Cell-free repair of small cartilage defects in the Goettinger minipig: which defect size is possible?

Purpose

Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed by treatment with cell-free collagen type-I gel plugs of three different sizes.

Methods

In 6 adult Goettinger minipigs, three full-thickness chondral defects were created in the trochlear groove of one knee of the hind leg. These defects were treated with a cell-free collagen type-I gel plug of 8, 10, or 12 mm diameter. All animals were allowed unlimited weight bearing. After 1 year, the animals were killed. Immediately after recovery, a non-destructive biomechanical testing was performed. The repair tissue quality was evaluated immunohistologically, collagen type-II protein was quantified, and a semiquantitative score (O’Driscoll score) was calculated.

Results

After 1 year, a high number of cells migrated into the initially cell-free collagen gel plugs and a hyaline-like repair tissue had been created. The O’Driscoll scores were: 8 mm, 21.2 (SD, 2.8); 10 mm, 21.5 (SD, 1.6); and 12 mm, 22.3 (SD, 1.0). The determination of the e-modulus, creep and relaxation revealed that mechanical properties of the two smaller defects were closer to unaffected hyaline cartilage.

Conclusions

As cell-free collagen type-I gel plugs of all three different sizes created hyaline-like repair tissue, this system seems suitable for the treatment of even larger defects.     

Fibrin glue does not improve the fixation of press-fitted cell-free collagen gel plugs in an ex vivo cartilage repair model

Purpose  

Adequate graft fixation over a certain time period is necessary for successful cartilage repair and permanent integration of the graft into the surrounding tissue. The aim of the present study was to test the primary stability of a new cell-free collagen gel plug (CaReS^?-1S) with two different graft fixation techniques over a simulated early postoperative period.     

Transplanted articular chondrocytes co-overexpressing IGF-I and FGF-2 stimulate cartilage repair in vivo

Purpose

The combination of chondrogenic factors might be necessary to adequately stimulate articular cartilage repair. In previous studies, enhanced repair was observed following transplantation of chondrocytes overexpressing human insulin-like growth factor I (IGF-I) or fibroblast growth factor 2 (FGF-2). Here, the hypothesis that co-overexpression of IGF-I and FGF-2 by transplanted articular chondrocytes enhances the early repair of cartilage defects in vivo and protects the neighbouring cartilage from degeneration was tested.

Methods

Lapine articular chondrocytes were transfected with expression plasmid vectors containing the cDNA for the Escherichia coli lacZ gene or co-transfected with the IGF-I and FGF-2 gene, encapsulated in alginate and transplanted into osteochondral defects in the knee joints of rabbits in vivo.

Results

After 3 weeks, co-overexpression of IGF-I/FGF-2 improved the macroscopic aspect of defects without affecting the synovial membrane. Immunoreactivity to type-I collagen, an indicator of fibrocartilage, was significantly lower in defects receiving IGF-I/FGF-2 implants. Importantly, combined IGF-I/FGF-2 overexpression significantly improved the histological repair score. Most remarkably, such enhanced cartilage repair was correlated with a 2.1-fold higher proteoglycan content of the repair tissue. Finally, there were less degenerative changes in the cartilage adjacent to the defects treated with IGF-I/FGF-2 implants.

Conclusion

The data demonstrate that combined gene delivery of therapeutic growth factors to cartilage defects may have value to promote cartilage repair. The results also suggest a protective effect of IGF-I/FGF-2 co-overexpression on the neighbouring articular cartilage. These findings support the concept of implementing gene transfer strategies for articular cartilage repair in a clinical setting.     

Cartilage repair in the knee with subchondral drilling augmented with a platelet-rich plasma-immersed polymer-based implant

Purpose

The aim of our study was to analyse the clinical and histological outcome after the treatment of focal cartilage defects in non-degenerative and degenerative knees with bone marrow stimulation and subsequent covering with a cell-free resorbable polyglycolic acid–hyaluronan (PGA-HA) implant immersed with autologous platelet-rich plasma (PRP).

Methods

Fifty-two patients (mean age 44 years) with focal chondral defects in radiologically confirmed non-degenerative or degenerative knees were subjected to subchondral drilling arthroscopically. Subsequently, defects were covered with the PGA-HA implant immersed with autologous PRP. At 2-year follow-up, the patients’ situation was assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and compared to the pre-operative situation and 3–12-month follow-up. Biopsies (n = 4) were harvested at 18–24 months after implantation and were analysed by histology and collagen type II immune staining.

Results

At 1- and 2-year follow-up, the KOOS showed clinically meaningful and significant (p < 0.05) improvement in all subcategories compared to baseline and to 3-month follow-up. There were no differences in KOOS data obtained after 2 years compared to 1 year after the treatment. Histological analysis of the biopsy tissue showed hyaline-like to hyaline cartilage repair tissue that was rich in cells with a chondrocyte morphology, proteoglycans and type II collagen.

Conclusions

Covering of focal cartilage defects with the PGA-HA implant and PRP after bone marrow stimulation improves the patients’ situation and has the potential to regenerate hyaline-like cartilage.

Level of evidence

Case series, Level IV.     

Autologous matrix-induced chondrogenesis combined with platelet-rich plasma gel: technical description and a five pilot patients report

Purpose  

This pilot study was designed to describe the technical details and to present the preliminary outcome of autologous matrix-induced chondrogenesis (AMIC) combined with platelet-rich plasma gel, the so called AMIC plus technique, for the treatment of patellar cartilage defects in the knee.     

Cell-free collagen type I matrix for repair of cartilage defects—clinical and magnetic resonance imaging results

Purpose

Several well-described techniques are available for the treatment of chondral and osteochondral defects. The aim of the study was to assess the efficacy of a single-stage procedure incorporating a new cell-free collagen type I gel for the treatment of small chondral and osteochondral defects in the knee evaluated at 2-year follow-up.

Methods

Fifteen patients were treated with a cell-free collagen type I gel matrix of 11?mm diameter. The grafts were implanted in the debrided cartilage defect and fixed by press-fit only. The clinical outcome was assessed preoperatively and at 6?weeks, and 6, 12 and 24?months after surgery using the International Knee Documentation Committee (IKDC) score, Tegner activity scale and visual analogue scale (VAS). Graft attachment rate was assessed 6?weeks postoperatively using magnetic resonance imaging (MRI). Cartilage regeneration was evaluated using the Magnetic Observation of Cartilage Repair Tissue (MOCART) score at 6, 12 and 24?months after implantation. Clinical results were correlated with MRI findings.

Results

Six male and nine female patients were included in this study, with a mean age of 26 (range: 19–40). No complications were reported. The mean VAS values after 6?weeks and the mean IKDC patient values after 6?months were significantly improved from the preoperative values (P?=?0.005 and P?=?0.009, respectively). This improvement remained up to the latest follow-up. There were no significant differences between the median preoperative and postoperative Tegner values (n.s.). Significant improvement of the mean MOCART score was observed after 12?months and remained by 24?months (P?Conclusions The present study reveals that the new method produces both good clinical and magnetic resonance imaging results. Use of press-fit only implanted grafts of a smaller diameter leads to a high attachment rate at 24-month follow-up.

Level of evidence

IV.     

The combination of microfracture and a cell-free polymer-based implant immersed with autologous serum for cartilage defect coverage

Purpose

The purpose of this short-term pilot study was to determine the clinical and MRI outcome of a combination of microfracture with a cell-free polymer-based matrix for the treatment of cartilage defects in the knee.

Methods

The technique was used for treatment of symptomatic cartilage defects in the knee. Five patients were prospectively evaluated during 2?years with use of the Knee injury and Osteoarthritis Outcome Score (KOOS), the Tegner activity scale and the visual analog scale (VAS). MRI data were analyzed based on the original and modified MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) scoring system at 6, 12 and 24?months of follow-up.

Results

A gradual clinical improvement was observed during the follow-up. Adverse reactions to the matrix were not observed. The scaffold was firmly fixed with the use of bioresorbable pins. Both MOCART scoring systems revealed no significant deterioration or improvement in the repair tissue during the follow-up period. However, the majority of the patients exhibited subchondral lamina and bone changes. The formation of an intralesional osteophyte was observed in one case.

Conclusions

The key finding in this study was that this procedure is safe for the treatment of cartilage defects in the knee. The patients showed a gradual clinical improvement postoperatively. Sixty percent (3/5) of the defects were adequately (complete or hypertrophic) filled with repair tissue at 2?years of follow-up.

Level of evidence

IV.     

A novel nano-structured porous polycaprolactone scaffold improves hyaline cartilage repair in a rabbit model compared to a collagen type I/III scaffold: in vitro and in vivo studies

Purpose

To develop a nano-structured porous polycaprolactone (NSP-PCL) scaffold and compare the articular cartilage repair potential with that of a commercially available collagen type I/III (Chondro-Gide^®) scaffold.

Methods

By combining rapid prototyping and thermally induced phase separation, the NSP-PCL scaffold was produced for matrix-assisted autologous chondrocyte implantation. Lyophilizing a water–dioxane–PCL solution created micro and nano-pores. In vitro: The scaffolds were seeded with rabbit chondrocytes and cultured in hypoxia for 6 days. qRT–PCR was performed using primers for sox9, aggrecan, collagen type 1 and 2. In vivo: 15 New Zealand White Rabbits received bilateral osteochondral defects in the femoral intercondylar grooves. Autologous chondrocytes were harvested 4 weeks prior to surgery. There were 3 treatment groups: (1) NSP-PCL scaffold without cells. (2) The Chondro-Gide^® scaffold with autologous chondrocytes and (3) NSP-PCL scaffold with autologous chondrocytes. Observation period was 13 weeks. Histological evaluation was made using the O’Driscoll score.

Results

In vitro: The expressions of sox9 and aggrecan were higher in the NSP-PCL scaffold, while expression of collagen 1 was lower compared to the Chondro-Gide^® scaffold. In vivo: Both NSP-PCL scaffolds with and without cells scored significantly higher than the Chondro-Gide^® scaffold when looking at the structural integrity and the surface regularity of the repair tissue. No differences were found between the NSP-PCL scaffold with and without cells.

Conclusion

The NSP-PCL scaffold demonstrated higher in vitro expression of chondrogenic markers and had higher in vivo histological scores compared to the Chondro-Gide^® scaffold. The improved chondrocytic differentiation can potentially produce more hyaline cartilage during clinical cartilage repair. It appears to be a suitable cell-free implant for hyaline cartilage repair and could provide a less costly and more effective treatment option than the Chondro-Gide^® scaffold with cells.     

Use of cell-free collagen type I matrix implants for the treatment of small cartilage defects in the knee: clinical and magnetic resonance imaging evaluation

Purpose

Articular cartilage defects of the knee are a common condition for which several repair techniques have been described. The aim of the present study was to assess medium-term results of a one-step procedure using a cell-free collagen type I matrix.

Methods

Fifteen patients with articular cartilage defects of the knee were treated with an 11-mm-diameter cell-free collagen type 1 matrix implant. The matrices were implanted in a press-fit manner into the defect after careful debridement down to the subchondral bone but without penetration of this margin. Follow-up examinations were carried out at 6 weeks, 6 months, and at 12, 24, 36, and 48 months after implantation. Clinical assessment included the visual analogue scale (VAS), the Tegner activity scale, and the International Knee Documentation Committee (IKDC) score. Radiological assessment for graft attachment and tissue regeneration was performed using the magnetic observation of cartilage repair tissue (MOCART) score.

Results

A total of 15 patients (males: n = 6 and females: n = 9) with a mean age of 26.4 years (range 19–40) were treated. The mean VAS improved significantly when compared to the preoperative values (P < 0.05). Six weeks after implantation, IKDC values were slightly lower than the preoperative values (n.s.), but increased significantly at final follow-up (P < 0.05). At 24 months, there were no significant differences in the median Tegner score between the post-operative values and the preoperative values (n.s.). However, after 36 months, a significant improvement was noted that lasted at least up to 48 months (P < 0.05). The MOCART score improved consistently up to 4 years after implantation, with significant improvements already observed after 12 months (P < 0.05). No correlation between the clinical scores and the MOCART score could be perceived.

Conclusion

The present study showed that the use of cell-free collagen type I matrix implants led to a significant and durable improvement in all the clinical and imaging scores investigated 4 years after implantation.

Level of evidence

IV.     

Patellar chondral defects: a review of a challenging entity

Purpose  

The aim of this study was to perform a review of the management of patellar cartilage defects, identify prognostic factors for better clinical outcomes, and propose a treatment algorithm of this challenging entity.     

Failed cartilage repair for early osteoarthritis defects: a biochemical, histological and immunohistochemical analysis of the repair tissue after treatment with marrow-stimulation techniques

Purpose

To examine the entire repair tissue resulting from marrow-stimulation techniques in patients with early osteoarthritis.

Methods

The repair tissue and adjacent articular cartilage after failed marrow-stimulation techniques (microfracture and Pridie drilling) of 5 patients (47–65 years old) with cartilage defects and radiographic early osteoarthritis (Kellgren–Lawrence grading 1 and 2) was removed during total joint arthroplasty (mean time until analysis: 8.8 months), analysed by histology, polarized light microscopy, immunohistochemistry, biochemistry and by histological score systems.

Results

Macroscopic cartilage repair assessment revealed ICRS grades of II (nearly normal) and III (abnormal). Cartilage defects were mostly completely filled with a fibrocartilaginous tissue that had small and large fissures. Cartilage-specific stains of the repair tissue were more intense than the surrounding native cartilage but reduced compared with normal articular cartilage. The subchondral bone was incompletely restored. A new tidemark was absent. The repair tissue always showed positive immunoreactivity for types II and X collagen, and was sometimes positive for type I collagen. Proteoglycan contents of the repair tissue were generally higher than of the surrounding cartilage. The repair tissue was always more cellular than the adjacent articular cartilage. Histological scoring of the repair tissue revealed a mean Sellers score of 17.6 ± 3.0 and an ICRS grading of 7–9.

Conclusion

Failed marrow stimulation of articular cartilage defects in patients with early osteoarthritis is characterized by fibrocartilaginous repair. The balance of cell number to extracellular matrix is shifted towards an increased cell number in this tissue. Articular cartilage repair did not reach the quality of normal hyaline articular cartilage.

Level of evidence

IV.     

Effectiveness and limitations of autologous osteochondral grafting for the treatment of articular cartilage defects in the knee

Purpose  

To evaluate the effectiveness and limitations of autologous osteochondral grafting for the treatment of articular cartilage defects in the knee.     

Osteochondral regeneration using a novel aragonite-hyaluronate bi-phasic scaffold in a goat model

Purpose

The objective of this study was to examine whether different mechanical modifications and/or impregnation of hyaluronic acid (HA) might enhance aragonite-based scaffold properties for the regeneration of cartilage and bone in an animal model.

Methods

Bi-phasic osteochondral scaffolds were prepared using coralline aragonite with different modifications, including 1- to 2-mm-deep drilled channels in the cartilage phase (Group 1, n = 7) or in the bone phase (Group 2, n = 8), and compared with unmodified coral cylinders (Group 3, n = 8) as well as empty control defects (Group 4, n = 4). In each group, four of the implants were impregnated with HA to the cartilage phase. Osteochondral defects (6 mm diameter, 8 mm depth) were made in medial and lateral femoral condyles of 14 goats, and the scaffolds were implanted according to a randomization chart. After 6 months, cartilage and bone regeneration were evaluated macroscopically and histologically by an external laboratory.

Results

Group 1 implants were replaced by newly formed hyaline cartilage and subchondral bone (combined histological evaluation according to the ICRS II-2010 and O’Driscoll et al. 34 ± 4 n = 7). In this group, the cartilaginous repair tissue showed a smooth contour and was well integrated into the adjacent native cartilage, with morphological evidence of hyaline cartilage as confirmed by the marked presence of proteoglycans, a marked grade of collagen type II and the absence of collagen type I. The average scores in other groups were significantly lower (Group 2 (n = 8) 28.8 ± 11, Group 3 (n = 8) 23 ± 9 and Group 4 (empty control, n = 4) 19.7 ± 15).

Conclusions

The implants with the mechanical modification and HA impregnation in the cartilage phase outperformed all other types of implant. Although native coral is an excellent material for bone repair, as a stand-alone material implant, it does not regenerate hyaline cartilage. Mechanical modification with drilled channels and impregnation of HA within the coral pores enhanced the scaffold’s cartilage regenerative potential. The modified implant shows young hyaline cartilage regeneration. This implant might be useful for the treatment of both chondral and osteochondral defects in humans.     

Strategies for patient profiling in articular cartilage repair of the knee: a prospective cohort of patients treated by one experienced cartilage surgeon

Purpose

The purpose of this study was to report on the clinical outcome of a large heterogenic cartilage repair population treated with the profiling strategies of one experienced cartilage surgeon to provide evidence based tools for treatment selection in a clinical environment.

Methods

A total of 216 patients were identified in this prospective single-surgeon study. For the primary and secondary treatment of smaller defects, microfracture (MF) was used. Hyalograft C was used for first and second line larger defects, while carbon-fiber rod and pad implantations were used as a salvage procedure.

Results

Three years after the initial procedure, the clinical improvement was excellent for MF and Hyalograft C (P?P?P?P?Conclusion This is the first study that provides an assessment of the treatment strategies used by an experienced cartilage surgeon. A treatment algorithm for cartilage repair in a heterogenic population was created that based on the findings of this study could be implemented in a clinical environment.

Level of evidence

Prospective clinical case series, Level IV     

Microfracture combined with osteochondral paste implantation was more effective than microfracture alone for full-thickness cartilage repair

Purpose

The aim of this study was to evaluate whether the microfracture combined with osteochondral paste implantation could promote the quality of the regenerated tissue in the knee joints of rabbits.

Methods

Sixty-six New Zealand white rabbits were used. Bilateral knee joints from the same rabbit were randomly divided into experimental group and microfracture group. An articular cartilage defect was established in the femoral trochlear groove. In the experimental group, the defect was microfractured and covered with osteochondral paste harvested from the intercondylar notch. The regenerated tissues were harvested for gross morphology, histology, biochemistry and gene expression analysis at 4, 8 and 12 weeks postoperatively.

Results

The regenerated tissue had a slowly mature process in both groups. At 12 weeks, the regenerated tissue in the experimental group appeared much more thicker and white with higher percentages of defect filling macroscopically. In histology, the experimental group found a majority of hyaline-like regenerate tissue with intense Safranin-O and collagen type II staining, while fibrocartilage-like tissue was mostly seen in the microfracture group with poor Safranin-O and collagen type II staining. The experimental group had higher Wakitani scores and narrower acellular zones than those in the microfracture group (P < 0.05). For biochemical analysis, both the GAG content and the DNA-normalized GAG content saw a time-dependent increase with a much higher value found in the experimental group at 8 and 12 weeks (P < 0.05). On the contrary, the total DNA content decreased with time in both groups, and the difference between the two groups was only found at 4 and 8 weeks (P < 0.05). For gene expression analysis, the experimental group had much higher expression levels than the microfracture group as for collagen type II and aggrecan, but not for collagen type I.

Conclusion

Microfracture combined with paste implantation can result in improved quality of the reparative tissue and may have a positive effect on the integration to the surrounding cartilage in the rabbit model. The technique offers a promising treatment option for cartilage defects and improves the regeneration of articular cartilage for patients with painful chondral lesions.     

The treatment of chondral and osteochondral defects of the knee with autologous matrix-induced chondrogenesis (AMIC): method description and recent developments

Purpose  

Articular resurfacing by treatment of chondral defects may include chondral abrasion, autologous chondrocyte Implantation (ACI), matrix-induced chondrocyte transplantation (MACT) or osteochondral autologous transplantation (OATS). This technical note describes the method of autologous matrix-induced chondrogenesis (AMIC), a one-step procedure combining subchondral microfracture with the fixation of a collagen I/III membrane with fibrin glue or sutures.     

Short-term outcome of the second generation characterized chondrocyte implantation for the treatment of cartilage lesions in the knee

Purpose

To evaluate short-term clinical and MRI outcome of the second generation characterized chondrocyte implantation (CCI) for the treatment of cartilage defects in the knee.

Methods

Thirty-two patients aged 15–51 years with single International Cartilage Repair Society (ICRS) grade III/IV symptomatic cartilage defects of different locations in the knee were treated with CCI using a synthetic collagen I/III membrane to cover the defect. Clinical outcome was measured over 36 months by the Knee injury and Osteoarthritis Outcome Score (KOOS) and Visual Analogue Scale (VAS) for pain. Serial magnetic resonance imaging (MRI) scans of 22 patients were scored using the original and modified Magnetic resonance Observation of Cartilage Repair Tissue (MOCART) system.

Results

The patients included in this study showed a significant gradual clinical improvement after CCI. The MRI findings of this pilot study were considered to be promising. No signs of deterioration were observed. A complete or hypertrophic filling was observed in 76.5% of the cases at 24 months of follow-up. No preventive effect of an avital membrane on the occurrence of hypertrophic repair tissue was observed on MRI. Three failures were observed among the 32 patients until now (9.4%).

Conclusions

This investigation provided useful information on the efficacy of this treatment. The short-term clinical and MRI outcome are promising. Large-scale and long-term trials are mandatory to confirm the results and the reliability of this procedure.

Level of evidence

IV.     

Platelet-rich plasma activation in combination with biphasic osteochondral scaffolds–conditions for maximal growth factor production

Purpose  

The combination of scaffolds and biological factors may enhance articular cartilage repair. Little is known regarding the activation and subsequent growth factor release of platelet-rich plasma (PRP) in contact with biosynthetic scaffolds. The purpose of this study was i) to identify whether the addition of thrombin was required to activate PRP in the presence of a collagen osteochondral scaffold and ii) to compare the activity of PRP when applied to both collagen- and polylactide-based osteochondral scaffolds.     

One-step osteochondral repair with cartilage fragments in a composite scaffold

Purpose

This study proposes a single-step therapeutic approach for osteochondral defects using autologous cartilage fragments loaded onto a scaffold composed of a hyaluronic acid (HA) derivative, human fibrin glue (FG) and autologous platelet-rich-plasma (PRP), in a rabbit model. The aim is to demonstrate the in vitro outgrowth of chondrocytes from cartilage fragments and the in vivo formation of a functional repair tissue.

Methods

In vitro: minced articular cartilage was loaded onto two different types of scaffold (paste or membrane) according to two different HA preparations (injectable HA-derivative or HA-derivative felt). In vivo: trochlear osteochondral defects were created in 50 adult rabbits, which were then assigned to 5 different treatment groups: cartilage fragments loaded onto membrane scaffolds with FG (Group 1) or without FG (Group 2); membrane scaffolds alone with FG (Group 3) or without FG (Group 4); empty defects (Group 5). Membrane scaffolds were used “in vivo” for simpler preparation and better adhesive properties. Repair processes were evaluated histologically and by immunohistochemistry at 1, 3, and 6 months.

Results

An in vitro time-dependent cell outgrowth from cartilage fragments was observed with both types of scaffolds. At 6 months, in vivo, cartilage fragment-loaded scaffolds induced significantly better repair tissue than the scaffold alone using histological scoring. Repair in Group 2 was superior to that in any of the control groups (p < 0.05).

Conclusion

Autologous cartilage fragments loaded onto an HA felt/FG/PRP-scaffold provided an efficient cell source, and allowed for an improvement of the repair process of ostechondral defects in a rabbit model. Human FG, however, hampered the rabbit healing process. These results may have clinical relevance as they show the potential of a novel one-stage repair technique for osteochondral defects.     

Graft hypertrophy of matrix-based autologous chondrocyte implantation: a two-year follow-up study of NOVOCART 3D implantation in the knee

Purpose

Graft hypertrophy is a major complication in the treatment for localized cartilage defects with autologous chondrocyte implantation (ACI) using periosteal flap and its further development, Novocart (a matrix-based ACI procedure). The aim of the present study is to investigate individual criteria for the development of graft hypertrophy by NOVOCART 3D implantation of the knee in the post-operative course of 2 years.

Methods

Forty-one consecutive patients with 44 isolated cartilage defects of the knee were treated with NOVOCART 3D implants. Individual criteria and defect-associated criteria were collected. Follow-up MRIs were performed at 3, 6, 12 and 24 months. The NOVOCART 3D implants were measured and classified. The modified MOCART Score was used to evaluate quality and integration of the NOVOCART 3D implants in MRI.

Results

Graft hypertrophy was observed in a total of 11 patients at all post-operative time points. We were able to show that NOVOCART 3D implantation of cartilage defects after acute trauma and osteochondritis dissecans (OCD) led to a significantly increased proportion of graft hypertrophy. No other individual criteria (age, gender, BMI) or defect-associated criteria (concomitant surgery, second-line treatment, defect size, fixation technique) showed any influence on the development of graft hypertrophy. The modified MOCART Score results revealed a significant post-operative improvement within 2 years.

Conclusion

The aetiology of cartilage defects appears to have a relevant influence for the development of graft hypertrophy. Patients, who were treated with NOVOCART 3D implants after an acute event (acute trauma or OCD), are especially at risk for developing a graft hypertrophy in the post-operative course of two years.

Level of evidence

Case series, Level IV.