Physical Examination of the Elbow




Key words

Elbow examination, ulnar collateral ligament, elbow instability

 




Introduction


A thorough history should be ascertained before a physical examination is performed on a patient with an upper extremity complaint. The upper extremity injury history should include the severity, duration, description, and onset of symptoms and effect on sport or performance as well as hand dominance, sport or profession, and associated conditions. Following the history, a visual inspection of the extremity for signs of trauma, side-to-side differences, and muscle wasting is undertaken before any physical examination maneuvers. Moreover, a basic understanding of anatomy is necessary before performing a physical examination of the upper extremity. Although not sufficient to make a diagnosis, it is critical to understand the basic anatomic structures and their healthy function before probing the extremity for signs of disease.




Anatomy


The Elbow Joint


The elbow joint is a complex synovial-hinged joint that consists of three separate articulations: the ulnohumeral, radiocapitellar, and proximal radioulnar joints. These three articulations allow the elbow 2 degrees of freedom, flexion and extension, as well as supination and pronation. In addition, the bony congruency of these three articulations, when combined with the surrounding ligamentous, capsular, and dynamic structures, serves to provide stability to the elbow throughout physiologic forces and ranges of motion. In contradistinction to the knee, there are no intraarticular cruciate joints that provide stability to the elbow.


Osseous Anatomy


The distal humeral and proximal radioulnar osseous anatomy is congruent and provides a degree of inherent stability to the elbow joint. The humerus fans out distally to lateral and medial epicondyles that serve as attachment points for the collateral ligaments. The distal humerus has 6 to 8 degrees of valgus tilt and 3 to 8 degrees of internal rotation when comparing the epicondylar axis and the humeral shaft. Additionally, the distal humeral articular surface is angled approximately 30 degrees anterior to the humeral shaft axis.


Continuing distally from the epicondyles, the distal humerus has two condyles that form the articular surfaces laterally and medially. The lateral condyle forms the articular surface of the capitellum that articulates with the radial head.


On the medial side, the articular portion of the more prominent medial condyle is the trochlea or “pulley” that articulates with the proximal ulna to create the ulnohumeral joint. ( Fig. 5.1 ) The lateral ridge of the trochlea is slightly more prominent than the medial ridge that gives the elbow the slight valgus angle that can be seen on radiographs ( Fig. 5.2 ).




Figure 5.1


Distal humerus anatomy.

A, Anterior View. B, Posterior View.

(Miyasaka KC. Anatomy of the elbow. Orthop Clin North Am. 1999;30:1-13.)



Figure 5.2


Radiographic anatomy of the distal humeral carrying angle ( ).

(Reprinted with permission from Goldfarb CA, Megan J, Patterson M, et al. Elbow radiographic anatomy: measurement techniques and normative data. J Shoulder Elbow Surg. 2012;21:1236-1246.)


The concave radial head and the convex capitellum create the radiocapitellar joint. The bony congruency of the radiocapitellar joint, as well as the radial head in the lesser sigmoid notch of the ulna, provides approximately 240 degrees of radial head rotation.


The trochlea articulates with the greater sigmoid notch of the ulna that consists of the olecranon posteriorly and the coronoid anteriorly. ( Fig. 5.3 ) During extension, the olecranon “screws out” creating a valgus carrying angle, and during flexion, the olecranon “screws in,” creating a normal varus angle.




Figure 5.3


Proximal ulna osseous anatomy.

A, AP view. B, Lateral View.

(Miyasaka KC. Anatomy of the elbow. Orthop Clin North Am. 1999;30:1-13.)


Ligamentous Anatomy


In addition to osseous congruency, the main sources of stability to the elbow are the ulnar (medial) collateral ligamentous complex, lateral collateral ligamentous complex, anterior ligament, posterior ligament, joint capsule, muscles, and tendons.


The ulnar collateral (medial) ligamentous complex runs from the medial condyle of the humerus to the sublime tubercle on the ulna. The ulnar collateral ligamentous complex can be further subdivided into three distinct bands: the anterior bundle, posterior bundle, and transverse ligaments ( Fig. 5.4 ). The anterior bundle runs from the medial humeral condyle to the medial side of the coronoid process of the ulna. These fibers are the most important for providing resistance to valgus instability. The posterior bundle runs from the medial condyle of the humerus to the medial portion of the olecranon process of the ulna. There are also transverse fibers running from the olecranon to the coronoid process of the ulna. These transverse fibers reinforce the underlying articular capsule but do not play any role in ligamentous stability. Anatomic studies have demonstrated that the anterior bundle actually consists of an anterior band and a posterior band that have reciprocal functions in providing elbow stability depending on the degree of elbow flexion.




Figure 5.4


Ulnar collateral (medial) ligament complex.

The posterior bundle, anterior bundle, and transverse ligament can be seen.

(Lynch JR, Waitayawinyu T, Hanel DP, et al. Medial collateral ligament injury in the overhand-throwing athlete. J Hand Surg Am. 2008; 33:430-437.)


The anterior band is the most important medial stabilizer from full extension to 85 degrees of flexion. The posterior band provides stability and is tensioned at elbow flexion greater than 55 degrees, and the posterior oblique ligament provides stability and is taught at flexion greater than 90 degrees.


The ulnar collateral ligament (UCL) consists of three portions. The anterior bundle is anatomically most discrete, and functionally it provides the most stability to the medial aspect of the joint. It arises from the lateral 80% of the medial epicondyle to insert on the medial edge of the coronoid process on the sublime tubercle.


The anterior ligament provides 70% of the valgus stability at the elbow, except in full extension where the radial head and anterior capsule provide the majority of valgus stability. The posterior portion of the UCL is a fan-shaped thickening of the posterior capsule, which originates from the posterior aspect of the medial epicondyle to insert on the medial semilunar notch. This structure does not provide significant valgus stability until the arm is flexed beyond 90 degrees. The transverse oblique segment is composed of horizontally arranged medial capsule fibers that traverse from the tip of the olecranon to the coronoid process. No contribution to stability is derived from this portion of the UCL complex as both its origin and insertion lie on the ulna.


The lateral collateral (radial) ligamentous complex runs from the lateral condyle of the humerus to the annular ligament with some fibers extending to the radial neck. The lateral collateral ligament complex consists of three components: the annular ligament, the radial collateral ligament (RCL), and the lateral ulnar collateral ligament (LUCL) ( Fig. 5.5 ). To avoid confusion, O’Driscoll suggests thinking of the lateral collateral ligament complex of consisting of a radial part (RCL), an annular part (the annular ligament), and an ulnar part (LUCL).




Figure 5.5


Lateral ulnar ligamentous complex.

The lateral ulnar collateral ligament (LUCL), annular ligament, and radial collateral ligament can all be seen.

(Lynch JR, Waitayawinyu T, Hanel DP, et al. Medial collateral ligament injury in the overhand-throwing athlete. J Hand Surg Am. 2008;33:430-437.)


The annular ligament almost completely surrounds the radial head, allowing radial rotation and stability of the radial head in the lesser sigmoid notch. The RCL is fan shaped and originates on the lateral epicondyle and inserts into and blends with the annular ligament. The LUCL originates from the lateral humeral epicondyle to insert on the tubercle of the supinator crest. The LUCL is a key component in preventing posterolateral and varus instability.


The anterior aspect of the elbow capsule is comparatively thick and performs a role in affording stability against hyperextension of the elbow. The posterior capsule also has thickened bands that are often considered the posterior ligament.


Elbow and Forearm Musculature


The biceps brachii has two origins called the short and long heads. The origin of the long head is the supraglenoid tubercle and is intimately associated with the shoulder joint. The long head may be diseased and a pain generator in patients presenting with shoulder pain. The origin of the short head is from the coracoid process of the scapula. The two heads join on top of the brachialis muscle on the anterior portion of the arm. The insertion of the biceps is at the radial tuberosity and the biceps aponeurosis, which blends with the forearm flexor sheath on the medial forearm. The major action of the biceps is supination of the forearm and elbow flexion. The biceps brachii receives its innervation from the musculocutaneous nerve from the C5 and C6 nerve roots.


The brachialis muscle originates on the anterior aspect of the humerus distal to the deltoid and coracobrachialis muscle insertions. The insertion is on the ulnar tuberosity situated on the lateral aspect of the proximal ulna. The brachialis is a flexor of the elbow, and its function does not depend on the degree of forearm supination or pronation. It is also receives innervation by the musculocutaneous nerve.


The supinator has multiple origins. It originates from the lateral, posterior aspect of the ulna distal to the olecranon, the lateral humeral epicondyle, the radial collateral ligament of the elbow, and the annular ligament of the radial head. It inserts onto the proximal lateral radius. Supination of the forearm with respect to the arm is the major function of this muscle. It is most effectively tested with the elbow fully flexed, which places the biceps at a mechanical disadvantage. The radial nerve innervates the supinator muscle from the root levels C6 and C7.


The brachioradialis muscle originates from the supracondylar ridge and lateral intermuscular septum on the lateral aspect of the humerus. It inserts near the radial styloid at the distal radial aspect of the radius. The major action of the brachioradialis is elbow flexion with the forearm in neutral rotation (thumb-up position). The radial nerve innervates the brachioradialis from the root levels C5 and C6. The triceps brachii muscle has three heads: the long head, medial head, and lateral head. The long head originates from the infraglenoid tubercle of the scapula. The medial head originates from the medial intermuscular septum and adjacent part of the distal humerus below the radial groove. The lateral head originates from the lateral intermuscular septum and the adjacent humerus proximal and lateral to the radial groove. The three heads join in the posterior aspect of the arm and insert at the proximal olecranon of the ulna. The major action of the triceps brachii is extension of the elbow. The radial nerve innervates the triceps muscle from the root levels C6, C7, and C8.


The anconeus muscle is a small muscle originating on the lateral epicondyle of the humerus; it inserts onto the lateral aspect of the olecranon of the ulna. Its major action is extension of the elbow. The radial nerve innervates the anconeus muscle from the root levels C7 and C8.


The pronator quadratus (PQ), as the name indicates, is a quadrangular shaped muscle with origin and insertion on the distal ulna and radius, respectively. The PQ assists pronation of the forearm and is the last muscle innervated by the anterior interosseous nerve (AIN), the root level most commonly sited at C7 and C8.


The palmaris longus (PL) is absent in a certain percentage of the population. The PL origin is at the medial epicondyle of the humerus from the common flexor tendon, and the insertion is at the palmar aponeurosis of the hand. Because it inserts on the palmar aponeurosis, it is not contained within the carpal tunnel. The major action of the PL is minor assistance wrist flexion. The median nerve innervates the PL, and the root levels are C7 and C8 and, occasionally, T1.


The flexor carpi radialis (FCR) is medial to the pronator teres and lateral to the PL and flexor carpi ulnaris. The FCR muscle’s origin is at the medial humeral epicondyle from the common flexor tendon, and the insertion is at the second and third metacarpal bones in the hand. The FCR does not go deep to the flexor retinaculum at the wrist; therefore, like the PL, it is not within the carpal tunnel. The major action of the FCR is wrist flexion with a slight pronation component. The major innervation is from the median nerve from the root levels C6 and C7.


The flexor carpi ulnaris (FCU) has two heads of origin from the common flexor tendon off of the medial humeral epicondyle and from the proximal posterior surface of the ulna just medial to the origin of the extensor carpi ulnaris. The major action of the FCU is wrist flexion with ulnar deviation. The major innervation is from the ulnar nerve from the root levels C8 and T1.


The flexor digitorum superficialis (FDS) also has two heads of origin from the medial to the humeral epicondyle at the common flexor tendon to the coronoid process and from the lateral radius just distal to the insertion of the supinator. The median nerve and the ulnar artery both lie deep to this muscle and pass between the two heads of the FDS. The FDS muscle gives rise to four flexor tendons in the distal forearm. These four tendons pass deep to the flexor retinaculum at the wrist, and therefore the FDS lies within the carpal tunnel at the wrist. The four tendons then continue on to the index, middle, ring, and small fingers and insert on their respective middle phalanges. Importantly, each tendon splits (decussates) just proximal to the final insertion to allow the tendon of the flexor digitorum profundus to pass through. The major action of the muscle is flexion of the proximal interphalangeal joints (PIPJs). In addition, this muscle can aid in flexion at the metacarpophalangeal (MCP) and wrist joints. The median nerve innervates the FDS from the root levels C7, C8, and T1.


The flexor digitorum profundus (FDP) has extensive origin from the anterior and medial ulna and adjacent interosseous membrane. The FDP muscle then gives rise to four tendons that pass deep to the flexor retinaculum at the wrist. Like the FDS, the FDP tendons lie within the carpal tunnel. The final insertion is on the volar base of the proximal aspect of the distal phalanges of the index, middle, ring, and small fingers. Recall that the FDP tendons past through the split tendons of the FDS muscle. The major action of the FDP is flexion of the distal phalanx. The FDP can also secondarily aid more proximal phalangeal flexion and wrist flexion. The FDP has dual innervation from both the anterior interosseous nerve (branch off of the median nerve) and the ulnar nerve. The radial portion of the FDP to the index and middle digits are innervated by the anterior interosseous nerve, whereas the ulnar portion to the ring and small digits are innervated by the ulnar nerve. The root levels innervating the FDP are C7 and C8.


The flexor pollicis longus (FPL) originates just lateral to the FDP on the interosseous membrane and the adjacent radial bone. The anterior interosseous nerve runs between the FPL and FDP and provides innervation to these muscles. The insertion of the FPL is at the volar base of the distal phalanx of the thumb. The FPL tendon passes within the carpal tunnel and is the most laterally situated tendon. The major action of the FPL is flexion of the interphalangeal joint of the thumb. The FPL can secondarily flex the MCP joint of the thumb. It is innervated by the anterior interosseous nerve from root levels C7 and C8.


Extensor Group


The extensor tendons of the wrist are best remembered and studied by focusing on the six dorsal extensor compartments in which they travel. The compartments are tunnels on the dorsum of the wrist that contain the extensor tendons. The extensor retinaculum covers these tunnels and prevents tendon subluxation.


The extensor carpi radialis longus (ECRL) originates at the lateral supracondylar ridge of the humerus, the adjacent intermuscular septum, and the lateral humeral epicondyle. It inserts at the base of the second metacarpal bone. The major action of the ECRL is extension of the wrist with a lateral or radial deviation. The innervation of the ECRL is from the radial nerve, root levels C7 and C8. The extensor carpi radialis brevis (ECRB) and the ECRL share a common tendon sheath and extensor compartment at the wrist. The ECRB inserts at the base of the third metacarpal. The major action of the ECRB is wrist extension. The radial nerve innervates the ECRB from the root levels C7 and C8. ECRB travels with ECRL in the first dorsal compartment.


The extensor pollicis brevis (EPB) originates on the posterior surface of the radius and the adjacent intermuscular septum. The insertion is at the base of the proximal phalanx of the thumb. The radial nerve innervates the EPB from root levels C7 and C8. Its major action is extension of the interphalangeal joint of the thumb. EPB runs in the second dorsal compartment.


The abductor pollicis longus (APL) originates on the proximal ulna, adjacent intermuscular septum, and the radius, just distal and posterior to the insertion of the supinator. The insertion of the APL is at the base of the first metacarpal. The major action of the APL is abduction of the thumb. The radial nerve innervates the APL from the root levels C7 and C8. The APL travels in the second dorsal compartment with the EPB.


The extensor pollicis longus (EPL) originates distal to the APL on the intermuscular septum and the ulna just lateral to the origin of the extensor carpi ulnaris. The insertion of the EPL is the proximal end of the distal phalanx of the thumb. Its major action is extension of the interphalangeal joint of the thumb. A secondary action of the EPL is wrist extension with radial deviation. The radial nerve innervates the EPL from root levels C7 and C8. The EPL travels in the third dorsal compartment and becomes prominent with thumb extension because of its acute radial turn.


The extensor indicis (EI) originates on the distal posterior radius and inserts on the extensor surface of the index finger at the middle and distal phalanx. Its major action is extension of the index finger. The EI is the last muscle innervated by the radial nerve from root levels C7 and C8. EI runs in the fourth dorsal compartment.


The extensor digitorum communis (EDC) originates from the common extensor tendon at the lateral humeral epicondyle and inserts into the middle and distal phalanges of the index, middle, ring, and small fingers. Its major action is extension of these digits. The radial nerve innervates the EDC from the root levels C7 and C8. The EDC tendons travel with the EI in the fourth dorsal compartment.


The extensor digiti minimi (EDM), also referred to as the extensor digiti quinti (EDQ), is a small muscle originating at the common extensor tendon of the lateral humeral epicondyle and runs immediately adjacent to the EDC. It inserts at the middle and distal phalanx of the small finger. The major action is to extend the small finger. The radial nerve innervates the EDM from the root levels C7 and C8. The EDM runs in the fifth dorsal compartment.


The extensor carpi ulnaris (ECU) originates from the lateral humeral epicondyle at the common extensor tendon and from the posterior surface of the proximal ulna. The ECU is the most medial muscle in the extensor group. It inserts at the base of the fifth metacarpal bone. The major action is extension of the wrist with ulnar deviation. The radial nerve innervates the ECU from the root levels C7 and C8. The ECU runs in the sixth dorsal compartment.


Nerves in the Upper Extremity


Four major nerves enter and innervate the upper extremity.


Musculocutaneous Nerve


The musculocutaneous nerve enters the arm as an extension of the lateral cord of the brachial plexus containing nerve fibers from cervical roots C5 and C6. The nerve enters the muscle belly of the coracobrachialis muscle and lies in the arm between the biceps and the brachialis muscles, innervating both. This nerve ends as a cutaneous nerve supplying the lateral forearm called the lateral antebrachial cutaneous nerve (LABCN).


Median Nerve


The median nerve is formed by nerve fibers from the lateral and medial cords of the brachial plexus containing nerve fibers from the cervical root levels C6–T1. This nerve enters the arm running with the ulnar nerve and the brachial artery and travels within the forearm just medial to the biceps tendon insertion and anterior to the elbow joint. The median nerve dives deep to the pronator teres (PT), between its two heads, and runs between the FDS and FDP muscles. The median nerve innervates the PT, PL, FDS, and FCR in the forearm. The median nerve gives off a branch, the AIN, just after crossing the elbow joint. The AIN runs deep to the FDP and innervates the FDP to digits 1 and 2, FPL, and PQ. The median nerve continues between the tendons of the FDS and FDP at the wrist, just radial (lateral) to the superficialis tendon, ulnar (medial) to the FCR, and just deep (and lateral) to the PL tendon. The median nerve gives off the palmar cutaneous branch just proximal to the flexor retinaculum. It then passes deep to the flexor retinaculum and supplies the (superficial head) flexor pollicis brevis (FPB), abductor pollicis brevis (APB), opponens pollicis (OP), and lumbricals 1 and 2.


Ulnar Nerve


The ulnar nerve enters the arm as the extension of the medial cord of the brachial plexus with nerve fibers from the cervical root levels C8 and T1. The nerve enters the arm slightly posterior to the brachial artery, innervating no muscles in the arm, and passes posterior to the medial humeral condyle in the ulnar groove. In the forearm, the ulnar nerve lies between the FCU and FDP and innervates the FDP to digits 3 and 4 and the FCU. Next, the ulnar nerve crosses the wrist joint medial to the FCU tendon and lateral to the ulnar artery. Once in the hand, the ulnar nerve passes medial to the pisiform bone, splitting into the superficial and deep palmar branches. These two branches enter the canal of Guyon together but exit to different end points. The space between the pisiform and the hook of the hamate forms the walls of Guyon canal. The roof of Guyon canal is the distal extension of the FCU tendon, and the floor is the pisohamate ligament. The superficial palmar branch supplies skin sensation to the medial half of the fourth and all of the fifth digits. The deep palmar branch travels (medial side) around the hook of the hamate and travels laterally to innervate the lumbricals 4 and 5, all interosseous muscles, all hypothenar muscles, the deep head of the FPB, and the adductor pollicis.


Radial Nerve


The radial nerve is the extension of the posterior cord of the brachial plexus with nerve fibers from the root levels C5–C8. It enters the upper arm through the quadrangular space (borders teres major, minor, long head of the triceps, and the humerus). In general, the radial nerve innervates all extensor muscles of the elbow, wrist, and fingers. The radial nerve has cutaneous innervation to the back of the arm, forearm, and hand. Once in the arm, the radial nerve lies against the humerus, traveling distally and laterally in the spiral groove of the humerus between the lateral and medial heads of the triceps. In the distal arm, the radial nerve lies between the anterior brachialis muscle and the posterior brachioradialis and ECRL muscles.


At the elbow, the radial nerve courses anterior to the lateral condyle of the humerus and splits into superficial and deep branches before entering the belly of the supinator. The superficial branch travels under the brachioradialis muscle becoming subcutaneous lateral to the tendon in the distal forearm. The superficial branch provides cutaneous innervation to the dorsum of the lateral hand and base of the thumb. The deep branch travels distally between the superficial and the deep extensor muscle groups. After innervating the supinator muscle, the radial nerve is called the posterior interosseous nerve (PIN). The deep branch of the PIN provides sensory input to the posterior of the wrist and carpal bones. The radial innervated muscles include triceps (all heads), brachioradialis, ECRL, ECRB, supinator, EDC, EDM, APL, extensor pollicis longus and brevis, and EI. The last radial innervated muscle is the EI, which becomes important in assessing for recovery following neuropraxia.




Inspection


Visual inspection of the elbow requires proper exposure of the extremity from the shoulder to the hand. In the anatomic position, the anterior aspect of the elbow is covered by the biceps muscle and tendon, which are easily visualized. The anterior forearm just distal to the biceps muscle belly and tendon is called the cubital fossa or antecubital fossa. The cubital vein can be observed and palpated as it passes anterior to the elbow joint just lateral to the biceps tendon. The cephalic vein can be observed on the lateral side of the biceps muscle in the arm. The medial epicondyle of the elbow is the origin of the flexor/pronator muscle mass or the common flexor tendon. On the lateral aspect of the elbow can be seen the muscles that overlie the lateral epicondyle.


The lateral epicondyle is the origin of the extensor muscle mass or the common extensor tendon. On the posterior elbow, the olecranon process of the ulna is noted and is most obvious with the elbow flexed at 90 degrees. The olecranon bursa overlies the posterior elbow. A patient with olecranon bursitis can have a visible swelling with tenderness and warmth over the olecranon.


Observing joint movements through their respective ranges of motion, both actively and passively, is part of inspection. The total joint motion is observed and documented from side to side with quality of movement also noted. The carrying angle in extension and range of motion of the elbow from maximal extension to maximal flexion and from maximal supination to maximal pronation with the elbow flexed to 90 degrees should be documented.


Joint swelling or discoloration and any skin lesions or ecchymosis, hypertrophy, hypotrophy, or frank atrophy of muscles in the arm or forearm should also be documented. Various injuries can be detected immediately through a comprehensive inspection of the extremity. Distally, observation for asymmetry between the hand and wrist in both the supinated and pronated positions, comparing the right with the left sides, is essential. Any tumors, angular deformities, or soft tissue prominence should be noted. Swelling or enlargement of the joints should be noted.




Palpation


Palpation is a key aspect of the physical examination of any body part and is of critical importance when palpating for potential pathology around the elbow. Palpating the elbow requires pinpointing the exact area of tenderness or pathology.


The medial epicondyle is easily palpable. Just anterior and distal to the medial epicondyle, one can palpate from proximal to distal the muscle origins of the pronator teres, FCR, PL, FDS, and FCU. Just posterior to the medial epicondyle, the ulnar groove can be palpated, as can the ulnar nerve traveling within. On the posterior aspect of the elbow, the olecranon process of the ulna is easily palpable, appreciating the triceps tendon insertion into the olecranon. Midway between the olecranon and the lateral epicondyle, one palpates the anconeus muscle. The lateral epicondyle is covered by a large mass of extensor muscle, called the extensor bundle or wad. From the lateral supracondylar ridge to the lateral epicondyle, one palpates a number of muscles. The muscles from proximal to distal are the brachioradialis, ECRL, ECRB, and EDC.


Deeper palpation about the lateral elbow can reveal ligamentous and bony abnormalities. The lateral “soft spot” is located between the radial head, lateral epicondyle, and olecranon tip. It should be palpated for fullness, indicating a joint effusion or hemarthrosis, or crepitus, indicating a loose body or fracture. About 2 cm distal to the capitellum, the radial head is palpated with the accompanying annular ligament that encircles the structure. In the face of trauma, crepitus and pain while pronating or supinating the forearm in the region of the radial head area should raise suspicion for a radial head fracture. The lateral collateral ligament is difficult to directly palpate because of the overlying musculature; however, the anterior bundle of the medial collateral ligament is usually palpable with the elbow flexed from 30 to 60 degrees.




Examination of Nerve Compression Syndromes


The nerves of the upper extremity all have multiple possible sites of compression and nerve entrapment. In order to be able to diagnose the point of entrapment, an intimate knowledge of both neuroanatomy and potential sites of compression is key. This chapter focuses on nerve compressions that are associated with or can be misdiagnosed as musculoskeletal injuries to the elbow.


Median Nerve Lesions


The median nerve innervates a number of important muscles in the upper extremity and hand. Sites of compression include the ligament of Struthers, which is a fibrous band off of an anomalous humeral supracondylar process, between the two heads of the pronator teres, by the lacertus fibrosis extension of the biceps tendon and between the fibrous arch of the FDS.


With compression at a supracondylar process on physical exam, the wrist flexors, PT, and median innervated hand muscles present with weakness. The sensation on the thenar and first three and a half digits can be impaired. Wrist flexion occurs with ulnar deviation, as the FCU remains innervated. Upon being asked to make a fist, the patient will be unable to flex the index finger, and in many cases, the middle finger as well, actively or against resistance. When both the index and middle finger cannot be flexed, the hand forms the “active papal hand” or “benediction sign.” Over time, high median nerve injuries may result in “ape hand” deformity, because the radial nerve innervating the APL, EPL, and EPB pull the first metacarpal into the plane of the palm.


Pronator Syndrome


As mentioned, entrapment may also occur under the lacertus fibrosus between the two heads of the PT or through its muscle belly ; these are collectively referred to as pronator syndrome. Pronator muscle function is spared because its innervation is established before the median nerve is compressed. However, all muscles distal to the PT are affected and will result in wrist flexor weakness or lost or impaired sensation over the thenar and lateral three and a half digits.


Symptoms of the pronator teres syndrome mimic carpal tunnel syndrome (CTS). In contrast to CTS, patients will often exhibit pain to palpation over the nerve entrapment site, which is proximal in the volar forearm. Additionally, there are characteristically fewer night symptoms than patients with CTS, and the palmar cutaneous branch of the median nerve that innervates the palm is involved, whereas in CTS, it is spared.


Two tests that have been described for pronator syndrome include the resisted elbow flexion with forearm supination ( Fig. 5.6 ) and the resisted elbow extension with forearm pronation ( Fig. 5.7 ) . The resisted pronation test is designed to compress the nerve between the two heads of the pronator teres, and the supination test is designed to compress the nerve under the lacertus fibrosus.


Jul 23, 2019 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on Physical Examination of the Elbow
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