The Role of Magnetic Resonance Imaging in Autologous Matrix-Induced Chondrogenesis for Osteochondral Lesions of the Talus: Analyzing MOCART 1 and 2.0

Abstract

Objective

To determine the role of magnetic resonance imaging (MRI) MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 1 and 2.0 scores in the assessment of postoperative outcome after autologous matrix-induced chondrogenesis (AMIC) for the treatment of osteochondral lesions of the talus (OLTs). It was hypothesized that preoperative patient factors or OLT morphology are associated with postoperative MOCART scores; yet postoperative clinical outcome is not.

Study Design

Cohort study; Level of evidence, 4. This study evaluated isolated AMIC that were implanted on the talus of 35 patients for the treatment of symptomatic OLT. Tegner and AOFAS (American Orthopaedic Foot and Ankle Society) scores were obtained at an average follow-up of 4.5 ± 1.8 years and postoperative MRI scored according to the MOCART 1 and 2.0.

Results

OLT size showed significant correlation with postoperative MRI scores (MOCART 1: P = 0.006; MOCART 2.0: P = 0.004). Bone grafting was significantly associated with a MOCART 1 subscale (signal intensity of repair tissue; P = 0.038). Age and defect size showed significant correlations with MOCART 2.0 subscales (P < 0.05). Patients with shorter follow-up had a significantly higher MOCART 1 score and a trend toward better MOCART 2.0 scores than patients with longer follow-up (64.7 vs. 52.9 months, P = 0.02; 69.4 vs. 60.6 months, P = 0.058). No MOCART score was associated with postoperative patient-reported outcomes (n.s.).

Conclusion

Osteochondral lesion size is associated with postoperative MOCART scores in patients treated with AMIC for OLTs, with decreasing MOCART scores over time. Yet clinical outcome does not correlate with any MOCART score. Thus, MOCART assessment seems to have no significant role in the postoperative treatment of asymptomatic patients that underwent AMIC for OLTs.

Keywords

autologous matrix-induced chondrogenesis osteochondral lesion talus MOCART osteoarthritis cartilage repair AMIC

Introduction

Osteochondral lesions of the talus (OLTs are defined as damage to the coating cartilage and subchondral bone due to repetitive microtrauma or traumatic injury to the ankle joint^1-3 whether through direct trauma (i.e., sports)^4-6 or joint instability.^7-9 Native hyaline cartilage is rich in collagen type II and maintains nutrition through physiologic loading and unloading.¹⁰ Once joint congruency is disturbed, however, successive joint degeneration results in osteoarthritis (OA) as adult cartilage has limited regenerative potential.² To prevent further degeneration and to improve clinical symptoms, numerous surgical treatment options for cartilage repair have been proposed.¹¹ Cell-based treatments such as autologous chondrocyte transplantation (ACI)^12-15 and matrix-induced autologous chondrocyte implantation (MACI)^16,17 require a 2-step procedure to initially harvest chondrocytes for incubation in the laboratory followed by implantation in a second surgery. Conversely, available 1-step procedures include osteochondral allograft implantation (OCA), which is limited in its availability of suitable allografts,^18-20 bone marrow stimulation (microfracturing) for smaller OLTs,^21-23 and autologous matrix-induced chondrogenesis (AMIC).²⁴ The AMIC technique comprises bone marrow stimulation of the subchondral bone with subsequent augmentation of a collagen type I/III bilayer membrane to contain the subchondral bleeding and provide a matrix for repair tissue maturation. Numerous studies reported good clinical improvement with high return to sport in the treatment of symptomatic OLTs,^25-30 superior to simple bone marrow stimulation.²⁴

Postoperative magnetic resonance imaging (MRI) is the most important noninvasive method for evaluation of surgical procedures for cartilage repair.^10,31-33 In 2004, Marlovits et al.³¹ introduced the MOCART score (Magnetic Resonance Observation of Cartilage Repair Tissue) based on a standard knee MRI protocol including intermediate-weighted sequences for cartilage evaluation. Originally, the score was designed for the evaluation of cartilage repair tissue after microfracturing, ACI, or MACI in the knee. The score considers 9 radiologic variables (degree of repair and defect filling, integration to border tissue, surface of repair tissue, structure of repair tissue, subchondral lamina, subchondral bone, adhesions, synovitis) and its use has found broad implementation for AMIC assessment in OLT.^{25,28,29,34,35}

While postoperative MRI assessment provides valuable information regarding structural integrity of the joint, the role of the MOCART score as a follow-up tool in cartilage repair of the ankle remains controversial.^28,36,37,40 Recently, Schreiner et al. presented an updated version of the original MOCART score, the MOCART 2.0 score,³³ to mirror recent progressions in surgical and imaging techniques. The updated version overworked the variables, degree of defect filling from 50% into 25% increments, the integration to neighboring native cartilage, surface repair assessment in reference to repair length in place of depth, subchondral bone was changed to subchondral changes, which now includes signal intensity for edema in the bone marrow, cysts, or osteonecrosis. Meanwhile, the variables subchondral lamina, adhesions, and synovitis were excluded from the score with its points being reallocated to the new variable bony defect or bony overgrowth. While the purpose of this update was to enhance validity of postoperative MR imaging in cartilage repair, its clinical relevance is still to be determined.

Thus, the goal of the current study was to determine the role of MR imaging, namely, MOCART 1 and 2.0 scores, in the assessment of postoperative outcome after AMIC for the treatment of OLTs at a follow-up between 2 and 8 years. It was hypothesized that preoperative patient factors or OLT morphology are associated with postoperative MOCART scores, yet postoperative clinical outcome is not.

Materials and Method

Our ethics review board approved this study before initiation. Data are regularly collected and stored for patients undergoing elective surgery at our institution. This database was used to identify patients who underwent isolated cartilage repair with AMIC for focal osteochondral defects in the talus between October 2009 and August 2015. The surgical treatment with AMIC was indicated for symptomatic focal full-thickness chondral and OLTs. AMIC was contraindicated in patients with inflammatory arthritis and/or advanced osteoarthritis.

Patients were included in this study if they underwent isolated AMIC to the talus with postoperative MR imaging and had clinical outcome available, namely, the American Orthopaedic Foot and Ankle Society (AOFAS; 0-100 points) score³⁸ for ankle function and the Tegner score³⁹ (0-10 points) for sports activity. Exclusion criteria comprised any prior ankle joint surgery or concomitant ankle procedure, and if patients did not have MRI acquisition performed at the same date as clinical scores were obtained.

Clinical notes and operative reports were reviewed to determine patient’s age at the time of surgery, sex, body mass index (BMI), smoking status, duration of symptoms, concomitant bone grafting, defect size, and location.

Surgical Technique

All patients’ OLT were accessed via an open approach through a medial (n = 32) or lateral (n = 3) malleolar osteotomy.^25,28,30

Undermined cartilage and flaps were sharply excised using a scalpel or curettage and cystic or necrotic bone lesions were debrided until vital bone tissue was visible. Next, the bone surface was microfractured by drilling with a K-wire (Ø 1.2 mm, DePuy Synthes, Oberdorf, Switzerland). When the extent of bone defect was cavernous or impressed the congruency, the semi-cylindrical joint surface of the talus was reconstructed with cancellous bone from the osteotomized tibia. Subsequently, the bilayer type I/III collagen matrix (Chondro-Gide, Geistlich Pharma AG, Wolhusen, Switzerland) was cut to fit the defect and placed on the lesion with the smooth side facing up. After checking if the lesion is filled up sufficiently, surgical fibrin glue was utilized to secure the membrane to the adjacent cartilage (Tissucol Duo S, Baxter International Inc., Deerfield, IL). Last, the joint was brought through full range of motion to ensure proper graft fixation, followed by open reduction and internal fixation of the malleolar osteotomy with two 2.5-mm titanium screws (medial) or compression plating (lateral) and standard wound closure.

MRI Assessment

Postoperative MRIs were performed on a 1.5 T MAGNETOM Avanto Fit system (Siemens Healthcare, Erlangen, Germany) with a dedicated 8-channel foot and ankle coil using a musculoskeletal protocol incorporating coronal, sagittal and axial turbo spin-echo (TSE) intermediate-weighted sequences with and without fat saturation, using the Dixon technique, and a 3-mm slice thickness ( Fig. 1 ).

Figure 1.

Postoperative intermediate-weighted coronal (A) and sagittal (B) MRI depicting an osteochondral lesion on the medial talar dome accessed via a medial malleolar osteotomy.

For the present imaging study, the previously published and validated comprehensive MOCART³¹ and MOCART 2.0³³ were utilized ranging from 0 to 100 points. Based on the original MOCART³¹ scoring system comprising 9 radiologic variables, renewals of the MOCART 2.0 score³³ were the following: the degree of repair and defect filling is hypertrophic when exceeding 150% of the defect depth and incomplete filling is now assessed in 25% increments. The integration only accounts ingrowth into the neighboring native cartilage. Instead of regarding the depth of repair, the grading of surface irregularities is now referenced to the repaired length. The signal intensity division was retitled to normal signal, minor abnormal, and severely abnormal signal alterations. The subchondral bone score was revised to subchondral changes and added osteonecrosis as monitor. Last, the variables subchondral lamina, adhesions, and synovitis were removed and replaced by bony defect or bony overgrowth, reflecting a more detailed assessment of the bony lesion compared to the original score, which just rated the subchondral lamina as intact or not.

All MRIs were evaluated by a fellowship-trained musculoskeletal radiologist.

Statistical Analysis

Descriptive statistics were used to determine patient and lesion characteristics. All data were assessed for normality utilizing the Shapiro-Wilk test. Accordingly, continuous variables were analyzed with the independent t test. Point biserial and Pearson correlation, chi-square, and Fisher’s exact test were used to assess the relationship of MOCART subscales with patient’s age, sex, smoking status, BMI, duration of symptoms, bone grafting, lesion size and location, follow-up, and postoperative AOFAS and Tegner scores. Lesion size was calculated utilizing the ellipse formula for OLTs (sagittal length × coronal length × 0.79).⁴¹ All statistical analyses were performed in SPSS for Mac (Version 23.0, SPSS Inc., Chicago, IL). Significance was set at P < 0.05.

Results

Thirty-five patients that underwent isolated AMIC for OLT at our institution with postoperative MRI and patient-reported outcomes were identified and included in this study. Mean postoperative MRI and clinical follow-up was obtained at 4.5 ± 1.8 years. Patient and lesion characteristics are presented in Table 1 .

Table 1.

Patient and Lesion Demographics.

Patient and Lesion Characteristics	Patients (n = 35)
Age, years, mean ± SD	34.4 ± 10.7
Female sex, n (%)	14 (40)
BMI, kg/m², mean ± SD	28.7 ± 5.4
Smoker, n (%)	17 (48.6)
DOS >12 months, n (%)	27 (77.1)
Defect size, cm², mean ± SD	0.9 ± 0.6
Defect location, medial/lateral	32/3
Bone grafting, yes/no	27/8

SD = standard deviation; BMI = body mass index; DOS = duration of symptoms.

At final follow-up, mean AOFAS score was 92.63 ± 8.3 and patients reported a mean Tegner score of 5.1 ± 1.8, which significantly increased from 3.7 ± 2.0 (P = 0.002) preoperatively. Both MRI assessments were significantly associated with each other with a mean MOCART 1 score of 59.0 ± 14.9 compared to a mean MOCART 2.0 score of 65.1 ± 13.9 (r = 0.885; P < 0.001). In fact, subscales of both MOCART scores were strongly correlated with each other, except “signal intensity” (P < 0.001 and P = 0.096, respectively; Table 2 ).

Table 2.

Bivariate Correlations of Postoperative MOCART 1 and MOCART 2.0 Subscales and Total Score.

MOCART 1	Mean ± SD	MOCART 2.0	Mean ± SD	r	P Value
Filling of defect	16.9 ± 3.4	Volume fill of cartilage defect	19.1 ± 2.8	0.693	<0.001
Integration to border zone	13.0 ± 4.1	Integration to border zone	13.9 ± 2.5	0.946	<0.001
Surface of repair tissue	6.4 ± 3.1	Surface of repair tissue	6.9 ± 3.0	0.813	<0.001
Structure of repair tissue	1.4 ± 2.3	Structure of repair tissue	2.9 ± 4.5	1	<0.001
Signal intensity of repair tissue	14.1 ± 7.2	Signal intensity of repair tissue	10.0 ± 3.2	0.286	0.096
Subchondral lamina	0.9 ± 1.9	Bony defect/bony overgrowth	3.7 ± 3.7	0.575	<0.001
Subchondral bone	0.4 ± 1.4	Subchondral changes	8.7 ± 5.9	0.510	0.002
Adhesion	3.1 ± 2.5	—	—	—	—
Effusion	2.7 ± 2.5	—	—	—	—
Total	59.0 ± 14.9	Total	65.1 ± 13.9	0.885	<0.001

Analyzing the influence of preoperative factors on postoperative MRI assessment, osteochondral lesion size was the only preoperative factor that showed significant correlation with postoperative MOCART 1 and 2.0 total scores (P = 0.006 and P = 0.004, respectively). Bone grafting was the only preoperative factor significantly associated with a MOCART 1 subscale (“signal intensity”). Both age and defect size showed significant inverse correlations with MOCART 2.0 subscales (P < 0.05; Table 3 ).

Table 3.

Significant Bivariate Correlations of Preoperative Patient and Lesion Parameters With Postoperative MOCART 1 and 2.0 Total Scores and Subscales.

	Correlation Coefficient	P Value
Total MOCART 1
Defect size	−0.453	0.006
Signal intensity of repair tissue
Bone grafting	0.530	0.038
Total MOCART 2.0
Defect size	−0.477	0.004
Volume fill of cartilage defect
Age	−0.401	0.017
Surface of repair tissue
Defect size	−0.421	0.012
Signal intensity of repair tissue
Defect size	−0.354	0.037

Stratifying patients based on their follow-up, patients with a shorter follow-up (less than 4.5 years) showed a significantly higher MOCART 1 score than patients with a follow-up longer than 4.5 years (64.7 ± 10.8 vs. 52.9 ± 16.6, P = 0.02). Patients with a shorter follow-up also exhibited a trend toward better MOCART 2.0 scores than patients with longer follow up (69.4 ± 12.4 vs. 60.6 ± 14.3, P = 0.058). Specifically, MOCART 1 and 2.0 “signal intensity” subscale was significantly better in patients with shorter follow-up (P = 0.016 and P = 0.031, respectively). Furthermore, MOCART 1 and 2.0 “structure of repair tissue” subscale showed a trend toward better results in patients with shorter follow-up (both, P = 0.06).

When correlating postoperative MRI scores with clinical outcome, neither MOCART 1 nor 2.0 total or subscale scores were related to AOFAS or Tegner scores (n.s.).

Discussion

The key finding of the study presented herein is that MOCART and MOCART 2.0 scores strongly correlate with each other but do not show a statistically significant association with clinical outcome after isolated AMIC for the treatment of symptomatic OLTs. Interestingly, defect size was the only preoperative factor that was correlated with both postoperative total MOCART scores, which both seem to decline with prolonged follow-up.

While no direct comparison between the MOCART scores or an evaluation of the relationship between MOCART 2.0 and postoperative clinical outcome after cartilage repair in the ankle has been established yet, some studies have assessed postoperative MR imaging after AMIC and have investigated its association with patient-reported clinical outcome. Kubosch et al.²⁸ presented a case series of 17 patients treated with the open AMIC procedure for medial OLTs. At a mean follow-up of 39.5 ± 18.4 months, postoperative MOCART scores averaged 52.7 ± 15.9 with AOFAS scores averaging 82.6 ± 13.4. Conversely to the presented results, the authors observed a statistically significant correlation between postoperative MOCART and AOFAS score (rho = 0.574, P = 0.04). Moreover, osteochondral lesion size ≥3 cm³ was significantly associated with inferior AOFAS scores in the studied cohort, a factor that was inversely correlated with MOCART and MOCART 2.0 scores in the current study.

In a recently published study by Weigelt et al.,²⁵ the authors reported good to excellent clinical outcome with high return to sport after AMIC for OLTs in 33 patients with a mean MOCART score of 60.6 ± 21.2. Correlating solely total MOCART scores, and not its subscales, to postoperative clinical outcome, no significant association was found. A similar finding was reported by Albano et al.,³⁴ who evaluated 16 patients at a mean follow-up of 30 ± 16.9 months after AMIC for OLT. MRI acquisition was obtained at 12 and 24 months postoperatively and correlated with clinical outcome, assessed by VAS and AOFAS. Though MOCART scores increased significantly from 41.9 ± 14.6 at 12 months to 51.9 ± 11.6 at 24 months, their change did not show any significant association with the clinical improvement measured by the AOFAS.

While none of these studies investigated the relationship between MOCART subscales and clinical outcome, they do partially reflect the findings of the current study that neither MOCART total nor subscale scores are related with clinical outcome after AMIC for OLT. In a report published by de Windt et al., the authors systematically reviewed the evidence whether morphological MRI is reliable in predicting clinical outcome after cartilage repair in the knee. Assessing a total of 32 studies, they concluded that a majority of MRI parameters including the MOCART score did not show a significant correlation with clinical outcome, yet highlighting the fact that developing more advanced imaging techniques are warranted in the field of cartilage repair.⁴²

On the other hand, the absence of correlation between MOCART and clinical outcome might be rooted in the particular postoperative time period MRI examinations were obtained. Ackermann et al.⁴³ presented a cohort study of 67 patients treated with ACI for cartilage defects in the knee. Analyzing the effect of chondrocytic gene expression on postoperative MR imaging and clinical outcome, the authors did not see any effect of increased chondrocytic gene expression on MOCART scores at final follow-up. When evaluating postoperative MRIs that were obtained at a follow-up between 12 and 30 months, however, increased gene expression was significantly associated with greater degree of defect filling, better integration at the border zone, and decreased effusion. It was theorized that 12 to 30 months might be the ideal time period for MRI evaluation of the repair tissue after ACI to the knee. They reasoned that ACI graft maturation requires 12 to 24 months to complete,⁴⁴ but graft aging with decreasing MOCART scores and general deterioration of the joint starts approximately after 30 months of follow-up.⁴⁵ Hence, 12 to 30 months represents a time period were a reliable evaluation of the repair tissue could be determined. Projecting this finding to the AMIC procedure, Gobbi et al.,⁴⁶ in a histological study, investigated the repair tissue after AMIC for OLTs. The study found that AMIC produced hyaline-like repair tissue in patients at 13.5 months postoperatively, suggesting complete maturation of the repair tissue. In the study presented herein, MRIs were obtained at a mean follow-up of 4.5 years with decreasing MOCART scores over time. This follow-up might explain the generally rather low overall MOCART scores as well as the absent association between MR findings and clinical outcome. Yet, follow-up did not affect the association between MOCART and clinical outcome in this study. However, future longitudinal studies are warranted to investigate if the clinical effect of early low MOCART scores might just occur at later time points postoperatively. Until then, it remains questionable if timing plays a role in evaluating repair tissue of OLT treated with AMIC as the minimum follow-up was 2 years and graft deterioration might have already begun. Consequently, postoperative MR assessment with MOCART seems to not provide any further valuable information regarding clinical outcome after 2 years in patients that underwent isolated AMIC for OLTs who do not experience any symptoms that require further MR imaging evaluation to assess joint integrity.

However, the more detailed increments of the MOCART 2.0 might have slightly increased some subscale sensitivity. In fact, volume fill of cartilage defect inversely correlated with patient’s age, meaning that younger patients presented with a more sufficient filling of the defect than patients of older age. This finding matches the report of Pestka et al.,⁴⁷ who analyzed cell quality in an in vitro examination of ACI cell cultivations. A total of 252 ACI patient samples were assessed for the cartilage relevant surface marker CD44 and the cartilage-specific differentiation markers aggrecan and collagen type II. The study revealed that patients younger than 20 years showed significantly higher expression rates of all 3 markers compared to older patients suggesting better cell quality. This might have contributed to the result seen in the current study; however, it will be of interest to see if similar observations can be made in cell-based therapies such as ACI and MACI utilizing the MOCART 2.0.

Last, defect size was the only preoperative factor that correlated with postoperative MOCART and MOCART 2.0 scores. While microfracturing is still referred to as the gold standard for lesions sizes up to 1.5 cm²,⁴⁸ AMIC has shown to result in favorable outcome in smaller as well as larger lesions without defect size being correlated with the postoperative clinical outcome.²⁵ Becher et al. treated 15 patients with mircrofracturing for OLTs and, similar to the results seen in the current study, found defect size to be a factor significantly associated with postoperative MOCART scores with higher scores found in patients with smaller lesions, yet this did not translate into improved clinical outcomes.⁴⁹

The authors acknowledge the limitations of this study. The study was retrospective in its design with unavailable preoperative clinical scores. Thus, clinical improvement can only be assumed with a postoperative AOFAS score averaging over 92 points and postoperative Tegner scores showing a significant improvement compared to the retrospectively collected preoperative Tegner scores. Further-more, both MOCART scores were originally designed for evaluating cartilage repair in the knee, yet its application in the assessment of cartilage repair in the ankle is widely accepted.^{25,28,29,34,35,37,50}

Conclusion

In summary, osteochondral lesion size is associated with postoperative MOCART scores in patients treated with AMIC for OLTs, with decreasing MOCART scores over time. Yet, clinical outcome does not correlate with any MRI parameter assessed by MOCART or MOCART 2.0. Thus, assessment of either MOCART score seems to have no significant role in the postoperative treatment of asymptomatic patients that underwent AMIC for OLTs.

Footnotes

Acknowledgments and Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

Ethical approval for this study was obtained from the cantonal ethics committee of Zurich (BASEC-Nr. 2019-02025).

Informed Consent

Written informed consent was obtained from all subjects before the study.

ORCID iDs

Fabio A. Casari

Christoph Germann

References

Hintermann

Regazzoni

Lampert

Stutz

Gächter

Arthroscopic findings in acute fractures of the ankle. J Bone Joint Surg Br. 2000;82(3):345-51.

Mankin

HJ.

The response of articular cartilage to mechanical injury. J Bone Joint Surg Am. 1982;64(3):460-6.

Ackermann

Fraser

Murawski

Desai

Vig

Kennedy

JG.

Trends of concurrent ankle arthroscopy at the time of operative treatment of ankle fracture: a national database review. Foot Ankle Spec. 2015;9(2):107-12.

Flick

Gould

Osteochondritis dissecans of the talus (transchondral fractures of the talus): review of the literature and new surgical approach for medial dome lesions. Foot Ankle. 1985;5(4):165-85.

O’Loughlin

Heyworth

Kennedy

JG.

Current concepts in the diagnosis and treatment of osteochondral lesions of the ankle. Am J Sports Med. 2010;38(2):392-404.

Holmer

Søndergaard

Konradsen

Nielsen

Jorgensen

LN.

Epidemiology of sprains in the lateral ankle and foot. Foot Ankle Int. 1994;15(2):72-4.

DiGiovanni

Fraga

Cohen

Shereff

MJ.

Associated injuries found in chronic lateral ankle instability. Foot Ankle Int. 2000;21(10):809-15.

Ferkel

Chams

RN.

Chronic lateral instability: arthroscopic findings and long-term results. Foot Ankle Int. 2007;28(1_suppl):24-31.

Bonnel

Toullec

Mabit

Tourné

Sofcot . Chronic ankle instability: biomechanics and pathomechanics of ligaments injury and associated lesions. Orthop Traumatol Surg Res. 2010;96(4):424-32.

10.

Imhof

Nöbauer-Huhmann

Krestan

Gahleitner

Sulzbacher

Marlovits

, et al. MRI of the cartilage. Eur Radiol. 2002;12(11):2781-93.

11.

Ambra

de Girolamo

Mosier

Gomoll

. Review: interventions for cartilage disease: current state-of-the-art and emerging technologies. Arthritis Rheumatol. 2017;69(7):1363-73.

12.

Imhoff

Paul

Ottinger

Wortler

Lammle

Spang

, et al. Osteochondral transplantation of the talus: long-term clinical and magnetic resonance imaging evaluation. Am J Sports Med. 2011;39(7):1487-93.

13.

Giannini

Vannini

Buda

Osteoarticular grafts in the treatment of OCD of the talus: mosaicplasty versus autologous chondrocyte transplantation. Foot Ankle Clin. 2002;7(3):621-33.

14.

Flynn

Ross

Hannon

Yasui

Newman

Murawski

, et al. Autologous osteochondral transplantation for osteochondral lesions of the talus. Foot Ankle Int. 2016;37(4):363-72.

15.

Kim

Park

Kim

Koh

Lee

JW.

Factors associated with the clinical outcomes of the osteochondral autograft transfer system in osteochondral lesions of the talus: second-look arthroscopic evaluation. Am J Sports Med. 2012;40(12):2709-19.

16.

Bellido

Wadhwani

Monzo

EG.

Matrix-induced autologous chondrocyte implantation grafting in osteochondral lesions of the talus: evaluation of cartilage repair using T2 mapping. J Orthop. 2019;16(6):500-3.

17.

Aurich

Bedi

Smith

Rolauffs

Muckley

Clayton

, et al. Arthroscopic treatment of osteochondral lesions of the ankle with matrix-associated chondrocyte implantation: early clinical and magnetic resonance imaging results. Am J Sports Med. 2011;39(2):311-9.

18.

Haene

Qamirani

Story

Pinsker

Daniels

TR.

Intermediate outcomes of fresh talar osteochondral allografts for treatment of large osteochondral lesions of the talus. J Bone Joint Surg Am. 2012;94(12):1105-10.

19.

Raikin

SM.

Fresh osteochondral allografts for large-volume cystic osteochondral defects of the talus. J Bone Joint Surg Am. 2009;91(12):2818-26.

20.

Heida

Jr Tihista

Kusnezov

Dunn

Orr

JD.

Outcomes and predictors of postoperative pain improvement following particulated juvenile cartilage allograft transplant for osteochondral lesions of the talus. Foot Ankle Int. 2020;41(5):572-81.

21.

Ferkel

Zanotti

Komenda

Sgaglione

Cheng

Applegate

, et al. Arthroscopic treatment of chronic osteochondral lesions of the talus: long-term results. Am J Sports Med. 2008;36(9):1750-62.

22.

Schuman

Struijs

van Dijk

CN.

Arthroscopic treatment for osteochondral defects of the talus. Results at follow-up at 2 to 11 years. J Bone Joint Surg Br. 2002;84(3):364-8.

23.

van Bergen

Kox

Maas

Sierevelt

Kerkhoffs

van Dijk

CN.

Arthroscopic treatment of osteochondral defects of the talus: outcomes at eight to twenty years of follow-up. J Bone Joint Surg Am. 2013;95(6):519-25.

24.

Volz

Schaumburger

Frick

Grifka

Anders

A randomized controlled trial demonstrating sustained benefit of autologous matrix-induced chondrogenesis over microfracture at five years. Int Orthop. 2017;41(4):797-804.

25.

Weigelt

Hartmann

Pfirrmann

Espinosa

Wirth

SH.

Autologous matrix-induced chondrogenesis for osteochondral lesions of the talus: a clinical and radiological 2- to 8-year follow-up study. Am J Sports Med. 2019;47(7):1679-86.

26.

Wiewiorski

Leumann

Buettner

Pagenstert

Horisberger

Valderrabano

Autologous matrix-induced chondrogenesis aided reconstruction of a large focal osteochondral lesion of the talus. Arch Orthop Trauma Surg. 2011;131(3):293-6.

27.

Wiewiorski

Werner

Paul

Anderson

Barg

Valderrabano

Sports activity after reconstruction of osteochondral lesions of the talus with autologous spongiosa grafts and autologous matrix-induced chondrogenesis. Am J Sports Med. 2016;44(10):2651-8.

28.

Kubosch

Erdle

Izadpanah

Kubosch

Uhl

Sudkamp

, et al. Clinical outcome and T2 assessment following autologous matrix-induced chondrogenesis in osteochondral lesions of the talus. Int Orthop. 2016;40(1_suppl):65-71.

29.

Valderrabano

Miska

Leumann

Wiewiorski

Reconstruction of osteochondral lesions of the talus with autologous spongiosa grafts and autologous matrix-induced chondrogenesis. Am J Sports Med. 2013;41(3):519-27.

30.

Behrens

Matrixgekoppelte Mikrofrakturierung. Arthros-kopie. 2005;18(3):193-7.

31.

Marlovits

Striessnig

Resinger

Aldrian

Vecsei

Imhof

, et al. Definition of pertinent parameters for the evaluation of articular cartilage repair tissue with high-resolution magnetic resonance imaging. Eur J Radiol. 2004;52(3):310-9.

32.

Marlovits

Singer

Zeller

Mandl

Haller

Trattnig

Magnetic resonance observation of cartilage repair tissue (MOCART) for the evaluation of autologous chondrocyte transplantation: determination of interobserver variability and correlation to clinical outcome after 2 years. Eur J Radiol. 2006;57(1_suppl):16-23.

33.

Schreiner

Raudner

Marlovits

Bohndorf

Weber

Zalaudek

, et al. The MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 2.0 Knee Score and Atlas. Cartilage. Epub 2019 August 17. doi:10.1177/1947603519865308

34.

Albano

Martinelli

Bianchi

Messina

Malerba

Sconfienza

LM.

Clinical and imaging outcome of osteochondral lesions of the talus treated using autologous matrix-induced chondrogenesis technique with a biomimetic scaffold. BMC Musculoskelet Disord. 2017;18(1_suppl):306.

35.

Galla

Duensing

Kahn

Barg

Open reconstruction with autologous spongiosa grafts and matrix-induced chondrogenesis for osteochondral lesions of the talus can be performed without medial malleolar osteotomy. Knee Surg Sports Traumatol Arthrosc. 2019;27(9):2789-95.

36.

Albano

Martinelli

Bianchi

Giacalone

Sconfienza

LM.

Evaluation of reproducibility of the MOCART score in patients with osteochondral lesions of the talus repaired using the autologous matrix-induced chondrogenesis technique. Radiol Med. 2017;122(12):909-17.

37.

Apprich

Trattnig

Welsch

Noebauer-Huhmann

Sokolowski

Hirschfeld

, et al. Assessment of articular cartilage repair tissue after matrix-associated autologous chondrocyte transplantation or the microfracture technique in the ankle joint using diffusion-weighted imaging at 3 Tesla. Osteoarthritis Cartilage. 2012;20(7):703-11.

38.

Van Lieshout

EMM

De Boer

Meuffels

Hoed

PTD

Van der Vlies

Tuinebreijer

, et al. American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score: a study protocol for the translation and validation of the Dutch language version. BMJ Open. 2017;7:e012884.

39.

Tegner

Lysholm

Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res. 1985;(198):43-9.

40.

Martinelli

Albano

Prati

ABC

Antonino

Malerba

Sconfienza

MOCART score is not a feasible tool for the assessment of osteochondral lesions of the talus. Foot Ankle Orthop. 2017;2(3):2473011417S2473000285.

41.

Choi

Park

Kim

Lee

JW.

Osteochondral lesion of the talus: is there a critical defect size for poor outcome?

Am J Sports Med. 2009;37(10):1974-80.

42.

de Windt

Welsch

Brittberg

Vonk

Marlovits

Trattnig

, et al. Is magnetic resonance imaging reliable in predicting clinical outcome after articular cartilage repair of the knee? A systematic review and meta-analysis. Am J Sports Med. 2013;41(7):1695-702.

43.

Ackermann

Merkely

Mestriner

Shah

Gomoll

AH.

Increased chondrocytic gene expression is associated with improved repair tissue quality and graft survival in patients after autologous chondrocyte implantation. Am J Sports Med. 2019;47(12):2919-26.

44.

Niethammer

Safi

Ficklscherer

Horng

Feist

Feist-Pagenstert

, et al. Graft maturation of autologous chondrocyte implantation: magnetic resonance investigation with T2 mapping. Am J Sports Med. 2014;42(9):2199-204.

45.

Rosa

Balato

Ciaramella

Soscia

Improta

Triassi

Long-term clinical results and MRI changes after autologous chondrocyte implantation in the knee of young and active middle aged patients. J Orthop Traumatol. 2016;17(1_suppl):55-62.

46.

Gobbi

Karnatzikos

Scotti

Mahajan

Mazzucco

Grigolo

One-step cartilage repair with bone marrow aspirate concentrated cells and collagen matrix in full-thickness knee cartilage lesions: results at 2-year follow-up. Cartilage. 2011;2(3):286-99.

47.

Pestka

Schmal

Salzmann

Hecky

Südkamp

Niemeyer

In vitro cell quality of articular chondrocytes assigned for autologous implantation in dependence of specific patient characteristics. Arch Orthop Trauma Surg. 2011;131(6):779-89.

48.

Dahmen

Lambers

KTA

Reilingh

van Bergen

CJA

Stufkens

SAS

Kerkhoffs

No superior treatment for primary osteochondral defects of the talus. Knee Surg Sports Traumatol Arthrosc. 2018;26(7):2142-57.

49.

Becher

Zuhlke

Plaas

Ewig

Calliess

Stukenborg-Colsman

, et al. T2-mapping at 3 T after microfracture in the treatment of osteochondral defects of the talus at an average follow-up of 8 years. Knee Surg Sports Traumatol Arthrosc. 2015;23(8):2406-12.

50.

Toale

Shimozono

Mulvin

Dahmen

Kerkhoffs

Kennedy

JG.

Midterm outcomes of bone marrow stimulation for primary osteochondral lesions of the talus: a systematic review. Orthop J Sports Med. 2019;7(10):2325967119879127.