Review Question - QID 214827

The accepted anatomic position of the top of the greater tuberosity is ~8 mm below the top of the native or prosthetic humeral head.

Arthroplasty is indicated for 4-part, head-split, and select severe 3-part fracture-dislocations of the proximal humerus. While reverse total shoulder arthroplasty is supported in older, less active patients, hemiarthroplasty is often more appropriate in younger and more active patients. Anatomic tuberosity repair and healing is vital toward obtaining good post-operative outcomes. The head-to-tuberosity (HTD) height should ideally be 7 to 8 mm below the most cephalic extent of the humeral head in order to best restore the native anatomy.

Huffman et al. performed a biomechanical cadaveric study to determine proper tuberosity placement after prosthetic shoulder reconstruction for proximal humeral fractures. Hemiarthroplasty was performed on 18 cadavers with preservation of anatomic tuberosity height (7-8 mm below the anatomic humeral head), and with 10 mm and 20 mm of inferior tuberosity displacement. The authors noted that glenohumeral joint forces shifted significantly superiorly at 30 degrees of abduction after both 10 mm and 20 mm of tuberosity inferiorization. The authors concluded that malpositioning the tuberosities inferiorly during hemiarthroplasty results in significant superior glenohumeral joint force-displacement.

Pijls et al. discussed a novel sling technique for tuberosity fixation in hemiarthroplasty for fractures of the proximal humerus. The authors reported on 31 uncemented hemiarthroplasties using this technique to repair the tuberosities with special emphasis on the head-to-tuberosity distance (HTD). They noted that the sling technique had an overall better tuberosity positioning in terms of HTD compared with the drill-hole technique (8 mm versus 1 mm). The authors concluded that the sling technique for tuberosity fixation provided more anatomic tuberosity position, thereby leading to significantly better functional outcome, patient satisfaction, and pain scores.

Illustration A is a radiograph depicting the head-tuberosity distance (HTD). Illustration B is the described sling-technique by Pijls et al showing the several phases of the sling technique: a) A sling is created by pulling the combined ends through the loop. b) Four slings are placed around the humeral shaft, two medially and two laterally. c/d) Final positioning and knotting.

Incorrect Answers:
Answers 1 and 4: The most cephalic extent of the prosthetic humeral head should be 5.6 cm from the superior border of the pectoralis major muscle tendon.
Answer 2: The top of the greater tuberosity should be inferior to the most cephalic extent of the humeral head in order to avoid impingement.
Answer 5: The top of the greater (NOT lesser) tuberosity should ideally be located 8 mm below the most cephalic extent of the prosthetic humeral head.