NB This page is from the 2005 Hyperbook.
Last evidence check November 2004.
The foot and ankle are a common site of pathology in rheumatoid arthritis. Michelson et al (1994) found that 79% of university outpatients had ankle disease and 67% MTPJ disease; in about half these sites were the main problem. Twenty-seven percent had midfoot disease but only 5% considered it their worst problem. Interestingly, only 4% had accommodative shoewear.
A number of studies of early RA have shown that the foot is one of the earliest sites affected, with 15% of first MTPJs affected within one year and 28% within 3 years (van der Heijde 1992). Bouysset (1992) found that 50% of RA patients had a flexible flatfoot within 5 years of disease onset, but by 9 years the same proportion had stiff flatfoot deformities. Recent interest has focused on the use of MRI to help make the diagnosis of RA, and the hands and feet are the most useful sites in early suspected disease(). Hence careful examination of the foot and ankle are essential in assessing every rheumatoid patient.
A few rheumatoid patients develop enthesopathy with pain in the attachments of the plantar fascia and tendons (especially the Achilles tendon). However, this is much commoner in seronegative arthropathies such as ankylosing spondylitis, psoriatic arthropathy and Reiter’s syndrome.
Rheumatoid patients are challenging to treat, because of:
It is important to work closely with other members of a team including:
Michelson’s study shows that ankle disease is commoner than is often realised. The ankle should be examined in every patient with rheumatoid forefoot disease.
Ankle disease usually presents with pain and swelling in the ankle joint line. The joint is painful to move. Although the ligaments are eroded the ankle is not usually unstable. Some patients with severe erosion of the ankle may also have hindfoot valgus, although this is usually due to a combination of abnormal limb biomechanics, subtalar/talonavicular erosion and tibialis posterior tendonopathy (see below). The proximal limb joints, overall limb alignment and the forefoot should also be assessed.
Plain radiographs will demonstrate joint damage, erosions and periarticular osteopenia – standing AP/lateral are standard views. If there is hindfoot valgus a standing hindfoot alignment view (Saltzmann and el-Khoury 1994) helps to define the contributions of ankle and subtalar tilt.
Steroid injections are often helpful on an empirical basis, although there is no good evidence base for their use and in other joints they may not be much better than placebo.
A long-term Japanese study reported recurrent disease in only 10% of ankles at 10-20 year follow-up of open synovectomy (Akagi et al 1997); however, other studies suggest that improvement is maintained for only 4 years, similar to radiation synovectomy (Nakamura et al 2004; van der Zant 2004).
Until recently this was the only real option for end-stage ankle arthritis of whatever aetiology. The traditional British method was that of Charnley with a destructive anterior transverse approach and external fixation with a semi-stable frame. This had a high incidence of infection and non-union. Arthrodesis is now normally carried out with an open or arthroscopic surgical technique, and fixation with screws, plates or an intramedullary nail. Arthroscopic surgery does less soft-tissue damage. Early studies suggested a high rate of non-union, but in experienced hands it probably results in quicker and less complicated union of the fusion (O’Brien et al 1999). However, it is difficult in very stiff ankles with large osteophytes, or where there is significant deformity. Long-term studies show OA developing in adjacent joints, although not always symptomatic, and of course this might have happened anyway without the fusion.
Has been around for over 30 years. However, early prostheses did not reproduce the biomechanics of the ankle well and had a very high failure rate. Second-generation prostheses from the late 1980s onward introduced improved engineering, often with three components. 10-20 year results are now being published (Kofoed 2004, Buechel et al 2004), indicating success in over 90% of patients. However, these are the series of the designers of the various prostheses, and further results from the “real world” may not be quite so optimistic. The Wrightington series (Wood and Deakin 2003) is a realistic and critical account with 5-8 year follow-up and 92% 5-year success. Results in OA and RA are similar. (Kofoed 2004, 1998; Wood and Deakin 2003). Ankle prostheses also seem to be best uncemented; the long term results of the STAR ankle have been significantly better in the uncemented design (Kofoed 2004). Like all joint replacements, failure occurs. The results of revision arthroplasty are not as good as at other sites, and fusion is usually required.
It is only appropriate to compare fusion and replacement for patients without major deformity, infection, bone loss or neuropathy – these would only be candidates for fusion. However, there have been no direct comparisons of replacement and fusion in patients in whom both would be an option. In addition, outcome measures in single-procedure series are so varied that it is difficult to compare them.
As might be expected, ankle fusion affects the range of motion and kinematics more than does replacement, and certain designs are closer to normal than others (Valderrabano et al 2004a,b). Gait analysis is much closer to normal in replaced than in fused ankles (Butcher et al 2004). Hence it is plausible that ankle replacements would place less stress on other joints, both in the tarsus and proximally. Nevertheless, this requires clinical confirmation.
A study of patients 20 years after ankle fusion (Fuchs et al 2003) reported reduced SF-36 pain, physical functioning and emotional disturbance scores, and moderate Olerud ankle scores. Most patients wore customised footwear, but few had walking aids. All but one had returned to work. There was significant progressive OA in the other hindfoot joints. The surgery included more external fixation than would be expected in a current population. Another study (Buchner et al 2003) reported little or no pain and restriction of activity in 92% of patients at an average of 9.3 years follow-up. An independent study of fusion in OA (Anderson et al 2002) found that the true fusion rate was 80-89% but the clinical and radiological outcomes were not the same. The longest follow-up of arthroscopic arthrodesis (Glick et al 1996) reported a 97% fusion rate at an average of 8years follow-up, with 88% good or excellent results. In rheumatoid disease, Felix et al (1998) reported union in 96% of 26 ankles at 2-8 year follow-up, and no pain 19.
These studies tend to highlight need for revision as the main outcome measure. At 12 years, the survivorship of the current cementless Buechel-Pappas implant was 92% (Buechel et al 2004), but clinical results were presented only as excellent 88%, good 5%, poor 7% (75 patients). Twelve-year survival for the STAR ankle was 95%, with a mean Kofoed ankle score of 91.7/100. The long-term survival rate is based on small numbers in each study. The Wrightington series (Wood and Deakin 2003), although shorter in follow-up (2-8.5 years), is also worthy of study, as it is very large, meticulously critical and realistic. The 5-year survival rate was 92.7%. The mean AOFAS hindfoot score for pain improved from 0/40 pre-operatively to 35 at final follow-up and the functional score from 28/60 to 35. Complications and the learning curve are detailed. None of these studies comment on OA in adjacent joints.
There is not enough data to indicate whether fusion or replacement is to be preferred for patients in whom either procedure would be an option. At about 10 years clinical success rates appear similar; possibly the onset of OA in other joints reduces the success of fusion thereafter. The improved kinematics of ankle replacement probably reduce the wear on adjacent joints, and this could be important, particularly in patients with multiple joint pathology. The improved range of movement is anecdotally useful to patients, but there are no comparative studies.
Rheumatoid disease of the hindfoot and midfoot joints was fairly common in Michelson’s series, although most patients found the ankle or forefoot more of a problem. Pain and swelling in the sinus tarsi is usually due to subtalar synovitis. Disease in the other tarsal joints usually presents with local pain and swelling.
Many rheumatoid patients develop a flatfoot deformity – 50% at 5 years in Bouysset’s (1992) series had a flexible deformity, but by 9 years tarsal joint destruction had developed and the deformity became rigid. The cause of the flexible deformity has been attributed to:
It seems likely that the deformity is due to a combination of these factors.
Patients with hindfoot valgus may do less well after forefoot surgery. Stockley (1990) found abnormal first ray loading and increased pain after Kates-Kessel-Kay procedures in patients with valgus hindfeet.
As at other sites, early disease can be managed medically or with local steroid injections. Clinical assessment of affected joint correlates relatively poorly with MR(), and so MR imaging may be useful in deciding which joints to inject.
The evidence on the use of orthotics is inconclusive, with effectiveness varying from study to study and no clear pattern emerging on the most useful device. Corrective orthotics can, of course, only be useful in patients with mobile deformities. In fixed deformities, accommodative orthotics may still be useful in improving comfort and preventing skin breakdown.
Most patients who require surgery for intractable pain or deformity will have disease in several hindfoot joints and require triple fusions (unlike patients with osteoarthritis, where disease affecting one joint predominantly is common and single joint fusion generally to be preferred). Flatfoot deformity may require quite extensive joint resections and medial column shortening (Henderson et al 2002). The results of triple fusion in rheumatoid disease are reasonably good. Stabilisation with compression screws or staples produce similar reported rates of union and clinical benefit. A technique of removing and rotating a dowel of bone, without stabilisation, has been described but produces a high symptomatic non-union rate.
The typical forefoot deformities are hallux valgus and clawing of the lesser toes. 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 ). 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.
Assessment of a patient with rheumatoid forefoot problems should always include a review of other joints, the overall limb alignment and examination of the joints and alignment of the ankle and hindfoot. Patients with hindfoot valgus do less well after forefoot reconstruction than those with normal hindfeet (Stockley 1990).
Check skin integrity and look for neuropathy and vasculitis.
Look under the forefoot for exposed metatarsal heads. Check the reducibility of toe deformities. If the MTP joint is reducible, how unstable is it? (draw test) Are the tender areas or calluses over the PIP joints dorsally or at the tips of plantar-flexed toes? If toe deformity is mild and most of the pain comes from the MTP joints, feel for synovitis – if in doubt an ultrasound can be helpful.
The first line of management of patients with rheumatoid forefoot is usually accommodative shoes with enough space to remove pressure on stiff deformities, and insoles to reduce pressure on the metatarsal heads. An off-the-shelf metatarsal dome insole is often enough, although patients with severe deformities or peripheral neuropathy may need full moulded total contact insoles.
Ulcers will usually heal with pressure relief as for diabetic ulcers, even if there is neuropathy. Occasionally early surgical debridement will be necessary for osteomyelitis related to an ulcer. Once healed, the foot can be protected with accommodative shoes and moulded insoles. Sometimes ulcers with break down again unless the pressure is relieved by surgical reconstruction, and the risk of this may be considered so high that early surgery is recommended.
Patients with pain and pressure problems which cannot be relieved by accommodation and orthoses may be offered surgical reconstruction. General control of systemic disease and, particularly, of vasculitis, should be established before surgery and ulcers should, if possible, be healed.
There are a number of controversies in rheumatoid forefoot surgery with many authors expressing particularly strong views.
The options are:
Excision of either the MT head or phalangeal base can produce an unstable pseudarthrosis, and recurrent symptomatic hallux valgus is one of the commonest causes of failure in excisional forefoot arthroplasty. Fusion of the 1 st MTP joint is intended to provide a stable 1 st ray pillar, improve forefoot loading and prevent recurrent valgus. Some series, such as Hughes, found that the rate of symptomatic non-union of 1 st MTP fusion was so high that it outweighed the instability of excision arthroplasty. Briggs and Stainsby (2002) performed careful soft tissue balancing of their Keller arthroplasties and found that, although there was some recurrence of the valgus, it was largely asymptomatic. However, fusion with modern fixation techniques such as lag screws and/or plates, produce low rates of non-union (Coughlin 2002). The 1st MTP joint has been replaced with silastic prostheses and, more recently, there has been interest in the use of prostheses using metal, plastic or ceramic bearings. A few rheumatoid patients present with hallux valgus and an apparently normal MTP joint without active arthritis. In these patients standard hallux valgus surgery may give poor results and a fusion or excision arthroplasty is probably better (Thordarson ).
Reduction of these joints will normally require skeletal shortening. The options are:
Excision of all lesser MT heads with a 1st ray procedure is the commonest procedure in most countries. This is often known in the UK as the “Fowler procedure” but it was described by Hoffman 30 years before Fowler, who added little of significance. Resection should be carried out in an arc to prevent prominent stumps. Stainsby has described a subtotal proximal phalangectomy with plantar plate reduction and stabilisation – this is intended to maintain metatarsal length relative to the plantar fascia and hence maintain some control of the toes. The 10-year results of Stainsby procedures to the lesser rays with a Keller procedure to the first MTP joint are comparable with those of the Hoffman procedure. However, many British surgeons (including the East Lancs service) do Stainsby procedures to the lesser rays and a 1st MTP fusion to stabilise the first ray. The long-term results of this approach have not been published. There have been reports from European surgeons of reduction of dislocated MTP joints with Weil osteotomies and PIPJ correction, but long term results are not yet available.