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Early radiographic and clinical results of Salto total ankle arthroplasty as a fixed-bearing device
Foot and Ankle Surgery 21 (2015) 91–96
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Early radiographic and clinical results of Salto total ankle arthroplasty as a fixed-bearing device John Chao MDa, Jae Hyuck Choi MDb, Benjamin J. Grear MDc, Shay Tenenbaum MDd,e,*, Jason T. Bariteau MDd, James W. Brodsky MDf a
Peachtree Orthopaedic Clinic, Atlanta, GA, USA Foot and Ankle Orthopedic Department, Veterans National Hospital Daegu, Daegu, Republic of Korea Campbell Clinic, 1400 S. Germantown Rd, Germantown, TN 38138, USA d Baylor University Medical Center, Dallas, TX, USA e Department of Orthopedic Surgery, Chaim Sheba Medical Center at Tel Hashomer, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel f Baylor University Medical Center, Human Motion and Performance Laboratory, 411 N. Washington Avenue, Ste. 2100, Dallas, TX 75246, USA b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 15 February 2014 Received in revised form 23 July 2014 Accepted 27 September 2014
Background: Total ankle replacement has increased in popularity in the management of severe tibiotalar arthritis. Most previous clinical reports focused on mobile-bearing designs. This study evaluates early radiographic and clinical results of the Salto fixed bearing design. Methods: Twenty-three Salto fixed-bearing implants were prospectively studied. Records were reviewed for clinical outcome scores (VAS, AOFAS, SF36), subsequent surgeries, complications, radiographic data and implant survivorship. Average follow-up was 36 months. Results: Statistically significant improvements in VAS, AOFAS ankle/hindfoot scores, and SF36 scores were shown at an average of 3 years postoperatively. At 3 years followup, survivorship of the implant was 82.6% with any reoperation as the endpoint and 95.6% for revision or removal of components. Seven patients had radiolucencies around the implant, one of which required revision to arthrodesis. Conclusion: The fixed-bearing Salto ankle replacement has comparable early radiographic and clinical results to reports of the mobile-bearing Salto of comparable followup. Level of evidence: Level IV ß 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Total ankle replacement Salto Fixed-bearing Arthroplasty
1. Introduction While tibiotalar arthritis was traditionally treated with an ankle arthrodesis, recent studies have shown equivalency of pain relief with total ankle replacement [1,2] and objective evidence of equivalent or even improved function [3]. There are two basic designs of total ankle replacements. Fixed-bearing implants have one articulation surface and have been described as partially conforming, while mobile-bearing implants have been described as having two separate, fully conforming articular surfaces [4].
* Corresponding author at: Baylor University Medical Center, Dallas, TX, USA. Tel.: +1 2145978219. E-mail addresses: [email protected] (J. Chao), [email protected] (J.H. Choi), [email protected] (B.J. Grear), [email protected] (S. Tenenbaum), [email protected] (J.T. Bariteau), [email protected] (J.W. Brodsky).
The Salto total ankle (Tornier SA, Montbonnot,France) was originally designed as a mobile-bearing implant, and the majority of the clinical reports, which are from Europe, report on the mobile-bearing device. However, the fixed-bearing Salto total ankle (Salto Talaris), which is the same as the mobile-bearing Salto total ankle with the exception that the polyethylene bearing is fixed to the tibial component, was approved in the United States [5]. To the best of our knowledge, there have been six American studies of this device to date. One of the recent studies reports on combined clinical outcomes of the Salto and Inbone total ankle replacement [6]. Other studies look at either kinematics of the ankle [7] or range of tibio-talar motion of the fixed-bearing Salto [8]. A cadaveric study reported on the effects of ankle dorsiflexion on final axial alignment using a mobile-bearing Salto prosthesis [9]. Swietzer et al. reported prospective data on the clinical outcomes of the Salto fixed-bearing implant [10]. The most recent study, similar to this work analyzed clinical and radiographic outcomes of Salto fixed bearing design [11].
http://dx.doi.org/10.1016/j.fas.2014.09.012 1268-7731/ß 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
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The purpose of this study is to report the early results of a prospective study of the early-term radiographic and clinical outcomes of the two-component, fixed-bearing design of the Salto total ankle replacement. 2. Methods and materials Patients treated with the fixed-bearing Salto total ankle replacement in 2008 through 2009 were identified for analysis. Twenty-three ankles with unilateral, symptomatic advanced arthritis in 23 patients were enrolled. All patients had failed nonoperative treatment, and the senior author performed all cases. The average follow-up was 36 months (range, 24–49). There were 17 females and six males, and the average age was 68.6 years (range, 53.2–85.4). There were 13 left ankles and 10 right ankles. The average weight was 79 kg (range, 58.9–111.1) and average BMI was 28.4 kg/m2 (range, 22.7–40.8). The diagnoses were posttraumatic arthritis in 12 (11 ankle fractures and one talus fracture), idiopathic osteoarthritis in eight, osteoarthritis associated with chronic instability in one, adjacent joint arthritis following prior triple arthrodesis in one, and rheumatoid arthritis in one.
Patient radiographs were reviewed to analyze preoperative deformity, postoperative alignment and deformity correction, and postoperative radiographic evidence of osteolysis and cyst formation. Three independent observers measured preoperative and postoperative tibial angle, talar angle, and tibial slope on weightbearing radiographs, as described by Bonnin [12]. These angles, as well as postoperative talocalcaneal angle, were measured at six months postoperatively and at most recent followup (Fig. 1). Implant subsidence was defined as a change of greater than five degrees in any of the angles measured preoperatively and postoperatively [13]. To analyze peri-implant radiolucencies and osteolysis, the tibia and talus were divided into 10 zones on anteroposterior (AP) and lateral X-rays as described by Bonnin (Fig. 2) [12]. Radiolucent lines were considered pathologic if greater than 2-mm or if present globally across the prosthesis [14–16]. The authors considered global radiolucency as all 10 zones on either the AP or lateral ankle X-ray having greater than 2 mm radiolucency. Radiolucencies present in less than all 10 zones were considered partial radiolucency. An osteolytic cyst was defined as a hypodense zone greater than 5 mm with peripheral sclerosis
Fig. 1. Angle measurements as described by Bonnin [12] (A&B) Preoperative and postoperative tibial angle. (C&D) Preoperative and postoperative talar angle. (E) Preoperative tibial slope. (F) Postoperative tibial slope and talocalcaneal angle.
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Fig. 2. (A&B) Regions of radiolucency and cyst appearance as described by Bonnin on AP and lateral ankle X-rays [12].
[12,17]. Subtalar joint arthritis was also evaluated on preoperative and postoperative radiographs using the Kellgren–Lawrence classification system (Table 1) [18]. Clinical records were reviewed to delineate patient demographics, operative procedures, complications, and survivorship. Endpoints of the study included implant removal and conversion rate to arthrodesis or reoperation for any reason. Clinical outcome scores collected preoperatively and postoperatively, included the Visual Analog Scale (VAS) pain score, the American Orthopedic Foot and Ankle Society (AOFAS) Ankle and Hindfoot Score, and the Short Form 36 (SF-36) scores. A paired t-test was used to compare preoperative and last followup data for each parameter for each patient. Statistical significance was set at p < 0.05. Patients were kept nonweightbearing in a cast for 6 weeks, followed by weightbearing in a removable walking boot for 4–6 weeks, followed by physiotherapy. The study was approved by the Institutional Review Board. 3. Results None of the patients in this study had significant preoperative coronal plane deformity, defined as greater than 158. Two patients had an 118 valgus deformity, one had a 148 varus deformity, and the remainder of the patients had less than 108 of coronal deformity. There were seven varus ankles in this cohort, and the average preoperative varus deformity was 4.6 (range, 1–14, SD 5) degrees. There were 16 valgus ankles, and the average preoperative valgus deformity was 5.6 (range, 0.5–11, SD 3.5) degrees. The average posterior talar slope preoperatively was 7.2 (range, 0.5–25, SD 5.8) degrees. The postoperative coronal plane alignment of the varus ankles was an average of 2 of (range, 0.6–3.3, SD 1.1) degrees. The postoperative coronal plane alignment of the valgus ankles was an average of 0.18 of varus (range, 5.1 varus to 5.38 valgus, SD 2.9). The average postoperative posterior slope was 5.9 (range, 0.6 to14.2, SD 3.8) degrees. One patient had a change in measurement of ankle prosthesis position of greater than 58 from early postoperative radiographs to last followup. This patient had loosening and severe subsidence of Table 1 Kellgren–Lawrence Grading Scale for osteoarthritis [9]. Grade
Joint Space
Osteophytes
1 2 3
Doubtful narrowing Definite narrowing Definite narrowing with some sclerosis and possible deformity of bone contour Marked narrowing with severe sclerosis and definite deformity of bone contour
Possible Definite Moderate multiple
4
Large osteophytes
the tibial component, which required removal of the prosthesis and conversion to ankle arthrodesis. Partial AP radiolucent lines along the prosthesis were observed in four tibial components (zone 1 in one, zone 3 in two, zone 4 in one, and zone 7 in one). Partial lateral radiolucent lines along the prosthesis were observed in one tibial component in zone 1. One patient had global tibia component AP radiolucency but not lateral radiolucency, and was asymptomatic. Another patient had global tibia component lateral radiolucency, but not AP radiolucency and was asymptomatic. The one patient who had both AP and lateral global tibial component radiolucency was the patient noted above to require revision to ankle arthrodesis. Seven bone cysts greater than 5-mm were present in six patients (26.1%), of which four cysts were in the tibia and three cysts in the talus. One patient had cysts in both tibia and talus. In the four patients with tibial cysts, the cyst was identified on AP radiographs in one patient, and located in the lateral tibial metaphysis, in a single zone, zone 7. In the other three patients, the cysts were identified on lateral radiographs, and located in the posterior tibia and each involving two zones, zones 5 and 6. In the three patients with talar cysts, all were identified on the lateral radiographs, and all involved a single zone, with one located in the posterior talus in zone 8, and two located in the anterior talus, in zone 10 (Table 2). Table 3 shows the radiographic degree of subtalar arthritis preoperatively and at last followup. Ten patients had radiographic progression of the subtalar arthritis, but were clinically asymptomatic. Four patients had subtalar arthrodesis concomitant with the ankle replacement for severe subtalar joint arthritis. Survivorship of the implant at 3 years follow-up was 95.7% (22/23) for arthrodesis/revision of components as the endpoint and 82.6% (19/23) for any reoperation as the endpoint. There were a total of nine patients with complications (39%), of which five were wound complications. Two patients had a wound complication requiring irrigation and debridement for anterior soft tissue loss that did not communicate with the joint. One healed with negative-pressure vacuum dressing treatment, and one required a free tissue flap transfer. The prosthesis was retained in both patients.
Table 2 Cyst location visualized on radiographs based on classification used by Bonnin [2]. Cysts seen on AP radiograph
Cysts seen on lateral radiograph
Zone
Number patients
Zone
Number patients
7
1
5 and 6 8 10
3 1 2
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Table 3 Subtalar joint arthritis preoperatively and at last followup.
None Mild Mod Severe Arthrodesis
Preoperative
Last followup
8 9 1 4 1
0 16 0 2 5
N = 23.
A third patient had incisional debridement and primary closure, and two patients had a small portion of the incision treated by local wound care and oral antibiotics. Intraoperatively, there were two medial malleolus fractures and one lateral malleolus fracture, all treated with internal fixation. The patient with tibial subsidence and conversion to arthrodesis was noted above. Clinical outcome scores improved on VAS, AOFAS ankle/ hindfoot, and SF-36 scores (Table 4). Mean VAS pain score decreased from 7.6 (range, 5–8.5) preoperatively to 1.3 (range, 0–4) at last followup (p < 0.05). AOFAS ankle/hindfoot score increased from 42.7 (range 25–58) preoperatively to 88 (range 74– 100) at last followup (p < 0.05). The SF-36 mental component summary scores (MCS) increased from 50 to 54.6 (p < 0.001) and physical component summary scores (PCS) increased from 31.6 to 43.4 (p < 0.001).
4. Discussion This study reports early-term radiographic and clinical outcomes of the two-component, fixed-bearing design of the Salto total ankle replacement. There are some theoretical biomechanical advantages for using a three-component mobile bearing design, namely better tolerance for component malposition, lower sheer forces across implantbone interface leading to less polyethylene wear and loosening [19]. Espinosa et al. reported that three-component design has lower contact pressure in the well-aligned position, and is generally less sensitive to misalignment, compared with the two-component design [20]. However, other authors have reported that there is no clear difference in clinical outcomes between mobile and fixed-bearing designs [19,21,22]. When assessing radiographic criteria and data, there is no absolute maximum coronal plane deformity in the literature that contraindicates total ankle replacement. However, coronal plane deformity greater than 158 was previously thought to be a relative contraindication [14,23]. The mean preoperative coronal plane deformity in this study was not severe, and the mean correction was satisfactory. Two patients had residual varus deformity of about 58. Computer simulations of coronal plane deformity suggest that greater than 58 of malalignment increases average contact stresses greater than the yield stress of polyethylene [20]. Because this cohort of patients has only 36 months followup, it is too soon to comment on the effect of the residual coronal plane deformity on the long-term outcome in these two patients. Table 4 Clinical outcomes data at average 36 months followup of the fixed-bearing Salto total ankle replacement.
VAS pain AOFAS SF 36 Physical (PCS) Mental (MCS) N = 23.
Preoperative
Final follow up
p-Value
7.6 42.7
1.3 88
<0.05 <0.05
31.6 50
43.4 54.6
<0.05 <0.05
Analysis of peri-implant radiolucencies suggests that these may be less prevalent in the fixed-bearing Salto than the mobilebearing Salto prostheses at early followup. In this study, eight of 23 patients (34%) had radiolucent lines, with one implant being loose (4.3%). A study by Bonin et al. on the mobile-bearing Salto implant with 35 month follow up reported 52% radiolucencies, and two of 98 ankles (2.0%) had clinically loose implants [24]. At nineyear followup, the same cohort of patients had partial radiolucent lines in numerous patients on the AP views, but none of the patients had global radiolucencies, suggesting that if radiolucencies are not progressive, they do not contribute to early implant failure [12]. In this study tibial radiolucencies were reported according to Bonnin’s seven regions versus the five regions described by Reuver et al. [25]. The current study’s rate of radiolucencies is smaller than the two-thirds rate reported by Reuver et al. in mobile-bearing Salto implants [25]. This is unlikely due to stress shielding, because the configuration of the metallic portion of the implants is the same, but may be attributable to polyethylene wear on both surfaces of the polyethylene in the mobile-bearing implant. Although we did not visualize any talar partial radiolucencies, it is noted Reuver et al. looked only at the tibial, but not talar side [25]. When compared to other fixed-bearing studies looking at radiolucencies, Schweitzer et al. noted 39% radiographic lucencies about the tibial component and 15% radiolucencies around the talar component [10]. However, it is difficult to draw firm conclusions from Schweitzer’s radiographic results since they do not define what was classified as radiolucency. Another study of 75 total ankle arthroplasties noted only 6 ankles with a total of 9 radiolucent lines [11]. Regarding global radiolucencies, one patient in this study with global radiolucency around the tibial component was revised to an arthrodesis due to implant subsidence. The other two patients, who had global tibial radiolucencies on either AP or lateral tibia radiographs, were not clinically symptomatic, and their radiographs have not shown component migration. Our migration rate (4.5%) was higher than Bonnin et al., who reported two out of 98 (2.0%) prostheses with obvious radiographic loosening [24]. Reuver et al. do not report on number of radiographic global radiolucencies, but do report that five ankles in their series required revision due to aseptic loosening and two due to deep infection. Nodzo et al. reported two patients with significant component migration (one talar and one tibial) in their study [11]. Because of the variable design of the total ankle replacements, it is not possible to compare rates of radiolucency between different implant systems. In the STAR ankle replacement, tibial radiolucency is considered a benign finding due to stress shielding and because the component does not have perfect apposition with the tibia [15,23]. Previous authors noted that radiolucencies around the STAR implant are very commonly present, and do not appear to affect the stability of the prosthesis if the radiolucencies are not progressive. This is consistent with Bonnin’s work on the Salto, as partial radiolucencies did not appear to affect implant stability. The long-term clinical impact and predictive value of radiographic changes is still uncertain. Despite the presence of seven cysts in six patients in this study, none had radiographic signs of migration or any clinical symptoms of pain. At 35 months followup, Bonnin noted two ankles out of 98 with large cysts that lead to clinical failure of the talar component [24], but the patients did not elect to have revision surgery. At nine year followup, the same cohort of patients developed an additional 17 cysts (19.4%) 5-mm or larger, and 11 patients required a subsequent surgery (eight had bone grafting and three had implant removal and ankle fusion) [12]. At this point in this study’s cohorts, none of the patients with cysts have
J. Chao et al. / Foot and Ankle Surgery 21 (2015) 91–96 Table 5 Survivorship and complications in studies comparing Salto implant.
Current study Schweitzer [24] Bonnin [3] Schenk [21] Reuver [19] Nodzo [16]
N
Followup (months)
Survivorship with Removal/arthrodesis
Survivorship any operation
23 67 98 218 59 75
36 34 35 29 36 43
95.6% 96% 94.9% 84% 86.6% 98%
82.6% 88.1% 91.8% N/A 83.1% 68%
required additional surgery. The etiology of bone cysts is agreed upon and is likely multifactorial [26]. Small nonprogressive cysts seem to be mechanical in nature and may occur in relation to a stress-shielding phenomena or bone remodeling in the distal tibia [27], but most are related to reactive changes in response to microscopic wear particles of the polyethylene [26]. The mobile-bearing Salto ankle replacement has had good results in multiple European studies. To the best of our knowledge, there are only two other recently published report that documents comparability of the three-part mobile-bearing and the two-part fixed-bearing versions of the Salto prosthesis [10,22]. There have also been four series reporting on the mobile-bearing Salto prosthesis with two years or longer followup [12,24,25,28]. Although this study’s cohort is smaller than those four studies [12,24,25,28], this study is quite similar and has a comparable followup to three of the four studies. Table 5 compares this study’s survivorship versus two fixed-bearing studies and three mobile bearing implants studies of similar followup. Despite similar followup duration, it is difficult to directly compare the survivorship results of this study to other ones because of heterogeneity of reporting results. Schenk Reuver, and Nodzo reported survivorship based on a Kaplan–Meier curve while Bonnin and Schweitzer did not [10–12,24,25,28]. Endpoints of studies are also varied. Schenk, Schweitzer and Reuver estimated survivorship with revision or arthrodesis as endpoint while Bonnin looked at survivorship with implant removal as the endpoint [10,12,24,25,28]. Nodzo however, reported survivorship based on both revision of implant or arthrodesis as one end point or any return to operating room as another endpoint [11]. The survivorship of the implant in the current study at 3 years with either implant revision or conversion to arthrodesis as the endpoint was 95.6%, which is similar to the 98% reported by Bonnin [24], 93.1% for Reuver et al. [25], 96% by Schweitzer [10] 98% by Nodzo [11] and somewhat higher than the 88.1% for Schenk et al. [28]. In the 2011 study by Bonnin et al. the implant survival was defined as revision or conversion to arthrodesis and declined
95
significantly to 85% at average 8.9 years post-operatively (based on Kaplan–Meier curve) [12]. Table 6 shows intraoperative and postoperative complications for this study, the other two fixed-bearing study, and three mobilebearing studies of comparable followup. To the extent the information was reported, complications were classified regarding need for subsequent surgery, as well as with regard to component retention (i.e., revision or conversion to arthrodesis). Because these studies report complications differently and with variable detail, it is difficult to compare complication rates. Bonnin et al. study did not report intraoperative complications or infection rates in comparable fashion to this study [24]. Similarly, in Schenk et al. paper, it is unclear whether the patients with delayed wound healing required subsequent surgeries [28]. This study’s complications are similar to the other fixed-bearing study by Schweitzer [24], except this study had a higher wound infection rate and much fewer subsequent surgeries after index total ankle arthroplasty. This studies survivorship is also similar to Nodzo et al. report of 98% when using revision arthrodesis as endpoint but is significantly higher when using any return to operating room as endpoint (82.6% vs. 68%) [11]. This study reported intraoperative malleolar fractures and wound complications treated with and without surgery, as did the studies by Reuver, Schenk, Nodzo, and Schweitzer (in the latter study, some of the patients have prophylactic fixation of the medial malleolus) [10–12,24,25,28]. Studies on three different ankle prostheses have shown that there is a significant learning curve regarding the incidence of complications, especially malleolar fractures, regarding operative experience with total ankle replacement [29–31]. These were the first 23 Salto ankles placed by the senior author, and we expect complication rates to be higher than authors who had performed greater numbers of Salto ankle replacements over a longer period of time. The work by Bonnin et al. may relate to the future trajectory of implant survival. From his first report with 3 year followup to his most recent one at 8.9 years followup, the component revision or arthrodesis rate increased from 2% to 11.2% [12,24]. A Kaplan– Meier curve demonstrated survivorship rate at 65%, i.e., an overall re-operation rate of 35%. By extrapolation, this appears to represent approximately 24% reoperation rate for other types of complications. This current study cohort demonstrates statistically significant improvements in all clinical outcome scores. The significant decrease in VAS pain scores, from 7.6 to 1.3 postoperatively, was consistent with pain relief reported by previous studies. Bonnin et al. reported that 72/96 patients were pain free [24], Schenk et al. [28] reported improvement of VAS from 7.4 to 2.0 and Reuver et al. [25] reported a post-op VAS of 3.2 [25]. Although only 78% of their
Table 6 Intraoperative and postoperative complications in current study and other comparable studies.
Current study Schweitzer [24] Bonnin [3] Schenk [21] Reuver [19] Nodzo [16] a
N
Intraoperative malleolar fracture
Wound infection treated with oral antibiotics
Wound infection treated with surgery and component retention
Noninfection surgery with component retention
Component revision
Arthrodesis
23 67 98 218 59 75
13% 3% NA 2.3% 0% 4%
8.7% 4.8% NA 2.3% 5.1% 0%
13% 0% NA 1.4% 1.7% 1.3%
0% 18.0% 2% 0% 3.4% 22.6%
0% 3%a 0% 11%b 8.5% 1.3%
4.3% 0% 2% 5.5%c 3.4%d 0%
One patient was scheduled for revision at time of surgery. Includes the three patients that had wound infection treated with surgery and component retention. Revision was done for wound healing deficit in two patients and one case of deep infection treated with two-stage revision. c Arthrodesis was done for deep infection in one patient. d Arthrodesis was done for deep infection in both patients. b
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patients had preoperative clinical data and 94% had postoperative data, Schweitzer et al. [10] reported an improvement on VAS from 7 preoperatively to 1.5 at 2 year followup. Nodzo et al. [11] did not report on VAS pain scale but showed significant improvement in pain component of FAOS. The AOFAS ankle/hindfoot scores improved 45.3 points from 42.7 to 88 in this current study. These scores are similar to those reported in the only other fixed-bearing study, which noted improvement in AOFAS ankle/hindfoot scores from 39.1 preoperatively to 78.7 at 2 years followup [10]. This cohort’s preoperative scores fall in between preoperative scores reported in mobilebearing studies by Bonnin (32.3) and Schenk (50.9) [24,28], and this cohort’s postoperative scores were slightly better than those reported in the mobile-bearing literature (75–83.2) [24,25,28]. SF-36 mental and physical component scores were all significantly improved, as previously reported by other studies [10,11]. The strengths of this study include the prospective collection of clinical data and the combined radiographic and clinical outcomes as measured by multiple outcome scores. Limitations of this study include the noncontrolled case series design, the relatively small number of patients, and the propensity for higher complications early in the learning curve of ankle arthroplasty [29–31]. 5. Conclusion This early-term analysis of the two-part Salto prosthesis with a fixed-bearing indicated satisfactory clinical and radiographic outcomes at an average of three years. These data show that at early followup, the clinical and radiographic results are comparable to published outcomes and complications for the three-part Salto prosthesis with a mobile-bearing [10,21,22,24,25,28]. Longterm outcomes and long-term comparability of the fixed-bearing version to the mobile-bearing original design remains to be elucidated by future studies. Conflict of interest statement None declared. References [1] Haddad SL, Coetzee JC, Estok R, Fahrbach K, Banel D, Nalysnyk L. Intermediate and long-term outcomes of total ankle arthroplasty and ankle arthrodesis. A systematic review of the literature. J Bone Joint Surg Am 2007;89:1899. [2] Saltzman CL, Mann RA, Ahrens JE, Amendola A, Anderson RB, Berlet GC, et al. Prospective controlled trial of STAR total ankle replacement versus ankle fusion: initial results. Foot Ankle Int 2009;30:579. [3] Brodsky JW, Polo FE, Coleman SC, Bruck N. Changes in gait following the Scandinavian total ankle replacement. J Bone Joint Surg Am Vol 2011;93:1890. [4] Cracchiolo III A, Deorio JK. Design features of current total ankle replacements: implants and instrumentation. J Am Acad Orthop Surg 2008;16:530. [5] Wiesel SW, Easley ME. Operative techniques in foot and ankle surgery. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011. [6] Queen RM, De Biassio JC, Butler RJ, DeOrio JK, Easley ME, Nunley JA. J. Leonard Goldner Award 2011: changes in pain, function, and gait mechanics two years following total ankle arthroplasty performed with two modern fixed-bearing prostheses. Foot Ankle Int 2012;33:535.
[7] Leszko F, Komistek RD, Mahfouz MR, Ratron YA, Judet T, Bonnin M, et al. In vivo kinematics of the salto total ankle prosthesis. Foot Ankle Int 2008;29:1117. [8] Schuberth JM, McCourt MJ, Christensen JC. Interval changes in postoperative range of motion of Salto–Talaris total ankle replacement. J Foot Ankle Surg 2011;50:562. [9] Moore AM, Kadakia AR, Hughes RE, Ruberte Thiele RA. Effect of ankle flexion angle on axial alignment of total ankle replacement. Foot Ankle Int 2010;31:1093. [10] Schweitzer KM, Adams SB, Viens NA, Queen RM, Easley ME, Deorio JK, et al. Early prospective clinical results of a modern fixed-bearing total ankle arthroplasty. J Bone Joint Surg Am Vol 2013;95:1002. [11] Nodzo SR, Miladore MP, Kaplan NB, Ritter CA. Short to midterm clinical and radiographic outcomes of the salto total ankle prosthesis. Foot Ankle Int 2014;35:22. [12] Bonnin M, Gaudot F, Laurent JR, Ellis S, Colombier JA, Judet T. The Salto total ankle arthroplasty: survivorship and analysis of failures at 7 to 11 years. Clin Orthop Relat Res 2011;469:225. [13] Pyevich MT, Saltzman CL, Callaghan JJ, Alvine FG. Total ankle arthroplasty: a unique design. Two to twelve-year follow-up. J Bone Joint Surg Am Vol 1998;80:1410. [14] Wood PL, Deakin S. Total ankle replacement. The results in 200 ankles. J Bone Joint Surg Br Vol 2003;85:334. [15] Valderrabano V, Hintermann B, Dick W. Scandinavian total ankle replacement: a 3.7-year average followup of 65 patients. Clin Orthop Relat Res 2004;424:47–56. [16] Koivu H, Kohonen I, Sipola E, Alanen K, Vahlberg T, Tiusanen H. Severe periprosthetic osteolytic lesions after the ankle evolutive system total ankle replacement. J Bone Joint Surg Br Vol 2009;91:907. [17] Besse JL, Brito N, Lienhart C. Clinical evaluation and radiographic assessment of bone lysis of the AES total ankle replacement. Foot Ankle Int 2009;30:964. [18] Kellgren JH, Lawrence JS. Radiological assessment of rheumatoid arthritis. Ann Rheum Dis 1957;16:485. [19] Valderrabano V, Pagenstert GI, Muller AM, Paul J, Henninger HB, Barg A. Mobile- and fixed-bearing total ankle prostheses: is there really a difference? Foot Ankle Clin 2012;17:565. [20] Espinosa N, Walti M, Favre P, Snedeker JG. Misalignment of total ankle components can induce high joint contact pressures. J Bone Joint Surg Am Vol 2010;92:1179. [21] Queen RM, Sparling TL, Butler RJ, Adams Jr SB, DeOrio JK, Easley ME, et al. Patient-reported outcomes. function, and gait mechanics after fixed and mobile-bearing total ankle replacement. J Bone Joint Surg Am Vol 2014;96: 987. [22] Gaudot F, Colombier JA, Bonnin M, Judet T. A controlled, comparative study of a fixed-bearing versus mobile-bearing ankle arthroplasty. Foot Ankle Int 2014;35:131. [23] Mann JA, Mann RA, Horton E. STAR ankle: long-term results. Foot Ankle Int 2011;32:S473. [24] Bonnin M, Judet T, Colombier JA, Buscayret F, Graveleau N, Piriou P. Midterm results of the Salto total ankle prosthesis. Clin Orthop Relat Res 2004;424:6– 18. [25] Reuver JM, Dayerizadeh N, Burger B, Elmans L, Hoelen M, Tulp N. Total ankle replacement outcome in low volume centers: short-term followup. Foot Ankle Int 2010;31:1064. [26] Purdue PE, Koulouvaris P, Potter HG, Nestor BJ, Sculco TP. The cellular and molecular biology of periprosthetic osteolysis. Clin Orthop Relat Res 2007;454:251. [27] Knecht SI, Estin M, Callaghan JJ, Zimmerman MB, Alliman KJ, Alvine FG, et al. The Agility total ankle arthroplasty. Seven to sixteen-year follow-up. J Bone Joint Surg Am Vol 2004;86-A:1161. [28] Schenk K, Lieske S, John M, Franke K, Mouly S, Lizee E, et al. Prospective study of a cementless, mobile-bearing, third generation total ankle prosthesis. Foot Ankle Int 2011;32:755. [29] Lee KT, Lee YK, Young KW, Kim JB, Seo YS. Perioperative complications and learning curve of the mobility total ankle system. Foot Ankle Int 2013;34:210. [30] Schuberth JM, Patel S, Zarutsky E. Perioperative complications of the agility total ankle replacement in 50 initial, consecutive cases. J Foot Ankle Surg 2006;45:139. [31] Haskell A, Mann RA. Perioperative complication rate of total ankle replacement is reduced by surgeon experience. Foot Ankle Int 2004;25:283.
Contents lists available at ScienceDirect
Foot and Ankle Surgery journal homepage: www.elsevier.com/locate/fas
Early radiographic and clinical results of Salto total ankle arthroplasty as a fixed-bearing device John Chao MDa, Jae Hyuck Choi MDb, Benjamin J. Grear MDc, Shay Tenenbaum MDd,e,*, Jason T. Bariteau MDd, James W. Brodsky MDf a
Peachtree Orthopaedic Clinic, Atlanta, GA, USA Foot and Ankle Orthopedic Department, Veterans National Hospital Daegu, Daegu, Republic of Korea Campbell Clinic, 1400 S. Germantown Rd, Germantown, TN 38138, USA d Baylor University Medical Center, Dallas, TX, USA e Department of Orthopedic Surgery, Chaim Sheba Medical Center at Tel Hashomer, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel f Baylor University Medical Center, Human Motion and Performance Laboratory, 411 N. Washington Avenue, Ste. 2100, Dallas, TX 75246, USA b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 15 February 2014 Received in revised form 23 July 2014 Accepted 27 September 2014
Background: Total ankle replacement has increased in popularity in the management of severe tibiotalar arthritis. Most previous clinical reports focused on mobile-bearing designs. This study evaluates early radiographic and clinical results of the Salto fixed bearing design. Methods: Twenty-three Salto fixed-bearing implants were prospectively studied. Records were reviewed for clinical outcome scores (VAS, AOFAS, SF36), subsequent surgeries, complications, radiographic data and implant survivorship. Average follow-up was 36 months. Results: Statistically significant improvements in VAS, AOFAS ankle/hindfoot scores, and SF36 scores were shown at an average of 3 years postoperatively. At 3 years followup, survivorship of the implant was 82.6% with any reoperation as the endpoint and 95.6% for revision or removal of components. Seven patients had radiolucencies around the implant, one of which required revision to arthrodesis. Conclusion: The fixed-bearing Salto ankle replacement has comparable early radiographic and clinical results to reports of the mobile-bearing Salto of comparable followup. Level of evidence: Level IV ß 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Total ankle replacement Salto Fixed-bearing Arthroplasty
1. Introduction While tibiotalar arthritis was traditionally treated with an ankle arthrodesis, recent studies have shown equivalency of pain relief with total ankle replacement [1,2] and objective evidence of equivalent or even improved function [3]. There are two basic designs of total ankle replacements. Fixed-bearing implants have one articulation surface and have been described as partially conforming, while mobile-bearing implants have been described as having two separate, fully conforming articular surfaces [4].
* Corresponding author at: Baylor University Medical Center, Dallas, TX, USA. Tel.: +1 2145978219. E-mail addresses: [email protected] (J. Chao), [email protected] (J.H. Choi), [email protected] (B.J. Grear), [email protected] (S. Tenenbaum), [email protected] (J.T. Bariteau), [email protected] (J.W. Brodsky).
The Salto total ankle (Tornier SA, Montbonnot,France) was originally designed as a mobile-bearing implant, and the majority of the clinical reports, which are from Europe, report on the mobile-bearing device. However, the fixed-bearing Salto total ankle (Salto Talaris), which is the same as the mobile-bearing Salto total ankle with the exception that the polyethylene bearing is fixed to the tibial component, was approved in the United States [5]. To the best of our knowledge, there have been six American studies of this device to date. One of the recent studies reports on combined clinical outcomes of the Salto and Inbone total ankle replacement [6]. Other studies look at either kinematics of the ankle [7] or range of tibio-talar motion of the fixed-bearing Salto [8]. A cadaveric study reported on the effects of ankle dorsiflexion on final axial alignment using a mobile-bearing Salto prosthesis [9]. Swietzer et al. reported prospective data on the clinical outcomes of the Salto fixed-bearing implant [10]. The most recent study, similar to this work analyzed clinical and radiographic outcomes of Salto fixed bearing design [11].
http://dx.doi.org/10.1016/j.fas.2014.09.012 1268-7731/ß 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.
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The purpose of this study is to report the early results of a prospective study of the early-term radiographic and clinical outcomes of the two-component, fixed-bearing design of the Salto total ankle replacement. 2. Methods and materials Patients treated with the fixed-bearing Salto total ankle replacement in 2008 through 2009 were identified for analysis. Twenty-three ankles with unilateral, symptomatic advanced arthritis in 23 patients were enrolled. All patients had failed nonoperative treatment, and the senior author performed all cases. The average follow-up was 36 months (range, 24–49). There were 17 females and six males, and the average age was 68.6 years (range, 53.2–85.4). There were 13 left ankles and 10 right ankles. The average weight was 79 kg (range, 58.9–111.1) and average BMI was 28.4 kg/m2 (range, 22.7–40.8). The diagnoses were posttraumatic arthritis in 12 (11 ankle fractures and one talus fracture), idiopathic osteoarthritis in eight, osteoarthritis associated with chronic instability in one, adjacent joint arthritis following prior triple arthrodesis in one, and rheumatoid arthritis in one.
Patient radiographs were reviewed to analyze preoperative deformity, postoperative alignment and deformity correction, and postoperative radiographic evidence of osteolysis and cyst formation. Three independent observers measured preoperative and postoperative tibial angle, talar angle, and tibial slope on weightbearing radiographs, as described by Bonnin [12]. These angles, as well as postoperative talocalcaneal angle, were measured at six months postoperatively and at most recent followup (Fig. 1). Implant subsidence was defined as a change of greater than five degrees in any of the angles measured preoperatively and postoperatively [13]. To analyze peri-implant radiolucencies and osteolysis, the tibia and talus were divided into 10 zones on anteroposterior (AP) and lateral X-rays as described by Bonnin (Fig. 2) [12]. Radiolucent lines were considered pathologic if greater than 2-mm or if present globally across the prosthesis [14–16]. The authors considered global radiolucency as all 10 zones on either the AP or lateral ankle X-ray having greater than 2 mm radiolucency. Radiolucencies present in less than all 10 zones were considered partial radiolucency. An osteolytic cyst was defined as a hypodense zone greater than 5 mm with peripheral sclerosis
Fig. 1. Angle measurements as described by Bonnin [12] (A&B) Preoperative and postoperative tibial angle. (C&D) Preoperative and postoperative talar angle. (E) Preoperative tibial slope. (F) Postoperative tibial slope and talocalcaneal angle.
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Fig. 2. (A&B) Regions of radiolucency and cyst appearance as described by Bonnin on AP and lateral ankle X-rays [12].
[12,17]. Subtalar joint arthritis was also evaluated on preoperative and postoperative radiographs using the Kellgren–Lawrence classification system (Table 1) [18]. Clinical records were reviewed to delineate patient demographics, operative procedures, complications, and survivorship. Endpoints of the study included implant removal and conversion rate to arthrodesis or reoperation for any reason. Clinical outcome scores collected preoperatively and postoperatively, included the Visual Analog Scale (VAS) pain score, the American Orthopedic Foot and Ankle Society (AOFAS) Ankle and Hindfoot Score, and the Short Form 36 (SF-36) scores. A paired t-test was used to compare preoperative and last followup data for each parameter for each patient. Statistical significance was set at p < 0.05. Patients were kept nonweightbearing in a cast for 6 weeks, followed by weightbearing in a removable walking boot for 4–6 weeks, followed by physiotherapy. The study was approved by the Institutional Review Board. 3. Results None of the patients in this study had significant preoperative coronal plane deformity, defined as greater than 158. Two patients had an 118 valgus deformity, one had a 148 varus deformity, and the remainder of the patients had less than 108 of coronal deformity. There were seven varus ankles in this cohort, and the average preoperative varus deformity was 4.6 (range, 1–14, SD 5) degrees. There were 16 valgus ankles, and the average preoperative valgus deformity was 5.6 (range, 0.5–11, SD 3.5) degrees. The average posterior talar slope preoperatively was 7.2 (range, 0.5–25, SD 5.8) degrees. The postoperative coronal plane alignment of the varus ankles was an average of 2 of (range, 0.6–3.3, SD 1.1) degrees. The postoperative coronal plane alignment of the valgus ankles was an average of 0.18 of varus (range, 5.1 varus to 5.38 valgus, SD 2.9). The average postoperative posterior slope was 5.9 (range, 0.6 to14.2, SD 3.8) degrees. One patient had a change in measurement of ankle prosthesis position of greater than 58 from early postoperative radiographs to last followup. This patient had loosening and severe subsidence of Table 1 Kellgren–Lawrence Grading Scale for osteoarthritis [9]. Grade
Joint Space
Osteophytes
1 2 3
Doubtful narrowing Definite narrowing Definite narrowing with some sclerosis and possible deformity of bone contour Marked narrowing with severe sclerosis and definite deformity of bone contour
Possible Definite Moderate multiple
4
Large osteophytes
the tibial component, which required removal of the prosthesis and conversion to ankle arthrodesis. Partial AP radiolucent lines along the prosthesis were observed in four tibial components (zone 1 in one, zone 3 in two, zone 4 in one, and zone 7 in one). Partial lateral radiolucent lines along the prosthesis were observed in one tibial component in zone 1. One patient had global tibia component AP radiolucency but not lateral radiolucency, and was asymptomatic. Another patient had global tibia component lateral radiolucency, but not AP radiolucency and was asymptomatic. The one patient who had both AP and lateral global tibial component radiolucency was the patient noted above to require revision to ankle arthrodesis. Seven bone cysts greater than 5-mm were present in six patients (26.1%), of which four cysts were in the tibia and three cysts in the talus. One patient had cysts in both tibia and talus. In the four patients with tibial cysts, the cyst was identified on AP radiographs in one patient, and located in the lateral tibial metaphysis, in a single zone, zone 7. In the other three patients, the cysts were identified on lateral radiographs, and located in the posterior tibia and each involving two zones, zones 5 and 6. In the three patients with talar cysts, all were identified on the lateral radiographs, and all involved a single zone, with one located in the posterior talus in zone 8, and two located in the anterior talus, in zone 10 (Table 2). Table 3 shows the radiographic degree of subtalar arthritis preoperatively and at last followup. Ten patients had radiographic progression of the subtalar arthritis, but were clinically asymptomatic. Four patients had subtalar arthrodesis concomitant with the ankle replacement for severe subtalar joint arthritis. Survivorship of the implant at 3 years follow-up was 95.7% (22/23) for arthrodesis/revision of components as the endpoint and 82.6% (19/23) for any reoperation as the endpoint. There were a total of nine patients with complications (39%), of which five were wound complications. Two patients had a wound complication requiring irrigation and debridement for anterior soft tissue loss that did not communicate with the joint. One healed with negative-pressure vacuum dressing treatment, and one required a free tissue flap transfer. The prosthesis was retained in both patients.
Table 2 Cyst location visualized on radiographs based on classification used by Bonnin [2]. Cysts seen on AP radiograph
Cysts seen on lateral radiograph
Zone
Number patients
Zone
Number patients
7
1
5 and 6 8 10
3 1 2
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Table 3 Subtalar joint arthritis preoperatively and at last followup.
None Mild Mod Severe Arthrodesis
Preoperative
Last followup
8 9 1 4 1
0 16 0 2 5
N = 23.
A third patient had incisional debridement and primary closure, and two patients had a small portion of the incision treated by local wound care and oral antibiotics. Intraoperatively, there were two medial malleolus fractures and one lateral malleolus fracture, all treated with internal fixation. The patient with tibial subsidence and conversion to arthrodesis was noted above. Clinical outcome scores improved on VAS, AOFAS ankle/ hindfoot, and SF-36 scores (Table 4). Mean VAS pain score decreased from 7.6 (range, 5–8.5) preoperatively to 1.3 (range, 0–4) at last followup (p < 0.05). AOFAS ankle/hindfoot score increased from 42.7 (range 25–58) preoperatively to 88 (range 74– 100) at last followup (p < 0.05). The SF-36 mental component summary scores (MCS) increased from 50 to 54.6 (p < 0.001) and physical component summary scores (PCS) increased from 31.6 to 43.4 (p < 0.001).
4. Discussion This study reports early-term radiographic and clinical outcomes of the two-component, fixed-bearing design of the Salto total ankle replacement. There are some theoretical biomechanical advantages for using a three-component mobile bearing design, namely better tolerance for component malposition, lower sheer forces across implantbone interface leading to less polyethylene wear and loosening [19]. Espinosa et al. reported that three-component design has lower contact pressure in the well-aligned position, and is generally less sensitive to misalignment, compared with the two-component design [20]. However, other authors have reported that there is no clear difference in clinical outcomes between mobile and fixed-bearing designs [19,21,22]. When assessing radiographic criteria and data, there is no absolute maximum coronal plane deformity in the literature that contraindicates total ankle replacement. However, coronal plane deformity greater than 158 was previously thought to be a relative contraindication [14,23]. The mean preoperative coronal plane deformity in this study was not severe, and the mean correction was satisfactory. Two patients had residual varus deformity of about 58. Computer simulations of coronal plane deformity suggest that greater than 58 of malalignment increases average contact stresses greater than the yield stress of polyethylene [20]. Because this cohort of patients has only 36 months followup, it is too soon to comment on the effect of the residual coronal plane deformity on the long-term outcome in these two patients. Table 4 Clinical outcomes data at average 36 months followup of the fixed-bearing Salto total ankle replacement.
VAS pain AOFAS SF 36 Physical (PCS) Mental (MCS) N = 23.
Preoperative
Final follow up
p-Value
7.6 42.7
1.3 88
<0.05 <0.05
31.6 50
43.4 54.6
<0.05 <0.05
Analysis of peri-implant radiolucencies suggests that these may be less prevalent in the fixed-bearing Salto than the mobilebearing Salto prostheses at early followup. In this study, eight of 23 patients (34%) had radiolucent lines, with one implant being loose (4.3%). A study by Bonin et al. on the mobile-bearing Salto implant with 35 month follow up reported 52% radiolucencies, and two of 98 ankles (2.0%) had clinically loose implants [24]. At nineyear followup, the same cohort of patients had partial radiolucent lines in numerous patients on the AP views, but none of the patients had global radiolucencies, suggesting that if radiolucencies are not progressive, they do not contribute to early implant failure [12]. In this study tibial radiolucencies were reported according to Bonnin’s seven regions versus the five regions described by Reuver et al. [25]. The current study’s rate of radiolucencies is smaller than the two-thirds rate reported by Reuver et al. in mobile-bearing Salto implants [25]. This is unlikely due to stress shielding, because the configuration of the metallic portion of the implants is the same, but may be attributable to polyethylene wear on both surfaces of the polyethylene in the mobile-bearing implant. Although we did not visualize any talar partial radiolucencies, it is noted Reuver et al. looked only at the tibial, but not talar side [25]. When compared to other fixed-bearing studies looking at radiolucencies, Schweitzer et al. noted 39% radiographic lucencies about the tibial component and 15% radiolucencies around the talar component [10]. However, it is difficult to draw firm conclusions from Schweitzer’s radiographic results since they do not define what was classified as radiolucency. Another study of 75 total ankle arthroplasties noted only 6 ankles with a total of 9 radiolucent lines [11]. Regarding global radiolucencies, one patient in this study with global radiolucency around the tibial component was revised to an arthrodesis due to implant subsidence. The other two patients, who had global tibial radiolucencies on either AP or lateral tibia radiographs, were not clinically symptomatic, and their radiographs have not shown component migration. Our migration rate (4.5%) was higher than Bonnin et al., who reported two out of 98 (2.0%) prostheses with obvious radiographic loosening [24]. Reuver et al. do not report on number of radiographic global radiolucencies, but do report that five ankles in their series required revision due to aseptic loosening and two due to deep infection. Nodzo et al. reported two patients with significant component migration (one talar and one tibial) in their study [11]. Because of the variable design of the total ankle replacements, it is not possible to compare rates of radiolucency between different implant systems. In the STAR ankle replacement, tibial radiolucency is considered a benign finding due to stress shielding and because the component does not have perfect apposition with the tibia [15,23]. Previous authors noted that radiolucencies around the STAR implant are very commonly present, and do not appear to affect the stability of the prosthesis if the radiolucencies are not progressive. This is consistent with Bonnin’s work on the Salto, as partial radiolucencies did not appear to affect implant stability. The long-term clinical impact and predictive value of radiographic changes is still uncertain. Despite the presence of seven cysts in six patients in this study, none had radiographic signs of migration or any clinical symptoms of pain. At 35 months followup, Bonnin noted two ankles out of 98 with large cysts that lead to clinical failure of the talar component [24], but the patients did not elect to have revision surgery. At nine year followup, the same cohort of patients developed an additional 17 cysts (19.4%) 5-mm or larger, and 11 patients required a subsequent surgery (eight had bone grafting and three had implant removal and ankle fusion) [12]. At this point in this study’s cohorts, none of the patients with cysts have
J. Chao et al. / Foot and Ankle Surgery 21 (2015) 91–96 Table 5 Survivorship and complications in studies comparing Salto implant.
Current study Schweitzer [24] Bonnin [3] Schenk [21] Reuver [19] Nodzo [16]
N
Followup (months)
Survivorship with Removal/arthrodesis
Survivorship any operation
23 67 98 218 59 75
36 34 35 29 36 43
95.6% 96% 94.9% 84% 86.6% 98%
82.6% 88.1% 91.8% N/A 83.1% 68%
required additional surgery. The etiology of bone cysts is agreed upon and is likely multifactorial [26]. Small nonprogressive cysts seem to be mechanical in nature and may occur in relation to a stress-shielding phenomena or bone remodeling in the distal tibia [27], but most are related to reactive changes in response to microscopic wear particles of the polyethylene [26]. The mobile-bearing Salto ankle replacement has had good results in multiple European studies. To the best of our knowledge, there are only two other recently published report that documents comparability of the three-part mobile-bearing and the two-part fixed-bearing versions of the Salto prosthesis [10,22]. There have also been four series reporting on the mobile-bearing Salto prosthesis with two years or longer followup [12,24,25,28]. Although this study’s cohort is smaller than those four studies [12,24,25,28], this study is quite similar and has a comparable followup to three of the four studies. Table 5 compares this study’s survivorship versus two fixed-bearing studies and three mobile bearing implants studies of similar followup. Despite similar followup duration, it is difficult to directly compare the survivorship results of this study to other ones because of heterogeneity of reporting results. Schenk Reuver, and Nodzo reported survivorship based on a Kaplan–Meier curve while Bonnin and Schweitzer did not [10–12,24,25,28]. Endpoints of studies are also varied. Schenk, Schweitzer and Reuver estimated survivorship with revision or arthrodesis as endpoint while Bonnin looked at survivorship with implant removal as the endpoint [10,12,24,25,28]. Nodzo however, reported survivorship based on both revision of implant or arthrodesis as one end point or any return to operating room as another endpoint [11]. The survivorship of the implant in the current study at 3 years with either implant revision or conversion to arthrodesis as the endpoint was 95.6%, which is similar to the 98% reported by Bonnin [24], 93.1% for Reuver et al. [25], 96% by Schweitzer [10] 98% by Nodzo [11] and somewhat higher than the 88.1% for Schenk et al. [28]. In the 2011 study by Bonnin et al. the implant survival was defined as revision or conversion to arthrodesis and declined
95
significantly to 85% at average 8.9 years post-operatively (based on Kaplan–Meier curve) [12]. Table 6 shows intraoperative and postoperative complications for this study, the other two fixed-bearing study, and three mobilebearing studies of comparable followup. To the extent the information was reported, complications were classified regarding need for subsequent surgery, as well as with regard to component retention (i.e., revision or conversion to arthrodesis). Because these studies report complications differently and with variable detail, it is difficult to compare complication rates. Bonnin et al. study did not report intraoperative complications or infection rates in comparable fashion to this study [24]. Similarly, in Schenk et al. paper, it is unclear whether the patients with delayed wound healing required subsequent surgeries [28]. This study’s complications are similar to the other fixed-bearing study by Schweitzer [24], except this study had a higher wound infection rate and much fewer subsequent surgeries after index total ankle arthroplasty. This studies survivorship is also similar to Nodzo et al. report of 98% when using revision arthrodesis as endpoint but is significantly higher when using any return to operating room as endpoint (82.6% vs. 68%) [11]. This study reported intraoperative malleolar fractures and wound complications treated with and without surgery, as did the studies by Reuver, Schenk, Nodzo, and Schweitzer (in the latter study, some of the patients have prophylactic fixation of the medial malleolus) [10–12,24,25,28]. Studies on three different ankle prostheses have shown that there is a significant learning curve regarding the incidence of complications, especially malleolar fractures, regarding operative experience with total ankle replacement [29–31]. These were the first 23 Salto ankles placed by the senior author, and we expect complication rates to be higher than authors who had performed greater numbers of Salto ankle replacements over a longer period of time. The work by Bonnin et al. may relate to the future trajectory of implant survival. From his first report with 3 year followup to his most recent one at 8.9 years followup, the component revision or arthrodesis rate increased from 2% to 11.2% [12,24]. A Kaplan– Meier curve demonstrated survivorship rate at 65%, i.e., an overall re-operation rate of 35%. By extrapolation, this appears to represent approximately 24% reoperation rate for other types of complications. This current study cohort demonstrates statistically significant improvements in all clinical outcome scores. The significant decrease in VAS pain scores, from 7.6 to 1.3 postoperatively, was consistent with pain relief reported by previous studies. Bonnin et al. reported that 72/96 patients were pain free [24], Schenk et al. [28] reported improvement of VAS from 7.4 to 2.0 and Reuver et al. [25] reported a post-op VAS of 3.2 [25]. Although only 78% of their
Table 6 Intraoperative and postoperative complications in current study and other comparable studies.
Current study Schweitzer [24] Bonnin [3] Schenk [21] Reuver [19] Nodzo [16] a
N
Intraoperative malleolar fracture
Wound infection treated with oral antibiotics
Wound infection treated with surgery and component retention
Noninfection surgery with component retention
Component revision
Arthrodesis
23 67 98 218 59 75
13% 3% NA 2.3% 0% 4%
8.7% 4.8% NA 2.3% 5.1% 0%
13% 0% NA 1.4% 1.7% 1.3%
0% 18.0% 2% 0% 3.4% 22.6%
0% 3%a 0% 11%b 8.5% 1.3%
4.3% 0% 2% 5.5%c 3.4%d 0%
One patient was scheduled for revision at time of surgery. Includes the three patients that had wound infection treated with surgery and component retention. Revision was done for wound healing deficit in two patients and one case of deep infection treated with two-stage revision. c Arthrodesis was done for deep infection in one patient. d Arthrodesis was done for deep infection in both patients. b
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patients had preoperative clinical data and 94% had postoperative data, Schweitzer et al. [10] reported an improvement on VAS from 7 preoperatively to 1.5 at 2 year followup. Nodzo et al. [11] did not report on VAS pain scale but showed significant improvement in pain component of FAOS. The AOFAS ankle/hindfoot scores improved 45.3 points from 42.7 to 88 in this current study. These scores are similar to those reported in the only other fixed-bearing study, which noted improvement in AOFAS ankle/hindfoot scores from 39.1 preoperatively to 78.7 at 2 years followup [10]. This cohort’s preoperative scores fall in between preoperative scores reported in mobilebearing studies by Bonnin (32.3) and Schenk (50.9) [24,28], and this cohort’s postoperative scores were slightly better than those reported in the mobile-bearing literature (75–83.2) [24,25,28]. SF-36 mental and physical component scores were all significantly improved, as previously reported by other studies [10,11]. The strengths of this study include the prospective collection of clinical data and the combined radiographic and clinical outcomes as measured by multiple outcome scores. Limitations of this study include the noncontrolled case series design, the relatively small number of patients, and the propensity for higher complications early in the learning curve of ankle arthroplasty [29–31]. 5. Conclusion This early-term analysis of the two-part Salto prosthesis with a fixed-bearing indicated satisfactory clinical and radiographic outcomes at an average of three years. These data show that at early followup, the clinical and radiographic results are comparable to published outcomes and complications for the three-part Salto prosthesis with a mobile-bearing [10,21,22,24,25,28]. Longterm outcomes and long-term comparability of the fixed-bearing version to the mobile-bearing original design remains to be elucidated by future studies. Conflict of interest statement None declared. References [1] Haddad SL, Coetzee JC, Estok R, Fahrbach K, Banel D, Nalysnyk L. Intermediate and long-term outcomes of total ankle arthroplasty and ankle arthrodesis. A systematic review of the literature. J Bone Joint Surg Am 2007;89:1899. [2] Saltzman CL, Mann RA, Ahrens JE, Amendola A, Anderson RB, Berlet GC, et al. Prospective controlled trial of STAR total ankle replacement versus ankle fusion: initial results. Foot Ankle Int 2009;30:579. [3] Brodsky JW, Polo FE, Coleman SC, Bruck N. Changes in gait following the Scandinavian total ankle replacement. J Bone Joint Surg Am Vol 2011;93:1890. [4] Cracchiolo III A, Deorio JK. Design features of current total ankle replacements: implants and instrumentation. J Am Acad Orthop Surg 2008;16:530. [5] Wiesel SW, Easley ME. Operative techniques in foot and ankle surgery. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011. [6] Queen RM, De Biassio JC, Butler RJ, DeOrio JK, Easley ME, Nunley JA. J. Leonard Goldner Award 2011: changes in pain, function, and gait mechanics two years following total ankle arthroplasty performed with two modern fixed-bearing prostheses. Foot Ankle Int 2012;33:535.
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