AO Standard Technique: Posterior Screw and Plate Fixation for Hoffa Fractures

1. Principles

Overview

Hoffa fractures involve critical weight‑bearing areas of the knee joint and require anatomic reduction and absolute stable fixation.  

A buttress plate combined with lag screws is generally recommended.  

For small fragments, lag screws alone may be used.  

Indirect anterior‐to‐posterior lag screws are not recommended because the long thread length does not provide sufficient stability or fragment compression.  

The same principles apply to bicondylar fractures.

Screw Types

All implants must not protrude above the articular surface; this can be achieved with countersunk lag screws (A) or headless compression screws (B).  

At least two screws should be used to prevent fragment rotation.  

Either 3.5 mm cannulated headless compression screws or standard 3.5 mm lag screws can be employed, with other sizes selected according to fragment dimensions.

2. Patient Positioning and Surgical Approach

Patient Positioning  

Supine position with the knee flexed 20°–30°.

Surgical Approaches  

- Lateral Hoffa fractures: Swashbuckler approach or Gerdy’s tubercle osteotomy approach.  

- Medial Hoffa fractures: Medial intermuscular approach (AO standard approach – medial distal femoral approach).

3. Reduction

Reduce the fracture using a small ball‐tip pusher and temporarily fix with K‑wires.  

Ensure that the K‑wires do not interfere with the planned plate position or screw trajectories.

4. Fixation

Principles of Fixation

To enhance stability and avoid axial loading on the fracture (especially in osteoporotic bone), a buttress plate is used to prevent proximal displacement of the fragment.  

The plate position should be determined by the unstable fragment; occasionally the fragment is more lateral.  

Various plates are available; in this example a 3.5 mm narrow, slightly pre‑contoured plate is used.

Plate Placement

Place the plate on the posterior aspect of the distal femur, as distal as possible without invading the joint surface.  

Insert one standard cortical screw in neutral position proximal to the fracture line to adapt the under‑contoured plate to the femur.  

Secure the plate proximally with one or more bicortical cortical screws in neutral position.  

If the distal part is extra‑articular, additional screws may be placed, all in neutral position.  

Intraoperative imaging shows the posterior Hoffa fracture reduced, temporarily fixed with K‑wires, and supported by a posterior buttress plate.  

Postoperative imaging confirms proper placement of the posterior buttress plate.

Guide Wire Insertion

Insert two guide wires perpendicular to the fracture line without penetrating the opposite cortex.  

Confirm guide wire position under fluoroscopy (lateral and oblique views).

Headless Compression Screw Insertion  

Insert headless compression screws using a cannulated driver; check screw length on lateral fluoroscopy.

Alternative: Standard Screws  

Insert cancellous lag screws under fluoroscopy using standard technique, with countersinking to avoid screw head prominence.

5. Case Example

If the plate is placed laterally or medially rather than posteriorly, fixation failure often occurs.  

Articular step‑off may be seen, requiring revision surgery.

6. Postoperative Management

Factors affecting knee function recovery after distal femoral fractures include soft‑tissue fibrosis around the metaphysis, capsular scarring, intra‑articular adhesions, and muscle weakness.  

After stable fixation, early motion should be initiated with an individualized rehabilitation programme developed by the surgeon and physiotherapist.

The following are guidelines, not mandatory protocols.

Functional Therapy

In the absence of other injuries or complications, knee motion is started immediately after surgery, combined with active and passive exercises for both knee and hip.  

Progressive quadriceps strengthening and straight‑leg raises are emphasised.  

Non‑weight‑bearing stationary cycling and passive ROM exercises facilitate optimal range of motion.

Weight‑Bearing

Partial weight‑bearing (10–15 kg) with crutches or a walker is permitted immediately after surgery for 6–10 weeks, primarily to protect the articular surface.  

At 6–10 weeks, transition to full weight‑bearing over 2–3 weeks; ideally, abandon walking aids at 12 weeks.

Follow‑Up

Wound healing is assessed at 2–3 weeks; then regular follow‑up at 6 weeks, 12 weeks, 6 months, and 12 months with serial X‑rays to monitor fracture healing.

Implant Removal

Not mandatory; if implant‑related symptoms develop after healing, removal may be discussed with the patient.

Thromboprophylaxis  

Thromboprophylaxis should follow local guidelines.