The establishment of a suitable animal model of repair of the rotator cuff is difficult since the presence of a true rotator cuff anatomically appears to be restricted almost exclusively to advanced primates. Our observational study describes the healing process after repair of the cuff in a primate model. Lesions were prepared and repaired in eight ‘middle-aged’ baboons. Two each were killed at four, eight, 12 and 15 weeks post-operatively. The bone-tendon repair zones were assessed macroscopically and histologically.

Healing of the baboon supraspinatus involved a sequence of stages resulting in the reestablishment of the bone-tendon junction. It was not uniform and occurred more rapidly at the sites of suture fixation than between them. Four weeks after repair the bone-tendon healing was immature. Whereas macroscopically the repair appeared to be healed at eight weeks, the Sharpey fibres holding the repair together did not appear in any considerable number before 12 weeks. By 15 weeks, the bone-tendon junction was almost, but not quite mature.

Our results support the use of a post-operative rehabilitation programme in man which protects the surgical repair for at least 12 to 15 weeks in order to allow maturation of tendon-to-bone healing.

While the evolution of the bony skeleton of the shoulder girdle is well described, there is little information regarding the soft tissues, in particular of the rotator cuff. We dissected the shoulders of 23 different species and compared the anatomical features of the tendons of the rotator cuff. The alignment and orientation of the collagen fibres of some of the tendons were also examined histologically. The behaviour of the relevant species was studied, with particular reference to the extent and frequency of forward-reaching and overhead activity of the forelimb.

In quadrupedal species, the tendons of supraspinatus, infraspinatus and teres minor were seen to insert into the greater tuberosity of the humerus separately. They therefore did not form a true rotator cuff with blending of the tendons. This was only found in advanced primates and in one unusual species, the tree kangaroo. These findings support the suggestion that the appearance of the rotator cuff in the evolutionary process parallels anatomical adaptation to regular overhead activity and the increased use of the arm away from the sagittal plane.

Introduction: The delivery of regional antibiotic prophylaxis has been described in reconstructive knee surgery as well as in the management of hand injuries. In this study, we describe a technique for the delivery of regional antibiotic prophylaxis to the upper extremity in patients undergoing elbow surgery, and compare tissue antibiotic concentrations achieved with this technique to those achieved with standard systemic intravenous antibiotic prophylaxis.

Methods: We collected bone and fat samples from eight patients undergoing elective elbow surgery who had received regional antibiotic prophylaxis, and measured tissue antibiotic concentration by high performance liquid chromatography. In these patients, prior to the surgical incision, we exsanguinated the arm, inflated the tourniquet, and delivered a standard dose of Cephazolin into a dorsal hand vein. For comparison, we measured antibiotic concentrations in bone and fat samples taken from eight patients undergoing elective shoulder surgery who had received standard systemic antibiotic prophylaxis.

Results: Mean tissue antibiotic concentrations were significantly higher in the patients who received regional antibiotic prophylaxis compared with those who received standard systemic prophylaxis (Bone: 1060 mcg/gm versus 41 mcg/gm; Fat: 649 mcg/gm versus 10 mcg/gm; p < 0.05.)

Discussion/conclusions: The delivery of regional antibiotic prophylaxis in elbow surgery achieved higher tissue antibiotic concentrations than those achieved with standard systemic delivery. This technique may help reduce the risk of acute infection in elbow surgery, and may be especially valuable in elective surgery in predisposed patients (e.g. rheumatoid arthritis), in the management of open fractures, as well as in protection against particularly virulent organisms.

In severe forearm injuries, the diagnosis of disruption of the interosseous membrane is frequently delayed and sometimes missed, giving difficulties in the salvage of forearm stability.

We studied the structure and function of the interosseous membrane in 11 cadaver preparations, using mechanical and histological analysis. Seven of the specimens tested in uniaxial tension sustained a mid-substance tear of the central band of the membrane at a mean peak load of 1038 ± 308 N. The axial stiffness was 190 ± 44 N/mm with elongation to failure of 10.34 ± 2.46 mm. These results provide criteria for the evaluation of reconstructive methods.

A preliminary clinical investigation of the use of ultrasound suggests that this may be of value in the screening of patients with complex fractures of the forearm, and for investigating the natural history of tears of the interosseous membrane.