Metal-on-metal hip implants can produce adverse tissue reactions to wear debris. Increased metal ion concentrations in the blood are measured as a proxy to wear and the complications it can trigger. Many studies have examined various factors influencing the metal ion concentrations. This is the first study to investigate the effect of physical activity level, as objectively measured in daily life, on blood ion levels, expecting higher concentrations for higher patient activity. Thirty-three patients (13F/20M, 55.8 ± 6.2 years at surgery) with a unilateral resurfacing hip prosthesis were included. At last follow-up (6.8 ± 1.5 years) cobalt and chromium concentrations in the blood were determined by inductively coupled plasma mass spectrometry. Physical activity was measured during 4 successive days using a 3D-acceleration-based activity monitor. Data was analysed using validated algorithms, producing quantitative and qualitative parameters. Acetabular cup position was measured radiographically. Correlations were tested with Pearson's r'.Background
Methods
The second generation metal-on-metal (MoM) prosthesis of the hip became a worldwide success in the 90s. However, after the placement of a MoM prosthesis the cobalt ion concentrations raise significantly. This may lead to systemic complaints and even cobalt toxicity. Sixty-one patients (26F/35M) with both an unilateral and bilateral resurfacing or large-head MoM (LHMoM) hip prosthesis were included. At last follow-up (5.77 ± 1.57 yrs) cobalt concentrations in the blood were determined by ICP-MS. Based on the known cobalt toxicity symptoms we developed a non-validated questionnaire. Analysis was done on two groups; a low cobalt concentration group and a high cobalt concentration group. We used 170 nmol/L as the upper limit of well functioning prosthesis as defined by the Dutch Orthopaedic Society (NOV). Independent samples T test and Pearson correlation coefficient were done.Background
Methods
A comparative study on CT- and MRI-based patient specific matched guides (PSG) from the same manufacturer for the implantation of total knee arthroplasty (TKA) has not been undertaken. A total of 64 knees operated with CT based PSG was divided into two groups, with (n=32, CTHK) or without (n=32, CTNA) a history of a knee operation, and matched with a control group operated with MRI based PSG(n=64). Alignment of the biomechanical axis of the leg (HKA angle) and accuracy of individual implant alignment were measured on digital long-standing AP and sagittal radiographs. HKA and implant angles <3° deviation of the preoperative planned alignment were defined as correct. Peroperative implant size, OR time (min) and blood loss (ml) were compared. The average HKA angle in the CTHK group (177.0, 170.5 to 181.5, p=0.016) and mean varus-valgus alignment of the tibia component in the MRI group (90.6, 85.6 to 94.1, p=0.003) were statistically significant different. None of the outcome on the frontal femoral and lateral tibial component were statistically significant different. Percentage <3° deviation of the preoperative planned femoral flexion-extension alignment was better in the MRI group (84%, p=0.002), compared to the CTHK and CTNA group (respectively 30% and 42%). Average operation time was statistically significant shorter in favour of the MRI group (53.1, 34 to 80, p≤0.00), compared to the CTHK(70.8, 44 to 114) and CTNA group (59.2, 41 to 78). There is discrepancy between CT and MRI based PSG from the same manufacture because of patients who were not suitable for MRI due to history of a knee operation in the past. Whether these differences are clinically relevant is questionable. Future research needs to emphasise whether one of these two modalities, MRI or CT is superior compared to the other.
This is the first report of a new technique for unicompartmental to total knee arthroplasty revision surgery in which patient specific guides are formed based on preoperative CT imaging. This technique can help to make revision surgery less technically demanding. Unicompartmental to total knee arthroplasty revision surgery can be a technically demanding procedure. Joint line restoration, rotation and augmentations can cause difficulties. This study describes a new technique in which single way fitting guides serve to position knee system cutting blocks.Summary Statement
Introduction
This paper is the first to compare the results of unicompartmental to total knee arthroplasty revision surgery between cases with explained pain and cases with unexplained pain. Revision surgery for unexplained pain usually results in a less favourable outcome. Although it is suggested in literature that results of UKA to TKA revision surgery improve when the mechanism of failure is understood, a comparative study regarding this topic is lacking.Summary Statement
Introduction
Alignment results did not differ between PSG and conventional instrumentation. A small reduction in operation time and blood loss was found with the PSG system, but is unlikely of clinical significance. Length of hospital stay was identical for both groups. Several techniques for aligning a TKA exist nowadays. Patient-specific guiding (PSG) has relatively recently been introduced to try to resolve the shortcomings of existing techniques while optimising the operative procedure. Still few reports have been published on the clinical outcome and on the peroperative results of this new technique. This prospective, double-blind, randomised controlled trial was designed to address the following research questions: 1. Is there a significant difference in outliers in alignment in the frontal and sagittal plane between PSG TKA and conventional TKA. 2. Is there a significant difference in operation time, blood loss and length of hospital stay between the 2 techniques.Summary
Introduction
Patient-specific guiding (PSG) is a relatively new technique for aligning a total knee arthroplasty (TKA). Limited data exist on the precise accuracy of the technique. The purpose of this study is to investigate whether there was significant difference between the alignment of the individual femoral and tibial components (in all three anatomical planes) as calculated pre-operatively and the actually achieved alignment Twenty-six patients were included. Software permitted matching of the pre-operative MRI-scan (and therefore calculated prosthesis position) to a pre-operative full-leg CT-scan. After surgery a post-operative full-leg CT-scan could be superimposed onto the pre-operative CT-scan to accurately determine deviations from planning (see figure 1 and 2). This 3D-technique has an accuracy of 0.7–1.0 degrees.Background:
Methods:
The full leg x-ray is a widely used imaging modality for post-operative assessment of total knee replacement (TKR). However, these assessments require controlled conditions and precise measuring in order to be accurate. inter-observer reliability remains a matter of concern as well. This study examines whether intersurgeon differences are significant. Post-operative lateral and full-leg frontal x-rays of 26 patients were assessed by 6 surgeons according to a strict measuring protocol. Four measurements (Figure 1 and 2) were taken of which two were on the femur (Femoral Varus Angle FVA and Femoral Flexion Angle FFA) and two, on the tibia (Tibial Varus Angle TVA; Tibial Slope Angle TSA). A random effects, two-way ANOVA was performed on the data using Minitab (v 16.0, Minitab Inc., Pennsylvania, USA) to determine whether a surgeon has influence on the results (α = 0.05). Intra-class correlation coefficients (ICC) and standard error of measurements (SEM) resulting in smallest detectable changes (SDC) were also calculated [1].Background
Method
The mean IL-6 concentration increased from 6.8 (contr) vs 1.3 (MIS) pg/ml to 68.8 (contr) vs 45.1 (MIS) pg/ml 6 hours postoperative. The mean myoglobin concentration increased in TKP group from 47.7 ug/l pre-operative to 90.1 ug/l 6 hours postoperative, the values for MIS were 27.8 μg/l preoperative and 202.3 ug/l 6 hours postoperative, with significant differences at 2, 4, 6 hrs and day 1 post-operative.
