3D C-arm navigated acromioclavicular joint stabilization.

INTRODUCTION: Surgical treatment options for acromioclavicular joint separations are varied. Frequently, suspension devices (SD) are inserted for stabilization under arthroscopic view. This study investigates the feasibility and accuracy of three-dimensional (3D) digital-volume-tomography (DVT) C-arm navigated implantation with regard to the general trend toward increasingly minimally invasive procedures. MATERIALS AND METHODS: The implantation of a TightRope® suture button system (SD) via a navigated vertical drill channel through the clavicle and coracoid was investigated in 10 synthetic shoulder models with a mobile isocentric C-arm image intensifier setup in the usual parasagittal position. Thereby, in addition the placement of an additive horizontal suture cerclage via a navigated drill channel through the acromion was assessed. RESULTS: All vertical drill channels in the Coracoclavicular (CC) direction could be placed in a line centrally through the clavicle and the coracoid base. The horizontal drill channels in the Acromioclavicular (AC) direction ran strictly in the acromion, without affecting the AC joint or lateral clavicle. All SD could be well inserted and anchored. After tensioning and knotting of the system, the application of the horizontal AC cerclage was easily possible. The image quality was good and all relevant structures could be assessed well. CONCLUSION: Intraoperative 3D DVT imaging of the shoulder joint using a mobile isocentric C-arm in the usual parasagittal position to the patient is possible. Likewise, DVT navigated SD implantation at the AC joint in CC and AC direction on a synthetic shoulder model. By combining both methods, the application in vivo could be possible. Further clinical studies on feasibility and comparison with established methods should be performed.

Individual transducer impulse response characterization method to improve image quality of array-based handheld optoacoustic tomography.

The physical properties of each transducer element play a vital role in the quality of images generated in optoacoustic (photoacoustic) tomography using transducer arrays. Thorough experimental characterization of such systems is often laborious and impractical. A shortcoming of the existing impulse response correction methods, however, is the assumption that all transducers in the array are identical and therefore share one electrical impulse response (EIR). In practice, the EIRs of the transducer elements in the array vary, and the effect of this element-to-element variability on image quality has not been investigated so far, to the best of our knowledge. We hereby propose a robust EIR derivation for individual transducer elements in an array using sparse measurements of the total impulse response (TIR) and by solving the linear system for temporal convolution. Thereafter, we combine a simulated spatial impulse response with the derived individual EIRs to obtain a full characterization of the TIR, which we call individual synthetic TIR. Correcting for individual transducer responses, we demonstrate significant improvement in isotropic resolution, which further enhances the clinical potential of array-based handheld transducers.

[Augmentation techniques for the treatment of osteoporosis-associated fractures of the extremities]. / Augmentationstechniken zur Versorgung osteoporoseassoziierter Frakturen der Extremitäten.

The current demographic development is leading to an increasing number of cases of osteoporosis-related fractures. Affected individuals are typically part of a vulnerable, predominantly geriatric patient group with limited physical resources. Additionally, the pathophysiological characteristics of osteoporotic bones with reduced bone quality and quantity, pose a significant challenge to the osteosynthesis techniques used. Achieving rapid postoperative mobilization and stable weight-bearing osteosynthesis to prevent postoperative medical complications are the main goals of the surgical management. In recent years augmentation techniques have gained in importance in the treatment of osteoporosis-related fractures by significantly enhancing the stability of osteosyntheses and reducing mechanical complication rates. The main options available are polymethyl methacrylate (PMMA) augmentation and various bioresorbable bone substitute materials with different properties. Implant augmentations can be applied at various locations in the extremity bones and standardized procedures are now available, such as for the proximal humerus and femur. When used correctly, low complication rates and promising clinical outcomes are observed. This article aims to provide an overview of available techniques and applications based on the current literature. Guidelines and substantial scientific evidence are still limited.

3D C-arm navigated suture button implantation for AC joint dislocations - the pilot study.

PURPOSE: The surgical treatment of acute traumatic AC joint dislocations is still a subject of scientific debate in the literature. The arthroscopically assisted stabilization procedure with a suture button system has been successfully established and is widely used in daily practice. It is minimally invasive and allows the anatomical reconstruction of the torn coracoclavicular ligaments in one step with a permanent implant that does not have to be removed in a second operation. This clinical pilot study is the first to describe the new method of navigated suture button implantation with the future aim of further reducing surgical invasiveness and further increasing surgical precision. MATERIALS AND METHODS: 10 patients with a Rockwood 3b/5 injury could be included in the prospective study (DRKS00031855) within 5 months according to inclusion and exclusion criteria. Surgical stabilization was performed with a suture button system via a navigated coracoclavicular drill tunnel. Demographic and radiological data as well as information on health and shoulder function were collected from patient records, X-rays, DVT scan and 3 questionnaires (DASH, NHS and Eq. 5D) at the preoperative, intraoperative and postoperative (discharge, 6 weeks and 3 months) time points. RESULTS: All operations could be performed within 8.8 days (± 6.81) after trauma. The average operation time was 50.3 min (± 8.81). The mean distance of the drill hole in the clavicle to the AC joint was 26.6 mm (± 2.63). The radiologically measured vertical coracoclavicular distance was 38.8 mm (± 6.16) at discharge and 41.11 mm (± 7.51) at 3 months. This loss of reduction was not statistically significant. In contrast, the DASH, NHS and Eq. 5D results showed significant improvement from discharge to 3 months postoperatively. CONCLUSION: Image-guided 3D C-arm navigated AC joint suture button stabilization is feasible in everyday surgical practice. It may be possible to achieve a further reduction in invasiveness while at the same time increasing the accuracy of implant positioning. Further clinical studies with a larger number of patients and a longer follow-up period are necessary to enable a comparison with conventional methods.

Spotlight on Nerves: Portable Multispectral Optoacoustic Imaging of Peripheral Nerve Vascularization and Morphology.

Various morphological and functional parameters of peripheral nerves and their vascular supply are indicative of pathological changes due to injury or disease. Based on recent improvements in optoacoustic image quality, the ability of multispectral optoacoustic tomography, to investigate the vascular environment and morphology of peripheral nerves is explored in vivo in a pilot study on healthy volunteers in tandem with ultrasound imaging (OPUS). The unique ability of optoacoustic imaging to visualize the vasa nervorum by observing intraneural vessels in healthy nerves is showcased in vivo for the first time. In addition, it is demonstrated that the label-free spectral optoacoustic contrast of the perfused connective tissue of peripheral nerves can be linked to the endogenous contrast of hemoglobin and collagen. Metrics are introduced to analyze the composition of tissue based on its optoacoustic contrast and show that the high-resolution spectral contrast reveals specific differences between nervous tissue and reference tissue in the nerve's surrounding. How this showcased extraction of peripheral nerve characteristics using multispectral optoacoustic and ultrasound imaging could offer new insights into the pathophysiology of nerve damage and neuropathies, for example, in the context of diabetes is discussed.

A novel method of image-based navigation in fracture surgery.

The treatment of three- and four-part fractures of the humeral head is still controversially discussed. Some advocate primary arthroplasty while the results of primary fixation seem to be superior if no necrosis of the humeral head develops. Today navigation is used in orthopaedic surgery mainly for interventions on the spine, the pelvis and arthroplasty. In trauma surgery it is still rarely used and some technical problems need to be overcome. We report on a case of a three part fracture of the humeral head with mini-open reduction and fixation with image-based guided headless compression screws. For the fixation each screw was placed on the first trial, total radiation time was 60 s. At 12-month follow-up assessment radiographs showed a consolidated fracture, no loosening of the screws and a good glenohumeral articulation. The patient had free function of the shoulder and no pain, the constant score was 98 and the dash score 0. There is no evidence of a necrosis of the humeral head. The literature focuses on shoulder arthroplasty. There are no reports on the use of image-based guidance in shoulder traumatology so far. In conclusion, the described technique allows an accurate fixation of the humeral head fracture as the guidance system (Surgix) ensures the "first try first hit" screw positioning. The new system was integrated in the workflow and supports the surgeon as an aiming device. The role of navigation system in enhancing minimally invasive surgery of the shoulder should be further explored.

Deep-Learning-Based Electrical Noise Removal Enables High Spectral Optoacoustic Contrast in Deep Tissue.

Image contrast in multispectral optoacoustic tomography (MSOT) can be severely reduced by electrical noise and interference in the acquired optoacoustic signals. Previously employed signal processing techniques have proven insufficient to remove the effects of electrical noise because they typically rely on simplified models and fail to capture complex characteristics of signal and noise. Moreover, they often involve time-consuming processing steps that are unsuited for real-time imaging applications. In this work, we develop and demonstrate a discriminative deep learning approach to separate electrical noise from optoacoustic signals prior to image reconstruction. The proposed deep learning algorithm is based on two key features. First, it learns spatiotemporal correlations in both noise and signal by using the entire optoacoustic sinogram as input. Second, it employs training on a large dataset of experimentally acquired pure noise and synthetic optoacoustic signals. We validated the ability of the trained model to accurately remove electrical noise on synthetic data and on optoacoustic images of a phantom and the human breast. We demonstrate significant enhancements of morphological and spectral optoacoustic images reaching 19% higher blood vessel contrast and localized spectral contrast at depths of more than 2 cm for images acquired in vivo. We discuss how the proposed denoising framework is applicable to clinical multispectral optoacoustic tomography and suitable for real-time operation.

Early Surgical Care of Anticoagulated Hip Fracture Patients Is Feasible-A Retrospective Chart Review of Hip Fracture Patients Treated with Hip Arthroplasty within 24 Hours.

Anticoagulative medication such as antiplatelet drugs (PAI, acetylsalicylic acid and direct platelet aggregation inhibitors), vitamin-K-antagonist Warfarin (VKA) or direct oral anticoagulants (DOAC) are common among hip fracture patients, and the perioperative management of these patients is a rising challenge in orthopaedic trauma. Our objective was to determine the effect of oral anticoagulation in patients receiving early endoprosthetic treatment within 24 h after their admission. For the period from 2016 to 2020, a retrospective chart review of 221 patients (mean age 83 ± 7 years; 161 women and 60 men) who were treated either with hemi- (n = 209) or total hip arthroplasty (n = 12) within 24 h after their admission was performed. We identified 68 patients who took PAI, 34 who took DOAC and 9 who took VKA medications. The primary outcome measures were the transfusion rate and the pre- and postoperative haemoglobin (Hb) difference. The secondary outcome measures were the in-patient mortality and the rate of postoperative haematomas that needed operative treatment. A logistic/ordinal regression was performed considering the related variables to prevent cofounding occurring. The mean time to surgery was significantly longer for the DOAC and VKA groups when they were compared to the controls (none 14.7 ± 7.0 h; PAI 12.9 ± 6.7 h; DOAC 18.6 ± 6.3 h; VKA 19.4 ± 5.5 h; p < 0.05). There was no difference in the preoperative Hb level between the groups. Overall, 62 patients (28%) needed blood transfusions during the in-patient stay with an ASA classification (p = 0.022), but the type of anticoagulative medication was not a significant predictor in the logistic regression. Anticoagulation with DOAC and grouped surgery times were positive predictors for a higher Hb difference in the patients who did not undergo an intraoperative blood transfusion (n = 159). Postoperative haematomas only occurred in patients taking anticoagulative medication (four cases in PAI group, and three cases in DOAC group), but the logistic regression showed that the anticoagulative medication had no effect. The in-patient mortality was significantly influenced by a high ASA grade (p = 0.008), but not by the type of anticoagulative medication in patients who were treated within 24 h. We conclude that the early endoprosthetic treatment of the anticoagulated hip fracture patient is safe, and a delayed surgical treatment is no longer justifiable.

Short-term outcome of fragility fractures of the pelvis in the elderly treated with screw osteosynthesis and external fixator.

BACKGROUND: The treatment of fragility fractures of the pelvis is rising challenge for orthopedic trauma surgeons. Operative treatment should allow immediate full weight bearing and early mobilisation but should also be as minimal invasive as possible. Sacroiliac (SI) or transsacral transiliac screws (TSTI) alone or depending on the fracture in combination with an external fixator meets both of these criteria. MATERIAL AND METHODS: The outcome of 121 operatively treated patients with fragility fractures of the pelvis were evaluated in this retrospective study. Depending on the type of fracture the patients were treated with navigated SI screw or TSTI screw alone or in combination with an external fixator. All patients were operated in supine position in a hybrid-OR, which consists of a fixed robotic 3D flatpanel detector (Artis zeego, Siemens Healthineers, Germany) and a navigation system (BrainLab Curve, BrainLab, Germany). RESULTS: 37 patients were treated with either one or two SI screws and 57 with one TSTI screw. An additional external fixator was combined with SI screws in 17 patients and with TSTI screws in 10 patients. The preoperative pain score was significantly higher compared to the postoperative score (5.1 ± 2.5 vs 2.2 ± 1.9, p < 0.05). Follow-up at 6 month was possible for 106 patients which showed screw loosening in 16.3% of the SI Screws (n = 49) compared to only 5.2% of TSTI screws (n = 57). No screw loosening was seen in the combination of TSTI-screw and external fixator (n = 10). There were two septic and three aseptic pin loosenings of the external fixator. Overall only one patient needed revision surgery due to screw loosening and local irritation. Overall 75.2% (n = 91) of the patients could be released in their home or in a rehabilitation unit and only 14% (n = 17) were released to a nursing home due to immobility despite the operation. Non-surgical complications rate was 21.5%. CONCLUSION: SI or TSTI screws with possible combination with an external fixator show early pain relief and allows most of the patients to keep their former level of independence. With an also low surgical complication rate, it proved to be a safe and reliable treatment for fragility fractures of the pelvis. Due the effective pain relief and the minimal invasive approach, early mobilisation is possible and might prevent typical non-surgical complications which are very common during conservative treatment.

Image processing improvements afford second-generation handheld optoacoustic imaging of breast cancer patients.

Background: Since the initial breast transillumination almost a century ago, breast cancer imaging using light has been considered in different implementations aiming to improve diagnostics, minimize the number of available biopsies, or monitor treatment. However, due to strong photon scattering, conventional optical imaging yields low resolution images, challenging quantification and interpretation. Optoacoustic imaging addresses the scattering limitation and yields high-resolution visualization of optical contrast, offering great potential value for breast cancer imaging. Nevertheless, the image quality of experimental systems remains limited due to a number of factors, including signal attenuation with depth and partial view angle and motion effects, particularly in multi-wavelength measurements. Methods: We developed data analytics methods to improve the accuracy of handheld optoacoustic breast cancer imaging, yielding second-generation optoacoustic imaging performance operating in tandem with ultrasonography. Results: We produced the most advanced images yet with handheld optoacoustic examinations of the human breast and breast cancer, in terms of resolution and contrast. Using these advances, we examined optoacoustic markers of malignancy, including vasculature abnormalities, hypoxia, and inflammation, on images obtained from breast cancer patients. Conclusions: We achieved a new level of quality for optoacoustic images from a handheld examination of the human breast, advancing the diagnostic and theranostic potential of the hybrid optoacoustic-ultrasound (OPUS) examination over routine ultrasonography.

Label-free concurrent 5-modal microscopy (Co5M) resolves unknown spatio-temporal processes in wound healing.

The non-invasive investigation of multiple biological processes remains a methodological challenge as it requires capturing different contrast mechanisms, usually not available with any single modality. Intravital microscopy has played a key role in dynamically studying biological morphology and function, but it is generally limited to resolving a small number of contrasts, typically generated by the use of transgenic labels, disturbing the biological system. We introduce concurrent 5-modal microscopy (Co5M), illustrating a new concept for label-free in vivo observations by simultaneously capturing optoacoustic, two-photon excitation fluorescence, second and third harmonic generation, and brightfield contrast. We apply Co5M to non-invasively visualize multiple wound healing biomarkers and quantitatively monitor a number of processes and features, including longitudinal changes in wound shape, microvascular and collagen density, vessel size and fractality, and the plasticity of sebaceous glands. Analysis of these parameters offers unique insights into the interplay of wound closure, vasodilation, angiogenesis, skin contracture, and epithelial reformation in space and time, inaccessible by other methods. Co5M challenges the conventional concept of biological observation by yielding multiple simultaneous parameters of pathophysiological processes in a label-free mode.

Postural control deficit in acute QTF grade II whiplash injuries.

STUDY DESIGN: Experimental in vivo study. OBJECTIVE: The objective was to investigate the balance control in patients with acute QTF grade II whiplash injuries of the cervical spine. SUMMARY OF BACKGROUND DATA: Tetra-ataxiametric posturography in chronic pain patients after whiplash injuries of the cervical spine has revealed an impaired regulation of balance. However, so far it is unclear if this is caused by the accident or other factors that are associated with the pain chronification process. METHODS: 40 patients with acute QTF grade II whiplash injuries and 40 healthy matched controls were examined on a posturography platform. The stability index ST(Sigma) and the Fourier analysis FA(Sigma) (0.10-1.00Hz) were established for eight standing positions and sum scores were calculated. The pain index was established using a visual analog scale ranging from 0 to 100. A follow-up examination was conducted for the patients after 2 months. RESULTS: The patients with acute whiplash injuries of the cervical spine achieved significantly poorer results for both ST(Sigma) and FA(Sigma) than the healthy controls. There were no differences between the eight standing positions for both ST(Sigma) and FA(Sigma). After 2 months, 17 patients had no change in the pain development, 21 patients showed an improvement in pain intensity and 2 patients had deteriorated. The subgroup of patients with improvement in pain intensity showed a significant improvement in balance control concerning the FA(Sigma) compared to patients with unchanged pain intensity. CONCLUSION: Patients with acute whiplash injuries have a reduced balance control as compared to matched controls. This study gives an indication that post-traumatic neck pain is associated with impairments of postural control.

Influence of anthropometry on the kinematics of the cervical spine and the risk of injury in sled tests in female volunteers.

The objective of this study was to investigate the influence of anthropometric data on the kinematics of the cervical spine and the risk factors for sustaining a neck injury during rear-end collisions occurring in a sled test. A rear-end collision with a velocity change (DeltaV) of 6.3 km/h was simulated in a sled test with eight healthy female subjects. The study analysed the association of anthropometric data with the initial distance between the head and the head restraint, defined kinematic characteristics, the neck injury criterion (NIC) and the neck injury criterion minor (NICmin). The head circumference is negatively associated (r=-0.598) with the initial distance between the head and the head restraint, the maximal head extension (r=-0.687) and the maximal dorsal angular head acceleration (r=-0.633). The body weight (r=0.800), body height (r=0.949) and thorax circumference (r=0.632) are positively associated with the maximal ventral head translation. The neck length correlates positively with the NIC (r=0.826) and negatively with the NICmin (r=-0.797). Anthropometric factors influence the kinematics of the cervical spine and the risk of injury. A high risk of injury may be assumed for individuals with a small head circumference, long neck, tall body height and high body weight.

Risk of injury of the cervical spine in sled tests in female volunteers.

BACKGROUND: The description of cervical spine motion and the risk to sustain a cervical spine injury is mainly based on cadaver studies. As the active influence of soft tissue is neglected in cadaver studies, our understanding of the kinematic model for whiplash is limited. Therefore the objective of this study was, to describe the in vivo cervical spine motion and acceleration during rear-end sled collisions to identify sequences of motion in which the risk of injury to the cervical spine is increased. METHODS: A rear-end collision with a speed change (DeltaV) of 6.3 km/h was simulated in a sled test with eight female subjects with no history of prior injury or pain of the cervical spine. A high-speed camera was used to document motion data. Acceleration data were recorded using accelerometers. Acceleration input to the cervical spine was assessed by the simultaneous analysis of the head angle and angular head acceleration as well as the simultaneous analysis of the relative motion and the relative acceleration between the head and T1 to define intervals of increased risk of cervical spine injuries during rear-end collision. FINDINGS: The motion sequence is characterized by the same phases that have already been described for male volunteers. Increasing angular head acceleration can explain facet joint injuries during the extension movement (100-120 ms) and hence occur about 50 ms later than shown in cadaver models. In the late rebound the combination of maximal ventral head acceleration and head movement is underestimated and can be responsible for soft tissue injuries. INTERPRETATION: The study shows that during the extension phase and the late rebound phase, acceleration and movement pattern occur that could lead to cervical spine injuries.

The PFNA® Augmented in Revision Surgery of Proximal Femur Fractures.

OBJECTIVES: Modern implants for proximal femur fracture treatment have clearly improved clinical results. However, complications, including cut-out and loss of reduction, requiring revision surgery still occur. A major challenge in these cases is a loss of bone stock due to the existing implant, which is usually exacerbated by osteoporosis. A potential solution is the augmentation of implants, for example, of the femoral neck blade using bone cement. MATERIALS AND METHODS: Ten patients (five loosening of femoral neck implant, two pseudarthrosis, two implant failures and one acute fracture) were included. The initial hardware was removed and a PFNA augmented was implanted. The perforated femoral neck blade was augmented using polymethyl methacrylate cement. Clinical and radiological follow-up was performed at a mean of 5.4 months (SD ±4.34). The main outcome parameters were fracture healing and implant-related complications. RESULTS: Technical handling was uneventful in all cases. No cement leakage into the joint occurred in any of the cases. The mean amount of cement injected was 5.3 ml. The fracture healed during follow-up in all cases except two patients who died from causes unrelated to the procedure and prior to complete consolidation. Problem-free elective hardware removal of the PFNA augmented was performed in two cases. DISCUSSION: The PFNA augmented is a potential implant for joint-preserving revision surgery in proximal femur fractures. The augmentation improves implant anchorage in the impaired bone stock. In this preliminary series, no negative biological side effects of the cement (i.e. osteonecrosis) were observed.

Muscle activity influence on the kinematics of the cervical spine in rear-end sled tests in female volunteers.

OBJECTIVE: Although much research has been performed to investigate the cervical spine kinematics during rear-end collisions, our understanding about the exact role of the musculature is limited. The question of the influence of muscle activity on cervical spine kinematics has been discussed. METHODS: A rear-end collision with a speed change (ΔV) of 6.3 km/h was simulated in a sled test with 8 female subjects to investigate the influence of the ventral and dorsal cervical spine musculature on cervical spine kinematics. A high-speed camera and accelerometers recorded the motion and acceleration data. The activity of the sternocleidomastoid muscles was recorded with surface electrodes. To avoid cross talk, an intramuscular recording of the semispinalis capitis muscles was performed with fine-wire electrodes. RESULTS: The analysis of the motion and acceleration parameters allowed the definition of 4 phases. The headrest contact began after a median of 84 ms and the sternocleidomastoid muscle force could be detected after a median of 81 ms, with 0 defining the time of the trigger signal. The maximal force of the sternocleidomastoid muscle and the maximal headrest effect began prior to the maximal ventral angular head acceleration and prior to the maximal ventral horizontal head acceleration relative to T1. The start of the semispinalis capitis muscle force was observed after a median of 159 ms and increased until a flexion of 20 to 25° was reached. CONCLUSIONS: The headrest effect and the sternocleidomastoid muscle force firstly supported the deceleration of the head relative to T1 toward dorsal, which was followed by an accelerating effect toward ventral. The semispinalis capitis muscle force exerted a late decelerating effect on head flexion and ventral translation movement.

Training effects of combined resistance and proprioceptive neck muscle exercising.

OBJECTIVES: To investigate training effects of two different resistance and proprioceptive exercising concepts of neck muscles. MATERIAL AND METHOD: Twenty-six healthy women participated in a randomized pilot trial. The test persons were randomized to two different neck-training programs (resistance training (RT) and proprioceptive resistance training (PRT)). They performed a standardized training program for the duration of ten weeks two times weekly. The neck strength, the cross-sectional area of three neck muscle groups (1. sternocleidomastoid muscles; 2. multifidus and semispinalis cervicis muscles; 3. semispinalis capitis and splenius muscles) and the proprioceptive capability evaluated by the dynamic joint repositioning error (DJRE) of the head were assessed pre- and post-intervention. RESULTS: Strength gain did not differ significantly between the two resistance training groups (PRT group: 8.2% to 29.3%; RT group: 1.4% to 19.8%). Change of hypertrophy of all neck muscle groups was significantly (p< 0.001 to p=0.013) greater in the PRT group (18.9% to 32.3%) than in the RT group (1.5% to 12.9%). The DJRE deteriorated with 35% in the RT group and did not change in PRT group (-2.0%). CONCLUSION: In combination with resistance training, proprioceptive training led to a significantly higher muscle hypertrophy and didn't effect a significant deterioration of the proprioceptive capability compared to isolated resistance training.

Mechanical quantification of local bone quality in the humeral head: a feasibility study.

OBJECTIVES: Surgical treatment of proximal humerus fractures can be challenging due to osteoporosis. The weak bone stock makes stable implant anchorage difficult, which can result in low primary stability. Accordingly, significant failure rates, even with modern locking plates, are reported in the literature. Intraoperative knowledge of local bone quality could be helpful in improving results. This study evaluates the feasibility of local bone quality quantification using breakaway torque measurements. MATERIALS AND METHODS: A torque measurement tool (DensiProbe™) was developed to determine local resistance to breakaway offered by the cancellous bone in the humeral head to quantify local bone quality. The tool was adapted to a standard locking plate (PHILOS, Synthes), allowing measurement in the positions of the six humeral head screws, as provided by the aiming device of the plate. Two hundred and seventy measurements were performed in 44 fresh cadaveric human humeri. RESULTS: Handling of the tool was straight forward and provided reproducible results for the six different positions. The method allows discrimination between the respective positions with statistical significance, and thus provides reliable information on the local distribution of bone quality within the humeral head. DISCUSSION: This study introduces a new method using breakaway torque to determine local bone quality within the humeral head in real time. Because DensiProbe is adapted to a standard locking plate, there is the potential for intraoperative application. The information provided could enable the surgeon to improve fixation of osteoporotic proximal humerus fractures.

In-vivo kinematics of the cervical spine in frontal sled tests.

The description of cervical spine motion and the risk to sustain a cervical spine injury in traffic accidents is mainly based on rear-end collisions. The knowledge about frontal collisions is comparable low. Therefore the objective of this exploratory study was, to describe the in-vivo cervical spine motion and acceleration during simulated frontal sled collisions and to identify sequences of motion in which the risk of injury is increased. A frontal collision with a speed change of 10.2km/h was simulated in a sled test with ten volunteers. Cervical spine kinematics was assessed by the simultaneous analysis of the angular head motion and acceleration as well as the simultaneous analysis of the relative motion and acceleration between the head and the first thoracic vertebral body. The motion sequence was divided into five phases. The combination of peak values of the angular head acceleration to ventral and the relative horizontal head acceleration to dorsal between the time period of 90ms and 110ms (early flexion phase) included - potential injury generating - shear forces. Although a hyperflexion (late rebound phase) as injury pattern didn't occur, dorsal soft tissue injuries due to eccentric muscle-sprain could not be ruled out completely. In conclusion the study showed under simulated test conditions that during the early flexion phase and the late rebound phase, acceleration and movement pattern occur that could lead to cervical spine injuries.

Muscle activity influence on the kinematics of the cervical spine in frontal tests.

OBJECTIVE: The question of muscle activity influence on the cervical spine kinematics during rear-end and frontal crash events has been discussed. Less data are available concerning frontal collisions. Therefore, the objective of this study was to investigate the influence of the ventral and dorsal neck muscles on the cervical spine kinematics during simulated frontal sled collisions. METHODS: A frontal collision with a velocity change (delta V) of 10.2 km/h was simulated in a sled test with 10 healthy subjects (7 female; 3 male). A high-speed camera and accelerometers recorded the motion and acceleration data. The activity of the sternocleidomastoid muscles was recorded with surface electrodes. To avoid cross-talk, an intramuscular recording of the semispinalis capitis muscles was performed with fine-wire electrodes. RESULTS: The sequence of both muscle activities was reproducible in all subjects. The maximal force of the sternocleidomastoid muscle was observed after a median of 152 ms, with 0 defining the time of the trigger signal. With earlier onset of muscle force, maximal dorsal horizontal acceleration of the head (r = -0.600) was reached later and the ventral translation (r = -0.733) and flexion movement (r = -0.755) set in earlier. The maximal force of the semispinalis capitis muscle was observed after a median of 160 ms. If the duration of muscle force was longer, the maximal head flexion (r = 0.685) and the maximal ventral head translation (r = 0.738) were reached later. CONCLUSIONS: The sternocleidomastoid muscle force is mainly associated with the horizontal head acceleration and influences the onset of the flexion and translation motion. To summarize, these temporal correlations allow the conclusion that the semispinalis capitis muscle force is mainly associated with the angular head acceleration and influences the duration of the flexion and translation motion.