Results of the Oxford Phase 3 mobile bearing medial unicompartmental knee arthroplasty from an independent center: 467 knees at a mean 6-year follow-up: analysis of predictors of failure.

A retrospective review of 467 Oxford UKAs was performed in 387 patients. Thirty-eight knees (8.1%) were revised to TKA at a mean of 49 months, most commonly for lateral compartment OA (47%). The 5-year cumulative survival using revision to TKA was 98.5%. Revisions required short stems in 26% and augments in 21% of cases. The mobile bearing dislocation rate was 0.64%. Correction of ≥3-5° from the preoperative alignment in a valgus direction was predictive of revision to TKA (P<.0001). Multivariate analysis revealed female gender (P=.002) also was associated with an increased risk of revision. Careful attention to the degree of mechanical axis correction with an overall maintained varus alignment may reduce revision rates for mobile bearing UKA.

Tumor endoprosthesis revision rates increase with peri-operative chemotherapy but are reduced with the use of cemented implant fixation.

Chemotherapy may reduce osseointegration of tumor endoprosthesis, while delaying chemotherapy may reduce survival. We studied the effects of chemotherapy and cemented fixation on tumor endoprosthesis survivorship with a retrospective analysis of 50 consecutive patients receiving lower limb salvage surgery. We compared rates of radiographic loosening/revision and effect of cement fixation between chemotherapy/no chemotherapy cohorts. Chemotherapy increased the total revision rate (HR = 3.8 [1-14], P = 0.033), but did not affect aseptic loosening. Cement fixation reduced revision for loosening (HR = 0.09 (0.008-0.98), P = 0.012) and showed less radiographic loosening (HR = 0.09 (0.02-0.51), P = 0.00066). Cement fixation had lower rates of revision for loosening and radiographic loosening regardless of whether chemotherapy was given. We conclude that for these implants, cement fixation provides superior results to uncemented fixation.

Reduction in bone volume resection with a newer posterior stabilized total knee arthroplasty design.

BACKGROUND: Posterior stabilized total knee arthroplasty requires an intercondylar notch to accommodate the cam housing that articulates with the tibial post to create femoral rollback required for deep flexion. The volume of bone resected for the intercondylar notch varies with implant design, and newer designs may accommodate high flexion with less bone resection. QUESTIONS/PURPOSES: This study aims to analyze the bone volume and density resected from the intercondylar notch for three posterior stabilized implants from a single company: a Posterior Stabilized (PS) system, a Hi-Flex system (HF), and a rounded new box-reamer (RB) system and to further assess whether the newer RB with a cylindrical cutting tool would preserve more native bone. MATERIALS AND METHODS: Using a computer model, the PS, HF, and RB femoral components were digitally implanted into CT scans of 19 cadaver femurs. Nine cadavers were fit with a size 4 implant, six with size 3, and four with a size 2. The volume of intercondylar bone resected digitally for femoral preparation was measured. Bone density was measured by CT scans in Hounsfield units (HU). A paired t test was used to compare the mean volume of bone resected for each implant. RESULTS: For the size 4 femurs, the newer RB design removed 8% less intercondylar bone than the PS design (7,832 ± 501 vs. 8,547 ± 377 mm(3), p < 0.001) and 28% less bone than the HF design (7,832 ± 501 vs. 10,897 ± 444 mm(3), p < 0.001). The average HU for size 4 femurs for RB design was 427 ± 72 (PS = 399 ± 69, p < 0.001; HF = 379 ± 66, p < 0.001). For the size 3 femurs, the RB design removed 12% less intercondylar bone than the PS (6,664 ± 786 vs. 7,516 ± 648 mm(3), p < 0.001) and 27% less bone than the HF (6,664 ± 786 vs. 9,078 ± 713 mm(3), p < 0.001). HU for size 3 femurs for the RB design was 452 ± 70 (PS = 422 ± 53, p < 0.1; HF = 410 ± 59, p < 0.01). For the size 2 femurs, the RB design removed 5% less intercondylar bone than the PS (5,730 ± 552 vs. 6,009 ± 472 mm(3), p < 0.01) and 22% less bone than the HF (5,730 ± 552 vs. 7,380 ± 532 mm(3), p < 0.001). HU for size 2 femurs for the RB design was 430 ± 48 (PS = 408 ± 55, p < 0.01; HF = 385 ± 56, p < 0.01). CONCLUSIONS: The newer RB design removes less bone from the intercondylar notch than the classic PS and HF designs in all sizes tested. The bone-conserving cuts incorporated into this newer implant design appear to preserve native bone without compromising design objectives.

Revision total knee arthroplasty: clinical outcome comparison with and without the use of femoral head structural allograft.

The use of femoral head structural allograft (FHSA) for the management of massive bony defects during revision total knee arthroplasty (TKA) is well documented in the literature. The purpose of this study was to compare the clinical outcomes of patients undergoing revision (TKA) with FHSA to those without. All patients undergoing revision TKA between January 2000 and August 2005 were reviewed. Two cohorts were generated: a study cohort--revision TKA using FHSA (n = 24)--and control cohort--revision TKA without FHSA (n = 48). The 2 study cohorts groups were comparable. All patients completed validated outcome questionnaires. The FHSA cohort was found to have significantly better outcome scores. This study demonstrates improved clinical outcomes for patients undergoing revision TKA using a structural allograft compared with those without.

Current concepts in instrumented knee-laxity testing.

BACKGROUND: Instrumented knee laxity testing devices have been used in both the clinical and research setting to evaluate persons with injuries about the knee. The ability to accurately and reproducibly quantify knee motion has the potential to greatly benefit both clinical practice and research by improving the validity of the research involving treatment of knee-ligament injuries. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: A thorough literature review was performed, and a systematic overview is provided evaluating the methods of use and the evidence for the use of instrumented knee laxity testing devices. RESULTS: Devices that provide measurements of knee laxity have evolved during the past 30 years. The authors describe in detail their proper use and the best estimates of their validity based on clinical studies. CONCLUSION: The review suggests that the KT-1000 knee arthrometer and the Rolimeter provide best results when testing anterior laxity at the knee, whereas the Telos device is superior for the assessment of posterior laxity.