Reduction strategies are dictated by fracture morphology, including the presence or absence of intraarticular extension and metaphyseal comminution. Extraarticular patterns may be reduced before plate application or with the use of the plate as a reduction aid. Extraarticular patterns can typically be reduced with longitudinal traction; the use of a well-placed bump; and the manipulation of fragments with K-wires, Schanz pins, and/or clamps. Although it is the authors' preference to achieve a reduction before plate application, the plate can also be used as a reduction tool. This involves positioning and fixing the plate distally and subsequently placing cortical screws proximally to draw the plate to the bone.
For intraarticular patterns, the surgeon may prefer to first reduce the articular block before stabilizing the metaphyseal implant (referred to as converting a "C-type" to an "A-type"). In the absence of metaphyseal comminution, however, the reduction of the articular block and metaphyseal segment may need to occur simultaneously, which can be very challenging. An alternative strategy is to reduce the largest articular fragment to the shaft and subsequently reduce the remaining articular fragments to these implants (converting a "C-type" to a "B-type").
The strategy for reducing intraarticular fragments depends on the location of the principle fracture planes. Medial Hoffa fragments are typically addressed first, with provisional clamp placement through the intercondylar notch followed by countersunk cortical screws in an anterior-to-posterior direction with divergent trajectories (Figure 3). The authors' preference is to use 2.7-mm cortical screws for this purpose, although headless compression screws and alternative sizes of interfragmentary screws remain viable options. When attempting to access very posterior Hoffa fragments, extreme hyperflexion of the joint combined with hyperextension of the metaphyseal segment will allow for optimal visualization. Hyperflexion of the joint in addition to hyperextension at the fractured metaphyseal segment allows for the posterior articular surface to be brought as anterior as possible, facilitating visualization when using an anterior-based or lateral-based approach.
Radiograph showing the distal femur fracture with a Hoffa fragment. This was fixed with divergent 2.7-mm screws. A model demonstrating clamp placement for the reduction of a medial Hoffa fragment.
With simple articular splits (usually in the sagittal plane, in contrast to the coronal plane Hoffa fractures), the use of a well-placed clamp can facilitate reduction. Often this clamp can be placed through the arthrotomy with tines on the medial and lateral epicondyles. K-wires or Schanz pins can be used as joysticks to help control the rotation of the condylar segments. It is important to avoid eccentric clamp placement because this can malreduce the fracture; anterior placement of the tines can cause compression of the anterior portion of the articular block and gapping of the posterior aspect of the articular block (Figure 4). Articular splits in the sagittal plane can be fixed with lateral-to-medial lag screws before definitive plate fixation (Figure 5).
A fluoroscopic image and a corresponding model demonstrating anterior clamp placement with resultant posterior gapping of the articular block.
Radiograph showing the proper placement of lag screws and the lateral plate. A lateral radiograph (left) is labeled with typical locations for lateral-to-medial lag screws. Lateral and AP fluoroscopy images (middle and right) demonstrate the appropriate position of a lateral plate with the posterior distal hole cranial to Blumensaat's line and the lateral contour of the plate matching the supracondylar flare of the distal femur.
Once the articular reduction is achieved, metaphyseal reduction can commence. As the articular block is often hyperextended relative to the shaft of the femur due to the pull of the gastrocnemius, longitudinal traction over a triangle with a well-placed bump can aid in reduction. For simple fracture patterns, a periarticular clamp can be placed with tines on the medial and lateral epicondyles for improved control of the articular block, allowing for the fine-tuning of varus, valgus, flexion, or extension relative to the shaft. A Schanz pin or Cobb elevator can also be used to help control articular block hyperflexion or hyperextension relative to the shaft. The Schanz pin is placed anterior to posterior in the distal articular block (Figure 6). A Cobb elevator placed on the articular block posterior cortex with a posterior-to-anterior–directed force can facilitate flexion.
J Am Acad Orthop Surg. 2021;29(18):770-779. © 2021 American Academy of Orthopaedic Surgeons