gms | German Medical Science

Objectives: Leg length discrepancies (LLD) are frequently associated with coronal angular deformities, in particular valgus deformity of the knee joint. Temporary hemiepiphysiodesis (HED) of the distal femur or proximal tibia represents a well-established procedure for valgus or varus deformity correction in children and adolescents. For treatment of LLD of more than 2 cm, on the other hand, limb lengthening with intramedullary lengthening devices has gained increasing popularity in recent years. To our knowledge, the application of both procedures for combined correction of LLD and valgus or varus deformity of the knee in skeletally immature patients has not yet been evaluated.

Methods: A retrospective chart review of 24 patients (12 female, 12 male) undergoing antegrade femoral lengthening with a magnetically controlled intramedullary lengthening nail (PRECICE®, NuVasive, USA) between 2014-2019 for treatment of LLD was conducted. Temporary HED through implantation of FlexTacks™ (FT; Merete, Germany) of the medial or lateral distal femur and/or proximal tibia was either performed before (n=9), simultaneously (n=11), or subsequently (n=4) to femoral lengthening. All patients were evaluated with regards to the pre- and postinterventional leg length as well as axis alignment. The mean follow-up (FU) period was 2.9 years.

Results and conclusion: Mean age at implantation of FT was 13.3 years and 13.7 years at implantation of lengthening nails. Mean initial LLD was 39 mm. 20 patients presented valgus and 4 varus deformity of the knee joint.

Equalization of LLD was achieved in 17/24 patients. Mean residual LLD after lengthening was 19 mm in 7/24 patients. In 5/7 patients who presented residual LLD, staged equalization of leg length, with a maximum of 50 mm for each lengthening procedure, had been planned due to a predicted final LLD of more than 10 cm. In 2/7 patients, residual LLD of 1 cm was tolerated due to preexisting fusion of the ankle joint.

Mean initial MAD was -27.2mm and +31mm, respectively. Through temporary HED an average correction of MAD of +10 mm and -6 mm was achieved, resulting in a mean MAD of +1 mm in the valgus and +6 mm in the varus group at the time of implant removal. Mean initial LDFA and MPTA were 83°/92° in the valgus and 94°/85° in the varus group. Through temporary HED, mean LDFA and MPTA were improved to 88°/89° and 88°/88°, respectively.

80% (19/24) of all patients had achieved skeletal maturity at the time of last FU.

The combination of antegrade femoral lengthening and distal temporary HED is a valuable option to correct LLD and angular deformity in the frontal plane in skeletally immature patients. Nonetheless, the reported technique ought to be thoroughly planned and executed. Regular clinical as well as radiological examinations until skeletal maturity are mandatory. In particular during the process of lengthening and growth modulation, timely detection and treatment of occurring complications, overcorrection and rebound of deformity are crucial.