Bone Density Distribution Pattern in the Lateral Wall of the Femoral Intercondylar Notch: Implications for the Direct Insertion of the Femoral ACL Attachment.

Background: The ideal position of the femoral bone tunnel in the anterior cruciate ligament (ACL) is controversial. The functional importance of the ACL fiber varies depending on where it is attached to the femur. Functionally important fibers can cause high mechanical stress on the bone, and the Wolff law predicts that bone mineral density will increase at high mechanical stress sites. Purpose/Hypothesis: The purpose of this study was to use computed tomography imaging to determine the distribution pattern of bone density in the lateral intercondylar wall. It was hypothesized that the high-density area (HDA) of the lateral intercondylar wall would reflect the functional insertion of the ACL as reported in previous anatomic studies. Study Design: Descriptive epidemiology study. Methods: Data from 39 knees without ACL injuries were retrospectively collected. The HDA of the lateral intercondylar wall was defined as the region containing the top 10% of the radiodensity values. The shape of the HDA was approximated as an ellipse, and the quadrant method was used to determine the center of the ellipse. The association between the ratio of the minor axis to the major axis of the ellipse and background characteristics was investigated. Results: According to the quadrant method, the center of the HDA ellipse was 33.6% in the deep-shallow direction and 23.4% in the high-low direction. The center of the ellipse was comparable to the anatomic center of the ACL footprint, as previously reported. The ratio of the minor axis to the major axis of the ellipse was 0.58 (95% CI, 0.54-0.62). There was a significant negative correlation between the ratio of the minor axis to the major axis of the HDA ellipse and the posterior tibial slope (r = -0.38, P = .02). Conclusion: The center of the HDA ellipse was found to be similar to the anatomic center of the ACL footprint. Considering the mechanical stress responses in bone, the HDA of the lateral intercondylar wall has the potential to represent the ACL insertion, especially functional insertion.

The Novel Ulnar Nerve Coverage Method Which Has the Potential to Prevent the Postoperative Ulnar Neuropathy after Plate Fixation of Distal Humerus Fractures: Three Case Reports.

Introduction: Postoperative ulnar neuropathy is still an unresolved complication in patients undergoing plate fixation of distal humerus fractures. We hypothesized that decreased blood flow to the ulnar nerve due to intraoperative procedures is an important factor in the development of postoperative ulnar neuropathy. We herein report three cases of distal humerus fractures in which the soft tissues surrounding the ulnar nerve were preserved as much as possible and finally not transferred anteriorly. Case Presentation. A 76-year-old woman, 82-year-old woman, and 34-year-old woman underwent plate fixation for distal humerus fractures. None of the patients developed postoperative ulnar neuropathy, and there were no complaints of numbness after postoperative day 1. Nerve conduction studies were performed after 3 months postoperatively and revealed that the motor nerve conduction velocities and compound motor nerve action potentials of the ulnar nerve in two of the three patients were higher than those of the noninjured side. In one of the three patients, these values were slightly lower than those of the noninjured side. All three patients achieved bony union after several months postoperatively. Conclusions: We obtained good outcomes with the ulnar nerve coverage method for preventing postoperative ulnar neuropathy in patients with distal humerus fractures. Preservation of blood flow to the ulnar nerve was considered important, and anatomical repositioning of the ulnar nerve after plate fixation has the potential to prevent adhesion between the ulnar nerve and the plate.