Stephen H. Colbert

Toward engineering functional organ modules by additive manufacturing.

Tissue engineering is emerging as a possible alternative to methods aimed at alleviating the growing demand for replacement tissues and organs. A major pillar of most tissue engineering approaches is the scaffold, a biocompatible network of synthetic or natural polymers, which serves as an extracellular matrix mimic for cells. When the scaffold is seeded with cells it is supposed to provide the appropriate biomechanical and biochemical conditions for cell proliferation and eventual tissue formation. Numerous approaches have been used to fabricate scaffolds with ever-growing complexity. Recently, novel approaches have been pursued that do not rely on artificial scaffolds. The most promising ones utilize matrices of decellularized organs or methods based on multicellular self-assembly, such as sheet-based and bioprinting-based technologies. We briefly overview some of the scaffold-free approaches and detail one that employs biological self-assembly and bioprinting. We describe the technology and its specific applications to engineer vascular and nerve grafts.

Nerve transfers in the hand and upper extremity surgery.

Modern nerve-to-nerve transfers represent one of the greatest advances in peripheral nerve surgery. Lessons of tendon transfers have taught that nerves to specific musculotendinous units are expendable, and greater understanding of peripheral nerve topography has revealed redundant fascicles in peripheral nerves. Transfer of these redundant or expendable nerves to recipient nerves close to the end organ allows for earlier reinnervation and preservation of those musculotendinous units. Such nerve transfers provide significantly better treatment options in many cases of nerve injury where previous outcomes were expected to be poor, such as with proximal injuries, long nerve gaps, or unavailability of the proximal injured segment. This article will review current nerve transfers in the hand and upper extremity.

Nerve transfers for brachial plexus reconstruction.

Brachial plexus injuries result in devastating loss of function for patients and present incredible challenges for peripheral nerve surgeons. Recently, nerve transfers have produced superior results compared with traditional interposition nerve grafts for brachial plexus reconstruction. The authors present a review of current surgical options for treatment of partial and complete adult brachial plexus injuries using nerve transfers.

Deep ulnar intraneural ganglia in the palm.

BackgroundWhile extraneural ganglion cysts are common and well known, intraneural ganglia are rare and misunderstood.MaterialsWe describe a patient with an intraneural ganglion in an unusual location, the deep branch of the ulnar nerve in the palm. We confirmed a connection to the triquetral-hamate joint on preoperative high-resolution MRI and intraoperatively, and observed distal extension of the cyst, a variant pattern of propagation. We wondered if these intraneural cysts followed the principles of the unifying articular (synovial) theory rather than the de novo (degenerative) theory suggested by others. We reviewed patients with ulnar intraneural ganglia at the wrist for joint connections and the pattern of propagation.ResultsA total of 35 cases of ulnar intraneural ganglia at the wrist were identified, of which only 10 were joint connected. In 14 cases involving the deep ulnar branch, only 4 had joint connections. We hypothesized and proved that an unrecognized joint connection would be identified in the most recently reported case of a deep ulnar intraneural cyst in which a joint connection had not been identified. Propagation patterns supported descent in all cases involving the deep branch and proximal ascent in those of the main ulnar nerve (n = 18) or the dorsal cutaneous branch (n = 3). We believe that the orientation of the articular branches may play an important role in directionality in these intraneural cysts.ConclusionContrary to popular opinion, our analysis of the literature would suggest that intraneural ganglia at this rare site obey the common principles of the articular theory described at more common sites for intraneural ganglia.

Vestibular function in Belgian Waterslager canaries (Serinus canarius)

The purpose of this study was to measure vestibular function in Belgian Waterslager canaries using short latency vestibular evoked potentials (VsEPs) elicited by linear acceleration stimuli. Responses were recorded with vertex to mastoid leads using traditional signal averaging. Response thresholds, latencies, and amplitudes were quantified and compared to non-Waterslager controls. Cochlear and vestibular organs were also processed for scanning electron microscopy. Results indicated that vestibular response thresholds were slightly, but significantly, higher for Belgian Waterslager canaries and response amplitudes at 0 dBre: 1.0 g/ms were significantly reduced compared to non-Waterslagers. Response peak latencies were not significantly different. The most striking morphological finding was that the stereociliary bundles of Waterslager saccular hair cells showed no common orientation. Previous reports have also found significantly less hair cells in Waterslager saccules (Weisleder and Park, Hear. Res. 80 (1994) 64-70); however, the present study did not confirm this finding. The utricle and ampullae appeared normal. The present results indicate that vestibular neural function, as measured with VsEPs, is affected in Belgian Waterslager canaries. The results also suggest that one structural correlate of the functional loss is the disordered stereociliary bundles in the sacculus.