Orthopedics

Feature Article 

Segmental Subtotal Corpectomy and Reconstruction With Titanium Cage and Anterior Plate for Multilevel Ossification of the Posterior Longitudinal Ligament

Tao Zhang, MD; Ying Guo, MD; Naiwu Hu, MD; Limin Chen, MD; Yin Wu, MD; Yang Wang, MD; Libing Liu, MD; Chengbin Zhao, MD

Abstract

This retrospective study assessed the outcomes of segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation for multilevel ossification of the posterior longitudinal ligament. The study included 34 patients with multilevel ossification of the posterior longitudinal ligament who underwent segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation from June 2005 to May 2011. Clinical and radiologic data were obtained. Neurologic function was evaluated by Japanese Orthopedic Association scores before and after surgery. No death, paralysis, or other surgically associated injuries occurred. After surgery, the bone graft fusion was firm, with no cases of lack of postoperative bone fusion, broken or loose titanium plate and screws, dislodged titanium cage, or injury to the vertebral artery, nerve root, or spinal cord. Cerebrospinal fluid leakage occurred in 2 cases. Japanese Orthopedic Association scores improved from 6.74±1.82 preoperatively to 11.33±3.5 postoperatively (P<.05). Neurologic outcomes were excellent or good in 84.21% of patients at follow-up of 1 to 6 years. No postoperative cerebrospinal fluid leakage occurred. Reasonable and skilled operation of the pneumatic drill is the key to successful surgery. Anterior corpectomy with titanium cage reconstruction and plate fixation and drilling applications can directly remove the hypertrophy and ossification of the posterior longitudinal ligament and relieve spinal cord compression. This technique retained the integrity of the vertebrae, increasing the possibility of bone graft healing. Segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation can be used for the treatment of multilevel ossification of the posterior longitudinal ligament. [Orthopedics. 2016; 39(6):e1140–e1146.]

Abstract

This retrospective study assessed the outcomes of segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation for multilevel ossification of the posterior longitudinal ligament. The study included 34 patients with multilevel ossification of the posterior longitudinal ligament who underwent segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation from June 2005 to May 2011. Clinical and radiologic data were obtained. Neurologic function was evaluated by Japanese Orthopedic Association scores before and after surgery. No death, paralysis, or other surgically associated injuries occurred. After surgery, the bone graft fusion was firm, with no cases of lack of postoperative bone fusion, broken or loose titanium plate and screws, dislodged titanium cage, or injury to the vertebral artery, nerve root, or spinal cord. Cerebrospinal fluid leakage occurred in 2 cases. Japanese Orthopedic Association scores improved from 6.74±1.82 preoperatively to 11.33±3.5 postoperatively (P<.05). Neurologic outcomes were excellent or good in 84.21% of patients at follow-up of 1 to 6 years. No postoperative cerebrospinal fluid leakage occurred. Reasonable and skilled operation of the pneumatic drill is the key to successful surgery. Anterior corpectomy with titanium cage reconstruction and plate fixation and drilling applications can directly remove the hypertrophy and ossification of the posterior longitudinal ligament and relieve spinal cord compression. This technique retained the integrity of the vertebrae, increasing the possibility of bone graft healing. Segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation can be used for the treatment of multilevel ossification of the posterior longitudinal ligament. [Orthopedics. 2016; 39(6):e1140–e1146.]

Surgical methods and procedures for treating multilevel ossification of the posterior longitudinal ligament remain controversial. Posterior approaches, such as laminectomy and laminoplasty, have been accepted as alternative methods for decompression of the spinal cord.1 Laminoplasty decompresses the spinal cord by widening the spinal canal through reconstruction of the lamina.2–4 The ossified lesion can be removed with an anterior approach that requires advanced surgical skills.5–7 Contiguous multisegmental corpectomy and fusion are often performed, but this technique has been associated with several complications, such as graft displacement and a high nonunion rate.8,9

It has been reported that anterior decompression is more effective than posterior decompression in the treatment of ossification of the posterior longitudinal ligament.4,10 Therefore, when selecting surgical procedures for the treatment of ossification of the posterior longitudinal ligament, surgeons should consider the safety of the procedure as well as adequate decompression of the spinal cord.

Segmental corpectomy decompression has been reported to be a safe, effective method to treat multilevel ossification of the posterior longitudinal ligament because it reduces complications and improves stability.11 Titanium cages can provide an effective support to restore cervical lordosis and prevent collapse, dislodgment, and kyphosis of long segmental bone grafts.12,13 In addition, the use of anterior cervical plating increases fusion rates for anterior diskectomy.14 This article reports surgical results and complications in 34 patients with multilevel ossification of the posterior longitudinal ligament who underwent segmental anterior subtotal corpectomy with titanium cage reconstruction and anterior plate fixation from June 2005 to May 2011.

Materials and Methods

Patient Population

This retrospective study included 34 patients (21 men and 13 women) with multilevel ossification of the posterior longitudinal ligament who underwent segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation from June 2005 to May 2011 (Table). Institutional review board approval was obtained, and all subjects provided informed consent. Average age at surgery was 52.62 years (range, 34–72 years). Mean duration of disease was 11.18 months (range, 2–38 months). No patient had a history of acute spinal injury. Major clinical manifestations were hypesthesia in the trunk and extremities (26 cases), weakness in the extremities (25 cases), decreased abdominal reflex or cremasteric reflex (22 cases), tendon hyperreflexia (24 cases), positive Hoffmann's sign (25 cases), and positive Babinski sign (22 cases). Neurologic function was evaluated in accordance with the guidelines of the Japanese Orthopedic Association (JOA).15 Preoperative JOA scores were 0 to 4 in 6 cases, 5 to 8 in 19 cases, and 9 to 12 in 9 cases. Mean preoperative JOA score was 6.97. Patients received conservative treatment for at least 2 months before surgery to relieve mild neck and shoulder pain. Patients whose symptoms and signs did not improve or were aggravated after conservative treatment underwent surgery.


Demographic and Clinicopathologic Features of Patients Before Surgerya

Table:

Demographic and Clinicopathologic Features of Patients Before Surgery

Radiologic Evaluation

All patients had plain radiography, 64-slice spiral computed tomography (CT), and magnetic resonance imaging (MRI) before surgery. Radiologic results showed that ossification of the posterior longitudinal ligament involved 3 or 4 vertebrae in all cases (Figure 1), specific segments in 17 cases (Figure 1), and contiguous segments in 9 cases (Figure 2). In 12 cases, mixed ossification of the posterior longitudinal ligament was noted. Mean Pavlov ratio calculated on radiograph was 0.69 (range, 0.38–0.78). Mean occupying rate calculated on CT images was 36.4% (range, 23.3%–62.3%). On MRI, spinal hyperintensity on T2-weighted images was found in 29 cases, and of these, vertebral disk herniation and osteophytes at the posterior margins of the vertebrae were found in 19 cases.


Radiologic images of a 53-year-old man with spinal cord compression as a result of disk hernia and ossification of the posterior longitudinal ligament with 4 segments treated with anterior segmental subtotal corpectomy and reconstruction with a titanium cage. The Japanese Orthopedic Association score improved from 8 preoperatively to 15 postoperatively. Sagittal magnetic resonance imaging of the cervical spine showing grade 3 compression as a result of ossification of the posterior longitudinal ligament and maximum compression at the disk level (A). Axial magnetic resonance imaging scanograms showing disk hernias at C3–C4 and C4–C5 (B) and C5–C6 and C6–C7 (C). Sagittal 3-dimensional computed tomography scans showing segmental-type ossification of the posterior longitudinal ligament from C3 to C7 (D). Axial computed tomography scanograms showing ossified ligaments with different shapes (E). Preoperative (F) and postoperative (G) radiographs showing anterior segmental subtotal corpectomy and reconstruction with a titanium cage.

Figure 1:

Radiologic images of a 53-year-old man with spinal cord compression as a result of disk hernia and ossification of the posterior longitudinal ligament with 4 segments treated with anterior segmental subtotal corpectomy and reconstruction with a titanium cage. The Japanese Orthopedic Association score improved from 8 preoperatively to 15 postoperatively. Sagittal magnetic resonance imaging of the cervical spine showing grade 3 compression as a result of ossification of the posterior longitudinal ligament and maximum compression at the disk level (A). Axial magnetic resonance imaging scanograms showing disk hernias at C3–C4 and C4–C5 (B) and C5–C6 and C6–C7 (C). Sagittal 3-dimensional computed tomography scans showing segmental-type ossification of the posterior longitudinal ligament from C3 to C7 (D). Axial computed tomography scanograms showing ossified ligaments with different shapes (E). Preoperative (F) and postoperative (G) radiographs showing anterior segmental subtotal corpectomy and reconstruction with a titanium cage.


Radiologic images of a 57-year-old man with continuous cervical ossification of the posterior longitudinal ligament treated with subtotal C3–C6 corpectomy and decompression and reconstruction with 2 titanium mesh cages filled with bone grafts. Preoperative radiographs (A, B), cervical plain computed tomography scans (C, D, E), and magnetic resonance images (F) showing compression of the spinal cord. Postoperative radiographs showing satisfactory reduction of compression with 2 titanium mesh cages and plates (G).

Figure 2:

Radiologic images of a 57-year-old man with continuous cervical ossification of the posterior longitudinal ligament treated with subtotal C3–C6 corpectomy and decompression and reconstruction with 2 titanium mesh cages filled with bone grafts. Preoperative radiographs (A, B), cervical plain computed tomography scans (C, D, E), and magnetic resonance images (F) showing compression of the spinal cord. Postoperative radiographs showing satisfactory reduction of compression with 2 titanium mesh cages and plates (G).

All patients underwent plain radiography during the follow-up period. Bony fusion was defined as the absence of radiolucent lines across the fusion site or around the screw sites and the presence of bridging trabeculae across the fusion site. If fusion was questionable, CT scan was performed to confirm bony fusion.

Surgical Technique

A 10-mm hole was drilled on the vertebra toward the lesion with a custom-designed trephine (diameter, 9 mm; length, 18 mm). From the created gutter, the inter-vertebral tissues and part of the vertebrae were removed with a pneumatic high-speed burr in combination with rongeurs and curettes until the posterior cortices of the vertebra and ossification of the posterior longitudinal ligament were exposed.

If the dura mater was ossified and adhered to the ossification of the posterior longitudinal ligament or if the ossification was too large, the ossified lesions were first thinned as much as possible because total removal of the ossification of the posterior longitudinal ligament is difficult and dangerous. The thinned ossified lesions were then cut off to reduce the residual ossified lesions as much as possible. If the dura mater closely adhered to the ossification of the posterior longitudinal ligament, anterior floating methods were used and the ossification of the posterior longitudinal ligament was separated from the vertebral wall,16 but remained attached to the dura mater. As a result, the ossified mass moved freely and did not compress the spinal cord. This floating method decompressed the dura mater and avoided dural tearing.

For patients with ossification of the posterior longitudinal ligament involving more than 3 vertebrae, at least 1 vertebra was kept. A titanium cage filled with autologous bone fragments from the excised vertebrae was used to restore the bone defect. Anterior cervical titanium plating was performed across the vertebrae for fixation. A negative pressure drainage tube was placed after internal fixation and removed 24 hours after surgery. Patients were allowed to move 3 days after surgery, with use of a cervical collar to immobilize the neck.

Evaluation of Neurologic Function

For each patient, neurologic function was evaluated by JOA scores17 before and after surgery. The improvement rate was calculated according to the following equation: improvement rate, %=[(postoperative score-preoperative score)/(17-pre-operative score)]×100%. Patients were categorized into 4 groups according to the rate of improvement: excellent, greater than 75%; good, 50% to 74%; fair, 25% to 49%; and poor, less than 25%.

Statistical Analysis

Statistical analysis was performed with SPSS version 13.0 software (SPSS Inc, Chicago, Illinois). Values are presented as mean±SD. Analysis of variance was used to assess the statistical significance between preoperative and postoperative JOA scores. P<.05 was considered statistically significant.

Results

Clinical Data

Mean surgical time was 2.3 hours (range, 1.5–2.5 hours), and mean blood loss was 150 mL (range, 50–600 mL). No death, paralysis, or other surgery-associated injuries occurred.

A secondary operation was performed in 1 patient 4 hours after the initial surgery. The patient suddenly felt weak and lost movement in both upper extremities. Muscle strength in the upper extremities was grade 0, but muscle strength in the lower extremities was grade 3. The patient was conscious, but aphasic. The secondary operation was performed immediately to remove the internal fixation, explore the wound, stop the bleeding, and remove the blood clot. Symptoms were relieved 1 hour after the second surgery, and muscle strength in the upper and lower extremities was grade 4. The patient had normal language function.

In addition, 1 patient suddenly had difficulty breathing and had wheezing 6 and 8 hours after surgery, respectively. Tension at the incision site had increased, but negative pressure drainage was normal. Bedside tracheotomy was performed to remove the hematoma. Symptoms were relieved after treatment, and the tracheotomy tube was removed later.

After surgery, symptoms improved in all patients. Decreased numbness in the extremities occurred in 26 cases, and decreased heaviness in the lower extremities was noted in 28 cases. An increase in muscle strength occurred in 24 cases. A decrease or disappearance of the sensory level on the trunk occurred in 17 cases. Improvement in urination and defecation occurred in 5 cases. In 14 patients, symptoms improved further during the follow-up period of 12 months to 6 years.

Neurologic Outcomes

Neurologic function was evaluated by JOA scores at postoperative follow-up of 12 months to 6 years (average follow-up, 22 months). Groups with excellent, good, fair, and poor function included 17 cases, 12 cases, 4 cases, and 1 case, respectively. Thus, postoperative neurologic outcomes were excellent or good in 85.29% of patients. The JOA scores improved significantly from 6.74±1.82 preoperatively to 11.33±3.5 postoperatively (P<.05), suggesting that subtotal corpectomy with titanium cage reconstruction and internal fixation significantly improved neurologic function.

Complications and Management

Complications during anterior corpectomy included cerebrospinal fluid leakage in 2 cases. This leakage was discovered during surgery and was caused by severe adhesion of the dura mater with ossification of the posterior longitudinal ligament. The patients had no other complications, such as lack of postoperative bone fusion, broken or loose titanium plate and screws, dislodged titanium cage, or injuries to the vertebral artery, nerve root, or spinal cord.

Radiologic Findings

During postoperative follow-up, 30 patients underwent MRI or CT at 3 weeks to 7 months (Figure 1). For all patients, plain radiographs also were performed 1 week, 3 months, and 6 months after surgery. Bony fusion was achieved in all patients by the 1-year postoperative follow-up (Figure 2). Radiologic findings showed sufficient decompression of the spinal cord and morphologic recovery of the dural sac and cerebrospinal fluid. No broken, loose, or dislodged titanium plates were observed. Preoperative spinal hyperintensity on T2-weighted images in 16 cases did not change postoperatively.

Discussion

Ossification of the posterior longitudinal ligament is treated surgically to reduce compression of the spinal cord. Anterior corpectomy decompression has been reported to be effective in the treatment of patients with ossification of the posterior longitudinal ligament because of its direct decompression.5,7,18 However, direct decompression cannot be performed in patients with severe adhesion of the posterior longitudinal ligament to the dura mater. Complete removal of ossification of the posterior longitudinal ligament can result in dural tearing and leakage of cerebrospinal fluid.

Posterior decompression, including laminectomy and laminoplasty, is an alternative treatment for multilevel ossification of the posterior longitudinal ligament. However, Chen et al4 found that anterior corpectomy with fusion was more effective than posterior laminoplasty in improving postoperative JOA scores and neurologic function in the treatment of multilevel ossification of the posterior longitudinal ligament. Kawano et al10 studied 75 patients with ossification of the posterior longitudinal ligament and found that anterior decompression produced a significantly higher rate of neurologic improvement (78%) compared with posterior decompression (46.1%) at 65-month follow-up.

When anterior decompression is used to treat ossification of the posterior longitudinal ligament involving multiple vertebrae, 3 or more contiguous vertebral bodies are partially removed and reconstructed with autologous grafts in a titanium cage with an anterior plate. This surgical technique has a poor fusion rate, and the complication rate increases as the number of decompression levels increases.8,19,20 In addition, contiguous multilevel corpectomy decompression decreases the stability of the vertebral column. Therefore, compared with contiguous corpectomy decompression, segmental corpectomy decompression is more feasible for the treatment of multilevel ossification of the posterior longitudinal ligament by reducing complications and improving stability. Segmental corpectomy decompression has been reported to be a safe, effective method to treat multilevel ossification of the posterior longitudinal ligament.11

Further, single-level subtotal corpectomy, combined with single-level or multilevel decompression, has been performed to treat multilevel cervical myelopathy.21 In the current study, 2-level segmental subtotal corpectomy, combined with single-level or 2-level decompression, was performed in 34 patients with multilevel ossification of the posterior longitudinal ligament. Bony fusion was observed in all patients at 1-year postoperative follow-up. The surgical technique used in this study achieved good mechanical stability, likely because the anterior plating prevented micromotions. Barsa et al22 reported that micromotion was a major risk factor for union failure in noninstrumented multilevel cervical fusion.

Titanium cages provide appropriate, biomechanically stable fixation and prevent collapse, dislodgment, and kyphosis of long segmental bone grafts.12,13 They also can provide effective support to restore cervical lordosis and maintain inter-vertebral height. When packed with bone grafts, this construct is sufficiently rigid to resist compression. The addition of an anterior plate helps to resist rotational forces, thus providing mechanical stability for the cage. Anterior cervical plating increases fusion rates for 2-level anterior cervical diskectomy and fusion.14 In this study, all patients had achieved bony fusion at 1-year follow-up, suggesting that the technique used was effective in the treatment of multilevel ossification of the posterior longitudinal ligament.

Postoperative hematoma is a severe complication of ossification of the posterior longitudinal ligament that can aggravate neurologic symptoms caused by compression of the spinal cord. In this study, postoperative hematoma occurred in 2 patients. Complete hemostasis during surgery is crucial to avoid postoperative hematoma.

In this study, patients were followed for 12 months to 6 years. Bony fusion occurs an average of 5 months postoperatively (range, 3–8 months).23 In this study, bony fusion occurred in all patients, including those with 6-month follow-up. There were 2 patients who were not followed or were lost to follow-up. The patient with the longest follow-up (6 years) had no subsidence or collapse of the metal cage. The findings suggest that segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation may produce good long-term outcomes in patients with multilevel ossification of the posterior longitudinal ligament. Future studies are needed to study long-term outcomes in these patients.

Conclusion

Segmental subtotal corpectomy with titanium cage reconstruction and anterior plate fixation was performed in 34 patients with multilevel ossification of the posterior longitudinal ligament. Good to excellent neurologic outcomes were achieved at follow-up of 12 months to 6 years, and no hardware complications occurred. The findings suggest that segmental subtotal corpectomy and reconstruction with titanium cage reconstruction and anterior plate fixation can be used to treat multilevel ossification of the posterior longitudinal ligament.

References

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Demographic and Clinicopathologic Features of Patients Before Surgerya

Patient No./Sex/Age, yDisease Duration, moHyperintensity on T2-Weighted ImageWeakness in ExtremitiesHypesthesia in Trunk and ExtremitiesHoffmann's SignBabinski SignJapanese Orthopedic Association Scoreb
1/M/464+Positive10
2/M/533PositivePositive9
3/F/5611+PositivePositive6
4/F/483Positive10
5/M/3826+Positive4
6/M/6712+Positive3
7/M/428+PositivePositive7
8/M/439+Positive7
9/F/4812+PositivePositive8
10/F/3814+Positive11
11/F/5622+PositivePositive3
12/F/6514+PositivePositive7
13/M/4216+Positive8
14/F/722Positive12
15/M/579+Positive5
16/M/526+Positive6
17/M/518+Positive8
18/F/4915+PositivePositive5
19/M/4718+Positive3
20/M/574Positive8
21/M/463+Positive11
22/M/629+PositivePositive5
23/F/575+PositivePositive8
24/F/485Positive9
25/F/5016+Positive8
26/M/494+Positive6
27/M/5420+Positive3
28/F/5112+PositivePositive8
29/M/7138+Positive4
30/M/6730+PositivePositive3
31/F/433+Positive10
32/M/486+Positive6
33/F/569+PositivePositive7
34/M/604+PositivePositive9
Authors

The authors are from the Fourth Affiliated Hospital of Harbin Medical University, NanGang District, Harbin, People's Republic of China.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Chengbin Zhao, MD, Fourth Affiliated Hospital of Harbin Medical University, 37 YiYuan St, Nan-Gang District, Harbin 150001, People's Republic of China ( zhaochengbin111@sina.com).

Received: April 16, 2015
Accepted: July 06, 2016
Posted Online: August 30, 2016

10.3928/01477447-20160819-07

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