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Monosegmental combined anterior posterior instrumentation for the treatment of a severe lumbar tuberculous spondylodiscitis: case report and literature review

Spinal tuberculosis (Pott disease) can produce severe deformities when it is not properly treated. Long instrumentations through single or combined double approaches are usually required to prevent and correct the deformity. The authors present a case of severe deformity secondary to tuberculous spondylodiscitis in the lumbar spine treated with a monosegmental instrumentation through a double approach in a patient with idiopathic scoliosis. Deformity correction and infection resolution through debridement and arthrodesis is observed after one year of follow-up.


Introduction
Tuberculosis (TBC) disease is an unsolved problem in developing countries, more than 80% represent a pulmonary disease, tuberculous spondylitis (Pott disease) represent a site for extra-pulmonary tuberculosis, it occurs in less than 1% of patients with tuberculosis. 1 Tuberculous spondylitis typical presentation can involve anterior elements, usually two adjacent vertebral bodies and the intervertebral disc, and forms a paravetebral abscess. It rarely involves the posterior elements (neural arch tuberculosis) in isolation or combination with lamina, spinouts process, transverse process, articular process and pedicles, it can also make an epidural abscess and/or pyomyositis of the posterior spinal muscles.
The typical clinical presentation is back pain, but in those when it involves posterior elements also may lead to the sudden onset of a neurological deficit. 2 The treatment of tuberculosis spondylitis is based on the structural damage secondary to bone and ligamentary destruction. In general; debridement and anterior or posterior fusion procedures are required. Approximately 5% of the Tuberculosis in the spine develops severe deformities 3 and surgical treatment represents a challenge in this scenario.
Short-instrumentation has been described previously for one level Tuberculosum spondylodiscitis and mild deformities, 4 however, to our knowledge, monosegmental instrumentation for the treatment of a severe deformity lumbar TBC has not been described previously.
We present the treatment of lumbar TBC treated by debridement and one-level anterior posterior arthrodesis of the lumbar spine in a patient with mild scoliosis.

Case report
A 23-years old female was previously treated in other institution because of psoas tear during three months, because of progressive severe lumbar pain she consulted to our institution. There was no neurological compromise. Weight lost was not detected and any other symptom was associated to the lumbar pain. Previous spinal radiography analysis showed right thoracic idiopathic scoliosis with a 22 degrees lumbar compensatory curve (Fig. 1).
MRI was then performed showing L2 vertebral body, L2-L3 disc and right psoas compromise (Fig. 2). Spondylodiscitis was then suspected. CT-scan was performed in order to evaluate al abdominal structures and to ruled-out another clinical problems related to this severe pain (Fig. 3). Severe L2-L3 compromise was observed on CT scan with increased curve deformity at this level. Percutaneous CT scan guided catheter intervention was performed with 60 cm 3 hematogenous material drainage ( Fig. 3) but the cultures were negative.
Surgery was planned to stabilize and correct spinal deformity, drainage of necrotic and inflammatory component and prevent neurological compromise.

Surgical treatment
Vertebral segmentary kyphosis and lateral angulation were 17 and 25 degrees respectively.
Monosegmentary instrumentation through a double antero-posterior approach was planned. First stage, a minimally invasive lateral right side approach for intersomatic and para-vertebral debridement was performed followed by a reconstruction with L2-L3 interbody titanium cage with rib bone autograft.
Posteriorly, with the same anesthesia, a posterior approach for L2-L3 pedicular instrumentation was performed and no normal spinal levels were instrumented (Fig. 4).
Estimated blood loss during the entire procedure was 850 ml. Both stages were performed under neurophysiologic monitoring including somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs).
No complications were observed during the procedure.

Histological analysis
Microscopic images (Fig. 5) showed granulomatosus reaction with multinucleated cells. Ziehl Neelsen coloration technique was negative, however, polymerase chain reaction (PCR) was positive for tuberculosis.

Postoperative treatment and follow up
A Thoraco-lumbo-sacral orthosis (TLSO) was indicated and used during three months. Clinical and radiological control was performed every three months, no deformities during follow up were observed, postoperative anterior and lateral segmental angles were 1 and 2 degrees respectively. Clinical parameters were improved and antituberculosis therapy was successful after 12 months of treatment (Fig. 6).  Postoperative protocol included four anti tuberculosis agents for two months (Isoniazide, Ethambutol, Pirazinamide, Rifampin) followed by two drugs for ten months (Isonizide, Rifampin).

Discussion
The treatment of spinal tuberculosis usually is non-surgical, by the administration of four anti-tuberculosis drugs and bracing. 5 There are some situations in which surgical treatment is required: loss of sagittal or coronal alignment of the spine due to extensive osteolysis and spread of an abscess into the para-spinal tissues and spinal canal, with progressive neurologic deficit, failed conservative treatment or uncertain diagnosis. 2 Posterior instrumentation with or without anterior fusion has demonstrated good clinical and surgical results. 6,7 Anterior fusion alone, is generally indicated for patients with single level compromise and minor or mild deformities, [8][9][10] additional posterior instrumentation is considered in multilevel compromise or severe deformity, however, short or long instrumentations are performed in order to prevent early failure and obtain more correction. 11 The anterior approach is possible only if the posterior column is intact, and it is demonstrated that can decrease the operating time, blood loss, and postoperative morbidity. However for a patient with pan vertebral disease, or with the need  for posterior column shortening to reduce kyphosis, or multilevel disease, posterior stabilization is necessary. 12 We present a case of severe lumbar deformity secondary to spondylitis tuberculosis treated through a double anterior posterior approach with monosegmental instrumentation, arthrodesis was observed after a follow-up of one year. This technique should be attempt after a carefully patient selection. More cases are required to reinforce this recommendation.
To our knowledge combined monosegmental instrumentation for the treatment of a severe spinal deformity secondary to Tuberculosum spondylitis have not been described. More cases are needed to support this treatment.