In-Service Exam
Lower Extremity - 2001





The percentage of persons who have absence of the plantaris muscle in one lower extremity is

(A) less than 5%
(B) 10% to 15%
(C) 25% to 30%
(D) 45% to 50%
(E) 75% to 80%

The correct response is Option B.

According to the results of several studies, the plantaris muscle has been shown to be absent in at least one lower extremity in approximately 10% to 15% of persons. This tendon can be used for grafting procedures. It provides a longer donor graft than the palmaris longus in the forearm; however, it is hidden on physical examination, making it more difficult to locate prior to surgery. Because the muscle may be absent in one or both lower extremities, ultrasonography can be helpful in determining its presence and location. Approximately 33% of patients have a plantaris muscle in only one lower extremity.

Other studies have shown that absence of the plantaris muscle occurs with slightly greater frequency in women, and the plantaris muscle is more likely to be absent in the left lower extremity. Differences based on race and/or ethnicity have not been studied. In addition, absence of the plantaris muscle is unrelated to absence of the palmaris longus muscle; in other words, a person who is missing one or both plantaris muscles may in fact have one or both palmaris longus muscles.

References
1. Bergman RA, Thompson SA, Afifi AK. Compendium of Human Anatomic Variation. 1998:12-27.
2. Ruggles G. Coincidence of palmaris longus and plantaris muscles. Anat Rec. 1953;110:521-523.

PHOTO

The above photograph is of a 45-year-old man with insulin-dependent diabetes mellitus who develops a gangrenous toe. Culture of the wound shows mixed aerobic and anaerobic organisms, including Bacteroides, Enterococcus, and Staphylococcus. Noninvasive vascular studies show an ankle-brachial index of 0.76. The patient wishes to undergo a single-stage surgical procedure.

Which of the following is the most appropriate type of amputation for this patient?

(A) Amputation at the level of the metatarsophalangeal joint
(B) Transmetatarsal amputation
(C) Lisfranc amputation
(D) Syme's amputation
(E) Below-knee amputation

The correct response is Option B.

Amputation is indicated in this patient who has obvious necrosis of the toe. Indeed, ischemic changes and wound problems are often seen in patients with diabetes mellitus. Because these patients are typically predisposed to further, more proximal amputations in the future, a conservative approach to amputation should be used in this instance. Several factors, including ankle-brachial index, help to predict the success rate in patients who undergo partial amputations of the foot; an ankle-brachial index of less than 0.7 indicates a markedly increased risk for wound healing problems following surgery. However, this patient has an ankle-brachial index of 0.76, which is an acceptable risk for complications following amputation. Therefore, an evaluation for the likelihood of revascularization should be undertaken prior to any amputation procedure. The surgeon should attempt to save as much of the foot as possible to allow for primary closure of the defect. As a result, the amputation should be performed at the metatarsal level in this patient. The surgeon should also be aware of the vascular supply to the adjacent toes during the amputation procedure in order to prevent any associated complications.

References
1. Ger R, Angus G, Scott P. Transmetatarsal amputation of the toe: an analytic study of ischemic complications. Clin Anat. 1999;12:407-411.
2. Pinzur MS, Bowker JH, Smith DG, et al. Amputation surgery in peripheral vascular disease. Instructional Course Lectures. 1999;48:687-691.
3. Smith DG. Principles of partial foot amputations in the diabetic. Instructional Course Lectures. 1999;48:321-329.

A 37-year-old man who has paraplegia to the level of T9 is referred for evaluation because he has had a chronic penetrating wound on the weight-bearing surface of the exposed left calcaneus for the past 10 years. He has also had several associated episodes of cellulitis that have resolved with conservative therapy consisting of wound care, elevation of the limb, and administration of antibiotics.

In order to exclude a diagnosis of osteomyelitis of the calcaneus, which of the following is the most appropriate diagnostic study?

(A) Measurement of erythrocyte sedimentation rate
(B) Plain radiographs of the heel
(C) High-resolution CT scan
(D) MRI
(E) Triple-phase bone scan

The correct response is Option D.

An MRI should be performed in this patient to exclude a diagnosis of osteomyelitis. Although all of the imaging studies listed above will show abnormalities of bone, only a gadolinium-enhanced MRI will delineate the signal characteristics of bone marrow and specific enhancement pattern characteristic of osteomyelitis.

Measurement of erythrocyte sedimentation rate is highly sensitive but nonspecific for osteomyelitis; this test is used instead as a follow-up for determining the efficacy of treatment in patients previously diagnosed with osteomyelitis.
d to an advanced stage. High-resolution CT scans are inferior to MRI for diagnosis of osteomyelitis.

References
1. Boutin RD, Brossman J, Sartoris DJ, et al. Update on imaging of orthopedic infections. Orthop Clin North Am. 1998;29:41-66.
2. Caballero E, Frykberg RG. Diabetic foot infections. J Foot Ankle Surg. 1998;37:248-251.
3. Erickson SJ, Johnson JE. MR imaging of the ankle and foot. Radiol Clin North Am. 1997;35:163-192.
4. Wrobel JS, Connolly JE. Making the diagnosis of osteomyelitis: the role of prevalence. J Am Podiatr Med Assoc. 1998;88:337-343.

A 65-year-old attorney has severe ischemia of the right leg. On examination, the leg is gangrenous and ulcerated; he has pain with motion and at rest. Noninvasive vascular studies show an ankle-brachial index of 0.16. He refuses to undergo amputation.

Which of the following is the most appropriate technique for limb salvage?

(A) Distal arterial bypass
(B) Distal venous arterialization bypass
(C) Endovascular stent placement
(D) Free muscle transfer
(E) Lumbar sympathectomy

The correct response is Option B.

The symptoms and findings of severe pain at rest, ulceration, and gangrene seen in this patient are indicative of limb ischemia, a critically urgent condition that results from occlusion of the pedal and crural arteries. Although amputation had been performed in the past for patients with this condition, distal venous arterialization bypass is now a recommended alternative method for limb salvage. According to one small study of 18 patients, limb salvage was successfully accomplished in 83% of patients at surgery and 75% of patients at follow-up examination one year later. In these patients, the distal bypass was performed to the venous vessels of the foot using a conduit of either vein, synthetic graft, or a combination of both. The valves of the venous system were destroyed, and arterial inflow was then provided by the most distal patent artery.

Because both the pedal and crural arteries are occluded in this patient, neither direct arterial bypass nor placement of an endovascular stent will address the problem. Both free muscle transfer and lumbar sympathectomy are associated with lower rates of limb salvage in patients with severe ischemia.

References
1. Blaisdell FW, Lim RC Jr, Hall AD, et al. Revascularization of severely ischemic extremities with an arteriovenous fistula. Am J Surg. 1966;112:166.
2. Pokrovsky AV, Dan VN, Chupin AV, et al. Arterialization of the foot venous system in the treatment of the critical lower limb ischaemia and distal arterial bed occlusion. Ang Vasc Surg. 1996;4:73-93.
3. Taylor RS, Belli AM, Jacob S. Distal venous arterialisation for salvage of critically ischaemic inoperable limbs. Lancet. 1999;354:1962-1965.

A 35-year-old man with insulin-dependent diabetes mellitus develops a 14 * 8-cm ulcer of the left posterior calf overlying the Achilles tendon. He underwent kidney transplantation two years ago and has been taking immunosuppressive agents since that time.

Which of the following is the most appropriate management?

(A) Growth factor therapy
(B) Skin grafting
(C) Free tissue transfer
(D) Syme's amputation
(E) Below-knee amputation

The correct response is Option C.

This 35-year-old man with diabetes mellitus who previously underwent kidney transplantation has a large ulcer overlying the left Achilles tendon. Because of his immunosuppressive state and concomitant diabetes mellitus, he is most likely to experience cardiovascular problems, neuropathy, and poor wound healing following any type of reconstructive surgery. However, despite these potential adverse sequelae, free tissue transfer is most appropriate for management of the ulcer. Appropriate work-up should be obtained before attempting any reconstructive procedure.

Growth factor therapy will not adequately heal this large ulcer. A skin graft alone is inappropriate for coverage of exposed tendons. Because amputations often increase cardiovascular demand in patients with diabetes mellitus, they should only be used as a last resort. An amputation is also inappropriate in a young patient because it will significantly alter his ability to perform activities of daily living. In addition, the Syme's amputation is used in wound management of the forefoot and not the distal calf.

References
1. Armstrong MB, Villalobos RE. Free-tissue transfer for lower-extremity reconstruction in the immunosuppressed diabetic transplant recipient. J Reconstr Microsurg. 1997;13:1-5.
2. Searles JM Jr, Colen LB. Foot reconstruction in diabetes mellitus and peripheral vascular insufficiency. Clin Plast Surg. 1991;18:467-483.