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.

Background and objective: 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. 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.

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.

Introduction.- Some of the recommended alternatives to increase the cementless acetabular cups stability are the plasma sprayed porous coated and HA and the press-fit impaction. The incorporation of three peripheral fins improves final fixation avoiding micromotion at the immediate post operative period. From 1992 we have implanted 4068 cups, the majority of them in primary cases (78%). The rest 22% in revision cases.

Cup characteristics: hemispheric with fins to improve prumary fixation and HA coating; ring-long ystem in common with other Biomet models, reason why liner are interchangeables.

Material and methods.- 4.068 Bihapro cups (Biomet-Merck) were implanted at a multicenter study in three Hospitals, adjoined to the University, between 1992 and 2003. This is a press-fit model with a porous surface coated with HA and three peripheral fins to improve primary fixation and also dome holes to allow the use ob bone screws.

Prymary indication: osteoarthritis (76%), AVN (7%), fractures (8%), dysplasias (3%), rheumatoid arthritis (6%). Surgical approach: lateral (49%), posterolateral (34,2%), anterior (16,8%). Prophylaxis: antitrombotic (LMWH), antibiotic (1st generation cephalosporins), heterotopic ossification (indomethacin).

Results.- Results. 24 patients showed dislocation and 47 % had some degree of periarticular ossification one year alter surgery; the approach used did not show significative differences. The survival study was done using Kaplan-Meier’s curve. The end-point for failure in this study was the need to perform aesptic revision surgery; being the survival at 9 years of 99.49 % (CI 95 % 99.08 – 99.90). Seven cases needed revision surgery (0.3 %); two cases for migration of the cup and five cases for iterative dislocations.

Conclusions.- Acetabular cups with Plasma Spray Porous Coating in combination with HA, results stable at mid term. The supplementary fixation of the three peripheral fins avoids micromotion optimizing long-term fixation.