Abstract
The objective of this study was to evaluate the accuracy of a customized individually
made total knee implant used in conjunction with patient-specific cutting guides in
restoring coronal plane mechanical axis alignment using computer-assisted surgery
(CAS). A consecutive series of 63 total knee arthroplasty (TKA) patients were prospectively
measured with intraoperative CAS. The patient-specific instruments and implants were
created utilizing a preoperative CT scan. CAS system was used for all patients, to
determine mechanical alignment. Bone cuts were made using the patient-specific instruments.
Both bone cuts and final coronal mechanical alignment were recorded utilizing the
navigation system for the assessment.
The patient-specific instruments and implants provided perfect neutral coronal mechanical
alignment (0°) in 53 patients. The remaining 10 patients had a postoperative alignment
within ± 2° of neutral. The average preoperative deformity was 5.57° versus 0.18°
postoperatively (p < 0.0001). The mean correction angle was 5.68°. No patients had postoperative extension
deficits as measured with CAS (7.50° pre-op for 40/63 patients). Customized, individually
made total knee implant with patient-specific cutting jigs showed results that are
comparable to those of CAS systems in this study. This technology restores the neutral
coronal mechanical axis very accurately, while offering unique benefits such as improved
implant fit and restoration of the patient's J-curves, which require further investigation.
Keywords
customized knee implant - mechanical alignment - patient-specific instruments - computer-assisted
surgery - total knee arthroplasty
