Part 1: Outcome of Posterior Pelvic Ring Injuries and Associated Prognostic Factors - A Five-Year Retrospective Study of One Hundred and Sixty Five Operated Cases with Closed Reduction and Percutaneous Fixation.

PURPOSES: The aim of this study was to evaluate: 1. the outcome of pelvic ring fractures treated by closed reduction and percutaneous fixation, 2. the prognostic factors associated with a poor quality reduction, 3. the prognostic factors associated with ilio-sacral screws misplacement and 4. the prognostic factors associated with nonunion. METHODS: Data from medical charts for all patients admitted with unstable posterior pelvic ring injuries from 2009 to 2013 were extracted. A total of 165 patients with a mean age of 40 years were included. One hundred and five patients were reviewed at a mean of 32 months of follow-up. The prognostic factors analyzed were clinical and radiological factors. Tile B and Tile C pelvic ring fractures were compared and analyzed separately. Then specific statistical analysis was performed using a logistic regression model to eliminate confusion factors. RESULTS: An excellent or good clinical result was achieved for 94 patients (90%). An excellent or good reduction was achieved for 141 patients (85%). Nonunion rate, smoking patients, bad reductions, age of patients and ISS score were significantly higher in Tile C group. To eliminate confusion factors we used a multivariate analysis logistic regression model. Only unstable vertical bilateral posterior injuries (Tile C2 and C3) were independent prognostic factors for unsatisfactory reduction (p = 0.001; OR = 4.72; CI 95% [2.08-16.72]). Screw misplacement was recorded for 30 patients (16%) and sacral dysmorphia was an associated prognostic factor (p = 0.0001; OR = 15.6; CI95% [3.41-98.11]). Nonunion was recorded for ten patients (6%) and smoking was an associated prognostic factor (p = 0.01, OR = 5.12; CI95% [1.1-24.1]). CONCLUSIONS: Posterior pelvic ring fractures treated by closed reduction and percutaneous fixation are associated with excellent/good clinical results if excellent/good reduction and bone healing are achieved without screw misplacement. Bilateral unstable vertical posterior pelvic ring injuries, and sacral dysmorphia are risk factors for bad quality reduction and screw misplacement respectively.

Bone regeneration and limb lengthening.

Regeneration of bone in the presence of stable fixation and the maintenance of the osteogenic tissue (marrow, endosteum, nutrient artery, and periosteum) required another factor to stimulation of bone regeneration: incremental distraction produces bone of both endosteal and periosteal origin. The soft tissues undergo to same growth phenomenon. The mechanism of ossification occurs without intermediate fibrocartilage.

Macroscopic and microscopic process of long bone fracture healing.

The growth of each type of callus (cortical, medullary and periosteal) depends on the mechanical condition of fracture fixation (elastic fixation and instability or rigid immobilization), the type of treatment (non-operative, close or open surgical procedure, intra-medullary nailing, external fixation, plate...) and the high or poor quality of soft tissue and the specific characteristics of the local vascularisation.

Optimization of perioperative management of proximal femoral fracture in the elderly.

Proximal femoral fracture in elderly subjects is a major event that is life-threatening in the medium-to-long term. Advanced age, male gender and number of comorbidities largely account for high mortality and require geriatric expertise. Protein-energy malnutrition and bone demineralization increase mortality. Mortality can, on the other hand, be reduced by acting on two variables accessible to medical intervention: daily activities and nutritional status. Functional and neurocognitive assessment allow the risk of dependency to be evaluated, and global geriatric work-up can prevent sudden breakdown of homeostasis. In the emergency setting, pain is to be alleviated, polymedication and anticoagulation therapy checked, and instability (notably cardiac and pulmonary) and confusion syndrome screened for on geriatric and anesthesiologic opinions. Surgery should be implemented without delay, within 48hours of admission, preferably using multimodal anesthesia. The technique should be geared to allow early weight-bearing and mobilization. The most comprehensive care plan involves team-work between emergency physicians, surgeons, orthopedic specialists, anesthesiologists, geriatricians, pharmacists, rehabilitation specialists and nursing staff, to reduce mortality and readmission and improve functional results. Post-fracture coordination seeks to prevent falls and further fractures and to treat bone demineralization.

Fluoroscopy-based navigation system in spine surgery.

The variability in width, height, and spatial orientation of a spinal pedicle makes pedicle screw insertion a delicate operation. The aim of the current paper is to describe a computer-assisted surgical navigation system based on fluoroscopic X-ray image calibration and three-dimensional optical localizers in order to reduce radiation exposure while increasing accuracy and reliability of the surgical procedure for pedicle screw insertion. Instrumentation using transpedicular screw fixation was performed: in a first group, a conventional surgical procedure was carried out with 26 patients (138 screws); in a second group, a navigated surgical procedure (virtual fluoroscopy) was performed with 26 patients (140 screws). Evaluation of screw placement in every case was done by using plain X-rays and post-operative computer tomography scan. A 5 per cent cortex penetration (7 of 140 pedicle screws) occurred for the computer-assisted group. A 13 per cent penetration (18 of 138 pedicle screws) occurred for the non computer-assisted group. The radiation running time for each vertebra level (two screws) reached 3.5 s on average in the computer-assisted group and 11.5 s on average in the non computer-assisted group. The operative time for two screws on the same vertebra level reaches 10 min on average in the non computer-assisted group and 11.9 min on average in the computer-assisted group. The fluoroscopy-based (two-dimensional) navigation system for pedicle screw insertion is a safe and reliable procedure for surgery in the lower thoracic and lumbar spine.

[Accuracy measurements of acetabular cup positioning using CT less navigation]. / Protocole d'évaluation du risque d'erreur dans le positionnement cotyloïdien par navigation sans imagerie tomodensitométrique préopératoire.

PURPOSE OF THE STUDY: Standard methodology is lacking for evaluating the accuracy of surgical navigation systems. The purpose of the present study was to propose a new approach to error measurements of an image-free navigation system used for total hip arthroplasty. MATERIAL AND METHODS: This new approach evaluates the overall accuracy of the system and quantifies the influence of clinical application on this global error. The majority of hip navigation systems use the anterior pelvic plane as part of the reference system. With image-free systems, anatomic pelvic landmarks must be acquired intraoperatively in order to define the anterior pelvic plane. This step could potentially introduce a significant error for navigation. Two studies were performed to measure this error, one on patients and the other on pelvic phantoms. Both used the difference between the intraoperative cup orientation, as displayed by the navigation system and the postoperative cup position, measured on computer tomography (CT) data. The CT measurements used the same reference system as the navigation system. RESULTS: The intraobserver measurement variability ranged from 48.4 degrees to 49.5 degrees for cup abduction and from 12 degrees to 13.5 degrees for anteversion. The interobserver variability ranged from 47.5 degrees to 19 degrees for cup abduction and from 11.8 degrees to 13.8 degrees for anteversion. Overall errors were calculated for cup abduction and anteversion. Cup navigation was accurate on pelvic bone phantoms. The anteversion error ranged from 0 degrees to 2.5 degrees (mean 0.9 degrees, standard deviation 0.7 degrees). For the clinical study, abduction errors ranged from 2.1 degrees to 16.7 degrees. The mean abduction error introduced by the acquisition of anatomic landmarks was 7.2 degrees. DISCUSSION: The proposed simple clinical end-to-end accuracy evaluation model provides the surgeon with sufficiently accurate information. The evaluation model was able to identify and more importantly to quantify the clinically induced error. This study proves that ameliorating the reference system acquisition would improve the system's overall accuracy.

[Computer assisted orthopedics surgery]. / L'expérience de la navigation chirurgicale dans l'ouest.

Computer-assisted surgery has become commonplace in orthopedic surgery. The number of applications grows steadily as does the number of patients benefiting from these new techniques. The hearty debates heard when these techniques were first introduced have now given way to more evidence-based evaluation. Our objective here is to continue this approach by presenting our six-year experience with navigation. We will not discuss the theoretical background of these technologies nor attempt to present an exhaustive review of the literature but rather focus attention on surgical skills acquired by a group of surgeons working in a wide range of areas. The common point is that all have now integrated computer-assisted navigation into their routine surgical practices including: a) first-intention and revision knee arthroplasty; b) hip arthroplasty; c) anterior cruciate ligament surgery; d) proximal tibial osteotomy; e) shoulder arthroplasty. We will terminate this round table with a presentation of future technological advances and propose our advice for an increasingly widespread use of these new techniques.

Epidemiology and treatment of acetabular fractures in a level-1 trauma centre: Retrospective study of 414 patients over 10 years.

BACKGROUND: Epidemiological studies of acetabular fractures (AFs) are scarce and, to our knowledge, the most recent one from France, by Letournel and Judet, dates back to 1993. Studies have suggested a decrease in high-energy AFs contrasting with an increase in low-energy AFs due to the longer life expectancy. However, a French case-series study failed to confirm these data. We therefore conducted a 10-year retrospective study in a level-1 trauma centre to: (1) characterise the epidemiological profile of AF; (2) and to describe the treatment strategy. HYPOTHESIS: The epidemiological profile of AF in France is consonant with data from European case-series studies. METHOD: All patients managed for AF between 2005 and 2014 were included in this single-centre retrospective study. All patients were re-evaluated at our centre or another facility 6 months after the fracture. The epidemiological data were compared in the three treatment groups: non-operative, open reduction and internal fixation (ORIF), and total hip arthroplasty (THA). RESULTS: Between 2005 and 2014, 414 patients were admitted for AF. Mean age was 49.4 years (range: 15-101 years). Treatment was non-operative in 231 (56%) older patients, most of whom had low-energy fractures involving the anterior wall. THA with or without acetabular reinforcement and screw-plate fixation was performed in 27 (7%) older patients, most of whom had posterior-wall fractures and experienced postoperative complications (26/27 patients, 96%). ORIF was used in 156 (38%) younger patients, most of whom had high-energy fractures of greater complexity. CONCLUSION: Our results reflect the current indications in AF management. The epidemiological characteristics in our population are comparable to those reported in the few recent European epidemiological studies. To our knowledge, this is the largest French epidemiological study since the landmark work by Letournel and Judet. LEVEL OF EVIDENCE: Level IV, retrospective study.

Posterior tibial slope accuracy with patient-specific cutting guides during total knee arthroplasty: A preliminary study of 50 cases.

BACKGROUND: Patient-specific cutting guides were recently introduced to facilitate total knee arthroplasty (TKA). Their accuracy in achieving optimal implant alignment remains controversial. The objective of this study was to evaluate postoperative radiographic outcomes of 50 TKA procedures with special attention to posterior tibial slope (PTS), which is difficult to control intraoperatively. We hypothesized that patient-specific cutting guides failed to consistently produce the planned PTS. MATERIAL AND METHODS: The Signature™ patient-specific cutting guides (Biomet) developed from magnetic resonance imaging data were used in a prospective case-series of 50 TKAs. The target PTS was 2°. Standardised digitised radiographs were obtained postoperatively and evaluated by an independent reader. Reproducibility of the radiographic measurements was assessed on 20 cases. The posterior cortical line of the proximal tibia was chosen as the reference for PTS measurement. Inaccuracy was defined as an at least 2° difference in either direction compared to the target. RESULTS: The implant PTS was within 2° of the target in 72% of knees. In the remaining 28%, PTS was either excessive (n=10; maximum, 9°) or reversed (n=4; maximum, -6°). The postoperative hip-knee-ankle angle was 0° ± 3° in 88% of knees, and the greatest deviation was 9° of varus. CONCLUSION: These findings support our hypothesis that patient-specific instrumentation decreases PTS accuracy. They are consistent with recently published data. In contrast, patient-specific instrumentation provided accurate alignment in the coronal plane.

CRIGOS: a compact robot for image-guided orthopedic surgery.

The CRIGOS (compact robot for image-guided orthopedic surgery) project was set up for the development of a compact surgical robot system for image-guided orthopedic surgery based on user requirements. The modular system comprises a compact parallel robot and a software system for planning of the surgical interventions and for supervision of the robotic device. Because it is not sufficient to consider only technical aspects in order to improve in clinical routine the therapeutic outcome of conventional interventions, a user-centered and task-oriented design process has been developed which also takes human factors into account. The design process for the CRIGOS system was started from requirement analysis of various orthopedic interventions using information gathered from literature, questionnaires, and workshops with domain experts. This resulted in identification of conventional interventions for which the robotic system would improve the medical and procedural quality. A system design concept has been elaborated which includes definitions of components, functionalities, and interfaces. Approaches to the acquisition of calibrated X-rays will be presented in the paper together with design and evaluation of a first human-computer interface. Finally, the first labtype parallel robot based on low-cost standard components is presented together with the first evaluation results concerning positioning accuracy.

Computer-assisted spine surgery.

The aim of this study was to improve the reliability of pedicle screw insertion. Transpedicle screw insertion may cause neurological, vascular, and mechanical complications. Previous studies of surgical procedures have shown a significant rate of incorrect placement of the screw ranging from 10 to 40%. A new technique that combines preoperative computed tomography (CT) imaging with intraoperative passive navigation was used to perform 64 pedicle screw insertions in the thoracolumbar region. At the same time, 64 pedicle screw insertions were performed manually in the same region and on the same vertebral levels. Surgery was followed in all cases by postoperative radiographs and computed tomography examination, which allowed measurements of screw position relative to pedicle position to be performed. A comparison between the two groups showed that six screws in 64 vertebra (9%) had incorrect placement with the computer-assisted technique whereas 28 screws in 64 vertebra (44%) had incorrect placement with manual insertion. The intraoperative accuracy provided by the computer after registration was better than 1 mm. The good results obtained are similar to those reported in the literature. The cortex penetration observed with the computer-assisted technique was not imputed to computer failure. Errors by the surgeon in acquiring data in the pre- and perioperative steps may explain the six incorrect screw placements. This clinical experience confirms that the accuracy and the reliability of this computer-assisted technique are good.

Bone morphing: 3D morphological data for total knee arthroplasty.

OBJECTIVE: The clinical outcome of a total knee arthroplasty (TKA) is mainly determined by the accuracy of the surgical procedure itself. To improve the final result, one must take into account (a) the alignment of the prosthesis with respect to the mechanical axis, and (b) the balance of the soft tissues. Therefore, morphologic data (such as the shape of the epiphysis) and geometric data are essential. We present a new method for performing TKA based on morphologic and geometric data without preoperative images. MATERIALS AND METHODS: The global method is based on the digitization of points with an optical 3D localizer. For the morphologic acquisitions, we use a method based on the registration of sparse point data with a 3D statistical deformable model. To build the mechanical axis, we use a kinematics method for the hip center and digitization of anatomical landmarks for the ankle centers. The knee center is not determined by digitization or kinematics of the knee, as this would not be accurate. The surgical planning relies totally on the soft-tissue balance, which is the key issue for a good kinematics result. RESULTS: We have used this system for 6 months in a randomized clinical trial involving 35 patients to date. For the first 11 patients that could be measured in the navigation group, the postoperative frontal alignment was within the range of 180 +/- 3 degrees. Fluoroscopic assessment of the soft-tissue balancing will be performed at the conclusion of an extended 2-year study to evaluate the results from a functional point of view. CONCLUSION: Bone Morphing is an accurate, fast, and user-friendly method that can provide morphologic as well as geometric data. We have introduced the important notion of soft-tissue balancing into the intraoperative planning step to optimize the kinematics as well as the anatomy. Therefore, this method should be considered as an alternative to the CT-based method.

Clinical results of percutaneous pelvic surgery. Computer assisted surgery using ultrasound compared to standard fluoroscopy.

This study presents early results of clinical experience with the application of Computer Assisted Surgery (CAS) to percutaneous iliosacral screwing, with comparison to a historical series of patients treated using percutaneous fluoroscopy. Four patients were instrumented using a CAS system, with 10 screws being inserted. Thirty patients were treated by percutaneous fluoroscopic screwing, with 51 screws being inserted. The follow-up assessment included the following criteria; operative time, parameters of radiation exposure, neurological examination, screw placement evaluation on CT-scan, antalgic drug consumption, pain, Majeed grading, and loosening of implants. In the CAS group, the average radiation time was 0.35 min per patient and 0.14 min per screw. No trajectories outside the bone and no postoperative neurological deficits were found. In the fluoroscopic group, the average radiation time was 1.03 min per patient and 0.6 min per screw. Twelve screws had outside-bone trajectories, and iatrogenic neurological deficits were found in seven patients. The average operative time was 50 min in the CAS group and 35 min in the fluoroscopic group. The present CAS technique shows better placement of iliosacral screws, with no outside-bone trajectories and lower radiation exposure.

[A hip prosthesis with a non-rigid femoral implant. The Butel iso-elastic prosthesis]. / Prothèse de hanche avec implant fémoral non rigide. La prothèse iso-élastique de Butel.

A new type of femoral prosthesis is described by the authors. This non-rigid implant respects the natural elasticity of bone and, because of this, avoids excessive stress protection of the bone. In addition, bone atrophy caused by rigid components and osteolysis provoked by cement are eliminated. Experimental studies and the clinical and radiological results five years after insertion seem to confirm the value of this concept.

[Implantation of iliosacral screws. Simulation of optimal placement by 3-dimensional X-ray computed tomography]. / Implantation des vis ilio-sacrées. Simulation de l'emplacement optimal par scanner 3D]

PURPOSE OF THE STUDY: Percutaneous iliosacral screws are used advantageously to fix unstable pelvic girdle avoiding the morbidity of open access for conventional screw fixation. The insertion technique must be precise due to the risk of injury to the lumbosacral nerve trunk, the cauda equina roots, and the first sacral nerve. We undertook a study of the implantation site of iliosacral screws looking for a means of standardizing the drilling procedure on the basis of 3D computed tomography (CT) data. MATERIAL AND METHODS: A CT series with 3D reconstruction was performed on 11 pelvis bones. We retained pelvis parameters and characterized the axis and narrow zone of the sacral wing. The insertion routes of 6.5 mm cancelous bone screws were simulated: two iliosacral routes fixing S1, and two iliosacroiliac routes fixing S1 and S2. The values of the pelvic parameters and the positions of the screws were compared with the Spearman correlation test and graphic regression. RESULTS: The pelvic incidence was a mean 47 degrees. The length of the sacral wing was a mean 73 mm. The narrow zone of the wing was 47 mm from the lateral iliac fossa. In the narrow zone, the wing section showed an oval shape: 22 mm largest diameter, 11 mm smallest diameter. The wing was oriented 84 degrees in the paracoronal plane perpendicular to the plane of the sacral plate, 67 degrees in the para-axial plane parallel to the sacral plate, and 37 degrees in the sagittal plane of the subject. The length of the upper S1 screw was a mean 80 mm. This upper screw was inclined 89 degrees in the para-coronal plant, 61 degrees in the para-axial plane and 28 degrees in the sagittal plane. The length of the lower S1 screw as a mean 80 mm. This lower screw was inclined 74 degrees in the para-coronal plane, 91 degrees in the para-axial plane and 110 degrees in the sagittal plane. The fixation screws could be inserted in 12 out of 22 cases. Correlations were found with height of the subject, length of the wing and the screw, and screw inclination. The inclination of the upper S1 screw in the para-coronal plane was correlated with the larger diameter of the sacral wing. DISCUSSION: The pelvis parameters measured were comparable with data in the literature. The very small dimensions of the narrow zone dictate a very precise drilling for the narrow zone. This narrow zone determines the inclination of the screw insertion. In the sagittal plane the standard deviation was very large making it impossible to interpret the data. The route of the upper screw runs obliquely forward in the plane parallel to the sacral plate. The lower screw runs upwardly in the plane perpendicular to the sacral plate. It does not appear possible to insert fixation screws in a routine procedure. Preoperative assessment would be necessary before percutaneous insertion. CONCLUSION: The 3D CT reconstructions of the sacral wing can be used to determine the precise optimal position of the two iliosacral screws. The principle orientations can be deducted from the plane of the sacral plate. Approximate indications can help reduce operative time and exposure to irradiation (patient and surgeon). Percutaneous iliosacroiliac screw fixation cannot be proposed for all patients.

[Three-dimensional rigidity of the Ilizarov external fixator (original and modified) implanted at the femur. Experimental study and clinical deductions]. / Rigidité tridimensionnelle de l'appareil d'Ilizarov (original et modifié) implanté au fémur. Etude expérimentale et déductions cliniques.

The application of the Ilizarov device to the femur creates several problems: anatomical (transfixion of the thigh), mechanical (asymetrical assembly) and clinical (patient acceptability and duration of treatment). Geometric modifications of the original fixator are proposed. These comprise the use of threaded pins proximally and special connecting pieces. Two large fixators were tested under load and after the introduction of certain variables led the authors to experiment with 18 different assemblies. Four loads were used (compression, flexion in the sagittal and coronal planes and torsion) and stiffness calculated in three dimensions. Three linear and three angular displacements were defined for each type and magnitude of external load. The following sequence of analysis was followed to select the best type of assembly; increased ridigity in torsion; moderate displacement in flexion and axial elasticity. These considerations also apply to the mechanics of fracture healing. After testing under load it was concluded that the original assembly gave the best compromise. The modified assemblies gave a slightly inferior mechanical performance but their geometrical configuration should give better patient tolerance if the following items are used: a proximal arc of 120 degrees, 5 mm diameter threaded pins for the adult and 4 mm diameter for the child.

[Neurological damage in pelvic injuries: a continuous prospective series of 50 pelvic injuries treated with an iliosacral lag screw]. / Lésions neurologiques des fractures de l'anneau pelvien. A propos d'une série prospective continue de 50 lésions pelviennes postérieures opérées par vissage ilio-sacré.

PURPOSE OF THE STUDY: The purpose of this study was to analyze lesions to the lumbosacral plexus related to pelvic injury and its treatment. MATERIAL AND METHODS: Forty-four patients presented 50 posterior osteoligamentary lesions of the pelvic girdle. All patients except eight had other injuries. Mean ISS was 27/75. Posterior lesions were: iliosacral disjunction (n=23), extra-foraminal fracture of the sacrum (n=4), transforaminal fracture (n=22), intra-foraminal fracture (n=1). Vertical posterior displacement was > 1 cm for 24 posterior lesions. Orthopedic reduction was performed at admission for all patients. Fluoroscopy-guided percutaneous lag screw fixation was performed in all cases, on the average eight days after the accident. Neurological involvement was evaluated at admission, after surgery, and at last follow-up. Data were recorded for skeletal muscles, lower limb dermatomes, tendon reflexes, and anal tone. Screw emplacement was checked on the CT-scan. Outcome was assessed subjectively with the Majeed score, a self-administered visual analog scale, and use of antalgesic drugs according to the WHO classification. RESULTS: The neurological examination could not be performed for ten patients at admission. Postoperatively, there was a neurological deficit associated with 26 osteoligamentary lesions (23 lesions of the lumbosacral trunk, 14 lesions of the S1 spinal nerve, 3 lesions of the pudendal nerve, 12 lesions of the superior gluteal nerve, and 10 lesions of the femoral nerve). Patients with neurological involvement had experienced more severe trauma. The iliosacral screw was partially extra-osseous in thirteen cases, with an associated iatrogenic neurological deficit in seven. At mean follow-up of 20 Months (range 4-50) there persisted ten major sequelae including eight cases of hallux extensor deficit. DISCUSSION: Neurological involvement is underestimated during the acute phase of trauma. After recovery, only the manifestations of major injuries persist. The prognosis is poor in the event of a stretched lumbosacral trunk or gluteal nerve due to iliosacral disjunction. Prognosis is good for nerve contusion due to sacral fracture because of early reduction. The femoral nerve is generally injured by compression due to a peri-fracture hematoma; recovery is the rule. Iliosacral screwing requires rigorous technique by a skilled and experienced surgeon. CONCLUSION: About 52% of posterior osteoligamentary injuries are associated with neurological symptoms. After recovery, permanent deficit persists in 21.7%. The most common sequelae are hallux extensor and gluteus medius palsy due to stretching of the lumbosacral trunk.

[In vitro study of the properties of bioresorbable lactic acid polymer materials]. / Etude du comportement in vitro des matériaux biorésorbables en polymère d'acide lactique.

PURPOSE OF THE STUDY: The potential applications of biodegradable osteosynthesis implants present many advantages over conventional metallic devices. Polyesters of the poly and hydroxy-acid type were recognized early as serious candidates. These polymers have demonstrated a very good biocompatibility and are biodegradable in vivo. After biological and chemical testing poly L. lactic acid 98 (PLA 98) was selected as a candidate. We used a static and dynamic investigation in vitro to assess firstly the material properties of PLA 98 and secondly how its characteristics could be modified within a physiological environment. MATERIAL: Michel Vert and colleagues have shown that polymers of lactic acid have a similar time to resorption providing they contain 98 per cent of the "L" form of the polymer. In vitro studies were assessed on bars made in PLA 98. METHODS: In a first time in vitro studies in traction and flexion on bars allowed an assessment of mechanical properties of PLA 98. In a second time stresses were applied on bars using a physiological environment (Haemacel - 37 degrees C). In a third time we assessed the mechanical properties at the temperature of 37 degrees C with dynamic tests on bars in traction and flexion. RESULTS: The stress-strain curves on bars showed that the material is fragile. Sterilisation with ethylene-oxide did not affect the mechanical properties. When bars were placed in a thermostatically controlled (37 degrees C) physiological environment, the stress-strain curve showed that the material became ductile. With a temperature of 37 degrees C and with a frequency better than one hertz, the dynamic tests on bars showed that the material endurance is good up to 20,000 cycles. At 37 degrees C and at the end of one month, the Young modulus and the maximal strain before breaking lose 50 per cent of their initial value. DISCUSSION: All things considered and as the digital value showed, the PLA 98 appear to be ten times less strong than steel. In a physiological environment the mechanical properties improved due to hydratation of the polymer. The material become quickly ductile or malleable. This allowed transient loading without causing breakage. CONCLUSION: The mechanical properties of bioresorbable materials are very different from those of stainless steel and there is a learning curve in their utilisation. The PLA 98 polymer has demonstrated a very good biocompatibility and is totally biodegradable in vivo. With these results we think that PLA 98 can be used in clinical practice. Indications and clinical use should remain limited to bones regions with low applied stresses.

[Proximal femoral fractures in patients over 75 years. Vital and functional prognosis of a cohort of 78 patients followed during 2.5 years]. / Fracture de l'extrémité supérieure du fémur après 75 ans. Pronostic vital et fonctionnel d'une cohorte de 78 patients suivie 2,5 ans.

PURPOSE OF THE STUDY: The purpose of this study was to highlight factors influencing vital and functional prognosis at 2.5 years of elderly people being treated for a proximal femoral fracture. MATERIAL: The study was based on 78 patients more than 75 years old admitted to the orthopedic department for emergency treatment. After post-operative care, patients were transferred to a geriatric readaptation unit. The average patient age at the time of surgery was 85 years. METHODS: This was a retrospective study. Survival graphs were established for the entire population as well as for the sub-populations characterized by a studied parameter. Mortality factors were compared via a univariable analysis. A multivariable logistical regression analysis isolated the factors explaining mortality at 12, 18, and 30 months and survival at 30 months, as well as factors explaining functional prognosis at 1 year. RESULTS: The overall mortality rate was 41 per cent, 48.5 per cent of deaths occur within the first year. Factors which are harmful for vital prognosis are the following: high degree of dependence before the fracture, the existence of a neuropsychiatric pathology, and age factor (more than 85 years). 61.5 per cent of surviving patients were independent for daily activities. 77 per cent of surviving patients lived in their usual place of residence. Factors which were harmful for functional prognosis were the following: type of the fall, symptomatic of an underlying pathological state, and existence of a neuropsychiatric pathology. Nutrition was also a predictive factor concerning the patient's out come. DISCUSSION: The average age of the studied population was higher than in most studies in literature. The treatment is mainly based on hip arthroplasty. The group of patients of over 85 have the highest mortality rate. However, a better survival rate at 18 months has been observed for patients older than 90 years. The delay before surgical care was significantly negative if longer than 6 days. However, a delay of 3 to 6 days was not significantly harmful for survival. Within the studied population, the maximum autonomy gain was observed during the first 6 months. The type of non-accidental fall, symptomatic of an associated pathology, was a factor for functional prognosis which has not been often mentioned. So was the biological deficit of nutrition. Social status acted as an indicator of functional status evolution. CONCLUSION: Therapeutic choices can only be guided by assessments of patients' vital and functional prognosis. A sophisticated or even expensive device should be demanded for patients with favorable prognosis. For patients with precarious functional and vital prognosis, priority should be given to less invasive techniques with immediate walking. The cost of the device should be correlated with patient's functional investment.

[Posterior dislocation of the hip associated with fracture of the neck of the femur. Apropos of 3 cases]. / Les luxations postérieures de la hanche associées à une fracture du "col" du fémur. A propos de 3 observations.

Three patients with posterior dislocation of hip associated with fracture of neck of femur were treated by early sanguineous reduction and osteosynthesis. This therapy was very effective since necrosis did not develop either in the short or long-term follow up (1, 3 and 4 years). These findings combined with documented data are in favor of anatomic reconstruction of upper end of femur by stable and solid osteosynthesis, at least in young adults. Early operation, an irreproachable operating tactic (orthopedic table, ventral decubitus, posterior approach), an immediate stable and solid synthesis and a deferred load bearing (beyond 6 months) should reduce the risk of femoral head necrosis to a minimum.