Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone

Advantages of customization of osseointegrated implants in transfemoral amputees: a comparative analysis of surgical planning

BACKGROUND

Commercially available osseointegrated devices for transfemoral amputees are limited in size and thus fail to meet the significant anatomical variability in the femoral medullary canal. This study aimed to develop a customized osseointegrated stem to better accommodate a variety of femoral anatomies in transfemoral amputees than off-the-shelf stems. Customization is expected to enhance cortical bone preservation and increase the stem-bone contact area, which are critical for the long-term stability and success of implants.

METHODS

A customized stem (OsteoCustom) was designed based on the statistical shape variability of the medullary canal. The implantability of the OsteoCustom stem was tested via 70 computed tomography (CT) images of human femurs and compared to that of a commercial device (OFI-C) for two different resection levels. The evaluations included the volume of cortical bone removed and the percentage of stem-bone contact area for both resection levels. Statistical significance was analyzed using paired and unpaired t tests.

RESULTS

The OsteoCustom stem could be virtually implanted in all 70 femurs, while the OFI-C was unsuitable in 19 cases due to insufficient cortical thickness after implantation, further emphasizing its adaptability to varying anatomical conditions. The OsteoCustom stem preserved a greater volume of cortical bone than did the OFI-C. In fact, 42% less bone was removed at the proximal resection level (3.15 cm³ vs. 5.42 cm³, p ≤ 0.0001), and 33% less at the distal resection level (2.25 cm³ vs. 3.39 cm³, p = 0.003). The stem-bone contact area was also greater for the OsteoCustom stem, particularly at the distal resection level, showing a 20% increase in contact area (52.3% vs. 32.2%, p = 0.002) compared to that of the OFI-C.

CONCLUSIONS

The OsteoCustom stem performed better than the commercial stem by preserving more cortical bone and achieving a greater stem-bone contact area, especially at distal resection levels where the shape of the medullary canal exhibits more inter-subject variability. Optimal fit in the distal region is of paramount importance for ensuring the stability of osseointegrated implants. This study highlights the potential benefits of customized osseointegrated stems in accommodating a broader range of femoral anatomies, with enhanced fit in the medullary canal.

Surface engineering of pure magnesium in medical implant applications

This review comprehensively surveys the latest advancements in surface modification of pure magnesium (Mg) in recent years, with a focus on various cost-effective procedures, comparative analyses, and assessments of outcomes, addressing the merits and drawbacks of pure Mg and its alloys. Diverse economically feasible methods for surface modification, such as hydrothermal processes and ultrasonic micro-arc oxidation (UMAO), are discussed, emphasizing their exceptional performance in enhancing surface properties. The attention is directed towards the biocompatibility and corrosion resistance of pure Mg, underscoring the remarkable efficacy of techniques such as Ca-deficientca-deficient hydroxyapatite (CDHA)/MgF2 bi-layer coating and UMAO coating in electrochemical processes. These methods open up novel avenues for the application of pure Mg in medical implants. Emphasis is placed on the significance of adhering to the principles of reinforcing the foundation and addressing the source. The advocacy is for a judicious approach to corrosion protection on high-purity Mg surfaces, aiming to optimize the overall mechanical performance. Lastly, a call is made for future in-depth investigations into areas such as composite coatings and the biodegradation mechanisms of pure Mg surfaces, aiming to propel the field towards more sustainable and innovative developments.

Migration Characteristics of a Proximally Coated Collarless Femoral Stem: A Prospective 2-Year Radiostereometric Analysis Study

Background

Collared femoral stems have been considered to reduce the risk of early subsidence over collarless stems. However, with advances in material technology, new surface treatments have been introduced into cementless stem design to enhance primary fixation and long-term stability. This study aims to analyze the early migration behaviors of a proximally coated collarless femoral stem and cementless acetabular component and compare the outcomes with commercially available cementless stems and acetabular cups.

Methods

A total of 24 patients (25 hips) undergoing total hip arthroplasty were recruited and followed up for 2 years. All patients received a Masterloc femoral stem (Medacta International SA, Castel San Pietro, Switzerland) and an Mpact acetabular component (Medacta International SA, Castel San Pietro, Switzerland) with tantalum beads embedded during the operation. Radiographs for radiostereometric analysis were taken immediately postsurgery, 6-months, 1-year, and 2-years postoperatively.

Results

The median condition number for this study was 59. The median stem subsidence was -0.08 mm (-2.47 to 0.40) at 2 years. The median cup subsidence was -0.03 mm (-0.38 to 0.57) at 2 years. The migration of the Masterloc stem was less than that of other cementless collarless, as well as collared stems, as reported in literature.

Conclusions

This study has demonstrated the high stability and fixation provided with the use of a collarless cementless stem. The subsidence seen in both this cementless femoral stem and acetabular cup at 2 years postoperative was below the range reported in literature for cementless collarless and collared stems.

Three-Dimensional-Printed Titanium Versus Polyetheretherketone Cages for Lumbar Interbody Fusion: A Systematic Review of Comparative In Vitro, Animal, and Human Studies

Interbody fusion is a workhorse technique in lumbar spine surgery that facilities indirect decompression, sagittal plane realignment, and successful bony fusion. The 2 most commonly employed cage materials are titanium (Ti) alloy and polyetheretherketone (PEEK). While Ti alloy implants have superior osteoinductive properties they more poorly match the biomechanical properties of cancellous bones. Newly developed 3-dimensional (3D)-printed porous titanium (3D-pTi) address this disadvantage and are proposed as a new standard for lumbar interbody fusion (LIF) devices. In the present study, the literature directly comparing 3D-pTi and PEEK interbody devices is systematically reviewed with a focus on fusion outcomes and subsidence rates reported in the in vitro, animal, and human literature. A systematic review directly comparing outcomes of PEEK and 3D-pTi interbody spinal cages was performed. PubMed, Embase, and Cochrane Library databases were searched according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. Mean Newcastle-Ottawa Scale score for cohort studies was 6.4. A total of 7 eligible studies were included, comprising a combination of clinical series, ovine animal data, and in vitro biomechanical studies. There was a total population of 299 human and 59 ovine subjects, with 134 human (44.8%) and 38 (64.4%) ovine models implanted with 3D-pTi cages. Of the 7 studies, 6 reported overall outcomes in favor of 3D-pTi compared to PEEK, including subsidence and osseointegration, while 1 study reported neutral outcomes for device related revision and reoperation rate. Though limited data are available, the current literature supports 3D-pTi interbodies as offering superior fusion outcomes relative to PEEK interbodies for LIF without increasing subsidence or reoperation risk. Histologic evidence suggests 3D-Ti to have superior osteoinductive properties that may underlie these superior outcomes, but additional clinical investigation is merited.

Observations of bony ongrowth and clinical fixation in two retrieved disc replacements

Total disc replacements utilize textured coatings to maximize bony ongrowth. However, the contribution of direct bony attachment to overall fixation for total disc replacements has not been reported. The goal of the present study was to document the extent of bony attachment to the surfaces of two clinically functional total disc replacements that were securely fixed at the time of revision. Two metal-and-polymeric disc replacements, one cervical and one lumbar, were evaluated following surgical retrieval. The cervical device was retrieved at 8 months and the lumbar device at 28 months post-operative. Both devices were reported well-fixed at the time of removal, with large bone masses attached to one endplate of each device. Visual inspections, non-destructive gravimetric measurements, and surface metrology were performed to assess fixation. These inspections suggested that both devices had been fixed at the time of removal with little in vivo mechanical damage, as surgical extraction damage was noted on both devices and provided imaging showed a lack of device migration. Devices were then embedded and sectioned to evaluate the bone-implant interface. High resolution photographs and contact microradiographs were taken to assess bony attachment. In contrast to initial analysis, these images revealed radiolucent gaps between the endplates and bone masses. Little direct contact between the bone and endplate surface was identified and the original surgical cuts were still visible. Both devices were clinically fixed at the time of removal and neither had complications associated with loosening. However, osseointegration was minimal in one of the devices and altogether absent from the other. The findings of the present study suggest that other factors may influence overall clinical fixation such as the surgical preparation of the vertebral bone or the surface roughness of the treated endplates. Despite the limitations of the present study, this information is unique to the current total disc replacement literature and the ongrowth and fixation of devices should be considered as a topic for future investigation.

[Physiological reactions in the interface between cementless implants and bone]

BACKGROUND

Surgical treatment of patients with osteoarthritis of the hip and persisting symptoms under conservative therapy has become increasingly important against the background of an aging population.

OBJECTIVES

What are the physiological reactions in the interface between cementless implants and bone?

METHODS

The literature is reviewed, expert opinions and animal models are analyzed and discussed.

RESULTS

Surface coating of implants with hydroxyapatite or titanium can have positive effects on osteointegration. Additional local application of mediators might be beneficial for osteointegration in the future.

CONCLUSION

Early peri-implant bone healing directly after implantation and late remodeling of the bone-implant interface are essential for secondary implant stability.

Near-Infrared Spectroscopy for the In Vivo Monitoring of Biodegradable Implants in Rats

Magnesium (Mg) alloys possess unique properties that make them ideal for use as biodegradable implants in clinical applications. However, reports on the in vivo assessment of these alloys are insufficient. Thus, monitoring the degradation of Mg and its alloys in vivo is challenging due to the dynamic process of implant degradation and tissue regeneration. Most current works focus on structural remodeling, but functional assessment is crucial in providing information about physiological changes in tissues, which can be used as an early indicator of healing. Here, we report continuous wave near-infrared spectroscopy (CW NIRS), a non-invasive technique that is potentially helpful in assessing the implant-tissue dynamic interface in a rodent model. The purpose of this study was to investigate the effects on hemoglobin changes and tissue oxygen saturation (StO₂) after the implantation of Mg-alloy (WE43) and titanium (Ti) implants in rats' femurs using a multiwavelength optical probe. Additionally, the effect of changes in the skin on these parameters was evaluated. Lastly, combining NIRS with photoacoustic (PA) imaging provides a more reliable assessment of tissue parameters, which is further correlated with principal component analysis.

Manipulation Under Anesthesia is Safe After Cementless Total Knee Arthroplasty: A Multicenter Study

BACKGROUND

Cementless total knee arthroplasty (TKA) is thought to facilitate durable, biological fixation between the bone and implant. However, the 4-12 weeks required for osseointegration coincides with the optimal timeframe to perform a manipulation under anesthesia (MUA) if a patient develops postoperative stiffness. This study aims to determine the impact of early MUA on cementless fixation by comparing functional outcomes and survivorship of cementless and cemented TKAs.

METHODS

A consecutive series of patients who underwent MUA for postoperative stiffness within 90 days of primary, unilateral TKA at 2 academic institutions between 2014 and 2018 were identified. Cases involving extensive hardware removal were excluded. Cementless TKAs undergoing MUA (n = 100) were propensity matched 1:1 to cemented TKAs undergoing MUA (n = 100) using age, gender, body mass index, and year of surgery. Both groups had comparable baseline Knee Injury and Osteoarthritis Outcome Scores (KOOS), Short Form (SF)-12 Physical, and SF-12 Mental scores. MUA-related complications as well as postoperative KOOS and SF-12 scores were compared.

RESULTS

MUA-related complications were equivalently low in both groups (P = .324), with only 1 patella component dissociation in the cementless group. No tibial or femoral components acutely loosened in the perioperative period. Postoperative KOOS (P = .101) and SF-12 Mental scores (P = .380) were similar between groups. Six-year survivorship free from any revision after MUA was 98.0% in both groups (P = 1.000).

CONCLUSION

Early postoperative MUA after cementless TKA was not associated with increased MUA-related complications or worse patient-reported outcomes compared to cemented TKA. Short-term survivorship was also comparable, suggesting high durability of the bone-implant interface.

Effect of femoral stem surface coating on clinical and radiographic outcomes of cementless primary total hip arthroplasty: a patient-matched retrospective study

PURPOSE

This study aims to determine whether changing the stem coating grants superior outcomes at a minimum follow-up of five years.

METHODS

Retrospective review of a consecutive series of primary total hip arthroplasties (THAs) operated by direct anterior approach between 01/01/2013 and 31/12/2014. Two stems were compared, which were identical except for their surface coating; "the Original stem" was fully coated with hydroxyapatite (HA), while "the ProxCoat stem" was proximally coated with plasma-sprayed titanium and HA. Matching was performed. Clinical assessment included modified Harris hip score (mHHS), Oxford hip score (OHS), and forgotten joint score (FJS). Radiographic assessment evaluated alignment, subsidence, pedestal formation, heterotopic ossification, radiolucent lines ≥ 2 mm, spot welds, cortical hypertrophy, and osteolysis.

RESULTS

232 hips received the Original stem and 167 the ProxCoat stem, from which respectively five hips (2.2%) and no hips (0%) underwent revision. Matching identified two groups of 91 patients, with comparable patient demographics. At > five years follow-up, there were no differences in OHS (16 ± 6 vs 15 ± 5; p = 0.075) nor FJS (81 ± 26 vs 84 ± 22; p = 0.521), but there were differences in mHHS (89 ± 15 vs 92 ± 12; p = 0.042). There were no differences in alignment, subsidence, pedestal formation, heterotopic ossification, cortical hypertrophy, and osteolysis. There were differences in prevalence of proximal radiolucent lines (12% vs 0%; p < 0.001) and distal spot welds (24% vs 54%; p < 0.001).

CONCLUSION

At a minimum follow-up of five years, this study on matched patients undergoing primary THA found that ProxCoat stems results in significantly fewer radiolucent lines, more spot welds, and less revisions than Original stems, thus suggesting better bone ingrowth.

A Novel Nanostructured Surface on Titanium Implants Increases Osseointegration in a Sheep Model

BACKGROUND

A nanostructured titanium surface that promotes antimicrobial activity and osseointegration would provide the opportunity to create medical implants that can prevent orthopaedic infection and improve bone integration. Although nanostructured surfaces can exhibit antimicrobial activity, it is not known whether these surfaces are safe and conducive to osseointegration.

QUESTIONS/PURPOSES

Using a sheep animal model, we sought to determine whether the bony integration of medical-grade, titanium, porous-coated implants with a unique nanostructured surface modification (alkaline heat treatment [AHT]) previously shown to kill bacteria was better than that for a clinically accepted control surface of porous-coated titanium covered with hydroxyapatite (PCHA) after 12 weeks in vivo. The null hypothesis was that there would be no difference between implants with respect to the primary outcomes: interfacial shear strength and percent intersection surface (the percentage of implant surface with bone contact, as defined by a micro-CT protocol), and the secondary outcomes: stiffness, peak load, energy to failure, and micro-CT (bone volume/total volume [BV/TV], trabecular thickness [Tb.Th], and trabecular number [Tb.N]) and histomorphometric (bone-implant contact [BIC]) parameters.

METHODS

Implants of each material (alkaline heat-treated and hydroxyapatite-coated titanium) were surgically inserted into femoral and tibial metaphyseal cancellous bone (16 per implant type; interference fit) and in tibial cortices at three diaphyseal locations (24 per implant type; line-to-line fit) in eight skeletally mature sheep. At 12 weeks postoperatively, bones were excised to assess osseointegration of AHT and PCHA implants via biomechanical push-through tests, micro-CT, and histomorphometry. Bone composition and remodeling patterns in adult sheep are similar to that of humans, and this model enables comparison of implants with ex vivo outcomes that are not permissible with humans. Comparisons of primary and secondary outcomes were undertaken with linear mixed-effects models that were developed for the cortical and cancellous groups separately and that included a random effect of animals, covariates to adjust for preoperative bodyweight, and implant location (left/right limb, femoral/tibial cancellous, cortical diaphyseal region, and medial/lateral cortex) as appropriate. Significance was set at an alpha of 0.05.

RESULTS

The estimated marginal mean interfacial shear strength for cancellous bone, adjusted for covariates, was 1.6 MPa greater for AHT implants (9.3 MPa) than for PCHA implants (7.7 MPa) (95% CI 0.5 to 2.8; p = 0.006). Similarly, the estimated marginal mean interfacial shear strength for cortical bone, adjusted for covariates, was 6.6 MPa greater for AHT implants (25.5 MPa) than for PCHA implants (18.9 MPa) (95% CI 5.0 to 8.1; p < 0.001). No difference in the implant-bone percent intersection surface was detected for cancellous sites (cancellous AHT 55.1% and PCHA 58.7%; adjusted difference of estimated marginal mean -3.6% [95% CI -8.1% to 0.9%]; p = 0.11). In cortical bone, the estimated marginal mean percent intersection surface at the medial site, adjusted for covariates, was 11.8% higher for AHT implants (58.1%) than for PCHA (46.2% [95% CI 7.1% to 16.6%]; p < 0.001) and was not different at the lateral site (AHT 75.8% and PCHA 74.9%; adjusted difference of estimated marginal mean 0.9% [95% CI -3.8% to 5.7%]; p = 0.70).

CONCLUSION

These data suggest there is stronger integration of bone on the AHT surface than on the PCHA surface at 12 weeks postimplantation in this sheep model.

CLINICAL RELEVANCE

Given that the AHT implants formed a more robust interface with cortical and cancellous bone than the PCHA implants, a clinical noninferiority study using hip stems with identical geometries can now be performed to compare the same surfaces used in this study. The results of this preclinical study provide an ethical baseline to proceed with such a clinical study given the potential of the alkaline heat-treated surface to reduce periprosthetic joint infection and enhance implant osseointegration.

3D-printed titanium cages without bone graft outperform PEEK cages with autograft in an animal model

BACKGROUND CONTEXT

Modernization of 3D printing has allowed for the production of porous titanium interbody cages (3D-pTi) which purportedly optimize implant characteristics and increase osseointegration; however, this remains largely unstudied in vivo.

PURPOSE

To compare osseointegration of three-dimensional (3D) titanium cages without bone graft and Polyether-ether-ketone (PEEK) interbody cages with autologous iliac crest bone graft (AICBG).

STUDY DESIGN

Animal study utilizing an ovine in vivo model of lumbar fusion.

METHODS

Interbody cages of PEEK or 3D-pTi supplied by Spineart SA (Geneva, Switzerland) were implanted in seven living sheep at L2-L3 and L4-L5, leaving the intervening disc space untreated. Both implant materials were used in each sheep and randomized to the aforementioned disc spaces. Computed tomography (CT) was obtained at 4 weeks and 8 weeks. MicroCT and histological sections were obtained to evaluate osseointegration.

RESULTS

MicroCT demonstrated osseous in-growth of native cancellous bone in the trabecular architecture of the 3D-pTi interbody cages and no interaction between the PEEK cages with the surrounding native bone. Qualitative histology revealed robust osseointegration in 3D-pTi implants and negligible osseointegration with localized fibrosis in PEEK implants. Evidence of intramembranous and endochondral ossification was apparent with the 3D-pTi cages. Quantitative histometric bone implant contact demonstrated significantly more contact in the 3D-pTi implants versus PEEK (p<.001); region of interest calculations also demonstrated significantly greater osseous and cartilaginous interdigitation at the implant-native bone interface with the 3D-pTi cages (p=.008 and p=.015, respectively).

CONCLUSIONS

3D-pTi interbody cages without bone graft outperform PEEK interbody cages with AICBG in terms of osseointegration at 4 and 8 weeks postoperatively in an ovine lumbar fusion model.

CLINICAL SIGNIFICANCE

3D-pTi interbody cages demonstrated early and robust osseointegration without any bone graft or additive osteoinductive agents. This may yield early stability in anterior lumbar arthrodesis and potentially bolster the rate of successful fusion. This could be of particular advantage in patients with spinal neoplasms needing post-ablative arthrodesis, where local autograft use would be ill advised.

Bioactive Surface Modifications through Thermally Sprayed Hydroxyapatite Composite Coatings: A Review over Selective Reinforcements

Hydroxyapatite (HA) has been an excellent replacement for the natural bone in orthopedic applications, owing to its close resemblance; however, it is brittle and has low strength. Surface modification techniques...

Biomimetic Composite Coatings for Activation of Titanium Implant Surfaces: Methodological Approach and In Vivo Enhanced Osseointegration

Innovative nanomaterials are required for the coatings of titanium (Ti) implants to ensure the activation of Ti surfaces for improved osseointegration, enhanced bone fracture healing and bone regeneration. This paper presents a systematic investigation of biomimetic composite (BC) coatings on Ti implant surfaces in a rat model of a diaphyseal femoral fracture. Methodological approaches of surface modification of the Ti implants via the usual joining methods (e.g., grit blasting and acid etching) and advanced physicochemical coating via a self-assembled dip-coating method were used. The biomimetic procedure used multi-substituted hydroxyapatite (ms-HAP) HAP-1.5 wt% Mg-0.2 wt% Zn-0.2 wt% Si nanoparticles (NPs), which were functionalized using collagen type 1 molecules (COL), resulting in ms-HAP/COL (core/shell) NPs that were embedded into a polylactic acid (PLA) matrix and finally covered with COL layers, obtaining the ms-HAP/COL@PLA/COL composite. To assess the osseointegration issue, first, the thickness, surface morphology and roughness of the BC coating on the Ti implants were determined using AFM and SEM. The BC-coated Ti implants and uncoated Ti implants were then used in Wistar albino rats with a diaphyseal femoral fracture, both in the absence and the presence of high-frequency pulsed electromagnetic shortwave (HF-PESW) stimulation. This study was performed using a bone marker serum concentration and histological and computer tomography (micro-CT) analysis at 2 and 8 weeks after surgical implantation. The implant osseointegration was evaluated through the bone–implant contact (BIC). The bone–implant interface was investigated using FE-SEM images and EDX spectra of the retrieved surgical implants at 8 weeks in the four animal groups. The obtained results showed significantly higher bone–implants contact and bone volume per tissue volume, as well as a greater amount of newly formed bone, in the BC-coated Ti implants than in the uncoated Ti implants. Direct bone–implant contact was also confirmed via histological examination. The results of this study confirmed that these biomimetic composite coatings on Ti implants were essential for a significant enhancement of osseointegration of BC-coated Ti implants and bone regeneration. This research provides a novel strategy for the treatment of bone fractures with possible orthopedic applications.

High-strength, porous additively manufactured implants with optimized mechanical osseointegration

Optimization of porous titanium alloy scaffolds designed for orthopedic implants requires balancing mechanical properties and osseointegrative performance. The tradeoff between scaffold porosity and the stiffness/strength must be optimized towards the goal to improve long term load sharing while simultaneously promoting osseointegration. Osseointegration into porous titanium implants covering a wide range of porosity (0%-90%) and manufactured by laser powder bed fusion (LPBF) was evaluated with an established ovine cortical and cancellous defect model. Direct apposition and remodeling of woven bone was observed at the implant surface, as well as bone formation within the interstices of the pores. A linear relationship was observed between the porosity and benchtop mechanical properties of the scaffolds, while a non-linear relationship was observed between porosity and the ex vivo cortical bone-implant interfacial shear strength. Our study supports the hypothesis of porosity dependent performance tradeoffs, and establishes generalized relationships between porosity and performance for design of topological optimized implants for osseointegration. These results are widely applicable for orthopedic implant design for arthroplasty components, arthrodesis devices such as spinal interbody fusion implants, and patient matched implants for treatment of large bone defects.

Use of a Plasma-Sprayed Titanium-Hydroxyapatite Femoral Stem in Hip Arthroplasty in Patients Older than 70 Years. Is Cementless Fixation a Reliable Option in the Elderly?

Background: Although cementless implants are increasing in popularity, the use of cementless femoral stems for total hip arthroplasty (THA) and hip hemiarthroplasty (HH) in elderly patients remains controversial. The aim of this study was to report the outcomes of a cementless stem used in a large multicentric cohort of elderly patients receiving elective THA and HH for displaced femoral neck fracture. Methods: A total of 293 patients (301 hips) aged 70 years or older (mean age, 78 years; range, 70–93) who received the same cementless plasma-sprayed porous titanium–hydroxyapatite stem were retrospectively evaluated after primary THA and HH to investigate stem survival, complications, and clinical and radiographic results. Results: Cumulative stem survival was 98.5% (95% CI, 96.4–99.4%; 91 hips at risks) with revision due to any reason as the end-point at 10-year follow-up (mean 8.6 years, range 4–12). No stem was revised due to aseptic loosening. The mean Forgotten Joint Score was 98.7. Radiographically, the implants showed complete osseointegration, with slight stress-shieling signs in less than 10% of the hips. Conclusion: The use of cementless stems was proven to be a reliable and versatile option even in elderly patients for elective THA and HH for femoral neck fracture.

Two-Year Outcomes After Total Ankle Replacement With a Novel Fixed-Bearing Implant

BACKGROUND

The Integra Cadence total ankle replacement (TAR) is a fourth-generation anatomic, fixed-bearing implant requiring minimal tibial and talar resection, which has been in clinical use since June 2016. The primary purpose of this study is to assess its short-term clinical and radiographic outcomes after TAR using this prosthesis.

METHODS

This is a prospective case series of consecutive patients that underwent TAR using this novel fourth-generation prosthesis between June 2016 and November 2017. The primary outcome of interest was the Ankle Osteoarthritis Scale (AOS). Secondary outcomes included Short Form Health Survey-36 (SF-36) scores, radiographic alignment, complications, reoperations, and revisions.

RESULTS

In total, 69 patients were included in our study. Fifty-one patients (73.9%) required a total of 91 ancillary procedures. Postoperatively, AOS pain scores decreased significantly by an average of 17.8±30.1 points from 45.9±18.2 to 28.4±27.3 (P < .001). AOS disability scores also decreased significantly following surgery by an average of 22.0±30.5 points from 53.9±18.5 to 32.5±27.9 (P < .001). The SF-36 physical component summary score improved 10.4±9.8 points from 33.1±9.1 to 42.6±9.1 (P < .001). Radiographic analysis demonstrated significant improvement to neutral coronal plane alignment, which was achieved in 97% of patients (P < .01) with no cyst formation at 2 years. There was 1 reported complication, 9 reoperations, and no metal or polyethylene component revisions. Overall, the 2-year implant survivorship was 100% in our cohort. Eighteen patients (26.1%) demonstrated fibrous ingrowth of the tibial component. However, outcome scores for these patients did not demonstrate any negative effects.

CONCLUSION

In our hands, this TAR system demonstrated excellent early clinical and radiographic outcomes. Patients reported improved physical health status, pain, and disability in the postoperative period. Total ankle instrumentation allowed for accurate and reproducible implantation with correction of coronal and sagittal plane deformities. Early results for the clinical use of this TAR system are promising, but further long-term prospective outcome studies are necessary.

LEVEL OF EVIDENCE

Level IV, case series.

An overview of assessment tools for determination of biological Magnesium implant degradation

Medical implants made of biodegradable materials are advantageous for short-term applications as fracture fixation and mechanical support during bone healing. After completing the healing process, the implant biodegrades without any long-term side effects nor any need for surgical removal. In particular, Magnesium (Mg) implants, while degrading, can cause physiological changes in the tissues surrounding the implant. The evaluation of structural remodeling is relevant, however, the functional assessment is crucial to provide information about physiological changes in tissues, which can be applied as an early marker during the healing process. Hence, non-invasive monitoring of structural and functional changes in the surrounding tissue during the healing process is essential, and the need for new assessing methods is emerging. This paper provides an assessment of Mg based implants, and an extensive review of the literature is presented with the focus on the imaging techniques for investigation of the Mg implants' biodegradation. The potential of a hybrid analysis, including Near-Infrared Spectroscopy (NIRS) and photoacoustic imaging (PAI) technology, is further discussed. A hybrid solution may play a significant role in monitoring implants and have several advantages for monitoring tissue oxygenation in addition to tissue's acidity, which is directly connected to the Mg implants degradation process. Such a hybrid assessment system can be a simple, ambulant, and less costly technology with the potential for clinically monitoring of Mg implants at site.

From pixel to image analysis

Over the past 50 years, computer technology has evolved enormously. This has made it possible to carry out radiography in a completely new way, allowing to process X-ray images in an advanced manner and to extract the information from the image data. This article gives an overview of some of the most important developments in dental radiology. These include capturing the images, analysing and interpreting the image information and using the images for 3D reconstruction.