Utility of STIR-MRI in Detecting the Pain Generator in Asymmetric Bilateral Pars Fracture: A Report of 5 Cases.

Lumbar spondylolysis usually occurs as a stress fracture in the pars interarticularis of the vertebra. It is a prevalent sports-related disorder and a common cause of low back pain. We encountered five athletes (4 males, 1 female) with severe low back pain. Mean age was 14.5 years. All five patients were found to have bilateral pars fracture. In all cases, staging based on the findings from computed tomography scan of the right and left pars fracture was different. On short tau inversion recovery magnetic resonance imaging (STIR-MRI) of the comparatively newer more recently injured side, high signal intensity changes were obvious and dominant at the intra- and extraosseous area, which would indicate tissue edema and/or bleeding. Furthermore, the imaging findings corresponded to the side of the low back pain. In conclusion, STIR-MRI can effectively distinguish between painful pars fracture and painless pars fracture.

Prevalence of Symptomatic Lumbar Spondylolysis in Pediatric Patients.

Lumbar spondylolysis, a stress fracture of the pars interarticularis, is prevalent in adolescent athletes. Recent advances in diagnostic tools and techniques enable early diagnosis before these fractures progress to complete fractures through the pars. However, because patients often consult family physicians for primary care of low back pain and these physicians may not have access to diagnostic modalities such as magnetic resonance imaging (MRI) and computed tomography, stress fractures can be missed. This study surveyed the prevalence of symptomatic spondylolysis in pediatric patients who consulted an orthopedic clinic for primary care and investigated whether such acute stress fractures may be overlooked without MRI. The prospective study investigated 264 patients who were younger than 19 years and had low back pain. Of the 153 patients (58.0%) with low back pain persisting for longer than 2 weeks, 136 who agreed to undergo MRI were included in the study. This group included 11 elementary school students, 71 junior high school students, and 54 high school students. The overall prevalence of lumbar spondylolysis was 39.7% (54 of 136) and was 9.3% in elementary school students (5 of 11, 45.5%), 59.3% in junior high school students (32 of 71, 45.1%), and 31.5% in high school students (17 of 54, 31.5%). All 54 patients with spondylolysis had a history of athletic activity. Primary care physicians should recognize that approximately 40% of pediatric patients presenting with low back pain persisting for longer than 2 weeks may have spondylolysis and should consider MRI in those with a history of athletic activity. Because the spine is immature in this age group, almost half of affected elementary school and junior high school students may have lumbar spondylolysis. [Orthopedics. 2016; 39(3):e434-e437.].

Analysis of MRI signal changes in the adjacent pedicle of adolescent patients with fresh lumbar spondylolysis.

PURPOSE: The purpose of this study is to investigate a discrepancy between MRI and computed tomography (CT) findings in the spinal level distribution of spondylolysis. Recent advances in MRI have led to the early diagnosis of spondylolysis. Therefore, bony healing can be expected before the condition has a chance to worsen. In this study, we used MRI to examine the changes in spinal level signals in the pedicles adjacent to the pars interarticularis in adolescents with fresh lumbar spondylolysis. We then compared spinal level distribution of spondylolysis with that of previous results obtained by multidetector CT. METHODS: The study included 98 adolescent patients (31 women and 67 men; mean age, 13.6 years; age range, 9-18 years) with fresh lumbar spondylolysis who showed MRI signal changes in the adjacent pedicle. An MRI signal change was defined as a high signal change on fat-suppressed imaging. RESULTS: MRI signal changes were detected in 150 adjacent pedicles of 101 vertebrae. Of these vertebrae, MRI signal changes in only 67 (66.3%) corresponded to L5, while changes in 34 (33.7%) corresponded to L3 or L4. In our follow-up study, the bone-healing rate with no vertebral defect was 100% at L3, 97.1% at L4, and 84.4% at L5. In addition, 11 of 34 (32.4%) vertebrae with signal changes at L3 or L4 occurred with L5 terminal-stage spondylolysis (no MRI signal change). CONCLUSION: MRI revealed a higher prevalence of L3 or L4 spondylolysis than observed with CT.

Measurements of ligamentum flavum thickening at lumbar spine using MRI.

INTRODUCTION: As the ligamentum flavum (LF) covers most of the posterolateral part of the lumbar spinal canal, its thickening can be attributed to the development of lumbar canal encroachment. Nevertheless, there have been few reports describing the natural history of the LF. METHOD: To investigate the natural history and to subsequently clarify the pathogenesis of LF thickening, we conducted a transverse radiological study of the LF at the lumbar spine using magnetic resonance images. PATIENTS: One hundred and sixty-two patients complaining of low back pain and/or leg pain were evaluated (n = 162; mean age 52.1 years). The thickness of LF was measured at L2-3, L3-4, L4-5 and L5-S levels (n = 648). The relationships among thickness, age, and spinal level were examined. PATIENTS: One hundred and sixty-two patients complaining of low back pain and/or leg pain were evaluated (n = 162; mean age 52.1 years). The thickness of LF was measured at L2-3, L3-4, L4-5 and L5-S levels (n = 648). The relationships among thickness, age, and spinal level were examined. RESULTS: The following results were obtained. (1) LF thickness increased with age; however, the increments at L4-5 and L3-4 were larger than one at L2-3 and L5-S1. (2) At L4-5, LF was over 3.0 mm thick in patients in the 20-29 age bracket, and in many of them it was more than 3.5 mm thick. (3) All patients with a thickened LF at L2-3 (>3.0 mm) had very thick LFs at all spinal levels. (4) In elderly patients, there was no correlation between the thickness of LF and the decrease of the disc height. In this study, we concluded that thickening of LF at L4-5 had already started in patients in the 30-39 age bracket and that thickening of the LF was not the buckling of the LF into the spinal canal with disc degeneration. The thickness of LF at L2-3 may serve as an indicator of lumbar spinal canal stenosis at multiple levels.

Vertebral rounding deformity in pediatric spondylolisthesis occurs due to deficient of endochondral ossification of the growth plate: radiological, histological and immunohistochemical analysis of a rat spondylolisthesis model.

STUDY DESIGN: A study using rat spondylolisthesis models. OBJECTIVE: To clarify pathomechanism of vertebral rounding deformity in pediatric spondylolisthesis. SUMMARY OF BACKGROUND DATA: For high-grade slippage, rounding of sacrum surface associated with L5 spondylolisthesis is reported to be the most responsible risk factor. However, the exact pathomechanism of the rounding deformity is yet to be clarified. METHODS: Spondylolisthesis rat model (4-week-old) was used. Radiographs were taken weekly for 5 weeks after the surgery. The lumbar spines were harvested for histology. Hematoxylin and eosin, alcian blue staining, and tartrate-resistant acid phosphatase staining were used. Immunohistochemically, the growth plate cartilage was studied for type II and X collagen. A modified bone histomorphometric analysis was also performed. RESULTS: Radiographs showed slippage 1 week after surgery. Rounding deformity was obvious 2 weeks after surgery. The rounding deformity progressed with time. Three weeks after surgery, the specific columns of growth plate were unclear at the anterior corner, which corresponded to the rounding surface observed on radiographs. Instead, a huge mass of cartilage was observed at that site. Tartrate-resistant acid phosphatase-positive cells were observed in the vicinity of the growth plate except in relation with the anterior corner. The growth plate and cartilage mass at the anterior corner stained positive for type II collagen. Chondrocytes in the hypertrophied layer stained positively for type X collagen; however, staining was faint at the anterior corner. The results suggested that the chondrocytes at the anterior did not form, morphologically and functionally, the normal growth plate. From histomorphometrical analysis, the normal posterior growth plate made endochondral bone growth in 510 +/- 20 microm for a week, whereas the anterior corner in 200 +/- 15 microm. CONCLUSION: Deficient endochondral ossification of the growth plate in the anterior upper corner of the vertebra could be the pathomechanism of the rounding deformity of the sacrum.

High-grade slippage of the lumbar spine in a rat model of spondylolisthesis: effects of cyclooxygenase-2 inhibitor on its deformity.

STUDY DESIGN: Radiographic and histologic evaluation of spondylolisthesis in a rat model. OBJECTIVES: To investigate the effects of etodolac, a cox-2 inhibitor, on the severity of spondylolisthesis in a 4-week-old rat model. SUMMARY OF BACKGROUND DATA: Spondylolisthesis occurs associated with spondylolysis in some pediatric patients. In such patients, the percent of forward slippage varies individually ranging between 0% and 100%. The factors determining the severity of forward slippage have not been clarified as yet. In earlier studies, we found that growth plate stress fracture was the basic lesion and that slippage was a consequence of the stress fracture. Hence, we hypothesized that the capacity of bone healing might be an important determinant of the degree of forward slippage. METHODS: A lumbar spine slippage model was prepared in 4-week-old rats with vertebral physis fracture. To disrupt the fracture healing, the cyclooxygenase-2 (cox-2) inhibitor etodolac was used, and its effects on slippage and deformity were evaluated radiologically and histologically. RESULTS: In the etodolac group, forward slip significantly increased (P < 0.05) to the Meyerding Grade III while in the control rats it was Grade I or II. Bone remodeling of the vertebral body was suppressed by etodolac. Histologically, epiphyseal separation with slippage was observed in all the control and etodolac-treated rats. However, in the etodolac-treated group, the epiphyseal plate was greatly separated and did not present periosteal thickening at the physis fracture site. CONCLUSION: Vertebral forward slippage occurred in young rats after epiphyseal separation. In the etodolac group, slippage increased as deterioration of the bone healing capacity increased. Poor bony healing is suggested as one of the determinants of high-grade spondylolisthesis in children and adolescents.

Vertebral forward slippage in immature lumbar spine occurs following epiphyseal separation and its occurrence is unrelated to disc degeneration: is the pediatric spondylolisthesis a physis stress fracture of vertebral body?

STUDY DESIGN: Radiographic and histologic evaluation of a rat model of lumbar spine slippage. OBJECTIVES: To clarify the pathomechanism of slippage in the immature spine. SUMMARY OF BACKGROUND DATA: There are controversial hypotheses regarding the pathogenesis of slippage of the pediatric spine with pars defects. Some studies supported that disc degeneration was its cause, while others indicated the growth plate injury was the cause. METHODS: An immature lumbar spine slippage model in 4-week-old rats was used. Following posterior destabilizing surgery, the lumbar spine was radiographically and histologically examined at 1, 3, 5, and 7 days after surgery. RESULTS: Radiographically, slippage occurred about 7% in the % slip on day 7, and no slippage was observed before day 5. Histologically, epiphyseal separation also appeared on day 7; before day 5, the growth plate showed no abnormalities. Within 7 days after the operation, the anulus fibrosus did not show any sign indicating degeneration. The nucleus pulposus was also normal up to day 7. CONCLUSION: The findings of this study support the hypothesis that vertebral forward slippage of the immature spine occurs following epiphyseal separation and its occurrence is unrelated to disc degeneration.

A new endoscopic technique to decompress lumbar nerve roots affected by spondylolysis. Technical note.

The authors describe a new endoscopic technique to decompress lumbar nerve roots affected by spondylolysis. Short-term clinical outcome was evaluated. Surgery-related indications were: 1) radiculopathy without low-back pain; 2) no spinal instability demonstrated on dynamic radiographs; and 3) age older than 40 years. Seven patients, four men and three women, fulfilled these criteria and underwent endoscopic decompressive surgery. Their mean age was 60.9 years (range 42-70 years). No subluxation was present in four patients, whereas Meyerding Grade I slippage was demonstrated in three. For endoscopic decompression, a skin incision of 16 to 18 mm in length was made, and fenestration was performed to identify the affected nerve root. The proximal stump of the ragged edge of the spondylotic lesion, and the fibrocartilaginous mass compressing the nerve root were removed. The follow-up period ranged from 6 to 22 months (mean 11.7 months). Clinical outcome was evaluated using Gill criteria; in three patients the outcome was excellent, and in four it was good. This new endoscopic technique was useful in the decompression of nerve roots affected by spondylolysis, the technique was minimally invasive, and the clinical results were acceptable.

The pathogenesis of slippage and deformity in the pediatric lumbar spine: a radiographic and histologic study using a new rat in vivo model.

STUDY DESIGN: Rat lumbar spines with posterior destabilizing surgery were evaluated radiographically and histologically. OBJECTIVES: To create an appropriate rat model showing the vertebral slippage and deformities frequently observed in pediatric patients with spondylolysis, and to clarify their pathogenesis. SUMMARY OF BACKGROUND DATA: There are controversial hypotheses regarding the pathogenesis of slippage and deformities of the pediatric spine with pars defects. Furthermore, there is no appropriate animal model mimicking those conditions. METHODS: After posterior destabilizing surgery, the lumbar spines of young (4-week-old) and adult (26-week-old) rats were radiographically examined at weekly intervals during 3 weeks, and histologically 3 weeks after the surgery. RESULTS: Slippage occurred in the young rats, but not in the adult rats. In the young rats, 7.2% slippage was observed 1 week after the surgery, whereas the slippage in the adult rats was 0%. The difference in percentage of slippage between the two groups was significant (P < 0.05). Lumbar deformity also was seen in the young rats, but not in the adult rats. The lumbar index of L6, as an indicator of L6 rounding, was 91.7% immediately after surgery. It had decreased to 87.7, 84.6, and 74%, respectively, 1, 2, and 3 weeks after surgery. Histologic examination showed growth plate injury in the young group and pronounced disc degeneration in the adult group. CONCLUSIONS: The young rat with posterior destabilizing surgery was an appropriate animal model, mimicking the slippage and deformities radiographically seen in pediatric patients with spondylolysis. The histologic examination indicated that vertebral growth plate impairment was the basic lesion causing such slippage and deformities in pediatric spines.

Normal and spondylolytic pediatric spine movements with reference to instantaneous axis of rotation.

STUDY DESIGN: A radiologic study of lumbar kinematics in the pediatric spine was conducted. OBJECTIVES: To clarify the kinematic alteration in the pediatric spine with pars defects by measuring the location of the instantaneous axis of rotation. SUMMARY OF BACKGROUND DATA: Vertebral slippage and deformities such as wedging of L5 are observed frequently in pediatric patients with spondylolysis. However, the kinematics of pediatric lumbar spine with pars defects has not yet been well documented. METHODS: Radiographs of 70 pediatric patients (57 boys and 13 girls) with low back pain were examined. The control group (without spondylolysis) consisted of 22 patients (15 boys and 7 girls; mean age, 14.6 years; range, 10-18 years), and the lysis group (with spondylolysis at L5) consisted of 48 patients (42 boys and 6 girls; mean age, 14.5 years; range, 11-18 years). The lysis group was further divided into four subgroups according to the stage of defects and existence of slippage: Group 1 (early stage defect), Group 2 (progressive stage defect), Group 3 (terminal stage defect without slippage), and Group 4 (terminal stage defect with slippage of more than 5%; olisthesis). The instantaneous axis of rotation at L4-L5 and L5-S1 from the extended to the flexed position was measured on lateral dynamic radiograms taken in with the subject in the recumbent position. The relation between lumbar index and the site of instantaneous axis of rotation at L5-S1 also was analyzed. RESULTS: The site of instantaneous axis of rotation at L5-S1 and L4-L5 in the control group was not located in the rotating cranial vertebra. In 1 of the 11 patients in the early-stage subgroup, the instantaneous axis of rotation at L5-S1 was found in the cranial vertebra. In 4 of the 11 patients in the progressive stage, 11 of the 16 patients in the terminal stage, and in 7 of the 10 patients in the olisthesis subgroup, the instantaneous axis of rotation was located in the cranial vertebra. Cranial deviation in the instantaneous axis of rotation was observed more frequently in the vertebra with severe deformity less than 80% of the lumbar index than in the vertebra with milder deformity. CONCLUSIONS: The instantaneous axis of rotation deviated cranially as the stage of pars defects advanced, and as the wedge deformity increased. Kinematic alteration of the lumbar spine in pediatric patients with spondylolysis may affect chondrocytes of the endplate, perhaps contributing to the consequent spine deformities occurring secondarily to spondylolysis.