For descriptive purposes, as well as for operative considerations, forearm fractures are classified by location, being categorized as proximal-third, middle-third, or distal-third fractures. The middle third of the radius stretches from the radial bow to the beginning of diaphyseal straightening. The ulna is relatively straight and can be divided by using longitudinal dimensions alone. (See also Forearm Fractures, Distal-Third Forearm Fractures, and Forearm Fractures in Emergency Medicine, as well as Galeazzi Fracture and Monteggia Fracture.)
Unlike fractures in infants and children, fractures of the adult forearm are unstable. Nonunions and malunions of both-bone forearm fractures are functionally and cosmetically limiting, with midshaft radius or ulna angulation substantially impeding forearm rotation. 
Treatment objectives for both-bone forearm fractures have remained relatively constant, with early extremity range of motion (ROM). To understand the management of forearm fractures, the idea of the forearm axis was created, combining the function and anatomy of the wrist, forearm, and elbow. The coordinated, independent function of the wrist, forearm, and elbow is necessary to place and orient the hand in space. Injury to any of these components can result in a significant deficit. The three basic stabilizers of the forearm are as follows:
Distal radioulnar joint
Proximal radioulnar joint
The ulna is the stable unit about which the radius rotates. Force transmission is initiated at the wrist (distal radioulnar joint) level and is translated longitudinally between the radius, ulna, and interosseous membrane, through the forearm axis, and to the elbow.
An applied compressive load travels along the proximal radius, transferring tension forces to the interosseous membrane, which transfers a compressive load to the proximal ulna.  This mechanism accounts for the inequality in the contact forces between the radius and the ulna at the wrist and elbow. Fracture or dislocation of the forearm lead to disruption of this longitudinal relation and affects wrist, forearm, and elbow function.
Middle-third, or diaphyseal, forearm fractures commonly result from a direct blow or a fall from a height. Other causes include gunshot wounds, motor vehicle accidents, and pathologic bone fractures.
According to the AO (Arbeitsgemeinschaft für Osteosynthesefragen [Association for Osteosynthesis]) documentation center, forearm fractures accounted for 10-14% of all fractures between 1980 and 1996.
Since the introduction of compression plating, the goal of forearm fracture treatment has been fracture union and the return of normal function.
In 1975, Anderson et al reported their experience with 4.5-mm compression plating of forearm fractures and noted a 97.9% rate of union for the radius and a 96.3% rate of union for the ulna.  Time to fracture union averaged 7.4 weeks and 7.3 weeks for radial and ulnar fractures, respectively. Additionally, the authors reported a 2.9% infection and nonunion rate. In this report, they developed a functional outcome evaluation scale, as follows:
Excellent - Union, less than 10º elbow and wrist flexion/extension loss for each joint, and less than 25% rotation loss
Satisfactory - Union, less than 20º elbow and wrist flexion/extension loss for each joint, and less than 50% rotation loss
Unsatisfactory - Union, more than 30º elbow and wrist flexion/extension loss, and more than 50% rotation loss
Failure - Malunion, nonunion, and unresolved chronic osteomyelitis
Using this scale, the authors recorded a combined 85% rate of excellent and satisfactory results for the treatment of 330 acute fractures in 244 patients. 
In 1989, Chapman et al reported their results from the treatment of 129 diaphyseal fractures of the radius and/or ulna using standard 3.5-mm compression plates.  They recorded a fracture union rate of 98%, an infection rate of 2.3%, and a 92% rate of excellent or satisfactory results using the Anderson forearm evaluation scale.
Similar results have been reported by a number of other authors. Complications in most series were thought to be associated with errors in judgment, with technique, and with a lack of attention to detail. Immediate open reduction with internal fixation (ORIF) is recommended for all open both-bone middle-third forearm fractures. Results have reportedly been excellent or good in 85% of fractures, with an infection rate of 4% and a nonunion rate of 7%.
Prasarn et al described a protocol for repair of infected nonunions of diaphyseal forearm fractures, consisting of aggressive surgical debridement, definitive fixation after 7-14 days, tricortical iliac crest bond grafting for segmental defects, leaving wounds open to heal by secondary intention, 6 weeks of culture-specific intravenous (IV) antibiotics, and early active ROM exercises.  Of 15 patients, 12 had at least 50º of supination/pronation and 30-130º of flexion/extension arc. Aside from one failure (46 months to resolution), average time to union was 13.2 weeks.
Guitton et al described 13 pediatric patients with an isolated diaphyseal fracture of the radius, of whom 10 were treated with manipulative reduction and immobilization with an above-elbow cast and three were treated with plate-and-screw fixation.  All 13 patients, with at least 1-year follow-up, regained full elbow flexion and extension and full forearm rotation. According to the authors, treatment of isolated diaphyseal radius fractures in skeletally immature patients is associated with a low complication rate and excellent functional outcome.
Teoh et al compared the differences in radiographic and functional outcomes in children with unstable both-bone diaphyseal forearm fractures after treatment with either intramedullary (IM) fixation or plate fixation with screws.  Plate fixation and IM nailing both resulted in good or excellent functional and radiologic outcomes.
For the patients with plates, radiographs showed complete healing, with reconstitution of the radial bow.  Three patients in the IM group did not regain their natural radial bow. No nonunion or malunion was observed, and there were no significant differences in the loss of forearm motion and grip strength between the two groups. Osteomyelitis was more likely to occur in the IM fixation group, and ulnar nerve palsy occurred in the plate-fixation group.
Du et al conducted a study to compare outcomes of single and double elastic stable intramedullary nailing (ESIN) in the treatment of pediatric both-bone forearm fractures.  They retrospectively analyzed 49 children with both-bone forearm fractures treated with ESIN, of whom 24 were treated with single-ESIN (S-ESIN) to fixate the radius only and 25 with double-ESIN (D-ESIN) to fixate both the radius and ulna.
In this study, duration of surgery, times of fluoroscopy, and cost of hospitalization were significantly lower in the S-ESIN group than in the D-ESIN group.  The average period of castoff was longer in the former, and the incidence of delayed union of the ulna was significantly higher in the latter. Mean angulation deformity of the ulna was significantly larger in the S-ESIN group than in the D-ESIN group, though both were acceptable (<10°), and there was no difference in loss of forearm motion or complication rates between the two groups.