Mediolateral force distribution at the knee joint shifts across activities and is driven by tibiofemoral alignment

AIMS

Tibiofemoral alignment is important to determine the rate of progression of osteoarthritis and implant survival after total knee arthroplasty (TKA). Normally, surgeons aim for neutral tibiofemoral alignment following TKA, but this has been questioned in recent years. The aim of this study was to evaluate whether varus or valgus alignment indeed leads to increased medial or lateral tibiofemoral forces during static and dynamic weight-bearing activities.

PATIENTS AND METHODS

Tibiofemoral contact forces and moments were measured in nine patients with instrumented knee implants. Medial force ratios were analysed during nine daily activities, including activities with single-limb support (e.g. walking) and double-limb support (e.g. knee bend). Hip-knee-ankle angles in the frontal plane were analysed using full-leg coronal radiographs.

RESULTS

The medial force ratio strongly correlated with the tibiofemoral alignment in the static condition of one-legged stance (R² = 0.88) and dynamic single-limb loading (R² = 0.59) with varus malalignment leading to increased medial force ratios of up to 88%. In contrast, the correlation between leg alignment and magnitude of medial compartment force was much less pronounced. A lateral shift of force occurred during activities with double-limb support and higher knee flexion angles.

CONCLUSION

The medial force ratio depends on both the tibiofemoral alignment and the nature of the activity involved. It cannot be generalised to a single value. Higher medial ratios during single-limb loading are associated with varus malalignment in TKA. The current trend towards a 'constitutional varus' after joint replacement, in terms of overall tibiofemoral alignment, should be considered carefully with respect to the increased medial force ratio. Cite this article: Bone Joint J 2017;99-B:779-87.

In vivo hip joint loads and pedal forces during ergometer cycling

The rising prevalence of osteoarthritis and an increase in total hip replacements calls for attention to potential therapeutic activities. Cycling is considered as a low impact exercise for the hip joint and hence recommended. However, there are limited data about hip joint loading to support this claim. The aim of this study was to measure synchronously the in vivo hip joint loads and pedal forces during cycling. The in vivo hip joint loads were measured in 5 patients with instrumented hip implants. Data were collected at several combinations of power and cadence, at two saddle heights. Joint loads and pedal forces showed strong linear correlation with power. So the relationship between the external pedal forces and internal joint forces was shown. While cycling at different cadences the minimum joint loads were acquired at 60RPM. The lower saddle height configuration results in an approximately 15% increase compared to normal saddle height. The results offered new insights into the actual effects of cycling on the hip joint and can serve as useful tools while developing an optimum cycling regimen for individuals with coxarthrosis or following total hip arthroplasty. Due to the relatively low contact forces, cycling at a moderate power level of 90W at a normal saddle height is suitable for patients.

Synthesis and in vitro Antiviral Properties of Amphiphilic Dinucleoside Phosphate Derivatives of 2′,3-dideoxycytidine (ddC)

N4-hexadecyl-5′-0-(4-monomethoxytrityl)-2′-deoxycytidine-3′-hydrogenphosphonate and 5′-0-(4-monomethoxytrityl)-2′-deoxythymidine-3′-0-hydrogenphosphonate were condensed with 2′,3′-dideoxycytidine (ddC) according to the hydrogenphosphonate method to yield N4-hexadecyl-2′-deoxycytidylyl-(3′-5′)-2′,3′-dideoxycytidine (N4-hexadecyldC-ddC) and 2′-deoxythymidylyl-(3′-5′)-N4-palmitoyl-2′,3′-dideoxycytidine (dT-N4-palmddC). N4-palmitoyl-2′,3′-dideoxycytidine (N4-palmddC) was synthesized by reacting palmitic anhydride with ddC. Both dinucleoside phosphates have amphiphilic properties and represent a new class of ddC derivatives in which in the case of the dinucleosides, the ddC-5′-monophosphate is masked with lipophilic residues of variable stability. The ddC derivatives can be solubilized in water by micelle formation and, because they have lipophilic residues, they can be incorporated into the lipid membranes of liposomes. The ddC derivatives were shown to have antiviral activities comparable to those of AZT and ddC when tested in vitro against HIV-1-infected HeLa and H9 cells as well as infected human monocytes/macrophages.

Systematic selection of small molecules to promote differentiation of embryonic stem cells and experimental validation for generating cardiomyocytes

Small molecules are being increasingly used for inducing the targeted differentiation of stem cells to different cell types. However, until now no systematic method for selecting suitable small molecules for this purpose has been presented. In this work, we propose an integrated and general bioinformatics- and cheminformatics-based approach for selecting small molecules which direct cellular differentiation in the desired way. The approach was successfully experimentally validated for differentiating stem cells into cardiomyocytes. All predicted compounds enhanced expression of cardiac progenitor (Gata4, Nkx2-5 and Mef2c) and mature cardiac markers (Actc1, myh6) significantly during and post-cardiac progenitor formation. The best-performing compound, Famotidine, increased the percentage of Myh6-positive cells from 33 to 56%, and enhanced the expression of Nkx2.5 and Tnnt2 cardiac progenitor and cardiac markers in protein level. The approach employed in the study is applicable to all other stem cell differentiation settings where gene expression data are available.

Prevalence and severity of foot pad alterations in German turkey poults during the early rearing phase

In the previously performed field study from 2007 to 2009, it became evident that foot pad alterations were already commonly found in turkeys at the age of 6 wk. At this early age, 45% of the clinically examined birds were diagnosed with epithelial necrosis. Therefore, it became important to specifically analyze the situation during the early rearing phase. The present study reflects the prevalence and severity of foot pad alterations of turkey poults up to the age of 35 d (5 wk), starting as early as the age of 3 d. From 24 turkey farms throughout Germany, in general 5,531 turkeys [3,131 male and 2,400 female] of the British United Turkeys 6 strain from 46 flocks, were examined to that effect. Prevalence and severity increased within the duration of stay in the stable, and the prevalence was higher (P < 0.001) during the second visit between d 22 to 35 (factor: 0.94). Therefore, 27.3% (d 3 to 5; male/female: 39.1/25.0%) and 63.3% (d 22 to 35: 61.3/65.7%) of the examined poults had alterations of the foot pads, such as hyperkeratosis (d 3 to 5: 20.4/14.2%; d 22 to 35: 17.6/17.1%), high-grade hyperkeratosis with adhesive dirt (d 3 to 5: 8.7/10.7%; d 22 to 35: 29.2/39.3%), and epithelial necrosis (d 3 to 5: 0.1/0.1%; d 22 to 35: 14.6/9.3%). Female poults showed a higher risk (P < 0.001) of developing food pad alterations (factor: 0.76) than male poults. Male poults developed a higher percentage of epithelial necrosis than hens shortly before relocation. A higher stocking density during the very early rearing phase (d 3 to 5) led to a worse foot pad health status (P < 0.001). Because even mild alterations in the foot pad condition can be indicators for suboptimal design of the rearing environment and are to be seen as a pre-state for severe cases of foot pad dermatitis, it is important to set the main focus on the early rearing phase.

Clinicopathological differences between breast cancer in patients with primary metastatic disease and those without: a multicentre study

OBJECTIVE

Approximately 6% of breast cancer (BC) patients present with primary metastatic disease (pmBC) at first diagnosis. The clinicopathological differences between tumours from patients who have metastatic disease and those who do not are unclear.

METHODS

This study was an exploratory analysis of patients with pmBC treated in 8 German breast cancer centres between 1998 and 2010. Phenotypes were defined using the following immunohistochemical markers: oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (Her2). The control arm included the group of patients who had neither local recurrence nor distant metastases at a follow-up of at least 30 months after initial diagnosis.

RESULTS

A total of 2214 patients were included. Of these, 1642 had non metastatic BC, and 572 had pmBC. Eighty-five patients (15%) with pmBC were diagnosed at stage T1. On multivariate analysis, factors associated with pmBC were as follows: positive lymph node status, grade 3, lobular histology and Luminal B phenotype (Her 2 positive). Of the sample, 197 patients (34%) with pmBC were diagnosed as stage T2, 90 patients (16%) were diagnosed as stage T3, and 200 patients (35%) were diagnosed as stage T4. Only positive lymph node status and grade 3 were reported as risk factors for distant metastases in patients with stage T3 and T4 cancer.

CONCLUSION

There are differences in the clinicopathological features among breast cancer patients with primary metastases and those without. Receptor expression and histological type play a minor role in the risk for metastasis in patients with stage T3 and T4 disease when compared to patients with T1 pmBC tumours. On initial diagnosis, lobular histology and Luminal B positivity (Her 2 positive) in T1 pmBC were determined to be risk factors for primary metastatic disease.

In vivo measurement of shoulder joint loads during walking with crutches

BACKGROUND

Following surgery or injury of the lower limbs, the use of walking aids like crutches can cause high loads on the shoulder joint. These loads have been calculated so far with computer models but with strongly varying results.

METHODS

Shoulder joint forces and moments were measured during crutch-assisted walking with complete and partial unloading of the lower limbs. Using telemeterized implants in 6 subjects axillary crutches and forearm crutches were compared. A force direction was more in the direction of the long humeral axis, and slightly lower forces were assumed using axillary crutches. Similar force magnitudes as those experienced during previously measured wheelchair weight relief tasks were expected for complete unloading. The friction-induced moment was hypothesized to act mainly around the medio-lateral axis during the swing phase of the body.

FINDINGS

Maximum loads of up 170% of the bodyweight and 0.8% of the bodyweight times meter were measured with large variations among the patients. Higher forces were found in most of the patients using forearm crutches. The hypothesized predominant moment around the medio-lateral axis was only found in some patients. More often, the other two moments had larger magnitudes with the highest values in female patients. The assumed different load direction could only be found during partial unloading.

INTERPRETATION

In general the force magnitudes were in the range of activities of daily living. However, the number of repetitions during long-lasting crutch use could lead to shoulder problems as a long-term consequence. The slightly lower forces with axillary crutches could be caused by loads acting directly from the crutch on the scapula, thus bypassing the glenohumeral joint. The higher bending moments in the female patients could be a sign of lacking muscle strength for centring the humeral head on the glenoid.