The influence of surgical technique guidance and surgeon's experience on the femoral head assembly in total hip arthroplasty.

INTRODUCTION: The importance of the assembly procedure on the taper connection strength is evident. However, existent surgical technique guides frequently lack comprehensive and precise instructions in this regard. The aim of our experimental study was to evaluate the influence of the surgical technique guide on the femoral head assembly procedure in surgeons with differing levels of experience in total hip arthroplasty. MATERIALS AND METHODS: Twenty-eight participants, divided into four groups based on their lifetime experience in total hip arthroplasty, conducted a femoral head assembly procedure in a simulated intraoperative environment before and after reviewing the surgical technique guide. Demographic information and the number of hammer blows were documented. Hammer velocity and impaction angle were recorded using an optical motion capturing system, while the impaction force was measured using a dynamic force sensor within the impactor. RESULTS: We observed a high variation in the number of hammer blows, maximum force, and impaction angle. Overall, the number of hammer blows decreased significantly from 3 to 2.2 after reviewing the surgical technique guide. The only significant intragroup difference in the number of hammer blows was observed in the group with no prior experience in total hip arthroplasty. No correlation was found between individual factors (age, weight, height) or experience and the measured parameters (velocity, maximum force and angle). CONCLUSIONS: The present study demonstrated a high variation in the parameters of the femoral head assembly procedure. Consideration of the surgical technique guide was found to be a limited factor among participants with varying levels of experience in total hip arthroplasty. These findings underline the importance of sufficient preoperative training, to standardize the assembly procedure, including impaction force, angle, and use of instruments.

The effect of a digital-assisted group rehabilitation on clinical and functional outcomes after total hip and knee arthroplasty-a prospective randomized controlled pilot study.

BACKGROUND: The rising number of total hip and knee arthroplasties and the decreasing availability of physiotherapists require clinically and economically effective rehabilitation approaches. Therefore, the present pilot study investigated the effect of a novel digital-assisted individualized group rehabilitation program on clinical and functional outcomes after total hip and knee arthroplasty. METHODS: In this randomized controlled pilot study, 26 patients undergoing total knee or hip replacement were randomly assigned to either the intervention group (IG, novel digital-assisted group therapy) or the control group (CG, standard postoperative physiotherapy currently carried out in Germany). The IG received the novel digital-assisted group therapy twice per week for a six-months period, while the CG received individual outpatient therapy depending on the prescription of the supervising physician. The number of therapy sessions was recorded. Moreover, subjective outcomes (EuroQol-5Dimensions (EQ-5D) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)), functional outcome (30 s sit to stand test and timed up and go test (TUG)), as well as gait parameters were quantified preoperatively as well as at three and six months after surgery. Data were analyzed using an analysis of covariance with baseline-adjustment. RESULTS: No patient-reported falls, pain, and hospital readmissions were recorded. On average, the IG received more therapy sessions. The clinical and functional outcomes were mainly not significantly different between groups at three- and six-months follow-up, but medium to large effect sizes for the differences in quality of life (EQ-5D) as well as pain, stiffness, and physical function (WOMAC), and TUG performance were observed in favor of the IG. However, the IG showed a higher variability of gait velocity after total joint replacement. CONCLUSION: The digital-assisted rehabilitation had positive effects on quality of life, pain, stiffness, physical function, and TUG performance. Nevertheless, the therapy concept may be improved by adding exercises focusing on gait performance to reduce gait variability. The results indicate that the digital-assisted therapy concept is effective and safe. Therefore, a consecutive full-scaled randomized controlled clinical trial is recommended. TRIAL REGISTRATION: This study was retrospectively registered on 14/02/2022 in the German Clinical Trial Register (DRKS00027960).

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. / Identifikation von potenziellen Risikopatienten auf Basis von PROMs in einem zertifizierten EndoProthetikZentrum am Beispiel der primären Knieendoprothetik.

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.

Computer-based analysis of different component positions and insert thicknesses on tibio-femoral and patello-femoral joint dynamics after cruciate-retaining total knee replacement.

BACKGROUND: Positioning of the implant components and tibial insert thickness constitute critical aspects of total knee replacement (TKR) that influence the postoperative knee joint dynamics. This study aimed to investigate the impact of implant component positioning (anterior-posterior and medio-lateral shift) and varying tibial insert thickness on the tibio-femoral (TF) and patello-femoral (PF) joint kinematics and contact forces after cruciate-retaining (CR)-TKR. METHOD: A validated musculoskeletal multibody simulation (MMBS) model with a fixed-bearing CR-TKR during a squat motion up to 90° knee flexion was deployed to calculate PF and TF joint dynamics for varied implant component positions and tibial insert thicknesses. Evaluation was performed consecutively by comparing the respective knee joint parameters (e.g. contact force, quadriceps muscle force, joint kinematics) to a reference implant position. RESULTS: The PF contact forces were mostly affected by the anterior-posterior as well as medio-lateral positioning of the femoral component (by 3 mm anterior up to 31 % and by 6 mm lateral up to 14 %). TF contact forces were considerably altered by tibial insert thickness (24 % in case of + 4 mm increase) and by the anterior-posterior position of the femoral component (by 3 mm posterior up to 16 %). Concerning PF kinematics, a medialised femoral component by 6 mm increased the lateral patellar tilt by more than 5°. CONCLUSIONS: Our results indicate that regarding PF kinematics and contact forces the positioning of the femoral component was more critical than the tibial component. The positioning of the femoral component in anterior-posterior direction on and PF contact force was evident. Orthopaedic surgeons should strictly monitor the anterior-posterior as well as the medio-lateral position of the femoral component and the insert thickness.

Experimental analysis of early periprosthetic femoral fractures with uncemented straight hip stems.

BACKGROUND: The periprosthetic femoral fracture is one of the most severe complications after total hip arthroplasty and is associated with an increased mortality. The underlying causes and the patient- and implant-specific risk factors of periprosthetic femoral fractures remain insufficiently understood. The aim of this study was to gain a more profound understanding of the underlying fracture mechanisms and to provide experimental datasets for validation of computational models. METHODS: Six cadaveric femurs were implanted with straight hip stems (Zweymueller design) and loaded until fracture reproducing the clinically relevant load cases stumbling and sideways fall. Displacements and the strain distribution on the surface of the femurs and implants, as well as the fracture load and implant subsidence were measured. FINDINGS: For the load case stumbling the mean fracture load was 6743 N and two different mechanisms leading to fracture could be identified: high subsidence with low femoral bending and small subsidence with high femoral bending. For the load case sideways fall the mean fracture load was 1757 N and both tested femurs fractured due to a rotation of the hip stem around its own axis. The detailed datasets provided by this study can be used in future computational models. INTERPRETATION: We demonstrated that the underlying fracture mechanisms of periprosthetic femoral fractures can be fundamentally different in the load case stumbling. The seating and exact position of the hip stem in the femur may correlate with implant subsidence and therefore lead to different types of fracture mechanisms resulting in different patient-specific fracture risks.

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. / Identifikation von potenziellen Risikopatienten auf Basis von PROMs in einem zertifizierten EndoProthetikZentrum am Beispiel der Hüftendoprothetik.

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.

Musculoskeletal Multibody Simulation Analysis on the Impact of Patellar Component Design and Positioning on Joint Dynamics after Unconstrained Total Knee Arthroplasty.

Patellofemoral (PF) disorders are considered a major clinical complication after total knee replacement (TKR). Malpositioning and design of the patellar component impacts knee joint dynamics, implant fixation and wear propagation. However, only a limited number of studies have addressed the biomechanical impact of the patellar component on PF dynamics and their results have been discussed controversially. To address these issues, we implemented a musculoskeletal multibody simulation (MMBS) study for the systematical analysis of the patellar component's thickness and positioning on PF contact forces and kinematics during dynamic squat motion with virtually implanted unconstrained cruciate-retaining (CR)-TKR. The patellar button thickness clearly increased the contact forces in the PF joint (up to 27%). Similarly, the PF contact forces were affected by superior-inferior positioning (up to 16%) and mediolateral positioning (up to 8%) of the patellar button. PF kinematics was mostly affected by the mediolateral positioning and the thickness of the patellar component. A medialization of 3 mm caused a lateral patellar shift by up to 2.7 mm and lateral patellar tilt by up to 1.6°. However, deviations in the rotational positioning of the patellar button had minor effects on PF dynamics. Aiming at an optimal intraoperative patellar component alignment, the orthopedic surgeon should pay close attention to the patellar component thickness in combination with its mediolateral and superior-inferior positioning on the retropatellar surface. Our generated MMBS model provides systematic and reproducible insight into the effects of patellar component positioning and design on PF dynamics and has the potential to serve as a preoperative analysis tool.

Periprosthetic Tibial Fracture with Nonunion and Ascending Prosthetic Joint Infection: A Case Report of an Individual Treatment Strategy.

INTRODUCTION: Periprosthetic fractures are severe injuries that demand the surgeon's full expertise and special diagnostic and therapeutic strategies. A major complication is the occurrence of an infectious nonunion, including an ascending infection from the fracture site to the arthroplasty. CASE REPORT: This case report presents on a patient with a well-functioning revision total knee arthroplasty (TKA) who suffered a periprosthetic tibia fracture. Initial treatment with plating failed and the fracture had to be revised due to an infectious non-union with a multidrug-resistant Staphylococcus epidermidis, and its eradication was complicated by septic loosening of the patient's knee arthroplasty. After multiple revisions of the nonunion, a two-stage exchange arthroplasty with a partial replacement of the distal femur due to a bone defect was necessary to obtain an acceptable result. CONCLUSION: The objective of this case report is to present an individual surgical strategy in a complex case of periprosthetic fracture and TKA with major complications. It is shown that the infection of the bone and implants is a challenging situation for surgical treatment. There is still no optimal management strategy due to missing standards as well as controversies in treatment.

A role for the neurotrophin receptor TrkB on maturing dendritic cells.

BACKGROUND: Neurotrophins are involved in neuroimmune interactions. However, the expression and role of neurotrophin receptors on dendritic cells have not been systematically studied. METHODS: The neurotrophin receptors p75NTR, TrkA, TrkB and TrkC were analyzed on immature and mature Human Monocyte-derived Dendritic Cells (HMDCs) using flow cytometry. In addition, we compared the impact of five different maturing protocols on the expression of neurotrophin receptors on HMDCs. Finally, the effect of neurotrophins on surface molecule expression and the survival of HMDCs was investigated. RESULTS: There was a low expression of p75NTR, TrkA and TrkB on immature HMDCs. HMDCs at different maturation stages did not show a significantly different expression of TrkA, as compared to immature HMDCs. By contrast, there was an upregulation of TrkB on suboptimally, but not optimally matured HMDC. In addition, there was a non-significant trend to a parallel increase of p75NTR expression on these cells. Functional experiments with maturing HMDCs revealed that both ligands of the TrkB receptor, Brain-derived neurotrophic factor (BDNF) and Neurotrophin 4 (NT-4), significantly increased the expression of markers of antigen presentation (HLA-DR and CD80) and the survival of maturing HMDCs. CONCLUSION: These data suggest that the TrkB ligands BDNF and NT-4 can directly influence human dendritic cells during their maturation.