Jack’s test

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Ewen Jack’s classic paper in 1953 stated: “Flat foot,,, is a highly controversial subject..” before going on to describe the merits and limitations of a ‘toe-raising test’ – now the eponymous Jack’s test (aka Hubscher’s manoeuvre, especially in the US).

In 2017 – some 64 years since Ewen Jack’s paper appeared in the British Journal of Bone and Joint Surgery [JBJS 35B(1):75-82, 1953; http://www.bjj.boneandjoint.org.uk/content/35-B/1/75.long ] – is there still a place for this simple clinical test, when examining paediatric foot posture? I think there is – with all the usual reservations and caveats about a single test needing to be considered in context, rather than being diagnostic – I think Jack’s test is helpful.

The windlass mechanism is a primary part of sagittal plane foot function, stability, and propulsive gait. Jack’s test, by manual dorsiflexion of the hallux at the 1st metatarsophalangeal joint, tightens the plantar fascia, shortening the distance between the metatarsal heads and the heel, and in doing so elevating the medial arch. Whilst observing the effect of the windlass tightening to the plantar fascia and medial arch height, an examiner can also visualize TNJ congruity, assess Tib Post / Tib Ant activity. It can be helpful for parents to see this manoeuvre, and can make it easier to explain their child’s gait.

So what if the medial arch doesn’t rise, or hallux dorsiflexion is really difficult, or not possible?

Jack’s test can be neutralized in some foot types eg ankle equinus, vertical/oblique talus, tarsal coalition, peroneal spasm. Children with hypotonia and/or ligament laxity often have an apropulsive walking gait (may also manifest with global developmental delays), and Jack’s test is frequently positive.

Whatever the result of Jack’s test clinically, gait is the more essential function to observe, and this entails, gait that is barefoot, shod (various shoes), normal walking pace, and running as relevant.

Have a look at the two brief videos, where Jack’s test is shown.

The first video shows a 5 year-old child, and the second video features an 8 year old.

Jack’s test 5

Jack’s test 8

 

Having viewed these, you have hopefully noted the difference in the findings of Jack’s test between the two children – the younger child showed the expected medial arch rise with Jack’s test, and the older child showed the opposite (until the foot was manually stabilised to enable the plantar fascia to tighten with hallux dorsiflexion – did you note the evident recruitment from both Tib Ant and Post?)

But what would you expect to see at these ages? What about gait – the more defining factor?

The 5 year old presented with the parent’s querying foot posture (Dad a keen runner). No findings of note in either the history or examination, and the parent’s were interested in Jack’s test, the markers of a propulsive gait, the influence of footwear, and the age-expected flatfoot posture that is a part of normal foot development.

The 8 year old also presented with concerns about flat feet, and the Mum had noted that “she bounces” – as gait revealed increased abduction, short contact phase, poor propulsion and ‘bounce’. There was no pain, but weak Tib Post, and surprisingly perhaps, no ankle equinus. Later to walk at 18 months, early mild motor delay was associated with hypotonia. Structured footwear and strengthening were the immediate actions, with follow up showing less abducted angle of gait, and the Mum noting: “she’s stopped bouncing”. (Review in 12 months).

What might exacerbate flatfoot in children and yield a positive Jack’s test and gait pattern?

Check the history – most information can be found there, and assess according to expectations for age. Amongst the many other differentials, consider muscle tone, range of motion – the two sub-types of presenting hypermobility.

Simple clinical tests like Jack’s test can be useful, but be realistic as to what it indicates – as a single, static test. Related to gait, age, presenting concerns, history details, Jack’s test can be helpful to explain aspects of foot posture and functioning to parents, and assist with shared decision-making.

 

Evidence Essentials
(Series 2 monographs) addresses Hypotonia, and covers developmental trends, diagnostic details and differential assessment. Hypotonia types, clinical tests and assessment criteria are presented in clear Tables – quick and easy reference for clinicians who need on-the-spot information.

Hypermobility, due to ligament laxity, has been addressed in Series 1, monograph 7.

Evidence Essentials – Series 2, dedicates a specific monograph to history taking, to present the best useable format and tools for clinicians in the paediatric setting. This is important for diagnosis and differential diagnoses, considerations around intervention, and for discussion with parents and other medical/health colleagues.

Evidence Essentials series subscribers will have received the Evidence Essentials ‘Quarterly’ – a seasonal paediatric foot ‘round up’ – the ‘Summer’ bumper edition featured 13 recent paediatric foot journal article commentaries, e-links. In the style of Evidence Essentials, the ‘Quarterly’ is pithy and pertinent – a quick read to glean the latest.

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You may like to review our latest results: http://jfootankleres.biomedcentral.com/articles/10.1186/s13047-016-0175-0

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Kind regards,

Angela Evans

Dr Angela Evans    PhD, FFPM RCPS(Glasg)

www.angelaevanspodiatrists.com.au