Hemiepiphysiodesis Corrects Lower Extremity Coronal Plane Deformity in Children with Skeletal Dysplasia Irrespective of Intra-Articular Malalignment.

Abstract

Background: Skeletal dysplasias (SkD) are a rare group of disorders characterized by abnormal growth and development of bone and cartilage, often causing limb deformity. Many patients also have ligamentous instability that can accentuate the malalignment. This ligamentous instability can present either a generalized ligamentous laxity or focal coronal plane intra-articular malalignment. Temporary hemiepiphysiodesis (HE) is a commonly employed minimally invasive surgical technique for correcting coronal plane limb deformities. This study evaluated the effectiveness of HE in the correction of knee coronal plane deformity in children with SkD and the correlation of concurrent joint laxity.

Methods: A retrospective cohort study was conducted to evaluate radiological outcomes of HE for coronal plane knee deformities in patients with SkD (aged <18 years) who had surgery between January 1, 2008 and December 31, 2020. Changes in distal femoral and proximal tibial mechanical angles, and knee joint line congruence angles (JLCA) prior to HE and at the final follow-up were analyzed. An increased JLCA of ≥±2° was considered a knee with ligamentous instability. Preoperative and postoperative patient-reported pain status was recorded.

Results: Fifty-six tibial and 42 femoral HE procedures in 32 children (mean age at HE: 9.8 ± 2.8 years) were included. The deformity was fully corrected in 23/32 (72%) children, at an average annual rate of 6.3° at the distal femur and 3.3° at the proximal tibia, over 21.9 ± 12.6 months. The overall pre-HE JLCA improved by an average of 5.3° (P < .05). The improvement was more pronounced in varus knees (n = 45; P < .05) than valgus knees (n = 12; P = .11) but regardless of the severity of joint instability, pre-HE JLCA did not impede the rate of femoral (r = -0.22) or tibial (r = -0.21) corrections. Preoperative pain was reported by 78% of patients whereas only 25% of patients reported pain postoperatively at the final follow-up (mean follow-up: 26.4 ± 13.5 months).

Conclusions: The presence of coronal plane intra-articular malalignment did not affect the rate and the magnitude of correction with HE in this cohort. Coronal plane deformities and JLCA improve with deformity correction by HE in children with SkD.

Key concepts: (1)Intra-articular malalignment at the knee does not impede the success of hemiepiphysiodesis in children with skeletal dysplasia.(2)While all coronal plane knee deformities improved, a more significant improvement was noted in children with varus than valgus.(3)Joint line congruency angles improved with guided growth for coronal plane deformities.

Level of evidence: III.