Emrick Sen Hui Quah, Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Jln Tan Tock Seng, Singapore. E-mail: emrickquah@gmail.com
Abstract
Introduction: Unlike in total knee arthroplasties, the rates of lateral flap numbness following medial unicompartmental knee arthroplasty (MUKA) and its impact on outcomes are not well-studied. Our study aims to investigate the prevalence and extent of numbness following MUKA and its impact on 2-year patient-reported outcomes. The study also aims to explore factors that predict recovery of lateral skin flap numbness following MUKA.
Methods: This level 3 prospective cohort study involved 20 patients (21 MUKAs) over a 2-year follow-up period. The area of pinprick and fine touch numbness around the knee were measured at 1- and 2-year post-MUKA. Pre-operative, 3 months, 1 year, and 2 years post-surgery Knee Society Scores (KSS) and 36-item short form survey scores were also obtained.
Results: The incidence of pinprick and fine touch numbness was 52% and 48% at 2 years, respectively. Between the 1st and 2nd year post-MUKA, the median area of numbness to fine touch sensation improved from 100 (interquartile range [IQR], 554) to 0 mm2 (IQR, 180), P = 0.008. Area of numbness to pinprick sensation also showed statistically significant improvement from median area 156 (IQR, 1079) to 43 mm2 (IQR, 279), P < 0.001. The recovery of numbness was not correlated with the patient’s age, body mass index (BMI), incision length, thigh or calf girth (P > 0.05). There was also no statistically significant correlation between recovery of numbness and improvement in patient-reported outcome measures (PROMs) (KSS, mental component score, physical component score) (P > 0.05).
Conclusion: Our study demonstrated that following MUKA, there is a significant proportion of patients that experience lateral flap numbness. Reassuringly, this numbness improves significantly over time and PROMs continue to improve significantly. Patient’s age, BMI, or incision length was not predictors for subsequent recovery of lateral skin flap numbness in patients with persistent numbness after 1-year post-MUKA.
Keywords: Medial unicompartmental knee arthroplasty, numbness, functional outcomes, outcome measures (patient-reported outcome measure).
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