Therapeutic Outcomes of Kalix II in Treating Juvenile Flexible Flatfoot

Objectives: To evaluate the therapeutic outcomes with Kalix II subtalar arthroereisis in sinus tarsi for juvenile flexible flatfoot.

Methods: A retrospective analysis of the data of 20 juveniles with symptomatic flexible flatfoot (27 feet) who underwent the Kalix II implant procedure from January 2008 to September 2012 was performed. The pain during daily activities was assessed and followed up by use of a standard 10-point visual analog scale (VAS), and function was evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle and hindfoot scoring system, and anteroposterior talar-first metatarsal angle, lateral talar-first metatarsal angle, calcaneal pitch angle, and talar declination angle at X-ray film were measured to assess the therapeutic outcomes. Patients were asked to grade the result of the procedure as excellent, good, fair, or poor at latest follow-up. The data was expressed as mean ± standard deviation (SD). A paired Student's t -test was used for comparisons of the preoperative and postoperative angular measurements for each foot, VAS scores, and AOFAS scores. In all tests, P < 0.05 was considered statistically significant.

Results: The mean age of the patients was 12.1 years (range, 7-16 years), and 16 left feet and 11 right feet were involved. All patients finished the follow-up with a mean period of 28.1 months (range, 23-60 months). Eleven feet were treated with subtalar arthroereisis combined with reconstruction of the end point of the posterior tibialis tendon after dissection of the accessory scaphoid. The subtalar arthroereisis device displaced in 1 foot due to a fall from the inversion position 3 months after surgery, and was replaced by a new device after the failure of conservative treatment. The mean VAS score decreased from 5.6 ± 0.5 preoperatively to 1.2 ± 0.2 (P < 0.001), and the mean AOFAS hindfoot and ankle score improved from 71.1 ± 6.1 preoperatively to 88.1 ± 6.3 (P < 0.001). Differences between preoperative and postoperative measurements for each radiographic variable were statistically significant (P < 0.001). Comparison of radiographic measurements showed that the anteroposterior talar-first metatarsal (Meary) angle decreased by a mean of 12.8° ± 1.5°, the lateral talar-first metatarsal (Meary) angle decreased by a mean of 15.4° ± 1.3°, the calcaneal pitch angle increased by a mean of -2.1° ± 0.7°, and the talar declination angle decreased by a mean of 17.9° ± 2.8°. Overall, 12 patients rated the result as excellent, 6 as good, and 2 as fair.

Conclusion: The application of Kalix II in subtalar arthroereisis combined with dissection of accessory scaphoid and reconstruction of posterior tibialis tendon is an effective therapy for flexible juvenile flatfoot.