| Topic | Findings (concise) | Evidence/citation |
|---|---|---|
| Key facts: Humeroradial synostosis — definition/overview | Rare congenital elbow synostosis/radiohumeral fusion caused by failure of longitudinal differentiation; often produces a functionally absent elbow joint and a longer single osseous segment from humerus-radius fusion. | Nema et al., 2012, *Malaysian Orthopaedic Journal* 6:41-42, DOI: https://doi.org/10.5704/moj.1211.010 (year 2012); Oliveira et al., 2023, *Rev Bras Ortop* 58:532-537, DOI: https://doi.org/10.1055/s-0040-1716757 (year 2023) (pqac-00000001, pqac-00000019) |
| Estimated number of reported cases | Literature estimates are approximately or slightly more than 150 described patients worldwide. | Nema et al., 2012, DOI: https://doi.org/10.5704/moj.1211.010 (year 2012); Oliveira et al., 2023, DOI: https://doi.org/10.1055/s-0040-1716757 (year 2023) (pqac-00000001, pqac-00000019) |
| Common associations | Frequently associated with ulnar longitudinal deficiency/ulnar hemimelia, especially Bayne type IV; also occurs within multiple synostoses syndromes and syndromic craniosynostosis spectra such as Antley-Bixler-like/CYP26B1-related disease. | Aggarwal et al., 2020, review/case summary of Bayne type IV association (year 2020); Oliveira et al., 2023, DOI: https://doi.org/10.1055/s-0040-1716757 (year 2023); Grand et al., 2021, *Am J Med Genet A* 185:2766-2775, DOI: https://doi.org/10.1002/ajmg.a.62387 (year 2021) (pqac-00000005, pqac-00000019, pqac-00000011) |
| Key genes | Syndromic/related genes include **FGF9** (multiple synostoses syndrome type 3), **GDF6** (SYNS4), **NOG** (SYNS1 / joint fusion syndromes), **GDF5** (SYNS2), and **CYP26B1** (AR craniosynostosis/multiple synostoses with radiohumeral involvement). | Schmetz et al., 2023, *Genes* 14:724, DOI: https://doi.org/10.3390/genes14030724 (year 2023); Terhal et al., 2018, *Am J Med Genet A* 176:225-229, DOI: https://doi.org/10.1002/ajmg.a.38503 (year 2018); Sentchordi-Montané et al., 2021, *Clinical Genetics* 99:309-312, DOI: https://doi.org/10.1111/cge.13876 (year 2021); Grand et al., 2021, DOI: https://doi.org/10.1002/ajmg.a.62387 (year 2021); Morton et al., 2016, *Am J Med Genet A* 170:2706-2710, DOI: https://doi.org/10.1002/ajmg.a.37804 (year 2016) (pqac-00000009, pqac-00000010, pqac-00000012, pqac-00000011, pqac-00000026) |
| Inheritance patterns | Isolated/ulnar-deficiency cases can be sporadic; familial forms exist. Reported patterns include autosomal dominant multiple synostoses syndromes (FGF9/GDF6/NOG/GDF5-related) and autosomal recessive CYP26B1-related disease; older classification also recognizes AD, AR, and non-germinal forms. | Aggarwal et al., 2020 (classification summary, year 2020); Schmetz et al., 2023, DOI: https://doi.org/10.3390/genes14030724 (year 2023); Morton et al., 2016, DOI: https://doi.org/10.1002/ajmg.a.37804 (year 2016) (pqac-00000005, pqac-00000010, pqac-00000028) |
| Key phenotypes | Core features: fixed elbow in flexion or extension, absent elbow motion, single forearm/arm bone due to humerus-radius fusion, forearm shortening/micromelia, radial bowing, oligodactyly/tridactyly/quadridactyly. Syndromic forms may add carpal/tarsal fusions, vertebral synostoses, craniosynostosis, conductive hearing loss, contractures, and developmental issues. | Nema et al., 2012, DOI: https://doi.org/10.5704/moj.1211.010 (year 2012); Aggarwal et al., 2020 (year 2020); Schmetz et al., 2023, DOI: https://doi.org/10.3390/genes14030724 (year 2023); Grand et al., 2021, DOI: https://doi.org/10.1002/ajmg.a.62387 (year 2021); Terhal et al., 2018, DOI: https://doi.org/10.1002/ajmg.a.38503 (year 2018) (pqac-00000020, pqac-00000005, pqac-00000015, pqac-00000011, pqac-00000009) |
| Management pearls | If function is acceptable, conservative management is often preferred. Synostosis resection has high recurrence/complete recidiva; positional osteotomy may improve function; early physiotherapy and selective soft-tissue procedures are used in deficiency cases. Fractures through the synostotic single bone require anatomic fixation that preserves pre-injury function. | Nema et al., 2012, DOI: https://doi.org/10.5704/moj.1211.010 (year 2012); Oliveira et al., 2023, DOI: https://doi.org/10.1055/s-0040-1716757 (year 2023); Aggarwal et al., 2020 (year 2020) (pqac-00000001, pqac-00000018, pqac-00000017, pqac-00000005) |


*Table: This table summarizes the core clinical, genetic, and management facts for humeroradial synostosis using only the cited evidence contexts. It is useful as a compact reference for disease definition, associations, genes, phenotypes, and practical care points.*