1. Introduction

Femoral neck fractures (FNFs) in young adults < 50 years are relatively rare fractures that often result from high-velocity trauma and may be a part of poly-trauma, with multiple fractures, including the ipsilateral femur [1, 2]. FNF patterns in the elderly differ from FNF patterns in young adults. Due to poor bone quality and low-energy injury mechanisms in elderly patients, a subcapital or mid-cervical FNF pattern is more common. Young adults typically have a basi-cervical, vertically oriented FNF pattern because of better bone quality and a higher energy mechanism [3, 4].

Over 330,000 hip fractures, half of which are FNFs, occur annually in the United States (U.S.) and are projected to double by 2050 [1, 5, 6]. Only 2%-3% of all FNFs occur in young adults [3]. Of all young adults with FNFs, only about 4% are treated with hip arthroplasty [7]. However, recent study findings indicate a rising use of hip arthroplasty, especially total hip arthroplasty (THA), among young adult patients in their 40s [8].

Depending on injury type, operative options for FNF include in situ fixation, closed or open reduction and internal fixation (CRIF and ORIF), hip hemiarthroplasty (HHA), and THA [1]. Due to concerns with functional outcomes and implant longevity, HHA and THA are typically avoided as first-line operations in young patients, and the consensus favors internal fixation, which salvages the femoral head [9, 10]. However, femoral head-preserving surgeries come with complications (such as nonunion, malunion, avascular necrosis, surgical site infection, and implant failure) affecting 5%–20% of patients and necessitating revision or conversion to hip replacement [11].

For young adult patients with risk factors for poor bone quality or failed fixation, hip arthroplasty may be performed: (1) THA may be considered depending on pre-morbid mobility and cognitive status; (2) Bipolar HHA may be preferable to THA if such patients have alcohol abuse because HHA might minimize the risk of dislocation associated with alcohol withdrawal or postsurgical intoxication [12]. Recently, more literature has reported the use of hip arthroplasty as first-line operation in patients under the age of 50 [8].

Unlike most existing studies focusing on hip arthroplasty for FNF in older populations, substantial gaps exist in the current knowledge of clinical outcomes of the few young adult patients with FNF who undergo hip arthroplasty as initial surgical treatment. This dearth of information may hinder clinical decision-making and resource allocation [13]. Thus, based on the most current data available in the National Inpatient Sample (NIS), we aim to determine if there is a difference between HHA and THA for young patients FNFs with regard to postoperative LOS (pLOS), prosthesis-related complications (PRCs), and total charges incurred.

2. Methods

3. Results

Among 174,776,205 patient records in the NIS from 2016 to 2020, FNF was the primary diagnosis in 15,590 young adults, representing 2.18% of all FNFs. Of these, 2970 patients (19.05%) underwent hip arthroplasty. Within the hip arthroplasty cohort, 1195 (40.2%) underwent HHA, and 1175 (59.8%) underwent THA (Figure 1).

3.2. Hip Arthroplasty Trends

There was no significant linear trend in the number of HHA or THA procedures performed between 2016 and 2020 (Figure 2).

3.3. In-Hospital Outcomes by Procedure Groups

3.3.1. Unadjusted Comparisons

The mean pLOS for patients undergoing HHA was 5.26 days, and the median pLOS was 4 days. Patients who underwent THA had a mean pLOS of 3.66 days and a median pLOS of 2 days (Table 3).

Table 3. In-hospital outcomes by hip arthroplasty procedure.

In-hospital outcome	HHA N = 1195 (40.2%)	THA N = 1775 (59.8%)	Total N = 2970 (100%)	p value
Mean pLOS (days)†	5.26 (5.99)	3.66 (4.55)	4.30 (5.24)	< 0.001
Median pLOS (days) ∗	4.0 (3.0–6.0)	2.0 (2.0–4.0)	3.0 (2.0–5.0)	< 0.001
PRC
-ML	10 (0.8%)	10 (0.6%)	20 (0.7%)	0.372
-PD	5 (0.4%)	20 (1.1%)	25 (0.8%)	0.038
-PPF	35 (2.9%)	20 (1.1%)	55 (1.9%)	< 0.001
-Aggregate PRC	35 (2.9%)	50 (2.8%)	85 (2.9%)	0.858
Mean adj. total charges ($)⋄	100,110.64 (72,873.48)	100,285.81 (69,404.55)	100,215.33 (70,808.63)	0.007
Median adj. total charges ($)♦	86,225.84 (58,904.00–114,145.27)	75,617.84 (57,296.06–116,572.98)	80,494.95 (58,374.00–114,791.00)	< 0.001

• Note: Percentages in brackets are column percentages. Percentages indicates direct comparison between HHA and THA amongst patients with FNF from year 2016–2020.
• Abbreviations: HHA = hip hemiarthroplasty, ML = mechanical loosening, PD = prosthesis dislocation, PPF = periprosthetic fracture, PRC = prosthesis-related complication, THA = total hip arthroplasty.
• ^†Expressed in mean ± SD days. Distribution is right-skewed (skewness value = 6.551).
•  ^∗Expressed in median days with the IQR in parentheses.
• ^⋄Expressed in mean ± SD U.S. Dollars. Distribution is right-skewed (skewness value = 2.810).
• ^♦Expressed in median U.S. Dollars with the IQR in parentheses.

PPF was the most common PRC following HHA, while PPF and PD were equally prevalent after THA. ML was the second most common PRC in patients who underwent HHA. More patients in the THA group developed PD than patients who had HHA, while patients who underwent HHA developed PPF at a higher rate than patients who had THA. There was no statistically significant difference in the 5-year incidence of ML among both groups (Table 3) (Figure 3).

Mean adjusted total charges incurred for HHA patients were lower than THA by $175.17. However, the median adjusted total charges incurred for HHA patients was higher than THA by $10,608 (Table 3).

3.3.2. Adjusted Comparisons

Controlling for demographic, clinical, and hospital characteristics, multivariable GLM Poisson log-linear analysis revealed a significant relationship between procedure type and pLOS, with patients in the HHA group experiencing a 22.4% longer pLOS compared to those in the THA group (Table 4).

Table 4. Multivariable estimates for in-hospital outcomes by hip arthroplasty procedure.

In-hospital outcome	HHA N = 1195 (40.2%)	THA N = 1775 (59.8%)	p-value
Mean pLOS [exp(B)]	1.224 (1.183, 1.266)	1.0 (REF)	< 0.001
PRC (aOR)
- PD	1.0 (REF)	6.00 (1.78, 20.24)	0.004
- PPF	9.06 (4.21, 19.48)	1.0 (REF)	< 0.001
Mean adj. total charges [exp(B)]	1.0 (REF)	1.033 (0.995, 1.075)	0.092

• Abbreviations: HHA = hip hemiarthroplasty, PD = prosthesis dislocation, PPF = periprosthetic fracture, PRC (aOR) = prosthesis-related complication, THA = total hip arthroplasty.

Multivariable logistic regression analysis adjusted for demographic, clinical and hospital characteristics, showed a significant association between procedure type and PRC for both PD and PPF. THA was associated with six times higher odds of PD than HHA while, HHA was associated with nine times higher odds of PPF compared to THA (Table 4).

No significant change in adjusted total charges between both procedure groups was observed after GLM with gamma and log link analysis, adjusted for demographic, clinical, and hospital characteristics (Table 4).

4. Discussion

The age range defining a young patient often spans from skeletal maturity to 50 years, though the upper limit varies among surgeons [9]. FNFs pose a significant treatment challenge in this population and while internal fixation has traditionally been the standard treatment for young patients with FNF, emerging data suggests a potential shift in these conventions [8, 13]. To our knowledge, this study is the first to utilize a national administrative database to compare in-hospital outcomes of HHA and THA among young adult patients in the U.S.

Our observation of a one-in-five rate of hip arthroplasty in young adults with FNFs represents a fivefold increase compared to prior estimates by Johnson et al., who surveyed orthopedic surgeons primarily in North America and Europe [8]. Similarly, Johnson et al. reported a fourfold increase (from 5.3% to 22.3%) in the use of THA between 2002 and 2014 [8], and Maman et al. documented a 19% THA rate among patients aged 35–44.9, a subset of our study population [13]. This rising use of THA likely reflects the durability of total hip implants as well as risks of avascular necrosis and hardware failures with internal fixation [8]. Our study uniquely identifies a higher-than-expected use of HHA, likely driven by the higher prevalence of comorbidities as well as alcohol abuse or dependence, which affected one out of every six patients in this cohort [12].

Our adjusted models demonstrated significantly higher pLOS among patients who underwent HHA compared to THA. Prior studies on pLOS for FNFs, largely focused on older populations, have shown mixed results [22–24]. Voskuji et al. observed a higher pLOS risk among hip arthroplasty patients with medical comorbidities, despite comparable pLOS between HHA and THA [24]. In our study, HHA patients had more comorbidities than THA patients, which may explain their longer pLOS.

PPF was the most common PRC overall, with patients in the HHA group having a significantly higher adjusted risk of PPF than patients in the THA group. This mirrors findings in previous literature where osteoporosis and wide femoral canals were identified as significant contributors to PPFs in patients who underwent HHA [25]. The relatively low incidence of PD in our study compared to previous studies was unexpected [26]; however, the higher adjusted odds of developing PD after undergoing THA than HHA was consistent with previous studies [26]. Surgical approach is known to influence hip stability, and the anterolateral approach is often recommended given the higher dislocation rates of the posterior approach [27].

Total charges recorded in the NIS vary from patient to patient but typically include charges for hospital rooms, supplies, medications, laboratory fees, and care staff (such as nurses). Total charges may include emergency charges prior to hospital admission but typically exclude professional fees (such as those for doctors) and noncovered expenses [17]. After adjusting for patient and hospital factors, we found no significant change in the adjusted total hospital charges between the procedure groups. In contrast, Slover et al. revealed that HHA patients, on average, had significantly lower costs than THA patients ($57,034 vs. $72,840) [28]. Other studies suggest that beyond the immediate post-op period, HHA may incur higher long-term costs than THA due to treatments for failed HHA or conversion surgeries [29, 30].

This study has several limitations. First, as a retrospective analysis of hospital admission data, it is restricted to inpatient events, making it difficult to assess the duration of FNF symptoms before presentation or long-term postsurgical outcomes. Second, the dataset lacks operative details such as anesthesia type, surgical duration, or blood loss, which are important considerations in surgical research [31]. Third, the small sample size of some PRCs resulted in a quasi-complete separation between PRCs and certain independent variables. To address this, we collapsed problematic variable levels for improved model stability [32].

5. Conclusion

In young adults with FNFs undergoing hip arthroplasty, HHA is associated with a longer pLOS and a higher risk of PPF, while THA is linked to a higher risk of PD. The costs between the two procedures are comparable. When hip arthroplasty is indicated, whether as a primary intervention or a revision after failed internal fixation, patient-specific factors should guide the choice of procedure to optimize outcomes. Further research is needed to clarify the benefits and risks of hip arthroplasty as its use continues to grow in this population.

Conflicts of Interest

The authors declare no conflicts of interest.

Author Contributions

Hembashima Gabriel Sambe contributed to the study concept, design, data acquisition, analysis, and manuscript drafting, revision, and submission. Urvish Patel refined the study design and data analysis and provided careful revisions to the final manuscript. All authors read and approved the final submitted manuscript.

Funding

The authors received no financial support from any third party, institution, organization, or company for the research, authorship, or publication of this article.