Biomechanical stability of single-screw versus two-screw fixation of an unstable slipped capital femoral epiphysis model: Effect of screw position in the femoral neck

Shyam Kishan, Vidyadhar Upasani, Andrew Mahar, Richard Oka, Tim Odell, Michael Rohmiller, Peter Newton, Dennis Wenger

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

PURPOSE: To biomechanically evaluate single screw and varying 2 screw fixations for an unstable slipped capital femoral epiphysis (SCFE) model using physiologically relevant loading. STUDY DESIGN: In vitro biomechanical study. METHODS: Twenty-four immature porcine proximal femurs were prepared to simulate a mild-to-moderate unstable SCFE. The femurs were randomized into 4 fixation groups: single screw, 2 screws horizontally placed, 2 screws vertically placed, and 2 oblique screws. Biomechanical testing determined maximum load to failure (N), load (N) at 2, 4, 6, and 8 mm of femoral head displacement, and stiffness (newtons per millimeter) for each group. RESULTS: No significant differences were found among the 3 different 2 screw configurations. The 2 screw constructs were 66% stiffer and 66% stronger than the single screw construct. In addition, whereas there was no difference at 2 mm of femoral head displacement, each subsequent displacement (4, 6, and 8 mm) demonstrated significantly higher failure loads when 2 screws were used for stabilization. CONCLUSIONS: Slipped capital femoral epiphysis stabilization with 2 screws leads to increased stability over single screw fixation; however, none of the 3 configurations/placement patterns of the 2 screw constructs seemed to be superior in fixation stability. CLINICAL RELEVANCE: These data support the use of a 2 screw construct in acute/unstable SCFE fixation. The biomechanical benefit of 2 screws needs to be considered in the face of greater potential for inadvertent penetration into the joint with an increased number of screws.

Original languageEnglish (US)
Pages (from-to)601-605
Number of pages5
JournalJournal of Pediatric Orthopaedics
Volume26
Issue number5
DOIs
StatePublished - Sep 1 2006

Keywords

  • Biomechanical analysis
  • SCFE fixation
  • Single versus 2 screws

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Orthopedics and Sports Medicine

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