Single-handed, double loaded

Musculoskeletal complaints (MSC) are highly prevalent among the general population. However, single-handed individuals, due to upper limb absence (ULA) or brachial plexus injury (BPI), are even more prone to the occurrence of MSCs. Development of MSCs may be explained by an imbalance between the biomechanical capacity, which is the anatomical and physical exertion that the body can endure without sustaining damage, and the loads put on the tissues in order to perform a functional activity. Performing activities single-handed or with the help of the remnant limb, with or without wearing a prosthesis, leads to a transfer of the loads to the remaining body structures. This increases force and repetition and may result in muscle fatigue, which can be determined with electromyography (EMG). Another way to compensate for the loss of a limb is by using alternative movement strategies and adjusted postures, which can be measured with kinematics. Another explanation for the development of MSC in this population is the presence of central sensitization. When the central nervous system becomes sensitized, the status of nociceptive neurons are changed, resulting in hypersensitivity, hyperalgesia, allodynia, temporal summation and expansion of painful areas. This study aims to investigate the biomechanical imbalance and presence of central sensitization to aid in the development of new/better treatment plans to prevent and to treat MSC. With this pilot study, imbalance and central sensitization outcomes are specified and identified for these populations. These results can be used in defining future research to further establish relationships.

The overarching aim of this project is to study the factors contributing to MSC in individuals with one functional hand. The two primary objectives are: (P1) to examine the presence of muscle fatigue, caused by imbalance between biomechanical loads and biomechanical capacity, in individuals with ULA or BPI and two-handed controls, and (P2) to examine the presence of central sensitization in individuals with ULA or BPI and two-handed controls. The secondary objectives are: (S1) to examine the effect of prosthesis use on the presence of muscle fatigue in individuals with ULA. (S2) To establish population specific results, to aid in the sample size calculations and methodology of future research.

In single-handed individuals it is hypothesized that the biomechanical loads are increased due to compensating for the limb loss by increasing force, repetition and by altering postures. Increasing the biomechanical loads, but maintaining the biomechanical capacity, leads to an imbalance which is hypothesized to lead to a higher prevalence of MSC in single-handed individuals. Additionally, it is hypothesized that single-handed individuals experience more nociplastic pain due to central sensitisation and that therefore the prevalence of MSC is increased.

After METC approval, we want to start in Januari 2020. We start with including participants with ULA and BPI, to each patient we an able bodied control on age and gender. The measurements are expected to be completed within a year.

A central sensitisation protocol with the Central Sensitization Inventory (CSI) questionnaire and the Quantitative Sensory Testing (QST). And a movement protocol consisting of maximum voluntary contractions (MVC) measurements, the Jebsen Taylor Hand Function Test (JTHFT) and the Functional Capacity Evaluation for One-Handed individuals (FCE-OH).