PubMed · 16791056
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Peter M Stevens, Stephen Aoki, Patrick Olson. Ball-and-socket ankle.. https://doi.org/10.1097/01.bpo.0000217713.80233.c5
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The performance of total ankle replacements (TARs) have not been comparable to those of the other major joints of the lower extremity. The aim of this work was to develop a new simulator test to compare the wear of a new mobile bearing TAR (Mobility) with one with a good clinical history, the Buechel Pappas, using kinematic inputs derived from the literature. The wear rate for the Mobility components was lower than that for the Buechel-Pappas ankle joints at all time points. The wear rate for both sets of components increased with the inclusion of an anterior/posterior displacement in the kinematic inputs. This was expected as the components are subjected to higher kinematic demands and reproduces similar effects found in knee prostheses. This study has demonstrated that it is possible to study wear of TARs in a modified simulator originally designed for total knee replacements. It was also shown that the new Mobility ankle compares favorably with the Buechel Pappas ankle, which has a successful clinical history, under the simulator test conditions described.
Joint contractures are the second major impairment affecting the locomotor system of children with Duchenne muscular dystrophy (DMD). While the negative influence of joint contractures has been documented, the passive moments produced by joint contractures could benefit the gait of patients with muscle weakness. We describe a biomechanical model that quantifies the mechanical contribution of ankle and hip flexion contractures to the gait of DMD children. Kinematic and kinetic parameters were measured under the same experimental conditions during the gait and passive resistance assessment of two subjects: one healthy child as a control, and one child with DMD. The child with DMD had a plantar flexion contracture and a greater ankle stiffness coefficient than the control child. During gait, the contribution of the ankle passive moment to the net moment was more important for the child with DMD than for the control child. At the hip, passive joint moments and passive moment contribution were more important for the control child but this was not related to the presence of hip flexion contracture. These preliminary results suggest the model might be used to evaluate contractures effect on a larger cohort of subjects.
Persons with haemophilia often experience their first joint haemorrhage in early childhood. Recurrent bleeding into a joint may lead to significant morbidity, specifically haemophilic arthropathy. Early identification of the onset and progression of joint damage is critical to preserving joint structure and function. Physical examination is the most feasible approach to monitor joint health. Our group developed the Colorado Haemophilia Paediatric Joint Physical Examination Scale to identify earlier signs of joint degeneration and incorporate developmentally appropriate tasks for assessing joint function in young children. This study's objectives were to establish normal ranges for this scale and assess interrater reliability. The ankles, knees and elbows of 72 healthy boys aged 1 through 7 years were evaluated by a physical therapist to establish normal ranges. Exactly 10 boys in each age category from 2 to 7 years were evaluated by a second physical therapist to determine interrater reliability. The original scale was modified to account for the finding that mild angulation in the weight-bearing joints is developmentally normal. The interrater reliability of the scale ranged from fair to good, underscoring the need for physical therapists to have specific training in the orthopaedic assessment of very young children and the measurement error inherent in the goniometer. Modifications to axial alignment scoring will allow the scale to distinguish healthy joints from those suffering frequent haemarthroses.