Humeral intramedullary nail placement through the rotator interval: an anatomic and radiographic analysis

Abstract

Antegrade humeral intramedullary nails are an effective fixation method for certain proximal humeral fractures and humeral shaft fractures. However, owing to potential rotator cuff damage during nail insertion, shoulder pain remains a common postoperative complaint. The purpose of this study was to provide quantitative data characterizing the anatomic and radiographic location of the rotator interval (RI) for an antegrade humeral intramedullary nail using a mini-deltopectoral approach. Six consecutive fresh-frozen intact cadaveric specimens (mean age, 69 ± 12.8 years) were obtained for our study. Demographic data were collected on each specimen. A mini-deltopectoral approach was used, followed by placement of a guidewire in the RI. Quantitative anatomic relationships were calculated using a fractional carbon fiber digital caliper. Radiographic measurements were performed by 2 orthopedic residents and 1 practicing fellowship-trained orthopedic surgeon. In addition to re-measurement of similar anatomic relationships on radiographs, the ratio of the distance from the lateral humeral edge to the starting point relative to the width of the humeral head on the anteroposterior (AP) view was calculated. Similarly, on the lateral view, the ratio of the distance from the anterior humeral edge to the starting point relative to the humeral head width was calculated. In all cases, the described approach allowed for preservation of the biceps tendon and access to the RI for guidewire insertion, with no subsequent rotator cuff or humeral articular cartilage damage identified following nail insertion. The ratio of the distance from the lateral humeral edge to the starting point relative to the humeral head width on the AP view was 0.4 ± 0.0. The ratio of the distance from the anterior humeral edge to the starting point relative to the humeral head width on the lateral view was 0.3 ± 0.0. This study demonstrates the clinical feasibility of a mini-deltopectoral approachand shows that the ideal starting point through the RI radiographically lies along the medial aspect of the lateral third of the humeral head on the AP viewand along the posterior aspect of the anterior third of the humeral head on the lateral view.