Biomedical subjects
Publications and source records attributed to J B Boyd.
The use of a "mini" skin paddle to monitor the fibular free flap for mandibular reconstruction is described. The paddle is easy to inset, can be excised later under local anesthesia, and yet is adequate for postoperative monitoring.
The iliac crest is reevaluated with respect to the rapid evolution of vascularized mandibular reconstruction. With more flaps to choose from, indications for the crest have become more specific-playing to the strengths of this particular transfer. Ideally, defects should exclude soft tissue and occupy lateral segments of the mandibular arch-up to and including a complete hemimandible. The composite flap is capable of reconstructing external skin with ease, but the color match leaves something to be desired. Mucosal defects are less well handled. The flap can replace soft tissue bulk as well as mandibular height following through-and-through excisions in the region of the chin. Where donor site cosmesis is of paramount importance, the iliac crest is simply the best flap available.
A functional evaluation was made of osteocutaneous radial forearm flap donor upper extremities at a mean 19.4 months postoperatively. Donor deficits were evaluated as follows: (1) skin: subjective appearance and durability; (2) skeleton: range of motion of adjacent joints; (3) vessels: cold intolerance, digital temperature, digital--brachial index; (4) muscle: key pinch; (5) nerve: two-point discrimination of dorsal first web space. Ten consecutive patients with a mean donor site area of 51.5 cm2 and mean length of harvested radius of 10.9 cm were studied. Incomplete skin graft take at the donor site (7 of 10 patients) and appearance of fair or poor (6 of 10 patients) were frequent cutaneous complications. Wrist range of motion was decreased with pronation (90%), flexion (90%), and extension (89%). Mean digital temperature, comparing extremities that did (operated) and did not (nonoperated) undergo surgery, or comparing the radial artery-supplied fingers to the ulnar artery-supplied fingers within the same operated hand showed no effect from the lost radial artery. Mean digital-brachial index was 1.24 for the nonoperated and 1.15 for the operated extremity. Key pinch on the operated side was a mean of 74% of the nonoperated side. Although raising the flap creates multiple tissue deficits, each with the potential to alter upper extremity function, detailed functional evaluation failed to demonstrate significant alteration in upper extremity function after flap harvest.
Through-and-through oral cancer (T4+) involving contiguous mucosa, mandible, and skin is a devastating disease with poor prognosis and represents one of the most difficult reconstructive challenges in head and neck surgery. Thirty-eight patients underwent immediate microvascular reconstruction following surgical tumor ablation. The purpose of the present review was to assess the value of microvascular reconstruction in these essentially palliative reconstructive efforts. The iliac crest osteocutaneous flap was used in the majority of patients and was found to be ideal for the reconstruction of large bony and soft-tissue defects present in this group of patients. Other methods, including pectoralis major, forehead, and latissimus dorsi flaps, also were used in the soft-tissue reconstruction. The mean follow-up was 16 +/- 2 months, and the mean hospitalization was 43 +/- 22 days. The majority of patients succumbed to recurrent or related diseases, yet a few went on to survival despite the initial advanced stage of disease. A number of complications were observed. However, most patients developed normal or easily intelligible speech (65 percent), and most (78 percent) had their tracheostomies closed and sustained themselves on an oral soft diet (84 percent). Bony union was noted in the majority of patients (73 percent). Although the prognosis in full-thickness oral carcinoma is grim, it appears that palliative surgery in these cases is well justified. The goals are to shorten the duration of hospitalization, reduce morbidity, and improve the remaining quality of life. Microvascular tissue transfer offers a means to achieve these goals in a single, reliable procedure. We feel that immediate one-stage bone and soft-tissue reconstruction restores dignity and relieves suffering in this unfortunate group of individuals.
Complete oral rehabilitation after oromandibular resection is a goal that is frequently difficult to attain. Poor speech, inability to eat a solid diet, and cosmetic deformity are all potential problems. The introduction of osseointegrated implants and free vascularized bone grafting are two techniques that have permitted improved results of oromandibular reconstruction. When used together they provide the best possibility for providing oral continence, a stable denture, and minimal cosmetic deformity. The free vascularized iliac crest has been used widely to reconstruct mandibular defects with the placement of enosseus implants. However, the radius provides a good alternative to reconstruct the mandible. We report four cases of mandibular reconstruction with the use of the free vascularized radius with subsequent placement of osseointegrated implants. The results of these cases suggest that enosseus implants can be used successfully in the radius. The radius is ideal to reconstruct small to moderate-sized defects of the lateral mandible with loss of oral mucosa.
The plate-flap option has a place in oromandibular reconstruction: It allows an expedient method to obtain an excellent cosmetic and functional result with minimal donor site disability. It is best for lateral and posterior low-volume defects in the debilitated, the elderly, and in those patients with a poor prognosis. This technique may be used as a preliminary to vascularized bone grafts in patients receiving postoperative radiotherapy. This method is no panacea. These are very specific indications for its use. Failure usually requires rescue with a vascularized bone graft. With proper selection of patients, however, this will rarely be necessary. A major weakness in the plating systems available at present is their tendency to fracture if they remain in place too long. The gauntlet is, therefore, thrown down to those in a position to develop more reliable hardware.
The treatment modality of choice for venous insufficiency after free tissue transfer or replantation remains surgical repair. When this is not technically possible, the use of medical leeches is a useful adjunct to treatment. This paper reviews the history of the use of leeches in medicine, the anatomy and physiology of Hirudo medicinalis, the techniques of leech therapy, and the complications and contraindications.
Microvascular surgery plays a vital role in head and neck reconstruction. This paper deals with the complications arising from this form of surgery. They can be classified as general complications, anastomotic problems, and specific problems related to particular donor and recipient sites.
Previous screens for autosomal genes that are necessary for resistance to DNA cross-linking agents but not to monofunctional agents have produced 6 mutations; all of which fall within the third chromosomal gene mus308. In an effort to identify analogous sex-linked genes, a screen of mutagenized X-chromosomes has been conducted for mutations that confer hypersensitivity to nitrogen mustard. This search has identified a new locus, mus115, through the recovery of a mutant that is strongly hypersensitive to nitrogen mustard but marginally sensitive to methyl methanesulfonate.
The excision repair capacity of the third chromosomal mus mutations of Drosophila has been re-evaluated. A partial deficiency in the excision repair of pyrimidine dimers originally observed in the mus304 mutants is now attributed to the presence of a secondary phr mutation in that stock. Since the mus306 and mus308 stocks also carry secondary phr mutations, their partial deficiency in repair of pyrimidine dimers may also be the result of that secondary mutation. Accordingly, the Drosophila mutations that are now definitively associated with defects in the incision step of pyrimidine dimers removal are mei-9, mus201 and phr. The genes mus302 and mus310 appear to play a role in later stages of excision repair.
Among the available mutagen-sensitive mutations in Drosophila, those at the mus308 locus are unique in conferring hypersensitivity to DNA cross-linking agents but not to monofunctional agents. Those mutations are also associated with an elevated frequency of chromosomal aberrations, altered DNA metabolism and the modification of a deoxyribonuclease. This spectrum of phenotypes is shared with selected mammalian mutations including Fanconi anemia in humans. In anticipation of the molecular characterization of the mus308 gene, it has been localized cytogenetically to 87C9-87D1,2 on the right arm of chromosome three. Nine new mutant alleles of the gene have been generated by X-ray mutagenesis and one was recovered following hybrid dysgenesis. Characterization of these new alleles has uncovered additional phenotypes of mutations at this locus. Homozygous mus308 flies that have survived moderate mutagen treatment exhibit an altered wing position that is correlated with reduced flight ability and an altered mitochondrial morphology. In addition, observations of elevated embryo mortality are potentially explained by an aberrant distribution of nuclear material in early embryos which is similar to that seen in the mutant giant nuclei.
One hundred and forty vascularized bone grafts were used for mandibular reconstruction in 135 patients. Most followed surgical ablation of squamous carcinoma recurring (or persisting) after irradiation. This paper analyzes the fixation techniques and their effects on bony union. Of 140 vascularized bone grafts, 132 survived and were reviewed. Fifty were stabilized using rigid techniques and 82 by interosseous wires. Rigid fixation had a success rate of 94 percent, while nonrigid techniques resulted in bony union in 96.3 percent. The three failed cases of rigid fixation occurred when short mandibular compression plates were used in iliac crest grafts. We conclude that vascularized bone grafts exhibit a high degree of bony union and that fixation technique--rigid versus nonrigid--appears unimportant in this context. Compression plating is clearly bone-dependent. Nevertheless, use of the reconstruction plate simplifies mandibular reconstruction, and the extra hardware does not appear to increase infection or other soft-tissue complications.
Historical cohort analysis compared free-flap survival rates in 226 irradiated and 108 nonirradiated head and neck reconstructions. The failure rate for the irradiated flaps (3.5 percent) did not differ significantly from that for the nonirradiated group (2.9 percent). A case-control study of the failed irradiated flaps revealed infection and lag time between radiotherapy and surgery as the only factors significantly associated with free flap failure. Salvage techniques (vein grafting, cephalic transposition, and Corlett looping) for recruiting recipient vessels into radically ablated head and neck beds are reviewed.
A classification of mandibular defects based on functional as well as aesthetic factors is presented. By taking into account the difficulties in restoring form and function and not simply relying on traditional anatomic landmarks, it is hoped that this method will allow different types of reconstructions to be fairly evaluated. It also should help surgeons to tailor individual reconstructive techniques to specific clinical situations. Major difficulties in mandibular reconstruction arise when a condyle requires replacement, when there is a mucosal and/or skin component to the defect, and when the area to be reconstructed involves the anterior arch. The classification is based on three upper-case and three lower-case characters: H, C, L and o, m, s. H defects are lateral defects of any length, including the condyle but not significantly crossing the midline; L defects are the same only without the condyle; C defects consist of the entire central segment containing the four incisors and the two canines. Combinations of these letters are possible (an angle-to-angle defect, for example, is represented as LCL). Thus H and L defects may reach or even extend slightly beyond the midline but are not referred to as LC or HC unless they contain the entire central segment. The letters o (neither a skin nor a mucosal component), s (skin), m (mucosa), and sm (skin plus mucosa) are added to denote the epithelial requirement.
A mitochondrial endonuclease from Drosophila melanogaster embryos was purified to near homogeneity by successive fractionation with DEAE-cellulose and heparin--avidgel-F, followed by FPLC chromatography on mono S, Superose 12 and a second mono S column. This enzyme digests double-stranded DNA more efficiently than heat-denatured DNA. The endonuclease activity has a molecular mass of 44 kDa, as determined under native conditions using a gel-filtration Superose 12 column. The prominent peptide detected by SDS/polyacrylamide gel electrophoresis likewise has a molecular mass of 44 kDa, suggesting a monomeric protein. The enzyme has an absolute requirement for divalent cations, preferring Mg2+ over Mn2+. No activity could be detected when these cations were replaced by Ca2+ or Zn2+. The pH optimum for this enzyme activity is 6.5-7.4 and its isoelectric point is 4.9. Both single-strand and double-strand breaks are introduced simultaneously into a supercoiled substrate in the presence of MgCl2 or MnCl2. Endonuclease-treated DNA serves as a substrate for DNA polymerase I from Escherichia coli, suggesting that 3'-OH termini are generated during cleavage. The enzyme is free from any detectable DNA exonuclease activity but not from RNase activity. Partial inhibition by antibodies raised against mitochondrial endonucleases derived from bovine heart and Saccharomyces cerevisiae have revealed a potential structural homology between these nucleases.
An efficient technique has been developed for performing in vivo site-directed mutagenesis in Drosophila melanogaster. This procedure involves directed repair of P-element-induced DNA lesions after injection of a modified DNA sequence into early embryos. An oligonucleotide of 50 base pairs, whose sequence spans the P-element insertion site, mediates base replacement in the endogenous gene. Restriction mapping, DNA sequencing, and polymerase chain reaction analysis demonstrate that base substitutions present in an injected oligonucleotide are incorporated into genomic sequences flanking a P insertion site in the white gene. This analysis suggests that progeny bearing directed mutations are recovered with a frequency of about 0.5 x 10(-3). Because Drosophila remains a premier organism for the analysis of eukaryotic gene regulation, this system should find strong application in that analysis as well as in the analysis of DNA recombination, conversion, repair, and mutagenesis.
Fanconi anemia is a human inherited disease that is characterized by cellular hypersensitivity to DNA cross-linking agents. A number of potential experimental models for that disorder have been developed by selecting mutants that are hypersensitive to bifunctional mutagens. The six mutants of that class in Drosophila, all of which map to the mus308 locus, express an alteration in a mitochondrial nuclease. A recent extension of that observation to cell lines from complementation group A of Fanconi anemia has established a new cellular phenotype for that disorder. In the current study an analogous enzyme has been analyzed in eight recently isolated Chinese hamster cell lines that are hypersensitive to cross-linking agents. Among these lines. V-H4 and V-B7 are shown to exhibit an enzyme modification analogous to that observed in the mutant Drosophila and human cells. These results validate the nuclease assay as an indicator of the Fanconi defect and further establish the V-H4 cell line as a valuable cellular model for analysis of the Fanconi A defect.
Massive pharyngocutaneous fistulae may be arbitrarily defined as those involving two-thirds or more of the circumference of the pharyngeal wall. Three such patients are presented, all after failed radiotherapy and surgery. The principles of management consist of salivary diversion, complete debridement, nutritional support, prophylactic antibiotics, and two-layer, well-vascularized overlapping closure. We currently recommend a radial forearm flap used in conjunction with a pectoralis muscle (or musculocutaneous) flap for rapid rehabilitation of these patients, particularly in the presence of obesity or an irradiated bed.