Selection of the optimal distal fusion level in posterior instrumentation and fusion for thoracic hyperkyphosis: The sagittal stable vertebra concept

Kyu Jung Cho, Lawrence G. Lenke, Keith H. Bridwell, Mitsuhiro Kamiya, Brenda Sides

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73 Scopus citations

Abstract

STUDY DESIGN.: Retrospective study. OBJECTIVE.: To determine the appropriate distal fusion level in posterior instrumentation and fusion for thoracic hyperkyphosis by investigating the relationship between the sagittal stable vertebra ([SSV]-the most proximal lumbar vertebral body touched by the vertical line from the posterior-superior corner of the sacrum), first lordotic vertebra (just caudal to the first lordotic disc), and selected lowest instrumented vertebra (LIV). SUMMARY OF BACKGROUND DATA.: It has been recommended that the distal end vertebra and the first lordotic disc beyond the transitional zone distally be included in distal fusion for thoracic hyperkyphosis; however, we have seen distal junctional breakdown even when these rules have been followed. METHODS.: Thirty-one patients (mean age: 18 years, range: 13-38) who underwent long posterior instrumentation and fusion for thoracic hyperkyphosis with a minimum 2-year follow-up were reviewed. Preoperative diagnoses included Scheuermann kyphosis (n = 29), post-traumatic kyphosis (n = 1), and postlaminectomy kyphosis (n = 1). According to the distal fusion level, patients were divided into 2 groups. Group I (n = 24): LIV included the SSV; group II (n = 7): the LIV was proximal to the SSV. Patients were evaluated using standing radiographs and chart review. RESULTS.: Preoperative mean thoracic kyphosis was 86.6 ± 8.5° and 53.0 ± 10.4° at final follow-up with a correction rate of 39%. Preoperative average sagittal balance was slightly negative (-0.24 ± 3.8 cm), and became slightly more negative (-1.33 ± 2.8 cm) by final follow-up. There were no statistical differences in thoracic kyphosis between the 2 groups. However, there was a statistically significant difference with group II having a more posterior translation of the center of the LIV from the posterior sacral vertical line before surgery and at final follow-up (P = 0.003). In group I, distal junctional problems developed in 2 of 24 (8%) patients and in group II, problems occurred in 5 of 7 (71%) patients (P < 0.05). Despite extending the fusion to the first lordotic vertebra, distal junctional problems developed in 3 of 8 (38%) patients. CONCLUSION.: The distal end of a fusion for thoracic hyperkyphosis should include the SSV. Levels that include the first lordotic vertebra but not the SSV are not always appropriate to prevent postoperative distal junctional kyphosis.

Original languageEnglish
Pages (from-to)765-770
Number of pages6
JournalSpine
Volume34
Issue number8
DOIs
StatePublished - Apr 15 2009

Keywords

  • Distal fusion level
  • Sagittal stable vertebra
  • Thoracic hyperkyphosis

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