Introduction

The surgical treatment of critical-sized bone defects with complex three-dimensional (3D) geometries is a challenge for the treating surgeon. Additive manufacturing such as 3D printing enables the production of highly individualized bone implants meeting the shape of the patient's bone defect and including a tunable internal structure. In this study, we showcase the design process for patient-specific implants with critical-sized tibia defects.

Critical-sized bone defects can result from trauma, inflammation, and tumor resection. Such bone defects, often have irregular shapes, resulting in the need for new technologies to produce suitable implants. Bioprinting is an additive manufacturing method to create complex and individualised bone constructs, which can already include vital cells.

In this study, we established an extrusion-based printing technology to produce osteoinductive scaffolds based on polycaprolactone (PCL) combined with calcium phosphate, which is known to induce osteogenic differentiation of stem cells.

The model was created in python based on the signed distance functions. The shape of the 3D model is a ring with a diameter of 20 mm and a height of 10 mm with a spongiosa-like structure. The interconnected irregular pores have a diameter of 2 mm +/− 0.2 mm standard deviation.

Extrusion-based printing was performed using the BIO X6. To produce the bioink, PCL (80 kDa) was combined with calcium phosphate nanopowder (> 150 nm particle size) under heating. After printing, 5 × 10⁶ hMSC were seeded on the construct using a rotating incubator.

We were able to print a highly accurate ring construct with an interconnected pore structure. The PCL combined with calcium phosphate particles resulted in a precise printed construct, which corresponded to the 3D model. The bioink containing calcium phosphate nanoparticles had a higher printing accuracy compared to PCL alone. We found that hMSC cultured on the construct settled in close proximity to the calcium phosphate particles. The hMSC were vital for 22 days on the construct as demonstrated by life/dead staining.

The extrusion printing technology enables to print a mechanically stable construct with a spongiosa-like structure. The porous PCL ring could serve as an outer matrix for implants, providing the construct the stability of natural bone. To extend this technology and to improve the implant properties, a biologised inner structure will be integrated into the scaffold in the future.

Aims

The management of periprosthetic joint infection (PJI) after total knee arthroplasty (TKA) is challenging. The correct antibiotic management remains elusive due to differences in epidemiology and resistance between countries, and reports in the literature. Before the efficacy of surgical treatment is investigated, it is crucial to analyze the bacterial strains causing PJI, especially for patients in whom no organisms are grown.

Introduction

Management of periprosthetic joint infection (PJI) after total knee arthroplasty (TKA) is a challenging task. Antibiotic management remains elusive due to differences in epidemiology and resistance between countries and reports. Increasing resistance of bacteria is a concern. The aim of this study was to investigate the development of antibiotic resistance of main causative bacteria in a single center.

Introduction

Differing levels of tendon retraction are found in full-thickness rotator cuff tears. The pathophysiology of tendon degeneration and retraction is unclear. Neoangiogenesis in tendon parenchyma indicates degeneration. Hypoxia inducible factor 1(HIF) and vascular endothelial growth factor (VEGF) are important inducers of neoangiogenesis. Rotator cuff tendons rupture leads to fatty muscle infiltration (FI) and muscle atrophy (MA). The aim of this study is to clarify the relationship between HIF and VEGF expression, neoangiogenesis, FI, and MA in tendon retraction found in full-thickness rotator cuff tears.

Aim: The assessment of shoulder mobility is essential for clinical follow-up of shoulder treatment. Only a few high sophisticated instruments for objective measurements of shoulder mobility are available. The interobserver dependency of conventional goniometer measurements is high. In the 1990s an isokinetic measuring system of BIODEX Inc. was introduced, which is a very complex but valid instrument. Since 2008 a new user-friendly system (DynaPort ShoulderTest-System) is available. Aim of this study is the validation of this measuring instrument with the BIODEX-System.

Methods: The DynaPort ShoulderTest-System is a small, light-weighted three-dimensional gyroscope that is fixed on the distal upper patient arm, recording abduction, fiexion and rotation. For direct comparison we fixed the DynaPort on the lever arm of the BIODEX-system. The accuracy of measurement was determined at different positions, angles and distances from the center of rotation as well as different motion speeds in the radius between 0° – 180° in steps of 20°. All measurements were repeated ten times and observed with a digital water level. As satisfactory accuracy we defined a difference between both systems below 5°. The statistical analysis was performed with a linear regression model.

Results: The evaluation showed very high accuracy of measurements. The maximum average deviation was 0,5°. Below 60° the DynaPort was underestimating comparing the BIODEX system, whereas in higher positions higher data was measured. At higher angles the differences between both got higher. The distance to the center of rotation as well as the position of the Dyna-Port on the lever arm and different motion speeds infiuenced the results. The highest significant matches were measured at highest distance from the center of rotation (1,8° vs. 3,1°, p < 0,05) and a highest motion speed (2,1° at 60°/s, vs. 3,1° at 30°/s, p < 0,05).

Conclusion: In summary the results showed a high correlation and good reproducibility of measurements. All deviations were inside the tolerance interval of 5 °. These laboratory trials are promising for the validation of this system in shoulder patients. The challenge for both systems will be the changing of the center of rotation in the shoulder joint at elevations higher than 90°.

Background: Increased contact stress with a femoral resurfacing prosthesis implanted in the medial femoral condyle and a non-functional meniscus is of concern for potential deleterious effects on tibiofemoral contact mechanics.

Methods: Peak contact pressures were determined in seven fresh frozen human cadaveric specimens using a pressure sensitive sensor placed in the medial compartment above the menisci. A knee simulator was used to test each knee in static stance positions (5°/15°/30°/45°) and through 10 dynamic knee-flexion cycles (5°–45°) with single body weight ground reaction force (GRF) which was adjusted to the living body weight of the cadaver donor. All specimens were tested in three different conditions: Untreated knee (A); Flush implantation of a 20mm resurfacing prosthesis (HemiCAP^®) in the weight bearing area of the medial femoral condyle (B); Complete radial tear at the posterior horn of the medial meniscus with the femoral resurfacing device in place (C).

Results: On average, flush device implantation resulted in no statistically significant differences when compared to the untreated normal knee. The meniscal tear resulted in a significant increase of the mean maximum peak contact pressures by 63%, 57%, and 57% (all P ≤ 0.05) at 15°, 30° and 45° static stance positions and 78% (P ≤ 0.05) through the dynamic knee flexion cycle. No significant different maximum peak contact pressures were observed at 5° stance position.

Conclusion: Possible effects of reduced meniscal tissue and biomechanical integrity of the meniscus must be considered in an in-vivo application of the resurfacing device.

Objectives: The aim of this study was to examine the influence of different prosthesis designs (Deep-Dish (DD) vs. posterior stabilized (PS)) on the patello-femoral pressure. The femoro-patellar pressure depends among other things on the AP stability of the knee joint. The use of DD has been described to be equally applicable with a resected or deficient PCL.

Methods: Fresh frozen human knee specimens (n = 8, 7 male, 1 female) underwent testing in a kinematic device simulating an isokinetic knee extension cycle from 120° of flexion to full extension. Knee motion was driven by a hydraulic cylinder applying sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. The amount of patellofemoral contact pressure and its distribution was measured by means of a pressure sensitive film (Tekscan^®, Inc., Boston, USA). Patellar contact pressure was examined first after implantation of a cruciate retaining TKA (Genesis II, Smith& Nephew, Memphis, USA). An 11 mm polyethylene (PE) DD insert was tested before and after resection of the PCL. Finally, the femoral component of the CR TKA was removed and replaced by a posterior stabilized (PS) model repeating measurements with an 11 mm PE inlay. The patella was not resurfaced throughout the whole procedure. A paired sampled t-test was applied for comparison of means and considered significant at p ≤ 0.05.

Results: There was no statistical significant difference of patello-femoral peak and mean contact pressures of the DD inlay before and after resection of the PCL. After implantation of the PS TKA peak pressure was significantly lower (Mean: 6.12 ± 2.37 MPa, Range: 10.68 – 3.30 MPa) in comparison with the DD type (7.12 ± 2.53 MPa, 11.94 – 3.55 MPa; p < 0.01) with a preserved PCL. Also the mean contact pressure turned out to be lower with the PS design (p < 0.006; PS: 3.58 ± 1.25 MPa, 5.91 – 2.08 MPa, DD: 4.27 ± 1.34 MPa, 6.66 – 2.18 MPa). The contact area was also significantly smaller with the PS design (p < 0.03, PS: 140.84 ± 40.04 mm2, 188.47 – 65.10 sq mm, DD: 175.97 ± 24.46 sq mm, 222.56 – 142.56 sq mm).

After resection of the PCL differences in contact pressures and contact area between DD and PS failed to reach statistical significance although there was an obvious tendency towards lower pressures with the PS-design.

Conclusions: The results of this study suggest that a posterior stabilized TKA design reduces the retropatellar peak and mean pressure as well as the contact area in comparison with a deep-dish design when the PCL is preserved. The better reproducible rollback with a PS model could serve as a possible explanation. However, this difference is less pronounced when a DD inlay is applied after resection of the PCL. Nevertheless, a PS rather than a DD design is recommended in the PCL deficient knee.

Objective: Decreased quadriceps strength may contribute to anterior knee pain after total knee arthroplasty (TKA). The quadriceps force necessary to establish full extension is strongly dependent on the position and the relative length of the lever arms over the knee joint. The purpose of this in vitro study was to investigate the amount of quadriceps force required to extend the knee isokinetically after TKA in dependence of different prosthesis designs and the state of the posterior cruciate ligament (PCL).

Methods: Eight fresh frozen human knee specimens were tested in a kinematic device that simulated an isokinetic knee extension cycle from 120° of flexion to full extension. Knee motion was driven by a hydraulic cylinder applying sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm. The quadriceps force was measured using a load cell attached to the quadriceps tendon after implantation of a cruciate retaining (CR) TKA (Genesis II, Smith& Nephew, Memphis, Tn, USA) applying a conventional and a highly conforming polyethylene (PE) inlay before and after resection of the PCL. Finally, the femoral component of the CR TKA was replaced by a posterior stabilized (PS) design and measurements were redone.

Results: No significant differences in the average quadriceps force were detected between the different PCL retaining inlays (CR, highly conforming) as long as the PCL was intact. However, after resection of the PCL, the required quadriceps force increased significantly for both designs (CR: 4.7%, p < 0.01, Highly conforming: 3.5%, p < 0.03). After implantation of the PS femoral component quad force decreased to its initial levels with forces significantly lower compared to the PCL deficient knees provided with a CR (−6.0%, p < 0.01) or highly conforming (−5.1%, p < 0.01) inlay. With a PS design average quadriceps extension force was not significantly different from cruciate retaining TKA inlays at an intact PCL.

Conclusions: The data of this in vitro study suggest that the quadriceps extension force is significantly higher for knees after cruciate retaining TKA with PCL deficiency, independent of the use of a CR or DD inlay. Thus, the integrity of the PCL should be secured in clinical practice when using a cruciate preserving TKA design.

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: Mobile bearing total knee arthroplasty (TKA) has been developed to theoretically provide a better, more physiological function of the knee and produce less polyethylene (PE) wear. The theoretical superiority of mobile bearing TKA’s over fixed bearing devices has not yet been proven in clinical studies.

The objective of the present study was to analyze in vivo the knee joint kinematics in the sagittal plane in a patient population that had received either a fixed or a mobile TKA in a prospective, randomized, patient- and observer-blinded, clinical study.

Methods: 31 patients were evaluated by means of fluoroscopy during unloaded flexion and extension against gravity, as well as during step-up and step-down with full weight bearing. In these 31 patients, 22 fixed bearing TKAs, 16 mobile-bearing TKAs and 19 natural knee joints were included.

All patients had been operated in a prospective, randomized, patient- and observer-blinded, clinical study, and had received either fixed or a mobile bearing, cruciate retaining Genesis II TKA for primary osteoarthritis.

Fluoroscopic radiographs were evaluated by measuring the „patella tendon angle” as a measure of antero-posterior translation as well as the “kinematic index” as a measure of reproducibility.

Results: During unloaded movement, fluoroscopic analysis did not show a significant difference between both types of prosthesis designs and the natural knee. In the weight-bearing movement, both types of TKA designs did not show the typically arched but a more linear patellar tendon angle curve, with a greater angle in extension and in flexion than the natural knees. This means that the femur glides anteriorly under load near extension and does not show the natural roll-back in flexion. In the mobile-bearing group, inter-individual deviations from the mean during weight-bearing movements were significantly less than in the fixed-bearing group.

Conclusions: In the present study, no functional advantage of mobile bearing TKA over fixed bearing devices could be found. Both TKA designs showed the typical kinematics of an anterior instability. Long-term follow-ups are necessary to elucidate the possible influence of lower PE wear on the incidence of aseptic loosenings.

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.

Purpose: In the treatment of acetabular dysplasia in adolescents and adults the triple osteotomy according to Tonnis is a common procedure. This retrospective study were undertaken to evaluate the clinical and radiological results and quality of life after triple osteotomy according to Tonnis.

Material and Methods: In our retrospective study 43 patients (f=32, m=11) with acetabular dysplasia after triple osteotomy procedure with an average age of 21.8 years (SD=7.6) were evaluated. The average follow-up was 9.3 years (range 0.6–19.1 ys). For clinical evaluation, the Harris Hip Score was used. The pre- and postoperative x-rays in ap and faux profile plane were evaluated for the CE-, VCA-, AC-, ACM-angle and the acetabular index. Quality of life was evaluated by the SF-36-health questionnaire.

Results: 48,8% of our patients achieved excellent or good results in the Harris Hip Score and 65,1% of the patients considered the subjective postoperative result as excellent or good. The CE angle improved significantly from preoperatively 8.8 to postoperatively 34.5 degrees. The VCA angle according to Lequesne and Seze improved significantly from 30.7 to 50.9 and the AC angle from 10.2 to 19.5 degrees. The ACM angle decreased significantly from 53.3 to 56 degrees and the acetabular index increased from 33.4 to 37.3 postoperatively. Range of motion of the operated extremity decreased significantly for hip flexion and internal roation. SF-36-health questionnaire results of the patient group showed significant differences for the parameters physical function, bodily pain and emotional role compared to those of a healthy reference group of the same age.

Four patients showed a pseudarthrosis of the ischial or pubic bone. Three patients had persisting pain of the pseudarthrosis and needed another operative procedure. Hypaesthesia in the area of N. cutaneus femoris lateralis occurred in seven cases.

Conclusion: The results of the operative treatment of an acetabular dysplasia with a triple osteotomy procedure according to Tonnis showed a satisfactory outcome, even though significant functional deficits and deficits of quality of life could be demonstrated in middle and long term follow-up.

Aim: Investigations on human hyaline cartilage of late stage degenerative arthritis showed that the vascular derived endothelian growth factor (VEGF) seems to play a role in the development of degenerative arthritis. The current study was designed to evaluate the expression of VEGF on chondrocytes of hyaline cartilage in the time course of degenerative arthritis.

Methods: In twelve white new-zealand-rabbits the anterior cruciate ligament was resected to create an anterior instability of the knee. In twelve control rabbits only a sham operation without resection of the ACL was done. Another four animals have not been operated at all (0 weeks). Four animals of each group were sacrificed at three, six and twelve weeks each. After opening of the knee joint, the degenerative arthritis was macroscopically graded and the hyaline cartilage of the load bearing area was evaluated histologically according to Mankin and by immunostaining for VEGF.

Results: The macroscopic and histological grade of degenerative arthritis according to Mankin showed a positive linear correlation to the time after surgery. The scores of the control group were constant in the time course. In the cartilage of the untreated animals (0 weeks) an average of 12 percent (SD 2.6) VEGF-positive chondrocytes were found. After 3 weeks the trial group (17.6%; SD 5.7) as well as the control group showed a significant increase (16.2%; SD 4.7). After 6 weeks the value in the control group dropped to normal (11.5%; SD 5.9) and remained constant after 12 weeks (11.6%; SD 3.3). In the trial group the percentage of VEGF positive chondrocytes rose steadily (19.4%; SD 4.6 after 6 weeks; 21.3%; SD 5.4 after 12 weeks). There was a positive linear correlation between the percentage of VEGF positive cells and the Mankin score (r=0.767; p< 0.01) and the macroscopic score (r=0.518; p=0.02).

Conclusion: The current study shows for the first time an in-vivo increase of VEGF expression on chondrocytes in the time course of osteoarthritis, which is dependent on macroscopic and histological grades. Further studies are needed to evaluate whether this pattern applies to human beings and whether new treatment approaches could evolve from this knowledge.

Aim: Previous investigations have shown the vital role of chondrocyte CD44 in cartilage homeostasis and matrix attachment and indicated a participation of CD44v5 in the development of osteoarthritis. However, all reports dealt with late stage human osteoarthritis, as human specimens are only available at the time of surgery. Thus, little is known about the expression of CD44v5 in the time course of osteoarthritis. The current study was designed to evaluate the expression of CD44v5 on chondrocytes of hyaline cartilage in the time course of osteoarthritis.

Methods: In twelve white new-zealand-rabbits the anterior cruciate ligament was resected to create an anterior instability of the knee. In twelve control rabbits only a sham operation without resection of the ACL was done. Four animals of each group were sacrificed at three, six and twelve weeks each. After opening of the knee joint, osteoarthritis was macroscopically graded and hyaline cartilage of the load bearing area was evaluated histologically according to Mankin and by immunostaining for CD44v5.

Results: In the trial group, macroscopic and histological grades of OA showed a positive linear correlation to the time after surgery. Immunostaining showed an increased expression of CD44v5 in the control group after 3 and 6 weeks, which dropped to normal after twelve weeks. There was no difference between control and trial groups after 3 and 6 weeks, but after 12 weeks. We found a significant positive correlation between CD44v5-expression and macroscopic (r=0.294) and histological (r=0.314) grades of OA.

Conclusion: The current study shows in-vivo an increase of expression of the hyaluronan receptor CD44v5 in the time course of osteoarthritis. Further studies are needed to evaluate whether this pattern applies to human beings and whether new treatment approaches could evolve from this knowledge.

Introduction: Mobile bearing total knee arthroplasty (TKA) has been developed to theoretically provide better, more physiological function of the knee and produce less PE wear. The theoretical superiority of mobile bearing TKAs over fixed bearing devices has not yet been proven in clinical studies. The objective of the present study was to prospectively analyze clinical and functional outcomes of randomized fixed and mobile bearing total knee arthroplasty patients by means of gait analysis, electromyography and established clinical scores.

Methods: In a prospective, randomized, patient- and observer-blinded, clinical study, 33 patients (mean age 63 years) received a cruciate retaining Genesis II TKA for primary osteoarthritis. 16 patients received a mobile bearing and 17 patients a fixed bearing device. The day before surgery and 24 months postoperatively, established clinical (KSS, HSS, WOMAC, UCLA, VAS) and quality of life (SF-36) scores were used to compare both patient groups. Electromyography of standardized locations was measured with the MyoSystem 2000 and analyzed with Myoresearch software. Gait analysis was performed with a six camera motion analysis system and force platforms.

Results: Both groups showed significant improvements between pre- and postoperative evaluation in gait analysis and electromyography, but gait analysis results as well electromyography did not show any difference between both groups at follow-up. Clinical and quality of life results significantly improved from pre- to postoperative evaluation, but only the Knee Society Score showed a significant superiority of the mobile bearing group (mean 159.0; SD 27.7; range, 105–196) over the fixed bearing group (mean 134.4; SD 41; range, 56–198) (p=0.0022).

Conclusions: In the present study, no functional advantage of mobile bearing TKA over fixed bearing devices could be found, although the mobile bearing group had better clinical results. Thus, long-term clinical results and in-vivo wear analyses have to be followed, and more subtle functional analyses (e.g. fluoroscopy) have to be employed to finally judge over the theoretical advantage of mobile bearing TKAs.

There is a high risk of venous thromboembolism when patients are immobilised following trauma. The combination of low-molecular-weight heparin (LMWH) with graduated compression stockings is frequently used in orthopaedic surgery to try and prevent this, but a relatively high incidence of thromboembolic events remains. Mechanical devices which perform continuous passive motion imitate contractions and increase the volume and velocity of venous flow.

In this study 227 trauma patients were randomised to receive either treatment with the Arthroflow device and LMWH or only with the latter. The Arthroflow device passively extends and plantarflexes the feet. Patients were assessed initially by venous-occlusion plethysmography, compression ultrasonography and continuous wave Doppler, which were repeated weekly without knowledge of the category of randomisation. Those who showed evidence of deep-vein thrombosis underwent venography for confirmation. The incidence of deep-vein thrombosis was 25% in the LMWH group compared with 3.6% in those who had additional treatment with the Arthroflow device (p < 0.001). There were no substantial complications or problems of non-compliance with the Arthroflow device. Logistic regression analysis of the risk factors of deep-vein thrombosis showed high odds ratios for operation (4.1), immobilisation (4.3), older than 40 years of age (2.8) and obesity (2.2).

Aim of the Study: Evaluation of differences in pro-prioception, gait analysis, electromyography in consideration of clinical results in patients with unicondylar and bicondylar knee arthroplasty.

Material and Methods: 17 patients with mean age of 62.5 years were examined after a mean time of 21.5 months after unicondylar knee arthroplasty and compared with 15 patients with a mean age of 67 years and a mean time of 31.9 months after bicondylar knee arthroplasty. For clinical examination the Knee Society, Hospital for Special Surgery and Patella Score were used. Proprioception was examined using the Balance test. In addition each patient was examined by gait analysis with three-dimensional-kinematics and force plate. M. rectus femoris, M. vastus medialis/lateralis, M. semiten-dinosus, M. biceps femoris, M. tibialis anterior and M. gastrocnemius were examined by electromyography.

Results: There were neither significant deviations in demographic data, clinical scores, electromyography results (except M. vastus lateralis), gait analysis nor in proprioception.

Conclusion: There were no deviations in any clinical or functional results in patients with unicondylar and bicon-dylar knee arthroplasty. Because of the uncertain long term results of unicondylar knee arthroplasty in respect of loosening and development of contralateral osteoarthritis, bicondylar knee arthroplasty can be approved.

Aim of the study: Results of total hip replacement in consideration of quality of life and their correlation to clinical radiologic findings were examined.

Material and methods: 46 of 61 patients with aseptic loosing and total hip replacement were examined in average 4,3 years after surgery with the Harris Hip Score, Merle d’Aubigne Score, Postel Score, WOMAC-Score and SF-36 Health Survey Score. The study of radiographs was completed by the Scores of Brooker, Lee and Gruen. Allograft were used in 38 (83,6%) cases.

Results: The result of the Merle d’Aubigne Score and Postel Score in average account for 11,5 points. Harris Hip Score obtains 62,7 points. The comparison form patient and control group with the SF-36-Score shows unpropitious results particularly for physical functioning, roll limitation because of physical health problems and roll limitation because of physical emotional problems. The outcome for general mental health and vitality show better results for the patients as for the control. Evaluation of the physical and psychical scale applies to impairments of daily life depending on the disease. Patients with hip arthroplasty shows in comparison to patients with cancer or cardiac infarction worst results for the physical category, whereas the best results for the psychical category. Radiographs of 33 patients were completely evaluated. In eight cases (24,2%) there were loosening lines in femur shaft area. In 18 cases (54,55%) there were loosening lines in the area of the acetabular cup, in three cases (9%) a migration

Conclusion: After a total hip replacement the physical functions are limited. Primary hip arthroplasty for young patients should be indicated reserved in consideration of above mentioned results, even if psychological results surprised.

Aim of the study: Documentation of changes in retropa-tellar pressure, contact area and force after total knee arthroplasty in comparison with and without patella resurfacing devices.

Material and method: six cadaver specimen were examined after implantation of a total knee endoprosthesis (Genesis I type) with and without patella resurfacing implants of the sizes “small” und “medium”. Contact pressure and area measurements were done with Fuji Prescale Film (type super low) in a knee flexion angle of 60°.

Results: In comparison to the results without patella implants the implantation of the patella implant size “small” caused a significant decrease of retropatellar contact area (p=0.03) and force (p=0.03). Average and maximum pressure did not change significantly (p=0.6 and p=0.35) even though pressure increased slightly. For the „medium“ size maximum pressure (p=0.03) increased significantly and force decreased significantly (p=0,0277) whereas contact area and average pressure increased slightly.

Discussion: The significant reduction of contact area seen after implantation of both patellar implants may lead to non physiologic loading of the patella as well as to an unfavorable sliding behaviour of the femur.

Clinical relevance: Implantation of a patella resurfacing device can not significant change retropatellar pressure and the decrease of contact area is unfavorable because a small contact area can lead to accelerate wear debris and loosening. Implant size does not have a significant influence.