A technique for humeral prosthesis placement in reverse total shoulder arthroplasty for fracture

Abstract

Recent trends have illustrated the benefits of treating displaced fractures of the proximal humerus with reverse total shoulder arthroplasty. Clinical results have demonstrated reliable restoration of function in situations where results following hemiarthroplasty have been variable and difficult to predict. Data have demonstrated landmarks to assist with humeral stem height in hemiarthroplasty. However, intraoperative landmarks to guide placement of the humeral component in reverse shoulder arthroplasty have not been described. In this technique, the superior border of the pectoralis tendon is utilized. A distance of 5.0 cm is used to assist in placement of the most superior aspect of the metallic humeral component and with humeral stem version. This technique can be used as a guide to assist a treating physician in situations where bony fracture and comminution make humeral stem height placement difficult to judge.

Introduction

The proximal humerus is one of the most common locations for fracture.¹ A four-part classification system for proximal humerus fractures was described by Neer in 1970.² Subsequently, Neer illustrated treatment options for displaced three- and four-part proximal humerus fractures. Management of four-part fractures with arthroplasty was noted to have superior outcomes when compared to management with closed or open reduction.³

The vast majority of proximal humerus fractures with minimal displacement are treated non-operatively.⁴ Fractures with significant displacement, articular damage, risk of osteonecrosis or non-union are treated with arthroplasty. Hemiarthroplasty has been considered the standard treatment, but results after hemiarthroplasty for displaced proximal humerus fractures have been variable.^5,6 Patient outcomes correlate closely with tuberosity healing and position.⁷ To further assist the treating surgeon with placement of the humeral component, data have demonstrated the pectoralis major tendon may be used to provide guidance for hemiarthroplasty height and version. This is of particular importance when comminution obscures bony landmarks.^8,9

Reverse shoulder arthroplasty (RSA) implants were introduced by Grammont et al.¹⁰ and have provided reliable outcomes in patients with glenohumeral arthritis and rotator cuff deficiency.^11–13 The utilization of RSA to treat proximal humerus fractures has the advantages of less reliance on function of the tuberosities. Early studies have demonstrated good results.^14–17 Comparison trials have started to examine the clinical outcome differences between RSA and hemiarthroplasty for proximal humerus fractures.¹⁸ To our knowledge, no study has been published illustrating the appropriate height for placement of an RSA humeral component during treatment of proximal humerus fracture.

Technique

The images and technique described utilize an RSA (Zimmer Warsaw, IN). The indication described for this technique is a displaced proximal humerus fracture in the elderly population where internal fixation is not amenable. The technique describes the height of humeral component implantation utilizing the pectoralis major tendon insertion as a reference.

The humeral component height was chosen based on prior clinical experience and a review of prior RSA procedures performed for indications other than fracture. The height was chosen based on two parameters. First, in review of prior clinical experience and radiographic images, the most superior metallic aspect of the humeral component was noted to correlate with the most superior aspect of the greater tuberosity. This correlated with the recommended technique for head cut and stem preparation. Second, data have shown the greater tuberosity is 5.0 to 8.0 mm inferior to the most superior aspect of the humeral head, and prior literature has suggested a hemiarthroplasty height of 5.6 cm about the pectoralis border. Thus, a height of 5.0 cm was chosen. This represents the distance between the most superior aspect of the pectoralis major tendon and the most superior aspect of the metallic humeral component.

At our institution, patients often undergo a regional anesthetic block and are positioned in a beach chair position. A deltopectoral approach is utilized for visualization of the proximal humerus and implant placement. Articular fragments are identified and removed. The fracture typically propagates just lateral to the lateral ridge of the bicipital groove. The greater and lesser tuberosities are mobilized, control of the tuberosities obtained, and #5 braided non-absorbable suture is placed through the tendons of the subscapularis, infraspinatus, and remaining supraspinatus. The superior border of the pectoralis major tendon is preserved, protected, and tagged for ease in later identification. The humeral stem is prepared by sequential reaming. A trial stem is reduced with the most superior metallic portion positioned 5.0 cm above the superior border of the pectoralis major tendon. This is demonstrated in Figure 1. Of note, if any of the medial calcar is intact, this height correlates closely with the medial aspect of the implant resting on the medial calcar fragment.

Figure 1.

The image demonstrates a trial humeral component positioned 5.0 cm above the superior border of the pectoralis major tendon insertion. This is measuring to the top of the metal trial stem.

The glenoid component is prepared and implanted in a standard fashion. The humeral canal is prepared, and the final humeral component is cemented into place at 5.0 cm above the pectoralis major tendon. This is demonstrated in Figure 2. The stem is cemented in 20 degrees of retroversion. Trial reductions are performed. In the experiences of the authors, a plus zero or a plus 3.0 mm can be used to achieve appropriate tension and stability. The final polyethylene spacer is compressed into place and the humeral head is reduced. Tension is evaluated and the shoulder is taken through a range of motion to assess for inferior and anterior impingement. Thereafter, the greater and lesser tuberosities are reduced and the non-absorbable braided sutures are sequentially tied around the proximal stem. Appropriate reduction is confirmed with fluoroscopic imaging. Following thorough irrigation with Betadine and sterile saline, 1 g of vancomycin powder is administered to the surgical site. The wound is closed with a 2-0 Monocryl interrupted subcutaneous stitch and a 3-0 Monocryl running subcuticular stitch. Post-operative rehabilitation involves a four to six-week period of non-weight bearing in a sling. This is followed therapy focused on active-assisted and active range of motion. Finally, once range of motion is restored, a strengthening protocol is initiated.

Figure 2.

The image on the left demonstrates the final implant 5.0 cm above the pectoralis major tendon insertion. An illustration is provided on the right.

Illustrative case

Figure 3 depicts injury radiographs of a 67-year-old female with a medical history of hypertension and hyperlipidemia who sustained a right displaced four-part proximal humerus fracture. Prior to injury, this patient functioned and performed activities of daily living independently. Given the severely displaced four-part fracture and pre-operative activity level, she was indicated for and underwent a right RSA. Intra-operatively, her rotator cuff tendons were confirmed to be attached to the respective tuberosities. Each tuberosity fragment was isolated and controlled with #5 Fiberwire. The humeral component was placed in 20 degrees of retroversion and 5 cm proximal to the superior border of the pectoralis major tendon. This is illustrated in Figure 2. Following placement and reduction of implants, the greater and lesser tuberosities were reduced and secured around the humeral stem. Reduction was confirmed via direct visualization and fluoroscopy.

Figure 3.

Injury radiographs of a displaced four-part proximal humerus fracture.

Radiographs at five months post-operatively demonstrate maintenance of tuberosity reduction and progression to union. This is illustrated in Figure 4. She experienced an uncomplicated post-operative course and enrolled in the post-operative rehabilitation regimen as described above. At five months post-operatively, the patient demonstrated active forward elevation to 170 degrees and active external rotation to 50 degrees. The patient reported resolution of pain and return to pre-injury level of function.

Figure 4.

Post-operative images five months after surgery.

Conclusion

This technique for determining humeral height in the setting of proximal humerus fractures offers the treating surgeon the ability to use the reliable landmark of the superior border of the pectoralis major tendon. In our experience, this has allowed for appropriate tensioning of the implant without the use of spacers. This technique has been used for the past two years without subsequent postoperative dislocation events.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Bradford O. Parsons, MD is a consultant for Arthrex and has royalties from Arthrex. Paul J. Cagle, MD and Wayne Reizner, MD, MBA have nothing to disclose.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical Review and Patient Consent

Patient consent was approved through informed consent and appropriate permission was obtained.