Femoral Nerve Palsy After Anterior Total Hip Arthroplasty: A Systematic Review

Abstract

Background

Femoral nerve palsy (FNP) is a rare but debilitating complication of total hip arthroplasty (THA). The direct anterior approach (DAA) has been gaining popularity in recent years. Concerns regarding the risk of FNP after DAA THA have been rising due to the anatomical proximity of the femoral nerve. This systematic review evaluates the risk and incidence of FNP after DAA THA.

Methods

A search was conducted using PubMed, Cochrane, Ovid Medline, and Scopus databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Data were extracted pertaining to incidence, comparison to other approaches and recovery. A qualitative analysis was done.

Results

Our study included 9 studies—1 randomized control trial, 3 retrospective reviews, 4 case series, and 1 case report. The total sample size of DAA THA patients was 16,258 with an incidence of 0.36% (95% confidence interval (CI), 0.28-0.47%). The 3 studies that compared DAA to other approaches reported a higher incidence of FNP with the DAA. Of the studies that included recovery, most cases of FNP demonstrated full motor recovery in 3-15 months.

Conclusions

FNP is a rare complication of THA that occurs more frequently in the DAA. Retractor placement, patient positioning, and patient related risk factors play a key role in increasing risk. Further high quality studies are needed to assess the risk and preventative measures.

Level of Evidence

V.

Introduction and background

Total hip arthroplasty (THA) can be performed via anterior, posterior, and lateral approaches, each with their own unique advantages and disadvantages [1,2]. The posterior and lateral approaches provide visualization of the proximal femur and acetabulum with the option to extend distally for a more extensile exposure of the femur [2]. Disruption of the posterior capsule and short external rotators with the posterior approach, however, raises concerns for increased postoperative dislocation rates [2]. The anterior approach, in comparison, is a muscle-sparing technique that is increasing in popularity due to its purported benefits. Recent studies suggest the anterior approach can provide earlier restoration of gait kinematics, lower dislocation rate, and decreased pain leading to overall faster recovery and increased hip stability [1,2].

In addition to postoperative dislocation, abductor insufficiency, periprosthetic, fracture, and iatrogenic nerve injury are other common concerns associated with THA. The reported prevalence of iatrogenic motor nerve injury after THA is around 1% and can occur due to trauma during dissection, retraction, or placement of implants [2]. The most common nerves injured are the superior gluteal, lateral femoral cutaneous, sciatic and femoral; with rates of lateral femoral cutaneous nerve injury reported as high as 81% [2,3]. Nerve palsy is the most common reason for medical litigation after THA, making it a very costly complication with the average payout of $1 million [4]. Concerns have emerged regarding the risk of femoral nerve palsy (FNP) associated with the direct anterior approach (DAA). Unlike other approaches, the DAA places the femoral nerve in close proximity to the surgical field, especially during anterior acetabular retraction. The femoral nerve is at risk during rigorous retraction of the anterior acetabulum with the rate of FNP after THA reported to be as high as 2.4% [2]. FNP can lead to significant symptoms, including weakness, sensory loss, and prolonged recovery [4]. Despite the rising use of the DAA, studies specifically evaluating the incidence of FNP following this technique remain extremely limited. Prior research has rarely compared the risk of FNP in the DAA to other surgical approaches in a comprehensive manner. Given the anatomical proximity of the femoral nerve during DAA THA and the serious impact of FNP on postoperative recovery and litigation risk, a focused evaluation is necessary. The goal of this systematic review is to close the gap in literature by assessing the incidence and risk of femoral nerve injury in the DAA for THA and to analyze the incidence in this approach compared to other surgical approaches.

This systematic review aims to do the following:

• 1.Determine the incidence of FNP following THA using the DAA,
• 2.Compare the incidence of FNP in DAA vs other surgical approaches,
• 3.Evaluate the extent and timeline of motor recovery in patients with FNP, and
• 4.Identify patient- and surgery-specific risk factors contributing to FNP in DAA THA.

Material and methods

Search strategy

This systematic review used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The study protocol was registered with PROSPERO international registry (ID: CRD420251077127). The search was performed using Pubmed, Cochrane, Ovid Medline, and Scopus databases. The search was performed on June 3, 2025, with no date restrictions on the search. The search phrases used were based on Medical Subject Headings (MeSH) terms and keywords related to THA, DAA, and FNP. The search strategy is summarized in Appendix A.

Study selection

The inclusion criteria were as follows: (1) clinical studies (cohort study, case-control study, randomized control trial (RCT), case series, case reports), (2) study population undergoing THA with the DAA, (3) studies reporting on the outcome of interest (FNP/femoral nerve injury). The exclusion criteria were as follows: (1) articles not published in English, (2) systematic reviews, commentary, letters, protocol, or technical notes, (3) cadaver studies, (4) abstracts only or articles without access to the full manuscript, and (5) studies that did not report relevant outcomes. Duplicate articles were removed. Titles and abstracts were independently screened by 2 authors, followed by full text screening for eligibility (M.Z. and A.M.). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart illustrates the article selection process (Fig. 1).

Figure 1.

PRISMA flow diagram. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Data extraction and risk of bias assessment

The Grading of Recommendations, Assessment, Development and Evaluation tool was used to assess the quality of the included studies (Table 1) [5]. The level of evidence of the included studies was assessed using the Oxford Center for Evidence-Based Medicine [6]. A qualitative data analysis was conducted due to the heterogeneity of the articles. Data from the included studies were extracted into a spreadsheet. Data collected included: article title, first author, journal, study type, level of evidence, follow-up time, demographic information (age, body mass index, sex), sample sizes of DAA groups and other approach groups, femoral nerve injury rates in direct anterior groups and control groups. Although a formal meta-analysis could not be conducted, a pooled incidence of FNP was calculated as a weighted average of event rates across the included studies. The 95% confidence interval was calculated using standard error and the normal approximation for bimodal distributions. All calculations were conducted using Microsoft Excel.

Table 1.

GRADE rating of included studies.

Study author	Publication year	Study design	ITT analysis	Blinding	Allocation Concealment	% Lost to follow-up	Controlled crossover effects	Randomization	GRADE quality
Fleischman et al.	2017	Retrospective review	N/A	No	N/A	Not specified	N/A	No	Low
Slaven et al.	2022	Retrospective review	N/A	No	N/A	Not specified	N/A	No	Low
Mjaaland et al.	2018	RCT	Yes	Not specified	Yes	<5%	Yes	Yes	High
Macheras et al.	2016	Retrospective review	N/A	No	N/A	Not specified	N/A	No	Low
Hallert et al.	2012	Case series	N/A	No	N/A	Not specified	N/A	No	Low
Alexandrov et al.	2014	Case series	N/A	No	N/A	Not specified	N/A	No	Low
Hoshino et al.	2019	Case series	N/A	No	N/A	Not specified	N/A	No	Low
Patton et al.	2018	Case series	N/A	No	N/A	Not specified	N/A	No	Low
Tam et al.	2024	Case report	N/A	No	N/A	0%	N/A	No	Very low

Summary of Included Studies: Femoral Nerve Palsy After Direct Anterior THA.

GRADE, Grading of Recommendations, Assessment, Development and Evaluation.

Results

Study selection

The initial search of our databases yielded 396 results which were screened for duplicates. Titles and abstracts were then screened and then 29 full-text articles were assessed for eligibility based on our inclusion and exclusion criteria. A total of 9 studies were included in our final systematic review (Fig. 1).

Study characteristics

Of the 29 articles assessed for eligibility, 9 were included in our review. There was 1 RCT, 3 retrospective review studies, 4 case series and 1 case report included. The overall Grading of Recommendations, Assessment, Development and Evaluation quality assessment was low or very low for all articles except the RCT which was graded high (Table 1). In total, there was a sample size of 16,258 patients who received a direct anterior THA. The average age of patients across all 9 studies was 63.4 years. The average follow-up time across the studies was 19.7 months.

Incidence of FNP after DAA

The overall incidence of FNP across all 9 studies was 0.36% (95% CI, 0.28%-0.47%).

Comparison to other approaches

Three studies directly compared the incidence of FNP between the DAA and other surgical approaches: Fleishman et al., Slaven et al., and Mjaaland et al. All of which reported a higher FNP incidence in DAA [[7], [8], [9]], with 1 (Fleishman et al.) reporting statistical significance (14.8-fold increased risk, P < .0001) [7].

Recovery outcomes

Among the 6 articles that reported recovery times, 79% of the patients had full motor recovery within 3-15 months [4,[10], [11], [12], [13], [14]]. Partial deficits persisted in rare cases [14].A summary of the studies included is shown in Table 2.

Table 2.

Summary of included studies.

Study	Study design	Sample size (DAA)	Average age (y)	FNP cases (DAA)	FNP incidence (DAA)(%)	Follow-up time (months)	Recovery reported (motor)
Fleischman et al.	Retrospective review	5797	61.9	26	0.4%	24	Not specified
Slaven et al.	Retrospective review	6592	68	13	0.2%	31.2	60% full recovery
Mjaaland et al.	RCT	84	66	3	3.6%	24	Not specified
Macheras et al.	Case series	1512	65.2	4	0.26%	29.4	Three of 4 recovered within 6 mo
Hallert et al.	Case series	200	67.4	1	0.5%	12	Not specified
Alexandrov et al.	Case series	43	62	2	4.6%	16.8	Both resolved in 3 mo
Hoshino et al.	Case series	273	61.7	3	1.1%	12	All recovered within 1 y
Patton et al.	Case series	1756	62.7	6	0.34%	13	All recovered within 13 mo
Tam et al.	Case report	1	56	1	100%	15	75% recovery at 15 mo

Patient- and surgery-specific risk factors

Reported risk factors included anterior retractor placement, aggressive retraction, hip extension/external rotation during surgery, female sex, hip dysplasia, large osteophytes, and cementless fixation [4,[7], [8], [9], [10], [11], [12], [13], [14]].

Discussion

FNP is a rare complication of THA, with a higher incidence when the DAA is used. Mechanistically, FNP may occur after entering the wrong interval during dissection, drifting medially into the femoral neurovascular interval instead of the intended DAA plane which is more lateral (between the tensor fasciae latae and sartorius). The anterior acetabular retractor may also be places too medially and compress the femoral nerve [2,4,[13], [14], [15], [16]]. Patients may present with weakness in the quadricep muscle, pain, and numbness in the anteromedial thigh [10]. Quadriceps weakness impairs knee extension, hip flexion, and balance which increases fall risk and may prolong recovery time [4,[10], [11], [12], [13], [14],17,19]. While most cases resolve over time, FNP can significantly affect patients' recovery postoperatively. In our systematic review, we found an overall incidence of 0.36% for FNP after DA THA. While 3 studies found a higher incidence of FNP after DAA when compared to other approaches, only Fleischman et al. reported a statistically significant difference and a 14.8 fold increased risk [[7], [8], [9]]. The remaining studies included in this review were retrospective series or case reports without control groups or statistical comparison between the different approaches. Therefore, caution should be taken in regards to generalizing the incidence or risk of FNP across all DAA cases. However, the consistency of reported mechanical factors, such as retractor related injury, warrants further investigation. More large, prospective, comparative studies are needed on this topic.

FNP has been reported across all surgical approaches, not just DAA. The current literature reports a much lower incidence rate of FNP in the posterior and direct lateral approaches compared to the DAA. Prior studies have reported FNP rates ranging from 0.01% to 0.1% in posterior approaches and near zero in lateral approaches [[17], [18], [19]]. The lower incidence in these approaches may be due to the femoral nerve’s increased distance from the operative site compared to the DAA where the retractors proximity to the neurovascular bundle increases the risk of mechanical injury.

The etiology of FNP in the DAA is multifactorial. Placement of the anterior acetabular retractor has been reported in many studies to be one of the greatest risk factors of FNP due to pressure and/or direct trauma to the femoral nerve [4,8,[13], [14], [15], [16]]. Aggressive soft tissue retraction, excessive limb lengthening, trauma to the iliopsoas, and excessive hip extension, abduction, and external rotation intraoperatively can also contribute to nerve injury [4,[7], [8], [9], [10], [11], [12], [13], [14]].

Preoperative planning plays a crucial role in minimizing nerve injury risks. Female sex, coagulation abnormalities, cementless fixation, hip dysplasia, and history of trauma are all patient-specific risk factors for FNP [8]. Additionally, the presence of large osteophytes can interfere with proper retractor placement and raise the risk of nerve compression [13]. This preoperative planning may entail using a low profile retractor or intermediate release of the anterior retractor in females or patients with suspected smaller soft tissue space [2,8,16]. Preoperative (CT) scans may be used in patients with prior trauma or large osteophytes in order to map and plan the safe interval [2,4,13,16]. Timed anticoagulation and a low threshold for hematoma development postoperatively are measures that may be taken in patients with coagulation abnormalities as FNP can result from a compressive hematoma [18,19].

Several studies reported complete resolution of motor symptoms after 6 to 15 months, however, not all studies included their long-term outcomes and recovery timeline, making it difficult to assess the rate of recovery vs permanent motor or sensory deficits [4,8,[11], [12], [13]]. Surgical intervention such as nerve reconstruction and tendon transfers may aid in restoring function in cases where full recovery does not occur [14].

DAA has regained popularity due to its benefits such as decreased pain postoperatively, lower dislocation rates, and earlier ambulation. However, it is important to consider the risk of femoral nerve injury in these cases. This review highlights the need for increased awareness, precise surgical technique, and the importance of patient selection for this approach.

Based on the findings of this study, several key research questions emerge: (1) what is the exact mechanism by which anterior retractor placement contributes to femoral nerve injury in DAA THA?, (2) what is the incidence of permanent vs transient FNP after DAA in long-term follow-up?, and (3) are there specific patient characteristics such as body mass index, anatomy, or pre-existing conditions that predispose patients to FNP? Future prospective, comparative studies are needed to address these questions and in order to further guide surgical technique and patient selection.

Limitations

There are several limitations to this review. The studies included were heterogeneous in design and reporting outcomes, with most consisting of case series or retrospective reviews, leading to an overall low level of evidence. The variable reporting outcomes made it difficult to assess factors such as recovery. Only a small number of studies directly compared DAA to other surgical approaches, restricting the ability to assess relative risk. Overall, there are not many studies published specifically on FNP after DAA THA.

Conclusions

FNP is a rare but clinically significant complication following THA, with an increased incidence found in the DAA. More high quality, prospective comparative studies are needed to better define the risk of FNP after DAA THA compared to other approaches. Studies assessing the positioning of the retractor and limb may offer insight into possible surgical modifications to decrease risk of FNP in DAA.

Conflicts of interest

Richard S. Yoon receives royalties from Arthrex, Inc. and Stryker; is a Paid consultant for Arthrex, Inc. CustomSurg, DePuy, A Johnson & Johnson Company, LifeNet Health, MiCare Health, ORTHOXEL, SI-Bone, Stryker, Synthes, Use-Lab, and OrthoGrid; owns Stock or stock options in CustomSurg, ORIntelligence, and WNT Scientific; receives Research support from AO Foundation, AO Innovation Translation Center, Biocomposites, Biomet, COTA, DePuy, A Johnson & Johnson Company, Irrimax, LifeNet Health, OMEGA, Organogenesis, Pacira, SI-Bone, Smith & Nephew, and Synthes; receives Royalties, financial or material support from Springer; and is a Board member/committee appointments for American Association of Hip and Knee Surgeons, Foundation for Orthopedic Trauma, Foundation for Physician Advancement, and Orthopaedic Trauma Association.

The other authors declare no potential conflicts of interest.

For full disclosure statements refer to https://doi.org/10.1016/j.artd.2025.101889.

CRediT authorship contribution statement

Mallery Zeiman: Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis, Data curation. Athena Makrides: Writing – original draft, Investigation, Formal analysis. Jason Lee: Writing – review & editing. Richard S. Yoon: Writing – review & editing, Supervision, Project administration, Conceptualization.