The U.S. Census Bureau defines middle age from 45

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1 172 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & Surgical Management of the Middle Age Arthritic Knee Michael G. Dennis, M.D., and Paul E. Di Cesare, M.D. The U.S. Census Bureau defines middle age from 45 to 64 years; however, some suggest that it is better defined as 30 to 70 years. Patients who are middleaged are typically more active and less likely to present with systemic disease than are older patients, and their expectations of maintaining their current mobility are more reasonable. Middle-aged patients with osteoarthritis of the knee thus require a different approach and treatment algorithm. This review describes the surgical options and their indications (i.e., patient selection factors) appropriate for the middle-aged population, along with the success rates and survivorship. To be considered for surgery, the patient should have failed a trial of nonoperative management e.g., activity modification, anti-inflammatory medication, intraarticular injections, physical therapy, bracing and assistive devices. Surgical options are of two types: arthroscopy, including arthroscopic debridement, meniscectomy, and subchondral penetration procedures; and reconstruction, including osteotomy and arthroplasty. Techniques such as meniscal transplantation, osteochondral allografts and autografts, and autologous chondrocyte implantation are basically preventive measures for the pre-arthritic knee and thus are outside the scope of this review. Arthroscopy Arthroscopic treatment ranges from diagnostic procedures to aggressive debridement. Arthroscopic knee surgery is generally well tolerated and leads to shorter recovery times. Arthroscopy may delay or avoid more extensive procedures. Michael G. Dennis, M.D., and Paul E. Di Cesare, M.D., are in the Musculoskeletal Research Center, NYU-Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, New York. Reprint requests: Paul E. DiCesare, M.D., NYU-Hospital for Joint Diseases Department of Orthopaedic Surgery, 301 East 17th Street, New York, New York Burman, reporting on 10 cases in 1934, was the first to report relief of arthritic knee pain after arthroscopic lavage. As his instruments were too primitive to allow any form of debridement, his success was attributed to a mechanical washout phenomenon. 1 In 1941, Magnuson reported complete recovery in 60 out of 62 of his patients using what he termed joint debridement, an open procedure to remove hypertrophic synovium, osteophytes, loose bodies, and diseased cartilage. 2 Arthroscopic lavage, which became a standard procedure largely as a result of these early reports, entails the complete removal of the byproducts of joint degeneration particulate debris, degradative enzymes and mediators as well as the beneficial anesthetic effects of saline. 3,4 Livesley and colleagues 5 compared 37 painful arthritic knees treated with arthroscopic lavage and physical therapy to a control group of 24 knees treated with therapy alone and reported better relief in the lavage group at 1 year. Edelson and associates, 6 in a prospective study of the efficacy of lavage in 29 osteoarthritic knees, reported 86% good or excellent results at 1 year and 81% at 2 years. Additionally, many of their patients reported decreased use or complete cessation of their anti-inflammatory medications. Merchan and Galindo 7 randomized 80 patients into nonoperative and arthroscopic groups. They reported the surgery to be useful according to a knee rating system at a mean follow-up of 2 years, with a 75% improvement at last follow-up. Aichroth and coworkers, 8 in a prospective study of 254 arthroscopy patients, reported that 75% had improved function and 85% were satisfied with their surgery. Moseley and colleagues 9 performed a prospective, randomized, placebo-controlled, blinded pilot study including 10 patients with symptomatic knee osteoarthritis. Five patients had skin puncture wounds only, 3 underwent arthroscopic lavage, and 2 had standard arthroscopic debridement. All 5 puncture-wounds-only patients reported pain improvement at 6 months follow-up.

2 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & Four out of 5 judged the procedure to be worthwhile and recommended the procedure to family and friends. The patients in the lavage and debridement groups experienced similar results. Recently, Moseley and colleagues 10 reported on 180 patients who completed the study. He concluded that there was no difference in the outcomes between the arthroscopic and placebo treatment groups. Several patient factors have been studied in order to determine who stands to benefit most from arthroscopic surgery. Salisbury and associates 11 retrospectively reviewed 52 patients with more than 2 years follow-up to determine whether a correlation exists between clinical results from arthroscopic debridement and preoperative angular deformity. They reported that 94% of normally aligned knees were acceptable versus 32% acceptable results in varus knees. In other studies, valgus knees were reported to have the worst results after arthroscopic surgery. 12,13 Harwin, 14 in a retrospective review of 204 knees after arthroscopy, found that 63.2% (129 knees) were better after surgery. When he categorized his results based on alignment, however, 84.2% of the normally aligned knees were better. In contrast, those knees with less than 5 of deformity had a 67.6% improvement rate, whereas those with a greater degree of malalignment had only a 26.7% improvement rate. Other investigators have examined the possible correlation between outcome and joint space narrowing noted in the preoperative radiographic assessment. 3,12 Mild to moderate narrowing tended to correlate with improved results. 13,15 In their series, Anderson and colleagues 16 reported good or excellent results in 68% of knees with joint spaces greater than 1 mm as compared to only 29% in knees with less preservation of joint space. Patients with symptoms of one year or less had markedly higher success rates with arthroscopic surgery. One study demonstrated a 72% success rate in a patient group with symptoms of one year or less versus 39% in patients with symptoms of longer duration. Additionally, 50% of patients with symptoms of longer duration failed versus a 14% failure rate in those with symptoms of shorter duration. 13,15,17 Nature and quality of symptoms have also been shown to have prognostic value. Patients with mechanical symptoms achieved good or excellent results nearly double that of patients with load-type symptoms. 12,15 In a separate series, a history of locking or twisting injury was shown to have a beneficial effect on subjective outcome. 13 Younger patient age significantly correlated with better outcome in one series. There was a 78% satisfaction rate in patients of less than 60 years of age versus 55% in the 60 year or older group. 8 Other investigators, however, have not found this correlation. 13,18 A history of previous knee surgery has been shown to have a negative effect on subjective outcome. 13 Ogilvie-Harris and Fitsialos 12 also reported a decreased success rate in patients with prior procedures: 61% of patients with prior surgery (mostly meniscectomies) had good results for more than two years; at four years follow-up, only 37% still had good results. Arthroscopic removal of unstable meniscal fragments has been shown to be beneficial. Aichroth and coworkers 8 reported 86% good to excellent results in patients with meniscal tears at 44 months. Rand 19 reported an 84% improvement rate in his series of 87 knees with meniscal tears at two years follow-up. Jackson and Rouse 18 were the first to report on partial arthroscopic meniscectomy in an older patient population (mean age: 53 years). They categorized 73 knees with meniscal tears based on the presence of degenerative changes. At 2.5 years follow-up, they reported 95% good or excellent results in those knees without degenerative findings and 80% good to excellent result in knees with degenerative changes. In a similar study, McBride and colleagues 20 compared the results of traumatic and degenerative meniscal tears at three years follow-up. Arthroscopic meniscectomy of traumatic tears resulted in a 95% success rate versus a 65% success rate in patients with degenerative tears. Pridie 21 popularized the concept of the subchondral penetration procedure. The objective is to drill through eburnated bone in order to stimulate reparative cartilage formation. This is performed as an open procedure and consists of debridement and drilling that leads to a fibrocartilage covering. He reported a 74% success rate in 62 knees. In a more recent series, Johnson 22 published a 78% improvement rate at two years follow-up in 95 knees after arthroscopic abrasion. Additionally, he reported that the fibrocartilage maintained its integrity with the host hyaline cartilage for up to six years. Steadman 23 reported a 75% improvement at three- to five-year follow-up using a microfracture technique. Other reports, however, demonstrated less favorable outcomes with these techniques. Rand, 3 who followed a group of patients with full-thickness cartilage defects, reported a 77% improvement rate in his debridement group versus a 39% improvement in his abrasion arthroplasty group. Furthermore, 57% of the patients in his abrasion group underwent total knee replacement within three years after surgery. Bert and Maschka 24 compared debridement and abrasion (59 patients) to debridement alone (67 patients); 51% of the abrasion group had good or excellent results at five years follow-up versus 66% good or excellent results in the debridement group. The results of several long-term studies of arthroscopic management of the degenerative knee are similar in the short term, with reported success rates in excess of 85% at three years follow-up. After that success rates decline to between 50% and 67%. 3,7,12,13 This trend has prompted some to evaluate the role of repeat arthroscopy. One such study reported subsequent arthroscopic debridements to yield much poorer results. Unless symptoms suggest the development of a new mechanical lesion, repeat arthroscopy may be difficult to justify. 12

3 174 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & High Tibial Osteotomy Valgus-producing high tibial osteotomy (HTO) is designed to treat varus knee deformities (Fig. 1). It is ideal for younger, more active individuals. Activities that may be inappropriate after total knee replacement surgery are possible for patients with proximal tibial osteotomy. 25,26 The lateral closing wedge osteotomy is the most popular method for varus deformities of more than 12 ; however, other options, such as the medial opening wedge, dome type, and supracondylar femoral osteotomy, are available to address more extensive deformities. The indications for high tibial osteotomy include unicompartmental arthritis confined to the medial side, age of less than 60 years, 10 to 12 varus deformity, arc of motion of at least 90, and flexion contracture of less than ,28 Contraindications to this procedure include more than 20 of needed correction, lateral tibial subluxation of less than 1 cm, medial bone loss of greater than 2 to 3 mm, panarthrosis, inflammatory arthritis, ligamentous instability, and lateral joint space narrowing on stress radiographs. 29,30 Coventry, 29 who popularized the concept of the HTO in America, reported on his long-term results in 213 patients: 61% had less pain and 65% had better function at 10 years follow-up. Nagel and colleagues 25 retrospectively reviewed 37 knees for a mean follow-up of eight years. Many patients were able to participate in active sports; 82% felt that the results met their expectations and would have the same operation again. Holden and colleagues 26 reported 70% good or excellent results at 10 years follow-up in 51 knees (patient mean age: 41 years). Their patients maintained a satisfying level of recreation. Additionally, they reported a positive correlation with improved result and increased angle of correction. In a more recent and longer-term follow-up study, Rinonapoli and associates 28 followed 60 knees in patients with a mean age of 61 years for a mean of 15 years (range: 10 to 21 years). There were 73.5% excellent or good results at 14 years. At 15 years or longer, there were 46% excellent or good results. Insall and coworkers 31 followed 95 knees for a mean of 8.9 years and reported 97% excellent or good results at two years. An excellent or good result was reported by 85% of patients at five years and by 63% at final followup. These investigators concluded that time was the most important factor in determining the result. In a similar study in Finland, 103 knees were followed for a mean of 6.9 years. At two years, there were 91% excellent or good results. At nine years, the number of good or excellent results declined to 73%. 32 Postoperatively, slight overcorrection to 8 to 10 of valgus is desirable. 30 Recurrence of varus deformity and osteoarthritis progression occurred in those knees that were undercorrected in one study. 33 Furthermore, an increased revision rate has been demonstrated in knees that were undercorrected. 34,35 Arthroscopy may be used to define the degree of lateral or patellofemoral arthrosis. Additionally, it may be of benefit Figure 1 in addressing concomitant intraarticular pathology such as loose bodies and meniscal tears. 30 One study that used arthroscopy to preoperatively evaluate patients for high tibial osteotomy, however, found arthroscopy to be a poor predictor of success following HTO. 36 In one study of patient factors performed in order to determine proper selection criteria for proximal tibial osteotomy, patients greater than 60 years of age had only a 52% good or excellent success rate versus 74% for patients 60 years of age or younger, 31 while another study found that patients over 60 had the same percentage of good or excellent results as younger patients. 36 The osteotomy is technically more difficult, as is postoperative immobilization, in obese patients. In their series, Coventry and colleagues 37 noted worse long-term results in patients who weighed more than 1.3 times their ideal body weight. Cosmetic concerns are one of the most common reasons for undercorrection. This can be particularly troublesome for some women. 25 It is imperative to inform the patient of the potential for asymmetric appearance (increased knock knee deformity) of the limbs after corrective surgery. A correlation has been observed between length of follow-up and varus recurrence with progression of osteoarthritis. 36 In one series, Stuart and assocates 38 noted that a 4% incidence of varus recurrence of greater than 5 at five years increased to 18% at nine years and established a correlation between the presence of pain and varus recurrence. Complications of proximal tibial osteotomy include nonunion, infection, peroneal nerve palsy, patella baja and infrapatellar scarring, under/overcorrection, intraarticular fracture, limb shortening, venous thrombosis, lateral ligament laxity, and popliteal artery injury. 28,31,32,37

4 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & Reported rates of revision of total knee replacement after HTO range from 10% to 20%. 35,39 The revision procedure is technically demanding; among the difficulties often encountered are patella baja, offset of tibial plateau from tibial shaft, prior skin incisions, previous fixation implants, increased blood loss, and difficulties with surgical exposure. Eversion of the patella is particularly difficult, and there is an increased risk of tubercle avulsion. 31,34 There is a lack of consensus in the literature with regard to the success rate of revision surgery. Several studies report results comparable to those of primary total knee replacement, 27,34,39,40 while other studies report inferior results. 41,42 Unicompartmental Knee Arthroplasty Unicompartmental knee arthroplasty (UKA), which has been performed since the 1970s, is considered by many to be an attractive alternative to osteotomy or total knee replacement surgery. It remains a controversial procedure, however, with respect to indications, survivorship, and conversion to total knee replacement (Fig. 2). Indications for unicompartmental replacement include unicompartmental arthritis, a 90 arc of motion, minimal flexion contracture (less than 5 ), and malalignment of less than Contraindications include inflammatory arthritides, panarthrosis, deformity of greater than 20, and absence of anterior cruciate ligament. Several investigators report contralateral and patellofemoral compartment disease to be relative contraindications. Less severe degenerative changes do not preclude UKA There are several advantages of unicompartmental knee replacement over total knee replacement. First, the cruciate ligaments are preserved, thereby allowing for improved proprioception and near-normal kinematics. 43,49,50 Several studies have demonstrated more rapid recovery and rehabilitation periods, less blood loss, and decreased incidence of deep venous thrombosis. Lastly, preservation of bone stock in the patellofemoral and contralateral compartments theoretically allows for easier revision to total knee replacement. 51,52 When compared to osteotomy, UKA has several advantages. There is a higher initial success rate and fewer early complications. 53,54 Internal derangements are easily addressed in the course of the procedure, as is intraarticular debridement. The undesirable postoperative valgus deformity often seen with proximal tibial osteotomy is avoided with unicompartmental replacements, and, as Kozinn 43 has noted, bilateral procedures are facilitated. Early reports of results of unicompartmental arthroplasty were disappointing, which undoubtedly sparked the controversy that surrounds UKA to the present. In 1978, Laskin, 55 studying 37 UKA patients with two years minimum followup, reported that only 65% had significant pain relief. Two years later, Insall and Aglietti 56 reported on 22 knees at six years follow-up; 36% had good or excellent results, and 28% were revised to total knee replacements. More recent reports have been much more favorable in Figure 2 Unicompartmental knee replacement. terms of patient satisfaction and survivorship. Kozinn and colleagues 43 reported a 92% good to excellent outcome at a mean follow-up of 5.5 years. Thornhill and colleagues 50 reported a 91% survival at nine years. Reports outside the United States have also been favorable. Olsen and associates 57 reported on 31 patients with 97% favorable results at a mean follow-up of 4.5 years. Mackinnon and coworkers 58 reported 90% excellent results with regard to pain relief at five years after surgery. Murray and associates, 45 studying 143 Oxford meniscal-bearing unicompartmental arthroplasties at a mean follow-up of 10 years, reported 98% implant survival. Tabor and Tabor, 44 in a long-term retrospective review of 67 knees, reported a 91%, 84%, and 79% implant survival rate at 5, 10, and 15 years, respectively; none of their revisions required supplemental bone grafting. The early experience with unicompartmental knee replacements led surgeons to reserve this procedure for older, less active patients. The mean age in successful series was 65 to 70 years. A higher failure rate was reported in patients less than 50 years of age. Increased activity level was believed to lead to excessive wear and loosening of the components. 48,59 Recent studies, however, have demonstrated that a younger patient age is not a contraindication to unicompartmental arthroplasty. 46 Schai and coworkers, 60 in their series of 28 knees with a mean patient age of 52 years (range: 37 to 60 years), reported a 90% good or excellent outcome with respect to both function and pain relief. Their patients achieved 124 mean knee flexion. In another study reviewing the results in a younger patient population, Engh and colleagues 61 reported an 80% success rate at 10 years follow-up in 49 patients ranging in age from 40 to 60. In a longer-term study performed by Tabor and Tabor, 44 survivorship and functional outcome

5 176 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & were not affected by patient age at time of surgery. An association has been reported between failure of unicompartmental arthroplasty and an absent or damaged anterior cruciate ligament: knees without a functional ACL failed 10 times more often, primarily due to loosening of the tibial component. 45,62 Patients who have more extensive degenerative joint involvement of the contralateral and patellofemoral compartments are also at increased risk for failure. Proper patient selection is thus a crucial factor in avoiding UKA failure. Polyethylene wear and aseptic loosening are the most common modes of UKA implant failure. Other causes of failure in UKA include degeneration of the uninvolved compartments, pes anserine bursitis, and infection. 47 Early implant designs used metal-backed tibial components, which led to increased polyethylene wear. Additionally, narrow femoral components led to subsidence. 53 Newer implant designs have minimized these complications, as has refinement of surgical technique: as opposed to conventional practice in high tibial osteotomy, in UKA the deformity should not be overcorrected, as overcorrection can hasten contralateral compartment arthrosis. 63 Several studies have compared unicompartmental arthroplasty with total knee replacement. Laurencin and associates 51 followed 23 patients with both a UKA and TKR implanted for a mean of 6.75 years. The knees with unicompartmental replacement had better ranges of motion (averaging 123 ), and 96% of UKAs were either painless or had slight discomfort, as compared to 83% of total knee replacements. Furthermore, patients more frequently chose their UKA side as the better feeling knee. In a similar study, Cobb and colleagues, 64 reporting on 42 patients who had both a unicompartmental knee replacement and a total knee replacement at a mean follow-up of 6.5 years, concluded that UKA allowed for better range of motion, function, and overall feel. In a randomized, prospective trial, Newman 52 followed 102 knees in patients who had either a UKA or a total knee replacement for a mean of five years. The unicompartmental group had a higher rate of excellent results (76% versus 57%), increased range of motion, decreased time to regaining range of motion, shorter hospital stay, and less perioperative morbidity. Several studies of revision of unicompartmental knees to total knee replacements have concluded that it is a technically demanding procedure. Bone loss is the major problem, and many knees will require bone grafting or metal augmentation wedges. Nevertheless, in the hands of an experienced surgeon, results comparable to those of primary total knee replacement have been achieved. 54,61,65 Total Knee Arthroplasty While total knee arthroplasty has been demonstrated to be a durable and predictable procedure in older patients, providing pain relief, improved function, and deformity correction, the advisability of performing this procedure in younger patients is less clear. A major concern is implant loosening and the attendant potential need for multiple revisions. Several studies reviewing the outcomes of total knee arthroplasty in younger patients with rheumatoid arthritis have reported favorable results It nevertheless remains questionable whether results of TKA in a young rheumatoid population can be applied to younger noninflammatory arthritis patients. Among the few studies of total knee replacement surgery for the middle-aged osteoarthritic knee, Stern and colleagues, 70 reporting on 68 knees with a mean patient age of 50 years, found 55 excellent and 13 good results at over six years follow-up. Diduch and colleagues, 71 following 103 knees with a mean patient age of 51 years for eight years mean followup (range: 3 to 18 years), reported 90% survivorship at 18 years; 18% of their patients activity scores indicated that they regularly participated in strenuous activities or work. Summary There are several options available for management of the middle-aged arthritic knee. Arthroscopic techniques continue to evolve, but the true natural history of the arthritic process is probably not altered. Good to excellent shortterm results can be expected with proper patient selection. Patient counseling is important in order to discuss the nature of the underlying disease process, the limited goals of the arthroscopic procedure, and the possible need for further surgery. Proximal tibial osteotomy for the treatment of medial compartment osteoarthritis can be effective for as long as 15 years. There is a deterioration of results over time that can often be correlated to the degree of correction achieved. Strict selection criteria can maximize success. Revision surgery to total knee replacement, albeit technically difficult, is a viable option with results similar to primary TKR. Unicompartmental knee arthroplasty remains a controversial procedure as its indications continue to evolve. Good to excellent results can be expected in 80% to 90% of patients at 10 years follow-up. Unicompartmental knee arthroplasty occupies a special niche in the treatment of unicompartmental osteoarthritis and supplements total knee replacement and high tibial osteotomy surgery. References 1. Burman MS, Finkelstein H, Mayer L: Arthroscopy of the knee joint. J Bone Joint Surg 16: , Magnuson PB: Joint debridement: surgical treatment of degenerative arthritis. Surg Gyn Obstet 73:1-9, Rand JA: Role of arthroscopy in osteoarthritis of the knee. Arthroscopy 7: , Stuart MJ: Arthroscopic management for degenerative arthritis of the knee. AAOS Instructional Course Lectures 48: , Livesley PJ, Doherty M, Needoff M, et al: Arthroscopic lavage of osteoarthritic knees. J Bone Joint Surg 73B: , Edelson R, Burks RT, Bloebaum RD: Short term effects of knee washout for osteoarthritis. Am J Sports Med 23: , 1995.

6 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & Merchan EC, Galindo E: Arthroscope-guided surgery versus nonoperative treatment for limited degenerative osteoarthritis of the femorotibial joint in patients over 50 years of age: a prospective comparative study. Arthroscopy 9: , Aichroth PM, Patel DV, Moyes ST: A prospective review of arthroscopic debridement for degenerative joint disease of the knee. Inter Orthop 15: , Moseley JB, Wray NP, Kuykendall D, et al: Arthroscopic treatment of osteoarthritis of the knee: a prospective, randomized, placebo-controlled trial. Am J Sports Med 24:28-34, Moseley JB, O Malley K, Petersen NJ, et al: A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med 347:81-88, Salisbury RB, Nottage WM, Gardner V: The effect of alignment on results in arthroscopic debridement of the degenerative knee. Clin Orthop 198: , Ogilvie-Harris DJ, Fitsialos DP: Arthroscopic management of the degenerative knee. Arthroscopy 7: , Wouters E, Bassett FH, Hardaker WT, et al: An algorithm for arthroscopy in the over-50 age group. Am J Sports Med 20: , Harwin SF: Arthroscopic debridement for osteoarthritis of the knee: predictors of patient satisfaction. Arthroscopy 15: , Baumgaertner MR, Cannon WD, Vittori JM, et al: Arthroscopic debridement of the arthritic knee. Clin Orthop 253: , Anderson JK, Goldstein WM: Arthroscopy in patients over the age of 50 years. Am J Arthroscopy 1:15-18, Timoney JM, Kneisl JS, Barrack RL, et al: Arthroscopy in the osteoarthritic knee: long-term follow-up. Orthop Rev 19: , Jackson RW, Rouse DW: The results of partial arthroscopic meniscectomy in patients over 40 years of age. J Bone Joint Surg 64B: , Rand JA: Arthroscopic management of degenerative meniscus tears in patients with degenerative arthritis. Arthroscopy 1: , McBride GG, Constine RM, Hofmann AA, et al: Arthroscopic partial meniscectomy in the older patient. J Bone Joint Surg 66A: , Pridie AH: A method of resurfacing osteoarthritic knee joints. J Bone Joint Surg 41B: , Johnson LL: Arthroscopic abrasion arthroplasty historical and pathological perspective: present status. Arthroscopy 2:54-69, Steadman JR: Microfracture technique for full thickness chondral defects. Operative Tech Bert JM, Maschka K: The arthroscopic treatment of unicompartmental gonarthrosis: a five-year follow-up study of abrasion arthroplasty plus arthroscopic debridement and arthroscopic debridement alone. Arthroscopy 5:25-32, Nagel A, Insall JN, Scuderi GR: Proximal tibial osteotomy: a subjective outcome study. J Bone Joint Surg 78A: , Holden DL, James SL, Larson RL, et al: Proximal tibial osteotomy in patients who are fifty years old or less: a long-term follow-up study. J Bone Joint Surg 70A: , Bergenudd H, Sahlström A, Sanzén L: Total knee arthroplasty after failed proximal tibial valgus osteotomy. J Arthroplasty 12: , Rinonapoli E, Mancini GB, Corvaglia A, et al: Tibial osteotomy for varus gonarthrosis: a 10- to 21- year follow-up study. Clin Orthop 353: , Coventry MB: Upper tibial osteotomy for gonarthrosis: the evolution of the operation in the last 18 years and long-term results. Orthop Clin North Am 10: , Port J, DiGioia AM, Kwoh CK, et al: A technique for valgus high tibial osteotomy. Am J Knee Surg 6: , Insall JN, Joseph DM, Msika C: High tibial osteotomy for varus gonarthrosis: a long-term follow-up study. J Bone Joint Surg 66A: , Vainionpää S, Läike E, Kirves P, et al: Tibial osteotomy for osteoarthritis of the knee: a five to ten-year follow-up study. J Bone Joint Surg 63A: , Hernigou P, Medevielle D, Debeyre J, et al: Proximal tibial osteotomy for osteoarthritis with varus deformity: a 10 to 13 year follow-up study. J Bone Joint Surg 66A: , Takai S, Yoshino N, Hirasawa Y: Revision total knee arthroplasty after failed high tibial osteotomy. Bull Hosp Joint Dis 56: , Odenbring S, Egund N, Knutson K, et al: Revision after osteotomy for gonarthrosis: a year follow-up of 314 cases. Acta Orthop Scand 61: , Keene JS, Monson DK, Roberts JM, et al: Evaluation of patients for high tibial osteotomy. Clin Orthop 243: , Coventry M, Ilstrup D, Wallrich S: Proximal tibial osteotomy: a critical long-term study of eighty-seven cases. J Bone Joint Surg 75A: , Stuart MJ, Grace JN, Ilstrup DM, et al: Late recurrence of varus deformity after proximal tibial osteotomy. Clin Orthop 260:61-65, Amendola A, Rorabeck CH, Bourne RB, et al: Total knee arthroplasty following high tibial osteotomy for osteoarthritis. J Arthroplasty 4:S11-S17, Staheli JW, Cass JR, Morrey BF: Condylar total knee arthroplasty after failed proximal tibial osteotomy for osteoarthritis. J Bone Joint Surg 69A:28-31, Katz MM, Hungerford DS, Krackow KA, et al: Results of total knee arthroplasty after failed proximal tibial osteotomy for osteoarthritis. J Bone Joint Surg 69A: , Mont MA, Antonaides S, Krackow K, et al: Total knee arthroplasty after failed high tibial osteotomy for osteoarthritis: a comparison with a matched group. Clin Orthop 299: , Kozinn SC, Scott R: Unicondylar knee arthroplasty. J Bone Joint Surg 71A: , Tabor OB, Tabor OB: Unicompartmental arthroplasty: a long term follow-up study. J Arthroplasty 13: , Murray DW, Goodfellow JW, O Connor JJ: The Oxford medial unicompartmental arthroplasty. J Bone Joint Surg 80B: , Murray DW: Unicompartmental knee replacement: now or never? Orthopedics 23: , Kitziger KJ, Lotke PA: Unicompartmental knee arthroplasty. Instr Course Lect 41:95-100, Marmor L: Unicompartmental knee arthroplasty: ten- to 13-

7 178 Bulletin Hospital for Joint Diseases Volume 61, Numbers 3 & year follow-up study. Clin Orthop 226:14-20, Rougraff BT, Heck DA, Gibson AE: A comparison of tricompartmental and unicompartmental arthroplasty for the treatment of gonarthrosis. Clin Orthop 273: , Thornhill RS, Scott R: Unicompartmental total knee arthroplasty. Orthop Clin North Am 20: , Laurencin CT, Zelicof SB, Scott RD, et al: Unicompartmental versus total knee arthroplasty in the same patient: a comparative study. Clin Orthop 273: , Newman JH, Ackroyd CE, Shah NA: Unicompartmental or total knee replacement? Five year results of a prospective, randomised trial of 102 osteoarthritic knees with unicompartmental arthritis. J Bone Joint Surg 80B: , Scott RD, Santore R: Unicondylar unicompartmental replacement for osteoarthritis of the knee. J Bone Joint Surg 62A: , Jackson M, Sarangi PP, Newman JH: Revision total knee arthroplasty: comparison of outcome following primary proximal tibial osteotomy or unicompartmental arthroplasty. J Arthroplasty 9: , Laskin RS: Unicompartmental tibiofemoral resurfacing arthroplasty. J Bone Joint Surg 60A: , Insall J, Aglietti P: A five to seven-year follow-up of unicondylar arthroplasty. J Bone Joint Surg 63A: , Olsen NJ, Ejsted R, Krogh P: St. Georg modular knee prosthesis: a two-and-a-half to six year follow-up. J Bone Joint Surg 68B: , MacKinnon J, Young S, Baily RA: The St. Georg sledge for unicompartmental replacement of the knee: a prospective study of 115 cases. J Bone Joint Surg 70B: , Jones WT, Bryan RS, Peterson LF, et al: Unicompartmental knee arthroplasty using polycentric and geometric hemicomponents. J Bone Joint Surg 63A: , Schai PA, Suh JT, Thornhill TS, et al: Unicompartmental knee arthroplasty in middle-aged patients: a 2- to 6- year follow-up evaluation. J Arthroplasty 13: , Engh GA, McAuley JP: Unicondylar arthroplasty: an option for high-demand patients with gonarthrosis. Instr Course Lect 48: , Goodfellow JW, Kershaw CJ, Benson MK, et al: The Oxford knee for unicompartmental osteoarthritis. J Bone Joint Surg 70B: , Kennedy W, White R: Unicompartmental total knee arthroplasty of the knee: postoperative alignment and its influence on overall results. Clin Orthop 221: , Cobb AG, Kozinn SC, Scott RD: Unicondylar or total knee replacement: the patient s preference. J Bone Joint Surg 72B:166, Gill T, Schemitsch EH, Brick GW, et al: Revision total knee arthroplasty after failed unicompartmental knee arthroplasty or high tibial osteotomy. Clin Orthop 321:10-18, Boublik M, Tsahakis PJ, Scott RD: Cementless total knee arthroplasty in juvenile onset rheumatoid arthritis. Clin Orthop 286:88-93, Dalury DF, Ewald FC, Christie MJ, et al: Total knee arthroplasty in a group of patients less than 45 years of age. J Arthroplasty 10: , Duffy GP, Trousdale RT, Stuart MJ: Total knee arthroplasty in patients 55 years old or younger: 10 to 17 year results. Clin Orthop 356:22-27, Ranawat CS, Padgett DE, Ohashi Y: Total knee arthroplasty for patients younger than 55 years. Clin Orthop 248:27-33, Stern SH, Bowen MK, Insall JN, et al: Cemented total knee arthroplasty for gonarthrosis in patients 55 years old or younger. Clin Orthop 260: , Diduch DR, Insall JN, Scott WN, et al: Total knee replacement in young active patients. J Bone Joint Surg 79A: , 1997.