Is TKA using patient-specific instruments comparable to conventional TKA? A randomized controlled study of one system.

BACKGROUND: Patient-specific CT-based instrumentation may reduce implant malpositioning and improve alignment in TKA. However, it is not known whether this innovation is an advance that benefits patients. QUESTIONS/PURPOSES: We evaluated (1) the precision of patient-specific TKA by comparing the incidence of outliers in postoperative alignment between TKAs using patient-specific instruments and TKAs using conventional instruments, and (2) the reliability of patient-specific instruments by intraoperatively investigating whether the surgery could be completed with patient-specific instruments alone. METHODS: In this randomized controlled trial, we compared patient-specific TKA instruments from one manufacturer (n = 50) with conventional TKA instruments (n = 50). Postoperative hip-knee-ankle angles, femoral component rotation, and coronal and sagittal alignments of each component were measured. The validity of the patient-specific instrument was examined using cross-checking procedures with conventional instruments during the surgeries. When the procedure could not be completed accurately with patient-specific instruments, the procedure was converted to TKA using conventional instruments, and the frequency of this occurrence was tallied. RESULTS: Outliers in the hip-knee-ankle angle were comparable between groups (12% in the patient-specific instrument group and 10% in the conventional instrument group). Other parameters such as sagittal alignment and femoral component rotation did not differ in terms of outliers. Patient-specific guides were abandoned in eight knees (16%) during the surgery because of malrotation of the femoral components and decreased slope of the tibia. CONCLUSIONS: Accuracy was comparable between TKAs done with patient-specific instruments and those done with conventional instruments. However, the patient-specific instrument procedures had to be aborted frequently, incurring expenses that did not benefit patients.

Preservation of the posterior cruciate ligament is not helpful in highly conforming mobile-bearing total knee arthroplasty: a randomized controlled study.

PURPOSE: The purpose of this study is to investigate whether the preservation of the posterior cruciate ligament (PCL) can be helpful for improving kinematics and clinical outcome in highly conforming mobile-bearing total knee arthroplasty (TKA). METHODS: Ninety osteoarthritic knees were randomly allocated to either the PCL-preserving group or the PCL-sacrificing group. Passive kinematics was recorded with a navigation system immediately after implantation. Three parameters (anterior/posterior translation, varus/valgus rotation, and internal/external rotation) were analysed from 0° to 120° flexion. RESULTS: The PCL-preserving group (42 knees) had more varus rotation over 90° flexion (p < 0.05) and more anterior translation of the femur in all ranges of flexion (p < 0.05) than those in the PCL-sacrificing group (44 knees). There was no difference in the internal/external rotation (p > 0.05). The range of motion, functional scores, and radiographic results did not significantly differ between the two groups at the final follow-up. Three knees in the PCL-preserving group were revised: two presented with instability caused by traumatic attenuation of the PCL and one with subluxation of the insert due to a tight PCL. CONCLUSION: The preservation of the PCL was not helpful for improving kinematics and clinical outcome in highly conforming mobile-bearing TKA.