[Value of preoperative planning in total hip arthroplasty]

Preoperative planning enables an assessment of the size of the implants needed before total hip replacement. Eggli and Müller demonstrated the reproduciblity of preoperative planning but did not evaluate its contribution to reducing limb length discrepancy. As femur lateralization and the position of the prosthetic center of rotation affect joint mechanics, it would be useful to assess their contribution to the efficacy of preoperative planning.

We reviewed the files of 57 patients who underwent total hip arthroplasty for primary joint degeneration or necrosis limited to one hip. The healthy hip served as a control. The surgical plan was elaborated from the preoperative pelvis x-rays (AP and lateral views) and anatomic measurements on films obtained three months postoperatively.

In 49 cases, preoperative planning predicted a restoration of the normal anatomy of the operated hip (center of rotation, femur lateralization, length of the operated limb). This objective was achieved in only 22.5% of the cases. Femur lateralization was the most difficult objective to achieve (59.2%). Equal limb length and good position of the center of rotation was achieved in 70% of the cases. For eight patients (14%) preoperative planning was not satisfactory, the implant offset not being adapted to the patient's anatomy.

There are limits to preoperative planning, particularly for restitution of adequate femur lateralization. This difficulty appears to be related to three factors: inadequate adaptation of the implant to hip anatomy (14% of the cases in our experience), stiff rotation in degenerative hips inhibiting proper assessment of the length of the femoral neck, and relative imprecision of operative evaluation of femoral anteversion affecting femur lateralization and the level of the femoral cut.

Although imperfect, preoperative planning is, in our opinion, essential before total hip arthroplasty in order to avoid major positioning errors and operative difficulties.