Surgical treatment of fragility sacrum fractures with percutaneous sacroiliac (SI) screw fixation is associated with high failure rates in terms of screw loosening, cut-through and turn-out. The latter is a common cause for complications, being detected in up to 20% of the patients. The aim of this study was to develop a new screw-in-screw concept and prototype implant for fragility sacrum fracture fixation and test it biomechanically versus transsacral and SI screw fixations. Twenty-seven artificial pelves with discontinued symphysis and a vertical osteotomy in zone 1 after Denis were assigned to three groups (n = 9) for implantation of their right sites with either an SI screw, the new screw-in-screw implant, or a transsacral screw. All specimens were biomechanically tested to failure in upright position with the right ilium constrained. Validated setup and test protocol were used for complex axial and torsional loading, applied through the S1 vertebral body. Interfragmentary movements were captured via optical motion tracking. Screw motions in the bone were evaluated by means of triggered anteroposterior X-rays. Interfragmentary movements and implant motions in terms of pull-out, cut-through, tilt, and turn-out were significantly higher for SI screw fixation compared to both transsacral screw and screw-in-screw fixations. In addition, transsacral screw and screw-in-screw fixations revealed similar construct stability. Moreover, screw-in-screw fixation successfully prevented turn-out of the implant, that remained at 0° rotation around the nominal screw axis unexceptionally during testing. From biomechanical perspective, fragility sacrum fracture fixation with the new screw-in-screw implant prototype provides higher stability than with the use of one SI screw, being able to successfully prevent turn-out. Moreover, it combines the higher stability of transsacral screw fixation with the less risky operational procedure of SI screw fixation and can be considered as their alternative treatment option

Variations in pelvic anatomy are a major risk factor for misplaced percutaneous sacroiliac screws used to treat unstable posterior pelvic ring injuries. A better understanding of pelvic morphology improves preoperative planning and therefore minimises the risk of malpositioned screws, neurological or vascular injuries, failed fixation or malreduction. Hence a classification system which identifies the clinically important anatomical variations of the sacrum would improve communication among pelvic surgeons and inform treatment strategy. 300 Pelvic CT scans from skeletally mature trauma patients that did not have pre-existing posterior pelvic pathology were identified. Axial and coronal transosseous corridor widths at both S1 and S2 were recorded. Additionally, the S1 lateral mass angle were also calculated. Pelvises were classified based upon the sacroiliac joint (SIJ) height using the midpoint of the anterior cortex of L5 as a reference point. Four distinct types could be identified:. Type-A – SIJ height is above the midpoint of the anterior cortex of the L5 vertebra. Type-B – SIJ height is between the midpoint and the lowest point of the anterior cortex of the L5 vertebra. Type-C – SIJ height is below the lowest point of the anterior cortex of the L5 vertebra. Type-D – a subgroup for those with a lumbosacral transitional vertebra, in particular a sacralised L5. Differences in transosseous corridor widths and lateral mass angles between classification types were assessed using two-way ANOVAs. Type-B was the most common pelvic type followed by Type-A, Type-C, and Type-D. Significant differences in the axial and coronal corridors was observed for all pelvic types at each level. Lateral mass angles increased from Types-A to C, but were smaller in Type-D. This classification system offers a guide to surgeons navigating variable pelvic anatomy and understanding how it is associated with the differences in transosseous sacral corridors. It can assist surgeons’ preoperative planning of screw position, choice of fixation or the need for technological assistance

Background. The anterior-posterior (AP) pelvis radiograph is crucial for diagnosis of neck of femur (NOF) fractures, especially as this is one of the commonest fractures in the elderly population. Anecdotally we found that initial AP pelvis radiographs for these suspected fractures did not always exhibit the bones sufficiently. Repeat radiographs were needed, leading to delays in diagnosis, treatment, and repeated radiation exposure. Missed diagnoses can have significant consequences for this patient group. We assessed how many initial AP pelvis radiographs taken for suspected NOF fracture fitted criteria for adequate diagnostic imaging. Methods. A retrospective study was carried out assessing the initial AP pelvis radiograph done for each patient presenting to our dedicated NOF unit with suspected NOF fracture for 1st June – 31st July 2014. European Guidelines for Diagnostic Imaging were used as the benchmark. Each radiograph was scored out of six, one for each criteria fulfilled. Guidelines deemed images scoring ≤3 as inadequate. Results. 76 images were assessed with mean patient age 85 years. 51.3% of images scored ≤3 and mean score was 3.59. The least-met criterion was “sharp reproduction of sacrum and vertebral foramina” (26.3%). Crucially only 52.6% achieved “visually sharp reproduction of spongiosa, trochanters and corticalis of both femurs”, important in diagnosis of NOF fractures. Conclusion. More than half initial AP pelvis radiographs taken for suspected NOF fracture were inadequate based on European Guidelines at a dedicated NOF unit. Part of the difficulty can be attributed to challenging patient demographics, however adequate initial radiographs should be aimed for, as repeat radiographs can lead to delays in diagnosis and treatment as well as repeated radiation exposure. Missed diagnoses can have significant consequences for this patient group; we particularly recommend care to be taken to sharply visualise the trochanters and proximal femora to avoid missing subtle fractures

Background. The measurement of pelvic kinematics is key to the analysis of aberrant movement patterns of lower back, yet to date technical issues of skin artefacts, body composition and optical motion tracking sensor occlusion [1] are unresolved. Methods. In this study, an alternative technical pelvic coordinate system to the standard right and left anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) is developed and evaluated in two healthy male subjects (slim and overweight). The alternative system consists of a cluster of 3 retro-reflective markers attached to the Sacrum, thus allowing position and motion of the pelvis to be measured. In order to use these technical markers a static trial must be performed. The ASISs were calibrated relative to the technical frame; and the anatomical frame of the pelvis was defined relative to the technical coordinate frame. Each participant completed 5 walking trials and the angular rotations of the two methods were investigated using Euler angles. Results. Results from both methods are in agreement with literature (posterior/anterior tilt −4°, Obliquity −2.3°, and posterior/anterior rotation 4.58°). Conclusions. The two methods were markedly different for the overweight subject, yet these were more similar for the slim subject. This allows the hypothesis to be developed that as the two methods are similar for the slim subject, the method that shows greater similarity between the slim and overweight measures is most likely to be the more robust measurement system. This is the case for the novel method; therefore this hypothesis should be tested in future studies. Conflicts of interest. None. Sources of funding. None

Osteoarthritis is a joint condition affecting an estimated eight million people in the UK. The kinematics of walking and the impact experienced are thought to play an important role in the initiation and progression of the disease. Previous studies have looked the effect of osteoarthritis on the kinematics of walking in a laboratory environment. This work is part of the Newcastle Thousand Families Study which has followed a cohort of 1142 members since birth in 1947. Optoelectronic gait analysis methods are unsuitable for this environment, so inertial measurement units are being used. This study focuses on the validation of a protocol using inertial sensors to assess gait in the clinical environment. The sensors measure orientation in three dimensions. Our hypothesis was that an attachment position that minimises the movement of the sensor relative to the segment during gait was more important than the proximity of the sensor to anatomical landmarks. The effect of sampling rate, fatty tissue movement and material type were also tested Seven sensors (Xsens, Netherlands) were attached to participants on top of the foot, on the tibial plateau, on the lateral surface of the femur 10cm proximal to the lateral epicondyle, and over the sacrum. Attachment is by Velcro straps over the top of clothing for the waist, thigh and shank sensors, and with double-sided hypoallergenic tape on the foot. Four calibration movements are performed followed by a walking trial of ten paces down a corridor at a self-selected speed. Data is recorded wirelessly at a sampling rate of 50Hz. The calibration movements and trials are repeated twice and the time taken is 20 minutes. Measurement of the joint angles in the sagittal plane was used to assess the effect of changing the sensor position, simulating fatty tissue movement, and variation of material type underneath the sensor. The foot and thigh sensors were displaced in the distal direction by up to 10cm, the shank and waist sensors were displaced in the proximal direction by 5cm. Material types of different elasticity were tested. Fatty tissue movement beneath the straps was simulated using hydration gel packs. Each attachment scenario was repeated five times on a single subject. A “normal” attachment scenario was used to establish a baseline for repeatability of hip, knee and ankle angle measurement (mean±standard deviation of 49±1.28°, 61.5±1.28° and 33.5±0.69° respectively). Repeatability is comparable to that reported for an opto-electronic system (45±1.8°, 63±1.9° and 36±1.5°). Displacement of the foot, shank and waist sensors had no effect on the repeatability. Displacement of the thigh sensor decreased the repeatability for the knee and hip joint angles (52±3.22° and 62.5±2.91°). As the thigh sensor moved closer to the knee the movement artefact experienced increased. Altering sampling rate and simulated fatty tissue did not decrease repeatability. Of the materials tested, denim had the greatest affect, decreasing hip and knee angle repeatability (50.0±2.04° and 61.0±1.75°). A sensor attachment position that minimises sensor movement relative to the segment has been shown to produce the greatest repeatability, irrespective of their proximity to bony landmarks. This is particularly true for the femur sensor

In order to determine the potential for an internervous safe zone, 20 hips from human cadavers were dissected to map out the precise pattern of innervation of the hip capsule. The results were illustrated in the form of a clock face. The reference point for measurement was the inferior acetabular notch, representing six o’clock. Capsular branches from between five and seven nerves contributed to each hip joint, and were found to innervate the capsule in a relatively constant pattern. An internervous safe zone was identified anterosuperiorly in an arc of 45° between the positions of one o’clock and half past two.

Our study shows that there is an internervous zone that could be safely used in a capsule-retaining anterior, anterolateral or lateral approach to the hip, or during portal placement in hip arthroscopy.

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.