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Chapter Summary
• Context: Adult spondylolisthesis primarily encompasses two distinct clinicopathological presentations: degenerative spondylolisthesis (DS) and isthmic spondylolisthesis (IS). DS results from progressive intervertebral disc and facet joint deterioration without a pars defect, predominating in women over 50 years of age and most frequently affecting the L4-L5 level. In contrast, IS stems from an abnormality in the pars interarticularis (stress fatigue fracture or congenital elongation), occurring more frequently in males and athletes exposed to repetitive lumbar hyperextension and rotatory loads, with highest incidence at L5-S1. Although both conditions can be discovered incidentally as asymptomatic radiographic findings, symptomatic patients suffer from axial low back pain, radiculopathy, and significant functional disability. The primary clinical challenge is to differentiate their underlying pathophysiological mechanics, correlate radiographic imaging with specific clinical symptoms, and select an individualized conservative or surgical strategy that avoids overtreatment while ensuring adequate neural decompression and sagittal stabilization.
• Chapter Objective: To equip the spine specialist with diagnostic differentiation and structured therapeutic algorithms for degenerative and isthmic spondylolisthesis in adults. The reader will master clinical and multi-modality imaging evaluation, formulate evidence-based conservative care, and define surgical indications based on segmental mechanical instability, neural compression, and the necessity of restoring regional and global sagittal alignment.
• Overview and Core FoundationsEpidemiology and Pathophysiology: Degenerative spondylolisthesis (DS) is characterized by anterior or posterior vertebral slippage with an intact neural arch, secondary to disc senescence and facet arthrosis. It presents a 17.4% prevalence in the general population, predominantly affecting females over 50 at L4-L5. Its natural history is typically benign, rarely exceeding Meyerding Grade II due to natural stabilization by osteophytosis, disc space collapse, and ligamentous traction spurs. Isthmic spondylolisthesis (IS) results from a pars defect, more common in males and athletes, predominantly affecting L5-S1 following bilateral juvenile spondylolysis.
Clinical Presentation and Imaging: Both entities present with back pain and radiculopathy. DS frequently causes neurogenic claudication secondary to central and lateral recess stenosis. IS commonly presents with hamstring spasm and mechanical pain, while severe claudication and sphincter loss are rare. Initial imaging requires standing full-spine AP/lateral radiographs and dynamic flexion-extension views to quantify translational and angular instability. MRI is the modality of choice for soft tissues, foraminal stenosis, and neural compromise. CT characterizes pars fractures, facet orientation, and pedicle morphology. SPECT is reserved for active or occult spondylolytic stress reactions.
Conservative and Surgical Management: First-line care involves NSAIDs, core physical therapy, weight management, and image-guided transforaminal epidural steroid injections (demonstrating higher efficacy in DS). Surgery is indicated after conservative failure or progressive neurological deficits. In low-grade slips (<50%), decision-making hinges on mechanical instability and sagittal alignment: (1) Without instability or malalignment: isolated decompression or limited fusion; (2) With instability: segmental fusion; (3) Requiring sagittal restoration: anterior or lateral interbody devices (ALIF, LLIF, OLIF, or Prone Transpsoas / PTP) restore disc height and segmental lordosis (Figure 1). In high-grade slips (>50%), decompression and solid stabilization are paramount. Partial reduction is indicated selectively to improve sagittal balance, always accompanied by wide neural decompression to avoid traction injuries. In fusions without reduction, extending fixation to L4 with S2-Alar-Iliac (S2AI) screws is recommended.
Future Directions: Modern evolution incorporates computer-assisted navigation, robotic guidance, full-endoscopic decompression, single-position prone transpsoas surgery (PTP), and machine learning predictive analytics for clinical outcomes.
• Clinical Application: In clinical practice, managing adult spondylolisthesis requires rigorous correlation between radiographic findings and patient symptomatology, avoiding surgery based solely on slip percentage. Standing flexion-extension radiographs define segmental dynamic instability, while MRI delineates central and subarticular stenosis. The choice between decompression alone and instrumented fusion rests on mechanical stability and the need for sagittal realignment. Standalone interbody cages must be used cautiously in osteoporotic or elderly patients due to subsidence risks. Anterior and lateral approaches (ALIF, LLIF, PTP) restore disc height and segmental lordosis, reducing adjacent-segment stress (Table 4). In high-grade slips, complete translational reduction should be avoided due to severe risk of L5 nerve root stretch neuropraxia; the priority is wide neuroforaminal release, restoring lumbosacral kyphosis, and achieving solid spinopelvic fusion.
