Introduction: Decompression and fusion in the setting of metastatic spine disease has historically been palliative in nature. With improvements in adjuvant treatments, both medical and radiotherapy, survival in this population is increasing. There is a lack of literature evaluating the long-term reciprocal changes observed in this population. Traditional surgery in cancer patients fixates minimum of 2 levels above and below index pathology. These long segment constructs lead to increased forces at adjacent levels. There is a lack of evidence supporting the decisions around how many vertebrae to instrument. We hypothesize that instrumenting 1-level cranial and caudal to the index pathology will reduce mechanical forces at adjacent levels.
Methods: This study was performed under IRB approval. Inclusion criteria were 1) spine surgery for metastatic spine disease, 2) minimum 1 year survival, 3) radiographic follow up minimum 1 year from index spine surgery. Patients who fit inclusion criteria were separated into cohorts for construct length +/-1 level (short segment) and +/- 2 or more levels (long segment). Retrospective chart review was performed collecting demographic and radiographic data. Statistics was performed using SPSS software (V29.0).
Results: A total of 27 patients met inclusion criteria with 16 having short segment constructs and 11 patients undergoing long segment fusion. The short segment cohort had significantly higher pre-operative SORG nomogram (214.5 ± 39.3 vs. 167.3 ± 36.5, p=0.004), as well as a higher proportion of cases done in the mobile spine per Spinal Neoplastic Instability Scale (SINS) with 3, 9, and 4 cases in the semi-rigid, mobile, and junctional spine, respectively compared to 4, 1, and 6 for long segment cases (p=0.044). Additionally, segmental lordosis and disc heights at levels above and below the construct were not significantly different. There was no significant difference in overall survival between cohorts. No other demographic or radiographic variables were significantly different between cohorts.
Conclusion : Despite having significantly worse pre-operative SORG nomogram, short segment constructs demonstrated non-inferiority with regard to global and segmental reciprocal changes in the spine. Construct length did not appear to impact survival. Further work is needed to evaluate indications for construct length in spine oncology patients.
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