Assessing the accuracy of patient-specific guides for total knee arthroplasty

Purpose Patient-specific guides have been introduced recently as a means of making accurate bone cuts through custom cutting blocks constructed based on pre-operative three-dimensional imaging. However, the controversy concerning the improved results of patient-specific guides have not been resolved yet; in addition, there have been no studies to investigate the causes of variable with inconsistent results and solutions for the causes. Methods Thirty eight patients (38 knees) underwent total knee arthroplasty with patient-specific guides. The mean age of the patients was 68 years (SD ± 6.3), and all patients had a minimum 2-year follow-up. An intra-operative alignment using navigation and the causes of outliers were evaluated. Results An average coronal alignment of PSI jigs was 0.5° (SD ± 0.9°) in femur and 0.1° (SD ± 0.8°) in tibia, and the number of outliers was two and three cases, respectively. An average sagittal alignment was 0.6° (SD ± 0.9°) in femur and 5.5° (SD ± 1.1°) in tibia, and the number of outliers was three and five cases, respectively. All outliers resulted from large osteophytes near the contact point of patient-specific guides which disturb sitting of the guide. Conclusion It was suggested that patient-specific guides were an effective and safe method to achieve accurate alignments, with no additional intra-operative complication. It is important to note that surgeons need to be precautious using the patient-specific instrumentation in patients with severe varus deformity. In addition, existing osteophytes which disturb sitting of the guides should be carefully evaluated pre-operatively and intra-operatively. Level of evidence IV.