Mark P. Gianoutsos

The neurovascular territories of the skin and muscles: anatomic study and clinical implications.

In 1987, the results of a series of total-body investigations of the arterial system of the skin and underlying deep tissues were published. This resulted in the angiosome concept. In 1990, a similar series of studies of the venous network was published. In both investigations, it was noted that “vessels hitchhike with nerves.” This anatomic study analyzes these neurovascular relationships in the skin and in the underlying muscles. Seven fresh human cadavers and nine animals were studied over a 2-year period. The entire integument of each and a total of 538 human and 72 animal muscles were removed and analyzed. Either the arterial or the venous system was injected with a radiopaque lead oxide mixture, and the dissected nerves were labeled with fine wires, being segregated later by a subtraction radiography technique. The results of these investigations are presented, with special emphasis placed on the design of long axial skin flaps placed along neurovascular systems and their relationship with the current design of skin flaps. The muscles are classified according to their extrinsic and intrinsic neurovascular supplies, and suggestions are made as to how they may or may not be subdivided into functional units for local and distant transfer. The cutaneous nerves, as well as the motor nerves of the muscles, were invariably accompanied by a longitudinal system of arteries and veins that often was the dominant supply to the region. Whether the nerves appeared together with the vessels, whether the nerves crossed them at an angle, or whether they approached the vessels from opposite directions, in each case the main trunk of the vessel or some of its branches soon “peeled off” to course parallel to the nerve. This information provides the basis for the design of long skin flaps placed along neurovascular systems. Indeed, it reveals that many of the current “axial” or “fasciocutaneous” skin flaps used in clinical practice are in fact neurovascular flaps. The muscles are classified into four types according to their extrinsic and intrinsic neurovascular supplies. Type I muscles are supplied by a single unbranched nerve. In type II muscles, the nerve branches before entering the muscle. Type III muscles receive multiple motor nerves from the same nerve trunk, and type IV muscles are supplied from multiple nerve trunks. Suggestions are made as to how muscles of each type may or may not be subdivided into functional neurovascular units for local and distant transfer. Our studies in the pig, monkey, dog, and rabbit reveal that the “blueprint” of the nerves is very similar when the animals are compared with each other and with humans. This information may help in planning future studies that focus on the neurovascular supply of the tissues in both the adult and the embryo.

The role of bone morphogenetic proteins BMP-2 and BMP-4 and their related postreceptor signaling system (Smads) in distraction osteogenesis of the mandible.

Distraction osteogenesis has become a widely used clinical approach in the treatment of craniofacial and orthopedic disorders. The exact biological mechanism of bone formation remains illusive, however. The aim of this study was to evaluate the role of bone morphogenetic protein-2, bone morphogenetic protein-4, and transforming growth factor-β superfamily-related postreceptor signaling glycoproteins Smads 1 through 5 in distraction osteogenesis. Twelve sheep randomly divided into two groups were distracted to 24 mm at 1 or 4 mm/d using a submandibular osteotomy and an external distractor. After a 5-week fixation period, the mandibles were harvested. Employing immunohistochemical techniques, the sections were investigated for the previous antigens. Osteoblasts and periosteal lining cells were strongly positive. The matrix did not stain for the antigens investigated. Osteocytes demonstrated weak staining for the antigens. No significant difference between the groups was noted. In fracture healing, bone morphogenetic proteins 2 and 4 have been localized to the cambial layer of the periosteum, where healing occurs by intramembranous ossification. Their diffuse staining of the osteoblasts in the distracted region supports a similar role in distraction osteogenesis, where bone formation is predominantly through intramembranous ossification. Furthermore, bone morphogenetic proteins 2 and 4 have been demonstrated to promote mesenchymal cell conversion to osteoblasts. This is similar to the process observed in distraction osteogenesis. The presence of related Smads confirms postreceptor activity of these bone morphogenetic proteins in the process of distraction osteogenesis. This study supports induction of bone morphogenetic proteins 2 and 4, their related postreceptor signaling system (Smads), and intramembranous bone formation associated with mechanical strain in distraction osteogenesis.

The role of transforming growth factor-beta, insulin-like growth factor I, and basic fibroblast growth factor in distraction osteogenesis of the mandible.

Distraction osteogenesis is a viable method for regenerating large amounts of bone. In contrast to fracture healing, the mode of bone formation in distraction osteogenesis is primarily intramembranous ossification. The basic biology of the process is still not well understood. The growth factor cascade is likely to play an important role in distraction. This study examines the growth factor cascade in a lengthened ovine mandible model. Twenty-four animals were divided into four groups with varying rates of distraction (1, 2, 3, and 4 mm/day). A unilateral distractor at the angle of the mandible was used. The mandibles were lengthened to 24 mm and fixed for a period of 5 weeks, after which the animals were killed. The sections were probed for transforming growth factor-beta, basic fibroblast growth factor, and insulin-like growth factor I. The growth factors studied were present in all four groups. Transforming growth factor-beta, basic fibroblast growth factor, and insulin-like growth factor I were present in both the bony matrix of the sections and the cytoplasm of the cells, osteoblasts, and a small number of mesenchymal cells. The sections obtained from groups distracted at faster rates showed stronger presence of the growth factors examined by more intense staining. In fracture healing, the localization of transforming growth factor-beta in stage I of healing corresponded with the precise region of intramembranous ossification in stage II. Diffuse presence of transforming growth factor-beta throughout the lengthened region corresponded with the process of intramembranous ossification observed in distraction. In fracture healing, insulin-like growth factor I and basic fibroblast growth factor have been shown to promote proliferation and differentiation of osteoblasts from precursor cells. The intense presence of insulin-like growth factor I and basic fibroblast growth factor in the distracted region may account for osteoblast proliferation and formation from precursor mesenchymal cells. Mechanical strain has been shown to increase the expression of transforming growth factor-beta and insulin-like growth factor I. Distraction may serve as a source of mechanical strain, which may explain, in part, the expression of these growth factors, particularly in the faster groups.

Effect of distraction rate on biomechanical, mineralization, and histologic properties of an ovine mandible model.

Craniofacial microsomia is a common congenital malformation. Ilizarov’s method of distraction osteogenesis applied to the mandible has yielded promising results both experimentally and clinically. Because the technique is used predominantly in a pediatric population, length of treatment and compliance may be problematic. To date, the limits of distraction rate in the craniofacial skeleton have not been defined. This study was designed to investigate the effects of distraction rate, in a large animal model, on the mineralization, biomechanical, and histologic properties of lengthened mandibles. Clinically faster distraction rates would decrease the overall treatment time. Twenty-four animals were divided into four groups, with varying rates of distraction (1, 2, 3, and 4 mm/day). A uniaxial distractor at the angle of the mandible was used. The mandibles were lengthened to 24 mm and fixed for a period of 5 weeks, when the animals were killed. The specimens were analyzed with respect to mineralization using dual energy x-ray absorptiometry, biomechanical strength, through a modified three-point bending test, and histologic properties with hematoxylin and eosin stains. Biomechanical, mineralization, and histologic analyses of the samples indicated that group 1 (1 mm/day) samples were significantly superior (p < 0.05) to those of group 4 (4 mm/day). Although bone formation was achieved in all groups, group 1 (1 mm/day) demonstrated the strongest biomechanical and histologic properties. Bone mineral density obtained using dual energy x-ray absorptiometry may be clinically useful as a reliable, noninvasive, and relatively cheap predictor for removal time of the fixator. (Plast. Reconstr. Surg. 105: 889, 2000.)

Biomechanical Properties of Four Circumferential Flexor Tendon Suture Techniques

PURPOSE We introduce 2 interlocking circumferential flexor tendon suture techniques: the interlocking cross-stitch and the interlocking horizontal mattress repair and biomechanically tested them against 2 commonly used methods. METHODS Thirty-two deep digital flexor tendons harvested from sheep hindlimbs were transected sharply. These were repaired without a core suture using 4 different circumferential repair techniques: group 1, simple running; group 2, cross-stitch; group 3, interlocking cross-stitch; group 4, interlocking horizontal mattress. All tendons were tested to failure at a distraction rate of 20 mm/min. Load to 2-mm gap formation, stiffness, load to failure, and method of failure all were assessed. RESULTS The mean load to 2-mm gap formation was 22.8, 20.7, 20.0, and 26.1 N for groups 1, 2, 3, and 4, respectively. The mean stiffness was 7.6, 8.1, 8.7, and 10.1 N/mm, and the mean load to failure was 30.9, 42.1, 49, and 52.9 N for groups 1, 2, 3, and 4, respectively. There was no statistically significant difference between groups 2 and 3. Group 4, however, was statistically better than the others in all measured parameters (except group 3 in load to failure). CONCLUSIONS The interlocking horizontal mattress was the best performer overall, with statistically greater loads to failure, 2-mm gap formation, and stiffness. This technique could be considered for use in any patient likely to begin an early postoperative finger mobilization program.

Prevalence and causes of visual impairment in craniosynostotic syndromes.

Background:  To assess the prevalence and causes of visual impairment in patients with craniosynostotic syndromes of Apert, Crouzon, Pfeiffer, Saethre–Chotzen and craniofrontonasal dysplasia.

The latissimus dorsi added fat flap for natural tissue breast reconstruction: report of 15 cases.

&NA; The latissimus dorsi added fat flap is an alternative method of natural tissue breast reconstruction. A significant volume of additional subcutaneous back fat is left attached to a traditional latissimus dorsi flap, avoiding the need for an additional implant. The surgical technique and results in 15 patients are discussed. (Plast. Reconstr. Surg. 97: 63, 1996.)

Stress relaxation and creep: viscoelastic properties of common suture materials used for flexor tendon repair.

PURPOSE The time-dependent mechanical behavior of common suture materials may have a pronounced influence on the quality of flexor tendon repairs with respect to gap formation. METHODS Sutures commonly used in plastic surgery, particularly for hand tendon repair, were tested in tension for analysis of stress relaxation and creep properties. The three materials tested were (1) Prolene, a monofilament polypropylene(Ethicon, Somerville, NJ); (2) Ethilon, a monofilament nylon(Ethicon, Somerville, NJ); and (3) Ticron, a braided polyester fiber (Sherwood, Davis & Geck, St. Louis, MO). All measurements were made with 1.5-mm (4-0) varieties of the sutures, in physiological buffered solution (0.9% phosphate-buffered saline [PBS]) at both room (22 degrees C) and body temperature (37 degrees C) conditions. RESULTS Ticron was the stiffest suture at both room and body temperature, followed by Prolene and Ethilon. Both Prolene and Ethilon showed statistically (p< .05) reduced stiffness at body temperature. Prolene exhibited statistically larger (p< .05) relaxation and creep ratios than the other two sutures, and it was the only material to show temperature effects in creep and relaxation. CONCLUSIONS Based on static and viscoelastic mechanical properties, Ticron is the most suitable suture for flexor tendon repairs when compared to Prolene and Ethilon.

Influence of Locking Stitch Size in a Four-Strand Cross-Locked Cruciate Flexor Tendon Repair

PURPOSE The 4-strand cross-locked cruciate technique (Adelaide technique) for repairing flexor tendons in zone II is a favorable method in terms of strength and simplicity. The purpose of this study was to investigate the effects of varying the cross-lock stitch size in this repair technique. Outcomes measured were load to failure and gap formation. METHODS We harvested 22 deep flexor tendons from adult pig forelimbs and randomly allocated them into 2 groups. After cutting the tendons at a standard point, we performed a 4-strand cross-locked cruciate repair using 3-0 braided polyester with either 2-mm cross-locks (n = 11) or 4-mm cross-locks (n = 11). All repairs were completed with a simple running peripheral suture using 6-0 polypropylene. Repaired tendons were loaded to failure and the mechanism of failure, load to failure, stiffness, and load to 2-mm gap formation were determined. RESULTS All repairs failed by suture breakage; we noted no suture pullout. There was no difference in load to failure (71.7-71.1 N; p = .89) or stiffness (4.1-4.6 N/mm; p = .23) between the 2-mm cross-lock and the 4-mm cross-lock groups. There was a trend toward higher resistance to 2-mm gap formation with the 4-mm cross-locks (55-62.2 N; p = .07). CONCLUSIONS Four-strand cross-locked cruciate repairs with cross-lock sizes of 2 and 4 mm provide high tensile strength and are resistant to pullout. Repairs with 4-mm cross-locks tend to provide a more central load distribution and better gapping resistance than repairs with 2-mm cross-locks.

The cephalic vein: an aid in free TRAM flap breast reconstruction. Report of 12 cases.

&NA; The harvesting of the cephalic vein is a simple and effective technique for providing or augmenting venous drainage in free TRAM flap breast reconstruction. It may be divided distally and rotated about the infraclavicular fossa as a cephalic vein transfer of used as a source of free vein grafts. It is easily harvested with minimal morbidity. Its anatomy, surgical technique, indications, and results of use are discussed. In some circumstances, a cephalic vein transfer may allow greater areas of the free TRAM flap to be used more safely. This is discussed. (Plast. Reconstr. Surg. 97: 71, 1996.)