Forefoot problems and classification
The typical forefoot problems are hallux valgus, toe clawing and dorsal dislocation of the lesser metatarsophalangeal joints, drawing the plantar fat pad anterior to the metatarsal heads. In this position it no longer provides padding to the metatarsal heads, which become prominent so that patients complain they are “walking on pebbles”. Ulceration may occur on the bony prominences (Firth 2008) and was present in nearly 10% of Firth’s patients. Despite the occurrence of peripheral neuropathy in RA, ulceration was rarely neuropathic in another study by Firth (2008) – it was associated with steroid therapy, pre-ulcerative lesions, peripheral vascular disease and disease activity.
Some patients present with early flexible or semi-flexible deformities (type 1 or 2). However, the majority have severe clawing with fixed subluxation or dislocation of the MTP joints when referred for surgery. The toes, dislocated onto the dorsum of the metatarsal heads, no longer share load bearing in late stance phase. The plantar plate of the MTP joint is also dislocated onto the top of the head and locks it down by the “plunger effect” (Stainsby 1997). The dislocated toe and plantar plate draw the plantar fat pad forward by their connections to the plantar fascia, leaving the metatarsal heads exposed in the sole. Hence these patients often complain of a sensation of “walking on pebbles”. This is discussed further in the page on lesser toe deformities.
There is some controversy about the relationship between the altered forefoot mechanics induced by the flatfoot deformity and the development of hallux valgus. The abnormal laxity induced in all the first ray joints, especially the 1st MTP joint, is probably most important in creating the valgus deformity.
Occasionally referral is precipitated by the development of an ulcer over a stiff deformity, usually the medial prominence of the 1st MT head, under a lesser MT head or over a PIP joint. Ulceration may be due to peripheral neuropathy.
A few patients present with stiff painful 1st MTP joints without deformity, more like hallux rigidus than valgus.
Doorn (2010) described a classification system for rheumatoid forefoot deformity, which they validated in a group of 94 patients with two observers; 61 patients also had foot pressure studies.
- Grade 0 – no clinical changes in the MTPJs, no or mild radiographic changes
- Grade 1 – decreased mobility of one or more joints in plantar flexion, fully reducible, adequate plantar soft tissues. Any degree of radiographic change.
- Grade 2 – loss of plantar flexion in one or more joints, unable to reduce plantar soft tissues under MT heads, inadequate plantar soft tissues. Any degree of radiographic change.
- Grade 3 – extension contracture of one or more MTPJ, with or without subluxation/dislocation. Any degree of radiographic change.
At grades 2-3, A represents hallux valgus >20°, B represents no hallux valgus.
It is surprising that subluxation/dislocation is not a clearly separate grade as the foot becomes more difficult to treat in the presence of dislocated MTPJs. Indeed the paper is not absolutely clear on this matter. If the classification can be validated in other settings it may be a useful tool.
Overall disease control should be optimized. MTP joint steroid injections can be useful although there is no major study of outcome or durability.
Hennessy (2012) carried out a systematic review of the evidence for custom orthoses in the rheumatoid foot. There was some evidence for pain relief but little for improvements in function or walking speed; none of the studies was of high quality. The paper does not distinguish between orthotic treatment of forefoot and hindfoot disease.
Traditionally, most forefoot surgery consisted of excision arthroplasties or fusion. The improvement in disease control with modern treatment has stimulated interest in conserving joint function and structure as far as possible. Unfortunately the medical treatment received, and degree of disease control, are not clearly defined in most of the series, leaving some doubt as to which patient populations they apply to. Further studies are required to enable us to advise patients on different treatment regimes, with different degrees of disease control and established joint damage. The series will be described in some detail to give an indication of the data available.
Thordarson (2002) painted an initially gloomy picture with a report of 8 chevron osteotomies, all of which failed at a median of 24 months, due either to recurrent hallux valgus or disease progression.
Three series (Barouk 2007, Berg 2007, Bhavikatti 2012) described a shortening scarf osteotomy for the first ray with Weil osteotomies to the lesser rays (not all patients had both procedures). Barouk’s paper does not contain outcomes. 79% of Berg’s patients were satisfied with the outcome at a minimum of 6 years, although 8/20 had recurrent hallux valgus, three of whom had been revised to 1st MTPJ fusion. Bhavikatti reported 59 patients followed up for just over 4 years. The mean AOFAS forefoot score improved from 40 to 89/100, all forefoot calluses resolved and there were 3/59 recurrent hallux valgus.
Nagashima (2007) reported 47 patients who had Hohmann osteotomies to the first ray and Helal osteotomies to the lesser rays, with a median 5.6y follow-up. 79% were satisfied; the satisfied patients had continued to improve after surgery while the dissatisfied ones did not.
Takakubo (2010) performed Mann osteotomies of the 1st MT and oblique lesser metatarsal osteotomies, with mean 3.6y follow-up, in 11 patients. The mean Japanese Foot Society score improved from 44 to 72 and three patients had recurrent hallux valgus.
Niki (2010) performed Lapidus procedures with basal shortening osteotomies of metatarsals 2-4 and distal 5th metatarsal osteotomies in 39 feet, with mean 3y follow-up. The mean Japanese Foot Society score improved from 52 to 90, all calluses disappeared and there were no recurrent deformities. While the Lapidus procedure is not indicated as a routine hallux valgus treatment, it may have a rationale in the presence of severe rheumatoid flatfoot, but this was not discussed in Niki’s paper.
In addition, van der Heide (2009) described PIPJ excision and open reduction of the lesser MTP joints for rheumatoid lesser toe deformities. 31 patients also had 1st MTP fusions, their mean foot function index scores reduced from 43 to 23 and 90% were satisfied. However, in 13 patients who had no 1st MTPJ surgery the FFI reduced only from 44 to 37 and only half were satisfied. There were four recurrent toe deformities.
Most of these series report relatively short term follow-up and it is notable that the highest rate of recurrent hallux valgus (40% recurred, 15% fused) occurred in the series with the longest follow-up at a maximum of 8 years. Clearly good results can be obtained but until better-defined series on modern DMARDs and with longer follow-up are reported, it seems reasonable to offer patients joint conservation where possible but to warn that revision may be required, particularly after 5 years or so. Most of these series excluded patients with severe joint destruction, who are still seen requiring surgery and will require a salvage procedure.
For severe arthritis of the 1st MTPJ the main options are
- Metatarsal head excision (Mayo)
- Base of proximal phalanx excision with sort tissue repair (Keller)
- Interposition or replacement arthroplasty
Each of these may be combined with a variety of lesser ray procedures and vice versa. However, the majority of reports in the literature describe lesser metatarsal head excision with either excision of the first metatarsal head or fusion of the 1st MTP joint.
There is one RCT. Grondal (2006) randomized 31 patients to Mayo arthroplasty or fusion, with lesser metatarsal head excision. 29 patients had clinical follow-up, FFI scoring and pedobarography at a mean of 6 years. There were no differences in FFI scores or satisfaction scores between the groups. The centre of pressure was significantly medialised in the Mayo patients compared to non-rheumatoid controls but not the fusion group. The main weakness of this study is the relatively low power, but there were no obvious trends that might be more apparent in a larger study.
Two larger retrospective comparative studies were reported by Vandeputte (1999) and Mulcahy (2003). Vandeputte found no clinical difference between 1st MTP fusion/ lesser metatarsal head excision and Keller/1st metatarsal head excision, though the pressures under the first metatarsal were higher in the Keller group. Mulcahy, however, reported increased patient satisfaction, less forefoot pain and higher AOFAS scores as well as less abnormal pressure distribution in patients with either 1st MTP fusion or unoperated first rays, as compared with all excision arthroplasties. In a smaller series of 58 patients, Rosenbaum (2011) reported no difference in foot function index or satisfaction between 1st MTP fusion or metatarsal head excision (with lesser metatarsal head excision in both groups), although once again pedobarography studies were more normal in the fusion group.
Overall, these comparative studies do not consistently support the widely held preference for 1st MTP fusion. Foot pressures are generally more improved following fusion, but in most cases this does not result in predictably improved clinical outcomes.
A few studies have reported silastic implant arthroplasty for RA. Hanyu (2001) reported 12-year results in 39 patients with good pain relief in 79% and satisfaction in 92%. Silicone synovitis was present in 21% and recurrent hallux valgus in 19%; grommets were not used and metatarsus primus varus was not corrected by osteotomy. Two RCTs have compared 1st MTP joint replacement to fusion and found no difference in outcome, but RA was an exclusion for both these studies.
Most series describe lesser metatarsal head excision, which can be done through transverse dorsal or plantar incisions, or multiple longitudinal incisions. Provided a smooth curve is obtained with no prominent heads or spikes this generally gives satisfactory results at the cost of shortening the foot. Mulcahy’s (2003) series is the only one to offer a little comparison between different methods, but not enough to prefer one method over another. Case series such as those of Mann (1984), Coughlin (2000), Karambande (2007) give a picture of fusion – resection while Harris (1997), Scott (2005) and Reize describe resection of all the metatarsal heads.
An alternative option is to preserve the metatarsal length with an excision arthroplasty of the proximal phalanx and repositioning of the plantar plate (Stainsby procedure). Briggs (2001) reported 93% of patients pain-free at 5y follow-up after Keller procedure to the great toe and Stainsby procedures to all lesser toes, mostly for inflammatory arthritis. Valgus position of all the lesser toes occurred in 20% but was asymptomatic. In the UK the Stainsby procedure is often combined with a 1st MTP fusion but few results have been reported.
Most older papers describe a transverse plantar approach for lesser metatarsal head excision, giving access directly to the prominent metatarsal heads. Often the 1st metatarsal head was also excised through this incision, although sometimes a medial or dorsomedial approach was used. Fowler (1959) added the excision of an ellipse of skin to draw the fat pad down, and this has been repeated by other authors eg Kates et al (1967). As Stainsby (1997) and Briggs (2001) showed, excision of a skin ellipse in unnecessary – the fat pad is controlled by its enclosing plantar fascia and will reduce with the plantar plate.
Concern about wound healing with a plantar approach, and the need to avoid early weightbearing, led to the use of dorsal approaches. A transverse dorsal approach gives excellent access to all MTP joints. Alternatively, longitudinal approaches on the first ray and 2nd and 4th intermetatarsal spaces also allow surgery on each MTPJ. For phalangectomies, incisions running into the toes are required. Briggs and Stainsby (2001) designed curved incisions in each to after studies on digital skin perfusion, and with careful soft tissue handling these heal with few problems.
In fact, plantar incisions generally heal with few problems. Barton (1973) reported 38% wound problems, but most series report 10% or fewer; indeed, van Loon (1992) had more wound healing problems (though fewer calluses) with dorsal incisions. It has been suggested that multiple dorsal incisions make it more difficult to resect metatarsal heads in a smooth arc, but Coughlin (2000) achieved a good arc in 45/47 feet. Patients who have plantar incisions are usually advised to avoid forefoot weightbearing in the early post-operative phase (eg Karambande 2007), which may interfere with rehabilitation in patients with multiple joint problems and poor balance.
Many rheumatoid patients have relatively low functional demands and can get useful improvements in their pain from most of the standard procedures provided these are well performed with attention to careful tissue handling, reducing the plantar fat pad and, where metatarsal heads are excised, obtaining a smooth curve. Our local preference has been a first MTPJ fusion with Stainsby procedures to the lesser rays. We generally discuss the option of a Keller procedure instead of a fusion and some less active patients prefer this as recovery is generally quicker.
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