Displacement of mandibular fractures: is there a correlation with sensory loss and recovery?

Fractures of the mandible are common. However, the correlation between the severity of the fracture and the recovery of any associated inferior dental (ID) nerve injury is still poorly understood. We aimed to examine the relationship between the amount of fracture displacement and how it relates to the recovery of sensation to the lower lip. One hundred and fifty patients requiring treatment of a mandibular fracture (where the fracture passed across the ID canal) were assessed. One hundred were initially assessed in a retrospective double-blinded study. A further 50 patients were then followed up prospectively. Both the maximal displacement of the fracture and the displacement specifically at the ID canal were measured. Sensory recovery, or persistence of numbness, was also recorded for each patient. Although there appeared to be a correlation between increasing displacement at the ID canal and a poorer recovery, there was not a clear relationship between the two, and there were many exceptions. Persistent numbness (>1 year) still occurred in fractures with relatively minimal displacement (</=3mm). Possible reasons for persistent numbness are discussed.