Plate fixation after lengthening with an external fixator in patients with achondroplasia

Background: This study compared internal fixation with a plate after lengthening (PAL) with an external fixator with the conventional method (CM) in terms of radiologic and clinical outcomes in the lower extremities of patients with achondroplasia. Methods: In this study 20 patients (50 lower extremity long bones) who underwent PAL or CM were divided into 2 cohort groups. The amount of lengthening, percentage lengthening, external fixator index (EFI), external fixator time, Li regeneration index, complication rate, and knee range of motion (ROM) were compared between the groups. Results: The median age was 9.4 years (range 6–16 years) in the PAL group and 12 years (range 9–16 years) in the CM group (p= 0.01). Males comprised 80% of the patients in the PAL group and 47% of the patients in the CM group (p= 0.02). The median amount of lengthening in the PAL and CM groups was 7.5 cm (range 5.5–9.5 cm) and 6.0 cm (range 5.5–9.0 cm), respectively (p< 0.01). The median percentage of lengthening in the PAL and CM groups was 44.6% (range 20.0–70.1%) and 43.0% (range 20.5–57.3%), respectively (p= 0.01). The median external fixator time in the PAL and CM groups was 127 days (range 94–185 days) and 180 days (range 105–355 days), respectively (p< 0.01). The median EFI in the PAL and CM groups was 21 days/cm (range 10–33 days/cm) and 27 days/cm (range 15–59 days/cm), respectively (p< 0.01). The Li regeneration index was 3 (interquartile range, IQR 2–4) in both groups (p= 0.2). The total complication rate was similar between the groups. Conclusion: In patients with achondroplasia, after lengthening with an external fixator, internal fixation with a plate can be a reliable alternative to the conventional method. Level of evidence: Level III therapeutic