Prevention of Femoral Head Deformity after Ischemic Necrosis Using Ibandronate Acid and Growth Factor in Immature Pigs

Background: Femoral head deformity is the most severe sequela of ischemic necrosis in skeletally immature patients. Development of severe deformity shortens useful survival time of the joint due to the appearance of early degenerative changes. Preservation of the trabecular architecture through inhibition of osteoclastic bone resorption may minimize the development of the deformity in an animal model of ischemic necrosis of the femoral head. Aims: To determine if a highly potent antiabsorptive agent, ibandronate, would inhibit bone resorption during necrotic femoral head repair to avoid subsequent flattening and deformity, to determine if the use of platelet-rich plasma stimulates bone repair and neovascularization of the damaged femoral head, and to evaluate if the combination of both therapies can preserve the femoral head while stimulating new bone formation in an animal model of ischemic necrosis. Methods: Ischemic necrosis of the femoral head was induced by surgical ligature of the circumflex vessels in 10 Landrace pigs. The animals were divided into four different groups and were administered ibandronate acid, platelet-rich plasma, or both. The contralateral, untreated femoral heads with surgical ligature of the circumflex vessels served as the control group. All animals were killed three months after surgery and the femoral head was evaluated both radiographically and histologically. The femur length was measured on radiographs and compared among the groups.Results: Final femoral length was significantly longer in the group treated with a combination of both therapies (platelet-rich plasma-ibandronate acid) compared to the others groups, with a significant difference between groups. The histological findings showed increased osteoblastic activity and thickened trabiculae, a higher rate of neovascularization, and focal hyperplasia greater bone resorption and neovascularization. Only slight changes (femoral length) were observed in the animals that received platelet-rich plasma in situ favoring revascularization that was, however, only seen in the first months of administration. Conclusions: Radiographic and histological studies showed that a combination of both therapies (platelet-rich plasma and ibandronate acid) preserved the trabecular architecture and prevented femoral head deformity in the early phase of ischemic necrosis repair in immature pigs, coinciding with reports by other authors. Clinical Relevance: These findings support the concept that a combination of antiresorptive and anabolic agents can significantly improve bone healing and decrease femoral head deformity following ischemic necrosis in the fragmentation stage. Further studies would be necessary to determine the optimal dose and longterm effectiveness for the use in pediatric patients.

Selective Posterior Epiphysiodesis of the Triradiate Cartilage of the Acetabulum: Preliminary Results of an Experimental Study in Rabbits

Background: Residual acetabular dysplasia is one of the main complications of developmental dysplasia of the hip (DDH). Without treatment, over time degenerative osteoarthritis of the joint will develop, inexorably leading to the need for joint replacement. Acetabular and/or femoral osteotomies do not avoid the appearance of osteoarthritis in a significant number of patients. The purpose of this study was to assess the possibility of provoking changes in the morphology of the acetabulum through selective epiphysiodesis of the extra-articular portion of the ilioischial arm of the triradiate cartilage, using a percutaneous cannulated screw with the guidance of an imaging intensifier in an experimental model in rabbits. Methods: In a pilot study, 3-week-old New Zealand rabbits (n = 20) were submitted to unilateral surgery of the hip while the contralateral hip of the same group was used as a control. Posterior epiphysiodesis to the triradiate cartilage of the acetabulum was performed by placement of a cannulated screw. The rabbits were followed-up until 18 weeks of life. Radiographic measurements of the hips were performed immediately postoperatively and at 12 weeks of life and before the rabbits were sacrificed at week 18. Three-dimensional computed tomography (3D-CT) scans were performed. Non-parametric tests for paired samples and the Wilcoxon test were used to compare the differences between group 1 and group 2. A p < 0.05 was considered significant. Results: The non-intervened hips showed that, when the rabbit matured, the acetabulum lost concavity and depth. When comparing the median differences of the angles evaluated at 12 weeks between groups, a statistically significant difference was found in all radiographic measurements: an increase in Wiberg’s angle but a decrease in acetabular index, acetabular angle of Sharp, acetabular depth index, and acetabular anteversion. Evaluating the operated hips at 12 and 18 weeks (three months after having removed the screw) using 3D-CT, we observed a rebound effect in the correction confirming that the effect obtained through selective epiphysiodesis did not cause the definitive closure of the cartilage. Conclusions: Selective growth arrest of the ilioischial arm of the triradiate cartilage (posterior epiphysiodesis) can alter growth and change the shape of the acetabulum in rabbits. A rebound effect was observed when the screw was removed, confirming that the technique did not provoke definitive closure of the physis. Level of evidence: Level-2, therapeutic study.