What are the pros and cons of subtalar arthroereisis implants as a treatment for flexible flatfoot?
There is no universally accepted definition for flatfoot. Clinically, a flatfoot is one that has a low or absent longitudinal arch. Determining flexibility (physiologic) or rigidity (pathologic) is the first step in management: a flexible flatfoot will have an arch that is present when the child is not bearing weight on the foot but this is lost when the child is bearing weight; a rigid flatfoot has loss of the longitudinal arch height even when the child is not bearing weight.
The majority of children with flexible flatfoot do not have clear symptoms and the long-term consequences are uncertain. Podiatric literature has found associations with various foot pathologies: hallux valgus, plantar keratosis, metatarsalgia, hammer toe syndrome, plantar neuroma, plantar heel pain but these have never been formally proven. Flexible flat feet may also be linked to a spectrum of foot pathologies found in people with flexibility of joints and hyperlaxity of the ligaments and could also be the cause of early arthrosis of the midtarsal and subtalar joints in children without neurological dysfunctions. None of this is yet proven.
Subtalar Arthroreisis:
Although orthopedic literature has emphasized non-surgical management of flexible flatfoot, procedure aim at the insertion of a medial longitudinal arch implant, such as the Subtalar Arthroreisis, has been appealing.
“Arthroereisis” is defined as limiting motion of an abnormally mobile joint. The insertion of implant into the sinus tarsi, the dorsal space between talus and the calcaneum, is one of the methods for subtalar arthroereisis.
Cases suitable for subtalar arthroereisis may be those with a painful flatfoot deformity unresponsive to prolonged nonsurgical management – such as heel-cup bracing or other foot orthosis – and possibly a severe deformity associated with excessive shoe-wear.
It is done at the age of 8 to 12 years, before closure of growth physes, it allows for remodeling of the tarsal bones. Only on rare occasions is operative intervention necessary to treat juvenile flexible flatfoot.
Often it is done in combination with various soft tissue and bone procedures, such as recession of the tight gastrocnemius muscles, flexor tendon transfer or calcaneal osteotomy. The goal of surgery is to realign the foot and to redistribute weight-bearing forces thereby improving foot endurance and reducing fatigue.
Possible Complications:
Like any operation, subtalar arthroereisis is not without risk. Potential complications include detritic synovitis, dislocation of the implant, failure to correct, subtalar joint arthritis, sinus tarsi syndrome, peroneal spastic flatfoot and intra-osseous cyst formation, avascular necrosis of the talus.
Dr. LUI, Tun-hing