Posterior Tibial Tendon Dysfunction: An Overview
Posterior Tibial Tendon Dysfunction (PTTD) is the most common cause of adult-acquired flatfoot. This condition occurs when the posterior tibial tendon becomes damaged or weakened, which plays a crucial role in stabilizing the foot’s arch and maintaining foot alignment. If untreated, PTTD can progress to deformity, causing significant functional impairment. As a medical professional, recognizing the early signs and staging of this condition is essential in preventing further complications and managing the disease effectively.
Anatomy of the Posterior Tibial Tendon
The posterior tibial tendon originates from the posterior aspect of the tibia, fibula, and the interosseous membrane. It travels along the deep posterior compartment of the leg and passes behind the medial malleolus, where its blood supply is the most limited. This area is particularly prone to tendon rupture due to its poor vascularization. As the tendon nears its insertion on the foot, it splits into several components: the main part inserts on the navicular tuberosity, the plantar portion attaches to the metatarsals and cuneiforms, and the recurrent component connects to the calcaneus. This complex structure is responsible for supporting the medial longitudinal arch and plays a critical role in foot inversion and overall stability during movement.
Pathophysiology of Posterior Tibial Tendon Dysfunction
PTTD primarily develops through tendinosis, a degenerative process caused by repeated microtrauma over time. The posterior tibial tendon, subjected to constant strain, begins to lose its elasticity and strength, eventually being replaced by ineffective fibrotic tissue. In its early stages, patients may not exhibit overt deformity; however, as the condition progresses, the medial longitudinal arch collapses, leading to the characteristic flatfoot appearance. Other deformities such as heel valgus, internal rotation of the tibia, and subtalar joint eversion are common as the tendon continues to weaken.
This condition can be aggravated by risk factors such as obesity, diabetes, hypertension, and prior trauma to the foot or ankle. The aging process also plays a role, with middle-aged women, particularly those over 40 years old, being most susceptible. Certain medications, such as steroids, and underlying conditions like seronegative spondylarthropathies, also contribute to the development of PTTD.
Clinical Presentation and Diagnosis
The progression of PTTD is often slow and insidious, with patients initially reporting medial foot pain, swelling, and weakness. They may describe difficulty standing on their toes or walking on uneven surfaces. As the disease progresses, the foot deformity becomes more apparent, with patients displaying the “too many toes” sign, a hallmark of PTTD where more than two toes are visible when viewed from behind. This sign is indicative of the foot’s inability to return to its normal position due to tendon dysfunction.
Examination typically reveals swelling and tenderness along the posterior tibial tendon, particularly around the medial malleolus. As the disease advances, patients may struggle with a single-leg heel raise, an essential test for diagnosing PTTD. Early stages may allow patients to complete this test, but as the disease progresses, they may be unable to perform the heel raise at all.
X-rays, ultrasound, and MRI are vital tools in diagnosing and staging PTTD. While X-rays may not show early changes, they become useful in advanced stages when deformity and joint degeneration are evident. MRI is particularly beneficial in detecting tendon degeneration and joint involvement, allowing for accurate staging and treatment planning.
Staging and Management of Posterior Tibial Tendon Dysfunction
The treatment of PTTD is highly dependent on the stage of the disease. Johnson and Strom’s classification system provides a framework for understanding the disease’s progression, from Stage I (tendinopathy without deformity) to Stage IV (advanced arthritis involving the ankle joint).
Stage I: Tendinopathy
At this early stage, the tendon remains intact but is inflamed. Conservative treatment is the mainstay of management, involving rest, anti-inflammatory medications, and the use of orthotics or ankle-foot orthoses (AFOs) to support the arch. Physiotherapy aimed at strengthening the posterior tibial tendon and stretching the Achilles tendon is also beneficial. If symptoms persist, a tendon synovectomy may be performed to remove damaged tissue.
Stage II: Ruptured Tendon
At this stage, the tendon has either ruptured or becomes nonfunctional, leading to a fixed flatfoot deformity. Nonoperative treatments may still be tried, but surgical intervention is often required. Surgical procedures typically involve tendon transfers and osteotomies to correct the deformity and restore function. Common procedures include flexor digitorum longus transfer and calcaneal osteotomy.
Stage III: Joint Degeneration
In Stage III, joint degeneration, particularly in the subtalar joint, is present, and the deformity becomes rigid. Surgical options at this stage usually involve arthrodesis (joint fusion) of the subtalar, calcaneocuboid, and talonavicular joints to correct the deformity and alleviate pain.
Stage IV: Advanced Degeneration
Stage IV represents the most advanced stage of PTTD, with involvement of the ankle joint. Surgical intervention is typically extensive, requiring joint fusion and possibly deltoid ligament reconstruction to restore stability and function. In severe cases, pan-talar fusion may be necessary, although outcomes in this stage are often less favorable.
Conclusion
Posterior Tibial Tendon Dysfunction is a progressive condition that can severely affect foot function and quality of life if not diagnosed and treated early. Recognizing the signs and symptoms in the initial stages and initiating appropriate treatment can prevent the need for more invasive surgeries later on. Early referral to an orthopedic surgeon is crucial for optimal management. With advancements in imaging techniques and surgical options, outcomes for patients with PTTD have greatly improved, and early intervention remains key to preserving foot function.
