Biomechanical changes associated with the osteoarthritic, arthrodesed, and prosthetic ankle joint

Clinically useful finite element models of the natural ankle - A review

BACKGROUND

Biomechanical simulation of the foot and ankle complex is a growing research area but compared to simulation of joints such as hip and knee, it has been under investigated and lacks consistency in research methodology. The methodology is variable, data is heterogenous and there are no clear output criteria. Therefore, it is very difficult to correlate clinically and draw meaningful inferences.

METHODS

The focus of this review is finite element simulation of the native ankle joint and we will explore: the different research questions asked, the model designs used, ways the model rigour has been ensured, the different output parameters of interest and the clinical impact and relevance of these studies.

FINDINGS

The 72 published studies explored in this review demonstrate wide variability in approach. Many studies demonstrated a preference for simplicity when representing different tissues, with the majority using linear isotropic material properties to represent the bone, cartilage and ligaments; this allows the models to be complex in another way such as to include more bones or complex loading. Most studies were validated against experimental or in vivo data, but a large proportion (40%) of studies were not validated at all, which is an area of concern.

INTERPRETATION

Finite element simulation of the ankle shows promise as a clinical tool for improving outcomes. Standardisation of model creation and standardisation of reporting would increase trust, and enable independent validation, through which successful clinical application of the research could be realised.

The effect of ankle and hindfoot malalignment on foot mechanics in patients suffering from post-traumatic ankle osteoarthritis

BACKGROUND

Ankle and hindfoot malalignment is a common finding in patients suffering from post-traumatic ankle osteoarthritis. However, no studies have addressed the effect of concomitant foot deformities on intrinsic foot kinematics and kinetics. Therefore, the objective of this study was to investigate the effect of ankle and hindfoot malalignment on the kinematics and kinetics of multiple joints in the foot and ankle complex in patients suffering from post-traumatic ankle osteoarthritis.

METHODS

Twenty-nine subjects with post-traumatic ankle osteoarthritis participated in this study. Standardized weight-bearing radiographs were obtained preoperatively to categorize patients as having cavus, planus or neutral ankle and hindfoot alignment, based on 4 X-ray measurements. All patients underwent standard gait assessment. A 4-segment foot model was used to estimate intrinsic foot joint kinematics and kinetics during gait. Statistical parametric mapping was used to compare foot kinematics and kinetics between groups.

FINDINGS

There were 3 key findings regarding overall foot function in the 3 groups of post-traumatic ankle osteoarthritis: (i) altered frontal and transverse plane inter-segmental angles and moments of the Shank-Calcaneus and Calcaneus-Midfoot joints in the cavus compared to the planus group; (ii) in cavus OA group, Midfoot-Metatarsus joint abduction sought to compensate the varus inclination of the ankle joint; (iii) there were no significant differences in inter-segmental angles and moments between the planus and neutral OA groups.

INTERPRETATION

Future studies should integrate assessment of concomitant foot and ankle deformities in post-traumatic ankle osteoarthritis, to provide additional insight into associated mechanical deficits and compensation mechanisms during gait.

Loss of Mechanical Ankle Function Is Not Compensated by the Distal Foot Joints in Patients with Ankle Osteoarthritis

BACKGROUND

Patients with isolated ankle osteoarthritis (OA) often demonstrate disturbed ankle biomechanics during walking. Clinicians often believe that this triggers the distal foot joints to compensate these altered ankle biomechanics and that these foot joints are consequently subjected to degenerative joint diseases due to overuse.

QUESTIONS/PURPOSES

Do patients with isolated ankle OA differ from those without ankle OA in terms of (1) ankle and foot joint kinematics and (2) ankle and foot joint kinetics as measured using three-dimensional (3-D) gait analysis? (3) Do these patients demonstrate compensatory strategies in their Chopart, Lisfranc, or first metatarsophalangeal joints in terms of increased joint kinematic and kinetic outputs?

METHODS

Between 2015 and 2018, we treated 110 patients with unilateral ankle OA, and invited all of them to participate in the gait analysis laboratory. Of those, 47% (52) of patients did so, and of these, 16 patients met the inclusion criteria for this study, which were (1) diagnosis of unilateral ankle OA; (2) absence of radiographical signs of OA in the contralateral foot or lower limbs; (3) ability to walk at least 100 m without rest; and (4) being older than 18 years of age. A control group (n = 25) was recruited through intranet advertisements at the University Hospitals of Leuven. Participants were included if their age matched the age-range of the patient group and if they had no history of OA in any of the lower limb joints. Patients were slightly older (55.9 ± 11.2 years), with a slightly higher BMI (28 ± 6 kg/m2) than the control group participants (47.2 ± 4.4 years; p = 0.01 and 25 ± 3 kg/m2; p = 0.05). All participants underwent a 3-D gait analysis, during which a multisegment foot model was used to quantify the kinematic parameters (joint angles and ROM) and the kinetic parameters (rotational forces or moments), as well as power generation and absorption in the ankle, Chopart, Lisfranc, and first metatarsophalangeal joints during the stance phase of walking. Peak values were the maximum and minimum values of waveforms and the latter were time-normalized to 100% of the stance phase.

RESULTS

Regarding joint kinematics, patients demonstrated a sagittal plane ankle, Chopart, Lisfranc, and first metatarsophalangeal joint ROM of 11.4 ± 3.1°, 9.7 ± 2.7°, 8.6 ± 2.3° and 34.6 ± 8.1°, respectively, compared with 18.0 ± 2.7° (p < 0.001), 13.9 ± 3.2° (p < 0.001), 7.1 ± 2.0° (p = 0.046) and 38.1 ± 6.5° (p = 0.15), respectively, in the control group during the stance phase of walking. With regard to joint kinetics in the patient group, we found a mean decrease of 1.3 W/kg (95% CI confidence interval 1.0 to 1.6) (control group mean: 2.4 ± 0.4 W/kg, patient group mean: 1.1 ± 0.5 W/kg) and 0.8 W/kg (95% CI 0.4 to 1.0) (control group mean: 1.5 ± 0.3 W/kg, patient group mean: 0.7 ± 0.5 W/kg) of ankle (p < 0.001) and Chopart (p < 0.001) joint peak power generation. No changes in kinetic parameters (joint moment or power) were observed in any of the distal foot joints.

CONCLUSION

The findings of this study showed a decrease in ankle kinematics and kinetics of patients with isolated ankle OA during walking, whereas no change in kinematic or kinetic functions were observed in the distal foot joints, demonstrating that these do not compensate for the mechanical dysfunction of the ankle.

CLINICAL RELEVANCE

The current findings suggest that future experimental laboratory studies should look at whether tibiotalar joint fusion or total ankle replacement influence the biomechanical functioning of these distal joints.

Investigation of the Average Shape and Principal Variations of the Human Talus Bone Using Statistic Shape Model

Due to the complexity of articular interconnections and tenuous blood supply to the talus, talus fractures are often associated with complications (e.g., avascular necrosis). Currently, surgically fusing the talus to adjacent bones is widely used as treatment to talus fractures, but this procedure can greatly reduce mobility in the ankle and hindfoot. Alternatively, customized talus implants have shown an overall satisfactory patient feedback but with the limitation of high expenses and time-consuming manufacturing process. In order to circumvent these disadvantages, universal talus implants have been proposed as a potential solution. In our study, we aimed to develop a methodology using Statistical Shape Model (SSM) to simulate the talus, and then evaluate the feasibility of the model to obtain the mean shape needed for universal implant design. In order to achieve this, we registered 98 tali (41 females and 57 males) and used the registered dataset to train our SSM. We used the mean shape derived from the SSM as the basis for our talus implant template, and compared our template with that of previous works. We found that our SSM mean shape talus implant was geometrically similar to implants from other works, which used a different method for the mean shape. This suggests the feasibility of SSM as a method of finding mean shape information for the development of universal implants. A second aim of our study was to investigate if one scalable talus implant can accommodate all patients. In our study, we focused on addressing this from a geometric perspective as there are multiple factors impacting this (e.g., articular surface contact characteristics, implant material properties). Our initial findings are that the first two principal components should be afforded consideration for the geometrical accuracy of talus implant design. Additional factors would need to be further evaluated for their role in informing universal talus implant design.

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.

Total ankle arthroplasty and ankle arthrodesis affect the biomechanics of the inner foot differently

Ankle arthrodesis and total ankle arthroplasty are the two primary surgeries for treatment of end-stage degenerative ankle arthritis. The biomechanical effects of them on the inner foot are insufficient to identify which is superior. This study compared biomechanical parameters among a foot treated by ankle arthrodesis, a foot treated by total ankle arthroplasty, and an intact foot using computational analysis. Validated finite element models of the three feet were developed and used to simulate the stance phase of gait. The results showed total ankle arthroplasty provides a more stable plantar pressure distribution than ankle arthrodesis. The highest contact pressure, 3.17 MPa, occurred in the medial cuneonavicular joint in the total ankle arthroplasty foot. Neither of the surgeries resulted in contact pressure increase in the subtalar joint. The peak stress in the metatarsal bones was increased in both surgical models, especially the second and third metatarsals. This study enables us to get visual to the biomechanics inside of an intact foot, and feet treated by total ankle arthroplasty and ankle arthrodesis during walking.

Outcomes of Salvage Arthrodesis and Arthroplasty for Failed Osteochondral Allograft Transplantation of the Ankle

BACKGROUND

Osteochondral allograft (OCA) transplantation is a useful treatment for posttraumatic ankle arthritis in young patients, but failure rates are high and reoperations are not uncommon. The aim of this study was to evaluate the outcomes of failed ankle OCA transplantation converted to ankle arthrodesis (AA) or total ankle arthroplasty (TAA).

METHODS

We evaluated 24 patients who underwent salvage procedures (13 AA and 11 TAA) after primary failed ankle OCA transplantation. Reoperations were assessed. Failure of the salvage procedure was defined as an additional surgery that required a revision AA/TAA or amputation. Evaluation among nonfailing ankles included the American Academy of Orthopaedic Surgeons Foot and Ankle Module (AAOS-FAM), pain, and satisfaction.

RESULTS

In the salvage AA cohort, 3 patients were classified as failures (2 revision AA and 1 amputation). The 10 nonfailing patients had a mean follow-up of 7.4 years. Eighty-eight percent were satisfied with the procedure, but 63% reported continued problems with their ankle (eg, pain, swelling, stiffness). Mean pain level was 1.9 and AAOS-FAM core score was 83±13. In the salvage TAA cohort, 2 patients were classified as failures (both revision TAA). The 9 nonfailing patients had a mean follow-up of 3.8 years. Fifty percent were satisfied with the procedure, but 40% reported continued problems with their ankle. The mean pain level was 1.3, and the median AAOS-FAM core score was 82±26.

CONCLUSION

Revision and reoperation rates for salvage procedures following failed OCA transplantation of the ankle are higher compared to published data for primary AA and TAA procedures. However, we believe OCA transplantation can serve as an interim procedure for younger patients with advanced ankle joint disease who may not be ideal candidates for primary AA or TAA at the time of initial presentation.

LEVEL OF EVIDENCE

Level IV, case series.

Using the Oxford Foot Model to determine the association between objective measures of foot function and results of the AOFAS Ankle-Hindfoot Scale and the Foot Function Index: a prospective gait analysis study in Germany

OBJECTIVE

After cross-cultural adaption for the German translation of the Ankle-Hindfoot Scale of the American Orthopaedic Foot and Ankle Society (AOFAS-AHS) and agreement analysis with the Foot Function Index (FFI-D), the following gait analysis study using the Oxford Foot Model (OFM) was carried out to show which of the two scores better correlates with objective gait dysfunction.

DESIGN AND PARTICIPANTS

Results of the AOFAS-AHS and FFI-D, as well as data from three-dimensional gait analysis were collected from 20 patients with mild to severe ankle and hindfoot pathologies.Kinematic and kinetic gait data were correlated with the results of the total AOFAS scale and FFI-D as well as the results of those items representing hindfoot function in the AOFAS-AHS assessment. With respect to the foot disorders in our patients (osteoarthritis and prearthritic conditions), we correlated the total range of motion (ROM) in the ankle and subtalar joints as identified by the OFM with values identified during clinical examination 'translated' into score values. Furthermore, reduced walking speed, reduced step length and reduced maximum ankle power generation during push-off were taken into account and correlated to gait abnormalities described in the scores. An analysis of correlations with CIs between the FFI-D and the AOFAS-AHS items and the gait parameters was performed by means of the Jonckheere-Terpstra test; furthermore, exploratory factor analysis was applied to identify common information structures and thereby redundancy in the FFI-D and the AOFAS-AHS items.

RESULTS

Objective findings for hindfoot disorders, namely a reduced ROM, in the ankle and subtalar joints, respectively, as well as reduced ankle power generation during push-off, showed a better correlation with the AOFAS-AHS total score-as well as AOFAS-AHS items representing ROM in the ankle, subtalar joints and gait function-compared with the FFI-D score.Factor analysis, however, could not identify FFI-D items consistently related to these three indicator parameters (pain, disability and function) found in the AOFAS-AHS. Furthermore, factor analysis did not support stratification of the FFI-D into two subscales.

CONCLUSIONS

The AOFAS-AHS showed a good agreement with objective gait parameters and is therefore better suited to evaluate disability and functional limitations of patients suffering from foot and ankle pathologies compared with the FFI-D.

Analysis of a generic talar prosthetic with a biological talus: A cadaver study

Treatment for talar avascular necrosis is challenging. This study evaluates the feasibility of a generic talar implant by cadaveric assessment. Ten cadaveric ankles were CT-scanned to determine talar implant size. The opposite ankles were CT-scanned with the biological talus and then with the implant. 3D ankle geometry was reconstructed and implant position was compared to the biological talus position. The averages among specimens' positive and negative average-deviations were 0.91 mm and 0.70 mm. Seventy percent of talar dome deviations between the biological talus and implant were within an acceptable range. This study yields promising results to support a generic talus bone prosthetic.

Active Ankle Circumduction to Identify Mobility Deficits in Subacute Ankle Sprain Patients

Assessment of ankle mobility is complex and of clinical relevance after an ankle sprain. This study develops and tests a biomechanical model to assess active ankle circumduction and its reliability. The model was then applied to compare individuals' ankle mobility between injured and noninjured ankles after a sprain episode. Twenty patients with subacute unilateral ankle sprain were assessed at 4 weeks and 10 weeks after the injury. They underwent a clinical exam and an ankle circumduction test during which the kinematics were recorded with an optoelectronic device. A biomechanical model was applied to explore ankle kinematics. Reliability of the ankle circumduction tests were good to excellent (ICC of 0.55-0.89). Comparison between noninjured and injured ankles showed a mobility deficit of the injured ankle (dorsiflexion = -27.4%, plantar flexion = -25.9%, eversion = -27.2%, and inversion = -11.6%). The model allows a graphical representation of these deficits in 4 quadrants. Active ankle circumduction movement can be reliably assessed with this model. In addition, the graphical representation allows an easy understanding of the mobility deficits which were present in all 4 quadrants in our cohort of patients with subacute ankle sprain.

Geometric analysis of the talus and development of a generic talar prosthetic

BACKGROUND

Trauma to the talus can result in fracture, avascular necrosis and structural collapse. Treatment has been limited to surgical fusion and total ankle arthroplasty. Total ankle arthroplasty may not be an appropriate treatment for avascular necrosis while surgical fusion of the joint limits mobility. Custom-made implants have recently been used to address these limitations but have lengthy delays between injury and surgery and higher associated costs. A generic talar prosthesis available in various sizes may serve as a suitable alternative.

METHODS

The geometric variation between shapes of individual tali was determined using 3D geometric models of 91 tali created from CT-scan data. Comparisons were done to determine if tali are one shape. The best shape was determined for each sex, and was compared to determine if a unisex implant would be possible. A geometric template for the implant in multiple sizes was created and compared to the models.

RESULTS

The average of the average deviation between tali after volume scaling was found to be less than 1mm on the main articulating surfaces. One shape group was found for the talus. The female and male tali were found to be similar and a unisex implant template was created.

CONCLUSIONS

Ten generic talar implant sizes were determined to be sufficient to match the size and shape of the 91 tali examined in this study.

Ratio of Range of Motion of the Ankle and Surrounding Joints After Total Ankle Replacement: A Radiographic Cohort Study

BACKGROUND

This study attempted to identify where motion occurs after total ankle replacement, the difference in range-of-motion contributions between fixed-bearing and mobile-bearing total ankle replacements, and the contribution of abnormal peritalar motion. We hypothesized that sagittal plane radiographic assessment would demonstrate that actual ankle motion through the prosthesis is less than the total arc of ankle motion that may be observed clinically secondary to contributions from adjacent joints.

METHODS

Patients underwent routine standardized weight-bearing maximum dorsiflexion and plantar flexion sagittal radiographs. Sagittal plane ankle and foot measurements were performed on each dorsiflexion and plantar flexion radiograph to determine the total arc of ankle motion, actual ankle motion through the prosthesis, motion through the subtalar and talonavicular joints, and midfoot motion. Motion radiographs were routinely made at 1 year postoperatively and at the time of the most recent follow-up. A minimum follow-up of 2 years was required of all patients.

RESULTS

There were 197 patients who met the inclusion criteria (75 INBONE, 52 Salto Talaris, and 70 STAR prostheses). The mean time to the latest radiographs (and standard deviation) was 42.9 ± 18.8 months. The mean actual ankle motion through the prosthesis was 25.9° ± 12.2°, which was significantly less (p < 0.001) than the mean total motion arc of 37.6° ± 12.0°. The motion of the ankle accounted for 68% of total range of motion, and motion of the peritalar joints accounted for 32%. There was no significant difference (p > 0.05) among the 3 prostheses or when comparing fixed and mobile-bearing designs for both ranges of motion.

CONCLUSIONS

This study demonstrates that actual ankle motion after total ankle replacement is approximately 12° less than the total arc of motion that might be observed clinically because of increased midfoot and subtalar motion.

LEVEL OF EVIDENCE

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

Multisegment Foot Kinematic and Kinetic Compensations in Level and Uphill Walking Following Tibiotalar Arthrodesis

BACKGROUND

Foot and ankle movement alterations following ankle arthrodesis are still not well understood, particularly those that might contribute to the documented increase in adjacent joint arthritis. Generalized tarsal hypermobility has long been postulated, but not confirmed in gait or functional movements. The purpose of this study was to more thoroughly evaluate compensation mechanisms used by arthrodesis patients during level and uphill gait through a variety of measurement modalities and a detailed breakdown of gait phases.

METHODS

Level ground and uphill gait of 14 unilateral tibiotalar arthrodesis patients and 14 matched controls was analyzed using motion capture, force, and pressure measurements in conjunction with a kinetic multisegment foot model.

RESULTS

The affected limb exhibited several marked differences compared to the controls and to the unaffected limb. In loading response, ankle eversion was reduced but without a reduction in tibial rotation. During the second rocker, ankle dorsiflexion was reduced, yet was still considerable, suggesting compensatory talar articulation (subtalar and talonavicular) motion since no differences were seen at the midtarsal joint. Also during the second rocker, subjects abnormally internally rotated the tibia while moving their center of pressure laterally. Third rocker plantarflexion motion, moments, and powers were substantially reduced on the affected side and to a lesser extent on the unaffected side.

CONCLUSION

Sagittal plane hypermobility is probable during the second rocker in the talar articulations following tibiotalar fusion, but is unlikely in other midfoot joints. The normal coupling between frontal plane hindfoot motion and tibial rotation in early and mid stance was also clearly disrupted. These alterations reflect a complex compensatory movement pattern that undoubtedly affects the function of arthrodesis patients, likely alters the arthrokinematics of the talar joints (which may be a mechanism for arthritis development), and should be considered in future arthrodesis as well as arthroplasty research.

LEVEL OF EVIDENCE

Level III, comparative study.

Effects of Ankle Arthrodesis on Biomechanical Performance of the Entire Foot

Background/Methodology

Ankle arthrodesis is one popular surgical treatment for ankle arthritis, chronic instability, and degenerative deformity. However, complications such as foot pain, joint arthritis, and bone fracture may cause patients to suffer other problems. Understanding the internal biomechanics of the foot is critical for assessing the effectiveness of ankle arthrodesis and provides a baseline for the surgical plan. This study aimed to understand the biomechanical effects of ankle arthrodesis on the entire foot and ankle using finite element analyses. A three-dimensional finite element model of the foot and ankle, involving 28 bones, 103 ligaments, the plantar fascia, major muscle groups, and encapsulated soft tissue, was developed and validated. The biomechanical performances of a normal foot and a foot with ankle arthrodesis were compared at three gait instants, first-peak, mid-stance, and second-peak.

Principal Findings/Conclusions

Changes in plantar pressure distribution, joint contact pressure and forces, von Mises stress on bone and foot deformation were predicted. Compared with those in the normal foot, the peak plantar pressure was increased and the center of pressure moved anteriorly in the foot with ankle arthrodesis. The talonavicular joint and joints of the first to third rays in the hind- and mid-foot bore the majority of the loading and sustained substantially increased loading after ankle arthrodesis. An average contact pressure of 2.14 MPa was predicted at the talonavicular joint after surgery and the maximum variation was shown to be 80% in joints of the first ray. The contact force and pressure of the subtalar joint decreased after surgery, indicating that arthritis at this joint was not necessarily a consequence of ankle arthrodesis but rather a progression of pre-existing degenerative changes. Von Mises stress in the second and third metatarsal bones at the second-peak instant increased to 52 MPa and 34 MPa, respectively, after surgery. These variations can provide indications for outcome assessment of ankle arthrodesis surgery.

One- and multi-segment foot models lead to opposite results on ankle joint kinematics during gait: Implications for clinical assessment

BACKGROUND

Biomechanical models representing the foot as a single rigid segment are commonly used in clinical or sport evaluations. However, neglecting internal foot movements could lead to significant inaccuracies on ankle joint kinematics. The present study proposed an assessment of 3D ankle kinematic outputs using two distinct biomechanical models and their application in the clinical flat foot case.

METHODS

Results of the Plug in Gait (one segment foot model) and the Oxford Foot Model (multisegment foot model) were compared for normal children (9 participants) and flat feet children (9 participants). Repeated measures of Analysis of Variance have been performed to assess the Foot model and Group effects on ankle joint kinematics.

FINDINGS

Significant differences were observed between the two models for each group all along the gait cycle. In particular for the flat feet group, opposite results between the Oxford Foot Model and the Plug in Gait were revealed at heelstrike, with the Plug in Gait showing a 4.7° ankle dorsal flexion and 2.7° varus where the Oxford Foot Model showed a 4.8° ankle plantar flexion and 1.6° valgus.

INTERPRETATION

Ankle joint kinematics of the flat feet group was more affected by foot modeling than normal group. Foot modeling appeared to have a strong influence on resulting ankle kinematics. Moreover, our findings showed that this influence could vary depending on the population. Studies involving ankle joint kinematic assessment should take foot modeling with caution.

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.

Sagittal subtalar and talocrural joint assessment with weight-bearing fluoroscopy during barefoot ambulation

BACKGROUND

Identifying talar position during ambulation has proved difficult as the talus lacks palpable landmarks for skin marker placement and more invasive methodologies such as bone pins are not practical for most clinical subjects. A fluoroscopic motion system was used to track the talus and calcaneus, allowing kinematic analysis of the talocrural and subtalar joints.

METHODS

Thirteen male subjects (mean age 22.9 ± 3.0 years) previously screened for normal gait were tested. A fluoroscopy unit was used to collect images at 120 fps during stance. Sagittal motion of the talocrural and subtalar joints were analyzed.

RESULTS

The intersubject mean and standard deviation values for all 58 trials of 13 subjects are reported. Maximum talocrural joint plantarflexion of 11.2 degrees (4.3 degrees of standard deviation) occurred at 11% stance and maximum dorsiflexion of -6.9 degrees (5.6 degrees of standard deviation) occurred at 85%. Maximum subtalar joint plantarflexion of 4.8 degrees (1.0 degrees of standard deviation) occurred at 96% stance and maximum dorsiflexion of -3.6 degrees (2.3 degrees of standard deviation) occurred at 30%. Talocrural and subtalar range of motion values during stance were 18.1 and 8.4 degrees, respectively.

CONCLUSION

Existing fluoroscopic technology was capable of defining sagittal plane talocrural and subtalar motion during gait. These kinematic results compare favorably with more invasive techniques. This type of assessment could support more routine analysis of in vivo bony motion during gait.

CLINICAL RELEVANCE

Fluoroscopic technology offers improved sagittal plane motion evaluation during weight-bearing with potential application in patients with end-stage ankle arthritis, postoperative ankle replacements and fusions, and orthotics and braces.

Radiographic and functional outcomes following bilateral ankle fusions

BACKGROUND

Ankle arthrodesis is considered to be a well-accepted technique for end-stage ankle arthritis. Our purpose was to evaluate outcomes of patients with bilateral ankle arthrodeses with attention to radiographic and functional outcomes.

METHODS

Medical records of 31 patients were reviewed from 1977 through 2007. All patients had 1 year of clinical follow-up after their contralateral ankle arthrodesis, with an average follow-up of 11.2 years following the initial arthrodesis. Pertinent patient demographics and information pertaining to the operative procedure, complications, and subsequent adjacent joint fusions was collected. Radiographs were reviewed for time to fusion and adjacent joint arthritis. Functional outcomes were measured using the Foot and Ankle Ability Measure (FAAM) and the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle and Hindfoot scale.

RESULTS

Ten females and 21 males underwent bilateral ankle fusions at an average age of 57 years at the time of the initial fusion. The contralateral fusion occurred on average 3.1 years following the initial fusion. Radiographic fusion occurred 12 weeks following the initial fusion and 14 weeks following the contralateral fusion. There was a significant increase (P = .0001) in the average AOFAS score postoperatively in both ankles. The average FAAM score at last follow-up was 70. Adjacent joint arthritis developed in the majority of patients; however, most of the patients were free from adjacent fusions and reported their function as "normal" or "nearly normal" at last follow-up.

CONCLUSION

Bilateral ankle arthrodesis was an acceptable treatment option for patients with bilateral, end-stage ankle arthritis.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Total ankle replacement in patients with end-stage ankle osteoarthritis: clinical results and kinetic gait analysis

BACKGROUND

Total ankle arthroplasty is being used more frequently as an alternative for arthrodesis in final stages of ankle osteoarthritis. However, there are few studies which describe the biomechanics of gait of these patients.

METHODS

Between March 2006 and May 2011, 17 patients (n=18 ankles) suffering end-stage osteoarthritis of the ankle who underwent an ankle replacement (HINTEGRA) were evaluated retrospectively. We evaluated clinical, radiological and biomechanical gait parameters using the NedAMH/IBV dynamometric platform.

RESULTS

At last follow-up (average: 37 months), the AOFAS score improved from 31 to 83 with a high rate of satisfaction (83.3%). Kinetic gait parameters were more similar to a healthy ankle. We detected a radiolucent line in 8 patients (44%) without any subsidence case.

CONCLUSIONS

Our study showed a high rate of satisfaction and biomechanics of the gait similar to a healthy ankle. The complication rate was analogous to those previously published in the literature.

Biomechanics of asymmetric ankle osteoarthritis and its joint-preserving surgery

More than half of the patients with ankle osteoarthritis have a malalignment of the hindfoot. These patients might benefit from joint-preserving realignment surgery. This article provides an overview of the effects of asymmetric ankle osteoarthritis on the patients' biomechanical and neuromuscular gait patterns in comparison to data from healthy subjects. Furthermore, data from gait analyses after joint-preserving realignment surgery are presented that give an indication of the biomechanical and neuromuscular adaptations to supramalleolar osteotomies.

Joint-preserving surgery of valgus ankle osteoarthritis

Patients with posttraumatic ankle osteoarthritis (OA) typically present with asymmetric involvement of the tibiotalar joint, resulting in valgus or varus deformity of the ankle and hindfoot. Without appropriate treatment, patients with asymmetric ankle OA typically develop full end-stage ankle OA. Ankles with valgus deformities suffer from a lateral joint overload with subsequent lateral tibiotalar joint degeneration, which causes further lateral load shift. In these cases patients may benefit from joint-preserving realignment surgery to unload the degenerated lateral area and normalize joint biomechanics. This article describes the authors' algorithm for the treatment of patients with asymmetric valgus ankle OA.