Biomedical subjects
Publications and source records attributed to T R Stevenson.
Static suspension remains an option for certain patients with facial paralysis. Endoscopically assisted facial suspension obviates the need for a counter-incision at the oral commissure to distally inset the fascia lata graft as described in the standard technique. The endoscopic technique is simple, allows secure placement of perioral fascial strips, and can be performed as an outpatient.
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A cadaver and clinical study was performed to determine the value of transantral endoscopy in diagnosis and treatment of orbital floor fractures. Six fresh cadaver heads were dissected using a 30 degree, 4-mm endoscope through a 1 cm2 antrotomy. In the cadaver, the orbital floor and the course of the infraorbital nerve were easily identified. The infraorbital nerve serves as a reference point for evaluation of fracture size; three zones of the floor are described that are oriented relative to the infraorbital nerve. In the clinical study, nine patients with orbital floor fracture initially underwent endoscopy at the time of fracture repair: three patients had comminuted zygomatico-orbital fractures, five had monofragmented tetrapod fractures, and one had an isolated orbital blowout fracture. Endoscopic dissection of the orbital fractures revealed seven fractures with an area > 2 cm2 and two fractures with an area of < 2 cm2. The isolated orbital floor blowout fracture had entrapped periorbital tissue, which was completely reduced endoscopically. A separate patient with a < 2 cm2 displaced fracture also had stable endoscopic reduction. In the remaining seven patients, the endoscopic technique assisted with the floor reconstruction by identifying the precise fracture configuration as well as identifying the stable posterior ledge of the orbital floor fracture. There have been no complications in any of our patients to date. We conclude: (1) Transantral orbital floor exploration allows precise determination of orbital floor fracture size, location, and the presence of entrapped periorbita. The information obtained through endoscopic techniques may be used to select patients who would not benefit from lid approaches to the orbital floor and may possibly eliminate nontherapeutic exploration. (2) Transantral endoscopic orbital floor exploration assists the reduction of complex orbital floor fractures and allows precise identification of the posterior shelf for implant placement. (3) Transantral endoscopic techniques can completely reduce entrapped periorbital tissue caught in a trapdoor type of fracture.
The purpose of this study was to compare the arterial blood supply of the lateral face lift flap when the flap is elevated either above or below the SMAS. The transverse facial artery supplies blood to a large portion of the lateral face lift flap. This vessel passes through the superficial musculoaponeurotic system (SMAS) in its course toward the flap. The transverse facial artery is at risk for transection during both elevation of the skin flap and elevation of the SMAS. Nine fresh cadavers underwent a single-plane rhytidectomy either superficial to the SMAS or in a sub-SMAS plane. In half the subjects, the transverse facial artery perforator was identified prior to dissection using surface landmarks and preserved. In the other half of dissected specimens, this perforator was transected by undermining through the transverse facial artery perforation site (near the zygomatic ligament). This transection is typically performed during a face lift. The facial artery and transverse facial artery were selectively injected with ink, and cutaneous staining was recorded. It was found that the pattern and total area of ink staining occurred in an all-or-none fashion depending on whether the transverse facial artery had been preserved or transected. Inclusion or exclusion of the SMAS layer in the dissected lateral face lift flap had no effect on the ink injection pattern, suggesting that the SMAS plays little or no role in lateral face lift flap viability.
It has been well documented that ischemic preconditioning limits ischemic-reperfusion injury in cardiac muscle, but the ability of ischemic preconditioning to limit skeletal muscle injury is less clear. Previous reports have emphasized the beneficial effects of ischemic preconditioning on skeletal muscle structure and capillary perfusion but have not evaluated muscle function. We investigated the morphologic and functional consequences of ischemic preconditioning, followed by a 2-hour period of tourniquet ischemia on muscles in the rat hindlimb. The 2-hour ischemia was imposed without preconditioning, or was preceded by three brief (10 minutes on/10 minutes off) preischemic conditioning intervals. We compared muscle morphology, isometric contractile function, and muscle fatigue properties in predominantly fast-twitch, tibialis anterior muscles 3 (n = 8) and 7 (n = 8) days after ischemia-reperfusion. Two hours of ischemia, followed by reperfusion, results in a 20 percent reduction of muscle mass (p < 0.05) and a 33 percent reduction in tetanic tension (p < 0.05) when compared with controls (n = 8) at 3 days. The same protocol, when preceded by ischemic preconditioning, results in similar decreases in muscle mass and contractile function. Neuromuscular transmission was also impaired in both ischemic groups 7 days after ischemia. Nerve-evoked maximum tetanic tension was 69 percent of the tension produced by direct muscle stimulation in the ischemia group and 65 percent of direct tension in the ischemic preconditioning/ischemia group. In summary, ischemic preconditioning, using the same protocol reported to be effective in limiting infarct size in porcine muscle, had no significant benefit in limiting injury or improving recovery in the ischemic rat tibialis anterior. The value of ischemic preconditioning in reducing imposed ischemic-reperfusion-induced functional deficits in skeletal muscle remains to be demonstrated.
Ten adult cadavers were used to accurately detail the vascular anatomy of posterior thigh skin. Fourteen posterior thigh specimens were dissected after blue latex injection of the internal and external iliac arteries. Six posterior thigh specimens underwent selective dye injection of individual profunda perforating arteries and the inferior gluteal artery. The findings reveal an extensive fascial plexus nourished primarily by fasciocutaneous branches of the first and second profunda perforating arteries and secondarily by a terminal fasciocutaneous branch of the inferior gluteal artery. From 1989 to 1992, 24 posterior thigh fasciocutaneous flaps were performed in 24 patients. There were 5 early postoperative complications (21 percent). All but one patient went on to satisfactory healing and stable wound coverage. Three posterior thigh fasciocutaneous flaps were used successfully despite ligation of their inferior gluteal artery blood supply in a previous surgical procedure. These anatomic and clinical findings confirm the reliability of a posterior thigh fasciocutaneous flap based primarily on the first and second profunda perforating arteries. The posterior thigh fasciocutaneous flap can survive in the absence of a patent inferior gluteal artery. Knowledge of the vascular anatomy extends the clinical applicability of the posterior thigh fasciocutaneous flap to patients who might otherwise be excluded because of prior injury or operative procedure.
This study was designed to define the age-related changes that occur in the F1 cross of the male Fischer 344 and brown Norway rats and to determine if these findings were associated with electrophysiologic abnormalities indicative of motor neuron loss. Contractility, morphologic, and histochemical studies were performed on the tibialis anterior muscles (TA) from 25 male rats at ages 6, 18 and 30-32 months. Tibialis anterior weight was 17% greater in the 18-mo vs 6-mo-old animals, but at age 32 months mean TA weight was 20% less than at 18 months. Other changes at 32 months included a 12% decrease in specific tension and reduced contractile/relaxation velocities of isometric twitches and maximal tetanic tension; findings associated with a 40% decrease in type IIb fiber cross-sectional area. Electrophysiologic studies on 15 rats revealed prolonged H-reflex latencies at 18 and 32 months. Needle electromyography demonstrated abnormal spontaneous activity consistent with peripheral axonal, not motor neuron loss. These findings demonstrate age-related changes in muscle mass and strength that are associated with changes in the peripheral nervous system. These findings are consistent with previous work in homozygous, inbred strains and help to establish the F1 cross of the Fischer 344 and brown Norway strains as a potentially useful rodent model in gerontologic studies of the neuromuscular system.
Experiments were conducted on 36 male, Sprague-Dawley rats. In 10 animals, neurorrhaphy was performed on the peroneal nerve with epineurial repair and, in 11 animals, with a tubular polyethylene nerve guide. The authors tested the hypothesis that, following transient denervation of a skeletal muscle by transection of a peroneal nerve, the restoration of maximum force and of maximum specific force developed after insertion of a tubular nerve guide, will not be different from that developed after microsurgical epineurial neurorrhaphy. The contractile properties of the extensor digitorum longus (EDL) muscle, innervated by the peroneal nerve, were evaluated after an average of 116 days. The maximum tetanic force of EDL muscles with epineurial repair and nerve guide were 84 percent and 75 percent, respectively, of the value for control EDL muscles. The specific forces of the muscles in both groups were not different from the control values. The conclusion is that, following stabilization after transection and repair, each of the two methods was equally effective in restoring the ability of the muscle to develop force.
The technique of combined scapular/parascapular reconstruction of the below-knee stump wound allows three-dimensional contouring of fasciocutaneous tissue into a conical shape. The flap can supply durable cover to the circumference of the stump with good functional results. This technique should be considered for reconstruction of extensive circumferential defects of the below-knee stump.
Bloodless surgical procedures on the extremities are achieved by application of a pneumatic tourniquet. The ischemia produced has deleterious effects on nerve and muscle function. It has been suggested that temporary interruption of ischemia by a reperfusion interval can prevent muscle and nerve injury. We investigated the muscle and nerve response to 3 hours of tourniquet ischemia, with and without a reperfusion interval after the first 2 hours of application, in a rodent model. Morphometric, contractile, and histologic parameters were measured. Tourniquet ischemia, with and without a reperfusion interval, results in muscle injury and a transient depression of muscle function. Introduction of a reperfusion interval reduces the severity of injury and increases the early rate of recovery. However, the later stages of recovery appear to be unaffected by reperfusion.
Microvascular free-tissue transfer is often employed to achieve limb salvage in traumatic leg wounds. Previous experience has shown that one cause of flap failure is placement of the microvascular anastomoses within the zone of injury and subsequent thrombosis. This observation has prompted surgeons to perform anastomoses on the proximal uninjured recipient vessels. However, access to the vessels distal to the injury site is often technically easier. An assessment was made of 23 free flaps used for leg reconstruction to evaluate the success of performing microvascular anastomoses distal to the zone of injury. Twenty-one flaps with distal anastomoses were successful (91 percent). Distally based free-flap reconstruction provides an acceptable alternative to the commonly employed proximal approach.
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The quality of a breast reconstruction is gauged by the symmetry achieved when the reconstructed and opposite breasts are compared. In order to produce a symmetrical appearance, it is often necessary to revise the contralateral, previously unoperated breast. A procedure on the opposite breast can be performed at the same time as breast reconstruction or can be delayed for several months. The purpose of this study was to compare the simultaneous TRAM flap and contralateral breast reduction/mastopexy with the TRAM flap alone according to selected parameters. Our results suggest that performing the combined procedure is safe and yields a satisfactory aesthetic result.
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The consensus in the literature is that fracture healing within the midface occurs via fibrous union. Clinical experience with the surgical correction of established traumatic deformities has not borne this out. An earlier histological examination with human biopsy specimens demonstrated that eventually repair occurred by direct bony union. However, a recent study in a rabbit model challenged this conclusion and indicated that the process of new formation resembles secondary bone formation as in endochondral formed bone. The purpose of our inquiry is to elucidate further the process of midfacial bony repair in an adult male Sprague-Dawley rat model.
Injuries of the fingertip and nailbed require treatment to minimize pain, speed healing, and shorten the time of functional impairment. Alternatives for therapy include simple dressing changes, graft coverage, and flap transposition. The choice of treatment is based on the location and severity of the injury.
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Sternal osteomyelitis complicates recovery in a small number of patients following median sternotomy. Techniques for operative treatment have in common the wide debridement of devitalised tissue and administration of culture-specific antibiotics. The resultant wound can be managed by delayed primary closure or transposition of well-vascularised adjacent tissue. Omentum, pectoralis major muscle and rectus abdominis muscle are suitable for transposition either alone or in combination. Our series is composed of ten patients who underwent rectus abdominis muscle transfer for the treatment of sternal osteomyelitis. The rectus abdominis obliterates dead space in the lower third of the wound, a difficult area to reach with the pectoralis major muscle. Five patients had one rectus abdominis muscle alone transposed, avoiding the aesthetic and functional deficits of pectoralis major transposition and the risks of omental transfer. Wound healing occurred in every case with a minimum of postoperative complications.