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BACKGROUND: Total knee arthroplasty (TKA) with all-polyethylene tibial (APT) components has shown comparable survivorship and clinical outcomes to that with metal-backed tibial (MBT). Although MBT is more frequently implanted, APT equivalents are considered a low-cost variant for elderly patients. A biomechanical analysis was assumed to be suitable to compare the response of the periprosthetic tibia after implantation of TKA NexGen APT and MBT equivalent. METHODS: A standardised load model was used representing the highest load achieved during level walking. The geometry and material models were created using computed tomography data. In the analysis, a material model was created that represents a patient with osteopenia. RESULTS: The equivalent strain distribution in the models of cancellous bone with an APT component showed values above 1000 µÎµ in the area below the medial tibial section, with MBT component were primarily localised in the stem tip area. For APT variants, the microstrain values in more than 80% of the volume were in the range from 300 to 1500 µÎµ, MBT only in less than 64% of the volume. CONCLUSION: The effect of APT implantation on the periprosthetic tibia was shown as equal or even superior to that of MBT despite maximum strain values occurring in different locations. On the basis of the strain distribution, the state of the bone tissue was analysed to determine whether bone tissue remodelling or remodelling would occur. Following clinical validation, outcomes could eventually modify the implant selection criteria and lead to more frequent implantation of APT components.

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Numerous studies have compared metal-backed components (MBTs) and all-polyethylene tibial components (APTs), but none of them specifically analysed the clinical results and the overall patient preference in patients who had undergone a staged bilateral knee replacement. The purpose of this study is to compare clinical results, perceived range of motion, and overall implant preference among patients who had undergone staged bilateral knee replacement with an APT and contralateral knee replacement with MBTs. A dataset of 62 patients from a single centre who underwent staged bilateral TKA between 2009 and 2022 was selected and retrospectively analysed. Tibial component removal was performed in three knees overall, all of which had MBTs. The mean measured Knee Score (KS) of knees with APTs was 78.37 and that of contralateral knees with MBTs was 77.4. The mean measured Function (FS) of knees with APTs was 78.22, and that of contralateral knees with MBs was 76.29. The mean flexion angle of knees with APTs was 103.8 and that for knees with MBTs was 101.04 degrees. A total of 54.8% of the patients preferred the knee that received APTs over contralateral MBTs. In our cohort, TKA with an APT in one knee and an MBT in the contralateral knee recorded similar clinical results and perceived ranges of motion. Patients in general preferred the knee that received an APT over contralateral knee with an MBT.

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OBJECTIVES: The purpose of our study was to compare the complication rate and the outcomes of custom-made spacers (C-spacers) and prefabricated articular spacers (P-spacers) in the treatment of periprosthetic infection. PATIENTS AND METHODS: In this retrospective study, 78 patients (44 females, 34 males; mean age: 68.5±9.48 years; range, 47 to 82 years) with articular spacers implanted in our institution were analyzed between January 2009 and December 2019. We recorded implant results as per mechanical complications, infection control, the interval from surgery to definitive hip replacement, and the rate of achieving recovery of joint function after stage two arthroplasty. RESULTS: There were 29 revised spacers; 18 of them were C-spacers and 11 were P-spacers (p=0.0383). A total of 16 dislocations were recorded, of which six were dislocations of C-spacers, and 10 were dislocations of P-spacers (p=0.0082). Additionally, we registered four spacer breakages, all of which occurred in C-spacers (p=0.295). C-spacers failed early, at an mean interval of 2.2 weeks after implantation, and P-spacers failed later, with an mean of 9.3 weeks after implantation (p=0.0187). A total of nine reinfection complications of spacers were registered; only one infection of P-spacers, and eight infections related to C-spacers (p=0.2583). Definitive revision total hip arthroplasty (rTHA) after spacer explantation and successful treatment of the infection occurred in 63 cases out of 78 patients. Definitive rTHA occurred after the use of C-spacers in 41 (78%) patients and after the use of C-spacers in 22 (84%) patients (p=0.7816). C-spacers had a mean interval from spacer implantation to definitive rTHA of 6.56±6.03 months, and P-spacers had a mean interval of 4±1.93 months (p=0.0164). CONCLUSION: Custom-made spacers were shown to have lower mechanical complication rates than prefabricated ones but more infection complications. Prefabricated spacers had more dislocations and fewer breakages. Custom-made spacer mechanical failures occurred earlier compared to prefabricated ones.

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PURPOSE: This study aims to compare total knee replacement (TKA) with NexGen All-Poly (APT) and NexGen Metal-Backed (MBT) in terms of implant survivorship, reasons leading to implant failure and functional results of defined age categories. METHODS: A single-centre, retrospective evaluation of 812 patients who underwent knee replacement with NexGen CR between 2005 and 2021, comparing a modern congruent APT component to a modular MBT equivalent component using a similar surgical technique at a notable mean follow-up duration. Implant survival, functional outcomes using the Knee Society Score and range of motion were evaluated and compared in different age categories. RESULTS: Of the 812 NexGen CR TKAs performed at our institution, 410 (50.4%) used APT components and 402 (49.6%) MBT components. The survival rate of NexGen APT was 97.1% and that of NexGen MBT was 93.2% (p = 0.36). Removal of the implant occurred overall in 15 cases, for MBT in ten cases, and for APT in four cases. The FS was proved to be significantly higher when APT components were implanted in younger patients than for MBT (p = 0.005). A similar range of motion between the components was recorded (p = 0.1926). CONCLUSION: Under defined conditions, we measured the clinical results of implants from a single manufacturer implanted in a single department using a similar surgical technique. Considering the limitations, we suggest that all-polyethylene tibial components are equal or even superior to metal-backed ones across the examined age categories.

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BACKGROUND AND OBJECTIVE: Total knee arthroplasty (TKA) with modern all-polyethylene tibial (APT) components has shown high long-term survival rates and comparable results to those with metal-backed tibial components. Nevertheless, APT components are primarily recommended for older and low-demand patients. There are no evidence-based biomechanical guidelines for orthopaedic surgeons to determine the appropriate lower age limit for implantation of APT components. A biomechanical analysis was assumed to be suitable to evaluate the clinical results in patients under 70 years. The scope of this study was to determine biomechanically the appropriate lower age limit for implantation of APT components. METHODS: To generate data of the highest possible quality, the geometry of the computational models was created based on computed tomography (CT) images of a representative patient. The cortical bone tissue model distinguishes the change in mechanical properties described in three parts from the tibial cut. The cancellous bone material model has a heterogeneous distribution of mechanical properties. The values used to determine the material properties of the tissues were obtained from measurements of a CT dataset comprising 45 patients. RESULTS: Computational modeling showed that in the majority of the periprosthetic volume, the von Mises strain equivalent ranges from 200 to 2700 µÎµ; these strain values induce bone modeling and remodeling. The highest measured deformation value was 2910 µÎµ. There was no significant difference in the induced mechanical response between bone models of the 60-year and 70-year age groups, and there was <3% difference from the 65-year age group. CONCLUSIONS: Considering in silico limitations, we suggest that APT components could be conveniently used on a bone with mechanical properties of the examined age categories. Under defined loading conditions, implantation of TKA with APT components is expected to induce modeling and remodeling of the periprosthetic tibia. Following clinical validation, the results of our study could modify the indication criteria of the procedure, and lead to more frequent implantation of all-polyethylene TKA in younger patients.

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We compared technical issues, postoperative outcomes and surgical complications of total hip arthroplasty when using the harmonic scalpel (HS) when compared with conventional techniques (CT) in a prospective, comparative observational study. Thirty patients undergoing total hip arthroplasty were assessed. Operative time, blood loss in drains, postoperative pain, soft tissue injury and complications were recorded. We found no significant differences between the HS and CT groups at baseline. Mean operative time was longer in the HS group compared with the CT of total hip arthroplasty (61 minutes vs. 54 minutes; P<0.05). We found no difference in postoperative pain using a visual analogue scale score, or use of paracetamol. The use of tramadol was reduced in the HS group compared to CT group at the 7th day (83.3 mg vs. 113.3 mg; P<0.05). Drainage volume was significantly lower in the HS group at 24 hours (332 ml vs. 429 ml; P<0.05) and at 48 hours (429 vs. 537 ml; P<0.05). C-reactive protein blood levels were significantly lower in the HS group 75 mg/l vs. 96 mg/l at the third day (P<0.05) and 26 mg /l vs. 54 mg /l at the seventh day (P<0.01). Creatine kinase blood levels were significantly lower in the HS group at 3 and 7 days (2.4 ukat/l compared to 5.3 ukat/l at the 3rd day (P<0.01), respectively 1.1 ukat/l compared to 1.8 ukat/l at the 7th day (P<0.01). We found no significant differences in blood myoglobin levels between the two groups. The use of the HS may reduce postoperative pain, drainage volume, and soft tissue injury in patients undergoing total hip arthroplasty, which may justify the cost of the technique. The use of HS may have further applications in revision hip arthroplasty and tumour surgery.

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