Background At the onset of rheumatoid arthritis (RA), the forefoot is involved in approximately 20% of all patients, and during the course of the disease more than 70% of such patients tend to suffer from foot trouble with wearing shoes. It is common for painful callosities to develop on the planter aspect of the forefoot due to typical deformities and localized high planter pressure.
Objectives The objective of this study was to investigate the relationship between planter pressure and the severity of forefoot deformities in patients with RA.
Methods Using F-Scans (Nitta company), the plantar pressure was measured in 235 feet from 129 inpatients from April 2012 to December 2013. A surgical correction of such forefoot deformities was thereafter required in 40 feet with severe deformities when conservative treatments using shoe inserts or corrective shoes proved to be ineffective. Foot radiographs under weight-bearing were taken and the hallux valgus angle (HVA), intermetatarsal angle between the first and the second metatarsals (M1M2), and intermetatarsal angle between the first and the fifth metatarsals (M1M5) were measured. The presence of any malalignment in the lower extremities and the spine were also assessed by radiographs. The distribution of the peak and the integrated foot pressures were measured at the first interphalangeal joint (IPJ), the 1st through the 5th metatarsophalangeal joints (MTPJs), the medial and the lateral mid-feet, and the hind-foot.
Results More than one-half of all the surgically-treated feet had painful plantar callosities at the 2nd and the 3rd MTPJs. The peak and the integrated pressures at the 1st MTPJ was significantly higher in the surgical group (n=40) than those in the non-surgical group (n=195) (P=0.01, P=0.02). Despite the fact that both the peak and the integrated pressures at the 5th MTPJ were low (P<0.01), the integrated pressure at the 4th MTPJ was also low in the surgical group (P<0.01). In feet with mild hallux valgus (HVA<20°), the pressure at the 5th MTPJ was low (P<0.05), while in feet with severe hallux valgus (HVA>40°), the peak pressure at the 1st IPJ was high (P=0.048). Similar results were noted in the patients without any malalignment in the lower extremities and the spine excluding the forefeet. HVA and M1M2 both increased proportionally, while M1M5 also increased.
Conclusions The plantar pressure was therefore found to be one of the determinants of severity in forefoot deformities. It tended to be high in the medial part of the forefoot in patients with severe hallux valgus who thus required surgical correction of the forefoot.
M. van der Leeden, M. Steultjens, J. H. Dekker et al. Forefoot joint damage, pain and disability in rheumatoid arthritis patients with foot complaints: the role of plantar pressure and gait characteristics. Rheumatology 2006; 45:465-469.
Disclosure of Interest None declared