Forearm Fractures and Fracture-Dislocations

Introduction

The forearm is unique in the orthopedic skeleton in that it is functionally not a single bone but a kinetic chain — two bones (radius and ulna) connected at both ends by joints (proximal and distal radioulnar joints) and along their length by the interosseous membrane, the entire complex acting as a single functional unit for the rotational motions of pronation and supination. The principle that follows from this anatomical configuration is that forearm shaft fractures must be treated to restore not merely length and alignment but also the anatomical relationship between radius and ulna — the radial bow, the interosseous space, and the integrity of both radioulnar joints. The orthopedic adage that the forearm fracture in the adult should be treated as an “intra-articular” fracture — requiring anatomical reduction and rigid internal fixation in essentially all cases — captures this principle. The associated fracture-dislocation patterns — the Monteggia injury at the proximal forearm and the Galeazzi injury at the distal forearm — represent disruptions of the radioulnar coupling and must be recognized to avoid the chronic disability that follows their inadequate treatment. This chapter draws on Rockwood and Green’s Fractures in Adults, AO Principles of Fracture Management, Apley & Solomon’s, and Miller’s Review of Orthopaedics.

Surgical Anatomy and Functional Considerations

The radius describes a characteristic lateral bow (“radial bow”), with its maximum prominence at the junction of the proximal and middle thirds; the magnitude and location of this bow are essential to the normal rotational arc of the forearm. The Schemitsch and Richards (1992) analysis of fracture treatment outcomes demonstrated that restoration of the radial bow within 5 percent of the contralateral side, in both magnitude and location, was the single most important determinant of good functional outcome after forearm shaft fracture fixation. Loss of bow or apex translation produces restricted pronation and supination — the classical functional consequence of inadequate forearm fracture reduction. The ulna is essentially straight along its length, providing a stable axis around which the radius rotates. The interosseous membrane runs between the radius and ulna with a characteristic obliquity that transmits axial load from the radius (at the wrist) to the ulna (at the elbow), permitting effective load sharing; disruption of the interosseous membrane in Essex-Lopresti injuries (covered in part in Topic Trauma-15) produces proximal migration of the radius with axial load. The proximal radioulnar joint (PRUJ) is stabilized by the annular ligament, the quadrate ligament, and the interosseous membrane. The distal radioulnar joint (DRUJ) is stabilized by the dorsal and palmar radioulnar ligaments (the principal stabilizers), the triangular fibrocartilage complex (TFCC), the ulnocarpal ligaments, the interosseous membrane, the pronator quadratus, and the ulnar collateral ligament. The orthopedic surgeon must understand that disruption of either radioulnar joint represents a fundamental compromise of forearm function.

The neurovascular relationships of the forearm are complex. The radial artery and the superficial branch of the radial nerve run along the radial side of the forearm; the ulnar artery and the ulnar nerve run along the ulnar side. The median nerve runs centrally, between the two bones. The posterior interosseous nerve (PIN) crosses the proximal radius around the arcade of Frohse at the proximal edge of the supinator and is vulnerable during exposures of the proximal radius and during reduction maneuvers in proximal forearm fractures. The anterior interosseous nerve (AIN) runs anterior to the interosseous membrane and supplies the deep volar compartment muscles.

Both-Bone Forearm Shaft Fractures

The AO/OTA classification (region 22) structures both-bone forearm fractures by the morphology of each component bone. Type A is simple (A1 ulna only fractured with radius intact, A2 radius only fractured, A3 both bones simple); Type B is wedge fracture in one or both bones; Type C is complex multifragmentary fracture in one or both bones. The treatment of adult both-bone forearm shaft fractures is virtually always operative because of the requirement for anatomical restoration of length, rotation, and radial bow to preserve forearm rotation. The standard technique is open reduction and internal fixation with 3.5-mm dynamic compression plates (DCP) or locking compression plates (LCP) applied through separate Henry (volar) approach for the radius and a direct ulnar (subcutaneous) approach for the ulna. The plate length should provide at least six to eight cortical screws (three to four bicortical screws) on each side of each fracture. Anatomical reduction with compression is the goal for simple patterns; bridge plating with restoration of length, rotation, and alignment is the goal for comminuted patterns where direct anatomical reduction of each fragment is not feasible. The use of bone graft is largely reserved for comminuted patterns with bone loss or for non-union; primary bone grafting at the time of acute fracture fixation is now rarely performed. The Henry approach to the radius develops the interval between brachioradialis (radial nerve) and pronator teres / flexor carpi radialis (median nerve), exposing the volar aspect of the radius. Proximally, the supinator and pronator teres are released from the radius with attention to the posterior interosseous nerve; distally, the pronator quadratus is released. The volar approach has the advantages of muscular coverage of the plate, lower hardware prominence than dorsal plating, and excellent access to the entire length of the radius. The dorsal (Thompson) approach to the radius is reserved for selected indications — primarily proximal-third radial fractures where the volar approach risks the posterior interosseous nerve. The interval between extensor carpi radialis brevis (radial nerve) and extensor digitorum communis (PIN) is developed, with the supinator carefully reflected from the radius (with attention to the PIN within the supinator) to expose the proximal radius. The direct ulnar approach exposes the subcutaneous border of the ulna without development of a true intermuscular interval; the FCU is reflected ulnarly and the ECU radially.

The reported outcomes of plate fixation of adult both-bone forearm fractures are generally excellent, with union rates above 95 percent and functional rotation outcomes correlated with restoration of the radial bow and the interosseous space.

Isolated Ulnar and Radial Shaft Fractures

Isolated Ulnar Shaft Fractures (“Nightstick” Fracture) The isolated ulnar shaft fracture, classically associated with a defensive injury where the forearm is raised to deflect a blow (the “nightstick” fracture), is approached differently from the both-bone forearm fracture. The functional consequences of isolated ulnar shortening and angulation are less severe than for both-bone fractures, and the ulnar shaft can tolerate moderate residual angulation. The classical Sarmiento criteria for non-operative management of isolated ulnar shaft fractures are: angulation less than 10 degrees, displacement less than 50 percent of bone diameter, fracture distal to the insertion of the pronator teres (avoiding proximal-third fractures where Monteggia variants must be excluded), and no proximal or distal radioulnar joint instability. Within these limits, non-operative management with a functional brace (similar in concept to the Sarmiento brace for the humerus) produces excellent outcomes. Outside these limits, plate fixation is indicated. Intramedullary nailing has had a small role in isolated ulnar fractures but is generally less favored than plate fixation.

Isolated Radial Shaft Fractures True isolated radial shaft fractures are uncommon and must prompt the suspicion of an unrecognized Galeazzi injury (see below) with subtle DRUJ disruption. Definitive treatment of true isolated radial fractures follows the same plate fixation principles as both-bone forearm fractures, with restoration of radial length, rotation, and bow.

The Monteggia Fracture-Dislocation

The Monteggia injury — fracture of the ulna with dislocation of the radial head — was described by Giovanni Battista Monteggia of Milan in 1814. The pathophysiology is the disruption of the proximal radioulnar coupling, with the radial head dislocating from the radial notch of the ulna because of the ulnar shaft fracture’s effect on the proximal forearm geometry. The Bado classification (José Luis Bado, 1967) organizes Monteggia injuries by direction of the radial head dislocation: • Type I: Anterior dislocation of the radial head with anterior angulation of the ulnar fracture. The most common adult type (60 to 70 percent), produced by hyperpronation or forced extension mechanism. • Type II: Posterior or posterolateral dislocation of the radial head with posterior angulation of the ulnar fracture. Less common in adults (10 to 15 percent), more

common in elderly patients with osteoporotic bone, classically associated with
concomitant radial head fracture.

• Type III: Lateral dislocation of the radial head with ulnar fracture, almost exclusively a pediatric injury. • Type IV: Combined radial and ulnar fractures with anterior dislocation of the radial head (the “Monteggia equivalent with radial fracture”), uncommon but technically challenging. Bado equivalents describe injuries with similar mechanisms but without strict adherence to the original criteria — for example, isolated radial head fracture with radial neck fracture, or radial head dislocation with proximal radial fracture (often termed “Monteggia equivalent of the radius”). Treatment of Monteggia Injuries The treatment of the adult Monteggia injury is open reduction and internal fixation of the ulnar fracture with reduction of the radial head dislocation, almost always operative. The principle is that anatomic reduction and rigid fixation of the ulna typically reduces the radial head; if the radial head does not reduce after anatomic ulnar fixation, an obstruction to reduction (interposed annular ligament, soft tissue, or radial head fragment) must be sought and addressed. Open reduction of the radial head with annular ligament reconstruction is occasionally needed. The pediatric Monteggia injury has more nuanced management — in children under 6 to 8 years, closed reduction of the ulnar greenstick or plastic deformation may be sufficient to reduce the radial head, with cast immobilization in supination (Bado type I) or pronation (Bado type II); operative management is reserved for irreducible or unstable injuries. Missed Monteggia injuries — radial head dislocation persisting because the ulnar fracture was inadequately reduced or the dislocation unrecognized — represent a challenging late presentation. Reconstruction options include open reduction of the radial head with annular ligament reconstruction, ulnar osteotomy with re-fixation in proper alignment, and (in chronic cases with degenerative changes) radial head excision or arthroplasty. The longer the delay between injury and reconstruction, the worse the outcome — emphasis on initial recognition is critical.

The Galeazzi Fracture-Dislocation

The Galeazzi injury — fracture of the radial shaft with dislocation of the distal radioulnar joint — was described by Riccardo Galeazzi of Milan in 1934, although the injury was recognized earlier (Astley Cooper described it in the early 19th century). The pathophysiology is the disruption of the distal radioulnar coupling, with the DRUJ dislocating because of the loss of radial length or rotational alignment. The classical features of Galeazzi injury include the radial shaft fracture (usually at the junction of the middle and distal thirds, the “Galeazzi point”), associated with one or more of: dislocation of the ulnar head from the sigmoid notch (visible on lateral wrist

radiograph), shortening of the radius greater than 5 mm (with positive ulnar variance), fracture of the ulnar styloid base, and widening of the DRUJ on the AP wrist radiograph. The clinical aphorism that the Galeazzi injury is the “fracture of necessity” — meaning that operative management is required for good outcomes — captures the fundamental treatment principle. Closed reduction and casting of the radial fracture, even with reasonable initial alignment, results in unacceptable outcomes (radial shortening, recurrent angulation, DRUJ subluxation) in the adult patient. The treatment is open reduction and internal fixation of the radial fracture with restoration of length and rotation, followed by assessment of DRUJ stability in pronation, supination, and the neutral position. If the DRUJ is stable after radial fixation (the most common outcome with anatomical fixation), no further surgery is needed and the forearm is immobilized in the position of greatest stability (typically full supination) for 4 to 6 weeks. If the DRUJ remains unstable, additional management is required: open or arthroscopic TFCC repair, ulnar styloid base fixation (when present), or transverse K-wire fixation across the DRUJ in addition to the cast immobilization. The wire is removed at 6 weeks and DRUJ stability is reassessed. The Galeazzi-equivalent injuries include distal radial physeal fractures in children with associated DRUJ disruption (treated by reduction of the physis with assessment of DRUJ) and isolated dorsal or volar dislocations of the DRUJ with associated radial deformity.

Special Patterns

Plastic Deformation In the pediatric forearm, plastic deformation of one or both bones — a bowing deformity without a discrete fracture line — may accompany or substitute for a frank fracture. The bowed bone resists reduction and may require deliberate over-correction in the operating room. Recognition of plastic deformation is important because a “missed” plastic deformation that produces persistent angulation may obstruct subsequent reduction of an associated fracture or dislocation.

Greenstick Fractures The pediatric greenstick fracture — incomplete fracture of one cortex with intact periosteum and bowing of the opposite cortex — is the classical pediatric pattern. Treatment principles include reduction of the angulation, occasionally completing the greenstick fracture to allow reduction, and immobilization in the position of correction. Forearm greenstick fractures often heal in functional positions without strict anatomical reduction because of the remarkable remodeling potential of the pediatric forearm, but residual angulation greater than 15 to 20 degrees and rotational malalignment do not remodel and require correction. Refracture After Hardware Removal Refracture after plate removal from the forearm is a recognized complication, with rates of 5 to 25 percent in older series and lower rates with modern protocols. The risk is

associated with early removal (less than 12 to 18 months postoperatively), young patients, large plates with extensive bone-plate contact, and persistent radiolucent areas at the screw holes after removal. Recommendations include deferral of hardware removal until at least 18 to 24 months postoperatively (or only with definite indication), use of LCP-style plates that minimize cortical bone contact, and patient counseling and gradual return to full activity after hardware removal.

Forearm Compartment Syndrome The forearm has three compartments (volar, dorsal, mobile wad) and is the second most common site of compartment syndrome after the leg. The classical setting is a closed forearm fracture with high-energy mechanism, particularly in the pediatric supracondylar fracture-dislocation; the management is decompressive fasciotomy by a curvilinear volar approach (Henry-extended) with carpal tunnel release, and a dorsal incision when needed. The historical exemplar of the consequences of untreated forearm compartment syndrome — Volkmann’s ischemic contracture — was discussed in detail in Topic Trauma-8.

Pediatric Forearm Fractures — A Brief Note

Pediatric forearm fractures form a substantial category in their own right and are particularly common in childhood, with the distal forearm being the single most common fracture site in children. The management principles are distinct from adult practice in several respects: The remodeling potential of the pediatric forearm permits acceptance of substantial residual angulation, particularly in younger children with more than two years of growth remaining. Acceptable angulation thresholds increase with younger age and with the proximity of the fracture to the more active distal physis. Rotational malalignment, however, does not remodel and must be corrected. The flexible intramedullary nailing (Métaizeau / titanium elastic nailing, TENS) has emerged as the preferred operative technique for displaced unstable pediatric forearm fractures. Two pre-bent flexible nails of approximately 40 percent of the medullary canal diameter are inserted retrograde through small incisions at the proximal radius and distal ulna (or vice versa for some configurations) and advanced across the fracture sites with controlled three-point fixation. The nails are removed at 4 to 6 months. Outcomes are excellent in selected indications. Plate fixation is reserved for adolescents near skeletal maturity or for irreducible fractures not amenable to flexible nailing. Closed reduction and casting remains the treatment of choice for the great majority of pediatric forearm fractures. The cast is typically a long arm cast for 3 to 4 weeks followed by a short arm cast for an additional 2 to 3 weeks, with the elbow in flexion and the forearm in a rotation appropriate to the fracture pattern.

Complications

Specific complications of adult forearm fracture management include nonunion (1 to 5 percent with plate fixation, generally amenable to plate revision with bone graft),

malunion with loss of forearm rotation (treated by corrective osteotomy with attention to the radial bow), radioulnar synostosis (heterotopic bone formation between radius and ulna producing complete loss of forearm rotation — risk factors include high-energy injury, both-bone fracture at the same level, head injury, and operative approach close to the interosseous membrane; treatment is surgical excision with interposition of soft tissue or with radiation prophylaxis), infection (1 to 3 percent), iatrogenic nerve injury (particularly PIN with proximal radial exposures), and chronic DRUJ instability or arthrosis (the long-term consequence of inadequately treated Galeazzi injury).

Summary and Take-Home Points

The forearm functions as a kinetic chain rather than as two independent bones, and the central principle of forearm fracture management is the restoration of the anatomical relationships among radius, ulna, and the two radioulnar joints. In the adult, this principle mandates open reduction and rigid plate fixation for virtually all both-bone forearm shaft fractures, with the radial bow, interosseous space, and length being the critical reconstructive parameters. Isolated ulnar shaft fractures (the nightstick fracture) tolerate non-operative functional bracing within Sarmiento limits; isolated radial shaft fractures must be evaluated carefully for occult Galeazzi components and are typically treated operatively. The Monteggia injury — ulnar fracture with radial head dislocation — is classified by the Bado system and is treated by anatomic ulnar fixation, which typically reduces the radial head; open reduction of the radial head is occasionally required for irreducible dislocations. The Galeazzi injury — radial fracture with DRUJ dislocation — is the “fracture of necessity” requiring operative reduction of the radius with assessment and management of DRUJ stability. Both injuries demand recognition of the radioulnar joint disruption — missed Monteggia and Galeazzi injuries are leading causes of chronic forearm disability. The pediatric forearm fracture, in contrast to its adult counterpart, is largely treated by closed reduction with substantial residual angulation accepted because of the remarkable remodeling potential of the growing skeleton; the flexible intramedullary nailing (TENS) technique is reserved for displaced unstable injuries that cannot be maintained in closed reduction. The complications of forearm fracture management — including radioulnar synostosis, refracture after hardware removal, and chronic DRUJ instability — emphasize the importance of meticulous initial management. The chapter that follows addresses the distal radius fracture, the single most common fracture in the adult and a central topic in board examinations.