Arthroscopic Correction of the Critical Shoulder Angle Through Lateral Acromioplasty: A Safe Adjunct to Rotator Cuff Repair

Abstract

To investigate whether arthroscopic lateral acromioplasty reliably decreases the critical shoulder angle (CSA) and whether it is associated with damage to the deltoid or other complications. Patients undergoing arthroscopic rotator cuff repair (RCR) with lateral but without anterior acromioplasty for degenerative, full-thickness rotator cuff tears and a CSA of 34° or greater were retrospectively reviewed. Patients with traumatic or irreparable rotator cuff tears, osteoarthritis, or previous surgery were excluded. Clinical and radiographic outcomes were assessed at a minimum of 12months' follow-up. We reviewed 49 consecutive patients (mean age, 56years; age range, 39-76years) at a mean of 30months (range, 12-47months). There were 7 RCR failures (14%). The mean CSA was reduced from 37.5° preoperatively (95% confidence interval [CI], 36.7°-38.3°) to 33.9° postoperatively (95% CI, 33.3°-34.6°; P < .001). There were no cases of dehiscence, increases in fatty infiltration, or significant atrophy of the deltoid. Scarring at the deltoid origin was noted in 18 patients (37%). The mean absolute and relative Constant scores increased from 59 points (95% CI, 54-64 points) to 74 points (95% CI, 70-78 points) and from 66% (95% CI, 61%-71%) to 83% (95% CI, 79%-87%) respectively, and the Subjective Shoulder Value increased from 45% (95% CI, 39%-50%) to 80% (95% CI, 74%-86%) (P< .001 for all 3 improvements). The postoperative CSA was significantly larger in failed than in healed repairs (P= .026). Patients with a healed RCR and a CSA corrected to 33° or less (n= 22) had 25% more abduction strength than patients with a healed cuff and a CSA corrected to 35° or greater (n= 14, P= .04). Arthroscopic lateral acromioplasty performed in addition to arthroscopic RCR can reduce the CSA without significantly compromising the deltoid origin, deltoid muscle, or function. It is not associated with any additional complications of arthroscopic RCR. Insufficiently corrected, abnormally large CSAs are associated either with a higher retear rate or with inferior strength of abduction if the tears heal. Level IV, case series, treatment study.