Coronal plane deformity in total knee arthroplasty is associated with increased operative time and disposition to skilled nursing facility

Purpose: Studies demonstrate similar long-term Total Knee Arthroplasty (TKA) outcomes in patients with significant versus minimal preoperative coronal plane deformity. Limited short-term outcomes data, which determine costs of care, exist.

Methods: We retrospectively explored the impact of preoperative coronal plane deformity on operative time, length of stay (LOS), and discharge to skilled nursing facility (SNF) in TKA. A total of 3,964 patients undergoing unilateral primary TKA at our institution from 2014 to 2019 were included (1,158 > 10˚ deformity: mean age 67.2 years, 47% male; 2,806 < 10˚ deformity: mean age 67 years, 37.4% male). The degree of coronal plane deformity (mechanical axis deviation on preoperative radiographs) was recorded. Patients with no knee radiographs ≤ 3 years preoperatively were excluded. Statistical analysis included Chi-Square tests, Student's t-tests, Mann-Whitney U tests, and uni- and multivariable linear and logistic regression analyses.

Results: The > 10˚ deformity cohort had a longer time from procedure start to finish (113.56 vs. 110.68 min; p = 0.020), greater deviation from surgeon mean operative time (+ 6.19 vs. + 0.69 min; p < 0.001), and higher proportion of cases requiring > 15 (26.8% vs. 22%;p = 0.001) and > 30 (12.3% vs. 7.8%;p < 0.001) additional minutes over their scheduled times. LOS was similar between cohorts (median 2 days, IQR 1-3). The deformity cohort more likely discharged to SNF (19.9% vs. 15.8%;p = 0.002). For every 1˚ increase in coronal plane deformity, operative time increased by 0.566 min (p = 0.000). The odds of SNF discharge increased with increasing coronal plane deformity (OR 1.029 [1.009,1.050]; p = 0.004).

Conclusion: Greater preoperative coronal deformity is associated with increased operative time and odds of discharge to SNF in TKA.