[Fibrous dysplasia of the proximal femur in children and teenagers: surgical results in 22 cases]. / La dysplasie fibreuse de l'extrémité proximale du fémur chez l'enfant et l'adolescent: résultats du traitement chirurgical dans 22 cas.

PURPOSE OF THE STUDY: Fibrous dysplasia is a rare benign bone tumor which occurs preferentially in the proximal femur. In children, there is a risk of repeated fractures and coxa vara deformity, particularly in the polyostotic form. The most common orthopedic problem is fibrous dysplasia of the proximal femur which generally requires surgical treatment. The purpose of this study was to analyze clinical and radiological outcome after surgical treatment. MATERIAL AND METHODS: All children who underwent surgical treatment for fibrous dysplasia of the proximal femur between 1979 and 2001 were reviewed retrospectively. The study cohort included 22 children (11 boys and 11 girls). Eight patients had a monostotic form and 14 a polyostotic form of the disease. For the monostotic forms, the type of treatment depended on the size of the tumor and its localization but curettage was used in all cases. For the polyostotic forms, treatment consisted in valgus osteotomy with "humeralization" in the event of associated coxa vara in combination with internal fixation, generally with a centromedullary nail. RESULTS: In the monostotic forms, the clinical outcome was considered good in all cases. Nearly total involution of the tumor was noted in 75% of patients. In the polyostotic forms, osteotomy with "humeralization" and centromedullary nailing provided stable correction of the deformation. Outcome was less satisfactory because of fractures and deformities. DISCUSSION: In light of our results and those reported in the literature, the prognosis of the monostotic form can be considered good after surgical treatment. For the polyostotic form, preventive fixation is necessary. Osteotomy with "humeralization" appears to correct the deformity and prevent coxa vara in certain cases. For the more severe forms, medical treatment with biphosphonates may be a useful complement to the surgical treatment.

[Scarf osteotomy for the treatment of hallux valgus: a review of 123 cases with 4.8 years follow-up]. / Ostéotomie Scarf dans le traitement de l'hallux valgus: à propos de 123 cas avec un recul moyen de 4,8 ans.

PURPOSE OF THE STUDY: Many different osteotomies can be used for the treatment of hallux valgus. The purpose of this study was to evaluate the Scarf osteotomy associated or not with phalangeal osteotomy and to search for deformation cutoff points beyond which corrections appear to be difficult to achieve. MATERIAL AND METHODS: This retrospective analysis included 87 patients (123 feet) among 130 who underwent hallux valgus surgery between October 1993 and November 2000. Mean follow-up was four years eight months. The serie included 83 women and 4 men. Mean age at surgery was 53.5 years. A Scarf diaphyseal osteotomy was performed in all patients associated or not with phalangeal osteotomy. Each patient was reviewed clinically and radiographically with anteroposterior and lateral views of the foot in the standing position. RESULTS: 84.6% of the patients were satisfied or very satisfied. There was a correlation between the index of satisfaction and clinical symptoms (metatarsalgia, stiff hallux, pain over exostosis). There was a statistically significant decrease in hallux valgus (31.2 degrees to 17.5 degrees ), of metatarsus varus (12.1 degrees to 7.5 degrees ), and articular angle of the distal metatarsus (13.3 degrees to 11.1 degrees ). Patients who had phalangeal osteotomy achieved the best hallux valgus correction (15 degrees versus 21.4 degrees ). Mean shortening of the first metatarsus was 2.2 mm with a decrease in the metatarsus-ground angle (19 degrees versus 20.1 degrees ). Cutoff limits for deformations which are difficult to correct satisfactorily were M1M2 angle > or = 15 degrees and distal metatarsal articular angle > or = 13 degrees . The overall Groulier score showed 70.7% very good and good results, 27.6% fair results and 1.7% poor results. DISCUSSION: The Scarf technique is a reliable method to achieve significant correction of hallux valgus deformation. It requires a rigorous technique with specific attention to the elevation of the first metatarsus and excessive shortening, two factors favoring metatarsalgia. Adding a phalangeal osteotomy can improve the radiological result, but it is very difficult to obtain satisfactory correction if the initial deformations are severe and associated. Rotation of the plantar fragment helps for better orientation of the articular surface of the first metatarsus but limits the correction of the metatarsus varus. Function is the basic objective of hallux valgus surgery and patient satisfaction is related solely to clinical symptoms.

[Biomechanical study and digital modeling of traction resistance in posterior thoracic implants]. / Etude biomécanique et modélisation numérique de la résistance à la traction des implants thoraciques postérieurs.

PURPOSE OF THE STUDY: The purpose of this experimental study was to compare posterior fixation systems using hooks and screws implanted in the thoracic spine. This study was completed by a digital analysis using the finished element method. MATERIAL AND METHODS: For the experimental study, we used 7 human thoracic spines. Forty-nine groups of 2 vertebrae were individualized. Traction was applied to maximum breaking force measured on an Instron. We used two types of instrumentations, alternating 4 pedicle screws and 2 pedicle-lamina hooks. For the digital study, we used a vertebral model composed of nearly 63 000 nodes and 14 000 elements. Elastic field calculations were carried out with a finished element abacus. RESULTS: The base of the pedicles broke when traction was applied to a pedicle-lamina hook assembly. The medial part of the pedicle broke when traction was applied to a pedicle screw assembly. Maximul break strength for hooks was 1 108 +/- 510 N. It was 820 +/- 418 N for 4 mm diameter screws and 1 395 +/- 435 for 5 mm screws. The most fragile vertebrae were T5-T6 and T7-T8. the screw-instrumented model showed that stress concentrated on the medial aspect of the pedicle, inside the medullary canal. Using a long screw did not reduce the stress force significantly. The hook-instrumented model showed that stress was greatest on the lower part of the pedicle. DISCUSSION: From a mechanical point of view, screw instrumentation is the more appropriate type of fixation. Screw fixation did not however demonstrate its superiority during the traction tests. For 4 mm screws, resistance was 23% weaker than with a hook assembly and for 5 mm screws, it was only 12% stronger. Pullout may be attributed to two principal causes, either fracture of the bony anchoring of the screw system or breakage of the pedicle. Bone thread pullout occurs when the screw threads do not penetrate sufficiently deep into the cortical bone due to the small diameter of the screw shaft. Using a larger diameter screw raises however the problem of damaging the pedicle. Pedicle breakage is seen with stronger stress forces and constitutes the upper limit of maximum break force. This leads us to formulate the hypothesis that in most cases, screw pullout occurs by breakage of the bony threading. Screws are less effective if they are not properly anchored in the pedicles, probably the reason for their relative weakness. Screw diameter should be adapted to the size of each pedicle. This would allow better transmission of stress from the screw to the pedicle. Hooks apply further stress to the vertebrae. The digital study showed that using a long screw crossing through the vertebra does not reduce the stress applied to the pedicles enough to justify its use.