Current Considerations With Bone Marrow Lesions

Bone marrow lesions (BMLs) of the talus are a commonly treated pathology of the foot and ankle. We treat these lesions operatively through arthroscopic debridement, microfracture techniques and cartilage restoration procedures. These lesions are often associated with cartilage loss and can lead to pathologic fractures. However, should we approach each of these lesions in the same manner? What do we really know about bone marrow lesions?

Bone marrow edema in and of itself is a non-specific, ill-defined area of hypointense and hyperintense signal on T1-weighted and fluid-sensitive sequences respectively.^1-3 When interpreting these images, we must also take into account the clinical history of these patients. 

The first differentiating factor for these lesions is determining whether they have a traumatic versus an atraumatic etiology. One would expect bone marrow lesions immediately following a traumatic injury. These lesions tend to be more poorly defined with heterogenous patterns within the subchondral bone.⁴ When there is cartilage injury associated with the adjacent bone marrow within the subchondral bone, then it is considered a true osteochondral injury.⁴ Bone marrow lesions with adjacent cartilage damage can result in insufficiency fractures, fatigue fractures or stress fractures, especially when one is exposed to continued repetitive trauma. 

Nontraumatic bone marrow lesions may not be as easy to diagnose. These lesions could include pathologies such as progression of avascular necrosis (which one may typically see after osteochondral collapse) and reactive inflammatory polyarthritis.

What Does This Mean From A Surgical Standpoint?  

Most of the literature regarding this topic starts in the knee and fair amount of the studies are in sports journals.  The available data shows us that persistence of post-operative edema-like signals in the subchondral bone is a predictor of poor clinical outcome scores after microfracture.⁵ This may be because the actual pathology of injury to the subchondral bone is not being addressed with microfracture itself. These lesions often involve both the cartilage and the subchondral bone and we need to address just that, the osteo-chondral unit. Surgeons must pay more attention to addressing not only the articular cartilage but the subchondral bone as well. We should consider more cartilage restoration and allograft reconstruction which address both problems. 

Are we possibly causing more harm than good with our current algorithms? What are our true outcomes after a microfracture of the talus? Are shoulder lesions really as bad as we think? Ultimately, when should we operate on these lesions? We should consider all of these questions in our next clinic session.

Dr. Pirozzi is a Fellow of the American College of Foot and Ankle Surgeons (FACFAS) and serves as Vice President for ACFAS Region 2. She is currently in practice in Phoenix, AZ. 

References

1. Schmid MR, Hodler J, Vienne P, Binkert CA, Zanetti M. Bone marrow abnormalities of foot and ankle: STIR versus T1-weighted contrast enhanced fat-suppressed spin-echo MR imaging. Radiology. 2002; 224:463–469. 
2. Weishaupt D, Schweitzer ME. MR imaging of the foot and ankle: patterns of bone marrow signal abnormalities. Eur Radiol. 2002;12:416–426. 
3. Rios AM, Rosenberg ZS, Bencardino JT, Rodrigo SP, Theran SG. Bone Marrow Edema Patterns in the Ankle and Hindfoot: Distinguishing MRI Features. Am J Radiol. 2011;197:720-729.
4. Saltzman BM, Riboh JC. Subchondral bone and the osteochondral unit: basic science and clinical implications in sports medicine. Sports Health. 2018;10(5):412-418.
5. Recht M, Bobic V, Borstein D, et al. Magnetic resonance imaging of articular cartilage. Clin Orthop Relat Res. 2001;391(suppl):S379-S396.