Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on surgical outcomes. The literature lacks studies that evaluate the limb alignment after lateral UKA or compare alignment outcomes between medial and lateral UKA. In this study, we retrospectively compare a single surgeon's alignment outcomes between medial and lateral UKA using a robotic-guided protocol. All surgeries were performed by a single surgeon using the same planning software and robotic guidance for execution of the surgical plan. The senior surgeon's prospective database was reviewed to identify patients who had 1) undergone medial or lateral UKA for unicompartmental osteoarthritis; and 2) had adequate pre- and post-operative full-length standing radiographs. There were 229 medial UKAs and 37 lateral UKAs in this study. Mechanical limb alignment was measured in standing long limb radiographs both pre- and post-operatively. Intra-operatively, limb alignment was measured using the computer assisted navigation system. The primary outcome was over-correction of the mechanical alignment (i.e, past neutral). Our secondary outcome was the difference between the radiographic post-operative alignment and the intra-operative “virtual” alignment as measured by the computer navigation system. This allowed an assessment of the accuracy of our navigation system for predicting post-operative limb alignment after UKA.Introduction
Methods
Computer assisted surgery (CAS) systems have been shown to improve alignment accuracy in total knee arthroplasty (TKA), yet concerns regarding increased costs, operative times, pin sites, and the learning curve associated with CAS techniques have limited its widespread acceptance. The purpose of this study was to compare the alignment accuracy of an accelerometer-based, portable navigation device (KneeAlignÒ 2) to a large console, imageless CAS system (AchieveCAS). Our hypothesis is that no significant difference in alignment accuracy will be appreciated between the portable, accelerometer-based system, and the large-console, imageless navigation system. 62 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the Achieve CAS computer navigation system. Subsequently, 65 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the KneeAlignÒ 2 to perform both the distal femoral and proximal tibial resections (femoral guide seen in Figure 1, and tibial guide seen in Figure 2). Postoperatively, standing AP hip-to-ankle radiographs were obtained for each patient, from which the lower extremity mechanical axis, tibial component varus/valgus mechanical alignment, and femoral component varus/valgus mechanical alignment were digitally measured. Each measurement was performed by two, blinded independent observers, and interclass correlation for each measurement was calculated. All procedures were performed using a thigh pneumatic tourniquet, and the total tourniquet time for each procedure was recorded.Introduction
Methods
