Early Fusion Status After Posterior Lumbar Interbody Fusion With Cortical Bone Trajectory Screw Fixation or Traditional Trajectory Screw Fixation: A Comparison Between the Titanium-coated Polyetheretherketone Cage and the Same Shape Polyetheretherketone Cage.

STUDY DESIGN: A retrospective analysis of prospectively collected data. OBJECTIVE: The aim was to examine whether posterior lumbar interbody fusion with cortical bone trajectory screw fixation (CBT-PLIF) is inferior to PLIF using traditional trajectory screw fixation (TT-PLIF) regarding early fusion status and whether the titanium-coated polyetheretherketone (PEEK) cage (TP cage) improves early fusion status compared with the same shape pure PEEK cage (P cage). SUMMARY OF BACKGROUND DATA: We recently reported that the fusion rate was relatively lower after CBT-PLIF than after TT-PLIF, although no significant difference was found and that compared with the carbon PEEK cage, the TP cage significantly reduced the incidence of vertebral endplate cysts (cyst signs) and slightly improved the early fusion rate at 1 year after CBT-PLIF. MATERIALS AND METHODS: The subjects were 37 patients undergoing TT-PLIF using P cages (TT-P group), 24 patients undergoing CBT-PLIF using P cages (CBT-P group), 32 patients undergoing TT-PLIF using TP cages (TT-TP group), and 20 patients undergoing CBT-PLIF using TP cages (CBT-TP group). On multiplanar reconstruction computed tomography at 6 months after surgery, cyst signs were evaluated and classified into diffuse or local cysts. Early fusion status was assessed using both dynamic plain radiographs and multiplanar reconstruction computed tomography at 1-year postoperatively. RESULTS: The incidence of the diffuse cyst was 27.0% in the TT-P group, 29.2% in the CBT-P group, 25.0% in the TT-TP group and 25.0% in the CBT-TP group (P>0.05). The early fusion rate was 75.7% in the TT-P group, 75.0% in the CBT-P group, 71.9% in the TT-TP group and 75.0% in the CBT-TP group (P>0.05). CONCLUSIONS: These results indicate that CBT-PLIF resulted in the equivalent early fusion status to TT-PLIF and that compared with the same shape P cage, the TP cage did not improve early fusion status after both TT-PLIF and CBT-PLIF.

Surgical outcomes after posterior lumbar interbody fusion using traditional trajectory screw fixation or cortical bone trajectory screw fixation: A comparative study between the polyetheretherketone cage and the same shape titanium-coated polyetheretherketone cage.

OBJECTIVE: To investigate whether or not the fusion rate after posterior lumbar interbody fusion with cortical bone trajectory screw fixation (CBT-PLIF) is lower than after PLIF using traditional trajectory screw fixation (TT-PLIF) and whether or not the titanium-coated polyetheretherketone (PEEK) cage (TiP cage) improves fusion status compared to the same shape uncoated PEEK cage (P cage). METHODS: The subjects were 37 patients undergoing TT-PLIF using P cages (P-TT group), 24 patients undergoing CBT-PLIF using P cages (P-CBT group), 32 patients undergoing TT-PLIF using TiP cages (TiP-TT group), and 20 patients undergoing CBT-PLIF using TiP cages (TiP-CBT group). All patients from the 4 groups underwent our unified PLIF procedure (total facetectomy, subtotal discectomy, and the same bone graft technique using the same shape cages) except for the screw trajectories and the surface materials of the cages. Clinical symptoms were assessed using the Japanese Orthopedic Association (JOA) score before surgery and at 2-year postoperatively. None of age at the time of surgery, gender, fused segment and preoperative JOA score showed significant differences among the 4 groups. On multiplanar reconstruction computed tomography (MPR-CT) at 6months after surgery, vertebral end plate cysts were evaluated and classified into local or diffuse cysts. Fusion status was assessed using both dynamic plain radiographs and MPR-CT at postoperative 2-year. RESULTS: Neither the mean JOA score nor the mean recovery rate of the JOA score at 2-year after surgery showed significant differences among the 4 groups. The incidence of the diffuse cyst (a known predictor of non-union) was 27.0% in the P-TT group, 29.2% in the P-CBT group, 25.0% in the TiP-TT group and 25.0% in the TiP-CBT group (P > 0.05). The fusion rate was 89.2% in the P-TT group, 91.7% in the P-CBT group, 90.6% in the TiP-TT group and 90.0% in the TiP-CBT group (P > 0.05). CONCLUSIONS: After our unified PLIF procedure except for the screw trajectories and the surface materials of the cages, CBT-PLIF resulted in the equivalent fusion rate to TT-PLIF and the TiP cage did not lead to the improved fusion rate compared to the same shape P cage.

Does Atherosclerosis Have Negative Impacts on Early Adjacent Segment Degeneration After Posterior Lumbar Interbody Fusion?

STUDY DESIGN: Retrospective study. OBJECTIVE: To examine whether atherosclerosis has negative impacts on early adjacent segment degeneration (ASD) after posterior lumbar interbody fusion using traditional trajectory pedicle screw fixation (TT-PLIF). METHODS: The subjects were 77 patients who underwent single-level TT-PLIF for degenerative lumbar spondylolisthesis. Using dynamic lateral radiographs of the lumbar spine before surgery and at 3 years postoperatively, early radiological ASD (R-ASD) was examined. Early symptomatic ASD (S-ASD) was diagnosed when neurologic symptoms deteriorated during postoperative 3-year follow-up and the responsible lesions adjacent to the fused segment were also confirmed on magnetic resonance imaging. According to the scoring system by Kauppila et al, the abdominal aortic calcification score (AAC score: a surrogate marker of systemic atherosclerosis) was assessed using preoperative lateral radiographs of the lumbar spine. RESULTS: The incidence of early R-ASD was 41.6% at the suprajacent segment and 8.3% at the subjacent segment, respectively. Patients with R-ASD had significantly higher AAC score than those without R-ASD. The incidence of early S-ASD was 3.9% at the suprajacent segment and 1.4% at the subjacent segment, respectively. Patients with S-ASD had higher AAC score than those without S-ASD, although there was no significant difference. CONCLUSIONS: At 3 years after surgery, the advanced AAC had significantly negative impacts on early R-ASD after TT-PLIF. This result indicates that impaired blood flow due to atherosclerosis can aggravate degenerative changes at the adjacent segments of the lumbar spine after PLIF.

Two-level Posterior Lumbar Interbody Fusion at the Lumbosacral Segment has a High Risk of Pseudarthrosis and Poor Clinical Outcomes: Comparison Between the Lumbar and Lumbosacral Segments.

STUDY DESIGN: This was a retrospective study. OBJECTIVES: The purposes of this study were to investigate the fusion rate and clinical outcomes of 2-level posterior lumbar interbody fusion (PLIF). SUMMARY OF BACKGROUND DATA: PLIF provides favorable clinical outcomes and a high fusion rate. However, most extant studies have been limited to the results of single-level PLIF. Clinical outcomes and fusion rate of 2-level PLIF are unknown. MATERIALS AND METHODS: In total, 73 patients who underwent 2-level PLIF below L3 between 2008 and 2016 (follow-up period >2 y) were included. Patients were divided into the 2 groups on the basis of surgical level. The lumbar group included 48 patients who underwent L3/4/5 PLIF, and the lumbosacral group included 25 patients who underwent L4/5/S PLIF. Fusion rate and clinical outcomes were compared. The Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and a visual analog scale were used for evaluation. RESULTS: Fusion rate was significantly lower in the lumbosacral group (lumbar 96% vs. lumbosacral 64%; P<0.001). Eight of 9 cases of pseudarthrosis occurred at the lumbosacral segment. Improvement in the mental health domain of the JOAPEQ was significantly lower in the lumbosacral group (lumbar 16 vs. lumbosacral 10; P=0.02). The VAS data showed that improvements in the following variables were significantly lower in the lumbosacral group than in the lumbar group: pain in low back (lumbar -38 vs. lumbosacral -23; P=0.004), pain in buttocks or lower leg (lumbar -48 vs. lumbosacral -29; P=0.04), and numbness in buttocks or lower leg (lumbar -44 vs. lumbosacral -33; P=0.04). CONCLUSIONS: Two-level PLIF at the lumbosacral segment demonstrated a significantly lower fusion rate and poorer clinical outcomes than that at the lumbar-only segments. Some reinforcement for the sacral anchor is recommended to improve fusion rate, even for short fusion like 2-level PLIF, if the lumbosacral segment is included. LEVEL OF EVIDENCE: Level III.

Early cephalad adjacent segment degeneration after posterior lumbar interbody fusion: a comparative study between cortical bone trajectory screw fixation and traditional trajectory screw fixation.

OBJECTIVE: Cortical bone trajectory (CBT) screw insertion through a caudomedial starting point provides advantages in limiting dissection of the superior facet joints and reducing muscle dissection and the risk of superior-segment facet violation by the screw. These advantages of the cephalad CBT screw can result in lower rates of early cephalad adjacent segment degeneration (ASD) after posterior lumbar interbody fusion (PLIF) with CBT screw fixation (CBT-PLIF) than those after PLIF using traditional trajectory screw fixation (TT-PLIF). Here, the authors investigated early cephalad ASD after CBT-PLIF and compared these results with those after TT-PLIF. METHODS: The medical records of all patients who had undergone single-level CBT-PLIF or single-level TT-PLIF for degenerative lumbar spondylolisthesis (DLS) and with at least 3 years of postsurgical follow-up were retrospectively reviewed. At 3 years postoperatively, early cephalad radiological ASD changes (R-ASD) such as narrowing of disc height (> 3 mm), anterior or posterior slippage (> 3 mm), and posterior opening (> 5°) were examined using lateral radiographs of the lumbar spine. Early cephalad symptomatic adjacent segment disease (S-ASD) was diagnosed when clinical symptoms such as leg pain deteriorated during postoperative follow-up and the responsible lesion suprajacent to the fused segment was confirmed on MRI. RESULTS: One hundred two patients underwent single-level CBT-PLIF for DLS and were followed up for at least 3 years (CBT group). As a control group, age- and sex-matched patients (77) underwent single-level TT-PLIF for DLS and were followed up for at least 3 years (TT group). The total incidence of early cephalad R-ASD was 12.7% in the CBT group and 41.6% in the TT group (p < 0.0001). The incidence of narrowing of disc height, anterior slippage, and posterior slippage was significantly lower in the CBT group (5.9%, 2.0%, and 4.9%) than in the TT group (16.9%, 13.0%, and 14.3%; p < 0.05). Early cephalad S-ASD developed in 1 patient (1.0%) in the CBT group and 3 patients (3.9%) in the TT group; although the incidence was lower in the CBT group than in the TT group, no significant difference was found between the two groups. CONCLUSIONS: CBT-PLIF, as compared with TT-PLIF, significantly reduced the incidence of early cephalad R-ASD. One of the main reasons may be that cephalad CBT screws reduced the risk of proximal facet violation by the screw, which reportedly can increase biomechanical stress and lead to destabilization at the suprajacent segment to the fused segment.

Conventional JOA score for cervical myelopathy has a rater's bias -In comparison with JOACMEQ.

BACKGROUND: The JOA (Japan Orthopaedic Association) score has been a standard outcome measure to evaluate cervical myelopathy in Japan. Despite its reliability and convenience, there can be a rating bias in the JOA score. The current study was conducted to delineate the rater's bias of the JOA score by comparing it with a new objective outcome measure. METHODS: Two hundred and thirty four operative candidates with cervical myelopathy were included in the study. The patients were divided into four groups according to the surgeon (92 patients in group A, 60 patients in group B, 38 patients in group C and 44 patients in group D). Each patient's preoperative JOA score was exclusively recorded by the surgeon himself, while JOACMEQ (Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire) was recorded by each patient. Disease severity, the most important prognostic factor, was equalized between patient groups by a special statistical method called inverse-probability weighting (IPW). To define similarity of the two groups, Cohen's d was used. RESULTS: After the adjustment, the differences of the JOA score were only 0.1 between groups A and D and 0 between groups B and C. The values of Cohen's d were also very small both between groups A and D (3%), and between groups B and C (0.3%). The averaged JOA scores of groups A and D were higher by 0.4-0.8 than those of groups B and C, while the averaged JOA scores were almost the same both between groups A and D, and between groups B and C. Surgeons A and D had the same tendency to give higher JOA scores than surgeons B and C did. CONCLUSIONS: The current study confirmed there is a definite rater's bias in the JOA score. JOACMEQ is to be applied as a more reliable outcome measure to evaluate myelopathy patients.

Improvement of thoracic myelopathy following bariatric surgery in an obese patient.

Revision spine surgery is extremely challenging in super-super obese patients (body mass index (BMI) ≥60 kg/m2). This is the first report describing how bariatric surgery was useful for a super-super obese patient with progressing myelopathy. A 44-year-old man with a BMI of 62.9 kg/m2 presented with an ambulatory disorder caused by thoracic ossification of the posterior longitudinal ligament (T7-8). Before this paraparesis, he had undergone four spinal operations, and was not considered a good candidate for a fifth spine surgery. At the time of the fourth operation, he had reached a maximum weight of 205 kg (BMI 69.3 kg/m2). Instead, he underwent a laparoscopic sleeve gastrectomy. Sixteen months later, his body weight had decreased to BMI 35.2 kg/m2, and he could walk without a walker. In addition to reducing our patient's load, a 'non-operative' form of dekyphosis due to altered thoracic spinal alignment secondary to weight loss may explain the improvement in his myelopathy.

Clinical Outcomes After Posterior Lumbar Interbody Fusion: Comparison of Cortical Bone Trajectory and Conventional Pedicle Screw Insertion.

STUDY DESIGN: This study is a retrospective cohort study using prospectively collected data. OBJECTIVE: To compare the effectiveness of posterior lumbar interbody fusion (PLIF) using the cortical bone trajectory (CBT) and conventional pedicle screw (PS) techniques. SUMMARY OF BACKGROUND DATA: There are few published studies to date comparing PLIF using CBT technique with PLIF using the conventional PS technique. METHODS: We studied 119 consecutive patients who underwent single-level PLIF between 2010 and 2014 with a minimum 12-month follow-up. Forty-two patients underwent CBT-PLIF (the CBT group) and 77 underwent conventional PS-PLIF (the PS group). Clinical outcomes were assessed by the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and visual analog scale (VAS). To assess perioperative pain, a 6-point Numeric Rating Scale score and the total amount of diclofenac sodium suppositories used were recorded. The operative time and blood loss were recorded. Muscle damage was evaluated by serum creatine kinase concentrations. Fusion status was evaluated using 3-dimensional computed tomography 12 months postoperatively. We used inverse probability of treatment weighting based on the propensity score to reduce confounding factors. RESULTS: There were no significant between-group differences in operative time or fusion rates, whereas the CBT group experienced significantly less blood loss, lower postoperative creatine kinase levels, less diclofenac sodium suppositories, and lower Numeric Rating Scale scores than the PS group did. The change in the JOABPEQ subdomain score for social life function 1 month postoperatively was the only significantly different factor among the JOABPEQ and VAS scores. CONCLUSIONS: Both procedures were comparable in terms of clinical outcomes and fusion rates, but CBT-PLIF provided the additional benefits of less blood loss, less intraoperative muscle damage, less perioperative pain, and earlier recovery to normal activities.

Preoperative retrolisthesis as a predictive risk factor of reoperation due to delayed-onset symptomatic foraminal stenosis after central decompression for lumbar canal stenosis without fusion.

BACKGROUND CONTEXT: For patients diagnosed with lumbar central canal stenosis with asymptomatic foraminal stenosis (FS), surgeons occasionally only decompress central stenosis and preserve asymptomatic FS. These surgeries have the potential risk of converting preoperative asymptomatic FS into symptomatic FS postoperatively by accelerating spinal degeneration, which requires reoperation. However, little is known about delayed-onset symptomatic FS postoperatively. PURPOSE: This study aimed to evaluate the rate of reoperation for delayed-onset symptomatic FS after lumbar central canal decompression in patients with preoperative asymptomatic FS, and determine the predictive risk factors of those reoperations. STUDY DESIGN: This study is a retrospective cohort study. PATIENT SAMPLE: Two hundred eight consecutive patients undergoing posterior central decompression for lumbar canal stenosis between January 2009 and June 2014 were included in this study. OUTCOME MEASURES: The number of patients who had preoperative FS and the reoperation rate for delayed-onset symptomatic FS at the index levels were the outcome measures. METHODS: Patients were divided into two groups with and without preoperative asymptomatic FS at the decompressed levels. The baseline characteristics and revision rates for delayed-onset symptomatic FS were compared between the two groups. Predictive risk factors for such reoperations were determined using multivariate logistic regression and receiver operating characteristics analyses. RESULTS: Preoperatively, 118 patients (56.7%) had asymptomatic FS. Of those, 18 patients (15.3%) underwent reoperation for delayed-onset symptomatic FS at a mean of 1.9 years after the initial surgery. Posterior slip in neutral position and posterior extension-neutral translation were significant risk factors for reoperation due to FS. The optimal cutoff values of posterior slip in neutral position and posterior extension-neutral translation for predicting the occurrence of such reoperations were both 1 mm; 66.7% of patients who met both of these cutoff values had undergone reoperation. CONCLUSIONS: This study demonstrated that 15.3% of patients with preoperative asymptomatic FS underwent reoperation for delayed-onset symptomatic FS at the index levels at a mean of 1.9 years after central decompression, and preoperative retrolisthesis was a predictive risk factor for such a reoperation. These findings are valuable for establishing standards of appropriate treatment strategies in patients with lumbar central canal stenosis with asymptomatic FS.

Preoperative retrolisthesis as a risk factor of postdecompression lumbar disc herniation.

OBJECT: In this study, the authors aimed to identify specific risk factors for postdecompression lumbar disc herniation (PDLDH) in patients who have not undergone discectomy and/or fusion. METHODS: Between 2007 and 2012, 493 patients with lumbar spinal stenosis underwent bilateral partial laminectomy without discectomy and/or fusion in a single hospital. Eighteen patients (herniation group [H group]: 15 men, 3 women; mean age 65.1 years) developed acute sciatica as a result of PDLDH within 2 years after surgery. Ninety patients who did not develop postoperative acute sciatica were selected as a control group (C group: 75 men, 15 women; mean age 65.4 years). Patients in the C group were age and sex matched with those in the H group. The patients in the groups were also matched for decompression level, number of decompression levels, and surgery date. The radiographic variables measured included percentage of slippage, intervertebral angle, range of motion, lumbar lordosis, disc height, facet angle, extent of facet removal, facet degeneration, disc degeneration, and vertebral endplate degeneration. The threshold for PDLDH risk factors was evaluated using a continuous numerical variable and receiver operating characteristic curve analysis. The area under the curve was used to determine the diagnostic performance, and values greater than 0.75 were considered to represent good performance. RESULTS: Multivariate analysis revealed that preoperative retrolisthesis during extension was the sole significant independent risk factor for PDLDH. The area under the curve for preoperative retrolisthesis during extension was 0.849; the cutoff value was estimated to be a retrolisthesis of 7.2% during extension. CONCLUSIONS: The authors observed that bilateral partial laminectomy, performed along with the removal of the posterior support ligament, may not be suitable for lumbar spinal stenosis patients with preoperative retrolisthesis greater than 7.2% during extension.

Vertebral osteolytic defect due to cellulose particles derived from gauze fibers after posterior lumbar interbody fusion.

Vertebral cystic lesions may be observed in pseudarthroses after lumbar fusion surgery. The authors report a rare case of pseudarthrosis after spinal fusion, accompanied by an expanding vertebral osteolytic defect induced by cellulose particles. A male patient originally presented at the age of 69 years with leg and low-back pain caused by a lumbar isthmic spondylolisthesis. He underwent a posterior lumbar interbody fusion, and his neurological symptoms and pain resolved within a year but recurred 14 months after surgery. Radiological imaging demonstrated a cystic lesion on the inferior endplate of L-5 and the superior endplate of S-1, which rapidly enlarged into a vertebral osteolytic defect. The patient underwent revision surgery, and his low-back pain resolved. A histopathological examination demonstrated foreign body-type multinucleated giant cells, containing 10-µm particles, in the sample collected just below the defect. Micro-Fourier transform infrared spectroscopy revealed that the foreign particles were cellulosic, presumably originating from cotton gauze fibers that had contaminated the interbody cages used during the initial surgery. Vertebral osteolytic defects that occur after interbody fusion are generally presumed to be the result of infection. This case suggests that some instances of vertebral osteolytic defects may be aseptically induced by foreign particles. Hence, this possibility should be carefully considered in such cases, to help prevent contamination of the morselized bone used for autologous grafts by foreign materials, such as gauze fibers.

C3-6 laminoplasty for cervical spondylotic myelopathy maintains satisfactory long-term surgical outcomes.

Study Design Prospective cohort study. Objective To clarify long-term surgical outcomes of C3-6 laminoplasty preserving muscles attached to the C2 and C7 spinous processes in patients with cervical spondylotic myelopathy (CSM). Methods Twenty patients who underwent C3-6 open-door laminoplasty for CSM and who were followed for 8 to 10 years were included in this study. Myelopathic symptoms were assessed using Japanese Orthopaedic Association (JOA) score. Axial neck pain was graded as severe, moderate, or mild. C2-7 angle was measured using lateral radiographs of the cervical spine before surgery and at final follow-up. Results Mean JOA score before surgery (11.7) was significantly improved to 15.2 at the time of maximum recovery (1 year after surgery), declining slightly to 14.9 by the latest follow-up. Late deterioration of JOA score developed in eight patients, but was unrelated to the cervical spine lesions in each case. No patient suffered from prolonged postoperative axial neck pain at final follow-up. The mean C2-7 angle before surgery (13.8 degrees) significantly increased to 19.2 degrees at final follow-up. Conclusions C3-6 laminoplasty preserving muscles attached to the C2 and C7 spinous processes in patients with CSM maintained satisfactory long-term neurologic improvement with significantly reduced frequencies of prolonged postoperative axial neck pain and loss of C2-7 angle after surgery.

Major surgical treatment of osteoporotic vertebral fractures in the elderly: a comparison of anterior spinal fusion, anterior-posterior combined surgery and posterior closing wedge osteotomy.

STUDY DESIGN: A retrospective study. PURPOSE: To clarify the differences among the three major surgeries for osteoporotic vertebral fractures based on the clinical and radiological results. OVERVIEW OF LITERATURE: Minimally invasive surgery like balloon kyphoplasty has been used to treat osteoporotic vertebral fractures, but major surgery is necessary for severely impaired patients. However, there are controversies on the surgical procedures. METHODS: The clinical and radiographic results of patients who underwent major surgery for osteoporotic vertebral fracture were retrospectively compared, among anterior spinal fusion (group A, 9 patients), single-stage combined anterior-posterior procedure (group AP, 8 patients) and posterior closing wedge osteotomy (group P, 9 patients). Patients who underwent revision surgery were evaluated just before the revision surgery, and the other patients were evaluated at the final follow-up examination, which was defined as the end point of the evaluations for the comparison. RESULTS: The operation time was significantly longer in group AP than in the other two groups. The postoperative correction of kyphosis was significantly greater in group P than in group A. Although the differences were not significant, better outcomes were obtained in group P in: back pain relief at the end point; ambulatory ability at the end point; and average loss of correction. CONCLUSIONS: The posterior closing wedge osteotomy demonstrated better surgical results than the anterior spinal fusion procedure and the single-stage combined anterior-posterior procedure.

Intramuscular pressure of the multifidus muscle and low-back pain after posterior lumbar interbody fusion: comparison of mini-open and conventional approaches.

OBJECT: This randomized study was designed to elucidate the time course of the perioperative development of intramuscular multifidus muscle pressure after posterior lumbar interbody fusion (PLIF) and to investigate whether the route of pedicle screw insertion affects this pressure and resultant low-back pain. Although several studies have focused on intramuscular pressure associated with posterior lumbar surgery, those studies examined intramuscular pressure generated by the muscle retractors during surgery. No study has investigated the intramuscular pressure after PLIF. METHODS: Forty patients with L4-5 degenerative spondylolisthesis were randomly assigned to undergo either the mini-open PLIF procedure with pedicle screw insertion between the multifidus and longissimus muscles (n = 20) or the conventional PLIF procedure via a midline approach only (n = 20). Intramuscular pressure was measured 5 times (at 30 minutes and at 6, 12, 24, and 48 hours after surgery) with an intraoperatively installed sensor. Concurrently, the FACES Pain Rating Scale score for low-back pain and the total dose of postoperative analgesics were recorded. RESULTS: With the patients in the supine position, for both groups the mean pressure values were consistently 40-50 mm Hg, which exceeded the critical capillary pressure of the muscle. With the patients in the lateral decubitus position, the pressure decreased over time (from 14 to 9 mm Hg in the mini-open group and from 20 to 10 mm Hg in the conventional group). Among patients in the mini-open group, the pressure was lower, but the difference was not statistically significant. Postoperative pain and postoperative analgesic dosages were also lower. CONCLUSIONS: To the authors' knowledge, this is the first study to evaluate postoperative intramuscular pressure after PLIF. Although the results did not demonstrate a significant difference in the intramuscular pressure between the 2 types of PLIF, mini-open PLIF was associated with less pain after surgery.

The use of cooled saline during bone drilling to reduce the incidence of upper-limb palsy after cervical laminoplasty: clinical article.

OBJECT: No previous hypothesis has attempted to fully account for the occurrence of upper-limb palsy (ULP) after cervical laminoplasty. The authors propose that friction-generated heat from a high-speed drill may cause thermal injury to the nerve roots close to the drilled bone, which may then lead to ULP. The authors investigated the effect of cooling the saline used for irrigation during the drilling on the incidence of upper-limb (C-5) palsy following cervical laminoplasty. METHODS: The irrigation saline for drilling was used at room temperature (RT, average temperature of 25.6°C) in operations of 79 patients (the RT group) and cooled to an average of 12.1°C in operations of 80 patients (the low-temperature [LT] group). The authors used a hand-held dynamometer to precisely assess muscle strength presurgery and 2 weeks postsurgery. RESULTS: There was a 7.6% and 1.9% decrease in the strength of the deltoid muscle, a 10.1% and 4.4% decrease in the strength of the biceps brachii, a 1.3% and 0.6% decrease in the strength of the triceps brachii, and a 7.6% and 3.1% decrease in grip strength in the RT and LT groups, respectively. Multivariate analysis revealed that a significant predictor for decreased deltoid muscle strength was the use of irrigation saline at RT. CONCLUSIONS: Using cooled irrigation saline during bone drilling significantly decreased the incidence of ULP and can thus be recommended as a simple method for the prevention of ULP.

Finger-tapping motion analysis in cervical myelopathy by magnetic-sensor tapping device.

STUDY DESIGN: Case-control study. OBJECTIVES: The purpose of this study is to determine finger motion of patients with cervical myelopathy during finger-tapping cycles. SUMMARY OF BACKGROUND DATA: A major symptom of patients with compressive cervical myelopathy is finger clumsiness. Therefore, understanding finger motion is prerequisite in assessing the severity of myelopathy. The popular grip-and-release test evaluates only the number of motion cycles, which is insufficient to fully describe complex finger motion. METHODS: Forty-three patients with cervical myelopathy and 41 healthy controls tapped their index fingers against their thumbs as rapidly as possible for 30 seconds and the motion was recorded by a magnetic-sensor coil attached to the nail surface. Output signals were stored in a computer, which automatically calculated tapping frequency, distance moved, ratio of opening/closing velocity and the SD of the tapping interval. RESULTS: The SD of the tapping interval was significantly greater and all other measures were significantly smaller in patients with cervical myelopathy, than in healthy controls. All indices significantly improved after surgical decompression of the cervical spine. Distance moved (Pearson correlation coefficient: r=0.590, P<0.001) and the SD of the tapping interval (r=-0.451; P=0.002) were significantly correlated with the Japanese Orthopedic Association score (neurological scale). CONCLUSION: The quantitative evaluation of finger paralysis was performed by this tapping device. Speed and regularity in repetitive motion of fingers were correlated with the severity of cervical myelopathy.

Postoperative 24-hour result of 15-second grip-and-release test correlates with surgical outcome of cervical compression myelopathy.

STUDY DESIGN: A prospective follow-up study to detect the early neurological improvement after decompression surgery and to clarify its correlation with the late neurological outcome in patients with cervical compression myelopathy. OBJECTIVE: To reveal the suitability of a simple performance, 15-second grip-and-release test for postoperative neurological recovery in patients with cervical myelopathy. SUMMARY OF BACKGROUND DATA: Although various parameters have been advocated as prognostic factors, there still remain arguments against them. Furthermore, neurological status after decompression surgery has been evaluated weekly or monthly in previous studies, but not hourly or daily. To follow the postoperative neurological recovery, we used our original performance test. METHODS: Forty-eight patients who were admitted to undergo decompressive laminoplasty for cervical myelopathy were enrolled in the study. Twenty-five patients who were admitted for lumbar spine surgery were used as controls. Subjects were asked to fully grip and release with their right (or left) hand fingers as fast as possible for 15 seconds, which was recorded by a digital camera. And the number of grip-and-release cycles was counted (15-second test) in the recorded video files. RESULTS: In the myelopathy group, the number of grip-and-release cycles before surgery and 4 hours, 24 hours, 48 hours, 1 week, and 2 weeks after surgery was 26.7 ± 10.0, 29.7 ± 9.9, 35.0 ± 11.3, 35.1 ± 9.8, 36.2 ± 9.6, and 37.2 ± 10.2, respectively. The number increased steeply after surgery until 24 hours, and the number was 94% after 24 hours of the number recorded 2 weeks after surgery. In the control group, the number of grip-and-release cycles at each time point was 37.9 ± 9.7, 34.7 ± 9.1, 39.2 ± 9.0, 38.5 ± 8.9, 38.9 ± 9.7, and 38.0 ± 9.3, respectively. There was a transient reduction 4 hours after surgery. CONCLUSION: Because the number recorded 24 hours after surgery was significantly correlated with both the maximum gain in the number on the 15-second test and the gain in the Japan Orthopaedic Association score, it could be used as a prognostic factor for neurological outcome in patients with cervical myelopathy.

Medium-term outcomes of C3-6 laminoplasty for cervical myelopathy: a prospective study with a minimum 5-year follow-up.

C3-6 laminoplasty preserving muscle insertions into the C7 spinous process is reportedly associated with a significantly decreased frequency of postoperative axial neck pain. However, no prospective study has reported medium-term outcomes of C3-6 laminoplasty. The purpose of this study was to elucidate medium-term outcomes after C3-6 laminoplasty. Subjects comprised 31 patients with cervical myelopathy who underwent C3-6 laminoplasty preserving all bilateral muscles attached to the C2 and C7 spinous processes and were followed for ≥5 years. Clinical and radiological data were prospectively collected. Neurological status was assessed using Japanese Orthopaedic Association (JOA) score. Axial neck pain was graded as severe, moderate or mild. Sagittal alignment of the cervical spine and progression of ossification of the posterior longitudinal ligament (OPLL) were assessed by comparing serial lateral radiographs. Mean JOA score improved significantly from 10.6 before surgery to 14.7 at the time of maximum recovery, and slightly declined to 14.3 at final follow-up. In six patients who developed late deterioration, these conditions were unrelated to the cervical spine. As of final follow-up, only one patient (3.2%) had complained of axial neck pain persisting for 5 years. Although progression of OPLL was found in 63.6% of patients, none had experienced neurological deterioration due to this progression. At final follow-up, sagittal alignment of the cervical spine was more lordotic than before surgery. Medium-term outcomes of C3-6 laminoplasty were satisfactory. Frequencies of persistent axial neck pain and loss of cervical lordosis after surgery remained significantly decreased for ≥5 years postoperatively.

Preservation of muscles attached to the C2 and C7 spinous processes rather than subaxial deep extensors reduces adverse effects after cervical laminoplasty.

STUDY DESIGN: Prospective study. OBJECTIVE: To examine whether preservation of subaxial deep extensor muscles plays any significant role in reducing axial neck pain and unfavorable radiologic changes after cervical laminoplasty in patients with cervical spondylotic myelopathy and to confirm the benefits of preserving muscles attached to the C2 and C7 spinous processes. SUMMARY OF BACKGROUND DATA: Axial neck pain and unfavorable radiologic changes after cervical laminoplasty have been reported to mostly result from detachment of cervical extensor muscles, particularly muscles attached to the C2 and C7 spinous processes. Other surgeons have reported that preservation of subaxial deep extensor muscles reduces these adverse effects after cervical laminoplasty. METHODS: Subjects comprised 36 patients with cervical spondylotic myelopathy who underwent C3-C6 open-door laminoplasty and were followed up for >24 months. Of these, 18 consecutive patients underwent our modified laminoplasty (muscles-preserved group) and the remaining 18 consecutive patients underwent the conventional procedure (muscles-disrupted group). Both procedures preserved all muscles attached to the C2 and C7 spinous processes. Subaxial deep extensor muscles on the hinged side were also preserved in the muscles-preserved group. Radiologic and clinical data were prospectively collected. RESULTS: Both groups achieved equal neurologic improvement. Frequencies of axial neck pain showed no significant differences between groups. This value did not vary according to the side of preservation of subaxial deep extensor muscles or the side of muscle disruption. Postoperative loss of lordosis and range of motion of the cervical spine also demonstrated no significant difference between groups. CONCLUSION: These results indicate that preservation of subaxial deep extensor muscles plays no significant role in reducing axial neck pain and unfavorable radiologic changes after cervical laminoplasty, supporting the hypothesis that these adverse effects after laminoplasty largely result from detachment of muscles attached to the C2 and C7 spinous processes.

Induction of early degeneration of the adjacent segment after posterior lumbar interbody fusion by excessive distraction of lumbar disc space.

OBJECT: Spinal fusion at the L4-5 disc space alters the normal biomechanics of the spine, and the loss of motion at the fused level is compensated by increased motion and load at the other unfused segments. This may lead to deterioration of the adjacent segments of the lumbar spine, called adjacent-segment disease (ASD). In this study, the authors investigate the distracted disc height of the fused segment, caused by cage or bone insertion during surgery, as a novel risk factor for ASD after posterior lumbar interbody fusion (PLIF). METHODS: Radiographic L3-4 ASD is defined by development of spondylolisthesis greater than 3 mm, a decrease in disc height of more than 3 mm, or intervertebral angle at flexion smaller than -5 degrees . Symptomatic ASD is defined by a decrease of 4 points or more on the Japanese Orthopaedic Association scale. Eighty-five patients with L-4 spondylolisthesis treated by L4-5 PLIF underwent follow-up for more than 2 years (mean 38.8 +/- 17.1 months). The patients were divided into 3 groups according to the final outcome. Group A comprised those patients without ASD (58), Group B patients had radiographic ASD (14), and Group C patients had symptomatic ASD (13). RESULTS: The L4-5 disc space distraction by cage insertion was 3.1 mm in the group without ASD, 4.4 mm in the group with radiographic ASD, and 6.2 mm in the group with symptomatic ASD, as measured using lateral spinal radiographs just after surgery. Multivariate analysis showed that distraction was the most significant risk factor. CONCLUSIONS: The excessive distraction of the L4-5 disc space during PLIF surgery is a significant and potentially avoidable risk factor for the development of radiographic, symptomatic ASD.