This is about understanding the arrangement of the structures in the anterior elbow. This is an anatomy video, but this can also help surgeons in knowing how to approach the insertion of the distal biceps for repair or how to approach the proximal radius fracture anteriorly. If you look at the bony structures of the anterior elbow, you need to find out where the common flexor tendon origin is, where the brachialis muscle is inserted, and where the biceps is, supinator and the pronator teres located. These structures are definitely part of the anterior elbow. The cubital fossa is a triangular depression located in front of the anterior elbow. The medial border is formed by the pronator teres, which arises from the medial epicondyle of the humerus. The lateral border of the cubital fossa is formed by the brachioradialis muscle which arises from the lateral supracondylar ridge of the humerus. The meeting of these two muscles forms the apex of the cubital fossa. The brachioradialis muscle overlaps the pronator teres, so the lateral border overlaps the medial border. The base of the cubital fossa is superior and is represented by a horizontal line connecting the two epicondyles of the humerus, the lateral and medial epicondyles.
Structures Located In and Around The Cubital Fossa
The base of the cubital fossa is seen as an imaginary line drawn between the medial epicondyle and the lateral epicondyle of the distal humerus. The pronator teres is the medial border, and the brachioradialis muscle forms the lateral border. The contents of the cubital fossa from medial to lateral are median nerve, brachial artery, biceps tendon, and radial nerve. The floor of the cubital fossa is made up of the lower part of the brachialis muscle medially and the supinator muscle laterally. The roof of the cubital fossa is made up of skin, fascia, and the bicipital aponeurosis.
The median nerve disappears by entering the forearm between the two heads of the pronator teres muscle. The brachial artery bifurcates into the ulnar artery and the radial artery. The brachial artery is over the brachialis muscle. The ulnar artery leaves the fossa by going under the deep head of the pronator teres muscle. The deep head of the pronator teres muscle separates the median nerve, which goes between two heads of the pronator teres muscle from the ulnar artery, which goes deep to the deep head of the pronator teres muscle. Another branch that is in the cubital fossa is the radial artery. The radial artery descends laterally and is overlapped by the brachioradialis muscle. The biceps tendon is lateral to the brachial artery within the cubital fossa. The biceps tendon has one main insertion laterally to the radial tuberosity and another insertion going medially to the bicipital aponeurosis. The bicipital aponeurosis covers and protects the vital structures medially to the biceps tendon (brachial artery and median nerve). The biceps tendon passes backwards (twisted) towards its insertion into the radial tuberosity. Lateral to the biceps tendon is the radial nerve and its major branch, the posterior interosseous nerve. Other important nerves in the vicinity of the cubital fossa include the superficial radial nerve which is below the brachioradialis and the lateral cutaneous nerve of the forearm which is a branch of the musculocutaneous nerve and lies below the biceps proximally and then finally lies laterally.
The best way to prevent surgical site infection, is optimizing the patient prior to surgery. The physician will want to make sure that the patient is nutritionally fit. Specific protocols will need to be followed for patients with conditions such as diabetes, are overweight, or who smoke. It is also important to improve the skin and soft tissue condition (area where the incision will be). The physician should try to reduce the bacterial burden that the patient is carrying. Immediately before surgery, the patient should be given prophylactic preoperative antibiotics and try to decrease the contamination in the operating room. The patient may bring organisms on themselves into the operating room (about 80% of these organisms are brought in by the patient). A screening for Methicillin-Sensitive Staphylococcus Aureus (MSSA) or Methicillin Resistant Staphylococcus Aureus (MRSA) and decolonization. Identifying the patients carrying diseases and treating the condition prior to going into the hospital will reduce the infection rate. Once patients are in the hospital, it is possible for them to spread bacteria to other patients. The best way to prevent the spread of bacteria is with PROPER HAND WASHING PRACTICES!
How can we decrease the bacterial burden of the patient bringing these organisms to the operating room? What are the tests that we should do? How can we help the situation when the patient is in the clinic or in the office?
The patient should be screened for MSSA or MRSA and then a decolonization should be done. Some patients have large reservoirs of bacteria (carriers) and these are the patients who will have an increased risk of surgical site infection. These reservoirs are located in the nose, axilla, groin, and perianal area. These patients will need to be identified so the bacteria can be eradicated and the risk of surgical site infection can decrease. Being a MRSA carrier will increase the chances of infection (about 10x more risk for surgical site infection). You wouldn’t know that the patient is a MRSA carrier unless you test them. It is important to identify these MRSA carriers so that proper antibiotics can be given. A MRSA “carrier” is an individual who can carry the bacteria without necessarily becoming ill. About 2% of the population are MRSA carriers.
MRSA is a contagious bacteria that is difficult to treat because it is resistant to most commonly used antibiotics. In the bacteria cell wall, there is a penicillin binding protein. When penicillin is able to bind to the binding protein of the cell wall, disruption of the cell wall and destruction of the bacteria is possible. However, if the staph aureus acquires the mecA gene, then it can alter the penicillin binding protein, making the bacteria resistant to all penicillin. The primary way of transmitting MRSA is through direct contact from another person, an object that has it, or from sneeze droplets of an infected person. 30% of staph bacteria lives in the nose. About 25-30% of the population is colonized with S. aureus.
This means that the bacteria is present; however, it is not causing an infection with S. aureus. Ironically, if you are a carrier, you are only 6 times as likely to receive an infection, while non-carriers are 10 times as likely. MRSA carriers are diagnosed by examining a swab or culture of the nose. The physician will want to identify these patients before bringing them to the hospital, and eradicate or decolonize the organisms by using a 2-4% chlorhexidine bath for 5 days. The patient should leave the chlorhexidine on the surface of the skin (it works better if kept on for a longer time), so it is better not to wash it off. A 2% nasal mupirocin for five days may also be used. By the screening and eradication program, you can drop the infection rate by about 40-60% or more depending on the compliance of the patient. Our institution showed that empiric treatment is less costly than S. aureus screening and decolonization in total joint arthroplasty patients. They find that the cost is much less than the cost of the standard screening and decolonization of the S. aureus. They found that the empiric treatment allows for more efficient workflow without compromising the patient.
The biceps muscle is attached to the bone at the elbow. The biceps muscle is inserted into the radial tuberosity by the distal biceps tendon. The biceps muscle is responsible for some elbow flexion and is the primary supinator of the forearm. Supination is the function used when turning a key or a door knob. The biceps muscle is responsible for over 50% of forearm supination. Rupture of the distal biceps tendon involves flexion of the elbow against resistance with eccentric loading and sudden tearing of the tendon. The muscle may retract into the upper arm causing a bump or “Popeye” sign. If the ruptured tendon is not repaired, the patient will lose the ability to supinate the forearm adequately. Injury to the lateral antebrachial cutaneous nerve may occur when treating a distal biceps tendon rupture. The lateral antebrachial cutaneous nerve lies between the brachialis and biceps muscles. The nerve can become injured from aggressive retraction. The lateral antebrachial cutaneous nerve originates cutaneous nerve originates from the musculocutaneous nerve. Injury to the nerve results in loss of sensation along the radial aspect of the forearm.
Treatment of a distal biceps tendon injury usually requires surgery due to the important supination function of the biceps muscle. Surgery may be done in the form of a single anterior incision or a two incision technique. Both of these techniques have their advantages and disadvantages. The anterior approach is easier with minimal risk of synostosis; however, there is a risk of injury to the posterior interosseous nerve. The two incision approach has less risk of injury to the posterior interosseous nerve, however there is a risk of synostosis. The lateral antebrachial nerve is the nerve most commonly injured during repair of a distal biceps tendon rupture regardless of the technique that is used. When treating the distal biceps tendon rupture, identify and protect the lateral antebrachial cutaneous nerve. Diffuse pain and paresthesia in the forearm after distal biceps tendon repair should be investigated for lateral antebrachial cutaneous nerve injury. In this situation, the nerve may need to be explored.
What is Lumbrical Plus Finger?
Lumbrical plus finger is a paradoxical extension of the IP joint when attempting finger flexion. It is usually caused by disruption of the flexor digitorum profundus tendon distal to the lumbrical origin. The lumbrical muscles in the palm of the hand arise from the tendons of the flexor digitorum profundus and are inserted into the dorsal extensor expansions on the backs of the proximal phalanges of the fingers. The flexor digitorum profundus tendon to the index finger is most commonly separate from the conjoined tendons to the long, ring, and little fingers. The flexor digitorum prfundus for the long, ring, and 5th finger share a common muscle belly. The patient cannot independently flex two digits without flexing the third digit.
The function of the four lumbricals (with help from interosseous muscles) is to flex the metacarpophalangeal joints and extend the interphalangeal joints. Contraction of the lumbricals relaxes the flexor pull on the DIP. In a normal finger, the lumbrical muscle relaxes to allow flexion of the interphalangeal joint. The lumbricals coordinate flexor and extensor systems. Extension of the IP joint paradoxically occurs through the lateral bands. The middle finger is most commonly involved.
Why does paradoxical extension of the finger occur?
The transected flexor digitorum profundus tendon retracts with active flexion. The lumbricals will pull on the lateral bands, creating PIP extension. Lumbrical plus finger can be caused by an FDP disrupted tendon distal to the origin of the lumbrical muscle, a distal amputation of the finger, a flexor tendon graft lax and long, and by avulsions of the FDP tendon. When testing for Lumbrical plus finger, when the patient is relaxed, the affected finger can be flexed passively. With the patient gripping all of the fingers, the affected finger extends actively at the IP joints. This is known as paradoxical extension. Treatment will be in the form of a lumbrical release from the flexor digitorum profundus tendon.