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Ankle Equinus

In a rebiomechanical  ankle equinus_clip_image002cent study Frykberg et al. discovered increased prevalence of equinus in diabetic versus non-diabetic patients, “Although we cannot prove causality, we found a significant association between equinus and ulceration”.  Read on further for the results of the study. Valmassy describes 4 types of Equinus as follows;

Congenital Gastrocnemius equines, generally the most common type of congenital equinus, primarily involves the Gastrocnemius muscle and tendon, Characterized by limited dorsiflexion with STJ in the neutral position with the knee full extended.  Flexion of the knee demonstrates normal range of motion.

Congenital Soleus equinus, the more rare type of equinus presents with dorsiflexion limited with knee in both flexed and extended positions,

Congenital Gastrocnemius-Soleus equinus, both muscle groups remain tight, exhibiting a limitation of ankle joint dorsiflexion with knee in both extended and flexed positions, in some cases with children or adolescents there may be osseous or a bony block of the talotibial articulation.   A soft tissue equinus will feel spongy at the maximum range of motion conversely the bony equinus is more abrupt.

Spastic equinus, typically associated with spastic diplegia (cerebral palsy), diastematomyelia, or hyperkinesias.  A limitation of the ankle joint with knee both flexed and extended, as well as posterior muscle group contraction.

Additionally Scarlato classified equinus deformity as being either uncompensated, partially compensated or fully compensated. Uncompensated equinus exhibits limited dorsiflexion or insufficient range of STJ or MTJ pronation.  Partially compensated is characterized by sufficient range of motion in regard to dorsiflexion, STJ and MTJ pronation but insufficient dorsiflex to enable the tibia to angulate 10* during gait resulting in early heel lift. Fully compensated equinus is similar to partially compensated only that the tibia can angluate 10* often resulting in a severely hypermobile flatfoot with the rearfoot maximally everted and the forefoot inverted to the rearfoot due to the excessive pronation of the subtalar joint resulting in unlocking and instability of the midtarsal joint.

Patient may exhibit one or more of the following:

  1. Premature heel lift
  2. Genu recurvatum
  3. Excessive knee flexion
  4. An abductory twist
  5. Lumbar lordosis
  6. Hip flexion
  7. Hamstring tightness
  8. STJ/MTJ pronation
  9. Achilles Tendinopathy
  10. plantar fasciitis

What does the evidence say? Study: Prevalence of equinus in diabetic versus nondiabetic patients. Frykberg RG, Bowen J, Hall J, Tallis A, Tierney E, Freeman D.
A prospective pilot survey of 102 outpatients (43 diabetic and 59 nondiabetic) was conducted. Demographic and historical data were obtained. Each patient underwent a standard lower-extremity examination, including the use of a biplane goniometer to measure ankle joint range of motion.

RESULTS:

Equinus, defined as ankle dorsiflexion measured at 0° or less, was found in 24.5% of the overall population. In the diabetes cohort, 16 of 43 patients (37.2%) were affected compared with 9 of 59 nondiabetic participants (15.3%) (P = .011). There was a threefold risk of equinus in the diabetic population (odds ratio [OR], 3.3; 95% confidence interval [CI], 1.28-8.44; P < .013). The equinus group had a history of ulceration in 52.0% compared with 20.8% of the nonequinus group (P = .003). Equinus, therefore, imparted a fourfold risk of ulceration (OR, 4.13; 95% CI, 1.58-10.77; P < .004). We also found a 2.8 times risk of equinus in patients with peripheral neuropathy (OR, 2.8; 95% CI, 1.11-7.09; P < .029)

CONCLUSIONS:

“Equinus may be more prevalent in diabetic patients than previously reported. Although we cannot prove causality, we found a significant association between equinus and ulceration.”

Treatment:
The aim is to regain adequate flexibility.  The first step should be to set the patient on a course of flexibility exercises. These can be performed by leaning against a wall or solid object,

but the foot should be held around the neutral position (usually by inverting the feet) to reduce pronation. Repeating the exercise with the knee flexed will stretch the soleus. Additionally the use of a stretching board can be the most effective method of increasing flexibility. The patient stands on the highest angle at which they can stand
upright until it becomes slightly uncomfortable, however short the period. This is repeated twice a day until they can stand on the slope for 4 minutes comfortably. The slope is then raised to the next level and the process begins again.

When decided on orthotic therapy in most cases the control of the device will need to be mitigated.  The degree of available subtalar joint compensation is important, in cases where the foot has attained a compensated position, attempting to control the foot position is often not appropriate. In these cases, a pronated orthotic to support the current position, in attempt to prevent further collapse of the foot, may be best option, the addition of a heel raise may also be used but with caution as further shortening of the soleus may occur.

After dispensing of the orthotic device the function should be reassessed. The aim is to facilitate the ankle and metatarsal rockers. This will allow knee and hip extension during the
former, followed by hip and knee flexion and ankle joint plantarflexion during the latter.

References

-Scarlato, T.E: A compendium of podiatric biomechanics.
-Prior, Vasylimedical Root M L, Orien W P, Weed J H, Clinical biomechanics
-Perry J, Basic Functions, In: Gait analysis; Normal andpathological function (Ed Perry), Slack Inc
-McPoil T,Cornwall M W, Relationship between subtalar joint neutral position and
pattern of rearfoot motion during walking, Foot & Ankle,
-Pierrynowski M R, Smith S B, Rearfoot inversion/eversion during
gait relative to the subtalar joint neutral position,Foot & Ankle
-Prevalence of equinus in diabetic versus nondiabetic patients. Frykberg RG
Bowen J, Hall J, Tallis A, Tierney E, Freeman D.
-Valmassy Clinical biomechanics of the lower extremities


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