Graft length change and radiographic assessment of femoral drill hole position for medial patellofemoral ligament reconstruction.

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction has been recognized as a useful treatment method for patella instability. However, the optimal fixation site has not been well investigated, and few reports have examined intraoperative graft length change. The purpose of the study is to evaluate the intraoperative graft length change and femoral drill hole position to find the optimal graft placement.

METHODS

The graft length change between the two points on patella and femur was measured using Isotac(®) and Isometric Positioner(®) during passive knee motion in 27 cases of MPFL. The location of Isotac(®) was also evaluated on the 2-directional radiograph. The pre- and postoperative radiographic assessments have been done in order to evaluate the effect of MPFL reconstruction on patellofemoral alignment.

RESULTS

There were 10 cases in which the distance between the two points became longer during knee flexion, 8 cases in which it became shorter and the remaining 9 cases in which the distance changed within 2 mm. The femoral drill hole position was assessed assuming that the maximum anterior-posterior (AP) diameter of the femur on the lateral radiograph was defined as 100%. The distance of the femoral tunnel position from the articular surface averaged 50% overall, 46% in the short group, 55% in the longer group and 48% in the isometric group (P < 0.001). Patella height seemingly affected the length change character. The intraoperative length change influenced the early recovery of knee range motion postoperatively.

CONCLUSIONS

The femoral tunnel position is reaffirmed to be an essential determinant for the graft length change in the MPFL reconstruction. Both graft length change measurements and intraoperative radiographic assessment are practical for proper graft placement.