Treating Posterior Tibial Tendon Dysfunction With An Absorbable Implant

Subtalar arthroereisis can limit excessive pronatory motion of the subtalar joint. Functionally, a subtalar joint arthroereisis prevents excessive pronation by stabilizing the calcaneus under the talus. The subtalar joint arthroereisis has been utilized for a posterior tibial tendon dysfunction (PTTD) as well as juvenile flexible flatfoot.

The implant is thought to act as an “internal orthotic,” placing the hindfoot in proper alignment. Over time, the implant may allow for adaptation of the soft tissue structures, thus diminishing the deforming forces that create the deformity. Our institution has been utilizing an isolated subtalar arthroeresis procedure for treatment of stage I PTTD.

A Look At Seven Patients Who Received Implants
Between August 2003 and June 2004, seven patients underwent an isolated subtalar arthroereisis in an outpatient setting. Surgeons corrected six left feet and one right foot. The patients’ age range was 21 to 80 years with a mean age of 54. All seven patients were female.
Four patients underwent treatment with the use of a metallic implant and three patients had an absorbable implant. The diagnosis was based on clinical and radiographic evaluation. Prior to any surgical management, all patients had MRIs that revealed significant fluid surrounding the posterior tibial tendon. All patients had clinically reducible deformities and were not responsive to conservative treatment.

Surgeons performed the procedures under intravenous anesthesia and an infiltrate of local anesthetic. Surgeons made a 1 cm incision over the lateral aspect of the sinus tarsi along relaxed skin tension lines. They then incised the deep fascia and penetrated the fascia with the use of a Kelly hemostat. They advanced the hemostat through the sinus tarsi from lateral to medial as far as possible. After removing the hemostat, surgeons placed arthroereisis sizers in the sinus tarsi.
We advanced the sizers lateral to medial until achieving adequate correction. One would determine this by everting the foot until accomplishing restricted excessive pronation. The sizer measurement at this point determines the implant size to be used. We then placed the appropriately sized implant on the insertion device and used it to insert the screw and sinus tarsi. One would perform the surgery under mini C-arm fluoroscopy control.
We inserted the implant firmly to the point where the tip of the insertion device meets the lateral margin of the talar neck on an AP view. We then removed the insertion device. One would then proceed to repair the deep fascia and close the wound in the usual fashion. One may place patients in CAM Walkers and allow partial weightbearing.

How Patients Fared Postoperatively
All patient complaints of considerable pre-op pain resolved after the procedure. The MRI obtained 16 weeks postoperatively revealed decreased fluid surrounding the posterior tibial tendon. No signs of cyst formation due to the implant were present on any radiographic views or post-op MRIs. There were no local or systemic reactions to the implant. Two implants required removal due to pain at the level of the sinus tarsi postoperatively. One Kalix implant was removed at three months postoperatively and one absorbable implant was removed at four months.

On radiographs, all patients had increased talar coverage percentage, decreased talar declination, an increased calcaneal inclination angle and a decreased cuboid abduction angle postoperatively compared to preoperative radiographic evaluation.

In Conclusion
Subtalar arthroereisis is a viable option for treatment for early stage PTTD. It has been documented over time to be a useful and simple procedure for correction of flexible flatfoot and acquired flatfoot in adults. The procedure facilitates decreased inflammation, support of the posterior tibial tendon and corrected position during the repair, which allows for adaptation of the foot.
The advantages of technique include ease of technique, minimal morbidity and progressive correction of deformity. Since this study was performed in 2004, an additional 13 patients in our practice have received absorbable implants via arthroereisis.

For related articles, see “A Closer Look At Subtalar Implants,” a supplement to the June 2005 issue of Podiatry Today.

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