Elsevier

Journal of Shoulder and Elbow Surgery

Volume 10, Issue 5, September–October 2001, Pages 434-437
Journal of Shoulder and Elbow Surgery

Original Articles
Acromial morphotype in the young asymptomatic athletic shoulder*

https://doi.org/10.1067/mse.2001.117124Get rights and content

Abstract

Several studies have documented an association between the type III acromion and rotator cuff tears. However, controversy exists as to whether the shape of the acromion is an innate anatomic characteristic. The purpose of this study was to evaluate the prevalence of the type III acromion in young asymptomatic athletes. Bilateral supraspinatus outlet radiographs were obtained in 100 Division 1 collegiate athletes (average age, 19.9 years). Only 4 (2%) of 200 shoulders were found to have a type III acromion by use of the standard subjective Bigliani classification. Eight (4%) acromion were found to be type III by the use of previously published objective criteria for acromial measurement. Our results show the type III acromion to be relatively rare in asymptomatic, young athletes, but the incidence of type III acromion in a general population of both young and older individuals is still not completely understood. However, our results accentuate the possibility that the higher incidence of type III acromion seen in older populations may in fact be related to secondary acromial changes. (J Shoulder Elbow Surg 2001;10:434-7.)

Section snippets

Materials and methods

One hundred asymptomatic male Division 1 collegiate athletes ranging in age from 18 to 26 years (mean, 19.9 years) volunteered for this study. None of these athletes had a history of any type of shoulder symptom, pathology, or history of shoulder surgery. Bilateral standardized supraspinatus outlet radiographs were obtained for each subject.11, 14 All radiographs were taken by the same radiographer with the subject standing erect, facing the film, with the hand of the examined shoulder placed

Results

The subjective interpretation and Bigliani classification of all shoulder supraspinatus outlet views are shown in Table I.

. Subjective classification by Bigliani criteria

Empty CellRight shoulderLeft shoulderTotal
Type I151328 (14%)
Type II8286168 (84%)
Type III314 (2%)
Of note, only a 2% incidence of type III acromial morphology was found. The distribution of acromial types was similar when right and left shoulders were compared. Morphology was of the same type in both shoulders of the same subject in 78 of

Discussion

The relation between the anatomy of the acromion and chronic impingement syndrome was first popularized by Neer.13 He stated that extrinsic impingement by the anterior undersurface of the acromion could affect the rotator cuff. Based on his vast clinical experience, he believed that 95% of rotator cuff tears were the result of mechanical impingement caused by movement of the cuff relative to the anterior acromion. Other authors, beginning with Codman,5 have contended that rotator cuff tears

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      The meta-analysis showed that hook-shaped acromion (type III) was indicative of a higher risk for rotator cuff tears. Previous studies have indicated that, rather than having a congenital origin, a type III acromion may be acquired progressively due to mechanical traction that, in turn, can lead to degenerative bone changes.80-82 Furthermore, acromion shape is more related to its anterior slope, which has no direct relationship with the rotator cuff.

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      These enthesophytes create an extended, more rigid, anterior lip of the acromion process but do not by themselves indent the supraspinatus tendon. The prevalence of the type 3 acromion process has also been shown to increase with age.55,56 The association with rotator cuff tears could have occurred because cuff tears are also more common with increasing age or because these enthesophytes are more likely to develop in patients with rotator cuff tears.

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      These findings were similar to those of Wang et al., who found 89% of patients with type I acromion had a successful response, 73% with type II, and 58.3% of type III (Wang et al., 2000). Whether acromial shape is congenital (Nicholson et al., 1996) or acquired with age (Bonsell et al., 2000; Edelson, 1995; Speer et al., 2001; Wang and Shapiro, 1997) remains controversial. Moreover, the acromial shape classification has been questioned because of poor interobserver reliability (Jacobson et al., 1995; Zuckerman et al., 1997).

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    *

    Reprint requests: Kevin P. Speer, MD, Cary Orthopaedics and Sports Medicine Specialists, 101 Southwest Cary Parkway, Suite 100, Cary, NC 27511 (E-mail: [email protected]).

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