Managing Equinus In Patients With Diabetes
The results showed plantarflexion of the talus and navicular, and dorsiflexion of the medial cuneiform and first metatarsal occurring through the naviculocuneiform joint. This occurs due to the dampening of the effect of the peroneal longus tendon eversion of the medial cuneiform that leads to locking of the midtarsal joint. This lack of midtarsal joint locking leads to the aforementioned medial column instability. This study showed the effect of equinus is not a stretching of the plantar ligaments over a period of time that leads to first ray instability but is in fact a dampening of the peroneus longus function that leads to first ray hypermobility.
The tragedy that is the diabetic Charcot deformity crystalizes with this understanding of medial column pathomechanics. This is why early equinus intervention is recommended in the acute Charcot deformity as patients can avoid much of the resultant deformity with release of the contracted gastroc-soleus complex. However, the biomechanical considerations of equinus are only one part of the understanding of this deformity.
Arriving At A Precise Definition Of Equinus
It is important to arrive at a standard definition of equinus before undertaking an evaluation of the deformity. The definition of equinus ranges from -10 degrees to + 22 degrees in the literature with +10 degrees as a consensus of 13 different studies. In 1975, Sgarlato first described the definition as +10 degrees with the subtalar joint in neutral position and the midtarsal joint locked.3
In 2002, DiGiovanni and co-workers examined ankle joint dorsiflexion in symptomatic patients and a control group, and the reliability of testing.4 The ankle joint dorsiflexion with the knee extended averaged 4.5 degrees in the symptomatic group and 13.1 degrees in the control group. The percentage of symptomatic patients with less than 5 degrees dorsiflexion was 65 percent and was 24 percent in the control group. The percentage of symptomatic patients with less than 10 degrees dorsiflexion was 88 percent and 44 percent in the control group respectively.
In regard to patients with less than 5 degrees of dorsiflexion, the study authors confirmed the correct diagnosis with an equinometer in 76 percent of the symptomatic group and 94 percent of the control group. For those with less than 10 degrees of dorsiflexion, researchers confirmed the correct diagnosis with the equinometer in 88 percent of the symptomatic group and 79 percent of the control group respectively.
Therefore, it becomes clear with the results of this study that equinus should be universally defined as less than 5 degrees of ankle joint dorsiflexion with the subtalar joint in neutral position and the midtarsal joint locked with the knee extended.4
Evaluating Equinus And Its Associated Pathologies
The clinical evaluation of equinus is one of the primary stumbling blocks between professions that inhibits effective communication. Clinicians can use the Silfverskiold test to determine the type of equinus. With this examination, one first places the subtalar joint in neutral position and locks the midtarsal joint by supinating the forefoot. Proceed to perform maximum dorsiflexion of the ankle with the knee in full extension. Then check this with the knee in flexion.