Preconditioning with Foam-mediated External Suction on Flap Microvasculature and Perfusion in a Rodent Model.

Foam-mediated external suction (FMES) has previously shown to improve tissue microcirculation. We hypothesized that preconditioning fasciocutaneous perforator flaps with FMES would augment perfusion and demonstrate greater capillary recruitment. METHODS: Gluteal perforator flaps were designed on sixteen 400 g rats. Continuous FMES at -125 mm Hg was applied on one side (intervention) to precondition tissue for 5 days, with the contralateral side as a paired control. In group A, we assessed changes following pretreatment, after surgery, and 7 days postprocedure, and in group B, we evaluated changes during preconditioning alone. In group A (N = 8), control and intervention flaps were assessed using laser-assisted indocyanine green fluorescence angiography. In group B, flap regions were assessed using 4-dimensional computed tomographic angiography. All flaps were analyzed for microvessel density using micro-computed tomography and histological assessment using hematoxylin and eosin and CD3 immunohistochemistry. RESULTS: Thirty-two flaps were included in this study (N = 16 intervention and matched controls). Four-dimensional computed tomographic angiography demonstrated 17% greater tissue perfusion in preconditioned flaps (mean, 78.7 HU; SD, 8.8) versus controls (mean, 67.3 HU; SD, 15.7; P < 0.01). Laser-assisted indocyanine green fluorescence angiography showed a 30% higher mean absolute intensity in preconditioned flaps versus controls (P < 0.01). Postsurgery mean absolute intensity in preconditioned flaps remained 21% higher than in controls (P = 0.03). Preconditioned flaps demonstrated a 2-fold increase in mean vessel volume of 9.1 mm3 (SD, 7) versus 4.5 mm3 (SD, 3) in controls (P = 0.04); there was a 33% higher mean area fraction of CD31 in preconditioned flaps, 3.9% (SD, 3) versus 2.9% (SD, 3) in controls (P = 0.03). CONCLUSION: FMES preconditioning has the potential to augment vascularity of tissue for flap harvest; however, further experimental studies are required to optimize strategies and evaluate long-term effects for clinical applications.

The Vascular Anatomy of the Scaphoid: New Discoveries Using Micro-Computed Tomography Imaging.

PURPOSE: The purpose of this study was to investigate the intraosseous vascular anatomy of the scaphoid using recent advances in micro-computed tomography (micro-CT) imaging and 3-dimensional reconstruction. We also studied the effect of scaphoid shape and screw position on the intraosseous vascular structure. METHODS: Thirteen upper extremities were injected with a contrast agent. The scaphoid bones were extracted and scanned using a micro-CT scanner. The vascular impact of screw insertion at various axes through the scaphoid was calculated and compared using the generated 3-dimensional models. The specimens were 3-dimensionally-printed and the morphology was assessed according to bone dimensions. A relationship between the internal vascular patterns and these morphological features was determined. RESULTS: All specimens received vascular inflow from the dorsal ridge forming a vascular network that supplied an average of 83% of the bone's volume. This network was supplemented in 4 specimens with volar vessels entering at the waist. Another network was identified, created by vessels entering volarly at the tubercle, which supplied the remainder of the scaphoid. One specimen did not receive any vessels at the tubercle. With regards to screw placement, screws placed in the central axis were the least disruptive to the internal vascularity, followed by the antegrade (dorsal) insertion axis. Two morphological bone types were identified: type I or full scaphoids and type II or slender scaphoids. Type I possessed a more robust internal vascular network than type II scaphoids. CONCLUSIONS: This study identifies 2 distinct types of scaphoid morphology with 1 of them having a less robust blood supply, which may prove to be related to development of nonunion, avascular necrosis, or Preiser disease. Central axis and antegrade (dorsal) screw fixation may be least disruptive to the internal blood supply. CLINICAL RELEVANCE: Safer fixation of the scaphoid bone may be achieved by knowledge of intraosseous vascular patterns.

The Vascular Anatomy of the Capitate: New Discoveries Using Micro-Computed Tomography Imaging.

PURPOSE: To study the intraosseous 3-dimensional microvasculature of the capitate bone using a novel high-resolution micro-computed tomography (µCT) imaging technology, and to examine the blood supply as it relates to the most common fracture types. METHODS: Ten cadaveric wrists were injected with a lead-based contrast agent. The capitates were harvested and imaged using a µCT scanner. The intraosseous vascularity was incorporated into a 3-dimensional image. We measured the vascular pattern as well as the vessels' cross-sectional area, number, and distribution. An average capitate fracture line was calculated using clinical data from 22 patients with capitate fractures. The fracture line was projected on the representative capitate to assess its relation with the nutrient vessels' entry points. RESULTS: The capitate is a well-vascularized carpal supplied by dorsal and volar vascular systems that anastomose in 30% of cases. There was no predominance of one vascular system over the other. Most vessels enter the capitate at the distal half and supply the proximal pole in a retrograde fashion. In addition, most specimens (70%) also had at least one vessel entering the proximal pole through the volar capitate ligaments and supplying the proximal pole directly. The average fracture line had an oblique orientation, and 90% of the specimens had a blood vessel entering proximal to that line. CONCLUSIONS: This µCT vascular study further verifies that the capitate receives most of its vasculature in a retrograde fashion, but the study also shows that most capitates have vessels supplying the proximal pole directly. These findings might explain why most capitate waist fractures do not progress to proximal pole avascular necrosis. CLINICAL RELEVANCE: This study characterizes the microvasculature of the capitate and might shed light on processes involved in bone healing and the etiology of capitate avascular necrosis.

Study of the Impact of the Location of a Perforator in the Perfusion of a Perforator Flap: The Concept of "Angle of Perfusion".

Background Perforator flaps remain challenging in their design, especially as free flaps. We used a cadaveric model to help refine the design of perforator flaps by studying their vascular features. We define the angle of perfusion of a perforator as a tool to achieve safer flap designs. Methods A total of 83 flaps were designed from 20 fresh cadaveric anterolateral thigh flaps. The most dominant perforator larger than 0.5 mm was used as the reference point on the midline of the flap, and the tip of the flap was set at 5 cm (n = 10), 2 cm (n = 5), or 10 cm (n = 5) from this perforator. The perforator was injected with contrast agent, and the flap was scanned with computed tomography (CT) angiography. The vascular territory of the injected perforator was drawn twice by two different investigators. Perfused volumes were then obtained through a computerized algorithm on the CT workstation. Flaps were then flushed with heparinized saline and cut at decreasing angles (120, 90, 60, and 45 degrees) and rescanned with contrast for each perfusion angle. The perfused volumes were calculated for each angle. Results Volume and percentage of perfusion were significantly decreased with decreasing angles of perfusion, regardless of perforator location (2 cm, p = 0.002; 5 cm, p = 0.02; 10 cm, p < 0.001). Conclusions Acute angles of perfusion were associated with fewer incorporated linking vessels and lower flap perfusion. This phenomenon was less apparent in centrally located perforators. Perfusion angle and perforator location influence flap vascularity in a cadaveric model.

A Three-Dimensional Micro-Computed Tomographic Study of the Intraosseous Lunate Vasculature: Implications for Surgical Intervention and the Development of Avascular Necrosis.

BACKGROUND: The purpose of this study was to use micro-computed tomography to demonstrate the intraosseous vascularity of the lunate within a three-dimensional orientation to identify areas of greatest perfusion and define vascular "safe zones" for surgical intervention. METHODS: Fourteen upper extremities were injected with a lead-based contrast agent. The lunates were harvested and scanned using a micro-computed tomography scanner. The intraosseous vascularity was incorporated into a three-dimensional image. Vessel number, diameter, distribution, and pattern were evaluated and analyzed. Vascularity of all specimens was projected onto one representative lunate to identity areas of higher and lower vascularity. RESULTS: Twelve specimens had nutrient vessels entering the bone from volar and dorsal; two specimens had no dorsal vessels. The intraosseous vascularity could be classified according to the Y, I, and X patterns described by Gelberman et al. Average number and diameter of vessels were 2.3 and 118.1 µm, respectively, for volar; and 1.4 and 135.8 µm, respectively, for dorsal. The long axis of the lunate showed the highest vascularity on both axial and lateral views. Lower vascularity was observed in the dorsoradial and volar-ulnar quadrants on the axial view, and in the proximal part on the lateral view. Lunate shape was not associated with an increase or decrease in nutrient vessels or vascular pattern. CONCLUSIONS: Vascular safe zones were identified, allowing for potentially safer surgical interventions to the lunate. Volar approaches to the lunate may result in localized ischemia in a subset of patients with absent dorsal nutrient vessels. This study may help to better define patients at risk for Kienböck disease.

Three-Dimensional Computed Tomographic Angiography Study of the Interperforator Flow of the Lower Leg.

BACKGROUND: The area perfused by a single perforator depends on its perforasome and its unique interperforator flow pattern. The purpose of this study was to clarify the interperforator flow patterns of the peroneal and posterior tibial artery perforators using three-dimensional computed tomographic angiography. METHODS: Thirteen whole-leg skin flaps were harvested in the subfascial plane from fresh cadavers. Peroneal, posterior tibial, anterior tibial, and sural artery perforators with a diameter greater than 0.5 mm were documented. Three-dimensional computed tomographic angiography with an injection of iodinated contrast medium into the peroneal or posterior tibial artery perforator was used to investigate the percentages of the area and the perforators that were perfused. RESULTS: The mean percentage of the total area perfused was as follows: peroneal artery perforator, 42.0 percent; posterior tibial artery perforator, 38.0 percent (p = 0.084). The mean percentage of the total perforators perfused was as follows: peroneal artery perforator, 55.0 percent; posterior tibial artery perforator, 44.2 percent (p = 0.004). Although the mean percentages of same-source artery perforators perfused by a peroneal artery perforator (73.6 percent) and by a posterior tibial artery perforator (77.2 percent) did not differ (p = 0.513), the mean percentages of other-source artery perforators perfused by a peroneal artery perforator (49.9 percent) and by a posterior tibial artery perforator (32.3 percent) were significantly different (p < 0.001). CONCLUSIONS: This study demonstrated that a single peroneal or posterior tibial artery perforator perfused approximately 40 percent of the whole leg surface and that peroneal and posterior tibial artery perforators had different interperforator flow patterns. The results of this study may improve preoperative planning for pedicled perforator flap surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

The Distally Based Dorsal Metatarsal Artery Perforator Flap: Vascular Study and Clinical Implications.

Background Intrinsic flaps based on the dorsal metacarpal arteries are useful for coverage of dorsal hand, finger, and thumb defects. The purpose of this study was to explore the anatomy of the dorsal metatarsal arteries (DMtAs) in the foot to help define their clinical utility. We observed the size and numbers of distal perforators from the DMtAs and quantified the vascular perfusion pattern of the DMtA perforator across the skin. Methods Ten fresh cadaver feet were injected with latex and dissected to assess the size and number of distal perforators from the DMtAs. Five DMtA perforator flaps were injected with methylene blue to visualize and quantify the vascular territory of the skin flap to understand the clinical possibilities. In addition, a clinical case is described and shown. Results Ten fresh cadaver feet were dissected. The first DMtA was absent in two specimens and the second, third, or fourth DMtA was absent in one specimen each. The available DMtAs had between two and five cutaneous perforators supplying the skin (average, 3.7 perforators per DMtA). The largest perforators to the skin were always seen in the distal half of the DMtA and ranged from 0.4 to 0.8 mm (average, 0.5 mm). Methylene blue injections showed an average flap surface of 21.6 × 47.6 mm. Conclusion This cadaveric study demonstrates the usefulness of the DMtA perforator flap. The flap is a valuable addition to the arsenal of flaps to cover the dorsum of the toe, webspace, or defects exposing tendons on the distal dorsum of the foot.

Three-dimensional CT angiography assessment of the impact of the dermis and the subdermal plexus in DIEP flap perfusion.

BACKGROUND: Single-stage breast reconstruction following skin-sparing or nipple-sparing mastectomy with free deep inferior epigastric perforator (DIEP) flap usually does not require a large skin paddle. Most of the flap skin paddle is removed, and the flap is placed under native, conserved skin to provide adequate volume to the reconstructed breast mound. We hypothesized that conservation of intact dermis and its subdermal plexus has a critical role in overall flap perfusion through recruitment of indirect linking vessels. The study goal was to investigate and compare the vascularity of DIEP flaps with intact dermis versus DIEP flaps with the dermis removed. METHODS: Twelve hemi-DIEP flaps were harvested from fresh cadavers. The largest dominant perforator was cannulated using a 24-gauge butterfly catheter. Flaps were imaged with computed tomography (CT) after injection of a contrast agent. After scanning, the contrast agent was flushed out of the flap. The flap skin was removed with cautery at the subdermal dissection plane. The flaps were reimaged with CT after injection of the contrast agent. Three-dimensional (3-D) CT angiographic reconstructions were obtained for each protocol stage, and the percentage of flap perfusion was calculated. Flap vascularity with and without dermis was compared. RESULTS: A mean difference of 25.9% in flap perfusion occurred when the dermis was removed (P < 0.001). The 3-D CT angiographic images showed that the impact of dermis excision was caused by interrupting the recurrent flow through the dermis and subdermal plexus via indirect linking vessels. CONCLUSION: The dermis has a significant role in enhancing overall DIEP flap perfusion through preservation of indirect linking vessels organized in the subdermal plexus. Despite being time consuming, a cautious de-epithelialization of the DIEP flap should be performed to retain dermis integrity. Enhancement of flap vascularity ultimately leads to a decrease in such complications as partial or total flap necrosis, as well as fat necrosis.

Lumbar and thoracic perforators: vascular anatomy and clinical implications.

BACKGROUND: Pedicled perforator flaps in the thoracic and lumbar regions allow reconstruction of the posterior trunk. They enable reconstruction of various local defects without microvascular anastomoses and with minimal donor-site morbidity and excellent cosmesis. The authors examined the locations of perforators in the lumbar and thoracic regions. METHODS: Ten cadaver hemithoraces and lumbar regions were freshly harvested and dissected. Intraarterial injections were performed with colored latex, followed by dissection in the suprafascial plane. Perforators with a diameter larger than 0.5 cm were located and measured from the midline and from C7 (thoracic) and coccygeal (lumbar) reference points. The most dominant perforators were injected with radiopaque dye and scanned with high-resolution computed tomography. The patterns were analyzed by the quadrat counting test (based on chi-square statistics) for the null hypothesis of complete spatial randomness. RESULTS: A total of 164 thoracic and 216 lumbar perforators were identified. These were clustered in highest density in two major areas within 10 to 20 cm of the C7 and coccygeal reference points and 10 cm from the midline; this pattern was not a random distribution (p < 0.001). Perforasomes of lumbar perforators in some instances crossed the midline, joining adjacent contralateral lumbar perforators by means of direct and indirect linking vessels. CONCLUSIONS: Lumbar and thoracic pedicled perforator flaps provide useful options for reconstructing complex defects. Use of these flaps is aided by anatomical knowledge of the location of major clusters of perforators.