Mack L. Cheney

A Polymer Foam Conduit Seeded with Schwann Cells Promotes Guided Peripheral Nerve Regeneration

Alternatives to autografts have long been sought for use in bridging neural gaps. Many entubulation materials have been studied, although with generally disappointing results in comparison with autografts. The purpose of this study was to design a more effective neural guidance conduit, to introduce Schwann cells into the conduit, and to determine regenerative capability through it in an in vivo model. A novel, fully biodegradable polymer conduit was designed and fabricated for use in peripheral nerve repair, which approximates the macro- and microarchitecture of native peripheral nerves. It comprised a series of longitudinally aligned channels, with diameters ranging from 60 to 550 microns. The lumenal surfaces promoted the adherence of Schwann cells, whose presence is known to play a key role in nerve regeneration. This unique channel architecture increased the surface area available for Schwann cell adherence up to five-fold over that available through a simple hollow conduit. The conduit was composed of a high-molecular-weight copolymer of lactic and glycolic acids (PLGA) (MW 130,000) in an 85:15 monomer ratio. A novel foam-processing technique, employing low-pressure injection molding, was used to create highly porous conduits (approximately 90% pore volume) with continuous longitudinal channels. Using this technique, conduits were constructed containing 1, 5, 16, 45, or more longitudinally aligned channels. Prior to cellular seeding of these conduits, the foams were prewet with 50% ethanol, flushed with physiologic saline, and coated with laminin solution (10 microg/mL). A Schwann cell suspension was dynamically introduced into these processed foams at a concentration of 5 X 10(5) cells/mL, using a simple bioreactor flow loop. In vivo regeneration studies were carried out in which cell-laden five-channel polymer conduits (individual channel ID 500 microm, total conduit OD 2.3 mm) were implanted across a 7-mm gap in the rat sciatic nerve (n = 4), and midgraft axonal regeneration compared with autografts (n = 6). At 6 weeks, axonal regeneration was observed in the midconduit region of all five channels in each experimental animal. The cross-sectional area comprising axons relative to the open conduit cross sectional area (mean 26.3%, SD 10. 1%) compared favorably with autografts (mean 23.8%, SD 3.6%). Our methodology can be used to create polymer foam conduits containing longitudinally aligned channels, to introduce Schwann cells into them, and to implant them into surgically created neural defects. These conduits provide an environment permissive to axonal regeneration. Furthermore, this polymer foam-processing method and unique channeled architecture allows the introduction of neurotrophic factors into the conduit in a controlled fashion. Deposition of different factors into distinct regions within the conduit may be possible to promote more precisely guided neural regeneration.

Atlas of regional and free flaps for head and neck reconstruction

Documenting in unprecedented detail the surgical procedures, techniques, and approaches used by the experts, this new atlas/text is the definitive full-color pictorial reference on major flap transfers for reconstructive head-and-neck surgery. The book chronicles three decades of innovations and progress in the field, and presents detailed descriptions of anatomy and anatomical variations, step-by-step guidance on identifying and preparing appropriate donor and recipient sites, and techniques for successfully grafting selected tissue. This one-of-a-kind atlas covers the spectrum of donor sites most frequently used in head-and-neck surgery, and through more than 300 color illustrations and a concise narrative text, the authors provide step-by-step guidance and invaluable technical advice. Each chapter includes the details of normal donor site anatomy as well as anatomic variations, and every section of the book presents the most important options in flap design and the most optimal and desirable application. The text also addresses important topics such as pre- and postoperative care and potential pitfalls and complications

Manufacture of porous polymer nerve conduits by a novel low-pressure injection molding process

A method to fabricate porous, biodegradable conduits using a combined injection molding, thermally induced phase transition technique was developed which produced conduits with dimensionally toleranced, longitudinally aligned channels. The geometry of the channels was designed to approximate the architecture of peripheral nerves and to support the monolayer adherence of physiologically relevant numbers of Schwann cells. The channel configuration could be varied from a single 1.35 mm diameter channel up to 100 0.08 mm diameter channels. A conduit with 100 channels has approximately 12.5 times the lumenal surface area of a single channel conduit and supports the adherence of five times the number of Schwann cells in the native peripheral nerve. In this study, poly(DL-lactide-co-glycolide) (DL-PLGA) was dissolved in acetic acid and injected into a cold mold which induced solid-liquid phase separation and, ultimately, solidification of the polymer solution. The acetic acid was removed by sublimation and the resulting foam had a macrostructure of high anisotropy. Semi-permeable skins formed on the outer and lumen diameters of the conduit as a consequence of rapid quenching. Macropores were organized into bundles of channels, up to 20 microm wide, in the DL-PLGA matrix and represented remnants of acetic acid that crystallized during solidification.

Effects of Aspirin and Low‐Dose Heparin in Head and Neck Reconstruction using Microvascular Free Flaps

Objective: The success of microvascular free‐tissue transfer to the head and neck has been greatly increased secondary to increased experience, yet postoperative anticoagulation continues to be routinely used to prevent pedicle thrombosis. However, there is currently no consensus as to what the ideal regimen, if any, is recommended for postoperative anticoagulation. This study reviews the outcome and incidence of perioperative complications in patients undergoing free flaps for head and neck reconstruction, using a simple postoperative anticoagulation regimen of aspirin and subcutaneous heparin (SQH).

Use of the radial forearm fasciocutaneous free flap and Montgomery salivary bypass tube for pharyngoesophageal reconstruction

Head and neck reconstructive surgeons involved in pharyngoesophageal reconstruction have several options available to repair the defect after partial or total laryngopharyngectomy. There is no uniform agreement among head and neck surgeons as to which of the most frequently used techniques offers the best results.

A Novel, Biodegradable Polymer Conduit Delivers Neurotrophins and Promotes Nerve Regeneration†

Objective/Hypothesis: A wide variety of substances have been shown to promote neuritic extension after nerve injury. An obstacle to achieving the maximal benefit from these substances has been the difficulty in effectively delivering the substances over a protracted time course that promotes maximal, directed growth. In this study the delivery of a growth‐promoting substance through a biodegradable conduit, using materials originally designed for drug delivery applications, was hypothesized to promote more robust neural regeneration than through conduits lacking the substance. The objectives of this study were to create a growth factor‐loaded biodegradable nerve guidance conduit, and to assess in vivo nerve regeneration through the conduit compared with that through conduits lacking the substance.

Multimodality Approach to Management of the Paralyzed Face

Objectives: Despite the ability of facial reanimation techniques to introduce meaningful movement to the paralyzed face, dynamic methods do not address all zones of the face. Our objective was to retrospectively review outcomes after multimodality management of the patient with facial paralysis, to describe several novel surgical methods that introduce subtle improvements in static facial balance, and to present an algorithm for comprehensive management of the paralyzed face.

Free Gracilis Transfer for Smile in Children: The Massachusetts Eye and Ear Infirmary Experience in Excursion and Quality-of-Life Changes

BACKGROUND Free muscle transfer for facial reanimation has become the standard of care in recent decades and is now the cornerstone intervention for dynamic smile reanimation. We sought to quantify smile excursion and quality-of-life (QOL) changes in our pediatric free gracilis recipients following reanimation. METHODS We quantified gracilis muscle excursion in 17 pediatric patients undergoing 19 consecutive pediatric free gracilis transplantation operations, using our validated SMILE program, as an objective measure of functional outcome. These were compared against excursion measured the same way in a cohort of 17 adults with 19 free gracilis operations. In addition, we prospectively evaluated QOL outcomes in these children using the Facial Clinimetric Evaluation (FaCE) instrument. RESULTS The mean gracilis excursion in our pediatric free gracilis recipients was 8.8 mm ± 5.0 mm, which matched adult results, but with fewer complete failures of less than 2-mm excursion, with 2 (11%) and 4 (21%), respectively. Quality-of-life measures indicated statistically significant improvements following dynamic smile reanimation (P = .01). CONCLUSIONS Dynamic facial reanimation using free gracilis transfer in children has an acceptable success rate, yields improved commissure excursion, and improves QOL in the pediatric population. It should be considered first-line therapy for children with lack of a meaningful smile secondary to facial paralysis.

Thin-profile platinum eyelid weighting: a superior option in the paralyzed eye.

Background: A devastating sequela of facial paralysis is the inability to close the eye. The resulting loss of corneal protection can lead to exposure keratitis, corneal ulceration, and potentially permanent vision loss. Methods to address lagophthalmos historically have included tarsorrhaphy, lid weighting, levator palpebrae superioris lengthening, chemodenervation to yield protective ptosis, and the placement of magnetic eyelid springs. The gold eyelid weight, introduced nearly 50 years ago, continues to enjoy immense popularity, despite high complication rates and nearly uniform visibility under the skin. The authors hypothesized that a commercially available, thin platinum weight would combat the visibility of the thicker gold weights and herein compare complication rates and visibility rates with literature-reported data for gold weights. Methods: Beginning in 2004, 100 consecutive patients presenting to the authors’ Facial Nerve Center with paralytic lagophthalmos requiring intervention were treated with thin-profile platinum eyelid weights. Ninety-six percent of cases were performed under local anesthesia in the office setting. Results: Median follow-up was 22 months. In 102 weights placed, there have been six complications (5.9 percent): three extrusions, two capsule formations, and one case of astigmatism. All of the extrusions involved irradiated patients with parotid malignancies. Conclusions: The authors report the first large series of thin-profile platinum eyelid weight implantations for the treatment of lagophthalmos. This implant significantly reduces both capsule formation phenomena and extrusion compared with gold weights and should be considered as alternative to the more conventional gold implants.

Assessing Outcomes in Facial Reanimation: Evaluation and Validation of the SMILE System for Measuring Lip Excursion During Smiling

T here is no current consensus for objectively evaluating postoperative smiling outcome. Several objective measurement systems have been proposed, but, owing to their complexity, cumbersome nature, or cost, no single system has been adopted. With such variation in the reporting of results, it is difficult to make comparisons and draw conclusions about the outcome of different surgical techniques. We propose a simple facial analysis system, the scaled measurement of improvement in lip excursion (SMILE), that obviates the need for expensive equipment, facial marking, or prolonged patient cooperation. The system uses the iris diameter (corneal white-to-white diameter) as a scale reference for all facial dimensions on the same photograph. Rüfer et al measured the corneal white-to-white diameter in 390 healthy subjects aged 10 to 80 years with the Orbscan II system (Bausch & Lomb, Rochester, New York). They found the mean(SD)cornealdiameterwas11.77(0.42)mm.Withsuch small variation inhuman irisdiameter, thisbuilt-in scale— inthesameplaneas theoralcommissure—allows“real-life” millimetricmeasurementsofhorizontal toverticalcommissureexcursion tobeextrapolated fromfrontalphotographs using readily available photoediting software.