The distance of the femoral neurovascular bundle from the hip joint: an intraoperative guide to reduce iatrogenic injury

The Anatomical Course of the Femoral Nerve with Regard to the Direct Anterior Approach for Total Hip Arthroplasty

BACKGROUND

Femoral nerve (FN) injury is noted as a serious neurological complication following total hip arthroplasty performed via a direct anterior approach (DAA). Therefore, we aimed to clarify the anatomical course of the FN around the acetabular rim and in relation to retractor placement during DAA.

METHODS

According to standard protocol, a DAA for total hip arthroplasty was performed on 69 hemipelves from formalin-preserved full-body donors. The surgery was halted after retractor placement at the anterior part of the acetabulum. Then dissection was performed to expose the FN and the iliopsoas muscle. Various measurements were taken using a reference line from the anterior superior iliac spine to the acetabulum's center. A total of 6 measurement points, one every 30° from 0° to 150° along the reference line were used to determine the association between the FN and the retractor tip (RT) and the anterior acetabular rim.

RESULTS

The mean distance from the RT to the FN was 22.5 millimeters (mm). The distance from the FN to the anterior acetabular rim decreased from 0 to 90°, where it was 18.8 mm, before increasing again to 27.3 mm at 150°.

CONCLUSIONS

In our cadaveric study, the FN was within 11 to 36 mm of the RT. Second, we found the FN to be closest to the anterior acetabular rim at 90° and 120°. Accordingly, special care should be taken during retractor placement, and if possible, placement at 90° and 120° avoided.

Optimal retractor insertion point for nerve safety during total hip arthroplasty: an anatomical study on the femoral and sciatic nerves in relation to hip motion

BACKGROUND

Nerve injury is one of the most serious complications of total hip arthroplasty (THA). It is suspected to be a result from nerve compression or direct injury caused by an acetabular retractor. The anatomical relationship between the acetabular rim and the femoral and sciatic nerves, including hip motion, has not been investigated. This study aimed to identify the optimal position for retractor insertion during THA to prevent nerve damage.

METHODS

A total of 28 hip joints from 14 freshly frozen cadavers were used. Using an anterolateral approach, each cadaver was immobilised in the lateral decubitus position and deployed to measure the distance between the nerves and the acetabular rim, while the hip joint was changed to the extension, neutral, and flexion positions.

RESULTS

Three femoral nerves were closest to the anterior margin of the acetabulum at 90° and 120° of extension and farthest away at 30° of flexion. The sciatic nerve was closest to the posterior margin of the acetabulum at 90° and 120° of flexion and farthest away at 30° and 150° of extension compared with the other points.

CONCLUSIONS

To prevent nerve damage during THA, we suggest that the retractor be inserted at the points where the nerves are the farthest away, such as at 30° and 150°. The femoral and sciatic nerves vary in their movements depending on the hip position. Therefore, the safe insertion of a retractor is recommended for hip flexion of the femoral nerve and extension of the sciatic nerve. Additionally, it is important to carefully insert the retractor along the acetabular margin without penetrating the joint capsule. Overall, this study provides valuable insights into the anatomical location and movement of the femoral and sciatic nerves in relation to hip motion and can help inform surgical techniques for safer THA.

Modified Smith-Petersen approach with rectus-sparing reduces severe avascular necrosis for developmental dysplasia of the hip at walking age: minimum 5-year follow-up

BACKGROUND

Developmental dysplasia of the hip (DDH) is one of the most common orthopedic malformations in children. Open reduction for DDH at walking age remains a major concern. The goal of this study is to evaluate the mid-term effect of a modified Smith-Petersen approach which preserves the rectus femoris on DDH at walking age, in particular avascular necrosis (AVN).

METHODS

A retrospective review of DDH patients aged between 12 and 24 months was carried out between January 2010 and June 2016. Open reduction through the Smith-Petersen approach (Group A) and modified Smith-Petersen approach, which preserves the rectus femoris (Group B), were both used. Measurement of hip geometry included acetabular index, the International Hip Dysplasia Institute classification, and AVN degree. Clinical records included operation time, bleeding volume, and abduction angle.

RESULTS

There were 101 children (119 hips) with DDH who met the inclusion criteria. There were 66 hips in Group A and 53 in Group B. The mean surgical age at open reduction was 17.0 ± 2.4 months, with a mean 104.9 ± 19.5 months at last follow-up. There was no statistical difference in surgical age between the two groups (17.2 vs. 16.4 months). There was no significant difference in the incidence of all types of clinically significant AVN between group A and group B (27.3 vs. 18.9%), but the incidence of severe AVN was lower in group B (19.7 vs. 5.7%, P = 0.026). In addition, the lower the age at the time of open reduction, the lower the severity of AVN (P = 0.002).

CONCLUSIONS

These mid-term data suggest that the modified Smith-Petersen approach with rectus-sparing could reduce severe AVN more than the classical Smith-Peterson approach in open reduction in DDH at walking age. In addition, early open reduction can reduce the postoperative degree of AVN.

Peroneal artery safe zone in the posterolateral approach to the distal tibia: A CT angiogram based anatomical study

OBJECTIVES

The posterolateral approach to the distal tibia is commonly used for stabilisation of ankle fractures as it allows good visualisation and direct reduction of the posterior distal tibia and malleolar fragments. This approach can also be used for internal fixation of an associated lateral malleolus fracture. The aim of our study is to describe the surgical anatomy of the peroneal artery (PA) in relation to the tibial plafond and the distal fibula; thereby suggesting a safe zone during proximal dissection of posterolateral approach.

METHODS

Using Computed Tomography Angiographic (CTA) study, the course of the PA in relation to the tibial plafond and distal fibula was analysed in 142 lower limbs (bilateral limbs of 71 adult patients; 43 males and 28 females). Axial, coronal, and sagittal CT sections were cross-linked to specify the position of the PA. The PA course was identified and the level of its distal bifurcation over the tibia was marked. Perpendicular measurements were made from this point to the tibial plafond and tip of distal fibula.

RESULTS

The PA bifurcated distally at mean 58.3±24.2mm (SD) (range: 37.0-115.0mm) proximal to the right tibial plafond and mean 81.9±24.4mm (range: 54.0-137.0mm) from the right distal fibular tip. In the contralateral side, the PA bifurcated at mean 57.9±23.3mm (range: 36.0-125.0mm) proximal to the left tibial plafond and 81.8±23.9mm (range: 54.0-147.0mm) from the left distal fibular tip. The difference between the right and the left side of distal bifurcation point diameter of the same patient was assessed, range (0.0-58.0mm) with median 2.0mm and IQR 10.0mm. Three different PA vasculature patterns were identified.

CONCLUSIONS

It is important for surgeons to be aware of the surgical anatomy of PA to avoid inadvertent injury during posterolateral approach to distal tibia. The PA may bifurcate as close as 36mm from the tibial plafond with possible variation bilaterally. Therefore, special attention needs to be considered by the operating surgeon while dissecting in this region due to the wide anatomical variation in vasculature. However, once the PA is mobilised, any fixation modality including posterior buttress plate could be safely performed.

Does surgical body position influence the risk for neurovascular injury in total hip arthroplasty? A magnetic resonance imaging study

BACKGROUND

Neurovascular injury is a critical complication in total hip arthroplasty (THA). However, neurovascular geographic variations around the hip joint in different body positions have not been examined. This study investigated the differences in hip neurovascular geography in the supine and lateral positions using magnetic resonance imaging (MRI).

HYPOTHESIS

The neurovascular geography of the hip is influenced by differences in surgical body position.

PATIENTS AND METHODS

This was a single-center prospective study of 15 healthy volunteers enrolled between January 2018 and March 2019. Each subject's bilateral hips were scanned with a 3-T MRI scanner in both the supine and lateral positions. In T1-weighted axial images at the level of the hip center, the anterior and posterior acetabular edges were defined as reference points at which retractors are commonly placed during surgery. We measured the distance between the anterior acetabular edge and the femoral nerve (dFN), femoral artery (dFA), and femoral vein (dFV), as well as that between the posterior acetabular edge and the sciatic nerve (dSN). The primary outcome measures were the distances in both the supine and lateral positions.

RESULTS

dFN, dFA, and dFV in the supine and lateral positions (mm, mean±standard deviation) were 25.8±5.6 and 32.4±6.4 (p<0.0001), 25.7±4.5 and 32.2±5.0 (p<0.0001), and 26.5±4.8 and 32.3±5.1 (p<0.0001), respectively. Most of these elements moved anteromedially in the lateral position compared to the supine position. There was no significant difference in dSN between the supine and lateral positions (23.7±4.9 and 24.5±6.5 (p=0.46).

DISCUSSION

THA in the supine position may be accompanied by a higher risk of femoral neurovascular injury than that in the lateral position. The application of our findings could reduce the risk of femoral neurovascular injury during THA.

LEVEL OF EVIDENCE

III; prospective diagnostic case control study.

The distance between the femoral nerve and anterior acetabulum is significantly shorter in hip osteoarthritis than in non-osteoarthritis hip

Background

The appropriate position of retractors to minimize the risk of femoral nerve palsy remains uncertain. The purpose of this imaging study was to evaluate the distance between the femoral nerve (FN) and anterior acetabulum (AA) in hip osteoarthritis (OA).

Methods

Forty-one patients with unilateral hip OA underwent magnetic resonance imaging. Three measurement levels were defined and the minimum distance between the femoral nerve (FN) margin and anterior acetabulum (AA) rim was measured on axial T1-weighted images on the OA and normal sides at each level, with reference to an advanced neurography view. The cross-sectional area (CSA) of the iliopsoas muscle was also measured at each level bilaterally by three observers. Distances and CSAs were compared between the OA and normal side. Multiple regression analysis was performed to identify variables associated with the distance in OA.

Results

The mean minimum FN to AA distances in OA were 19.4 mm at the top of the anterior inferior iliac spine (AIIS), 24.3 mm at the bottom of the AIIS, and 21.0 mm at the tip of the greater trochanter. These distances were significantly shorter than in normal hips at the top and bottom of the AIIS, with mean differences of 1.6 and 5.8 mm, respectively (p = 0.012, p < 0.001). CSAs of the iliopsoas in OA were significantly smaller at all levels (all p < 0.001), with reductions of 10.5 to 17.9%. The CSA of the iliopsoas at the bottom of the AIIS was associated with the FN to AA distance at the same level (p = 0.026). Interobserver reliabilities for measurements were very good to perfect (intraclass correlation coefficients 0.897 to 0.966).

Conclusions

To minimize the risk of femoral nerve palsy, surgeons should consider the change of the femoral nerve to anterior acetabulum distance in osteoarthritic hip surgery.

Anatomic Relationship of the Femoral Neurovascular Bundle in Patients With Congenital Femoral Deficiency

BACKGROUND

Congenital femoral deficiency (CFD) is a rare condition that affects the morphology of the hip and surrounding soft tissues. Bony deformity and distorted muscular anatomy are well known, but no studies have described the relationship of the femoral neurovascular (NV) bundle to surgically relevant anatomic landmarks. The authors compared the location of the femoral NV bundle on the affected side in patients with CFD with the unaffected side. The authors hypothesized that the bundle on the pathologic side would be in an abnormal position relative to the unaffected side.

METHODS

Thirty-three patients diagnosed with unilateral CFD who had undergone preoperative magnetic resonance imaging of the pelvis were included in our study. The authors identified the femoral NV bundle on the axial cuts and measured its distance from the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), and lesser trochanter (LT). Anatomic percent change and absolute measurements were then compared and correlated with associated boney deformities and the Paley classification.

RESULTS

The distance from the femoral NV bundle to the ASIS, AIIS, and LT was significantly different compared with the unaffected side. The AIIS absolute distance and AIIS percent change significantly correlated with the neck-shaft angle of the proximal femur.

CONCLUSIONS

In patients with CFD, the femoral NV bundle seems to be further from the LT and closer to the AIIS on the affected side when compared with the unaffected side. magnetic resonance imaging may be helpful to understand the course of the femoral NV bundle before reconstruction in patients with CFD; however, the authors recommend identification of the femoral NV bundle before transection of the proximal rectus femoris tendon to provide safe surgical care.

LEVEL OF EVIDENCE

Level IV-case-control study of diagnostic studies.

Location of Femoral Vessels Around the Acetabulum in Crowe Type 4 Dysplastic Hips

BACKGROUND

There are anatomical differences in the femur and acetabulum on the dysplastic hips. Yet, although there are detailed researches on bony structure differences, studies regarding anatomical differences for the vascular structure are insufficient. The study aimed to determine the relationship between the femoral artery and vein with acetabulum in computed tomography evaluation of Crowe type 4 hips and to compare with normal hip femoral vein and artery anatomic position.

METHODS

Forty patients with one side hip Crowe type 4 deformity and opposite side normal hip were found suitable for the study. Pelvis CT was previously applied to all patients for the planning of total hip arthroplasty surgery. Normal hip acetabulum and the true acetabulum of the dysplastic hip were marked with the Ranawat's triangle and were then divided into quarters with four axial slices of the acetabulum; as dome, proximal one-fourth, center, and distal three-fourths. The shortest distance from the femoral vessels to the pelvis was measured at these 4 axial slices at the dysplastic side and compared with the healthy side.

RESULTS

The distance of the vein to the acetabulum is closer to the dysplastic side. At distal three-fourths of Ranawat's triangle axial images, both femoral artery and femoral vein are closer to acetabulum at the dysplastic side.

CONCLUSION

The analysis of preoperative images in cases of Crowe type 4 hip shows that the femoral vessels are closer to the anterior wall of the dysplastic true acetabulum at the level of the center of the hip (vein, mean: 2.7 mm closer) and below the center of the hip (vein, mean: 3 mm; and artery, mean: 3.3 mm closer) when compared with the normal acetabulum. Anatomic relationships knowledge can be used intraoperatively to avoid iatrogenic vascular injury during Crowe type 4 dysplastic hip arthroplasty surgery.

Anatomical Implications Regarding Femoral Nerve Palsy During a Direct Anterior Approach to Total Hip Arthroplasty: A Cadaveric Study

BACKGROUND

Femoral nerve palsy is a serious neurological complication following total hip arthroplasty (THA) via a direct anterior approach. One hypothesis is that the nerve injury is caused by malpositioning of retractors over the anterior wall of the acetabulum. The purpose of this cadaveric study was to clarify the anatomical features of the femoral nerve around the anterior acetabular rim and the potential risk of nerve injury during a direct anterior approach to THA.

METHODS

We dissected 84 cadaveric hips from 44 formalin-embalmed cadavers. When the cadavers were supine, the iliopsoas muscle and the femoral nerve were exposed and the anterior joint capsule and labrum were resected. The measurement points were determined along the acetabular rim every 30°, and a reference line was drawn from the anterior superior iliac spine to the center of the acetabulum, with the intersection of the rim at 0°. The minimum distance to the femoral nerve margin was measured from 0° to 150° (6 points). Other anatomical structures were measured to determine their association with the distance of the shortest measurement points.

RESULTS

The mean minimum distances to the femoral nerve were 33.2 mm at 0°, 24.4 mm at 30°, 18.4 mm at 60°, 16.6 mm at 90°, 17.9 mm at 120°, and 23.2 mm at 150°, showing that the distance at 90° was the shortest (p < 0.001). The thickness of the iliopsoas muscle and the femoral length were positively associated with the distance to the femoral nerve at 90°.

CONCLUSIONS

In this cadaveric study, the femoral nerve was within 16.6 to 33.2 mm of the acetabular rim at points from 0° to 150° of a line drawn from the anterior superior iliac spine. The nerve was closest to the rim at 90°, indicating that this is an area of high risk during retractor placement.

CLINICAL RELEVANCE

Retractor placement at 90° to the anterior acetabular rim should be avoided to reduce the risk of femoral nerve injury.