γδT Cells Are Essential for Orthodontic Tooth Movement.

Sustained mechanical forces applied to tissue are known to shape local immunity. In the oral mucosa, mechanical stress, either naturally induced by masticatory forces or externally via mechanical loading during orthodontic tooth movement (OTM), is translated, in part, by T cells to alveolar bone resorption. Nevertheless, despite being considered critical for OTM, depletion of CD4+ and CD8+ T cells is reported to have no impact on tooth movement, thus questioning the function of αßT cells in OTM-associated bone resorption. To further address the role of T cells in OTM, we first characterized the leukocytes residing in the periodontal ligament (PDL), the tissue of interest during OTM, and compared it to the neighboring gingiva. Unlike the gingiva, monocytes and neutrophils represent the major leukocytes of the PDL. These myeloid cells were also the main leukocytes in the PDL of germ-free mice, although at lower levels than SPF mice. T lymphocytes were more enriched in the gingiva than the PDL, yet in both tissues, the relative fraction of the γδT cells was higher than the αß T cells. We thus sought to examine the role of γδT cells in OTM. γδT cells residing in the PDL were mainly Vγ6+ and produced interleukin (IL)-17A but not interferon-γ. Using Tcrd-GDL mice allowing conditional ablation of γδT cells in vivo, we demonstrate that OTM was greatly diminished in the absence of γδT cells. Further analysis revealed that ablation of γδT cells decreased early IL-17A expression, monocyte and neutrophil recruitment, and the expression of the osteoclastogenic molecule receptor activator of nuclear factor-κß ligand. This, eventually, resulted in reduced numbers of osteoclasts in the pressure site during OTM. Collectively, our data suggest that γδT cells are essential in OTM for translating orthodontic mechanical forces to bone resorption, required for relocating the tooth in the alveolar bone.

Development and Function of γδT Cells in the Oral Mucosa.

To successfully withstand a wide variety of microbial and mechanical challenges, the immune system of the oral mucosa is composed of tissue-resident and specially recruited leukocytes. These leukocytes facilitate the establishment and maintenance of local homeostasis but are also capable to cause oral pathologies when are unrestrained. γδT cells represent an important tissue-resident innate T-cell population in various mucosal and nonmucosal barrier tissues, in which they are ideally located to assist in immunosurveillance, tissue repair, and homeostasis. Whereas most works studying γδT cells were focused on tissues such as the skin and intestine, these cells in the oral mucosa were only recently thoroughly studied. The findings obtained by those studies appear to be both complementary and contradicting, likely reflecting differences in the experimental settings and the type of transgenic mouse modalities employed by each study. Nevertheless, oral γδT cells were shown to consist of developmentally distinct tissue-resident Vγ6 cells and circulating Vγ1 and Vγ4 subsets that are independently maintained in the oral mucosa. In the gingiva, a particularly challenging barrier tissue due to its proximity to the dental plaque, γδT cells are strategically positioned close to the plaque and represent the major source of IL-17. While this suggests that γδT cells might be involved in controlling the dental biofilm, conflicting data were reported in this regard. In vivo studies have shown that γδT cells either play a protective role during age-associated bone loss or, alternatively, have no impact in this process. Also, recent reports suggested opposing data concerning the impact of γδT cells in experimental periodontitis based on the ligature model. This review summarizes and discusses the most up-to-date literature on oral γδT cells, providing a balanced perspective regarding our current understanding on the development of oral γδT cells and their role under physiologic conditions and certain oral pathologies.

Use of Tekscan K-scan sensors for retropatellar pressure measurement avoiding errors during implantation and the effects of shear forces on the measurement precision.

Pressure-sensitive K-Scan 4000 sensors (Tekscan, USA) provide new possibilities for the dynamic measurement of force and pressure in biomechanical investigations. We examined the sensors to determine in particular whether they are also suitable for reliable measurements of retropatellar forces and pressures. Insertion approaches were also investigated and a lateral parapatellar arthrotomy supplemented by parapatellar sutures proved to be the most reliable method. The ten human cadaver knees were tested in a knee-simulating machine at a torque of 30 and 40 Nm. Each test cycle involved a dynamic extension from 120° flexion. All recorded parameters showed a decrease of 1-2% per measurement cycle. Although we supplemented the sensors with a Teflon film, the decrease, which was likely caused by shear force, was significant. We evaluated 12 cycles and observed a linear decrease in parameters up to 17.2% (coefficient of regression 0.69-0.99). In our opinion, the linear decrease can be considered a systematic error and can therefore be quantified and accounted for in subsequent experiments. That will ensure reliable retropatellar usage of Tekscan sensors and distinguish the effects of knee joint surgeries from sensor wear-related effects.

2D-fluoroscopic based navigation for Gamma 3 nail insertion versus conventional procedure- a feasibility study.

BACKGROUND: Intramedullary nailing is a standard surgical procedure for fixation of proximal femoral fractures, but is associated with considerable radiation exposure for controlling the implant placement, due to the percutaneous insertion technique.The aim of this study was the evaluation of potential benefits of 2D-fluoroscopic based navigation focused on the reduction of radiation exposure, a decrease of procedure time, as well as an increase of accuracy for Gamma3 nail insertions. METHODS: Twenty randomized Gamma3 nail insertions were performed in non-fractured synthetic femora according to the manufactures operation guidelines (group I) or with use of a 2D-fluoroscopic based navigation system (group II). Time of different steps of the procedure and the radiation exposure were measured, as well as the accuracy evaluated in postoperative CT scans. RESULTS AND DISCUSSION: All Gamma3 nails were placed without any technical problems. Independent of the used procedure, the overall operating time (group I: 584 ± 99.2 sec; group II: 662 ± 64.9 sec; p=0.06) and accuracy of the final nail-positions were equivalent, but the radiation exposure was significantly reduced (92% reduction in fluoroscopic images and 91% reduction in fluoroscopic time, p< 0.01), using the 2D fluoroscopic based navigation procedure. CONCLUSIONS: 2D-fluoroscopic based navigation for Gamma3 nail insertion facilitates a relevant reduction of radiation exposure with equivalent accuracy of the final implant position and no prolonged operating time. This promising procedure modification is independent of different cephalomedullary implant manufacturers and specific implant designs, but needs to be evaluated in further clinical settings.

Navigation in femoral-shaft fractures--from lab tests to clinical routine.

INTRODUCTION: This study evaluates the use of a navigation system (BrainLAB, Feldkirchen, Germany) to intra-operatively check for correct length, axis and rotation in intramedullary nailing of femoral-shaft fractures in an experimental setting and in clinical routine. MATERIALS AND METHODS: We tested the navigation system in two experimental settings before introducing it into clinical routine. In the first experiment, 10 osteotomised model femora were fixed with intramedullary nails by using a navigation system. The goal was a locking fixation in predefined values for length and rotation. In the second experiment, eight examiners assessed values for rotation and length of one femur 10 times to examine the accuracy and reproducibility of that determination. Following this, we navigated 40 femoral nailing procedures in our department. Preoperatively, we assessed values of femur geometry on the contralateral side in a computed tomography (CT) scan and reproduced these values intra-operatively on the fractured side, guided by the navigation system. During the intervention, we recorded the length of the procedure steps and the fluoroscopy time. We verified the intra-operative values achieved with the navigation system in a postoperative CT scan and documented differences in rotation and length. After the assessment, we analysed the data for different findings on femur geometry, fluoroscopy time and procedure duration. RESULTS: The experimental evaluation showed a range of ±5° for anteversion differences and ±2.3 mm for length differences. We estimated this accuracy as sufficient to use the system in clinical routine. The navigation system was used for 40 fracture fixations. All our criteria for restoring femoral geometry could be achieved by navigation guidance in these procedures. Setting up the system took on average 33±11.5 min. An additional fluoroscopy time of 36±22 s was needed to acquire the reference X-rays and to verify pin placement. The differences between anteversion values assessed in intra-operative planning steps on the navigation system and values assessed with a postoperative CT were on average 5.4±3.5°, whilst femur length differed on average by 4±4 mm. DISCUSSION: Many authors judge intra-operative control of anteversion in femoral-shaft fracture fixation as problematic. Neither our experimental navigation assessment nor our clinical navigated evaluation showed relevant anteversion differences to a postoperative CT assessment of femur geometry. After initial training, guidance by a navigation system achieves consistent results in a clinical situation. CONCLUSIONS: The use of a navigation system to align axis, length and rotation led to a secure way of avoiding any relevant malalignment in complex femur-shaft fractures whilst exposing patients to an acceptable amount of additional procedure sequences. Malalignment can be avoided by using a navigation system in the operative treatment of femoral-shaft fractures and may be integrated into clinical routine in specialised centres.

[Current treatment concepts for mid-shaft fractures of the clavicle - results of a prospective multicentre study]. / Aktuelle Behandlungskonzepte der Klavikulaschaftfraktur - Ergebnisse einer prospektiven Multicenterstudie.

BACKGROUND: Mid-shaft clavicular fractures are mainly treated conservatively with an average incidence of non-union in 4.5 %. Gender, age, grade of fragment dislocation and comminution are risk factors to develop a pseudarthrosis. In contrast to patients who where operated on, conservative treatment was also associated with a higher complication rate and pain level as well as a poor shoulder function and cosmetic result. Therefore more patients are treated operatively, especially modern minimally invasive techniques have been developed and remain as equals to the standard plate fixation. PATIENTS/MATERIAL: Within a period of 24 months patients with a mid-shaft clavicular fracture were included into a prospective, non-randomised multicentre study. A modified AO classification was used. Patients were treated either conservatively, by plating or intramedullary nailing. Pain level, cosmetic result, shoulder function and complication rate were documented as well as the influence of the profession on the therapeutic strategy and duration of unfitness for work. RESULTS: 120 patients (95 male, 25 female) were included in the study. Fractures were caused in 35 (29 %) by a direct, in 85 (71 %) by an indirect trauma mechanism. Because of their lower grade fractures with overlapping fragments 47 (39 %) patients were treated conservatively with a figure-of-eight-bandage. Patients with higher graded fractures and fragment displacement were stabilised either by intramedullary nailing (n = 20, 27 %) or plate fixation (n = 53, 73 %). 96 (80 %) patients were examined at a follow-up of eight weeks and eight months after injury. Early freedom from pain (p = 0.014), a better cosmetic result (p = 0.1) and an improved subjective (p = 0.004) and objective (p = 0.01) shoulder function were statistically significant in operated patients. Clavicle shortening was often found to be significant in conservatively treated patients (p = 0.006). Duration of unfitness for work depended on the physical activity in the job. The complication rate was 15 % for each therapy, non-union was detected in one (0.8 %) patient. CONCLUSION: Mid-shaft clavicular fractures have to be classified by the criteria contact and number of fragments. Advantages of operative procedures are early freedom from pain and shoulder function recovery. Non-displaced low grade shaft fractures without shortening should be treated conservatively, whereas displaced low-grade shaft fractures have a better result after intramedullary nailing. Plate fixation should be predominantly used in dislocated and comminuted fractures as well as in patients with a high level of physical activity in their jobs.

[Delayed diagnosis of fractures of the capitulum of the humerus. Successful internal fixation 6 weeks after the accident]. / Verzögert diagnostizierte capitulum-humeri-frakturen beidseits. Erfolgreiche osteosynthese 6 wochen nach unfall.

Fractures of the capitulum of the humerus are rare and difficult to recognize. At present conservative therapy is only indicated in a few cases with no dislocation of the fracture. Otherwise an anatomical reduction and internal fixation should be done as early as possible. This article reports the case of a 51-year-old female patient with bilateral fractures of the capitulum of the humerus which were diagnosed 6 weeks after trauma. In spite of the extra risk of fragment necrosis, a reduction and internal fixation were performed. After rehabilitation, the patient was free of complaints except for a minimal limited range of motion.

[Sustentaculum tali screw placement for calcaneus fractures--different navigation procedures compared to the conventional technique]. / Sustentaculum-tali-Schraubenplatzierung bei der Versorgung von Kalkaneusfrakturen--verschiedene Navigationsverfahren im Vergleich zur konventionellen Technik.

AIM: Precise placement of the sustentaculum tali screw is essential for fixation of calcaneus fractures to achieve the best fixation strength. In the clinical practice, this procedure is demanding due to the complex anatomic configuration of the calcaneus and the limited visualisation in the intraoperative fluoroscopic images. The aim of this study was an evaluation of the accuracy for the sustentaculum tali screw placement by using different navigation procedures compared to the standard procedure. The different navigation specific workflows were evaluated and the feasibility of each procedure proven in clinical applications. METHOD: Eight sustentaculum screws per group were placed in an artifical Synbone model. Different navigation procedures were evaluated: 2D-fluoroscopy (group I), 3D-fluoroscopy (group II), fluoro-free (group III) and compared to the conventional screw placement without navigation (group IV). For each screw the time of fluoroscopy and the duration of the procedure were measured. The accuracy was evaluated postoperatively by computed tomography using axial slices and coronary as well as sagittal reformations. Furthermore, the workflow of each navigation procedure was analysed and proven in clinical applications. RESULTS: In the experimental setup, no radiation exposure was mandatory for the conventional and fluoro-free procedures, whereas mean fluoroscopy times of 17 +/- 1.03 und 66.8 +/- 0.9 were measured for 2D- and 3D-navigation procedures. In line with this, the overall mean procedure times for the screw placement were 1.26 +/- 0.05 (group IV), 3.49 +/- 0.26 (group III), 13.32 +/- 0.49 (group I) und 19.04 +/- 1.41 minutes (group II). No significant differences were observed for the accuracy of screw placement. In the clinical practice a better orientation was achieved by use of a navigation system. The fluoro-free procedure can be easily integrated into the common operation workflow, whereas the workflow of both image-based navigation procedures is technically demanding. CONCLUSION: Navigation procedures seem to be helpful for the precise placement of sustentaculum tali screws in cases of operative calcaneus fracture fixation. The kind of application to be used depends on the infrastructure of the department and the navigation-experience of the operating room team. Whereas the fluoro-free procedure is intuitive in use, the 2D-navigation does not justify the extra efforts. The 3D-procedure is the recommended application for surgeons familiar with navigation, providing the best orientation due to the slice image visualisation in all three dimensions.

[Necrotizing fasciitis after "banal" back pain. An unusual course of a retrocoecal appendicitis and its sequellae]. / "Banale" Rückenschmerzen als erstes Symptom einer nekrotisierenden Fasziitis : Ungewöhnlich verlaufende retrozökale Appendizitis und ihre Folgen.

Necrotizing fasciitis is a life-threatening disease which can only be successfully treated by an interdisciplinary team. An immediate and radical debridement with opening of all compartments and debridement of the affected fascia is the basis for a successful therapy. We report about the treatment of a 21-year-old man who was taken to hospital due to "banal" back pain which was caused by a perforated appendicitis. In only 2 days necrotizing fasciitis developed which spread out over the complete right leg.

[Navigation-assisted nailing of femoral shaft fractures--experimental and clinical results]. / Navigationsgestützte Marknagelung von Femurschaftfrakturen - experimentelle und klinische Ergebnisse.

AIM: The aim of the study was to evaluate the application of a navigation system (Brainlab) to control length and torsion intraoperatively while nailing a femoral shaft fracture. METHOD: At first the system was tested with 10 fractured synthetic bones. The postoperatively reached length and torsion were measured and the difference to the envisioned values statistically evaluated. Clinically we used the navigation system for patients with complex femoral shaft fractures. We always performed a preoperative computed tomography of the opposite leg to analyse the axis and fixed the fractured leg on these parameters using the navigation system. We noticed as improvement opportunities, the duration of the operative steps and the radiation exposure. The operative result was radiologically controlled and the torsion and length differences to the intraoperative measurement evaluated. Furthermore, we analysed the duration of the operation steps including the additional radiation exposure. RESULTS: There were no technical problems during operations on the synthetic bones. The accuracy was with +/- 5 degrees or +/- 2 mm good enough to use the already approved system clinically. The navigation system was used for 17 operations. All navigation-assisted operations were completed successfully. It took an average time of 32 min to install the navigation system and required an additional X-ray time of 44 sec. The average postoperative rotational deviation was 5.5 degrees . The average difference in length was 2 mm. CONCLUSION: The application of a navigation system for repositioning of femoral shaft axes and controlling the length and torsion while nailing complex femoral shaft fractures is associated with some additional work. Nevertheless, in our study a relevant rotational deviation can be avoided by using the navigation system. To prove the advantage of the navigation system over the conventional technique, clinical studies with larger number of cases are necessary.

[2D-fluoroscopic navigated screw osteosynthesis of acetabular fractures: A preliminary report]. / 2D-fluoroskopisch navigierte perkutane Schraubenosteosynthese von Azetabulumfrakturen: Erste Ergebnisse einer neuen Methode.

INTRODUCTION: The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. In this study we report the early results of percutaneous screw osteosynthesis of acetabular fractures in 14 cases, using a computer navigation system to reduce screw misplacement, approach associated risks and radiation exposure. RESULTS: All 36 acetabular screws were placed correctly without any perioperative complication. The mean operation time per screw was 54 min, the mean fluoroscopic time per screw was 87 s. In the follow-up examinations (current rate: 71 %, mean follow-up: 13.1 +/- 1.8 months) no fixation failure or development of post-traumatic osteoarthritis was seen. One wound infection occured. CONCLUSION: Our first experience with this novel approach is promising and serious advances of fluoroscopic navigated percutaneous screw osteosynthesis of well selected acetabular fractures can be expected.

[Treatment of bilateral distal tibial nonunions. Use of an intramedullary compression nail and a modified locking compression plate osteosynthesis]. / Differenzierte Behandlung beidseitiger distaler Tibiapseudarthrosen. Modifizierte winkelstabile Plattenosteosynthese und Kompressionsmarknagel.

Operative treatment of distal tibial fractures remains a challenge for the surgeon even today. The soft tissues demand atraumatic operative techniques, although an anatomical reduction of the articular fracture component is mandatory. The nonunion rate increases with disturbed local blood supply, widened fracture gap, unstable fixation. If a nonunion occurs, an individual treatment concept is required, so that even difficult situations can be successfully managed, as described in our case with bilateral tibial nonunions.

[Effects of harvesting the central third of the patella tendon on the kinetics of the knee joint and the retropatellar pressure]. / Auswirkungen der Entnahme des mittleren Patellarsehnendrittels auf die Kinematik des Kniegelenkes und den retropatellaren Druck.

AIM: This biomechanical study was performed to evaluate the consequences of removing the central part of the patellar tendon on the kinematics and kinetics of the femoro-patellar joint. The tendonectomy was performed in the same manner as is frequently done during anterior cruciate ligament reconstructions. Of particular interest in this study was to identify potential factors of the patellar tendon resection which could result in anterior knee pain. METHOD: A simulated isokinetic knee extension from 120 degrees of flexion to full extension was performed on nine human knee cadaver specimens. Joint kinematics was evaluated with ultrasound sensors, and retropatellar contact pressure was measured using a thin-film resistive ink pressure measuring system. Data were taken before and after resection of the central third of the patellar tendon. RESULTS: Harvesting of the central third of the patellar tendon resulted in an elongation of the remaining patellar tendon by less then 0.5 mm. Furthermore, increases in patellar flexion lower than 1 degree were observed. Small changes in retropatellar pressure were also observed. CONCLUSION: The shortening of the patellar tendon due to tendon removal, as already suggested in several previous studies, is not attributed to the removal of the central portion of the tendon itself, but more likely due to secondary scarring contraction of the tissue. The changes of the patellarkinematics and the retropatellar pressure observed in this study are probably not of any clinical significance.