Tomoya Terai

MRI signal changes of the pedicle as an indicator for early diagnosis of spondylolysis in children and adolescents : A clinical and biomechanical study

Study Design. Clinical review of pediatric patients with lumbar spondylolysis and biomechanical analysis using finite-element lumbar spine model. Objectives. To evaluate the usefulness of the signal changes observed on MR images of the pedicle for the early diagnosis of spondylolysis, and to investigate the pathomechanism of the signal changes based on the stresses in pedicles, as predicted using finite-element analyses. Furthermore, to evaluate the usefulness of the signal change to predict the bony healing following conservative treatment. Summary of Background Data. Since early-stage spondylolysis can achieve osseous healing conservatively, it is important to diagnose this disorder as early as possible. Presently, there is no well-established, noninvasive, and reliable diagnostic tool for the early diagnosis. Methods. Thirty-seven pediatric patients with spondylolysis were included. Sixty-eight defects were examined and their stages as revealed on CT scans were recorded. High signal changes (HSC) of the pedicles on axial T2-weighted MRI were compared with the CT-based stages of the defect. Among them, 16 patients, including 15 boys and 1 girl, were treated conservatively for at least a 3-month period. Bony healing of the fracture site was evaluated on CT, and the results were compared between two groups with or without HSC at the initial consultation. Using a three-dimensional nonlinear finite-element model of the L3–L5 segment, stress distributions in the pars and pedicle regions were analyzed in response to 400 N compression and 10.6 Nm moment. Results. Based on CTs, 68 pars defects were classified as follows: 8 very early, 24 late-early, 16 progressive, and 20 terminal stages. All defects in very early and late-early stages (100%) showed HSC on T2-weighted MRI at the ipsilateral pedicle. Among 16 progressive stages, eight (50%) showed HSC, while no defects of the terminal stage (0%) were found to have HSC. In total, 29 pars defects were treated conservatively out of 16 patients. In 19 of the HSC positive defects, 15 (79%) showed bony healing after the conservative treatment, whereas none of the 10 HSC negative defects (0%) showed any healing. The results were statistically significant at P < 0.05 (&khgr;2). Stress results from the finite-element model indicated that pars interarticularis showed the highest value in all loading modes, and the pedicle showed the second highest. Conclusions. The correlation between the high stresses in the pedicle and the corresponding HSC suggest that signal changes in MRI could be used as an indicator for early diagnosis of spondylolysis. The HSC of the pedicle provided useful information to diagnose early stage spondylolysis. Furthermore, the HSC may be a good indicator as to whether a bony union will result from conservative treatment.

Cross-sectional magnetic resonance imaging study of lumbar disc degeneration in 200 healthy individuals

OBJECT The current cross-sectional observational MR imaging study aimed to investigate the prevalence and risk factors of lumbar disc degeneration in a healthy population and to establish the baseline data for a prospective longitudinal study. METHODS Two hundred healthy volunteers participated in this study after providing informed consent. The status of lumbar disc degeneration was assessed by 3 independent observers, who used sagittal T2-weighted MR imaging. Demographic data collected included age, sex, body mass index, episode(s) of low-back pain, smoking status, hours of standing and sitting, and Roland-Morris Disability Questionnaire scores. There were 68 men and 132 women whose mean age was 39.7 years (range 30-55 years). Eighty-two individuals (41%) were smokers, and the Roland-Morris Disability Questionnaire scores were averaged to 0.6/24. RESULTS The prevalence of disc degeneration was 7.0% in L1-2, 12.0% in L2-3, 15.5% in L3-4, 49.5% in L4-5, and 53.0% in L5-S1. A herniated disc was observed at the corresponding levels in 0.5, 3.5, 6.5, 25.0, and 35.0% of cases respectively. Spondylolisthesis was observed in < 3% of this population. Multiple logistic regression analysis demonstrated that age and hours sitting were significantly related to L4-5 disc herniation. Episode of low-back pain, smoking status, body mass index, and hours standing did not affect the prevalence of disc degeneration. CONCLUSIONS The current study established the baseline data of lumbar disc degeneration in a 30- to 55-year-old healthy population for a prospective longitudinal study. Hours spent sitting significantly increased the prevalence of disc herniation, but episode of low-back pain, smoking status, obesity, and standing hours were not significant risk factors.

Fractures of the distal end of radius in elderly patients: a comparative study of anatomical and functional results.

The functional and anatomical results of distal end of radius fractures with severe displacement in 22 elderly patients are reviewed in this retrospective study. The mean age of the patients was 69.4 years (range, 60–88 years) and the mean follow-up period was 24 months (range, 12–53 months). According to the sum of demerit points (Saito, 1983), the latest follow-up functional end results were ‘excellent’ in 64% of fractures and ‘good’ in 36%. As for the anatomical results at follow-up, the average radial tilt was 20.7°, ulnar variance was 4.0 mm, and palmar tilt was −2.7° respectively. Though most of the patients had satisfactory outcome and the functional results did not correlate with the radiographic evidence of minor deformities, the functional results of the patients with radial shortening of 6 mm or over were poor. Furthermore, the grip power was the most significant factor related to subjective evaluation and did not improve significantly in patients with the nondominant hand injured.

Three dimensional finite element analysis of the pediatric lumbar spine. Part II: biomechanical change as the initiating factor for pediatric isthmic spondylolisthesis at the growth plate

A non-linear 3-dimensional finite element pediatric lumbar spine model with vertebral growth plate and apophyseal bony ring was developed. Lumbar spondylolysis was simulated in the model. The Von Mises stresses in the structures surrounding the vertebral growth plate, including apophyseal bony ring and osseous endplate were calculated in various loading modes. Instantaneous axis of rotation (IAR) path from flexion to extension was also analyzed. The results were compared with those of the intact model and the literature. The IAR path was at the posterior disc-endplate space of the lower vertebra in the intact spine, and moved cranially towards the upper-posterior disc space in the lytic spine. This was in agreement with in vivo radiological data by Sakamaki et al. [19]. During various loading modes, stresses in the spondylolytic pediatric model were higher than that of the intact model; ranging from 1.1 to 6.0 times, with the highest value in extension at the growth plate. In conclusion, FE models indicate that stress concentrations in the lytic model increase at the growth plate which may lead to physis stress fracture leading to spondylolisthesis.

Biomechanical comparison of lumbar spine with or without spina bifida occulta. A finite element analysis

Study design:Biomechanical study using finite element model (FEM) of lumbar spine.Objectives:Very high coincidence of spina bifida occulta (SBO) has been reported more than in 60% of lumbar spondylolysis. The altered biomechanics due to SBO is one considerable factor for this coincidence. Thus, in this study, the biomechanical changes in the lumbar spine due to the presence of SBO were evaluated.Setting:United States of America (USA).Methods:An experimentally validated three-dimensional nonlinear FEM of the intact ligamentous L3-S1 segment was used and modified to simulate two kinds of SBO at L5. One model had SBO with no change in the length of the spinous process and the other had a small dysplastic spinous process. Von Mises stresses at pars interarticularis were analyzed in the six degrees of lumbar motion with 400 N axial compression, which simulates the standing position. The range of motion at L4/5 and L5/S1 were also calculated.Results:It was observed that the stresses in all the models were similar, and there was no change in the highest stress value when compared to the intact model. The range of motion was also similar in all the models. The lumbar kinematics of SBO was thus shown to be similar to the intact model.Conclusion:SBO does not alter lumbar biomechanics with respect to stress and range of motion. The high coincidence of spondylolysis in spines with SBO may not be due to the mechanical factors.

Relationship between limb length discrepancy and load distribution across the sacroiliac joint--a finite element study.

We assessed the relationship between leg length discrepancy (LLD) and the load distribution across the sacro‐iliac joint (SIJ). A finite element model of the spine–pelvis was developed with different amounts of LLD by increasing the length of the right femur in the model. Peak stresses and contact loads across the SIJ were computed for different amounts of LLD (1, 2, and 3 cm). The load and the peak stresses across the SIJ articular surfaces progressively increased with the increase in the LLD. Trying to offset the LLD surgically by lengthening of the short side, shortening or stunting the growth (epiphysiodesis) of the long side, or by shoe lifts should decrease the load across the SIJ and should theoretically decrease SIJ pain.

Spondylolysis originates in the ventral aspect of the pars interarticularis: A CLINICAL AND BIOMECHANICAL STUDY

Lumbar spondylolysis is a stress fracture of the pars interarticularis. We have evaluated the site of origin of the fracture clinically and biomechanically. Ten adolescents with incomplete stress fractures of the pars (four bilateral) were included in our study. There were seven boys and three girls aged between 11 and 17 years. The site of the fracture was confirmed by axial and sagittal reconstructed CT. The maximum principal tensile stresses and their locations in the L5 pars during lumbar movement were calculated using a three-dimensional finite-element model of the L3-S1 segment. In all ten patients the fracture line was seen only at the caudal-ventral aspect of the pars and did not spread completely to the craniodorsal aspect. According to the finite-element analysis, the higher stresses were found at the caudal-ventral aspect in all loading modes. In extension, the stress was twofold higher in the ventral than in the dorsal aspect. Our radiological and biomechanical results were in agreement with our clinical observations.

Operated and adjacent segment motions for fusion versus cervical arthroplasty: a pilot study.

BackgroundAnterior cervical discectomy and fusion (ACDF) represent the standard treatment for cervical spondylolytic radiculopathy and myelopathy. To achieve solid fusion, appropriate compressive loading of the graft and stability are essential. Fusion may lead to adjacent segment degeneration. Artificial discs have been introduced as motion-preserving devices to reduce the risk of fusion-related complications.Questions/purposesWe therefore asked: (1) Does the use of a plate reduce motion at the operated level and bone graft compression compared to fusion with bone graft alone; and (2) is adjacent-segment motion higher after fusion with a plate?MethodsMotions and compressive loads in the graft were quantified for intact, C4–C5 ACDF without and with a plate, and total disc arthroplasty in human cadaver spines.ResultsAt the surgery level all motions decreased for ACDF with a plate. The motions were similar to intact motions after total disc arthroplasty. The motions across the adjacent segment increased after fusion in all loading modes except lateral bending and were closer to the intact for the total disc arthroplasty case. The plate maintained a compressive load on the graft with a maximum increase in extension.ConclusionsUnlike fusion, the arthroplasty can restore motion to normal at the surgery and adjacent segments, compared to fusion cases. A cervical plate with a precompression of the graft provides enhanced stability and fusion due to improved compression.Clinical RelevanceOur findings support the clinical observations that fusion may lead to the degeneration of the adjacent segments. Disc arthroplasty may be able to circumvent the adjacent segment degeneration.

Cervical spondylolysis in a judo player: a case report and biomechanical analysis

Study designA case report and a biomechanical study using a finite element method.ObjectivesTo report a case with the cervical spondylolysis and to understand the biomechanics of the cervical spine with spondylolysis at C6.Summary of background dataCervical spondylolysis, although not a common spinal disorder, can occur in athletes. Presently, the exact pathology, natural history and biomechanics are not known. Thus, treatment strategies for this disorder in athletes are in controversy. To treat and/or advise patients with cervical spondylolysis, the cervical spine biomechanics regarding this disorder should be understood.MethodsA case of a 12-year-old male judo player is presented. The patient presented with occipital and upper neck pain. Plain radiographs, reconstructed CT scan and MRIs of this patient were reviewed. Biomechanically, stress distributions were analyzed in response to 73.6 N axial compression and 1.5-Nm moment in flexion, extension, lateral bending, and axial rotation using a FE model of the intact ligamentous C3 to C7 segment. Bilateral spondylolysis was created in the model at C6. The stress results from the bilateral defect model were compared to the intact model predictions.ResultsPlain radiographs showed bilateral C6 spondylolysis, and grade I spondylolisthesis. MRI showed mild disc degeneration at C6/7. With conservative treatment, the symptoms disappeared. In the spondylolysis model, the maximum Von Mises Stresses at C6/7 increased in all cervical spine motions, as compared to the intact case. Specifically, in axial rotation, the stress increase was 3.7-fold as compared to the intact model. The range of motion at C6/7 increased in the spondylolysis model as well. Again, during axial rotation, the increase in motion was 2.3-fold when compared to the intact model.ConclusionsCervical spondylolysis can cause biomechanical alterations, especially in axial rotation, leading to increased disc stresses and range of motion. The increased stresses in the disc and the hypermobility would be a dangerous condition for athletes participating in contact sports such as judo. Thus, we recommended that judo players with cervical spondylolysis should change to non-contact sports, such as jogging.

Adult onset tethered cord syndrome associated with intradural dermoid cyst. A case report.

Study design:A case report and a review of literature.Objectives:To describe a rare case of adult onset tethered cord syndrome associated with intradural dermoid cyst.Setting:General Orthopedics, Japan.Methods:A 50-year-old woman was referred to us because of right leg pain and pollakiuria. Neurological examinations and radiological assessments including myelography, computerized tomography scan and Magnetic resonance image were carried out. We diagnosed it as the adult onset tethered cord syndrome associated with an intradural cystic lesion.Results:The cystic lesion was totally removed following laminectomy from L5 through S4. Histologically, the tumor was diagnosed as a dermoid cyst.Conclusions:Intradural dermoid could produce adult onset tethered cord syndrome, but it was not reported in the English literatures to our knowledge.