Equinus Deformity

Original Editor - Aya Alhindi Top Contributors - Aya Alhindi, Aminat Abolade, Rucha Gadgil and Kirenga Bamurange Liliane

Introduction

equinus foot X-ray

Pes Equinus is a condition in which the upward bending motion of the ankle joint (dorsiflexion) is limited. It has been known to start due to osseous limitations, neuromuscular disorders, or contractures of the gastrocnemius complex or surrounding soft tissues including Hallux valgus and most commonly seen in flat foot or pes cavus.

In this deformity, an alteration in gait may occur; a patient may also have difficulty climbing stairs, dressing and in lifting the foot up so a patient may need to lift the leg on the affected side up higher, to “step over” the foot.

Classification

Equinus can be classified in multiple ways. According to aetiology, apex of equinus, spastic and non-spastic forms in addition to soft tissue causes of joint restriction.

Etiology/Causes

Equinus is frequently caused by tightness in the calf muscles (the soleus and/or gastrocnemius muscles) or the Achilles tendon. Some people may have this feature congenitally (existing at birth) or inherited it. Others develop this tightness as a result of wearing high-heeled shoes frequently, being in a cast or using crutches. Other contributing factors include diabetes or having a shorter leg than other. The patient may develop equinus if a bone or bone fragment restricts movement of the ankle (for instance, after an ankle injury). Rarely, calf muscular spasms can induce equinus and may be a symptom of an underlying neurologic condition.

Foot Problems Related to Equinus

A number of foot problems can arise depending on how a patient compensates for their inability to bend appropriately at the ankle, including:

• Plantar fasciitis (arch/heel pain)
• Calf cramping
• Tendonitis (inflammation in the Achilles tendon)
• Metatarsalgia (pain and/or callusing on the ball of the foot)
• Flat foot
• Arthritis of the midfoot (middle area of the foot)
• Pressure sores on the ball of the foot or the arch
• Bunions and hammer toes
• Ankle pain
• Shin splints or Medial tibial stress syndrome.

Diagnosis

When people initially contact the doctor, the majority of those with equinus are not aware they have this condition. Instead, they come seeking relief for equinus-related foot issues.

Key diagnostic factors

• positive family history.
• equinus deformity.
• hind foot in varus and adduction.
• adduction of forefoot.

Other diagnostic factors

• Male sex.
• hip dysplasia.
• neurologic or chromosomal abnormalities.
• smaller lower extremity.

Investigations

• anteroposterior and lateral radiographs of the foot.
• dynamic hip ultrasound.
• pelvic radiographs.
• CT foot.

Special test

The Silfverskiöld test can be used to differentiate gastrocnemius tightness from an achilles tendon contracture by evaluating ankle dorsiflexion with the knee extended and then flexed.

Technique

The test is performed with the patient seated or in supine. Two hands are utilized to perform the technique, with one hand neutralizing and locking the subtalar (ST) joint and the other stabilizing the talonavicular (TN) joint and forefoot in order to isolate the ankle joint motion. Then the forefoot is supinated and foot is dorsiflexed with knee in full extension. Measurement is taken of the DF range. Then the test is repeated with the knee flexed at 90 degrees.

• Less dorsiflexion with a soft and spongy feel when the knee is extended is considered as an indication for gastrocnemius contracture.
• Equally limited dorsiflexion with the knee flexed and extended is considered as an indication for soleal equinus or an osseous block.

Non-surgical Treatment

Non surgical treatment strategies are aimed at relieving the symptoms and conditions associated with equinus rather than correcting the deformity itself. Some examples include:

• Night splint
• Heel lifts
• Arch supports or orthotic devices:

Ankle-foot orthoses (AFO) are regarded as an efficient conservative treatment for slowing the progression of equinus deformities because they serve to restrict ankle plantar flexion and offer passive stretching for the tight soft tissues.

AFO

Physical Therapy

Therapeutic interventions such as stretching and active movement of calf muscles are recommended to help remedy muscle tightness.

Gastro-soleal complex stretch

Stretching techniques for gastro-soleal muscle group can vary from weight-bearing to non-weight bearing with the knee flexed or extended. Also assistive devices can be included to facilitate stretching.Most common technique for equinus is called Runner’s stretch or wall push stretch.

• To avoid Runner’s stretch potential errors:

1. Back heel must stay down on the ground.
2. Back knee must stay fully extended.
3. Front knee is bent.
4. Back should remain straight.
5. Body weight should be forward.
6. Foot must be supinated; this is considered critical and the most difficult factor to perform the stretch correctly.

• The correct position of the subtalar joint should be in supination so that allows external rotation of the tibia and therefore full knee extension, locking of the midtarsal joint to prevent dorsiflexion occurring through the midfoot.

Surgery

If a bone or tight tendon is restricting the motion of the ankle, surgery may occasionally be required to treat the underlying condition that is causing equinus. There are some risks that are associated with all surgeries, and they differ from patient to patient. Most complications are small, manageable, and unlikely to have an impact on patients.