Effects of the Insertion Type and Depth on the Pedicle Screw Pullout Strength: A Finite Element Study.

PURPOSE: The pedicle screw is a surgical device that has become widely used in spinal fixation and stabilization. Postsurgical complications such as screw loosening due to fatigue loading and screw breakage still need investigations. Clinical parameters such as the screw insertion type and depth, the bone density, and the patient degree of mobility greatly affect the mechanisms of the implant's failure/success. METHODS: The current finite element study focused on the prediction of the pedicle screw pullout strength under various conditions such as insertion type, insertion depth, bone quality, and loading mode. RESULTS: As depicted in this study, the preservation of the pedicle cortex as in the N1 insertion technique greatly enhances the pullout resistance. In addition, the higher the screw-anchoring depth, permitting to gear a maximum number of threads, the better the protection against premature breakouts of pedicle screws. CONCLUSIONS: In agreement with experimental data, the type of insertion in which the first screw thread is placed immediately after the preserved pedicle cortex showed the best pullout resistance for both normal and osteoporotic bone.

[Effect of polymorphisms on key enzymes in homocysteine metabolism, on plasma homocysteine level and on coronary artery-disease risk in a Tunisian population]. / Effet des polymorphismes des enzymes clés du métabolisme de l'homocystéine sur l'homocystéinémie et le risque coronarien chez une population tunisienne.

BACKGROUND: Hyperhomocysteinemia is known as an independent-risk factor for coronary-artery disease (CAD). However, the effect of homocystein metabolic enzymes polymorphisms on CAD is still controversed. We investigated the relation between homocystein metabolic key enzymes polymorphisms, homocystenemia and coronary stenosis in a Tunisian population. METHODS: Samples were collected from 251 CAD patients documented by angiography. Genotyping were performed for C677T methylene-tetrahydrofolate reductase (MTHFR), A2756G methionine-synthase (MS) and 844ins 68 cystathionine-beta-synthase (CBS). We measured fasting plasma tHcy, folate and vitamin B12. RESULTS: There was significant increase in homocysteinemia for homozygous genotypes of C677T MTHFR (p<0.001) and A2756G MS (p=0.01), but not for 844ins68 CBS (p=0.105). Potential confounders adjusted odds-ratios for significant coronary stenosis, associated with MTHFR TT, MS GG and CBS insertion, were respectively 1.78 (p=0.041); 2.33 (p=0.036) and 0.87 (p=0.823). The effect of mutated MTHFR genotype was more pronounced on homocysteinemia (21.4+/-9.1 micromol/L; p<0.001) and coronary stenosis (OR=2.73; p=0.033) at low folatemia (< or =6.1 ng/mL). CONCLUSION: MTHFR TT and MS GG genotypes increase tHcy concentration and coronary stenosis risk, especially with low folatemia.

Participatory rural appraisal in smallholder dairy systems in Tunisia.

Participatory Rural Appraisal (PRA) was carried out by a multidisciplinary team on a total of 60 smallholder dairy farms in three different geographical areas of Tunisia. Farms with less than three cows were excluded. Those participating had between three and 10 cows. Average milk production ranged between 8 and 32 litres per cow per day. 70% or over of milk produced was sold off the farms. Average intercalving intervals--measured from month of calving only--ranged from 12.9 months to 19. Age at first calving varied from two to nearly three years. Most work was done by the families. PRA revealed that the farmers in all three regions perceived unbalanced nutrition, which included availability of forages, to be the most important constraint, followed by poor reproductive efficiency. Reseeding with new species was instituted for grazing and hay. Farmers from the different regions were taken on exchange visits to see how these approaches worked. Training in reproductive management and milking hygiene was introduced. Seasonal ration formulation depending on local forage analysis was instituted. Two farms are participating in a programme of evaluation of olive oil extraction by-product as a ruminant feed. Partial budget analysis of these interventions will be carried out.

[Supracondylar femoral extension osteotomy for knee flexion contracture correction in poliomyelitic conditions]. / Ostéotomie fémorale supra-condylienne d'extension dans la correction des flexums post-poliomyélitiques du genou.

PURPOSE OF THE STUDY: Knee flexion contracture due to quadriceps paralysis is a major handicap in poliomyelitis patients. The patient has to stabilize the knee with the ipsilateral hand to achieve weight bearing and the deformed knee precludes use of orthopedic devices. Extension can be achieved with supracondylar femoral osteotomy if the knee flexion contracture is less than 30 degrees. We assessed functional and anatomic outcome. MATERIAL AND METHODS: We reviewed the files of 87 patients who had undergone 93 supracondylar femoral osteotomies for knee flexion contracture (6 bilateral cases); mean age was 18 years and mean flexion was 25 degrees. The surgical correction was achieved by diaphyseal metaphyseal impaction with resection of an anterior wedge and preservation of the posterior component of the articulation. If some gluteus maximus activity was retained and the tibiotarsal joint was in a slightly equine position, weight bearing in a stable locked position became an automatic postural event even in case of total paralysis of the quadriceps. Osteotomy was not possible if the contracture flexion was greater than 30 degrees due to excessive tension on the vaculonervous bundles. The procedure was equally impossible in children under 12 years of age due to the risk of recurrence subsequent to migration and callus remodeling with bone growth. RESULTS: Complete extension of the knee was achieved peroperatively in all cases. The most serious complications were three cases of septic arthritis that led to an irreducible stiff knee. In addition, we had two cases of transient paralysis of the common fibular nerve that recovered spontaneously. Bone fusion was achieved in all cases within 30 days. Recurrent flexion contracture was observed in 5 cases and required a revision using the same procedure in 3 or them. Postoperatively, the amplitude gained in knee extension corresponded to the amplitude lost for flexion. Sixty-three patients were able to walk independently without manual stabilization and a knee extension orthesis could be installed for 19 others. Three patients were still unable to walk despite the correction of the knee flexion contracture due to failure of poorly accepted orthopedic devices. DISCUSSION: Several conservative methods (physiotherapy, manipulations, successive corrective casts) and surgical procedures (release of posterior soft tissues, Ilizarov technique) have been proposed for the correction of paralytic knee flexion contracture. Supracondylar femoral osteotomy for extension can be useful after the end of growth if the flexion contracture remains below 30 degrees. The procedure is simple and morbidity is relatively low compared with the regularly successful results. When the flexion contracture exceeds 30 degrees, the supracondylar osteotomy cannot be employed due to the risk of stretching the vasculonervous bundles and due to the instability and disorganization of the lower femur. Progressive correction can be proposed for these patients: regular monitoring of the neurological and vascular situation is required. Functional improvement is considerable after correction of knee flexion contracture. The patients can walk more easily, no longer need to stabilize their knee with their hand, and can benefit from orthopedic devises due to the more favorable biomechanical conditions.

[Tuberculosis of the trochanter. Apropos of 17 cases]. / Les trochantérites tuberculeuses. A propos de 17 cas.

This paper presents a short study of 17 cases of tuberculosis of the greater trochanter seen during a period of 19 years at the National Orthopaedic Institute in Tunis. The onset of the infection is slow with patients presenting at a mean of 7 years after initial symptoms. The diagnosis is confirmed by biopsy and culture of the organism. Management is based on treatment with antituberculous drugs, although surgical excision of the lesion is sometimes required. Successful resolution of the symptoms is usually achieved unless the hip joint becomes involved. Our patients showed good results at a mean follow up of 5 1/2 years.

[Extended melanocytic tumor of the cervical spine. Apropos of a case of melanotic schwannoma]. / Tumeur mélanique étendue du rachis cervical. A propos d'un cas de schwannome mélanotique.

A case of melanotic tumour was described localized close to the right cervical spine, destroying C6 and C7 vertebral bodies and pedicles, on a 27 years old woman. Histological and immunohistochemical findings, correlated with clinical and X-rays data, led up to the diagnosis of a melanotic schwannoma. Six years after the beginning of the illness, the outcome was preceded by a local vertebral involvement without metastasis and paradoxically with a good general state. The tumoral localization and the finding of nervous structures allowed to evoke a development from a cervical nerve root. On histological basis, we propose to classify this tumour along the new concept described by the Mayo Clinic pathologists team, under the name of psammomatous melanotic schwannoma. Some authors evoke a congenital outset in a context of endocrine disorders.

[Early severe spinal lesions in Bourneville's tuberous sclerosis]. / Atteinte rachidienne précoce et sévère au cours d'une sclérose tubéreuse de Bourneville.

An exceptional case of tuberous sclerosis with marked extensive lesion of the spine in the first year of life is reported. This lesion required orthopedic treatment at the age of 3 years and surgery at the age of 6 years.

Elbow dislocation with avulsion of the medial humeral epicondyle.

After dislocation of the elbow with avulsion of the medial epicondyle, the management of the latter is controversial. Of 28 children followed up after initial closed reduction of the elbow, 19 had a satisfactory closed reduction of the epicondyle and were treated in plaster. At follow-up, 11 children had a normal elbow and eight had lost an average of 15 degrees of flexion. Nine children had had open reduction and internal fixation of the fragment, one for an open injury, three for displacement of the epicondyle and six for intra-articular entrapment of the fragment. Five of these children had ulnar nerve contusion or compression, four requiring anterior transposition of the nerve. At review, only three had normal elbows and six had lost an average of 37 degrees of flexion. We agree with other authors that surgery is indicated only for children in whom the epicondyle is trapped in the joint or is significantly displaced after closed reduction.

Vertebral hydatidosis and paraplegia.

We report the management of two children and 11 adults with paraplegia secondary to vertebral hydatidosis. Destruction of pedicles, posterior vertebral elements and discs as well as the vertebral bodies was common and all six patients with thoracic disease had involvement of adjacent ribs. The 13 patients had a total of 42 major surgical procedures; two patients died from postoperative complications and four from complications of the disease and paraplegia. All eight patients initially treated by laminectomy or anterior decompression alone relapsed within two years and seven required further surgery. Circumferential decompression and grafting gave the best results, six of nine patients being in remission an average of three years and six months later. The prognosis for such patients is poor; remission is the aim, rather than cure. Anthelminthic drugs may improve the prognosis, but radical surgery is likely to remain the keystone of treatment in the foreseeable future.

[Isolated posterior pre-marginal hernia. Apropos of 6 cases]. / La hernie pré-marginale postérieure isolée. A propos de 6 cas.

Posterior pre-marginal disk hernia, a rare lesion, was diagnosed in six young adults with lumbago. Lateral lumbar spine radiographic images showed an unusual appearance, combining a posterior marginal defect of a vertebral corner and a small bony spicule projecting into lumbar canal. A literature review revealed 27 similar cases, mostly in adolescents. These vertebral disk anomalies are considered by some authors to be fractures of the posterior margin border. A more plausible hypothesis is a pre-marginal hernia, because of lack of a history of injury, the radiologic appearance comparable with that of sequelae of Scheuermann's disease, and the frequent association of these lesions with a spinal growth dystrophy.

Human apolipoprotein B. Evidence for its immunochemical heterogeneity using monoclonal antibodies and an immunoenzymometric assay.

Predefined monoclonal antibodies (Mabs) were used in an immunoenzymometric assay to study the immunochemical heterogeneity of lipoproteins and to search for potential epitopes with pathological importance. By measuring apolipoprotein B (apo B) epitopes in patients with and without angiographically documented coronary artery disease and in patients with type IIa hyperlipoproteinemia, we have found that both types of patients have a significant increase in Apo B-containing particles specifically recognized by one Mab (BL3). We have also observed that the effects of fenofibrate on type IIa patients vary greatly depending on the plasma concentrations of various Apo B-containing lipoproteins. The greatest effects occurred in patients with epitopes recognized by BL3. Lastly, by sequential precipitation of specific epitopes by BL3, we have obtained evidence that the residual epitope(s) may be related to one or more lipoprotein particles.

[Genetic study of eight cases of spondylo-epiphyseal dysplasia tarda and its autosomal recessive transmission]. / Etude génétique de huit observations de dysplasie spondylo-épiphysaire d'apparition tardive et de transmission autosomique récessive.

Spondylo-epiphyseal dysplasia tarda is an hereditary disease of bone first described by Maroteaux in 1957. The disease affects only boys, then is transmitted on X-linked recessive pattern. The authors describe two tunisians families with 8 patients presenting clinical and radiologic symptoms resembling spondylo-epiphyseal dysplasia tarda but affecting both sexes. Autosomal recessive inheritance is probable in these families. Conclusion is that genetic heterogeneity of the disease must be precise.