Indications
The gastrocnemius muscle is routinely used for soft tissue loss and bone coverage over the proximal one-third of the tibia.
For the middle tibia, the soleus flap is used, and distal to that a free flap is needed.
Either the medial or lateral heads of the gastrocnemius can be used, though the proximity to the Peroneal nerve and its shorter length make the lateral less desirable.
Anatomic considerations
Each head of the gastrocnemius muscle recevies its blood supply from a sural artery, medial and lateral respectively, which are branches off the Popliteal artery
The sural arteries pass directly into the proximal portion of each head of the gastrocnemius muscle. The arteries branch off 3 cm distal to the joint line beyond which they traverse the entire length of the muscle.
The main disadvantage with acquisition of these flaps is that a portion of proximal Achilles tendon must be divided to free the medial or lateral head of the gastrocnemius muscle.
Surgical Details: Medial
- Make a longitudinal incision along the posterior border of the fibula, extending from the tibial plateau to a point 10 cm above the ankle joint. (If the flap is going to be tunneled under a skin bridge, it is necessary to place the incision further posterior to minimize the risk of compromising the intervening skin bridge. In this procedure, the saphenous vein is left intact on the medial aspect of the extremity.)
- The gastrocnemius is separated from the overlying subcutaneous tissue.
- A surgical plane is created between the medial head of the gastroc and the underlying soleus muscle.
- Small vessels may be encountered at the median raphe, or junction of the medial and lateral heads. The sural nerve can be located at the midline between the two heads, but it then passes lateral to the raphe.
- As you move distally, release the attachment of the medial head (along with a small portion of the achilles tendon attached to the flap).
- The neurovascular pedicle is isolated and the length of the flap may be increased undermining the fascia longitudinally on the deep surface of the muscle.
Surgical Details: Lateral
- The lateral gastrocnemius flap is accessed via a longitudinal incision 3 cm posterior to the fibula.
- The muscle belly is released from the tibia, fibula, and both lateral and anterior crural compartments, while the common peroneal nerve is identified at the level of the fibular neck. T
- his flap is shorter than the medial flap but allows for coverage of the region between the lateral aspect of the knee joint and the patella.
Results
Both the medial or lateral heads of the gastrocnemius muscle can be expended with little or no deficit when walking or in normal running.
A study was conducted to assess the donor-site morbidity and functional deficit following gastrocnemius flap coverage. They concluded that the functional donor-site morbidity after harvest of one head of the gastrocnemius muscle is mild in subjects who have had a complete recovery from their initial injury. Normal level gait wass possible, however deficits were seen in more demanding tasks such as fast walking or uphill walking.
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