Gait analysis is an indispensable tool for scientific assessment and treatment of individuals whose ability to walk is impaired. The high cost of installation and operation are a major limitation for wide-spread use in clinical routine.

Advances in Artificial Intelligence (AI) could significantly reduce the required instrumentation. A mobile phone could be all equipment necessary for 3D gait analysis. MediaPipe Pose provided by Google Research is such a Machine Learning approach for human body tracking from monocular RGB video frames that is detecting 3D-landmarks of the human body.

Aim of this study was to analyze the accuracy of gait phase detection based on the joint landmarks identified by the AI system.

Motion data from 10 healthy volunteers walking on a treadmill with a fixed speed of 4.5km/h (Callis, Sprintex, Germany) was sampled with a mobile phone (iPhone SE 2nd Generation, Apple). The video was processed with Mediapipe Pose (Version 0.9.1.0) using custom python software. Gait phases (Initial Contact - IC and Toe Off - TO) were detected from the angular velocities of the lower legs. For the determination of ground truth, the movement was simultaneously recorded with the AS-200 System (LaiTronic GmbH, Innsbruck, Austria).

The number of detected strides, the error in IC detection and stance phase duration was calculated.

In total, 1692 strides were detected from the reference system during the trials from which the AI-system identified 679 strides. The absolute mean error (AME) in IC detection was 39.3 ± 36.6 ms while the AME for stance duration was 187.6 ± 140 ms.

Landmark detection is a challenging task for the AI-system as can clearly be seen be the rate of only 40% detected strides. As mentioned by Fadillioglu et al., error in TO-detection is higher than in IC-detection.

In a consecutive retrospective analysis of 190 patients treated with the Masquelet technique at the BG Klinikum Hamburg from January 2012 to January 2022, defect-specific features such as the extent and morphology of the defect were recorded, and their influence on the time to reach full weight-bearing of the affected limb was investigated.

A total of 217 defects were treated in 190 patients using the Masquelet technique. 70% of all defects were located in the tibia, followed by 22% in the femur and only about 7% in the upper extremity. The average length of all defects was 58 mm (+/−31 mm), with the largest defect measuring 180 mm and the smallest measuring 20 mm. 89% of the patients achieved full weight-bearing at the end of therapy. The average time from initiation of therapy to reaching safe full weight-bearing was 589 days. There was a significant correlation between defect length and time to reach full weight-bearing (p = 0.0134). These results could serve as a basis for creating a score for prognostics and evaluation of bone healing after treatment with the Masquelet technique. Additionally, the results could help guide indications for secondary stabilization using internal fixation.

The objectives of this study are to evaluate the impact of the CoVID-19 pandemic on the development of relevant emerging digital healthcare trends and to explore which digital healthcare trend does the health industry need most to support HCPs.

A web survey using 39 questions facilitating Five-Point Likert scales was performed from 1.8.2020 – 31.10.2020. Of 260 participants invited, 90 participants answered the questionnaire. The participants were located in the Hospital/HCP sector in 11.9%, in other healthcare sectors in 22.2%, in the pharmaceutical sector in 11.1%, in the medical device and equipment industry in 43.3%. The Five-Point Likert scales were in all cases fashioned as from 1 (strongly disagree) to 5 (strongly agree).

As the top 3 most impacted digital health care trends strongly impacted by CoVID-19, respondents named:

- remote management of patients by telemedicine, mean answer 4.44

- shared data governance under patient control, mean answer 3.80

- new virtual interaction between HCP´s and medical industry, mean answer 3.76

Respondents were asked which level of readiness of the healthcare system currently possess to cope with the current trend impacted by CoVID-19.

- Digital and efficient healthcare logistics, mean answer 1.54

- Integrated health care, mean answer 1.73

- Use of big data and artificial intelligence, mean answer 2.03

Asked if collaborative research in the form of digital data platforms for research data sharing and increasing collaboration with multi-centric consortia would have a positive impact on the healthcare sector, the agreement was high with a value of mean 4.10 on the scale.

We can conclude that the impact of COVID-19 appears to be a high agreement of necessary advances in digitalization in the health care sector and in the collaboration of HCPs with the health care industry. Health care professional are unsure, in how far the national health care sector is capable of transformation in healthcare logistics and integrated health care.

A promising application of Mesenchymal stem cells (MSCs) is the treatment of non-unions. Substituting bone grafts, MSCs are directly injected into the fracture gap. High cell viability seems to be a prerequisite for therapeutic success. Administration of the MSCs via injection creates shear stresses possibly damaging or destroying the cells.

Aim of this study was to investigate the effect of the injection process on cell viability.

MSCs were isolated and cultivated from femoral tissue of five subjects undergoing arthroplasty. Prior to injection, the cells were identified as MSCs. After dissolving to a concentration of 1 Million cells/ml, 1 ml of the suspension was injected through a cannula of 200 mm length and 2 mm diameter (14 G) with flow rates of 38 and 100 ml/min. The viability of the MSCs at different flow rates was evaluated by staining to detect the healthy cell fraction. It was analyzed statistically against a control group via the Kruskal-Wallis-test and for equivalence via the TOST procedure. Significance level was set to 5 %, equivalence margin to 20 %.

The healthy cell fraction of the control group was 85.88 ± 2.98 %, 86.04 ± 2.53 % at 38 ml/min and 85.48 ± 1.64 % at 100 ml/min. There was no significant difference between the fraction of healthy cells (p = 0.99) for different volume flows, but a significant equivalence between the control group and the two volume flows (38 ml/min: p = 0.002, 100 ml/min: p = 0.001).

When injecting MSC solutions, e.g. into a non-union, the viability of the injected cells does not deterioriate significant. The injecting technique is therefore feasible.

Vacuum orthoses are being applied in the care of patients with foot and lower leg conditions, as ankle fractures or sprains. The lower leg is protected and immobilized, which increases mobility. Due to the design, the orthoses lead to a difference in leg length, i.e. the side with the orthosis becomes longer, which changes the gait kinematics. To prevent or mitigate the unfavourable effects of altered gait kinematics, leg length-evening devices (shoe lifts) are offered that are worn under the shoe on the healthy side. Our aim was to evaluate the effect of such a device on the normality of gait kinematics.

Gait analysis was conducted with 63 adult, healthy volunteers having signed an informed consent form that were asked to walk on a treadmill at a speed of 4.5km/h in three different conditions:

Data was sampled using the gait analysis system MCU 200 (LaiTronic GmbH, Austria). The positions of the joint markers were exported from the software and evaluated for the joint angles during the gait cycle using custom software (implemented in DIAdem 2017, National Instruments).

A normality score using a modification of the Gait Profile Score (GPS) was calculated in every 1%-interval of the gait cycle and evaluated with a Wilcoxon signed rank test.

The GPS value was reduced by 0.33° (0.66°) (median and IQR) while wearing the shoe lift. The effect was statistically significant, and very large (W = 1535.00, p < .001; r (rank biserial) = 0.52, 95% CI [0.29, 0.70]).

The significant reduction of the GPS value indicates a more normal gait kinematics while using the leg length-evening device on the contralateral shoe. This rather simple and inexpensive device thus might improve patient comfort and balance while using the vacuum orthoses.

Introduction

The degeneration of the adjacent segment in lumbar spine with spondylodesis is well known, though the exact incidence and the mechanism is not clear. Several implants with semi rigid or dynamic behavior are available to reduce the biomechanical loads and to prevent an adjacent segment disease (ASD). Randomized controlled trials are not published. We investigated the biomechanical influence of dynamic and semi rigid implants on the adjacent segment in cadaver lumbar spine with monosegmental fusion (MF).

Bone shape variability within a specific population has been seldom investigated and used to optimize implant design. There is insufficient anatomical fitting of the existing prebend periarticular plates for the distal fibula. We developed a methodology for design of orthopaedic implants that fit a maximum percentage of the target population, both in terms of geometry and biomechanical stability. In co-operation with an implant manufacturer and different academic institutions, a virtual bone database has been developed that contains anatomical data of more than 1000 CT datasets with the implemented possibility to generate idealized implant fits for different anatomical sites. This program (Stryker Virtual Bone Database (VBD) is able to generate statistical anatomical shapes for different populations like age groups or ethnical groups. Based on this, an implant for the distal fibula has been developed (VariAx Distal Lateral Fibula Locking Plate) for distal fibula fracture treatment. Aim of this study was to develop and validate an implant that is optimized for the specific anatomical area. It should be precontoured and still fit to the majority of patients sustaining a distal fibular fracture. Another objective was to create a distally tapered design as there is less soft tissue cover in that anatomic area.

Purpose of the study: Implants with multidirectional locking screws theoretically have many advantages for the treatment of periprosthetic fractures. In the event of osteoporotic bone, this system of plate fixation ensures stability and better bone fixation. Using screws anchored in the different angles, we proposed rigid fixation around the prosthesis. We conducted a retrospective analysis of outcomes obtained after treatment of perprosthetic femoral fractures, Vancouver B1 and C, comparing two types of implants with angular stability (straight plate and folded plate).

Material and methods: From June 1999 to December 2007, we treated 58 patients with periprothetic fractures of the femur using locking plates. Mean age was 72.4 years, 40 patients were female. Thirty-two patients (55.2%) had a total hip prosthesis, 21 a total knee prosthesis and 5 both types of prosthesis (8.6%). We noted: peri- and postoperative complications, degree of bone healing, degree of mobility (Barthel Mobility index and stand up and go test) as well as the social status of the patients.

Results: Bone healing was obtained in 56 cases (96.5%). In two patients, the implant was dislocated and in four others there were general complications. The mean time necessary to obtain total weight-bearing two-leg stance was 8.6 weeks. Forty-six patients (78%) had the same social status as before the fracture. For mobility, 52 patients (89%) achieved the same level as before fracture. Four other patients required a crutch for walking and two needed a walker. Mean Barthel index was 85 points (max 100) and improved 35 points at onset of rehabilitation. Mean stand up and go was 22 s.

Conclusion: According to the review of the literature, 35% of plates dislocate after osteosynthesis of periprosthetic fractures. In our study, the rate was 3.5%, with 7% general complications. We can thus conclude that the methods presented here enable good bone healing in the majority of cases.

Implants with multidirectional locked screws have theoretical advantages in the treatment of periprosthetic fractures. In osteoporotic bone those locked plate systems with multidirectional applicable screws give a high stability. With the possibility of fixing screws in various angles, a rigid fixation in the presence of a prosthetic implant can be achieved. We concluded a retrospective study of a consecutive series of the outcome of Vancouver B1 and C femoral injuries using two specific locked implants (Straight and wave plate).

From June 1996 to December 2004 we treated 58 patients with a periprosthetic fracture of the femur with a locked plate. The mean age at the index procedure was 72.4 years, 40 patients were female (69%). In 32 cases (55.2%) we saw a hip endoprosthesis, in 21 cases (36.2%) a knee endoprosthesis and in 5 cases both (8.6%). Outcome measures were intra- and postoperative complications, bony union, degree of mobility and social status, Barthel mobility index and “stand up and go” test.

Union occurred in 56 cases (96.5%) after the index procedure. Twice the implant failed, we saw 4 general complications. The mean duration until full weight bearing status in these patients was 8.6 weeks.

At follow up 46 patients (78%) had maintained the same social status as before the fracture. Regarding the mobility status 52 patients (89%) had regained their previous level, 4 patients walking without aid before now required a cane and two patients a walking frame. The mean Barthel Index was 85 points of possible 100 and improved from 35 points at point of beginning of the rehabilitation. The mean stand-up& go time was measured as 22 seconds.

Conclusion: Overall failure rates of osteosynthesis after periprosthetic fractures of up to 35% are reported (20). With 3.5% implant related failures and 7% general complications, the presented Methods: achieve bony union and mobility in a high percentage of cases.

Introduction: Less invasive surgical technique in THA is expected to minimize soft tissue damage and expedite rehabilitation. Due to this, it is now in widespread use in elective THA. The large geriatric patient population suffering a fractured neck of femur thereby would also benefit of this technique. Aim of this study was to evaluate if this technique is feasible in the non-elective setting of geriatric patients and if there are benefits regarding clinical and social outcome.

Patients and Methods: Study setup is a prospective randomized trial with a positive Ethical Committee vote. Included were patients under legal care of a third party. Inclusion criteria were the indication for bipolar hip arthroplasty including grade ASA 4; exclusion criteria included neoplastic disease and rheumatoid arthritis. Setting is a large university hospital. After biometrical evaluation, each arm was set as 30 patients. Primary end point was the modified Barthel index. 48 patients were female. Mean age for female patients was 85.5, for male 82.9 years. There was no detectable difference in the groups regarding age, sex and BMI. As a less invasive approach, the well described „Direct Anterior Approach-DAA”(modified Smith-Petersen approach) was chosen. In the other arm the Watson-Jones approach was used. The ABG II stem with a bipolar UHR head (Stryker) were used in both groups. To minimize the learning curve, 10 cadaver- and 15 clinical procedures were performed with the DAA approach before the study. The pre- and postoperative regimen was identical in both arms. The modified Barthel index and other clinical parameter were determined preoperatively and at 4 postoperative intervals up to 40 days.

Results: There were no statistical differences between both groups for intra- and postoperative complications. The mean theatre time was 4.8 minutes longer for the DAA group, in the first 10 patients this difference was measured with 16 minutes. The Barthel Index was only statistically different at 40 days, at this time the DAA patients had reached their preoperative mobility level whilst the conventional approach patients (with a pre-operative level of 42.5) were measured with 25 points. The hemoglobin levels on day 5 and 16 were significantly different with a higher Hb for the DAA group. All other parameters showed no significant difference.

Conclusion: The DAA approach has a clear learning curve. Once this has passed, the theatre time is only slightly longer. There is a detectable benefit regarding early rehabilitation and a slight but significantly reduced blood loss.

Cemented modular metal backed total hip prostheses have the theoretical advantage to allow different inlays to be used. Asymetric or snap inlays are some of the options. First attempts with this kind of implant failed due to PE quality. A novel implant has been specifically designed and constructed for the use of cement. In vitro testing has shown results equal to other cemented cups. Aim of this study is to investigate the first clinical results of this implant with special consideration to intraoperative complications, intraoperative change of inlays, postoperative complications and clinical results.

Patients and Methods: Study setup was prospective, location a university hospital, approval for this study was granted by the local ethical committee. Inclusion criteria were patients with a biological age over 70 years that suffered a recent fractured neck of femur with the general indication for arthroplasty. Exclusion criteria were the inability for full informed consent, ASA IV and current infection. Thirty patients were included in this study. Mean age was 78.6 years (55.1 to 88.6), 23 patients were female (77%). The mean BMI was 25.3 (17.5–41).

The implant under investigation was a cemented modular acetabular component (C-MIC, ESKA Implants, Germany). The inlays are manufactured of highly crosslinked polyethylene. The standard protocols regarding DVT prophylaxis and antibiosis for HHS and the Barthel index.

Results: Implantation of the C-MIC component was possible in all cases. In 1 case (3.3%) the inlay was changed and replaced by an asymmetrical anti-luxation inlay intraoperatively as there was a luxation tendency. There were no other intraoperative complications. There was no case of infection or significant hematoma. In 1 case there was a DVT of the lower leg diagnosed by ultrasound on day 21. The mean Barthel index preop. was determined with 96.5 of 100, the mean Harris Hip Score with 89. At 3 months F/U the Barthel index was mean 96.1, at 6 months 96. The Harris Hip Score at 3 months was mean 72 points (17 pts below the preoperative status), at 6 months mean 79 points (10 pts below preoperative status).

Discussion: The C-MIC acetabular component does not show increased complication rates when compared to published results of hemiarthroplasty. The Barthel index as an outcome measurement of mobility and activities of daily living showed a return to the preoperative level. The HHSshowed a satisfactory result at 12 weeks, it also showed that patients of a geriatric population have problems to regain their full hip function after a fractured neck-of-femur.

We can conclude that the C-MIC acetabular component is safe to use. Due to limitations of this study we are not able to state if THA is superior to hemiarthroplasty in geriatric patients.

Introduction: The rotational fiexibility of the occipito-atlanto-axial complex is infiuenced by several ligaments, capsules and the alarian ligament (AL). For the development of a biomechanical model simulating dens fractures and stabilization techniques, we investigate the rotational range of motion of the atlantodental joint reducing sequentially the infiuence of capsules and additional ligaments in two different groups (segments C0–C2 and segments C1–C2). The torque affecting the dens axis was analyzed.

Methods: 7 fresh C0–C2 + 7 fresh C1–C2 cadaver segments with the integrity of all ligaments and joint capsules were mounted on a custom made rotational testing device (RTD) of a universal mechanical testing machine (UTM). Pure axial torque with a rotational speed of 5°/s was applied clockwise and counter-clockwise. To acquire the physiological range of motion (ROM) between C1 and C2, a maximal axial torque of ±1.5Nm was applied. Consecutively, all the ligaments which do not attach to the odontoid were transected and the ligaments which attach to or contact with the odontoid were preserved. The previously recorded rotation was applied to the specimens with the RTD. The torque between C1 and C2 was recorded.

Results: The group C0–C2 had a mean unidirectional ROM of 23.45° at 0.3Nm and of 32.87° at 1.5Nm respectively. The group C1–C2 had a larger ROM of 27.41° at 0.3Nm and of 35.47° at 1.5Nm. After resection of ligaments the torque in Group C0–C2 was reduced by 38% (0.3 Nm) and 61% (1.5Nm) respectively. The group C1–C2 showed a higher reduction of the transmitted torque: 90% (0.3Nm) and 80% (1.5Nm) respectively.

Discussion: Evaluating the direct torque forces on the atlantodental joint, we sequentially cut the ligamentous junction of the C1–C2 complex. ROM measurements at 0.3 Nm correlate well to previous data. Measurements in the group with cut AL (C1–C2) had an increased ROM. Comparing the reduction of the transmitted torque between the two groups, 90% (0.3Nm) and 80% (1.5Nm) in group C1–C2 in contrast to only 38% (0.3Nm) and 61% (1.5Nm) in group C0–C2, the rotationally stabilizing meaning of the AL in the occipito-atlantodental complex is punctuated. Higher torques (1.5Nm) increased the reduction of the transmitted torque in group C0–C2 between the measurements with intact and with cut ligaments. We hypothesize that the torque acting on the atlantodental joint is dominated by the AL at smaller angles and has to be considered in the evaluation of upper cervical models. In higher angles the torque is predominately determined by the capsules. Transferring the data to a model simulating the torque on the dens, a clear distinction has to be made based upon the region of the ROM. For larger angles at the borders of the ROM, the infiuence of the facet joint capsules cannot be neglected.

Intracortical osteosarcoma is a comparatively rare and distinct tumor separated from conventional osteosarcoma and other osteosarcoma variants. At first, the lesion was described in two patients by Jaffe in 1960. To date, 17 cases have been described in the literature. In all cases, the tumor occured in the cortex of the shaft of the femur or tibia. En-bloc resection was performed as primary therapeutic approach in most cases, sometimes in combination with neoadjuvant or adjuvant chemotherapy.

We, for the first time, describe a case of intracortical osteosarcoma of the midshaft of the right ulna which was found accidentaly in a patient taking part in a screening programm for heriditary breast cancer.

The patient underwent en-bloc resection without additional chemotherpapy and shows no reccurence after 18-months follow up.

The operative therapy of intraarticular fractures of the calcaneus is nowadays established surgical standard. Aim is an accurate reduction with reconstruction of the Boehler’s angle, the length and the subtalar joint. 3D-fluoroscopy with the Siremobil Iso-C 3D? mobile C-arm radiography system is a valuable assistance for the accurate reconstruction of the anatomical structures. Remaining incongruities can be recognized and corrected intraoperatively. The achieved reduction can be safely fixed by the advantages of a locked implant In the period of 10/2002 until 10/2004 we operated 59 patients with intraarticular fractures of the calcaneus by means of anatomical reduction and locked plate (Calcaneus TiFix, Litos, Germany) under control of 3D-fluoroscopy. After routine CT diagnostics, fractures were classified according to Sanders: 18 fractures were type II, 33 fractures type III and 9 were classified type IV.

Results: Surgical treatment of the fractures took place according on average after an interval of 8.5 days (7 to 11). A 3D-fluoroscopy was performed after reduction and temporary fixation of the fracture. There was no technical fault of the device. Median theatre time was 72 minutes (53–112 minutes) including 3-D-fluoroscopy. In 22 cases a remaining incongruity of > 1 mm could be seen on intraoperative 3-D-fluoroscopy. In these cases a reduction was performed again. The Boehler’s angle could be raised on average by 18° (11° to 22°), shortening of the hindfoot could be improved on average by 13 picture millimetres (9 to 17mm). Bone graft was not required in any case. At 6 months follow up, all patients had returned to work, or if unemployed, where judged fit to work by their GP. Three patients changed their position. 25 Patients were completely pain free at follow-up. In all cases the achieved reduction could be fixed by the implant until full weight bearing was reached.

Conclusion: The use of 3D Fluoroscopy had a real impact in the treatment of calcaneal fractures. If this short term advantage influences the long term result has to be shown in further follow up.

Introduction: In the last ten years there is a clear favour toward internal fixation. We evaluated the technique and the clinical long term results of external fixation in a triangular frame.

Patients and Methods: From 1994 to 2001 a consecutive series of 95 patients with end stage arthritis of the ankle joint were treated. Retrospectively the case notes were evaluated. Mean age at the index procedure was 45.4 years (18–82), 67 patients were male (70.5%). In all cases the arthritic deformity was due to a posttraumatic condition. The index procedure took place on average 129 months (6–516 months) after trauma. Preoperatively 43 patients had a relevant mal-alignment. In 41 patients the range of motion (ROM) was decreased with a remaining ROM of < 20°, in further 37 cases the remaining ROM was < 10° ROM. Via a bilateral approach the malleoli and the joint surfaces were resected. An AO fixator was applied with four Steinmann-nails inserted. Follow up examination at mean 4.4 years included a standardised questionnaire and a clinical examination including the criteria of the AOFAS-Score and radiographs.

Results: In all cases the index procedure was possible although in 2 cases soft tissue contracture meant that a pes equinus position of approximately 15° was required. After mean 12.3 (8–16) weeks radiographs confirmed satisfactory union and the fixator was removed. There were no cases of DVT or PE detected in the postoperative period. In 9 cases (10.1%) we saw a reversible irritation of the dorsal cutaneous nerve. In 18 cases a pin tract infection developed (20.2%) which healed under conservative measures. In one case (1.1%) a bony infection around a pin site developed, one patient suffered a fracture of the tibia at the site of the former proximal tibial pin site due to a minor trauma. In 4 patients a non-union of the ankle arthrodesis developed (4.5%). The mean AOFAS score improved from 20.8 (Std. dev.16.2) to 69.3 at F/U (Std.dev. 21.5, p = 0,004–30, T-test). The largest improvements were found regarding to pain and walking distance. Whilst preoperatively only one patient had mild pain, at follow up 54 patients had no or only mild pain. The maximal walking distance improved from mean 675 metres to mean 3245 m (T-test, p < 0,025 –18). Analysis of the insurance status showed patients that patients insured under a workers injury compensation scheme had a mean score of 63.6 compared to 75.1 for the remaining (T-test, p=0,027).

Discussion: Non-union rates and clinical results of arthrodesis by triangular external fixation of the ankle joint do not differ to internal fixation

Methods: The complication rate and the reduced patient comfort reserve this method mainly for infected arthritis and complicated soft tissue situations.

Fully automated robots for the planning and implantation of total hip arthroplasty have completely withdrawn from the market. Reasons were technical problems during the reaming process that lead to postoperative neurological problems. This lead, especially in Germany, to numerous court cases and created a hostile environment regarding robotic orthopaedic surgery.

The first steps in the development of a robotic assisted system for total hip arthroplasty are presented. This system will be able to plan and mill both femoral and acetabular implant seat. This project aims to combine the advantages of minimally invasive techniques and navigational systems with the accuracy that robotic assisted bone milling can provide. One of the main goals is the study of the technical problems of previous systems and to develop methods to prevent those.

The project-name is RomEo (Robotic minimally invasive Endoprosthetics), the main project partners are the Helmut-Schmidt University/Hamburg and the Department of Trauma and Orthopaedics of the BG Trauma Hospital Hamburg. The paper focuses on:

The determination of forces acting on the femur during milling: The determination of the ideal minimally invasive access route in cadaver operations

The “workspace” created in minimally invasive hip surgery as determined in cadaver operations, including a 3D reconstruction

Possible solutions of the problems of non-invasive patient fixation as determined in cadaver testing with different fixation methods

Feasibility of 3D operation simulation using Voxelman data, access route data and implant CAD data

Introduction: Trauma surgeons are often less exposed to large caseloads of primary osteoarthritis, compared to purely “elective”orthopaedic surgeons. The experience in total knee arthroplasty is thereby markedly On the other hand, posttraumatic knee arthrosis is often accompanied by severe deformity and axis deviation. In theory, navigated arthroplasty can overcome some of the problems in this setting.

Aim: Evaluation of the navigated technique of total knee arthroplasty (TKA), including the technical difficulties, the learning curve and the feasibility in severe bony deformity. Setting is a level I trauma center. Study setup was prospective, follow up period on average 14.5 months (11–25 months).

Patients: Between 7/04–6/05 we treated 36 patients with arthritis of the knee related to trauma. 18 patients were male. Average age at TKA was 59 (32–77) years. On average patients had 2.83 previous operations.

Methods: The navigational system used is manufactured by PRAXIM (La Tronche/France). It uses infrared-tracking and bone-morphing software. The implant was a mobile bearing LCS knee (DePuy/USA). Follow up included radiographs, clinical examination and the knee society scores.

Results: In three cases the procedure was finished in a conventional technique, reasons were suspicion of the surgeon about the cuts recommended by the system, a missing femoral cut block and a broken screw of the tracker-fixation. There was no failure of the navigational system. There was a clear learning curve regarding procedure time. Preop mean extension deficit was improved from av. 7.1° (0–30°) to 1.67° (0°–10°) postop., flexion contracture improved from av. 95° to 103°. The combined knee society score (max. 200 pts) improved from 77 pts preop to 156 pts at follow up.

Conclusions: Navigated knee endoprosthesis is reliable tool for the trauma surgeon with few technical problems. Especially for surgeons with less experience in TKA, planning of implant size and position is very helpful. With posttraumatic deformity the surgeon can gain valuable information and assistance to improve alignment and ligamentous balancing.