Dynamic Hip Screw Blade Research Articles

Study of surgical management of trochanteric fracture of the femur with dynamic hip screw

Background: The use of a dynamic hip screw (DHS) for stable trochanteric hip fracture fixation has been successfully applied in fracture healing for more than 20 years. DHS fixation on unstable trochanteric fractures still has a more failure rate, particularly in osteoporosis patients. Thus, this study is aimed to investigate the biomechanical property of the DHS system to provide the lesser trochanter fragment stable fixation. Material and methods: This cross-sectional, observational, and follow-up study was conducted in the Department of Orthopedics, GSL Medical College and General Hospital, Rajamahendravaram with a total of 40 cases of trochanteric fractures. All surgeries were performed under spinal anesthesia. Surgery done was an internal fixation with DHS and 135-degree angled blade plate. Results: Among 40 cases, 32.5% were Type I, and 67.5% were Type II Trochanteric fractures. 40% cases had grade 3 osteoporosis and 30% had grade4-osteoporosis rest of the patients were having grade 2 (20%), grade 5 (7.5%), grade 6 (2.5%) and grade1 (0%), according to Singh’s index. The clinical and functional outcomes of the procedure were excellent in 10 hips (25%), Good in 20 hips (50%), Fair in 6 hips (15%), and 4 (10%) of the patients had poor results. Conclusions: Trochanteric fractures are essentially fractured of the elderly, with osteoporotic bones. The dynamic hip screw is the operative treatment of choice for stable trochanteric fractures.

Evaluation of Dynamic Hip Screw Blade in Extracapsular Fracture Neck of Femur in the Elderly

Evaluation of Dynamic Hip Screw Blade in Extracapsular Fracture Neck of Femur in the Elderly

Cannulated compression screw versus dynamic hip screw-blade in the treatment of femoral neck fractures

Objective To compare the curative effect and biomechanical performance of cannulated compression screw (CCS) and dynamic hip screw-blade (DHS-B) in the treatment of patients with femoral neck fracture.Methods Between February 2010 and February 2014,102 patients with femoral neck fracture were treated with CCS or DHS-B at our department.They were 54 males and 48 females,aged from 15 to 86 years.There were 30 subcapital fractures,51 transcervical ones and 21 base ones.CCS was used in 60 patients and DHS-B in 42.In-hospital data were collected retrospectively to compare the curative effects in 2 groups.Furthermore,femoral neck fracture models were established using 12 adult cadaveric femoral specimens.The 12 models were randomized into 2 equal groups (n =6).Group A was subjected to fixation by 3 CCSs and group B to fixation by DHS-B.The 2 groups were compared in terms of axial loading test,rotation test and destructive axial loading test.Results The operation time (59.4 ± 20.2 min),incision size (4.1 ±0.6 cm) and intraoperative blood loss (25.9 ±9.9 mL) in the CCS group were significantly less than those in the DHS-B group (88.6±22.9 min,12.1 ±1.2cmand 156.7±107.1 mL) (P ＜0.05).The Harris hip score for the DHS-B group (91.9±9.8) was significantly higher than that for the CCS group (87.2 ± 9.2) (P ＜ 0.05).There were no significant differences between the 2 groups in hospital stay,partial weight-bearing time,or postoperative complications (P ＞ 0.05).At 500 N vertical loading,the stress values at both medial and lateral sides of the femur in group A were significantly smaller than those in group B (P ＜ 0.05).There were no significant differences between groups A and B in the average sinking displacement of femoral head or the torque at a torsion angle of 6° (P ＞ 0.05).The maximum load in group A (2,135 ±120 N) was significantly smaller than that in group B (2,986 ± 98 N) (P ＜ 0.05).Conclusion In treatment of femoral neck fracture,DHS-B fixation is obviously superior to CCS fixation,because the former is in better agreement with the femoral biomechanical property,and performs better in anti-rotation and anti-compression,leading to better functional recovery of the affected hip.

Influence of implant design on the method of failure for three implants designed for use in the treatment of intertrochanteric fractures: the dynamic hip screw (DHS), DHS blade and X-BOLT.

The dynamic hip screw (DHS) has been widely adopted as the implant of choice in the treatment of intertrochanteric fractures. There have been attempts over the years to improve on the DHS lag screw design in order to reduce failure in the form of "cut out". The purpose of this study was to investigate how two new design variations of the DHS, the DHS blade and the X-BOLT, behave within bone, and if these design modifications do indeed improve the fixation achieved and lead to a reduction in failure due to cut out. "Pushout" tests were chosen as the means of investigating the failure modes and patterns for these implants that lead to cut out. These pushout studies were performed in artificial bone substrate in the form of polyurethane foam blocks and in cadaveric femoral heads. The results demonstrated that each individual implant produces its own specific distinct force-displacement curve or pattern of failure, and that despite the very different implant designs and methods of fixation, all of the implants tested reached very similar peak forces in each of the test materials used. The results demonstrated that implant design only influences the pattern of failure, and that the peak forces reached by each implant are determined by the quality of the bone or test material into which they are placed. However, altering the force-displacement curve or pattern of failure may be enough to improve the fixation achieved and to provide an increased resistance to cut out.

A Biomechanical Study Comparing Helical Blade with Screw Design for Sliding Hip Fixations of Unstable Intertrochanteric Fractures

Dynamic hip screw (DHS) is a well-established conventional implant for treating intertrochanteric fracture. However, revision surgery sometimes still occurs due to the cutting out of implants. A helical blade instead of threaded screw (DHS blade) was designed to improve the fixation power of the osteoporotic intertrochanteric fracture. In this study, the biomechanical properties of DHS blade compared to the conventional DHS were evaluated using an unstable AO/OTA 31-A2 intertrochanteric fracture model. Fifty synthetic proximal femoral bone models with such configuration were fixed with DHS and DHS blade in five different positions: centre-centre (CC), superior-centre (SC), inferior-center (IC), centre-anterior (CA), and centre-posterior (CP). All models had undergone mechanical compression test, and the vertical and rotational displacements were recorded. The results showed that DHS blade had less vertical or rotational displacement than the conventional DHS in CC, CA, and IC positions. The greatest vertical and rotational displacements were found at CP position in both groups. Overall speaking, DHS blade was superior in resisting vertical or rotational displacement in comparison to conventional DHS, and the centre-posterior position had the poorest performance in both groups.

Dynamic Hip Screw Blade Fixation for Intertrochanteric Hip Fractures

To assess the one-year outcome of a dynamic hip screw (DHS) blade in the treatment of AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures. 35 men and 65 women aged 47 to 100 (mean, 83) years underwent fixation with a DHS blade for A1 (n=47) and A2 (n=53) intertrochanteric hip fractures after a low-energy injury. Patients were operated on within 48 hours of admission. Anteroposterior and lateral radiographs were examined for the tip-apex distance and femoral shortening. Potential complications were looked for, including implant migration, cut-out, loosening, or breakage. Functional outcome was based on the Parker mobility score. The 30-day and one-year mortality rates were 5% and 20%, respectively. At the one-year follow-up, 81 patients were available, and all fractures had healed without varus deformity. The mean tip-apex distance was 14.1 (range, 5.7-31.1; SD, 4.3) mm. The mean femoral shortening was 4.9 (range, 0-20.2; SD, 4.8) mm. The mean Parker score decreased to 3.8 at one-year follow-up from 5.9 before injury (p<0.001). There was one loss of fixation secondary to a non-traumatic subcapital fracture at 3 months, for which a bipolar hemiarthroplasty was performed. CONCLUSION; The DHS blade system is effective in treating AO/OTA 31-A1 and 31-A2 intertrochanteric hip fractures and results in a low complication rate.

Validity of synthetic bone as a substitute for osteoporotic cadaveric femoral heads in mechanical testing

IntroductionThe objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.MethodsPushout studies were performed with the dynamic hip screw (DHS) and the DHS Blade in both cadaveric femoral heads and artificial bone substitutes in the form of polyurethane foam blocks of different density. The pushout studies were performed as a means of comparing the force displacement curves produced by each implant within each material.ResultsThe results demonstrated that test material with a density of 0.16 g/cm3 (block A) produced qualitatively similar force displacement curves for the DHS and qualitatively and quantitatively similar force displacement curves for the DHS Blade, whereas the test material with a density of 0.08 g/cm3 (block B) did not produce results that were predictive of those recorded within the osteoporotic cadaveric femoral heads.ConclusionThis study demonstrates that synthetic material with a density of 0.16 g/cm3 can provide a good substitute for cadaveric osteoporotic femoral heads in the testing of implants. However we do recognise that no synthetic material can be considered as a definitive substitute for bone, therefore studies performed with artificial bone substrates may need to be validated by further testing with a small bone sample in order to produce conclusive results.

Biomechanical Study. The Role of Osteoporotic or Osteoarthritic Bone in Determining the Fixation Achieved Within the Femoral Head by the Lag Screw Elements of the Dynamic Hip Screw (DHS) and DHS Blade

Objective This study was conducted to investigate the fixation that the lag screw elements of two different implants used in the treatment of intertrochanteric fractures achieve within osteoporotic and osteoarthritic femoral heads, as a practical means of comparing the mechanical properties of osteoporotic bone against those of osteoarthritic bone. Methods The lag screw elements of the Dynamic Hip Screw (DHS) and DHS Blade were the two lag screws that were chosen to conduct this study with. “Pushout” tests were performed as the means to investigate the fixation that each lag screw achieved within the femoral heads, as the most common mode of failure with these devices is ‘cut-out’ Results The results demonstrate that the difference in mechanical properties between osteoporotic and osteoarthritic bone in cadaveric femoral heads mean that the devices used in the fixation of intertrochanteric fractures achieve a much greater fixation within osteoarthritic bone. The results also demonstrate that the overall failure patterns were similar for each device within both the osteoporotic and osteoarthritic bone apart from the large difference in forces achieved. Conclusion The results demonstrate, that as expected when the density of the bone increases, in general the implants achieve better fixation within it. However this study also demonstrates that it is the implant that dictates the pattern of failure and not the bone.

Dynamic hip screw versus DHS blade

We biomechanically investigated whether the standard dynamic hip screw (DHS) or the DHS blade achieves better fixation in bone with regard to resistance to pushout, pullout and torsional stability. The experiments were undertaken in an artificial bone substrate in the form of polyurethane foam blocks with predefined mechanical properties. Pushout tests were also repeated in cadaveric femoral heads. The results showed that the DHS blade outperformed the DHS with regard to the two most important characteristics of implant fixation, namely resistance to pushout and rotational stability. We concluded that the DHS blade was the superior implant in this study.

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.

Does cancellous bone compaction due to insertion of a blade implant influence the cut-out resistance? A biomechanical study

Background For the treatment of hip fractures helically shaped implants, like the Dynamic Hip Screw (DHS) Blade, are often used. One consequence of blade implantation, the compaction of cancellous bone, is still believed to increase cut-out resistance. This in vitro study investigates implant anchorage of Dynamic Hip Screw Blades in femoral heads due to insertion with or without predrilling under cyclic physiological loading conditions. Methods Six pairs of fresh frozen (− 20 °C) human cadaveric proximal femora were instrumented with DHS Blades. Bone pairs were randomly assigned to two study groups: 1) predrilled; 2) non-predrilled. Prior instrumentation, bone mineral density was determined in the center of the femoral head by Xtreme-CT measurement. After instrumentation biomechanical testing was performed under cyclic loading. The bone-implant interface was monitored by means of fluoroscopic imaging throughout the experiment. Paired t-tests were performed to identify differences regarding bone mineral density, stiffness and cycles to failure. Findings No significant differences were found between study groups with regard to axial stiffness ( P = 0.626) and number of cycles to failure ( P = 0.961). Interpretation This in vitro study did not show differences in biomechanical stability of proximal femora instrumented with a helical blade implant with or without predrilling. Clinically, the findings suggest that predrilling may be performed to ease the surgical procedure without compromising the implant anchorage.