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.

The leading indication for revision total hip arthroplasty (THA) remains aseptic loosening owing to wear. The younger, more active patients currently undergoing THA present unprecedented demands on the bearings. Ceramic-on-ceramic (CoC) bearings have consistently shown the lowest rates of wear. The recent advances, especially involving alumina/zirconia composite ceramic, have led to substantial improvements and good results in vitro.

Alumina/zirconia composite ceramics are extremely hard, scratch resistant and biocompatible. They offer a low co-efficient of friction and superior lubrication and lower rates of wear compared with other bearings. The major disadvantage is the risk of fracture of the ceramic. The new composite ceramic has reduced the risk of fracture of the femoral head to 0.002%. The risk of fracture of the liner is slightly higher (0.02%).

Assuming that the components are introduced without impingement, CoC bearings have major advantages over other bearings. Owing to the superior hardness, they produce less third body wear and are less vulnerable to intra-operative damage.

The improved tribology means that CoC bearings are an excellent choice for young, active patients requiring THA.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):14–17.

Intact abductors of the hip play a crucial role in preventing limping and are known to be damaged through the direct lateral approach. The extent of trauma to the abductors after revision total hip replacement (THR) is unknown. The aim of this prospective study was to compare the pre- and post-operative status of the gluteus medius muscle after revision THR. We prospectively compared changes in the muscle and limping in 30 patients who were awaiting aseptic revision THR and 15 patients undergoing primary THR. The direct lateral approach as described by Hardinge was used for all patients. MRI scans of the gluteus medius and functional analyses were recorded pre-operatively and six months post-operatively. The overall mean fatty degeneration of the gluteus medius increased from 35.8% (1.1 to 98.8) pre-operatively to 41% (1.5 to 99.8) after multiple revision THRs (p = 0.03). There was a similar pattern after primary THR, but with considerably less muscle damage (p = 0.001), indicating progressive muscle damage. Despite an increased incidence of a positive Trendelenburg sign following revision surgery (p = 0.03) there was no relationship between the cumulative fatty degeneration in the gluteus medius and a positive Trendelenburg sign (p = 0.26). The changes associated with other surgical approaches to the hip warrant investigation.

Cite this article: Bone Joint J 2014;96-B:1618–22.

Objectives: Skeletal muscle trauma leads to severe functional deficits. Present therapeutic treatments are unsatisfying and insufficient posttraumatic regeneration is a problem in trauma and orthopaedic surgery. Mesenchymal stem cell (MSC) therapy is a promising tool in the regeneration of muscle function after severe trauma. Our group showed increased contraction forces compared to a non-treated control group 3 weeks after MSC transplantation (TX) into a skeletal muscle trauma. In addition we demonstrated a dose-response relationship of the amount of MSC and force enhancement. We furthermore investigated the fate of the transplanted MSC labelled with very small iron oxide particles using 7 Tesla-MRI. Histological analysis revealed fusion events between existing myofibers but only to a low amount. The increase of muscle force can not be explained by these events only. Before further steps are taken the impact of paracrine effects and the homing to the site of trauma of the MSC has to be evaluated. Experimental studies about the functional regeneration of traumatized skeletal muscule after systemic MSC-TX do not exist.

Methods: 36 female SD-rats received open crush trauma of the left soleus muscle. One week after trauma 2.5 x 106 autologous MSC, harvested from tibial biopsies, were transplanted intraarterially (i.a., femoral arte-ria, group 1) or intravenously (i.v., tail vein, group 2) (n=18). Control animals received saline (i.a.: group 3; i.v.: group 4) (n=18). Histological analysis and biomechanical evaluation by in vivo muscle force measurement was performed 3 weeks after TX.

Results: Twitch stimulation of the healthy right soleus muscles resulted in a contraction force of 0.52±0.14 N. Forces of tetanic contraction in the uninjured muscles reached 0.98±0.27 N. The i.a. MSC-TX improved the muscle force of the injured soleus significantly compared to control (twitch: 82,4%, p=0.02, tetany: 61.6%, p=0.02). Contraction forces of muscles treated i.v. (MSC vs. saline) showed no significant difference. The histological analysis showed no differences in the amount of fibrotic tissue.

Conclusions: The presented study demonstrates the effect of systemic MSC-TX in the treatment of severe skeletal muscle injuries. Interestingly, the functional regeneration could only be increased by i.a. application. The entrapment of MSC in the lungs and the dilution effect in the circulation, when injecting the MSC i.v. could be the reason. For possible future therapeutic approaches a systemic application is considered to be favourable compared to local injections due to the better distribution of the cells in the target muscle.

Skeletal muscle injuries often lead to severe functional deficits. Mesenchymal stem cell (MSC) therapy is a promising but still experimental tool in the regeneration of muscle function after severe trauma. One of the most important questions, which has to be answered prior to a possible future clinical application is the ideal time of transplantation. Due to the initial inflammatory environment we hypothesized that a local injection of the cells immediately after injury would result in an inferior functional outcome compared to a delayed transplantation.

Twenty-seven female Sprague Dawley rats were used for this study. Bone marrow was aspirated from both tibiae of each animal and autologous MSC cultures obtained from the material. The animals were separated into three groups (each n=9) and the left soleus muscles were bluntly crushed in a standardized manner. In group 1 2×106 MSCs were transplanted into the injured muscle immediately after trauma, whereas group 2 and 3 received an injection of saline. Another week later the left soleus muscles of the animals of group 2 were transplanted with the same number of MSCs. Group 1 and 3 received a sham treatment with the application of saline solution in an identical manner. In vivo functional muscle testing was performed four weeks after trauma to quantify muscle regeneration.

Maximum contraction forces after twitch stimulation decreased to 39 ± 18 % of the non injured right control side after crush trauma of the soleus muscles as measured in group 3. Tetanic stimulation showed a reduction of the maximum contraction capacity of 72 ± 12 % of the value obtained from intact internal control muscles. The transplantation of 2 x 106 MSCs one week after trauma improved the functional regeneration of the injured muscles as displayed by significantly higher contraction forces in group 2 (twitch: p = 0.014, tetany: p = 0.018). Local transplantation of the same number of MSCs immediately after crush injury was able to enhance the regeneration process to a similar extent with an increase of maximum twitch contraction forces by 73.3 % (p = 0.006) and of maximum tetanic contraction forces by 49.6 % (p = 0.037) compared to the control group.

The presented results underline the effectivity of MSC transplantation in the treatment of severe skeletal muscle injuries. The most surprising finding was that despite of the fundamental differences of the local environment into which MSCs had been transplanted, similar results could be obtained in respect to functional skeletal muscle regeneration. We assume that the effect of the MSC after immediate injection can partly be explained by their known immunomodulatory competences. The data of our study provide evidence for a large time window of MSC transplantation after muscle trauma.

Background: Autologous mesenchymal stem cells (MSC) have been shown to improve the functional outcome after severe skeletal muscle trauma. The reasons for this improvement have yet not been revealed. Up to now insufficient techniques of cell labelling, which could only be used for histologic analysis ex vivo, have been a problem.

The development of iron oxide nanoparticles, which are taken up and endosomally stored by stem cells, allows the evaluation of cellular behaviour in the muscle with the use of magnetic resonance imaging (MRI). Previous work has shown that labelling does not affect the proliferation and neurogenic differentiation capacity of embryonic stem cells. In the present study we are currently investigating the in vivo distribution and migration of locally transplanted MSC after blunt muscle trauma in a rat model.

Methods: MSC cultures are derived from tibial biopsies of Sprague Dawley rats via plastic adherence. A standardized open crush injury of the left soleus muscle is performed in each animal. 24 hours before transplantation cells are labelled with very small superparamagnetic iron oxid particles (VSOP-C200, Ferropharm, Teltow, Germany) and Green Fluorescent Protein (GFP). One week after trauma different amounts of stem cells (5×105, 1×106 and 5×106) are transplanted into the soleus muscle by local injection. Distribution and migration of the cells are evaluated over time by the repeated performance of high resolution-MRI at 7 Tesla (Bruker, Rheinstetten, Germany). At the endpoint of the study, three and six weeks after transplantation, the muscles are harvested and histologically and immunohistochemically analysed.

Results: Cells could be visualised inside the soleus muscle in the MRI 24 hours after transplantation showing characteristic signal extinctions in T2*-weighed images. The hypointense signal could be followed over the longest investigated time of six weeks and could be easily discriminated from the structures of the injured muscle. Preliminary results show that the cell pool changed its shape over time with the loss of an initially depicted injection canal and an increase in the surface/volume ratio. First histologic Prussian Blue stained sections showed co-localisation of the respective MRI signal and nanoparticle labelled cells. Fusion events of marked cells with regenerating myofibers could be observed.

Conclusion: Magnetic labelling of MSC is a powerful tool to analyse the in vivo behaviour of the cells after transplantation into a severly injured skeletal muscle. For the first time the observation of an intraindividual time course of the distribution of the transplanted cells is possible. Our preliminary results are promising and the ongoing work will further characterise migration processes and the correlation of the MRI results with muscle function evaluated by contraction force measurements.