Where Are We Now?
It is well known that in clinical practice, stiffness of the ankle joint leads to hypermobility of an intact subtalar and chopart joints. The degree of deformity and stiffness compensation of the ankle joint depends on the constitutional laxity of the ligaments, asymmetric muscular activity (eg, spastic or paralytic paresis), the active correction of the hindfoot position to avoid pain through weight bearing, and the degree of the arthritis of the subtalar and chopart joints. Therefore, the degree of compensation of ankle joint malalignment is multifactorial. The question is whether a compensatory subtalar and chopart hypermobility leads to a decrease of pain and a better hindfoot function or causes pain and increases subtalar and chopart osteoarthritis?
Where Do We Need To Go?
Radiological studies can only measure the degree of compensation in weight bearing radiographs. The current study by Saltzman and colleagues shows a negative correlation between compensation of hindfoot deformity and osteoarthritis in the subtalar joint. A subtalar compensation of a varus deformity in the ankle joint appears more often and is more excessive, which can easily be explained by the plane of the dorsal facet of the subtalar joint, which predisposes for valgus deformity. A subtalar varus compensation of a valgus deformity of the ankle joint may be explained by an active contraction of the tibialis anterior and posterior muscles to reduce pain in the lateral tibiotalar joint. The subtalar valgus compensation is a passive process that may become irreversible in time because of a lack of spontaneous correction in the unbeared position. The varus compensation on the other hand, which is an active process and exhausting for the patient, is mostly reversible. Therefore, it is essential to correlate the radiological findings of the current study with the clinical appearance of hindfoot deformities.
How Do We Get There?
To get a better understanding on the compensation of ankle deformities and stiffness, prospective clinical radiological long-term followup studies are needed. These studies should address the clinical symptom at the time of the radiological examination, including localization of pain to pressure and translation, under weight bearing, passive and active ROM of the ankle, subtalar and chopart joints, areas of weight bearing at the sole, and optional pedobarography. Patients treated conservatively and operatively should be reinvestigated periodically to get prognostic data on different hindfoot deformities. These data would help determine the efficacy of operative and conservative treatment and the right time to change between both.
Footnotes
This CORR Insights® is a commentary on the article “Does the Subtalar Joint Compensate for Ankle Malalignment in End-stage Ankle Arthritis?” by Wang and colleagues available at: DOI: 10.1007/s11999-014-3960-8.
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The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR ® or the Association of Bone and Joint Surgeons®.
This CORR Insights® comment refers to the article available at DOI: 10.1007/s11999-014-3960-8.