Inadvertent Screw Stripping During Ankle Fracture Fixation in Elderly Bone

A. Feroz Dinah, Simon C. Mears, Trevor A. Knight, Sandeep P. Soin, John T. Campbell, Stephen M. Belkoff

Research output: Contribution to journalReview articlepeer-review

Abstract

Poor screw purchase because of osteoporosis presents difficulties in ankle fracture fixation. The aim of our study was to determine if cortical thickness, unicortical versus bicortical purchase, and bone mineral density are predictors of inadvertent screw stripping and overtightening. Ten paired cadaver ankles (average donor age, 81.7 years; range, 50-97 years) were used for the study. Computed tomography scanning with phantoms of known density was used to determine the bone density along the distal fibula. A standard small-fragment, 7-hole, one-third tubular plate was applied to the lateral surface of the fibula, with 3 proximal bicortical cortical screws and 2 distal unicortical cancellous screws. A posterior plate, in which all 5 screws were cortical and achieved bicortical purchase, was subsequently applied to the same bones and positioned so that the screw holes did not overlap. A torque sensor was used to measure the torque of each screw during insertion (Ti) and then stripping (Ts). The effect of bone density, screw location, cortical thickness, and unicortical versus bicortical purchase on Ti and Ts was checked for significance (P < .05) using a general linearized latent and mixed model. We found that 9% of the screws were inadvertently stripped and 12% were overtightened. Despite 21% of the screws being stripped or being at risk for stripping, we found no significant predictors to warn of impending screw stripping. Additional work is needed to identify clinically useful predictors of screw stripping.

Original languageEnglish (US)
Pages (from-to)86-89
Number of pages4
JournalGeriatric Orthopaedic Surgery & Rehabilitation
Volume2
Issue number3
DOIs
StatePublished - May 2011

Keywords

  • ankle fracture
  • bone density
  • inadvertent stripping
  • insertion torque
  • stripping torque

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine
  • Rehabilitation
  • Geriatrics and Gerontology

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