Abstract
Background
Severe hallux rigidus can be treated with total or hemi arthroplasty to preserve motion in the 1st metatarsophalangeal joint (MTPJ). Decreased dorsiflexion impairs the rollover motion of the 1st MTPJ and recent studies of patients with 1st MTPJ osteoarthritis show increased plantar forces on the hallux.
Objectives
Our aim was to examine the plantar force variables under the hallux and the 1st, 2nd, and 3rd – 5th distal metatarsal head (MH) on patients operated with a proximal hemiarthroplasty (HemiCap) in the 1st MTPJ and compare to a control group of healthy patients. Secondary aims: To examine correlations between the force and the 1st MTPJ range of motion (ROM) and pain.
Study Design & Methods
Seventy patients operated with HemiCap were invited. 41 were included, (10 men, 31 women), median operation date 2011(range 2007–2014), age 63(47–78), 37 unilateral and 4 bilateral. Dorsal ROM of the 1st MTPJ was measured by goniometer and by x-ray. Pain evaluated by visual analog scale (VAS 1–10) during daily activities (DA) and during testing (DT). Emed (Novel) Foot Pressure Mapping system was used to measure peak force (N) and force/time integral (N/s) under the hallux, 1st and 2nd and 3–5th metatarsal heads (MH). Statistics: Force variables between operated feet and control group were compared by independent two-sample t-test or Wilcoxon rank sum test. Force variables association to ROM and pain by linear regression models.
Results
Median (range) for HemiCap/Control group: Peak force (N): Hallux: 12(1–26)/20(4–30), 1st MH: 17(8–41)/24(14–42), 2nd MH 24(15–37)/28(24–37), 3rd–5th MH: 27(18–36)/30(25–35). Force/time integral (N/s): Hallux: 1(1–4)/4(1–12), 1st MH: 5(2–18)/7(3–11), 2nd MH 8(4–13)/10(7–13), 3rd–5th MH: 9(6–15)/10(8–14). Significant difference between HemiCap patients and healthy controls in peak force and force/time integral was found under the hallux (p<0.01), 1st (p<0.05) and 2nd MH (p<0.05), and max force under the 3–5th MH (p<0.01). Dorsal ROM of the operated feet was 45 degrees (10–75) by goniometer and 41 degrees (16–70) by x-ray. An increase in dorsal ROM decreased the peak force and force/time integral under the hallux (p>0.05) but not under the MHs. Most patients reported no pain (VAS 1: 62% DA, 78% DT), only 2 patients reported VAS>3. No significant correlation between pain and force or force/time integral.
Conclusions
A mid-term hemiarthroplasty do not restore the joint motion to normal. The loading patterns are in opposition to AO patients as as assfgjkdfgjkfdgjk the HemiCap patients show a significantly decreased peak force and force/time integral under the hallux compared to the control group and the larger the dorsiflexion achieved postoperatively the smaller the force/time integral becomes. It may reflect a patient reluctance to load the 1st ray and 2nd MH. The plantar forces are not linked to pain. Most report minimal pain, but the pain score is biased by missing numbers and exclusion of revisions
