Injury incidence and specific injury patterns in app-based bodyweight training (Freeletics): results of an international survey with 3668 participants.

BACKGROUND: The aim of this study was to analyze incidences and sport-specific injury patterns among users of a bodyweight-based training method instructed by a smartphone app (Freeletics Bodyweight App). METHODS: An online questionnaire based on current validated epidemiological observation methods was designed using the statistic website Surveymonkey. Subscribers of the Freeletics Bodyweight App were contacted via an online link. Injury incidence, defined as an event leading to a training pause of at least 1 day, was recorded. The type of injury was reported and classified. Furthermore, all participants were asked whether they recognized any positive or negative effects on their subjective health status. The collected data were analyzed using Surveymonkey statistic services. RESULTS: A total of 4365 Freeletics users responded to the questionnaire, 3668 completed forms were subject of further investigation. The injury period prevalence reported by users of the Freeletics App was 24% in men and 21% in women. The most frequently reported site of injury was the shoulder (29%) and the knee joint (28%), with strains (28.5%) and other muscle injuries (14.4%) being the most frequently reported types of injuries. An injury incidence rate of 4.57 per 1000 h was calculated, with injuries occurring less frequently in experienced users. Most participants reported a distinct positive effect of the app-based training on their health status. CONCLUSION: In comparison to other sports activities app-based bodyweight training is associated with a comparably low injury period prevalence. The vast majority of injuries were reported to have resolved within one week.

Abnormal bone architecture in mice expressing MyD88 in cells of the osteoclast lineage.

The adapter protein myeloid differentiation primary response gene 88 (MyD88) links the intracellular domains of interleukin receptors 1 and 18, and most Toll-like receptors (TLRs) to interleukin 1 receptor associated kinase (IRAK) signaling and subsequent NF-κB-mediated transcription. Previous work showed that mice with global deficiency of MyD88 (MyD88-/-) have osteopenic cancellous bone along with a reduction in osteoblastic but also osteoclastic surfaces. To further elucidate the role of MyD88 in bone, we utilized mice with osteoclast-restricted MyD88 expression in bone (MyD88OC). Bones of MyD88OC and wild type (wt) mice were examined by microCT analysis. Mechanical properties of bones were tested by three-point bending, and gene expression measured using quantitative real-time polymerase chain reaction. In MyD88OC mice, no osteopenic traits were observed, however, a drastic reduction in geometric parameters was detected. In trabecular bone a loss of connectivity density (-44%, p less than 0.0001) was measured and in cortical bone Imax (-31%, p less than 0.0001), Imin (-20%, p less than 0.001), J (-26%, p less than 0.0001) were reduced. Mechanical testing showed increased load to failure (77%, p less than 0.01) and decreased deflection at failure (-68%, p less than 0.01) of the femur. On the molecular level, relative gene expression analysis showed a (-29%, p less than 0.01) reduction in receptor activator of nuclear factor κ B ligand (RANKL) and no difference in osteoprotegerin (OPG) or RANK. Further, the bone resorption markers cathepsin K (CTSK) and tartrate-resistant acid phosphatase 5 (TRAP) were unchanged. In contrast, the bone formation markers collagen type 1 (COL1A1) and osteocalcin (OC) were decreased by -72% (p less than 0.0001) and -82% (p less than 0.0001), respectively. Together, our data suggests that the function of MyD88 in osteoclasts is sufficient to maintain bone mass, while it fails to preserve bone geometry, likely through dysfunctions in osteoblasts.

The natural alpha angle of the femoral head-neck junction: a cross-sectional CT study in 1312 femurs.

Aims: Asphericity of the femoral head-neck junction is common in cam-type femoroacetabular impingement (FAI) and usually quantified using the alpha angle on radiographs or MRI. The aim of this study was to determine the natural alpha angle in a large cohort of patients by continuous circumferential analysis with CT. Methods: CT scans of 1312 femurs of 656 patients were analyzed in this cross-sectional study. There were 362 men and 294 women. Their mean age was 61.2 years (18 to 93). All scans had been performed for reasons other than hip disease. Digital circumferential analysis allowed continuous determination of the alpha angle around the entire head-neck junction. All statistical tests were conducted two-sided; a p-value < 0.05 was considered statistically significant. Results: The mean maximum alpha angle for the cohort was 59.0° (sd 9.4). The maximum was located anterosuperiorly at 01:36 on the clock face, with two additional maxima of asphericity at the posterior and inferior head-neck junction. The mean alpha angle was significantly larger in men (59.4°, sd 8.0) compared with women (53.5°, sd 7.4°; p = 0.0005), and in Caucasians (60.7°, sd 9.0°) compared with Africans (56.3°, sd 8.0; p = 0.007) and Asians (50.8°, sd 7.2; p = 0.0005). The alpha angle showed a weak positive correlation with age (p < 0.05). If measured at commonly used planes of the radially reconstructed CT or MRI, the alpha angle was largely underestimated; measurement at the 01:30 and 02:00 positions showed a mean underestimation of 4° and 6°, respectively. Conclusion: This study provides important data on the normal alpha angle dependent on age, gender, and ethnic origin. The normal alpha angle in men is > 55°, and this should be borne in mind when making a diagnosis of cam-type morphology. Cite this article: Bone Joint J 2018;100-B:570-8.

[Surgical therapy of ischiofemoral impingement by lateralizing intertrochanteric osteotomy]. / Chirurgische Therapie des ischiofemoralen Impingements mittels lateralisierender intertrochantärer Korrekturosteotomie.

OBJECTIVE: Lateralizing, derotating intertrochanteric varus osteotomy to increase the ischiofemoral space to counter painful impingement of the lesser trochanter and the os ischium with resulting entrapment of quadratus femoris muscle. INDICATIONS: Symptomatic ischiofemoral impingement (IFI) caused by Coxa valga et antetorta, Coxa valga or Coxa antetorta, or a short femoral neck. CONTRAINDICATIONS: Anatomic configuration suggestive of IFI in asymptomatic patients. Symptomatic IFI caused by another underlying pathology. Valgus deformity of the knee. SURGICAL TECHNIQUE: Measurement of femoral antetorsion. Planning of the osteotomy, lateralization, varus angle for correction, rotation and offset correction, leg length change, and osteosynthesis plate. General or spinal anesthesia in supine or lateral position. Skin incision (15 cm) beginning lateral of the greater trochanter tip, distally along the axis of the femur. Preparation onto the femur by L­shaped dissection of the vastus lateralis from the bone. A Kirschner(K-)wire is then positioned along the anterior femoral neck to designate the femoral neck antetorsion. A triangle set on the lateral femoral cortexis is used to determine the osteotomy angle. In the thus determined angle, a second K­wire is shot centrally along the femoral neck axis just inferior to its cranial cortex. About 5 mm distal to the second wire, the entry for the blade is prepared using a drill. Using the blade setting instrument, the blade is introduced into the femoral neck, then slightly pulled back. The rotation is then marked on the anterior femoral cortex proximal and distal to the planned osteotomy and the osteotomy is performed. A blade plate without displacement is impacted. The osteotomy is then reduced, the distal fragment pulled laterally onto the plate, and the screws inserted after compression of the osteotomy with a tension device. POSTOPERATIVE MANAGEMENT: Touch-toe bearing for 6 weeks, then radiological assessment of osteotomy healing before an increase in weight bearing (15 kg/week). Hip flexion limited to 90° for 6 weeks. Elective implant removal after 12-18 months. RESULTS: Studies of this lateralizing varus osteotomy have not been published. The 25-year results of the conventional derotating intertrochanteric varus osteotomy technique show good functional results and low complication rates, with non-union being the most common. Arthroscopic resection of the lesser trochanter has been reported as a surgical alternative in the treatment of IFI in case reports and small series. Advantages of the osteotomy are the restoration of biomechanics and preservation of iliopsoas tendon insertion.

[Hip dislocation after revision arthroplasty : Risk assessment and treatment strategies]. / Luxation nach Hüfttotalendoprothesenrevision : Analyse von Risikofaktoren und Lösungsstrategien.

With a dislocation rate of up to 35% after revision total hip arthroplasty (THA), instability is one of the major causes why this procedure fails. Independent factors for patients at risk are age, sex, and the type of revision needed. The surgical approach, implant choice, and positioning of the components are factors that the surgeon can influence to keep the dislocation rate low. Large femoral heads or double mobility (DM) cups can increase the stability of the joint. After detailed failure analysis, targeted use of different technical innovations enhances stability in revision THA and prevents further revisions.

[Importance of revision- and tumor-endoprosthetics in the treatment of periprosthetic fractures of the lower extremity]. / Stellenwert der Revisions- und Tumorendoprothetik bei der Versorgung periprothetischer Frakturen der unteren Extremität.

Periprosthetic fractures of hip and knee prostheses are gaining clinical significance due to the increasing numbers of of primary arthroplasties. Additionally, these fractures are often associated with poor bone quality or present in patients after multiple revision procedures and concomitant excessive bone defects precluding those patients to be adequately treated by conventional osteosynthesis. Revision implants provide a wide range of options for the treatment of these fractures in order to achieve good clinical results. In the acetabular region cavitary defects associated with periprosthetic fractures can be treated by the use of megacups. Extensive segmental defects and pelvic discontinuity necessitate the use of cups with additional iliac support or even customized implants. Proximal femoral fractures can usually be fixed with modular stems and diaphyseal anchorage. Periprosthetic knee joint fractures can be treated with revision implants with modular sleeves or augment-combinations allowing sufficient bridging of bony defects. Functional reconstruction or refixation of the extensor mechanism is of crucial importance.