Revision total knee arthroplasty using a novel 3D printed titanium augment: A biomechanical cadaveric study

Three-Dimensional Printed Knee Implants: Insights into Surgeons' Points of View

Three-dimensional printing is a technology that has been developed and applied in several medical specialties, especially orthopedic surgery. Knee arthroplasty is the most commonly performed procedure. To fit the morphology of each knee, surgeons can choose between different standardized off-the-shelf implant sizes or opt for customized 3D-printed implants. However, routine adoption of the latter has been slow and faces several barriers. Existing studies focus on technical improvements or case studies and do not directly address the surgeon's perspective. Our study invited surgeons to express themselves freely and answer the question "What do you think about the manufacture of a prosthesis by 3D printing?". The questionnaire was completed by 90 surgeons. On average, they had more than 10 years of experience (52, 57.8% ± 10.2%), worked in public hospitals (54, 60% ± 10.1%), and performed between 0 and 100 prostheses per year (60, 66.7% ± 9.7%). They also reported not using planning software (47, 52.2% ± 9.7%), navigation systems, or robots (62, 68.9% ± 9.6%). Regarding the use of technological innovation, they agreed on the extra surgical time needed (67, 74.4% ± 9.0%). The answers obtained were classified according to two criteria: (i) opinions, and (ii) motivations. Among the respondents, 51 (70% ± 9.5%) had positive and 22 (30% ± 9.5%) had negative opinions about 3D printing. The motivations were distributed among seven categories (surgery, materials, costs, logistics, time, customization, and regulatory) and mainly related to "pre-surgery" and "post-surgery" concerns. Finally, the results showed that the use of navigation systems or robots may be associated with a more positive view of 3DP. The purpose of our study was to examine knee surgeons' perceptions of 3DP at a time of significant expansion of this technology. Our study showed that there was no opposition to its implementation, although some surgeons indicated that they were waiting for validated results. They also questioned the entire supply chain, including hospitals, insurance companies, and manufacturers. Although there was no opposition to its implementation, 3D printing is at a crucial point in its development and its full adoption will require advances in all areas of joint replacement.

Bioreactor analyses of tissue ingrowth, ongrowth and remodelling around implants: An alternative to live animal testing

Introduction: Preclinical assessment of bone remodelling onto, into or around novel implant technologies is underpinned by a large live animal testing burden. The aim of this study was to explore whether a lab-based bioreactor model could provide similar insight. Method: Twelve ex vivo trabecular bone cylinders were extracted from porcine femora and were implanted with additively manufactured stochastic porous titanium implants. Half were cultured dynamically, in a bioreactor with continuous fluid flow and daily cyclic loading, and half in static well plates. Tissue ongrowth, ingrowth and remodelling around the implants were evaluated with imaging and mechanical testing. Results: For both culture conditions, scanning electron microscopy (SEM) revealed bone ongrowth; widefield, backscatter SEM, micro computed tomography scanning, and histology revealed mineralisation inside the implant pores; and histology revealed woven bone formation and bone resorption around the implant. The imaging evidence of this tissue ongrowth, ingrowth and remodelling around the implant was greater for the dynamically cultured samples, and the mechanical testing revealed that the dynamically cultured samples had approximately three times greater push-through fixation strength (p < 0.05). Discussion: Ex vivo bone models enable the analysis of tissue remodelling onto, into and around porous implants in the lab. While static culture conditions exhibited some characteristics of bony adaptation to implantation, simulating physiological conditions with a bioreactor led to an accelerated response.

Use of Customized 3D-Printed Titanium Augment With Tantalum Trabecular Cup for Large Acetabular Bone Defects in Revision Total Hip Arthroplasty: A Midterm Follow-Up Study

Aims: In revision total hip arthroplasty (THA), large acetabular bone defects pose challenges for surgeons. Recently, wide application of trabecular tantalum, which has outstanding biocompatibility and mechanical properties, and the development of three-dimensional (3D) printing have led to the introduction of new schemes for acetabular reconstruction. However, few studies have focused on the treatment of bone defects with customized 3D-printed titanium augments combined with tantalum trabecular cup. Thus, we aimed to evaluate the effect of this therapy in patients who underwent revision THAs.

Patients and Methods: We included 23 patients with Paprosky type III acetabular bone defects who underwent revision THA between January 2013 and June 2019. The preoperative hip rotation center and functional score were compared with those at 2–7 years (average 4.7 years) postoperatively to evaluate the midterm prognosis of our treatment choice.

Results: Postoperatively, the rotation centres of all hips were comparable with those of the contralateral hips. Hip function improved with average Harris Hip Score improved from 33.5 (22.7–40.2) to 86.1 (73.5–95.6) and average Oxford Hip Score improved from 8.3 (0–14) to 38.8 (35–48) during follow-up. One dislocation, which occurred due to extreme hip flexion within 6 weeks, was treated with closed reduction, and no recurrent dislocation occurred. No nerve injury, infection, aseptic loosening, or osteolysis were observed and no re-revision was performed in any patient.

Conclusion: Satisfactory midterm outcomes were obtained with 3D-printed titanium augment combined with tantalum cup for the treatment of acetabular defects in revision THA. Changes in the Harris Hip Score and Oxford Hip Score suggested a significant improvement in hip function.

Translation of 3D printed materials for medical applications

During the past 30 years, 3D printing (3DP) technologies significantly influenced the manufacturing world, including innovation in biomedical devices. This special issue reviews recent advances in translating 3DP biomaterials and medical devices for metallic, ceramic, and polymeric devices, as well as bioprinting for organ and tissue engineering, along with regulatory issues in 3DP biomaterials. In our introductory article, besides introducing selected 3DP processes for biomaterials, current challenges and growth opportunities are also discussed. Finally, it highlights a few success stories for the 3D printed biomaterials for medical devices. We hope these articles will educate engineers, scientists, and clinicians about recent developments in translational 3DP technologies.

Validity of repeated-measures analyses of in vitro arthroplasty kinematics and kinetics

In vitro models of arthroplasty enable pre-clinical testing and inform clinical decision making. Repeated-measures comparisons maximise resource efficiency, but their validity without testing order randomisation is not known. This study aimed to identify if there were any large testing order effects for cadaveric models of knee and hip arthroplasty. First, the effect of testing order on total knee arthroplasty (TKA) biomechanics was assessed. Extension moments for TKAs (N = 3) implanted into the native knee (TKA-only) were compared to a dataset of TKAs (N = 24) tested after different combinations of partial knee arthroplasty (TKA-last). The effect of repeatedly testing the same knee five times over 36 h on patellofemoral and tibiofemoral kinematics was also quantified. Second, the effect of testing order on capsular ligament function after total hip arthroplasty (THA) was assessed. Randomisation was removed from a previously published dataset to create increasing and decreasing head size groups, which were compared with t-tests. All three TKA-only extension moments fell within the 95% CI of the TKA-last knees across the full range of knee flexion/extension. Repeated testing resulted in root-mean-squared kinematics errors within 1 mm, 1°, or < 5% of total range of motion. Following THA, smaller head-size resulted in greater laxity in both the increasing (p = 0.01) and decreasing (p < 0.001) groups. Testing order did not have large effects on either knee or hip arthroplasty biomechanics measured with in vitro cadaveric models.

A new robotically assisted system for total knee arthroplasty: A sheep model study

BACKGROUND

We investigated the accuracy and safety of a new HURWA robotic-assisted total knee arthroplasty (TKA) system in a sheep model.

METHODS

Ten male small-tailed Han sheep were used in this study. Sheep were imaged by computed tomography scan before and after bone resection and the cutting errors between actual bone preparation and preoperative planning of the femur and tibia in three dimensions were measured.

RESULTS

The overall accuracies after surgery compared with that from preoperative surgical planning of the left and right femurs were 1.93 ± 1.02° and 1.93 ± 1.23°, respectively. Additionally, similarly high overall accuracies for the left and right tibia of 1.26 ± 1.04 and 1.68 ± 0.92°, respectively, were obtained. The gap distances of the distal cut, anterior chamfer, anterior cut, posterior chamfer and posterior cut on the medial side were 0.47 ± 0.35 mm, 0.41 ± 0.37 mm, 0.12 ± 0.26 mm, 0.41 ± 0.44 mm and 0.12 ± 0.23 mm, respectively. No intraoperative complications, such as intraoperative fracture, massive bleeding or death, occurred.

CONCLUSION

This new HURWA robotic-assisted TKA system is an accurate and safe tool for TKA surgery based on the sheep model.