Clinical Utility and Safety of Bone Cement Augmentation in Intramedullary Nailing for Proximal Femur Fractures: A Multicenter Prospective Observational Study

Abstract

Introduction

Proximal femur fractures are common in older adults and are associated with high morbidity and mortality. Bone cement augmentation during intramedullary nailing has been reported to improve implant stability; however, its clinical utility and safety in Japan remain unclear.

Materials and Methods

This multicenter prospective observational study included patients aged ≥45 years who underwent intramedullary nailing for trochanteric or basicervical femoral fractures between May 1, 2021, and July 31, 2023. Cement augmentation was applied exclusively to patients aged ≥60 years. Femoral neck fractures were excluded. Patients were treated with cement augmentation (CA group) or without augmentation (N group). The primary outcome was screw cut-out within 6 months postoperatively. Secondary outcomes included sliding distance (>5 mm), reoperation, nonunion, postoperative infection, and other complications. Group comparisons were performed using two-sided statistical tests with p < 0.05 considered significant.

Results

A total of 300 patients were analyzed (CA, n=97; N, n=203; mean age 86.8 years). No cut-out occurred in the CA group, whereas four cases (1.9%) occurred in the N group (p = 0.12). Sliding distance >5 mm was observed in 2 patients (2.0%) in the CA group and 12 patients (5.9%) in the N group (p = 0.108). Postoperative complications occurred in 2 patients (2.1%) in the CA group and 12 patients (5.9%) in the N group (p = 0.12). No cement-related adverse events were observed.

Conclusions

Cement augmentation during intramedullary nailing was safe and showed numerically lower rates of cut-out and excessive sliding compared with non-augmented fixation. Although statistical significance was not reached, these findings suggest a potential clinical role in elderly patients at high risk of fixation failure. Randomized controlled trials are warranted.

Keywords

proximal femur fracture cement augmentation intramedullary nailing cut-out sliding distance

1. Introduction

Owing to the rapid aging of the global population, proximal femur fractures have become one of the most common and serious injuries among older adults. The reported 1-year mortality after such fractures ranges from 10% to 30%, reflecting their major clinical and socioeconomic impact.^1,2 Early surgical fixation and prompt mobilization are essential for survival, functional recovery, and prevention of complications.

Intramedullary nailing is widely used for trochanteric and basicervical femoral fractures, and secure fixation of the femoral head element is crucial for maintaining fracture stability and enabling early weight-bearing. However, in elderly patients with osteoporosis, reduced bone quality weakens implant anchorage and increases the risk of mechanical failure such as screw cut-out or excessive sliding, which may lead to pain, delayed rehabilitation, and the need for revision surgery.³

Bone cement augmentation using polymethylmethacrylate (PMMA) has been introduced to improve the fixation strength of femoral head elements. Several clinical and biomechanical studies from Western countries have demonstrated improved rotational stability and reduced cut-out rates with cement augmentation. Recent cohort studies have also reported potential benefits in early postoperative mobility and mechanical stability when cement augmentation is used in elderly patients with unstable trochanteric fractures.

In routine clinical practice, however, the decision to use cement augmentation is influenced by multiple factors, including patient age, bone quality, fracture pattern, and the surgeon’s assessment of fixation stability. In Japan, cement augmentation is not indicated for true femoral neck fractures but is increasingly considered for elderly patients with trochanteric or basicervical fractures at high risk of fixation failure. Despite its growing use, real-world multicenter data evaluating its effectiveness and safety in Japan remain limited.^4-6

Therefore, we conducted a multicenter prospective observational study to evaluate the clinical utility and safety of bone cement augmentation in intramedullary nailing for proximal femur fractures in elderly patients. We compared outcomes between patients treated with and without cement augmentation, using cut-out as the primary outcome and sliding distance and postoperative complications as secondary outcomes.

2. Materials and Methods

2.1. Study Design and Participants

This was a multicenter, prospective observational cohort study conducted in accordance with the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. The study was performed at five participating hospitals in Japan, including tertiary care centers and regional core hospitals that routinely provide surgical treatment for proximal femur fractures in elderly patients.

All surgeries were performed by board-certified orthopedic surgeons or senior orthopedic residents under direct supervision, following standard institutional protocols for intramedullary nailing. The choice of using bone cement augmentation or not was made by the treating surgeon based on routine clinical judgment, reflecting real-world clinical practice rather than randomized allocation.

2.2. Participants

Patients aged 45 years or older who underwent intramedullary nailing for proximal femur fractures between May 1, 2021 and July 31, 2023 were prospectively registered. True femoral neck fractures were excluded in accordance with Japanese clinical guidelines, which do not indicate cement augmentation for intracapsular fractures. Basicervical femoral fractures were included as a separate category, as these fractures are commonly treated with intramedullary nailing in Japan and are clinically distinct from true femoral neck fractures. Although the registry included patients aged 45 years or older, cement augmentation was applied exclusively to older patients in actual clinical practice. All patients who received cement augmentation were aged 60 years or older. Inclusion and exclusion criteria are detailed in Table 1. Written informed consent was obtained from all patients or their legal representatives. In patients who underwent cement augmentation, intramedullary fixation was performed using the Trochanteric Femoral Nail Advanced (TFNA) Proximal Femoral Nailing System (DePuy Synthes, West Chester, PA, USA), which allows controlled delivery of polymethylmethacrylate cement through a fenestrated femoral head element. In the non-augmentation group, standard intramedullary nailing systems routinely used at each participating institution were employed. A flow diagram illustrating patient selection and group allocation is shown in Figure 1.

Table 1.

Inclusion and Exclusion Criteria

Inclusion criteria
①	Patients aged 45 years or older at the time of surgery
②	Patients who are deemed suitable for initial nail fixation surgery using or not using bone cement-based augmentation techniques
③	Patients (or their representatives, such as spouse, guardian, or other equivalent individuals) who can provide written consent (signature)
④	Patients who, with the support of themselves or their representatives, can understand and follow the surgical and research procedures (such as answering questions in Japanese) and whose comprehension or capability is confirmed by the principal investigator or sub-investigator.
Exclusion criteria
①	Women who are pregnant or breastfeeding.
②	Patients with obvious deformities in the femoral head and acetabulum.
③	Patients scheduled to use artificial bone augmentation.
④	Patients already enrolled in this study for the opposite femur.
⑤	Patients with fractures in the opposite femur.
⑥	Patients with a history of vascular reconstructive fixation surgery on the affected femur.

Figure 1.

Flow diagram of patient selection, exclusion, and allocation to the cement augmentation (CA) and non-augmentation (N) groups

2.3. Exposure

The exposure of interest was the use of polymethylmethacrylate (PMMA) bone cement augmentation delivered through a fenestrated femoral head element of the Trochanteric Femoral Nail Advanced (TFNA) system during intramedullary nailing.

2.4. Outcomes

The primary outcome was screw cut-out within 6 months after surgery. Secondary outcomes included sliding distance, reoperation, nonunion, infection, and perioperative complications. Sliding distance was defined as >5 mm collapse of the head–neck segment relative to the femoral shaft, measured on standardized anteroposterior radiographs. All radiographs and CT images were anonymized and centrally reviewed. Fractures were classified using the Evans, Ikuta, and Ochi systems.

2.5. Statistical Analysis

Continuous variables were compared using the Student’s t-test or Mann–Whitney U test as appropriate. Categorical variables were compared using the chi-square test or Fisher’s exact test. A two-sided p-value < 0.05 was considered statistically significant. Because this elderly population was expected to have incomplete follow-up, the study protocol was designed to prospectively capture key outcomes during hospitalization and scheduled visits. Analyses were performed using available data without imputation. An a priori power analysis was performed based on an expected clinically meaningful difference in cut-out rates between groups (10% vs 5%), with a two-sided α level of 0.05 and 80% statistical power.

3. Results

Of the 350 patients aged 45 years or older who underwent surgery for proximal femur fractures at the five participating facilities, 300 were followed up. Among them, 97 patients who received augmentation were included in the case group (the CA group), and 203 patients without augmentation were included in the control group (the N group).

The average age was 87.2 years in the CA group and 86.6 years in the N group (p = 0.793). The CA group included 19 men and 77 women (one unknown), and the N group included 50 men and 152 women (one unknown) (p = 0.444). Based on the Evans classification, the CA group had Type 1 fractures: Group 1, 18 cases; Group 2, 44 cases; Group 3, 25 cases; Group 4, 9 cases; and Type 2, 1 case. In the N group, Type 1 had Group 1 with 50 cases, Group 2 with 100 cases, Group 3 with 39 cases, and Group 4 with 13 cases (p = 0.232). Based on the Ikuta classification, the CA group had subtype N in 40 cases, subtype A in 21 cases, and subtype P in 35 cases, whereas the N group had subtypes N (97 cases), A (32 cases), and P (74 cases) (p = 0.247). According to the Ochi classification, the CA group had 37 cases of anatomical type, 47 cases of medial type, and 15 cases of lateral type, whereas the N group had 83 cases of anatomical type, 79 cases of medial type, and 41 cases of lateral type (p = 0.311) (Table 2).

Table 2.

Demographic Data

		Total (n=300)	CA group (n=97)	N group (n=203)	p
sex	Male	69	19	50	0.444
	Female	229	77	152
	unknown	2	1	1
age		86.8	87.2	86.6	0.793
Evans	Type1 group1	68	18	50	0.232
	Type1 group2	144	44	100
	Type1 group3	64	25	39
	Type1 group4	22	9	13
	Type2	1	1	0
	Unknown	0	0	0
Ikuta	Subtype A	53	21	32	0.247
	Subtype N	137	40	97
	Subtype P	109	35	74
	Unknown	1	1	0

Data are presented as number (%). Group comparisons were performed using the chi-square test or Fisher’s exact test as appropriate. All tests were two-sided, and p < 0.05 was considered statistically significant.

The main outcome, cut-out, was observed in 4 cases, all in the N group (the CA group: 0% vs. the N group: 1.9%, p = 0.12). Sliding distance >5 mm was observed in 14 cases, with 2 cases in the CA group and 12 cases in the N group, but there was no significant difference (the CA group: 2.0% vs. the N group: 5.9%, p = 0.108) (Table 3).

Table 3.

Complication Occurrence

		Total (n=300)	CA group (n=97)	N group (n=203)	p
Cut-out	(+)	4	0	4	0.12
Cut-out	(-)	296	97	199	0.12
Sliding distance	(+)	14	2	12	0.108
Sliding distance	(-)	286	95	191	0.108
Outcome	Dead	7	2	5	0.832
Outcome	Survive	293	95	198	0.832

In a subgroup analysis based on the Evans classification, for the stable types, Evans Type 1 Groups 1 and 2, the cut-out and sliding distance were as follows: the CA group had 0 cases and the N group had 4 cases (0% vs. 2.7%, p = 0.324) for cut-out; the CA group had 1 case and the N group had 9 cases (1.6% vs. 6.0%, p = 0.287) for a sliding distance (Table 4). On the other hand, for the unstable types, Evans Type 1 Groups 3 and 4, the cut-out cases were 0 in both the CA group and the N group. For the sliding distance, there was 1 case in the CA group and 3 cases in the N group (2.9% vs. 5.8%, p = 1) (Table 5).

Table 4.

Comparison in the Evans Classification Type 1 Groups 1 and 2

		Total (n=212)	CA group (n=62)	N group (n=150)	p
Sex	Male	50	11	39	0.281
	Female	160	50	110
	unknown	2	1	1
Age		86.2	85.9	86.9	0.742
Cut-out	(+)	4	0	4	0.324
Cut-out	(-)	208	62	146	0.324
Sliding distance	(+)	10	1	9	0.287
Sliding distance	(-)	202	61	141	0.287
Cut-out+Sliding distance	(+)	11	1	10	0.182
Cut-out+Sliding distance	(-)	201	61	140	0.182
Outcome	Dead	6	1	5	0.674
Outcome	Survive	206	61	145	0.674

Table 5.

Comparison in the Evans Classification Type 1 Groups 3 and 4

		Total (n=86)	CA group (n=34)	N Group (n=52)	p
Sex	Male	19	8	11	0.797
Sex	Female	67	26	41	0.797
Age		88.0	87.7	88.2	0.989
Cut-out	(+)	0	0	0
Cut-out	(-)	86	34	52
Sliding distance	(+)	4	1	3	1
Sliding distance	(-)	82	33	49	1
Cut-out+Sliding distance	(+)	4	1	3	1
Cut-out+Sliding distance	(-)	82	33	49	1
Outcome	Dead	1	1	0	0.395
Outcome	Survive	85	33	52	0.395

There were 14 cases of postoperative complications, with 2 cases in the CA group and 12 cases in the N group (2.1% vs. 5.9%, p = 0.12). There were 7 deaths: 2 in the CA group and 5 in the N group (2.1% vs. 2.5%; p = 0.832). No adverse events related to the cement augmentation were observed in the CA group.

4. Discussion

In this study, among the 97 patients who received cement augmentation, no cases of cut-out were observed. In the group without cement augmentation, four cases (1.9%) had a cut-out, while no significant differences in patient backgrounds were found between the groups. Previous reports indicate that the cut-out rate for proximal femoral fractures ranges from 1.6–5.3% or 1.0–6.9%.^7,8 Cut-out often requires screw removal or additional surgery, causing physical and emotional stress in patients, as well as increased medical costs.⁹ Therefore, preventing cut-outs is crucial in the surgical treatment of proximal femoral fractures.¹⁰

Factors that contribute to cut-out include surgical factors such as implant placement and fracture alignment and patient-related factors such as poor bone quality.^11,12 Although surgical factors can be improved using medical techniques, it is difficult to influence patient-related factors, particularly in urgent cases. Proximal femoral fractures are more common in women, particularly after menopause, due to the rapid decrease in bone density. Women have approximately twice the risk of fractures compared to men, making bone quality a major concern for many patients.¹³ Cement augmentation improves the stability of the implant by injecting polymethylmethacrylate (PMMA) bone cement into the femoral head, which enhances the rotational stability and resistance to cut-out.¹⁴ In this study, the overall cut-out rate was low, and no cut-out was observed in the augmentation group.

Patients with proximal femoral fractures often experience various postoperative complications, making prevention crucial. Early surgery and mobilization are essential, and the fracture must be firmly stabilized to enable early weight bearing. Cut-out is one of the most critical postoperative complications; however, excessive sliding distance, which can cause pain and instability at the fracture site, is also problematic. These issues can hinder rehabilitation and make it more difficult for patients to resume daily activities. This study suggests that cement augmentation may help prevent excessive sliding distance by providing strong fixation between the implant and the femoral head. Biomechanical studies have shown that cement augmentation increases the resistance of both screws and blades, which lowers the cut-out rate.^15,16 Although this study did not directly evaluate early functional outcomes, reduced sliding distance may contribute to improved rehabilitation. Because this was an observational study, the decision to use cement augmentation was not randomized and may have been influenced by factors such as age, sex, fracture type, and bone quality. Although baseline characteristics were similar between groups, residual confounding cannot be excluded. Nevertheless, this multicenter prospective design reflects real-world practice in Japan and provides clinically relevant evidence regarding the effectiveness and safety of cement augmentation in elderly patients at high risk of fixation failure.

Bone cement syndrome (BCS) is a serious complication associated with the use of PMMA bone cement. BCS can cause sudden hypoxia, low blood pressure, and loss of consciousness, and, in some cases, cardiac arrest.¹⁷ In this study, no adverse events were observed in the 97 patients who underwent cement augmentation. Proximal femoral fractures primarily affect elderly patients, especially those aged ≥ 65 years. The rate of fractures increases with age owing to the progression of osteoporosis and muscle weakness, with even minor falls leading to fractures. According to Orimo, the incidence of proximal femur fractures in Japan has risen with aging, especially among women aged > 75 years.¹⁸ In this study, the average patient age was 86.8 years, and even minor complications could have been serious. This study’s secondary aim was to assess the safety of cement augmentation. No adverse events were noted during surgery, likely due to careful injection technique, slow pressurization, and vigilant anesthetic monitoring.

The main limitation of this study is its observational nature, which may introduce selection bias regarding the choice of cement augmentation. Moreover, the surgical techniques may not have been consistent across facilities. However, we obtained informed consent from all patients, and the study was prospectively conducted at multiple facilities. No significant differences in patient backgrounds were found between the augmentation and non-augmentation groups, suggesting that our evaluation of the cut-out rate, sliding distance occurrence, and complication rate is more reliable than retrospective single-facility studies.

Although an a priori power analysis was performed, this study was designed as a prospective observational cohort study rather than a randomized controlled trial. However, the results suggest a potential role of cement augmentation in reducing the risk of cut-outs. Future prospective interventional studies with controlled surgical techniques are planned to confirm the effectiveness of cement augmentation.

5. Conclusion

This study’s findings suggest that bone cement augmentation with intramedullary nailing may be associated with improved mechanical stability and a reduced risk of complications in elderly patients. While further research and clinical trials are crucial, this method shows promise as a valuable treatment option for the future.

Footnotes

Acknowledgements

We thank Ayaka Suganami for her writing assistance.

ORCID iDs

Masahiro Matsumoto

Daisuke Enomoto

Yuta Hieda

Ethical Considerations

This study was approved by the Ethics Committee of Yokohama City University Hospital (Approval No. B210100012).

Consent to Participate

Patients provided informed consent to participate. Written informed consent was obtained from all participants.

Consent for Publication

Informed consent for publication was obtained from the participants or their legally authorized representatives. Non-essential identifying details have been omitted to protect the privacy of the participants. The authors hold written informed consent.

Author Contributions

Masahiro Matsumoto: Conceptualization, data collection, manuscript drafting, corresponding author. Hyonmin Choe: Study design, data analysis, manuscript revision. Naomi Kobayashi: Data interpretation, supervision. Kazuyoshi Yamamoto: Clinical data collection, critical revision. Kousuke Matsuo: Clinical data collection, validation. Hiroyuki Makita: Clinical data collection, supervision. Daisuke Enomoto: Data acquisition, investigation. Yuta Hieda: Data analysis, validation. Yutaka Inaba: Supervision, critical review of manuscript. All authors reviewed and approved the final version of the manuscript.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by Johnson & Johnson K.K.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.*

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