A recent update on the fixation techniques for femoral neck fractures: A narrative review

Abstract

Femoral neck fractures present significant challenges in orthopedic surgery, particularly due to technical difficulties and a high complication rate. Surgical intervention is generally recommended, with osteosynthesis and arthroplasty being the main treatment options. Osteosynthesis techniques, including dynamic hip screw (DHS), multiple cannulated screws (MCS), and the femoral neck system (FNS), aim to achieve stable fixation and facilitate fracture healing. Factors influencing the choice of osteosynthesis include fracture displacement, bone quality, patient age, and the presence of posterior tilt. While DHS offers high stability, MCS is preferred in stable type fractures with minimal invasive procedures. FNS, a newer technique, combines the advantages of DHS and MCS, providing strong fixation with minimal soft tissue damage. Considering the comprehensive findings of biomechanical and clinical studies to date, when performing osteosynthesis for unstable femoral neck fractures, caution should be exercised with MCS as it may have slightly inadequate fixation strength compared to DHS and FNS. FNS, being the newest technique, demonstrates superior fixation strength comparable to DHS and is as minimally invasive as MCS. However, it is essential to remember that long-term follow-up results are lacking for FNS.

1. Introduction

Femoral neck fractures present notable clinical hurdles in orthopedic surgery, especially given their correlation with elevated morbidity and mortality rates. In young age groups, femoral neck fractures often occur due to high-energy trauma, which can be associated with other concomitant injuries, making it a high-risk scenario. In the contrary, the elderly population, fractures frequently result from low-energy injuries associated with osteoporosis, but mortality and morbidity are often higher due to underlying diseases.¹

Generally, the treatment for femoral neck fractures now reaches a consensus favoring surgical intervention as the primary approach.² Surgical treatment can broadly be categorized into two main options: osteosynthesis and arthroplasty. The femoral head receives its blood supply from three sets of vessels: the superior, inferior, and anterior retinacular arteries.³ The extent of vascular damage is closely linked to the displacement of the fracture, which in turn affects the likelihood of femoral head osteonecrosis (ONFH).⁴ Consequently, the choice between osteosynthesis and arthroplasty considers the level of fracture displacement, alongside factors like compromised bone quality and patient age, which could heighten the risks of fixation failure, nonunion, or malunion. These complications can impair patient function and affect quality of life.

Osteosynthesis serves as a fundamental approach in the management of femoral neck fractures. Over the years, a myriad of osteosynthesis techniques has been developed and refined to achieve stable fixation, facilitate fracture healing, and restore optimal function.

This review aims to provide an in-depth exploration of the diverse osteosynthesis techniques utilized in the treatment of femoral neck fractures, encompassing with the decision of osteosynthesis, contemporary surgical options, and emerging trends.

2. Decision of osteosynthesis

Before discussing various techniques of osteosynthesis, it is necessary to first address the appropriate indications for osteosynthesis. According to literature, the surgical failure and reoperation rates of femoral neck fractures range from 8 % to 21 %, showing significant variability.^5,6 Therefore, understanding the factors and risk factors that may influence the successful outcome of osteosynthesis is crucial.

Firstly, the identification of fracture displacement is important to determining the appropriate treatment for femoral neck fractures. Fracture displacement is closely linked with the prediction of vascular injury. Despite the development and utilization of various classification systems to categorize fracture displacement, none of them adequately capture the treatment approaches and prognosis for femoral neck fractures. To date, the Garden classification stands as the most commonly employed system in clinical practice. Introduced by British orthopedic surgeon Robert Symon Garden in 1961, this classification system divides femoral neck fractures into four groups based on fracture displacement, completeness, and the relationship of bony trabeculae in the femoral head and neck.⁷ According to this classification, Garden types I and II are considered nondisplaced fractures, with Garden I indicating a valgus-impacted incomplete fracture and Garden II indicating a complete but nondisplaced fracture. Generally, internal fixation is preferred by many surgeons in such cases.⁸

The concept of the Pauwel angle, which indicates the verticality of the fracture, is also crucial in determining treatment decisions. According to the Pauwels classification, femoral neck fractures are categorized into three grades based on the orientation of the fracture line. Pauwels grade I fractures have angles <30°, grade II fractures have angles between 30° and 50°, and grade III fractures have angles >50°. In this classification system, fractures with vertically oriented fracture lines are considered more unstable and carry a higher risk of failure compared to horizontally oriented fractures, as they are subjected to greater shearing forces.⁹ Therefore, when treating femoral neck fractures with a large Pauwel angle, it is important to be aware that the prognosis with osteosynthesis may not be favorable.

However, merely the presence of initial fracture displacement does not solely determine the prognosis of femoral neck fracture osteosynthesis. There are instances where osteosynthesis yields favorable outcomes even in cases of severe displacement, while osteosynthesis failure may occur in fractures with minimal displacement. Another crucial factor influencing the outcome of femoral neck fracture osteosynthesis is bone quality, closely associated with patient age. While other important factors, including surgical reduction, also play a role, it is undeniable that severe osteoporosis and poor bone quality, coupled with old age, become independent risk factors for fixation failure.^10,11

Additionally, there is an opinion that the posterior tilt, also known as apex anterior fracture angulation, may influence the outcome of femoral neck fracture osteosynthesis. The posterior tilt, as measured by their methodology, encompasses both posterior angulation and displacement between the femoral head and neck. Both of these factors can influence the stability of the fracture and the integrity of the vessels traversing the fracture site.¹² According to the study findings of Palm et al., a posterior tilt of ≥20° was the only predictor of reoperation.¹² For the treatment of femoral neck fracture, despite its ease of use and longstanding tradition, the Garden classification mentioned earlier has a significant drawback: very low inter-observer reliability. The interobserver Kappa value is known to range between 0.03 and 0.56, indicating poor reliability,⁷ particularly in accurately reflecting posterior tilt. Therefore, it is crucial to exercise caution when planning osteosynthesis solely based on the appearance of nondisplaced fractures resembling Garden types I or II on simple hip anterior-posterior X-rays. Moreover, when posterior tilt is prominent, careful attention should be given to correcting it, and sometimes opting for arthroplasty rather than osteosynthesis may be preferable.

Another crucial factor in determining the prognosis of fixation is the timing of internal fixation. It is a generally accepted consensus that early surgical intervention is recommended to theoretically reduce the risks of post-traumatic ONFH and nonunion. According to one recent meta-analysis by Papakostidis et al.,¹³ while there was no statistically significant relationship between the timing of surgery and the incidence of ONFH during the osteosynthesis of femoral neck fractures, it was reported that the risk of nonunion significantly increases if more than 24 h elapse after the injury (OR 0.33, P < 0.01).

When considering reduction techniques, one must decide whether to perform open reduction or closed reduction prior to surgery. While open reduction is advantageous for achieving anatomic reduction compared to closed reduction, it is also more invasive. Consequently, open reduction is typically considered for displaced patterns. In the treatment of displaced femoral neck fractures, the option of arthroplasty exists in addition to osteosynthesis, which results in a higher frequency of closed reduction compared to open reduction for femoral neck fracture osteosynthesis. Additionally, a recent meta-analysis and randomized controlled trial found no significant differences between open and closed reduction regarding nonunion, ONFH, or total complications in the treatment of femoral neck fractures.^14,15 Moreover, Patterson et al.¹⁵ reported in a multicenter study conducted at twelve Level 1 North American trauma centers that open reduction of displaced femoral neck fractures in nonelderly adults is associated with a greater hazard of reoperation without significantly improving reduction. Therefore, open reduction should be chosen with caution.

When performing osteosynthesis for femoral neck fractures, there are concepts of length-stable fixation and intraoperative compression. Length-stable fixation offers the advantage of reducing postoperative shortening. However, in cases of severe fracture comminution, the length-stable fixation may lead to decreased stability, increasing the risk of nonunion or fixation failure.¹⁶ Recent studies have also indicated a higher reoperation rate in such cases.¹⁷ Therefore, caution should be exercised, particularly when attempting length-stable fixation in femoral neck fractures with significant comminution.

In the surgical fixation of femoral neck fractures, there is still ongoing debate and numerous clinical papers and biomechanical studies are being published regarding which fixation device is optimal. Additionally, new implants and fixation techniques are continuously being developed. The following are the types of implants currently used and the latest updated research results on them.

3. Contemporary osteosynthesis techniques

• (1)Dynamic Hip Screw (DHS)

The Dynamic Hip Screw (DHS) is one of the most common systems used for osteosynthesis of femoral neck fractures, with a long history dating back to its initial design by Robert Danis in 1934.¹⁸ It was originally developed as a device for stabilizing femoral neck fractures. Over time, it has been improved by Ernst Pohl, Willis L. Pugh, John Charnley, and others, evolving into the modern type of DHS. Nowadays, it is not only used for femoral neck fractures but also across the spectrum of fixation for proximal femur fractures (Fig. 1).

Fig. 1.

51 years male who underwent DHS surgery due to unstable femoral neck fracture. The preoperative (A) anterior-posterior and (B) lateral view X-rays were shown displaced type femoral neck fracture, and the (C) anterior-posterior and (D) lateral view X-rays of postoperative 2-year without any complications.

The DHS system represents a cornerstone in the surgical armamentarium for femoral neck fractures, predicated on the principles of load-sharing and controlled impaction. This technique entails the insertion of a lag screw across the fracture line, complemented by a side plate affixed to the femoral shaft, facilitating axial compression and fracture stabilization. DHS fixation is particularly indicated for stable fractures with minimal displacement, offering favorable outcomes in terms of union rates and functional recovery.

Compared to the commonly compared multiple cannulated screw fixation method for femoral neck fracture osteosynthesis, the DHS technique typically requires more soft tissue stripping and may result in somewhat higher blood loss.^19,20 However, it offers a more stable condition by utilizing a screw-plate system. Deneka et al. observed in their biomechanical comparison of internal fixation methods for managing unstable basicervical femoral neck fractures that DHS offers greater fixation strength compared to using multiple cannulated screws.²¹ Furthermore, for the clinical results of recent systematic review and meta-analysis from Lim et al., have indicated that in vertically oriented Pauwels type II and type III femoral neck fractures, DHS fixation demonstrates a lower nonunion rate compared to multiple cannulated screw fixation (OR = 0.32; 95 % CI, 0.11–0.96; p = 0.04) which means the favorable result of DHS.²²

There are regional preferences as well. According to a cross-sectional survey conducted by Bhandari et al. using regression analysis,²³ surgeons in Europe were more likely to recommend a DHS device over multiple cannulated screws than North American surgeons. However, it is a fact that both biomechanical and clinical studies report DHS to have equivalent or superior fixation strength compared to multiple cannulated screws. This is particularly evident in highly vertical fractures such as Pauwels type II and III,²² or unstable fractures such as Garden type III-IV,¹⁹ where DHS is considered to have an advantage.

• (2)Multiple Cannulated Screws (MCS)

Cannulated screw fixation has emerged as a versatile alternative to DHS constructs, especially in younger patients with femoral neck fractures characterized by favorable bone quality and minimal displacement. This technique involves the percutaneous insertion of multiple screws across the fracture site, guided by fluoroscopy or intraoperative imaging modalities. Cannulated screws afford several advantages, including preservation of the femoral head vascularity, reduced surgical morbidity, and expedited rehabilitation protocols (Fig. 2).

Fig. 2.

79 years male who underwent MCS due to femoral neck fracture. (A) The initial preoperative (A) anterior-posterior and (B) lateral view X-ray, immediate postoperative status (C) anterior-posterior and (D) lateral view X-ray, and postoperative 5-years final follow-up (E) anterior-posterior and (F) lateral view X-ray.

MCS techniques saw widespread use from the 1960s to the 1970s following reports by Garden et al. and Barnes et al..^24,25 However, starting from the mid-1980s, there was a transition towards utilizing parallel screws due to their capability to facilitate collapse at the fracture site.²⁶ A biomechanical investigation by Selvan et al. demonstrated that the triangular configuration outperforms other configurations in terms of resistance against failure.²⁷ Consequently, parallel and triangular screw insertion techniques gained widespread acceptance starting in the early 2000s.

According to a recent meta-analysis by Lim et al.,²⁸ the parallel alignment of screws in MCS fixation for femoral neck fractures does not correlate with either the rate of fracture nonunion or the occurrence of postoperative ONFH. Recent efforts have been made to find the ideal screw configuration using computer-aided design modules.²⁹ In 2011, Filipov³⁰ introduced the Biplane Double-Supported Screw Fixation trajectory technique to provide additional cortical support. However, it is common practice to insert three cannulated screws in a reverse triangular configuration, where the first screw is inserted into the calcar region, the second screw into the posterior cortex, and the third screw contacts the anterior cortex.

In contrast to DHS, the procedure is less invasive, results in lower blood loss, and in some cases, it can be performed percutaneously without making an incision, reducing soft tissue stripping and potentially shortening hospital stays.²⁰ Additionally, it is more cost-effective than other methods.³¹

However, caution must be exercised, particularly in the case of displaced femoral neck fractures, and attention must be paid to reduction. According to a study by Kim et al. on femoral neck fractures in individuals under 60 years of age,³² which underwent multiple cannulated screw (MCS) fixation, complications including osteonecrosis of the femoral head (ONFH) and nonunion occurred in 51.5 % of the 52 consecutive patients, all of whom had Garden type III or IV fractures, indicating unstable types. It was reported that in the group where complications occurred, the posterior tilt, i.e., the anterior-posterior angulation on lateral view, was significantly larger (16.9° vs. 10.3°, P = 0.026).³²

• (3)Femoral Neck System (FNS)

The recently developed FNS (DePuy Synthes, West Chester, PA, USA), comprises the theoretical mechanical advantages of combining compression and anti-rotation qualities during internal fixation.³³

The FNS design offers an effective solution through the screw-plate construct, providing stronger fixation. Moreover, the integration of a blade and an anti-rotation screw enhances both axial and rotational stability. Moreover, compared to DHS, the FNS technique involves minimal soft tissue stripping, making it minimally invasive with reduced bleeding risk.^34,35 Thus, the FNS fixation device can be considered to combine the advantages of both DHS and MCS techniques.

Numerous biomechanical studies have demonstrated that the FNS offers comparable axial and rotational stability to traditional MCS and DHS fixation.^34,35 Following the Stoffel et al.,³⁵ the FNS showed biomechanical stability comparable to the DHS and superior to MCS in unstable intracapsular femoral neck fractures especially Pauwel type III fractures. Moreover, Moon et al. reported in their biomechanical study that the FNS demonstrated non-inferiority to DHS even in extracapsular femoral neck fractures, particularly investigated for displaced basicervical femoral neck fractures.³⁴

In addition to theoretical considerations, actual clinical studies also support the superiority of FNS in the treatment of adult femoral neck fractures. According to a recent systematic review and meta-analysis conducted by Patel et al.,³⁶ comprising a total of 8 papers, FNS was reported to be superior to traditional MCS in terms of complication rate (P < 0.001), postoperative femoral neck shortening, fracture union (P < 0.001), and functional outcome score (P < 0.001).

Despite the favorable outcomes reported in numerous theoretical and clinical studies to date, it is important to note that FNS has not been on the market for long, and thus long-term clinical follow-up data are lacking. Additionally, there are still drawbacks in terms of cost-effectiveness. It is essential to bear in mind the need for further research, particularly regarding potential issues that may arise during implant removal. In fact, according to recent studies by Yoon et al., among 43 consecutive cases, implant removal was performed in 5 cases, with reports of distal locking screw stripping occurring in 3 of 5 (60 %).³⁷

Fig. 3 shows the 60 years old female case who underwent FNS surgery due to the stable femoral neck fracture.

• (4)Additional Considerations: Modified Techniques and Additional Fixation Techniques

Fig. 3.

60 years old female who underwent FNS surgery due to the stable femoral neck fracture. The preoperative anterior-posterior and lateral view X-rays were shown in (A) and (B), and the (C) anterior-posterior and (D) lateral view X-rays of postoperative 1-year without any complications.

One of the modified techniques used when considering osteosynthesis for unstable femoral neck fractures is osteosynthesis combined primary trochanteric valgus angulation osteotomy.^38,39 This technique is primarily used in Garden type III and IV unstable fractures with a vertical fracture line. It is employed as one of the techniques to prevent high complication rates in these types of fractures by performing valgus osteotomy of the trochanter simultaneously with osteosynthesis, thereby correcting the vertical fracture plane.

There is also the additional technique for fixing femoral neck fractures known as anteromedial buttress plating. This method typically involves the use of a reconstruction plate to provide medial buttressing. This technique enhances the standard laterally based fixation technique by adding additional plating to the calcar, offering increased stability, and is particularly used in younger patients with good bone quality.⁴⁰ Although there are clinical and biomechanical studies on this technique,^41,42 it is not commonly used.

4. Conclusion

In the management of femoral neck fractures, osteosynthesis is a crucial treatment that must be carefully considered, as it is essential for the foundation of femoral neck fracture management. The most commonly used contemporary techniques for osteosynthesis are MCS, DHS, and FNS. Considering the comprehensive findings of biomechanical and clinical studies to date, when performing osteosynthesis for unstable femoral neck fractures, caution should be exercised with MCS as it may have slightly inadequate fixation strength compared to DHS and FNS. FNS, being the newest technique, demonstrates superior fixation strength comparable to DHS and is as minimally invasive as MCS. However, it is essential to remember that long-term follow-up results are lacking for FNS.

CRediT authorship contribution statement

Chul-Ho Kim: writing – review & editing, writing – original draft, conceptualization. Ji Wan Kim: writing – review & editing, writing – original draft, conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.