Changes in posterior condylar offset after total knee arthroplasty cannot be determined by radiographic measurements alone

Restoration of femoral posterior condylar offset (PCO) may contribute to maximum flexion after total knee arthroplasty. Accurate radiographic measurement of postoperative PCO is possible, as the prosthesis margins can be easily identified; however, preoperative measurement of PCO may be inaccurate, as the remaining cartilage thickness of the posterior condyles is not included. This error may contribute to the controversy surrounding the importance of PCO. In this institutional review board-approved study, the cartilage thickness of posterior condylar specimens resected during total knee arthroplasty was measured. Mean cartilage thicknesses of the posterior condyles were 1.7 mm (range, 0-4 mm) medially and 2.0 mm (range, 0-5 mm) laterally. As the cartilage thickness is variable, future studies of PCO must adjust the preoperative radiographic measurements by the cartilage thickness measured intraoperatively.