Position of the prosthesis components in total ankle replacement and the effect on motion at the replaced joint

Placing the tibial component of an ankle prosthesis: results of a CT-based simulation in healthy adults

PURPOSE

To characterize the 3D geometry of the distal tibia resection area from healthy individuals using CT-based digital implantation for proper preoperative sizing of TAA tibia component placement.

METHODS

Standardized CT images of healthy ankle joints serving as intra-individual references for treatment of contralateral injuries were identified. The tibial cross section dedicated to virtually host the tibial component was digitally prepared, and the size of the virtual contact surface was calculated. Finally, out of five prototypes the one fitting best in terms of size and alignment was identified.

RESULTS

CT scans taken from 319 subjects were used for the virtual implantation procedure. Body height and size of the distal tibia contact area correlated (r = 0.49 and 0.42 in females and males, each p < 0.001). Prosthesis sizes 2 and 3 fit well for the vast majority of patients, while the smallest and largest sizes are rarely required.

CONCLUSIONS

Digital implantation of the tibial component should be considered a valuable tool for preoperative planning as well as for the development of new implant types.

Accuracy of patient-specific instrumentation for implant positioning in custom-made total ankle arthroplasty

Purpose

This retrospective radiological analysis aimed to assess the accuracy of implant positioning in patients with ankle arthritis undergoing custom-made total ankle arthroplasty (TAA) with patient-specific instrumentation (PSI) compared with preoperative planning.

Methods

Patients who underwent custom-made TAA with PSI from January 2018 to March 2023 were retrospectively evaluated, focusing on the tibial anterior surface (TAS) angle, tibial lateral surface (TLS) angle and tibiotalar ratio (TTR). Additionally, data regarding the time from the preoperative computed tomography (CT) scan to surgery, associated procedures and complications were recorded.

Results

No associated procedures were performed, and only one intraoperative complication, an iatrogenic lateral malleolar fracture, was recorded. In the coronal plane, custom-made TAA with PSI consistently achieved precise positioning of prosthetic components, even in cases with significant preoperative deformities or bone deficits. However, a statistically significant deviation from the planned values was observed in the sagittal plane (p = 0.007). A notable correlation was identified between the time elapsed from the preoperative CT scan to surgery and the deviation from the planned to the actual postoperative TAS angle (p < 0.001).

Conclusion

This study underscores the efficacy of PSI systems in achieving precise positioning in the coronal plane, in accordance with preoperative planning. In contrast, sagittal plane positioning did not demonstrate the same level of accuracy, as evidenced by a statistically significant difference between the planned and postoperative TLS values. Nevertheless, all measurements remained within the recommended range according to the existing literature.

Level of Evidence

Level IV.

Definitions and Measurements of Hindfoot Alignment and Their Biomechanical and Clinical Implications

This article presents a critical review of the past and the current state of the art in defining and measuring hindfoot, ankle, and subtalar alignment. It describes the transition occurring at present from two-dimensional to three-dimensional (3D) alignment measurements, which accompany the emergence of new, functional, high-resolution imaging modalities such as the weight-bearing cone-beam computerized tomography (CT) imaging. To ease and enhance the transition and acceptability of 3D alignment measurements, new acceptable standards for different clinical application are highly desirable.

Total Ankle Replacement: Biomechanics of the Designs, Clinical Outcomes, and Remaining Issues

The present review paper aimed at discussing the current major issues in total ankle replacement, both the technical and biomechanical concepts, and the surgical and clinical concerns. Designers shall target at the same time restoration of natural ankle kinematics and congruity of the artificial surfaces throughout the range of motion. Surgeons are recommended to expand biomechanical knowledge on ankle joint replacement, and provide appropriate training and key factors to make arthroplasty a good alternative to arthrodesis. Moreover, adequate selection of patients and careful rehabilitation are critical. In the future, custom-made prosthesis components and patient-specific instrumentation are major developments for more complex cases.

An Analysis of 50 Consecutive Total Ankle Replacements Undergoing Preoperative Computerized Tomography Scan-Based, Engineer-Provided Planning From a Single Noninventor, Nonconsultant Surgeon

Preoperative computerized tomography (CT) scan-based, engineer-provided alignment plans and patient-specific pinning blocks for total ankle replacement (TAR) are available for use in the United States. However, nonbiased studies that justify the additional expense associated with this technology through support of the marketed benefits of less procedural complexity, less intraoperative radiation and reduced surgical time, are lacking. Therefore, to verify the manufacturer's proposed benefits, we sought to investigate our experience with this preoperative CT scan-based, engineer-provided plan and patient-specific pinning blocks during primary TAR. In review of our 50 TAR patients, we found that "perfect" radiographic alignment was not consistently achieved and the accuracy of component prediction was modest. Furthermore, the preoperative plans and patient-specific pinning blocks did not simplify the complexity of our operations since the operative time, intraoperative image intensification time and radiation dose per case all exceeded published historical TAR controls. Interestingly, we identified a significant difference in placement accuracy between the arced and flat-top talar component types that were implanted with the arced being more frequently malaligned. We did not find associations between preoperative deformity severity and accuracy of postoperative alignment. These findings suggest that it is imperative to have surgeons continue to rely on their own surgical planning and experience to achieve optimum radiographic alignment rather than depending on engineer-based recommendations or "surface matched" pinning blocks. Ultimately, we were unable to support the purported benefits of this CT scan-based, engineer-provided alignment plan and patient-specific pinning blocks for this manufacturer's primary TAR systems.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Patient-specific instrumentation in total ankle arthroplasty

The recent increase in the adoption of total ankle arthroplasty (TAA) reflects the improvements in implant designs and surgical techniques, including the use of preoperative navigation system and patient-specific instrumentation (PSI), such as custom-made cutting guides. Cutting guides are customized with respect to each patient's anatomy based on preoperative ankle computed tomography scans, and they drive the saw intra-operatively to improve the accuracy of bone resection and implant positioning. Despite some promising results, the main queries in the literature are whether PSI improves the reliability of achieving neutral ankle alignment and more accurate implant sizing, whether it is actually superior over standard techniques, and whether it is cost effective. Moreover, the advantages of PSI in clinical outcomes are still theoretical because the current literature does not allow to confirm its superiority. The purpose of this review article is therefore to assess the current literature on PSI in TAA with regard to current implants with PSI, templating and preoperative planning strategies, alignment and sizing, clinical outcomes, cost analysis, and comparison with standard techniques.

Effect of artificial surface shapes and their malpositioning on the mechanics of the replaced ankle joint for possible better prosthesis designs

BACKGROUND

The clinical outcomes of total ankle replacement are limited by prosthesis component malpositioning during surgery. The goal of this study is to assess the mechanical impact of this malpositioning in a validated computer model.

METHODS

In a previously developed multi-body dynamic model of the human ankle complex three different artificial implants were designed, each one presenting a different approximation of the natural articular surfaces of the corresponding specimen. The most common implant translational and rotational malpositionings were defined and mimicked. Dynamic simulations of joint motion were run for the various surfaces and malpositionings. The same input loading conditions derived from a previous in-vitro experiment on the corresponding natural specimen were applied.

FINDINGS

From load-displacement graphs it was observed that all three artificial surfaces reproduced well physiological motion between the calcaneus and the tibia/fibula, with a maximum difference of 2°. It was found that antero-posterior translation of either the tibial or the talar component and inclination of the tibial component in the sagittal plane led to considerable increases in the range of motion. Antero-posterior and dorsiflexion of the tibial component resulted in an increased internal-external rotation by up to 3.5° and 4.0°, respectively. The corresponding increase of inversion-eversion was 5.0° and 6.5°.

INTERPRETATION

This study showed that relatively small surgical errors have great consequences in replaced joint mechanics. The present model can be used in future studies to analyse the effect of malpositioning with any specific current total ankle prosthesis.

Custom-Made Total Talonavicular Replacement in a Professional Rock Climber: Functional Evaluation With Gait Analysis and 3-Dimensional Medical Imaging in Weightbearing at 5 Years' Follow-Up

With the goal to restore ankle and foot function also in the long term, custom-made prostheses are becoming more frequently possible solutions for severe bone loss and avascular necrosis of the talus. A young professional rock climber was implanted with a custom-made talonavicular prosthesis, and short-term (30 months) assessment has been published. A thorough assessment at the intermediate term (60 months), with state-of-the-art gait and medical imaging analyses, is reported here. Level walking and more demanding motor tasks were analyzed with both a full-body and a multisegment foot protocol on the operated and contralateral limbs. Cone-beam computer-tomography was also used to obtain 3-dimensional (3D) position and orientation of bone models on the operated ankle. These models were also used for a 3D video fluoroscopy analysis, with the ankle in 3 joint positions at the extremes of motion. Distance map analysis was performed to check for possible changes over time of bone morphology and joint contact areas, in all 3 joint positions. Very satisfactory functional results were observed, with large and symmetric joint motion and physiological muscular recruitment even in demanding motor tasks. Distance map analyses revealed that very small morphologic and contact patterns changes occurred in the replaced ankle between 30 and 60 months. Concerns about possible wear of the cartilage in the tibial mortise are not yet supported by experimental evidence.

Anterior placement of the talar component in total ankle arthroplasty: A risk factor for talar component subsidence

BACKGROUND

Component subsidence is considered as a cause of revision surgery. The talar component subsidence may be a risk factor for revision surgery; however, there are no reports regarding talar component placement and subsidence amount following total ankle arthroplasty (TAA). We therefore investigated the relationship between talar component placement and subsidence amount.

METHODS

Fifty-two ankles from 49 patients (age: 71 years [range 62-83], 13 male/ 36 female), who underwent TAA with mean follow-up of 36 months (range 12-83), were included. The subjects were divided into two groups based on talar component placement: anterior placement (n = 20, group A) and posterior placement (n = 32, group P) using weight-bearing lateral plain radiographs. The amount of the talar component subsidence and clinical outcomes, which included the Japanese Society for Surgery of the Foot (JSSF) scale, range of the motion (ROM) and the revision rate, were compared between the groups.

RESULTS

Talar component subsidence was significantly higher in group A (2.1 ± 2.0 mm) than in group P (0.6 ± 1.4 mm, P = .017). There was no significant difference in the JSSF scale and ROM between group A and group P. The revision rate was 10.0% in group A and 6.3% in group P, albeit not statistically significant.

CONCLUSION

Greater talar component subsidence was observed when the talar component was placed more anteriorly, suggesting that anterior placement of the talar component may need to be avoided during the surgery in order to minimize the postoperative talar component subsidence.

Range of motion of foot joints following total ankle replacement and subtalar fusion

BACKGROUND

In severe cases of ankle and subtalar arthritis, arthrodesis of the subtalar joint is performed in combination with ankle arthroplasty. In these special cases gait analysis reveals real motion at the replaced tibiotalar joint.

METHODS

Twenty-three patients affected by ankle and subtalar arthritis, treated either with a 3-component or a 2-component prosthesis in combination with subtalar arthrodesis, were clinically evaluated preoperatively and at a minimum of 1-year follow-up. Gait analysis was performed postoperatively using a multi-segment foot protocol. Foot kinematics were compared to corresponding data from a healthy control group.

RESULTS

Clinical scores significantly improved from preoperative to follow-up. The clinically measured passive ankle dorsiflexion/plantarflexion significantly improved at the follow-up. Patients' normalized walking speed and stride length were significantly lower than those in control. With exception of the ankle frontal-plane motion, sagittal-plane mobility of foot joints was about 50% than that in healthy joints.

CONCLUSIONS

Improvement in clinical scores was found for both prostheses. Normal spatio-temporal parameters were not restored. In these patients, fusion of the subtalar joint appeared to be compensated by larger frontal-plane motion at the tibiotalar joint.

LEVEL OF EVIDENCE

Level III- retrospective comparative study. The study was approved by the local Ethics Committee as protocol MAT (protocol registration at clinicaltrials.gov NCT03356951).

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.

Methodology for Measurement of in vivo Tibiotalar Kinematics After Total Ankle Replacement Using Dual Fluoroscopy

Biomechanical data could improve our clinical understanding of failures in total ankle replacement (TAR) patients, leading to better surgical approaches and implant designs. Kinematics of the prosthetic tibiotalar joint in TAR patients have yet to be measured using dual fluoroscopy. With dual fluoroscopy, computed tomography (CT) images are acquired to track bone motion. One challenge with this approach is dealing with metal artifact in the CT images that distorts implant visualization and the surrounding bone to implant interfaces. The aim of this study was to develop a methodology to measure in vivo TAR kinematics using inputs of computer-aided design (CAD) models, dual fluoroscopy and CT imaging with metal artifact reduction. To develop this methodology, we created a hybrid three-dimensional (3D) model that contained both: (1) the segmented bone; and (2) the CAD models of the TAR components. We evaluated a patient following total ankle replacement to demonstrate feasibility. The patient performed a self-selected overground walk during which dual fluoroscopy images were collected at 200 Hz. In vivo tracking verifications were performed during overground walking using a distance calculation between the implant articular surfaces to evaluate the model-based tracking 3D solution. Tracking verification indicated realistic alignment of the hybrid models with an evenly distributed distance map pattern during the trial. Articular surface distance calculations were reported as an average of 1.3 mm gap during the entirety of overground walking. The successful implementation of our new tracking methodology with a hybrid model presents a new approach to evaluate in vivo TAR kinematics. Measurements of in vivo kinematics could improve our clinical understanding of failures in TAR patients, leading to better long-term surgical outcomes.

Metal artifact reduction MRI for total ankle replacement sagittal balance evaluation

BACKGROUND

Restoration of anatomical relationship between talus and tibia is crucial for longevity of total ankle replacement (TAR). Weight-bearing (WB) radiographs are the standard for evaluating the sagittal balance alignment, but are prone to rotational misalignment and altered measurements. Metal artifact reduction sequence (MARS) MRI allows visualization of periprosthetic landmarks and alignment of the image plane to the true sagittal axis of the implant. The purpose of this study was to compare TAR sagittal balance measurements on MARS MRI and WB radiographs.

METHODS

Twenty-three subjects with TAR [10 men/13 women, age 60 (41-73) years; 13 (3-24) months post-op] underwent MARS MRI and standard lateral WB radiographs. Standardized MARS MR images were aligned to the sagittal talar component axis. Three observers performed sagittal balance alignment measurements twice in an independent, random and blinded fashion. Lateral Talar Station (LTS), tibial axis-to-talus (T-T) ratio and normalized tibial axis-to-lateral-process (T-L) distance were measured. Concordance correlation coefficients (CCC) and intraclass correlation coefficients (ICC) were used for statistical analysis. In addition, mixed effects linear models were employed to assess overall concordance of the two image types.

RESULTS

The intraobserver agreement was excellent for radiographic (CCC=0.96) and MRI (CCC=0.90-0.97) measurements. Interobserver agreements were good-to-excellent with overall slightly higher agreements for MRI (ICC=0.78-0.94) than radiography (ICC=0.78-0.90) measurements. The T-T ratios of radiographs and MRI showed a high degree of concordance, whereas LTS was significantly lower on MRI when compared with radiographs, and T-L distance showed notable disagreement between the two imaging types.

CONCLUSION

Sagittal balance measurements performed on standardized weight-bearing radiographs and standardized MARS MRI demonstrate substantial correlation and similarity. Given its high intra and interobserver agreement, MARS MRI may be helpful for the evaluation of TAR sagittal balance.

LEVEL OF EVIDENCE

Level II - Prospective Comparative Study.

Comparison of cartilage and bone morphological models of the ankle joint derived from different medical imaging technologies

Background

Accurate geometrical models of bones and cartilage are necessary in biomechanical modelling of human joints, and in planning and designing of joint replacements. Image-based subject-specific model development requires image segmentation, spatial filtering and 3-dimensional rendering. This is usually based on computed tomography (CT) for bone models, on magnetic resonance imaging (MRI) for cartilage models. This process has been reported extensively in the past, but no studies have ever compared the accuracy and quality of these models when obtained also by merging different imaging modalities. The scope of the present work is to provide this comparative analysis in order to identify optimal imaging modality and registration techniques for producing 3-dimensional bone and cartilage models of the ankle joint.

Methods

One cadaveric leg was instrumented with multimodal markers and scanned using five different imaging modalities: a standard, a dual-energy and a cone-beam CT (CBCT) device, and a 1.5 and 3.0 Tesla MRI devices. Bone, cartilage, and combined bone and cartilage models were produced from each of these imaging modalities, and registered in space according to matching model surfaces or to corresponding marker centres. To assess the quality in overall model reconstruction, distance map analyses were performed and the difference between model surfaces obtained from the different imaging modalities and registration techniques was measured.

Results

The registration between models worked better with model surface matching than corresponding marker positions, particularly with MRI. The best bone models were obtained with the CBCT. Models with cartilage were defined better with the 3.0 Tesla than the 1.5 Tesla. For the combined bone and cartilage models, the colour maps and the numerical results from distance map analysis (DMA) showed that the smallest distances and the largest homogeneity were obtained from the CBCT and the 3.0 T MRI via model surface registration.

Conclusions

These observations are important in producing accurate bone and cartilage models from medical imaging and relevant for applications such as designing of custom-made ankle replacements or, more in general, of implants for total as well as focal joint replacements.

Influence of Tibial Component Position on Altered Kinematics Following Total Ankle Arthroplasty During Simulated Gait

BACKGROUND

Ankle and hindfoot kinematics following total ankle arthroplasty (TAA) are poorly understood and it is unclear whether patients can replicate physiologic motion after TAA. Furthermore, the effect of implant position on TAA kinematics is unknown. The objective of this study was to compare ankle and hindfoot kinematics pre- and post-TAA during simulated gait and determine to what degree tibial component position correlated with variations in ankle kinematics.

METHODS

Eight midtibia cadaveric specimens were utilized in this institutional review board-approved study. The stance phase of gait was simulated both pre- and post-TAA in each specimen using a 6 degrees of freedom robotic platform. Ankle and hindfoot kinematics were measured from reflective markers attached to bones via surgical pins. The effect of tibial component position on absolute differences in ankle kinematics was assessed using linear regression.

RESULTS

No differences were observed in ankle sagittal and coronal plane motion between the intact and TAA conditions. Differences in ankle joint kinematics were identified in the transverse plane, where internal talar rotation was significantly increased following TAA compared with the native condition. The medial-lateral position of the tibial component was found to correlate with the altered transverse plane motion observed after TAA (β = 1.861 degrees/mm, R² = 0.72, P = .008). No significant differences in subtalar and talonavicular joint kinematics in any plane were observed comparing the pre- and post-TAA condition.

CONCLUSION

This study demonstrated an increased internal rotation of the ankle in the transverse plane following TAA. This increase was correlated with the medial-lateral position of the tibial implant.

CLINICAL RELEVANCE

This finding could have clinical implications for how tibial components are positioned during the operative procedure, and how implant design and position may affect ankle kinematics following TAA.

The Effect of Sagittal and Coronal Balance on Patient-Reported Outcomes Following Mobile-Bearing Total Ankle Replacement

Total ankle replacement (TAR) is an established technique for the treatment of end-stage ankle arthritis. The aims of TAR include pain relief, preservation of tibiotalar movement, protection of adjacent joints, and restoration of anatomic alignment in the coronal and sagittal planes. The aims of this study were to determine the relative importance of pre- and post-TAR coronal and sagittal balance on postoperative patient-reported outcome measures (PROMs). A total of 101 ankles in 99 patients were included in this retrospective cohort study. Patients were scored preoperatively and at a minimum of 2 years by using the Foot and Ankle Outcome Score (FAOS), the American Orthopedic Foot and Ankle Society (AOFAS) hindfoot-ankle score, the Short Form-36 measures, and a set of radiographic measurements to define the sagittal and coronal alignment. There was no significant difference between the groups regarding the anterior or posterior translation of the talus preoperatively. There were no statistically significant correlations between any preoperative measure and any domain of the PROM data. Significant correlations were observed between postoperative medial distal tibial angle and the function domain of the FAOS and the AOFAS hindfoot-ankle score. Preoperative coronal and sagittal plane deformity are not markedly different, depending on the diagnosis. Preoperative deformity does not appear to correlate significantly with postoperative function, as measured by the PROM scores. Postoperative sagittal plane alignment does not correlate significantly with postoperative function, as measured by PROMs. Coronal plane alignment, as measured by the medial distal tibial angle, may be associated with postoperative function, as measured on the AOFAS hindfoot-ankle and FAOS function subscales.

Joint-Preserving Procedures in Patients with Varus Deformity: Role of Supramalleolar Osteotomies

The most common cause for end-stage ankle osteoarthritis is posttraumatic, sometimes resulting from concomitant supramalleolar deformity. Aims of the supramalleolar osteotomy include restoring the lower-leg axis to improve intraarticular load distribution and retarding degeneration of the tibiotalar joint. Preoperative planning is based on conventional weight-bearing radiographs. Often advanced imaging, including computed tomography and/or MRI, is needed for a better understanding of the underlying problem. Postoperative complications are not uncommon, including progression of tibiotalar osteoarthritis in up to 25% within 5 years of all patients who have supramalleolar osteotomies.

Experience with Navigation in Total Ankle Arthroplasty. Is It Worth the Cost?

Optimal placement of correctly sized total ankle replacement (TAR) implants is elemental to prolonging the working life. The negative mechanical effects of implant malalignment are well characterized. There is one FDA-approved navigated TAR system with limited but encouraging outcomes data. Therefore, its value can be estimated only based on benefits other than a proven clinical outcomes improvement over conventional systems. These include unique preoperative planning through 3-dimensional templating and virtual surgery and the patient-specific cut guides, which also reduce overall instrumentation needed for the case. To better inform this conversation, well-observed longitudinal outcomes studies are warranted.

Effect of Coronal and Sagittal Alignment on Outcome After Mobile-Bearing Total Ankle Replacement

BACKGROUND

Comparably high revision rates are reported after total ankle replacement (TAR). Therefore, further critical analysis of the influence of implant position on clinical outcome is necessary.

METHODS

We analyzed the reliability and predictive value of previously published pre- and postoperative coronal and sagittal parameters in routine ankle radiographs on the clinical outcome of 84 HINTEGRA total ankle replacements (Newdeal, Lyon, France; Integra, Plainsboro, New Jersey). Mean follow-up was 4.0 years, and 15.5% of the TARs had revision surgery.

RESULTS

Mean postoperative American Orthopaedic Foot & Ankle Society ankle-hindfoot score was 71.3; mean postoperative verbal rating scale for pain was 3.1; and mean postoperative ankle range of motion was 26.4 degrees. Most tested radiologic parameters showed moderate or high intra- and interobserver reliability. With the numbers available, no significant difference in clinical outcome for all tested radiologic parameters could be detected.

CONCLUSION

Our results indicate that mild malalignment of TAR, as assessed on routine ankle radiographs, did not affect midterm clinical outcome after TAR. Further multicenter studies with longer follow-up are needed to support our findings.

LEVEL OF EVIDENCE

Level III, comparative series.

Poor accuracy of plain radiographic measurements of prosthetic migration and alignment in total ankle replacement

BACKGROUND

The rotational position of the leg substantially influences measurements in ankle radiographs after total ankle replacement (TAR). The aim of our study was to further specify the influence of different projections on radiographic parameters used to assess component position after TAR.

METHODS

The effect of varying degrees of internal rotation, flexion, and ab-/adduction on reference lines in anteroposterior and lateral ankle radiographs was investigated in a cadaveric TAR model. Observed variations were then compared with those found in 34 consecutive patients that received a HINTEGRA total ankle prosthesis in our department.

RESULTS

A change of rotation of 20° resulted in a variation of measured reference lines of more than 1.3 cm in anteroposterior radiographs and more than 1 cm in lateral radiographs in our experimental setting. Even higher intraindividual changes of up to 1.4 cm were observed in our in vivo series.

CONCLUSIONS

The findings suggest that rotational position of the leg highly influences measurements in ankle radiographs after TAR. It further raises the question, if previously described radiographic parameters do provide accurate information for the outcome after TAR in clinical routine as suggested in literature.

Single-stage supramalleolar osteotomy for coronal plane deformity

A variety of surgical procedures are utilized for management of ankle osteoarthritis. The most common etiology in patients with ankle osteoarthritis is post-traumatic often resulting in asymmetric ankle osteoarthritis with concomitant valgus or varus deformity. A substantial part of tibiotalar joint is often preserved, therefore, in appropriate patients, joint-preserving surgery holds the potential to be a superior treatment option than joint-sacrificing procedures including total ankle replacement or ankle arthrodesis. This review is designed to describe indications and contraindications for single-stage supramalleolar realignment surgery. Complications associated with this type of surgery and postoperative outcome are highlighted using recent literature.

Supramalleolar osteotomies for degenerative joint disease of the ankle joint: indication, technique and results

Patients with varus or valgus hindfoot deformities usually present with asymmetric ankle osteoarthritis. In-vitro biomechanical studies have shown that varus or valgus hindfoot deformity may lead to altered load distribution in the tibiotalar joint which may result in medial (varus) or lateral (valgus) tibiotalar joint degeneration in the short or medium term. The treatment of asymmetric ankle osteoarthritis remains challenging, because more than half of the tibiotalar joint surface is usually preserved. Therefore, joint-sacrificing procedures like total ankle replacement or ankle arthrodesis may not be the most appropriate treatment options. The shortand midterm results following realignment surgery, are very promising with substantial pain relief and functional improvement observed post-operatively. In this review article we describe the indications, surgical techniques, and results from of realignment surgery of the ankle joint in the current literature.

Postoperative range of motion trends following total ankle arthroplasty

BACKGROUND

It is still unknown how ankle range of motion changes following total ankle arthroplasty. This study was undertaken to more accurately address patient expectations, guide postoperative rehabilitation, and improve our understanding of how ankle range of motion changes with time.

METHODS

119 total ankle replacements of 3 different prosthetic designs from 1 surgeon were retrospectively examined and compared. Ankle dorsiflexion and plantar flexion ranges of motion were calculated and analyzed preoperatively and postoperatively at 6 weeks, 3 months, 6 months, and 1 year. The different ankle replacement systems were analyzed individually and together to determine whether trends were replicated.

RESULTS

No significant increase in ankle range of motion was found 6 months postoperatively (P = .75). Mean combined postoperative range of motion did not change significantly from 24.3 degrees at 1 year versus a preoperative mean of 22.7 degrees (P = .75). Mean dorsiflexion improved significantly at the 6-week postoperative stage by 5.5 degrees (P < .001), whereas plantar flexion only improved by 2.9 degrees (P = .06). Mean dorsiflexion improved from preoperative levels by 5.4 degrees (P = .001), whereas mean plantar flexion decreased by 3.7 degrees (P = .004).

CONCLUSIONS

We found no notable improvement in ankle range of motion after 6 months following total ankle arthroplasty. We also found a disproportionately higher increase in dorsiflexion compared with plantar flexion following surgery and an overall reduction in mean plantar flexion range compared with preoperative values. Notwithstanding this discrepancy, total mean ankle range of motion 1 year postoperatively was similar to preoperative values. Reasons for the discrepancy between dorsiflexion and plantar flexion are unclear.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Three-dimensional morphometric study of the trapezium shape of the trochlea tali

The trapezium shape of the talar dome limits the use of 2-dimensional plain radiography for morphometric assessment because only 2 of the 4 required parameters can be measured. We used computed tomography data to measure the 4 morphologic parameters of the trochlea tali: anterior width, posterior width, trochlea tali length, and angle of trapezium shape. A total of 99 subjects underwent computed tomography scanning, and the left and right talus bones were both virtually modeled in 3 dimensions. The 4 morphologic parameters were measured 3 times each to obtain the intraclass correlation, and analysis of variance was used to check for any significant differences between the repeated measurements. The average intraclass correlation coefficient for the measurements for 2 to 3 trials was 0.94 ± 0.04. Statistical analyses were performed on the data from all 198 talus bones using SAS software, comparing male and female and left and right bones. All 4 morphometric values were greater in the male group. No significant differences were found between the left and right talus bones. A strong positive correlation was observed between the trochlea tali length and the anterior width. The angle of trapezium shape showed no correlation with the other 3 parameters. The measurements were compared with the dimensions of the current talar components of 4 total ankle arthroplasty implants. However, most of them did not perfectly match the trapezium shape of the talus from our population. We successfully analyzed the trapezium shape of the trochlea tali using reliable virtual 3-dimensional measurements. Compared with other published reports, our study showed a relatively smaller dimension of the trochlea tali than the European counterparts.

Functional performance of a total ankle replacement: thorough assessment by combining gait and fluoroscopic analyses

BACKGROUND

A thorough assessment of patients after total ankle replacement during activity of daily living can provide complete evidence of restored function in the overall lower limbs and replaced ankle. This study analyzes how far a possible restoration of physiological mobility in the replaced ankle can also improve the function of the whole locomotor apparatus.

METHODS

Twenty patients implanted with an original three-part ankle prosthesis were analyzed 12 months after surgery during stair climbing and descending. Standard gait analysis and motion tracking of the components by three-dimensional fluoroscopic analysis were performed on the same day using an established protocol and technique, respectively.

FINDINGS

Nearly physiological ankle kinematic, kinetic and electromyography patterns were observed in the contralateral side in both motor activities, whereas these patterns were observed only during stair climbing in the operated side. Particularly, the mean ranges of flexion at the replaced ankle were 13° and 17° during stair climbing and descending, respectively. Corresponding 2.1 and 3.1mm antero/posterior meniscal-to-tibial translations were correlated with flexion between the two metal components (p<0.05). In addition, a larger tibiotalar flexion revealed by fluoroscopic analysis resulted in a physiological hip and knee moment.

INTERPRETATION

The local and global functional performances of these patients were satisfactory, especially during stair climbing. These might be associated to the recovery of physiological kinematics at the replaced ankle, as also shown by the consistent antero/posterior motion of the meniscal bearing, according to the original concepts of this ankle replacement design.

Total ankle arthroplasty versus ankle arthrodesis. Comparison of sports, recreational activities and functional outcome

PURPOSE

Ankle arthrodesis (AAD) and total ankle replacement (TAR) are the major surgical treatment options for severe ankle arthritis. There is an ongoing discussion in the orthopaedic community whether ankle arthrodesis or ankle fusion should be the treatment of choice for end stage osteoarthritis. The purpose of this study was to compare the participation in sports and recreational activities in patients who underwent either AAD or TAR for end-stage osteoarthritis of the ankle.

METHODS

A total of 41 patients (21 ankle arthrodesis /20 TAR) were examined at 34.5 (SD18.0) months after surgery. At follow-up, pre- and postoperative participation in sports and recreational activities has been assessed. Activity levels were determined using the ankle activity score according to Halasi et al. and the University of California at Los Angeles (UCLA) activity scale. Clinical and functional outcome was assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score. The percentage of patients participating in sports and recreational activities, UCLA score and AOFAS score were compared between both treatment groups.

RESULTS

In the AAD group 86% were active in sports preoperatively and in the TAR group this number was 76%. Postoperatively in both groups 76% were active in sports (AAD, p = 0.08). The UCLA score was 7.0 (± 1.9) in the AAD group and 6.8 (± 1.8) in the TAR group (p = 0.78). The AOFAS score reached 75.6 (± 14) in the AAD group and 75.6 (± 16) in the TAR group (p = 0.97). The ankle activity score decrease was statistically significant for both groups (p = 0.047).

CONCLUSIONS

Our study revealed no significant difference between the groups concerning activity levels, participation in sports activities, UCLA and AOFAS score. After AAD the number of patients participating in sports decreased. However, this change was not statistically significant.

A systematic review of outcome and failure rate of uncemented Scandinavian total ankle replacement

PURPOSE

The purpose of this study was to provide cumulative data about the intermediate to long-term outcome of Scandinavian total ankle replacement (STAR) in the literature and to provide a summary of survival rate, implant failure rate and reasons.

METHODS

A comprehensive search for all relevant articles published in English and German from January 1995 to May 2011 was conducted. Two reviewers evaluated each study to determine whether it was eligible for inclusion and, if so, collected data of interest. The intermediate to long-term outcomes were determined. Evidence-based meta-analytic pooling of results across studies was performed to determine survival and failure rates.

RESULTS

Sixteen primary studies with 2,088 implants were identified. The mean American Orthopaedic Foot and Ankle Society (AOFAS) score was 77.8 points, and the mean Kofoed ankle score was 76.4 points. The pooled mean five year survival rate was 85.9% [95% confidence interval (CI) 80.9-90.3], and the pooled mean ten year survival rate was 71.1% (95% CI 60.9-81.5). Pooled failure rate was 11.1% (95% CI 7.6 -14.9), with a mean follow-up time of 52 months; 41% failed within one year of initial operation. The first three reasons associated with implant failure were aseptic loosening (5.2%), malalignment (1.7%) and deep infection (1.0%).

CONCLUSIONS

We found that STAR prosthesis achieved encouraging results in terms of intermediate to long-term outcome. The five and ten year survival rates were acceptable. However, the failure rate was still high. The major reasons for implant failure were aseptic loosening and malalignment. Maybe the increase of surgeons' experience and patient selection could improve outcomes and decrease failure rate.