OREF recognizes research on rotator cuff disease
By Sally Chapralis
The award-winning paper presents 20 years of research on rotator cuff disease by Dr. Gerber and his colleagues
Christian Gerber, MD, FRCSEd (hon), has received the 2007 Orthopaedic Research and Education Foundation (OREF) Clinical Research Award for his manuscript on “Rotator Cuff Disease: From Scientific Understanding to Patient Care.” Dr. Gerber is a professor and chairman of the department of orthopaedic surgery at the University of Zurich, Switzerland, and an international member of the AAOS and the American Shoulder and Elbow Surgeons.
The award-winning paper presents 20 years of research on rotator cuff disease by Dr. Gerber and his colleagues. Their studies have examined the anatomic criteria predisposing to rotator cuff disease, the possibilities of diagnosis by clinical examination and imaging and the pathophysiology of muscular changes after rotator cuff tear and repair. The author has introduced these findings into the current clinical practice of management of rotator cuff surgery. These studies have directed research toward the entire muscle-tendon-bone unit, rather than to the tendon alone, and have led to new surgical procedures for treatment of rotator cuff tearing.
Dr. Gerber’s research on rotator cuff disease encompasses several areas, including anatomic descriptions, clinical diagnosis, radiographic diagnosis, causes of rotator cuff repair failure from mechanical and biologic perspectives, clinical evaluations of rotator cuff repairs, and salvage surgeries for irreparable rotator cuff tears.
His studies on the mechanical properties of sutures, tendon grasping techniques and anchoring the tendon to bone have resulted in new tendon-to-bone repair techniques. After being validated in both experimental animals and humans, these techniques have established the current standard of reference for rotator cuff repair.
To address tears beyond repair, Dr. Gerber’s team introduced the concept of tendon transfers into shoulder surgery. He pioneered the latissimus dorsi tendon transfer as a salvage procedure for the treatment of irreparable posterosuperior tears.
Dr. Gerber’s anatomic studies, delineated “the relationship between rotator cuff tears and glenoid orientation, but also between rotator cuff tear and lateral overhang of the acromion.” Dr. Gerber’s team “identified an association between rotator cuff tear and the
orientation of the glenoid relative to the axis of the supraspinatus fossa and concluded that greater glenoid retroversion is predictive of an anterior cuff injury whereas greater anteversion is predictive of a posterior cuff injury and that rotator cuff tearing was associated with a wide lateral extension of the acrion.”
The team’s study of isolated tears of the tendon of the subscapularis muscle was the first to describe the lift-off test as a “reliable way to diagnose or exclude subscapularis insufficiency…as a source of a patient’s pain.” Dr. Gerber’s study also concluded that “while other case reports noted an instability episode with a subsequent subscapularis tear, no patients in this series report instability but rather a forceful adduction or hyperextension of an adducted arm as the traumatic mechanism.”
Another study focused on isolated ruptures of the subscapularis tendon. This study, the first to evaluate the clinical outcome of surgical repair, introduced the diagnostic belly-press test. A patient with a subscapularis insufficiency is unable to forcibly press his palm to his abdomen and keep his elbow anterior to his abdomen or to actively internally rotate his arm to maintain the press against his abdomen. This study also demonstrated that open subscapularis repair is an effective treatment for this condition.
Three studies addressed the diagnostic effectiveness of magnetic resonance (MR) imaging techniques. MR arthrography was found to be accurate for detecting lesions of the subscapularis; MR spectroscopy was established as useful in quantifying fatty infiltration of rotator cuff musculature; and MR imaging after rotator repair almost always showed subacromial bursitis-like findings. Small retears or residual defects, however, were not necessarily associated with symptoms.
Mechanical causes for rotator cuff repair failure
Dr. Gerber’s six studies in this area tested and improved potentially “weak mechanical links in the rotator cuff repair construction,” ranging from “anchor pullout, anchor strength, effect of eyelet, strength and type of suture, to type of suture fixation of the tendon.”
One study, for example, addressed the influence of test temperature and test speed on the mechanical strength of absorbable suture anchors. The results of this study showed that “testing implants at room temperature can falsely improve results by a factor of 50, and that it is mandatory to test absorbable implants at body temperature, preferably at slower speeds.”
Biologic causes for rotator cuff repair failure
After reviewing problematic mechanical links in rotator cuff repair, the team looked at biologic sources of failure, such as osteopenia of the humeral head, the tissue ramifications of delayed cuff repair, the assessment of fatty infiltration, and the biomechanical manifestations of this infiltration.
Recognizing the importance of bone quality for the secure fixation of tendon to bone, Dr. Gerber examined the association of osteopenia of the humeral head with full-thickness rotator cuff tears. This study compared the bone density of cadaveric humeral heads with a full-thickness rotator cuff tear to those without a tear, using microcomputed tomography. Specimens with a tear had reduced cancellous bone and higher bone density under the articular surface compared to the greater tuberosity, leading to a recommendation that surgeons place sutures or anchors subcortically or under the articular surface.