Aseptic osteonecrosis of the femoral head in patients with sickle cell anemia.

Sickle cell disease (SCD) is a genetic trouble of the hemoglobin synthesis inherited as an autosomal recessive trait, whose prevalence can vary from 5 to 25% in the different parts of the world. It is characterized by the presence of abnormal hemoglobin HbS instead of hemoglobin A. Patients suffering from major forms of SCD present the risk of developing epiphyseal necrosis. Aseptic osteonecrosis of the femoral head (AOFH) caused by ischemia, or bone infarction can affect between 20 and 50% of SCD patients. The femoral head is the most frequent epiphyseal location with a range of 74.6%. AOFH can affect patients at any age, but is mainly detected in men under 50 years. Indeed, a large majority of cases, in a range of 60%, have been diagnosed at an early radiological stage in young adults whose average age varies, in the literature, between 27 and 36 years. A surgical procedure becomes sometimes necessary due to the severity of pain and the functional consequences, frequently following the mechanical collapse of the osteonecrosis area. It is estimated that approximately 25-30% of SCD patients will undergo a total hip arthroplasty before 50y. Although the mortality rate, between 0.2-2.6%, tends to be similar to the general population rate undergoing a prosthetic surgery, the perioperative complications vary from 11.5 to 67%. Here, we clarify the epidemiological data and present an exhaustive update on the different preventive and therapeutic strategies, as well as the perioperative management in patients with an AOFH caused by SCD and risking multiple complications.

Contribution of minimally invasive bone augmentation to primary stabilization of the osteosynthesis of Schatzker type II tibial plateau fractures: Balloon vs bone tamp.

BACKGROUND: Schatzker type II tibial plateau fractures necessitate the least invasive treatment possible. Arthroscopic reduction by bone tamp followed by osteosynthesis is the current gold standard for this type of tibial plateau fracture. The objective of this study was to compare this technique to anterior approach tuberoplasty with balloon reduction. The comparison criteria were residual articular step off, metaphyseal cavity volume formed during reduction, and mechanical strength to separation and to depression displacement. METHODS: Fractures were created on 12 human cadaveric tibiae and reduced by a minimally invasive approach in six specimens by a balloon, and by bone tamp in the six others. Articular step off and metaphyseal-epiphyseal cavity volume were measured by TDM. Mechanical tests were performed up to assembly failure to characterize structural strength. Secondary displacements, fracture depression displacement and separation were measured by optical methods. FINDINGS: There was no significant difference in step off measurement after balloon reduction or bone tamp (0.29 cm vs 0.37 cm; p = 0.06). The cavity volume formed by balloon reduction was significantly smaller than the volume created by bone tamp reduction (0.45 cm3 vs 5.12 cm; p = 0.002). The compressive load required for assembly failure was significantly greater in the balloon group than in the bone tamp group (1210.17 N vs 624.50 N; p = 0.015). INTERPRETATION: There exists a correlation between load to failure of the assembly frame and the metaphyseal volume required for bone fracture reduction. The minimally invasive balloon technique has fewer negative effects on the osseous stock, thereby enabling better primary structural strength of the fracture.

Role for cementoplasty in intra-articular distal radius fractures: Cadaver study and application to arthroscopy.

BACKGROUND: Die-punch intra-articular fractures of the distal radius raise surgical challenges. The residual articular step-off must be less than 1mm to prevent the development of radio-carpal osteoarthritis. The objectives of this cadaver study were to evaluate whether cementoplasty was effective in reducing die-punch fractures and to determine whether this technique was feasible as an arthroscopic procedure. HYPOTHESIS: Cementoplasty performed as an arthroscopic procedure is effective in treating die-punch fractures. MATERIAL AND METHODS: Eleven cadaver forearms collected at a laboratory were studied. In each, a depressed fracture of the lunate fossa of the radial articular surface was created using a Tinius Olsen H25K-S compression test machine. A Kyphon XPander® balloon (Medtronic) was used to lift the depressed area, and calcium-phosphate cement was then injected to stabilise the reduction. Cementoplasty under arthroscopic guidance was performed on an additional forearm. RESULTS: Computed tomography of the wrists after fracture induction showed a mean depression of 4.66mm (range, 4.01-5.25mm). Arthroscopic cementoplasty proved feasible with the arthroscope inserted through the 3-4 radio-carpal portal. Positioning the balloon under the depressed area ensured satisfactory reduction and allowed the injection of cement. DISCUSSION: Cementoplasty may be useful for the treatment of die-punch fractures. Additional indications may be other types of distal radius fractures with articular surface depression. LEVEL OF EVIDENCE: IV, cadaver study.

Biomechanical study comparing Pulvertaft suture to step-cut suture.

Tendon grafts are a component of the therapeutic arsenal for managing chronic flexor tendons injuries in the hand, especially during two-stage Hunter reconstruction. The purpose of this anatomical study was to compare the strength of the Pulvertaft weave versus the step-cut suture used for flexor tendon reconstruction to determine their role in early active mobilization. We performed a biomechanical study with cadaver specimens. Thirty-four hands were randomized and the tendons from both hands were equally assigned to each group. A comparison of the Pulvertaft weave (group 1) versus the step-cut suture (group 2) using the flexor digitorum profundus from the fourth finger and the longus palmaris was carried out. The main variable was the failure load in both repair groups. We also evaluated the cross-sectional area (CSA) and the tensile strength of the repairs. Thirty hands were included in our study. There was no significant difference in the failure load between the two groups (116N for group 1 versus 103N for group 2, P=0.2). The CSA was significantly smaller in the step-cut group compared to Pulvertaft group (19.8mm2 versus 35mm2, P<0.01). The tensile strength was significantly higher in the step-cut group than in the Pulvertaft group (5.3N/mm2 versus 3.4N/mm2, P<0.01). Early active mobilization requires a minimum repair strength of 75N. In our study, the step-cut suture appears strong enough and thin enough to decrease the fibrosis, which would lead to better functional results. No other study of this type has been published. The specimens in which the repair strength was less than 75N all involved a thin, weak longus palmaris. Other biomechanical studies should be done to define the anatomical criteria required for use of the palmaris longus tendon. The step-cut suture seems to be strong enough and thin enough to provide sufficient proximal attachment during flexor tendon reconstruction to allow early active mobilization.

Can a target zone safer than Lewinnek's safe zone be defined to prevent instability of total hip arthroplasties? Case-control study of 56 dislocated THA and 93 matched controls.

BACKGROUND: Various factors contribute to instability of total hip arthroplasty (THA), with implant orientation being a major contributor. We performed a case-control study with computed tomography (CT) data to determine whether: 1) orientation contributes to THA instability and 2) a safer target zone for stability than Lewinnek's classic safe zone can be defined. MATERIAL AND METHODS: We included prospectively 363 cases of THA dislocation that occurred during the calendar 2013 year in 24 participating hospitals. Of the 128 dislocations that occurred in patients who underwent THA at these centers, 56 (24 anterior, 32 posterior) had CT scans, thus were included in the analysis. The control group was matched 4:1 based on implant type, year of implantation, age, sex, bearing types and THA indication. Of the 428 matched control THA cases, 93 had CT scans. In all, the CT scans from 149 cases (56 unstable, 93 stable) were analyzed to determine the acetabular cup's inclination and anteversion, and the femoral stem's anteversion. RESULTS: In the unstable THA group, cup inclination was 46.9°±7.4°, cup anteversion was 20.4°±10.8° and stem anteversion was 14.2°±9.9°. In the stable THA group, cup inclination was 44.9°±5.3° (P=0.057), cup anteversion was 22.1°±5.1° (P=0.009) and stem anteversion was 13.4°±4.4° (P=0.362). The optimal total anteversion (cup+stem) of 40-60° was achieved in 16.5% of unstable THA cases and 13.9% of stable THA cases, thus this parameter does not predict stability (odds ratio [OR] of 0.40, P=0.144). The cup was positioned in Lewinnek's safe zone in 44.6% of patients in the unstable group and 68.2% of those in the stable group (OR 3.74, P=0.003). A target zone defined as 40-50° inclination and 15-30° anteversion was better able to distinguish between unstable cases (23.2%) and stable cases (71.6%) resulting in an OR of 13.91 (P<0.001). DISCUSSION: Implant positioning was the only risk factor for instability found in this study. Moreover, our findings reinforce the theory put forward by other authors that Lewinnek's safe zone is not specific enough to differentiate between stable and unstable THA implantations. The target zone for acetabular cups proposed here (40-50° inclination and 15°-30° anteversion) is related to a lower risk of instability. This orientation can be used as a guide, but must be combined with other technical elements to optimize stability. By balancing stability and biomechanics, the 40-50° inclination and 15°-30° anteversion target zone redefines the optimal positioning window. LEVEL OF EVIDENCE: III case-control study.

Radiologic study of disc behavior following compression fracture of the thoracolumbar hinge managed by kyphoplasty: A 52-case series.

INTRODUCTION: Kyphoplasty has proved effective for durable correction of traumatic vertebral deformity following Magerl A fracture, but subsequent behavior of the adjacent discs is unclear. The objective of the present study was to analyze evolution according to severity of initial kyphosis and quality of fracture reduction. MATERIAL AND METHOD: A single-center prospective study included cases of single compression fracture of the thoracolumbar hinge managed by Kyphon Balloon Kyphoplasty with polymethylmethacrylate bone cement. Radiology focused on traumatic vertebral kyphosis (VK), disc angulation (DA) and disc height index (DHI) in the adjacent discs. Linear regression assessed the correlation between superior disc height index (SupDHI) and postoperative VK on the one hand and correction gain on the other, using the Student t test for matched pairs and Pearson correlation coefficient. RESULTS: Fifty-two young patients were included, with mean follow-up of 18.6 months. VK fell from 13.9° preoperatively to 8.2° at last follow-up. DHI found significant superior disc subsidence (P=0.0001) and non-significant inferior disc subsidence (P=0.116). DA showed significantly reduced superior disc lordosis (P=4*10(-5)). SupDHI correlated with VK correction (r=0.32). Preoperative VK did not correlate with radiologic degeneration of the adjacent discs. CONCLUSION: Correction of traumatic vertebral deformity avoids subsidence and loss of mechanical function in the superior adjacent disc. The underlying disc compensates for residual deformity. Balloon kyphoplasty is useful in compression fracture, providing significant reduction of traumatic vertebral deformity while conserving free and healthy adjacent discs. LEVEL OF EVIDENCE: IV.

Tibial plateau fractures: reproducibility of three classifications (Schatzker, AO, Duparc) and a revised Duparc classification.

INTRODUCTION: Since the reproducibility of the Schatzker and AO tibial plateau fracture classification systems has already been assessed, the goal of this study was to evaluate the Duparc classification system and compare it to the other two. HYPOTHESES: CT scan is better than X-rays for analyzing and classifying tibial plateau fractures. The Duparc classification system is more effective than the other two systems but could be improved by adding elements of each. MATERIALS AND METHODS: Six observers analyzed images from 50 fractures and then classified them. Each fracture was evaluated on X-rays. Two weeks later, these same fractures were evaluated on X-rays and CT scans. The same process was repeated four weeks later. The Kappa coefficient (κ) was used to measure agreement and contingency tables were built. RESULTS: The interobserver reproducibility for the X-ray analysis was poor for the Duparc and AO classifications (κDuparc=0.365; κAO=0.357) and average for the Schatzker classification (κSchatzker=0.404). The reproducibility was improved overall when CT scans were also analyzed (κDuparc=0.474; κAO=0.479; κSchatzker=0.476). A significantly greater number of fractures could not be classified in the Schatzker system than in the others (14.3% versus 2% for Duparc and 7.33% for AO). Review of the contingency tables revealed that the Schatzker and AO classification systems did not take certain fracture types into account. Seventy-one percent (71%) of the lateral unicondylar split fractures were found to be combined fractures when CT scan analysis was added. DISCUSSION: Our results showed CT scan to be better at analyzing and classifying fractures. We also found the Duparc classification to be advantageous because it allowed more fractures to be classified than in other classification systems, while having similar reproducibility. Based on our study findings, the Duparc classification was revised by adding elements of the other two. We propose using the modified Duparc classification system to analyze tibial plateau fractures going forward. LEVEL OF EVIDENCE: Level IV. Retrospective study.

[Neurotization of the deep branch of ulnar nerve and the thenar branch of median nerve with the pronator quadratus branch of anterior interosseous nerve by end-to-side transfer. An anatomic study]. / Étude anatomique concernant le transfert du nerf interosseux antérieur innervant le pronator quadratus sur le rameau profond du nerf ulnaire et sur la branche motrice thénarienne du nerf médian par anastomose termino-latérale.

Proximal or middle lesions of median or ulnar nerves are responsible for a great loss of hand motor function. Neurotization of either deep ulnar branch of ulnar nerve (DBUN) or recurrent (thenar) branch of median nerve (RBMN) with the nerve to quadratus pronator (NPQ) from the anterior interosseous nerve (AION) could reduce length of axonal growth and therefore the reinnervation lead-time of hand intrinsic muscles. We studied the anatomy of these three nerves, to help surgeon choosing his (her) technique and approach. Twenty-three cadaver forearms were dissected. End-to-side sutures were performed to mimic these neurotizations. Distances between nerve sutures and ulnar styloid process (USP) or trapeziometacarpal joint (TM) were measured. All the sutures but one RBMN could be done. On average sutures were distant from USP by 44±17mm (neurotization of DBUN), from TM by 62±15mm (neurotization of RBMN). Knowledge of average distance to perform these neurotizations should allow choosing the best reduced approach of RBMN and DBUN. Neurotizations of DBNU and RBMN with NPQ were feasible for lesions located at 6.1cm upstream USP and 7.7cm upstream TM, respectively. End-to-side sutures remain to be clinically evaluated.

Tuberoplasty: minimally invasive osteosynthesis technique for tibial plateau fractures.

Fractures of the tibial plateau are in constant progression. They affect an elderly population suffering from a number of comorbidities, but also a young population increasingly practicing high-risk sports and using two-wheeled vehicles. The objective of this study was therefore to propose a new technique for the treatment of this type of fracture. There are a variety of classical pitfalls of conservative treatment such as defective reduction resulting in early osteoarthritis and alignment defects. Conventional treatments lead to joint stiffness and amyotrophy of the quadriceps, caused by the open technique and late loading. We propose an osteosynthesis technique for tibial plateau fractures with minimally invasive surgery. A minimally invasive technique would be more appropriate to remedy all of the surgical drawbacks resulting from current practices. The surgical technique that we propose uses a balloon allowing progressive and total reduction, associated with percutaneous screw fixation and filling with polymethylmethacrylate (PMMA) cement. The advantages are optimal reduction, minimal devascularization, soft tissues kept intact, as well as early loading and mobilization. This simple technique seems to be a good alternative to conventional treatment. The most comminuted fractures as well as the most posterior compressions can be treated, while causing the least impairment possible. Arthroscopy can be used to verify fracture reduction and cement leakage. At the same time, it can be used to assess the associated meniscal lesions and to repair them if necessary.

[Functional results of homodigital pedicle island flaps for finger-pulp defects. Evaluation of 15 cases]. / Évaluation fonctionnelle après lambeau homodactyle en îlot antérograde pour perte de substance pulpaire des doigts longs. À propos de 15 cas.

OBJECTIVES: Fingertip amputations are very common. The aim of the treatment is to restore the sensibility of the finger pulp, with adequate pulp padding. The homodigital pedicle island flaps are used in zone 2 or 3 of Allen's classification. This study evaluates the functional results of this type of flap. METHODS: Fifteen patients were reviewed. The clinical evaluation noted complications, satisfaction level, use of the finger, cold intolerance and increased sensibility signs. The Weber test and the Semmes monofilaments were used for sensory evaluation. The joint mobility was measured and the Quick-DASH score calculated. RESULTS: The mean time between surgery and the revision was 21 months. The average flap advancement was 12 mm. Six of the patients were very satisfied. The finger use was normal in seven cases, and excluded in only one. The average Quick-DASH was 18.18. Sixty percent of the nails were deformed, 20% were hooked. Eight patients experienced cold intolerance, and five had increased local sensibility. The average Weber score was 7 mm and the monofilaments were at 3.61. The flexion of the joint was limited in six cases. CONCLUSION: For specific indications in finger-pulp amputation, the homodigital pedicle island flaps give satisfying aesthetic and functional results, allowing considerable advancement. Nevertheless, they are often a source of cold intolerance, finger joint stiffness and require long healing periods.

Vertebral body cage use in thoracolumbar fractures: outcomes in a prospective series of 23 cases at 2 years' follow-up.

INTRODUCTION: One objective of surgery in thoracolumbar spine fracture is to restore correct and lasting spinal statics. This may involve vertebral body replacement using an anterior approach. We here report results on a prospective series of 23 trauma patients managed by vertebral body replacement using an expandable cage. PATIENTS AND METHODS: The sex ratio was 2.28. Fifteen cases involved primary treatment of recent fracture and eight secondary surgery for non-union or malunion. In 12 cases, posterior osteosynthesis was associated. Six patients were operated on using a classical approach and 17 using a video-assisted minimally invasive approach. Pre- and perioperative data were recorded, with clinical scores (VAS and Oswestry) at 6 weeks, 3 months, 6 months, 1 year and 2 years. Radiologic follow-up assessed regional traumatic kyphosis (RTK), enabling calculation of regional traumatic angulation (RTA), with control CT to check fusion. RESULTS: Minimum follow-up was 2 years. There were no cases of postoperative neurological deterioration. There were three major postoperative complications: one hemothorax, one adhesive bowel occlusion, and one bilateral pneumothorax at 1 month. Mean Oswestry score at 6 months was 20%, and mean VAS score at 2 years was 0.36. Postoperative RTA showed a mean 7.34° improvement. Mean RTA reduction loss was 1.95° at 3 months, subsequently unchanged. All arthrodeses showed fusion at 6 months. CONCLUSION: Results were satisfactory with this technique, comparable to those reported in the literature. The development of minimally invasive approaches and improved instrumentation procedures optimize surgery and enhance anterior reconstruction tolerance. Lasting restoration of sagittal spinal curvature improves trauma patients' functional recovery.

Percutaneous internal fixation combined with kyphoplasty for neurologically intact thoracolumbar fractures: a prospective cohort study of 24 patients with one year of follow-up.

INTRODUCTION AND HYPOTHESIS: Neurologically intact lumbar and thoracolumbar fractures are frequent but their treatment is not codified. The purpose of this study was to evaluate the effectiveness of minimally invasive treatment of such fractures by percutaneous fixation associated with balloon kyphoplasty. PATIENTS AND METHODS: Between November 2008 and July 2010, 24 patients were treated. There were 12 men and 12 women, with a mean age of 53 years (range 20-88 years). Fractures were classified as one Magerl lesion type A1, one type A2, 19 A3 (five A31, 10 A32, four A33), and three type B2. The treatment was kyphoplasty of the fractured vertebra followed by percutaneous fixation of the vertebra above and below the fracture. Patient follow-up included an analysis of pain using the visual analogic score, the Oswestry score, and functional X-ray and CT analysis. RESULTS: Surgery lasted a mean 99 minutes. At the last follow-up, the mean pain was scored at 0.9 and the Oswestry score was 13.2. Reduction of vertebral kyphosis was 8.6° and reduction of the corrected regional angle was 7.1°. The gain in vertebral height was 17%. All pedicle screws were positioned correctly and no neurological, septic, or thromboembolic complications were observed. DISCUSSION AND CONCLUSION: Percutaneous osteosynthesis combined with balloon kyphoplasty is a valuable surgical technique in the treatment of thoracolumbar and lumbar fractures with no neurologic deficit. The clinical results are good and the technique allows the patient to return home earlier without having to wear a corset. The X-ray result scores are very encouraging, with corrections similar to conventional surgery in terms of vertebral height and kyphosis. This technique can be an alternative to conventional open surgery. LEVEL OF EVIDENCE: IV: Prospective observational study.

Complications following rotating hinge Endo-Modell (Link) knee arthroplasty.

BACKGROUND: Rotating hinge knee prostheses are indicated in revisions especially when major ligament laxity or substantial AP deformities are present. These situations make ligament balancing difficult with less constrained design implants. Despite its use for nearly 50 years, this type of prosthesis continues to have a poor reputation due to a high complication rate. HYPOTHESIS: Complications are frequent after this type of arthroplasty and the complication rate is similar in primary or revision arthroplasties. The objective of this study is to report the medium-term results of these implants and determine the eventual predictive factors of complications in order to refine operative indications. MATERIAL AND METHODS: In this retrospective study of patients operated on between 1998 and 2006, 85 Endo-Modell (Link) rotating hinge knee prostheses had been used in 61 females and 24 males. The mean age at surgery was 72.4 years (range, 32-92 years). Fifty-two arthroplasties were primary and 33 were revisions either for loosening (24) or deep infections (9). The mean follow-up was 36 months+/-22 (range, 0-75 months). RESULTS: Complications were observed in 24 patients (28.2%): nine deep infections, four patellar complications, and three cases of aseptic loosening. No significant difference was found between the primary arthroplasties and the revisions regarding all complication types. A significant relation was established between the occurrence of a complication and presence of several associated comorbidity factors (obesity, heart disease, diabetes, etc.). DISCUSSION: The use of this type of implant carries a high risk of complications, higher than the one pertaining to unconstrained design prostheses; this fact is noted irrespective of the surgical indication and other comparison elements. The leading criteria to poor functional results appear to be the indication (gonarthrosis with substantial ligament laxity at primary surgery) and the number of associated comorbidities. These prostheses should therefore be restricted to selected indications, notably in view of the fact that less constrained prostheses give superior outcomes. LEVEL OF EVIDENCE: Level IV. Retrospective therapeutic study.

[Biomechanical evaluation of posterior instrumentation for lumbar burst fracture: comparison of two internal devices]. / Evaluation biomécanique d'une instrumentation rachidienne postérieure dans une fracture lombaire de type << burst >>: comparaison de deux montages.

PURPOSE OF THE STUDY: Burst fractures generally occur due to trauma to the thoracolumbar spine. Surgery is indicated for unstable fractures. Posterior instrumentation with pedicular screws is generally proposed. In certain circumstances, hooks may be preferred due to excessive risk of insertion of the pedicular screw. The purpose of this study was to compare two posterior instrumentations, one using pedicular screws on either side of the fracture each protected by hoods and a second composed of the same pedicular screws inserted under the fracture hooks above. MATERIAL AND METHODS: Twelve spinal specimens from human cadavers composed of segments T10 to L2 were used. Range of flexion, extension, lateral inclination, and rotation were noted on T10 up to application of 7 Nm. Spinal segments were tested first intact, then in four configurations: 1) instrumented without lesion, 2) lesion simulating burst fracture of L1 without section of the interspinous ligament, 3) and with section of the interspinous ligament, and 4) with L1 corporectomy. Finally a test to rupture was performed by applying a flexion moment up to fracture. RESULTS: Mean flexion-extension of the instrumented spine was limited compared with the intact spine for both instrumentation configurations and irrespective of the lesion. The same behavior was observed for lateral inclination with less pronounced motion with the first instrumentation. For rotation, the range of motion increased clearly with the second instrumentation and this with the first lesion while with the first instrumentation, rotation amplitude remained below that of the intact spine. There was however an increase in the vertical displacement during flexion-extension for both instrumentations. For the rupture test, the mean flexion moment at rupture was 14.4 Nm (10.6-22 Nm) with no difference between the two instrumentations. DISCUSSION: This mode simulating burst fractures of the spine appears to be reproducible and more realistic than corporectomy. Attention should be taken concerning the limits of this type of study since fractures can occur for forces as small as 10.6 Nm. Thus we observed that pedicle screw configurations and also fractures produced mean ranges of motion greater than intact segments irrespective of the type of lesion simulated. However, the net increase in motion was observed during rotation movements when hooks were used, even when they were placed only below the fracture. Putting pressure on the hooks does not prevent them from slipping along the lamina. But neither of these two configurations controls the fracture gap. A vertebral reinforcement might be necessary.

[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.

[Metacarpophalangeal prosthesis modeling. Comparison of stress factors in a normal and a prosthetic metacarpophalangeal joint using finite element analysis]. / Modélisation d'une prothèse métacarpophalangienne. Comparaisons de l'état de contraintes par la méthode des éléments finis d'une articulation métacarpophalangienne saine et munie d'une prothèse.

INTRODUCTION: Prosthetic replacement of the metacarpophalangeal joints of long fingers is a problematical technique for the surgeon. The aim of the present study was to examine and compare, by means of finite element analysis, stress distribution in a normal metacarpophalangeal joint and to compare this with the findings in a similar joint with a prosthesis in order to better determine the risk of aseptic loosening, and also to examine possible solutions to limit these risks. METHOD: Finite element modelling was carried out using Abaqus software. Various criteria were taken into account including anatomical data, stress distribution, mechanical characteristics of the materials used, and different positions of the phalanx. RESULTS: A comparison of the results showed two significant stress distribution factors, i.e., a reduction of normal stress in the cortical bone of the finger fitted with a prosthesis; and the appearance of a flexion moment which completely modified the stress distribution throughout the metacarpal and therefore also in the opposite phalanx. DISCUSSION: To reduce the risk of aseptic loosening, two solutions were proposed: a) to reduce Young's module. The problem which arises, as in the case of total hip prosthesis, is that of finding a material with a Young's module which is closer to that of cortical bone, and which at the same time has a high elastic limit and breakage point and good biocompatibility; b) to reduce the inertia of the prosthesis, which seems the more likely of the two propositions, as it is based on the results of the modelling. The inertia of the prosthesis on stress distribution can be reduced by modifying two parameters, namely by producing a hollow section and shortening the structure of the prosthesis.

[Surgical treatment of scoliosis due to Duchenne muscular dystrophy]. / Traitement chirurgical des scolioses de la dystrophie musculaire de Duchenne.

PURPOSE OF THE STUDY: The purpose of this retrospective study is to demonstrate the advantages of early surgical operation for patients suffering from Duchenne muscular dystrophy scoliosis. PATIENTS AND METHODS: Since 1992, 37 patients suffering from Duchenne muscular dystrophy were operated on for scoliosis. Mean age was 12 years. Vital capacity was 62 +/- 17% and left ventricular ejection fraction 55 +/- 7%. Insertion of flexible vertebral instrumentation included a pedicular screwing system in the lumbo-sacral area and transversal attachments with steel threads at the thoracic level. A sub-laminar fastening was placed at L1. Bone bank arthrodesis was performed only at lumbo-sacral level, in order to maintain flexibility in the thoracic part of the assembly and to enable growth. RESULTS: Assisted ventilation was necessary in three children during 1.5 month. Superficial sepsis was treated locally with an antibiotherapy without the removal of material in four patients. There was one stem rupture two years after operation, caused by a road traffic accident. No further procedure was necessary for technical reasons. There was no death during the longest follow-up period among the first 24 patients (mean follow-up: 57 months). In the frontal plane, the preoperative Cobb angle, which was 19 degrees, was brought to 5.2 degrees at the postoperative stage, and 9.5% at the latest measurement, i.e., a loss of angular correction of 4.3 degrees. In the sagittal plane, there were physiological curvatures. Pelvic balancing was correct and results have held over time. Vital capacity was reduced by 3.6% per year. CONCLUSION: These results encourage early operation on these patients in order to avoid anaesthetic, peri- and postoperative complications. Likewise, giving support to minor curves reduces mechanical constraints during the first postoperative years. The absence of thoracic arthrodesis enables growth of about 5 cm when patients are operated on at about the age of 12 years. Stabilization of the myopath's spine enables the child to remain in an upright sitting position. The assembly's thoracic suppleness enables an increase in the range of movement in the upper limbs. It seems appropriate to operate on such patients when they cease walking, around the age of 12 years. Cardiorespiratory function and life expectancy are not improved, but most patients and families are very satisfied by the comfort brought about by the surgical operation.

[Approach to severe functional deficiencies: evaluating the efficacy of a special multidisciplinary consultation]. / Approche des déficiences fonctionnelles graves: bilan de l'activité d'une consultation pluridisciplinaire dédiée.

A global approach is required to evaluate severe functional deficits. We have developed a multidisciplinary consultation and assessed its usefulness after one year. A total of 62 patients were evaluated (mean age 35 years), usually for neurological functional deficit (50%). Among the 62 patients, surgery was proposed in 72.6% (operations performed in 66%). Others were managed with non-surgical procedures or abstention. The functional outcome as assessed by patients and physicians was poor (or no result) for 6%, fair for 15%, good or very good for 79%. These results suggest that such a multidisciplinary approach is worth being pursued. Some adjustments for psychological dysfunction may further improve outcomes.

[Acetabular reconstruction using bone allograft in the revision of total hip prosthesis]. / Reconstruction cotyloïdienne par allogreffe osseuse dans les révisions de prothèse totale de hanche.

PURPOSE OF THE STUDY: Aseptic loosening of the acetabular component is the most worrying problem after hip arthroplasty. During revision surgery we prefer to rebuild a solid bony acetabulum close to the anatomy in which the implant will be cemented. On the basis of the first 48 acetabular reconstructions using deep-frozen bony allografts, we carried out a review of our results in a pathology which will surely increase in the future. MATERIAL: 48 hips were operated according to this technique. It has been possible to review 38 of them, with an average follow-up of 7.3 years (extremes 5 years, and 9.6 years). The average age of the population at the time of surgery was 63 years. Two etiologies predominated: congenital hip dislocation sequelae and primitive hip arthritis. In 10 cases of massive deterioration, a Muller's ring was used to stabilize the allograft. METHODS: The results were analyzed at 6 months, 2 years, 4 years, and at maximum follow-up, clinically, according to Merle d'Aubigné grading system. Radiologically, Ranawat's criteria were used to assess the re-centering of the reconstructed hips. The development of radiolucent lines and implants migration were also assessed. RESULTS: Clinically, the patients' comfort was always improved by pain relief. Radiologically, average acetabular upward migration of 5 mm and medialisation of 3.5 mm were observed. 24 hips presented radiolucent lines. 19 radiolucent lines were below 2 mm. 5 were greater than 2 mm and leaded to loosening. In 4 of these 5 cases of radiolucent lines, there were acetabular migrations with failure. The radiological image remained stable afterwards. In these cases there was a real loosening, necessitating further surgery. In all cases, partial resorption of the graft was observed. DISCUSSION: Study of our first 38 cases shows that bony allograft and cemented acetabulum, sometimes including an armature, is one possible solution to the problem of difficult acetabular reconstructions. However, with an average follow-up of 7.3 years, we already have 5 (13 per cent) aseptic acetabular loosening, of which one has been operated on. Radiological analysis of these does not question the allograft, but rather imperfect re-centering. Analysis of the good results, 33 (87 per cent) stable acetabulum indicates re-fixing in quasi-anatomical position, in conditions close to those of a first time arthroplasty, with the aid of perfectly stabilized bony transplants, and where contact with the receiver acetabulum is maximal. CONCLUSION: Our follow-up is one of the longest in literature. But with a migration rate already of 13 per cent, it is not yet sufficient for us to be permanently assured about the future of our patients, even if their age is greater and their activity less than those of patients having a first hip arthroplasty.