Background Lateral flap numbness is a known side-effect of midline skin incision in total knee arthroplasty (TKA) and a cause of patient dissatisfaction. Anterolateral incision is an alternative approach which preserves the infrapatellar branches of the saphenous nerve and avoids numbness. Studies have compared both incisions, but in different patients. However, different patients may assess the same sensory deficit dissimilarly, because of individual variations in anatomy and healing responses. We compared the two incisions in the same patient at the same time, using an anterolateral incision on one knee and a midline incision on the other knee in simultaneous bilateral TKA. Other surgical steps including medial arthrotomy were idential. We also correlated subjective and objective findings. Materials and methods Twenty patients were prospectively randomized. Sensory loss and skin healing were assessed at 6, 12 and 52 weeks. Subjective preference for the knee with less numbness was charted on Wald's Sequential Probability Ratio Test. Sensation scores for touch, vibration, static and moving two-point discrimination were measured. Scar healing was evaluated using the Patient and Observer Scar Assessment Scale (POSAS). Functional scores were measured. Results A statistically significant difference favoring knees with anterolateral incision was observed in patient preference at all assessment points and this correlated with sensation scores. A statistically significant difference was observed in POSAS score favoring knees with anterolateral incision at 6 and 12 weeks which became statistically insignificant at 1 year. Functional scores remained comparable. Conclusion We recommend anterolateral incision as a safe and effective method to circumvent the problem of lateral flap numbness with midline incision. Level of evidence I.
Rotating-platform knee implants have successively undergone modifications to improve postoperative flexion. The cruciate-sacrificing Low Contact Stress (LCS) implant (DePuy Orthopaedics, Inc, Warsaw, Indiana) was modified into the cruciate-substituting PFC Sigma RP (ΣRP) implant and further into the PFC Sigma RPF (ΣRPF) implant (DePuy Orthopaedics, Inc). The goal of this study was to determine whether these modifications improved postoperative flexion. Postoperative flexion at 2 years was compared against preoperative flexion with regard to the general demographics of each group.Statistical analysis showed that the pre- to postoperative flexion changes achieved by the ΣRP (14.6°) and the ΣRPF (2.9°) were better (P<.001) than that achieved by the LCS (-10.3°); however, between the ΣRP (14.6°) and the ΣRPF (2.9°), the change was statistically insignificant (P=.045). In subgroups with preoperative flexion less than 125°, postoperative flexion achieved was 100.1° with the LCS, 119.8° with the ΣRP, and 121.3° with the ΣRPF. The difference between the ΣRP and ΣRPF and the LCS was statistically significant (P<.001), but between the ΣRP and the ΣRPF was statistically insignificant (P=.621). In subgroups with preoperative flexion 125° or more, postoperative flexion was 125° with the LCS, 132° with the ΣRP, and 130° with the ΣRPF, with no significant difference between groups (P=.416). Both cruciate-substituting designs produced better postoperative flexion than the cruciate-sacrificing design. The ΣRP, despite less preoperative flexion (P=.004), achieved statistically better postoperative flexion than the LCS (P<.001). In subgroups with comparable preoperative flexion, no statistical difference in postoperative flexion was achieved by the ΣRP and the ΣRPF.
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