Cubital Fossa, Popliteal Fossa, & Femoral Triangle

Cubital Fossa, Popliteal Fossa, & Femoral Triangle

Arrangement of the neurovascular structures in these areas is important, but complicated. The purpose of this video is to describe briefly the contents of these structures.

Cubital Fossa

ccThe contents of the cubital fossa from medial to lateral are the median nerve (most medial structure). The second structure is the brachial artery. The brachial artery bifurcates into the ulnar artery and the radial artery. The biceps tendon is lateral to the brachial artery. 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). Lateral to the biceps tendon is the radial nerve and its major branch, the posterior interosseous nerve.

Popliteal Fossa

pp.PNGThe popliteal fossa is a shallow depression located at the back of the knee joint. The structures of the popliteal fossa from medial to lateral are the popliteal artery, popliteal vein, small saphenous vein, tibial nerve, and the common peroneal nerve which runs across the upper lateral border of the popliteal fossa.

Femoral Triangle

f.PNGThe femoral triangle is a superficial triangular space located on the anterior aspect of the thigh just inferior to the inguinal ligament. The femoral triangle contains three important structures from lateral to medial: the femoral nerve, the femoral artery, the femoral vein, and the the deep inguinal lymph nodes.

Lachman Test ACL Injury

Lachman’s test is the most sensitive examination test for the ACL injury. The anterior cruciate ligament is located in the front of the knee. The primary function of the ACL is to resist anterior translation of the tibia relative to the femur and provide some rotational stability to the knee. Rupture of the anterior cruciate ligament (ACL) is a condition commonly seen in sports due to a non-contact pivoting injury. ACL rupture is usually a complete rupture.aa

Patient Evaluation

  • Patient usually feels or hears a “POP” within the knee.
  • Sudden knee pain.
  • Swelling within hours.
  • The patient gives a history of the knee “giving away”.
  • Exam is usually difficult and limited by the pain.
  • There is usually hemorrhage within the knee joint (hemarthrosis).

If aspiration of the knee shows hemarthrosis, then there is a 75% chance of an ACL tear and a meniscal injury (usually the lateral meniscus). The Lachman test is the most useful and sensitive test for the diagnosis of ACL tear in the acute setting. To perform the Lachman test, the patient should be lying supine and completely relaxed. Ensure that the patient’s hip muscles, quadriceps, and hamstring muscles are all relaxed. Bend the knee to about 20-30 degrees. Stabilize the femur with one hand and with the other hand, pull the tibia anteriorly and posteriorly against the femur. With an intact ACL, as the tibia is pulled forward, the examiner should feel an end point. With an ACL rupture, the ACL will be lax, and the examination will feel softer with no endpoint. The tibia can be pulled forward more than normal (anterior translation). A sense of increased movement and lack of a solid end point indicates an ACL injury. Lachman’s test is the best examination test to diagnose a tear of the ACL. Be aware that a PCL tear may give posterior subluxation of the tibia and gives a false positive Lachman’s test.

ACL Injury Grades Using the Lachman’s Testaaa

  • Grade I
    • 3-5mm of translation
  • Grade II
    • 5-10mm of translation
  • Grade III
    • More than 10mm of translation

In addition to assessing the amount of translation of the tibia and the quality of the end point of the Lachman exam, you will need to examine the patellar tendon and quadriceps tendons, because rupture of the ACL and rupture of these tendons may be confused with each other. Other tests may diagnose an ACL tear, but they are not as good as the Lachman test.

Other Tests for Diagnosis of ACL Tear

  • Anterior Drawer Test
    • Not as reliable as the Lachman Test
  • Pivot Shift Test
    • Done by going from extension to flexion of the knee, and the tibia will be reduced at 20-30 degrees of flexion.
    • This test measures the functional instability of the knee, the “giving away” of the knee.
    • Pivot shift is pathognomic for an ACL tear and is best demonstrated in a chronic setting.
    • Pivot shift test is a more difficult test than the Lachman Test.

Rupture of the ACL causes anterolateral rotatory instability. The tibia moves anterolaterally in extension, however when you flex the knee, the IT band becomes a flexor of the knee. The IT band pulls back and reduces the tibia. The pivot shift test goes from extension (tibia sublexed) to flexion, with the tibia reduced by the iliotibial band. Both the Lachman Test and the Pivot Shift Test are associated with 20-30 degrees of knee flexion. The Lachman Test starts at 20-30 degrees of flexion. With the Pivot Shift Test, you feel the clunk at 20-30 degrees of flexion. So it seems that 20-30 degrees of flexion is important for examination of the ACL.

aaaaUsually the diagnosis of ACL rupture is confirmed with an MRI. In addition to the ACL tear, the MRI of the knee joint can show bone bruises or injuries that can be consistent with an ACL tear. These injuries are typically located at the middle of the femoral condyle and the posterior part of the tibia laterally.

Lateral Circumflex Femoral Artery

https://www.youtube.com/watch?v=xRR6CPCIg6c

Lateral Circumflex Femoral Arteryl.png

The lateral circumflex femoral artery is a branch of the profunda femoris artery. The profunda femoris artery is the main blood supply to the thigh. The profunda femoris artery gives two circumflex arteries and four perforating branches. The two circumflex arteries are

  1. The medial circumflex femoral artery
  2. The lateral circumflex femoral artery

The lateral circumflex artery is directed towards the lateral side. From the femoral triangle of the thigh, the femoral nerve is lateral to the femoral artery. As the lateral circumflex femoral artery branches off of the profunda artery and goes laterally, it crosses the femoral nerve and passes under the Sartorius muscle, which is the lateral boundary of the femoral triangle. The lateral circumflex femoral artery gives three branches:

  1. Ascending Branch
  2. Descending Branch
  3. Transverse Branch

llThe ascending branch passes upwards beneath the tensor fascia lata and goes up to the anterior superior iliac spine (ASIS). The descending branch descends to the knee joint. The transverse branch goes towards the greater trochanter and also goes to the cruciate anastomosis. The ascending branch of the LCFA is important. The LCFA is at risk of injury with Smith-Petersen Approach or anterior approach to the hip. The LCFA is found in the intervenous plane between the tensor fascia lata and the Sartorius muscle. It also passes under the rectus femoris muscle. The LCFA will be found deeper to that and this artery must be found and ligated to prevent excessive bleeding.

Cubital Fossa

Cubital Fossa

Cubital FossaThis 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. CFS

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.