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Biomedical subjects

Geoffrey G Hallock

Publications and source records attributed to Geoffrey G Hallock.

At least 37 records · Page 2Linked to original sources

Lower extremity muscle perforator flaps for lower extremity reconstruction.

A true muscle perforator flap is distinguished by the requisite intramuscular dissection of its musculocutaneous perforator to capture the same musculocutaneous territory but with total exclusion of the muscle, and thereby results in minimal functional impairment. Adhering to this definition, several lower extremity donor sites now are available, each with specific attributes especially useful for consideration in the treatment of lower extremity defects. In this author's experience over the past two decades, 20 lower extremity muscle perforator flaps using multiple donor sites proved advantageous for lower extremity coverage problems as either a local pedicled flap or as a microsurgical tissue transfer. Significant complications occurred in 30 percent of flaps (six of 20) in that further intervention was required. Venous insufficiency and bulkiness were found to be the major inherent shortcomings. However, giant flaps, lengthy and large-caliber vascular pedicles, and the possibility for combined flaps were important assets. The choice of a lower extremity muscle perforator flap for lower extremity reconstruction limited the surgical intervention and morbidity to a single body region.

Female↗

Comparison of TRAM and DIEP flap physiology in a rat model.

Dynamic and physiologic studies objectively comparing the attributes of the transverse rectus abdominis musculocutaneous (TRAM) and deep inferior epigastric perforator (DIEP) flaps would be most practical in an animal model. This has now been accomplished using the ventral abdomen of the Sprague-Dawley rat. A conventional TRAM flap, a multiple perforator DIEP flap, and a solitary perforator DIEP flap were raised in three equal groups of five rats each. Flow studies using laser Doppler flowmetry demonstrated the highest flow in zone I in the TRAM flap group (87.6 +/- 15.4 percent), which was a statistically significant difference from the multiple perforator DIEP flap group (45.4 +/- 13.3 percent) and the solitary perforator DIEP flap group (43.4 +/- 26.4 percent) (p = 0.005). Flow in zone IV was proportionately lower for all groups, with no significant difference noted between TRAM and DIEP flaps (p = 0.736). Although ultimate flap survival was greatest for the TRAM flap group (96.1 +/- 6.7 percent) when compared with the multiple perforator DIEP flap (79.8 +/- 15.2 percent) or the solitary perforator DIEP flap groups (77.1 +/- 23.0 percent), this difference was not statistically significant (p = 0.183). In summary, relative flow to these rat ventral abdomen models was directly proportional to the number of retained musculocutaneous perforators, but a single perforator only could routinely allow near-total survival.

Animals↗

Restoration of quadriceps femoris function with a dynamic microsurgical free latissimus dorsi muscle transfer.

Loss of knee extension caused by quadriceps femoris muscle disruption can be a disabling injury. Attempts at reconstructing the large muscle deficit after oncological resections of the quadriceps have previously had some success using a dynamic free latissimus dorsi muscle transfer. This concept proved to be similarly valuable after a gunshot wound to the thigh resulted in an isolated loss of the quadriceps mechanism. A reinnervated latissimus dorsi muscle bridging the quadriceps muscle gap proved to have active contraction and permitted full active knee extension, demonstrating the value of this muscle also for restoration of function after traumatic injuries.

Adult↗

Turnover TRAM flap as a diaphragmatic patch.

A hole in the diaphragm requiring an exogenous material for repair is exceedingly unusual. Unfortunately, many nearby potential flap options for this role have frequently already been violated by prior thoracotomies. The ipsilateral superior-pedicled lower transverse rectus abdominis musculocutaneous (TRAM) flap could then be an important maneuver for salvage. Via a tunnel leading into the chest cavity, a deepithelialized TRAM flap can readily reach basilar thoracic defects, and[U0292] thus is particularly suited as an autogenous patch for the diaphragm.

Aged↗

The medial sural MEDIAL GASTROCNEMIUS perforator free flap: an 'ideal' prone position skin flap.

The medial sural MEDIAL GASTROCNEMIUS perforator flap is a potentially large, thin cutaneous flap that encompasses the calf skin territory. Its medial sural vascular pedicle has a long leash of large caliber that simplifies microanastomoses when used as a free flap. Because the identification of the requisite perforators and their subsequent intramuscular dissection is facilitated with the patient in a prone position, this can be an "ideal" skin free flap for the posterior aspect of the body. This is especially true for the lower limb where all surgical morbidity could then be restricted to the ipsilateral extremity. This approach has been used in 5 clinical cases, with success except once when the flap was aborted as a result of anatomic anomalies, which is always a concern with muscle perforator flaps.

Foot Injuries↗

Conventional liposuction-assisted debulking of muscle perforator flaps.

Late recontouring of the usual bulky cutaneous flap via conventional liposuction is an accepted practice and usually without fear of tissue necrosis. Muscle perforator flaps, on the other hand, initially depend only on often fragile, minuscule vessels that could readily be traumatized by any form of suction-assisted lipectomy. Single-staged muscle perforator flap debulking was thus performed with some trepidation for 8 flaps in 7 patients. All flaps ultimately remained successful, but in 2 cases obvious tissue ischemia delayed healing. It can only then be assumed that this adjunctive technique places all perforators at jeopardy for injury. Survival of the given flap may then depend solely on neovascularization from the recipient site, and that must be protected to retain pedicle independence, or otherwise flap necrosis would ensue. Thus, the timing of muscle perforator flap debulking could then be critical. Although that averaged 9.1 months (range, 3-15 months) after flap transfer in this series, the observed ischemia occurred at both ends of this spectrum.

Achilles Tendon↗

The preexpanded anterolateral thigh free flap.

The anterolateral thigh flap has many of the attributes of the ideal soft-tissue flap. However, a major detriment is the potential conspicuous donor site deformity, especially if skin grafted. In elective situations, preexpansion of the lateral thigh with subsequent transfer of even a wide anterolateral thigh flap can permit primary donor site closure and avoidance of a skin graft. This has been achieved successfully in 2 compliant patients, and is a reasonable solution to minimize the morbidity of this otherwise important donor site.

Burns↗

The medial sural(MEDIAL GASTROCNEMIUS) perforator local flap.

The medial sural(MEDIAL GASTROCNEMIUS) perforator flap has previously been described as a free flap distinguished by the potential for a large yet thin cutaneous flap that incorporates the calf skin territory. Its medial sural vascular pedicle can be tailored to allow reach extending from the popliteal fossa to the suprapatellar area also as a local flap without any need for microsurgery. Two variations presented are possible as either a broad-based peninsular or island flap. Both are alternatives to the more traditional medial gastrocnemius muscle flap and, because this is a true muscle perforator flap, function is always preserved.

Adult↗

Long-term superiority of composite versus muscle-only free flaps for skull coverage.

Long-term follow-up of free flaps used for skull coverage in this experience has revealed that serious sequela are more likely after muscle-only free flaps. Over the past 2 decades, 8 muscle and 6 composite free flaps have been used in 12 patients. Debulking was the only secondary procedure necessary in 1 composite flap. However, implant extrusion through 1 muscle flap and chronic ulcerations after minor trauma in 2 other muscle flaps could be directly attributed to the thinness of these flaps. Whether these problems were a consequence of inevitable muscle atrophy or improper selection of too thin a muscle flap from the outset is unknown. Thus, it must be suggested that either a composite flap or a known thick muscle should be chosen initially if a permanent trouble-free outcome is to be expected.

Follow-Up Studies↗

The perforator-based conjoint (chimeric) medial Sural(MEDIAL GASTROCNEMIUS) free flap.

The prototypical conjoint or so-called "chimeric" free flap heretofore has been composed of several large independent flaps, each supplied by a separate major branch, that ultimately arise from a common source vessel. The perforator-based type of chimeric flap is a relatively new concept, usually involving multiple muscle perforator flaps each based on a solitary musculocutaneous perforator, but still arising from the same "mother" vessel. This principle of split cutaneous perforator flaps has been now successfully adapted to the medial suralMEDIAL GASTROCNEMIUS perforator free flap on 2 separate occasions. As a chimeric flap, there was greater flexibility in insetting, and overall flap width may be larger but still narrow enough to allow primary donor site closure; and yet, by definition, only a single recipient site was needed for any microanastomoses. This is further proof that the perforator-based chimeric free flap may be an option for any muscle perforator flap donor site, so that potential donor territories for conjoint flaps have become virtually unlimited.

Adult↗

Doppler sonography and color duplex imaging for planning a perforator flap.

The most critical factor to predict viability for any muscle perforator flap is an adequate circulation. Therefore, it is advantageous during preoperative planning to have the capability to localize the requisite cutaneous perforator. Color duplex imaging fulfills this requirement and permits the identification of additional characteristics, including caliber, course, and flow velocity of essential perforators and any source vessel. Nevertheless, with the current state of technology, Doppler sonography remains a more rapid, convenient, and simpler method for perforator localization.

Blood Vessels↗

Venous interruption is unnecessary to achieve an adequate delay in the rat TRAM flap model.

Staged division of any or all inferior dominant pedicles to the human lower transverse rectus abdominis musculocutaneous (TRAM) flap has previously been attempted to invoke the delay phenomenon to enhance the rate of success with the superior-pedicled version, especially for patients at high risk for complications. Regardless of the specific vessels ligated, this has usually been accomplished by division of the source artery and its accompanying vein. Whether division of both vessels is essential remains unclear, however. This issue was investigated by using the authors' standard rat TRAM flap model in 43 female Sprague-Dawley rats, which were randomly assigned to four groups. In group A, both the predominant ipsilateral cranial epigastric artery and the cranial epigastric vein were divided 2 weeks before elevation of the TRAM flap. In group B, only the artery was divided; in group C, only the vein was divided. In an undelayed control group, the TRAM flap was elevated immediately, with no prior pedicle division. The percentages of flap survival in group A (89.3 +/- 7.0 percent) and group B (88.8 +/- 6.5 percent) (both with division of the predominant artery) were significantly greater than that in the control group (64.6 +/- 20.5 percent) (p < 0.001) or that in the group in which the vein alone was divided (73.9 +/- 11.3 percent) (p < 0.01). There was no significant difference between the group that underwent vein division only and the control group (p = 0.102). The clinical implication is that arterial division is critical for TRAM flap delay and that arbitrary venous interruption is unnecessary.

Abdominal Muscles↗

Direct and indirect perforator flaps: the history and the controversy.

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Recognize the major role of the vascular supply to a cutaneous flap. 2. Predict its reliability. 3. Understand basic schemes for classification. 4. Realize that the evolution of these concepts is an ongoing dynamic process. Currently, the vascular supply to the fascial plexus is considered the factor of greatest importance in ensuring the reliability of any skin-bearing flap. The multiplicity of origins of the deep fascial perforators to this plexus has led to a bewildering array of terminology intended to encompass all possible flap options. A brief review of the history of the evolution of cutaneous flaps provides insight essential in understanding a simple proposal for their classification. Because all fascial perforators course either directly from a source vessel or indirectly first through some other tissue to ultimately reach the suprafascial layer, the corresponding flaps based on any such perforators could most simply be termed either direct perforator flaps or indirect perforator flaps, respectively.

Fascia↗

Cranial epigastric perforator flap: a rat model of a true perforator flap.

The major advantage of a true perforator flap is the ability to capture the skin portion of what previously was a musculocutaneous flap, while totally excluding the muscle for function preservation. To understand better the physiology and dynamics of this flap subtype, a comparable and reliable animal model is essential. This has now been accomplished in the Sprague-Dawley rat using the same abdominal skin territory of the standard rat transverse rectus abdominis musculocutaneous flap, but differing in that all rectus abdominis fascial perforators are isolated via an intramuscular dissection back to the cranial epigastric artery source vessel. Hence, this has appropriately been termed the cranial epigastric perforator flap. From a series of eight rats to date, consistent survival of this flap was as predicted. The dissection itself can be somewhat tedious, but it became easier with experience, making this an excellent training model for learning proper technique in the elevation of any true perforator flap.

Animals↗

Sequential use of a true perforator flap and its corresponding muscle flap.

A true perforator flap completely spares the underlying muscle that was previously required as essentially a passive carrier of that musculocutaneous unit. Thus, a perforator flap and its related muscle can now be simultaneously transferred as independent but conjoint flaps based on the same source pedicle, or sometimes also in a metachronous fashion if the requisite source vessels remain intact. The latter principle proved feasible after failure of 2 medial sural perforator flaps that were subsequently successfully replaced by a conventional medial gastrocnemius muscle flap. At least theoretically, depending on the extent of intramuscular dissection, another advantage that can be applied to all perforator flaps is that the muscle can be held in reserve for sequential use as necessary.

Arthroplasty, Replacement, Knee↗