Nerve entrapment and gene therapy.

Peripheral entrapment neuropathy is a common cause of upper-extremity pain, paresthesias, and weakness. Although any of the major nerves can be affected, compression of the median nerve at the carpal tunnel is the commonest site of clinically significant nerve compression. Etiologically, carpal tunnel syndrome (CTS) has numerous causes, but the idiopathic group greatly outnumbers the rest. Moreover, the pathophysiology of CTS patients claiming work-related repetitive hand motion as a basis for their disorder has been the subject of intensive study because of its economic ramifications for industry. CTS can serve as a model for reviewing the pathophysiology and biochemical changes of the nerve and its exterior milieu at the cellular level, as well as the possibilities of modifying these changes at the molecular level.

Reconstruction of long cervical esophageal defects with the radial forearm flap.

The radial forearm flap has been used for reconstruction of the cervical esophagus most often as a patch or for circumferential repair of short defects (less than 5 cm). In the following three cases, the radial forearm flap was used to reconstruct circumferential cervical esophageal defects ranging from 5 to 12 mm in length. These procedures were successfully carried out in three patients in whom the intraoperative defect was unexpectedly large or the intra-abdominal viscera harvest would have been difficult. These patients had reliable esophageal function 8 to 24 months after surgery. We conclude that the radial forearm flap can be used for reconstruction of large circumferential defects of the cervical esophagus.

Biochemistry of carpal tunnel syndrome.

Although carpal tunnel syndrome (CTS) occurs due to intrinsic or extrinsic causes, the idiopathic group outnumbers the rest by far. Compression of the median nerve may be due to mechanical or ischemic causation. The cause of idiopathic CTS is thought to be intermittent compression of the median nerve in predisposed people, especially working females, producing ischemia of the nerve. Reperfusion injury may occur during periods of recovery. Intermittent perfusion of the cellular tissue following ischemia releases free oxygen radicals. With continued oxidative stress, the normal antioxidant system is overwhelmed and cellular injury ensues, affecting both nerve and synovial cells. This is confirmed by changes seen locally in nerve and synovial tissue both serologically and histologically. These changes are reverted or checked by the use of antioxidants in vitro. Simulated compression of the nerve in laboratory animals also confirms these findings, further corroborating the pathophysiology and suggesting means of preventing idiopathic CTS.

Evaluation of fructose 1,6 diphosphate for salvage of ischemic gracilis flaps in rats.

Fructose 1, 6 diphosphate (FDP), a metabolic intermediate, provides an alternative mechanism to circumvent the rate-limiting step in the Kreb's cycle. This agent has been observed to prevent the effects of ischemia on heart tissue and kidney function and the effects of endotoxic shock. It has been shown conclusively to minimize the adverse effects of ischemia-reperfusion injury in experimental pedicled skin flaps in animals. The present study was done to evaluate the effect of intra-arterial administration of FDP on salvage of ischemic microvascular transfer of gracilis muscle flaps in rats, with the premise that it might prolong the ischemia time of muscle flaps at room temperature, thus increasing chances of flap survival. Irrigation with FDP did not change the quantitative survival of the flaps, but there was qualitative improvement on histologic evaluation and DNA analysis. Decreased inflammatory damage and DNA fragmentation were seen at the 2.5-hr period. Histologic staining for mitochondrial oxygenation in gracilis muscle also showed increased uptake in the FDP-treated group vs. control at the 2.5-hr ischemia period. Further experiments with different modes of FDP administration should be carried out to identify more effective means of amelioration of flap ischemia.

Skeletal fixation in digital replantation.

Although the primary objective of replantation is revascularization and ultimately viability of the amputated digit(s), skeletal stabilization is an important cornerstone of the composite repair and reconstructive process. If performed rapidly and securely, anatomic (or near anatomic) fracture reduction and fixation may contribute profoundly to the protection of the revascularization and the repair or reconstruction of nerves, tendons, and integument; reliable fracture healing; functional restoration; and final outcome. Conversely, less than anatomic (or near anatomic) reduction or unreliable and insecure fixation may deter successful early revascularization and, later, good function. This article reviews the various methods of fracture stabilization that may be employed, and their advantages and disadvantages. We believe that anatomic (or near anatomic) fracture reduction, reliable and stable fracture fixation, minimal additional dissection, and early active range-of-motion exercises will have a substantial effect on both viability and functional outcome in digital replantation.

Absorptive properties of synovium harvested from the carpal tunnel.

Ischemia-induced reperfusion injury seems to play an important role in the pathophysiology of "idiopathic" carpal tunnel syndrome (CTS). The common final pathway in this developmental sequence is thought to be an intermittent increase in interstitial pressure, leading to degenerative changes in the flexor tenosynovium and fibrotic changes in the perineural tissue. We hypothesize that this concurrently leads to alteration in the physical properties of the synovium, leading to its rapid and persistent swelling. A prospective study was conducted on synovial tissue obtained from 27 CTS patients. The in vitro synovial absorption rate of CTS patients was significantly higher in the first hour compared to controls (n = 7). This difference was maintained up to 5-6 h, albeit at a slower rate. Rapid absorption and retention of fluid by the synovium led to increased interstitial pressure and nerve compression, resulting in early and persistent manifestation of symptoms in sensitized patients.