Abstract
BackgroundKnee replacement is a very effective and indispensable treatment option for end-stage knee arthritis, and the number of cases has been increasing worldwide. A replaced knee joint without patient joint awareness is thought to be the ultimate goal of artificial knees. Joint awareness reportedly correlates with patient satisfaction. Although numbness around a replaced knee is a minor but common problem, its effect on postoperative outcome is controversial. Joint awareness also is sensitive to subtle abnormalities of the joint, so it must be negatively affected by numbness. Although numbness is minor, it cannot be ignored to further improve knee replacement outcomes. This study investigated the relationship between patient-reported numbness and other patient-reported outcome measures (PROMs), including joint awareness, and kneeling. We developed a numbness score based on a 5-point Likert scale on frequency of numbness, with an intraclass correlation coefficient of 0.76 and higher scores indicating less numbness.MethodsThe numbness score, New Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score-12 (FJS-12), and other clinical and radiological data from 311 patients (394 primary knee replacements) were analyzed. Kneeling ability was evaluated by using kneeling-specific items in the KSS (KSS-Kneeling).ResultsNo numbness was found in 170 knees (43.1%), and some degree of numbness was found in the remaining 224 knees (56.9%). The numbness score showed weak-to-moderate correlations with KSS-Symptoms (r = 0.44), KSS-Satisfaction (r = 0.41), KSS-Activities (r = 0.29), and all KOOS subscales (r = 0.23–0.44), and FJS-12 (r = 0.42). Multiple regression analyses suggested that midline incision positively affected the numbness score over the anteromedial incision (p = 0.04) and that a better numbness score (p = 0.001), male sex (p < 0.0001), and better postoperative knee flexion angle (0.04) positively affected kneeling.ConclusionsThe numbness score positively correlated with PROMs and positively affected kneeling. Knee replacements performed via an anteromedial incision may be at higher risk for numbness.
Highlights
Knee replacement is a very effective and indispensable treatment option for end-stage knee arthritis, and the number of cases has been increasing worldwide
Jariwala et al [13] reported that 53% of 258 total knee arthroplasties (TKAs) resulted in complaints of numbness around the operated knee, but the numbness did not correlate with patient-reported outcome measures (PROMs), such as the New Knee Society Score (KSS) [15] at 1 year after the surgery
Blackburn et al [14] reported that 68% of 56 TKAs resulted in complaints of numbness but the numbness did not correlate with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score [16] or the Knee Injury and Osteoarthritis Outcome Score (KOOS) [17]
Summary
Knee replacement is a very effective and indispensable treatment option for end-stage knee arthritis, and the number of cases has been increasing worldwide. In 2010, knee replacement in the United States was performed in 1.5% of the general population and 10.4% of the population > 80 years old [7], and the number of cases is expected to increase worldwide [8, 9] Major complications, such as deep infection, loosening, and instability, often require revision surgery, whereas minor complications, such as discomfort around the scar [10] and noise from the knee [11], seldom require revision. Jariwala et al [13] reported that 53% of 258 total knee arthroplasties (TKAs) resulted in complaints of numbness around the operated knee, but the numbness did not correlate with patient-reported outcome measures (PROMs), such as the New Knee Society Score (KSS) [15] at 1 year after the surgery. Numbness around the replaced knee is a relatively common minor complication, how it may be associated with clinical outcomes remains controversial
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