Interim results showed that the HATCP material was not non-inferior to the AUTO graft.

The purpose of this study is to determine whether structural calcium ceramic bone graft substitute (ReproBone™) is non-inferior compared to autologous tricortical iliac crest bone graft in lateral calcaneal lengthening osteotomies in pediatric patients and reduces postoperative pain.

To groups of patients (age 5-16) will be compared. One group randomized to autologous bone graft and the other group randomized to calcium ceramic.

The evaluation will be based on radiostereometric analysis, pedobarography, Patient reported outcome assessment (Oxford Ankle Foot Questionnaire), and pain (measured by visual analog scale and numerical range scale).

Study C: HA-β TCP (ReproBone™) vs. autologous tricortical iliac crest bone graft in a calcaneal lengthening osteotomy in children with pes planovalgus. A clinical randomized controlled non-inferiority study with 12 months of follow-up.

Purpose. To investigate the clinical and radiographic findings of a calcaneal lengthening osteotomy by comparing autologous bonegraft and HA-β-TCP graft in a group of children with hindfoot valgus deformities. The primary outcome measure the stability of the osteotomy measured by migrations in the x-translation by RSA.

Design. Prospective, randomized controlled non-inferiority study.

Randomization: Children who fulfill the criteria for inclusion together with their parents/guardian receive information about the project. The patients are randomized to respectively HA-ß-TCP and iliac crest bone graft.

Surgical procedure: Calcaneal lengthening osteotomy is performed between the anterior and middle facet of the subtalar joint. The corticalis of the calcaneus is bilaterally cut through. The planovalgus deformity is corrected and with a graft matching the wedged osteotomy is inserted. Tantalum balls are inserted into calcaneus on each side of the osteotomy and in cuboideum. Postoperative pain treatment consist of a tibial nerve catheter which is used the first 24 hours. Patients in whom graft is harvested from the iliac crest get local infiltration analgesics accordingly to a standardized procedure. The pain is registered by the use of a visual analog scale (VAS, NRS, faces scale) a 3, 8 and 12 hours postoperative. The amounts of used analgesics are registered. The stability of the osteotomy is assessed by radiostereometric assay (RSA) at the following time points: Baseline (first/second postoperative day) after 6 weeks, 8 weeks, 6 months and 12 months.

Power and significance: The primary parameter is stability of the osteotomy, measured as x-translations by the RSA software. We used continuous non-inferiority sample size calculations. With alpha 0.05 and power 0.9, non-inferiority limit 2 mm and sd 1.5 mm we estimated the sample size to 10 patients in each group. To secure against drop-out, we plan to include 15 patients in each group.

For ethical considerations an interim analysis was planned when 10 patients completed 6 months RSA follow-up. Primary outcome was compression of the osteotomy. We used a 99.8% confidence interval.

Inclusion Criteria:

• Children aged between 5-16 years with symptomatic planovalgus deformity admitted to the Department of Children's Orthopaedics, Aarhus University Hospital during the period 2012 to 2016. The surgical procedure is performed in about 10 children a year.

Pain and/or callosities. Informed written consent from the child custody/guardianship. Ambulatory function No severe cognitive deficits

Exclusion Criteria:

Reoperation will exclude patients from further follow-up