Objective: We analyzed the posterior condylar offset (PCO) and the postoperative flexion angle in two prostheses often used for total knee arthroplasty (TKA) using the “pre-cut trial” technique.
Methods: The “pre-cut trial” technique is based on a measured resection technique for distal femoral cutting and step-by step fitting for posterior femoral cutting to obtain a proper flexion gap and/or femoral rotational alignment. A total of 149 knees (FINE® Total Knee System CR: 69 knees, LCS® CompleteTM Knee System: 80 knees), on which TKA was performed from January 2012 through March 2013, were evaluated for the range of motion (ROM) and improvement rate of the ROM before and at 3, 6, and 12 months after surgery. In addition, we examined the relationship between the PCO ratio (division of PCO by the maximum anterior to posterior diameter of the distal femur) and the ROM.
Results: The mean flexion angles in the FINE® and LCS® knee systems were 114.7°and 117.8°before, and 124.8°and 123.6°one year after surgery, respectively. The improvement rates were 112.5% and 111.6%, respectively, one year after surgery. The preoperative PCO ratios in the FINE® and LCS® knee systems were 0.49±0.04 and 0.47±0.04, and the postoperative rate was 0.49±0.03 in both systems, without a significant change in both prostheses before and after surgery. The improvement rate of the flexion angle did not correlate with the PCO ratio before or after surgery (R<0.3). Furthermore, there was no clear correlation between the posterior tibial slope and the postoperative flexion angle (R<0.3). Conversely, there was a correlation between preoperative and postoperative flexion angles, as reported in previous studies.
Conclusion: There appeared to be no clear relationship between the ROM and PCO in the two prostheses when TKA was performed using the “pre-cut trial” technique that could suppress a PCO reduction and ensure consistency.
