A prospective clinical and biomechanical analysis of feet following first metatarsophalangeal joint arthrodesis for end stage hallux rigidus

Background
Hallux Rigidus is the result of degeneration of the 1st metatarsophalangeal joint (1st MTPJ). In end-stage hallux rigidus, treatment is mainly surgical with arthrodesis being a favourable option. Although the biomechanical effects of arthrodesis have been examined, a detailed comparison of pre- and post-operative biomechanics has yet to be conducted.

Research Question
Does 1st MTPJ arthrodesis positively affect foot kinematics and plantar pressure distribution?

Methods
Twelve 1st MTPJ arthrodesis were performed in patients with a mean age of 53.5 ± 5.4 years and follow up time of 6.9 ± 1.0 months. Pre- and post-operative data were collected at a CMAS (Clinical Movement Analysis Society) accredited gait laboratory using a BTS motion capture system and pedobarographic pressure plates. Patient outcome measures were also assessed using the MOXFQ. Statistical analysis was conducted using a two-way repeated measures ANOVA.

Results
Significant changes in stride length, cycle duration, cadence and velocity were identified following 1st MTPJ arthrodesis. A significant reduction in forefoot-hallux dorsiflexion at toe-off was identified for the operated foot from the pre-operative (20.23 ± 5.98°) to post-operative (7.56 ± 2.96°) assessment. Post-operative sagittal and transverse plane changes in the operated foot were also identified. Peak pressure and PTI results indicated significant lateralisation of load for the operated foot, but importantly this was not influenced following arthrodesis. Finally, there was a significant improvement in MOXFQ score.

Significance
Following 1st MTPJ fusion there is an improvement in overall gait mechanics which accompanied by the improved MOXFQ score indicates a reduction in pain and improved confidence during gait. The lack of post-operative dorsiflexion at forefoot-hallux caused load to remain lateralised and compensatory mechanisms to occur at the more proximal joints within the foot. These results provide valuable information for clinicians and will enable more accurate counselling to be provided to patients with end-stage hallux rigidus.