Towards the simulation of bone-implant systems with a stratified material model.

BACKGROUND: The clinical performance of medical devices is becoming increasingly important for the requirements of modern development processes and the associated regulations. However, the evidence for this performance can often only be obtained very late in the development process via clinical trials or studies. OBJECTIVE: The purpose of the presented work is to show that the simulation of bone-implant systems has advanced in various aspects, including cloud-based execution, Virtual Clinical Trials, and material modeling towards a point where and widespread utilization in healthcare for procedure planning and enhancing practices seems feasible. But this will only hold true if the virtual cohort data build from clinical Computer Tomography data are collected and analysed with care. METHODS: An overview of the principal steps necessary to perform Finite Element Method based structural mechanical simulations of bone-implant systems based on clinical imaging data is presented. Since these data form the baseline for virtual cohort construction, we present an enhancement method to make them more accurate and reliable. RESULTS: The findings of our work comprise the initial step towards a virtual cohort for the evaluation of proximal femur implants. In addition, results of our proposed enhancement methodology for clinical Computer Tomography data that demonstrate the necessity for the usage of multiple image reconstructions are presented. CONCLUSION: Simulation methodologies and pipelines nowadays are mature and have turnaround times that allow for a day-to-day use. However, small changes in the imaging and the preprocessing of data can have a significant impact on the obtaind results. Consequently, first steps towards virtual clinical trials, like collecting bone samples, are done, but the reliability of the input data remains subject to further research and development.

10-year follow-up of the Columbus knee prostheses system in a prospective multicenter study.

INTRODUCTION: As endpoint of a prospective multicenter 10-year documentation using the Columbus system, this evaluation carried out results of clinical scores (Knee Society Score and Oxford Knee Score), an evaluation of radiological imaging, survival rates and a collection of complication statistics. MATERIALS AND METHODS: There was a multicenter prospective recruitment of consecutive patients with the indication for total knee replacement (TKR). Preoperatively and 10 years after implantation, clinical scores, range of motion and radiological imaging was performed. During this period, a detailed documentation of complications was made. RESULTS: A total of 210 patients were recruited in 5 centers. 140 patients were available for endpoint examination 10 years after surgery. A survival rate of 96.6% (CI 95%) for the implanted Columbus prostheses after 10 years was demonstrated. Cumulative KSS showed an improvement of 75.3 (± 38.1) points and was highly significant (p < 0.0001, t test). The average functional improvement in the Oxford score was 20.6 (± 9.5) points and was also highly significant (p < 0.0001). The ROM improved from 106.5° (± 20.5) preoperatively to 116.0° (± 11.5) (p < 0.0001, t test). There were no implant-related complications as well as no new complication documented between 5- and 10-year follow-up. CONCLUSIONS: The endpoint analysis after an observation period of 10 years provided good clinical and radiographic results. In particular, an excellent survival rate of 96.6% after 10 years was demonstrated. The data published in this study are the first to be available in a prospective multicenter study on this system, which leads to a high level of clinical significance.

Heterogeneity of penicillin-non-susceptible group B streptococci isolated from a single patient in Germany.

OBJECTIVES: Streptococcus agalactiae [group B streptococci (GBS)] have been considered uniformly susceptible to penicillin. However, increasing reports from Asia and North America are documenting penicillin-non-susceptible GBS (PRGBS) with mutations in pbp genes. Here we report, to the best of our knowledge, the first two PRGBS isolates recovered in Europe (AC-13238-1 and AC-13238-2), isolated from the same patient. METHODS: Two different colony morphologies of GBS were noted from a surgical abscess drainage sample. Both were serotyped and antimicrobial susceptibility testing was performed by different methodologies. High-throughput sequencing was done to compare the isolates at the genomic level, to identify their capsular type and ST, to evaluate mutations in the pbp genes and to compare the isolates with the genomes of other PRGBS isolates sharing the same serotype and ST. RESULTS: Isolates AC-13238-1 and AC-13238-2 presented MICs above the EUCAST and CLSI breakpoints for penicillin susceptibility. Both shared the capsular type Ia operon and ST23. Genomic analysis uncovered differences between the two isolates in seven genes, including altered pbp genes. Deduced amino acid sequences revealed critical substitutions in PBP2X in both isolates. Comparison with serotype Ia clonal complex 23 PRGBS from the USA reinforced the similarity between AC-13238-1 and AC-13238-2, and their divergence from the US strains. CONCLUSIONS: Our results support the in-host evolution of ß-lactam-resistant GBS, with two PRGBS variants being isolated from one patient.

[5-year follow-up of 210 Columbus knee prostheses : A prospective multicentre study]. / 5-Jahres-Follow-up von 210 Columbus-Knietotalendoprothesen : Eine prospektive multizentrische Studie.

INTRODUCTION: As part of 10-year documentation using the Columbus system, the interim evaluation was carried out 5 years after implantation with a collection of clinical scores, evaluation of radiological imaging and collection of statistics concerning complications. METHODS: There was a multicentre prospective recruitment of consecutive patients with the indication of implantation of a surface replacement prosthesis (Columbus CR, Deep Dish fixed inlay). Preoperatively, clinical scores were recorded (KSS and Oxford score). Five years postoperatively a new evaluation of clinical scores, the range of motion (ROM) and a radiological check-up including full leg imaging under load was performed. During this period, detailed complication documentation was made. RESULTS: A total of 210 patients were recruited in five centres. 187 patients were available for examination 5 years after surgery. Cumulative KSS increased from 87.5 (±26.6) preoperatively to 170 (±29.1) 5 years postoperatively. The cumulative KSS improvement was 81.5 (±35.2) points and was highly significant (p < 0.0001; t­test). The average functional improvement in the Oxford score between the preoperative and 5­year follow-up was 21.7 (±8.8) points and was also highly significant (p < 0.0001). The ROM improved from 106.3° (±20.2) preoperatively to 114.0° (±12.1) 5 years postoperatively (p < 0.0001; t test). Five years after implantation, the average mechanical leg axis was 178.0° (±2.1). There was no clinically apparent or native radiologic visible aseptic loosening of the femoral or tibial joint component. There were 33 complications, but no implant-related complications such as inlay dislocation, material fracture or aseptic loosening. In total, 6 revision surgeries were performed during the follow-up period, which corresponds to a survival rate of 97.1% (CI 95%) for the implanted Columbus knee in the present patient collective for 5 years. CONCLUSION: The interim analysis at 5 years of long-term observation of the Columbus system provided good clinical and radiographic results.

Correct Assessment of Acetabular Component Orientation in Total Hip Arthroplasty From Plane Radiographs.

BACKGROUND: Correct positioning of the cup is an important factor in total hip arthroplasty. Assessing its position from a plain anteroposterior pelvic radiograph is known to be hampered by systemic errors. This study focuses on developing a correction method to adjust for these potential sources of error and to eliminate them based on a 3D geometric analysis. METHODS: Computed tomography scans of 113 (66 male, 47 female) pelvices were reconstructed and virtually projected onto a plain radiograph with varying rotational and translational positions. Thus cup inclination and anteversion as measured on a 2D-radiograph and in the 3D environment were correlated. Projected offset of the symphysis from the mid-sacrum served as a mean to measure pelvic right/left-rotation. Pelvic tilt was determined from the projected height of the contour of the small pelvis. Correction formulas were verified by projecting a gimbal-mounted artificial pelvis with a cup implanted in a known position. RESULTS: We found gender-specific formulas that correct for malrotated and off-centered radiographs. Applying these formulas cup inclination was assessed as close as 1.3° (±1.90°) to the true 3D value and cup anteversion as close as 1° (±1.91°) although deviations between directly measured plain values and corrected values rose up to 18°. CONCLUSION: Inherent effects of central projection and malrotations due to pelvic tilt, pelvic rotation, and noncentered radiographs are corrected. Evaluation of radiographic inclination and anteversion of acetabular cups from plain 2D-radiographs show improved precision. Real values are approached better than 1.3° when applying our correction formulas.

[Prosthetic Joint Infection after Total Hip Arthroplasty: Results of an Online Questionnaire about Current Diagnostic and Therapeutic Procedures in 107 German Hospitals]. / Die infizierte Hüfttotalendoprothese: Eine Onlineumfrage zum aktuellen diagnostischen und therapeutischen Vorgehen in 107 deutschen Krankenhäusern.

Background Prosthetic hip joint infection is a common severe complication with a high socio-economic impact. The inconsistency of the available data and the absence of binding guidelines lead to a variety of diagnostic and therapeutic strategies. The aim of this study is to present the current diagnostic and therapeutic approach to treating infections after total hip arthroplasties in German hospitals, link it with current evidence, and evaluate the willingness of these hospitals to participate in prospective multicentre trials. Material and Methods An online questionnaire for digital processing was sent to hospitals performing joint replacement procedures. These institutions included district hospitals, private hospitals, non-university maximum care facilities, statutory accident insurance hospitals, and university hospitals. Results A total of 107 hospitals took part in the survey, corresponding to a response rate of 27.6%. These hospitals perform approximately 2,951 revisions of infected total hip arthroplasties per year. Two-stage revision arthroplasty is the preferred procedure after prosthetic hip infections. The algorithm proposed by Zimmerli et al. is widely recognised. There is a lack of uniformity in the key features for revision of prosthetic joint infections - long vs. short interval in case of two-stage revision, duration of intravenous and oral administration of antibiotics, cemented vs. cement-free implant procedures, and follow-up intervals after revision surgery. The willingness to participate in clinical trials is high. Conclusion The controversial data leads to multiple treatment approaches. The high willingness to participate in adequately funded clinical trials offers a potential for multicentre trials to be conducted. There is an urgent need for funding to make this research possible.

Factors influencing treatment success of negative pressure wound therapy in patients with postoperative infections after Osteosynthetic fracture fixation.

BACKGROUND: Negative Pressure Wound Therapy (NPWT) is being increasingly used to treat postoperative infections after osteosynthetic fracture fixation. The aim of the present study was to analyze the influence of epidemiological and microbiological parameters on outcome. METHODS: Infections following operative fracture fixation were registered in a comprehensive Critical Incidence Reporting System and subsequently analyzed retrospectively for characteristics of patients including comorbidity, bacteria, and clinical factors. The influence of the investigated parameters was analyzed using logistic regression models based on data from 106 patients. RESULTS: Staged wound lavage in combination with NPWT allowed implant preservation in 44% and led to successful healing in 73% of patients. Fermentation characteristics, load and behavior after gram staining revealed no statistically significant correlation with either healing or implant preservation. Infecting bacteria were successfully isolated in 87% of patients. 20% of all infections were caused by bacterial combinations. We observed a change in the infecting bacterial species under therapy in 23%. Age, gender, metabolic diseases or comorbidities did not influence the probability of implant preservation or healing. The delayed manifestation of infection (>4 weeks) correlated with a higher risk for implant loss (OR 5.1 [95% CI 1.41-17.92]) as did the presence of bacterial mixture (OR 5.0 [95% CI 1.41-17.92]) and open soft-tissue damage ≥ grade 3 (OR 10.2 [CI 1.88-55.28]). Wounds were less likely to heal in conjunction with high CRP blood levels (>20 mg/l) at the time of discharge (OR 3.6 [95% CI 1.31-10.08]) or following a change of the infecting bacterial species under therapy (OR 3.2 [95% CI, 1.13-8.99]). CONCLUSIONS: These results indicate that the delayed manifestation of infection, high CRP blood levels at discharge, and alterations in the infecting bacterial species under therapy raise the risk of NPWT failure.

Plate fixation of periprosthetic femur fractures: What happens to the cement mantle?

Osteosynthesis of periprosthetic femur fractures by screw fixation around the implanted prosthetic stem is currently regarded as the biomechanically superior option compared with cerclage. The aim of this biomechanical study was damage analysis of the cement mantle after revision screw insertion. A prosthetic stem (Bicontact) was implanted in 20 cadaveric femora in cemented technique. A locking compression plate (Synthes) was then applied to the lateral femur at the level of the prosthetic stem. The method of plate fixation to the femur was assigned randomly to three groups: bicortical non-locking screws, monocortical locking screws, and bicortical locking screws. This was followed by applying a fluctuating axial load (2100 N, 0.5 Hz) for 20,000 cycles. After testing, macroscopic and microscopic evaluations of the cement mantle were conducted. Cracks formed in the cement mantle in 14% of the 80 screw holes. The type of screw (bicortical or monocortical; locking or non-locking) had no significant effect on the number of cracks (p = 0.52). The relationship between manifestation of crack damage and cement mantle thickness was not significant (p = 0.36), whereas the relationship between crack formation and screw position was significant (p = 0.019). Those screws whose circumference was only partially within the cement mantle yielded a significantly lower number of cracks compared with screws positioned completely within the cement mantle or even touching the prosthetic stem. In order to reduce the incidence of crack formation in the cement mantle during plate osteosynthesis of periprosthetic femur fractures, the screws should not be either placed within the cement mantle or make direct contact with the stem.

Osteoarthritic changes rather than age predict outcome following arthroscopic treatment of femoroacetabular impingement in middle-aged patients.

BACKGROUND: Our purpose was to evaluate outcome following arthroscopic treatment of femoroacetabular impingement (FAI) in middle-aged patients and to define risk factors for conversion to total hip arthroplasty (THA). METHODS: This was a retrospective case series of 79 consecutive patients (40 to 65 years) undergoing arthroscopic treatment of FAI (follow-up ≥12 months). Outcome at follow-up was assessed using Hip outcome score (HOS). Alpha angle, Kellgren Lawrence grade (K-L grade), joint space width (JS), lateral center edge (LCE) angle, caput-collum-diaphysis (CCD) angle and acetabular index (AI) were analysed retrospectively. THA group and Non-THA group were compared. RESULTS: Seventy-nine patients (mean age 48.6 years, mean follow-up 32 months) were included. 18 patients (22.8 %) were converted to THA. Mean HOS score in the Non-THA group at time point of follow-up was 80.2. Non-THA group and THA group showed no significant differences for mean age (48.2 years vs. 49.9 years, p = 0.278), alpha angel (p = 0.541), LCE (p = 0.294), CCD (p = 0.101) and AI (p = 0.661) in contrast to differences for JS (p = <0.001) and K-L grade (p = <0.001). Risk of conversion to THA was higher for patients with K-L grade 3 (p = 0.003) or joint space less or equal 2 mm (p = 0.001). CONCLUSIONS: One fifth of the middle-aged patients required early conversion to THA. Advanced JS narrowing and K-L grade rather than age alone can be considered as risk factor for conversion to THA.

When is the stability of a fracture fixation limited by osteoporotic bone?

This article is concerned with the search for threshold values for bone quality beyond which the risk of fixation failure increased. For trochanteric fractures we recognized a BMD lower than 250mg/cm(3) as an additional risk for cut out. For medial femoral neck fractures since joint replacement surgery is available and produces excellent functional results, we see no indication for further differentiation or analysis of bone quality in relation to fracture fixation. In the area of osteoporotic vertebral body fractures, there are many experimental studies that try to identify BMD limits of screw fixation in the cancellous bone on the basis of QCT analysis. However, these values have not yet been introduced for application in clinical practice. In case of indication for surgical fixation, we favor minimally invasive, bisegmental, fourfold dorsal instrumentation with screw-augmentation for a T-value less than -2.0 SD (DXA analysis, total hip or total lumbar spine). For proximal humerus fractures, BMD value of 95mg/cm(3) could be seen as a threshold value below which the risk of failure rises markedly. In relation to osteoporotic distal radius fractures, based on our clinical experience and scientific analyses there are virtually no restrictions as far as bone quality is concerned on the application of palmar locking implants in the surgical management of distal radius fractures. Optimization of preoperative diagnostics might help to revise the treatment algorithm to take bone density into account, thus reducing the risk of failure and, at the same time, acquiring additional data for future reference.

Effect of Rotational Component Alignment on Clinical Outcome 5 to 7 Years After TKA With the Columbus Knee System.

The aim of the study was to examine the effects of rotational component alignment on outcome after total knee arthroplasty (TKA) with a minimum follow-up of 5 years. For this study, 96 patients were available for follow-up at a mean of 5.7 years after TKA. Computed tomography scans were available in 55 patients. Outcome (Oxford Knee Score [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], 36-item Short Form Health Survey) was correlated with postoperative femoral and tibial component malrotation or femorotibial rotational alignment mismatch. Results showed that femoral or tibial component malrotation or femorotibial mismatch were present in 15.5%, 38.2%, and 29.1% of patients, respectively. Although femoral componoent malrotation was associated with significantly poorer, KSS and KOOS scores, outcome was comparable for patients with or without tibial component malrotation or femorotibial mismatch. In conclusion, both internal and external rotational femoral malalignment exceeding 3° is associated with significantly poorer subjective and objective outcome 5 to 7 years after TKA. Tibial component malrotation and femorotibial mismatch were more common, but did not significantly compromise outcome. [Orthopedics. 2016; 39(3):S50-S55.].

Oblique Axis Body Fracture: An Unstable Subtype of Anderson Type III Odontoid Fractures-Apropos of Two Cases.

Purpose. Anderson type III odontoid fractures have traditionally been considered stable and treated conservatively. However, unstable cases with unfavorable results following conservative treatment have been reported. Methods. We present the cases of two patients who sustained minimally displaced Anderson type III fractures with a characteristic fracture pattern that we refer to as "oblique type axis body fracture." Results. The female patients aged 90 and 72 years, respectively, were both diagnosed with minimally displaced Anderson type III fractures. Both fractures had a characteristic "oblique type" fracture pattern. The first patient was treated conservatively with cervical spine immobilization in a semirigid collar. However, gross displacement was noted at the 6-week follow-up visit. The second patient was therefore treated operatively by C1-C3/4 posterior fusion and the course was uneventful. Conclusions. Oblique type axis body fractures resemble a highly unstable subtype of Anderson type III fractures with the potential of severe secondary deformity following conservative treatment, irrespective of initial grade of displacement. The authors therefore warrant a high index of suspicion for this injury and suggest early operative stabilization.

Diagnosis of prosthetic joint infections using UMD-Universal Kit and the automated multiplex-PCR Unyvero i60 ITI(®) cartridge system: a pilot study.

BACKGROUND: Prosthetic joint infections (PJI) are associated with high morbidity and costs. Various efforts have been made to improve the diagnosis of PJI over the past years, but only few studies have assessed the diagnostic utility of nucleic acid amplification test (NAAT) techniques in this context. Here, we report our experience with a commercial 16S rRNA gene PCR and an automated multiplex-PCR cartridge system in identifying pathogens causing PJI. MATERIALS AND METHODS: A prospective single-centre study was performed including 54 patients with either septic or aseptic prosthetic joint replacement or surgical revision between February 2012 and April 2013. Conventional cultures of periprosthetic tissue samples were compared with the results of broad-range 16S rRNA gene real-time PCR (UMD-Universal Pathogen DNA Extraction and PCR Analysis, Molzym GmbH, Germany) and the multiplex-PCR Unyvero ITI(®) cartridge system (U-ITI; Curetis AG, Germany). Conventional culture and broad-range 16S rRNA gene real-time PCR were performed on all samples. U-ITI was used in a subgroup of 28 cases including all culture-positive cases. The agreement of the results from the methods was assessed. RESULTS: Of 54 cases, seven were culture-positive. Broad-range 16S rRNA gene real-time PCR gave 6, U-ITI 3 concordant positive results. Of the 47 culture-negative samples, 46 were also negative by broad-range 16S rRNA gene real-time PCR resulting in a 96 % (52/54) agreement between 16S rRNA gene PCR and culture. Of the 21 culture-negative samples analysed with U-ITI, 20 gave negative results, including the single 16S rRNA gene PCR-positive/culture-negative specimen. The rate of agreement between U-ITI and culture results was 82 % (23/28). CONCLUSION: This pilot study gave no indication of superiority of the used NAATs over conventional culture methods for the microbiological diagnosis of PJI. Drawbacks are susceptibility to contamination in the case of 16S rRNA gene real-time PCR, labour-intensive DNA extraction and limited pathogen panel in the case of the multiplex cartridge PCR system. More prospective trials are needed to evaluate the diagnostic performance of NAATs and their impact on the clinical management of PJI.

Sliding of the load carrier in third-generation intramedullary nails for proximal femur fractures: an in vitro mechanical comparison study.

Dynamic osteosynthesis of proximal femur fractures facilitates compression at the fracture site through distal glide of the femoral head load carrier in the intramedullary nail. Modern implants are currently designed according to diverse gliding principles. The aim of this study was to compare the sliding mechanisms of different types of nails. As in other similar mechanical studies the load patterns occurring around the femoral head load carrier and the intramedullary nail under full load were simulated for three different types of intramedullary nail - PFNA, Targon PFT and Trigen Intertan. The load necessary to trigger distal displacement of the femoral head implant in the nail was determined. The lengths of the load carriers were varied. For the three lengths of load carrier, mechanical testing showed that the Targon PFT started to slide at a significantly lower load compared to the other two implants. Comparison of the PFNA and Trigen Intertan in terms of load to dynamization for 77 mm carriers revealed a significantly lower load for the PFNA. Slide efficacy for the PFNA and the Trigen Intertan was found to improve as the length of the blade/screw was shortened. The dynamization properties of the Targon PFT with its cylindrical sliding mechanism, similar to the DHS, were far better compared to the PFNA and the Trigen Intertan that have more complex sliding actions. Since theoretical considerations indicate that a less efficient gliding action leads to a higher complication rate, implants of the next generation should be optimized in this regard.

Biomechanical testing of an innovative fixation procedure to stabilize olecranon osteotomy.

UNLABELLED: For the treatment of distal humerus an approach involving olecranon osteotomy is frequently preferred as it offers a clearer view, especially in cases of complex intraarticular fractures. It is however associated with the high risk of osteotomy-related complications such as nonunion, delayed healing, implant failure and migration of wires. The aim of the present study was to evaluate the stability of different new procedures that stabilize olecranon osteotomy compared with conventional tension band wiring. We hypothesize that the new implants provide equivalent stability as the conventional tension band wiring. To test the hypothesis 27 biomechanically evaluated synthetic ulnae were osteotomized and stabilized with either the application of tension band wiring, the Olecranon Hook LCP (Synthes, Switzerland), or the Olecranon Osteotomy nail (Synthes, Switzerland). Loading was performed providing a tensile load to simulate the tensile force applied by the triceps muscle. Cyclic force-controlled loading was performed at 300 alternating forces between 10N and 500N at a speed of 200N/sec. An ultrasound-based system measured displacement to an accuracy of 0.1 mm. Statistical analysis showed significantly less displacement in the Olecranon Hook LCP and Olecranon Osteotomy nail groups compared with tension banding. Comparison of plate and nail yielded no differences in stability. Biomechanical testing did however show significantly higher stability for newer fixation methods for olecranon osteotomies compared with the frequently applied technique of tension band wiring. Whether the use of these implants will also lower complication rates remains to be evaluated in future clinical studies. LEVEL OF EVIDENCE: Basic Science Study, Biomechanical Study.

Periprosthetic joint infection--effect on quality of life.

PURPOSE: Relatively little is known about the extent to which periprosthetic joint infections (PJI) affect the patient's long-term quality of life (QoL). Our study aim was to assess the effect of a periprosthetic infection on our patients' QoL. METHODS: We collected data retrospectively of patients who had undergone surgery in our institution between 2006 and 2011. To capture their overall QoL, we telephoned the patients who could be reached and asked them the questions on the SF-12 questionnaire. RESULTS: In 84 patients (53 male, 31 female, 43 TKA and 41 THA), 88 % of the hip infections and 62 % of the knee infections had been successfully treated. The hip infections' cure rate was significantly higher than that of the knee joint infections. The average SF-12 score was 36.2 points on the physical scale and 52 on the mental scale. The difference in QoL between patients with and without successful infection therapy was not significant, nor did the site of the infection (knee or hip) influence QoL significantly. Comparison of our patients' QoL data to that from the general population revealed a significant difference in the physical scale but not the mental scale. CONCLUSION: From these results QoL is substantially reduced after a prosthetic infection. We did however observe that post-Girdelstone procedure patients or those with an arthrodesis attained an acceptable QoL, and that those methods remain therapeutic alternatives as far as patient-perceived QoL is concerned.

Digital templating in total knee and hip replacement: an analysis of planning accuracy.

PURPOSE: The aim of this study was to determine how well pre-operative size selection for total knee and hip arthroplasties based on the digital imaging with and without additional referencing correlated with the size actually implanted. METHODS: Size selection planning of total knee arthroplasty by digital templating was documented in 46 cases with reference ball (group A) and in 48 cases without ball (group B). In addition, prospective analysis of pre-operative planning was conducted for 52 acetabular components with reference ball (group C) and 69 without ball (group D) as well as stem planning in 38 cases with ball (group E) and 54 cases without ball (group F). The data were analysed and compared with the size of the final component selected during surgery. RESULTS: The correlation between planned and implanted size for total knee arthroplasty in group A resulted in femoral anteroposterior (AP) r = 0.8622 and lateral r = 0.8333 and in group B AP r = 0.4552 and lateral r = 0.6950. Tibial in group A was AP r = 0.9030 and lateral r = 0.9074 and in group B AP r = 0.7000 and lateral r = 0.6376. For the acetabular components, the results in group C were r = 0.5998 and group D r = 0.6923. For stems, group E was r = 0.5306 and group F r = 0.5786. No correlation between BMI and the difference between planned and implanted size was found in any of the groups. CONCLUSION: In the case of total hip arthroplasty there was a relatively low correlation between planned and implanted sizes with or without reference ball. For total knee arthroplasties the already high precision of size planning was further improved by the additional referencing with a reference ball.

Tibial cleaning method for cemented total knee arthroplasty: An experimental study.

BACKGROUND: The survival rate of cemented knee prosthesis depends among other factors on optimal cement-bone contact, nevertheless no standard exists for cementing technique of tibial components. The aim of this study was to determine which tibial surface preparation technique leads to the best bone-cement contact. MATERIALS AND METHODS: HUMAN TIBIAL PLATEAU SPECIMENS WERE CLEANED IN FOUR DIFFERENT WAYS BEFORE CEMENTING: a) no cleaning, b) manual syringe irrigation, c) fracture brush cleaning, and d) pulsatile jet-lavage. The specimens were cut into transverse sections and the bone cement contact distance was calculated for every 10 mm and the cement penetration depth was measured. Both values were statistically analyzed (ANOVA). RESULTS: The longest bone-cement contact (62 mm) was seen after PJL, the shortest (10.6 mm) after no cleaning at all. The deepest cement penetration (4.1 mm) again was seen after PJL, the least (0.7 mm) after no cleaning. Statistically, PJL yielded the longest bone-cement contact and deepest cement penetration. CONCLUSION: The results supports the use of pulsatile jet-lavage before cementing tibial components in knee arthroplasty.

Modular sleeves with ceramic heads in isolated acetabular cup revision in younger patients-laboratory and experimental analysis of suitability and clinical outcomes.

PURPOSE: One possibility in hip arthroplasty revisions is to combine a modular ceramic head with an adapter or sleeve in isolated acetabular cup replacement. This study consisted of an experimental part to analyse the reliability of taper damage predictions, and a clinical part to analyse the outcomes of modular ceramic head implantation in a case series of isolated cup replacements. METHODS: Analysis of scratch size on 11 explanted hip stems were examined macroscopically and by stereomicroscopy to classify damage to the conical taper. The second part consisted of a prospective analysis of isolated cup revisions using a modular ceramic head, performed in two orthopedic centres. RESULTS: Analysis of scratch size on the taper yielded inter-observer correlations of 0.545-0.909; comparison with stereomicroscopic data recordings yielded a moderate correlation, with values between 0.545 and 0.090. The clinical study included 47 isolated acetabular cup revisions involving modular ceramic heads. Ceramic head failure did not occur during the average clinical and radiological observation period of 26 months. Mean Harris Hip Score (HHS) at follow-up was 70 points. CONCLUSION: From these results, it can be concluded that damage to the implanted stem taper cannot be reliably predicted intraoperatively. Nevertheless, the clinical outcomes did show that there were no problems with the ceramic heads over the short observation period. The application of modular ceramic heads in younger patients requiring isolated cup replacement requires proper risk-benefit analysis, but is possible and appears to be a safe procedure.