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Yasuji Kato, Motoki Iwasaki, Takeshi Fuji, Kazuo Yonenobu and Takahiro Ochi

Object. This retrospective study was performed to assess the long-term results of cervical laminectomy in treating ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

Methods. The authors reviewed medical records in 44 of 52 patients who underwent cervical laminectomy between 1970 and 1985 (mean follow up 14.1 years). The neurological recovery rate after laminectomy was 44.2% after 1 year and 42.9% after 5 years. The surgical outcome was maintained after 5 years but worsened between 5 and 10 years postsurgery: the recovery rate at the last follow-up review was 32.8%. Using multivariate stepwise analysis, the preoperative factors that affected clinical results were found to be the age at operation, the severity of preexisting myelopathy, and a history of trauma. Late neurological deterioration was observed in 10 (23%) of 44 patients. The earliest deterioration occurred at 1 year and the latest was at 17 years postsurgery (mean 9.5 years). The most frequent cause of deterioration was trauma due to a fall (six patients), followed by ossification of the ligamentum flavum (three patients). Postoperative spread of the OPLL was noted in 70% of the patients, but it was clearly the cause of neurological deterioration in only one of them. After laminectomy, postoperative progression of kyphotic deformity was observed in 47% of patients, but these changes did not cause neurological deterioration.

Conclusions. The authors recommend early surgical decompression for OPLL because the outcome is better for younger patients and for those with a higher score as measured by the Japanese Orthopedic Association's system.

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Yoshihiro Mukai, Shota Takenaka, Noboru Hosono, Toshitada Miwa and Takeshi Fuji

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. Clinical trial registration no.: UMIN000010069 (www.umin.ac.jp/ctr/index.htm).

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Shota Takenaka, Noboru Hosono, Yoshihiro Mukai, Toshitada Miwa and Takeshi Fuji

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.

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Shota Takenaka, Kosuke Tateishi, Noboru Hosono, Yoshihiro Mukai and Takeshi Fuji

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.

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Shota Takenaka, Yoshihiro Mukai, Noboru Hosono, Kosuke Tateishi and Takeshi Fuji

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.

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Hiroyuki Aono, Tetsuo Ohwada, Noboru Hosono, Hidekazu Tobimatsu, Kenta Ariga, Takeshi Fuji and Motoki Iwasaki

Object

Neurological deterioration due to spinal epidural hematoma (SEH) is a rare but significant complication of spinal surgery. The frequency of hematoma evacuation after spinal surgery is reportedly 0.1%–3%. The objective of this study was to investigate the symptomatology of SEH and the frequency of evacuation for each surgical procedure after spinal decompression surgery.

Methods

This is a retrospective study of 26 patients who underwent SEH evacuation after spinal decompression surgery between 1986 and 2005. During this period, 6356 spinal decompression surgeries were performed. The factors studied were the frequency of SEH evacuation for each surgical procedure, symptoms, time to SEH evacuation, comorbidities, and neurological recovery.

Results

The frequency of SEH evacuation was 0.41% (26 of 6356) for all operations. The frequency for each surgical procedure was 0% (0 of 1568) in standard lumbar discectomy, 0.50% (8 of 1614) in lumbar laminectomy, 0.67% (8 of 1191) in posterior lumbar interbody fusion, 4.46% (5 of 112) in thoracic laminectomy, 0.44% (4 of 910) in cervical laminoplasty, and 0.21% (1 of 466) in cervical anterior spinal fusion. Nine patients had comorbidities involving hemorrhage. Spinal epidural hematoma evacuation was performed between 4 hours and 8 days after the initial operation. Whereas severe paralysis was observed within 24 hours in most patients undergoing cervical and/or thoracic surgery, half of the patients undergoing lumbar surgery had symptoms of SEH such as leg pain or bladder dysfunction after suction drain removal. The shorter the period to evacuation, the better were the results of neurological recovery.

Conclusions

Postoperative SEH was most frequent after thoracic laminectomy. In cervical and thoracic surgeries, symptoms of SEH were noted within 24 hours, mostly severe paralysis, and almost half of the lumbar surgery patients had symptoms after suction drain removal.

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Takashi Kaito, Noboru Hosono, Takahiro Makino, Noriyoshi Kaneko, Masato Namekata and Takeshi Fuji

Object

Double-door laminoplasty using hydroxyapatite (HA) spacers has been widely performed for compressive cervical myelopathy and has provided good neurological outcome. Although HA spacers are used for preventing reclosure of the opened laminae, they are often displaced or dislocated from their original position. The authors investigated the incidence and patterns of postoperative HA spacer displacement to determine the reasons for this unfavorable event.

Methods

Eighty-six patients with compressive myelopathy underwent double-door laminoplasty in which a total of 278 HA spacers were used. The displacement of HA spacers and opened laminae were assessed using postoperative lateral radiographs and CT scans.

Results

Postoperative dorsal migration > 2 mm was found in 116 (42%) of 278 implanted HA spacers. In addition, 33 (38%) of 86 HA spacers rotated > 10° and 29 (34%) of the 86 opened laminae tilted > 10°. Moreover, deformation of the newly formed spinal canal was observed in 51 (59%) of 86 cases, and bone fusion between the HA spacer and spinous process was achieved in only 15 (8.7%) of 172 cases. Neurological worsening and neck pain, however, were not associated with displacement of HA spacers or deformation of the spinal canal.

Conclusions

In double-door laminoplasty, postoperative displacement of the HA spacer with deformation of the enlarged spinal canal occurred frequently. Hydroxyapatite spacers tend to become displaced after surgery. Placing the HA spacer at the base of the spinous process close to the dura mater may prevent postoperative displacement.

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Noboru Hosono, Masato Namekata, Takahiro Makino, Toshitada Miwa, Takashi Kaito, Noriyoshi Kaneko and Takeshi Fuji

Object

Although posterior lumbar interbody fusion (PLIF) is an excellent procedure to attain circumferential decompression, it is technically demanding and can lead to various surgical complications. The authors retrospectively reviewed consecutive patients with nonisthmic spondylolisthesis who underwent PLIF to reveal the incidence and risk factors for perioperative complications of PLIF.

Methods

A total of 240 patients underwent PLIF. The fusion level was at L4–5 in 220, L3–4 in 18, and L5–S1 in 2. The medial walls of the fusion segment's facet joints were resected, and the VSP Spine System was used for the pedicle screw instrumentation. The operations were performed by 7 surgeons, who were divided into 4 groups according to their level of experience with spinal surgery.

Results

The average operation time was 175 ± 49 minutes, and the estimated blood loss was 746 ± 489 ml. A total of 90 patients (37.5%) experienced complications; 41 (17%) experienced transient neurological complications, and 18 (7.5%) experienced permanent neurological complications. The mean neurological score according to the Japanese Orthopaedic Association improved from 14.3 ± 3.8 to 24.7 ± 4.0 in the patients without complications and from 14.8 ± 3.6 to 24.0 ± 3.9 in the patients with complications. Multivariate analysis concerning the relationship between complications and risk factors (operation time, estimated intraoperative blood loss, and surgeon experience) revealed that operation time was the only significant risk factor for complications.

Conclusions

Perioperative complications of PLIF were more frequent in this homogeneous study group than in other studies of various implants. Total excision of the facet joints might preclude neurological complications.

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Yoshihiro Mukai, Noboru Hosono, Hironobu Sakaura, Takahiro Ishii, Tsuyoshi Fuchiya, Keiju Fijiwara, Takeshi Fuji and Hideki Yoshikawa

Object. Although controversy exists regarding surgical treatment for rheumatoid subaxial lesions, no detailed studies have been conducted to examine the efficacy of laminoplasty in such cases. To discuss indications for laminoplasty in rheumatoid subaxial lesions, the authors retrospectively investigated clinical and radiological outcomes in patients who underwent laminoplasty for subaxial lesions.

Methods. Thirty patients (11 men and 19 women) underwent laminoplasty for rheumatoid subaxial lesions. The patients were divided into those with mutilating-type rheumatoid arthritis (RA) and those with nonmutilating-type RA according to the number of eroding joints. As of final follow-up examination laminoplasty resulted in improvement of myelopathy in 24 patients (seven with mutilating- and 17 with nonmutilating-type RA) and transient or no improvement in six (five with mutilating- and one with nonmutilating-type RA). In the group with mutilating-type RA, significantly poorer results were displayed (p < 0.05). In most patients preoperative radiographs demonstrated vertebral slippage less than or equal to 5 mm at only one or two levels. Postlaminoplasty deterioration of subaxial subluxation and unfavorable alignment change occurred significantly more often in patients with mutilating-type RA (p < 0.05).

Conclusions. Patients with nonmutilating-type RA can benefit from laminoplasty for myelopathy due to subaxial lesions.

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Takashi Kaito, Noboru Hosono, Yoshihiro Mukai, Takahiro Makino, Takeshi Fuji and Kazuo Yonenobu

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°. 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.