A comparison of 1st MTPJ arthrodesis and total joint replacement, a clinical and biomechanical analysis

R Rajan, J Shrestha, V Upadhyay, J Vhanda, D Ananda-Rajan

Background: Both 1st MTPJ arthrodesis and total joint arthroplasty (TJA) are performed for end stage hallux rigidus.

Research Question: The objective of this study is to compare/contrast these two surgical procedures to determine any significant clinical and biomechanical differences.

Methods: Kinematic data was collected at our CMAS (Clinical Movement Analysis Society) UK accredited gait laboratory during the gait cycle together with pressure plate pressure readings and a validated patient outcome measure before surgery and at 6 months after surgery.

Results: i) There is a *clinically meaningful difference in the velocity post-op when comparing TJA and arthrodesis in favour of TJA, but this increase in velocity is not statistically significant. There was a statistically significant increased velocity following both these procedures individually from the pre-op condition. ii) There is a statistically significant reduction in forefoot hindfoot plantar flexion in the sagittal plane at the last 20% of the stance phase of the gait cycle (toe-off) in the arthrodesis group. iii) There is a statistically significant increase in the 1st metatarsal head peak pressure (MHPP), 1st/5th MHPP ratio and 1st MH pressure time integral (PTI) regardless of type of surgery post-op. There is a clinically significant increase in the medial column pressure and loading only following TJA compared to arthrodesis. (Increased 1st MHPP, increased 1/5 MHPP and increased 1st MHPTI from pre-op to post-op in the TJA group greater than the respective calculated minimal differences calculated, not so in the arthrodesis group). iv) There is a clinically significant increase in 5th MHPTI following arthrodesis but not following TJA, suggesting increased lateral loading following arthrodesis. v) There is a statistically significantly improved MOXFQ following both types of surgeries.

Conclusion: TJA was found to restore the foot pressures and kinematics towards the normal pressure ratios while arthrodesis results in a compromised gait.