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Biomechanical Analysis of the Distal Metaphyseal Ulnar Shortening Osteotomy
Jeffrey A. Greenberg, MD, MS1; Frederick W. Werner, MME, PE2; Jared Smith, BA2
1The Indiana Hand to Shoulder Center, Indianapolis, IN; 2Department of Orthopedic Surgery, Upstate Medical University at Syracuse, Syracuse, NY

Hypothesis: Distal metaphyseal ulnar shortening osteotomy (DMUSO) decreases load transmitted to the distal ulna, therefore, is an effective alternative to traditional ulnar shortening osteotomy.

Methods: 7 fresh frozen cadaver arms were dissected retaining all interosseous membrane structures and tendons. Zero rotation view x-rays were obtained.  The arms were mounted in the wrist simulator.

Six degree of freedom load cells (AMTI, Boston , MA) were mounted to the distal radius and ulna.  Electromagnetic sensors (Fastrak, Polhemus , VT) were used to measure wrist motion. Cyclic flexion-extension cycles from 30 degrees of extension to 30 degrees of flexion (fe30), 30 degrees of extension to 50 degrees of flexion (fe50), radioulnar deviation from 10 degrees of radial deviation to 20 degrees of ulnar deviation (ru15) and a dart throw motion from 30 degrees of extension and 10 degrees of radial deviation to 30 degrees of flexion and 10 degrees of ulnar deviation (dart) were used to evaluate ulnar load before and after DMUS0. Load before and after DMUSO was also measured at static wrist positions of neutral, 20 degrees of flexion, 20 degrees of extension, 10 degrees of radial deviation and 20 degrees of ulnar deviation.

The ulnar osteotomy was performed after measurements were taken in the intact specimens.  A 2mm high closing wedge osteotomy was made and compressed with a single mini-Accutrak®  screw (Acumed, Beaverton , OR). Post-osteotomy x-rays were obtained to determine correction of ulnar variance.

Differences in the static and dynamic forces transmitted were examined by a 2 way repeated measures ANOVA.  If a difference in measured forces was found to be statistically significant p<0.05, a paired t test was performed at each wrist position.

Results: At each static position, statistically significant decreases in ulnar load were noted after DMUS0.  In addition, mean and maximum loads decreased for each dynamic cycle.  Ulnar variance decreased in all specimens.


  • DMUSO decreases load across the ulna.
  • Decreased loads are evident at static positions and during dynamic cyclical wrist ranges of motion. 
  • Decreased ulnar load is the goal of surgical treatment for ulnar impaction and, biomechanically, DMUSO achieves this goal. 
  • Correlation will be necessary to determine if the biomechanical results translate into clinical symptomatic relief.

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