Elsevier

European Journal of Radiology

Volume 80, Issue 2, November 2011, Pages e132-e139
European Journal of Radiology

Validity of T2 mapping in characterization of the regeneration tissue by bone marrow derived cell transplantation in osteochondral lesions of the ankle

https://doi.org/10.1016/j.ejrad.2010.08.008Get rights and content

Abstract

Objective

Bone marrow derived cell transplantation (BMDCT) has been recently suggested as a possible surgical technique to repair osteochondral lesions. To date, no qualitative MRI studies have evaluated its efficacy. The aim of our study is to investigate the validity of MRI T2-mapping sequence in characterizing the reparative tissue obtained and its ability to correlate with clinical results.

Methods and materials

20 patients with an osteochondral lesion of the talus underwent BMDCT and were evaluated at 2 years follow up using MRI T2-mapping sequence. 20 healthy volunteers were recruited as controls. MRI images were acquired using a protocol suggested by the International Cartilage Repair Society, MOCART scoring system and T2 mapping. Results were then correlated with AOFAS clinical score.

Results

AOFAS score increased from 66.8 ± 14.5 pre-operatively to 91.2 ± 8.3 (p < 0.0005) at 2 years follow-up. T2-relaxation time value of 35–45 ms was derived from healthy ankles evaluation and assumed as normal hyaline cartilage value and used as a control. Regenerated tissue with a T2-relaxation time value comparable to hyaline cartilage was found in all the cases treated, covering a mean of 78% of the repaired lesion area.

A high clinical score was related directly to isointense signal in DPFSE fat sat (p = 0.05), and percentage of regenerated hyaline cartilage (p = 0.05), inversely to the percentage of regenerated fibrocartilage. Lesion's depth negatively related to the integrity of the repaired tissue's surface (tau = −0.523, p = 0.007), and to the percentage of regenerated hyaline cartilage (rho = −0.546, p = 0.013).

Conclusions

Because of its ability to detect cartilage's quality and to correlate to the clinical score, MRI T2-mapping sequence integrated with Mocart score represent a valid, non-invasive technique for qualitative cartilage assessment after regenerative surgical procedures.

Introduction

Hyaline articular cartilage is a highly specialized and multitask tissue. Because of its poor reparative capability, injuries may be irreversible and lead to chronic pain, joint swelling and premature osteoarthritis. Therefore, surgical repair is frequently needed [1]. Cartilage repair in osteochondral lesions is now more than ever an hot topic for research. Clinical results and durability over time of the repaired tissue are believed to be strictly dependent from the quality of the tissue itself [2]. Various surgical options have been proposed over time to restore an adequate cartilaginous layer on the talar dome, but among them, only ACI and mosaicplasty have shown the ability to provide a repair with hyaline cartilage, although disadvantages are reported [3], [4]. Recently, bone marrow derived cell transplantation (BMDCT) has been proposed as a technique capable to provide a repair of the lesion by hyaline cartilage and this result was confirmed by 3 biopsies [5].

Qualitative evaluation of postoperative outcome in cartilage repair techniques is still an issue. Second-look biopsy of the repaired tissue is invasive, jeopardizes the integrity of the repaired surface and information regarding only the small portion of the regenerated area harvested are provided. On the contrary, standard MRI can provide important structural information – such as percentage of defect filling, integration of the reparative tissue with the cartilage surrounding the lesion edge or integrity of the surface – about all the regenerated area [6], but it cannot be used to evaluate the biochemical or molecular composition of reparative tissue [7]. An advanced MRI T2-mapping sequence [8], [9] provides supplemental information about the matrix of reparative tissue and, for this reason, it is becoming increasingly popular for the evaluation or knee's lesions and has been recently suggested a valid sequence to study ankle's pathology [10], [11].

The aim of this study was to determine the validity of T2 mapping in evaluating the quality of the reparative tissue obtained following bone marrow derived cell transplantation (BMDCT) for osteochondral lesions repair in a series of ankles and its ability to correlate with the clinical result.

Section snippets

Methods and materials

20 patients (12 females and 8 males) affected by focal osteochondral lesions of the talar dome and treated by arthroscopic BMDCT were enrolled for the study [5].

Surgical treatment consisted in a “one-step” surgical procedure with bone marrow harvesting, concentration and arthroscopic BMDC transplantation.

Arthritis of the ankle joint, kissing lesions and rheumatoid arthritis were considered exclusion criteria to the procedure. Twelve patients underwent associated surgical procedures (even more

Clinical outcomes

Clinical outcomes, evaluated by AOFAS score, increased from 66.8 ± 14.5 pre-operatively to 91.2 ± 8.3 at 24 months follow-up after surgery (p < 0.0005). Results were rated respectively as excellent in 12 (60%) patients, good in 5 (25%); fair in 3 (15%).

No intra-operative nor post-operative complications were noticed and no revision surgeries were required.

Mocart score

MRI results evaluated by Mocart score [16] in DPFSE fat sat are reported in detail in Table 1. In 9 patients (45%) the defect filling was complete,

Discussion

The arthroscopic “one-step” technique represents an advance in cartilage repair. This technique allowed to achieve satisfactory clinical results at 2 years follow-up [5]. The resulting reparative tissue is very similar to the health hyaline cartilage. Furthermore, “one-step” technique is free from the major typical disadvantages of previous techniques, such as the very high costs and the need of multiple surgical sessions [5]. Nevertheless, routinely qualitative evaluation at follow-up of the

Conclusions

The integration of the parameters of Mocart score and T2 mapping was essential to obtain a complete and accurate non-invasive evaluation of the repaired site, enhancing the interpretation of clinical score. T2-mapping sequence was adequate for a qualitative evaluation of cartilage, being able to distinguish hyaline cartilage from fibrocartilage and to correlate with the clinical result.

In conclusion T2 mapping is a valid non-invasive alternative to biopsy for the evaluation of cartilage repair

Conflicts of interest

The authors declare that they have no conflicts of interest.

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