Reliability of Intraoperative Manual Varus-Valgus Stress Assessment in Total Knee Arthroplasty

Intraoperative soft-tissue balance is a key determinant of outcomes after total knee arthroplasty (TKA). In computer-assisted TKA, soft-tissue balance is often assessed using manual varus-valgus stress testing; however, the accuracy of this approach remains unclear.

This study aimed to compare quantitative intraoperative assessment using a tensor device with manual stress assessment and to evaluate the reliability of manual stress testing.

Twenty-six patients (27 knees) undergoing primary cruciate-retaining TKA using a navigation system were included. Medial and lateral compartment gaps were measured intraoperatively at 10°, 30°, 60°, and 90° of knee flexion using a tensor device and manual varus-valgus stress. Intra-observer and inter-observer reliability of manual stress assessment were evaluated using intraclass correlation coefficients.

Manual stress assessment demonstrated good intra-observer reliability. Compared with tensor-based measurements, manual stress assessment yielded significantly smaller gap values in both compartments in flexion, while lateral gap values were significantly larger at 10° of flexion.

In computer-assisted TKA, manual stress assessment may underestimate joint laxity in flexion and overestimate lateral laxity near extension. Awareness of these limitations and adjunctive quantitative evaluation may facilitate more accurate intraoperative soft-tissue balancing.