Experimental animal models
MRI and histology of collagen template disc implantation and regeneration in rabbit temporomandibular joint: preliminary report

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Abstract

Introduction

We aimed to evaluate regeneration of injured temporomandibular joint (TMJ) discs following reconstituted collagen template implantation in rabbits using contrast-enhanced magnetic resonance imaging (MRI) and to correlate these findings with histology.

Methods

Twenty-four adult rabbits were divided into five groups: group A, partial discectomy without implantation (n = 6); group B, partial discectomy with collagen template implantation (n = 6); group C, partial discectomy with subdermal graft implantation (n = 6); group D, sham operation (n = 4); and group E, control (n = 2). All rabbits received baseline MRI scans before surgery and follow-up MRI studies at 3 months after surgery. All rabbits were sacrificed for histologic analysis after the follow-up MRI.

Results

In group A, follow-up MRI showed marked joint effusion in all six injured TMJs, which was accompanied by bony erosion at the tympanic fossa and mandibular condyle. In group B, MRI showed a homogenous low signal intensity in five of six discs, suggestive of regeneration. One disc showed higher signal intensity at its lateral portion than that of the original disc, indicating partial regeneration. MRI of group C depicted a low signal intensity, bandlike regenerative structure in four of the six discs. One disc with partial regeneration demonstrated relatively high signal intensity. The disc in the sixth animal of this group showed no evidence of regeneration. All of the MRI findings were in agreement with the histologic findings.

Conclusion

TMJ discs can regenerate following implantation of a reconstituted collagen template in discectomied rabbits. Contrast-enhanced MRI can be used to monitor and determine the degree of disc regeneration.

Section snippets

Materials and methods

Adult male New Zealand rabbits (n = 24; 3 months of age; 2.5 kg) were divided into five groups: group A, partial discectomy without implantation (n = 6); group B, partial discectomy with reconstituted collagen template implantation (n = 6); group C; partial discectomy with subdermal graft implantation (n = 6); group D, sham operation (n = 4); and group E, normal control (n = 2). All MRI studies were performed at week 0 (baseline) and at 3 months after surgery. All rabbits were sacrificed after

Results

The average weight of rabbits in the four groups at 3 months was 1.2 kg (group A), 1.5 (group B), 1.4 (group C), and 1.8 kg (group D), representing a gain over baseline. In group E, MR images showed well-delineated concave morphology of low signal intensity discs in the coronal plane. The histology revealed that the discs were coronally concave in shape and composed of dense connective tissue. In group D, all sham-operated TMJ discs had morphology and signal intensity similar to other discs on

Discussion

Alteration of the distribution of proteoglycans and water content can contribute to the signal changes in the MRI of the TMJ disc.5 The MRI contrast agent used in the present study has two negative charges, which should accumulate in the tissue inversely to the negative charges of glycosaminoglycans of the proteoglycans in cartilage, resulting in a decreased T1 relaxation time of the tissue. Our findings support the observation by previous authors6 that the MRI appearance of TMJ discs and

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This study was supported in part by grants (NSC89-2320-B-038-018-M08) from the National Science Council in Taiwan.

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