Effect of arthroscopic acromioplasty on reducing critical shoulder angle: a protocol for a prospective randomized clinical trial

Abstract

Background: The critical shoulder angle (CSA), which helps to predict patients who are at risk of rotator cuff tears (RCTs) with large degree and who are susceptible to osteoarthritis with low angle, has been identified as one of the most vital acromial parameters; anterolateral and lateral acromioplasties have been proven to be valid ways to reduce CSA. However, no study has compared the effect of different acromioplasties on the reduction of the large CSA (≥33°) clinically. Additionally, either anterolateral or lateral acromioplasty could not precisely correct large CSAs to a favorable range (30-33°) in each patient. Thus, we will propose a novel precise acromioplasty technique for the purpose of reducing CSA accurately and effectively, and compare the effectiveness of different acromioplasties on the reduction of the CSA.

Methods: A total of 60 RCT patients who have indications for arthroscopic rotator cuff repair and with pre-operative CSA ≥33° will be recruited in outpatient center of Sun Yat-sen Memorial Hospital. Eligible participants will be randomly allocated to Group A (anterolateral acromioplasty), Group B (lateral acromioplasty) or Group C (precise acromioplasty) via a random, computer-generated number system. Three surgical plans will be made for each participant respectively by one professional surgeon according to the results of randomization allocation. The post-operative CSA will be measured 2 days post-operation. Follow-up will be maintained at 3, 6, and 12 months after surgery including the visual analog scale score, the University of California at Los Angeles score, the Constant Shoulder Score and the American Shoulder and Elbow Surgeon Shoulder Assessment Form. Finally, all outcomes will be assessed by two researchers who are blinded to the recruitment and allocation.

Discussion: This is the first clinical trial to evaluate the impact of different acromioplasties on the reduction of the CSA. Additionally, this study will provide a new precise acromioplasty technique, which is a novel precision and individualized treatment to prevent degenerative RCTs by reducing the CSA.

Trial registration: ChiCTR2000032343 . Registered on April 26th, 2020.

Keywords: 3D reconstruction; Acromioplasty; Critical shoulder angle; Rotator cuff tears.

Fig. 1

Study flow diagram

Fig. 2

The procedure of the precise acromioplasty. a Simulating virtual acromioplasty on computer. The pre-operative CSA (critical shoulder angle) is 36°(green line), the post-operative target CSA is set to be 30°(red line), and the green regions is planned to be resected. b Measurement of the resected bone border (green regions) by software. A, anterolateral corner; B, anteromedial resection margin; C, posterolateral resection margin; distance from A to B is about 10 mm, distance from A to C is about 22 mm. c Marking acromion and determining the resection margin on the patient’s skin. d View from the posterior portal: The spinal needles mark the points A, B and C, the line BC is the resection line. # undersurface of the acromion. e View from the lateral portal: After the precise resection of the acromion. * delta muscle fibers; ## resection surface of the acromion. f Measurement of post-operative CSA (29.4°) on standard anteroposterior radiography of the shoulder

Fig. 3

The measurement of the critical shoulder angle (CSA) on 3D scapula (a) and X-ray (b)