Journal of Clinical Neuroscience 21 (2014) 2102–2106

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Clinical Study

Surgical strategies for ossified ligamentum flavum associated with dural ossification in thoracic spinal stenosis Jingcheng Sun 1, Chao Zhang 1, Guangzhi Ning, Yulin Li, Yan Li, Pei Wang, Shiqing Feng ⇑ Department of Orthopedics, Tianjin Medical University General Hospital, Tianjin Heping District, Anshan Road 154, Tianjin 300052, PR China

a r t i c l e

i n f o

Article history: Received 6 August 2013 Accepted 8 February 2014

Keywords: Dura mater Myelopathy Ossification Ossification of the ligamentum flavum Thoracic spinal stenosis

a b s t r a c t We describe two surgical strategies for treating thoracic spinal stenosis (TSS) with ossification of the ligamentum flavum (OLF) and dural ossification (DO), and discuss their postoperative efficacy. From January 2004 to June 2008, 147 patients underwent TSS surgery. Thirty three of those with intraoperative evidence of OLF and DO were included in the present study. Based on the different intraoperative treatment of the dura, these 33 patients were divided into two groups: Group A, 17 patients who had their dura slit and the ossification excised, and Group B, 16 patients treated by floating the ossified dura by thinning it with a drill. All patients underwent outpatient follow-up. Pre- and postoperative Japanese Orthopaedic Association (JOA) scores and recovery rates were evaluated. The mean follow-up period was 42 months. The incidence of DO with OLF in TSS was 22%. At 1 year follow-up, the mean JOA score improved from 5.12 ± 1.17 to 6.94 ± 0.90 in Group A and from 5.25 ± 1.34 to 7.13 ± 1.41 in Group B. Additionally, the mean JOA score improved from 5.18 ± 1.24 to 7.03 ± 1.16 in TSS patients with DO and from 5.52 ± 1.21 to 7.21 ± 1.18 in TSS patients without DO. The increased cross-sectional area of the pre- and postoperative dural sac at the level of stenosis suggested that decompression was complete. Both decompression methods are feasible for curing TSS with OLF and DO. Moreover, slitting the dura for ossified dura and ligamentum flavum removal to relax the spinal cord is a safe and reliable method. Even though it increased the surgical difficulties and risks, DO did not affect postoperative neurological recovery. Ó 2014 Elsevier Ltd. All rights reserved.

1. Introduction

2. Materials and methods

Over the last several decades, researchers have reached the consensus that ossified ligamentum flavum (OLF) is a primary contributor to thoracic spinal stenosis (TSS). Publications from Japan have highlighted the unusually high prevalence of this condition in an Asian population [1,2]. The disease usually occurs in adults between 40 and 60 years of age and frequently affects the lower thoracic spine. When treating TSS with OLF associated with dural ossification (DO), surgeons encounter specific difficulties and risks. The neurological symptoms of these patients may not improve or become worse when an inadequate surgical procedure is used. Therefore, choosing an appropriate surgical procedure is important. To the best of our knowledge, no detailed report concerning surgical strategies for DO in TSS has been published. In the present retrospective study, we describe 33 patients and two different procedures for treating ossified dura.

2.1. Patient population

⇑ Corresponding author. Tel.: +86 13920286292, fax: +86 022 8836 6139. 1

E-mail address: [email protected] (S. Feng). These authors have contributed equally to the manuscript.

http://dx.doi.org/10.1016/j.jocn.2014.02.027 0967-5868/Ó 2014 Elsevier Ltd. All rights reserved.

Between January 2004 and June 2008, 33 patients underwent surgery in our Spine Surgery Department for DO associated with OLF induced TSS (Table 1). These patients are still undergoing follow-up examinations. The inclusion criteria for patients were systematic physical examination, complete preoperative investigations (thoracic radiography, CT scan, MRI) and intraoperative evidence which confirmed OLF associated with DO. The patient population included 18 men and 15 women aged 35 to 75 years (mean 57.5 years) at the time of surgery. The patients had experienced symptoms for 15 days to 36 months (mean 9.1 months). The patients were divided into two groups according to the different operative procedures used for the dura. Group A (nine men and eight women) included patients whose dura was decompressed by slitting the dura. Group B (nine men and seven women) included patients whose dura was decompressed by floating the dura. The mean age at operation was 58.4 years and 56.4 years for Group A and B, respectively. Disease duration ranged

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J. Sun et al. / Journal of Clinical Neuroscience 21 (2014) 2102–2106 Table 1 Summary of patients with thoracic spinal stenosis caused by ossification of the ligamentum flavum associated with dural ossification Patient

Age, years, sex

Signs and symptoms (duration)

JOA

1 2 3 4 5 6 7 8 9 10

59, 61, 56, 45, 56, 70, 52, 65, 57, 58,

F F M M M F M F F M

11 12 13 14 15

51, 50, 59, 54, 52,

M M F F F

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

75, 73, 54, 61, 57, 42, 58, 65, 55, 35, 53, 50, 64, 56, 72, 58, 56, 49,

M M M M F M F F M F F F M M M F M M

Back pain, numbness and sensory deficit (4 mos) Lower limb weakness, numbness and hypesthesia below T9 (5 mos) Gait disturbance, numbness and sensory deficit (2 mos) Gait disturbance, leg pain (2 mos) Leg pain, numbness and gait disturbance (3 mos) Progressive paraparesis, urinary incontinence and gait disturbance (30 days) Lower–limb weakness, zonesthesia around chest (2 mos) Gait disturbance, numbness, fecal and urinary incontinence (2 mos) Back pain, numbness and lower limb weakness (12 mos) Post-trauma urinary incontinence, numbness and neurological claudication (30 days) Lower–limb weakness, numbness and sensory deficit (12 mos) Post-trauma numbness and gait disturbance (7 mos) Gait disturbance, numbness and hypesthesia below T12 (5 mos) Back pain, numbness and lower limb weakness (24 mos) Numbness, gait disturbance, sensory deficit and lower limb weakness (12 mos) Numbness, urinary incontinence (24 mos) Lower limb weakness, numbness and urinary incontinence (24 mos) Numbness, sensory deficit and lower limb weakness (6 mos) Numbness, sensory deficit and gait disturbance (3 mos) Gait disturbance, numbness and lower limb weakness (8 mos) Back pain, leg pain (36 mos) Zonesthesia around abdomen, numbness and gait disturbance (36 mos) Leg pain, numbness and gait disturbance (12 mos) Numbness and sensory deficit (24 mos) Lower limb weakness, gait disturbance and urinary incontinence (3 mos) Back pain and hypesthesia below T6 (2 mos) Gait disturbance, numbness and hypesthesia below T5 (3 mos) Gait disturbance, numbness and lower limb weakness (4 mos) Gait disturbance, numbness and lower limb weakness (2 mos) Back pain, leg pain, fecal and urinary incontinence (15 days) Back pain, numbness and hypesthesia below T6 (2 mos) Leg pain, numbness and lower limb weakness (5 mos) Numbness and sensory deficit (12 mos)

Max compression

Laminectomy

Follow-up, mos

Pre

Post

7 4 6 6 6 4 6 5 7 5

7 6 7 7 7 6 8 6 9 8

T9–11 T9–11 T10–12 T9–12 T3–4 T2–3 T6–8 T9–11 T10–12 T11–12

T9–11 T9–11 T10–12 T10–12 T2–4 T1–4 T6–8 T9–11 T10–12 T11–12

36 36 12 12 34 34 63 63 62 60

5 5 6 4 4

7 7 8 7 7

T10–11 T10–11 T9–11 T11–12 T11–12

T10–11 T10–11 T9–11 T11–12 T11–12

60 60 59 28 48

4 3 4 6 5 4 6 6 5 3 7 6 7 3 4 7 6 5

6 6 6 8 6 6 8 7 7 4 9 8 9 6 6 10 8 7

T9–11 T9–11 T11–12 T2–3 T6–8 T11–L1 T6–8 T4–5 T11–12 T6–8 T4–5 T3–5 T8–9 T7–8 T5–T8 T2–3 T10–11 T10–11

T9–11 T9–11 T11–12 T2–3 T6–8 T12–L1 T6–8 T4–5 T11–12 T6–8 T4–5 T2–4 T8–9 T7–8 T6–8 T3–4 T10–11 T10–11

19 43 58 58 52 58 57 48 12 13 14 16 42 44 49 49 48 47

F = female, JOA = Japanese Orthopaedic Association, M = male, Max = maximum, mos = months, post = postoperatively, pre = preoperatively.

from two to 120 months (mean 34.1 months) in Group A and two to 96 months (mean 22.1 months) in Group B.

2.2. Surgical procedure All 33 patients underwent decompression under general anaesthesia. Laminectomy was performed for all patients [3]. The range of resection included one lamina above and one lamina below the diseased segments, and the facet joints were preserved. A C-arm image intensifier x-ray was used to determine the presence and position of the lesions pre- and postoperatively. The laminectomy was restricted to the levels of compression according to the preoperative plan and intraoperative analysis. After routine exposure of the laminae of the diseased segment, the spinous process was excised using rongeurs. Simultaneously, the laminae were flattened using rongeurs or a high-speed burr. The ligamentum flavum was incised from the normal intervertebral space to explore whether the OLF and compressed dura were adhered to each other. Two different methods were used to manage the ossified dura mater in the patients in the two groups. In Group A, the dura mater was incised using a knife blade and a nerve stripper to visualise the spinal cord. Then the dura was pulled away to enlarge the visible field. Generally, the void between the ossification and the spinal cord can be utilized to excise the entire ossification. The dural defect was repaired in different ways according to the area of the defect, as described in Table 2.

In Group B, the entire ossification was thinned as much as possible using a high-speed burr, and, instead of excising the dura, it was dissociated from the ossification to cause it to bulge naturally. Care was taken to avoid damaging the nerve roots and spinal cord during the dissociation drilling. A subfascial drain was placed in all patients, and the wound was sutured closed in layers. To prevent spinal instability, internal fixation was employed for patients whose laminectomy level spanned both the thoracic and lumbar spine regions. During the operation, to prevent the development of spinal cord edema and secondary injury to the neurons, methylprednisolone (500 mg) was infused intravenously after decompression. 2.3. Postoperative evaluation All 33 patients were followed closely postoperatively and underwent repeated physical examination for pain, function and neurological status. The patients were scored according to the Japanese Orthopaedic Association (JOA) scoring system for cervical myelopathy with the modification for thoracic myelopathy of excluding the upper extremity scores [4]. The postoperative outcome was evaluated using the JOA scoring system and by calculating the recovery rate as (postoperative JOA score preoperative JOA score)/(11 preoperative score)  100. The outcomes were ranked based on the recovery rate as good (>50%), fair (10–49%), unchanged (0–9%), or worse ( 0.05). Additionally, we compared the pre- and postoperative JOA scores for the patients with and without DO, as shown in Table 5; no significant difference in efficacy was found between these groups (t = 0.63, p > 0.05). 4. Discussion The process by which the ligamentum flavum and dura ossify together to form a huge ossification that causes myelopathy is slow. OLF is a pathological ectopic ossification that forms from the spinal ligament [11]. It usually affects the lower thoracic spine, especially T9–T12 [12]. Over the last several decades, researchers have reached the consensus that surgery is the optimal treatment for TSS [13]. It is being increasingly recognised that the cause of TSS is OLF. As Aizawa et al. [14] reported, there is a high prevalence of this disease among the Japanese. Recently, OLF has gained the attention of researchers throughout the world, and an increasing

Table 4 Japanese Orthopaedic Association score of two different methods of treating ossified dura in thoracic stenosis with ossified ligamentum flavum

Preoperative 12 months postoperatively

Group A, slitting dura

Group B, floating the dura

5.12 ± 1.17 6.94 ± 0.90

5.25 ± 1.34 7.13 ± 1.41

Data are presented as mean ± standard error of the mean.

Table 5 Japanese Orthopaedic Association score for thoracic spinal stenosis with and without dural ossification

Preoperative 12 months postoperatively

TSS with DO

TSS without DO

5.18 ± 1.24 7.21 ± 1.17

5.52 ± 1.21 7.21 ± 1.18

Data are presented as mean ± standard error of the mean. DO = dural ossification, TSS = thoracic spinal stenosis.

number of reports have been published [2,15,16]. Therefore, it is important to completely understand the various facets of this disease. 4.1. Imaging features As observed, DO is usually caused by OLF. Therefore, on the axial CT scan, the extensive ossification, hyperattenuation of bone and integration of ossification can be found. This feature has been reported by Aizawa et al. and Sato et al., and named the ‘‘comma sign’’ [5] as shown in Figure 2. Additionally, the ‘‘tram track sign’’ has been reported by several authors [5,17]. However, we have noted that the tram track sign can be a sign of incomplete ossification of the ligamentum flavum which is rarely seen with true DO in our clinical observation. Figure 2B demonstrates the typical imaging for the tram track sign and this patient proved to not have DO at intraoperative examination. This requires further observation and evidence accumulation. 4.2. Surgical strategy for DO According to the outcomes of these 33 patients, there were no significant differences between the two surgical methods of treating the DO. However, the floating method is more likely to traumatise the dura due to the possibility of the drill slipping. Additionally, the remnant of ossification that remains afterwards may allow recurrence of ossification. However, during follow-up, we have not yet observed any re-ossification. Undoubtedly longterm follow-up is needed to confirm these results. It is simple and safe with the slitting dura procedure to resect the ossification, but careful attention should be paid to the treatment of the dural defect to avoid cerebrospinal fluid leak. Additionally, internal fixation may be used to avoid postoperative instability of the

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lamina and the entire vertebra. When several lower segments of the lamina of the vertebra were resected, internal fixation was used selectively [17]. Although the use of internal fixation is still in dispute, considering the factors that may lead to instability, a pedicle screw rod system was used in two patients. Instability did not occur during follow-up.

[2]

[3]

[4]

5. Conclusions [5]

Both dural slitting and floating methods for decompression are feasible for treatment of DO. With thinning the lamina and bony fragments, slitting the dura for ossified dura and ligamentum flavum removal in order to relax the spinal cord is a safe and reliable method for curing TSS caused by DO. Despite increasing the surgical difficulties and risks, DO did not have an influence on postoperative neurological recovery.

[6] [7] [8]

[9]

Conflicts of Interest/Disclosures

[10]

The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication.

[11] [12]

Acknowledgements [13]

We express thanks to the staff of Medical Record Room of Tianjin Medical University General Hospital for their help with looking up records. This study was supported by grants from the National Natural Science Foundation of China (81330042, 81070982, 81201400), and Tianjin science and technology plan projects (13RCGFSY19000).

[14] [15] [16] [17]

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Surgical strategies for ossified ligamentum flavum associated with dural ossification in thoracic spinal stenosis.

We describe two surgical strategies for treating thoracic spinal stenosis (TSS) with ossification of the ligamentum flavum (OLF) and dural ossificatio...
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