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.

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

Comparison of means for Synbone showed that the BrainLab MIRATM system was the most stable (mean peak torque 5.60+/− 1.21 Nm) followed by the Stryker systemTM (2.53+/− 0.53 Nm) and the Schanz screw(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).

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.

Introduction: Homogenous cell distribution and suffi-cient initial scaffold stability remain key issues for successful tissue engineered osteochondral constructs. The purpose of this study was to investigate the application of initial compression forces during the first 24 hours of cell culture followed by different stress patterns.

Methods: Bone marrow stromal cells were harvested from the iliac crest during routine trauma surgery. The cells were expanded in a 2-dimensional culture and then seeded into the biologic hybrid scaffold with a concentration of 1x10E6 cells per ml. Pressure and vacuum forces were applied in a specially developed glass kit. The constructs were exposed to two different protocols of compression combined as oteochondral matrices of CaReS (collagen I) and Tutobone (Ars Arthro, Esslingen, Germany and Tutogen Medical GmbH, Neunkirchen a. Br., Germany). Controls were resected osteochondral fragments from patients with articular fractures and uncompressed constructs. These effects were evaluated using light microscopy after standard staining to identify matrix penetration. Biomechanical tests were conducted, too using a modified biomechanical testing machine. The ‘constrained compression’, maximum load to failure, modulus, and strain energy density were determined.

Results: Histology: Penetration and cell distribution was demonstrated homogenous and vital, respectively. Mechanical tests showed a significant enhancement of primary matrix stability. The following stress patterns did not enhance significantly stability over seven days.

Discussion: The aim of this project was to investigate the response and cell distrubution of human bone marrow stromal cells seeded on a 3-dimensional biologic hybrid scaffold using compression and vacuum forces.

The integration of mechanical stimulation in the tissue engineering process may lead to a progress in the structural and biomechanical properties of these tissues and offers new possibilities in the management of bone injuries and degenerative diseases.

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-C^3D 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-C^3D navigation (23 s; 22 to 24) compared with 2D fluoroscopy-based navigation (14 s, 11 to 17).

Tibial rotation and translation provide important stability parameters after ACL reconstruction. An accurate tool for a combined pre- intra- and postoperative stability measurement is not in clinical use so far. Navigation of the drill canals for the ACL placement and evaluation of possible impingement problems has been introduced for some years already, while measurement of the tibial translation and rotation is only available for a short time and only available for a few navigation modules. Navigation provides an accuracy of 1mm/1°, therefore navigated measurement of tibial rotation and translation were evaluated in this study with a new developed mechanical device and directly compared to conventional measurement techniques.

Accuracy of navigation was compared with the KT1000 for the anterior-posterior (AP) translation and to a new developed goniometer tool concerning the rotational range of motion. Comparative tests included plastic whole leg models and specimens. Tests were repeated with intact and dissected ACL′s. A conventional navigation system (Vector Vision, Brainlab, Germany) was used in all cases. This included software developed for fluoroscopy based navigated ACL reconstruction. The following knee kinematics were detectable with the navigation system: Flexion/Extension degrees of the knee joint (°); AP translation of the tibia in relation to the femur (mm); Axial tibial rotation relative to the femur (°).

Validation of Navigation: first neutral tibial rotation was defined and marked in the knee joint in neutral position. All rotational measurements were done with a new developed goniometer tool and compared to the navigated technique. Then the knee was rotated externally until 45° (maximum) and internally 45° (maximum), by single 2.5° steps. These measurements were repeated in 0°, 30°, 60° and 80° knee flexion. All tests were repeated three times and performed by 3 different observers. A total of 1296 measurements were done. Measurements of the tibial translation were compared with the KT 1000 for the specimen testing.

Results revealed: accurate navigated measurement of tibial rotation in plastic and specimen models; variation of absolute AP translation values between KT1000 and navigation; variation of the AP translation corresponding to the ACL condition; increased range of total tibial rotation after dissecting the ACL compared to the intact ligament.

Restoration of the rotational stability and limiting of the AP translation is necessary to provide normal knee kinematics after ACL reconstructions. Intraoperative measurements of these stability parameters are demanding and so far not established with navigation systems or conventionally. As our results show, navigation offers an accurate technique for measurement of the AP translation and rotation of the knee with intact and dissected ACL’s under laboratory conditions. General use in the evaluation of a successful ACL reconstruction becomes possible intraoperative and might be reproducible for further measurements. Clinical studies are needed to improve our results.

Anatomic reduction and appropriate implant placement is essential for optimal treatment of intraarticular tibial plateau fractures. Standard intraoperative fluoroscopy provides limited visualization of the reduction and hardware placement compared with pre- or postoperative 3-D imaging modalities. As such, post-operative computer tomography (CT) has become a common procedure to evaluate the quality of the reduction and fixation. The Iso-C3D provides 3-D intraoperatively imaging to dynamically assess the surgical reduction and fixation at different anatomic regions. We report on our first 19 clinical tibial plateau fractures scanned intra-operatively with the Iso-C 3D.

Between January and November 2003, 19 intraarticular tibia plateau fractures were scanned intraoperatively with the Iso-C3D (Siemens, Germany). No formal selection criteria were utilised except for the presence of a tibial plateau fracture. Operative procedures included 14 cases of open reduction internal fixation and 5 cases of internal fixation with arthroscopic assisted reduction.

Imaging Technique: All patients were positioned on full-carbon tables for the operative procedure. After initial operative reduction and fixation, conventional two-dimensional fluoroscopic imaging was performed using standard AP and lateral projections. These images were evaluated by the operating surgeon; if the reduction and fixation was judged to be appropriate, Iso-C3D imaging was initiated

In 21% (n=4) of all cases an immediate revision of the operative procedure was performed after Iso-C3D imaging. These revisions were not deemed necessary with conventional fluoroscopy alone. In two cases, significant intra-articular incongruencies (greater than two millimetres) were noted. Additionally, in two cases, implant mal-position was detected. All patients had a postoperative CT scan. All CT scans confirmed the intraoperative Iso-C imaging, no further additional articular incongruencies or malpositioned implants were identified. When compared to conventional C-arm images, the Iso-C 3D scans demonstrated improved ability to identify the articular malreduction and implant mal-position in all cases.

We have demonstrated that the Iso-C3D provides reliable intraoperative evaluation of reduction and hardware placement compared to traditional CT scans for tibial plateau fractures. In addition, clinically relevant intra-operative information was gained with its use in this study. In four (21%) cases, the operative treatment was modified due to the use of the multiplanar imaging modality. On average, 10 minutes of additional operative time was required for the use of Iso-C3D scanning and the evaluation of the images. Further prospective clinical studies are needed to improve our findings.

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° ± 15°) (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.

For femoral shaft fracture, damage control orthopaedics entails primary external fixation and subsequent conversion to an intramedullary device (IMN). Sub-clinical contamination of external fixator pin sites is common and it is argued that such an approach risks subsequent local infective complications. We aimed to determine the rate of wound infection following DCO procedures and primary IMN for femoral fracture stabilisation.

Retrospective analysis of a prospectively assembled adult patient database was carried out. Inclusion criteria were femoral #, New Injury Severity Score (NISS) above 20 and survival more than 2 weeks. Two groups, damage control (DCO) and early total care (ETC) (Primary Nail), were formed. Contamination was positive culture from the wound or fixator pin-sites without clinical infection. Superficial infection was a combination of positive bacterial swabs and local or systemic signs of infection. Deep infection was any case requiring surgical intervention with a sub-group requiring removal of femoral metal work (ROMW) also defined.

173 patients met the criteria for inclusion, with 192 fractures (19 bilateral). The mean follow up was 19 months. Patients in the damage control group were more severely injured than those undergoing primary intramedullary nailing (NISS 36 vs 25, p 0.001). There were also more severe (Grade 3 A,B or C) local soft tissue injuries in this group (p 0.05). 98 of the 111 DCO patients underwent subsequent IMN. Others either died without conversion being appropriate, or it was elected to complete treatment with external fixation. The mean time of exchange an ex/fix to a nail was 14.1 days.

Though contamination rates were higher in the DCO group (12.6% vs 3.7%, p 0.05), there was no excess of infective complications (11.1% vs 10.8%). Contamination increased significantly in patients who underwent conversion to IMN after 14 days. Grade 3 open injury was significantly associated with infection irrespective of treatment.

This study demonstrates that infection rates following DCO for femoral fractures are not significantly different to those observed following primary intramedullary nailing. Whilst the overall risk of deep infection in the DCO group did not show any correlation with the timing of converting the external fixator to a nail, the risk of contamination was higher in patients where the exchange nailing was performed after a period of 2 weeks.

Background /Methods: Abbreviated Injury Scale based systems; the ISS, NISS, and AISmax, are used to assess trauma patients. The merits of each in predicting outcome are controversial. A large prospective database was used to assess their predictive capacity using receiver operator characteristic curves.

Results: 13,301 adult patients met the inclusion criteria. All systems were significant outcome predictors for sepsis, multiple organ failure (MOF), length of hospital stay, length of ICU admission and mortality (p 0.0001). NISS was a significantly better predictor than the ISS for mortality (p 0.0001). NISS was equivalent to the AISmax for mortality prediction and superior in patients with orthopaedic injuries. NISS was significantly better for sepsis, MOF, ICU stay and total hospital stay (p 0.0001). Analysis of the ROC curves revealed that the traditional ISS cut-offs for severity of 16, 25 and 50 should be increased to 20, 30 and 55 to provide patients with equivalent outcome.

Conclusions: NISS is superior or equivalent to the ISS and AISmax for prediction of all investigated outcomes in a population of blunt trauma patients. As NISS is easier to calculate, its use is recommended to stratify patients for clinical and research purposes.

Introduction Correct postoperative leg alignment and stability of total knee prothesis over the full range of movement is one critical factor for successful TKA. This can only be achieved by correct implantation of prothesis and soft tissue handling. Still arthrotomy, surgical approach and handling of patella are discussed controversially.

Materials and Methods In a cadaver specimen study we evaluated the influence of everted or subluxated patella on limb axis during balancing of the knee in three different standard surgical approaches. For each approach we operated five knees. Leg alignment was visualised by Ci CT-free DePuy/BrainLAB navigation system. First, physiological leg alignment was measured. Then the different approaches were performed and a.p. leg axis was first measured and compared as well with everted as with subluxed patella in extension and second in 90 degrees flexion.

Results Eversion of patella leads to an alteration in leg axis compared to subluxed patella of 0.58 degrees (SD: 0.03, range: 0.54–0.6) limb axis in valgus direction in full extension. In 90 degrees flexion we found a mean deviation of leg axis of 0.48 degrees (SD: 0.11, range: 0.38–0.6) with everted patella compared to subluxed patella.

Discussion The surgeon has to be aware of this falsifying influence of everted patella to the a.p. limb axis.

Purpose: Intravasation of intramedullary contents and immune activation under the stimulus of cytokines and other inflammatory mediators released during canal preparation are presumed to be significant factors in the evolution of acute lung injury following stabilization of femoral shaft fractures with intramedullary nailing.

We aimed to quantify the development of acute endo-thelial permeability changes (within 4hours from canal instrumentation) with the reamed (RFN) and unreamed (UFN) nailing technique and assess the effect of coexisting lung contusion.

Materials and methods: A standardized sheep model (n=8 animals/group) was used. In the control groups, a thoracotomy without lung injury was performed prior to canal instrumentation. In the study groups a lung contusion of the right middle and lower lobe was induced. Osteosynthesis of the femur was carried out by the reamed (group RFN; standard Synthes reamer, old version) and unreamed technique (group UFN). Bronchoalveolar lavage was performed in order to assess the extent of lung parenchymal damage (permeability). The amount of protein leakage (determination of protein (Lowry assay) and urea (biochemical test) in BALF and serum) at different time points was analysed. Polymorphonuclear leukocyte activation was quantified by chemi-luminescence. IL-8 and coagulatory disturbances (Protein C) were also measured. All animals were sacrificed four hours following canal instrumentation and histological analysis was performed.

Results: In the control groups both the reamed and the unreamed nailing techniques were associated with a significant increase in pulmonary permeability compared to baseline values, p< 0.05. The experimental lung contusion induced prior to canal instrumentation caused also a significant increase in pulmonary permeability compared to baseline values. However, the subsequent canal instrumentation amplified further, significantly so, the degree of pulmonary permeability only in the reamed group (RFN).Both the activation of leukocytes and IL-8 release were also significantly raised following lung contusion and reamed femoral nailing compared to the UFN group with lung contusion (data not shown). Histological analysis illustrated the presence of fat globules in the pulmonary vasculature.

Conclusion: In a standardised sheep model without chest injury, instrumentation of the femoral canal with the reamed and the unreamed nailing techniques induced a rise in pulmonary permeability changes. In the presence of lung contusion, reamed intramedullary femoral nailing provoked a further increase in pulmonary permeability damage, IL-8 release and leukocyte activation. The findings of this study support the view that reaming of the femoral canal can act as an additional stimulus for adverse outcome in the presence of co-existing chest trauma.

We describe the results after open reduction and internal fixation of 22 consecutive displaced fractures of the glenoid with a mean follow-up of ten years. A posterior approach was used in 16 patients and an anterior in six, the approach being chosen according to the Ideberg classification of the fractures. The fixation failed in two patients, one of whom required a further operation. There were two cases of deep infection.

At follow-up the median Constant score was 94% (mean 79%, range 17 to 100). The score was less than 50% in four patients, including the two who became infected. A further two had an associated complete palsy of the brachial plexus.

Intramedullary nailing of metaphyseal fractures may be associated with deformity as a result of instability after fixation. Our aim was to evaluate the clinical use of Poller screws (blocking screws) as a supplement to stability after fixation with statically locked intramedullary nails of small diameter.

We studied, prospectively, 21 tibial fractures, 10 in the proximal third and 11 in the distal third in 20 patients after the insertion of Poller screws over a mean period of 18.5 months (12 to 29).

All fractures had united. Healing was evident radiologically at a mean of 5.4 ± 2.1 months (3 to 12) with a mean varus-valgus alignment of −1.0° (−5 to 3) and mean antecurvatum-recurvatum alignment of 1.6° (−6 to 11). The mean loss of reduction between placement of the initial Poller screw and follow-up was 0.5° in the frontal plane and 0.4° in the sagittal plane. There were no complications related to the Poller screw.

The clinical outcome, according to the Karström-Olerud score, was not influenced by previous or concomitant injuries in 18 patients and was judged as excellent in three (17%), good in seven (39%), satisfactory in six (33%), fair in one (6%), and poor in one (6%).

Rotational deformity following intramedullary nailing may cause symptoms and require surgical correction by osteotomy. Reamed, locked intramedullary nailing may be performed, but concern about cortical blood supply and potential pulmonary dysfunction from reaming have led many surgeons to limit this and use smaller diameter nails. Slotted nails are commonly used but are less stiff in torsion than the newer unslotted nails, particularly at the lower diameters.

We report two cased of recurrent femoral rotational deformity after using statically interlocked slotted intramedullary nails to correct existing femoral rotational deformities. These patients show that small diameter statically interlocked femoral nails with diminished bone-nail contact must be stiff enough in rotation to avoid potential recurrence.

The accuracy of templates used for the preoperative planning of the fixation of intramedullary fractures depends on radiological magnification. To study the accuracy of these templates, we randomly selected 100 femoral and 100 tibial radiographs taken after stabilisation by an intramedullary nail using a standard technique. We then compared the known nail length with the corresponding measurements on the radiographs.

The mean magnification factor for the femur was 9% and for the tibia 7%; these differ considerably from the range of magnification of the manufacturers’ templates (femur, 15% to 17%; tibia 10% to 15%). We conclude that templates are unreliable for the selection of implant length and that this should be done by intraoperative measurements.