Changes in gait following the Scandinavian Total Ankle Replacement

3D kinematics of tibiotalar motion in patients with mobile bearing and fixed bearing total ankle arthroplasty: In vivo videofluoroscopic feasibility study

BACKGROUND

As total ankle arthroplasty (TAA) is an increasingly common surgical intervention for patients with end-stage ankle arthritis, there is a need to better understand the dynamic performance of prosthetic implants during activities of daily living. Our purpose was to quantify and compare relative tibiotalar motion during gait in persons with a fixed-bearing (FB) and mobile-bearing (MB) total ankle arthroplasty. We hypothesized a FB prosthesis would have lower tibiotalar range of motion (ROM).

METHODS

Patients at least 12 months postoperative with either a FB (n=5) or MB (n=3) total ankle arthroplasty were tested. We used high-speed biplanar videoradiography to quantify tibiotalar kinematics during self-selected gait. Angular and linear ROM in three axes were compared between the groups.

RESULTS

ROM for dorsiflexion-plantarflexion, internal-external rotation, and inversion-eversion angles in FB subjects averaged 7.47±4.05°, 7.39±3.63°, and 4.51±2.13°, respectively. ROM in MB subjects averaged 6.74±2.04°, 6.28±4.51°, and 5.68±2.81°, respectively. Linear ROM along anteroposterior, mediolateral, and superior-inferior axes in FB subjects averaged 1.47±2.07 mm, 1.13±1.49 mm, and 0.28±0.30 mm, respectively. Linear ROM in MB subjects averaged 0.68±1.44 mm, 0.60±1.41 mm, and 0.20±0.13 mm, respectively. We found no significant difference between the two groups for any of these ROM parameters (p>0.05).

CONCLUSION

Total ankle arthroplasty using either FB or MB design appears to confer similar ankle motion during the gait cycle in this biplanar fluoroscopic model.

LEVEL OF EVIDENCE

Level IV, case series.

Change of Segmental Motion Following Total Ankle Arthroplasty Using a 3-Dimensional Multi-segment Foot Model

Background

Total ankle arthroplasty (TAA) enhances patients' subjective outcomes with respect to pain and function. The aim of this study was to analyze the biomechanical changes of the affected limb following TAA using gait analysis with a 3-dimensional multi-segment foot model (3D MFM).

Methods

We reviewed medical records, simple radiographs, and gait analyses using a 3D MFM of patients who underwent TAA for severe varus ankle arthritis. Preoperative and postoperative gait data of 24 patients were compared. Postoperative gait analyses were done at least 1 year after surgery.

Results

TAA significantly increased stride length (p = 0.024). The total range of motion of all planes in the hindfoot and forefoot showed no significant changes between preoperative and postoperative states. Hindfoot was significantly plantarflexed and pronated after TAA, while forefoot was significantly supinated in all phases. After appropriate calculations, the genuine coronal motion of the hindfoot showed no changes after TAA in all phases.

Conclusions

TAA did not result in biomechanical improvements of segmental motions in the forefoot and hindfoot, except for changes to the bony structures. Therefore, it is important to point out to patients that TAA will not result in significant improvement of ankle function and range of motion. Clinicians can consider this information during preoperative counseling.

Discrepancies Between Intraoperative and Postoperative Ankle Motion Measured for Anterior-Approach Total Ankle Arthroplasty

BACKGROUND

Although intraoperative ankle motion serves as a foundational reference for anticipated motion after surgery and guides the addition of procedures to enhance ankle motion in total ankle arthroplasty (TAA), the relationship between intraoperative and postoperative ankle motion remains unclear. This study aimed to investigate the discrepancy between intraoperative and postoperative ankle range of motion (ROM) following TAAs using the anterior-approach, fixed-bearing systems.

METHODS

This study retrospectively reviewed 67 patients (67 ankles) who underwent primary TAA at a single institution. Three different types of anterior-approach, fixed-bearing TAA systems were included. Intraoperative fluoroscopy was used to document the maximal dorsiflexion and plantar flexion at the end of the case. Standardized weightbearing maximum dorsiflexion and plantar flexion sagittal radiographs were obtained pre- and postoperatively, following a previously described method. The motion between 3 different time points (preoperative, intraoperative, and postoperative [mean 11.4 months]) was compared using pairwise t tests, and their differences were quantified.

RESULTS

The mean total tibiotalar ROM was 38.1 degrees (SD 7.8) intraoperatively, and the postoperative total tibiotalar ROM was 24.2 degrees (SD 9.7) (P < .001), indicating that a mean of 65.3% (SD 26.7) of the intraoperative motion was maintained postoperatively. Intraoperative dorsiflexion (mean 11.6 [SD 4.5] degrees) showed no evidence of difference from postoperative dorsiflexion (mean 11.4 [SD 5.8] degrees, P > .99), indicating that a median of 95.6% (interquartile range: 66.2-112) of the intraoperative maximum dorsiflexion was maintained postoperatively. However, there was a significant difference between intraoperative plantarflexion (mean 26.4 [SD 6.3]) and postoperative plantarflexion (12.8 [SD 6.9] degrees, P < .001), indicating a mean 50.6% (SD 29.6) of intraoperative motion maintained in the postoperative assessment. There was an improvement of 2.5 degrees in the total tibiotalar ROM following TAA with statistical significance (P < .043).

CONCLUSION

This study revealed a significant difference between intraoperative ankle ROM and ankle ROM approximately 1 year after anterior-approach, fixed-bearing TAA, mainly due to plantarflexion motion restriction. Minimal difference in dorsiflexion suggests the importance of achieving the desired postoperative dorsiflexion motion during the surgery using the best possible adjunct procedures.

LEVEL OF EVIDENCE

Level IV, case series.

Three-dimensional gait analysis of orthopaedic common foot and ankle joint diseases

Walking is an indispensable mode of transportation for human survival. Gait is a characteristic of walking. In the clinic, patients with different diseases exhibit different gait characteristics. Gait analysis describes the specific situation of human gait abnormalities by observing and studying the kinematics and dynamics of limbs and joints during human walking and depicting the corresponding geometric curves and values. In foot and ankle diseases, gait analysis can evaluate the degree and nature of gait abnormalities in patients and provide an important basis for the diagnosis of patients' diseases, the correction of abnormal gait and related treatment methods. This article reviews the relevant literature, expounds on the clinical consensus on gait, and summarizes the gait characteristics of patients with common ankle and foot diseases. Starting from the gait characteristics of individuals with different diseases, we hope to provide support and reference for the diagnosis, treatment and rehabilitation of clinically related diseases.

Influence of Joint Line Level on Clinical Outcomes and Range of Motion in Total Ankle Arthroplasty

BACKGROUND

Ankle arthritis leads to an elevated joint line compared to the nonarthritic ankle, as measured by the "joint line height ratio" (JLHR). Previous work has shown that the JLHR may remain elevated after total ankle arthroplasty (TAA). However, the clinical impact of this has yet to be determined. This study assessed the correlation between postoperative JLHR, post-TAA range of motion (ROM), and 1-year Patient-Reported Outcome Measurement Information System (PROMIS) scores.

METHODS

A retrospective review of 150 patients who underwent primary TAA was performed. Preoperative and postoperative JLHR, as well as postoperative dorsiflexion, plantarflexion, and total ROM, was calculated on weightbearing radiographs at a minimum of 1-year follow-up. Correlation between JLHR, post-TAA ROM, and 1-year PROMIS scores was investigated using Pearson correlation and multiple linear regression models. Interobserver reliability for the JLHR was also calculated.

RESULTS

Interobserver reliability for the JLHR was excellent (r = 0.98). Mean (SD) JLHR changed from 1.66 (0.45) to 1.55 (0.26) after TAA (P < .001), indicating that the joint line was lowered after TAA. An elevated joint line was correlated with decreased post-TAA dorsiflexion (r = -0.26, P < .001), total ROM (r = -0.18, P = .025), and worse 1-year PROMIS physical function (r = -0.22, P = .046), pain intensity (r = 0.22, P = .042), and pain interference (r = 0.29, P = .007). There was no correlation between the JLHR and post-TAA plantarflexion (r = -0.025, P = .76). Regression analysis identified a 0.5-degree reduction in post-TAA dorsiflexion with each 0.1-unit increase in JLHR (Coeff. = -5.13, P = .005).

CONCLUSION

In this patient cohort, we found that an elevated joint line modestly correlated with decreased postoperative dorsiflexion, total ROM, and worse 1-year PROMIS scores. These data suggest that effort likely should be made toward restoring the native joint line at the time of TAA. In addition, future studies investigating the clinical outcomes after TAA may consider including a measure of joint line height, such as the JLHR, because we found it was associated with patient-reported outcomes.

LEVEL OF EVIDENCE

Level III, retrospective review of prospectively collected data.

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.

Republication of "Perspectives in Treatments of End-Stage Ankle Arthritis Among Orthopaedic Surgeons: Analysis of an American Orthopaedic Foot & Ankle Society (AOFAS) Member Survey"

Background

This study aimed to assess the preferred operative treatment for patients over the age of 60 with end-stage ankle arthritis and perspectives on total ankle replacement (TAR) among American Orthopaedic Foot & Ankle Society (AOFAS) members. Associated factors were analyzed for potential contraindications among members with different levels of experience.

Method

A questionnaire containing 6 questions was designed and sent to 2056 members of the AOFAS. Responses were received from 467 orthopaedic surgeons practicing in the United States (76%), Canada (5%), and 26 other countries (20%). Participants were grouped for response comparisons according to country as well as experience level. Differences in contraindications were compared using χ2 tests or exact tests.

Results

Respondents practicing in the United States and surgeons who perform 11 or more TARs per year tended to recommend operative treatments favoring TAR and displayed recognition of its increasing role (P < .05). Overall, respondents felt that 41% of typical patients over 60 years old with end-stage arthritis would be best treated with TAR. Talus avascular necrosis, morbid obesity (body mass index >40 kg/m2), and poorly controlled diabetes with neuropathy were most recognized as the absolute contraindications to TAR. Surgeon's experience affected the consideration of these clinical factors as contraindications.

Conclusions

Total ankle replacement has a substantial and increasing role in the treatment of end-stage ankle arthritis in patients over the age of 60. Absolute and potential contraindications of the procedures were indicated from a cross-sectional survey of AOFAS members. Surgeons more experienced with total ankle replacement felt more comfortable employing it in a wider range of clinical settings.

Level of Evidence

Level III, therapeutic.

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.

The Rise of Total Ankle Arthroplasty Use: A Database Analysis Describing Case Volumes and Incidence Trends in the United States Between 2009 and 2019

BACKGROUND

Ankle arthrodesis has been the mainstay treatment for end-stage ankle arthritis. The popularity of total ankle arthroplasty (TAA) has been on the rise due to improved implant design and postoperative outcomes. The purpose of this study was to describe the basic epidemiology and trends of annual procedure volumes and incidence in the general American population as well as in different population subgroups from 2009 to 2019. We hypothesize that the incidence of TAA has significantly risen while the median length of hospital stay has decreased nationwide.

METHODS

The IBM MarketScan database was queried for patients who underwent TAA from January 2009 to December 2019 based on Current Procedural Terminology coding. Population estimates from the US Census Bureau were used to calculate the annual incidence of TAA. Procedural volume and incidence were calculated for annual sums, gender, age subgroups, inpatient and outpatient TAA, as well as in four statistical geographic regions in the United States. Median length of hospital stay was calculated and trended annually for inpatient TAA.

RESULTS

A total of 41,060 primary TAAs were identified in the database from 2009 to 2019, in which 52.5% were performed in males. Annual volumes increased by 136.1%, from 2180 to 5147 procedures nationwide. Incidence reported per 100 000 population increased by 120.8%. Both inpatient and outpatient procedures have increased, by 242.5% and 86.6%, respectively. Median length of hospital stay decreased from 3 days in 2009 to 1 day in 2019 and did not differ between genders. Growth in incidence was demonstrated in males and females above the age of 54 years with the largest growth in annual incidence found between 65 and 74 years. Incidence rose in the South and West of the United States by 111.8% and 136.5%, respectively.

CONCLUSION

We found that annual volumes and incidence rates of primary TAA has increased between 2009 and 2019. Although both inpatient and outpatient surgery have become more frequent, inpatient volumes and incidence have increased almost 3 times more than those of outpatient surgery. Length of hospital stay decreased over the study years. When adjusted for the same study period, the cumulative annual growth rates of TAA were found to be 2 times greater than total knee arthroplasty and 3.6 times greater than total hip arthroplasty.

LEVEL OF EVIDENCE

Level III, retrospective database review.

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.

Tranexamic Acid Associated With Less Wound Complications in Ankle and Hindfoot Surgery: Level III, Retrospective Cohort Study

INTRODUCTION

The purpose of this study was to determine whether total ankle arthroplasty (TAA) and ankle/hindfoot fusion patients receiving tranexamic acid (TXA) exhibit fewer wound complications.

METHODS

A retrospective review was conducted of 212 patients (217 feet) undergoing TAA (n = 72), ankle (n = 36), tibiotalocalcaneal (n = 20), pantalar (n = 1), or hindfoot fusion (ie, subtalar = 47, double = 33, and triple = 8) between 2015 and 2020 by a fellowship-trained foot and ankle surgeon at an academic medical center. Demographics, medical history, complications, and union status were compared between TXA (n = 101) and non-TXA (n = 116) cohorts. The mean follow-up was 1.24 years (range, 0.25 to 4.68).

RESULTS

The TXA group had significantly less postoperative infections (5.9% versus 15.5%, P = 0.025). Within a subgroup analysis of ankle/hindfoot fusions, the TXA group exhibited significantly more Charcot neuroarthropathy (20.7% versus 5.7%, P = 0.006) and shorter follow-up duration (0.96 versus 1.30 years, P = 0.030); however, TXA was associated with shorter time to fusion (146 versus 202 days, P = 0.049) and fewer revision surgeries (8.6% versus 21.8%, P = 0.036). Subgroup analysis excluding feet with Charcot also demonstrated less postoperative infections (4.5% versus 14.4%, P = 0.020). Subgroup analysis of TAAs showed fewer cases of superficial infections (2.3% versus 27.6%, P = 0.002) and delayed wound healing (25.6% versus 48.3%, P = 0.047) in the TXA cohort.

DISCUSSION

TXA use in ankle/hindfoot surgery was correlated with a reduction in superficial infections and radiographic time to union. The use of TXA in TAA correlated with fewer superficial infections and cases of delayed wound healing. Thus, in addition to other areas of orthopaedics, TXA seems to be beneficial in hindfoot and ankle surgery.

DATA AVAILABILITY AND TRIAL REGISTRATION NUMBERS

All data were obtained from our institution's medical records. This study is not associated with a clinical trial.

Cadaveric Gait Simulation of the Effect of Subtalar Arthrodesis on Total Ankle Replacement Kinematics

BACKGROUND

Patients undergoing total ankle replacement (TAR) often have symptomatic adjacent joint arthritis and deformity. Subtalar arthrodesis can effectively address a degenerative and/or malaligned hindfoot, but there is concern that it places abnormal stresses on the TAR and adjacent joints of the foot, potentially leading to early TAR failure. This study hypothesized that ankle and talonavicular joint kinematics would be altered after subtalar arthrodesis in the setting of TAR.

METHODS

Thirteen mid-tibia cadaveric specimens with neutral alignment were tested in a robotic gait simulator. To simulate gait, each specimen was secured to a static mounting fixture about a 6-degree of freedom robotic platform, and a force plate moves relative to the stationary specimen based on standardized gait parameters. Specimens were tested sequentially in TAR and TAR with subtalar arthrodesis (TAR-ST_fuse). Kinematics and range of motion of the ankle and talonavicular joint were compared between TAR and TAR-ST_fuse.

RESULTS

There were significant differences in kinematics and range of motion between TAR and TAR-ST_fuse groups. At the ankle joint, TAR-ST_fuse had less internal rotation in early-mid stance (P < .05), with decreased range of motion in the sagittal (-2.7 degrees, P = .008) and axial (-1.8 degrees, P = .002) planes in early stance, and increased range of motion in the coronal plane in middle (+1.2 degrees, P < .001) and late (+2.5 degrees, P = .012) stance. At the talonavicular joint, there were significant differences in axial and coronal kinematics in early and late stance (P < .05). Subtalar arthrodesis resulted in significantly decreased talonavicular range of motion in all planes in early and late stance (P < .003).

CONCLUSION

In ankles implanted with the TAR design used in this study, kinematics of the ankle and talonavicular joint were found to be altered after subtalar arthrodesis. Aberrant motion may reflect altered contact mechanics at the prosthesis and increased stress at the bone-implant interface, and affect the progression of adjacent joint arthritis in the talonavicular joint.

CLINICAL RELEVANCE

These findings may provide a correlate to clinical studies that have cited hindfoot arthrodesis as a risk factor for TAR failure.

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.

Total Ankle Arthroplasty With Valgus Deformity

BACKGROUND

A substantial coronal plane deformity is common in the context of end-stage ankle osteoarthritis. Recent literature shows a trend toward extending the indication of total ankle arthroplasty in increasingly severe coronal deformities, showing promising results when correct alignment is achieved. Nevertheless, the results of lateral transfibular total ankle replacement (LTTAR) in valgus has not been extensively studied. We aimed to evaluate if the outcomes of LTTAR in ankles with valgus deformity were similar to those with no major deformity at short-term follow-up.

METHODS

This retrospective cohort study included 228 LTTARs. Patients were classified into 2 groups according to the preoperative coronal plane tibiotalar angle (TTS): neutral (less than 10 degrees of coronal deformity, 209 patients) and valgus (above 10 degrees of valgus, 19 patients). Clinical evaluation was performed using the American Orthopaedic Foot & Ankle Society (AOFAS) score, visual analog scale (VAS), 12-Item Short Form Health Survey 12 (SF-12) regarding its Physical and Mental Component Summary items. The radiographic evaluation considered anteroposterior and lateral ankle radiographs. Complications were also registered and classified as major or minor. The minimum follow-up was 2 years.

RESULTS

The average AOFAS, VAS, and SF-12 scores improved significantly postoperatively (P < .001), without differences between groups. At final radiographic follow-up, the valgus alignment group did not show significant differences with the neutral alignment group regarding TTS, lateral distal tibial angle, or anterior distal tibial angle (P > .05).

CONCLUSION

LTTAR in cases with valgus deformity achieved and maintained correction at short-term follow-up, as obtained in neutral alignment ankles. Clinical outcomes improved significantly regardless of preoperative valgus deformity.

LEVEL OF EVIDENCE

Prognostic Level III, retrospective cohort study.

Correlation of Patient-Reported Outcomes With Physical Function After Total Ankle Arthroplasty

BACKGROUND

Total ankle arthroplasty (TAA) is successful by both subjective patient-reported outcome measures (PROMs) and objective functional improvements of gait. Each is reproducible and valid, but they are entirely distinct methods. This study investigated the correlation between subjective and objective outcomes of TAA.

METHODS

Seventy patients underwent gait analysis preoperatively and 1 year after TAA. The 36-Item Short-Form Health Survey (SF-36) and visual analog score (VAS) for pain and American Orthopaedic Foot & Ankle Society (AOFAS) Ankle-Hindfoot Scores were recorded at each interval. A Student t test, a multivariate regression, and a Pearson correlation coefficient were used to measure the correlation between parameters of gait and PROMs.

RESULTS

Patients had statistically significant improvements in gait velocity, total range of motion (ROM), maximum plantarflexion, ankle power, and SF-36 Physical, VAS, and AOFAS scores. The SF-36 Physical score had a moderate positive correlation with preoperative walking speed, step length, and ankle power and postoperative walking speed and ankle power. No correlation between VAS score and function was detected. The AOFAS score had a moderate positive correlation with postoperative walking speed, step length, and ankle power, and improvement in walking speed, cadence, and ankle power.

CONCLUSION

Statistically significant correlations were found between numerous preoperative and postoperative comparisons of PROMs and the AOFAS score with the objective biomechanical outcomes of gait. Walking speed and ankle push-off power correlated most with patient perceptions of function and improvement, while pain and ROM did not. Subjective PROMs and objective biomechanical outcomes were complementary in the assessment of surgical outcomes and, combined, helped to address the dilemma of the confounding effect of other lower extremity pathologies on PROMs.

LEVEL OF EVIDENCE

Level III, comparative series.

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.

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.

Achilles tendon moment arm changes with total ankle arthroplasty

Prior research on total ankle arthroplasty (TAA) has focused on improvements in pain and function following the surgical treatment of ankle arthritis, but its effect on ankle joint mechanics has received relatively little attention. The plantarflexion moment arm of the Achilles tendon is a critical determinant of ankle function with the potential to be altered by TAA. Here we investigate the effect of TAA on Achilles tendon moment arm assessed using two methods. Standing sagittal-plane radiographs were obtained for ten patients presurgery and postsurgery, from which anterior-posterior distance between the posterior calcaneus and the center of the talar dome was measured. Ultrasound imaging and three-dimensional (3D) motion capture were used to obtain moment arm pre- and post-TAA. The absolute changes in moment arm pre- to post-TAA were significantly different from zero for both methods (9.6 mm from ultrasound and 4.6% of the calcaneus length from radiographs). Only 46% of the variance in postoperative 3D Achilles tendon moment arm was explained by the preoperative value (r²  = 0.460; p = .031), while pre- and post-TAA values from radiographs were not correlated (r²  = 0.192, p = .206). While we did not find significant mean differences in Achilles tendon moment arm between pre- and post-TAA, we did find absolute changes in 3D moment arm that were significantly different from zero and these changes were partially explained by a change in location of the talar dome as indicated by measurements from radiographs (r²  = 0.497, p = .023).

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.

Return to Sports and Activity After Total Ankle Arthroplasty and Arthrodesis: A Systematic Review

BACKGROUND

There is no consensus regarding participation in sports and recreational activities following total ankle replacement (TAR) and ankle arthrodesis (AA). This systematic review summarizes the evidence on return to sports and activity after operative management with either TAR or AA for ankle osteoarthritis (OA).

METHODS

A literature search of MEDLINE, EMBASE, CINAHL, and Cochrane Library databases was performed. Risk of bias of included studies was assessed using Methodological Index for Non-Randomized Studies (MINORS) criteria. Included studies reported sport and activity outcomes in patients undergoing TAR and AA, with primary outcomes being the percentage of sports participation and level of sports participation.

RESULTS

Twelve studies met inclusion criteria for analysis. There were 1270 ankle procedures, of which 923 TAR and 347 AA were performed. The mean reported patient age was 59.2 years and the mean BMI was 28 kg/m². The mean follow-up was 43 months. Fifty-four percent of patients were active in sports preoperatively compared with 63.7% postoperatively. The mean preoperative activity participation rate was 41% in the TAR cohort, but it improved to 59% after TAR, whereas the preoperative activity participation rate of 73% was similar to the postoperative rate of 70% in the AA cohort. The most common sports in the TAR and AA groups were swimming, hiking, cycling, and skiing.

CONCLUSION

Participation in sports activity was nearly 10% improved after operative management of ankle OA with TAR and remains high after AA. The existing literature demonstrated a large improvement in pre- to postoperative activity levels after TAR, with minimal change in activity after AA; however, AA patients were more active at baseline. The most frequent postoperative sports activities after operative management of ankle OA were swimming, hiking, cycling, and skiing. Participation in high-impact sports such as tennis, soccer, and running was consistently limited after surgery. This review of the literature will allow patients and foot and ankle surgeons to set evidence-based goals and establish realistic expectations for postoperative physical activity after TAR and AA.

LEVEL OF EVIDENCE

Level III, systematic review.

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.

Comparison of Tibial and Talar Bone Density in Patients Undergoing Total Ankle Replacement vs Non-Ankle Arthritis Matched Controls

BACKGROUND

Bone quality in the distal tibia and talus is an important factor contributing to initial component stability in total ankle replacement (TAR). However, the effect of ankle arthritis on bone density in the tibia and talus remains unclear. The objective of this study was to compare bone density of tibia and talus in arthritic and nonarthritic ankles as a function of distance from ankle joint.

METHODS

We retrospectively reviewed 93 end-stage ankle arthritis patients who had preoperative nonweightbearing ankle computed tomography (CT) and identified a cohort of 83 nonarthritic ankle patients as a demographic-matched control group. A region of interest tool was used to calculate Hounsfield unit (HU) values in the cancellous region of the tibia and talus. Measurements were obtained on axial cut CTs from 6 to 12 mm above the tibial plafond, and 1 to 4 mm below the talar dome. HU measurements between groups and the decrease of HU at the relative level in each group were compared.

RESULTS

Arthritic ankles demonstrated significantly greater mean bone density than nonarthritic ankles at between 6 and 10 mm above the joint in the tibia (P < .05). No significant difference in bone density between 10 and 12 mm from the joint in the tibia nor at any level of the talus was found between groups. In both groups, bone density decreased significantly at each successive level away from the ankle joint.

CONCLUSION

Ankle arthritis patients demonstrated greater or equal bone density in both the tibia and talus compared to demographic-matched controls. In both groups, bone density decreased with increasing distance away from the articular surface. In TAR, tibial bone resection between 6 and 8 mm may provide improved initial implant stability.

LEVEL OF EVIDENCE

Level III, comparative study.

Repeatability of a Multi-segment Foot Model with a 15-Marker Set in Normal Children

Background

The use of three-dimensional multi-segment foot models (3D MFMs) is increasing since they have superior ability to illustrate the effect of foot and ankle pathologies on intersegmental motion of the foot compared to single-segment foot model gait analysis. However, validation of the repeatability of the 3D MFMs is important for their clinical use. Although many MFMs have been validated in normal adults, research on MFM repeatability in children is lacking. The purpose of this study is to validate the intrasession, intersession, and interrater repeatability of an MFM with a 15-marker set (DuPont foot model) in healthy children.

Methods

The study included 20 feet of 20 healthy children (10 boys and 10 girls). We divided the participants into two groups of 10 each. One group was tested by the same operator in each test (intersession analysis), while the other group was tested by a different operator in each test (interrater analysis). The multiple correlation coefficient (CMC) and intraclass correlation coefficient (ICC) were calculated to assess repeatability. The difference between the two sessions of each group was assessed at each time point of gait cycle.

Results

The intrasession CMC and ICC values of all parameters showed excellent or very good repeatability. The intersession CMC of many parameters showed good or better repeatability. Interrater CMC and ICC values were generally lower for all parameters than intrasession and intersession. The mean gaps of all parameters were generally similar to those of the previous study.

Conclusions

We demonstrated that 3D MFM using a 15-marker set had high intrasession, intersession, and interrater repeatability in the assessment of foot motion in healthy children but recommend some caution in interpreting the hindfoot parameters.

Perspectives in Treatments of End-Stage Ankle Arthritis Among Orthopaedic Surgeons

Background:

This study aimed to assess the preferred operative treatment for patients over the age of 60 with end-stage ankle arthritis and perspectives on total ankle replacement (TAR) among American Orthopaedic Foot & Ankle Society (AOFAS) members. Associated factors were analyzed for potential contraindications among members with different levels of experience.

Method:

A questionnaire containing 6 questions was designed and sent to 2056 members of the AOFAS. Responses were received from 467 orthopaedic surgeons practicing in the United States (76%), Canada (5%), and 26 other countries (20%). Participants were grouped for response comparisons according to country as well as experience level. Differences in contraindications were compared using χ2 tests or exact tests.

Results:

Respondents practicing in the United States and surgeons who perform 11 or more TARs per year tended to recommend operative treatments favoring TAR and displayed recognition of its increasing role ( P < .05). Overall, respondents felt that 41% of typical patients over 60 years old with end-stage arthritis would be best treated with TAR. Talus avascular necrosis, morbid obesity (body mass index >40 kg/m2), and poorly controlled diabetes with neuropathy were most recognized as the absolute contraindications to TAR. Surgeon’s experience affected the consideration of these clinical factors as contraindications.

Conclusions:

Total ankle replacement has a substantial and increasing role in the treatment of end-stage ankle arthritis in patients over the age of 60. Absolute and potential contraindications of the procedures were indicated from a cross-sectional survey of AOFAS members. Surgeons more experienced with total ankle replacement felt more comfortable employing it in a wider range of clinical settings.

Level of Evidence:

Level III, therapeutic.

A three-year prospective comparative gait study between patients with ankle arthrodesis and arthroplasty

BACKGROUND

End-stage ankle arthritis is a debilitating condition that often requires surgical intervention after failed conservative treatments. Ankle arthrodesis is a common surgical option, especially for younger and highly active patients; however, ankle arthroplasty has become increasingly popular as advancements in implant design improve device longevity. The longitudinal differences in biomechanical outcomes between these surgical treatments remain indistinct, likely due to the challenges associated with objective study of a heterogeneous population.

METHODS

Patients scheduled for arthroplasty (n = 27) and arthrodesis (n = 20) were recruited to participate in this three-year prospective study. Postoperative functional outcomes were compared at distinct annual time increments using measures of gait analysis, average daily step count and survey score.

FINDINGS

Both surgical groups presented reduced pain, improved survey scores, and increased walking speed at the first-year postoperative session, which were generally consistent across the three-year follow-up. Arthrodesis patients walked with decreased sagittal ankle RoM, increased sagittal hip RoM, increased step length, and increased transient force at heel strike, postoperatively. Arthroplasty patients increased ankle RoM and cadence, with no changes in hip RoM, step length or heel strike transient force.

INTERPRETATION

Most postoperative changes were detected at the first-year follow-up session and maintained across the three-year time period. Despite generally favorable outcomes associated with both surgeries, several underlying postoperative biomechanical differences were detected, which may have long-term functional consequences. Furthermore, neither technique was able to completely restore gait biomechanics to the levels of the contralateral unaffected limb, leaving potential for the development of improved surgical and rehabilitative treatments.

Finite element analysis of biomechanical effects of total ankle arthroplasty on the foot

Background

Total ankle arthroplasty is gaining popularity as an alternation to ankle arthrodesis for end-stage ankle arthritis. Owing to the complex anatomical characteristics of the ankle joint, total ankle arthroplasty has higher failure rates. Biomechanical exploration of the effects of total ankle arthroplasty on the foot and ankle is imperative for the precaution of postoperative complications. The objectives of this study are (1) to investigate the biomechanical differences of the foot and ankle between the foot with total ankle arthroplasty and the intact foot and (2) to investigate the performance of the three-component ankle prosthesis.

Methods

To understand the loading environment of the inner foot, comprehensive finite element models of an intact foot and a foot with total ankle arthroplasty were developed to simulate the stance phase of gait. Motion analysis on the model subject was conducted to obtain the boundary and loading conditions. The model was validated through comparison of plantar pressure and joint contact pressure between computational prediction and experimental measurement. A pressure mapping system was used to measure the plantar pressure during balanced standing and walking in the motion analysis experiment, and joint contact pressure at the talonavicular joint was measured in a cadaver foot.

Results

Plantar pressure, stress distribution in bones and implants and joint contact loading in the two models were compared, and motion of the prosthesis was analysed. Compared with the intact foot model, averaged contact pressure at the medial cuneonavicular joint increased by 67.4% at the second-peak instant. The maximum stress in the metatarsal bones increased by 19.8% and 31.3% at the mid-stance and second-peak instants, respectively. Force that was transmitted in three medial columns was 0.33, 0.53 and 1.15 times of body weight, respectively, at the first-peak, mid-stance and second-peak instants. The range of motion of the prosthetic ankle was constrained in the frontal plane. The lateral side of the prosthesis sustained higher loading than the medial side.

Conclusion

Total ankle arthroplasty resulted in great increase of contact pressure at the medial cuneonavicular joint, making it sustain the highest contact pressure among all joints in the foot. The motion of the prosthesis was constrained in the frontal plane, and asymmetric loading was distributed in the bearing component of the ankle prosthesis in the mediolateral direction.

The translational potential of this article

Biomechanical variations resulted from total ankle arthroplasty may contribute to negative postoperative outcomes. The exploration of the biomechanical performance in this study might benefit the surgeons in the determination of surgical protocols to avoid complications. The analysis of the performance of the ankle prosthesis could enhance the knowledge of prosthetic design.

Role of Total Ankle Arthroplasty in Stiff Ankles

BACKGROUND

The decision tree for the operative treatment of end-stage ankle arthritis involves either ankle arthrodesis (AA) or total ankle arthroplasty (TAA). Although both have documented success providing diminished pain, improved patient-centered outcomes, and improved objective measures of function, arthroplasty is unique in its ability to preserve motion at the tibiotalar joint. Arthroplasty procedures are normally thought of as a motion-sparing surgery rather than a motion-producing procedure, which may limit its success in patients with stiff ankles. Our hypothesis was that there would be improvements in parameters of gait even in patients with a low degree of preoperative total sagittal range of motion.

METHODS

A retrospective review was conducted on patients who underwent total ankle arthroplasty with greater than 1-year follow-up. Seventy-six patients were available who underwent isolated TAA for end-stage ankle arthritis with greater than 1-year follow-up. Patient demographics and preoperative and postoperative gait analyses were evaluated. Using a linear regression model, the effect sizes for the variables of age, gender, BMI, preoperative diagnosis, and preoperative total sagittal range of motion were calculated. Multivariate analysis was used to determine the influence each individual variable had on the many parameters of preoperative gait, postoperative gait, and change in gait after surgery. A post hoc analysis was conducted in which patients were divided into 4 quartiles according to preoperative range of motion. A 1-way analysis of variance (ANOVA) was used to compare improvement in parameters of gait for the 4 subgroups.

RESULTS

Although a greater degree of preoperative sagittal range of motion was predictive of greater postoperative sagittal range of motion, patients with limited preoperative range of motion experienced a greater overall improvement in range of motion, and clinically meaningful absolute improvements in range of motion, and other parameters of gait. The post hoc analysis demonstrated that patients in the lowest quartile of preoperative motion had both statistically and clinically significant greater improvements across numerous parameters of gait, although the absolute values were lower than in the patients with higher preoperative ROM. Age, gender, BMI, and preoperative diagnosis did not correlate with changes in parameters of gait after total ankle arthroplasty.

CONCLUSION

Preoperative range of motion was predictive of overall postoperative gait function. On one hand, a low preoperative range of motion resulted in a lower absolute postoperative function. On the other hand, patients with stiff ankles preoperatively had a statistically and clinically greater improvement in function as measured by multiple parameters of gait. This suggests that total ankle arthroplasty can offer clinically meaningful improvement in gait function and should be considered for patients with end-stage tibiotalar arthritis even in the setting of limited sagittal range of motion.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Comparison of Multisegmental Foot and Ankle Motion Between Total Ankle Replacement and Ankle Arthrodesis in Adults

BACKGROUND

Total ankle replacement (TAR) and ankle arthrodesis (AA) are usually performed for severe ankle arthritis. We compared postoperative foot segmental motion during gait in patients treated with TAR and AA.

METHODS

Gait analysis was performed in 17 and 7 patients undergoing TAR and AA, respectively. Subjects were evaluated using a 3-dimensional multisegmental foot model with 15 markers. Temporal gait parameters were calculated. The maximum and minimum values and the differences in hallux, forefoot, hindfoot, and arch in 3 planes (sagittal, coronal, transverse) were compared between the 2 groups. One hundred healthy adults were evaluated as a control.

RESULTS

Gait speed was faster in the TAR ( P = .028). On analysis of foot and ankle segmental motion, the range of hindfoot sagittal motion was significantly greater in the TAR (15.1 vs 10.2 degrees in AA; P = .004). The main component of motion increase was hindfoot dorsiflexion (12.3 and 8.6 degrees). The range of forefoot sagittal motion was greater in the TAR (9.3 vs 5.8 degrees in AA; P = .004). Maximum ankle power in the TAR (1.16) was significantly higher than 0.32 in AA; P = .008). However, the range of hindfoot and forefoot sagittal motion was decreased in both TAR and AA compared with the control group ( P = .000).

CONCLUSION

Although biomechanical results of TAR and AA were not similar to those in the normal controls, joint motions in the TAR more closely matched normal values. Treatment decision making should involve considerations of the effect of surgery on the adjacent joints.

LEVEL OF EVIDENCE

Level III, case-control study.

Assessing the Utilization of Total Ankle Replacement in the United States

BACKGROUND

Total ankle arthroplasty (TAR) has been shown to be a cost-effective procedure relative to conservative management and ankle arthrodesis. Although its use has grown considerably over the last 2 decades, it is less common than arthrodesis. The purpose of this investigation was to analyze the cost and utilization of TAR across hospitals.

METHODS

Our analytical sample consisted of Medicare claims data from 2011 and 2012 for Inpatient Prospective Payment System hospitals. Outcome variables of interest were the likelihood of a hospital performing TAR, the volume of TAR cases, TAR hospital costs, and hospital profit margins. Data from the 2010 Cost Report and Medicare inpatient claims were utilized to compute average margins for TAR cases and overall hospital margins. TAR cost was calculated based on the all payer cost-to-charge ratio for each hospital in the Cost Report. Nationwide Inpatient Sample data were used to generate descriptive statistics on all TAR patients across payers.

RESULTS

Medicare participants accounted for 47.5% of the overall population of TAR patients. Average implant cost was $13 034, accounting for approximately 70% of the total all-payer cost. Approximately, one-third of hospitals were profitable with respect to primary TAR. Profitable hospitals had lower total costs and higher payments leading to a difference in profit of approximately $11 000 from TAR surgeries between profitable and nonprofitable hospitals. No difference was noted with respect to length of stay or number of cases performed between profitable and nonprofitable hospitals. TAR surgeries were more likely to take place in large and major teaching hospitals. Among hospitals performing at least 1 TAR, the margin on TAR cases was positively associated with the total number of TARs performed by a hospital.

CONCLUSION

There is an overall significant financial burden associated with performing TAR with many health systems failing to demonstrate profitability despite its increased utilization. While additional factors such as improved patient outcomes may be driving utilization of TAR, financial barriers may exist that can affect utilization of TAR across health systems.

LEVEL OF EVIDENCE

Level III, comparative study.

Functional and clinical outcomes of total ankle arthroplasty in elderly compared to younger patients

BACKGROUND

Total ankle arthroplasty (TAA) is becoming an increasingly utilized procedure for the management of end-stage ankle arthritis. Elderly patients are the fastest growing segment of the population in the western world, creating a unique challenge to the health economics of our era. Determining if elderly patients with end-stage ankle arthritis demonstrate the same improvements in clinical outcomes and functional measures of gait following TAA would be valuable. This can aid to evaluate the utilization of TAA in this enlarging cohort of our population.

METHODS

Consecutive series of twenty-one patients over the age of 70, who underwent TAA for end-stage ankle arthritis, was prospectively compared to a series of twenty-one patients aged 50-60, who underwent the same procedure by single surgeon during same time period. Clinical outcomes were measured with outcome scores including VAS pain score, AOFAS Ankle and Hindfoot Score, and the SF-36. Three-dimensional gait analysis was performed preoperatively and at a minimum of one year postoperatively, to measure temporal-spatial, kinematic, and kinetic parameters of gait. Mixed model multivariate statistical analysis was used to evaluate and compare the independent contributions to outcomes of the surgical intervention over time; of patient age; and of time-plus-age interaction, as these influenced both the clinical outcomes and the functional gait outcomes.

RESULTS

Statistically significant improvements in VAS pain scores, AOFAS ankle/hindfoot scores, and SF-36 scores were demonstrated in both age groups. Following surgery, there were improvements in all parameters of gait, including temporal-spatial parameters as step length and walking velocity; kinematic parameters, including, increase in total range of motion to a total of 17-19°; and kinetic parameters, including increase in ankle power and moment. The improvements both in clinical and gait outcomes were equivalent in the two age groups.

CONCLUSIONS

In this comparative study, it is shown that both elderly patients over the age of 70 and younger patients aged 50-60 demonstrated equivalent improvements clinical and gait outcomes following ankle arthroplasty. This may be important data both for clinical decision-making and the health economics for our ageing population.

Kinematics and Function of Total Ankle Replacements Versus Normal Ankles

End-stage ankle arthritis produces severe functional disability, quantifiable by gait abnormalities. In all categories of gait parameters, total ankle arthroplasty (TAA) satistically significantly improves function, compared to patients' preoperative function. There are increases in step length, cadence and velocity; in sagittal plane motion of the ankle, as well has hip and knee motion, and in ankle power and moment. These functional gait improvements correspond to clinical improvements of pain relief and satisfaction. Although these improvements fail to reach the functional performance of healthy controls, the improvement over preoperative function is clinically meaningful and statistically significant.

Etiology and Treatment of Delayed-Onset Medial Malleolar Pain Following Total Ankle Arthroplasty

BACKGROUND

Total ankle arthroplasty (TAA) has become a successful treatment for end-stage ankle arthritis. Some patients may still have pain or may present with new pain. Suggested sources of medial pain include tibialis posterior tendonitis, impingement, or medial malleolar stress fracture. Etiology and treatment remain unclear. The objective of our study was to evaluate patients with delayed-onset medial malleolar pain following TAA who underwent treatment with percutaneous medial malleolar screw placement and propose an etiology.

MATERIALS AND METHODS

Patients who had undergone TAA at our institution were reviewed and those with medial malleolar pain were identified. Clinical and radiographic examinations were performed pre- and postoperatively. Radiographs were compared with those from a cohort of controls without a history of medial pain. All affected patients failed conservative therapy and were treated with percutaneous placement of medial malleolar screws positioned from the malleolar tip and extending proximally beyond the tibial component. Postoperatively, patients were placed in an ace wrap and allowed to be weightbearing to tolerance, except for 1 patient initially restricted to partial weightbearing. Visual analog scale (VAS) scores were recorded. Seventy-four (74) patients underwent TAA by the corresponding author. All (100%) were female with an average age of 66 (range, 57-73) years. Average follow-up since screw placement was 21.4 (range, 10-41) months.

RESULTS

Six (8.1%) underwent placement of 2 percutaneous medial malleolar screws. Patients presented with pain an average of 12 (range, 4-24) months postoperatively and underwent screw placement an average of 2.8 (range, 1-6) months after presentation. At the time of TAA, none had a coronal plane deformity and none underwent a deltoid ligament release as part of balancing. All (100%) patients had pain and swelling directly over the medial malleolus prior to screw placement. Postoperatively, 1 (17%) had mild pain clinically at this site and 2 (33%) had occasional pain medially with activity. Average VAS scores improved from 5.7 (range, 4-6) preoperatively to 1.3 (range, 0-3) postoperatively (P < .05). Three (50%) patients had a bone density test and all were normal. Prior to screw placement, radiographs demonstrated no signs of stress fracture or misalignment. Average minimum width of the medial malleolus at the level of the tibial component was 10.2 mm (range, 9.2-11.0), which was significantly less (P < .05) than the control group of 19 patients whose distance measured 12.2 mm (range, 8.5-14.8).

DISCUSSION

Patients who present with new-onset medial malleolar pain with normal radiographs following TAA may have medial malleolar insufficiency fracture. These patients can be treated successfully with minimal morbidity by placement of percutaneous medial malleolar screws. Etiology may be related to deltoid traction, subacute stress fracture, and/or impingement of the talus component on the medial malleolus. Medial malleolar pain may be misdiagnosed as tibialis posterior tendonitis, impingement, or implant failure. This diagnosis should be considered in patients who have pain at the medial malleolus, particularly if they are female or have medial malleolus thickness less than 11 mm at the level of the tibial implant. Placement of prophylactic medial malleolar screws may be considered at the time of TAA when these conditions exist.

LEVEL OF EVIDENCE

Level IV, case series.

Motion at the Tibial and Polyethylene Component Interface in a Mobile-Bearing Total Ankle Replacement

BACKGROUND

Normal biomechanics of the ankle joint includes sagittal as well as axial rotation. Current understanding of mobile-bearing motion at the tibial-polyethylene interface in total ankle arthroplasty (TAA) is limited to anterior-posterior (AP) motion of the polyethylene component. The purpose of our study was to define the motion of the polyethylene component in relation to the tibial component in a mobile-bearing TAA in both the sagittal and axial planes in postoperative patients.

METHODS

Patients who were a minimum of 12 months postoperative from a third-generation mobile-bearing TAA were identified. AP images were saved at maximum internal and external rotation, and the lateral images were saved in maximum plantarflexion and dorsiflexion. Sagittal range of motion and AP translation of the polyethylene component were measured from the lateral images. Axial rotation was determined by measuring the relative position of the 2 wires within the polyethylene component on AP internal and external rotation imaging. This relationship was compared to a table developed from fluoroscopic images taken at standardized degrees of axial rotation of a nonimplanted polyethylene with the associated length relationship of the 2 imbedded wires. Sixteen patients were included in this investigation, 9 (56%) were male and average age was 68 (range, 49-80) years. Time from surgery averaged 25 (range, 12-38) months.

RESULTS

Total sagittal range of motion averaged 23±9 (range, 9-33) degrees. Axial motion for total internal and external rotation of the polyethylene component on the tibial component averaged 6±5 (range, 0-18) degrees. AP translation of the polyethylene component relative to the tibial component averaged 1±1 (range, 0-3) mm. There was no relationship between axial rotation or AP translation of the polyethylene component and ankle joint range of motion (P > .05).

CONCLUSION

To our knowledge, this is the first investigation to measure axial and sagittal motion of the polyethylene component at the tibial implant interface in patients following a mobile-bearing TAA. Based on outcome scores and range-of-motion measurements, we believe the patients in this study are a representative cross section of subjects compared to other TAA research results. The results from this investigation indicate the potential for a mobile-bearing TAA to fall within the parameters of normal polyaxial ankle motion. The multiplanar articulation in a mobile-bearing TAA may reduce excessively high peak pressures during the complex dynamic tibial and talar motion, which may have a positive influence on gait pattern, polyethylene wear, and implant longevity.

LEVEL OF EVIDENCE

Level IV, case series.

Biomechanics of the ankle

This paper provides an introduction to the biomechanics of the ankle, introducing the bony anatomy involved in motion of the foot and ankle. The complexity of the ankle anatomy has a significant influence on the biomechanical performance of the joint, and this paper discusses the motions of the ankle joint complex, and the joints at which it is proposed they occur. It provides insight into the ligaments that are critical to the stability and function of the ankle joint. It describes the movements involved in a normal gait cycle, and also highlights how these may change as a result of surgical intervention such as total joint replacement or fusion.

Reproducibility of gait parameters at different surface inclinations and speeds using an instrumented treadmill system

Instrumented treadmill systems allow the practical assessment of gait parameters under several walking conditions. Aim of this study was to evaluate the reproducibility of gait parameters at different surface inclinations and walking speeds using an instrumented treadmill system in healthy individuals. A total of 20 subjects (10 women) with a mean age of 31 years were evaluated with an instrumented treadmill system (FDM-T, Zebris Medical GmbH) during two identical test sessions. Spatial (step length, step width, foot rotation), temporal (cadence, single-limb support, step time) and ground reaction force (heel force, toe force, time to heel force, time to toe force) gait parameters were assessed at three treadmill inclinations (level, uphill, downhill) and five speeds (2, 3, 4, 5, 6 km/h). Between-day reproducibility was evaluated with smallest detectable changes for agreement and intraclass correlation coefficients for reliability. Low agreement and reliability were observed for (i) step length, cadence and step time during slow (2 and 3 km/h) and uphill walking and (ii) time to heel force and time to toe force under the majority of walking conditions. The instrumented treadmill system used in this study provided reproducible measurements for the majority of the evaluated spatial, temporal and ground reaction force gait parameters in healthy individuals. The assessment of time to heel/toe force should be however avoided, and particular care should be taken for some spatial (step length) and temporal (cadence and step time) parameters while walking uphill and/or at slow speeds.

Early radiographic and clinical results of Salto total ankle arthroplasty as a fixed-bearing device

BACKGROUND

Total ankle replacement has increased in popularity in the management of severe tibiotalar arthritis. Most previous clinical reports focused on mobile-bearing designs. This study evaluates early radiographic and clinical results of the Salto fixed bearing design.

METHODS

Twenty-three Salto fixed-bearing implants were prospectively studied. Records were reviewed for clinical outcome scores (VAS, AOFAS, SF36), subsequent surgeries, complications, radiographic data and implant survivorship. Average follow-up was 36 months.

RESULTS

Statistically significant improvements in VAS, AOFAS ankle/hindfoot scores, and SF36 scores were shown at an average of 3 years postoperatively. At 3 years followup, survivorship of the implant was 82.6% with any reoperation as the endpoint and 95.6% for revision or removal of components. Seven patients had radiolucencies around the implant, one of which required revision to arthrodesis.

CONCLUSION

The fixed-bearing Salto ankle replacement has comparable early radiographic and clinical results to reports of the mobile-bearing Salto of comparable followup.

LEVEL OF EVIDENCE

Level IV.

Current Concepts in the Management of Ankle Osteoarthritis: A Systematic Review

Ankle osteoarthritis is less common than hip or knee osteoarthritis; however, it is a relatively common presentation and is predominantly related to previous trauma. Treatments have traditionally consisted of temporizing measures such as analgesia, physiotherapy, and injections until operative treatment in the form of arthrodesis is required. More recently, interest has been increasing in both nonoperative and alternative operative options, including joint-sparing surgery, minimal access arthrodesis, and new arthroplasty designs. The present systematic instructional review has summarized the current evidence for the treatment options available for ankle osteoarthritis.

The effect of simulated elbow contracture on temporal and distance gait parameters

BACKGROUND

Elbow contractures can be functionally debilitating. Extensive research has been published on treatments to restore elbow motion, but few have discussed clinical implications beyond the affected extremity. Reciprocal arm swing in normal gait has been shown to increase stability and reduce energy expenditure. The importance of arm swing has been clinically demonstrated in patients with cerebral palsy, stroke and Parkinson's disease. We hypothesized that elbow contractures would result in an abnormal spatio-temporal gait parameters.

METHODS

Forty volunteer subjects walked on the Gaitmat II which provided real-time analysis of temporal and distance gait parameters. Five conditions were tested: no brace (control 1), elbow brace unlocked (control 2) and brace locked in 30°, 90° or 120° flexion (simulating fixed elbow contractures). Condition order was randomized for each subject. Each condition consisted of five walking trials.

RESULTS

All three fixed elbow conditions (120°, 90° and 30°) demonstrated significantly decreased gait velocity (1.37, 1.39 and 1.39m/s) and stride length (1.45, 1.46 and 1.46m) compared to the control condition (1.42m/s and 1.48m, respectively). Single limb stance and double support times were decreased and increased, respectively, compared to control. There was no significant difference in cadence or limb asymmetry in the three fixed elbow conditions.

CONCLUSIONS

Despite well-established functional limitations in elbow contracture patients and importance of arm swing in normal gait, the impact of elbow contractures on gait is unknown. This study demonstrates that simulated elbow contracture results in significant differences in spatio-temporal gait parameters suggesting that elbow contractures have a broader functional impact beyond the affected extremity.

LEVEL OF EVIDENCE

II.

Force-controlled dynamic wear testing of total ankle replacements

Currently, our knowledge of wear performance in total ankle replacements is limited. The aim of this study is to develop a scenario for force-controlled testing and wear testing of total ankle replacements. A force-controlled wear test was developed: based on cadaver measurements, the passive stabilization (ligaments and soft tissue) of the ankle joint was characterized and a restraint model for ankle stabilization was developed. Kinematics and kinetics acting at the replaced ankle joint were defined based on literature data and gait analysis. Afterwards, force-controlled wear testing was carried out on a mobile, three-component, total ankle replacement design. Wear was assessed gravimetrically and wear particles were analyzed. Wear testing resulted in a mean wear rate of 18.2±1.4mm(3)/10(6) cycles. Wear particles showed a mean size of 0.23μm with an aspect ratio of 1.61±0.96 and a roundness of 0.62±0.14. Wear testing of total ankle replacement shows that a relevant wear mass is generated with wear particles in a biologically relevant size range. The developed wear test provides a basis for future wear testing of total ankle replacements.

Functional and clinical evaluation at 5-year follow-up of a three-component prosthesis and osteochondral allograft transplantation for total ankle replacement

BACKGROUND

Severe ankle arthritis is a life-limiting condition which often requires surgery. Ankle arthroplasty via artificial or "biological" reconstruction is a viable option in those patients who are not comfortable with arthrodesis. More functional studies are needed to compare the performance and outcomes of the two function-preserving arthroplasties.

METHODS

In this study two groups of 10 patients affected by severe ankle arthritis were treated either with a 3-component ankle prosthesis or with bipolar fresh osteochondral allograft transplantation. Patients were evaluated pre-operatively and at 5-year follow-up. The American Orthopaedic Foot and Ankle Society score was used for clinical evaluation, and gait analysis for functional assessment. Activation pattern of lower limb muscles was obtained by surface electromyography (EMG). In each group, kinematic, kinetic, and EMG data were compared between pre-op and follow-up assessments, and also versus corresponding data from a 20 healthy subject control group. The median clinical score significantly increased between pre-op and follow-up from 53 to 74.5 in the transplantation and from 28.5 to 80 in the prosthesis group. Spatio-temporal parameters showed a statistically significant improvement in cadence and cycle time. Improvement of gait speed was also observed only in the prosthesis group. EMG patterns at follow-up were strongly correlated with the corresponding control data for both groups. Although no significant amelioration in the joints' range of motion was detected in either surgical procedure, preservation of the functional conditions at medium-term, along with significant improvement of the clinical score, may be considered a positive outcome for both techniques.

Early to mid-term results of fixed-bearing total ankle arthroplasty with a modular intramedullary tibial component

BACKGROUND

There has been a continuing increase in the use of total ankle arthroplasty for the treatment of end-stage ankle arthritis. Our aim was to determine the clinical, radiographic, and functional outcomes of total ankle arthroplasties done with a prosthesis with a modular intramedullary stem and intramedullary referencing to align the tibia.

METHODS

A consecutive series of patients who underwent total ankle arthroplasty with the INBONE Total Ankle Replacement from June 2007 to December 2010 were enrolled in this study. Pain and patient-reported function were assessed with use of a visual analog scale (VAS) for pain, the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score, the Short Musculoskeletal Function Assessment (SMFA), and the Short Form-36 (SF-36) Health Survey. Objective function was measured with assessment of walking speed, the Timed Up and Go (TUG) test, the Sit-to-Stand (STS) test, and the Four Square Step Test (4SST). Standardized weight-bearing radiographs obtained preoperatively and after total ankle arthroplasty were evaluated. We analyzed clinical, functional, and radiographic measurements with a series of repeated-measures analyses of variance (ANOVAs) with post-hoc testing to assess differences between preoperative, one-year postoperative, and most recent follow-up data. On the basis of the number of statistical comparisons, a Bonferroni correction was completed (alpha < 0.003).

RESULTS

We identified 194 primary INBONE total ankle arthroplasties with a mean duration of clinical follow-up of 3.7 years (range, 2.2 to 5.5 years). Patients demonstrated a significant improvement (p < 0.003) in VAS pain, AOFAS, SMFA, and SF-36 scores at the time of final follow-up, compared with preoperative values, and in walking speed, STS time, TUG time, and 4SST time at two years postoperatively, compared with preoperatively. The mean coronal tibiotalar angle for varus and valgus ankles significantly improved postoperatively and was maintained until the time of final follow-up. The prevalence of unstable subsidence leading to impending failure was 5%, and the prevalence of revision was 6%.

CONCLUSIONS

Patients who underwent total ankle arthroplasty with the INBONE Total Ankle Replacement demonstrated significant improvement in radiographic, functional, and patient-reported outcome scores at a mean of 3.7 years postoperatively. The overall implant survival rate was 89%.

LEVEL OF EVIDENCE

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

Improvement in gait following combined ankle and subtalar arthrodesis

BACKGROUND

This study assessed the hypothesis that arthrodesis of both the ankle and the hindfoot joints produces an objective improvement of function as measured by gait analysis of patients with severe ankle and hindfoot arthritis.

METHODS

Twenty-one patients with severe ankle and hindfoot arthritis who underwent unilateral tibiotalocalcaneal arthrodesis with an intramedullary nail were prospectively studied with three-dimensional (3D) gait analysis at a minimum of one year postoperatively. The mean age at the time of the operation was fifty-nine years, and the mean duration of follow-up was seventeen months (range, twelve to thirty-one months). Temporospatial measurements included cadence, step length, walking velocity, and total support time. The kinematic parameters were sagittal plane motion of the ankle, knee, and hip. The kinetic parameters were sagittal plane ankle power and moment and hip power. Symmetry of gait was analyzed by comparing the step lengths on the affected and unaffected sides.

RESULTS

There was significant improvement in multiple parameters of postoperative gait as compared with the patients' own preoperative function. Temporospatial data showed significant increases in cadence (p = 0.03) and walking speed (p = 0.001) and decreased total support time (p = 0.02). Kinematic results showed that sagittal plane ankle motion had decreased, from 13.2° preoperatively to 10.2° postoperatively, in the operatively treated limb (p = 0.02), and increased from 22.2° to 24.1° (p = 0.01) in the contralateral limb. Hip motion on the affected side increased from 39° to 43° (p = 0.007), and knee motion increased from 56° to 60° (p = 0.054). Kinetic results showed significant increases in ankle moment (p < 0.0001) of the operatively treated limb, ankle power of the contralateral limb (p = 0.009), and hip power on the affected side (p = 0.005) postoperatively. There was a significant improvement in gait symmetry (p = 0.01).

CONCLUSIONS

There was a small loss of sagittal plane motion in the affected limb postoperatively. There were marked increases in gait velocity, ankle moment, and hip motion and power, documenting objective improvements in ambulatory function. The data showed that preoperative ankle motion was greatly diminished. This may suggest that pain is more important than stiffness in asymmetric gait.

Are our expectations bigger than the results we achieve? a comparative study analysing potential advantages of ankle arthroplasty over arthrodesis

PURPOSE

Prior studies have reported improved gait performance and kinematics after total ankle arthroplasty (TAR) compared to ankle arthrodesis (AAD). Given these findings, AAD has been primarily considered as a salvage procedure that may lead to adjacent joint degeneration.

METHODS

A total of 101 TAR and 40 screw arthrodeses were enrolled in a retrospective study with a prospectively designed follow-up examination that included gait analysis and outcome assessment with the AOFAS hindfoot score and FAOS questionnaire.

RESULTS

Significant asymmetry in gait and reduced range of motion compared to normal remained after both procedures. Subjective outcome improved after both procedures, and pain was significantly better after TAR. Limited functional gains after TAR and joint degeneration to the same degree after both procedures was seen in the mid-term. Hindfoot fusion seemed to have a greater impact on postoperative function than ankle arthrodesis.

CONCLUSION

Considering only minor functional gains of TAR compared to AAD the implantation of current TAR designs in large patient series may be questioned.

Bilateral differences in gait mechanics following total ankle replacement: a two year longitudinal study

BACKGROUND

Following total ankle replacement (TAR) patients demonstrate improvements in gait. The purpose of this study was to assess the changes in gait symmetry from a pre-operative assessment through two years following TAR.

METHODS

Seventy-eight patients who received a primary TAR and had no contralateral pain were examined. Three-dimensional joint mechanics and ground reaction forces were collected during seven walking trials pre-operatively, and 1 and 2-years post-operatively. Data was analyzed using a 2×3 repeated measures ANOVA to determine significant differences between limbs and across time points (α=0.05).

FINDINGS

Walking speed improved from pre-operative to each post-operative time point (P<.001; ES=1.5). Peak dorsiflexion was not changed across time or between sides, however, the dorsiflexion angle at heel strike was increased on the nonsurgical side (P=0.049; ES=0.32). Peak plantar flexion moment (P<.001; ES=.80), stance (P<.001; ES=.29) and step time (P<.001; ES=.41) were improved from pre-op to 1year post-surgery on the surgical side. Step (P<.001; ES=1.2) and stride length (P<.001; ES=1.2) demonstrated improvements across all time points, while the weight acceptance (P<.001; ES=.27) and propulsion ground reaction forces (P<.001; ES=.22) showed improvements between pre-op and 1year post-op.

INTERPRETATION

The results of the study indicate that the patients are able to walk faster and demonstrate an improvement in gait symmetry; however, this improvement does not return the patient to a symmetric walking pattern by 2years post-TAR.

Effects of supramalleolar osteotomies for ankle osteoarthritis on foot kinematics and lower leg muscle activation during walking

BACKGROUND

Early stages of asymmetric ankle osteoarthritis can be treated by joint preserving supramalleolar osteotomies that surgically realign the ankle and unload degenerated cartilage. While studies have already shown pain relief and functional improvements, the effects on gait biomechanics are largely unknown. This study investigated patients' gait pattern after supramalleolar osteotomies by focusing on foot kinematics and lower leg muscle activation.

METHODS

An instrumented three-dimensional gait analysis with simultaneous electromyography of gastrocnemius medialis and lateralis, soleus, peroneus longus, and tibialis anterior muscles was performed on 12 patients with ankle osteoarthritis, seven of which were followed up 12-18months postoperatively. Additionally, seven different long-term follow-up patients (8-9years postoperatively) and 15 healthy control subjects were measured. The waveforms of the foot kinematics and muscle activation were analyzed using principal component analysis.

FINDINGS

Compared to healthy controls, principal component scores that affected the sagittal range of motion of the hindfoot and hallux were lower in all patient groups, while scores that affected the timing of the peaks in the sagittal forefoot motion were mainly altered in short-term follow-up patients. Lower principal component scores in patients with ankle osteoarthritis and short-term follow-up patients resulted in a less pronounced peak activation of gastrocnemius medialis and soleus.

INTERPRETATION

Both postoperative patient groups showed similar adaptations in their gait pattern as those observed in patients with ankle osteoarthritis. These changes are probably related to the lower ankle mobility. However, the reduced mobility seems to affect the patients' well-being less than a painful joint.

Biomechanics of the natural, arthritic, and replaced human ankle joint

The human ankle joint complex plays a fundamental role in gait and other activities of daily living. At the same time, it is a very complicated anatomical system but the large literature of experimental and modelling studies has not fully described the coupled joint motion, position and orientation of the joint axis of rotation, stress and strain in the ligaments and their role in guiding and stabilizing joint motion, conformity and congruence of the articular surfaces, patterns of contact at the articular surfaces, patterns of rolling and sliding at the joint surfaces, and muscle lever arm lengths.

The present review article addresses these issues as described in the literature, reporting the most recent relevant findings.