Magnetic Resonance Imaging of Total Ankle Arthroplasty: State-of-The-Art Assessment of Implant-Related Pain and Dysfunction

Total ankle arthroplasty (TAA) is an effective alternative for treating patients with end-stage ankle degeneration, improving mobility, and providing pain relief. Implant survivorship is constantly improving; however, complications occur. Many causes of pain and dysfunction after total ankle arthroplasty can be diagnosed accurately with clinical examination, laboratory, radiography, and computer tomography. However, when there are no or inconclusive imaging findings, magnetic resonance imaging (MRI) is highly accurate in identifying and characterizing bone resorption, osteolysis, infection, osseous stress reactions, nondisplaced fractures, polyethylene damage, nerve injuries and neuropathies, as well as tendon and ligament tears. Multiple vendors offer effective, clinically available MRI techniques for metal artifact reduction MRI of total ankle arthroplasty. This article reviews the MRI appearances of common TAA implant systems, clinically available techniques and protocols for metal artifact reduction MRI of TAA implants, and the MRI appearances of a broad spectrum of TAA-related complications.

Printable functionally graded tibial implant for TAR: FE study comparing implant materials, FGM properties, and implant designs

Tibial implants with functionally graded material (FGM) for total ankle replacement (TAR) can provide stiffness similar to the host tibia bone. The FGM implants with low stiffness reduce stress shielding but may increase implant-bone micromotion. A trade-off between stress shielding and implant-bone micromotion is required if FGMs are to substitute traditionally used Ti and CoCr metal implants. The FGM properties such as material gradation law and volume fraction index may influence the performance of FGM implants. Along with the FGM properties, the design of FGM implants may also have a role to play. The objective of this study was to examine FGM tibial implants for TAR, by comparing implant materials, FGM properties, and implant designs. For this purpose, finite element analysis (FEA) was conducted on 3D FE models of the intact and the implanted tibia bone. The tibial implants were composed of CoCr and Ti, besides them, the FGM of Ti and HA was developed. The FGM implants were modelled using exponential, power, and sigmoid laws. Additionally, for power and sigmoid laws, different volume fraction indices were taken. The effect of implant design was observed by using keel type and stem type TAR fixation designs. The results indicated that FGM implants are better than traditional metal implants. The power law is most suitable for developing FGM implants because it reduces stress shielding. For both power law and sigmoid law, low values of the volume fraction index are preferrable. Therefore, FGM implant developed using power law with 0.1 vol fraction index is ideal with the lowest stress shielding and marginally increased implant-bone micromotion. FGM implants are more useful for keel type fixation design than stem type design. To conclude, with FGMs the major complication of stress shielding can be solved and the longevity and durability of TAR implants can be enhanced.

A numerical investigation for the development of functionally graded Ti/HA tibial implant for total ankle replacement: Influence of material gradation law and volume fraction index

Stress shielding is one of the major concerns for total ankle replacement implants nowadays, because it is responsible for implant-induced bone resorption. The bone resorption contributes to the aseptic loosening and failure of ankle implants in later stages. To reduce the stress shielding, improvements can be made in the implant material by decreasing the elastic mismatch between the implant and the tibia bone. This study proposes a new functionally graded material (FGM) based tibial implant for minimizing the problem of stress shielding. Three-dimensional finite element (FE) models of the intact tibia and the implanted tibiae were created to study the influence of material gradation law and volume fraction index on stress shielding and implant-bone micromotion. Different implant materials were considered that is, cobalt-chromium, titanium (Ti), and FGM with Ti at the bottom and hydroxyapatite (HA) at the top. The FE models of FGM implants were generated by using different volume fractions and the rule of mixtures. The rule of mixtures was used to calculate the FGM properties based on the local volume fraction. The volume fraction was defined by using exponential, power, and sigmoid laws. For the power and sigmoid law varying volume fraction indices (0.1, 0.2, 0.5, 1, 2, and 5) were considered. The geometry resembling STAR® ankle system tibial implant was considered for the present study. The results indicate that FGMs lower stress shielding but also marginally increase implant-bone micromotion; however, the values were within the acceptable limit for bone ingrowth. It is observed that the material gradation law and volume fraction index influence the performance of FGM tibial implants. The tibial implant composed of FGM using power law with a volume fraction index of 0.1 was the preferred option because it showed the least stress shielding.

Outcomes of Total Ankle Arthroplasty After Periprosthetic Cyst Curettage and Bone Grafting

Total ankle arthroplasty (TAA) has become a popular management option for ankle arthritis. Periprosthetic osteolysis is one of the most common causes for reoperation in TAA. A CT scan should be done in all suspected osteolysis cases to confirm location, quantify size and aid in surgical planning. These patients are often asymptomatic with limited evidence regarding appropriate management. Smaller lesions should be monitored for progression in size. Periprosthetic cysts measuring 10-15mm in all three axes should be considered for debridment and curettage with autogenous bone grafting. The authors believe that bone grafting of large asymptomatic periprosthetic cysts could prevent implant failure.

Magnetic Resonance Imaging of Total Ankle Arthroplasty: State-of-The-Art Assessment of Implant-Related Pain and Dysfunction

Total ankle arthroplasty (TAA) is an effective alternative for treating patients with end-stage ankle degeneration, improving mobility, and providing pain relief. Implant survivorship is constantly improving; however, complications occur. Many causes of pain and dysfunction after total ankle arthroplasty can be diagnosed accurately with clinical examination, laboratory, radiography, and computer tomography. However, when there are no or inconclusive imaging findings, magnetic resonance imaging (MRI) is highly accurate in identifying and characterizing bone resorption, osteolysis, infection, osseous stress reactions, nondisplaced fractures, polyethylene damage, nerve injuries and neuropathies, as well as tendon and ligament tears. Multiple vendors offer effective, clinically available MRI techniques for metal artifact reduction MRI of total ankle arthroplasty. This article reviews the MRI appearances of common TAA implant systems, clinically available techniques and protocols for metal artifact reduction MRI of TAA implants, and the MRI appearances of a broad spectrum of TAA-related complications.

CT Scan Assessment and Functional Outcome of Periprosthetic Bone Grafting After Total Ankle Arthroplasty at Medium-term Follow-up

BACKGROUND

Periprosthetic cysts can occur in up to 95% of total ankle arthroplasties (TAA) and have been correlated with implant failure. The aim of this study was to determine the clinical and radiologic outcomes, using computed tomographic (CT) scan, after periprosthetic cyst bone grafting and assess for the minimum cyst size that should be grafted.

METHODS

A retrospective review was performed of all TAA procedures performed between 2007 and 2014 (n=93). A CT scan was done to assess cyst size and operative planning. Eight patients with 9 periprosthetic cysts larger than 1.75 cm³ were grafted and specimens sent for histology. The mean time to bone grafting was 7.3 (3.8-9.5) years. Functional outcome was assessed using the American Orthopaedic Foot & Ankle Society ankle score, visual analog scale, and Self-reported Foot and Ankle Score. A CT scan was performed at follow-up to assess graft incorporation and cyst size progression. The mean time to CT scan post grafting was 3.0 (0.7-4.7) years.

RESULTS

There was no implant malalignment identified and no differences in the pre- and postoperative functional scores. Preoperatively cysts had a mean volume of 8.16 (2.04-14.03) cm³. The mean percentage incorporation was 89% (69%-100%). Eight of the grafted cysts were considered successful on CT, with the ninth having 69% incorporation. Five cysts were not grafted, as they were below 1.75 cm³, and remained the same size or had minimal enlargement.

CONCLUSION

The satisfactory results in this small cohort suggests that prophylactic bone grafting may extend implant survival. We recommend that periprosthetic cysts greater than 1.75 cm³ be prophylactically bone grafted, and that cysts smaller than 1.75 cm³ be monitored for progression in size.

LEVEL OF EVIDENCE

Level IV, Case Series.

Bone SPECT/CT in the Evaluation of Painful Total Ankle Replacement: Validation of Localization Scheme and Preliminary Evaluation of Diagnostic Patterns

PURPOSE

Third-generation total ankle replacement (TAR) is an increasingly popular and effective treatment for end-stage osteoarthritis, yet identifying causes of failure remains challenging. We evaluated integrated bone SPECT/CT in recurrent pain after TAR by validating a standardized reporting scheme, identifying uptake patterns, and assessing diagnostic performance and impact on clinical management.

PATIENTS AND METHODS

A total of 24 TARs in 16 patients with persistent or recurrent pain received integrated bone SPECT/CT using diagnostic CT settings. Images were retrospectively reviewed, and a novel localization scheme was validated by assessing interrater agreement. Distinct uptake patterns were identified, and diagnostic test characteristics were estimated. Reference standard consisted of clinical follow-up, laboratory findings, and subsequent procedures, including revision surgery.

RESULTS

Standardized scoring of bone SPECT/CT uptake was highly reproducible (intraclass correlation coefficient, 0.79; 95% confidence interval [CI], 0.75-0.82). The final diagnoses were gutter impingement (n = 12), periprosthetic (stress) fracture (n = 5), loosening (n = 5), tarsal arthritis (n = 1), and erysipelas (n = 1). Overall, the diagnostic test characteristics of bone SPECT/CT were as follows: sensitivity of 100% (95% CI, 82%-100%), specificity of 80% (95% CI, 28%-99%), and accuracy of 96% (95% CI, 79%-100%). Gutter impingement, periprosthetic fracture, and loosening were correctly identified in all cases revealing distinct uptake patterns. Importantly, persistent diffuse uptake was frequently observed, warranting cautious interpretation. Bone SPECT/CT impacted clinical management in 86%, with symptomatic improvement in 83% of patients.

CONCLUSIONS

Integrated bone SPECT/CT of painful TARs may benefit from standardized localization to reveal distinct uptake patterns representing common complications after TAR. Initial results show highly promising diagnostic value with potentially important impact on clinical management.

Positive and negative factors for the treatment outcomes following total ankle arthroplasty? A systematic review

BACKGROUND

Patient selection, surgeon's experience and implant design play an integral role and affect the treatment outcomes of total ankle arthroplasty (TAA). The aims of this study were to investigate the positive and negative attributes that correlate with different clinical and radiographic outcomes.

METHODS

Eight-nine studies matched the inclusion criteria: (1) studies of primary TAA with uncemented prosthesis; (2) mean follow-up of no less than 2-year; (3) reports of clinical and radiographic outcomes, and exclusion criteria: (1) non-English study; (2) more than one type of prosthesis without separated data; (3) kin studies with shorter follow-up or smaller cohort. Age, etiology, preoperative deformity, surgeon's experience, follow-up duration and prosthetic type were studied with respect to different outcomes by mixed-effects logistic regression analysis.

RESULTS

Patients factor: older patients reported less pain or stiffness and demonstrated less radiographic loosening which did not require additional surgical intervention. More traumatic arthritis experienced adjacent joints degeneration after TAA. Surgeon factor: less experienced surgeons had more intraoperative complications. Lack of experience for complications management without implant retrieval during early period might result in more revisions or fusion was done. Prosthetic factor: updated instrumentation decreased malalignment. If the polyethylene (PE) insert was significantly narrower than the metal components more implant instability and subsequent severe particulate wear was seen. Designs with flat-on-flat articulation and ridge at the center of the talar component associated with more PE fracture. Minimal bone resection reduced postoperative fractures. A flat cut of the tibial component and a flat undersurface with press-fit by two screws or pegs of the talar component demonstrated less postoperative fractures, whereas a syndesmosis fusion and a small triangular shape with one central fin of the talar component experienced more loosening which did not require additional surgery. Anatomic conical shape of the talar component seemed to reduce adjacent joint degeneration. Finally, fewer failures were found in patients who received HINTEGRA and Salto Talaris.

CONCLUSIONS

Based on our investigation, some positive and negative factors for different clinical and radiographic outcomes were found, which should be taken into consideration in clinical practice and ankle implant design.

What Is the Definition of Acute and Chronic Periprosthetic Joint Infection (PJI) of Total Ankle Arthroplasty (TAA)?

RECOMMENDATION

There is a paucity of data for defining acute or chronic periprosthetic joint infection (PJI) following total ankle arthroplasty (TAA) in the literature. Any discussion of PJI after ankle replacement is entirely reliant on the literature surrounding knee and hip arthroplasty.

LEVEL OF EVIDENCE

Consensus.

DELEGATE VOTE

Agree: 100%, Disagree: 0%, Abstain: 0% (Unanimous, Strongest Consensus).

Diagnostic Criteria and Treatment of Acute and Chronic Periprosthetic Joint Infection of Total Ankle Arthroplasty

Background:

Prosthetic joint infection (PJI) after total ankle arthroplasty (TAA) is a serious complication that results in significant consequences to the patient and threatens the survival of the ankle replacement. PJI in TAA may require debridement, placement of antibiotic spacer, revision arthroplasty, conversion to arthrodesis, or potentially below the knee amputation. While the practice of TAA has gained popularity in recent years, there is some minimal data regarding wound complications in acute or chronic PJI of TAA. However, of the limited studies that describe complications of PJI of TAA, even fewer studies describe the criteria used in diagnosing PJI. This review will cover the current available literature regarding total ankle arthroplasty infection and will propose a model for treatment options for acute and chronic PJI in TAA.

Methods:

A review of the current literature was conducted to identify clinical investigations in which prosthetic joint infections occurred in total ankle arthroplasty with associated clinical findings, radiographic imaging, and functional outcomes. The electronic databases for all peer-reviewed published works available through January 31, 2018, of the Cochrane Library, PubMed MEDLINE, and Google Scholar were explored using the following search terms and Boolean operators: “total ankle replacement” OR “total ankle arthroplasty” AND “periprosthetic joint infection” AND “diagnosis” OR “diagnostic criteria.” An article was considered eligible for inclusion if it concerned diagnostic criteria of acute or chronic periprosthetic joint infection of total ankle arthroplasty regardless of the number of patients treated, type of TAA utilized, conclusion, or level of evidence of study.

Results:

No studies were found in the review of the literature describing criteria for diagnosing PJI specific to TAA.

Conclusions:

Literature describing the diagnosis and treatment of PJI in TAA is entirely reliant on the literature surrounding knee and hip arthroplasty. Because of the limited volume of total ankle arthroplasty in comparison to knee and hip arthroplasty, no studies to our knowledge exist describing diagnostic criteria specific to total ankle arthroplasty with associated reliability. Large multicenter trials may be required to obtain the volume necessary to accurately describe diagnostic criteria of PJI specific to TAA.

Level of Evidence:

Level III, systematic review.

Total ankle arthroplasty: what are the risks?: a guide to surgical consent and a review of the literature

AIMS

Total ankle arthroplasty (TAA) surgery is complex and attracts a wide variety of complications. The literature lacks consistency in reporting adverse events and complications. The aim of this article is to provide a comprehensive analysis of each of these complications from a literature review, and to compare them with rates from our Unit, to aid clinicians with the process of informed consent.

PATIENTS AND METHODS

A total of 278 consecutive total ankle arthroplasties (251 patients), performed by four surgeons over a six-year period in Wrightington Hospital (Wigan, United Kingdom) were prospectively reviewed. There were 143 men and 108 women with a mean age of 64 years (41 to 86). The data were recorded on each follow-up visit. Any complications either during initial hospital stay or subsequently reported on follow-ups were recorded, investigated, monitored, and treated as warranted. Literature search included the studies reporting the outcomes and complications of TAA implants.

RESULTS

There were wound-healing problems in nine ankles (3.2%), superficial infection in 20 ankles (7.2%), and deep infection in six ankles (2.2%). Intraoperative fractures occurred in medial malleoli in 27 ankles (9.7%) and in lateral malleoli in four ankles (1.4%). Aseptic loosening and osteolysis were seen 16 ankles (5.8%). Fracture of the polyethylene component occurred in one ankle (0.4%) and edge-loading in seven ankles (2.5%). We observed medial gutter pain in 31 ankles (11.1%). The incidence of thromboembolism occurred in two ankles (0.7%). The results were found to be comparable to the previously reported complications of total ankle arthroplasty in the literature.

CONCLUSION

Total ankle arthroplasty continues to evolve and improve the ankle function. Despite high overall complication rates with TAA surgery, most complications appear to be minor and do not affect final clinical outcome. Our results and literature review will help in the consent process and provide detailed complication rates for an informed consent. Cite this article: Bone Joint J 2018;100-B:1352-8.