To evaluate the biomechanical performance of the Femoral Neck System (FNS) versus the Hansson Pin System (Hansson Pins) with two parallel pins in a Pauwels II femoral neck fracture model with posterior comminution. Forty-degree Pauwels II femoral neck fractures AO 31-B2.1 with 15° posterior wedge were simulated in fourteen paired fresh-frozen human femora, followed by instrumentation with either FNS or Hansson Pins in pair-matched fashion. Implant positioning was quantified by measuring shortest implant distances to inferior cortex (DI) and posterior cortex (DP) on anteroposterior and axial X-rays, respectively. Biomechanical testing was performed in 20° adduction and 10° flexion with simulated iliopsoas muscle tension. Progressively increasing cyclic loading was applied until construct failure. Interfragmentary femoral head-to-shaft movements were measured with optical motion tracking. Cycles to 10° varus deformation were significantly higher for FNS (23007 ​± ​5496) versus Hansson Pins (17289 ​± ​4686), P ​= ​0.027. Cycles to 10° femoral head dorsal tilting (FNS: 12765 ​± ​3425; Hansson Pins: 13357 ​± ​6104) and cycles to 10° rotation around the femoral neck axis (FNS: 24453 ​± ​5073; Hansson Pins: 20185 ​± ​11065) were comparable between the implants, P ​≥ ​0.314. For Hansson Pins, the outcomes for varus deformation and dorsal tilting correlated significantly with DI and DP, respectively (P ​≤ ​0.047), whereas these correlations were not significant for FNS (P ​≥ ​0.310). From a biomechanical perspective, by providing superior resistance against varus deformation and performing in a less sensitive way to variations in implant placement, the angular stable Femoral Neck System can be considered as a valid alternative to the Hansson Pin System for the treatment of Pauwels II femoral neck fractures. therapeutic, Level V. The translational potential of this article is to compare the performance of the FNS with Hansson Pins in a AO 31-B2.1 fracture model featuring a 15 posterior wedge to show the implants behavior concerning the dorsal tilting tendency.

Background: Incidence of pelvic ring fractures has increased over the past four decades, especially after low-impact trauma—classified as fragility fractures of the pelvis (FFP). To date, there is a lack of biomechanical evidence for the superiority of one existing fixation technique over another. An FFP type IIc was simulated in 50 artificial pelvises, assigned to 5 study groups: Sacroiliac (SI) screw, SI screw plus supra-acetabular external fixator, SI screw plus plate, SI screw plus retrograde transpubic screw, or S1/S2 ala–ilium screws. The specimens were tested under progressively increasing cyclic loading. Axial stiffness and cycles to failure were analysed. Displacement at the fracture sites was evaluated, having been continuously captured via motion tracking. Results: Fixation with SI screw plus plate and SI screw plus retrograde transpubic screw led to higher stability than the other tested techniques. The S1/S2 ala–ilium screws were more stable than the SI screw or the SI screw plus external fixator. Conclusions: In cases with displaced fractures, open reduction and plate fixation provides the highest stability, whereas in cases where minimally invasive techniques are applicable, a retrograde transpubic screw or S1/S2 ala–ilium screws can be considered as successful alternative treatment options.

Purpose: The purpose of this study was to investigate the learning curve associated with robotic assisted knee arthroplasty (RAS KA). Therefore, the evaluation of the influence of an experienced surgeon on the overall team performance of three surgeons regarding the learning curve in RAS KA was investigated. It was hypothesized that the presence of an experienced surgeon flattens the learning curve and that there was no inflection point for the learning curve of the surgical team.Methods: Fifty‐five cases consisting of 31 total knee arthroplasties (TKA) and 24 unicompartmental arthroplasties (UKA) performed by three surgeons during 2021 were prospectively investigated. Single surgeon and team performance for operation time learning curve and inflection points were investigated using cumulative sum analysis (CUSUM).Results: A downward trend line for individual surgeons and the team performance regarding the operation time learning curve was observed. No inflexion point was observed for the overall team performance regarding TKA and UKA. The surgeon that performed all cases with the assistance of the experienced surgeon had significantly shorter surgical times than the surgeon that only occasionally received assistance from the experienced surgeon (p = 0.004 TKA; p = 0.002 UKA).Conclusion: The presence of an experienced surgeon in robotically assisted knee arthroplasty can flatten the learning curve of the surgical team formerly unexperienced in robotic assisted systems. Manufacturers should provide expanded support during initial cases in centres without previous experience to robotic assisted knee arthroplasty.Level of evidence: III.

Comminuted patellar fractures represent a challenging clinical problem. Treatment aims to restore the integrity of the extensor mechanism and the congruity of patellofemoral joint. Controversy exists regarding the ideal fixation method. Metallic constructs aiming to convert pulling forces on the anterior aspect of the patella into compression forces across the fracture site are the standard of care. More recently, low profile plates have been described in the management of comminuted patellar fractures. The aims of this study were to (1) develop a novel unstable patellar fracture model and (2) to compare biomechanically three different constructs for fixation comminuted patellar fractures. We hypothesized that an orthogonal biplanar disposition of the screws within an anteriorly placed locking plate provides the best biomechanical properties in the management of comminuted fractures. Six-part complex AO 34–C3 patella fractures were simulated in 18 human cadaveric knees by means of osteotomies including comminution around the distal patellar pole. The specimens were randomly assigned to 3 fixation techniques (n ​= ​6) for either anterior plating, antero-lateral plating, or tension band wiring (TBW). Biomechanical testing was performed over 5000 cycles in active extension and passive flexion, followed by ultimate destructive quasi-static testing. Interfragmentary movements were captured by means of optical motion tracking. Displacement between the proximal and distal medial patella fragments was lower after anterior plating compared to both antero-lateral plating (P ​= ​0.084) and TBW (P ​< ​0.001). Moreover, displacement between the proximal and distal lateral fragments was significantly lower after anterior plating compared to both other techniques (P ​≤ ​0.032). In addition, it was significantly lower for antero-lateral plating versus TBW (P ​< ​0.001). Rotation around the medio-lateral axis between the proximal and distal medial fragments was significantly lower after anterior plating compared to TBW (P ​= ​0.017). Anterior mesh plating with biplanar placement of locking screws provides superior stability for fixation of comminuted patellar fractures when compared to both antero-lateral mesh plating and TBW. The latter is associated with considerably inferior performance.

Background: Periprosthetic femoral fractures (PFFs) represent a major cause for surgical revision after hip arthroplasty with detrimental consequences for patients. The Vancouver classification has been traditionally used since its introduction in 1995. The Unified Classification System (UCS) was described in 2014, to widen the spectrum by aiming for a more comprehensive approach. The UCS also aimed to replace the Vancouver classification by expanding the idea of the Vancouver classification to the whole musculoskeletal apparatus. After introduction of the UCS, the question was raised, whether the UCS found its place in the field of analysing PFFs. Therefore, this systematic review was performed to investigate, the use of the UCS compared to the established Vancouver classification.Methods: Medline was searched for reports published between 1 January 2016 and 31 November 2020, without language restriction. Included were original articles, irrespective of the level of evidence and case reports reporting on a PFF and using either the Vancouver or the UCS to classify the fractures. Excluded were reviews and systematic reviews.Results: One hundred forty-six studies were included in the analysis. UCS has not been used in a single registry study, giving a pooled cohort size of 3299 patients, compared to 59,178 patients in studies using the Vancouver classification. Since 2016, one study using UCS was published in a top journal, compared to 37 studies using the Vancouver classification (p=0.29). During the study period, the number of yearly publications remained stagnant (p=0.899).Conclusions: Despite valuable improvement and expansion of the latter UCS, to date, the Vancouver system clearly leads the field of classifying PFFs in the sense of the common use.

Background: The Oxford Knee Score (OKS) has been designed for patients with knee osteoarthritis and has a widespread use. It has 12 questions, with each question having the same weight for the overall score. Some authors have observed a significant ceiling effect, especially when distinguishing slight postoperative differences. We hypothesized that each questions’ weight will depend significantly on the patient’s sociodemographic data and lifestyle. Methods: In this international multicentric prospective study, we included patients attending a specialist outpatient knee clinic. Each patient filled out 3 questionnaires: (a) demographic data and data pertaining to the OKS, (b) the standard OKS, and (c) the patient gave a mark on the weight of the importance of each question, using a 5-point Likert scale (G OKS). Linear regression models were used for the analysis. Results: In total 203 patients (106 female and 97 male) with a mean age of 64.5 (±12.7) years and a mean body mass index (BMI) of 29.34 (±5.45) kg/m² were included. The most important questions for the patients were the questions for pain, washing, night pain, stability, and walking stairs with a median of 5. In the regression models, age, gender, and driving ability were the most important factors for the weight of each of the question. Conclusion: The questions in the OKS differ significantly in weight for each patient, based on sociodemographic data, such as age, self-use of a car, and employment. With these differences, the Oxford Knee Score might be limited as an outcome measure. Adjustment of the OKS that incorporates the demographic differences into the final score might be useful if the ceiling effect is to be mitigated. Level of Evidence: Level II prospective prognostic study