Research Article: Deltoid muscle volume affects clinical outcome of reverse total shoulder arthroplasty in patients with cuff tear arthropathy or irreparable cuff tears

Date Published: March 29, 2017

Publisher: Public Library of Science

Author(s): Jong Pil Yoon, Anna Seo, Jeong Jun Kim, Chang-Hwa Lee, Seung-Hun Baek, Shin Yoon Kim, Eun Taek Jeong, Kyung-Soo Oh, Seok Won Chung, Ara Nazarian.

http://doi.org/10.1371/journal.pone.0174361

Abstract

We aimed to estimate the interrelation between preoperative deltoid muscle status by measuring the 3-dimensional deltoid muscle volume and postoperative functional outcomes after reverse total shoulder arthroplasty(RTSA). Thirty-five patients who underwent RTSA participated in this study. All patients underwent preoperative magnetic resonance imaging(MRI) as well as pre- and postoperative radiography and various functional outcome evaluations at least 1 year. The primary outcome parameter was set as age- and sex-matched Constant scores. The 3-dimensional deltoid muscle model was generated using a medical image processing software and in-house code, and the deltoid muscle volume was calculated automatically. Various clinical and radiographic factors comprising the deltoid muscle volume adjusted for body mass index(BMI) were analyzed, and their interrelation with the outcome parameters was appraised using a multivariate analysis. As a result, all practical consequences considerably improved following surgery(all p<0.01). Overall, 20 and 15 indicated a higher and a lower practical consequence than the average, respectively, which was assessed by the matched Constant scores. The deltoid muscle volume adjusted for BMI(p = 0.009), absence of a subscapularis complete tear (p = 0.040), and greater change in acromion-deltoid tuberosity distance(p = 0.013) were associated with higher matched Constant scores. Multivariate analysis indicated that the deltoid muscle volume was the single independent prognostic factor for practical consequences(p = 0.011). In conclusion, the preoperative deltoid muscle volume significantly affected the functional outcome following RTSA in patients with cuff tear arthropathy or irreparable cuff tears. Therefore, more attention should be paid to patients with severe atrophied deltoid muscle who are at a high risk for poor practical consequences subsequent to RTSA.

Partial Text

Reverse total shoulder arthroplasty (RTSA) is a useful treatment option for patients with irreparable massive rotator cuff tears and cuff tear arthropathy (CTA).[1,2,3,4] Even though recently a less medialized design of reverse shoulder prosthesis is gaining popularity, the RTSA is grounded on the Grammont concept of fixed fulcrum prosthesis, medialization and lowering of the center of glenohumeral rotation. [1,5] The goal of RTSA is to compensate the dysfunctional rotator cuff after CTA and to improve a stability of shoulder joint, thus allowing elevation of the upper extremity with alternative function of the deltoid muscle.[6]

All practical consequences comprising pain VAS, active forward flexion and external rotations, and diverse outcome measurements considerably enhanced following surgery (all p<0.01) (Table 2). In this study, we explained the correlation between preoperative deltoid muscle volume and postoperative practical consequences following RTSA in patients with CTA or irreparable rotator cuff tears. Age- and sex-matched Constant scores were employed as the practical consequence measurement. As the Constant score covers the clinically most relevant domains and shows high responsiveness, and has been reported to be the most objective shoulder functional outcome instrument, with a total of 65 points for objective measures compared with other instruments, we selected this tool. [34,35] In this study, higher deltoid volumes, absence of a complete subscapularis tear, and greater change in the acromion-deltoid tuberosity distance were associated with the postoperative practical consequences in the univariate analyses. Among these, the deltoid muscle volume was the single independent prognostic factor for the practical consequences, which is the main finding of this study. The practical consequences after reverse shoulder arthroplasty in patients with CTA or irreparable rotator cuff tears were considerably impacted by the preoperative deltoid muscle volume. Therefore, more attention should be paid to patients with severe atrophied deltoid muscle who are at a high risk for poor practical consequences after RTSA.   Source: http://doi.org/10.1371/journal.pone.0174361

 

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