throughout the history of THA and reported complications have changed the mode of operation many times during the last few decades (Ninomiya et al. 2017). Complications guide clinical practice, with the main goal of THA being to predict and prevent complications which are very unpleasant for patients and are expensive to treat. A typical indication for surgery is primary osteoarthrosis in both THA and HRA, but the difference from HRA is that it cannot be used in more complex and higher complication risk operations. However, HRAs have shown to have overall higher revision rates than THAs in all age and gender groups (Clarke et al. 2015). Typical complications following THA are infection and peri-prosthetic fractures, as well as leg length discrepancy (LLD), dislocation, nerve damage and thromboembolic events (Hofmann et al.

2000, Upadhayay et al. 2007).

Periprosthetic joint infection (PJI) is a leading cause of the failure of THA, with contemporary yearly infection burden varying from 0.76–1.24% (SHAR 2015, AOANJRR 2016, Springer et al. 2017). A large number of studies have been performed with the aim of reducing infection rates, but no improvement has been seen to date in implant registers (SHAR 2015, AOANJRR 2016, NJR 2016). Postoperative THA infections are severe complications and can result in substantial morbidity to patients, multiple procedures, increased costs and lengthy hospitalisations (Ninomiya et al. 2017). One study projects that revisions due to PJI will increase over the next decades compared to other modes of failure, with the anticipation that over 60% of all revisions will be due to infection (Kurtz et al. 2008).

Periprosthetic fractures may occur years or even decades after the index surgery.

Periprosthetic fracture may be caused by a trauma or periprosthetic bone loss may led to implant loosening and further on to fracture (Knutsen et al. 2017). The incidence of femoral

(36)

peri-prosthetic fractures after THA is raising worldwide (Streit et al. 2013). It is expected that the incidence of peri-prosthetic fractures overall will increase by a mean of 4.6% every decade for at least the next three decades (Pivec et al. 2015). The risk of femoral periprosthetic fracture after index surgery in 10-year follow-ups has varied between 0.64% – 1.6% (Lindahl 2007, Streit et al. 2014). The operative treatment of femoral periprosthetic fracture is the third most common cause of hip joint revision arthroplasty (Lindahl 2007). Periprosthetic fractures are costly, disabling and also morbid; these types of femoral fractures often require surgical treatment (Lindahl et al. 2005, Moloney et al. 2014). HRA has a unique type of complication, which is femoral neck fracture and femoral component loosening due to osteonecrosis, as well as adverse femoral neck remodelling (Campbell et al. 2000, Amstutz et al. 2004, Amstutz 2012).

The early neck fractures typically occur within 3-4 months after surgery and are attributed to different factors such as uncovered bone, leaving the component proud, notching the neck, osteopenia, cysts, impingement and trauma (Shimmin et al. 2005).

Leg length discrepancy (LLD) following THA is a significant source of patient dissatisfaction and a common reason for litigation (Hofmann et al. 2000, Upadhayay et al.

2007). Patients who are at risk of postoperative limb length discrepancies are those who have undergone previous hip surgery, trauma, infection, growth plate arrest and congenital dysplasia (Sculco et al. 2016). Significant lengthening of the leg may lead to sciatic nerve palsy and lower back pain and limping. Preventing LLD is achieved by evaluating leg length preoperatively by using physical and radiological methods. Physically true leg length is determined by a distance from the anterior superior iliac spine to the medial malleolus. There are few radiological methods to determine leg length and preoperatively template the correct level of femur neck osteotomy, neck length and femoral offset (Maloney et al. 2004). LLD is mainly caused by improper femoral component positioning (Al-Amiry et al. 2017). LLD

>1.5cm is defined as severe LLD because this size of stretch in leg length can affect hip joint function by changing the hip rotation centre and causing abductor dysfunction (Dong et al.

2016). HRAs do not have same problem related to LLD as THAs due to different surgical technique where in HRA femoral neck is preserved and head is resurfaced.

Medical complications are a heterogeneous group of problems related to surgery and anaesthesia and are typically caused by multiple aetiological factors. Of these complications, the most typical is venous thromboembolism (VTE) which is a term including DVT and PE.

The true incidence of VTE is not well-defined because symptoms of DVT might be mild and can remain undiagnosed. In different parts of the world, there are many guidelines for antithrombotic prophylaxis after THA which makes a comparison of the true incidence of VTE challenging (AAOS 2011, Flack-Ytter et al. 2012, NICE 2015). Fujita et al. showed that the overall incidence of VTE after THA is 4.4% in patients receiving recommended antithrombotic prophylaxis (Fujita et al. 2015). In a cohort study of over 58,000 patients, 0.9% had pulmonary embolism after primary THA (Phillips et al. 2003). In the revision THA cohort of over 12,000 patients, complication rates were higher than in primary THA, and PE was diagnosed in 0.8%

of the patients during the first six months after THA (Phillips et al. 2003). Optimal prophylaxis of prevention of DVE after THA is debated. Ideal prophylaxis would have a high efficacy in preventing DVE and PE, with minimal bleeding, cost-effectiveness and ease of administration (Agaba et al. 2017). Commonly used prophylactic pharmacological agents are antiplatelet agents (aspirin), low molecular weight heparin (LMWH), vitamin K antagonists (warfarin), synthetic indirect inhibitors of activated Factor Xa (fondaparinux) and selective and reversible direct Factor Xa inhibitors (apixaban and rivaroxaban) (Agaba et al. 2017). Mechanical compression devices can also be used for VTE prevention together with pharmacological prophylactic agents.

(37)

2.4.2.1 Aseptic loosening

The cementless component requires good initial fixation to allow bony ingrowth to occur (Pilliar et al. 1986, Haddad et al. 1987). The initial press-fit is typically achieved by under- reaming the acetabulum or by using non-hemispherical (flanged) components. Cementless femoral component is force impacted in femur to achieve press-fit stability. In cementless MoM THAs, revision typically occurs during early follow-up. In a recent study of 80 MoM hips that underwent acetabular revision, 92.5% of revisions were performed within 3 years of the index surgery (Fadi et al. 2012).

Various factors such as bone quality, female gender, elderly age and geometry of the acetabulum have been postulated as factors influencing primary fixation of the cementless acetabular component (Dorr et al. 2000, Piarulli 2013). In addition, underlying systemic diseases like RA and osteoporosis affect the properties of bone and also influence implant osseointegration (Aro et al. 2012, Zwartelé et al. 2012). From a mechanical point of view, acetabular component malpositioning or failure to restore the centre of rotation of the hip joint may lead to impingement and increased edge-loading, which may lead to a lack of bony ingrowth into the porous surface and subsequent early loosening of the acetabular component (Brown et al. 2014).

Compared to conventional modular acetabular components, the suggested benefits of the monoblock components used in LDH MoM THA and HRA are the reduced risk of dislocation and better biomechanics (Stroh et al. 2013). On the other hand, monoblock components do not allow supplementary screw fixation. Another drawback to monoblock components is the difficulty in assessing whether the component is fully seated to the acetabulum as the bone bed cannot be visualised through holes in the component. This may lead to a complication where the acetabulum component is not steady enough in index surgery and components may spin-off over a short period of time (Figure 7). In addition, aseptic loosening of the hemispherical acetabular components was recently shown to be one of the leading causes of early failure of primary THA (Carcia-Rey et al. 2012, Fadi et al. 2012).

Results and complications of large diameter head cementless metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty

uef.fi

Dissertations in Health Sciences

SIMO MIETTINEN

RESULTS AND COMPLICATIONS OF LARGE DIAMETER HEAD CEMENTLESS METAL-ON-METAL TOTAL HIP ARTHROPLASTY AND HIP RESURFACING ARTHROPLASTY

SIMO MIETTINEN

Results and complications of large diameter head cementless metal-on-metal total hip

arthroplasty and hip resurfacing arthroplasty

To Outi, Selma and Armi

Acknowledgements

List of the original publications

Contents

Abbreviations

1 Introduction

2 Review of the literature