Accuracy and Reproducibility Using Patient-Specific Instrumentation in Total Ankle Arthroplasty

Effect of Preoperative Coronal Plane Alignment on Actual Versus Predicted Alignment Using Patient Specific Instrumentation in Total Ankle Replacement

Alignment in total ankle replacement is important for success and implant survival. Recently there has been the introduction and adoption of patient specific instrumentation for implantation in total ankle replacement. Current literature does not evaluate the effect of preoperative deformity on accuracy of patient specific instrumentation. A retrospective radiographic analysis was performed on 97 consecutive patients receiving total ankle replacement with patient specific instrumentation to assess the accuracy and reproducibility of the instrumentation. Subgroup analysis evaluated the effect of preoperative deformity. All surgeries were performed by fellowship trained foot and ankle surgeons without industry ties to the implants used. Preoperative and postoperative films were compared to plans based on computerized tomography scans to assess how closely the plan would be implemented in patients. Overall postoperative coronal plane alignment was within 2° of predicted in 87.6% (85 patients). Similarly, overall postoperative sagittal plane alignment was within 2° of predicted in 88.7% (86 patients). Tibial implant size was accurately predicted in 81.4% (79 patients), and talus implant size was correct in 75.3% (73 patients). Patients with preoperative varus deformity had a higher difference between predicted and actual postoperative alignment compared to valgus deformity (1.1° compared to 0.3°, p = .02). A higher average procedure time was found in varus patients, and more adjunctive procedures were needed in patients with varus or valgus deformity, but these were not significant, p > .5. Surgeons can expect a high degree of accuracy when using patient specific instrumentation overall, but less accurate in varus deformity.

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.

Patient-Reported Outcomes in Total Ankle Arthroplasty: Patient Specific Versus Standard Instrumentation

BACKGROUND

Total ankle arthroplasty (TAA) can now be performed using patient-specific instrumentation (PSI). Advantages include the ability to preoperatively plan and reduce the number of intraoperative surgical steps. The aim of this study was to compare PSI with standard instrumentation (SI) in a nonrandomized retrospective cohort study with respect to patient-reported outcome measures (PROMs). Secondary aims were to compare complications, reoperations, tourniquet time, fluoroscopy time, and postoperative alignment.

METHODS

In all, 159 patients (111 men, 48 women) undergoing a total of 168 Infinity TAA (Stryker, Memphis, TN) using PSI (Prophecy, Stryker, Memphis, TN) or SI between 2014 and 2021 were included with a minimum follow-up of 12 months. The PROMs were obtained preoperatively and at 1 year, and included the Manchester-Oxford Foot Questionnaire (MOXFQ), Ankle Osteoarthritis Scale (AOS), and European Quality of Life 5 Dimension 3 Level (EQ-5D-3L). Coronal plane deformity correction was assessed using the midline tibiotalar angle (MTTA). Demographics, tourniquet time, and intraoperative fluoroscopy times were obtained from the hospital records.

RESULTS

There were 61 TAAs in the PSI group and 107 TAAs in the SI group. There was no significant difference in total MOXFQ, AOS, or EQ-5D. There was a significantly reduced tourniquet time (PSI mean: 95.39 minutes, SI mean: 116.87 minutes, P < .001) and radiation exposure (PSI mean: 31 seconds, SI mean: 53 seconds, P < .001). Angular correction was more accurate in the PSI group (PSI mean: 1.29°, SI mean: 2.26°, P = .005).

CONCLUSION

This study supports the use of PSI to decrease operative time, reduce intraoperative fluoroscopy, improve accuracy of implantation, and improve postoperative alignment in TAA. There was a significant difference (P = .032) in favor of PSI in the walking/standing domain of the MOXFQ at 12 months but no significant difference in overall PROMs.

LEVELS OF EVIDENCE

Level III, Retrospective.

Midfoot Tarsectomy in Cavovarus: Why PSI Makes a Difference?

The cavovarus foot is a complex deformity that can be treated using multiple surgical procedures, ranging from soft tissue surgery to triple arthrodesis. Among these options, anterior midfoot tarsectomy is a three-dimensional closed-wedge osteotomy, traditionally performed slowly and progressively in a blind fashion, and remaining a challenge for unexperimented surgeons with variable outcomes. As such, we investigated and discussed the use of patient-specific cutting guides (PSCGs) in computer-assisted anterior midfoot tarsectomy in terms of accuracy, reproducibility, and safety.

Accuracy of a Patient-Specific Total Ankle Arthroplasty Instrumentation

BACKGROUND

Total ankle arthroplasty (TAA) is a preferred surgical option for end-stage ankle osteoarthritis; however, it is a demanding procedure with a higher historical rate of revision compared with ankle fusion. Patient-specific instrumentation (PSI) has been introduced to optimize prosthesis alignment and theoretically overall improve TAA outcomes. The goal of this study is to report on the experience and surgical outcomes of one implant with specific evaluation of the accuracy and reproducibility of the system with respect to prosthesis alignment and prediction of implant size.

METHODS

A retrospective, multicentered study involving 4 foot and ankle fellowship-trained orthopaedic surgeon's patients undergoing TAA between January 1, 2015, and December 31, 2018, using the PROPHECY PSI system.

RESULTS

80 TAA procedures were performed. On average the postoperative tibial component alignment was 89.9 (range, 86.1-96.5) degrees in the coronal plane, with a mean sagittal alignment of 88.1 (range, 81.3-96.7) degrees. The mean deviation from neutral sagittal alignment improved from 4.9 ± 3.9 degrees preoperatively to 2.7 ± 1.7 degrees postoperatively, whereas the mean coronal alignment improved from 3.3 ± 2.5 degrees to 1.3 ± 1.1 degrees. The PSI software correctly determined the tibial implant size in 70 patients (89%). Prediction of talar implant sizing was less accurate than the tibial component, with 56 patients (71%) using the predicted sized implant. The overall implant survival at a mean follow-up of 45 months (range, 27-76) was 97.5%.

CONCLUSION

We found that this PSI system accurately and reliably assisted in implant total ankle prosthesis positioning within a clinically acceptable margin and without significant outliers. Prediction of implant size was not as accurate as component orientation.

LEVEL OF EVIDENCE

Level III, retrospective study.

Robotic-assisted foot and ankle surgery: a review of the present status and the future

The surgical application of robotics has increased significantly since its first application in 1985 for a brain biopsy acquisition. Robotic-assisted surgery has been one of the viable options in various surgical areas, and also in orthopaedic surgery. Robotic-assisted orthopaedic surgery has gained popularity as a mean of improving accuracy, reducing complications and achieving better patient satisfaction. Numerous clinical research studies have demonstrated advantages of robotic-assisted orthopaedic surgery, however, most of that researches were about the total knee arthroplasty, total hip arthroplasty and spine surgery. The application of robotic technology in foot and ankle surgery is in a very nascent stage. Furthermore, there has been little research on intraoperative use of robotics in foot and ankle surgery in literature. A review of previous preclinical studies in foot and ankle robotics and clinical research studies in various fields of robot-assisted orthopaedic surgery shows that its potential application and benefits over conventional techniques, such as total ankle arthroplasty, minimally invasive surgery for foot and ankle trauma or other corrective procedure, and intraoperative biomechanical testing. More studies on practical application of robotic technology to surgical procedure in the field of foot and ankle surgery are needed to confirm its clinical usefulness and cost effectiveness.

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.

Computed Tomography Derived Patient-specific Instrumentation Total Ankle Arthroplasty Survivorship Outcomes

Computed tomography (CT) derived patient-specific total ankle arthroplasty (TAA) systems have been utilized for improved accuracy and reproducible implant alignment. The purpose of the present study was to report the overall implant survivorship as well as radiographic analysis of patients who underwent primary TAA utilizing CT-derived patient-specific instrumentation. A retrospective review of medical charts and radiographs were performed on patients who had undergone primary TAA at a single institution in the Midwest region from March 2013 to October 2020. Radiographic analysis included preoperative, initial postoperative, and final follow-up coronal and sagittal tibiotalar alignment as well as periprosthetic radiolucency. A total of 96 patients with a mean follow-up of 3 years (range, 0.3-7.3 years) were included. Implant survivorship was found to be 92% at median follow-up of 3 years. A total of 8 cases (8.3%) required revision/reoperation, with 6 (6.3%) of these reoperations directly related for failure of one of the metallic implant components. There was significant improvement in both coronal and sagittal tibiotalar alignment from preoperative to initial postoperative follow-up (p < .001). At latest postoperative follow-up, there were 88% of TAAs that remained in a neutral alignment following surgery. A total of 10 cases were found to have radiolucency at latest follow-up. In conclusion, the use of CT derived patient-specific TAA showed high implant survivorship with significant improvement of sagittal and coronal tibiotalar alignment. With better implant alignment and position, it potentially reduces the risk of early implant failure or implant loosening in long-term follow-up.

Robotic Technology in Foot and Ankle Surgery: A Comprehensive Review

Recent developments in robotic technologies in the field of orthopaedic surgery have largely been focused on higher volume arthroplasty procedures, with a paucity of attention paid to robotic potential for foot and ankle surgery. The aim of this paper is to summarize past and present developments foot and ankle robotics and describe outcomes associated with these interventions, with specific emphasis on the following topics: translational and preclinical utilization of robotics, deep learning and artificial intelligence modeling in foot and ankle, current applications for robotics in foot and ankle surgery, and therapeutic and orthotic-related utilizations of robotics related to the foot and ankle. Herein, we describe numerous recent robotic advancements across foot and ankle surgery, geared towards optimizing intra-operative performance, improving detection of foot and ankle pathology, understanding ankle kinematics, and rehabilitating post-surgically. Future research should work to incorporate robotics specifically into surgical procedures as other specialties within orthopaedics have done, and to further individualize machinery to patients, with the ultimate goal to improve perioperative and post-operative outcomes.

Preliminary Report of a Hybrid Total Ankle Arthroplasty Combining a Stemmed Intramedullary Tibial Component With Chamfer-Cut Talar Dome

Total ankle arthroplasty (TAA) is a viable treatment for end-stage ankle arthritis. In our experience, a stemmed intramedullary tibial component combined with a chamfer-cut talar component provides the most stable construct for TAA. We present our technique for placement of this hybrid prosthesis utilizing the INBONE tibial component in combination with the INFINITY talar component. This technique differs from the standard protocol by minimizing use of both patient-specific and standard intraoperative guides. The primary aim of this study is to report our preliminary outcomes with our novel technique. Secondarily, we aim to demonstrate that placement of this hybrid prosthesis is radiographically reproducible and accurate. The first 10 patients undergoing this technique with at least 1 year of follow-up were retrospectively reviewed. Average visual analog pain scale decreased from 7.4 preoperatively to 0.5 at 1 year postoperatively. The average time to weightbearing was 6.4 weeks. Complications were minimal, and no implant-related complications were encountered. First weightbearing ankle radiographs postoperatively were evaluated by 3 reviewers to determine accuracy of the tibial intramedullary stem in relation to the anatomical axis of the tibia. We found that the deviation of the tibial implant from the anatomic axis was on average 0.9°± 0.5° in the coronal plane, and 2.2°± 2.7° in the sagittal plane. Inter-rater reliability was 83%. We conclude that this hybrid technique utilizing a stemmed intramedullary tibial component in combination with a chamfer-cut talar component for TAA is reproducible, accurate, and safe.

Effects of Patient-Specific Instrumentation and Ancillary Surgery Performed in Conjunction With Total Ankle Implant Arthroplasty: Postoperative Radiographic Findings

Accuracy and reproducibility when performing total ankle implant arthroplasty (TAA) are essential for longevity of the implant, maintaining relative stability of the joint, and theoretically reducing the formation of adjacent joint arthritis in the subtalar and knee joints. Studies have helped to illustrate the accuracy of implantation when using patient-specific instrumentation in both knee and ankle implant arthroplasty. Despite the findings of these studies, few have gone on to evaluate the effects of ancillary procedures on TAA; particularly their effects on postoperative implant congruity when performed simultaneously with joint replacement surgery. In this study, preoperative plans on implant alignment based on patient-specific computed tomography images were compared with the alignment observed on immediate postoperative radiographs. Additionally, postoperative joint congruity was measured, and operative reports were assessed to determine if concomitant procedures performed with total ankle replacement had a significant effect on overall alignment. In our population, 46/47 implants were within 1.5° of their anticipated placement in the coronal plane, and 100% were within 2° of anticipated placement in the sagittal plane. Using a spearman's rank-order correlation, our data failed to show any significant relationship between conducting additional procedures in conjunction with TAA (rho = 0.178; p value = .232) and postoperative congruency of the implant. These findings help support the accuracy of ankle implantation using patient-specific instrumentation, while also supporting the appropriate use of indicated procedures in conjunction with total ankle replacement to help obtain a congruent joint postoperatively.

Patient-Specific Instrumentation vs Standard Referencing in Total Ankle Arthroplasty: A Comparison of the Radiologic Outcome

BACKGROUND

Existing literature on the superiority of patient-specific instrumentation (PSI) in total ankle arthroplasty (TAA) over standard referencing (SR) is limited. Advantages presented include better implant alignment, shorter operating times, and increased accuracy of implant size prediction. The aim of this retrospective study was to analyze PSI in the hands of an experienced foot and ankle surgeon new to both PSI and SR for this specific implant, in regard to determining implant alignment, operative times, and radiologic short-term outcome and predicting implant size for tibial and talar components.

METHODS

Twenty-four patients undergoing TAA using PSI were compared to 25 patients using SR instrumentation. Outcome measures included alignment of the tibial component (α coronal plane, γ sagittal plane), the tibiotalar tilt (β), and the talar offset x on the sagittal view as well as the presence of radiolucent lines, operation time, and wound healing. Postoperative outcome was assessed at 6 weeks, 4 months, and 1 year postoperatively.

RESULTS

Implant positioning was similar in both groups, and no advantage in regard to the operative time could be seen when comparing TAA using PSI to SR. Implant size prediction was more reliable for the tibia than for the talus. Three patients (1 from the SR group and 2 from the PSI group) showed radiolucent lines around the tibial component. Two patients (both SR group) suffered delayed wound healing, albeit not requiring any additional measures.

CONCLUSION

The PSI method did not show an advantage over SR in regard to positioning of the components or the duration of the surgery. The current study suggests that no initial advantage of PSI over SR are to be expected in standard total ankle replacement.

LEVEL OF EVIDENCE

Level III, retrospective study.

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.

Accuracy of CT-Derived Patient-Specific Instrumentation for Total Ankle Arthroplasty: The Impact of the Severity of Preoperative Varus Ankle Deformity

BACKGROUND

Significant preoperative varus tibiotalar deformity was once believed to be a contraindication for total ankle arthroplasty (TAA). Our primary goal was to evaluate the influence of increasing preoperative varus tibiotalar deformity on the accuracy of final implant positioning using computed tomography (CT)-derived patient-specific guides for TAA.

METHODS

Thirty-two patients with varus ankle arthritis underwent TAA using CT-derived patient-specific guides. Patients were subcategorized into varying degrees of deformity based on preoperative tibiotalar angles (0°-5° neutral, 6°-10° mild, 11°-15° moderate, and >15° severe). Postoperative weightbearing radiographs were used to measure coronal plane alignment of the tibial implant relative to the target axis determined by the preoperative CT template. Average follow-up at the time of data collection was 36.8 months.

RESULTS

Average preoperative varus deformity was 6.06° (range: 0.66°-16.3°). Postoperatively, 96.9% (30/31) of patients demonstrated neutral implant alignment. Average postoperative tibial implant deviation was 1.54° (range: 0.17°-5.7°). Average coronal deviation relative to the target axis was 1.61° for the neutral group, 1.78° for the mild group, 0.94° for the moderate group, and 1.41° for the severe group (P = .256). Preoperative plans predicted 100% of tibial and talar implant sizes correctly within 1 size of actual implant size. Conclusion. Our study supports the claim that neutral postoperative TAA alignment can be obtained using CT-derived patient-specific instrumentation (PSI). Furthermore, final implant alignment accuracy with PSI does not appear to be impacted by worsening preoperative varus deformity. All but one patient (96.9%) achieved neutral postoperative alignment relative to the predicted target axis.

LEVEL OF EVIDENCE

Level IV, Clinical Case Series.

Preoperative Guidance With Weight-Bearing Computed Tomography and Patient-Specific Instrumentation in Foot and Ankle Surgery

The use of preoperative and intraoperative guidance in foot and ankle surgery has grown substantially in recent years. Weight-bearing computed tomography (WBCT) and patient-specific instrumentation (PSI) are used in total ankle arthroplasty (TAA) to achieve precise bone cutting and implant positioning, and intraoperative 3-dimensional (3D) imaging has been used to reduce complications and improve clinical outcomes in other foot and ankle surgical procedures. This narrative review of the literature focuses on the evidence supporting the use of WBCT and PSI in TAA and looks at other promising technologies used to guide foot and ankle surgery.

Accuracy of Weightbearing CT Scans for Patient-Specific Instrumentation in Total Ankle Arthroplasty

Background:

Total ankle arthroplasty (TAA) is a popular and viable option for end-stage ankle arthritis. Posttraumatic arthritis is the most common etiology of ankle arthritis, which creates the additional challenge of osseus deformity. Accuracy and reproducibility in placing the implant on the mechanical axis has been shown to be paramount in all joint arthroplasty including total ankle replacement. Patient-specific preoperative navigation is a relatively new technology for TAA, and up until this past year has been based off of nonweightbearing (NWBCT) or simulated weightbearing computed tomography (WBCT). Our institution has created a protocol to use WBCT in the preoperative patient-specific navigation for TAA using the Prophecy system. The purpose of our study was to compare the accuracy and reproducibility of implant alignment and size using WBCT vs prior studies using NWBCT for the Prophecy reports.

Methods:

All patients from July 2019 through October 2020 who underwent TAA were evaluated. Inclusion criteria consisted of primary TAA using patient-specific preoperative navigation who had postoperative radiographs in the 4-6-week time frame. Prophecy predictions and measurements were then compared to actual implant placement and size.

Results:

Ten patients met our inclusion criteria of WBCT Prophecy preoperative planning using 2 different implant systems. Preoperative deformities in this cohort were small. The average postoperative coronal alignment was 0.84 degrees, range 0.19 to 2.4 degrees. Average postoperative sagittal plane deformity was 1.9 degrees, range 0.33 to 5.05 degrees. Tibial component size was properly predicted in all patients, talar component in 9 of 10.

Conclusion:

This initial report supports accuracy and reproducibility in preoperative patient-specific navigation when using WBCT for TAA with these implants. All TAAs were within the intended target of less than 5 degrees varus or valgus.

Level of Evidence:

Level III, retrospective comparative analysis.

Patient-specific instrumentation (PSI) in total ankle arthroplasty: a systematic review

BACKGROUND

Patient-specific instrument (PSI) may theoretically make total ankle arthroplasty (TAA) more accurate. Several studies have reported the outcomes of PSI TAA. The aim of this study is to systematically review the literature of PSI TAA.

METHODS

PubMed, Embase, Web of Science, and Cochrane Library databases were systematically reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines for PSI TAA. The quality of the included studies was evaluated according to Methodological Index for Non-Randomized Studies (MINORS).

RESULT

Nine articles were ultimately included in the systematic review. The implant position and function outcome of TAA was similar between PSI and SI. Prediction accuracy of implant size remained great difference. PSI can shorten the operative time and fluoroscopy time. The quality of current studies on PSI TAA is insufficient to produce high-level evidence.

CONCLUSION

PSI can get similar implant position and clinical outcome in TAA compared to SI, but current evidence is not strong enough to evaluate PSI TAA.

Establishing a New Patient-Specific Implantation Technique for Total Ankle Replacement: An In Vitro Study

BACKGROUND

Revision rates after total ankle replacements (TARs) are higher compared with other total joint replacements. The present study aimed to establish a new patient-specific implantation (PSI) technique for TAR.

MATERIAL AND METHODS

A total of 10 complete Caucasian cadaver legs had whole leg computed tomography scans. The individual geometrical ankle joint axis was determined, and based on this axis, the position of the prosthesis was planned. We assessed prosthesis placement, guiding block position, and preoperative and postoperative ankle rotational axes.

RESULTS

The guiding block position interobserver reliability was 0.37 mm 0.45 (mean ± SD) for the tibial guiding block. The value for the first talar guiding block was 1.72 ± 1.3 mm and for the second talar guiding block, 0.61 ± 0.39 mm. The tibial slope as well as the frontal angles of the anatomical tibial axis compared to the tibial and talar articular surfaces showed no statistically relevant differences with numbers available. The deviation of the assessed preoperative joint axis to the postoperative joint axis was 14.6° ± 7.8.

CONCLUSION

The present study describes the results of an establishing process of a new PSI technique for TAR. The reliability of guiding block positioning and, thereby, prosthesis placement is sufficient.

LEVEL OF EVIDENCE

Biomechanical study.

Total Ankle Arthroplasty Radiographic Alignment Comparison Between Patient-Specific Instrumentation and Standard Instrumentation

BACKGROUND

Several benefits are published supporting patient-specific instrumentation (PSI) in total ankle arthroplasty (TAA). This study seeks to determine if TAA with PSI yields different radiographic outcomes vs standard instrumentation (SI).

METHODS

Sixty-seven primary TAA patients having surgery using PSI or SI between 2013 and 2015 were retrospectively reviewed using weightbearing radiographs at 6-12 weeks postsurgery. Radiographic parameters analyzed were the medial distal tibia angle (MDTA), talar-tilt angle (TTA), anatomic sagittal distal tibia angle (aSDTA), lateral talar station (LTS), and talar component inclination angle (TCI). A comparison of the 2 groups for each radiologic parameter's distribution was performed using a nonparametric median test and Fisher exact test. Furthermore, TAAs with all radiographic measurements within acceptable limits were classified as "perfectly aligned." The rate of "perfectly aligned" TAAs between groups was compared using a Fisher exact test with a significance of .05.

RESULTS

Of the 67 TAAs, 51 were done with PSI and 16 with SI. There were no differences between groups in MDTA (P = .174), TTA (P = .145), aSDTA (P = .98), LTS (P = .922), or TCI angle (P = .98). When the rate of "perfectly aligned TAA" between the 2 groups were compared, there was no significant difference (P = .35).

CONCLUSION

No significant radiographic alignment differences were found between PSI and SI implants. This study showed that both techniques achieve reproducible TAA radiographic coronal and sagittal alignment for the tibial component when performed by experienced surgeons. The talar component's sagittal alignment is similar whether or not PSI was used but is noticeably different from normal anatomic alignment by design.

LEVEL OF EVIDENCE

Level III, retrospective cohort study using prospectively collected data.

From Patient to Procedure: The Process of Creating a Custom 3D-Printed Medical Device for Foot and Ankle Pathology

Three-dimensional (3D) printing technology has advanced greatly over the past decade and is being used extensively throughout the field of medicine. Several orthopaedic surgery specialties have demonstrated that 3D printing technology can improve patient care and physician education. Foot and ankle pathology can be complex as the 3D anatomy can be challenging to appreciate. Deformity can occur in several planes simultaneously and bone defects either from previous surgery or trauma can further complicate surgical correction. Three-dimensional printing technology provides an avenue to tackle the challenges associated with complex foot and ankle pathology. A basic understanding of how these implants are designed and made is important for surgeons as this technology is becoming more widespread and the clinical applications continue to grow within foot and ankle surgery.Levels of Evidence: Level V.

Infinity ankle arthroplasty with traditional instrumentation and PSI prophecy system: preliminary results

Ankle arthrodesis has been considered the surgical Gold Standard for advanced ankle arthritis; prosthetic replacement of the tibio-talar joint played a secondary role.The introduction of last generation ankle prostheses lead to better outcome and a lower rate of complication. PSI represents the most recent innovations introduced on the market of ankle arthroplasty:PSI is proposed as a surgical technique capable of making ankle arthroplasty more accurate and more reproducible compared to standard referencing guides Aim of the study is to report early clinical and radiographic outcomes obtained from a single surgeon experience by implanting the same ankle prosthesis using a standard (STD) or a PSI instrumentation Unlike no difference in the average increment of normalized sub score related to function in each group (PSI vs STD), the analysis of normalized pain sub score pointed out a greater average improvement in the PSI group(+75%)compared to the STD group(+62%);this result has been adovacated to the absence of post operative gutter impingement syndrome in the PSI group compared to the STD referencing group. The analysis of radiographic angles revealed a more accurate and reproducible positioning of the components in the PSI group; ankle arthroplasty performed with PSI reported a reduction of both surgical times and the need of intraop.fluoroscopy. PSI ankle arthroplasty achived more accurate and reproducible clinical and radiographic results compared to STD instrumentation;long-term follow-up are needed to demonstrate whether a better positioning of the implant is associated with an increased survival of the prosthesis and therefore justifies the additional costs of PSI.

Clinical applications of custom 3D printed implants in complex lower extremity reconstruction

Background

Three dimensional printing has greatly advanced over the past decade and has made an impact in several industries. Within the field of orthopaedic surgery, this technology has vastly improved education and advanced patient care by providing innovating tools to complex clinical problems. Anatomic models are frequently used for physician education and preoperative planning, and custom instrumentation can assist in complex surgical cases. Foot and ankle reconstruction is often complicated by multiplanar deformity and bone loss. 3D printing technology offers solutions to these complex cases with customized implants that conform to anatomy and patient specific instrumentation that enables precise deformity correction.

Case presentation

The authors present four cases of complex lower extremity reconstruction involving segmental bone loss and deformity – failed total ankle arthroplasty, talus avascular necrosis, ballistic trauma, and nonunion of a tibial osteotomy. Traditional operative management is challenging in these cases and there are high complication rates. Each case presents a unique clinical scenario for which 3D printing technology allows for innovative solutions.

Conclusions

3D printing is becoming more widespread within orthopaedic surgery. This technology provides surgeons with tools to better tackle some of the more challenging clinical cases especially within the field of foot and ankle surgery.

A new ligament-compatible patient-specific 3D-printed implant and instrumentation for total ankle arthroplasty: from biomechanical studies to clinical cases

Background

Computer navigation and patient-specific instrumentation for total ankle arthroplasty have still to demonstrate their theoretical ability to improve implant positioning and functional outcomes. The purpose of this paper is to present a new and complete total ankle arthroplasty customization process for severe posttraumatic ankle joint arthritis, consisting of patient-specific 3D-printed implant and instrumentation, starting from a ligament-compatible design.

Case presentation

The new customization process was proposed in a 57-year-old male patient and involved image analysis, joint modeling, prosthesis design, patient-specific implant and instrumentation development, relevant prototyping, manufacturing, and implantation. Images obtained from a CT scan were processed for a 3D model of the ankle, and the BOX ankle prosthesis (MatOrtho, UK) geometries were customized to best fit the model. Virtual in silico, i.e., at the computer, implantation was performed to optimize positioning of these components. Corresponding patient-specific cutting guides for bone preparation were designed. The obtained models were printed in ABS by additive manufacturing for a final check. Once the planning procedure was approved, the models were sent to final state-of-the-art additive manufacturing (the metal components using cobalt-chromium-molybdenum powders, and the guides using polyamide). The custom-made prosthesis was then implanted using the cutting guides. The design, manufacturing, and implantation procedures were completed successfully and consistently, and final dimensions and location for the implant corresponded with the preoperative plan. Immediate post-op X-rays showed good implant positioning and alignment. After 4 months, clinical scores and functional abilities were excellent. Gait analysis showed satisfactory joint moment at the ankle complex and muscle activation timing within normality.

Conclusions

The complete customization process for total ankle arthroplasty provided accurate and reliable implant positioning, with satisfactory short-term clinical outcomes. However, further studies are needed to confirm the potential benefits of this complete customization process.

Level of evidence

5. Case report.

Intraoperative Assessment of the Axial Rotational Positioning of a Modern Ankle Arthroplasty Tibial Component Using Preoperative Patient-Specific Instrumentation Guidance

BACKGROUND

The use of patient-specific instrumentation (PSI) in modern total ankle replacement (TAR) has augmented positioning of the tibial component, eliminating the need for complex jigs. Coronal and sagittal alignment are intuitive with this design and have been studied, but axial rotation has not. The purpose of this study was to assess the relationship between the planned preoperative axial rotation as set by the PSI guide and the rotation determined intraoperatively with non-PSI instrumentation.

METHODS

This was a prospective cohort study of 22 consecutive cases. The axial rotation angle between the medial gutter and the tibial implant position on the preoperative CT-scan based plan was extracted. At the time of surgery, the medial gutter alignment instrument from the non-PSI instrumentation was inserted and an intraoperative axial photograph obtained to record the angle between the medial gutter and the axial rotation guide pins set by the PSI instrumentation. The 2 measurements were compared and further statistical analysis included Pearson correlation and paired Student t test.

RESULTS

The average axial rotation angle between the medial gutter and the implant on the PSI preoperative plan was 5.4 ± 2.9 degrees, whereas the intraoperative photograph from the medial gutter alignment instrument to the pin was 5.9 ±3.8 degrees. This demonstrated a Pearson correlation of R = 0.54 and a P value of .53. The average difference between the two was -0.46 (95% CI: -2.04, 1.10), meaning that components were either slightly externally rotated or that the fork was aimed internally. Based on this group, 50% (11/22) were within 2 degrees of the target and 77% (17/22) were within 4 degrees of the target.

CONCLUSION

Patient-specific guides allowed for reproducible rotational tibial component implantation in modern TAR. Further work is needed to better understand the biomechanical effects of the rotational profile and consequences on survivorship.

LEVEL OF EVIDENCE

Level IV, case series.

Total Ankle Replacement Options

Total ankle arthroplasty has been in development for more than 40 years. Although early designs were experimental with high failure rates, current implants are significantly improved, showing promising functional results and clinical outcomes. Total ankle replacement designs are split into mobile-bearing and fixed-bearing designs. When deciding whether to perform ankle arthroplasty, many factors need to be considered to determine if the patient is suitable and which implant is the best fit for patient and surgeon. Many prostheses are available in the United States today and the purpose of this article is to outline options for foot and ankle surgeons.

Accuracy of patient-specific instrumentation in total ankle arthroplasty: A comparative study

BACKGROUND

Patient-specific instrumentation (PSI) for TAA is a novel technology with several potential benefits. The primary goal of this study was to compare the use of PSI with the standard referencing guide (SRG) in regards to accuracy of tibial implant positioning. Operative time, fluoroscopy time and accuracy of PSI preoperative reports were also evaluated.

METHODS

A retrospective analysis of 99 patients who underwent a primary TAA with the INFINITY prosthesis (Wright Medical, Memphis, TN) was performed. Patients were divided in two groups based on the type of instrumentation used during the TAA (75 in the PSI group vs 24 in the SRG group). There was no significant difference between groups in regards to age at the time of surgery (P=0.122), sex (P=0.138), number of concomitant procedures performed during surgery (P=0.567) and etiology (P=0.841). However, preoperative deformity was significantly smaller in the PSI group (P=0.002).

RESULTS

Tibial implant positioning was similar between groups. In the coronal plane, the absolute deviation of the tibial implant from the intended alignment was 1.7±1.4° for the SRG and 1.6±1.2° for PSI (P=0.710). In the sagittal plane, the absolute alignment deviation of the tibial implant was 1.8±1.4° for the SRG and 1.9±1.5° for PSI (P=0.675). Operative time (167 vs 190min, P=0.040) and fluoroscopy time (85 vs 158s, P<0.001) were significantly decreased in the PSI group. The PSI preoperative plan report correctly predicted the implant size in 73% of cases for the tibial component and in 51% of cases for the talar component.

CONCLUSIONS

PSI provided similar tibial component alignment as standard instrumentation. Additionally, PSI preoperative plan reports were poor predictors of implant sizing. Therefore, the final decision should always be based on surgeon's experience in order to prevent errors in implant sizing and positioning.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The Infinity Total Ankle System: Early Clinical Results With 2- to 4-Year Follow-up

AIMS

This study presents the first report of clinical and radiographic outcomes of the Infinity Total Ankle System (Wright Medical, Memphis, TN) with minimum 2-year follow-up.

PATIENTS AND METHODS

The first 67 consecutive patients who underwent primary total ankle arthroplasty (TAA) with the Infinity system at 2 North American sites between August 2013 and May 2015 were reviewed in a prospective, observational study. Demographic, radiographic, and functional outcome data were collected preoperatively, at 6 to 12 months postoperatively, and annually thereafter.

RESULTS

The overall implant survival rate was 97% (65 of 67 implants) at a mean follow-up of 35.4 months (27 to 47 months). Two cases underwent talar component revision for aseptic loosening. Six of the 67 cases (9%) required a nonrevision reoperation. Mean Foot Function Index and Ankle Osteoarthritis Scale scores at latest follow-up improved from preoperative by 21.6 ( P < .0001) and 34.0 ( P < .0001), respectively. No radiographic loosening of any talar or tibial components was identified in the 65 nonrevised cases.

CONCLUSION

Early clinical and radiographic outcomes with the Infinity TAA are promising and compare favorably to those reported for both fixed- and mobile-bearing third-generation TAA designs, even when used in cases with deformity and increased case complexity.

LEVELS OF EVIDENCE

Level IV.

Increased Early Revision Rate With the INFINITY Total Ankle Prosthesis

BACKGROUND:

A number of new 2-component total ankle arthroplasty systems that emphasize minimal bone resection have been introduced for which few clinical outcomes reports are available. Our aim was to identify the rate of early revision among patients receiving the 2-component INFINITY prosthesis.

METHODS:

Patients from 2 prospectively collected databases at the authors' institution were screened for inclusion in the present study. All patients who underwent a primary total ankle arthroplasty (TAA) with the INFINITY prosthesis and who were at least 1 year postoperative were included. A total of 159 ankles with a mean 20 months of follow up (range, 12-37) met these criteria. All surgeries were performed by 1 of 2 orthopedic foot and ankle surgeons with extensive experience in TAA. The primary outcome was the need for revision surgery, defined as removal of 1 or both metal components. Peri-implant lucency at most recent follow-up was a secondary outcome. Weightbearing radiographs at most recent follow-up were graded for lucency independently by 2 reviewers.

RESULTS:

Sixteen ankles (10%) underwent revision at a mean 13 months postoperatively. The most common reasons for revision were symptomatic tibial component loosening and deep infection (6 patients each, 3.8%). Of the 108 ankles with retained components and at least 1 year of radiographic follow-up, 8 (7.4%) had global lucency around the tibial component suggestive of loosening at most recent follow-up.

CONCLUSIONS:

Our initial review of patients undergoing TAA with this new 2-component prosthesis demonstrates an elevated early revision rate due to tibial component loosening compared to other implant systems.

LEVEL OF EVIDENCE:

Level IV, case series.

Templating of Syndesmotic Ankle Lesions by Use of 3D Analysis in Weightbearing and Nonweightbearing CT

BACKGROUND:

Diagnosis and operative treatment of syndesmotic ankle injuries remain challenging due to the limitations of 2-dimensional imaging. The aim of this study was therefore to develop a reproducible method to quantify the displacement of a syndesmotic lesion based on 3-dimensional computed imaging techniques.

METHODS:

Eighteen patients with a unilateral syndesmotic lesion were included. Bilateral imaging was performed with weightbearing cone-beam computed tomography (CT) in case of a high ankle sprain (n = 12) and by nonweightbearing CT in case of a fracture-associated syndesmotic lesion (n = 6). The healthy ankle was used as a template after being mirrored and superimposed on the contralateral ankle. The following anatomical landmarks of the distal fibula were computed: the most lateral aspect of the lateral malleolus and the anterior and posterior tubercle. The change in position of these landmarks relative to the stationary, healthy fibula was used to quantify the syndesmotic lesion. A control group of 7 studies was used.

RESULTS:

The main clinical relevant findings demonstrated a statistically significant difference between the mean mediolateral diastasis of both the sprained (mean [SD], 1.6 [1.0] mm) and the fracture group (mean [SD], 1.7 [0.6] mm) compared to the control group ( P < .001). The mean external rotation was statistically different when comparing the sprained (mean [SD], 4.7 [2.7] degrees) and the fracture group (mean [SD], 7.0 [7.1] degrees) to the control group ( P < .05).

CONCLUSION:

This study evaluated an effective method for quantifying a unilateral syndesmotic lesion of the ankle. Applications in clinical practice could improve diagnostic accuracy and potentially aid in preoperative planning by determining which correction needs to be achieved to have the fibula correctly reduced in the syndesmosis.

LEVEL OF EVIDENCE:

Level III, retrospective comparative study.

[Progress of total ankle arthroplasty for end-stage ankle osteoarthritis]

Objective

To review the progress of total ankle arthroplasty (TAA) in treatment of end-stage ankle osteoarthritis (AOA).

Methods

The domestic and foreign literatures about TAA in recent years were reviewed. The current status and progress of TAA were summarized from the results of traditional and computer-assisted TAA clinical outcomes.

Results

End-stage AOA often leads to severe pain and dysfunction, and arthrodesis is still the main selective treatment option. In recent years, with the advancement of surgical techniques and prosthesis design, TAA which can remain joint mobility has increased gradually, and the surgical results also have significant progress. Accurate prosthesis implant and mechanical alignment restoration are critical factors for TAA, and surgery-related malalignment is correlative to the prosthesis failure. Computer assisted patient-specific guide can simplify the TAA procedures and obtain the accuracy of tibia and talus osteotomy.

Conclusion

The clinical efficiency of preoperative CT based patient-specific guide technology for TAA needs further clinical follow-up. Meanwhile, it is necessary to further develop intraoperative navigation and robotic surgery system suitable for TAA.

Computed Navigation Guidance for Ankle Replacement in the Setting of Ankle Deformity

Total ankle replacement (TAR) has evolved over the past decade as a treatment for end-stage ankle arthritis with improved survivorship. Despite the improving outcomes, ankle deformity represents a challenge to the foot and ankle surgeon with increased risk of implant failure. The use of preoperative computer-assisted guidance has led to better understanding the 3-dimensional ankle anatomy and associated deformities and allows for reproducible, anatomic placement of the TAR components.