Selection of the Optimal Distal Fusion Level in Posterior Instrumentation and Fusion for Thoracic Hyperkyphosis The Sagittal Stable Vertebra Concept
Department of Orthopedic Surgery, Inha University, Incheon, Korea. Spine
(Impact Factor: 2.3).
04/2009; 34(8):765-70. DOI: 10.1097/BRS.0b013e31819e28ed
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).
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.
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.
Preoperative mean thoracic kyphosis was 86.6 +/- 8.5 degrees and 53.0 +/- 10.4 degrees 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.
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.
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ABSTRACT: OBJECTIVE: Posterior surgical correction and instrumented fusion of Scheuermann' s Disease (SD) is an effective and safe treatment option in severe cases at adulthood. MATERIALS and METHOD: Two groups of 15 patients each were treated with two different instrumented systems. The effi cacy of different posterior instrumentation systems composed of laminar and pedicular hooks (=hybrid) in group 1 and all level-pedicle screw instrumentation in group 2 were compared retrospectively. RESULTS: Mean preoperative thoracal kyphosis values in group 1 were reconstructed from 78.02 degrees to 45.067 degrees postoperatively and measured as 57.4 degrees at the fi nal follow-up. Mean preoperative thoracal kyphosis values in group 2 were reconstructed from 80.46 degrees to 41.73 degrees postoperatively and measured as 45.53 degrees at the fi nal follow-up. Lumbar curves resolved spontaneously in both groups. All level pedicular screw instrumentation was found to be slightly better than hybrid constructs in maintaining the initially corrected kyphotic deformity until the osseous fusion. CONCLUSION: Regression from initial correction of sagittal balance might be seen in patients with SD who undergo posterior instrumented fusion with claws and hooks. We recommend meticulous follow-up of these patients in the postoperative period.
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Available from: Yunus Atici
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