The change in the distance of linear separation between each pair of osseous fiber attachment sites of the posterior cruciate ligaments was measured and plotted as a function of the knee flexion angle from 0 degree to 120 degrees. Data were collected under four sequential test conditions that had in common quadriceps relaxation, absence of tibial rotation forces, and horizontal femoral stabilization. The posterior cruciate ligament fibers were intact or transected (excursion wires left intact) with gravitational joint distraction of the lower leg unconstrained or constrained. The small, posterior oblique fiber region was the most isometric of the four tested fiber regions. Progressively increasing deviations from isometry were seen in the posterior longitudinal, central, and anterior fiber regions, in that order. Transection of the posterior cruciate ligament, combined with unconstrained gravitational distraction of the knee joint, further increased the magnitude of deviation from isometry of the anterior and central fibers, but only changed the pattern of deviation for the more nearly isometric posterior fibers. Under simulated operative conditions, most of the posterior cruciate ligament's anatomic attachment sites exhibit nonisometric behavior, with near isometry demonstrated only by the relatively small posterior fiber attachment sites. If isometry alone is used for bone tunnel placement, the large anterior and central fiber regions will be left largely unreconstructed. Because the normal behavior of most of the fibers of the posterior cruciate ligament involves 4 to 6 mm of end-to-end length increase with progressive knee flexion, this pattern and degree of deviation from isometry should be sought to approximate an anatomic reconstruction of the anterocentral bulk of the ligament.
Considerable debate has taken place concerning cutaneous basosquamous carcinomas. Some authors believe they are merely a variant of basal cell carcinoma, based on the apparent rare occurrence of metastases. This comparative study of 33 cases of basosquamous, 1, 7% cases of basal cell, and 736 cases of squamous carcinomas arising in the head and neck demonstrates that the basosquamous lesion has the potential to recur and to metastasize, which is similar to squamous cell lesions. An aggressive primary treatment program is recommended.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.