Sequential Temporary Apical Rod Technique for Segmental Reduction of Thoracic Kyphosis: Results in 26 Consecutive Adult Patients

• e - Medtronic Sofamor Danek

Introduction: Most reports on surgical correction of kyphosis do not discuss in detail the technique used for reduction. Sources which do, including the SRS Spinal Instrumentation Manual, usually describe cantilever maneuvers based on a proximal or distal anchor point. While effective, these methods focus stress on the upper and lower instrumented vertebrae (UIV, LIV) requiring forceful maneuvers that may be difficult to control, resulting in loosening of fixation points, poor correction or junctional kyphosis. A method which allows more gradual and controlled posterior shortening starting from the apex and working outward, without concentrating reduction stress at the LIV and UIV, may be safer and more effective.

Purpose: To report our radiographic results and complications in 26 consecutive adult thoracic kyphosis patients treated with a new Sequential Temporary Apical Rod (STAR) technique, adaptable to any posterior rod system.

Methods: 26 consecutive adults surgically treated for thoracic kyphosis with minimum 2 year follow-up (25- 61 mos) were evaluated. All were instrumented posteriorly with Sequential Temporary Apical Rod (STAR) reduction technique. There were 7 males and 19 females, mean age 44.1 years (19-67). Diagnoses included Scheuermann’s Kyphosis (9), Degenerative (5), Post-traumatic (4), Osteopenia (3), Neuromuscular (3), Ankylosing Spondylitis (1) and Congenital (1). Surgery included additional thoracoscopic anterior discectomy & fusion (11), open anterior discectomy & fusion (8) or posterior only (7). All patients had multi-level posterior apical Smith-Peterson osteotomy (avg. 4.8 levels). The STAR reduction commences with a short 1 or 2 segment left rod (#1) inserted at the apex. Compression is gradually applied while anteriorly directed manual pressure assists reduction. Once apical correction is obtained, this rod is temporarily set. While rod #1 maintains the apex reduction, a slightly longer rod (#2) is placed on the right spanning one segment above and below the first. Rod #2 is then gradually compressed, reducing the two segments adjacent to apex rod #1. While rod #2 maintains this periapical reduction, rod #1 is removed and a new longer left rod (#3) is placed, spanning one more segment above and below #2. The reduction continues in alternating sequence using progressively less reduction force to a point 1 or 2 segments from the end vertebrae. While the final (longest) temporary rod maintains reduction, the 2 permanent full-length rods are then placed with minimal stress required at UIV or LIV.

Results: Average preop kyphosis was 86.1º (range 64-121º) and was corrected to 32.7º postop (range 19- 55º). The mean net thoracic correction was 51.2º (range 36-74º) in this rigid adult population. Sagittal balance averaged + 3.8 cm preop (+8.8 to -1.6 cm) and -0.7 cm at follow-up (+1.9 to -2.9 cm). There were no neurologic complications, infections, pseudoarthrosis or reoperations. Instrumentation utilized a 6.35 mm rod in all cases and implants were hook only (6), screws only (7) or hooks & screws (13). Reduction related complications were 1 minor intra-op laminar fracture (bypassed with final rods), 1 unilateral UIV hook dislodgement (age 62) and 1 late junctional compression fracture at T2 (age 65). These later 2 osteopenic patients (7.6%) were the only ones with any junctional kyphosis at the UIV, and none occurred at the LIV.

Conclusion: In rigid adult kyphosis >85º, the STAR reduction technique allows for gradual, controlled reduction resulting in net correction of 51.2º. UIV complications were only seen in 2 older patients (7.6%). This apical-based technique minimizes stresses at end vertebrae, reducing fixation failures or junctional kyphosis while restoring sagittal balance. The STAR technique can be used with any rod system and is a useful alternative to cantilever reduction.

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