The occurrence of tarsal injuries in male mice of C57BL/6N substrains in multiple international mouse facilities

Abstract

Dislocation in hindlimb tarsals are being observed at a low, but persistent frequency in group-housed adult male mice from C57BL/6N substrains. Clinical signs included a sudden onset of mild to severe unilateral or bilateral tarsal abduction, swelling, abnormal hindlimb morphology and lameness. Contraction of digits and gait abnormalities were noted in multiple cases. Radiographical and histological examination revealed caudal dislocation of the calcaneus and partial dislocation of the calcaneoquartal (calcaneus-tarsal bone IV) joint. The detection, frequency, and cause of this pathology in five large mouse production and phenotyping centres (MRC Harwell, UK; The Jackson Laboratory, USA; The Centre for Phenogenomics, Canada; German Mouse Clinic, Germany; Baylor College of Medicine, USA) are discussed.

Fig 1. Dorsal view of unaffected right tarsus and rounded, swollen tarsus (reader’s left).

Fig 2. (a) X-ray image of the normal position of the calcaneus (arrow) within the tarsal joint and (b) with caudo-dorsal dislocation of the calcaneus.

Fig 3. (a) The unaffected tarsus with the calcaneus (black arrow head) forming an approximate 90° angle with the tibia (black star), (b) Affected tarsus (black arrow head) with dislocation of the calcaneus caudo-dorsally to form an approximate 15° angle with the tibia (black star).

The black arrow indicates the direction of movement of the calcaneus. Scale bar = 2mm.