INTRODUCTION

Thoracic disc prolapse constitutes about 0.15-0.75 of all symptomatic disc herniation of the whole spine¹. Disc herniation at T12-L1, L1-L2 and L2-L3 represents about 5% of all lumbar disc herniation². surgery for thoracic spine disc prolapse constitutes about one percent of operations for disc prolapse^3,4 and most of patients with such disease had manifestations related to spinal cord compression (motor, sensory and sphincteric affection) and hence management of disc herniation at this region is very important and should be planned very well⁵. Conservative treatment is indicated for asymptomatic patients discovered accidentally and for those with mild pain that respond to medical treatment however, surgery is highly recommended for any case with myelopathy^3,6,7,8. Laminectomy is not accepted as a viable surgical approach due to the unacceptable high complications reported in the literature from marked spinal cord retraction during surgery. and so many alternative approaches were invented to access this region without dural retraction⁶ which include lateral and dorsolateral approaches (costotransversectomy,

lateral extracavitary and transpedicular) and ventrolateral transthoracic approaches either extrapleural or transpleural^7,9,10,11. Results obtained by these approaches were satisfactory, however they are extensive approaches, need much more experience and in addition the transthoracic and lateral extracavitary approaches may be contraindicated in old age patients.^7,12,13,14

In this study, we adopted the transfacet pedicle sparing approach described by Stillerman et al.¹⁴ aiming to study it’s efficiency  as   a simple and safe approach which enable the surgeon to access this region through the transfacet area without any dural retraction and without the need for pedicle removal.

PATIENTS AND METHODS

Twelve patients with discs at thoracic and upper lumbar spine (L1-L2) were subjected to the this  approach in Cairo University hospitals from Jan 2006 to Jan 2009 and included in this study with five cases at T12-L1, four case at L1-L2, and one case at each of these level T8-T9, T10-T11 and T11-T12. The age ranging from 28-56 (mean age 42 year). Male to female ratio was 9/3=3:1.

All patients had manifestations of spinal cord compression except for two cases herniated disc at L1-L2 as they had back and radicular manifestations not responding to medical treatment. Radiological investigation was performed in the form of Magnetic Resonance Imaging (MRI), computed tomography (CT) scan and plain x-ray. The special importance of CT scan is to diagnose calcified discs. In this study, central calcified discs were excluded because the transthoracic approach is more appropriate.

Operative Technique (Figure 1):

The operative room should be properly equipped especially with c-arm fluoroscopy, high speed drill and microscope .all patients received preoperative antibiotics. Under General anesthesia with patient in prone position fluoroscopy was used for level identification. It should be noted that both anteroposterior and lateral views are needed for accuracy. We used midline incision at the required level and subperiosteal muscle separation was done until full exposure of the facet transverse process complex. Transpedicular Screws was inserted guided by fluoroscopy(as usual). Bone removal was done with the drill and ranging from partial to complete. Complete variety include removal of the spinous process, lamina and the facet complex is removed either unilaterally in herniated disc at one side or bilaterally in central soft disc. This extensive method of removal is done in all cases with myelopathy to provide widening of spinal canal with optimum spinal cord decompression. In this step we remove spinous process at the required level and then drill is used to remove the lamina and inferior articular facet followed by the superior one which removed until proper exposure of disc space. Partial removal was done in two cases with disc at L1-L2 level that presented with only back and radicular manifestation and MRI showed that these two discs was unilateral without canal stenosis, bone removal was done in the form of hemilaminectomy and facet complex is removed on one side preserving the  lamina and facets of other side. After bone removal as previously mentioned, the discs can be approached without any dural manipulation and removed.

Statistical Analysis:

Data were expressed as mean, frequency, percentage using Microsoft Excel 2003.

Figure 1. (A, B) exposure of the required level and insertion of transpedicular screws. (C, D) show bone removal (both partial and complete technique) to access the disc without dural retraction. (E, F) operative views show the disc removal without any dural retraction.

RESULTS

The transfacet pedicle sparing technique was done in all twelve cases without any complication (Table 1) and all patients discharged from the hospital within two days after surgery and CT scan was done post operatively to assess the technique. These patients were followed up for about twelve months. All cases showed improvement as regard to local, radicular pain  motor and bladder manifestation. Sensory parasthesia was persistent in one case inspite of improvement in all other manifestation.

Figure 2, 3 shows preoperative and postoperative MRI of two patients included in the study.

Table 1. Clinical data and outcome of twelve patients with manifesting herniated disc at the thoracic and upper lumbar spine (L1-L2) operated upon by the transfacet pedicle sparing approach and included in this study.

Figure 2. Preoperative MRI of lumbar spine (A) sagittal view (B) axial view. Both views show herniated disc at L1-L2 with spinal cord compression (C postoperative CT scan axial views show disc removal through the transfacet approach which done bilaterally.

Figure 3. Preoperative MRI of thoracolumbar spine (A) sagittal view, (B) axial view. Both views show herniated disc at T11-T12 with spinal cord compression, (C) postoperative CT scan axial views  show disc removal through the transfacet approach on the right side.

DISCUSSION

Thoracic and thoracolumbar disc herniation is uncommon, about 0.15-4% of all disc operations¹⁵. The special importance of this region is the spinal cord and hence manifestations can be misdiagnosed clinically with other pathologies as tumors, inflammations and demyelinating diseases. Manifestations usually have a gradual onset and progressive course^3,5. Back and lower limbs pain are the most common manifestations and usually precede the development of myelopathy^5,15. It is noteworthy that manifestation of thoracic disc herniation are not only related to mechanical compression but also traction and vascular affection play a major role. Thoracic cord is partially fixed by denticulate ligaments, hence mechanical compression can produce cord affection through traction³. MRI is the gold standard investigation in diagnosing thoracic disc herniation and excluding any other pathology^16,17,18. However, MRI alone is not enough and should be supplemented with CT scan images to exclude calcification as central calcified discs are difficult to be removed by any approach except the transthoracic approach¹⁷. Radiological findings cannot predict the neurological status and hence surgical decision should be taken on the basis of clinical findings that correlate with MRI and CT findings³. Asymptomatic patients or those with minor symptoms that respond to medical treatment should be followed up regularly but for those with myelopathy, surgery is the only management^5-8.

The early surgery was done through laminectomy but was associated with high morbidity^7,10,11,19. Perot and Munro²⁰ reported 16 from 90 patients with postoperative paraplegia. Patterson²¹ noted that 45% of patients in his study either became paraplegic or showed no improvement. These results directed spine surgeons to search for different approaches to access the ventral aspect of this region without cord manipulation. These approaches can be classified into dorsolateral, lateral and ventrolateral approaches^7,10,11,19.

Lateral approaches include costotransvers-ectomy and its direct extension which called lateral Extracavitary approach. These approaches provide satisfactory results^9,10,11. But these approaches are extensive and need great experience and necessitate removal of great part of bone (both pedicles above and below the disc, facet joint and posterior part of vertebral bodies)^12,14. In addition most of studies showed that these approaches cannot provide optimum results with calcified central disc^6,22. Ventrolateral approaches (transthoracic, thoraco-abdominal) provide optimum access for all types of discs at this region even calcified discs^6,23 but they are not suitable for high thoracic disc prolapse T1-T3.²² In addition, there are many respiratory complications reported with such approaches there are  many respiratory complications reported with such approaches. Many studies  reported 10% loss of pulmonary function for few months. Pneumonia ,lung contusion and respiratory distress was reported in many cases. failure of lung expansion which called trapped lung  is one  of the reported serious complications. Other complications include broncho-pleural fistula, empyema and effusion. So the transthoracic approach is preferred   in certain cases with central calcified discs that will be difficult to be removed through any other approaches provided that the patient has good general condition to tolerate such approach.^7,8,10,12

Currently, two simpler techniques are available for thoracic disc surgery. The first one is Thoracoscopy. However this technique is still in progress and need great training and experience^8,22,23. The other technique is the dorsolateral approach^3,21,24 especially the transpedicular^3,21 and the transfacet pedicle sparing approach¹⁴. Transpedicular approach was initially used by Patterson and Arbit²¹. This approach allows posterolateral removal of soft central and calcified lateral discs at all levels. Patterson et al.²¹ and Le Roux et al.³ used this approach with good results as regard to myelopathy and radicular pain. However postoperative back pain was reported in many patients and mostly related to complete disruption of facet pedicle complex¹⁴.

Stillerman et al.¹⁴ developed the transfacet approach which has many advantages. Firstly, it is a very simple technique that most spinal surgeons are familiar with, secondly, it is less risky than other techniques. Thirdly, it has a lower incidence of postoperative local back pain than the transpedicular approach. This approach was done by small incision centered over the disc and after muscle separation, the facet complex on the side with disc protrusion is partially removed with high speed drill to access the disc space without any cord manipulation. In our study, this  approach was used but with some modification as we drill most of facet complex especially the inferior facet and the lamina in order to provide complete spinal cord decompression which was present preoperatively in most of our cases. This was associated with segmental fixation to avoid post operative instability which should be taken into consideration with such approach^20,25. The main disadvantage of this approach is the difficulties during removal of the central part of the disc, so, it is unsuitable for cases with central calcified discs. This coincides with the same operative details obtained by Stillerman et al study¹⁴. Our post operative results with this approach was satisfactory with improvement of myelopathy, local and radicular pain in all cases. There is no reported postoperative complication.

Conclusion

The transfacet pedicle sparing approach combined with laminectomy and segmental fixation offers a safe means of decompression and stabilization at this region especially for lateral disc whether soft or calcified and  central soft disc.

[Disclosure: Authors report no conflict of interest]

REFERENCES

1.      Delfini R, Di Lorenzo N, Ciappetta P, Bristot R, Cantore G. Surgical treatment of thoracic disc herniation: a reappraisal of Larson's lateral extracavitary approach. Surg Neurol. 1996 Jun; 45(6): 517-22.

2.      Kim JS, Lee SH, Moon KH, Lee HY. Surgical results of the oblique paraspinal approach in upper lumbar disc herniation and thoracolumbar junction. Neurosurgery. 2009 Jul; 65(1): 95-9.

3.      Le Roux PD, Haglund MM, Harris AB. Thoracic disc disease: experience with the transpedicular approach in twenty consecutive patients. Neurosurgery. 1993 Jul; 33(1): 58-66.

4.      Stillerman CB, Weiss MH. Management of thoracic disc disease. Clin Neurosurg. 1992; 38: 325-52.

5.      Tokuhashi Y, Matsuzaki H, Uematsu Y, Oda H. Symptoms of thoracolumbar junction disc herniation. Spine (Phila Pa 1976). 2001 Nov 15; 26(22): E512-8.

6.      D'Aliberti G, Talamonti G, Villa F, Debernardi A, Sansalone CV, LaMaida A, et al. Anterior approach to thoracic and lumbar spine lesions: results in 145 consecutive cases. J Neurosurg Spine. 2008 Nov; 9(5): 466-82.

7.      Mulier S, Debois V. Thoracic disc herniations: transthoracic, lateral, or posterolateral approach? A review. Surg Neurol. 1998 Jun;49(6):599-606; discussion 606-8.

8.      Yi S, Kim SH, Shin HC, Kim KN, Yoon DH. Outcome of surgery for a symptomatic herniated  thoracic disc in relation to preoperative characteristics of the disc. Acta Neurochir (Wien). 2007 Nov; 149(11): 1139-45.

9.      Kim KD, Babbitz JD, Mimbs J. Imaging-guided costotransversectomy for thoracic disc herniation. Neurosurg Focus. 2000 Oct 15;9(4):e7.

10.    Lidar Z, Lifshutz J, Bhattacharjee S, Kurpad SN, Maiman DJ. Minimally invasive, extracavitary approach for thoracic disc herniation: technical report and preliminary results. Spine J. 2006 Mar-Apr; 6(2): 157-63.

11.    Sagan LM, Madany L, Lickendorf M. Costotransversectomy and interbody fusion for treatment of thoracic dyscopathy. Ann Acad Med Stetin. 2007; 53(1): 23-6.

12.    McCormick WE, Will SF, Benzel EC. Surgery for thoracic disc disease. Complication avoidance: overview and management. Neurosurg Focus. 2000 Oct 15; 9(4): e13.

13.    Nannapaneni R, Marks SM. Posterolateral thoracic disc disease: clinical presentation and surgical experience with a modified approach. Br J Neurosurg. 2004 Oct; 18(5): 467-70.

14.    Stillerman CB, Chen TC, Day JD, Couldwell WT, Weiss MH. The transfacet pedicle-sparing approach for thoracic disc removal: cadaveric morphometric analysis and preliminary clinical experience. J Neurosurg. 1995 Dec; 83(6): 971-6.

15.    Blumenkopf B. Thoracic intervertebral disc herniations: diagnostic value of magnetic resonance imaging. Neurosurgery. 1988 Jul; 23(1): 36-40.

16.    Parizel PM, Rodesch G, Balériaux D, Zegers de Beyl D, D'Haens J, Noterman J, et al. Gd-DTPA-enhanced MR in thoracic disc herniations. Neuroradiology. 1989; 31(1): 75-9.

17.    Ross JS, Perez-Reyes N, Masaryk TJ, Bohlman H, Modic MT. Thoracic disk herniation: MR imaging. Radiology. 1987 Nov; 165 (2): 511-5.

18.    Wallace CJ, Fong TC, MacRae ME. Calcified herniations of the thoracic disk: role of magnetic resonance imaging and computed tomography in surgical planning. Can Assoc Radiol J. 1992 Feb; 43(1): 52-4.

19.    Chen TC. Surgical outcome for thoracic disc surgery in the postlaminectomy era. Neurosurg Focus. 2000 Oct 15; 9(4): e12.

20.    Perot PL Jr, Munro DD. Transthoracic removal of midline thoracic disc protrusions causing spinal cord compression. J Neurosurg. 1969 Oct; 31(4): 452-8.

21.    Patterson RH Jr, Arbit E. A surgical approach through the pedicle to protruded thoracic discs. J Neurosurg. 1978 May;48(5): 768-72.

22.    Eichholz KM, O'Toole JE, Fessler RG. Thoracic microendoscopic discectomy. Neurosurg Clin N Am. 2006 Oct;17(4): 441-6.

23.    Gille O, Soderlund C, Razafimahandri HJ, Mangione P, Vital JM. Analysis of hard thoracic herniated discs: review of 18 cases operated by thoracoscopy. Eur Spine J. 2006 May;15(5):537-42.

24.    Bilsky MH. Transpedicular approach for thoracic disc herniations. Neurosurg Focus.2000 Oct 15; 9(4): e3.

25.    Nishiura T, Hagihara N, Masaoka T, Miyata I, Ishimitsu H, Harada Y. Anterior decompression of the thoracic spine through the posterior approach: its usefulness, indications, technique, and the preservation of  postoperative spinal stability. No Shinkei Geka. 1994 Apr; 22(4): 377-82.