UCL Reconstruction: The Andrews Technique

Comprehensive Introduction and Patho-Epidemiology

The Ulnar Collateral Ligament (UCL) serves as the primary static restraint to valgus stress at the human elbow, functioning most critically between 20 and 120 degrees of flexion. In the overhead athlete, and most quintessentially in the baseball pitcher, the biomechanics of throwing generate extraordinary forces across the medial elbow. During the late cocking and early acceleration phases of the throwing motion, valgus torque can reach or exceed 64 Newton-meters (Nm). Given that the ultimate tensile failure strength of the native UCL is approximately 32 to 34 Nm, the ligament is routinely subjected to near-failure loads. This biomechanical paradox dictates that the dynamic stabilizers—specifically the flexor-pronator musculature—must absorb the remaining kinetic energy. When these dynamic restraints fatigue, the UCL absorbs the brunt of the force, leading to a predictable cascade of microtrauma, plastic deformation, attenuation, and eventual macroscopic rupture.

The surgical management of UCL insufficiency represents one of the most celebrated triumphs in modern sports medicine, revolutionized initially by Dr. Frank Jobe in 1974. However, the classic Jobe technique, while groundbreaking, necessitated the detachment and subsequent reattachment of the common flexor-pronator mass from the medial epicondyle. This extensive surgical dissection frequently resulted in prolonged rehabilitation timelines, significant flexor-pronator morbidity, and a notable incidence of postoperative ulnar neuropathy. Recognizing these limitations, Dr. James Andrews and his colleagues at the American Sports Medicine Institute (ASMI) introduced a critical evolutionary modification. The Andrews technique eschews flexor-pronator detachment in favor of a muscle-splitting approach through the flexor carpi ulnaris (FCU).

By meticulously navigating the internervous and intermuscular planes, the Andrews technique preserves the native flexor-pronator origin. This preservation minimizes iatrogenic trauma, maintains the crucial dynamic medial stability of the elbow, and accelerates the early phases of postoperative rehabilitation. Furthermore, the Andrews technique systematically incorporates an anterior transposition of the ulnar nerve. This step proactively addresses concomitant cubital tunnel syndrome, ulnar nerve subluxation, and the friction neuritis that frequently accompanies the valgus extension overload (VEO) cascade.

The epidemiology of UCL injuries has shifted dramatically over the past two decades. Once considered an exclusive injury of the aging professional pitcher, UCL insufficiency has reached epidemic proportions among adolescent and collegiate athletes. Year-round play, single-sport specialization, and the relentless pursuit of maximum velocity have exponentially increased cumulative workload and subsequent valgus stress on the developing elbow. Understanding the patho-epidemiology of this injury is paramount for the orthopedic surgeon, as it directly informs both the surgical rationale and the rigorous, phased rehabilitation required to return these athletes to their prior level of elite competition.

Detailed Surgical Anatomy and Biomechanics

A profound, three-dimensional understanding of medial elbow osteology, ligamentous topography, and neurovascular relationships is mandatory for the successful execution of the Andrews technique. The medial ligamentous complex of the elbow is classically divided into three distinct anatomical bundles: the anterior bundle, the posterior bundle, and the transverse bundle (often referred to as Cooper’s ligament). The anterior bundle of the medial collateral ligament (AMCL) is the undisputed primary static restraint to valgus stress. It originates on the anteroinferior aspect of the medial epicondyle, slightly posterior to the axis of rotation, and inserts distally on the sublime tubercle of the proximal ulna.

The anterior bundle is further subdivided biomechanically into anterior and posterior bands. The anterior band is taut in extension and serves as the primary restraint up to 90 degrees of flexion, whereas the posterior band becomes increasingly taut in deeper flexion, acting as the primary restraint from 90 to 120 degrees. The posterior bundle of the UCL, which forms the floor of the cubital tunnel, is a secondary restraint that only becomes biomechanically significant at flexion angles greater than 90 degrees. The transverse bundle originates and inserts entirely on the ulna; thus, it does not cross the ulnohumeral joint and contributes negligibly to overall valgus stability.

The concept of isometry is central to the biomechanical success of UCL reconstruction. True isometry—where the distance between the origin and insertion remains perfectly constant throughout the entire arc of motion—is a theoretical ideal rather than a strict anatomical reality in the human elbow. However, the surgical objective of the Andrews technique is to place the humeral tunnel at the exact anatomic origin of the anterior bundle, effectively establishing the "isometric point." If the humeral graft origin is placed too far anteriorly, the graft will be excessively tight in flexion and loose in extension. Conversely, posterior placement results in a graft that is tight in extension and lax in flexion. Precision in identifying the isometric footprint on the medial epicondyle is therefore the most critical determinant of postoperative joint kinematics.

Overlying the UCL complex is the flexor-pronator mass, a robust muscular confluence comprising the pronator teres (PT), flexor carpi radialis (FCR), palmaris longus (PL), flexor digitorum superficialis (FDS), and flexor carpi ulnaris (FCU). The FCU is unique as it possesses two distinct heads: a humeral head originating from the medial epicondyle and an ulnar head originating from the olecranon. The Andrews technique exploits the anatomical interval between these two heads, allowing the surgeon to bluntly dissect down to the sublime tubercle without compromising the tendinous origin of the flexor-pronator mass. Deep within this regional anatomy lies the ulnar nerve, descending posterior to the medial intermuscular septum, passing through the arcade of Struthers, and entering the cubital tunnel beneath Osborne’s fascia. Meticulous management of this nerve and its delicate vascular leash is a cornerstone of the procedure.

Exhaustive Indications and Contraindications

The decision to proceed with operative intervention for UCL insufficiency must be predicated on a comprehensive synthesis of the patient's clinical history, physical examination, advanced imaging, and athletic aspirations. Patients typically present with an insidious onset of medial elbow pain localized to the late cocking and early acceleration phases of throwing. A precipitating "pop" followed by acute pain and an immediate inability to throw is classic for an acute rupture, though many patients describe a more chronic, progressive "dead arm" sensation characterized by a loss of velocity and control. Clinical examination must include the moving valgus stress test and the milking maneuver, both of which are highly sensitive for AMCL pathology. Concomitant ulnar neuritis, presenting as paresthesias in the ring and small fingers or a positive Tinel's sign at the cubital tunnel, must be carefully documented.

Conservative management—consisting of absolute rest from throwing, nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroid or biologic injections (such as Platelet-Rich Plasma), and a structured flexor-pronator rehabilitation program—is typically the first line of treatment for partial thickness tears or chronic attenuation. However, in the elite overhead athlete with a full-thickness rupture, or in those who have failed a minimum of three to six months of non-operative management, surgical reconstruction is definitively indicated. The threshold for surgical intervention is significantly lower in competitive athletes whose careers depend on the restoration of absolute valgus stability.

Contraindications to UCL reconstruction must be rigorously respected to avoid catastrophic postoperative failures. Advanced degenerative joint disease of the ulnohumeral or radiocapitellar joints represents a strong relative, if not absolute, contraindication, as restoring ligamentous stability will not alleviate the pain associated with severe arthrosis. Patients with a history of non-compliance or those unwilling to commit to the grueling 12-to-18-month postoperative rehabilitation protocol are poor surgical candidates. Furthermore, in non-throwing athletes or low-demand individuals, conservative management or primary repair with internal bracing may be more appropriate than complex reconstruction.

Pre-Operative Planning, Templating, and Patient Positioning

Preoperative planning for the Andrews technique demands meticulous attention to both the primary ligamentous pathology and the potential need for concomitant procedures. Advanced imaging is non-negotiable. Standard radiographs, including anteroposterior (AP), lateral, and axillary views, are evaluated for medial epicondyle avulsion fractures, loose bodies, and the posteromedial osteophytes characteristic of valgus extension overload (VEO). Magnetic Resonance Arthrography (MRA) remains the gold standard imaging modality. The intra-articular contrast distends the joint, allowing for the precise identification of partial undersurface tears of the anterior bundle—often visualized as the classic "T-sign" where contrast leaks medial to the sublime tubercle.

Graft selection is a critical component of preoperative templating and must be finalized prior to the induction of anesthesia. The presence or absence of the palmaris longus (PL) tendon must be documented clinically using Schaeffer’s test (opposing the thumb and small finger while flexing the wrist). The ipsilateral palmaris longus is the undisputed gold standard graft for the Andrews technique due to its anatomical proximity, appropriate length (typically 12–15 cm), robust tensile strength, and negligible harvest morbidity. If the ipsilateral PL is congenitally absent (occurring in approximately 15% of the population) or deemed inadequate, the contralateral PL is the secondary option. When neither PL is available, the gracilis tendon is an excellent tertiary alternative, providing a thick, robust graft, though its harvest necessitates a separate surgical field on the lower extremity. Plantaris or fourth toe extensor tendons remain viable but rarely utilized quaternary options.

Anesthetic management typically involves general endotracheal anesthesia to ensure absolute patient immobility during the delicate neurovascular dissection and precise tunnel drilling. This is frequently supplemented with a regional block, such as a supraclavicular or interscalene brachial plexus block, which provides profound postoperative analgesia and limits the need for systemic opioids. The anesthesia team must be advised to avoid long-acting paralytics to allow for intraoperative monitoring of the ulnar nerve if necessary, though direct visualization usually suffices.

Patient positioning is paramount for optimal surgical ergonomics. The patient is placed supine on the operating table with the operative arm extended onto a radiolucent hand table. The shoulder is abducted to approximately 90 degrees, and the arm is externally rotated to present the medial aspect of the elbow to the surgeon. A sterile tourniquet is applied as proximally as possible on the brachium to ensure a bloodless field, which is absolutely critical during the identification and mobilization of the ulnar nerve and its microscopic vascular leash. The arm is prepped and draped in a standard sterile fashion, ensuring exposure from the proximal humerus down to the distal palmar crease of the hand, facilitating both the elbow reconstruction and the distal graft harvest.

Step-by-Step Surgical Approach and Fixation Technique

Diagnostic Arthroscopy (Optional but Recommended)

Unless the patient presents with an acute, massive medial rupture with gross instability, a limited diagnostic arthroscopy is highly recommended prior to the open reconstruction. Utilizing a standard anterolateral portal, the surgeon systematically evaluates the radiocapitellar joint for chondromalacia, which can result from chronic lateral compressive forces secondary to medial laxity. The arthroscope is then directed to the posteromedial compartment to assess for osteophytes associated with valgus extension overload; these are resected using an arthroscopic burr to restore terminal extension. Finally, a dynamic valgus stress test is performed under direct visualization. A medial joint space opening of greater than 1 to 2 millimeters confirms functional UCL insufficiency and validates the decision to proceed with reconstruction.

Incision and Superficial Dissection

Following arthroscopy, the arm is exsanguinated, and the sterile tourniquet is inflated to 250 mmHg. An 8 to 10 cm longitudinal incision is made, centered directly over the medial epicondyle. The incision extends approximately 3 cm proximally along the medial intermuscular septum and 5 cm distally over the flexor-pronator mass. Subcutaneous dissection is performed with meticulous hemostasis. The most critical aspect of this superficial phase is the identification and protection of the medial antebrachial cutaneous nerve (MABC). The MABC is highly variable, often presenting as a single large trunk with multiple delicate arborizations crossing the operative field. Iatrogenic injury to the MABC is a leading cause of postoperative dissatisfaction, leading to painful neuromas or dysesthesias. The nerve branches must be gently mobilized and retracted using silastic vessel loops, strictly avoiding excessive traction.

Ulnar Nerve Management

The Andrews technique mandates an anterior transposition of the ulnar nerve to prevent postoperative friction neuritis and to facilitate the safe, unhindered FCU-splitting exposure. Skin flaps are elevated to expose the deep fascia. The ulnar nerve is identified proximally as it pierces the medial intermuscular septum and is traced distally into the cubital tunnel. Osborne’s fascia (the cubital tunnel retinaculum) is sharply incised. Dissection proceeds proximally to release the arcade of Struthers. A 2 to 3 cm portion of the medial intermuscular septum is excised to prevent kinking or impingement of the nerve once it is transposed anteriorly. Distally, the fascia of the FCU is incised along the course of the nerve. Small articular branches to the elbow joint are sacrificed to allow adequate excursion, but the surgeon must meticulously preserve the motor branches innervating the FCU and the flexor digitorum profundus. The nerve is then transposed anteriorly into a secure, tension-free subcutaneous pocket.

The Muscle-Splitting Exposure

With the ulnar nerve safely transposed, attention is turned to the flexor-pronator mass. The surgeon identifies the longitudinal raphe separating the humeral and ulnar heads of the FCU. A blunt, muscle-splitting dissection is performed along this interval, navigating between the muscle bellies down to the joint capsule and the insertion of the anterior bundle of the UCL on the sublime tubercle. The interval is developed from distal to proximal, as the tissue planes are more distinct at the ulnar insertion. Small, blunt Hohmann or self-retaining retractors (such as a Gelpi) are placed to retract the flexor muscles anteriorly and posteriorly. This crucial maneuver provides full, panoramic visualization of the native ligament without detaching the flexor-pronator origin, thereby preserving the dynamic medial stability of the elbow.

Ligament Evaluation and Graft Harvest

A longitudinal incision is made directly in line with the fibers of the native anterior bundle. The undersurface of the ligament is inspected for detachment, intrasubstance attenuation, or calcific deposits. Crucially, the native ligament is not excised. The remnants of the native UCL are preserved to be repaired over the reconstructed graft, providing a robust vascular envelope that accelerates graft ligamentization and augments the overall biomechanical strength of the repair. Attention is then temporarily diverted to the distal forearm for graft harvest. A 2-cm transverse incision is made at the distal wrist flexor crease to identify the palmaris longus tendon. Using a specialized closed tendon stripper, the graft is harvested, avoiding the morbidity of multiple skip incisions. On the back table, the graft is meticulously prepared. Adipose and muscle tissue are debrided, and a No. 1 braided nonabsorbable suture (e.g., Ethibond Excel OS-2 or FiberWire) is placed in a locking Krackow fashion at both ends of the tendon. The graft is kept wrapped in a saline-soaked sponge to prevent desiccation.

Tunnel Preparation

Precision in tunnel placement dictates the biomechanical success of the operation. The sublime tubercle is subperiosteally exposed. Using a No. 3 burr or a 3.2 mm drill, two converging tunnels are created: one anterior and one posterior to the sublime tubercle. It is absolutely imperative that a robust 2-cm bony bridge remains between these two tunnels to prevent iatrogenic fracture during graft tensioning. The tunnels are connected using a small curved curet, and a looped 2-0 passing suture is shuttled through the ulnar tunnel. On the humeral side, the anatomic origin of the anterior bundle is identified on the anterior half of the medial epicondyle. Using a No. 4 burr, a primary longitudinal blind tunnel is directed up the axis of the epicondyle to a depth of exactly 15 mm. The superior border of the epicondyle is then exposed, and using a 2.0 mm drill bit, two small exit tunnels (separated by 5 to 10 mm) are created, converging into the apex of the primary 15 mm tunnel. Passing sutures are shuttled through these superior tunnels into the primary socket to facilitate graft docking.

Graft Passage and Tensioning

Before passing the graft, the longitudinal split in the native UCL is partially repaired at its base with 2-0 absorbable sutures. The graft is then passed through the ulnar tunnel from anterior to posterior. The sutured limbs of the graft are shuttled into the primary humeral tunnel, and the Krackow suture tails are pulled out through the two small superior exit tunnels. The tensioning protocol is the most critical biomechanical step. The elbow is reduced, the forearm is placed in supination (to unlock the radiocapitellar joint), and a gentle varus stress is applied to close the medial joint space. The elbow is flexed and extended through a full range of motion while maintaining tension on the suture tails; this cycles the graft and eliminates viscoelastic creep. The final tensioning is performed with the elbow at approximately 30 to 45 degrees of flexion, where the anterior bundle is naturally taut. The graft is marked, any excess tendon is trimmed, and the sutures are tied securely over the superior bony bridge of the medial epicondyle. The native ligament is then imbricated over the graft to complete the reconstruction.

Complications, Incidence Rates, and Salvage Management

While the Andrews technique boasts an exceptionally high success rate—with over 85% to 90% of elite athletes returning to their pre-injury level of sport—surgeons must remain hyper-vigilant regarding potential complications. The anatomical complexity of the medial elbow renders the procedure unforgiving to technical errors. Comprehensive knowledge of these pitfalls, their incidence, and their salvage management is essential for the operating surgeon.

Ulnar neuropathy remains the most common postoperative complication, occurring in approximately 5% to 8% of cases, despite the routine anterior transposition utilized in the Andrews technique. This complication typically arises from aggressive handling of the nerve, devascularization due to excessive stripping of the extrinsic blood supply, or mechanical kinking. Kinking most frequently occurs at the proximal extent of the transposition if the medial intermuscular septum is inadequately excised, or distally if the fascial sling constructed to prevent posterior subluxation is excessively tight. Management begins with conservative measures, including oral corticosteroids and gabapentinoids. Refractory cases may require surgical exploration, neurolysis, and potential revision of the transposition into a submuscular plane.

Iatrogenic injury to the medial antebrachial cutaneous nerve (MABC) is another significant source of postoperative morbidity, with an incidence of 2% to 5%. Aggressive retraction or inadvertent transection of the MABC branches leads to painful neuromas or hyperesthesia over the medial forearm. Prevention through meticulous superficial dissection is paramount. If a neuroma develops and fails conservative management (desensitization therapy, localized injections), surgical excision of the neuroma and burying of the proximal nerve stump deep into the adjacent muscle belly is the salvage procedure of choice.

Structural failures, though rare, are catastrophic. Fracture of the ulnar bone bridge occurs in less than 1% of cases but is a direct result of placing the ulnar tunnels too close together. A minimum 2-cm bridge must be maintained. If a fracture occurs intraoperatively, salvage requires the use of suture anchors placed directly into the sublime tubercle to secure the graft. Loss of terminal extension is a more common biomechanical complication, often resulting from over-tensioning the graft in extension rather than the recommended 30 to 45 degrees of flexion, or from prolonged postoperative immobilization. Early, controlled range of motion in a hinged brace is critical to mitigating this risk.

Phased Post-Operative Rehabilitation Protocols

Rehabilitation following the Andrews technique for UCL reconstruction is a lengthy, rigorous, and biologically driven process. The protocol must respect the complex physiological process of graft ligamentization—where the avascular tendon graft undergoes necrosis, revascularization, cellular proliferation, and eventual remodeling into a ligament-like structure. Premature stress across the joint can lead to graft elongation and catastrophic failure, while overly conservative immobilization results in debilitating arthrofibrosis.

Phase I (0–2 Weeks): Immediate Postoperative Phase
The primary goals of this phase are the protection of the healing graft, mitigation of edema, and prevention of distal stiffness. The patient is immediately immobilized postoperatively in a posterior splint with the elbow at 90 degrees of flexion and neutral forearm rotation. Strict elevation is enforced. Active range of motion (AROM) of the wrist, fingers, and shoulder (avoiding external rotation, which places valgus stress on the elbow) is initiated immediately to promote venous return and prevent capsular contractures in adjacent joints.

Phase II (2–6 Weeks): Intermediate Range of Motion Phase
At two weeks, the posterior splint is removed, and the patient is transitioned to a hinged elbow brace. The brace is initially locked from 30 to 90 degrees. Range of motion is gradually advanced by 5 to 10 degrees per week in both extension and flexion, with the goal of achieving full ROM by week 6. Submaximal, pain-free isometric exercises for the flexor-pronator mass, biceps, and triceps are initiated. Scapular stabilization exercises and core strengthening are heavily emphasized, recognizing that the elbow is merely the terminal link in the kinetic chain of throwing.

Phase III (6–12 Weeks): Advanced Strengthening Phase
Once full, painless range of motion is achieved (typically around week 6), the hinged brace is discontinued. The focus shifts to aggressive isotonic strengthening. The "Thrower’s Ten" program is initiated, focusing on eccentric control of the flexor-pronator musculature, rotator cuff strengthening, and correction of any underlying scapular dyskinesia. Plyometric exercises are gradually introduced toward the end of this phase to prepare the neuromuscular system for the explosive forces of throwing.

Phase IV & V (3–12+ Months): Return to Throwing and Competition
At approximately 3 to 4 months postoperatively, assuming normal clinical examination and symmetric strength, the athlete initiates a highly structured interval throwing program (ITP) on flat ground. The ITP strictly dictates throwing distance, volume, and intensity, progressively loading the medial elbow. By months 9 to 12, the pitcher progresses to throwing off the mound, initially focusing on fastball mechanics before introducing breaking pitches. Return to competitive, in-game pitching is typically achieved between 12 and 18 months postoperatively. This timeline is entirely contingent upon the restoration of absolute dynamic stability, flawless throwing mechanics, and the complete absence of pain.

Summary of Landmark Literature and Clinical Guidelines

The evolution of UCL reconstruction is chronicled through several landmark publications that have shaped the current standard of care. Dr. Frank Jobe’s original 1986 publication in the Journal of Bone and Joint Surgery (JBJS) detailed the first 16 cases of UCL reconstruction using a free tendon graft with flexor-pronator detachment. While revolutionary, Jobe reported a significant incidence of ulnar neuropathy and prolonged return-to-play timelines, sparking the search for technical refinements.

The paradigm shifted significantly in 1995 when Dr. James Andrews and Dr. Laura Timmerman published their pivotal work describing the muscle-splitting approach. By meticulously navigating the