Gait in thoracolumbar/lumbar adolescent idiopathic scoliosis: effect of surgery on gait mechanisms

For patients whose scoliosis progresses, surgery remains the ultimate way to correct and stabilise the deformity while maintaining as many mobile spinal segments as possible. In thoracolumbar/lumbar adolescent idiopathic scoliosis (AIS), the spinal fusion has to be extended to the lumbar spine. The use of anterior spinal fusion (ASF) instead of the classic posterior fusion (PSF) may preserve more distal spinal levels in attempt to limit the consequences of surgery on trunk mobility. The effects of surgery on body shape, pain and the decompensation phenomenon have all been well evaluated. Very few studies have addressed the effect of ASF or PSF on basic activities, such as walking. Before any treatment, AIS patients already have reduced pelvis, hip and shoulder motion when walking at a normal speed compared with adolescents without scoliosis (control group). Additionally, they have longer contraction time of the lumbar and pelvic muscles leading to an excessive energy cost and reduced muscle efficiency. In addition, if these changes are associated with spinal stiffness, spinal fusion could further negatively affect this pre-surgical inefficient walk. The goals of this study were (a) to compare pre- and 1-year post-surgery conditions in order to assess the effects of spinal arthrodesis on gait parameters and (b) to compare the anterior versus the posterior surgical approaches. Nineteen young females with thoracolumbar/lumbar AIS were assessed by radiological and clinical examination and by conventional gait analysis before surgery and at almost 12 months after surgery. Seven subjects underwent surgery using ASF and 12 using PSF. Three-dimensional gait analysis was performed on a motor-driven treadmill at spontaneous self-selected speed to record kinematic, electromyographic (EMG), mechanical and energetic measurements synchronously. Although it was expected that the instrumentation would modify the characteristics of normal walking, this study showed that surgery does not induce asymmetric gait or any significant differences between the ASP and the PSF surgery groups. One year after surgery, the changes observed consisted of improvements in the gait and mechanical parameters. In the PSF group, 11-14 vertebrae were fused while only 3-4 were fused in the ASF group. In both AIS groups, step length was increased by 4% and cadence reduced by 2%. There was a slight increase in pelvis and hip frontal motion. Only the transverse shoulder motion was mildly decreased by 1.5 degrees . All the other gait parameters were left unchanged or were improved by surgery. Notably, the EMG timing activity did not change. The total muscular mechanical work (W (tot)) increased by 6% mainly due to the external work (W (ext)), i.e. the work performed by the body muscles to move the body in its surroundings. The energy cost, although showing a tendency towards a reduction, remained globally excessive, probably due to the excessive co-contraction of the lumbo-pelvic muscles.

Gait in adolescent idiopathic scoliosis. Kinematics, electromyographic and energy cost analysis

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) can affect spine mobility and gait mechanisms. Nowadays little is known about the effects of scoliosis on gait.

OBJECTIVES

To evaluate the effects of untreated scoliosis on gait.

MATERIALS AND METHODS

Fifty-four females (13 healthy girls and 41 AIS with thoracolumbar/lumbar curve) were assessed by gait analysis. Xrays allowed classifying AIS patients into three groups, depending on the scoliosis severity. Gait analysis included synchronous bilateral kinematic and electromyographic (EMG) measurements, assessment of external (W(ext)), internal (W(int)), total mechanical work (W(tot)), oxygen consumption (V O(2)), energy cost (C) and muscular efficiency (W(tot)/C).

RESULTS

Shoulder, pelvis and hip motions were significantly reduced in all AIS patients. The reduced motion correlated with decreased W(tot). V O(2) and C were increased by 30 %. Muscle efficiency was decreased by 29 %. Increased C correlated with prolonged timing activity of lumbo-pelvic muscles (LPMTA).

DISCUSSION

Reduction of W(tot) can be explained by decrease of external work. Increase of V O(2) and energy cost could be due to bilateral increase of LPMTA.

CONCLUSION

Similar gait alterations were observed in all AIS patients, whatever the severity of the scoliosis. The observed alterations may be considered as the manifestation of an underlying neuromuscular disease or as a consequence of the stiffening effect of scoliosis. The observed "careful walking" strategy could also be a compensatory mechanism to minimize energy expenditure.

Gait in adolescent idiopathic scoliosis: energy cost analysis

Walking is a very common activity for the human body. It is so common that the musculoskeletal and cardiovascular systems are optimized to have the minimum energetic cost at 4 km/h (spontaneous speed). A previous study showed that lumbar and thoracolumbar adolescent idiopathic scoliosis (AIS) patients exhibit a reduction of shoulder, pelvic, and hip frontal mobility during gait. A longer contraction duration of the spinal and pelvic muscles was also noted. The energetic cost (C) of walking is normally linked to the actual mechanical work muscles have to perform. This total mechanical work (W(tot)) can be divided in two parts: the work needed to move the shoulders and lower limbs relative to the center of mass of the body (COM(b)) is known as the internal work (W(int)), whereas additional work, known as external work (W(ext)), is needed to accelerate and lift up the COM(b) relative to the ground. Normally, the COM(b) goes up and down by 3 cm with every step. Pathological walking usually leads to an increase in W (tot) (often because of increased vertical displacement of the COM(b)), and consequently, it increases the energetic cost. The goal of this study is to investigate the effects of scoliosis and scoliosis severity on the mechanical work and energetic cost of walking. Fifty-four female subjects aged 12 to 17 were used in this study. Thirteen healthy girls were in the control group, 12 were in scoliosis group 1 (Cobb angle [Cb] < or = 20 degrees), 13 were in scoliosis group 2 (20 degrees < Cb < 40 degrees), and 16 were in scoliosis group 3 (Cb > or = 40 degrees). They were assessed by physical examination and gait analysis. The 41 scoliotic patients had an untreated progressive left thoracolumbar or lumbar AIS. During gait analysis, the subject was asked to walk on a treadmill at 4 km h(-1). Movements of the limbs were followed by six infrared cameras, which tracked markers fixed on the body. W(int) was calculated from the kinematics. The movements of the COM(b) were derived from the ground reaction forces, and W(ext) was calculated from the force signal. W(tot) was equal to W(int) + W(ext). Oxygen consumption VO2 was measured with a mask to calculate energetic cost (C) and muscular efficiency (W(tot)/C). Statistical comparisons between the groups were performed using an analysis of variance (ANOVA). The external work (W(ext)) and internal work (W(int)) were both reduced from 7 to 22% as a function of the severity of the scoliosis curve. Overall, the total muscular mechanical work (W(tot)) was reduced from 7% to 13% in the scoliosis patients. Within scoliosis groups, the W(ext) for the group 1 (Cb > or = 20 degrees) and 2 (20 < or = Cb < or = 40 degrees) was significantly different from group 3 (Cb > or = 40 degrees). No significant differences were observed between scoliosis groups for the W(int). The W(tot) did not showed any significant difference between scoliosis groups except between group 1 and 3. The energy cost and VO2 were increased by around 30%. As a result Muscle efficiency was significantly decreased by 23% to 32%, but no significant differences related to the severity of the scoliosis were noted. This study shows that scoliosis patients have inefficient muscles during walking. Muscle efficiency was so severely decreased that it could be used as a diagnostic tool, since every scoliosis patient had an average muscle efficiency below 27%, whereas every control had an average muscle efficiency above 27%. The reduction of mechanical work found in scoliotic patients has never been observed in any pathological gait, but it is interpreted as a long term adaptation to economize energy and face poor muscle efficiency. With a relatively stiff gait, scoliosis patients also limit vertical movement of the COM(b) (smoothing the gait) and consequently, reduce W(ext) and W(int). Inefficiency of scoliosis muscles was obvious even in mild scoliosis (group 1, Cb < 20 degrees) and could be related to the prolonged muscle contraction time observed in a previous study (muscle co-contraction).

Fluoride effects on bone formation and mineralization are influenced by genetics

INTRODUCTION

A variation in bone response to fluoride (F(-)) exposure has been attributed to genetic factors. Increasing fluoride doses (0 ppm, 25 ppm, 50 ppm, 100 ppm) for three inbred mouse strains with different susceptibilities to developing dental enamel fluorosis (A/J, a "susceptible" strain; SWR/J, an "intermediate" strain; 129P3/J, a "resistant" strain) had different effects on their cortical and trabecular bone mechanical properties. In this paper, the structural and material properties of the bone were evaluated to explain the previously observed changes in mechanical properties.

MATERIALS AND METHODS

This study assessed the effect of increasing fluoride doses on the bone formation, microarchitecture, mineralization and microhardness of the A/J, SWR/J and 129P3/J mouse strains. Bone microarchitecture was quantified with microcomputed tomography and strut analysis. Bone formation was evaluated by static histomorphometry. Bone mineralization was quantified with backscattered electron (BSE) imaging and powder X-ray diffraction. Microhardness measurements were taken from the vertebral bodies (cortical and trabecular bones) and the cortex of the distal femur.

RESULTS

Fluoride treatment had no significant effect on bone microarchitecture for any of the strains. All three strains demonstrated a significant increase in osteoid formation at the largest fluoride dose. Vertebral body trabecular bone BSE imaging revealed significantly decreased mineralization heterogeneity in the SWR/J strain at 50 ppm and 100 ppm F(-). The trabecular and cortical bone mineralization profiles showed a non-significant shift towards higher mineralization with increasing F(-) dose in the three strains. Powder X-ray diffraction showed significantly smaller crystals for the 129P3/J strain, and increased crystal width with increasing F(-) dose for all strains. There was no effect of F(-) on trabecular and cortical bone microhardness.

CONCLUSION

Fluoride treatment had no significant effect on bone microarchitecture in these three strains. The increased osteoid formation and decreased mineralization heterogeneity support the theory that F(-) delays mineralization of new bone. The increasing crystal width with increasing F(-) dose confirms earlier results and correlates with most of the decreased mechanical properties. An increase in bone F(-) may affect the mineral-organic interfacial bonding and/or bone matrix proteins, interfering with bone crystal growth inhibition on the crystallite faces as well as bonding between the mineral and organic interface. The smaller bone crystallites of the 129P3/J (resistant) strain may indicate a stronger organic/inorganic interface, reducing crystallite growth rate and increasing interfacial mechanical strength.

The genetic influence on bone susceptibility to fluoride

INTRODUCTION

The influence of genetic background on bone architecture and mechanical properties is well established. Nevertheless, to date, only few animal studies explore an underlying genetic basis for extrinsic factors effect such as fluoride effect on bone metabolism.

MATERIALS AND METHODS

This study assessed the effect of increasing fluoride doses (0 ppm, 25 ppm, 50 ppm, 100 ppm) on the bone properties in 3 inbred mouse strains that demonstrate different susceptibilities to developing enamel fluorosis (A/J a "susceptible" strain, 129P3/J a "resistant" strain and SWR/J an "intermediate" strain). Fluoride concentrations were determined in femora and vertebral bodies. Bone mineral density was evaluating through DEXA. Finally, three-point bend testing of femora, compression testing of vertebral bodies and femoral neck-fracture testing were performed to evaluate mechanical properties.

RESULTS

Concordant with increasing fluoride dose were significant increases of fluoride concentration in femora and vertebral bodies from all 3 strains. Fluoride treatment had little effect on the bone mineral densities (BMD) in the 3 strains. Mechanical testing showed significant alterations in "bone quality" in the A/J strain, whereas moderate alterations in "bone quality" in the SWR/J strain and no effects in the 129P3/J strain were observed.

CONCLUSION

The results suggest that genetic factors may contribute to the variation in bone response to fluoride exposure and that fluoride might affect bone properties without altering BMD.

Assessment of teeth as biomarkers for skeletal fluoride exposure

Skeletal fluorosis and dental fluorosis are diseases related to fluoride (F) ingestion. Bone is the largest storage site of F in our body. Therefore, bone F concentrations are considered biomarkers for total F body burden (exposure). However, difficult accessibility limits its use as a biomarker. Thus, a more accessible tissue should be considered and analyzed as a biomarker for total F body burden. The objective of this study, which was divided into two parts, was to evaluate teeth as a biomarker for skeletal F exposure. In part 1 of the study, 70 mice of three different strains (SWR/J, A/J and 129P3/J) were exposed to different levels of water fluoridation (0, 25, 50 and 100 ppm). Bone (femora and vertebrae) and teeth from these mice were then analyzed for F concentration using Instrumental Neutron Activation Analysis (INAA). In part 2 of the study, human teeth (enamel and dentin) and bone from 30 study subjects were collected and analyzed for F concentration using INAA. Study subjects lived in areas with optimum levels of water fluoridation (0.7 and 1 ppm) and underwent therapeutic extraction of their unerupted third molars. The values of bone and teeth F concentration were correlated for parts 1 and 2 of this study. The results showed that in the animal model, where animals were exposed to a wide range of F in their drinking water, tooth [F] correlated with bone [F]. However, no correlation was seen between bone and enamel F concentrations or between bone and dentin F concentrations in the human samples. Therefore, teeth are not good biomarkers for skeletal F exposure in humans when exposure is confined to optimum levels of F in the drinking water.

Myxofibrosarcome intra-articulaire de la hanche chez un enfant de 10 ans

We report a case of intra-articular myxofibrosarcoma with acetabular involvement observed in a 10-Year-old boy. Myxofibrosarcoma is a frequent soft tIssue sarcoma usually observed in elderly subjects. It is extremely rare in children and has not been reported previously before the age of 22 Years. Myxofibrosarcoma is a specific type of soft tIssue tumor. Discussion continues concerning its relation with the myxoid variant of malignant fibrous histiocytoma. The myxoid matrix harbors fibroblastic cells with a curvilinear vessel configuration. Prognosis is good after complete resection and careful surveillance. Local recurrence may occur generally with progression of the tumor stage and risk of later metastasis. This is the first report of an intra-articular localization. We discuss the therapeutic options.

Pediatric seatbelt injuries: unusual Chance's fracture associated with intra-abdominal lesions in a child

The authors report the case of a 7-year-old child involved in a motor vehicle accident. She sustained an unusual flexion-distraction vertebral injury. This spinal injury was related to seatbelt use and was associated with intra-abdominal lesions. The spinal lesion consisted of a posterior ligamentous disruption with widening of the posterior intervertebral space at two adjacent lumbar levels. The purpose of this case report is to describe an atypical and perhaps often unrecognized spinal lesion and to explain our approach to diagnosis and treatment.

Unusual upper cervical fracture in a 1-year-old girl

Injuries to the child's cervical spine are rare and, unlike adults, most common from the occiput to C3. Most odontoid fractures in children occur through the basilar synchondrosis and only the dens is displaced anteriorly. The authors report the clinical and radiologic evaluation of a child who sustained an unusual cervical injury during a motor vehicle accident. The lesion consisted of an epiphyseal fracture-separation between the body and the neural arches of C2. There was also an associated spinal cord lesion.

[Botulinum A in the treatment of equinus dynamic spasticity in children with cerebral palsy. Preliminary study]

PURPOSE OF THE STUDY

The purpose of this clinical prospective study is to better assess the efficacy of intramuscular injections of botulinum-A toxin in the treatment of spastic dynamic equinus deformities in children with cerebral palsy.

MATERIAL

Ten walking children (14 feet) with cerebral palsy were treated with botulinum-A toxin (the American type, Botox) for spastic dynamic equinus, equinovalgus or equinovarus deformity of the foot. The mean age was 6 years (range 4 to 12 years of age).

METHOD

Two units of botulinum-A toxin per kilogram were injected in each involved extremity: the lateral and medial gastrocnemius were injected in equinus or equinovalgus foot and one more injection was done in the tibialis posterior in equinovarus foot. A clinical assessment (based on opinion of caretakers, functional evaluation of gait, detailed orthopaedic clinical evaluation and video of the gait) and a gait analysis were performed prior to the first injections and then at 1, 3 and 6 months afterwards.

RESULTS

All patients showed a clinical improvement. The functional possibilities increased in 6 out of the 10 children. Five children showed a better endurance in their walking capacities. The clinical orthopaedic exam showed improvement for 10 out of the 14 injected feet in passive dorsiflexion from 3 to 15 degrees at one month. Twelve feet improved their score on the Physician Rating Scale from 1 to 4 points. For gait analysis, 6 children (8 feet) had an improvement often minor of their curves in terms of improvement of the dorsal flexion of the ankle and the EMG of the gastrocnemius was improved in terms of decrease of spastic activity in 7 children (10 feet). The response to the injections was seen within 10 days (3 to 10 days) and lasted 3 to 6 months except in one child where it stopped already after 1 month. No side effect was noted.

DISCUSSION

All ten patients of our study showed some type of improvement even if only minor or limited in time in some of them. These data corroborate previous studies performed by other authors. Since this study, the recommended dosage has greatly increased (from 2 U/kg up to 10 U/kg or even more). The most interesting new element is that we noted that it seems to increase the endurance of the patient regarding walking distance.

CONCLUSION

The intramuscular injection of botulinum-A toxin in spastic dynamic equinus deformities in children with cerebral palsy is an useful treatment modality, but the indications have to be respected scrupulously. The subject needs more study with the higher dosage and clinical evaluation to confirm the possible increased endurance.