Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Restores Patellofemoral Contact Areas and Pressures More Closely Than Nonanatomic Single-Bundle Reconstruction

Purpose: To investigate the effects of anterior cruciate ligament (ACL) deficiency and nonanatomic single-bundle (SB) and anatomic double-bundle (DB) ACL reconstruction on the contact characteristics of the patellofemoral (PF) joint. Methods: By use of a materials testing system, 7 fresh-frozen human cadaveric knees were tested. The following states were tested: ACL-intact knee, nonanatomic SB ACL reconstruction, anatomic DB ACL reconstruction, and ACL-deficient knee. Hamstring autografts were used. PF contact pressures and areas were measured with pressure-sensitive film at 30 degrees, 60 degrees, and 90 degrees of knee flexion with a constant 100-N load on the quadriceps tendon. Results: The total contact area of ACL-deficient and nonanatomic SB ACL-reconstructed knees (123.8 +/- 63.9 and 149.6 +/- 79.3 mm(2), respectively) significantly decreased when compared with those of the intact knee (206.1 +/- 83.6 mm(2)) at 30 degrees of knee flexion. The lateral-facet peak pressure of ACL-deficient and nonanatomic SB ACL-reconstructed knees (1.12 +/- 0.52 and 1.22 +/- 0.54 MPa, respectively) significantly decreased when compared with those of the intact knee (0.68 +/- 0.38 MPa) at 90 degrees of knee flexion. Anatomic DB ACL reconstruction restored the contact pressures and areas to values similar to those of the intact knee (no significant difference). Conclusions: ACL deficiency resulted in a significant decrease in the total and medial PF contact areas and in an increase in the lateral PF contact pressure. Anatomic DB ACL reconstruction more closely restored normal PF contact area and pressure than did nonanatomic SB ACL reconstruction. Clinical Relevance: Our findings suggest that the changes in the PF contact area and pressures in ACL deficiency and after nonanatomic SB ACL reconstruction may be one of the causes of PF osteoarthritis or other related PF problems found at long-term follow-up. Anatomic DB ACL reconstruction may reduce the incidence of PF problems by closely restoring the contact area and pressure.