The outside- in technique was developed as a means of minimizing the chance of neurovascular injury that was often seen with inside-out repairs [7]. First described by Warren et al in 1985, this arthroscopically guided technique involves the percutaneous passage of suture into the joint through a cannulated needle placed across the tear [16, 17]. The suture is subsequently retrieved through a second needle, and final fixation is performed extracapsularly via a small portal-sized counterincision. It is most suited for repairing anterior horn tears and middle third tears, and advantages of this method stem from the fact that it is simple, minimally invasive, and inexpensive [18, 19].

There are variations in outside-in repair technique. In its most simple form, all that is required is an 18-gauge needle, suture, and an arthroscopic grasper [20] (Fig. 7.3). Simple “Mulberry Knots” can be created using absorbable suture; however, the authors favor the creation of a vertical mattress configuration. A small needle is percutaneously inserted at the joint line across the tear. If the location is satisfactory, then a small portal like incision is made. First, a 15 blade is used to open the skin and then a hemostat is used to spread down to the capsule. An 18-gauge needle is preloaded with a long (40 cm) suture, either braided or mono-filament, making sure that approximately 10 cm of the suture extends passed the tip of the needle. This will affect a loop when the meniscal tissue is penetrated. While visualizing the tear through the contralateral portal, the needle is passed from the new portal into the joint percutaneously. It should cross the inner and outer rim of the tear, making sure that it ultimately exits the superior surface of the inner rim. A probe can be used to aid in reduction of the tear during passage of the needle while keeping the inner rim from being pushed away from the needle. Once the needle is passed, a grasper is used to grab the created loop of suture at the meniscal inner rim. The needle is then carefully removed from the joint, unloading the remaining suture, making sure not to pull the suture loop from the joint. The 18-gauge needle is then reinserted along the same portal, this time perforating just the outer meniscal rim and again exiting across the superior meniscal surface. This needle should be directed so that it perforates the meniscus to create a vertical or oblique mattress configuration. A separate suture is then passed through the needle and into the joint. A grasper is inserted in the ipsilalteral portal and directed through the loop of the first suture to grab the protruding limb of the second suture. The needle is carefully removed and then the suture is delivered out of the ipsilateral portal. The suture creating the loop is pulled out of the joint, and in effect, the second suture is shuttled through the path of the first insertion, thereby creating a vertical mattress configuration with the second suture. The suture is then tied under arthroscopic visualization to ensure proper tension on the knots.

Commercial kits, such as the Meniscus Mender II (Smith and Nephew Endoscopy, Andover, MA), have also become available for outside-in techniques. With this repair system, two needles are again placed in and outside-to in fashion across the desired sites of fixation. Wire loop stylets are then inserted into the needles. Suture is introduced into the joint via the ipsilateral anterior portal and subsequently fed through one of the loops. The loop stylet is pulled back, capturing the suture, and the loop and needle are carefully removed from the joint. The process is repeated again for the free suture limb within the joint. A knot is similarly tied down extracapsularly using a small portal-sized counterincision.

Smaller counterincisions in the outside-in technique have minimized risk to the neurovascular structures. However, these neurovascular structures must be respected: the common peroneal nerve in the lateral aspect of the knee and the saphenous nerve/vein in the medial aspect. The outside-in technique has proven to be successful in the tears of anterior meniscal tears; however, it is more difficult for tears in the posterior horns of the menisci.

The all-inside repair, otherwise known as the “all-arthroscopic” technique, was first introduced to the field of orthopaedics by Morgan et al in 1991 [21]. In this study, the authors utilized posterior accessory portals and suture hooks to shuttle absorbable suture through posterior horn meniscal tears. Subsequent all-inside techniques obviated the need for posterior portals by using meniscal fixators. The orthopedic world has since seen the rapid evolution of the all-inside repair, from rigid devices with barbs to suture-based configurations that allow tensioning after when inserting. Owing to their ease of use, decreased operative time, and lesser risk to neurovascular structures, these all-arthroscopic meniscal fixators have revolutionized the way in which meniscal repairs are performed. Furthermore, newer generations afford pull out strength comparable to inside-out repairs [22–25].

The evolution of fixators came about as a response to the difficulties that arose with the first-generation suture hooks. Many orthopedic surgeons found the tools to be cumbersome and the technique technically demanding [26]. Additionally, given the necessity of creating accessory, posterior portals for passage of instruments, the neurovascular structures were still deemed to be at risk. Thus, the second generation of constructs relied on the use “suture anchors”—implants placed across the tear and affixed along the outer meniscal rim. One such device is the T-fix (Smith & Nephew), an implant comprised of a 3 mm polyethylene bar connected to a 2.0 braided suture at its midpoint. Using a spinal needle, the implant is delivered across the meniscal tear, and to the other surface of the meniscus. A second anchor is passed and deployed adjacent to the first anchor, and a knot pusher is used to tie the two sutures arthroscopically. This technique represented the first all-inside suture technique that did not require the use of any accessory portals. Though results from use of the T-Fix were favorable, the desire for improved compression paved the way for the next generation of fixators [26].