ObjectivesWound complications are reported in up to 10% hip and knee arthroplasties and there is a proven association between wound complications and deep prosthetic infections. In this randomised controlled trial (RCT) we explore the potential benefits of a portable, single use, incisional negative pressure wound therapy dressing (iNPWTd) on wound exudate, length of stay (LOS), wound complications, dressing changes and cost-effectiveness following total hip and knee arthroplasties.MethodsA total of 220 patients undergoing elective primary total hip and knee arthroplasties were recruited into in a non-blinded RCT. For the final analysis there were 102 patients in the study group and 107 in the control group.ResultsAn improvement was seen in the study (iNPWTd) group compared to control in all areas. Peak post-surgical wound exudate was significantly reduced (p = 0.007). Overall LOS reduction (0.9 days, 95% confidence interval (CI) -0.2 to 2.5) was not significant (p = 0.07) but there was a significant reduction in patients with extreme values of LOS in the iNPWTd group (Moses test, p = 0.003). There was a significantly reduced number of dressing changes (mean difference 1.7, 95% CI 0.8 to 2.5, p = 0.002), and a trend to a significant four-fold reduction in reported post-operative surgical wound complications (8.4% control; 2.0% iNPWTd, p = 0.06).ConclusionsBased on the results of this RCT incisional negative pressure wound therapy dressings have a beneficial role in patients undergoing primary hip and knee arthroplasty to achieve predictable length of stay, especially to eliminate excessive hospital stay, and minimise wound complications.Cite this article: S. L. Karlakki, A. K. Hamad, C. Whittall, N. M. Graham, R. D. Banerjee, J. H. Kuiper. Incisional negative pressure wound therapy dressings (iNPWTd) in routine primary hip and knee arthroplasties: A randomised controlled trial. Bone Joint Res 2016;5:328–337. DOI: 10.1302/2046-3758.58.BJR-2016-0022.R1

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Autologous Chondrocyte Implantation (ACI) is a cell-based therapy used mainly for the treatment of chondral defects in the knee. It involves surgically inserting isolated chondrocytes or mesenchymal stem cells (MSCs), previously expanded in culture, into the defect region. These chondrocytes then proliferate and migrate, in the process forming extracellular matrix (ECM) and new cartilage. In the case of MSCs, the process of forming new cartilage is initiated only after differentiation of the stem cells into chondrocytes. Many details of the repair process following insertion in humans are unknown. To enable better understanding of the repair process, we present a mathematical model of cartilage regeneration after cell therapy. The key mechanisms involved in the regeneration process are simulated by modelling cell migration, proliferation and differentiation, nutrient diffusion and depletion, and ECM synthesis and degradation at the defect site, both spatially and temporally. The model successfully simulates the progression of cartilage regeneration. The model predicts a time frame of about 18 months for the defect to reach full maturation which corresponds with results from clinical studies and demonstrates that cartilage regeneration is a slow process. Moreover, the model also suggests that regeneration using stem cells alone is no better than that using chondrocytes. The stem cells need to first differentiate into chondrocytes before forming ECM and new cartilage, a process that is initiated only after the stem cell density exceeds a threshold value. Furthermore, with chondrocytes alone, the matrix seems to develop from the subchondral bone interface as compared to the normal cartilage interface, in the case of stem cells alone. The influence of initial conditions and parameters, such as the initial cell seeding densities and cell proliferation rates, are shown to not significantly influence the general evolution characteristics other than accelerating the initial growth process. The model presented here is a first approach towards better understanding of cartilage regeneration after cell therapy techniques.

This paper addresses an anomaly which exists in the current literature regarding stress fractures. Analysis of the data on fatigue strength of bone samples in vitro would conclude that these fractures should never occur at the strain levels known to occur in vivo. This anomaly can be resolved by including in the analysis the effect of stressed volume, whereby larger volumes of material are expected to have worse fatigue properties. A Weibull analysis was used to predict the probability of failure, pt; this was an upperbound prediction because it did not include the effects of remodelling and adaptation. Combining this analysis with a finite element model of the human tibia, we predicted a Pf value of 21% after five weeks of strenuous exercise, which is comparable with reported incidences in military personnel. The high incidence of stress fractures in the cannon bone of racehorses could also be predicted (Pr = 62'%, compared to 70% experimentally). The approach can be used to investigate the effect of variables in the exercise regime such as the distance run per day and the use of improved footwear. It can also predict the increased risk of stress fractures in elderly people. The results suggest certain simple rules which may be of clinical value in designing exercise regimes and in understanding the risk factors for this type of injury.

High hopes have been pinned on regenerative medicine strategies in order to prevent the progression of cartilage damage to osteoarthritis, particularly by autologous chondrocyte implantation (ACI). The loss of chondrocyte phenotype during in vitro monolayer expansion, a necessary step to obtain sufficient cell numbers, may be a key limitation in ACI. In this study, it was determined whether a shorter monolayer expansion approach could improve chondrogenic differentiation. The effects of two supplement types, foetal bovine serum (FBS) and Stemulate™ (a commercial source of human platelet lysate), on the expansion and re-differentiation potential of human chondrocytes, isolated from five individuals, were compared. Chondrocytes were expanded with 10 % FBS or 10 % Stemulate™. Pellets were cultured for 28 d in chondrogenic differentiation medium and assessed for the presence of cartilage matrix molecules and genes associated with chondrogenicity. Stemulate™ significantly enhanced the proliferation rate [average population doubling times: FBS, 25.07 ± 6.98 d (standard error of the mean, SEM) vs. Stemulate™, 13.10 ± 2.57 d (SEM)]. Sulphated glycosaminoglycans (sGAG), total collagen and qRT-PCR analyses of cartilage genes showed that FBS-expanded chondrocytes demonstrated significantly better chondrogenic capacity than Stemulate™-expanded chondrocytes. Histologically, FBS-expanded chondrocyte pellets appeared to be more stable, with a more intense staining for toluidine blue, indicating a greater chondrogenic capacity. Although Stemulate™ positively influenced chondrocyte proliferation, it had a negative effect on chondrogenic differentiation potential. This suggested that, in the treatment of cartilage defects, Stemulate™ might not be the ideal supplement for expanding chondrocytes (which maintained a chondrocyte phenotype) and, hence, for cell therapies (including ACI).

HighlightsExpression of orphan receptor GPR15/BOB was examined in RA and non-RA subjects.GPR15/BOB protein was observed on macrophages in synovia and increased in RA.GPR15/BOB messenger RNA was detected in all RA and a minority of non-RA synovia.GPR15/BOB protein increased on blood monocytes and neutrophils in RA.The orphan receptor is up-regulated in a chronic inflammatory disease.

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The role of bone-graft extenders in impaction revision surgery is becoming increasingly important. Tricalcium phosphate and hydroxyapatite have been shown to be both biocompatible and osteoconductive, yet many surgeons remain reluctant to use them. The difficulty in handling bone-graft extenders can be partly alleviated by using porous particles and adding clotted blood. In an in vitro model we measured the cohesive properties of various impaction graft mixes. Several factors were evaluated including the use of pure bone graft compared with mixes with extender, washing the bone and the addition of clotted blood. Our findings showed that pure allograft bone particles had significantly higher cohesion than when mixed with extender (p < 0.001). Washing had no effect on cohesion. The addition of clotted blood significantly increased the cohesion of both pure bone (p < 0.019) and mixes with pure bone and with porous graft extender (p < 0.044).