Total ankle replacement Total ankle replacement The early results of

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					  Total ankle replacement. The early results of 140 consecutive

                      cases of the AES prosthesis.


Mr N J Harris, FRCS (Tr&Orth), Consultant Orthopaedic Surgeon
Mr S W Sturdee, FRCS (Tr&Orth), Specialist Registrar
Mr M Farndon, MRCS, Specialist Registrar




Department of Orthopaedics and Trauma,
The General Infirmary at Leeds,
Great George Street,
Leeds.
West Yorkshire.
LS1 3EX. United Kingdom.
Tel: 0113 243 2799



WORK ATTRIBUTED TO:

Department of Orthopaedics and Trauma,
The General Infirmary at Leeds,
Great George Street,
Leeds.
West Yorkshire.
LS1 3EX. United Kingdom.

AUTHOR RESPONSIBLE FOR CORRESPONDANCE:

Mr N J Harris,
Department of Orthopaedics and Trauma,
The General Infirmary at Leeds,
Great George Street,
Leeds.
West Yorkshire.
LS1 3EX. United Kingdom.

Email nickjohnharris@btinternet.com




                                         -1-
Abstract



Between 2003 and 2006 we implanted 140 mobile bearing AES total ankle

replacements. None was lost to follow-up for reasons other than the death of a patient.

The mean follow-up was 20 months (6 – 48).



The mean AOFAS ankle and hindfoot score was 79 and 97% of patients rated their

outcome as better, much better or excellent.



A complication requiring further surgery developed in twenty ankles. At the time of

follow up no implant had been revised or removed. The most frequent complication

requiring surgery was edge loading in sixteen ankles. Other complications include

delayed wound healing and fracture of a malleolus.




                                          -2-
Introduction



The first known total ankle replacement (TAR) that is described in the literature was

performed in 1970.1 This was an inverted hip prosthesis and not surprisingly it failed.

Since this date there have been numerous designs utilising different biomechanical

principles. Many of these early prosthesis, however, had disappointing results.2-7 Over

the last decade, however, there have been several prostheses with much improved

early results. These newer prostheses have resulted from a greater understanding and

knowledge of ankle joint biomechanics, and the mechanisms of failure of the earlier

designs. There are two main types of prosthesis, the mobile bearing design such as the

Scandinavian Total Ankle Replacement (STAR) (W. Link GmbH & Co, Hamburg,

Germany) and the Buechal Pappas (BP) (Endotec, South Orange, New Jersey, USA),

and the semi constrained design such as the Agility (DePuy, Warsaw, Indiana, USA).

The short term results by the designers of these prostheses as well as others do show

improved results compared with the earlier studies previously described.8-16



The AES (Ankle Evolutive System) TAR (Biomet, Europe) is based on the revision

Buechel Pappas TAR and is a three component mobile bearing design (Fig.1). The

tibial and talar components are made from cobalt chrome, grit blasted and are coated

with hydroxyapatite. The mobile bearing is made of ultra-high-molecular-weight

polyethylene (UHMWPE). The AES TAR has been is use since 1999 and the only

published results are from Germany.17 This series is a total of 15 TAR with a mean

follow up of 8.5 months.




                                          -3-
We describe a consecutive series of 140 AES TAR performed over a four-year period.

The aim of this study was to clinically and radiologically assess the early outcome of

the AES TAR.




                                         -4-
Patients and methods



Between August 2002 and August 2006 the senior author (NJH) performed 140 TAR

using the AES prosthesis. All the patients had painful arthritic ankles that severely

restricted their mobility. The 140 TAR were performed consecutively and all were

prospectively entered into this study. We have broken the diagnoses into four main

groups    (post-traumatic   arthritis,   primary   osteoarthritis,   inflammatory     and

miscellaneous) (Table 1). 82 patients had post-traumatic arthritis, and of these 54

were as a result of a previous ankle fracture and 28 had a history of a significant soft

tissue ankle injury. 40 patients had primary osteoarthritis, 11 had an inflammatory

arthritis (Rheumatoid arthritis). Other diagnoses included 3 cases of cavovarus feet, 1

revision from a STAR TAR, 1 non-union of ankle arthrodesis, one haemophiliac and

one case of haemochromatosis. A full breakdown of the diagnoses is shown in table 2.

Many of these arthritic patients had coexisting arthritis affecting the other major joints

of the lower limb, some of which had also been replaced surgically.

At the beginning of the series only patients with well-aligned ankles were offered a

replacement (Figures 1 and 2). As our experience grew patients with increasing

degrees of varus (Figures 3 and 4) and valgus (Figure 5) deformities were also offered

replacements together with appropriate soft tissue balancing and realignment. Overall

in the series there were 36 varus, 26 valgus and 78 neutrally aligned ankles. The range

of deformity was from 40 degrees of valgus to 20 degrees of varus.



The operative technique was the same for all cases and the TAR was inserted through

an anterior approach to the ankle with a general anaesthetic and femoral and sciatic

nerve blocks. A tourniquet was used in all cases and antibiotics were given



                                           -5-
preoperatively and two doses postoperatively. One deep drain was used which was

removed on the first postoperative day. Oxygen was administered by nasal cannula

for two days postoperatively and the patients rested with the leg elevated until the 3rd

postoperative day when mobilisation is begun non weight bearing in the below knee

plaster. After two weeks the plaster was changed and partial weight bearing was

permitted. A plaster was used for a total of six weeks and then a removal rigid ankle

foot orthosis was used for a further six weeks.

Clinical assessment of outcome. This was assessed using the American Orthopaedic

Foot and Ankle Surgeons (AOFAS) ankle and hindfoot score.18 The AOFAS score

was done at every clinical follow up after six months. The AOFAS score is out of 100

points and assesses pain (40 points), function (50 points), and alignment (10 points).

If revision was needed it was classified as a failure and revision was defined as

exchange of either the tibial or talar components or fusion of the ankle.

Subjective assessment of outcome. This was assessed by asking the patients at

follow up visits how satisfied they were with the ankle replacement. They were asked

if they were worse off, no better, better, much better or excellent.

Radiological assessment of outcome. All the radiographs taken both before and after

the surgery were weight bearing and a goniometer was used to measure the angles.

The coronal alignment of the talus in the ankle mortise was measured before the

operation to determine if the ankle was neutral, varus or valgus. Post operatively

coronal alignment of the tibial and talar components was measured in relation to the

long axis of the tibia. The sagittal alignment of both components was also measured

in relation to the tibia with the ankle in a plantigrade position. If the implant was

within 5 degrees of the neutral position this was recorded as normal. The interface of




                                           -6-
the tibial and talar component was assessed for osseous integration, cavitation and

migration. Any lucency around the implants was recorded.




                                        -7-
Results



The patients were reviewed clinically at two weeks, six weeks, three months, six

months, twelve months, and then annually. Radiographs were taken at 6 weeks, three

months, six months, twelve months, and then annually. None of the 140 ankles have

been lost to follow up. Two patients have since died. This left us with 138 TAR’s that

have been followed up as described. The mean follow up was 20 months (6 - 48).



Clinical assessment of outcome. The mean AOFAS ankle and hindfoot score was 79

(Range 52 – 100). If we stratify this score by removing the patients that had other

joint problems such as knee or hip arthritis (27 patients) then the mean score is 82

(Range 54 – 100). At the time of review no tibial or talar implant had been revised or

removed.



Subjective assessment of outcome. 97% of patients rated their outcome as better,

much better or excellent, with 44 % rating it as excellent and 42% as much better.



Radiological assessment of outcome. Eleven ankles had malposition of the implant

greater than five degrees in the coronal and or sagittal planes. Seven of these were in

the first 32 ankles in the series. Nine ankles had some gaps or lysis around the

implants but none of these were symptomatic. Three ankles over the follow up period

had migration of the talar component but none of these have required further surgery.




                                          -8-
Complications.

Twenty patients had undergone an additional surgical procedures at the time of follow

up. 16 of these were because of edge loading, one for a dislocated insert and 3 for

additional plastic surgical procedures because of soft tissue problems. These are all

described below and are summarised in table 3.

Edge loading of UHMPE bearing. Seventeen ankles developed edge loading and

sixteen required surgery to correct this. A wide range of procedures was necessary.

Varus edge loading was most common. A medial release was performed first through

a separate incision protecting the tibialis posterior tendon. In one case a ‘z’

lengthening of the tibialis posterior was also undertaken. If the ankle remained

unstable a lateral ligament reconstruction was also undertaken using a peroneus brevis

transfer through the fibula. If the hindfoot remained in varus a lateral heel shift was

performed. In two cases a dorsiflexion osteotomy of the first metatarsal was also

undertaken. Valgus edge loading was less common and more difficult to treat. A

lateral release or fibular lengthening osteotomy was performed first. In 3 cases this

was combined with a deltoid ligament reconstruction using either a free hamstring

graft or FDL transfer. A medial heel shift was undertaken if there was persisting

hindfoot valgus. In all cases the UHMPE bearing was replaced with a larger size until

the joint was balanced.

Delayed wound healing. Nine ankles had delayed wound healing of more than two

weeks. Six of these healed with conservative treatment. Two needed a split skin graft

and one required a local fascio-cutaneous flap. Two of these have gone onto

developed deep infections in the ankle joint. Both however are controlled with

antibiotics with no evidence of lysis or loosening. Both still feel better off since the

surgery.



                                          -9-
Fracture of a malleolus at the time of surgery. Five ankles sustained a malleolar

fracture during the surgery. The medial malleolus was fractured four times and the

lateral malleolus once. Two of the medial malleolus fractures were undisplaced and

internal fixation was not undertaken and two were displaced and had internal fixation

with screws. All these malleolar fractures went onto full union.

Fracture of a malleolus after surgery. Two ankles sustained a fatigue fracture of the

medial malleolus after the surgery. Both were treated conservatively and went onto

full union.

Thromboembolic event. One patient had a deep vein thrombosis in the leg of the

operated side and had a low probability of a pulmonary embolism on a ventilation

perfusion scan. This was treated by anticoagulation with warfarin.




                                          - 10 -
Discussion
                                                                  (8-23)
Our early results compare well with the published literature           . After a mean

follow-up of 20 months 97% of patients rated their surgery as better, much better or

excellent. The mean AOFAS score was 79. No implant was removed or revised to a

fusion. Twenty patients required additional procedures.

The most frequent complication was edge loading. As the pre-operative coronal

deformity increased so did the risk of edge loading. This has been reported before
(16,24)
      .

Varus edge loading was the most common type in our series. This was corrected

initially with a medial release which in many instances was sufficient, combined with

a larger mobile bearing. If the ankle remained unstable then a lateral ligament

reconstruction was also undertaken. Any persistent hindfoot varus was corrected with

a heel shift. A dorsiflexion osteotomy of the first metatarsal was undertaken in two

cases with pre-operative cavo-varus deformities. Valgus edge loading was less

common and was initially corrected with a lateral release or lengthening osteotomy of

the fibular combined with a larger mobile bearing. The medial ligament can also be

reconstructed using a free hamstring graft. Again any persistent hindfoot deformity

was corrected with a heel shift.

Meticulous surgical technique and careful handling of the soft tissues should reduce

the incidence of soft tissue complications. Despite this in our series 9 patients still

suffered delayed wound healing. Two patients required split skin grafts and 1 a fascio-

cutaneous flap.

The incidence of peri-operative malleolar fractures seems to relate to surgical

experience and reduced over time in our series. Undisplaced fractures were treated

conservatively and displaced fractures with reduction and fixation.



                                         - 11 -
Our initial experience with the AES Total Ankle Replacement is encouraging and we

continue to use the implant.




                                      - 12 -
Acknowledgements



The authors wish to thank Dr Jo Ascencio, Consultant Orthopaedic Surgeon, Nimes,

France and Mr Peter Black, Consultant Orthopaedic Surgeon, Hamilton, New Zealand

for their support and help in this study.



No benefits in any form have been received or will be received from a commercial

party related directly or indirectly to the subject of this article.




                                             - 13 -
References



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      résultats. A propos de 12 observations. Rev Chir Orthop 1973;59:139-51.

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      2002;51:143-51.



                                       - 14 -
11. Buechel FF, Pappas MJ, Iorio LJ. New Jersey low contact stress total ankle

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                                    - 15 -
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                                   - 16 -
Table 1 Breakdown of diagnosis and age for 140 patients with total ankle

replacement.




Diagnosis                  Gender        Number of ankles   Mean age

                                                            (Range) yrs



Post traumatic arthritis   M             58                 64 (47 – 83)



Post traumatic arthritis   F             24                 61 (47 – 74)



Primary osteoarthritis     M             29                 66 (53 – 81)



Primary osteoarthritis     F             11                 69 (61 – 78)



Inflammatory arthritis     M             1                  55 (55 – 55)



Inflammatory arthritis     F             10                 55 (38 – 66)



Miscellaneous              M             5                  61 (50 – 71)



Miscellaneous              F             2                  64 (53 – 74)




                                    - 17 -
Table 2 Full breakdown of all diagnoses for all 140 AES Ankles



Diagnosis                                       Numbers          Sub group



Post-traumatic arthritis                        82

       Previous ankle Fracture                                   54

       Previous soft tissue injury                               28



Primary osteoarthritis                          40



Rheumatoid arthritis                            11



Cavo varus foot (Polio)                         2



Cavo varus foot (Idiopathic)                    1



Haemophilia                                     1



Haemochromatosis                                1



Non union ankle arthrodesis                     1



Revision from a STAR TAR                        1




                                      - 18 -
Table 3 List of complications and the need for further surgery




                                                 No further      Surgery for

                                                 surgery         complication




Edge loading of UHMPE bearing (n = 17)           1               16



Delay of would healing (n = 9)                   6               3



Fractured malleolus at time of surgery (n = 5)   5               0



Fractured malleolus after surgery (n = 2)        2               0



Thromboembolic event (n = 1)                     1               0




                                       - 19 -
Figure 1 Pre-operative AP and Lateral radiograph, Neutral alignment




Figure 2 Post-operative AP and Lateral radiograph, Neutral alignment pre-operatively




                                        - 20 -
Figure 3 Pre-operative AP and Lateral radiograph, Varus alignment




Figure 4 Post-operative AP and Lateral radiograph, Varus alignment pre-operatively.




                                        - 21 -
Figure 5 Pre-operative and Post-operative AP radiograph, Valgus alignment




                                       - 22 -

				
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