Salvage of avascular bone from frostbite with free tissue transfer.

Traditional management of frostbite injury of the hands and fingers has been to allow demarcation to occur between viable and nonviable tissues, corresponding to the level of amputation required. In this case report, phalangeal length in mummified digits was maintained with free tissue transfer followed by evidence of bony revascularization on bone scan. Rather than waiting for tissue demarcation to occur, the authors propose that consideration be given to debridement of soft tissues in the frostbitten fingers followed by free tissue transfer to salvage length and function in the digital bony skeleton.

Subunit conformation and dynamics in a heterodimeric protein: studies of the hybrid isozyme of creatine kinase.

Several physical properties of creatine kinase (EC 2.7.3.2) isozymes MM (CK-MM, muscle-type) and BB (CK-BB, brain-type), both homodimers, and isozyme MB (CK-MB), a heterodimer, were compared to determine how formation of the hybrid modifies subunit conformation and dynamics. Circular dichroic spectra revealed additional alpha-helical content for the hybrid isozyme. Double-beam absorption difference spectra between CK-MB and a stoichiometric mixture of CK-MM and CK-BB revealed decreased exposure of intrinsic chromophores in the hybrid. The relative intensity of the intrinsic fluorescence of CK-MB was between the two homodimers, but was 16% closer to the less fluorescent CK-MM. Steady state anisotropy spectra and decay of the anisotropy of CK derivatized on a single subunit with the fluorescent sulfhydryl reagent 5-[2-(iodoacetyl)amino-ethyl]aminonaphthalene-1-sulfonate indicated that the derivatized sites are more flexible in the heterodimer. The slow component in the anisotropy decay suggests that hybridization results in a small increase in the packing density or contraction of overall conformation of the B-subunit. The KM for MgATP with singly derivatized CK-MB was the same as the KM for the native enzyme. However, derivatization of a single subunit caused the Vmax to decrease by greater than 50%, which indicates that subunit-subunit interactions may modulate the activity of CK. A model for assembly of CK-MB is proposed which includes subunit characteristics more similar to those found in the muscle-type homodimer than in the brain-type homodimer and increased flexibility of the active site domain of both subunits.

Purification, characterization, and hydrodynamic properties of arginine kinase from gulf shrimp (Penaeus aztecus).

Arginine kinase from the tail muscle of the Gulf shrimp (Penaeus aztecus) was purified to apparent homogeneity, using a rapid, high-yield method. The protein exhibits a molecular weight of 40 kDa according to the methods of gel filtration and gel electrophoresis in sodium dodecyl sulfate, also indicating that arginine kinase from shrimp is a monomer. The amino acid content of arginine kinase from shrimp is similar to arginine kinases from several species and to creatine kinase from rabbit muscle. Arginine kinase derivatized at the reactive sulfhydryl with 2-(4'-(iodoacetamido)anilino)naphthalene-6-sulfonic acid exhibits significant changes in fluorescence anisotropy only in the presence of the guanidino substrate and the so-called "dead-end complex" containing arginine + MgADP. Several compounds structurally similar to arginine, e.g., ornithine do not interact with arginine kinase, suggesting a narrow specificity for substrate binding. The most suitable description of the decay of the fluorescence of arginine kinase derivatized with 5-[(((acetyl)-amino)ethyl)amino]naphthalene-1-sulfonate (AEDANS-AK), from among discrete and distributed models, is a triple exponential discrete decay. The presence of the dead-end complex only marginally increases the rate of decay, but significantly shifts the magnitude of the preexponentials (amplitudes) between the two major decay components. One interpretation of these results is that multiple conformational isomers may occur, in which the relative concentrations are dependent upon the presence of the dead-end complex. Measurement of the time-dependent anisotropy decay of AEDANS-AK reveals a two-term decay law with rotational correlation times of 0.88 and 15.2 ns. The slower component is close to the theoretical value of 16.7 ns for an isotropic rotator of the molecular mass of arginine kinase. This finding suggests that the overall conformation of arginine kinase may differ considerably from the prolate ellipsoidal subunits of the functionally analogous creatine kinase.

Endoscopic carpal tunnel release.

Endoscopic carpal tunnel release is a technically demanding and precise procedure, but one that can be mastered to the benefit of our patients. Once mastered, the rewards of shorter operating times, reduced postoperative pain, earlier return to activities of daily living and employment, and more satisfied patients can be realized.

Radial nerve laceration and retraction associated with a supracondylar fracture of the humerus.

Supracondylar fracture of the humerus can be associated with varying degrees of radial nerve injury. Complete laceration of the nerve is rare. We report a case of radial nerve laceration after a supracondylar fracture in which the proximal segment of the nerve retracted into the axilla. Successful treatment resulted from long segmental sural nerve grafting.

Congenital pseudarthrosis of the forearm.

Congenital pseudarthrosis of the forearm is a rare condition in which traditional treatment methods have proven unsatisfactory. We report a case of congenital pseudarthrosis of the radius and ulna successfully treated by resection of the distal ulna and excision of the radial pseudarthrosis with replacement by an interpositional free vascularized fibular graft.

Management of burned long bones.

The management of severely burned and exposed supportive osseous tissues is not fully standardized. We present two patients in whom extensive debridement and decortication of the involved bone may have contributed to subsequent stress fractures. We propose an alternative therapeutic approach for this problem, including: minimal debridement of the bone, early coverage of the exposed bone with vascularized muscle, and adequate prophylactic protection.

Use of ultrasound to locate a "lost" tissue expander injection port.

We have presented a rapid and reliable method of finding lost injection valves. (A frustrating footnote, however, is that 1 week later the port had again migrated and could not be located. Since the further anticipated gain was marginal, the bladder was already nearly expanded, and the expense for repeated ultrasound was a consideration, no further attempts were made to locate this port by ultrasound for further filling).

Tissue expansion as an adjunctive technique for the management of difficult wounds.

Replacement of lost or injured tissues with similar tissues is a major goal of the reconstructive surgeon. A relatively new modality, tissue expansion, appears to be an helpful adjunct in achieving this goal by providing tissues for reconstruction that are near at hand, possess similar characteristics to the lost tissue, and can even enhance vascularity within an ischemic area. Although the technique is a useful one, its indications and contraindications are incompletely defined. We have used this technique 65 times in 42 patients during a 2 1/2 year period. The overall complication rate has been 22 percent, similar to other reconstructive techniques, but the consequences of these complications have been relatively minor and have not, for the most part, added significantly to patient morbidity.

Repeated skin expansion to resurface a massive thigh wound.

We report here a patient who sustained posttraumatic skin and soft-tissue loss of the right thigh. Replacement of approximately 750 cm2 of split-thickness skin graft with adjacent skin serially expanded and advanced demonstrates the applicability of this technique to cover large tissue defects. Despite infection and exposure, we believe that expansion can proceed safely on an outpatient basis, providing that systemic toxicity does not develop and the exposure does not mechanically preclude expansion.