35: Lumbar Total Disk Arthroplasty

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Procedure 35 Lumbar Total Disk Arthroplasty

Michael F. Duffy, Jack E. Zigler

Indications

image Symptomatic, single-level degenerative disk disease in the lumbar spine (L3-S1) in skeletally mature patients with no more than grade I spondylolisthesis at the involved level and who have failed nonsurgical treatments for at least 6 months.

Indications Pitfalls

• Active systemic infection or infection localized to the site of implantation

• Osteopenia or osteoporosis defined as dual energy x-ray absorptiometry (DEXA) bone density–measured T-score less than −1.0

• Bony lumbar spinal stenosis

• Allergy or sensitivity to implant materials (cobalt, chromium, molybdenum, polyethylene, titanium)

• Isolated radicular compression syndromes, especially resulting from herniation

• Pars defect

• Involved vertebral end plate dimensionally smaller than 34.5 mm in the medial to lateral and/or 27 mm in the anterior to posterior directions

• Clinically compromised vertebral bodies at affected level because of current or past trauma

• Lytic spondylolisthesis or degenerative spondylolisthesis of grade greater than 1

• Scoliosis (lumbar curve greater than 11 degrees)

• Absolute contraindications for an anterior approach are significantly calcified aorta, and extensive abdominal wall reconstructions.

• Relative contraindications for the anterior approach are age, morbid obesity, previous intraabdominal or retroperitoneal surgery, history of severe pelvic inflammatory disease, and previous anterior spinal surgery.

Indications Controversies

• Diagnosis of diskogenic syndrome by diskography is considered controversial by some authors.

• The upper limits of disk height loss for arthroplasty are not clearly defined.

Examination/Imaging

image Figure 35-1, A and B show flexion/extension lateral radiographs showing disk height loss and degeneration at L5-S1. Note the absence of instability.

image Use T2 weighted-sagittal magnetic resonance imaging (MRI) to document disk degeneration (Figure 35-2).

image Use axial MRI images to assess significant facet joint degeneration, which would be a contraindication for arthroplasty.

image Perform preoperative DEXA scan to verify adequate bone density (T-score greater than −1.0) before the procedure.

image Figure 35-3 is a computed tomography (CT) diskogram showing morphologic changes at L5-S1; the patient reported 10/10 concordant pain. The L4-5 level was normal with minimal discomfort.

image image

FIGURE 35-1, A-B

image

FIGURE 35-2

image

FIGURE 35-3

Treatment Options

• Continued conservative treatment with medications, physical therapy, and injections

• Fusion of the involved segment—various techniques

• Artificial disk replacement at the involved level

Surgical Anatomy

image During anterior exposure at the L5-S1 level, the disk space is found between the left and right iliac veins (Figure 35-4).

image For L3-4 and L4-5 procedures, the vessels should be dissected off the anterior spine and retracted to the right to expose the spine (Figure 35-5).

image

FIGURE 35-4

image

FIGURE 35-5

(Reproduced with permission from Martinez JL, Wang MY. Anterior lumbar interbody fusion. In: Jandial RJ, McCormick PC, Black PM, editors. Core Techniques in Operative Neurosurgery. Philadelphia: Elsevier-Saunders; 2011; Figure 72-5.)

Positioning

image The patient is positioned supine on a regular operating table with arms padded at the elbow and taped across the chest.

Positioning Pearls

• Have the surgical disk level at the “break” in the table to extend the lumbar spine during the procedure for better access to disk space.

• Keep the plane of pelvis parallel to the floor to aid in correct placement of the implant (use leveler device to verify).

Positioning Pitfalls

• Do not use static bumps or pillows under the pelvis.

• Lithotomy position is optional (widely used in Europe; less frequently used in the United States).

Portals/Exposures

image The anterior approach to the lumbar spine is used through either a transverse or horizontal incision.

image The rectus fascia is incised in line with the skin incision, and the midline fascial raphe of the rectus is identified.

image The retroperitoneal dissection starts on the medial border of the rectus and proceeds lateral and posterior to the muscle belly, having less potential chance of denervation of the rectus.

image The plane is bluntly dissected superficial to the abdominal contents along the left abdominal wall outside the peritoneum and taken posteriorly toward the psoas muscle (Figure 35-6).

image The entire peritoneal sac (with the ureter) can be bluntly dissected off the abdominal wall and retracted toward the midline with a handheld retractor.

image Insertion of a screw or bent needle into the disk space should be done to verify the level and verify the midline of the disk space with fluoroscopic imaging (mark the position on the anterior spine with Bovie cautery before removing marker).

image

FIGURE 35-6

Portals/Exposures Pearls

• Use of intraoperative fluoroscopy to show angle and level of disk space is helpful to plan an incision, especially when using a horizontal incision.

• For larger patients, a vertical incision is preferred.

• Avoid injury to the inferior epigastric vessels on the underbelly of the rectus muscle.

• The ureter should be identified and retracted along with the peritoneal sac and never dissected separately.

• For L5-S1 procedures, the middle sacral artery should be identified and ligated.

• For L3-4 and L4-5 procedures, segmental vessels may need to be identified and ligated.

• At L4-5, the ascending lumbar vein may limit vascular mobilization and require ligation.

Portals/Exposures Pitfalls

• Horizontal incisions placed improperly hinder the remainder of the operation.

Portals/Exposures Equipment

• Use of either handheld retractors or self-retaining abdominal retractors is acceptable.

Portals/Exposures Controversies

• Use of an access surgeon is recommended.

• The retroperitoneal approach has a 10-fold lower incidence of retrograde ejaculation in males than the transperitoneal approach.

Procedure

Step 1: Diskectomy

image Perform a complete diskectomy (leaving only the lateral annulus and posterior longitudinal ligament), with removal of cartilaginous end plate from both superior and inferior vertebral bodies (Figure 35-7).

image

FIGURE 35-7

Step 1 Pearls

• A thorough diskectomy in the posterior corners is crucial for successful implantation.

• Use a midline marking to create a symmetric diskectomy.

Step 1 Pitfalls

• Violation of the end plate should be avoided during diskectomy.

Step 2: Remobilization

image Release of the posterior longitudinal ligament (PLL) off of the posterior vertebral bodies should be completed using a small curved curette (Figure 35-8).

image Specialized distractors and paddles are inserted into the disk space to help with remobilization (Figure 35-9).

image

FIGURE 35-8

image

FIGURE 35-9

Step 2 Pearls

• It is important to fully restore the disk height to recreate a mobile segment and avoid expulsion of the implant because of tight soft tissues.

Step 2 Pitfalls

• When using the disk space distractors, they must be inserted to the posterior aspect of the disk space to use solid peripheral bone; otherwise, an end plate fracture can occur.

• Use of curettes during release of the PLL should be visualized under fluoroscopic imaging to minimize risk.

Step 3: Trial Insertion

image Based on midline marking, insert appropriately sized trial into disk space under lateral fluoroscopy and visualize on anteroposterior (AP) fluoroscopy for verification (Figure 35-10).

image Start with a 10-mm trial, and increase in size depending on the resistance felt and amount of disk height restoration on the lateral fluoroscopic images.

image

FIGURE 35-10

Step 3 Pearls

• Depending on intended implant, know all available sizes.

• If the trial is translated off-center, further diskectomy or annulotomy may be required to “balance” the disk space, thereby allowing the trial to center.

Step 3 Pitfalls

• Improper position of trial can lead to poorly placed implant and eventual failure of the arthroplasty.

Step 4: Keel Preparation

image For keeled total disk arthroplasty devices, the keels should be cut under lateral fluoroscopy to visualize depth (Figure 35-11).

image

FIGURE 35-11

Step 5: Device Insertion

image The arthroplasty device should be inserted as far posterior as possible within the disk space (Figure 35-12).

image Lateral fluoroscopic images should be used frequently to verify the angle at which the device is being inserted and the depth.

image A final AP image should be taken to verify that the device is positioned in the midline (Figure 35-13).

image

FIGURE 35-12

image

FIGURE 35-13

Step 5 Pearls

• Double check assembly of the device on the instrumentation before insertion.

• If the device is difficult to insert, extend the lumbar spine by using the table controls (restore to neutral before final positioning of device).

Step 5 Pitfalls

• For keeled devices, if the trial was not placed posterior enough in the disk space, the implant will also not be posterior enough.

Postoperative Care and Expected Outcomes

image Patient should be admitted for inpatient observation.

image Start with clear liquid diet, and advance as tolerated.

image Ambulation should commence on the day of surgery.

image A corset brace should be used for comfort until the wound has healed.

Postoperative Pearls

• Physical therapy can commence after wound healing; patients must avoid extension exercises for 6 weeks.

• Return to activities without restriction is at 3 months. Low-impact sports are then acceptable (i.e., golf, tennis, skiing, basketball).

Evidence

Bertagnoli R, Yue JJ, Shah RV, et al. The treatment of disabling single-level lumbar diskogenic low back pain with total disc arthroplasty utilizing the ProDisc prosthesis: a prospective study with 2-year minimum follow-up. Spine. 2005;30:2230-2236.

This is a prospective study with 2-year follow-up presenting the results of total disk replacement (TDR) in 118 patients with diskogenic low back pain. A single-level TDR was performed at L3-S1, with outcome measurements taken at 3, 6, 12, and 24 months after surgery. The authors found that improvements in the Visual Analogue Scale, the Oswestry Disability Index, and patient satisfaction occurred at 3 months and were maintained at 24 months, all with statistical significance. At the index level, disk height increased from 4 to 13 mm, and segmental motion increased from 3 to 7 degrees, both with statistical significance as well. They concluded that TDR is a successful alternative to fusion, with consistent results at 2-years follow-up. Although this is a prospective case series, it legitimizes TDR as a treatment option for disabling low back pain resulting from diskogenic syndrome.

Blumenthal S, McAfee PC, Guyer RD, et al. A prospective, randomized, multicenter Food and Drug Administration Investigational Device Exemptions study of lumbar total disc replacement with the CHARITE Artificial Disc versus lumbar fusion: part I: evaluation of clinical outcomes. Spine. 2005;30:1565-1575.

This is a Level I study comparing total disk replacement (TDR) with anterior lumbar interbody at a single level from L4-S1. A total of 304 patients were randomized. Both groups showed significant improvement following surgery. Patients in the TDR group were found to have lower levels of disability at every time interval from 6 weeks to 24 months. At the 24-month follow-up period, a greater percentage of patients in the TDR group were satisfied with their treatment compared with the fusion group (P < .05). The complication rates were similar between the groups, and the hospital stay was significantly shorter for TDR than for fusion patients. Reoperation was higher in the fusion group (9.1% versus 5.4%).

Brau SA, Delamarter RB, Schiffman ML, et al. Vascular injury during anterior lumbar surgery. Spine J. 2004;4:409-412.

This publication is a retrospective case series of 1315 consecutive patients who underwent anterior approach to the lumbar spine. A significant vascular complication rate of 1.9% was reported. Six patients had left iliac artery thrombosis, and 19 patients had major venous injuries. The study concluded that anterior lumbar surgery is safe, although special attention should be given during mobilization of the vessels to avoid serious complications.

David T. Long-term results of one-level lumbar arthroplasty: minimum 10-year follow-up of the CHARITE Artificial Disc in 106 patients. Spine. 2007;32:661-666.

This was a Level III study with long-term follow-up of total disk arthroplasty patients. Eighty percent of patients reported excellent or good clinical success after Charité total disk replacement (TDR) at a mean of 13.2-years follow-up. Ninety percent of the prostheses were still mobile. The reoperation rate for TDR patients was 7.5% and the adjacent level degeneration rate was found to be 2.8%. Almost 90% of the patients returned to work after TDR. The complications rate was 4.6%, with a 2.8% rate of subsidence and less than a 2% rate of core subluxation.

Guyer RD, McAfee PC, Banco RJ, et al. Prospective, randomized, multicenter Food and Drug Administration Investigational Device Exemption study of lumbar total disc replacement with the CHARITE Artificial Disc versus lumbar fusion: five-year follow-up. Spine J. 2009;9:374-386.

This represents a Level I study comparing total disk replacement (TDR) and fusion at the 5-year follow-up time point. Five-year follow-up was completed by 133 randomized patients. Overall success was defined as improvement of at least 15 points on the Oswestry Disability Index (ODI) versus baseline, no device failure, absence of major complications, and maintenance or improvement of neurologic status. The overall success was 57.8% in the TDR group versus 51.2% in the fusion group. Changes from baseline for ODI, Visual Analogue Scale pain scores, and SF-36 Health Survey Scores were similar for both groups. In patient satisfaction surveys, 78% of TDR patients were satisfied versus 72% of fusion patients. Higher rates of employment were noted in the TDR group. Long-term disability was higher in the fusion group by nearly threefold (P = .0441). Additional index-level surgery was also higher for the fusion group. Radiographic data were similar to that reported in the 2-year follow-up study (see Blumenthal et al, 2005, this section).

Guyer RD, Tromanhauser SG, Regan JJ. An economic model of one-level lumbar arthroplasty versus fusion. Spine J. 2007;7:558-562.

A cost-minimization model comparing costs of total disk replacement (TDR) to three spinal fusion procedures: anterior lumbar interbody fusion (ALIF) with iliac crest bone graft (ICBG), ALIF with INFUSE Bone Graft and LT-Cages, and instrumented posterior lumbar interbody fusion (IPLIF) with ICBG. The hospital perspective compares direct medical costs during the index hospitalization. The payer perspective considers direct medical costs of the index hospitalization and those incurred in the following 2-year period. Compared with TDR, hospital costs are 12.0% higher for ALIF with ICBG, 36.5% higher for ALIF with INFUSE, and 36.5% higher for IPLIF. For payers, compared with TDR, ALIF with ICBG has 4.4% lower cost, whereas ALIF with INFUSE and IPLIF have costs of 16.1% and 27.1% higher, respectively. The study concluded that the overall economic effect of one-level TDR procedures (for payers and hospitals) is at worst equivalent to fusion.

Lemaire JP, Carrier H, Sariali el-H, et al. Clinical and radiological outcomes with the Charité Artificial Disc: a 10-year minimum follow-up. J Spinal Disord Tech. 2005;18:353-359.

This is a long-term series with a minimum follow-up of 10 years. A total of 107 patients underwent lumbar total disk replacement (TDR): 54 one-level and 45 two-level procedures, and 1 three-level procedure. Clinically, 62% had an excellent outcome, 28% had a good outcome, and 10% had a poor outcome. Greater than 90% of eligible patients returned to work. Motion measurements showed 10.3 degrees of flexion/extension for all levels. No subluxation of the implants was noted, and no cases of arthrodesis occurred. Five patients required a secondary posterior arthrodesis because of poor clinical outcomes, not because of catastrophic device failure.

Zigler J, Delamarter R, Spivak JM, et al. Results of the prospective, randomized, multicenter Food and Drug Administration Investigational Device Exemption study of the ProDisc-L total disc replacement versus circumferential fusion for the treatment of 1-level degenerative disc disease. Spine. 2007;32:1155-1162.

This is another Level I study comparing total disk replacement (TDR) to circumferential spinal fusion for the treatment of diskogenic pain at a single level between L3 and S1. The study involved 286 patients. No major complications occurred in the investigational group. At 2-years follow-up, 77.2% of investigational and 64.8% of control patients met the Oswestry Disability Index improvement criteria of at least 15%. Overall neurologic success in the investigational group was superior to the control group. Visual Analogue Scale improvement was superior at 24 months in the investigational group versus the control group (P = .015). Radiographic range of motion averaged 7.7 degrees in the TDR patients and was of normal values in more that 90% of these. TDR not only showed non-inferiority to fusion, it showed superiority on several clinical parameters.

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