5.3. Evaluation of patients with the Trp2 and Trp3 alleles (II and III)

5.3.1. Demographic and clinical characteristics

The medical history and demographic characteristics of the patients with the Trp2 allele did not differ from the other 153 sciatic patients, except that they had significantly more often sedentary job (p < 0.05; Table 2). Patients with the Trp3 allele had generally higher education (chi-square p < 0.05), but otherwise they did not differ from the patients without the allele on the basis of age, gender, height or sciatic history. They had, however, significantly longer symptom duration before the index visit (3.0 months vs. 2.4 months, p < 0.05; Table 2).

Patients with the Trp2 allele were significantly more flexible by the modified Schober measure than the others (p < 0.05), but otherwise their symptoms and signs did not differ significantly from the other sciatic patients. Likewise, patients with the Trp3 allele did not differ from the other sciatic patients on the basis of clinical symptoms and findings (Table 2). Both two patients homozygous for the allele were male (39 and 50 years of age). The clinical symptoms and findings of the homozygous did not differ significantly from those heterozygous for the allele.

5.3.2. MRI findings

With respect to the Trp2 allele, no significant differences were detected in intervertebral disc degeneration, end-plate degeneration, Schmorl’s nodes, dorsal transverse tears and HIZ lesions at any lumbar level. Three of the patients (3 of 6) with the Trp2 allele had radial rupture in nonherniated disc at the L4-5 level, but not at other levels. The controls had no radial ruptures in nonherniated discs (0 of 18). The difference at the L4-5 level did not, however, reach statistical significance (p = 0.055). Two of the three patients with a radial tear in nonherniated disc had also oedema in the symptomatic nerve root. Family members with the Trp2 allele were slightly (but not significantly) older than members without the Trp allele. They had significantly more intervertebral disc and end-plate degeneration at the L5-S1 level (p < 0.05 for both), but not at any other level. Otherwise, the MRI findings did not differ significantly. Interestingly, three of the family members with the Trp2 allele (3 of 11) had a radial tear in a nonherniated disc, and none of the family members without the Trp2 allele (0 of 11). Two of the family members with a radial tear at the L4-5 level, were symptomatic at the time of the investigation. The third family member was asymptomatic and had a radial tear at the L3-4 level.

Comparison of patients with the Trp3 allele with their matched controls revealed no differences in end-plate degeneration, dorsal transverse tears, or HIZ-lesions. Patients with the Trp3 allele had, however, significantly more disc degeneration at the L4-5 level compared to the matched controls (P = 0.007). Disc degeneration at the other levels was similar in both groups. The number of Schmorl’s nodes tended to be higher at the L1-2 level in the Trp3 allele positive patients (5 of 34 vs. 0 of 34; P = 0.06).

5.3.3. Thoracolumbar Scheuermann’s disease (TLS)

Fifteen of 34 (44%) patients with the Trp3 allele were positive for TLS compared to 23 of 119 (19%) sciatic patients without the allele. This difference was highly significant (p=0.003). Two of the patients with the Trp2 allele were also positive for TLS, but this difference was not statistically significant. Other determinants significantly associated with TLS included gender (p=0.001), occupational load (p=0.009) and body mass index (p=0.04). Analyzed by stepwise logistic regression analysis, the final model for the presence of TLS contained three significant determinants: male sex (OR 4.7; 95% CI, 1.8–12.2; p<0.001), the Trp3 allele (OR 4.7; 95% CI, 1.8–12.1; p=0.001) and physical job (OR 7.1; 95% CI, 2.1–23.6; p=0.04; Table 3). Both individuals homozygous for the Trp3 allele had LS in MRI. Otherwise, their MRI scans were similar to those of the heterozygous patients (Figure 5).