title: Biomechanics of superior oblique Z-tenotomy.
abstract: BACKGROUND
  A recent report suggests that 70%-80% Z-tenotomy of the superior oblique tendon is necessary to effectively treat A-pattern strabismus associated with over depression in adduction. To clarify the clinical effect, we compared the biomechanics of Z-tenotomy on the superior oblique tendon, superior rectus tendon, and isotropic latex material.
  
  
  METHODS
  Fresh bovine superior oblique tendons were trimmed to 20 mm × 10 mm dimensions similar to human superior oblique tendon and clamped in a microtensile load cell under physiological conditions of temperature and humidity. Minimal preload was applied to avoid slackness. Tendons were elongated until failure following Z-tenotomies, made from opposite tendon margins, spaced 8 mm apart and each encompassing 0%, 20%, 40%, 50%, 60%, or 80% tendon width. Digitally sampled failure force was monitored using a precision strain gauge. Control experiments were performed in similar-sized specimens of bovine superior rectus tendon and isotropic latex.
  
  
  RESULTS
  Progressively increasing Z-tenotomy of latex caused a linearly graded reduction in force. In contrast, Z-tenotomy of up to 50% in superior oblique and superior rectus tendons caused nonlinear reduction in force transmission that reached a negligible value at 50% tenotomy and greater.
  
  
  CONCLUSIONS
  Z-tenotomy up to 50% progressively reduces extraocular tendon force transmission, but Z-tenotomy of ≥50% is biomechanically equivalent in vitro to complete tenotomy.
authors: Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles; Department of Mechanical and Aerospace Engineering, University of California, Los Angeles.
authors: Andrew
authors: A
authors: Shin
authors: Lawrence
authors: L
authors: Yoo
authors: Joseph L
authors: JL
authors: Demer
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D023421:Models, Animal; D009801:Oculomotor Muscles / Q000502:physiology* / Q000601:surgery; D013314:Stress, Mechanical; D013710:Tendons / Q000502:physiology* / Q000601:surgery; D058971:Tenotomy / Q000379:methods*; D013718:Tensile Strength / Q000502:physiology*