Total Ankle Arthroplasty

Original Editor - Carlos De Coster

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What is an Ankle Arthroplasty?

Ankle arthroplasty is when the ankle joint (Talocrural Joint) is replace with prosthetic components comprised of polyethylene and metal and is preferred to ankle arthrodesis (fusion) as range of movement and function an not compromised. Main objectives of the arthroplasty are to

1. Replicate ROM of the talocrural joint
2. Function well under weight bearing
3. Be wear resistent 
4. Maintain alignment and stability 

History of Total Ankle Arthroplasty 

Ankle replacement surgery has been available for over two decades however it is a far less common procedure than hip or knee arthroplasty owing to the less frequent incidence of osteoarthritis ankle pathology. The majority of ankle osteoarthritis is secondary to trauma.

Until relatively recently, ankle joint arthrodesis (fusion) was the gold standard of treatment, but this was not without its complications, e.g. non-union, osteoarthritis in the other mid/hind foot joints and stiffness and loss of proprioception

Total ankle replacement was developed in the 1970's but initially was plagued with high long term failure rates. The older prosthesis loosened or malfunctioned and frequently needed to be removed.  In the late 70's Dr. Frank G. Alvine an orthopedic surgeon from Sioux Falls, SD developed the Agility Ankle which was the first FDA approved total ankle implant in use in the United States. Since its introduction the Agility Ankle System has gone through several modifications. Currently the Agility Ankle System is the most widely used ankle prosthesis. With more than 20 years of experience it has the longest followup of any fixed bearing device.

On May 29, 2009 the medical news today announced the FDA approved the first mobile bearing device called the Scandinavian Total Ankle Replacement System (STAR). As a condition of FDA approval the company (Small Bone Innovations Inc.) must evaluate the safety and effectiveness of the device during the next eight years.

In a systematic review of the literature published in the Journal of Bone and Joint Surgery in 2007, the intermediate outcome of total ankle arthroplasty appears to be similiar to that of ankle arthrodesis however data was sparse.  In a study comparing reoperation rates following ankle arthrodesis and total ankle arthroplasty SooHoo, Zingmond and Ko confirmed that ankle replacement is associated with a higher risk of complications as compared with ankle fusion, but also has potential advantages in terms of a decreased risk of the patient requiring subtalar joint fusion.  In a seven to sixteen year follow up on the Agility Total Ankle Arthroplasty, Knecht, Estin, Callagham et al concluded that the relatively low rates of radiographic hindfoot arthritis and revision procedures at an average of nine years after the arthroplasty are encouraging.

Although interest in total ankle replacements is increasing, midterm clinical results to date are few and often have not been validated by independent pratitioners. In addition no level I or II studies have been published.

Poor patient satisfaction, high rates of revision due to loosening, and high wound complications rates were all very problematic when total ankle arthroplasty (TAA) surgeries were first introduced in the 1970’s. In 1990, noncemented prostheses were shown to allow for bony ingrowth and less bone removal as compared to cemented. Beyond the transition to cementless, further advances in technology over the years has led to new surgical arthroplasty techniques, primarily moving from a two-component design to a 3-component model.

An observational study analyzed advantages of arthroplasty over arthrodesis stating individuals with monoarticular or polyarticular disease who undergo arthroplasty have less gait abnormalities and fewer adverse effects to other joints in the lower extremity. A systematic review provided that in 852 individuals undergoing TAA's, there was a 78% implant survival 5 years post-op and 77% at 10 years post-op and overall only had a 7% revision rate. This provides evidence that the procedure yields satisfactory results and should be considered for potential candidates that are appropriate for surgical corrections.

The Arthroplasty

Indication for Procedure

There is no well-defined indication for a Total Ankle Arthroplasty. Surgery is considered only when conservative treatment has been attempted with no improvement. The operation is mainly being executed in patients who suffer from different types of arthrides. This cause advanced arthritic changes of disabling pain and loss of ankle motion. The ankle is most frequently affected by post-traumatic arthritis. Total ankle joint replacement is also indicated following unsuccessful ankle arthrodesis  the ‘ideal’ patient for ankle joint replacement is an elderly person with the low physical demands who has good bone stock, normal vascular status, no immune-suppression, and excellent hind foot-ankle alignment. Generally here are common indications for arthroplasty:

1. Primary or post-traumatic osteoarthritis
2. Severe rheumatoid arthritis
3. Rejected arthrodesis

Indications: According to Saltzman, there are no exact indications for receiving a total ankle arthroplasty. The “ideal” patient who would typically undergo this intervention is one who is elderly with a healthy immunity, normal vascular status, good bone density, and a proper hindfoot-ankle alignment who has not had success with conservative treatment measures. Individuals with debilitating ankle arthritis, unresponsive to nonoperative approaches, or have failures with the outcome of their ankle arthroplasty are typically treated with an arthrodesis procedure to fuse the joint.

Contraindications: Arthroplasty is contraindicated for those with neuroarthropathic degenerative joint disease, infection, avascular necrosis of the talus, osteochondritis dessicans, malalignment of the hindfoot-ankle, severe benign joint hypermobility syndromes or soft tissue problems, or decreased sensation or motion in the lower extremities. In individuals with rheumatoid arthritis (RA), inflammatory processes may occur before signs of swelling, tissue reaction, and joint destruction are seen. In the first and second year of this disease process, structural damage (ie. joint erosion) can be seen with X-ray imaging. Diabetic patients may develop gouty arthritis in their ankle joint. This is caused by uric acid changing into urate crystals, which is deposited into the joint.

Thus, RA and diabetic individuals may or may not be candidates for ankle arthroplasty depending on the severity of joint degeneration found with radiographic imaging.

Common contraindications are:

1. Severe talus subluxation, severe valgus or varus deformity
2. Substantial osteoporosis
3. Neurological disorders or recurrent infection

Pre-operative Procedure and Definitive Diagnosis

Weight bearing A-P and lateral mortise views of bilateral ankles is required to make effective preparation and anticipation of that will be required in the surgery. The rearfoot alignment (Cobey/Saltzman) view is essential to evaluate the ankle joint and identify any calcaneal-totibial deformities. This is performed by getting the patient to stand, elevated with a cassette positioned at 15 degres anteriorly inclined with the x-ray bemed perpendicular to the film. This position is altered if deformities are present, after this has been taken anterior distal tibial angle (ADTA) is measured. The ADTA is formed by the mechanical axis of the tibia and the joint orientation line of the ankle in the sagittal plane and measures 80° ± 3° in the normal lower extremity. In the coronal plane, the lateral distal tibial angle (LDTA), the tibial-talar angle and the calcaneal tibial alignment should be measured. The LDTA is formed by the distal tibial articular surface and the anatomical axis of the tibia and measures 89° ± 3°.29, if this is decreased this represents a varus deformity. The tibial-talar angle (Figure 3C) is defined by the tibial and talar articular surfaces in the ankle joint. When the tibialtalar angle is >10° the joint is defined as incongruent (unstable).

"If an abnormal ADTA or LDTA is present (sagittal or coronal deformity), the center of rotation of angulation (CORA) is measured. The CORA is the intersection of the mid-diaphyseal line and the line starting from the middle of the joint and perpendicular to the abnormal ADTA or LDTA (Figure 4). The CORA can be located at the joint line level (usually due to anatomical joint line malalignment or to ankle degeneration) or proximally (usually due to tibial deformities/fractures)". So as you can see there are many consideration to be taken, and multiple angles to be analysed and this is important and any  instability and malalignment of the new prosthesis can be excessively worn or may even fail.

Medical Management

First generation:

Early ankle prosthesis attempts involved cementing a stemmed metal ball into the tibia and a polyethylene cup cemented into the talus. Throughout the 1970’s, prosthesis evolved into using a vitallium component cemented into the talus. All designs used methylmethacrylate cement, which became the defining element of first generation prosthesis.

Types:

• Constrained - Increased stability due to only allowing dorsiflexion and plantarflexion. Loosening of the prosthesis was common from increased torque at the joint.
• Nonconstrained - Allows full ROM, resulting in decreased stability that commonly caused impingement against the medial and/or lateral malleoli.
• Semiconstrained - A combination of contrained and nonconstrained models, allowing greater ROM and medial-lateral stability. The Imperial College, London Hospital prosthesis uses a concave polyethylene in the tibia and a stainless steel component on the talus.

Unfortunately, by the early 1980’s, first generation ankle arthroplasties were not recommended by the majority of orthaepedic surgeons. Numerous studies showed loosening of the cement fixation, wound issues, and low patient satisfaction . As a result of the poor outcomes and high complication rate, surgeons began to recommended ankle arthrodesis.

Second generation:

Second generation arthroplasties are cementless, using bony ingrowth to stabilize the implant. Compared to cement, bony ingrowth prosthesis have less bone resection, damage to soft tissue and complications of the cement such as cement displacement.

Surgical Factors:

• Fixation: Ingrowth implants tend to have either a beaded surface along the bony interface, hydroxyapatite layer or a combination of both. Current surgical designs tend to use the combination fixation technique. Between types of prosthesis the number of articulating surfaces and components both need to be considered..
• Components:
  • Articulating surfaces: Current designs vary on the articulations that need to be resurfaced. Resurfacing may occur at the superior tibiotalar joint, superior and medial articulations, or medial, lateral, and superior joints. Determining which patients would benefit the most from each type of surgery is ongoing.

Design components:

• 2 component implants include a tibial and talar articulating component. Implants may also incorporate syndesmosis fusion to resurface the medial and lateral recesses of ankle and converting the ankle from a 3-bone joint to a 2-bone joint. Known designs: Agility, Salto Talaris, Eclipse, INBONE
  • Advantages: decreased shear and torsion on prosthesis, syndesmosis decreases shear force and increase the bony support for the tibial component
  • Disadvantages: increased bony resection, likelihood of soft tissue compromise, accelerated polyethylene wear, and possibility of syndesmosis fusion failure.

2 Component Ankle Replacement Examples

Salto Talaris	Agility

• 3 component implants include a “mobile bearing” of polyethylene between the tibial plate and talar component. Known designs: Buechel-Pappas, Scandinavian Total Ankle Replacement (STAR), Mobility, HINTEGRA
  • Advantages: low polyethylene wear rates, allow multiplanar motion, increased congruency, minimal bony resection
  • Disadvantages: mobile bearing segment may dislocate, more involved surgery, abnormal ligamentous stress due to malalignment of axis of rotation

3 Component Ankle Replacement Examples

STAR	Buechel Pappas

Both component designs permit semiconstrained motion, specifically allowing some inversion and eversion during sagittal plane ankle movement. The four 2 component designs have been approved by the U.S. Food and Drug Administration (FDA). The STAR was recommended for approval by the FDA in 2008. There is insufficient evidence determining the life expectancy of current prosthesis designs.

Surgical Procedure

To perfrom the procedure the patient is positioned supine with the hip slightly elevated and a tourniquet on the proximal thigh to restrict blood flow during the procedure. Next a 10 cm incision is made over the centre of the joint line to expose the relevent anatomical structures. Once the structures have been exposed the crucial nerves and tendons are identified as to protect and ensure their integrity to minimise operative complications, these include; peroneal nerves, tibialis anterior and extensor hallucis longus. This is also to achieve correct talocrural alignment and soft tissue balance to ensure the prosthesis can achieve plantar grade in standing. It is also important to debride and correct any osteophytes or any other structures that can contribute to malalignment. Depending on the natural angle of the talocrural joint (varus or valgus) more bone medially or laterally may have ot be removed, this also may occur if the joint is deep or shallow as it may need to be reduced or elevated.

Once the joints have been corrected and bones properly aligned the new components are trialed making sure rull ROM and stability is achieved. If dorsiflexion is limited and not due to malalignment then achilles tendon lengthening is required, the same goes for if there is instability in inversion or eversion the ligaments are reconstructed. Persistent malalignment can occure and may need separate procedures to correct such as subtalar fusion depending on severity and correctability. 

Alternate Option:

Ankle Arthrodesis

Ankle arthrodesis or fusion was the recommended surgical option after the failure of the first generation ankle arthroplasty. The procedure includes resecting the articular surfaces of the joint, realignment the talus and tibia and fusing the bones together. As a result, the ankle joint doesn’t allow any motion. The goal of ankle arthrodesis is pain relief. Unfortunately, the lack of ankle motion can cause elevated stress on the knee and hindfoot and in addition, increases motion at the hindfoot that may become arthritic. Other complications of fusion include accelerated degeneration of adjacent joint and limitations in activity.

Used with permission by Susan Barber Lindquist, Media Relations Coordinator, Mayo Clinic Health System

Outcome Measures

• Foot and Ankle Disability Index
• Foot Function Index (FFI)
• Foot and Ankle Ability Measure (FAAM)

Physical Therapy Management

As it will be explained in the pre-operation and post-operation phase the multi-disciplinary team involved with the patient have a big role in making the arrangements before and after the surgery, this may involve physiotherapists, occupational therapists, discharge nurses, staff nurses, healthcare assistants as well as doctors. Both pre and post operative phases are integral to the progress of the patient and the pre-op should not be overlooked as important as it can be easy to focus on post-op.

Pre-Operative Phase

Before the surgery one of the main job for the team is to educate the patient about what will happen before, during and after the surgery as this will give the patient the opportunity to prepare, mentally rehearse, ensure smooth transition through short-term to long-term goals but also help control and reduce post-operative pain

ROM, muscle strength, gait and deviations will all be recorded as to compared before and after arthroplasty and ensure the patient is as optimal strength prior to operation if possible. For safety and ease of transition is can be important that the patient learns how to walk with crutches so they can perform ADL’s as soon as possible post arthroplasty but also understand that they will be non-weight bearing after the arthroplasty.

As will all procedures under general anesthetic there are common pulmonary postoperative complications (PPC's) which need to be controlled and risk reduced and this can be explained at this stage as well. 

Post-Operative Phase

It is important to ensure the risk of PPC's are reduced and respiratory physiotherapy may be used at this early stage, cough, deep breathing exercises and early mobility are essential here to reduce atelectasis and reinstate the muscoscilliary elevator as soon as possible. 

Atelecatsis occurs in 90% of anesthetized patients which leads to a 16-20% reduction in functional residual capacity which is why the alveoli tend collapse resulting in increased work of breathing, hypoxia, reduced compliance, V/Q mismatch and risk of pneumonia. There is a 9% chance of developing pneumonia and this is where physiotherapy intervention is crucial at reducing the rate of all of these complications.

IT IS IMPORTANT TO KNOW YOUR OWN HOSPITALS/SURGEONS GUIDELINES FOLLOWING ARTHROPLASTY OR ANY OPERATION AND THE FOLLOWING SHOULD ONLY BE USED TO EDUCATE AND CONSIDER SOME BASIC/COMMON PROTOCOLS

THIS SHOULD NOT BE USED IN REPLACEMENT OF THE SURGEONS PROTOCOL

THIS IS A PROTOCOL BY THE ROYAL NATIONAL ORTHOPAEDIC HOSPITAL NHS TRUST, utilising the best available evidence

As can be expected after any type of surgery, pain and inflammation must be controlled. This is the case especially after ankle replacement because pain and inflammation can last up to 12 months after surgery. Surrounding muscles can be damaged during surgery and can result in decreased range of motion and strength. Damage to joint proprioceptors during excision of the capsule may cause deficits in both static and dynamic balance. These components can lead to gait disability and decreased efficiency of locomotion. Correction of gait posture and ambulation deficiencies will be a target of therapy once the patient is ambulating independently.

Physical Therapy Goals:

• Decrease pain
• Decrease inflammation
• Increase strength
• Increase range of motion
• Improve dynamic and static balance
• Improve proprioception
• Proper independent ambulation
  

Assessment

• Mechanism of injury or etiology of illness
• Date of surgery and type of implant
• Use of assistive device with weight bearing status
• Use of controlled ankle motion (CAM) walker/walking boot
• Functional deficits/assistance with ADLs/adaptive equipment
• Pain/ Symptom history: Location, duration, type, intensity (VAS), aggravating and relieving factors, 24 hour symptom behavior
• Relevant Current/Past Medical history: Other lower extremity arthritis or injuries,upper extremity issues that may limit ability to ambulate with an AD and comorbid diagnoses
• Medications for current/previous diagnoses
• Diagnostic tests
• Sleep disturbance
• Barriers to learning
• Social/occupational history
• Patient’s goals
• Vocation/avocation and associated repetitive behaviors
• Living environment
  

Relevant Tests & Measures:

• Observation/inspection/palpation: Skin and incision assessment, edema, muscle atrophy
• Circulation: Dorsal pedal pulse
• Sensory and proprioception testing
• Range of motion and Muscle length: Average postoperative arc of motion (dorsifexion and plantarfexion) is 23°
• Muscle strength
• Posture: Increased pronation/supination in standing, ability to maintain wait bearing status
• Assess assistive and adaptive devices for need and proper fit
• Balance: Static and dynamic standing balance, unilateral balance of the unaffected extremity (especially if patient is still non-weight bearing). Patient may demonstrate dynamic postural imbalance, less reliance on ankle strategy and deficit of motor control ability
• Functional mobility
  • American Orthopaedic Foot and Ankle Society ankle-hindfoot score, Outcome measures
  • Self-selected normal walking speed
  • Assess safety in mobility
• Gait Assessment
  

Initial Rehab 0-4 Weeks

Restrictions:

• Non-weight bearing 2/52 with a back slab
• Below knee POP at 2/52 and begin full weight bearing in this POP
• POP removed at 4/52 and aircast boot is considered
• Elevation
• If sedentary employment, return to work at 4/52 as long as elevated and protected

Goals:

• Safe and independent mobility with walking aid
• Independent with exercise programme
• Know monitoring and protection

Treatment:

• POP
• Pain-relief
• POLICE
• Basic circulatory exercises
• Mobility

Progress when:

Out of POP, fully weight bearing, no complications and then refer to physiotherapy out patients

Recovery Rehab 4 weeks - 3 months

Restrictions:

• No strengthening against resistance until 3 months if any tendon transfers 
• No stretching tendons if transferred

Goals:

• Independent from aircast boot
• Achieve full ROM 

Treatment:

• Pain relief, swelling management
• Advice, education, postural advice, monitoring complications, pacing
• Gait re-education
• Exercises --> PROM,AAROM, AROM, light strengthening, core stability, balance/proprioception, stretching
• Hydrotherapy
• Orthotics
• Manual therapy --> SSTM's, mobilisations

Progress when:

Full ROM, independently mobile, neutral foot position in standing

Intermediate Rehab 12 weeks - 6 months

Restrictions: 

• None

Goals:

• Independent with no aids
• Normal footwear
• Grade 5 strength
• Grade 4 strength in tendons transferred

Treatment:

• Pain relief, swelling management
• Advice, education, postural advice, monitoring complications, pacing
• Gait re-education
• Exercises --> PROM,AAROM, AROM, light strengthening, core stability, balance/proprioception, stretching
• Hydrotherapy
• Orthotics
• Manual therapy --> SSTM's, mobilisations

Progress when:

Normal footwear, independent with no aids, pain controlled, strength 5/5 (4/5 if tendon transferred)

Final Rehab 6 months - 1 year

Goals:

• Return to gentle no-impact/low impact sports
• Grade 5 strength in transferred tendons

Treatment:

• Maximise function
• End stage exercises, balance and proprioception and sport specific
• Manual therapy
  

Muscles to Consider

Here is a unfinished list of some of the major muscles of the lower leg and foot, consider these in your rehabilitation and mechanism of pathology. Some may have had tendons moved or stretched and now need to be specifically rehabilitated as the proprioceptive function may now have changed.

Posterior Compartment - Superficial

• Gastrocnemius
• Plantaris
• Soleus

Posterior Compartment - Deep

• Popliteus
• Flexor Hallucis Longus
• Flexor Digitorum Longus
• Tibialis Posterior

Lateral Compartment

• Peroneus Longus
• Peroneus Brevis

Anterior Compartment

• Tibialis Anterior
• Extensor Hallucis Longus
• Extensor Digitorum Longus
• Peroneus Tertius

Sample Exercises

Balance c perturbation	Ball toss	Standing reach

Standing reach	Seated rocker board	DF theraband
Ankle eversion	DF stretch	Ankle PF

Additional Information

After the surgery it is important that the patient keeps moving and performing his daily activities. However there is still discussion between physicians about when the patient should start again with exercising. There are some that allow exercise immediately after surgery. But some say it is considered best to wait until there is a satisfactory bony in growth as shown radio graphically. However it’s the job of the physician to try to improve:  the patient’s ROM of the ankle, maintain the ROM in the hip and knee, increase the muscle strength with exercise for the Gluteus Maximus, Quadriceps femoris muscles and the muscles that are responsible for dorsal flexion and the plantar flexion of the ankle. Postoperative mobilization begins early, with rapid progression to resumption of normal activities. The goal is to obtain 10° of dorsal flexion and 30° of plantar flexion. For patients who have almost no motion in their ankle is any motion an improvement. 

In early postoperative period it is important that the incision heals and the implant becomes solidly fixed to the bony bed to do this they will use a below knee non-weight bearing immobilization. This is maintained until there is satisfactory bony in growth. ^. Another goal is to increase the ROM of the ankle and maintain the hip and the knee ROM.

After a few months the patient needs to make an appointment with the doctor. Here they will take X-ray scans to see if there are no complications like: joint debridement for osseous impingement; the next most common procedures were extra-articular procedures for axial misalignments and component replacements. 

Prognosis & Outcome

Outcome of ankle arthroplasty includes pain, function implant survival and complications. There are numerous studies looking at survival rate of implants and rates are reported around 67-94% at 5 years and 75% at ten years which is reasonably reliable. 

A systematic review of intermediate and long term outcomes of arthrolplasty and arthrodesis performed by Haddal et al had interesting results. It reviewed 49 primary studies of 1262 patients and utilised the AOFAS score (Americal Orthopaedic Foot and Ankle Society). This score is out of 100 (0=worst outcome, 100=best outcome) broken into 8 sections of pain, function walking distance, walking surface, gait abnormality, sagittal mobility, hindfoot mobility, ankle hindfoot mobility and alignment. The score has mixed reviews and the objective aspect of the score is hard to make reliable between therapists. 

The mean AOFAS score was 78.2 points for the patients treated with total ankle arthroplasty and 75.6 points  for those treated with arthrodesis. Meta-analytic mean results showed 38% of the patients treated with total ankle arthroplasty had an excellent result, 30.5% had a good result, 5.5% had a fair result, and 24% had a poor result. In the arthrodesis group, the corresponding values were 31%, 37%, 13%, and 13%. The five-year implant survival rate was 78% and the ten-year survival rate was 77%. The revision rate following total ankle arthroplasty was 7% with the primary reason for the revisions being loosening and/or subsidence (28%). The revision rate following ankle arthrodesis was 9% , with the main reason for the revisions being nonunion (65%). One percent of the patients who had undergone total ankle arthroplasty required a below-the-knee amputation compared with 5% in the ankle arthrodesis group. Their conclusion was that on the basis of these findings,

"the intermediate outcome of total ankle arthroplasty appears to be similar to that of ankle arthrodesis; however, data were sparse. Comparative studies are needed to strengthen this conclusion".