Correlation between frontal knee alignment and bone resection thicknesses during total knee arthroplasty without precision-enabling device: a retrospective study.

Introduction: Proper knee alignment is critical for optimizing postoperative function and implant longevity in total knee arthroplasty (TKA). While robotic-assisted surgery offers precision in bone resections, most surgeons still rely on conventional instrumentation. This study evaluates the relationship between pre- and postoperative frontal knee alignment and bone resections in TKA performed without precision-enabling devices to establish a correlation between thickness of resection and frontal angular correction.

Materials and methods: This retrospective, single-center study analyzed data from patients undergoing TKA for end-stage osteoarthritis between June 2021 and April 2024. Intraoperative cuts were measured in a standard way. All procedures were performed by a single experienced surgeon without precision-enabling devices. Preoperative and six-week postoperative weight-bearing goniometry and anteroposterior (AP) radiographs were collected. The cohort consisted of 130 patients: 69 varus (= 177° HKA), 30 neutral (177°-183° HKA) and 31 valgus (= 183° HKA) knees. Patients were 36.9% male, with a mean age of 70.1 years (SD 8.2) and a BMI of 30.8 kg/m² (SD 5.6). Hip-knee-ankle (HKA) angle, anatomical and mechanical tibiofemoral angles and joint line convergence angles (JLCA) were measured. Statistical analysis was conducted to determine correlations between resection measurements and angular parameters.

Results: The correlation between tibial resection (ΔT) and medial proximal tibial angle modification measured on goniometry (ΔMPTA(g)) followed a linear regression with a Spearman's correlation coefficient (r = 0.553). A weak positive correlation was observed between ΔT and ΔMPTA on AP radiographs (r = 0.505), as well as between distal femoral resection (ΔDF) and lateral distal femoral angle modification (ΔLDFA(g)) on goniometry (r = 0.350) and on AP radiographs ΔLDFA(s) (r = 0.187).

Conclusion: This study suggests a moderate correlation between tibial resection thickness and angular correction in the coronal plane. However, the high variability observed indicates that surgical planning should not rely solely on this correlation.