Last evidence check April 2010

There are many different potential causes for forefoot pain. Some are quite discrete entities which present as pain in a distinct area which helps diagnosis:

Others are imbalances in foot function which seem to increase the likelihood of forefoot pain:

Some of these have clearer support in the evidence base than others (diGiovanni 2002, Toth 2007). However, at best they show an association between the index condition and forefoot pain (for example, diGiovanni found that ankle dorsiflexion of <5deg was present in 65% of people with forefoot pain and 24% of asymptomatic controls) – they do not “prove” that the imbalance is the “cause” of the pain in any particular patient. Here another interesting study is that of Orendurff (2006). In diabetic patients, loss of ankle dorsiflexion was significantly corelated with peak forefoot pressure. However, equinus accounted for only 15% of the variance in forefoot pressure and other factors much be relevant.

Moreover, many patients have several putative “causes” for forefoot pain. Barrie and Roberts (2000) reviewed 388 patients with forefoot pain. Only 104 (27%) had a single apparent “cause”. 154 patients (40%) had two possible factors, 80 (21%) had three, up to two patients who had six plausible factors.

In some cases, clinical assessment and simple tests will allow one to judge which factors are the most important and likely to be influenced by treatment. However, there is always a degree of uncertainty, and this needs to be shared with the patients in an appropriate way.

Two other factors should be mentioned which can cloud good decision-making:

Neither of these examples are intended to dismiss colleagues who are trying to construct a theoretical framework for understanding forefoot pain. They do, however, illustrate how much more complex the matter is than simply assuming a facile connection between observed abnormalities and a presumed “cause” of the pain which can be predictably corrected.

Causes to consider

The following are recognised factors which may contribute to the development of forefoot pain. Some of them are covered in more detail elsewhere in the Hyperbook. They should be considered in the light of the preceding discussion.

Hallux valgus and metatarsalgia

Metatarsalgia is often quoted as an important complication of hallux valgus surgery, with most studies quoting incidences of up to 10%. The Keller procedure, in particular, has been credited with up to 75% (Flamme 1998), although this may be less with cautious resection and soft tissue repair (Schneider and Knahr 2002).

However, hallux valgus itself alters forefoot loading during stance phase: pressure under the hallux is reduced while it is increased under the lateral metatarsals(Hutton and Dhanendran 1981). Hallux valgus correction has been reported to improve loading patterns back towards normal (Dhukaram et al 2006), although this has not been reported in all studies (Stokes 1979), nor does it seem to be consistent across different procedures. It takes at least a year to reach a final pressure pattern.

Although there is not always a direct relationship between correction of plantar pressures and relief of symptoms, hallux valgus correction can improve metatarsalgia. In 17 studies of hallux valgus surgery in which data was given for the prevalence of metatarsalgia before and after surgery, or at least for the changes in prevalence, 362 patients had metatarsalgia before metatarsal osteotomy and 189 afterwards. Eight different procedures were represented (Wilson, scarf, Ludloff, Mann, distal chevron, proximal chevron, McBride and Mitchell) and only after the Wilson osteotomy did more patients have metatarsalgia than pre-operatively. Patients who had non-Wilson osteotomies were 40% as likely to have metatarsalgia after surgery than before, and (where this data was available) four times as likely to be relieved of pre-operative metatarsalgia than to acquire it for the first time after surgery. Of course, this was only a small minority of the series reporting the results of hallux valgus surgery, so there is considerable potential for selection bias; and it was not always clear whether other procedures had been performed that might have had an effect on metatarsalgia (such as hammertoe correction).

The main factors that seem to be associated with the development of metatarsalgia after hallux valgus surgery are first metatarsal shortening and dorsal malunion, and instability of the great toe. Merkel (1983) found that patients with more than 10mm first metatarsal shortening had only 71% good/excellent results compared with 90% in those with less shortening - most of the poor results seem to have been due to metatarsalgia. The centre of pressure was more lateral in those with a short first metatarsal. Jung et al reprted a cadaver study in which pressures were measured under the metatarsal heads after osteotomies of the irst metatarsal simulating 10deg dorsal angulation, 5mm shortening and 10mm shortening. 1st MT pressures were reduced from baseline and 2nd (and to a lesser extent 3rd and 4th) MT pressures increased, with the greatest difference in the 10mm shortening model. No larger shortenings were studied. Toth reported a strong association between 1st metatarsal shortening after Lindgren-Turan (2007) and Wu (modified Mitchell) (2008) osteotomies, although the mean shortening was only 3.8mm in the Lindgren-Turan series and the mean length increased minimally in the Wu series. Unfortunately relatively little detailed information was provided in these papers.

Overall, hallux valgus can defunction the first ray enough to cause or contribute to metatarsalgia. This pain is likely to be improved by a hallux valgus correction. However, about 5-10% of patients who have a hallux valgus correction develop lateral forefoot pain for the first time. This is associated with metatarsal shortening and dorsiflexion, but other factors are also relevant and procedures should not be condemned out of hand simply because they shorten the first metatarsal. For instance, shortening is a recognised part of the Mitchell and scarf osteotomies and is compensated by plantar flexion or displacement of the metatarsal head.