Introduction and Objective

Found in bone-associated prosthesis, Cutibacterium acnes (C. acnes) is isolated in more than 50% of osteoarticular prosthesis infections, particularly those involving shoulder prostheses. Ongoing controversies exist concerning the origin of C. acnes infection. Few reports construct a reasonable hypothesis about probable contaminant displaced from the superficial skin into the surgical wound. Indeed, despite strict aseptic procedures, transecting the sebaceous glands after incision might result in C. acnes leakage into the surgical wound. More recently, the presence of commensal C. acnes in deep intra-articular tissues was reported. C. acnes was thus detected in the intracellular compartment of macrophages and stromal cells in 62.5% of the tested patients who did not undergo skin penetration. Among bone stromal cells, mesenchymal stem cells (MSCs) are predominantly found in bone marrow and periosteum. MSCs are the source of osteogenic lines of cells capable of forming bone matter. In this study, the pathogenicity of C. acnes in bone repair context was investigated.

Prosthetic Joint Infections (PJIs) are increasing with the use of orthopedic devices on an ageing population. Cutibacterium acnes is a commensal organism that plays an important role in the ecosystem healthy human skin, yet this species is also recognized as a pathogen in foreign body infection: endocarditis, prostatitis and specifically in PJIs. C. acnes is able to escape the immune system. This phenomenon could reflect two bacterial behaviour: the bacterial internalization by host cells and the biofilm formation. In this study, we studied different clinical strains of C. acnes. We noticed that C. acnes isolated from PJIs form 2 fold-more biofilm than the strains isolated from a normal skin in two models (Crystal violet staining and fluorescent microscopy (p=0.04 and p=0.02, respectively, Mann-Whitney test). We did not observe any difference in the internalization rate of those strains by osteoblasts. However, the quantity of biofilm formed by C. acnes before and after the internalization was compared. A significant increase in biofilm formation was observed for the strains isolated from the skin (x2.3±0.07; p=0.008, Mann-Whitney test). However, the hydrophobicity of the skin strains is significantly less important than for the PJIs strains (24.8±13% vs 56.6±12% respectively; p=0.003, Mann-Whitney test) but this did not change after internalization suggesting that there is no cell wall evolution. In conclusion, we studied for the first time the impact of bacterial internalization by osteoblasts on the virulent behaviour of C. acnes, which could explain the hided pathogenicity of this commensal bacterium.

Aim

Chronic osteomyelitis of the calcaneus is a frequent problem in a population of diabetic patients, patients with neurologic disorders or bedridden patients with ulcers. Partial calcanectomy is an alternative option which avoid major amputation. The aim of this retrospective study was to determine the effectiveness of partial calcanectomy for treating chronic osteomyelitis of the calcaneux.

Accurate and reproducible measurement of three-dimensional shoulder kinematics would contribute to better understanding shoulder mechanics, and therefore to better diagnosing and treating shoulder pathologies. Current techniques of 3D kinematics analysis use external markers (acromial cluster or scapula locator) or medical imaging (MRI or CT-Scan). However those methods present some drawbacks such as skin movements for external markers or cost and irradiation for imaging techniques. The EOS low dose biplanar X-Rays system can be used to track the scapula, humerus and thorax for different arm elevation positions. The aim of this study is to propose a novel method to study scapulo-thoracic kinematics from biplanar X-rays and to assess its reliability during abduction in the scapular plane.

This study is based on the EOS™ system (EOS Imaging, Paris, France), which allows acquisition of 2 calibrated, low dose, orthogonal radiographs with the subject standing at 30 to 40° angle of coronal rotation to the plane of one of the X-ray beams, in order to limit superimposition with the ribcage and spine. Seven abduction positions in the scapular plane were maintained by the subjects for 10 seconds, during X-ray acquisition. Between two positions, the subjects returned at rest position. Arm elevations were approximately 0, 10, 20, 30, 60, 90 and 150° (position 1 to 7). Six subjects were enrolled to perform a reproducibility study based on the 3D reconstructions of 2 experienced observers three times each. For each subject, a personalised 3D reconstruction of the scapula was created. The observer digitises clearly visible anatomical landmarks on both stereoradiographs for each arm position. These landmarks are used to make a first adjustment of a parameterised 3D model of the scapula. This provides a pre-personalised model of the subject's scapula which is then rigidly registered on each pair of X-rays until its retroprojection fits best on the contours that are visible on the X-rays. The thorax coordinate system (CS) was built following the ISB (International Society of Biomechanics) recommendations. The CS associated to the scapula was a glenoid centred CS based on the ellipse which fit on the glenoid rim on the 3D model of scapula. Scapular CS orientation and translation in the thorax CS was calculated following a Y,X,Z angle sequence for each position.

Each 3D reconstruction of the scapula was performed in approximately 30 minutes. The most reproducible rotation was upward/downward rotation (along X axis) with a 95% confidence interval (95% CI) from 2.71° to 3.61°. Internal/external rotation and anterior/posterior tilting were comprised respectively between 5.18° to 8.01° and 5.50° to 7.23° (CI 95%). The most reproducible translation was superior-inferior translation (along Y axis) with a 95% CI from 1.22mm to 2.46mm. Translation along X axis (antero-posterior) and Z axis (medio-lateral) were comprised respectively between 2.49mm to 4.26mm and 2.47mm to 3.30mm (CI 95%).

We presented a new technique for 3D functional quantitative analysis of the scapulo-thoracic joint. This technique can be used with confidence; uncertainty of the measures seems acceptable compared to the literature. Main advantages of this technique are the very low dose irradiation compared to the CT-Scan and the possibility to study arm elevation above 120°.

Purpose of the study: Within the framework of a regional study, we compared the efficacy of pinning using the PY technique and the Kapandji method for the treatment of fractures of the distal radius with posterior displacement.

Material and methods: This was a prospective study designed as a phase III randomised therapeutic trial in parallel groups. An open monocentric study with multiple operators compared the PY and Kapandji techniques. Two comparable groups were established: the PY group and the Kapandji group (K) for which we measured: quality of reduction using the radiographic frontal and sagittal radial inclination (FRI and SRI), radial length and inferior radioulnar index. Objective and subjective functional outcome assessed range of motion and the DASH and Jakim scores. The quality of the intra-articular reduction of articular fractures was assessed arthroscopically at the time of implant removal during the sixth week.

Results: The series included 97 patients followed for one year. The preoperative FRI was 15.17 with mean posterior shift of −19.2. At one year, the RI was 25.5 in the PY group versus 22.6 in the K group (p=0.009) and the SRI 10.5 in the PY group versus 3.7 in the K group (p=0.04). For fractures with a posteromedian fragment and Gerard-Marchand fractures, the DASH at one year was 2 in the PY group versus 32 in the K group. The Jakim score was 71 in the PY group versus 58 in the K group (p=0.03) for posteromedian fragment fractures. The arthroscopic control at six weeks of articular fractures did not reveal any significant difference in intra-articular reduction. There were no tendon tears in this series.

Discussion: This series shows the quality of pin fixation for wrist fractures, comparable with plating. It emphasizes the importance of adapting the type of pinning to the fracture type and the patient.

Conclusion: Treatment of fractures of the distal radius with posterior displacement with pin fixation remains a treatment of choice, reserving PY osteosynthesis for fractures with a posteromedian fragment and Gerard-Marchand fractures and Kapandji osteosynthsis for simple Colles fractures.