Meniscus Replacement?

Summary: Meniscal replacement by allograft is increasingly common in our practice. In order to succeed, a replacement must duplicate the mechanical function of the original meniscal cartilage. The technique of replacement described in this article permits minimal disruption of the joint tissues, accurate placement of the meniscal horns, and secure fixation of the meniscal synovial junction. Key Words: Meniscus-Cartilage-Collagen-Surgical technique.

Meniscal cartilage replacement by allograft, prosthesis, and regeneration scaffolds has advanced from the laboratory to clinical practice (1-5). To facilitate meniscal cartilage replacement, specific instruments and techniques have been developed to ensure accurate and reproducible placement of the meniscal implants. For meniscal cartilage replacement to succeed, the following goals must be accomplished:

The torn portion of the meniscal cartilage is evaluated. If meniscal repair cannot be accomplished due to severity of the tear or poor quality of the tissue, then preparation of the meniscal rim is undertaken by removing the torn portions of the cartilaginous tissue (Fig. 1). In the setting of allograft replacement, nearly all of the remaining meniscus is removed. Additionally, for allograft replacement, resection of the meniscal horns and preparation of bony tunnels to accept bone plugs may be required. In the setting of scaffold replacement, only the damaged portions are removed, preserving the peripheral rim and horns for attachment of the scaffold. If absolutely no meniscal rim is present, then meniscal scaffolding should not be performed. If the joint is excessively tight, a joint distractor may be applied or the medial collateral ligament may be partially released.

For medial or lateral meniscal replacement, place the arthroscope in the mid-lateral or anterior lateral portal and the tibial guide through the anterior medial portal. The tip of guide is brought first to the posterior horn of the meniscus. It should be noted that the posteromedial horn inserts on the posterior slope of the tibial eminence. A drill pin is then brought from the anterior medial side of the tibial tuberosity to the posterior horn insertion (Fig. 2). The pin placement can be confirmed by passing the arthroscope through the intercondylar notch and viewing the exit site of the pin. Extreme care must be undertaken to avoid penetration through the posterior capsule of the knee, endangering the neurovascular bundle. When the pin position is confirmed, the pin is then overdrilled with a 4.5-mm cannulated drill bit with the option of a drill stop to prevent posterior capsular penetration (Fig. 3). The bit is left in place and used as a tunnel to pass a suture passer with a #2 ethibond (Johnson & Johnson) suture. The suture is passed up the bore of the drill bit, the drill bit removed, and the suture left in place.

Attention is now turned to the anterior drill hole. For the medial meniscus, it must be noted that the anterior medial meniscus insertion varies considerably. Most often it can be found anterior to the medial tibial eminence. The anterior horn of the lateral meniscus inserts just posterior to the ACL. Identify this insertion and place the tip of the drill guide so that a relatively vertical hole will be made (Fig. 4). Place the drill pin, then overdrill with the cannulated drill bit, and place the suture passer. Alternatively, the anterior horn of the medial meniscus may be affixed with a suture anchor directly to bone.

Before grasping the suture from the anterior and posterior drill holes, widen the anterior portal to approximately 2 cm. The suture grasper should then be passed through the widened portal, and both the anterior and the posterior sutures brought out simultaneously. This technique prevents the sutures becoming entangled in two different planes of the fat pad and capsular tissue. The importance of this step cannot be overstated; occasionally the posterior suture will pass through one tissue plane, and the anterior through another plane, causing the implant to become stuck in the soft tissues.

The implant is now brought onto the field. Two horizontal mattress sutures of #2-0 ethibond are placed through each horn of the implant with the free ends exiting the inferior surface (Fig. 5). The two posterior sutures are then drawn through the knee and out the posterior tibial tunnel (Fig. 6). If viewing from a mid-lateral portal, the anterolateral portal can be used for probe insertion to push the implant medially into place through a 1-inch incision. No insertion cannula is required. The anterior sutures are then similarly passed. The horn sutures are then tied over the anterior tibial bony bridge.

Next, zone specific meniscal repair cannulae are brought into place. For medial insertions, a posterior medial vertical incision is made one third of the distance from posterior to anterior for protection of the saphenous nerve and for retrieval of the insideout meniscal repair needles. A second vertical incision is usually required further anteriorly, next to the anterior medial arthroscopy portal, to capture the anterior exiting needles. Through these two incisions, the suture needles can be captured and the knots placed directly over the capsule (Fig. 7). Although nonabsorbable suture is used for the meniscal horns for added strength, absorbable suture [2-0 polydioxone (PDS)] is recommended for the body of the scaffold. The smooth monofilament is less abrasive and resorbs as the scaffold is metabolized.

When using the meniscal repair needles, the posterior cannulae should be used first, with the sutures placed vertically and evenly spaced. Progress from posterior to anterior so that a buckle is not produced within the implant. Tie each knot as it is placed to avoid the chance of suture tangling. Space the knots approximately 4 mm apart. Cycle the knee through several complete ranges of motion to ensure that the implant moves smoothly without impingement.

When performing a lateral meniscal replacement, we have found the medial portal for implant insertion to be effective. This may require excision of the ligamentous mucosa and removal of a portion of the fat pad. The drill guide for the posterior horn of the lateral meniscus is inserted through the anteromedial portal. The posterior slope of the lateral tibial spine must be identified for accurate meniscal horn insertion. The anterior horn inserts on the anterior slope of the spine in approximation to the lateral aspect of the anterior cruciate ligament. The advantage of drilling these holes from the medial side is that the tunnel divergence will be greater, providing a larger bony bridge between the horn insertions. The remainder of the insertion technique remains the same, except that great care should be taken to protect the neurovascular bundle when suturing the posterior horn. Accessing posterolateral exposure is necessary to safeguard the common peroneal nerve and expose the lateral capsule. If there is any doubt about the suture placement, open posterior horn suturing should be performed in the standard fashion.

Routine skin closure and dressings are applied. Thirty milliliters of 0.5% Marcaine (Astra) with epinephrine may be instilled if desired.

REFERENCES

From private practice,The Stone Clinic, San Francisco, Califomia (K.R.S.) Address correspondence and reprint requests to Kevin R. Stone, M.D., 3727 Buchanan St., San Francisco, CA 94123, U.S.A.

Konsensusrapport vedr. menisk transplantation
(Consensus declaration regarding meniscus transplantation).

On September 5, 1998 a number of orthopaedic surgeons from Denmark and Sweden met at Bispebjerg Hospital in Copenhagen, Denmark to have a consensus discussion about meniscal transplation, based on the information and views presented at a symposium held the previous two days.

The consensus discussion was divided in two sections: First a general consensus was made, followed by a discussion and consensus of whether meniscal transplantation shall be offered as a treatment option in Denmark.

The consensus group could consult a board of experts: Clinical professor, M.D. E. Marlowe Goble (Salt Lake City, Utah), Professor, M.D., dr. med. Dieter Kohn (Homburg/Saar, Germany), Professor, M.D., Ph. D. René Verdonk (Gent, Belgium), assistant professor, M.D., Ph.D. Karola Messner (Linköping, Sweden), M. D. Henrik Aagaard (Copenhagen, Denmark), and M. D. Benn Duus (Copenhagen, Denmark). The views and oppinions presented in the consensus are not nessesarily shared by all members of this advisory board.

The results of meniscus transplantation has been studied in animals. There is no proof from these experiments that replacement of a meniscus can reduce the risk for athrosis, but there are indications that it can decrease the development of cartilage degeneration.

In humans the results of meniscus transplantation have been reported in several series of patients, operated with different techniques. There are no controlled studies of meniscus replacement in humans.

There are indications that replacement of a meniscus in patients with pain after a meniscectomy under some circumstances can reduce the pain, but the mechanism for pain reduction is unknown. There is no proof or indication that replacement of a meniscus in humans can avoid or reduce the risk for arthrosis or degenerative changes of the cartilage.

After meniscus replacement, primary healing of the transplant generally occurs within 4 to 6 weeks. After 6-8 months the transplant has healed to the capsule in 90 % of the patients (irradiated grafts have a lower healing rate). In animal experiments the transplants have never obtained the same mechanical properties as a normal meniscus. Experience from the human series of patients with meniscus replacement indicates that the mechanical properties of the transplants are inferior to a normal meniscus, but this has not been scientically investigated.

Generalized immunological responses to meniscus allograft replacement have been reported in animals and humans, but no major adverse reactions or rejection has been seen. There is no indication that the immunological respons has any negative influence on the graft.

The horns of the meniscal transplant can be fixed to the tibia with either bone blocks or sutures. There are no controlled studies in animals regarding fixation of the transplant, but from the experience in humans there are indications that bone blocks give a better fixation of the meniscal horns. There is no information about the rate of successful healing of the transplant to the capsule dependent on which fixation has been used for the horns. In all series meniscal replacements have been fixed to the capsule with sutures, so it is not known if it heals as well if meniscal arrows are used instead of sutures.

It is not known if there are any differences in the rates of successful healing and mechanical properties of the transplanted meniscus dependent on whether a fresh vital or a frozen transplant is used. It is documented that irradiated grafts have inferior mechanical properties compared to non-irradiated, and the rate of successful healing seems to be lower. With respect to disease transmission, irradiated grafts (2.5 MHz) are safest, but it not know whether there is any difference between fresh vital and frozen grafts. The risk for early or late side effects dependent of the type of graft is unknown.

With the present knowledge from uncontrolled, clinical series, meniscus replacement can be expected to decrease pain in patients with pain from the same compartment as meniscectomy has been performed, no matter whether radiological signs of degenerative joint disease is present in the compartment or not. Meniscus replacement can not be expected to be beneficial for patients with degenerative joint disease in other compartments than the one in which meniscectomy has been performed. With the present knowledge there is no indication that meniscus replacement can prevent arthrosis, so meniscus replacement is not recommended for pain-free patients who are missing a meniscus, no matter whether there are signs of degenerative joint disease in the same compartment or not. Therefore the indication to perform meniscus replacement is to reduce diabeling pain and not to get patients back to knee-stessing activities like high level sport. It is unknown if meniscus replacement can be beneficial for patients who have had partial meniscal resection performed.

The present clinical experience indicates that mechanical unstable knees, in which meniscus replacement is performed, should be surgically stabilized, either before or at the same time as meniscus replacement is done. The outcome of meniscus replacement may be positively influenced by this (increased rate of successful healing, better preservation of meniscal tissue etc.), although it is undocumented. In meniscectomized patients with pain and deformity (medial pain, medial meniscectomy and varus deformity or lateral pain, lateral meniscectomy and valgus deformity), an osteotomy should be performed to correct the deformity, before meniscal replacement is considered. If pain persists after the osteotomy has healed (4-6 months), a meniscal replacement may be indicated.

Even though no studies have compared the results of autograft tendon transplantation with allograft meniscus transplantation in meniscal replacement, and even though tendon transplantation has only been performed on a select patient group and in combination with concominant surgery, the clinical outcome of tendon transplantation seems to be comparable to meniscus transplantation. The disadvantages of tendon autografts are the lack of bony horn fixation, that it can be performed as an open procedure only, and that is weakens the extensor apparatus (as the graft is taken from the quadriceps tendon). The advantages of tendon autografts are that they are autografts (no disease transmission, no storage, harvesting or preservation problem) and that there is no sizing problem, as the tendon can always be made to fit the rim of the joint.

Scaffold implementering for partial meniscus loss is still experimental. Experiments with meniscal regeneration has been performed in animals but never in humans, and is also experimental.

There are no scientifically based guidelines for rehabilitation after meniscus transplantation, and the current regimens follow the guidelines for rehabilitation after meniscus suturing. Healing seems to be obtained in nearly all cases.

Meticulous post-operative control and long-term follow-up after meniscus replacement is mandatory (suggested control after surgery: 6 months, 1 year, and yearly). The minimum requirements for investigations are: weightbearing x-ray (15 degrees of flexion with footprints on patient envelope to ensure identical rotation between investigations), questionnaire (pain score, arthritis score and outcome questionnaire) and if possible MRI. Control arthroscopy is suggested to ensure meniscus healing and evaluate the cartilage status.

Optimal postoperative evaluation would be to assess the biomechanical properties of the transplant non-invasively (dynamic MRI), and the changes in subcondral bone.

Marianne Backer (Bispebjerg), Allan Buhl (Viborg), Bent Wulff Jakobsen (Århus), Uffe Jørgensen (Gentofte), Gert Kristensen (Aalborg), Michael Krogsgaard (Bispebjerg), Harald Roos (Hälsingborg), Søren Winge (Hvidovre)

There are indications that meniscus replacement can be beneficial for some patients. But no controlled studies have been performed on this subject in humans, and many questions remain unanswered.

The consensus group recommends that meniscus transplantation is performed in Denmark, but it should not be offered as a general treatment, but only as part of a controlled trial. This trial should optimally involve the other Scandinavian countries as well, because the basic conditions for health care are the same all over Scandinavia, and because there is a long tradition for scientific and clinical collaboration between the Scandinavian countries

The indication is pain from the compartment of the knee in which meniscectomy has been performed earlier with or without radiological signs of degenerative joint disease in the same compartment. There must be no sign of general degenerative joint disease of the knee and if deformity is present, it should be corrected first, and meniscus replacement only considered, if pain persists.

The number of candidates for meniscus replacement is probably between 10 and 50/ year in Denmark (5 million inhabitants).

It is recommended that frozen, non-irradiated grafts are used. Bone plug fixation is recommended. The most minimal invasive procedure, that the surgeon masters should be used. For lateral meniscus replacement this will probably be an arthroscopic procedure, and for medial replacement probably an open procedure. In an inter-Scandinavian trial it is of course essential that the same operative procedures are used by all surgeons.

Because of the small number of operations, the procedure should be performed by one surgeon in Denmark. It is recommended that operations are performed by one surgeon in each of the Scandinavian countries (if an inter-Scandinavian trial is established), and that practical and technical problems (f. i. banking) are solved in cooperation.

Optimal postoperative evaluation would be to assess the biomechanical properties of the transplant non-invasively (dynamic MRI), and the changes in subcondral bone.

Because of all the unsolved questions with regard to meniscus replacement, it is important that good clinical and experimental research is done in addition to surgery. Possible topics for future research are:

Is meniscus replacement better than debridement as pain treatment ? How long time does it help on pain ?

The effect of meniscus transplantation and combined surgery (ACL, cartilage etc.) on pain, activity and arthrosis prevention should be addressed.

A further characterization of the immunological events happening after meniscus replacement.

Development of measurement tools for in vivo assessment of meniscus properties, cartilage and subchondral bone. Results obtained with these tools are to be compared with animal studies.

Some of these questions can be answered in animal experiments, but it is essential that that the joint size and weight bearing of te animal can be compared to humans to make the results transferable to human clinic.

The Danish Society for Sportstraumatology will work out a suggestion for a meniscus transplantation group in Denmark and suggestions for clinical protocols. The Society will also contact orthopedic organizations in the other Scandinavian countries to establish a Scandinavian group and an inter-Scandinavian trial regarding meniscus transplantation. The Society will initiate contact between the Scandinavian group and surgeons in Europe and USA with interest in meniscus replacement.

Marianne Backer (Bispebjerg), Allan Buhl (Viborg), Bent Wulff Jakobsen (Århus), Uffe Jørgensen (Gentofte), Gert Kristensen (Aalborg), Michael Krogsgaard (Bispebjerg), Søren Winge (Hvidovre).

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Meniscus Replacement?

Technical Note

Surgical Technique of Meniscal Replacement

Kevin R. Stone, M.D.

REFERENCES