Distal Femur Fracture
Classification systems
- Descriptive: supracondylar, unicondylar, intercondylar T or Y, Hoffa coronal fragment
- Periprosthetic classification systems for fractures above a knee replacement
Mechanism
Bimodal. High-energy axial loading with a varus, valgus or rotational component in the young, often a dashboard injury with the knee flexed. Low-energy twisting falls in the osteoporotic elderly, frequently around an existing knee replacement where the bone above the implant is stress-shielded.
Age considerations
- Paediatric
- The distal femoral physis is the most productive in the body, so physeal injury here carries a high risk of growth arrest and angular deformity; anatomical reduction and careful counselling about growth follow-up are essential.
- Young adult
- Articular restoration and axial alignment are the priorities. Search deliberately for a coronal Hoffa fragment, which is missed on plain films and requires cross-sectional imaging and its own anteroposterior lag screw fixation.
- Elderly
- Osteoporotic metaphyseal bone and periprosthetic patterns dominate. Constructs must permit early mobilisation because prolonged non-weight bearing is not achievable; retrograde nailing or a long locking plate, sometimes both, are used.
Management options
Lateral locking plate fixationshowhide
Indication
Most extra-articular and intra-articular distal femoral fractures, including periprosthetic fractures above a well-fixed knee replacement.
Implant design notes
Anatomically pre-contoured lateral plate with a fixed-angle distal cluster of locking screws forming an internal fixed-angle device in soft metaphyseal bone. Length and screw spread control the working length; overly stiff short constructs over a comminuted metaphysis are a recognised cause of non-union.
Approach
Lateral or anterolateral approach, with a lateral parapatellar arthrotomy when the articular surface must be visualised; minimally invasive submuscular sliding for extra-articular patterns.
Steps overview
- Position supine with a radiolucent bolster; assess and document distal neurovascular status
- Obtain cross-sectional imaging to identify a coronal Hoffa fragment before planning
- Reduce and lag-fix the articular block first, placing Hoffa screws from anterior to posterior
- Restore length, axial alignment and rotation of the metaphysis indirectly under fluoroscopy
- Slide the plate submuscularly along the lateral cortex and fix distally in the condylar block
- Check coronal and sagittal alignment and knee rotation before proximal fixation
- Use a long plate with spread-out proximal screws to give an appropriate working length
- Begin immediate knee motion; define weight bearing by construct and bone quality
Notes
Varus collapse and non-union at the metaphyseal zone are the recognised failures; consider medial augmentation or a nail-plate combination in very osteoporotic or comminuted cases.
Resident summary compiled from standard orthopaedic trauma teaching; verify against your departmental protocol.
Retrograde intramedullary nailingshowhide
Indication
Extra-articular or simple intra-articular fractures with a sufficient distal segment, particularly in osteoporotic bone and in patients needing early weight bearing; compatible periprosthetic implants.
Implant design notes
Nail inserted through an intercondylar entry with multiplanar distal locking, working close to the mechanical axis and load-sharing to permit earlier weight bearing. Requires an open intercondylar notch and an implant-compatible box if a knee replacement is present.
Approach
Small medial parapatellar or transtendinous approach to the intercondylar notch.
Steps overview
- Supine with the knee flexed over a bolster to allow instrumentation
- Enter at the centre of the intercondylar notch, confirmed on both views
- Reduce the articular block and lag it before passing the nail if it is split
- Ream and insert the nail to the appropriate depth, buried below the articular surface
- Lock distally in multiple planes for rotational control, then proximally
- Confirm alignment and rotation and start early motion and weight bearing
Notes
Knee pain from the entry site and difficulty controlling a short distal segment are the drawbacks. Combining a nail with a plate is a legitimate strategy in very poor bone.
Resident summary compiled from standard orthopaedic trauma teaching; verify against your departmental protocol.
Viva pearls
- Actively look for the coronal Hoffa fragment; it needs cross-sectional imaging and anteroposterior lag screws, and missing it guarantees failure.
- Restore the articular block first, then the alignment of the shaft to the block — that sequence earns marks.
- A short, very stiff bridging construct over a comminuted metaphysis causes non-union; length of plate and screw spread matter.
- In periprosthetic fractures, decide first whether the implant is well fixed — that determines fixation versus revision arthroplasty.
- The distal femoral physis is the most active in the body; a paediatric injury here needs growth follow-up.
- Check the popliteal artery and the peroneal nerve, and consider vascular imaging in a displaced supracondylar injury.
Sources for further reading
- Rockwood and Green's Fractures in Adults — distal femur
- Standard operative orthopaedics textbook — fractures about the knee
- AO principles of fracture management — articular reconstruction and bridge plating
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Resident-authored study summary in original wording, not reproduced from copyrighted source text.