Experimental guide wire placement for total shoulder arthroplasty in glenoid models: higher precision for patient-specific aiming guides compared to standard technique without learning curve.

BACKGROUND: Patient-specific aiming devices (PSAD) may improve precision and accuracy of glenoid component positioning in total shoulder arthroplasty, especially in degenerative glenoids. The aim of this study was to compare precision and accuracy of guide wire positioning into different glenoid models using a PSAD versus a standard guide. METHODS: Three experienced shoulder surgeons inserted 2.5 mm K-wires into polyurethane cast glenoid models of type Walch A, B and C (in total 180 models). Every surgeon placed guide wires into 10 glenoids of each type with a standard guide by DePuy Synthes in group (I) and with a PSAD in group (II). Deviation from planned version, inclination and entry point was measured, as well as investigation of a possible learning curve. RESULTS: Maximal deviation in version in B- and C-glenoids in (I) was 20.3° versus 4.8° in (II) (p < 0.001) and in inclination was 20.0° in (I) versus 3.7° in (II) (p < 0.001). For B-glenoid, more than 50% of the guide wires in (I) had a version deviation between 11.9° and 20.3° compared to ≤ 2.2° in (II) (p < 0.001). 50% of B- and C-glenoids in (I) showed a median inclination deviation of 4.6° (0.0°-20.0°; p < 0.001) versus 1.8° (0.0°-4.0°; p < 0.001) in (II). Deviation from the entry point was always less than 5.0 mm when using PSAD compared to a maximum of 7.7 mm with the standard guide and was most pronounced in type C (p < 0.001). CONCLUSION: PSAD enhance precision and accuracy of guide wire placement particularly for deformed B and C type glenoids compared to a standard guide in vitro. There was no learning curve for PSAD. However, findings of this study cannot be directly translated to the clinical reality and require further corroboration.

Vertebropexy as a Ligamentous Stabilization for Degenerative Low-Grade Spondylolisthesis: A Report of 3 Cases.

CASE: Three patients with low-grade spondylolisthesis were treated with vertebropexy, a new surgical technique that replaces rigid fusion with ligamentous stabilization. Clinical outcomes, functional radiographs, and magnetic resonance imaging were used to document the early clinical results of this biomechanically established and promising new surgical method. CONCLUSION: Vertebropexy may be a valuable alternative to rigid fusion in the treatment of low-grade degenerative spondylolisthesis.

Prospective evaluation of clinical and radiographic 10-year results of Fitmore short-stem total hip arthroplasty.

BACKGROUND: Short stems were introduced into total hip arthroplasty (THA) to preserve bone stock, to transmit more load to the proximal femur, and to enable minimal invasive approaches. This study is the first long-term study (with a follow-up of 10 years) of the survival as well as the clinical and radiographic outcomes of the Fitmore hip stem, a short curved uncemented stem. METHODS: In total, 123 Fitmore hip stems were prospectively evaluated. At the final 10-year follow-up, 80 Fitmore stems (78 patients: 30 female, 48 male) were eligible for evaluation. Clinical parameters were thigh pain, EQ-5D, Harris Hip Score (HHS) and Oxford Hip Score. Radiographic parameters were cortical hypertrophy (CH), bone condensation, cortical thinning, radiolucency, reactive lines, calcar rounding, calcar resorption, subsidence and varus/valgus position. RESULTS: After 10 years, there was a survival rate of 99% (1 revision because of aseptic stem loosening). HHS had improved from 59 to 94 and Oxford Hip Score from 22 to 43. CH rate after 1 year was 69% and after 10 years 74%. In the first year, radiolucency was found in 58% and in 17.5% after 10 years. Subsidence after 1 year was 1.6 ± 1.6 mm and 5.0 ± 3.1 mm after 10 years. CONCLUSIONS: The Fitmore hip stem showed a survival rate of 99% as well as good clinical and radiographic outcomes in the long-term follow-up of 10 years.

Biomechanical Comparison of Intramedullary Versus Extramedullary Implants for Fixation of Simple Pertrochanteric Fractures.

OBJECTIVES: To evaluate the biomechanical performance of the intramedullary TFN-ADVANCED Proximal Femoral Nailing System (TFNA) versus the extramedullary Femoral Neck System (FNS) for fixation of simple pertrochanteric fractures in a human cadaveric model. METHODS: Ten human cadaveric femoral pairs were implanted pairwise with either TFNA or FNS. A simple pertrochanteric fracture OTA/AO 31-A1 was created and all specimens were biomechanically tested under progressively increasing cyclic loading until failure. Interfragmentary and bone-implant movements were monitored by motion tracking. RESULTS: Axial stiffness was comparable between TFNA and FNS, P = 0.34. Similarly, varus deformation, femoral head rotation around neck axis and implant migration remained without significant differences between TFNA and FNS after 3000 cycles (800 N peak load), P ≥ 0.10. However, cycles to 15-mm leg shortening were significantly higher for TFNA versus FNS, P < 0.01. CONCLUSIONS: From a biomechanical perspective, with its current design, FNS does not seem to be a valid alternative to TFNA for treatment of simple pertrochanteric fractures.

Locking Plates With Computationally Enhanced Screw Trajectories Provide Superior Biomechanical Fixation Stability of Complex Proximal Humerus Fractures.

Joint-preserving surgical treatment of complex unstable proximal humerus fractures remains challenging, with high failure rates even following state-of-the-art locked plating. Enhancement of implants could help improve outcomes. By overcoming limitations of conventional biomechanical testing, finite element (FE) analysis enables design optimization but requires stringent validation. This study aimed to computationally enhance the design of an existing locking plate to provide superior fixation stability and evaluate the benefit experimentally in a matched-pair fashion. Further aims were the evaluation of instrumentation accuracy and its potential influence on the specimen-specific predictive ability of FE. Screw trajectories of an existing commercial plate were adjusted to reduce the predicted cyclic cut-out failure risk and define the enhanced (EH) implant design based on results of a previous parametric FE study using 19 left proximal humerus models (Set A). Superiority of EH versus the original (OG) design was tested using nine pairs of human proximal humeri (N = 18, Set B). Specimen-specific CT-based virtual preoperative planning defined osteotomies replicating a complex 3-part fracture and fixation with a locking plate using six screws. Bone specimens were prepared, osteotomized and instrumented according to the preoperative plan via a standardized procedure utilizing 3D-printed guides. Cut-out failure of OG and EH implant designs was compared in paired groups with both FE analysis and cyclic biomechanical testing. The computationally enhanced implant configuration achieved significantly more cycles to cut-out failure compared to the standard OG design (p < 0.01), confirming the significantly lower peri-implant bone strain predicted by FE for the EH versus OG groups (p < 0.001). The magnitude of instrumentation inaccuracies was small but had a significant effect on the predicted failure risk (p < 0.01). The sample-specific FE predictions strongly correlated with the experimental results (R2 = 0.70) when incorporating instrumentation inaccuracies. These findings demonstrate the power and validity of FE simulations in improving implant designs towards superior fixation stability of proximal humerus fractures. Computational optimization could be performed involving further implant features and help decrease failure rates. The results underline the importance of accurate surgical execution of implant fixations and the need for high consistency in validation studies.

Advanced CT visualization improves the accuracy of orthopaedic trauma surgeons and residents in classifying proximal humeral fractures: a feasibility study.

PURPOSE: Osteosynthesis of proximal humeral fractures remains challenging with high reported failure rates. Understanding the fracture type is mandatory in surgical treatment to achieve an optimal anatomical reduction. Therefore, a better classification ability resulting in improved understanding of the fracture pattern is important for preoperative planning. The purpose was to investigate the feasibility and added value of advanced visualization of segmented 3D computed tomography (CT) images in fracture classification. METHODS: Seventeen patients treated with either plate-screw-osteosynthesis or shoulder hemi-prosthesis between 2015 and 2019 were included. All preoperative CT scans were segmented to indicate every fracture fragment in a different color. Classification ability was tested in 21 orthopaedic residents and 12 shoulder surgeons. Both groups were asked to classify fractures using three different modalities (standard CT scan, 3D reconstruction model, and 3D segmented model) into three different classification systems (Neer, AO/OTA and LEGO). RESULTS: All participants were able to classify the fractures more accurately into all three classification systems after evaluating the segmented three-dimensional (3D) models compared to both 2D slice-wise evaluation and 3D reconstruction model. This finding was significant (p < 0.005) with an average success rate of 94%. The participants experienced significantly more difficulties classifying fractures according to the LEGO system than the other two classifications. CONCLUSION: Segmentation of CT scans added value to the proximal humeral fracture classification, since orthopaedic surgeons were able to classify fractures significantly better into the AO/OTA, Neer, and LEGO classification systems compared to both standard 2D slice-wise evaluation and 3D reconstruction model.

One size may not fit all: patient-specific computational optimization of locking plates for improved proximal humerus fracture fixation.

BACKGROUND: Optimal treatment options for proximal humerus fractures (PHFs) are still debated because of persisting high fixation failure rates experienced with locking plates. Optimization of the implants and development of patient-specific designs may help improve the primary fixation stability of PHFs and reduce the rate of mechanical failures. Optimizing the screw orientations in locking plates has shown promising results; however, the potential benefit of subject-specific designs has not been explored yet. The purpose of this study was to evaluate by means of finite element (FE) analyses whether subject-specific optimization of the screw orientations in a fixed-angle locking plate can reduce the predicted cutout failure risk in unstable 3-part fractures. METHODS: FE models of 19 low-density proximal humeri were generated from high-resolution computed tomographic images using a previously developed and validated computational osteosynthesis framework. The specimens were virtually osteotomized to simulate unstable malreduced 3-part fractures and fixed with the PHILOS plates using 6 proximal locking screws. The average principal compressive strain in cylindrical bone regions around the screw tips-a biomechanically validated surrogate for the risk of cyclic screw cutout failure-was defined as the main outcome measure. The angles of the 6 proximal locking screws were optimized via parametric analysis for each humerus individually, resulting in subject-specific screw orientations (SSO). The average peri-implant strains of the SSO were statistically compared with the previously reported cohort-specific (CSO) and original PHILOS screw orientations (PSO) for females vs. males. RESULTS: The optimized SSO significantly reduced the peri-screw bone strain vs. CSO (6.8% ± 4.0%, P = .006) and PSO (25.24% ± 7.93%, P < .001), indicating lower cutout risk for subject-specific configurations. The benefits of SSO vs. PSO were significantly higher for women than men. CONCLUSION: The findings of this study suggest that subject-specific optimization of the locking screw orientations could lead to lower cutout risk and improved PHF fixation. These computer simulation results require biomechanical and clinical corroboration. Further studies are needed to evaluate whether the potential benefit in stability could justify the increased efforts related to implementation of individualized implants. Nevertheless, computational exploration of the biomechanical factors influencing the outcome of fracture fixations could help better understand the fixation failures and reduce their incidence.

Angular stable locking in a novel intramedullary nail improves construct stability in a distal tibia fracture model.

INTRODUCTION: Intramedullary nails are frequently used for treatment of unstable distal tibia fractures. However, insufficient fixation of the distal fragment could result in delayed healing, malunion or nonunion. Recently, a novel concept for angular stable nailing was developed that maintains the principle of relative stability and introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction. The aim of this study was to investigate the biomechanical competence of the novel angular stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared to a conventional nail locking in a human cadaveric model under dynamic loading. MATERIALS AND METHODS: Ten pairs of fresh-frozen human cadaveric tibiae with a simulated AO/OTA 42-A3.1 fracture were assigned to 2 groups for reamed intramedullary nailing using either a conventional (non-angular stable) Expert Tibia Nail (ETN) with 3 distal screws or the novel Tibia Nail Advanced (TNA) system with 2 distal angular stable locking low-profile retaining screws. The specimens were biomechanically tested under conditions including initial quasi-static loading, followed by progressively increasing combined cyclic axial and torsional loading in internal rotation until failure of the bone-implant construct. Both tests were monitored by means of motion tracking. RESULTS: Initial nail toggling of the distal tibia fragment in varus and flexion under axial loading was lower for TNA compared to ETN, being significant in flexion, P = 0.91 and P = 0.03. After 5000 cycles, interfragmentary movements in terms of varus, flexion, internal rotation, axial displacement, and shear displacement at the fracture site were all lower for TNA compared to ETN, with flexion and shear displacement being significant, P = 0.14, P = 0.04, P = 0.25, P = 0.11 and P = 0.04, respectively. Cycles to failure until both interfragmentary 5° varus and 5° flexion were significantly higher for TNA compared to ETN, P = 0.04. CONCLUSION: From a biomechanical perspective, the novel angular stable intramedullary nail concept provides increased construct stability and maintains it over time while reducing the number of required locking screws without impeding the flexibility of the nail itself and resists better towards loss of reduction under dynamic loading, compared to conventional locking in intramedullary nailed unstable distal tibia fractures.

Biomechanical analysis of peri­implant fractures in short versus long cephalomedullary implants following pertrochanteric fracture consolidation.

INTRODUCTION: Pertrochanteric femur fracture fixation with use of cephalomedullary nails (CMN) has become increasingly popular in recent past. Known complications after fracture consolidation include peri­implant fractures following the use of both short and long nails, with fracture lines around the tip of the nail or through the interlocking screw holes, resulting in secondary midshaft or supracondylar femur fractures, respectively. Limited research exists to help the surgeon decide on the use of short versus long nails, while both have their benefits. The aim of this biomechanical study is to investigate in direct comparison one of the newest generations short and long CMNs in a human anatomical model, in terms of construct stability and generation of secondary fracture pattern following pertrochanteric fracture consolidation. METHODS: Eight intact human anatomical femur pairs were assigned to two groups of eight specimens each for nailing using short or long CMNs. Each specimen was first biomechanically preloaded at 1 Hz over 2000 cycles in superimposed synchronous axial compression to 1800 N and internal rotation to 11.5 Nm. Following, internal rotation to failure was applied over an arc of 90° within one second under 700 N axial load. Torsional stiffness as well as torque at failure, angle at failure, and energy to failure were evaluated. Fracture patterns were analyzed. RESULTS: Outcomes in the study groups with short and long nails were 9.7 ± 2.4 Nm/° and 10.2 ± 2.9 Nm/° for torsional stiffness, 119.8 ± 37.2 Nm and 128±46.7 Nm for torque at failure, 13.5 ± 3.5° and 13.4 ± 2.6° for angle at failure, and 887.5 ± 416.9 Nm° and 928.3 ± 461.0 Nm° for energy to failure, respectively, with no significant differences between them, p ≥ 0.17. Fractures through the distal locking screw holes occurred in 5 and 6 femora instrumented with short and long nails, respectively. Fractures through the lateral entry site of the head element were detected in 3 specimens within each group. For short nails, fractures through the distal shaft region, not interfacing with the implant, were detected in 3 specimens. CONCLUSION: From a biomechanical perspective, the risk of secondary peri­implant fracture after intramedullary fixation of pertrochanteric fractures is similar when using short or long CMN. Moreover, for both nail versions the fracture pattern does not unexceptionally involve the distal locking screw hole.

Metabolite Shifts Induced by Marathon Race Competition Differ between Athletes Based on Level of Fitness and Performance: A Substudy of the Enzy-MagIC Study.

This study compared metabolite shifts induced by training for, participation in, and recovery from a marathon race competition among athletes divided into three groups based on fitness (relative maximum oxygen uptake (VO2max)) and performance levels (net running time). Plasma samples from 76 male runners participating in the Munich Marathon were analyzed for metabolite shifts using a targeted metabolomics panel. For the entire cohort of runners, pronounced increases were measured immediately after the race for plasma concentrations of acylcarnitines (AC), the ratio (palmitoylcarnitine + stearoylcarnitine)/free carnitine that is used as a proxy for the activity of the mitochondrial enzyme carnitine palmitoyltransferase, and arginine-related metabolites, with decreases in most amino acids (AA) and phospholipids. Plasma levels of AA and phospholipids were strongly increased 24 and 72 h post-race. Post-race plasma concentrations of AC and arginine-related metabolites were higher in the low compared to top performers, indicating an accumulation of fatty acids and a reliance on protein catabolism to provide energy after the marathon event. This study showed that marathon race competition is associated with an extensive and prolonged perturbation in plasma metabolite concentrations with a strong AC signature that is greater in the slower, less aerobically fit runners. Furthermore, changes in the arginine-related metabolites were observed.