The Elbow
Anatomy
The elbow is a 'ginglymus' or hinge-joint (see Figure 1.0) connecting the distal or lower end of the humerus to the proximal ends of both the ulna and the radius. The joint of the elbow consists of the humeral head, the capitellum which articulates with the greater sigmoid cavity of the ulna, and the cup-shaped depression in the head of the radius. These articular surfaces are covered with a thin layer of cartilage that prevents bone rubbing. The joint is stabilized by the anterior, posterior, internal lateral, and external lateral ligaments which encompass the joint and the cartilage that surrounds the joint. The motion of the elbow joint is approximately 160 degrees along its long axis. This motion of the elbow is achieved by the flexion and the extension of the various muscles that connect to the elbow (Clayman 1989).
The bones that come together to make up the elbow joint, while different in size and shape all have similar osteologic characteristics. Bone can be broken down into four main types of distinctly different tissue. Figure 2.0 points out these parts of the bone. The epiphysis is the tissue that makes up the knob or the end of the bone where a joint occurs. This tissue is covered by the periosteum, which is a cartilage layer covering the outside of the bone. The diaphysis is the central part or shaft of the bone. Running perpendicular to the bone shaft and through the epiphysis is the epiphyseal plate which is the cartilage layer more commonly known as the growth plate (Gray 1974). The epiphyseal makes new cartilage that moves into the inside of the epiphysis where it becomes hard bone by a process called ossification. Under the surface of the epiphysis lies tiny capillaries which supply the head of the bone and the epiphyseal with nutrient blood (Clayman 1989).
Forces Applied to the Elbow Joint
A force is an influence on a body that causes a change in motion or shape of the body. The elbow takes compressional, rotational, and shearing forces and displaces them into the normal motions of the elbow. When the arm is bent, in a state of flexion, the forces of pressure that run across the elbow joint transfer force between the humerus to the ulna. Conversely, in a state of extension, the arm is open in a straight position and the forces are applied across the humerus and the radius (Weiker 1993). The surface area of the radial head is much smaller than that of the ulna; therefore, the humerus places a greater force per unit area on the radius as opposed to the ulna. As Figure 3.0 shows, these forces on the straight elbow are intensely focused on the radial head.
The process by which the elbow displaces these forces is very complex. For the most part, the ligaments and muscles take these stresses and dissipate them. The articluar cartilage in the elbow also works as a buffer between the bones so that the bones do not absorb these strains. If the cartilage were called upon to take an enormous stress over a period of many trials, the cartilage would flatten and become worn quickly (Siffert 1981). This result occurs frequently in the elbows of many gymnasts, and this force loading on the radius can cause a whole host of pathological problems, one of which is Osteochondrosis Dissecans.
Osteochondrosis Dissecans
Nature of the Condition
Osteochondrosis Dissecans is a condition where the capillaries that are in the tissue of the head of the radius are damaged so much that they do not bring the necessary nutrients to the bone and the bone eventually dies. Osteochondrosis Dissecans is usually characterized by the separation of a bone fragment from the bone within the joint capsule and its subsequent reattachment or 'loose body' formation which inhibits normal movement of the joint. Osteochondrosis is distinguished by the abnormal ossification of the epiphyseal causing a malformed epiphysis because of stresses applied to the articular region. The articular or joint surface becomes rough and irregular because of this disorderly bone formation and calcification (Jawish 1993). Very often repetitive trauma to the elbow results in necrosis, or selective death of tissue of the bone which produces cracks in the bone called lesions. These lesions can crack off pieces of bone that develop into 'loose bodies' in the joint. This process is very painful and is usually accompanied by an inflammation of the area.
Occurrence of the Condition
Osteochondrosis affects many different areas of the body and many different people. Osteochondrosis Dissecans is more common in males than females. Also it is more prevalent in young people because their bones have not completely developed. In young bone, the growth at the epiphyseal is very important to proper bone formation. When extreme trauma disrupts this growth at the epiphyseal, the occurrence of Osteochondrosis and other osteopathic conditions increases. The age group to show the highest incidence of this condition is 10- to 20-year olds. This may be due to the high amount of activity coupled with the fast growth of the epiphyseal that is characteristic of this age range (Jawish 1993).
There are many other sites for Osteochondrosis Dissecans other than the elbow. It occurs very frequently in the knee and is by far the most common in the hip joint. Famed football and baseball player Bo Jackson was forced to stop playing footbal because of Osteochondrosis of the hip.
One group besides gymnasts that is at a high risk of Osteochondrosis Dissecans of the elbow is baseball pitchers. The whip-like activity of pitching a baseball places eccentric and excessive strain on the elbow. Osteochondrosis Dissecans is especially common among Little League pitchers. Because their developing bones are very sensitive at the growth areas, the motions of throwing a baseball really take a toll on their bone formation and articular regions (Siffert 1981).
Progression of the Condition
The damage caused by continual traumatic loads on the elbow is first characterized by inflammation and soreness. After a while, the inflammation becomes more frequent and the pain becomes more intense. If the person does not stop the activity which caused the inflammation, the articular incongruity may continue and result in an epiphyseal fragmentation. This fragmentation can lead to a 'loose body' in the articular region that could inhibit the range of motion and in some cases prevent all motion. The necrotic bone loses its structural support and may flatten the articular region, causing problems that are almost incurable. If this happens, the dead bone creates a very uneven and rough joint surface, where bone rubs bone and makes joint movement very painful (Bruns 1993).
Treatment
The incidence of cases of Osteochondrosis is rapidly increasing; however, the research conducted thus far on the condition has been superficial. Consequently, the prevention and the treatment of "Osteochondrosis" are relatively underdeveloped areas of knowledge.
Although many methods for treating Osteochondrosis Dissecans have been tried, they have been specific to the individual case. Most often, physicians diagnose the disease, given its painful symptoms, before any articular malformation occurs, and treatment involves discontinuing all activity involving that joint. If the condition has evolved past this stage, then, depending on the case, two surgical options are available. If loose bodies appear in the joint, physicians can perform arthroscopic surgery to remove those fragments and perhaps smooth out the bone surface. In extreme cases where the cartilage degeneration and articular incongruity is large, the methods of drilling and possibly grafting the affected area are used to prevent further loss (Bruns 1993). The bone graft, which involves placing healthy bone from one part of the body to a damaged area to encourage bone growth in that area, has been the most successful.
To completely understand the mechanics involved in this condition, further research must be done to determine the type of pressure causing the necrosis and the forces the joint can withstand without pathological damage. If the points of pressure on the bones can be identified, perhaps a brace for the exterior of the body can be designed to alleviate some of the stress. With this knowledge, a brace could be made or a technique of alleviating the stress could be created so that the grace and beauty of gymnastics can be enjoyed without the pain.
Works Cited
Bruns, J. Sonographic Imaging at the Elbow Joint - Loose Bodies and Osteochondritis Dissecans. Ultraschall in Der Medizin, 1993.
Clayman, Charles B., MD Encyclopedia of Medicine. New York: Random House, Inc., 1989.
Gray, Henry, F.R.S. Gray's Anatomy Philadelphia: Running Press, 1979.
Jawish, R. "Osteochondritis Dissecans of the Humeral Capitellum in Children". European Journal of Pediatric Surgery. 1993.
Siffert, Robert S. "The Osteochondrosis Symposium". Clinical Orthapaedics and Related Reaserch no. 158, Philadelphia: J.B. Lippencott, 1981.
Weiker, Gerald MD. Personal interview 14 September 1993.