Limb Lengthening for Congenital Deficiencies Using External Fixation Combined With Flexible Intramedullary Nailing: A...

Area of Science:

• Orthopedics
• Biomaterials Science
• Regenerative Medicine

Background:

• Hydroxyapatite (HA)-coated flexible intramedullary nails (FIN) are known to stimulate osteogenic activity.
• The specific impact of HA-coated FIN on bone lengthening outcomes, particularly the External Fixation Index (EFI), remains incompletely understood in cases of congenital lower limb discrepancy.

Purpose of the Study:

• To quantitatively assess the influence of HA-coated FIN on the EFI in patients undergoing bone lengthening for congenital lower limb discrepancy.
• To compare the EFI between patients treated with HA-coated FIN and those treated with non-coated titanium (Ti) FIN.

Main Methods:

• A cohort of 70 patients with congenital lower limb discrepancy underwent lengthening using external fixation combined with either Ti-FIN or HA-coated FIN.
• Follow-up assessments were conducted at least 12 months post-frame removal to evaluate the EFI.
• Statistical analyses, including 2-way ANOVA and posthoc tests, were employed to determine the influence of nail type, age, and their interactions on EFI.

Main Results:

• No significant difference in mean EFI was observed between patients treated with HA-coated and non-coated FIN across all subgroups.
• A significant interaction between nail type and age was found to affect EFI in tibial bifocal lengthening.
• A positive correlation was noted between the nail diameter/medullary shaft diameter ratio and EFI in non-HA-coated tibial bifocal lengthening.
• A statistically significant negative correlation between nail diameter and fracture occurrence at the lengthening site was observed in the non-HA-coated group, with a ratio <0.15 indicating higher fracture risk.

Conclusions:

• Both Ti-FIN and HA-coated FIN yield good to excellent outcomes for monosegmental femoral and tibial lengthening, with reduced EFI.
• In congenital disorders without abnormal bone, HA-coated and non-coated FIN demonstrate comparable EFI.
• A nail diameter to medullary canal diameter ratio below 0.15 is associated with an increased risk of post-frame removal fractures at the lengthening site.