Hoffa fractures involve important load-bearing areas of the knee joint surface, and the principles of anatomical reduction and absolute stability of fixation apply.
In cases of very small posterior fragments, the indirect lag screw technique from anterior is not applicable as the thread will be too long and will not achieve compression of the fragment.
In addition, in small fragments, it is difficult to aim the K-wire from anterior into the fragment.
For this procedure, 3.5 mm cannulated headless compression screws are preferable. Standard 3.5 mm lag screws can be used in larger fragments.
Similar principles apply if both condyles are fractured.
None of the implants is allowed to project above the articular surface. This can be achieved by countersunk lag screws (A) or headless compression screws (B). At least two screws should be used, in order to prevent fragment rotation.
2. Patient preparation and approach
This procedure is normally performed with the patient in a prone position
Reduce the fracture using a small ball-spiked pusher and secure it temporarily with a K-wire.
Note: patient is lying prone.
Insert two guide wires. Make sure not to penetrate the far cortex.
Check guide-wire insertion
Check the guide-wire position under image intensifier control, in the lateral and oblique views.
If standard partially threaded lag screws are used, countersink manually prior to screw length measurement.
Do not perform countersinking when planning headless compression screws.
Pitfall: countersinking too deeply Be aware of countersinking too deeply into the cancellous bone, which often happens using a power tool.
Screw length measurement
Determine the appropriate screw lengths over the guide wires, making sure that the measuring device enters the countersunk holes.
Fixation – sunken screw
Insert the screws using the manual, not powered, screw driver. Tighten judiciously, as the denser subchondral bone can be fractured by over-tightening.
Illustration showing the completed osteosynthesis using standard partially threaded lag screws.
Alternative: headless compression screws
Insert headless compression screws, using the cannulated screw driver, and check under image intensifier control in the lateral view to confirm that the screw length was chosen appropriately.
5. Aftercare following screw fixation of partial articular fractures
Introduction Impediments to the restoration of full knee function after distal femoral fracture are fibrosis and adhesion of injured soft tissues around the metaphyseal fracture zone, joint capsular scarring, intra-articular adhesions and muscle weakness.
Continuous passive motion is a low load method of restoring movement and is a useful tool n the early post operative phase. It must be used in combination with muscle strengthening programs. With stable fracture fixation, the surgeon and the physical therapy staff will design an individual program of progressive rehabilitation for each patient.
The regimens suggested here are for guidance only and not to be regarded as proscriptive.
Functional treatment Unless there are other injuries, or complications, joint mobilization may be started immediately postoperatively. Both active and passive motion of the knee and hip can be initiated immediately postoperatively. Emphasis should be placed on quadriceps strengthening and straight leg raises. Static cycling without load, as well as firm passive range of motion exercises of the knee, allow the patient to regain optimal range of motion.
Weight bearing Touch-down weight bearing (10-15 kg) may be started immediately with crutches, or a walker. This will be continued for 6 weeks postoperatively. After that, touch-down weight bearing progresses to full weight bearing gradually over the next 2 weeks. In general, patients are full weight bearing, without devices (e.g., cane), by 8 weeks.
Follow up Wound healing should be assessed at two to three weeks postoperatively. Subsequently 6 week, 12 week, 6 month, and 12 month follow-ups are usually made. Serial x-rays allow the surgeon to assess the healing of the fracture.
Implant removal Implant removal is not recommended as all implants are buried, or absorbed.
Thrombo-embolic prophylaxis Consideration should be given to thrombo-embolic prophylaxis, according to local treatment guidelines.