Invasive electrical stimulation in the treatment of avascular osteonecrosis of the femoral head - mid-term results

The study aimed to evaluate the outcomes of osteonecrosis of the femoral head (ONFH) in adults after surgical treatment including invasive electromagnetic osteostimulation (E-Stim). Further, the influence of disease stage and several comorbidities on the joint preservation rate should be examined. Sixty patients (66 hip joints) with ONFH were included in this retrospective cross-sectional analysis (mean follow-up: 58 months, 19-110 months). Potential ONFH risk factors and comorbidities (ONFH stage, age, sex, alcohol, smoking, cortisone medication, chemotherapy) were recorded. The influence of specific parameters on the joint preservation rates was evaluated by a multivariate logistic regression analysis. Finally, patients with preserved hip joints underwent an assessment of their last available X-rays. The joint preservation rate depended on the initial ONFH Steinberg stage (I+II: 82.8%, III: 70.8%, ≥ IVa: 38.5%). Initially collapsed ONFH (p ≤ 0.001) and cortisone therapy (p = 0.004) significantly decreased the joint preservation rates. In case of progressed ONFH, the presence of ≥ 2 risk factors resulted in higher THA conversion rates (stage III: OR 18.8; stage ≥IVa: OR 12). In 94% of the available X-rays, the ONFH stage improved or did not progress. No complications could be attributed to the E-Stim device or procedure. The present surgical protocol including minimally invasive E-Stim revealed high joint preservation rates for non-collapsed ONFH after mid-term postoperative follow-up. Especially in progressed ONFH, the-risk profile seems to be crucial and hence, for joint preserving surgery, careful patient selection is recommended.

Identification of Potentially High-risk Patients on the Basis of PROMs in a Certified Centre for Joint Replacement (EndoProthetikZentrum) Using the Example of Primary Knee Arthroplasty

BACKGROUND

The subjective evaluation of the patient's state of health with the help of Patient-reported Outcome Measurements (PROMs) provides valuable information for assessing the treatment outcome and for treatment planning. However, the use of PROMs in the field of arthroplasty is not mandatory, so that there is a lack of standardised recording and interpretation. The present study aims to identify patients, who have not achieved the intended treatment goals with regard to pain, function and quality of life after total knee arthroplasty, more easily in the future on the basis of postoperative PROMs.

MATERIAL AND METHODS

Data collection (for 3-month postoperative follow-up) included a standardised clinical follow-up (NU) and a questionnaire of different PROMs (Oxford Knee Score [OKS], OKS Pain Score [OKSS] and EndoCert Risk Score [ERS]). During the specialist follow-up examination, it was decided whether further medical therapy had to be initiated. Accordingly, patients were grouped into four post-treatment categories (NU not required/further diagnostics/new prescription/revision required).

RESULTS

For individual scores and questions, there were significant differences between the respective groups of consequences resulting from the follow-up examination. The OKS, OKS Pain Score and the ERS are suitable for detecting thresholds to determine the need for a follow-up examination. The postoperative thresholds of the scores are 24 for the OKS total score, 52 for the OKS pain score and 4 for the ERS pain intensity score.

CONCLUSION

In the initial three months after knee arthroplasty, certain PROMs are suitable for identifying patients for whom further diagnostics and therapy are indicated. In particular, the OKS and the pain intensity score of the ERS are suitable for detecting a potentially unfavourable development in rehabilitation after total knee arthroplasty.

Net Promoter Score: a prospective, single-centre observational study assessing if a single question determined treatment success after primary or revision hip arthroplasty

BACKGROUND

Our study aimed to identify the relationship between treatment outcome assessed by patient-reported outcomes (PROMs) and satisfaction measured by calculation of the Net Promoter Score (NPS), which identifies promoters, following total hip arthroplasty (THA). The aim was to evaluate this association separately in primary and revision THA and to determine thresholds based on PROMs that identify detractors of the surgical procedure or the centre.

METHODS

A total of 1,243 patients who underwent primary or revision THA at our hospital were asked to complete questionnaires of the Oxford Hip Score (OHS), Euroquol-5D (EQ-5D) and information on pain intensity preoperatively, three and 12 months after surgery. Postoperatively, the patients were additionally asked about their satisfaction with the procedure and the hospital by using three different NPS questions. The association between PROMs and NPS was evaluated based on group comparisons of primary or revision THA and receiver operating characteristics analysis (ROC) to determine threshold values.

RESULTS

At 12 months the NPS of all three questions were invariably linked to treatment outcome in patients after primary THA and patients with a single revision. In these two treatment groups, promoters always showed significantly better PROM scores than detractors. The NPS score was always higher in the primary group in comparison to the single revision group, e.g. 66.4% would undergo the procedure again in the first group, while only 33.0% would opt for this in the latter group. The high thresholds for the PROMs at 12 months, that were calculated by ROC analysis to identify promoter/detractors, indicate that patients` satisfaction required very good joint function and pain relief. However, the NPS was not a suitable tool to identify patients who need further care in an early phase after surgery.

CONCLUSIONS

With NPS already a single question or a single parameter provides the desired information regarding patient satisfaction and also treatment success.

TRIAL REGISTRATION

The study was approved by the Ethics Committee at the Medical Faculty of the University Rostock: "Ethikkommission an der Medizinischen Fakultät der Universität Rostock", Address: St.-Georg Str. 108 18055 Rostock, Germany, reference number: A2015-0055.

Constrained metal-on-metal hip arthroplasty: ever heard of a 50-year survival story?

BACKGROUND

The history of total hip arthroplasty dates back to the first half of the twentieth century. Data on hip endoprostheses implanted during the 1960s and 1970s suggest widely varying survival rates of the prosthesis.

CASE

A case of a patient who underwent total hip arthroplasty in 1972 using a Sivash prosthesis, developed in 1956 in the former Soviet Union, is presented in this article. The prosthesis has remained unrevised in the patient's body for 50 years and he continues to be widely free of implant-related symptoms. Despite the constrained metal-on-metal design of the implant, which can lead to adverse reactions to metal debris, no elevated systemic metal ion levels were detected.

CONCLUSION

The likelihood of encountering patients with prosthesis survival beyond 50 years is still rare. Nevertheless, changing demographics and the steadily improving designs and materials of hip endoprostheses may likely result in such cases.

Identification of Potential High-Risk Patients on the Basis of PROMs in a Certified Centre for Joint Replacement (EndoProthetikZentrum) Using the Example of Hip Arthroplasty

BACKGROUND

In addition to clinical parameters, the subjective assessment by the patient to evaluate the operative outcome of an arthroplasty is becoming increasingly important. Questionnaires are used to identify patients who have not achieved the treatment goal at an early stage so that further interventions can be indicated.

MATERIAL AND METHODS

A questionnaire consisting of different PROMs was completed pre- and 3 months postoperatively by patients who had been treated with a hip arthroplasty. A standardised follow-up examination of these patients was carried out 12 to 16 weeks postoperatively, after which it was determined whether further therapy was necessary to achieve the treatment goal. Different consequences were defined for this.

RESULTS

Significant differences were found between the groups of consequences of follow-up examinations over both time points, but also when postoperative scores were considered exclusively. Furthermore, the correlations for the postoperative scores and some consequences of the clinical follow-up for the Oxford Hip Score (OHS), the OHS functional score and the Euroquol-5D show moderate effects. Thus, the collection of these postoperative scores is sufficient to identify potential high risk patients. Based on a receiver operating characteristic (ROC) analysis, threshold values could be determined for these scores, for which a follow-up examination is recommended.

CONCLUSION

Patients who could not achieve functional improvement, pain reduction and improvement in quality of life after implantation of a total hip replacement must be identified at an early stage. The results of our study show that with the help of the Oxford Hip Score and Euroquol-5D, which are answered by the patients three months postoperatively, such high risk patients can be identified. This finding is an added value for the further development of the EndoCert certification system and holistic quality assurance in arthroplasties, while the personnel and time effort remain manageable.

[Individual megaspacers in two-stage revision of infected total hip arthroplasty-clinical and functional results after 2 years : Individual metal-endoskeleton cement spacer (iMECS)]

BACKGROUND

Large femoral defects in late periprosthetic infection (PPI) after total hip arthroplasty (THA) often require the use of large, individual metal endoskeleton-reinforced cement spacers (iMECS).

OBJECTIVES

The aim was to record the clinical, radiological and functional results (Harris Hip Score HHS) up to the 2 years after treatment of a PPI using an iMECS. Major patient-specific parameters were to be evaluated with regard to the treatment outcome.

MATERIALS AND METHODS

The collective of this single-center retrospective cohort study comprised 29 patients. The mean follow-up was 24.4 months (range: 23.0 to 27.6 months). The absence of infection after endoprosthetic hip joint reconstruction was rated as successful treatment. The two patient groups (successful (S)/not successful (nS)) were compared with regard to gender distribution, the Charlson comorbidity index (CCI), the number of previous septic changes, and the rate of polymicrobial and difficult-to-treat infections.

RESULTS

The average CCI in the total collective was 6.4 points. Joint reconstruction was possible in 23 of 29 patients (79%); 2 years after PPI treatment 4 patients were not available for a follow-up examination (2 deceased, 2 unable to participate). At the time of the follow-up, 17 of the 29 patients had received a joint reconstruction and were free of infection, with an average HHS of 75 points. There were no iMECS-associated complications requiring revision. Only the initial CCI (S: 4.1 points; nS: 9.7 points) differed significantly between the patient groups (p < 0.05).

CONCLUSIONS

In the case of large femoral defects, iMECS provide secure temporary stabilization. The chance of a successful joint reconstruction is closely related to the individual comorbidities profile.

Periprosthetic Fungal Infections in Severe Endoprosthetic Infections of the Hip and Knee Joint-A Retrospective Analysis of a Certified Arthroplasty Centre of Excellence

The treatment of periprosthetic joint infections (PJI), and especially of re-infections, poses a highly complex problem in orthopaedic surgery. While fungal infections are rare, they present a special challenge. The therapy is often protracted and based on limited evidence. A total of 510 hip and knee revision surgeries were analysed for the occurrence of bacterial and fungal PJI. In patients with PJI, the duration of the hospital stay and the incidence of disarticulation of the infected joint were recorded. Out of the analysed revision arthroplasties, 43.5% were due to PJI. Monomicrobial infection occurred in 55.2%, dual microbial infection in 21.4%, and polymicrobial (≥3 different bacterial or fungal species) infection in 17.2% of the cases. Overall, Candida species were detected in 12.4% cases. Candida albicans was the main fungal pathogen. In 6.9% of cases, disarticulation of the joint was the only option to control PJI. The detection of polymicrobial infection more than doubled in follow-up revisions and there was a strong association between detection of Candida infection and disarticulation (OR 9.39). The majority of fungal infections were mixed infections of bacteria and Candida albicans. The choice of a biofilm penetrating antimycotic, e.g., caspofungin, together with a sufficient standard procedure for detection and surgical treatment can help to control the infection situation. Fungal infection often proves to be more difficult to treat than anticipated and is more frequent than expected.

[Total knee arthroplasty in the young patient-an update]

The absolute number of total knee arthroplasties (TKA) continues to rise every year. About 10% of the patients are less than 55 years of age, although it is known that functional results and patient satisfaction are lower combined with an increased likelihood of revision compared to older patients. Higher physical activity and patient expectations are a major challenge in this age group. At the same time, the incidence of posttraumatic/postoperative alterations is high, including ligamentous or bony deficiencies, which can make the surgical procedure challenging. In view of these facts conservative treatments and joint sparing procedures should always be considered first. The potential correction of lower-limb deformities and unicompartmental knee arthroplasties need to be carefully evaluated before considering total knee arthroplasty. Only in advanced cases of osteoarthritis in more than one compartment of the knee of with combined ligamentous instability, can a TKA provide satisfactory results in the young patient. However, the strongest predictor of satisfaction is a realistic expectation.

Primary stability of a cementless modular revision hip stem in relation with the femoral defect size: A biomechanical study

PURPOSE

Cementless modular fluted hip stems are commonly used in revision arthroplasty. Nevertheless, there is a wide spectrum of recommendations concerning the minimum bone stock required to enable osseous ingrowth and implant-bone micromotions <100 µm. This experimental study investigated the primary stability of a tapered cementless fluted revision stem depending on different types of bone defects.

METHODS

Implant-bone interface movements with a bimodular stem were examined under cyclic axial and torsional loading using composite femora. In four degrees of freedom, the implant subsidence and micromotions were captured with linear variable differential transformers for the intact femora and seven different defects ranging from Paprosky type I to type IIIB.

RESULTS

With a 7-cm length of intact diaphysis proximal to the isthmus (Paprosky IIIA), mean implant-bone micromotions of 66 µm occurred. An implant-bone contact zone of only 5 cm (Paprosky IIIA) resulted in micromotions notably over 100 µm and significantly increased subsidence (p < 0.05). With a Paprosky IIIB defect (3 cm of intact diaphysis) rotational instability occurred in all specimens.

CONCLUSIONS

Aside from critically increased interfacial micromotions (>100 µm), rotational instability emerged as a mechanism of fixation failure when the implant-bone contact zone was only 5 cm or less. Hence, future studies investigating the implant fixation in the case of femoral bone defects should consider both axial and torsional loading. With regard to the clinical application, our data suggest maintaining 7 cm of diaphyseal implant-bone contact for a safe anchorage of cementless fluted hip revision stems.

[Management of suspected early infection after osteosynthesis]

The infection rate after fracture osteosynthesis depends on many factors. The postoperative infection rate after osteosynthesis (inpatient treatment) was between 1.15% and 2.04% for the years 2017-2019. The total number of postoperative wound infections was estimated at around 225,000 annually in 2018. Essential factors for reducing the infection rate after osteosynthesis are the favorable choice of the timing of the operation and the surgical procedure as well as the treatment of relevant secondary diseases. If a postoperative wound infection is suspected critical assessment of the wounds in the postoperative course is essential in order to be able to identify and treat this complication at an early stage. After osteosynthesis, early diagnosis of a peri-implant infection and differentiated surgical and antibiotic treatment are the prerequisites for the best possible treatment success.

[Medical device training in arthroplasty : National practice and quality standards]

The qualified training of users of medicinal products is enshrined in law by the Medical Devices Act. In this article, a survey and analysis of the training measures for arthroplasty of the large joints offered by distributors of medical devices is carried out. To that end, the internet presence of suppliers of medical devices was evaluated with regard to the training measures on offer, and selected suppliers were sent questionnaires. The presentation of the available training programmes on the websites was incomplete. Even after the amendment of the Medical Devices Act, this has only slightly changed; however, legally required instructions for use were available for all distributors questioned. In some cases, there are large gaps in the range of modern training methods on offer, such as practical instruction, multimedia offerings or visual-haptic training methods.

Micromotion and subsidence of a cementless conical fluted stem depending on femoral defect size - A human cadaveric study

BACKGROUND

Cementless modular endoprostheses with tapered fluted stems cover a wide spectrum of femoral defects in reconstructive surgery of the hip. Nevertheless, for these hip stems the recommendations concerning the minimum diaphyseal anchorage distance differ widely. The present experimental study investigated the primary stability of a conical fluted revision stem depending on different types of femoral bone defects.

METHODS

Using six fresh frozen human femora, the relative movement of a bi-modular revision stem within the implant-bone interface was examined under cyclic loading conditions. Implant subsidence as well as micromotions at the bone-implant interface were captured with linear variable differential transformers for the intact femora and three different defects ranging from Paprosky type II to type IIIB.

FINDINGS

Compared to the intact femur, the infliction of a Paprosky type IIIB defect (3 cm of intact diaphysis) notably increased mean stem subsidence (13-389 μm per 500 load cycles; P = 0.116) but the mean interface micromotion vector sum remained unchanged (50 μm vs. 53 μm). In Paprosky IIIB defects the subsidence component resulting from rotation (horizontal plane) was significantly higher than with the intact femur and a Paprosky II defect (P ≤ 0.041).

INTERPRETATION

With optimal bone quality and ideal femur preparation a 3 cm conical fixation was sufficient to meet the set criteria of bony ingrowth in vitro. A conical fixation of 7 cm should be recommended to limit rotational subsidence, especially in case of impaired diaphyseal bone quality or expected difficulties with partial weight-bearing.

[What do orthopedic and trauma surgeons expect from radiologists when interpreting imaging of the elbow?]

CLINICAL ISSUE

The elbow is a complex joint with a multitude of acute and chronic pathologies. In addition to the clinical examination, radiological diagnostics play a decisive role in the further therapeutic management.

DIAGNOSTIC WORK-UP/PERFORMANCE

While acute traumatic injuries often present with obvious structural changes and the need for rapid treatment decisions, chronic processes can present with less evident alterations. Especially in these cases there is a need for clear communication between the treating physician and the radiologist with respect to managing optimal imaging as the basis for a certain diagnosis and therefore optimal treatment. Basic prerequisites on both sides are detailed knowledge of all elbow pathologies, classifications and the spectrum of radiological diagnostic imaging.

ACHIEVEMENTS/PRACTICAL RECOMMENDATIONS

From the point of view of orthopedic surgeons the radiologist is responsible for the correct performance and interpretation of the necessary imaging procedures. The aim of this article is to give an overview of important aspects in the imaging of typical orthopedic/traumatic pathologies.

Antibiotics release from cement spacers used for two-stage treatment of implant-associated infections after total joint arthroplasty

Two‐stage revision arthroplasty is the treatment of choice for periprosthetic infection, a serious complication after knee or hip arthroplasty. Our prospective clinical trial aimed to investigate the concentrations of gentamicin and vancomycin in wound exudate and tissue in two‐stage revision arthroplasty. Wound exudate and periprosthetic membrane samples were collected from 18 patients (10 hip and eight knee patients), who were due for two‐stage treatment after a periprosthetic joint infection. Samples were taken during insertion of antibiotic‐impregnated spacers and after their removal. The concentrations of gentamicin and vancomycin in wound exudates and adjacent tissue were analyzed using high‐performance liquid chromatography mass spectrometry. Average time period of spacer implantation was 13.6 weeks (9.3–22.6 weeks). The concentration of vancomycin in wound exudate decreased from a median of 43.28 μg/mL (0.28–261.22) after implantation to 0.46 μg/mL (0.13–37.47) after the removal of the spacer. In the adjacent tissue, vancomycin concentration was mainly undetectable prior to spacer implantation (0.003 μg/g [0.003–0.261]) and increased to 0.318 μg/g [0.024–484.16] at the time of spacer removal. This was also observed for gentamicin in the tissue of patients who previously had cement‐free implants (0.008 μg/g [0.008–0.087] vs. 0.164 μg/g [0.048–71.75]) while in the tissue of patients with previously cemented prosthesis, baseline concentration was already high (8.451 μg/g [0.152–42.926]). Despite the rapid decrease in antibiotics release from spacer cement observed in vitro, in vivo antibiotics are much longer detectable, especially in the adjacent soft tissue. © 2018 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published By Wiley Periodicals, Inc. J Biomed Mater Res B Part B, 2019. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1587–1597, 2019.

Experimental analysis of insertion torques and forces of threaded and press-fit acetabular cups by means of ex vivo and in vivo measurements

PURPOSE

In THA a sufficient primary implant stability is the precondition for successful secondary stability. Industrial foams of different densities have been used for primary stability investigations. The aim of this study was to analyse and compare the insertion behaviour of threaded and press-fit cups in vivo and ex vivo using bone substitutes with various densities.

METHODS

Two threaded (Bicon Plus®, Trident® TC) and one press-fit cup (Trident PSL®) were inserted by orthopaedic surgeons (S1, S2) into 10, 20 and 31 pcf blocks, using modified surgical instruments allowing measurements of the insertion forces and torques. Furthermore, the insertion behaviour of two cups were analysed intraoperatively.

RESULTS

Torques for the threaded cups increased while bone substitute density increased. Maximum insertion torques were observed for S2 with 102 Nm for the Bicon Plus® in 20 pcf blocks and 77 Nm for the Trident® TC in 31 pcf blocks, which compares to the in vivo measurement (85 Nm). The average insertion forces for the press-fit cup varied from 5.2 to 6.8 kN (S1) and 7.2-11.5 kN (S2) ex vivo. Intraoperatively an average insertion force of 8.0 kN was determined.

CONCLUSIONS

Implantation behaviour was influenced by acetabular cup design, bone substitute and experience of the surgeon. No specific density of bone substitute could be favoured for ex vivo investigations on the implantation behaviour of acetabular cups. The use synthetic bone blocks of high density (31 pcf) led to problems regarding cup orientation and seating. Therefore, bone substitutes used should be critically scrutinized in terms of the comparability to the in vivo situation.

Patient-specific factors influencing the traction forces in hip arthroscopy

INTRODUCTION

The application of traction in hip arthroscopy is associated with peri-operative complications. Within a therapeutic case series, patient-related factors correlating with high-traction forces during hip arthroscopy and occurring complications should be identified.

MATERIALS AND METHODS

In 30 male and 38 female patients (mean age: 44.5 years), intra-operative traction forces were monitored continuously using a specialised measurement device. A multivariate analysis was employed to identify patient-related factors influencing the traction force. Peri-operative complications (follow-up: 12 weeks) were evaluated by performing a single-case analysis.

RESULTS

The mean initial force prior to penetration of the capsule ("initial force") was 477 N (men: 517 N; women: 444 N), decreasing after capsulotomy by an average of 17 %. The male gender (p < 0.001), Kellgren and Lawrence radiographic stage (p = 0.037), low minimum joint-space width (p = 0.029) and high body height/weight (p = 0.003/0.037) correlated significantly with higher distraction forces. The patient age and type of anaesthesia (general versus spinal) were not relevant. Complications were observed in ten patients on the first post-operative day. In two of these patients a partial sensory deficit of the lateral cutaneous femoral nerve persisted after 12 weeks. All patients with complications required initial traction forces of >400 N.

CONCLUSIONS

The study revealed several patient-specific risk factors correlating with high-traction forces during hip arthroscopy. With view to potential complications, these patient groups require special attention during surgical treatment as well as in future studies.

[Injuries in Karate Sports: A Survey Performed During the World Championship 2014]

Background: In literature, the competitive sport of modern karate is almost always characterised as a combat sport involving injuries caused by impact effects and physical contact with opponents. There is a lack of data regarding the outcome after karate injuries, specifically with a view to the contact-free Kata karate. Methods: Performing a random test using a questionnaire, we collected data concerning regular medical treatment, prior surgeries of the locomotor system, and medical care. This study included 300 athletes from 65 countries (average age: 24.1 years; 176 male, 124 female) participating in the Karate World Cup 2014. Seven participants competed in both disciplines, 87 only in the Kata discipline, and 206 only in Kumite (the discipline involving physical contact with opponents). The statistical analysis was performed using a two-sided Chi-square test and the Fisher's exact test. Results: Recurrent medical treatment was most commonly required for the knee region (Kata 28.7 %, Kumite 26.7 %). In Kata the shoulder region came second (22.9 %), in Kumite the ankle region (21.8 %), followed by hand and foot in both groups. Medical treatment of the elbow area was more frequent in the Kata Group (p = 0.033), while in Kumite athletes' hand (p = 0.002) and foot injuries (p = 0.007) prevailed. Prior surgeries of athletes of both disciplines most commonly concerned the knee, followed by the ankle region in the Kata group and by the hand and head region in the Kumite group. Statistically significant differences between the two disciplines were found in head injuries (p = 0.004), which commonly do not occur in the Kata discipline. During the World Cup, 56.0 % of the athletes had no individual medical care and 24.6 % received no sports-related medical care in their home countries. Conclusion: Although the risk of injuries in Kumite Karate has been reduced by the introduction of gumshields, hand and foot protectors as well as a reform of the scoring system, the potential for chronic physical damage should not be underestimated. Since in athletes competing in the Kata discipline the rate of surgeries and injuries is only slightly lower than in the Kumite group, Kumite Karate may be regarded as a martial arts competitive sport with a relatively low risk of injuries. In contrast, the risk of chronic musculoskeletal damage in Kata athletes seems to be underestimated thus far. Suggested improvements concern the training techniques and conditions (i. e. the tatami material), and there is a need for regular medical care, including preventative care, to be provided for these athletes.

Prospective comparative clinical study of ceramic and metallic femoral components for total knee arthroplasty over a five-year follow-up period

BACKGROUND

The aim of this prospective comparative study was to evaluate the clinical and radiological outcomes of a TKA system, comparing a ceramic (BIOLOX® delta) and metallic (Co28Cr6Mo) femoral component over a five-year follow-up period.

METHODS

Forty-three TKA patients (17 metallic and 26 ceramic femoral components) were enrolled in the study. Clinical and radiological evaluations were performed preoperatively and at three, 12, 24 and 60months postoperatively, using the HSS-, WOMAC- and SF36-Scores, in addition to standardized X-rays.

RESULTS

The HSS-Score improved significantly from 58.7±12.7 points preoperatively to 88.5±12.3 points at five-years postoperative in the ceramic group, and 60.8±7.7 to 86.2±9.4 points in the metallic group. WOMAC- and SF-36-Scores showed significant improvement over time in both groups. There were no significant differences between groups for HSS-, WOMAC- and SF-36-Scores, nor for range of motion (p≤0.897) at any follow-up evaluation. Furthermore, radiological evaluation showed no implant loosening or migration in either group.

CONCLUSIONS

Mid-term outcomes for the ceramic femoral components demonstrated good clinical and radiological results, as well as comparable survivorship to the metallic femoral component of the same total knee system, and to other commonly used metallic total knee systems. Therefore, ceramic knee implants may be a promising solution for the population of patients with osteoarthritis and metal sensitivity. Long-term studies are required in order to confirm the positive mid-term clinical results, and to follow the implant survival rate in regard to the enhanced wear resistance of ceramic implants.

Press-fit versus threaded acetabular cups in total hip arthroplasty: Functional and radiological results after five years

Prospectively the outcome after total hip replacement with a new threaded acetabular cup design was compared to an established press-fit cup. After 1, 2 and 5 years, the 36-item Short Form Health Survey, Western Ontario and McMaster University Osteoarthritis Index and Harris Hip Score revealed no significant differences between the two groups (each group: n=42 patients), except for a higher Harris Hip Score in the threaded cup group after five years (p=0.02). After five years, one threaded cup had a mild radiolucent line without further signs of loosening. All other cups of both groups (98.6%) showed a full osseous integration. The cup inclination angle ranged from 41-58° (threaded cups) to 39-77° (press-fit cups). The new threaded cup provides equivalent clinical outcomes and osseous integration but more precise implant positioning compared to the press-fit design. No complications typically ascribed to threaded cups (acetabular fractures, bone resorption, nerve impairment) occurred.

Coexistent lumbar spine disorders have a crucial impact on the clinical outcome after total hip replacement

BACKGROUND

Degenerative hip and spine disease are known to frequently coexist. Lumbar spine disorders (LSDs), as opposed to other patient-related factors, are disregarded in the assessment of the clinical outcome after total hip replacement (THR). This prospective study investigates the influence of LSDs on the pre- and postoperative health-related quality of life and functional outcome of patients undergoing THR.

METHODS

According to clearly defined criteria, 42 patients scheduled for cementless THR were assigned either to the LSD (13 patients with LSDs) or non-LSD group (29 patients without LSDs). A clinical assessment was performed preoperatively as well as 12, 24 and 60 months postoperatively using the Harris hip score (HHS), the Western Ontario and McMaster University osteoarthritis index (WOMAC) and the 36-item short form health survey (SF-36).

RESULTS

The statistical analysis comparing the pre- and postoperative status within both groups showed an ongoing improvement of mean HHS and WOMAC after THR. The non-LSD group had a significantly higher postoperative HHS and WOMAC after 12, 24 and 60 months as well as SF-36 after 24 and 60 months. The LSD group improved significantly in the HHS at 24 and 60 months and the WOMAC at 12, 24 and 60 months postoperatively, whereas the SF-36 improvement was not significant. Comparison of preoperative data in both groups revealed a significantly higher SF-36 in the non-LSD group but no difference between the HHS and WOMAC. At each postoperative assessment, the HHS, WOMAC and SF-36, including its physical and mental health sum scores, were significantly higher in the non-LSD group, except for the WOMAC after 60 months.

CONCLUSION

Owing to their crucial impact on hip function scores and health-related quality of life, it is recommended to consider LSDs preoperatively in studies dealing with the clinical outcome after THR.

Laser engravings as reason for mechanical failure of titanium-alloyed total hip stems

INTRODUCTION

Two revisions of broken β-titanium total hip stems had to be performed in our hospital after 2 and 4 years in situ. Since both fractures were located at the level of a laser engraving, a failure analysis was conducted.

MATERIALS AND METHODS

Both retrieved hip stems were disinfected and collected in our retrieval database after patient's signed agreement. Each fragment was macroscopically photographed. Fracture surfaces were analyzed using scanning electron microscopy (SEM). Quantification of element content was conducted using energy dispersive X-ray (EDX) analysis.

RESULTS

Both stems show fatigue fracture, as displayed by the lines of rest on the fracture surface. The origin of fracture was identified directly at the laser engraving of the company logo at both stems by means of SEM. The EDX analysis showed an oxygen level beneath the laser engraving about twice as high as in the substrate, causing material embrittlement.

CONCLUSIONS

Laser engravings need to be reduced to a minimum of necessary information, and should be placed at locations with minimum mechanical load. Biomechanical analyses are recommended to identify less loaded areas in implant components to avoid such implant failures.

Evaluation of electric field distribution in electromagnetic stimulation of human femoral head

Electromagnetic stimulation is a common therapy used to support bone healing in the case of avascular necrosis of the femoral head. In the present study, we investigated a bipolar induction screw system with an integrated coil. The aim was to analyse the influence of the screw parameters on the electric field distribution in the human femoral head. In addition, three kinds of design parameters (the shape of the screw tip, position of the screw in the femoral head, and size of the screw insulation) were varied. The electric field distribution in the bone was calculated using the finite element software Comsol Multiphysics. Moreover, a validation experiment was set up for an identical bone specimen with an implanted screw. The electric potential of points inside and on the surface of the bone were measured and compared to numerical data. The electric field distribution within the bone was clearly changed by the different implant parameters. Repositioning the screw by a maximum of 10 mm and changing the insulation length by a maximum of 4 mm resulted in electric field volume changes of 16% and 7%, respectively. By comparing the results of numerical simulation with the data of the validation experiment, on average, the electric potential difference of 19% and 24% occurred when the measuring points were at a depth of approximately 5 mm within the femoral bone and directly on the surface of the femoral bone, respectively. The results of the numerical simulations underline that the electro-stimulation treatment of bone in clinical applications can be influenced by the implant parameters.

In vivo monitoring of implant osseointegration in a rabbit model using acoustic sound analysis

Implant osseointegration can currently only be assessed reliably post mortem. A novel method that relies on the principle of acoustic sound analysis was developed to enable examination of the longitudinal progress of osseointegration. The method is based on a magnetic sphere inside a hollow cylinder of the implant. By excitation using an external magnetic field, collision of the sphere inside the implant produces a sound signal. Custom-made titanium implants equipped thusly were inserted in each lateral femoral epicondyle of 20 New Zealand White Rabbits. Two groups were investigated: Uncoated, machined surface versus antiadhesive surface; and calcium phosphate-coated surface versus antiadhesive surface. The sound analysis was performed postoperatively and weekly. After 4 weeks, the animals were euthanized, and the axial pull-out strengths of the implants were determined. A significant increase in the central frequency was observed for the loose implants (mean pull-out strength 21.1 ± 16.9 N), up to 6.4 kHz over 4 weeks. In comparison, the central frequency of the osseointegrated implants (105.2 ± 25.3 N) dropped to its initial value. The presented method shows potential for monitoring the osseointegration of different implant surfaces and could considerably reduce the number of animals needed for experiments.

Bacteriology swabs in primary total knee arthroplasty

Objective: An early detection of possible periprosthetic infection may lead to an earlier and potentially less invasive treatment of infected total knee arthroplasty TKA). The purpose of the present study was to evaluate retrospectively our current, affordable clinical practice of intra-operative swab taking during primary TKA.

Methods: A total of 206 primary TKA were analysed retrospectively for intra-operative bacteriology swabs and subsequent periprosthetic infection. All bacteriology swabs were obtained in a standardized manner including a tissue sample. Data was statistically evaluated concerning standard descriptive statistics and using the chi-square test.

Results: Bacteria were identified in 43.4% with coagulase-negative staphylococci being the most frequently isolated pathogens (52.2%). Regarding the contingency tables and chi-squared tests, generally no association was found between positive intra-operative swabs and subsequent periprosthetic infection as well as all other parameters investigated (timing of the antibiotic prophylaxis and pre-operative laboratory results).

Conclusions: Bacteriology swabs during primary total knee arthroplasty are no adequate measure to predict subsequent periprosthetic infections, even if augmented with a tissue sample.

Influence of cementless hip stems on femoral cortical strain pattern depending on their extent of porous coating

The extent of porous coating of cementless total hip stems is held responsible for radiological periprosthetic changes, the rate of thigh pain, and even its long-term success. However, there is only sparse knowledge on how the biomechanical loading conditions of the femur are influenced by the extent of porous coating in the early phase after implantation of a cementless hip stem. Aiming to evaluate the effect of surface structuring on the strain pattern of the femur, we implanted three anatomic hip stems with different extents of porous coating (full, two-thirds proximal, and penguin type) in second-generation composite femora coated with a photoelastic layer. A cortical strain mapping was conducted before and after insertion of the implants under standardized loading conditions considering relevant muscle forces. The results of the statistical analysis of three different implantation sequences proved that composite femora are suitable for repeated measurements within the applied experimental setup. Cortical strain changes including stress-shielding effects medially (-60%) and laterally (-50%) were validated with a cadaver femur. The extent of porous coating had no significant influence on the surface strain pattern for an immediate postoperative situation.

How stiffness and distal interlocking of revision hip stems influence the femoral cortical strain pattern

BACKGROUND

Stress shielding and nonphysiological load transfer after primary or revision total hip replacement (THR) prepare the ground for resorptive bone remodeling. The quality of the bone stock influences the risk of periprosthetic fractures and the severity of future revision surgeries. The question of whether or not bending stiffness and distal screw interlocking influence load transfer of a modular revision hip stem with a solid, hollow, and hollow-slotted stem extension led to the conception of this experimental study. The results were compared with a standard hip stem for primary THR.

METHODS

Revision stems were implanted in photoelastically coated composite femora. Cortical strain mapping was conducted before and after insertion of the implants under standardized loading conditions, considering the relevant muscle forces. Statistical analysis was based on a 95% confidence interval and a variance analysis for repeated measurements.

RESULTS

Significant stress shielding was observed after insertion of all types of hip stems compared with the intact femora. There was also a marked difference between strain alterations induced by standard and revision hip stems. With revision stems, the most distinct stress shielding effects were registered with the solid stem extension, particularly in the femoral diaphysis. Distal interlocking screws only had a local action on strain pattern and tended to enhance stress shielding at the midstem area when using the more flexible components.

CONCLUSION

More flexible revision stems provide a cortical strain pattern of the femur closer to the preoperative status. This may reduce resorptive bone remodeling in the long term. However, any type of revision stem tested in this study caused higher stress shielding than the hip stem for primary THR, especially in the diaphyseal region medially and laterally. With sufficient proximal anchorage, the influence of distal interlocking screws on the femoral strain pattern was localized.

Titanium-copper-nitride coated spacers for two-stage revision of infected total hip endoprostheses

Within the first two years after total hip arthroplasty implant-associated infection has become the second most common reason for a revision surgery. Two-stage implant exchange is frequently conducted using temporary spacers made of antibiotic-loaded cement in order to prevent a bacterial colonization on the spacer. Avoiding several disadvantages of cement spacers, a conventional hemi-endoprosthesis was equipped with a copper-containing implant coating for inhibition of bacterial biofilms. In the present paper details of this novel treatment concept are presented including a case report.

Two-stage revision of implant-associated infections after total hip and knee arthroplasty

Septic loosening of total hip and knee endoprostheses gains an increasing proportion of revision arthroplasties. Operative revisions of infected endoprostheses are mentally and physically wearing for the patient, challenging for the surgeon and a significant economic burden for healthcare systems. In cases of early infection within the first three weeks after implantation a one-stage revision with leaving the implant in place is widely accepted. The recommendations for the management of late infections vary by far. One-stage revisions as well as two-stage or multiple revision schedules have been reported to be successful in over 90% of all cases for certain patient collectives. But implant associated infection still remains a severe complication. Moreover, the management of late endoprosthetic infection requires specific logistics, sufficient and standardized treatment protocol, qualified manpower as well as an efficient quality management. With regard to the literature and experience of specialized orthopaedic surgeons from several university and regional hospitals we modified a commonly used treatment protocol for two-stage revision of infected total hip and knee endoprostheses. In addition to the achievement of maximum survival rate of the revision implants an optimisation of the functional outcome of the affected artificial joint is aimed for.

[Biphosphonate-induced femoral stress fractures : A new problem and knowledge so far - case report]

During the last several years the treatment of osteoporosis with bisphosphonates has become accepted as a safe and effective procedure. However, recently there have been increasing numbers of reports of rare complications in the literature. Particularly the occurrence of atypical fractures of the femur has become a focus of interest but the problem is insufficiently known and only rarely addressed in the scientific discussion. The case illustrated here and a survey of the important facts in the recent literature highlight essential aspects of long-term bisphosphonate therapy.

Spondylodiscitis of the lumbar spine in a non-immunocompromised host caused by Yersinia enterocolitica O:9

Here presented is an extremely rare case of a spinal osteomyelitis (L5-S1) with epidural empyema in a non-immunocompromised 62-year-old man caused by Yersinia enterocolitica O:9. The infection occurred acutely and required immediate surgical treatment. Y. enterocolitica was cultured from the empyema fluid, wound swabs of the intervertebral disc L5-S1 and stool cultures. Following the surgical decompression and antibiotic treatment, the patient recovered completely, without neurological deficits. A review of the literature revealed only sparse cases of spondylodiscitis due to other Y. enterocolitica serogroups. To our knowledge, we report here the first case of a spondylodiscitis of the lumbar spine caused by Y. enterocolitica serovar O:9 in a non-immunocompromised patient.

[Influence on load transfer of different femoral neck endoprostheses]

AIM

Aiming to reduce known complications of stemmed implants, such as resorptive bone remodeling or bone damage in revision, implants with only epi-metaphyseal anchorage have been developed. In the following study the influence of three different femoral neck endoprostheses, CUT, CIGAR (ESKA Implants Lübeck) and TPP (SulzerMedica) on the postoperative load transfer to the femur was investigated in comparison to a cementless hip stem.

METHODS

Using a composite femur model and photoelastic coating technique, the pre- and postoperative osseous strain was measured under static loading. The load corresponded to the absolute maximum of the hip joint load during walking. Statistical analysis was based on the interval of 99 % confidence which was generated by the preoperative measurements.

RESULTS

The different anchorage concepts of the femoral neck endoprostheses exhibited a significant influence on the load transfer, especially along the medial and lateral cortical bone. But, in comparison, the cementless hip stem caused more pronounced stress-shielding which can induce resorptive bone remodelling.

CONCLUSION

One specific femoral neck anchorage concept led to a change from preoperative tension to postoperative compression at the lateral cortical bone. This regionally limited effect may influence in the mid- or long-term the local bone remodeling in a negative manner.