P35: Alterations of forces applied under the feet in patients with epidermolysis bullosa simplex during gait

Manrup Hunjan,^1,2 Valter Devecchi,³ Ajoy Bardhan,^1,2 Natasha Harper,¹ Mark O’Sullivan,¹ Deborah Falla³ and Adrian Heagerty^1,2

¹National Adult Epidermolysis Bullosa Service, Solihull Hospital, University Hospitals Birmingham NHS Trust, Solihull, UK; and ²Institute of Clinical Sciences & Institute of Inflammation and Ageing, College of Medicine & Dental Sciences and ³Centre for Sports Exercise and Rehabilitation University of Birmingham, Birmingham, UK

Epidermolysis bullosa simplex (EBS) is an inherited condition that is usually a result of mutations in either KRT5 or KRT14. Affected individuals develop painful blistering and keratoderma causing significant difficulty walking. The impact that blistering, keratoderma and pain may have on gait pattern has not yet been evaluated. We hypothesized that such impairment will affect gait pattern and the distribution of forces applied under the surface of feet, with potential implications upon gait stability and motor control. This study aimed to assess ground reaction forces (GRFs) in patients with EBS during gait. Adults aged ≥ 18 years with a clinical and molecular diagnosis of EBS were recruited. Exclusion criteria included comorbidities that could independently affect gait (e.g. hemiplegia, inflammatory arthritis and previous injury). Patients with EBS were asked to walk barefoot on an 8 m straight, level walkway at a self-selected spontaneous speed. Two force plates embedded in the middle of the walkway were used to collect the GRF components along the anteroposterior (Fy), mediolateral (Fx) and vertical (Fz) axes under the feet. During each step, two peaks which correspond to the braking and propulsive phases of gait were identified for each GRF component (Fx, Fy, Fz). All peaks were normalized to the body weight. Extracted data from patients with EBS were matched by sex and age with a control group obtained from a published dataset of gait in asymptomatic adults (Schreiber C, Moissenet F. A multimodal dataset of human gait at different walking speeds established on injury-free adult participants. Sci Data 2019; 6: 111). Comparisons between groups were conducted using general linear models. There were 21 adults in each group with nine males and 12 females. Fourteen patients with EBS had KRT14 mutations and seven had KRT5 mutations. Mean age was 45.8 years and 45.0 years in the EBS and control groups, respectively. After controlling for potential co-founders (body mass index, gait speed), patients with EBS showed a reduction of forces to control the braking phase of gait (heel-strike) along the mediolateral (P = 0.01) and anteroposterior (P < 0.01) directions. Also, a reduction in the anteroposterior force was observed during the pushing phase (P < 0.01). Patients with EBS walk with a reduction in the mediolateral and anteroposterior components of the forces applied under the surface of feet, a strategy probably adopted to minimize pain and reduce shear forces and friction, which might exacerbate blistering. Such gait patterns might impair stability to external perturbations and irregular surfaces, while altering the biomechanical loading on foot structures. These data will inform future targeted interventions, including balance exercises, as well as bespoke orthotics to help redistribute pathological pressures across the foot.