Minimally invasive plate osteosynthesis of diaphyseal forearm fractures—indications and surgical technique
Operative treatment of diaphyseal fractures of the ulna and radius in adult patients is routinely performed using open reduction and internal fixation (ORIF). Restoration of the normal anatomy is crucial in order to preserve normal wrist motion as well as forearm pronation and supination. Furthermore, due to the complex arrangement of the neurovascular structures, open fracture treatment has been classically advocated to avoid iatrogenic injury. Finally, simple fracture patterns are ideally stabilized with absolute stability using interfragmentary compression with either lag screws or dynamic plates [ 1]. In comminuted fractures, bridge plating may be the preferred method of stabilization to preserve local biology and allow for secondary healing, while restoring length and obtaining adequate alignment [ 2]. In other regions of the body minimally invasive fixation techniques have shown favorable healing rates and lower complication rates than conventional open techniques [ 3]. However, there have been few studies about minimally invasive fracture fixation in shaft treatment of shaft fractures of the forearm.
Indications for MIPO, planning, and anatomy
Simple diaphyseal fractures of the forearm managed with anatomical reduction should be treated with conventional ORIF, achieving absolute stability. We consider that fractures with comminution in one or both bones of the forearm, including fragmented wedges that are difficult to reduce (ie, B1.2, B2.2, B2.3, C1.3, C2.3, C3.2, and C3.3) represent the ideal indication for minimally invasive techniques.
Planning should include surgical approaches, type and positioning of implants, and reduction maneuvers ( Fig 25-109 ). Tourniquet use, while not indispensable, can be very helpful for improving field visualization. Image intensification, on the other hand, is essential to perform these procedures.
Fixation is started with the least comminuted bone, which may require ORIF in case of simple fractures which are amenable for anatomical reduction and stable fixation. Open reduction and internal fixation will allow restitution of length, axis, and rotation, and will therefore aid in obtaining adequate reduction of the more complex fracture.
A step-by-step preoperative plan for MIPO of the forearm involves:
Patient positioning in the supine position using a radiolucent arm board. A tourniquet is applied.
Distal approach to the radius and/or ulna.
Proximal approach to the radius and/or ulna.
Soft-tissue tunneling between proximal and distal window.
Plate insertion from proximal to distal.
Distal fixation with one or two screws.
Indirect reduction by traction.
Proximal fixation with one screw.
Confirmation of pronation-supination and alignment with image intensification.
Complete proximal fixation with one additional screw.
Irrigation and closure.
The minimally invasive approaches are performed using windows of the classic volar palmar Henry or dorsal Thompson approach to the radius, and subcutaneous approach to the ulna.
Utilizing internervous planes between muscle groups is important when selecting an optimal surgical approach. There are three groups of muscles in the forearm.
The first group is the mobile wad which is formed by the brachioradialis and extensor carpi radialis longus (ECRL) which are innervated by the radial nerve; and the ECRB which is innervated by the posterior interosseous nerve (PIN).
The second group consists of the flexor pronator muscles. These are innervated by the median and ulnar nerves and are arranged in three layers: superficial, intermediate, and deep. The superficial layer comprises the pronator teres, flexor carpi radialis (FCR), palmaris longus, and flexor carpi ulnaris (FCU). The intermediate layer comprises the flexor digitorum superficialis (FDS) and the deep layer of the flexor digitorum profundus (FDP), flexor pollicis longus (FPL) and pronator quadratus.
The third group is that of the extensors which are innervated by the radial nerve.
The anterior approach runs between the mobile wad and the flexor pronator group. The structures at risk are the PIN and the radial artery. The PIN is close to the radial neck proximally, and courses distally in the substance of the supinator muscle. Therefore, it has to be protected especially during fixation of proximal fractures. Complete forearm supination displaces the interosseous nerve laterally and posteriorly out of the surgical field. By incising the supinator muscle at its insertion onto the radius, rather than splitting it, the PIN will remain safe. Branches of the recurrent radial artery are frequently found over the supinator muscle and require ligation to allow for deeper access. In less proximal fractures the surgical approach is easier and involves less risk for PIN injury.
This approach is performed in the interval between the extensors and the mobile wad. Proximal exposure of the supinator muscle is achieved by dissecting between the ECRB and EDC to expose the PIN. As for the volar approach, exposure of the nerve is not required in low proximal fractures ( Fig 25-110 ). Distally, however, careful dissection is required to preserve the sensory branch of the radial nerve ( Fig 25-111 ).
This is the simplest approach, since it is performed along the subcutaneous border of the ulna between the extensor and flexor/pronator groups. When distal dissection is required, the cutaneous branch of the ulnar nerve should be identified and protected.
After preoperative templating has been performed, the chosen implant is placed over the forearm and the surgical windows are selected with image intensifier guidance ( Fig 25-111 ).
Using careful blunt dissection, the periosteum is partially elevated from the aspect of the radius or ulna where the plate will be placed. It is important to verify that the dissection proceeds on bone, especially in proximity of the fracture site where image intensification may be useful for confirmation ( Fig 25-112a–b ). Subsequently the plate is introduced through the tunnel. By advancing a silk suture loop that has been passed through one of the holes, plate insertion can be facilitated ( Fig 25-112c ). The fracture is fixed initially with two screws distally, followed by x-ray confirmation of adequate fracture alignment ( Fig 25-113 ).
Frequently, fracture reduction is obtained as fragments are reduced onto the plate. This can be further improved through manual traction or with the use of a bone spreader and a push screw ( Fig 25-114 ), or with an external fixator.
Fracture reduction is additionally assessed by evaluating distal radioulnar joint congruity. Proximal fracture fixation is subsequently performed with a single screw. The presence of adequate pronation and supination is then checked ( Fig 25-115 ) and once confirmed, fixation is completed, usually with a total of two or three screws proximally and distally ( Fig 25-116 ). The wounds are closed in a standard fashion.
Postoperative management does not require immobilization and rehabilitation is started as soon as edema and pain allow.