Increased risk of aseptic loosening for posterior stabilized compared with posterior cruciate-retaining uncemented total knee replacements: a cohort study of 13,667 knees from the Dutch Arthroplasty Registry.

BACKGROUND AND PURPOSE: While registry studies have suggested a higher risk of revision for posterior-stabilized (PS) compared with posterior cruciate-retaining (CR) total knee replacements (TKR) using cement, it is unknown whether this is also the case for uncemented TKR. We aimed to compare the revision rates of PS and CR designs in patients receiving primary uncemented TKR. PATIENTS AND METHODS: Data from the Dutch arthroplasty register (LROI) was analyzed, comprising 12,226 uncemented primary CR TKRs and 750 uncemented PS TKRs registered between 2007 and 2022. Competing risk and multivariable Cox regression analyses were used to compare revision rates, risks of revision, and reasons for revision between groups. Sensitivity analyses were performed to analyze the risk, concerning the 5 most commonly used implants and performing hospitals for each group. RESULTS: Uncemented PS TKRs had higher 10-year revision rates for any reason and aseptic loosening (6.5%, 95% confidence interval [CI] 4.6-9.2 and 3.9%, CI 2.6-6.7) compared with uncemented CR TKRs (4.2%, CI 3.8-4.7 and 1.4%, CI 1.2-1.7). PS TKRs were 1.4 and 2.5 times more likely to be revised for any reason and aseptic loosening, respectively. These results remained consistent after adjustment for age, sex, BMI, previous surgeries, bearing mobility, and surface modification, with sensitivity analyses. CONCLUSION: We found that uncemented PS implants have a higher rate of revision than uncemented CR implants, mainly due to a higher risk of aseptic loosening.

6-month migration sufficient for evaluation of total knee replacements: a systematic review and meta-analysis.

BACKGROUND AND PURPOSE: This updated meta-analysis evaluates the migration pattern of the tibial component of primary total knee replacements measured with radiostereometric analysis (RSA). We aimed to evaluate whether 6-month maximum total point motion (MTPM) values could be used instead of 1-year MTPM for RSA threshold testing and to present the pooled migration patterns for different implant designs that can be used as a benchmark. PATIENTS AND METHODS: The search included all published RSA studies on migration patterns of tibial components until 2023. Study groups were classified according to their prosthesis brand, fixation, and insert (PFI). Sub-analyses were performed to compare the mean tibial component migration patterns of different implant variables, stratified according to fixation. RESULTS: 96 studies (43 new studies), including 197 study groups and 4,706 knees, were included. Most migration occurred within the first 6 postoperative months (126 study groups: mean 0.58 mm, 95% confidence interval [CI] 0.50-0.65), followed by minimal migration between 6 and 12 months (197 study groups: mean 0.04 mm, CI 0.03-0.06), irrespective of the fixation method used. Distinct migration patterns were observed among the different fixation methods. No differences were found in migration patterns among cemented components in any of the sub-group analyses conducted. For uncemented implants, trabecular metal surfaced components seemed to migrate less than porous-coated or uncoated components Conclusion: Based on the small difference between MTPM values at 6 months and 1 year, MTPM at 6 months could be used instead of MTPM at 1 year for RSA threshold testing. The pooled migration patterns can be used as benchmark for evaluation of new implants by defining fixation-specific RSA thresholds when combined with implant survival.

Antimicrobial activity of ion-substituted calcium phosphates: A systematic review.

In this systematic review, the antimicrobial effect of ion-substituted calcium phosphate biomaterials was quantitatively assessed. The literature was systematically searched up to the 6th of December 2021. Study selection and data extraction was performed in duplo by two independent reviewers with a modified version of the OHAT tool for risk of bias assessment. Any differences were resolved by consensus or by a referee. A mixed effects model was used to investigate the relation between the degree of ionic substitution and bacterial reduction. Of 1016 identified studies, 108 were included in the analysis. The methodological quality of included studies ranged from 6 to 16 out of 18 (average 11.4). Selenite, copper, zinc, rubidium, gadolinium, silver and samarium had a clear antimicrobial effect, with a log reduction in bacteria count of 0.23, 1.8, 2.1, 3.6, 5.8, 7.4 and 10 per atomic% of substitution, respectively. There was considerable between-study variation, which could partially be explained by differences in material formulation, study quality and microbial strain. Future research should focus on clinically relevant scenarios in vitro and the translation to in vivo prevention of PJI.

Influence of surface characteristics of implant materials on MRSA biofilm formation and effects of antimicrobial treatment.

Introduction: One of the main causes of treatment failure in bacterial prosthetic joint infections (PJI) is biofilm formation. The topography of the biofilm may be associated with susceptibility to antimicrobial treatment. The aims of this study were to assess differences in topography of biofilms on different implant materials and the correlation thereof with susceptibility to antimicrobial treatment. Methods: Methicillin-resistant Staphylococcus aureus (MRSA) 7-day mature biofilms were generated on disks made from titanium alloys (Ti-6Al-7Nb and Ti-6Al-4V), synthetic polymer and orthopedic bone cement, commonly used in implant surgery. The surface topography of these implant materials and the biofilms cultured on them was assessed using atomic force microscopy. This provided detailed images, as well as average roughness (Ra) and peak-to-valley roughness (Rt) values in nanometers, of the biofilm and the material surfaces. Bacterial counts within biofilms were assessed microbiologically. Antimicrobial treatment of biofilms was performed by 24-h exposure to the combination of rifampicin and ciprofloxacin in concentrations of 1-, 5- and 10-times the minimal bactericidal concentration (MBC). Finally, treatment-induced differences in bacterial loads and their correlation with biofilm surface parameters were assessed. Results: The biofilm surfaces on titanium alloys Ti-6Al-7Nb (Ra = 186 nm) and Ti-6Al-4V (Ra = 270 nm) were less rough than those of biofilms on silicone (Ra = 636 nm). The highest roughness was observed for biofilms on orthopedic bone cement with an Ra of 1,551 nm. Interestingly, the roughness parameters of the titanium alloys themselves were lower than the value for silicone, whereas the surface of the bone cement was the roughest. Treatment with 1- and 5-times the MBC of antibiotics resulted in inter-material differences in colony forming units (CFU) counts, ultimately showing comparable reductions of 2.4-3.0 log CFU/mL at the highest tested concentration. No significant differences in bacterial loads within MRSA biofilms were observed between the various implant materials, upon exposure to increasing concentrations of antibiotics. Discussion: The surface parameters of MRSA biofilms were determined by those of the implant materials on which they were formed. The antibiotic susceptibility of MRSA biofilms on the various tested implant materials did not differ, indicating that the efficacy of antibiotics was not affected by the roughness of the biofilm.

Evaluation of Quality of Lower Limb Arthroplasty Observational Studies Using the Assessment of Quality in Lower Limb Arthroplasty (AQUILA) Checklist.

UNLABELLED: This study used the assessment of quality in lower limb arthroplasty (AQUILA) checklist to assess the quality of lower limb arthroplasty observational studies. Among 132 studies the mean reporting quality score was 5.4 (SD=1.2) out of 8 possible points. Most studies adequately reported reasons for revisions (98%) and prosthesis brand and fixation (95%) in sufficient detail. Only 3% of studies adequately reported the number of patients unwilling to participate, 15% stated a clear primary research question or hypothesis, 11% reported a worst-case analysis or competing risk analysis for endpoints, and 42% reported more than 5% of patients were lost to follow-up. There is significant room for improvement in the reporting and methodology of lower limb arthroplasty observational studies. LEVEL OF EVIDENCE: Level III.

Alternative humeral tubercle fixation in shoulder hemiarthroplasty for fractures of the proximal humerus.

HYPOTHESIS: We hypothesize that the sling technique provides better long term tuberosity fixation in hemiarthroplasty for severe fractures of the proximal humerus. BACKGROUND: After hemiarthroplasty for proximal humeral fractures, problems exist with deterioration of shoulder function by secondary displacement of the initially fixated humeral tuberosities. This study evaluated a new technique for fixation of the greater and lesser tuberosities in uncemented hemiarthroplasties in severely displaced 3- or 4-part proximal humeral fractures. MATERIALS AND METHODS: A consecutive series of 31 uncemented hemiarthroplasties using the new sling technique to repair the tuberosities was evaluated clinically and radiographically with special emphasis on the head-to-tuberosity distance (HTD). A historical cohort of 10 similar uncemented hemiarthroplasties was the control group in which the drill-hole technique was used for fixation of the humeral tuberosities. RESULTS: The sling technique had an overall better tuberosity positioning in terms of HTD compared with the drill-hole technique (8 vs 1 mm; P = .025, U test). There were significantly more normal HTD values in the sling-technique group (81% vs 44%; P = .032, chi(2) test). In the anatomic HTD group, the Constant score (70 vs 52; P = .009), patient satisfaction (7.1 vs 5.7; P = .038), and visual analog scale score (3.2 vs 5.2; P = .025) were statistically significantly superior compared with the nonanatomic HTD group. CONCLUSION AND DISCUSSION: The sling technique for tuberosity fixation seems to provide solid fixation. In this study, anatomic HTD fixation was associated with significantly better functional outcome, patient satisfaction, and pain scores.