Koichiro Okuyama

Stability of transpedicle screwing for the osteoporotic spine. An in vitro study of the mechanical stability.

The influence of bone mineral density on the stability of transpedicle screwing was studied in the human cadaveric lumbar vertebrae. The pull-out force correlated with bone mineral density. The tilting moment (load needed to tilt the screw 4 degrees cranially at the screw-plate junction) and the cut-up force (load needed to tip the end plate up by the screw) correlated with bone mineral density. A correlation was also found between the maximum insertion torque of the screw and bone mineral density. The maximum insertion torque correlated with the pull-out force, the tilting moment, and the cut-up force. In the cyclic tilting test (200 cycles), the mean value of the tilting moment at the 200th cycle was 67.4 +/- 6.1%, compared with the first cycle. The results suggest that preoperative measurement of BMD is necessary for transpedicle screwing in osteoporotic cases, and that the cyclic tilting motion decrease its mechanical stability. The authors have also concluded that the maximum insertion torque could predict the mechanical stability.

Outcome of One-level Posterior Lumbar Interbody Fusion for Spondylolisthesis and Postoperative Intervertebral Disc Degeneration Adjacent to the Fusion

Study Design. Review of the clinical and radiologic records of patients who underwent one-level posterior lumbar interbody fusion (PLIF) at L4–L5. Objective. To determine whether adjacent intervertebral disc degeneration after PLIF affects the clinical results, and whether preoperative caudal disc (L5–S1) degeneration affects postoperative clinical results. Summary of Background Data. There is little reliable information in the literature regarding clinical results and adjacent disc degeneration after PLIF. Methods. Forty-five patients who underwent L4–L5 PLIF for spondylolisthesis with more than 5 years of postoperative observation were included in this study. PLIF was performed in conjunction with posterior instrumentation. The posterior lumbar intervertebral grafting was performed using both autograft and a ceramic spacer. Intervertebral disc heights at L2–L3, L3–L4, and L5–S1 were measured before and after surgery. The patients were divided into two groups based on the presence or absence of the preoperative L5–S1 narrowing. Correlation between clinical status evaluated by the recovery rate of the Japanese Orthopedic Association (JOA) score and disc heights were determined. Results. All intervertebral disc heights adjacent to the fusion decreased after surgery (P < 0.05). However, no significant correlation was seen between clinical results estimated by the recovery rate and postoperative disc narrowing. There was also no significant difference in clinical results between patients with or without preoperative L5–S1 narrowing. Conclusions. There is no evidence from the results that postoperative narrowing of the adjacent disc andpreoperative narrowing of the L5–S1 disc affects the clinical outcome of L4–L5 PLIF.

Posterior lumbar interbody fusion: A retrospective study of complications after facet joint excision and pedicle screw fixation in 148 cases

We retrospectively evaluated neurological and other complications related to posterior lumbar interbody fusion (PLIF) performed by facet joint excision and pedicle screw fixation, in 148 consecutive patients with degenerative disorders. Their mean age at surgery was 59 (19-80) years. The mean follow-up period was 3 (2-6.5) years. Overall, 91 complications in 75 cases were observed. Although no permanent neural damage was detected, transient neural palsy occurred in 8% of the cases. Dural tear, partial misplacement, loosening, breakage of the pedicle screw and loss of correction were seen in 6, 6, 4, 1 and 1 of the cases, respectively. Deep infection of the fused segment developed in 2 cases. We conclude that PLIF, performed by facet joint excision and pedicle screw fixation, demonstrated a very low incidence of osteosynthesis failure, such as screw loosening, breakage and loss of correction. However, the high incidence of other complications, particularly neurological impairment, is still a disadvantage of this technically-demanding procedure.

Can Insertional Torque Predict Screw Loosening and Related Failures? : An In Vivo Study of Pedicle Screw Fixation Augmenting Posterior Lumbar Interbody Fusion

STUDY DESIGN An investigation of the relation between intraoperative insertional torque of pedicle screws, bone mineral density of the vertebra, and development of screw loosening in vivo. OBJECTIVES To determine the usefulness of intraoperative measurement of the insertional torque of pedicle screws. SUMMARY OF BACKGROUND DATA Some biomechanical studies have demonstrated that the insertional torque is highly correlated with bone mineral density and the stability of pedicle screws in vitro. METHODS Pedicle screw fixation was performed with posterior lumbar interbody fusion in 62 consecutive patients. The mean age of the patients at the time of surgery was 58 years. The insertional torque of pedicle screws was measured intraoperatively in all patients. The mean follow-up period was 2.7 years. RESULTS The mean insertional torque was 1.28 +/- 0.37 Nm in patients with screw loosening and 1.50 +/- 0. 40 Nm in patients without the problem. The mean insertional torque in patients with compression fractures in the upper vertebra adjacent to the fixed segment was 0.83 +/- 0.23 Nm. There was no significant difference between the mean insertional torque in patients with screw loosening and those without the condition. The mean insertional torque in patients without screw loosening was significantly greater than in patients with compression fractures (P < 0.01). A high correlation was found between insertional torque and bone mineral density (P < 0.01). CONCLUSIONS Although a high correlation was found between the insertional torque of pedicle screws and bone mineral density in vivo, the insertional torque could not objectively predict screw loosening.

Total spondylectomy for primary malignant, aggressive benign, and solitary metastatic bone tumors of the thoracolumbar spine.

The records of 14 patients with malignant or aggressive benign vertebral tumors of the thoracolumbar spine who underwent total spondylectomy (TS) were evaluated retrospectively. Total spondylectomy was performed by bisecting the affected vertebra through the pedicle using fine threadwire saws and removing the vertebra en bloc through the posterior procedure alone or the one-stage anteroposterior combined procedure. Remarkable pain relief and ambulation after surgery were achieved in all 14 patients. No serious complications occurred. Nerve roots were sacrificed in seven cases. A marginal surgical margin was achieved in 10 cases and an intralesional surgical margin was achieved in four. At the site of the osteotomized pedicle, the surgical margin was marginal, with the possibility of tumor-cell contamination in 10 cases. Local recurrence was found in three cases of posterior total spondylectomy at 0.3 to 3.5 years (mean, 3.2 years) follow-up evaluation at the other site of the osteotomized pedicle. These results suggest that this type of total spondylectomy is effective in controlling local recurrence without incurring major complications and is a clinically useful procedure.

Improving the pullout strength of pedicle screws by screw coupling

The objective of this study was to determine the effect of pedicle screw coupling on the pullout strength of pedicle screws in the osteoporotic spine. The vertebral bone mineral density (BMD) of 33 cadaveric lumbar vertebrae were measured by quantitative computed tomography. Pedicle screws were inserted into each pedicle. The pullout strength and displacement of the screws, without coupling and with single or double couplers, were studied, and the relationship between pullout strength and BMD was analyzed. The average pullout strength of the pedicle screws without screw coupling was 909.3 +/- 188.6 N (n = 9), that coupled with a single coupler was 1,409.0 +/- 469.1 N (n = 9), and that with double couplers was 1,494.0 +/- 691.6 N (n = 9). The pullout strength of the screws coupled with single or double couplers was significantly greater than that of screws without couplers (p < 0.01); however, there was no significant difference between the groups of single and double couplers. The improvement of pullout strength by screw coupling was significant in a test group with BMD of more than 90 mg/ml (p < 0.01), but was not in the group with BMD less than 90 mg/ml (p = 0.55). These results suggest that the coupling of pedicle screws improves pullout strength; however, the effect tends to be less significant in severely osteoporotic spines.

Vertebral pedicle diameter as determined by computed tomography: inaccuracies observed by direct measurement of cadaveric lumbar spine

The isthmic diameter of the vertebral pedicle is an important dimension affecting the stability of transpedicular screwing. The isthmic diameter of the pedicle was measured in the lumbar spines of 18 Japanese cadavers (10 male, 8 female) by axial computed tomographic (CT) scan and directly with calipers. In L1 and L2, there was no significant difference between the average value of the isthmic diameter as determined by the two methods (Students t-test). However, in L3-5, the average value of the isthmic diameter as determined by axial CT scan was significantly greater than that given by caliper measurement. In view of the fact that caudally the longitudinal axis of the pedicle diverges to wards the mid-line of the vertebral body in the coronal plane, the plane of the CT scan cannot be parallel to the real isthmic diameter of the pedicle. Therefore, it is suggested that below L2 the diameter as determined by axial CT scanning is greater than the real isthmic diameter.

Dumb-bell-type teratoma in the lumbar spine.

Abstract We report a case of a lumbar teratoma in a 50-year-old woman. The teratoma showed a dumb-bell-type expansion at the level of the left L3/4 foramen with massive erosion of the L3 vertebral body. MRI revealed inhomogeneous signal changes in the tumor, which were histologically compatible with a mixture of bone, muscle, fat, and cyst containing sebaceous material. Complete resection of the tumor and spinal arthrodesis with pedicle screw fixation was necessary to obtain stability of the affected spinal segment.

Huge solitary osteochondroma at T11 level causing myelopathy : case report

A solitary osteochondroma of the vertebral column is rare, and also it will rarely cause neurological deficits. Myelopathy from a tumour usually presents insidiously with neurological deficits. We report a case of a huge solitary osteochondroma at T11 level with an acute onset of myelopathy induced by a minor trauma.MRI findings of a spinal osteochondroma has rarely been described. In our patient, the MRI demonstrated an outer osteochondral layer and an ossified centre of the mass. A literature review has also been undertaken.

Clinical diagnosis of upper lumbar disc herniation: Pain and/or numbness distribution are more useful for appropriate level diagnosis

OBJECTIVE The purpose of this study is to disclose the characteristic symptoms and signs in L2, L3 and L4 nerve root disturbance. MATERIALS AND METHODS Fifty eight patients who underwent lateral herniotomy were analyzed. Breakdowns are 15 patients with L2/3 lateral disc herniation (group A), 20 patients with L3/4 lateral disc herniation (group B), and 23 patients with L4/5 lateral disc herniation (group C). The following items were examined: 1) localization of the subjective pain and numbness, 2) objective neurological findings, including deep tendon reflex, manual muscle strength (MMT), straight leg raising test (SLRT) and femoral nerve stretch test (FNST). RESULTS In group A, subjective pain and/or numbness was present in the thigh aspect, proximal to the knee joint in all patients. In group B, 80% of the patients had subjective pain and/or numbness in the medial site of the knee joint. In group C, the subjective pain and/or numbness was localized in various aspects of the lower extremity. Weakness in the iliopsoas, the femoral quadriceps, and the anterior tibial muscle were observed in 60-95%, 27-70%, 0-43% of three groups, respectively. Depression or absence of the patella tendon reflex was present in 27-100% of three groups. SLRT and FNST were positive in 13-87% and 91-95% of three groups. CONCLUSION Symptomatic levels of nerve root disturbance in the upper lumbar spine could not be accurately identified by objective neurological findings alone. Pain and/or numbness localized in the thigh area proximal to the knee joint is a specific sign of L2 nerve root disturbance. Either subjective pain or numbness in the medial knee joint aspect is another key sign which strongly suggests L3 nerve root disturbance.