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Lateral Distal Femur Plate for Periprosthetic Fracture

Yarboro, Seth R. MD

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Journal of Orthopaedic Trauma: August 2018 - Volume 32 - Issue - p S30-S31
doi: 10.1097/BOT.0000000000001199

Abstract

The case demonstrated here is a 68-year-old woman who sustained a left periprosthetic distal femur fracture during a twisting injury from a ground-level fall. She had severe pain and inability to bear weight, and radiographs demonstrated a distal oblique periprosthetic femur fracture with a well-fixed total knee arthroplasty. The patient elected to undergo plate fixation of her distal femur fracture (see Video, Supplemental Digital Content 1, http://links.lww.com/JOT/A388).

The use of modern implants and careful surgical technique has advanced the care of distal femur fractures. Lateral locked plates have improved the ability to stabilize distal femur fractures, especially those with comminution. Although questions regarding technical details of plating persist, there are principles used in this case that can guide decision making during surgery to optimize outcomes.

Standard workflow for plate application in this case is as follows: appropriate alignment and reduction are achieved through manipulation of the fracture, traction, and strategic placement of bumps. A bump under the fracture helps address typical recurvatum deformity by relaxing the pull of the gastrocnemius. Next, the plate is placed through the distal incision and passed submuscularly proximally along the lateral femur. On a perfect lateral view of the distal femur, the plate is provisionally pinned with a K-wire in the appropriate position relative to the femoral component. Then, the proximal portion of the plate is pinned to the shaft to maintain the proximal plate's position. A periarticular clamp can be used to compress the plate to the distal lateral cortex, and the central screw is inserted with care taken to match the alignment of the screw to the distal femoral articular angle (typically 4–7 degrees valgus). Subsequent distal fixation is then undertaken. Finally, proximal (shaft) fixation is undertaken with nonlocking screws placed by the percutaneous fluoroscopic technique. If locking screws are preferred, an aiming arm can be attached to the plate to facilitate locking screw placement with minimal soft-tissue exposure.1

Minimally invasive techniques should be undertaken when possible.2 As described in minimally invasive plate osteosynthesis technique, a distal incision is used for plate application (and fracture reduction in distal fractures), and then proximal diaphyseal screws are placed through percutaneous incisions. Extensive exposure and stripping of the fracture site is avoided to preserve soft-tissue attachments and fracture biology.

Construct considerations to modulate stiffness has seen recent interest in orthopaedic trauma.3 Plate length has been associated with risk of failure, with longer plates (>10 hole) associated with lower risk of failure.4 The working length is defined as the distance between proximal and distal screws (ie, the most distal shaft screw and the most proximal of the screws in the distal fragment). Very short working lengths result in excessive stiffness and may result in nonunion and/or implant failure. Although ideal working length has yet to be established, this parameter is dependent on fracture pattern and comminution and likely no single rule can determine the ideal construct. Locking screws are associated with an overall stiffer construct, and this variable should be considered when deciding on a working length during plate application.

Furthermore, locking screws may be desirable for their ability to avoid excessive medialization of the distal fracture fragment and appropriate plate placement.5 In that instance, the nonlocking screws would medialize the distal fragment by pulling the shaft against the plate. Locking screws do not require contact between the bone and the plate, and the construct works like an “internal” external fixator.

The ideal number of screws in the shaft has not been clearly determined, although biomechanical and clinical data suggest that 3–4 screws are typically adequate, and using more than 3 screws does not impact construct stiffness.6 In this case, 5 screws were used because of concerns regarding bone density in the setting of nonlocking screws.

In this case, the patient began knee range of motion with therapy and protected weight bearing for 6 weeks. Although there is some emerging opinion that early weight bearing after distal femur open reduction internal fixation may be advantageous, clear data to support this position have yet to be published.

Plate fixation is commonly used for distal femur fractures, although retrograde nail fixation can be considered in some cases. Specifically, total knee arthroplasty femoral components that are cruciate retaining can accommodate retrograde nail placement. Also, those posterior stabilized components that have an “open box” design will also allow nail placement.

Although more research is needed to better define the ideal construct for fixation of distal femur fractures, these principles of using long plates with adequate working length and careful handling of soft tissues will optimize outcomes.

REFERENCES

1. Yarboro SR, Ostrum RF. Extraarticular distal femur fractures. In: Castoldi F, Bonasia DE, eds. Fractures Around the Knee. Switzerland: Springer; 2016.
2. Ricci WM, Loftus T, Cox C, et al. Locked plates combined with minimally invasive insertion technique for the treatment of periprosthetic supracondylar femur fractures above a total knee arthroplasty. J Orthop Trauma. 2006;20:190–196.
3. Hak DJ, Toker S, Yi C, et al. The influence of fracture fixation biomechanics on fracture healing. Orthopedics. 2010;33:752–755.
4. Ricci WM, Streubel PN, Morshed S, et al. Risk factors for failure of locked plate fixation of distal femur fractures: an analysis of 335 cases. J Orthop Trauma. 2014;28:83–89.
5. Collinge CA, Gardner MJ, Crist BD. Pitfalls in the application of distal femur plates for fractures. J Orthop Trauma. 2011;25:695–706.
6. Stoffel K, Dieter U, Stachowiak G, et al. Biomechanical testing of the LCP—how can stability in locked internal fixators be controlled?. Injury. 2003;34(suppl 2):B11–B19.
Keywords:

distal femur; periprosthetic; locking plate; supracondylar; MIPO

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