"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.

Interobserver variability using a commercially available system of archived digital radiography with integrated computer-assisted measurements for scoliosis Cobb angles.

BACKGROUND: The purpose of this study was to determine if digital enhancements could improve upon published and interobserver variability for Cobb angle measurements of idiopathic scoliosis using a commercially available PACS system. The study also sought to determine if experience of the observer affected overall variability and to evaluate the time required to measure Cobb angles using 3 different techniques. As the decision for scoliosis treatment requires serial radiographic measurements by 1 or more observers at different times, precise landmark identification and curve measurement should decrease variability and improve accuracy. METHODS: Fifty-four consecutive digital radiographs of 49 children with idiopathic scoliosis were collected and archived, yielding a total of 117 curves. Five observers, ranging from a PGY2 resident to a senior level faculty member, measured each radiograph in 3 different ways. Technique A involved measuring the curves as the image first appeared on the computer screen. Technique B consisted of 2 extra steps: enlarging the image until the spine filled the screen and using an edge enhancement tool. Technique C utilized the steps in B and further enlarging each vertebra to adjust each measurement. Each technique was timed for each observer. RESULTS: Technique C had the lowest variability that was significantly different from technique A. Technique B also had lower variability than technique A. The 2 observers with the greatest experience demonstrated the least intraobserver and interobserver variability. Techniques B and C decreased the variability of less experienced observers. The average time required for techniques A, B, and C was 25, 29, and 40 seconds, respectively. Confounding variables such as obesity did not affect the measurements, but curve location did, with thoracic curves causing greater variability for less experienced observers. DISCUSSION: The results demonstrate that less experienced observers using the relatively rapid technique A for digital radiographs are more likely to have clinically significant discrepancies in their measurements, which could affect treatment decisions. Taking 4 extra seconds using technique B significantly decreases variability and improves accuracy in the evaluation and management of scoliosis patients. LEVEL OF EVIDENCE: I (testing of previously developed diagnostic criteria).

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.