Salto Talaris Total Ankle Arthroplasty: Clinical Results at a Mean of 5.2 Years in 78 Patients Treated by a Single Surgeon

Hofmann, Kurt J. MD; Shabin, Zabrina M. MD; Ferkel, Eric MD; Jockel, Jeffrey MD; Slovenkai, Mark P. MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.16.00090
Scientific Articles
Abstract

Background: In recent years, the number of total ankle arthroplasty procedures performed has increased dramatically. We sought to report the clinical results of the largest cohort of patients treated with a modern fixed-bearing total ankle arthroplasty by a single surgeon.

Methods: We retrospectively reviewed the charts of 78 consecutive patients (81 ankles) who underwent total ankle arthroplasty with a minimum clinical follow-up of 2 years. Sixty-three patients completed standardized questionnaires including the Foot and Ankle Disability Index (FADI), the Short Musculoskeletal Function Assessment (SMFA), the Short Form (SF)-36v2, and a visual analog scale (VAS) for pain. In addition, each patient underwent serial range-of-motion examination and radiographic implant evaluation at each follow-up appointment.

Results: Implant survival was 97.5% at a mean follow-up time of 5.2 years. There was 1 revision of a tibial component and 1 revision of a talar component. Thirty-six patients underwent a concurrent procedure at the time of the index surgery, with the most common being removal of previous hardware. Seventeen patients underwent additional procedures following the index surgery, with the most common being gutter debridement. Total range of motion averaged 35.5° preoperatively and 39.9° postoperatively (p = 0.02). Fifty-seven ankles (70%) had >2 years of radiographic follow-up, and 25 ankles (31%) displayed evidence of lucency around a metallic component at the final radiographic follow-up. Outcome scores at a mean of 5.2 years revealed promising results for the cohort, with a mean VAS pain score of 17.7 and a mean FADI score of 79.1.

Conclusions: Modern fixed-bearing total ankle arthroplasty had excellent implant survival, improved plantar flexion and total range of motion, and had good-to-excellent functional outcome at a mean follow-up of 5.2 years.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Author Information

1Department of Orthopaedics, New England Baptist Hospital, Boston, Massachusetts

2Department of Orthopaedics, Tufts Medical Center, Boston, Massachusetts

3Southern California Orthopaedic Institute, Van Nuys, California

4Orthopaedics Department, Colorado Permanente Medical Group, Denver, Colorado

E-mail address for K.J. Hofmann: khofmann@nebh.org

Article Outline

For decades, the treatment for end-stage ankle arthritis has been ankle arthrodesis1,2. However, technological innovations and equivalent clinical results have renewed enthusiasm in total ankle arthroplasty (TAA) as a treatment modality in this realm3-12. Recent meta-analyses, which revealed equivalent pain relief and improved functional outcomes in arthroplasty patients13-15, continue to fuel interest in these procedures, as do the theoretically lower rate of adjacent-joint degeneration and improved gait mechanics16,17. The popularity of these implants continues to rise dramatically.

Recent studies have shown improved rates of survivorship of these implants, especially when compared with first-generation TAA systems18-22. The Salto Talaris TAA system (Tornier U.S.) was approved by the U.S. Food and Drug Administration for use in 200623. This fixed-bearing system was derived from the Salto mobile-bearing system, which was first introduced in Europe in 199724-26.

There are limited clinical outcome data available for the fixed-bearing Salto Talaris TAA27,28. Recent cohort studies with short-term follow-up revealed excellent survivorship of the metallic components29-31. We present the clinical and radiographic outcomes of 78 consecutive patients who underwent TAA with the fixed-bearing Salto Talaris system and had a minimum clinical follow-up of 2 years. To our knowledge, this is the largest cohort of patients treated by a single surgeon with this modern fixed-bearing TAA system that has been reported to date.

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Materials and Methods

Prior to the collection of data, our research protocol was approved by our institutional review board. We retrospectively identified and evaluated 81 consecutive ankles in 78 patients who were treated with the Salto Talaris TAA prosthesis for end-stage ankle arthritis from September 2007 to June 2012. The senior author (M.P.S.) performed all of the TAA procedures at a single tertiary referral center. Patients who had severe comorbid conditions (active septic arthritis or osteomyelitis, uncontrolled diabetes mellitus, or severe peripheral vascular disease) or high-risk musculoskeletal issues (posttraumatic compromise of soft-tissue envelopes, severe bone stock deficiencies, or severe malalignment) were deemed not to be candidates for TAA. Alignment was assessed using preoperative weight-bearing ankle radiographs, and the degree of deformity was evaluated at the ankle joint. Severe malalignment was defined as >20° of valgus or >30° of varus in the coronal plane at the joint line. Patients who had severe planovalgus or cavovarus foot deformities as well as patients who had clinical and/or radiographic evidence of ligament or tendon incompetence that would threaten the survival of the implants were also excluded. No patients were excluded because of lack of adequate follow-up. A discussion was held with all patients who presented with end-stage ankle arthritis during the study period regarding the risks and benefits of TAA versus ankle arthrodesis. In general, patients were deemed to be good candidates for TAA if they were >55 years old (excluding patients with rheumatoid arthritis), had ipsilateral hindfoot or midfoot arthritis, and were interested in pursuing TAA.

The surgical technique was carried out according to the manufacturer’s recommended protocol. Patients received a combination of general and regional anesthesia (a popliteal fossa block). Deformity correction was qualitatively assessed intraoperatively, using the tibial plafond as an internal control. Fluoroscopy was used to obtain orthogonal images of the ankle to ensure that the talus remained reduced under the tibia on all views. Ankle stability and range of motion were evaluated using trial components. Final components were impacted into place without the use of bone cement.

Postoperatively, all patients were placed in a short leg splint and made non-weight-bearing. They were admitted to the hospital for pain control and 24 hours of intravenous antibiotics. Patients returned to the office 3 weeks postoperatively for splint and suture removal and were then placed in a removable walker boot, remaining toe-touch weight-bearing for another 3 weeks. All patients received 4 weeks of venous thromboembolic prophylaxis. At 6 weeks postoperatively, patients began a formal physical therapy protocol and advanced to full weight-bearing while weaning out of the walking boot over the next 6 weeks.

The mean clinical follow-up for our cohort was 5.2 years (range, 3.4 to 8.2 years). The mean age at the time of surgery was 64.3 years (range, 35 to 85 years). Three patients had bilateral TAAs performed in a staged fashion during the study period. For those patients, each ankle was analyzed individually with respect to outcome. The most common diagnosis was osteoarthritis (n = 35), followed by posttraumatic arthritis (n = 33). The mean body mass index (BMI) for the cohort was 29.4 kg/m2 (range, 19.0 to 48.7 kg/m2). The mean length of hospital stay was 2.2 days (range, 1 to 5 days), with 25.6% of the cohort discharged on postoperative day 1. Additional demographic data are summarized in Table I.

Postoperative visits were scheduled at 3 and 6 weeks, 3 and 6 months, 1 year, and then yearly following the index surgery. Preoperative weight-bearing anteroposterior, mortise, and lateral ankle radiographs of the involved extremity were obtained for all patients. Preoperative radiographic measurements32-34 are shown in Figure 1. Postoperative radiographic evaluation was performed at each follow-up visit except for the initial postoperative visit and consisted of weight-bearing anteroposterior, mortise, and lateral ankle radiographs of the operatively treated extremity. Postoperative radiographic measurements35 are shown in Figure 2. All parameters were calculated by the primary author at the time of study commencement using our institution’s digital PACS (picture archiving and communication system) (Viztek Opal-RAD).

The alignment of the prostheses was evaluated on each set of follow-up radiographs and compared with the initial postoperative radiographs taken at the 6-week visit. Signs of prosthetic loosening or subsidence were documented by the primary author (K.J.H.) at each radiographic interval. At the final radiographic evaluation for each patient, areas of lucency were identified around the tibial and talar components3, then classified by zones30, and the amount of lucency was calculated in millimeters by the primary author using our digital PACS.

Active ankle range of motion was evaluated clinically and documented by the senior author during physical examination at the preoperative visit and was compared with the active ankle range of motion documented during physical examination at the 1-year follow-up visit23. Functional outcomes were assessed by means of a visual analog scale (VAS) for pain, the Short Musculoskeletal Function Assessment (SMFA), the Foot and Ankle Disability Index (FADI), and the Short Form (SF)-36v2 Health Survey via mail at the time of study commencement.

Statistical analysis was performed using SAS (version 9.3; SAS Institute). The normality of the data was checked using the Shapiro-Wilk test. Normally distributed data were analyzed using a 2-sided 2-sample t test. Non-normally distributed data were analyzed using a Mann-Whitney test. A p value of 0.05 was considered significant.

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Results

Survivorship of the arthroplasty components was 97.5% at a mean follow-up of 5.2 years (Fig. 3). Two ankles (2.5%) required revision of metallic components (Fig. 4; see Appendix). There were no deep infections requiring resection arthroplasty. No patients underwent conversion to an ankle arthrodesis.

Thirty-six ankles (44%) required a total of 50 concurrent procedures at the time of the index TAA (Table II). The 2 most common procedures were removal of previous hardware (n = 10) and percutaneous Achilles tendon lengthening (n = 8). Such lengthening was performed if the ankle did not achieve >10° of passive dorsiflexion after the final implants were placed. There were no Achilles ruptures as a result of lengthening.

Seventeen ankles (21%) required a total of 36 subsequent procedures following the TAA (Table III). The most common cause for reoperation was gutter impingement. The mean time between the index procedure and a subsequent procedure was 18.5 months (range, 1 to 51 months). The indications for a subsequent procedure were based on pain elucidated during clinical examination and verified by radiographic findings, if necessary (i.e., fracture). In addition, some procedures (i.e., Achilles tendon lengthening) that were more commonly performed during the index TAA were performed in a subsequent fashion if patients were unhappy with the final active range of motion. Of the 12 patients who underwent gutter debridement, 1 (8%) returned to the operating room for another subsequent procedure (superficial irrigation and debridement).

Glazebrook et al.36 defined a high-grade complication as deep infection, aseptic loosening, or implant failure. They concluded that these complications would lead to failure of a TAA >50% of the time. In our cohort, we found 4 cases of aseptic loosening and no deep infections (Table IV). The involved components in all 4 cases of aseptic loosening subsided, leading to subsidence of 1 tibial and 3 talar components. Two of these cases went on to frank implant failure (1 tibial and 1 talar component), which resulted in revision TAA (see Appendix). The remaining 2 cases of aseptic loosening and subsidence (2 talar components) were clinically asymptomatic, and the patients did not desire revision surgery (Fig. 5). The mean BMI in the remaining 2 cases of talar subsidence was 46.7 kg/m2; both patients had previously undergone a triple arthrodesis prior to the TAA, and both were on an immunosuppressive medication at the time of the TAA.

Overall, the most common complication was wound-healing problems (n = 7), followed by postoperative bone fracture (n = 6). All postoperative bone fractures were diagnosed radiographically during a follow-up visit. These consisted of 4 medial malleolar fractures, 1 fibular fracture, and 1 tibial stress fracture above the tibial prosthesis (Table V). Three of the medial malleolar fractures were treated with open reduction and internal fixation (ORIF) (Fig. 6), and the rest of the fractures were treated nonoperatively.

We encountered 5 intraoperative fractures (3 medial malleolar, 1 fibular, and 1 anterolateral tibial) although care was taken to protect these structures during the procedure by not oversizing the tibial component. All intraoperative bone fractures were treated with reduction and internal fixation, and all fractures went on to heal uneventfully.

The mean preoperative coronal alignment (Fig. 1) was 0.2° varus (range, 19.6° valgus to 27.2° varus). The mean preoperative talar tilt was 4.7° (range, 0° [neutral] to 22.3°). The mean sagittal translation of the talus was 1.7 mm anterior (range, 13 mm posterior to 14 mm anterior).

Postoperative radiographic measurements are shown in Figure 2 and results are summarized in Table VI. On initial radiographic analysis, the mean tibial coronal alignment for the cohort was 1.8° varus (range, 3.6° valgus to 9.1° varus). At the time of the final radiographic analysis, the mean tibial coronal alignment was 2.3° varus (range, 3.4° valgus to 9.8° varus). Forty-five ankles (56%) had a tibial coronal alignment within 3° of neutral on the final radiographs (Fig. 7). Figure 8 shows the tibial coronal alignment values for the cohort over time. There was no significant difference between the preoperative alignment and final postoperative alignment (p = 0.07). There was also no significant change in the tibial coronal alignment from the initial follow-up to final follow-up.

The mean time to the final radiographs was 22.6 months (range, 3 to 65 months). Sixty-nine ankles (85%) had >1 year of radiographic follow-up, 57 (70%) had >2 years, 35 (43%) had >3 years, and 18 (22%) had >4 years. Final postoperative radiographs showed lucencies around a metallic component (Fig. 9) in 25 ankles (31%). These were classified into previously described zones30 (Table VII). The majority of the lucencies were found around the tibial component, and the mean amount of lucency was 0.9 mm (range, 0.5 to 1.6 mm). The patient who underwent tibial component revision developed lucencies around the tibia in zones 2 and 4 on the anteroposterior radiograph and zones 2, 6, and 7 on the lateral radiograph prior to the revision. In the 3 patients who developed talar subsidence, there were 2 lucencies in zone 5 on the anteroposterior radiograph, 2 lucencies in zones 8 and 10 on the lateral radiograph, and 1 lucency in zone 9 on the lateral radiograph.

Comparison of the range of motion preoperatively and at 1 year of follow-up revealed a significant increase in total range of motion (35.5° to 39.9°, p = 0.02) and in plantar flexion (26.6° to 29.1°, p = 0.04) but not in dorsiflexion (8.9° to 10.8°, p = 0.05). The overall improvement was slightly lower than in previous reports23-25,30 and likely has little clinical importance.

Two patients died during the study period and 1 declined to participate; 63 (84%) of the remaining 75 patients completed the outcome surveys at a mean of 5.2 years postoperatively (Table VIII). The cohort was then subdivided into 2 groups, termed “at-risk” and “low-risk.” The at-risk group contained 18 ankles in patients who were diabetic, currently smoking, or taking immunosuppressive medications. The low-risk group contained the remaining 48 ankles. The at-risk group showed significantly lower outcome scores for the FADI (69.9 compared with 82.6, p = 0.0069), SMFA function index (27.1 compared with 17.1, p = 0.012), and 4 of the 10 SF-36 domains (physical function, general health, role emotional, and physical component summary) (Table IX). It is unclear whether these lower scores were a direct result of the TAA or some continued contribution from the patients’ underlying medical conditions. Wound complications, reoperations, and revision TAAs did not differ significantly between the risk groups.

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Discussion

The primary outcome in this retrospective review of the Salto Talaris fixed-bearing TAA system was implant survivorship. Survivorship of the metallic components was 97.5% at a mean of 5.2 years. This survivorship rate is consistent with previously reported data24,29,30 and now demonstrates durability of these implants at a mean of 5.2 years. Although 4 ankles had aseptic loosening and subsidence, only 2 went on to revision TAA. The remaining 2 cases of talar subsidence may have been due, in part, to elevated patient BMI, and we are now more cautious with regard to elevated BMI when considering patients as candidates for TAA. Patients who did not have a discernable cause of trauma to the ankle were assigned the diagnosis of osteoarthritis, which likely led to a higher rate of this diagnosis in our study compared with others29,30.

As has been previously reported24,29,30, concurrent procedures are often performed during and after a TAA. In our cohort, 44% of ankles had a concurrent procedure performed, and 21% of ankles required return to the operating room for any reason. The most common reason for reoperation was gutter impingement. We now recommend aggressive gutter debridement at the time of the index TAA.

Postoperative radiographic analysis revealed the presence of lucencies around the metallic components in 31% of our cohort, with the majority of these lucencies found around the tibial component. However, radiographic lucency alone was not an indication for revision surgery. In our cohort, there was no association between the degree of preoperative coronal deformity and development of radiographic lucencies postoperatively. In addition, the patients who developed radiographic lucencies postoperatively did not have a higher risk of revision surgery, nor did they have significantly lower outcome scores.

Our study has several limitations. First, the retrospective nature of the review limits the strength of the conclusions that can be drawn about the Salto Talaris TAA. However, to our knowledge, this study reports the longest follow-up for this implant, and it shows implant survivorship equal to that in previously reported short-term studies.

Although we showed a significant improvement in total range of motion for our cohort, our range-of-motion data were gathered clinically in the office and thus have inherent limitations. We recommend the use of dedicated weight-bearing dorsiflexion and plantar-flexion lateral radiographs to truly evaluate the range of motion through the ankle joint in future studies.

There continues to be no consensus on the appropriate outcome measures to use to assess patients who have undergone TAA. We chose a combination of validated instruments (VAS, SF-36v2, FADI, and SMFA) that have been used in previous studies22,29,37,38 to evaluate our cohort. We lacked preoperative comparison data for our cohort, but we compared our final follow-up data with the final follow-up data of Schweitzer et al.29 and found similar scores for each instrument (VAS, 17.7 compared with 15; SMFA function index, 19.8 compared with 18.6; SMFA bother index, 20.3 compared with 18.3; FADI, 79.1 compared with 84.1).

Although this study expands the current literature on TAA, there are several areas in which future studies can be enhanced. The first is the collection of data both preoperatively and postoperatively using validated outcome instruments. This would allow surgeons to better identify the potential differences between TAA and ankle arthrodesis and communicate them to patients. Second, improvements in radiographic analysis can be made in 2 specific domains. The use of radiographs in range-of-motion calculations would more accurately determine the range of motion coming from the ankle joint and its correlation with gait mechanics. Also, the statistical relationship of radiographic lucencies to implant loosening and outcomes can provide important prognostic information for both the surgeon and patient. Third, evaluation of preoperative and postoperative range of motion could be performed by individuals not involved with the care of the patient using blinding (ankles examined covered in light stockings that conceal surgical scars). Finally, longer follow-up studies are needed to determine the long-term survival of these implants.

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Appendix Cited Here...

Details regarding the 2 patients who underwent revision TAA are available with the online version of this article as a data supplement at jbjs.org.

Investigation performed at the New England Baptist Hospital, Boston, Massachusetts

Disclosure: No external funding has been received in support of this research. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work.

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