Longitudinal assessment of femoral knee cartilage quality using contrast enhanced MRI (dGEMRIC) in patients with anterior cruciate ligament injury-comparison with asymptomatic volunteers
Neuman P, Tjorstrand J, Svensson J, Ragnarsson C, Roos H, Englund M, Tiderirus C.J., & Dahlberg. Osteoarthritis Cartilage. 2011; 19: 977-983: doi: 10.1016/j.joca.2011.05.002 https://www.ncbi.nlm.nih.gov/pubmed/21621622 
Anterior cruciate ligament (ACL) tears commonly occur in athletics and increase the risk of developing knee osteoarthritis (OA).  One of the early OA changes, prior to radiographic signs of OA, is an alteration in the composition of cartilage.  These early cartilage changes can be detected with magnetic resonance imaging, particularly delayed gadolinium (a contrast)-enhanced MRI of cartilage (dGEMRIC).  dGEMRIC has detected differences in cartilage between knees 3 weeks after an ACL injury compared to healthy knees but this technique has never been used to follow ACL injured knees for longer periods of time. The purpose of this study was to examine cartilage composition of healthy knees at one time point and ACL injured knees at 3 weeks and within 5 years post ACL injury (on average 2.4 years after injury).  This study included 29 patients (19 men; average age = 27 years) who had suffered an ACL tear.  All patients were evaluated utilizing dGEMRIC within 3 weeks post-injury and compared to 24 healthy controls (14 men, average age = 25 years).  At the longer-term follow up assessment, 14 of the 29 ACL injured patients underwent ACL reconstruction after the initial assessment and were compared to the remaining 15 who did not undergo ACL reconstruction (conservative-care group).  Demographics for these two cohorts were not reported, however there were no differences in the numbers of patients that underwent partial meniscectomies between surgical or conservative care groups.  Furthermore, the two groups had similar mean activity levels and Lysholm knee scores (signs and symptoms score) at 3 week post injury and at the longer-term follow-up. Outcome measures were cartilage composition in the weight-bearing regions of the medial and lateral femoral cartilage.  Overall, the ACL injured knees had different cartilage composition than healthy controls.  Within the ACL injured group, the lateral femoral cartilage composition improved over time but the medial cartilage did not.  ACL injured knees that underwent partial meniscectomy had greater changes in cartilage composition in the cartilage adjacent to the surgical meniscus (e.g., medial meniscus and medial cartilage) than knees that did not have a partial meniscectomy. Cartilage composition was not different between ACL reconstructed knees and non-ACL reconstructed knees (conservative care).  
This study is important because it demonstrates ACL injured knees have compromised cartilage compositions when compared to healthy controls, especially with concomitant meniscal injury.  As a community, we need to start looking at how we can reduce the risk of OA for these athletes during early stages of joint degeneration when interventions may be most effective. This study also demonstrates that small cartilage composition changes, prior to major structural changes on x-rays, can be detected utilizing dGEMRIC.  It would be interesting to see this study follow the patients longer prospectively to see how cartilage composition changes correspond to structural changes on standard x-rays (the current gold standard for diagnosing OA).  As the authors also note, it would be ideal if we could study the cartilage composition before injury to see how the changes relate to the health of the cartilage prior to injury.  Eventually, it would also be very interesting to see the effects of interventions (e.g., exercise, injections) and other potential influential factors (e.g., time to return to play) on this marker to identify possible disease modifying interventions. While the sample size is limited, this study does provide further possible evidence that supports the theory that current ACL reconstruction techniques do not reduce the risk of knee OA.
Written by: Nicole Cattano
Reviewed by: Jeffrey Driban

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