This operation will benefits the amputee in the following ways:
Initially, the old scar is removed and tissue planes are separated to identify the layers of muscle, blood vessels, and finally, bone.Next, a bone-bridge is created between the two lower extremity bones, the tibia and the fibula. By forming a synostosis, this provides a bony framework, recreating a heel type structure with weight bearing capabilities. [Figure 1, Figure 2]
This framework prevents the fibula from separating from its tibial relation and being pulled away by its tendinous attachments. Without this bony stabilization, the fibula may “wander” from the tibia with each step, causing unnecessary and non-physiological motion, irritating the soft tissues and nerves.Also, the bony bridge prevents a rotational motion of the below-knee stump within it prosthesis, thereby creating additional stability in the rotational axis of the patient’s limb.
Another advantage is the recreation of a closed bone marrow cavity, which is also accomplished in the above-knee amputation by osteoperiosteal flaps. This is a principle in the Osteomyoplasticamputation procedure that has been supported by biomedical experimentation. In conventional amputation techniques, the bones are transected exposing the medullary cavity. If the bone marrow cavity is allowed to remain open, abnormal vascular tissue will proliferate from the bone ends, called arterio-venous fistulas. These fistulas cause compromised circulation, pain and dysfunction, all contributing to an un-physiological mass at the bone end. In the above-knee amputations, osteoperiosteal closure of the bone marrow cavity also prevents crown sequestration (a 1.5–2.5 cm. ring of necrotic bone at the amputation boneend caused by endosteal and periosteal stripping).[Figure 3]
With time, a full-contact prosthesis is used allowing full weight bearing. This is in contrast to the frequently used patellar tendon bearing (PTB) prosthesis, which utilizes the kneecap (patella) and femoral condyles for prosthesis suspension. Within this PTB prosthesis, the amputated stump becomes inactive, leading to disuse-atrophy and may become ulcerated from pressure irritation.
Following the creation of the bony architecture (foundation), the “motor” of the extremity, i.e. the muscles, are reconstructed. This step is accomplished by performing a myoplasty, which re-establishes a length-tension relationship of opposing muscle groups. A second purpose of the myoplasty is to restore the pumping action of the “peripheral heart,” which refers to how contracting
muscles in the lower limb aid the return of venous blood back to the central circulation and heart. This advantage cannot be over-emphasized as it helps cardiac output and improves the amputee’s walking ability. [Figure 4]
Special attention is given to dissecting the extremity’s arteries, veins and nerves. In stump reconstruction, nerves are commonly found adherent to localized scar tissue as well as to the skin itself. This scarring restricts the normal gliding motion of the nerves and leads to pain from traction applied to the nerve while walking. For this reason among others, each structure is identified and isolated from its surrounding attachments as well as each other. The arteries and veins are separately ligated and allowed to retract to prevent communication between the two.
Finally, the skin is approached and flaps are contoured to the shape of the underlying muscle. A smooth surface is constructed to facilitate the fitting of a full-contact endweight-bearing prosthesis.