If decompression and fusion with instrumentation is elected, inclusion of L2 or S1 should be considered. The quality of bone should also be taken into account with long constructs such as these which require that either a laterally directed sacral alar screw or an iliac screw be used to increase the stability of the construct. The use of titanium polyaxial screws and rods are recommended for improved MRI compat- ibility, more appropriate material elastic modulus, and ease of instrument insertion.
The patient underwent decompression and instrumented fusion from L2 through L5 because of the multiple levels of unstable spondylolisthesis and stenosis (Figure 8-2).
Because the L5-S1 segment was transitional and already fused, there was no need to instrument to S1.
FIGURE 8-2 Postoperative images showing placement of instrumentation. A, AP radiograph of lumbar spine. B, Lateral radiograph of lumbar spine.
E E
FIGURE 8-1, cont’d E, T2-weighted axial MRI images of the lumbar spine. MRI images show degen- erative Modic end-plate changes at L5-S1; lumbar stenosis at L3-5 secondary to facet arthropathy that is greater at L3-4 than at L4-5; and a hypertrophic ligamentum flavum. The spondylolisthesis at L3-4 and disk herniation at this level contribute to central and lateral recess stenosis. Note the hyper- intense signal within the facet joints bilaterally, which can indicate instability.
FUNDAMENTAL TECHNIQUE
After induction of general anesthesia, a gravity-draining Foley catheter is placed and a preoperative antibiotic (usually cefazolin) is given. The patient is turned prone onto an Andrews table, and all pressure points of the face, torso, and extremities are carefully padded. The patient is converted to a kneeling position, and care is taken to make sure the belly hangs free to limit pressure on the inferior vena cava, which aids in minimizing blood loss. Standard landmarks of the iliac crest and palpation up from the sacrum are used to delineate L2 through S1 with a marking pen. Taking radiographs at this time with a needle in place between spinous processes can help in centralizing the incision. The skin is cleansed and draped in sterile fashion. After the skin incision is made, Bovie electrocautery is used to dissect the paraspinal muscles subperiosteally so that the facet capsules and transverse processes are exposed bilaterally at each level. Care is taken not to violate facet capsules that do not need to be fused. Using standard landmarks, pilot holes are drilled, and the pedicles of L2 through S1 are probed and circum- ferential bone is confirmed with a ball-tip probe. These holes are covered with thrombin-soaked absorbable gelatin sponges. From the preoperative images, it is clear that the neurogenic claudication symptoms in the patient described in the Case Presentation were related primarily to the significant stenosis at L3-4 and less so to that at L4-5. In such cases, bilateral laminectomies from L3 through L5 are performed with decompression centrally and along the lateral recesses at L3-4.
Ideally, leaving at least 5 mm and, if possible, 7 mm of the pars interarticularis is recommended to avoid postoperative pars fracture when the patient is upright.
When undercutting to achieve a medial facetectomy, an attempt should be made to ensure that 50% of a functional facet joint complex remains, inclusive of a functioning superior facet and inferior facet. A Woodson dental instrument is used to palpate after decompression to ensure that adequate bilateral foraminotomies have been performed. A high-speed drill bur is used to decorticate the transverse processes bilaterally and the facet complexes. Locally harvested bone autograft from the spinous processes, lamina, and facets is morselized and placed in the lateral gutters to achieve posterolateral arthrodesis. Part of the pain experienced by the patient described in the Case Presentation was related to hypermobility at L3 through L5, and posterior instrumentation with a pedicle screw and rod con- struct provides immediate fixation and symptomatic improvement (Tips from the
A B
FIGURE 8-2 Postoperative images showing placement of instrumentation. A, AP radiograph of lumbar spine. B, Lateral radiograph of lumbar spine.
Masters 8-2). A cross-link can be added to increase the overall rigidity and resist rotational forces.
Tips from the Masters 8-2 • Check standing neutral and flexion-extension radiographs
preoperatively to assess for hypermobility. This can be confirmed intraoperatively with distraction on the spinous processes at L2-3 with a towel clamp, and a decision to change pedicle screw and rod instrumentation to include L2 can be made.
DISCUSSION OF BEST EVIDENCE
Studies comparing conservative treatment, laminectomy, and fusion with or without instrumentation for degenerative grade I spondylolisthesis are discussed. Investiga- tions of the use of posterior spinous process devices are excluded. Whenever pos- sible degenerative spondylolisthesis should be considered separately from stable lumbosacral spinal stenosis.3
The results of surgical intervention versus conservative treatment were evalu- ated by Matsudaira and colleagues4 in a retrospective study involving 55 patients.
At 2 years of follow-up they found that 19 patients who underwent laminectomy alone and 20 patients who underwent laminectomy with posterior instrumenta- tion had better Japanese Orthopaedic Association (JOA) scores than 16 medi- cally treated patients. There were no significant differences in clinical outcomes between the laminectomy and fusion groups, but both surgical arms had better outcomes than the medical therapy group. Progression of slip increased in the medical treatment and primary laminectomy groups. Weinstein and associates5 evaluated results for an experimental cohort randomly assigned to a treatment method and an observational cohort selecting treatment in consultation with their physicians (304 and 303 patients, respectively). They found that patients with degenerative spondylolisthesis and spinal stenosis treated surgically with decom- pressive laminectomy with or without fusion had significantly greater improvement in pain and function during a 2-year period than patients treated nonsurgically.
Weinstein and colleagues6 later reported an “as treated” analysis of these same cohorts at 4-year follow-up. The advantages of surgery over nonsurgical care were maintained, with reduced bodily pain and increased physical function in the surgi- cally treated group.
Fischgrund and co-workers7 evaluated the role of instrumentation along with laminectomy in a prospective randomized trial involving 76 patients, although only 89% were available for 2-year follow-up. They concluded that instrumentation with posterolateral fusion increased the likelihood of arthrod- esis compared with no instrumentation, but there was no significant difference in clinical outcome with the two procedures. In a retrospective study Kimura and colleagues8 looked at results for 28 patients who underwent decompres- sion and fusion without instrumentation and 29 who underwent decompres- sion and instrumented fusion, with a 6-year follow-up for the noninstrumented group and a 3-year follow-up for the instrumented group. They found no sig- nificant benefit for instrumentation. A systematic review by Martin and asso- ciates9 of studies with a minimum follow-up of 1 year concluded that fusion leads to better clinical outcomes than decompression alone. The addition of instrumentation results in better fusion rates and less pseudoarthrosis, but no significant differences in clinical outcome were seen for instrumented and non- instrumented fusion.
A prospective study by Herkowitz and Kurz10 compared outcomes in 25 patients treated with decompression and 25 patients undergoing decom- pression with fusion. At 3-year follow-up the group undergoing decompres- sion with fusion had significantly more improvement of low back pain and leg pain than the group treated with decompression alone. In the most recent of several retrospective studies, Ghogawala and associates11 looked at results for 20 patients undergoing laminectomy and 14 undergoing laminectomy with
posterior instrumented fusion. At 6- and 12-month follow-up they found an 83% fusion rate in the latter group. Oswestry Disability Index (ODI) scores improved by 27.5 points in the decompression and fusion group and 13.6 points in the decompression only group. Scores on the Short Form 36 (SF- 36) Health Survey also showed improved functional outcome in the patients undergoing decompression and fusion. Lombardi and colleagues12 retro- spectively looked at data for 47 patients, including 6 undergoing wide lami- nectomy, 20 undergoing standard laminectomy with preserved facets, and 21 undergoing standard laminectomy and fusion. Mean follow-up was 2.7 years.
The authors concluded that decompression with transverse process fusion was superior to decompression alone. Postacchini and Cinotti13 retrospectively reviewed results for 8 patients treated with bilateral laminectomy and 10 patients treated with laminectomy with fusion after a mean follow-up of 8.6 years. Satis- factory results were achieved in 80% of the group undergoing fusion compared with 33% of the group undergoing decompression only. There were 16 patients with degenerative spondylolisthesis; 10 of the 16 had concomitant fusion. The authors concluded that decompression with fusion provided satisfactory long- term results. An earlier study by Postacchini and colleagues14 retrospectively evaluated results for 32 patients after a mean 2.8-year follow-up. Fifteen had decompression alone, and 17 underwent laminectomy and fusion. The authors concluded that the addition of instrumentation led to good to excellent out- comes (100% for the instrumented group vs. 67% for the noninstrumented group). In a prospective study Bridwell and co-workers15 compared results in 44 patients, only 43 of whom were available for 2-year follow-up. Nine patients had laminectomy only; the rest underwent fusion with or without instrumenta- tion. Patients undergoing fusion with instrumentation (24 patients) were found to have a higher fusion rate and a lower proportion of slippage than patients undergoing fusion without instrumentation (10 patients). In addition, patients with stable spondylolisthesis had longer walking distances.
Controversy exists regarding whether posterior lumbar interbody fusion (PLIF) improves fusion rates or provides beneficial clinical outcomes beyond that pro- vided by posterior instrumentation and onlay arthrodesis. In a retrospective analysis Rousseau and associates16 looked at outcome data for 24 patients undergoing decompression and posterior fusion. Eight of the 24 also had PLIF.
Mean follow-up was 2.8 years, with 75% of patients followed for longer than 2 years. The authors concluded that the addition of PLIF adds marginal benefit to posterior decompression and fusion alone. In another retrospective study Yone and colleagues17 evaluated results for 7 elderly patients undergoing lami- nectomy and 10 undergoing laminectomy and instrumented fusion, and found that decompression plus fusion was better than decompression alone in indi- viduals older than 60 years of age. Gibson and Waddell’s18 meta-analysis and systematic review of 31 randomized controlled trials revealed that instrumenta- tion improved fusion rates, but clinical outcomes were only marginally better with instrumentation, and instrumentation was associated with a higher risk of complications. Mardjetko and colleagues19 performed a meta-analysis of stud- ies encompassing 889 patients: 216 treated with laminectomy, 500 undergoing laminectomy with noninstrumented fusion, 101 undergoing laminectomy with posterior instrumented fusion, and 72 treated with anterior fusion. The authors found that the addition of fusion with or without instrumentation yielded bet- ter clinical outcomes than decompression alone; however, the use of instru- mentation did not improve clinical outcomes or fusion rates compared with uninstrumented fusion. The Spine Patient Outcomes Research Trial (SPORT) also evaluated in situ fusion, pedicular fusion, and 360-degree fusion and found no significant differences among any of the fusion techniques in outcome at 4 years.20
Booth and co-workers,21 studying the results of decompression and instrumented posterior fusion for the treatment of degenerative spondylolisthesis, identified 41 patients who were followed for 5 to 10.7 years. Clinical outcome measures were
available for 36 patients. Eighty-three percent reported high satisfaction with the procedure, 86% had reduced back and leg pain, and 46% had increased function.
Kornblum and associates22 evaluated results for 47 patients undergoing a noninstru- mented fusion procedure and found that 22 of 47 patients achieved a solid fusion.
The authors found that patients with solid fusion had statistically better clinical out- comes than those with a pseudoarthrosis as determined from responses on the Swiss Spinal Stenosis Questionnaire at 5 to 14 years. Abdu and colleagues20 analyzed data for 380 surgical patients enrolled in SPORT, of whom 21% underwent posterolat- eral noninstrumented fusion, 56% were treated with pedicle screw instrumentation and fusion, 17% received pedicle screws and an interbody device, and 6% under- went decompression alone. At 4-year follow-up, there was no consistent difference among the three fusion groups in clinical outcome.
COMMENTARY
Controversy remains as to whether decompression alone, noninstrumented fusion, or instrumented fusion provides more long-lasting benefits for patients. Results of short- and long-term studies show a trend toward superior clinical results for decom- pression alone compared with the natural history of degenerative spondylolisthesis.
If the spine is unstable when viewed on dynamic radiographs or intraoperatively, then fusion is likely a prudent adjunct to the decompression. In those patients with significant instability, decompression with the addition of instrumentation assists in achieving solid fusion and likely reducing the pain associated with abnormal seg- mental motion. The studies reviewed earlier are highly heterogeneous; some report results in terms of commonly used standardized clinical outcome measures, but in others standardized outcome measures are not used. Many investigations provide only rudimentary grading of patient satisfaction, which makes it difficult to compare findings across studies. Ultimately, the decision to fuse or not to fuse should be individualized for each patient, based on preoperative radiographs and MRI images in conjunction with intraoperative observation of abnormal motion and overall bone quality.
REFERENCES
1. Herbiniaux G: Traite sur divers accouchements laborieux et sur les polypes de la matrice, Brussells, 1782, JL Boubers. First report of slipped vertebrae or defects of the pars interarticularis.
2. Wiltse LL, Newman PH, McNab I: Classification of spondylolysis and spondylolisthesis, Clin Orthop Rel Res 117:23–29, 1976.
3. Pearson A, Blood E, Lurie J, et al: Degenerative spondylolisthesis versus spinal stenosis: does a slip matter? Comparison of baseline characteristics and outcomes (SPORT), Spine 35(3):298–305, 2010.
“As treated” analysis of SPORT data for patients with degenerative spondylolisthesis and patients with spinal stenosis revealed that after surgery spondylolisthesis patients were more likely to achieve fusion than lumbar stenosis patients. Outcome measures of bodily pain, physical function, and ODI score were all better in the spondylolisthesis patients undergoing surgery. Nonsurgical outcomes were similar in both cohorts.
4. Matsudaira K, Yamazaki T, Seichi A, et al: Spinal stenosis in grade I degenerative lumbar spondylolis- thesis: a comparative study of outcomes following laminoplasty and laminectomy with instrumented spinal fusion, J Orthop Sci 10(3):270–276, 2005. Japanese comparative study with 2-year follow-up including 16 patients treated conservatively, 18 undergoing lumbar laminoplasty, and 19 undergoing laminectomy with instrumented fusion. Surgery was shown to be superior to conservative therapy, but no clinical difference was seen between laminoplasty and laminectomy combined with instrumented fusion.
5. Weinstein JN, Lurie JD, Tosteson TD, et al: Surgical versus nonsurgical treatment for lumbar degen- erative spondylolisthesis, N Engl J Med 356(22):2257–2270, 2007. Prospective randomized multicenter trial included a randomized cohort of 304 patients and an observational cohort of 303 patients. Cross- over in the randomized cohort was about 40% in each direction, and 17% in the observational cohort crossed over to surgery. “As treated” analysis showed that patients with degenerative spondylolisthesis treated surgically were substantially better after 2 years of follow-up.
6. Weinstein JN, Lurie JD, Tosteson TD, et al: Surgical compared with nonoperative treatment for lum- bar degenerative spondylolisthesis. Four-year results in the Spine Patient Outcomes Research Trial (SPORT) randomized and observational cohorts, J Bone Joint Surg Am 91(6):1295–1304, 2009. Same cohorts as in the previous study were followed out to 4 years. “Intention to treat” analysis was limited due to crossover to nonassigned group. “As treated” analysis showed that improvements in bodily pain, physical function, and ODI scores were maintained at 4 years.
7. Fischgrund JS, Mackay M, Herkowitz HN, et al: 1997 Volvo Award winner in clinical studies. Degen- erative lumbar spondylolisthesis with spinal stenosis: a prospective, randomized study compar- ing decompressive laminectomy and arthrodesis with and without spinal instrumentation, Spine 22(24):2807–2812, 1997. In this prospective study 76 patients were randomly assigned to undergo posterior decompression and arthrodesis with or without instrumentation; 67 patients were available for follow-up at 2 years. Excellent or good clinical outcomes were found in 85% of patients in the non- instrumented group and in 76% of patients in the instrumented group. Successful fusion occurred in 45% and 82%, respectively, but clinical outcome did not correlate with successful arthrodesis.
8. Kimura I, Shingu H, Murata M, et al: Lumbar posterolateral fusion alone or with transpedicular instrumentation in L4-L5 degenerative spondylolisthesis, J Spinal Disord 14(4):301–310, 2001. Japa- nese retrospective analysis of outcomes in 57 patients with L4-L5 degenerative spondylolisthesis who underwent decompression with noninstrumented and instrumented fusion and were followed for 2 years. Fusion rates were 82.8% and 92.8% in the noninstrumented and instrumented fusion groups, respectively, and rates of satisfactory outcome were 72.4% and 82.1%; these differences were found to be nonsignificant.
9. Martin CR, Gruszczynski AT, Braunsfurth HA, et al: The surgical management of degenerative lum- bar spondylolisthesis: a systematic review, Spine 32(16):1791–1798, 2007. Thirteen randomized con- trolled and comparative observational studies were included in this review. The authors concluded that spinal fusion may lead to a better clinical outcome than decompression alone. However, no con- clusions could be drawn about the clinical benefit of instrumenting a spinal fusion.
10. Herkowitz HN, Kurz LT: Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis, J Bone Joint Surg Am 73(6):802–808, 1991. Thirty-six women and 14 men with degenerative lumbar spondy- lolisthesis were randomly assigned to undergo decompression alone or decompression with transverse process arthrodesis (25 patients in each group). At follow-up of 2.4 to 4 years, the group treated with arthrodesis was found to have greater relief of back and leg pain.
11. Ghogawala Z, Benzel EC, Amin-Hanjani S, et al: Prospective outcomes evaluation after decompres- sion with or without instrumented fusion for lumbar stenosis and degenerative grade I spondylo- listhesis, J Neurosurg Spine 1(3):267–272, 2004. Prospective study of 20 patients who underwent laminectomy alone and 14 patients who had laminectomy with instrumented fusion. At 1 year, ODI score had improved by 27.5 in the instrumented group and 13.6 in the laminectomy alone group. SF-36 scores corroborated this finding. The authors concluded that surgery improves outcomes as evaluated by standardized measuring scales and that fusion leads to greater clinical improvement.
12. Lombardi JS, Wiltse LL, Reynolds J, et al: Treatment of degenerative spondylolisthesis, Spine 10(9):821–827, 1985. Retrospective analysis of data for 47 patients undergoing surgical treatment of spondylolisthesis who were followed for 2 to 7 years. Good or excellent results were achieved in only 33% of the patients undergoing wide laminectomy and facetectomy; in contrast, 88% of those under- going laminectomy with preservation of facet had good or excellent results, and adding transverse process fusion increased the proportion to 90%.
13. Postacchini F, Cinotti G: Bone regrowth after surgical decompression for lumbar spinal stenosis, J Bone Joint Surg Br 74(6):862–869, 1992. Retrospective review of outcomes for 40 patients treated surgically for lumbar stenosis with an average follow-up of 8.6 years. Of the 16 patients with degen- erative spondylolisthesis treated with laminectomy or laminotomy, 10 had concomitant fusion. Bone regrowth was more severe in those who did not undergo concomitant fusion, and this correlated with less satisfactory clinical results.
14. Postacchini F, Cinotti G, Perugia D: Degenerative lumbar spondylolisthesis. II. Surgical treatment, Ital J Orthop Traumatol 17(4):467–477, 1991. Italian retrospective review analyzing treatment results for 32 patients with degenerative spondylolisthesis undergoing unilateral laminotomy, bilateral laminotomy with or without transverse process fusion, bilateral laminectomy with or without spinal fusion, and lami- nectomy with spinal fusion and interspinous wiring. Satisfactory results were achieved in 84%, and 76%
of patients showed progression of spondylolisthesis. The authors recommended no fusion when spon- dylolisthesis is mild and there is no significant hypermobility on lateral flexion-extension radiographs.
15. Bridwell KH, Sedgewick TA, O’Brien MF, et al: The role of fusion and instrumentation in the treat- ment of degenerative spondylolisthesis with spinal stenosis, J Spinal Disord 6(6):461–472, 1993.
Prospective nonrandomized study encompassing 44 patients, of whom 43 were followed for 2 years or longer. Nine patients were treated with decompression surgery without fusion, 19 patients underwent transverse process fusion with autogenous bone graft, and 24 patients had transverse process fusion with the addition of instrumentation. Instrumentation enhanced the chances for successful fusion and was associated with reduced progression of spondylolisthesis. Nonprogression of spondylolisthesis correlated with better clinical outcomes.
16. Rousseau MA, Lazennec JY, Bass EC, et al: Predictors of outcomes after posterior decompression and fusion in degenerative spondylolisthesis, Eur Spine J 14(1):55–60, 2005. French retrospective review examining results for 24 patients undergoing surgery for lumbar spondylolisthesis, of whom 8 were lost to follow-up after a minimum of 0.87 years. Beaujon functional score was improved and fusion was seen in all cases. The authors concluded that the addition of an interbody device leads to higher scores than decompression with pedicle screw fusion.
17. Yone K, Sakou T, Kawauchi Y, et al: Indication of fusion for lumbar spinal stenosis in elderly patients and its significance, Spine 21(2):242–248, 1996. Japanese study evaluating outcomes for 34 elderly patients with spinal stenosis, of whom 17 were considered to have instability as determined by Pos- ner’s method. Ten of these 17 patients with instability underwent decompression and fusion, whereas 7 underwent decompression alone. The patients who did not show instability had decompression only.