Level III.

Progressive lengthening using an external fixator has only recently been applied to the phalanges of the hand. A number of technical challenges exist, especially in pediatric cases, such as the size of the bone involved, the existence of the physis, and the risk of infection and neurovascular compromise. Here, we report a case of lengthening of a short distal phalanx following osteomyelitis in a 7-year-old child with a uniplanar mini-external fixator. Elongation of 63% was obtained, reaching 80% of the contralateral phalanx, with complete resolution of the preoperative functional impairment, and an acceptable cosmetic result for the patient. A mild limitation of the distal interphalangeal joint flexion as well as mild effort-related discomfort was still present at the last follow-up. No complications were recorded. Gradual lengthening of the phalanges using uniplanar minifixators can be performed safely in children with good results as long as appropriate indications and technical limitations are respected.

Soft tissue deformation(STD) causes the most prominent source of error in skin marker (SM) based motion analysis, commonly referred to as Soft Tissue Artifact (STA). To compensate for its effect and to accurately assess in vivo joint kinematics, quantification of STD in three-dimension (3D) is essential. In the literature, different invasive and radiological approaches have been employed to study how STA propagates in joint kinematics. However, there is limited reference data extensively reporting distribution of the artifact itself in 3D. The current study was thus aimed at quantifying STD in 10 subjects along three anatomical directions. Biplanar X-ray system was used to determine true bone and SM positions while the subjects underwent quasi-static single leg flexion. STD exhibited inter-subject similarity. A non-uniform distribution was observed at the pelvis, thigh and shank displaying maximum at the thigh (up to 18.5 mm) and minimum at the shank (up to 8 mm). STD at the pelvis and thigh displayed inter-marker similarity. STD at the pelvis was found direction independent, showing similar distribution in all the 3 directions. However, the thigh and shank exhibited higher STD in the proximal-distal direction of the bone embedded anatomical reference frame. These findings may provide more insights while interpreting motion analysis data as well to effectively strategize STA compensation methods.

No abstract