Background: Post-arthroscopic osteonecrosis of the knee (PAONK) is a rare disorder condition. In addition, no studies have analyzed the relationship between the meniscus extrusion and PAONK. The purposes of this retrospective study are to report 10 cases of PAONK and to evaluate location of the MM in the joint space, including the meniscus extrusion, before and after the meniscectomy in these 10 knees.
Methods: Ten knees with PAONK were found in 876 knees which had undergone arthroscopic partial meniscectomy of the medial meniscus (MM). We retrospectively collected the clinical, surgical, and radiological data of these 10 patients. To evaluate intraarticular location of the menisci in the joint space, Extrusion width and Inner width were defined on magnetic resonance images, and they were statistically compared.
Results: In the 10 patients (2 men and 8 women; the age ranged between 60 and 80 years), knee pain recurred within 12 weeks after the meniscectomy. Preoperatively, the Extrusion width of the MM (the mean, 4.7 mm) was significantly greater (P<0.0001) than that of the LM (0.2 mm). At the time of diagnosis of PAONK, the Extrusion width of the MM significantly increased by 1.2 mm and the Inner width was significantly reduced by 3.9 mm, compared with the preoperative values (P<0.0001).
Conclusion: This is the first report that, in each of the 10 knees with PAONK, the MM had been extruded before the meniscectomy, and then, the Inner width of the MM almost disappeared postoperatively due to not only the increased meniscal extrusion but the partial meniscal resection. This study suggested that the intraarticular abnormal location of the MM, including the meniscal extrusion, is a critical factor that should be evaluated in future studies to clarify causative factors of PAONK.