Knee Osteoarthritis After Anterior Cruciate Ligament Injury

s of 2199 studies were reviewed from the systematic searches. The systematic searches resulted in 1769 abstracts in PubMed and 85 abstracts in EMBASE. A search using the search terms anterior cruciate ligament injury and osteoarthritis identified 16 abstracts in AMED and 329 abstracts in PubMed. Based on the inclusion criteria, 33 studies were included. Seven studies were assessed as prospective, and 26 studies were assessed as retrospective. Twenty-four studies were identified in PubMed, 2 studies were included from EMBASE, and 7 were identified by manual searches of journals and reference lists in relevant studies. These 7 studies did not appear in the systematic searches because of the missing citation term osteoarthritis. Two of the studies were later excluded owing to use of the same study population as that of later published studies. No additional studies were identified in AMED. Finally, 7 prospective studies and 24 retrospective studies were included. Only 1 of the prospective studies was a randomized study evaluating long-term results after primary repair or nonsurgical treatment of ACL injury. The characteristics of the studies are presented in Appendix 2 (available online at http://ajs.sagepub.com/ supplemental/). The total number of subjects included was 3069, with sample sizes ranging from 24 to 328 patients. Twenty studies included radiologic assessment of 1114 surgically treated subjects, and 5 studies included radiologic assessment of 276 nonsurgically treated subjects. Three studies evaluated 517 surgically and nonsurgically treated subjects including radiologic assessment. Three studies included radiologic assessment of 273 nonsurgically and surgically treated separately. Hence, radiologic evaluation was carried out on 2180 of the included subjects, resulting in a radiologic follow-up rate of 71%. Eleven studies reported radiologic results for the contralateral knee, involving 666 knees. Surgical procedures for the ACL injury reported in the studies were primary repair with or without augmentations, bone–patellar tendon–bone grafts, looped semitendinosus tendon grafts, or fascia lata allografts. The mean follow-up time in the included studies was 13.7 years, with a variation from 10 to 27 years. Preinjury activity level was reported in 11 studies with a mean Tegner score of 6.7, with the lowest score of 5.7 and the highest score of 9. Fifteen studies reported follow-up activity level with a mean Tegner score of 5.1, with the lowest score of 3.7 and the highest score of 6.4 (Appendix 2). Methodological Quality The results of the study quality assessments are presented in Table 2. For part A, “type of study” and “number of treatment procedures” gave the lowest scores. For part B, the lowest scores were achieved for “outcome criteria” and “description of subject selection process. ” None of the studies fulfilled all the criteria (modified CMS of 90); however, 1 study revealed a modified CMS of 88. The mean modified CMS was 52 ± 13, which corresponds to a CMS of 58 when transferred to a 0 to 100 score. The lowest score achieved was 22, and the highest was 88 (Table 3). The prospective studies achieved a mean modified CMS of 69, with a highest score of 88 and a lowest score of 61. The retrospective studies correspondingly achieved a mean modified CMS of 47, with a highest score of 59 and a lowest score of 22. Prevalence of Knee OA The overall prevalence of OA in the tibiofemoral joint varied between 1% and 100%. The corresponding prevalence in the contralateral knees revealed 0% to 38%. The prospective studies reported prevalences of knee OA between 1% and 100%, and the retrospective studies reported prevalences of knee OA between 13% and 100% (Table 3). Studies that reported results for isolated and combined ACL injuries separately reported knee OA between 0% and 39% and between 21% and 100%, respectively (Table 3). Two nonrandomized studies, 1 of which revealed the highest methodological score, reported a significant difference in knee OA development between nonsurgically treated and surgically treated. No differences were reported for the prevalence of knee OA between surgically treated (29%-51%) and nonsurgically treated subjects (24%-48%) for other included studies. Studies including subjects with a preinjury Tegner score of more than 7 or studies that included only soccer players reported a prevalence of knee OA between 8% and 100%. Studies including subjects with lower preinjury Tegner scores reported a prevalence between 11% and 66%. Radiologic Classification Methods Seven different radiologic classification methods were used in the 31 included studies. Five studies used the Fairbank classification system with a reported prevalence References 13, 22, 34, 36, 43, 47, 49-51, 54, 55, 58, 61-63, 68, 69, 75, 77-79, 83, 86, 88, 90, 94. at UIO BIBLIOTEK FOR MEDISIN OG on July 8, 2009 ajs.sagepub. com Downloaded from Vol. 37, No. 7, 2009 Knee Osteoarthritis After ACL Injury 1437 of knee OA between 8% and 100%. Two studies used the Ahlbäck classification system with a reported prevalence of knee OA between 11% and 44%. Two studies reported a prevalence of knee OA between 16% and 50% using a combination of Fairbank classification system and Ahlbäck classification system. The Kellgren and Lawrence classification system was used in 5 studies, and the Osteoarthritis Society Research International classification system was used in 3 studies, with a reported prevalence of knee OA of 24% to 48% and 16% to 48%, respectively. Ten studies used the IKDC classification system. The reported prevalence of knee OA in these studies was between 1% and 100%. Four studies did not specify radiologic classification system but used a combination of joint space narrowing (JSN) and osteophyte formation. These studies reported a prevalence of knee OA between 21% and 77% (Table 3). Most of the studies reported that the radiographs were performed with the patients in the standing position with full weightbearing (n = 30) and with a knee flexion angle of 15° to 45° (n = 17). Risk Factors for the Development of Knee OA Identification of risk factors using regression analysis was conducted in only 3 studies. Risk factors identified in these 3 studies were ACL surgery, age, body mass index, <90% on single-legged hop test compared with the uninjured side 1 year after surgery, loss of extension, and laxity. In the remaining studies, risk factors were identified using group comparisons. Risk factors reported were meniscectomy, patients older than 25 years at injury, obesity, more than 6 months between injury and surgery, high level of sports activity, OA of the contralateral knee, chondral lesions, knee joint laxity, and duration of follow-up. Meniscal injury and meniscectomy were the most frequently reported risk factors (Table 3).