Syndesmotic ankle injuries are present in one fourth of all ankle trauma and may lead to chronic syndesmotic instability as well as posttraumatic ankle osteoarthritis. The main challenge remains distinguishing them from other types of ankle trauma. Currently, the patient's injured and non-injured ankles are compared using plain radiographs to determine pathology. However, these try to quantify 3D displacement using 2D measurements techniques and it is unknown to what extent the 3D configuration of the normal ankle syndesmosis is symmetrical.

We aimed to assess the 3D symmetry of the normal ankle syndesmosis between the right and left side in a non- and weightbearing CT.

In this retrospective comparative cohort study, patients with a bilateral non-weightbearing CT (NWBCT; N=28; Mean age=44, SD=17.4) and weight-bearing CT (WBCT; N=33; Mean age=48 years; SD=16.3) were analyzed. Consecutive patients were included between January 2016 and December 2018 when having a bilateral non-weightbearing or weightbearing CT of the foot and ankle. Exclusion criteria were the presence of hindfoot pathology and age less than 18 years or greather than 75 years. CT images were segmented to obtain 3D models. Computer Aided Design (CAD) operations were used to fit the left ankle on top of the right ankle. The outermost point of the apex of the lateral malleolus (AML), anterior tubercle (ATF) and posterior tubercle (PTF) were computed. The difference in the coordinates attached to these anatomical landmarks of the left distal fibula in the ankle syndesmosis with respect to right were used to quantify symmetry. A Cartesian coordinate system was defined based on the tibia to obtain the direction of differences in all six degrees of freedom. Statistical analysis was performed using the Mann-Whitney U test to allow comparison between measurements from a NWBCT and WBCT. Reference values were determined for each 3D measurement in a NWBCT and WBCT based on their 2SD. The highest difference in translation could be detected in the anterior-posterior direction (Mean AP_NWBCT= −0.01mm; 2SD=3.43/Mean AP_WBCT=−0.1mm; 2SD=2.3) and amongst rotations in the external direction (Mean AP_NWBCT=−0.3°; 2SD=6.7/Mean AP_WBCT=-0,2°; 2SD=5.2). None of these differences were statistically significant in the normal ankle syndesmosis when obtained from a NWBCT compared to a WBCT (P>0.05).

This study provides references values concerning the 3D symmetry of the normal ankle syndesmosis in weightbearing and non-weightbearing CT-scans. These novel data contribute relevantly to previous 2D radiographic quantifications. In clinical practice they will aid in distinguishing if a patient with a syndesmotic ankle lesion differs from normal variance in syndesmotic ankle symmetry.

Objectives: Microbial biofilms protect planctonic bacteria growing on the implants surfaces from detection and antibiotic treatment. To investigate the efficacy of sonication cultures in our patients with prosthetic joint infections we compared our findings with the results to those of periprosthetic tissue cultures and histology.

Methods: The sonication cultures of the explanted prosthesis were cultured according to the protocol by Trampuz et al. in the New England Journal of Medicin and using the routine method incubating the aspirated pus and periprosthetic material in brain-heart-infusion broth without sonication. To assess the most frequently affected component of the prosthesis all components were “sono-cultured” separately. The diagnosis of infection was based on the presence of bacteria or leucocytes in pus or tissue plus local signs and symptoms and/or systemic markers of inflammation (fever, leucocytosis, increased C-reactive protein)

Results: We investigated 60 patients with 40 septically and 20 aseptically explanted components of total knee (n=24), hip (n=21) tumor (n=6) and shoulder (n=2) endoprosthesis, as well as osteosynthetic material (n=6) and spinal instrumentation (n=1). The most frequently affected component of the hip prosthesis was the femoral head (100%) and the inlay (88%), of the knee prosthesis was the Patella (58%) and the tibia plateau (56%), of the tumor prosthesis were the polyethylene components (100%), of the shoulder prosthesis was the sphere and stem (each 100%), of the osteosynthesis material were the plate and screws (each 33%) and of the spine instrumentation were the rod and the screws (each 100%). From all detected pathogens in sonication cultures the most frequently were Staphylococcus aureus (25%), Staphylococcus epidermidis (22%) and Streptococci (13%). The sensitivity of sonication cultures and periprosthetic tissue cultures was 85% and 78% without preoperative antibiotic therapy compared with histological analysis of 100% sensitivity. The specificity was 89% for sonication cultures, 95% for periprosthetic tissue cultures and 100% for histological analysis.

Conclusion: Our results of separating the explanted components for sonication culture proved the detection of valid pathogens for every kind of endoprosthesis or implants and supplied further information for the focus of infection.

Background: We present a prospective two to ten year follow-up of soft tissue balancing surgery at the subluxated second MTP joint. The purpose of this study was to find out the effect of soft tissue balancing techniques of the second MTP joint on long term VAS and AOFAS results. As second hypotheses we compared the results of two different techniques, one group with additional transarticular Kirschner wire (KW) fixation of the second MTP joint temporary for 3 weeks postoperative and the other group without.

Materials and Methods: Fifty-four patients, 45 women and nine men, with a total of 62 operative interventions were included in our follow-up evaluation. Soft tissue balancing techniques we used were capsulotomy, lengthening of the extensor tendons, incision of the collateral ligaments and intrinsic muscles with or without temporary transarticular Kirschner wire (KW) fixation.

Pre- und postoperative VAS and AOFAS scores, as well as clinical and radiological findings were analyzed. One weightbearing and one without weightbearing dorsoplantar radiograph as well as a 45 degrees rotated radiograph were done pre and postoperatively to proof the position of the second toe.

Results: The statistical calculations showed a highly significant outcome (p< 0.0001) comparing pre- to postoperative scores.

Explorative data analysis as well as chi-square tests comparing the two groups - 29 second toes with and 33 second toes without temporarily additional transarticular KW fixation of the MTP joint - showed homogeneous distribution of all scores.

Conclusion: Our evaluation showed highly significant improvement with soft tissue balancing for subluxated second MTP joint of the second metatarsal, but no benefit from additional KW fixation of the MTP joint.

Introduction: Total knee arthroplasty in obese patients remains a challenge to most surgeons. Surgical complication rates as well as perioperative morbidity are higher than total knee arthroplasty in the nonobese. The purpose of this paper is to review our experience with total knee arthroplasty in superobese patients (BMI> 50).

Methods: From 1998–2005, 84 patients underwent 148 knee arthroplasties. Sixty-four patients underwent simultaneous bilateral total knee arthroplasties and 20 patients underwent unilateral knee arthroplasties. They were compared with similar group of nonobese patients who underwent knee arthroplasties during the same time period. All patients received combined regional and general anesthesia.

Results: Mean follow-up was 3.8 years (2–7). Knee society scores improved by 36 points in the superobese (pre-op 47 to 83 post-op) and by 45 points in the non-obese (pre-op 47 to 93 post-op) (p< .05). There was a greater incidence of complications in the superobese group, namely superficial wound infections and deep vein thrombosis. There was late loosening in three tibial components and instability in two patients that required revision in the superobese group. No reoperations in the nonobese group.

Conclusion: Although total knee arthroplasty may be safely performed in the superobese, it may be complicated by infection, loosening, instability, and lower knee scores.

Between 11/2005, and 9/2006 a first series of patients has undergone transpedicular instrumentation with 3D robotic assistance in the lumbar spine at our Orthopaedic Department. This technology must not be confused with standard spine navigation and will be presented in detail.

16 patients (12m, 4f, avg. age 55 yrs.) were randomly selected from our clientele for lumbar fusion or dynamic stabilization via transpedicular instrumentation. After informed consent they obtained thin slice CT scans of the operating field prior to surgery.

The Mazor computer system then imported the scans, allowing 3-D planning of screw placement. A fixation device was then attached to the patient and the system was calibrated in connection with a standard fluoro-scope. On the device a robotic device with a working arm was mounted. Automatic matching algorithms then moved the robot, pointing its arm towards the designated pedicle screw portals. The screws could then be placed through the working arm, either cannulated (ICON) via K-wires, or solid (XIA) via standard awls. Percutaneous MIS insertion was also feasible. Instrumentation was then set forth after removal of the robot as usual. The CT accuracy of screw placement in all robot-assisted patients was scored according to Mattes et al. postoperatively.

1 patient had to be instrumented manually for reasons unrelated to the system. In 2 early obese patients the system denied robotic access due to insufficient imaging, thus enforcing standard manual technique. In the remaining patients a total of 58 screws had to be placed. No clinical complication related to the Mazor system occurred. A total of 6 screws could not be placed by the system due to steep lumbosacral angles. Additional time of surgery could be reduced to 40 minutes per case during the series.

None of the robotic screws was misplaced in the final CT. 1 of the 6 non-robotic screws was misplaced at the S1 level and needed replacement due to apparent nerve contact without palsy. The robotic screws reached an average Mattes score of 1.5 which can be considered superior to sole fluoroscopic techniques (2.5). Additional decompression did not impede the system which does not rely on surface matching. On the basis of the clinical application, additional features were developed, e.g. robot mounting wedges for hyperlordosis, and oblique fluoro view acquisition. The planning software also avoids “supercharging” of the pedicle due to screw oversize. In one case this inevitably would have happened in conventional technique.

This is the first report worldwide about the beginning of robotic assisted pedicle screw placement in Europe in daily routine. The Mazor System now has proven its usefulness and potential. Additional most recent data will be available at time of presentation as the system is further evolving and under continuous use.

We treated 106 patients with a peripheral osteoid osteoma by conventional surgical methods; 81 had curettage and 25 en-bloc resection.

The rate of local recurrence after curettage was 12% and after en-bloc resection 4.5%. Postoperative fractures were observed in 3% after curettage and in 4.5% after en-bloc resection.

We compared our findings with those reported in the literature after minimally invasive treatment and concluded that curettage can be regarded as the treatment of choice in patients in whom minimally invasive methods do not offer any advantage, for example, for subperiosteal tumours which are readily accessible, or when the diagnosis is unclear and further histological analysis is required.

Anatomisches Institut der Georg-August-Universität Göttingen, Germany

Biomedical Research Centre, Dept. of Orthopaedic Surgery, Academic Hospital, Pretoria, South Africa

To date, no animal model for disc degeneration has gained much acceptance, mostly due to the fact that most animals are quadrupeds and thus lack basic biomechanical characteristics of human spines. An adequate model would be of invaluable interest for degeneration related research.

In a standardized series of animal experiments in 18 adult Minipigs and 20 adult Cercopithecus aethiops monkeys all animals obtained nucleotomy in one lumbar FSU from a ret-roperitoneal approach and were sacrificed at last 24 weeks afterwards. The Minipigs were x-rayed at time of sacrifice, the monkeys prior to operation and at termination of the experiment. Vice versa, the Minipigs obtained intradiscal pressure recordings at these occasions. The Minipig spines were formol fixed whereas the monkey spines were harvested after perfusion with PBS, fresh frozen, and obtained CT and MRI scans prior to thawing, fixation and comprehensive histological evaluation.

The lumbar FSU of Minipig and Cercopithecus mainly consists of the same elements as in man. There are certain differences concerning the porcine endplates which ossify as an epiphyseal-like formation with ossification starting in its center, different from the so-called “Randleiste”. Whereas the operative procedure in the Minipigs came in handy, in the Cercopithecus monkey it proved to be demanding, though feasible, due to relatively wide transverse processes and thick psoas muscle structures. The psoas could not be easily detached and needed to be split instead, thus directly exposing the segment nerves. The histological, standard radiological, CT, MRI, and mechanical observations were very similar to those which can be made during the natural aging process of the disc in man.

Both animal models are recommendable for further research: Cercopithecus FSUs are more difficult to expose. Logistic reasons may favour Minipigs in Europe. In case of fusion related experiments the use of primates yet seems inevitable.