Exploratory study to identify mechanical factors that may ...€¦ · foot; 2nd and 4th toes, and 2nd and 4th meta-tarsophalangeal joints (MTP) of the left foot (fig 2). Temporal

Exploratory study to identify

mechanical factors that may contribute to

toe dactylitis in patients with psoriatic arthritisRichard A Wilkins, Dr Heidi J Siddle, Prof. Anthony C Redmond, Dr Philip S Helliwell

BackgroundDactylitis (sausage digit) is one of the most

commonly reported features of psoriatic arthritis

(PsA) (Fig 1).

It has been hypothesised that dactylitis is a

functional enthesitis at the proximal

interphalangeal joints (hands and feet), resulting

in synovitis, tenosynovitis, bone and soft tissue

oedema to the digit.

Trauma and physical insult to the digit have been

suggested as a possible cause

Aim• To explore mechanical factors that may

contribute to the occurrence of dactylitis in

patients with PsA.

• To explore the impact of dactylitis on

impairment, function, activity and limitations.

• To provide insight into plantar pressure

distributions in PsA

Methods12 participants with PsA and a history of dactylitis

(group i), 12 participants with PsA and no history

of dactylitis (group ii), 12 control participants

(group iii) were recruited.

Plantar pressure measurements were undertaken

barefoot and in footwear.

Peak plantar pressure and pressure time integral

were analysed at the most common and second

most common sites of dactylitis reported in the

foot; 2nd and 4th toes, and 2nd and 4th meta-

tarsophalangeal joints (MTP) of the left foot (fig 2).

Temporal and spatial parameters of gait were

collected

Patient reported impairment and footwear

(FISAP), and activity limitation and participant

restriction (FISIF) were reported using the Foot

Impact Scale for Rheumatoid Arthritis (FIS-RA).

Results PsA patients in both groups had a mean

disease duration of 4.5 years

• Mean FIS-RAIF out of 21

- PsA Dactylitis 7.16

- PsA no history of dactylitis 6.83

- Controls 0.41

• Mean FIS-RAAP Out of 30

- PsA Dactylitis 8.75

- PsA no history of dactylitis 5.75

- Controls 0.16

ANOVA analysis and subsequent post-hoc

testing using Games-Howell test yielded

significance in FIS-RA mean scores.

No Significant difference in plantar

pressures or gait variables between

groups

Conclusions• This is the first exploratory study to

investigate the mechanical factors that

may cause dactylitis in PsA

• FIS-RA scores indicate PsA patients have

significant limitations compared to

controls, but a history of dactylitis does

not worsen patient reported outcomes.

• Although no significant differences

could be reported in plantar pressure

data or gait variables, the study was

underpowered.

• Exploration of shear and friction in the

forefoot may provide insight for a

biomechanical trigger to dactylitis.

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Figure 1; Dactylitis of the 3rd 4th and 5th toes

Figure 2; Plantar pressure with masking

Results