Distal Femur Fracture ORIF (Isolated, Non-Periprosthetic)

AO/OTA 33 Classification

The distal femur is segment 33 in the AO/OTA system. The three types define the relationship of the fracture to the articular surface and drive the entire fixation strategy.

Surgical Indications

Operative Indications (most isolated distal femur fractures)

• Displaced intra-articular fracture (33-B and 33-C) — anatomic joint restoration required
• Displaced/unstable extra-articular fracture (33-A) with shortening, angulation or rotation
• Open fracture (debridement plus stabilisation)
• Polytrauma / floating knee requiring early stabilisation and mobilisation
• Failed non-operative management (loss of reduction in a cast/brace)

Relative / Non-operative Indications

• Truly undisplaced, stable fracture in a low-demand patient who can be reliably braced
• Non-ambulatory patient where surgical risk outweighs benefit (consider palliative bracing)

Contraindications to ORIF

Absolute:

• Active infection at the operative site (treat first)
• Non-reconstructable articular surface in an elderly low-demand patient — consider distal femoral replacement (arthroplasty) instead

Relative:

• Severe osteoporosis with poor purchase — favours retrograde nail or augmentation
• Massive soft-tissue compromise — staged management (spanning external fixator first)

Goals of Fixation (the exam framework)

1. Anatomic reduction of the articular surface (absolute stability — lag screws)
2. Restoration of length, alignment and rotation of the metaphysis/diaphysis
3. Relative stability across the metaphyseal zone (bridge plating / nail — callus healing)
4. Preservation of the soft-tissue envelope and blood supply (biological/MIPO technique)
5. A construct stable enough for early knee motion but NOT so stiff it prevents callus

Deforming Forces — the Core Anatomy

Understanding muscle pull predicts the deformity and the reduction manoeuvre.

The single most important point: the gastrocnemius tilts the distal fragment APEX-POSTERIOR (extension/recurvatum) and drives it posteriorly toward the popliteal vessels. Reduction must actively counter this — flex the knee to relax gastrocnemius and support the fragment from behind (bolster, bump, or femoral distractor).

Neurovascular Anatomy

• Popliteal artery and vein lie directly posterior to the distal femoral metaphysis; the artery is tethered proximally at the adductor (Hunter's) hiatus and distally at the soleal arch — this fixation makes it vulnerable to the posteriorly-displaced distal fragment.
• Tibial and common peroneal nerves run in the popliteal fossa; the common peroneal nerve courses around the fibular neck (relevant if the limb is malpositioned or over-distracted).
• Perforating branches of the profunda femoris supply the distal femur — preserve the medial soft tissue and periosteum (the biological argument for MIPO).

Surgical Approaches

Implant Options — the Decision

Positioning and Preparation

Patient position: Supine on a radiolucent table. Place a bolster/bump under the knee (or a sterile triangle) to flex the knee ~30-60° — this RELAXES the gastrocnemius and helps correct the apex-posterior (recurvatum) deformity. Have the contralateral limb available/draped for length and rotation comparison if needed.

Imaging: Image intensifier from the opposite side; confirm you can obtain a true AP, a true lateral (essential for sagittal alignment) and a clear intercondylar/notch view. Bring the C-arm in before scrubbing.

Anaesthesia / adjuncts: General or regional. Tourniquet optional (high thigh) — many surgeons avoid it to read perfusion and because it tethers the quadriceps. Tranexamic acid per local protocol. Antibiotic prophylaxis at induction.

Consent: Counsel for nonunion/delayed union (notably medial supracondylar nonunion), malunion (valgus, recurvatum, rotation, shortening), infection, knee stiffness/arthrofibrosis, hardware irritation/failure, neurovascular injury (popliteal), DVT/PE, and possible need for revision or bone grafting.

Step-by-Step — Lateral Locking Plate (33-C example)

Step 1: Approach and Joint Exposure

For a complex articular fracture, use a lateral parapatellar / swashbuckler approach to visualise the joint. Incise skin, split the iliotibial band, elevate vastus lateralis off the lateral intermuscular septum (ligate perforators), and open the joint to inspect the articular surface. For extra-articular patterns, a small distal lateral incision plus submuscular (MIPO) plate passage preserves biology.

Step 2: Articular Reduction (Absolute Stability)

Reduce the articular surface ANATOMICALLY. Use pointed reduction clamps and provisional K-wires (placed so they do not block the plate or definitive screws). Confirm joint congruity directly and on imaging. Fix with interfragmentary LAG screws placed to compress the articular block — typically anterior-to-posterior and/or transverse, kept out of the path of the plate and intramedullary devices.

Step 3: Restore Length, Alignment and Rotation

Reattach the reconstructed articular block to the shaft. Restore LENGTH (femoral distractor or manual traction against the shortening quadriceps/hamstrings), correct the sagittal apex-posterior deformity (counter the gastrocnemius — support the fragment from behind, confirm on a true lateral), set the coronal axis (avoid valgus — restore the anatomic lateral distal femoral angle, aLDFA ~81°), and match ROTATION to the contralateral limb (condylar profile, lesser trochanter shape).

Step 4: Apply the Lateral Locking Plate (Relative Stability over the Metaphysis)

Position the plate on the lateral column flush against bone, distal screws parallel to the joint and subchondral for fixed-angle purchase. BRIDGE the metaphyseal comminution: a long plate, a LONG bridging working length (no screws immediately adjacent to the comminuted zone), and a mix of locked and non-locked screws to avoid an excessively stiff construct. Do not compress across comminution — relative stability allows the callus this fracture needs.

Step 5: Address the Medial Column

Assess medial support. If the medial cortex is in contact and the construct is balanced, the lateral plate alone may suffice. If there is medial comminution, a medial gap, or an unstable/osteoporotic pattern, add a MEDIAL plate (dual plating) through a separate medial interval to restore the medial column and prevent varus collapse and nonunion.

Step 6: Final Checks and Closure

Confirm articular congruity, alignment (AP, true lateral, notch view), screw lengths and that no screw is intra-articular. Re-check distal pulses. Lavage, achieve haemostasis, repair the IT band/quadriceps interval, and close in layers over a drain if needed. Apply a soft dressing — early knee motion is the goal.

Alternative — Retrograde Intramedullary Nail

Indications

• Extra-articular (33-A) and simple intra-articular (33-C1/C2) patterns
• Osteoporotic bone and obese patients (central load path, load-sharing)
• NOT for comminuted articular splits requiring formal reconstruction

Technique Outline

1. Reduce any simple articular split first and hold with lag screws OUTSIDE the nail path.
2. Flex the knee ~30-45° over a bolster (relaxes gastrocnemius, opens the entry).
3. Make a medial parapatellar or transpatellar tendon portal; establish the entry point in the intercondylar notch just anterior to the PCL origin, in line with the canal on AP and lateral.
4. Ream and pass the nail; lock distally first to control the short distal segment, then proximally — confirm length, alignment and rotation before final locking.
5. Beware entry-point malposition — too anterior causes recurvatum, off-centre causes coronal malalignment.

Post-operative Protocol

Early Phase (Week 0-6)

• Knee motion: Begin EARLY active and active-assisted knee range of motion as the construct allows — the rationale for a stable but not over-stiff fixation. Aim for a functional flexion arc to prevent arthrofibrosis.
• Weight-bearing: Traditionally NON or TOUCH weight-bearing for ~6-12 weeks for comminuted/intra-articular patterns; the trend (especially in older patients and load-sharing constructs) is toward EARLIER protected/progressive weight-bearing where fixation is robust.
• Analgesia and VTE prophylaxis: Multimodal analgesia; mechanical plus pharmacological thromboprophylaxis per protocol.
• Wound care: Inspect at 48 hours and ~2 weeks; suture/clip removal at 2 weeks.

Intermediate Phase (Week 6-12)

• Progress weight-bearing guided by radiographic callus (bridging callus on AP/lateral) and pattern.
• Quadriceps and hamstring strengthening; continue ROM work to regain full flexion/extension.
• Watch for early signs of delayed union — escalate if no callus by 3 months.

Late Phase (Beyond 12 weeks)

• Advance to full weight-bearing once united.
• Functional and proprioceptive rehabilitation; return to activity/work per occupation and union.
• Hardware removal only if symptomatic and after solid union.

Weight-bearing — the Nuance

There is no single rule. The decision balances fracture pattern (comminuted intra-articular = more cautious), implant (load-sharing nail tolerates earlier loading than a bridged lateral plate over comminution), bone quality, and patient factors. In frail elderly patients, prolonged non-weight-bearing is poorly tolerated and itself harmful — favour constructs (nail, dual plate, nail-plate) that permit earlier weight-bearing. A 2024 systematic review and meta-analysis of geriatric distal femur fractures found NO difference in nonunion, malunion, infection or implant-complication rates between early and delayed weight-bearing — supporting earlier mobilisation when the fixation is robust.

Special Considerations

Osteoporotic / Very Distal Fractures

• Fixed-angle distal locking, longer constructs, consider augmentation (cement around screws), retrograde nail or NAIL-PLATE combination for added stability.
• Lower threshold for distal femoral replacement in non-reconstructable joints in low-demand patients.

The Nonunion-Prone Construct — Recap

• The classic culprit is a SHORT, STIFF, all-locked lateral plate spanning an unsupported MEDIAL gap.
• Counter with: longer plate, longer bridging working length, mixed (locked + non-locked) screws, restored medial contact, and dual plating when the medial column is comminuted.

Guidelines, Registries & Global Practice

• Implant choice (lateral locking plate, retrograde nail, dual plating, nail-plate) is converging internationally toward pattern- and patient-specific selection rather than a single default.
• Weight-bearing: international practice is shifting toward earlier protected weight-bearing in older patients to reduce the morbidity of prolonged immobilisation, where the construct permits.
• Distal femoral replacement is increasingly used worldwide for non-reconstructable fractures in elderly low-demand patients to enable immediate mobilisation.