St. Georg–Buchholz Ankle Prosthesis

The St. Georg–Buchholz ankle prosthesis is a semiconstrained prosthesis type introduced in 1973. However, the use of this prosthesis was abandoned after eight TARs because of the high failure rate.48,97 Hay and Smith¹³⁵ implanted this prosthesis in 15 patients. At a mean follow-up of 10 years, 11 early and 32 late complications were reported.¹³⁵

Imperial College of London Hospital Prosthesis

The Imperial College of London Hospital (ICLH) TAR was a two-component, constrained total ankle design with a polyethylene tibial component.105,179 For implantation, cemented fixation with polymethyl methacrylate bone cement was used. Freeman et al¹⁰⁵ reported laboratory wear and fixation tests and their clinical experience of 2 years.¹⁰⁵ Bolton-Maggs et al³⁸ retrospectively reviewed midterm outcomes of 62 TARs performed between 1972 and 1981, using the ICLH ankle prosthesis Mark VII. This version of the prosthesis had a polyethylene tibial component that could be trimmed to an appropriate size at the time of operation.²⁹⁷ At the mean follow-up of 5.5 years, 41 ankles were clinically reviewed. Only 13 patients had satisfactory results. The authors reported high complication rates, including wound healing problems, talar collapse, and loosening of the prosthesis components. By midterm, 13 ankles had to be revised and converted to ankle fusion. Therefore the authors suggested ankle fusion as a superior treatment option, regardless of the underlying etiology of ankle osteoarthritis (OA).³⁸ Samuelson et al²⁹⁷ published their results obtained in 75 patients who received an ICLH prosthesis. The majority of patients (70%) reported acceptable results. The most frequently reported complication was delayed wound healing. Despite acceptable results reported by many patients, complication rates were high; thus the authors stated that the use of this prosthesis should be approached with caution.²⁹⁷ Herberts et al¹⁴³ performed 18 ICLH ankle arthroplasties in 16 patients and followed them for a mean of 36 months. In four cases, an aseptic loosening was observed; radiolucent zones greater than 2 mm were seen in another 7 ankles. Despite the acceptable results, the authors indicated that the failure rate may increase with longer follow-up.¹⁴³

Irvine Total Ankle Replacement

The Irvine ankle design (also known as the Howmedica prosthesis) was one of the first ankle prostheses in which a special talus anatomy was closely considered (Fig. 22-1).³⁶⁵

The prosthesis designers performed anatomic measurements of 32 tali to establish the morphology of talus.³⁶⁵ Evanski and Waugh¹⁰² performed 29 cemented TARs before December 1975, using 25 Irvine ankle prostheses and 4 Smith prostheses. In all patients, significant functional improvement, including increased range of motion and pain relief, was observed. However, the mean follow-up was only 9 months, and already in this short postoperative period, malalignment occurred in two patients, one of whom needed revision surgery. In two patients, a prosthesis failure was observed (Fig. 22-2). The analysis of failures showed that the unconstrained prosthesis design in combination with its surface geometry led to increased rotation between both components, resulting in an overload of surrounding soft tissue and ligaments. Despite these poor short-term results, the authors stated that TAR would be an acceptable alternative treatment to ankle fusion.¹⁰² However, no longer-term results in patients who underwent Irvine TAR are available in the current literature.

Richard Smith Total Ankle Replacement

Richard Smith TAR is a nonconstrained, so-called ball-and-socket (spherocentric) prosthesis that was introduced in 1975 (Fig. 22-3).¹⁸⁴ This prosthesis design included a metal tibial component (“socket”) and polyethylene talar component (“ball”); both components were fixed with cement. Besides the aforementioned study by Evanski and Waugh,¹⁰² only a few studies have been published addressing the outcome in patients who underwent Richard Smith TAR. Kirkup¹⁸⁴ performed 24 Richard Smith TARs in 21 patients (three cases were bilateral). Eighteen ankles were available for a mean follow-up of 7 years. Seven patients developed loosening of the tibial component, requiring revision arthroplasties using Bath-Wessex TAR in three cases at 4.1, 4.3, and 6.8 years, respectively. In one case with loosening, a deep infection occurred, resulting in ankle arthrodesis. The remaining three cases were under observation. In 7 patients, delayed wound healing was observed. Most patients in this cohort experienced substantial pain relief. Because of a high revision rate, the recommendation was not to use this prosthesis design.¹⁸⁴ Dini and Bassett⁸⁸ used the Richard Smith prosthesis in 21 patients. At a mean follow-up of 27 months, failure occurred in five ankles; in other patients, significant pain relief and improved function of the ankle were observed.⁸⁸

Conaxial Beck-Steffee Ankle Prosthesis

The Conaxial Beck-Steffee TAR is a highly constrained prosthesis type.²³⁰ Wynn and Wilde³⁷⁸ presented clinical results in 30 patients treated with Conaxial Beck-Steffee prosthesis between 1975 and 1977. All patients were reviewed at a mean follow-up of 10.8 years. Early postoperative complications were common and included wound healing problems (39%), deep infection (6%), malleoli fractures (22%), and painful talofibular impingement (14%). At 2-year follow-up, 27% of all prosthesis components already showed significant loosening. This negative tendency was confirmed at later follow-ups, resulting in a 90% loosening rate at 10 years. Therefore the authors did not recommend the further use of this prosthesis.³⁷⁸

Newton Ankle Implant

In the 1970s, St. Elmo Newton²⁵² reported that fused ankles may produce additional stress on the knee and midtarsus joints, thus accelerating the advancement of preexisting degenerative changes.^250,251 Therefore he performed 50 TARs since 1973, using a nonconstrained cemented prosthesis, including the high-density polyethylene tibial and Vitallium talar components (Fig. 22-4). In 75% of ankles, aseptic loosening was observed.²⁵¹ Eighteen failures occurred at a minimum follow-up of 1 year. This finding may explain related increased polyethylene wear caused by incongruency of TAR components: the tibial component was a portion of a cylinder, and the talar component was a portion of a sphere with a slightly smaller radius. Regarding the high failure rate, the following contraindications for TAR were identified: any recent infections, valgus or varus deformity of the talus of 20 degrees or greater, significant ligamentous instability of the ankle, avascular necrosis of the talus, nonunion of prior ankle fusion, and rheumatoid arthritis in patients having long-term steroid therapy.^250,251

Bath-Wessex Total Ankle Replacement

The Bath-Wessex TAR is an unconstrained, two-component total ankle design. Carlsson et al⁵⁶ reported a 10-year survivorship analysis of 69 Bath-Wessex prostheses implanted between 1984 and 1996.⁵⁶ The initial acceptable results published in another earlier study (5-year survivorship of 81%)⁵⁵ were not maintained in this study (10-year survivorship of 66%).⁵⁶ Eighteen ankles had to be revised (12 ankle fusions and 6 revision arthroplasties). In the remaining ankles, at least one component showed radiologic loosening signs (67% of all tibial and 82% of all talar components). Therefore the authors strongly discouraged use of this prosthesis type as a standard prosthesis.⁵⁶

Mayo Total Ankle Replacement

The Mayo TAR was designed as a constrained design by Stauffer in the 1970s. It was a highly congruent two-component design, including a polyethylene tibial component with cement fixation.320,321 Stauffer and Segal³²⁰ performed 102 TARs using the Mayo Total Ankle between 1974 and 1977. At a mean follow-up of 23 months, 53 complications were observed in 54% of ankles with posttraumatic OA and in 23% of those with rheumatoid OA. Loosening of prosthesis components in 7 ankles resulted in five revision arthroplasties and two fusions.³²¹ Kitaoka et al¹⁸⁷ reported on 204 primary Mayo TARs between 1974 and 1988 at the Mayo Clinic. The mean follow-up in this patient cohort was 9 years, with a range of 2 to 17 years. The overall 5-, 10-, and 15-year survivorship was 79%, 65%, and 61%, respectively. Because of the high failure rate, the use of this prosthesis was not recommended, especially in younger patients.^186,187 Demottaz et al⁸⁰ published a clinical gait analysis study, including 21 TARs performed between 1974 and 1977. Different prosthesis types were used in the study: 14 patients received a single-axis prosthesis (Mayo, Thompson-Parkridge-Richard [TPR], Buchholz, or Oregon) and 7 patients received a multiple-axis prosthesis (Waugh or Smith). At the mean follow-up of 15 months, pain relief and functional improvement results were disappointing. Also, the rate of progressively increasing loosening was alarmingly high at 88%. Therefore the authors suggested ankle fusion as the treatment of choice for ankle OA.⁸⁰ Lachiewicz et al²¹² reviewed 17 TARs (14 Mayo ankle prostheses and 1 Buchholz ankle prosthesis) performed between 1976 and 1981.²¹² The indication for the surgery in all patients was rheumatoid OA. At a mean follow-up of 39 months, all patients experienced pain relief and improved range of motion (ROM). No patients required revision surgeries; however, radiolucencies at the bone–cement interface and the subsidence of six components were observed in 11 ankles.²¹² The same patient group was included in a long-term study by Unger et al.³⁴⁰ Overall, 21 patients who were treated with TAR were enrolled for retrospective review at a mean follow-up of 5.6 years, with a range of 2 to 10 years. Eight from a final group of 17 available patients reported their results to be fair or poor. In 14 of 15 cases, subsidence and loosening were observed. Twelve tibial components had tilting; however, the postoperative position of the implant showed no significant correlation with radiolucency around the component.³⁴⁰

Oregon Ankle Prosthesis

The Oregon ankle is a single-axis, two-component TAR design. Groth and Fitch¹²⁶ performed 71 primary cemented TARs using Oregon ankle prosthesis between 1975 and 1985. At a mean follow-up of 6.5 years, reoperations were necessary in 19 patients, including 11 ankle fusions and 5 revision arthroplasties. The authors concluded that TAR should be limited to patients with rheumatoid arthritis and to elderly less-active patients with posttraumatic OA.¹²⁶ In 1986, McGuire et al²³¹ performed a retrospective comparative study addressing outcome and complication rates in patients who underwent TAR versus ankle arthrodesis. The TAR group consisted of 25 patients with six different prosthesis types (Oregon, TPR, Richard Smith, Newton, Mayo, and Buchholz). The mean follow-up was 3.8 years. Four patients with TAR had infections (vs. 5 of 18 in the arthrodesis group). Loosening occurred in 5 patients with TAR (vs. 6 nonunions in arthrodesis group). The authors concluded that TAR should not be performed in younger patients with posttraumatic OA.²³¹

Thompson-Richard Prosthesis

The Thompson-Richard prosthesis (TRP) was introduced in 1976 as a two-component semiconstrained cemented implant. The prosthesis design included the polyethylene tibial component with a concave articular surface and a lip on each side designed to avoid too-excessive transversal movement of the talar component.28,377 Wood et al³⁷⁷ compared the clinical and radiologic outcome of the cemented TRP prosthesis (seven ankles replaced during 1991 and 1992) and cementless STAR prosthesis (also seven ankles). The mean follow-up for TRP and STAR groups was 7.2 and 5.4 years, respectively. In the TRP prosthesis group, four tibial components showed significant loosening, requiring ankle fusion in two cases, while all components of the STAR prosthesis remained stable at the latest follow-up.³⁷⁷ A similar comparative study—TRP versus STAR prosthesis—was performed by Schill et al,³⁰² including 27 TRP and 22 STAR implants. At a follow-up ranging from 1 to 12 years, 37 patients with 20 TRP and 19 STAR prostheses were reviewed. In patients with TRP prostheses, a high rate of radiolucency around the tibial component (53.3%) was seen; also, in three ankles talar components were found to have significant subsidence. In patients with STAR implants, only three cases showed small radiolucent lines of the flat tibial component, while the talar components showed no signs of loosening or migration. In the TRP group, two revisions were performed, because of prosthesis loosening and malleolar fracture, resulting in a 12-year cumulative survivorship of 87%. In the STAR group, two revisions were necessary because of one meniscal-bearing breakage and correction of meniscal-bearing height, resulting in a 6-year cumulative survivorship of 94.3%.³⁰² Jensen and Kroner¹⁷⁴ observed a high rate of radiolucency around prosthesis components in 52% of 30 reviewed ankles. Revision was necessary in only two cases; however, only 69% of all patients were satisfied with the results obtained at a follow-up of 5 years.¹⁷⁴

New Jersey or Cylindrical Total Ankle Replacement

The New Jersey Cylindrical Replacement design was developed in the 1970s by Michael Pappas, a bioengineer, and Frederick Buechel, an orthopaedic surgeon.²⁶¹ During the development of the design rationale, the authors recognized essential problems regarding ankle anatomy (normal ligamental function, physiologic ROM, intrinsic stability during ROM), surgical technique (component biocompatibility, minimal resection of bone, preservation of blood supply to the talus and distal tibia, postoperative rehabilitation), and mechanical objectives (optimal force transfer at bone–prosthesis interface, minimal wear, anteroposterior [AP] shear load resistance). The treatment options in case of ankle failure (ability to remove prosthesis with minimal tissue damage, revision arthroplasty vs. ankle fusion) were also thoroughly discussed.²⁶¹ Although the clinical results with the first generation of the New Jersey Cylindrical Replacement design were not satisfactory, the authors identified numerous problems regarding the design of TARs that were addressed later by other surgeons and designers.³⁶⁰

Indications for Total Ankle Replacement

End-stage ankle arthritis is the main indication for this procedure. Unlike the hip and knee, the ankle joint is rarely affected by primary osteoarthritis. In clinical and epidemiologic studies, previous trauma has been shown to be the most common cause of ankle osteoarthritis.295,348 Rotational ankle fractures with consecutive cartilage damage was identified as the most common reason for posttraumatic ankle osteoarthritis.³⁴⁸ However, repetitive ligament injuries can also result in posttraumatic ankle osteoarthritis.³⁴³ Other common indications for TAR are systemic (rheumatoid) arthritis^279,280,372 and secondary osteoarthritis. Secondary OA has been found to be associated with underlying diseases and/or pathologies, such as hemophilia,^{22,225,283,357} hereditary hemochromatosis,^23,77 gout,^29,207 postinfectious arthritis,^40,271 and avascular talar necrosis.^{39,49,103,200} Patients with bilateral ankle osteoarthritis are good candidates for this procedure because bilateral ankle fusion generally has a detrimental influence on gait and functional outcome.^{113,243,253,288} This can be particularly important in patients with secondary osteoarthritis resulting from hemochromatosis or hemophilia,^22,23 and bilateral TAR can be performed in two separate stages.^{34,104,114,207,358} However, in patients with bilateral end-stage ankle osteoarthritis, simultaneous bilateral TAR has been reported,^25,28,178 resulting in significant pain relief and functional improvement comparable to the results achieved with a unilateral procedure.^25,28 Patients considered for simultaneous bilateral TAR should be informed about a prolonged initial recovery period.²⁸ In patients with previously performed subtalar, triple, and/or midfoot fusion, the tibiotalar fusion would completely “stiffen” the hindfoot, while the TAR may preserve the functional motion as mentioned before. The clinical outcome of TAR when combined with hindfoot fusion is comparable to that of ankle replacement alone.¹⁸³

With increased use, an emerging indication for TAR is salvage of failed primary TAR.* A major concern in revision arthroplasty of the ankle can be anchorage of prosthesis components in deficient bone stock to ensure long-term prosthesis stability.^153,160 After removal of the prosthesis component and careful debridement, if the residual bone stock is not sufficient, ankle fusion may be a better option.^†

Another special indication for total ankle arthroplasty is the salvage of painful nonunion or malunion of prior ankle fusion.14,122,154,155 Conversion of fused ankle to TAR is a technically demanding procedure that should be performed only if remaining bone stock is sufficient and soft tissue conditions are not too compromised (especially in patients with previous long-standing ankle arthrodesis).¹⁵⁵ The conversion ankle arthroplasty should be limited only to experienced surgeons with adequate experience in primary TAR. If performed by experienced surgeons, this procedure has shown promising early results with low intraoperative and postoperative complication rates comparable to those observed in patients with primary TAR.^122,154

Contraindications for Total Ankle Replacement

The contraindications for TAR may be divided into two major groups: absolute and relative contraindications.

The absolute contraindications127,151,156,290 for this procedure include acute or chronic infections. In several studies, avascular necrosis of the talus has been identified as an absolute contraindication for TAR.^‡ In patients with avascular necrosis of more than one third of the talus, the use of a standard prosthesis component may lead to significant subsidence and loosening of the talar component and failure.* In these patients, a revision talar component¹⁶⁰ or a custom-made talar prosthesis^132,214,330 should be used. Patients with neuromuscular disorders, neuroarthropathy (e.g., Charcot arthropathy of the midfoot and/or hindfoot), massive joint laxity (e.g., patients with Marfan disease), or diabetes with clinically significant distal polyneuropathy should be excluded. Patients with severe instability and/or lower-leg malalignment that cannot be surgically corrected (e.g., by corrective osteotomies^194,195,259) should not be considered for TAR. At present, there is no concensus for a clinically relevant cut-off for the degree of coronal deformity that can be corrected at the implantation of TAR. In general, a moderate preoperative coronal deformity of less than 10 degrees can be corrected intraoperatively by modification of bone cuts (especially on the talar side). In patients with a coronal deformity of more than 10 degrees, the deformity should be corrected before the implantation of the prosthesis component (as a one- or two-stage procedure). Suspected or documented metal allergy or intolerance is rarely observed; however, these patients should be excluded preoperatively.

Although many authors suggest that previous ankle infection is an absolute contraindication for TAR,* the current authors cannot fully embrace this opinion. In a series of 17 consecutive patients with this history, who underwent HINTEGRA total ankle arthroplasty, Dr. Hintermann achieved good functional results and did not observe any recurrence of infection (unpublished data). Eichinger et al⁹³ and Espinosa and Klammer⁹⁸ also recommend TAR in patients with ankle OA resulting from previous infection.

The relative contraindications127,151,156,290 for this procedure include significantly reduced bone quality (e.g., resulting from severe osteoporosis, immunosuppressive therapy, or long-term therapy with steroids) and diabetes without clinically significant polyneuropathy. Smoking is another relative contraindication because it is associated with higher risk of perioperative complications, including wound breakdown.³⁶⁸ Patients with high (e.g., contact sports, jumping) or increased (e.g., jogging, tennis, downhill skiing) demands for physical activities should be informed about possible mechanical failure caused by edge loading with increased wear and a potentially higher rate of aseptic loosening.^246,351

Significant preoperative varus or valgus deformity (more than 10 degrees) has also been seen as a contraindication for TAR. With three-part ankle replacements, Doets et al⁸⁹ found that preoperative deformity in the frontal plane is difficult to correct, causing instability and subluxation of the mobile bearing, which may result in the prosthesis failure.⁸⁹ In their study of 200 STAR implants, Wood and Deakin³⁷³ observed that preoperative varus or valgus deformity of more than 15 degrees may cause edge loading of the mobile bearing. Therefore the authors stated that this may be a relative contraindication for TAR.^372,373 However, the preoperative hindfoot deformity should not be an absolute contraindication, as long as additional realignment procedures (supramalleolar and/or calcaneal osteotomies, ligament reconstruction, subtalar fusion) can correct the deformity.^{47,82,183,195} Karantana et al¹⁷⁷ did not observe any differences in functional outcome and prosthesis component survivorship between the patients with and without preoperative deformities, as long the deformity is addressed at the time of prosthesis implantation. Daniels et al⁷⁶ demonstrated that correction of moderate-to-severe varus deformities is possible and results in good functional outcome and stability of prosthesis components. Kim et al¹⁸³ reported that the clinical outcome of TAR performed in ankles with preoperative varus deformity of more than 10 degrees is comparable to that of neutrally aligned ankles. However, simultaneous surgical procedures addressing the preoperative deformity are necessary to achieve good results.¹⁸³

Finally, and perhaps most importantly, the patient and the surgeon must have realistic expectations of this surgery.34,96,213 The high satisfaction of rheumatoid osteoarthritis patients after total ankle arthroplasty likely reflects the low demands and low expectations of this patient cohort.²⁹⁸ On the other hand, the expectations of patients with posttraumatic ankle osteoarthritis are generally higher than those of patients with non-posttraumatic ankle osteoarthritis.²⁴⁶ In particular, predictions regarding postoperative improvement in range of motion should be made carefully; as with current implants (all with an anterior approach), postoperative improvement in ankle range of motion is relatively small (generally <10 degrees) and therefore is not one of the expected benefits from this procedure.^20,120

“Ideal Candidate” for Total Ankle Replacement

Based on the authors’ clinical experience27,290 and results published in the current literature, these are criteria for the “ideal candidate” with end-stage ankle osteoarthritis when assessing for TAR:

Clinical Examination

All previous medical reports (e.g., surgery reports) and imaging data are collected and carefully analyzed. Especially in patients with posttraumatic ankle osteoarthritis and previously performed surgeries (e.g., open reduction and internal fixation), the exact type of hardware should be identified to ensure the hardware can be removed without any difficulty before implantation of prosthetic components. Actual the patients’ history is carefully assessed to specifically address the following aspects: actual pain (e.g., using a visual analog scale ranging from 0 = no pain to 10 = maximal pain),¹⁶⁹ limitations in daily activities and quality of life (e.g., using the SF-36 questionnaire),³⁶³ sports activities (e.g., using the following scoring: 0 = none, 1 = moderate, 2 = normal, 3 = high, 4 = elite),³⁵¹ and current and previous treatment. Patients with any of the aforementioned absolute contraindications are excluded. Especially in patients with significant comorbidities, a consultation in neurology and/or internal medicine should be arranged before planning TAR.

The routine physical examination starts with careful inspection of the foot and ankle while sitting, standing, and walking, allowing dynamic comparison of changes at weight bearing versus non–weight bearing. The eventually observed pathologic findings should be compared with the contralateral nonaffected limb. Skin and soft tissue are carefully evaluated, with special attention given to previous surgical scars. Hindfoot stability is assessed manually, with the patient sitting (e.g., using the anterior drawer test).15,69,70 Ankle alignment, including supramalleolar deformities and the position of heel in relation to the longitudinal axis of the lower leg, is assessed with the patient standing. However, clinical assessment of the ankle and hindfoot alignment should be interpreted carefully because visual alignment assessment is often not accurate enough.¹⁰⁷ Range of motion of the tibiotalar joint is determined using a goniometer placed along the lateral border of the leg and foot. All goniometric measurement should be performed in the weight-bearing position according to the method described by Lindsjö et al.²²² Intrarater and interrater reliability of the goniometric measurements is usually not very high.³⁸² However, the accuracy of the goniometric measurements of the tibiotalar joint range of motion was assessed by direct comparison with ankle range-of-motion measurements obtained from radiographs.^{20,66,154,157} Another alternative for assessing ankle dorsiflexion and stiffness is the Iowa Ankle Range of Motion (IAROM) device, which provided valid and reliable measurements (Fig. 22-7).³⁶⁹ Because many patients with end-stage osteoarthritis present with lower leg muscular atrophy,³⁴⁹ basic muscle function should be assessed (e.g., the function of tibial and peroneal muscles).

Radiographic Examination

Radiographic examination of affected ankles includes weight-bearing radiographs with anteroposterior and lateral views of the foot and an anteroposterior view of the ankle. All radiographs should be performed in the weight-bearing manner for appropriate evaluation of foot and ankle alignment, statics, and biomechanics because non–weight-bearing radiographs are often misleading (Fig. 22-8).^95,167,237 Furthermore, the standing position of patients at radiographic examination may standardize the radiographic technique, resulting in a more reliable comparison between preoperative and postoperative radiographs. All possible coexisting degenerative changes in the adjacent joints as well as any deformities (e.g., flattening of the longitudinal arch of the foot) should be identified and carefully analyzed.

Concomitant deformities in the osteoarthritic ankles may occur on the supramalleolar, intraarticular, and/or inframalleolar level. Supramalleolar ankle alignment is measured in coronal and sagittal planes by measurement of the medial distal tibial angle and the anterior distal tibial angle, respectively.192,227,323 The medial distal tibial angle has been measured to be 92.4 ± 3.1 degrees (range, 88-100 degrees) in a radiographic study¹⁹² and 93.3 ± 3.2 degrees (range, 88-100 degrees) in a cadaver study.^172,192 The measurement of the medial distal tibial angle depends on radiograph technique.^24,323 The anterior distal tibial angle has been measured to be 83.0 ± 3.6 degrees (range, 76-97 degrees).²²⁷ The inframalleolar ankle alignment (especially the heel position in relation to the longitudinal axis of the lower leg) is measured using the hindfoot alignment view.²⁹³ The hindfoot alignment view is taken at a 20-degree angle to the floor, with the foot placed with its medial border parallel to the radiographic beam.²⁹³ As already mentioned, the visual assessment of the hindfoot alignment is not accurate; therefore the hindfoot alignment view should be performed routinely for appropriate measurement of inframalleolar hindfoot deformities.^106,107 A computed tomography (CT) scan may be helpful to assess the bony defects and to analyze the joint incongruency. In patients with degenerative changes of the adjacent joint, single photon emission computed tomography (SPECT-CT) may help to evaluate the morphologic changes and their biologic activities.^193,258 Preoperative magnetic resonance imaging (MRI) may help to assess the concomitant ligamental injuries,^136,149 pathologic changes of tendons,^60,149 and avascular necrosis of osseous structures.^136,149

Pedobarography

One of the most widely measured parameters for gait analysis is assessment of plantar pressure distribution. In patients with ankle osteoarthritis, the following variables usually are specifically assessed: maximum force, contact time, peak pressure, contact area, and center of pressure index.163,176 The patients are asked to walk at their own preferred speed because prescribed speed may influence and change the normal gait pattern.²⁴² For sufficient reliability of the pressure measurement, at least five dynamic trials of each foot should be recorded.¹⁶⁵ For reliable and easier analysis, the pressure distribution measurements are commonly divided into four regions, including hindfoot, midfoot, forefoot, and toes.¹⁶³

Outcome Instruments in Studies on Total Ankle Arthroplasty

Reliable and accurate assessment of preoperative and postoperative patients’ functional outcomes is crucial in monitoring the effectiveness of TAR. Naal et al²⁴⁷ performed a systematic literature review including 79 original studies. Authors identified a total of 15 outcome instruments. The most commonly used ones were the AOFAS hindfoot score (n = 41),¹⁸⁵ the Kofoed ankle score (n = 15),¹⁹⁸ the visual analog scale assessing pain (n = 15),¹⁶⁹ and the generic SF-36 (n = 6).³⁶³ The use of the very popular AOFAS hindfoot score is not without problems because this score has not been validated. This questionnaire has been shown to have enough discriminatory capacity to assess postoperative improvement in patients who underwent TAR.²⁶³ However, the research committee of the AOFAS published a policy statement recommending not to use this outcome assessment instrument.²⁶⁴

Hung et al¹⁶⁶ developed a lower-extremity physical-function computerized adaptive testing instrument based on the Patient Reported Outcomes Measurement Information System (PROMIS) physical function items. This novel outcome instrument had high reliability and content and construct validity; therefore it should be used in patients with lower-extremity problems, including degenerative changes of the ankle joint.¹⁶⁶

1. General or regional anesthesia can be used for TAR.

2. The patient is positioned supine with the feet on the edge of the table. A bump is placed under the ipsilateral hip until a strictly upward position of the lower extremity is obtained.

3. A pneumatic thigh tourniquet is applied.

4. If significant concomitant deformity has to be corrected, the unaffected lower extremity should be also draped to allow intraoperative comparison.

5. The surgical site is prepared in a sterile manner; in addition, a skin drape may be used.

6. After exsanguination by elevation, the thigh tourniquet is inflated. In most cases, a pressure of 250 to 350 mm Hg is sufficient. A total tourniquet time of 2 hours should not be exceeded.

7. A standard anterior ankle approach is used (Fig. 22-9). An anterior longitudinal incision (10-15 cm) is made in line with the extensor hallucis tendon (EHL) tendon.

8. The incision is brought down through the skin only. The medial fascicles of the superficial peroneal nerve’s medial branch are identified and dissected free into the foot. These are usually retracted laterally. Occasionally, the authors intentionally transect a fine fascicle, coursing medially across the neck of the talus to gain more exposure. Before the operation, the authors tell the patient not to be surprised postoperatively by areas of numbness along the medial aspect of the foot.

9. After the nerve has been carefully retracted and the anterior tibial tendon is identified, the authors open the extensor retinaculum in line with EHL tendon sheath and retract the EHL medially. The retinaculum is the thickening of the deep fascia above the ankle, running from tibia to fibula.1,255

10. During preparation of the soft tissue envelope, special attention is paid to the tibialis anterior vascular bundle, which is located behind the extensor hallucis longus or between the extensor hallucis longus and the extensor digitorum longus.³¹⁴

11. The deep neurovascular bundle is gently teased free and retracted laterally. This preserves the lateral branch of the dorsalis pedis. This vessel supports the extensor digitorum brevis muscle, which is the best local muscle for the salvage of soft tissue coverage for anterior wound dehiscence.

12. The incision is deepened to the level of the joint. The authors to try to preserve the periosteum for later closure. In patients with rheumatoid arthritis or soft bones, the subperiosteal dissection can result in inadvertent malleolar avulsions. Care must be taken to do this gently in those at risk for bone injury. The EHL interval allows the surgeon to see into the lower lateral recessus with reflection of the anterior talofibular ligament.

13. After the ankle joint is sufficiently exposed, a capsulotomy is performed.

14. If a self-retaining retractor is applied to control the soft tissue envelope, it must be relieved when not necessary. Skin hooks should not be used much so as not to disturb wound healing. A deep blunt retractor used strategically at critical times for exposure may protect the tissues best.

15. After the joint is sufficiently exposed, the first step is to remove osteophytes on the tibia (especially on the anterolateral aspect) and the talar neck; however, the bone cortex should not be destroyed.

16. Implantation is performed by following the guidelines of the manufacturer. Every effort must be made to avoid injury to the “shoulder” region of the medial malleolus because this can cause intraoperative or postoperative malleolar fracture, a common intraoperative complication of TAR. Because the lateral malleolus in some patients is relatively more posterior, it can be inadvertently cut with approaches from front to back.

17. All distractors are removed, and the stability and motion of the ankle is checked.

18. The position of prosthesis components is checked and documented using fluoroscopy.

19. Wound closure is performed sequentially in layers, starting with the periosteum, then the extensor retinaculum, subcutaneous tissue, and skin. Skin is usually closed using 4-0 nylon. Drainage with suction may be used but is generally not necessary.

20. Soft wound dressing is used to avoid any pressure so as not to compromise wound healing. A splint is used to keep the foot in a neutral position.

21. Elevation for the first 2 days is absolutely critical. Some surgeons permit early motion.

22. The anterior approach can be used for ankle fusion procedures. It gives excellent visibility of the joint. Anterior plating (single plate or double plates)²⁶⁹ can be used to secure fixation. In some cases, a more limited incision than described here works very well and limits operative time and morbidity.