Acute-Onset Footdrop Caused by Intraneural Ganglion Cyst of the Common Peroneal Nerve: The Effects of Extraneural Pressure Gradients on Cyst Propagation.

Ganglion cysts are relatively common entities, but intraneural ganglia within peripheral nerves are rare and poorly understood. We present a case of a 51-year-old man who presented with acute left dropfoot. Initial magnetic resonance imaging (MRI) was misinterpreted as common peroneal neuritis consistent with a traction injury corroborated by the patient's history. However, after surgical decompression and external neurolysis were performed, the patient's symptoms worsened. Repeated MRI revealed an intraneural ganglion cyst of the common peroneal nerve with connection to the superior tibiofibular joint by means of its anterior recurrent branch that was evident retrospectively on preoperative MRI. It is crucial to carefully inspect atypical cases to further recognize and appreciate the dynamic aspect of this disease or "roller-coaster" phenomenon. Intraneural ganglion cysts rely heavily on intraneural and extraneural pressure gradients for propagation, which can be drawn from the expanded work of the unifying articular theory. This report emphasizes the importance of understanding the pathoanatomical and hydraulic factors to appropriately identify and treat intraneural ganglion cysts. Increased recognition of this pathologic entity as a differential diagnosis for acute onset dropfoot is also highlighted.

A bi-radial approach to define the sagittal geometry of the healthy ankle.

BACKGROUND: Previous descriptions of the sagittal geometry of the tibia and talus have involved single radius curves. The purpose of this investigation was to: determine if the sagittal curvature of the medial and lateral sides of the talus and tibia can be described by dividing the condyles into anterior and posterior regions, determine tibiotalar congruency, and categorize the morphological configurations of the talus and tibia. METHODS: Eighteen subjects underwent weightbearing CT scans and the osseous curvature was analyzed. RESULTS: For the talus, the medial anterior radius was smaller than the lateral anterior radius. For the distal tibia, the lateral posterior radius was smaller than the medial posterior radius. Tibiotalar congruency varied by region. The most common geometric configuration was two cones, one anterior and one posterior, pointed in opposite directions. CONCLUSION: The sagittal profiles of the tibia and talus can be more accurately described using a bi-radial approach as compared to a single radius.

Spontaneous Rupture of Multiple Tendons in the Lower Extremity Following the Diagnosis of Lyme Disease.

Over a time frame of less than 1 year, a 23-year-old competitive horseback rider experienced a midsubstance tear of both the tibialis anterior and extensor hallucis longus tendons without inciting injury. It was after the second spontaneous tear that the patient's recent diagnosis of Lyme disease became the likely culprit. Often, patients with chronic Lyme disease present with an elaborate clinical picture that can mimic many more common diagnoses such as septic arthritis, transient synovitis, ligamentous sprain, and various other traumatic injuries. With the pathognomonic erythema migrans rash reported to be present less than 50% of the time in late-stage infections, the diagnosis of Lyme disease can often be difficult, with a high rate of underdiagnosis. It is important that Lyme disease be included in the differential diagnosis of spontaneous tendon pathology, especially for physicians practicing in highly endemic areas. The treatment is relatively simple and successful-especially for an acute infection-and it is important to initiate treatment promptly to prevent disability.