Biomechanical evaluation of the upper extremity in patients with osteogenesis imperfecta - a pilot study

Osteogenesis imperfecta (OI) (‘brittle bone disease’) is a rare genetic disorder, which is associated with inadequate morphological and mechanical properties of the bone. In consequence, OI-affected patients might suffer from bone fractures and severe deformities. Up to now, a few studies have investigated the gait biomechanics of patients with OI and have revealed differences to healthy subjects [1]. However, the function of the upper extremities (UE) has only been investigated by questionnaires. To the author’s knowledge, kinematics and function of the upper extremity in OI-affected persons have not been quantified with movement analysis to date. The study aimed to investigate the kinematics and function of the upper extremity in patients affected by OI in comparison with non-affected persons. We conducted a cross-sectional study and recorded the kinematics of 14 OI-affected patients (OIAP; median age: 34.5 y, range 64 y) (17 Vicon® cameras) while performing the Southampton Hand Assessment Procedure (SHAP) and isolated joint motion. Nine segments were defined in the upper body and joint angles were calculated with the ISB-Recommendation based ULEMA algorithm. The function was evaluated with the SHAP, which consists of 26 activities of daily living (ADLs) and quantified by the Linear Index of Function (LIF) which represents the time of execution. The Arm Profile Score (APS) quantifies the deviation in the joint angles in comparison with healthy controls (HC). Additionally, the active Range of Motion (ROM) of all relevant joints was evaluated by conducting isolated joint motion. All data were descriptively compared with healthy controls (n=20, median age: 26.5 y, range: 28 y). Overall, OIAP shows a lower median LIF (95.3±2 vs. 99.1±0.2) and a higher median APS (18.4°±3.4° vs. 5°±0.7°) in the SHAP. In 24/26 ADLs the LIF and APS of OIAP is outside mean±1*std and in 17/26 ADLs outside mean±2*std of HC. No ROM deviations were observed in OIAP outside mean±1*std of HC, except less pro/supination (absolute: -28°, relative: -24%). Regarding shoulder rotation, OIAP shows mentionable reduced ROM (-10°, - 8%). However, this remains within mean±1*std of HC. We provide the first biomechanical description of the upper extremity in OI-affected children and adults. The study revealed relevant differences in kinematics and function of the upper extremity between OIAP and HC. OIAP performs the SHAP slower than HC (reduced LIF), which is associated with a reduced function. We see more deviation in the joint kinematics (higher APS) as well, which is associated with compensatory movements. Only rotational degrees of freedom of the elbow and shoulder appears to be affected by a reduced ROM. The OIAS group is quite heterogeneous in age, which appears critically regarding the SHAP [2]. Further studies with bigger samples and age-matched control groups are necessary.