Animal studies examining tendon-bone healing have demonstrated that the overall structure, composition, and organization of direct type entheses are not regenerated following repair. We examined the effect of Low-Intensity Pulsed Ultrasound (LIPUS) on tendon-bone healing. LIPUS may accelerate and augment the tendon-bone healing process through alteration of critical molecular expressions.

Eight skeletally mature wethers, randomly allocated to either control group (n=4) or LIPUS group (n=4), underwent rotator cuff surgery following injury to the infraspinatus tendon. All animals were sacrificed 28 days post surgery to allow examination of early effects of LIPUS. Humeral head – infraspinatus tendon constructs were harvested and processed for histology and immunohistochemical staining for BMP2, Smad4, VEGF and RUNX2. All the growth factors were semiquantitative evaluated. T-tests were used to examine differences which were considered significant at p < 0.05. Levene's Test (p < 0.05) was used to confirm variance homogeneity of the populations.

The surgery and LIPUS treatment were well tolerated by all animals. Placement of LIPUS sensor did not unsettle the animals. Histologic appearance at the tendon-bone interface in LIPUS treated group demonstrated general improvement in appearance compared to controls. Generally a thicker region of newly formed woven bone, morphologically resembling trabecular bone, was noted at the tendon-bone interface in the LIPUS-treated group compared to the controls. Structurally, treatment group also showed evidence of a mature interface between tendon and bone as indicated by alignment of collagen fibres as visualized under polarized light. Immunohistochemistry revealed an increase in the protein expression patterns of VEGF (p = 0.038), RUNX2 (p = 0.02) and Smad4 (p = 0.05) in the treatment group. There was no statistical difference found in the expression patterns of BMP2. VEGF was positively stained within osteoblasts in newly formed bone, endothelial cells and some fibroblasts at the interface and focally within fibroblasts around the newly formed vessels. Expression patterns of RUNX2 were similar to that of BMP-2; the staining was noted in active fibroblasts found at the interface as well as in osteoblast-like cells and osteoprogenitor cells. Immunostaining of Smad4 was present in all cell types at the healing interface.

The results of this study indicate that LIPUS may aid in tendon to bone healing process in patients who have undergone rotator cuff repair. This treatment may also be beneficial following other types of reconstructive surgeries involving the tendon-bone interface.

Introduction Displaced fractures of the midshaft clavicle often results in malunion with angulation and foreshortening. The purpose of this study is to determine the secondary effects of clavicular shortening on the sternoclavicular joint and scapulo-thoracic relationship, and to evaluate the symptomatic and biomechanical outcome in these patients.

Methods A series of 10 patients each with a malunited fractured clavicle defined by relative shortening of more than 15 mm were examined. A self-administered questionnaire for assessment of symptoms and function of the ipsilateral shoulder was completed for each patient. Computer tomography and three dimensional reconstructions of both shoulders were undertaken for static anatomical measurements. Biomechanical testing comparing both shoulders in each patient measured strength and velocity of movement. All subjects were symptomatic in the injured shoulder.

Results There were statistically significant differences between injured and uninjured shoulders for both mean shoulder scores and visual analog global assessments of shoulder function. Clavicular shortening produced statistically significant increased upward angulation of the clavicle at the sternoclavicular joint (p< 0.005), increased lateral displacement of the scapula on the posterior wall, and anterior scapular version (p< 0.05). Biomechanical differences were also recorded including a reduction in muscular strength for adduction, extension, and internal rotation of the humerus and also a reduced peak abduction velocity in the injured shoulder (p< 0.05).

Conclusions Changes in static sternoclavicular and scapulothoracic relationships occur following short malunion of the clavicle and are possible mechanisms limiting shoulder function after this injury. This study provides evidence that consideration should be given to prevention of clavicle malunion by open reduction and internal fixation, especially in the young and active age group.