[Paraplegia after isolated rupture of the spinal cord - a rare injury]

INTRODUCTION

Complex vertebral fractures can lead to injury of the spinal cord with resulting paraplegia. High-speed accidents are common causes, especially in younger patients. Malignant or inflammatory processes play an important role in the elderly. Less common reasons for a spinal cord injury are congenital malformations. We here report about a 17-year-old patient who suffered from paraplegia after an isolated rupture of the spinal cord without an injury of the vertebral bodies, intervertebral disc or ligamentous structures. This type of injury has not been reported in the literature before.

PATIENT AND METHOD

We report about a 17-year-old patient, referred to our hospital, presenting with lumbal paraplegia after a high-speed accident 8 days prior to admission. After initial stabilisation of the polytraumatised patient, he was referred to our hospital for further treatment.

RESULTS AND CONCLUSION

The radiological examination showed a bilateral acetabular fracture, a right anterior pelvic ring fracture and shaft fractures of the left humerus and right femur. Furthermore, the spinal cord at thoracic level 10/11 was ruptured. Interestingly, there was no injury of the vertebral bodies, intervertebral disc or ligamentous structures. A tethered cord as a possible anatomic variation could be excluded in this case by MRI. However, anatomic variations could be the reason for this injury and should be kept in mind.

[Arm wrestling injuries--report on 11 cases with different injuries]

INTRODUCTION

Arm wrestling may cause severe injuries. Various injuries after arm wrestling have been reported in the literature, whereas the most common injury is the humeral shaft fracture. In this context we report on eleven cases with different injuries during arm wrestling.

MATERIAL AND METHODS

All patients were analyzed using a standardized questionnaire. The effect of drugs, pre-existing conditions and injuries as well as sport activities were examined. Furthermore we report about a 24 year old patient who sustained a radial shaft fracture which has not been reported in the literature yet.

RESULTS

8 patients suffered from a fracture. The humerus was the most affected bone in 7 cases. 3 patients had a muscle strain, whereas in all 3 cases the patients were regularly sportive active and warmed-up be for the injury. Ten patients were reintegrated into the previous job after an average time period of 6 weeks. One patient was out of work.

CONCLUSIONS

Regular sport activity and the muscle strength are important factors for the injury intensity. Further studies are necessary to confirm this theory.

Radiolunate fusion in the rheumatoid wrist with Shapiro staples: clinical and radiological results of 22 cases

We performed a retrospective clinical and radiological case control study on 22 rheumatoid wrists following radiolunate fusion via Shapiro staples with a mean follow-up of 5 years. Radiographs showed one early loosening through dorsal staple migration and four nonunions. Six wrists fused in mild ulnopalmar dislocation of the lunate. Primary intra-articular positioning of a staple was found in nine wrists, secondary intra-articular staple dislocation was found in two wrists. Dorsal staple dislocation was found in four fused arthrodeses. Osteolysis around the staples was found in all but two wrists. In contrast to unsatisfactory radiological results the clinical results were good or excellent in 18 patients. Good and excellent clinical results in the majority of the patients following radiolunate fusion does not depend on the fixation device. Nevertheless staple fixation of the radiolunate joint in the rheumatoid wrist is associated with a high rate of radiological complications.

Implementation of a new navigated parallel drill guide for femoral neck fractures

Trauma navigation modules often use conventional mechanical surgical tools for basic simulation of drilling procedures or single screw placement. However, the precise parallel placement or specific angles that may be required are not displayed on the navigation screen. A more complex mechanical tool, a parallel drill guide (PDG) for femoral neck fractures, was integrated into a navigation module as part of this study, thus combining the advantages of mechanical tools with the benefits of fluoroscopic navigation. To implement a conventional PDG with a conventional navigation system, the tool was equipped with a non-detachable reflective marker array. Navigation engineers adapted the software to enable the navigated PDG to be displayed. We evaluated the conventional technique in comparison with the navigated technique using plastic bone models and a fresh frozen cadaver. Implementation of the navigated PDG did not pose any problems, in terms of either the software or the surgical procedure itself. The total operation time was extended by 30%, but the radiation time for the navigated group was reduced by 50%. No software or hardware-related failures occurred. Complete integration of a cannulated parallel drill guide into a navigation system has been successfully implemented. Continuous display of the mechanical guide with two parallel trajectories on the navigation screen enables safe, efficient screw placement within mechanical guidelines, without the need for additional radiographic control once initial registration has been completed.

Computer-assisted antetorsion control prevents malrotation in femoral nailing: an experimental study and preliminary clinical case series

MATERIALS AND METHODS

The effect of fluoroscopy-based navigation for femoral fracture reduction on the prevention of malrotation was examined in an experimental setting followed by a first case series. Eleven cadaver femurs were used. All femurs were reduced by closed methods. An optoelectronic navigation system was utilized to check for fragment reduction and alignment. Fluoroscopic control without navigation was used as the control group. The Six Sigma Analysis [offset capability index (C (pk)) = 1.3] was used to compare the probability of outliers of more than 15 degrees . In the clinical case series the same navigation tool was used in ten non-consecutive patients with femoral fractures. Torsional differences between both legs were measured postoperatively by CT scan.

RESULTS

The highest malrotation in the navigated group was 7.0 degrees for the cadaver testings, while two femurs in the control group showed a difference of more than 10 degrees (10.3 degrees , 17.4 degrees). Only the navigated group showed a sufficient offset capability index (C (pk-navigated) = 1.83; C (pk-conventional) = 0.59). In the clinical series nine femurs were successfully reduced by navigation control. The average malrotation was 6.6 degrees . No patient had a torsional difference of more than 10 degrees.

CONCLUSION

Navigated femoral nailing reduces the risk for outliers of postoperative torsional differences and might avoid revision surgery for malrotation.

LEVEL OF EVIDENCE

IV.

Accuracy of navigated surgery of the pelvis after surface matching with an a-mode ultrasound probe

Computer-aided surgery (CAS) allows for real-time intraoperative feedback resulting in increased accuracy, while reducing intraoperative radiation. CAS is especially useful for the treatment of certain pelvic ring fractures, which necessitate the precise placement of screws. Flouroscopy-based CAS modules have been developed for many orthopedic applications. The integration of the isocentric flouroscope even enables navigation using intraoperatively acquired three-dimensional (3D) data, though the scan volume and imaging quality are limited. Complicated and comprehensive pathologies in regions like the pelvis can necessitate a CT-based navigation system because of its larger field of view. To be accurate, the patient's anatomy must be registered and matched with the virtual object (CT data). The actual precision within the region of interest depends on the area of the bone where surface matching is performed. Conventional surface matching with a solid pointer requires extensive soft tissue dissection. This contradicts the primary purpose of CAS as a minimally invasive alternative to conventional surgical techniques. We therefore integrated an a-mode ultrasound pointer into the process of surface matching for pelvic surgery and compared it to the conventional method. Accuracy measurements were made in two pelvic models: a foam model submerged in water and one with attached porcine muscle tissue. Three different tissue depths were selected based on CT scans of 30 human pelves. The ultrasound pointer allowed for registration of virtually any point on the pelvis. This method of surface matching could be successfully integrated into CAS of the pelvis.

Value of 3D fluoroscopic imaging of acetabular fractures comparison to 2D fluoroscopy and CT imaging

PURPOSE

Intraoperative two-dimensional (2D) fluoroscopy of acetabular fractures is difficult due to the complex three-dimensional (3D) anatomy. Intraoperative 3D fluoroscopy may have particular utility in the evaluation of acetabular fractures. We compared the accuracy of 3D fluoroscopic imaging in evaluating acetabular fracture displacement and implant placement with fluoroscopy and computed tomography (CT) scans.

METHODS

In 24 cadaveric acetabuli, a transverse acetabular fracture was created. First a 2 mm step-off of the articular surface was created and reconstruction plates placed on the anterior and posterior columns. In 12 specimens, two screws were placed intraarticularly, protruded by 2 mm. In the remaining 12 specimens, the same constructs were used but the screws remained extraarticular. Second tests were designed to simulate an impaction injury. After hardware removal, a hollow trephine (diameter of 14.9 mm) was used to core a bone cylinder on the dome of the acetabulum, and impacted until it was recessed into the articular surface by 2 mm. Plates were placed, and screws were placed intraarticularly in 12 specimens, as in the first set of tests. All cadavers were imaged with standard 2D-, 3D fluoroscopy and CT. Three observers randomly evaluated all imaging studies for all specimens.

RESULTS

For detection of intraarticular screws, both the Iso-C3D and the CT scans were significantly more sensitive (96 and 96%, respectively) and specific (96 and 100%, respectively) in detecting the intraarticular position compared to 2D fluoroscopy (75%; P < 0.05). Sensitivity of articular step-off detection was no different between the Iso-C3D (83%), CT (79%), and 2D fluoroscopy (87%). Articular impaction was correctly identified in 79% of specimens with the Iso-C 3 D technique, while the CT was accurate in 92%. 2D fluoroscopy was accurate in 62% for the impactions (P < 0.05 vs. CT).

CONCLUSIONS

3D-fluoroscopic imaging appears to be extremely accurate in evaluating acetabular fracture constructs. Its sensitivity and specificity for evaluating intraoperative hardware was greater than with 2D fluoroscopy and equivalent to CT scan. Volumetric impactions were also reliably demonstrated on both of the 3D modalities, which were both superior to 2D fluoroscopy. Overall, Iso-C3D multiplanar imaging yields information regarding implant placement and articular reduction that is more detailed and accurate than standard fluoroscopy and is comparable to CT.

Influence of lower limb rotation in navigated alignment analysis: implications for high tibial osteotomies

Inaccurate coronal plane realignment is a common problem after high tibial osteotomy. It has been shown that lower limb rotation has an effect on the two-dimensional measurement of lower limb alignment. Although alignment errors are known to occur due to limb rotation, the magnitude of this effect is unknown. Navigation systems allow for the measurements of coronal plane alignment and dynamically rotational and sagittal plane. Our study evaluated the effect of rotational leg movements on coronal plane alignment as determined by image-free navigation. We hypothesized that a linear relationship exists between rotation and angular measurements. Eight cadavers were used, while three test conditions of the complete lower limbs were established: (1) solid knee arthrodesis, (2) provisional knee arthrodesis and (3) unconstrained knee conditions. Navigated measurements of coronal and sagittal lower limb axis were done initially without knee flexion for defined internal/external rotations of 5 degrees, 10 degrees and maximal values for all test series. Repeated test for the unconstrained knee included stepwise knee flexion of 5 degrees, 10 degrees and 20 degrees. Statistical analysis comparing the test conditions 1, 2 and 3 and comparison between flexion movements of the unconstrained knee were done. Results revealed no significant differences between the different rotations of test condition 1 (mean 0.34 degrees, SD 0.23, range, 0 degrees-0.8 degrees). Condition 2 similarly did not result in significant deviations (mean 0.51 degrees, SD 0.24, range 0.1 degrees-0.9 degrees). Measurement deviations ranging from 0.4 degrees to 4.3 degrees were found for condition 3, the unconstrained knee. However, no statistically different testings from the arthrodesed knee were found (P=0.099-0.410). Knee flexion from 5 degrees, 10 degrees or 20 degrees, showed significant deviations (P<0.05) for all rotations at all degrees of flexion. Rotation and flexion of 5 degrees led to significant alignment errors of 3.4 degrees and 2.8 degrees, respectively, for internal and external rotations. Measurement failures due to the rotational movements of 1 degree-4 degrees might add to additional sources of errors causing relevant under- or over-corrections of the mechanical leg axis. Discrepancies of the axis due to rotational movements as well as flexion of the knee joint can be avoided and corrected immediately with the help of navigation.

Die navigierte Scaphoidschraube

INTRODUCTION

Up to now, the use of navigation systems for the placement of scaphoid screws has been impossible, mainly because there have been no ways of fixing the reference markers. Faulty placement rates in internal fixation of the scaphoid show there is a current need for a 3D image-based navigation system and intraoperative monitoring of how successful the procedure will be. For this reason, we have developed a new radiotransparent hand fixation device (Scaph-Splint), which allows reliable and accurate drilling of the scaphoid using 3D navigation. Tests of this device and the simultaneous precise placement of screws securing an internal fixation device are described in this paper.

MATERIAL AND METHODS

Relative movements between the wrist and fixation device were measured with a 3-D ultrasound motion analyser system. Five cadaveric upper extremity specimens were then used for further navigated test applications. Each specimen was placed in the fixation device, and both the forearm and hand were secured to the two surfaces, with the wrist in approximately 80 degrees of extension. A reference marker was then securely fixed to the fixation device. A commercial navigation system and 3-D fluoroscopic imaging were used for each trial. Under navigation, the scaphoid was drilled in retrograde fashion, and a screw was placed into the drilled hole. Following screw placement, a 3D scan was performed to evaluate its position. The screw placement was analysed blindly to optimal placement and drill or screw perforation, and the image quality was rated on a visual analog scale (VAS).

RESULTS

There were few artefacts, and the image quality of the 3-D scan was judged as as good (VAS 79). Deviations of >or=0.2 mm between planned trajectory and drilling tunnal were not found in any of the specimens; there were deviations of >or=1 mm in one case, and all other cases showed deviations of <or=1 mm. There were no registration failures of the navigation system, indicating that no loosening of the reference marker or movement of the hand occurred. There was one case of scaphoid perforation at the distal pole.

DISCUSSION

We found that the Scaph-Split allowed complete immobilisation of the hand and carpus. This allowed for adequate reference tracker stability and subsequent successful 3D navigated fluoroscopic drilling and screw placement in the scaphoid. While further tests on fresh-frozen cadavers is warranted, this technique may prove clinically to be very useful for surgeons treating scaphoid fractures.

[A new parallel drill guide for navigating femoral neck screw placement. Development and evaluation]

BACKGROUND

Trauma navigation applications employ conventional mechanical surgical instruments for the simulation of drilling trajectories. Few complex mechanical targeting instruments, such as guides with fixed angles or with multiple parallel cannulas, have been adapted into trauma navigation systems. We have integrated a complex mechanical tool, the parallel drill guide (PDG) for the minimally invasive treatment of femoral neck fractures, into a trauma navigation module. The combined advantage of a complex yet commonly used mechanical tool with the benefits of fluoroscopic navigation was evaluated.

MATERIAL AND METHODS

To adapt the conventional PDG to a fluoroscopic navigation system, the instrument was fitted with a non-detachable reflective marker array. Navigation engineers developed custom software to enable visualization of the navigated PDG. A comparison of conventional versus navigated PDG techniques was performed on plastic bone models and cadavers. No software or mechanical failures occurred with the navigated PDG procedures.

RESULTS

While the total operative time was 30% more with navigation compared with conventional techniques, the total radiation time for the navigated group was reduced by more than 60%. This study demonstrates the successful integration of a cannulated parallel drill guide with a fluoroscopic navigation system.

CONCLUSION

The continuous display of the complex PDG mechanical instrument, with multiple parallel virtual trajectories, enables safe and accurate parallel screw placement. The integration of complex mechanical instrumentation with navigation for the accurate placement of hardware represents an attractive direction in multiple trauma applications.

Navigated percutaneous pelvic sacroiliac screw fixation: experimental comparison of accuracy between fluoroscopy and Iso-C3D navigation

Percutaneous sacroiliac screw fixation is technically demanding and can result in complications mainly related to imaging problems. Furthermore, the conventional technique performed using fluoroscopic control is associated with a long radiation exposure. The purpose of this study was to evaluate the accuracy of two navigation technologies used in traumatology; fluoroscopy and Iso-C3D navigation. A total of 40 screws were placed (20 with Iso-C3D, 20 with 2D fluoroscopy) at levels S1 and S2. With both technologies, all S1 screws could be placed correctly, but four (10%) incorrect placements were seen at S2 with fluoroscopy navigation. With all Iso-C3D navigated drillings, no perforation was seen. Iso-C3D navigation therefore proved superior to 2D fluoroscopy navigation for sacroiliac screw fixation in an experimental set-up designed to assess accuracy.

Accuracy analysis of Iso-C3D versus fluoroscopy-based navigated retrograde drilling of osteochondral lesions

The aim of this pilot study was to evaluate the accuracy of two different methods of navigated retrograde drilling of talar lesions. Artificial osteochondral talar lesions were created in 14 cadaver lower limbs. Two methods of navigated drilling were evaluated by one examiner. Navigated Iso-C3D was used in seven cadavers and 2D fluoroscopy-based navigation in the remaining seven. Of 14 talar lesions, 12 were successfully targeted by navigated drilling. In both cases of inaccurate targeting the 2D fluoroscopy-based navigation was used, missing lesions by 3 mm and 5 mm, respectively. The mean radiation time was increased using Iso-C3D navigation (23 s; 22 to 24) compared with 2D fluoroscopy-based navigation (14 s, 11 to 17).

[A web-based e-learning tool in academic teaching of trauma surgery. First experiences and evaluation results]

There are lots of possibilities for universities to offer contents of teaching to students by the Internet. Often the students can download slides or a special lecture note from the intranet of the university. Another way is to make a movie of the lecture and post this lecture movie on the Internet. In the Hanover Medical School we employed an alternative. It was developed by the Trauma Surgery Clinic and the Institute of Medical Informatics at the Hanover Medical School. Our goal was to use just one web-based content resource for the lecture and for the work at home. The Institute of Medical Informatics used a web-based content management system (CMS) Schoolbook to implement this e-learning application.Since October 2005 the Trauma Surgery Schoolbook has been used in the lecture on trauma surgery in all terms, and we evaluated the academic year 2005/2006. The results of the evaluation showed us that the students were very interested in using this e-learning application. The possibility to reinforce the learning material at home is a good chance for the students. Also the organisation of lectures was improved because the materials were all in one place. The lecturer needs to learn several new tasks, but we also got a positive response. Our experiences of the last academic year showed that it was a good way to use one web-based content resource for teaching and learning in the context of a lecture.

Percutaneous bone biopsy. A new application for 3D navigation: a pilot study

Computer Tomography (CT) guided percutaneous bone biopsy has been established as a minimally invasive method for the rapidly obtaining samples from osseous lesions for histological examination. With this method, an overall accuracy of 90% can be obtained without a significant radiation exposure. The aim of this study was to develop a navigated sleeve for the Jamshidi needle in order to perform navigated, percutaneous bone biopsies with the help of Iso-C-3D. Utilizing this navigated biopsy needle, the procedure was analyzed for several parameters including precision, total operating time, and level of radiation exposure. By using the Iso-C-3D navigation the total operating time was 11.7 min (8-14.3) and radiation exposure was 1.6 (0.67-2.12 min). This study demonstrates that navigated percutaneous bone biopsies can be obtained fast and with low radiation exposure. The feasibility of Iso-C-3D navigated bone biopsies is tempered by the requirement a rigidly fixed dynamic reference frame.

Reference marker stability in computer aided orthopedic surgery: a biomechanical study in artificial bone and cadavers

INTRODUCTION

In computer assisted orthopaedic surgery, rigid fixation of the Reference Marker (RM) system is essential for reliable computer guidance. A minimum shift of the RM can lead to substantial registration errors and inaccuracies in the navigation process. Various types of RM systems are available but there is little information regarding the relative stabilities of these systems. The aim of this study was to test the rotational stability of three commonly used RM systems.

MATERIALS AND METHODS

One hundred and thirty Synbones and 15 cadavers were used to test the rotational stability of three different RM systems (Schanz' screw, RM B and RM C adjustment systems). Using a specially developed testing device, the peak torque sustained by each RM system was assessed in various anatomical sites.

RESULTS

Comparison of means for Synbone showed that the RM C was the most stable (mean peak torque 5.60 +/- 1.21 Nm) followed by the RM B system (2.53 +/- 0.53 Nm) and the RM A (0.77 +/- 0.39 Nm) (p<0.01). The order of stability in relation to anatomical site was femoral shaft, distal femur, tibial shaft, proximal tibia, anterior superior iliac spine, iliac crest and talus. Results from the cadaver experiments showed similar results. Bi-cortical fixation was superior to mono-cortical fixation in the femur (p<0.01) but not the tibia (p=0.22).

CONCLUSION

The RM system is the vital link between bone and computer and as such the stability of the RM is paramount to the accuracy of the navigation process. In choosing RM systems for computer navigated surgery surgeons should be aware of their relative stability. Anatomical site of RM placement also affect the stability. Mono-cortical fixation is generally less stable than bi-cortical.