Kosaku Higashino

Pathomechanism of loss of elasticity and hypertrophy of lumbar ligamentum flavum in elderly patients with lumbar spinal canal stenosis.

Study Design. A histologic, biologic, and immunohistochemical assessment using human samples of lumbar ligamentum flavum. Objective. To clarify the pathomechanism of loss of elasticity and hypertrophy of the lumbar ligamentum flavum (LF) in the elderly population. Summary of Background Data. The most common spinal disorder in elderly patients is lumbar spinal canal stenosis, causing low back and leg pain, and paresis. Canal narrowing, in part, results from hypertrophy of the LF. Although histologic and biologic literature on this topic is available, the pathomechanism of loss of elasticity and hypertrophy of the LF is still unknown. Methods. One fetus, 5 young, and 5 elderly LF were obtained for histologic study. Hematoxylin and eosin, Alcian blue, Masson Trichrome, and Elastica Van Gieson stains were performed for each LF. Nine LF were collected and were used for biologic study of real time RT-PCR to quantitatively measure mRNA expression of Type I collagen and elastin in each LF. Results. In the LF of the fetus, elastic fibers accounted for about 75% of the entire area. In the dural aspect of the LF in the young and elderly group, the ratio was also around 75%; however, the ratio of the dorsal aspect decreased with age. Almost half of the area showing loss of elastic fibers was shown to be converted to cartilaginous tissue producing Type II collagen and proteoglycan by Alcian blue and Type II collagen immunohistochemistry. The area, which did not stain black with EV nor blue with AB stain, was positively stained blue with T stain, indicating scarring. The area of the normal dural layer was 18.0 ± 2.3 and 33.8 ± 4.3 (mm2), for young and elderly group, respectively. Accordingly, it was 3.2 ± 0.8 and 18.0 ± 10.2 (mm2), for the dorsal abnormal layer. Elastin mRNA showed a relatively strong correlation (r = 0.44) with age; however, the slope was very gentle. Type I collagen mRNA showed a very strong correlation (r = 0.80) with age. The slope was steeper, and the value reached at 1000% (10-fold) around 65 years old when compared with the LF from younger patient. Elastin mRNA showed a weak correlation (r = 0.36) with thickness, and the slope was gentle. Type I collagen mRNA showed relatively strong correlation (r = 0.52) with thickness. The slope was steeper, and the line reached at 1000% (10-fold) around 6.5 (mm) when compared with a thin LF. Conclusion. Decreased elasticity of LF in the elderly is due to the loss of elastic fibers and a concomitant increase of collagenous fibers in the dorsal aspect. LF hypertrophy could be due to the thickening of the normal elastic layer as well as of the abnormal collagenous layer.

Stromal Cell-Derived Factor-1 Potentiates Bone Morphogenetic Protein-2 Induced Bone Formation

The mechanisms driving bone marrow stem cell mobilization are poorly understood. A recent murine study found that circulating bone marrow-derived osteoprogenitor cells (MOPCs) were recruited to the site of recombinant human bone morphogenetic protein-2 (BMP-2)-induced bone formation. Stromal cell-derived factor-1α (SDF-1α) and its cellular receptor CXCR4 have been shown to mediate the homing of stem cells to injured tissues. We hypothesized that chemokines, such as SDF-1, are also involved with mobilization of bone marrow cells. The CD45(-) fraction is a major source of MOPCs. In this report we determined that the addition of BMP-2 or SDF-1 to collagen implants increased the number of MOPCs in the peripheral blood. BMP-2-induced mobilization was blocked by CXCR4 antibody, confirming the role of SDF-1 in mobilization. We determined for the first time that addition of SDF-1 to implants containing BMP-2 enhances mobilization, homing of MOPCs to the implant, and ectopic bone formation induced by suboptimal BMP-2 doses. These results suggest that SDF-1 increases the number of osteoprogenitor cells that are mobilized from the bone marrow and then home to the implant. Thus, addition of SDF-1 to BMP-2 may improve the efficiency of BMPs in vivo, making their routine use for orthopaedic applications more affordable and available to more patients.

Fresh stress fractures of lumbar pedicles in an adolescent male ballet dancer: Case report and literature review

Stress fracture in the pars interarticularis is a common cause of low back pain in young athletes. Pedicle stress fractures have also been reported in adolescent sport players, and most of them were associated with contralateral spondylolysis. Only a few cases with bilateral pedicle stress fractures have been reported. We report a 14-year-old ballet dancer with fresh bilateral pedicle fractures treated conservatively, together with a review of the literature.

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 bonegrowth in 510 ± 20 &mgr;m for a week, whereas the anterior corner in 200 ± 15 &mgr;m. 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.

Do the Adjacent Level Intervertebral Discs Degenerate After a Lumbar Spinal Fusion? An Experimental Study Using a Rabbit Model

Study Design. A rabbit model of disc degeneration adjacent to a lumbar spinal fusion. Objective. To use a rabbit model to determine the long-term changes in the intervertebral discs at the levels above (cephalad) and below (caudad) 2 fused lumbar levels. Summary of Background Data. Lumbar spinal fusion is generally carried out to eliminate motion at a specific lumbar level. However, it is commonly thought that by eliminating motion at a level, one increases the motion at the adjacent levels cephalad and caudad the fused levels. There have been studies that have reported on degeneration occurring at the cephalad and caudad levels adjacent to the fused levels. Methods. A total of 9 New Zealand white, female rabbits: 4 rabbits in the control group and 5 rabbits in the experimental group. The 5 rabbits in the experimental group underwent a posterolateral 2-level lumbar spinal fusion from L3 to L5. The changes in the lumbar discs were assessed using radiographs, magnetic resonance (MR) images, and histology at 6 months and 12 months. Results. The results at 6 months are less clear than those at 12 months. The results at 12 months for the experimental group are (1) the intervertebral disc height decreased at the caudad adjacent level and to a lesser extent at the cephalad adjacent level; (2) the MRI scores for the discs at the caudad and cephalad adjacent levels showed severe loss of signal intensity as compared to the discs at the same levels in the control group. This loss was more pronounced at the caudad level where the loss of signal intensity was similar to that seen at the fused levels; (3) the histologic analysis showed severe degenerative changes with a lack of live cells in the nucleus pulposus and in the endplate at the caudad adjacent level. At the cephalad level, live cells were apparent (albeit few) in the nucleus pulposus, and there was a more normal looking endplate with live cells. Conclusion. The intervertebral discs at both the cephalad and the caudad levels adjacent to the 2 fused lumbar levels in this rabbit-model experiment carried out over 12 months after surgery showed degenerative changes asassessed using disc-height measurements, MR images, and histology, and the effect was more severe at the caudad adjacent level.

Pedicle screws can be 4 times stronger than lateral mass screws for insertion in the midcervical spine: a biomechanical study on strength of fixation.

Study Design: A biomechanical study. Objective: To compare, in cervical vertebrae (C3–C6), the pullout strengths of pedicle screws and lateral mass screws after both types of screw had been subjected to a period of cyclic loading in 2 planes. Summary of Background Data: In posterior subaxial cervical fixation systems, screws are usually inserted into the lateral mass. As an alternative to lateral mass fixation, pedicle screw fixation became popular in the 1990s and was first used for lower cervical spine trauma cases. However, it is controversial as to whether lateral mass screw fixation in the upper-middle cervical spine offers as much biomechanical security as compared with pedicle screw fixation. Methods: For each of the 32 vertebrae, 1 side was randomly chosen to receive a pedicle screw and the other side a lateral mass screw. The pedicle or lateral mass screws inserted into the first 16 vertebrae were cyclically loaded to simulate torsion and the remaining 16 vertebrae were cyclically loaded to simulate flexion/extension of the spine. At the end of the cyclic loading each screw was pulled out along its long axis. Results: For the torsion group, the mean pullout strength of the pedicle screws was nearly 4 times greater than the mean pullout strength of the lateral mass screws (cf 762 N with 191 N). In contrast, the mean pullout strength of the pedicle screws in the flexion/extension group was only twice the mean pullout strength of the lateral mass screws (cf 571 N with 289 N). Conclusions: Not forgetting the potential risks of inserting pedicle screws in cervical vertebrae, pedicle screws are a better biomechanical choice than lateral mass screws for cervical fixation at the levels C3 through to C6.

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.].

Extension of contained rupture of an abdominal aortic aneurysm into a lumbar intervertebral disc. Case report.

Chronic contained rupture of an abdominal aortic aneurysm (AAA) is a rare event, making its diagnosis difficult. A delayed diagnosis and delayed surgical repair compromise the outcome. In this paper the authors report the case of a chronic contained rupture of an AAA causing spinal destruction, in which diagnosis was difficult because the lesion produced symptoms mimicking those of pyogenic spondylitis.

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.

Complete Resolution of a Case of Calcific Tendinitis of the Longus Colli with Conservative Treatment

Acute calcific tendinitis of the longuscolli is a self-limiting inflammatory condition caused by calcium hydroxyapatite deposition in the longuscolli tendon. Although several case reports have described its radiological presentation, few reports provide detailed chronological accounts through symptomatic and radiologic resolution. A 59-year-old woman presented with severe neck pain and stiffness of a few days duration as well as moderate discomfort when swallowing. Lateral radiographs revealed a large calcium deposit anterior to the C1.C2 joint and swelling of the prevertebral soft tissue from C1 to C5. CT and magnetic resonance imaging showed fluid in the retropharyngeal gap.A soft collar and non-steroidal anti-inflammatory drug were prescribed, without antibiotics. At 4 months after presentation, the calcium deposit and all symptoms had resolved completely. Although this disease is comparatively rare, physicians should keep it in mind when a patient presents with acute severe neck pain.