Flatfoot Surgery

Margaret J. Lobo, MD

Samantha Francucci, PT, DPT

Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Francucci and Dr. Lobo.

Introduction

The degenerative breakdown of the medial longitudinal arch is commonly referred to as adult acquired flatfoot and is a separate entity from a congenital arch deformity. It is a common biomechanical problem with a complex etiology. The medial longitudinal arch is comprised of both static and dynamic stabilizers. The bony longitudinal arch and the supporting ligaments—the spring and deltoid ligaments—are the static components, while the posterior tibial tendon, flexor digitorum longus, flexor hallucis longus, and the gastrocnemius/soleus complex are the main dynamic arch stabilizers. A breakdown of the medial longitudinal arch occurs when the dynamic stabilizers of the arch weaken, placing increased stresses and ultimately failure of the ligaments that support the bony arch (Table 54.1). The characteristic acquired flatfoot deformity consists of hindfoot valgus, subtalar eversion and forefoot abduction as the foot rotates dorsally and laterally relative to the talus (Figure 54.1).

Although some cases of acquired flatfoot may be managed with orthotics and shoe modifications, surgery is indicated in cases of pain, progressive deformity, and difficulty with ambulation. The goals of the surgical procedure are to preserve the mechanics of the foot, providing push off while walking. Flatfoot surgery usually includes osseus and soft-tissue procedures to correct the static and dynamic imbalances. The common soft-tissue procedures done for flatfoot reconstruction include a gastrocnemius recession (lengthening) and a flexor digitorum longus transfer (to augment the posterior tibial tendon). The bone procedures may include a medial slide calcaneal osteotomy, an anterior lengthening calcaneal osteotomy, and fusions or osteotomies of medial column joints, such as a first metatarsal medial cuneiform fusion (the Lapidus procedure) and the navicular cuneiform fusion. When the talonavicular joint, subtalar joint, and calcaneocuboid joint have significant degeneration, a triple arthrodesis is performed. A rigid adult acquired flatfoot deformity is also best treated with a deformity correcting hindfoot fusion (see Chapter 55). A preoperative assessment, including clinical examination and radiographs, is used to determine the combination of procedures required to correct the flatfoot deformity, particularly assessing the stiffness and degree of the deformity.

Postoperative rehabilitation is a critical component in the recovery of these patients. The flatfoot deformity occurs slowly over several years and results in weakening of the foot intrinsic musculature as well as contractures and imbalance of the calf. The deformity and altered gait pattern associated with flatfoot affects the knee, hip, and back. All of these areas need rehabilitation postoperatively.

Surgical Indications

Dysfunction of the posterior tibial tendon
Progressive planovalgus deformity
Pain refractory to orthotics and shoe modifications

Contraindications

Limited ambulator
Neuropathy or peripheral vascular disease posing high risk for wound healing problems and infection
Medical conditions precluding safe surgery

Surgical Procedures

Flexor Tendon Transfer

In the flatfoot deformity, the posterior tibial tendon (PTT) is compromised. The PTT may have significant tendinopathy, an interstitial tear, or be completely ruptured at the time of surgery. The flexor digitorum longus (FDL) tendon is used to either augment or replace the injured PTT. The FDL is transferred to the medial aspect of the navicular, the primary insertion site for the posterior tibial tendon. This muscle is directly posterior to the PTT and acts at the same phase of the gait cycle, making it a good candidate for transfer (Figure 54.2). The FDL tendon may be transferred to the navicular bone without significant loss of lesser toe flexion.

This procedure is performed through a longitudinal skin incision along the PTT from the tip of the medial malleolus to
the navicular cuneiform joint. The sheath is opened and the PTT is exposed and assessed. A section of the PTT is resected 1 cm proximal to the navicular insertion and at the level of the medial malleolus. The FDL tendon is located by making a small incision in the posterior aspect of the PTT sheath. It is sharply dissected to the level of the knot of Henry, then sectioned at this level. A bone tunnel is made from the plantar to dorsal aspect of the medial navicular for passage of the FDL tendon. Once the other bone and soft-tissue procedures are completed, the FDL tendon is sutured to the remaining PTT and itself. The tendon is tensioned with the ankle in dorsiflexion and slight inversion when securing the tendon transfer. Approximately
8 to 12 weeks is required for the tendon to become strongly incorporated into the bony tunnel. Thus, passive range of motion (PROM) and active strengthening exercises should be limited and gentle until weeks 8 to 10.

Table 54.1 FLATFOOT DEFORMITY INSTIGATING FACTORS

Figure 54.1 Photographs of a single-limb heel rise demonstrating normal heel height and inversion (A) in comparison to hindfoot valgus with double-limb heel rise (B). Note that the Achilles and calcaneal tuberosity are lateral to the midline in the flatfoot deformity.

Figure 54.2 Clinical photograph demonstrating flexor digitorum longus tendon just posterior to the posterior tibial tendon. The posterior tibial tendon has been removed and the remaining 1 cm of the tendon is visualized at the navicular.

Gastrocnemius Recession

The gastrocnemius muscle originates on the distal femur and joins the soleus muscle in the lower leg coalescing to the Achilles tendon, which inserts on the calcaneal tuberosity. With a contracture of the Achilles tendon, or isolated to the gastrocnemius muscle, a plantigrade heel can only be achieved with abduction through the transverse tarsal joints. Consequently, a valgus hindfoot results. This contracture can be the primary cause of the adult acquired flatfoot deformity or a secondary cause occurring after the arch collapse. An integral part of flatfoot reconstruction is releasing the contracture of the gastrocnemius muscle. An isolated contracture of the gastrocnemius can be determined by the Silfverskiöld test, which tests passive ankle dorsiflexion with the knee extended and then flexed. Insufficient dorsiflexion with the knee extended, and increased ankle dorsiflexion with the knee bent confirms a gastrocnemius contracture.

The gastrocnemius recession can be done via a posterior or medial approach, but is typically approached medially in combination with flatfoot reconstruction. An incision is made at the musculotendinous junction of the gastrocnemius and soleus, approximately two fingerbreadths posterior to the tibia. Blunt dissection is then performed to locate the superficial posterior fascia. Care must be taken to identify and protect the saphenous nerve and vein. The gastrocnemius muscle is then bluntly separated from the fascia posteriorly and the soleus muscle anteriorly. The foot is brought into dorsiflexion and the tendinous portion of the gastrocnemius tendon is cut sharply. The gastrocnemius lengthens until the soleus is tense (the soleus is still intact); thus, overlengthening is usually not possible. The incision is then closed in layers, including the fascia, subcutaneous tissue, and skin.

During the rehabilitation process, it is important to maintain gastrocnemius flexibility. Emphasis should be placed on maintaining the foot in a dorsiflexed position while immobilized and daily stretching of the gastrocnemius/soleus complex once out of a cast. Strengthening of the gastrocnemius will be important after the third month.

Posterior Calcaneal Osteotomy (Medial Slide)

The flatfoot deformity includes hindfoot valgus, a condition in which the heel tuber is lateral to the midline. The medial calcaneal slide (Figure 54.3) repositions the heel to be centered under the midline axis. This allows the Achilles vector to pull the hindfoot in varus in the toe-off phase of gait and thereby assists in locking the transverse tarsal joints.

The procedure is performed via a lateral approach. An oblique incision is made from the superior to the inferior calcaneal recess. Once the skin is incised, blunt dissection is used to reach the periosteum. An osteotomy in line with the skin incision is made anterior to the Achilles tendon and exiting in the inferior recess of the calcaneus. The plantar calcaneal tuberosity is then translated medially up to 1 cm. It is secured by large screws placed percutaneously from the point of the heel. Bone healing occurs rapidly in this osteotomy, but occasionally pain may be experienced from the screw heads during the initial transition to full weight bearing (FWB).

Figure 54.3 A tangential radiograph of the calcaneus demonstrating a medial slide osteotomy.

Anterior Calcaneal Osteotomy (Lateral Column Lengthening)

A “lateral column lengthening” (Figure 54.4) is performed to bring the forefoot back medially around the talus, correcting forefoot abduction, hindfoot valgus, and medial arch sag. By extending the length of the calcaneus at the location of the talonavicular joint, the talonavicular joint can be rotated from an abducted to neutral alignment. There are minor variations to this procedure.

The Evans osteotomy (common variety of lateral column lengthening) is a transverse osteotomy made in line with the calcaneocuboid joint. A longitudinal skin incision is made along the anterior aspect of the calcaneus from the sinus tarsi to the calcaneocuboid joint. The periosteum and tendon is then elevated off the calcaneocuboid joint and the calcaneus. The osteotomy is made parallel to the calcaneocuboid joint and approximately 1 cm proximal to the joint surface. An opening wedge is made ranging from 4 to 12 mm and filled with structural graft secured with either a plate or screws. Care must be taken to prevent superior migration of the distal portion of the osteotomy as well as to avoid overlengthening the lateral column, as this will lead to stiffness with eversion and pain. Closure is performed in layers of the fascia, subcutaneous tissue, and the skin.

Figure 54.4 Anteroposterior and lateral radiographs demonstrating a lateral column lengthening, first tarsometatarsal fusion, and medial slide osteotomy and flexor digitorum longus transfer preoperatively and postoperatively. A, C, Preoperative planovalgus foot; note in C the plantar gapping demonstrating medial arch instability. B, D, Correction with medial and lateral bone and soft-tissue work.

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