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Magnetic Resonance Imaging Findings in Relation to the COL9A2 Tryptophan Allele Among Patients With Sciatica

Karppinen, Jaro, MD,*; Pääkkö, Eija, MD, PhD,†; Räinä, Susanna, MC,‡; Tervonen, Osmo, MD, PhD,†; Kurunlahti, Mauno, MD,†; Nieminen, Pentti, PhD; Ala-Kokko, Leena, MD, PhD,‡; Malmivaara, Antti, MD, PhD; Vanharanta, Heikki, MD, PhD*

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Study Design.  The phenotype of patients with sciatica who have the Trp2 allele is characterized cross-sectionally.

Objective.  To determine whether it is possible to differentiate patients with the Trp2 allele clinically or by magnetic resonance imaging.

Summary of Background Data.  Several studies have indicated a positive family history for intervertebral disc disease. Previously, a dominantly inherited defect was identified in the COL9A2 gene that changed a codon for glutamine to that for tryptophan in the α2 chain of collagen IX (Trp2 allele). This change may render intervertebral discs more fragile.

Methods.  Clinical findings, clinical symptoms, and magnetic resonance imaging (1.5-T) findings from 159 patients with sciatica were evaluated according to the presence of the Trp2 allele. Additionally, the magnetic resonance imaging scans of 22 family members from three families were evaluated. These scans were analyzed intervertebral disc and endplate degeneration, Schmorl’s nodes, transverse tears (hyperintensity in the region of Sharpey’s fibers), high-intensity zone lesions (bright spots in the dorsal anulus), and radial tears (hyperintense linear area from the nucleus to the outer part of the anulus on T2 sequences).

Results.  Six patients with sciatica and 11 family members had the Trp2 allele. No homozygotes were found. Clinical symptoms of patients with and those without the Trp2 allele were similar. Patients with sciatica who had the Trp2 allele were significantly more flexible (P < 0.05), according to the modified Schober measure. The disc and endplate degeneration in 6 patients with the Trp2 allele and their 18 controls (matched for age, occupation, gender) without the allele did not differ significantly, whereas family members with the Trp2 allele had a greater degree of disc and endplate degeneration at L5–S1. The overall prevalence of endplate degeneration was high in this study. The prevalences of dorsal transverse tears, high-intensity zone lesions, and Schmorl’s nodes did not differ among patients with sciatica or family members according to the presence of the Trp2 allele. There was, however, a trend for increased prevalence of radial tears in nonherniated discs among the Trp2 allele–positive subjects (3 of 6 patients with sciatica and 3 of 11 family members), as compared with the Trp2-negatives subjects (none of 18 “matched” patients or 11 family members).

Conclusion.  The patients with the Trp2 allele were more flexible, and more often tended to have a radial tear in a nonherniated disc than their control counterparts.

From the *Departments of Physical Medicine and Rehabilitation,

the Department of †Radiology,

the ‡Collagen Research Unit, Biocenter and Department of Medical Biochemistry, University of Oulu,

the §Medical Informatics Group, University of Oulu, and the

¶Finnish Institute of Occupational Health and Orton Hospital, Invalid Foundation, Helsinki, Finland.

Supported by grants from the Yrjö Jahnsson Foundation and the National Research and Development Center for Welfare and Health, Finland to Jaro Karppinen, and from the Academy of Finland to Leena Ala-Kokko.

Acknowledgment date: January 9, 2001.

First revision date: March 30, 2001.

Second revision date: May 21, 2001.

Acceptance date: May 29, 2001.

Device status category: 1.

Conflict of interest category: 14.

Address reprint requests to

Jaro Karppinen, MD

Department of Physical Medicine and Rehabilitation

Oulu University Hospital

Kajaanintie 50

FIN-90220 Oulu

Finland

E-mail: jaro.karppinen@ppshp.fi

© 2002 Lippincott Williams & Wilkins, Inc.