Impact of Patient-specific Factors and Spinopelvic Alignment on the Development of Adjacent Segment Degeneration After Short-segment Lumbar Fusion

Multifidus Degeneration: The Key Imaging Predictor of Adjacent Segment Disease

Study DesignRetrospective cohort study.ObjectivesTo identify imaging predictors on pre- and perioperative imaging that are associated with a future revision surgery for adjacent segment disease (ASD) following lumbar fusion.MethodsPatients undergoing open posterior lumbar fusion between 2014-2022 were followed-up for >2-year. The initial MRI was evaluated for disc degeneration by Pfirrmann (grade 1-5); Modic changes (0-3); as well as fatty infiltration and functional cross-sectional area (fCSA) of the multifidus, erector spinae, and psoas. Spinopelvic alignment was measured pre- and postoperatively.ResultsOf 216 patients, 14.8% (n = 32) required revision surgery for ASD in the further course. There were no significant differences in Modic changes or Pfirrmann grades between the ASD group and controls. Fatty infiltration was significantly higher in the ASD group for both the erector spinae (40.5% vs 36.9%, P = 0.043) and multifidus muscles (61.0% vs 53.9%, P = 0.003). Additionally, the multifidus fCSA was smaller in patients who developed ASD (5.7 cm2 vs 6.7 cm2). Pre- and postoperative spinopelvic parameters were not significantly different between groups, and no other MRI measurements showed a significant difference. In a multivariable logistic regression model adjusting for age and sex, multifidus fatty infiltration emerged as the only significant predictor of ASD revision surgery (P = 0.004). Patients with more than 58% multifidus fatty infiltration had over double the risk of developing ASD (OR 2.7, 95% CI: 1.1-6.5, P = 0.032).ConclusionsMultifidus fatty infiltration is the key imaging predictor for the development of ASD requiring surgical revision. Disc degeneration and spinopelvic alignment appear to have less impact.

Impact of iatrogenic alterations on adjacent segment degeneration after lumbar fusion surgery: a systematic review

PURPOSE

Adjacent segment degeneration (ASDeg) and disease (ASDis) remain significant challenges following lumbar spinal fusion surgery, with reported incidences of 36% for ASDeg and 11% for ASDis within two to seven years post-operation. However, the mechanisms leading to the development of ASDeg are still poorly understood. This comprehensive review aims to elucidate the multifactorial etiology of ASDeg by examining important iatrogenic alterations associated with spinal fusion.

METHODS

A systematic review following PRISMA guidelines was conducted to identify clinical studies quantifying the occurrence of ASDeg and ASDis after lumbar fusion surgery. An EMBASE and citation search up to April 2023 yielded 378 articles. Data extracted encompassed study design, fusion type, sample size, patient age, and incidence of ASDeg and ASDis. A total of 87 publications were analyzed in the context of iatrogenic alterations caused by surgical access (muscle damage, ligament damage, facet joint damage) and instrumentation (fusion angle, immobilization).

RESULTS

Ligament damage emerged as the most impactful iatrogenic factor promoting ASDeg and ASDis development. Similarly, muscle damage had a significant impact on long-term musculoskeletal health, with muscle-sparing approaches potentially reducing ASDis rates. Immobilization led to compensatory increased motion at adjacent segments; however, the causal link to degeneration remains inconclusive. Fusion angle showed low evidence for a strong impact due to inconsistent findings across studies. Facet joint violations were likely contributing factors but not primary initiators of ASDeg.

CONCLUSION

Based on the analyzed literature, ligament and muscle damage are the most impactful iatrogenic factors contributing to ASDeg and ASDis development. Minimally invasive techniques, careful retractor placement, and ligament-preserving decompression may help mitigate these effects by reducing undue muscle and ligament trauma. Although it is not possible to definitively advocate for one or more techniques, the principle of selecting the most tissue-sparing approach needs to be scaled across surgical planning and execution. Further research is necessary to fully elucidate these mechanisms and inform surgical practices to mitigate ASDeg risk.

Segmental Lordosis Restoration During Lumbar Degenerative Spinal Fusion: Surgical Techniques and Outcomes

The science of spinal alignment has progressed rapidly since Jean Doubousset described the cone of economy in the 1970s. It is now clearly established that global and regional spinal alignment are associated with improved patient-reported outcome and rates of success of lumbar spinal fusion. Evidence has now emerged that segmental level-by-level alignment is also associated with positive patient outcomes. As such, restoring sagittal alignment matched to spinopelvic morphology during degenerative lumbar surgery can optimize surgical outcomes by preventing adjacent segment pathology. This review focuses on the vital importance of spinal alignment in different spinal conditions, provides a guide for measurement of spinopelvic parameters, and outlines literature regarding lumbar restoration in degenerative spinal fusion.

Sagittal Alignment in the Degenerative Lumbar Spine: Surgical Planning

➤ Sagittal alignment of the spine has gained attention in the field of spinal deformity surgery for decades. However, emerging data support the importance of restoring segmental lumbar lordosis and lumbar spinal shape according to the pelvic morphology when surgically addressing degenerative lumbar pathologies such as degenerative disc disease and spondylolisthesis.➤ The distribution of caudal lordosis (L4-S1) and cranial lordosis (L1-L4) as a percentage of global lordosis varies by pelvic incidence (PI), with cephalad lordosis increasing its contribution to total lordosis as PI increases.➤ Spinal fusion may lead to iatrogenic deformity if performed without attention to lordosis magnitude and location in the lumbar spine.➤ A solid foundation of knowledge with regard to optimal spinal sagittal alignment is beneficial when performing lumbar spinal surgery, and thoughtful planning and execution of lumbar fusions with a focus on alignment may improve patient outcomes.