Conditions Arising from Repetitive Trauma and Occupational Vascular Problems

Clinical Findings and Risk Factors

The Stockholm Workshop Scale staging system is presented in Table 184.1 . This scale is a modification of the original Taylor–Pelmear scale. Significant changes include a simplified classification scheme, with removal of level of functional disability, seasonal and subjective neurological criteria from the original scale. Classically, the distal tips of one or more fingers experience attacks of cold-induced, vasospastic blanching. With continued progression, the affected area increases in size, and the blanching extends proximally to eventually span the entire digit. Attacks of white finger typically last approximately 1 hour and terminate with reactive hyperemia (red flush) and considerable pain. Prolonged cold exposure may induce bluish black cyanosis in the affected fingers. Only approximately 1% of cases progress to ulceration or gangrene.

Vibrating handheld machines (e.g., pneumatic hammers and drills, grinders, and chain saws) have been implicated in HAVS. Such injury potential is not restricted to a few types of tools but applies to a variety of situations in which workers’ hands are subjected to transmission of vibration energy. There appears to be a linear relationship between the acceleration exposure dose (amount of acceleration and years of exposure) and the onset and HAVS severity.

The exact mechanism of injury is unknown. The frequency and intensity of vibration affect the extent of damage to the endothelium. Local platelet adhesion seems to be an important factor in arterial occlusion. It has been shown that sympathetic hyperactivity, in combination with local factors such as vibration-induced hyperresponsiveness of the digital vessels to cold, may be responsible for the finger-blanching attacks. In those with exposure to vibration injury, appearance of symptoms has also been correlated to smoking status. Lower levels of serotonin, as well as polymorphism variants of the HTR1B, have also been shown to increase susceptibility to symptoms. Studies have shown that vibrational energy releases endothelin-1, a potent vasoconstrictor, impairing nitric oxide release from the damaged endothelium.

Diagnosis

Key features in the history include use of vibrating tools and symptoms of Raynaud phenomenon. For a vasospastic condition, the most promising single objective test is cold provocation and recording of the time until digital temperature recovers (see Ch. 20 , Clinical Evaluation of the Venous and Lymphatic Systems). Digital artery occlusion is best detected by recording the systolic pressure of the affected fingers with transcutaneous Doppler ultrasound or duplex scanning. In advanced disease, arteriography is helpful. Barker and Hines documented arterial occlusion by brachial arteriography in workers who complained of hand blanching and attacks of numbness. Other authors have reported on the use of arteriography in this injury. Use of magnetic resonance imaging is described by Poole and Cleveland to differentiate HAVS from hypothenar hammer syndrome.

Arteriographic changes can include multiple segmental occlusions of the digits and a corkscrew configuration of vessels in the hands. The extent of digital artery occlusion appears dependent on the frequency and duration of exposure. Of 80 workers (chippers) with HAVS investigated at the Blood Flow Laboratory at Northwestern University, 25 (31%) exhibited a significant reduction in systolic pressure in one or more digits. In 6 of the 25 workers, arteriography showed digital artery occlusion ( Fig. 184.1 ). Incompleteness of the palmar arch was seen not only in the symptomatic hand but also in the contralateral, asymptomatic one. Raynaud phenomenon was present in 73 of 80 workers (91%). An abnormal cold response was observed in 53% of these workers.

Treatment and Prevention

With onset of neurovascular symptoms that interfere with social or work activities, the initial treatment is discontinuation of use of vibratory tools. Other preventable causes of vascular injury, such as smoking, should also be discontinued. In advanced cases, calcium channel blockers such as nifedipine (30–120 mg daily) may be useful. Calcium antagonists inhibit the response of arterial smooth muscle to norepinephrine and have been reported to be effective. Intravenous infusion of a prostanoid (prostaglandin E1, prostacyclin, or iloprost) is usually reserved for patients with digital gangrene. Surgical treatment, such as cervical sympathectomy or digital sympathectomy, is rarely needed.

Prevention is likely to be more effective than treatment. Personal protective equipment, such as anti-vibration gloves that limit exposure to cold and dampen transmission of vibration, should be used. Standards that limit the dose and duration of exposure to vibration have been set in place for factories and workplaces in the United States and internationally.