Thomas Goesling

Pose Estimation of Cylindrical Fragments for Semi-Automatic Bone Fracture Reduction

We present an approach for estimating the relative transformations between fragments of a broken cylindrical structure in 3d. To solve this problem, we first measure the orientation and position of the cylinder axes for each fragment by an adapted kind of Hough Transformation. The cylinder axes are an important feature for separation of fractured areas and for calculation of an initial reposition solution (constraining 4 DOFs). After these processing steps, we compute the relative transformations between corresponding fragments by using well-known surface registration techniques, like 2d depths correlation and the ICP (Iterative Closest Point) algorithm. One goal of our project is to use the proposed method for estimation of relative transformations between fragments of fractured long bones for computer aided and semi-automatic bone alignment and fracture reduction in surgery.

Polyaxially-locked plate screws increase stability of fracture fixation in an experimental model of calcaneal fracture

Different calcaneal plates with locked screws were compared in an experimental model of a calcaneal fracture. Four plate models were tested, three with uniaxially-locked screws (Synthes, Newdeal, Darco), and one with polyaxially-locked screws (90 degrees +/- 15 degrees ) (Rimbus). Synthetic calcanei were osteotomised to create a fracture model and then fixed with the plates and screws. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1000 cycles at 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). During cyclic loading, the plate with polyaxially-locked screws (Rimbus) showed significantly lower displacement in the primary loading direction than the plates with uniaxially-locked screws (mean values of maximum displacement during cyclic loading: Rimbus, 3.13 mm (sd 0.68); Synthes, 3.46 mm (sd 1.25); Darco, 4.48 mm (sd 3.17); Newdeal, 5.02 mm (sd 3.79); one-way analysis of variance, p < 0.001). The increased stability of a plate with polyaxially-locked screws demonstrated during cyclic loading compared with plates with uniaxially-locked screws may be beneficial for clinical use.

Differences in the mechanical properties of calcaneal artificial specimens, fresh frozen specimens, and embalmed specimens in experimental testing

Background. Artificial calcanei, fresh-frozen cadaver specimens, and embalmed cadaver specimens were compared in experimental testing under biocompatible loading to clarify the biocompatibility of artificial calcaneal specimens for implant testing. Methods. Two different artificial calcaneal bone models (Sawbone™, Pacific Research Laboratories, Vashon, WA, and Synbone™, Synbone Inc., Davos, Switzerland), embalmed cadaver calcaneal specimens (bone density, 313.1 ± 40.9 g/cm 2 age, 43.8 ± 7.9 years), and fresh-frozen cadaver calcanei (bone density, 238.5 ± 30.0 g/cm 2 age, 44.4 ± 8.2 years) were used for testing. Seven specimens of each model or cadaver type were tested. A mechanical testing machine (Zwick Inc., Ulm, Germany) was used for loading and measurements. Cyclic loading (preload 20 N, load was increased every 100 cycles by 100 N from 1,000 to 2,500 N, 0.5 mm/s) and load to failure (0.5 mm/s) were performed. The loads were applied through an artificial talus in a physiological loading direction. The displacement of the posterior facet in the primary loading direction was measured. Results. The four different specimen groups showed different stability and different displacement in the primary loading direction during cyclic loading. The variation of the maximal displacement in the primary loading direction for the entire cyclic loading was higher in artificial specimens than in the cadaver specimens. Conclusions. Artificial calcanei (Sawbone™, Synbone™) showed different biomechanical characteristics than cadaver bones (embalmed and fresh-frozen) in this experimental setup with biocompatible cyclic loading. These results do not support the use of artificial calcanei for biomechanical implant testing. Fresh-frozen and embalmed specimens seem to be equally adequate for mechanical testing. The low variation of mechanical strength in the unpaired cadaver specimens suggests that the use of paired specimens is not necessary.

68 Ga-DOTANOC PET/CT for the detection of a mesenchymal tumor causing oncogenic osteomalacia

A 54-year-old female patient had presented with clinical features of hyperphosphaturia, hypophosphatemia and osteomalacia. These findings were suggestive of oncogenic osteomalacia, a rare paraneoplastic disorder that is usually associated with a phosphaturic mesenchymal tumor [1]. Conventional morphologic imaging including whole-body computed tomography (CT) failed to localise the primary tumor. The patient underwent additional positron emission tomography (PET)/CT using Ga-DOTANOC, a highly sensitive and specific tracer for imaging of somatostatin receptor overexpression, which has recently proven potential in oncogenic osteomalacia [2, 3]. Abnormal focal tracer uptake was seen in the right distal femur (A). Using image fusion and three-dimensional volume-rendering techniques, the localisation of the suspected primary tumor was clearly visualised (B). Notably, no morphologic correlative was observed in the corresponding low-dose CT (C). Based on the PET/CT findings, the patient underwent segmental resection and compound osteosynthesis of the distal femur. The hematoxylin and eosin-stained section (D) demonstrated randomly organised spindle cells with slight cellular and nuclear atypia and a sparse intercellular matrix. Immunohistochemistry was negative for myogenic, neural, vascular and epithelial markers. These histopathologic findings were consistent with the diagnosis of a benign phosphaturic, mesenchymal tumor.

Intraprosthetic fixation techniques in the treatment of periprosthetic fractures-A biomechanical study

AIM To develop new fixation techniques for the treatment of periprosthetic fractures using intraprosthetic screw fixation with inserted threaded liners. METHODS A Vancouver B1 periprosthetic fracture was simulated in femur prosthesis constructs using sawbones and cemented regular straight hip stems. Fixation was then performed with either unicortical locked-screw plating using the less invasive stabilization system-plate or with intraprosthetic screw fixation using inserted liners. Two experimental groups were formed using either prostheses made of titanium alloy or prostheses made of cobalt chrome alloy. Fixation stability was compared in an axial load-to-failure model. Drilling was performed using a specially invented prosthesis drill with constantly applied internal cooling. RESULTS The intraprosthetic fixation model with titanium prostheses was superior to the unicortical locked-screw fixation in all tested devices. The intraprosthetic fixation model required 10 456 N ± 1892 N for failure and the unicortical locked-screw plating required 7649 N ± 653 N (P < 0.05). There was no significant difference between the second experimental group and the control group. CONCLUSION Intraprosthetic screw anchorage with special threaded liners enhances the primary stability in treating periprosthetic fractures by internal fixation.

Human-robot interaction for 3D telemanipulated fracture reduction

Today, femoral shaft fractures are usually stabilized by means of intramedullary nails. This video presents the development of a telemanipulator system, which, by supporting the fracture reduction process, aims at achieving reliable operation results with high reduction accuracies. First, we present a system using 2D X-ray images as base information for the surgeon to guide the reduction. We show the advantages but also the limitations of this approach, which finally led to the development of a telemanipulator system that is based on 3D imaging data instead.

Secondary Collapse of an Expandable Cage After Vertebral Corpectomy

Expandable vertebral body replacement systems have been increasingly used for anterior stabilization of spine. We report a secondary collapse of an expandable vertebral body replacement system. This specific complication has not been reported in the literature so far. The most obvious reason for failure was insufficient tightening of a locking screw. This paper emphasizes the importance of correct technical application.

The Use of Poller Screws for Metaphyseal Tibia and Femur Fractures Treated With Small-Diameter Intramedullary Nails

Summary The intramedullary nailing of metaphyseal fractures is associated with an increased incidence of deformities, which can result from instability after fracture fixation. Poller screws or blocking screws, placed adjacent to an intramedullary nail, block transverse nail translation and enhance the stability of the bone-implant construct. The purpose of this article is to describe the clinical use of blocking screws in supplementing metaphyseal tibia and femur fractures stabilized with a small-diameter, statically interlocked intramedullary nail.