Biomechanical evaluation of interlocking lag screw design in intramedullary nailing of unstable pertrochanteric fractures

Hip biomechanics in early recovery following fixation of intertrochanteric fractures: Results from a randomised controlled trial

Single and dual integrated screw femoral nails are both commonly used to treat intertrochanteric fractures. This study investigated if using single or dual integrated screw femoral nails result in different post-operative hip joint loading. In the presence of differences, we investigated potential contributing factors. Patients were randomised for treatment via single screw (Stryker, Gamma3) or dual-integrated screw nail (Smith and Nephew, Intertan). Pre-injury mobility levels were collected at enrolment. Hip radiographs and gait data were collected at six weeks (Gamma: 16; Intertan: 15) and six months (Gamma: 14; Intertan: 13) follow-up. The resultant hip joint reaction forces and abductor muscle forces were estimated using electromyography-assisted neuromusculoskeletal modelling during level walking gait. Our primary analysis focused on the resultant hip joint reaction force and abductor muscle forces. We compared between groups, across stance phase of walking gait, using statistical parametric mapping. At six weeks, the Intertan group showed a short (∼5% of stance phase) but substantial (33 % [0.3 × body weight] greater magnitude) resultant hip joint reaction force when compared to the Gamma group (P = 0.022). Higher gluteus medius forces (P = 0.009) were demonstrated in the Intertan group at six weeks. Harris Hip Scores followed the trend seen for the biomechanical outcomes with superior scores for the Intertan group at six weeks postoperative (P = 0.044). The use of dual-integrated screw femoral nails over single screw devices may allow for hip biomechanics more closely resembling normal hip function at earlier post-operative timepoints, but these appear to resolve by six months postoperative.

Biomechanical Research of Three Parallel Cannulated Compression Screws in Oblique Triangle Configuration for Fixation of Femoral Neck Unstable Fractures

OBJECTIVE

Surgical treatment with internal fixation, specifically percutaneous fixation with three cannulated compression screws (CCSs), is the preferred choice for young and middle-aged patients. The mechanical advantage of the optimal spatial configuration with three screws provides maximum dispersion and cortical support. We suspect that the spatial proportion of the oblique triangle configuration (OTC) in the cross-section of the femoral neck isthmus (FNI) may significantly improve shear and fatigue resistance of the fixed structure, thereby stabilizing the internal fixation system in femoral neck fracture (FNF). This study aims to explore the mechanical features of OTC and provide a mechanical basis for its clinical application.

METHODS

Twenty Sawbone femurs were prepared as Pauwels type III FNF models and divided equally into two fixation groups: OTC and inverted equilateral triangle configuration (IETC). Three 7.3 mm diameter cannulated compression screws (CCSs) were used for fixation. The specimens of FNF after screw internal fixation were subjected to static loading and cyclic loading tests, respectively, with five specimens for each test. Axial stiffness, 5 mm failure load, ultimate load, shear displacement, and frontal rotational angle of two fragments were evaluated. In the cyclic loading test, the load sizes were 700 N, 1400 N, and 2100 N, respectively, and the fracture end displacement was recorded. Results were presented as means ± SD. Data with normal distributions were compared by the Student's t test.

RESULTS

In the static loading test, the axial stiffness, ultimate load, shear displacement, and frontal rotational angle of two fragments were (738.64 vs. 620.74) N/mm, (2957.61 vs. 2643.06) N, (4.67 vs. 5.39) mm, and (4.01 vs. 5.52)° (p < 0.05), respectively. Comparison between the femoral head displacement after 10,000 cycles of 700N cyclic loading and total displacement after 20,000 cycles of 700-1400N cyclic loading showed the OTC group was less than the IETC group (p < 0.05). A comparison of femoral head displacement after 10,000 cycles of 1400N and 2100N cycles and total displacement after 30,000 cycles of 700-2100N cycles showed the OTC group was less than another group, but the difference was not significant (p > 0.05).

CONCLUSION

When three CCSs are inserted in parallel to fix FNF, the OTC of three screws has obvious biomechanical advantages, especially in shear resistance and early postoperative weight-bearing, which provides a mechanical basis for clinical selection of ideal spatial configuration for unstable FNF.

Biomechanical evaluation of a new intramedullary nail compared with proximal femoral nail antirotation and InterTAN for the management of femoral intertrochanteric fractures

Purpose: Surgical treatment is the main treatment method for femoral intertrochanteric fractures (FIFs), however, there are lots of implant-related complications after surgery. Our team designed a new intramedullary nail (NIN) to manage such fractures. The purpose of this study was to introduce this new implant and compare it with proximal femoral nail antirotation (PFNA) and InterTAN for treating FIFs. Methods: An AO/OTA 31-A1.3 FIF model was built and three fixation models were created via finite element method, comprising PFNA, InterTAN, and the NIN. Vertical, anteroposterior (A-P) bending, and torsional loads were simulated and applied to the three fixation models. Displacement and stress distribution were monitored. In order to compare PFNA and the NIN deeply, finite element testing was repeated for five times in vertical load case. Results: The finite element analysis (FEA) data indicated that the NIN possessed the most outstanding mechanical properties among the three fixation models. The NIN model had lower maximal stress at implants compared to PFNA and InterTAN models under three load conditions. The trend of maximal stress at bones was similar to that of maximal stress at implants. Besides, the NIN model showed smaller maximal displacement compared with PFNA and InterTAN models under vertical, A-P bending, and torsional load cases. The trend for maximal displacement of fracture surface (MDFS) was almost identical with that of maximal displacement. In addition, there was significant difference between the PFNA and NIN groups in vertical load case (p < 0.05). Conclusion: Compared with PFNA and InterTAN, the NIN displayed the best mechanical properties for managing FIFs, including the lowest von Mises stress at implants and bones, and the smallest maximal displacement and MDFS under vertical, A-P bending, and torsional load cases. Therefore, this study might provide a new choice for patients with FIFs.

Lessons learned from biomechanical studies on cephalomedullary nails for the management of intertrochanteric fractures. A scoping review

INTRODUCTION

The increasing socioeconomic need for optimal treatment of hip fractures in combination with the high diversity of available implants has raised numerous biomechanical questions. This study aims to provide a comprehensive overview of biomechanical research on the treatment of intertrochanteric fractures using cephalomedullary devices.

METHODS

Following the PRISMA-P guidelines, a systematic literature search was performed on 31.12.2022. The databases PubMed/MEDLINE and Web of Science were searched. Scientific papers published between 01.01.2000 - 31.12.2022 were included when they reported data on implant properties related to the biomechanical stability for intertrochanteric fractures. Data extraction was undertaken using a synthesis approach, gathering data on criteria of implants, sample size, fracture type, bone material, and study results.

RESULTS

The initial search identified a total of 1459 research papers, out of which forty-three papers were considered for final analysis. Due to the heterogeneous methods and parameters used in the included studies, meta-analysis was not feasible. A comprehensive assessment of implant characteristics and outcome parameters was conducted through biomechanical analysis. Various factors such as proximal and distal locking, nail diameter and length, fracture model, and bone material were thoroughly evaluated.

CONCLUSION

This scoping review highlights the need for standardization in biomechanical studies on intertrochanteric fractures to ensure reliable and comparable results. Strategies such as avoiding varus, maintaining a sufficient tip-apex-distance, cement augmentation, and optimizing lesser trochanteric osteosynthesis enhance construct stability. Synthetic alternatives may offer advantages over cadaveric bone. Further research and meta-analyses are required to establish standardized protocols and enhance reliability.

Do Long-Segment Blocking Screws Increase the Stability of Intramedullary Nail Fixation in Proximal Tibia Fractures, Eliminating the "Bell-Clapper Effect?"

OBJECTIVES

To determine change in stiffness and horizontal translation of a geriatric extra-articular proximal tibia fracture model after intramedullary nailing with distal (long)-segment blocking screws versus proximal (short)-segment blocking screws.

METHODS

Unstable extra-articular proximal tibia fractures (OTA/AO 41-A3) were created in 12 geriatric cadaveric tibias. Intramedullary nails were locked with a standard construct (4 proximal screws and 2 distal screws). Specimens were then divided into 2 groups (6 matched pairs per group). Group 1 had a blocking screw placed lateral to the nail in the proximal segment (short segment). Group 2 had a blocking screw placed 1 cm distal to the fracture and medial to the nail (long segment). Specimens were then axially loaded and cycled to failure or cycle completion (50,000 cycles).

RESULTS

Long-segment blocking screws significantly decreased the amount of horizontal translation at the fracture site compared with short-segment screws (0.77 vs. 2.0 mm, P = 0.039). They also resulted in a greater trend towards greater baseline stiffness, (807.32 ± 216.95 N/mm vs. 583.12 ± 130.1 N/mm, P = 0.072). There was no difference in stiffness after cyclic loading or survival through 50,000 cycles between the long-segment and short-segment groups.

CONCLUSION

Long-segment blocking screws added to an intramedullary nail construct resulted in decreased horizontal translation at the fracture site compared with short-segment screws in this model of a geriatric proximal tibia fracture.

CLINICAL RELEVANCE

Blocking screws are commonly used to aid in fracture alignment during intramedullary nailing of proximal tibia fractures. Even when not required to attain or maintain alignment, the addition of a blocking screw in either the proximal or the distal (long) segment may help mitigate the "Bell-Clapper Effect" in geriatric patients.

Meta-analysis of InterTan, PFNA and PFNA-II internal fixation for the treatment of unstable intertrochanteric fractures in elderly individuals

Elderly individuals are often affected by osteoporosis and have poor stability after fracture reduction. Moreover, there is still controversy regarding the clinical effects of the treatment for unstable intertrochanteric fractures in the elderly. The Cochrane, Embase, PubMed, and other databases were searched, and a meta-analysis of the literature on the treatment of unstable intertrochanteric fractures of the elderly with InterTan, PFNA, and PFNA-II was conducted. Seven studies were screened, with a total of 1236 patients. Our meta-analysis results show that InterTan is not significantly different from PFNA in terms of operation and fluoroscopy times, but it takes longer than PFNA-II. In terms of postoperative screw cut, pain, femoral shaft fracture, and secondary operations, InterTan is superior to PFNA and PFNA-II. Conversely, in terms of intraoperative blood loss, hospital stay, and postoperative Harris score, there is no significant difference between InterTan and PFNA and PFNA-II. Compared to PFNA and PFNA-II, InterTan internal fixation has advantages in the treatment of unstable intertrochanteric fractures in elderly individuals in terms of screw cutting, femoral shaft fractures, and secondary operations. However, InterTan operation and fluoroscopy times take longer than PFNA and PFNA-II.

Biomechanical analysis analyzing association between bone mineral density and lag screw migration

A proximal femoral nail using a helical blade (HB) is commonly utilized to treat proximal femoral fracture but cut through failure of the lag screws is one of the devastating complications following the surgery. While controversial, one of the potential risk factors for cut through failure is poor bone strength which can be predicted by measuring bone mineral density (BMD). In this study, we performed a biomechanical test on the fractured femoral head to validate whether the indirectly measured BMD from the contralateral hip or that measured directly from the retrieved femoral head can elucidate the structural strength of the fractured femoral head and thereby can be used to predict migration of lag screws. Our result showed that directly measured BMD has a significant correlation with the HB migration on the osteoporotic femoral head. However, while the BMDs measured from the contralateral femoral neck or total hip is the most widely used parameter to predict the bone strength of the fractured femur, this may have limited usability to predict HB migration.

Biomechanical analysis of recently released cephalomedullary nails for trochanteric femoral fracture fixation in a human cadaveric model

BACKGROUND

Recently, two novel concepts for intramedullary nailing of trochanteric fractures using a helical blade or interlocking dual screws have demonstrated advantages as compared to standard single-screw systems. However, these two concepts have not been subjected to a direct biomechanical comparison so far. The aims of this study were to investigate in a human cadaveric model with low bone quality (1) the biomechanical competence of nailing with the use of a helical blade versus interlocking screws, and (2) the effect of cement augmentation on the fixation strength of the helical blade.

METHODS

Twelve osteoporotic and osteopenic human cadaveric femoral pairs were assigned for pairwise implantation using either a short TFN-ADVANCED Proximal Femoral Nailing System (TFNA) with a helical blade head element or a short TRIGEN INTERTAN Intertrochanteric Antegrade Nail (InterTAN) with interlocking screws. Six osteoporotic femora, implanted with TFNA, were augmented with bone cement. Four groups were created: group 1 (TFNA) paired with group 2 (InterTAN), both consisting of osteopenic specimens, and group 3 (TFNA augmented) paired with group 4 (InterTAN), both consisting of osteoporotic specimens. An unstable trochanteric AO/OTA 31-A2.2 fracture was simulated and all specimens were tested until failure under progressively increasing cyclic loading.

RESULTS

Stiffness in group 3 was significantly higher versus group 4, p = 0.03. Varus (°) and femoral head rotation around the femoral neck axis (°) after 10,000 cycles were 1.9 ± 1.0/0.3 ± 0.2 in group 1, 2.2 ± 0.7/0.7 ± 0.4 in group 2, 1.5 ± 1.3/0.3 ± 0.2 in group 3 and 3.5 ± 2.8/0.9 ± 0.6 in group 4, being significantly different between groups 3 and 4, p = 0.04. Cycles to failure and failure load (N) at 5° varus or 10° femoral head rotation around the neck axis in groups 1-4 were 21,428 ± 6020/1571.4 ± 301.0, 20,611 ± 7453/1530.6 ± 372.7, 21,739 ± 4248/1587.0 ± 212.4 and 18,622 ± 6733/1431.1 ± 336.7, being significantly different between groups 3 and 4, p = 0.04.

CONCLUSIONS

Nailing of trochanteric femoral fractures with use of helical blades is comparable to interlocking dual screws fixation in femoral head fragments with low bone quality. Bone cement augmentation of helical blades provides significantly greater fixation strength compared to interlocking screws constructs.

Innovations in orthopaedic trauma: Top advancements of the past two decades and predictions for the next two

The first Trauma and Orthopaedic unit dates back to 1780, originally dedicated to the treatment of children's deformities. The specialty has subsequently become multifaceted, with a plethora of subspecialty areas of which orthopaedic trauma is the most commonly practiced. Recently there has been a significant demand for an evidence base with more than 130,000 of the 162,000 publications in the last century occurring within the past 20 years. This narrative review will summarise some of the more landmark changes within orthopaedic trauma that have been made within the past 20 years, whilst also attempting to predict where the specialty will continue to develop as we move forward.

Benefit of lag screw placement by a single- or two-screw nailing system in elderly patients with AO/OTA 31-A2 trochanteric fractures

Objective

To retrospectively analyze the clinical outcomes of two intramedullary fixation devices, the INTERTAN nail and Gamma3 nail, for treatment of AO/OTA 31-A2 trochanteric fractures in elderly patients.

Methods

In total, 165 elderly patients underwent treatment for AO/OTA 31-A2 trochanteric fractures in our hospital from June 2017 to June 2018 (INTERTAN group, n = 79; Gamma3 group, n = 86). All patients underwent radiological and clinical investigations and were followed up for an average of 12 months. Age, sex, fracture type, surgical time, intraoperative blood loss, fracture healing time, and complications were compared between the two groups.

Results

The surgical time was significantly shorter and the intraoperative blood loss volume was significantly lower in the Gamma3 than INTERTAN group (58.2 ± 2.5 vs. 81.7 ± 14.2 minutes and 170 ± 29 vs. 220 ± 16 mL, respectively). However, there were no significant differences in the reduction quality, hospital stay, fracture healing time, Harris hip score, postoperative complications, or 1-year postoperative mortality.

Conclusion

Both INTERTAN and Gamma3 nails may be effective for surgical treatment of AO/OTA 31-A2 trochanteric fractures in elderly patients. However, the Gamma3 nail was superior to the INTERTAN nail in terms of surgical time and intraoperative blood loss.

The effect of medullary fill on varus collapse in AO 31A3 intertrochanteric (reverse obliquity) fracture treated with cephalomedullary nails

OBJECTIVE

Cephalomedullary nails are tools commonly used for surgical fixation in proximal femoral fractures. The most common complications in their use are varus collapse and screw cutout of the femoral head. The objective of this study is to examine the effects of intramedullary nail movement on varus collapse and screw cutout.

MATERIALS AND METHODS

The study was conducted on 70 composite femur models treated with PFNA. We divided the femurs into 4 groups based on the differences in nail diameter, fracture type and filling of the distal intramedullary area. All femurs were exposed to axial cyclic loading. Each femur was examined in terms of intramedullary nail movement and amount of erosions in femoral medulla [amount of erosion in femoral head (FT distance), amount of erosion in femoral neck (FB distance), amount of erosion in trochanteric major (TB distance) and expansion of trochanter tip (TT distance)].

RESULTS

We found that degree of nail movement in the intramedullary region was inversely correlated with nail diameter and directly correlated with instability of fracture. One of the parameters used to evaluate varus development, FB distance, was affected by the degree of intramedullary nail movement and fracture type. TB distance was affected by nail diameter.

CONCLUSIONS

Nail diameter and fracture type are effective in intramedullary nail movement. Varus collapse progress is accelerated by the increase in nail movement in the intramedullary region. Thus, we conclude that it is important to strengthen diaphyseal adherence, which decreases intramedullary movement of the nail.

LEVEL OF EVIDENCE

III; well-design case control study.

Biomechanical comparison of medial sustainable nail and proximal femoral nail antirotation in the treatment of an unstable intertrochanteric fracture

AIMS

Restoration of proximal medial femoral support is the keystone in the treatment of intertrochanteric fractures. None of the available implants are effective in constructing the medial femoral support. Medial sustainable nail (MSN-II) is a novel cephalomedullary nail designed for this. In this study, biomechanical difference between MSN-II and proximal femoral nail anti-rotation (PFNA-II) was compared to determine whether or not MSN-II can effectively reconstruct the medial femoral support.

METHODS

A total of 36 synthetic femur models with simulated intertrochanteric fractures without medial support (AO/OTA 31-A2.3) were assigned to two groups with 18 specimens each for stabilization with MSN-II or PFNA-II. Each group was further divided into three subgroups of six specimens according to different experimental conditions respectively as follows: axial loading test; static torsional test; and cyclic loading test.

RESULTS

The mean axial stiffness, vertical displacement, and maximum failure load of MSN-II were 258.47 N/mm (SD 42.27), 2.99 mm (SD 0.56), and 4,886 N (SD 525.31), respectively, while those of PFNA-II were 170.28 N/mm (SD 64.63), 4.86 mm (SD 1.66), and 3,870.87 N (SD 552.21), respectively. The mean torsional stiffness and failure torque of MSN-II were 1.72 N m/° (SD 0.61) and 16.54 N m (SD 7.06), respectively, while those of PFNA-II were 0.61 N m/° (SD 0.39) and 6.6 N m (SD 6.65), respectively. The displacement of MSN-II in each cycle point was less than that of PFNA-II in cyclic loading test. Significantly higher stiffness and less displacement were detected in the MSN-II group (p < 0.05).

CONCLUSION

The biomechanical performance of MSN-II was better than that of PFNA-II, suggesting that MSN-II may provide more effective mechanical support in the treatment of unstable intertrochanteric fractures. Cite this article: Bone Joint Res 2020;9(12):840-847.

Biomechanical Comparison of INTERTAN Nail and Gamma3 Nail for Intertrochanteric Fractures

Objective

To compare the biomechanical stabilities of Gamma3 nail and INTERTAN nail (ITN) for stable (AO/OTA 31A1.1) and unstable (AO/OTA 31A2.2) femoral intertrochanteric fracture.

Methods

Twenty‐four synthetic femora were randomly divided into four groups. After internal fixation (Gamma3 nail or ITN) had been implanted, stable and unstable intertrochanteric fracture models were produced. A cyclic testing protocol with increasing loads was performed for both stable and unstable intertrochanteric fracture models, and then torsional test and axial compression failure test were conducted. Stiffness, failure load, torque, and fragment displacement were recorded.

Results

For stable fracture model: fragment displacement in ITN group were smaller than Gamma3 nail group (Gamma3 nail: 1.66 ± 0.13 mm; ITN: 1.55 ± 0.1 mm); stiffness (Gamma3 nail: 1142.6 ± 161.1 N/mm, ITN: 1159.3 ± 203.5 N/mm, P = 0.872) and failure load (Gamma3 nail: 5715.42 ± 616.34 N, ITN: 5690.27 ± 625.59 N, P = 0. 951) of the two nails were similar after cyclic test; torque of the ITN group was larger than the Gamma3 nail group. For unstable fracture model: fragment displacement in ITN group was significantly smaller than in the Gamma3 nail group when the axial load was larger than 800 N (Gamma3 nail: 3.59 ± 0.19 mm; ITN: 2.93 ± 0.28 mm); ITN group showed a significantly higher failure load than Gamma3 nail group (Gamma3 nail: 2942.77 ± 573.4 N, ITN: 3672.3 ± 790.5 N, P = 0. 011); torque was significantly higher for the ITN group compared to the Gamma3 nail group for three different angles.

Conclusions

Both ITN and Gamma3 nail can maintain sufficient biomechanical stability for stable intertrochanteric fractures, but ITN was a better choice for unstable intertrochanteric fractures.

Comparison of clinical outcomes with proximal femoral nail anti-rotation versus InterTAN nail for intertrochanteric femoral fractures: a meta-analysis

Background

A meta-analysis to access the pros and cons of proximal femoral nail anti-rotation (PFNA) versus InterTAN nail for intertrochanteric femoral fractures including available evidence extracted from literature.

Methods

According to the Cochrane systemic analysis method, randomized control trials (RCTs) and retrospective comparative observational studies which were related to the comparison of PFNA and InterTAN nail in the treatment of the elderly with intertrochanteric fractures were retrieved. Data were independently extracted from the included studies by two reviewers and analyzed using RevMan 5.3, and the quality of the studies was assessed.

Results

Two RCTs and seven observational studies were recruited, which consisted of 681 patients with PFNA and 651 patients with InterTAN nail. The meta-analyses showed no significant differences between the two approaches on Harris Hip Score, operation time, blood loss, time to union, mean hospital stay, union problems, intraoperative complications, hematoma, infection, and other complications in both RCTs and observational studies. In terms of other outcomes, for the RCTs, results showed that there were shorter tip–apex distance and reduced pain at thigh or hip in InterTAN nail than in PFNA; however, InterTAN nail was not superior to PFNA in cutout, reoperation, and femoral shaft fracture; for observational studies, the risk of the screw migration (RR = 5.13, 95%CI [1.33,19.75], P = 0.02), cutout (RR = 3.26, 95%CI [1.64,6.47], P = 0.0008), the varus collapse of the femoral head (RR = 7.19, 95%CI [2.18,23.76], P = 0.001), femoral shaft fracture (RR = 5.73, 95%CI [2.24,14.65], P = 0.0003) treated by InterTAN nail were significantly decreased, compared with those by PFNA; however, no significant differences were observed in the aspects of tip–apex distance and pain at thigh or hip between these two groups.

Conclusion

Analysis of a large number of relevant clinical indicators available shows that InterTAN nail has better clinical manifestation than PFNA in treating unstable femoral intertrochanteric fractures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-020-02031-8.

Bio-inspired biomaterial Mg-Zn-Ca: a review of the main mechanical and biological properties of Mg-based alloys

The toxicity of alloying elements in magnesium alloys used for biomedical purposes is an interesting and innovative subject, due to the great technological advances that would result from their application in medical devices (MDs) in traumatology. Recently promising results have been published regarding the rates of degradation and mechanical integrity that can support Mg alloys; this has led to an interest in understanding the toxicological features of these emerging biomaterials. The growing interest of different segments of the MD market has increased the determination of different research groups to clarify the behavior of alloying elements in vivo. This review covers the influence of the alloying elements on the body, the toxicity of the elements in Mg-Zn-Ca, as well as the mechanical properties, degradation, processes of obtaining the alloy, medical approaches and future perspectives on the use of the Mg in the manufacture of MDs for various medical applications.

Proximal Femoral Nail Unlocked versus Locked (ProFNUL): a protocol for a multicentre, parallel-armed randomised controlled trial for the effect of femoral nail mode of lag screw locking and screw configuration in the treatment of intertrochanteric femur fractures

INTRODUCTION

Intertrochanteric fractures are common fragility injuries in the elderly. Surgical fixation using intramedullary devices are one of the widely used management options. To date, evidence demonstrating the effects of lag screw configuration and the mode of lag screw locking in these devices is lacking. The purpose of this study is to investigate whether the lag screw configuration (single vs integrated dual interlocking screw) and the mode of lag screw locking (static vs dynamic) of a femoral nail device result in differences in clinical and functional outcomes.

METHODS AND ANALYSIS

A multicentre, pragmatic, single-blinded randomised controlled trial (RCT) with a three-arm parallel group design is proposed. Nine-hundred patients with intertrochanteric fractures (A1 and A2 AO/OTA) will be randomised to fracture treatment using a Gamma3 nail (Stryker; proximally dynamic) or a Trigen Intertan nail (Smith & Nephew) in a dynamic or static lag screw configuration. The primary outcome measure consists of radiological evidence of construct failure within 6 months following surgery, with failure being defined as breakage of the femoral nail or distal locking screw, a change in tip-apex distance of more than 10 mm or lag screw cut-out through the femoral head. Secondary outcomes include surgical data (operation time, fluoroscopy time), complications (surgical site infection, reoperation, patient death), return to mobility and home circumstances, functional independence, function and pain. Patients who are able to walk independently with or without a mobility aid and are able to answer simple questions and follow instructions will be asked to participate in three dimensional gait analysis at 6 weeks and 6 months to assess hip biomechanics from this cohort. Additional secondary measures of gait speed, hip range of motion, joint contact and muscle forces and gross activity monitoring patterns will be obtained in this subgroup.

ETHICS AND DISSEMINATION

The Central Adelaide Local Health Network Human Research Ethics Committee has approved the protocol for this RCT (HREC/17/RAH/433). The results will be disseminated via peer-reviewed publications and presentations at relevant conferences.

TRIAL REGISTRATION NUMBER

ACTRN12618001431213.

Single screw type of lag screw results higher reoperation rate in the osteosynthesis of basicervical hip fracture

BACKGROUND

Basicervical hip fractures are relatively rare with greater biomechanical instability compared to the other types of hip fractures. Several studies have reported ambivalent surgical outcomes of basicervical hip fractures. The purpose of this multicenter study was to analyze surgical outcomes of basicervical hip fractures according to the fixation type of proximal femur and lag screw type.

METHODS

Among 3220 hip fractures, 145 were classified as basicervical hip fractures. Of those, 106 patients treated with osteosynthesis were included to analyze the surgical complications according to fixation type of proximal femur: sliding hip screw(SHS) and cephalomedullary nail (CMN) groups. Surgical complications including the excessive displacement of fracture and the occurrence of reoperation were evaluated at the final follow up. We further evaluated surgical complications according to lag screw type with subgroup analysis in CMN group: single screw type, blade type and two integrated screw type.

RESULTS

Ten patients (9.4%) sustained surgical complications (5 excessive displacements and 5 reoperations). For fixation type of proximal femur, SHS group showed higher tendency of excessive displacement despite no statistical difference between the two groups (p = 0.060). For lag screw type with subgroup analysis in CMN group, single screw type showed statistically high rates of reoperation compared to the other types of lag screw (p = 0.022).

CONCLUSION

Basicervical hip fractures treated with osteosynthesis resulted to high rates of surgical complications in this study. However, they could be drastically reduced if CMN with blade type or two integrated screw type were used in the osteosynthesis of basicervical hip fractures.

Biomechanics of Osteoporotic Fracture Fixation

PURPOSE OF REVIEW

Fractures of osteoporotic bone in elderly individuals need special attention. This manuscript reviews the current strategies to provide sufficient fracture fixation stability with a particular focus on fractures that frequently occur in elderly individuals with osteoporosis and require full load-bearing capacity, i.e., pelvis, hip, ankle, and peri-implant fractures.

RECENT FINDINGS

Elderly individuals benefit immensely from immediate mobilization after fracture and thus require stable fracture fixation that allows immediate post-operative weight-bearing. However, osteoporotic bone has decreased holding capacity for metallic implants and is thus associated with a considerable fracture fixation failure rate both short term and long term. Modern implant technologies with dedicated modifications provide sufficient mechanical stability to allow immediate weight-bearing for elderly individuals. Depending on fracture location and fracture severity, various options are available to reinforce or augment standard fracture fixation systems. Correct application of the basic principles of fracture fixation and the use of modern implant technologies enables mechanically stable fracture fixation that allows early weight-bearing and results in timely fracture healing even in patients with osteoporosis.

Supplementation of Lateral Locked Plating for Distal Femur Fractures: A Biomechanical Study

OBJECTIVES

To investigate the biomechanical properties of a lateral locked plate alone or in combination with a supplemental medial plate or an intramedullary nail (IMN).

METHODS

Intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C) were simulated with a standardized model in 28 synthetic femora and divided into 4 groups. Group I was instrumented with a 4.5-mm lateral locked distal femoral plate alone, group II with a lateral locked plate plus a low-profile precontoured 3.5-mm medial distal tibial plate, group III with a lateral locked plate plus a medial 3.5-mm reconstruction plate, and group IV with a lateral locked plate plus a retrograde IMN. Specimens were then axially loaded and cycled to failure or runout. Outcomes of interest were baseline stiffness, survivability, and cycles to failure.

RESULTS

Groups III and IV have a significantly higher baseline stiffness (P < 0.001) when compared with groups I and II. Furthermore, groups III and IV had a higher max load to failure (P < 0.01) when compared with groups I and II. The survivability in groups III and IV was 71% and 100%, respectively, while no specimens in group I or II survived maximum loading. There was no significant difference between group III and IV regarding stiffness, survivability, and cycles to failure.

CONCLUSION

When considering fixation for intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C), we found that supplementation of a lateral locked plate with a medial plate or an IMN to be biomechanically superior to lateral locked plating alone regarding stiffness, survivability, and cycles to failure. A low-profile precontoured plate did not add significantly to the construct stiffness in this study.

Is rotation the mode of failure in pertrochanteric fractures fixed with nails? Theoretical approach and illustrative cases

PURPOSE

The present article reviews data from biomechanical and clinical studies which indicate that rotational instability can cause failure of fixation due to the particular characteristics of the fracture, the mechanical properties of the chosen implant or flaws in surgical technique.

METHODS

Although radiographs give a similar impression in failure of fractures fixed with cephalomedullary nails, different mechanisms involving rotation of the femoral head may play a key role.

RESULTS

The incidence of failure in pertrochanteric fracture fixation is decreasing as implants continue to evolve. It is possible that currently reported low failure rates do not apply equally to all subtypes of this diverse group of fractures. Since the introduction of sliding hip screws, "cut-out" due to varus collapse of the proximal fracture fragment has been the only reported mode of failure.

CONCLUSION

Excessive rotation leading to eventual "cut-out" has not been adequately studied, and thus, available evidence is not sufficient to definitely prove this theoretical approach. As nailing is gradually overtaking extramedullary fixation as the treatment of choice, especially for comminuted pertrochanteric fractures which can be rotationally unstable, further research is warranted to improve our understanding of the pathogenetic mechanisms of failure.

Migration of the Lag Screw after Intramedullary Treatment of AO/OTA 31.A2.1-3 Pertrochanteric Fractures Does Not Result in Higher Incidence of Cut-Outs, Regardless of Which Implant Was Used: A Comparison of Gamma Nail with and without U-Blade (RC) Lag Screw and Proximal Femur Nail Antirotation (PFNA)

The best intramedullary nail for the treatment of unstable AO/OTA 31.A2.1-3 fractures remains uncertain. A total of 237 patients (45 male, 192 female) were eligible for the assessment with an average age of 81.9 ± 10.5 years and a minimum follow-up of six months. We assessed the cut-out rate, the TAD and calTAD (Tip Apex distance) of three different implants. An overall cut-out rate of 2.5% (n = 6) was observed. The cut-out rate was 1.2% (n = 1) in the Proximal Femur Nail Antirotation (PFNA) group, 3.7% (n = 3) in the Gamma Nail group and 2.9% (n = 2) in the Gamma3^® with a U-Blade (RC) lag-screw group. The TAD and calTAD differed between the cut-out and non-cut group-20.0 mm vs. 18.5 mm and 13.1 mm vs. 15.3 mm, respectively. A significantly higher TAD of 32.5 mm could be seen in the cut-out after PFNA (p < 0.0001). The only significant change in follow-up using Parker's ratio was observed in the PFNA group (p < 0.0001). The rate of patients requiring surgery after complications was 8.4% (n = 20) without any significant difference between the three groups. The PFNA blade showed significant migration within the femoral head, however the cut-out rate remained the smallest compared to Gamma3 with or without additional U-Blade (RC) lag screw.

Clustering of morphological fracture lines for identifying intertrochanteric fracture classification with Hausdorff distance-based K-means approach

OBJECTIVES

The aim of this study was to develop a systematic three-dimensional (3D) classification of intertrochanteric fractures by clustering the morphological features of fracture lines using the Hausdorff distance-based K-means approach and assess the usefulness of it in the clinical setting.

METHODS

We retrospectively analyzed the data of 504 patients with intertrochanteric fractures who underwent closed reduction and intramedullary internal fixation. The morphological fracture lines of all patients extracted from computed tomography were transcribed freehand onto the template. All fracture lines were then clustered into five distinct types using the Hausdorff distance-based K-means clustering method. Five radiographic parameters and four functional parameters were used to evaluate the postoperative functional states and mobilization levels. Postoperative complications were also recorded.

RESULTS

Intertrochanteric fractures were classified into five types: type I (108/504, 21.4%), simple fracture with intact lateral femoral wall and greater trochanter fragment; type II (85/504, 16.9%), simple fracture with intact lateral femoral wall with/without lesser trochanter detachment; type III (147/504, 29.2%), fractures with intertrochanteric crest detachment involving the lesser trochanter and greater trochanter with an intact lateral femoral wall; type IV (113/504, 22.4%), fractures with large intertrochanteric crest detachment and large lesser trochanter and greater trochanter detachment partially involving the lateral femoral wall and less medial cortical support; type V (51/504, 10.1%), a combination of pertrochanteric and lateral fracture line involving the entire lateral femoral wall and lesser trochanter detachment. Parameters of femoral neck-shaft angle and sliding distance of the cephalic nail were significantly different among types. The complication rate generally increased from type I to type V (P = 0.035).

CONCLUSIONS

The unsupervised clustering can achieve identification of the type of intertrochanteric fractures with clinical significance. The Tang classification can be used to describe fracture morphology, predict the possibility of achieving stable reduction and the risk of complications following intramedullary fixation.

Medial sustainable nail versus proximal femoral nail antirotation in treating AO/OTA 31-A2.3 fractures: Finite element analysis and biomechanical evaluation

OBJECTIVES

Using finite element analysis and biomechanical tests, the biomechanical behaviors of Medial Sustainable Nail (MSN) and Proximal Femoral Nail Antirotation (PFNA) were compared for the fixation of fracture type of AO/OTA 31-A2.3.

METHODS

Finite element software Abaqus 6.14 was used to conduct axial loading of 2100 N and we analyzed the von Mises stress distribution and the model displacement of two implant models. Biomechanical tests were separately conducted in the axial stiffness test and axial cyclical loading test on a mechanical testing machine.

RESULTS

The results indicate that von Mises stress of MSN was lower than that of PFNA, and the model displacement in the MSN group was lower than that in the PFNA group. In the axial stiffness tests, MSN group was stiffer than PFNA construct. With respect to the axial load to ultimate failure, the PFNA construct exhibited higher loads exceeding 4000 N while the MSN construct withstood 3313.8 ± 92.8 N. Specifically, F_10mm was 2178.6 ± 133.2 N of the MSN group and 1822.6 ± 93.1 N of the PFNA group (P = 0.001). Additionally, X_2100N was 9.8 ± 0.5 mm of the MSN group and 11.7 ± 0.7 mm of the PFNA group (P = 0.002). The MSN group exhibited superior performances in terms of the mean value of the vertical displacement, frontal rotation angle, and lateral rotation angle.

CONCLUSIONS

The results indicated that the MSN construct might exhibit a better biomechanical performance when compared with that of the PFNA in reducing displacement and anti-varus in fracture type of AO/OTA 31-A2.3.

Biomechanical Investigation of an Integrated 2-Screw Cephalomedullary Nail Versus a Sliding Hip Screw in Unstable Intertrochanteric Fractures

OBJECTIVE

To compare the efficacy of 2 intertrochanteric (IT) fracture fixation devices in conferring mechanical stability to unstable IT femur fractures.

METHODS

Nine pairs of cadaveric female femurs with a groupwise average bone quality indicative of osteopenia were used. An unstable IT fracture without calcar support (OTA/AO 31-A2) was created and stabilized with either a sliding hip screw and side plate (SHS) or a cephalomedullary nail using an integrated dual-screw fixation [InterTAN (ITN)]. Constructs were evaluated under stepwise and increasing cyclic loading up to 50,000 cycles (1500 N) or by failure in a test model that may best simulate hip joint contact forces at heel strike. Number of cycles to failure, failure load, and femoral head rotation about the screw axis were compared between groups.

RESULTS

The average number of cycles in the ITN group was greater compared with that in the SHS group (48,383 vs. 31,403 cycles, P = 0.046). Similarly, the average maximum load survived by the ITN group was greater than that of the SHS group (1456 vs. 1113 N, P = 0.046). The number of constructs that survived up to the maximum applied load of 1500 N was greater in the ITN group (8/9, 89%) when compared with that of the SHS constructs (3/9, 33%) (P = 0.049). Finally, the ITN group conferred greater rotational control of the femoral head compared with the SHS constructs (1.5 vs. 5.5 degrees, P = 0.018), and reduced the amount of varus collapse (11.1 vs. 31.1 degrees, P = 0.038).

CONCLUSIONS

The integrated dual-screw construct appeared to confer significantly greater fracture stability compared with a sliding hip screw and side plate using a worst-case model that simulates heel strike during gait. Study data provide biomechanical evidence that the ITN device may provide more stability and rotational resistance than a sliding hip screw in the elderly female patient population with an unstable IT fracture and compromised bone quality.

Long Segment Blocking Screws Increase the Stability of Retrograde Nail Fixation in Geriatric Supracondylar Femur Fractures: Eliminating the "Bell-Clapper Effect"

OBJECTIVES

To determine the change in stiffness and horizontal translations of a geriatric supracondylar femur fracture model with the addition of distal segment blocking screws versus proximal (long) segment blocking screws to the standard retrograde intramedullary nail construct.

METHODS

Unstable supracondylar femur fractures (OTA/AO 33-A3) were created; all specimens were instrumented with a retrograde intramedullary nail. Specimens were divided into 2 groups (6 matched pairs per group). Group 1 compared the standard construct (1 proximal screw and 3 distal screws) to a distally augmented construct, with blocking screws placed in the distal metaphyseal segment. Group 2 compared the distally augmented construct to one in which blocking screws were placed just proximal to the fracture (long segment blocking screws). Specimens were then axially loaded and cycled to failure or run-out.

RESULTS

There was no significant difference in baseline stiffness, survival through cyclic loading, stiffness after cyclic loading, or cycles to failure between femurs treated with distal blocking screws and femurs treated without blocking screws (group 1). Femurs with blocking screws in the long proximal segment had significantly greater baseline stiffness, stiffness after cyclic loading, and less horizontal translation at the fracture site (group 2). There was no difference in survival through cyclic loading or cycles to failure.

CONCLUSION

Long segment blocking screws are biomechanically superior to blocking screws in the distal segment or no blocking screws initially and after cyclic loading in an unstable geriatric supracondylar femur fracture model treated with intramedullary nail.

CLINICAL RELEVANCE

Surgeons may use blocking screws to aid in fracture alignment during retrograde nail fixation. In addition, the placement of long segment blocking screws can help resist failure of fixation in geriatric patients by eliminating the "Bell-clapper effect."

Helical Blade or the Integrated Lag Screws: A Matched Pair Analysis of 100 Patients With Unstable Trochanteric Fractures

OBJECTIVES

To compare the radiological and clinical results with PFNA-II and InterTan in the treatment of unstable trochanteric fractures in the elderly.

DESIGN

Retrospective, multicenter, matched pair.

SETTING

Three tertiary level trauma centers.

PATIENTS

Hundred elderly patients who underwent intramedullary stabilization with either the PFNA-II or the InterTan for osteoporotic unstable trochanteric fractures.

INTERVENTIONS

Fifty matched pairs consisting of OTA/AO-A2 and A3 fractures were created from a cohort of 290 patients who underwent internal fixation for unstable trochanteric fractures with the PFNA-II or InterTan nails.

OUTCOME MEASUREMENTS

Radiological assessment was performed to compare union rates, varus collapse, medial or lateral screw/blade migration, and cut-out. Functional outcome at 1 year was assessed and compared using Harris hip score, Timed Up and Go test, and the mobility score.

RESULTS

Union rates, fracture reduction, neck shaft angle, and tip-apex distance were similar in both groups. The PFNA-II group had a significantly higher degree of lateral sliding of the helical blade (P < 0.001). The InterTan group had a better Harris hip score, mobility score, Timed Up and Go test scores, and abductor strength (P < 0.05) at 1 year. The incidence of varus collapse and medial blade migration were higher in the PFNA-II group (P > 0.05). The need for repeat surgery to address surgery-related complications were significantly high in the PFNA-II group (P = 0.045).

CONCLUSIONS

The InterTan may provide superior functional outcome and reduced complications than does the Proximal Femur Nail - Antirotation in elderly patients with unstable trochanteric fractures.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Clinical analysis of peri-operative hidden blood loss of elderly patients with intertrochanteric fractures treated by unreamed proximal femoral nail anti-rotation

The purpose of this study was to quantify the peri-operative blood loss of elderly patients with intertrochanteric fractures treated by unreamed proximal femoral nail anti-rotation (PFNA) and analyze whether the substantial hidden blood loss was induced by initial trauma or the operation. The clinical data of 123 patients with intertrochanteric fracture treated with unreamed PFNA from Jan 2013 to Apr 2017 were analyzed retrospectively. Blood routine on admission day (ADM), pre-operative day one (PRE), post-operative days one and three (POD1 and POD3) and the visible blood loss (VBL) were obtained. The total blood loss (TBL) from ADM to POD1 and POD3 were 693.5 ± 359.6 ml and 863.8 ± 429.9 ml, of which the corresponding hidden blood loss (HBL) was 86.8% and 89.4% respectively. The mean TBL and HBL from ADM to PRE (375.5 ± 242.0 ml, 375.5 ± 242.0 ml) were higher than that from PRE to POD1 (318.0 ± 183.4 ml, 226.5 ± 163.2 ml), p < 0.001 respectively. There was no significant difference between HBL from ADM to PRE and HBL from PRE to POD3 (375.5 ± 242.0 ml, 396.7 ± 254.0 ml, p = 0.361). The majority of peri-operative HBL occurred before surgery, it was mainly associated with the initial trauma rather than the operation.

Cephalomedullary Nail Fixation of Intertrochanteric Femur Fractures: Are Two Proximal Screws Better Than One?

OBJECTIVES

To analyze radiographic changes in intertrochanteric (IT) fracture alignment after treatment with either a single sliding lag screw or an integrated compressed and locked, dual screw, cephalomedullary nail construct.

DESIGN

Retrospective comparative study.

SETTING

Level 1 regional trauma center.

PATIENTS

1004 OTA/AO 31A, 31B2.1 fractures treated with either a single screw cephalomedullary nail (Gamma 3) or an integrated dual screw cephalomedullary nail (InterTAN) between February 1, 2005, and June 30, 2013. Four hundred thirteen remained after exclusion criteria; 130 were treated with a single screw device (79 stable and 51 unstable), and 283 with an integrated dual screw device (155 stable and 128 unstable).

INTERVENTION

Cephalomedullary nail insertion.

OUTCOME MEASURES

Radiographic analysis included fracture pattern, fracture reduction, neck-shaft angle (NSA), and femoral neck shortening (FNS) differences at 3, 6, and 12 months. Measurements were normalized using known lag screw dimensions, digitally corrected for magnification. Rotation between x-rays was controlled using a ratio of known to measured dimensions. The Mann-Whitney U test was used for statistical analysis.

RESULTS

The single screw device resulted in 2.5 times more varus collapse (NSA) and 2 times more FNS over 1 year, as compared to the locked, integrated dual screw device, regardless of stability (P < 0.001). NSA and FNS changes were greater for both devices in unstable fracture patterns, but significantly less movement occurred with the dual screw device (P < 0.001).

CONCLUSIONS

A cephalomedullary nail with 2 integrated proximal screws that can be compressed and then locked seems to maintain initial IT fracture reduction and subsequent position over time, with less varus collapse and less shortening than a single screw device.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Screw-blade fixation systems in Pauwels three femoral neck fractures: a biomechanical evaluation

OBJECTIVES

To reduce mechanical complications after osteosynthesis of femoral neck fractures, improved fixation techniques have been developed including blade or screw-anchor devices. This biomechanical study compares different fixation systems used for treatment of unstable femoral neck fractures with evaluation of failure mode, load to failure, stiffness, femoral head rotation, femoral neck shortening and femoral head migration.

METHODS

Standardized Pauwels type 3 fractures (AO/OTA 31-B2) with comminution were created in 18 biomechanical sawbones using a custom-made sawguide. Fractures were stabilized using either SHS-Screw, SHS-Blade or Rotationally Stable Screw-Anchor (RoSA). Femurs were positioned in 25 degrees adduction and ten degrees posterior flexion and were cyclically loaded with an axial sinusoidal loading pattern of 0.5 Hz, starting with 300 N, with an increase by 300 N every 2000 cycles until bone-implant failure occurred.

RESULTS

Mean failure load for the Screw-Anchor fixation (RoSA) was 5100 N (IQR 750 N), 3900 N (IQR 75 N) for SHS-Blade and 3000 N (IQR 675 N; p = 0.002) for SHS-Screw. For SHS-Screw and SHS-Blade we observed fracture displacement with consecutive fracture collapse as the main reason for failure, whereas RoSA mainly showed a cut-out under high loadings. Mean stiffness at 1800 N was 826 (IQR 431) N/mm for SHS-Screw, 1328 (IQR 441) N/mm for SHS-Blade and 1953 (IQR 617) N/mm for RoSA (p = 0.003). With a load of 1800 N (SHS-Screw 12° vs. SHS-Blade 7° vs. RoSA 2°; p = 0.003) and with 2700 N (24° vs. 15° vs. 3°; p = 0.002) the RoSA implants demonstrated a higher rotational stability and had the lowest femoral neck shortening (p = 0.002), compared with the SHS groups. At the 2700 N load point, RoSA systems showed a lower axial (p = 0.019) and cranial (p = 0.031) femoral head migration compared to the SHS-Screw.

CONCLUSIONS

In our study, the new Screw-Anchor fixation (RoSA) was superior to the comparable SHS implants regarding rotational stability and femoral neck shortening. Failure load, stiffness, femoral head migration, and resistance to fracture displacement were in RoSA implants higher than in SHS-Screws, but without significance in comparison to SHS-Blades.

Controversies in Intramedullary Fixation for Intertrochanteric Hip Fractures

Intertrochanteric hip fractures are common and costly. Intramedullary fixation has gained popularity as a means of stabilizing intertrochanteric hip fractures. This review article presents some of the controversies surrounding the treatment of intertrochanteric fractures using a cephalomedullary nail. These topics include nail length, the need for distal interlocking, proximal screw design, the number of proximal lag screws, and integrated proximal sliding lag screws.

LEVEL OF EVIDENCE

Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

The visible and hidden blood loss of Asia proximal femoral nail anti-rotation and dynamic hip screw in the treatment of intertrochanteric fractures of elderly high- risk patients: a retrospective comparative study with a minimum 3 years of follow-up

Background

The purpose of this study was to evaluate whether PFNA-II (Asia proximal femoral nail anti-rotation) and DHS (dynamic hip screw) carry substantial post-operative hidden blood loss and to compare PFNA-II with DHS in terms of post-operative hidden blood loss in elderly high-risk patients with intertrochanteric femur fractures(IFFs).

Methods

The clinical data from Jan 2005 to Apr 2015 of 186 patients with PFNA-II and 177 patients with DHS were analyzed retrospectively. Indexes including pre- and post-operative blood routine, intra- and post-operative blood loss and blood transfusion situation were analyzed. The situation of perioperative blood loss (visible and hidden) was assessed.

Results

The intra-operative blood loss in the PFNA-II group was 34.7 ± 2.5 ml, the post-operative visible blood loss was 54.7 ± 2.5 ml, and the hidden blood loss was 277.2 ± 7.6 ml. In the DHS group, the intra-operative blood loss was 102.0 ± 7.0 ml, the post-operative visible blood loss was 78.8 ± 4.7 ml, and the hidden blood loss was 139.3 ± 9.6 ml. The intra-operative blood loss and the post-operative visible blood loss in the PFNA-II group were significantly less than in the DHS group (p < 0.01). However, the post-operative hidden blood loss and the total blood loss in the PFNA-II group were larger than in the DHS group (p < 0.01).

Conclusion

This study demonstrated that with PFNA-II and DHS, much post-operative hidden blood loss exists in the treatment of intertrochanteric fractures in elderly high-risk patients and DHS is more favourable than PFNA-II in terms of post-operative hidden blood loss.

Failure of fracture fixation in osteoporotic bone

This manuscript will provide an overview of how the age and osteoporosis related changes in mechanical properties of bone affect the stability of osteosynthesis constructs, both from a mechanical as well as from a clinical perspective. The manuscript will also address some of the principles of fracture fixation for osteoporotic fractures and discuss applications of osteoporotic fracture fixation at sites typically affected by fragility fractures, namely the distal radius, the proximal humerus, the femur and the spine. The primary aim of operative treatment in elderly individuals is the avoidance of immobilization of the patient. In selected cases conservative treatment might be required. Generally, choice of treatment should be individualized and based on the evaluation of patient-specific, fracture-specific and surgeon-specific aspects. The orthopaedic surgeon plays an essential role in enabling functional recovery by providing good surgery but a multidisciplinary approach is essential in order to support the patient to regain his/her quality of life after fragility fracture. Overall, the therapy of fractures in osteoporotic bone in the elderly requires a multidisciplinary therapeutic acute care concept including treatment of co-morbidities and correct choice of timing, and technique of the operative intervention.

Comparison of Femoral Head Rotation and Varus Collapse Between a Single Lag Screw and Integrated Dual Screw Intertrochanteric Hip Fracture Fixation Device Using a Cadaveric Hemi-Pelvis Biomechanical Model

OBJECTIVE

This study compared the stabilizing effect of 2 intertrochanteric (IT) fracture fixation devices in a cadaveric hemi-pelvis biomechanical model.

METHODS

Eleven pairs of cadaveric osteopenic female hemi-pelves with intact hip joint and capsular ligaments were used. An unstable IT fracture (OTA 31-A2) was created in each specimen and stabilized with a single lag screw device (Gamma 3) or an integrated dual screw (IDS) device (InterTAN). The hemi-pelves were inverted, coupled to a biaxial apparatus and subjected to 13.5 k cycles of loading (3 months) using controlled, oscillating pelvic rotation (0-90 degrees) plus cyclic axial femoral loading at a 2:1 body weight (BW) ratio. Femoral head rotation and varus collapse were monitored optoelectonically. For specimens surviving 3 months of loading, additional loading was performed in 0.25 × BW/250 cycle increments to a maximum of 4 × BW or failure.

RESULTS

Femoral head rotation with IDS fixation was significantly less than the single lag screw construct after 3 months of simulated loading (P = 0.016). Maximum femoral head rotation at the end of 4 × BW loading was 7× less for the IDS construct (P = 0.006). Varus collapse was significantly less with the IDS construct over the entire loading cycle (P = 0.021).

CONCLUSIONS

In this worst-case model of an osteopenic, unstable, IT fracture, the IDS construct, likely owing to its larger surface area, noncylindrical profile, and fracture compression, provided significantly greater stability and resistance to femoral head rotation and varus collapse.

A retrospective analysis of the InterTan nail and proximal femoral nail anti-rotation-Asia in the treatment of unstable intertrochanteric femur fractures in the elderly

BACKGROUND

The purpose of this study was to compare the clinical outcomes of elderly patients undergoing surgery for treatment of unstable trochanteric fractures receiving either proximal femoral nails anti-rotation-Asia (PFNA-IIs) or InterTan nails (ITs).

METHODS

Between January 1, 2012, and June 31, 2015, 168 elderly patients with unstable intertrochanteric femur fractures enrolled in this study. The only intervention was ITs or PFNA-IIs of the unstable trochanteric femur fractures. Follow-up was at 1, 3, 6, and 12 months postoperatively and yearly thereafter. Intraoperative variables and postoperative complications were compared between the two groups.

RESULTS

Eight patients died, six were too infirmed for follow-up, and seven were lost during follow-up, leaving 147 patients meeting the criteria were evaluated at a mean follow-up of 20 months (range 16-26 months). Significant differences were observed between the two groups regarding local complications (IT, n = 10 vs. PFNA-II, n = 20), varus collapse of the head/neck or femoral shaft fractures at the tip of the nail (IT, n = 1 vs. PFNA-II, n = 8), femoral neck shortening (IT, 4.4 ± 1.1 mm vs. PFNA-II, 7.4 ± 2.4 mm), fracture healing time (IT, 14.7 ± 2.1 weeks vs. PFNA-II, 15.7 ± 2.4 weeks), femoral shaft fractures (IT, n = 0 vs. PFNA-II, n = 4), rotational loss of reduction (IT, n = 0 vs. PFNA-II, n = 9), lateral cortex fractures of the proximal femur or lateral greater trochanter fractures (IT, n = 8 vs. PFNA-II, n = 1), operative time (IT, 71.9 ± 6.8 min vs. PFNA-II, 52.3 ± 4.0 min), intraoperative blood loss (IT, 190.6 ± 6.0 mL vs. PFNA-II, 180.9 ± 10.8 mL), fluoroscopy time (IT, 5.0 ± 0.48 min vs. PFNA-II, 2.8 ± 0.33 min), hospital stay (IT, 9.65 ± 0.95 days vs. PFNA-II, 8.58 ± 0.93 days), cut-out (IT, n = 0 vs. PFNA-II, n = 6), and tip-apex distance (IT, 26.7 ± 0.91 mm vs. PFNA-II, 23.2 ± 1.22 mm). No significant differences existed for the other observation indexes (p > 0.05).

CONCLUSIONS

The IT nail may have more advantage for patients with unstable intertrochanteric fractures of the femur. However, for those complicated with lateral greater trochanter fractures, lateral cortex fractures of the proximal femurs, or unfit for surgery, the PFNA-II nail could be a good option. In addition, a large-sample, multicenter observational study is required for evaluation of its long-term efficacy, and optimal management strategies for specific unstable fracture patterns, different sorts of bone quality, and different levels of patient demand.

Rotationally Stable Screw-Anchor With Locked Trochanteric Stabilizing Plate Versus Proximal Femoral Nail Antirotation in the Treatment of AO/OTA 31A2.2 Fracture: A Biomechanical Evaluation

OBJECTIVES

Third-generation cephalomedullary nails currently represent the gold standard in the treatment of unstable trochanteric femur fractures. Recently, an extramedullary rotationally stable screw-anchor system (RoSA) has been developed. It was designed to combine the benefits of screw and blade and to improve stability using a locked trochanteric stabilizing plate (TSP). The purpose of this study was to compare the biomechanical behavior of RoSA/TSP and the proximal femoral nail antirotation (PFNA).

METHODS

Standardized AO/OTA 31A2.2 fractures were induced by an oscillating saw in 10 paired human specimens (n = 20; mean age = 85 years; range: 71-96 years). The fractures were stabilized by either the RoSA/TSP (Koenigsee Implants, Allendorf, Germany) or the PFNA (DePuy Synthes, Zuchwil, Switzerland). Femurs were positioned in 25 degrees of adduction and 10 degrees of posterior flexion and were cyclically loaded with axial sinusoidal pattern at 0.5 Hz, starting at 300 N, with stepwise increase by 300 N every 500 cycles until bone-implant failure occurred. After every load step, the samples were measured visually and radiographically. Femoral head migration was assessed.

RESULTS

The stiffness at the load up to the clinically relevant load step of 1800 N (639 ± 378 N/mm (RoSA/TSP) vs. 673 ± 227 N/mm (PFNA); P = 0.542) was comparable, as was the failure load (3000 ± 787 N vs. 3780 ± 874 N; P = 0.059). Up to 1800 N, no femoral head rotation, head migration, or femoral neck shortening were observed either for RoSA/TSP or PFNA. Whereas failure of the PFNA subsumed fractures of the greater trochanter and the lateral wall, a posterior femoral neck fracture with a significantly increased femoral neck shortening (1.7 mm vs. 0 mm; P = 0.012) was the cause of failure with RoSA/TSP. This specific kind of failure was induced by a femoral neck weakening caused by the posterior TSP stabilizing screw.

CONCLUSIONS

There was no significant difference in biomechanical properties between the RoSA/TSP and the PFNA for the fracture pattern tested. However, failure modes differed between the 2 implants with greater femoral neck shortening observed in the RoSA/TSP group.

Hot Topics in Biomechanics: Hip Fracture Fixation

Geriatric hip fractures continue to increase in frequency as the population ages, and intertrochanteric femur fractures are a significant part of these injuries. Plate fixation for intertrochanteric fractures of the proximal femur has been in use for many years, and application of the sliding hip screw has also been a mainstay of treatment. Recent data suggest there may be a benefit to using implants that add rotational stability to the proximal intertrochanteric fragment. Although preliminary data are promising, there is need for improved investigation to demonstrate the benefit of these new implant designs. In this era of increasing emphasis on cost, quality, and value, better data are needed to help clinicians determine the best therapy for their patients.

What is the underlying mechanism for the failure mode observed in the proximal femoral locking compression plate? A biomechanical study

PURPOSE

Recently, several cases of clinical failure have been reported for the Proximal Femoral Locking Compression Plate (PF-LCP). The current study was designed to explore biomechanically the underlying mechanism and to determine whether the observed failure was due to technical error on insertion or to implant design.

METHODS

A foam block model simulating an unstable intertrochanteric fracture was created for 3 study groups with 6 specimens each. Group C was correctly instrumented according to the manufacturer's guidelines. In Group P and Group A, the first or second proximal screw was placed with a posterior or anterior off-axis orientation by 2° measured in the transversal plane, respectively. Each construct was cyclically tested until failure using a test setup and protocol simulating complex axial and torsional loading. Radiographs were taken prior to and after the tests. Force, number of cycles to failure and failure mode were compared.

RESULTS

A screw deviation of 2° from the nominal axis led to significantly earlier construct failure in Group P and Group A in comparison to Group C. The failure mode was characterised by loosening of the off-axis screw due to disengagement with the plate, resulting in loss of construct stiffness and varus collapse of the fracture.

CONCLUSIONS

In our biomechanical test setup, the clinical failure modes observed with the PF-LCP were reproducible. A screw deviation of 2° from the nominal axis consistently led to the failure. This highlights how crucial is the accurate placement of locking screws in the proximal femur.

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.

Intramedullary nailing in pertrochanteric fractures of the proximal femur

INTRODUCTION

Pertrochanteric fractures of the proximal femur should be treated surgically, unless the medical condition of the patient does not allow it. Currently, there are two ways to fix these fractures; either with a sliding hip screw or with an intramedullary nail. However, there is much debate over which implant is the best for pertrochanteric fracture fixation. The sliding hip screw has been used over time with good clinical results. While it was true that with first generation intramedullary nails the risk of complications was higher, there is evidence supporting the superiority of intramedullary nails in these fractures when compared with sliding hip screws. This evidence is based on the good clinical results and fewer complications, due to an improvement in the design of the implants and surgical technique used by surgeons. In stable fractures, despite the method chosen for fixation, obtaining a good reduction prior to placing the implant is the most important factor that can be controlled by the surgeon. In stable fractures the surgeon experience is a strong factor to account for when choosing the type of implant. Clearly there are fracture patterns (reverse oblique and subtrochanteric extension) that benefit from the use of intramedullary devices due to the high risk of failure if plates are used.

CONCLUSION

It is very important that the surgeon identifies these fractures, so the type of fixation device which is chosen achieves the greatest stability possible. The aim of this paper is not to convince the surgeon about using intramedullary nails, but highlight the potential benefits intramedullary nailing has when compared with the use of extramedullary devices.