Comparative study on the clinical efficacy of femoral neck system and cannulated cancellous screw in the treatment of femoral neck fractures in young patients

Abstract

Objective

To investigate the clinical efficacy of femoral neck system and hollow compression screw in the treatment of femoral neck fractures in young patients.

Methods and materials

A retrospective study was conducted on young patients with femoral neck fractures who underwent treatment with either the Femoral Neck System (FNS) or Cannulated Cancellous Screws (CCS) between June 2018 and June 2023. The primary outcome was evaluated using the Harris Hip Score (HHS) to assess hip functional outcomes. Secondary outcomes included operative time, intraoperative blood loss, satisfactory Visual Analogue Scale (VAS) scores, fluoroscopy frequency, fracture healing time, complications, and femoral neck shortening at 3 and 6 months postoperatively.

Results

A total of 70 patients were included (35 in the FNS group and 35 in the CCS group), with follow-up ranging from 24 to 120 weeks. The mean follow-up duration was 74.22 ± 33.27 weeks in the FNS group and 75.17 ± 27.52 weeks in the CCS group. No statistically significant difference was observed in Harris Hip Scores (HHS) between the two groups. However, the fracture healing time in the FNS group (14.44 ± 2.42 weeks) was significantly shorter than that in the CCS group (16.42 ± 2.84 weeks) (P < 0.05). Similarly, the time to full weight-bearing was earlier in the FNS group (11.83 ± 3.98 weeks) compared to the CCS group (19.32 ± 4.12 weeks) (P < 0.05). The FNS group also demonstrated lower fluoroscopy frequency (P < 0.05) and superior femoral neck shortening outcomes (P < 0.05) postoperatively. Regarding complications, the FNS group exhibited a lower rate of internal fixation failure. No statistically significant differences were observed between the two groups in other perioperative parameters, postoperative efficacy metrics, or additional complication rates (P > 0.05).

Conclusion

For young patients with femoral neck fractures, while both FNS and CCS achieved similar final functional outcomes, the FNS system facilitates a more favorable recovery course by promoting faster fracture healing, enabling earlier weight-bearing, and most importantly, significantly reducing the risk of major postoperative complications. These advantages are attributable to its enhanced biomechanical stability.

Introduction

Femoral neck fractures are highly prevalent among hip fractures and are regarded as a major challenge in orthopedics due to the associated high risk of avascular necrosis [1, 2]. These fractures predominantly occur in elderly populations, typically resulting from low-energy trauma. In contrast, femoral neck fractures in younger patients (under 65 years of age) are more commonly caused by high-energy injuries [3, 4]. For younger patients, the primary goals of surgical treatment are to preserve the femoral head, promote fracture healing, and prevent avascular necrosis [5, 6]. Among head-preserving treatment options, dynamic hip screws (DHS) and cannulated cancellous screws (CCS) are widely used [7, 8]. Nevertheless, these conventional approaches may still lead to complications such as nonunion, femoral head necrosis, and implant displacement [3, 9, 10]. Studies indicate that the femoral artery and its branches play a critical role in blood supply. Femoral neck fractures or related surgical procedures may damage the femoral artery, resulting in nonunion at the fracture site or femoral head necrosis. These complications not only impose significant financial burdens on patients but also present substantial challenges to clinical practice [11].

Given this, orthopedic surgeons must be especially vigilant in minimizing radiation exposure and associated complications during surgery, particularly in young patients. In recent years, the Femoral Neck System (FNS), a new internal fixation technique, has been applied to treat femoral neck fractures. This technique offers outstanding angular stability, anti - rotation stability, and continuous sliding compression, along with simple operation and minimally - invasive benefits. The FNS consists of a plate, locking nail, 10 - mm bolt, and anti - rotation screw, with the locked anti - rotation screw permitting relative sliding at the fracture site. Yet, it’s still unclear whether FNS is better than cannulated cancellous screws. So, this study aims to compare the clinical effects of FNS and cannulated cancellous screws for young femoral neck fracture patients.

Methods

Patients

This retrospective study was conducted at the Department of Orthopedic Trauma, The First Affiliated Hospital of Naval Medical University. We followed young patients with femoral neck fractures treated between June 2018 and June 2023. The study protocol was approved by the Ethics Committee of The First Affiliated Hospital of Naval Medical University and adhered to the principles of the revised 1975 Helsinki Declaration (2013 amendment).

Inclusion and exclusion criteria

Inclusion criteria

1. Age 18–65 years old; 2.Unilateral closed fresh femoral neck fracture (fracture time < 3 weeks); 3. The follow-up time was ≥ 12 months.

Exclusion criteria

1. Accompanied by high risk factors of femoral head necrosis (long-term history of taking hormones.) or femoral head necrosis; 2. Patients with other fractures of the ipsilateral femur; 3. Patients with pathological fractures; 4. Combined with other diseases or conditions that affect the efficacy; 5. Other patients who are not suitable for surgical treatment or whose systemic conditions cannot tolerate surgery.

The gender, age, body mass index, fracture type and injury causes of the two groups were compared in Table 1. There was no statistical significance in the comparison of general data between the two groups (P > 0.05), which was comparable.

Table 1.

Patient demographics and characteristics [mean (SD)]

	FNS	CCS	P Value
Cases	35	35
Gender[women/men]	18/17	17/18	0.81
Age[years]	54.17 ± 2.83	54.03 ± 4.96	0.88
Body mass index[kg/m²]	24.85 ± 2.03	25.21 ± 2.01	0.46
Cause of injury
Motor vehicle collision	27	20	0.75
Fall(s)	8	15
Garden classification			0.66
Ⅰ	1	2
Ⅱ	20	15
Ⅲ	5	7
Ⅳ	9	11
Pauwels type			0.21
Ⅰ	2	1
Ⅱ	24	18
Ⅲ	9	16
Follow-up times (months)	74.22 ± 33.27	75.17 ± 27.52	0.89

Preoperative preparation

Preoperatively, patients are required to undergo anteroposterior and lateral X-ray films of the hip joint, as well as computed tomography (CT) scans. Additionally, anticoagulants will be administered to prevent or manage deep vein thrombosis (DVT).

Surgery

Patients will receive either spinal/general anesthesia. The patient is positioned supine on an orthopedic traction table. After confirming satisfactory fracture reduction under C-arm fluoroscopy guidance, routine sterilization and disinfection procedures are performed. The Garden alignment index is utilized to assess the quality of fracture reduction.

FNS group

In the FNS group, the procedure begins with routine disinfection and draping. Next, a Kirschner wire is inserted anteriorly on the femoral neck to temporarily stabilize the reduced fracture. A longitudinal incision is made from the insertion point of the FN guide wire to the distal end, through the skin, subcutaneous tissue, and down to the femoral lateral wall. The guide device is placed tightly against the lateral wall of the femoral shaft, and a guide wire is inserted along the long axis of the femoral neck. Using C-arm fluoroscopy, the position of the guide wire is confirmed to be central within the femoral neck, with the tip of the wire positioned no more than 5 millimeters subchondrally. After drilling, reaming, and depth measurement along the guide wire, the FNS set is inserted, and the anti-rotation screw is screwed in via the handle guide. Finally, locking screws are added to secure the lateral locking plate. Once proper placement is confirmed by C-arm fluoroscopy, the wound is irrigated and closed layer by layer, which can be seen in Fig 1.

Fig. 1.

A 24-year-old male diagnosed with femoral neck fracture treated with FNS system. A The anteroposterior and lateral positions of preoperative X-rays. B The anteroposterior and lateral positions of post-operative X-rays. C The anteroposterior and lateral positions of post-operative X-rays at 6 months. D The anteroposterior and lateral positions of post-operative X-rays at 12 months

CCS group

In the CCS group, routine disinfection and draping were performed. All procedures utilized the inverted triangle technique with three cannulated screws to optimize biomechanical stability. Under C-arm fluoroscopy guidance, the first guide wire was inserted inferiorly and posteriorly, positioned parallel and adjacent to the medial cortex (calcar femorale) of the femoral neck on the anteroposterior view, and centered within the femoral neck on the lateral view. This strategically placed inferior screw was designed to provide a crucial internal buttress effect against varus deformation. Subsequently, the second and third guide wires were inserted into the superior quadrant of the femoral neck in an anteroposterior orientation, forming the apex of the inverted triangle. Care was taken to ensure all guide wires reached to within 5 millimeters of the subchondral bone to maximize purchase in the dense cancellous bone of the femoral head. The positions of all wires were confirmed to be parallel on both fluoroscopic views. After confirming satisfactory positioning, small incisions were made at the entry points. The drilling depth was measured, and three cannulated cancellous screws of appropriate length were inserted over the guide wires. Particular attention was paid to ensuring the inferior screw achieved cortical contact along the medial femoral neck to enhance its buttressing function. Final fluoroscopic imaging confirmed that all screws were placed centrally within the femoral neck and head, providing adequate compression and rotational stability. The wound was then irrigated and closed in layers, which can be seen in Fig 2.

Fig. 2.

A 26-year-old male diagnosed with femoral neck fracture treated with CCS system. A The anteroposterior and lateral positions of preoperative X-rays. B The anteroposterior and lateral positions of post-operative X-rays. C The anteroposterior and lateral positions of post-operative X-rays at 6 months. D The anteroposterior and lateral positions of post-operative X-rays at 12 months

Postoperative management

Postoperatively, low-molecular-weight heparin (LMWH) is administered for analgesia and anticoagulation. Patients are encouraged to initiate ambulation within 24 h after surgery. On the following day, radiographic imaging (X-ray) and computed tomography (CT) scans are performed to evaluate the quality of reduction and implant positioning. By the second postoperative week, patients begin ambulation with crutches, avoiding straight leg raises and weight-bearing activities, with a focus on bed rest. Partial weight-bearing exercises are introduced at 6 weeks, progressing to full weight-bearing and crutch-free walking based on the patient’s recovery progress. Radiographic follow-up is conducted at 1, 2, 3, 6, 12, 18, and 24 months postoperatively.

Evaluation

All clinical data of length of hospital stay, operative time, operative blood loss, fluoroscopy frequency, length of hospital stay, visual analogue score of satisfaction (VAS), Harris hip score (HHS), fracture healing time, postoperative complications (infection, femoral shortening, femoral nonunion, femoral neck necrosis, nail removal, excision and internal fixation) were evaluated.

Functional outcomes were graded based on the HHS as follows: excellent (≥ 90), good (80–89), fair (70–79), and poor (< 70). The excellent and good rate was calculated as the combined proportion of patients with excellent and good outcomes.

Implant positioning was assessed by measuring the Tip-Apex Distance (TAD), defined as the sum of the distances from the tip of the lag screw to the apex of the femoral head on anteroposterior and lateral radiographs, corrected for magnification.

Statistical analysis

Continuous variables are presented as mean ± SD and analyzed using the t-test. Categorical variables are analyzed using the Chi-square test. Ranked data are analyzed using the Mann-Whitney U test. All statistical analyses are performed using SPSS 25.0. A p-value < 0.05 is considered statistically significant.

Results

Patient characteristics

Both seventy patients were included in this study, the average age was 54.17 ± 2.83 years old in the FNS group and 54.03 ± 4.96 years old in the CCS group. 18 patients were female in the FNS group and 17 patients were female in the CCS group. The main cause of injury was Motor vehicle collision in the both groups. All femoral neck fractures were classified by Garden classification system and Pauwels type system. The baseline date of both groups was shown in Table 1, which demonstrated that patients in the distribution of each characteristic were similar in the two groups.

Clinical data analysis

Operation time was 77.82 ± 27.19 min in the FNS group and 69.84 ± 28.66 min in the CCS group (P = 0.24, Table 2). Intraoperative blood loss was 50.80 ± 8.69 ml in the FNS group and 22.48 ± 10.96 ml in the CCS group (P < 0.01). Fluoroscopy frequency was 16.77 ± 2.50 times in the FNS group and 25.25 ± 3.86 times in the CCS group (P < 0.01). Hospital stays was 7.43 ± 1.43 days in the FNS group and 7.62 ± 1.48 days in the CCS group (P = 0.58). VAS score was 86.76 ± 13.00 in the FNS group and 83.60 ± 13.40 in the CCS group (P = 0.32). Harris hip score was 91.42 ± 4.12 in the FNS group and 90.24 ± 4.14 in the CCS group (P = 0.24). Excellent and good rate was 30(85.7%) in the FNS group and 28(80%) in the CCS group (P = 0.53). Fracture healing time was 14.44 ± 2.42 weeks in the FNS group and 16.42 ± 2.84 weeks in the CCS group (P < 0.01). Femoral neck shortening was 3.69 ± 2.48 mm in the FNS group and 4.62 ± 0.57 mm in the CCS group (P < 0.05). Full weight bearing time was 11.83 ± 3.98 weeks in the FNS group and 19.32 ± 4.12 weeks in the CCS group (P < 0.05). Garden alignment index was 94.3% in the FNS group and 91.4% in the CCS group (P = 0.64). TAD was 20.1 ± 3.2 mm in the FNS group and 21.3 ± 4.1 in the CCS group (P = 0.16). Moreover, the complication rates were 2.86% (1/35) in the FNS group and 37.14% (13/35) in the CCS group (P < 0.01).

Table 2.

Comparisons of surgical outcomes in the two groups [mean (SD)]

	FNS	CCS	P Value
Surgical time (min)	77.82 ± 27.19	69.84 ± 28.66	0.24
Surgical blood loss (ml)	50.80 ± 8.69	22.48 ± 10.96	< 0.01
Fluoroscopy frequency (times)	16.77 ± 2.50	25.25 ± 3.86	< 0.01
Length of hospital stay (day)	7.43 ± 1.43	7.62 ± 1.48	0.58
Satisfaction VAS	86.76 ± 13.00	83.60 ± 13.40	0.32
Harris hip score (HHS)	91.42 ± 4.12	90.24 ± 4.14	0.24
Excellent and good rate	30(85.7%)	28(80%)	0.53
Fracture healing time (weeks)	14.44 ± 2.42	16.42 ± 2.84	< 0.01
Femoral neck shortening (mm)	3.69 ± 2.48	4.62 ± 0.57	< 0.05
Full weight bearing time(weeks)	11.83 ± 3.98	19.32 ± 4.12	< 0.05
Garden Alignment Index	94.3%	91.4%	0.64
TAD (mm)	20.1 ± 3.2	21.3 ± 4.1	0.16
Complications			< 0.01
Nonunion	0	1
Femoral head necrosis	1	6
Implant back-out	0	3
Cut out the internal fixation	0	3

Discussion

In young patients, unstable femoral neck fractures are usually caused by high - energy trauma, which often results in a large Pauwels angle [12]. This means internal fixation devices must bear shear, compressive, separation, and rotational stresses from the hip joint until fracture healing. Despite its wide application, the CCS technique has poor angular stability and shear stress resistance, leading to high postoperative complication rates.

Since its introduction, the FNS system has been biomechanically proven superior to CCS. Stoffel et al. showed FNS can bear greater axial stress and offers better angular and anti - rotation stability [13]. Its sliding nail ensures dynamic compression during surgery and sustained pressure support during early recovery. As FNS is increasingly used clinically, evidence shows it reduces complications, lessens postoperative femoral neck shortening, and improves hip function prognosis. Additionally, it allows earlier full weight - bearing, facilitating faster recovery, which aligns with this study’s findings.

In this study, the perioperative data revealed that the FNS group required a longer operative time and experienced greater intraoperative blood loss than the CCS group, which may be attributed to the initial learning curve associated with the novel FNS technique. However, the FNS procedure demonstrated a significant advantage in requiring a substantially lower intraoperative fluoroscopy frequency, underscoring the efficiency and reproducibility of its dedicated guide system for implant placement. In postoperative recovery, the FNS group exhibited a significantly shorter fracture healing time and an earlier time to full weight-bearing compared to the CCS group. These findings, coupled with a markedly lower complication rate, substantiate the clinical significance of FNS’s superior biomechanical stability in treating young patients with unstable femoral neck fractures [14, 15].

In postoperative complication analysis, the CCS group had a higher rate of internal fixation failure than the FNS group. In the FNS group, only one case experienced internal fixation failure due to avascular necrosis of the femoral head eight months postoperatively. This case differed from others with femoral neck shortening as it had a larger tip-apex distance during implantation, making the main nail more prone to cut out from the deformed femoral head. Some scholars have different views on TAD selection in FNS treatment [16]. Su et al. found that when TAD < 25 mm during FNS implantation, there was less postoperative femoral neck shortening, smaller changes in the neck-shaft angle, and higher Harris scores for hip function [17]. Clinical and finite element analyses indicate that the FNS pre-sliding technique (a 5-mm gap between the plate and femoral shaft) can effectively adjust bolt depth, placing it closer to the subchondral bone of the femoral head. This technique offers better fracture stability than standard fixation for Pauwels III fractures. However, whether extending the anti-rotation screw enhances internal fixation stability remains unclear. Although the CCS group had no internal fixation failure from cut-out or breakage, all its failures were due to severe femoral neck shortening and implant back-out. Postoperative femoral neck shortening data showed that the FNS group had a technical advantage in reducing shortening, especially at six months postoperatively. The dynamic compression of FNS ensures maximum fracture healing during recovery and exercise, reducing femoral neck shortening caused by bone loss and poor healing. In contrast, CCS only provides temporary intraoperative compression and no sustained postoperative support, which may explain why the FNS group performed better than the CCS group in reducing femoral neck shortening at six months. Additionally, the CCS group was more prone to internal fixation failure associated with femoral neck shortening and implant back-out.

The significantly lower incidence of avascular necrosis (AVN) in the FNS group compared to the CCS group is likely attributable to the superior biomechanical stability of the FNS construct, which directly and indirectly preserves the precarious blood supply to the femoral head. In young patients with high-energy femoral neck fractures, significant shear and rotational forces challenge fixation. The CCS, while providing excellent compression, offers poor resistance to these forces, leading to micromotion at the fracture site. This instability can mechanically disrupt the delicate process of revascularization by stretching and compromising the vulnerable residual vessels, ultimately leading to ischemia and AVN. In contrast, the integrated FNS design—combining a dynamic compression bolt, an anti-rotation screw, and a locking plate—creates a rigid environment with exceptional angular and rotational stability. This minimizes harmful micromotion, thereby protecting the revascularization process. Furthermore, this stability manifests in reduced catastrophic failures; the CCS group exhibited cases of nail withdrawal and cut-out, often associated with loss of reduction and non-union, which are direct precursors to secondary AVN. The FNS’s ability to prevent such failures and significantly reduce femoral neck shortening, as shown in our results, further safeguards femoral head viability. Finally, the surgical technique itself may play a role; the FNS procedure, utilizing a central bolt and a single anti-rotation screw, is potentially less disruptive to the intraosseous vascular network compared to the multiple passes required for three CCS screws. Thus, the synergistic effect of superior biomechanics, reduced implant failure, and a less invasive technique collectively explain the pronounced reduction in AVN incidence with the FNS.

This study has several limitations. The primary constraints include the retrospective design and surgeon preference-based assignment, which may introduce selection bias, as evidenced by the CCS group containing more unstable Pauwels type III fractures (16 vs. 9)—a clinically relevant disparity despite lacking statistical significance (p = 0.21)—potentially influencing outcomes. Additionally, the small sample size (partly constrained by local economic and educational conditions) resulted in insufficient statistical power, particularly for assessing rare endpoints like femoral head necrosis. Furthermore, several potential confounding factors, such as osteoporosis and bone loss, were not fully accounted for. Finally, fracture healing time was subjectively assessed by outpatient physicians using follow-up imaging and influenced by variable follow-up durations, potentially introducing measurement bias. Consequently, these findings should be considered exploratory and require validation through large-scale, multicenter prospective studies.

Conclusion

In summary, the Femoral Neck System (FNS) demonstrates significant potential as a viable alternative to Cannulated Cancellous Screws (CCS) in treating femoral neck fractures in young patients. Based on our analysis, FNS facilitates a superior recovery course characterized by faster fracture healing, earlier weight-bearing, and a markedly lower incidence of major complications, attributable to its enhanced biomechanical stability. However, the interpretation of our findings must be tempered by the study’s limitations, including its retrospective design, modest sample size, and potential for selection bias. These factors highlight the need for cautious interpretation of the results. Consequently, the definitive establishment of FNS superiority requires validation through large-scale, multicenter, prospective randomized controlled trials with extended follow-up periods. Such future research is essential to confirm the long-term benefits, particularly regarding the risk of avascular necrosis, and to solidify the role of FNS in the management of these challenging fractures.

Authors’ contributions

W.D. and R.W wrote the main manuscript text, Q.W., H.L. and S.N. prepared tables. All authors reviewed the manuscript.

Funding

The National Natural Science Foundation of China supported this study (No. 82172431).

Data availability

The datasets analysed during the current study are not publicly available due privacy but are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Medical Research Ethics Board of Navel Military Medical University (Shanghai, China) (No. 20201005). which waived the need for written informed consent due to the retrospective nature of the study. All methods were carried out in accordance with relevant guidelines and regulations. Research involving human participants, human material, or human data, must have been performed in accordance with the Declaration of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.