Better accuracy and reproducibility of a new robotically-assisted system for total knee arthroplasty compared to conventional instrumentation: a cadaveric study.

PURPOSE: Robotically-assisted total knee arthroplasty (TKA) has been shown to improve alignment and decrease outliers, an important goal in TKA procedures. The purpose of this cadaveric study was to compare the accuracy and reproducibility of a recently introduced TKA robotic system to conventional instrumentation for bone resections. METHODS: This cadaveric study compared 14 robotically-assisted TKA with 20 conventional TKAs. Four board-certified high volume arthroplasty surgeons with no prior experience in robotics (except one) performed the procedures with three different implant systems. Angle and level of bone resections obtained from optical navigation or calliper measurements were compared to the intra-operative plan to determine accuracy. Group comparison was performed using Student t test (mean) and F test (variance), with significance at p < 0.05. RESULTS: The robotic group demonstrated statistically more accurate results (p < 0.05) and fewer outliers (p < 0.05) than conventional instrumentation when aiming for neutral alignment. Final limb alignment (HKA) had an accuracy of 0.8° ± 0.6° vs 2.0° ± 1.6°, with 100% vs 75% of cases within 3° and 93% vs 60% within 2°. For the robotically-assisted knees, the accuracy of bone resection angles was below 0.6° with standard deviations below 0.4°, except for the femur flexion (1.3° ± 1.0°), and below 0.7 mm with standard deviations below 0.7 mm for bone resection levels. CONCLUSION: This in vitro study has demonstrated that this novel TKA robotic system produces more accurate and more reproducible bone resections than conventional instrumentation. It supports the clinical use of this new robotic system. LEVEL OF EVIDENCE: Cadaveric study, Level V.

Midterm clinical and radiographic results of the medial pivot total knee system.

PURPOSE: The ADVANCE® Medial Pivot Knee System was designed with a highly congruent medial compartment and a less conforming lateral compartment to more closely mimic the kinematics of the normal knee. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of this total knee arthroplasty (TKA) system. METHODS: Between January 1998 and December 2006, 421 primary TKAs were performed in 373 subjects using this system and a surgical technique that resects the posterior cruciate ligament. Of these, 365 TKAs in 320 subjects were available for a follow-up visit occurring at a mean of 5.3 years. Subjects were evaluated using Knee Society Scores, range of motion, and radiographic review. RESULTS: The average Knee Society clinical score was 95.5 at final follow-up, with 358 (98%) TKAs having excellent or good results. Range of motion increased from a preoperative mean of 115 to 119° at final follow-up. Component survivorship, excluding revisions for infection or trauma, was 96.6% at five years. CONCLUSIONS: This study demonstrates subjects implanted with the ADVANCE® Medial Pivot Knee System achieved satisfactory clinical and radiographic midterm outcomes.

Changes in load distribution in the knee after opening-wedge or closing-wedge high tibial osteotomy.

The treatment of unicompartmental osteoarthritis of the knee by high tibial osteotomy has been carried out by closing-wedge osteotomy. The advantages for opening-wedge osteotomy are ease of procedure and improved correction with comparable short-term to midterm results. It is not known how the opening-wedge high tibial osteotomy procedure alters the load distribution between the medial and lateral compartments of the knee. The current biomechanical study investigated opening-wedge vs closing-wedge osteotomies in 5 pairs of cadaver knees. The results showed that at 5 degrees osteotomy, the closing-wedge provided superior results of load transfer from medial to lateral compartment than that seen with opening-wedge, but at 10 degrees osteotomy, there was no significant difference in load transfer in the knee compartments between the 2 surgery modes.