The Correlative Study Of Subchondral Focal Lesions Of The Knee

Objective: To evaluate the correlation of subchondral focal lesions of the knee,inculding osteoarthritis subchondral pseudocyst (OAPC),SONK(spontaneous osteonecrosis of the knee) ,OCD (osteochondritis dissecans) and other T₂WI high signal (T₂HS). The relationship between clinical features and image findings of the subchondral focal lesions were also analysed.Methods: 99 patients who showed subchondral focal lesions by MRI were prospectively collected between June 2005 and January 2007, Including 32 men and 67 women.According to the literature on the diagnostic criteria for the above disease,there were 27 patients of OAPC, SONK 15 patients, OCD 13 patients and 44 T₂HS patients .The clinical symptoms was graded by M-L(Michel-lequesen) pain severe score of knee.for each,the following clinical features were identified:age,gender,BMI(body mass index),duration of symptoms,perceived history of excessive stress.All were examined with MRI,20cases with CT and plain film together.Other5 cases with CT solitary,other 8cases with plain film solitary.The following subchondral focal lesions image features were identified: lesion size, location, bone marrow edema, and defect of cartilage, abnormalities of meniscus and ligaments,jiont effusion.The clinical and image features of subchondral focal lesions were analysised with statistical software.The main factors affected area of subchondral focal lesions was tested by stepwise regression method. The relationship between painful symptoms and abnormalities of intra-articular structure were also by correlative analysis.Each two SONK, OCD and T₂HS were followed up within 1 year by conservative therapy.Result:1 Clinical featureThe statistical results showed a small age of OCD patients, the mean age was 25.2 years, there was significant difference among OCD ,OAPC, SONK and T₂HS patients. The mean age of OAPC, SONK and T₂HS patients were respective 58.4 years,58.7 years, 57.9years.The BMI of OCD patients was 21.6, there was significant difference among OCD, SONK ,OAPC and T₂HS patients. by multiple comparison,there was no significant difference among OAPC ,SONK and T₂HS patients. They were respective 26.2, 27.0, 25.9.The statistical results showed the duration of symptoms of OAPC was 25.8months, there was significant difference among them. SONK, OCD and T₂HS patients were respective 19.1months, 14.6 months, 15.6 months, By multiple comparison, there was significant difference between SONK and OCD patients.The statistical results showed the history of excessive stress among OAPC, SONK, OCD and T₂HS intensity patients were respective 29%(8/27), 33%(5/15), 69%(9/13), 34%(15/44), there was no significant difference among them.2 Image features2.1 The 99 patients were examined with unilateral knee , 118 subchondral lesions were found by MRI, 67 patients with 1 abnormality ,24 patients with 2 abnormalities,8 patients with 3 to 6 abnormalities.The statistical results showed MRI was superior to CT and plain film,CT was superior to plain film on showing subchondral lesions.2.2 OAPC,SONK,OCD and T₂HS imaging performance were summarized as followingMRI findings of OAPC showed subchondral semicircular area of medial femoral condyle or tibial plateau ,size ranging from single or multiple with low signal in T₁WI and high signal in T₂WI. CT and Plain film showed radiolucent oval abnormality underlying the cortical bone surface of the medial femoral condyle surrounded by sclerosis, including joint space narrowing , sclerosis of articular surface ,osteophytes.The imaging of SONK and OCD were not distinguished clearly,MRI findings of them all showed subchondral semicircular area of medial femoral condyle or tibial plateau with low signal in T₁WI and high signal in T₂WI,surrounded with low single band.CT or plain film showed normality at early stage.With the lesions progressed, CT or plain film showed radiolucent oval abnormality underlying the cortical bone surface of the medial femoral condyle surrounded by sclerosis,when the osteochondral fragment detached from bone, also showed osteochondral defect and loosing body.MRI findings of T₂HS showed semicircular or irregular area of medial femoral condyle or tibial plateau with low signal in T₁WI and high signal in T₂WI,with single or multiple area. CT or plain film always showed normality.2.3 The locational proportion in weight-bearing zone and non-weight-bearing zone of subchondral focal lesions among OAPC, SONK, OCD and T₂HS patients were respective 89%(24/27), 93%(14/15), 46%(6/13), 91%(32/44), there was significant difference among them. Next by multiple comparison,there was no significant difference among SONK,OAPC and T₂HS intensity patients.The abnormality of meniscus among SONK,OAPC and T₂HS patients were respective 33%(5/15),7%(2/27),64%(28/44), OCD patients was 38%(5/13), there was significant difference among them.The abnormality of patellar ligament (PL)among OAPC, SONK, OCD and T₂HS patients were respective 7%(2/27),33%(5/15),77%(10/13),32%(14/44), there was significant difference among them.Next by multiple comparison,there was no significant difference among SONK, OAPC and T₂HS patients. The abnormality of anterior cruciate ligament (ACL),posterior cruciate ligament(PCL), medial collateral ligament(MCL) and lateral collateral ligament (LCL)among OAPC, SONK,OCDand T₂HS patients were no significant difference.2.4 There were 62 patients with subchondral lesions corresponded to teared meniscus of all 99 patients.There were 37 patients with subchondral lesions discorresponded to teared meniscus ,including 20 patients with grade 0 abnormality of meniscus.The ratio of abnormalities of ACL, PCl and PL in patients with subchondral lesions discorresponded to teared meniscus were higher than patients with subchondral lesions corresponded to teared meniscus.3 Tested by stepwise regression method, the area of subchondral lesions were mainly affected by defect of cartilage and abnormalities of menicius and anterior cruciate ligament.4 The relationship between painful symptoms and abnormal structure of knee in subchondral focal lesionsThe area of subchondral focal lesions, abnormality of meniscus, ACL and PCL, joint effusion were strongly related to increasing painful symptoms.5 The results of following upThe subchondral lesion of one OCD patient was absorbed wholely. the subchondral lesion of anther OCD patient , two SONK and two T₂HS patients were unchanged clearly.Conclusion: 1 The knee OAPC,SONK,OCD and T₂HS were strongly related to subchondral focal excessive stress . they might had same pathogenesis and represented pathologic different stages.Deduced that T₂HS represented early stage, next to SONK and OCD, last to OAPC with progress.2 SONKand OCD were suggested to reduce to a kind of disease nominated stress osteonecrosis, T₂HS was nominated focal stress contusion of bone.3 The area of subchondral lesion, abnormality of meniscus,abnormality of ACL and PCL , joint effusion were strongly related to increasing clinical painful symptoms of subchondral focal lesions of the knee.