Ankle OA

Last evidence check July 2010

Principal authors: Jim Barrie, Aamir Zubairy and Richard Freeman

Osteoarthritis presents less commonly in the ankle than in other lower limb joints. This is, perhaps, surprising, as the stresses in the ankle are high and the joint surfaces area lower than in other joints. In the ankle OA is often, but not always, secondary.

Causes

Assessment

History

Most patients present with pain in the ankle. Sometimes it is described in the posterior foot or midfoot, or up the leg. Radiation above the mid-tibia should make one suspect proximal problems. Some patients complain the ankle locks or gives way, which may be due to a loose body but usually just represents attacks of severe pain with reflex inhibition of the supporting muscles. Midfoot pain may also arise from OA of the talonavicular, calcaneocuboid or lesser tarsal joints.

It is important to find out what has already been tried. It is quite common to see a patient referred for an ankle fusion or replacement who is not even taking regular analgesics. There may be several non-surgical options to explore, or the patient may have tried all these and needs counselling about definitive surgery.

As noted above, patients with arthritic ankles often have other joints involved, which may affect the surgical option and likely outcomes. Others have had a severe or repeated injury or infection, which may have affected their soft tissue envelope or left troublesome scars or nerve problems. A history of deep infection will restrict definitive surgical reconstruction possibilities – almost certainly to a fusion, possibly with an Ilizarov or other external frame.

Cigarette smoking increases the risks of ankle non-union by at least three times, and may affect wound healing after any procedure.

Examination

Investigation

The main investigation is a standing AP and lateral radiograph of the ankle. This will allow assessment of remaining joint space, spurs and loose bodies. If there is malalignment, a standing hindfoot alignment view will show at which level – ankle, subtalar or both – the malalignment is occurring.

Where there is loss of bone stock or complex anatomy post trauma or infection a CT can be helpful

MR will show joint surface lesions such as osteochondritis dissecans, and soft tissue abnormalities including infection and sinuses.

If there is osteonecrosis, usually of the talus, MR will show the extent of the abnormality, which will help surgical planning, but an isotope bone scan is required to show how much revascularisation has occurred.

Standard blood tests may be required to rule out inflammatory arthropathy, gout or residual infection.

Treatment planning

After history, physical examination and appropriate investigation, it should be possible to decide whether

If surgery is appropriate:

Non-surgical treatment

Most patients presenting with arthritic ankles can be managed with simple measures:

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. In general, Heidari (2010) found the anterolateral portal slightly more accurate for ankle injection, with a 86.1% success rate compared with 77.5% for the anteromedial portal, although the difference was not statistically significant.

Hyaluronan supplementation injections have been described in other joints. Three small RCTs have been reported in the ankle (Salk 2006, Karatosun 2008, Cohen 2008). Salk and Cohen compared hyaluronate to saline injections in 17 and 28 patients respectively. The main outcome measure was the Ankle Osteoarthritis Scale. In each case there was a significant improvement in AOS in hyaluronate-treated patients, but this also occurred after saline injection and a significant difference between treatment groups occurred only at one time-point in one trial. Karatosun compared hyaluronate injections to exercise therapy in 30 patients. Again, both groups improved on the AOFAS ankle score, and there were no significant differences between the groups. Larger trials are required to assess the real significance of the differences found. At the moment hyaluronate should probably be used only in the context of such trials.

Surgical options

Surgery is an option where non-surgical treatment has failed to control the patient’s symptoms and they are seriously affecting the patient’s activities of daily living, work and sleep.

Arthroscopic debridement

Can be useful where the joint is reasonably well preserved, especially if the main problem is impingement from synovitis or spurs, or loose bodies. Arthroscopic debridement for impingement had a 75% success rate at 5 years in the presence of spurs, but only 50% with loss of joint space (Tol et al 2001). Ogilvie-Harris et al (1995) found limited improvement in about 2/3 of 27 patients.

Distraction arthroplasty

An Ilizarov external fixation frame is applied across the ankle and a distraction force applied. The frame is articulated to allow active joint movement. Useful improvement in pain and movement have been reported (Marijnissen et al 2003). Weightbearing radiographs suggest that joint cartilage thickness is regenerated. This technique requires complex apparatus and specialised staff. Tellisi (2009) reported 23 patients who had distraction with a circular frame that allowed weightbearing and ankle movement. 5mm distraction was applied for 12 weeks. At a mean of 30 months follow-up the mean AOFAS score was 74/100. Pain scores improved in 21/23 patients and there was some improvement in SF-36 scores but this did not reach sttistical significance. Patients with pre-operative equinus gained dorsiflexion, but the average range of movement of the group overall did not change.

Periarticular osteotomies

Distal tibial malalignment may be secondary to injury, intra-or extra-articular or involving the growth plate; or it may be an intrinsic deformity. Realignment is an option where the joint is reasonably well preserved – an arthroscopy may be required to check. Where the joint is severely arthritic an arthrodesis or replacement is more appropriate.

Arthrodesis

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. Arthroscopic fusion has deveoped to the point where it is now the standard techniue for most foot and ankle surgeons.

Arthroscopic ankle fusion is normally performed with the patient supine using anterior portals. The technique of forming the portals is described in the section on arthroscopy.

Open fusion can be done using anterior, posterior and lateral approaches. A short medial arthrotomy is sometimes a useful adjunct to a lateral approach, although an extensile medial approach can be used to access talonavicular, subtalar and ankle joints. The lateral approach exposes the lateral malleolus, which can be excised and morcellised for graft, or removed, decorticated and attached as a large graft at the end. An alternative technique for graft harvest is to use an acetabular reamer to remove the lateral malleolus. The superficial peroneal and sural nerves, and their communicating branches, are at risk.

The anterior approach is the same as for ankle replacement, between tibialis anterior and EHL and exposing back to both malleoli. The deep peroneal/dorsalis pedis bundle is at risk, and the medial branch of the superficial peroneal nerve can cross the incision.

In arthroscopic fusion, synovitis and spurs are cleared to expose the joint line. Curettes and burrs are then used to remove the remaining articular cartilage and freshen the subchondral bone so that multiple bleeding points are seen. It is important to clear all the way to the back, usung the FHL tendon, usually seen through the posterior ankle capsule, as a landmark. It is also important to clear the gutters, the malleoli and the medial and lateral surfaces of the talus and to ensure that no osteophytes on the talus prevent compression of the talus into the mortise.  Once preparation is complete, fixation is usually with two or three cancellous lag screws inserted over guidewires. Intra-operative check Xrays often show a gap between the joint surfaces, but as long as it is is not too big and fixation is secure, the gap will disappear as healing progresses.

Many series of open ankle fusion have used flat cuts with a power saw or osteotome to excise the joint. Others use techniques to increase stability and congruency, such as anatomical resection of the joint surfaces in the manner of arthroscopic fusion, or a chevron cut (Kopp 2004). Preservation of the malleoli increases stability.

However the joint surfaces are prepared, the ankle should be positioned in neutral plamtar/dorsiflexion, 5 deg valgus and 5-10 deg external rotation (Buck 1987). Fixation in most series was with 2-4 cancellous bone screws. The stability of the fusion can be increased with an anterior or lateral plate, blade plate or ring fixator.

The ankle is normally protected with a backslab immediately after surgery and this is converted to a cast when the wounds are satisfactory. Where the construct is stable enough, partial to full weightbearing can begin quite early; we allow patients with arthroscopic fusions to bear weight to comfort at 2 weeks. There are a variety of regimes for reducing splintage, but no clear evidence of what regime is best to optimise fusion rates without spending unnecessary time in cast.

Results

Arthroscopic fusion

Over 15 series of arthroscopic ankle fusions have been reported. The largest series is that of Winson (2005). 118 fusions were reported, of which 105 were followed clinically for a mean of 65m. 109/118 procedures fused at a mean of 12weeks. Most non-unions happened early in the series, and subsequently the authors immobilised all patients for a minimum of 12 weeks. Smoking was twice as common in non-unions. There were three superficial and one deep infection, one malunion and two pulmonary emboli. Winson recommended arthroscopic fusion even if the ankle was in valgus or varus provided the forefoot was plantigrade.

Gougiolias (2007), however, carried out arthroscopic fusions even if there was mortise deformity and the foot was not plantigrade, by excising bone from the mortise arthroscopically to align the ankle. 30/78 patients had a pre-operative coronal deformity of >15deg, but none had more than 3deg post-operatively. Five patients had simultaneous arthroscopic subtalar fusion. There were 5 delayed unions and 2 non-unions; time to union was 2months extra in smokers. There was one PE, one nerve injury and 6 patients had subtalar pain.

Overall about 550 arthroscopic fusions have been reported with a total fusion rate of 93.3%. Several series have commented on the quicker rate of union in arthroscopic procedures although this can be influenced by the intervals at which radiographs are taken, and all series diagnosed union on plain radiography rather than CT. Myerson (1996) noted a mean time of fusion of 8.7 weeks in arthroscopic versus 14.5 weeks in open fusions, while Nielsen (2008) noted that 90% of arthroscopic and 57% of open fusions were united at 12 weeks.

The arthroscopic technique is now the standard method of fusing the ankle unless there is severe deformity, bone loss or revision surgery. However, it requires advanced arthroscopic skills. It is feasible in patients whose soft tissues would not be suitable for open surgery. However, there has never been a RCT comparing open and arthroscopic fusion.

Open fusion

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, and most patients had what would now be considered mal-unions. 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. In rheumatoid disease, Felix et al (1998) reported union in 96% of 26 ankles at 2-8 year follow-up, and no pain. Although many studies are quite old and use techniques that are uncommon now, the risk of non-union is almost certainly higher in open than arthroscopic fusion.

Revision fusion

Cheng (2003) reported 18 revisions, 10 of which were for non-union, 7 for mal-union and one for infection. Screw fixation was used in all but one case and 17/18 fused including the infected case, taking a mean of 4.8months. At a mean follow-up of 40months the mean AOFAS score was 71/100 (range 38-86). Easley (2008) reported 45 patients including 8 infected cases. 11 had screw fixation, 12 had a tibiotalocalcaneal fusion with a nail and 22 with bone loss or infection had a ring fixator. At a mean 50months follow-up, 40/45 were fused, 5 of whom had required revisions. There were 5 amputations and 4 malunions and most complications were in the patients who had the ring fixators.

Total ankle replacement

Replacement of the ankle 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. This has now been updated (Wood 2008) with 80.3% survival at 10 years.

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 and may require revision replacement or fusion. The failure rate for revision arthroplasty is high and most patients will be better revised to a tibiotalocalcaneal fusion.

Fusion versus ankle replacement

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 RCTs comparing 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.

The only comparative study is that of Saltzmann (2009, 2010). This was an FDA approval study in which patients were assigned to STAR ankle replacement or open ankle fusion through a fibular osteotomy with screw fixation, according to the surgeon doing the procedure. There was also an open series of ankle replacements. The main outcome measure was the Buechel-Pappas ankle score. This improved by a mean of 40 pints for the STAR group and 26 points for the fusions, mainly accounted for by significant improvements in most of the functionss cores. However, there was no significant difference in pain relief or patient satisfaction. There were more intra-operative problems, nerve injuries and wound problems in the STAR group, but similar infection rates of 4.4% in the replacements and 7.6% in the fusions (all but one minor). The union rate in the fusions was 64/66 and there appear to have been 7/415 loose replacements at 24 months (this is not easy to work out), with one revision for wear and 4 mobile bearing fractures. At an average follow-up of 4 years the clinical results of TAR were similar to those of fusion (Saltzman 2010). However, the arthroplasty group showed better pain relief and more postoperative complications that required surgery.

A systematic review of the literature by Haddad et al (2007)  found the overall reported results of both procedures to be similar, with about 70% satisfactory results after both procedures. The overall non-union rate for ankle fusion was 10% and the arthroplasty survival rate 77% at 10 years. There was more variation in results for arthroplasty.

Clinical series of ankle replacement

Gougoulias (2009) published a systematic review of 13 series amounting to 1105 ankle replacements, of which the Agility, STAR and Hintegra were commonest. Only 4 studies had more than 10 years’ follow-up. Survivorship rates were variable, satisfaction rates varied from 79-97% but 23-60% of patients still had some pain. The Swedish arthroplasty register figures (Henricson 2007) found a 5-year survival of 78%, but this improved to 86% after the first 3 cases. The Nowegian register (Fevang 2007) reported 5-year survival of 89% and 10-year of 76% in mostly STAR ankles. The Finnish register (Skytta 2010) reported a 95% 5-year survival in a 50% rheumatoid population using mostly AES and STAR ankles.

Wood (2009) reported the only RCT in ankle replacement, comparing 100 STAR ankles with 100 Buechel-Pappas ankles. The survival rates at 6 years were 955 for the STAR and 79% for the BP (the difference was not significant) In both groups survivorship was lower with increasing coronal plane deformity.

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 2008), reported 200 ankles followed for a minimum of 5years and a mean of 7.3 years. The 5-year survival was 93.3% and the 10-year survival 80.3%. 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 40. Complications and the learning curve are detailed. As in the RCT with the BP ankle, survivorship was significantly lower in the presence of coronal plane deformity, and Wood recommends 15deg valgus or varus as the maximum for successful ankle replacement. However, Hobson (2009) reported 123 STAR ankles including 32 with coronal plane deformity of 10-30deg, mostly varus. Survival at 5 years was 86% for the neutral ankles and 75% for the deformed ankles, which was not a significant difference. Nine patients in the deformed group needed additional corrections – 6 calcaneal osteotomies and 3 lateral ligament reconstructions.

None of these studies comment on OA in adjacent joints.

Kinematics and gait

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 2004, Piriou 2008). 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.

Naal (2009) found that 2/3 of 101 patients were active in sports 4 years after ankle replacements. The commonest sports were swimming, cycling, fitness training and downhill skiing and the patients participated for an average of 4.4hr/week. 35% had radiolucencies around the tibial implant but this did not affect the likelihood of sports activity.

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. Ankle replacement probably has a small functional advantage but failure rates vary widely and there is a much higher rate of secondary surgery.

It is possible that 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.

References