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Introduction The first weeks after total knee arthroplasty (TKA) are crucial for the functional outcome. To improve knee mobility, a continuous passive motion (CPM) motor rail is commonly used during in-hospital rehabilitation. The single-joint hybrid assistive limb (HAL-SJ) is a new therapy device. The aim of the study was to improve patients’ range of motion (ROM), mobility, and satisfaction using the active-assistive support of the HAL-SJ. Materials and methods Between 09/2017 and 10/2020, 34 patients, who underwent TKA and matched the inclusion criteria, were randomized into study (HAL-SJ) and control (CPM) group. Treatment began after drain removal and was carried out until discharge. Primary outcome parameters were raised pre- and postoperatively and included the Oxford knee score (OKS), visual analog scale (VAS), and acquired range of motion. Furthermore complications caused by the device were recorded. Results OKS increased in both groups postoperatively, but only significantly in the HAL-SJ group. Postoperative pain improved in both groups without significant differences. Flexion improvement was significant in both groups between days 3/7 and 8 weeks postoperatively. We did not encounter any complications related to HAL-SJ. Conclusions In conclusion, use of the HAL-SJ during rehabilitation in the early postoperative period after TKA was safe without disadvantages compared to the control group and seems to have advantages in terms of daily life impairment.

ObjectivesVenous thromboembolism (VTE) is a major potential complication following orthopaedic surgery. Subcutaneously administered enoxaparin has been used as the benchmark to reduce the incidence of VTE. However, concerns have been raised regarding the long-term administration of enoxaparin and its possible negative effects on bone healing and bone density with an increase of the risk of osteoporotic fractures. New oral anticoagulants such as rivaroxaban have recently been introduced, however, there is a lack of information regarding how these drugs affect bone metabolism and post-operative bone healing.MethodsWe measured the migration and proliferation capacity of mesenchymal stem cells (MSCs) under enoxaparin or rivaroxaban treatment for three consecutive weeks, and evaluated effects on MSC mRNA expression of markers for stress and osteogenic differentiation.ResultsWe demonstrate that enoxaparin, but not rivaroxaban, increases the migration potential of MSCs and increases their cell count in line with elevated mRNA expression of C-X-C chemokine receptor type 4 (CXCR4), tumor necrosis factor alpha (TNFα), and alpha-B-crystallin (CryaB). However, a decrease in early osteogenic markers (insulin-like growth factors 1 and 2 (IGF1, IGF2), bone morphogenetic protein2 (BMP2)) indicated inhibitory effects on MSC differentiation into osteoblasts caused by enoxaparin, but not by rivaroxaban.ConclusionsOur findings may explain the adverse effects of enoxaparin treatment on bone healing. Rivaroxaban has no significant impact on MSC metabolism or capacity for osteogenic differentiation in vitro.Cite this article: Dr H. Pilge. Enoxaparin and rivaroxaban have different effects on human mesenchymal stromal cells in the early stages of bone healing. Bone Joint Res 2016;5:95–100. DOI: 10.1302/2046-3758.53.2000595.

BackgroundLow-molecular-weight heparins (e.g. Enoxaparin) are widely used to prevent venous thromboembolism after orthopaedic surgery, but there are reports about serious side effects including reduction in bone density and strength. In recent years new oral antithrombotic drugs (e.g. direct Factor Xa-inhibitor, Rivaroxaban) have been used to prevent venous thromboembolism. However, there is lack of information on the effects of these new drugs on human mesenchymal stromal cells during osteogenic differentiation and, therefore, effects during postoperative bone healing.MethodsWe evaluated the effects of Rivaroxaban and Enoxaparin on the proliferation, mRNA and surface receptor expression as well as differentiation capacity of primary human mesenchymal stromal cells during their osteogenic differentiation.ResultsEnoxaparin, but not Rivaroxaban treatment significantly increased human mesenchymal stromal cell (hMSC) proliferation during the first week of osteogenic differentiation while suppressing osteogenic marker genes, surface receptor expression and calcification.ConclusionsThis is the first paper to demonstrate that Rivaroxaban had no significant influence on hMSC differentiation towards the osteogenic lineage, indicating a less affected bone healing process compared with Enoxaparin in vitro. Based on these findings Rivaroxaban seems to be superior to Enoxaparin in early stages of bone healing in vitro.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-016-0966-2) contains supplementary material, which is available to authorized users.