Biomedical subjects
Publications and source records attributed to C A Hergrueter.
Failure of an ileal pouch-anal anastomosis may result in unsuccessful completion of the anastomosis or removal of an ischemic pouch. We report a technique for preservation of the muscular wall of the rectum after mucosal dissection, which allowed a successful delayed pull-through.
This study was designed to determine whether tissue expansion after vascular pedicle implantation would increase the survival area of prefabricated skin flaps. In 20 New Zealand white rabbits, the vascular pedicle consisting of the central artery and vein of the left ear was implanted into the neck. At the time of pedicle implantation a subcutaneous pocket was created measuring 5 x 14 cm beneath the implantation site. Tissue expanders of three different sizes and volumes were implanted in the rabbits of three treatment groups. No tissue expander was implanted in the animals of the control group. All flaps were transposed after 3 weeks to the contralateral ear, and flap survival was assessed 1 week later. The increased area of the flap survival was statistically significant in all three treatment groups compared to the nonexpanded flaps (P = 0.003, P = 0.004, P < 0.0001, respectively). In addition there was a statistically significant larger area of survival using a 100-cc expander measuring 5 x 14 cm (the same size as the elevated flap) compared to 40-cc (3 x 5 cm) or to 60-cc (4 x 8 cm) expanders (P < 0.001, P = 0.004, respectively). The one-way analysis of variance and the t-test were used to show statistical differences. We conclude that the time necessary for neovascularisation of the skin flap could be used to expand the tissue, not only increasing the amount of available tissue, but also enhancing the vascularity.
Flap prefabrication is dependent on the neovascular response that occurs between the implanted arteriovenous pedicle and the recipient tissue. Augmentation of this neovascular response with angiogenic growth factors would maximize flap survival and minimize the interval between pedicle implantation and flap rotation. Maximizing the biologic activity of endogenous growth factors would likewise positively impact upon flap survival. This study examined the role of basic fibroblast growth factor, a known potent angiogenic growth factor, on flap survival in a rabbit ear prefabrication model. Sucrose octasulfate, a substance that binds basic fibroblast growth factor, stabilizes it, and protects it from degradation, was also studied to determine its impact on flap survival. Flap survival was increased using basic fibroblast growth factor, sucrose octasulfate, and the two substances combined together. The use of substrates designed to maximize the biologic activity of endogenous growth factors, rather than relying on the artificial addition of exogenous growth factors, represents a new approach in the search for methods that will improve flap survival.
A locally active thrombolytic agent, human tissue-type plasminogen activator (t-PA), given over a finite time period (24 hours) by local infusion, maintains long-term microvascular patency (7 days) in a proven thrombosis model using an arterial inversion graft in the rabbit model. Thirteen rabbits in the control group and 16 rabbits in the experimental group underwent an arterial inversion graft followed by continuous infusion (24 hours) with human tissue-type plasminogen activator (experimental) or normal saline (control). No significant clinical bleeding or alteration of coagulation parameters was noted in hematologic studies in both experimental and control groups. Scanning electron microscopy of the postoperative human tissue-type plasminogen activator-perfused arteries suggests an interaction of the human tissue-type plasminogen activator with specific platelet receptors in reversing microvascular thrombosis by decreasing or preventing further platelet aggregation and adhesion. Human tissue-type plasminogen activator infused locally for a finite period (24 hours) allows adequate time for platelet metamorphosis to occur in converting a thrombogenic to a nonthrombogenic vessel surface. The clinical ramifications in preventing or reversing microvascular thrombosis in free-tissue transfers and replantation surgery are apparent. Further study in this area will enhance our understanding of the pathogenesis and prevention of microvascular thrombosis.
The role of growth factors in a variety of bone and soft tissue healing processes has been studied extensively in numerous recent models, yet little is known about the specific growth factors that may be playing a role in flexor tendon healing. We used a number of established protein purification techniques and bioassays to isolate and partially characterize a heparin-binding growth factor from unoperated canine tendons. Our data provide evidence that basic fibroblast growth factor, a potent angiogenic growth factor, is present in normal canine intrasynovial flexor tendons. We then studied repaired canine flexor tendons to further elucidate the role of growth factors in the tendon healing process. Heparin-sepharose elution profiles from three repair intervals (3, 10, and 17 days) were graphed and compared to known profiles of isolated growth factors. The three repair intervals demonstrated two elution profile peaks, consistent with varying amounts of platelet-derived growth factor and epidermal growth factor. Although additional experimentation is required to identify definitively the various protein isolates, these data provide compelling evidence that a variety of growth factors are present in uninjured and healing digital flexor tendons.
The descending branch of the lateral femoral circumflex artery is a large-caliber artery that passes obliquely across the upper third of the thigh and descends between the vastus lateralis and rectus femoris muscles. It sends perforators through the septum between these muscles and through the vastus lateralis muscle and supplies a large area of skin on the anterolateral aspect of the thigh. We report our experience with our first 44 consecutive anterolateral thigh flaps, which were used for a variety of soft-tissue deficits. Twenty-five of these flaps were used for lower extremity reconstruction. 10 were used in the upper extremity, and 9 were used in the head and neck. The overall success rate was 96%. Six flaps required reoperation; of these, 2 flaps were lost, one from a venous thrombosis and the other from arterial thrombosis, both of which were in the lower extremity. In approximately one third of cases, the flap was raised as a septofasciocutaneous flap, but in two thirds it was necessary to include a small segment of vastus lateralis muscle as well as fascia with the flap. The flap has been particularly useful for lower extremity reconstruction, and in patients who are not fit for general anesthesia, it is possible to perform the flap transfer with epidural anesthesia. The flap has the advantage of a long vascular pedicle with large-caliber vessels and thus is suitable as a flow-through flap. It may also be sensate and has provided a versatile soft-tissue coverage option with minimal long-term donor-site complications.
As flap prefabrication becomes a more commonly used clinical tool, it is necessary to investigate the limitations of this technique. Reconstructive procedures of the face often require "custom fitted" flaps to satisfy esthetic demands. This study examines and compares the safety of manipulating thin prefabricated skin flaps versus established axial pattern skin flaps. Twenty-seven New Zealand white rabbits were used to determine if prefabricated flaps can be folded 180 degrees around the edge of the rabbits' ears. The survival of these folded prefabricated flaps was compared with the survival of axial pattern flaps sutured into an identically recipient site. In addition, flaps prefabricated in the same manner were sutured onto a straight recipient bed to evaluate the viability of the newly vascularized tissue. The folded prefabricated flaps had reduced survival (56%) compared to equivalent folded axial pattern flaps (85%), P < 0.005. The nonmanipulated prefabricated flaps and axial pattern flaps survived completely.
Neovascularisation of thin skin flaps after arteriovenous pedicle implantation (flap prefabrication) and the impact of the delay mechanism on the viability of these flaps were investigated. Twenty-four full thickness skin flaps were raised in twelve New Zealand white rabbits. Delay incisions were made at the lateral borders of the planned flaps at the same time as pedicle implantation, 1 week before pedicle implantation, or 1 week after pedicle implantation and the flaps based on the implanted vessels raised at 2 weeks after implantation. Flap survival assessed at 1 week was found to be improved when flap delay was performed 1 week before or after pedicle implantation. Angiographic studies demonstrated an increased density and linearity of the vascular pattern in these delay group flaps. The combination of the time-tested concept of delaying a flap with the newer technique of flap prefabrication appears to improve flap viability.
In a group of patients where breast reconstruction was performed at the time of mastectomy, the incidence of complications was studied. One hundred one consecutive patients had an autologous reconstruction using the transverse rectus abdominis musculocutaneous flap, and 115 consecutive patients had a prosthetic reconstruction with tissue expanders or with tissue expander and/or implant. One patient in the autologous reconstruction group had a cardiac arrhythmia requiring monitoring, but there were no other serious complications. Infection was more common in the group undergoing prosthetic reconstruction (5% compared with 3% in the autologous reconstruction group). A total of 8% of the patients in the group undergoing prosthetic reconstruction had to have their implants removed because of infection or exposure of the implant. Seven percent of the transverse rectus abdominis musculocutaneous flap patients had significant necrosis of a portion of the flap. Secondary surgical revision of the reconstructed breast was much more common (20%) in the prosthetic reconstruction group compared with 6% in the autologous reconstruction group.
We have developed a new model of thin flap prefabrication in the rabbit with an exteriorised vascular pedicle in a skin tube. Study of these prefabricated flaps after transfer demonstrated that distal flap survival improved as the interval between implantation and flap transfer increased. Exteriorising the pedicle minimises both donor deformity and pedicle trauma and allows easier experimental study of the neovascularisation process in flap prefabrication.
OBJECTIVE: The authors prospectively studied the impact of immediate breast reconstruction on patients undergoing mastectomy. SUMMARY BACKGROUND DATA: Despite the advocation of a breast-conserving approach to the treatment of breast cancer, many women continue to medically require or choose mastectomy for the treatment of breast cancer. In recent years, immediate breast reconstruction has become an alternative to either mastectomy alone or to delayed reconstruction. METHODS: A prospective database of 216 patients who underwent mastectomy with immediate reconstruction was established. In this series, 94 procedures involved implants or tissue expanders, and 124 tissue transfers were performed. RESULTS: The overall complication rate was 15.3%; only 9% of patients who underwent autologous tissue transfers required secondary procedures. When implants were performed, the overall rate of prosthetic loss was 8%. The majority of patients (n = 101) underwent transverse rectus abdominis musculocutaneous (TRAM) flaps. Twenty-six of the 38 (17.5%) patients who required transfusion were from this group. Partial flap losses in this group (7%) were correlated to a history of heavy smoking. With a median follow-up of 33.2 months, only two patients had recurred locally. According to patient opinion, autologous tissue transfers resulted in a statistically better cosmetic result. CONCLUSIONS: Immediate reconstruction can be performed safely and with excellent cosmetic results.
Recent studies have demonstrated an intrinsic neovascular response in intrasynovial healing tendons, introducing the possibility of mitogenic and/or angiogenic capability of intrasynovial tendon. To explore this hypothesis, healing canine flexor tendons were treated with early passive mobilization and the repair sites analysed at three, ten and 17 days. Specimens were mechanically digested and subjected to a standard BALB/c 3T3 mitogenic assay, which measures the capacity of tissue extracts to induce DNA synthesis and cell division in fibroblasts. Results revealed that both control and repaired flexor tendons possessed mitogenic activity, with the greatest activity observed in control specimens. Decreasing activity was noted as the time between repair and analysis increased. These data provide increasing evidence for the flexor tendon's active role in the healing process, and support the concept that mitogenic or growth-promoting factors are associated with flexor tendons and may be released following injury, during the early stages of healing.
Four techniques for permanent skin replacement with skin substitutes are described. A claim of superiority to conventional skin grafting on upper extremity and hand burns is not made, but some clinical observations and histologic evidence of different healing characteristics are shown. The composite grafts described appear to effectively replace the bilayered structure of skin and seem to have good subjective resistance to shear forces. If the skin replacement is durable and heals with less scarring than conventional skin grafts, the inexorable course to stiffness and contracture may be altered. Further basic science and clinical investigation may provide us with a better way of managing these difficult problems.
A new potent thrombolytic agent, human tissue type plasminogen activator (t-PA), has become available for study through recombinant DNA technology. In this series of experiments, we have tested t-PA in a reliable microvascular thrombosis model previously developed in our laboratory. Its action in preventing thrombus formation and lysing fresh clot by direct local infusion and systemic infusion was tested. The results revealed that t-PA was able to keep locally infused vessels open for 4 hours and reopen them after they were allowed to clot in 100 percent of the animals tested. Those vessels exposed only to systemic levels of t-PA achieved by the same local infusion remained thrombosed and were unaffected. Laboratory studies showed no evidence of activation of the systemic lytic state or alteration in coagulation parameters. t-PA has proved to be a protein with characteristics that make it attractive for use in microvascular surgery. The results suggest that further research may lead the way toward clinical use.
A patient who has undergone successful replantation of seven of eight amputated digits is presented. Survival in the last viable digit was seen 39 hours after amputation with cold ischemia preservation. No graded ischemia-related changes in the digits have been appreciated over 35 months of follow-up.