Background: Angular deformities at the knee are common in children with congenital or acquired below-knee or Syme amputations. These deformities can be well compensated and accommodated with prosthetic modifications. However, as children grow, these prosthetic modifications become more difficult and mechanical axis correction becomes necessary. These deformities have previously been treated with osteotomies and internal or external fixation devices, which necessitate prolonged periods without use of their prosthesis. This study examines the results of hemiepiphysiodesis to correct the mechanical axis and improve prosthetic fitting in a pediatric amputee population.
Methods: Mechanical axis correction using hemiepiphysiodesis in 22 pediatric Symes or transtibial amputees with 22 involved limbs were retrospectively reviewed. Hemiepiphysiodesis was performed with 8-plates (10), staples (6), or drilling and curetting (6). Postoperatively, children were allowed to resume prosthetic use after their wounds healed and they indicated no pain while wearing their prosthesis. Seventeen patients presented with valgus and 5 with varus deformity of their residual limb. Mean age at time of surgery was 11 years and 11 months (range, 7 y and 11 mo to 15 y and 8 mo). Mechanical axis deviation (MAD) was measured before initial surgery and again after hardware removal or physis closure.
Results: The mean preoperative MAD was -29.6 mm for the valgus deformities and +10.6 mm for the varus deformities. The mean postoperative MAD was +3.1 mm for the varus knees and -6.0 mm for the valgus knees The mean total mechanical axis correction was 21.8 mm. One patient failed to achieve any mechanical axis correction and 1 hardware failure (broken 8-plate) occurred. Most patients had the staples or 8-plates removed, either after correction was achieved and physes were still open, or due to hardware prominence after physeal closure.
Conclusions: Hemiepiphysiodesis provides reliable correction of angular deformity in pediatric amputees. Surgical intervention while skeletally immature allows for correction using guided growth, without the need for osteotomy with internal or external fixation and the resultant disruptions in prosthetic wear.
Level of evidence: Case Series, Level IV.