Intramedullary Humeral Nail Placement through the Rotator Interval: An Anatomic and Radiographic Analysis.

Abstract Background Antegrade intramedullary humeral nails (IMNs) are an effective fixation method for certain proximal humerus and humeral shaft fractures. However, due to potential rotator cuff damage during nail insertion, shoulder pain remains a common postoperative complaint. The purpose of this study is to provide quantitative data characterizing the anatomic and radiographic location of the rotator interval (RI) for an antegrade intramedullary humeral nail, utilizing a mini-deltopectoral approach. Methods Six consecutive fresh-frozen intact cadaveric specimens (mean age, 69±12.8 yrs) were obtained for our study. Demographic data was collected on each specimen. A mini-deltopectoral approach was used followed by placement of a guidewire in the rotator interval. Quantitative anatomic relationships were calculated using a fractional carbon fiber digital caliper. Radiographic measurements were performed by two orthopedic residents and one practicing fellowship trained orthopedic surgeon. In addition to remeasuring similar anatomic relationships on radiographs, the ratio of the distance from the lateral humeral edge to the start point relative to the width of the humeral head on the AP view was calculated. This ratio was replicated on the lateral view, in which the ratio of the distance from the anterior humeral edge to the start point relative to the humeral head width was calculated. Results In all cases, this approach allowed for preservation of the biceps tendon and access to the rotator interval 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. Conclusion This study demonstrates the clinical feasibility of a mini-deltopectoral approach, and the ideal starting point through the RI radiographically lies along the medial aspect of the lateral third of the humeral head on the AP view, and along the posterior aspect of the anterior third of the humeral head on the lateral view.