Patientenspezifische Instrumente und Implantate beim Teilgelenkersatz des Kniegelenkes (ConforMIS iUni, iDuo)

Deferoxamine functionalized alginate-based collagen composite material enhances the integration of metal implant and bone interface

Poor osseointegration markedly compromises the longevity of prostheses. To enhance the stability of titanium implants, surface functionalization is a proven strategy to promote prosthesis-bone integration. This study developed a hydrogel coating capable of simultaneous osteoangiogenesis and vascularization by incorporating deferoxamine (DFO) into a sodium alginate mineralized collagen composite hydrogel. The physicochemical properties of this hydrogel were thoroughly analyzed. In vivo and in vitro experiments confirmed the hydrogel scaffold's osteogenic and angiogenic capabilities. Results indicated that sodium alginate notably enhanced the mechanical characteristics of the mineralized collagen, allowing it to fully infiltrate the interstices of the 3D-printed titanium scaffold. Furthermore, as the hydrogel degraded, collagen, calcium ion, phosphate ion, and DFO were gradually released around the scaffolds, altering the local osteogenic microenvironment and strongly inducing new bone tissue growth. These findings offer novel perspectives for the creation and utilization of functionalized bone implant materials.

Insufficient evidence to confirm benefits of custom partial knee arthroplasty: a systematic review

PURPOSE

The purpose of this systematic review was to synthesise the available literature and critically appraise current evidence on the functional and radiographic outcomes as well as reoperation and revision rates of custom partial knee arthroplasty, i.e., unicompartmental knee arthroplasty (UKA), bicompartmental knee arthroplasty (BKA), and patellofemoral arthroplasty (PFA).

MATERIAL AND METHODS

This systematic review was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and a protocol was registered with Prospero. On 25 May 2021, two authors independently searched and screened Level I-IV studies that reported on outcomes of custom partial knee arthroplasty using the databases of MEDLINE^®, EMBASE^®, and the Cochrane Library without restriction on date of publication. Findings from eligible articles were synthesised and tabulated, and quality assessments were done according to the guidelines of the Joanna Briggs Institute (JBI) Checklists.

RESULTS

Fifteen articles were eligible for data extraction, of which two comparative and four case series were on custom UKA (follow-up, 0-9 months), one comparative and five case series on custom BKA (follow-up, 0.25-72 months), and three case series on custom PFA (follow-up, 2-119 months). Three studies on custom UKA reported mean Knee Society Score (KSS) Knee of 86-94 and mean KSS Function of 94-95, and two studies on custom BKA reported mean KSS Knee of 90-94 and KSS function of 81, whereas one study on custom PFA reported KSS Knee of 91 and KSS Function of 89. Custom implants tended to have less bone-implant mismatch compared to off the shelf (OTS) implants. Revision rates were 3-25% for custom UKA (at 0-109 months), 3-5% for custom BKA (at 12-72 months), and 0-14% for custom PFA (at 2-119 months).

CONCLUSION

Due to the small number of comparative studies and lack of consistency in reported outcomes, it remains difficult to ascertain the benefits of custom partial knee arthroplasty. Anecdotal evidence suggests that, compared to OTS implants, custom implants result in less bone-implant mismatch and that 78-91% of patients are either satisfied or very satisfied after custom partial knee arthroplasty.

LEVEL OF EVIDENCE

IV.

Anatomic Total Shoulder Arthroplasty: Component Size Prediction with 3-Dimensional Pre-Operative Digital Planning

Background

The rate, complexity, and cost of total shoulder arthroplasty (TSA) continues to grow. Technology has advanced pre-operative templating. Reducing cost of TSA has positive impact for the patient, manufacturer, and hospital. The aim of this study was to evaluate the accuracy of implant size selection based on 3-D templating. Our hypothesis was that pre-operative templating would enable accurate implant prediction within one size.

Methods

Multicenter retrospective study of anatomic TSAs templated utilizing 3-D virtual planning technology. This program uses computed tomography (CT) scans allowing the surgeon to predict component sizes of the glenoid and humeral head and stem. Pre-operative templated implant size were compared to actual implant size at the time of surgery. Primary data analysis utilized unweighted Cohen's Kappa test.

Results

111 TSAs were analyzed from five surgeons. Pre-operative templated glenoid sizes were within one size of actual implant in 99% and exactly matched in 89%. For patients requiring a posterior glenoid augment (n = 14), 100% of implants were within one size of the template and 93% matched exactly. For stemless humeral components (n = 87) implanted, 98% matched the pre-operative template within one size with 79% exactly matched. For stemmed components (n = 24), 88% of cases were within one size of the preoperative plan and exactly matching in 83%. Humeral head diameter matched within one size of the pre-operative template in 84% of cases and exactly matched in 72%.

Conclusion

Pre-operative 3-D templating for TSAs can accurately predict glenoid and humeral component size. This study sets the groundwork for utilization of pre-operative 3-D templating as a potential method to reduce overall TSA costs by managing cost of implants, reducing inventory needs, and improving surgical efficiency.

Relevant changes of leg alignment after customised individually made bicompartmental knee arthroplasty due to overstuffing

PURPOSE

The purpose of this study is to analyse the change in knee alignment after customised individually made (CIM) bicompartmental knee arthroplasty (BKA) and the subsequent consequences for patellar tracking.

METHODS

Medical records of 23 patients who received 26 CIM BKA (ConforMIS iDuo G2) at our clinic between November 2015 and July 2018 were reviewed. The objective part of the Knee Society Score (KSS), the hip-knee-ankle angle (HKA), the tibial mechanical angle (TMA) and femoral mechanical angle (FMA) were recorded preoperative and four months postoperative. Leg alignment was classified as neutral (HKA = 180° ± 3°), varus (HKA < 177°) or valgus (HKA > 183°). Furthermore, patellar tracking was determined on skyline view radiographs and adverse events were recorded. Implant survival rate was determined with the Kaplan-Meier method. Patient-reported outcome measures (PROMs) were pain, satisfaction, overall improvement and if the patient would undergo the surgery again.

RESULTS

The mean KSS improved from 61 points preoperative [standard deviation (SD) 14] to 90 points postoperative (SD 7, p < 0.001). The mean change for HKA was 6.3° (SD 3.5), for TMA 1.5° (SD 1.2) and for FMA 3.8° (SD 2.3). Postoperative leg alignment was neutral in 13 CIM BKA (50%), varus in two (8%) and valgus in 11 (42%) and patella tracking was central in 19 CIM BKA (73%) and lateral in seven (27%), respectively. Adverse events occurred in five CIM BKA: three patients required a patella resurfacing and one patient with bilateral CIM BKA needed a revision to a total knee arthroplasty. Implant survival rate was 92.3% at a follow-up of 3.2 years (SD 0.8). PROMs for CIM BKA without revision surgery were available at a mean follow-up of 3.2 years (SD 0.8). Mean pain with level walking decreased to 0.8 points (SD 1.4, p < 0.001) and mean pain with stairs or inclines to 1.6 points (SD 1.3, p < 0.001). Patient satisfaction was very satisfied or satisfied (78%), neutral (17%) or unsatisfied (4%). Overall improvement was much better or considerably better for 91% of all patients; 87% would undergo the surgery again.

CONCLUSION

A relevant change of the leg axis away from the treated femorotibial compartment due to overstuffing was observed. Although, neutral leg alignment was not restored in every case, clinical and patient-reported outcomes improved significantly. Further studies with long-term clinical and patient-reported outcomes are required to evaluate whether patients with bicompartmental knee osteoarthritis benefit from CIM BKA.

LEVEL OF EVIDENCE

IV, case series.

Design and Development of An Instrumented Knee Joint for Quantifying Ligament Displacements

Recently, robotic assistive leg exoskeletons have gained popularity because an increased number of people crave for powered devices to run faster and longer or carry heavier loads. However, these powered devices have the potential to impair knee ligaments. This work was aimed to develop an instrumented knee joint via rapid prototyping that measures the displacements of the four major knee ligaments—the anterior cruciate ligament (ACL), posterior crucial ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL)—to quantify the strain experienced by these ligaments. The knee model consists of a femur, lateral and medial menisci, and a tibia-fibula, which were printed from three dimensional (3D) imaging scans. Nonstretchable cords served as main fiber bundles of the ligaments with their desired stiffnesses provided by springs. The displacement of each cord was obtained via a rotary encoder mechanism, and the leg flexion angle was acquired via a closed-loop four-bar linkage of a diamond shape. The displacements were corroborated by published data, demonstrating the profiles of the displacement curves agreed with known results. The paper shows the feasibility of developing a subject-specific knee joint via rapid prototyping that is capable of quantifying the ligament strain via rapid prototyping.

Customised bi-compartmental knee arthroplasty shows encouraging 3-year results: findings of a prospective, multicenter study

PURPOSE

The purpose of this study was to assess the clinical and patient-reported outcomes of a customised, individually made (CIM) bi-compartmental knee arthroplasty (BKA).

METHODS

A prospectively recruited cohort of 79 patients was implanted with a CIM-BKA (patello-femoral plus either medial or lateral tibio-femoral, iDuo G2 system, Conformis, Billerica MA) at eight centres in the US and Germany. Patients were assessed for the 2011 KSS, KOOS, and ROM pre-operatively and at 2 weeks, 6 weeks, 12 weeks, 1 year, and 2 years post-operatively.

RESULTS

The objective KSS score significantly improved from 69 at the pre-operative visit, to 94 at the 2-year post-operative time-point. Similar improvements were observed for the KSS function and satisfaction domains. Significant improvements from pre-operative levels were observed across all five domains of the KOOS. Two patients have undergone surgery to revise their CIM-BKA implant to total knees, resulting in a survivorship rate of 97.5% at an average follow-up of 2.6 years.

CONCLUSIONS

CIM-BKA compares favourably to published scores as well as revision rates for previously available monolithic OTS-BKA implants. CIM-BKA implants provide surgeons with a viable and patient-specific monolithic implant solution as an option for patients presenting with bi-compartmental disease, who might, otherwise, be treated by performing uni-condylar + patello-femoral joint or bicruciate sparing TKA surgeries. Longer follow-up and higher numbers have to be awaited for further validation of these encouraging early results.

LEVEL OF EVIDENCE

3b (individual case-controlled study).

[Current concepts and new developments of 3D printing in trauma surgery]

The use of 3D printing (synonyms "rapid prototyping" and "additive manufacturing") has played an increasing role in the industry for many years and finds more and more interest and application in musculoskeletal surgery, especially orthopedic trauma surgery.In this article the current literature is systematically reviewed, presented and evaluated in a condensed and comprehensive way according to anatomical (upper and lower extremities) and functional aspects. As many of the publications analyzed were feasibility studies, the degree of evidence is low and methodological weaknesses are obvious and numerous; however, this pioneering work is extremely stimulating and important for further development because the technical, medical and economic potential of this technology is huge and interesting for all those involved in the treatment of musculoskeletal problems.

Patient satisfaction - A comparison between patient-specific implants and conventional total knee arthroplasty

Background

Despite recent innovations in total knee arthroplasty, 20% of the patients are not completely satisfied with the clinical results. Regarding patient-specific implants (PSI), the study aims to compare individual and off-the-shelf implant (OSI) total knee arthroplasty (TKA) concerning the postoperative outcome like function and global patient satisfaction.

Methods

In 2013/14 228 patients received a TKA due to primary osteoarthritis with an indication for a bicondylar, cruciate retaining prosthesis. 125 patients received a PSI and 103 an OSI TKA. The outcome after surgery was evaluated retrospectively by two questionnaires and a clinical follow-up examination. The Knee Society Score (KSS) was used to evaluate function. To compare the satisfaction the Knee Injury and Osteoarthrosis Outcome Score (KOOS) and a modified EuroQol (EQ) including five additional questions were used. Finally, 84 patients with PSI and 57 with OSI completed follow-up.

Results

Concerning demographic data, the PSI group showed a significantly younger age, five years on average. The ROM was comparable in both groups. The KSS and the separate function score achieved significantly better results in the PSI group. For subjects with PSI TKA, the global satisfaction showed significant better values.

Conclusions

The significantly higher values in KSS and its function score lead to a better basic daily function in PSI group. In addition, the PSI TKA achieved a higher global patient satisfaction. Nevertheless, both should mainly be assessed in the context of average younger age and the influence of expectations.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

Evaluation of implant fit and frontal plane alignment after bi-compartmental knee arthroplasty using patient-specific instruments and implants

INTRODUCTION

The goals of successful bi-compartmental knee arthroplasty are to achieve correct fit and positioning of the implant, while appropriately correcting the mechanical alignment of the leg after surgery. As these requirements are not always reliably fulfilled using off-the-shelf implant systems, newer approaches for bi-compartmental resurfacing have been explored.

MATERIAL AND METHODS

In this article we report the radiographic results of 30 patients with anteromedial osteoarthritis (OA) who were treated with a novel patient-specific fixed-bearing bi-compartmental knee resurfacing system using custom-made implants and instruments. Utilizing standardized pre- and postoperative radiographic analyses (based on anterior-posterior and lateral, anterior-posterior weight-bearing full-length radiographs, patella skyline views and preoperative computed tomography (CT) scanning) implant fit and positioning as well as correction of the mechanical axis (hip-knee-ankle angle, HKA) were determined.

RESULTS

On average, HKA was corrected from 173.4 ±3.47° preoperatively to 179.4 ±2.85° postoperatively. The coronal femoro-tibial angle was corrected on average 5.61°. The preoperative tibial slope measured on lateral views was 6.38 ±2.4°, while the average slope in the CT-based planning protocol (iView) was 6.14 ±2.40°. Postoperative lateral tibial slope was determined to be 5.77 ±1.97°. The thickness of the posterior femoral cuts was measured intraoperatively and, in all cases, corresponded well to the targeted thickness of the cuts provided by the iView. The joint line was preserved in all cases and the average Insall-Salvati index was 1.078 ±0.11 pre- and 1.072 ±0.11 postoperatively. The fit of the implant components measured by over- or underhang was excellent throughout (< 1.01 mm).

CONCLUSIONS

Custom-made bicompartmental knee arthroplasty can ensure optimized fitting and positioning of the implant with restoration of the leg axis. These implants could be considered as an alternative primary solution for knee surgeons treating bi-compartmental disease.

Bicompartmental individualized knee replacement : Use of patient-specific implants and instruments (iDuo™)

OBJECTIVE

Bicompartmental knee replacement in patients with combined osteoarthritis (OA) of the medial or lateral and patellofemoral compartment. Patient-specific instruments and implants (ConforMIS iDuo™) with a planning protocol for optimal implant fit.

INDICATIONS

Bicompartmental OA of the knee (Kellgren & Lawrence stage IV) affecting both the medial or lateral and patellofemoral compartment after unsuccessful conservative or joint-preserving surgery.

CONTRAINDICATIONS

Tricompartmental OA, knee ligament instabilities, knee deformities >15° (varus, valgus, extension deficit). Relative contraindication: body mass index >40; prior unicompartmental knee replacement or osteotomies.

SURGICAL TECHNIQUE

Midline or parapatellar medial skin incision, medial arthrotomy; identify mechanical contact zone of the intact femoral condyle (linea terminalis); remove remaining cartilage and all osteophytes that may interfere with the correct placement of the individually designed instruments. Balance knee in extension with patient-specific balancing chips. Resection of proximal tibia with an individual cutting block; confirm axial alignment using an extramedullary alignment guide, balance flexion gap using spacer blocks in 90° flexion. Final femur preparation with resection of the anterior trochlea. After balancing and identification of insert heights, final tibial preparation is performed. Implant is cemented in 45° of knee flexion. Remove excess cement and final irrigation, followed by closure.

POSTOPERATIVE MANAGEMENT

Sterile wound dressing; compressive bandage. No limitation of active/passive range of motion (ROM). Partial weight bearing the first 2 weeks, then transition to full weight bearing. Follow-up directly after surgery, at 12 and 52 weeks, then every 1-2 years.

RESULTS

In all, 44 patients with bicompartmental OA of the medial and patellofemoral compartment were treated. Mean age 59 years. Minimum follow-up 12 months. Implant converted to TKA due to tibial loosening (1 patient); patella resurfacing (3 patients). No further revisions or complications. Radiographic analyses demonstrated ideal fit of the implant with less than 2 mm subsidence or overhang. KSS pain scores improved from preoperatively 5.7 to 1.7 postoperatively with level walking, and from 7.3 preoperatively to 2.8 postoperatively with climbing stairs or inclines. The WOMAC score improved from preoperatively 43 to 79 postoperatively.