Introduction. Mesenchymal stem cells (MSCs) are identified by having the ability to differentiate into various tissues and typically used to generate bone tissue by a process of resembling intramembranous ossification, namely by direct osteoblastic differentiation. However, most bones develop by endochondral ossification, namely via remodeling of hypertrophic cartilaginous templates. To date, reconstruction of bone defects by endochondral ossification using mesenchymal stem cell-derived chondrocytes (MSC-DCs) have not been reported. The purpose of this study was to evaluate the effects of the transplantation of MSC-DCs on bone healing in segmental defects in rat femurs. Methods. Segmental bone defects (5, 10, 15-millimeter) were produced in the mid-shaft of the femur of the Fisher 344 rats and stabilised with an external fixator. Bone marrow was aspirated from the rat's femur and tibia at 4 weeks before operation. MSCs were isolated and grown in culture and seeded on a Poly dl-lactic-co glycolic acid (PLGA) scaffold. Subsequently, the scaffold was cultured using chondrogenic inducing medium for 21 days. The characteristics of the PLGA scaffold are radiolucent and to be absorbed in about 4 months. The Treatment Group received MSC-DCs, seeded on a PLGA scaffold, locally at the site of the bone defect, and Control Group received scaffold only. The healing processes were monitored radiographically and studied biomechanically and histologically. Results. 5-millimeter defect model: The bone defects in the Treatment Group healed radiographically with a bridging callus formation at 4 weeks after the procedure. Micro-CT scans showed that newly formed bone volume in the Treatment Group at 16 weeks was 1.5 times larger than that of the unaffected side. Biomechanical testing revealed that the Treatment Group showed more than 100% higher bending strength compared to the unaffected side at 8 weeks after the procedure. Histological examination showed that the implanted scaffold of the Treatment Group were covered with recipient periosteum-derived bridging callus and filled with cancellous bone-like tissues derived from endochondral ossification. Bone marrow was reconstituted at about 16 weeks after the procedure. Immunostaining examination revealed that the Type 2 collagen, that is the main component of cartilage (MSC-DCs) gradually disappeared and the Type 1 collagen became to be stained better by degrees, i.e. bone was formed clearly. 10, 15-millimeter defect model: Morphological changes were equivalent to 5-millimeter defect model, and the speed of bone regeneration did not depend on the size of the defect length. On the other hand, none of the Control Group achieved bone union. Conclusion. The results of this study suggested that ossification mechanism of MSC-DCs was very close to endochondral ossification. The quality, quantity, and speed of ossification overwhelm those of past similar models, and further development to new bone regeneration can be expected using this method. Summary. Transplantation of mesenchymal stem cell-derived chondrocytes (MSC-DCs) surprisingly enhances bone healing in segmental bone defects in rats significantly better than the previously reported similar therapy using MSCs

Purpose: We performed a biometric evaluation of the femoral trochlea in the human foetus and compared measurements with those observed in the adult in order to search for correlations with other biometric parameters of the human femur. Material: Twenty-two foetuses with no orthopaedic anomalies were preserved in formol. The 44 knees were studied. Fœtal age varied from 26 to 40 weeks. Method: After anatomic dissection, digital photographic documents were analysed using angular measurement software. The following dimensions were measured on the distal epiphysis: anteroposterior thickness of the condyles, protrusions of the lateral and medial trochleal edges, the difference in condyle height, the trochlear opening angle alpha, trochlear slope. Femoral anteversion, length of the femoral neck, and the neck-shaft angle were measured on the AP view of the femur. Spearman’s test was used to search for correlations. Results were compared with those measured under the same conditions in a series of 32 adult knees published by Wanner. Results: The alpha angle of trochlear opening was 148° with a coefficient of variability of 4%. The alpha angle was greater than 150° in 18 trochleae. The lateral edge of the trochlea was higher than the medial edge in 37/44 trochleae. There was no correlation by age and sex. The femoral measurements showed 27.01° anteversion with very wide variability (coefficient 46%) and no correlation with trochlear opening. No significant differences were observed between the fœtal and adult measurements. Discussion: Our data are the first reporting anatomic measurements of the fœtal trochlea. The morphology of the lower extremity of the femur during the third trimester of pregnancy is globally the same as in adult femurs. Morphological changes of the proximal femur occurring during growth do not appear to modify the morphology of the distal femur. The deep and asymmetrical engagement of the patella onto the trochlea is a characteristic of modern man and is considered to be a consequence of bipedal stance. Our study would appear to confirm that the anatomic characteristics of the human trochlea have been integrated into the genome in the course of evolution. This suggests that a genetic origin of trochlea dysplasia, as suggested by Dejour, is a reasonable hypothesis

Purpose of the study: Revision acetabular surgery with bone stock deficiency is a difficult problem. The use of cementless component and bioactive ceramics seemed to be a promising alternative. Since 1996, we have been filling bone defect at the time of revision with macroporous calcium phosphate ceramic. We reported our first experience between 1996 and 1999. Material and methods: The procedure was carried out in 35 hip reconstructions ( 35 patients ) at a mean follow-up of 6 years ( range 5 to 7,4). The average age of the patients was 56 years( range 28 to 83). 2 patients died of a cause unrelated to the procedure and 2 patients were lost of follow-up. Bone defect were classified into type I ( 4 hips), type IIA ( 8 hips ), type IIB ( 5 hips), type IIC ( 9 hips), IIIA ( 4 hips ), type IV ( 5 hips ) according to Paprosky classification. The functional status of the patients was evaluated according to the Merle d’Aubign ip rating.. The interfaces bioactive ceramics/bone base and bioactive ceramics/cementless component, as well as the homogeneity and the density of the graft were examined radiologically. Results: Functionally, the Merle d’Aubigné hip rating improved, increasing from11,3 to 15,9. Failure of fixation of the acetabular component occurred in 11,4 % of the acetabular reconstructions ( 4 hips in 35 patients). One was diagnosed as loose on the basis of radiographic criteria alone and the other three hips had a loose acetabular component at reoperation. We observed no failed reconstruction when the acetabular component is in direct contact with host bone on 50 % or more of its surface area. We saw no radiolucent lines or spaces at the interface between bioactive ceramics and the host bone. Morphological changes or a decreased in graft volume were not seen, except for the patient with the loose cup. Discussion-Conclusion: The findings of the present study support the use of bioactive ceramics and cement-less acetabular component in the presence of loss bone in order to achieve the goals of a revision hip replacement, provided that at least 50 % support of the cup can be obtained with host-bone

Objectives

We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells.