प्रोनेटर और एआईएन रिलीज़

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Anatomy & Pathophysiology¶

Bony Anatomy¶

• The elbow is a trocho-ginglymoid joint consisting of medial and lateral articulations that provide bony stability [3].
• The trochlea articulates with the ulna within the greater sigmoid notch to create the ulnohumeral, hinged, or trochoid portion of the elbow joint [3].
• The ulnohumeral articulation has highly congruent anatomy through almost 180° of articular contact, with the exception of the bare area of the greater sigmoid notch which is devoid of cartilage [3].
• The coronoid has a medial and lateral facet which buttresses the trochlea anteriorly [3].
• The sublime tubercle is located just distal and medial to the coronoid and provides the attachment site for the anterior bundle of the medial ulnar collateral ligament [3].
• The medial epicondyle forms the attachment site for the origins of the flexor pronator mass and is larger and more posteriorly oriented than the lateral epicondyle [3].
• The capitellum and radial head form the radiocapitellar joint [3].
• The radius is held in close approximation to the ulna at the proximal radioulnar joint by the annular ligament [3].
• The area of the ulna which articulates with the margin of the radial head at the proximal radioulnar joint is known as the lesser sigmoid notch [3].
• The radial head is a concave elliptical structure covered with articular cartilage along the radiocapitellar joint and approximately 270° of the articular margin [3].
• The radial head articulates with both the capitellum and the lesser sigmoid notch [3].
• The lateral epicondyle is the origin of the lateral extensor musculature [3].
• The origin of the lateral ulnar collateral ligamentous complex is located just distal to the lateral epicondyle at the geometric center of the radiocapitellar articulation [3].
• The distal humeral articulation is angled 30° from the longitudinal axis [3].
• The anterior humeral line should pass through the center of the axis of rotation [3].
• The axis of rotation is 5° to 7° angulated in the coronal plane to the epicondylar axis, with the medial side more distal than the lateral side [3].
• The angulation of the distal humeral articulation accounts for the change in a valgus carrying angle to a more varus position as the elbow is flexed [3].
• There is a high correlation between the size of the radius and capitellum on the left and right sides in the same individual [3].
• The olecranon allows for a broad attachment site of the triceps [3].
• The ulna medially bends approximately 8° at 8 cm from the tip of the olecranon [3].
• There is a slight anterior bow to the proximal ulna [3].
• The articulation to the tip of the coronoid is approximately 30° from the long axis of the ulna in the sagittal plane [3].

Ligaments and Capsule¶

• The medial ulnar collateral ligaments are areas of capsular thickening which provide stability to the medial side of the elbow joint [3].
• The medial ulnar collateral ligament is the primary valgus stabilizer [4, 5].
• The anterior bundle of the medial ulnar collateral ligament is the most important component for stability [4, 5].
• The posterior bundle of the medial ulnar collateral ligament has the greatest change in length and becomes taut at flexion beyond 120 degrees [4, 5].
• The lateral ulnar collateral ligament is the posterolateral stabilizer [4, 5].
• Osborne’s ligament stabilizes the ulnar nerve in the cubital tunnel [4, 5].
• The ligament of Struthers is a variant anatomy arising from the supracondylar process to attach to the medial epicondyle and is a potential site of median nerve compression [4, 5].
• The elbow capsule allows maximum distension at approximately 70 to 80 degrees of flexion [4, 5].
• The anterior capsule attaches at a point approximately 6 mm distal to the tip of the coronoid [4, 5].
• The coronoid tip is an intraarticular structure that is visualized during elbow arthroscopy [4, 5].
• Tensile forces are present at the medial elbow and compressive forces are present at the lateral elbow [4, 5].

Muscles¶

• The brachialis is the strongest elbow flexor and attaches to the coronoid 11 mm distal to the tip [4, 5].
• The biceps brachii inserts at the ulnar margin of the radial tuberosity, with the long head inserting proximally and the short head distally [4, 5].
• The biceps brachii is a powerful supinator of the forearm [4, 5].
• The triceps is the primary elbow extensor and inserts on the olecranon process [4, 5].
• The mobile wad consists of the brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis [4, 5].
• The flexor-pronator mass consists of the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis [4, 5].

Biomechanics and Motion¶

• The normal elbow has a range of motion from 0° to 140° from extension to flexion [1].
• The normal elbow has a range of motion of 75° in pronation and 85° in supination [1].
• A functional arc for flexion and extension is 100° [1].
• A functional arc for forearm rotation is 100° [1].
• Elbow stability is determined by primary and secondary stabilizers [1].
• The three primary stabilizers of the elbow are the ulnohumeral articulation, the medial ulnar collateral ligament, and the lateral ulnar collateral ligament complex [1].
• The secondary stabilizers of the elbow are the radiocapitellar articulation, the common flexor tendon, the common extensor tendon, and the joint capsule [1].

Investigations¶

History and Physical Examination¶

• The physical examination of the elbow is directed by the history and the location of the patient's pain in the anterior, posterior, medial, or lateral aspect of the elbow [1].
• Active and passive flexion, extension, supination, and pronation should be evaluated using a goniometer for accurate measurement [9].
• The contralateral elbow should be examined for comparison during range of motion assessment [9].
• If the elbow has less than 90° to 100° of flexion, the posterior bundle of the medial collateral ligament is contracted and must be released to restore flexion [9].
• Pain assessment during the mid-arc or at the terminal ends of motion is required, with mid-arc pain being more common with intrinsic disease [9].
• The ulnar nerve is of utmost importance in the examination due to its anatomic proximity to the elbow [9].
• Electromyography and nerve conduction velocity studies should be performed if there is any question about neurologic dysfunction [9].
• An assessment for ulnar nerve subluxation should be performed, as subluxation is a relative contraindication for arthroscopic procedures due to the risk of iatrogenic nerve injury [9].
• The status of any prior ulnar nerve transposition should be verified if there is a history of previous surgical procedures [9].
• Patients with valgus extension overload syndrome report posteromedial elbow pain that occurs during the deceleration phase of throwing as the elbow reaches terminal extension [11].
• Crepitus and tenderness over the posteromedial olecranon may be noted in patients with valgus extension overload syndrome [11].
• Pain is reproduced when the elbow is forced into extension in patients with valgus extension overload syndrome [11].
• Elbow flexion contracture may be seen in patients with valgus extension overload syndrome [11].
• Patients with osteoarthritis of the elbow typically present with loss of terminal extension and flexion and painful catching, clicking, or locking of the elbow [13].
• Pain in osteoarthritis of the elbow is typically noted at the end ranges of motion and not through the midrange [13].
• Forearm rotation is relatively preserved until later in the disease process of osteoarthritis [13].
• Ulnar neuropathy is present in up to 50% of patients with osteoarthritis of the elbow [13].

Imaging¶

• Plain radiographs remain the hallmark and the best screening test for elbow evaluation [1].
• AP, lateral, and oblique radiographs are standard for elbow evaluation [9].
• Serial radiography is used as follow-up when heterotopic ossification is present [9].
• Primary bony landmarks identified on radiographs include the ulnohumeral joint, coronoid process, radial head, capitellum, radiocapitellar joint, olecranon tip, coronoid/olecranon fossae, and trochlear ridge [9].
• CT is helpful when assessing for malunion architecture and the location and pattern of osteophytes and/or loose bodies [9].
• Three-dimensional CT is used to check for heterotopic ossification [9].
• CT is not necessary when elbow stiffness is entirely soft-tissue related [9].
• CT is beneficial if any joint incongruity or abnormal bony anatomy is present [9].
• MRI can be used to evaluate ligaments and tendons, but it is rarely indicated for elbow stiffness [9].
• AP, lateral, oblique, and axillary views of the elbow may reveal posteromedial olecranon osteophytes and/or loose bodies in valgus extension overload syndrome [11].
• CT with two-dimensional reconstruction and three-dimensional surface rendering best visualizes the pathology of valgus extension overload syndrome [11].
• MRI may be most helpful in evaluating associated injuries including partial or complete tears of the medial collateral ligament in valgus extension overload syndrome [11].
• Radiographs typically show osteophyte formation at the coronoid process, coronoid fossa, radial fossa, radial head, olecranon tip, and olecranon fossa in osteoarthritis [13].
• Joint spaces at the ulnohumeral joint are usually preserved in osteoarthritis [13].
• Joint spaces at the radiocapitellar joint are mildly narrowed in osteoarthritis [13].
• Loose bodies may be evident on radiographs, which typically underestimate the number present in osteoarthritis [13].
• CT may be useful for surgical planning in osteoarthritis, allowing a detailed assessment of osteophytes and the presence of loose bodies [13].
• Radiographic evaluations are essential when diagnosing an osteochondritis dissecans lesion of the elbow [12].
• Important aspects of osteochondritis dissecans lesions may be better seen with MRI [12].

References¶

[1] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy, Biomechanics, Physical Examination, and Imaging of the Elbow > Summary and Conclusions.

[3] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy, Biomechanics, Physical Examination, and Imaging of the Elbow > Anatomy > Bony Anatomy.

[4] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > TABLE 2.3 Shoulder Spaces.

[5] Miller S Review Of Orthopaedics. Genetics of musculoskeletal conditions and abnormalities are summarized in Table 1.27 > TABLE 2.3 Shoulder Spaces.

[9] Aaos Comprehensive Orthopaedic Review 3. Elbow Stiffness* > IV. Evaluation.

[11] Aaos Comprehensive Orthopaedic Review 3. Elbow Injuries in the Athlete* > III. Valgus Extension Overload Syndrome and Posterior Impingement.

[12] Orthopaedic Knowledge Update. Osteochondritis Dissecans of the Knee and Elbow* > Summary.

[13] Aaos Comprehensive Orthopaedic Review 3. Arthritis and Arthroplasty of the Elbow > I. Osteoarthritis.