Deep Subcutaneous Gluteal Fat Compartments: Anatomy and Clinical Implications.

BACKGROUND: Advances in gluteal fat grafting have resulted in diminished risks through improved understanding of regional anatomy and technical nuances. No anatomic studies identifying the presence or absence of buttock fat compartments have yet been reported. OBJECTIVES: The aim of this cadaveric study was to identify and characterize the deep subcutaneous gluteal fat compartments to further understand the nuanced differences between deep and superficial subcutaneous fat layers. METHODS: A cadaveric study was performed to identify the fat compartments. Latex injection into the iliac artery and vein was used to prepare 4 fresh (N = 8 hemibuttocks) hydrated cadavers for dissection. Preliminary work identified the likely position of deep gluteal fat compartments. The cannula was positioned under ultrasound guidance in between the superficial and deep gluteal layers. Cadaveric buttocks were infiltrated by the static technique with dyed human fat, dyed applesauce, and dyed saline in an attempt to identify the gluteal deep subcutaneous fat compartments. RESULTS: Dissection identified and characterized 7 discrete deep gluteal fat compartments. These comprise 3 medial fat compartments (superior, middle, and inferior); a central fat compartment; and 3 lateral (superior, middle, and inferior) deep fat compartments. CONCLUSIONS: Seven deep gluteal fat compartments have been identified that have distinct boundaries and maintain injected contents separate from each other above the gluteal muscle fascia. These compartments can be selectively expanded for buttock augmentation. Knowledge of these compartments enables surgeons to perform gluteal augmentation by static infiltration, injecting autologous fat under ultrasound guidance in the deep subcutaneous fat layer, while optimizing aesthetic considerations.

The Value of Integrating Fluorescent Imaging and Immunohistochemistry for Future Anatomical Studies in Aesthetic Surgery: Lessons From the Cerebrospinal Fluid Circulatory System of Human Nerves and Brain.

BACKGROUND: During their work on the cerebrospinal fluid (CSF) circulatory system of human nerves and brain, the authors applied imaging and tissue techniques that complemented basic anatomical dissection. OBJECTIVES: The authors sought to show how integrating fluorescent imaging and basic immunohistochemistry (IHC) with facial anatomy can address current problems in aesthetic surgery. METHODS: The authors developed an algorithm and a set of principles from their work on the CSF circulatory system and applied these to 3 problems in aesthetic surgery: the functional anatomy of the vermilion-cutaneous junction; chemosis; and the functional anatomy of periosteal fixation. RESULTS: Integrating fluorescent imaging and IHC with anatomical dissection characterizes structural and functional anatomy. Fluorescent imaging helps to identify and locate easily missed structures. IHC defines cell type and function. The vermilion-cutaneous junction is defined by a major lymphatic vessel. Lymphatic flow from the medial limbus to the lateral canthus suggests the etiology of chemosis. Periosteal sites of fixation prevent shear where dural CSF vessels drain directly to subcutaneous lymphatics. CONCLUSIONS: Integrating anatomical dissection with fluorescent imaging and basic IHC characterizes structural and functional anatomy and helps to better understand many problems encountered in aesthetic surgery.

SMAS Fusion Zones Determine the Subfascial and Subcutaneous Anatomy of the Human Face: Fascial Spaces, Fat Compartments, and Models of Facial Aging.

BACKGROUND: Fusion zones between superficial fascia and deep fascia have been recognized by surgical anatomists since 1938. Anatomical dissection performed by the author suggested that additional superficial fascia fusion zones exist. OBJECTIVES: A study was performed to evaluate and define fusion zones between the superficial and the deep fascia. METHODS: Dissection of fresh and minimally preserved cadavers was performed using the accepted technique for defining anatomic spaces: dye injection combined with cross-sectional anatomical dissection. RESULTS: This study identified bilaminar membranes traveling from deep to superficial fascia at consistent locations in all specimens. These membranes exist as fusion zones between superficial and deep fascia, and are referred to as SMAS fusion zones. CONCLUSIONS: Nerves, blood vessels and lymphatics transition between the deep and superficial fascia of the face by traveling along and within these membranes, a construct that provides stability and minimizes shear. Bilaminar subfascial membranes continue into the subcutaneous tissues as unilaminar septa on their way to skin. This three-dimensional lattice of interlocking horizontal, vertical, and oblique membranes defines the anatomic boundaries of the fascial spaces as well as the deep and superficial fat compartments of the face. This information facilitates accurate volume augmentation; helps to avoid facial nerve injury; and provides the conceptual basis for understanding jowls as a manifestation of enlargement of the buccal space that occurs with age.

The anatomical basis for wrinkles.

BACKGROUND: Light and electron microscopy have not identified a distinct anatomical structure associated with either skin wrinkles or creases, and a histological difference between wrinkled and adjacent skin has not been identified. OBJECTIVES: The authors investigate whether facial wrinkles are related to underlying lymphatic vessels and perilymphatic fat. METHODS: Lymphatic vessels with a specialized tube of perilymphatic fat were identified beneath palmar creases. Sections of skin, adipose tissue, and muscle were harvested from each of 13 cadavers. Three sites were investigated: the transverse forehead crease, lateral orbicularis oculi wrinkle (crow's feet), and the nasojugal crease. The tissue was paraffin embedded and processed. Two-step indirect immunohistochemistry was performed, and images were examined using laser confocal microscopy. Measurements were taken with software. RESULTS: Every wrinkle examined was found above and within ±1 mm of a major lymphatic vessel and its surrounding tube of adipose tissue. The results satisfied our null hypothesis and were statistically significant. Lymphatic vessels were identified by positive immunofluorescence as well as histological criteria. These findings have been further validated by fluorochrome tracer studies. CONCLUSIONS: An anatomical basis for wrinkles was identified among the specimens studied. Lymphatic vessels, along with the surrounding distinct perilymphatic fat, traveled directly beneath wrinkles and creases. Lymphatic dysregulation leads to inflammation, scarring, and fibrosis, but inadvertent injection of these vessels can be avoided with anatomical knowledge.

Identification of a novel path for cerebrospinal fluid (CSF) drainage of the human brain.

How cerebrospinal fluid (CSF) drains from the human brain is of paramount importance to cerebral health and physiology. Obstructed CSF drainage results in increased intra-cranial pressure and a predictable cascade of events including dilated cerebral ventricles and ultimately cell death. The current and accepted model of CSF drainage in humans suggests CSF drains from the subarachnoid space into the sagittal sinus vein. Here we identify a new structure in the sagittal sinus of the human brain by anatomic cadaver dissection. The CSF canalicular system is a series of channels on either side of the sagittal sinus vein that communicate with subarachnoid cerebrospinal fluid via Virchow-Robin spaces. Fluorescent injection confirms that these channels are patent and that flow occurs independent of the venous system. Fluoroscopy identified flow from the sagittal sinus to the cranial base. We verify our previous identification of CSF channels in the neck that travel from the cranial base to the subclavian vein. Together, this information suggests a novel path for CSF drainage of the human brain that may represent the primary route for CSF recirculation. These findings have implications for basic anatomy, surgery, and neuroscience, and highlight the continued importance of gross anatomy to medical research and discovery.

Cerebrospinal Fluid Flow Extends to Peripheral Nerves.

Cerebrospinal fluid (CSF) is an aqueous solution responsible for nutrient delivery and waste removal for the central nervous system (CNS). The three-layer meningeal coverings of the CNS support CSF flow. Peripheral nerves have an analogous three-layer covering consisting of the epineurium, perineurium, and endoneurium. Peripheral axons, located in the inner endoneurium, are bathed in "endoneurial fluid" similar to CSF but of undefined origin. CSF flow in the peripheral nervous system has not been demonstrated. Here we show CSF flow extends beyond the CNS to peripheral nerves in a contiguous flowing system. Utilizing gold nanoparticles, we identified that CSF is continuous with the endoneurial fluid and reveal the endoneurial space as the likely site of CSF flow in the periphery. Nanogold distribution along entire peripheral nerves and within their axoplasm suggests CSF plays a role in nutrient delivery and waste clearance, fundamental aspects of peripheral nerve health and disease. One Sentence Summary: Cerebrospinal fluid unites the nervous system by extending beyond the central nervous system into peripheral nerves.

Ventricular Infusion and Nanoprobes Identify Cerebrospinal Fluid and Glymphatic Circulation in Human Nerves.

Growing evidence suggests that cerebrospinal fluid circulates in human nerves. Several conditions encountered by the plastic surgeon may be related to dysregulation of this system, including nerve transection, stretch injuries, and peripheral neuropathy. The purpose of this study was to show how ventricular infusion and nanoprobes identify CSF and glymphatic circulation in neural sheaths of human nerves. METHODS: The technique of ventricular infusion using buffered saline was developed in 2017. The technique was used in a series of eight fresh cadavers before dissection of the median nerve, and combined with fluorescent imaging and nanoprobe injections in selected specimens. RESULTS: Eight cadaver specimens underwent ventricular infusion. There were six female and two male specimens, ages 46-97 (mean 76.6). Ventricular cannulation was performed successfully using coordinates 2 cm anterior to coronal suture and 2.5 cm lateral to sagittal suture. Depth of cannulation ranged from 44 to 56 mm (mean 49.7). Ventricular saline infusion complemented by nanoprobe injection suggests CSF flows in neural sheaths, including pia meninges, epineurial channels, perineurium, and myelin sheaths (neurolemma). CONCLUSIONS: Ventricular infusion and nanoprobes identify CSF flow in neural sheaths of human nerves. CSF flow in nerves is an open circulatory system that occurs via channels, intracellular flow, and cell-to-cell transport associated with glial cells. Neural sheaths, including neurolemma, may participate in glucose and solute transport to axons. These techniques may be used in anatomic dissection and live animal models, and have been extended to the central nervous system to identify direct ventricle-to-pia meninges CSF pathways.

Is intraorbital fat extraorbital? Results of cross-sectional anatomy of the lower eyelid fat pads.

BACKGROUND: Prominent fat pads of the lower eyelids are a frequent complaint prompting patients to seek cosmetic surgery. Previous studies have stated that these fat pads exist as three compartments in the lower eyelids. An accepted anatomic concept is that these lower eyelid fat pads are intraorbital. OBJECTIVE: This study evaluates the possibility of distinct compartments of lower eyelid fat pads not being different from each other, but rather being separate from posterior intraorbital fat. METHODS: This study used eight hemifacial cadaver dissections. Methylene blue injections were used to stain the middle and medial fat pads on each side. Sagittal cross-sections were obtained to visualize the area of fat staining. An axial cross-section of one additional specimen was obtained as confirmatory evidence. RESULTS: Each specimen showed that lower eyelid fat pads stain as discrete fat compartments that are not in continuity with the posterior intraorbital fat. Their anterior boundary is the orbital retaining ligament at the anterior aspect of the inferior orbital rim. Their posterior boundary is an insertion point on the floor of the orbit in line with the midpoint of the globe, called the circumferential intraorbital retaining ligament. CONCLUSIONS: Lower eyelid fat pads are not in continuity with posterior intraorbital fat. They can accurately be described as partially intraorbital and partially extraorbital in location. This information augments our previous understanding of the anatomy of the lower eyelid fat pads and is important for studies that attempt to determine their etiology.

Curve analysis of the aging orbital aperture.

It was hypothesized that skeletal aging results in curve distortion of the orbital aperture. Data were compiled from a cross-sectional study of the Robert J. Terry human skull collection at the Smithsonian Institution, Washington, D.C. Statistical analyses suggest that postadult differential growth results in progressive distortion of the orbital aperture. These changes may have both cosmetic and functional consequences.

The Science and Theory behind Facial Aging.

SUMMARY: The etiology of age-related facial changes has many layers. Multiple theories have been presented over the past 50-100 years with an evolution of understanding regarding facial changes related to skin, soft tissue, muscle, and bone. This special topic will provide an overview of the current literature and evidence and theories of facial changes of the skeleton, soft tissues, and skin over time.

Great auricular nerve injury, the "subauricular band" phenomenon, and the periauricular adipose compartments.

BACKGROUND: Experience with anatomical dissection has suggested that two potential complications of rhytidectomy are related to the anatomy of the periauricular adipose compartments: great auricular nerve injury and the "subauricular band" phenomenon. This study describes this anatomy and its relationship to these potential complications. METHODS: The results of 24 fresh hemifacial cadaver dissections were included in this study. Injections included the use of methylene blue and fixable dye injected into specific regions around the ear. The study incorporated digital macro photography, time-lapse photography, and three-dimensional cross-sections in multiple planes (coronal, sagittal, and axial planes) to identify structural relationships. RESULTS: This study defined five periauricular adipose compartments. The main branch of the great auricular nerve always ran within the subauricular membrane. The subauricular membrane was located between the subauricular and inferior adipose compartments. Inadequate dissection of the lateral neck and postauricular area along with failure to release this membrane completely results in banding of the lateral neck, a stigma of face lift surgery. McKinney's point was consistently found to lie where the great auricular nerve travels deep to the inferior border of Lore's fascia and the tail of the parotid. Below this point, the great auricular nerve is closer to the skin surface and more susceptible to potential injury. CONCLUSION: Two possible complications of rhytidectomy, great auricular nerve injury and the "subauricular band" phenomenon, are avoidable by understanding the anatomy of the periauricular adipose compartments.

The low transverse extended latissimus dorsi flap based on fat compartments of the back for breast reconstruction: anatomical study and clinical results.

BACKGROUND: Despite many modifications to the extended latissimus dorsi flap, its use in autologous breast reconstruction remains limited because of insufficient volume and donor-site morbidity. Through a detailed analysis of the deposition of back fat, this study describes a low transverse extended latissimus dorsi flap harvest technique that increases flap volumes and improves donor-site aesthetics. METHODS: Eight fresh cadaver hemibacks were used to identify the anatomical location of the fat compartments. Correlation between the fat compartments and the fat folds was made using photographic analysis of 216 patients. Retrospective case note review was conducted of all patients who had a low transverse extended latissimus dorsi flap performed by the senior author (M.S.-C.). RESULTS: Cadaveric dissection and photographic analysis confirmed the presence of the four distinct fat compartments in the back. The lower compartments 3 and 4 were the most frequently identified and the largest, with mean values of 367 cm and 271 cm, respectively. The clinical series comprised eight high-body mass index patients who underwent 12 pure autologous breast reconstructions using the low transverse skin paddle harvest technique. Donor-site complications included partial dehiscence (n=2) and minor infection (n=3). There were no instances of seroma, and fat necrosis (<5 percent) occurred in one breast. CONCLUSIONS: The low transverse skin paddle extended latissimus dorsi flap is reliable and provides sufficient volume for purely autologous breast reconstruction with low donor-site morbidity and improved body contouring for a select group of patients. The authors' initial experience with high-body mass index patients shows promising results with this flap in a challenging group.

The subplatysmal supramylohyoid fat.

BACKGROUND: Liposuction of the neck has an established role in selected patients undergoing cervicoplasty. Some authors have suggested a role for subplatysmal fat removal. Observations in the anatomy laboratory suggested the presence of discrete regions of subplatysmal fat. This information may be useful during surgical procedures in the subplatysmal plane. METHODS: Five fresh cadaver dissections were performed. There were four male specimens and one female specimen with an age range of 66 to 78 years. Sequential dissection of the cervical layers included skin, supraplatysmal fat, platysma muscle, and subplatysmal fat. Loupe magnification was used to aid dissection. RESULTS: Subplatysmal fat is found in three compartments: central, medial, and lateral. Their relationship to the platysma and digastric muscles is consistent. The mylohyoid muscle represents the posterior boundary of these compartments. Central fat is easily distinguished from medial and lateral fat due to differences in color and appearance. These three compartments abut one another and together form the subplatysmal fat layer. Differences in thickness of these compartments were noted. CONCLUSIONS: Subplatysmal fat occurs as distinct regions. These can be identified during surgery by their relationship to the platysma, digastric, and mylohyoid muscles. Knowledge of the regional differences in appearance is a further aid in identification. Knowledge of this anatomy can facilitate dissection when performed in the subplastysmal plane.