Bioengineered Approach to the Design of a Fat Graft Based on Mathematical Modeling that Predicts Oxygen Delivery.

BACKGROUND: Fat grafting is a common procedure in plastic surgery. A major limitation is unpredictable graft retention, in part caused by inadequate oxygen delivery during the early posttransfer period. METHODS: The authors present a bioengineered approach to the design of a fat graft based on mathematical theory, which can estimate the limitations of oxygen delivery. To simplify the problem, four variables were defined: (1) recipient-site oxygen partial pressure; (2) adipose tissue oxygen permeability; (3) adipose tissue oxygen consumption rate; and (4) fat graft size. Recipient-site oxygen partial pressure and adipose tissue oxygen permeability were estimated from literature, whereas adipose tissue oxygen consumption rate was measured using stirred microchamber technology. Calculations were performed in both spherical and planar geometry to calculate the maximum allowable fat graft size from an oxygen delivery standpoint. RESULTS: As expected, planar geometry is less favorable for oxygenation but represents a realistic configuration for a fat graft. Maximum allowable fat graft thickness is only approximately 1 to 2 mm at external oxygen partial pressures of 10 to 40 mm Hg; any thicker and an anoxic or necrotic core likely develops. Given a reasonably large surface area and assuming several planes of injection, the maximum allowable fat graft volume is tens of milliliters. CONCLUSIONS: A systematic bioengineered approach may help better design a fat graft. Applying principles of mass transfer theory can predict whether a fat graft has a favorable chance of surviving from an oxygen delivery standpoint and can direct the development of strategies for improved fat graft oxygenation.

Scalp reconstruction: a review of the literature and a unique case of total craniectomy in an adult with osteomyelitis of the skull.

OBJECTIVE: Osteomyelitis of the skull is a rare condition that can lead to systemic illness, bone loss, intracranial complications, and mortality. Osteomyelitis of the skull typically presents as the boney invasion of an overlying infection of the scalp or sinuses, and it is typically treated with antibiotics and proper wound care. Surgical debridement of the affected bone in the form of a craniectomy may be initiated to stop the progression of the infection when antibiotics fail and the underlying bone becomes grossly eroded. METHOD: The authors present the case of a 54-year-old woman who required a total craniectomy after developing full-thickness osteomyelitis. A free omental flap along with dermal grafts and split-thickness skin grafts were utilized for soft tissue coverage. A semi-rigid helmet was used to provide durable protection to the brain. RESULTS: Omental free flap with skin graft coverage provided this patient with durable and long-term soft tissue coverage for a total craniectomy defect, as well as the ability to regain mental status. CONCLUSIONS: Many factors must be analyzed when approaching composite defects of the scalp. Modality of treatment must be customized to the individual, and the decisions should be based on whether the defect is composed of soft tissue, bone or both, its size, etiology, and presence of a cerebral spinal fluid leak. The goals of treatment are restoration of durable soft tissue coverage, protection of vital underlying structures and control of cerebral spinal fluid leaks.

CASE REPORT Simultaneous Latissimus Dorsi Myocutaneous Flap Transfer and Revision Total Knee Arthroplasty With Allograft Extensor Mechanism Reconstruction: A Case Report.

INTRODUCTION: We present the case of a patient undergoing simultaneous reconstruction of a massive soft tissue deficit of the right knee along with total knee arthroplasty and allograft reconstruction of the extensor mechanism after multiple failed attempts to repair and revise the affected joint. METHODS: A latissimus dorsi myocutaneous flap was transferred to fill the soft-tissue deficit of the right knee. During the same procedure, a previously placed antibiotic-cement spacer was removed and a new total knee prosthesis was implanted. What remained of the damaged extensor mechanism was excised and replaced with a cadaveric allograft. RESULTS: The latissimus dorsi flap provided the necessary soft-tissue coverage of the revision. The new knee components and allograft extensor mechanism were satisfactorily implanted. One year after simultaneous reconstruction, the knee remains functional and free of infection. DISCUSSION: Although current literature may have indicated conversion to arthrodesis or prophylactic soft-tissue repair prior to revision, simultaneous soft-tissue and extensor mechanism repair along with revision total knee arthroplasty have yielded promising results in this patient.

CASE REPORT Removal of Exposed Titanium Reconstruction Plate After Mandibular Reconstruction With a Free Fibula Osteocutaneous Flap With Large Surgical Pin Cutters: A Case Report and Literature Review.

Locking reconstruction plates have led to significant improvement in osteosynthesis and graft anchorage in mandibular reconstruction following the free fibula osteocutaneous flap. Plate extrusion is the most common complication associated with mandibular reconstruction, occurring in approximately 20% to 48% of cases; often necessitating plate removal once the bone flap has united to the mandible. Radiation therapy is a known risk factor to the development of such a complication and it presents further challenges to the successful removal of the reconstruction plate. Several reports have been published regarding plate removal in the setting of orthopedics that describe the management of jammed or stripped locking screws, but few in the setting of mandibular reconstruction. In this case, we report the successful removal of an exposed titanium mandibular reconstruction plate from a 41-year-old woman 12 months after her initial reconstruction with a free fibula osteocutaneous flap and radiation therapy. The approach was selected because the chin and neck skin could not be expected to be raised for full plate exposure secondary to radiation-induced skin changes (thinning and friability). We also discuss the use of previously employed methods of plate removal in various settings as well as their inherent strengths and weaknesses.