Volume 10 · Number 5 · September/October 2000
Prosthetic Primer: Pain and the Inactive Residual Extremity Syndrome
by Jan Ertl
Although the prosthetic industry has made significant advances over the past 40 years, pain is still a common feature in many lower extremity amputees. Prosthetists have been required to correct and relieve these painful and sensitive areas by whatever means possible. Often symptomatic or tolerable improvement is achieved, however, further surgical intervention is often necessary. Pain in lower extremity amputees may originate from a number of areas and structures including bone, muscle, nerve, blood vessels and skin. These painful symptoms will usually lead to significant disability, difficulty with daily activities, and decreased ability to wear the prosthesis.
In 1920, Professor Janos Ertl, Sr., MD, of Hungary, developed the Ertl procedure in order to return a high number of amputees to the work force. During this time, amputees had significant problems with pain and difficulty with prosthetic wear. The prosthetic industry and surgical techniques were not as developed or refined, resulting in the residual limb used as a passive attachment for a prosthesis. In essence, the residual limb became an inactive participant in ambulation. Through his clinical observations and using his regenerative surgical principles, Dr. Ertl sought to reestablish a pain-free residual extremity that would actively participate in ambulation. The problems he wished to combat continue to exist today and we have termed this complex set of symptoms as "The Inactive Residual Extremity Syndrome (IRES)."
The IRES consists of pain from nerve and bone endings, bone and soft tissue atrophy, muscle retraction, fibular instability and soft tissue scarring - leading to a non-physiologic state and inactive participation of the residual extremity in ambulation. The surgery attempts to recreate a durable, pain-free and potentially weight-bearing limb within the prosthesis. The Ertl procedure has not changed in its application of the biologic and regenerative surgical principles although some modifications have been implemented.
The Ertl procedure is a combination of the synergistic action of multiple procedures, the foundation being the "flexible bone graft," based on osteoperiosteal dissection, which has also been applied to other orthopedic areas including spine, hand, non-union and mandibular defects.
In transtibial (below knee amputations), attention is initially directed towards the tibia and fibula bones and fibular instability. Fibular instability is defined as excessive motion of the fibula bone relative to the tibia bone due to the actions of the musculo-tendinous attachments and lack of distal bony attachment (stability), leading to a "chop-sticking" effect of the two bones when walking with prosthesis. In turn, this leads to irritation of both soft tissue and nerves and rotational instability within the prosthesis. A flexible osteoperiosteal bone graft is elevated from the distal ends of both the tibia and fibula. The flexibility allows the leafs to be sutured together in tube-like fashion creating a synostosis, providing a bony framework which solidifies over time, stabilizing the fibula. In addition to creating a synostosis, the medullary canals of both bones are closed, reestablishing a normal intramedullary pressure and improving the surrounding bone and soft tissue blood supply. The Ertl procedure is not exclusive to transtibial amputees, however, it also applied to the transfemoral (above the knee) amputee population and other amputated areas with open medullary canals. The same principles as described for the transtibial level are applied to the transfemoral level, however, only one bone is involved as the medullary canal is covered with the flexible bone graft.
The medullary canal is normally a closed system maintaining a normal pressure gradient, delivering blood (nutrition) to the bone. In conventional amputation techniques, the bone is transected, exposing the medullary canal. The normal intramedullary pressure is lost; the nutrition to the bone is decreased and vascular proliferation from the bone ends occurs. This results in arterio-venous fistula formation (connection between artery and vein) and an inefficient vascular system leading to pain and dysfunction. In the conventional amputation technique, an abnormal or non-physiologic state is created and with closure of the intramedullary canal, the physiologic circulatory dynamics are reestablished.
Once the bony foundation is accomplished, attention is directed toward the functional muscular reactivation of the limb. In conventional amputation, the muscles are transected and allowed to retract or are limited to reattachment of one muscle. Muscle attachments create a circular continuity with bone requiring a bony attachment both proximally and distally, establishing a length-tension relationship within the muscle. This attachment allows the muscle to lengthen and shorten with muscular contraction in order to generate power or motion. This can be compared to a distracted circular rubber band, which is able to generate power. Once the rubber band is cut, the two ends of the rubber band retract and the stored power is lost.
In the Ertl procedure, a myoplasty is performed, securing the retracted ends of the muscle to one another, reestablishing a length-tension relationship. A myoplasty is performed in both transfemoral and transtibial amputation levels and the muscles are additionally secured to the bony foundation at both levels. An additional benefit of the myoplasty is the recreation of the skeletal peripheral heart - referring to the muscles pumping action in the lower limbs during ambulation, providing the return of venous blood back to the heart. Through the reestablishment of the muscle length-tension relationship by myoplasty, the muscles can now actively contract and return blood to the heart more efficiently.
Attention is then directed to isolate the arteries, veins and nerves. In primary amputations, this isolation is along the anatomic lines and can be easily performed; however, in conventional (traditional) amputation surgery the nerve, artery and veins are usually sewn together in one mass and become scarred together. The artery and vein usually form connections to each other and lead to an inefficient blood supply to the residual limb. This, in turn, can lead to weakened bone (osteopenia) and an excessive strain on the heart. In addition, the nerve, which is now tied to the artery, will be constantly stimulated from the pulsations of the artery. In secondary amputation reconstruction, significant scar tissue is present binding blood vessels and nerve endings together, which in turn is scarred to the muscle or overlying skin. Traction or tension applied to the scarred nerve endings through shearing motion (traction) or pressure from the prosthesis leads to painful stimulation of the nerve. Treatment of the arteries and veins include careful dissection, isolation and separate ligation. The nerves are transected under tension and allowed to retract into their soft tissue bed where no tension or traction can be applied. Treatment of nerves, arteries and veins are the same for both above and below knee amputations.
Lastly, the skin is contoured to the underlying myoplasty leading to a smooth transition or surface. A smooth interface is created to promote full contact between the leg (residual limb) and prosthetic socket avoiding air leaks and shear. Postoperative physical therapy is important to maintain muscular contraction and control, as well as aid in desensitization of the residual extremity. Prosthetic fitting is performed at six to eight weeks with emphasis on full contact end bearing capabilities. The potential end weight bearing ability of the residual limb assists in reestablishing the proprioceptive modalities of the lower extremity, increasing the patient's stability, confidence and endurance.
Even against great odds it is our goal as surgeons to salvage limbs by whatever means possible, in order to maintain the whole of the individual. Often it is impossible to save a damaged or diseased limb or symptoms of pain and disability become too frequent, interfering with life's daily activities, leaving amputation as the only option. In the event of limb amputation, it should be our goal to anatomically and physiologically reconstruct as functional and pain free a limb as possible. With carefully done surgery the inactive residual extremity syndrome can be avoided and the residual extremity again become an active participant in ambulation and not only utilized as an attachment for a prosthesis.
In summary, the Ertl procedure attempts to reconstruct the amputated lower extremity limb through anatomic and physiologic means in attempt to avoid the inactive residual extremity syndrome. The benefits of reconstruction include:
- Prevention and stabilization of excessive fibular motion by creation of a bony bridge between the tibia and fibula;
- Closure of the medullary canal reestablishing intramedullary pressure and prevention of arterio-venous connections at the bone ends in both above (transfemoral) and below (transtibial) knee amputation;
- Prevention of bone spurs (crown sequestrations) in transfemoral amputations;
- Improved venous return to the heart through myoplasty (reconstruction of the peripheral muscular pumping action assisting in returning blood to the heart);