Bone contusions (bone marrow like edema [BMEL]), are present in 80% of anterior cruciate ligament (ACL) tears. Its clinical and pathologic meaning is still uncertain.
Objectives
(1) Describe the pattern of BMEL's after knee sprain; (2) correlate the severity of BMEL's with articular injuries.
Methods
Inclusion: age > 18 years, knee MRI with key word “sprain” in the exam prescription, and “bony contusion(s)”, “bone marrow edema”, “medullary contusion(s)” and “medullary edema” in the MRI report. Exclusion: ipsilateral knee surgery, active infectious, inflammatory or neoplastic disease. Gender and age were recorded. Evaluated data: injury to the ACL, Posterior Cruciate Ligament (PCL), Internal Collateral Ligament (ICL), External Collateral Ligament (ECL), Internal (IM) or External Meniscus (EM). BMEL's localization was divided as Internal (IFC) or External Femoral Condyle (EFC), and Internal (ITP) or External Femoral Condyle (EFC). A correlation of the geographic distribution and severity of BMEL's with intra-articular injury patterns was assessed. The statistical analysis was performed with SPSSy22.0.
Results
Four hundred and nine patients (207 male [M] and 202 females [F]) were included. Ninety-one (22%) presented BMEL in their MRI (54 M, 37 F), averaging 30.2 ± 7.3 years old. Eighty-eight percent presented at least one articular injury: the most frequent were menisci (59%) (IM 58%, EM 35%, IM + EM 23%) and ACL tear (54%). BMEL distribution: ICF −42%, ECF −49%, ITP −41%, ETP −44%. BMEL frequency analysis revealed one area of contusion in 48% of patients, 2 in 33%, 3 in 13% and 4 in 6% of the patients. Correlation of BMEL localization with the injured structure was statistically significant: IM-ETP in 46% (p = 0.05), EM-ETP in 59% (p = 0.029) and ITP in 56% (p = 0.026), and Central Pivot-ETP in 69% (p = 0.001). Internal areas of contusion more associated with IM injuries (p = 0.023), and external areas with LCA tears (p = 0.001). Patients with IM + EM injuries had significantly increased number of Bells (p = 0.039). Injuries to more than 2 structures correlated with increased number of BMEL's (p = 0.01). Men presented more contusions in the lateral compartment (78% vs 57%, p = 0.036) and 70% had associated menisci and ACL injuries (vs 30% in women, p = 0.032).
Discussion
Although gender did not affect contusion severity, men appeared to show increased severity of articular injuries. EM tears correlated with BMELs in the tibial plateau and it is interesting that EM lesion is more likely when an internal contusion is present, possibly due to the mechanism of injury. ETP contusions appear to correlate significantly with ACL tears, as described in previous studies. Deranged articular structures seem to increase with the increasing number of BMEL areas.
Conclusions
BMEL's appear to reflect injury mechanism and severity after knee sprains.
