Six week old male Sprague-Dawley rats were administered intravenous clozapine, quetiapine, haloperidol or vehicle once daily for a period of 42 days with access to only high fat diet and their weight was monitored regularly. At the end of the study the rats were killed and the tibiae excised and bone mineral density (BMD) measured with dual X-ray absorptiometry and bone architecture assessed with micro-computed tomography (micro-CT) and associated software. Results were subjected to one-way ANOVA and post hoc Dunnetts multiple comparison test.

All treatment groups were compared to control. There were no significant differences in body weight between the different groups at completion of the study. Clozapine treated animals alone showed a significant reduction in bone mineral density (p<0.05) however no differences were seen with haloperidol and quetiapine. Both haloperidol and quetiapine, but not clozapine, treatment showed a significant reduction in the bone to tissue volume ratio (BV/TV) by approximately 23% (p<0.05) and an increase in trabecular number (TbN) by approximately 21% (p<0.05). Trabecular bone architecture parameters for haloperidol and quetiapine, but not clozapine, showed more rod like and disconnected structure as reflected in the increases in structure model index (SMI) of around 15% (p<0.05) and trabecular pattern factor (TbPf) by 22% (p<0.05).

This data demonstrates that in rats receiving a high fat diet, haloperidol and quetiapine have an adverse effect on bone micro-architecture without significant change in whole body bone mineral density.

Clozapine did not affect bony architecture in a significant manner as reported in our earlier study, though bone mineral density was reduced. Reasons for the different effect of clozapine in this study are still uncertain but may be related to the significant weight loss seen at the end point of the previous study. Causes for osteoporosis and increased fracture risk in schizophrenia may include smoking history, malnutrition, limited sun exposure and compliance.

Long term administration of both typical and atypical anti-psychotics may have a negative effect on bone and is a further factor that can influence this risk. An awareness of this relationship is useful in the orthopaedic management of schizophrenic patients.

Aim

Review causes of anchor fixation failures in patients who underwent arthroscopic rotator cuff repair.

Aim: Review causes of anchor fixation failures in patients who underwent arthroscopic rotator cuff repair.

Methods: Between 2003 and 2006, 650 arthroscopic rotator cuff repairs were performed by the senior author. Of these, anchor fixation failure occurred in fifteen patients. A retrospective review was undertaken to find out the reasons for their failure.

Results: There were ten women and five men, age range 46–84 (mean age 64). Thirteen underwent repair with metallic knotless anchors (Arthrocare), and two with 5.5mm biodegradable screw anchors (Arthrotek). Knotless anchors were used to repair six massive, one large, three medium and three small tears. The two patients with biodegradable anchor repair had only small tears, each held with a single anchor. All but one failure was apparent at six weeks. One metallic anchor failed at four months. Twelve knotless anchors failed through pull-out and one broke. Both biodegradable anchors broke at the eyelet.

Discussion: The increasing strength of suture material has shifted the weak point away from the suture-tendon interface towards the anchor-bone interface. Arthroscopic techniques permit a wider age range of patients suitable for surgery, each with varying degrees of osteoporosis in the proximal humerus, increasing risk of anchor pull-out. Multiple anchor insertions to reduce stiff, retracted tears may also lead to weakening of the bone table in the footprint area of the greater tuberosity. Incomplete anchor deployment, commonly at the curved cortical bone edge of greater tuberosity can also lead to failure.

Conclusion: Anchors failed if tension in the repair exceeds the bones capacity to retain the anchor, if the anchor is incompletely deployed or if one anchor is stressed beyond its tension capability. We recommend that consideration is given to spreading the tension of the tissue repair amongst the anchors placed in the greater tuberosity.