Vascularized Olecranon Bone Graft: An Anatomical Study and Novel Technique.

PURPOSE: Autologous bone grafting is commonly used in reconstructive hand surgery. Various sources of nonvascularized autologous bone grafts have been described in the literature. However, in some situations, a vascularized bone graft may be needed. Popular vascularized bone grafts are taken from the distal radius, iliac crest, and medial femoral condyle. The purpose of this study was to examine the feasibility of harvesting a free vascularized bone flap from the proximal ulna. METHODS: Latex was injected via the brachial artery to facilitate visualization of perforators in 10 cadaveric specimens. Dissections were performed of the olecranon; all periosteal perforators were noted, and their lengths and diameters recorded. Corticocancellous bone flaps with their supplying pedicles were harvested. Three additional fresh specimens were injected with india ink via the pedicles to demonstrate perfusion of the harvested bone flap. RESULTS: Consistent vascular anatomy supplied the olecranon. A perforator from the posterior ulnar recurrent artery supplied the proximal ulna and olecranon, from which a vascularized bone flap can be harvested. Branches to the flexor carpi ulnaris muscle may allow chimeric flaps to be harvested. Average pedicle length was 5.8 cm and average pedicle diameter was 2.4 mm. India ink injection of the pedicles showed perfusion of the periosteum as well as intraosseous cancellous bone. CONCLUSIONS: A vascularized olecranon free flap can be harvested based on the posterior ulnar recurrent artery. Vascular anatomy is consistent and flap harvest is simple and straightforward in all cadaveric specimens. CLINICAL RELEVANCE: A vascularized olecranon free flap represents a potential new surgical option when vascular bone flap reconstruction is considered.

Repair of the musculocutaneous nerve using the vagus nerve as donor by helicoid end-to-side technique: an experimental study in rats.

Although several donor nerves can be chosen to repair avulsed brachial plexus nerve injury, available nerves are still limited. The purpose of this study is to validate whether the vagus nerve (VN) can be used as a donor. Eighteen Sprague-Dawley male rats were divided into three groups (n = 6). The right musculocutaneous nerve (McN) was transected with differing subsequent repair. (1) HS-VN group: a saphenous nerve (SN) graft-end was helicoidally wrapped round the VN side (epi-and perineurium was opened) with a 30 ° angle, distal SN end was coapted to the McN with end-to-end repair. (2) EE-PN group: a SN was interpositionally grafted between the transected phrenic nerve (PN) and the McN by end-to-end coaptation. (3) Sham control group: McN was transected and not repaired and postoperative vital signs were checked daily. At three months, electrophysiology, tetanic force, wet biceps muscle weight, and histology were evaluated. Every tested mean value in HS-VN group was significantly greater than the EE-PN or the sham control groups (p < 0.05 or p < 0.005). The mean recovery ratio of regenerated nerve fibers was 96% and, in HS-VN group, the mean recovery ratio of CMAP was 79%. No vital signs changed in any group. There was no statistical difference (p > 0.5) between the mean VN nerve-fiber numbers of the segments proximal (2237 ± 134) and distal (2150 ± 156) to the VN graft-attachment site. Histological analysis revealed no axon injury or intraneural scarring at any point along the VN. This study demonstrated that VN is a practical and reliable donor nerve for end-to-side nerve transfer. © 2017 Wiley Periodicals, Inc.

Best time window for the use of calcium-modulating agents to improve functional recovery in injured peripheral nerves-An experiment in rats.

Peripheral nerve injury can have a devastating effect on daily life. Calcium concentrations in nerve fibers drastically increase after nerve injury, and this activates downstream processes leading to neuron death. Our previous studies showed that calcium-modulating agents decrease calcium accumulation, which aids in regeneration of injured peripheral nerves; however, the optimal therapeutic window for this application has not yet been identified. In this study, we show that calcium clearance after nerve injury is positively correlated with functional recovery in rats suffering from a crushed sciatic nerve injury. After the nerve injury, calcium accumulation increased. Peak volume is from 2 to 8 weeks post injury; calcium accumulation then gradually decreased over the following 24-week period. The compound muscle action potential (CMAP) measurement from the extensor digitorum longus muscle recovered to nearly normal levels in 24 weeks. Simultaneously, real-time polymerase chain reaction results showed that upregulation of calcium-ATPase (a membrane protein that transports calcium out of nerve fibers) mRNA peaked at 12 weeks. These results suggest that without intervention, the peak in calcium-ATPase mRNA expression in the injured nerve occurs after the peak in calcium accumulation, and CMAP recovery continues beyond 24 weeks. Immediately using calcium-modulating agents after crushed nerve injury improved functional recovery. These studies suggest that a crucial time frame in which to initiate effective clinical approaches to accelerate calcium clearance and nerve regeneration would be prior to 2 weeks post injury. © 2017 Wiley Periodicals, Inc.

Effect of calcitonin on cultured schwann cells.

INTRODUCTION: After nerve injury, calcium concentrations in intranerve fibers quickly increase. We have shown that functional recovery of injured nerves correlates with calcium absorption. A slight increase in calcium reduces the number of Schwann cells present. Calcitonin therapy greatly improves regeneration by accelerating calcium absorption. We examined the effect of adding calcitonin to higher concentration calcium media on cultured Schwann cells. METHODS: The cells, isolated from intact sciatic nerves, were cultured with normal or higher concentration calcium media with or without calcitonin. Schwann cells were incubated with anti-S-100, goat-anti-mouse, and propidium iodide and then viewed through fluorescent light and phase-contrast microscopy for observation and analysis. RESULTS: The cells in each calcitonin-containing medium showed many Schwann cells, however, the cells in the higher concentration calcium media showed fewer and more defective Schwann cells. CONCLUSION: These results show that calcitonin protects against the harmful effects of excessive calcium encountered in peripheral nerve injury. Muscle Nerve 56: 768-772, 2017.

Increasing Calcium Level Limits Schwann Cell Numbers In Vitro following Peripheral Nerve Injury.

Background After peripheral nerve injury, there is an increase in calcium concentration in the injured nerves. Our previous publications have shown that increase in calcium concentration correlated well with degree of nerve injury and that local infusion of calcitonin has a beneficial effect on nerve recovery. Schwann cells play a pivotal role in regeneration and recovery. We aim to examine cultured Schwann cell survivals in various concentrations of calcium-containing growth media and the effect of calcitonin in such media. Methods To establish baseline in postinjury state, crush injury was induced in male Sprague-Dawley rats' sciatic nerves. Extra- and intraneural calcium concentrations were measured. To study Schwann cell survival, uninjured sciatic nerve segment was harvested and cultured in media containing various amounts of calcium. To study the effect of calcitonin, nerve harvest and culture were done in four additional media: (1) normal control, (2) normal control with calcitonin, (3) high calcium medium, and (4) high calcium medium with calcitonin. Schwann cells were studied and analyzed under fluorescent conditions. Results With increasing calcium concentration, there was a significant decrease in the number of Schwann cells. For the experimental groups, in which calcitonin had been added to the growth medium, there were similar amounts of Schwann cells present in both high and low calcium-containing medium. Conclusion Schwann cells are sensitive to increasing calcium concentration. Calcitonin counteracts the detrimental effects of high calcium on Schwann cell survival. This can have significant future clinical implications for patients with peripheral nerve injuries.

Neural systemic impairment from whole-body vibration.

Insidious brain microinjury from motor vehicle-induced whole-body vibration (WBV) has not yet been investigated. For a long time we have believed that WBV would cause cumulative brain microinjury and impair cerebral function, which suggests an important risk factor for motor vehicle accidents and secondary cerebral vascular diseases. Fifty-six Sprague-Dawley rats were divided into seven groups (n = 8): 1) 2-week normal control group, 2) 2-week sham control group (restrained in the tube without vibration), 3) 2-week vibration group (exposed to whole-body vibration at 30 Hz and 0.5g acceleration for 4 hr/day, 5 days/week, for 2 weeks), 4) 4-week sham control group, 5) 4-week vibration group, 6) 8-week sham control group, and 7) 8-week vibration group. At the end point, all rats were evaluated in behavior, physiological, and brain histopathological studies. The cerebral injury from WBV is a cumulative process starting with vasospasm squeezing of the endothelial cells, followed by constriction of the cerebral arteries. After the 4-week vibration, brain neuron apoptosis started. After the 8-week vibration, vacuoles increased further in the brain arteries. Brain capillary walls thickened, mean neuron size was obviously reduced, neuron necrosis became prominent, and wide-ranging chronic cerebral edema was seen. These pathological findings are strongly correlated with neural functional impairments.

Calcitonin pump improves nerve regeneration after transection injury and repair.

INTRODUCTION: After nerve injury, excessive calcium impedes nerve regeneration. We previously showed that calcitonin improved nerve regeneration in crush injury. We aimed to validate the direct effect of calcitonin on transected and repaired nerve. METHODS: Two rat groups (n = 8) underwent sciatic nerve transection followed by direct repair. In the calcitonin group, a calcitonin-filled mini-osmotic pump was implanted subcutaneously, with a catheter parallel to the repaired nerve. The control group underwent repair only, without a pump. Evaluation and comparison between the groups included: (1) compound muscle action potential recording of the extensor digitorum longus (EDL) muscle; (2) tetanic muscle force test of EDL; (3) nerve calcium concentration; and (4) nerve fiber count and calcified spot count. RESULTS: The calcitonin pump group showed superior recovery. CONCLUSIONS: Calcitonin affects injured and repaired peripheral nerve directly. The calcitonin-filled mini-osmotic pump improved nerve functional recovery by accelerating calcium absorption from the repaired nerve. This finding has potential clinical applications.

Cumulative Brain Injury from Motor Vehicle-Induced Whole-Body Vibration and Prevention by Human Apolipoprotein A-I Molecule Mimetic (4F) Peptide (an Apo A-I Mimetic).

BACKGROUND: Insidious cumulative brain injury from motor vehicle-induced whole-body vibration (MV-WBV) has not yet been studied. The objective of the present study is to validate whether whole-body vibration for long periods causes cumulative brain injury and impairment of the cerebral function. We also explored a preventive method for MV-WBV injury. METHODS: A study simulating whole-body vibration was conducted in 72 male Sprague-Dawley rats divided into 9 groups (N = 8): (1) 2-week normal control; (2) 2-week sham control (in the tube without vibration); (3) 2-week vibration (exposed to whole-body vibration at 30 Hz and .5 G acceleration for 4 hours/day, 5 days/week for 2 weeks; vibration parameters in the present study are similar to the most common driving conditions); (4) 4-week sham control; (5) 4-week vibration; (6) 4-week vibration with human apolipoprotein A-I molecule mimetic (4F)-preconditioning; (7) 8-week sham control; (8) 8-week vibration; and (9) 8-week 4F-preconditioning group. All the rats were evaluated by behavioral, physiological, and histological studies of the brain. RESULTS: Brain injury from vibration is a cumulative process starting with cerebral vasoconstriction, squeezing of the endothelial cells, increased free radicals, decreased nitric oxide, insufficient blood supply to the brain, and repeated reperfusion injury to brain neurons. In the 8-week vibration group, which indicated chronic brain edema, shrunken neuron numbers increased and whole neurons atrophied, which strongly correlated with neural functional impairment. There was no prominent brain neuronal injury in the 4F groups. CONCLUSIONS: The present study demonstrated cumulative brain injury from MV-WBV and validated the preventive effects of 4F preconditioning.

Comparison of Peripheral Nerve Axonal Area Differences in Central and Peripheral Zones of Injured and Repaired Nerves.

BACKGROUND: Histological analysis remains a cornerstone approach for the investigation of peripheral nerve regeneration. This study investigates a newly recognized histological difference between peripheral and central zones within the regenerating nerve trunks. PURPOSE: The purpose of the study was to determine if the nerve axonal area (NXA) in regenerating peripheral nerves differs within central and peripheral areas, when viewed in cross-section. METHODS: A total of 14 rats were divided into two groups, and subjected to different injuries to the right sciatic nerve. Group 1: Transection injury with immediate repair. Group 2: Crush injury without any treatment. The left sciatic nerve was left uninjured and served as a control in each rat. Following 4 weeks of recovery, nerve trunk cross-sections were prepared. Computerized techniques were then employed to divide nerve sections into central and peripheral zones and calculate corresponding NXA values for subsequent statistical analysis. RESULTS: NXA of injured nerves was greater within peripheral as compared with the central zones, independent of injury type (p < 0.05). No statistically significant difference existed within the control groups or between the injury methods with regards to NXA regeneration extent. CONCLUSION: NXA in regenerating peripheral nerves was greater in the peripheral zones than within the central zones.

C7 nerve root sensory distribution in peripheral nerves: a bold functional magnetic resonance imaging investigation at 9.4 T.

INTRODUCTION: In this study we used a rat model to elucidate the linear make-up of each major nerve of the upper limb by the C7 root through sensory stimulation and functional magnetic resonance imaging (fMRI). METHODS: The C7 nerve root and major nerves of the right forelimb were stimulated electrically. Blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) was performed concurrently. Voxel overlap within the primary sensory cortex was calculated. RESULTS: C7 comprised sensation in <1% in the musculocutaneous nerve, 6% in the ulnar nerve, 16% in the radial nerve, and 19% in the median nerve (P<0.005 for each). The overlap was always <25% for each major nerve. CONCLUSIONS: This study helps explain why C7 is a suitable donor for brachial plexus injury treatment and why there is only a transient sensory deficit after transfer.

A new computerized morphometric analysis for peripheral nerve study.

The commonly used methods to quantify axon numbers and mean area include manual and semiautomated procedures. The authors introduce a new fully automated method of morphometric analysis using ImageJ and Paint.net software to improve efficiency and accuracy. A total of six rat sciatic nerves were examined for their axon numbers and mean axon area by comparing the manual method or semiautomated MetaVue method with the new ImageJ method. It was observed that the number of axons for manual counting and ImageJ were 4,630 ± 403 and 4,779 ± 352, respectively, and the difference was not statistically significant (p > 0.5, t-test). The mean axon area measured was 13.44 ± 2.62 µm2 for MetaVue and 8.87 ± 0.78 µm2 for ImageJ, respectively, and the difference was statistically significant (p < 0.01, t-test). The standard error and coefficient of variation of MetaVue were 1.07 and 0.195; and for ImageJ were 0.32 and 0.087. The authors conclude that their new approach demonstrates improved convenience, time efficiency, accuracy, and less operator error or bias.

Transhemispheric cortical plasticity following contralateral C7 nerve transfer: a rat functional magnetic resonance imaging survival study.

PURPOSE: To perform contralateral C7 nerve transfer in a controlled, survival rat functional magnetic resonance imaging model, so as to understand the extent of cortical plasticity after brachial plexus injury and surgical manipulation with this procedure. METHODS: A total of 24 rats divided into 3 groups underwent surgery followed by functional magnetic resonance imaging in this study. Group I rats served as sham controls. Group II injury rats underwent complete right brachial plexus root avulsion. Group III repair rats underwent complete right brachial plexus root avulsion and then contralateral C7 nerve transfer to the right median nerve. We assessed cortical response to median nerve stimulation at 0, 3, and 5 months after injury using functional magnetic resonance imaging at 9.4 T. We concurrently performed sensory and motor functional testing. RESULTS: We noted a progression in cortical activation in the repair rats over 0, 3, and 5 months. Initially, right median nerve stimulation in the repair group showed complete loss of activation in the contralateral somatosensory cortex. Nerve stimulation at 3 months produced primarily ipsilateral cortical activation; at 5 months, 3 patterns of cortical activation emerged: ipsilateral, bilateral, and contralateral activation. After right median nerve stimulation, injury rats maintained a lack of cortical activation and control rats maintained exclusive contralateral activation throughout all time points. Functional testing revealed a degree of return of sensory and motor function over time in the repair group compared with the injured group. CONCLUSIONS: A high degree of transhemispheric cortical plasticity occurred after contralateral C7 nerve transfer. There appears to be a predilection for the rat brain to restore the preinjury somatotopic representation of the brain. CLINICAL RELEVANCE: Understanding the cortical changes after nerve injury and repair may lead to specific pharmacologic or behavioral interventions that can improve functional outcomes.

The correlation between calcium intensity and histopathological changes in brachial plexus nerve injuries.

BACKGROUND: After nerve injury, an influx of calcium exceeds the homeostatic capacity, which damages peripheral nerves. Previous studies identified that following nerve crush, function improves as calcium levels normalize. METHODS: Electrophysiological analysis was performed to measure the compound muscle action potential of 15 patients' damaged nerves. These samples were evaluated for calcium level and also stained with a Luxol fast blue and neurofilament antibodies to evaluate the myelin sheath and neurofilaments of the nerves. Based on the Sunderland scale, we identified three exclusive types of peripheral nerve injury groups. RESULTS: There was a correlation between histopathological damage and calcium levels of 0.81 (p < 0.005). The average relative fluorescence units (RFUs) was 235.28 ± 19, which corresponds to 5.3 × 10⁻7 M of calcium, five times the normal value. CONCLUSION: Our study shows promising clinical implications via faster pathology results by the RFU technique. This approach of calcium staining, though still in clinical trials, offers significant clinical application, allowing physicians to get the clinically diagnostic nerve injury degree faster and will also facilitate better strategies for further treatment or future surgeries.

Helicoid end-to-side and oblique attachment technique in repair of the musculocutaneous nerve injury with the phrenic nerve as a donor: an experimental study in rats.

The purpose of this study was to identify if a modified end-to-side repair can achieve equal results of nerve regeneration compared to an end-to-end repair using donor phrenic nerves in repair of the musculocutaneous nerve and also pulmonary protection. Eighteen rats were divided into three groups of six each comparing two nerve graft techniques: helicoid end-to-side plus distal oblique repair vs. traditional end-to-end repair, using a donor phrenic nerve. The saphenous nerve was used as a graft between the phrenic nerve and the musculocutaneous nerve. The third group was used as control; the musculocutaneous nerve was transected without any repair. Three months postoperatively, electrophysiology, tetanic force, moist muscle weight, histology, nerve fiber counting, and chest X-ray were evaluated. All results have shown that this modified end-to-side repair was superior to the end-to-end repair. The former did not compromise the diaphragm function, but the latter showed an elevation of the diaphragm. Little recovery was seen in the third group. The conclusion is that this modified end-to-side repair can replace the traditional end-to-end repair using donor phrenic nerves with better results of nerve regeneration without diaphragm compromise.

The correlation between calcium absorption and electrophysiological recovery in crushed rat peripheral nerves.

The correlation between calcium ion (Ca2+) concentration and electrophysiological recovery in crushed peripheral nerves has not been studied. Observing and quantifying the Ca2+ intensity in live normal and crushed peripheral nerves was performed using a novel microfine tearing technique and Calcium Green-1 Acetoxymethyl ester stain, a fluorescent Ca2+ indicator. Ca2+ was shown to be homogeneously distributed in the myelinated sheaths. After a crush injury, there was significant stasis in the injured zone and the portion distal to the injury. The Ca2+ has been almost completely absorbed after 24 weeks in the injured nerve to be similar to the controls. The process of the calcium absorption was correlated with the Compound Muscle Action Potential recovery process of the injured nerves. This correlation was statistically significant (r = -0.81, P < 0.05). The better understanding of this process will help us to improve nerve regeneration after peripheral nerve injury.

Qualitative effect on mRNAs of injury-associated proteins by cell phone like radiation in rat facial nerves.

Rats were exposed to cell phone radiation for 6 hours per day for 18 weeks. The buccal and mandibular branches of the facial nerve were evaluated for this study. The mRNA levels of four proteins that are usually up regulated when an injury has occurred were investigated; included were Calcium ATP-ase, Endothelin, Neural Cell Adhesion Molecule, and Neural Growth Factor. These isolated mRNAs were subjected to RT-PCR and all four were up regulated. The mandibular nerve showed a higher and broader level of up regulation than the buccal nerve. All four mRNA up regulations for the mandibular nerve and two for the buccal nerve were also statistically significant. These specific injury-related findings were mild. As the use of these cell phones continues, there most likely will be permanent damage to these tissues over the years and the likelihood of tumors, cancers, and system failures will potentially increase.

Distally Based Pedicled Flexor Carpi Ulnaris Muscle Flap: An Anatomical Study and Clinical Application.

BACKGROUND: Proximally based, pedicled flexor carpi ulnaris (FCU) muscle flap has been described previously for soft tissue coverage of the proximal forearm and elbow. No studies have been done on the distal muscular perforators and its use as a distally based flap. METHODS: Ten fresh-frozen cadaveric dissections were done. Specimens were injected with latex to facilitate identification of the perforators. Distal muscular perforators were dissected and distances of the pedicles from the distal wrist crease and ulnar styloid were measured and recorded. A clinical case is also presented where a distally based FCU muscle flap was used for coverage in a patient with median nerve neuroma. RESULTS: A distal muscular perforator and a second more proximal perforator were identified in all specimens. The average distance from the most distal muscular perforator to the ulnar styloid was 3.0 cm. The average distance to the wrist crease was 4.6 cm. The more proximal perforators had an average distance to the ulnar styloid and wrist crease of 7.3 cm and 8.8 cm, respectively. At 7 months post-op, the patient who underwent median nerve neurolysis and coverage with pedicled FCU flap had much improved sensation, with complete resolution of pain and tingling, and without any functional deficits. CONCLUSIONS: The use of a distally based FCU muscle flap is a good option for soft tissue coverage of the distal forearm, wrist, and hand. The distal muscular perforators from the ulnar artery exhibit a relatively consistent anatomy.

Upregulation of specific mRNA levels in rat brain after cell phone exposure.

Adult Sprague-Dawley rats were exposed to regular cell phones for 6 h per day for 126 days (18 weeks). RT-PCR was used to investigate the changes in levels of mRNA synthesis of several injury-associated proteins. Calcium ATPase, Neural Cell Adhesion Molecule, Neural Growth Factor, and Vascular Endothelial Growth Factor were evaluated. The results showed statistically significant mRNA up-regulation of these proteins in the brains of rats exposed to cell phone radiation. These results indicate that relative chronic exposure to cell phone microwave radiation may result in cumulative injuries that could eventually lead to clinically significant neurological damage.

Evidence for frequency-dependent arterial damage in vibrated rat tails.

The effects of single 4-hr bouts of continuous 30, 60, 120, and 800 Hz tail vibration (49 m/sec2, root mean squared) were compared to assess frequency-amplitude-related structural damage of the ventral caudal artery. Amplitudes were 3.9, 0.98, 0.24, and 0.0055 mm, respectively. Vibrated, sham-vibrated, and normal arteries were processed for light and electron microscopy. The Curry rat tail model of hand-arm vibration (Curry et al. Muscle Nerve 2002;25:527-534) proved well-suited for testing multiple frequencies. NFATc3 immunostaining, an early marker of cell damage, increased in smooth muscle and endothelial cells after 30, 60, and 120 Hz but not 800 Hz. Increased vacuolization, which is indicative of smooth muscle contraction, occurred for all frequencies except 800 Hz. Vacuoles increased in both endothelial and smooth muscle cells after 60 and 120 Hz. Only 30 Hz showed pronounced smooth muscle cell vacuolization along the internal and external elastic membranes, suggesting stretch-mediated contraction from the large amplitude shear stress. Discontinuities in toluidine blue staining of the internal elastic membrane (IEM) increased for all frequencies, indicating vibration-induced structural weakening of this structure. Patches of missing IEM and overlying endothelium occurred in approximately 5% of arteries after 60, 120, and 800 Hz. The pattern of damage after 800 Hz suggests that the IEM is disrupted because it resonates at this frequency. Vibration acceleration stress and smooth muscle contraction appear to be the major contributors to arterial damage. The pattern of vibration-induced arterial damage of smooth muscle and endothelial cells is frequency-amplitude-dependent.

The vascular supply of the extended tensor fasciae latae flap: how far can the skin paddle extend?

The vascular supply of the tensor fasciae latae flap and of the lateral thigh skin was studied in 10 cadavers to evaluate whether the lateral thigh skin toward the knee could be incorporated into an extended tensor fasciae latae flap. Within each cadaver, vascular injection of radiopaque material preceded flap elevation in one limb and followed flap elevation in the contralateral limb. Flaps raised after vascular injection were examined radiographically to evaluate the vascular anatomy of the lateral thigh skin independent of flap elevation. When vascular injection was made into the profunda femoris, the upper two-thirds of the flaps was better visualized than the distal third. When the injection was made into the popliteal artery, the vasculature of the distal third of the flaps was better visualized. Flaps raised before vascular injection were examined radiographically to delineate the anatomical territory of the vascular pedicle that had been injected. In these flaps, consistent cutaneous vascular supply was only seen in the skin overlying the tensor fasciae latae muscle, confirming that musculocutaneous perforators are the predominant means by which the pedicle of the tensor fasciae latae flap supplies the skin of the lateral thigh. Extended tensor fasciae latae flaps were elevated bilaterally in one cadaver, and selective methylene blue injections were made into the lateral circumflex femoral artery on one side and into the superior lateral genicular artery on the contralateral side. Methylene blue was observed in the proximal and distal thirds of the skin paddles, respectively, leaving unstained midzones. The vascular network of the lateral thigh skin could be divided into three zones. The lateral circumflex femoral artery and the third perforating branches of the profunda femoris artery perfuse the proximal and middle zones of the lateral thigh skin, respectively. The superior lateral genicular artery branch of the popliteal artery perfuses the distal zone. The middle and distal zones meet 8 to 10 cm above the knee joint, where the skin paddle of the tensor fasciae latae flap becomes unreliable. These data indicate that if the aim is to incorporate the skin over the distal thigh in an extended tensor fasciae latae flap without resorting to free-tissue transfer, then either a carefully planned delay procedure or an additional anastomosis to the superior lateral genicular artery is required.