INTRODUCTION TO UPPER EXTREMITY MALUNIONS

Malunions of the upper extremity, specifically involving the forearm and humerus, severely disrupt the intricate kinematic chain required for spatial positioning of the hand. Unlike the lower extremity, where weight-bearing alignment is the primary concern, the upper extremity relies on complex rotational axes—particularly forearm pronation and supination, and elbow flexion and extension. Deformities in these regions can lead to profound functional impairment, early-onset osteoarthritis, and secondary ligamentous instability.

This comprehensive guide delineates the pathoanatomy, biomechanical considerations, and operative techniques required to address malunions of the proximal radius and ulna, the humeral shaft, and the distal humerus.

PROXIMAL THIRD OF THE RADIUS AND ULNA

The proximal radioulnar joint (PRUJ) and the ulnohumeral articulation form a highly constrained, interdependent functional unit. Malunions of the proximal third of the radius and ulna can be systematically classified into five distinct categories:
1. Malunions of the radial head
2. Malunions of the radial neck
3. Malunions of the olecranon
4. Malunions of the proximal third of the ulna with anterior dislocation of the proximal radius (Monteggia fracture-dislocation)
5. Malunions complicated by radioulnar synostosis

Radial Head Malunions

Malunion of the radial head with only mild deformity may remain asymptomatic and not be functionally disabling. If symptoms are isolated to mechanical impingement caused by a small, abnormal prominence of bone, simple resection of the offending prominence may provide complete relief.

However, severe deformity invariably causes pain, limits forearm pronation and supination, and occasionally restricts terminal flexion or extension of the elbow. Historically, the gold standard for severe, symptomatic radial head malunion has been radial head excision, utilizing techniques identical to those employed for acute, irreparable fractures.

Surgical Technique: Radial Head Excision
When performing an excision, meticulous surgical technique is paramount to prevent heterotopic ossification.
* Approach: A standard Kocher (extensor carpi ulnaris and anconeus interval) or Kaplan (extensor digitorum communis and extensor carpi radialis brevis interval) approach is utilized.
* Resection: The radial head is resected at the level of the annular ligament.
* Debridement: All loose fragments of bone, excess osteophytes, scar tissue, periosteum, and remnants of the damaged annular ligament must be excised carefully to mitigate the formation of new bone in the resection void.

SURGICAL WARNING: Excising the radial head can result in complete restoration of function in a select cohort; however, the results are frequently disappointing. Patients must be counseled extensively regarding potential complications, which include loss of grip strength, chronic wrist pain, distal radioulnar joint (DRUJ) instability, and valgus instability of the elbow.

Joint-Preserving and Prosthetic Alternatives
Because of the adverse sequelae of excision, joint-preserving osteotomies have gained traction. Rosenblatt et al. reported on intraarticular osteotomies of the radial head in patients with symptomatic, healed, displaced articular fractures. Following osteotomy, the average Mayo Elbow Performance Index (MEPI) score improved significantly from 74 to 88, yielding good or excellent results in the majority of patients.

Prosthetic radial head replacement is strictly indicated for patients with radial head malunions associated with:
* Distal radioulnar joint pain or instability (Essex-Lopresti phenomenon).
* Laxity or insufficiency of the medial ulnar collateral ligament (MUCL) complex of the elbow.
* Concomitant coronoid deficiency (terrible triad sequelae).

Radial Neck Malunions

While most acute radial neck fractures can be managed successfully with nonoperative modalities, symptomatic malunions occasionally occur due to severe initial angulation or translation. A malunited radial neck fracture alters the rotational axis of the radius, leading to pain, crepitance, elbow laxity, and a mechanical block to both elbow flexion/extension and forearm pronation/supination.

Because of the known adverse sequelae following radial head excision, it is highly desirable to maintain radial length and restore the congruity of the radiocapitellar articulation—provided the articular cartilage of the radial head remains viable. Corrective osteotomy of the radial neck, utilizing a closing or opening wedge technique stabilized with miniature locking plates or headless compression screws, should be the first-line consideration for symptomatic malunions.

Olecranon Malunions

The management of olecranon malunions deviates significantly from standard long-bone malunion principles.

CLINICAL PITFALL: In malunion of the olecranon, corrective osteotomy and realignment of the fragments should generally not be attempted. Experience dictates that osteotomy in this region almost always increases elbow disability due to joint stiffness and hardware prominence.

Instead, function of the elbow can be improved considerably by excising the deformed, malunited portion of the bone and advancing the triceps. Biomechanical studies have repeatedly demonstrated that a substantial portion of the olecranon can be excised without causing significant elbow instability, provided the critical stabilizing structures are respected.

Biomechanical Guidelines for Olecranon Excision:
The exact amount of olecranon that can be safely excised is determined through rigorous preoperative radiographic templating:
1. Obtain a true lateral radiograph of the elbow flexed to exactly 90 degrees.
2. Draw a line through the center of the longitudinal axis of the humerus, extending across the joint.
3. The 0.3 cm Rule: At least 0.3 cm of the olecranon must project posterior to this longitudinal line. This specific volume of the olecranon is the absolute minimum required to prevent anterior subluxation of the proximal ulna under the pull of the brachialis and biceps.
4. The remainder of the malunited olecranon proximal to this point can be safely excised.
5. The triceps tendon must then be reattached accurately and firmly to the proximal ulna using heavy non-absorbable sutures passed through transosseous drill holes or robust suture anchors.

Monteggia Fracture Malunions (Proximal Ulna with Radial Head Dislocation)

If a Monteggia fracture unites in a poor position, the resulting deformity is profoundly disabling. The malunited ulnar bow prevents the radial head from articulating with the capitellum, leading to chronic radial head dislocation, progressive valgus deformity, and tardy posterior interosseous nerve (PIN) palsy.

Almost any reconstructive effort is worth a trial, as the natural history of a neglected Monteggia malunion is severe functional loss. At 1 year or more after the initial injury, the radiocapitellar joint may become so damaged that restoring near-normal elbow function becomes impossible.

Reconstructive Principles:
* Ulnar Osteotomy: The cornerstone of treatment is an opening wedge or distraction osteotomy of the malunited ulna. Restoring the anatomic length and dorsal angulation of the ulna is an absolute prerequisite; without it, the radial head cannot be reduced.
* Radial Head Reduction: Once the ulna is lengthened and plated, the radial head often reduces spontaneously.
* Annular Ligament Reconstruction: If the radial head remains unstable, an annular ligament reconstruction (e.g., Bell-Tawse procedure using a slip of the triceps tendon or palmaris longus autograft) is required.

MIDDLE THIRD OF THE HUMERAL SHAFT

Moving proximal to the forearm, malunions of the middle third of the humeral shaft present a different clinical paradigm. The shoulder and elbow joints possess a massive compensatory range of motion. Consequently, shortening, rotational deformity, and mild-to-moderate angulation of the humeral shaft impair overall upper extremity function far less than similar deformities in the femur or tibia.

Unless angulation is severe (typically >20 degrees of anterior/posterior angulation or >30 degrees of varus/valgus angulation) or there is a cosmetically unacceptable deformity, malunion of the middle third of the humerus rarely requires operative correction.

Surgical Correction Principles:
When operative intervention is indicated, the same principles used in correcting malunions of other long bones are applied:
1. Approach: An anterolateral or posterior approach is utilized, with meticulous identification and protection of the radial nerve.
2. Osteotomy: The deformity is corrected via a closing wedge, opening wedge, or dome osteotomy at the apex of the deformity.
3. Fixation: A robust 4.5-mm broad dynamic compression plate (DCP) or locking compression plate (LCP) is applied.
4. Biological Augmentation: Because diaphyseal osteotomies in cortical bone often fail to unite rapidly, cancellous bone grafts (autograft from the iliac crest or allograft) must be placed circumferentially around the osteotomy site. Alternatively, a structural onlay cortical bone graft can be utilized for added biomechanical stability.

DISTAL HUMERUS MALUNIONS

Malunions of the distal humerus are complex, multiplanar deformities that typically develop as sequelae to the following fractures:
1. Supracondylar fractures (most common in the pediatric population).
2. T-fractures or Y-fractures of the condyles.
3. Fractures of the distal condylar articular surface (e.g., capitellum or trochlea).
4. Isolated fractures of the medial or lateral condyles.

The Pathoanatomy of Cubitus Varus

Historically, cubitus varus (the "gunstock deformity") resulting from a malunited pediatric supracondylar fracture was considered merely a cosmetic nuisance. However, contemporary orthopedic literature has definitively proven that cubitus varus is a progressive biomechanical hazard.

Recent reports have strongly associated long-standing cubitus varus with a cascade of late-onset complications, including:
* Ulnar nerve dislocation and tardy ulnar neuropathy.
* Snapping of the medial head of the triceps over the medial epicondyle.
* Secondary distal humeral or lateral condylar fractures (due to altered force transmission).
* Osteonecrosis of the distal humeral epiphysis.
* Joint ganglia and early-onset osteoarthritis.

Posterolateral Rotatory Instability (PLRI) and Cubitus Varus:
Cubitus varus deformity after childhood elbow fracture has been directly linked to severe elbow instability in adulthood—sometimes presenting up to 51 years later. O’Driscoll et al. provided landmark insights into this phenomenon, noting that lateral elbow pain typically precedes the overt symptoms of instability.

BIOMECHANICAL PEARL: With cubitus varus, the mechanical axis of the upper extremity, the olecranon, and the triceps line of pull are all displaced medially. This medial shift generates a repetitive external rotation torque on the ulna during elbow flexion and extension. Over decades, this chronic torque stretches the lateral collateral ligament (LCL) complex, inevitably leading to posterolateral rotatory instability (PLRI).

Physical findings in these patients include:
* Obvious clinical cubitus varus.
* Tenderness over the LCL complex and the common extensor tendon.
* A prominent, palpable tendon of the medial head of the triceps.
* Positive PLRI signs: Posterolateral rotatory apprehension test, lateral pivot-shift test, and posterolateral rotatory drawer signs.
* Dynamic snapping of the medial triceps and ulnar nerve during flexion.

Furthermore, the abnormal mechanics of the varus elbow predispose the joint to severe ligamentous injury or fracture during a routine fall on an outstretched hand.

Surgical Correction of Distal Humerus Malunions

Corrective osteotomy for distal humeral malunion, particularly cubitus varus, requires meticulous preoperative planning. The goal is to restore the normal carrying angle (valgus), correct any internal rotation deformity, and restore the anatomic mechanical axis to offload the LCL complex.

Step-by-Step Surgical Technique:

1. Preoperative Templating: Precise calculation of the corrective wedge is performed using bilateral anterior-posterior and lateral radiographs. A lateral closing-wedge osteotomy, dome osteotomy, or step-cut (French) osteotomy is templated.
2. Surgical Approach: A posterior approach with an olecranon osteotomy or a triceps-sparing/triceps-reflecting approach is utilized, depending on the need for intra-articular visualization. The ulnar nerve is routinely identified, decompressed, and often transposed anteriorly to prevent postoperative neuropathy.
3. Osteotomy Execution: Divide the bone with a sharp osteotome or a reciprocating motor saw precisely through the apex of the angulation. Remove the templated wedge and close the osteotomy to correct the varus and rotational deformity.
4. Rigid Internal Fixation: Fix the fragments securely. While a standard 4.5-mm compression plate can be used, a modern proximal humeral locking plate (contoured for the distal humerus) or dual orthogonal distal humerus locking plates provide optimal, biomechanically superior fixation, especially in osteopenic bone.
5. Bone Grafting: Place cancellous autograft or allograft around the osteotomy site to accelerate osseous union and prevent delayed union or hardware failure.

Postoperative Care and Rehabilitation:
* Immobilization: Immediately postoperatively, the extremity is immobilized in an abduction humeral brace or a well-padded posterior splint and sling to protect the osteosynthesis.
* Early Mobilization: To prevent devastating elbow stiffness, shoulder and elbow active-assisted range of motion (ROM) exercises are initiated within the first postoperative week.
* Strengthening: Progressive resistance exercises are delayed until radiographic evidence of bridging callus is observed, typically at 6 to 8 weeks postoperatively.

By adhering to these strict biomechanical principles and executing precise surgical techniques, the orthopedic surgeon can successfully restore function, alleviate pain, and prevent the long-term degenerative sequelae associated with upper extremity malunions.