Extra-cellular matrix rigidity may dictate the fate of injury outcome.

After injury, while regeneration can be observed in hydra, planaria and some vertebrates, regeneration is rare in mammals and particularly in humans. In this paper, we investigate the mechanisms by which biological tissues recover after injury. We explore this question on adipose tissue, using the mathematical framework recently developed in Peurichard et al., J. Theoret. Biol. 429 (2017), pp. 61-81. Our assumption is that simple mechanical cues between the Extra-Cellular Matrix (ECM) and differentiated cells can explain adipose tissue morphogenesis and that regeneration requires after injury the same mechanisms. We validate this hypothesis by means of a two-dimensional Individual Based Model (IBM) of interacting adipocytes and ECM fiber elements. The model successfully generates regeneration or scar formation as functions of few key parameters, and seems to indicate that the fate of injury outcome could be mainly due to ECM rigidity.

Compressed Fixation Combined with Vacuum-Assisted Closure for Treating Acute Injury of the Heel Fat Pad.

BACKGROUND Treating acute injury of the heel fat pad is different from treating common soft tissue damage. Due to the paucity of literature on the topic, we described our initial experience treating acute injury of the heel fat pad to determine the ideal treatment method. MATERIAL AND METHODS A total of 53 patients with acute injury of the heel fat pad admitted to our hospital were selected for the study and were randomly divided into 2 groups: the compressed fixation combined with vacuum-assisted closure group and the only reimplanted and sewn group. Twenty-seven of the heel fat pads were compressed and fixed using a flat, hard piece of plastic and hollow screws; then, they were covered with a vacuum-assisted closure device. The other 27 were only sewn without tension. The clinical results were evaluated according to the American Orthopedic Foot and Ankle Society hindfoot score and the British Medical Research Council function evaluation criteria RESULTS In the compressed fixation combined with vacuum-assisted closure group, flaps of 12 feet with retrograde avulsion injury survived successfully. Partial flap necrosis occurred in 8 feet. Seven feet underwent repair using the neurocutaneous vascular resupinated island flap. Results were excellent or good for 74% of patients according to the AOFS. However, in the only reimplanted and sewn group, results were excellent or good for 44% of patients according to the AOFS. CONCLUSIONS Compressed fixation with vacuum-assisted closure is effective for treating acute injury of the heel fat pad, with high success rates and good utility.

The Enigma of "Traumatic Pseudolipoma" and "Traumatic Herniation of Buccal Fat Pad": A Systematic Review and New Classification System of Post-Traumatic Craniofacial Fatty Masses.

PURPOSE: Intraoral traumatic herniation of the buccal fat pad has been reported using various terms such as traumatic pseudolipoma, traumatic prolapse of buccal fat pad, and traumatic avulsion of buccal fat pad. Because there is no uniformity in nomenclature, this condition needs to be distinguished from other entities such as post-traumatic pseudolipoma and lipoma and pseudoherniation of the buccal fat pad. MATERIALS AND METHODS: A systematic review and thorough search of the literature was planned in online databases such as PubMed, Medline, Scopus, Embase, and Google Scholar. The keywords used were traumatic pseudolipoma, traumatic herniation of buccal fat pad, and traumatic prolapse of buccal fat pad. Of 95 articles initially screened, 45 were included in the study. All pertinent data were extracted by the authors independently. Extracted data were cross-examined for any discrepancy. Summary statistics were not used because the research question did not support pooling of data. RESULTS: Only 24 cases were found to have reported the condition correctly. Terms such as traumatic pseudolipoma were used synonymously and erroneously for this condition. CONCLUSION: Based on the gross inaccuracy in reporting, the authors propose a new comprehensive classification of post-traumatic craniofacial fatty masses.

Evaluation of Paraspinal Fat Pad as an Indicator of Posterior Ligamentous Complex Injury in Cervical Spine Trauma.

Purpose To determine if the obliteration of a cervical space, the paraspinal fat pad (PFP), can be used as an indicator at computed tomography (CT) of an injury of cervical spine posterior ligamentous complex (PLC). Materials and Methods This retrospective study was approved by the institutional board review; written informed consent was obtained from healthy subjects and was waived for patients. First, PFP appearance was evaluated in an anatomic specimen and in 10 healthy subjects on spine CT scans by three radiologists (readers 1, 2, and 3) working in consensus. Then, in 85 patients with suspicion of cervical spine trauma following high-velocity trauma, readers 2 and 3 reviewed in consensus the cervical spine CT (reference for fracture and luxation) and 1.5-T magnetic resonance images (T1, T2, and short inversion time inversion-recovery sequences; reference for ligament and disk injuries and contusion or occult fracture) for traumatic injuries. CT appearance of PFP was independently analyzed by readers 1 and 2, and interobserver agreement (weighted kappa) was calculated. Relationships between PFP changes and injuries and descriptive analysis were calculated by using logistic regression and Fisher test, respectively. Results The PFP could be identified as a well-circumscribed fatty area between cervical spine and posterior muscles. Interobserver agreement was 0.76. An abnormal PFP was associated with PLC (P < .001) and arch (P = .006) injuries but not with body (P = .056), longitudinal ligaments (P = .412), or disk (P = .665) injuries. Sensitivity, specificity, positive predictive value, and negative predictive value for PLC injuries were 55% (11 of 20), 97% (38 of 39), 92% (11 of 12), and 81% (38 of 47), respectively. Conclusion PFP changes on CT scans are significantly associated with injuries of PLC in patients with spine cervical trauma. © RSNA, 2016 Online supplemental material is available for this article.

Magnetic resonance imaging of Hoffa's fat pad and relevance for osteoarthritis research: a narrative review.

OBJECTIVE: To give an illustrative overview of Hoffa's fat pad pathology with a radiologic emphasis on the anatomy, on technical considerations, and on imaging differential diagnoses in the context of osteoarthritis (OA) imaging research. DESIGN: A PubMed database search including only English literature and covering a 20 year period was performed. The search was based on but no limited to the query terms "Hoffa", "Hoffa's fat pad" or "infrapatellar fat pad (IPFP)" in combination with "synovitis", "OA", and "magnetic resonance imaging (MRI)". The literature search yielded 289 publications that were screened for relevance; additional references were included when these were considered of importance. RESULTS: Several anatomic variants and pathologic conditions may be encountered when assessing Hoffa's fat pad including tumors and tumor-like lesions such as osteochondroma, tenosynovial giant cell tumor (TGCT) (and pigmented nodular synovitis) and arthrofibrosis, traumatic changes including contusions and anatomic variants such as recesses. The latter may be accountable for differences in cross-sectional area or volume changes over time. Signal changes are commonly used in OA research as surrogate markers for synovitis but are non-specific findings. CONCLUSIONS: Quantitative approaches to evaluate 3D parameters of Hoffa's fat pad are increasingly applied and their role in regard to structural progression and clinical manifestations of disease needs to be further elucidated. In applying such approaches, knowledge of the detailed anatomy and potential pitfalls that may be a result of anatomical variants, inflammatory disease manifestations and additional diverse pathologies encountered seems to be paramount.

Role of adiponectin in adipose tissue wound healing.

The purpose of this study was to investigate the mechanism behind adipose tissue wound healing (ATWH). The preadipocyte cell line 3T3-L1 was cultured and expression of adiponectin receptors (AdipoR1/2) was detected by immunohistochemistry and reverse transcription polymerase chain reaction. The concentration of adiponectin secreted at different cell densities was measured by enzyme-linked immunosorbent assay, while preadipocyte proliferation and migration were determined in vitro by MTT and wound closure assays. AdipoR1/2 were found to be expressed in 3T3-L1 preadipocytes. There were no statistically significant differences in the concentrations of adiponectin secreted by cell solutions of different densities (P > 0.05). In addition, adiponectin was seen to promote the growth and migration of preadipocytes. In conclusion, adiponectin may regulate ATWH by promoting preadipocyte proliferation and migration, and its systemic and/or local application is proposed as a promising therapeutic approach for the treatment of wounds incurred as a result of surgery.

Non-invasive temperature monitoring and hyperthermic injury onset detection using X-ray CT during HIFU thermal treatment in ex vivo fatty tissue.

PURPOSE: This paper examines X-ray CT, to serve as an image-guiding thermal monitoring modality for high intensity focused ultrasound (HIFU) treatment of fatty tissues. MATERIALS AND METHODS: Six ex vivo porcine fat tissue specimens were scanned by X-ray CT simultaneously with the application of HIFU. Images were acquired during both heating and post-ablation stages. The temperature at the focal zone was measured simultaneously using a thermocouple. The mean values of the Hounsfield units (HU) at the focal zone were registered and plotted as a function of temperature. RESULTS: In all specimens studied, the HU versus temperature curves measured during the heating stage depicted a characteristic non-linear parabolic trajectory (R(2) > 0.87). The HU-temperature trajectory initially decreased to a minimum value at about 44.5 °C and then increased substantially as the heating progressed. The occurrence of this nadir point during the heating stage was clearly detectable. During post-ablation cooling, on the other hand, the HU increased monotonically with the decreasing temperature and depicted a clearly linear trajectory (R(2) ≥ 0.9). CONCLUSIONS: Our results demonstrate that the HU-temperature curve during HIFU treatment has a characteristic parabolic trajectory for fat tissue that might potentially be utilised for thermal monitoring during HIFU ablation treatments. The clear detection of 44.5 °C, presumably marking the onset of hyperthermic injury, can be detected non-invasively as an occurrence of a minimum on the HU-time curve without any need to relate the HU directly to temperature. Such features may be helpful in monitoring and optimising HIFU thermal treatment for clinically applicable indications such as in the breast by providing a non-invasive monitoring of tissue damage.

Surgical removal of traumatic herniation of buccal fat pad in young children.

Intraoral herniation of the buccal fat pad is traumatic lesion of oral cavity occurring in young children. It frequently presents as an expanding pedunculated mass of soft tissue emanating from the buccal mucosa following a minor trauma to the buccal soft tissues. This article aims to report an interesting and rare lesion, wherein a tiny traumatic perforation of the buccal mucosa and buccinator muscle forced a large portion of the buccal fat pad to extrude into the oral cavity in a young boy. Such a situation can alarm any clinician and reinforces the importance of careful history taking and thorough examination, before treating patients.

Injury-induced insulin resistance in adipose tissue.

Hyperglycemia and insulin resistance are common findings in critical illness. Patients in the surgical ICU are frequently treated for this 'critical illness diabetes' with intensive insulin therapy, resulting in a substantial reduction in morbidity and mortality. Adipose tissue is an important insulin target tissue, but it is not known whether adipose tissue is affected by critical illness diabetes. In the present study, a rodent model of critical illness diabetes was used to determine whether adipose tissue becomes acutely insulin resistant and how insulin signaling pathways are being affected. There was a reduction in insulin-induced phosphorylation of IR, IRS-1, Akt and GSK-3ß. Since insulin resistance occurs rapidly in adipose tissue, but before the insulin resistance in skeletal muscle, it may play a role in the initial development of critical illness diabetes.

Adipose injury-associated factors mitigate hypoxia in ischemic tissues through activation of adipose-derived stem/progenitor/stromal cells and induction of angiogenesis.

Based on the analysis of exudates from injured adipose tissue, we prepared a mixture containing the injury-associated growth factors at the same proportion as the exudates, named adipose injury cocktail (AIC). We hypothesized that AIC induces a series of regenerating and angiogenic processes without actual wounding. The purpose of this study is to elucidate the therapeutic potentials of AIC. AIC preferentially activated adipose-derived stem/progenitor/stromal cells (ASCs) to proliferate, migrate, and form networks compared with vascular endothelial cells, whereas vascular endothelial growth factor did not induce mitogenesis or chemotaxis in human ASCs. Each component growth factor of AIC was differently responsible for the ASC activation. AIC-treated ASCs tended to differentiate into adipocytes or vessel-constituting cells rather than into other cell types. In ischemic adipose tissues of mice, induced by either a surgical intervention or diabetes, AIC administration enhanced proliferation, especially of CD31(-)/CD34(+) ASCs, and mitigated tissue hypoxia by increasing capillary density and reducing fibrogenesis. These results suggest that AIC may have therapeutic potentials for various ischemic/hypoxic conditions by inducing adipose remodeling and neovascularization through activation of ASCs and other cells. Treatment with AIC has many advantages over cell-based therapies regarding morbidity, cost, and physical risks and may be used as an alternative therapy for improving tissue oxygen.

Initial extremity war wound debridement: a multidisciplinary consensus.

A joint meeting of the Limb Trauma and Wounds Working Groups resulted in the establishment of 29 consensus recommendations for the conduct of initial extremity war wound debridement. Pre-operative, operative and post-operative phases of debridement were considered along with wound irrigation and dressings. Wounds where a different surgical approach is required, such as superficial soft tissue wounds at one end of the spectrum and complex wounds sustained in close proximity to explosions at the other, were also discussed. The recommendations represent the consensus opinion of orthopaedic, vascular and plastic surgeons, as well as nursing officers, from across the Defence Medical Services and are intended to provide useful guidance to the deploying surgeon, regardless of their own personal experience.

MRI of the Morel-Lavallée lesion - a case series.

INTRODUCTION: The aim of the study was to review the appearances of Morel-Lavallée (ML) lesions on magnetic resonance imaging (MRI). PATIENTS AND METHODS: 14 patients diagnosed with the ML lesion on MRI were analysed retrospectively (mean age = 35 years). Mechanism of injury, time frame from injury to MRI, location, shape, T1 and proton-density fat-suppression (PDFS) signal intensity (SI), presence of a (pseudo)capsule, septations or nodules within the collection, mass effect and fluid-fluid levels were analyzed. The Mellado and Bencardino classification was utilized to classify the lesions. RESULTS: In most cases, mechanism of injury was distortion. Mean time frame between the injury and MRI was 17 days. Lesions were located around the knee in 9 patients and in the peritrochanteric region in 5 patients. Collections were fusiform in 12 patients and oval in 2 patients. 9 collections were T1 hypointense and PDFS hyperintense. 4 collections had intermediate T1 and high PDFS SI. 1 collection had intermediate T1 and PDFS SI. (Pseudo)capsule was noted in 3 cases. Septations or nodules were found in 4 cases. According to the Mellado and Bencardino, collections were classified as seroma (type 1) in 9, subacute hematoma (type 2) in 1 and chronic organizing hematoma (type 3) in 4 cases. CONCLUSIONS: Characteristic features of ML lesion include a fusiform fluid collection between the subcutaneous fat and the underlying fascia after shearing injury. Six types can be differentiated on MRI, with the seroma, the subacute hematoma and the chronic organizing hematoma being the commonest.

Comparison of fibrogenesis caused by dermal and adipose tissue injury in an experimental model.

Mammalian skin is composed of three layers, the epidermis, the dermis, and the subcutis, which is composed primarily of adipose tissue. The dermal and adipose tissues are involved simultaneously when partial and full-thickness burns occur, and often induce scar formation. However, little is known about the role of the dermis and adipose tissue injury in scar formation or the difference in fibrogenesis between the two tissues. In this study with female red Duroc pigs, we created flaps of skin with a dermal plane of injury or deeper flaps with an adipose plane of injury on the back. We compared the extent of fibrogenesis by observing the deposition of extracellular matrix as well as the characteristics of cells in the injured area. In skin flaps with a dermal level of tissue injury, scar formation that was characterized by more extracellular matrix deposition and less apoptotic myofibroblasts in the injured area was observed. Our results suggest that scar formation does not correlate with injury at the level of the adipose tissue, and that adipose tissue might serve to alleviate fibrogenesis.

Floating fat in the wrist joint and in the tendon sheaths.

A traumatic fat effusion in a tendon sheath is an unreported entity. We report on the clinical and imaging features, including radiography and computed tomography (CT), of a fat-density effusion in the wrist joint and tendon sheaths of the extensor pollicis longus, extensor carpi radialis longus, and extensor carpi radialis brevis in a 28-year-old patient after a roller-skating accident. Radiographs showed a fracture of the distal radius and a wrist joint effusion. Preoperative CT examination exhibited two distinct layers resulting in a fat-fluid level pathognomonic of lipohemarthrosis in the radiocarpal joint. In addition, a fat-density effusion was noted in the sheaths of the second and third compartment extensor tendons. The lipohemarthrosis depicted on imaging classically results from the extrusion of fat from bone marrow into the joint space after an intraarticular fracture. Similarly, a traumatic fat effusion in a tendon sheath presents characteristic imaging features that may help to diagnose a potentially overlooked fracture.

Anatomical assessment of the Hoffa fat pad during insertion of a tibial intramedullary nail--comparison of three surgical approaches.

BACKGROUND: Interlocking nailing is a standard procedure in the surgical treatment of tibial fractures. Despite it has been described to be a safe technique with excellent functional results compared with conservative treatment, a common problem is the development of anterior knee pain. The anatomic relation of Hoffa's fat pad with its nociceptors to the nail entry point has not been investigated, yet. METHODS: Eighteen formalin-fixed lower cadaver extremities of 11 cadavers (five females, six males) were matched into three groups: three approaches (medial paratendinous, transligamentous, and lateral paratendinous) were performed and the anterosuperior tibial cortex was opened with a cheese cutter. To investigate the relationship of the nail entry point and Hoffa's fat pad, the joint capsule was incised, and Hoffa's fat pad was exposed and then dissected carefully. Damage to the fat pad was recorded as well as meniscal lesions, cartilage lesions, and ligamentous lesions. After full extension and flexion of the knee joint, the motion of Hoffa's fat pad (millimeter) was recorded with a measuring gauge. The zone for safe nail insertion (millimeter square) without any lesion to intra-articular structures was recorded. RESULTS: Violation of Hoffa's fat pad was recorded if the lateral and transligamentous approach were used. With the medial approach, no damage of the fat pad was recorded. Total mean lateralization of the fat pad from extension to flexion over 90 degrees was 18.5 mm compared with its location in the fully extended knee. The safe zone for nail insertion without violation of menisci, cartilage, or ligaments was a triangle in the posteromedial aspect of the Hoffa with a mean dimension of 19.4 mm2. CONCLUSION: On the basis of our results, we can recommend the nail insertion via a medial paratendinous surgical approach to avoid injuries to the Hoffa fat pad and to menisci, cartilage, and ligaments.

Temporal dissection technique that prevents temporal hollowing in coronal approach.

Temporal hollowing after lateral facial skeletal exposure via a coronal approach is not uncommon. This is caused by injury to the superficial temporal fat pad. However, to prevent facial nerve injury at the zygomatic arch, incision of the superficial layer of the temporalis fascia (TF) and exposure of the temporal fat pad are accompanied with most coronal approaches. Here we introduce our method of dissection of the suprasuperficial layer of the TF without exposure of the temporal fat pad and report on its safety and efficacy. Temporal dissection just superficial to the superficial layer of the TF was performed to the superior border of the zygomatic arch. After identifying the zygomatic arch, an incision was made at the posterosuperior aspect of the arch, when exposure of the arch was necessary for access to the lateral skeleton. From 1989 to 2008, 522 patients undergoing craniofacial surgery via coronal approach were analyzed retrospectively. No patient developed temporal hollowing. However, 14 patients (2.7%) developed frontal weakness immediately postoperatively, and 2 of them had permanent paresis. The frequency of this motor morbidity was low compared with that of other reports. Preservation of the temporal fat pad in coronal approach is essential for the prevention of temporal hollowing, and for this, we recommend suprasuperficial layer of TF dissection.

Tumors and tumor-like lesions of infrapatellar fat pad and surrounding tissues: A review of the literature.

The infrapatellar fat pad (IFP) is an intracapsular structure with critical importance both mechanically and endocrinologically. Its dysfunction must be considered while clinically investigating the symptoms arising from the knee joint. Infrapatellar fat pad may be subject to trauma, impingement, inflammation or tumoral formations. Although tumors arising within or adjacent to IFP are not extremely rare, the literature can only provide limited information about them. This article aims to briefly review the current literature on tumors and tumor-like lesions of the IFP and surrounding tissues; focusing on diagnosis and treatment management.

Fat Fracture: A Rare Cause of Anterior and Medial Knee Pain in a Professional Baseball Player.

Blunt trauma to the anterior knee typically results in a contusion or fracture of the patella. Additionally, injury to the extensor mechanism may come from a partial or full disruption of the patellar or quadriceps tendon. A professional baseball player suffered an injury to his knee after he collided with an outfield wall. Acute swelling in the suprapatellar soft tissues concealed a palpable defect, which initially was suspected to be an injury to the quadriceps tendon. Magnetic resonance imaging of the knee revealed an intact extensor mechanism; moreover, a fracture of the subcutaneous fat anterior to the quadriceps tendon was evident and diagnosed as a fat fracture. Fat fracture is a rare diagnosis, and to the best of our knowledge, this is the first reported diagnosis in a professional athlete. Conservative management including, but not limited to, range of motion exercises, hydrotherapy, and iontophoresis effectively treated the athlete's injury.