Joint Coordination Variability In Anterior Cruciate Ligament Reconstructed Subjects During Stair Ambulation Using a Vector Coding Technique

Anterior cruciate ligament (ACL) rupture is a common injury, with an estimated incidence of 120,000 to 200,000 per year in the United States. ACL reconstruction surgery is the standard treatment for this injury to restore knee joint stability and function. While surgical reconstruction has been shown to restore laxity of the knee, current literature lacks consensus on return to normal knee joint kinematics following surgery. Additionally, re-injury is a major risk for those who return to sports activity after reconstruction surgery. Dynamical systems methods for quantifying joint coordination variability have been explored as a method for detecting differences between ACL reconstructed (ACLR) subjects and healthy control subjects. Specifically, altered joint coordination variability has been linked to lower extremity instability, which may indicate re-injury risk. The aim of this study was to assess joint coordination and joint coordination variability using a vector coding technique in ACLR subjects after recovery and return to normal activity. Our hypothesis was that joint coordination variability of ten selected intra-limb knee-knee and knee-hip couplings would be altered in the ACLR group compared to a group of healthy control subjects based on previous findings using similar methods. Thirty subjects (15 ACLR and 15 normal) were analyzed using a motion capture camera system and force plates. Subjects were asked to ascend a staircase in a step-over-step manner at a self-selected pace, turn around on the elevated platform, then descend from the platform down the steps and return to the starting location. We employed a vector coding method using a custom Matlab script to measure coupling angle variability of knee-knee and hip-knee coupled motion during the stair activity. Individuals with ACLR were found to have differences in joint coordination variability (both increased and decreased) in 5 of the 10 joint couplings analyzed as compared with a healthy control group during the stair descent activity. The majority of differences were found to be reductions in variability in the ACLR group as compared with controls. It is believed that there is an optimal amount of variability in any motor system that differentiates between the ability to adapt to environmental instability and the risk for injury. Reduced joint coordination variability indicates avoidance of a particular movement and results in the inability to adapt movement strategies in a dynamic environment. Decreased variability in ACLR subjects has also been linked to re-injury in at least one prospective study. These results combined with previous works provide insight into coordinative function after ACLR and may be useful in improving rehabilitation protocols following surgery as well as identifying those at risk of re-injury

Spectrum of dominant mutations in the desmosomal cadherin desmoglein 1, causing the skin disease striate palmoplantar keratoderma

The adhesive proteins of the desmosome type of cell junction consist of two types of cadherin found exclusively in that structure, the desmogleins and desmocollins, coded by two closely linked loci on human chromosome 18q12.1. Recently we have identified a mutation in the DSG1 gene coding for desmoglein 1 as the cause of the autosomal dominant skin disease striate palmoplantar keratoderma (SPPK) in which affected individuals have marked hyperkeratotic bands on the palms and soles. In the present study we present the complete exon-intron structure of the DSG1 gene, which occupies approximately 43 kb, and intron primers sufficient to amplify all the exons. Using these we have analysed the mutational changes in this gene in five further cases of SPPK. All were heterozygotic mutations in the extracellular domain leading to a truncated protein, due either to an addition or deletion of a single base, or a base change resulting in a stop codon. Three mutations were in exon 9 and one in exon 11, both of which code for part of the third and fourth extracellular domains, and one was in exon 2 coding for part of the prosequence of this processed protein. This latter mutation thus results in the mutant allele synthesising only 25 amino acid residues of the prosequence of the protein so that this is effectively a null mutation implying that dominance in the case of this mutation was caused by haploinsufficiency. The most severe consequences of SPPK mutations are in regions of the body where pressure and abrasion are greatest and where desmosome function is most necessary. SPPK therefore provides a very sensitive measure of desmosomal function