ACQUIRED ADULT FLATFOOT DEFORMITY
[a.k.a. posterior tibial tendon dysfunction]
Summary
Acquired adult flatfoot deformity is a chronic foot condition where the structures on the inside aspect of the ankle are subject to repetitive load and eventually become symptomatic. This condition is typically associated with longstanding flatfoot deformity. This type of deformity leads to increased loading through the inside aspect of the ankle with pain in this area and a resulting limp. This condition can often be treated without surgery by strengthening the involved muscles and tendons and by bracing the ankle. When non-operative treatment fails surgery to repair or replace the injured tendons and reposition the foot can be beneficial although the recovery time is prolonged.
Clinical Presentation
Patients with acquired adult flatfoot deformity typically give a history of longstanding flatfeet (Figure 1). Symptoms of pain may have developed gradually or they may be traced to one minor injury. Symptoms typically include pain on the inside (medial) aspect of the ankle. However, some patients will also experience pain over the outside (lateral) aspect of the hindfoot. Patients may walk with a limp and often will not able to take a completely normal stride. They may also have noticed worsening of their flatfoot deformity.
Figure 1: Flatfoot deformity
Physical Examination
Looking at the patient when they stand will usually demonstrate marked flattening of the medial longitudinal arch. The front part of the foot (forefoot) is often splayed out to the side. This leads to the presence of a “too many toes” sign (Figure 2).
Figure 2: "Too many toes” Sign
This sign is present when the toes can be seen from directly behind the patient. The gait is often somewhat flatfooted as the patient has the inability to reconstitute the rigid lever of the foot immediately prior to the heel rise base of gait. Palpation will often demonstrate tenderness and sometimes swelling over the inside of the ankle just below the bony prominence (the posteromedial hindfoot just distal to the medial malleolus). There may also be pain in the outside aspect of the ankle. This pain originates from impingement in the weightbearing position.
A single-leg heel rise test is used to determine whether the posterior tibial tendon is intact or whether it has become dysfunctional. If the patient can stand on one foot and raise the heel off of the ground 3-5 times, this suggests that the posterior tibial tendon is intact (Figure 3 [left]). If they are unable to do this, the posterior tibial tendon is dysfunctional (Figure 3 [right]).
Figure 3: Ability to do a single leg heel rise (left picture)
Inability to do a single leg heel rise (right picture)
Imaging Studies
Weightbearing, x-rays of the foot allow the physician to assess the extent of the flatfoot deformity (Figure 4).
Figure 4:
Normal Foot X-Ray
X-Ray of Flatfoot Deformity
MRI is usually not indicated for patients with acquired adult flatfoot deformity. The diagnosis and the classification can be established on physical examination. However, if there are other clinical signs that suggest either a problem within the ankle or subtalar joint (intraarticular pathology) or another source of pain, then an MRI may be indicated.
Classification
Acquired adult flatfoot deformity has been classified into four categories.
First Stage
The first stage represents inflammation and symptoms originating from an irritated posterior tibial tendon, which is still functional.
Second Stage
The second stage represents incompetence and dysfunction of the posterior tibial tendon as illustrated by the inability to perform a single-leg heel rise.
Third Stage
The third stage is dysfunction of the posterior tibial tendon combined with arthritis or stiffness of the hindfoot joints.
Fourth Stage
The fourth phase is a stage 3 with associated ankle arthritis.
The vast majority of patients with acquired adult flatfoot deformity are stage 2 by the time they seek treatment from a physician.
Treatment
Non-Operative Treatment
Nonoperative treatment of stage 1 and 2 acquired adult flatfoot deformity can be successful.
General components of the treatment include:
- The use of comfort shoes.
- Activity modification to avoid exacerbating activities.
- Weight loss if indicated.
Specific components of treatment that over time can lead to marked improvement in symptoms include:
- A high repetition, low resistance strengthening program
- Appropriate bracing or a medial longitudinal arch support.
Providing the posterior tibial tendon is intact, a series of exercises aimed at strengthening the elongated and dysfunctional tendon complex can be successful. In stage 2 deformities, this is combined with and ankle brace (such as anArizona ankle lacer) for a period of 2-3 months until the symptoms resolve. At this point, the patient is transitioned to an orthotic with a medial longitudinal arch support. In patients with stage 1 deformity, immediate progression to the arch support can be made.
Operative Treatment
Until recently, operative intervention was indicated for most patients with stage 2 deformities. However, with the establishment of a potenitally effective nonoperative management protocol, operative treatment is indicated for those patients that have failed nonoperative management.
The principles of operative treatment of stage 2 deformities include:
- Augmenting the dysfunctional posterior tibial tendon, usually with flexor hallucis longus,
- Reconstructing the shape of the foot so that less force is being channeled through the inside aspect of the foot, and preserve the important hindfoot joints. Changing the shape of the foot can be achieved by one or more of the following procedures:
- Medializing calcaneal osteotomy
- Lateral column lengthening
- Medial column stabilization
- Equinus contracture correction with either a gastrocnemius resection, or a percutaneous tendon of Achilles lengthening.
Stage 3 acquired adult flatfoot deformity is treated operatively with a triple arthrodesis. It is important when a triple arthrodesis is performed that it be done in such a way that the underlying foot deformity is corrected first. Simply fusing the hindfoot joints in place is no longer acceptable.
Potential Surgical Complications:
Wound-healing problems
Infection
Failure to heal bone (non-union)that has been cut or joints that have be fused
Deep Vein Thrombosis (DVT)
Pulmonary embolism
Neurological injury
Vascular Injury
Continued pain and deformity
Recovery from Surgery
The recovery from surgery is dependent upon the particular combination of procedures that are performed. However, if significant bony procedures are performed (cutting and repositioning bones, or fusing joints) a typical recovery would be:
- Healing Phase: 6 weeks of non-weightbearing is usually required
- Rehabilitation Phase: a period of gradual rehabilitation following Healing Phase
It is common for a patient to take 4-6 months to achieve much of their recovery and 12-18 months before they reach their point of maximal improvement.