Biomechanical comparison of two side plate fixation techniques in an unstable intertrochanteric osteotomy model: Sliding Hip Screw and Percutaneous Compression Plate

Anteromedial cortical support reduction of intertrochanteric fractures-A review

The intertrochanteric fracture is a common fragility fracture typically resulting from low-energy falls. The functional outcome of intertrochanteric fractures is closely linked to the patient's underlying physical condition, intraoperative procedures, and postoperative complications. In terms of surgery, while timely surgery and appropriate internal fixation have demonstrated favorable outcomes, attention to intraoperative reduction is crucial. In recent years, there have been further developments in the evaluation of reduction of intertrochanteric fractures, particularly in the anteromedial cortical reduction, and these advances have been further scientifically elucidated in terms of their ability to provide stable fracture reduction and resist loss of reduction. In order to gain a comprehensive understanding of the anteromedial cortex theory, this article reviewed the anatomy, related theoretical progress, and controversies in recent years.

Geriatric proximal femur fracture updates

Proximal femur fractures in the aging population present a variety of challenges. Physiologically, patients incurring this fracture are typically frail, with significant medical comorbidities, yet require early surgical treatment to restore mobility to prevent deterioration. Socioeconomically, the occurrence of a fragility fracture may be the beginning of the loss of independence, and the burdens of rehabilitation and support are borne by the individual patient and health care systems.

Physicomechanical, morphological and tribo-deformation characteristics of lightweight WC/AZ31B Mg-matrix biocomposites for hip joint applications

Exploring high strength materials with a higher concentration of reinforcements in the alloy proves to be a challenging task. This research has explored magnesium-based composites (AZ31B alloy) with tungsten carbide reinforcements, enhancing strength for medical joint replacements via league championship optimisation. The primary objective is to enhance medical joint replacement biomaterials employing magnesium-based composites, emphasising the AZ31B alloy with tungsten carbide reinforcements. The stir casting method is utilised in the manufacture of magnesium matrix composites (MMCs), including varied percentages of tungsten carbide (WC). The mechanical characteristics, such as micro-hardness, tensile strength, and yield strength, have been assessed and compared with computational simulations. The wear studies have been carried out to analyse the tribological behaviour of the composites. Additionally, this study investigates the prediction of stress and the distribution of forces inside bone and joint structures, therefore offering significant contributions to the field of biomedical research. This research contemplates the use of magnesium-based MMCs for the discovery of biomaterials suitable for medical joint replacement. The study focuses on the magnesium alloy AZ31B, with particles ranging in size from 40 to 60 microns used as the matrix material. Moreover, the outcomes have revealed that when combined with MMCs based on AZ31B-magnesium matrix, the WC particle emerges as highly effective reinforcements for the fabrication of lightweight, high-strength biomedical composites. This study uses the league championship optimisation (LCO) approach to identify critical variables impacting the synthesis of Mg MMCs from an AZ31B-based magnesium alloy. The scanning electron microscopy (SEM) images are meticulously analysed to depict the dispersion of WC particulates and the interface among the magnesium (Mg) matrix and WC reinforcement. The SEM analysis has explored the mechanisms underlying particle pull-out, the characteristics of inter-particle zones, and the influence of the AZ31B matrix on the enhancement of the mechanical characteristics of the composites. The application of finite element analysis (FEA) is being used in order to make predictions regarding the distribution of stress and the interactions of forces within the model of the hip joint. This study has compared the physico-mechanical and tribological characteristics of WC to distinct combinations of 0%, 5%, 10% and 15%, and its impact on the performance improvements. SEM analysis has confirmed the findings' improved strength and hardness, particularly when 10%-15% of WC was incorporated. Following the incorporation of 10% of WC particles within Mg-alloy matrix, the outcomes of the study has exhibited enhanced strength and hardness, which furthermore has been evident by utilising SEM analysis. Using ANSYS, structural deformation and stress levels are predicted, along with strength characteristics such as additional hardness of 71 HRC, tensile strength of 140-150 MPa, and yield strength closer to 100-110 MPa. The simulations yield significant insights into the behaviour of the joint under various loading conditions, thus enhancing the study's significance in biomedical environments.

Three-Dimensional Mapping of Medial Wall in Unstable Pertrochanteric Fractures

OBJECTIVE

Unstable pertrochanteric fractures are usually treated with internal fixation, and the integrity of the anteromedial cortex is an important factor for stability and healing. In this study, we described and analyzed the three-dimensional mapping technology and morphological characteristics of pertrochanteric fractures.

METHODS

Fifty-nine pertrochanteric fractures (OTA/AO 2007 types 31A2) were retrospectively reviewed. Computed tomographic (CT) images for all fractures were superimposed on a standard template. Medial wall integrity was analyzed, and three-dimensional fracture maps were created.

RESULTS

Pertrochanteric fractures always have a posterior defect in the medial cortex. The mean width of the defect, in our study, was 21.5 mm (SD: 6.1 mm, range: 10-40 mm), 56.3% (SD: 13.7%, range: 27.5-100%). Bone segments that contact by the anteromedial cortex were 16.5 mm (SD: 5.3 mm, range: 0-29 mm).

CONCLUSION

The integrity of the anteromedial cortex should be considered during internal fixation of femoral trochanteric fractures. These morphological characteristics could be used to form postoperative cortical contact and improve stability of the fixation. Three-dimensional mapping technology can help establish a typical fracture model, thereby improving doctors' understanding of fracture characteristics.

Experimental validation of finite elements model in hip fracture and its clinical applicability

Fracture of the proximal extremity of the femur is the subject of research interest. The complexity of the bone framework and the structural inefficiency associated with ageing leave many variables yet to be understood from an experimental perspective. However, there is no clearly defined structural and biomechanical research model for hip fracture. The hypothesis of this paper is that it is possible to create a computational experimentation model that characterises the bone of the proximal extremity of the femur as a heterogeneous material from directly translating the mechanical parameters obtained from anatomical experimentation specimens.

MATERIAL AND METHOD

An experimental paper comparing real experimentation on cadavers and a numerical model based on finite element analysis (FEA). The variables uses were: the start point of the fracture, propagation of the fracture, progressive load and maximum load until fracture. The real mechanical parameters obtained from the anatomical specimens were translated to the computational model based on the relationship between the Hounsfield units of the high resolution CAT scan and the bone mineral density of each virtual element, whereas the propagation of the fracture was modelled by the research team's own computational design, reducing the mechanical properties of the damaged elements as the fracture line advanced.

RESULTS

The computational model was able to determine the start point of the fracture, with a slight tendency towards anatomical medialisation of this point compared to what happened experimentally. The degree of correlation was very high on comparing the real value of progressive deformation of the samples compared to that obtained by the computational model. Over 32 points analysed, a slope of 1.03 in lineal regression was obtained, with a relative error between the deformations of 16% and a Pearson's coefficient of R²=.99. The computational model slightly underestimated the maximum fracture load, with a relative error of approximately 10%.

CONCLUSION

The FEA computational model developed by this multi-disciplinary research team could be considered, as a whole, a complete FEA model of the proximal extremity of the femur with future clinical applicability since it was able to simulate and imitate the biomechanical behaviour of human femurs contrasted with a traditional experimental model made from anatomical specimens. On this basis, qualitative and quantitative interactions can be assessed which consolidate it as a powerful computational experimentation test bench for the human proximal femur.

Comparison of Outcomes of Intertrochanteric Fracture Fixation Using Percutaneous Compression Plate Between Stable and Unstable Fractures in the Elderly

OBJECTIVES

To evaluate the outcomes of treatment with a percutaneous compression plate (PCCP) in stable and unstable intertrochanteric hip fractures.

DESIGN

Clinical prospective nonrandomized cohort study.

SETTING

San Cecilio University Hospital, Granada (Spain). A tertiary-care hospital.

PATIENTS

Patients older than 65 years undergoing surgery for an intertrochanteric hip fracture (n = 657) were divided according to the OTA/AO classification, into stable (31-A1) (group A, n = 363) and unstable fractures (31-A2) (group B, n = 294).

INTERVENTION

Osteosynthesis with a PCCP (Orthofix Inc).

MAIN OUTCOME MEASUREMENTS

Blood loss, wound complications, postoperative pain, operative and fluoroscopy time, functional outcomes, device-related complications, consolidation time, and mortality.

RESULTS

Patients with unstable fractures were significantly worse with respect to postoperative pain, immediately (P = 0.020), at 6 weeks (P = 0.0001), and at 3 months (P = 0.009), and with respect to independent walking ability at 6 weeks. No other significant differences were observed.

CONCLUSIONS

The outcomes of osteosynthesis with PCCP seem to be equally satisfactory in stable and unstable intertrochanteric fractures, with stable fractures having less pain and a greater ability to walk earlier.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Locked plating versus cephalomedullary nailing of unstable intertrochanteric femur fractures

BACKGROUND

Proximal femur locking plates (PFLP) have received increased attention as an alternative for the treatment of proximal femur fractures. However, recent clinical data on these implants has raised concern about higher than expected failure rates.

QUESTION/PURPOSE

The purpose of the present study was to compare outcomes of unstable pertrochanteric femur fractures (AO/OTA 31A3) treated at a level-1 trauma center using either PFLP or cephalomedullary nailing (CMN).

PATIENTS AND METHODS

Sixty-two patients (31 PFLP and 31 CMN, 55 % female, average age 63 years, range 21-94) with 64 OTA 31A3 fractures (32 PFLP and 32 CMN) treated between 2003 and 2007 were retrospectively reviewed. No differences were found with regard to gender, BMI, diabetes and time to surgery.

RESULTS

One patient (5 %) in the CMN group underwent a reoperation (debridement with hardware removal), while eight PFLP patients (25 %) did (two debridements, two hardware removals, four nonunion repairs). One mechanical failure (5 %) occurred in the CMN group and 12 (38 %) in the PFLP group (p = 0.007). One nonunion (5 %) was observed in the CMN group, while 6 (19 %) occurred in the PFLP group.

CONCLUSION

A higher rate of reoperation and mechanical failure can be expected for unstable intertrochanteric femur fracture when treated with PFLP than with CMN.

Locked minimally invasive plating versus fourth generation nailing in the treatment of AO/OTA 31A2.2 fractures: A biomechanical comparison of PCCP(®) and Intertan nail(®)

INTRODUCTION

Locked minimally invasive plating and fourth generation nailing potentially could reduce the complication rate in the treatment of trochanteric femur fractures by its rotational stability and providing better lateral cortical support. The purpose of this study was (1) to compare the biomechanical properties of the Percutaneous compression plate (PCCP) and the Intertan nail (IT) with regards to implant failure and (2) to assess dynamic stability coefficients in an unstable AO/OTA 31A2.2 fracture model.

METHODS

In paired femurs, a standardised unstable trochanteric femur fracture was induced by an oscillating saw. The fractures were stabilised by either the PCCP (Orthofix, McKinney, TX, USA) or the IT (Smith & Nephew, Memphis, TN, USA). All femurs were loaded with 300N, followed by an increase in load until failure using 300N each time (2000 cycles each, 0.5Hz). After every load step the samples were assessed visually and radiographically. We measured migration and performed a survival analysis.

RESULTS

16 fractures were induced in 8 paired human specimens (mean age: 84 years, 61-100 years). The mean stiffness (PCCP vs. IT: 249±124N/mm vs. 273±153N/mm; p=0.737) was comparable. The IT proved superior to the PCCP with regard to the number of cycles reached before failure occurred (PCCP vs. IT: 12,691±4733 vs. 15,313±4875 cycles; p=0.023). Except for a higher axial migration of the IT at failure point (PCCP vs. IT: 1.3mm vs. 4.3mm; p=0.028) there were no differences between the intra- and extramedullary implants, not even in terms of rotational stability along the femoral neck axis. A fracture of the femoral neck caused test abortion in both implants in most cases.

CONCLUSION

This study showed a superiority of the IT compared with the PCCP with regards to number of cycles achieved under sequential load increases for unstable trochanteric femur fractures. The stiffness was comparable. Both implants showed a high rotational stability and a support of the lateral wall.

STUDY TYPE

Biomechanical study.

Correlation of corrosion and biomechanics in the retrieval of a single modular neck total hip arthroplasty design: modular neck total hip arthroplasty system

Increased modularity of total hip arthroplasty components has occurred, with theoretical advantages and disadvantages. Recent literature indicates the potential for elevated revision rates of modular neck systems and the potential for local pseudotumor and metallosis formation at the modular neck/stem site. Retrieval analysis of one modular neck implant design including SEM (SCANNING ELECTRON MICROSCOPY) assessment was done and correlated with FEA (finite element analysis) as well as clinical features of patient demographics, implant and laboratory analysis. Correlation of the consistent corrosion locations to FEA indicates that the material and design features of this system may result in a biomechanical reason for failure. The stem aspect of the modular neck/stem junction may be at particular risk.

Statistical consequences of using bone mineral density to pair cadaver femurs in comparative ex vivo hip fracture studies

Objective

In ex vivo hip fracture studies femoral pairs are split to create two comparable test groups. When more than two groups are required, or if paired femurs cannot be obtained, group allocation according to bone mineral density (BMD) is sometimes performed. In this statistical experiment we explore how this affects experimental results and sample size considerations.

Methods

In a hip fracture experiment, nine pairs of human cadaver femurs were tested in a paired study design. The femurs were then re-matched according to BMD, creating two new test groups. Intra-pair variance and paired correlations in fixation stability were calculated. A hypothetical power analysis was then performed to explore the required sample size for the two types of group allocation.

Results

The standard deviation (sd) of the mean paired difference in fixation stability increased from 2 mm in donor pairs to 5 mm in BMD-matched pairs. Intra-pair correlation was 0.953 (Pearson’s r) in donor pairs and non-significant at -0.134 (Pearson’s r) in BMD-matched pairs. Required sample size to achieve a statistical power of 0.8 increased from ten pairs using donor pairs to 54 pairs using BMD-matched pairs.

Conclusion

BMD cannot be used to create comparable test groups unless sample size is increased substantially and paired statistics are no longer valid.

Cite this article: Bone Joint Res 2014;3:317–20.

Percutaneous compression plate versus dynamic hip screw for treatment of intertrochanteric Hip fractures: a meta-analyse of five randomized controlled trials

BACKGROUND

Percutaneous compression plating (PCCP) has been advocated to reduce blood loss, relieve pain, and lead to faster rehabilitation for the treatment of intertrochanteric fractures. The purpose of this meta-analysis was to estimate the outcomes and complications of the PCCP versus dynamic hip screw (DHS) fixation for intertrochanteric fractures.

METHODS

All randomized controlled trials (RCT) that compared PCCP with DHS in treating adult patients with intertrochanteric fractures were included. Main outcomes were collected and analysed using the RevMan 5.1 version.

RESULTS

Five trials met the inclusion criteria. Compared with DHS, PCCP had similar operation time (95% CI: -26.01~4.05, P = 0.15), length of hospitalization (95% CI: -1.79~1.25, P = 0.73), mortality (95% CI: 0.37~1.02, P = 0.06), incidence of implant-related complications (95% CI: 0.29~1.82, P = 0.49), and reoperation rate (95% CI: 0.41~3.05, P = 0.83). But blood loss (95% CI: -173.84~-4.81, P = 0.04) and transfusion need (95% CI: -0.53~-0.07, P = 0.01) significantly favored the PCCP.

CONCLUSIONS

The PCCP was associated with reduced blood loss and less transfusion need, but similar to DHS in other respects. Owing to the limitations of this systematic review, more high-quality RCTs are still needed to assess the clinical efficiency of PCCP.

Treatment of AO/OTA 31-A3 intertrochanteric femoral fractures with a percutaneous compression plate

OBJECTIVE

AO/OTA 31-A3 intertrochanteric femoral fractures have completely different fracture line directions and biomechanical characteristics compared with other types of intertrochanteric fractures. The choice of the fixation method has been a focus of dispute among orthopedic trauma surgeons. The purpose of this study was to review the outcomes of these fractures treated with a percutaneous compression plate at our institute.

METHOD

Seventeen patients with AO/OTA 31-A3 intertrochanteric femoral fractures were treated with a percutaneous compression plate at our institute from January 2010 to December 2011. The clinical data and imaging results were retrospectively analyzed.

RESULTS

The medical complication of popliteal vein thrombosis occurred in one patient. Sixteen patients were followed up for 12 to 21 months. Two patients had malunion and mild pain. Fracture collapse occurred in two patients, with one having head penetration. These two patients had moderate pain. There were no occurrences of nonunion or reoperation. The mean Harris hip score obtained during the last follow-up was 84.1 (61-97). Patients with a poor quality of reduction were more likely to have pain results (p = 0.001). A trend existed toward the presence of a poor quality of reduction (p = 0.05) in patients with a collapse of fracture. Patients with poor preoperative mobility were more likely to have a lower Harris hip score (p = 0.000).

CONCLUSION

The percutaneous compression plate is an alternative device for the treatment of AO/OTA 31-A3 intertrochanteric femoral fractures. Good fracture reduction and an ideal placement position of the neck screw are important in the success of the device.

Biomechanical femoral neck fracture experiments--a narrative review

INTRODUCTION

Orthopaedic implants can be introduced in clinical practice if equivalency to an already approved implant can be demonstrated. A preclinical laboratory test can in theory provide the required evidence. Due to the lack of consensus on the optimum design of biomechanical experiments, setups vary considerably. This review aims to make femoral neck fracture models more accessible for evaluation to orthopaedic surgeons without any particular background in biomechanics. Additionally, the clinical relevance of the different setups is discussed.

METHODS

This is a narrative review based on a non-systematic search in PubMed, Scopus and Cochrane.

SUMMARY

Biomechanical femoral neck fracture experiments should aim at optimizing the recreation of the in vivo situation. The bone quality of the experimental femurs should resemble the hip fracture population, hence cadaveric bones should be preferred to the available synthetic replica. The fracture geometry must be carefully selected to avoid bias. The load applied to the specimen should result in forces within the range of in vivo measured values and the magnitude should be related to the actual weight of the donor. A well designed biomechanical experiment can prevent harmful devices from being introduced in clinical practice, however, positive results can never exclude the necessity of subsequent clinical studies.

A biomechanical evaluation of proximal femoral nail antirotation with respect to helical blade position in femoral head: A cadaveric study

OBJECTIVE

Despite new developments in the management of osteoporotic fractures, complications like screw cutout are still found in the fixation of proximal femur fractures even with biomechanically proven better implants like proximal femoral nail antirotation (PFNA). The purpose of this cadaveric study was to investigate the biomechanical stability of this device in relation to two common positions (center-center and inferior-center) of the helical blade in the femoral head in unstable trochanteric fractures.

MATERIALS AND METHODS

Eight pairs of human cadaveric femurs were used; in one group [center-center (C-C) group], the helical blade of PFNA was fixed randomly in central position both in anteroposterior and lateral view, whereas in the other group it was fixed in inferior one-third position in anteroposterior and in central position in lateral view [inferior-center (I-C) group]. Unstable intertrochanteric fracture was created and each specimen was loaded cyclically till load to failure

RESULTS

Angular and rotational displacements were significantly higher within the C-C group compared to the I-C group in both unloaded and loaded condition. Loading to failure was higher in the I-C group compared to the C-C group. No statistical significance was found for this parameter. Correlations between tip apex distance, cyclic loading which lead to femoral head displacement, and ultimate load to failure showed a significant positive relationship.

CONCLUSION

The I-C group was superior to the C-C group and provided better biomechanical stability for angular and rotational displacement. This study would be a stimulus for further experimental studies with larger number specimens and complex loading protocols at multicentres.

Side plate fixation vs. intramedullary nailing in an unstable medial femoral neck fracture model: A comparative biomechanical study

BACKGROUND

The objective of this study was to investigate primary stability of the proximal femoral nailing antirotation for the indication of unstable medial femoral neck fractures. The device was compared to the dynamic hip screw blade, which is a "gold standard" in the treatment of proximal femoral fractures.

METHODS

Six pairs of human cadaver femurs were tested in a cyclic loading model with loads up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. Iliotibial tract was simulated by a chain that applied forces on the greater trochanter during loading. In vitro combined axial and bending loads were applied. Angular displacements during loading were recorded in all directions, and loads to failure were recorded.

FINDINGS

For the cyclic loading test no statistically significant differences between the two groups could be detected. Specimens fixed with the dynamic hip screw blade showed higher displacements in the varus direction at 400 N and 600 N, in the external rotation at 200 N, 400 N and 600 N, and in the anterior direction at 400 N. Load to failure revealed no statistical difference between the two implants.

INTERPRETATION

The proximal femoral nailing antirotation achieves primary stability comparable to the dynamic hip screw blade. The proximal femoral nailing antirotation combines the biomechanical favorable concept of intramedullary fixation with a minimally invasive surgical technique, which theoretically may be advantageous in clinical use. Further biomechanical studies are required to clarify to what extent the results of the present study can be transferred to the clinical situation.

Biomechanical in vitro assessment of fixed angle plating using a new concept of locking for the treatment of osteoporotic proximal humerus fractures

Locked plating attempts to improve mechanical stability via better anchorage of the screws in the bone. In 22 paired osteoporotic humeri an AO/ASIF 11-B 1 fracture was created. Locked and conventional plating using the same device of the latest generation was performed. Torsional loading around three axes (x = varus/valgus, y = flexion/extension, z = axial rotation) with an increasing moment (2, 3.5, 5 and 7.5 N·m) was applied. Interfragmentary motion within the locked group was lower for all three axes with higher cumulative survival rates (p < 0.05). The typical mode of failure was loss of fixation in the humeral head occurring earlier in the conventional group. The locking mechanism investigated provides more ultimate strength in an osteoporotic proximal humerus fracture model. Correlation with BMD suggests that this device may especially be suitable for use in osteoporotic bone.