T.K Fredricks, J.E. Fernandez, and M.A. Pirela-Cruz
From The International Journal of Occupational Medicine an Enviromental Health. Vol 10, 1997
INTRODUCTION
Cumulative Trauma Disorders (CTD) pose a major industrial problems, in terms of increased medical costs, lost productivity and degraded worker health and safety. According to the U.S. Department of Labour Statistics the number of disorders associated with repeated trauma, in 1981 was 23,000 which comprise 18% of all occupational diseases. In 1991, there were 223,600 new cases, which comprise 61 % of all occupational diseases. Hence, the number of reported illness cases have increased both absolutely and proportionally. The staggering rise in the numbers, as well as the associated costs, has lead to a great deal of research in the areas of prevention and early identification of CTD.
Generally, it has been accepted that CTD is a collective term for syndromes characterised by discomfort, disability or persistent pain in joints, muscles, tendons and other soft tissues. Other terms which are also used to describe these disorders include repetitive trauma injuries, repetitive strain injuries muscoskeletal disorders, and occupational overuse syndrome. Since these injuries develop over relatively long periods of time (months or years), it is difficult to determine how often CTD really do occur. CTD are generally considered to be work related. In other words, these disorders tend to be more prevalent among working people than among the general population.
From an anatomical view, Putz-Anderson outlined upper extremity CTD into three major categories: tendon disorders, neurovascular disorders, and nerve disorders. Tendon disorders often occur at or near the joints where the tendons rub nearby ligaments. The most frequently noted symptoms are a dull aching sensation over the tendon, discomfort with specific movements and tenderness to touch. Nerve disorders occur when repeated or sustained work activities expose the nerves to pressure from hard, sharp edges of the work surface, tools, or nearby bones, ligaments and tendons. Neurovascular disorders are those CTD's which are characterised by injury to nerves and adjacent blood vessels.
Up until these categories seemed to cover the proposed spectrum of CTD of the upper extremity, however, Kienbock's disease, a typically less common disease and one that does not fit into the established CTD categories, has been observed to exhibit CTD characteristics (develops in time with repeated stress to wrist) and does not appear in the manufacturing environment (possibly work related). The most common types of employment observed to exhibit individuals with this disease are carpentry, jobs involving the use of pneumatic tools (wrench), spot welders, sheet metal work, farmers and factory workers. The present article makes a critical examination of this disease and proceeds to initiate into the literature a new category of upper extremity CTD: bone disorders.
ANATOMY OF THE WRIST
The hand and wrist are the most active and intricate parts of the upper extremity. Because of this, they are vulnerable to injury and do-not respond well to serious trauma. Their mobility is enhanced by a wide range of movement at the shoulder and complementary movement at the elbow. The boundaries of the wrist are somewhat imprecise, depending on description. It consists of the distal radius and ulna, the proximal ends of five metacarpals, and the intercalated proximal and distal carpal bones. The mobility of the wrist is determined by the shapes of the bones making up this complex as well as by the attachments and lengths of the various ligaments.
The bone element that makes up the wrist joint consist of the distal end of the radius and ulna with their connecting ligaments and the distal radioulnar joint. Beyond this there are eight carpal bones. These bones are small irregularly shaped and conveniently described as being in two rows: the scaphoid, lunate, triquetrum, and pisiform in the proximal row; the trapezium, trapezoid, capitate, and hamate in the distal row.
Movement of the hand and wrist is made possible by the architecture of the joints among the bones. The distal radioulnar joint is a uniaxial pivot joint that has one degree of freedom. Although the radius moves over the ulna the ulna does not remain stationary. It moves back and laterally during pronation and forward and medially during supination.
The deviation between ulna and radius, ulnar variance is of anatomical importance. Gelberman and associates described a method for establishing the degree of ulnar variance. This is done by extending a line from the distal radial articular surface forward toward the ulna and measuring the distance between this line and the carpal surface of the ulna. Another method for determining ulnar variance, proposed by Palmer and associates, involves superimposing a transparent templet with concentric circles over a radiograph of the wrist. The sclerotic cortical rim of the distal radius matches one of the circles, while the distal portion of ulnar head matches one of the other circles. The distance between these two circles is the ulna variance, which is zero or neutral if both the radius and ulna are on the same circle, positive if the ulna is longer, and negative if the ulna is shorter. The radiocarpal (wrist) joint is biaxial ellipsoid joint. The radius articulates with scaphoid and the lunate. The lunate and triquetrum also articulate with the cartilaginous disc and not the ulnar. The disc extends from the ulnar. side of the distal radius (sigmoid notch) and attaches to the ulna at the base of the ulnar. styloid process. The disc adds stability to the wrist through its attachment to the triangular fibrocartilage complex (TFCC). It creates a close relationship between the ulna and carpal bones and binds together the distal end of the radius and ulna. With the disc in place, the radius bears 60 per cent of the load and the ulna bears 40 per cent. If the disc is removed, the radius transmits 95 per cent of the axial load and the ulna transmits 5 per cent . Thus the cartilaginous disc acts as a cushion for the wrist joint. The disc can be damaged by forced extension and pronation. The distal end of the radius is concave and the proximal row of the carpals is convex, but the curvatures are not equal. The joint has two degrees of freedom, and the resting position is neutral with slight ulnar deviation.
The intercarpal joints are considered to be the joints between the individual bones of the proximal row of the carpal bones and the joints between the individual bones and the distal row of carpal bones. They are bound together by small intercarpal ligaments (dorsal, palmar, and interosseous) that allow only a slight amount of gliding movement between the bones. The close packet position is extension, and the resting position is neutral or slight flexion.
Although not described in this section other joints within the wrist and hand which contribute to the functioning system include: the pisotriquetral joint, the midcarpal joints, the carpometacarpal joint, the intermetacarpal joints, the metacarpophalangeal joints, the interphalangeal joints, proximal interphalangeal joints and distal. interphalangeal joints.
ETIOLOGY
The details of lunatomalacia were first reported by Kienbock in 1910. Kienbock's disease is an isolated disorder of the lunate in which there is progressive collapse of the lunate. Often the early stages of the disease are clinically and radiographically indistinguishable from the other causes of wrist pain. It has been noted that in the early stages the radiographs may appear normal which impedes the identification of this disease. However, it is possible for a magnetic resonance imaging (MRI) and bone scans to be positive in the early stages. The injured is usually young, 20 to 40 years old, and may complain of dorsal wrist pain, usually associated with synovitis, limitation of movement and decrease in grip strength . The male to female ratio is two to one. The incidence of bilateral Kienbock's disease is extremely low, and there are two reports of this occurrence.
The various names (lunatomalacia, aseptic necrosis, osteochondritis, traumatic osteoporosis, osteitis) used synonymously for Kienbock's disease are an indication that its exact aetiology remains in dispute. The currently accepted theories state that Kienbock's disease is caused either by repeated minimal trauma or a single acute episode. Repeated minimal trauma as an etiology has been inferred from high incidence of this disease among people whose occupation involves frequent impact to the wrist, such as occurs from using a hammer.
Peste, in 1843, first described collapse of the carpal lunate. His discovery before the development of x-rays, was based on studies of anatomical specimens. He believed the lesion to be a fracture with traumatic etiology. Kienbock in 1910, also thought this lesion to be a result of trauma. He believed that repeated sprains, contusions or subluxations lead to ligaments and vascular injury, resulting in loss of blood supply to the lunate. Since that time numerous authors have described the pathological changes as a vascular necrosis
Acute fracture or trauma as an etiology has been implicated in many series as the majority of patients report a history of injury predating the exacerbation of in place, the radius bears 60 per cent of the load and the ulna bears 40 per cent. If the disc is removed, the radius transmits 95 per cent of the axial load and the ulna transmits 5 per cent . Thus the cartilaginous disc acts as a cushion for the wrist joint. The disc can be damaged by forced extension and pronation. The distal end of the radius is concave and the proximal row of the carpals is convex, but the curvatures are not equal. The joint has two degrees of freedom, and the resting position is neutral with slight ulnar deviation.
The intercarpal joints are considered to be the joints between the individual bones of the proximal row of the carpal bones and the joints between the individual bones and the distal row of carpal bones. They are bound together by small intercarpal ligaments (dorsal, palmar, and interosseous) that allow only a slight amount of gliding movement between the bones. The close packet position is extension, and the resting position is neutral or slight flexion.
Although not described in this section other joints within the wrist and hand which contribute to the functioning system include: the pisotriquetral joint, the midcarpal joints, the carpometacarpal joint, the intermetacarpal joints, the metacarpophalangeal joints, the interphalangeal joints, proximal interphalangeal joints and distal. interphalangeal joints.
ETIOLOGY
The details of lunatomalacia were first reported by Kienbock in 1910. Kienbock's disease is an isolated disorder of the lunate in which there is progressive collapse of the lunate. Often the early stages of the disease are clinically and radiographically indistinguishable from the other causes of wrist pain. It has been noted that in the early stages the radiographs may appear normal which impedes the identification of this disease. However, it is possible for a magnetic resonance imaging (MRI) and bone scans to be positive in the early stages. The injured is usually young, 20 to 40 years old, and may complain of dorsal wrist pain, usually associated with synovitis, limitation of movement and decrease in grip strength . The male to female ratio is two to one. The incidence of bilateral Kienbock's disease is extremely low, and there are two reports of this occurrence.
The various names (lunatomalacia, aseptic necrosis, osteochondritis, traumatic osteoporosis, osteitis) used synonymously for Kienbock's disease are an indication that its exact aetiology remains in dispute. The currently accepted theories state that Kienbock's disease is caused either by repeated minimal trauma or a single acute episode. Repeated minimal trauma as an etiology has been inferred from high incidence of this disease among people whose occupation involves frequent impact to the wrist, such as occurs from using a hammer.
Peste, in 1843, first described collapse of the carpal lunate. His discovery before the development of x-rays, was based on studies of anatomical specimens. He believed the lesion to be a fracture with traumatic etiology. Kienbock in 1910, also thought this lesion to be a result of trauma. He believed that repeated sprains, contusions or subluxations lead to ligaments and vascular injury, resulting in loss of blood supply to the lunate. Since that time numerous authors have described the pathological changes as a vascular necrosis
Acute fracture or trauma as an etiology has been implicated in many series as the majority of patients report a history of injury predating the exacerbation of symptoms. Backenbaugh and coworkers found lines suggestive of fracture of radiographs of 82 per cent of their patients. More and more investigators are documenting the presence of fractures in Kienbock's disease, particularly with tomographic techniques; however, it remains unclear whether these fractures are the cause or the result of a vascular necrosis.
SUMMARY
In summary, CTD is a collective term for syndromes characterised by discomfort, disability or persistent pain in the joints, muscles, tendons, and other soft tissues. The most frequently noted symptoms are a dull aching sensation, discomfort with specific movements, tenderness to the touch, and reduction in grip strength. CTD are generally considered to be work related because they are more prevalent among the working population than the general population. From an anatomical view, 3 major categories, tendon disorders, neurovascular disorders, and nerve disorders, have been used to describe CTD.
Up until recently these categories seemed to cover the proposed spectrum of CTD of the upper extremity, however, Kienbock disease does not fit into the established CTD categories that has been observed to exhibit CTD characteristics. Complaints of dorsal wrist pain, limitation of movement, and decreased grip strength are associated with this disease. The exact etiology remains in dispute, however, one currently accepted theory emphasises repeated minimal trauma as a potential candidate. This theory has emerged due to the high incidence among people whose occupation involves frequent impact to the wrist.
Some similarities between Kienbock's disease and CTD, in terms of aetiology and symptoms, have been established. This relationship is especially unusual since Kienbock's disease does not fit into one of the existing classifications of CTD. Should further similarities exist, as will be illuminated in: "Kienbock's Disease: Risk Factors, Diagnosis, and Ergonomic Interventions. Part II", it is being proposed that a new category of CTD, bone disorders, be introduced into the literature.