Development and biomechanical analysis of an axially controlled compression spinal rod for lumbar spondylolysis.

BACKGROUND: To elucidate the differences in mechanical performance between a novel axially controlled compression spinal rod (ACCSR) for lumbar spondylolysis (LS) and the common spinal rod (CSR). METHODS: A total of 36 ACCSRs and 36 CSRs from the same batch were used in this study, each with a diameter of 6.0 mm. Biomechanical tests were carried out on spinal rods for the ACCSR group and on pedicle screw-rod internal fixation systems for the CSR group. The spinal rod tests were conducted following the guidelines outlined in the American Society for Testing and Materials (ASTM) F 2193, while the pedicle screw-rod internal fixation system tests adhered to ASTM F 1798-97 standards. RESULTS: The stiffness of ACCSR and CSR was 1559.15 ±â€…50.15 and 3788.86 ±â€…156.45 N/mm (P < .001). ACCSR's yield load was 1345.73 (1297.90-1359.97) N, whereas CSR's was 4046.83 (3805.8-4072.53) N (P = .002). ACCSR's load in the 2.5 millionth cycle of the fatigue four-point bending test was 320 N. The axial gripping capacity of ACCSR and CSR was 1632.53 ±â€…165.64 and 1273.62 ±â€…205.63 N (P = .004). ACCSR's torsional gripping capacity was 3.45 (3.23-3.47) Nm, while CSR's was 3.27 (3.07-3.59) Nm (P = .654). The stiffness of the pedicle screws of the ACCSR and CSR group was 783.83 (775.67-798.94) and 773.14 (758.70-783.62) N/mm (P = .085). The yield loads on the pedicle screws of the ACCSR and CSR group was 1345.73 (1297.90-1359.97) and 4046.83 (3805.8-4072.53) N (P = .099). CONCLUSION: Although ACCSR exhibited lower yield load, stiffness, and fatigue resistance compared to CSR, it demonstrated significantly higher axial gripping capacity and met the stress requirement of the human isthmus. Consequently, ACCSR presents a promising alternative to CSR for LS remediation.

Are trunk muscle sizes different between acute lumbar spondylolysis and nonspecific low back pain?

INTRODUCTION: Morphological differences in the trunk muscles between adolescent athletes with lumbar spondylolysis (LS) and nonspecific low back pain (NSLBP) have not been fully elucidated. This study aimed to investigate the differences in physiological cross-sectional areas (CSA) of the trunk muscles between athletes with acute LS and those with acute NSLBP. METHODS: Magnetic resonance images of 48 patients aged 13-14 years diagnosed with acute LS or NSLBP were retrospectively evaluated. The CSA of the paraspinal, psoas major, and rectus abdominis muscles at the L4-5 intervertebral disc level were measured. RESULTS: CSA of the left and right paraspinal muscles in the acute LS group were significantly larger than those in the acute NSLBP group (left: mean difference, 276.0 mm2; 95% confidence interval [CI], 68.5-483.6 mm2; P = 0.01; right: mean difference, 228.8 mm2; 95% CI, 7.6-450.1 mm2; P = 0.04). The ratio between the left paraspinal muscles and left psoas major in the acute LS group was significantly larger than that in the acute NSLBP group (mean difference, 0.2; 95% CI, 0.0-0.4; P = 0.03). CONCLUSIONS: Trunk muscle size may differ between adolescent athletes with acute LS and those with NSLBP. Future research involving healthy controls is required to better understand the morphological characteristics of these injuries.

Identifying Acute Lumbar Spondylolysis in Young Athletes with Low Back Pain: Retrospective Classification and Regression Tree Analysis.

STUDY DESIGN: Case-control study. OBJECTIVE: The aim of this study was to establish an algorithm to distinguish acute lumbar spondylolysis (LS) from nonspecific low back pain (NSLBP) among patients in junior high school by classification and regression tree (CART) analysis. SUMMARY OF BACKGROUND DATA: Rapid identification of acute LS is important because delayed diagnosis may result in pseudarthrosis in the pars interarticularis. To diagnose acute LS, magnetic resonance imaging (MRI) or computed tomography is necessary. However, not all adolescent patients with low back pain (LBP) can access these technologies. Therefore, a clinical algorithm that can detect acute LS is needed. METHODS: The medical records of 223 junior high school-aged patients with diagnosed acute NSLBP or LS verified by MRI were reviewed. A total of 200 patients were examined for establishing the algorithm and 23 were employed for testing the performance of the algorithm. CART analysis was applied to establish the algorithm using the following data; age, sex, school grades, days after symptom onset, history of LBP, days of past LBP, height, passive straight leg raising test results, hours per week spent in sports activities, existence of spina bifida, lumbar lordosis angle, and lumbosacral joint angle. Sensitivity and specificity of the algorithm and the area under the ROC curve were calculated to assess algorithm performance. RESULTS: The algorithm revealed that sex, days after symptom onset, days of past LBP, hours per week spent in sports activities, and existence of spina bifida were key predictors for identifying acute LS versus NSLBP. Algorithm sensitivity was 0.64, specificity was 0.92, and the area under the ROC curve was 0.79. CONCLUSION: The algorithm can be used in clinical practice to distinguish acute LS from NSLBP in junior high school athletes, although referral to MRI may be necessary for definitive diagnosis considering the algorithm's sensitivity.Level of Evidence: 4.

Minimally Invasive Approach Toward Percutaneous Direct Pars Repair: An Observational Study.

BACKGROUND: Spondylolysis refers to a defect of the vertebral pars interarticularis. Percutaneous direct pars repair using a minimally invasive technique was performed in a group of young patients to maintain their spinal segment movement and to restore their normal anatomy. The aim of this study was to present the clinical, functional, and radiologic outcomes of pars defects that were repaired percutaneously via the minimally invasive technique. METHODS: This was a single-center, nonrandomized, prospective study of the demographic, clinical, functional, and radiographic outcomes of 18 patients (age range, 18-32 years). The visual analog scale for back pain and the Oswestry Disability Index were used to evaluate the functional outcomes. The Macnab criteria were applied to evaluate patient satisfaction after surgery. RESULTS: All patients were admitted with bilateral pars fracture at the level of L4 (n = 4) or L5 (n = 14). The average duration of clinical follow-up was 16.04 months (range, 12-28 months). With reference to the Macnab criteria, 17 patients (94%) showed perfect or good outcomes. Fusion or bridging of bones was observed on computed tomography in 14 patients (77%) at the last radiological examination. CONCLUSIONS: Minimally invasive surgery to treat symptomatic spondylolysis is a safe option that minimizes muscle and soft tissue dissection. In this study, good clinical and functional outcomes were achieved in young patients with low complications and high fusion rates using completely percutaneous treatment.

Comparison of symptomatic spondylolysis in young soccer and baseball players.

BACKGROUND: Spondylolysis is the main cause of low back pain (LBP) in young athletes. There are few studies analyzing the difference of spondylolysis among young athletes with different sports activities. The purpose of this study was to compare the clinical factors and distribution of the lesions of spondylolysis on magnetic resonance imaging (MRI) scans in young soccer and baseball players with symptomatic spondylolysis. METHODS: The medical records of 267 young athletes aged 7 to 18 years old who underwent MRI to evaluate the cause of LBP between 2017 and 2020 were retrospectively reviewed to identify patients with spondylolysis. Of the young athletes with symptomatic spondylolysis, clinical factors and MRI findings in soccer and baseball players were retrospectively evaluated. The clinical factors were age, sex, interval from onset of LBP to MRI, and side of the dominant leg in the sports field. MRI findings included number, lumbar level, and side of the lesions. RESULTS: A total of 33 soccer players (mean age, 15.4 ± 1.4 years) and 49 baseball players (mean age, 15.4 ± 1.6 years) with symptomatic spondylolysis were enrolled. All patients were male. No significant differences were noted in age and the interval from onset of LBP to MRI between the groups. Soccer players had greater numbers of multiple (p < 0.001) and bilateral (p < 0.001) lesions than baseball players. The dominant side of the hand for pitching or batting was correlated with the contralateral-side lesions in baseball players (p = 0.001). CONCLUSIONS: The distribution of the lesions of spondylolysis differed in young soccer and baseball players. Pitching or batting with the dominant-side hand would be associated with contralateral-side lesions in baseball players. Sports-specific movements and the side of the dominant leg should be considered when treating young athletes with symptomatic spondylolysis.

Comparison of the sacral table angles by progression stage of lumbar spondylolysis.

STUDY DESIGN: Retrospective study. OBJECTIVES: The purpose of this study was to investigate sacral table angle (STA) values in early-stage spondylolysis. Several studies suggested that the STA of patients with L5 spondylolysis or spondylolisthesis was significantly lower than that of healthy controls. Separation of the pars interarticularis creates shear stress between the upper sacral end plate and L5 vertebra. This was considered the cause of low STA in patients with spondylolysis or spondylolisthesis. However, if a low STA value is obtained in the early stage of L5 spondylolysis, it suggests that low STA does not result in the remodeling of the sacral end plate. METHODS: Patients with L5 spondylolysis and those with low back pain without pars defect were retrospectively identified from a hospital database in 2014-2016. Pars defect of the spondylolysis was classified into three categories based on CT and MRI results: early, progressive, or terminal stage. The STA difference between groups was calculated using one-way analysis of variance and Scheffe F test, which were used for post hoc testing. RESULTS: A total of 84 cases of L5 spondylolysis and 70 cases of low back pain were identified. No significant difference was found between the STAs of the early- or progressive-stage spondylolysis and the terminal-stage L5 spondylolysis and low back pain patients. The STA of the terminal-stage L5 spondylolysis was significantly lower than that of low back pain patients. CONCLUSIONS: In conclusion, patients with early- or progressive-stage spondylolysis do not have low STA. Low STA is seen only in patients with terminal-stage spondylolysis, suggesting that low STA is associated with remodeling changes in response to shear force after onset of spondylolysis. STA value might not important as a prognostic parameter about development of the spondylolysis. LEVEL OF EVIDENCE: Level IV.

The Thoracic Spine in the Overhead Athlete.

Overhead athletes are susceptible to many injuries, particularly in the shoulder and lumbar spine. Due to the heterogeneity of these two regional injuries, it is difficult to pinpoint the exact origin. A potential contributing factor that should be thoroughly evaluated is the thoracic spine. It can be challenging to quantify exactly how much thoracic spine mobility or lack thereof plays a role toward injury. Despite this, when examining mechanics of an overhead athlete, if neuromuscular control of the thorax is impaired, adjacent motion segments often take the brunt of the required movements. This article addresses the need to incorporate the thoracic spine when analyzing the entire kinetic chain. Clinical pearls regarding thoracic neuromuscular control and rehabilitation were explored, as well as a review of recent literature. Further investigation of thoracic spine therapeutic interventions should be considered when treating overhead athletes.

Outcome of Conservative Management in the Treatment of Symptomatic Spondylolysis and Grade I Spondylolisthesis.

BACKGROUND: Bracing (thoraco-lumbar-sacral orthosis) has been accepted as mainstay of treatment for symptomatic spondylolysis (SP) and grade I spondylolisthesis (SPL1). However, increasing costs and patient noncompliance can make bracing prohibitive and difficult to manage. The purpose of this study was to determine if SP and SPL1 can be effectively treated using physical therapy and other non-bracing conservative management techniques in order to relieve pain and restore physical function. METHODS: We performed a cross-sectional study in which patients who presented from June 1, 2004, to May 1, 2015, with symptomatic SP and SPL1 who were treated with nonbracing conservative management, entailing a universal 6-week physical therapy program and restriction of offending activity, were considered for the study. Physical therapy included core strengthening activities, hamstrings stretching, and spine range of motion exercises. Patients meeting inclusion criteria were contacted via phone interview and asked to complete an Oswestry Disability Questionnaire (ODQ) in order to generate a disability score to assess their current pain and daily function. Patients were then stratified into groups based on their level of disability as denoted by their disability score; minimal disability = disability score of 0% to 19.9%, moderate disability = 20% to 39.9%, severe disability = 40% to 59.9%, crippled = 60% to 79.9%, and bed bound or exaggerating = 80% to 100%. RESULTS: Fourty-six patients were identified as meeting inclusion criteria (28 with SP and 18 with SPL1). Twenty-three of 46 were successfully contacted and agreed to complete the ODQ (10/23 with SP and 13/23 with SPL1). Twenty-two of 23 (96%) patients had a minimal disability score (0% to 19.9%), One of 23 (4%) patients had a moderate disability score (20% to 39.9%), and 18/23 (78%) patients had a disability score of zero, denoting no pain or limitation of function. CONCLUSION: The results of this study suggest that, in patients with symptomatic spondylolysis and grade I spondylolisthesis, pain relief and restoration of function can be achieved using conservative management techniques without use of a brace.

A patient specific computational biomechanical model for the entire lumbosacral spinal unit with imposed spondylolysis.

BACKGROUND: A biomechanical model of the lumbosacral spinal unit between L1-S1 was developed to investigate the behavior of normal and select pathological states. Our aims were to generate predictive structural models for mechanical deformation including critical stresses in the spine components and to investigate the probability of subsequent lumbar spine fractures in the presence of unilateral spondylolysis. METHODS: A non-linear three-dimensional finite element pathology-free model of the L1-S1 lumbosacral unit was generated using patient-specific computerized tomography scans and calibrated by comparing it to experimental data of a range of motion modes consisting of flexion, extension, left and right lateral bending, and left and right axial rotation. Unilateral and bilateral pars defects were created on the isthmus of L5 to simulate spondylolysis. FINDINGS: Results showed that under flexion, left lateral bending and right axial rotation, stresses were higher on the contralateral L5 pars-interarticularis, whereas, no significant changes occurred on the left-right isthmus of the L2-L4 and S1. Significant changes in the range of motion compared to the pathology-free model were observed in bilateral spondylolysis not only adjacent to the pars defect area but also in other lumbar spine levels. INTERPRETATION: The proposed pathology-free lumbosacral unit model showed good correlation with experimental tests for all loading cases. In unilateral spondylolysis, a subsequent pars defect was observed within the same vertebra. The overall modeling approach can be used to study different pathological states.

Diagnostic Accuracy of Magnetic Resonance Imaging and Computed Tomography Scan in Young Athletes With Spondylolysis.

The objective of this study was to determine diagnostic accuracy of magnetic resonance imaging (MRI) and computed tomography (CT) scans in young athletes diagnosed with spondylolysis. A cross-sectional study was used. Twenty-two young athletes (14.7 ± 1.5 years) were diagnosed as spondylolysis based on a single-photon emission CT. Following the diagnosis, participants underwent MRI and CT scan imaging tests on the same day. The sensitivity and false-negative rate of the MRI and CT scans were analyzed. MRI test confirmed 13 (+) and 9 (-) results while CT test showed 17 (+) and 5 (-) results. The sensitivity and false-negative rate of MRI were, respectively, 59.1% (95% confidence interval [CI] = 36.7% to 78.5%) and 40.9% (95% CI = 21.5% to 63.3%). Furthermore, the sensitivity and false-negative rate of CT scan were 77.3% (95% CI = 54.2% to 91.3%) and 22.7% (95% CI = 0.09% to 45.8%). Our results indicated that CT scan is a more accurate imaging modality to diagnose spondylolysis compared with MRI in young athletes.

Physical features of pediatric patients with lumbar spondylolysis and effectiveness of rehabilitation.

The purpose of this study was to evaluate the physical features of pediatric patients with lumbar spondylolysis (LS), factors that increase the load during compensatory movements at the lumbar spine, and the outcomes of rehabilitation. Twenty patients were included. Fifteen items were used:fingertip-to-floor distance (FFD), straight leg raising (SLR), heel-to-buttock distance (HBD), tightness of the rectus femoris, the lateral and medial rotator muscles, iliopsoas, tensor fascia lata, adductor muscles, soleus muscle, and latissimus dorsi, and trunk rotation, sit-ups and endurance of the abdominal and back muscles. Initial findings were judged as positive or negative using previously reported cut-off values and were re-evaluated 2 or 3 months later. Positive tests were found for HBD and tightness of the rectus femoris in 85% of the patients, for endurance of the abdominal muscles in 75%, SLR and sit-ups in 70%, and FFD and tightness of the external rotator muscles in 60%. The physical features varied according to the type of sport played, and some patients were refractory to rehabilitation. Only 17.6%, 33.3%, and 40.0% of patients with initially positive findings for HBD, tightness of the external rotator muscles, and endurance of the abdominal muscles, respectively, achieved improvements after rehabilitation. J. Med. Invest. 65:177-183, August, 2018.

Biomechanical analysis of spino-pelvic postural configurations in spondylolysis subjected to various sport-related dynamic loading conditions.

PURPOSE: To study the risks of spondylolysis due to extrinsic loading conditions related to sports activities and intrinsic spino-pelvic postural parameters [pelvic incidence (PI) and sacral slope (SS)]. METHODS: A comprehensive osseo-disco-ligamentous L4-S1 finite element model was built for three cases with spondylolysis representing three different spino-pelvic angular configurations (SS = 32°, 47°, 59° and PI = 49°, 58°, 72°, respectively). After simulating the standing posture, 16 dynamic loading conditions were computationally tested for each configuration by combining four sport-related loads (compression, sagittal and lateral bending and axial torque). For each simulation, the Von Mises stress, L5-S1 facet contact force and resultant internal loads at the sacral endplate were computed. Significant effects were determined with an ANOVA. RESULTS: The maximal stress and volume of cancellous bone in the pars with stress higher than 75% of the ultimate stress were higher with 900 N simulated compression (2.2 MPa and 145 mm3) compared to only the body weight (1.36 MPa and 20.9 mm3) (p < 0.001). Combined compression with 10 Nm of flexion and an axial torque of 6 Nm generated the highest stress conditions (up to 2.7 MPa), and L5-S1 facet contact force (up to 430 N). The maximal stress was on average 17% higher for the case with the highest SS compared to the one with lowest SS for the 16 tested conditions (p = 0.0028). CONCLUSIONS: Combined flexion and axial rotation with compression generated the highest stress conditions related to risks of spondylolysis. The stress conditions intensify in patients with higher PI and SS. These slides can be retrieved under Electronic Supplementary Material.

High defect stage, contralateral defects, and poor flexibility are negative predictive factors of bone union in pediatric and adolescent athletes with spondylolysis.

PURPOSE: To identify predisposition to spondylolysis and physical characteristics associated with "bone union" following conservative spondylolysis treatment among pediatric and adolescent athletes. METHODS: We retrospectively analyzed pediatric and adolescent athletes with spondylolysis who underwent conservative treatment and rehabilitation for three or more consecutive months following sports activity cessation. Patients with terminal spondylolysis or who did not discontinue sports activities were excluded. We compared physical fitness factors in the union and nonunion groups and examined the association between bone union and spondylolysis severity by logistic regression analysis. RESULTS: Of 183 patients with spondylolysis who underwent rehabilitation over a four-year period, 127 patients with 227 defects were included in the final analysis. Bone union was achieved in 66.5% (151/227) of the pars interarticularis defects and 70.1% (89/127) of the patients. On multivariate analysis, stage of pars interarticularis defect (odds ratio [OR], 0.26;p = 0.0027), stage of contralateral pars interarticularis defect (OR, 0.51;p = 0.00026), and straight leg-raising test (OR, 1.06;p = 0.028) were significantly associated with bone union. CONCLUSIONS: High defect stage, stage of the contralateral pars interarticularis defect, and poor flexibility were negative prognostic factors of bone healing in athletes with spondylolysis. J. Med. Invest. 65:126-130, February, 2018.

Properties of Paraspinal Muscles in Japanese High School Baseball Players With Terminal-Stage Lumbar Spondylolysis.

BACKGROUND: Lumbar spondylolysis is a defect in the pars interarticularis that is common in young athletes; the stress distribution at the pars interarticularis is the highest in extension and rotation movements. The paraspinal muscles play an important role in stabilization of the lumbar spine; however, no study has assessed the properties of paraspinal muscles in athletes with lumbar spondylolysis. OBJECTIVE: To evaluate the properties of paraspinal muscles in athletes with lumbar spondylolysis. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Six high school baseball players with terminal-stage lumbar spondylolysis and 11 high school baseball players without organic lumbar lesions of similar anthropometric characteristics. METHODS: All subjects performed the unsupported trunk holding test combined with surface electromyographic (EMG) power spectral analysis until exhaustion. The results of EMG power spectral analysis were compared between the spondylolysis and control groups. MAIN OUTCOME MEASUREMENTS: The median frequency (MF) was computed from the raw EMG signal of the erector spinae and multifidus during trunk holding test using fast Fourier transform spectrum analysis. The initial MF and MF slope were calculated. RESULTS: No significant differences in endurance time were found between the spondylolysis and control groups. The initial MF and the MF slopes of the erector spinae and multifidus were significantly lower in the spondylolysis group than in the control group. CONCLUSIONS: The results suggest lower fast-twitch motor unit recruitment in the erector spinae and multifidus of high school baseball players with terminal-stage lumbar spondylolysis compared with the control. LEVEL OF EVIDENCE: IV.

Active stretching for lower extremity muscle tightness in pediatric patients with lumbar spondylolysis.

BACKGROUND: It was reported that hamstring muscle tightness may increase mechanical loading on the lumbar spine. Therefore, we attempt to decrease tightness in the leg muscles in pediatric patients. METHODS: Forty-six pediatric patients with spondylolysis underwent rehabilitation. We applied active stretching to the hamstrings, quadriceps, and triceps surae. Tightness in each muscle was graded as good, fair, or poor. We educated each patient on how to perform active stretching at home. They were re-evaluated for muscle tightness 2 months later. RESULTS: Tightness at baseline and after 2 months was as follows: for the hamstrings, good in 3 patients, fair in 9, and poor in 34 and significant improved after 2 months (p<0.05), with improvement by least 1 grade seen in 86% of patients with fair or poor at baseline; for the quadriceps, 7, 3, and 30 patients had good, fair and poor, with significant improvements in 72% (p<0.05). For the triceps surae, 6, 3 and 10 patients had good, fair and poor, which improved significantly (p<0.05). CONCLUSION: Home-based active stretching was effective for relieving muscle tightness in the leg in a pediatric population. Adolescent athletes should perform such exercise to maintain flexibility and prevent lumbar disorders. J. Med. Invest. 64: 136-139, February, 2017.

Classification of spondylolytic clefts in patients with spondylolysis or isthmic spondylolisthesis using positional MRI.

Background Posterior instability is a pathologic movement occurring in the spondylolytic cleft. Purpose To present a new classification system for the evaluation of spondylolytic cleft by positional magnetic resonance imaging (MRI) and determine the prevalence of the different types. Material and Methods A total of 176 segments of the lumbar spine with spondylolysis or isthmic spondylolisthesis were examined using positional MRI. Scans were obtained in neutral sitting, flexion, and extension positions. No visible movement in the cleft was defined as type A, fluid displaced into the cleft as type BI, displacement of the flava ligaments at the level of the cleft as type BII, and intraspinal cysts arising from the spondylolytic cleft as type BIII. The movements were characterized by a radiologist and a neurosurgeon experienced in positional MRI. Clinical findings were correlated with the different types of instability. Results A high agreement was found between the two observers. In total, 131 segments were characterized as type A, six as type BI, 24 as type BII, and 10 as type BIII. In five segments, the type differed between the right and the left side. Two patients had a mixed type BI/II, another two patients had a mixed type BII/III, and one patient had a mixed type BI/III. Patients with type BII and BIII instabilities suffered more often from radicular symptoms compared to patients without any instability. Conclusion The presented classification might help to better understand and study changes encountered in the spondylolytic cleft in patients with spondylolysis and isthmic spondylolisthesis using positional MRI.

Conservative Treatment for Bony Healing in Pediatric Lumbar Spondylolysis.

STUDY DESIGN: A retrospective review of prospectively collected data. OBJECTIVE: The aim of this study was to investigate recent outcomes of conservative treatment for bony healing in pediatric patients with lumbar spondylolysis (LS) and to identify the problems that need to be resolved. SUMMARY OF BACKGROUND DATA: Several diagnostic and therapeutic techniques for LS have been developed recently, leading to better outcomes for bony healing. METHODS: Overall, 63 consecutive pediatric patients (53 boys and 10 girls) with LS (average age: 13.8 years; range: 6-17 years) were analyzed. Diagnosis and staging (very early, early, progressive, and terminal) were based on multidetector computed tomography (CT) scans and magnetic resonance imaging (MRI). For all patients except those with terminal-stage pars defect, conservative treatment included rest, avoidance of sports, and the use of a thoraco-lumbo-sacral-type trunk brace. Follow-up MRI was performed monthly. When the signal changes resolved, CT scans were obtained to assess bony healing. RESULTS: Three patients dropped out during the study period. A total of 60 patients were included (50 boys and 10 girls) in this study (follow-up rate: 95.2%), with 86 instances of LS (very early: 36, early: 16, progressive: 15, terminal: 19) in 65 laminae. In the very early stage, the bony healing rate was 100%, and average treatment period was 2.5 months (range: 1-7 months). In the early stage, the bony healing rate was 93.8%, and the average treatment period was 2.6 months (range: 1-6 months). In the progressive stage, the bony healing rate was 80.0%, and the average treatment period was 3.6 months (range: 3-5 months). The average overall recurrence rate was 26.1%. All patients showing recurrence eventually achieved bony healing. CONCLUSION: High bony healing rates and short treatment periods were observed with conservative treatment in pediatric patients with LS. However, the recurrence rates were relatively high. This issue should be targeted in future studies. LEVEL OF EVIDENCE: 2.

Is Preventative Long-Segment Surgery for Multi-Level Spondylolysis Necessary? A Finite Element Analysis Study.

OBJECTIVE: For multi-level spondylolysis patients, surgeons commonly choose to fix all the segments with pars interarticularis defect even those without slippage and not responsible for clinical symptoms. In this study, we tried to study the necessity of the preventative long-segment surgery for the defected segment without slippage in treatment of multi-level spondylolysis patients from a biomechanical perspective. METHOD: We established a bi-level spondylolysis model with pars defects at L4 and L5 segments, and simulated posterior lumbar interbody fusion (PLIF) and pedicle screw fixation at L5-S1 level. Then we compared the biomechanical changes at L4 segment before and after surgery in neutral, flexion, extension, lateral bending and axial rotation position. RESULTS: The stress on L4 pars interarticularis was very similar before and after surgery, and reached the highest in axial rotation. The L3-L4 intradiscal pressure was almost the same, while L4-L5 intradiscal pressure changed a little in lateral bending (increase from 1.993 to 2.160 MPa) and axial rotation (decrease from 1.639 to 1.307 MPa) after surgery. The PLIF surgery caused a little increase of range of motion at adjacent L4-L5 and L3-L4 levels, but the change is very tiny (1 degree). CONCLUSION: The PLIF surgery will not cause significant biomechanical change at adjacent segment with pars defect in multi-level spondylolysis. On the contrary, excessive long-segment surgery will damage surrounding soft tissues which are important for maintaining the stability of spine. So a preventative long-segment surgery is not necessary for multi-level spondylolysis as long as there are no soft tissue degeneration signs at adjacent level.

Dysplastic spondylolysis is caused by mutations in the diastrophic dysplasia sulfate transporter gene.

Spondylolysis is a fracture in part of the vertebra with a reported prevalence of about 3-6% in the general population. Genetic etiology of this disorder remains unknown. The present study was aimed at identifying genomic mutations in patients with dysplastic spondylolysis as well as the potential pathogenesis of the abnormalities. Whole-exome sequencing and functional analysis were performed for patients with spondylolysis. We identified a novel heterozygous mutation (c.2286A > T; p.D673V) in the sulfate transporter gene SLC26A2 in five affected subjects of a Chinese family. Two additional mutations (e.g., c.1922A > G; p.H641R and g.18654T > C in the intron 1) in the gene were identified by screening a cohort of 30 unrelated patients with the disease. In situ hybridization analysis showed that SLC26A2 is abundantly expressed in the lumbosacral spine of the mouse embryo at day 14.5. Sulfate uptake activities in CHO cells transfected with mutant SLC26A2 were dramatically reduced compared with the wild type, confirming the pathogenicity of the two missense mutations. Further analysis of the gene-disease network revealed a convergent pathogenic network for the development of lumbosacral spine. To our knowledge, our findings provide the first identification of autosomal dominant SLC26A2 mutations in patients with dysplastic spondylolysis, suggesting a new clinical entity in the pathogenesis of chondrodysplasia involving lumbosacral spine. The analysis of the gene-disease network may shed new light on the study of patients with dysplastic spondylolysis and spondylolisthesis as well as high-risk individuals who are asymptomatic.

A review of the pathomechanism of forward slippage in pediatric spondylolysis: the Tokushima theory of growth plate slippage.

Spondylolysis is a stress fracture of the pars interarticularis, which in some cases progresses to spondylolisthesis (forward slippage of the vertebral body). This slip progression is prevalent in children and occurs very rarely after spinal maturation. The pathomechanism and predilection for children remains controversial despite considerable clinical and basic research into the disorder over the last three decades. Here we review the pathomechanism of spondylolytic spondylolisthesis in children and adolescents, and specifically the Tokushima theory of growth plate slippage developed from our extensive research findings. Clinically, we have observed the slippage site near the growth plate on MRI; then, using fresh cadaveric spines, we found the weakest link against forward shear loading was the growth plate. We subsequently developed an immature rat model showing forward slippage after growth plate injury. Moreover, finite element analysis of the pediatric spine clearly showed increased mechanical stress at the growth plate in the spondylolytic pediatric spine model compared with the intact pediatric spine. Thus, spondylolysis progresses to spondylolisthesis (forward slippage) in children and adolescents with the growth plate as the site of the slippage. Repetitive mechanical loading on to the growth plate may serve to separate the growth plate and subsequently progress to spondylolisthesis.