The accuracy of external calibration markers in digital templating using the double marker and single marker method: a comparative study.

BACKGROUND: Digital templating is an essential step in the preoperative planning of total hip arthroplasty (THA). Previous studies have suggested that templating with the double marker method may be more accurate than a single marker method in the general population and in obese patients. The purpose of this study was to compare the accuracy in the preoperative component selection between the King Mark calibration device and the conventional metal ball method. Additionally, we examined whether King Mark offered any advantage over the standard metal ball in the preoperative selection of component sizes for obese patients. METHODS: We retrospectively reviewed patients who underwent preoperative digital templating for THA in our center from January 2014 to January 2016 with King Mark device and marker ball. We compared the preoperative template component size and offset with the intraoperative definite implant size. The accuracy was defined as the difference between preoperative and intraoperative component sizes. The overall accepted calibration was defined as an exact match ± one size. Patients were stratified into two cohorts according to the calibration method: standard marker ball technique and King Mark technique. RESULTS: 126 THA underwent digital calibration. 79 patients underwent a preoperative templating using the King Mark calibration device. 47 patients were templated using a conventional marker ball. The overall adequate preoperative planning of the acetabular cup (exact or ± 1 size match) in the King Mark group did not differ from the single marker method (74.7% and 74.5%, respectively, p = 0.979). No significant difference was noted in the overall accepted calibration of the femoral stem (exact or ± 1 size match) between the marker ball group and the King Mark group (58.2% and 70.2%, respectively, p = 0.179). The King Mark group showed a better preoperative planning for the stem's offset compared to the marker ball group (77.2% % and 61.7%, respectively, p = 0.062). For the obese patient cohort, no significant difference was noted between the King Mark group and the marker ball group in the exact prediction of the acetabular cup and the femoral stem, (p = 0.31 and p = 0.15, respectively). CONCLUSIONS: Our study found no difference between the King Mark method and the conventional metal ball method in the ability to accurately predict component sizes. In the subgroup of obese patients, the King Mark technique offered no advantage for accurately predicting component sizes.

Heparanase is expressed in adult human osteoarthritic cartilage and drives catabolic responses in primary chondrocytes.

OBJECTIVES: The chondrocytes' pericellular matrix acts as a mechanosensor by sequestering growth factors that are bound to heparan sulfate (HS) proteoglycans. Heparanase is the sole mammalian enzyme with HS degrading endoglycosidase activity. Here, we aimed to ascertain whether heparanase plays a role in modulating the anabolic or catabolic responses of human articular chondrocytes. METHODS: Primary chondrocytes were incubated with pro-heparanase and catabolic and anabolic gene expression was analyzed by quantitative polymerase chain reaction (PCR). MMP13 enzymatic activity in the culture medium was measured with a specific fluorescent assay. Extracellular regulated kinase (ERK) phosphorylation was evaluated by Western blot. Human osteoarthritis (OA) cartilage was assessed for heparanase expression by reverse-transcriptase PCR, by Western blot and by a heparanase enzymatic activity assay. RESULTS: Cultured chondrocytes rapidly associated with and activated pro-heparanase. Heparanase induced the catabolic genes MMP13 and ADAMTS4 and the secretion of active MMP13, and down-regulated the anabolic genes ACAN and COL2A1. PG545, a HS-mimetic, inhibited the effects of heparanase. Heparanase expression and enzymatic activity were demonstrated in adult human osteoarthritic cartilage. Heparanase induced ERK phosphorylation in cultured chondrocytes and this could be inhibited by PG545, by fibroblast growth factor 2 (FGF2) neutralizing antibodies and by a FGF-receptor inhibitor. CONCLUSIONS: Heparanase is active in osteoarthritic cartilage and induces catabolic responses in primary human chondrocytes. This response is due, at least in part, to the release of soluble growth factors such as FGF2.

When and where do patients with bone metastases actually break their femurs?

AIMS: Accurate estimations of the risk of fracture due to metastatic bone disease in the femur is essential in order to avoid both under-treatment and over-treatment of patients with an impending pathological fracture. The purpose of the current retrospective in vivo study was to use CT-based finite element analyses (CTFEA) to identify a clear quantitative differentiating factor between patients who are at imminent risk of fracturing their femur and those who are not, and to identify the exact location of maximal weakness where the fracture is most likely to occur. METHODS: Data were collected on 82 patients with femoral metastatic bone disease, 41 of whom did not undergo prophylactic fixation. A total of 15 had a pathological fracture within six months following the CT scan, and 26 were fracture-free during the five months following the scan. The Mirels score and strain fold ratio (SFR) based on CTFEA was computed for all patients. A SFR value of 1.48 was used as the threshold for a pathological fracture. The sensitivity, specificity, positive, and negative predicted values for Mirels score and SFR predictions were computed for nine patients who fractured and 24 who did not, as well as a comparison of areas under the receiver operating characteristic curves (AUC of the ROC curves). RESULTS: The sensitivity of SFR was 100% compared with 88% for the Mirels score, and the specificity of SFR was 67% compared with 38% for the Mirels score. The AUC was 0.905 for SFR compared with 0.578 for the Mirels score (p = 0.008). CONCLUSION: All the patients who sustained a pathological fracture of the femur had an SFR of > 1.48. CTFEA was far better at predicting the risk of fracture and its location accurately compared with the Mirels score. CTFEA is quick and automated and can be incorporated into the protocol of CT scanners. Cite this article: Bone Joint J 2020;102-B(5):638-645.