Does ulnar variance change with age and what is the influence of training and biological characteristics in this change? A short-term longitudinal study in Portuguese artistic gymnasts.

Objective: To analyze the variability and longitudinal stress-related changes in ulnar variance (UV) in a group of immature artistic gymnasts. The relationship between UV and a group of biological and training variables was also investigated. Design: Prospective cohort study. Setting: Portuguese Federation of Gymnastics. Participants: Twenty-five Portuguese skeletally immature gymnasts competing nationally. Assessment of Risk Factors: Skeletal age (Tanner–Whitehouse 3 method), stature, body mass and body mass index (BMI) (Seca stadiometer), fat-free mass and percentage of body fat mass (Tanita BC 418), handgrip strength (Takei dynamometer), and training data (interview). Main Outcome Measures: To determine UV stress-related changes over time, left UV was obtained using Hafner procedure. Ulnar variance values and biological characteristics were tested twice (at baseline and after 18 months of training). Results: Analysis of covariance analysis presented a significant interaction between age and time effect in UV at baseline. Each category of UV reacted differently to the interaction between age and training time. Significant relationships between UV and biological and training variables (chronological and skeletal age, body mass, BMI, handgrip strength, hour per week, and years of training) were evident in at least one of the moments of data collection. Conclusions: The gymnasts showed significant longitudinal UV changes toward less negative UV over the training period. Nevertheless, we could not find a significant correlation between UV and the majority of the researched variables. Thus, although UV has been broadly studied, this phenomenon is complex because it depends on different intrinsic and extrinsic factors that are difficult to control, making necessary additional research on this topic. Clinical Relevance: The gymnast's wrist has been associated with a high incidence of painful symptomatology and injuries, leading to the formulation of several hypotheses related to the UV ethiology. Knowledge about the possible intrinsic or extrinsic factors related to UV changes and/or different UV categories (negative, neutral, and positive), as well as their consequent specific injuries in gymnasts' wrists may contribute to a primary prevention or reduction in the occurrence, recurrence and severity of pain, functional disability, or injuries in radius–ulnocarpal joint, thereby improving gymnasts' performance.