The position of Kirschner wires (K-wires) has an influence on the outcome of modified tension-band wiring (MTBW) in fixing patella fractures. However, the instruction for K-wires positioning is not clear enough. This study tried to clarify the effect of K-wires positioning and provide evidence for a more definite instruction. The sagittal position (SP) suitable for placing K-wires was evenly divided into SP 1–5 from anterior to posterior, and the finite element models of midpatella transverse fractures fixed by the figure-of-eight or figure-of-zero MTBW were built up at each SP. Separating displacement of the fracture, stress of the fracture, and stress of the internal fixations were measured at 45° knee flexion by using finite element analysis. The separating displacement of the fracture was smaller at SP 3–5 (23% smaller than SP 1–2). From SP 1 to 5, the compression of the fracture surfaces increased (R = 0.99, P = 0.001); the improper stress area of the fracture surfaces decreased (R = − 0.96, P = 0.01), and so was the stress of K-wires (R = − 0.93, P = 0.02). However, the stress of stainless steel wires showed a stable trend. The SP of K-wires plays a role in the function of MTBW in the surgical management of transverse patella fracture. At 45° knee flexion, posteriorly placed (close to the articular surface) K-wires enable optimal stability and stress for the fracture, which provides basis for the positioning of K-wires in clinical practice.

Vertical femoral neck fractures in patients younger than 65 years of age often require hip‐conserving surgeries. However, traditional fixation strategies using three parallel cannulated screws often fail in such patients due to an unfavorable biomechanical environment. This study compared different cannulated screw fixation techniques in patients via patient‐specific finite element analysis with linear tetrahedral (C3D4) elements. Forty vertical femoral neck fracture models were created based on computed tomography images obtained from eight healthy participants. Five different fixation strategies: alpha, buttress, rhomboid, inverted triangle, and triangle were assessed in walking status. Biomechanical parameters including stiffness, interfragmentary motion in two directions (detachment and shearing), compression force, and maximal implant stress were evaluated. The mean relative coefficient of strain distribution between the finite element analysis and experiment was from 0.78 to 0.94. Stiffness was highest (p < .05) in the buttress group (923.1 N/mm), while interfragmentary motion was lowest (p < .05) in the alpha group. Maximal stress was highest (p < .05) in the buttress group and lowest in the alpha group. Shearing values were significantly lower in the alpha group than in the rhomboid group (p = .004). Moreover, Shearing values were significantly higher (p = .027), while detachment values were significantly lower (p = .027), in the inverted triangle than in the triangle group. Clinical significance: Our results suggest that alpha fixation is the most reliable and biomechanically efficient strategy for young patients with vertical femoral neck fractures. Regular and inverted triangular fixation strategies may be suitable for fractures of different skeletal constructions due to antidetachment/shearing abilities.

Vertical femoral neck fractures (VFNFs) are one of the most difficult fractures to stabilize, with high non-union (17%), avascular necrosis (AVN, 21%), and femoral neck shortening (FNS, 29.0%) rates. The objective of this investigation was to directly compare the long-term clinical complication rates of VFNFs repaired by crossed (Alpha fixation) or parallel screws in non-geriatric patients. We conducted a retrospective comparative study of VFNFs in patients (<60 years) between January 2014 and December 2017, with at least 2 years of follow-up. VFNFs were fixed with either three parallel screws (G-TRI) or augmented with a crossed screw (G-ALP). Confounding variables included age, gender, initial displacement, ISS (Injury Severity Score), general comorbidities, combined fractures, Pauwels angle, reduction quality. Complications, including non-union, AVN of the femoral head and FNS were compared as outcome indicators. Risk factors associated with these variables were further analysed using multivariate analysis. A total of 157 patients (97 G-TRI; 60 G-ALP) met inclusion criteria. G-ALP had a significantly lower rate of FNS (8.3% vs. 28.9%, p = 0.039) than that of G-TRI. non-union (3.3% vs. 11.3%), AVN (21.7% vs. 25.8%), and reoperation rates (21.7% vs. 23.7%) were lower in G-ALP than G-TRI but was not statistically significant. Multivariate analyses showed significant relationships between NU and unacceptable reduction quality (OR=7.610; 1.823-31.770, adjusted-p = 0.015); between AVN and initial displacement (Garden III and IV) (OR=7.885; 1.739-35.744, adjusted-p = 0.021); and between FNS and screw configuration (OR=5.713; 1.839-17.743, adjusted-p = 0.009). For the treatment of VFNFs, satisfactory reduction still remains the key surgical goal that prevents NU, while the incidence of AVN strongly depends on the initial displacement at the time of injury. Crossed screws were associated with a markedly lower FNS rate than parallel screws, which promote further randomised controlled trials to establish a guideline for optimal fixation selection in VFNFs.

As the commonly used fixation strategy of medial malleolar fractures, cancellous screws (CS) have been challenged for instability, bone destruction, and metal prominence. It is still unclear whether a locking compression plate (LCP) is a better choice in such fractures. Our purpose is to compare the mechanical efficacy of LCP with traditional 4.0-mm CS for transverse, oblique, and vertical medial malleolar fractures by using finite element analysis. In this study, 3-dimensional models of the distal tibia were reconstructed from a computed tomography scan of a young healthy male adult. Conditions included 3 fracture lines at 30°, 60°, and 90°; 2 groups of fixation (LCP and CS); and 3 adduction loads of 300, 500, and 700 N applied to the medial malleolar joint surface. The proximal part of the tibia was fixed for all degrees of freedom. The fracture displacements of the LCP were smaller than those of CS (p < .05). The stiffness of the LCP constructs was much higher than that of the CS constructs, especially in the 90° fractures (490.3 versus 163.6 N/mm). The mean stress around the CS was higher than that in LCP for 60° and 90° fractures, but there was no difference for 30°. Maximal bone stress increased (19.84 to 50.86 MPa) and concentrated on cortical bone in LCP, whereas it concentrated on cancellous bone in CS. The results showed that LCP could improve stability, preventing bone destruction in oblique and vertical medial malleolar fractures. However, in transverse fractures, CS provides sufficient stability, with no need to use LCP.