Gradual Deformity Correction with a Computer-assisted Hexapod External Fixator in Blount's Disease

Area of Science:

• Orthopedic surgery
• Pediatric orthopedics
• Limb reconstruction

Background:

• Blount's disease, including infantile (IBD) and late-onset (LOBD) forms, often requires complex correction strategies.
• Recurrent cases and severe deformities present significant challenges in pediatric limb reconstruction.
• Obesity is a common comorbidity in children with Blount's disease, potentially impacting treatment outcomes.

Purpose of the Study:

• To evaluate the efficacy and complication rates of gradual correction for recurrent infantile and late-onset Blount's disease using a computer-assisted hexapod external fixator.
• To assess the degree of deformity correction achieved in terms of key angular and rotational parameters.
• To compare outcomes between infantile and late-onset Blount's disease cohorts.

Main Methods:

• Retrospective review of 19 children (25 limbs) with recurrent IBD or LOBD treated with a hexapod external fixator.
• Measurement of correction using medial proximal tibial angle (MPTA), anatomic posterior proximal tibial angle (aPPTA), and anatomic tibio-femoral angle (TFA).
• Analysis of complication categories, treatment duration, and follow-up outcomes.

Main Results:

• Significant correction of MPTA, aPPTA, and TFA was achieved, with post-operative alignment rated as "good" or "acceptable" in 90% of cases.
• The mean duration for correction was 16 days, with a mean frame time of 136 days.
• Minor pin track infections were common (Category 1), with fewer Category 2 and 3 complications; two patients experienced recurrence before skeletal maturity.

Conclusions:

• Computer-assisted hexapod external fixator use enables effective gradual correction of recurrent IBD and LOBD, even in severe cases.
• While complications are present, they are often manageable with timely intervention.
• Correction prior to skeletal maturity increases the risk of recurrence.