Unicompartmental knee arthroplasty with the oxford prosthesis in patients with medial compartment arthritis.

BACKGROUND: The mobile-bearing feature of the Oxford unicompartmental knee replacement has the potential to optimize polyethylene wear, thereby leading to longer-term function of the implant. The function of the bearing requires intact soft tissues, with the ligaments being balanced throughout the range of motion intraoperatively through bone resection only. Final limb alignment is determined by the restored soft-tissue tension. The purposes of this study were to determine the limb alignment achieved in the absence of ligament release and to investigate the interplay of failure mode, survivorship, and limb alignment. METHODS: Fifty-five knees in fifty-one patients with medial compartment osteoarthritis had a unicompartmental replacement with an Oxford prosthesis. Evaluation included Knee Society clinical scores, radiographic evaluation, survivorship analysis, and modes of failure. The average duration of clinical follow-up was 11.8 years. Only two patients (three knees) were lost to follow-up. RESULTS: The mean postoperative Knee Society knee score and function score at the latest follow-up evaluation were 75 and 90 points, respectively. The overall alignment of the knee was restored to neutral, averaging 5.6 degrees of valgus alignment. Forty-seven of the fifty-five knees had the mechanical axis crossing the central 50% of the tibial plateau. Seven knees had revision surgery, and six of them required conversion to a total knee prosthesis. The main reason for revision was the progression of arthritis in the lateral compartment, which occurred in four knees at an average of 10.2 years postoperatively. These four knees had not been overcorrected into excessive valgus at the time of the original surgery, and we found no correlation, with the numbers studied, between alignment and bearing size. Survivorship analysis showed that the rate of survival at ten years was 85% with failure for any reason as the end point, 90% with progression of lateral compartment arthritis as the end point, and 96.3% with component loosening as the end point. CONCLUSIONS: With this unicompartmental knee arthroplasty, the mechanical limb alignment resulting from balancing the knee ligaments, accomplished without releasing them, was consistently through the center of the knee. Progression of arthritis in the lateral compartment was the most common reason for late failure in this series and was not related to the initial postoperative alignment.

A comparison of highly instrumented and minimally instrumented unicompartmental knee prostheses.

In this study, two specific implants are compared: the Oxford prosthesis, which uses a highly instrumented technique and was placed through a traditional arthrotomy; and the Repicci prosthesis, which uses a minimally instrumented technique and was placed with a minimally invasive surgical approach. The study looked specifically at limb alignment, because achieving appropriate alignment is correlated with the best long-term implant function and achieving alignment is a function of the implant instrumentation. The rationale of more instrumentation for a surgical technique is to add precision and reproducibility; less instrumentation requires less surgical exposure and therefore is more minimally invasive. The senior author presents his long-term experience with the Oxford implant (55 implants; average followup 10.4 years) and short-term experience with the Repicci implant (164 implants; average followup 1.3 years for the first 30 implants.). With available followup, the clinical results using both implants have been favorable. The average alignment of the Oxford prosthesis was 5.6 degrees valgus and the average alignment of the Repicci prosthesis was 4.5 degrees valgus. Side-to-side long-term comparison is not yet available, although the literature would suggest that both implants can have satisfactory long-term results. Specific implant selection probably is not as important as precise patient selection.

Clinical and radiographic analysis of the Mallory-Head femoral component in revision total hip arthroplasty. A minimum 8.8-year and average eleven-year follow-up study.

BACKGROUND: Although many designs of cementless femoral stems are available for revision hip arthroplasty, there is no consensus about which design features are required to achieve an optimal clinical outcome and maximum preservation of bone. The purpose of this study was to report the clinical and radiographic results for a specific design. METHODS: A selected series of 107 revision total hip arthroplasties with use of the Mallory-Head calcar-replacement prosthesis was reviewed with clinical and radiographic evaluation. The study group consisted of sixty-six hips (sixty patients), with an average follow-up of 11.5 years (range, 8.8 to 14.5 years). All revisions in this series were performed because of failure of a cemented or cementless femoral component of standard length. All revision stems were 220 mm long. RESULTS: Three of the 107 original stems demonstrated subsidence of 3, 7, and 9 mm. Two stems had definite loosening, resulting in a 1.9% rate of mechanical failure. The rate of survival was 94% with revision for any reason as the end point and 97.1% with revision because of mechanical failure (aseptic loosening) as the end point. The Harris clinical score was 49 points preoperatively and 80 points postoperatively. Radiographic analysis demonstrated that the average percentage of the diaphysis filled by the prosthesis was 86%. Fifty-four (88.5%) of the sixty-one hips with complete radiographic follow-up showed no stress-shielding on final radiographs, whereas seven hips (11.4%) showed some stress-shielding. CONCLUSIONS: This proximal load-bearing calcar-replacement design achieves reliable fixation and stability at intermediate-term follow-up. There is no deterioration in the clinical outcome or radiographic findings at an average of eleven years of follow-up. The prevalence of disuse osteopenia from stress-shielding is very low. Proper surgical technique includes maximum fill of the diaphysis of the femur, with contact of the collar on part of the proximal aspect of the femoral shaft.

A multimodality regimen for deep venous thrombosis prophylaxis in total knee arthroplasty.

Data indicate that deep venous thrombosis (DVT) occurs at the time of knee arthroplasty. Nevertheless, literature concerning DVT prophylaxis has only recently addressed this contention. This prospective study evaluated the efficacy of a perioperative prophylactic regimen. Between January 1996 and June 2001, 1,308 knees (964 surgeries) underwent total knee arthroplasty. Patients were treated routinely with intraoperative heparin (1000 units intravenous push before inflation of the tourniquet and 500 units at deflation), hypotensive epidural anesthesia (MAP 70-90), external pneumatic compression boots, and aspirin (325 mg, PO, BID for 6 weeks). Duplex venous ultrasonography was performed before discharge. DVT was detected in 4% of cases (1% proximal and 3% distal). Bleeding complications occurred in 1%, and perioperative medical complications occurred in 12%.

Comparison of a mobile with a fixed-bearing unicompartmental knee implant.

Two well-matched groups of patients with unicompartmental knee arthroplasties were compared. The first 51 knees were treated with a fixed-bearing knee implant and the second 50 knees were treated with a mobile meniscal-bearing implant. Followup was 7.7 years for the patients with fixed-bearing implants and 6.8 years for patients with mobile-bearing implants. Both groups functioned well clinically. Radiographic analysis with 3-foot standing views taken preoperatively showed both groups had an average varus alignment of -2 degrees. Postoperatively patients with fixed-bearing implants had an average +2.6 degrees alignment and the patients with mobile-bearing implants had +5.5 degrees alignment, which was significantly different. Survivorship analysis based on component loosening and revision showed a 99% survival for the meniscal-bearing implant and 93% survival for the fixed-bearing implant at 11 years. However, the fixed-bearing knee implants failed significantly more often because of tibial component failure, in six of eight knees, at an average of 6.3 years. The mobile-bearing implants showed a trend to fail because of arthritic degeneration in the lateral compartment, at an average of 10 years, although not statistically significant. The mobile-bearing implants had no tibial component failures. These differences may be attributable to implant design or surgical technique.

Comparison of a static with a mobile spacer in total knee infection.

Patients with infections of a total knee arthroplasty were stratified by medical status. Twenty-six knees in 26 patients treated with a static antibiotic-impregnated polymethylmethacrylate block spacer before 1995 were compared with 22 knees in 22 patients treated after 1995 with a mobile articulating spacer. Both groups were treated with 6 weeks of parenteral antibiotics and had reimplantation within 6 to 12 weeks after placement of the spacer. Followup for the patients who had block spacers was an average 7.5 years (range, 2.8-12.7 years), and followup for the patients with a mobile spacer was an average of 3.8 years (range, 2.6-6.4 years). Results showed that the patients with the mobile spacers had significantly better average range of motion at followup compared with patients who had block spacers (107.8 degrees compared with 93.7 degrees ). The reinfection rate was the same between the two groups at 36 months, 7.6% (two of 26) for the patients with block spacers and 9% (two of 22) for the patients with mobile spacers. Extended followup available for the patients who had block spacers revealed a late reinfection rate of 23% (six of 26) with a new organism. There was no difference in the reinfection rate, with new or old organisms, in healthy hosts compared with patients with as many as two medical problems.

A comparison of cemented and cementless titanium femoral components used for primary total hip arthroplasty: a radiographic and survivorship study.

Titanium has a low modulus of elasticity that makes it an attractive metal for femoral hip components. We directly compared 2 similar titanium stems, one cemented (n = 102 hips) and the other cementless (n = 78 hips), controlling for the most important surgical variables. The average radiographic follow-up was 6.7 and 7.0 years. Osteolysis below the joint line, zones 2 through 6, was 12.7% (13 of 102) in the cemented group and 0% in the cementless group (P<.001). There were 17 acetabular revisions in each study group. The cementless group had no femoral revisions, whereas 9 acetabular revisions in the cemented group had a simultaneous femoral revision (P=.005). Survivorship, defined as revision of the femur, was 84% for the cemented group and 100% for the cementless group at 10 years. Cementless titanium stems are more resistant to osteolysis and mechanical failure compared with similar cemented titanium stems.