PRINCIPLE: A good disarticulation/amputation can provide better comfort and function than some deformity and malformation reconstructions. (see Management Principle #29, Chapter 4).
Syme Ankle Disarticulation
1. Indications
a. Severe malformations, deformities, and injuries of the foot and/or leg, in which a good heel pad exists (see Management Principle #29, Chapter 4).
b. Forefoot gigantism (transverse macrodactyly) with a normal heel pad (see Macrodactyly, Chapter 6)
2. Technique (see Figure 6-7, Chapter 6) (Figure 7-40)
a. Make a fishmouth incision at the ankle/hindfoot
i. Incise across the anterior ankle from the tip of the medial malleolus to the tip of the lateral malleolus (or the lateral hindfoot if there is no lateral malleolus, as in the case of fibula hemimelia)
ii. Create a U-shaped flap extending across the plantar midfoot starting at the medial extent of the anterior ankle incision and ending at the lateral extent of the anterior ankle incision
b. Dorsally, isolate the superficial peroneal nerve branches, pull them distally, sharply transect them, and allow them to retract proximally
Figure 7-39. Plantar-medial plication. A. The posterior tibialis is cut in a Z-fashion releasing the dorsal slip from the navicular. B. The TN joint capsule is released from dorsolateral to plantar-lateral around the medial side, including release of the spring ligament. A 5- to 7-mm-wide strip of redundant capsule is resected from its plantar–medial aspect. C. The strip of redundant capsule has been resected. D. The plantar and medial aspects of the TN joint capsule are repaired anterior to posterior with large-gauge dissolving suture material (outlined by purple oval), having already resected the redundant capsule. The proximal slip of the posterior tibialis is advanced distally through a slit in the distal stump of the tendon. E. This Pulvertaft weave is repaired under firm tension with large-gauge dissolving sutures. F. A very cosmetic and sound repair is achieved. By performing the plications in this way, one can avoid creating excessive soft tissue bulk that might otherwise be as prominent as the head of the talus was initially. (From Mosca VS. Calcaneal lengthening osteotomy for valgus deformity of the hindfoot. In: Skaggs DL and Tolo VT, editors. Master Techniques in Orthopaedic Surgery: Pediatrics. Philadelphia: Lippincott Williams & Wilkins, 2008; 263–276.)
c. Isolate the anterior tibialis, extensor hallucis longus, extensor digitorum communis, and peroneus tertius, pull them distally, sharply transect them, and allow them to retract proximally
d. Isolate the anterior tibial NV bundle. Isolate the deep peroneal nerve, pull it distally, sharply transect it, and allow it to retract proximally. Ligate the artery and vein.
e. Release the anterior ankle capsule from the medial malleolus to the lateral malleolus
f. Release the medial and lateral collateral ligaments
g. Release the anterior edge of the flexor retinaculum (laciniate ligament) on the medial side of the hindfoot
h. Bluntly elevate the soft issues, including the posterior tibial NV bundle, from the flexor tendons and the talus and calcaneus. The NV bundle remains with the heel pad.
Figure 7-40. Syme amputation. A. Foot malformation in an infant with Streeter dysplasia (amniotic band syndrome). The deep band on the lower leg was previously reconstructed by Z-plasty and time has passed to ensure establishment of good vascularity and lymphatic flow to and from the distal part. B.The planned fishmouth incision is marked. C. All dorsal tendons and nerves are pulled distally, cut proximally, and allowed to retract. Vascular structures are ligated. D. The posterior tibial NV bundle is carefully protected and retracted with the heel pad away from the hindfoot bones. After the foot is disarticulated from the ankle, the plantar soft tissues are transected transversely at the midfoot. The medial and lateral plantar nerves are pulled distally, cut proximally, and allowed to retract. The arteries and veins are ligated/coagulated. E. Medial view of the limb after disarticulation of the foot. F.Appearance of the residual limb after repair of the midfoot soft tissues to the anterior ankle soft tissues. A Penrose drain is visible laterally.
i. Release the posterior tibialis (PT) tendon sheath, pull the PT distally, sharply transect it, and allow it to retract proximally
j. Release the flexor digitorum longus (FDL) tendon sheath, pull the FDL distally, sharply transect it, and allow it to retract proximally
k. Release the flexor hallucis longus (FHL) tendon from the sustentaculum tali, pull the FHL distally, sharply transect it, and allow it to retract proximally
l. Release the peroneus longus and brevis tendon sheaths, pull the peroneal tendons distally, sharply transect them, and allow them to retract proximally
m. Release the posterior ankle capsule
n. Pull the foot anteriorly out of the ankle joint with a towel clip
o. Sharply resect all soft tissues off the calcaneus
p. At the plantar midfoot, in line with the previously created transverse skin incision, sharply transect the plantar soft tissues. Identify and coagulate/ligate the medial and lateral plantar posterior tibial vascular structures. Pull the medial and lateral plantar posterior tibial nerves distally, cut them proximally, and allow them to retract.
q. Finally, pull the foot distally, isolate the tendo-Achilles far proximally, and transect the tendo-Achilles as far proximally as possible. Remove the foot from the surgical site.
r. The cartilaginous malleoli can be shaved off with a scalpel
s. Release the tourniquet and achieve complete hemostasis, while also confirming excellent vascularity to the entire heel pad
t. Place a small Penrose drain transversely in the posterior aspect of the resection cavity exiting through a stab wound through the skin on the lateral side
u. Adjust the length of the plantar flap to ensure that the heel pad can be pulled slightly anteriorly, thereby positioning the posteroplantar corner of the heel pad directly distal to the tibial shaft. In case of posterior heel pad migration, there will still be heel pad distal to the tibia (Figure 7-41).
v. Suture the plantar fascia to the anterior ankle capsule with #0 absorbable sutures
w. Approximate the skin edges with interrupted subcutaneous 3-0 absorbable sutures and a running subcuticular 4-0 absorbable suture
x. Apply a single hip spica cast in an infant (to prevent the cast from falling off), and a long-leg, bent knee cast in an older child (Figure 7-42)
y. Maintain the cast for 6 weeks, then use a stump shrinker for at least one week before molding for the Syme prosthesis
3. Pitfalls
a. Shaving unossified cartilage off the calcaneus that will eventually ossify
b. Poor design of the fishmouth incision resulting in excessive tension on the wound closure
Figure 7-41. Syme amputation in a 4-year-old boy with complex malformations of the left lower extremity. A. Lateral view of the fishmouth incision marked on the skin. B. Medial view of the fishmouth incision marked on the skin. C. Disarticulation of the foot at the ankle is near completion. D. The foot has been disarticulated. The large cartilaginous medial and lateral malleoli have been shaved off with a scalpel to provide a flat weight-bearing surface. E. Lateral view of the residual limb after removal of the foot. F. The plantar flap is pulled proximally to determine whether the appropriate amount of soft tissue has been resected to place the posteroplantar corner of the heel pad in line with the axis of the tibial shaft. If not, more needs to be resected. G. The closure has been completed with layers of absorbable sutures. H. Lateral view of the repair with the heel pad appropriating aligned and with the Penrose drain exposed.
Figure 7-42. A. Single hip spica cast applied following Syme amputation in an infant. B. Long-leg bent knee cast applied following Syme amputation in a 4-year-old child.
c. Excessive posterior positioning of the heel pad under the tibia that may contribute to posterior migration of the heel pad
4. Complications
a. Damage to the posterior tibial NV structures resulting in necrosis and/or loss of sensation of the heel pad
i. Avoid by careful isolation and retraction of the NV bundle with the heel pad before releasing the flexor tendons and resecting the soft tissues off the calcaneus. Transect the NV bundles at the edge of the plantar incision.
b. Posterior migration of the heel pad
i. Avoid by
• transecting the tendo-Achilles as far proximally as possible
• positioning the posteroplantar corner of the heel pad directly distal to the tibial shaft, anticipating slight posterior migration over time