Additional benefit of ultrasonography to evaluate nerve root condition of degenerative cervical spine disease.

STUDY DESIGN: A cross-sectional explanatory study. OBJECTIVES: To clarify the nerve root condition and the association between nerve root cross-sectional area (CA) on ultrasonography (US) and other examinations such as MRI or compound muscle action potentials (CMAPs) in degenerative cervical spine diseases. SETTING: A university hospital in Japan. METHODS: Fifty-one patients diagnosed with proximal cervical spondylotic amyotrophy (CSA) (13 patients), cervical radiculopathy of C5 or C6 nerve root (CR) (26 patients), or cervical spondylotic myelopathy (CSM) (12 patients), and twenty-nine healthy volunteers were included in this study. Neurological findings, US findings and CMAPs of deltoid and biceps muscles of all participants were evaluated. In addition, CSA, CR, and CSM patients underwent MRI. RESULTS: A significant correlation was not observed between CA and CMAP amplitude or foraminal diameter on MRI (P > 0.05). In the US examination, the C6 CA of the affected side of the CR group was significantly larger than that of both the normal side and the other groups (P < 0.001). The C5 CA of the affected side of the CSA group clearly showed a bimodal distribution: enlarged and small CA groups. In the CMAP findings, CSA cases respectively showed the lower amplitude of deltoid and bicep CMAPs on both the normal and the affected side (P ≦ 0.01). CSM and healthy volunteers were nearly identical in CA and CMAPs. CONCLUSION: Utilizing US in addition to NCS and MRI can contribute towards an evaluation of the nerve root condition of degenerative cervical spine disease. SPONSORSHIP: no sponsorship.

Finger trembling improvement after surgery in Hirayama disease: a case report.

INTRODUCTION: Finger trembling is a characteristic physical finding in Hirayama disease. Although conservative treatment is recommended to stop disease progression, surgery is optional in some cases. However, the postoperative recovery of finger trembling is scarcely reported. CASE PRESENTATION: A 26-year-old Japanese female patient whose chief complaint was left finger trembling with active finger extension presented at our hospital. Hand weakness without muscle atrophy of the left arm was observed. MRI showed left-side oriented intramedullary signal change with concomitant cord atrophy at C4-5 and C5-6. The CT myelogram (CTM) on flexion showed anterior cord compression and anterior shift of posterior dura matter from C4 to C6. And CTM on extension showed the resolution of both findings. Electrophysiological studies showed active and chronic neuronal damage and preserved motor neuron pool of hand muscle. Since she had exhibited a gradual aggravation of symptoms over a period of 5 years, she underwent anterior cervical discectomy and fusion after careful assessment of both conservative and surgical treatment. Finger trembling recovered soon after surgery. DISCUSSION: Finger trembling is an unfamiliar physical finding in terms of postoperative recovery prediction. Anterior horn cell impairment is postulated as a cause of finger trembling. Postural restoration of spinal cord shape and cerebrospinal fluid around the cord with preserved neural function could facilitate functional recovery.

Nontraumatic Spondylolisthesis of the Axis with Cervical Kyphosis.

This study aimed at presenting a rare nontraumatic spondylolisthesis of the axis and considering its possible cause. Traumatic spondylolisthesis of the axis, called hangman's fracture, frequently occurs as a high-energy trauma. However, nontraumatic spondylolisthesis of the axis is quite rare, and relevant literature on this condition is scarce. We reported a case of a 49-year-old man who had spondylolisthesis of the axis without experiencing a traumatic episode. Plain radiograph and CT image showed 7.0 mm anterolisthesis of the axis. Both C2 and C3 facet joints positioned asymmetrically, and the unilateral side oriented coronally, which was less resistant to rotational motion. These facet joint abnormalities could cause segmental instability and spondylolisthesis of the axis. Due to the resultant myelopathy, the slip with cord compression was surgically corrected by posterior decompression with instrumented fusion.

Effects of MRgFUS Treatment on Musculoskeletal Pain: Comparison between Bone Metastasis and Chronic Knee/Lumbar Osteoarthritis.

Local bone denervation by magnetic resonance-guided focused ultrasound (MRgFUS) is a promising tool for alleviation of pain in patients with painful bone metastasis (BM). Considering the underlying mechanism of pain alleviation, MRgFUS might be effective for various bone and joint diseases associated with local tenderness. This study was conducted to clarify the therapeutic effect of focused ultrasound in patients with various painful bone and joint diseases that are associated with local tenderness. Ten patients with BM, 11 patients with lumbar facet joint osteoarthritis (L-OA), and 19 patients with knee osteoarthritis (K-OA) were included. MRgFUS treatment was applied to the bone surface with real-time temperature monitoring at the target sites. Pain intensity was assessed using a 100 mm numerical rating scale (NRS) at various time points. Pressure pain threshold (PPT) was evaluated on the sonication area and control sites. Compared to baseline, the pain NRS scores significantly decreased in all groups 1 month after treatment, and PPT at the treated sites significantly increased in all groups 3 months after treatment. The percentage of patients who showed a ≥ 50% decrease in pain NRS scores at 1 month after treatment was 80% in BM, 64% in L-OA, and 78% in K-OA groups. PPTs were significantly higher after treatment at all evaluation time points. This study indicated that MRgFUS is effective in reducing pressure pain at the site of most severe tenderness in patients with painful bone and joint diseases. Treatment response was comparable between patients with BM, L-OA, and K-OA.

Discrepancy between functional recovery and cutaneous silent period change in surgically treated degenerative cervical myelopathy: a prospective pilot study.

STUDY DESIGN: Exploratory research OBJECTIVES: Cutaneous silent periods (CSPs) that reflect the inhibitory spinal cord reflex, can sensitively detect spinal cord dysfunction, and contribute to the diagnosis of degenerative cervical myelopathy (DCM). However, CSP changes after DCM surgery related to functional improvement have not been reported. SETTING: University hospital in Nankoku, Japan METHODS: CSP recorded at four time points-before surgery, 3, 6, 12 months after surgery-were investigated in 31 hands of 16 DCM patients. CSPs were categorized as follows: normal, delayed onset latency, shortened duration, onset delay with shortened duration, and absent CSP. Myelopathic symptoms were evaluated by the Japanese Orthopaedic Association score (JOA score). RESULTS: Normal CSPs were observed in five hands (16%) before surgery and six hands (19%) twelve months after surgery (P > 0.05). Either onset delay or shortened duration or both were observed in 18 hands (58%) before surgery and 16 hands (52%) twelve months after surgery (P > 0.05). Absent CSPs were observed in eight hands (26%) before surgery and nine hands (29%) twelve months after surgery (P > 0.05). Measured values of onset latency and duration also did not change throughout the study period (P > 0.05). On the other hand, JOA scores improved after surgery. (P = 0.003). CONCLUSIONS: CSP abnormalities persisted after surgery in most cases, indicating irreversible damage of the intramedullary reflex circuit. JOA score recovery without CSP recovery provides insight into postoperative neural recovery in DCM.

Comparison of Rigid and Soft-Brace Treatments for Acute Osteoporotic Vertebral Compression Fracture: A Prospective, Randomized, Multicenter Study.

While bracing is the standard conservative treatment for acute osteoporotic compression fracture, the efficacy of different brace treatments has not been extensively studied. We aimed to clarify and compare the preventive effect of the different brace treatments on the deformity of the vertebral body and other clinical results in this patient cohort. This multicenter nationwide prospective randomized study included female patients aged 65⁻85 years with acute one-level osteoporotic compression fractures. We assigned patients within four weeks of injury to either a rigid-brace treatment or a soft-brace treatment. The main outcome measure was the anterior vertebral body compression percentage at 48 weeks. Secondary outcome measures included scores on the European Quality of Life-5 Dimensions (EQ-5D), visual analog scale (VAS) for lower back pain, and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). A total of 141 patients were assigned to the rigid-brace group, whereas 143 patients were assigned to the soft-brace group. There were no statistically significant differences in the primary outcome and secondary outcome measures between groups. In conclusion, among patients with fresh vertebral compression fractures, the 12-week rigid-brace treatment did not result in a statistically greater prevention of spinal deformity, better quality of life, or lesser back pain than soft-brace.

Unilateral repetitive tibial nerve stimulation improves neurogenic claudication and bilateral F-wave conduction in central lumbar spinal stenosis.

BACKGROUND: Repetitive electrical nerve stimulation of the lower limb may improve neurogenic claudication in patients with lumbar spinal stenosis (LSS) as originally described by Tamaki et al. We tested if this neuromodulation technique affects the F-wave conduction on both sides to explore the underlying physiologic mechanisms. METHODS: We studied a total of 26 LSS patients, assigning 16 to a study group receiving repetitive tibial nerve stimulation at the ankle (RTNS) on one leg, and 10 to a group without RTNS. RTNS conditioning consisted of a 0.3-ms duration square-wave pulse with an intensity 20% above the motor threshold, delivered at a rate of 5 Hz for 5 min. All patients underwent the walking test and the F-wave and M-wave studies for the tibial nerve on both sides twice; once as the baseline, and once after either the 5-min RTNS or 5-min rest. RESULTS: Compared to the baselines, a 5-min RTNS increased claudication distance (176 ± 96 m vs 329 ± 133 m; p = 0.0004) and slightly but significantly shortened F-wave minimal onset latency (i.e., increased F-wave conduction velocity) not only on the side receiving RTNS (50.7 ± 4.0 ms vs 49.2 ± 4.2 ms; p = 0.00081) but also on the contralateral side (50.1 ± 4.6 ms vs 47.9 ± 4.2 ms; p = 0.011). A 5-min rest in the group not receiving RTNS neither had a significant change on claudication distance nor on any F-wave measurements. The M response remained unchanged in both groups. CONCLUSIONS: The present study verified a beneficial effect of unilaterally applied RTNS of a mild intensity on neurogenic claudication and bilateral F-wave conduction. Our F-wave data suggest that this type of neuromodulation could be best explained by an RTNS-induced widespread sympathetic tone reduction with vasodilation, which partially counters a walking-induced further decline in nerve blood flow in LSS patients who already have ischemic cauda equina.

Localization of the primary sites of involvement in the spinal sensory and motor pathways for multilevel MRI abnormalities in degenerative cervical myelopathy.

STUDY DESIGN: Exploratory clinical study. OBJECTIVES: To localize the sites of conduction block in the spinal sensory and motor pathways for minimizing the level of surgical intervention despite MRI evidence of compression at several levels in degenerative cervical myelopathy (DCM). SETTING: Kochi Medical School Hospital, Japan. METHODS: We analyzed 83 DCM patients (69 ± 12 years) who underwent serial intervertebral recording of both ascending (A-SCEPs) and descending spinal cord-evoked potentials (D-SCEPs) after epidural and transcranial stimulation, respectively, during surgery before decompression procedures. The site of conduction block was identified by an abrupt reduction of the negative peak accompanied by an enlargement of the initial-positive peak. T1-weighted MRI allowed quantitative assessments of cord compression in relation to the level of conduction block. RESULTS: The A-SCEP and D-SCEP studies revealed conduction blocks at the same single level in 78 patients (94%) and at two separate levels in five patients (6%) for MRI abnormalities extending to 3.1 ± 1.1 levels. The site of conduction block had intense cord compression on MRI with either the smallest (81%) or the second smallest (19%) anteroposterior diameter and cross-sectional area of the cord. Based on the SCEP findings, 44 patients were treated by a single-level (35) or a two-level (9) anterior operation for MRI abnormalities of 2.7 ± 1.1 levels. CONCLUSIONS: Combined A-SCEP and D-SCEP studies served as useful additions to MRI in localizing the primary sites responsible for myelopathy, which helped exclude clinically silent compressions to minimize surgical intervention in 34 patients with anterior operation.

Complications Associated With Lateral Interbody Fusion: Nationwide Survey of 2998 Cases During the First 2 Years of Its Use in Japan.

STUDY DESIGN: Retrospective nationwide questionnaire-based survey of complications. OBJECTIVE: To elucidate the incidence of complications and risk factors associated with lateral interbody fusion (LIF). SUMMARY OF BACKGROUND DATA: After its introduction to Japan in February 2013, the numbers of LIF cases have increased substantially because of the advantages of this minimally invasive procedure. However, LIF has the potential risk of several complications unique to the procedure. Although there are many reports of complications, no nationwide survey has been conducted. METHODS: Questionnaires were sent to all Japanese Society for Spine Surgery and Related Research (JSSR) members. Questionnaires requested information about surgical procedures (XLIF or OLIF), patient characteristics, preoperative diagnosis, complications, salvage procedures, final outcomes, and the surgeon's experience of LIF. The data from replies received between March 2013 and April 2015 were recorded on a web site and the details of complications were analyzed by a JSSR research team. RESULTS: Seventy-one institutions (12.3%) answered "yes" to LIF experience and 2998 cases (1995 XLIF and 1003 OLIF) were enrolled in this study. The response rate was 86.1%. A total of 540 complications were reported, of which 474 (84.8%) could be further analyzed. The overall complication rate was 18.0%. The most frequent complications were sensory nerve injury (5.1%) and psoas weakness (4.3%) and the majority resolved spontaneously. The rates of major vascular injury, bowel injury, and surgical site infection were 0.03%, 0.03%, and 0.7%, respectively. The overall reoperation rate was 2.2%. Higher rates of sensory nerve injury and psoas weakness were reported for XLIF and higher rates of peritoneal laceration and ureteral injury were reported for OLIF. CONCLUSION: A nationwide survey of complications associated with LIF was conducted. Although the majority of complications were minor, a relatively high rate of complications was reported. Approach-related specific features of the two procedures were identified. LEVEL OF EVIDENCE: 4.

A Delayed Postoperative C5 Palsy due to Spinal Cord Lesion: A Typical Clinical Presentation but Unusual Imaging Findings.

Postoperative C5 palsy (C5 palsy) is a troublesome complication after cervical spine surgery and its etiology is still unclear. We experienced a case of C5 palsy after anterior decompression with fusion for cervical ossification of posterior longitudinal ligament with the typical clinical presentation of left deltoid and bicep weakness and left-arm pain without deterioration of myelopathy symptoms, albeit with the unusual imaging findings not shown preoperatively of a swelling in the spinal cord, and intramedullary high intensity change on T2-weighed MRI. The additional posterior surgery was carried out to decompress the swollen spinal cord. The abnormal findings disappear on MRI taken three weeks following the second surgery and the weakness improved fully within three months after the second surgery. This case report highlights the possibility of spinal cord lesion due to circulatory impairment as a cause of C5 palsy.

Recurrence of cervical myelopathy secondary to a strut graft fracture 20 years after anterior decompression and fusion: a case report.

This study reports on a 70-year-old man with recurrent cervical myelopathy 20 years after anterior decompression and fusion of C4-7 using a free vascularised strut graft. The recurrent myelopathy was secondary to a kyphotic deformity of a fractured graft and residual ossification of the posterior longitudinal ligament with stenosis at C3/4. Intraoperative spinal cord-evoked potentials indicated that spinal cord traction secondary to progressive kyphosis of the cervical spine after the graft fracture was the cause. The patient underwent laminoplasty at C3 and laminectomy at C4 to decompress the stenosis at C3/4 as well as posterior cervical spinal fusion at C3-7 with pedicle screws and a lateral mass screw and a bone graft to prevent further progression of the kyphosis. At postoperative 18 months, the patient's Japanese Orthopaedic Association score had improved to 14 from 8, and he could walk without support.

Influence of tibial trancutaneous repetitive electrical nerve stimulation on neurogenic claudication and F-wave in lumbar spinal stenosis.

OBJECTIVES: To determine whether repetitive tibial nerve stimulation (RTNS) affects neurogenic claudication and F-wave conduction in lumbar spinal stenosis. DESIGN: An intervention study: before/after trial. SUBJECTS: Data for 12 central lumbar spinal stenosis patients were compared with 13 age- and sex-matched healthy volunteers. METHODS: A conditioning RTNS at the ankle, 0.3-ms duration square-wave pulses with an intensity 20% higher than the motor threshold, was applied at a rate of 5/s for 5 min. We assessed the effects of RTNS on the claudication distance at which the lumbar spinal stenosis patients can no longer continue walking due to increasing leg symptoms, and on tibial F-wave measurements. RESULTS: A comparison between mean pre-RTNS and post-RTNS revealed a significant difference in claudication distance (66 m (standard deviation (SD) 19) vs 133 m (SD 37); p = 0.003), mean F-wave minimal latency (48.3 ms (SD 1.7) vs 44.8 ms (SD 1.0); p = 0.007) and mean F-wave conduction velocity (53.3 m/s (SD 2.0) vs 55.5 m/s (SD 1.9); p = 0.009) in the lumbar spinal stenosis group, but not in the control group. CONCLUSION: RTNS has beneficial effects on neurogenic claudication and F-wave conduction in central lumbar spinal stenosis patients. This phenomenon may have practical value in providing a new therapeutic modality for lumbar spinal stenosis.

Descending spinal cord evoked potentials in cervical spondylotic myelopathy: characteristic waveform changes seen at the lesion site.

OBJECTIVES: To characterize waveform changes of descending spinal cord evoked potentials (D-SCEPs) seen in cervical spondylotic myelopathy (CSM). METHODS: Intraoperative D-SCEP recording from serial intervertebral discs after transcranial electrical stimulation in 19 CSM patients with cord compression at a single level. RESULTS: Compared to the baseline (100%) obtained one level rostrally, the D-SCEP recorded at the compression site showed a significantly (p<0.001) decreased amplitude (48%) and area (48%) of negative peak and increased amplitude (171%) and area (279%) of initial-positive peak. The degree in reduction of negative peak remained the same irrespective of the cord level involved, whereas enhancement of the positive peak tended to diminish with a more caudal compression. CONCLUSIONS: In intraoperative electrophysiological studies of CSM with D-SCEP, an abrupt reduction of the negative peak accompanied by an enhancement of the initial-positive peak helps identify the site of conduction block. We speculate that progressive loss of the descending motor volleys at the synapses in the cervical enlargement may account for limited or absent enhancement of positive peak seen caudally. SIGNIFICANCE: The current finding helps us understand the pros and cons of various electrophysiologic techniques for intraoperative localization of maximal cord involvement in CSM.

Differential blood contamination levels and powder-liquid ratios can affect the compressive strength of calcium phosphate cement (CPC): a study using a transpedicular vertebroplasty model.

PURPOSE: Calcium phosphate cement (CPC) is a potentially useful alternative to polymethylmethacrylate (PMMA) for transpedicular injection into osteoporotic vertebral fractures. Unlike PMMA, CPC is both biocompatible and osteoconductive without producing heat from polymerization, but it has lower compressive strength compared to PMMA. This in vitro model experiment analyzed how different CPC powder-liquid ratios (P/L ratios) and injection methods may minimize blood contamination in the CPC and, thereby its reduction in compressive strength. METHODS: (1) CPC of different P/L ratios of 4.0, 3.5, and 3.2 was equally mixed with different amounts of freshly obtained human venous blood, producing cylindrically shaped CPC samples. (2) Using a transpedicular vertebroplasty model containing blood in the bottom, CPC pastes of different P/L ratios were injected with the nozzle of an injection gun affixed either to the bottom (Bottom method) or to the top of the container (Top method). All cylindrical CPC samples thus obtained were immersed in simulated body fluid and then underwent compressive strength tests at 3 h-7 days post-immersion. RESULTS: In CPC equally mixed with blood, lower P/L ratios and a larger amount of blood contamination reduced compressive strength more significantly. Of the two methods of CPC injection, the 'Bottom method' produced significantly greater compressive strength values than the 'Top method'. CONCLUSIONS: When performing CPC-assisted vertebroplasty, a greater load bearing-support can be obtained by injecting CPC paste of a high P/L ratio of 4.0 into the deepest part of the space inside the vertebral body to minimize blood contamination.

Comparison of in vivo bioactivity and compressive strength of a novel superporous hydroxyapatite with beta-tricalcium phosphates.

INTRODUCTION: Superporous hydroxyapatite (HAp-S) is a novel bone substitute that contains three-dimensionally interconnected macropores with micropores, which stimulate bone ingrowth into the material. METHOD: We investigated the in vivo behaviour of HAp-S by comparing its bioactivity and biomechanical properties with beta-tricalcium phosphates (ß-TCP). HAp-S or ß-TCP was implanted in the lateral femoral condyle of rabbits. In vivo bioactivity of each material, including bone ingrowth and material resorption, was quantitatively evaluated by micro-CT and the ultimate compressive strength of the bone-material composite was also measured. Micro-CT showed that bone ingrowth in the HAp-S group significantly increased over time, while no significant increase was observed after 8 weeks in the ß-TCP group. RESULTS: Although both materials showed gradual material resorption, ß-TCP resorption was significantly greater than HAp-S. The ultimate compressive strength in the HAp-S group significantly increased over time up to six times its original value, while there was no significant increase in the ß-TCP group. These results show that HAp-S resorption is concurrent with bone ingrowth, resulting in increasing compressive strength over 12 weeks. On the other hand, ß-TCP resorption is fast but unaccompanied by bone ingrowth; consequently, it remains relatively fragile at least in the early period after implantation. Although these highly porous materials themselves are structurally and mechanically similar, there are significant differences in in vivo behaviour depending on the material composition. CONCLUSION: These findings should be kept in mind when choosing the highly porous ceramics.

Factors predicting progression in early degenerative lumbar scoliosis.

PURPOSE: To review early radiographs of patients with de novo degenerative lumbar scoliosis to determine factors predicting early scoliosis progression. METHODS: Standing anteroposterior and lateral radiographs of 7 men and 20 women aged 48 to 83 (mean, 63) years with Cobb angles between >5º and <20º were reviewed. They were followed up for a mean of 12 (range, 10-18) years. Radiographic variables measured included (1) the Cobb angle, (2) the grade of rotation of the apical lumbar vertebra, (3) the presence of a lateral vertebral translation of ≥3 mm, (4) the degree of osteoporosis, and (5) the Harrington factor (the degree of scoliosis divided by the number of vertebrae involved). RESULTS: During the follow-up period, the mean Cobb angle increased 5.3º from 10.1º to 15.4º, representing an increase of 0.4º per year. In initial radiographs, the apical vertebral rotation was rated as grade 0 in 3 patients, grade 1 in 19, grade 2 in 4, and grade 3 in one. A lateral vertebral translation of ≥3 mm was noted in 9 patients. The degree of osteoporosis was rated as grade 0 in 9 patients, grade 1 in 11, grade 2 in 5, and grade 3 in 2. The mean Harrington factor was 2.4. In the multiple regression analysis, only the grade of apical vertebral rotation was significantly correlated with scoliosis progression (regression coefficient=0.502, p=0.009). CONCLUSION: Apical vertebral rotation may help predict the scoliosis progression and determine the timing of surgical intervention in patients with early degenerative lumbar scoliosis.

Incidence and risk factors of postoperative delirium in cervical spine surgery.

STUDY DESIGN: Retrospective clinical review and prospective report of postoperative delirium after cervical spine surgeries. OBJECTIVE: To investigate factors contributing to the development of delirium after cervical surgery and see whether amended therapeutic protocols could improve or alter postoperative outcomes. SUMMARY OF BACKGROUND DATA: Important consequences of postoperative delirium for the orthopedic patients include impaired recovery and increased morbidity and mortality. Although its risk factors have been reported in orthopedic surgery, there are a very few reports regarding postoperative delirium in spine surgery. METHODS: Eighty-one cervical myelopathy patients were retrospectively examined about the incidence of postoperative delirium and the risk factors. Similarly, 41 patients who received postoperative care under modified protocols were prospectively examined. RESULTS: Postoperative delirium occurred more commonly in patients over 70 years and those with hearing impairment. Patients who received high-dose methylprednisolone (>1000 mg) demonstrated an increased incidence of postoperative delirium. Under modified protocol, we reduced the usage of methylprednisolone and encouraged free body movement with cervical orthosis immediately after surgery. The incidence of postoperative delirium was significantly lower under the modified protocol. CONCLUSION: Early commencement of mobilization after cervical spine surgery would be crucial to the prevention of postoperative delirium in the elderly.

Enhancement of pedicle screw stability using calcium phosphate cement in osteoporotic vertebrae: in vivo biomechanical study.

We conducted an experimental study using female beagles with and without ovariectomy-induced osteoporosis to determine the effect of calcium phosphate cement (CPC) on the mechanical stability of inserted pedicle screws. A drill hole was created from the base of the transverse process to the vertebral body; CPC was injected into the hole, and then a screw was inserted into the same hole. In the presence of osteoporosis evidenced by dual X-ray absorptiometry, the stability of the inserted screw augmented by CPC against pull-out and cephalocaudal forces were significantly greater by 28% and 54% at 1 week after operation, 48% and 71% at 2 weeks, and 56% and 68% at 4 weeks compared with those without CPC. The pull-out strength increased progressively with time after surgery, probably reflecting new-bone growth from the surrounding cancellous bone, which was in direct contact with the CPC, as shown in the histologic study. At each time point the cephalocaudal rigidity was similar and the pull-out strength greater than that for the screws inserted without CPC in nonporotic dogs. These findings suggest that CPC augments the stability of the inserted pedicle screws and increases the stiffness of fixed osteoporotic motion segments using instrumentation.

[Vertebroplasty for osteoporotic vertebral compression fractures].

Vertebroplasty for osteoporotic vertebral compression fractures is a minimally invasive procedure which could provide immediate pain relief by injecting PMMA into the vertebral body percutaneously. Kyphoplasty, which is designed to restore the vertebral height by inflating balloon, has recently been developed and the excellent early clinical results were reported. Calcium phosphate cement may have potential advantages over the PMMA for the use in vertebroplasty or kyphoplasty.