Accuracy of total knee arthroplasty using hospital-based 3D printed patient-specific instrumentation: A radiology research

Background: Patient-specific instruments (PSIs) were reported to improve implant position and rotation accuracy in total knee arthroplasty (TKA), among other benefits. Most PSIs used in TKA were commercial products from implant manufacturers, which could be time-consuming and could potentially affect accuracy as they relied on engineer's decision. This study aimed to present the radiological outcomes of PSI produced by the 3D printing facility at our hospital, with direct involvement of the surgeon in its design. Methods: This prospective study enrolled 45 patients who underwent mechanically aligned TKA. Preoperative whole-limb 3D-CT scans were obtained to create the sizing plan. The surgeon identified the position of the cut plane and guide pin locations on software, which were then forwarded to engineers for further processing. Subsequently, the PSI was fabricated using in-hospital 3D resin printers. During surgery, after removing all remaining cartilage, the PSI was utilized on the bone surfaces to assist surgeons in drilling pinhole positions for the manufacturer's cutting instruments. Post-surgery, CT scans were acquired and overlaid onto the 3D model of the implant to compare to the plan. Results: On average, it took three days to prepare for the surgery using PSI. 100 % of patients had implant sizes that matched the preconception template. The mean postoperative hip-knee angle was 178.1 degrees f 1.34 degrees. The mean femoral component rotation angle relative to the surgical transepicondylar axis (sTEA) and the mean rotation mismatch between the femur and tibial component were 0.99 degrees f 0.84 degrees and 0.91 degrees f 1.61 degrees, respectively. Conclusions: Preliminary radiological results demonstrated that in-hospital PSI was a useful technique for improving the accuracy of implant positioning in TKA, especially in controlling the rotational alignment.