Agili-C implant promotes the regenerative capacity of articular cartilage defects in an ex vivo model

Report on Evolving Indications, Techniques, and Outcome of Novel and Innovative Surgical procedure - Agili C®

BACKGROUND

Purpose of review Agili-C® (CartiHeal, Smith & Nephew) is an off-the-shelf aragonite-based (inorganic calcium carbonate) scaffold approved for clinical use in 2022 to treat chondral and osteochondral lesions eventually also in the context of mild to moderate knee osteoarthritis (Kellgren-Lawrence 0-3). The successful preclinical studies justified the subsequent clinical trials which reported both clinical and radiological significant improvements over time as well as superiority over standard surgical techniques for cartilage lesions treatment (i.e. microfractures/debridement). The aim of the present review is to summarize the available preclinical and clinical evidence and to report the current indications, surgical techniques and outcomes of this novel and innovative osteochondral scaffold.

RECENT FINDINGS

A total of six clinical reports, four single cohorts studies and a recent double arm randomized control trial followed by an analysis differentiating between femoral and trochlear lesions, have been published on Agili-C® safety and efficacy. Supported with an excellent safety profile, Agili-C® provided statistically significant clinical benefits at short and medium-term follow up in patients affected by knee joint surface lesions also when presenting in the context of mild to moderate knee osteoarthritis (Kellgren-Lawrence 0-3). Agili-C® (CartiHeal, Smith & Nephew) is an innovative aragonite-based osteochondral scaffold. It is an CE-marked and FDA approved off-the-shelf, cell-free, and cost-effective implant designed to treat knee joint surface lesions in the form of chondral and osteochondral defects. Its indications, supported by consistent clinical evidence, are single or multiple knee joint surface lesions (ICRS grade III or IV), with a total treatable area of 1-7cm2, without severe knee OA (Kellgren-Lawrence grade 0-3).

Female patients report comparable results to males after the implantation of an aragonite-based scaffold for the treatment of knee chondral and osteochondral defects: a gender-based analysis of a RCT at 4 years' follow-up

BACKGROUND

The aim of the study was to provide a gender-based analysis of the results of a large, multi-centre randomized controlled trial (RCT) comparing a novel cell-free aragonite-based scaffold with the standard of care (i.e. debridement/microfractures) for the treatment of chondral/osteochondral defects in knees with or without concurrent osteoarthritis.

MATERIALS AND METHODS

A total of 251 patients were included: 167 patients in the scaffold group and 84 in the control. In the scaffold group, there were 105 males and 59 females, whereas the control group consisted of 51 males and 32 females. Patients were evaluated up to 48 months after the treatment. The primary endpoint was the change from baseline to 48 months in the KOOS overall score. Treatment failures were defined as any secondary invasive intervention, including intra-articular injection or any surgery in the treated joint. All patients underwent magnetic resonance imaging (MRI) at 12 and 24 months to assess the percentage of defect fill after surgery.

RESULTS

Both males and females in the scaffold group achieved significantly better results than controls in any KOOS subscale, as well as in KOOS overall, up to the final 48 months follow-up. Outcomes reported by females were non-inferior to those of males in the implant group. At 24 months' MRI evaluation, 86.2% of male patients in the scaffold group presented at least 75% defect fill compared with 32.6% in the control group. In the scaffold group, 87.6% of female patients presented at least 75% defect fill, compared with 28% in the control group (p < 0.0001 in both cases). Responders' rate and failure rate were also significantly better in the scaffold group for both males and females.

CONCLUSION

The aragonite scaffold outperformed the control group at 48 months' evaluation. The gender-based analysis proved that males and females in the scaffold group presented comparable clinical and radiographical results, both significantly better than their counterparts treated by debridement/microfractures.

LEVEL OF EVIDENCE

I-Randomized controlled trial.

TRIAL REGISTRATION

Clinicaltrial.gov ID: NCT03299959 (registered on 14 September 2017).

Novel Treatment Options for Knee Cartilage Defects in 2023

Articular cartilage lesions are a common injury that have become increasingly treatable with joint preservation procedures. Well-documented allograft and cellular treatments for these lesions are detailed elsewhere in this volume. This article discusses three new unique options for addressing these defects taking three different paths to address these complex injuries. Agili-C is an existing FDA- and EMEA-approved option using an acellular aragonite-based scaffold to treat both chondral and osteochondral lesions, with or without concurrent arthritis. Cartistem is a stem-cell-based product composed of culture-expanded allogeneic human umbilical cord blood-derived mesenchymal stem cells and hyaluronic acid hydrogel, which is in its final clinical trial stages in the United States, but already has regulatory approval in Korea. IMPACT and RECLAIM studies have shown the safety and efficacy of a new one-stage procedure utilizing autologous chondrons combined with allogeneic mesenchymal stem cells (MSCs) that can provide another effective single-stage treatment option.

Treatment of knee cartilage lesions in 2024: From hyaluronic acid to regenerative medicine

Abstract

Intact articular cartilage plays a vital role in joint homeostasis. Local cartilage repairs, where defects in the cartilage matrix are filled in and sealed to congruity, are therefore important treatments to restore a joint equilibrium. The base for all cartilage repairs is the cells; either chondrocytes or chondrogeneic cells from bone, synovia and fat tissue. The surgical options include bone marrow stimulation techniques alone or augmented with scaffolds, chondrogeneic cell implantations and osteochondral auto- or allografts. The current trend is to choose one-stage procedures being easier to use from a regulatory point of view. This narrative review provides an overview of the current nonoperative and surgical options available for the repair of various cartilage lesions.

Level of Evidence

Level IV.

Bridging bench to body: ex vivo models to understand articular cartilage repair

With little to no ability to self-regenerate, human cartilage defects of the knee remain a major clinical challenge. Tissue engineering strategies include delivering specific types of cells and biomaterials to the injured cartilage for restoration of architecture and function. Pre-clinical models to test the efficacy of the therapies come with high costs and ethical issues, and imperfect prediction of performance in humans. Ex vivo models represent an alternative avenue to trial cartilage tissue engineering. Defined as viable explanted cartilage samples, ex vivo models can be cultured with a cell-laden biomaterial or tissue-engineered construct to evaluate cartilage repair. Though human and animal ex vivo models are currently used in the field, there is a need for alternative methods to assess the strength of integration, to increase throughput and manage variability and to optimise and standardise culture conditions, enhancing the utility of these models overall.

Phase transitions of aqueous solutions of Pluronic F68 in the presence of Diclofenac Sodium

In recent years, advancements in bioengineering and materials science have witnessed increasing interest in synthetic polymers capable of fulfilling various applications. Owing to their distinctive properties, Pluronics can be used as nano-drug carriers, to deliver poorly water-soluble drugs, and as model systems to study colloidal science by tuning amphiphilic properties. In this work, we investigated the effect of diclofenac sodium on the self-assembly and thermoresponsive crystallization of Pluronic F68 in water solutions, by employing experimental rheology and Nuclear Magnetic Resonance (NMR). We built a complete phase diagram as a function of temperature and concentration for 45 wt% Pluronic F68 with various amounts of diclofenac sodium in water. The morphological transitions were followed as a function of temperature via linear rheology. We extrapolated the transition temperatures - identifying distinct phases - as a function of the drug concentration and proposed an empirical model for their prediction. NMR analysis provided further information on the structural characteristics of the systems, shedding light on the interactions between F68 and diclofenac sodium. Although dealing with a pharmaceutical salt, the study is focused on a colloidal system and its interaction with a binding molecule, that is of general interest for colloidal science.

Aragonite-Based Scaffold Versus Microfracture and Debridement for the Treatment of Knee Chondral and Osteochondral Lesions: Results of a Multicenter Randomized Controlled Trial

BACKGROUND

Lesions of the articular cartilage, with or without involvement of the subchondral bone, are a common cause of pain and dysfunction in the knee. Although several treatment options have been developed, the majority of previous clinical trials examined patients with isolated or focal midsized defects, which rarely represent the condition found in the general population. Rather, cartilage lesions are often associated with the presence of mild to moderate osteoarthritic changes.

PURPOSE

The present multicenter randomized controlled trial compared the clinical and radiographic outcomes of an aragonite-based osteochondral implant with a control group (arthroscopic debridement/microfractures) in patients affected by joint surface lesions of the knee, including those with concurrent mild to moderate osteoarthritis.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 251 patients were enrolled in 26 medical centers according to the following criteria: age 21 to 75 years, up to 3 cartilage defects of International Cartilage Regeneration & Joint Preservation Society grade 3a or above located on the femoral condyles and/or trochlea, total treatable area from 1 to 7 cm², bony defect depth ≤8 mm, and knee osteoarthritis grade 0 to 3 according to Kellgren-Lawrence score. Patients were randomized to the aragonite-based implant or debridement/microfracture control arm in a 2:1 ratio. Evaluation was performed at 6, 12, 18, and 24 months based on overall Knee injury and Osteoarthritis Outcome Score (KOOS) as the primary endpoint, and the KOOS subscales (Pain, Quality of Life, Activities of Daily Living), percentage of responders, and International Knee Documentation Committee (IKDC) subjective score as the secondary endpoints. Patients also underwent magnetic resonance imaging evaluation at 12 and 24 months to assess defect fill grade. Failures (ie, need for any secondary treatment) and adverse events were also recorded.

RESULTS

The implant group showed a statistically superior outcome in the primary endpoint and all secondary endpoints at each follow-up. The magnitude of improvement in the implant group was twice as large as that in the control group in terms of mean KOOS improvement at 2 years. Responder rate (defined as at least a 30-point improvement in overall KOOS) was 77.8% in the implant group as opposed to 33.6% in the control (P < .0001). Statistically superior results were seen in the IKDC score as well. At 24 months, 88.5% of the implanted group had at least 75% defect fill on magnetic resonance imaging as compared with 30.9% of controls (P < .0001). The failure rate was 7.2% for the implant group versus 21.4% for control.

CONCLUSION

This aragonite-based scaffold was safe and effective in the treatment of chondral and osteochondral lesions in the knee, including patients with mild to moderate osteoarthritis, and provided superior outcomes as compared with the control group.

REGISTRATION

NCT03299959 (ClinicalTrials.gov identifier).

Biomaterials for meniscus and cartilage in knee surgery: state of the art

Meniscus and cartilage injuries of the knee joint lead to cartilage degeneration and osteoarthritis (OA). The research on biomaterials and artificial implants as substitutes in reconstruction and regeneration has become a main international focus in order to solve clinical problems such as irreparable meniscus injury, postmeniscectomy syndrome, osteochondral lesions and generalised chronic OA. In this review, we provide a summary of biomaterials currently used in clinical practice as well as state-of-the-art tissue engineering strategies and technologies that are developed for articular cartilage and meniscus repair and regeneration. The literature was reviewed over the last 5 years on clinically used meniscus and cartilage repair biomaterials, such as Collagen Meniscal Implant, Actifit, NUsurface, TruFit, Agili-C and MaioRegen. There are clinical advantages for these biomaterials and the application of these treatment options should be considered individually. Standardised evaluation protocols are needed for biological and mechanical assessment and comparison between different scaffolds, and long-term randomised independent clinical trials with large study numbers are needed to provide more insight into the use of these biomaterials. Surgeons should become familiar and stay up to date with evolving repair options to improve their armamentarium for meniscal and cartilage defects.

Algorithm for Treatment of Focal Cartilage Defects of the Knee: Classic and New Procedures

OBJECTIVE

To create a treatment algorithm for focal grade 3 or 4 cartilage defects of the knee using both classic and novel cartilage restoration techniques.

DESIGN

A comprehensive review of the literature was performed highlighting classic as well as novel cartilage restoration techniques supported by clinical and/or basic science research and currently being employed by orthopedic surgeons.

RESULTS

There is a high level of evidence to support the treatment of small to medium size lesions (<2-4 cm2) without subchondral bone involvement with traditional techniques such as marrow stimulation, osteochondral autograft transplant (OAT), or osteochondral allograft transplant (OCA). Newer techniques such as autologous matrix-induced chondrogenesis and bone marrow aspirate concentrate implantation have also been shown to be effective in select studies. If subchondral bone loss is present OAT or OCA should be performed. For large lesions (>4 cm2), OCA or matrix autologous chondrocyte implantation (MACI) may be performed. OCA is preferred over MACI in the setting of subchondral bone involvement while cell-based modalities such as MACI or particulated juvenile allograft cartilage are preferred in the patellofemoral joint.

CONCLUSIONS

Numerous techniques exist for the orthopedic surgeon treating focal cartilage defects of the knee. Treatment strategies should be based on lesion size, lesion location, subchondral bone involvement, and the level of evidence supporting each technique in the literature.

Joint Surface Lesions in the Knee Treated with an Acellular Aragonite-Based Scaffold: A 3-Year Follow-Up Case Series

OBJECTIVE

The study aimed to evaluate the clinical outcome and repair capacity of a cell-free aragonite-based scaffold in patients with an isolated symptomatic joint surface lesion (JSL) of the knee.

DESIGN

Thirteen patients (age 33.5 ± 8.9; female 23%; body mass index 25.3 ± 3.4, K/L [Kellgren-Lawrence] 1.8) with a JSL (2.6 ± 1.7 cm² [1.0-7.5 cm²]) of the distal femur were enrolled in a single-center prospective case series. Safety and clinical outcome was assessed by the KOOS (Knee Injury and Osteoarthritis Outcome Score), IKDC (International Knee Documentation Committee), Lysholm, and Tegner activity scale at baseline and 6, 12, 18, 24, and 36 months follow-up. The MOCART 2.0 and scaffold integration were evaluated on magnetic resonance imaging at 12, 24, and 36 months postoperatively.

RESULTS

Primary outcome (KOOS pain) improved with 36.5 ± 14.7 points at 12 months (P = 0.002) and 41.2 ± 14.7 points at 36 months (P = 0.002) follow-up. Similar increasing trends were observed for the other KOOS subscales, IKDC, and Lysholm score, which were significantly better at each follow-up time point relative to baseline (P < 0.05). Activity level increased from 2.75 ± 1.6 to 4.6 ± 2.2 points at final follow-up (P = 0.07). The MOCART was 61.7 ± 12.6 at 12 months and 72.9 ± 13.0 at 36 months postoperatively. Sixty-six to 100% implant integration and remodeling was observed in 73.3% cases at 36 months. No serious adverse events were reported.

CONCLUSION

The study demonstrated that the biphasic aragonite-based scaffold is a safe and clinically effective implant for treating small-medium sized JSLs of the distal femur in a young and active patient cohort. The implant showed satisfying osteointegration and restoration of the osteochondral unit up to 3 years postimplantation.

Articular cartilage and osteochondral tissue engineering techniques: Recent advances and challenges

In spite of the considerable achievements in the field of regenerative medicine in the past several decades, osteochondral defect regeneration remains a challenging issue among diseases in the musculoskeletal system because of the spatial complexity of osteochondral units in composition, structure and functions. In order to repair the hierarchical tissue involving different layers of articular cartilage, cartilage-bone interface and subchondral bone, traditional clinical treatments including palliative and reparative methods have showed certain improvement in pain relief and defect filling. It is the development of tissue engineering that has provided more promising results in regenerating neo-tissues with comparable compositional, structural and functional characteristics to the native osteochondral tissues. Here in this review, some basic knowledge of the osteochondral units including the anatomical structure and composition, the defect classification and clinical treatments will be first introduced. Then we will highlight the recent progress in osteochondral tissue engineering from perspectives of scaffold design, cell encapsulation and signaling factor incorporation including bioreactor application. Clinical products for osteochondral defect repair will be analyzed and summarized later. Moreover, we will discuss the current obstacles and future directions to regenerate the damaged osteochondral tissues.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

Osteochondral tissue engineering: Perspectives for clinical application and preclinical development

The treatment of osteochondral defects (OCD) remains challenging. Among currently available surgical treatments for OCDs, scaffold-based treatments are promising to regenerate the osteochondral unit. However, there is still no consensus regarding the clinical effectiveness of these scaffold-based therapies for OCDs. Previous reviews have described the gradient physiological characteristics of osteochondral tissue and gradient scaffold design for OCD, tissue engineering strategies, biomaterials, and fabrication technologies. However, the discussion on bridging the gap between the clinical need and preclinical research is still limited, on which we focus in the present review, providing an insight into what is currently lacking in tissue engineering methods that failed to yield satisfactory outcomes, and what is needed to further improve these techniques. Currently available surgical treatments for OCDs are firstly summarized, followed by a comprehensive review on experimental animal studies in recent 5 years on osteochondral tissue engineering. The review will then conclude with what is currently lacking in these animal studies and the recommendations that would help enlighten the community in developing more clinically relevant implants.

The translational potential of this article

This review is attempting to summarize the lessons from clinical and preclinical failures, providing an insight into what is currently lacking in TE methods that failed to yield satisfactory outcomes, and what is needed to further improve these implants.

Editorial Commentary: Minimally Invasive Strategies for Osteoarthritis: From Platelets to Mesenchymal Stem Cells

The range of biological agents to treat osteoarthritis is in constant expansion, and recent trials suggest that amnion-derived products (such as umbilical cord stem cells or amniotic allograft suspension) may provide significant symptomatic relief and functional improvement compared with traditional injectables. Anyway, in many countries, stringent limitations exist on the manipulation and homologous use of placenta-derived products, and therefore, collecting more data is mandatory to endorse their use for musculoskeletal diseases in a safe and clearly regulated way. More in general, an increasing interest toward orthobiology has been observed in recent years, which led to the introduction in clinical practice of many minimally invasive strategies to treat osteoarthritis, from platelet-rich plasma to mesenchymal stem cells. On the basis of this trend, which involves physicians from different specialties, it would be fundamental to have clear guidelines establishing the correct use of these products in the setting of clinical routine not only to safely provide patients the most advanced therapeutic options but also to protect our practice from potential legal issues.

Complex Osteochondral Lesions of the Talus Treated With a Novel Bi-Phasic Aragonite-based Implant

To present initial results of a novel, bi-phasic, porous, biodegrade, and cell-free aragonite-based scaffold for treating complex osteochondral lesions of the talus (OLT). Four subjects (2 males and 2 females; 34-61 years old) were operated on their ankles due to chronic and deep OLT-Hepple grades 4 or 5 (1.8-2.2 cm²). Three subjects had OLT on the medial central trochlea, and 1 had a combined medial and lateral lesions. OLT were exposed through medial malleolus osteotomy, with an additional lateral arthrotomy in the combined lesions. Bi-phasic porous osteochondral scaffolds (single implant or 2 implants) were implanted in a press-fit manner using a designated surgical toolset. Treatment outcome was followed clinically (Foot and Ankle Outcome Score, EQ-5D 3L, Tegner activity scale) and by medical imaging (radiographs, magnetic resonance imaging) from 18 to 32 months. All Foot and Ankle Outcome Score values increased from preoperative to final follow-up values (Symptoms 62 to 71, Pain 53 to 84, ADL 60 to 89, Sport 19 to 65, and QoL 18 to 47). EQ-5D 3L increased from 0.59 to 0.76, and Tegner activity values increased from 1.5 to 3. Kellgren-Lawrence ankle radiographic scores remained stable (2 to 2). Postoperative MR evaluation demonstrated cartilage defect fill of 75% to 100% respect to the native cartilage in 3 subjects (4 OLTs), while 1 lesion was filled 25% to 50%. No graft related serious adverse events or graft failures were reported. The use of a bi-phasic osteochondral biodegradable aragonite-based scaffold in the treatment of complex OLT during the reported period presented positive and promising clinical and radiologic outcome, without serious adverse events or graft failures.

Aragonite-Based Scaffold for the Treatment of Joint Surface Lesions in Mild to Moderate Osteoarthritic Knees: Results of a 2-Year Multicenter Prospective Study

BACKGROUND

Osteoarthritis (OA) is considered a contraindication to most cartilage repair techniques. Several regenerative approaches have been attempted with the aim of delaying or preventing joint replacement, with controversial results. Currently, there is a paucity of data on the use of single-step techniques, such as cell-free biomimetic scaffolds, for the treatment of joint surface lesions (JSLs) in OA knees.

PURPOSE

To present the 2-year follow-up clinical and radiological outcomes after implantation of a novel, cell-free aragonite-based scaffold for the treatment of JSLs in patients with mild to moderate knee OA in a multicenter prospective study.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 86 patients, 60 male and 26 female, with a mean age of 37.4 ± 10.0 years, mild to moderate knee OA, and a mean defect size of 3.0 ± 1.7 cm², were recruited at 8 medical centers according to the following criteria: radiographic mild to moderate knee OA (Kellgren-Lawrence grade 2 or 3); up to 3 treatable chondral/osteochondral defects (International Cartilage Repair Society grades 3 and 4) on the femoral condyles or trochlea; a total defect size ≤7 cm²; and no concurrent knee instability, severe axial malalignment, or systemic arthropathy. All patients were evaluated at baseline and at 6, 12, 18, and 24 months after implantation using the Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) subjective score. Additionally, magnetic resonance imaging (MRI) was performed to assess the amount of cartilage defect filling at the repaired site.

RESULTS

Significant improvement on all KOOS subscales was recorded from baseline (Pain: 49.6 ± 13.1; Activities of Daily Living [ADL]: 56.1 ± 18.4; Sport: 22.8 ± 18.8; Quality of Life [QoL]: 23.5 ± 16.5; Symptoms: 55.4 ± 19.9) to the 24 months' follow-up (Pain: 79.5 ± 21.1 [P < .001]; ADL: 84.1 ± 21.4 [P < .001]; Sport: 60.8 ± 31.9 [P < .001]; QoL: 54.9 ± 30.4 [P < .001]; Symptoms: 77.7 ± 21.2 [P < .001]). The IKDC subjective score showed a similar trend and improved from 37.8 ± 14.7 at baseline to 65.8 ± 23.5 at 24 months (P < .001). MRI showed a significant increase in defect filling over time: up to 78.7% ± 25.3% of surface coverage after 24 months. Treatment failure requiring revision surgery occurred in 8 patients (9.3%).

CONCLUSION

The use of an aragonite-based osteochondral scaffold in patients with JSLs and mild to moderate knee OA provided significant clinical improvement at the 24-month follow-up, as reported by the patients. These findings were associated with good cartilage defect filling, as observed on MRI.

Management of Large Focal Chondral and Osteochondral Defects in the Knee

Large, focal articular cartilage defects of the knee (> 4 cm²) can be a source of significant morbidity and often require surgical intervention. Patient- and lesion-specific factors must be identified when evaluating a patient with an articular cartilage defect. In the management of large cartilage defects, the two classically utilized cartilage restoration procedures are osteochondral allograft (OCA) transplantation and cell therapy, or autologous chondrocyte implantation (ACI). Alternative techniques that are available or currently in clinical trials include a hyaluronan-based scaffold plus bone marrow aspirate concentrate, a third-generation autologous chondrocyte implant, and an aragonite-based scaffold. In this review, we will focus on OCA and ACI as the mainstay in management of large chondral and osteochondral defects of the knee. We will discuss the techniques and associated clinical outcomes for each, while including a brief mention of alternative treatments. Overall, cartilage restoration techniques have yielded favorable clinical outcomes and can be successfully employed to treat these challenging large focal lesions.

Treatment of hallux rigidus by a novel bi-phasic aragonite-based implant: results of a two year multi-centre clinical trial

PURPOSE

The two year results of a multi-centre clinical trial were examined to evaluate surgical treatment of hallux rigidus using a novel, bi-phasic, biodegradable, and cell-free aragonite-based scaffold (Agili-C™, CartiHeal Ltd, Israel).

METHODS

Twenty patients with moderate-to-severe hallux rigidus were recruited. After thorough metatarsophalangeal joint (MTPJ-1) debridement, the scaffolds were implanted into the defect centre. Eight patients received concomitant osteotomy. Treatment outcome was followed clinically (Pain VAS, FAAM-ADL, FAAM-Sport, AOFAS-HMIS, maximum active range of extension ROM-EXT, and flexion ROM-FLEX), and by medical imaging, at six month intervals for two years. Adverse events were recorded throughout the study follow-up period.

RESULTS

Significant clinical improvement over time was observed in all evaluated parameters (screening to final evaluation averages: Pain VAS 59 to 26, FAAM-ADL 57 to 77, FAAM-Sport 39 to 66, AOFAS-HMIS 51 to 81, ROM-EXT 18° to 36°), except for ROM-FLEX. Radiographs showed stable MTPJ-1 width over the two years in 17/18 cases (94%). MRI demonstrated progressive implant biodegradation, coupled with articular cartilage and subchondral bone regeneration, with a repair tissue defect fill of 75-100% in 14/17 (82%) subjects at their final visit. Revision surgery with implant removal was performed in two patients.

CONCLUSION

Bi-phasic, osteochondral, biodegradable, aragonite-based scaffold demonstrated positive clinical outcome and a good safety profile in the treatment of medium-to-advanced hallux rigidus. According to the medical imaging, this implant has the potential to restore the entire osteochondral unit of metatarsal head.

Osteochondral Injury, Management and Tissue Engineering Approaches

Osteochondral lesions (OL) are a common clinical problem for orthopedic surgeons worldwide and are associated with multiple clinical scenarios ranging from trauma to osteonecrosis. OL vary from chondral lesions in that they involve the subchondral bone and chondral surface, making their management more complex than an isolated chondral injury. Subchondral bone involvement allows for a natural healing response from the body as marrow elements are able to come into contact with the defect site. However, this repair is inadequate resulting in fibrous scar tissue. The second differentiating feature of OL is that damage to the subchondral bone has deleterious effects on the mechanical strength and nutritive capabilities to the chondral joint surface. The clinical solution must, therefore, address both the articular cartilage as well as the subchondral bone beneath it to restore and preserve joint health. Both cartilage and subchondral bone have distinctive functional requirements and therefore their physical and biological characteristics are very much dissimilar, yet they must work together as one unit for ideal joint functioning. In the past, the obvious solution was autologous graft transfer, where an osteochondral bone plug was harvested from a non-weight bearing portion of the joint and implanted into the defect site. Allografts have been utilized similarly to eliminate the donor site morbidity associated with autologous techniques and overall results have been good but both techniques have their drawbacks and limitations. Tissue engineering has thus been an attractive option to create multiphasic scaffolds and implants. Biphasic and triphasic implants have been under explored and have both a chondral and subchondral component with an interface between the two to deliver an implant which is biocompatible and emulates the osteochondral unit as a whole. It has been a challenge to develop such implants and many manufacturing techniques have been utilized to bring together two unalike materials and combine them with cellular therapies. We summarize the functions of the osteochondral unit and describe the currently available management techniques under study.

Clinical Application of the Basic Science of Articular Cartilage Pathology and Treatment

The joint is an organ with each tissue playing critical roles in health and disease. Intact articular cartilage is an exquisite tissue that withstands incredible biologic and biomechanical demands in allowing movement and function, which is why hyaline cartilage must be maintained within a very narrow range of biochemical composition and morphologic architecture to meet demands while maintaining health and integrity. Unfortunately, insult, injury, and/or aging can initiate a cascade of events that result in erosion, degradation, and loss of articular cartilage such that joint pain and dysfunction ensue. Importantly, articular cartilage pathology affects the health of the entire joint and therefore should not be considered or addressed in isolation. Treating articular cartilage lesions is challenging because left alone, the tissue is incapable of regeneration or highly functional and durable repair. Nonoperative treatments can alleviate symptoms associated with cartilage pathology but are not curative or lasting. Current surgical treatments range from stimulation of intrinsic repair to whole-surface and whole-joint restoration. Unfortunately, there is a relative paucity of prospective, randomized controlled, or well-designed cohort-based clinical trials with respect to cartilage repair and restoration surgeries, such that there is a gap in knowledge that must be addressed to determine optimal treatment strategies for this ubiquitous problem in orthopedic health care. This review article discusses the basic science rationale and principles that influence pathology, symptoms, treatment algorithms, and outcomes associated with articular cartilage defects in the knee.

Mechanical Stress Inhibits Early Stages of Endogenous Cell Migration: A Pilot Study in an Ex Vivo Osteochondral Model

Cell migration has a central role in osteochondral defect repair initiation and biomaterial-mediated regeneration. New advancements to reestablish tissue function include biomaterials and factors promoting cell recruitment, differentiation and tissue integration, but little is known about responses to mechanical stimuli. In the present pilot study, we tested the influence of extrinsic forces in combination with biomaterials releasing chemoattractant signals on cell migration. We used an ex vivo mechanically stimulated osteochondral defect explant filled with fibrin/hyaluronan hydrogel, in presence or absence of platelet-derived growth factor-BB or stromal cell-derived factor 1, to assess endogenous cell recruitment into the wound site. Periodic mechanical stress at early time point negatively influenced cell infiltration compared to unloaded samples, and the implementation of chemokines to increase cell migration was not efficient to overcome this negative effect. The gene expression at 15 days of culture indicated a marked downregulation of matrix metalloproteinase (MMP)13 and MMP3, a decrease of β1 integrin and increased mRNA levels of actin in osteochondral samples exposed to complex load. This work using an ex vivo osteochondral mechanically stimulated advanced platform demonstrated that recurrent mechanical stress at early time points impeded cell migration into the hydrogel, providing a unique opportunity to improve our understanding on management of joint injury.

Reconstruction of Large Osteochondral Defects Using a Hemicondylar Aragonite-Based Implant in a Caprine Model

PURPOSE

To investigate the safety and regenerative potential of a hemicondylar aragonite-based scaffold in the reconstruction of large osteochondral lesions occupying an extensive portion of the medial femoral condyle in a goat model.

METHODS

Eight Saanen goats were treated by the implantation of an aragonite-based scaffold (size: 19 × 8 × 8 mm) on a previously prepared hemicondylar osteochondral defect located in the right medial femoral condyle of the knee. Goats were euthanized after 12 months and the specimens underwent X-ray imaging, macroscopic, micro-computed tomography, histology, and immunohistochemistry evaluations to assess subchondral bone and cartilage regeneration.

RESULTS

In all 8 goats, no adverse event or persistent inflammation was observed. The evaluations performed showed integration of the scaffold, which almost completely resorbed at 12 months. In all animals, no signs of osteoarthritis progression were seen. Concurrent regeneration of the osteochondral unit was observed, with trabecular bone tissue replacing the implant and restoring the subchondral layer, and the formation of an overlying hyaline cartilage surface, well integrated within the surrounding native tissue, also was observed.

CONCLUSIONS

The use of the hemicondylar biphasic aragonite-based implant in the treatment of osteochondral defects in the goat model proved to be technically feasible and safe. The scaffold degraded and was replaced by regenerated tissue within the 12-month study period, restoring the osteochondral unit both at the level of the cartilaginous layer and the subchondral bone.

CLINICAL RELEVANCE

The present animal study describes a scaffold-based procedure for the treatment of large condylar defects, which often require massive allograft or unicompartmental replacement. The aragonite-based implant promoted a regeneration of both cartilage and subchondral bone, and its use as a "biologic" unicondylar prosthesis might be feasible also in the clinical setting.