ABSTRACT
BACKGROUND: Patient-specific instrumentation (PSI) may potentially improve unicompartmental knee arthroplasty (UKA) implant positioning and alignment. The purpose of this study was to compare early radiographic coronal alignment of medial UKA performed using PSI versus conventional instrumentation (CI) for tibial resections. METHODS: A consecutive series of 47 knees (47 patients) received medial UKA, with the tibial resections performed using CI (first 22 knees) or PSI (next 25 knees), while femoral resections were performed with CI in both groups. The target mechanical medial proximal tibial angle (mMPTA) was 87° ± 3°, and the target hip-knee-ankle (HKA) angle was 177° ± 2°. The postoperative mMPTA and HKA were evaluated from postoperative radiographs at a follow-up of 2 months. RESULTS: Differences in postoperative mMPTA (p = 0.509) and HKA (p = 0.298) between the two groups were not statistically significant. For the mMPTA target, 24% of knees in the PSI group (85.6° ± 2.1°) and 32% of the CI group (85.0° ± 3.6°) were outliers. For the HKA target, 44% of knees in the PSI group (176.3° ± 2.8°) and 18% of the CI group (177.1° ± 2.3°) were outliers. Considering the two criteria simultaneously, 60% of knees in the PSI group and 45% of knees in the CI group were outside the target zone (p = 0.324), whereas 28% of knees in the PSI group and 41% of knees in the CI group were outside the target zone by more than 1° (p = 0.357). CONCLUSIONS: The results of the present study revealed no statistically significant difference in radiographic coronal alignment of UKA performed using PSI versus CI for tibial resections.
ABSTRACT
The success of posterior cruciate ligament (PCL) reconstruction is dependent on appropriate tunnel placement. Computed tomography (CT) provides detailed images of intra-articular osseous anatomy. The objective of this study was to analyze by CT the position of femoral and tibial tunnels relative to intra-operative goals following arthroscopic-assisted PCL reconstruction. Nineteen patients who underwent single-bundle PCL reconstruction were evaluated 16 months post-operatively. Each underwent a CT scan and tunnel locations were identified in the coronal, sagittal, and axial planes. The coronal plane tibial tunnel location was within 5mm of the intra-operative goal (48% of the total tibial plateau width from the medial border of the plateau) in 16 patients (84%). The sagittal plane tibial tunnel location was within 5mm of the intra-operative goal (the middle of the posterior half of the retrospinal surface) in 14 patients (74%). In the sagittal plane, the femoral tunnel location was within 5mm of the intra-operative goal (10mm from in the distal articular margin of the medial femoral condyle) in 15 patients (79%). In the notch, the femoral tunnel was between 10:30 and 11:30 for left knees or between 12:30 and 1:30 for right knees (the intra-operative goal was 11 o'clock for left knees and 1 o'clock for right knees) in 18 patients (95%). Arthroscopic PCL reconstruction results in tunnel positions near intra-operative goals. Further work is necessary to define CT-specific criteria for the assessment of PCL tunnel position.
