The well established importance of the meniscus in load transmission across the knee joint has led to the development of techniques to repair meniscal tears. Advances in our understanding of the basic biology and the healing of the meniscus have improved our ability to select appropriate tears for repair and to design methods to enhance meniscal healing. Both open and arthroscopic repair techniques have been found to be effective for meniscal suturing. The outside-in technique of arthroscopic repair of the meniscus was developed by Warren as a method to decrease the risk of injury to the peroneal nerve during arthroscopic repair of the lateral meniscus37. This technique is especially useful for repairing tears in the anterior portion of the meniscus, for suturing a meniscal replacement (such as an allograft or a collagen meniscal implant), and for inserting a fibrin clot into a repair site. This paper reviews the technique, indications, and results of meniscal repair with use of the outside-in method.
*Printed with permission of the American Academy of Orthopaedic Surgeons. This article, as well as other lectures presented at the Academy's Annual Meeting, will be available in March 2000 in Instructional Course Lectures, Volume 49. The complete volume can be ordered online at www.aaos.org, or by calling 800-626-6726 (8 A.M.—5 P.M. Central time).
†No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
‡The Hospital for Special Surgery, 535 East 70th Street, New York, N.Y. 10021. E-mail address: rodeos@hss.edu.
The indications for meniscal repair have been well defined. The important factors for consideration include the location of the tear, the type of tear, the quality of tissue, chronicity, the age of the patient, and the stability of the knee. The most important factor in determining repairability is the location of the tear, as tears in the vascular periphery of the meniscus can mount a healing response. The ideal tear is an acute, vertical, longitudinal tear in the peripheral one-third of the meniscus in a young patient who has a stable knee or will have concomitant reconstruction of the anterior cruciate ligament. Because of the importance of the meniscus, repair can be considered for tears that extend into the central, avascular zone of the meniscus in younger patients. In support of invasive attempts to repair such tears, Rubman et al. reported that 159 (80 percent) of 198 knees in which a tear in the central, avascular zone had been repaired had no symptoms at the time of follow-up28. Most bucket-handle tears are repairable as long as the handle fragment is not extensively deformed. Flap tears and horizontal cleavage tears generally are not repairable. Radially oriented tears in the posterior horn of the meniscus may be repaired because of the rich blood supply in this region, but radial tears in the middle portion of the meniscus have a poorer potential for healing7. However, an attempt at repair of a large, radial split tear should be considered in a young patient, as a radial tear through the entire width of the meniscus may effectively render the meniscus nonfunctional because of the loss of the ability to transmit hoop stresses. Because clinical studies have demonstrated that the rates of healing after repairs of the lateral meniscus are better than those after repairs of the medial meniscus, there are broader indications for repair of the lateral meniscus7,20,21,35. Similarly, studies have demonstrated the highest rates of healing after concomitant reconstruction of the anterior cruciate ligament, with these rates having been better even than those for knees with a stable cruciate ligament7,20,21; thus, more intensive attempts at repair may be indicated if reconstruction of the anterior cruciate ligament is also being performed.
Although both acute and chronic tears can be successfully repaired, Henning et al.13 as well as Tenuta and Arciero31 reported better rates of healing after acute repairs. Many studies have demonstrated higher rates of failure after meniscal repairs performed in knees with an injury of the anterior cruciate ligament, and thus concomitant reconstruction of the anterior cruciate ligament is recommended5,26,27. However, repair should still be considered for an unstable knee if the tear is otherwise repairable (especially if the tear is in the lateral meniscus) and the patient is young. In that situation, the clinician needs to carefully inform the patient that persistent instability of the knee increases the risk of failure. It is generally believed that there is poorer potential for healing in older patients, but successful repair of tears in patients who were more than fifty years of age has been reported21,28.
Degenerative meniscal tissue is believed to have a poorer potential for healing; thus, careful attention should be paid to the appearance and consistency of the meniscus at the time of the operation. Abnormally increased intrameniscal signal intensity on magnetic resonance imaging studies is also helpful in the assessment of meniscal integrity. Tears that occur atraumatically in a stable knee may be due to intrinsic meniscal degeneration and probably have a poor potential for healing. A final factor that the clinician should consider when determining if a meniscal tear is repairable is the axial alignment of the limb. For example, Habata et al. reported an association between atraumatic tears of the medial meniscus and varus deformity12. Although preservation of the meniscus may be even more important in a knee with axial malalignment (because of higher compressive loads in the involved compartment), the rate of healing may be lower and the patient must be appropriately counseled.
Partial-thickness tears, tears that are stable when probed (usually tears less than one centimeter in length), and shallow radial tears (those that are less than three millimeters in depth) generally do not need to be repaired. Small, vertical, longitudinal tears posterior to the popliteus tendon and small avulsion tears of the posterior horn, in the setting of injury of the anterior cruciate ligament, may remain asymptomatic and only observation is indicated11.
Several techniques are available for meniscal repair; these include the outside-in, inside-out, and all-inside methods. Most repairable meniscal tears can be repaired with any of these techniques. A major advantage of the outside-in method is that sutures can be placed without the need for a rigid cannula. The use of such a cannula with an inside-out technique is associated with a risk of scraping the articular surfaces. There is some risk of causing minor damage to the articular surfaces when needles are introduced from outside the joint, but as the needles enter under direct visualization there is only a very small chance of substantial injury to the articular cartilage. Another major advantage of the outside-in technique is that a large posterior incision for placement of a posterior retractor is not needed. Only a small incision is made to tie the sutures over the capsule. The outside-in technique also allows precise placement of sutures in areas to which there is limited access, as only small needles are used instead of the larger cannulas or needle-holder used in the inside-out technique. This use of small needles can facilitate the vertical placement of sutures. The use of a distractor is rarely required, as only a small needle needs to enter the joint space. Except in very tight medial compartments, excellent visualization is possible, as there are no instruments between the meniscal tear and the arthroscopic view.
Injury to the peroneal nerve is easily avoided with use of the outside-in method for repair of the lateral meniscus, as the starting point for entry of the needle is controlled and the nerve can remain untouched. On the medial side, injury to the saphenous nerve and vein is avoided by starting the point of entry of the needle posterior to the semitendinosus tendon with the knee in extension, as the saphenous nerve and the infrapatellar branches cross the medial joint line anterior to the semitendinosus tendon when the knee is in extension. It is easy to gain access to tears in the anterior portion of the meniscus with this technique.
The outside-in method is also useful for suturing a meniscal replacement (such as an allograft or a synthetic device) to the capsule (Fig. 1). Implantation of a collagen meniscus implant, which is currently being assessed as a segmental meniscal replacement in clinical trials, may be facilitated with use of the outside-in technique. Implantation of this device requires introduction of a grasping instrument into the joint through an anterior portal to hold the implant; thus, suturing may be easier if the needles are placed from outside to inside. The outside-in method is also useful for securing materials such as a fibrin clot or a carrier containing growth factors to a repair site. A suture can be placed across the tear, and then the implant or fibrin clot can be attached to the suture and brought into the site of the tear (Fig. 2). Future treatments for meniscal tears may include novel biologically based implants, such as tissue-engineered meniscal tissue or genetically altered cells. Implantation of such devices may be facilitated by arthroscopic techniques of repair that allow placement of a suture at a precise spot along the meniscus.
Van Trommel et al. recently reported successful repair of complete radial tears of the lateral meniscus with use of the outside-in technique with an exogenous fibrin clot34. Recently, the outside-in technique has also been found to be very useful for repair of unstable Wrisberg-type discoid mensici in young children with small joints. The rigid cannula used for the inside-out technique is sometimes too large for small joints, and its use in such joints is associated with a risk of injury to the cartilage.
There are several disadvantages to the outside-in technique. It can be difficult to place sutures perpendicular to the surface of a tear that is far posterior, and this difficulty can result in oblique orientation of sutures and possibly less coaptation force across the tear35. In this setting, the inside-out technique with a posterior incision may be preferable. All inside techniques are also advantageous for tears of the posterior horn. If knot-end sutures (so-called Mulberry knots) are used with the outside-in technique, the knot may potentially abrade the articular surface before absorption, although to my knowledge this has not been reported and has not been observed in my experience. Another relative disadvantage is that, in order to use permanent sutures with the outside-in technique, they must be brought in through the anterior portal (described in the sections on Technique), as most braided sutures are difficult to push through the spinal needle. Lastly, since the needle comes across the tear blindly from the outside, experience is required to become accurate at placement of the needle. Secure repair of a meniscal tear or replacement often may require a combination of methods, and thus the surgeon should be comfortable with several techniques.
The outside-in method requires only 18-gauge spinal needles, an arthroscopic grasper, and material for sutures26. A tourniquet is placed proximally on the thigh but is rarely inflated during meniscal repair. The limb should be placed on the operating table in such a position that when the end of the table is flexed the end of the thigh protrudes over the table break. This provides access to the posteromedial corner of the knee. If a limb-holder is used, it should be placed high enough on the thigh to allow access to the posterior corners of the knee. A careful arthroscopic inspection is performed first. Visualization of the posterior horn is facilitated by inserting the arthroscope through the anterolateral portal and passing it between the posterior cruciate ligament and the medial femoral condyle. Viewing in this position may also be facilitated by the use of a 70-degree arthroscope, which allows accurate evaluation of the posterior meniscosynovial junction. The tear is carefully probed to determine if the torn fragment is unstable and to define the length of the tear accurately.
It is important to abrade the surfaces of the tear before placement of the sutures in order to create a bleeding bed at the repair site and to stimulate vascular ingrowth. This may be accomplished with a rasp or a 3.5-millimeter full-radius resector. The surgeon may also consider abrading the synovial membrane immediately adjacent to the tear to stimulate additional vascularity as well as using a fibrin clot to augment healing in isolated meniscal repairs. Ritchie et al. showed that abrading the parameniscal synovial membrane for the repair of centrally located tears (tears with marginal vascularity) in a goat model resulted in healing in seven of eight knees24. A rasp or shaver may be introduced through a posteromedial portal. The site of entry for a posteromedial portal may first be localized with a spinal needle. The portal is made posterior and proximal to the medial joint line, remaining anterior to the pes anserinus tendons with the knee in flexion.
Once the site of the tear has been prepared, the knee is placed in approximately 10 degrees of flexion for repair of the medial meniscus and a valgus load is applied to open the medial compartment. A valgus load also approximates the capsule to the meniscus, thus aiding in accurate meniscal repair. The starting point for entry of the needle is located by palpation and by the use of topographical landmarks. Transillumination may be used to identify the saphenous nerve and vein. While the meniscus is viewed arthroscopically, the needle is placed across the site of the tear from the outside. The needle passes across the meniscal tear and penetrates the inner segment of the meniscus, coming through either the superior (femoral) or the inferior (tibial) surface. Placement of the needle across the meniscus may be made easier by the use of a probe or a small loop curet introduced through the anteromedial portal to provide counterpressure on the meniscus. Since most tears of the medial meniscus extend into the posterior aspect of the meniscus, the site for entry of the needle should be posterior to the palpable semitendinosus tendon because the saphenous nerve and its infrapatellar branches are anterior to the semitendinosus tendon when the knee is in extension. Curved needles (commercially available or prebent by the surgeon) may be used for posterior tears to decrease the need for a posterior starting point and thus to decrease the risk of neurovascular injury. For tears of the anterior horn, the knee can be placed in 50 to 60 degrees of flexion, and the site of entry of the needle is then anterior to the pes anserinus tendons and the saphenous nerve branches.
A second needle is then passed from the meniscus adjacent to the first needle to achieve proper orientation of the suture. It is helpful to place both needles across the site of the tear before passing the sutures in order to avoid cutting a previously placed suture with the second needle. Polydioxanone (absorbable) suture (Ethicon, Somerville, New Jersey) is passed into each needle, grasped inside the joint, and pulled out through the anterior portal. Polydioxanone suture is used because it is rigid enough to be pushed through the needle. If the needle points down toward the tibial surface as it enters the joint, the suture will be difficult to pass into the joint because the needle will hit the tibial surface. This problem can be solved by the use of a probe passed through the anterior working portal to hold up the tip of the needle and thus allow easier passage of the suture into the joint. The needle can also be manipulated from the outside to place the tip in a position that will allow easy passage of the suture into the knee.
The position of the second needle depends on how the sutures are going to be secured, as there are several ways to complete the repair. A knot may be made in the end of the suture with three or four throws in a standard square-knot configuration. For this method, the suture is grasped inside the joint and pulled out through the anteromedial portal. A cannula should be used in the anteromedial portal to prevent entrapment of the sutures in soft tissue. An arthroscopic cannula with a seven-millimeter diameter allows passage of most standard arthroscopic grasping instruments. Once the suture has been pulled out through the anterior portal, the knot is made and then pulled back into the joint so that the knot lies against the meniscus and maintains the tear in a reduced position (Fig. 3). If this method is used, the first needle should enter the superior meniscal surface and then the second needle can enter the inferior meniscal surface adjacent to the first needle (Fig. 4). This results in a vertical suture orientation when these adjacent sutures are tied over the capsule. After one set of sutures has been placed, these sutures should be tied and pulled back into the knee before the next set of sutures is placed in order to avoid the tangling of adjacent sets of sutures inside the knee. Placement of sutures should alternate between the femoral and tibial surfaces of the meniscus in order to evenly coapt the meniscus to the capsule. If there is difficulty in placing the needle to enter the tibial side of the meniscus, a probe introduced through the anteromedial portal can be used to tilt the meniscus up, resulting in easier placement of the needle. Each pair of sutures is clamped together until the sutures are ready to be tied at the end of the repair. Sutures should be placed three to four millimeters apart.
An alternative way to complete the repair is to tie adjacent sutures together outside the anterior portal with use of a standard square knot. As mentioned before, a cannula should be used in the anteromedial portal to prevent entrapment of the sutures in soft tissue. The knot is then pulled through the meniscus. This may be facilitated by placing a smaller so-called dilator knot in front of the knot holding the two ends together and then pulling the sutures so that this dilator knot passes through the meniscus before the larger knot does (Fig. 5). This technique allows the creation of a mattress suture. If this technique is chosen, the needles may be placed so as to create either a vertical or a horizontal mattress suture across the tear (Fig. 6). A vertically oriented suture has been demonstrated to have greater pull-out strength than a horizontally oriented suture, most likely because the vertical orientation can more effectively capture the circumferentially oriented collagen fibers of the meniscus22. Vertically stacked sutures may be placed with use of this technique: one needle is placed across the tear, entering on the femoral surface of the meniscus, and the other needle of the pair is placed across the synovial junction proximal to the meniscus. The next set is placed with the first needle entering the tibial surface of the meniscus and the second needle entering across the synovial junction distal to the meniscus. This orientation of the sutures will provide a very secure repair and may be used for the repair of a tear in an unstable knee or if delayed healing is expected because of marginal vascularity.
Another method for passing the suture after the needles are placed across the site of the tear is to pass a wire cable loop (commercially available) through one cannulated needle, place the suture through the other needle, and then place the emerging suture into the wire loop (Figs. 7-A and 7-B). The suture is then pulled through the meniscus, creating a mattress suture. The wire cable loop and cannulated needle are pulled out together, as the doubled suture may not fit easily into the spinal needle. The advantage of this method is that it eliminates the need to pull the sutures out through the anterior portal, where they may entrap soft tissue unless a cannula is used. Use of this method also eliminates the need to pull the knot through the meniscus in order to make a mattress stitch.
In order to use a permanent, braided suture with the outside-in technique, a wire cable loop must be placed across the tear, as was described. The end of the suture is brought into the joint through the anterior portal with use of an arthroscopic grasper and is placed into the wire cable loop (Fig. 8). The suture is then pulled through the meniscus, after which the process is repeated, with the wire cable loop passing the other end of the suture through the adjacent needle14. If the wire cable loop is not available, a polydioxanone suture is placed with use of the standard technique. This suture is brought out through the anterior portal, the desired permanent suture is tied to the polydioxanone suture, and the sutures are pulled back across the meniscus. Adjacent permanent sutures placed in this fashion are then tied together and the knot is pulled back through the meniscus, resulting in a mattress suture.
Most tears that are repaired have a vertical, longitudinal orientation. For a large bucket-handle tear, the first suture should be placed in the middle of the bucket-handle fragment. Traction applied to this suture reduces the bucket handle. Subsequent sutures are then alternately placed anterior and posterior to this first suture until the tear is fully secured. A probe may be introduced through the anteromedial portal to hold the bucket-handle fragment in a reduced position and to prevent displacement of this fragment. For radially oriented tears, a purse-string orientation of sutures is used. One suture limb is placed on each side of the tear, each entering near the inner edge of the meniscus. Ideally, one such set of purse-string sutures is placed on the tibial surface of the meniscus and one set is placed on the femoral surface.
Once the first set of sutures has been pulled back into the knee to reduce the meniscal tear (with either Mulberry knots or a mattress stitch), a small incision is made in the skin and the subcutaneous tissue is spread down to the capsule. Usually, this incision does not need to be longer than ten to fifteen millimeters. It is important to identify and protect the saphenous nerve and vein on the medial side of the knee. All subsequent passes of the needle should be made through this incision, if possible. If repair of a long tear necessitates the placement of sutures over a broader area, a second small incision may be needed more anteriorly. Adjacent sutures are then tied together subcutaneously over the capsule. There do not appear to be any adverse consequences of passing sutures for meniscal repair through the medial collateral ligament, especially if absorbable sutures are used. If there is a possibility of entrapment of some fibers of the medial collateral ligament or the semimembranosus tendon, absorbable (rather than permanent) sutures should be used.
After all sutures have been placed, the tear is reduced and the sets of sutures are tied. Extension of the knee has been noted to reduce the posterior horn of the meniscus to the capsule, and thus the knee is maintained in extension while the sutures are being tied. This position also prevents the entrapment of the posterior part of the capsule and the creation of a flexion contracture. Tying of the sutures begins with the most posterior sutures and proceeds anteriorly. The tear should be carefully inspected after all of the sutures have been tied. A suture that is found to be loose can be tied to an adjacent suture to make it tighter, which avoids the need to replace it. When reconstruction of the anterior cruciate ligament is being done concomitantly, the sutures for meniscal repair are placed first, but they are not tied until the ligament graft has been secured.
The basic sequence of steps for repair of the lateral meniscus is similar to that for repair on the medial side. The patient should be positioned on the operating table so that the knee can be placed into a so-called figure-of-four position (flexion of the knee and external rotation of the hip). In this position, the lateral side of the knee can project over the edge of the table, providing access to the posterolateral joint line. This position also places a varus force across the knee, opening the lateral compartment. The most important consideration in arthroscopic repair of the lateral meniscus is avoiding injury to the peroneal nerve. This is reliably done by keeping the knee in 90 degrees of flexion while passing the needles, as in this position the peroneal nerve falls posterior to the joint line. Injury to the peroneal nerve is avoided with the outside-in technique because needles can be kept anterior to the biceps tendon.
Careful inspection is first performed with the arthroscope in the anterolateral portal. Visualization of the most anterior portion of the lateral meniscus is aided by placement of the arthroscope in the anteromedial portal. It is important to recognize that the lateral meniscus is normally more mobile than the medial meniscus32. The site of the tear is debrided with a rasp or shaver as described for tears of the medial meniscus. An accessory posterolateral portal can be used to aid in the preparation of tears of the posterior horn. This portal is made posterior and proximal to the joint line with the knee in flexion, with care being taken to keep it anterior to the biceps tendon. Localization with a spinal needle is recommended before the posterior capsular puncture.
Needles are then passed across the tear in a similar fashion to that described for repair of the medial meniscus. Curved needles may be used for posterior tears to decrease the need for a posterior starting point and thus to decrease the risk of injury to the peroneal nerve. I recommend avoiding the placement of sutures through the popliteus tendon; however, I have not noted any adverse consequences from the passing of sutures through the popliteus tendon or the fibular collateral ligament, and none have been reported to my knowledge. If there is a chance of entrapment of some fibers of these structures, I recommend the use of absorbable sutures. The sutures are pulled out through a cannula in the anteromedial portal. For tears in the anterior portion of the lateral meniscus, viewing is facilitated with the arthroscope placed in the anteromedial portal and the sutures are then retrieved through the anterolateral portal. The sutures may be secured by the same methods as described for repair of the medial meniscus. When making the small incision in the skin and dissecting down to the capsule to tie the sutures, the surgeon should take care to avoid the inferior lateral geniculate artery, which courses along the posterolateral joint line.
I currently recommend the use of a fibrin clot in addition to parameniscal synovial abrasion for most isolated repairs of the meniscus, especially for treatment of tears with marginal vascularity. The use of a fibrin clot is supported by the study by Henning et al., who reported failure of seven of seventeen isolated meniscal repairs performed without use of a fibrin clot compared with failure of only one of thirteen isolated repairs performed with use of a fibrin clot13. As far as I know, a fibrin clot has not been used with concomitant reconstruction of the anterior cruciate ligament because the rates of meniscal healing are highest in that setting, most likely due to the presence of a hemarthrosis7,20,21. The fibrin clot is prepared from thirty to forty milliliters of the patient's blood, obtained by venipuncture26. The blood is placed in a sterile glass container and stirred with a sintered glass rod to promote clot formation, which occurs within three to five minutes. The formed clot is one to two centimeters in diameter and has a firm consistency. It is rinsed with sterile saline solution and gently blotted between gauze sponges to remove serum and red blood cells. The clot then can be inserted by tying it to one or two previously placed sutures that have been brought out of the anterior portal through a large cannula. This suture with the attached fibrin clot is then pulled back into the knee (Fig. 9), and sutures are tied to the adjacent sutures for meniscal repair. I have found it most useful to use a cannula without a bladder when inserting the clot, since the clot may be pulled apart when passing through the narrow bladder on a standard cannula. The clot may also be placed in a plastic tube with a pusher and then inserted into the tear through the tube, or it may be injected through a syringe with a blunt needle. However, I recommend tying the clot to a suture in order to secure the clot at the site of the repair. Most tears are filled by 1.5 to two milliliters of clot. The clot should be placed underneath the meniscus and can be secured by wedging it between the meniscus and the tibia. A probe or Freer elevator may be used to push the clot into position.
As explained, there are three ways to secure the sutures in a repair performed with use of the outside-in technique. Each suture can be secured as a knot-end suture (a Mulberry knot), two adjacent sutures can be tied together and pulled through the meniscus to form a mattress suture (vertical or horizontal), or a wire cable loop can be used to place a mattress suture without the need to pull the sutures out through an anterior portal. Sometimes mattress sutures and knot-end sutures are used together. Several studies have demonstrated that vertical sutures have a higher strength to failure than do horizontal sutures17,22,23. Knot-end sutures have been reported to have a strength to failure that is approximately equal to that of horizontal mattress sutures and lower than that of vertical sutures22. For comparison, the strength to failure of an absorbable implant made of self-reinforced polylactic acid for arthroscopic meniscal repair has also been reported to be equivalent to that of a horizontal mattress suture1,9. Importantly, the loads placed on the site of a meniscal repair during rehabilitation activities are unknown. Furthermore, in the just mentioned in vitro studies, the load to failure was measured immediately after placement of the sutures. The mechanical properties of meniscal sutures following repetitive cyclic loading or resorption of the sutures are unknown. Clinical reports have indicated that all of these suture configurations can be used successfully for arthroscopic repair of the meniscus3,13,20,21,27-29.
There has been some discussion in the literature regarding the type of sutures used for meniscal repair; in particular, the choice between permanent and absorbable sutures has been an area of debate. The use of permanent sutures may be preferable for repair of tears that have a poor potential for healing, such as tears in older patients, chronic tears, or tears with marginal vascularity. Barrett et al. demonstrated a lower prevalence of clinical symptoms and a much lower rate of failure after repairs of menisci performed with permanent sutures6. The better results associated with permanent sutures are thought to be due to the fact that they allow for longer and more stable fixation, permitting more complete maturation and remodeling of the healing meniscus. Polydioxanone suture has the longest resorption time of the absorbable sutures and is rigid enough to be easily pushed through the spinal needle. Successful repairs have been reported with use of both permanent and absorbable sutures20,28,29,34.
Postoperative rehabilitation after meniscal repair continues to be an area of controversy. The important variables to consider are range of motion, weight-bearing, and return to sports. In the early days of meniscal repair, a conservative approach was taken, with limitation of weight-bearing and of motion. More recently, investigators have evaluated the results of meniscal repair followed by an accelerated rehabilitation protocol4,5. Recent basic investigations on the effects of immobilization and weight-bearing have provided evidence in support of earlier and more intensive rehabilitation. Klein et al. showed that immobilization and non-weight-bearing in a dog model resulted in substantial atrophy of meniscus, ligament, and bone15. Those authors subsequently demonstrated that such atrophy could be prevented by active joint motion in this non-weight-bearing dog model16. Anderson et al. used a sheep model to demonstrate that the tensile properties of the meniscus were not significantly affected if even only limited joint motion was allowed2. More recently, Dowdy et al. showed that prolonged immobilization leads to a decrease in collagen content within the healing meniscus, thus suggesting that knees treated with isolated meniscal repair should either be immediately mobilized after the operation or be immobilized for only a short period10.
These basic laboratory studies have been supported by clinical studies demonstrating good rates of meniscal healing following an accelerated protocol for rehabilitation. These studies do not support restrictions of activity after meniscal repair4,5. An accelerated protocol for rehabilitation was initially advocated by Shelbourne et al., who reported no difference in the rates of meniscal healing between an accelerated and a conventional rehabilitation program30. Barber also reported no difference in the results when comparing an accelerated rehabilitation protocol with a restricted, standard rehabilitation protocol4. Similar results were also reported by Mariani et al.18.
It should be noted that in most studies meniscal healing has been assessed on the basis of clinical symptoms only, rather than with objective evaluation with use of arthroscopy, arthrography, or magnetic resonance imaging, and it has been reported that a tear may be asymptomatic even if it is only partially healed21. The long-term prognosis of such partially healed tears is unknown; a recent study by Asahina et al. raised concerns about them3. In that study, six of thirteen patients who had a partially healed tear (as seen arthroscopically) had an additional operation on the meniscus within an average of four years, whereas only five of fifty patients who had a completely healed tear had an additional meniscal operation. Thus, despite the good clinical results reported in association with intensive protocols for rehabilitation, additional basic and clinical studies should be conducted to continue to define the postoperative regimen that will result in the best possible meniscal healing.
At this time, consideration should be given to tailoring the postoperative protocol to the type of meniscal tear and to the basic-science information that is currently available. For example, a vertical, longitudinal tear may be closed by compressive loads applied with the knee in extension, but weight-bearing while the knee is in excessive flexion should be avoided, as the meniscus is subjected to greater stress in this position36. This finding is supported by the observation by Morgan et al. that extension appears to reduce the meniscus to the capsule, whereas flexion causes tears in the posterior horn to displace from the capsule20. In contrast, it is possible that compressive loading even in full extension may cause distraction of a radially oriented tear, and thus weight-bearing should be delayed for this type of tear. Thompson et al. demonstrated that the meniscus translates posteriorly with flexion; however, meniscal movement was at a minimum at less than 60 degrees of flexion32. Thus, consideration should be given to limiting flexion to 60 degrees during the early period of healing. Clinical outcome studies will be important in determining if such modifications in the postoperative protocol can improve the rates of meniscal healing.
My current protocol for rehabilitation involves the use of a hinged, double-upright brace for the first four to six weeks postoperatively. Early range-of-motion exercises, including full extension, are begun immediately after the operation. Flexion is limited to 70 degrees during the first four weeks to protect repairs of the posterior horn and is increased progressively after that time. Full weight-bearing with the brace locked in full extension is allowed after repairs of bucket-handle and vertical, longitudinal tears. Beginning at four weeks, the hinge of the brace is opened to allow a range of motion during walking. Closed-kinetic-chain strengthening exercises are begun in the second week and are increased progressively. Weight-bearing out of the brace is allowed at four to six weeks. Sport-specific activities are initiated at six to eight weeks for further development of strength and proprioception. Running is begun at three to four months after the operation, and the patient returns to full athletic participation by five months.
Only toe-touch weight-bearing is recommended for the first three weeks after repairs of radial or complex tears (such as double longitudinal tears), and flexion is limited to 70 degrees during the first four weeks. The range of motion and weight-bearing are increased progressively beginning three to four weeks after the repair of these difficult tears. As a fibrin clot is often used in these repairs, this regimen may also serve to protect the clot from dislodging due to excessive loads. Squatting and hyperflexion are discouraged for as long as six months after the repair.
A less intensive protocol for rehabilitation may be considered if there is axial malalignment of the limb (for example, after a repair of a medial meniscus in a varus knee), as the meniscus may be subjected to higher (potentially detrimental) loads in that situation. The clinician may even consider the use of a so-called unloader brace, which serves to shift the weight-bearing stresses to the opposite tibiofemoral compartment. However, I am not aware of any available data on the ability of such a brace to improve meniscal healing.
Additional studies are necessary to define the magnitude and types of stress (shear or compression) that may impair meniscal healing.
If there is concomitant reconstruction of the anterior cruciate ligament, the usual protocol for rehabilitation of the anterior cruciate ligament is used, with the only modifications being a limitation in flexion and delayed weight-bearing after repairs of radial or complex tears, as described earlier. Early full extension is emphasized. To my knowledge, no limitations of flexion have occurred with use of this protocol.
Complications are rare when the surgeon pays careful attention to operative technique and local anatomy. Injury to the peroneal nerve is avoided by performing a repair of the lateral meniscus with the knee in 90 degrees of flexion and starting placement of the needle anterior to the biceps tendon. The saphenous nerve can be injured during passage of the needle on the medial side or if the sutures are inadvertently tied around the nerve or its branches, but careful dissection combined with transillumination decreases this risk. There may be a higher risk of wound infection if careful soft-tissue coverage over the sutures is not achieved; a two-layered closure of the wound over the sutures is recommended. Local acidity during degradation of absorbable sutures may contribute to the risk of infection. Intensive, early treatment of an infection is recommended to prevent intra-articular extension of the infection and to salvage the repair.
Theoretically, limitation of extension can occur because of entrapment of the posterior part of the capsule if the knee is in too much flexion when sutures that pass through the posterior part of the capsule are being tied, especially on the medial side. However, in actuality, limitation of extension is quite unlikely to occur because during arthroscopic repairs the sutures are usually placed with valgus load applied to the knee and with the knee nearly extended, and in this position the capsule is closely apposed to the meniscus. The use of absorbable sutures decreases the risk of permanent entrapment of the posterior part of the capsule. Healing can fail to occur because of poor selection of the tear for repair (that is, selection of a tear associated with inadequate vascularity, degenerative tissue, and so on), instability of the knee, inadequate stabilization of the tear with sutures, too-oblique orientation of sutures across the tear, lack of early protection of the repair, and repeat injury. Careful attention to patient selection, operative technique, and postoperative rehabilitation will minimize the risk of failure.
There are very few reports of the results of meniscal repair performed with use of the outside-in technique. Morgan and Casscells, apparently the first to report the results of procedures performed with this approach, noted good results based on clinical evaluation after an average duration of follow-up of eighteen months19. Their evaluation was based on a physical examination and symptoms only. A subsequent report by Morgan et al. was one of the first to describe objective examination of the healing meniscus with use of second-look arthroscopy20. In a series of seventy-four meniscal repairs performed through the outside-in technique with use of polydioxanone suture, those authors reported an overall rate of meniscal healing of 84 percent (sixty-two), with 65 percent (forty-eight) of the menisci healed and 19 percent (fourteen) incompletely healed. The rate of failure was 16 percent (twelve) at the time of the second-look arthroscopy. Eleven of the twelve failures occurred after repairs of tears of the posterior horn of the medial meniscus, and all failures occurred in knees with injuries to the anterior cruciate ligament. Morgan et al. found that complete healing and disappearance of the absorbable suture was evident with second-look arthroscopy by approximately four months. Those authors were one of the first groups to point out that incompletely healed menisci could be clinically asymptomatic. Mariani et al. reported good clinical results for seventeen of twenty-two patients who had had outside-in repair of a tear of the medial meniscus in conjunction with reconstruction of the anterior cruciate ligament18. They also reported failure, defined with use of clinical criteria for a repeat meniscal tear, in three of twenty-two patients. Those authors reported that magnetic resonance imaging demonstrated a gap larger than one millimeter at the site of the repair in the patients who had clinical symptoms of a repeat meniscal tear.
The outcomes of outside-in meniscal repairs performed at The Hospital for Special Surgery by Warren from 1984 to 1988 were reported21. Of ninety-six patients, six were lost to follow-up, leaving a study group of ninety patients. The minimum duration of follow-up was three years, with an average duration of follow-up of forty-six months (range, thirty-six to eighty-nine months). There were seventy-four male patients and sixteen female patients, and the average age was twenty-five years (range, eleven to fifty-four years). The interval from the injury to the repair averaged eleven months (range, one week to eleven years). Eighty-seven percent (seventy-eight) of the ninety patients were injured while participating in athletics, and the other twelve patients reported an insidious onset of symptoms. The posterior horn of the meniscus was torn in 91 percent (eighty-two) of the group. The peripheral third of the meniscus was torn in 87 percent (seventy-eight). Eighty percent (seventy-two) of the repairs were medial, and 20 percent (eighteen) were lateral.
All ninety patients were evaluated with a physical examination and radiographs, and eighty-six patients had an objective evaluation of the meniscus with computed tomographic arthrography, magnetic resonance imaging, or arthroscopic inspection. This objective evaluation of meniscal healing allowed exclusion of asymptomatic residual tears from the success group. Complete meniscal healing was determined by the absence of contrast medium leaking into the site of the tear as noted on an arthrogram, and partial healing was demonstrated by contrast medium intruding into one surface of the tear but not penetrating to the other side of the tear. Failure of healing was indicated by persistent contrast medium throughout the entire thickness of the tear. The criteria for full healing as demonstrated by magnetic resonance imaging included low or moderate signal intensity at the site of the tear, with complete apposition of the edges of the tear33. Partial healing was indicated by persistent high signal intensity but normal meniscal morphology at the site of the tear, whereas failure of healing was demonstrated by high signal intensity and abnormal meniscal morphology at the site of the tear.
Overall, 87 percent (seventy-eight) of the ninety patients had a successful outcome (Table I). Sixty-nine percent (sixty-two) were asymptomatic and had objective evidence of complete healing of the meniscus (Group I), 18 percent (sixteen) were slightly symptomatic and had objective evidence of partial healing (Group II), and 13 percent (twelve) had a meniscus that failed to heal (Group III). These results are very similar to those reported by Morgan et al.20. There was a significant difference in the rates of healing between the patients who had a stable knee and those who had an unstable knee with an injury to the anterior cruciate ligament (p < 0.05). The repair failed in five of the thirteen unstable knees, 15 percent (five) of the thirty-three stable knees, and only 5 percent (two) of the thirty-eight knees that had concomitant reconstruction of the anterior cruciate ligament. Numerous reports on healing after meniscal repair have demonstrated that the rates of healing are highest after concomitant reconstruction of the anterior cruciate ligament, most likely because of the presence of serum-derived factors from the hemarthrosis5,20,26,27.
Repairs failed more commonly in the central, less vascular portion of the meniscus21. One of twenty-three repairs at the meniscocapsular junction failed compared with four of ten repairs in the middle third of the meniscus (p = 0.02). The rate of failure of repairs of the medial meniscus was higher than that of repairs of the lateral meniscus: eleven of seventy-two repairs of the medial meniscus failed compared with one of eighteen repairs of the lateral meniscus. Repairs of tears that involved the posterior horn of the medial meniscus had the highest rate of failure, especially in the setting of injury of the anterior cruciate ligament. This is most likely due to the fact that the medial meniscus serves as an important restraint to anterior tibial translation in the knee when the anterior cruciate ligament is injured. It is thus likely that when the anterior cruciate ligament is injured the medial meniscus is exposed to higher shear stresses and is thereby susceptible to injury.
There were fifty-two chronic and thirty-eight acute repairs (defined as repairs performed within one month after the injury)21. There was no difference in the rates of healing between these groups. The rate of failure was higher for patients who were more than thirty years old, although the difference did not reach significance with the numbers available (p > 0.05). The rate of partial healing was higher in the older patients, with 32 percent (eight) of twenty-five patients who were more than forty years old having partial healing. Complete or partial healing was found in eight of the twelve patients who had had an insidious onset of symptoms compared with 90 percent (seventy) of seventy-eight patients in whom the onset of symptoms followed a traumatic event. Patients with an insidious onset of symptoms may have an element of underlying meniscal degeneration that may result in a lower potential for healing.
An exogenous fibrin clot was used in seventeen repairs in an attempt to augment healing25. Seven of the repairs in which the fibrin clot was used were performed in the middle third of the meniscus (the so-called red-white region). Of the seventeen repairs in which a fibrin clot was used, six failed. Three of these failures were attributed to an unrepaired injury of the anterior cruciate ligament, and three were due to a complex tear in the avascular zone of the meniscus. Because the fibrin clot was used for tears with an inherently higher rate of failure, no conclusions can be made regarding the efficacy of insertion of a fibrin clot. A randomized, prospective study is required to assess the efficacy of the use of the fibrin clot in meniscal repair.
The rate of complications was 3 percent (three of ninety). There was one superficial infection, one case of thrombophlebitis, and one entrapment of the saphenous nerve. The patient who had entrapment of the saphenous nerve was managed with immediate exploration, at which time the nerve was found to be entrapped by the sutures. Immediate exploration of the saphenous nerve is recommended if the patient has burning paresthesias in the distribution of the saphenous nerve directly following the operation and extension of the knee makes these symptoms worse. If there is only numbness in the distribution of the saphenous nerve, observation is recommended. Exploration is recommended if symptoms persist after six to twelve weeks.
A recent study from my institution demonstrated different regional rates of healing with use of the outside-in technique35. In this study of fifty-one tears, twenty-three (45 percent) healed completely, sixteen (31 percent) healed partially, and twelve (24 percent) did not heal. There was a significantly lower rate of healing of tears in the posterior horn of the medial meniscus (p < 0.05), which was thought to be due to the obliquity of the sutures in this region. It can be difficult to place the needles perpendicular to the tear in the far posterior zone of the meniscus, and this can result in oblique placement of the sutures. The coaptation force of the sutures may be decreased if they are not perpendicular to the tear. This could explain the lower rate of healing in the posterior zone. Therefore, use of the inside-out technique should be considered for repair of tears in the posterior horn of the medial meniscus.
The results after meniscal repair with use of the outside-in technique are very similar to the reported results after repair with use of the inside-out technique. Cannon recently reported on 172 meniscal repairs8. With use of strict criteria for healing based on evaluation with either arthroscopy or arthrography, they found that 120 (70 percent) of 172 repairs were followed by satisfactory (complete or partial) healing. Satisfactory healing was observed in 100 (75 percent) of 134 patients who had had concomitant reconstruction of the anterior cruciate ligament but in only twenty (53 percent) of thirty-eight patients who had had an isolated meniscal repair. The rate of healing was superior for tears with a narrower rim (more peripheral tears). It was also better for repairs of the lateral meniscus compared with repairs of the medial meniscus. With the numbers available, age was not found to have an effect on meniscal healing.
With use of arthroscopic inspection, Rosenberg et al. found healing after twenty-four (83 percent) of twenty-nine repairs at a minimum of three months postoperatively27. These results closely parallel the outcomes of the outside-in technique and are similar to previously reported results of the inside-out technique29.
The outside-in technique of arthroscopic repair is effective for repair of most meniscal tears. The overall indications for the use of this technique are similar to those for the commonly used inside-out technique. The outside-in technique is especially useful for suturing the anterior horn of the meniscus as well as for suturing meniscal replacement devices such as a collagen meniscal implant or a meniscal allograft. Other specific advantages of this technique include the ability to predictably avoid neurovascular injury without the need for a large posterior incision. A particular disadvantage is the difficulty of achieving perpendicular orientation of sutures when a tear is adjacent to the site of attachment of the posterior horn. Use of the inside-out technique or an all-inside implant is suggested for these tears.
The use of this suturing technique is facilitated by attention to several technical points. The knee should be maintained in flexion for repair of tears of the lateral meniscus (to avoid injury to the peroneal nerve) and in nearly full extension for repair of the posterior aspect of the medial meniscus (to avoid injury to the saphenous nerve and its branches). Care must be taken to avoid tying the sutures around a branch of the saphenous nerve during repair of the medial meniscus. The sutures should be retrieved through a cannula in the anterior portal to avoid the entrapment of the sutures in soft tissue. A probe can be used to prevent displacement of the inner fragment of a bucket-handle tear when the needles are placed across the tear, as the entering needles may push the torn fragment into the knee. A vertical suture orientation is preferred in order to evenly coapt the meniscus to the capsule. If knot-end sutures (so-called Mulberry knots) are used, two sutures can be vertically stacked, with one on each surface of the meniscus. If a mattress suture is used, a vertical orientation is easily achieved with the outside-in technique. Use of an exogenous fibrin clot is suggested for isolated tears. The clot can be secured to the site of repair by a suture that has been placed through a spinal needle with the outside-in method. Delayed weight-bearing should be considered as postoperative management for patients who have had repair of a tear with a radial component or repair of a complex tear in which a fibrin clot was used.
Previous studies8,20,21,35 have demonstrated that the location of the tear and the condition of the anterior cruciate ligament are important factors in determining the success of meniscal repair. The overall results with use of the outside-in technique are comparable with those reported with use of the inside-out method8,20,21,27,29. Patients with concomitant tears of the medial meniscus and the anterior cruciate ligament should have combined meniscal repair and reconstruction of the anterior cruciate ligament. As healing was demonstrated in eight of thirteen patients with an unrepaired tear of the anterior cruciate ligament21, consideration should still be given to meniscal repair in patients who refuse reconstruction of the anterior cruciate ligament. In this setting, it may be advisable to use multiple permanent sutures, and the patient must be counseled regarding the higher rate of failure with this approach. Repairs of the lateral meniscus have a higher rate of success, and repair of the lateral meniscus should be considered even in the presence of injury of the anterior cruciate ligament.
Albrecht-Olsen, P.; Lind, T.; Kristensen, G.; and Falkenberg, B.: Failure strength of a new meniscus arrow repair technique: biomechanical comparison with horizontal suture. Arthroscopy,13: 183-187, 1997.13183
1997
[PubMed]
Anderson, D. R.; Gershuni, D. H.; Nakhostine, M.; and Danzig, L. A.: The effects of non-weight-bearing and limited motion on the tensile properties of the meniscus. Arthroscopy,9: 440-445, 1993.9440
1993
[PubMed]
Asahina, S.; Muneta, T.; Hoshino, A.; Niga, S.; and Yamamoto, H.: Intermediate-term results of meniscal repair in anterior cruciate ligament-reconstructed knees. Am. J. Sports Med.,26: 688-691, 1998.26688
1998
[PubMed]
Barber, F. A.: Accelerated rehabilitation for meniscus repairs. Arthroscopy,10: 206-210, 1994.10206
1994
[PubMed]
Barber, F. A., and Click, S. D.: Meniscus repair rehabilitation with concurrent anterior cruciate reconstruction. Arthroscopy,13: 433-437, 1997.13433
1997
[PubMed]
Barrett, G. R.; Richardson, K.; Ruff, C. G.; and Jones, A.: The effect of suture type on meniscus repair. A clinical analysis. Am. J. Knee Surg.,10: 2-9, 1997.102
1997
[PubMed]
Cannon, W. D.: Meniscal healing. In Arthroscopic Meniscal Repair, pp. 7-12. Edited by W. D. Cannon. Rosemont, Illinois, American Academy of Orthopaedic Surgeons, 1999.
Cannon, W. D.: Techniques of meniscus repair. In Arthroscopic Meniscal Repair, pp. 25-27. Edited by W. D. Cannon. Rosemont, Illinois, American Academy of Orthopaedic Surgeons, 1999.
Dervin, G. F.; Downing, K. J.; Keene, G. C.; and McBride, D. G.: Failure strengths of suture versus biodegradable arrow for meniscal repair: an in vitro study. Arthroscopy,13: 296-300, 1997.13296
1997
[PubMed]
Dowdy, P. A.; Miniaci, A.; Arnoczky, S. P.; Fowler, P. J.; and Boughner, D. R.: The effect of cast immobilization on meniscal healing. An experimental study in the dog. Am. J. Sports Med.,23: 721-728, 1995.23721
1995
[PubMed]
Fitzgibbons, R. E., and Shelbourne, R. D.: "Aggressive" nontreatment of lateral meniscal tears seen during anterior cruciate ligament reconstruction. Am. J. Sports Med.,23: 156-159, 1995.23156
1995
[PubMed]
Habata, T.; Ishimura, M.; Ohgushi, H.; Tamai, S.; and Fujisawa, Y.: Axial alignment of the lower limb in patients with isolated meniscal tear. J. Orthop. Sci.,3: 85-89, 1998.385
1998
[PubMed]
Henning, C. E.; Lynch, M. A.; Yearout, K. M.; Vequist, S. W.; Stallbaumer, R. J.; and Decker, K. A.: Arthroscopic meniscal repair using an exogenous fibrin clot. Clin. Orthop.,252: 64-72, 1990.25264
1990
[PubMed]
Johnson, L.: Meniscus repair: the outside-in technique.In Reconstructive Knee Surgery. Master Techniques in Orthopaedic Surgery, pp. 51-68. Edited by D. W. Jackson. New York, Raven Press, 1995.
Klein, L.; Player, J. S.; Heiple, K. G.; Bahniuk, E.; and Goldberg, V. M.: Isotopic evidence for resorption of soft tissues and bone in immobilized dogs. J. Bone and Joint Surg.,64-A: 225-230, Feb. 1982.64-A225
1982
Klein, L.; Heiple, K. G.; Torzilli, P. A.; Goldberg, V. M.; and Burstein, A. H.: Prevention of ligament and meniscus atrophy by active joint motion in a non-weight-bearing model. J. Orthop. Res.,7: 80-85, 1989.780
1989
[PubMed]
Kohn, D., and Siebert, W.: Meniscus suture techniques: a comparative biomechanical cadaver study. Arthroscopy,5: 324-327, 1989.5324
1989
[PubMed]
Mariani, P. P.; Santori, N.; Adriani, E.; and Mastantuono, M.: Accelerated rehabilitation after arthroscopic meniscal repair: a clinical and magnetic resonance imaging evaluation. Arthroscopy,12: 680-686, 1996.12680
1996
[PubMed]
Morgan, C. D., and Casscells, S. W.: Arthroscopic meniscus repair: a safe approach to the posterior horns. Arthroscopy,2: 3-12, 1986.23
1986
[PubMed]
Morgan, C. D.; Wojtys, E. M.; Casscells, C. D.; and Casscells, S. W.: Arthroscopic meniscal repair evaluated by second-look arthroscopy. Am. J. Sports Med.,19: 632-637, 1991.19632
1991
[PubMed]
Nicholas, S. J.; Rodeo, S. A.; Ghelman, B.; Buss, D. D.; and Warren, R. F.: Arthroscopic meniscal repair using the outside-in technique. Read at the American Orthopaedic Society for Sports Medicine Specialty Day Meeting, Anaheim, California, 1991.
Post, W. R.; Akers, S. R.; and Kish, V.: Load to failure of common meniscal repair techniques: effects of suture technique and suture material. Arthroscopy,13: 731-736, 1997.13731
1997
[PubMed]
Rimmer, M. G.; Nawana, N. S.; Keene, G. C.; and Pearcy, M. J.: Failure strengths of different meniscal suturing techniques. Arthroscopy,11: 146-150, 1995.11146
1995
[PubMed]
Ritchie, J. R.; Miller, M. D.; Bents, R. T.; and Smith, D. K.: Meniscal repair in the goat model. The use of healing adjuncts on central tears and the role of magnetic resonance arthrography in repair evaluation. Am. J. Sports Med.,26: 278-284, 1998.26278
1998
[PubMed]
Rodeo, S. A.; Warren, R. E.; and Arnoczky, S. P.: Meniscal repair using an exogenous fibrin clot. Tech. Orthop.,8: 113-119, 1993.8113
1993
Rodeo, S. A., and Warren, R. F.: Meniscal repair using the outside-to-inside technique. Clin. Sports Med.,15: 469-481, 1996.15469
1996
[PubMed]
Rosenberg, T. D.; Scott, S. M.; Coward, D. B.; Dunbar, W. H.; Ewing, J. W.; Johnson, C. L.; and Paulos L. E.: Arthroscopic meniscal repair evaluated with repeat arthroscopy. Arthroscopy,2: 14-20, 1986.214
1986
[PubMed]
Rubman, M. H.; Noyes, F. R.; and Barber-Westin, S. D.: Arthroscopic repair of meniscal tears that extend into the avascular zone. A review of 198 single and complex tears. Am. J. Sports Med.,26: 87-95, 1998.2687
1998
[PubMed]
Scott, G. A.; Jolly, B. L.; and Henning, C. E.: Combined posterior incision and arthroscopic intra-articular repair of the meniscus. J. Bone and Joint Surg.,68-A: 847-861, July 1986.68-A847
1986
Shelbourne, K. D.; Patel, D. V.; Adsit, W. S.; and Porter, D. A.: Rehabilitation after meniscal repair. Clin. Sports Med.,15: 595-612, 1996.15595
1996
[PubMed]
Tenuta, J. J., and Arciero, R. A.: Arthroscopic evaluation of meniscal repairs: factors that effect healing. Am. J. Sports Med.,22: 797-802, 1994.22797
1994
[PubMed]
Thompson, W. O.; Thaete, F. L.; Fu, F. H.; and Dye, S. F.: Tibial meniscal dynamics using three-dimensional reconstruction of magnetic resonance images. Am. J. Sports Med.,19: 210-215, 1991.19210
1991
[PubMed]
van Trommel, M. F.; Potter, H. G.; Ernberg, L. A.; Simonian, P. T.; and Wickiewicz, T. L.: The use of non-contrast magnetic resonance imaging in evaluating meniscal repair: comparison with conventional arthrography. Arthroscopy,14: 2-8, 1998.142
1998
[PubMed]
van Trommel, M. F.; Simonian, P. T.; Potter, H. G.; and Wickiewicz, T. L.: Arthroscopic meniscal repair with fibrin clot of complete radial tears of the lateral mensicus in the avascular zone. Arthroscopy,14: 360-365, 1998.14360
1998
[PubMed]
van Trommel, M. F.; Simonian, P. T.; Potter, H. G.; and Wickiewicz, T. L.: Different healing rates with the outside-in technique for meniscal repair. Am. J. Sports Med.,26: 446-452, 1998.26446
1998
[PubMed]
Walker, P. S., and Erkman, M. J.: The role of the menisci in force transmission across the knee. Clin. Orthop.,109: 184-192, 1975.109184
1975
[PubMed]
Warren, R. F.: Arthroscopic meniscus repair. Arthroscopy,1: 170-172, 1985.1170
1985
[PubMed]