Radial Longitudinal Deficiency: Severity Differences Between U.S. and Japanese Cohorts

Area of Science:

• Orthopedics
• Pediatric Surgery
• Genetics

Background:

• Radial longitudinal deficiency (RLD) is a spectrum of forearm malformations with varying associated conditions.
• Limited comparative data exists on RLD presentation across different countries.
• Understanding international variations in RLD is crucial for diagnosis and treatment.

Purpose of the Study:

• To compare the presentation of RLD, including severity of forearm deficiency, thumb hypoplasia, and associated syndromes, between patient cohorts in the United States and Japan.
• To test the hypothesis that RLD presentation is similar between the two countries.

Main Methods:

• Retrospective chart review of RLD patients from two pediatric hospitals (US and Japan) over 15 years.
• Assessment of RLD and thumb hypoplasia severity using modified Bayne and Klug and Blauth classifications.
• Correlation analysis of RLD severity, thumb hypoplasia, and co-occurring medical conditions.

Main Results:

• The US cohort (107 patients) presented with more severe RLD and higher bilaterality (63%) compared to the Japanese cohort (194 patients, 50%).
• Japanese patients exhibited a higher incidence of associated syndromes (68%) versus US patients (38%), notably VACTERL and Holt-Oram syndromes.
• A strong correlation was found between increased RLD severity and increased thumb hypoplasia severity in both cohorts.

Conclusions:

• US patients experienced more severe RLD and bilaterality, whereas Japanese patients had a higher prevalence of associated syndromes and radial polydactyly.
• Forearm severity consistently correlated with thumb hypoplasia severity across both populations.
• Findings highlight distinct epidemiological patterns of RLD between the US and Japan, informing clinical understanding.