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Hybrid locked-plate fixation provides optimal fixation of distal femur fractures
Hybrid locked plates take advantage of the benefits of both traditional and locked plates.
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When treating distal femur fractures above the knee, one expert advocates the use of open reduction and internal fixation with locked plating systems used in “hybrid” mode by combining the use of locked and nonlocked screws.
“For most distal femur fractures we’re going to do open reduction, internal fixation (ORIF), with locked plates combined with indirect reduction techniques to preserve the biology. In select cases we will use an intramedullary nail, in which I would advocate a long, rather than a short nail,” said William M. Ricci, MD.
He discussed the optimal implants for treating these fractures at the American Academy of Orthopaedic Surgeons 74th Annual Meeting.
Various fixation options
When treating supracondylar fractures surgeons aim to achieve anatomic reduction of the articular surface with stable fixation, Ricci said.
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Images: Ricci WM |
Fixation, whether with nails, plates or external fixators, should be stable enough for early rehabilitation including range of motion to prevent the quadriceps from being bound down.
“If you’re going to nail a supracondylar fracture, the vast majority of the time you are going to place it retrograde,” Ricci said. He explained that the starting point for any nail is one of the most critical portions of the procedure: It should be central and the insertion angle should be co-linear with the long axis of the distal fragment.
Short supracondylar screws have fallen out of favor because they do not engage the isthmus of the femur and do not provide sufficient stability, Ricci said. “There is little reason not to use a full-length nail and engage the isthmus of the femur.”
Traditional and locked plating systems are advantageous in different situations with locked plates and screws being applicable in a wider range of fractures, Ricci told Orthopedics Today.
“Locked plates allow multiple fixed-angle screws in the distal fragment, providing much more opportunity to get multiple points of locked fixation than traditional 95° plates,” he said.
With locked plating systems, the head of the screw is threaded and securely locked into the plate – contrary to conventional nonlocked screws. Therefore, locked plates and screws, because of their fixed-angle nature, eliminate the need for additional medial hardware to prevent varus collapse. Traditional plating systems with nonlocking screws, on the other hand, are prone to varus collapse, he explained.
Moreover, Ricci said, current locked plating systems are technically easier to work with than blade plates and dynamic condylar screws.
“A fundamental difference between locked and nonlocked screws is that nonlocked screws are absolutely reliant on the friction between the plate and bone for construct stability.”
Because locked plating systems do not rely on friction and tightness of the screws, they are more favorable for osteoporotic bone, where traditional nonlocked screws are prone to stripping, Ricci said. However, locked plates and screws cannot be used as reduction tools like the traditional plates and screws, because locked screws will not pull the bone to plate.
Combining locked, non-locked
Hybrid locked plating systems provide the best of both worlds: Surgeons use locked screws and traditional screws in the same construct, Ricci said.
“Nonlocked screws use the plate as a reduction tool and then you’re going to add locked screws for one or two reasons: fixed angle support distally to prevent that varus collapse and improved fixation in osteoporotic bone in the diaphysis,” Ricci said.
Nonlocked screws should be placed before the locked screws, because if locked screws go in first it will not compress plate to bone.
Failure of the construct in the diaphyseal segment of a supracondylar fracture will occur if the screws loosen or if they fracture. When axial loading and a varus moment occur, the screws that are farthest or closest to the fracture will be under the most stress. To avoid fracture or loosening, use a longer plate for better mechanical advantage and make sure that the locked screws are securely tightened and are not cross-threaded, Ricci said.
Distal failure in supracondylar fractures is less common, but possible for locked plates. Most commonly, these are fatigue fractures at the plate-screw interface, Ricci said. To avoid this complication, he suggested using the largest screws available.
Finally, the construct may fail in the working distance of the plate over the fracture, which is the most difficult failure to avoid, Ricci said. “I would advocate judicious radiographic monitoring and judicious use of bone grafting in situations with bone loss or delayed healing to avoid plate fracture.”
For more information:
- William M. Ricci, MD, can be reached at Washington University Orthopedics, Campus Box 8233, 660 South Euclid Ave., St. Louis, MO 63110; 314-747-2811; e-mail: ricciw@wudosis.edu, or www.ortho.wustl.edu. He receives research or institutional support from AO North America and Smith & Nephew. He is a consultant for Smith & Nephew.
Reference:
- Ricci WM. Fractures about the knee: New treatment methods and stabilization choices – Supracondylar femur fractures. Symposium W. Presented at the American Academy of Orthopaedic Surgeons 74th Annual Meeting. Feb. 14-18, 2007. San Diego.