The discoid medial meniscus is rare with an estimated prevalence of 0.12% . Surgical intervention is often required for symptomatic discoid meniscus. Biomechanical studies have shown that the meniscus plays an important function in load transmission, stability, lubrication and nutrition of the articular cartilage [6,7,11,12]. Historically, total menisectomy was the treatment of a symptomatic discoid meniscus, however this results in progressive osteoarthritis and a poor prognosis . Arthroscopic partial excision and/or saucerisation of the meniscus have been recommended for symptomatic discoid meniscus and better results have been reported with this [6,9,14]. Ogata  demonstrated excellent results in 86% of 76 patients who underwent partial menisectomy for symptomatic discoid meniscus, with no patients requiring repeat operations for poor results.
The meniscus in the normal knee joint plays an important function, thus partial menisectomy is the preferred arthroscopic treatment of symptomatic discoid meniscus [6,14,15]. There have been many reported methods of arthroscopic partial menisectomy such as open excision, one or two piece excision, and piece-meal arthroscopic excision [3,16-18]. Piecemeal excision of a discoid meniscus can potentially be difficult to perform if working space is limited, including the need for a larger portal to remove a large piece of meniscus .
It is important to leave a rim of meniscus, free of any remaining tears. By doing so, the remaining portion performs the function of the meniscus, preventing instability from total menisectomy . The width of the remaining meniscus rim are dependent on the type of meniscus and on the shape and extent of the torn meniscus . Hayashi et al.,  left widths of 6 mm and 8 mm for complete and incomplete type lesions respectively. Ogata  would routinely leave a peripheral rim of 6 to 8 mm. Vandermeer and Cunningham  have left widths of 4 to 5 mm. We felt a width of 5 to 6 mm provided a stable rim with no impingement of the femoral condyle against the remaining rim.
Arthroscopic treatment of a complete discoid meniscus is a technically demanding procedure. The one piece excision technique described by Kim  requires a third portal, repeated changes in instrumentation, and a large portal for removal of a large piece of meniscus. Other piecemeal excision techniques can prove to be difficult and time consuming, with difficulty in initiating the excision point, frequent passage of instruments and the possibility of leaving excised meniscus in the joint .
To our knowledge, there have been no reports of arthroscopic coblation for saucerisation of a discoid meniscus. We found that there were a number of advantages to our technique compared with other described techniques. We had few changes in instrumentation when resecting a portion of the discoid meniscus. The progressive nature of resection allows constant evaluation of the amount resected and the shape of the remaining rim, whereas many other techniques involve excising the portion in one go. It also avoids piecemeal excision, which would otherwise produce free floating pieces of meniscus which need to be removed. The Arthrowand suction draws free-floating tissue to the electrodes, negating the need for chasing evasive tissue. This has the added advantage of reduced operative tourniquet times. The 50 degree angle on the coblator allows a wider degree of freedom and working angle, which we found to be suitable for shaping the meniscus. Post-operative MR scans demonstrate the remaining rim of meniscus, closely resembling a ‘normal shaped meniscus’ and preserved chondral surfaces (Figure 7). This technique is theoretically reproducible with different manufactures of coblators. Our reasons for using the Arthrocare Arthrowand Super Vac 50 was due to surgeon training/familiarity and product availability as well as some of the features of this product. The estimated temperature at the tip of the instrument is 20-60 degrees centigrade. Safety features include a 100μm - 200μm plasma field allows for precise removal of soft tissue with minimal damage to untargeted tissue. Nevertheless meticulous technique and care must still be taken to avoid iatrogenic damage. Various manufacturers offer different technologies to the safety and efficacy of their products, but it is not within the scope of this article to discuss further. Although this is presented as a new technique for a rare condition, we see no reason why this technique may not be applied to more common presentations, such as a lateral discoid meniscus or meniscal tears, but strongly advocate proper training and education in the use of such instruments. We also eagerly await the long terms results following our use of this technique to confidently confirm adequacy of resection and the benefits and safety of this technique.
In summary, we have demonstrated a simple technique for the saucerisation of a medial discoid meniscus which is easy and quick to perform in comparison with other known techniques.