Surgical treatment of Isthmic vs. degenerative spondylolisthesis: complications and outcomes

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Decompression and instrumented fusion is a well-established treatment for symptomatic low-grade spondylolisthesis, whether isthmic (IS) or degenerative (DS). Additionally, reduction of the slip has theoretical advantages of indirect foraminal decompression, improved sagittal balance, and more room for an interbody cage. Disc distraction alone often improves the slip for DS, but not IS. When reduction is advantageous (collapsed disc and foramina, grade 2 listhesis), accomplishing both slip reduction and transforaminal lumbar interbody fusion (TLIF) can be technically demanding. The surgical treatment of IS vs DS has never been studied.



This is the largest series of complications and outcomes for surgical treatment of low-grade spondylolisthesis, comparing IS to DS after single and multilevel arthrodesis.


Study Design

A review of prospectively collected clinical and radiographic data


Patient Sample

249 consecutive adults with grade 1 - 2 spondylolisthesis (DS-199, IS-50). Age: DS 65.4 years (34-85 years); IS 50.5 years (14 – 82 years).


Outcomes Measured

VAS, Oswestry (ODI), and pain medication records recorded pre-op, 1 and 2 years post-op. Radiographs were obtained pre-op, 1 and 2 years. Arthrodesis was defined as bridging bone across the interspace, no motion on flexion/extension, and no sign of screw or cage loosening at 2 years.



All underwent laminectomy and pedicle screw fixation. Instrumented correction of listhesis was done for grade 2 slips (1/3 of the series). Excluded: high-grade slips, retro or rotational listhesis, spondylolisthesis with scoliosis. Prior surgery was common: laminectomy-36, fusion-37. Thirty-one were smokers. Posterior arthrodesis averaged 2.6 levels (1-4 levels), similar for both DS and IS. TLIF was performed in 165 at average 1.6 levels.



Follow-up averaged 57 months (12-114 months). Complications were similar between DS and IS: wound infection (2%), and 1 each for nonunion, painful hardware, and radiculopathy. DS had more degeneration related complications: adjacent level degeneration (DS–43%, IS-2%), herniated disc (DS–6%, IS–0%), foot drop (3 vs. 0) and additional surgery for any reason (DS-9%, IS-2%). These differences were not statistically significant. Both single (DS-72, IS-28) and multi-level (DS-127, IS-22) fusions improved clinically. Single-level: VAS for IS: 6.01 pre-op, 2.4 at 2 years (p=0.001); DS: 6.1 pre-op to 2.4 at 2 years (p=0.001). ODI for IS: 46.8 pre-op to 26 at 2 years (p=0.057); DS ODI improved from 47.3 pre-op to 22 at 2 years (p=0.002). Multi-level: VAS for IS: 5.7 pre-op to 2.4 at 2 years (p<0.001); DS: 6.0 pre-op, 2.8 at 2 years (p=0.038). ODI for IS: 45 pre-op, 29 at 2 years (p=0.008); DS ODI improved from 46 pre-op to 26 (p<0.001) at 2 years.



For both DS and IS, surgical decompression, fusion, and listhesis reduction when advantageous result in similar long-term clinical outcomes for single and multi-level constructs, despite age and pathology difference. The differences in complications appear related to degenerative disease. DS patients were 15 years older on average, had much more adjacent level disease, and underwent more revision surgery over nearly 5 years follow-up than did patients treated for IS.