Although upper-extremity vascular disorders are less common than lower-extremity disorders, they nonetheless affect approximately 10% of the population. Causes of vascular compromise include the following:
General symptoms following vascular compromise include the following:
The vascular system plays the critical role of delivering nutrients and clearing metabolic waste products from peripheral tissues, as well as maintaining systemic core temperature. Vascular flow is controlled by various processes, including vessel anatomy; vascular tone, which is controlled by neuroendocrine hormones along with autonomic nervous influence; and end-organ metabolic requirements. Unfortunately, vascular competence can often become compromised, leading to various disease pathologies.
It is of the utmost importance to stress to patients with vaso-occlusive disease that their vascular pathology may or may not be curable. In general, generalized vaso-occlusive disorders cannot be cured, whereas focal vascular disorders often are curable. Therefore, any treatments provided, whether conservative or surgical, may only be temporizing measures.
NextMultiple factors determine vascular flow, including the following:
Vasoconstriction can result from increased sympathetic tone or alpha-adrenergic–stimulating humoral mediators, such as norepinephrine. In contrast, vasodilation may be prompted by parasympathetic tone (inhibiting the sympathetic tone), release of nitric oxide by endothelial cells, or myogenic autoregulatory mediators arising from increased cellular waste products, such as adenosine.
Considerable interest has been focused on the effect of endothelium on vascular tone, because of its capacity to produce two competing molecules: nitric oxide, a vasodilatory, endothelium-derived relaxing factor, and endothelin, a potent vasoconstrictor. Sympathetic nerves typically penetrate the arterial and venous walls, affecting the muscularis component at frequent intervals. These nerves travel variable distances in peripheral nerves prior to entering the perivascular adventitia.
In vasospastic disorders, abnormal vascular control can arise from abnormal receptor expression or from response to agonists, abnormal levels of local humoral mediators, aberrant myogenic and metabolic control mechanisms, and overwhelming sympathetic tone. In contrast, vascular insufficiency may result from physical trauma to vessels, with resulting transection or thrombotic or embolic sequelae.
Ultimate interstitial flow is determined by the pressure gradient across a single vascular lumen, as well as the total (potential) capacity of the arteriolar-capillary-venular bed. Vasospasm, which is observed in hypothenar hammer syndrome and Raynaud disease, may cause pressure gradients to fall below critical levels without affecting the total capacity of the vascular bed.
In contrast, peripheral occlusive diseases, such as those seen in scleroderma, impede the pressure gradient as well as the total potential capacity of the vascular bed. This distinction is important because it affects indications for treatment and prognosis after surgery or other interventions.
Environmental factors, such as external toxins and ambient temperatures, affect vascular patency. This is of interest because the interaction between the external environment and the internal autonomic system has dynamic interplay. For example, for a period following digit replantation, the external temperature may affect inflow pressures at the amputation site but will not affect the vessels of the amputated part, since the sympathetic system of the adventitia will have been disrupted.
In most patients, the dominant blood supply to the hand is provided by the superficial palmar arch, a continuation of the ulnar artery, and to a lesser degree by the deep palmar arch, a continuation of the radial artery. Minor blood supply to the hand is provided for by intraosseous channels via the radial and ulnar bones, as well as by the median artery, which is present in a minority of patients.
In approximately 80% of patients, the deep and superficial palmar arches are connected and are referred to as complete. This results in a dual perfusion supply to the common and proper digital vessels. This is an important attribute of hand vascular architecture, providing collateral blood flow in the event of vascular pathology affecting one of these palmar arches.
The vascular supply to the thumb is unique and includes sources directly from the radial artery and from the deep and superficial arch. In addition to its direct supply, the radial artery gives rise to a large dorsal artery, which passes distally to supply the thumb. The palmar blood supply to the thumb is provided by the princeps pollicis artery, which is derived from the first palmar metacarpal artery, the deep arch, the wrist dorsal metacarpal artery, or a terminal branch of the superficial palmar arch.
The four terminal arteries to the thumb are the ulnar and radial palmar arteries and the ulnar and radial dorsal arteries. Vessels have been categorized arbitrarily based on their diameter and include macrovessels measuring 100 μ m or greater in diameter versus microvessels measuring less than 100 μ m.
Human skin provides the termination of the microcirculation, composed of nutritional papillary capillary beds, as well as nonnutritional thermoregulatory vessels. Interestingly, in normal physiology, 80-90% of microcirculation passes only through thermoregulatory vessels.
General symptoms following vascular compromise include dysesthesias, paresthesias, pallor, cold intolerance, ulceration, and tissue necrosis. Vascular competence can often become compromised, leading to various disease pathologies.
No current findings identify any one race as having a particular propensity for developing vascular occlusive syndromes.
The onset of vascular occlusive disorders is affected by the sex of the patient. For example, Raynaud disease affects women aged 30-50 years. In contrast, males are affected in a bimodal fashion. Acute traumatic vascular disorders are more common in younger males because of the high incidence of motor vehicle accidents in this age group. In contrast, repetitive traumatic vascular disorders occur most often in middle-aged males who are employed in manual-type labor. In the latter case, the labor usually involves handheld vibrating tools that cause chronic trauma.
Patient age also determines propensity for vascular occlusive disorders. As mentioned above, Raynaud disease affects women aged 30-50 years. Males have a bimodal affliction, with young males (because of the high incidence of motor vehicle accidents among them) most often suffering acute traumatic vascular disorders and middle-aged males (specifically, those involved in manual-type work) being most frequently affected by repetitive traumatic vascular disorders.
Clinical Presentation
Copyright © www.orthopaedics.win Bone Health All Rights Reserved
