A improved posterior approaches in treating benign primary spinal tumor: a preliminary retrospective report.


 Background: Primary spine tumors are rare, accounting for fewer than 5% of all tumors of the spine. Unlike metastatic spine tumors, primary tumors localized to a single location offer the potential for true cure, so a minority of the primary benign lesions will require surgical treatment. Although the development of surgical techniques and instrumentation, few literatures had reported transpedicluar lateral debridement ,bone grafting ,and posterior instrumentation for primary spinal tumors. In the current study, we evaluate the efficacy of posterior instrumentation after transpedicular lateral debridement and bone grafting in patients with primary spinal tumors at a single institution.Methods: 21 patients (13 males and 8 females; average age 30 years) with primary spinal benign tumor underwent transpedicular lateral debridement, bone grafting, and instrumentation. The average follow-up period was 29.5 months (range 12–48months). The medical records and radiographic findings of the patients were reviewed.Results: all patients who had involvement of one vertebra. Before surgery, there were one patients with Frankel grade B, three with grade C, six with grade D, and eleven with grade E. During the last follow-up examination, in ten patients with neurological deficit, one patients improved one grade, seven patients improved two grades, and the neurologic status remained unchanged in two patients. Stable bone union was observed in all cases and the average time required for fusion was 6.5 months. The kyphosis Cobb angle improved from the preoperative average of 18.61 (range 0–48) to a average of 3.9(range 13 to 0) during the follow-up period. During the follow-up period, there were no grafts or instrumentation-related stabilization problems. There was no other recurrence of tumorsConclusions: transpedicluar lateral debridement ,bone grafting ,and posterior instrumentation are safe and effective methods in the surgical management of primary spine benign tumors.


Introduction
Primary spine tumors are rare, accounting for fewer than 5% of all tumors of the spine [1]. Unlike metastatic spine tumors, primary tumors localized to a single location offer the potential for true cure [2]. Over the past several decades, the survival of patients with spinal tumors has trended toward improvement. Furthermore, the improvement in medical and stereotactic radiotherapy for the treatment of tumors within the vertebral column has led to a decrease in surgery for spinal tumors.
However, surgery continues to play a critical role in the treatment of primary benign tumors with aggressive. Over the period of -20 years, surgical capability in the treatment of spinal tumor has been considerably enhanced by advances in anesthesia [3]. Depending on the location of the tumor and the goal of the operation, an anterior, posterior, or lateral approach, or a combination of them, may be used. Although the anterior approach often supply the most direct route to the lesion, it carry a high

Patient population
From January 2007 to December 2014, 21 patients with primary spine benign tumors at the first affiliated xiangya hospital of central south university of china formed the study group. The patients with the any following conditions were excluded: cervical lesion, tumor involving the posterior elements, destructed the vertebral cortex. Among them, There were 13 males and 8 females with an average age of 36.6 years (range 10-65 years). These patients' hospital medical records as well as radiographs were reviewed, and the demographic data were recorded. The preliminary diagnosis of primary spinal tumors was based on medical history, clinical symptoms, radiologic imaging (plain radiograph, computed tomography and magnetic resonance imaging),and pathological examination [4,5].

Symptoms and signs
All the patients exhibited back and waist pain,. Other symptoms ,such as limb weakness and diminished sensation below the sensory level of the tumor was evident in 10 patient at presentation.
The back and waist pain was evaluated by visual analog scale. The neurologic status was graded according to the Frankel scoring system [6]. Before surgery, there were one patients with grade B, three with grade C, six with grade D, and eleven with grade E (Table 2).

Preoperative management
Radiologic imaging (plain radiograph, computed tomography and magnetic resonance imaging) of the spine had been performed before surgery for all patients. The angle between the first normal vertebra above the lesion and the first normal vertebra below the lesion on the lateral radiographs was used to evaluated Kyphosis angle (cob angle) [7]. all patients who had involvement of one vertebrae, The average preoperative kyphosis angle was 18.61(range0-48). three-dimensional reconstruction computed tomography of the spinal lession was obtained to confirm the extent of bony destruction.
Routine laboratory procedures including chest radiograph, blood complete count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), tuberculin test, blood sugar, urine analysis, liver, and renal function tests were performed. Concurrent disease were routinely controlled, anemia and hypoproteinemia were rectified completely .then ,the surgery was carried out.

Operation indication
The indications for surgery were radiological demonstration of vertebral lesion, bone destruction with progressive kyphotic deformity and severe pain, poor response to medical treatment, deterioration in neurological status and mechanical instability

Operative technique
The operation was performed under general endotracheal anesthesia., the patients was placed at prone position. A midline longitudinal incision was made over the spinous process of the destructed vertebra. The posterior spinal construction was exposed, including the spinous processes, lamina, facet joints. In most cases, the screws could not be placed into the affected vertebra, the two superior and one inferior levels were incorporated into the instrumentation system with C-arm fluoroscopy assistance. The vertex reconstruction system (sofamor Danek, Medtronic, USA) was used in all 21 patients. The screws were fixed to a temporary rod on one side where neurological and radiological manifestation was lesser to distract of the involved level. Then the other transverse and lateral pedicle was bited, and the inner side of the pedicle was reserved (Fig.1A). Curettes of various sizes and angles were used from transpedicular lateral approach to remove lesions.completely (Fig.1B). A locking plate-and-screw system of appropriate length was used to achieve posterior fixation in all the patients. After washing with 20ml hydrogen peroxide and a large amount of physiological saline, Allograft bone (NO. SPSZGKDG/SD; Aorui Biological Material Co. Ltd., Shanxi, China) transplantation was used to reconstruct the Vertebral defect and maintain spinal integrity. The 8W units gentamicin was routinely used in the surgical area as local antibiotic therapy. At last,a local drainage tube was inserted from the incision to normal tissue, then closed the operative incision. Specimens from each patient were taken during the operation and subjected to pathologic examination.

Postoperative management
When the volume was <20ml per 24h, the drainage tube was pulled out. And intravenous antibiotic drugs were administered to all patients after surgery for three to five days. Patients remained in bed for 2 weeks and then walk around under the effective support of a spinal brace for 3-6months.
According to the general condition, all patients were asked to take nutritional support and performed early application of physical therapy and rehabilitation training after surgery. When the patients were discharged from our hospital, all patients were asked to reexamine at a month interval for the first 3 months, then every 3 months until 12 th month, and every 6 months up to 24 months after treatment ,and thereafter, once a year to the final follow-up. The follow-up care include radiographic examinations ,an assessment of neurologic status and pain.

Statistical analysis
A paired t test was used for comparison between preoperative and postoperative period on kyphotic angle, and VAS score. SPSS for Windows (version 15.0; SPSS, Inc., Chicago, IL, USA) was used for the analysis. A p value of less than .05 was customarily considered as statistical significant

Results
The surgeries were performed by the same surgeons, and all patients withstood surgery well. This patient was a 10-year-old man with moderate back pain for 3 months. Neurologic examination revealed grade E according to the Frankel scoring system. Preoperative Radiologic studies showed destruction of T9 vertebrae (Fig. 5). The patient underwent transpedicluar lateral debridement ,bone grafting ,and posterior instrumentation (Fig. 6). Pain relief was observed immediately after surgery .No recurrence of tumor was noted in this patient during the follow-up period (Figs.7). Discussion primary spinal tumors represent 5% of all primary bone tumors, and the latter occur in 0.8 to 8.0 per 100,000 population [8,9]. The more frequently encountered benign spinal tumors in surgical practice are osteoid osteoma and osteoblastoma, neural sheath tumors, aneurysmal bone cyst, benign fibrous tumor, giant cell tumor, and aggressive hemangioma. Although the most common primary benign lesions can be controlled by conservative treatments, unlike metastatic spine tumors, primary tumors localized to a single location offer the potential for true cure. A minority of the more common primary benign lesions will require surgical treatment. For the primary spinal tumors, the main surgery treatments included intralesional resection and en bloc resection. Then, benign primary tumors, such as aneurysmal bone cyst, giant cell tumor, and osteoblastoma, may be safely treated with intralesional resection, radiotherapy, or both to reduce the risk of surgical morbidity [10][11][12]. So for benign but aggressive lesions in the spine, intralesional resection is generally recommended [13,14].
Depending on the location of the tumors and the goal of the operation, some surgery approaches may be used, including an anterior, posterior, or lateral approach, or a combination of them. The most of primary benign tumors often only invade the vertebral body. ;therefore, the anterior, or lateral approach often can supply the most direct route to the lesion. But, the literatures reported that the anterior and lateral approaches often carry a high risk of the intraoperative or postoperative complications, such as adjacent organ and vascular injury, cerebral spinal fluid leak, or wound healing impairment. By contrast, the posterior approaches allows direct access to spinal cord and obviated the extensive bone resection generally required with anterior approaches [15]. As the meanwhile, most spine surgeons were greater familiarity with the posterior approach, thus, the spine surgeons were prefer to select the posterior approach for spinal decompression and stabilization.
Although posterior approach has some advantages compared with other approaches, it often sacrifice the parapophysis, facet joints, pedicle, or lamia for providing better operating field. So that it may don't maintenance of the spinal posterior column structural stabilization; meanwhile extension bone resection for providing greater intraoperative visualization will increase the amount of blooding loss. Then, the muscle tissue which is at the lateral of the complexity was stretched to opposite as much as possible, exposing a large enough field of view, and along the pedicle into the vertebral body, carried debridement. By using tanspendiclular lateral approach to cure primary spinal tumors., we can achieve adequate visualization ,only sacrifice the outside of pedicle and a part of facet joints. From our experiences, three reasons will induce us to select this approach. First of all, compared with other approaches, we can keep the stability of the spine posterior column to a greatest extent. Secondly, little bone resection can achieve adequate vislulization, Further, the amount of blooding loss will decrease. Then the circulation system can maintain stable and the blood pressure level can keep spinal cord perfusion. Last, by preserved the inside of the pedicle, we didn't destructed the integrity of the spinal canal. The spine cord still be protected by integral spinal canal. So we don't worry to injury spine cord, and the complication of the neurological injury and cerebral spinal fluid leak will decrease. Of course, there are also some limitations on this approach. Primary malignant tumors, metastatic tumors, multiply spinal tumors were not suitable to use this approach.

Conclusion
This preliminary study indicates that transpedicluar lateral debridement ,bone grafting ,and posterior instrumentation are safe and effective techniques with good clinical and radiologic outcomes for patients with primary spine tumor, especially for those who had benign tumor affecting one vertebrae. The procedure has the advantage of minor surgical invasion, less complications.