Three-dimensional load displacement properties of posterior lumbar fixation

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Spinal Surgery

Background:

• Segmental spinal instability necessitates effective posterior stabilization.
• Pedicular fixation devices are hypothesized to outperform sublaminar wire systems.
• Minimizing immobilization of normal motion segments is a key consideration.

Purpose of the Study:

• To compare the biomechanical performance of three posterior spinal stabilization systems.
• To evaluate the efficacy of pedicular screw fixation in stabilizing posterior segmental defects.
• To assess stabilization performance under compressive and rotational loads.

Main Methods:

• Human cadaveric lumbosacral specimens were utilized.
• Testing involved intact, destabilized (laminectomy and facetectomy at L3/L4), and instrumented states.
• Three fixation systems were compared: Hartshill rectangle, Acromed/Steffee, and Synthes/Dick.
• Constructs spanned two to four vertebral levels.

Main Results:

• The Acromed/Steffee system with pedicular screws (L2-L5) significantly reduced intersegmental distraction under compression.
• Posterior constructs augmented stability of posterior segmental defects.
• Pedicular fixation immediately above and below the defect provided stable fixation.

Conclusions:

• Posterior spinal constructs significantly enhance stability in posterior segmental defects.
• Pedicular fixation is effective for stabilizing the resected lumbar spine segments.
• The Acromed/Steffee system demonstrated robust stabilization capabilities.