Anterior Decompression and Fusion for Ossification of the Posterior Longitudinal Ligament of the Thoracic Spine: Procedure and Clinical Outcomes of Transthoracic and Transsternal Approaches
Kazuichiro Ohnishi
1, Kei Miyamoto
2, Hideo Hosoe
2, and Katsuji Shimizu
2Introduction
Progressive myelopathy caused by ossifi cation of the posterior longitudinal ligament (OPLL) of the thoracic spine has a poor prognosis, and early diagnosis and surgical treatment are necessary [1–4]. The clinical out- comes of posterior decompression have been reported to be poor, and anterior decompression is thought to be reasonable for surgical treatment of this disease [1–6]. The range over which spinal compression exists often shows multilevel involvement, and extensive anterior decompression is often required. In our depart- ment, the anterior procedure via the transthoracic or transsternal approach is used to accomplish safe and signifi cant anterior decompression.
Surgical treatment is indicated for cases of progres- sive myelopathy due to thoracic OPLL. The anterior compression of the spinal cord may be observed by magnetic resonance imaging (MRI), myelography, and computed tomography (CT) myelography.
Surgical Technique
The choice of surgical procedure in our department is anterior decompression and fusion through the ante- rior approach. The transsternal approach is indicated for cases of OPLL located above T3, and the transtho- racic approach is indicated for those below T4.
Transsternal Approach
The patient is placed in the supine position, and a lon- gitudinal incision is made between the manubrium and xiphoid process. The sternum is split along the midline using a bone saw. Resection of the left sternoclavicular
joint is sometimes necessary for decompression of T1.
The trachea and esophagus are retracted to the right, the left common carotid artery is retracted to the left, and the brachiocephalic trunk is retracted inferiorly.
Meticulous dissection of these vessels with the help of a cardiovascular surgical team enables the better expo- sure of the surgical fi eld required for anterior decom- pression. Retraction of these structures allows exposure of the anterior aspect of the upper thoracic spine.
Corpectomy and anterior decompression are then performed with an air drill under a microscope. A graft from the fi bula or iliac bone is inserted into the decompression space. After irrigation, a suction tube is inserted and the wound is closed. Immobilization with a halo vest is applied postoperatively.
Transthoracic Approach
The patient is placed in the lateral decubitus position, and a skin incision is made over the rib scheduled for resection. A scapular elevator is sometimes necessary to expose the middle to upper thoracic spine. Resection of the crus of the diaphragm may be necessary when using the approach to the thoracolumbar lesion. The parietal pleura covering the vertebral body is incised, and the posterior parts of the vertebral bodies and OPLL are resected under a microscope. The resected rib is cut into struts and inserted into the space where decompression was performed. We use spinal instrumentation, as it secures solid fusion and enables ambulation earlier after surgery. The pleural defect over the implant is repaired with a Gore-Tex sheet to avoid pulmonary injury. After irrigation, a chest tube is inserted into the extrapleural space, and continuous negative pressure of 10 cm H2O is applied postoperatively. The drain tube is removed when the pleural effusion becomes less than 100 ml/day.
Patients and Methods
Between May 1997 and February 2003, we treated nine patients (three men, six women) with a mean age of 56.3
1Department of Orthopedic Surgery, Hirano General Hospital, 176-5 Kurono, Gifu 501-1192, Japan
2Department of Orthopedic Surgery, Gifu University School of Medicine, 1-1 Yanagido, Gifu 501-1193, Japan
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232 K. Ohnishi et al.
years (range 44–68 years) with OPLL of the thoracic spine. The mean length of time between the onset of symptoms and diagnosis was 37.3 months (range 13–65 months). Symptoms included weakness of the lower limbs in fi ve cases, sensory disturbance in the trunk or lower limbs (or both) in nine cases, urinary symptoms in four cases, and back pain in one case. Hyperfl exia and pathological refl exes of the lower limbs were observed in all nine cases. The location of OPLL was between C7 and L3, and the most commonly affected levels were T2 and T8. Surgical approaches were the transthoracic approach in fi ve cases, transsternal approach in three cases, and a combination of the two approaches (two-staged operation) in one case.
The magnitude of surgical invasion was assessed based on the operating time and blood loss. Preopera- tive and postoperative symptoms were evaluated by the modifi ed Japanese Orthopaedic Association (JOA) score for thoracic myelopathy (the JOA score for cervi- cal myelopathy excludes points for the upper extremi- ties) [1–4,7,8]. Wilcoxon’s signed-rank test was used for comparison of pre- and postoperative JOA scores and subscores (lower limb motor function, sensory function, bladder function). The JOA score recovery rate was calculated using the method of Hirabayashi et al. [9]. The fi nal results were classifi ed into fi ve groups according to recovery rate: excellent (75%–100%), good (50%–74%), fair (25%–49%), unchanged (0%–24%), and worse (<0%).
Results
The mean operating time was 443 min (320–650 min) with the transthoracic approach and 345 min (285–
390 min) with the transsternal approach. The mean blood loss was 1630 g (305–3010 g) with the transtho- racic approach and 671 g (560–780 g) with the trans- sternal approach. Regarding the JOA score, the mean value for lower limb motor function (total score 4 points) was increased from 0.9± 0.8 to 1.6 ± 0.7 points after surgery (P= 0.068), the mean value for sensory
function (total score 4 points) was increased from 1.0± 1.1 to 1.4± 1.3 (P = 0.345), the mean value for bladder function (total score 3 points) was increased from 1.9± 1.1 to 2.6± 0.5 (P = 0.068), and the total score (total score 11 points) was increased from 3.8± 2.6 to 5.8 ± 2.6 (P = 0.059) (Fig. 1). Although the changes in the values were not statistically signifi cant, strong trends toward increases in value were observed for lower limb motor function, bladder function, and the total score.
The mean recovery rate was 18.6%± 25.4% (0%–67%) for lower limb function, 7.4%± 52.3% (75% to 100%) for sensory function, 28.7% ± 38.4% (0%–100%) for bladder function, and 19.6%± 31.8% (−33% to 60%) for the total score. The fi nal result was excellent in no cases, good in two cases (transsternal and transthoracic approaches in one case each), fair in two cases (trans- thoracic two cases), unchanged in four cases (trans- sternal two cases, transthoracic one case; combination of the two approaches one case), and worse in one case (transthoracic). Postoperative complications included a subcutaneous abscess in the skin incision in one case (transthoracic), postoperative kyphotic deformity in one case (transthoracic), and paresis of recurrent laryngeal nerve in two cases (both transsternal).
Case Presentation
A 65-year-old man developed muscle weakness of the upper extremity and underwent anterior decompres- sion and fusion between C5 and C6 at age 49 years. Five years later he visited our department because he had developed weakness of the lower limbs, sensory distur- bance below the umbilicus, and urinary dysfunction.
OPLL and anterior compression of the spinal cord were detected between T1 and T2 on MRI, myelography, and CT-myelography (Figs. 2, 3, 4). The preoperative JOA score was 0 points for lower limb motor function, 0 points for sensory function, 1 point for bladder function, and 1 point for the total score. Anterior decompression and fusion was performed through the transsternal approach between C6 and T2. A bone graft
Fig. 1. Comparison of each parameter and total Japanese Orthopaedic Association (JOA) scores pre- operatively and postoperatively. Lower limb func- tion, bladder function, and the total score showed tendencies to increase after the operation
Fig. 2. Preoperative T2-weighed sagittal magnetic resonance imaging (MRI). Compression of the spinal cord by ossifi cation of the posterior longitudinal ligament (OPLL) was observed between T1 and T2
Fig. 4. Preoperative computed tomography (CT) myelogram at the level of T1–T2. The spinal cord was compressed by massive OPLL
was harvested from the fi bula (Fig. 5). The muscle weakness, sensory disturbance, and urinary symptoms decreased postoperatively. Postoperative JOA scores were 2 points for lower limb motor function, 3 points for sensory function, 2 points for bladder function, and 7 points for the total score. The recovery rate was 60%, and the fi nal result was classifi ed as good.
Discussion
The prognosis of myelopathy caused by OPLL of the thoracic spine is poor, and diagnosis of this disease is often diffi cult, with a differential diagnosis from other disorders (e.g., motor neuron disease) being necessary [1–3]. Clinicians must be aware of the potential for this disease in patients without myelopathy that does not include symptoms of the upper limbs; early diagnosis and surgical treatment are required in cases where there is progressive worsening of symptoms [1–3].
Surgical methods used for its treatment are classifi ed into anterior decompression and posterior decompres- sion. The prognosis of posterior decompression repre- sented by laminectomy is poor because of insuffi cient decompression and postoperative kyphotic deformity [1–6,10–12]. Anterior decompression has been per- formed using the anterior approach [1–7,10–15], poste-
rior approach [8,16], and lateral approach [10,12–14,17].
Although these methods seem to provide effective decompression of the spinal cord, the anterior approach is associated with some problems, such as surgical inva- siveness, skill required to perform the procedure, and Fig. 3. Preoperative myelogram spinal compression is obser- ved at the level of T1–T2
234 K. Ohnishi et al.
postoperative complications (including major vessel injury, leakage of liquor, recurrent laryngeal nerve injury, pulmonary disorder, intercostal nerve injury, and postoperative paresis among others) [4,10,13].
We have used the transthoracic and transsternal approaches for anterior decompression of the thoracic spine, as they provide suffi cient exposure to perform safe, extensive decompression and fusion [1–5,7, 11,14,15]. Fujimura et al. reported a negative correla- tion between the recovery rate and age, preoperative severity of myelopathy, and duration of illness [1,2,15].
Similarly, in the present study the clinical outcomes for patients with a long duration of symptoms were poor.
Therefore, we emphasize the need for early diagnosis and treatment of progressive myelopathy caused by OPLL of the thoracic spine.
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976 Fig. 5. Postoperative T2-weighed sagittal MRI. Spinal com-
pression between T1 and T2 was alleviated by decompression and fusion between C6 and T2 via the transsternal approach
