title: Influence of wrist position on maximum grip force in a post-operative orthosis.
abstract: BACKGROUND
  Flexor tendon repair in the hand remains challenging in avoiding tendon rupture and adhesion formation. Post-operative mobilization has been shown to be critical in regaining functional range of motion.
  
  
  OBJECTIVE
  The objective of this study is 2-fold: to assess the influence of wrist position on maximum grip force generated in a post-operative orthosis and to determine the correlation between this maximum grip force and an individual's grip strength.
  
  
  METHODS
  Clinical measurement Methods: A total of 30 uninjured wrists of right-handed men were given a post-operative orthosis with an incorporated Caroli-hinge. The maximum grip force was measured according to a different wrist position ranging from -30° extension until 80° of flexion using a 10° interval. These measurements were plotted out on a graph for regression analysis. A correlation was determined between measurements in a neutral wrist position and maximum grip strength generated without an orthosis. To assess the coherence of the measurements, a mean intraclass correlation coefficient was used.
  
  
  RESULTS
  The maximum grip force values were statistically significantly different in every wrist position and decreased progressively with an increasing flexion angle ( p < 0.05). This relationship is expressed in a logistic regression curve f( x) = -4.98 + 16.92/(1 + (x/8.59))2.24. A wrist position of 4.4° of flexion was derived from this function to cause a maximum grip force reduction of 33%. Further analysis showed a force decrease of 50% at 23.2° and 66% at 51.8° of wrist flexion. The grip strength measured without an orthosis showed a positive correlation with previous measurements (Spearman's correlation coefficient = 0.74 for the right hand and 0.72 for the left hand ( p < 0.001)).
  
  
  CONCLUSIONS
  The obtained logistic function allowed to derive the wrist position needed in a post-operative orthosis to obtain a desired amount of maximum grip force reduction. Clinical relevance Measuring a high grip force in a clinical setting of flexor tendon repair on the contralateral non-affected hand could indicate the use of an increased flexion angle in a post-operative orthosis. This reduces the load transferred on the tendon repair when involuntary contractions take place, for example, during sleeping when positioned in a post-operative orthosis.
authors.affiliation: 1 Department of Hand Surgery, AZ Groeninge, Kortrijk, Belgium.|2 Department of Orthopaedic Surgery, AZ Groeninge, Kortrijk, Belgium.
authors.forename: Arne
authors.initials: A
authors.lastname: Burssens
authors.affiliation: 3 V!GO Campus Wetteren, Wetteren, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Schelpe
authors.affiliation: 2 Department of Orthopaedic Surgery, AZ Groeninge, Kortrijk, Belgium.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Vanhaecke
authors.affiliation: 2 Department of Orthopaedic Surgery, AZ Groeninge, Kortrijk, Belgium.
authors.forename: Marleen
authors.initials: M
authors.lastname: Dezillie
authors.affiliation: 2 Department of Orthopaedic Surgery, AZ Groeninge, Kortrijk, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: Stockmans
mesh_terms: D000328:Adult; D004867:Equipment Design; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009989:Orthotic Devices; D011182:Postoperative Care; D016059:Range of Motion, Articular / Q000502:physiology; D014955:Wrist Joint / Q000502:physiology*; D055815:Young Adult
keywords: Biomechanics of prosthetic/orthotic devices; biomechanics; orthopedic surgery; rehabilitation