Biomechanical comparisons of three minimally invasive Achilles tendon percutaneous repair suture techniques

BACKGROUND

While no gold standard exists for the management of Achilles tendon ruptures, surgical repair is common in healthy and active patients. Minimally invasive repair methods have become increasingly popular, while biomechanical equivalency hasn't been proven yet.

METHODS

A mid-substance Achilles tendon rupture was created 6 cm proximal to the calcaneal insertion in 27 fresh-frozen cadaveric ankles. Specimens were randomly allocated to 1 of 3 repair techniques: Huttunen et al. (2014) (1) PARS Achilles Jig System, Nyyssönen et al. (2008) (2) Achilles Midsubstance SpeedBridge™, Schipper and Cohen (2017) (3) Dresdner Instrument and subsequently subjected to cyclic loading with 250 cycles each at 1 Hz with 4 different loading ranges (20-100 N, 20-200 N, 20-300 N, and 20-400 N).

FINDINGS

After 250 cycles no significant differences in elongation were observed between PARS and Dresdner Instrument(p = 1.0). Furthermore, SpeedBridge™ repairs elongated less than either Dresdner Instrument (p = 0.0006) or PARS (p = 0.102). Main elongation (85%) occurred within the first 10 cycles with a comparable elongation in between 10 and 100 and 100-250 cycles. While all repairs withstood the first 250 cycles of cyclic loading from 20 to 100 N, only the PARS (468 ± 175) and Midsubstance SpeedBridge™ (538 ± 208) survived more cycles. Within all 3 groups suture cut out was seen to be the most common failure mechanism.

INTERPRETATION

Within all groups early repair elongation was seen. While this was least obvious within the SpeedBridge™ technique, ultimate strengths of repairs (cycles to failure) were comparable across PARS and SpeedBridge™ with a decline in the Dresdner Instrument group.

The results of health-related quality of life assessment depend on the prevailing rhythm at the assessment: Experience from the CAPTAF trial (Catheter Ablation Compared with Pharmacological Therapy for Atrial Fibrillation)

AIMS

To assess whether the prevailing rhythm at the time of replying to symptom and health-related quality of life (HR-QoL) questionnaires impacts the findings.

METHOD

A total of 150 patients from the randomized Catheter Ablation Compared with Pharmacological Therapy for Atrial Fibrillation-trial, comparing atrial fibrillation (AF) ablation versus drugs, were included. The effect of the prevailing rhythm on the outcome results of the HR-QoL 36-Item Short-Form Health Survey, the symptom severity questionnaire (SSQ), and the European Heart Rhythm Association (EHRA) score for classification of AF-related symptoms was assessed.

RESULTS

AF as the prevailing rhythm was independently associated with a significantly lower Vitality score; 18.4 points lower (95% confidence interval -32.7 to -4.1, p = .01) compared with sinus rhythm when adjusted for AF burden, median duration of episode, number of episodes, beta-blocker use, type of AF, and sex. The presence of AF did not affect the General Health score compared with sinus rhythm, nor did it influence symptoms assessed by the SSQ or EHRA score.

CONCLUSION

The observation that the presence of AF versus sinus rhythm when conducting HR-QoL tests had a negative impact on its outcome, leaving symptom-related questionnaires unaffected, implies that the prevailing rhythm should be taken into account when results of HR-QoL questionnaires are interpreted.

Atrial fibrillation burden, episode duration and frequency in relation to quality of life in patients with implantable cardiac monitor

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Assessing the relationship between atrial fibrillation and quality of life.

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Implantable loop recorders assessed rhythm continuously in symptomatic patients.

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Atrial fibrillation burden, episode duration and frequency were included.

•

Higher atrial fibrillation burden was associated with impaired quality of life.

Aims

To assess the relation between atrial fibrillation (AF) characteristics and health-related quality of life (QoL), and which AF characteristic had the greatest impact.

Method

The AF characteristics burden (percentage of time in AF), duration and number of AF episodes/month were obtained from implantable cardiac monitors during the 2-month run-in period in 150 patients included in the randomized CAPTAF trial comparing early ablation and antiarrhythmic drug therapy. The QoL was measured by the General Health and Vitality dimensions of the 36-Item Short-Form Health Survey. AF characteristics were analysed continuously and in quartiles (Q1-Q4).

Results

Greater AF burden (p = 0.003) and longer AF episodes (p = 0.013) were associated with impaired QoL (Vitality score only) in simple linear regression analyses. Greater AF burden was, however, the only AF characteristic associated with lower QoL, when adjusted for sex, type of AF, hypertension, heart rate above 110 beats per minute during AF, and beta-blocker use in multiple linear regression analyses. For every 10% increase in AF burden there was a 1.34-point decrease of Vitality score (95% confidence interval (CI) −2.67 to −0.02, p = 0.047). The Vitality score was 12 points lower (95% CI −22.73 to −1.27, p = 0.03) in patients with an AF burden > 33% (Q4) versus those with < 0.45% (Q1), but only in unadjusted analysis.

Conclusion

AF burden had a greater impact on QoL (Vitality), than the duration and number of AF episodes, corroborating that AF burden may be the preferred outcome measure of rhythm control in trials including relatively healthy AF populations.

[Does the certification according to EndoCert lead to a better quality of treatment?]

BACKGROUND

Certification according to EndoCert in the field of arthroplasty in Germany aims at standardization of treatment and with this optimization of its quality. However, huge capital investment and efforts are necessary. There are currently more than 400 certified centres in Germany. Our Department of Orthopaedics at a German medical school was certified in the pilot phase. The aim of this study was to analyse whether there was a difference in the quality in the year after the certification. A second aim was to analyse whether the defined quality criteria are adequate for a university hospital.

MATERIALS AND METHODS

The quality criteria as defined by EndoCert were analysed in the year before (2011) and after certification (2012). The observed complications were noted for 1 year postoperatively. The clinical outcome was analysed with Western Ontario and McMaster University Osteoarthritis Index Score (WOMAC) 1 year postoperatively.

RESULTS

There was no difference concerning the criteria analysed, including the clinical outcome in the year before and that after certification. In both years, nearly all criteria could be reached except the operation time and the infection rate in hip and knee revision surgery.

CONCLUSION

Certification did not lead to a measurable change of the quality of care. Nearly all criteria, except the infection rate in revision arthroplasty (required: less than 3% at 1 year postop.) and the operation duration could be fulfilled. This rate as well as the operation duration should be revised. Certification according to EndoCert is an important tool to prove quality care, however big efforts and capital are needed. The criteria should be constantly revised and reduced, as these resources should not be missed in patient care.

[What can we learn in future from the data of the German Arthroplasty Registry (EPRD) in comparison to other registries?]

The German Arthroplasty Registry (EPRD) was founded in 2010 and has been in full operation since 2014. Previous attempts at a systematic data collection of elective and non-elective knee and hip replacement in Germany failed mainly because of the long-term lack of funding. The EPRD is an interdisciplinary collaborative partnership between the German Association of Orthopedics and Orthopedic Surgery (DGOOC), all implant manufacturers of the German Medical Technology Association (BVMed), health insurers (AOK and the Association of Additional Healthcare Insurance) and hospitals (German Hospital Federation). As part of this cooperation a worldwide unique implant database has been set up, which includes all relevant components and a detailed description of implant specifications. This implant library enables a detailed evaluation of implant survival, revision rates and possible inferior implant performance of knee and hip replacements in Germany. At the end of 2015 the EPRD encompassed over 200,000 registered operations. Due to the high number of hip and knee arthroplasties in Germany with many different implants from different manufacturers there will be a rapid growth of data that are available for a national and also international comparison of the results.

Long-term stability of Cu surface nanotips

Sharp nanoscale tips on the metal surfaces of electrodes enhance locally applied electric fields. Strongly enhanced electric fields trigger electron field emission and atom evaporation from the apexes of nanotips. Together, these processes may explain electric discharges in the form of small local arcs observed near metal surfaces in the presence of electric fields, even in ultra-high vacuum conditions. In the present work, we investigate the stability of nanoscale tips by means of computer simulations of surface diffusion processes on copper, the main material used in high-voltage electronics. We study the stability and lifetime of thin copper (Cu) surface nanotips at different temperatures in terms of diffusion processes. For this purpose we have developed a surface kinetic Monte Carlo (KMC) model where the jump processes are described by tabulated precalculated energy barriers. We show that tall surface features with high aspect ratios can be fairly stable at room temperature. However, the stability was found to depend strongly on the temperature: 13 nm nanotips with the major axes in the [Formula: see text] crystallographic directions were found to flatten down to half of the original height in less than 100 ns at temperatures close to the melting point, whereas no significant change in the height of these nanotips was observed after 10 [Formula: see text] at room temperature. Moreover, the nanotips built up along the [Formula: see text] crystallographic directions were found to be significantly more stable than those oriented in the [Formula: see text] or [Formula: see text] crystallographic directions. The proposed KMC model has been found to be well-suited for simulating atomic surface processes and was validated against molecular dynamics simulation results via the comparison of the flattening times obtained by both methods. We also note that the KMC simulations were two orders of magnitude computationally faster than the corresponding molecular dynamics calculations.

Development and validation of a weight-bearing finite element model for total knee replacement

Total knee arthroplasty (TKA) is a successful procedure for osteoarthritis. However, some patients (19%) do have pain after surgery. A finite element model was developed based on boundary conditions of a knee rig. A 3D-model of an anatomical full leg was generated from magnetic resonance image data and a total knee prosthesis was implanted without patella resurfacing. In the finite element model, a restarting procedure was programmed in order to hold the ground reaction force constant with an adapted quadriceps muscle force during a squat from 20° to 105° of flexion. Knee rig experimental data were used to validate the numerical model in the patellofemoral and femorotibial joint. Furthermore, sensitivity analyses of Young's modulus of the patella cartilage, posterior cruciate ligament (PCL) stiffness, and patella tendon origin were performed. Pearson's correlations for retropatellar contact area, pressure, patella flexion, and femorotibial ap-movement were near to 1. Lowest root mean square error for retropatellar pressure, patella flexion, and femorotibial ap-movement were found for the baseline model setup with Young's modulus of 5 MPa for patella cartilage, a downscaled PCL stiffness of 25% compared to the literature given value and an anatomical origin of the patella tendon. The results of the conducted finite element model are comparable with the experimental results. Therefore, the finite element model developed in this study can be used for further clinical investigations and will help to better understand the clinical aspects after TKA with an unresurfaced patella.

Biological activity and migration of wear particles in the knee joint: an in vivo comparison of six different polyethylene materials

Wear of polyethylene causes loosening of joint prostheses because of the particle mediated activity of the host tissue. It was hypothesized that conventional and crosslinked polyethylene particles lead to similar biological effects around the knee joint in vivo as well as to a similar particle distribution in the surrounding tissues. To verify these hypotheses, particle suspensions of six different polyethylene materials were injected into knee joints of Balb/C mice and intravital microscopic, histological and immunohistochemical evaluations were done after 1 week. Whereas the biological effects on the synovial layer and the subchondral bone of femur and tibia were similar for all the polyethylenes, two crosslinked materials showed an elevated cytokine expression in the articular cartilage. Furthermore, the distribution of particles around the joint was dependent on the injected polyethylene material. Those crosslinked particles, which remained mainly in the joint space, showed an increased expression of TNF-alpha in articular cartilage. The data of this study support the use of crosslinked polyethylene in total knee arthroplasty. In contrast, the presence of certain crosslinked wear particles in the joint space can lead to an elevated inflammatory reaction in the remaining cartilage, which challenges the potential use of those crosslinked polyethylenes for unicondylar knee prostheses.

Simvastatin reduces leucocyte- and platelet-endothelial cell interaction in murine antigen-induced arthritis in vivo

OBJECTIVES

The use of statins in the prevention and treatment of cardiovascular diseases is well established. Their use as anti-inflammatory and immunomodulatory agents in the treatment of rheumatoid arthritis (RA) has also been investigated, with several clinical and experimental studies indicating an anti-inflammatory effect of statins for RA, but other studies showing no effect or even the opposite. The current study was designed to examine the effect of simvastatin in an in vivo murine model of arthritis using intravital microscopy.

METHOD

We assigned four groups (n = 7, female C57Bl6 mice), two with and two without antigen-induced arthritis (AiA), from which one of the non-AiA groups and one of the AiA groups were treated with simvastatin 40 mg/kg i.p. daily for 14 consecutive days after induction of arthritis. Platelet- and leucocyte-endothelial cell interaction was assessed by measurement of rolling and adherent fluorescence-labelled platelets and leucocytes, functional capillary density (FCD) was evaluated, and knee joint diameter was determined as a clinical parameter.

RESULTS

In arthritic mice treated with simvastatin, a significant reduction in platelet- and leucocyte-endothelial cell interaction was observed in comparison to arthritic mice treated with vehicle. In addition, a significant reduction in FCD was seen in arthritic mice treated with simvastatin, along with a reduction in knee joint swelling of the AiA mice.

CONCLUSIONS

Treatment of AiA mice with simvastatin showed significant reductions in platelet- and leucocyte-endothelial cell interactions, in FCD, and in the swelling of the knee joint. These results support the hypothesis of the anti-inflammatory effects of statins in the treatment of RA.

[Modified mini-Hardinge access for hip prosthesis implantation in the supine position]

OBJECTIVE

Total hip arthroplasty with a minimal-incision technique that can be performed in the widely used supine position. The accustomed and good overview of this position allows safe positioning of the implant and combines this with the advantage of a soft tissue preserving technique. All standard instruments and implants can be further applied.

INDICATIONS

Primary and secondary coxarthrosis, femoral head necrosis.

CONTRAINDICATIONS

Revision surgery, severe anatomic deformity, implantation of hip resurfacing arthroplasty.

SURGICAL TECHNIQUE

Supine position. The skin incision runs from the innominate tubercle proximally and falls slightly in the dorsal direction (20-30°). Incision of the iliotibial tract and exposure of the vastogluteal muscle sling. Starting from the greater trochanter, the sinewy onset of the minimal and medium gluteal muscle is split with an arched-shaped incision, which also falls proximally in the dorsal direction. Exposition of the joint capsule, longitudinal incision and resection of the ventrolateral parts. Dislocation of the hip by a combined adduction and external rotation movement. Osteotomy of the femoral neck and resection of the femoral head are performed in a figure-of-four position without adduction. To prepare the acetabulum and to insert the cup, the leg is placed in neutral position with a slight flexion of 20° in the hip. Preparation of the femur and implantation of the stem is again performed in a figure-of-four position in adduction. Reduction of the hip and stepwise wound closure.

POSTOPERATIVE MANAGEMENT

Mobilization on postoperative day 1. Starting with half weight bearing and after completed wound healing rapid increase to full weight bearing. Intensive physiotherapy and rehabilitation. Thrombosis prophylaxis according to guidelines.

RESULTS

The mini-incision approach has successfully been used in our clinic for years. Between September 2004 and November 2005, the less-invasive technique was evaluated in a randomized controlled trial with 51 patients (52 hips). Compared to the standard approach a significantly shorter incision length (8.9 vs. 14.0 cm) and a slightly lower blood loss (502 vs. 660 ml) were observed for the modified mini-Hardinge. Moreover, the mini-incision group showed slightly better functional results in the early course. A higher rate of implant malpositioning or a higher peri- and postoperative complication rate was not observed.

Polyethylene wear particles induce TLR 2 upregulation in the synovial layer of mice

A cellular and receptor mediated response to ultra-high-molecular-weight-polyethylene (UHMWPE) wear particles results in a release of proinflammatory cytokines and induces an inflammatory reaction causing osteolysis in total joint replacement. This investigation offers insight into the toll-like receptor (TLR) mediated activation by polyethylene wear particles in the synovial layer of mice. We hypothesized that, similar to recent in vitro results, UHMWPE particles lead to an upregulation of TLR 1 and 2 and TLR 4 in vivo in the synovial tissue of mice as well. Therefore, UHMWPE particles were generated in a common knee simulator according to the ISO standard, separated by acid digestion and determined by scanning electron microscopy. Endotoxin was removed using a method based on ultracentrifugation. A particle suspension (50 μl; 0.1 vol./vol.%) was injected into the left knee joint of female Balb/c mice (n = 8). In a control group, phosphate-buffered saline was injected into the left knee of Balb/c mice (n = 8). The mice were sacrificed after 7 days. Immunohistochemical staining was performed with TLR 1, 2 and 4 polyclonal antibodies for Balb/c mice and evaluated by light microscopy. The particle-stimulated group showed a thickened synovial layer, an increased cellular infiltration and a TLR 2-upregulation in the synovial layer compared to the control group. An increased expression of TLR 1 and TLR 4 could not be demonstrated. These results indicate a mainly TLR 2-induced inflammation to polyethylene wear debris in the synovial layer of mice.

Elevated cytokine expression of different PEEK wear particles compared to UHMWPE in vivo

Due to their mechanical properties, there has been growing interest in poly-ether-ether-ketone (PEEK) and its composites as bearing material in total and unicompartmental knee arthroplasty. The aim of this study was to analyze the biological activity of wear particles of two different (pitch and PAN) carbon-fiber-reinforced- (CFR-) PEEK varieties in comparison to ultra-high-molecular-weight-polyethylene (UHMWPE) in vivo. The authors hypothesized no difference between the used biomaterials. Wear particle suspensions of the particulate biomaterials were injected into knee joints of Balb/c mice, which were sacrificed after seven days. The cytokine expression (IL-1β, IL-6, TNF-α) was analyzed immunohistochemically in the synovial layer, the adjacent bone marrow and the articular cartilage. Especially in the bone marrow of the two CFR-PEEK varieties there were increased cytokine expressions compared to the control and UHMWPE group. Furthermore, in the articular cartilage the CFR-PEEK pitch group showed an enhanced cytokine expression, which could be a negative predictor for the use in unicondylar knee systems. As these data suggest an increased proinflammatory potential of CFR-PEEK and its composites in vivo, the initial hypothesis had to be refuted. Summarizing these results, CFR-PEEK seems not to be an attractive alternative to UHMWPE as a bearing material, especially in unicompartmental knee arthroplasty.

Levels of Cr, Co, Ni and Mo in erythrocytes, serum and urine after hip resurfacing arthroplasty

BACKGROUND

Hip resurfacing arthroplasty is known to increase the metal ion concentration in the serum, urine and whole blood, with potentially adverse effects on the organism. However, only few data are available about the metal ion concentrations in erythrocytes, although they are directly exposed to the higher concentrations of the serum.

METHODS

The ion levels of chromium, cobalt, nickel and molybdenum in erythrocytes of 25 patients with a hip resurfacing implant were analysed with high resolution ICP-sf-MS (inductively-coupled-plasma-sector-field-mass-spectrometry). The results were compared to the ion levels in the serum and urine of the patients, and also to the ion levels of 27 control persons without an implant.

RESULTS

Compared to the control group, ion levels in the erythrocytes of the hip resurfacing group were markedly increased for cobalt (0.10 vs. 3.26 microg/kg) and slightly for chromium (6.04 vs. 7.38 microg/kg). In contrast, ion levels in the serum of the hip resurfacing group were increased for cobalt (0.21 vs. 1.92 microg/l), chromium (1.48 vs. 5.64 microg/l), nickel (1.53 vs. 4.25 microg/l) and molybdenum (2.17 vs. 3.78 microg/l).

CONCLUSION

Ion concentrations of cobalt and chromium are also increased in erythrocytes after hip resurfacing arthroplasty. Further research is required to evaluate the impact of the elevated ion levels on the erythrocytes, and to evaluate if metal ions also accumulate in other tissues of the body.

Comparison of tenocytes and mesenchymal stem cells seeded on biodegradable scaffolds in a full-size tendon defect model

In order to investigate cell-based tendon regeneration, a tendon rupture was simulated by utilizing a critical full-size model in female rat achilles tendons. For bridging the defect, polyglycol acid (PGA) and collagen type I scaffolds were used and fixed with a frame suture to ensure postoperatively a functional continuity. Scaffolds were seeded with mesenchymal stem cells (MSC) or tenocytes derived from male animals, while control groups were left without cells. After a healing period of 16 weeks, biomechanical, PCR, histologic, and electron microscopic analyses of the regenerates were performed. Genomic PCR for male-specific gene was used to detect transplanted cells in the regenerates. After 16 weeks, central ossification and tendon-like tissue in the superficial tendon layers were observed in all study groups. Biomechanical test showed that samples loaded with tenocytes had significantly better failure strength/cross-section ratio (P < 0.01) compared to MSC and the control groups whereas maximum failure strength was similar in all groups. Thus, we concluded that the application of tenocytes improves the outcome in this model concerning the grade of ossification and the mechanical properties in comparison to the use of MSC or just scaffold materials.

Is there a benefit to a routine preoperative screening of infectivity for HIV, hepatitis B and C virus before elective orthopaedic operations?

PURPOSE

Before elective operations, particularly orthopaedic surgery, national guidelines in Germany recommend testing for human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) to reduce the risk of transmission of the virus through a needlestick or cutting injury. Such testing is expensive. The number of new and unknown diagnoses of viral infections that can be detected by routine screening has not yet been evaluated.

METHODS

The aim of our department of orthopaedic surgery is to screen every adult patient listed for an operation for HBV, HCV and HIV. We retrospectively analysed the number of operations in this single centre from 2001 to 2010, correlated this number with the total number of screens and calculated the number of newly diagnosed infections. An additional cost:benefit ratio was calculated.

RESULTS

A total of 20,869 operations were performed by the department between 2001 and 2010. After exclusion of all interventions in children and all patients who had multiple operations, 15,482 patients remained. Test results were found for 10,011 of these patients during this period (screening rate 65 %). Of those screened, in only four cases (0.4 ‰) was a previously unknown infection detected.

CONCLUSIONS

Two-thirds of the patients included in our study actually underwent screening; this rate was lower than expected. The incidence of newly detected infections was low, putting the benefit of a routine preoperative screening for HBV, HCV and HIV into question. From an economic point of view the low detection rate is a strong argument in favour of omitting routine preoperative screening. Screening only those patients with risk factors may be as safe as screening every patient and would help reduce costs.

[Does increased tibial slope reduce the wear rate of unicompartmental knee prostheses? An in vitro investigation]

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) has become a standard procedure with good clinical outcome in patients with isolated medial osteoarthritis of the knee. However, the survival rates of UKA are still inferior compared to that of total knee arthroplasty. Aseptic loosening and wear are responsible for more than 50% of revisions. Therefore, this study evaluated the influence of the tibial slope on the wear rate in a medial UKA.

MATERIALS AND METHODS

The wear rate of a medial mobile-bearing UKA (Univation® Aesculap, Tuttlingen, Deutschland) was evaluated according to the ISO 14243-1:2002(E) norm with a customized four-station servo-hydraulic knee wear simulator (EndoLab, Thansau, Germany). In the first group, the prostheses was medially implanted with 0° slope (n = 3) and in the second group the prostheses was medially implanted with 8° slope (n = 3). The lateral side was kept constant with 0° in both groups. For each implant, a total of 5.0 million cycles was performed and after every 0.5 million cycles the gravimetric wear rate was determined.

RESULTS

The wear rate in the 0° slope group was 3.46 ± 0.59 mg/million cycles and therefore significantly higher than in the 8° slope group with 0.99 ± 0.42 mg/million cycles (p < 0.01).

DISCUSSION

An increase in the tibial slope leads to a reduced wear rate in a mobile-bearing UKA. Therefore, at least for this mobile-bearing UKA a higher tibial slope seems favorable to reduce the wear. However, before an optimal position of the tibial slope can be recommended, further investigations are required to evaluate the influence of the tibial slope on other factors, such as the ligament tension or the strain on the lateral compartment.

[Implant position of total hip arthroplasty shafts. Establishment of a new method for comparison between planned and achieved shaft positions]

BACKGROUND

One of the main goals of the preoperative planning of hip prostheses is adequate shaft positioning with reconstruction of leg length and offset. The purpose of this study was to compare the planned and achieved shaft positions using a modified program for migration measurement.

METHODS

In 60 cases of total hip replacement the preoperative planning was compared with the postoperative radiograph using a modified version of the well-established EBRA-FCA program. The results of this new measurement were compared to conventional measurements. In 25 cases the intraobserver and interobserver reliability was determined.

RESULTS

The novel measurements correlated best with the measured distance between the greater trochanter and the center of rotation and yielded the best intraobserver and interobserver reliability. In general, cementless stems had a slightly more proximal position (0.65 mm) compared to cemented stems.

CONCLUSIONS

The modified program for migration measurement facilitates a reproducible and fast comparison of the planned and achieved shaft positions thus implementing an early and objective control of postoperative shaft position.

[Anatomy and biomechanics of the patellofemoral joint: physiological conditions and changes after total knee arthroplasty]

The patellofemoral joint constitutes a complex anatomical and functional entity. The tensile force of the quadriceps femoris muscle is transmitted through the patella and patellar ligament onto the tibial tuberosity. This particular three-dimensional arrangement increases the torsional moment acting on the knee joint. Dynamic alignment of the patella is determined by trochlear geometry and is supported by active muscular and passive connective tissue stabilizers. In addition to the retinaculum of the patella, the medial patellofemoral ligament is attracting increasing clinical attention. Multidirectional motion of the patella is closely connected to retropatellar pressure distribution which can be modulated by moving the patellar ligament insertion. Implantation of a knee endoprosthesis changes the joint surface geometry and consequently patella kinematics and retropatellar pressure distribution. Finite element analysis provides the possibility to assess retropatellar pressure distribution before and after implantation of prostheses.

Scaffold-free 3D cellulose acetate membrane-based cultures form large cartilaginous constructs

Scaffold-free three-dimensional (3D) cultures provide clinical potential in cartilage regeneration. The purpose of this study was to characterize a scaffold-free 3D membrane-based culture system, in which human articular chondrocytes were cultivated on a cellulose acetate membrane filter, and compare it to pellet and monolayer cultures. Chondrocytes were expanded in monolayer culture for up to 5 passages, transferred to membrane-based or pellet cultures and harvested after 7 or 21 days. The chondrogenic potential was assessed by histology (toluidine blue, safranin-O), immunohistochemistry for collagen type II and quantitative analysis of collagen type II α(1) (COL2A1). Membrane-based cultures (P1) formed flexible disc-like constructs (diameter 4000 µm, thickness 150 µm) with a large smooth surface after 7 days. Positive safranin-O and collagen type II staining was found in membrane-based and pellet cultures at P1-3. Expression of COL2A1 after 7 days was increased in both culture systems compared to monolayer culture up to P3, whereas cells from monolayer > P3 did not redifferentiate. The best results for COL2A1 expression were obtained from membrane-based cultures at P1. After 21 days the membrane-based cultures did not express COL2A1. We concluded that membrane-based and pellet cultures showed the ability to promote redifferentiation of chondrocytes expanded in monolayer culture. The number of cell passages had an impact on the chondrogenic potential of cells. Membrane-based cultures provided the highest COL2A1 expression and a large, smooth and cartilage-like surface. As these are appropriate features for clinical applications, we assume that membrane-based cultures might be of use in cartilage regeneration if they displayed similar results in vivo.

The influence of adjuvants on local recurrence rate in giant cell tumour of the bone

INTRODUCTION

Intralesional surgery of giant cell tumour of the bone (GCT) may result in a high rate of local recurrence. The introduction of local adjuvants, such as cementation, cryosurgery or phenolization, has proved to be successful in the reduction of recurrence rates. This study presents the results of a single institution in surgery of GCT with an evolution in treatment strategies.

MATERIAL & METHODS

Forty primary and 25 recurrent surgical procedures in 46 patients with GCT of the bone with a median follow-up of 72 months were reviewed retrospectively. The mean age was 32.6 years (range 13.6-57.9 years). Forty-seven curettages and 18 resections were performed. For the curettages, a large bone window was cut followed by high speed burring and bone grafting or cementation. In 34 of 47 curettages and 7 of 18 resections, phenol was additionally applied.

RESULTS

Two patients showed pulmonary metastasis, one died due to metastatic disease. In total, a third of the patients developed local recurrence (32.3%). This was evenly spread among primary and recurrent diesease (32.5% vs. 32%). Seven of 13 curettages without adjuvant recurred (53.9%), compared to 11 of 34 curettages with adjuvant phenol (32.4%). Three of 18 resections developed a recurrence (16.7%). No complications in respect to the use of phenol were seen.

DISCUSSION

Phenolization is a safe local adjuvant therapy for GCT. Although the recurrence rate was lower with the use of phenol, this drop was not significant. The comparable high recurrence rate in our study, even if phenol was used, might be due to the fact that curettage was our favoured treatment, even in cases with an extensive juxta-articular tumour. We recommend adjuvant phenolization in the treatment of GCT of the bone after thorough curettage in applicable cases, including where cementation is used for defect filling.

[Cementing techniques in hip arthroplasty: an overview]

For decades the cemented anchorage of hip prostheses, especially for elderly patients, is the standard procedure. The cementing technique has turned out to be the determining factor for the survival of the implant. In the last few years developments in this field have been able to further improve the long-term survival. Established components of the modern cementing technique are vacuum-mixed cements, medullary canal plugs, centralising elements und the use of jet-lavages. The design of the cemented shaft depends on the more important surface finish. In the most clinical studies, polished shafts turned out to be slightly superior as compared to shafts with rough surfaces.

Influence of design and bearing material on polyethylene wear particle generation in total knee replacement

Periprosthetic osteolysis is one of the main reasons for revision of arthroplasty. The osteolytic reaction is influenced by the dose, size and shape of the wear particles. For arthroplasty, a low number and biologically less active particles are required. This is the first study which analyzes the impact of different knee designs, combined with crosslinked polyethylenes (sequentially irradiated and annealed as well as remelted techniques), on the amount, size and shape of particles. Overall, six material combinations, four of them with crosslinked polyethylene (XPE) and two of them with ultra-high molecular weight polyethylene (UHMWPE) inserts, including fixed and mobile bearings, were tested in a knee joint simulator. After isolation nearly 100,000 particles were analyzed in size, shape and number by scanning electron microscopy and image analysis. For all the designs, the wear was predominantly smooth and granular with few fibrillar particles. The Scorpio design with the X3 insert, the Natural Knee II design with the Durasul insert and the LCS design, also combined with a crosslinked polyethylene insert, generated statistically significant (P<0.05) lower particle numbers. The particle size was independent of the radiation dose. The wear generated by the LCS knee design (XPE and UHMWPE) had a higher percentage fraction of particles >1microm in size (equivalent circle diameter). The NexGen design, tested with the Prolong insert, showed a high number of particles in the biologically active size range compared with the other crosslinked designs, which could be a predictor for higher biological reactivity.

[Prognosis-adapted surgical management of bone metastases]

Surgery in metastatic disease to the bone is the most common procedure in orthopaedic oncology. To assess an adequate therapeutic approach we analysed 513 surgeries performed on 453 patients between 1980 and 2005 and reviewed the literature.The most significant factor is the histology of the primary tumour. A biopsy is mandatory to confirm the diagnosis in an unknown primary tumour, especially in cases of solitary lesions. Pulmonary carcinoma has an unfavourable prognosis compared to breast and renal cell carcinoma patients. Radical resection in isolated metastatic disease in renal cell carcinoma reduces the risk of local recurrence and even may result in a long progression-free survival. In breast cancer osseous and visceral dissemination is the most decisive factor for prognosis. An interdisciplinary approach is mandatory in every patient.

In vivo interactions of platelets and leucocytes with the endothelium in murine antigen‐induced arthritis: the role of P‐selectin

OBJECTIVE

Platelets are thought to participate in the pathogenesis of chronic inflammatory diseases such as rheumatoid arthritis (RA). We showed recently an in vivo increase in platelet-endothelial cell interactions in mice with antigen-induced arthritis (AiA). The underlying mechanisms are not yet clear. The aim of this study was to investigate the impact of P-selectin in AiA by means of intravital fluorescence microscopy (IVM).

METHODS

C57/Bl6 mice and P-selectin-deficient mice were divided into four groups (n = 7; control/AiA per strain). The extent of AiA was assessed by measuring knee joint swelling and by histological scoring. Rolling and adherent fluorescence-labelled platelets and leucocytes were investigated by IVM.

RESULTS

In arthritic P-selectin-deficient mice (rolling: 0.05+/-0.01; adherent: 130+/-20 mm(-2)), compared to arthritic C57/Bl6 mice (rolling: 0.20+/-0.04; adherent: 1910+/-200 mm(-2)), platelet interaction was significantly reduced (p<0.05) and reached the level of both control groups without AiA. In addition, interaction of leucocytes in P-selectin-deficient arthritic animals (rolling: 0.12+/-0.06; adherent: 387+/-37 mm(-2)) was significantly decreased in comparison to arthritic C57/Bl6 animals (rolling: 0.21+/-0.06; adherent: 1492+/-284 mm(-2); p<0.05). Swelling of the knee joint and histological scoring were reduced in arthritic P-selectin-deficient mice compared to arthritic C57/Bl6 mice.

CONCLUSION

We have demonstrated for the first time in vivo a significant decrease in the interaction of platelets and leucocytes with the endothelium in P-selectin-deficient mice with AiA and a reduction in clinical and histological symptoms of arthritis. These findings suggest that leucocyte-endothelial cell interactions depend at least partially on platelet P-selectin and therefore platelets may be responsible for the leucocyte tissue damage in AiA.

[Hip dislocation following THA]

In the event of a hip dislocation following THA analysis of its mechanism is the main priority. In addition, the time since the operation and the direction of the dislocation need to be taken into account. When the cause of the dislocation is analysed the formation of the neocapsule plays a part at least in the case of early dislocations (within the first 6 weeks after the operation). Most dislocations happen during this postoperative period, and these can usually be treated nonoperatively by closed reduction with only a short period of general anaesthesia. Late dislocations (in the 7th and subsequent postoperative week) generally occur because of malpositioning or migration of the components of the prosthesis and quite often do need operative treatment. Dislocation after implantation of a total hip replacement is a serious complication; it should be treated quickly, and initially it confronts the operator with many unanswered questions, from the causes to their treatment.

The compression—rotation stem: An experimental study on the primary stability of a new revision hip stem

In revision hip arthroplasty with bone defects of the proximal femur, a well-established treatment method is reconstruction with impacted allograft spongiosa chips and cemented implantation of a polished stem. Building on this principle of impacted bone grafting, a femoral implant, which is suited to uncemented hip arthroplasty as well as for uncemented revisions, was designed. This so-called compression—rotation stem (CR stem) is collarless and has flanks which compress the impacted bone chips during implantation and thereby increase the rotational stability. To evaluate the primary stability of this new shaft after impaction grafting, the micromotion was determined using six motion transducers. Under physiological loading conditions with simulation of the muscle activities at the proximal femur the application was dynamically loaded for 15 000 cycles with 1000 ± 500 N and afterwards for 5000 cycles with 1300 ± 1000 N. Uncemented CR stems and the control Exeter stems were implanted in a standardized manner according to the X-Change method. Therefore they were implanted into artificial femora that had been previously resected, hollowed, and filled with impacted human spongeous bone allograft to simulate bone defects. Subsequently, the femora were loaded under identical conditions and the micromotions measured. In the majority of the implantations, no significant differences could be found. In conclusion, similar clinical results for the two stems should be expected.

Selective inhibition of platelets by the GPIIb/IIIa receptor antagonist Tirofiban reduces leukocyte-endothelial cell interaction in murine antigen-induced arthritis

OBJECTIVE

Inflammation is associated with the invasion of leukocytes into affected tissues and with the up-regulation of platelet activation and adhesion. Assuming that leukocyte accumulation is linked to platelet aggregation, the aim of our study was to examine the effects of selective platelet inhibition by the glycoprotein (GP) IIb/IIIa receptor antagonist Tirofiban on the leukocyte-endothelial cell interaction.

MATERIAL AND METHODS

We used the model of antigen-induced arthritis (AiA) to induce inflammatory changes in the synovial microcirculation. Ex vivo labelled platelets and in vivo fluorescence-labelled leukocytes were visualized by intravital microscopy (IVM). C57/Bl6 mice were allocated to four groups; two control groups with saline or Tirofiban and two groups with AiA that also received either saline or Tirofiban (0.5 microg/g BW) intravenously.

RESULTS

There was no significant change in platelet- or leukocyte- endothelial cell interaction in the endothelium in healthy control animals. In contrast, after selective inhibition of platelets, the platelet- and leukocyte-endothelial cell interaction was significantly reduced in arthritic mice and reached the level of the healthy control groups.

CONCLUSION

Selective platelet inhibition by Tirofiban resulted in reduced leukocyte-endothelial cell interactions in AiA. Consequently, platelets contribute to leukocyte adhesion in AiA via GPIIb/IIIa and therefore platelet inhibition could become an additional therapy option in chronic arthritic disease.

Platelet P-selectin is significantly involved in leukocyte-endothelial cell interaction in murine antigen-induced arthritis

There is growing evidence that platelets play an important role in the development and maintenance of rheumatoid arthritis. Activation and adherence of platelets in the synovial microcirculation might be in part responsible for endothelial damage and activation of leukocytes. Recent findings show a direct influence of P-selectin on platelet- and leukocyte-endothelial cell interaction in mice with Antigen-induced Arthritis (AiA). P-selectin is only expressed by platelets and endothelial cells, not by leukocytes. Therefore, the aim of the present study was to investigate the differential influence of platelet and endothelial P-selectin on the extent of inflammation in AiA. AiA was induced in wild-type mice and in P-selectin-deficient mice from the same genetic background (four groups: each n = 7). Intravital fluorescence microscopy (IVM) was used to visualize platelets and leukocytes in the synovial microcirculation at day 8 after AiA. Platelets from either strain were fluorescence-labelled ex vivo and transferred into either strain. We were able to demonstrate a significant decrease of platelet- and leukocyte-endothelial cell interaction in P-selectin-deficient mice with AiA in comparison to wild-type mice with AiA. When wild-type platelets were donated into P-selectin-deficient AiA recipients, the leukocyte-endothelial cell interaction was significantly increased compared to the group consisting of P-selectin-deficient recipient and donor mice. These are the first in vivo results showing that the P-selectin stored in platelets is at least partly responsible for the leukocyte-endothelial cell interaction and the resulting tissue damage in AiA. In the future, a suppression of platelet P-selectin could potentially become a treatment option for reducing the effects of rheumatoid arthritis.

[The dislocated shoulder prosthesis--an avoidable disaster?]

Instability after shoulder arthroplasty is a common problem, even though complete dislocations are rare. A distinction can be made between vertical and horizontal instabilities. The most common type of vertical instability is superior migration of the humeral head caused by rotator cuff insufficiency; the shoulder prosthesis should be changed for an inverse prosthesis if the patient is symptomatic. Horizontal instabilities can certainly lead to acute dislocation, but it is far more common for them to result in eccentric loading of the glenoid and in turn to increased wear and loosening. When a prosthesis is first implanted it is essential to reproduce the original bony situation before the deformity caused by arthrosis, arthritis or fracture, as this is the only way to prevent instability. This requires careful preoperative planning including evaluation of CT or MRI scans so that during the operation it will be possible, for example, to reorientate an eccentrically torn glenoid using a bone graft or by eccentric reaming and restore the original torsion. At least as much importance attaches to the treatment of the soft tissue, meaning careful release and later closure of the rotator cuff and capsule complex, as to the bony situation. In the authors' own institution 190 prostheses were implanted between 2000 and 2006 and there were three dislocations (1.6%).

Proximal loading of the femur leads to low subsidence rates: first clinical results of the CR-stem

INTRODUCTION

A new femoral stem was developed with a design that leads to compression of cancellous bone in the calcar region which results in proximal loading. The cross-sectional design of the implant provides rotational stability.

MATERIALS AND METHODS

In the first clinical investigation ten patients underwent uncemented total hip arthroplasty between January 1999 and May 1999 using the CR-stem((R)) (Implantcast GmbH, Buxtehude, Germany). Results were investigated using the Harris-hip-score (HHS) and antero-posterior and lateral radiographs. Migration was evaluated with the EBRA-FCA-method with a follow-up of 7 years.

RESULTS

We demonstrated a mean subsidence rate of 2.23 +/- 1.13 mm 7 years after implantation thus providing basic data for extensive testing in a clinical environment.

DISCUSSION

As small subsidence rates are regarded as predictor for superior long-term results in uncemented total hip arthroplasty according to the literature, the CR-stem shows promise for excellent long-term results.

[Atypical course in Stickler syndrome]

We report about a 12-year-old boy with a Stickler syndrome. Because of osteonecrosis in the femoral head in MRI the initial diagnosis was dysplasia epiphysealis capitis femoris. The patient developed a progressive stiffness of the hip and a retinal detachment. A molecular investigation showed a Stickler syndrome. Stickler syndrome is an autosomal dominant hereditary disease. It has a very low incidence and a rare association with hip disease. Usually the patients suffer from hypermobility. In our case the course was atypical and diagnosis delayed.

Endothelial iNOS versus platelet iNOS: Responsibility for the platelet/leukocyte endothelial cell interaction in murine antigen induced arthritis in vivo

OBJECTIVE

Since an increase of platelet-endothelial cell interactions has been observed in mice with Antigen- induced-Arthritis (AiA) as well as an increase of NO expression, the aim of our study was to investigate in vivo the influence of NO, especially the platelet and endothelial inducible NO Synthase, on the platelet- and leukocyte endothelial cell interaction.

MATERIAL AND METHODS

C57/Bl6 mice and iNOS deficient mice were disposed in 6 groups (each=7). After induction of AiA, rolling and adherent fluorescence labelled platelets and leukocytes were investigated by intravital microscopy (IVM) on day 8 after AiA. Rank SUM Test and ANOVA on ranks have been performed regarding the data.

RESULTS

All arthritic mice presented an increase in platelet and leukocyte interaction with the endothelium compared to control groups. The arthritic iNOS deficient mice showed a more intense interaction of platelets and leukocytes with the endothelium in comparison with the wild-type arthritic mice. The group using arthritic wild-type recipient and iNOS deficient donor mice showed an increase in cell-interactions, leading to an endothelial effect, compared to the group using iNOS deficient arthritic recipient and wild-type donor mice.

CONCLUSION

The IVM data lead to an anti-inflammatory effect of NO, since NO followed an increase in platelet- and leukocyte- endothelial cell interaction in iNOS deficient mice with AiA. In addition, we have shown for the first time in vivo that platelet NO produced by iNOS seems to have a minor influence on the leukocyte induced tissue damage in contrast to endothelial iNOS. Therefore, selective platelet inhibition would not interfere with the protective effect of NO.

Prognostische Faktoren zur Beurteilung der Wertigkeit der ASK bei Gonarthrose

AIM

The value of athroscopy in osteoarthritis(oa) of the knee remains uncertain. Many studies claim to prove efficacy of arthroscopy in oa of the knee, while other authors report that there is no such effect. The purpose of this study was to identify factors to predict the outcome of arthroscopy in oa of the knee.

METHOD

The modified Lysholm score was used to assess the outcome of arthroscopy in 49 patients after a follow up of 2.5 yrs. This was a retrospective outcome study.

RESULTS

No correlation between modified Lysholm score and patient age and gender could be detected. There were significantly better outcomes in the group of patient with no deviation of axis and in the group of patients which did not show a progression of oa of the knee in the radiographs during follow-up. Even if the patients had more severe osteoarthritis.

CONCLUSION

Patient selection is an important factor for a good outcome after arthroscopy in older patients with oa of the knee. Deviation of the axis and the "activity" of the osteoarthritis at the time of surgery are predictors for outcome. There is the need to establish diagnostic tools to measure the "activity" of oa of the knee before surgery.

Timing of cervical spine stabilisation and outcome in patients with rheumatoid arthritis

One complication of rheumatoid arthritis (RA) is the involvement of the cervical spine (CS). Although prophylactic stabilisation is recommended, the timing at which this should occur is poorly defined. The aim of our study was to evaluate the course of neurological symptoms in terms of the timing of surgery. A total of 34 patients with RA and CS involvement were surgically stabilised. These patients were classified using the Ranawat (RW) score both preoperatively and at an average of 54 months post-operatively. For each patient, the presence of atlantoaxial and subaxial subluxation as well as vertical migration of the odontoid was recorded. The anterior atlantodental interval was also assessed pre- and post-operatively. Improvement was obtained in 20 patients, the clinical situation remained unchanged in three patients and three patients manifested disease progression. In terms of the RW score, the 16 patients with pre-operative RW grades I-II showed no deterioration at the post-operative follow-up, with 13 of these patients showing an improvement; the 12 patients with pre-operative RW grades IIIA-IIIB did not show any improvement of neurological symptoms at follow-up, although seven of these patients subjectively assessed the symptoms to be less severe after surgery; three other patients showed a worsening of symptoms. Our results suggest that preventive stabilisation of CS in RA leads to acceptable results, although the complications of the surgery are obvious. However, early operative treatment may delay the detrimental course of cervical myelopathy in RA.

Spannungsoptische Oberflächenanalyse an humanen Femurpräparaten vor und nach Implantation unterschiedlicher Schenkelhalsprothesenmodelle

AIM

The aim of this study was the detection of areas at risk at the proximal femur after implantation of different femur neck prostheses using the photoelastic stress analysis.

METHODS

Twelve pairs of human femurs were used as examination material. The analysis of the stress pattern was done with a stepwise increasing load up to the quadruple of body weight before and after implantation of three models of femur neck prostheses which were implanted cementless. The "CUT" and "Cigar" models are coated with a tripod structure. The "Cigar" model has a lateral thrust plate. The lateral end of the "CUT" model is curved and this end is attached to the lateral corticalis. The third model, the "rip prosthesis" has two layers for rotational stability. Subsequently, the micromotions of the implanted prosthesis in the femural neck were examined with alternating weight loads (1000 +/- 700 N).

RESULTS

The Cigar prosthesis showed the most changes of stress distribution because of the lateral thrust plate with concentration of isochromatic lines to the lateral boring. In the region of the oseotomy an increase of strain up 1440 microm/m could be detected for the Cigar and up to 1000 microm/m for the rib prosthesis. The stress pattern after implantation of the CUT prosthesis remained very similar apart from a slight increase of stress values (720 microm/m). Only for the Cigar prostheses were the measured micromotions below the critical value for a possible osteointegration with a mean value of 134 microm/m.

CONCLUSION

The stress pattern after implantation of the CUT prosthesis remained most similar to the preinterventional stress distribution. Because of this, it is to be expected that the osseous modification would stay at a low level. The question of osteointegration can only be answered in long-term in-vivo studies.

Classification of Non-Bacterial Osteitis: Retrospective study of clinical, immunological and genetic aspects in 89 patients

OBJECTIVE

To define non-bacterial osteitis (NBO) as a clinical entity possibly associated with autoimmune manifestations. Patients with sterile osteitis were analysed to develop diagnostic criteria.

METHODS

A total of 89 patients with non-bacterial inflammatory bone lesions were observed for a median of 49 months. History, diagnostic imaging, laboratory and histological data were obtained. Mutation analysis in the genes PSTPIP1 and PSTPIP2 was performed.

RESULTS

Patients had an onset of disease at a median age of 10 yrs [interquartile range (IQR) 7.5-12] and suffered a median period of 21 (IQR 9-52) months with a median of three foci per patient. Twenty percent of all the patients demonstrated associated autoimmune disorders, particularly of the skin and bowel. The majority of bone lesions were located in the vertebrae and metaphyses. Slight-to-moderate elevation of inflammation values were found in all the patients and antinuclear antibodies were elevated in 30%. Non-steroidal anti-inflammatory drugs (NSAIDs) were effective in 85% of the patients. HLA-B27 and Human Leukocyte Antigen-DR (HLA-DR)-classification did not differ from the general population. Autoimmune diseases in 40% of all the families, multiply affected family members, linkage to 18q21 and mouse models strongly indicate a genetic basis for NBO. We observed three different courses of disease regarding the duration of complaints, rate of complications and associated autoimmune manifestations leading to a new classification of NBO.

CONCLUSIONS

Clinical analysis of our cohort leads us to define NBO as a distinct disease entity with three clinical presentations: acute NBO, chronic recurrent multifocal osteomyelitis or persistent chronic NBO. Diagnostic criteria were proposed to differentiate NBO from diseases with similar clinical presentation.