The accuracy of a patient-specific femoral planning and delivery system for total hip arthroplasty.

Introduction: A primary objective when performing a total hip arthroplasty (THA) is to restore hip biomechanics in accordance with a chosen surgical plan. The aim of this study was to assess the accuracy of a 3D-printed patient-specific guide for delivering a planned femoral osteotomy for both a posterior and an anterior approach.

Methodology: 40 patients (20 anterior and 20 posterior) scheduled for THA received a preoperative work-up allowing for patient-specific implant sizing and positioning.

Simulation of hip bony range of motion (BROM) corresponds to the observed functional range of motion (FROM) for pure flexion, internal rotation in deep flexion, and external rotation in minimal flexion-extension - A cadaver study.

Background: The study investigated the relationship between computed bony range of motion (BROM) and actual functional range of motion (FROM) as directly measured in cadaveric hips. The hypothesis was that some hip movements are not substantially restricted by soft tissues, and therefore, computed BROM for these movements may effectively represent FROM, providing a reliable parameter for computational pre-operative planning.

Methods: Maximum passive FROM was measured in nine cadaveric hips using optical tracking.

How Do Changes in Femoral Anteversion Impact Femoral Rotation and Anterior Offset After Total Hip Arthroplasty?

Background: The impact of femoral anteversion changes on femoral rotation and anterior offset following total hip arthroplasty (THA) has not been well studied. This study therefore investigated the relationship among femoral anteversion, anterior offset, and femoral rotation before and after THA.

Methods: There were 995 patients who had staged primary bilateral THAs who received a preoperative supine computerized axial tomography (CT) scan, following a standardized protocol, for surgical planning prior to each THA.

Hip-spine parameters change with increasing age.

Aims: Spinopelvic pathology increases the risk for instability following total hip arthroplasty (THA), yet few studies have evaluated how pathology varies with age or sex. The aims of this study were: 1) to report differences in spinopelvic parameters with advancing age and between the sexes; and 2) to determine variation in the prevalence of THA instability risk factors with advancing age.

Methods: A multicentre database with preoperative imaging for 15,830 THA patients was reviewed.

Reliability of the transverse acetabular ligament as a landmark for functional cup anteversion in total hip arthroplasty.

Background: The transverse acetabular ligament (TAL) can be a useful and reproducible landmark in the orientation of the acetabular cup in total hip arthroplasty (THA). Its role in guiding cup orientation when aiming to implant in a functional anteversion orientation is unclear. The aim of this study was to assess the relationship between the TAL and the planned acetabular cup anteversion when implanted in a function orientation.

Accuracy of intraoperative approximation of pelvic tilt using preoperative standing radiographs.

Background: Anterior approach surgeons who utilize intraoperative fluoroscopy often try to match a preoperative radiograph as a reference for intraoperative cup position. Every degree of inaccuracy in tilt leads to a roughly 0.7° change in anteversion.

Excessive posterior pelvic tilt from preoperative supine to postoperative standing after total hip arthroplasty.

Aims: Excessive posterior pelvic tilt (PT) may increase the risk of anterior instability after total hip arthroplasty (THA). The aim of this study was to investigate the changes in PT occurring from the preoperative supine to postoperative standing position following THA, and identify factors associated with significant changes in PT.

Methods: Supine PT was measured on preoperative CT scans and standing PT was measured on preoperative and one-year postoperative standing lateral radiographs in 933 patients who underwent primary THA.

Evaluating computed bony range of motion (BROM) by registering in-vitro cadaver-based functional range of motion (FROM) to a hip motion simulation.

Background: While modern hip replacement planning relies on hip motion simulation (HMS), it lacks the capability to include soft-tissues and ligaments restraints on computed bony range of motion (BROM), often leading to an overestimation of the in-vivo functional range of motion (FROM). Furthermore, there is a lack of literature on BROM assessment in relation to FROM. Therefore, the study aimed to assess computed BROM using in-vitro cadaver-derived FROM measurements, registered to a CT-based in-house HMS, and to further investigate the effect of functional and anatomical hip joint centres (FHJC and AHJC) on BROM.

Total Hip Arthroplasty and the Spinopelvic Relationship: What's the Latest!

Although total hip arthroplasty (THA) has proved to be a successful surgical procedure, both prosthetic and bone impingement resulting in dislocation continue to occur. Studies have shown that spine pathology resulting in lumbar stiffness and hip arthritis often coexist. Spinopelvic mobility patterns during postural changes affect three-dimensional acetabular component position, which affects the incidence of prosthetic impingement and THA instability.

Increased Cup Anteversion May Not Prevent Posterior Dislocation in Patients With Abnormal Spinopelvic Characteristics in Total Hip Arthroplasty.

Background: The aims of this study were to (1) assess the degree of variation in acetabular component placement and combined anteversion in a large cohort of dislocating total hip arthroplasties; (2) assess the spinopelvic characteristics of the cohort; and (3) examine the association between cup anteversion and reported direction of instability.

Methods: A commercial database of 245 dislocating total hip arthroplasties referred for postoperative computed tomography and functional radiographic imaging and analysis were reviewed. Spinopelvic parameters and cup and stem positions were measured in the supine, standing, flex-seated, and anterior pelvic plane (APP) positions.

Variation in Functional Pelvic Tilt in Female Patients Undergoing Total Hip Arthroplasty With Acetabular Dysplasia.

Background: As the pelvis is a dynamic structure, the quantification of pelvic tilt (PT) should be done in different hip positions prior to total hip arthroplasty (THA). We sought to investigate functional PT in young female patients undergoing THA and explore the correlation of PT with the extent of acetabular dysplasia. Additionally, we aimed to define the PS-SI (pubic symphysis-sacroiliac joint) index as a PT quantifier on AP pelvis X-ray.

Does Individualization of Cup Position Affect Prosthetic or Bone Impingement Following Total Hip Arthroplasty?

Background: Spinopelvic (SP) mobility patterns during postural changes affect three-dimensional acetabular component position, the incidence of prosthetic impingement, and total hip arthroplasty (THA) instability. Surgeons have commonly placed the acetabular component in a similar "safe zone" for most patients. Our purpose was to determine the incidence of bone and prosthetic impingement with various cup orientations and determine if a preoperative SP analysis with individualized cup orientation lessens impingement.

Defining "Normal" Static and Dynamic Spinopelvic Characteristics: A Cross-Sectional Study.

Unlabelled: Spinopelvic characteristics influence the hip's biomechanical behavior. However, there is currently little knowledge regarding what "normal" characteristics are. This study aimed to determine how static and dynamic spinopelvic characteristics change with age, sex, and body mass index (BMI) among well-functioning volunteers.

Development of bony range of motion (B-ROM) boundary for total hip replacement planning.

Background And Objective: Pre-operative surgical planning using computer simulation is increasingly standard practice before Total Hip Arthroplasty (THA), in order to determine the optimal implant positions, and thereby minimise post-operative complications such as dislocation, wear and leg length discrepancy. One of the limitations of current methods, however, is the lack of information on the subject-specific reference range of motion (ROM) that could be used as targets for surgical planning. Only a limited number of hip motions are considered, which are neither subject-specific, nor representative of all the hip motions associated with all the activities of daily livings (ADLs).

High Prevalence of Spinopelvic Risk Factors in Patients With Post-Operative Hip Dislocations.

Background: Excessive standing posterior pelvic tilt (PT), lumbar spine stiffness, low pelvic incidence (PI), and severe sagittal spinal deformity (SSD) have been linked to increased dislocation rates. We aimed to determine the prevalence of these 4 parameters in a cohort of unstable total hip arthroplasty (THA) patients and compare these to a large representative control population of primary THA patients.

Methods: Forty-eight patients with instability following primary THA were compared to a control cohort of 9414 THA patients.

Sacral Slope Change From Standing to Relaxed-Seated Grossly Overpredicts the Presence of a Stiff Spine.

Background: Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSS) identifies a patient with a stiff lumbar spine and has suggested the use of dual-mobility bearings for such patients undergoing a total hip arthroplasty (THA). The aim of this study was to assess how accurately ΔSS can identify patients with a stiff spine.

Methods: A prospective, multicentre, consecutive cohort series of 312 patients had standing, relaxed-seated, and flexed-seated lateral radiographs prior to THA.

Pelvic incidence significance relative to spinopelvic risk factors for total hip arthroplasty instability.

Aims: Pelvic incidence (PI) is a position-independent spinopelvic parameter traditionally used by spinal surgeons to determine spinal alignment. Its relevance to the arthroplasty surgeon in assessing patient risk for total hip arthroplasty (THA) instability preoperatively is unclear. This study was undertaken to investigate the significance of PI relative to other spinopelvic parameter risk factors for instability to help guide its clinical application.

Does total hip arthroplasty with high hip centre in dysplasia compromise acetabular bone stock?

Background: The placement of uncemented acetabular components during total hip arthroplasty (THA) in Crowe II and Crowe III dysplasia can be at the anatomic or high hip centre position.

Purposes: Using computerised tomography data, we simulated acetabular cup placement at the anatomic hip centre and the high hip centre positions to assess whether there is a difference between the 2 in terms of bone loss from acetabular reaming and in acetabular coverage by host bone.

Methods: The study population included a consecutive cohort of 19 patients (22 hips) with Crowe II or III dysplasia.

Spinopelvic mobility affects accuracy of acetabular anteversion measurements on cross-table lateral radiographs.

Aims: Cross-table lateral (CTL) radiographs are commonly used to measure acetabular component anteversion after total hip arthroplasty (THA). The CTL measurements may differ by > 10° from CT scan measurements but the reasons for this discrepancy are poorly understood. Anteversion measurements from CTL radiographs and CT scans are compared to identify spinopelvic parameters predictive of inaccuracy.

The Effect of a Degenerative Spine and Adverse Pelvic Mobility on Prosthetic Impingement in Patients Undergoing Total Hip Arthroplasty.

Background: Despite the placement of acetabular components in the traditional "safe-zone", dislocations and all parts of the instability spectrum, including impingement, continue to be an issue. Recent research has established the importance of a degenerative spine and adverse pelvic mobility on functional acetabular orientation. The purpose of this study is to quantify the clinical consequences of a degenerative spine and adverse pelvic mobility on prosthetic impingement in patients undergoing total hip arthroplasty.

Prevalence of Risk Factors for Adverse Spinopelvic Mobility Among Patients Undergoing Total Hip Arthroplasty.

Background: Patients with adverse spinopelvic mobility have higher complication rates following total hip arthroplasty (THA). Risk factors include a stiff lumbar spine, standing posterior pelvic tilt ≤ -10°, and a severe sagittal spinal deformity (pelvic incidence minus lumbar lordosis mismatch ≥20°). The purpose of this study is to define the spinopelvic risk factors and quantify the prevalence of risk factors for pathologic spinopelvic mobility.

Lewinnek Safe Zone References are Frequently Misquoted.

Background: Optimal acetabular component orientation in total hip arthroplasty (THA) is a necessity in achieving a stable implant. Although there has been considerable debate in the literature concerning the safe zone, to date, there has not been any review to determine if these references are consistent with the definition applied by Lewinnek et al. in 1978.

The effect of varus stem placement on joint offset during total hip arthroplasty: a virtual study.

Introduction And Aims: With total hip replacement (THR), varus alignment of an uncemented stem will increase offset which can have significant detrimental effects on muscular balance, leg length and overall satisfaction. Thus, we used 3D planning software to determine the change in joint offset with increasing varus stem placement.

Methods: Eight patients undergoing THR had routine computed tomography (CT) scans to allow for 3D hip planning.

Does Prosthetic or Bony Impingement Occur More Often in Total Hip Arthroplasty: A Dynamic Preoperative Analysis.

Background: Impingement is a leading cause for instability resulting in revision total hip arthroplasty (THA). Impingement can be prosthetic, bony, or soft tissue. The purpose of this study is to investigate, using a virtual simulation, whether bony or prosthetic impingement presents first in well-positioned THAs.