The morphology of the abductor pollicis brevis muscle was studied in 20 patients suffering from hand–arm vibration syndrome. The main morphological changes observed were centrally located myonuclei and fibre type grouping (found in all 20 muscle biopsies), angulated muscle fibres (found in 19 biopsies), ring fibres and regenerating fibres (found in 18 biopsies) and fibrosis (found in 17 biopsies). The observed abnormalities are believed to reflect damage to both the muscle fibres and the motor nerve. The changes were related to different vibration exposure parameters. The number of fibres demonstrating centrally located nuclei correlated significantly with the cumulative vibration exposure, while the number of angulated fibres correlated significantly with the total vibration exposure time. This indicates that the vibrating tools may cause direct damage to muscle fibres as well as nerves.

Hand muscle strength was compared between workers regularly exposed to hand-held vibrating tools (n=81) and a non-exposed control group (n=45). Maximal voluntary strengths of hand grip, thumb pinch, thumb palmar abduction and index and little finger abduction were measured. The exposed workers had significantly weaker extrinsic (7%, P<0.01) and intrinsic (19%, P<0.0001) muscles than the controls. Reduced vibration perception was noted in nine vibration-exposed workers who presented with symptoms of hand muscle weakness (P<0.01). Cold intolerance following vibration exposure was found to precede sensorineural and vasospastic symptoms. We therefore postulate that cold intolerance may be a valuable marker for early detection of the adverse effects of vibration. This study emphasizes the need for tests of intrinsic muscle strength in order to evaluate the impairment of hand function observed in vibration-exposed workers.

Six female Wistar rats were anaesthetised and attached to a vibrating table, (80 Hz/32 m/s2) five hours daily for two days. Histological, enzyme and immunohistochemical, and morphometric analyses of the directly exposed and opposite control plantar muscles were made. Neither fibre necrosis nor regenerative activity were seen. The mean (SD) area (micron2) of vibration-exposed muscle fibres was significantly increased compared with controls (682 (274) and 642 (230), p < 0.05). Both type 1 and 2C fibres were significantly larger after vibration (773 (293) and 650 (223) compared with 683 (209) and 579 (149), p < 0.05) while type 2A and 2AB fibres were not significantly enlarged. The percentage of centrally located nuclei was significantly increased after vibration. This study shows that short term vibration can induce changes in size in muscle fibres. We postulate that this is the first indication of a vibration-induced muscle injury that may develop into chronic impairment of muscle function if the exposure continues for an extended period of time.

The early skeletal muscle response to vibration stimulus at two different displacement levels was examined. Twelve rats were anaesthetized and the hind limb was exposed to vibration, 80 Hz, 63 μm rms (root mean square) (group 1) and 40 Hz; 130 μm rms (group 2) for 5 hours/day for 2 days. Cross-sectional areas of vibrated muscle fibres were significantly larger in group 2. Sizes of different fibre types were differently affected: the slow-twitch type 1 fibres were significantly enlarged in both groups, while the fast-twitch type 2 fibres demonstrated a mixed response pattern. Centrally positioned muscle fibre nuclei increased significantly after vibration in group 2. It is concluded that the level of tissue displacement is a crucial factor for development of vibration-induced muscle injury.

The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.

The effects of controlled vibrations of defined frequency (80 Hz), acceleration (32 m/s2 root mean square), and duration (5 hours daily, 2 or 5 days) induced to the hind limb of rats on the regeneration potential in the sciatic nerve after a test crush lesion were determined. Exposure to vibration induced a marked and significant increase in outgrowth length of axons from the crush injury as evaluated after 3 and 6 days with the pinch reflex test. This effect was still observed 1 month but not 3 months after exposure to vibration. Even such a short duration of vibration exposure as 2 days induced an increased length of outgrowth. Such a conditioning effect may be due to local changes in the environment of the axons or to changes in the nerve cell bodies in the dorsal root ganglion. The results indicate that an alarm reaction exists in the nerve at a time point where no structural changes are observed in the nerve. By inducing such a conditioning lesion to nerve tissue, vibration represents a trauma corresponding to a crush lesion or transection of the nerve.

The perception thresholds for vibration stimuli of the hand at seven frequencies (8-500 Hz) were evaluated in 300 patients referred to the Department of Hand Surgery in Malmö during the years 1985-1990 for various types of neuropathy (carpal tunnel syndrome, vibration-induced neuropathy, cervical rhizopathy, brachialgia, ulnar neuropathy, radial tunnel syndrome, and polyneuropathy). A sensibility index was calculated by dividing the integrated area under the obtained vibrogram curve of each object tested (areaT) by that of the corresponding area under a superimposed and age matched reference curve (areaR). Sensibility index of less than 0.8 was regarded as the cut off value. The index and little fingers bilaterally were tested to reflect median and ulnar nerve function. There were considerable variations in patterns of pathology among the various groups of patients. In patients with unilateral carpal tunnel syndrome only 10 patients (23%) had abnormalities limited to one recording, while 21 patients (47%) showed abnormalities in all four recordings. This indicates that an isolated carpal tunnel syndrome may reflect more generalised disease of the peripheral nervous system.

Twenty patients who had been treated with a silicone rubber trapezial implant for degenerative changes in the first carpometacarpal joint were evaluated radiologically and clinically. After a mean follow up of 4.5 years, 11 of the 20 required reoperation and removal of the prosthesis for persisting pain and weakness. In all hands in which the prosthesis remained radiographs showed bone resorption or carpal bone cysts typical of silicone particle synovitis. In the light of these results we now do not recommend this procedure for the treatment of arthritis of the first carpometacarpal joint.

Between 1980 and 1983, 10 patients received high performance silicone rubber condylar implants for the treatment of isolated degenerative changes of the scaphotrapezial joint. Early clinical and radiographic results (at a mean of 15 months) were excellent. Late follow up of these 10 together with a further 11 patients, however, showed migration of the implant and radiological signs of silicone particle synovitis in all but two. We no longer recommend this operation for treatment of isolated arthrosis of the scaphotrapezial joint.

The hind leg of adult rats was exposed to vibrations (82 Hz; amplitude peak-to-peak 0.21 mm) for 4 hours during 5 consecutive days. Light and electron microscopic examination of the plantar and sciatic nerves were done immediately after the exposure period or after a 2- or 4-week recovery period. Light microscopic examination did not reveal any distinct signs of injury. However, ultrastructurally unmyelinated fibers in the plantar nerves showed distinct changes, with deranged axoplasmic structure and/or accumulation of smooth endoplasmatic reticulum. These changes were to a large extent reversible in 2 weeks and appeared normalized after a 4-week recovery period. No ultrastructural changes could be observed in the sciatic nerve. However, when the sciatic nerve was crushed after 5 days of vibration exposure, axonal outgrowth was increased 23% as compared with controls. These findings confirm that vibration induces nerve fiber damage, in this experimental model expressed as a "conditioning effect" contributing to increased regeneration potential of the corresponding neurones.

Peripheral neuropathy represents a well-known complication from long-term exposure to vibration. In the present study an experimental model is presented with the purpose of analyzing the formation of intraneural edema following vibration exposure. Vibration (82 Hz, peak-to-peak amplitude 0.21 mm) was induced in the hind limb of rats by the use of vibrating electric motors during 4 h/d for 5 d. Tracer techniques (with albumin Evans blue and horseradish peroxidase) were used to study the permeability of intraneural microvessels after the vibration exposure on day 5. It was found that the vibration trauma in this model induced epineurial edema in the sciatic nerve. It is hypothesized that the formation of intraneural edema may be an important pathophysiological factor in the occurrence of vibration-induced neuropathy.

Excision of the trapezium is always followed by instability and proximal migration of the first metacarpal base. In the present report, a modification of a previously suggested technique of metacarpal fixation is presented. The base is trapped between the APL- and FCR-tendons by means of a strip from the ECRL-tendon. This technique was applied in 44 thumbs with trapezial arthrosis. Stability and mobility were restored in all thumbs and the results as to strength and freedom from pain were successful in 80%. The suggested procedure is simple both technically and in regard to post-operative care and is particularly suitable in older patients.

Thirteen wrists with Kienböck's disease, stage III or IV, were denervated. Three wrists were examined repeatedly over a period of 2 1/2 years prior to operation, showing the natural course of lunate compression. The remaining 10 wrists were operated on sooner after diagnosis and the lunate compression was compared with the natural compression course. The hypothesis that wrist denervation was detrimental to the lunate was not supported by the present material.

The results of lunate implant arthroplasty are unpredictable and many untoward postoperative problems are encountered. A retrospective review of 19 patients operated on for lunatomalacia (Kienböck's disease) by Silastic (HP) implant arthroplasty suggests that prevention of postoperative scapholunate dissociation seems to be the key to successful results. Knowledge of the predominant role played by the palmar ulnolunate and radiolunate ligaments is important to the understanding of this mechanism. The intrinsic stability accomplished by the geometry of the carpal bones requires adequate ligamentous support. This restraint, however, may be weakened by pre-existing absence of certain palmar fibres, by the disease process or by the surgery. In the present study three operative methods have been assessed: dorsal approach and implant stem fixation; dorsal approach, removal of implant stem and Kirschner-wire fixation; volar approach, removal of implant stem, no internal fixation but palmar capsuloligamentous reinforcement. Consistently good results have been obtained using the latter technique. It seems as if most of the usual postoperative problems of lunate implant arthroplasty can be avoided by this method which warrants continued trial.

Degenerative changes of the scaphotrapezial trapezoidal (ST) joint commonly cause pain and weakness. These patients do not respond to conservative treatment, and for several years effort has been made to find an easy way to relieve symptoms. In a previous report a silicone interposition arthroplasty was described and considered to be a useful method. However, the durability of the elastomer was insufficient, and implant fractures and migration of fragments occurred. Since then the procedure has been modified, and high performance Silastic has been used for interposition. Ten patients have been reviewed, with a follow-up from 6 to 36 months (average 15 months). All patients have had lasting relief from pain and consider they have full hand function, without stiffness or limited thumb or wrist motion. Roentgenographic reviews have neither revealed deterioration nor dislocation or migration of the implant. Untoward bone reactions have not been observed. Implant hemiarthroplasty is indicated only when the degenerative changes are solely confined to the ST joint.