Abstract
Background
The anterior-based muscle-sparing (ABMS) approach, using the intramuscular interval between the tensor fascia lata and gluteus medius, is an increasingly popular total hip arthroplasty (THA) approach. Its incidence of lateral femoral cutaneous nerve (LFCN) numbness has not been defined. The incidence of LFCN symptoms in direct anterior THA ranges from 7%-32% at 1-year follow-up. The purpose of this study is to determine the incidence of LFCN symptoms in patients who underwent ABMS THA at 1-year follow-up.
Methods
This was a single-center, multisurgeon retrospective study of ABMS THAs with minimum 1-year follow-up data between January 2014 and September 2021. Eight hundred sixty-nine THAs were included. Mean age of the patients was 67.2 years, with 43.4% male and 56.5% female. Mean body mass index was 26.8, and mean American Society of Anesthesiologists was 2.3. Statistical analysis included chi-square tests, 2-sample t-test, and binomial logistic regression. A P-value of .05 was considered statistically significant for all tests.
Results
Nine patients (1%) reported LFCN-associated symptoms at 1-year follow-up. The most common complaint was numbness (n = 5, 55.6%), followed by diminished sensation (n = 2, 22.2%), burning (n = 1, 11.1%), and generalized pain (11.1%). There was no difference in age, sex, body mass index, or American Society of Anesthesiologists between the group that experienced symptoms and the group that did not (P = 1.00, P = .34, P = .74, P = .80).
Conclusions
The incidence of LFCN dysfunction is 1% at 1 year after surgery with the ABMS approach. Additional studies may elucidate all risks and benefits of the ABMS approach with respect to LFCN injuries.
Keywords: Total hip arthroplasty, Anterior-based muscle-sparing approach, Watson-Jones approach, Lateral cutaneous femoral nerve, Patient-reported outcomes
Introduction
Total hip arthroplasty (THA) is a successful and definitive treatment for end-stage hip osteoarthritis. In the United States, the number of hip replacement operations is projected to rise to 635,000 per year by 2030 [1].
When performing a total hip replacement, there are several types of surgical approaches that can be utilized. Anterior approaches to THA have become increasingly popular in the orthopaedic community as there is mounting evidence of improved early patient recovery [2]. Total hip arthroplasty using the anterior approach can be further differentiated into the direct anterior (DA) approach and the anterior-based muscle-sparing (ABMS) approach.
In the DA approach, the patient is in the supine position, and the interval between the tensor fasciae latae and sartorius is developed to access the hip [3]. In this approach, the lateral femoral cutaneous nerve (LFCN) is vulnerable to injury distally as it travels into the proximal thigh, often through the interval between the sartorius and the tensor fasciae latae. A cadaveric study looked at the variations in the distal branching patterns of the LFCN and found 3 main patterns among specimens: a sartorius type branching pattern, a posterior type branching pattern, and a fan type branching pattern. The sartorius-type pattern depicts the distal LFCN coursing mostly along the lateral aspect of the sartorius muscle; a posterior-type pattern is dominated by a posterior nerve branch running laterally over the tensor fasciae latae muscle; and a fan-type pattern involves multiple spreading branches over the anterolateral region of the proximal thigh between the sartorius and the tensor fasciae latae. Sixty-two percent of the LFCN branches entered the proximal aspect of the thigh medial to the anterior superior iliac spine (ASIS); 27%, above; and 11%, lateral to the ASIS [4]. Given the location of the LFCN as well as the anatomical variation, the DA has been associated with high rates of injury to the LFCN, with estimates ranging from 7%-32% at 1-year follow-up [[5], [6], [7]].
The ABMS approach, alternatively called the Watson-Jones or Röttinger approach, utilizes the interval between the tensor fasciae latae and the gluteus medius muscles and maintains the posterior capsule. One potential advantage is the proposed lower risk of LFCN injury (LFCN) due to the lateral incision.
Injuries to the LFCN are typically reported by patients as numbness and/or a burning sensation on the anterolateral thigh and can be quite distressing to the patient, often leading to patients perceiving a poor result for their THA. As mentioned, the incidence of LFCN dysfunction after DA has been well studied. [[6], [7], [8]] However, the rates of LFCN complications for the ABMS approach have not been well elucidated. The purpose of this study was to document the prevalence of LFCN injury (mostly reported as numbness, burning, or tingling) in an ABMS cohort. Given the larger distance between the ABMS incision and the LFCN, we hypothesize that there is a lower risk of LFCN injury with the ABMS approach when compared to the literature rates with the DA approach.
Material and methods
This project was a single-center, multisurgeon retrospective study approved by the Institutional Review Board prior to its initiation. Patients who underwent THA performed by 2 surgeons utilizing the ABMS approach between January 2014 and September 2021 were identified by an institutional database and included in the study. THAs with incomplete records or not performed by the ABMS approach were excluded from the study.
Patients were identified using our prospectively collected institutional database. The electronic medical record was reviewed for demographic information including age, sex, preoperative body mass index (BMI), and American Society of Anesthesiologists (ASA) grade. Postoperative notes for the 12 months following surgery were reviewed for complaints of neurological symptoms falling into the distribution of the LFCN. Patients were routinely asked at the first postoperative visit about numbness, pain, and other symptoms. Any LFCN-related complaints disclosed during the follow-up visits meeting these criteria were recorded regardless of the length of time from surgery (up to 12 months) or later resolution of symptoms. Symptoms were classified categorically as tingling, burning, numbness, pain, dysesthesias, or “other.”
Demographic statistics were calculated for the population. LFCN complication rates were reported as a percentage of the total sample and further characterized by subtype of symptomatology. The frequency of complication was also tested for association with sex, age, ASA, and BMI. Dichotomous variables were compared using chi-square tests, continuous outcomes were assessed using a 2-sample t-test, and a binomial logistic regression was used to assess for factors associated with LFCN dysfunction. A P-value of .05 was considered statistically significant for all analyses performed. Statistical analysis was performed with the assistance of RStudio Version 2022.1.1.419 (RStudio, Boston, MA) and Excel (Microsoft Inc., Redwood, WA).
Results
The records of 1813 patients who underwent THAs by 2 fellowship-trained arthroplasty surgeons between January 2014 and September 2021 were reviewed. 944 patients were excluded for a non-ABMS approach or incomplete records, leaving 869 THAs in our study population. Of this sample, 378 patients were male and 491 were female; the mean age was 67.2, mean ASA was 2.3, and mean BMI was 26.8 (Table 1).
Table 1.
Demographics.
| Total number of patients included | 869 | |
|---|---|---|
| Male | 378 | 43.4% |
| Female | 491 | 56.5% |
| Mean age | 67.2 | SD: 12.9 |
| Mean ASA | 2.3 | SD: 0.58 |
| Mean BMI | 26.8 | SD: 5.0 |
SD, standard deviation.
Nine patients (1%) experienced LFCN-associated symptoms after ABMS THA (Table 2). The most common complaint was numbness (55.6%), followed by diminished sensation (22.2%), burning (11.1%), and generalized pain (11.1%) in the anterolateral thigh. One patient had a prior medical history of lumbar stenosis, and one patient had a prior medical history of bilateral lower extremity neuropathy. Seven patients with LFCN symptoms did not have any prior nerve pathology.
Table 2.
Symptoms reported among those who had LFCN dysfunction.
| Symptom | Number of patients with each reported symptom (total of 9 patients) |
|---|---|
| Numbness | 5 (55.6%) |
| Diminished sensation | 2 (22.2%) |
| Pain | 1 (11.1%) |
| Burning | 1 (11.1%) |
Of the 9 patients with symptoms, 55.6% were female, the mean age was 55.6, mean BMI was 26.2, and mean ASA was 2.2. Among those without symptoms, 56.6% were female, the mean age was 67.2, mean BMI was 26.7, and mean ASA was 2.3 (Table 3). There was no significant difference in sex, age, BMI, or ASA between the 2 groups (P = 1.00, P = .34, P = .74, and P = .80, respectively). Binomial logistic regression revealed no significant association between LFCN and the demographic characteristics.
Table 3.
Patients with LFCN symptoms at 1 year postoperatively and their associated demographics.
| Variable | LFCN dysfunction | No dysfunction | P-value |
|---|---|---|---|
| Number of patients with LFCN dysfunction at 1 year | 9 (1%) | 860 (99.0%) | |
| Sex (female [%]) | 5 (55.6%) | 486 (56.6%) | 1.00 |
| Age (SD) | 63.0 (13.6) | 67.2 (12.9) | .34 |
| BMI (SD) | 26.2 (5.9) | 26.7 (5.0) | .74 |
| ASA (SD) | 2.2 (0.44) | 2.3 (0.57) | .80 |
SD, standard deviation.
Discussion
Total hip replacement is the standard for treating hip pain and restoring hip function after end-stage degeneration. Anterior approaches are popular, with 2 well-described exposures: the DA approach and the anterior-based muscle-sparing (ABMS) approach. Our case-control study found that the incidence of LFCN dysfunction following the ABMS approach was approximately 1% at 1-year follow-up from index surgery. Interestingly, the 1% incidence recorded may reflect the similarly reported rate of rare, aberrant courses of the LFCN.
Several studies have reported that the 1-year incidence of LFCN dysfunction after DA THA range from 7%-32% at 1-year follow-up [[5], [6], [7]]. The incidence of LFCN dysfunction after the ABMS approach in this study is lower compared to the reported risk after the DA approach. One study that compared outcomes of 550 patients (447 primaries, 103 revisions) THA with the ABMS (n = 212), DA (n = 79), posterolateral (n = 79), and Muller-modified Hardinge (n = 180) approaches found no significant differences in THA perioperative complications between the DA and ABMS groups except for the incidence of LFCN injury, which was 0/185 patients after primary ABMS THA and 7/77 patients after primary DA THA [8].
The strength of this study lies in the sample size of just under 900 patients, which allowed detection of a low-rate finding. The potential limitations of this study include the retrospective nature of the study, which can lead to recall bias. Additionally, there may be some inconsistencies in patient-reported symptoms and documentation within the electronic medical record. The presence of LFCN symptoms was recorded if patients reported any numbness, burning, tingling, or dysesthesias in response to questioning. There was no standardized questionnaire given out to patients. Another limitation is that there were no objective nerve conduction or nerve physical exam tests to differentiate true LFCN dysfunction vs self-reported terminology resembling nerve dysfunction.
Conclusions
This study found that the 1-year postoperative incidence of LFCN dysfunction after THA is 1% when using the ABMS approach, which is lower than established rates using the DA approach. To date, this is the largest and only study to report on the rate of LFCN dysfunction as a primary endpoint after THA using the ABMS approach.
Conflicts of interest
R. P. Shah is a paid consultant for Link Orthopaedics, Monogram, and Zimmer; is an unpaid consultant for OnPoint; has stock options in Parvizi Surgical Innovations; and is a board/committee member of the American Association of Hip and Knee Surgeons and the US Food and Drug Administration. J. A. Geller receives royalties from Smith & Nephew; is a Smith & Nephew speaker; is a paid consultant for Nimble Health and Smith & Nephew; has stock options in Zimmer; receives research support from Orthopaedic Scientific Research Foundation, OrthoSensor, and Smith & Nephew; and is an editorial/governing board member of Clinical Orthopaedics and Related Research, Journal of Arthroplasty, Journal of Bone and Joint Surgery-British. H. J. Cooper is a 3M speaker; is a paid consultant for 3M, Canary, DePuy, Polaris, and Zimmer Biomet; has stock options in Polaris; receives research support from Smith and Nephew; is an editorial board member of the Journal of Bone and Joint Surgery (American); and is a board/committee member of AAOS and the Eastern Orthopaedic Association. All other authors declare no potential conflicts of interest.
For full disclosure statements refer to https://doi.org/10.1016/j.artd.2024.101449.
CRediT authorship contribution statement
Alaka Gorur: Writing – original draft, Methodology, Investigation, Formal analysis, Data curation. Joseph Genualdi: Methodology, Investigation, Formal analysis, Data curation. Taylor Paskey: Writing – review & editing, Methodology, Data curation. Christopher Blum: Validation, Methodology. Alexander L. Neuwirth: Validation, Methodology. H. John Cooper: Validation, Methodology. Roshan P. Shah: Writing – review & editing, Validation, Supervision. Jeffrey A. Geller: Writing – review & editing, Validation, Supervision, Conceptualization.
Appendix A. Supplementary Data
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