Neuronavigation of the spine has evolved over many years from plain radiography to fluoroscopy, to frameless stereotactic guidance and now ultimately to virtual fluoroscopy. The development of these newer technologies has aided surgeons in more accurate placement of instrumentation. Current neuro-navigation systems employ either frameless stereotactic systems or virtual fluoroscopy. By being able to place spinal instrumentation with millimetric or submillimetric accuracy, the changes for vascular or neurological injury are reduced. Other benefits such as decreased operating time, was well as reduced patient's and surgeon's exposure to ionizing radiation have also been reallized.

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In currently used expansive laminoplasties (ELAP) of the cervical spine, axial symptoms and loss of lordotic curvature have been significant postoperative problems. Recent papers have suggested that intraoperative injury to the paravertebral muscles is one of the major factors causing these problems. To prevent them, the author developed skip laminectomy and interlaminar decompression. Twenty-four patients of cervical spondylotic myelopathy (CSM) underwent one of either of these procedures. In skip laminectomy, consecutive four-level decompression between C3-4 and C6-7 is accomplished by removing every other laminae (C4 and C6), the cephalad half of the C5 and C7 laminae and the ligamenta flava at those four levels. The laminae and the spinous processes of C3, C5 and C7 as well as the attaching bilateral semi-spinalis cervicis and multifidus muscles are preserved. The lamina to be removed was selected by the preoperative radiological findings, bearing in mind the need to minimize damage to the posterior extensor mechanism including the deep extensor muscles. Instead of laminectomy, interlaminar decompression was performed at the level where anterior spinal cord compression was less significant. Interlaminar decompression is accomplished by removing the cephalad half of the lamina and the ligamentum flavum at the interlaminar space, leaving the spinous processes and the attaching muscles completely undisturbed. The amount of intraoperative blood loss averaged 37 grams. The operation time averaged 133 minutes. A soft collar was used postoperatively by 20 patients for an average period of 3.5 days. Five patients did not use one at all. The follow-up period averaged 8.5 months. The average recovery rate according to JOA scores was 64.3%. None of the patients complained of axial symptoms. Spinal curvature index calculated by Ishihara's method was reduced postoperatively in one of 24 patients. Skip laminectomy and interlaminar decompression are less invasive to the deep extensor muscles than ELAP.

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The correlation of pre-operative high signal intensity spinal cord lesions in MRI T2-weighted images and neurological symptoms is reported concerning 78 operated cases of cervical spondylosis and ossified posterior longitudinal ligaments. The case numbers in the 0, 1 and 2 high signal intensity lesions group were 41, 28 and 9 respectively. Pre- and post-operative ADL were significantly worse in the group with high signal intensity lesions. Pre- and postoperative Japan orthopedic surgical association score and Hirabayashi's improvement ratio were worse when high signal intensity lesions (T2-weighted MRI) became much more or much dense especially in the higher cervical region. The number of compressed spinal cord levels were also much more in these groups. So early diagnosis and operation is recommended in the case of multiple spinal cord compression lesions with progressive neurological symptom.

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Lumbosacral transitional vertebra is a common variation in the lumbosacral spine. It is not known whether the function of the nerve roots is altered when this variation is present. We retrospectively reviewed the charts of 46 patients who underwent microdiscectomy for lumbar herniated discs in our institution, and examined the preoperative neurological and radiological findings. We compared the distribution of muscle weakness and sensory disturbance of patients with lumbosacral transitional vertebra with those with normal configuration. Lumbarized S1 vertebra was found in 8 (17%) of the 46 patients. The level of the herniated disc was L5/S1 in all 8 cases. The distribution of motor weakness caused by S1 nerve root compression was significantly different in patients with lumbarized S1 from those with normal lumbosacral configuration. The pattern of muscle weakness caused by S1 root compression in patients with lumbarized S1 closely resembled that of L5 root compression in patients with normal configuration. A similar finding was obtained in the analysis of sensory disturbance. Our results suggest that the function of lumbosacral nerve roots is altered in patients with lumbarized S1 in such a way that the S1 nerve root serves the usual function of an L5 nerve root.

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新狭窄の要因としては男女差のみが有意であった.新狭窄の発生部位については, 全例固定の上位椎に狭窄性変化を生じた.一般的に腰仙椎固定を加えないいわゆるfloating fusionの場合には, 固定の下位隣接椎間関節に著明な変化と狭窄を生じるとされる[20, 23].今回の症例では, 固定に際しL4/5のみでなくL5/S1の部分にも移植骨が接するようにした例や, intercrestal lineがL4棘突起を通る例, L5横突起の大きな例などが含まれていた.これらではL5/S1椎間関節は制動的に働いていて変性性変化が起こりにくいと考えられた[11, 19].一方, 固定椎間の上位椎には過度の負荷がかかるため, 椎間関節の変化や黄色靭帯の肥厚を生じたり, 負荷に耐えきれずにヘルニアを生じたものと考えられる[14].固定術の目的は, 術後に腰椎が不安定化し, 症状が再発するのを予防することである[10, 18].しかし腰椎変性性すべり症に対して, 除圧術だけを行っても不安定化は2.7%のみであったとの報告[3]や, 後方要素を十分に除圧すると腰椎の不安定化を生じるが, 自家骨後側方固定ではすべりの防止効果はなかったとの報告など, 固定術の不要論もある[12].その一方で, 除圧術後有意にすべりが増加したとの報告もあり[8], 一般的には何らかの固定術が加えられることが多い[16].しかし経過が長期におよべば, 固定術の隣接椎間への影響は無視できず, 非責任椎間にpost fusion stenosisが発生する[14, 21, 22].固定術後, 隣接椎間に同様の変化をきたしunstable phaseとなれば, 後に隣接椎間にも固定術が必要となることも有り得る.また周辺支持組織の損傷も高度になることは避けられない.従って, 自然固定の時期にある症例では出来るだけ手術侵襲を少なくした除圧術にとどめるべきと考えられる.固定が必要と判断される場合, 固定力を重要視した内器具固定がもてはやされている昨今ではあるが, PLF in-situは, 固定術の中でも比較的侵襲が少なく今後も生き残って行く治療法であると思われる.その適応については, 除圧術のみの例や, 他の固定術などと長期観察結果を比較検討するべきであろう.

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Between January 1996 and December 1998, we have performed open carpal tunnel release through a small vertical skin incision on 26 hands in 25 patients. The skin incisions were limited to the proximal palm and were not extended to the wrist flexion crease. Preoperative paresthesia was relieved in all patients at discharge. Five complications occurred : one scar pain, two wound infections, two transient occurrences of palmar swelling. Since endoscopic carpal tunnel release has been introduced by Okutsu et al., open vs endoscopic methods have been compared, and their advantages and disadvantages have been discussed in the literature. Our technique of open carpal tunnel release is useful because of its simplicity, the lower cost of instrumentation and there being no extension of a vertical scar causing contracture of the wrist flexion crease.

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Cervical spine compromised by fibrous dysplasia, especially atlantoaxial instability in single bone involvement is extremely rare. Due to its scarce occurrence, definite treatment strategy and outcome could not be demonstrated yet. Surgical interventions to atlantoaxial instability in this setting are to be discussed further. The authors report a rare case of monostotic fibrous dysplasia involving the axis, which are accompanied by atlantoaxial instability due to the fracture of the odontoid process. For restabilization, transarticular screw fixation augmented with the Halifax interlaminar clamp and interspinous cadaveric graft was applied. The postoperative clinical course and radiograms showed favorable results, respectively. The relevant literatures concerning fibrous dysplasia and atlantoaxial instability were reviewed.

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Neurogenic intermittent claudication is a well known symptom of lumbar canal stenosis. But few people know that the symptom is also provoked by spinal cord lesions. Spinal intermittent claudication is a rare symptom caused by cord compression. We reported two cases with spinal intermittent claudication caused by ossification of the thoracic yellow ligament (OYL). In neither case was any other lesion depicted at any spinal level. Both patients experienced either hyperreflexia or sensory disturbances in the lower limbs. One of them also showed sensory niveau at T8. After surgical removal of OYL, intermittent claudication disappeared promptly, though other neurological findings remained unchanged. When thoracic OYL is the cause of the spinal intermittent claudication, we recommend operative removal as the treatment of first choice.

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