Evaluation of component alignment in total knee arthroplasty using patient-specific instrumentation versus conventional guides: a retrospective study

Background: To evaluate whether the use of patient-specific instrumentation (PSI) or conventional instrumentation (CI) is associated with superior implant positioning and knee alignment in total knee arthroplasty (TKA). Methods: Clinical data, pre- and post-operative knee X-rays of 95 patients, who underwent TKA with use of either patient-specific instrumentation (group PSI) or conventional intra-/extramedullary cutting guides (group CI) were retrospectively collected. Preoperative measurements of knee alignment were done by assessing the femorotibial axis, the lateral femoral distal angle, and the medial tibial proximal angle. Postoperative measurements of the mechanical TKA alignment were performed by assessing the relative position of components to the femur and tibia and the femorotibial axis angle. Only when all three parameters were within generally accepted limits was the postoperative radiological outcome considered optimal. Results: Preoperative measurements and demographics were similar among the two groups. No statistically significant differences were found between postoperative radiographic findings in patients operated on with PSI or CI. A restoration of the femorotibial axis was achieved in 87.8% and 87.0% of patients treated with PSI and CI, respectively (p = 0.583). Coronal alignment of the femoral component was within acceptable limits in 97.6% and 94.4% (p = 0.631) of patients of the PSI and CI groups, respectively. The respective percentages for the tibial component were 85.3% and 83.3% (p = 0.510) of patients. An accurate coronal plane radiological outcome was achieved in 82.9% and 77.8% of patients treated with PSI and CI, respectively (p = 0.611) Conclusions: The use of PSI does not increase the accuracy of component positioning and leg axis restoration compared to CI in TKA in patients with mild deformity.