Airplane Test: An Intraoperative Assessment for Flexion Contracture in Total Knee Arthroplasty

Total knee arthroplasty (TKA) effectively relieves pain and restores function in patients with degenerative knee diseases. Complications like postoperative flexion contracture (FC) can impair functional outcomes. Assessing FC intraoperatively remains challenging due to the limitations imposed by surgical drapes. The "Airplane Test" offers a novel intraoperative assessment method for FC, addressing the limitations of traditional evaluation techniques. This study evaluates its utility in FC correction and predicting postoperative resolution.

A prospective cohort study evaluated 126 knees in 122 patients undergoing primary TKA. Our data included demographics, comorbidities, and clinical findings such as FC severity. Intraoperative FC assessments using the Airplane Test guided surgical adjustments, including additional femoral cuts or posterior capsular release. Statistical analyses compared outcomes between groups with and without initial FC.

Demographics revealed a predominantly female cohort (88.52%) with a median age of 68 years. Preoperative FC averaged 8.5°, with a higher prevalence of severe FC (>15°) in males. In a comparison between patients with or without preoperative FC, despite significant difference in early postoperative FC, by 6 months, both groups achieved a comparable FC resolution (≤5°) and ROM. With negative Airplane Test, more than 99% of patients with or without preoperative FC experienced spontaneous resolution (≤5°) of postoperative FC after 6 months.

The Airplane Test is a simple intraoperative tool for assessing and addressing FC during TKA. Patients with negative Airplane Test results achieved near-complete FC resolution (≤5°), supporting its role in intraoperative decision-making. Ethical constraints precluded a control group with uncorrected FC.

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