How are bone contusions and bone bruises classified?
A brief search through the literature for the terms 'bone contusion' and 'bone bruise' will leave you confused due to the lack of clarity and consensus on this topic. Attempts to classify bone contusions have been met with little acceptance by practicing clinicians.(1,2,3) To date, there is no classification of these conditions that allows clinicians to objectively predict the extent to which a bone contusion may or may not heal.
A survey of the literature on bone contusions and bone bruises brought up a number of articles, but the best I found came out of Meath, Ireland. Published in The International Society of Arthroscopy, Knee Surgery and Orthopedic Sports Medicine, Drs. Niall and Bobic summarize the topic in a paper entitled, 'Bone Bruising and Bone Marrow Edema Syndromes: Incidental Radiological Findings or Harbingers of Future Joint Degeneration? (4) The authors describe bone edema and bone contusions as an area of swelling within the bone with or without microtrabecular fracture, without disruption of the bone cortex or adjacent cartilage. Their article focuses primarily on the knee and bone contusions associated with ACL tears. They summarize that bone contusions are unique and poorly classified injuries that do qualify as fractures.
Magnetic resonance imaging (MRI) has helped to identify several characteristics of these injuries that were previously poorly seen with plain x-ray images. As such, MRI has helped to identify breaches in the cortical bone, and when the injury is associated with overlying cartilage, MRI has been able to clearly identify disruption of the cartilage from the subchondral bone.
Are bone contusions really fractures? In many cases yes. When the outer cortical bone is violated, or when the subcortical or subchondral bone is compressed, these injuries really do represent fractures.
Granted, the mechanism of injury will vary, and the affected joint may be different (hip/knee/ankle). These variations will make classification much more difficult. For instance, the mechanism of injury in the ankle will be vastly different from that of the hip. Although MRI cannot differentiate the mechanism of injury, it can quantitate many characteristics of these injuries such as dept of bone edema, pattern of bone edema and disruption of cortical bone. Although the interpretation of this information by the clinician remains subjective, it does act as a guide for prognostic interpretation of the injury. This knowledge can help clinicians discuss long term sequelae with their patients and predict future viability of the joint.
- Lynch TCP, Crues JV, Morgan FW et al. Bone Abnormalities of the knee: prevalence and significance at MR imaging. Radiology 1989; 171:761-6.
- Mink JH, Deutsch AL. Occult cartilage and bone injuries of the knee: Detection, classification and assessment with MR imaging. Radiology 1989; 170:823-9.
- Vellet AD, Marks PH, Fowler PJ et al. Occult post-traumatic osteochondral lesions: Prevalence, classification and short-term sequelae evaluated with MR imaging. Radiology 1991; 178:271-6.
- Niall D, Bobic V. Bone Bruising and Bone Marrow Edema Syndromes: Incidental Findings or Harbingers of Future Joint Degeneration?(undated publication)