Incidence and trend of antiresorptive agent-related osteonecrosis of the jaw from 2016 to 2020 in Kure, Japan.

We investigated the incidence/trend of osteonecrosis of the jaw by antiresorptive agent dose over a 5-year period in Kure city, Japan. The incidence was 24 times higher among osteoporosis patients with low-dose agents and 421 times higher among cancer patients with high-dose agents than in the population without agents. PURPOSE: We launched the registry system of osteonecrosis of the jaw (ONJ) cases in 2015 to investigate the trend in ONJ incidence. The purpose of our study was to estimate the ONJ incidence among patients with antiresorptive agent use by dosage and people without antiresorptive agent use in Kure and its trend from 2016 to 2020. METHODS: From 2016 to 2021, 98 eligible ONJ patients were enrolled. Medication-related ONJ (MRONJ) was diagnosed based on the American Association of Oral and Maxillofacial Surgeons criteria. The annual number of those with and without antiresorptive agents was obtained from the claims database. Antiresorptive agents used for cancer and osteoporosis patients were defined as high- and low-dose medications, respectively. RESULTS: The annual incidence of high-dose MRONJ was 2305.8 per 100,000 and that of low-dose MRONJ was 132.5 per 100,000, while the ONJ incidence among people without antiresorptive agents was 5.1 per 100,000. The incidence ratio was 23.6 (p < 0.001, 95% confidence interval (CI) 13.3-41.8) among osteoporosis patients who used low-dose antiresorptive agents and 420.6 (p < 0.001, 95% CI 220.8-801.4) among cancer patients who used high-dose agents compared with people who did not use these agents. MRONJ incidence increased from 2016 to 2020, but the incidence of high-dose MRONJ decreased, although this was nonsignificant. CONCLUSION: We demonstrated the incidence and trend of ONJ by antiresorptive agent dose over a 5-year period in Kure after launching the multiprofession study. This collaborative study for the early detection and prevention of ONJ will continue.

Prognostic factors for spontaneous spinal epidural hematoma: a multicenter case-control study.

BACKGROUND: To determine the optimal treatment for spontaneous spinal epidural hematoma (SSEH). The aim of this study was to identify factors associated with SSEH. METHODS: In 62 patients with SSEH, several patient-related parameters were analyzed as candidate factors associated with Frankel grade before treatment or at the last follow-up. These parameters were compared between patients with and without surgery. In addition, multivariate ordinal logistic regression analysis was used to identify factors significantly associated with Frankel's grade before treatment or at the last follow-up. RESULTS: There were significant differences in age, location of the hematoma, and Frankel grade before treatment and at the last follow-up between surgical and nonsurgical cases in all patients, but there were no significant differences in any of these parameters when comparing patients with pre-treatment Frankel grade C. The location of the hematoma was significantly associated with the severity of paralysis before treatment. In surgical cases, the time from onset to surgery and the location of the hematoma was significantly associated with the prognosis. When the time from onset to surgery was evaluated using the criteria of 12, 24, and 48 h, 24 and 48 h had a significant impact on the prognosis. In the analysis of nonsurgical cases, only the vertical size of the hematoma was significantly associated with prognosis. CONCLUSION: The time from onset to surgery and the location of the hematoma were prognostic factors in surgical cases, while the vertical size of the hematoma was a prognostic factor in nonsurgical cases.

Microscopic Posterior Transdural Resection of Cervical Retro-Odontoid Pseudotumors.

Retro-odontoid pseudotumors are noninflammatory masses formed posterior to the odontoid process. Because of their anatomy, the optimal surgical approach for resecting pseudotumors is controversial. Conventionally, 3 approaches are used: the anterior transoral approach, the lateral approach, and the posterior extradural approach; however, each approach has its limitations. The posterior extradural approach is the most common; however, it remains challenging due to severe epidural veins. Although regression of pseudotumors after fusion surgery has been reported, direct decompression and a pathologic diagnosis are ideal when the pseudotumor is large. We therefore developed a new microscopic surgical technique; transdural resection. After C1 laminectomy, the dorsal and ventral dura was incised while preserving the arachnoid. Removal of the pseudotumor was performed and both of the dura were repaired. The patient's clinical symptoms subsequently improved and the pathologic findings showed degenerative fibrocartilaginous tissue. In addition, no neurological deterioration, central spinal fluid leakage, or arachnoiditis was observed. Currently, the usefulness of the transdural approach has been reported for cervical and thoracic disk herniation. According to our results, the transdural approach is recommended for resection of retro-odontoid pseudotumors because it enables direct decompression of the spinal cord and a pathologic diagnosis.

Surgical treatment of high-grade dysplastic spondylolisthesis using intraoperative electrophysiological monitoring: report of two cases and review of the literature.

Treatment of high-grade dysplastic spondylolisthesis in adolescents remains challenging. Surgical treatment of spondylolisthesis has been recommended in adolescents with pain refractory to conservative treatment, slippage progression, or severe slippage on presentation. Controversy exists as to the optimal surgical approach for high-grade spondylolisthesis. Moreover, some authors reported the incidence of L5 root palsy during the reduction procedure. We performed 2 cases of surgical treatment using intraoperative electrophysiological monitoring for patients with high-grade dysplastic spondylolisthesis in adolescence. Each patient received treatment consisting of decompression of nerve with surgical microscope, reduction, and circumferential fusion with transpedicular and monosegmental fixation surgery with intraoperative neurological monitoring with transcranial electric motor evoked potentials and continuous spontaneous electromyography recording. Intraoperative monitoring did not show any abnormal changes. The patients got well after surgery, and they showed no postoperative motor paralysis of the extremities. A postoperative radiogram showed reduction of the slippage, and computed tomogram showed bone union between L5 and S1 vertebral body. This report describes 2 cases of surgical treatment using intraoperative electrophysiological monitoring with transcranial electric motor evoked potentials and continuous spontaneous electromyography for patients with high-grade dysplastic spondylolisthesis in adolescence. We successfully perform the surgery without any neurological deficit using intraoperative electrophysiological monitoring.

Physical Signs and Clinical Features of Cervical Myelopathy in Elderly Patients, Especially 80 Years or Older: Comparison of 100 Consecutive Operative Cases across Three Age Groups.

STUDY DESIGN: Retrospective cohort study. PURPOSE: The present study aimed to examine the characteristics of physical signs in elderly patients with cervical myelopathy (CM) and to compare the findings in three different age groups. OVERVIEW OF LITERATURE: As the global population ages, the incidence of CM in elderly patients is increasing. METHODS: We evaluated 100 consecutive surgical patients with CM and divided them into the following groups: 80s (34 patients; mean age, 83.9 years), 70s (33 patients; mean age, 73.9 years), and 69 or younger (33 patients; mean age, 60.9 years). The clinical symptoms and physical signs were evaluated and recorded. RESULTS: Although the recovery rate decreased with increasing age, all groups demonstrated a significant improvement in clinical symptoms relative to preoperative values. The Hoffman sign and hyperreflexia of the triceps tendon were, respectively, present in 82% and 88% of patients in the 80s group, 74% and 64% of those in the 70s group, and 69% and 82% of those in the 69 or younger group, with no significant difference among the groups. In contrast, the rates of hyperreflexia of the patellar and Achilles tendons were, respectively, 59% and 32% in the 80s group, 85% and 48% in the 70s group, and 91% and 70% in the 69 or younger group, with significant differences. CONCLUSIONS: The positivity rate of the lower extremity hyperreflexia decreased significantly with increasing age in patients with CM. The absence of hyperreflexia, particularly lower extremity, is not uncommon in elderly patients with suspected CM.

Incomplete Atypical Femoral Fracture Treated by Prophylactic Intramedullary Nail Fixation: A Case Series.

Long-term bisphosphonate use may be associated with atypical femoral fractures. In this report, we describe three cases of bisphosphonate-associated incomplete atypical femoral fracture, treated by prophylactic intramedullary nail fixation. Patients with long-term intake of bisphosphonates must be carefully monitored; atypical femoral fracture should be suspected in the presence of symptoms such as thigh pain. Its early identification is important to avoid a complete fracture and invasive surgery, and prophylactic fixation is recommended for incomplete atypical femoral fractures.

Incidence of fractures among patients receiving medications for type 2 diabetes or chronic obstructive pulmonary disease and glucocorticoid users according to the National Claims Database in Japan.

According to information from the National Health Insurance and Claims database, the risk for hip, radius, and clinical vertebral fractures was higher among patients receiving medication for type 2 diabetes, COPD, or glucocorticoids than among the whole Japanese population after middle age. PURPOSE: The aim of this study was to determine the incidence of fractures among patients receiving medications for type 2 diabetes or chronic obstructive pulmonary disease (COPD) and using glucocorticoids (GC) according to the National Database of Health Insurance Claims (NDB) in Japan. METHODS: We obtained data on the number of fractures and patients receiving medications for type 2 diabetes, COPD, or GC from the NDB. The claims data included sex, age group, injury/illness name, hospitalization, outpatient, surgery/medical treatment, and drugs used between January and December 2017. RESULTS: The risk of hip fracture was higher among patients receiving medications for diabetes or COPD and GC users than in the Japanese population, with standardized incidence ratios (SIRs) of 1.71 (95% confidence interval [CI]1.6-1.75), 1.35 (95% CI 1.28-1.42), and 1.62 (95% CI 1.53-1.71) in men and 1.81 (95% CI 1.79-1.84), 1.67 (95% CI 1.54-1.80), and 1.71 (95% CI 1.66-1.76) in women, respectively. There was also a significantly higher incidence of radial fractures in women and clinical vertebral fractures in both men and women. A greater risk of hip fracture was found among diabetic patients starting in their late 40 s. CONCLUSIONS: Real-world data revealed that the incidence of hip, radius, and clinical vertebral fractures was significantly higher among patients receiving medications for diabetes or COPD and GC users than in the Japanese population after middle age.

Quantitative assessment of myelopathy patients using motor evoked potentials produced by transcranial magnetic stimulation.

Motor evoked potentials (MEPs) study using transcranial magnetic stimulation (TMS) may give a functional assessment of corticospinal conduction. But there are no large studies on MEPs using TMS in myelopathy patients. The purpose of this study is to confirm the usefulness of MEPs for the assessment of the myelopathy and to investigate the use of MEPs using TMS as a screening tool for myelopathy. We measured the MEPs of 831 patients with symptoms and signs suggestive of myelopathy using TMS. The MEPs from the abductor digiti minimi (ADM) and abductor hallucis (AH) muscles were evoked by transcranial magnetic brain stimulation. Central motor conduction time (CMCT) is calculated by subtracting the peripheral conduction time from the MEP latency. Later, 349 patients had surgery for myelopathy (operative group) and 482 patients were treated conservatively (nonoperative group). CMCTs in the operative group and nonoperative group were assessed. MEPs were prolonged in 711 patients (86%) and CMCTs were prolonged in 493 patients (59%) compared with the control patients. CMCTs from the ADM and AH in the operative group were significantly more prolonged than that in the nonoperative group. All patients in the operative group showed prolongation of MEPs or CMCTs or multiphase of the MEP wave. MEP abnormalities are useful for an electrophysiological evaluation of myelopathy patients. Moreover, MEPs may be effective parameters in spinal pathology for deciding the operative treatment.

Pedicle screw augmentation with polyethylene tape: a biomechanical study in the osteoporotic thoracolumbar spine.

STUDY DESIGN: Biomechanical study using human thoracolumbar spines. OBJECTIVE: To assess the strength of fixation of pedicle screws augmented with Nesplon tape applied sublaminar or applied subpars. SUMMARY OF BACKGROUND DATA: There are no reports on the biomechanical assessment of Nesplon tape used for pedicle screw augmentation. METHODS: Experiment 1: pedicle screws were inserted into bilateral pedicles as follows: (1) pedicle screw alone connected to a rod (PS alone), (2) pedicle screw augmented with Nesplon tape applied sublaminar, connected to a rod [pedicle screw applied sublaminar (PSSL)], and (3) pedicle screw augmented with tape applied subpars, connected to a rod [pedicle screw applied subpars (PSSP)]. The rods were pulled and pushed until the pedicle screw was loose. Experiment 2: 6 thoracolumbar spines were biomechanically tested as follows: axial compression, flexion, extension, left and right lateral bending, and left and right axial rotation. This sequence was applied to: (1) the intact spine; (2) the spine made unstable; (3) the spine fixed by pedicle screws and rods (PS alone); (4) the same as 3, but with the pedicle screws augmented using Nesplon tape applied sublaminar (PSSL); and (5) the same as 3, but with pedicle screws augmented using tape applied subpars (PSSP). From the load-deformation curves, stiffness values were calculated. RESULTS: Experiment 1: the pedicle screws augmented by sublaminar or subpars tape (PSSL or PSSP) showed significantly greater fixation strength compared with those pedicles that were not augmented by tape (PS alone). Experiment 2: a pedicle screw/rod construct augmented by tape provided a stiffer construct than the same construct without augmentation. CONCLUSIONS: Pedicle screws that are inserted into the osteoporotic thoracolumbar spine and augmented by Nesplon tape applied sublaminar or subpars provide firmer fixation of the screws and a stiffer pedicle screw/rod construct than the same construct without augmentation by tape.

Spinal instrumentation for sacral-pelvic fixation: a biomechanical comparison between constructs ending with either S2 bicortical, bitriangulated screws or iliac screws.

STUDY DESIGN: A biomechanical study of 2 fixation techniques for lumbosacral fixation. OBJECTIVE: To evaluate 2 techniques, one using S1 screws combined with bicortical, bitriangulated (BCBT) S2 screws, and the other using S1 screws combined with iliac screws. SUMMARY OF BACKGROUND DATA: Common to the 2 techniques of sacral-pelvic fixation is S1 pedicle screws; the difference lies between S2 screws versus iliac screws. Iliac screws are clinically effective, yet present clinical disadvantages that S2 screws can potentially obviate, for example, wide dissection, soft tissue coverage, crossing the sacroiliac joint, and interference with bone graft harvesting. In an effort to optimize S2 fixation, we have used a BCBT S2 technique. METHODS: Eight fresh human sacral-pelvic specimens were harvested (average age 78.7 y; bone density 0.75 g/cm2). Screws were placed bilaterally: (1) at S1: 7.5 mm diameter screws were placed bicortical; (2) at S2: 7.5 mm diameter by 60 mm long screws were placed bicortical and bitriangulated; (3) the ilium received 7.5 mm diameter by 80-mm-long screws. Sacral-pelvic constructs were assembled and biomechanical stiffness testing was performed. The stiffness in each loading mode was calculated. After the stiffness tests were completed, each BCBT S2 screw and each iliac screw were individually loaded to determine fixation strength of each type of screw. RESULTS: There was no significant difference in stiffness between the 2 constructs, although S1 and the BCBT S2 construct tended to be stiffer in all modes. However, for the fixation strength of screws, the iliac screws loosened at loads that were significantly greater than those for BCBT S2 screws (c.f. 435.9 N with 144.7 N). CONCLUSIONS: Iliac screws maybe the better choice in cases with poor bone quality. However, the S1-BCBT-S2 screw construct is biomechanically an appropriate alternative to the S1-iliac screw construct and it presents clinical advantages.

Incidence of clinical vertebral fractures and hip fractures of the elderly (65 years or over) population-large-scale data analysis using claim database in Kure City, Hiroshima, Japan.

Using the claim database, we investigated the incidence rate of clinical vertebral fractures per 1,000 in the elderly residents, over 65 years of age, in Kure city. The incidence rate, of clinical vertebral fractures, was 15.58 (7.29 male, 21.17 female, 2.90 female/male ratio). PURPOSE: To elucidate the incidence of clinical vertebral and hip fractures using the claim database, in those over 65 years of age in Kure city, and to compare with the previous reports. METHODS: We used, for residents in 2015, the medical care information of the National Health Insurance or Senior Elderly Care System in Kure City (Hiroshima Prefecture, Japan). Those with vertebral fractures as disease name, and either treatment/operation/hospitalization were defined as clinical vertebral fractures. Among the claim database, we extracted the clinical vertebral fracture and investigated the number of occurrences and the incidence rate per 1,000. We also investigated the incidence rate of hip fractures and compared those to the clinical vertebral fractures. RESULT: The incidence rate of clinical vertebral fractures of the elderly population (65 years or over) per 1,000 was 15.58 (7.29 male, 21.17 female, 2.90 female/male ratio). In both men and women, the incidence rate increased with aging. The incidence rate of hip fractures per 1,000 was 9.17 (3.55 male, 12.96 female, 3.65 male/female ratio). Clinical vertebral fractures were more frequent than hip fractures, and the ratio of incidence rate of vertebral fractures to hip fractures was 1.70 (male, 2.05, female, 1.63). For both fractures, the incidence rate increases with age, apart from the women where the incidence of vertebral fracture reduces slightly in the older age group CONCLUSION: This is the first report that investigated the incidence rate of the clinical vertebral fractures using the claim database, which covered almost the whole number of 230,000 population area.

Biomechanical assessment of minimally invasive decompression for lumbar spinal canal stenosis: a cadaver study.

STUDY DESIGN: A biomechanical study on the cadaveric human lumbar spine. OBJECTIVE: We focused on a biomechanical comparison of the changes wrought on motion segments after a minimally invasive decompression and after a conventional medial facetectomy. SUMMARY OF BACKGROUND DATA: Minimally invasive posterior decompression using a microscope or an endoscope is becoming popular for elderly patients with lumbar spinal canal stenosis. An advantage of the technique is that the cauda equina and nerve roots are in clear view and the facet joints, paravertebral muscles, and spinous process are well preserved. METHODS: Eight human lumbar motion segments were used in this study. Each specimen was tested according to the following loading protocol: axial compression, flexion, extension, lateral bending to the right and to the left, and axial rotation to the right and to the left. This loading protocol was applied to each motion segment after the following surgical interventions: (1) left fenestration, (2) bilateral decompression via unilateral approach, (3) medial facetectomy, and (4) total facetectomy. The relative stiffness of the motion segments was determined and compared with a normalized stiffness for the specimen when intact. RESULTS: Bilateral decompression via unilateral approach produces less biomechanical effect in terms of stiffness changes as compared with medial facetectomy. Bilateral decompression leaves the spine more than 80% as stiff as the intact spine. CONCLUSIONS: These results go toward supporting a minimally invasive bilateral decompression. Minimally invasive bilateral decompression, as opposed to a conventional medial facetectomy, preserves the facet joints as much as possible. Preserving the facet joints during the decompression should produce less postoperative instability.

Expansive laminoplasty for cervical myelopathy with interconnected porous calcium hydroxyapatite ceramic spacers: comparison with autogenous bone spacers.

STUDY DESIGN: Expansive cervical laminoplasties with interconnected porous calcium hydroxyapatite ceramic (IP-CHA) spacers were performed in cervical myelopathy patients. OBJECTIVES: To evaluate the usefulness and osteoconductive capability of IP-CHA spacers in expansive laminoplasty. SUMMARY OF BACKGROUND DATA: Expansive laminoplasty for cervical myelopathy is designed to preserve the posterior structures, so as to prevent postoperative development of instability and cervical kyphosis. The technique requires successful reconstruction of the laminae of vertebral arches, as sinking or nonunion of the expanded laminae may induce neurologic regression, segmental motor paralysis, and postoperative axial pain. A novel IP-CHA with sufficient biocompatibility and mechanical strength was developed as an artificial bone substitute. METHODS: Expansive open-door laminoplasties were performed in 88 cervical myelopathy patients, and both autogenous bone spacers harvested from the spinous processes and IP-CHA spacers in combination with bone marrow were alternately grafted into the opened side of each lamina. All patients were followed up with computerized tomography scans, and bonding rates for both the IP-CHA and autogenous spacers, bone fusion rates of the hinges of the laminae, and complications associated with the implants were examined. RESULTS: Clinical symptoms significantly improved in all patients without major complications related to the procedure. The IP-CHA spacers demonstrated comparable bone bonding to the autogenous spacers on postoperative computerized tomography scans. The expanded laminae withstood expanded positions without sinking or floating throughout the followups, and the hinges completely fused in more than 95% of patients in both groups within 1 year. CONCLUSIONS: The IP-CHA spacer contributed to high bone fusion rates of the spacers and hinges of the laminae, and there were no complications associated with their use. Cervical laminoplasty with the IP-CHA spacers is a safe and simple method that yields sufficient fixation strength and provides sufficient bone bonding within a short period of time after operation.

Significant correlation between corticospinal tract conduction block and prolongation of central motor conduction time in compressive cervical myelopathy.

We examined the relationship between the CMCT and features of spinal cord evoked potentials (SCEPs) among 25 patients with compressive cervical myelopathy to elucidate the mechanism underlying the prolonged central motor conduction time (CMCT) in patients with compressive cervical myelopathy. CMCT values were calculated by measuring motor evoked potentials from the abductor digiti minimi muscles (ADMs) and abductor hallucis muscles (AHs) following transcranial magnetic stimulation and peripheral conduction times determined in the ulnar and tibial nerves. SCEPs following transcranial electrical stimulation were recorded intraoperatively from C2-3, C6-7 and T11-12. The shorter/longer CMCTs between the patients' right and left ADMs and AHs were 9.5+/-3.2/11.5+/-3.8 and 16.2+/-2.8/18.8+/-3.3 ms, respectively (mean+/-SD). The percentage ratio of the amplitude of the D-wave at C6-7 or T11-12 to that at C2-3 was 19.4+/-14.2 or 3.2+/-3.1%, respectively. The CMCT value was significantly correlated with the attenuation of SCEP amplitude, but not with SCEP latency both at C6-7 and T11-12, suggesting that CMCT prolongation is primarily due to corticospinal conduction block rather than conduction delay. Spinal motor neurons might need more time to fire in patients with compressive cervical myelopathy when corticospinal potentials, but not conduction, are attenuated, thereby resulting in prolonged CMCT.

Bone marrow stromal cells promoting corticospinal axon growth through the release of humoral factors in organotypic cocultures in neonatal rats.

OBJECT: The transplantation of bone marrow stromal cells (BMSCs) is considered to be an alternative treatment to promote central nervous system regeneration, but the precise mechanisms of this regeneration after transplantation of BMSCs have not been clarified. In the present study, the authors assessed the effects of BMSC transplantation on corticospinal axon growth quantitatively, and they analyzed the mechanism of central nervous system regeneration in the injured and BMSC-treated spinal cord using the organotypic coculture system. METHODS: Bone marrow stromal cells derived from green fluorescent protein-expressing transgenic Sprague-Dawley rats were transplanted to the organotypic coculture system in which brain cortex and spinal cord specimens obtained in neonatal Sprague-Dawley rats were used. The axon growth from the cortex to the spinal cord was assessed quantitatively, using anterograde tracing with 1,1 '-ioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate. To identify the differentiation of transplanted BMSCs, immunohistochemical examinations were performed. In addition, BMSCs were analyzed using reverse transcriptase polymerase chain reaction (RT-PCR) for mRNA expression of the growth factors. The transplantation of BMSCs beneath the membrane, where the transplanted cells did not come into direct contact with the cultured tissue, promoted corticospinal axon growth to the same extent as transplantation of BMSCs on the tissues. The RT-PCR showed that the transplanted BMSCs expressed the mRNA of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). Con CONCLUSIONS: ese findings strongly suggest that humoral factors expressed by BMSCs, including BDNF and VEGF, participate in regeneration of the central nervous system after transplantation of these cells.

Magnetic targeting of bone marrow stromal cells into spinal cord: through cerebrospinal fluid.

We established a new magnetic targeting system in which bone marrow stromal cells migrate through the cerebrospinal fluid to the desired site in the spinal cord in rats. Subarachnoid injection has been reported as a minimally invasive method of transplantation of bone marrow stromal cells for spinal cord injury. It may be, however, less effective than direct injection into the spinal cord in terms of cell delivery. After implantation of a magnet, subarachnoid injection of bone marrow stromal cells labeled with magnetic beads was performed. Greater numbers of bone marrow stromal cells aggregated on the surface of the spinal cord owing to the magnetic force. This targeting system may be a useful tool in minimally invasive transplantation of bone marrow stromal cells for the treatment of spinal cord injury.

Characterization of labeled neural progenitor cells for magnetic targeting.

For many diseases and injuries of the central nervous system, transplantation of neural progenitor cells is being evaluated as a possible treatment option. Although local, intravenous and subarachnoid injections have been reported as administration methods of neural progenitor cells, each of these methods has limitations. More effective and minimally invasive cell delivery systems are necessary for transplanting neural progenitor cells. In this study, we have developed a technique to form magnetically labeled neural progenitor cells for a magnetic targeting system. We demonstrated that neural progenitor cells can couple with magnetic beads, and that the labeled neural progenitor cells preserve the characteristics of non-labeled neural progenitor cells, and that they can be localized by magnetic force in vitro. Labeled neural progenitor cells have the potential to be used in magnetic targeting systems in-vivo models.

The effect of pedicle screw redirection after lateral wall breach--a biomechanical study using human lumbar vertebrae.

BACKGROUND CONTEXT: Currently, pedicle screw segmental fixation of the spine is considered a standard of care for a number of conditions. Most surgeons employ a free-hand technique using various intraoperative modalities to improve pedicle screw accuracy. Despite continued improvements in technique, pedicle breach remains a frequent occurrence. Once a breach is detected intraoperatively, the most common corrective maneuver is to medially redirect the pedicle screw into the pedicle. To our knowledge, the biomechanical impact of medially redirecting a pedicle screw after a lateral pedicle breach has not been examined. PURPOSE: To compare the fixation strength of perfectly placed pedicle screws to the fixation strength of pedicle screws that were correctly placed after having been redirected (RD) following a lateral pedicle breach. STUDY DESIGN/SETTING: A biomechanical study using human lumbar vertebrae. METHODS: Ten fresh human lumbar vertebrae were isolated from five donors. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect center-center (CC) screw path was created using direct visualization and fluoroscopy. A 6.0-mm-diameter cannulated tap and a pedicle probe were used to develop the pedicle for the 7.0-mm-diameter by 45-mm-long cannulated pedicle screw, which was placed using a digital torque driver. On the contralateral side, an intentional lateral pedicle wall breach was created at the pedicle-vertebral body junction using a guide wire, a 6.0-mm-diameter cannulated tap, and a pedicle probe. This path was then redirected into a CC position, developed, and instrumented with a 7.0-mm-diameter by 45-mm-long cannulated pedicle screw: the RD screw. For each pedicle screw, we assessed four outcome measures: maximal torque, seating torque, screw loosening, and post-loosening axial pullout. Screw loosening and axial pullout were assessed using an MTS machine. RESULTS: The biomechanical cost of a lateral pedicle breach and the requirement to redirect the pedicle screw are as follows: an overall drop of 28% (p<.002) in maximal insertion torque and 25% (p<.049) in seating torque, a drop of 25% (p<.040) in resistance to screw loosening, and a drop in axial pullout force of 11% (p<.047). CONCLUSIONS: Compared with a CC lumbar pedicle screw, an RD lumbar pedicle screw placed after a lateral wall breach is significantly weaker in terms of maximal insertional torque, seating torque, screw loosening force, and axial pullout strength. These significant decreases in biomechanical properties are clearly important when RD pedicle screws are placed at the cephalad or caudal end of a long construct. In this situation, augmentation of the RD screw is an option.

Plate-only open door laminoplasty maintains stable spinal canal expansion with high rates of hinge union and no plate failures.

STUDY DESIGN: Prospective clinical series. OBJECTIVE: To evaluate the ability of plate-only laminoplasty to achieve stable laminar arch reconstruction and to determine the rate and time course with which bony healing occurs in such constructs. SUMMARY OF BACKGROUND DATA: Reconstruction of a stable laminar arch with sufficient room for the decompressed spinal cord is a desired goal when performing cervical laminoplasty for myelopathy. Traditional forms of laminoplasty fixation, such as sutures, bone struts, and ceramic spacers, may be associated with complications including loss of fixation, dislodgement with neurologic compromise, and premature laminoplasty closure. Plates, in contrast, provide more rigid fixation. Plate-only laminoplasty is gaining popularity as a method of laminoplasty fixation, but there is little data on its effectiveness. METHODS: Fifty-four patients who underwent open door laminoplasty for cervical myelopathy and had available postoperative computed tomography (CT) scans formed the basis of this study. In all cases, a 4-mm round burr was used to create the hinge at the junction of the lateral mass and lamina by completely removing the dorsal cortex and thinning the ventral cortex until a greenstick deformation of the hinge could be produced. Laminoplasty plates were used as the sole method of fixation. No supplemental bone graft struts were used on the plated side, and the hinge side was not bone grafted. Axial CT scans obtained at 3, 6, and 12 months postoperatively were assessed for plate complications and bony healing of the hinge. RESULTS: No plate failures, dislodgements, or premature closures occurred in any of the levels at any time postoperatively. Computed tomography scan review demonstrated that 55% of levels were healed at 3 months, 77% at 6 months, and 93% at 12 months. At each timepoint, C6 and C7 had the highest hinge healing rates. Laminar screw backout was seen in 5/217 (2.3%) of levels, but was not associated with plate dislodgement, laminoplasty closure, or neurologic consequences, and did not occur in any case in which 2 laminar screws had been placed. CONCLUSION: Plate-only laminoplasty provided stable reconstruction of an expanded laminar arch with no failures, dislodgements, adverse neurologic consequences, or premature closures in 217 levels. Ninety-three percent of hinges demonstrated radiographic union at 12 months, and even those that did not heal by CT scan criteria maintained patent expansion of the spinal canal without adverse neurologic consequences. Supplemental bone graft does not appear necessary when plated laminoplasty is performed.