Bone morphogenetic proteins and Smad expression in ovine tendon-bone healing.

PURPOSE: Bone morphogenetic proteins (BMPs) are being developed to improve tendon-bone healing. To do this, it is essential to understand the endogenous expression of BMPs and their downstream signal transduction factors, Smads, during tendon-bone healing. METHODS: An extra-articular patellar tendon-bone healing ovine model was set up, and histologic evaluation of the healing progress at the tendon-bone interface at 1, 2, 3, and 6 weeks was performed. Immunohistochemical staining of BMP-2, BMP-7, Smad1, Smad4, and Smad5 was carried out in all sections. RESULTS: The model revealed formation of a loose granuloma tissue layer between the tendon and bone at 1 week, remodeling starting at 2 weeks, and Sharpey-like collagen fiber formation at 3 and 6 weeks. All detected factors were elevated at the tendon-bone interface during healing, and the expression peaked at 2 to 3 weeks. The cells involved were osteoblastic-like cells, osteoclastic-like cells, mesenchymal cells, and fibroblasts. BMP-7 staining was mainly at the interface close to the bony side, whereas BMP-2 expression shifted to the tendon side at 6 weeks. The expression pattern of Smad1 and Smad5 was similar to that of BMP-7. Smad1 was also found to be expressed in osteoclastic-like cells at 1 and 2 weeks. Smad4 expression was the highest among all of the factors at all time points. CONCLUSIONS: The data suggest that endogenous BMP-2 and BMP-7 participate in tendon-bone healing and their functions involve their downstream signal transduction mediators, Smad1, Smad4, and Smad5. CLINICAL RELEVANCE: The temporal expression of BMPs should be considered when setting up therapeutic strategies using BMPs.

Midterm results using a medial pivot total knee replacement compared with the Australian National Joint Replacement Registry data.

BACKGROUND: In order to emulate normal knee kinematics more closely, and thereby potentially improve wear characteristics and implant longevity, the medial pivot-type knee replacement geometry was designed. In the current study the outcome of 50 consecutive knee replacements using a medial pivot-type knee replacement was compared with the results in the Australian Orthopaedic Association National Joint Replacement Registry. METHODS: Pre- and post-operatively at follow-up evaluation consisted of the Knee Society score system and the Western Ontario and McMaster Universities Arthritis Index Score. Patient satisfaction was documented using 5-point Likert-type scales. Standard radiographs were used to assess signs of radiographic failure. Revisions were subcategorized into major total, major partial and minor. Patient records were cross-referenced against the Australian Orthopaedic Associations National Joint Replacement Registry's and the outcome compared with the registry's subset of data on the medial pivot knee used. RESULTS: According to the patients' Knee Society score system and Western Ontario and McMaster Universities Arthritis Index scores, there was good pain relief and functional improvement; none of the implants showed radiographic signs of failure. There was one minor revision. There was no statistically significant difference in revision rate compared with the registry results. DISCUSSION: The medial pivot knee-type implant in this series provided pain relief, functional improvement and a revision rate, similar to what is reported in the literature after a longer follow-up period, which is reassuring for those who use this type of implant on a day-to-day basis.