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Degenerative and rheumatoid arthritis (including joint replacement)
Orthopaedic IV: degenerative/paediatric disorders
Degenerative and rheumatoid arthritis (including joint replacement)
Classification of arthritis • Non-inflammatory: osteoarthritis, neuropathic arthropathy • Inflammatory: rheumatoid arthritis, systemic lupus erythromatosis, spondyloarthropathies (e.g. ankylosing spondylitis), Reiter’s syndrome, psoriatic and entropathic arthritis, crystalline arthropathy (e.g. gout, pseudo gout) • Infectious: pyogenic, tuberculous, fungal and Lyme disease • Haemorrhagic: haemophilia, sickle cell, pigmented villonodular synovitis
Amir Salama Andrew J Hamer
Abstract
Table 1
Arthritis is very common, and usually presents with pain, loss of function (stiffness) and deformity. There are several types of arthritis and each has particular features. Osteoarthritis and rheumatoid arthritis are the commonest; they are usually progressive and result in significant disability and pain if untreated. Medical management is usually the first line of action. Weight reduction and physiotherapy (if needed) can help control pain and increase mobility and, in rheumatoid arthritis, can modify the disease course. Surgery to replace arthritic joints usually leads to satisfactory relief of pain, but should be carefully considered and applied because it can lead to devastating complications. Joint replacement can be total or partial.
and often starts in the third or fourth decade. Multiple joints are often symmetrically involved, particularly the hands (meta carpophalangeal joints; ulnar deviation and subluxation) and the feet (metatarsophalangeal joints; halux valgus, claw toes); it also affects the elbows, knees, shoulders and cervical spine. Osteoarthritis and rheumatoid arthritis are enormous con sumers of healthcare resources; >50,000 hip replacements and 45,000 knee replacements are done in England and Wales every year.
Pathology and pathogenesis
Keywords arthritis; osteoarthritis; rheumatoid; degenerative; joint
Osteoarthritis is characterized by the loss of the normal structural integrity of the hyaline cartilage of a joint, possibly due to failure of chondrocytes to repair damaged cartilage, predominantly in areas of high contact load (e.g. superolateral area of acetabulum, medial knee compartment). Conditions predisposing to osteoarthritis do so by increasing the load concentrated across the joint (obesity, accumulative sports injury, joint incongruity, limb misalignment), reducing the capacity of the hyaline cartilage to withstand the applied loads (hereditary, septic arthritis, crystal diseases) or both (intra-articular fractures). The other principal pathological features (radiological characteristics) are narrowing of the joint space, subchondral sclerosis, subchondral cysts and osteophyte formation at the joint periphery (Figure 1).
replacement; arthrosis; inflamatory; arthroplasty
Classification Arthritis can be classified into four categories (Table 1). Osteoarthritis is the commonest form of arthritis in ‘developed’ countries, usually affecting males more than females in the later decades of life. It is characterized by progressive loss of articular cartilage with associated formation of new bone and capsular fibrosis. Osteoarthritis mainly affects the hip, knee (commonest), first carpometacarpal joint and the first metatarsophalangeal joint. • Primary osteoarthritis is of unknown cause but genetic factors may be involved. • Secondary osteoarthritis may occur after trauma (e.g. intraarticular fracture), previous septic arthritis, as a result of avascular necrosis (e.g. corticosteroids, alcoholism, thalassaemia, sickle cell anaemia). Congenital conditions (e.g. developmental dys plasia of the hip (see page 176), slipped capital femoral epiphysis, Perthes disease (see page 181) may also result in osteoartritis.
Rheumatoid arthritis: the cause of rheumatoid arthritis is unknown, but it is part of a systemic process, possibly triggered by an infectious agent. Patients may be predisposed to rheumatoid arthritis if they express the HLA-DR4 and DW4 antigens as part of their major histocompatibility complex (see King, CROSS REFERENCES). The pathophysiology is typified by a T-cell autoimmune response initially to synovium and soft tissue and subsequently against cartilage and bone. Joint destruction follows with the growth of a ‘pannus’ across the articular cartilage, and the de velopment of periarticular bone erosions. The extra-articular features of rheumatoid arthritis include: • anaemia (exacerbated by NSAIDs) • pulmonary fibrosis (pneumonitis with methotrexate) • vasculitis leading to an increased cardiac morbidity • mononeuritis • cervical myelopathy due to subaxial subluxation • peripheral nerve entrapment (carpal tunnel syndrome; see Ellis, CROSS REFERENCES).
Rheumatoid arthritis is the commonest form of inflammatory arthritis. It affects 3% of females and 1% of males in the UK,
Amir Salama FRCS(Orth) is a Specialist Registrar in Orthopaedic Surgery on the North Trent Training Programme, UK. Andrew J Hamer FRCS(Orth) is a Consultant Orthopaedic Surgeon at Northern General Hospital, Sheffield, UK.
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• subcutaneous nodules over bony prominences, extensor surfaces or in juxta-articular regions • positive laboratory tests (raised erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, immunoglobulin- M) • radiographic findings (periarticular erosions, osteopenia).
Medical management Osteoarthritis: management aims to reduce associated pain and improve function. No interventions can arrest or reverse the arthritic process once it is under way. Conservative measures must be used initially and should include advice about: • weight reduction • activity modification • alterations in working practice • simple analgesics (e.g. paracetamol). Walking sticks can provide considerable benefit to a patient with arthritis of the lower limbs (held on opposite side of the affected hip and on the same side of the affected knee). Other measures include NSAIDs, (e.g. glucosamine, chondroitin sulphate) and intra-articular corticosteroid injections in selected cases; synthetic analogues of hyaluronic acid have been used but data are inconclusive. Surgery may be indicated if these measures fail. Arthroscopic lavage, particularly in the knee, is widely practised, but response is unpredictable. Arthroplasty may be indicated if pain relief is still not achieved.
Figure 1 Radiograph of the pelvis showing the left hip affected by osteoarthritis. The features are narrowing of the joint space, sclerosis in the subchondral region (red arrow), subchondral cysts (blue arrow) and adjacent osteophyte formation. A cemented Exeter™ hip replacement was done on the right side three years previously.
Systemic manifestations of the disease occur in 5% of cases and may predate joint symptoms. Fever and weight loss may mimic sepsis (see Hargunani, CROSS REFERENCES) or malignancy. Several syndromes are described: • palindromic rheumatoid arthritis (hyperacute episodic rheumatoid arthritis always progresses to chronic rheumatoid arthritis) • Felty syndrome (rheumatoid arthritis with neutropenia, splenomegaly and lymphadenopathy) • Still’s disease (acute-onset rheumatoid arthritis in children with fever, rash and splenomegaly) • Sjögren syndrome (rheumatoid arthritis with reduced salivary and lachrymal secretion).
Rheumatoid arthritis: management should concentrate on the overall function of the individual, not on the individual joints involved. A multidisciplinary approach (rheumatologist, physiotherapist, orthotist, occupational therapist, orthopaedic surgeon) is required. Suitable footwear may delay the need for foot surgery, and splintage may help the painful ankle or wrist. Adapted household items (e.g. large-handled cutlery, long-handled shoe horns) should be considered. A pyramid approach to drug therapy should be used depending on disease progression. • NSAIDs (first-line therapy). • Disease-modifying agents (methotrexate, sulphasalazine, penicillamine, gold). • Corticosteroids. • Cytotoxic drugs. • Anti-cytokine therapy. Tumour necrosis factor-α is a key cytokine overproduced in rheumatoid arthritis synovium. Antitumour necrosis factor-α therapy is used in highly active disease in adults if two standard disease-modifying drugs fail to elicit response. Surgery may be indicated if these measures are exhausted; many patients ultimately require multiple joint replacements or other procedures.
Diagnosis Diagnosis is on history and examination, distribution of the affected joints, and radiological features. Local pain (due to joint degeneration) must be differentiated from referred pain (e.g. from spine to buttock; from hip to knee). Local anaesthetic injections into the knee or hip can be used if there is doubt about the main source of pain. Osteoarthritis: the diagnosis is usually confirmed radiologically. The typical features of osteoarthritic joint are pain that increases with activity, swelling, deformity, reduced range of movement and crepitus. The swelling is usually due to joint effusion and may vary during the disease course.
Surgical management
Rheumatoid arthritis: the following criteria (American Rheum atism Association) are often used for the diagnosis of rheumatoid arthritis: • morning stiffness that lasts for at least one hour before maximal improvement • joint swelling
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The surgical options for the treatment of degenerate joints are listed in Table 2. Arthroplasty and arthrodesis are the mainstays of surgical treatment, but osteotomy may also be carried out. Arthoscopic lavage and debridement: arthroscopic examination allows direct assessment of the hyaline cartilage and an 161
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load distribution across the joint. Such procedures are technically very demanding, and may have unpredictable outcomes. Patients who do well after such procedures often have minimal degenerative change before surgery.
Surgical options for the treatment of degenerate joints Arthroscopic lavage and debridement Synovectomy (for rheumatoid arthritis) Osteotomy (alteration of joint biomechanics by joint realignment) Arthroplasty (replacement of diseased joint); total or partial replacement Arthrodesis (surgical fusion of the joint)
Arthroplasty: excision arthroplasty was practised historically for the treatment of infected and degenerate joints, and was popularized for the treatment of tuberculosis of the hip in the 1940s in the UK. The modern indication for this procedure is often an infected joint arthroplasty if other treatment methods have failed. Total prosthetic joint replacement in the hip was pioneered in late 1960s and early 1970s in the UK, after largely unsuccessful attempts at joint resurfacing using cup arthroplasties or acrylic femoral head replacements. Total joint replacement of the knee, shoulder, elbow and metacarpophalangeal joints is widely practised. Total hip and knee replacement have well-documented beneficial effects on quality of life. Bone preservation techniques of joint arthroplasty (e.g. metalon-metal hip resurfacing, unicondylar knee replacement) are becoming popular in carefully selected patients.
Table 2
pportunity to remove damaged intra-articular structures i.e. o meniscal tears in the knee. Lavage and debridement of the knee in early osteoarthritis is common, but the benefit is not always clear. A study comparing arthroscopic washout to an operation where only sham incisions were made showed no added benefit.
Arthrodesis: surgical removal of the surface of diseased joints, followed by the fusion of the joint, was previously popular for the treatment of painful knee and hip arthritis in young, active people, and often occurred spontaneously in the hip in patients with tuberculosis. It is still occasionally indicated in these large joints, but arthrodesis is more commonly carried out for osteoarthritis of the first carpometacarpal joint, the first metatarsophalangeal joint, the ankle and the subtalar joint. Arthrodesis is usually done for smaller joints where prosthetic replacement has been unsuccessful. Arthrodesis is an excellent procedure for pain relief, but in evitably leads to the problems of a stiff joint, with the resultant loss of function. A stiff painless joint may be the best treatment for a young manual labourer who might prematurely wear out a prosthetic joint. The complications of arthrodesis include non-union, infection, and degenerative change in the joints adjacent to the fusion as a result of the greater forces applied to these joints. The joints adjacent to a proposed arthorodesis must be flexible and not already degenerate.
Osteotomy: realignment of a diseased joint may alleviate symptoms by altering the load on one part of the joint (e.g. treatment of osteoarthritis of the medial compartment of the knee, Figure 2). The chances of success are greater in young patients with a good range of movement, confirmed unicompartmental disease and lack of excessive deformity in a stable joint. Osteotomy has also been practised around the hip joint; the periacetabular osteotomies of Ganz and Tonnis are described for the treatment of pain from dysplastic hips by improving the
Degenerative and rheumatoid arthritis
Medial compartment osteoarthritis
Prosthetic joint replacement Design considerations The design of hip prostheses usually involves a metal femoral stem and an ultra-high-molecular-weight polyethylene (UHMPE) acetabular component. Most implants used in the UK are cemented in place with polymethyl-methacrylate (PMMA) bone cement. Typical stem designs are shown in Figure 3.
Osteotomy site Varus angulation of tibia Angulation corrected
Uncemented designs were developed because bone cement particles were thought to be responsible for the loosening process. This may be true in certain situations, but UHMPE particles are the more likely culprits. Various surface finishes have been applied to prostheses to encourage bone ingrowth, including beads, mesh- and plasma-sprayed titanium. Hydroxyapatite, a synthetic bone substitute, has been applied to many prostheses to encourage bony incorporation, but this may be most effective if applied to a surface that is already textured. Early (<5 years)
The knee tends to adopt a varus position with medial compartment osteoarthritis, which in turn increases the load on the medial compartment, accelerating the arthritic process. Good results can be achieved in suitable patients by carrying out a ‘high tibial osteotomy’ through the metaphyseal bone at the proximal end of the tibia and by correcting the varus deformity.
Figure 2
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Metal-on-metal bearings have good friction characteristics, but may release metal ions; cobalt and chromium ions have been found in the reticulo-endothelial systems of patients with such bearings post mortem. Such metallic debris may predispose to sarcoma formation, but it is unproven. Total knee arthroplasty: current designs allow the replaced knee to simulate the natural motion of the knee joint, allowing flexion and extension and controlled amounts of rotation and abduction/adduction (Figure 4). Modern designs use metal femoral components articulating with polyethylene tibial articular surfaces, supported by metal tibial trays (Figure 5). With the development and validation of resurfacing-type prostheses designed to simulate normal knee movements, knee arthroplasty offers as good long-term outlook as hip arthroplasty. Other joints (e.g. shoulder, elbow, metacarpophalangeal joints) are less commonly replaced, and long-term (20-year) results are not available. The replacement of other joints (e.g. first metatarsophalangeal, ankle) is difficult and results are not encouraging. a Uncemented stem design for biological fixation; the tronion can accept a metal or ceramic head. b Polished tapered Exeter™ stem and metal head.
Indications and contraindications for total joint replacement The absolute indication for joint replacement is management of pain that has not been controlled by other means. It is incorrect to suggest to a patient that his new artificial joint will return to him the mobility that he had in his twenties (although some patients expect this!) Age is no bar to arthroplasty, as long as extensive counseling has taken place to warn of long-term loosening and future revision surgery. Heavy manual tasks, particularly in men, are not compatible with hip and knee arthroplasty; heavy repetitive exercise or impact exercise should be discouraged.
Figure 3
delamination of hydroxyapatite has been observed in smoothsurfaced femoral stems. Uncemented femoral components are becoming more popular in the UK, but many thousands are implanted in Europe with good results. Uncemented acetabular components remain in widespread use, often in conjunction with cemented femoral stems in a ‘hybrid’ fashion. The long-term outcome of their use remains unclear.
Pain at night or at rest is a good indication for surgery; rapidly decreasing walking distance or radiological disintegration of a joint is useful pointers to the timing of surgery. Assessment – pain and disability can be assessed using various scoring systems (e.g. Oxford Hip Score, Knee Society Score).
Resurfacing of the hip is becoming popular. The main advantage lies in its potential use in the relatively young population, in preserving bone stock and allowing a more stable range of movement. It is a technically difficult and notching the femoral neck can lead to fracture of the femoral neck.
Movement of the centre of rotation of the knee during flexion and extension
Developments in materials and design in conventional total hip replacement have largely eliminated femoral stem fractures, and most implants are made of stainless steel, cobalt chrome or titanium. Stainless steel is strong and relatively easy to work, cobalt chrome produces the best bearing surfaces, and titanium is the most biocompatible.
This allows the knee to flex through a range of movement >120°
Instant centres 0
Bone loss: one of the most difficult problems in total joint replacement is bone loss (osteolysis), which results from the response of multinucleate cells to polyethylene wear debris. Each step that a patient takes with a metal-on-UHMPE bearing may liberate millions of UHMPE wear particles, which escape into the joint space. These may gain access to the bone–cement interface by cracks in the cement mantle, and particles <1 micron in diameter may be taken up by macrophages. The macrophages are unable to digest the particles, and produce cytokines, which activate local osteoclasts to produce unopposed bone loss and ultimately lead to prosthetic loosening. To overcome this problem, many hip designs are available with metal-on-metal articulations or ceramic- onceramic bearings; ceramic-on-UHMPE bearings are also used.
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0
20 120
50 80
50 120
Figure 4
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Modern techniques have reduced the deep infection rates to 0.5% for primary hip and knee arthroplasty. The following measures have an additive effect in reducing the incidence of infection: • surgery in an ultra-clean air enclosure • prophylactic antibiotics (see Hampson, CROSS REFERENCES) • waterproof drapes and gowns • theatre staff body exhaust (to remove organisms shed by theatre staff) • double gloving. The approach to the replaced joint should minimize muscle damage and allow post-implantation reconstruction. The hip can be replaced via an anterolateral approach (carefully avoiding the superior gluteal nerve when dividing gluteus medius) or via a posterior approach (taking care to protect the sciatic nerve). The anterolateral approach may predispose to a limp because abductor function may be reduced; the posterior approach may be more prone to dislocation. A well-fixed joint resists early loosening, and attention to the preparation of the implantation surfaces is vital. A bloodfree surface is important if the component is to be cemented. Good cement mixing produces strong durable cement, and good cementing technique avoids holes in the cement that may initiate cracks. Cement is applied under pressure to prevent the entry of blood to the bone–cement interface.
Figure 5 Total condylar knee replacement design. The curved femoral condylar surfaces are on the left, the tibial implant on the right. This design has a polyethylene tibial tray with a central peg for added stability and is backed with metal. The stem for insertion into the tibia is below the tray.
Such systems allow the prospective assessment of disability, and can be used to compare the outcome of procedures. Contraindications for joint arthroplasty are listed in Table 3.
Complications Complications of knee and hip arthroplasty are relatively rare but can have devastating effects.
Preoperative assessment Thorough history-taking and examination should be done preoperatively to ensure that cardiorespiratory function is optimal. Large-joint arthroplasties are major procedures with potential blood loss and adequate cardiac reserve is vital. Full blood count, crossmatch, serum electrolytes, ECG and chest radiograph are required. Most UK hospitals run preoperative assessment clinics where such investigations can be done, and abnormal results acted upon before admission. Many patients undergoing joint replacement are elderly, and there may be associated social care problems that can be tackled at the preoperative assessment clinic. Careful screening for septic foci is also important, because infection at the time of joint replacement is disastrous. Poor dentition should be managed, urinary tract infection (see Bishop, CROSS REFERENCES) excluded, and skin infection treated before surgery.
Deep infection occurs in 0.5–1.5% of cases, and can be adequately treated only by complete removal of the implant, cement and all infected tissue; followed by the delivery of local antibiotics (via cement-impregnated beads) and the reimplantation of another joint 8–12 weeks later. The functional result of this procedure is usually not as good as the original primary joint. Deep venous thrombosis (see Menon, CROSS REFERENCES) occurs in about 40–50% of lower-limb joint replacements, if sought on venography, but the clinical incidence is lower (3%). The need for anti-thromboembolism prophylaxis is controversial because it may increase the rate of postoperative haematomas, predisposing to sepsis.
Principles of surgery The aim of joint replacement is to provide a pain-free, flexible, stable sterile joint that lasts many years. Attention to detail at the time of prosthetic joint implantation is essential.
Pulmonary embolism is significant; fatal pulmonary embolism may occur in 0.5% of patients. Dislocation of hip arthroplasties is seen in 1–3% of cases.
Contraindications for joint arthroplasty
Nerve injuries: the sciatic nerve is at risk with the posterior approach to the hip, but injuries to the femoral and obturator nerves have also been recorded. Injury to the lateral popliteal nerve may occur after knee arthroplasty, the chance being increased in a preoperative valgus deformity or if epidural anaesthesia is used. Desaturation can very occasionally occur when cement is introduced, due to the volatile monomer used in bone cement or due to fat embolism.
• Uncontrolled medical problems • Skeletally immature • Active infection • Neuropathic (Charcot) joint • Progressive neurological disease • Muscle weakness around joint Table 3
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rate <10% at 10 years should be used in routine practice; this limits choice to 3–4 implants. Newer implants should be used only in closely controlled studies in centres specializing in hip or knee surgery. Joint ‘failure’ is often defined as the need for revision surgery, but many joints may be painful without being revised. This begs the question ‘what is an adequate early indicator of joint success or failure?’ Work is being done on the radiological measurement of implant migration in the early years, with the intention of identifying implants at risk of early loosening. The development of prostheses is evolving, and there is much work to be done to refine the bearing surfaces in an attempt to rid the implants of wear products (e.g. metal-on-metal, ceramicon-ceramic). There is also a possible place for medical therapy in the prevention of implant loosening. Bisphosphonates are used in the treatment of osteoporosis (see Crosbie, CROSS REFERENCES) and may be useful in implant patients. They reduce the activity of osteoclasts, activated by macrophages trying to digest UHMPE particles as described above. There is some evidence that these drugs may be useful, but their role in hip and knee arthroplasty is not clear. Resurfacing of the articular surfaces of the hip with metal-onmetal bearing surfaces has seen a resurgence in the UK. It may confer benefit in younger patients, but long-term outcome has not been evaluated. ◆
Rehabilitation Most patients should be in hospital for about five days after hip and knee arthroplasty. Drains are usually removed at 24 hours, and mobilization started as soon as possible. Careful watch should be kept for possible complications of surgery. Routine postoperative radiographs are taken to document the position of the implants. Patients are usually discharged with crutches to protect against weightbearing after hip and knee replacement, discarding walking aids six weeks after surgery. Patients are advised to drive when safe, usually six weeks after surgery. Outcome Long-term survival of the implants is affected by: • type of implant • underlying diagnosis • sex • cement type • surgical technique. Many patients have to be studied to determine the effect of each factor on the long-term survival of the implant, and the most detailed information comes from the Swedish Hip Register; every hip arthroplasty done in Sweden since 1979 has been included, allowing the technique of hip replacement to be refined on the basis of the information obtained. Overall, the twenty-year survival for hip replacement in women is 88.8% and for men is 85.4%. The National Joint Registry has been set up in England and Wales to collect similar data. Revision arthroplasty Revision of a total replacement should be undertaken only after the mechanism of failure has been established. Loosening, breakage, bone loss, periprosthetic fracture, recurrent dislocation and instability are easily identified; infection and other uncommon causes of joint replacement less so. The patient population tends to be older then those undergoing primary implantation, and the perioperative complications more common. Revision surgery accounts for about 10% of arthroplasty surgery in the lower limb, and has very significant cost implications. The challenges of revision surgery include the eradication of infection and the restoration of lost bone stock with bone grafting (see Marsh, CROSS REFERENCES).
Cross references Bishop MC. Urinary tract infection. Surgery 2005; 23(4): 134–6. Crosbie D, Reid DM. Osteoporosis. Surgery 2006; 24(11): 386–7. Ellis H. The carpal tunnel. Surgical and clinical anatomy for the MRCS examination. www.surgeryjournal.co.uk Hampson FG, Ridgway EJ. Prophylactic antibiotics in surgery. Surgery 2005; 23(8): 290–3. Hargunani R, Stotz M. Sepsis, SIRS and MODS. Surgery 2005; 23(8): 299–301. King CA, Wills MR. Immunology II: acquired immunity. Surgery 2005; 23(9): 319–23. Marsh JL. Principles of bone grafting: non-union, delayed union. Surgery 2006; 24(6): 207–10. Menon J, Hamilton G. Deep venous thrombosis. Surgery 2004; 22(11): 300–2.
Future of arthroplasty surgery The UK National Centre for Health and Clinical Excellence, has produced guidance suggesting that only prostheses with a failure
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Degenerative and rheumatoid arthritis (including joint replacement)
Classification of arthritis • Non-inflammatory: osteoarthritis, neuropathic arthropathy • Inflammatory: rheumatoid arthritis, systemic lupus erythromatosis, spondyloarthropathies (e.g. ankylosing spondylitis), Reiter’s syndrome, psoriatic and entropathic arthritis, crystalline arthropathy (e.g. gout, pseudo gout) • Infectious: pyogenic, tuberculous, fungal and Lyme disease • Haemorrhagic: haemophilia, sickle cell, pigmented villonodular synovitis
Amir Salama Andrew J Hamer
Abstract
Table 1
Arthritis is very common, and usually presents with pain, loss of function (stiffness) and deformity. There are several types of arthritis and each has particular features. Osteoarthritis and rheumatoid arthritis are the commonest; they are usually progressive and result in significant disability and pain if untreated. Medical management is usually the first line of action. Weight reduction and physiotherapy (if needed) can help control pain and increase mobility and, in rheumatoid arthritis, can modify the disease course. Surgery to replace arthritic joints usually leads to satisfactory relief of pain, but should be carefully considered and applied because it can lead to devastating complications. Joint replacement can be total or partial.
and often starts in the third or fourth decade. Multiple joints are often symmetrically involved, particularly the hands (meta carpophalangeal joints; ulnar deviation and subluxation) and the feet (metatarsophalangeal joints; halux valgus, claw toes); it also affects the elbows, knees, shoulders and cervical spine. Osteoarthritis and rheumatoid arthritis are enormous con sumers of healthcare resources; >50,000 hip replacements and 45,000 knee replacements are done in England and Wales every year.
Pathology and pathogenesis
Keywords arthritis; osteoarthritis; rheumatoid; degenerative; joint
Osteoarthritis is characterized by the loss of the normal structural integrity of the hyaline cartilage of a joint, possibly due to failure of chondrocytes to repair damaged cartilage, predominantly in areas of high contact load (e.g. superolateral area of acetabulum, medial knee compartment). Conditions predisposing to osteoarthritis do so by increasing the load concentrated across the joint (obesity, accumulative sports injury, joint incongruity, limb misalignment), reducing the capacity of the hyaline cartilage to withstand the applied loads (hereditary, septic arthritis, crystal diseases) or both (intra-articular fractures). The other principal pathological features (radiological characteristics) are narrowing of the joint space, subchondral sclerosis, subchondral cysts and osteophyte formation at the joint periphery (Figure 1).
replacement; arthrosis; inflamatory; arthroplasty
Classification Arthritis can be classified into four categories (Table 1). Osteoarthritis is the commonest form of arthritis in ‘developed’ countries, usually affecting males more than females in the later decades of life. It is characterized by progressive loss of articular cartilage with associated formation of new bone and capsular fibrosis. Osteoarthritis mainly affects the hip, knee (commonest), first carpometacarpal joint and the first metatarsophalangeal joint. • Primary osteoarthritis is of unknown cause but genetic factors may be involved. • Secondary osteoarthritis may occur after trauma (e.g. intraarticular fracture), previous septic arthritis, as a result of avascular necrosis (e.g. corticosteroids, alcoholism, thalassaemia, sickle cell anaemia). Congenital conditions (e.g. developmental dys plasia of the hip (see page 176), slipped capital femoral epiphysis, Perthes disease (see page 181) may also result in osteoartritis.
Rheumatoid arthritis: the cause of rheumatoid arthritis is unknown, but it is part of a systemic process, possibly triggered by an infectious agent. Patients may be predisposed to rheumatoid arthritis if they express the HLA-DR4 and DW4 antigens as part of their major histocompatibility complex (see King, CROSS REFERENCES). The pathophysiology is typified by a T-cell autoimmune response initially to synovium and soft tissue and subsequently against cartilage and bone. Joint destruction follows with the growth of a ‘pannus’ across the articular cartilage, and the de velopment of periarticular bone erosions. The extra-articular features of rheumatoid arthritis include: • anaemia (exacerbated by NSAIDs) • pulmonary fibrosis (pneumonitis with methotrexate) • vasculitis leading to an increased cardiac morbidity • mononeuritis • cervical myelopathy due to subaxial subluxation • peripheral nerve entrapment (carpal tunnel syndrome; see Ellis, CROSS REFERENCES).
Rheumatoid arthritis is the commonest form of inflammatory arthritis. It affects 3% of females and 1% of males in the UK,
Amir Salama FRCS(Orth) is a Specialist Registrar in Orthopaedic Surgery on the North Trent Training Programme, UK. Andrew J Hamer FRCS(Orth) is a Consultant Orthopaedic Surgeon at Northern General Hospital, Sheffield, UK.
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• subcutaneous nodules over bony prominences, extensor surfaces or in juxta-articular regions • positive laboratory tests (raised erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, immunoglobulin- M) • radiographic findings (periarticular erosions, osteopenia).
Medical management Osteoarthritis: management aims to reduce associated pain and improve function. No interventions can arrest or reverse the arthritic process once it is under way. Conservative measures must be used initially and should include advice about: • weight reduction • activity modification • alterations in working practice • simple analgesics (e.g. paracetamol). Walking sticks can provide considerable benefit to a patient with arthritis of the lower limbs (held on opposite side of the affected hip and on the same side of the affected knee). Other measures include NSAIDs, (e.g. glucosamine, chondroitin sulphate) and intra-articular corticosteroid injections in selected cases; synthetic analogues of hyaluronic acid have been used but data are inconclusive. Surgery may be indicated if these measures fail. Arthroscopic lavage, particularly in the knee, is widely practised, but response is unpredictable. Arthroplasty may be indicated if pain relief is still not achieved.
Figure 1 Radiograph of the pelvis showing the left hip affected by osteoarthritis. The features are narrowing of the joint space, sclerosis in the subchondral region (red arrow), subchondral cysts (blue arrow) and adjacent osteophyte formation. A cemented Exeter™ hip replacement was done on the right side three years previously.
Systemic manifestations of the disease occur in 5% of cases and may predate joint symptoms. Fever and weight loss may mimic sepsis (see Hargunani, CROSS REFERENCES) or malignancy. Several syndromes are described: • palindromic rheumatoid arthritis (hyperacute episodic rheumatoid arthritis always progresses to chronic rheumatoid arthritis) • Felty syndrome (rheumatoid arthritis with neutropenia, splenomegaly and lymphadenopathy) • Still’s disease (acute-onset rheumatoid arthritis in children with fever, rash and splenomegaly) • Sjögren syndrome (rheumatoid arthritis with reduced salivary and lachrymal secretion).
Rheumatoid arthritis: management should concentrate on the overall function of the individual, not on the individual joints involved. A multidisciplinary approach (rheumatologist, physiotherapist, orthotist, occupational therapist, orthopaedic surgeon) is required. Suitable footwear may delay the need for foot surgery, and splintage may help the painful ankle or wrist. Adapted household items (e.g. large-handled cutlery, long-handled shoe horns) should be considered. A pyramid approach to drug therapy should be used depending on disease progression. • NSAIDs (first-line therapy). • Disease-modifying agents (methotrexate, sulphasalazine, penicillamine, gold). • Corticosteroids. • Cytotoxic drugs. • Anti-cytokine therapy. Tumour necrosis factor-α is a key cytokine overproduced in rheumatoid arthritis synovium. Antitumour necrosis factor-α therapy is used in highly active disease in adults if two standard disease-modifying drugs fail to elicit response. Surgery may be indicated if these measures are exhausted; many patients ultimately require multiple joint replacements or other procedures.
Diagnosis Diagnosis is on history and examination, distribution of the affected joints, and radiological features. Local pain (due to joint degeneration) must be differentiated from referred pain (e.g. from spine to buttock; from hip to knee). Local anaesthetic injections into the knee or hip can be used if there is doubt about the main source of pain. Osteoarthritis: the diagnosis is usually confirmed radiologically. The typical features of osteoarthritic joint are pain that increases with activity, swelling, deformity, reduced range of movement and crepitus. The swelling is usually due to joint effusion and may vary during the disease course.
Surgical management
Rheumatoid arthritis: the following criteria (American Rheum atism Association) are often used for the diagnosis of rheumatoid arthritis: • morning stiffness that lasts for at least one hour before maximal improvement • joint swelling
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The surgical options for the treatment of degenerate joints are listed in Table 2. Arthroplasty and arthrodesis are the mainstays of surgical treatment, but osteotomy may also be carried out. Arthoscopic lavage and debridement: arthroscopic examination allows direct assessment of the hyaline cartilage and an 161
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load distribution across the joint. Such procedures are technically very demanding, and may have unpredictable outcomes. Patients who do well after such procedures often have minimal degenerative change before surgery.
Surgical options for the treatment of degenerate joints Arthroscopic lavage and debridement Synovectomy (for rheumatoid arthritis) Osteotomy (alteration of joint biomechanics by joint realignment) Arthroplasty (replacement of diseased joint); total or partial replacement Arthrodesis (surgical fusion of the joint)
Arthroplasty: excision arthroplasty was practised historically for the treatment of infected and degenerate joints, and was popularized for the treatment of tuberculosis of the hip in the 1940s in the UK. The modern indication for this procedure is often an infected joint arthroplasty if other treatment methods have failed. Total prosthetic joint replacement in the hip was pioneered in late 1960s and early 1970s in the UK, after largely unsuccessful attempts at joint resurfacing using cup arthroplasties or acrylic femoral head replacements. Total joint replacement of the knee, shoulder, elbow and metacarpophalangeal joints is widely practised. Total hip and knee replacement have well-documented beneficial effects on quality of life. Bone preservation techniques of joint arthroplasty (e.g. metalon-metal hip resurfacing, unicondylar knee replacement) are becoming popular in carefully selected patients.
Table 2
pportunity to remove damaged intra-articular structures i.e. o meniscal tears in the knee. Lavage and debridement of the knee in early osteoarthritis is common, but the benefit is not always clear. A study comparing arthroscopic washout to an operation where only sham incisions were made showed no added benefit.
Arthrodesis: surgical removal of the surface of diseased joints, followed by the fusion of the joint, was previously popular for the treatment of painful knee and hip arthritis in young, active people, and often occurred spontaneously in the hip in patients with tuberculosis. It is still occasionally indicated in these large joints, but arthrodesis is more commonly carried out for osteoarthritis of the first carpometacarpal joint, the first metatarsophalangeal joint, the ankle and the subtalar joint. Arthrodesis is usually done for smaller joints where prosthetic replacement has been unsuccessful. Arthrodesis is an excellent procedure for pain relief, but in evitably leads to the problems of a stiff joint, with the resultant loss of function. A stiff painless joint may be the best treatment for a young manual labourer who might prematurely wear out a prosthetic joint. The complications of arthrodesis include non-union, infection, and degenerative change in the joints adjacent to the fusion as a result of the greater forces applied to these joints. The joints adjacent to a proposed arthorodesis must be flexible and not already degenerate.
Osteotomy: realignment of a diseased joint may alleviate symptoms by altering the load on one part of the joint (e.g. treatment of osteoarthritis of the medial compartment of the knee, Figure 2). The chances of success are greater in young patients with a good range of movement, confirmed unicompartmental disease and lack of excessive deformity in a stable joint. Osteotomy has also been practised around the hip joint; the periacetabular osteotomies of Ganz and Tonnis are described for the treatment of pain from dysplastic hips by improving the
Degenerative and rheumatoid arthritis
Medial compartment osteoarthritis
Prosthetic joint replacement Design considerations The design of hip prostheses usually involves a metal femoral stem and an ultra-high-molecular-weight polyethylene (UHMPE) acetabular component. Most implants used in the UK are cemented in place with polymethyl-methacrylate (PMMA) bone cement. Typical stem designs are shown in Figure 3.
Osteotomy site Varus angulation of tibia Angulation corrected
Uncemented designs were developed because bone cement particles were thought to be responsible for the loosening process. This may be true in certain situations, but UHMPE particles are the more likely culprits. Various surface finishes have been applied to prostheses to encourage bone ingrowth, including beads, mesh- and plasma-sprayed titanium. Hydroxyapatite, a synthetic bone substitute, has been applied to many prostheses to encourage bony incorporation, but this may be most effective if applied to a surface that is already textured. Early (<5 years)
The knee tends to adopt a varus position with medial compartment osteoarthritis, which in turn increases the load on the medial compartment, accelerating the arthritic process. Good results can be achieved in suitable patients by carrying out a ‘high tibial osteotomy’ through the metaphyseal bone at the proximal end of the tibia and by correcting the varus deformity.
Figure 2
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Metal-on-metal bearings have good friction characteristics, but may release metal ions; cobalt and chromium ions have been found in the reticulo-endothelial systems of patients with such bearings post mortem. Such metallic debris may predispose to sarcoma formation, but it is unproven. Total knee arthroplasty: current designs allow the replaced knee to simulate the natural motion of the knee joint, allowing flexion and extension and controlled amounts of rotation and abduction/adduction (Figure 4). Modern designs use metal femoral components articulating with polyethylene tibial articular surfaces, supported by metal tibial trays (Figure 5). With the development and validation of resurfacing-type prostheses designed to simulate normal knee movements, knee arthroplasty offers as good long-term outlook as hip arthroplasty. Other joints (e.g. shoulder, elbow, metacarpophalangeal joints) are less commonly replaced, and long-term (20-year) results are not available. The replacement of other joints (e.g. first metatarsophalangeal, ankle) is difficult and results are not encouraging. a Uncemented stem design for biological fixation; the tronion can accept a metal or ceramic head. b Polished tapered Exeter™ stem and metal head.
Indications and contraindications for total joint replacement The absolute indication for joint replacement is management of pain that has not been controlled by other means. It is incorrect to suggest to a patient that his new artificial joint will return to him the mobility that he had in his twenties (although some patients expect this!) Age is no bar to arthroplasty, as long as extensive counseling has taken place to warn of long-term loosening and future revision surgery. Heavy manual tasks, particularly in men, are not compatible with hip and knee arthroplasty; heavy repetitive exercise or impact exercise should be discouraged.
Figure 3
delamination of hydroxyapatite has been observed in smoothsurfaced femoral stems. Uncemented femoral components are becoming more popular in the UK, but many thousands are implanted in Europe with good results. Uncemented acetabular components remain in widespread use, often in conjunction with cemented femoral stems in a ‘hybrid’ fashion. The long-term outcome of their use remains unclear.
Pain at night or at rest is a good indication for surgery; rapidly decreasing walking distance or radiological disintegration of a joint is useful pointers to the timing of surgery. Assessment – pain and disability can be assessed using various scoring systems (e.g. Oxford Hip Score, Knee Society Score).
Resurfacing of the hip is becoming popular. The main advantage lies in its potential use in the relatively young population, in preserving bone stock and allowing a more stable range of movement. It is a technically difficult and notching the femoral neck can lead to fracture of the femoral neck.
Movement of the centre of rotation of the knee during flexion and extension
Developments in materials and design in conventional total hip replacement have largely eliminated femoral stem fractures, and most implants are made of stainless steel, cobalt chrome or titanium. Stainless steel is strong and relatively easy to work, cobalt chrome produces the best bearing surfaces, and titanium is the most biocompatible.
This allows the knee to flex through a range of movement >120°
Instant centres 0
Bone loss: one of the most difficult problems in total joint replacement is bone loss (osteolysis), which results from the response of multinucleate cells to polyethylene wear debris. Each step that a patient takes with a metal-on-UHMPE bearing may liberate millions of UHMPE wear particles, which escape into the joint space. These may gain access to the bone–cement interface by cracks in the cement mantle, and particles <1 micron in diameter may be taken up by macrophages. The macrophages are unable to digest the particles, and produce cytokines, which activate local osteoclasts to produce unopposed bone loss and ultimately lead to prosthetic loosening. To overcome this problem, many hip designs are available with metal-on-metal articulations or ceramic- onceramic bearings; ceramic-on-UHMPE bearings are also used.
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20 120
50 80
50 120
Figure 4
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Modern techniques have reduced the deep infection rates to 0.5% for primary hip and knee arthroplasty. The following measures have an additive effect in reducing the incidence of infection: • surgery in an ultra-clean air enclosure • prophylactic antibiotics (see Hampson, CROSS REFERENCES) • waterproof drapes and gowns • theatre staff body exhaust (to remove organisms shed by theatre staff) • double gloving. The approach to the replaced joint should minimize muscle damage and allow post-implantation reconstruction. The hip can be replaced via an anterolateral approach (carefully avoiding the superior gluteal nerve when dividing gluteus medius) or via a posterior approach (taking care to protect the sciatic nerve). The anterolateral approach may predispose to a limp because abductor function may be reduced; the posterior approach may be more prone to dislocation. A well-fixed joint resists early loosening, and attention to the preparation of the implantation surfaces is vital. A bloodfree surface is important if the component is to be cemented. Good cement mixing produces strong durable cement, and good cementing technique avoids holes in the cement that may initiate cracks. Cement is applied under pressure to prevent the entry of blood to the bone–cement interface.
Figure 5 Total condylar knee replacement design. The curved femoral condylar surfaces are on the left, the tibial implant on the right. This design has a polyethylene tibial tray with a central peg for added stability and is backed with metal. The stem for insertion into the tibia is below the tray.
Such systems allow the prospective assessment of disability, and can be used to compare the outcome of procedures. Contraindications for joint arthroplasty are listed in Table 3.
Complications Complications of knee and hip arthroplasty are relatively rare but can have devastating effects.
Preoperative assessment Thorough history-taking and examination should be done preoperatively to ensure that cardiorespiratory function is optimal. Large-joint arthroplasties are major procedures with potential blood loss and adequate cardiac reserve is vital. Full blood count, crossmatch, serum electrolytes, ECG and chest radiograph are required. Most UK hospitals run preoperative assessment clinics where such investigations can be done, and abnormal results acted upon before admission. Many patients undergoing joint replacement are elderly, and there may be associated social care problems that can be tackled at the preoperative assessment clinic. Careful screening for septic foci is also important, because infection at the time of joint replacement is disastrous. Poor dentition should be managed, urinary tract infection (see Bishop, CROSS REFERENCES) excluded, and skin infection treated before surgery.
Deep infection occurs in 0.5–1.5% of cases, and can be adequately treated only by complete removal of the implant, cement and all infected tissue; followed by the delivery of local antibiotics (via cement-impregnated beads) and the reimplantation of another joint 8–12 weeks later. The functional result of this procedure is usually not as good as the original primary joint. Deep venous thrombosis (see Menon, CROSS REFERENCES) occurs in about 40–50% of lower-limb joint replacements, if sought on venography, but the clinical incidence is lower (3%). The need for anti-thromboembolism prophylaxis is controversial because it may increase the rate of postoperative haematomas, predisposing to sepsis.
Principles of surgery The aim of joint replacement is to provide a pain-free, flexible, stable sterile joint that lasts many years. Attention to detail at the time of prosthetic joint implantation is essential.
Pulmonary embolism is significant; fatal pulmonary embolism may occur in 0.5% of patients. Dislocation of hip arthroplasties is seen in 1–3% of cases.
Contraindications for joint arthroplasty
Nerve injuries: the sciatic nerve is at risk with the posterior approach to the hip, but injuries to the femoral and obturator nerves have also been recorded. Injury to the lateral popliteal nerve may occur after knee arthroplasty, the chance being increased in a preoperative valgus deformity or if epidural anaesthesia is used. Desaturation can very occasionally occur when cement is introduced, due to the volatile monomer used in bone cement or due to fat embolism.
• Uncontrolled medical problems • Skeletally immature • Active infection • Neuropathic (Charcot) joint • Progressive neurological disease • Muscle weakness around joint Table 3
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rate <10% at 10 years should be used in routine practice; this limits choice to 3–4 implants. Newer implants should be used only in closely controlled studies in centres specializing in hip or knee surgery. Joint ‘failure’ is often defined as the need for revision surgery, but many joints may be painful without being revised. This begs the question ‘what is an adequate early indicator of joint success or failure?’ Work is being done on the radiological measurement of implant migration in the early years, with the intention of identifying implants at risk of early loosening. The development of prostheses is evolving, and there is much work to be done to refine the bearing surfaces in an attempt to rid the implants of wear products (e.g. metal-on-metal, ceramicon-ceramic). There is also a possible place for medical therapy in the prevention of implant loosening. Bisphosphonates are used in the treatment of osteoporosis (see Crosbie, CROSS REFERENCES) and may be useful in implant patients. They reduce the activity of osteoclasts, activated by macrophages trying to digest UHMPE particles as described above. There is some evidence that these drugs may be useful, but their role in hip and knee arthroplasty is not clear. Resurfacing of the articular surfaces of the hip with metal-onmetal bearing surfaces has seen a resurgence in the UK. It may confer benefit in younger patients, but long-term outcome has not been evaluated. ◆
Rehabilitation Most patients should be in hospital for about five days after hip and knee arthroplasty. Drains are usually removed at 24 hours, and mobilization started as soon as possible. Careful watch should be kept for possible complications of surgery. Routine postoperative radiographs are taken to document the position of the implants. Patients are usually discharged with crutches to protect against weightbearing after hip and knee replacement, discarding walking aids six weeks after surgery. Patients are advised to drive when safe, usually six weeks after surgery. Outcome Long-term survival of the implants is affected by: • type of implant • underlying diagnosis • sex • cement type • surgical technique. Many patients have to be studied to determine the effect of each factor on the long-term survival of the implant, and the most detailed information comes from the Swedish Hip Register; every hip arthroplasty done in Sweden since 1979 has been included, allowing the technique of hip replacement to be refined on the basis of the information obtained. Overall, the twenty-year survival for hip replacement in women is 88.8% and for men is 85.4%. The National Joint Registry has been set up in England and Wales to collect similar data. Revision arthroplasty Revision of a total replacement should be undertaken only after the mechanism of failure has been established. Loosening, breakage, bone loss, periprosthetic fracture, recurrent dislocation and instability are easily identified; infection and other uncommon causes of joint replacement less so. The patient population tends to be older then those undergoing primary implantation, and the perioperative complications more common. Revision surgery accounts for about 10% of arthroplasty surgery in the lower limb, and has very significant cost implications. The challenges of revision surgery include the eradication of infection and the restoration of lost bone stock with bone grafting (see Marsh, CROSS REFERENCES).
Cross references Bishop MC. Urinary tract infection. Surgery 2005; 23(4): 134–6. Crosbie D, Reid DM. Osteoporosis. Surgery 2006; 24(11): 386–7. Ellis H. The carpal tunnel. Surgical and clinical anatomy for the MRCS examination. www.surgeryjournal.co.uk Hampson FG, Ridgway EJ. Prophylactic antibiotics in surgery. Surgery 2005; 23(8): 290–3. Hargunani R, Stotz M. Sepsis, SIRS and MODS. Surgery 2005; 23(8): 299–301. King CA, Wills MR. Immunology II: acquired immunity. Surgery 2005; 23(9): 319–23. Marsh JL. Principles of bone grafting: non-union, delayed union. Surgery 2006; 24(6): 207–10. Menon J, Hamilton G. Deep venous thrombosis. Surgery 2004; 22(11): 300–2.
Future of arthroplasty surgery The UK National Centre for Health and Clinical Excellence, has produced guidance suggesting that only prostheses with a failure
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