April 11, 2012.Qs 1.Elbow is basically a hinge joint which is made up of radius, humerus and ulna bones. The stability of the elbow is primarily given by the ligaments of ulnar collateral on the inside part of the elbow. Elbow joint is found at the place where all the three bones of the elbow meet. Humerus forms the upper part of the joint and it is the one that is normally felt at the sides of the elbow. Ulna is on the inside part and it is cup shapes which allows articulation with the humerus.
Radius is he smaller bone and it is normally on the outside part of the joint (Bland & Rudolfer, 2003, p. 131). The radius has a round head and it is cup shaped which allows moving round the humerus. The elbow has three joints. One that is formed between the humerus and ulna (humeroulnar) and it allows us to bend and straighten our elbows. The other joint is between humerus and radius (humeroradial) and allows extension and flexion of the hand. Another one is proximal/pronation joint that is between ulna and radius. There are three types of ligaments that support the elbow.
One is the medial collateral ligaments. This has two triangular bands the anterior and the posterior. These originate from medial epicondyle and go over the elbow joint on the inside part. Lateral collateral ligament which is also known as radial collateral is narrow and short. It passes to the annular ligament from the lateral epicondlye base. Annular ligament is made of fibers that cover the top of radius and it maintains contact between the humerus and the radius (Kathryn & Stevens, 2010, p.
69). Elbow has large muscles which allow extension; flexions as well as supination. There are main muscles which are mostly the ones that get injured. These include biceps brachii which arises from the shoulder blade and they extend down to the arm, they cross the elbow joint and then join the radius. Its main purpose is to flex the elbow and supinate the forearm. Others include triceps brachii, brachialis, brachioradialis, and pronator teres (Carmichael, 2009, p. 99) Qs. 2The best position to place a patient for elbow MRI is the supine position.
The arms of the patient should be on the sides and the elbow together with the forearm should be supinated. This is a good position as it reduces the rotation of proximal radial ulnar joint and the forearm. This is in relation to capitellum of distal humerus. Again this is a good position as it allows extensor tendons, medial and lateral ligaments to be viewed in a single coronal plane. Placing the patient obliquely against the bore of the magnet is also a good position for such viewing but it can be limited depending on the size of the patient.
Auto shimming might be necessary especially for fat suppression sequences as the region of interest is near the peripheryQs 3In elbow MRI a number of artifacts can be encountered. Examples include intravascular signal void which is caused by effects of time of flight. The flow of blood can cause turbulent dephasing and echo dephasing. The flow of blood cause movement of hydrogen nuclei and there is change of location between the time that the nuclei get radio frequency pulse and the time the signal that is emitted get to be received (Lu, et. al, 2004, p.
243). This is because the repetition time (RP) is asynchronous with pulsative flow. These artifacts can be reduced by reducing the phase shifts with flow compensation. Saturation pulses can also be used to suppress the blood signal and make them parallel to the slices. Another way of reducing these artifacts is by synchronizing the imaging sequence with heart cycle.