Long adult deformity fusions to L5 and the sacrum. A matched cohort analysis.
METHODS
A matched cohort analysis of long adult deformity fusions according to distal fusion level (L5 vs. S1). OBJECTIVE.: To compare the results of long adult deformity fusions to either L5 or the sacrum in the presence of a "healthy" 5-1 disc using a matched cohort analysis.


BACKGROUND
For adult spinal deformity, the decision often arises whether to terminate a long fusion at L5 or the sacrum. The decision is especially challenging in the presence of a "healthy" (Grade 0 to 1 degeneration) 5-1 disc.


METHODS
A total of 95 adult deformity patients that underwent fusion from the thoracic spine to either L5 or the sacrum were sorted according to five preoperative criteria: 5-1 disc status, patient age, smoking status, number of levels fused, and sagittal balance. Two cohorts (L5, 27 patients; sacrum, 12 patients) were precisely matched according to the five criteria. Patients were evaluated at 2-year minimum follow-up according to radiographic data, complications, and SRS-24 outcomes.


RESULTS
Correction of sagittal imbalance was superior for sacrum patients (C7 plumb line: L5, 0.9 cm; sacrum, 3.2 cm; P = 0.03). At latest follow-up (L5, 5.2 years; sacrum, 3.7 years), 67% of L5 patients had radiographic evidence of advanced 5-1 disc degeneration and the L5 cohort tended to have inferior sagittal balance (C7 plumb line: L5, +4.0 cm; sacrum, +1.2 cm; P = 0.06). The sacrum cohort, however, required more surgical procedures (L5, 1.7; sacrum, 2.8; P = 0.03) and experienced a greater frequency of major complications (L5, 22%; sacrum, 75%; P = 0.02), including nonunion (L5, 4%; sacrum, 42%; P = 0.006) and medical morbidity (L5, 0%; sacrum, 33%; P = 0.001). SRS-24 scores reflected a similar patient assessment of outcome and function for the two cohorts (L5, 89; sacrum, 87).


CONCLUSIONS
At 3 to 5 years' mean follow-up, long adult fusions to the sacrum required more procedures and had a higher frequency of complications than similar fusions to L5. For fusions to L5, subsequent subjacent disc degeneration is common and may be associated with a forward shift in sagittal balance. The ultimate influence of these factors on long-term outcomes remains to be seen.
Edwards
Charles C
CC
Washington University School of Medicine, Department of Orthopaedic Surgery, St. Louis, MO 63110, USA.
Bridwell
Keith H
KH
Patel
Alpesh
A
Rinella
Anthony S
AS
Berra
Annette
A
Lenke
Lawrence G
LG
D000328:Adult; D015331:Cohort Studies; D015299:Discitis / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D008923:Missouri / Q000453:epidemiology; D009038:Motion; D010003:Osteoarthritis / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D017060:Patient Satisfaction; D011183:Postoperative Complications / Q000453:epidemiology / Q000473:pathology; D011300:Preoperative Care; D011542:Pseudarthrosis / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D011859:Radiography; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods* / Q000706:statistics & numerical data; D016896:Treatment Outcome