Journal of Orthopaedic Surgery 2010;18(3):312-9
The practice of unicompartmental knee arthroplasty in the United Kingdom Oliver S Schindler,1 W Norman Scott,2,3 Giles R Scuderi2,3
BMI Droitwich Spa Hospital, Droitwich Spa, Worcestershire, United Kingdom Insall Scott Kelly Institute for Orthopaedics and Sports Medicine, New York, USA 3 Lennox Hill Hospital, New York, USA 1 2
ABSTRACT Purpose. To survey the current practice of unicompartmental knee arthroplasty (UKA) in the United Kingdom. Methods. Questionnaires were sent to all 341 local members of the British Association for Surgery of the Knee to inquire into their practice of UKA, including clinical indications, preoperative investigations, surgical approach, preferences in implant design, and the role of UKA in relation to high tibial osteotomy. Result. 56% of respondents performed less than 16 UKAs per year, whereas 16.5% performed over 30 per year. 89.5% of the respondents used anteroposterior radiographs as their main investigation tool. Only 30% and 16.5% used posteroanterior 30º flexion and varus/valgus stress radiographs, respectively, despite being better investigation tools. 57% considered arthroscopy, despite its invasive nature. The main contra-indications to UKA were anterior cruciate ligament deficiency with instability (95%), focal gradeIII osteoarthritis in the contralateral compartment
(87%), and osteoporosis with rheumatoid arthritis (80.5%), but only 59% of respondents considered an inability to passively correct a pre-existing varus or valgus deformity as a contra-indication. 51.5% of respondents preferred minimally invasive approach, 96% preferred cemented fixation, and over two thirds used the mobile bearing design. 72% of respondents expressed preference for total knee arthroplasty over UKA in localised lateral compartment osteoarthritis. Conclusion. Modern UKA has gained popularity in properly selected patients with localised medial compartment osteoarthritis, provided the knee is not anterior cruciate ligament deficient and any deformity is passively correctable. Key words: arthritis; data collection; Great Britain; knee joint
INTRODUCTION According to the National Joint Register of England and Wales, 3892 unicompartmental knee arthroplasties (UKAs) were performed in 2005,
Address correspondence and reprint requests to: Mr Oliver S Schindler, PO Box 1616, Bristol, BS40 5WG, United Kingdom. E-mail:
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representing 6.6% of all knee arthroplasties.1 In the same period, the proportions of UKAs performed in Sweden and Australia were 9.5% and 11.8%, respectively.2,3 Early reports suggested that UKA was not a viable long-term solution because of its relatively high failure rate except for lateral unicondylar
arthroplasty.4–6 Improvement in prosthetic design, surgical technique, and patient selection for UKA in the 1980s enabled UKA to achieve 10-year outcomes similar to those of total knee arthroplasty (TKA). This was encouraging especially when considering the more conservative nature of UKA.7–9 Its increasing popularity and use in younger patients with
Table Responses to questionnaire on the practice of unicompartmental knee arthroplasty (UKA) Question How many UKAs do you perform per year? 45 What are your main preoperative investigation tools? (multiple answers allowed) Anteroposterior radiographs Arthroscopy Posteroanterior 30º flexion radiographs Varus/valgus stress radiographs Magnetic resonance imaging Long leg alignment radiographs Skyline radiographs What are the main advantages of UKA over total knee arthroplasty (TKA)? (multiple answers allowed) Better range of motion Reduced postoperative morbidity Quicker recovery Improved proprioception Time delay before TKA is required Ability to perform sporting activities What are the main contra-indications for UKA? (multiple answers allowed) Anterior cruciate ligament deficiency with instability Focal grade-III osteoarthritis within the contralateral compartment Osteoporosis & rheumatoid arthritis Anterior cruciate ligament deficiency without instability Inability to passively correct varus/valgus deformity Anterior knee pain Focal grade-II osteoarthritis within the contralateral compartment Asymptomatic patellofemoral osteoarthritis Obesity (body mass index of >30 kg/m2) Which activities would you disallow after UKA? (multiple answers allowed) Football Squash Jogging Skiing Tennis Golf Which are the most suitable age groups for UKA? (multiple answers allowed) 75 years No age limit What approach do you use? Minimally invasive (5 to 7.5 cm incision) Limited medial parapatellar (10 to 12.5 cm incision) Standard medial parapatellar (17.5 to 25 cm incision)
% of respondents 13.0 43.0 27.5 10.0 6.5 89.5 57.0 30.0 16.5 15.5 13.5 12.0 59.0 41.5 36.0 33.5 18.5 8.0 95.0 87.0 80.5 63.0 59.0 32.5 27.5 9.5 8.0 97.0 70.0 61.5 22.5 19.0 3.5 18.0 36.5 13.0 3.5 50.0 51.5 45.5 3.5
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Question What is your preferred fixation method? Cemented fixation Cementless fixation Hybrid fixation What are your surgical options for localised lateral compartment osteoarthritis? (multiple answers allowed) TKA Fixed bearing UKA Osteotomy Mobile bearing UKA What is your % of lateral UKAs out of all UKAs performed? 0% 25% Do you use image-guided technology for UKA? Never Sometimes Always Do you think image-guided technology an important adjunct in UKA? No Yes How many high tibial osteotomy do you perform per year? 0 30 Do you see high tibial osteotomy & UKA as competing techniques with identical clinical indications? No Yes Where do you see the main indications for high tibial osteotomy compared to UKA? Younger patients (30 per year
% of respondents 96.0 2.0 2.0 72.0 56.0 41.5 16.5 60.0 27.0 9.0 2.0 2.0 91.5 8.5 0.0 40.5 59.5 40.0 30.0 27.5 2.5 0.5 82.0 18.0 92.5 66.0 48.5 31.5 62.0 12.5 10.5 4.0 2.0 2.0 2.0 1.5 1.5 1.0 1.0 95.0 5.0 95.5 4.5 80.5 19.5 42.0 38.0 16.5 3.5
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unicompartmental arthritis has marginalised alternative procedures such as high tibial osteotomy.10 Compared to TKA, UKA usually provides shorter rehabilitation time, better overall flexion, and retains more physiological joint kinematics.11–13 In addition, the use of a minimally invasive surgical approach in UKA has gained wide support,14 and its mid- to long-term outcomes are equivalent to those achieved through conventional techniques.15–17 Modern-type UKAs in properly selected patients have yielded survival rates of up to 98% at 10 years and 90% at 15 years.8,18–21 This study aimed to survey the current practice of UKA in the United Kingdom.
range of motion (Fig. 4), less postoperative morbidity, and faster postoperative recovery, respectively.
(a)
(b)
MATERIALS AND METHODS Questionnaires were sent to all 341 local members of the British Association for Surgery of the Knee to inquire into their practice of UKA. There were 23 questions; multiple answers were allowed in some.
Figure 1 (a) Anteroposterior and (b) posteroanterior 30º flexion radiographs of the same knee. The true extent of the degenerative process is more clearly demonstrated in the latter.
RESULTS Of 252 (74%) members who replied, 13 (5%) had retired from active surgery and 39 (15%) did not perform UKA. Results were analysed based on the remaining 200 respondents (Table). DISCUSSION To ensure long-term success of UKA, stringent patient selection criteria should be applied when determining patients’ suitability.7,9,11,20,22 The decision should be based on thorough clinical assessment using various investigation tools. In this study, 89.5% of the respondents used anteroposterior radiographs as their main investigation tool, compared to 30% who preferred posteroanterior 30° flexion radiographs, although the latter are more likely to reveal the true extent of the degenerative process (Fig. 1). Varus/ valgus stress radiographs are used by only 16.5% of respondents (Fig. 2), despite their ability to reliably verify competence of the contralateral compartment and any ligament contracture. In addition, 59% of respondents would refrain from performing UKA in cases where a varus or valgus deformity is not passively correctable (Fig. 3). 57% considered arthroscopy as the investigation of choice, despite its invasive nature. Compared to TKA, 59%, 41.5%, and 36% of respondents considered that UKA achieves a better
Figure 2 Posteroanterior 30º flexion and valgus stress radiographs of a patient with bilateral medial compartment osteoarthritis. Varus deformities are fully correctable while maintaining lateral compartment height.
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Figure 3 Passive correction of a varus deformity (secondary to medial compartment osteoarthritis) to neutral mechanical axis alignment (Illustrations adapted from Laskin RS. Total knee replacement, Orthop Clin North Am 1979;10:223–47. Reproduced with kind permission and copyright of Elsevier, Philadelphia).
Figure 4 Lateral radiograph of the knee in full flexion with a medial unicompartmental knee arthroplasty in situ.
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This is likely due to the less-invasive nature of the procedure and the closer resemblance to normal knee kinematics.22 In patients with lateral compartment osteoarthritis, more respondents preferred TKA to fixed bearing UKA or osteotomy (72% vs. 56% vs. 41.5%). Although lateral UKA is a viable alternative, 60% of respondents performed none in clinical practice. The main contra-indications to UKA were anterior cruciate ligament deficiency with instability (95%), focal grade-III osteoarthritis in the contralateral compartment (87%), and osteoporosis and rheumatoid arthritis (80.5%). Abnormalities within the patellofemoral joint are less emphasised.23,24 Only 9.5% of respondents regarded asymptomatic patellofemoral osteoarthritis as a contra-indication for UKA, whereas 32.5% refrained from UKA in patients with anterior knee pain.25 Some authors advocate UKA for patients with up to grade-IV chondromalacia in the medial patellofemoral articulation if associated with medial tibiofemoral osteoarthritis.24,26,27 Although excellent functional mid-term results have been reported in patients with limited patellofemoral osteoarthritis who underwent UKA using a mobile bearing prosthesis, it remains unclear whether similar results may be achievable with fixed bearing and other mobile bearing designs.24,26 In addition, 8% of respondents considered obesity as a contraindication for UKA. Concerns of implant overload and susceptibility to loosening and polyethylene wear in obese patients may be counteracted by the benefits of decreased physical activity in such patients together with improved surgical techniques and implant design.28–31 Suitable candidates for a UKA are those with unicompartmental non-inflammatory osteoarthritis with mechanical axis deviation of
