44 Angulation in Metacarpal Fractures
44.1 Patient History Leading to the Specific Problem
A 20-year-old man presents 2 weeks after an injury to his right hand (▶Fig. 44.1). He reports punching a wall and experiencing immediate pain over the ulnar hand. Pain, swelling, and inability to extend his fingers have led to decreased function of his hand. He is subsequently diagnosed with displaced right ring and small finger metacarpal fractures.
44.2 Anatomic Description of the Patient’s Current Status
The patient has displaced metacarpal fractures of the ring and small fingers. Angulation is 10 degrees in the coronal plane and 45 degrees in the sagittal plane. This patient exhibits the most common pattern of displacement in regard to angulation in metacarpal shaft fractures. Volar angulation or apex dorsal angulation is caused by the pull of the intrinsic and extrinsic muscle tendon units. While sagittal angulation is tolerated better than rotational and coronal angulation in the setting of metacarpal shaft fractures, this patient was considered for surgery for multiple reasons. The coronal angulation due to the pull of the hypothenar musculature is measured at 10 degrees. Failure to correct coronal angulation in metacarpal fractures may negatively alter function. Nonanatomic coronal alignment may lead to overlapping of the fingers upon making a composite fist, compromising functional grip. Sagittal angulation in the setting of metacarpal fractures may lead to extensor lag and/or cosmetic deformity of the hand. Acceptable sagittal angulation in metacarpal shaft fractures can be reviewed in ▶Table 44.1. In isolated central metacarpal fractures, the adjacent intact metacarpals may help prevent displacement due to intact intermetacarpal ligaments and structural stability of the carpometacarpal (CMC) joints. Surgery was ultimately recommended for this patient to correct both coronal and sagittal malalignment to restore metacarpal cascade, alignment, active extension, and maximize recovery of function.
Table 44.1 Acceptable sagittal alignment of metacarpal shaft fractures
Index | 10–20 degrees |
Middle | 10–20 degrees |
Ring | 20–30 degrees |
Small | 30–40 degrees |
Fig. 44.1 (a) Lateral radiograph showing transverse metacarpal fractures of the ring and small fingers with 45 degrees of angulation. (b) Posteroanterior radiograph showing 10 degrees of coronal malalignment and translation of the fractures.
44.3 Recommended Solution to the Problem
• Coronal, sagittal, and rotational alignment must be corrected.
• Stability for fracture healing must be maintained.
• Reduction and application of instrumentation should be performed in the least invasive way necessary.
• Instrumentation should not interfere with intrinsic or extrinsic mobile muscle–tendon units.
• Options for this patient include the following:
– Closed reduction and percutaneous fixation.
– Open reduction and percutaneous fixation.
– Open reduction and intramedullary fixation.
– Open reduction and plate fixation.
• Wire fixation construct options:
– Tension band.
– Cross-pinning.
– Transverse pinning.
– Intramedullary wire fixation.
• Due to the delay in presentation, an open technique was used to obtain reduction of both fractures, followed by fixation using multiple intramedullary wires.
44.4 Technique
The patient is placed supine on the operating table with the arm on a radiolucent arm board. In this patient, regional anesthesia with sedation was used; however, surgeon preference dictates anesthetic choice. A nonsterile tourniquet is placed on the upper arm and the arm is prepped and draped in the usual sterile manner. The incision was made between the fourth and fifth metacarpals from the metacarpal base to the fracture site. If exposure of the fracture site is not needed, the incision is generally smaller and over the metacarpal base. Blunt dissection is used to ensure protection and retraction of the extensor tendons and the periosteum is exposed. The intrinsics attached to the metacarpal shaft are released, the periosteum is incised and elevated at the level of the fracture, and the fracture ends are exposed.
After fracture exposure, early callus is debrided until an adequate reduction can be obtained. In addition, the medullary canals are opened. Next, the base of the metacarpal is exposed. A 3.5-mm drill is then used to enter the intramedullary canal at the metacarpal base (▶Fig. 44.2a). Intraoperative imaging can be used at this point to assist in obtaining an accurate starting point. The starting point for the index, middle, and ring metacarpals is in line with the shaft on the metacarpal base distal to the CMC joint. The starting point for the small finger is along the ulnar border of the metacarpal base, again distal to the CMC joint. In order to facilitate wire passage, the drill is started perpendicular to the dorsal surface of the metacarpal. The drill is run at full speed and as the drill gains traction in the dorsal cortex, the bit is aimed distal by slowly lowering the drill to the dorsal forearm in line with the metacarpal (▶Fig. 44.2b). Once the dorsal cortex is breached, the drill should be at a 30-degree angle to the dorsal cortex. The unicortical hole is elongated with the drill on full speed to prevent iatrogenic fracture. Once access to the intramedullary canal has been obtained, wire selection and preparation for fracture stabilization can begin.
The ring finger metacarpal has the smallest isthmus and thus fewer and smaller diameter wires are used. In general, the intramedullary canal can accommodate between two and five wires in the canal and sizes vary from 0.028 to 0.045 inches. Wire preparation starts by cutting off the sharp tips to prevent engagement and inadvertent cortical penetration (▶Fig. 44.3). One end of the wire is bent slightly at the tip to facilitate passage of the wire and fragment manipulation.
Once the wire is prepared, a T-handle chuck or heavy needle driver is used to hold and manipulate the wire. The wire is then inserted in antegrade fashion into the entry point with the bent tip pointing dorsally (▶Fig. 44.4a). The small bend allows for the wire to glance off the volar cortex and facilitates passage down the medullary canal without embedding into the cortex. Intraoperative imaging is used to ensure wire passage across the fracture site and engagement into the distal fragment (▶Fig. 44.4b). Both manual manipulation of the fractures and rotation of the wire will assist in passage of the wire.
