Aperture fixation instead of transverse tunnels at the patella for medial patellofemoral ligament reconstruction.

PURPOSE: Medial patellofemoral ligament (MPFL) reconstruction is an effective option for the treatment of recurrent patellar instability. Most techniques utilize the passage of a tendon graft through tunnels at the patella with the risk of patellar fracture. The purpose of this study was to investigate the strength of the recent MPFL reconstruction techniques (transverse tunnel, interference screw, anchor, and docking technique).

METHODS

Thirty-six saw bones were divided into four groups (transverse tunnel, interference screw, anchor fixation, and docking technique) with nine patellae in each. Patella-tendon constructs were pre-loaded to 10 N and cyclically loaded for 20 cycles from 2 to 30 N under load control at a rate of 5 N/sec. The construct was then tested to failure at a constant displacement rate of 6 mm/sec. Ultimate load (N), stiffness (N/mm), and failure mode were recorded for each specimen.

RESULTS

The docking group had lower ultimate load [106 (SD 41) N] and stiffness [14 (SD 2) N/mm] values than the other groups tested (P = 0.007). The anchor group had lower stiffness [21 (SD 6) N/mm] values than the tunnel group [28 (SD 3) N/mm (P = 0.01)] and the interference screw group [31 (SD 6) N/mm, (P = 0.004)]. There was no significant difference in the ultimate load between anchor [299 (SD 116) N], tunnel [304 (SD 140) N], and interference screw groups [241 (SD 103) N] (n.s.).

CONCLUSION

Aperture fixation techniques, especially interference screw fixation, were as strong as the technique utilizing tunnels in the patella for MPFL reconstruction.