Preoperative Diagnosis Can Predict Conversion Total Knee Arthroplasty Outcomes

Abstract

Background: Compared to total knee arthroplasty (TKA) for primary osteoarthritis, conversion TKAs in the post-traumatic setting are associated with increased operative times, infection rates, and readmissions. We aim at determining how post-traumatic osteoarthritis and previous knee surgery influence postoperative outcomes in conversion TKA.

Methods: Seventy-two conversion TKA procedures with prior knee trauma at a single institution between April 2012 and 2016 were examined. Twenty-seven (37.5%) cases had a preoperative site-specific diagnosis such as fracture of the proximal tibia, distal femur, or patella whereas 45 (62.5%) cases had a preoperative diagnosis of significant soft-tissue trauma. These 2 groups were compared in terms of total implant cost, length of stay, complications, and readmission and reoperation rates. A subanalysis was conducted to evaluate the effects of previous knee surgery on surgical outcomes.

Results: The postfracture TKA cohort suffered significantly higher early surgical site complications (22% vs 4.4%, P = .02) and 90-day readmissions (14.8% vs 2.2%, P = .042) compared to the soft-tissue trauma cohort. Operative time, total implant costs, length of stay, medical complications, 30-day readmissions, and 90-day reoperation rates did not significantly differ. It was also found that patients with multiple prior knee surgeries compared to one prior knee surgery are younger (53.0 vs 63.1, P = .003), healthier, and receive significantly more expensive implants (1.72 vs 1.07, P = .026). In addition, patients with previous open reduction internal fixations experience more surgical site complications than patients with previous arthroscopies (31% vs 3.3%, P = .042).

Conclusion: Patients with previous site-specific fracture are more likely to experience surgical site complications and 90-day readmissions after conversion TKA than patients with previous soft-tissue knee trauma. Multiple previous knee surgeries appear to serve as an independent factor in the selection of costlier implants irrespective of preoperative diagnosis.

Keywords: conversion total knee arthroplasty; implant cost; post-traumatic osteoarthritis; readmissions; total knee arthroplasty.