Trans-sacral Approach to Chronic Low Back Pain

History

A 35-year-old Caucasian male presents with a history of chronic low back pain for about 10 years and intermittent episodes of sciatica. He has undergone 2 prior lumbar microdiscectomy procedures, both at the L5-L6 level. The patient has a partially lumbarized S1 that is referred to here as L6. These surgeries have resulted in good relief of his leg symptoms on each occasion.

The first surgery was performed in 1996, the second in 2003. For the last 14 months he has developed progressive worsening of his low back pain and for 11 months has had pain radiating down both legs; left worse than right.

Past surgical history includes his 2 back surgeries and a right rotator cuff repair.

Medications: Soma^®, Percocet^®. No known drug allergies.

Past medical history is otherwise negative.

Examination

Physical exam reveals a well-developed, well-nourished 5'11" tall 195-pound male. He has a small, well-healed surgical scar. There is no midline tenderness, mild paraspinous muscle spasm, no step-offs. His neurological examination is normal, including negative straight leg raises, although this provokes his back pain. He has limited range of motion in flexion and lateral bending.

There is mild paresthesia in the left foot. His low back pain is mechanical, worse with flexion, and partially relieved by lying down.

Visual Analog Scale

Low back	90
Left leg	70
Right leg	40

Prior Treatment

He has been treated with 8 weeks of physical therapy (PT), a TENS unit, some chiropractic manipulation, 2 series of 3 epidural steroid injections each, pain medications, heat, ice, and acupuncture.

Images

Provocative discography is negative at L2-L3, L3-L4, and L4-L5; positive at L5-L6, with low pressure and 10/10 concordant pain at that level. (Figs. 1A, 1B)

Figure 1A

Figure 1B

T2 sagittal MRIs. (Figs. 2A, 2B, 2C)

Figure 2A

Figure 2B

Figure 2C

Sagittal CT scans. (Figs. 3A, 3B, 3C)

Figure 3A

Figure 3B

Figure 3C

Coronal CT scans (Figs. 4A, 4B, 4C)

Figure 4A

Figure 4B

Figure 4C

Figure 5. Axial MRIs

Diagnosis

Degenerative disc disease and discogenic low back pain with radiculopathy, disc protrusion L5-L6, and left lumbar radiculopathy.

Selected Treatment

The patient was brought to the operating room, anesthetized and intubated. A mini bowel prep had been done the evening prior to surgery. The patient was positioned prone and the lower back and upper buttocks were sterilely prepped and draped.

A 2 cm vertical incision was drawn adjacent to the tip of the coccyx. This was infiltrated with local anesthetic and incised. Dissection was carried down through the fascia and the ligament was bluntly penetrated. The blunt obturator was advanced, under biplanar fluoroscopic control along the ventral sacrum in the midline, and docked at the sacral promontory. A K-wire was impacted into the L5-S1 disc space. A working channel was created with dilators and a 10 mm cannula was docked in the sacrum.

Intra-operative anterior posterior fluoroscopy. (Figs. 6A-6F)

Figure 6A

Figure 6B

Figure 6C

Figure 6D

Figure 6E

Figure 6F

A drill was advanced to the inferior endplate of L5 and the bone reaming was saved as autograft. Ring curettes were used to complete a discectomy, and coiled wire brushes extracted the disc and cartilage material.

A mixture of Vitoss^® (OrthoVita^®, Malvern, PA) synthetic bone graft extender, bone morphogenic protein (off-label use), and the sacral autograft was injected into the disc space. A drill was used to ream into L5, rod length was measured using a K-wire, the 10 mm working cannula was exchanged for a larger working channel, and the final rod was placed. A moderate distraction rod was utilized.

The cannula was then removed and the wound was closed in layers. Dermabond^® (Ethicon, Inc., a Johnson & Johnson Company) was applied. A small stab incision was then made over the L3 spinous process. A percutaneous obturator was docked on the L5-S1 facet joint. A K-wire was then drilled across the facet into the S1 pedicle. An overdrill was advanced and withdrawn, followed by a tap. A 4 mm by 30 mm facet screw was then placed over the K-wire. This process was then repeated on the contralateral side. The incision was closed with a subcutaneous purse-string stitch and subcuticular skin stitch followed by Dermabond.

Intra-operative lateral fluoroscopy. (Figs. 7A-7F)

Figure 7A

Figure 7B

Figure 7C

Figure 7D

Figure 7E

Figure 7F

Postoperative sagittal CT images. (Figs. 8A-8F)

Figure 8A

Figure 8B

Figure 8C

Figure 8D

Figure 8E

Figure 8F

Postoperative coronal CT scans. (Figs. 9A, 9B, 9C)

Figure 9A

Figure 9B

Figure 9C

Figure 10. Axial CT scans

Outcome

Surgery took 89 minutes. The patient was ambulatory 5 hours postop and discharged the following morning.

VAS: 6 Weeks Postoperative

Low back	25
Left leg	10
Right leg	0 (zero)

The patient returned to work at 8 weeks and off narcotics.

VAS: One Year Postoperative

Low back	10
Left leg	0 (zero)
Right leg	0 (zero)

Case Discussion

First and foremost, Dr. Hart has chosen an excellent candidate for surgical intervention. Thoughtful patient selection remains the most reliable predictor of treatment outcome in patients with discogenic low back pain, or degenerative disc disease. This patient has longstanding pain which has been refractory to nonoperative treatment. Surgery should not be pursued in patients with short-term pain as several studies have shown that up to 90% of patients improve without surgery after one year (Deyo, New England Journal of Medicine, 1986; Weber, Spine 1983). Although not explicitly stated, the patient is currently employed. Other important considerations are a history of depression and narcotic abuse, both of which are negative predictors of outcome (Parker et al., Spine 1996).

Preoperative evaluation shows that he has single level disease both on MRI and by provocative discography. Although neither are independent predictors of surgical outcomes, expert opinion in this field is generally consistent that patients with multiple levels of disk degeneration and/or multiple levels with positive discogram results are poor candidates for fusion surgery when pain is the only clinical manifestation (Derby et al., Spine 1999). Fritzell et al (Spine 2001) showed convincingly that fusion for degenerative disk disease leads to improved outcomes compared to non-operative treatment. The key criteria in their study, was successful fusion. Thus, any reasonably safe method by which fusion can be achieved will likely lead to good results in the properly selected patient. Although peer-reviewed studies are yet to be published, a relatively large experience with the trans-sacral fixation technique has been presented at several scientific meetings that show it has a relatively low complication rate and high fusion rates (Smith and Rodgers, Society of Minimally Invasive Spine Surgery (SMISS) 2008, Las Vegas, Nevada; Rodgers et al., Spine Arthroplasty Society, SAS9, London).

The preoperative analysis of patient anatomy remains an important consideration for determining the preferred method of treatment. For trans-sacral fixation, sagittal images of the entire sacrum should be obtained to ensure that a proper trajectory can be obtained. In patients with a highly curved sacrum, the approach trajectory will place the cephalad end of the device near the posterior wall of the vertebral body or conversely the caudad end of the device too anterior within the sacrum. Furthermore, the presence of aberrant presacral structures, such as an enlarged middle sacral artery should be ruled out. Given that such anatomic challenges are absent, the TranS1 device for trans-sacral fixation offers an innovative, minimally invasive alternative strategy for lumbar arthrodesis.

The results of this case, both radiographic and clinical, are excellent. However, it is obvious that this surgical technique is unique and requires proper training for its safe implementation. It is imperative that such novel, minimally invasive strategies undergo rigorous analysis of the learning curve to determine the risk of adverse events during the surgeons' first few cases. This should be concomitant with peer-reviewed multi-center studies of trans-sacral fixation that will ascertain the overall fusion rate as well the incidence of device and technique-related complications.

Author's Response

I thank Dr. Kim for his wonderful analysis. He has keenly struck upon what are, by far, the most critical issues regarding this case. Patient selection is indeed crucial, including assessment of the psychosocial factors he discussed. Careful pre-operative assessment of the patient's anatomy, with particular attention to the anatomy of the sacrum and presacral space, is mandatory. Being prepared to accept that there are cases for which this technique cannot be successfully applied is necessary. As Dr. Kim and other leaders in minimally invasive spine surgery will readily acknowledge, better data is needed to support what we have seen in our own practices regarding the benefits of these techniques.