Popliteal artery pseudoaneurysm: an unusual complication of tibial traction.

Traction pins are an essential tool in the orthopedic surgeon's armamentarium. Historically a definitive treatment for some fractures, they are mainly used as a temporizing measure today. Despite their frequent use and relative simplicity, traction pins can have complications, many of which can be subtle and easily overlooked. Here we report on an unusual complication that was difficult to diagnose but caused significant morbidity before being diagnosed and treated. Pseudoaneurysms can cause a range of symptoms and usually present as a painful, tender, pulsatile mass, but in this instance the popliteal artery pseudoaneurysm presented as chronic, painful lower extremity swelling. With diagnosis and treatment, the patient's symptoms resolved. We discuss the complications associated with traction-pin placement.

Footprint of the lateral ligament complex of the ankle.

BACKGROUND: We describe the topographic anatomy of the lateral ligament complex of the ankle using 3-dimensional (3D) computed tomography (CT) imaging. METHODS: Dissection of the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL) was performed on 8 unpaired fresh-frozen cadaver feet. Ligaments were sharply dissected from bone, and the footprint was outlined with radio-opaque paint. The specimen underwent a 0.625-mm slice CT scan of the ankle with 3D reconstructions. Software was used to determine the surface area of the ligament footprint as well as measure the distance from the peroneal tubercle to the center of the CFL footprint. Data are presented as mean ± standard error. RESULTS: Six specimens had a bifid ATFL. Seven ankles had a bifid ATFL footprint on the talus. All specimens had intact CFL fibers. The intact superior and inferior limbs of the ATFL measured 19.7 ± 1.2 mm and 16.7 ± 1.1 mm. The CFL measured 24.8 ± 2.4 mm. The area of the footprints of the superior ATFL and inferior ATFL on the talus measured 1.5 ± 0.26 cm(2) and 0.90 ± 0.07 cm(2). The CFL and ATFL origins on the fibula were continuous and measured 3.48 ± 0.39 cm(2). The CFL insertion on the calcaneus measured 2.68 ± 0.20 cm(2). The CFL was found 27.1 ± 1.0 mm posterior and superior from the peroneal tubercle. CONCLUSIONS: In presumably uninjured specimens, both the ATFL and its footprint on the talus were bifid. The CFL and ATFL origins have a single confluent footprint on the anterior border of the distal fibula. The CFL footprint on the calcaneus is almost 3 cm posterior and superior to the peroneal tubercle. CLINICAL RELEVANCE: This study may assist surgeons in anatomically reconstructing the lateral ligament complex of the ankle.

Mechanical noise enhances signal transmission in the bullfrog sacculus.

Noise has been commonly thought to degrade the performance of sensory systems. However, it is now clear that the detection and transmission of weak signals in sensory systems can be enhanced by noise via stochastic resonance (SR). In hair cells, the quality of mechanoelectrical transduction is enhanced up to twofold by nanometer level mechanical noise acting on the hair bundle. We wanted to know whether these gains could be preserved, perhaps even enhanced, as information flows across hair cell synapses, and into the stream of action potentials that in the frog conveys acoustic information to the central nervous system. To approach this question, we studied the effects of noise on the signal-to-noise ratio (SNR) of the 8th nerve's response to small mechanical stimuli directly applied to the amphibian sacculus. We found that approximately 2.5 nm of mechanical noise enhanced the response of the saccular nerve up to fourfold, suggesting that the positive effects of low-amplitude mechanical noise result in improved transmission of acoustic information.