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Biomedical subjects

R K Khouri

Publications and source records attributed to R K Khouri.

17 recordsLinked to original sources
PubMed1992

Thigh adductor flap: an experimental model for free flap transfer in the rat.

A new model of rat muscle free flap transfer is presented. The flap is based on a long pedicle originating from the femoral vessels and continuing down to the distal saphenous margin at the ankle. The distal portion of the semitendinosus muscle is harvested along with the saphenous artery and great saphenous vein. A larger muscle flap may be harvested by including the distal portions of the posterior and anterior gracilis muscles. The flap can be transferred to remote sites on the animal, with a vascular pedicle of up to 3 cm in length. The diameters of the vessels repaired are of standard microsurgical size. This model has distinct advantages of simplicity, speed of dissection, high success rate after microvascular transfer, and versatility in placement of the muscle mass (due to the long pedicle).

Anastomosis, Surgical↗
PubMed1992

Salvage in a case of ring avulsion injury with an immediate second-toe wrap-around flap.

A nonreplantable complete degloving injury to the small finger of a young woman was treated with the immediate microsurgical transfer of a second-toe wrap-around flap. One year after the operation, the donor foot was free of symptoms, and the reconstructed finger had an excellent cosmetic appearance, a range of motion of 0/90 degrees at both the metacarpophalangeal and the proximal interphalangeal joints, and a two-point discrimination of 6 mm. In selected patients, when the degloved skin envelope cannot be revascularized and when the skeletal and tendinous units are still intact, an immediate second-toe wrap-around flap may be a good alternative to amputation.

Adult↗
PubMed1992

Principles of flap prefabrication.

Clinical flap prefabrication can be classified according to the basic technique of plastic surgery used for the prefabrication. There are currently three methods: (1) delay or expansion; (2) grafting; and (3) vascular induction by staged transfer. Illustrative cases are given to point out the advantages and indications for each method. A fourth, still experimental, method is based on cell biology advances that are looming on the horizon and may have revolutionary future clinical applications.

Adult↗
PubMed1992

Free flap surgery. The second decade.

After 2 decades of increasing expertise, microvascular free tissue transfer has gradually evolved from being a procedure of last resort to become a first choice reconstructive procedure. Improved success rates, reduced operative time, and patient morbidity have widened the indications for the procedure. This has profoundly affected our reconstructive principles and, in many instances, reversed some well-established dogmas of wound care, cancer resectability, and salvage of multilated parts. As the constraints of tissue survival decrease, more attention can be given to the artistry and functional restoration.

Humans↗
PubMed1992

Avoiding free flap failure.

To obtain up-to-date statistics on free flap success rates, a survey of 644 consecutive free flaps performed by nine expert microsurgeons was conducted in 1991. Analysis of the failures shed light on the current problem areas. Because operative experience is the most important factor related to improved success rates, a questionnaire aimed at probing the experts for the lessons learned as their success rates improved was sent to 12 expert microsurgeons. From this source of data, and from the author's experience, a breakdown of the causes of free flap failure is given.

Humans↗
PubMed1992

Refinements in hand coverage with microvascular free flaps.

The specialized tissue requirements or dorsal and palmar skin are analyzed and options for full-thickness replacement outlined in detail. Thoughtful and accurate preoperative planning is the key to success. Dorsal coverage with a variety of pedicled and free fasciocutaneous flaps are quite satisfactory. Palmar coverage is more difficult and the need for sensation more critical. Free vascularized temporoparietal fascial flaps covered with full-thickness skin grafts are currently the treatment of choice for most complex wounds.

Aged↗
PubMed1992

Advances in total phalloplasty and urethroplasty with microvascular free flaps.

This article focuses on the lateral arm free flap as the option that comes closest to meeting the diverse aesthetic and functional goals of phalloplasty. The authors introduce a new technique for incorporating a prefabricated neourethra within the lateral arm to permit the coexistence of an erectile prosthesis alongside a fully vascularized urethra that extends to the distal tip. The unrecognized value of the radial forearm free flap for urethroplasty is also discussed and a case of reconstruction following urethral loss is presented. Also described is how the prefabricated urethra technique may be useful for repairing severe hypospadias defects.

Humans↗
PubMed1992

Monitoring of free flaps with surface-temperature recordings: is it reliable?

Surface-temperature recording (STR) is one of the oldest and simplest methods of postoperative monitoring of free flaps. Its usefulness, however, remains poorly documented, and its problems, not well understood. To assess its value, we reviewed our series of 600 consecutive free flaps where surface-temperature recording was the main method of monitoring used and a detailed temperature record was kept. Seventy flaps suffered a postoperative microvascular compromise necessitating a surgical reexploration. Of these, 62 charts were satisfactory for review and were matched with 62 charts from similar but uncomplicated flaps. The derived value C delta T, which represents the change in temperature difference (delta T) between flap and control sites over a specified time period, was calculated at each time point. Of 10,000 derivations, only once did C delta T greater than 1.8 degrees C fail to identify a microvascular thrombosis, and 17 times a false alarm was given. Therefore, when properly applied and interpreted, the sensitivity of surface-temperature recording is 98 percent, and its predictive value is 75 percent, making it a simple, inexpensive, and highly reliable technique of free-flap monitoring. The thermodynamics behind surface-temperature recording is reviewed, pointing out the pitfalls that have to be avoided in order to improve the reliability of this technique.

Humans↗
PubMed1991

Tissue transformation into bone in vivo. A potential practical application.

The transformation of mesenchymal tissue, such as muscle, into cartilage and bone can be induced by the recently purified osteoinductive factor, osteogenin, and by its parent substratum, demineralized bone matrix. We investigated the possibility of transforming readily available muscle flaps into vascularized bone grafts of various shapes that could be used as skeletal replacement parts. In a rat experimental model, thigh adductor muscle island flaps were placed inside bivalved silicone rubber molds. Prior to closure of the mold, 18 flaps were injected with osteogenin and coated with demineralized bone matrix. Five flaps served as controls and were injected with the vehicle only, and not coated with demineralized bone matrix. The molds were implanted subcutaneously in the rats' flanks and reopened 10 days later. The control flaps consisted of intact muscle without any evidence of tissue transformation, whereas the flaps treated with osteogenin and demineralized bone matrix were entirely transformed into cancellous bone that matched the exact shape of the mold. Using tissue transformation, we were able to generate in vivo, autogenous, well-perfused bones in the shapes of femoral heads and mandibles.

Animals↗
PubMed1991

The fasciovascular pedicle for revascularization of other tissues.

A fasciovascular pedicle based on the epigastric vessels was developed in a rat model to determine if it could be used as a "universal carrier" to revascularize a new composite flap. The effects of time course, carrier size, and flap ischemia on the revascularization process were studied. A 2.5 x 4-cm or 1 x 4-cm fascial patch pedicled on the vessels was transferred under bipedicled 2.5 x 4-, 6-, or 8-cm abdominal panniculocutaneous flaps. At different time intervals, the flap was raised as an island flap connected only by it vascular bundle and then sutured back in place. The skin perfusion by dermofluorometry and flap survival were both markedly increased on day 5 (p less than 0.001). The wide carrier had a 93% survival area, whereas the narrow carrier had only 71%. The wide carrier induced relatively faster and better revascularization (p less than 0.05). Moderate ischemia promoted revascularization (p less than 0.01). An india ink injection study and histological examination provided visual evidence of revascularization. This fasciovascular pedicle is a promising model for prefabrication of complex new composite flaps and for studying the process of revascularization between the layers. Based on these findings and further investigations, a thin, prefabricated abdominal free flap was successfully transferred for facial resurfacing in humans.

Abdomen↗
PubMed1991

Bilateral lower limb salvage with free flaps in a patient with sickle cell ulcers.

A patient with long-standing bilateral circumferential lower extremity sickle cell ulcerations refractory to conservative management was successfully treated with bilateral free latissimus muscle transfers. This report confirms the value of free tissue transfer in the treatment of these difficult skin ulcerations. Exchange transfusions that brought the SS hemoglobin below 30% were crucial to the prevention of sickling in the microcirculation of the flap during its obligate period of ischemia. Furthermore, they protected the flap during a period of ischemia that exceeded 4 hours following a postoperative arterial thrombosis. In the presence of severe thrombocytosis associated with sickle cell disease, prophylactic treatment with aspirin may be of significant value.

Adult↗
PubMed1991

Prefabrication of composite free flaps through staged microvascular transfer: an experimental and clinical study.

The feasibility of prefabricating free flaps by inducing, through the process of staged reconstruction, an arteriovenous bundle and its surrounding fascia to perfuse a selected block of tissue was investigated experimentally and clinically. Sixteen rat knee joints were wrapped with their ipsilateral superficial inferior epigastric (SIE) fascia. In 8 joints, the composite flaps were resected en bloc and were immediately replaced orthotopically pedicled upon the superficial inferior epigastric vessels. In the remaining joints, the resection and orthotopic transfer were performed 2 weeks later. Only the joints in the latter group, which benefited from the staging period, were found to be perfused. The long finger proximal interphalangeal joint of a child was reconstructed by the staged microvascular transfer of his second toe proximal interphalangeal joint. At the first stage, a temporalis fascia flap was wrapped around the toe proximal interphalangeal joint and revascularized to the dorsalis pedis vessels. Six weeks later, the joint and its temporalis fascia envelope were dissected, and the "prefabricated" joint flap was transferred to the hand and revascularized to the wrist vessels. Bony union progressed uneventfully with excellent recovery of the range of motion. We conclude that regardless of the indigenous vascular anatomy, an unlimited array of composite free flaps can be constructed and transferred based on induced large vascular pedicles.

Animals↗
PubMed1990

Thrombosis of microvascular anastomoses in traumatized vessels: fibrin versus platelets.

Thrombosis is the end result of two closely interrelated processes: the coagulation cascade and the platelet aggregation process. To determine their relative contribution, we used pharmacologic agents that selectively block each process. The specific effect of each pharmacologic agent on either fibrin deposition or platelet activity was confirmed morphologically by scanning electron microscopy and was substantiated with ADP-induced platelet aggregation and blood clotting time determinations. Forty-two rats had both femoral arteries subjected to a standardized crush-avulsion injury. A total of 84 femoral microvascular anastomoses were subsequently performed. None of the 24 control anastomoses treated with saline remained patent, whereas 6 of 24 of the anastomoses treated with dazmagrel (a selective thromboxane synthetase and platelet aggregation inhibitor), 2.5 mg/kg IV, remained patent and 18 of 24 of those treated with a single dose of heparin, 200 U/kg IV, remained patent. All 12 anastomoses treated with both drugs remained patent but developed a 33 percent hematoma rate. We conclude that in this microvascular model, fibrin mesh deposition is a more significant factor than platelet aggregation in the pathogenesis of occlusional thrombosis within traumatized arteries. Its temporary inhibition with a single dose of heparin yielded a 75 percent improvement in patency rate.

Anastomosis, Surgical↗
PubMed1989

Effects of neurite-promoting factors on rat sciatic nerve regeneration.

Neurite promoting factors (NPF), fibroblast growth factor, and laminin were instilled inside autologous venous nerve conduits (AVNC) interposed across a 1 cm gap in the rat sciatic nerve. Axonal regeneration was measured electrophysiologically and histologically and was compared to control AVNC and autologous nerve grafts (ANG) in 45 rats. By 1 month, the AVNC group with NPF recovered an average nerve conduction velocity twice that of the ANG group (24 m/sec vs. 12 m/sec). The gastrocnemius muscle action potential of NPF grafts was twice that of the control AVNC and was similar to the ANG (1.63 mV vs. 0.87 mV). In subsequent months, the advantage of NPF disappeared; these grafts were grossly reduced to fibrous bands. Histological examination of these grafts at 5 months revealed a florid intraluminal fibrovascular proliferation, which appeared to be "choking off" the regenerating axons. It is suggested that more refined mixtures of NPF should be instilled inside AVNC so that the improved axonal regeneration is maintained while the late inhibitory fibrosis is avoided.

Animals↗
PubMed1989

Reconstruction of the lower extremity with microvascular free flaps: a 10-year experience with 304 consecutive cases.

A retrospective review of 304 consecutive microvascular free flaps to the lower extremity was done to identify the patterns of usage, results, and problems. The most common indication (91%) was for the replacement of extensive tissue loss caused by motor-vehicle injuries. Most of the defects were below the mid-tibia (73%). The associated compound fractures were predominantly gradable as Gustilo type IIIb&c. The latissimus dorsi, the rectus abdominus, and the scapular skin were the flaps used most commonly for coverage (77%). The overall flap failure rate was 8%, compared with 3% for our series of non-lower extremity cases, and 0% for the non-traumatic lower extremity cases. The magnitude of the traumatic insult was the most significant factor associated with anastomotic failure. The rate of anastomotic thrombosis doubled in the presence of vascular trauma, increased threefold in the presence of larger bony defects, and increased fivefold when vein grafts were needed. Experience was important in reducing the complications and improving the results. Fourteen patients (6%) underwent an amputation within the first 3 months, ten of them because of flap failure. Of 85 patients followed up for over one year, 91% had recovered good to excellent leg function. The ability to add healthy and well vascularized tissue to the traumatized limb is critical for the achievement of: 1) early definitive wound healing and restoration of function; 2) salvage of many impending amputations; 3) better prosthetic stump reconstructions; 4) better esthetic results.

Amputation, Surgical↗
PubMedDate not supplied

The effect of basic fibroblast growth factor on the neovascularisation process: skin flap survival and staged flap transfers.

Forty-two male Sprague-Dawley rats were utilised to determine whether the angiogenic property of basic fibroblast growth factor (bFGF) could be applied to improve the survival of the ischaemic portion of a random skin flap and to accelerate the process of staged flap transfer. In the ischaemic flap model, bFGF enhanced the development of vascular connections between the bed and the flap and prevented marginally perfused areas from undergoing necrosis. No effect was observed in the staged reconstruction model using the same dosage of bFGF. A speculative explanation is given for the differential effect of BFGF in these two models. The application of angiogenic factors may improve the survival of the random portion of skin flaps. Further investigations are needed to determine whether exogenously applied angiogenic factors can have a beneficial effect in staged flap reconstructions.

Angiogenesis Inducing Agents↗