Yucel Erk

Tissue pH monitoring in microsurgery: a preliminary evaluation of continuous tissue pH monitoring as an indicator of perfusion disturbances in microvascular free flaps

In an experiment using a continuous tissue pH monitoring system, selective occlusion of the vessels supplying lower abdominal island flaps in Sprague-Dawley rats resulted in predictable tissue pH changes. Arterial occlusion resulted in a rapid fall in pH. In all three experimental groups, the steepest rate of pH drop occurred during the first 30 minutes postocclusion. In a series of 9 patients who underwent microvascular free-flap surgery the continuous pH monitor was employed postoperatively. Tissue pH was (and remained) normal in well-perfused free flaps. Tissue pH fell almost immediately with anastomotic failures. These findings demonstrate that pH measurement offers the microvascular surgeon a new, simple, and reliable approach to perfusion assessment in free flaps. Perhaps improved survival rates will result from earlier anastomotic exploration in compromised free flaps that exhibit falling pH values.

Blood loss and transfusion rates during repair of craniofacial deformities.

Surgical procedures for correction of craniofacial deformities resulted in unavoidable and extensive blood loss in small children and infants. Almost all of the patients undergoing these procedures will undergo a blood transfusion either during or immediately after the operation. A retrospective review of 30 patients who underwent craniofacial surgery was performed in this study to determine the magnitude of transfusion required for craniofacial surgery, document transfusion morbidity, and identify variables associated with the transfusion. The mean estimated blood loss was 566.8 mL, the mean intraoperative transfusion was 394.8 mL, the mean postoperative transfusion was 103.2 mL, and the mean total transfusion was 505 mL. The mean operative time was 450 minutes, the mean preoperative hemoglobin and the mean postoperative hemoglobin before hospital discharge were 11.6 g/dL and 10.3 g/dL, respectively. Craniofacial surgical procedures involve extensive scalp dissection and calvarial and facial bone osteotomies in patients with a low total blood volume. Every medical and surgical strategy for minimizing the need for blood transfusion should be considered.

Solvent-dehydrated calvarial allografts in craniofacial surgery.

Craniofacial surgery almost always requires the use of bone grafting. Although autografts are the standard procedure for bone grafting, it is sometimes not possible to harvest bone, and autografts have particular risks. The use of allograft bone provides a reasonable alternative to meet the need for graft material. Solvent dehydration is a multistage procedure in which human cadaveric bone is processed by osmotic exchange baths and gamma sterilization. This processing avoids the risk of infection transmission, decreases antigenicity, and does not weaken the mechanical properties of the bone. Solvent-dehydrated, gamma-irradiated human calvarial bone allografts were used for reconstruction of craniofacial deformities in 24 patients between 1988 and 2002. Resorption of the allografts and results of the surgical intervention were evaluated with plain radiographs and three-dimensional computed tomography 12 months after surgery, in 21 patients. Serologic tests for human immunodeficiency virus-1 antibody, hepatitis B surface antigen, and hepatitis C antigen were also performed. Biopsy specimens were taken from the allografts. Average follow-up in this group was 30 months (range, 8 to 60 months), and results of serologic tests were negative in all patients. Seventy-one percent of the patients (15 of 21) showed no resorption, with partial and complete allograft fusion. One patient had nearly total graft loss and the remaining five patients had 10 to 25 percent graft resorption. Rigid fixation of the allograft, contact with the dura and periosteum, and prevention of dead spaces around the allograft are the most important factors in achieving a satisfactory result. In solvent-dehydrated bone allografts, sterilization and antigenic tissue cleaning are achieved after several steps with a minimal dose of radiation. The result is a nonantigenic, sterile mechanical scaffold that can tolerate external forces. Although autografts are the standard in craniofacial surgery, solvent-dehydrated calvarial bone allografts produced successful results in selected cases.

Effect of use of slow release of bone morphogenetic protein-2 and transforming growth factor-Beta-2 in a chitosan gel matrix on cranial bone graft survival in experimental cranial critical size defect model.

Bone grafts, used for providing structural integrity of cranial vault remodeling, could not always integrate with the remaining bone structures. All efforts are focused on increasing incorporation of the applied bone grafts. Allografts were covered by chitosan so that slow release of bone morphogenetic protein-2 (BMP-2) and Transforming growth factor-beta-2 (TGF-beta-2) was achieved. Two hundred forty Wistar-Albino rats were distributed equally in 8 study groups. Study groups were designed as; defect group, autograft group, allograft group, chitosan group, allograft + chitosan, TGF-beta-2 group, BMP-2 group, and TGF-Beta-2 +BMP-2 group. Bone biopsies were obtained at second, eight, and 14th weeks. Bone regeneration was evaluated by morphologic studies detecting histologic bone healing and radiologic studies detecting bone density. Histologic findings were evaluated in 2 categories; tissue response to the implant and defect healing. Additionally, scanning electron microscopy for detailed morphologic evaluation was done. Bone density of the applied scaffold and the parietal bone at the same computed tomography section were measured in Hounsfield scale and this ratio was used for densitometry evaluations. Kruskal-Wallis test was used to analyze difference among groups according to the histologic and radiologic data. Pairwise comparisons were done using Mann-Whitney U test with Bonferroni correction. P < 0.05 was considered significant. In the morphologic studies, bone regeneration in BMP-2 group was found to be compatible with bone regeneration in gold standard autograft group and even better than it within 15 days. Chitosan is a biocompatible material. TGF-Beta-2 alone is not effective enough in bone regeneration; BMP-2 alone has a positive effect in every step of bone regeneration. Combining TGF-Beta-2 with BMP-2 does not lead to a better bone regeneration than using BMP-2 alone. A synergistic effect is not obtained by using these 2 factors together.

Vascular Augmentation of Skin and Musculocutaneous Flaps

In a series of rats, pigs, and dogs, a method for ligating an expendable vessel and placing it under a skin flap or using the vessel to create a new pedicle (neovascular pedicle) for a musculocutaneous flap by the process of neovascularization is demonstrated. No ischemic stimulus is necessary to induce this process of transmural neovascularization.

Results of botulinum toxin: an application to blepharospasm Schwartz-Jampel syndrome.

Schwartz-Jampel syndrome (SJS) is a rare congenital disorder of continuous myotonia, causing visual and eyelid problems such as blepharospasm, acquired ptosis, and blepharophimosis. We report the management of blepharospasm in two sisters with Schwartz-Jampel syndrome with application of botilinum toxin type A (BTX-A), as an alternative to the surgical treatments, such as orbicularis oculi myectomy, levator aponeurosis resection, and lateral canthopexy as described in the literature. Three consequent doses of commercially available BTX-A (Botox®-Allergan, Inc. 100 u/via) were injected to orbicularis oculi muscle in two sisters with Schwartz-Jampel syndrome. At the least, the authors waited for a six-month interval to prevent development of sensitivity to BTX-A in patients. No significant improvement was observed after the injection of first dose of BTX-A, with the total dose of 25 units of BTX-A to each orbicularis oculi muscle of the eyes. The muscle tone weakened after the second dose, which was the twice as such of the first applied total dose (50 units of BTX-A to each orbicularis oculi muscle of the eyes) and significant functional and cosmetic improvements were achieved after injection of the third dose, in which the total applied dose was the same as the one applied in second dose. The blepharospasm and eyelid alterations caused by Schwartz-Jampel syndrome should be treated to provide functional and cosmetic improvements. Application of BTX-A to orbicularis oculi muscle for the treatment of blepharospasm could be considered as an alternative to levator resection, and lateral canthopexy in Schwartz-Jampel syndrome.

DIMETHYL SULFOXIDE ALTERATION OF COLLAGEN

In vitro incubation of human scar in our laboratory with 99% DMSO demonstrated, by electron microscopy, the disruption of the collagen fibers. This may prove to be a useful preparatory step for selective enzymatic assault upon exuberant or undesirable scar tissue in the clinical setting. Further study of this concept is planned.

Mandibular reconstruction in Goldenhar syndrome using temporalis muscle osteofascial flap.

Goldenhar syndrome is a well-known developmental anomaly of the maxillofacial skeleton and hemifacial soft tissue. Maxillofacial anomalies of that syndrome can be managed by a variety of means such as inlay- or onlay-applied nonvascularized bone grafts, vascularized osteocutaneous/osseous flaps, or distraction osteogenesis. Vascularized full-thickness calvarial bone grafting is an important option for mandibular reconstruction for cases in which, for one reason or another, other techniques are not available, not applicable, or have failed. A mandibular defect of a 6-year-old boy presenting with bilateral preauricular skin tags, right microtia, right mandibular hypoplasia (with missing right condylar head and ascending ramus of the mandible) was reconstructed with right vascularized full-thickness calvarial bone grafting. Preoperative three-dimensional computed tomographic scans were used to acquire the stereolithographic biomodeling of the patient for assessing the amount of bone defect and precise planning of the surgery. Panoramic, anteroposterior, and lateral cephalograms and three-dimensional computed tomographic scans were obtained before and after the surgery and in the follow-up period for the evaluation of amount of relapse in the follow-up period. Clinical follow up and bone scintigraphy were used to assess the viability of transferred vascularized calvarial bone graft in the postoperative period. Plain radiographic evaluation with anteroposterior radiographs showed that mandibular symmetry increased and normooclusive closure of incisive teeth was achieved after surgery and retained in the postoperative period. Radiographs taken 1 year after surgery demonstrated that there was a slight relapse (1 mm) to the right side in the mandible when the results were compared with early postoperative ones. Postoperative three-dimensional computed tomographic evaluation of bony structures 3 months after operation showed that the transferred bone retained its volume. Sequential bone scintigraphies, performed to assess the vascularity of the grafts 1 week, 1 month, and 1 year after the operation, demonstrated the viability of transferred vascularized bone graft. The temporalis muscle osteofascial flap is a reliable method for mandibular reconstruction. It lessens the operative time, lessens surgical team labor, minimizes postoperative morbidity and discomfort, minimizes the hospital stay period, and minimizes financial expenses without renouncing the bone-healing capacity and increases aesthetic outcome by camouflaging the donor site scar in scalp and minimizing the facial scarring.

Electric Current Arterial Injury: A Laboratory Model

A laboratory model capable of creating reproducible, nonlethal, fourth-degree type electrical extremity burns in rats was developed. Fifty-seven rats were studied immediately after burn to 90 days after burn with microdissections, light microscopy, microangiography, and flow studies. Progressive necrosis was not observed. Minimal major vessel arterial injury was demonstrated. This significant finding supports the concept of early debridement and reconstruction to include possible free tissue transfer.

Midface distraction using spring scale attached to rigid external device.

Distraction osteogenesis has become an al-ternative technique for treatment of craniofa-cial dysplasias. The success of the halo distrac-tion device in the treatment of severe maxillaryhypoplasia associated with cleft palate patientshas led to the application of this device to treatmany more complex craniofacial anomalies.