Relative instability ratios of bone wall defects in trochanteric hip fractures: A finite element analysis.

Background: For decades, medial and lateral wall fragments of trochanteric hip fractures were considered two pivotal factors that could influence the stability of postoperative femur-implant complex. However, most studies seemed to misunderstand the concept of the posteromedial fragment and equated it with the medial wall, which overlooked vital roles of the anteromedial wall. Roles of the posterior coronal bone fragment were also highlighted in some research. However, influences of the bone walls above the trochanteric fracture instability are yet to be investigated and quantified by means of finite element analysis. Methods: Eight trochanteric fracture fixation models with different wall defects were constructed. Outcome indicators were the von Mises stress of the implant models, the maximum/minimum principal strain, the risky tensile/compressive volume and the volume ratios of the bone models, the femoral head vertex displacement, and the fracture surface gap. Based on these indicator values, the relative instability ratios were computed. Results: Outcome indicators, absolute values, and nephograms of all models showed the same upward and concentrating trends with exerted hip contact loads shifting from static walking to dynamic climbing. Similarly, these indicators also exhibited the same trends when the eight models were solved in sequence. Moreover, the relative instability ratio of the medial wall (100%), particularly the anteromedial part (78.7%), was higher than the figure for the lateral wall (36.6%). Conclusion: The anteromedial wall played relatively pivotal stabilizing roles in trochanteric hip fractures compared with the posteromedial wall and the lateral wall, which indicated that orthopedic surgeons should attach more importance to the anteromedial cortex support in an operating theatre.

The Impact of Banana-Shaped Fragments on Trochanteric Hip Fractures Treated by PFNA.

Background: Regarding trochanteric hip fractures, one type of posterior coronal fragments was described as the "banana-shaped fragment", while the impact of the banana-shaped fragment on mechanical stability has not been further studied. The current study investigated the association between the banana-shaped fragment and mechanical complications after surgery. Methods: This retrospective cohort study included 273 patients treated by proximal femoral nail antirotation (PFNA) in the full analysis. The age, the sex, the fracture side, the follow-up time, the American Society of Anesthesiologists classification, the operators, the fracture classification, the tip-apex distance, the blade positions, the reduction quality and the bone mineral density were analyzed in relation to mechanical complications, through univariate and multivariate approaches. Results: Mechanical complications happened in 33 patients. The banana-shaped fragment (adjusted odds ratio 5.240, 95% CI 2.172 to 12.641; p < 0.001), the tip-apex distance and the reduction quality showed significant association with mechanical complications in both univariate and multivariate analysis. Moreover, for 118 patients with the banana-shaped fragment, we found that the use of wire cerclage couldn't significantly lower the rates of mechanical complications (p = 0.648). Conclusions: The banana-shaped fragment had a negative impact on mechanical stability of trochanteric hip fractures treated by PFNA. In the perioperative period, the BSF should be carefully evaluated, and its specific handling deserves further study.

Computational evaluation of the axis-blade angle for measurements of implant positions in trochanteric hip fractures: A finite element analysis.

BACKGROUND: Recently, a novel approach axis-blade angle (ABA) was developed to measure implant positions during trochanteric hip fracture surgery. It was defined as the sum of two angles α and ß measured between the femoral neck axis and helical blade axis in anteroposterior and lateral X-ray films, respectively. Although its clinical practicability has been confirmed, the mechanism is yet to be investigated by means of finite element (FE) analysis. METHODS: Computed tomography images of four femurs and dimensions of one implant at three angles were obtained to construct FE models. For each femur, 15 FE models in an arrangement (intramedullary nails at three angles multiplying five blade positions) were established. Under the simulation of normal walking loads, the ABA, von Mises stress (VMS), maximum/minimum principal strain and displacement were analyzed. RESULTS: When the ABA increased, all outcome indicators initially decreased till reaching inferior-middle site and then increased while the blade positions within the femoral head shifted from the superior-anterior quadrant toward the inferior-posterior quadrant, where the ABA were higher. Only the peak VMS of implant models in the inferior-posterior quadrant (particularly the inferior-middle site within) with blades in did not reach the yielding (risky) cut-off. CONCLUSIONS: From the perspective of angles, ABA, this study demonstrated the inferior-posterior quadrant as the relatively stable and safe regions, especially the inferior-middle site within. This was similar but more elaborate compared with previous studies and clinical practice. Therefore, ABA could be employed as a promising approach to anchor the implants into the optimal region.

[Experimental study of constructing vertebral canal on rabbit model with bone marrow mesenchymal stem cells].

OBJECTIVE: To construct the artificial lamina of vertebral arch with bone marrow mesenchymal stem cells transplanted in collagen sponge on a rabbit model and observe the growth of new bone. METHODS: To draw out the bone marrow blood from the femur of 2 weeks old rabbit and get the bone marrow mesenchymal stem cells by centrifugal and adhesive effect. To induce the MSCs to osteoblasts and transplant the induced cells in collagen sponge to construct the tissue engineering bone. To divide 48 rabbits into 3 groups randomly, namely group A, group B and group C. All of the rabbits are taken laminectomy in L6, and to group B and C, collagen sponge and tissue engineering bone are implanted in the operation area respectively. The artificial lamina of vertebral arch is determined qualitatively and quantitatively by methods including imageology and histomorphometry. RESULTS: The artificial lamina of vertebral arch is successfully constructed 4 weeks after operation in group C, CT examination at 4 weeks shows that new lamina of vertebral arch is formed, and the vertebral canal is intact. CONCLUSIONS: The artificial lamina of vertebral arch can be constructed successfully with the usage of tissue engineering bone transplanted bone marrow mesenchymal stem cells.

When to Reduce and Fix Displaced Lesser Trochanter in Treatment of Trochanteric Fracture: A Systematic Review.

Purpose: To systematically evaluate the benefits of reducing and fixing displaced lesser trochanter (LT) of trochanteric fractures and when this procedure is worth the effect. Methods: From database establishment through March 2021, four online databases (PubMed, Cochrane, Embase, and Web of Science) were searched for relevant literature that investigated reduction and fixation for displaced LT of trochanteric fractures. The papers were then screened by two reviewers independently and in duplicate according to prior inclusion and exclusion criteria. Demographic data as well as data on fracture types, surgical protocols, and surgical outcomes were recorded, analyzed, and interpreted. Results: Total 10 clinical studies with 928 patients were included, in which 48 cases had intact LT and 880 cases involved the displaced LT, of which 196 (22.27%) cases underwent reduction and fixation for LT while the rest of 684 (77.73%) cases not. In these studies, complications were evaluated as a more applicable predictive parameter for operation than postoperative hip function. Conclusion: It was beneficial to reduce and fix the displaced LT when one of the conditions below occurred: displacement distance of LT ≥2 cm, quantity of comminuted LT fragments ≥2, and range of LT fragments in medial wall ≥75%; the fracture line of LT fragments reaching or exceeding the midline of the posterior wall.

A novel angle on helical blade placement in trochanteric fractures - The axis-blade angle.

INTRODUCTION: For trochanteric fractures, helical blade placement is crucial to the prognosis of operations. Existing measurement methods used for blade placement include the Cleveland zone, the tip-apex distance (TAD), the calcar-referenced tip-apex distance (CalTAD), and the Parker's ratio. These methods all lack a direct view on blade direction. The current study proposed the axis-blade angle (ABA) to solve direction problem and investigated its clinical applicability. METHODS: A retrospective study collected 156 patients between May 2014 and February 2018. The occurrence of mechanical complications was analyzed in relation to age, gender, fracture side, American Society of Anesthesiologists classification, fracture classification, reduction quality, bone quality, the Cleveland zone, the Parker's ratio, the TAD, the CalTAD, and the ABA. RESULTS: 119 patients, including 25 with mechanical complications, were suitable for full analysis. In the univariate analysis, the Cleveland zone, reduction quality, the TAD, the CalTAD and the ABA were statistically associated with mechanical complications. In the multivariate analysis, reduction quality (p = 0.008) and the ABA (p < 0.001; adjusted OR 0.86;95% CI 0.77 to 0.96) showed significant results, which indicated that reduction quality and the ABA were two independent influencing factors for mechanical complications. Calculation of the receiver operating characteristic (ROC) curve indicated that the ABA was a reliable predictor of mechanical complications at the cut-off of -10°. CONCLUSIONS: The ABA provides instruction for the intraoperative adjustment of guide wire direction. Placing the helical blade with an ABA > -10° can effectively reduce the risk of mechanical complications.