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Eiichi Murakami, Daisuke Kurosawa and Toshimi Aizawa

OBJECTIVE

The authors evaluated the outcomes of sacroiliac joint (SIJ) arthrodesis via an original anterior approach to the upper anterior surface of the SIJ in patients with a minimum of 5 years’ follow-up.

METHODS

The authors performed anterior SIJ arthrodesis in 45 patients between 2001 and 2015. Of these patients, 27 (11 men and 16 women; mean age at surgery 49 [24–86] years) were followed up for a minimum of 5 years (average 113 months, range 61–157 months). In the 14 patients in the earlier period of this study, the authors used an anterior approach to expose the SIJ by separating the iliac muscle from the iliac bone and performed internal fixation. In the 13 patients later in the study, the authors changed to a pararectal approach, which involved an incision along the lateral border of the rectus abdominal muscle. Then, extraperitoneally, the upper anterior surface of the SIJ was exposed between the psoas major muscle and the iliac muscle.

RESULTS

Among the 27 patients, 21 had unilateral anterior arthrodesis alone, 4 required additional posterior arthrodesis, and 2 required pelvic ring arthrodesis because of later pain on the opposite side. In the 21 patients with a unilateral anterior arthrodesis, outcome according to the modified Macnab criteria was excellent in 7, good in 11, and fair in 3. Outcomes were excellent, good, fair, and poor in 1 patient each among the 4 with additional posterior fusion. Outcomes were good and poor for 1 patient each among those with pelvic ring arthrodesis. All 27 patients demonstrated bone union of the SIJ on CT. Lateral femoral cutaneous neuralgia developed in 7 of the 27 patients; 6 patients had undergone the initial anterior method and 1 the later method.

CONCLUSIONS

Anterior SIJ arthrodesis was effective in most patients with severe SIJ pain resistant to conservative therapy. This approach has the advantage of direct curettage and bone graft into the wide area of the SIJ, which result in good bone union. In particular, the authors’ current pararectal approach could decrease the potential risk of lateral cutaneous injury.

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Linghua Kong and Wenbao Wang

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Vincent C. Traynelis

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Takashi Kusakabe, Fumio Kasama, Toshimi Aizawa, Tetsuro Sato and Shoichi Kokubun

Object

The authors define facet cyst as a cyst located beside the facet joint and exhibiting a communication with the joint, as demonstrated on arthrography and subsequent computed tomography (CT) of the joint space. The purpose of this study was to determine the pathogenesis of facet cysts based on their radiological and histological features.

Methods

Forty-six juxtafacet cysts in 45 patients (26 men and 19 women, age range 41–82 years) were surgically treated after evaluation by arthrography and subsequent CT scanning. A communication channel between the cyst and the joint was confirmed in all cases and thus the lesions were designated facet cysts. In almost all patients the involved facet joint showed moderate to severe degeneration. After a thorough preoperative radiological evaluation, these cysts were excised en bloc by medial facetectomy with the entire ligamentum flavum. The specimens were cut axially at the maximum diameter and were histologically investigated.

Morphologically, the cysts exhibited three shapes, appearing as: 1) a small protrusion, 2) a semicircular cyst, or 3) a round cyst. The cyst walls consisted of elastic and collagen fibers undergoing fibrinoid degeneration, but no synovial lining cells were detected. The cystic cavities were regularly filled with fibrinoids, and myxoid degeneration was found particularly in the larger cysts.

Conclusions

Facet cysts are closely related to the degeneration of the neighboring facet joint. Analysis of the findings in this histological study suggests that there are several shapes of facet cysts. The authors propose that the shape could depend on the stage of the cyst’s development.

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Hiroshi Ozawa, Shoichi Kokubun, Toshimi Aizawa, Takeshi Hoshikawa and Chikashi Kawahara

Object

The authors analyzed a series of 118 cases of spinal dumbbell tumors to elucidate the feature of the tumors.

Methods

Of 674 cases of spinal cord tumors, the incidence of dumbbell tumors was studied. The tumors were analyzed, and the authors focus on the distribution of age and sex, the pathological diagnoses, their locations, Eden classification, and the surgical methods used.

Results

The incidence of dumbbell tumors was 18%. The mean patient age was 43 years, which was younger than that for all spinal cord tumors (mean 50 years). There were 11 patients younger than 10 years of age. The rate of dumbbell tumors in the cervical spine was significantly higher than that of all spinal cord tumors. Fifteen (18%) of the 81 schwannomas were observed in the C-2 nerve root, thus having a higher incidence than those in the other nerve roots. In 99 cases (84%), the tumors were removed through a hemilaminectomy with or without a facetectomy and posterior fusion. Of 118 cases, 69% of the tumors were schwannomas, and malignant tumors were found in 10 cases (8.5%). Seven (64%) of 11 patients younger than 10 years of age had malignant tumors. Three patients older than 10 years of age had malignant tumors, thus accounting for 2.8% of the 107 older patients.

Conclusions

The incidence of dumbbell tumors was 18%, and they are not uncommon. Malignant dumbbell tumors were more common in children younger than 10 years of age than in older patients.

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Toshimi Aizawa, Tetsuro Sato, Yasuhisa Tanaka, Koshi Kishimoto, Mika Watanabe and Shoichi Kokubun

✓ Intraspinal plasma cell granuloma, which is a nonneoplastic entity, is extremely rare. To date, only four cases have been documented in the spinal meninges. The authors report the first case of a C7—T1 intramedullary plasma cell granuloma. After excision of the lesion, the patient's gait and bladder dysfunction improved. This plasma cell granuloma initially showed no delineated mass on T1-weighted magnetic resonance (MR) images, low signal intensity on T2-weighted images, and was well enhanced after administration of gadolinium diethylenetriamine pentaacetic acid. The latter MR imaging modality should help to detect this tumorous lesion. Histologically, the granuloma needs to be distinguished from lymphoplasmacyte-rich meningioma and plasmacytoma.

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Toshimi Aizawa, Tetsuro Sato, Hirotoshi Sasaki, Takashi Kusakabe, Naoki Morozumi and Shoichi Kokubun

Object

Data obtained in patients with thoracic myelopathy caused by ossification of the ligamentum flavum (OLF) were retrospectively reviewed to clarify clinical features and surgical outcomes in the Japanese population.

Methods

Seventy-two patients who underwent surgery for OLF-induced myelopathy in the Miyagi Prefecture, Japan, between 1988 and 2002 were observed for at least 2 years. Clinical data were collected from medical and operative records. The patients were evaluated pre- and postoperatively using the modified Japanese Orthopaedic Association (JOA) scale (maximum score 11). The relationships among various factors (age, sex, and preoperative duration of symptoms) affecting the preoperative severity of myelopathy and postoperative improvement were also examined.

Conclusions

In this series the surgical outcome was relatively good and depended on the severity of myelopathy; thus early and correct diagnosis is required to avoid poorer results. The male/female ratio was 3.2 and the mean patient age at surgery was 61 years for men and 68 for women. The patients commonly noticed numbness or pain in their lower legs or gait disturbances. In a total of 104 decompressed intervertebral disc levels, more than 80% of the ossified ligaments were at the T9–10 level or lower. The mean preoperative JOA score of 5.1 improved to 7.9 after an average of 46 months. The postoperative results statistically depended on the preoperative severity of myelopathy. Among studies of patients with OLF-related myelopathy, the present study had the largest sample size, which should help clarify the clinical features of OLF myelopathy.

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Hiroshi Ozawa, Takashi Kusakabe, Toshimi Aizawa, Takeshi Nakamura, Yushin Ishii and Eiji Itoi

The authors describe 2 patients with C-2 nerve root tumors in whom the lesions were located bilaterally in the lateral portions of the C1–2 interlaminar space and compressed the spinal cord when the atlantoaxial joint was rotated.

The patients were adult men with neurofibromatosis. Each presented with clumsiness of both hands and motor weakness of the extremities accompanied by spastic gait. Magnetic resonance imaging of the cervical spine performed with the neck in the neutral position showed tumors at the bilateral lateral portion of the C1–2 interlaminar space without direct compression of the spinal cord. The spinal cord exhibited an I-shaped deformity at the same level as the tumors in one case and a trapezoidal deformity at the same level as the tumors in the other case. Computed tomography myelography and MRI on rotation of the cervical spine revealed bilateral intracanal protrusion of the tumors compressing the spinal cord from the lateral side. The tumors were successfully excised and occipitocervical fusion was performed.

The tumors were pushed out into the spinal canal from the bilateral lateral portion of the interlaminar spaces due to rotation of the atlantoaxial joint. This was caused by a combination of posteromedial displacement of the lateral mass on the rotational side of the atlas and narrowing of the lateral portion of the interlaminar space on the contralateral side due to the coupling motion of the lateral bending and extension of the atlas. The spinal cord underwent compression from both lateral sides in a one-way rotation. Without sustained spinal cord compression, intermittent long-term dynamic spinal cord compression from both lateral sides should induce a pathognomonic spinal cord deformity and the onset of paralysis. To the authors' knowledge, there have been no reports of the present conditions—that is, the bilateral protrusion of tumors from the bilateral lateral portion of the C1–2 interlaminar spaces into the spinal canal due to atlantoaxial rotation.

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Shoichi Kokubun, Hiroshi Ozawa, Toshimi Aizawa, Ngo Minh Ly and Yasuhisa Tanaka

Object

Tethered cord syndrome (TCS) is a disorder involving an abnormal stretching of the tethered spinal cord caused by several pathological conditions and presents with a variety of neurological symptoms. Untethering (tethered cord release) is the gold standard treatment for TCS. However, untethering carries risks of spinal cord injury and postoperative retethering. To avoid these potential risks, the authors applied spine-shortening osteotomy to adult patients with TCS, and report on the surgical procedure and treatment outcomes.

Methods

Eight patients with TCS caused by a lipomyelomeningocele were surgically treated by the authors' original procedure of spine-shortening osteotomy. Six patients were male and 2 were females; average age at the time of surgery was 31 years old. Spine-shortening osteotomy was performed at the level of L-1 in all but 2 patients, in whom it was performed at T-12, with spinal fusion between T-12 and L-2 or T-11 and L-1 using a pedicle screw–rod system. The average follow-up period was 6.2 years and the patients' pre- and postoperative conditions were evaluated clinically and radiologically.

Results

Preoperatively, all patients displayed severe neurological deficits such as motor disturbance, muscle atrophy, and bladder dysfunction. Several months before surgery, all showed progressive symptoms. Those symptoms showed initial improvement in 6 patients and stabilized in 2 postoperatively, but the improved symptoms worsened again in 4 of the 6 patients. The osteotomized vertebrae were shortened by 21 mm on average, and all spines showed complete bone union without loss of correction. At the final follow-up evaluations, 6 patients showed stabilization as per the modified Japanese Orthopaedic Association score for thoracic myelopathy.

Conclusions

Spine-shortening osteotomy successfully helps reduce the spinal cord tension without causing direct neural damage. At minimum, it stabilized the patients' symptoms and/or helped delay neurological deterioration for a period of time. Spine-shortening osteotomy might be a feasible mode of treatment for adult TCS caused by a spinal lipoma.

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Haruo Kanno, Toshimi Aizawa, Hiroshi Ozawa, Takeshi Hoshikawa, Eiji Itoi and Shoichi Kokubun

The authors report a rare case of tethered cord syndrome with low-placed conus medullaris complicated by a vertebral fracture that was successfully treated by a spine-shortening vertebral osteotomy. The patient was a 57-year-old woman whose neurological condition worsened after a T-12 vertebral fracture because a fracture fragment and the associated local kyphotic deformity directly compressed the tethered spinal cord. An osteotomy of the T-12 vertebra was performed in order to correct the kyphosis, remove the fracture fragment, and reduce the tension on the spinal cord. Postoperative radiographs showed the spine to be shortened by 22 mm, and the kyphosis between T-11 and L-1 improved from 23° to 0°. Two years after the surgery, the patient's neurological symptoms were resolved. The bone union was complete with no loss of correction.