AO Standard Technique: Anterior Screw Fixation for Hoffa Fractures
1. Surgical Principles
Hoffa fractures involve critical weight-bearing articular surfaces of the knee joint. Surgery must adhere to two main principles: anatomic reduction and stable, rigid fixation.
These fractures are conventionally treated via a posterior approach, using tibial screws and a buttress plate for reduction and fixation. Anterior-only fixation is reserved for a few exceptional cases; however, this construct provides poor stability and is generally not recommended in clinical practice.
Indirect anterior fixation may be performed using 3.5‑mm or 4.5‑mm screw systems, with cannulated screw systems being preferred for better outcomes.
When the fracture fragment is small in volume, direct fixation should be performed through a posterior approach.
At least two screws should be inserted to prevent rotational displacement of the fragment and to achieve effective interfragmentary compression.
All implants must not violate the articular surface.
The same principles apply to bicondylar fractures.
2. Preoperative Preparation and Surgical Approaches
Patient Positioning
Any of the following positions may be used:
1. Supine with the knee flexed at 30°
2. Supine with the knee flexed at 90°
3. Lateral decubitus (preferred in obese patients)
Surgical Approaches
Commonly used approaches include:
- Minimally invasive lateral / anterolateral approach
- Medial parapatellar approach
- Lateral parapatellar approach
- Direct medial approach
These difficult fractures can be reduced and fixed via an anterior approach; if the posterior condylar fragment is large, the fracture line can be clearly visualized through a parapatellar approach.
For more superficial fragment locations, a standard lateral or anterolateral approach is required to adequately expose the posterior fracture site; alternatively, a direct posterior approach may be chosen.
For medial fractures, a straight medial incision can be used, with care taken to protect the infrapatellar branch of the saphenous nerve to avoid iatrogenic nerve injury.
3. Fracture Reduction
Reduction is achieved using a periosteal elevator and a large pointed reduction forceps. The joystick technique may also be employed by placing a small Schanz screw into the extra-articular bone surface, which is practical and convenient.
4. Implant Fixation Technique
Guide Wire Placement
Guide wires should be inserted as perpendicular as possible to the fracture plane.
Confirmation of Guide Wire Position
Fluoroscopy is used to verify guide wire placement; the guide wire must not penetrate the condylar articular surface.
Screw Insertion
Under fluoroscopic guidance, lag screws are inserted following standard cancellous bone lag screw technique.
Screw heads must not protrude or be prominent.
Postoperative Imaging
Postoperative imaging confirms adequate fixation. This fixation method provides reliable long-term outcomes; however, clinical practice routinely requires augmentation with a posterior buttress plate.
5. Postoperative Rehabilitation and Management Protocol
Restoration of knee function after distal femoral fractures is limited mainly by fibrosis of soft tissues around the metaphysis, adhesions, capsular scar formation, intra‑articular adhesions, and lower limb muscle weakness.
Early postoperative initiation of joint motion exercises facilitates rapid recovery of range of motion.
Once fracture fixation is deemed stable, the surgeon, in conjunction with rehabilitation staff, develops an individualized, stepwise rehabilitation program for the patient.
The following protocol is provided as a clinical reference and is not a rigid standard of care.
Functional Rehabilitation Exercises
In the absence of associated injuries or postoperative complications, knee motion exercises can be initiated immediately after surgery, simultaneously starting active and passive range‑of‑motion exercises for both the knee and hip joints.
Progressive strengthening of the quadriceps muscle should be emphasized, with consistent straight‑leg raises.
Non‑weight‑bearing stationary cycling and supervised passive knee flexion‑extension exercises help patients achieve optimal joint range of motion.
Weight‑bearing Training
Immediately after surgery, patients may begin toe‑touch weight‑bearing with crutches or a walker, limiting weight to 10–15 kg, for 6 to 10 weeks.
This weight‑bearing restriction is primarily intended to protect the injured articular surface, not the diaphyseal fracture site.
From 6 to 10 weeks postoperatively, a gradual transition to full weight‑bearing over 2–3 weeks is implemented. Under ideal conditions, patients can achieve independent full weight‑bearing without assistive devices by 12 weeks postoperatively.
Postoperative Follow‑up
Wound healing is assessed at 2–3 weeks postoperatively. Subsequent routine follow‑up visits are scheduled at 6 weeks, 12 weeks, 6 months, and 12 months, with serial imaging to evaluate fracture healing progress.
Implant Removal
Routine implant removal is not required after fracture union. If implant‑related symptoms develop after complete healing, elective removal may be discussed with the patient and scheduled at an appropriate time.
Thromboembolism Prophylaxis
Thromboprophylaxis should be strictly implemented in accordance with local clinical practice guidelines for lower extremity venous thromboembolism prevention.