Comparable results in total knee arthroplasty using the ROSA knee system versus the conventional technique: A retrospective propensity-matched cohort study.

PURPOSE: Robotic-assisted total knee arthroplasty (RA-TKA) is an increasingly popular alternative that may increase the accuracy of conventional TKA techniques. This study aims to evaluate RA-TKA accuracy and compare its radiographic and clinical outcomes to conventional TKA (cTKA). METHODS: A retrospective examination of patients with bi- or tricompartmental knee osteoarthritis who underwent RA-TKA (RObotic Surgical Assistant system) or cTKA and were prospectively documented in the TKA registry. Accuracy was assessed using standardized radiographic implant position evaluations, namely femoral and tibial coronal angles and femoral and tibial sagittal angles. Baseline demographics, surgery details and 6- and 12-month post-TKA patient-reported outcomes (PROMs; e.g., Oxford Knee Score [OKS] and Core Outcome Measures Index) were compared between RA-TKA and propensity score-matched cTKA patients. RESULTS: Overall correlation between preset and 6-week postoperative angle measurements for RA-TKA was low with significant differences noted only for mean tibial sagittal angles (84.6° [RA-TKA] vs. 82.3° [cTKA]) (p < 0.001). The study groups were demographically similar, although RA-TKA patients had slightly longer operative times and higher blood loss but shorter inpatient stays. There were sustainable improvements in all PROMs already at 6 months, yet RA-TKA patients had significantly higher OKS values over their conventional counterparts at this time point. CONCLUSION: Radiological and clinical outcomes were comparable between RA-TKA and cTKA. The robotic-assisted system demonstrated higher accuracy in the coronal than sagittal plane and RA-TKA patients achieved better short-term outcomes for pain and disability. While both methods are similar in the hands of a skilled surgeon, long-term studies are necessary to establish clear method superiority. LEVEL OF EVIDENCE: Therapeutic, Level III.

Football-related injuries are the major reason for the career end of professional male football players.

PURPOSE: Little is known about the consequences of injuries on professional male football players' career and retirement period. The aim of this study is to investigate the impact of injuries that male professional football players endure during their career, reasons for the end of their career and the post-career phase of retirement. METHODS: In a retrospective cross-sectional cohort study, retired male professional football players of the German Bundesliga were investigated by a standardised questionnaire to analyse the history of injuries sustained during their professional football career, the reasons for ending their career, their current health status and their suggestions for future prevention strategies. RESULTS: Most of the 116 analysed players (n = 73 (62.9%)) stated an injury as the reason for ending their professional career. Relevant injuries were mainly located in the lower extremities (n = 587 (61.3%)) with a focus on the knee (p < 0.001) and ankle (p < 0.001). A significant majority of the participants who had retired due to injury described degenerative symptoms, such as pain or instability, and were diagnosed with osteoarthritis after retirement (p < 0.001). These players had also often been affected by symptoms of depression during their career, which had decreased significantly after retirement. Moreover, players who had not retired due to injury had significantly better overall health status and quality of life after retirement. CONCLUSION: Football-related injuries have a significant impact on the career end of professional male football players and their health status after retirement. Future prevention strategies need to particularly address injuries to the knees and ankles and to implement measures for preventing osteoarthritis after retirement. LEVEL OF EVIDENCE: Level III.

[Comparison of DRG revenues between fast and slow-track procedures for a two-stage replacement of prostheses for periprosthetic hip infections in the aG-DRG system 2020]. / Vergleich der DRG-Erlöse zwischen Fast- und Slow-Track-Verfahren beim zweizeitigen Prothesenwechsel bei periprothetischen Hüftinfektionen im aG-DRG-System 2020.

BACKGROUND: The treatment of periprosthetic hip infections is usually cost intensive, so it is generally not cost effective for hospitals. In chronic infections, a two-stage procedure is often indicated, which can be done as a fast-track procedure with a short prosthetic-free interim interval (2-4 weeks) or as a slow-track procedure with a long prosthetic-free interim interval (over 4 weeks). AIM: The aim of this study was to elucidate the revenue situation of both forms of treatment in the aG-DRG-System 2020, taking into account revenue-relevant influencing factors. METHODS: For fast-track and slow-track procedures with two-stage revision and detection of a staphylococcus aureus (MSSA), treatment cases were simulated using a grouper software (3M KODIP Suite) based on the diagnoses (ICD-10-GM) and procedures (OPS) and then grouped into DRGs. Revenue-relevant parameters, such as length of stay and secondary diagnoses (SD), were taken into account. In addition, two real treatment cases with fast-track and slow-track procedures were compared to each other. RESULTS: The total revenues for the slow-track procedure with a length of stay of 25 days (without SD) were 27,551 € and for a length of stay of 42 days (with SD) even 40,699 €, compared to 23,965 € with the fast-track procedure with a length of stay of 25 days (without SD) and 27,283 € for a length of stay of 42 days (with SD). The real treatment cases also showed a big difference in the total revenues of 12,244 € in favor of the slow-track procedure. DISCUSSION: Even in the aG-DRG-System 2020, the two-stage revision procedure with a long interim interval seems to be more interesting from a financial point of view and the hospital perspective compared to the fast-track procedure, especially with multimorbid patients. This creates a financial barrier to the treatment of such patients with a short interim interval.

[Analysis of injury incidences in a trauma surgery university hospital during the SARS-CoV­2 pandemic]. / Analyse des Trauma-Aufkommens in einer unfallchirurgischen Universitätsklinik während der SARS-CoV­2-Pandemie.

INTRODUCTION: The corona crisis of 2020 posed previously unknown challenges to hospitals providing acute care. In addition to the treatment of COVID-19 patients, universities and other acute care hospitals had to provide emergency medical care, including for patients undergoing trauma surgery. The challenge was that no reliable planning figures were available regarding the expected volume for such a crisis situation and therefore no reliable resource planning was possible in this respect. Therefore, the aim of this work was to record the incidence of polytrauma and other injuries during the pandemic crisis in a university trauma surgery clinic and to compare it with the years 2017-2019. METHODS: In this single-center study, a retrospective analysis of the injury incidence during calendar weeks with existing exit restrictions (12th-19th week) for the year 2020 for trauma surgery patients of a university hospital was performed. At first, the treatment of COVID-19 patients was recorded daily in order to objectify the burden and expenditure of inpatient treatment for these patients. Then, for the evaluation period from 20.03.2020 to 06.05.2020, the numbers of 1. polytrauma, 2. work-related accidents and 3. leisure-related trauma patients were recorded and compared with the numbers from 2017-2019 during the same period. RESULTS: In total, 118 patients were treated with COVID-19 as inpatients during the period under study, of which up to 43 patients had to be treated simultaneously in intensive care on 1 day. Overall, the number of polytrauma, work-related accidents and leisure-time accident patients was lower in 2020 than in the previous years. Nevertheless, with a decline of only -28% (22 ± 4.9 vs. 16), a considerable number of polytrauma patients were recorded, while all work-related accidents (44%, 304 ± 31.3 vs. 170) and also leisure-time accidents (39%, 173 ± 22.7 vs. 106) considerably decreased. In the group of leisure-time accidents, there was initially a remarkable decline in the number of cases per week after the initial restrictions began, but as the duration of the restrictions increased, the number per week has risen to the level of previous years. DISCUSSION: Even in exceptional situations such as the corona pandemic, there were a significant number of patients in need of acute treatment, especially polytrauma patients. This should be considered in the future in the event of similar exceptional situations in the inpatient care framework when providing trauma surgery care capacities.

Patient-reported outcome after patient-specific unicondylar knee arthroplasty for unicompartmental knee osteoarthritis.

BACKGROUND: Unicondylar knee arthroplasty was introduced in the late 1960s and remains a topic of controversial discussion. Patient-specific instruments and patient-specific implants are not yet the standard of care. The question remains whether this time-consuming and costly technique can be beneficial for the patient. The aim of this study was to evaluate whether a custom-made unicondylar knee arthroplasty leads to improved patient-reported outcome. METHODS: This retrospective study evaluates the patient-reported outcome after custom-made unicondylar knee arthroplasty (CM-UKA, ConforMIS™ iUni® G2, ConforMIS Inc., Billerica, MA, USA). We evaluated 29 patients (31 knees) at an average of 2.4 years (range 1.2-3.6 years) after operation for unicondylar osteoarthritis of the knee. The target zone for the postoperative leg axis was a slight under-correction of 0-2° varus. Follow-up evaluation included the Forgotten Joint Score (FJS), the Knee Society Score (KSS), a Visual Analogue Scale (VAS) and a radiographic evaluation including a long-leg radiograph. Primary outcome measure was patient satisfaction based on the Forgotten Joint Score. RESULTS: We found an excellent postoperative health-related quality of life with a mean FJS of 76.8 (SD 17.9) indicating a low level of joint awareness after CM-UKA. The mean preoperative KSS was 66.0 (SD 13.71) and 59.4 (17.9) for the KSS function score. The increase was 22.8 points for the KSS knee score (p < 0.0001) and 34.8 points for the KSS function score (p < 0.0001). The VAS for pain decreased from a mean of 5.4 (SD 1.8) to 1.1 (SD 1.2) (p < 0.0001). The malalignment rate with a postoperative deviation of more than 2° in the leg axis was 29%. There was no evidence of component loosening after a mean follow-up of 2.4 years. CONCLUSIONS: Custom-made unicondylar knee arthroplasty (CM-UKA) can provide improved clinical and functional outcomes for patients with isolated knee osteoarthritis of the medial compartment. We found excellent results regarding patient satisfaction and a low malalignment rate for CM-UKA. Further studies are needed to investigate long-term survivorship of the implant. LEVEL OF EVIDENCE: Level IV. TRIAL REGISTRATION: Trial Registration number: Z-2014-0389-10 Regensburg Clinical Studies Center (REGCSC) 09/07/2014.

Bone block augmentation from the iliac crest for treatment of deep osteochondral defects of the knee resembles biomechanical properties of the subchondral bone.

PURPOSE: Bone block augmentation from the iliac crest can be used for reconstruction of the osteochondral unit to restore the underlying subchondral bone upon restoration of the cartilaginous layer via matrix-induced chondrocyte transplantation. To critically understand the successful restoration of the defect, biomechanical and histological analysis of the implanted bone blocks is required. The aim of the study was to analyse the ability of the bone block technique to restore huge bone defects by mimicking the physiological subchondral zone. METHODS: The experiments were performed using lateral femoral condyles and iliac crest bone grafts from the same cadavers (n = 6) preserved using the Thiel method. CT scans were made to evaluate bone pathology. Bone mineral density of all specimens was evaluated in the femoral head prior to testing. A series of tests were conducted for each pair of specimens. A static compression test was performed using an electro dynamic testing machine with maximal strength and failure behavior analyzed. Biomechanical tests were performed in the medial-lateral direction for iliac crest and for femoral condyles with and without removal of the cartilage layer. Histological analysis was performed on decalcified specimens for comparison of the condyle at lesion site and the graft. RESULTS: No significant difference in failure load could be found for iliac crest (53.3-180.5 N) and femoral condyle samples upon cartilage removal (38.5-175.1 N) (n.s.). The femoral condyles with an intact cartilage layer showed significantly higher loads (118.3-260.4N) compared to the other groups indicating that native or regenerated cartilage can further increase the failure load (p < 0.05). Bone mineral density significantly influenced failure load in all study groups (p < 0.05). Histological similarity of the cancellous bone in the femoral condyle and in the iliac crest was observed. However, within the subchondral zone, there was a higher density of sponge like organized trabeculae in the bone samples from the iliac crest. Tide mark was only detected at the osteochondral interface in femoral condyles. CONCLUSION: This study demonstrated that, bone blocks derived from the iliac crest allow a biomechanical appropriate and stable restoration of huge bony defects by resembling the subchondral zone of the femoral condyle. Therefore, bone augmentation from the iliac crest combined with matrix-induced autologous chondrocyte transplantation seems to be a reasonable method to treat these challenging injuries.

Reduced joint-awareness in bicruciate-retaining total knee arthroplasty compared to cruciate-sacrificing total knee arthroplasty.

PURPOSE: There is rising impact of patient-reported outcome (PRO) measurement in joint arthroplasty over the past years. Bicruciate-retaining implants have shown more physiologic knee kinematics and provide superior proprioceptive capacities. The aim of this study was to evaluate if the functional properties of this new implant design lead to improved PRO results after total knee arthroplasty (TKA). METHODS: This prospective, controlled trial compares PRO of bicruciate-retaining total knee arthroplasty (BCR-TKA) to unicondylar knee arthroplasty (UKA) and standard posterior-stabilized total knee arthroplasty (PS-TKA). We evaluated 102 patients (34 patients in each group) 18 months postoperatively after knee arthroplasty. Primary outcome measure was the Forgotten Joint Score (FJS). RESULTS: The BCR-group showed the same level of joint awareness as the UKA-group (p = 0.999). The second control group of PS-TKA patients had a lower mean score value in the FJS compared to the BCR-group (p = 0.035) and UKA-group (p = 0.031). There was no correlation of age, gender, body mass index (BMI) and the FJS. No relevant floor- or ceiling effects occurred. CONCLUSIONS: This study found reduced joint awareness for BCR-TKA compared to a standard total knee arthroplasty. The score values of the BCR-group were equal to the UKA-group. Further prospective, randomized studies to investigate long-term survivorship of bicruciate-retaining implants are needed. LEVEL OF EVIDENCE: Level II.

The final implant position of a commonly used collarless straight tapered stem design (Corail®) does not correlate with femoral neck resection height in cement-free total hip arthroplasty: a retrospective computed tomography analysis.

BACKGROUND: In total hip arthroplasty, inadequate femoral component positioning can be associated with instability, impingement and component wear and subsequently with patient dissatisfaction. In this study, we investigated the influence of femoral neck resection height on the final three-dimensional position of a collarless straight tapered stem (Corail®). We asked two questions-(1) is neck resection height correlated with version, tilt, and varus/valgus alignment of the femoral component, and (2) dependent on the resection height of the femoral neck, which area of the stem comes into contact with the femoral cortical bone? MATERIALS AND METHODS: Three-dimensional computed tomography scans of 40 patients who underwent minimally invasive, cementless total hip arthroplasty were analyzed retrospectively. We analyzed the relationship between femoral neck resection height and three-dimensional alignment of the femoral implant, as well as the contact points of the implant with the femoral cortical bone. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011). RESULTS: Mean femoral neck resection height was 10.4 mm (± 4.8) (range 0-20.1 mm). Mean stem version was 8.7° (± 7.4) (range - 2° to 27.9°). Most patients had a varus alignment of the implant. The mean varus/valgus alignment was 1.5° (± 1.8). All 40 patients (100%) had anterior tilt of the implant with a mean tilt of 2.2° (± 1.6). Femoral neck resection height did not correlate with stem version, varus/valgus alignment, or tilt. Independent from femoral neck resection height, in most patients the implant had contact with the ventral and ventromedial cortical bone in the upper third (77.5%) and the middle third (52.5%). In the lower third, the majority of the implants had contact with the lateral and dorsolateral cortical bone (92.5%). CONCLUSION: Femoral neck resection height ranging between 0 and 20.1 mm does not correlate with the final position of a collarless straight tapered stem design (Corail®). LEVEL OF EVIDENCE: Level 3.

Patient-related outcome of unstable pelvic ring fractures stabilized with a minimal invasive screw-rod system.

BACKGROUND: Clinical and radiological outcomes of operatively treated unstable pelvic ring fractures are well documented, whereas little is known about the patient's related outcome. The purpose of this study is to evaluate the patient-reported outcome after minimal invasive treatment of pelvic ring fractures using the SF-36 and EQ-5D medical outcome scores. METHODS: Patients with unstable pelvic ring fractures treated in our trauma department with a minimal invasive screw-rod system between 01/2004 and 12/2014 were included. Next to patient data (sex, age), injury related details (fracture type, additional injuries, Injury Severity Score (ISS)) as well as operation details (method, time to operation, general complications, adverse events associated with the surgical procedure, revision surgery, fracture reduction) were assessed. The patient related outcome was evaluated using the SF-36 and the EQ-5D score. RESULTS: A total of 105 patients (57 men; 48 women; mean age 56 ± 21 years) were identified as candidates for the study. 60 patients completed the SF-36 and EQ-5D score after a mean follow-up of five years (60.5 months (14-142 months)). Of these patients 77% were multiply injured with a mean ISS of 26 ± 19. Within the respondent group 22% showed type B and 78% type C pelvic ring fractures. In 82% the dorsal pelvic ring fracture was stabilized using a minimally invasive transiliac internal fixator, in 18% an iliolumbar fixation was performed respectively. The mean physical component score of the SF-36 was 37.9 ± 12.0, the mean mental component score was 49.8 ± 12.5. The mean EQ-5D VAS reached 70.5 ± 24.4. CONCLUSION: Patients being multiply injured and treated with minimal invasive treated dorsal pelvic ring fractures were suffering more especially concerning physical domains compared to the healthy reference population. Nevertheless, the overall patient-related outcome is comparable to pelvic ring fractures in general. TRIAL REGISTRATION NUMBER: Clinical Trial Registry University of Regensburg Z-2017-0878-3 . Registered 22. July 2017. Retrospectively registered.

Posterior lesser trochanter line should not be used as reference for assessing femoral version in CT scans: a retrospective reliability and agreement study.

Background The estimation of femoral version in preoperative planning of total hip arthroplasty and to assess complications after total hip arthroplasty is crucial. Recent studies have recommended the posterior lesser trochanter line as an intraoperative reference for estimating femoral version. We hypothesized, that if there is a correlation, the posterior lesser trochanter line could be used to assess femoral version in computed tomography (CT) scans. Purpose To evaluate the correlation between the posterior lesser trochanter line and the posterior femoral condyle axis. Material and Methods CT scans of 126 patients after unilateral total hip arthroplasty were analyzed by means of a newly developed digital planning software for CT scans. Both hips were measured, the angle between the posterior lesser trochanter line and the posterior femoral condyle axis was determined, and the relationship between both lines was evaluated. Results We found significant differences between male and female patients ( P < 0.001) and between left and right femora ( P = 0.001). There was no significant difference between healthy hips and hips with osteoarthritis after total hip arthroplasty ( P = 0.901). Conclusion There is no reliable correlation between posterior lesser trochanter line and posterior femoral condyle axis. Therefore, posterior lesser trochanter line should not be used to assess femoral version in CT scans. As a consequence, the gold standard for measuring femoral version should still be a three-dimensional CT scan of the whole femur.

Lesser Trochanter Size on Plain Anteroposterior Radiographs Correlates With Native Femoral Anteversion.

BACKGROUND: Assessing femoral version in orthopedic surgery is important for preoperative planning of total hip arthroplasty, especially for recognizing excessive anteversion or retroversion. The present study addressed the following: (1) Is the position of the lesser trochanter correlated to the femoral neck axis? (2) If so, may femoral version be assessed by means of plain pelvic radiographs? METHODS: Three-dimensional computed tomography scans of 60 patients undergoing minimally invasive cement-free total hip arthroplasty were retrospectively analyzed, particularly with regard to the relation between the femoral neck axis and the lesser trochanter, the femoral version, and the size of the projected lesser trochanter in different rotational positions. Based on linear regression, a biomathematical formula was developed to assess femoral anteversion on plain radiographs depending on the visible part of the lesser trochanter. RESULTS: The mean difference between the location of the lesser trochanter axis and the femoral neck axis was 43.3° ± 6.2°. Eighty-seven percent of patients (52 of 60) had a deviation of <10° from the mean value of 43.3°. By virtual rotation of the femur in steps of 10°, the visible part of the lesser trochanter linearly increased with anteversion of the femur: femoral version = (lesser trochanter size - 5.57) × 4.17. There was a high correlation between the visible part of the lesser trochanter and femoral version (R2 = 0.75; P < .001). The lesser trochanter was no longer visible with femoral retroversion in each of the 60 data sets. CONCLUSION: The projected size of the lesser trochanter as available on plain pelvic AP radiographs correlates with native femoral anteversion.

Soft tissue restricts impingement-free mobility in total hip arthroplasty.

PURPOSE: Impingement is a major source for decreased range of motion (ROM) and dislocation in total hip arthroplasty (THA). In the current study we analyzed the impact of soft tissue impingement on ROM compared to bony and/or prosthetic impingement. METHODS: In the course of a prospective clinical trial 54 patients underwent cementless total hip arthroplasty in the lateral decubitus position using imageless navigation. The navigation device enabled intra-operative ROM measurements indicating soft tissue impingement. Post-operatively, all patients received postoperative 3D-CT. Absolute ROM without bony and/or prosthetic impingement was calculated with the help of a collision-detection-algorithm. RESULTS: Due to soft tissue impingement we found a reduced ROM of over 20° (p < 0.001) compared to bony and/or prosthetic impingement regarding flexion, extension, abduction and adduction and of over 10° regarding external rotation (p < 0.001). In contrast, soft tissue impingement showed less impact on internal rotation in 90° of flexion (p = 0.76). Multivariate analysis showed an association between BMI and flexion, whereas all other ROM directions were independent of BMI. CONCLUSIONS: Soft tissue has a major impact on impingement-free ROM after THA. For the majority of movements, soft tissue restrictions are more important than bony and prosthetic impingement. Future models of patient individual joint replacement including pre-operative (CT) planning and intra-operative navigation should include algorithms additionally accounting for soft tissue impingement.

Leukocyte-reduced platelet-rich plasma increases proliferation of tenocytes treated with prednisolone: a cell cycle analysis.

INTRODUCTION: The purpose of this study was to evaluate the effect of allogenic leukocyte-reduced platelet-rich plasma on human tenocytes after treatment with prednisolone and to develop a standardization of its application for clinical practice. METHODS: A leukocyte-reduced PRP was produced using the Arthrex Double Syringe (Arthrex, Inc., Naples, FL, USA), in a modified single-spin separation method. Human tenocytes were isolated from discarded rotator cuff segments. Tenocytes were cultured in the presence of PRP and prednisolone, both alone and in combination. Control samples were treated in media containing 2% FCS for 72 h. After 72 h of incubation, cell cycle kinetics of tenocytes were analyzed to assess proliferation. RESULTS: Incubation of the tenocytes with PRP alone for 48 h led to high proliferation rate (10% PRP, 28.0 ± 10.5%; 20% PRP, 40.9 ± 3.3%). Incubation in the presence of prednisolone led to a significant decrease of the proliferation rate (5.2 ± 3.1%; p < 0.05). Treatment with PRP for 48 h significantly increased the proliferation of tenocytes in a dose-dependent manner (10% PRP, 28.0 ± 10.5%; 20% PRP, 40.9 ± 3.3%; p < 0.05). The presence of prednisolone resulted in a decreased tenocyte proliferation (5.2 ± 3.1%; p < 0.05), whereas addition of PRP for 24 and 48 h after prednisolone exposure did not show any compensating effect independent of PRPs concentration (10% PRP, 3.7 ± 3.0%; 20% PRP, 2.5 ± 2.5%). However, a significantly increased cell proliferation of tenocytes was evident when PRP was applied 24 h after prednisolone incubation for 48 h (31.0 ± 3.4 and 34.3 ± 4.7%). CONCLUSION: The use of leukocyte-reduced PRP stimulates the proliferation of tenocytes and antagonizes the negative effect of prednisolone 24 h after treatment. Addition of PRP 48 h after treatment with prednisolone has no positive effect on the proliferation rate of tenocytes.

Native femoral anteversion should not be used as reference in cementless total hip arthroplasty with a straight, tapered stem: a retrospective clinical study.

BACKROUND: Improper femoral and acetabular component positioning can be associated with instability, impingement, component wear and finally patient dissatisfaction in total hip arthroplasty (THA). The concept of "femur first"/"combined anteversion", incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position of the stem relative to the cup intraoperatively. In the present study we asked two questions: (1) Do native femoral anteversion and anteversion of the implant correlate? (2) Do anteversion of the final broach and implant anteversion correlate? METHODS: In a secondary analysis of a prospective controlled trial, a subgroup of 55 patients, who underwent computer-assisted, cementless THA with a straight, tapered stem through an anterolateral, minimally invasive (MIS) approach in a lateral decubitus position were examined retrospectivly. Intraoperative fluoroscopy was used to verify a "best-fit" position of the final broach. An image-free navigation system was used for measurement of the native femoral version, version of the final broach and the final implant. Femoral neck resection height was measured in postoperative CT-scans. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011). RESULTS: The mean difference between native femoral version and final implant was 1.9° (+/- 9.5), with a range from -20.7° to 21.5° and a Spearman's correlation coefficient of 0.39 (p < 0.003). In contrast, we observed a mean difference between final broach and implant version of -1.9° (+/- 3.5), with a range from -12.7° to 8.7° and a Spearman's correlation coefficient of 0.89 (p < 0.001). In 83.6 % (46/55) final stem version was outside the normal range as defined by Tönnis (15-20°). The mean femoral neck resection height was 7.3 mm (+/- 5.6). There was no correlation between resection height and version of the implant (Spearman's correlation coefficient 0.14). CONCLUSION: Native femoral version significantly differs from the final anteversion of a cementless, straight, tapered stem and therefore is not a reliable reference in cementless THA. Measuring anteversion of the final "fit and fill" broach is a feasible assistance in order to predict final stem anteversion intraoperatively. There is no correlation between femoral neck resection height and version of the implant.

Current standard rules of combined anteversion prevent prosthetic impingement but ignore osseous contact in total hip arthroplasty.

PURPOSE: In this prospective study of 135 patients undergoing cementless total hip arthroplasty (THA) we asked whether six current definitions of combined anteversion prevent impingement and increase postoperative patient individual impingement-free range-of-motion (ROM). METHODS: Implant position was measured by an independent, external institute on 3D-CT performed six weeks post-operatively. Post-operative ROM was calculated using a CT-based algorithm detecting osseous and/or prosthetic impingement by virtual hip movement. Additionally, clinical ROM was evaluated pre-operatively and one-year post-operatively by a blinded observer. RESULTS: Combined component position of cup and stem according to the definitions of Ranawat, Widmer, Dorr, Hisatome and Yoshimine inhibited prosthetic impingement in over 90 %, while combined osseous and prosthetic impingement still occurred in over 40 % of the cases. The recommendations by Jolles, Widmer, Dorr, Yoshimine and Hisatome enabled higher flexion (p ≤ 0.001) and internal rotation (p ≤ 0.006). Clinically, anteversion rules of Widmer and Yoshimine provided one-year post-operatively statistically but not clinically relevant higher internal rotation (p ≤0.034). CONCLUSION: Standard rules of combined anteversion detect prosthetic but fail to prevent combined osseous and prosthetic impingement in THA. Future models will have to account for the patient-individual anatomic situation to ensure impingement-free ROM.

Visual intraoperative estimation of range of motion is misleading in minimally invasive total hip arthroplasty.

INTRODUCTION: Generally range of motion (ROM) in total hip arthroplasty (THA) is intraoperatively assessed by eye. Can we assume that visual estimation of ROM is reliable? METHODS: 60 patients underwent cementless THA in a subgroup analysis of a clinical prospective trial using a minimally invasive anterolateral approach in lateral decubitus position. Four experienced surgeons intraoperatively estimated ROM visually by assessment of the femur relative to the alignment of the patient's pelvis. These estimations were compared with computer navigation measurements. RESULTS: We found a mean difference between navigation measurements and intraoperative estimations by eye of -5.6° (±10.9°; -17° to 30°) for flexion, respectively, -0.4° (±10.7°; -24° to 30°) for extension, 8.7° (±9.0°; -10° to 34°) for abduction, 5.9° (±18.3°; -58° to 68°) for external rotation and -5.8° (±12.1°; -38° to 22°) for internal rotation. Multivariate analysis showed no association between the visual accuracy of estimation of ROM and patient characteristics, such as BMI, sex, grade of osteoarthritis and treatment side except for a significant correlation of visual accuracy of estimation of extension and the level of professional experience. Otherwise, the level of professional experience had no impact on the accuracy of estimation of ROM by eye. CONCLUSIONS: Even the experienced surgeon's intraoperative estimation of ROM by eye is not reliable and differs up to 30° compared to objective measurements in minimally invasive THA. For accurate intraoperative assessment of ROM, the use of technical devices is recommended. TRIAL REGISTRATION: DRKS00000739.

Visual intraoperative estimation of cup and stem position is not reliable in minimally invasive hip arthroplasty.

Background and purpose - In hip arthroplasty, acetabular inclination and anteversion-and also femoral stem torsion-are generally assessed by eye intraoperatively. We assessed whether visual estimation of cup and stem position is reliable. Patients and methods - In the course of a subgroup analysis of a prospective clinical trial, 65 patients underwent cementless hip arthroplasty using a minimally invasive anterolateral approach in lateral decubitus position. Altogether, 4 experienced surgeons assessed cup position intraoperatively according to the operative definition by Murray in the anterior pelvic plane and stem torsion in relation to the femoral condylar plane. Inclination, anteversion, and stem torsion were measured blind postoperatively on 3D-CT and compared to intraoperative results. Results - The mean difference between the 3D-CT results and intraoperative estimations by eye was -4.9° (-18 to 8.7) for inclination, 9.7° (-16 to 41) for anteversion, and -7.3° (-34 to 15) for stem torsion. We found an overestimation of > 5° for cup inclination in 32 hips, an overestimation of > 5° for stem torsion in 40 hips, and an underestimation < 5° for cup anteversion in 42 hips. The level of professional experience and patient characteristics had no clinically relevant effect on the accuracy of estimation by eye. Altogether, 46 stems were located outside the native norm of 10-20° as defined by Tönnis, measured on 3D-CT. Interpretation - Even an experienced surgeon's intraoperative estimation of cup and stem position by eye is not reliable compared to 3D-CT in minimally invasive THA. The use of mechanical insertion jigs, intraoperative fluoroscopy, or imageless navigation is recommended for correct implant insertion.

The impact of standard combined anteversion definitions on gait and clinical outcome within one year after total hip arthroplasty.

PURPOSE: Different target areas within the concept of combined cup and stem anteversion have been published for total hip arthroplasty (THA). We asked whether component positioning according to eight standard combined anteversion rules is associated with (1) more physiological gait patterns, (2) higher improvement of gait variables and (3) better clinical outcome after THA. METHODS: In a prospective clinical study, 60 patients received cementless THA through an anterolateral MIS approach in a lateral decubitus position. Six weeks postoperatively, implant position was analysed using 3D-CT by an independent external institute. Preoperatively, six and 12 months postoperatively range of motion, normalized walking speed and hip flexion symmetry index were measured using 3D motion-capture gait analysis. Patient-related outcome measures (HHS, HOOS, EQ-5D) were obtained by an observer blinded to 3D-CT results. Eight combined anteversion definitions and Lewinnek's "safe zone" were evaluated regarding their impact on gait patterns and clinical outcome. RESULTS: Combined cup and stem anteversion according to standard combined anteversion definitions as well as cup placement within Lewinnek's "safe zone" did not influence range of motion, normalized walking speed and/or hip flexion symmetry index six and 12 months after THA. Similarly, increase of gait parameters within the first year after THA was comparable between all eight combined anteversion rules. Clinical outcome measures like HHS, HOOS and EQ-5D did not show any benefit for either of the combined anteversion definitions. CONCLUSIONS: Standard combined cup and stem anteversion rules do not improve postoperative outcome as measured by gait analysis and clinical scores within one year after THA.

The PJI-TNM classification for periprosthetic joint infections.

Aims: This study aimed to evaluate the clinical application of the PJI-TNM classification for periprosthetic joint infection (PJI) by determining intraobserver and interobserver reliability. To facilitate its use in clinical practice, an educational app was subsequently developed and evaluated. Methods: A total of ten orthopaedic surgeons classified 20 cases of PJI based on the PJI-TNM classification. Subsequently, the classification was re-evaluated using the PJI-TNM app. Classification accuracy was calculated separately for each subcategory (reinfection, tissue and implant condition, non-human cells, and morbidity of the patient). Fleiss' kappa and Cohen's kappa were calculated for interobserver and intraobserver reliability, respectively. Results: Overall, interobserver and intraobserver agreements were substantial across the 20 classified cases. Analyses for the variable 'reinfection' revealed an almost perfect interobserver and intraobserver agreement with a classification accuracy of 94.8%. The category 'tissue and implant conditions' showed moderate interobserver and substantial intraobserver reliability, while the classification accuracy was 70.8%. For 'non-human cells,' accuracy was 81.0% and interobserver agreement was moderate with an almost perfect intraobserver reliability. The classification accuracy of the variable 'morbidity of the patient' reached 73.5% with a moderate interobserver agreement, whereas the intraobserver agreement was substantial. The application of the app yielded comparable results across all subgroups. Conclusion: The PJI-TNM classification system captures the heterogeneity of PJI and can be applied with substantial inter- and intraobserver reliability. The PJI-TNM educational app aims to facilitate application in clinical practice. A major limitation was the correct assessment of the implant situation. To eliminate this, a re-evaluation according to intraoperative findings is strongly recommended.

In vivo knee kinematics of an innovative prosthesis design.

Up to 20% of patients after total knee arthroplasty (TKA) are not satisfied with the result. Several designs of new implants try to rebuild natural knee kinematics. We hypothesized that an innovative implant design leads to better results concerning femoral rollback compared to an established implant design. For this pilot study, 21 patients were examined during TKA, receiving either an innovative (ATTUNETM Knee System (DePuy Inc.), n = 10) or an established (PFCTM (DePuy Inc.), n = 11) knee system. All patients underwent computer navigation. Knee kinematics was assessed after implantation. Outcome measure was anterior-posterior translation between femur and tibia. We were able to demonstrate a significantly higher femoral rollback in the innovative implant group (p < 0.001). The mean rollback of the innovative system was 11.00 mm (95%-confidence interval [CI], 10.77-11.24), of the established system 8.12 mm (95%-CI, 7.84-8.42). This study revealed a significantly increased lateral as well as medial femoral rollback of knees with the innovative prosthesis design. Our intraoperative finding needs to be confirmed using fluoroscopic or radiographic three-dimensional matching under full-weight-bearing conditions after complete recovery from surgery.