Elbow and Forearm Infections
Normal Elbow and Forearm Anatomy
The elbow and forearm form a functional unit whose primary role is to accurately position the hand in space. The elbow has a long lever arm and moves the forearm and hand 130 degrees covering much of the functional space used in our activities of daily living and in this sense the elbow is considered the most important single joint of the upper limb, second only to the thumb carpometacarpal joint. The functional space is defined as the space directly in front of a person’s body that lies below eye level and above the belly button. Because the elbow joint covers the entire functional space by virtue of its arc of motion, there has never been a satisfactory position to fuse an elbow joint if it were ever destroyed by injury or disease.
The elbow anatomy is best understood by thinking of it in three layers. The first layer is the bony layer, the second layer is the ligament layer and the third layer is the muscular layer within which the arteries and nerves travel.
Elbow & Forearm Elbow Joint Front View & Side View
The first layer is comprised of three bones that unite to form the elbow joint. The elbow joint is located at the lower end of the arm bone (humerus), and the proximal end (towards the shoulder) of the radius and ulna which are the two forearm bones. These three bones allow the elbow to bend (Flex) and straighten (Extend) in a hinged type motion and the forearm to rotate the hand in a palm up (supination) and palm down position (pronation). The joint surfaces of the elbow are covered by hyaline cartilage which forms a cushioned layer that allows for smooth gliding and painless elbow motion.
Elbow & Forearm Ligament LayerElbow Joint Ligament Layer
Lateral Elbow Ligament View Medial Elbow Ligament View
The second layer in the elbow and forearm is the capsular ligament layer made up of collagen tissue. The ligament layer in the forearm is called the interosseous membrane. The collagen tissue forming the elbow joint capsule is normally very thin except on the inside (medial) and outside (Lateral) sides of the elbow where thickenings in the collagen substance form the ligaments of the elbow. These ligaments provide passive stability to the elbow joint keeping the humerus, radius and ulna together, allowing them to function as a unit.
Foerarm Flexor CompartmentForearm Flexor & Mobile Wad Compartments
Elbow Flexor Muscles Elbow Extensor Muscles
The third layer of the elbow and forearm is the muscle layer and is formed by the various muscle groups that pass through the elbow and forearm either originating (beginning) or ending in the elbow and forearm. The muscles of the arm that pass through the elbow include the triceps muscle in the back of the arm and the brachialis and biceps muscles in the front of the arm. The forearm muscles that cross the elbow joint are divided into three compartments with each compartment containing several muscles that work to move the elbow, forearm, wrist and hand in specific directions.
The three compartments are:
- 1. the extensor compartment
2. the flexor compartment and
3. the mobile wad of Henry compartment. The median, ulnar, and radial nerves pass through the elbow and forearm within the muscle layers and innervate the muscles within these compartments as well as, the muscles of the hand.
Pathology
The elbow, like the shoulder is well perfused with ample blood supply allowing for circulating white blood cells to offer excellent protection against infection and, consequently an elbow infection is uncommon. In spite of this however, there a certain conditions can predispose individuals to having an elbow and forearm infection:
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1. A penetrating elbow or forearm injury that is not cleaned and repaired properly or timely. This is why all penetrating injuries should seek medical advice for prophylactic antibiotics, a tetanus booster if one has not been received within a 10 year period for clean injuries and within a five year period for dirty wounds and surgical exploration, debridement of the wound with repair of any injured structures encountered.
2. A Postoperative wound infection is another cause of an elbow infection. During the post-operative period, the fresh wound is covered in sterile gauze until it seals which takes about seven days, to prevent organisms that are normal skin flora from invading the wound and cause an infection. This is why patients after surgery are advised to keep the dressing on and the wound dry for at least one week after surgery.
3. After an elbowjoint replacement (Arthroplasty) there is a risk of infection if similar care is not provided to the post-operative wound. With a joint replacement the risk for an infection is increased because the implant is a foreign object in the human body where micro-organisms can hide and avoid antibiotics. Individuals can also seed an implant in the body from infections elsewhere that travel thought the bloodstream, like a tooth abscess. This is why prophylactic antibiotics are recommended when visiting a dentist for a dental procedure in patients that have undergone a joint replacement.
4. A patient with a weak immune system. Examples includea chronic medical condition like diabetes or kidney failure, a patient with an inflammatory condition on immunosuppressive medication that suppresses the protective effects of the immune system (like rheumatoid arthritis) or a patient with AIDS that has had a penetrating injury, surgery or a blood born infection have increased risk of infection.
Treatment
The treatment of an elbow or forearm infection depends on several factors which include:
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1. The initial cause of the infection
2. Whether the infection is superficial or deep and which tissues are involved
3. The length of time the infection has been present
4. The type of organism causing the infection
5. The general medical condition and nutrition of the patient
6. Whether an implant or other foreign body is present
When an infection is superficial, oral antibiotics, warm soaks and resting the extremity will often resolve the problem. If the infection has spread and lymph node involvement, fever, chills or other systemic causes accompany the infection, hospital admission for intravenous antibiotics, fluids and systemic support is preferred. If the infection is well loculated and fluctuant (soft) it is a surgical condition requiring incision and drainage. When a joint replacement has been done, it is prudent to admit the patient to the hospital for IV antibiotics and have a low threshold for washing out the wound. If the infection of the joint replacement occurs weeks or months after the surgery, the implant is usually removed and later reimplanted after the organism has been identified and IV antibiotics givenfor six weeks. If the patient with a joint replacement has poor health or has a poor immune status, leaving the joint without an implant may be the best option.