Stefan Schleifenbaum

Human Vagus Nerve Branching in the Cervical Region

Background Vagus nerve stimulation is increasingly applied to treat epilepsy, psychiatric conditions and potentially chronic heart failure. After implanting vagus nerve electrodes to the cervical vagus nerve, side effects such as voice alterations and dyspnea or missing therapeutic effects are observed at different frequencies. Cervical vagus nerve branching might partly be responsible for these effects. However, vagus nerve branching has not yet been described in the context of vagus nerve stimulation. Materials and Methods Branching of the cervical vagus nerve was investigated macroscopically in 35 body donors (66 cervical sides) in the carotid sheath. After X-ray imaging for determining the vertebral levels of cervical vagus nerve branching, samples were removed to confirm histologically the nerve and to calculate cervical vagus nerve diameters and cross-sections. Results Cervical vagus nerve branching was observed in 29% of all cases (26% unilaterally, 3% bilaterally) and proven histologically in all cases. Right-sided branching (22%) was more common than left-sided branching (12%) and occurred on the level of the fourth and fifth vertebra on the left and on the level of the second to fifth vertebra on the right side. Vagus nerves without branching were significantly larger than vagus nerves with branches, concerning their diameters (4.79 mm vs. 3.78 mm) and cross-sections (7.24 mm2 vs. 5.28 mm2). Discussion Cervical vagus nerve branching is considerably more frequent than described previously. The side-dependent differences of vagus nerve branching may be linked to the asymmetric effects of the vagus nerve. Cervical vagus nerve branching should be taken into account when identifying main trunk of the vagus nerve for implanting electrodes to minimize potential side effects or lacking therapeutic benefits of vagus nerve stimulation.

On the permanent hip-stabilizing effect of atmospheric pressure

Hip joint dislocations related to total hip arthroplasty (THA) are a common complication especially in the early postoperative course. The surgical approach, the alignment of the prosthetic components, the range of motion and the muscle tone are known factors influencing the risk of dislocation. A further factor that is discussed until today is atmospheric pressure which is not taken into account in the present THA concepts. The aim of this study was to investigate the impact of atmospheric pressure on hip joint stability. Five joint models (Ø 28-44 mm), consisting of THA components were hermetically sealed with a rubber capsule, filled with a defined amount of fluid and exposed to varying ambient pressure. Displacement and pressure sensors were used to record the extent of dislocation related to intraarticular and ambient pressure. In 200 experiments spontaneous dislocations of the different sized joint models were reliably observed once the ambient pressure was lower than 6.0 kPa. Increasing the ambient pressure above 6.0 kPa immediately and persistently reduced the joint models until the ambient pressure was lowered again. Displacement always exceeded half the diameter of the joint model and was independent of gravity effects. This experimental study gives strong evidence that the hip joint is permanently stabilized by atmospheric pressure, confirming the theories of Weber and Weber (1836). On basis of these findings the use of larger prosthetic heads, capsular repair and the deployment of an intracapsular Redon drain are proposed to substantially decrease the risk of dislocation after THA.

Biomechanical analysis of stiffness and fracture displacement after using PMMA-augmented sacroiliac screw fixation for sacrum fractures

Abstract Cement augmentation of pedicle screws is the gold standard for the stabilization of osteoporotic fractures of the spine. In-screw cement augmentation, in which cement is injected through the cannula, is another option for fracture stabilization of fragility fractures of the sacrum. However, biomechanical superiority of this technique compared to conventional sacroiliac screw fixation has not been tested. The present study compares the stability of cement-augmented and non-cement-augmented sacroiliac screw fixation in osteoporotic sacrum fractures under cyclic loading. Eight human donor pelvises with intact ligaments and 5th lumbar vertebra were dissected. A vertical shear fracture was created as a combination of a sacrum fracture and cutting of the symphysis. Both sides were tested in a single-limb-stance setup with 10,000 loading cycles applied. Stiffness of the pelvis and displacement of the fracture were measured using a hydraulic testing machine and a 3D image correlation system. The augmented screw fixation failed in two of eight pelvises, and the non-augmented screws failed in three of eight pelvises. CT scans showed no leakage of cement. In-screw polymethylmethacrylate (PMMA) augmentation showed no advantage based on measured displacement of the sacrum fractures or stiffness for sacroiliac screw fixation of fragility fractures of the sacrum.

Acellularization-Induced Changes in Tensile Properties Are Organ Specific - An In-Vitro Mechanical and Structural Analysis of Porcine Soft Tissues.

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin.

Teaching surgical exposures to undergraduate medical students: an integration concept for anatomical and surgical education

BackgroundDecreasing numbers of students are interested in starting a surgical career, posing substantial challenges to patient care in the next years. The anatomy course is one of the key subjects in medical training, especially in surgical disciplines. Innovative teaching concepts that integrate surgically relevant anatomy and manual dexterity might help boost student interest in surgery.MethodsA preclinical workshop entitled “Surgical exposures” was developed. A team of anatomists and surgeons introduced the surgical exposures, demonstrating the procedures on Thiel-fixed body donors. Following this introduction, students practiced the exposures in an operating room-like manner. A six-point Likert scale was used to evaluate the workshop and to compare it to the first-year dissection course.ResultsThe overall evaluation result for the surgical exposures was excellent, proving to be a significantly better result when compared to the first-year dissection course. The students were more satisfied with the teaching time invested by the peers and regarded the workshop as clinically highly relevant. Furthermore, they felt that questions were addressed better and that the overall atmosphere was better than in the gross anatomy course. Subject to criticism was the course size and practicing time in both cases.DiscussionThe surgical exposures workshop provides preclinical students with clinically relevant anatomy and manual dexterity. It may positively influence the decision to follow a surgical career. This course, however, requires extensive teaching resources. The given concept may help implement practical medical skills in the preclinical curriculum, strengthening the professional identity of surgeons and anatomists.

Pelvic Belt Effects on Health Outcomes and Functional Parameters of Patients with Sacroiliac Joint Pain.

Introduction The sacroiliac joint (SIJ) is a common source of low back pain. However, clinical and functional signs and symptoms correlating with SIJ pain are widely unknown. Pelvic belts are routinely applied to treat SIJ pain but without sound evidence of their pain-relieving effects. This case-control study compares clinical and functional data of SIJ patients and healthy control subjects and evaluates belt effects on SIJ pain. Methods 17 SIJ patients and 17 healthy controls were included in this prospective study. The short-form 36 survey and the numerical rating scale were used to characterize health-related quality of life in patients in a six-week follow-up and the pain-reducing effects of pelvic belts. Electromyography data were obtained from the gluteus maximus, biceps femoris, rectus femoris and medial vastus. Alterations of muscle activity, variability and gait patterns were compared in patients and controls along with the belts’ effects in a dynamic setting when walking. Results Significant improvements were observed in the short-form 36 survey of the SIJ patients, especially in the physical health subscores. Minor declines were also observed in the numerical rating scale on pain. Belt-related changes of muscle activity and variability were similar in patients and controls with one exception: the rectus femoris activity decreased significantly in patients with belt application when walking. Further belt effects include improved cadence and gait velocity in patients and controls. Conclusions Pelvic belts improve health-related quality of life and are potentially attributed to decreased SIJ-related pain. Belt effects include decreased rectus femoris activity in patients and improved postural steadiness during locomotion. Pelvic belts may therefore be considered as a cost-effective and low-risk treatment of SIJ pain. Trial Registration ClinicalTrials.gov NCT02027038

Sind höhere Preise für größere Kopfdurchmesser in der Hüftendoprothetik medizinökonomisch vertretbar? Eine Analyse der Kosten und Effekte in Deutschland

Background: In total hip arthroplasty (THA), femoral head diameter has not been regarded as a key parameter which should be restored when reconstructing joint biomechanics and geometry. Apart from the controversial discussion on the advantages and disadvantages of using larger diameter heads, their higher cost is another important reason that they have only been used to a limited extent. The goal of this study was to analyse the price structure of prosthetic heads in comparison to other components used in THA. A large group of patients with hip endoprostheses were evaluated with respect to the implanted socket diameter and thus the theoretically attainable head diameter. Materials and Methods: The relative prices of various THA components (cups, inserts, stems and ball heads) distributed by two leading German manufacturers were determined and analysed. Special attention was paid to different sizes and varieties in a series of components. A large patient population treated with THA was evaluated with respect to the implanted cup diameter and therefore the theoretically attainable head diameter. Results: The pricing analysis of the THA components of two manufacturers showed identical prices for cups, inserts and stems in a series. In contrast to this, the prices for prosthetic heads with a diameter of 36-44 mm were 11-50 % higher than for 28 mm heads. Identical prices for larger heads were the exception. The distribution of the head diameter in 2719 THA cases showed significant differences between the actually implanted and the theoretically attainable heads. Conclusion: There are proven advantages in using larger diameter ball heads in THA and the remaining problems can be solved. It is therefore desirable to correct the current pricing practice of charging higher prices for larger components. Instead, identical prices should be charged for all head diameters in a series, as is currently established practice for all other THA components. Thus when reconstructing biomechanics and joint geometry in THA, it should be possible to recover not only leg length, femoral offset and antetorsion of the femoral neck, but also to approximately restore the diameter of the femoral head and thereby optimise the functional outcome.

Größere Köpfe kompensieren erhöhte Hüft-TEP-Luxationsgefahr bei Hochrisikopatienten

BACKGROUND Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered. OBJECTIVES This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered. MATERIALS AND METHODS All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed. RESULTS During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported. CONCLUSION Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

[Larger heads compensate for an increased risk of THA dislocation in high-risk patients].

BACKGROUND Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered. OBJECTIVES This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered. MATERIALS AND METHODS All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed. RESULTS During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported. CONCLUSION Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

Novel concept of a modular hip implant could contribute to less implant failure in THA: a hypothesis

BackgroundThe modularity in total hip arthroplasty (THA) allows orthopaedic surgeons for an exact reconstruction of hip biomechanical parameters especially in revision and tumor arthroplasty. Modular structured femoral stems using taper junctions showed increased implant breakage in the recent past.Presentation of the hypothesisWe hypothesize that a novel modular stem-neck-interface leads to less implant breakage compared to conventional femoral stems.Testing of the hypothesisFor this purpose, a novel modular femoral stem for THA was to design and manufacture. Therefore, three different variants of interface mechanisms were developed that enable a simple connection between the stem and the neck modules and allow for intra-operatively adjustment. Three prototypes A, B and C were manufactured and subsequently dynamic fatigue (ISO 7206–6) and body donor tested.Implication of the hypothesisModularity in THA is mainly applied in THA as well as in revision and tumor arthroplasty. Modular implants are barely used because of the high risk of breakage. Another risks in this context are taper fretting, corrosion and disconnection. With the novel design, it should be possible to detach the stem and neck module intra-operatively to adapt the anatomical situation. The novel coupling mechanism of the rotating interface seems to be the most suitable for a secure stem-neck connection and is characterized by good intraoperative handling.