Fueling the debate: Are outcomes better after posterior lumbar interbody fusion (PLIF) or after posterolateral fusion (PLF) in adult patients with low-grade adult isthmic spondylolisthesis?

Abstract

Study design: Retrospective cohort study.

Clinical question: Do more adult patients affected by low grade isthmic spondylolisthesis have significant clinical and radiological improvement following posterior lumbar interbody fusion (PLIF) than those who receive posterolateral fusion (PLF)?

Methods: One hundred and fourteen patients affected by adult low grade isthmic spondylolisthesis, treated with posterior lumbar interbody fusion or posterolateral fusion, were reviewed. Clinical outcome was assessed by means of the questionnaires ODI, RMDQ and VAS. Radiographic evaluation included CT, MRI, and x-rays. The results were analyzed using the Student t-test.

Results:The two groups were similar with respect to demographic and surgical characteristics. At an average follow-up of 62.1 months, 71 patients were completely reviewed. Mean ODI, RMDQ and VAS scores didn’t show statistically significant differences. Fusion rate was similar between the two groups (97% in PLIF group, 95% in PLF group). Major complications occurred in 5 of 71 patients reviewed (7%): one in the PLIF group (3.6%), four in the PLF group (9.3%). Pseudarthrosis occurred in one case in the PLIF group (3,6%) and in two cases in PLF group (4.6%).

Conclusions:In our series, there does not appear to be a clear advantage of posterior lumbar interbody fusion (PLIF) over posterolateral fusion (PLF) in terms of clinical and radiological outcome for treatment of adult low grade isthmic spondylolisthesis.

References

• 1 Möller H, Hedlund R. Surgery versus conservative management in adult isthmic spondylolisthesis – a prospective randomized study: part 1.  Spine. 2000;  1; 25 (13) 1711-1715
• 2 Kaneda K, Satoh S, Nohara Y. et al . Distraction rod instrumentation with posterolateral fusion in isthmic spondylolisthesis. 53 cases followed for 18–89 months.  Spine. 1985;  10 (4) 383-389
• 3 Hanley Jr E N, Levy J A. Surgical treatment of isthmic lumbosacral spondylolisthesis. Analysis of variables influencing results.  Spine. 1989;  14 (1) 48-50
• 4 Boos N, Marchesi D, Heitz R. et al . [Surgical treatment of spondylolisthesis with mild displacement by pedicular fixation and posterolateral fusion in adults].  Rev Chir Orthop Reparatrice Appar Mot. 1992;  78 (4) 228-235. Review. French.
• 5 Thalgott J S, Sasso R C, Cotler H B. et al . Adult spondylolisthesis treated with posterolateral lumbar fusion and pedicular instrumentation with AO DC plates.  J Spinal Disord. 1997;  10 (3) 204-208
• 6 Nooraie H, Ensafdaran A, Arasteh M M. Surgical management of low-grade lytic spondylolisthesis with C-D instrumentation in adult patients.  Arch Orthop Trauma Surg. 1999;  119 (5–6) 337-339
• 7 McGuire R A, Amundson G M. The use of primary internal fixation in spondylolisthesis.  Spine. 1993;  15; 18 (12) 1662-1672
• 8 Thomsen K, Christensen F B, Eiskjaer S P. et al . 1997 Volvo Award winner in clinical studies. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study.  Spine. 1997;  15; 22 (24) 2813-2822
• 9 France J C, Yaszemski M J, Lauerman W C. et al . A randomized prospective study of posterolateral lumbar fusion. Outcomes with and without pedicle screw instrumentation.  Spine. 1999;  15; 24 (6) 553-560
• 10 Möller H, Hedlund R. Instrumented and noninstrumented posterolateral fusion in adult spondylolisthesis – a prospective randomized study: part 2.  Spine. 2000;  1; 25 (13) 1716-1721
• 11 Ekman P, Möller H, Tullberg T. et al . Posterior lumbar interbody fusion versus posterolateral fusion in adult isthmic spondylolisthesis.  Spine. 2007;  15; 32 (20) 2178-2183
• 12 Suk S I, Lee C K, Kim W J. et al . Adding posterior lumbar interbody fusion to pedicle screw fixation and posterolateral fusion after decompression in spondylolytic spondylolisthesis.  Spine. 1997;  15; 22 (2) 210-219; discussion 219–220
• 13 Kim N H, Lee J W. Anterior interbody fusion versus posterolateral fusion with transpedicular fixation for isthmic spondylolisthesis in adults. A comparison of clinical results.  Spine. 1999;  15; 24 (8) 812-816; discussion 817
• 14 Swan J, Hurwitz E, Malek F. et al . Surgical treatment for unstable low-grade isthmic spondylolisthesis in adults: a prospective controlled study of posterior instrumented fusion compared with combined anterior-posterior fusion.  Spine J. 2006;  6 (6) 606-614. Epub 2006 Oct 2
• 15 Videbaek T S, Christensen F B, Soegaard R. et al . Circumferential fusion improves outcome in comparison with instrumented posterolateral fusion: long-term results of a randomized clinical trial.  Spine. 2006;  1; 31 (25) 2875-2880
• 16 Carragee E J. Single-level posterolateral arthrodesis, with or without posterior decompression, for the treatment of isthmic spondylolisthesis in adults. A prospective, randomized study.  J Bone Joint Surg Am. 1997;  79 (8) 1175-118

Editorial staff perspectives

This is a CoE III treatment study.

Comparing outcomes from patients treated with PLIF with those treated with PLF is a commendable goal and important in the debate about the best treatment options for low-grade adult spondylolisthesis. In order to improve the quality of evidence available to settle the debate, future studies need to address a number of key factors.

Patient selection:

Methodologically, selecting patients based on the completeness of follow-up at a specific time or studies where > 85% are lost to follow-up creates the possibility of selection bias. By selecting patients with a minimum of 4-years follow-up, it is possible that those with less complete follow-up may have different clinical or other characteristics (and outcomes!) that could influence the evaluation of the study outcome and thus bias results. For example, if those who are lost to follow-up are more likely to have a good outcome for a one of the treatments, the analysis would not potentially include as many patients with a good outcome for that treatment and the results may be biased to show that it is less effective than its comparator.

Treatment allocation:

How treatment was allocated was not well described in this paper, ie, what factors determined whether a patient received PLIF versus PLF aside from what appears to be institutional preference (see web appendix). Ideally, patients would be randomized to treatment groups using an appropriate method of concealed allocation. It is common for studies to describe treatment allocation based on surgeon preference or patient presentation. This has the potential to bias study results. For example if patients with more severe disease are more likely to receive one treatment over the other and also have the potential for worse outcomes, the results may not be an accurate reflection of either treatment in patients with the same disease severity. Allocation based on the institution's preference may also bias results as other factors may also differ across institutions. Factors such BMI and previous surgery may influence choice of procedure and therefore outcomes and need to be described.

Retrospective versus prospective approaches:

In this study (and most retrospective studies), it isn't clear that a consistent perioperative protocol (for clinical care or outcomes measurement) was used in both study groups. With prospective study design, there is the potential to decrease study bias compared with retrospective designs. Protocols for patient selection and treatment allocation, perioperative care, collection of data and follow-up that are specified prospectively help assure less biased allocation of patients to treatment and similarity of care and measurement for both groups.

Outcomes:

Definition and evaluation of fusion status is long-held area of controversy. In this study, it is unclear how fusion was determined and if its assessment was independent. Factors such as use of BMP or grafts which may influence fusion and functional outcomes need to be detailed and evaluated for their potential to influence the outcomes. In addition factors such as reduction of deformity, disc height and restoration of lordosis should be evaluated.

Final comments:

This study's use of validated outcomes measures and length of follow-up are two primary strengths. The authors' acknowledgement of the significant loss to followup and limitations imposed by retrospective, nonrandomized studies is commendable.