Fibrin Clot Augmentation for Meniscal Repairs: A Practical Review

Stephen Dalgleish, MBChB, MRCS, FRCS, UNITED KINGDOM Peter Samuel Edward Davies, MBChB, FRCS (Tr&Orth), PG Cert Med Ed, MFST (Ed), UNITED KINGDOM Randeep Singh Aujla, MBChB ChM FRCS (Tr&Orth) MFSEM, UNITED KINGDOM Jimmy Ng, BMBS, FRCS, UNITED KINGDOM Michael James Grant, MBChB, FRCS Tr & Orth, PGCERTMedEd, PGDip SEM, UNITED KINGDOM Shahbaz S. Malik, BSc, MB BCh, MSc (Orth Engin), LLM, FRCS (Tr&Orth), UNITED KINGDOM Peter D'Alessandro, MBBS (Hons), FAOrthA, FRACS, AUSTRALIA

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Introduction

Meniscal preservation remains a cornerstone of contemporary knee surgery, driven by the well-established evidence that maintaining native meniscal tissue reduces the long-term risk of osteoarthritis and improves functional outcomes.¹ With the expanding emphasis on the benefits of meniscal preservation, continual advances in repair techniques have been accompanied by a rapid growth in biologic augmentation strategies aimed at improving healing rates and clinical outcomes. Among these strategies, fibrin clot augmentation has gained increasing interest—particularly for complex tear patterns—as reflected in the rising volume of publications and presentations at international surgical meetings.^1,2

Although the evidence base supporting fibrin clot augmentation continues to grow, there remains considerable variability among the described preparation and delivery techniques.³ Most published methods or presentations reference the use of specific equipment—such as glass or metal beakers, or glass syringes and dedicated stirring rods—that may not be readily available in low-resource settings. In many regions, regulatory hurdles or limited procurement pathways can further restrict access to this equipment, creating barriers to adopting an otherwise simple and biologically sound technique.⁴

In this article, we outline a range of practical, universally accessible options for fibrin clot preparation and delivery, using equipment commonly found in standard orthopaedic theatres. By highlighting adaptable, low-cost methods, our aim is to broaden global access to fibrin clot augmentation and support wider adoption of meniscal-preserving surgery across diverse healthcare environments.⁵

Biological Rationale: Why Fibrin Clot?

Meniscal healing potential varies dramatically across vascular zones. The peripheral red–red zone benefits from an established vascular network, but the intermediate red–white and central white–white zones demonstrate progressively poorer healing due to limited blood supply. These poorly vascularised tears, particularly those with horizontal cleavage, radial, and complex patterns, have historically been considered less amenable to repair.

Fibrin clots provide the following:

• A biologic scaffold rich in fibrin fibres, supporting cellular migration.
  
• Platelet-derived growth factors that stimulate fibrovascular ingrowth.
  
• A provisional matrix that stabilises the repair microenvironment.^1,3

While modern platelet-rich products and proprietary scaffolds also aim to enhance healing, they require processing devices, disposables, or commercial preparations that are not universally available. A fibrin clot, by contrast, can be prepared with nothing more than a syringe and needle, sterile bowl, and a stirring instrument—materials that are accessible even in resource-limited surgical settings.

When to Consider Fibrin Clot Augmentation

While fibrin clot can be used with almost any meniscal repair, it is particularly well-suited to the following:

• Horizontal cleavage tears
• White–white or red–white border tears
• Radial tears
• Revision meniscal repairs
• Cases in which biologic healing potential is uncertain

In young, active patients—especially adolescents—biological support may enhance outcomes in cases in which the repair is technically challenging but preservation is strongly preferred.^1,2

Technique Overview

Although variations exist, the core steps of fibrin clot preparation remain straightforward.

Preoperative Preparation

The following equipment can be pre-opened and placed onto a surgical tray (Fig 1).

• Bowl (plastic, metal or glass)
• Stirring rod (bone file, bone rasp, cobb elevator or glass stirring rod)
• 2-0 Vicryl Rapide sutures
• 1-mL sterile syringe with the tip cut off
• Suction device/arthroscopic cannula/size 5-6 paediatric endotrachealtube
• Meniscal repair devices

Fig. 1. Set up of required equipment.

Blood Collection

The anaesthetic/surgical team draws 30-60 mL of blood from a peripheral vein, usually in the upper limb, using sterile venepuncture with a 50-mL syringe. This step can be performed shortly before or after surgical draping. Anecdotal evidence suggests that the administration of intravenous tranexamic acid at the time of anaesthetic induction can help with fibrin clot formation.

Clot Preparation

The collected blood is expelled from the syringe into a sterile plastic gallipot on one of the scrub trolleys. While there are biochemical and biomechanical advantages to using a glass container and stirring rod (e.g., faster and potentially stronger fibrin clot formation), the use of a plastic or metal bowl can still produce very effective fibrin clot. The blood is left to sit undisturbed for a short period to allow for initial fibrin polymerization, which helps to generate a dense, pliable fibrin clot. How long to leave the blood to rest is usually judged visually when the blood is no longer purely liquid and has started to gelatinize at the surface.

One of the key components of clot preparation is the gentle and slow stirring of the blood in the bowl with use of a glass stirring rod or metal instrument (e.g., a bone rasp, Cobb elevator, or bone file) until fibrin fibres aggregate into a soft clot¹. Blood is stirred slowly because fibrin polymerisation is mechanically sensitive. Slow, gentle mixing produces a stronger, more uniform, and biologically effective clot, whereas fast stirring creates a weak, disrupted fibrin network (Fig 2).

Fig. 2. Slow stirring of blood to form fibrin clot.

We have also found that using two stirring instruments allows a larger clot to form between the two instruments. Other low-cost techniques include putting two diathermy scratch pads together and cutting them into four pieces to increase the surface area and adding blood to form a fibrin clot. Clot formation generally takes 10-20 minutes and requires no mechanical device or centrifugal equipment. The clot is then teased from the stirring instrument(s), washed in normal saline to improve arthroscopic visualisation, and cut with scissor to a suitable size and shape or sutured with passing sutures (Fig. 3), depending on surgeon preference and the mode of clot delivery.

Fig. 3. Clot preparation with use of passing suture (2-0 Vicryl Rapide).

Clot Delivery

The procedure is performed as a standard arthroscopy with irrigation. The tear is prepared with rasping or mechanical abrasion of the tear edges with or without trephination/needling.

Clot delivery depends on the tear pattern, repair technique, and surgeon preference. The clot can be inserted with graspers, with atraumatic forceps, or after being inserted into a sterile 1-mL plastic syringe with the tip cut off (Fig 4).

Fig. 4. Clot preparation for delivery with 1-mL syringe (with the tip cut off).

If the clot has been sutured, it can be delivered into the tear using an arthroscopic cannula, a paediatric endotrachealtube (Size 5-6), or a standard suction handle (Frazier size 6Fr).

The key advantage is that all of these steps can be performed at low cost with instruments that are routinely available in most orthopaedic operating theatres.

Suture Strategies and Biomechanical Considerations

The augmentation does not replace high-quality mechanical repair. Instead, it complements it. Vertical mattress sutures, circumferential stitches, hash tag repairs, and modern low-profile all-inside implants can all be used in conjunction with fibrin clot. Where access to newer implants is limited, inside-out and outside-in repairs using simple needles and sutures remain highly effective, and fibrin clot adds biological support without adding cost. With inside-out repair, sutures can be placed first before the fibrin clot is delivered, and then sutures are sequentially tied off to hold the clot in place (Fig 5).

Fig. 5. Final repair following clot delivery.

Evidence: What Do We Currently Know?

The evidence base for fibrin clot augmentation spans several decades, beginning with early work in the 1980s and 1990s that demonstrated promising healing rates in patients with avascular meniscal tears.^1,4,5 While most published series have been case reports, case series, or comparative cohort studies rather than large RCTs, several consistent findings have emerged, as described below.

Improved Healing Rates in Avascular Zones

Studies examining horizontal and white–white zone tears have shown increased rates of MRI-confirmed healing and reduced re-tear rates when fibrin clot is used compared with repair alone.^2,3,5

Enhanced Outcomes in Complex and Revision Cases

Complex tear patterns, especially in younger athletic populations, appear to benefit from the added biologic stimulus. Revision repairs—a challenging subgroup due to scar tissue and limited vascularity—also have shown improved healing trends².

Low Complication Profile

Because the fibrin clot is autologous, risks such as foreign-body reaction or disease transmission are non-existent. Complications related to the technique are virtually absent in the literature.^1,4

Comparable Outcomes to More Advanced Biologics

While PRP and other biologic injectables have gained popularity, comparative studies have suggested that fibrin clot may provide similar biological benefits at a fraction of the cost and without the need for specialised kits or proprietary processing systems.⁴

Gaps in Current Evidence

High-quality, prospective randomised trials remain limited. Many studies have had heterogenous patient groups, varying surgical techniques, and inconsistent imaging follow-up. Nevertheless, the overall signal across the literature is positive, supporting fibrin clot as a viable biologic adjunct.⁴

Technical Tips and Pearls for Optimal Results

To help maximise success, several practical considerations are worth highlighting:

• Be patient during stirring. Patience ensures adequate fibrin formation. Underdeveloped clots may fragment during insertion, so slow is best.
• Shape the clot for the specific tear. Cylindrical for radial tears, flat/elongated for cleavage tears.
• Use a cannula when visualisation is limited. A standard suction device/arthroscopic cannula/ paediatric ET tube (size 5-6) works well to shield the clot during insertion.
• Secure the clot mechanically. Sutures should close the tear snugly around the clot to prevent migration.

Limitations and Areas for Future Research

Despite encouraging results, several limitations deserve acknowledgement:

• Lack of high-level evidence. More randomised controlled trials comparing fibrin clot to non-augmented repair and to newer biologics are needed.
• Technique variability. Differences in clot size, preparation time and technique, and insertion technique may influence outcomes.
• Imaging variability. Many studies rely on MRI, which can be unreliable in the early postoperative period.

Nonetheless, the technique’s low cost, biological plausibility, and accessibility make it a promising candidate for widespread adoption, particularly in global settings where affordability and simplicity are essential.

Conclusion

Fibrin clot augmentation represents an elegant combination of biological potential and surgical practicality. It is a useful adjunct to have in the reconstructive knee surgeons’ armamentarium to help improve outcomes and healing rates for challenging primary or revision cases in which meniscal preservation is of paramount importance.

Hopefully, by dispelling some myths, showcasing the simplicity of the technique, and raising awareness, the present report can allow surgeons with budget restrictions, limited inventory, or highly regulated environments to offer biologically enhanced meniscal repair without financial or logistical obstacles.

While modern biologics are becoming increasingly complex and expensive, some of the most effective tools remain the simplest. By advancing innovation and widening access to fibrin clot augmentation, we can deepen our understanding and unlock its full therapeutic potential, ensuring that this valuable adjunct reaches the patients who need it most.

References

1. Chahla J, Kennedy NI, Geeslin AG, Moatshe G, Cinque ME, DePhillipo NN, LaPrade RF. Meniscal repair with fibrin clot augmentation. Arthrosc Tech. 2017;6:e1–e6.
2. Davies PSE, Goldberg M, Anderson JA, Dabis J, Stillwell A, McMeniman TJ, Myers PT. Fibrin clot augmentation of high-risk meniscal repairs may result in clinical healing in up to 90% of cases. J ISAKOS. 2024;9(6):100316. doi:10.1016/j.jisako.2024.100316
3. Chrysanthou C, Laliotis N, Paraskevas GK, Anastasopoulos N, Packer G. Enhancing meniscal repair: investigating the impact of an exogenous fibrin clot. Cureus. 2024;16(1):e53083. doi:10.7759/cureus.53083
4. Keller RE, O’Donnell EA, Medina GIS, Linderman SE, Cheng TTW, Sabbag OD, Oh LS. Biological augmentation of meniscal repair: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2022;30(6):1915-1926. doi:10.1007/s00167-021-06849-5
5. Henning CE, Lynch MA, Yearout KM, Vequist SW, Stallbaumer RJ, Decker KA. Arthroscopic meniscal repair using an exogenous fibrin clot. Clin Orthop Relat Res. 1990 Mar;(252):64-72

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