Shigeru Soshi

An Experimental Study on Transpedicular Screw Fixation in Relation to Osteoporosis of the Lumbar Spine

In order to elucidate the relationship between the severity of osteoporosis and the fixation strength of a pedicle screw, screw pull-out tests were performed using cadaveric lumbar vertebrae. The severity of osteoporosis was evaluated by the Jikei osteoporosis grading scale (Jikei method), bone mineral density, and microdensitometry. When a 7.0-mm screw was used, the pull-out force of the screw was 1,056.4 N in the normal group (as determined by the Jikei method), while it was 495.6 N in the Grade I osteoporosis and 269.5 N in the Grade II osteoporosis groups, respectively. There were also positive correlations between the pull-out force and bone mineral density and each parameter of the microdensitometry method. When bone cement was used in an osteoporotic vertebra, twofold stronger pull-out force was obtained in comparison to that obtained without bone cement.

Effect of Hyper‐ and Microgravity on Collagen Post‐Translational Controls of MC3T3‐E1 Osteoblasts

We attempted to study the effects of microgravity (by clinostat) and hypergravity (using centrifugation) on collagen metabolism using murine MC3T3‐E1 osteoblasts, especially focusing on collagen cross‐link formation. We found that altered gravitational load affected the post‐translational modification of collagen, particularly the collagen maturation pathway, through altered expression of enzymes involved in cross‐link formation.

Effect of low- and high-intensity pulsed ultrasound on collagen post-translational modifications in MC3T3-E1 osteoblasts.

Different intensities of pulsed ultrasound have distinct biological effects on bone mineralization in the process of bone fracture repair, even across a narrow range (e.g., 30–120 mW/cm2). The aim of our study was to elucidate the effect of low-intensity (30 mW/cm2) and high-intensity (120 mW/cm2) pulsed ultrasound on collagen metabolism by using MC3T3-E1 osteoblasts. Of special interest was the relationship between posttranslational collagen quality and prostaglandin E2 activity. Cells with or without a cyclooxygenase-2 inhibitor, NS398, were exposed every day for four consecutive days to high-level or low-level intensities of pulsed ultrasound. We examined the, expression patterns of cyclooxygenase-2, lysyl oxidase, telopeptidyl lysyl hydroxylase (TLH), and helical lysyl hydroxylase by real-time polymerase chain reaction analysis. Quantitative analyses of reducible immature and nonreducible mature cross-links were also performed. Ultrasound at 30 mW/cm2 upregulated TLH messenger RNA (mRNA) expression and enzyme activity compared to the control and resulted in increased relative concentrations of telopeptidyl hydroxylysine–derived cross-links. In addition to upregulated lysyl oxidase mRNA expression, increased total reducible and nonreducible cross-links were observed by 30 mW/cm2 exposure compared to the control. In contrast, ultrasound at 120 mW/cm2 had no obvious effect on collagen metabolism owing to high levels of endogenous prostaglandin E2 induced by ultrasound. Our results showed that (1) low-intensity, but not high-intensity, ultrasound may accelerate the formation of the unique molecular packing of collagen fibers conducive to bone mineralization and that (2) the high dose of endogenous prostaglandin E2 induced by pulsed ultrasound may be detrimental to calcifiable cross-link formation.

A rare case of spinal injury: bilateral facet dislocation without fracture at the lumbosacral joint

Lumbosacral dislocations are rare disorders; since they were first reported by Watson-Jones [1], only 100 cases have appeared in the literature [2]. A traumatic bilateral lumbosacral dislocation is even rarer, with a mere 10 cases reported [3]. Because of its low incidence and atypical location, the lesion may often go unnoticed on initial clinical assessment [4]. Surgical treatment modalities are not defined, but open reduction and internal fixation are often necessary because of a three-column involvement [5]. In this paper, we report on an initially misdiagnosed case of lumbosacral dislocation treated with open reduction and internal fixation.

Insertional Torque in Cervical Vertebrae Lateral Mass Screw Fixation: Magerl Technique Versus Roy-Camille Technique.

Study Design: This is a prospective multicenter comparison study. Objective: To measure the insertional torque (IT) for cervical vertebra lateral mass screw (LMS) fixation using the Magerl and Roy-Camille methods, at the discretion of the surgeon. Summary of Background Data: Current fixation methods for patients with preoperative cervical spine instability use LMSs; however, few studies have closely examined intraoperative IT. Patients’ bone quality was not measured. Methods: A total of 637 posterior cervical multiaxial screws were inserted for LMS (C3–C6) (Magerl technique, 423; Roy-Camille technique, 214) in 107 cases. Patients’ mean age was 66 years. Patients treated with the Magerl method were divided into 2 groups, with the men in the MM group and the women in the MF group. Similarly, patients treated with the Roy-Camille method were divided into 2 groups, with the men in the RM group and the women in the RF group. The contralateral cortex was penetrated, and the IT at cerclage was measured at the last time. Results: IT of the lateral mass screw was 53.8±22.4, 45.4±21, 45.5±16.9, and 34±16.4 cN.m in the MM group (258), MF group (165), RM group (163), and RF group (51), respectively. The MM group had a significantly higher IT than the other 3 groups, and the RM group had a significantly higher IT than the RF group. When the correlation between screw length and IT was evaluated, IT was significantly (P<0.05) higher with a longer screw by the Magerl method. Conclusions: The IT was higher with the Magerl method with a longer screw. Screw length and IT were not correlated with the Roy-Camille method; furthermore, the Roy-Camille method went through bilateral cortical bone perpendicularly, so that IT was determined by the fixation power in the cortical part of the bone, which was not thought to be affected by screw length. Level of Evidence: Level III.

Progressively worsening paraesthesia of the left leg, gait disturbances and constipation in a 63-year-old man: diagnosis and discussion

Cauda equina syndrome (CES) is a well-known but rare and poorly understood complication of ankylosing spondylitis (AS). CES manifests late in the course of AS, often at a time when the AS is no longer active [1]. MRI characteristically shows an enlarged caudal thecal sac and dorsal arachnoid diverticula that fill the erosions of the bony spinal canal [2, 3]. Our patient had the typical features of CES in AS, i.e. sensory changes in lumbosacral dermatomes, constipation and moderate motor deficits in the left lower limb. However, what made this case unique was the presence of ventral arachnoid diverticula. MRI of the lumbosacral spine demonstrated localised scalloping of the posterior aspect of the L1 and L2 vertebral bodies and ventral arachnoid diverticula without neural tissue herniation. Ventral shift and adhesion of the conus medullaris and the cauda equina were also seen (Figs. 1, 2 in the case presentation). To date, only three cases have been reported regarding ventral dural abnormalities associated with CES in AS (Table 1) [1, 4, 5]. Arachnoid diverticula formation in AS is thought to result from an inflammatory process affecting the vertebral column [6]. In our case, the L1/2 intervertebral disc showed a high signal, similar to that of bone marrow or perivertebral fat on T1and T2-weighted images (Figs. 1, 2 in the case presentation). These findings are thought to be a reflection of normal disc tissue being replaced by fatty bone marrow following an ossification process after severe discitis in the past [7]. This process was accompanied by destruction of cartilaginous endplates and subchondral bone plates, resulting in fusion of the L1 and L2 vertebral bodies. The direction of arachnoid diverticula formation is thought to be dependent on the direction of the force of increased CSF pulse pressure and the “give” of the structures surrounding the spinal canal [1]. If structures posterior to the canal are firm and there is a relatively “soft” spot in the posterior aspect of the vertebral body, erosion could occur anterior to the spinal canal. In our case, we speculate, severe enthesitis of the discovertebral junction at the posterior aspect of the L1/2 vertebral bodies occurred in the past and created a “soft” spot. After the inflammatory process ceased to be active, formation of arachnoid diverticula through a dural defect at this spot occurred over many years. Several possible mechanisms for nerve root damage have been proposed. These include inflammatory injury from arachnoiditis, gravitational traction injury resulting from the presence of arachnoid diverticula, and traumatic damage from excessive CSF pressure fluctuations caused by reduced elasticity and compliance of the caudal sac exposed to inflammatory changes [6, 8, 9]. In our case, we The case presentation can be found at doi:10.1007/s00256-009-0756-0. D. Hayashi (*) : T. Yonenaga :K. Fukuda Department of Radiology, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-Ku, Tokyo 105-8461, Japan e-mail: daichi.hayashi@jikei.ac.jp