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Total Shoulder Arthroplasty Using a Bone-Sparing, Precision Multiplanar Humeral Prosthesis

Publish date: February 1, 2018

References

1. Williams GR Jr, Wong KL, Pepe MD, et al. The effect of articular malposition after total shoulder arthroplasty on glenohumeral translations, range of motion, and subacromial impingement. J Shoulder Elbow Surg. 2001;10(5):399-409.

2. Nyffeler RW, Sheikh R, Jacob HA, Gerber C. Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study. J Bone Joint Surg Am. 2004;86-A(3):575-580.

3. Iannotti JP, Spencer EE, Winter U, Deffenbaugh D, Williams G. Prosthetic positioning in total shoulder arthroplasty. J Shoulder Elbow Surg. 2005;14(1 Supple S):111S-121S.

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5. Denard PJ, Raiss P, Sowa B, Walch G. Mid- to long-term follow-up of total shoulder arthroplasty using a keeled glenoid in young adults with primary glenohumeral arthritis. J Shoulder Elbow Surg. 2013;22(7):894-900.

6. Figgie HE 3rd, Inglis AE, Goldberg VM, Ranawat CS, Figgie MP, Wile JM. An analysis of factors affecting the long-term results of total shoulder arthroplasty in inflammatory arthritis. J Arthroplasty. 1988;3(2):123-130.

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Next, the surgeon trials humeral implants to determine the correct implant size (Figure 9). Once the proper humeral size is chosen, the trial is removed and the humeral cover is placed over the prepared humeral head. The surgeon then proceeds to glenoid preparation (Figure 10), which is easily accessible and facilitated by angled planar cuts on the humeral head. Glenoid technique will be discussed in a subsequent article.

After glenoid preparation and insertion, the humerus is delivered anteriorly. The proximal humerus is washed and dried, and cement is applied to the peg holes in the humerus bone and the underside of the humeral implant. The implant is then inserted using the humeral impactor to apply pressure and assure that the implant is fully seated. Once the humeral cement is hardened, the glenohumeral joint is irrigated and closure begins. Postoperative radiograph is shown in Figure 11.

DISCUSSION

Numerous authors have demonstrated that accurate implant placement is crucial for restoring normal glenoid kinematics and motion,^1-4 while some authors have reported worsening clinical outcomes and higher rates of pain and implant loosening when the implants were not placed anatomically.^5-8This is such an important concept that it essentially was the primary inspiration for creating this TSA system. In addition, the system utilizes a nonspherical, elliptical humeral head that more closely matches the anatomy of the proximal humerus,^14,15 and this type of shape has shown improved biomechanics in laboratory testing.¹²

Good results have been demonstrated in restoring the normal anatomy using stemmed devices on the radiographic analysis of cadavers.¹⁶ The creation of stemmed implants with variable inclination and offset has improved computer models¹⁷ compared with previous studies,¹⁸ with the exception of scenarios with extreme offset.

In theory, resurfacing implants and implants without a canal stem should have a better implant placement than that with stemmed implants; however, the ability to restore the center of rotation was even worse for resurfacing prostheses, with 65% of all implants being measured as outliers postoperatively in one study.¹⁹ Most of the resurfacing implants and their instrumentation techniques offer little to help the surgeon control for implant height. The depth of the reaming is variable, not calibrated, and not correlated with the implant size, frequently leading to overstuffing after surgery. Second, the use of spherical prostheses forces the surgeon to choose between matching the superior-inferior humeral size, leading to overhang of the implant, or matching the anteroposterior, leading to frequent undersizing in the coronal plane. The nonspherical, elliptical head shape can potentially simplify implant selection.

In summary, new techniques have been developed in an attempt to achieve increased consistency and precision in TSA. By more accurately reproducing the proximal humeral anatomy, it is proposed that clinical outcomes in terms of the range of motion and patient satisfaction may also be improved through newer techniques. Cadaver studies have validated the anatomic precision of this technique.¹⁰ Clinical data comprising of patient-reported outcome measures and radiographic outcome studies are currently underway for this arthroplasty system.