Objective:To assess the midterm clinical and radiological outcomes of internal fixation and fusion for the treatment of Hirayama disease and to evaluate the clinical significance and value of this procedure.Methods:In the study,36 patients were treated with anterior cervical internal fixation and fusion.The clinical outcomes including muscle strength and atrophy were recorded.The radiological outcomes including range of motion of cervical spine and the cross-sectional area of spinal cord at each level on MRI scan were measured before and at 3 month,1 year and 2 years follow-up time points after surgery.Results:(1) Clinical outcomes:all the patients showed no further progression of symptoms except one patient with mild progression of muscular weakness and atrophy.As the time passed by,the ratio of the patients with muscle strength and atrophy improvement increased.There were 26.5 ％ of patients in 3 months,36.0％ in 1 year and 85.7％ in 2 years who experienced muscle strength improvement.8.8％ of patients in 3 months,24.0％ in 1 year and 35.8％ in 2 years felt muscle atrophy improvement.And 12 of the 14 patients showed improved muscle strength and atrophy at the end of 2 years period follow-up.(2) Radiological outcomes:the range of motion (ROM) of C2-C7 was significantly decreased after the operation.The ROM of preoperation was 62.25° ±2.10° and that of 2 years postoperation was 13.67° ± 7.51°(P ＜ 0.01).The spinal cord was of no compression on flexion MRI.The cross-section area of spinal cord on MRI was significantly increased only at C6 level (P ＜0.05) at the end of three months follow-up.The level of increased cross-section area rose to C4-C5-C6 levels (P ＜0.01) in 1 year and to C4-C5-C6-C7 levels at the end of 2 years follow-up P ＜ 0.05).The cross-section area increased 15.60％ at C4,19.08％ at C5,21.60％ at C6 and 23.91％ at C7 with significant difference (P ＜0.05) 2 years after the operation.Conclusion:Anterior cervical internal fixation and fusion is an effective surgical treatment for Hirayama disease and may provide preferable midterm clinical and radiological outcomes.This procedure has clinical significance and value in terms of control of the progression and outcome of this disease.

BACKGROUNDS: Cervical posterior decompression surgery is used to relieve ventral compression indirectly by incorporating a backward shift of the spinal cord, and this indirect decompression is bound to be limited. This study aimed to determine the decompression limit of posterior surgery and the effect of the decompression range. METHODS: We retrospectively reviewed the data of 129 patients who underwent cervical open-door laminoplasty through 2008 to 2012 and were grouped as follows: C4-C7 (n = 11), C3-C6 (n = 61), C3-C7 (n = 32), and C2-C7 (n = 25). According to the relative location of spinal levels within a decompression range, the type of decompression at a given level was categorized as external decompression (ED; achieved at the levels located immediately external to the decompression range margin), internal decompression (ID; achieved at the levels located immediately internal to the decompression range margin), and central decompression (CD; achieved at the levels located in the center, far from the decompression range margin). The vertebral-cord distance (VCD) was used to evaluate the decompression limit. The C2-C7 angle and VCD on post-operative magnetic resonance images were analyzed and compared between groups. The relationship between VCD and decompression type was analyzed. Moreover, the relationship between the magnitude of the ventral compressive factor and the probability of post-operative residual compression at each level for different decompression ranges was studied. RESULTS: There was no significant kyphosis in cervical curvature (> -5°), and there was no significant difference among the groups (F = 2.091, P = 0.105). The VCD of a specific level depended on the decompression type of the level and followed this pattern: ED < ID < CD (P < 0.05). The decompression type of a level was sometimes affected by the decompression range. For a given magnitude of the ventral compressive factor, the probability of residual compression was lower for the group with the larger VCD at this level. CONCLUSIONS Our study suggests that the decompression range affected the decompression limit by changing the decompression type of a particular level. For a given cervical spinal level, the decompression limit significantly varied with decompression type as follows: ED < ID < CD. CD provided maximal decompression limit for a given level. A reasonable range of decompression could be determined based on the relationship between the magnitude of the ventral compressive factor and the decompression limits achieved by different decompression ranges.