Our patient for this case study is a teenage female soccer player complaining of pain in her left arch with an associated bony enlargement present. A similar non-painful bump is also present on the other foot. No specific causation has been determined for the onset of the swelling and pain in the area, but due to the patient’s pursuit of a college scholarship in soccer, she plays or practices on a daily basis. Physical examination and x-rays confirmed the diagnosis of Accessory Navicular Syndrome, Type II. Goals of treatment include pain relief, improved functionality, biomechanical control of underlying deformity.
Support of a weakened medial arch is the hallmark of custom foot orthotic therapy. Overpronation of the foot, leading to overuse syndromes of many types, shows up in our offices everyday. In this case, the overpronation syndrome is coupled with a congenital deformity involving a secondary growth center of the Navicular bone. The Posterior Tibial Tendon is intimately related to the deformity, with the aponeurosis lying directly inferior to the accessory bone, and the all important Plantar Calcaneonavicular (spring) ligament lying deeper beneath the TaloNavicular joint. These structures serve as somewhat of a shock absorber for the foot, as the foot naturally pronates at contact with the ground, the motion is slowed, then stopped, then reversed by the medial arch structures to prepare for the conversion of the foot into a more supinated and stable configuration in which to propulse forward into the next step.
An orthotic device needs to limit the range and velocity of eversion of the heel during contact phase. During midstance, the frame of the orthotic device needs to conform adequately to the medial arch of the foot and control how much the arch “drops”. As the weight bearing force moves anteriorly from the midfoot to the forefoot, the orthotic device should promote adequate plantarflexion of the first ray against the ground and promote strong propulsion through the 1st MTPJ and distally to the great toe. This is the basic, bottom line biomechanics of medial arch weakness. Many other factors exist, too numerous to mention here, either to exacerbate or mitigate these basic treatment goals. Three orthotic models were referenced in this article, the P12, Pes Planus model, the P10, Pediatric Flatfoot model, along with S7,soccer specific model. The first two along with the P2 model for Adult Acquired Flatfoot are designed specifically to limit strain on the medial arch. Their designs are generic in nature and a good starting point for the novice practitioner, in designing an orthotic build for a specific patient.
The science of biomechanics, and its practical application, can lead to consistent success in the successful treatment of a wide range of lower extremity conditions. It is also necessary to have a grasp of the requirements of treating the person attached to that foot. In our case, a successful soccer career is the prime objective, so now we have to balance the biomechanical needs of a structurally and functionally weakened foot, and optimize the ability of this young lady to reach her potential in her sport. A low volume, flexible shoe, running in multiple directions on a grass field, maintaining a flexible lightweight platform and promoting the ability to kick a ball using the inside edge of the forefoot are all factors to be considered when designing an orthotic for an elite soccer player.
