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.

Purpose: To assess the safety and efficacy of using mini-incisions (? 10 cm) in the implantation of total hip prostheses.

Materials and methods: A prospective study was carried out to compare a cohort of 25 total hip prostheses implanted using a posterior approach through mini-incisions (mean length 9.4 cm, range: 8–10) with another 25-patient cohort where the incisions were of standard length. Patients in both groups had a similar gender distribution, similar ages (± 3 years), weight (± 3 kg) and height (± 3 cm). The type of implant used was also similar. Statistical analysis used: Chi-square, Mann-Whitney U test and Student’s t test.

Results: After 6 months, no significant differences were observed in the body mass index, femoral cortical index, intraoperative or postoperative complications, cup diameter, stem size, cup inclination, stem alignment, quality of femoral cementation, metaphyseal and isthmic filling of the stem, leg length discrepancy, number of blood units transfused, hemoglobin and hematocrite levels 6 hours post-op, in the decline of these levels from those of the preop period or in the Harris Hip Score values. The mini-incision group showed higher haemoglobin and hematocrite levels after 48 hours and a lower reduction of these values from preop to 48 hours after surgery and a lower suction drain. Fewer patients of these patients needed a transfusion, they were the first to sit and start walking and they had significantly shorter hospital stays. Mean follow-up was 20 months.

Conclusions: Total hip prostheses can be implanted through mini-incisions in a safe and reproducible way and lead to a better, faster recovery without additional complications, with the same degree of precision and similar clinical results.

Purpose: To assess the performance of a constrained liner in an unstable hip prosthesis.

Materials and methods: This is a retrospective study of 66 hip prostheses implanted in 66 patients by means of the same constrained cup (Lefevre, Lepine Group, France). The cup was implanted into 15 primary prostheses and 51 revision ones in order to treat recurrent dislocations (10 cases) or to prevent dislocations (56 cases with a deficit of the periarticular musculature or mental or neuromuscular disorders). The mean age was 76.7 years, 75.7% were female, 53% were operated in the right side and the mean follow up was 30.2 months.

Results: By the time the last review was made, four patients died for reasons not related to their hip surgery. One patient showed a dissociation between the femoral head and the stem at the level of the Morse taper; the head was trapped in the retentive liner and an open reduction was needed to replace the existing prosthetic head by a new one with a long neck. Another patient had a prosthetic infection that was treated by means of a two-stage replacement. Radiolucent lines were observed in de DeLee’s zone 1 in 1.5% of patients, in 3% the lines were in zone II and in 3% they were in zone. However, according to Hodgkinson’s radiographic criteria, no cups were loose.

Conclusions: Although retentive cups do address hip instability, the various cases of failure that have occurred, the appearance of radiolucencies and the concerns about their long-term fixation suggest that their use should be carefully weighted.

Purpose: To assess the use of cortical allografts (bone plates?) in hip replacement surgery.

Materials and methods: This is a retrospective study of 43 bone plates in 36 hip prostheses. In 18 cases they were implanted to treat a periprosthetic fracture (an associated replacement of the femoral component was performed in 5 cases) and in 18 they were implanted to replace a loosened stem in a hip with large bone defects. Standard long uncemented stems were implanted in 7 cases and standard cemented stems associated with morselized compacted allografts were implanted in 16 cases. 14 patients were only given bone plates and in 22 these bone plates were associated to a metal plate. The mean age was 69.1 years (range: 38–82). 61.1% were female, 18% were implanted in the right side and the mean follow-up was 45.4 months.

Results: At the time of the last review, three patients had died but for reasons not related to their hip surgery. Transient sciatic nerve palsy was observed in one patient, prosthetic dislocation in three cases (two of them were successfully treated with bracing and the other had to be given a constrained cup), there was an infection (treated with a two-stage replacement) and two re-fractures (after 3 and 13 months) treated with a new osteosynthesis with a bone plate associated to a metal plate. All the fractures healed and the imaging tests showed an integration of the bone plate with the host bone with no signs of prosthetic loosening.

Conclusions: Cortical allografts can fulfill two functions: a mechanical one (they behave as if they were a plate) and a biological one (they increase bone stock on integration).