Total ankle replacement revisited

Republication of "Keeping It in the Fairway: Golf Handicap Following Total Ankle Arthroplasty"

Background

Total ankle arthroplasty (TAA) provides a surgical alternative to tibiotalar arthrodesis when treating end-stage ankle arthritis. TAA preserves range of motion at the tibiotalar joint leading to improved postoperative function. Many patients who undergo TAA wish to maintain a high level of activity, including participation in low-impact sports such as golf. There are several studies in the total hip and total knee arthroplasty literature that have looked at the effect of total joint arthroplasty on golf handicap. We hypothesized that similar to hip and knee arthroplasty research, TAA is likely to result in a postoperative increase in golf handicap.

Methods

After obtaining institutional review board approval, we retrospectively identified 60 patients (from 140 consecutive TAAs performed between August 2016 and February 2017) who had undergone TAA, played golf pre- and postoperatively, and had at least 1 year of postoperative follow-up. The average postoperative follow-up for the cohort was 28.1 months. Variables including preoperative and postoperative golf handicaps, swing laterality, age, gender, surgical laterality, implant used, and operating surgeon were recorded.

Results

The average preoperative and postoperative handicaps were 19.7 and 17.9, respectively, which did not represent a statistically significant difference (P = .07). Patients who played 3 or more rounds per week had better preoperative and postoperative handicaps compared to patients who played 2 rounds or less; however, the change in their handicap following TAA and the number of rounds played per week was not affected. There was no association between the change in handicap and the follow-up period, handedness of golf shot, surgical laterality, implant used, or the operating surgeon.

Conclusion

Our findings showed that golf handicap was not negatively affected following TAA in this series.

Level of Evidence

Level IV, case series.

Randomized Controlled Trial Comparing Early Mobilization vs Six Weeks of Immobilization in a Walking Cast Following Total Ankle Replacement

Rehabilitation for patients after total ankle replacement traditionally involves weeks of immobilization in a plaster cast followed by progressive mobilization. In a small randomized trial, we compared teh outcomes of patients who received a 3-component cementless, unconstrained, mobile-bearing prosthesis and were initially immobilised in a plaster cast for 6 weeks to thoese who received the same prosthesis but were allowed to mobilise early. Gait, clinical, patient-reported, and radiologic outcomes were measured. The study included 20 patients, 10 in the plaster cast group and 10 in the early mobilization group, and the demographics of the groups did not differ significantly. All patients were followed-up for 24 months. There were no significant differences between the 2 groups 2 years after surgery in ankle dorsiflexion, spatiotemporal gait characteristics, American Orthopaedic Foot and Ankle Society ankle-hindfoot scores, Timed Up and Go Test times, WOMAC (pain, stiffness, function) scores, SF-36 (quality-of-life) scores, or patient satisfaction (pain relief, daily-living, recreational activities, and overall) (all p > .05). Bone mineral density decrease of the medial malleolus and increase at middle tibia, calculated with DEXA scans, was significantly better in early mobilization than plaster cast group at one and 2 years postoperatively, but this was also the case preoperatively. The lack of differences in outcomes suggests that early ankle mobilization may be a safe and reliable method to enhance recovery following ankle arthroplasty with a 3-component cementless, unconstrained, mobile-bearing prosthesis. Compared to traditional plaster casting, patients who are engaged in early mobilization after arthroplasty may enjoy similar functional, mobility, quality-of-life, pain relief, activity level, and satisfaction outcomes.

Failure rates and patient-reported outcomes of revision of total ankle arthroplasty

INTRODUCTION

Despite the increasing number of revision total ankle arthroplasty (TAA), the literature on indications, surgical options, and outcomes is limited. This study reports on failure rates and patient-reported outcomes (PROM) for a cohort of 122 patients who underwent revision of TAA.

MATERIALS AND METHODS

A retrospective review of revision TAA between 2006 and 2020 was performed at one institution. Patient's demographics and different surgical procedures were analyzed with particular attention to comparing polyethylene exchange with revision of both metallic components and to additional interventions for axis correction. Failure rates and the European Foot and Ankle Society (EFAS) score were collected. The average follow-up period was 70.37 ± 46.76 months.

RESULTS

122 patients were treated with an exchange procedure. The surgery included 69 polyethylene exchanges, 12 revisions of one metallic component, and 41 revisions of both metallic components. The overall failure rate was 14.75%. The EFAS score, completed by 94 of the 122 patients, was used to evaluate clinical outcomes. Median EFAS score was 12.51 ± 5.53, and median EFAS sports score was 2.97 ± 3.04. Revision rates after polyethylene exchange were significantly higher than after exchanging both metallic components (p value = 0.03), while the EFAS score showed slightly better results in patients treated with polyethylene exchange. Adding procedures to induce axis correction led to significantly lower revision rates (p value = 0.03), and the EFAS score was also improved but without statistical significance.

CONCLUSIONS

The high failure rate of polyethylene exchange indicates that the intervention does not address the actual cause of failed TAA in many cases. Additional axis correction should be considered more frequently. If the underlying issues of prosthesis failure can be identified and sufficiently addressed, the results of revision surgery are likely to improve.

Computational Model Validation of Contact Mechanics in Total Ankle Arthroplasty

Revision rates in total ankle arthroplasty (TAA) are nearly double compared with hip or knee arthroplasty procedures. Contact mechanics for metal-polyethylene articulation in TAA is critical due to the reduced size of the implant and higher expected load, compared with a hip or knee joint. This study was focused on developing a validated computational model to predict contact area in a polyethylene tibial bearing articulating with a metallic talar component in a bicondylar TAA design. Contact area was evaluated at five different flexion angles in an experimental test and in a computational model, per ASTM F2665. The overall contact area values predicted in the computational model matched closely (within 8%) with that measured in the comparator; well within the range reported in the literature. The credibility of the model to sufficiently predict the outputs relative to the experimental data was discussed using the guidelines provided by the recently published ASME V&V 40-2018 standard. Various sensitivities associated with both the model and the comparator, were explored. It was concluded that the validated modeling approach presented in this study demonstrated sufficient accuracy to support the use of modeling for evaluation of contact area of TAA designs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1063-1069, 2020.

The Relationship Between Polyethylene Insert Size and Complications in Total Ankle Replacement

The purpose of this study was to compare complication rates after total ankle replacement in 2 groups of patients based on polyethylene insert size. The total cohort was divided into 2 groups based on insert size. Group 1 included patients with polyethylene insert size less than 10 mm in thickness. Group 2 included patients with polyethylene insert sizes 10 mm and larger. Available charts were reviewed for patients who underwent primary total ankle arthroplasty by one surgeon. Patient demographics, polyethylene insert size, implant used, concomitant procedures, postoperative complications, and patient-reported outcome scores were recorded. One hundred patients were available for follow-up and were included in this study, which ranged from March 2012 to July 2017. The average follow-up was 31.3 months (range = 10-60 months). Forty-eight females and 52 males were included in this study. There were a total of 63 patients in group 1 and 47 patients in group 2. The total complication rate for patients in group 1 was 11.1% (7/63), and in group 2 it was 16.2% (6/32). There was no statistical significance in complication rates when comparing the 2 groups (P = 0.5427). All patients underwent at least one concomitant procedure at the time of initial ankle replacement. Our findings show that total ankle replacement complication rates are equal when comparing large polyethylene inserts commonly utilized to correct deformities, versus small polyethylene inserts commonly utilized in primary resurfacing. Levels of Evidence: Level IV, Retrospective comparative study.

Optimizing Outpatient Total Ankle Replacement from Clinic to Pain Management

Outpatient total ankle arthroplasty is a potential significant source of cost savings. The ability to institute an effective outpatient total ankle program depends on appropriate patient selection, surgeon experience with total ankle replacement, addressing preoperative patient expectations, the involvement of an experienced multidisciplinary care team including experienced anesthesiologists, nurse navigators, recovery room nursing staff and physical therapists, and most importantly, such a program requires complete institutional logistical support.

Keeping It in the Fairway

Background:

Total ankle arthroplasty (TAA) provides a surgical alternative to tibiotalar arthrodesis when treating end-stage ankle arthritis. TAA preserves range of motion at the tibiotalar joint leading to improved postoperative function. Many patients who undergo TAA wish to maintain a high level of activity, including participation in low-impact sports such as golf. There are several studies in the total hip and total knee arthroplasty literature that have looked at the effect of total joint arthroplasty on golf handicap. We hypothesized that similar to hip and knee arthroplasty research, TAA is likely to result in a postoperative increase in golf handicap.

Methods:

After obtaining institutional review board approval, we retrospectively identified 60 patients (from 140 consecutive TAAs performed between August 2016 and February 2017) who had undergone TAA, played golf pre- and postoperatively, and had at least 1 year of postoperative follow-up. The average postoperative follow-up for the cohort was 28.1 months. Variables including preoperative and postoperative golf handicaps, swing laterality, age, gender, surgical laterality, implant used, and operating surgeon were recorded.

Results:

The average preoperative and postoperative handicaps were 19.7 and 17.9, respectively, which did not represent a statistically significant difference ( P = .07). Patients who played 3 or more rounds per week had better preoperative and postoperative handicaps compared to patients who played 2 rounds or less; however, the change in their handicap following TAA and the number of rounds played per week was not affected. There was no association between the change in handicap and the follow-up period, handedness of golf shot, surgical laterality, implant used, or the operating surgeon.

Conclusion:

Our findings showed that golf handicap was not negatively affected following TAA in this series.

Level of Evidence:

Level IV, case series.

The effects of total ankle replacement on ankle joint mechanics during walking

BACKGROUND

End-stage ankle arthritis impairs joint function and patients' mobility. Total ankle replacement is a surgical procedure to treat severe ankle arthritis. Salto Talaris Anatomic Ankle^TM (STAA) was designed to mimic the normal ankle anatomy and flexion/extension of the ankle movement. The purpose of this study was to examine the effect of an STAA ankle replacement on ankle joint function and mechanics during gait.

METHODS

Five patients with end-stage unilateral ankle arthritis were recruited. Patients performed level walking in a laboratory setting on 2 occasions, prior to and 3 months after the STAA ankle surgeries. American Orthopedic Foot and Ankle Society (AOFAS) hindfoot score was obtained. A 12-camera motion capture system was used to perform walking analysis. Gait temporo-spatial parameters and ankle joint mechanics were evaluated. Paired Student's t tests and non-parametric Wilcoxon matched tests were performed to examine the differences in biomechanical variables between the pre- and post-surgery walking conditions.

RESULTS

Compared to the pre-surgical condition, at 3 months of post-STAA surgery, patients experienced greater improvement in AOFAS hindfoot score (p = 0.0001); the STAA ankle demonstrated a 31% increase in ankle joint excursion (p = 0.045), a 22% increase in ankle plantarflexor moment (p = 0.075), a 60% increase in ankle power absorption (p = 0.023), and a 68% increase in ankle power production (p = 0.039). Patients also demonstrated a 26% increase in walking speed (p = 0.005), a 20% increase in stride length (p = 0.013), a 15% decrease in double support time (p = 0.043), and a 5% decrease in total stance time (p = 0.055).

CONCLUSION

Three months after surgeries, the STAA patients experienced improvements in ankle function and gait parameters. The STAA ankle demonstrated improved ankle mechanics during daily activities such as walking.

Results at a minimum follow-up of 5 years of a ligaments-compatible total ankle replacement design

BACKGROUND

A new design of 3-part ankle replacement was developed to achieve compatibility with the natural ligaments by allowing certain fibers to remain isometric during passive motion.

METHODS

We evaluate 75 ankle prostheses implanted from July 2003 to December 2008, at a mean follow-up 6.5±1.1years (range 5-9 years). The mean age at surgery was 62±13years (range 29-82).

RESULTS

The mean AOFAS scores achieved at pre-op and at last follow-up were respectively 37±5 (23-45) and 78±8 (64-98). (p<0.001). Clinical range of motion of the ankle measured by goniometer pre op was 1°±2 of dorsiflexion and 12°±4° of plantarflexion; at last follow-up range of motion increased to 6°±5° in dorsiflexion (p<0.01) and 18°±7° in plantarflexion (p<0.05). Radiographs showed no loosening and little signs of radiolucency. Two revisions necessitated component removal, neither for implant loosening. The overall survival rate was 97.3%.

CONCLUSIONS

Function and Range-of-motion showed significant improvements. These results demonstrate that ligaments-compatible shaped talar and tibial components, with a fully conforming interposed meniscal bearing, can provide satisfactory survival rates and clinical outcomes in the middle term.

Impact of Diabetes on Outcome of Total Ankle Replacement

BACKGROUND

As the incidence of diabetes mellitus (DM) grows, managing patients with diabetes and concomitant ankle arthritis poses a challenging clinical dilemma. While diabetes is known to be a risk factor for complications relating to open reduction and internal fixation of ankle fractures, it is unclear if DM is a risk factor for negative outcomes after total ankle replacement (TAR).

METHODS

We retrospectively identified a consecutive series of 813 primary TARs performed between 2002 and November 2013 that had a minimum follow-up of 1 year. Within that larger group, we identified 50 patients with DM and used a control group without DM for comparison (n = 55). Clinical outcomes including wound issues, infection rates, complications, and failure rates were then compared. Functional outcomes, including American Orthopaedic Foot & Ankle Society hindfoot score, Short Form-36 (SF-36), Short Musculoskeletal Function Assessment, Foot and Ankle Disability Index, and visual analog scale, were also compared. Median patient follow-up was 2.3 years in the DM group and 3.1 years in the control group (P = .239).

RESULTS

The body mass index, age, preoperative American Society of Anesthesiologists (ASA) grading, and smoking history in the DM were significantly higher than in the control group. While 5 patients (10%) in the DM group had secondary operations related to the TAR, no patients had a superficial or deep infection. Eight patients (14.5%) in the control group had secondary operations, including 1 patient who needed a flap. There was no statistical differences in secondary operations (P = .562), revisions (P = .604), or failure rates (P = .345). For both the diabetes and control groups, all functional outcome scores except SF-36 General Health significantly improved at 1 year postoperatively; these improvements were maintained at most recent follow-up. There was no statistically significant difference between the groups regarding functional outcomes except that at 1 year, the magnitude of improvement in SF-36 General Heath was significantly better in the control group.

CONCLUSIONS

Total ankle arthroplasty appears to be an effective and safe means for providing pain relief and improving function in patients with diabetes and ankle arthritis. While patients with DM were heavier and had worse ASA preoperative grades, they did not have a significantly different complication or infection rate.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Total ankle replacement: a historical perspective

In the early 1970s, total ankle replacement was criticized because of poor outcomes with initial implant designs. Modifications were made that lead to the development of several generations of implants. The early shortcomings gave researchers and surgeons the impetus to improve implant designs and surgical technique. Total ankle replacement has become more widely accepted in recent years because of improved design and survivorship rates for the implants, as well as improved patient satisfaction scores. Indications for total ankle replacement have broadened. To continue these successes, it is important for surgeons to select appropriate patients for this procedure.

BIOMECHANICS OF THE INTACT AND REPLACED HUMAN ANKLE JOINT

The main objective of the study was to develop advanced biomechanical models of the intact human ankle complex. It was also aimed at designing a total ankle replacement which would better reproduce the physiological function of the joint. Passive flexion was analyzed in a number of lower-leg preparations with stereophotogrammetry and radiostereometry. The articular surfaces and fibres within the calcaneofibular and tibiocalcaneal ligaments were observed to prescribe the changing positions of bones, ligaments and instantaneous axis of rotation. Joint motion included rolling as well as sliding. Computer-based models elucidated this kinematics at the intact joint, and how changing positions of the centre of rotation and muscle lines of action affect lever arm length at different flexion angles. The mechanical response of the joint to anterior drawer and talar tilt tests was explained in terms of fibre recruitment. The experimental evidence and the geometrical models gave the basis for the design of a novel ankle replacement. A three-component, convex-tibia prosthesis was developed with articular surface shapes that are compatible with the geometry of the ligaments. The proposed prosthesis based on ligament/shape compatibility is showing encouraging results in initial implantation.

Early clinical results of the BOX ankle replacement are satisfactory: a multicenter feasibility study of 158 ankles

A new design for a 3-part ankle replacement was developed in an effort to achieve compatibility with the naturally occurring ligaments of the ankle by allowing certain fibers to remain isometric during passive motion. In order to test the design concept clinically, 158 prostheses were implanted in 156 patients within a 9-center trial and were followed up for a mean of 17 (range 6 to 48) months. The mean age at the time of surgery was 60.5 (range 29.7 to 82.5) years. Outcome measures included the American Orthopaedic Foot & Ankle Surgery hindfoot-ankle score and range of motion measured on lateral radiographs of the ankle. The preoperative American Orthopaedic Foot & Ankle Surgery score of 36.3 rose to 74.6, 78.6, 76.4, and 79.0, respectively, at 12, 24, 36, and 48 months. A significant correlation between meniscal bearing movement on the tibial component (mean 3.3 mm; range 2 to 11 mm) and range of flexion at the replaced ankle (mean 26.5°; range 14° to 53°) was observed in radiograms at extreme flexions. Two (1.3%) revisions in the second and third postoperative years necessitated component removal (neither were for implant failure), and 7 (4.4%) further secondary operations were required. The results of this investigation demonstrated that non-anatomic-shaped talar and tibial components, with a fully conforming interposed meniscal bearing, can provide safety and efficacy in the short term, although a longer follow-up period is required to more thoroughly evaluate this ankle implant.

Subchondral bone remodeling is related to clinical improvement after joint distraction in the treatment of ankle osteoarthritis

OBJECTIVE

In osteoarthritis (OA), subchondral bone changes alter the joint's mechanical environment and potentially influence progression of cartilage degeneration. Joint distraction as a treatment for OA has been shown to provide pain relief and functional improvement through mechanisms that are not well understood. This study evaluated whether subchondral bone remodeling was associated with clinical improvement in OA patients treated with joint distraction.

METHOD

Twenty-six patients with advanced post-traumatic ankle OA were treated with joint distraction for 3 months using an Ilizarov frame in a referral center. Primary outcome measure was bone density change analyzed on computed tomography (CT) scans. Longitudinal, manually segmented CT datasets for a given patient were brought into a common spatial alignment. Changes in bone density (Hounsfield Units (HU), relative to baseline) were calculated at the weight-bearing region, extending subchondrally to a depth of 8mm. Clinical outcome was assessed using the ankle OA scale.

RESULTS

Baseline scans demonstrated subchondral sclerosis with local cysts. At 1 and 2 years of follow-up, an overall decrease in bone density (-23% and -21%, respectively) was observed. Interestingly, density in originally low-density (cystic) areas increased. Joint distraction resulted in a decrease in pain (from 60 to 35, scale of 100) and functional deficit (from 67 to 36). Improvements in clinical outcomes were best correlated with disappearance of low-density (cystic) areas (r=0.69).

CONCLUSIONS

Treatment of advanced post-traumatic ankle OA with 3 months of joint distraction resulted in bone density normalization that was associated with clinical improvement.

Stresses in the ankle joint and total ankle replacement design

The ankle is a highly congruent joint with a surface area of 11-13 cm(2). Total ankle replacements have been attempted since the early 1970s and design has continually evolved as the early designs were a failure. This was because the stresses involved and the mutiaxial motion of the ankle has not been understood until recently. It has been shown that the talus slides as well as rolls during the ankle arc of motion from plantarflexion to dorsiflexion. Furthermore, the articular surfaces and the calcaneofibular and tibiocalcaneal ligaments have been shown to form a four bar linkage dictating ankle motion. A new design ankle replacement has been suggested recently which allows multiaxial motion at the ankle while maintaining congruency throughout the arc of motion. The early results of this ankle replacement have been encouraging without any reported failures due to mechanical loosening.

Total ankle replacement compatible with ligament function produces mobility, good clinical scores, and low complication rates: an early clinical assessment

BACKGROUND

A three-part ankle replacement was developed to achieve compatibility with the natural ligaments by allowing fibers on the medial and lateral sides to remain isometric during passive motion. Unlike all current prostheses, the new design uses nonanatomically shaped components on the tibia and talus and a fully conforming interposed meniscal bearing.

QUESTIONS/PURPOSES

Does this new design restore ankle mobility, improve clinical score, and result in low complication and early revision rates?

PATIENTS AND METHODS

We reviewed 51 patients in whom 51 prostheses were implanted in a seven-center trial from July 2003 to July 2006. The mean age of the patients at surgery was 61.5 years (range, 35.1-82.5 years). We used the AOFAS score to assess clinical outcome. We used lateral radiographs to assess function. The minimum followup was 24 months (mean, 30 months; range, 24-48 months).

RESULTS

The mean preoperative AOFAS score of 38.5 increased to 76.9, 79.1, 76.4, and 79.0 at 12, 24, 36, and 48 months, respectively. We observed a correlation between meniscal bearing movement on the tibial component (mean, 3.4 mm; range, 2-12 mm) and range of flexion at the replaced ankle (mean, 27.4º; range, 16º-53º). We revised one arthroplasty in the second postoperative year for lateral impingement, providing a 3-year cumulative survival rate of 97% and performed one other secondary operation for hindfoot pain.

CONCLUSIONS

These data suggest the new prosthesis can provide short-term restoration of ankle mobility, a good clinical score, and low complication and failure rates. Longer followup with larger numbers is required.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Treatment of isolated ankle osteoarthritis with arthrodesis or the total ankle replacement: a comparison of early outcomes

BACKGROUND

Ankle arthrodesis and replacement are two common surgical treatment options for end-stage ankle osteoarthritis. However, the relative value of these alternative procedures is not well defined. This study compared the clinical and radiographic outcomes as well as the early perioperative complications of the two procedures.

METHODS

Between January 2, 1998 and May 31, 2002, 138 patients were treated with ankle fusion or replacements. Seventy one patients had isolated posttraumatic or primary ankle arthritis. However, patients with inflammatory arthritis, neuropathic arthritis, concomitant hind foot fusion, revision procedures and two component system ankle replacement were excluded. Among them, one group of 42 patients had a total ankle replacement (TAR), whereas the other group of 29 patients underwent ankle fusion. A complete follow-up could be performed on 89% (37/42) and 73% (23/29) of the TAR and ankle fusion group, respectively. The mean follow-up period was 4.2 years (range, 2.2 to 5.9 years).

RESULTS

The outcomes of both groups were compared using a student's t-test. Only the short form heath survery mental component summary score and Ankle Osteoarthritis Scale pain scale showed significantly better outcomes in the TAR group (p < 0.05). In the radiographic evaluation, there was no significant difference in preoperative and postoperative osteoarthritis between the TAR and fusion groups.

CONCLUSIONS

The clinical results of TAR are similar to those of fusion at an average follow-up of 4 years. However, the arthroplasty group showed better pain relief and more postoperative complications that required surgery.

Analysis of joint laxity after total ankle arthroplasty: cadaver study

BACKGROUND

Clinical results of total ankle arthroplasty with early designs were disappointing. Recently-developed ankle prostheses have good mid-term results; however, limited information is available regarding effects of total ankle arthroplasty on ankle laxity.

METHODS

Eight cadaveric lower extremities were tested with a custom device which enabled measurement of multi-axial forces, moments, and displacement during applied axial, shear, and rotational loading. Tests consisted of anterior-posterior and medial-lateral translation and internal-external rotation of the talus relative to the tibia during axial loads on the tibia simulating body weight (700 N) and an unloaded condition (5 N). Tests were performed in neutral, dorsiflexion, and plantarflexion. Laxity was determined for the intact ankle, and following insertion of an unconstrained total ankle implant, comparing load-displacement curve.

FINDINGS

Laxity after total ankle arthroplasty did not approximate the normal ankle in most conditions tested. Displacement was significantly greater for total ankle arthroplasty in both posterior and lateral translation, and internal rotation, with 5 N axial loading, and anterior-posterior, medial-lateral translation, and internal-external rotation for 700 N axial loading. For the 700 N axial load condition, in the neutral ankle position, total anterior-posterior translation averaged 0.4 mm (SD 0.2 mm), but 6.0 mm (SD 1.5 mm) after total ankle arthroplasty (P<0.01). This study demonstrated more laxity in the replaced ankle than normal ankle for both unloaded and 700 N axially loaded conditions.

INTERPRETATION

These data indicate the increased responsibility of the ligaments for ankle laxity after total ankle arthroplasty and suggest the importance of meticulous ligament reconstruction with total ankle arthroplasty operations.

Intermediate term outcome of the agility total ankle arthroplasty

BACKGROUND

Although ankle arthrodesis provides pain relief and improved function, newer generation total ankle arthroplasty designs, with improved kinematic properties, have emerged and showed encouraging results. The purpose of this study was to review the intermediate term outcome of the Agility Total Ankle Arthroplasty prosthesis.

MATERIALS AND METHODS

A retrospective review was performed on 28 total ankle arthroplasty procedures performed over a period of 5 years. The American Orthopedic Foot and Ankle Society (AOFAS) questionnaire was used for evaluation. Pre-existing medical and surgical conditions that could potentially affect outcome were recorded. The mean age at surgery was 68.5 years with 39% males and 61% females.

RESULTS

The mean AOFAS Ankle-Hindfoot score improved significantly from 34.9 to 76.4 (p < 0.001). Pain relief was the main factor in improving the score followed by improved function. Complications varied from delayed wound healing, wound infection, painful hardware, iatrogenic malleolar fracture and arterial injury, to patients requiring free flap coverage. Despite the high rate of complications, which were successfully treated, most patients were satisfied at the last followup.

CONCLUSION

Total ankle arthroplasty using the Agility Total Ankle Arthroplasty prosthesis has clinically encouraging outcomes; however the high complication rate should prompt surgeons to carefully select patients for this procedure.

Prospective controlled trial of STAR total ankle replacement versus ankle fusion: initial results

BACKGROUND

Mobile-bearing ankle replacements have become popular outside of the United States over the past two decades. The goal of the present study was to perform a prospective evaluation of the safety and efficacy of a mobile-bearing prosthesis to treat end stage ankle arthritis. We report the results of three separate cohorts of patients: a group of Scandanavian Total Ankle Replacement (STAR) patients and a control group of ankle fusion patients (the Pivotal Study Groups) and another group of STAR total ankle patients (Continued Access Group) whose surgery was performed following the completion of enrollment in the Pivotal Study.

MATERIALS AND METHODS

The Pivotal Study design was a non-inferiority study using ankle fusion as the control. A non-randomized multi-centered design with concurrent fusion controls was used. We report the initial perioperative findings up to 24 months following surgery. For an individual patient to be considered an overall success, all of the following criteria needed to be met: a) a 40-point improvement in total Buechel-Pappas ankle score, b) no device failures, revisions, or removals, c) radiographic success, and d) no major complications. In the Pivotal Study (9/00 to 12/01), 158 ankle replacement and 66 arthrodesis procedures were performed; in the Continued Access Study (4/02 to 10/06), 448 ankle replacements were performed, of which 416 were at minimum 24 months post-surgery at time of the database closure.

RESULTS

Major complications and need for secondary surgical intervention were more common in the Pivotal Study arthroplasty group than the Pivotal Study ankle fusion group. In the Continued Access Group, secondary procedures performed on these arthroplasty patients decreased by half when compared with the Pivotal Arthroplasty Group. When the Pivotal Groups were compared, treatment efficacy was higher for the ankle replacement group due to improvement in functional scores. Pain relief was equivalent between fusion and replacement patients. The hypothesis of non-inferiority of ankle replacement was met for overall patient success.

CONCLUSION

By 24 months, ankles treated with STAR ankle replacement (in both the Pivotal and Continued Access Groups) had better function and equivalent pain relief as ankles treated with fusion.

Biomechanics of the ankle joint and clinical outcomes of total ankle replacement

Until the 1970s ankle arthrodesis was considered to be the "gold-standard" to treat arthritis. But the low fusion rate of ankle arthrodeses along with the inability to achieve normal range of motion led to the growing interest in the development of total ankle replacements. Though the short-term outcomes were good, their long-term outcomes were not as promising. To date, most models do not exactly mimic the anatomical functionality of a natural ankle joint. Therefore, research is being conducted worldwide to either enhance the existing models or develop new models while understanding the intricacies of the joint more precisely. This paper reviews the anatomical and biomechanical aspects of the ankle joint. Also, the evolution and comparison of clinical outcomes of various total ankle replacements are presented.

Robotic cadaver testing of a new total ankle prosthesis model (German Ankle System)

BACKGROUND

An investigation was carried out into possible increased forces, torques, and altered motions during load-bearing ankle motion after implantation of two different total ankle prostheses. We hypothesized that the parameters investigated would not differ in relation to the two implants compared.

METHODS

We included two different ankle prostheses (Hintegra, Newdeal, Vienne, France; German Ankle System, R-Innovation, Coburg, Germany). The prostheses were implanted in seven paired cadaver specimens. The specimens were mounted on an industrial robot that enables complex motion under predefined conditions (RX 90, Stäubli, Bayreuth, Germany). The robot detected the load-bearing (30 kg) motion of the 100(th) cycle of the specimens without prostheses as the baseline for the later testing, and mimicked that exact motion during 100 cycles after the prostheses were implanted. The resulting forces, torques, and bone motions were recorded and the differences between the prostheses compared.

RESULTS

The Hintegra and German Ankle System, significantly increased the forces and torques in relation to the specimen without a prosthesis with one exception (one-sample-t-test, each p < or = 0.01; exception, parameter lateral force measured with the German Ankle System, p = 0.34). The force, torque, and motion differences between the specimens before and after implantation of the prostheses were lower with the German Ankle System than with the Hintegra (unpaired t-test, each p < or = 0.05).

CONCLUSIONS

The German Ankle System prosthesis had less of an effect on resulting forces and torques during partial weightbearing passive ankle motion than the Hintegra prosthesis. This might improve function and minimize loosening during the clinical use.

Posttraumatic ankle arthritis: an update on conservative and surgical management

This manuscript offers current information regarding the examination, conservative treatment, and surgical treatment for individuals with posttraumatic arthritis. Although inflammatory and osteoarthritis can occur, posttraumatic arthritis is the most common form of arthritis to affect the ankle. Posttraumatic ankle arthritis occurs in a generally younger, active population. It is radiographically characterized by an asymmetrical degenerative process and may be associated with a history of trauma, instability, and/or lower extremity malalignment. When choosing between conservative/nonoperative versus surgical intervention, the extent of subchondral bone exposed and the time over which the arthritis has developed are factors that should be considered. The role and effectiveness for conservative treatment, such as medication, patient education, shoe modification, bracing, stretching, mobilization, strengthening, and symptom management, needs to be further determined. Surgical procedures for posttraumatic ankle arthritis can include distraction arthroplasty, arthrodesis, or total ankle arthroplasty. Unlike the relatively new procedure of distraction arthroplasty, the outcomes for arthrodesis have been well defined. Arthrodesis generally has a good outcome, but its limitations have been recognized. These limitations include the extended time required to achieve fusion, potential for nonunion, arthritis developing in adjacent joints, leg length discrepancy, malalignment, chronic edema, symptoms due to the hardware, stress fractures, and continued pain. While first generation total ankle arthroplasty led to poor results, advancements in prosthetic design and surgical technique have revived optimism regarding total ankle arthroplasty as an alternative to arthrodesis. The key for the future of total ankle arthroplasty may not be related to the development of newer ankle components but rather in refining the criteria to determine who would best benefit from joint replacement versus fusion.

Mathematical models of passive motion at the human ankle joint by equivalent spatial parallel mechanisms

The paper presents a theoretical model of the ankle joint, i.e. tibio-talar articulation, which shows how the articular surfaces and the ligaments, acting together as a mechanism, can control the passive kinematics of the joint. The authors had previously shown that, in virtually unloaded conditions, the ankle behaves as a single degree-of-freedom system, and that two ligament fibres remain nearly isometric throughout the flexion arc. Two different equivalent spatial parallel mechanisms together with corresponding kinematic models were formulated. These assumed isometricity of fibres within the calcaneal-fibular and tibio-calcaneal ligaments and rigidity of the articulating surfaces, taken as three sphere-plane contacts in one model, and as a single spherical pair in the other. Geometry parameters for the models were obtained from three specimens. Motion predictions compare quite well with the measured motion of the specimens. The differences are accounted for by the simplifications adopted to represent the complex anatomical structures, and might be reduced by future more realistic representations of the natural articular surfaces.

The mini-arthrotomy ankle arthrodesis: a review of nine cases

The authors report on the retrospective follow-up of 9 patients (6 women and 3 men) who underwent a mini-arthrotomy ankle arthrodesis by means of small incisions for exposure, cartilage resection, and internal fixation with crossed interfragmental compression screws. Patients were kept non-weight-bearing in a short leg cast for 12 weeks postoperative. At a mean follow-up of 55 months, outcomes were assessed by clinical examination, radiographs, and patient satisfaction questionnaires. Fusion was obtained in all patients, and there were no cases of delayed union, infection, or cutaneous compromise. Modified American Orthopaedic Foot and Ankle Society ankle and hindfoot rating scale scores significantly improved (P < .001) from a mean of 38 points preoperatively to 72 points at follow-up. A categorical assessment of functional ability in the postoperative period revealed 6 patients graded as excellent, 2 as good, and 1 as fair. In regard to a categorical assessment of clinical outcome in the postoperative period, 7 patients were graded as excellent and 2 as good. All of the patients stated that they were satisfied with their results and would undergo the procedure again. The mini-arthrotomy ankle arthrodesis with crossed interfragmental compression screw fixation appears to be a useful alternative to traditional open arthrodesis for selected patients with ankle arthritis.

Meniscal wear at a three-component total ankle prosthesis by a knee joint simulator

Despite the fundamental value of wear simulation studies to assess wear resistance of total joint replacements, neither specialised simulators nor established external conditions are available for the human ankle joint. The aim of the present study was to verify the suitability of a knee wear simulator to assess wear rates in ankle prostheses, and to report preliminary this rate for a novel three-component total ankle replacement design. Four intact 'small' size specimens of the Box ankle were analysed in a four-station knee wear simulator. Special component-to-actuator holders were manufactured and starting spatial alignment of the three-components was sought. Consistent load and motion cycles representing conditions at the ankle joint replaced exactly with the prosthesis design under analysis were taken from a corresponding mechanical model of the stance phase of walking. The weight loss for the three specimens, after two million cycles, was 32.68, 14.78, and 62.28mg which correspond to a linear penetration of 0.018, 0.008, and 0.034mm per million-cycle, respectively for the specimens #1, #2, and #3. The knee wear simulator was able to reproduce load-motion patterns typical of a replaced ankle. Motion of the meniscal bearing in between the tibial and talar components was smooth, this component remaining in place and in complete congruence with the metal components throughout the test.

Management of failed total ankle replacement with a retrograde short femoral nail: a case report

Arthrodesis of the ankle joint after failed total ankle replacement using internal fixation with plates and screws is problematic because of the significant bone loss. An external fixator has the disadvantage of prolonged treatment until complete consolidation, frequently complicated by pin track infections. Recently an intramedullary fixation has been described for tibio-talo-calcaneal arthrodesis for posttraumatic osteoarthritis of the ankle joint. We report on the use of this technique plus bone graft in a case of failed total ankle replacement complicated by cystic talus degeneration and a massive bony defect. The advantages include early mobilization and weightbearing provided by the stability of the fixation.

Finite element analysis of a total ankle replacement during the stance phase of gait

Total ankle replacement (TAR) designs have still several important issues to be addressed before the treatment becomes fully acceptable clinically. Very little is known about the performance, in terms of the contact pressures and kinematics of TAR when subjected to daily activities such as level gait. For this purpose, an explicit finite element model of a novel 3-component TAR was developed, which incorporated a previously validated mechanical model of the ankle ligament apparatus. The intermediate mobile polyethylene meniscal bearing was modelled as an elastic-plastic continuum while the articulating surfaces of the tibial and talar metal components as rigid bodies. Overall kinematics, contact pressures and ligament forces were analysed during passive, i.e. virtually unloaded, and active, i.e. stance phase of gait, conditions. Simulation of passive motion predicted similar kinematics as reported previously in an analytical four-bar linkage model. The meniscal bearing was observed to move 5.6 mm posteriorly during the simulated stance and the corresponding antero-posterior displacement of the talar component was 8.3 mm. The predicted pattern and the amount (10.6 degrees ) of internal-external rotation of the ankle complex were found to be in good agreement with corresponding in vivo measurements on normal ankles. A peak contact pressure of 16.8 MPa was observed, with majority of contact pressures below 10 MPa. For most ligaments, reaction forces remain within corresponding physiological ranges. A first realistic representation of the biomechanical behaviour of the human ankle when replaced by prosthetic joints is provided. The applied methodology can potentially be applied to other TAR designs.

Stresses in Polyethylene Liners in a Semiconstrained Ankle Prosthesis

A finite element model of a semiconstrained ankle implant with the tibia and fibula was constructed so that the stresses in the polyethylene liner could be computed. Two different widths of talar components were studied and proximal boundary conditions were computed from an inverse process providing a load of five times body weight appropriately distributed across the osseous structures. von Mises stresses indicated small regions of localized yielding and contact stresses that were similar to those in acetabular cup liners. A wider talar component with 36% more surface area reduced contact stress and von Mises stresses at the center of the polyethylene component by 17%.

Initial stability of ankle arthrodesis with three-screw fixation. A finite element analysis

OBJECTIVE

Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws.

DESIGN

Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and subjected to loads likely to affect the ankle postoperatively.

BACKGROUND

More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces.

METHODS

Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis.

RESULTS

Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis.

CONCLUSIONS

Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site.

A new semi-automated measurement technique based on X-ray pictures for ankle morphometry

Knowledge of human joint morphology is important in orthopaedic surgery and in prosthesis design. The literature on quantitative morphological analysis of the ankle joint is particularly scarce. A semi-automated radiographic measurement method was developed to collect morphological measures of the ankle joint. The method was based on standard lateral and antero-posterior X-ray pictures of the ankle joint. These were then scanned and analysed by means of specialized software designed for the purpose, which requires minimal operator contribution. Accuracy of the method was experimentally assessed by in vitro direct measurements. Intra- and inter-operator variability was also tested. Accuracy was assessed to be within 1mm for most measurements. Repeatability was not affected by operator skill and was within 2mm. The newly proposed method was applied successfully on 15 male adult subjects and relevant results are reported. The method allows ankle morphology to be analysed in a large number of subjects providing reliable data for anthropometric statistics.

Mobility of the human ankle and the design of total ankle replacement

Our prior research has shown that currently available total ankle implants fail to restore physiologic ankle mobility. Most of the modern mobile-bearing designs that feature a flat tibial component and a talar component with anatomic curvature in the sagittal plane function nonphysiologically with the natural ligament apparatus. To establish a more natural relationship between the implanted components and the retained ankle ligaments, we have developed a new design. According to our prior research, we suggest that physiologic ankle mobility is reproduced best with a design featuring a spherical convex tibial component, a talar component with radius of curvature in the sagittal plane longer than that of the natural talus, and a fully conforming meniscal component. Our preliminary observations in trial implantation and in a few patients suggest that while reproducing physiologic ankle mobility, the new design is capable of maintaining complete congruence at the two articulating surfaces of the meniscal bearing over the entire motion arc, with the prospect of minimizing wear of this component.

Total ankle replacement in rheumatoid arthritis

We reviewed 21 patients with rheumatoid arthritis who had a total ankle replacement between 1984 and 2000. The average follow-up was 72 (15-169) months. Clinical results were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) score. At the latest review, three ankles had been revised. Two ankles were excellent, seven good, three fair, and 12 poor. Eleven patients with 13 ankles had residual pain, with radiographs showing a high incidence of radiolucent lines. Migration of the tibial component was seen in 13 ankles and collapse of talus in nine. Although clinical results were poor, patient satisfaction was not.

Progressive post-traumatic ankle arthrosis treated with total ankle joint replacement: a case review

This article discusses the joint degeneration progression associated with post-traumatic arthrosis of the ankle. A representative case study of this debilitating condition was outlined, and treatment with total ankle joint replacement was presented. Although ankle arthrodesis continues to be a standard option following the progression of severe post-traumatic osteoarthritis, total ankle replacement is maturing as a viable option for this condition.

Total ankle arthroplasty

First-generation total ankle arthroplaty designs had unacceptably high complication and failure rates compared with ankle arthrodesis. More recent prostheses have had encouraging intermediate results because of refined surgical techniques and improved designs. Mobile-bearing designs theoretically offer less wear and loosening through full conformity and minimal constraint. The less complex fixed-bearing designs avoid bearing dislocation and the potential for added wear from a second articulation. Four second-generation designs have demonstrated reasonable functional outcomes: the Scandinavian Total Ankle Replacement, the Agility Ankle, the Buechel-Pappas Total Ankle Replacement, and the TNK ankle. Intermediate results are promising but should be interpreted with care.

Total ankle arthroplasty

Ankle arthritis has traditionally been treated surgically with arthrodesis (fusion) after conservative measures have been exhausted. The success of joint arthroplasty in the knee, hip, and shoulder inspired many attempts over the past 30 years to construct a workable ankle prosthesis. The failures of first generation prostheses caused skepticism regarding the feasibility of total ankle arthroplasty (TAR), but the mistakes of the past have been transformed into improvements and modifications. Today's second generation total ankle designs show promise, and outcomes are encouraging. The Agility Ankle (DePuy, Warsaw, IN) designed by Dr. Frank Alvine is featured in this article. The method of implant and postoperative management are reviewed.