Although numerous classifications of meniscus tears exist, the one proposed by O’Connor has proved useful. It classified the patterns of meniscus tears into the following categories: (1) longitudinal tears, (2) horizontal tears, (3) oblique tears, (4) radial tears, and (5) variations, which include flap tears, complex tears, and degenerative meniscus tears [11]. Horizontal tears tend to be more common in older patients, with the horizontal cleavage plane occurring from shear, which divides the superior and inferior surfaces of the meniscus. Many flap tears and complex tears begin with a horizontal cleavage component. These are more commonly seen in the posterior half of the medial meniscus or the midsegment of the lateral meniscus.
For the degenerative horizontal tear of the medial meniscus, even no significant difference exist between arthroscopic meniscectomy and non-operative management with strengthening exercises in terms of relief in knee pain, improved knee function, or increased satisfaction in patients after 2 years of follow-up [12]. When considering the risk vs. the benefits of the treatment, conservative therapy is recommended [13]. However, the horizontal tear at the midsegment of the lateral meniscus is most likely located in the popliteal hiatus region. In most instances, either the superior or the inferior leaf is resected to reserve the stable leaf. Based on previous research, the total perimeter of the lateral meniscus was 8.9 ± 0.7 cm, and the length of the hiatus was 1.3 ± 0.1 cm [4]. Without such a distance of the meniscus fixation from the coronary ligament and the knee joint capsule, the remaining superior or inferior leaf is not stable, especially when the tear extends anterior to posterior. On the other hand, a total or partial meniscectomy may result in negative outcomes, including joint alignment, contact pressure, and degenerative changes, which should be avoided [1, 5, 14].
Recently, a case series report recommended a novel arthroscopic all-inside suture technique using the Fast-Fix 360 system (Smith & Nephew, Andover, MA) for repairing horizontal meniscus tears. In this case series, all three patients were athletes and able to resume sport activities a year after surgery. Their postoperative mean Lysholm knee score was 99.7, with absence of pain, complications, and recurrence of meniscus tear. And the MRI signal intensity of all the horizontal tears decreased after surgery, suggesting healing of the repaired tear [15]. A systematic review shows that studies of repaired horizontal cleavage tears show a comparable success rate with repairs of other types of meniscus tears [16]. As a result, repair may be an option, especially for a recent tear and younger patients. When compared with other suturing methods, the all-inside meniscus repair systems have increased in popularity, since they have been shown to be faster and simpler than other methods for meniscus repair, such as meniscus arrows (Bionx Implants, Malvern, PA), Fast-Fix system (Smith & Nephew, Andover, MA), and RAPIDLOC meniscus repair system (Depuy Mitek, Johnson & Johnson, USA) [7]. Usually, sutures are inserted anterior and posterior to the popliteal tendon, with a minimum interval of 1.3 ± 0.1 cm along the length of the hiatus, which may leave the meniscus in the interval unstable. Iatrogenic injury may occur on the adjacent popliteal tendon, common peroneal nerve, and ILGA due to sharp contact of these meniscus repair systems when penetrate them to outside of joint capsule. Use of the outside-in or inside-out technique may injure the common peroneal nerve and ILGA if they have not been protected in advance [7, 8, 17]. The ILGA mainly supplies blood to the lateral meniscus avascular zone adjacent to the popliteus tendon, which is critical for meniscal healing after repair [18]. Insertion of surgical anchors of the meniscus arrows or sutures through the popliteal tendon may lead to iatrogenic injury or irritation to this structure and suture loosening during knee movement [19]. In addition, these repair methods lock the joint capsule with remnant meniscus tissue which was relatively free to the joint capsule, resulting in a reduction of normal movement of the meniscus and the size of popliteal hiatus as well. Both of these outcomes may interrupt the normal biomechanics and kinematics of the lateral knee compartment. However, additional studies are needed to determine and evaluate how the knee joint is affected by these. The current suture method may decrease the risk of complications mentioned above. Firstly, it may preserve more meniscus tissue when compared with a meniscectomy, which benefits the joint alignment and contact pressure. Also, it increases stability of the remnant meniscus which can be achieved if the two leaves heal together, unlike the instability of single laminae alone without fixation from the coronary ligament and knee joint capsule. The most important point is that it is truly all-inside and the intracapsular procedures may avoid injuring the adjacent extracapsular structures [20, 21].
Healing of the reserved meniscus shows a comparable success rate of repair for horizontal cleavage tears; it may be lower at the popliteal hiatus region because of the absence of peripheral vasculature [22]. Postoperative recovery was determined by MRI scan at 6 months because second-look surgery was always rejected in cases without many discomforts. Surgical follow-up was evaluated by the Lysholm knee score. Because the high intensity in MRI may last for a long time, according to Muellner T, the grade III and IV signal alterations can be present on MRI scans in more than 50% of the repaired menisci even after 12 years [23]. Although nine cases still showed a high intensity on T2-weighted MRI in reserved meniscus tissue, all repair cases were considered successful according to the Lysholm knee score. It is suspected that the successful outcomes could be due to the sutures that bind the two separate laminae together and maintain the stability of the lateral menisci. At this time, it is unclear which suture, absorbable or nonabsorbable, is superior. Unfortunately, no nonabsorbable sutures with a similar diameter as the one in Fast-Fix system (Smith & Nephew, Andover, MA) were available at our facility. Another concern is that nonabsorbable sutures remain permanently in the joint cavity. Consequently, an absorbable suture with a suitable diameter (1–0 VICRYL PLUS®, Ethicon, Somerville, NJ) was used in all cases, which is a synthetic, braided suture, made from copolymer (polyglactin-910) of glycolide and lactide, and is absorbed through hydrolysis. Its unique coating and braided feature is easy for smooth passage through tissue, knot tying and knot security. But is need to be worried that its tensile strength of the suture in soft tissue can decrease to 75% after 2 weeks, 50% after 3 weeks and 25% after 4 weeks, and it is completely absorbed within 56–70 days. But it is still unclear about the decline rate of tensile strength in knee joint because of lack of report. Anyway, as indicated in Campbell’s Operative Orthopaedics, the ideal suture material has not been determined, because the human meniscus requires several months to heal completely, the suture selected for meniscal repair should be capable of providing adequate support for this period.Most early reports of meniscal repair advocated the use of an absorbable suture, such as polyglycolic acid (Dexon), polyglactin-910 (Vicryl), or polydioxanone (PDS). As a matter of fact, the mechanical effects of normal joint motion probably cause failure of even nonabsorbable sutures over time [24]. As a result, several movements are banned in 6 months including squatting, excessive flexion, and sitting with legs crossed.
This study still has some limitations. Firstly, we did not evaluate postoperative healing with a second-look surgery which is the current gold standard. MRI follow-up was preferred to avoid complications and pain issues from an additional surgery. Secondly, due to our low subject count and short follow-up period, additional patients need to be recruited with a longer follow-up of up to 2 years, including additional MRI scans for healing assessment. An additional limitation was that this study was uncontrolled. It will be more convincing with comparison groups using an alternative meniscal repair technique or non-surgical management.