No abstract

No abstract

No abstract

No abstract

No abstract

BackgroundAseptic loosening of the tibial component remains a major cause of failure in unicompartmental knee arthroplasty (UKA) and may be related to micro-motion at the cement-bone interface due to insufficient cement penetration depth. Cement penetration is therefore taken as an indicator of solid fixation strength and primary stability. However, its non-invasive clinical assessment remains difficult in vivo as conventional x-ray is prone to distortion and CT-scans (computed tomography) are difficult to assess due to metal artifacts. The purpose of this study was to develop and validate a reliable in vivo measuring technique of cement penetration depth in human tibial UKA.MethodsIn an experimental setting, twelve UKA were implanted in fresh-frozen human cadaver knees using a minimal-invasive medial approach. Cement penetration depth was then measured via 1) virtual 3D-models based on metal artifact reduced CT-scans and 2) histological evaluation of nine serial cross-section cuts through the implant-cement-bone-interface. Subsequently, a concordance analysis between the two measuring techniques was conducted.ResultsThe average cement penetration depth was 1) 2.20 mm (SD 0.30 mm) measured on metal artifact reduced CT-scans and 2) 2.21 mm (SD = 0.42) measured on serial cuts (p = 0.956). The mean difference between both techniques was 0.01 mm (SD 0.31 mm) and the Person correlation coefficient was r = 0.686 (p = 0.014). All differences were within the upper and lower limit of agreement. There was no evidence of any significant proportional bias between both techniques (p = 0.182).ConclusionsCT-based non-invasive measurement of cement penetration depth delivers reliable results in measuring the penetration depth in tibial UKA. Thereby, it enables clinicians and researchers to assess the cement penetration for in vivo diagnostics in the clinical setting as well as in vitro biomechanical research with subsequent application of load to failure on the implant-cement-bone-interface.

Background Periprosthetic joint infection (PPI) is one of the most common reasons for revision in total knee arthroplasty (TKA). Percutaneous synovial biopsy is considered as a well-established diagnostic tool in ambiguous cases of chronic pain after TKA. The exact number of undetected low-grade infections remains unclear. Objectives The aim of this prospective study was to compare the diagnostic accuracy of arthroscopically guided and unguided synovial biopsy. Additionally, the prevalence of initially undetected PPI during synovial biopsy and revision surgery was assessed. Materials and Methods 40 patients suffering from chronic pain after TKA and the clinical suspicion of PPI were included in the study. Synovial biopsies were collected in a standardized manner first without and then with arthroscopic visual control. Using both techniques, six samples were collected each (5 for microbiology, 1 for histology). 19 patients, initially classified aseptic, underwent revision surgery later. Results The diagnosis of PPI was made in 10.0% of unguided biopsies (4 cases, 2× microbiologically, 2× histologically), 7.5% of arthroscopic biopsies (3 cases, 3× histologically) and 12.5% (5 cases, 3× histologically, 2× microbiologically) of all cases. Only histologic evaluation led to concordant positive findings using both techniques in two patients. The proportion of non-representative biopsies was twice as high after unguided tissue collection than after arthroscopic biopsy (30.0 vs. 15.0%). Microbiologic evaluation of arthroscopically collected biopsies did not lead to the diagnosis of PPI, which might have been essential to the selection of the appropriate antimicrobial therapy. During revision surgery the diagnosis of PPI was made in 22.2% of cases. Conclusions In patients suffering from chronic pain after TKA, periprosthetic low-grade infection was diagnosed in a relevant proportion of cases. Therefore, synovial biopsies for histological and microbiological evaluation should be collected whenever thereʼs clinical suspicion of PPI. For histological evaluation, samples should be collected using arthroscopic control and ideally multiple biopsies should be taken. For microbiological evaluation, excessive joint lavage should be avoided.

Background: Unicompartmental knee arthroplasty is an established treatment option for anteromedial osteoarthritis. However, large registry studies report higher rates of aseptic loosening compared to total knee arthroplasty. The objective of this study was to assess the impact of bone density on morphological cement penetration. Moreover, an alternative regional bone density measuring technique was validated against the established bone mineral density assessment. Methods: Components were implanted on the medial side of 18 fresh-frozen cadaver knees using a minimally invasive approach. Bone density has been quantified prior to implantation using Hounsfield units and bone mineral density. Morphological cement penetration has been assessed in different areas and was correlated with local bone density. Findings: A highly significant correlation between Hounsfield units and trabecular bone mineral density was detected (r = 0.93; P < 0.0001), and local bone density was significantly increased in the anterior and posterior area (P = 0.0003). The mean cement penetration depth was 1.5 (SD 0.5 mm), and cement intrusion into trabecular bone was interrupted in 31.8% (SD 23.7%) of the bone-cement interface. Bone density was correlated significantly negative with penetration depth (r = − 0.31; P = 0.023) and positive with interruptions of horizontal interdigitating (r = + 0.33; P = 0.014). Cement penetration around the anchoring peg was not significantly correlated with bone density. Interpretation: Areas with high bone density were characterized by significantly lower penetration depths and significantly higher areas without cement penetration. Anchoring pegs facilitate cement intrusion mechanically. Regional quantification of bone density using Hounsfield units is a simple but valuable extension to the established determination of bone mineral density.