title: Quantitative assessment of dynamic control of fingertip forces after pollicization.
abstract: Dexterity after finger pollicization (reconstruction to thumb) is critical to functional outcomes. While most tests of hand function evaluate a combination of strength, coordination, and motor control, the Strength-Dexterity (S-D) paradigm focuses on the dynamic control of fingertip forces. We evaluated 10 pollicized and 5 non-pollicized hands from 8 participants ages 4-17 years (2 female, 6 male; 10.6 ± 4.5 years). Participants partially compressed and held an instrumented spring prone to buckling between the thumb and first finger to quantify dynamic control over the direction and magnitude of fingertip forces. They also completed traditional functional tests including grip, lateral pinch, and tripod pinch strength, Box and Blocks, and 9-hole peg test. Six of 10 pollicized hands and all non-pollicized hands had S-D scores comparable to typically developing children. However, dynamical analysis showed that pollicized hands exhibit greater variability in compression force, indicating poorer corrective action. Almost all pollicized hands scored below the normal range for the traditional functional tests. The S-D test Z-scores correlated moderately with Z-scores from the other functional tests (r = 0.54-0.61; p = 0.02-0.04) but more weakly than amongst the other functional measures (r = 0.58-0.83; p = 0.0002-0.02), suggesting that the S-D test captures a different domain of function. A higher incidence of radial absence in the hands with poor S-D scores (3/4 vs. 0/6 in hands with normal S-D scores, p = 0.03) was the only clinical characteristic associated with S-D outcome. Overall, these results suggest that while most pollicized hands can control fingertip forces, the nature of that control is altered.
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, Los Angeles, CA, USA; Orthopaedic Surgery Department, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Nina
authors.initials: N
authors.lastname: Lightdale-Miric
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, Los Angeles, CA, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Mueske
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA.
authors.forename: Sudarshan
authors.initials: S
authors.lastname: Dayanidhi
authors.affiliation: Division of Rehabilitation Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Loiselle
authors.affiliation: Division of Rehabilitation Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA.
authors.forename: Jamie
authors.initials: J
authors.lastname: Berggren
authors.affiliation: Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA.
authors.forename: Emily L
authors.initials: EL
authors.lastname: Lawrence
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, Los Angeles, CA, USA.
authors.forename: Milan
authors.initials: M
authors.lastname: Stevanovic
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA; Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Valero-Cuevas
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, Los Angeles, CA, USA; Orthopaedic Surgery Department, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA; Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA. Electronic address: twren@chla.usc.edu.
authors.forename: Tishya A L
authors.initials: TA
authors.lastname: Wren
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005385:Fingers / Q000503:physiopathology* / Q000601:surgery; D006226:Hand Deformities / Q000503:physiopathology / Q000601:surgery*; D018737:Hand Strength; D006801:Humans; D008297:Male; D019651:Plastic Surgery Procedures; D013933:Thumb / Q000002:abnormalities* / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome
keywords: Dexterity; Hand function; Pollicization; Strength–dexterity; Surgical outcome