"Zone of vulnerability" for radial nerve injury: anatomic study.

The authors of this study sought improved understanding of the radial nerve course through the brachium and hypothesized that the most proximal aspect of the triceps tendon (PATT) serves as a useful superficial landmark for localizing the nerve. It was also hypothesized that a poorly appreciated area of vulnerability for nerve injury exists where the radial nerve runs along the lateral cortex of the humerus proximal to its transit through the lateral intermuscular septum (LIMS). The authors assessed 33 fresh-frozen cadaveric specimens. A 6.7-cm span of the nerve lies directly on the periosteum of the humerus before piercing the LIMS. The proximal 4.6~cm abuts the posterior cortex. The final 2.1~cm just proximal to the LIMS runs along the lateral cortex. The nerve at the posterior midline of the humerus is 2.3~cm proximal to the level of the PATT. The radial nerve lies directly on the lateral humeral cortex for 2~cm proximal to its transit through the LIMS. The PATT appears to be a consistent and practical superficial landmark to determine the location of the radial nerve from a posterior approach.

Two-incision versus one-incision repair for distal biceps tendon rupture: a cadaveric study.

HYPOTHESIS: The purpose of this study was to accurately map the insertional footprint of the distal biceps tendon and to test our hypothesis that a superior anatomic repair can be achieved by a 2-incision technique when compared with a 1-incision technique. METHODS: We randomly assigned 20 cadaveric arms to 1 of 2 groups: 1 incision (group I) or 2 incision (group II). The bicipital tuberosity was exposed through either a single anterior incision (group I) or a posterolateral approach (group II). A guide pin was placed into the tuberosity to mark the axis for creating a virtual bone tunnel. Each radius was harvested with the biceps insertion intact. The length, width, and area of the insertion footprint for each tendon were determined with a 3-dimensional computerized digitizer. A 7.5 mm-diameter virtual bone tunnel was centered over the drill hole created by the guidewire. The percentage of the virtual tunnel within the original footprint was determined. RESULTS: The percentage of the virtual tunnel (repair site) within the original tendon footprint was 73.4% for the posterolateral approach and only 9.7% for the anterior approach. There was a statistically significant difference (P ≤ .001) in the median values of footprint covered when the 2 types of repair were compared. DISCUSSION AND CONCLUSION: The 2-incision technique results in a significantly improved anatomic repair of the biceps tendon to the original insertion site. Prospective clinical studies directly comparing the 2 techniques with regard to the strength of supination after repair may be helpful.

Pectoralis major insertional ratio in proximal humerus fractures: a method to reconstruct humeral head height in arthroplasty.

A key factor for a successful outcome after hemiarthroplasty for a 4-part proximal humerus fracture is accurately restoring humeral length. Our hypothesis was that the pectoralis major insertion is not at a constant distance on the humerus, as has been previously suggested, but varies depending on the length of the humerus, and our goal was to determine if a consistent ratio exists for the insertion as it relates to total humeral length. Thirty-eight cadaver arms were dissected to expose the pectoralis major insertion. Using a digital caliper, measurements were made from the top of the humeral head to the superior aspect of the pectoralis major insertion (HP), and from the pectoralis insertion to the lateral epicondyle (PL). The predictive ability of PL for HP was examined via regression, and the average prediction error was computed. The final predictive regression model had the following formula: pHP=0.2323xPL, where pHP is predicted HP. This equation had an average prediction error of 4.11 mm. The PL can be measured intraoperatively during hemiarthroplasty for proximal humerus fractures. The proportionality relationship can then be used to predict HP with an average prediction error <5 mm. This relationship may facilitate accurate intraoperative reconstruction of prosthetic head height and enhance existing techniques for assessment of implant positioning.