Towards understanding Müller-Weiss disease from an analysis of 95 cases.

Background: The single existing classification of Müller-Weiss Disease (MWD), based solely upon Méary's angle, serves neither as guide for prognosis nor treatment. This accounts for lack of gold standard in its management.

Methods: Navicular compression, medial extrusion, metatarsal lengths, Kite's, lateral and dorsoplantar talo-first metatarsal angles were measured in 95 feet with MWD. Joints involved, presence and location of navicular fracture were recorded.

Results: Group 1 "early-onset" MWD feet (n = 11) had greatest compression and medial extrusion, and lowest Kite's angles. All except 1 were index minus and had lateral navicular fracture. Only 1 had moderate degeneration at the talonavicular joint (TNJ) with none requiring surgery yet. Group 2 "Müller-Weissoid" feet (n = 23) had radiologically normal navicular in their fifties and developed MWD on average 5 years later. They had the lowest compression and extrusion, and highest Kite's angles. None had complete fracture. All had TNJ arthritis, with early changes at lateral naviculocuneiform joint (NCJ) in 43%. Group 3 "late-onset" MWD presented in the sixth decade. Only TNJ was involved in Group 3 A (n = 16). Group 3B (n = 20) affected TNJ more than NCJ and had the greatest number of Maceira stage V disease. Group 3 C "reverse Müller-Weiss disease", which affected NCJ more than TNJ (n = 25), had greatest midfoot abduction and overlength of the second metatarsal. No fracture occurred in group 3 A compared to 65% and 32% in groups 3B and 3 C, respectively.

Conclusions: With need to compare like-for-like pathology, the proposed classification provides a common platform for reporting outcomes of different treatments. We theorize pathogenetic pathways in the various groups.