Jérôme Sales de Gauzy

Scoliosis in Patients With Prader-Willi Syndrome

OBJECTIVE. Our goals were to determine the prevalence and estimate the evolution of spinal deformities in patients suffering from Prader-Willi syndrome; find out which kind of spine deformity predominates regarding genotype and clinical patterns; and evaluate the affect of growth-hormone treatment on the onset and progression of spinal deformities. PATIENTS AND METHODS. This was a retrospective longitudinal, clinical, and radiologic study. One hundred forty-five children followed between 1980 and 2006 were studied in 2 referral centers for Prader-Willi syndrome. Genetic testing confirmed the diagnosis in 133 patients. Ninety-three patients (64%) received growth-hormone therapy. For statistical analysis, age-adjusted comparison between groups was performed by using multivariate logistic regression. RESULTS. Mean age of the patients was 10.2 ± 6.2 years. Sixty-three (43.4%) patients were afflicted with scoliosis. Scoliosis frequency steadily rose with age, and a large majority of patients were affected at skeletal maturity (66.7%). Scoliosis prevalence was not affected by the genotype or by growth-hormone treatment. Patients with higher BMI values had an increased risk of developing a kyphotic deformity in association with scoliosis. We found a statistical association between kyphotic deformity and the need for surgical treatment. CONCLUSIONS. Scoliosis is a major concern for patients with Prader-Willi syndrome, and a regular (annual) systematic back examination is mandated. The role of growth-hormone treatment on the natural history of scoliosis could not be determined, and careful monitoring during treatment is recommended.

Spinal cord monitoring in scoliosis surgery using an epidural electrode. Results of a prospective, consecutive series of 191 cases

Study Design. Retrospective analysis of a prospectively accrued series of 191 consecutive patients who underwent intraoperative neurophysiologic monitoring during scoliosis corrective surgery. Objectives. To compare the monitoring outcome of idiopathic and neuromuscular scoliosis. To demonstrate the usefulness of the epidural electrode. To report sensitivity and specificity of the monitoring method employed at a single institution. Summary of Background Data. Reports in the literature emphasized the difficulty to obtain data in neuromuscular patients. Multimodality spinal cord monitoring has been recommended. Despite their still debated composition, neurogenic motor-evoked potentials have proven their validity in clinical practice. Methods. Somatosensory and neurogenic evoked potentials were attempted in all patients presenting for scoliosis correction between 1999 and 2005. Study patients were divided into 3 groups: group 1, idiopathic; group 2, neuromuscular; and group 3, miscellaneous origins. Results. The use of the epidural electrode demonstrated significant usefulness in the ability of monitoring otherwise nonmonitored patients, especially in group 2. Inability to obtain any evoked potentials occurred in 4 cases (2.1%). Five cases were found to be true positives. An adapted and rapid intervention permitted to avoid new postoperative deficit in all cases. There was no instance of false-negative data. The overall method sensitivity was 100%, and specificity was 52.69%. Conclusions. The use of a single epidural electrode allowing somatosensory evoked potentials recording and spinal cord stimulation alternately is a safe and valid method of intraoperative monitoring.

Influence of Location, Fluid Flow Direction, and Tissue Maturity on the Macroscopic Permeability of Vertebral End Plates

Study Design. We implemented a pilot study in a growing animal model. The macroscopic permeability of the vertebral endplates was measured. The influence of location, tissue maturity, and fluid flow direction was quantified. Objective. We hypothesized that the macroscopic permeability of vertebral endplate may decrease with maturity of the vertebral segment. Summary of Background Data. The alternation of loading induced by the diurnal cycle generates convective flux into the vertebral segment with the dominant flow path through the vertebral endplates. The alteration of mass transport at the disc-vertebrae interface may interrupt the mechanobiologic balance, and have an effect such as degenerative changes or scoliosis. Methods. A previously validated method for measuring permeability, based on the relaxation pressure caused by a transient-flow rate was used. Three specimens were extracted from each L1 to L5 endplate. Seventy-one specimens were frozen, and 64 were stored fresh in a standard culture media. A microscopic analysis completed the biomechanical analysis. Results. At 2, 4, and 6 months, the mean permeability (10−14 m4/N · s, flow-in/flow-out) of the central zone was respectively: 1.23/1.66, 1.03/1.29, and 0.792/1.00. Laterally, it was 1.03/1.19, 1.094/1.001, and 0.765/0.863. For all groups, cartilage endplate and growth plate were both thinner in the center of the plate. Weak differences of the vascular network were detected, except for a small increase of vascular density in the central zone. Conclusion. The results from this animal study showed that the central zone of the vertebral endplate was more permeable than the periphery and the flow-out permeability was up to 35% greater than the flow-in permeability. Increase of permeability with decrease of cartilage thickness was noticed within the same age group. We also found a statistically significant decrease of the macroscopic permeability correlated with the tissue maturity.

Complications of scoliosis surgery in Prader-Willi syndrome.

Study Design. Retrospective case series of 16 consecutive patients. Objective. To evaluate the results of scoliosis surgery in Prader-Willi syndrome (PWS) with special emphasis on the complications and their risk factors. Summary of Background Data. PWS is a rare genetic disorder characterized by obesity, hypotonia, and frequent scoliosis. The literature dealing with scoliosis surgery in PWS consists of only few case reports. Surgical treatment was reported to be difficult with frequent and severe complications. Methods. Sixteen patients (3 males, 13 females) in 63 presenting scoliosis and PWS were operated on between 1974 and 2004. Preoperative, postoperative and last follow-up clinical and radiologic data were analyzed. Complications, treatment, and outcome were investigated. Results. Mean age at scoliosis diagnosis was 6.2 years (range 0.5–13.5). Mean age at surgery was 12.3 years (range 5–15). Mean follow-up was 5.4 years (range 2–18). There were 9 major complications (4 severe kyphosis above fusion, 2 deep infections, 1 transient paraplegia, 1 pseudarthrosis, 1 delayed wound healing). The 4 kyphosis required reoperation, 3 of which were complicated with permanent spinal cord injury. Minor complications affected 6 patients. Conclusion. Scoliosis surgery is frequently necessary in PWS and is associated with high rate of complications. These are often related to specific features of this syndrome the surgeon should recognize and consider.

Hypophosphatasia may lead to bone fragility: don’t miss it

Hypophosphatasia is an inheritable disorder characterised by defective bone mineralisation due to the impaired activity of tissue-non-specific alkaline phosphatase (AP). Clinical presentation ranges from stillbirth without mineralised bone to pathological fractures in late adulthood. During childhood, the main manifestations include rickets, growth delay and dental problems. Fractures and bone pain usually characterise the adult form. A 9-year-old girl was referred for repetitive fractures after minimal trauma. She had normal growth, normal sclerae, no rickets and minimal dental abnormalities. Her sister had also presented fractures. The proband, her sister and mother had low total and bone-specific AP levels and E435K mutation in exon 12 of the liver/bone/kidney AP gene. Low AP levels must lead to genetic analysis. Bone fragility and repetitive fractures may be symptoms of hypophosphatasia in childhood, which must not be neglected. Associated factors such as vitamin D or calcium deficiency must be prevented. In conclusion, hypophosphatasia must not be forgotten as an aetiological factor of repetitive fractures or bone pain in children and AP activity should be checked accurately.

Ulnar styloid fracture in children: a retrospective study of 46 cases.

Ulnar styloid fractures are frequently ignored in the treatment of wrist fractures in children. Forty-six untreated ulnar styloid fractures (40 tip and six base fractures) associated with radial injuries (45 patients) were retrospectively analysed. At the removal of the cast, we recorded that 80% had a nonunion of the styloid fracture. Thirty-five patients were reviewed at an average of 19 months after treatment. Thirty tip fractures and five base avulsions were found. We recorded 28 patients with a good clinical result despite 21 cases of nonunion, whereas seven patients (all nonunions) had a fair result. All the fair results suffered from intermittent pain during sports and movement, radioulnar joint instability and tears of the triangular fibrocartilage complex. It can be concluded that both distal radius and ulnar styloid fractures should be taken into account in the initial treatment and pain associated with a nonunion of the ulnar styloid in a child may be due to a tear of the triangular fibrocartilage complex.

Classification of chance fracture in children using magnetic resonance imaging.

Study Design. MRI study of pediatric Chance fracture. Objective. To evaluate bone and soft tissue lesions in pediatric Chance fracture. Summary of Background Data. Several descriptions and classifications have been already developed for Chance fracture, but mainly for adult. Furthermore, they are all based only on radiographic studies. Methods. MRI and radiographs of 18 children with Chance fracture were analyzed before treatment. Results. On MRI, in all cases, no abnormal signs were noted on the intervertebral disc. Six patients had a bone fracture going through the pedicle and the vertebral body. Twelve patients had a physeal injury located on the superior or on the inferior vertebral endplate. Three types of lesions could be identified according to the location of the lesion in relation to the pedicle. Conclusion. MRI is useful in the diagnosis of pediatric Chance fracture. It allows physeal injury to be clearly identified from disc injury.

Correlations between effective permeability and marrow contact channels surface of vertebral endplates

Homeostasis of the intervertebral disc relies on nutrient supply and waste clearance through the dense capillary network that is in contact with the cartilage endplate (CEP). We developed a micro‐computerized tomography (micro‐CT) method to quantify the marrow contact channel surface (MCCS) with the CEP and to validate the hypothesis according to which MCCS was correlated to the effective permeability of the vertebral endplate (VEP) and influenced by the mechanical stimuli. The influence of compression loading on local vascularization was investigated. Six 4‐week‐old skeletally immature pigs were instrumented with left pedicle screws and rod at both T5–T6 and L1–L2 levels to create asymmetrical spine tethers. After 3 months of growth, three cylindrical specimens of the VEP (one central and two lateral right and left) were obtained from both the instrumented and the control levels. We used a previously validated method for measuring permeability. Micro‐CT analysis (resolution 12 µm) yielded a gray‐scale 2D‐image of the discal end of each specimen converted into a binary 2D‐image to derive the MCCS. Correlations between MCCS and effective permeability were assessed. Effective permeability and MCCS were significantly decreased compared to the control group especially on the tethered side (−41.5%, p = 0.004 and −52.5%, p = 0.0009, respectively). Correlations were significant and showed maximal value (r2 = 0.430, p < 0.0001) on the tethered side involving maximal compressive loadings. Mechanical stimuli, due to unbalanced growth, altered the vascularization and the convective properties of the CEP. The cascade of mechanobiological events should offer perspectives for research on disc degeneration and attempted treatment.

Complications in pediatric spine surgery using the vertical expandable prosthetic titanium rib: the French experience.

Study Design. Multicenter retrospective study of 54 children. Objective. To describe the complication rate of the French vertical expandable prosthetic titanium rib (VEPTR) series involving patients treated between August 2005 and January 2012. Summary of Background Data. Congenital chest wall and spine deformities in children are complex entities. Most of the affected patients have severe scoliosis often associated with a thoracic deformity. Orthopedic treatment is generally ineffective, and surgical treatment is very challenging. These patients are good candidates for VEPTR expansion thoracoplasty. The aim of this study was to evaluate the potential complications of VEPTR surgery. Methods. Of the 58 case files, 54 were available for analysis. The series involved 33 girls and 21 boys with a mean age of 7 years (range, 20 mo–14 yr and 2 mo) at primary VEPTR surgery. During the follow-up period, several complications occurred. Results. Mean follow-up was 22.5 months (range, 6–64 mo). In total, 184 procedures were performed, including 56 VEPTR implantations, 98 expansions, and 30 nonscheduled procedures for different types of complications: mechanical complications (i.e., fracture, device migration), device-related and infectious complications, neurological disorders, spine statics disturbances. Altogether, there were 74 complications in 54 patients: a complication rate of 137% per patient and 40% per surgery. Comparison of the complications in this series with those reported in the literature led the authors to suggest solutions that should help decrease their incidence. Conclusion. The complication rate is consistent with that reported in the literature. Correct determination of the levels to be instrumented, preoperative improvement of nutritional status, and better evaluation of the preoperative and postoperative respiratory function are important factors in minimizing the potential complications of a technique that is used in weak patients with complex deformities. Level of Evidence: 4

Quantification of intervertebral disc volume properties below spine fusion, using magnetic resonance imaging, in adolescent idiopathic scoliosis surgery.

Study Design. Prospective clinical study. A quantification of volume and hydration variation of the intervertebral discs, using magnetic resonance imaging (MRI), in the lumbar spine before and after surgery performed in adolescent idiopathic scoliosis (AIS). Objectives. To evaluate an objective quantification of volume and hydration of intervertebral discs below spine fusion in scoliosis surgery. Summary and Background Data. Repercussion of long spine fusion on the free lower lumbar spine is one of the major concerns of scoliosis surgery. However, the evolution of lumbar intervertebral disc below thoracolumbar fusions remains unknown. Methods. MRI performed in the clinical protocol, concerned 28 patients having an idiopathic scoliosis. They underwent posterior instrumentations. MRI was obtained before surgery, after surgery at 3 months and for 15 patients at 1 year. MRI data were posttreated using a custom-made image processing software to semiautomatically derive volume properties of disc, anulus fibrosus, and nucleus pulposus. The nucleus-disc volume ratio was also an indicator of the hydration level. Results. The reliability of the three-dimensional reconstruction process was initially verified using an intraoperator reproducibility test. Original preoperative data on disc volume properties were then derived. Postoperative volume variations were quantified in discs below spine fusion taking into account the level of the arthrodesis and the disc location. It showed that the postoperative volume criteria increased significantly for nucleus, disc, and nucleus-disc volume ratio and some magnitude modulation could be conditioned by the location of surgical instrumentation. Some stabilization or reduction depending on disc level and arthrodesis size between 3 months and 1 year is observed in the follow-up. It tended to prove that the recovery of balance physiologic positioning and inherent biomechanical loads could induce a restored hydration of disc, which should favor the remodeling of free segments. Conclusions. This work was the first report dealing with consequences of scoliosis surgery on subjacent disc in term of volume and hydration properties.