39 T_h e hip

ANATOMY AND BIOMECHANICS Applied anatomy
Arthroscopy of the hip
CONDITIONS AFFECTING THE HIP
DEGENERATIVE AND INFLAMMATORY DISORDERS OF THE HIP Osteoarthritis
DEGENERATIVE AND INFLAMMATORY DISORDERS OF THE HIP
Diagnostic hip injection
Extra-articular hip pathology
Femoroacetabular impingement
HIP PRESERVATION PROCEDURES
Hip dysplasia in young adults
Introduction
Inﬂammatory arthritis
Learning objectives
Osteotomies around the hip
Primary total hip replacement
Revision total hip replacement
SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITION
SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITIONS Arthrodesis of the hip
Surgical approaches to the hip, postoperative cour
Surgical approaches to the hip, postoperative course and complications

ANATOMY AND BIOMECHANICS Applied anatomy

The hip is a ball-and-socket joint formed by the head of the femur and the cup-shaped acetabulum (Latin: ‘little vinegar cup’) ( Figure 39.1 ). The joint allows a considerable range of movement in di ﬀ erent planes and is still inherently stable because of its bony anatomy and the static and dynamic stabilisers. The static stabilisers are composed of the iliofemoral and pubofemoral ligaments anteriorly and the ischiofemoral ligament posteriorly; together with the joint capsule and the labrum ( Figure 39.1 ). The muscles running across the joint (short external rotator muscles and gluteus maximus posteri orly , the iliopsoas anteriorly and the hip abductors laterally) constitute the dynamic stabilisers. The acetabular labrum is a ﬁbrocartilaginous structure that is triangular in cr oss-section and attaches to the rim of the acetabulum, except at its base, where it is replaced by a ligament called the transverse acetabular ligament. The labrum helps in deepening the socket, thereby enhancing stability . It also acts as a ﬂuid seal and thereby helps to improve joint lubrication. The femoral head derives its blood supply mainly from the retinacular branches of the medial circumﬂex femoral artery and has a small contribution from the artery of the ligamentum teres. Summary box 39.1 Anatomy /uni25CF - /uni25CF /uni25CF /uni25CF

Sacrum Ilium Acetabular labrum Acetabular fossa Femoral head Capsule attachment Ligamentum teres Figure 39.1 Anatomy of the hip joint. The principles of joint replacement including important • complications The advances in surgical practice in this /f_i eld • The hip joint is a ball-and-socket joint, with both static and dynamic stabilisers Static stabilisers include the capsule, ligaments and labrum Dynamic stabilisers consist of the muscles acting across the joint Blood supply to the femoral head is mainly derived from the medial circum /f_l ex femoral artery Pubofemoral ligament Iliofemoral ligament Greater trochanter Lesser trochanter Pubis Ischium Pubic symphysis

Kinetic analysis reveals that forces as high as three times body weight can be exerted across the hip joint during activities of daily living, and eight times body weight during physically demanding activities. This is primarily the result of contraction of muscles crossing the hip joint. The abductors, because of their insertion at the greater trochanter, help in supporting the pelvis when the patient stands on the ipsilateral leg and thereby form the basis of the Trendelenburg test ( Figure 39.2 ). Summary box 39.2 Forces going through the hip joint /uni25CF /uni25CF /uni25CF

Lifting leg from bed – one and a half times body weight Standing on one leg – three times body weight Running and jumping - ten times body weight

ANATOMY AND BIOMECHANICS Applied anatomy

Lifting leg from bed – one and a half times body weight Standing on one leg – three times body weight Running and jumping - ten times body weight

ANATOMY AND BIOMECHANICS Applied anatomy

Lifting leg from bed – one and a half times body weight Standing on one leg – three times body weight Running and jumping - ten times body weight

Arthroscopy of the hip

The hip joint presents challenges to arthroscopy in terms of access and instrumentation of the deeply recessed femoral head in the acetabulum and the surrounding thick ﬁbrocapsular and muscular envelope. Technical advances, including an improved ability to manage the capsule and gain exposure, have led to symptomatic labral tears, FAI and the removal of loose bodies, e .g. synovial chondromatosis. Arthroscopy allows a clear view of the femoral and acetabular articular surfaces, the labrum, the ligamentum teres and the head–neck junction, along with the surrounding synovium and its folds, and the peritrochan - teric space. Advantages include minimally invasiv e access to all these structures coupled with rapid recovery , in comparison with open surgery . However, there is a steep learning curv e with hip arthroscopic procedures and adequate training of this procedure with a mentored independent practice in the early part of a surgeon’s career is an essential part of achieving a successful outcome. Arthroscopy of the hip

CONDITIONS AFFECTING THE HIP

Common hip pathologies in the paediatric age group and secondary to trauma are covered in Chapters 29, 32 and 44 This chapter focuses on the acquired pathological conditions in the adult. Friedrich Trendelenburg , 1844–1924, Professor of Surgery successively at Rostock (1875–1882), Bonn (1882–1895) and Leipzig (1895–1911), Germany . The Trendelenburg position was ﬁrst described in 1885. A caisson is a watertight chamber used to protect construction workers during the building of underwater structures by means of pressurised air introduction. Philippe Charles Ernest Gaucher , 1854–1918, physician, Hôpital St Louis, Paris, France, described familial splenic anaemia in 1882. Georg Clemens Perthes , 1869–1927, Professor of Surgery , Tübingen, Germany , described osteochondritis of the femoral capital epiphysis in 1910. Avascular necrosis (A VN), or osteonecrosis of the femoral head, occurs because of an interruption in the blood supply to the femoral head, leading to bone death. This results in collapse of the femoral head initially , and eventually secondary osteo - arthritis (OA). A VN can be primary (idiopathic) or secondary to other pathology ( Table 39.1 ). /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF . /uni25CF /uni25CF /uni25CF

muscle force Biomechanical schematic representation of loads pivoted on a beam. The hip joint is the fulcrum W 3W Abductor x 3x muscle force 4W TABLE 39.1 Aetiology of avascular necrosis of the femoral head. Steroids Alcohol excess Idiopathic (see Perthes’ disease; see Chapter 44 ) Sickle cell disease Haemoglobinopathies Caisson disease (‘the bends’ in divers) Hyperlipidaemia Systemic lupus erythematosus Gaucher’s disease Chronic liver disease Antiphospholipid antibody syndrome Radiotherapy Chemotherapy Human immunode /f_i ciency virus Hypercoagulable states (protein C and protein S de /f_i ciency) Joint re action force Abductor W Body weight Body weight Figure 39.2 Load on the hip joint when a subject weighing W stands on one leg. Hopping increases the load from 4 W to 10 W .

Clinical features A VN usually a ﬀ ects men aged 35–45 and is bilateral in over 50% of patients. The patient is frequently asymptomatic in the early stages. As the disease progresses the patient may complain of an ache in the groin and walk with a limp. Clin ical examination in the early stages is usually normal but may reveal a positive Thomas’s test and limitation in the range of movement as the disease progresses. Investigations A weight-bearing anteroposterior (AP) radiograph of the pelvis along with a lateral radiograph will show the classical features of A VN, including increased sclerosis in the early stages and the crescent sign indicating subchondral bone resorption. Hugh Owen Thomas , 1834–1891, general practitioner, Liverpool, UK. He is regarded as the founder of orthopaedic surgery although never holding a hospital appointment, preferring to treat patients in their own homes. He introduced the Thomas splint in 1875. R Paul Ficat , 1917–1986, Professor of Clinical Orthopaedic Surgery and Traumatolog Marvin E Steinberg , contemporary , Professor of Orthopedic Surgery , Philadelphia, PA, USA. indicating the onset of arthritis ( Figure 39.3 ), and ﬂattening, indicating a segmental head collapse. However, radiographs ma y be nor mal in the early stages of the disease and, there - fore, the most sensitive and speciﬁc way of investigating these patients is with magnetic resonance imaging (MRI). MRI allows accurate assessment of the extent of involvement of the femoral head and can also identify associated bone marrow his helps in early diagnosis and the prediction of changes. T prognosis ( Figure 39.4 ). In 1985, Ficat classiﬁed the disease into ﬁve stages. In 1995, Steinberg modiﬁed this classiﬁcation into seven stages (0–VI) based upon both radiograph and MRI appearance ( Table 39.2 ). Stages I–IV are further divided according to the extent of femoral head involvement (A; mild, B; moderate and C; severe). Management Conservative treatment in well-established cases usually leads to poorer outcomes and is therefore not recommended. The choice of surgical treatment depends upon whether the femoral head has collapsed or not. In the pre-collapse stage the prin - ciple is to preserve and preferably encourage revascularisation of the femoral head, whereas in the collapse stage the aim is to bring the undamaged parts of the femoral head into the load-bearing zone of the hip joint. The surgical treatment for the pre-collapse stage ession, which is aimed at relieving the includes core decompr intravascular congestion in the femoral head and thereby - pain. This can be achieved with or without bone grafting with bone-marrow-derived cell therapies; a or combined vascularised bone graft can also be used to stimulate bone formation and support the femoral head. Once the femoral head has collapsed, either a femoral osteotomy (which aims to transfer the weight-bearing area of the femoral head and thereby protect the collapsed segment) or a joint replacement (if degenerative changes have set in) is the preferred option (see Primary total hip replacement ). y , Université Paul Sabatier, Toulouse, France.

Figure 39.3 Radiological appearance of avascular necrosis of the femoral head of the left hip. There is evidence of femoral head sclero sis (dashed line and arrow) as a consequence of avascular necrosis. (a) (b)

Figure 39.4 Magnetic resonance imaging scan of the hip joint showing avascular necrosis (arrows). (a) Coronal view; (b) sagittal view.

Summary box 39.3 AVN of the femoral head /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

necrosis of the femoral head based on the type of radiological change on radiographs and magnetic resonance imaging (MRI). Stage Description 0 Normal or non-diagnostic radiograph, bone scan or MRI I Normal radiograph, abnormal MRI or bone scan II Sclerosis and cysts III Subchondral collapse, crescent sign IV Flattening of the head, normal acetabulum V Acetabular involvement VI Obliteration of joint space Patients can be asymptomatic in the early stages and therefore a high index of suspicion is necessary for initial diagnosis MRI scan is required for early diagnosis Treatment is based on whether the patient presents before or after the femoral head has collapsed In the pre-collapse stage treatment focuses on revascularisation of the femoral head In the collapsed stage, the aim is to reorient the damaged area of the femoral head or replace the joint if degenerative changes have set in Prognosis is dependent upon the extent of femoral head involvement

CONDITIONS AFFECTING THE HIP

Figure 39.3 Radiological appearance of avascular necrosis of the femoral head of the left hip. There is evidence of femoral head sclero sis (dashed line and arrow) as a consequence of avascular necrosis. (a) (b)

Figure 39.4 Magnetic resonance imaging scan of the hip joint showing avascular necrosis (arrows). (a) Coronal view; (b) sagittal view.

Summary box 39.3 AVN of the femoral head /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

CONDITIONS AFFECTING THE HIP

Figure 39.3 Radiological appearance of avascular necrosis of the femoral head of the left hip. There is evidence of femoral head sclero sis (dashed line and arrow) as a consequence of avascular necrosis. (a) (b)

Figure 39.4 Magnetic resonance imaging scan of the hip joint showing avascular necrosis (arrows). (a) Coronal view; (b) sagittal view.

Summary box 39.3 AVN of the femoral head /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

DEGENERATIVE AND INFLAMMATORY DISORDERS OF THE HIP Osteoarthritis

OA is referred to as primary when no predisposing cause can be found, and secondary when it develops after an insult to the hip joint. A multitude of factors, including genetic, in the development of primary OA. The exact mechanism for the development of primary OA remains unknown and it is therefore termed idiopathic. However, FAI has been proposed as an aetiological factor responsible for the development of OA by a Swiss group in 1999 (see Further reading ). Secondary OA develops following trauma, A VN, dysplasia, slipped capital femoral epiphysis, inﬂammatory arthropathy or other known predisposing causes. The causes of OA of the hip are provided in Table 39.5 . /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF Clinical features OA of the hip a ﬀ ects 10–25% of those aged 65 years or older. The most consistent symptoms are groin pain and limitation of movement. The pain may also radiate down to the knee joint; in some cases the only presenting feature may be a painful knee. In the early stages of the disease, pain is activity related but as the disease progresses the patient also complains of pain at rest. The patient frequently complains of night pain and may also ﬁnd it di ﬃ cult to get into a comfortable position while sleeping. Functionally , any activity that involves ﬂexion and rotation is di ﬃ cult to perform, e.g. putting on shoes and socks and getting into and out of a bath or a car. As the pain increases the hip joint gradually loses its movement because of muscle spasm, capsular contracture and osteophyte formation, leading to further limitation of activities. Clinical examination may reveal gluteal muscle wasting. There may also be a limp, with a positive Trendelenburg’s test. Leg length discrepancy , usually shortening, and limitation of movement, particular ly internal rotation, are consistent fea tures. Many patients present with a ﬁxed ﬂexion deformity that is best elicited by a modiﬁed Thomas’s test (see Chapter 35 Investigations The characteristic features on a plain radiograph are (i) a reduction of the joint space, (ii) sclerosis in the subchondral bone, (iii) subchondral cysts, and (iv) osteophyte formation ( Figure 39.7 ). Eventually , a collapsed femoral head may also be evident. Management There is no speciﬁc pharmacological therapy for OA; however, non-operative treatment with non-steroidal anti- inﬂammatories, regular exercise, physiotherapy and - ). modiﬁcation of lifestyle with loss of weight does help. Patients should also be encouraged to use walking aids (usually a walk - ing stick in the opposite hand) to o ﬄ oad the a ﬀ ected hip joint and to reduce the workload of the ipsilateral abductors. The indications for surgery are relentless pain (usually night pain), limitation of lifestyle and activities of daily living and failure of non-operative treatment. The surgical options include an arthrodesis (fusion), an osteotom y (realignment)

TABLE 39.5 Aetiology of osteoarthritis. Primary Cause unknown, termed idiopathic Associations: for example, genetics, obesity Secondary Trauma Avascular necrosis In /f_l ammatory arthropathy (e.g. rheumatoid arthritis) Perthes’ disease Developmental dysplasia of the hip Slipped capital femoral epiphysis Septic arthritis Femoroacetabular impingement implicated as a possible cause (b) Figure 39.7 (a) Anteroposterior radiograph of the hip joint showing severe osteoarthritis of the right hip (arrow) and a cemented total hip replacement on the left; (b) lateral view of the right hip.

or a joint replacement ( Figures 39.7a, 39.8 and 39.9 indications are based on limitation of lifestyle and individual needs, thereby making it a truly life-improving and life- changing operation. Summary box 39.4 OA of the hip /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF ). The

(b) Figure 39.8 Radiographs showing a cemented total hip replacement in situ . (a) Anteroposterior view and (b) lateral view. OA is a degenerative condition leading to progressive damage of the articular cartilage and other joint structures The most consistent clinical features are groin pain and limitation of movement Characteristic radiological features are reduced joint space, subchondral sclerosis, subchondral cysts and osteophyte formation Non-operative treatment includes walking aids, non-steroidal analgesics, physiotherapy and weight loss Surgical options include osteotomy, arthrodesis or a joint replacement (b) Figure 39.9 Radiographs of an uncemented total hip replacement. (a) /uni00A0 Anteroposterior view and (b) lateral view.

DEGENERATIVE AND INFLAMMATORY DISORDERS OF THE HIP

DEGENERATIVE AND INFLAMMATORY DISORDERS OF THE HIP Osteoarthritis

Diagnostic hip injection

Identiﬁcation of the source of symptoms is essential to ensure appropriate management. Since the hip joint is deeply seated, several extra-articular pathologies can present with hip and groin pain and the diagnostic hip injection can help elucidate whether the pain is extra- or intra-articular in origin. This is performed as a day case procedure under image intensi ﬁer (portable x-ray machine) guidance under appropriate anaesthesia. Using aseptic precautions, a long spinal needle is inserted into the hip joint. The position of the needle is conﬁrmed by injecting either a small amount of radio-opaque contrast d ye or air to provide a contrast arthrogram. Once the intra-articular position is conﬁrmed, a mixture of local anaesthetic and steroid is injected into the hip joint. The procedure can also be therapeutic and is an essential tool that can help in prognosis as well prior to proceeding with hip preservation procedures (arthroscopy or osteotomy), espe cially in cases of uncertainty relating to the source of the pain and therefore the diagnosis. Diagnostic hip injection

Extra-articular hip pathology

). The Hip pain can also occur as a result of impingement of extra-articular structures resulting in restriction of activities. - Table 39.3 shows the common causes of extra-articular hip impingement. Snapping hip syndromes (shown in Table 39.3 ) can also present with hip pain. Imaging modalities such as ultrasound and MRI may aid the diagnosis. Treatment begins with non-operative measures such as physiotherapy with surgical procedures aimed at treating the primary pathology in refractory cases. See Further reading for additional . information.

(c) Figure 39.5 Radiograph showing cam femoroacetabular impingement deformity. (c) Anteroposterior radiograph and (d) a subtle cam lesion picked up on the lateral view. The alpha angle measurement is used to assess the severity of cam deformity (normal ≤ 55°). The lateral centre–edge angle (LCEA) is a measure of acetabular coverage (normal = 25–40°). LCEA Acetabular index LCEA Alpha angle (d) (a) , marked over the femoral head (b) with the arrow pointing to the cam Figure 39.6 Plain radiograph showing bilateral hip dysplasia: uncovering of the femoral head as measured by a centre–edge angle (CEA) of less than 20°. Normal CEA is 25–40°. A CEA of 20–25° is categorised as borderline dysplasia of the hip. An acetabular index of >10° is suggestive of hip dysplasia.

externally snapping hip syndromes. Pathology Description Extra-articular hip impingement Iliopsoas impingement Impingement between the iliopsoas muscle and the labrum, resulting in distinct anterior labral pathology Subspine Impingement between an enlarged or impingement malorientated anterior inferior iliac spine and the distal anterior femoral neck Ischiofemoral Compression of the quadratus femoris impingement muscle between the lesser trochanter and the ischial tuberosity Deep gluteal Entrapment of the sciatic nerve in the syndrome deep gluteal space resulting in pain in the buttock Snapping hip syndromes Internal snapping hip Iliopsoas tendon glides over the hip joint, syndrome producing a snapping sensation and eventually leading to labral tear External snapping hip Iliotibial band glides over the greater syndrome trochanter and snaps, producing an audible and/or visible snap

Extra-articular hip pathology

Femoroacetabular impingement

Femoroacetabular impingement (FAI) has recently been recognised as a cause of hip pain in the young adult and may lead to secondary hip OA. Two distinct types of FAI have been described – cam and pincer – although many patients have a mixed picture with both morphologies occurring simultane ously . Cam FAI is secondary to abnormal morphology of the femoral head and neck junction whereas pincer FAI is a result of anterior overcoverage or retroversion of the acetabulum. The cam deformity is typically described as an abnormal bony bump at the femoral head–neck junction ( Figure 39.5a measured as an alpha angle of >55° ( Figure 39.5b,d alpha angle is ideally measured on the Dunn view , which is a 45° lateral view of the hip. This view is useful to identify subtle cam deformities that are not clearly visible on the AP radio graph ( Figure 39.5c,d , arrow pointing to the cam deformity). The alpha angle can be measured on the AP radiograph if severe but the extent is accurately assessed on the Dunn view . The alpha angle is the angle made by a line along the centre of the femoral neck to the centre of the femoral head and another from the centre of the femoral head to the point on the femoral head outside the imaginary circle, as shown in Figure 39.5b,d Denis M Dunn , 1916–2001, consultant orthopaedic surgeon at the Colchester and District Hospital Group and honorary assistant surgeon at The London Hospital, London, UK. Dietrich Tönnis , 1927–2010, German paediatric orthopaedic surgeon. He had an interest in the hip joint, especially dysplastic hips. centre–edge angle (LCEA) measured on the AP radiograph ( Figure 39.5b ) of over 40° (normal 25–40°). The LCEA is the angle formed between an imaginar y vertical line from the centre of the femoral head and another from the centre of the femoral head to the lateral edge of the acetabulum. The impingement, which occurs during deep hip ﬂexion or earlier with internal rotation as a result of the abnormal morphology , results in damage to the labrochondral junction. Patients typically present with groin pain and limita tion of activities related to deep bending and rotation. Plain radiographs are useful in evaluating the bony deformity . Further evaluation with MRI typically reveals acetabular labral and chondral lesions and abnormal femoral head morphology in the case of cam deformity . Computed tomography (CT) scan, especially three-dimensional (3D) CT , is helpful in accurately assessing the proximal femoral morphology , acetabular coverage and posterior joint space and allows for planning management. Treatment options for FAI depend on the patient’s symptoms and vary from non-operative treatment to hip preservation procedures that aim to address labral, chondral and bony pathology; this can be achieved with arthroscopy , safe surgical hip dislocation or osteotomy of the femur and/or acetabulum. Femoroacetabular impingement

HIP PRESERVATION PROCEDURES

For the conditions above, in which degenerative change is not predominant, a variety of surgical procedures are now described with the aim of preserving the hip joint. HIP PRESERVATION PROCEDURES

For the conditions above, in which degenerative change is not predominant, a variety of surgical procedures are now described with the aim of preserving the hip joint.

Hip dysplasia in young adults

Hip dysplasia is a condition in which there is under-coverage of the femoral head, secondary to a shallow acetabulum. Hip dysplasia is deﬁned as an LCEA of <20° and/or an acetabular index of >10° ( Figure 39.6 ). The acetabular index (also called the Tönnis angle) is the angle formed by an imaginary line through the superior weight-bearing portion of the acetabu - lum and an imaginary horizontal line ( Figure 39.6 ). Thorough screening and timely management of devel - opmental dysplasia of the hip (DDH) as a child is aimed at preventing problems during early adulthood. In mild cases of DDH symptoms are not present until the person is a teenager or an adult. Abnormal biomechanics in hip dysplasia leads to progressive chondral damage and labral tears . Treatment - options depend on the severity of dysplasia and the extent of damage in the hip joint, with options being hip arthroscopy , periacetabular osteotomy or total hip replacement (THR) in cases where there is evidence of arthritis. ), Hip dysplasia in young adults

Introduction

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Inﬂammatory arthritis

The hip joint can also be a ﬀ ected by inﬂammatory arthritides; however, these are not as common as OA. This group includes rheumatoid arthritis, ankylosing spondylitis, gout and chon - drocalcinosis, juvenile rheumatoid arthritis and systemic lupus erythematosus. Inﬂammatory arthritis

Learning objectives

To understand: The anatomy and biomechanics of the hip and their • clinical implications The clinical presentation, aetiology and management of • common hip pathologies Learning objectives

To understand: The anatomy and biomechanics of the hip and their • clinical implications The clinical presentation, aetiology and management of • common hip pathologies

Osteotomies around the hip

The goal of an osteotomy around the hip is to redistribute forces evenly across the joint, thereby eliminating excessive point loading. This can be achieved by performing an oste - otomy on the femoral or the acetabular side, depending upon the desired goal, e.g. an excessive valgus neck–shaft angle and an uncovered femoral head on the lateral aspect can be corrected by carrying out a v arus femoral osteotomy . Similarly , a redirection osteotomy on the acetabular side can also be performed to improve coverage of the femoral head in cases of hip dysplasia. The common indications for an osteotomy around the hip in the adult age group are shown in Table 39.4 . Ideally , an osteotomy should be considered in a young patient who maintains a good range of movement of the hip and whose imaging studies (radiographs and/or CT scan or MRI scan) show a joint devoid of signiﬁcant degenerative change. - Thorough preoperative planning is essential to assess whether the desired position can be achieved. Increasingly 3D CT scans are used for preoperative planning. In addition, 3D printing has been used to understand the problem and plan surgical correction. Computer navigation and robotics are novel adjuncts that are aimed at obtaining an accurate correc - - tion of the concerned deformity .

TABLE 39.4 Indications for osteotomy around the hip in the adult age group. Femoral osteotomy Periacetabular osteotomy (PAO) Developmental dysplasia of Perthes’ disease the hip Osteoarthritis in a young patient Acetabular retroversion (reverse Slipped capital femoral PAO) epiphysis Avascular necrosis

Osteotomies around the hip

Primary total hip replacement

Over 95 /uni00A0 000 primary THRs are performed annually in the UK (National Joint Registry , UK). The success rate for THR is very high and the evidence supports the results being more than encouraging. In the modern era, with evidence-based technique and selection of prosthesis, over 95% of patients will have a well-functioning THR at 10 years after surgery . In the best series, 85% will still be functioning at 20 years, although some are still in place because the patient may have increasing comorbidities, preventing revision of the THR. Following surgery , pain is reduced and there is improvement in mobility and sleep, as well as social and sexual function. Nevertheless, with the ever-increasing number of patients with joint replace ments, the number of patients whose replacement has failed and come to the point of revision, or even re-revision, is rising. Principles and design of hip replacements Joint replacement should be biocompatible and made of inert materials. It should be well ﬁxed to the host tissue and the design should incorporate features that allow a good range of move ment and stability . The bearing surfaces should produce low friction and minimise the amount of wear particles produced which in turn prevents early loosening. The material released from the bearing surface should be non-toxic. The procedure should remove the minimum amount of the patient’s bone so that revision is possible, and it should create a biomechanically stable joint. Finally , any implanted joint should ideally outlive the patient and be cost-e ﬀ ective. Materials for the femoral component Implants available currently are made of cobalt chrome alloy , stainless steel or titanium. Metal implants are able to withstand high loads, are relatively inert and can be manufactured easily . However, they do pose problems in terms of ion release if they are used as bearing surfaces. Also, corrosion can be a cause for concern if two dissimilar metals are used. Bearing surfaces The design described by Charnley in 1961 revolutionised THR and became a gold standard by using a bearing surface of metal on high-density polyethylene. This is described as a hard-on-soft bearing surface and has a low coe ﬃ cient of friction, which in turn produces lower wear of the polyethylene Sir John Charnley , 1911–1982, Professor, Wrightington Hospital, UK, pioneer in hip replacement design, particularly the concept of low-friction arthroplasty . Features of an ideal joint replacement /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF component, resulting in longer survival of the prosthesis. Hence the phrase low-friction arthroplasty was given to this implant. High-density polyethylene has good shock-absorbing properties but does wear slowly over the years, producing small particles that can stimulate an inﬂammatory response in the joint, which then leads to osteolysis and aseptic loosening of the implants. The activated macrophages resorb bone and may also stimulate osteoclasts to do the same. There has therefore been a move towards using bearing surfaces with a lower wear rate, such as ceramic on ceramic. With metal-on-metal bearing surfaces, although the wear rate is lower, the wear - particles are smaller (nano rather than micro) and can lead to an adverse reaction, particularly in the soft tissues, resulting in failure. There is increasing evidence that these implants are less forgiving than conventional metal-on-polyethylene THRs, appearing to require more precise implant positioning. Ceramic femoral head bearings on polyethylene cups are low friction, but ceramic femoral heads on ceramic acetabular cups - have the lowest friction of all. However, ceramic-on-ceramic bearings are expensive to manufacture, and are another example of hard-on-hard bearings and produce small-sized wear particles. A summary of the advantages and disadvantages of each bearing surface is provided in Table 39.6 . Fixation of implants Artiﬁcial joints must be securely ﬁxed to the bone on each side of the joint so that the implant does not work loose. This can be achieved with the help of cement or biological interdigitation between the prosthesis and bone ( Table 39.7 ). Traditionally , hip replacements were ﬁxed into a bed of polymethylmethacrylate (PMMA) cement ( Figure 39.8 ). The cement acts as a grout (spacer) and not as a glue between the implant and the bone. In the majority of cases, it gives an excellent outcome as sho wn by data in several national joint registries. However, it can cause potential problems: cement pressurisation can result in release of cement and marrow contents into the patient’s blood stream. This can cause a drop in blood pressure. Improvements in cementing techniques allow for no gaps in the cement mantle between the femoral component and the bone. In spite of all the measures taken, occasionally there may be small areas in the cement mantle without cement.

Biocompatible Well /f_i xed to the host tissue, stable and allowing a good range of movement Bearing surfaces should be designed to minimise friction and have improved wear characteristics Material released from the bearings should be non-toxic Remove the minimum amount of bone Produce mechanical stability Should ideally outlive the patient

On the other hand, this problem can be obviated by using an uncemented prosthesis in which biological ﬁxation can be achieved by providing a rough surface on the prosthesis for bone to grow into the porous surface of the prosthesis or by coating the surface of the prosthesis with hydroxyapatite, an osteoconductive agent, to encourage bone to bond to the prosthesis ( Figure 39.9 ). These uncemented devices have also shown good long-term outcomes, although they can be associ ated with higher implant costs, increased risk of intraoperative fracture and di ﬃ culty in removing them if revision surgery is required in the future.

Type of bearing Advantages Metal on polyethylene Proven ef /f_i cacy; easy to manufacture; cheap Ceramic on polyethylene Lower wear rate Metal on metal Lower wear rate Ceramic on ceramic Newer delta ceramics have the lowest wear rate UHMWPE, ultra-high-molecular-weight polyethylene. TABLE 39.7 Fixation of implants. Method of /f_i xation Component Advantages Cemented Femur Implant does not need to /f_i t cavity exactly; well-proven results Acetabulum Cheap, can be used in osteoporotic bone Uncemented Femur No cement required; /f_i xation more secure; dynamic and biological /f_i xation Acetabulum Good /f_i xation into acetabulum; can be augmented with screws to secure /f_i xation

Primary total hip replacement

Revision total hip replacement

Revision of a THR is required if the patient is symptomatic secondary to failure of the implant by loosening ( Figure 39.11 ), recurrent dislocations or a periprosthetic fracture. Rarely the femoral prosthesis itself can fracture, leading to pain and disability requiring revision surgery . Loosening of the implant can occur as a result of an infection or aseptic loosening. Aseptic osteolysis is caused by an inﬂammatory response secondary to particle wear, which can be from either poly - ethylene or metal. In the initial stages of loosening the patient complains of pain, which is experienced mainly on weight-bearing. - Thorough assessment to rule out infection is essential to plan infection (can also be reported as further treatment. A histor y of problems with wound healing) in the immediate postoperative period may suggest infection as a cause of premature implant Staphylococcus loosening. The infection can be low grade, with - - - -

Figure 39.11 Signi /f_i cant acetabular wear, eccentric position of the femoral head (arrow indicating left side wear) and osteolysis behind the acetabular component. Right hip wear is also seen (thin arrow). Distance X should be equal to distance Y . Here, distance X is con- siderably smaller than distance Y , indicating eccentric wear of the polyethylene (thin arrow).

and therefore normal measures of infection such as a raised C-reactive protein (CRP) may be equivocal (see Chapter 43 The Musculoskeletal Infection Society (MSIS) has deﬁned several criteria (major and minor) to help with the diagnosis of prosthetic joint infection. The diagnosis of infection is aided by an elevated CRP and erythrocyte sedimentation rate; a joint aspirate or biopsy is also useful to identify a pathogen. In addition, a labelled white cell scan and single photon emission CT (SPECT) can provide additional information. Revision THR can be a single-stage or a two-stage procedure depending on the indication. If the loosening is secondary to infection, a two-stage revision is usually preferred. The ﬁrst stage consists of implant remov al, thorough debridement and implantation of an antibiotic-loaded cement spacer. Multiple deep specimens are sent for bacteriology to determine the organism and its antimicrobial sensitivity . The patient is subsequently prescribed an appropriate antibiotic regime (see Chapter 43 ). At the second stage of the procedure, the cement spacer is removed and a new prosthesis implanted. In the case of aseptic loosening, revision is performed as a single-stage procedure. If there has been a signiﬁcant amount of bone loss, bone grafting or trabecular metal augments may be required. The results following a revision hip replacement are not as good as those following a primary THR and the rate of complications, especially dislocation, is also higher. Specialised acetabular components such as dual-mobility implants are favoured in a revision setting, especially for recurrent dislocation in those with poor muscle function. Ben-Shlomo Y , Blom A, Boulton C et al . The National Joint Registry 18th ). annual report 2021 . London: National Joint Registry; 2021. Available from https://www .ncbi.nlm.nih.gov/books/NBK576858/ Bulstrode C, Wilson-MacDonald J, Eastwood DM et al . Oxford textbook of trauma and orthopaedics , 2nd edn. Oxford: Oxford University Press, 2017. Ganz R, Parvizi J, Beck M et al . Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop . 2003; 417 : 112–20. Houcke JV , Khanduja V , Pattyn C, Audenaert E. The history of biomechanics in total hip arthroplasty . Indian J Orthop 2017; 51 (4): 359–67. Erratum in: Indian J Orthop 2017; 51 (5): 629. Khanduja V , Villar RN. Arthroscopic surgery of the hip: current concepts and recent advances. J Bone Joint Surg Br 2006; 88 (12): 1557–66. Magrill ACL, Nakano N, Khanduja V . Historical review of arthroscopic surgery of the hip. Int Orthop 2017; 41 (10): 1983–94. Matsumoto K, Ganz R, Khanduja V . The history of femoroacetabular impingement. Bone Joint Res 2020; 9 (9): 572–7. Miller M, Thompson SR. Miller’s review of orthopaedics , 8th edn. Philadelphia: Elsevier, 2019. Nakano N, Yip G, Khanduja V . Current concepts in the diagnosis and management of extra-articular hip impingement syndromes. Int Orthop 2017; 41 (7): 1321–8. Palmer AJR, Ayyar Gupta V , Fernquest S et al. FAIT Study Group. Arthroscopic hip surgery compared with physiotherapy and activity modiﬁcation for the treatment of symptomatic femoroacetabular impingement: multicentre randomised controlled trial. BMJ 2019; 364 : l185. Erratum in: BMJ 2021; 372 : m3715. Parvizi J, Tan TL, Goswami K et al . The 2018 deﬁnition of periprosthetic hip and knee infection: an evidence-based and validated criteria. J Arthroplasty 2018; 33 (5): 1309–14.e2. Sunil Kumar KH, Rawal J, Nakano N et al . Pathogenesis and contemporary diagnoses for lateral hip pain: a scoping review . Knee Surg Sports Traumatol Arthrosc 2021; 29 (8): 2408–16. Warwick D, Blom A, Whitehouse M. Apley and Solomon’s concise system of orthopaedics and trauma , 5th edn. Abingdon: CRC Press, 2022. Revision total hip replacement

SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITION

SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITIONS Arthrodesis of the hip

Arthrodesis or fusion of the hip is an uncommon operation. It is generally reserved for young patients with severe OA who have to fail early . The aim is to achieve a painless joint by fusing it in a functional position, which is about 30° of ﬂexion, 15° of external rotation and 5° of abduction. This can be achieved by an intra-articular dynamic hip screw or by an extra-articular plate with screws. Several problems can occur following an arthrodesis, including altered gait and excessive loading of the ipsilateral knee, the contralateral hip and the spine. Degenerative change in these joints in the long term is the rule rather than the exce ption. SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITIONS Arthrodesis of the hip

SURGICAL PROCEDURES FOR DEGENERATIVE HIP CONDITIONS Arthrodesis of the hip

Surgical approaches to the hip, postoperative cour

Surgical approaches to the hip, postoperative course and complications

The operation can be performed via a posterior approach, a trochanteric osteotomy , an anterolateral or Hardinge approach or an anterior approach ( Table 39.8 ). Each approach has its own advantages and disadvantages. Minimally invasive Kevin Hardinge , b. 1939, orthopaedic surgeon, Wrightington Hospital, UK, described the direct lateral approach to the hip in 1982. surgery has been described that shortens the size of the incision and attempts to lessen soft-tissue damage. As access can be restricted, specialised instruments have been developed to facilitate this. Although the concept is attractive, no long - term beneﬁts have been conclusiv ely shown in minimally inva - sive hip surgery over the conventional technique. Eventually , whichever approach is used, it is essential to be able to implant - a prosthesis so as to reproduce the patient’s anatomy such that the implant has the correct o ﬀ set, is at the correct centre of rotation with the correct component orientation, restores leg length and carries minimal risk of complications. The postoperative course generally involves a 2- to 3-day stay in hospital but day case hip replacements are being per - formed in a select group of patients in some centres. The physiotherapist encourages the patient to mobilise safely and inde pendently , avoiding any movements that might lead to a dislocation ( Figure 39.10 ). Postopera tive plain radiographs are essential to ensure that implants are in correct alignment and orientation, and rule out any iatrogenic fracture. Prior to dis - charge, the occupational therapist assesses the patient’s home circumstances and arranges for any modiﬁcations that may be

Disadvantages Current use Favourable in older age group >70 Comparatively high friction; high years wear rates; wear particles excite an in /f_l ammatory response that leads to osteolysis Expensive; ceramic fracture can be Preferrable in younger patients a problem <70 years. Newer polyethylene – UHMWPE – has low wear rate Only a select group of patients – Problem with metal ion release young male. Use head size larger leading to adverse reaction to than 48 /uni00A0 mm metal debris and severe osteolysis. Published examples of failure requiring early revision; implant recalls; expensive Very expensive; ceramic can High-functioning young patients fracture; squeaking Disadvantages Cement polymerisation is exothermic with possibility of thermal injury; fragments may cause third-body wear and stimulate aseptic loosening; dif /f_i cult to remove at revision Higher shear forces leading to failure Risk of fracture; /f_i t must be perfect; osseous integration may not be established; expensive Improper technique can lead to acetabular fracture

required to assist the patient, e.g. a raised toilet seat. For the ﬁrst 6 weeks patients are advised to avoid movements that make the THR prone to dislocation. Outpatient follow-up visits are arranged at 6 weeks and at 1 year post surgery . Although THR is generally a successful and safe procedure, it does have asso ciated complications. A comprehensive list of complications is provided in Table 39.9 . Perioperative administration of vention of infection antibiotics is a very important part in pre in addition to adequate aseptic precautions in the operating theatre. V enous thromboembolism is a risk following THR and deep vein thrombosis (DVT) is relatively common if no precautions are taken to reduce this risk. DVT can lead to pul monary embolism (PE), which can be fatal. Hence steps need to be taken to minimise the risk for both DVT and PE, includ ing adequate hydration, the use of regional anaesthesia and early postoperative mobilisation. In addition, both mechani rent [TED] stockings, foot cal device (thromboembolic deter pumps or intermittent pneumatic calf compression devices) hemical thromboprophylaxis (low-molecular-weight hep and c arin, warfarin or oral anticoagulants) are commonly prescribed 4–6 weeks after surgery to reduce the risk of for a period of DVT (this depends on local and national guidelines). /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF

Figure 39.10 Anteroposterior radiograph showing dislocation of a left hybrid total hip replacement (cemented femoral stem and unce mented acetabular component). TABLE 39.8 Surgical approaches to the hip. Surgical approach Anatomical interval and muscle Posterior Along the /f_i bres of the gluteus maximus, and dividing the short external rotators Trochanteric A trochanteric osteotomy is required Anterolateral/ Parts of the gluteus medius and minimus are Hardinge re /f_l ected off the greater trochanter Anterior The interval is developed between the sartorius and tensor fascia lata super /f_i cially and rectus femoris and gluteus medius deeply Intraoperative Nerve injury – sciatic, femoral and complications obturator nerves Vascular injury – femoral vein and artery Femoral or acetabular fracture Fragments of cement left in joint Postoperative Infection complications Deep vein thrombosis and pulmonary embolism Leg length inequality Dislocation Heterotopic ossi /f_i cation Septic/aseptic loosening Implant breakage/failure

Surgical approaches to the hip, postoperative course and complications