How to Estimate Femoral Stem Anteversion During Direct Anterior Approach Total Hip Arthroplasty

Background

There are various traditional landmarks used to estimate the femoral component version, yet none are widely accepted by direct anterior surgeons. The purpose of this study was to compare bony landmarks easily accessible to direct anterior surgeons and to estimate which one provides the best estimate of femoral component anteversion.

Methods

A computed tomography database was used to identify 736 left entire-femur computed tomography scans. Seven visible anatomic landmarks were identified using a computer model in which a 45° virtual neck resection was made at 10 mm above the lesser trochanter. Thirteen axes, to reference the femoral stem position, were created between the 7 landmarks. Means and standard deviations (SDs) of angles between each axis and the transepicondylar axis (TEA) were compared for their precision.

Results

The traditional lesser trochanter predicted anteversion from the TEA was 34.1° (SD 9.7°). Predicted anteversion from the TEA was 3.3° (SD 8.1°) when aligned from the center of the canal to the middle of the medial calcar; 14.0° (SD 8.1°) from the center of the canal to the anterior 1/3 of the medial calcar; and 24.8° (SD 8.5°) from the center of the canal to the most anterior point on the medial calcar.

Conclusions

Compared to the lesser trochanter, 7 axes were more precise (lower SD) when predicting the version. Estimating the femoral component position, via simulated data, using 3 points along the medial calcar is a relatively precise and easily accessible tool for surgeons.

The use of virtual reality to assess the bony landmarks at the knee joint - The role of imaging modality and the assessor's experience

BACKGROUND

At present, extended reality technologies such as virtual reality (VR) have gained popularity in orthopedic surgery. The first aim of this study was to assess the precision of VR and other imaging modalities - computed tomography (CT), magnetic resonance imaging (MRI) - to localize bony landmarks near the knee joint. Secondly, the impact of the educational level of the assessor - medical master students, orthopedic residents, and orthopedic surgeons - on the precision with which landmarks near the knee joint could be localized was analyzed.

METHODS

We included a total of 77 participants: 62 medical master students, 10 orthopedic residents, and 5 orthopedic surgeons to analyze three cadaver legs. Every participant localized a series of sixteen bony landmarks on six different imaging modalities (CT, MRI, 3D-CT, 3D-MRI, VR-CT, VR-MRI).

RESULTS

Concerning the imaging modality, the inter- and intra-observer variability were lowest for 3D and VR, higher for MRI (respectively 7.6 mm and 6.9 mm), and highest for CT (respectively 9 mm and 8.7 m).Concerning the educational level of the assessor, inter- and intra-observer variability in VR were lowest for surgeons, (respectively 3.2 mm and 3.6 mm), higher for residents (respectively 5.9 mm and 6.5 mm) and medical students (respectively 5.9 mm and 5.8 mm).

CONCLUSIONS

VR can be considered a reliable imaging technique. Localization of landmarks tends to be more precise in VR and on 3D than on conventional CT and MRI images. Furthermore, orthopedic surgeons localize landmarks more precisely than orthopedic residents and medical students in VR.

Can ultrasound-guided radiofrequency ablation of genicular nerves of the knee, be performed without locating corresponding arterial pulsations-a cadaveric study

INTRODUCTION

Given the rising prevalence of knee osteoarthritis, radiofrequency ablation of genicular nerves (RFA) has emerged as a promising treatment option for knee pain. The knee has an extremely complex and variable innervation with nearly 13 genicular nerves described. The frequently ablated genicular nerves are the superomedial (SMGN), the superolateral (SLGN), and the inferomedial (IMGN) genicular nerves. Conventionally, under ultrasound guidance, these nerves are ablated near the corresponding arterial pulsations, but due to the rich vascular anastomosis around the knee joint, identifying the arteries corresponding to these constant genicular nerves can be tedious unless guided by some bony landmarks. In this study, we have evaluated whether it is possible to accurately target these three genicular nerves by just locating bony landmarks under ultrasound in human cadaveric knee specimens.

METHODS

Fifteen formalin-fixed cadaveric knee specimens were studied. SMGN was targeted 1 cm anterior to the adductor tubercle in the axial view. For SLGN, in the coronal view, the junction of the lateral femoral condyle and shaft was identified, and at the same level in the axial view, the crest between the lateral and posterior femoral cortex was targeted. For IMGN in the coronal view, the midpoint between the most prominent part of the medial tibial condyle and the insertion of the deep fibers of the medial collateral ligament was marked. The medial end of the medial tibial cortex was then targeted at the same level in the axial view. The needle was inserted from anterior to posterior, with an in-plane approach for all nerves. Eosin, 2% W/V, in 0.1 ml was injected. Microdissection was done while keeping the needle in situ. Staining of the nerve was considered a positive outcome, and the percentage was calculated. The nerve-to-needle distance was measured, and the mean with an interquartile range was calculated.

RESULT

The accuracies of ultrasound-guided bony landmarks of SMGN, SLGN, and IMGN were 100% in terms of staining, with average nerve-to-needle distances of 1.67, 3.2, and 1.8 mm respectively.

CONCLUSION

It is with 100% accuracy, that we can perform RFA of SMGN, SLGN, and IMGN under ultrasound guidance, by locating the aforementioned bony landmarks.

Proposal of a Novel Anatomic Guide to the Sphenoid Sinus

BACKGROUND

Landmarks for transsphenoidal surgery have been described to facilitate resection for pituitary lesions. However, carrying out sphenoidotomy for access to the sellar floor could still be challenging, especially for young surgeons during the steep learning curve.

OBJECTIVE

We describe the LUTH (Lagos University Teaching Hospital) line as a simple anatomic guide to avoid missing the trajectory to the sella during anterior sphenoidotomy in microscopic transsphenoidal pituitary surgery.

METHODS

We identified this line as an impression on the floor of the sphenoid sinus across the point at which the floor of the anterior cranial fossa and the bony projection from the clivus meet. We carried out a literature review of articles describing landmarks for anterior sphenoidotomy using data obtained from PubMed and Ovid MEDLINE databases according to PRISMA guidelines.

RESULTS

A total of 80 patients were operated using the LUTH line as a guide for anterior sphenoidotomy during microscopic transsphenoidal pituitary. We did not find any previous description of this anatomic landmark over the anterior sphenoid sinus in the literature. The LUTH line was clearly identified in all 80 cases. The line was used as a bony landmark to the sphenoid sinus in all cases and was found to be consistently accurate.

CONCLUSIONS

The LUTH line is a consistent and easy-to-identify landmark that could be useful in preventing potential complications of access to the pituitary sella through the sphenoid sinus. We believe it to be useful in the absence of intraoperative guidance, especially for young surgeons who are just starting off their career in pituitary surgery.

New landmarks for ideal positioning of syndesmotic screw: a computerised tomography based analysis and radiographic simulation

PURPOSE

A lack of specific intra-operative markers for accurate positioning of the syndesmotic screw can result in its malpositioning. Knowledge of the axial orientation of the syndesmosis can help in reducing this risk of malpositioning of the syndesmotic screw. In this CT-based study, we investigated the axial relationships of intact syndesmoses with various rigid bony landmarks around the ankle joint that were independent of foot and horizontal plane.

METHODS

We analyzed 126 CT-based studies of uninjured normal ankle joints and defined the following bony landmarks: posteromedial and posterolateral surface of the distal tibia, bimalleolar tips, and anterior and posterior extents of both malleoli. Axial differences between coronal plane through the central axis of syndesmosis and modified coronal planes through these bony landmarks were then measured. Software-based lateral radiographs were created with the reference coronal plane for each radiograph being kept perpendicular to the plane of the viewing screen.

RESULTS

The mean axial differences parting the syndesmotic axis from the modified coronal planes based on distal tibial posteromedial surface, distal tibial posterolateral surface, bimalleolar tips, anterior bimalleolar extents, and posterior bimalleolar extents were - 3.15°, 13.73°, 4.10°, 11.95°, and 12.24°, respectively. With the exception of the posterolateral surface of the distal tibia, all other bony landmarks were radiologically identifiable in the majority of cases.

CONCLUSION

Our study attempts to provide a solution to the issues related to malpositioning of the syndesmotic screw by providing new bony landmarks that can be clinically and fluoroscopically used for syndesmotic-screw positioning. The relationships of bimalleolar tips, anterior and posterior bimalleolar extents, and the posteromedial surface can be reliably used as landmarks for directing syndesmotic screws.

Tibial insertion of the anterior cruciate ligament and anterior horn of the lateral meniscus share the lateral slope of the medial intercondylar ridge: A computed tomography study in a young, healthy population

BACKGROUND

The central intercondylar ridge (CIR) is an anatomical bony landmark that bisects the slope of the medial intercondylar ridge (MIR) between the tibial insertion of the anterior cruciate ligament (ACL) and anterior horn of lateral meniscus (AHLM) and was recently revealed by computed tomography (CT) evaluation corresponding to histologic slices of cadaveric knees. The purpose of this study was to clarify the shape and size of ACL and AHLM tibial insertion in young, healthy knees using the new bony landmark (CIR) and previously reported landmarks.

METHODS

The contralateral healthy knees in 34 ACL-reconstructed patients (18 male patients, 16 female patients, mean age: 24.0 years) were scanned by CT. In the reconstructed coronal/sagittal images, bony landmarks of ACL (anterior: anterior ridge, posterior: blood vessel in tubercle fossa, medial: MIR, lateral: CIR) and AHLM (medial: CIR, lateral: bottom of the slope) were plotted for evaluation. The length of sagittal slices and the width in five coronal slices of the insertion were measured.

RESULTS

The ACL insertion consistently showed a boot-like-shape adjacent to the square shape of AHLM on three-dimensional imaging. The mean ACL sagittal length was 14.5 ± 1.9 mm, while the mean ACL widths (in mm) from anterior to posterior were 12.7 ± 2.7, 8.1 ± 1.9, 7.9 ± 2.0, 7.5 ± 1.5, and 7.2 ± 1.6, which was highly correlated with the tibial plateau size.

CONCLUSIONS

The boot-like-shape of the ACL tibial footprint insertion shared the slope of MIR with the rectangular shape of AHLM in young, healthy knees. This study may provide useful information for safe tibial tunnel creation at the time of ACL reconstruction.

Intra-rater reliability of determining positions of cervical spinous processes and measuring their relative distances : An update to define rigid bodies of the cervical spine in a movement laboratory setting

Objectives

A reliable detection of bony landmarks of the spine is necessary in order to determine rigid bodies and to reduce the variability of marker placement in a movement laboratory setting. In a first study on the thoracic and lumbar spine, we demonstrated that placing markers on their relative positions between two major landmarks was superior to palpation of specific bony landmarks. The aims of this study were to examine the intra-rater reliability when palpating for spinous processes (SPs) of the second (C2) and seventh cervical vertebrae (C7), to determine the distances between C2 and C7 and the relative position of C7 along the length between C2 and the posterior superior iliac spine (PSIS) level.

Results

The intra-rater reliability in determining the distance between C2 and C7 was found to be substantial, with an intra-rater reliability of 0.75 (95% confidence limits 0.55–0.99) and a standard error of the measurement of 0.34 cm. The relative distance of C7 along the total C2–PSIS length was estimated to be 11.5%. The determination of the relative positions of spinal landmarks through measurement is considered superior to their palpation, because it relies on a reproducible and comparable definition of rigid bodies.

Variation in bony landmarks and predictors of success with sacral neuromodulation

INTRODUCTION AND HYPOTHESIS

We assessed variations in sacral anatomy and lead placement as predictors of sacral neuromodulation (SNM) success. Based solely on bony landmarks, we also assessed the accuracy of the 9 and 2 protocol for locating S3.

METHODS

This is a retrospective cohort study performed from October 2008 to December 2016 at the University of North Carolina at Chapel Hill. Fluoroscopic images were used to assess sacral anatomy and lead location. Success was defined as >50% symptom improvement after stage I and clinical response at most recent follow-up.

RESULTS

Of 249 procedures, 209 were primary implants and 40 were revisions among 187 (89.5%) women and 22 (10.5%) men. Success rate was 83.3% for primary implants and 89.4% for revisions. Success was associated with shorter implant duration (21.3 ± 22.2 vs 33.6 ± 25.8 months), higher body mass index (30.3 ± 7.8 vs 27.6 ± 6.1 kg/m²), and straight vs curved lead (90.5% vs 80.5%) (all p = .05), but not with sacral anatomy or lead placement. In assessing the 9 and 2 protocol, mean distance from coccyx to S3 did not equal 9 cm: 7.4 ± 1.0 vs 7.2 ± 0.8 cm (p = .26), while mean distance from midline to S3 did equal 2 cm: 1.9 ± 0.4 vs 2.0 ± 0.7 cm (p = .37).

CONCLUSIONS

Variations in sacral anatomy and lead placement did not predict SNM success. The 2-cm protocol was verified while the 9-cm protocol was not, although neither was predictive of success, which may obviate the need to mark bony landmarks prior to fluoroscopy.

Distances between bony landmarks and adjacent nerves: anatomical factors that may influence retractor placement in total hip replacement surgery

Background

Retractor placement is a leading cause of intraoperative nerve injury during total hip replacement (THR) surgery. The sciatic nerve, femoral nerve, and superior gluteal nerve are most commonly affected. This study aimed to identify the distances from bony landmarks in the hip to the adjacent nerves on magnetic resonance imaging (MRI) and the associations between anatomical factors and these distances that would guide the placement of retractors during THR surgery, in order to minimize the risk of nerve injury.

Methods

We reviewed hip MRIs of 263 adults and recorded the distances from (1) the anterior acetabular rim to the femoral nerve; (2) the superior acetabular rim to the superior gluteal nerve; (3) the posterior acetabular rim to the sciatic nerve; and (4) the greater trochanter to the sciatic nerve. The effects of anatomical factors (i.e., gender, age, body height, body mass index (BMI), pelvic width, and acetabular version and morphology) on these distances were analyzed.

Results

Distances from bony landmarks to adjacent nerves (in cm) were 2.06 ± 0.44, 2.23 ± 0.28, 1.94 ± 0.81, and 4.83 ± 0.26 for the anterior acetabular rim, superior acetabular rim, posterior acetabular rim, and greater trochanter, respectively, and were shorter in women than in men (P < 0.001). Multivariate analysis identified body height as the most influential factor (P < 0.001). Linear regression demonstrated a strong positive linear correlation between body height and these distances (Pearson’s r = 0.808, 0.823, 0.818, and 0.792, respectively (P < 0.001)).

Conclusions

The distances from bony landmarks to adjacent nerves provide useful information for placing retractors without causing nerve injury during THR surgery. Shorter patients will have shorter distances from bony landmarks to adjacent nerves, prompting more careful placement of retractors.