Arthroscopic lateral discoid meniscectomy. Case discussion and review of literature

摘要

Discoid meniscus is a morphological anomaly which was described for the first time in the late nineteenth century. It is most commonly found on the lateral aspect of the knee and can be associated with significant morbidity. With the advent of arthroscopic surgical management, either partial or sub-total meniscectomy (depending upon the type of the anomaly) is replacing older techniques. We present our experience with four cases of discoid meniscus treated with arthroscopic partial meniscectomy. Introduction Discoid meniscus, a morphological anomaly of the normal meniscus [1], was first described in a dissecting room specimen as early as 1889 by Young. This anomaly occurs almost exclusively on the lateral side of the knee joint, reportedly resulting in 1.2% to 5.2% of all meniscectomies [2]. However, Ikeuchi [3] reported that, during a twenty-year period, almost half of the patients whom he managed for a meniscal lesion had a discoid lateral meniscus. He found a lateral discoid in 17% of the knees that were examined arthroscopically. Watanabe [4] classified this anomaly based on the degree of coverage of the tibial plateau and the presence or absence of normal posterior attachment. He identified these as complete, incomplete, and the Wrisberg-ligament type. The most common symptoms, which usually occur during childhood and adolescence, are a clunking sound with flexion of the knee, pain, and a decreased range of motion. Vague and intermittent symptoms associated with discoid meniscus may cause difficulty and delay in the diagnosis. Precise diagnosis has become possible using magnetic resonance imaging (MRI) and arthroscopy of the lesion. In the past, failure of conservative treatment has led to open total resection of the anomalous structure [2] but nowadays arthroscopy permits a more accurate diagnosis and treatment of the lesion [5-7]. Recent biomechanical studies of knee function have revealed the importance of the menisci, and partial, instead of total resection of the meniscus is advocated to avoid stress concentration [8]. In 1957, Kaplan [9] recommended complete excision of a discoid meniscus through two incisions. Since then, several authors [10-12] have recommended partial arthroscopic meniscectomy. However, Aichroth et al. [5] preferred a total meniscectomy if the discoid lateral meniscus is unstable (Wrisberg-ligament type). The short-term (three-to-seven-year) clinical and radiographic results after partial or total removal of symptomatic discoid lateral menisci in children have been favorable [6, 13, 14]. However, studies of the long-term effects of partial or total lateral meniscectomy suggest that there is a high prevalence of osteoarthritic changes [2, 10, 12]. In addition, lateral instability has been reported after total removal of a discoid lateral meniscus, especially in children [8].Abdon et al [1] reported that out of eighty-nine patients fifty-two (58%) had satisfactory results after total removal of a normal shaped meniscus with use of the Smillie technique [15]. According to the grading system of Ahlb?ck [16], as modified by Johnson et al.[17] thirty-five patients (39%) had grade-I osteoarthrosis and eight (9%) had grade-II or III osteoarthrosis at a mean of seventeen years after the operation. We report our experience with discoid meniscus and treatment of four cases with arthroscopic partial meniscectomy. Case Series A total of 4 patients were diagnosed with lateral discoid meniscus at our institution from March 2002 to March 2007. Pertinent patient characteristics have been included in Table 1. All cases had unilateral knee involvement and underwent partial meniscectomy following arthroscopy. The tabulated results were obtained at the last follow-up examination.* Based on pre-operative MRI scan and arthroscopic finding