William K. Lindsay

Digital flexor tendons: An experimental study: Part I. The significance of each component of the flexor mechanism in tendon healing

Summary Digital flexor tendon healing has been studied. The chicken foot was used for the experimental preparations because it was sufficiently comparable to the human digit. The contribution of each component of the flexor mechanism to the healing process was analysed. The sheath and perisheath tissues contributed little to the actual healing process but were related to adhesion formation. The epitenon and endotenon initiate the process which is finalised by tendon cell activity. The main blood supply to the tendon affected the rate of healing and the adhesion formation but to a degree which was not significant. The relationship of trauma, even that of mild plastic surgery instrument handling, to the repair process was alarming.

Augmentation of blood flow in delayed random skin flaps in the pig: effect of length of delay period and angiogenesis.

Skin capillary blood flow and angiogenesis were studied by radioactive microsphere and morphometry technique, respectively, in delayed random skin flaps in the pig. Skin flaps were delayed for 2, 3, 4, 6, or 14 days. Blood flow was measured 6 hours after complete raising of acute and delayed random skin flaps on the opposite flanks of the same pig. It was observed that the capillary blood flow increased significantly (p less than 0.05) within 2 days of delay compared to the acute skin flaps. This capillary blood flow further increased by about 100 percent between days 2 and 3, started to plateau after day 3, and remained unchanged between days 4 and 14 of delay. This increase in capillary blood flow was mainly in the distal portion of the delayed skin flaps. There was no indication of an increase in the density of arteries in all delay periods studied. Our observations did not support the hypotheses that the delay phenomenon involves angiogenesis or long-term adaptation to ischemia, as have been hypothesized previously. The possible mechanism of delay is discussed.

Dose and time effects of nicotine treatment on the capillary blood flow and viability of random pattern skin flaps in the rat

The deleterious effects of nicotine treatment on skin haemodynamics and survival of 4 X 10 cm acute random pattern skin flaps constructed on the dorsum of the rat were studied. Rats were injected subcutaneously with 0.2 ml of saline containing varying doses (0, 1, 2, 4 or 8 mg kg-1; bid) of nicotine for 5 weeks, starting 4 weeks before flap surgery. It was observed that nicotine treatment at the dose of 2 mg kg-1 (bid), or higher, significantly (p less than 0.05) decreased the length and area of skin flap survival compared with the control. This dose of nicotine treatment also significantly (p less than 0.05) decreased the capillary blood flow and distal perfusion in the skin flaps compared with the control. However, the detrimental effect of nicotine treatment on the survival of acute random pattern skin flaps was not seen if the treatment was started 2 instead of 4 weeks preoperatively. It is concluded that nicotine may cause hypoperfusion and necrosis in acute random pattern skin flap surgery, and the deleterious effects are time-dependent.

Abnormal carotid arteries in the velocardiofacial syndrome: a report of three cases.

Internal carotid arteries of unusual size and tortuosity were found before or at the time of pharyngeal flap surgery in three children who had the velocardiofacial syndrome with velopharyngeal insufficiency. In two cases, medial displacement of the arteries prevented surgery, and in the other, hypernasality persisted because only a narrow, asymmetrical flap could be raised. Medial displacement of the internal carotid arteries inhibits surgical treatment of velopharyngeal insufficiency, necessitating treatment with a prosthetic speech device in such children. Since displacement and tortuosity may be associated Findings in the velocardiofacial syndrome, the exact location of the internal carotids should be ascertained when pharyngeal flap surgery is planned.

Pathogenesis of Ischemic Necrosis in Random-pattern Skin Flaps Induced by Long-term Low-dose Nicotine Treatment in the Rat

The objectives of the present experiments were to study the effects of long-term low-dose nicotine treatment on skin hemodynamics, viability, and microvascular morphology in 4 × 10 cm dorsally based acute random-pattern skin flaps in the rat. In addition, the reversibility of the nicotine-induced detrimental effects on skin-flap viability following cessation of nicotine treatment also was investigated. Low-dose nicotine (0.6 mg/kg) administered twice daily and subcutaneously for 24 weeks significantly (p < 0.05) decreased skin-flap capillary blood flow, distal perfusion, and length and area of skin viability compared with the saline-treated control (n = 15). However, these same parameters in rats (n = 15) whose nicotine treatment had been withheld for 2 weeks prior to skin-flap surgery were not significantly different from the control, thus indicating that the detrimental effects of this long-term, low-dose nicotine treatment were reversible. The mean plasma level of nicotine in the nicotine-treated rats was 8.1 ± 0.4 μg/dl and was within the range of plasma nicotine levels reported for human heavy cigarette smokers. Light and electron microscopic studies did not show evidence of histologic damage to the cutaneous microvasculature in acute random-pattern skin flaps and samples of normal (nonoperated) skin in nicotine-treated rats. It is concluded that long-term plasma levels of nicotine similar to those of heavy cigarette smokers are detrimental to the capillary blood flow and viability of random-pattern skin flaps in the rat. These deleterious effects can be avoided if skin flaps are raised 2 weeks after cessation of nicotine treatment. This low-dose nicotine treatment does not cause histologic damage to the microvasculature. Other pathogenic mechanisms of nicotine-induced skin flap ischemia are discussed.

Functional, Mechanical, and Biochemical Assessment of Ultrasound Therapy on Tendon Healing in the Chicken Toe

We studied the therapeutic effect of ultrasound treatment on the functional recovery of surgically repaired profundus tendon in the right third toe of mature White Leghorn hens. Ultrasound treatment was given daily for 5 minutes for a total of 20 treatment days, starting immediately after 4 weeks immobilization. Ultrasound (frequency 3.0 mHz; intensity 0.75 W/cm2) was delivered to the right leg by a 5-cm2 probe through distilled water in a bath kept at 35°C. The flexion of the toe was measured preoperatively for 4 consecutive days and daily for 6 weeks after the start of ultrasound treatment for the calculation of percent of functional recovery of the flexor tendon. The non-ultrasound-treated group of birds went through the same manipulations except that no ultrasound was given when the right leg was immersed in the water bath. Ultrasound treatment significantly (p < 0.01) improved the functional recovery of the repaired tendons (<5-mm gap) starting on the third week of treatment (94 ± 2 percent) compared with the non-ultrasound-treated group (79 ± 4 percent). Ultrasound treatment had no effect on gap formation or breaking (tensile) strength of the repaired tendons. It is concluded that ultrasound enhanced functional return of repaired flexor tendons in the hen, and the clinical implication is discussed.

Digital flexor tendons: An experimental study: Part III The fate of autogenous digital flexor tendon grafts

Summary A series of tendon grafts have been studied in the digital sheath region in chickens. While functional results were poor, histological studies indicate that the graft as a whole survives, and is reconstructed by a process of repair—by an increase in numbr of mature fibroblasts, a revascularisation of the graft and a gradual reconstitution or replacement of the original collagen. At the sutured or injured ends, however, union is accomplished by a process of regeneration: the collagen fibres of the acellular tissues are lysed and the spaces so formed are filled in with new vascular fibrogenic tissue which later becomes orientated and mature.

Deferoxamine attenuates ischemia-induced reperfusion injury in the skin and muscle of myocutaneous flaps in the pig

&NA; The dose effect of deferoxamine treatment in attenuation of ischemia-induced reperfusion injury in the skin and muscle of latissimus dorsi myocutaneous flaps was studied in pigs weighing 19.7 ± 0.5 kg. The latissimus dorsi myocutaneous flaps were subjected to 4, 6, or 8 hours of warm global ischemia. The length and area of viable and nonviable skin and muscle were assessed 48 hours after the ischemic insult by using the fluorescein and nitroblue tetrazolium dye tests, respectively. It was observed that perioperative deferoxamine treatment (250 mg/kg IV) was effective (p < 0.05) in attenuation of ischemia-induced reperfusion injury in the skin but not in the muscle of latissimus dorsi myocutaneous flaps subjected to 4, 6, or 8 hours (n = 10) of ischemia compared with the saline-treated control (n = 10). In a separate study, it was observed that preoperative deferoxamine treatment (250 mg/kg per day × 2 days, IM) plus perioperative deferoxamine treatment (250 mg/kg IV) was effective (p < 0.05) in attenuation of muscle ischemia-induced reperfusion injury in latissimus dorsi myocutaneous flaps subjected to 4 hours of ischemia and 48 hours of reperfusion (n = 10) compared with the saline-treated control (n = 10). Morphologic studies with light and electron microscopy also provided evidence to indicate that preoperative plus perioperative deferoxamine treatment, but not perioperative deferoxamine treatment alone, remarkably reduced ischemia-induced reperfusion injury in the skeletal muscle of latissimus dorsi myocutaneous flaps compared with the saline-treated control. It is concluded that deferoxamine is effective in the attenuation of ischemia-induced reperfusion injury in the skin and muscle of pig latissimus dorsi myocutaneous flaps, but a longer period and/or higher dose of deferoxamine treatment is required for the muscle than for the skin. The pharmacologic actions and metabolism of deferoxamine relating to mitigation of ischemia-induced reperfusion injury in the pig skin and muscle are discussed.

Congenital giant pigmented nevi: Clinical features and risk of malignancy

MJ Weinberg, M Al-Qattan, RM Zuker, HG Thomson, WK Lindsay. Can J Plast Surg 1996;4(2):94-98. There is general agreement that congenital giant pigmented nevi (CGPN) are precursors to malignant melanoma; however, the magnitude of the risk of malignant transformation is the subject of wide controversy. The goal of this study was to present the authors’ experience with CGPN and more specifically their experience with the risk of malignancy. To identify the general features of CGPN a detailed retrospective chart review was performed at The Hospital for Sick Children in Toronto (1979 to 1994, n=84). There were 39 boys and 45 girls. The average size at presentation was 5.24% of the body surface area, and 36.9% of the nevus were located on the head and neck. An important finding was the high percentage of associated extra cutaneous disorders in patients with CGPN (23%) including a case of leptomeningeal melanocytosis. Tissue expansion was the most commonly used treatment modality. One case of malignant melanoma arising from CGPN was identified. To ensure that all cases of malignant melanoma were identified in this cohort, a questionnaire was sent to all plastic surgeons in Ontario (n=118), and data from the Ontario Cancer Registry were reviewed using the diagnostic codes for malignant melanoma and for pigmented nevus. One case of malignant melanoma was identified in all records. Thus CGPN poses a significant management challenge to the plastic surgeon and the risk of malignancy is low.

Effect of Glucocorticoid Treatment on Skin Capillary Blood Flow and Viability in Cutaneous and Myocutaneous Flaps in the Pig

The effect of methylprednisolone treatment on skin-flap viability and capillary blood flow was studied in a series of four experiments. Intramuscular methylprednisolone injections (30 mg/kg per day), given in single or divided doses preoperatively or postoperatively, had no effect in augmenting skin viability in arterialized cutaneous, myocutaneous, or random skin flaps compared with the control. Capillary blood flow was studied in arterial buttock flaps and latissimus dorsi myocutaneous flaps raised on animals treated preoperatively with methylprednisolone or saline (control), and no significant difference in capillary blood flow was noted between the treatment and control flaps. It was concluded that methylprednisolone has no significant therapeutic effect either in increasing flap viability or in increasing capillary blood flow in skin flaps in pigs.