Roland S. Kent, Christopher A. Kurtz, and Kevin F. Bonner
DEFINITION
An estimated 850,000 meniscal procedures are performed yearly in the United States.
Although meniscus preservation is always preferable, large irreparable tears often require partial or subtotal meniscal excision.
Many patients will become symptomatic in the meniscaldeficient compartment as the result of increased articular cartilage contact stresses and progressive cartilage deterioration.
Meniscal allograft transplantation is an option in the carefully selected patient with symptomatic meniscal deficiency.
ANATOMY
The menisci are semilunar fibrocartilaginous discs made of predominantly type I collagen. Water, which accounts for 70% of meniscal composition, is trapped within the matrix by negatively charged glycosaminoglycans (FIG 1).
Only the peripheral third of the meniscus is vascularized (10% adjacent to popliteal hiatus). Blood is supplied via the perimeniscal capillary plexus with contributions from the superior and inferior medial and lateral geniculate arteries.
Medial meniscus
The medial meniscus covers a smaller percentage of medial compartment surface than the lateral meniscus.
A portion of the anterior cruciate ligament (ACL) tibial insertion footprint lies between the anterior and posterior horn attachment sites.
Lateral meniscus
The lateral meniscus covers a relatively larger percentage of the articular surface in its respective compartment than the medial meniscus.
The anterior horn attaches adjacent to the ACL and the posterior horn attachment is behind the intercondylar eminence.
The anterior and posterior horn attachments are closer to each other than the medial meniscus without a ligament insertion footprint interposed between the two sites. This makes the lateral meniscus more amenable to a bone bridge transplantation technique.
A discoid variant is found in 3.5% to 5% of patients.
The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.
Drs. Kent and Kurtz are military service members (or employees of the U.S. Government). This work was prepared as part of their official duties. Title 17 U.S.C. 105 provides that ‘Copyright protection under this title is not available for any work of the United States Government.' Title 17 U.S.C. 101 defines a United States Government work as a work prepared by a military service member or employee of the United States Government as part of that person's official duties.
PATHOGENESIS
Meniscal pathology is generally of two types:
Acute traumatic tears
These injuries typically occur in a previously relatively “healthy” meniscus in patients younger than 35.
They may also occur in older individuals, but typically in the setting of an acute ACL tear.
Traumatic tears often include unstable longitudinal tears in the vascular zone, which are optimal candidates for meniscal repair.
They often occur in association with combined knee injuries (ACL, medial collateral ligament).
Degenerative tears
This is a more complex tear pattern that typically occurs in patients older than 35.
Often a relatively minor trauma or event “breaks the camel's back” and a tear propagates through degenerative meniscal tissue.
These are not repairable.
Risk factors for meniscal tears include sports participation (especially jumping and cutting sports at risk for concurrent ACL injury), age, higher body mass index, occupational kneeling and squatting (associated with degenerative rather than acute traumatic meniscal lesions), level of activity, and ACL instability.
The association of meniscal tears with ACL tears is well documented. Lateral meniscal injuries occur more frequently with acute ACL disruption, while medial meniscal injuries occur more often in the setting of chronic ACL insufficiency.
Irreparable tear patterns or failed previous meniscal repairs often necessitate arthroscopic meniscal excision of the tear component. The degree of tear propagation typically dictates the resection required.
NATURAL HISTORY
Meniscectomy can decrease contact area by 75% and increase joint contact stresses by over 200%.1
Contact stresses increase as a function of the amount of meniscus resected.
These increases in joint contact stress often lead to premature cartilage deterioration and the development of osteoarthritis. Although patients often remain relatively asymptomatic until they have advanced degenerative changes, many patients (who tend to be younger and more active) develop pain earlier in the degenerative process.
Lateral meniscectomy is considered to have a poorer prognosis than medial meniscectomy.
The medial meniscus is the secondary stabilizer to anterior tibial translation. Medial meniscectomy (posterior horn) in the ACL-deficient knee often increases tibial translation and instability.
FIG 1 • Meniscal anatomy.
Meniscus implantation decreases peak stresses and improves contact mechanics but does not restore perfect knee mechanics.5,9
PATIENT HISTORY AND PHYSICAL FINDINGS
Potential transplant patients are typically younger than 40 years of age, with an absent or nonfunctioning meniscus, who are symptomatic from their meniscal insufficiency. The upper limit is generally age 50 (not absolute) for highly active patients who are not good candidates for arthroplasty.
A detailed history includes specific symptoms, prior injuries, and subsequent surgery. Arthroscopy pictures are helpful in determining the degree of meniscal resection and the condition of the articular cartilage.
Symptomatic postmeniscectomy patients typically present with joint line pain (sometimes subtle), swelling, and pain associated with barometric pressure changes. Symptoms are usually activity-related.
The physical examination should focus on determining pain location, ligament stability, and alignment, assessing the cartilage, and ruling out elements of the differential diagnosis.
Palpating the joint line for tenderness will localize the source of pain.
Sharp pain on the McMurray test may indicate recurrent meniscal injury or chondral lesion versus meniscal insufficiency (dull ache).
The Lachman test assesses for concomitant ACL pathology, which should be addressed at the time of surgery.
Concerns about malalignment and gait problems necessitate long-leg alignment films.
Symmetric range of motion is needed before the transplant.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs
Anteroposterior (AP) view of both knees in full extension (FIG 2A): Look for subtle joint space narrowing.
FIG 2 • A. AP weight-bearing bilateral knee views showing subtle medial compartment joint space narrowing of the right knee (arrow). B. MRI showing deficient medial meniscus. C. Arthroscopic image of right knee showing deficient medial meniscus.
Weight-bearing 45-degree flexion posteroanterior view: Look for subtle joint space narrowing.
Merchant view
Non-weight-bearing lateral views
Long-leg alignment films (if malalignment is suspected)
MRI: to assess menisci, articular cartilage, and subchondral bone) (FIG 2B)
Bone scan can be considered and may reveal increased activity in the involved compartment. However, it is not typically used and its sensitivity in this setting is unknown.
Diagnostic arthroscopy is often recommended.
It will accurately define the extent of meniscectomy and the degree of arthrosis if previous arthroscopic images are unavailable or unclear, or if more than 1 year has elapsed since the last arthroscopy (FIG 2C).
Outerbridge grade III or less articular cartilage damage is acceptable (grade I or II is preferable) unless a focal grade IV lesion is addressed concurrently with a cartilage resurfacing procedure.
DIFFERENTIAL DIAGNOSIS
Recurrent meniscal tear
Chondral or osteochondral lesion (may be the primary cause of pain but may require chondroprotection of meniscus transplant)
Advanced bipolar degenerative arthritis
Synovitis
Patellofemoral pain (radiating medial)
Extra-articular sources (ie, hamstring or pes tendinitis)
NONOPERATIVE MANAGEMENT
Activity modification (nonimpact activities and exercises)
Appropriate pharmacologic therapy
Injection therapy (may be helpful for diagnostic purposes as well)
Unloader braces
A potential exception to nonsurgical management may be in the setting of the chronically ACL-insufficient knee or failed ACL-reconstructed knee with medial meniscal deficiency.
A concomitant reconstruction of the ACL with meniscal allograft replacement may improve joint stability, ACL graft survival, and eventual clinical outcome.
This is a new relative indication.
SURGICAL MANAGEMENT
Indications are patient younger than 40 years with an absent or nonfunctioning meniscus and with pain due to meniscal insufficiency or progressive joint space narrowing.
Upper limit is generally age 50 for highly active patients who are not good candidates for arthroplasty.
Contraindications to surgery include immunodeficiency, inflammatory arthritis, prior deep knee infection, osteophytes indicating bony architectural changes, marked obesity, Outerbridge grade IV articular changes (focal chondral defects can be addressed concurrently), knee instability, or marked malalignment (unless these issues are corrected).
Preoperative Planning
Graft sizing: Although size matching of meniscal allografts to recipient knees is thought to be critical, the tolerance of size mismatch is unknown. While various sizing methods have been proposed, measurements based on plain radiographs and MRI are most commonly used (Table 1).
Meniscal allografts are procured under strict aseptic conditions within 12 hours of cold ischemic time in accordance with standards established by the American Association of Tissue Banks for donor suitability and testing (Table 2).
All equipment should be ordered and readily available (ie, commercially available meniscal workstations).
An experienced assistant is very valuable for this procedure.
Positioning
The patient is placed in the supine position with the knee at the table break (FIG 3).
For a lateral meniscal transplant, there is the option of a figure 4 position versus the leg over the table break for femoral distractor application (see Approach).
FIG 3 • Patient positioned with the knee at the table break. Femoral distractor optimizes compartment distraction with the knee flexed.
On occasion it may be helpful to use a femoral distractor to optimize and maintain distraction of the involved compartment with the knee in flexion (currently not used by the senior author [KFB]).7
Approach
For the lateral meniscus, a lateral parapatellar arthrotomy with posterolateral meniscus repair approach is used.
For the medial meniscus, a medial parapatellar arthrotomy with posteromedial meniscus repair approach is used.
TECHNIQUES
LATERAL MENISCUS GRAFT PREPARATION
A previously size-matched lateral meniscus with the attached tibial plateau is thawed in a saline and antibiotic solution.
Remove soft tissue from the meniscus (capsular tissue) (TECH FIG 1A).
Always use the bone bridge-in-slot technique; it maintains the bridge of bone between the anterior and posterior insertion sites.
Commercially available meniscus workstations can facilitate bone bridge preparation into various shapes that will match tibial recipient sites (Arthrex, Naples, FL) (TECH FIG 1B,C).
The most common bone preparation techniques include keyhole, dovetail, and slot configurations (TECH FIG 1D).
Prepare the bone bridge shape between the meniscus insertion sites using the appropriate workstation (TECH FIG 1E).
During bone preparation, be careful not to injure the meniscus insertion sites.
Mark the superior surface of the meniscus and the popliteal hiatus with a surgical marker.
Using 10-inch flexible meniscus repair needles (Ethibond, Somerville, NJ), place one or two vertical mattress sutures (may place up to four if desired) through the posterior horn of the meniscus (TECH FIG 1F,G). Do not cut off the needles. These will serve as passage sutures and are used for fixation as well.
TECH FIG 1 • Lateral meniscus graft preparation. A. Prepreparation lateral meniscus graft (after capsular soft tissue has been removed). B. Preparing a keyhole graft with the workstation. C. Dovetail workstation.
TECH FIG 1 • (continued) D. Common bone bridge shapes. E. Dovetail preparation. F. Dovetail graft with single passage suture. G. Keyhole graft with four passage sutures.
LATERAL MENISCUS APPROACH AND TIBIAL PREPARATION
A combined arthroscopic and lateral parapatellar arthrotomy approach is performed.
Perform an arthroscopic débridement and excoriation to the far peripheral meniscal rim or joint capsule with a shaver or meniscal rasp.
A no. 15 blade may be used to excise the anterior horn and any remnant of the body.
Use an arthroscopic burr to create a small trough in line with the anterior and posterior horn attachments (guide for recipient site) (TECH FIG 2A).
Expose the proximal tibia through a small lateral parapatellar arthrotomy in line with the trough (TECH FIG 2B).
Commercially available instrumentation will facilitate creation of the tibial recipient site in line with the anterior and posterior horn attachments (Arthrex, Naples, FL) (TECH FIG 2C–E).
Take care to avoid penetration through the posterior cortex.
Perform posterolateral exposure to receive inside-out sutures (meniscus repair approach) (TECH FIG 2F).
TECH FIG 2 • Lateral meniscal approach and tibial preparation. A. Creation of a small trough between the anterior and posterior horn attachments. B. Lateral parapatellar approach. C. Preparation of keyhole recipient site. (continued)
TECH FIG 2 • (continued) D. Preparation of dovetail recipient site. E. Completed keyhole recipient site. F. Posterolateral exposure.
DELIVERY AND FIXATION OF LATERAL MENISCUS
Before delivery of the graft into the recipient site, place the 10-inch needles from the passage sutures through the miniarthrotomy and posterolateral capsule to assist in delivery of the graft (TECH FIG 3A).
Exposure, retraction, and needle retrieval are identical to an inside-out repair technique.
Plan optimal placement of sutures through the capsule relative to their position in the meniscus (TECH FIG 3B). Use the popliteus tendon and the popliteal hiatus in the graft as a guide for suture placement.
By simultaneously inserting the shape-matched donor graft into the tibial recipient site and pulling on the posterior inside-out passage suture, the graft is delivered to re-establish the normal insertion site (TECH FIG 3C).
A varus stress to the knee, combined with pulling on the posterior passage sutures, will help reduce the posterior horn under the femoral condyle (TECH FIG 3D).
Matching the anterior cortices (graft and recipient) and bringing the knee through a range of motion will assist in final anteroposterior positioning.
Place additional inside-out meniscus sutures with the suture cannula placed in the medial portal. The scope is placed into the miniarthrotomy.
TECH FIG 3 • Delivery of lateral meniscus. A. Ten-inch needles from the passage suture are placed through the posterolateral capsule and retrieved by the assistant. B. Inside-out vertical sutures are placed through the appropriate location within the posterolateral capsule. (continued)
TECH FIG 3 • (continued) C,D. The dovetail graft is delivered into the recipient site. E. Posterior horn is reduced by pulling on the posterior passage suture combined with varus stress to the knee. F.Completed lateral meniscus transplant.
Additional anterior sutures can be placed through the anterior arthrotomy using standard open suturing techniques.
Tie sutures with the knee in flexion (TECH FIG 3E,F).
An interference screw or transosseous suture fixation may be placed with the slot technique, but this is typically unnecessary with the dovetail and keyhole technique.
MEDIAL MENISCUS GRAFT PREPARATION
A previously size-matched medial meniscus with the attached tibial plateau is thawed in a saline and antibiotic solution. Remove soft tissue as described for the lateral meniscus.
Medial meniscal allografts may be fashioned with or without bone plugs at the anterior and posterior horn insertion sites (TECH FIG 4A,B).
For preparation without bone plugs, detach the anterior and posterior horns from the bone block and whipstitch each horn with heavy nonabsorbable suture. We do not typically use this technique unless a plug fractures.
For preparation with bone plugs (recommended), place a 2.4-mm Beath guide pin through the bone block into the posterior insertion site at about a 60-degree angle. Place a commercially available collared pin into the 2.4-mm hole. Ream over the collared pin using an 7- or 8-mm coring reamer (creates a plug 6 or 7 mm in diameter) (TECH FIG 4C). Trim and taper the end to create a 10-mm-long plug.
TECH FIG 4 • Medial meniscus graft preparation. A. Without bone plugs. B. With bone plugs. (continued)
TECH FIG 4 • (continued) C. Coring reamer over collared pin.
Repeat these steps for the anterior horn insertion, but angle the guide pin approximately 20 degrees and create a bone plug 10 mm in diameter. Place a heavy nonabsorbable suture (no. 2 FiberWire) up the guide pin hole, through the meniscal tissue, then back down the guide pin hole for each bone plug.
Place a vertical passing stitch of nonabsorbable suture at the junction of the posterior and middle thirds of the meniscus.
Mark the anterior and posterior horns on the superior meniscal surface.
MEDIAL MENISCUS APPROACH AND TIBIAL PREPARATION
The case is performed via arthroscopic, medial parapatellar, and posteromedial meniscal repair approaches (TECH FIG 5A).
The remaining meniscus is débrided, leaving 1 mm of meniscal rim. The surrounding capsule and meniscal bed is abraded with the shaver and rasps.
To visualize and access the posterior horn insertion site, perform a small notchplasty of the medial wall of the notch inferior to the posterior cruciate ligament (PCL) insertion. Likewise, débride back the medial tibial spine until easy access is obtained (TECH FIG 5B).
Perform a medial parapatellar incision, extending distally to allow access to the anteromedial proximal tibia. Do not perform the arthrotomy portion until the posterior tunnel is complete.
TECH FIG 5 • Medial meniscus technique. A. Medial approach. B. Notchplasty performed under posterior cruciate ligament. C,D. Guide pin placement into the posterior horn insertion. E. Shuttle suture through the posterior tunnel exiting the medial portal. F. Anterior arthrotomy incorporating medial portal.
Under direct visualization, position a variable-angle ACL-PCL tibial drill guide such that the guide pin will exit in the center of the native posterior horn insertion site footprint (TECH FIG 5C,D).
Drill a 9-mm tibial tunnel. Débride and chamfer the intra-articular portion of the tunnel. Pass a shuttle suture up the tunnel and out the medial portal (TECH FIG 5E).
Complete the medial parapatellar arthrotomy, incorporating the medial portal (do not cut the shuttle suture) (TECH FIG 5F).
Perform posteromedial exposure to receive inside-out sutures (meniscus repair approach).
DELIVERY AND FIXATION OF MEDIAL MENISCUS
Shuttle-exchange the shuttle sutures with the posterior bone plug suture and allograft passing suture. Via the parapatellar arthrotomy, deliver the meniscal allograft into the knee and fully seat the posterior bone plug into the posterior tunnel (TECH FIG 6A,B). Apply a valgus stress to the knee while pulling on the posterior bone plug sutures and the posterior passing sutures.
Using zone-specific cannulas (Linvatec, Largo, FL), suture the allograft to the periphery approximately two thirds of the way posterior to anterior with multiple vertical mattress sutures.
Through the parapatellar arthrotomy, determine the anterior horn insertion site and place a Beath guide pin in its center.
Drill a blind 10-mm tunnel vertically to a depth sufficient to accept the anterior allograft bone plug (TECH FIG 6C).
Drill a 2-mm hole perpendicular to the tunnel from the anterior tibial cortex entering the tunnel base.
TECH FIG 6 • A,B. Meniscus delivery. Shuttle suture and delivery of the posterior bone plug and meniscus. C. Anterior recipient tunnel created by reaming over guide pin. D. Anterior bone plug seated into tunnel. E. Bone plug sutures tied over anterior bone bridge. (continued)
TECH FIG 6 • (continued) F. Schematic of bone plug and meniscus fixation. G. Arthroscopic view of final graft in position.
Place a shuttle stitch through the 2-mm hole and exit up the anterior tunnel.
Shuttle-exchange the shuttle stitch and the anterior bone plug suture. Deliver and fully seat the anterior bone plug in the tunnel (TECH FIG 6D).
Tie the bone plug sutures over the bone bridge rather than tying the sutures over a plastic ligament button. (TECH FIG 6E).
Complete the meniscal repair to the anterior capsule using an open repair technique (TECH FIG 6F,G).
POSTOPERATIVE CARE
Postoperative rehabilitation may need to be altered based on concomitant procedures.
A hinged knee brace locked in extension is used for 6 weeks.
Weight bearing as tolerated is typically permitted with the knee braced in full extension (this may be limited by other procedures).
Range of motion is limited between 0 and 90 degrees for the first 6 weeks. Flexion is increased between 6 and 12 weeks.
Closed-chain exercises, cycling, and swimming are started at 6 weeks.
Running may begin at 4 to 6 months.
Squatting and pivoting sports are not allowed for 6 to 9 months.
OUTCOMES
With appropriate indications, current success rates for allograft meniscus transplantation are about 75% to 85%.3,4,6,10
Bone plug fixation may improve outcomes, although this is controversial.
Poor results are typically associated with more advanced articular cartilage degeneration.
Meniscus transplants that are combined with articular cartilage resurfacing or realignment procedures can yield favorable outcomes.
One study reported that 86% of patients with a combined ACL reconstruction and meniscus transplant had normal or near-normal International Knee Documentation Committee (IKDC) scores, with an average maximum KT arthrometer side-to-side difference of 1.5 mm.12
COMPLICATIONS
Nonhealing or incomplete healing
Infection
Neurovascular injury
Loss of motion
Meniscus tear or extrusion (late)
Persistent or progressive symptoms (typically related to articular cartilage)
REFERENCES
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