Elbow — Surgical Anatomy and Approaches

Introduction

The elbow joint, with its complex combination of hinge motion (humeroulnar articulation) and pivot motion (proximal radioulnar joint) within a single capsule, presents distinct anatomical and surgical challenges. The surrounding muscular envelope is relatively thin compared with the shoulder, and the proximity of the ulnar nerve, the radial nerve and its branches (particularly the posterior interosseous nerve), the median nerve, and the brachial artery to the joint demand careful attention during surgical approaches. The orthopedic surgeon working at the elbow has multiple approach options, each providing access to different regions of the joint: the Kocher approach for the lateral side and radial head/capitellum, the posterior approaches (triceps-splitting, paratricipital, reflecting, and olecranon osteotomy) for the distal humerus and ulnohumeral joint, the medial approaches for the medial collateral ligament and ulnar nerve, and the anterior approaches for vascular and neural exploration. This chapter draws on Orthopaedic Surgical Approaches, Netter’s Concise Orthopaedic Anatomy, and Gray’s Anatomy.

Bony and Articular Anatomy

The elbow joint comprises three articulations within a single synovial capsule: Humeroulnar joint: Hinge articulation between the trochlea of the distal humerus and the trochlear notch of the proximal ulna. Provides flexion-extension (normal range approximately 0 to 145 degrees of flexion; functional range 30 to 130 degrees). Humeroradial joint: Articulation between the capitellum of the distal humerus and the radial head. Participates in flexion-extension and forearm rotation. Proximal radioulnar joint: Pivot articulation between the radial head and the radial notch of the ulna, with the annular ligament holding the radial head in position. Provides forearm rotation (normal supination approximately 85 degrees, pronation approximately 85 degrees). The carrying angle of the extended elbow is approximately 11 degrees of valgus in females and 7 to 11 degrees in males. Loss of carrying angle (e.g., from supracondylar malunion) produces cubitus varus (gunstock deformity); excessive carrying angle produces cubitus valgus. The distal humerus anatomy was detailed in Topic Trauma-15: divergent medial and lateral columns, trochlea (spool-shaped), capitellum (rounded), olecranon and coronoid fossae. The proximal ulna comprises the olecranon (with triceps insertion), coronoid process (anterior buttress), and trochlear notch. The proximal radius has the disc-shaped radial head (with the annular ligament around it), radial neck, and radial tuberosity (biceps insertion).

Ligamentous Anatomy

The medial collateral ligament (MCL) complex has three bundles: Anterior bundle: From the inferior anterior surface of the medial epicondyle to the sublime tubercle of the coronoid. The primary restraint to valgus stress in mid-range elbow flexion. Injured in throwing athletes (Tommy John surgery candidates). Posterior bundle: From the medial epicondyle posteriorly to the medial olecranon. Reinforces the medial joint capsule. Transverse bundle (Cooper’s ligament): Between the olecranon and the coronoid. Minor contribution to stability. The lateral collateral ligament (LCL) complex includes: Lateral ulnar collateral ligament (LUCL): From the lateral epicondyle posteriorly to the supinator crest of the ulna. The primary restraint to posterolateral rotatory instability — described by O’Driscoll in 1991 and central to the understanding of complex elbow injuries. Radial collateral ligament: From the lateral epicondyle to the annular ligament. Annular ligament: Around the radial head, attached to the anterior and posterior margins of the radial notch of the ulna. Accessory lateral collateral ligament: From the inferior aspect of the annular ligament to the supinator crest. Reinforces the LUCL.

Neurovascular Structures

Ulnar Nerve The ulnar nerve descends through the posterior medial intermuscular septum and enters the cubital tunnel between the medial epicondyle and the olecranon. The tunnel is bounded medially by the Osborne ligament (the arcuate ligament between the two heads of the flexor carpi ulnaris) and laterally by the medial collateral ligament. The nerve then passes between the two heads of the flexor carpi ulnaris and enters the forearm. The cubital tunnel syndrome (the second most common compression neuropathy in the upper extremity, after carpal tunnel) is a recognized entity. Tinel’s sign over the cubital tunnel, and elbow flexion test with maintained flexion for 1 minute reproducing symptoms, are positive in cubital tunnel syndrome. Surgical treatment options include in situ decompression (release of the cubital tunnel retinaculum), submuscular anterior transposition (transferring the nerve anterior to the medial epicondyle with the muscle protection), and subcutaneous anterior transposition (similar but without muscle covering). The ulnar nerve is at risk in any medial elbow approach and is routinely identified and protected during distal humerus surgery.

Median Nerve and Brachial Artery The median nerve and brachial artery pass through the cubital fossa, with the artery typically lateral to the nerve at the elbow. The artery and nerve are deep to the bicipital aponeurosis (lacertus fibrosus), a fibrous expansion of the biceps tendon that crosses the cubital fossa medially. The brachial artery bifurcates into the radial and ulnar arteries near the level of the radial neck. The median nerve continues distally between the two heads of the pronator teres (where it is occasionally compressed in pronator syndrome), then passes deep to the flexor digitorum superficialis arch and enters the forearm. Radial Nerve The radial nerve approaches the elbow anteriorly (after piercing the lateral intermuscular septum in the distal arm) and passes through the cubital fossa lateral to the biceps tendon, between the brachialis (medial) and the brachioradialis (lateral). At the level of the radial head, the nerve divides into: Superficial branch (sensory): Continues distally beneath the brachioradialis to the distal forearm, where it becomes superficial. Deep branch (posterior interosseous nerve, PIN): Passes through the arcade of Frohse (the fibrous proximal margin of the supinator) and through the supinator muscle to enter the posterior forearm. The PIN supplies the extensor compartment muscles. The PIN is at risk in lateral approaches to the proximal radius and the radial head, particularly during pronation of the forearm (which moves the nerve closer to the operative field; the forearm should be supinated during surgery to displace the nerve laterally). The PIN is also at risk in radial head dislocation and in surgical manipulation of the radial head. Cubital Vessels The cubital fossa contains the median nerve, brachial artery, and brachial veins, with the bicipital aponeurosis crossing the artery superficially. The superficial veins (median cubital vein, cephalic vein, basilic vein) traverse the cubital fossa subcutaneously.

The Kocher Approach (Lateral)

The Kocher approach is the classical lateral approach to the elbow joint, providing access to the radial head, capitellum, coronoid process (from the lateral side), lateral collateral ligament complex, and posterolateral elbow capsule. Patient Positioning The patient is supine with the affected arm on a hand table or arm board, or lateral decubitus with the arm supported in front of the body. The elbow is positioned to expose the lateral aspect.

Surface Landmarks and Incision The lateral epicondyle is the principal landmark. The skin incision extends from approximately 4 to 6 cm proximal to the lateral epicondyle distally over the radial head to approximately 4 to 6 cm distal to the radial head. The total length is approximately 8 to 12 cm.

Approach The skin and subcutaneous tissue are incised. The fascia is opened in line with the skin incision. The Kocher interval between the anconeus (posterior, supplied by the radial nerve) and the extensor carpi ulnaris (ECU) (anterior, supplied by the PIN) is identified — this is the classical internervous plane that gives the Kocher approach its name. The interval is developed bluntly, with the dissection carried down to the lateral elbow capsule. The annular ligament is identified at the level of the radial head. For exposure of the radial head, the annular ligament can be incised and reflected. The radial head and capitellum are then visualized. For more proximal exposure (capitellum, lateral epicondyle, lateral column of the distal humerus), the incision can be extended proximally with elevation of the common extensor origin from the lateral epicondyle. For more distal exposure (proximal radius, supinator), the dissection extends distally with forearm supination to protect the PIN (which moves laterally away from the operative field with supination). Complications The complications of the Kocher approach include PIN injury (the principal concern; minimized by forearm supination during dissection and avoidance of vigorous lateral retraction of the supinator), damage to the lateral collateral ligament complex (with iatrogenic posterolateral rotatory instability), and stiffness of the elbow if the approach is extensive. Modifications The extensor digitorum communis (EDC) split approach uses the muscle-splitting plane within the EDC rather than the Kocher interval, providing more direct access to the anterior aspect of the radial head. The PIN considerations are similar.

Posterior Approaches to the Elbow

The posterior approaches were discussed in detail in the context of the distal humerus approaches in Topic Anatomy-3 (arm/humerus). They include: Triceps-splitting approach: Midline split of the triceps muscle, providing access to the distal humerus.

Paratricipital (Bryan-Morrey) approaches: Retraction of the triceps medially or laterally, preserving the triceps insertion. Triceps-reflecting (Bryan-Morrey) approach: Detachment of the triceps insertion from the olecranon with reflection proximally. Olecranon osteotomy approach: Chevron-shaped osteotomy of the olecranon to expose the distal humeral articular surface for complex intra-articular fractures. The choice among these approaches for elbow surgery depends on the planned procedure. For distal humerus fracture ORIF, the olecranon osteotomy provides the best visualization. For total elbow arthroplasty, the paratricipital approach (or triceps- reflecting in older techniques) is preferred to preserve the olecranon and triceps insertion. For simple distal humerus exposure (e.g., for biopsy, tumor resection without articular involvement), the triceps-splitting or paratricipital approach may suffice.

Medial Approach to the Elbow

The medial approach provides access to the medial epicondyle, medial collateral ligament, ulnar nerve, and medial coronoid process. Patient Positioning The patient is supine with the affected arm on a hand table, or the arm positioned across the chest for medial access. Surface Landmarks and Incision The medial epicondyle is the principal landmark. The skin incision extends from approximately 5 cm proximal to the medial epicondyle distally for approximately 8 to 10 cm, centered over the medial epicondyle.

Approach The skin and subcutaneous tissue are incised, with attention to the medial antebrachial cutaneous nerve (branches typically cross the operative field and should be preserved). The medial intermuscular septum is identified proximally, and the ulnar nerve is identified posterior to the medial epicondyle. The ulnar nerve is mobilized and protected throughout the procedure. For MCL reconstruction (Tommy John surgery), the common flexor mass origin from the medial epicondyle is incised vertically (the “muscle-splitting” approach of Jobe) or the common flexor origin is detached (the “detachment” approach). The native MCL is exposed and the reconstruction proceeds (typically with a palmaris longus or hamstring tendon graft passing through bony tunnels). For medial coronoid fracture fixation (particularly the anteromedial facet pattern of O’Driscoll discussed in Topic Trauma-15), the medial approach with medial Hotchkiss “over the top” modification provides access to the coronoid.

For ulnar nerve transposition, the nerve is mobilized from the cubital tunnel and transposed anteriorly (subcutaneously or submuscularly) anterior to the medial epicondyle. Complications The complications of the medial approach include ulnar nerve injury (the principal concern; the nerve must be identified and protected throughout), medial antebrachial cutaneous nerve injury (with painful neuroma formation), and flexor mass disruption (with grip strength loss if the common flexor origin is not adequately repaired).

Anterior Approach to the Elbow (Henry Approach to Elbow)

The anterior approach is used for vascular injury repair (brachial artery), distal biceps tendon repair, and selected exposures of the anterior elbow. Patient Positioning The patient is supine with the affected arm on a hand table, forearm supinated. Surface Landmarks and Incision The incision is a lazy S or lazy J that crosses the cubital crease at an angle to avoid scar contracture across the flexion crease. Approach The skin and subcutaneous tissue are incised. The lacertus fibrosus (bicipital aponeurosis) is identified and incised, providing access to the cubital fossa. The brachial artery and median nerve are identified and protected. For distal biceps tendon repair, the distal biceps tendon is identified after disruption of the lacertus and traced to its retracted location. Repair to the radial tuberosity is performed through a single anterior approach (with the additional risk of PIN injury during posterior tuberosity preparation) or through the classical two-incision (Boyd-Anderson) approach with a separate posterior incision for the radial tuberosity. For vascular injury repair, the brachial artery is directly exposed and repaired. For anterior capsulectomy (in stiff elbow surgery), the anterior approach provides access to the anterior capsule and the coronoid fossa. Complications The complications of the anterior approach include median nerve injury, brachial artery injury, lateral antebrachial cutaneous nerve injury, and PIN injury (particularly during distal biceps tendon repair from the anterior approach).

Surgical Approaches to the Cubital Tunnel and Ulnar Nerve

The cubital tunnel is approached through a longitudinal incision posterior to the medial epicondyle. The Osborne ligament (the arcuate ligament between the two heads of the flexor carpi ulnaris) is identified and released, providing in situ decompression of the ulnar nerve. For anterior transposition, the nerve is further mobilized and brought anteriorly, either: Subcutaneously: The nerve is placed in the subcutaneous tissue anterior to the medial epicondyle, with a fascial sling or tendon turn-up sometimes used to maintain position. Submuscularly: The flexor pronator origin is detached, the nerve is placed deep to the muscle, and the muscle is reattached over the nerve. The submuscular position provides more protection but requires more dissection. Intramuscularly: The nerve is placed within a groove created in the flexor pronator muscle mass. This technique is less commonly used. Medial epicondylectomy is an alternative procedure that removes the medial epicondyle, allowing the nerve to lie naturally anterior; it has fallen out of favor because of concerns about MCL function and persistent pain.

Summary and Take-Home Points

The elbow joint, with its complex combination of hinge and pivot articulations, requires careful attention to the surrounding neurovascular structures during surgical approaches. The Kocher approach uses the internervous interval between anconeus (radial nerve) and extensor carpi ulnaris (PIN) to access the lateral elbow, with the posterior interosseous nerve being the principal neurological concern, minimized by forearm supination during dissection. The approach provides access to the radial head, capitellum, and lateral collateral ligament complex. The posterior approaches (triceps-splitting, paratricipital, triceps-reflecting, olecranon osteotomy) provide access to the distal humerus and ulnohumeral joint, with the choice depending on the planned procedure. The olecranon osteotomy provides the best visualization for complex intra-articular distal humerus fractures. The medial approach provides access to the medial epicondyle, MCL, and ulnar nerve, with the ulnar nerve being the principal neurological concern. The approach is used for MCL reconstruction (Tommy John surgery), medial coronoid fixation, and ulnar nerve transposition. The anterior approach uses a lazy-S incision crossing the cubital crease at an angle to avoid scar contracture, with development through the lacertus fibrosus to expose the brachial artery, median nerve, and the cubital fossa contents. The approach is used for vascular injury repair, distal biceps tendon repair, and anterior capsulectomy in stiff elbow surgery.

The principal neurovascular structures at risk in elbow surgery are the ulnar nerve (cubital tunnel), the posterior interosseous nerve (arcade of Frohse), the median nerve and brachial artery (cubital fossa), and the medial antebrachial cutaneous nerve (subcutaneous, vulnerable to neuroma formation). The chapter that follows turns to the forearm, where the principles of anatomical reduction for forearm rotation (Topic Trauma- 16) are revisited from the anatomical perspective and the principal surgical approaches to the radius and ulna are addressed.