Medial Meniscal Root Repair and Double Medial Femoral Condyle Aragonite-Based Scaffold Implantation

Abstract

Background:

Medial meniscal root tears often occur alongside cartilage lesions, leading to altered load distribution and accelerated joint degeneration. Addressing both pathologies is critical to restoring joint mechanics and improving outcomes. Cell-free aragonite-based scaffold implants are emerging as cost-effective, off-the-shelf options.

Indications:

These scaffolds are indicated to address between 1 and 3 focal International Cartilage Repair Society grade 3 or 4 femoral lesions <7 cm² contained by a surrounding wall of vital bone of at least 2 mm without severe osteoarthritis.

Technique Description:

Standard arthroscopic portals reveal a posterior medial meniscal root tear and 2 grade 4 chondral defects on the medial femoral condyle. The meniscal root is prepared with a ringed curette and shaver. Two 4.5-mm parallel transtibial tunnels are drilled, emerging at the posterior meniscal root insertion. Two sutures are passed through the meniscal root and fixated at the anteromedial tibial cortex with a PEEK suture anchor. The anteromedial portal is then extended to a parapatellar arthrotomy to reveal the osteochondral defects. The 2 aragonite scaffolds are then implanted according to standard steps. A perpendicular aligner is centered over the defect. Then, a K-wire is drilled into the defect, and a drill sleeve is positioned before drilling to a set depth with a drill bit. A reamer is introduced over the K-wire to establish the 2° taper of the socket. A cartilage cutter tool or scalpel is used to smooth the cartilage edges; the implant is then inserted manually and/or with a rubber tamper.

Results:

Aragonite-based scaffolds have demonstrated superior outcomes compared with microfracture in randomized trials, including higher Knee injury and Osteoarthritis Outcome Score and International Knee Documentation Committee scores, increased defect fill (>75% in 88% of cases), and lower failure rates. Integration with host bone and cartilage remodeling has been confirmed on imaging by 12 months, with clinical improvements sustained at 2 and 3 years.

Conclusion:

This technique provides a single-stage, accessible solution for addressing combined medial meniscal root tears and focal osteochondral lesions. Aragonite-based scaffolds offer promising clinical and radiographic outcomes but must be used within defined indications as further comparative studies emerge.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

We present our technique for medial meniscal posterior root repair and double medial femoral condyle aragonite-based scaffold implant.

Background

Medial meniscal root tears often occur alongside cartilage lesions, leading to altered load distribution and accelerated joint degeneration. ⁸ Addressing both pathologies is critical to restoring joint mechanics and improving outcomes. While meniscal root repair has become the standard treatment for medial meniscal root tears, concomitant cartilage lesions may require additional intervention. Treatment options for cartilage defects include microfracture, osteochondral grafting, autologous chondrocyte implantation (ACI), and an emerging scaffold-based technique (Agili-C; CartiHeal Ltd), which has shown superior defect filling and improved functional scores compared with microfracture alone. ¹

Aragonite-based scaffold techniques consist of a novel off-the-shelf acellular option that leverages the biphasic nature of the osteochondral unit. A deep layer of loosely packed aragonite provides a porous subchondral phase that permits ingrowth and remodeling by osteoblasts and osteoclasts, while the articular-facing portion is mechanically drilled with channels and covered in hyaluronic acid to foster the migration and differentiation of bone marrow and synovial stem cells into hyaline cartilage. ⁷ These implants are a promising new option to treat cartilage lesions, outperforming other cartilage-based procedures in both preclinical and clinical studies.^1,6

Current indications include between 1 and 3 focal International Cartilage Repair Society grade 3 or 4 trochlear or condylar femoral lesions <7 cm² contained by a surrounding wall of vital bone of at least 2 mm in the context of nonsevere osteoarthritis ⁴ (Kellgren-Lawrence grade ≤3).

Indications

We present a case of a 51-year-old female with a remote history of a medial meniscal tear and medial collateral ligament sprain treated nonoperatively. For the past several years, the patient endorsed achy, dull, intermittent medial right knee pain that cyclically flared up during weightlifting. She had recently developed clicking but no catching, locking, or instability. Her symptoms had been unresponsive to nonsteroidal anti-inflammatory drugs and physical therapy.

On examination, she had no appreciable swelling, and the range of motion was from −2° to 125° of flexion. Strength testing was 5/5. There was tenderness over the medial joint line, and the patient had a positive medial McMurray test and negative Lachman, pivot shift, and posterior drawer tests.

Four-view radiographs of the left knee demonstrated varus alignment with mild medial compartment and lateral patellofemoral osteoarthritis with no fractures or foreign bodies.

Magnetic resonance imaging (MRI) revealed a posterior medial meniscal root tear and high-grade full-thickness chondral thinning in the weightbearing aspect of the medial femoral condyle.

After a thorough discussion of treatment options, the patient opted to proceed with surgical intervention, including transtibial medial meniscal posterior root repair and transplantation of a cell-free aragonite-based scaffold to address focal osteochondral defects of the medial femoral condyle (MFC) of the knee.

Technique Description

Patient Positioning and Diagnostic Arthroscopy

Standard anterolateral and anteromedial portals are established, revealing a posterior root tear of the medial meniscus and 2 focal grade 4 chondral lesions on the MFC, each approximately 2 cm in diameter.

The tibial footprint is prepared using a ring curette and motorized shaver to remove residual fibrocartilage and expose a bed of bleeding subchondral bone. A root-specific aiming guide (Smith & Nephew) is introduced through the anteromedial portal, and the tip is positioned at the anatomic footprint of the posterior meniscus root, medial to the posterior cruciate ligament and posterior to the medial tibial eminence. A 2.4-mm guide pin is drilled from the anteromedial tibial cortex and overdrilled with a 4.5- or 5-mm cannulated reamer. Using an offset guide, the second tunnel is placed approximately 5 mm anterior to the first tunnel (Smith & Nephew). Proper tunnel trajectory is confirmed arthroscopically, and the drill cannulas are left in place to assist with suture passage.

Two No. 2 sutures (ULTRABRAI; Smith & Nephew) are passed using the suture passer (FIRSTPASS MINI; Smith & Nephew) 5 mm from the lateral root edge in a horizontal cinch-loop configuration. All suture limbs are retrieved through the transtibial tunnel using nitinol wires. The root is anatomically reduced to the prepared footprint at 90° of knee flexion, and both sutures are sequentially tensioned and fixated to the anteromedial tibia with a 4.5-mm PEEK suture anchor (FOOPRINT PK; Smith & Nephew) below the tibial tunnels. The repair is then probed for stability.

Next, the anteromedial portal is extended into a 5-cm medial parapatellar mini-arthrotomy. Blunt dissection exposes the MFC, and Z retractors are placed to optimize exposure. Then:

1. The perpendicular aligner is centered perpendicularly and confirmed flush on the defect. A guidewire is inserted through the central cannulation until the laser mark reaches the alignment guide.

2. The defect is overdrilled and reamed to a uniform depth of 2 mm using the calibrated system, irrigating to remove debris.

3. A shaper is used to optimize socket geometry. After removing the wire, the cartilage rim is trimmed to regularize the socket rim and prevent implant overhang or step-off.

4. A 7.5-mm aragonite-based scaffold is manually implanted using direct thumb pressure and/or a silicone-covered tamper. The implants are seated 1 to 2 mm recessed relative to the native cartilage. A silicone-covered tamper may assist in final seating if necessary. Mallets should be avoided, as the brittle porous implant may fissure.

The steps are repeated for the second plug. Note the importance of preparing the defect walls and margins to allow a flush, press-fit, congruent with the implant’s 2° taper.

Arthroscopic visualization confirms the stable seating of both osteochondral implants. The joint is then thoroughly irrigated, the tourniquet is deflated, and all incisions are closed in standard layered fashion.

Outcomes

Avoid scaffold-based implants in cases of avascular necrosis, tibial-sided lesions, malalignment >8°, body mass index of >35 kg/m2, infection, uncontained lesions with <2 mm surrounding vital bone wall, or a subchondral bone defect or cyst deeper than 8 mm. ⁴ Additionally, plugs should be placed manually or with a soft tamper, rather than malleted, as the brittle porous structure may fracture.

Rehabilitation after aragonite-based scaffold implantation follows a phased approach to support healing and return to activity. Weeks 0 to 6 focus on protection, with 2 weeks nonweightbearing and gradual progression to full weightbearing and range of motion. Weeks 6 to 12 emphasize strengthening of the quadriceps and hip muscles. From weeks 12 to 24, training shifts to power development and light jogging. After 24 weeks, patients may return to full activity if pain-free with full range of motion.

Results

Aragonite-based scaffolds show superior clinical and radiographic outcomes compared with microfracture or debridement. In a multicenter randomized controlled trial, patients treated with the scaffold had significantly higher Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) scores and greater achievement of minimal clinically important difference for IKDC. ¹ MRI demonstrated ¹ >75% defect filling in 88% of scaffold cases versus 30% in the microfracture group, with lower failure rates (7.2% vs 21.4%). A 2-year study ⁵ in mild-to-moderate osteoarthritis knees reported sustained improvements and a 9% failure rate. Imaging showed scaffold integration with cartilage and bone remodeling by 12 months. A case series ⁹ with 3-year follow-up demonstrated KOOS and IKDC scores in the 90s, with durable regeneration.

Cartilage treatment options range from simple, inexpensive options to complex, time-consuming, and costly options, tailored to address specific chondral lesions. ³ Debridement and microfracture are bone marrow stimulation techniques effective for small focal lesions but may not be suited for larger lesions or those involving subchondral bone. ACI is suitable for larger surface-based chondral lesions without significant subchondral bone defects, while the osteochondral autograft transfer system (OATS) is suitable for smaller focal osteochondral lesions and osteochondral allograft transplantation (OCA) for larger or more complex osteochondral lesions. However, these are advanced surgeries that may not be readily accessible in all centers and may be cost-prohibitive.^2,3

In selected cases, synthetic osteochondral scaffolds have emerged as simple, relatively inexpensive, and easily accessible single-stage alternatives capable of addressing both cartilage and subchondral bone defects. Although comparative studies have demonstrated superiority to microfracture, further studies are needed to establish its role in addressing complex osteochondral pathology compared with other advanced techniques, such as OATS, OCA, or ACI.

Conclusion

Key takeaways from this technique include that aragonite-based scaffolds are fast and accessible options for superficial chondral and subchondral lesions. As it is an emerging treatment option, it is important to respect the indications and contraindications until further comparative effectiveness studies are developed.