Are There Differences in Gait Mechanics in Patients With A Fixed Versus Mobile Bearing Total Ankle Arthroplasty? A Randomized Trial

Median age of patients undergoing total ankle replacement has not significantly changed between 1999 and 2023: A systematic review of prospective studies

INTRODUCTION

Total ankle replacement (TAR) is an effective treatment for end-stage osteoarthritis. The aim of this systematic review was to assess the age of patients undergoing TAR in prospective comparative studies. Our hypothesis is that the age reported in most recent papers might be lower than those reported in older papers.

METHODS

This systematic review was performed using Pubmed, Scopus, EMBASE and Cochrane databases. Only Level I and II studies dealing with TAR were included. Data regarding demographics, study design, number of cohorts in each study, year of publication and year/years in which surgery was performed were extracted. A two-fold analysis was conducted building groups of patients based on the year of publication and creating 1) two groups (before and after the median year) and 2) three groups (using tertiles) in order to compare age of patients operated in different period of times. A comparison was also performed considering the median year of surgery for patients undergoing TAR.

RESULTS

Overall 59 cohorts (42 studies, published between 1999 and 2023; median year of publication: 2017) were included (6397 ankles, 6317 patients, median age 63 years). The difference between the median age for 27 cohorts published until 2016 (weighted median 63 years; IQR, 62.5-64) and the median age for 32 cohorts published after 2017 (weighted median 63.2 years; IQR, 63-67.8) was not statistically significant (p = 0.09). The division in tertiles did not reveal any significant change in the weighted median age at surgery (T1 (1999-2014; 63.2 years; IQR, 62.8-64.1), T2 (2015-2018; 63 years; IQR,63-63.5) and T3 (2019-2023; 63.2 years; IQR, 62.6-67.8)) over time (p = 0.65). The median age of patients operated between 1999 and 2008 vs 2009 and 2023 (data from 48 cohorts) was not different either (p = 0.12).

CONCLUSION

According to this review of prospective studies published between 1999 and 2023, the median age for patients undergoing TAR over the last two decades has been 63 years, remaining steady with no significant changes over time.

LEVEL OF EVIDENCE

Level II - systematic review including Level I and Level II studies.

comparison of postoperative gait parameters after total ankle arthroplasty and ankle fusion: A systematic review

Ankle pathology, such as severe arthritis, often necessitates surgical intervention to restore mobility and alleviate pain. Two commonly performed procedures for end-stage ankle disease are ankle fusion (AF) and total ankle arthroplasty (TAA). This review aims to compare the impact of AF and TAA on postoperative gait parameters. An extensive search in PubMed, Scopus, and Web of Science electronic databases was conducted with the use of the keywords ("ankle arthrodesis" OR "ankle fusion") AND ("ankle replacement" OR "ankle arthroplasty") AND "gait." Clinical studies in terms of postoperative gait parameters were included in this review. At least one of the following gait parameters, included in gait analysis, should be researched: spatiotemporal variables and joint kinematics and kinetics. An initial search revealed 221 studies. After the removal of duplicates and screening of titles,10 studies (7 prospective and 3 retrospective case series) were included for qualitative analysis. In the majority of studies, there is no significant difference in spatiotemporal parameters, such as walking speed, cadence, stance duration, step length, and stride length among AF and TAA patients. Postoperative sagittal ankle ROM, mainly maximum ankle dorsiflexion angle is significantly higher in TAA patients, while results concerning hip and knee ROM are variable. The comparison of AF and TAA in terms of postoperative gait parameters has shown variable results. In the majority of studies, there is no significant difference in spatiotemporal and kinetic parameters among AF and TAA patients. Further high-quality prospective studies are needed to fully elucidate the comparison of postoperative gait parameters.

Gait asymmetry persists following unilateral and bilateral total ankle arthroplasty

Total ankle arthroplasty (TAA) improves gait symmetry in patients with unilateral end-stage ankle arthritis but has not been studied in patients undergoing bilateral TAA (B-TAA), and few studies compare TAA patients to control subjects. The purpose of this study was to compare gait symmetry in U-TAA and B-TAA patients and healthy controls. Using prospective databases, 19 unilateral and 19 bilateral ankle arthritis patients undergoing TAA were matched to 19 control subjects by age, sex, and BMI. The Normalized Symmetry Index (NSI) was determined for joint mechanics and ground reaction forces (GRF) during walking trials at a single visit for controls and preoperatively and 1 to 2 years postoperatively for TAA patients. Data was analyzed using linear mixed-effects models to determine differences among time points and cohorts at a significance of α = 0.05. Following surgery, B-TAA and U-TAA experienced improved peak plantarflexion moment symmetry (p = 0.017) but remained less symmetric than controls. B-TAA patients had more symmetry than U-TAA patients during peak weight acceptance GRF (p = 0.002), while U-TAA patients had greater peak dorsiflexion symmetry than B-TAA patients. TAA patients demonstrated more asymmetry compared to control subjects for all outcome measures. There was no significant impact of TAA on gait symmetry for GRF or peak ankle angles, and neither U-TAA nor B-TAA was consistently associated with higher gait symmetry. These results indicate that TAA improves symmetry during peak plantarflexion moment, and that significant gait asymmetry persists for B-TAA and U-TAA patients compared to healthy participants.

Total ankle arthroplasty improves discrete and continuous stance phase gait symmetry

BACKGROUND

Total ankle arthroplasty (TAA) is used to treat symptomatic end-stage ankle arthritis (AA). However, little is known about TAA's effects on gait symmetry.

RESEARCH QUESTION

Determine if symmetry changes from before surgery through two years following TAA utilizing the normalized symmetry index (NSI) and statistical parametric mapping (SPM).

METHODS

141 patients with end-stage unilateral AA were evaluated from a previously collected prospective database, where each participant was tested within two weeks of surgery (Pre-Op), one year and two years following TAA. Walking speed, hip extension angle and moment, hip flexion angle, ankle plantarflexion angle and moment, ankle dorsiflexion angle, weight acceptance (GRF1), and propulsive (GRF2) vertical ground reaction forces were calculated for each limb. Gait symmetry was assessed using the NSI. A linear mixed effects model with a single response for each gait symmetry variable was used to examine the fixed effect of follow-up time (Pre-Op, Post-1 yr, Post-2 yr) and the random effect of participant with gait speed as a covariate in the model. A one-dimensional repeated measures analysis of variance (ANOVA) statistical parameter mapping (SPM) was completed to examine differences in the time-series NSI to determine regions of significant differences between follow-up times.

RESULTS

Relative to Pre-Op values, GRF1, and GRF2 showed increased symmetry for discrete metrics and the time-series NSI across sessions. Hip extension moment had the largest symmetry improvement. Ankle plantarflexion angle was different between Pre-Op and Post-2 yr (p=0.010); and plantarflexion moment was different between Pre- Op and each post-operative session (p<0.001). The time-series Ankle Angle NSI was greater during the early stance phase in the Pre-Op session compared to Post-2 yr.

SIGNIFICANCE

Symmetry across most of the stance phase improved following TAA indicating that TAA successfully improves gait symmetry and future work should determine if these improvements restore symmetry to levels equivalent with health age-match controls.

The effect of total ankle arthroplasty on mechanical energy exchange

Total ankle arthroplasty (TAA) is a common surgical solution for patients with debilitating arthritis of the ankle. Prior to surgery patients experience high levels of pain and fatigue and low mechanical energy recovery. It is not known if TAA restores healthy levels of mechanical energy recovery in this patient population. This study was designed to determine whether mechanical energy recovery was restored following TAA. Ground reaction forces during self-selected speed walking were collected from patients with symptomatic, unilateral ankle arthritis (N = 29) before and one and two years after primary, unilateral TAA. The exchange of potential (PE) and kinetic (KE) energy was examined, and direction of change (%congruity) and energy exchange (%recovery) between the two curves was calculated, with those subjects with low congruity experiencing high energy recovery. Linear regressions were used to examine the impact of walking speed, congruity, and amplitude of the center of mass (COM) displacement on %recovery, while ANOVA and ANCOVA models were used to compare energy recovery and congruity across the three time points. Gender, BMI, and age at surgery had no effect in this study. TAA improved walking speed (p = 0.001), increased energy recovery (p = 0.020), and decreased congruity (p = 0.002), and these levels were maintained over at least two years. Differences in congruity were independent of walking speed. In some patients, especially those who are severely debilitated by ankle arthritis, TAA is effective in restoring mechanical energy recovery to levels similar to an asymptomatic population of a similar age recorded by other studies.

Changes in Relative Work of the Lower Extremity and Distal Foot Joints After Total Ankle Replacement: An Exploratory Study

Ankle osteoarthritis does not only led to lower ankle power generation, but also results in compensatory gait mechanics at the hip and Chopart joints. Much of previous work explored the relative work distribution after total ankle replacement (TAR) either across the lower extremity joints where the foot was modelled as a single rigid unit or across the intrinsic foot joints without considering the more proximal lower limb joints. Therefore, this study aims, for the first time, to combine 3D kinetic lower limb and foot models together to assess changes in the relative joint work distribution across the foot and lower limb joints during level walking before and after patients undergo TAR. We included both patients and healthy control subjects. All patients underwent a three-dimensional gait analysis before and after surgery. Kinetic lower limb and multi-segment foot models were used to quantify all inter-segmental joint works and their relative contributions to the total lower limb work. Patients demonstrated a significant increase in the relative ankle positive joint work contribution and a significant decrease in the relative Chopart positive joint work contribution after TAR. Furthermore, there exists a large effect toward decreases in the relative contribution of the hip negative joint work after TAR. In conclusion, this study seems to corroborate the theoretical rationale that TAR reduces the compensatory strategy in the Chopart and hip joints in patients suffering from end-stage ankle osteoarthritis.

Concomitant Triceps Surae Lengthening in Total Ankle Arthroplasty Affects the Mechanical Work at the Ankle Joint

BACKGROUND

Previous studies have examined the effect of concomitant triceps surae lengthening on ankle dorsiflexion motion at the time of total ankle arthroplasty (TAA). As plantarflexor muscle-tendon structures are important for producing positive ankle work during the propulsive phase of gait, caution should be exercised when lengthening triceps surae, as it may decrease plantarflexion strength. In order to develop an understanding of the work of the anatomical structures crossing the ankle during propulsion, joint work must be measured. The aim of this explorative study was to assess the effect of concomitant triceps surae lengthening with TAA on the resultant ankle joint work.

METHODS

Thirty-three patients were recruited to the study and divided into 3 groups of 11. The first group underwent both triceps surae lengthening (Strayer and TendoAchilles) and TAA (Achilles group), the second group underwent only TAA (Non-Achilles group), and the third group underwent only TAA, but had a greater radiographic prosthesis range of motion (Control group) compared to the first 2 groups. The 3 groups were matched in terms of demographic variables and walking speed. All patients underwent a 3D gait analysis 1 year after surgery to measure intersegmental joint work using a 4-segmented kinetic foot model. An analysis of variance (ANOVA) or Kruskal-Wallis test was used to compare the 3 groups.

RESULTS

The ANOVA showed significant differences between the 3 groups. Post hoc analyses suggested that (1) the Achilles group had less positive work at the ankle joint than the Non-Achilles and Control groups; (2) the Achilles group produced less positive work performed by all foot and ankle joints than the Control group; and (3) the Achilles and Non-Achilles groups absorbed less energy across all foot and ankle joints during the stance phase than the Control group.

CONCLUSION

Concomitant triceps surae lengthening in TAA may reduce the positive work at the ankle joint.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Developing a core outcome set for foot and ankle disorders in rheumatic and musculoskeletal diseases: A scoping review and report from the OMERACT 2022 foot and ankle special interest group session

OBJECTIVES

Foot and ankle involvement is common in rheumatic and musculoskeletal diseases, yet high-quality evidence assessing the effectiveness of treatments for these disorders is lacking. The Outcome Measures in Rheumatology (OMERACT) Foot and Ankle Working Group is developing a core outcome set for use in clinical trials and longitudinal observational studies in this area.

METHODS

A scoping review was performed to identify outcome domains in the existing literature. Clinical trials and observational studies comparing pharmacological, conservative or surgical interventions involving adult participants with any foot or ankle disorder in the following rheumatic and musculoskeletal diseases (RMDs) were eligible for inclusion: rheumatoid arthritis (RA), osteoarthritis (OA), spondyloarthropathies, crystal arthropathies and connective tissue diseases. Outcome domains were categorised according to the OMERACT Filter 2.1.

RESULTS

Outcome domains were extracted from 150 eligible studies. Most studies included participants with foot/ankle OA (63% of studies) or foot/ankle involvement in RA (29% of studies). Foot/ankle pain was the outcome domain most commonly measured (78% of studies), being the most frequently specified outcome domain across all RMDs. There was considerable heterogeneity in the other outcome domains measured, across core areas of manifestations (signs, symptoms, biomarkers), life impact, and societal/resource use. The group's progress to date, including findings from the scoping review, was presented and discussed during a virtual OMERACT Special Interest Group (SIG) in October 2022. During this meeting, feedback was sought amongst delegates regarding the scope of the core outcome set, and feedback was received on the next steps of the project, including focus group and Delphi methods.

CONCLUSION

Findings from the scoping review and feedback from the SIG will contribute to the development of a core outcome set for foot and ankle disorders in RMDs. The next steps are to determine which outcome domains are important to patients, followed by a Delphi exercise with key stakeholders to prioritise outcome domains.

How long do ankle arthroplasties last?

Despite the increasing numbers of ankle arthroplasties, there are limited studies on their survival and comparisons between different implants. The primary aim of this study was to determine the failure rates of primary ankle arthroplasties commonly used in the UK. A data linkage study combined National Joint Registry (NJR) data and NHS Digital data. The primary outcome of failure was defined as the removal or exchange of any components of the implanted device. Life tables and Kaplan-Meier survival charts were used to illustrate survivorship. Cox proportional hazards regression models were fitted to compare failure rates between 1 April 2010 and 31 December 2018. Overall, 5,562 primary ankle arthroplasties were recorded in the NJR. Linked data show a one-year survivorship of 98.8% (95% confidence interval (CI) 98.4% to 99.0%), five-year survival in 2,725 patients of 90.2% (95% CI 89.2% to 91.1%), and ten-year survival in 199 patients of 86.2% (95% CI 84.6% to 87.6%). The five-year survival for fixed-bearing implants was 94.3% (95% CI 91.3% to 96.3%) compared to 89.4% (95% CI 88.3% to 90.4%) for mobile-bearing implants. A Cox regression model for all implants with over 100 implantations using the implant with the best survivorship (Infinity) as the reference, only the STAR (hazard ratio (HR) 1.60 (95% CI 0.87 to 2.96)) and INBONE (HR 0.38 (95% CI 0.05 to 2.84)) did not demonstrate worse survival at three and five years. Ankle arthroplasties in the UK have a five-year survival rate of 90.2%, which is lower than recorded on the NJR, because we have shown that approximately one-third of ankle arthroplasty failures are not reported to the NJR. There are statistically significant differences in survival between different implants. Fixed-bearing implants appear to demonstrate higher survivorship than mobile-bearing implants.

Reflections on Presurgical and Postsurgical Gait Mechanics After 50 Years of Total Ankle Arthroplasty and Perspectives on the Next Decade of Advancement

Although not the most prevalent form of lower limb pathology, ankle arthritis is one of the most painful and life-limiting forms of arthritis. Developing from overuse and various traumatic injuries, the effect of ankle arthritis on gait mechanics and effective treatment options for ankle arthritis remain an area of extensive inquiry. Although nonsurgical options are common (physical therapy, limited weight-bearing, and steroidal injections), surgical options are popular with patients. Fusion remains a common approach to stabilize the joint and relieve pain. However, starting in the early 1970s, total ankle arthroplasty was proposed as an alternative to fusion.

Early-Term Results of the Cadence Total Ankle Prosthesis: An European Noninventor Study

BACKGROUND

Although considerable literature can be found on the outcome of total ankle replacement (TAR), only a few studies have reported the results of the fixed-bearing Cadence prosthesis. This noninventor study reports a consecutive series of 60 Cadence TAR systems with a mean of 2.9 years' follow-up, focusing on clinical and radiographic outcomes and early complications. This study is the first to assess true postoperative radiographic ankle prosthesis range of motion (ROM) and to report an unanticipated serious adverse device effect.

METHODS

Sixty patients who underwent primary TAR with the Cadence prosthesis between July 2016 and July 2019 were clinically and radiographically evaluated preoperatively and at last follow-up after the procedure. Revisions, additional procedures, implant failure, and complications were reported according to the classifications of Vander Griend and Glazebrook. Radiographic outcomes included radiographic TAR ROM, bone-implant interface, and alignment parameters.

RESULTS

The survival rate of the prosthesis was 98.3%. The mean radiographic ankle ROM at the last follow-up was 24 degrees (9 degrees of dorsiflexion and 15 degrees of plantarflexion). The coronal and sagittal alignment of TAR was 90.8 degrees and 3.9 degrees, respectively. Bone-implant interface analysis revealed osteolysis in 9 ankles (15%) and radiolucent lines in 33 ankles (55%) occurring at both component interfaces. Intraoperative complications were 3 periprosthetic malleolar fractures (5%). Five talar implant fractures (implant failure of 8.3%) were observed, and 1 unexplained persistent pain that required a conversion from TAR to a tibiotalocalcaneal arthrodesis.

CONCLUSION

Clinical, radiograph ROM, implant position outcomes, and survival rate at an early-term follow-up of 2.9 years were similar to those reported in recent Cadence studies. However, this study reports 5 unanticipated talar implant fractures and a high rate of posterior radiolucent lines.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Decreased Mechanical Work Demand in the Chopart Joint After Total Ankle Replacement

BACKGROUND

The success of total ankle replacement (TAR) must be based on restoring reasonable mechanical balance with anatomical structures that can produce mechanical joint work through elastic (eg, tendons, fascia) or viscoelastic (eg, heel pad) mechanisms, or by active muscle contractions. Yet, quantifying the work distribution across the affected joint and the neighboring foot joints after TAR is lacking. Therefore, the objective of this study was to investigate if there is a change in the joint work distribution across the Ankle, Chopart, Lisfranc and Metatarsophalangeal joints during level walking before and after patients undergo TAR.

METHODS

Fifteen patients with end-stage ankle osteoarthritis scheduled for primary TAR for pain relief were recruited and peer-matched with a sample of 15 control subjects. All patients underwent a 3D gait analysis before and after surgery, during which a kinetic multisegment foot model was used to quantify intersegmental joint work.

RESULTS

The contribution of the Ankle joint (P = .007) to the total foot and ankle positive work increased significantly after TAR. In contrast, a significant decrease in the contribution to the total foot and ankle joint positive work (P < .001) were found at the Chopart joint after TAR. The foot joints combined produced a significant increase in a net mechanical work from +0.01 J/kg before surgery to +0.05 J/kg after TAR (P = .006).

CONCLUSION

The findings of this study corroborate the theoretical rationale that TAR reduces significantly the compensatory strategy in the Chopart joint in patients with end-stage ankle osteoarthritis after TAR. However, the findings also showed that the contribution of the ankle joint of patients after TAR to the total foot and ankle joint positive work remained impaired compared to the control group.

The motion between components in a mobile-bearing total ankle replacement measured by cone-beam CT scanning

BACKGROUND

To measure the motion of polyethylene insert and implant components of mobile-bearing total ankle replacement (TAR) by cone-beam CT scanning.

METHODS

10 TAR patients with high amount of clinical motion after the CCI implant (Ceramic Coated Implant; Wright Medical Technology, Arlington, TN, USA) with average age at operation 64,3 years (range 47-84) and average clinical total range of motion 42 degrees (range 35-55) were included.

RESULTS

The average total range of motion between the insert and the tibial component was 0.8mm (range 0-2) in the coronal plane, and 2.9mm (range 1-6) in the sagittal plane. There was wide variation in the axial rotation measurements between the components.

CONCLUSION

We found measurable motion between the mobile-bearing insert and the tibial component in all planes. The relevance of this motion to the function and long-term survival of the TAR remains to be determined.

Multi-segment foot kinematics during gait following ankle arthroplasty

Ankle arthritis is a debilitating disease marked by pain and limited function. Total ankle arthroplasty improves pain while preserving motion and offers an alternative to the traditional treatment of ankle fusion. Gait analysis and functional outcomes tools can provide an objective balanced analysis of ankle replacement for the treatment of ankle arthritis. Twenty-nine patients with end-stage ankle arthritis were evaluated before and after ankle arthroplasty. Multi-segment foot and ankle kinematics were assessed annually following surgery (average 3.5 years, range 1-6 years) using the Milwaukee Foot Model and a Vicon video motion analysis system. Functional outcomes (American Orthopedic Foot and Ankle Society [AOFAS] ankle/hindfoot scale, short form 36 [SF-36] questionnaire) and temporal-spatial parameters were also assessed. Kinematic results were compared to findings from a previously collected group of healthy ambulators. AOFAS and SF-36 mean scores improved postoperatively. Walking speed and stride length increased after surgery. There were significant improvements in tibial sagittal range of motion in terminal stance and hindfoot sagittal range of motion in preswing. Decreased external rotation of the tibia and increased external rotation of the hindfoot were noted throughout the gait cycle. Pain and function improved after ankle replacement as supported by better outcomes scores, increased temporal-spatial parameters, and significant improvement in tibial sagittal range of motion during terminal stance and hindfoot sagittal range of motion during preswing. While multi-segment foot kinematics were improved, they were not restored to control values. Statement of clinical significance: Total ankle arthroplasty does not fully normalize mutli-segment gait kinematics despite improved patient-reported outcomes and gait mechanics.

Outcome Reporting in Total Ankle Arthroplasty: A Systematic Review

Total ankle arthroplasty is an increasingly utilized treatment for ankle arthritis due to decreasing failure rates and improved outcomes. However, the literature on this procedure remains heterogeneous with large variability in outcome reporting methods. PRISMA guidelines were used to systematically review outcome reporting measures used in prospective studies and randomized control trials on total ankle arthroplasty published in 15 high-impact journals between Jan 1, 2009-May 1, 2020. A total of 43 studies were included and outcome measures were grouped into seven categories: pain, subjective function, patient satisfaction, complications, objective function, implant survivorship, and imaging. The most common topic of study was implant design followed by differences in outcomes when comparing total ankle arthroplasty and arthrodesis. The most commonly reported outcome measure was post-surgical complications. No study reported on all seven categories, while 22 (51.2%) studies reported on four or more. Subjective measures had significant variability with fifteen different Patient Reported Outcome Measures used across the studies. While the included studies were quite comprehensive, there was little consistency in reporting outcomes after total ankle arthroplasty. With improving outcomes and techniques in total ankle arthroplasty, and thus an expected increase in utilization and number of published studies, efforts should be made to use commonly employed outcome reporting methods to facilitate comparison of results across studies.

The effect of ankle osteoarthritis and total ankle arthroplasty on center of pressure position

Total ankle arthroplasty (TAA) is a common surgical approach for patients with end-stage ankle osteoarthritis (OA). However, very little is known about the path of the center of pressure (COP) of the foot, and thus important aspects of load transfer, muscle mechanical advantage, and balance, in patients before or after surgery. The objective of this study was to trace the pathway of the COP under the foot in patients with symptomatic ankle OA, comparing asymmetry between affected and unaffected limbs. From force plate data, proximodistal and mediolateral positions of the COP beneath the foot were calculated and compared for the affected and unaffected foot in patients with unilateral ankle OA (N = 93) before and after TAA. Gender and age at surgery had little or no effect in this study. Patients with ankle OA had minimal COP position asymmetry before surgery, and this asymmetry was reduced following surgery. Before surgery, patients had a slower walking speed and a shorter path of the COP which began relatively distal to the heel and ended relatively proximal to the hallux. TAA increased the proximodistal distance the COP traveled under both the unaffected and affected foot, a pattern that was maintained for over 2-year postsurgery. TAA allows patients with ankle OA to maintain a longer COP path than they had before surgery on both sides that is closer to that reported for unaffected individuals, extending effectively from the heel to the hallux, potentially improving pedal mechanics.

Long-term Functional Results of Total Ankle Arthroplasty in Stiff Ankles

BACKGROUND

Total ankle arthroplasty (TAA) is advocated over ankle arthrodesis to preserve ankle motion (ROM). Clinical and gait analysis studies have shown significant improvement after TAA. The role and outcomes of TAA in stiff ankles, which have little motion to be preserved, has been the subject of limited investigation. This investigation evaluated the mid- to long-term functional outcomes of TAA in stiff ankles.

METHODS

A retrospective study of prospectively collected functional gait data in 33 TAA patients at a mean of 7.6 (5-13) years postoperatively used 1-way analysis of variance and multivariate regression analysis to compare among preoperative and postoperative demographic data (age, gender, body mass index, years postsurgery, and diagnosis) and gait parameters according to quartiles of preoperative sagittal ROM.

RESULTS

The stiffest ankles had a mean ROM of 7.8 degrees, compared to 14.3 degrees for the middle 2 quartiles, and 21.0 degrees for the most flexible ankles. Patients in the lowest quartile (Q1) also had statistically significantly lower step length, speed, max plantarflexion, and power preoperatively. Postoperatively, they increased step length, speed, max plantarflexion, and ankle power to levels comparable to patients with more flexible ankles preoperatively (Q2, Q3, and Q4). They had the greatest absolute and relative increases in these parameters of any group, but the final total ROM was still statistically significantly the lowest.

CONCLUSION

Preoperative ROM was predictive of overall postoperative gait function at an average of 7.6 (range 5-13) years. Although greater preoperative sagittal ROM predicted greater postoperative ROM, the stiffest ankles showed the greatest percentage increase in ROM. Patients with the stiffest ankles had the greatest absolute and relative improvements in objective function after TAA, as measured by multiple gait parameters. At intermediate- to long-term follow-up, patients with stiff ankles maintained significant functional improvements after TAA.

LEVEL OF EVIDENCE

Level III, comparative study.

Damage patterns in polyethylene fixed bearings of retrieved total ankle replacements

INTRODUCTION

Poor long-term outcomes continue to hinder the universal adoption of total ankle replacements (TAR) for end stage arthritis. In the present study, polyethylene inserts of TARs retrieved at revision surgery were analyzed for burnishing, scratching, mechanical damage, pitting, and embedded particles.

METHODS

Fourteen retrieved polyethylene inserts from a fixed bearing total ankle replacement design currently in clinical use were analyzed. Duration of time in vivo was between 11.5 months and 120.1 months. Three investigators independently graded each articular surface in quadrants for five features of damage: burnishing, scratching, mechanical damage, pitting, and embedded particles.

RESULTS

No correlation was found for burnishing between the anterior and posterior aspects (p = 0.47); however, scratching and pitting were significantly higher on the posterior aspect compared to the anterior aspect (p < 0.03). There was a high correlation between burnishing and in vivo duration of the implant (anterior: R = 0.67, p = 0.01, posterior: R = 0.68, p = 0.01).

CONCLUSION

The higher concentration of posterior damage on these polyethylene inserts suggested that prosthesis-related (design) or surgeon-related (technique) factors might restrict the articulation of the implant. The resulting higher stresses in the posterior articular surfaces may have contributed to the failure of retrieved implants Keywords: Retrieval, Polyethylene Damage, Total Ankle Replacement.

Functional Outcomes of Total Ankle Arthroplasty at a Mean Follow-up of 7.6 Years: A Prospective, 3-Dimensional Gait Analysis

BACKGROUND

In vivo gait analysis provides objective measurement of patient function and can quantify that function before and after ankle reconstruction. Previous gait studies have shown functional improvement for up to 4 years following total ankle arthroplasty (TAA), but to date, there are no published studies assessing function at ≥5 years following TAA. We hypothesized that patients who underwent TAA would show significant improvements in walking function at a minimum follow-up of 5 years, compared with their preoperative function, as measured by changes in temporospatial, kinematic, and kinetic gait parameters.

METHODS

Three-dimensional gait analysis with a 12-camera digital motion-capture system and double force plates was utilized to record temporospatial, kinematic, and kinetic measures in 33 patients who underwent TAA with either the Scandinavian Total Ankle Replacement (Stryker; n = 28) or Salto Talaris Ankle (Integra LifeSciences; n = 5). Gait analysis was performed preoperatively and at a minimum follow-up of 5 years (mean, 7.6 years; range, 5 to 13 years).

RESULTS

Significant improvements were observed in multiple gait parameters, with temporospatial increases in cadence (+9.5 steps/min; p < 0.0001), step length (+4.4 cm; p = 0.0013), and walking speed (+0.2 m/s; p < 0.0001), and kinematic increases in total sagittal range of motion (+2.0°; p = 0.0263), plantar flexion at initial contact (+2.7°; p = 0.0044), and maximum plantar flexion (+2.0°; p = 0.0488). Kinetic analysis revealed no loss of peak ankle power, despite patients aging.

CONCLUSIONS

To our knowledge, this is the first study to report 7-year functional outcomes of TAA, quantified by objective, in vivo measurements of patient gait. Patients were shown to have sustained improvement in multiple objective parameters of gait compared with preoperative function.

LEVEL OF EVIDENCE

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

Differences in Gait and Stair Ascent After Total Ankle Arthroplasty and Ankle Arthrodesis

BACKGROUND

Ankle arthrodesis has historically been the standard of care for end-stage ankle arthritis; however, total ankle arthroplasty (TAA) is considered a reliable alternative. Our objective was to compare 3-dimensional foot and ankle kinetics and kinematics and determine the ankle power that is generated during level walking and stair ascent between TAA and ankle arthrodesis patients.

METHODS

Ten patients who underwent TAA with a modern fixed-bearing ankle prosthesis and 10 patients who previously underwent ankle arthrodesis were recruited. Patients were matched for age, sex, body mass index, time from surgery, and preoperative diagnosis. A minimum of 2-year follow-up was required. Patients completed instrumented 3D motion analysis while walking over level ground and during stair ascent. Between-group differences were assessed with a 2-tailed Mann-Whitney exact test for 2 independent samples.

RESULTS

Sagittal ankle range of motion (ROM) was significantly higher in the TAA group (21.1 vs 14.7 degrees, P = .003) during level walking. In addition, forefoot-tibia motion (25.3±5.9 degrees vs 18.6±5.1 degrees, P = .015) and hindfoot-tibia motion (15.4±3.2 degrees vs 12.2±2.5 degrees, P = .022) were significantly greater in the TAA group. During stair ascent, sagittal ankle ROM (25 vs 17.1 degrees, P = .026), forefoot-tibia motion (27.6 vs 19.6 degrees, P = .017), and hindfoot-tibia motion (16.8 vs 12 degrees, P = .012) was greater.

CONCLUSION

There were significant differences during level walking and stair ascent between patients with TAA and ankle arthrodesis. TAA patients generated greater peak plantarflexion power and sagittal motion within the foot and ankle compared to patients with an ankle arthrodesis. Further investigation should continue to assess biomechanical differences in the foot and ankle during additional activities of daily living.

LEVEL OF EVIDENCE

Level III, comparative study.

Impact of foot modeling on the quantification of the effect of total ankle replacement: A pilot study

BACKGROUND

Kinematic and kinetic foot models showed that computing ankle joint angles, moments and power with a one-segment foot modeling approach alters kinematics and tends to overestimate ankle joint power. Nevertheless, gait studies continue to implement one-segment foot models to assess the effect of total ankle replacement.

RESEARCH QUESTION

The objective of this pilot study was to investigate the effect of the foot modeling approach (one-segment versus multi-segment) on how total ankle replacement is estimated to benefit or degrade the patient's biomechanical performance.

METHODS

Ten subjects with post-traumatic ankle osteoarthritis scheduled for total ankle replacement and 10 asymptomatic subjects were recruited. A one-segment and a multi-segment foot model were used to calculate intrinsic foot joints kinematics and kinetics during gait. A linear mixed model was used to investigate the effect of the foot model on ankle joint kinematic and kinetic analysis and the effect of total ankle replacement.

RESULTS

Differences in range of motion due to the foot model effect were significant for all the gait subphases of interest except for midstance. Peak power generation was significantly overestimated when computed with the one-segment foot model. Ankle and shank-calcaneus joint dorsi-/plantarflexion range of motion did not increase post-operatively except during the loading response phase. A significant 'group' effect was found for stance and pre-swing phase range of motion, with total ankle replacement patients showing lower range of motion values than controls for dorsi/plantarflexion.

SIGNIFICANCE

The outcome of this study showed that the 'foot model' had a significant effect on estimates of range of motion and power generation. The findings in our study therefore emphasize the clinical interest of multi-segment foot modeling when assessing the outcome of a therapeutic intervention.

Retrospective comparison between a two- and three-component ankle arthroplasty: clinical and functional evaluation via gait analysis

BACKGROUND

Total ankle arthroplasty is intended to restore physiological joint function in case of severe ankle arthritis. However, little is known about the functional outcome associated to different prosthesis designs. The aim of this retrospective study was to compare clinical and functional outcomes via gait analysis of two ankle prostheses designed to preserve ankle ligamentous isometry.

METHODS

Two groups of twenty patients who underwent ankle arthroplasty using either a three-component or a two-component prosthesis, were clinically evaluated, both pre-operatively and at minimal 2-year follow-up, by means of the AOFAS score. The spatio-temporal parameters, along with the kinetics and kinematics of the lower limb joints were also assessed at follow-up via gait analysis. The non-parametric Kruskal-Wallis test was used to assess differences in functional data between the two patient groups and with respect to those from a control group of 20 healthy subjects.

FINDINGS

All AOFAS scores significantly improved from pre-operative to post-operative assessment in both patient groups (P < 0.05). Most spatio-temporal and functional parameters in the patients were worse than those in the control group, but no significant differences were observed between the two arthroplasty groups.

INTERPRETATION

Both patient groups showed improved clinical outcome at follow-up, with a few differences in gait parameters. However, neither of the two groups achieved normal locomotion patterns. Since both prostheses were designed to preserve ligamentous isometry, the choice of one implant over the other should be due to preferences in the surgical approach and to other patient-specific factors.

A Systematic Review of Unsystematic Total Ankle Replacement Wear Evaluations

BACKGROUND

Numerous studies have reported the use of laboratory multistation joint simulators to successfully predict wear performance and functionality of hip and knee replacements. In contrast, few studies in the peer-reviewed literature have used joint simulation to quantify the wear performance and functionality of ankle replacements. We performed a systematic review of the literature on joint simulator studies that quantified polyethylene wear in total ankle arthroplasty. In addition to the quantified wear results, the load and motion parameters were identified and compared among the studies.

METHODS

A search was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to identify articles reporting total ankle replacement polyethylene wear using joint simulators.

RESULTS

Nine studies that used joint simulators and 1 study that used a computer simulation were found. Although all studies used physiological multidirectional motions (i.e., internal/external rotation, plantar flexion/dorsiflexion, anterior/posterior translation), there was large variability among the studies in the magnitudes of these motions. Among these studies, mean non-cross-linked polyethylene wear ranged from 3.3 ± 0.4 to 25.8 ± 3.1 mm per million cycles. In contrast, mean highly cross-linked polyethylene wear ranged from 2.1 ± 0.3 to 3.3 ± 0.4 mm per million cycles. The wide distribution in wear rates was attributable to the highly inconsistent kinematic parameters and loads applied as well as differences in implant design and materials.

CONCLUSIONS

There is a severe lack of clinically applicable data on wear performance of total ankle replacements in the peer-reviewed literature. No universal set of kinematic load parameters has been established. Furthermore, only 2 of the published studies have validated their findings using independently derived data, such as retrieval analysis. These shortcomings make it difficult to compare findings as a function of design parameters and materials, or to draw clinically relevant conclusions from these simulations. More work is required to enhance the predictive capability of in vitro simulations of total ankle replacements.

CLINICAL RELEVANCE

The results of joint wear simulator studies may not accurately represent in vivo wear of total ankle replacements. Joint simulator studies should establish that they are accurately replicating in vivo wear, thus enabling use of their predictive capabilities for new materials and designs.

Change in gait biomechanics after total ankle replacement and ankle arthrodesis: a systematic review and meta-analysis

BACKGROUND

The aim of this systematic review with meta-analysis was to determine the change in gait biomechanics after total ankle replacement and ankle arthrodesis for end-stage osteoarthritis.

METHODS

Electronic databases were searched up until May 2019. Peer-reviewed journal studies including adult participants suffering from end-stage ankle osteoarthritis and reporting pre- and post-operative kinematics, kinetics and spatio-temporal effects of total ankle replacement and ankle arthrodesis during walking were included with a minimum of 12 months follow-up. Seventeen suitable studies were identified and assessed according to methodological and biomechanical qualities. Meta-analysis was performed by calculating the effect size using standard mean differences between pre- and post-operative gait status.

FINDINGS

Seventeen studies with a total of 883 patients were included. Meta-analysis revealed moderate evidence of an improvement in lower limb kinematics, kinetics and spatio-temporal parameters after total ankle replacement. Moderate evidence indicated an increase in ankle moment, hip range of motion and walking speed after ankle arthrodesis.

INTERPRETATION

The currently available evidence base of research papers evaluating changes in gait biomechanics after total ankle replacement and ankle arthrodesis is limited by a lack of prospective research, low sample sizes and heterogeneity in the patho-etiology of ankle osteoarthritis. Following total ankle replacement, improvements were demonstrated for spatio-temporal, kinematic and kinetic gait patterns compared to the pre-operative measures. Improvements in gait mechanics after ankle arthrodesis were limited to walking speed and ankle moment. Increased hip range of motion after ankle arthrodesis could represent a sign of compensation for the lack of ankle motion.

Musculoskeletal modeling of total ankle arthroplasty using force-dependent kinematics for predicting in vivo joint mechanics

In vivo load and motion in the ankle joint play a key role in the understanding of the failure mechanism and function outcomes of total ankle arthroplasty. However, a thorough understanding of the biomechanics of the ankle joint in daily activities is lacking. The objective of this study was to develop a novel lower extremity musculoskeletal multibody dynamics model with total ankle arthroplasty considering the 6 degrees of freedom of the ankle joint motions and the deformable contact mechanics of the implant, based on force-dependent kinematics method. A patient who underwent total ankle arthroplasty surgery was considered. The walking gait data of the patient was measured in a gait laboratory and used as the input for the patient-specific musculoskeletal modeling. The predictions from the musculoskeletal model of total ankle arthroplasty included dorsiflexion-plantar flexion, inversion-eversion, internal-external rotation, anterior-posterior translation, inferior-superior translation, and medial-lateral translation of the tibiotalar joint, the ankle contact forces, the muscle activations, and the ligament forces. The magnitudes and tendencies of the predicted results were all within reasonable ranges, as compared with the data available in the literature. The predicted peak total ankle contact force was 6.55 body weight. In addition, the peak contact forces of the lateral and medial compartments were 4.22 body weight and 2.59 body weight, respectively. This study provides a potential new platform for the design of a better ankle prosthesis, the improvement of the operation techniques of the clinicians, and the accelerated postoperative recovery of the patients.

Prospective Randomized Trial Comparing Mobile-Bearing and Fixed-Bearing Total Ankle Replacement

BACKGROUND

Outcomes of total ankle replacement for the treatment of end-stage ankle arthritis continue to improve. Debate continues whether a mobile-bearing total ankle replacement (MB-TAR) or a fixed-bearing total ankle replacement (FB-TAR) is superior, with successful outcomes reported long term for MB-TAR and at intermediate- to long-term follow-up for newer generation FB-TAR. Although comparisons between the 2 total ankle designs have been reported, to our knowledge, no investigation has compared the 2 designs with a high level of evidence. This prospective, randomized controlled trial conducted at a single institution compares patient satisfaction, functional outcomes, and radiographic results of the mobile-bearing STAR and the fixed-bearing Salto-Talaris in the treatment of end-stage ankle arthritis.

METHODS

Between November 2011 and November 2014, adult patients with end-stage ankle osteoarthritis failing nonoperative treatment were introduced to the study. With informed consent, 100 patients (31 male and 69 female, average age 65 years, range 35-85 years) were enrolled; a demographic comparison between the 2 cohorts was similar. Exclusion criteria included inflammatory arthropathy, neuropathy, weight exceeding 250 pounds, radiographic coronal plane deformity greater than 15 degrees, or extensive talar dome wear pattern ("flat-top talus"). Prospective patient-reported outcomes, physical examination, and standardized weightbearing ankle radiographs were obtained preoperatively, at 6 and 12 months postoperatively, and then at yearly intervals. Data collection included visual analog pain score, Short Form 36, Foot and Ankle Disability Index, Short Musculoskeletal Functional Assessment, and American Orthopaedic Foot & Ankle Society ankle-hindfoot score. Surgeries were performed by a nondesign team of orthopedic foot and ankle specialists with total ankle replacement expertise. Statistical analysis was performed by a qualified statistician. At average follow-up of 4.5 years (range, 2-6 years) complete clinical data and radiographs were available for 84 patients; 7 had incomplete data, 1 had died, 4 were withdrawn after enrolling but prior to surgery, and 4 were lost to follow-up.

RESULTS

In all outcome measures, the entire cohort demonstrated statistically significant improvements from preoperative evaluation to most recent follow-up with no statistically significant difference between the 2 groups. Radiographically, tibial lucency/cyst formation was 26.8% and 20.9% for MB-TAR and FB-TAR, respectively. Tibial settling/subsidence occurred in 7.3% of MB-TAR. Talar lucency/cyst formation occurred in 24.3% and 2.0% of MB-TAR and FB-TAR, respectively. Talar subsidence was observed in 21.9% and 2.0% of MB-TAR and FH-TAR, respectively. Reoperations were performed in 8 MB-TARs and 3 FH-TARs, with the majority of procedures being to relieve impingement or treat cysts and not to revise or remove metal implants.

CONCLUSION

With a high level of evidence, our study found that patient-reported and clinical outcomes were favorable for both designs and that there was no significant difference in clinical improvement between the 2 implants. The incidence of lucency/cyst formation was similar for MB-TAR and FH-TAR for the tibial component, but the MB-TAR had greater talar lucency/cyst formation and tibial and talar subsidence. As has been suggested in previous studies, clinical outcomes do not necessarily correlate with radiographic findings. Reoperations were more common for MB-TAR and, in most cases, were to relieve impingement or treat cysts rather than revise or remove metal implants.

LEVEL OF EVIDENCE

Level I, prospective randomized study.