Medial Epicondyle

FIGURE 49.25 Very small locus of instant center of rotation for the elbow joint demonstrates that the axis may be replicated by a single line drawn from the inferior aspect of the medial epicondyle through the center of the lateral epicondyle, which is in the center of the lateral projected curvature of the trochlea and capitellum. (From Morrey B.F. and Chao E.Y.S. 1976. /. Bone Joint Surg. 58A 501. With permission.)... 

Sleeve avulsion fractures are a particular form of avulsion injury seen in the unossified skeleton which differs from avulsions in adults because the sleeve of periosteum which is pulled off can continue to form bone if not treated. The typical location is at the lower pole of the patella, but the upper pole of the patella, the olecranon and the medial epicondyle can also be affected. Ultrasound demonstrates a sleeve of cartilage that has been avulsed usually with a small fragment of bone (Hunt and Somashekar 2005). In some cases a double cortical sign may be present, indicating elevation of a superficial layer of cortex from the underlying bone. There maybe associated haemarthrosis and patella alta (Fig. 4.14). 

Fig. 7.17. a Irregular ossification centre for the trochlea is projected over the joint space with rotation (arrow). This also produces simulated dislocation of the ossification centre for the medial epicondyle (arrowhead), normally sited on the AP view (b)... 

An estimation of the distribution of fracture patterns about the elbow is supracondylar (70%), lateral condyle (15%), medial epicondyle (10%), olecranon (5%), radial neck (1%), medial condyle (1%), capitel-lum (1%), T condylar (<1 %). 

Medial epicondyle 5-8 Years 7-9 Years 20 Years 20 Years... 

Avulsion fractures of the medial epicondyle are seen between the ages of 9 and 15, after the apophysis becomes a separate ossification nucleus from the epiphysis of the distal humerus and before it fuses with the distal humerus. The medial epicondyle is a traction apophysis for the flexor group of forearm muscles, and also serves as an attachment for the ulnar collateral ligaments and the joint capsule. This injury accounts for up to 10% of elbow fractures. 

Based on AP and lateral radiographs, the normal curve following around the medial condyle is disrupted. In type III injuries, it can be easy to misinterpret the radiographs as normal, since the fragment may be difficult to identify, particularly on the AP view. It is important that the acronym CRITOE is used to assess the ossification centres about the elbow joint. The medial epicondyle ossifies before that of the trochlea. If the trochlea is seen then the medial epicondyle must be present (Fig. 18.14). A displaced medial epicondyle lying within the elbow joint should not be confused with the ossification centre of the trochlea. The diagnosis should always be considered if the epicond)de cannot be visualised at an age when it should be present. 

Chronic stress injury of the medial epicondyle can cause degeneration of the common flexor tendon and enlargement, sclerosis, fragmentation and phy-seal widening around the medial epicondyle. It is often found in children involved in throwing sports due to repeated valgus stress around the elbow. It is often called little leaguers elbow . 

Fig. 18.14. AP radiograph showing a displaced medial epicondyle within the joint mimicking the trochlea. The epicondyle was replaced at surgery...

Fig. 18.15a,b. Two children with moderately a and minimally b displaced fractures of the medial epicondyle... 

Fig. 18.16. a Fracture of the medial epicondyle associated with dislocation of the elbow (type IV). b Image intensifier radiograph demonstrates reduction of the elbow but the epicondyle is stuck in joint rather than in an anatomical position - arrowed, c Epicondyle fixed in correct position. 

Fractures of the radial neck maybe isolated injuries but can occur in association with medial epicondyle avulsions, fractures of the olecranon and dislocations of the elbow joint. 

Metaphyseal fractures can be classified according to mechanism of injury. The majority of injuries occur with the elbow in extension, the olecranon locked in the olecranon fossa and the maximum stress developed in the proximal metaphyseal region leading to fracture. When a valgus stress is applied, there may be asso ciated compression fractures of the radial neck and avulsion of the medial epicondyle. Varus stress is associated with radial head subluxation. 

B Extension Valgus Ulnar metaphysis fracture +/- medial epicondyle avulsion +/-radial neck fracture... 

The ulnar nerve may be palpated in the groove between the medial epicondyle and the... 

Tinel test This is performed by tapping over the ulnar nerve as it passes between the olecranon and medial epicondyl. Marked sensitivity may be indicative of a neuroma or inflammation of the ulnar nerve. 

Epicondylitis is a common elbow problem, generally called tennis elbow if the lateral epicondyle is involved and golfer s elbow if the medial epicondyle is involved. This is an overuse syndrome that is associated with any activity that requires repetitive pronation and supination, such as gripping a tennis racquet, golf club, screwdriver, or doorknob. The wrist extensor muscles are involved in lateral epicondylitis. 

Dynamic US of the elbow can be used to help demonstrate abnormal dislocation of the ulnar nerve, with or without snapping triceps syndrome. This finding typically occurs in the cubital tunnel, an osteofibrous tunnel formed by a groove between the olecranon and the medial epicondyle and bridged by the Osborn retinaculum. As described in Chapter 8, dynamic scanning during full elbow flexion can allow continual depiction of the intermittent dislo-... 

Struthers , which joins the anomalous bony process and the medial epicondyle. Clinically, this condition typically affects young sportsmen as a result of intense muscular activity in the elbow and forearm and may start with pain and numbness in the first three fingers and weakness of forearm muscles innervated by the median nerve (Sener et al. 1998). US can demonstrate the relationship of the median nerve with the anomalous bone and ligament. Although not yet reported in the radiological literature, displacement of the nerve by these structures may represent an indicator of entrapment. Therapy includes excision of the ligament of Struthers and ablation of the supracondylar process. The brachial artery can also be compressed by an anomalous insertion of the pronator teres muscle into the supracondylar process (Talha et al. 1987). 

Anterior Elbow Pathology 371 Distal Biceps Tendon Tear 371 Bicipitoradial (Cubital) Bursitis 372 Medial Elbow Pathology 376 Medial Epicondylitis (Epitrochleitis) 376 Medial Collateral Ligament Injury 377 Epitrochlear Lymphadenopathies 377 Lateral Elbow Pathology 378 Lateral Epicondylitis 378... 

The medial collateral ligamentous complex, also known as the ulnar collateral ligament, is composed of three bands in continuity with each other anterior, posterior and oblique (Fig. 8.3a). The anterior band is the most conspicuous and extends from the medial epicondyle to the medial aspect of the coronoid process, providing the major constraint to valgus stress. The posterior band arises from the posterior aspect of the medial epicondyle and inserts into the medial edge of the olecranon. The oblique band, commonly referred to as the ligament of Cooper , is the weakest and bridges the insertions of the anterior and posterior bands on the ulna. 

The medial compartment includes the pronator teres and the superficial flexor muscles of the wrist and hand that arise from the medial epicondyle as the common flexor tendon . The pronator teres is the most superficial and anterior of the medial muscles. It has two proximal attachments one (humeral head) immediately proximal to the medial epicondyle and the common flexor tendon, the other (ulnar... 

The anconeus epitrochlearis is a small accessory muscle (prevalence ranging from 1% to 34%) that forms the roof of the cubital tunnel, replacing the Osborne retinaculum and joins the posterior aspect of the medial epicondyle with the medial aspect of the olecranon.. This muscle is often bilateral and can cause ulnar neuropathy by occupying space within the cubital tunnel and decreasing its free volume during full elbow flexion. Somewhat equivalent to the anconeus epitrochlearis, an anomalous myotendinous junction of the triceps may also be prominent over the posteromedial side of the cubital tunnel (see Sect. 8.5.4.S). 

For evaluation of the posteromedial aspect of the joint, including the cubital tunnel and the ulnar nerve, the patient s elbow should be placed in forceful external rotation to enable visualization and palpation of the medial epicondyle and olecranon (Fig. 8.7a). This can be obtained either with the patient seated and the elbow extended and hyper-pronated with its dorsal aspect facing the exam-ineror, at least for the right side, with the patient... 

Fig. 8.23. Normal ulnar nerve. Long-axis 12-5 MHz US image of the normal ulnar nerve obtained over the cubital tunnel with extended elbow. The relationships of the nerve (arrows) with the medial epicondyle (ME) and the flexor carpi ulnaris muscle (feu) are shown. The ulnar nerve exhibits a hypoechoic appearance and a fairly uniform thickness throughout the tunnel. The insert at the upper left side of the figure indicates probe positioning...

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