R.W. Nyffeler, C.M.L. Werner, A. Sukthankar, M.R. Schmid, and C.
Gerber reply:We thank Drs. Bhatia, deBeer, and du Toit for their interest in our
article. They remarked that humeral head medialization in patients with
massive cuff tears can influence the "acromion index" and
suggested that a large lateral extension of the acromion therefore may be
relative rather than absolute and that its association with rotator cuff tears
may be a consequence rather than a cause.We agree that medialization of the humeral head secondary to degeneration
of the articular cartilage, flattening of the humeral head, and glenoid
erosion decreases the distance from the glenoid plane to the lateral aspect of
the proximal part of the humerus and therefore increases the acromion index.
These morphological changes were typically present in the group of patients
with primary osteoarthritis and an intact cuff, who were managed with an
anatomical total shoulder prosthesis (Group 2 in our study). The patients with
a full-thickness rotator cuff tear involving at least the supraspinatus tendon
(Group 1) had no or only mild degenerative changes of the joint surfaces. No
patient in our study had a cuff tear arthropathy requiring the insertion of an
extended humeral head prosthesis or a reverse total shoulder prosthesis. The
patients in Group 1 were managed with a cuff repair and in some cases with an
additional latissimus dorsi tendon transfer. The acromion index for the
rotator cuff tear group was significantly higher than that for the
osteoarthritis group with a medialized humeral head.