Repositioning of the humeral tuberosities can be guided by pectoralis major insertion.

Alec Cikes,Étienne Trudeau-Rivest,Dominique M Rouleau,Fanny Canet,Jonah Hébert-Davies

doi:10.1007/s11751-014-0205-z

Abstract

In complex proximal humerus fractures, positioning of the tuberosities can be a challenge. This study demonstrates the constant angle between the pectoralis major (PM) and the medial lip of the bicipital groove (BG) on the horizontal axial plane. This angle can be used to determine the rotation, as well as the positioning of the tuberosities, when planning a hemiarthroplasty or a reconstruction. Thirty-one shoulder MRIs were reviewed by three independent observers. The measurements were taken by superposing the axial cut of the proximal humerus, at the level of the distal bicipital groove, and the cut at the top of the PM insertion. By aligning the centers of rotation, we could determine the arcs of rotation between the insertion of the PM and the lips of the medial and lateral bicipital groove (MBG and LBG). Both angles were compared in terms of reliability, reproducibility, and precision. The mean PM–MBG angle was 3.7° [standard deviation (SD) 14.7°] and 27.4° (SD 14.4°) for the PM–LBG angle. We obtained good and very good intra-class correlation coefficient (ICC) results for inter- (0.675) and intra-observer (0.793) reliabilities on the medial angle, plus excellent results for the lateral angle (inter-observers 0.962 and intra-observer 0.895). This study demonstrates that the repositioning of humeral tuberosities can be guided by pectoralis major insertion. This will help achieve proper positioning of the metaphysis in relation to the diaphysis during surgery for complex proximal humerus fractures.

Highlights

Proximal humerus anatomy varies substantially between individuals and even from side to side in the same individual [1]
This study demonstrates the constant angle between the pectoralis major (PM) and the medial lip of the bicipital groove (BG) on the horizontal axial plane
All skeletally mature patients with all types of pathologies not affecting the anatomy of the humerus were included, but all MRIs performed for proximal humerus fractures, pathologies of the pectoralis major, or any other abnormality affecting bony anatomy were excluded

Summary

Introduction

Proximal humerus anatomy varies substantially between individuals and even from side to side in the same individual [1]. Recent literature has identified standard values for tuberosity height in open reduction and internal fixation (ORIF) as well as implant height in shoulder arthroplasty [3,4,5,6]. While some recommend putting shoulder hemiarthroplasty in 20 degrees of retroversion for fractures [7], finding proper rotation in ORIF is challenging. While humerus rotation can be assessed reliably by computerized tomography (CT scan), as in this case of humeral malunion (Fig. 1), no intra-operative method is described. Proximal humerus fractures are the third most frequent type of osteoporotic fractures [8], and surgical success depends on correct tuberosity positioning and healing [9]. There are two goals for reduction: The greater tuberosity height should be 5 mm lower than the top of the humeral head [12], and on the axial plane, both tuberosities

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Discussion

Conclusion