Adult acquired flatfoot

and tibialis posterior tendonopathy

Staging and classification

Hattrup and Johnson (1989) proposed a staging system which is in general use in the orthopaedic foot and ankle community. They recognised three basic stages:

stage 1 with tendonopathy but normal tendon length and no deformity
stage 2 with tendon lengthening and flexible planovalgus deformity
stage 3 with tendon lengthening and fixed planovalgus deformity

Myerson added a stage 4, where there is fixed foot deformity and tilting of the talus in the ankle mortise. Dereymaeker also proposed a stage 0, where there is biomechanical abnormality but no symptoms – this acknowledges the more importance of pre-existing biomechanics but implies that stage 0 feet are likely to progress.

Hattrup and Johnson’s classification was based on clinical examination, with treatment recommendations as follows:

Stage	1	2	3
Tendon condition	peritendonitis/degeneration	elongation	elongation
Hindfoot	mobile, normal	mobile, valgus	fixed, valgus
Pain	medial, focal	medial, along tendon	medial + sinus tarsi/lat ankle
Single heel rise	mild weakness	marked weakness	marked weakness
"Too many toes" sign	normal	positive	positive
Pathology	synovitis/degeneration	degeneration	degeneration
Treatment	conservative/debridement	FDL => tib post transfer	subtalar arthrodesis

Unfortunately, there are a number of problems with the Hattrup and Johnson staging system:

the organising concept in the text of the paper seems to be the state of the tendon, but the basis of the actual staging system is the physical signs
most of the physical signs are those of planovalgus deformity rather than tendon disease, yet conclusions are drawn about the state of the tendon
the paper and the staging system imply that the foot begins in a neutral posture, yet many patients have a pre-existing flatfoot
no account is taken of different degrees of flexibility in the hindfoot and forefoot – indeed Johnson denied the existence of this (the two-piece concept of the foot – see below under subtalar fusion)
no account is taken of the severity of deformity
Conti et al described a separate MR classification of tendon abnormalities which cannot be readily integrated into the Hattrup and Johnson classification
Hattrup and Johnson’s paper contains no actual data and no subsequent publication has examined the reliability and reproducibility of the classification, or how it affects clinical decision making

For all these reasons, it is probably time to re-evaluate the classification and staging of adult acquired flatfoot, acknowledging both the seminal work of Hattrup and Johnson and subsequent work. A revised classification should probably incorporate:

a clinical classification of flatfoot deformity based on that of Hattrup and Johnson, but taking account of severity of deformity and stiffness at different levels
radiological staging of deformity
a classification of tibialis posterior tendonopathy, probably based on the MR classification of Conti et al and recognising that some patients with adult flatfoot deformity have no tibialis posterior disease
rigorous evaluation for reliability, validity and effect on clinical decision making

A development of the Johnson and Strom classification was described by Parsons (the Truro classification). It principally divides stage 2 into three stages, depending on the severity and reducibility of the classification, and also recognises that stage 1 patients may have a pre-existing flatfoot deformity:

Stage 1: no deformity, or flatfoot deformity which has not progressed and is similar to the opposite foot.
Stage 2: Flatfoot deformity which has progressed but is fully passively correctible and in which forefoot varus is less than 15deg.
Stage 3: Flatfoot deformity which has progressed but is fully passively correctible and in which forefoot varus is greater than 15deg.
Stage 4: Flatfoot deformity which has progressed; the hindfoot is fully passively correctible but the forefoot is not.
Stage 5: Flatfoot deformity which is not correctible
Stage 6: Flatfoot deformity in association with tilting of the talus in the ankle mortise on standing radiography.

Preliminary studies show the Truro classification is usable by different professional groups and is fairly reproducible. The greatest discrepancies occur between stages 2 and 3.

Truro staging in Suneja (2006)
Truro stage	Patients
1	26
2	84
3	25
4	22
5	6
6	4

Suneja reported the clinical characteristics of the complete consecutive Blackburn series. Half their patients were in stage 2. Stage 4 (whose existence was denied by Johnson) accounted for 13%.

They drew attention to an additional group of patients previously alluded to by the Seattle group. Eighty percent of their series persented with symptoms related primarily to the tibialis posterior tendon, spring ligament and deltoid ligament. However, the remaining 20% had mainly arthritic symptoms, especially in the 1st TMT joint, were slightly older and much more likely to require surgery.

Myerson has proposed that there should be radiological criteria of the severity of deformity and is evaluating such criteria. It seems likely that there will be a revised classification within the next five years.

The natural history is believed to be a progression from tendonopathy without deformity, through a mobile deformity to a foxed deformity. However, few patients have been followed to demonstrate progression of the condition. In the Blackburn series (Suneja 2006) the median age of Truro stage 1 patients was 15 years less than that of the rest. Patients in stages 4-6 (stiffer deformities) were slightly older than in stages 2-3 (flexible deformities) but the difference was not significant. Only about 5% of Blackburn patients had progressed under observation, although follow-up was incomplete.