Patient-Specific Instrumentation Versus Standard of Care in Total Knee Arthroplasty in an Obese Population: Minimum...

Patient-specific instrumentation (PSI) in total knee arthroplasty (TKA) was developed to improve alignment accuracy by using custom cutting guides. Obese patients pose unique technical challenges, and enhanced alignment methods may be especially beneficial. This study compared PSI with standard of care (SOC) using conventional instrumentation in obese patients undergoing primary TKA.

Patients who had a body mass index greater than 30 and undergoing primary TKA were randomized to SOC or PSI. Patients were followed for five years postoperatively. Patient-reported outcome measures, surgical information, postoperative lower extremity alignment, complications, and revision rates were recorded. There were 158 patients included (80 in PSI and 78 in SOC).

The primary radiographic outcome, medial proximal tibial angle, showed a statistically significant, but not clinically meaningful, difference between the groups (PSI = 88.2 ± 2.2, SOC = 88.7 ± 1.8, P = 0.02). No significant differences were observed in the anatomic femoral-tibial angle (P = 0.075) or lateral distal femoral angle (P = 0.53). Patient-reported outcomes, including Western Ontario and McMaster Universities Arthritis Index (PSI: 82.5 ± 18.7, SOC: 83.2 ± 15.9, P = 0.83), 12-Item Short-Form Survey physical and mental composite scores (P = 0.35 and P = 0.40), and Knee Society Score total scores (PSI: 177.3 ± 24.3, SOC: 168.2 ± 31.2, P = 0.08), were similar between the groups. A higher rate of deviation from the preoperative surgical plan was observed in the PSI group (30.2%) compared to SOC (5.1%). Complication and revision rates were comparable between the groups.

Use of PSI in primary TKA did not result in clinically relevant improvements in radiographic alignment compared to SOC. Despite increased preoperative planning, intraoperative deviations from the PSI surgical plan were common. There were no differences in patient-reported outcome measures, complications, or revision rates observed at five years.