Staging classification of atypical ulnar fractures

Area of Science:

• Orthopedics
• Radiology
• Pharmacology

Background:

• Atypical ulnar fractures (AUFs) are rare and linked to long-term bisphosphonate therapy.
• The progression patterns of AUFs are not well understood.
• Current treatment strategies for AUFs are not definitively established.

Purpose of the Study:

• To classify atypical ulnar fractures based on imaging characteristics.
• To elucidate the characteristic progression patterns of AUFs.

Main Methods:

• Retrospective review of 12 AUFs in 11 patients with long-term bisphosphonate use.
• Classification of fractures into three stages based on imaging findings: Stage I (dorsal cortex involvement), Stage II (ventral cortex involvement), and Stage III (osteosclerosis).

Main Results:

• Initial classification: 2 Stage I, 8 Stage II, 2 Stage III.
• Two fractures progressed from Stage I to Stage II during follow-up.
• Observed a consistent progression pattern: dorsal cortical thickening, extension to the ventral cortex, and development of osteosclerosis.

Conclusions:

• AUFs initiate with cortical bone thickening and advance to complete fractures.
• Over time, complete AUFs can develop osteosclerosis, mimicking pseudoarthrosis.
• The proposed imaging classification may guide treatment decisions for AUFs.