The use of the constrained prosthesis in the difficult primary knee arthroplasty

Background: The constrained knee prosthesis has the basic indication in revision arthroplasty, but the latest literature reveals that it takes place also in primary total knee arthroplasty in cases of knee osteoarthritis associated with major deformities. Material and methods: Present study is based on the surgical treatment, using the constrained knee prosthesis in the primary total knee arthroplasty, during 2019-2021, of 28 patients with knee osteoarthritis associated with severe deformities in varus or valgus, in the Big Joint Replacement Department, Clinical Hospital of Traumatology and Orthopedics, Chisinau. Results: In this study, the following criteria were evaluated: the type of deformity – valgus (10 cases) and varus (18 cases); the degree of deformation – for varus knees was on average 300 , and for valgus knee – 250 ; bone attrition – 11 cases with bone defects where it was necessary to use augmentations; affected side – in 19 cases the right knee was affected and 9 cases the left one; the women/men ratio was 4/1; the mean age of the patients was 67.5 years; average duration of the intervention – 140 minutes; in 5 cases a lateral para-patellar approach was performed, of which 2 cases with tibial tuberosity osteotomy; complications – 1 case with intra-operative periprosthetic fracture and 2 cases with superficial infections of the operated joints. Conclusions: Osteoarthritis of the knee progresses rapidly, leading to severe deformities, significant bone defects and joint instability, which are indications to use the constrained prosthesis in the primary total knee arthroplasty, long-term follow-up is necessary to obtain the last conclusion, but from this study the constrained knee prosthesis like primary implant for special indication had promising results.

OP220 What Factors Do Clinicians Value Most In Selecting Physician Preference Items? A Survey Among Italian Orthopaedists

IntroductionPhysician preference items (PPIs) are high-cost medical devices on which clinicians express firm preferences with respect to a particular manufacturer and a specific product. The aim of this research is to understand what are the most important factors, as well as their relative importance, in the choice of new PPIs (that is, hip or knee prosthesis) adoption on behalf of orthopaedic clinicians in Italy.MethodsBased on a literature review and clinical experts’ opinions, we identified a number of key factors (for example, health technology assessment (HTA) recommendation) and their corresponding levels (for example positive HTA recommendation). We administered an online survey to hospital orthopaedists using two experimental techniques for preference elicitation (that is, discrete choice experiment (DCE) and case 1 best-worst scaling (BWS)). BWS data were analysed through descriptive statistics (that is, best-minus-worst score) and conditional logit model. A mixed logit model was applied to DCE data, and a willingness-to-pay (WTP) was estimated. All analyses were conducted using Stata 16.ResultsA total of ninety orthopaedists (95% male; mean age: 52.8 years) were enrolled in the survey. In BWS, the most important factor was ‘clinical evidence’, followed by ‘quality of products’, ‘HTA recommendations’ and ‘previous experience’, while the least important was ‘cost’. DCE results suggested that orthopaedists prefer high-quality products with robust clinical evidence, positive HTA recommendation and affordable cost, and for which clinicians have a consolidated experience of use and a good relationship with the sales representative. The WTP for a high-quality product was estimated at EUR1,733, and for a good relationship at EUR2,843.ConclusionsThis is the first study aimed at analysing the multidimensionality of clinician's decision-making process in selecting new PPIs in orthopaedics in Italy. Despite the quality of products being declared as one of the most important dimensions in BWS, when other factors populate a hypothetical DCE scenario, physicians are not willing to accept quality at any cost (for example, high quality and very bad support from the producer or with uncertain clinical evidence).

Intra-wound vancomycin powder for the eradication of periprosthetic joint infection after debridement and implant exchange: experimental study in a rat model

Background Intra-wound vancomycin powder (VP) has been used in clinical practice to prevent periprosthetic joint infection (PJI) after primary knee/hip arthroplasty. The role of intra-wound VP in the setting of debridement and implant exchange after PJI remains undefined. This study aimed to explore the efficacy and safety of intra-wound VP in the control of methicillin-resistant S. aureus (MRSA) infection after debridement and implant exchange. Methods PJI modeling by knee prosthesis implantation and MRSA inoculation, debridement and implant exchange were performed in Wistar rats successively to mimic the one-stage exchange arthroplasty of PJI patients. Two weeks of systemic vancomycin (SV) or/and intraoperative intra-wound VP of single dosage were applied after revision surgery. Results No post-surgery deaths, incision complications and signs of drug toxicity were observed. The microbial counts of SV or intra-wound VP group were significantly reduced compared with the control group, while bacteria were still detected on the bone, soft-tissue and prosthesis. The elimination of bacterial counts, along with improvement of tissue inflammation and serum inflammatory markers, were observed in the rats with SV plus intra-wound VP. Serum levels of vancomycin in all groups were lower than that of causing nephrotoxicity, while no statistic difference was observed in the serum biochemical marker among the groups. Conclusions Intra-wound VP is effective after debridement and implant exchange in our current rat PJI model. Neither SV nor intra-wound VP alone could eradicate the bacteria within a two-weeks treatment course, while SV plus intra-wound VP could eliminate the MRSA infection, without notable hepatic or renal toxicity and any incision complications.

Defect free optimization of a polycentric prosthetic knee design using imperialist competition-inspired optimization method

The disability of lower limbs is one of the major problems facing human lives. In order to restore the missing functionality and aesthetic feature of the amputee's locomotion, finding the optimal design of the human lower limb knee prosthesis is crucial. This paper focuses the design optimization of a four bar knee mechanism capable to reproduce the complex flexion/extension knee joint motion in the sagittal plane with variable instantaneous center of rotation positions. Thus an optimization approach with appropriate constraints is formulated in order to consider the degree of compatibility between the instantaneous center of rotation trajectories of the human reference knee joint and the four bar knee mechanism. To solve this high nonlinear optimization problem, an algorithm based on multi-objective modified imperialist competitive method is proposed where all the constraints are managed with the penalty method. The results obtained by the multi-objective modified imperialist competitive method showed the capability to reach a small tracking error. The obtained results prove the effectiveness of the proposed optimization approach for the optimal synthesis of the four bar knee mechanism, compared with other literature techniques.