♦ Hind foot arthritis is usually treated orthotically but may need surgical fusion
♦ Severe ankle arthritis requiring surgical intervention is uncommon
♦ Arthroscopic debridement of early ankle arthritis is effective
♦ End stage ankle arthritis can be treated by fusion or arthroplasty
♦ Ankle replacement has a higher failure rate than hip or knee arthroplasty
♦ Correct alignment of the hind foot and forefoot are essential for good results.
The ankle, hindfoot, and midfoot function as a mobile unit, which provides shock absorption in the early stance phase of gait, and changes to a rigid unit in the late stance phase allowing transmission of power necessary for push off.
Within this complex, the ankle moves principally in dorsiflexion and plantarflexion, the subtalar joint in inversion/eversion, and the midfoot in rotation.
In early stance phase, the plantar fascia and interosseous ligaments are relaxed, the arch is low, and the joints of the hind- and midfoot are mobile, allowing shock absorption by the foot without damaging impacts being transmitted that could cause injury to the foot, the leg, and the trunk.
In later stance phase, the plantar fascia tightens and the arch is restored (by the windlass mechanism, Figure 9.1.1), and all the interosseous ligaments tighten, making the foot rigid. This allows power to be transmitted through the foot, and the weight of the body to be transferred forward without the foot collapsing.
This rigidity is critical to function of the hind- and mid foot, and the patient’s ability to stand and walk, so the mainstay of treating disorders of these regions is directed to relieving pain and stabilizing the foot—usually by orthotics or fusion—whereas in the ankle movement may be more important so joint replacement is sometimes performed.
The outcomes of all midfoot, hindfoot, and ankle procedures are often limited, achieving a ‘second best’ result of a stable pain-free foot, with the ability to walk and function domestically, but rarely restoring the levels of function required for running, and athletic or high demands.
The problems of the hind- and midfoot and the ankle will be considered separately for clarity, although deformity and pain often occur together in all.
Hindfoot and midfoot arthritis
The hindfoot comprises the talus, calcaneus, and navicular bones, as well as their articulations, which are responsible for most of the inversion/eversion of the foot (subtalar joint) and rotation (talonavicular and calcaneocuboid joints).
In the midfoot the cuboid and cuneiform bones articulate to increase rotation of the foot, but the movements in the midfoot are less than those of the hindfoot.
Dorsiflexion of the foot complex is really limited to the ankle and metatarsophalangeal level.
Each of the joints of the hindfoot and midfoot allow some plantarflexion from their neutral position—contributing about 50% of the overall dorsiflexion/plantarflexion movement of the foot/ankle complex—but none of these joints allow any significant dorsiflexion.
The hindfoot and midfoot rely on a complex arrangement of ligaments between joints for stability, and on tendons which insert into or cross the region for movement.
The blood and nerve supplies of the region are rich, with abundant vessels and nerves which have to be respected by surgical approaches.
In contrast, the soft tissue envelope is thin, prone to injury, and gives little cover to underlying tissues or implanted metalwork.
Swelling of the soft tissues after surgery, especially with dependency during immobilization, makes the area prone to soft tissue break down. Furthermore, the bones of the hindfoot and midfoot generally (with the exception of the calcaneus) have few, if any, muscle attachments and therefore have relatively poor blood supplies. Hence the incidence of delayed or non-union after fusion is higher than in other areas of the body.
When arthritis and collapse occur, the pathological anatomy is changed, with complex deformities produced by unbalanced forces acting on bones and joints producing simultaneous subluxation, dislocation, and bone and joint deformity.
Correction of the deformities is difficult, and although it is tempting to plan simple angular corrections, careful consideration based on findings on clinical examination, biplanar radiographs, and, if necessary, scans often shows rotational and multilevel deformity. If function is to be restored, the deformities have to be corrected in all planes.
Thus, surgery in this area is fraught with potential problems due to geometric complexity and problems with healing. Surgeons undertaking this surgery need to understand these factors and also be able to manage the postoperative splintage, rehabilitation, and orthotic management of the patients.
For all these reasons, and at a time when experience of this type of surgery is waning—because of the virtual disappearance of polio and spina bifida within the United Kingdom— surgery to the mid- and hindfoot is now increasingly limited to specialist tertiary referral centres.
Some degree of arthritis in the hind-/midfoot is extremely common with advancing age. Most commonly there is gradual collapse of the arch, leading to increasing stiffness and aching with pain on exertion, but rest pain is rare.
Although such arthritis is common, it is mostly self-treated by supportive footwear and restriction of activity, or in the community by orthotics provided by podiatrists.
Only the severe end of the spectrum, with increasing pain during and after exercise, is usually referred to an orthopaedic department.
There is a strong association between deformity and arthritis. Deformity causes abnormal and unequal loading, leading to arthritic wear and tear, and conversely arthritis often causes collapse of individual bones and abnormal alignment of joints affecting the stability of the longitudinal and transverse arches.
The causes fall into five groups (Box 9.1.1).
A history of trauma is common in patients presenting to tertiary referral centres.
The hindfoot and midfoot are constantly exposed to low levels of trauma, being vulnerable with every trip and slip, and cumulative effects may account for the wear and tear changes commonly found with advancing age.
More major trauma has an association with arthritis, especially when joint integrity is affected.
Injuries to the talus are associated with avascular necrosis due to its poor blood supply, especially after fractures of the neck of the talus, and dislocations. Peritalar arthritis affecting ankle, subtalar and/or talonavicular arthritis then often occur.
Complex calcaneal fractures also often lead to subtalar arthritis. However, even badly destroyed joints sometimes lead to more stiffness than pain, and this may give relatively little restriction.
The risk of developing painful arthritis is linked to the severity of the original injury. The method of early treatment is less well associated with outcome. So open treatment of calcaneal fractures may not decrease the risk of later pain, but anatomical reduction makes any later reconstructive surgery easier and more effective.
In the midfoot, arthritis may follow fracture dislocations including Lisfranc injuries.
Good reduction of the fractures and dislocations is important, because with a well-shaped foot, orthotic management can often control symptoms without resorting to reconstructive surgery.
Systemic arthropathy (Figure 9.1.2A)
All forms of arthritis present in the hind- and midfoot.
Seronegative arthropathies present with heel pain due to enthesopathy.
Generalized osteoarthrithis presents with painful arch collapse, or localized arthritis - usually of the subtalar or talonavicular joints.
Rheumatoid arthritis commonly affects the region and may take one of two general forms. Proliferative synovitis can cause laxity, dislocation of the joints, and collapse of the arch, leading to planovalgus collapse with secondary arthritic changes.
In another group of patients—often with severely painful but less swollen joints—spontaneous ankylosis and eventually arthrodesis can occur. This is a common pattern in patients with rapidly progressive disease and in juvenile chronic arthritis.
Deformity may occur due to weakness or imbalance. Two common patterns of deformity occur:
♦ Planovalgus deformity due to weakness of the tibialis posterior tendon (described in Chapter 9.5)
♦ Equinocavovarus occurs secondary to muscle imbalance between weak dorsiflexors and evertors and relatively stronger invertors and plantarflexors and is common in neurological disease and after other foot deformities, including congenital clubfoot.
Secondary to restricted movement
Congenital coalitions of the hind- and midfoot lead to pain and degeneration. The commonest coalitions—calcaneo navicular, and subtalar—lead to pain and degeneration in the talonavicular and subtalar joints respectively. These often present later as pain in adult life, and by this time degeneration is often established and take down of the joints is rarely indicated.
Stiffness, including surgically induced stiffness, may also lead to secondary degeneration.
Neuropathic (Figure 9.1.2B)
Charcot’s joints are joints with severe degeneration—often with collapse and deformity—and occur in the presence of any sensory neuropathy. They are commonest in diabetes, usually in severe diabetes, and as such are dealt with in Chapter 9.3.
The careful clinician will always test for sensory loss when presented with a case of hind- and midfoot degeneration, using a tuning fork to test for vibration, and a Semmes–Weinstein filament to touch light sensation. A significant number of patients with early diabetes and other causes, including reversible neuropathies, will be diagnosed by these simple means—supplemented by blood screening for neuropathy when abnormalities are found.
Arthritis of the hind- and midfoot leads to stiffness, pain, or, more commonly, a combination of both.
Stiffness is not usually a great problem except when single joints are affected in younger people who still participate in sporting activities, or in patients where spontaneous ankylosis of the whole complex occurs (usually in rheumatoid arthritis). In these situations, stiffness may impose extra demands on other joints in the foot, ankle, or elsewhere.
Pain, whether in single or multiple joints, tends to be present on standing and walking, and absent when sitting, lying, or asleep.
Pain which wakens the patient from sleep can occur as an end stage of joint destruction, but should alert the clinician to the risks of infection or tumour.
Examination (Figure 9.1.3)
Examination of pulses, perfusion, and sensation are essential parts of examination of any foot condition.
Clinical examination also involves observing the foot standing (Figure 9.1.3A,B) and on tip-toe standing (Figure 9.1.3C), measuring dorsiflexion/plantarflexion (Figure 9.1.3D,E) of the foot (including ankle movement, Figure 9.1.3F), inversion and eversion (Figure 9.1.3G,H) and rotation (9.1.3I,J), as well as simple examination of power of the muscle groups (Figures 9.1.3K–N).
Simple investigation is usually more helpful than complex scanning, which is reserved for a minority of cases.
Blood tests may be indicated to investigate arthritis and accompanying neuropathy.
Plain x-rays taken non-weight bearing will show structure, but weight-bearing films will show loss of joint space and deformity which may occur only on standing (Figure 9.1.3A). Oblique views may be useful to show coalition and Cobey (skiers) views will show the relative contributions of the ankle and the subtalar joints to deformity of the hindfoot in standing (Figure 9.1.3B).
Magnetic resonance imaging (MRI) scans can be useful to isolate a single inflamed joint, and computed tomography (CT) scans to demonstrate structure in complex situations, but when surgical intervention is considered, selective diagnostic injection of affected joints is the most useful supplementary investigation. The reason for this is that the joints are difficult or impossible to differentiate clinically—even by the most experienced clinician. The worst affected joint on x-ray is not always the most painful joint.
Long-acting local anaesthesia is injected under image intensifier control along with x-ray contrast medium (Figure 9.1.4) to confirm that the correct joint has been injected, and that there are no connections into other joints (which occur commonly). The patient is instructed to undertake activity which would normally be painful and to complete a pain diary over the subsequent 12h to demonstrate whether the pain has been temporarily relieved. This can usually be performed by radiologists as an outpatient procedure, but when the joint is grossly destroyed this may require general anaesthesia. It may, on occasion, entail several injections to correctly identify which joint or combination of joints is symptomatic. This may seem tedious, but is preferable to the pain, inconvenience, frustration, and disability which arise if the wrong joints are fused.
Blind or x-ray guided injections of depot steroids are more effective, but again are more usually combined with orthotic treatment, otherwise the pain inevitably recurs.
Orthotic management (Box 9.1.2)
Orthoses work by restoring anatomical alignment—reducing overload of affected joints by shock absorption and immobilization.
In general, orthoses will only be effective if deformity is corrected and deforming forces neutralized. Appropriate orthoses are described in Chapter 9.4 and may range from soft accommodative insoles, through to structural solutions such as ankle–foot orthoses (AFOs) or calipers.
Whatever type of orthotic appliance is used, it is important to remember to include adequate shock absorption in the system and consider footwear modification.
Surgical treatment (Box 9.1.3)
Surgical treatment of hind- and midfoot arthritis is almost entirely limited to arthrodesis to relieve pain and correct deformity.
Arthroscopy of the subtalar joint is now performed in specialist centre but open surgery is still the norm.
It is important that deformity is reduced, and that muscle power is balanced to prevent recurrence.
Arthrodesis can be difficult to achieve with the poor blood supply to the bones and fragile soft tissue envelope. The patient often has problems surviving the postoperative period, especially if they cannot bear weight through the leg and have generalized arthritis.
The principles of achieving successful arthrodesis are the same for all joints:
♦ Clearance of articular cartilage from the joint surface with minimal disruption to vascular supply
♦ Fixation of the arthrodesis (almost always by internal fixation)
♦ Protection of the limb from movement and/or weight bearing.
A bewildering range of screws of different metals and design, static and memory staples, and low profile and reconstruction plates are available to assist this surgery, but the commonest causes of failure remain poor tissue healing due to smoking or infection, inadequate surface preparation, or poor correction of deformity rather than inadequate fixation.
Although any joint in the hind- or midfoot may be fused in isolation, the commonest fusions performed are of the talonavicular joint or subtalar joint in isolation and triple fusion (of the talonavicular, subtalar, and calcaneocuboid joints).Technique is briefly described because standard textbooks and operative guides tend to describe outmoded techniques.
Talonavicular joint fusion (Figure 9.1.5A)
This is most commonly performed for isolated single joint arthritis to relieve pain. Although a limited degree of rotational correction can be achieved when performed as part of a flat foot correction, it does not generally correct deformity well.
Preliminary examination and investigation is directed towards identifying predisposing factors, such as coalitions which may continue to generate pain if not addressed directly or by more extensive fusion.
In almost every case a preoperative, diagnostic injection arthrogram with local anaesthetic should be performed prior to surgery.
The joint is approached through a medial or dorsal approach. The articular cartilage is then removed from both joint surfaces.
The medial approach has the advantage of preserving cutaneous nerves, but in stiff joints it can be difficult to fully clear the lateral side of the joint. If it is not well cleared the remaining cartilage holds the joint open, and the risk of non-union is increased.
The dorsal approach gives easier clearance of the joint surfaces, but at the expense of producing numbness on the dorsum of the foot in about 50% of cases, after division of the medial branch of the superficial peroneal nerve.
Whichever approach is used, the arthrodesis should be rigidly fixed, usually by compression screws or staples.
The foot is elevated and protected in a cast or splint until the wound is healed, and then mobilization allowed—retaining the splint for at least 6 more weeks. Usually the patient will remain non-weight bearing during this time, unless a decision is made that because of general disease and/or excellent fixation this can be over-ridden.
After 8 weeks, radiographs are taken, and if union is seen to be proceeding, gradual weight bearing is allowed, usually in a lighter brace, followed by supportive insoles which are often retained in the long term.
The time to recovery is often prolonged, and we advise patients that it will take 6 months to return to the preoperative level of pain and function, and much longer to achieve their final result.
Although some papers describe a high rate of non-union in isolated talonavicular fusion, this need not be the case with thorough joint clearance and rigid fixation, and in non-smokers rates of union around 95% should be expected.
The theoretical advantages of isolated fusion are less than might be expected, and mechanical studies of isolated talonavicular fusion show that it creates considerable stiffness throughout the hindfoot complex.
Subtalar arthrodesis (Figure 9.1.5B)
Subtalar arthrodesis may be performed for pain relief, for correction of deformity, for stabilization, or a combination of these.
The principles of foot correction (discussed earlier) must be adhered to strictly to ensure good results.
The standard approach to the subtalar joints (posterior, middle, and anterior facets) is via a lateral approach, starting at the tip of the fibula and directed towards the base of the fourth toe. Older transverse incisions such as the Ollier incision unnecessarily destroy nerves and vessels and are of historical interest only. Medial approaches are useful for correction of severe valgus.
The lateral incision exposes the sinus tarsi, which is cleared to show the three facets of the joint. These are cleared using osteotomes or burrs, using upward-cutting spinal bone cutters to clear the medial edges, to ensure safety of the posterior tibial nerve.
Once the surfaces are cleared and corrective cuts made, the joint is accurately reduced to place the hindfoot beneath the leg, checking that the midfoot and forefoot are well aligned. Bone graft may be inserted if large defects are present, but are not usually needed. Internal fixation is performed with compression screws, which may be inserted from above or below. Screws passed from below have the advantage of greater grip of the thread in the talus, and ease of passage, but may suffer sinkage into the calcaneum on compression, or cause screw prominence and damage to the heel pad.
Screws from above may give less reliable compression, and have a small increased risk of nerve damage, but are convenient when other surgery is performed at the same time as other procedures (such as ankle replacement). They minimize the risk of heel pad damage, and are easy to remove when needed if subsequent ankle arthroplasty is performed.
There are many modifications to technique and in some centres the procedure is performed arthroscopically.
Postoperative management mirrors that of talonavicular fusion, but the threshold for allowing weight bearing may be lower due to the essentially horizontal configuration of the joint.
Triple fusion (Figure 9.1.5C)
Triple fusion is performed to treat painful arthritis and correct deformity around the hind- and midfoot.
When correcting deformity, preoperative clinical assessment of the foot is critical to ensure that the necessary degree of correction is achieved, and also to ensure that any osteotomies, tendon transfers, etc. are performed at the same time. Triple fusion is often combined with other procedures such as heel osteotomy, dorsiflexion osteotomy of the first ray, and tendon lengthening, augmentation, or transfer.
Triple fusion starts with the technique described earlier for subtalar fusion. The incision is extended distally to allow the extensor digitorum brevis muscle to be split, exposing the calcaneocuboid joint whose joint surfaces are prepared.
Talonavicular preparation is performed as for isolated talonavicular fusion, and then after corrective wedges etc. have been cut if needed, the joints are internally fixed—fixing the subtalar joint first, then the talonavicular and calcaneocuboid joints—carefully ensuring the exact position of the midfoot and forefoot, because the foot after triple fusion will be stiff to rotation and very intolerant of any overload, especially lateral overload of the midfoot.
Union occurs in more than 90% of cases. Non-union is 16 times more common in smokers. Recovery is often very prolonged, especially with regards to swelling and start-up pain.
The foot after triple fusion is stiff and often needs a total contact insole within the shoe. Walking should be possible without a limp, but the patient will often limp when running, and be unable to participate in active sports.
Ankle arthritis (Box 9.1.4)
Incidence and aetiology
Arthritis affecting the ankle is surprisingly uncommon when one considers the large number of injuries which are sustained at the ankle.
The number of operations performed for ankle arthritis is much less than the number performed for hip and knee arthritis. Although this may reflect the relatively successful outcomes of the latter procedures compared with procedures for ankle arthritis, the size of the discrepancy is such that it seems the ankle is relatively protected from arthritis and its effects.
In many cases of ankle arthritis a predisposing cause can be identified. The causes fall mainly into three groups:
2) Associated with systemic arthropathy
3) As a consequence of bleeding and bleeding diatheses.
Many patients give a history of previous fracture, often many years previously. There is an association between severe fractures, incompletely reduced fractures, fracture dislocations, malunited fractures, and arthritis.
Minor undisplaced, or well-reduced fractures do not appear to convey significant risk of later deterioration, but fractures (including tibial shaft fractures) which lead to angular deformity at the ankle may.
From a medicolegal standpoint, it appears that the fractures which have a significant chance of causing arthritis in the medium and long term will start to cause symptoms early, and certainly within 2 years of injury. It is uncommon for there to be a long completely symptom-free latent period before the onset of arthritis.
Less certain is the association between soft tissue injury and arthritis. Single soft tissue injuries rarely lead to ongoing problems, but recurrent instability of the ankle may do. Patients presenting with arthritic ankles frequently give a history of recurrent giving way and instability, and arthroscopic studies of ankles with chronic instability have shown universal chondral or osteochondral damage.
Secondary to systemic arthropathy
Of the inflammatory causes of ankle arthritis, rheumatoid arthritis is by far the commonest, although the ankle is also frequently affected in juvenile chronic arthritis (often in association with the other peritalar joints).
About half the patients admitted for inpatient treatment of rheumatoid arthritis have been noted to have significant affectation of the ankles. The ankle is also disproportionately involved in some other inflammatory arthritides.
Bleeding and bleeding disorders
Trauma to the ankle is a common occurrence for those with bleeding disorders, as in the general population. The ensuing haemorrhage causes arthritis. The number of patients affected is small, but the difficulties presented by their management and the requirement for resources can be great.
Damage due to repeated haemorrhage may also occur secondary to pigmented villonodular synovitis.
For most purposes, the ankle may be considered as a simple, stable hinge joint, with stability provided by its bony shape and ligamentous restraints allowing controlled dorsiflexion and plantarflexion of the foot.
The tibial surface bears most of the load transmitted from the talus, and the curved surfaces of these two bones allows restricted dorsiflexion and plantarflexion to occur within the restraints of ligaments and capsule, with inherent lateral stability provided by the medial and lateral malleoli as well as the ligaments.
A deeper understanding of topographical and functional anatomy is necessary to understand pathological processes about the ankle, to plan surgical interventions, and to design prostheses for ankle replacement.
The ankle joint is in fact a composite joint, comprising the tibiotalar mortise joint and tibiofibular syndesmosis.
The fibula lies posteriorly as well as laterally. The fibula displaces and rotates during ankle movement. It also carries between 6–16% of the axial load during stance.
In the sagittal plane the talus is slightly saddle-shaped with a depressed centre and lateral condylar projections. This matches reciprocal shaping of the tibia, and thereby imparts lateral stability to the joint, which increases on weight bearing, and is additional to the restraint of the malleoli.
Both talus and tibia have curved surfaces when viewed from the side, but the radius of curvature of the talus is shorter than that of the tibial surface, so they are incongruent (Figure 9.1.6). The movement of this complex system is one of rotation about a moving instant centre aligned obliquely across the joint.
Anatomical changes in the arthritic ankle
During the development of ankle arthritis, the tibia usually first develops an anterior osteophyte. The changes have been described by Scranton and Mc Dermott as four stages of osteophyte formation:
♦ Stage 1: osteophyte on tibia only, less than 3mm
♦ Stage 2: osteophyte on tibia only, greater than 3mm
♦ Stage 3: tibial osteophyte greater than 3mm ± fragmentation, talar response
♦ Stage 4: tibia osteophyte greater than 3mm, talar osteophyte, degenerative changes.
Early arthritic changes present with symptoms and signs of inflammatory or mechanical arthritis, or with a combination of both.
Inflammatory changes cause swelling around the ankle, and stiffness after immobility. The ankle is painful to all movements, and the joint line is tender.
Mechanical symptoms and signs are more common. Early mechanical symptoms are typified by the symptoms of ‘footballer’s ankle’.
As osteophytes develop anteriorly, impingement occurs in dorsilexion (late stance phase). This progresses to pain during and after exercise, worse in dorsiflexion, such as ascending slopes and stairs. Patients may report relief of pain when wearing high heels. Later, posterior pain may develop due to ‘hinge-opening’.
Later degeneration of the articular surface occurs. The gross changes observed arthroscopically usually affect the talus first. The region of the talus in contact with the osteophyte is often disproportionately affected, with longitudinal striations visible on the anterior surface of the talus.
The anterior joint line should be palpated. Osteophytes are rarely palpable, but are often tender. Both feet should be examined and the range of dorsiflexion compared. Any restriction of dorsiflexion is significant. Osteophytes are always visible on radiographs, but oblique views may be needed to detect anteromedial or anterolateral osteophytes.
In moderate arthritis there will be pain on palpation of the joint line, and on joint movement, as well as swelling. The range of movement is restricted, often dramatically, with dorsiflexion lost first.
Deformity is not a constant feature in ankle arthritis, but may occur if degeneration occurs unequally across the joint. Once deformity begins, it increases abnormal loading and both the arthritis and the deformity often progress.
Oral non-steroidal anti-inflammatory drugs may be helpful in early arthritis. When symptoms occur during and after sport, they are most effective taken just prior to activity.
Injection of the joint may be useful for occasional overuse, for an exacerbation in a generalized arthropathy, for an isolated acute inflammatory episode, but has no place in the long-term management.
In early arthritis, silicone heel inserts can impart relief by acting as shock absorbers. They also act to raise the heel slightly, reducing anterior impingement.
More often, an AFO is required. The orthosis should restore anatomical alignment, hold the joint rigidly, and provide shock absorption. Some mechanism should be incorporated to allow walk-through gait (for example, by adding a rocker to the shoe).
A well-tailored rigid AFO with a shock absorbing heel will be effective for many cases, but when major deformity needs to be corrected a caliper with strap may be more effective.
Surgical treatments (Box 9.1.5)
Takakura from Japan performed tibial osteotomy on 18 ankles (in 18 patients) with intermediate disease and tibial deformity and found improvements in pain, walking, and ability to perform activities of daily living over an average of nearly 7 years, although range of movement was not improved.
Osteotomy is reserved for cases occurring in young patients with deformity and preserved joints.
Around the same time in Europe, Van Valburg described applying long-term joint distraction using an Ilizarov apparatus for 18–34 weeks. All showed an improvement in pain and range of movement with five gaining complete relief.
The length of treatment limits its use to cases in young patients.
Arthroscopy of the ankle can help in arthritis by synovectomy, anterior cheilectomy, surgery to chondral and osteochondral lesions, or by more extensive surgery such as distraction/debridement or arthroscopic arthrodesis (which is described later in the arthrodesis section).
Anterior spurs or osteophytes presenting as ‘footballer’s ankle’ are dealt with as effectively arthroscopically as by open means, but with more rapid recovery—a return to preoperative activity is expected within 6–8 weeks.
Larger and more advanced (grade III/IV) osteophytes can also be removed arthroscopically, in isolation, or with general debridement of joint surfaces, although on occasions the increased range of movement is accompanied by increased pain.
Arthroscopic debridement can be combined with rigid intraoperative distraction (Figure 9.1.7). The method does not work for patients with significant deformity or instability, but may avoid or delay arthrodesis in about half the cases, and can be useful for young patients wanting to avoid fusion.
Arthrodesis of the ankle has for many years been the mainstay of surgical treatment for ankle arthritis, but it remains difficult surgery. Sir John Charnley highlighted this and wrote that ‘in the ankle it would appear that this joint does not possess the same natural potential for bony union as exists in the soft cancellous bone of the knee’ and stated that the operation had ‘a narrow latitude for technical error’.
Almost every approach to the ankle has been described for arthrodesis. The methods of obtaining fusion are:
1) Open arthrodesis using internal fixation
2) Open arthrodesis using external fixation
3) Arthroscopic arthrodesis using internal fixation.
Compression arthrodesis is now favoured, using internal fixation when there is no infection and external fixation in the presence of infection.
Whichever method is used to obtain arthrodesis, the position of the foot after arthrodesis is important. The ankle should be held in neutral position with regard to both varus/valgus and plantar/dorsiflexion as well as in slight external rotation. The talus should be positioned directly beneath the tibia.
Gait analysis has shown that even small amounts of calcaneous (5 degrees) give a stiff gait with no push off (due to absence of third rocker) and equinus position imposes a vaulting gait.
Excessive varus is poorly tolerated by the subtalar joint and the foot, with painful callous forming on the outer side of the foot, and pain in the mid and forefoot occurring with only minor deformities. Excessive valgus may lead to painful fibula impingement or peroneal tendinitis, and both may lead to secondary pain in the knee.
If the foot is fused in neutral then the gross appearance of the gait is normal, but gait analysis shows that the walking speed is decreased, as are step length and single stance duration.
Preoperative conditions often dictate the risk of failure, with large deformities, previous ulceration or infection, and poor bone stock being bad prognostic factors. Rates of failure up to 20% occur in mixed series with large numbers of rheumatoid and elderly patients, and rates of 5% or less achieved in selected series with predominantly fit osteoarthritic patients. Cobb has shown that the rate of non-union is substantially increased by smoking.
Open arthrodesis using internal fixation
Medial, lateral, posterior, anteromedial, anterolateral, anterior, and combination approaches are all used and in specific instances each will be indicated. The posterior approach may be appropriate when friable skin or skin graft lies anteriorly, medial approaches may be used to excise bone and correct valgus deformity, and conversely lateral approaches allow easy correction of varus.
The lateral approach (excising the fibula) and the anterior approach are currently the most popular open approaches. Whichever approach is adopted, it must allow full exposure of tibial and talar plafonds, and lateral aspects of the joint, with small accessory portals made if necessary to allow adequate internal fixation and correction of deformity. Lateral impingement of bone or peroneal tendons can be problematic after some approaches, but is avoided by partial fibula excision.
Postoperative regimens vary, but require 8–12 weeks minimum of cast immobilization to obtain union, with a similar period of protection in an orthosis or splint whilst consolidation occurs. A rocker bottom to the shoe is then frequently helpful.
Patients should be warned that they will get bony pain for up to 4 months after coming out of plaster, and this may continue to improve for a long time after surgery as full bony remodelling occurs.
Arthrodesis using external fixation
Charnley popularized the use of external fixation for ankle arthrodesis. His method was originally mainly used for patients with polio and other neurological conditions and used a transverse incision (dividing extensor tendons as well as vessels and nerves), with through and through compression pins anteriorly through the tibia and calcaneum. It is no longer performed this way. Most surgeons now use triangulated frames or ring external fixators with fine wires reserving external fixation for the treatment of infected non-union, and for more complicated procedures performed with bone transport, skin transfer, etc.
Arthroscopic arthrodesis (Figure 9.1.8)
In cases of painful articular arthritis with minimal (less than 10 degrees) varus or valgus tilt, arthroscopic arthrodesis may be performed. The degree of deformity which can be corrected increases with experience.
It has advantages in terms of postoperative pain (allowing early mobilization and short inpatient stay), and in speed and rate of union. It is particularly appropriate in patients with poor vascular supply, with bleeding disorders, or with skin grafts around the ankle.
A distractor is applied to the ankle, and after synovial clearance, anterior cheilectomy is performed to allow good visibility. The articular surfaces are then cleared down to cancellous bone using power burrs, and the lateral and medial gutters are similarly cleared of articular cartilage. Two cannulated screws are then passed (from the medial tibia down into the talus) under x-ray control.
A plaster is applied, and early weight bearing can be allowed within the bounds of pain.
The immediate postoperative radiographs almost always appear to have a substantial gap, but within a few weeks this fills in. Union may be observed as early as 4 weeks after surgery and is more rapid than after open surgery. External immobilization is usually maintained for 8 weeks, and then mobilization is encouraged from an appropriate brace. Although the initial and postoperative pain levels are much lower than after open surgery, it still often takes many months before all bone pain around the ankle subsides.
Ankle arthroplasty (Figure 9.1.9)
Historically, ankle arthroplasty has been unsuccessful, with high rates of early and late failure, often of 10% or more per annum.
Clinical development has been slowed because of these failures, and because ankle arthrodesis is an effective treatment to relieve pain in many cases. However, arthrodesis has several drawbacks. The restriction of movement always imparts some disability and in patients with bilateral disease, and those with generalized disease, this may be severe. Both bilateral disease and multiple lower limb joint disease are common in patients with rheumatoid arthritis, and development of ankle prostheses has continued mainly because of the requirements of these patients.
Over more than 25 years a variety of designs have been tried, with hinge and non-constrained designs all described, but with high rates of failure.
The main causes of failure were sepsis and aseptic loosening. Constrained implants failed at a rate of around 10% per annum, with semiconstrained failing generally above 5% per annum.
The most popular designs of ankle replacements in Europe have a planar tibial surface, a curved talar surface, and a semiconstrained meniscal component. Early results suggest pain relief is good, functional restoration is reasonable, and the revision rate is around 1.5% per annum (although the confidence intervals are large due to small numbers).
There is a role for using a semiconstrained meniscal ankle replacement in bilateral disease, in rheumatoid disease, and in other circumstances where other joints are affected (Box 9.1.6).
Hindfoot and midfoot arthritis cause pain and deformity or instability. Most cases can be helped by orthotic management. When orthotic management is inadequate, surgical treatment usually comprises of fusion in an anatomical position.
Ankle arthritis is rarer than arthritis of the hip or knee. The mainstay of surgical treatment is arthrodesis, which gives good results when union can be obtained in good position, but has a failure rate of 3–10 %. After arthrodesis, degeneration of surrounding joints may be accelerated.
As an alternative to arthrodesis, and for less severe cases, arthroscopic surgery may provide relief, and osteotomy may be considered to correct varus deformity.
Ankle arthroplasty has been unsuccessful in the past, but modern meniscal designs show better results, and may offer an alternative to arthrodesis in some circumstances such as bilateral disease, and multiple joint involvement.
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