Background: Although cemented total knee arthroplasty (TKA) is considered the standard fixation technique, the emerging trend toward cementless fixation has created the need for a detailed comparison. In a previous study, we reported the 5-year results comparing cementless and hybrid cemented TKAs using the same implant design. The purpose of this study was to assess the long-term follow-up at a minimum of 10 years. Methods: A retrospective analysis was performed on 120 TKAs (60 cementless, 60 hybrid cemented) conducted between 2003 and 2007 using the e.motion posterior cruciate-retaining knee prosthesis with a floating-platform mobile polyethylene bearing (Aesculap, Tuttlingen, Germany). Demographic and clinical data were collected; radiographic follow-up was performed with attention to signs of loosening, while complications and revision surgery were assessed using competing risk analysis. Operative time was recorded as an indicator of surgical efficiency. Results: At 10 years, 59 TKAs (54 patients) were available for long-term follow-up. Both fixation groups demonstrated significant improvement in Knee Society Scores (KSSs) compared to preoperative values (p < 0.001). However, there was no significant difference in KSSs between the two groups at 10 years follow-up (p = 0.480). The 10-year cumulative incidence of revision was 8.4% in both groups (p = 0.721), and that of aseptic loosening was identical at 3.4% (p = 0.967). Although radiolucent lines were noted in three tibial components of the cementless group, the difference was not statistically significant (p = 0.075). Notably, the cementless group demonstrated a significantly shorter operative time with a mean difference of 10 min (p = 0.017). Conclusions: At a minimum follow-up of 10 years, there were no significant differences between the hybrid cemented and cementless groups in revision rates, cumulative incidences, clinical scores, or radiological signs of loosening, confirming the long-term effectiveness of both fixation methods in clinical practice.

Background: The reproducible measurement of tibial torsion (TT) is essential for the diagnosis and evaluation of rotational deformities of the tibia, particularly in the planning of tibial derotational osteotomy. While various CT-based methods for determining the distal tibial axis have been described for adult patients, rotational Magnetic Resonance Imaging (MRI) represents a radiation-free alternative, especially for assessing lower limb rotation in pediatric patients. The aim of this study was to analyze the reliability of TT measurements as well as to investigate potential differences in the application of rotational MRI within a pediatric orthopedic cohort. Methods: In this retrospective study, 78 lower legs from 39 patients aged 4 to 18 years who underwent rotational MRI were included. Measurements for TT were performed using the Jend method, the Waidelich method, and the bimalleolar method. Reliability assessments were conducted by three different examiners, and the results were determined using the intraclass correlation coefficient (ICC). Results: All three methods demonstrated excellent interobserver reliability. The highest intraobserver reliability was achieved using the bimalleolar method (ICC: 0.947). When comparing the assessment of TT, the Jend method showed the highest mean values (34°, standard deviation (SD) 11.0°) followed by the Waidelich method (29°, SD 10.2°) and the bimalleolar method (26°, SD 9.9°). Measurement methods showed a mean difference of up to 8° (p < 0.001). Conclusions: Rotational MRI is a feasible radiation-free option to assess tibial torsion in pediatric and adolescent patients. All tested methods show excellent inter- and intraobserver reliability. Notably, significant differences were found between the measurement methods, with the bimalleolar method showing lower mean values. This has to be taken into account for preoperative planning of rotational and derotational tibial and supramalleolar osteotomies.

Background: Balance and gait are critical for functional recovery and fall prevention following total hip (THA) and knee arthroplasty (TKA). Despite improvements in pain and joint function, residual impairments often persist. The Timed Up and Go (TUG) test and Tinetti Performance-Oriented Mobility Assessment (POMA) objectively measure postoperative mobility and balance, while patient-reported outcome measures (PROMs) assess perceived function and well-being. This study longitudinally evaluates functional measurement and PROMs to explore their interrelationships and compare recovery trajectories in THA and TKA cohorts. Methods: In this prospective study, 22 THA and 21 TKA patients were assessed preoperatively and at 4-6 days, 6 weeks, 3 months, and 12 months postoperatively using TUG, Tinetti, Hip Disability and Osteoarthritis Outcome Score (HOOS), Knee Injury and Osteoarthritis Outcome Score (KOOS), and clinical scores (Harris Hip Score (HHS) for THA, Knee Society Score (KSS) for TKA). Pearson correlation assessed relationships between measures. Results: Both cohorts demonstrated significant immediate postoperative declines in balance and mobility, recovering to baseline by 6 weeks and surpassing it by 3 and 12 months (p < 0.001). PROMs showed earlier and sustained improvements. Objective balance and mobility measures showed minimal correlation with PROMs but were highly interrelated from 6 weeks onward. Conclusions: THA and TKA patients experience early postoperative balance impairments, suggesting heightened fall risk, with functional recovery lagging behind perceived well-being, highlighting the need for cautious rehabilitation strategies.

The aim of this study was to assess the reliability of Delta angle (DA) as a parameter of microinstability compared to established radiographic instability parameters. It was assessed whether the morphology of the Ligamentum teres (LT) was affected by DA, established instability parameters. Further, the correlation between clinical status and microinstability parameters was assessed. Data was retrospectively analysed from a single centre database for hip preservations surgery. All patients underwent a comprehensive and standardized radiographic and clinical assessments. Sixty patients, with a mean age of 29.7 years (Standard Deviation [SD] 8.02),, with 63 hips (40 right [63.5

Background/Objectives: Accurately diagnosing a periprosthetic joint infection (PJI) represents a challenging and complex task. Especially in the case of low-grade infections, important diagnostic modalities may be inconclusive and synovial markers such as white blood cell count (WBC) and polymorphonuclear percentage (PMN) gain relevance. We therefore aim to assess WBC and PMN in different clinical and microbiological settings. Methods: We performed a retrospective analysis of 115 patients with a diagnosed PJI. WBC and PMN were compared between patients with low- and high-virulent infections, negative and positive histology, symptom duration ≤ 4 weeks and >4 weeks, and positive and negative pathogen detection. Results: Synovial WBC was significantly higher in patients with successful pathogen detection (42.44 [87.0] G/L vs. 16.35 [32.0] G/L; p < 0.01), as was PMN (86.0 [60.0]% vs. 91.0 [89.0]%; p < 0.01). PJIs with high-virulent pathogens showed higher WBC compared to low-virulent pathogens (58.27 [102.0] G/L vs. 27.27 [46.0] G/L; p < 0.01). Patients with onset of symptoms ≤ 4 weeks demonstrated higher WBC (58.27 [112.0] G/L vs. 16.42 [46.0] G/L]; p < 0.01) as well as higher PMN (91.5 [9.0]% vs. 88.0 [20.0]%); p = 0.042). Cases with negative histology showed significantly lower WBC (16.73 [44.0] G/L vs. 42.86 [87.0] G/L; p < 0.01) and lower PMN (86.0 [67.0]% vs. 91.0 [9.0]%; p = 0.036). Conclusions: WBC and PMN show high variability and appear to be influenced by virulence, histology, onset of symptoms, and pathogen detection.

BackgroundArtificial intelligence (AI), particularly AI-based large language models (LLM) like ChatGPT, is increasingly shaping how information is accessed, offering patients a new source for understanding complex medical conditions. Given the physical, emotional, and logistical challenges that parents are faced when their baby is diagnosed with developmental dysplasia of the hip (DDH), the demand for clear and accessible educational resources is high. This study aimed to evaluate the quality and reliability of ChatGPT's responses to frequently asked questions about DDH.MethodsThis study assessed the quality of responses generated by the AI chatbot ChatGPT 4o to eight frequently asked questions about DDH, derived from real consultations in a pediatric orthopedic clinic Responses were generated during one interaction per question using a ChatGPT account not previously exposed to medical information. Responses were evaluated by two individual readers using a standardized rating system, comparing them to current literature, patient education resources, and consensus guidelines. Each response was categorized by its level of informational accuracy and completeness, and descriptive statistics were calculated to quantify performance.ResultsChatGPT 4o was able to generate structured responses to all eight parental questions. The responses were rated in 12.5% excellent, 25.0% satisfactory with minimal clarification, 50.0% satisfactory with moderate clarification, and 12.5% unsatisfactory due to missing or inaccurate information.ConclusionChatGPT provided satisfactory answers to questions about DDH and may serve as a useful supplementary information resource for parents. However, due to limitations in presenting detailed diagnostic and treatment pathways, it should be viewed as an adjunct to, not a replacement for, specialist medical consultation.

Aims Histology is widely used for diagnosis of persistent infection during reimplantation in twostage revision hip and knee arthroplasty, although data on its utility remain scarce. Therefore, this study aims to assess the predictive value of permanent sections at reimplantation in relation to reinfection risk, and to compare results of permanent and frozen sections. Methods We retrospectively collected data from 226 patients (90 hips, 136 knees) with periprosthetic joint infection who underwent twostage revision between August 2011 and September 2021, with a minimum follow - up of one year. Histology was assessed via the SLIM classification. First, we analyzed whether patients with positive permanent sections at reimplantation had higher reinfection rates than patients with negative histology. Further, we compared permanent and frozen section results, and assessed the influence of anatomical regions (knee versus hip), low- versus high - grade infections, as well as first revision versus multiple prior revisions on the histological result at reimplantation. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), chi- squared tests, and Kaplan - Meier estimates were calculated. Results Overall, the reinfection rate was 18%. A total of 14 out of 82 patients (17%) with positive permanent sections at reimplantation experienced reinfection, compared to 26 of 144 patients (18%) with negative results (p = 0.996). Neither permanent sections nor fresh frozen sections were significantly associated with reinfection, with a sensitivity of 0.35, specificity of 0.63, PPV of 0.17, NPV of 0.81, and accuracy of 58%. Histology was not significantly asso - ciated with reinfection or survival time for any of the analyzed sub- groups. Permanent and frozen section results were in agreement for 91% of cases. Conclusion Permanent and fresh frozen sections at reimplantation in twostage revision do not serve as a reliable predictor for reinfection.

Background/Objectives: We evaluated the outcomes of patients undergoing en bloc total vertebrectomy at our institution within the last three decades. The aim of our study was to analyse the oncological and neurological outcomes and the changes over time. Methods: We included 22 consecutive patients treated with a total vertebrectomy at our institution between January 1990 and December 2022. The standard follow-up protocol for sarcoma patients was performed. Early complications were defined as complications within the first three months postoperatively. Local recurrence was defined as the reoccurrence of a tumour at least four months after surgery. Adequate statistical methods were applied to evaluate the survival rates and the influence of potential risk factors. A p-value of <0.05 was considered statistically significant. Results: From 1990 to 2010, five total vertebrectomies were performed each decade, whereas twelve patients underwent the procedure in the period from 2010 to 2022. The mean follow-up period was 101.25 months (±112; 2–339). The one-, five- and ten-year overall survival rates were 91% (CI = (0.79; 1.00)), 59% (CI = (0.37; 0.81)) and 51% (CI = (0.27; 0.75)), respectively. For soft tissue tumours, the average overall survival was 6.2 years, whereas, for bone sarcomas, it was 13.6 years. None of the patients with wide surgical margins developed local recurrence. Complications necessitating revision procedures occurred in 54% of all cases. Conclusions: A total vertebrectomy is a highly demanding procedure, requiring accurate patient selection, meticulous preoperative planning and a highly collaborative interdisciplinary team. Adequate surgical treatment seems to be indispensable when aiming for curative treatment. Owing to the rarity of the indications, this procedure should be restricted to large tumour centres.

Background: Meta-diaphyseal fixation of straight, tapered, uncemented stems has been proven to be very reliable for total hip arthroplasty in 10 to 20 years of follow-up studies. The aim of the study was to evaluate whether the implant survival as well as radiological and functional outcome have changed in patients with a minimum follow-up of 30 years.Methods: From a total of 210 patients, who received a straight, rectangular, tapered cementless stem and a threaded cup, there were 37 total hip arthroplasties (33 patients) still available for follow-up after a minimum of 30 years. Patients were examined clinically and radiographically, and revision surgeries were recorded.Results: There was a low rate of revisions of the femoral stem with a survival probability of 0.92 (confidence interval 0.85 to 0.96) at 30 years. Survival probability of the acetabular component decreased drastically with 0.45 (confidence interval 0.30 to 0.59). Radiographic analysis of the stem revealed ra-diolucencies in 73% (n 1/4 16), but only in the proximal/metaphyseal part and none of the stems were radiographically loose.Conclusion: In this minimum 30-year follow-up study, a straight rectangular cementless implant continues to provide excellent implant survival and high patient satisfaction. However, survival rates of the whole total hip replacement system were reduced by a high revision rate due to wear-related problems.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The use of rotating hinge (RH) prostheses for severe primary as well as revision arthroplasty is widely established. Aim of this study was to investigate long term results of a new RH prosthesis (EnduRo®, B Braun, Germany), which uses carbon-fiber reinforced poly-ether-ether-ketone (CFR PEEK) as a new bearing material, first time used in knee arthroplasty. Fifty-six consecutive patients, who received the EnduRo® RH prosthesis were included in this prospective study: 21 patients (37.5%) received the prosthesis as a primary total knee arthroplasty (TKA) and 35 patients (62.5%) underwent revision total knee arthroplasties (rTKA). Clinical and radiographic examinations were performed preoperatively as well as postoperatively after 3 and 12 months and annually thereafter. Min. Follow up was 7 and mean follow up 9,3 years. Clinical examination included Knee Society Score (KSS), Western Ontario and McMaster Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), and range of motion (ROM). Competing risk analysis was assessed for survival with respect to indication and failure mode. KSS, WOMAC, OKS, and ROM significantly improved from the preoperative to the follow up investigations (p < 0.0001). There was no difference in clinical outcome between the primary and the revision group. The overall cumulative incidence for revision for any reason was 23.6% and the cumulative incidence for complications associated with failure of the prothesis was 5.6% at 7 years, respectively. Complications occurred more frequently in the revision group (p = 0.002). The evaluated RH prosthesis provided reliable and durable results with a minimum follow-up of 7 years. Prosthesis survival was successful considering the complexity of cases. The use of this RH system in primary patients showed high survival rates. Long-term functional and clinical results proved to be satisfying in both revision and primary cases. No adverse events were associated with the new bearing material CFR-PEEK.

Several authors observed a loss of correction after performing Chiari pelvic osteotomy (CPO) in young patients. Hence, the aim of this study was to answer two questions: (1) Does the Chiari pelvic osteotomy affect the development of the acetabulum in skeletally immature patients in the long term? (2) Is there any evidence of the previously described “Anti-Chiari” effect after a mean follow-up of 36 years? Data from 21 patients (27 hips) undergoing CPO before the age of 16 years were clinically assessed, and the evolution of radiological parameters over time was analyzed. The mean age at CPO was 11.2 years (±3; 4.4–15.7). The 20- and 30-year survival rates of the CPO were 100% and 92.6%, respectively. Mean postoperative medialization was 54% (±18; 23–99). The average osteotomy angle was 11° (±7; 2–28). No significant changes were found for the center-edge angle (CEA) and acetabular index (AI) over time; the angle of Idelberger and Frank (ACM) almost reached normal values at follow-up (FU); for the acetabular-head index (AHI), a slight shift toward the initial situation could be detected. The morphology of the acetabulum remained unchanged over time. The “Anti-Chiari effect” seems to be primarily caused by insufficient coverage of the femoral head rather than damage to the apophysis due to surgery.

Background: The use of rotating hinge (RH) prostheses for severe primary as well as revision arthroplasty is widely established. Due to the steadily increasing number of RH prostheses, we aimed to assess the complication frequencies, complication types and clinical outcomes of a modern RH hinge prosthesis using a new bearing material with a minimum follow-up of 7 years.Methods: Fifty-six consecutive patients who received the EnduRo® RH prosthesis using carbon-fiber reinforced poly-ether-ether-ketone (CFR-PEEK) as bearing material were included in this prospective study: 21 patients (37.5%) received the prosthesis as a primary total knee arthroplasty (TKA) and 35 patients (62.5%) underwent revision total knee arthroplasties (rTKA). Clinical and radiographic examinations were performed preoperatively, postoperatively after three and 12 months and annually thereafter. Clinical scores were documented for each patient. Competing risk analysis was assessed with respect to indication and failure mode.Results: Knee Society Score (KSS), Western Ontario and McMaster Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS) and range of motion (ROM) improved significantly compared to preoperative values (p < 0.0001). The overall cumulative incidence for revision surgery was 23.6% at 7 years and the cumulative incidence for complications associated with failure of the prothesis was 5.6% at 7 years, respectively. Complications occurred more frequently in the revision group (p = 0.002).Conclusion: The evaluated RH prosthesis provided reliable and durable results for a minimum follow-up of 7 years. Prosthesis survival was successful considering the complexity of the cases. The use of this RH system in primary patients showed high survival rates and long-term functional outcomes and clinical outcomes proved to be satisfying in both revision and primary cases. No adverse events were associated with the new bearing material CFR-PEEK.

Aneurysmal bone cysts (ABC) are benign tumors mostly occurring in children and young adults. Different open and minimal invasive surgical approaches have been proposed for the treatment of ABCs and yet no consensus is defined to date. The aim of this study was to retrospectively review data of a large single center series of ABCs with patients treated by open curettage with or without filling of the cavity or en-bloc resection. We asked: (1) What was the local recurrence rate of ABC after surgical treatment at our institution? (2) What were positive or negative predictors for local recurrence? (3) Was there a benefit from adjuvant burring, phenolization or filling, respectively? (4) Where there changes in recurrence free survival in different time periods of primary surgery? By retrospective data analysis of the Vienna Bone and Soft Tissue Tumor Registry, 123 patients surgically treated for primary aneurysmal bone cysts were identified. After exclusion of 33 patients (27%) due to a postoperative follow up below one year, 90 patients who were treated for primary ABCs between 1986 and 2009 were evaluated. These included 50 males and 40 females with a mean age of 16 years (SD 10 years; range: 2 to 51 years). The mean follow-up was 99 months. (SD 72 months, range: 13 to 329 months) Curettage was performed in 84 patients, while 45 patients received adjuvant phenolization. Local recurrence occurred in 28 patients after a mean time of 16 months, with a corresponding local recurrence free survival (RFS) of 83% after one year, 77% after 2 years and 66% after 5 years. ABCs located in hands and feet (p = 0.044) showed a superior RFS, while younger patients (p = 0.001) displayed an inferior RFS. Regarding adjuvant surgical techniques, mechanical cavity burring (p = 0.004) and filling with autologous cancellous bone graft (p = 0.024) showed protective effects on RFS. Patients treated between 1986 and 1999 (n = 47) had a higher RFS than patients treated between 2000 and 2009 (n = 43, p = 0.011), as surgeons and surgical indications changed over time. Although curettage, burring, phenolization and reconstruction with bone grafts came with a relatively high risk of local recurrence, open surgery is still justified in aggressively growing ABCs of critical localizations. IV; therapeutic study.

The adult acquired flatfoot is a deformity with slow progression, which may leads to pain and restrictions of activities of daily living if untreated. Various treatment strategies, depending on the clinical and radiological presentation, exist. Therefore, an individual therapy approach is necessary for optimal treatment. This article covers etiopathologic aspects, conservative and operative treatments as well as postoperative mobilization and rehabilitation.

Background. - Aneurysmal bone cysts (ABC) are benign tumors mostly occurring in children and young adults. Different open and minimal invasive surgical approaches have been proposed for the treatment of ABCs and yet no consensus is defined to date. The aim of this study was to retrospectively review data of a large single center series of ABCs with patients treated by open curettage with or without filling of the cavity or en-bloc resection. Questions/purposes We asked: (1) What was the local recurrence rate of ABC after surgical treatment at our institution? (2) What were positive or negative predictors for local recurrence? (3) Was there a benefit from adjuvant burring, phenolization or filling, respectively? (4) Where there changes in recurrence free survival in different time periods of primary surgery? Methods. - By retrospective data analysis of the Vienna Bone and Soft Tissue Tumor Registry, 123 patients surgically treated for primary aneurysmal bone cysts were identified. After exclusion of 33 patients (27%) due to a postoperative follow up below one year, 90 patients who were treated for primary ABCs between 1986 and 2009 were evaluated. These included 50 males and 40 females with a mean age of 16 years (SD 10 years; range: 2 to 51 years). The mean follow-up was 99 months. (SD 72 months, range: 13 to 329 months)Results. - Curettage was performed in 84 patients, while 45 patients received adjuvant phenolization. Local recurrence occurred in 28 patients after a mean time of 16 months, with a corresponding local recurrence free survival (RFS) of 83% after one year, 77% after 2 years and 66% after 5 years. ABCs located in hands and feet (p = 0.044) showed a superior RFS, while younger patients (p = 0.001) displayed an inferior RFS. Regarding adjuvant surgical techniques, mechanical cavity burring (p = 0.004) and filling with autologous cancellous bone graft (p = 0.024) showed protective effects on RFS. Patients treated between 1986 and 1999 (n = 47) had a higher RFS than patients treated between 2000 and 2009 (n = 43, p = 0.011), as surgeons and surgical indications changed over time.Conclusion. - Although curettage, burring, phenolization and reconstruction with bone grafts came with a relatively high risk of local recurrence, open surgery is still justified in aggressively growing ABCs of critical localizations. Level of evidence. - IV; therapeutic study.(c) 2021 L'Auteur(s). Publie par Elsevier Masson SAS. Cet article est publie en Open Access sous licence CC BY (http://creativecommons.org/licenses/by/4.0/).

Introduction Multiple revision hip arthroplasties and critical trauma might cause severe bone loss that requires proximal femoral replacement (PFR). The aim of this retrospective study was to analyse complication- and revision-free survivals of patients who received modular megaprostheses in an attempt to reconstruct massive non-neoplastic bone defects of the proximal femur. Questions/purposes (1) What were general complication rates and revision-free survivals following PFR? (2) What is the incidence of complication specific survivals? (3) What were risk factors leading to a diminished PFR survival? Materials and methods Twenty-eight patients with sufficient follow-up after receiving a modular proximal femoral megaprosthesis were identified. The indications for PFR included prosthetic joint infection (PJI), periprosthetic fracture, aseptic loosening, non-union and critical femoral fracture. Complications were grouped according to the ISOLS-classification of segmental endoprosthetic failure by Henderson et al. Results Overall, the complication-free survival was 64.3% at one year, 43.2% at five years and 38.4% at ten years, with 16 patients (57%) suffering at least one complication. Complications were dislocation in eight patients (29%), PJI in 6 patients (21%), periprosthetic fracture in five patients (18%), and aseptic loosening in six patients (21%). Prosthesis stem cementation showed a lower risk for revision in a cox proportional hazard model (95% CI 0.04–0.93, HR 0.2, p = 0.04). Conclusion PFR with modular megaprostheses represents a viable last resort treatment with high complication rates for patients with severe proximal femoral bone loss due to failed arthroplasty or critical fractures. In revision arthroplasty settings, PFR cementation should be advocated in cases of impaired bone quality.

BACKGROUND Distal femur replacement is frequently used for limb salvage after bone tumor resections. It is also used in patients with severe bone loss because of traumatic conditions or revision TKA. Some studies on distal femur replacement reported on revision-free survival without distinguishing between patients with oncologic diagnoses and those without, although these patients might be incomparable because of their differences in important patient- and disease-specific characteristics. This may lead to an inaccurate and undifferentiated interpretation of the results of survival analyses. QUESTIONS/PURPOSES (1) What is the overall cumulative incidence of revision surgery after cemented and cementless distal femoral replacement, as determined with a competing risk analysis? (2) Does the cumulative incidence of revision surgery change over time? (3) Are there differences in the cumulative incidence of revision surgery between patients with oncologic conditions and those without who are treated with cemented or cementless distal femoral replacement? METHODS A total of 403 patients were possible candidates for distal femoral replacement. Of these, 56 patients elected to undergo different procedures, 83 were excluded because an expendable growing prosthesis was implanted, and 28 were lost to follow-up. Therefore, 229 patients who underwent distal femoral replacement for oncologic or non-oncologic reasons between 1983 and 2016 were retrospectively included in this study. The type of fixation method (cemented or cementless) was obtained from the patients' medical records, operation reports, and radiographic analyses from plain radiographs. All radiographs were standardized and obtained at standard time intervals in our institution. No algorithm regarding the fixation approach was followed. According to our data, patients receiving cementless fixation were younger and therefore likely to be more active than those receiving cemented fixation. The median follow-up duration of the overall cohort was 85 months (range 0.1-391 months). Patients who died or had revision surgery before the 2-year minimum follow-up interval were adequately considered using competing risk calculation. The reasons for revision surgery were classified using the classification system proposed by the International Society for Limb Salvage. A competing risk analysis was performed to estimate the cumulative incidence function of revision, accounting for death as a competing event. To evaluate the influence of potential prognostic factors, including diagnosis (oncologic versus non-oncologic), fixation (cemented versus cementless), year of distal femoral replacement, age, and sex on the occurrence of revision surgery, univariate and multivariable Fine and Gray models were applied. RESULTS The competing risks analysis revealed cumulative incidences of revision surgery for any cause (Types 1 to 5) of 26% (95% CI, 20.3%-31.9%) at 12 months, 37.9% (95% CI, 31.3%-44.4%) at 24 months, 52.6% (95% CI, 45.1%-59.5%) at 5 years, and 58.2% (95% CI, 50.1%-65.4%) at 10 years for all patients. Rotating hinge-type prostheses showed a lower cumulative incidence of revision surgery (41.6%; 95% CI, 31.8%-51%) than fixed-hinge prostheses did (64%; 95% CI, 50.5%-74.5% ) at 5 years (Gray's test: p = 0.01). According to the multivariate Fine and Gray model, the year of surgery did not have any effect on the risk of revision surgery (1994 to 2003: hazard ratio 0.70; 95% CI, 0.46-1.07); 2004 to 2016: HR 0.83; 95% CI, 0.52-1.34; p = 0.26). The multivariate analysis, adjusted for disease, sex, age, cementation, and year of surgery, revealed a difference in the risk of revision surgery between patients with oncologic disease and those with non-oncologic disease (HR 0.44 for oncologic versus non-oncologic; 95% CI, 0.22-0.87; p = 0.02) and a reduction in the risk of overall revision with cemented fixation in patients with oncologic disease (HR 0.53; 95% CI, 0.29-0.98; p = 0.03). CONCLUSION This study indicates that even with newer implants, there was a high incidence of revision surgery after distal femoral replacement. According to our analysis, patients with oncologic diagnoses have a lower likelihood of revision when the stem is cemented whereas the type of fixation did not impact patients with non-oncologic diagnoses. Because of differences in patient demographics (age, etiology of disease, and use of chemotherapy) and outcomes of fixation, oncologic and non-oncologic patients should be analyzed separately in survival studies about distal femoral replacement. LEVEL OF EVIDENCE Level III, therapeutic study.

Administration of bisphosphonates following total joint arthroplasty might be beneficial to reduce aseptic loosening. However, their effects on peri-implant bone formation and bone-implant interface strength have not been investigated yet. We used a physiologically loaded mouse implant model to investigate the short-term effects of postoperative systemic alendronate on osseointegration. A titanium implant with a rough surface was inserted in the proximal tibiae of 17-week-old female C57BL/6 mice (n = 44). Postimplantation mice were given alendronate (73 μg/kg/days, n = 22) or vehicle (n = 22) 5 days/week. At 7- and 14-day postimplantation, histology and histomorphometry were conducted. At 28 days, microcomputed tomography and biomechanical testing were performed (n = 10/group). Postoperative alendronate treatment enhanced osseointegration, increasing maximum pullout load by 45% (p < .001) from 19.1 ± 4.5 N in the control mice to 27.6 ± 4.9 N in the treated mice, at day 28 postimplantation. Alendronate treatment increased the bone volume fraction by 139% (p < .001) in the region distal to the implant and 60% (p < .05) in the peri-implant region. At 14-day postimplantation, alendronate treatment decreased the number of osteoclasts per bone perimeter (p < .05) and increased bone volume fraction (p < .01) when compared with the control group. Postimplantation, short-term alendronate treatment enhanced osseointegration as demonstrated by increased bone mass, trabecular bone thickness, and maximum pullout load. Alendronate decreased peri-implant osteoclasts while preserving peri-implant osteoblasts and endothelial cells, in turn, increasing bone volume fraction. This data supports the postoperative clinical use of bisphosphonates, especially in patients with high risks of aseptic loosening.

Substantial bone loss following failed total knee arthroplasty (TKA) represents a major challenge in revision arthroplasty, that can require distal femoral reconstruction (DFR). In this study, we aimed to assess the clinical outcome and the complication frequencies of individuals who underwent DFR with modular megaprostheses. Additionally, we aimed to compare functional outcome measures after DFR in these sophisticated cases to an age-matched control group of total knee prostheses to quantify the potential loss of function. A retrospective chart review of 30 consecutive patients after DFR from 1997 to 2017 with a mean age of 74.38 years (± 10.1) was performed. Complications were classified according to the Henderson classification. Knee Society Score (KSS) was calculated and range of motion (ROM) was assessed. Thirteen (43.3%) patients had at least one complication requiring revision surgery. Revision-free survival was 74.8% at one year, 62.5% at three and 40.9% at 10 years post-op. Soft-tissue failure complications were found in three (10.0%) patients, aseptic loosening in four (13.3%) patients, structural failure in one (3.3%) patient and infection in eight (26.6%) patients. Of those with infection, five (16.6%) experienced ongoing prosthetic joint infection and three (10.0%) developed new infection after distal femur reconstruction. Patients with DFR achieved 69.3% of KSS pain score, 23.1% KSS function score and 76.2% of ROM compared to patients with primary TKA. DFR after failed TKA represents a treatment procedure with high risk for complication in this particular group. Despite the prospect of rapid postoperative mobilization, reduced functionality, range of motion and mobilization have to be considered when choosing this treatment option.