Meniscus Regeneration with Biologic or Synthetic Scaffolds

Meniscus Regeneration with Biologic or Synthetic Scaffolds

William G. Rodkey *

Chapter Synopsis

• Efforts should be made to preserve the meniscus, but if this is not possible, meniscus regeneration with biologic or synthetic scaffolds may be an option. Multicenter clinical trials and reports have demonstrated new tissue formation and fewer reoperations after collagen scaffold implantation compared with partial meniscectomy alone for at least 10 years. A synthetic scaffold showed biocompatibility and successful early tissue ingrowth at 1 year. Research continues to develop and refine novel acellular scaffolds to support regeneration and regrowth of lost or damaged meniscus tissue.

Important Points

• Meniscus scaffolds are indicated for partial meniscus loss, whereas meniscus allografts are indicated for total meniscectomy.

• Two meniscus scaffolds, one biologic and one synthetic, are available for human clinical use (not currently in the United States).

• Intact anterior and posterior horn attachments and an intact rim of the involved meniscus are required.

• Knee ligamentous stability and proper axial alignment are necessary before scaffold implantation.

• Meniscus scaffolds are contraindicated in knees with advanced osteoarthritis.

• Successful scaffold implantation is technique specific and dependent.

• Proper postoperative rehabilitation must be followed to avoid early damage to the scaffold.

Clinical and Surgical Pearls

• Preparation of the implant site results in a full-thickness meniscus defect with no residual flaps or loose or degenerative tissue.

• The defect size must be measured accurately, and then the implant should be trimmed by oversizing by about 10%.

• The implant can be delivered into the joint with an atraumatic clamp through an extended portal.

• The scaffold must be sutured to the meniscus rim, preferably with all-inside or inside-out sutures.

• Do not overtighten the sutures; that could damage the implant.

• If the medial compartment is tight, partial release of the medial collateral ligament should be considered.

• If there are comorbidities (e.g., axial malalignment, full-thickness chondral injuries, ligament instability), consider staging the procedures.

Clinical and Surgical Pitfalls

• Inadequate lesion preparation may result in the implant not making uniform contact with the host meniscus rim.

• Improper measuring of the defect or cutting the implant too short leaves the defect incompletely filled.

• Excessive tension on the fixation sutures can damage the scaffold implant.

• Damage to the articular cartilage with the implant delivery device or with the suture devices can occur, especially in a tight knee.

• Placing the implant in a knee with untreated comorbidities can result in excessive biomechanical forces on the scaffold and lead to its damage or prevent adequate cell ingrowth and new tissue formation.

Contemporary thinking related to the meniscus focuses on preservation, restoration, and reconstruction. The menisci are critical for shock absorption, force transmission, and load distribution across the knee in addition to contributing to stability, joint congruence, articular cartilage nutrition, articular cartilage protection, joint lubrication, and proprioception. Because meniscus injuries often are irreparable, tissue engineering techniques have been used to develop acellular materials to support regrowth of lost meniscus tissue. For an engineered matrix to function as a resorbable meniscus template, of particular importance are the biomechanical properties of the matrix template because the template initially serves the biomechanical function of the meniscus. Thus strength of the engineered template and the subsequent biomechanical properties of the regenerated and remodeled tissue must be adequate for the device to survive initially in the hostile environment of the knee, and then ultimately to function like meniscus tissue. In addition, the scaffold must be conductive for cells as well as permeable to nutrients. Intrinsic biologic signals (e.g., growth factors) and cells must incorporate into the template to enhance the overall regeneration and remodeling process and provide an ideal biologic environment for cellular infiltration and new matrix synthesis.

Preoperative Considerations

Specific indications and contraindications have been developed for meniscus scaffolds.1–13

Indications

• For use in patients with either acute or chronic meniscus injuries

• Prior loss of meniscus tissue with intact anterior and posterior horn attachments and an intact rim over the entire circumference of the involved medial meniscus

• Irreparable meniscus tears requiring partial meniscectomy and requiring greater than 25% removal and with the lesion extending at least into the red-white zone

• Partial meniscus loss in the presence of early osteoarthritis (OA) with Kellgren-Lawrence grade 1 or 2 changes radiographically or Outerbridge grade III or lower changes arthroscopically

• Anterior cruciate ligament (ACL) deficiencies corrected within 12 weeks of the implant surgery

• Patients able and willing to follow postoperative rehabilitation program described later

Contraindications

• Complete meniscus loss or absence of one or both horn attachments.

• Repairable meniscus tear.

• Uncorrected ligamentous instability or insufficiency in the involved knee.

• Uncorrected Outerbridge grade IV (full-thickness) degenerative cartilage lesions and/or advanced OA in the affected joint. Limited clinical observations have suggested that the irregular surfaces of an untreated chondral lesion adjacent to the implant may damage or destroy the implant during the early stages of the regenerative process. No controlled studies have been conducted to confirm these observations, nor have studies been done to evaluate the consequences of having degenerative chondral lesions in other compartments of the involved joint that receives the scaffold.

• Uncorrected malformations or axial malalignment in the lower extremity. Malalignment may excessively overload the involved compartment, possibly resulting in damage to the implant during the early regenerative process. No controlled studies have been conducted to confirm this possibility. Whether or not there is a coexisting OA with the malalignment, consideration should be given to correcting those abnormalities before or at least concurrently with the scaffold implantation.

• Documented allergy to any product of animal or synthetic origin or a history of anaphylactoid reaction.

• Systemic or local infection.

• Medical history that is positive for, but not restricted to, severe degenerative osteoarthrosis, rheumatoid arthritis, relapsing polychondritis, or inflammatory arthritis.

Surgical Technique

Two different meniscus scaffolds have been used clinically in humans and are in common use in several parts of the world. They are discussed in this chapter. Both the Collagen Meniscus Implant (CMI)1–8,11–13 (Ivy Sports Medicine, Montvale, NJ) as well as Actifit^9,10 (Orteq Sports Medicine, London, United Kingdom) have comparable surgical implantation techniques. Therefore the techniques and steps described here pertain equally to both.

The patient is prepared and positioned for knee arthroscopy in a standard manner. General anesthesia is preferred. The arthroscopic portals should be the same as those preferred by the surgeon for meniscus repair.

Surgical Steps

Box 60-1 outlines the surgical steps of this procedure.

Box 60-1 Surgical Steps

1. Complete a thorough arthroscopic diagnostic examination, inspecting all geographic areas of the knee. Perform all other intra-articular procedures before completing the meniscus scaffold implantation.

2. Prepare the implant site to ensure a full-thickness meniscus defect (i.e., no residual flaps, loose or degenerative tissue). The remaining meniscus rim should be intact over the entire length. The prepared defect site should maintain a uniform width of the meniscus rim extending to the red-white or red-red zone.

3. The defect size must be measured accurately; then the implant should be trimmed by oversizing it by about 10%.

4. The appropriately sized implant is inserted into the joint through an enlarged portal with a curved atraumatic vascular clamp (e.g., 14- to 16-cm-long Cooley clamp). With the insertion clamp, the implant is guided into the prepared defect.

5. With the implant positioned properly, it is fixed to the host meniscus rim, preferably with all-inside or inside-out sutures. During tying or tightening, the sutures should be tensioned just enough to allow apposition of the implant to the meniscus rim, but not overtightened, which could damage the scaffold.

6. If the medial compartment is tight, partial release of the medial collateral ligament should be considered.

7. If there are comorbidities (e.g., axial malalignment, full-thickness chondral injuries, ligament instability), consider staging the procedures.

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Sep 11, 2016 | Posted by admin in SPORT MEDICINE | Comments Off

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