Surgical Approaches to OA Therapy: Osteotomy and Arthroplasty

Abstract

Total hip and knee replacement are among the most successful surgical procedures in medicine. The long-term survival of total hip replacements for which both the femoral and acetabular components were fixed to the surrounding bones with cement demonstrates durable results [1, 3], even in young patients [11]. For example, 35-year follow-up of cemented total hip replacements revealed a survival rate of 78% with the need for revision surgery for any reason as the end point [3]. In younger patients, the 25-year survival is 93% for the femoral component, though only 77% for the cemented acetabular component [11]. The introduction of newer designs that relies on biologic fixation through bone ingrowth into porous coatings on the metallic components has also proven durable. Twenty-year survival of porous-coated acetabular components has been reported at 86% [6] with revision for any reason associated with the acetabular component as the end point. In a direct comparison of cemented and cementless acetabular components performed by the same surgeon [8], survival at 18 years improved from 81% to 94%. Long-term results for porous-coated femoral components are just as impressive [2, 7, 9]. Joint replacement patients enjoy function which is comparable to their peers without osteoarthritis. Patient-reported outcomes such as the short-form health outcomes survey (the SF-36), together with objective functional measures, such as the 6-min walk, show no meaningful differences between total hip patients and normative values (Fig. 1). Fig. 1 SF-36 scores for total hip replacement patients (“Study”), those patients with two or more comorbidities, and normative values (“Norm”) demonstrate that total hip patients reach levels found in the normal age-matched population ... The major problem remaining in total hip replacement is the bearing surface. Osteolysis caused by the biological reaction to wear debris remains a common mode of failure. Considerable improvement has been made in the wear resistance of bearing surfaces, most recently by the widespread adoption of highly cross-linked polyethylene for acetabular components. Randomized clinical trials comparing cross-linked to conventional polyethylene show reductions in wear and osteolysis [13], though follow-up is not long enough at this time to determine the impact of these improvements on the need for revision surgery. Like total hip replacement, total knee replacement has similar durable results up to 10 to 20 years [4, 8–20]. Unicondylar knee replacement, in which only one compartment is replaced, has similar outstanding results, at least in older patients, though younger patients have not fared as well at long-term follow-up [17]. As with hip replacement, wear and osteolysis are major issues, particularly with modular designs for which backside wear between the polyethylene insert and the metallic tray provides an added source of debris [14]. This appears to apply especially in young, active osteoarthritis patients [16]. Similarly, mobile-bearing designs which incorporate a second bearing surface between the tibial insert and the tibial tray have an excellent long-term survival, but osteolysis secondary to an increased burden of wear debris appears to increase with time [4]. Cementless fixation has not gained acceptance in total knee replacement as it has in total hip replacement, despite promising long-term results [10]. Osteotomies are another surgical treatment for osteoarthritis, aimed at realigning joint surfaces and thus delaying disease progression. Newer procedures for osteotomies around the hip are encouraging at mid-term follow-up, with acceptable complications when performed by well-trained surgeons [5]. Knee procedures include closing and opening wedge osteotomies performed in the proximal tibia. Closing wedge osteotomies have produced unpredictable results that are not always durable [15]. Newer opening wedge osteotomies may provide more durable and more predictable results, but no long-term follow-up is available.