The use of crude mortality and morbidity data to assess the outcome from surgical intervention can be both dangerous and misleading. Furthermore, differences in outcome when comparing differing units or surgeons may be explained merely by variations in case mix and the type of surgery.

In recent years there have been a number of attempts to devise a reliable method for assessing the outcome from surgical intervention. In the general surgical setting, the POSSUM system has proved to be the most reliable and accurate of all scoring systems so far devised. It is widely applicable in other specialities as it allows comparison based on the patient’s physiological status and the magnitude of surgery. It could be used in any hospital, in elective and emergency operations. The present study attempted to validate the application of this new method of assessing the outcome after orthopaedic surgery.

All consecutive patients admitted to the orthopaedic wards in a district general hospital during a 12 month period in which orthopaedic surgery was performed on a non-day case basis were assessed using the new orthopaedic POSSUM system. POSSUM is an acronym for Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity. POSSUM is a two-part system that scores both physiological and operative factors. It is developed of multivariate discriminate and logistic regression analysis of 62 variables reduced to: * 12 factors, 4 grade physiological score and * 6 factors, 4 grade operative severity score. When these are combined, a numerical estimate of both mortality and morbidity is obtained. Mortality prediction for individual patients was estimated using this equation: Log [risk − (1 − risk)] =−7.04 + (0.13 physiological score) + (0.16 operative severity score)

During the 12 month period, 2326 patients underwent orthopaedic surgery. 44% were in elective setting, 56% were in emergencies. Using the POSSUM logistic regression equations yielded an overall predicted mortality of 53 patients (versus 51 observed) and a predicted morbidity of 254 patients (versus 252 observed).

The present study indicates that orthopaedic POSSUM is accurate in assessing outcome after an orthopaedic operation and can be used as an audit aid to assess the quality of surgical care.

The overall incidence of cuff tears increases with age, individuals over 80years having a 51% incidence of a tear. Currently, the aetiology of rotator cuff tears remains unclear and successful repair is achieved in only 30% patients. Matrix metalloproteinases (MMPs) have roles in a wide range of physiological processes including placentation and embryogenesis, tissue remodelling and wound healing. However, the ability of MMPs to dissolve extracellular matrix has been linked to a variety of pathological processes including rheumatoid arthritis, osteoarthritis, periodontitis and multiple sclerosis, which involve excessive matrix destruction. Production of gelatinase MMPs by torn rotator cuff has been demonstrated. The objectives of this study were to examine the expression of MMPs and their association with histological changes in full thickness tears of the rotator cuff.

Rotator cuff tissue was obtained from ten patients (age 40–80years) undergoing surgical repair. The size of tear was 1–4.5cm; time from presentation to surgery was 1 month (acute) to between 0.5–4years (chronic). Immunohistochemical staining with commercial monoclonal antibodies to a range of MMPs, endothelial, macrophage and fibroblast markers was performed. Production of gelatinase MMPs was measured by gelatin zymography on tissue culture supernatant. Visualisation used a standard DAB chromagen technique.

In the acute specimens there was an infiltrate of macrophages with little collagen degeneration; the fibro-blasts were MMP1 positive and endothelial cells MMP2 positive. At 12 months post-tear mature collagen, plump fibroblasts and proliferating endothelial cells were identified adjacent to the resection edge. Towards the torn edge areas of lower cellularity, sparse vascularity and collagen degeneration were observed. Vimentin positive, CD68 negative cells within this matrix were rounded with foamy cytoplasm, and intensely positive for MMP1 and MMP2, and positive for MMP-3, -10, -11, -13 and -14. Tissue culture supernatant demonstrated active and latent MMP2 production in all cases.

The prolonged interval between trauma and surgical repair, with potential pharmacological intervention, remedial physiotherapy and disuse immobility, make assessment of the factors contributing to tendon degeneration difficult to determine. Fatty infiltration, dystrophic calcification and patchy collagen degeneration were common. However, clear evidence of cellular activities typical of wound repair were also identified, including fibroblast and endothelial cell proliferation. The most striking finding was the association between areas of poor collagen structure with fibroblasts staining intensely for both MMP1 and MMP2 and positive for other matrix metalloproteinases. The production of MMP1 and MMP2 may contribute to active remodelling of the tendon matrix. Success of repair could be influenced by both the quality of the matrix and the cell types and activities in the tissue at the resection edge.