Evaluation of alignment in total knee arthroplasty: a prospective study

Successful results of knee arthroplasty demand precise surgical technique, sound implant design, kinematics, appropriate materials and patient compliance with rehabilitation. The precision with which the implants are placed directly affects patient outcome as implant position and alignment influence the stability, durability and patellar tracking. Evaluating the alignment in total knee arthroplasty and functional outcome with respect to the alignment is the need of the hour. AIM AND OBJECTIVE OF THE STUDY: (1) To evaluate the accuracy of the overall limb alignment and component alignment in jig-assisted TKR. (2) To evaluate the functional outcome with respect to the alignment parameters.

This is a prospective study of 120 knees in 80 patients that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Patients were selected according to the inclusion and exclusion criteria and evaluated using knee society score at regular follow-up. Preoperative and postoperative standing 'long-leg radiographs' and postoperative CT scans were taken from all the patients. In our study, we had 54 female patients and 26 male patients. Indications were OA in 72 and RA in 48 knees. The average follow-up period was 36 months.

Preoperatively, all the patients had moderate to severe pain. Mechanical and tibiofemoral axes were outside the acceptable range. Postoperatively, with respect to mechanical axis, the inliers had significantly better knee score (p = 0.026) compared to the outliers. But the functional score did not show any significant difference between these two groups (p = 0.2093). Inliers in tibiofemoral axis alignment parameter had extremely significant better knee score (p = 0.0001) and also functional score (p = 0.0082) compared to outliers group. Sagittal and rotational femoral component angles in all 120 cases were coming within the 'inliers group'. Similarly, the sagittal, the coronal and the rotational component angles of tibia were also coming under inliers group in all 120 replaced knees.

Aligning the mechanical axis, tibiofemoral angle within (0° ± 3°) and placement of prostheses within (0° ± 3°) to the normal alignment in all the three planes significantly produce excellent result with respect to functional outcome.