Osteoarthritis of the second metatarsophalangeal joint associated with hallux valgus deformity.

BACKGROUND: Hallux valgus is speculated to increase the load on the second metatarsophalangeal (MTP) joint, possibly inducing degenerative osteoarthritis. In addition, the severity of arthritis may be correlated with the severity of hallux valgus. This study evaluated the association of arthritis of the second MTP joint in hallux valgus patients and the relationship between arthritis of the second MTP joint and hallux valgus deformity. METHODS: A total of 382 patients (509 feet) underwent surgery for symptomatic hallux valgus deformities by the 2 senior authors (KTL, YUP) from November 2011 to December 2012. A total of 54 patients (61 feet), all female, were included in the osteoarthritis (OA) group. The rest were assigned to the nonosteoarthritis (NOA) group. There were 328 patients (448 feet) consisting of 16 men and 432 women. Osteoarthritis patients were then evaluated and classified according to joint space narrowing (JSN) and osteophyte (OP) formation. A statistical analysis was conducted to compare the 2 groups in terms of their hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), hypermobility of the first metatarsal ray, the length of the second metatarsal bone, and the length ratio of the first and second metatarsal bones. Correlation coefficients were calculated to compare the severity of hallux valgus and the degree of osteoarthritis of the second MTP joint. RESULTS: The IMA of the OA group was 16.2 ± 2.9 degrees, and that of the NOA group was 15.4 ± 3.3 degrees (P = .034, Mann-Whitney U test). The DMAA of the OA group was 18.2 ± 8.3 degrees, and that of the NOA group was 16.1 ± 8.0 degrees (P = .029, Mann-Whitney U test). There were no significant differences between the 2 groups in terms of the HVA, hypermobility, the length of the second metatarsal bone, and the length ratio of the second and first metatarsal bones. In the OA group, there was a positive correlation between the HVA and the degree of osteoarthritis (osteophyte formation) (É£ = 0.278, P = .030). In addition, there was a positive correlation between the IMA and the degree of osteoarthritis (É£ = 0.284 [JSN], 0.327 [OP] for the HVA, P = .026 [JSN], .010 [OP]). However, there was no significant difference between hypermobility and the degree of osteoarthritis (P = .356 [JSN], .635 [OP], Mann-Whitney U test). Furthermore, there were no positive correlations between the DMAA, the length of the second metatarsal bone, and the metatarsal length ratio. CONCLUSION: Our study demonstrated a positive correlation between HVA, IMA, and osteoarthritis of the second MTP joint. Other studies will be needed to determine the factors that are responsible for this correlation. LEVEL OF EVIDENCE: Level III, retrospective comparative series.