Purpose: To assess the use of abdominal aorta cryopreserved allografts as guided regeneration membranes in long bone defects.

Materials and methods: This is a prospective randomized blind study of 10 White New Zealand rabbits. 10 mm-long diaphyseal defects were created in both radii: on one side the defect was separated from the surrounding tissue by means of a tube-shaped cryopreserved aortic allograft; the contralateral radius (control) was left to develop spontaneously with no membrane. The animals were put down after 6, 12, 24 and 30 months. A whole range of different studies were made: x-rays, CT, MRI, morphodensitometric techniques and optical and electronic microscopy.

Results: No complete bone regeneration was observed in any of the controls. In 9 out of the 10 defects for which an aortic allograft was used complete bone regeneration was achieved as well as a restoration of continuity with a corticomedullary pattern. A progressive increase in density and thickness was observed in the regenerated cortex, which reached values similar to those of normal bone. A gradual reduction of the medullary/cortical thickness index was also detected.

Discussion: The microscopic images taken suggest that cryopreserved arterial allografts used in guided regeneration behave like barrier membranes and as osteoinductive agents because of the osteoblastic differenciation of endothelial and/or muscular cells and/or ossification secondary to proteic changes in the extracellular matrix of the artery. This could be regarded as the application of artery calcification and ossification (usually associated with arteriosclerosis, ageing, diabetes and renal failure) to the regeneration of bone defects.

Conclusions: It is possible to use cryopreserved aortic allografts as osteostimulating membranes in the guided regeneration of bone defects.

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).

Aims: Clinical and radiographic evaluation of retinacular lateral releases using an arthroscopic approach, for anterior knee pain in cases with slight patelar axial malposition Methods: Prospective study in 34 patients. Evaluation according to the Insall clinical score, patient opinion, and change in radiographic angles and index from pre-operative to post-operative. Results: Postoperative clinical score (Insall 1983): 82% excellent; 6% good; 6% poor; 6% bad. Angular values: patelar index (Cross 1976) of 7,1 and sulcus angle (Brattstrom 1964) of 139,6∞. Radiographic correction: from 15,7 to 17,9 in patello-femoral angle (Laurin 1978); from −5,6 to −5,3∞ in congruency angle (Merchant 1974); and from 1,37 to 1,12 in patello-femoral index (Laurin 1978). Conclusions: Clinical results, patient satisfaction, and radiographic correction of congruency angle, patello-femoral angle and patello-femoral index make justifiable the use of arthroscopic lateral releases in the treatment of selected cases of patello-femoral pain.