- Lateral parapatellar approach to the distal femur
Exposure of the articular surface
The lateral parapatellar approach provides a good view of the articular surface of the distal femur. With a longitudinal division of the quadriceps tendon and extensor mechanism, the patella can be dislocated medially.
In general, there are no neurovascular structures at risk. The common peroneal nerve is safe posterior and distal to the approach.
There is only the lateral superior genicular artery to avoid, or ligate.
The surgical approach exploits only the extensor mechanism. No significant neurovascular risks are present.
Extensions of the lateral parapatellar approach
For most intra articular distal femoral fractures, the lateral parapatellar approach (1) includes:
- A minimally invasive approach to the midshaft, or proximal, femoral region (2), which aids the surgeon in ensuring that the plate is in the appropriate position on the proximal, lateral aspect of the femur
- Small 1.0–1.5 cm stab incisions for percutaneous screw insertion (3)
The lateral parapatellar approach may also be used in isolation (only using incision 1) for for lateral sagittal or coronal fractures, in which a plate is not inserted by sliding into a submuscular tunnel.
Antibiotics are administered according to local antibiotic policy and specific patient requirements. Many surgeons use gram-positive prophylactic antibiotic cover for closed fractures, adding gram-negative prophylactic cover for open fractures. Always remember that antibiotic therapy will never compensate for poor surgical technique.
Tourniquets can be helpful to minimize blood loss and to improve the view of the articular surface. In the trauma patient, the surgeon must consider the effects of ischemia / reperfusion and the potential effects of tourniquet use in the presence of a compromised soft-tissue envelope.
Consideration of tourniquet use should be part of the preoperative planning process. A tourniquet may, or may not, be used depending on the morphology of the fracture and soft-tissue injury. If the fracture margins approach the vicinity of the tourniquet site, a tourniquet is not used.
The surgeon has to take into account that the inflated tourniquet can complicate the reduction of the fracture by fixing the quadriceps in a shortened position. To avoid this, the knee should be carefully flexed beyond 90° with gentle traction applied and the patella manually pushed distally, in order to gain as much length as possible before the tourniquet is inflated. In some cases it may be helpful to deflate the tourniquet while reducing the fracture.
A thigh tourniquet should be not left on longer than 120 min., and for a shorter time in older patients or those with known vascular disease.
AO teaching video: MIPO Femur, Distal Lateral Parapatellar Approach
Place a rolled towel under the knee to produce 20° to 30° of knee flexion.
Mark the tibial tubercle and the patella. The incision can be either directly midline, or preferably, slightly lateral to midline (as shown).
A common mistake is to make the incision too short, which will later on not permit medial patellar dislocation. The incision is generally 15–18 cm in length.
A deep dissection exposes the lateral aspect of the patella.
The extensor retinaculum is preserved over front of the patella.
The skin incision is long enough for the surgeon to define both the medial and the lateral aspects of the quadriceps tendon.
Make a full thickness, longitudinal incision through the lateral parapatellar retinaculum and the quadriceps tendon. It begins slightly lateral to midline (40% lateral; 60% medial) and curves to the lateral aspect of the patella. It should leave an 8–10 mm cuff of parapatellar retinaculum on the lateral aspect of the patella.
The split in the quadriceps tendon extends approximately 10 cm above the superior pole of the patella. If an adequate release is not performed, the surgeon risks patellar tendon avulsion during patellar dislocation.
Distal extension of the deep dissection
Carry the division down distally to the lateral aspect of the patellar tendon and then, by flexion of the knee and medial traction on the extensor mechanism, the patella is dislocated medially.
Tibial tubercle osteotomy
In difficult situations, where exposure of the distal femur is not adequate, a tibial tubercle osteotomy can be performed. The tibial tubercle can be elevated with a block of bone and retracted superiorly. This technique can damage the blood supply to the patellar tendon and the patella, and should only be used with extreme caution.
A tibial tubercle osteotomy is only necessary when the surgeon chooses a lateral approach to the distal femur and then, intraoperatively, sees that there is an unrecognized medial femoral condylar Hoffa fracture.
Close the quadriceps tendon and cuff of tissue along the lateral aspect of the patella with interrupted #2, or larger, sutures. Suction drain usage may be considered. Close the skin and subcutaneous tissue in a routine manner.
Minimally invasive approach to the midshaft or proximal femoral region
Make a short incision along an imaginary line (dashed line) between the lateral femoral epicondyle and the greater trochanter.
The starting point and the length of the incision depend on the operational requirements for the minimally invasive procedure.
Opening the fascia lata
Incise the fascia lata and expose the muscle fascia of the vastus lateralis.
Incision of the fascia vastus lateralis
Carefully incise the muscle fascia of the vastus lateralis.
Exposure of the femur
Dissect the muscle fibers apart bluntly down to the femur. Normally, with a formal approach to the lateral aspect of the femur, the entire muscle belly of the vastus lateralis is elevated anteriorly from the lateral intermuscular septum. However, with minimally invasive techniques, this is not possible. Therefore, the muscle belly is split in the line of its fibers to approach the lateral aspect of the femur.
Two Hohmann lever retractors are recommended - one anterior and one posterior - for a secure exposure of the femoral shaft.
Pearl: use of Hohmann retractors
Hohmann retractors ensure appropriate plate positioning on the femur. It is wise first to ensure that the most proximal screw hole of the plate is centrally located, before any other screws are inserted in the proximal plate.
Close the iliotibial band with absorbable sutures. The use of suction drains may be considered. Close the subcutaneous tissues and skin in a routine manner.
Stab incisions for percutaneous screw placement
Make a 1-1.5 cm wide incision in line with the screw hole of the plate. This incision is made as a single stab through the skin, subcutaneous tissue, iliotibial band, fascia of the vastus lateralis, and finally through the muscle belly of the vastus lateralis. A common mistake is to make the stab incision too small. A 1–1.5 cm wide incision is sufficient for most screw insertions.
If two screws need to be placed close to each other a smaller version of the lateral approach to the femur can be used for this purpose.
Close the iliotibial band with absorbable sutures. Close the subcutaneous tissues and skin in a routine manner.