INTRODUCTION: In guided tissue regeneration a membrane is used for defect isolation to protect it against invasion from surrounding tissues and to keep intrinsic healing factors ‘in situ’. This technique has been successfully used in maxillo-facial surgery, but short experience has been reported in long-bone defects, with synthetic membranes and with variable results. In the other hand, calcification and ossification inside the arterial wall have been described.

OBJECTIVE: The aim of the study was to evaluate the use of cryopreserved aorta allografts as membranes for guided tissue regeneration in comparison with expanded poly-tetra-fluoro-ethylene (e-PTFE) synthetic membranes.

MATERIAL & METHODS: Prospective, randomized, blinded study in 15 New-Zeland rabbits. 10 mm mid-diaphyseal defects were created in both radii: 10 defects were covered with a cryopreserved aortic allograft as a tube, 10 with an e-PTFE membrane and 10, with no barrier membrane, served as controls. Animals sacrifice at 6–12–24–30 months. Studies: X-rays, CT, MR, morpho-densitometric analysis, electronic and optical microscopy. Immuno-cytochemistry on tissues and arterial wall cells cultured.

RESULTS: None of the control defects healed. Nine defects covered with an artery completely reconstituted, but only six of those covered with e-PTFE, with a nearly normal cortical-medullar pattern and with progressive increasing in density and thickness of medullar and cortical to values similar to those of the normal bone. Histological studies showed no inflammatory response to the arterial graft, direct union between the artery and the regenerated bone and even mature bone between the elastic laminae of the arterial wall, suggesting superior biocompatibility properties. Immuno-cytochemistry and ultrastructural studies suggest that arterial allografts could act not only as membrane barriers, with additional osteoinductive properties due to trans-differentiation of viable arterial wall cells (endothelial, smooth muscle and/or tissue specific stem cells) towards osteoblastic cells, and also due to ossification secondary to changes in proteins of the arterial extracellular matrix. This could be the application of the process of arterial wall calcification and ossification (usually seen in arteriosclerosis, gender, diabetes or kidney failure) for regeneration of long-bone defects.

CONCLUSION: Cryopreserved aortic allografts can be used as membrane barriers for guided bone regeneration, with superior results to e-PTFE membranes.

Aims: To compare the vastus muscle-splitting approach and the classical medial parapatellar in total knee replacement. Methods: Prospective clinical and radiographic study in 50 cemented cruciate-retaining prostheses (Interax, Stryker-Howmedica-Osteonics): midvastus approach in 25 and parapatellar medial in 25. Results: There were no differences (p> 0.05) in postoperative femoro-tibial or patelar tilt angles, duration of surgery, drainage bleeding, Hemoglobine and Hematocrite at postoperative day 3, units of blood transfused, complications, hospital stay, range of motion, and score of the American Knee Society at 1, 6, 12 or 24 months. However, the midvastus approach showed less intraoperative lateral retinacular releases, more patients were able to get independent terminal knee extension at postoperative day 5, and the range of motion at discharge was higher (p< 0.05). Conclusions: The midvastus splitting approach can reduce the need to perform lateral retinacular releases, with advantages in the early postoperative range of motion and knee extension ability.

Aims: Clinical and radiographic comparison between a fixed polyethylene prostheses and mobile bearing design. Methods: Prospective study in 147 tricompartimental cemented cruciate-retaining prostheses (Interax, Stryker- Howmedica-Osteonics): 90 conventional fixed polyethylene and 57 mobile bearing (antero-posterior slide and rotation over an axis in the medial plateau). No differences in preoperative age, sex, range of motion, deformity, rheumatoid arthritis or osteo-arthritis, and Ahlback stage. Results: At 1, 6, 12 and 24 months there were no differences between both groups (p> 0.05) in femorotibial angles, radiolucencies, duration of surgery, pain at rest or walking, stairs, arise from chair, walking ability, range of motion, supports (cane or crutches), complications and score of the American Knee Society. Conclusions: With 2-year follow-up there are no differences in clinical or radiographic results between fixed and mobile bearing knee prostheses. Further investigations with long-time follow-up are mandatory in order to determine differences and advantages in polyethylene wear or implant survival.

Aims: To determine whether the use of Biphasic Calcium Phosphate (BCP) plus local autogenous graft modifies our clinical results and fusion rate, in comparison with iliac crest graft alone. Methods: Prospective and nonrandomized study. 40 patients were operated on with pedicle instrumentation and posterolateral fusion. Degenerative lumbar disease was the etiology. 25 patients had one level fusion and 15 two or more. Minimum follow-up: 1 year. 15 patients were smokers (17.4 cig/day). The Oswestry disability index at 0, 3, 6 and 12 months was filled in to see the evolution and final clinical result. To evaluate the fusion, X-ray criteria were used. Results: Oswestry test changed from 63,8 to 16,4 at the end of the study. 3 patients did not achieve fusion (7,5%), none of them smokers. Up to date we have been working with the same idea but trying to increase the fusion rate by adding bone marrow to BCP and grafts. The initial results are very encouraging. Conclusions: We have no difference in our non-union rate between previous historic register and the new technique.

Similar clinical results were obtained but the proportion of excellent/good has improved with iliac crest preservation.