Current concepts in hip-spine relationships: making them practical for total hip arthroplasty

Application of artificial intelligence-based three dimensional digital reconstruction technology in precision treatment of complex total hip arthroplasty

PURPOSE

To evaluate the predictive ability of AI HIP in determining the size and position of prostheses during complex total hip arthroplasty (THA). Additionally, it investigates the factors influencing the accuracy of preoperative planning predictions.

METHODS

From April 2021 to December 2023, patients with complex hip joint diseases were divided into the AI preoperative planning group (n = 29) and the X-ray preoperative planning group (n = 27). Postoperative X-rays were used to measure acetabular anteversion angle, abduction angle, tip-to-sternum distance, intraoperative duration, blood loss, planning time, postoperative Harris Hip Scores (at 2 weeks, 3 months, and 6 months), and visual analogue scale (VAS) pain scores (at 2 weeks and at final follow-up) to analyze clinical outcomes.

RESULTS

On the acetabular side, the accuracy of AI preoperative planning was higher compared to X-ray preoperative planning (75.9% vs. 44.4%, P = 0.016). On the femoral side, AI preoperative planning also showed higher accuracy compared to X-ray preoperative planning (85.2% vs. 59.3%, P = 0.033). The AI preoperative planning group showed superior outcomes in terms of reducing bilateral leg length discrepancy (LLD), decreasing operative time and intraoperative blood loss, early postoperative recovery, and pain control compared to the X-ray preoperative planning group (P < 0.05). No significant differences were observed between the groups regarding bilateral femoral offset (FO) differences, bilateral combined offset (CO) differences, abduction angle, anteversion angle, or tip-to-sternum distance. Factors such as gender, age, affected side, comorbidities, body mass index (BMI) classification, bone mineral density did not affect the prediction accuracy of AI HIP preoperative planning.

CONCLUSION

Artificial intelligence-based 3D planning can be effectively utilized for preoperative planning in complex THA. Compared to X-ray templating, AI demonstrates superior accuracy in prosthesis measurement and provides significant clinical benefits, particularly in early postoperative recovery.

Neurovascular Structural Deviations in Patients Who Have Fused Hips: Implications for Total Hip Arthroplasty

BACKGROUND

The purpose of this study was to compare the fused and normal sides of patients who have fused hips to determine the differences in neurovascular structures and factors that increase the risk of neurovascular injury.

METHODS

We evaluated 38 patients who underwent total hip arthroplasty, with a fused hip between 2003 and 2021. Excluding patients who had bilateral lesions, differences in the location of neurovascular structures were measured by comparing the fused side with the normal side. The position of neurovascular structures was measured by the distance from the acetabular rim and the shortest distance to the particular bony structure. In addition, the patient's sex, weight, body mass index cause of fused hips, estimated age of fusion onset, and preoperative range of motion were investigated to examine the correlations with neurovascular deviation and these factors.

RESULTS

The neurovascular distances for all the measured neurovascular structures were significantly reduced on the fused side compared with the normal side. Sex-based analysis revealed that women had significantly shorter distances to the femoral neurovascular bundle than men. Although height and body weight were associated with differences in neurovascular distances, body mass index was not associated with significant differences, except for the femoral nerve distance from the nearest bone. When classified by the estimated age of fusion onset, significant differences in neurovascular distances were found between the adolescent- and adult-onset groups.

CONCLUSIONS

In patients who have fused hips, neurovascular structures are located closer to the bone than on the normal side. Moreover, patients in whom the fusion occurred before the completion of growth may exhibit a shorter neurovascular distance, thereby increasing the potential risk of direct injury during total hip arthroplasty .

Factors associated with the progression of sagittal spinal deformity after total hip arthroplasty: a propensity score-matched cohort study

PURPOSE

The functional interaction between the hip and spine in patients undergoing total hip arthroplasty (THA) is clinically significant, as it impacts post-operative outcomes. Therefore, this study aimed to identify factors associated with the progression of sagittal spinal deformity and assess the association with patient-reported outcomes.

METHODS

This retrospective case-control study included 200 patients who underwent primary THA and completed a mean follow-up duration of 42.2 months (range, 24.0-78.0). We employed a multivariate logistic regression to identify variables predictive of a post-THA sagittal vertical axis (SVA) ≥ 50 mm, which was indicative of a spinal sagittal imbalance. Propensity score-matched cohorts for age, sex, body mass index, follow-up duration, hip flexion contracture, developmental dysplasia, pelvic incidence (PI), and SVA were created, and the outcomes were compared between the two groups.

RESULTS

PI (odds ratio 1.39; 95% confidence interval 1.04-1.86, p = 0.033) was associated with an SVA ≥ 50 mm. After successfully matching patients with (n = 50) and without (n = 50) an SVA ≥ 50 mm, the minimum clinically important difference showed significant differences between the 50 matched pairs (p = 0.016 for EuroQol-5D, p = 0.003 for Hip Disability and Osteoarthritis Outcome Score Joint Replacement, and p < 0.001 for low back pain).

CONCLUSION

PI is associated with the development of a positive sagittal spinal malalignment post-THA. This finding can assist surgeons in managing patient expectations and in optimising outcomes. Feasible strategies are warranted to minimise the risk of spinal deformity progression post-THA.

Effect of lumbosacral transitional vertebra on developmental alterations of the hip: a quantitative investigation of the lumbo-pelvic-hip complex via whole-body computed tomography

Background

Lumbosacral transitional vertebra (LSTV) is a common spinal variant, with the reported prevalence varying from 8.1% to 36%. LSTV has been shown to alter the lumbo-pelvic parameters and reduce the benefits of total hip arthroplasty, but the specific effects of LSTV on hip development remain unclear. The aim of this study was thus to investigate the impact of LSTV on developmental alterations of the hip.

Methods

A total of 310 individuals were categorized into three groups according to whole-body computed tomography (CT) imaging: a group with sacralization of 23 presacral vertebrae (PSV) (n=102), a group with lumbarization of 25 PSV (n=108), and a normal control group with 24 PSV (n=100). Quantitative parameters of the lumbo-pelvic-hip complex (LPHC) including lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), axial and sagittal acetabular anteversion angle (AAA), center-edge (CE) angle, Sharp angle, and femoral neck-shaft angle (FNSA) were measured and analyzed. Statistical analyses were used to compare the differences of these quantitative parameters among the three groups and to assess the relationship between hip and lumbar-pelvic parameters.

Results

Significant differences between each pair of three groups and the LSTV subgroups were only found in the sagittal AAA (left side: P=0.008; right side: P<0.001), with no differences found for the other parameters. Compared to the normal group (24 PSV), both the 23 PSV and 25 PSV groups exhibited increased values in the sagittal AAA, especially in the right side of the 23 PSV group. Only the sagittal AAA showed low-to-moderate positive correlations with pelvic parameters of PI (r=0.195-0.429; P=0.001-0.08) and PT (r=0.239-0.605; P=0.001-0.03).

Conclusions

Variations of LSTV are correlated with the hip anatomical development via LPHC transmission and may potentially reduce the sagittal acetabular coverage, particularly in the 23 PSV subtype on the right side.

Accuracy of cup placement compared with preoperative surgeon targets in primary total hip arthroplasty using standard instrumentation and techniques: a global, multicenter study

BACKGROUND

Acetabular cup positioning in total hip arthroplasty (THA) is closely related to outcomes. The literature has suggested cup parameters defined by the Lewinnek safe zone; however, the validity of such measures is in question. Several studies have raised concerns about the benefits of using the Lewinnek safe zone as a predictor of success. In this study we elected to use prospective surgeon targets as the basis for comparison to see how successful surgeons are positioning their cup using standard instruments and techniques.

METHODS

A prospective, global, multicenter study was conducted. Cup positioning success was defined as a composite endpoint. Both cup inclination and version needed to be within 10° of the surgeon target to be considered a success. Radiographic analysis was conducted by a third-party reviewer.

RESULTS

In 170 subjects, inclination, target versus actual, was 44.8° [standard deviation (SD 0.9°)] and 43.1° (SD 7.6°), respectively (p = 0.0029). Inclination was considered successful in 84.1% of cases. Mean version, target versus actual, was 19.4° (SD 3.9°) and 27.2° (SD 5.6°), respectively (p < 0.0001). Version was considered successful in 63.4% of cases, and combined position (inclination and version) was considered successful in 53.1%.

CONCLUSION

This study shows that with traditional methods of placing the cup intraoperatively, surgeons are only accurate 53.1% of the time compared with a predicted preoperative plan. This study suggests that the inconsistency in cup positioning based on the surgeon's planned target is potentially another important variable to consider while using a mechanical guide or in freehand techniques for cup placement in THA.

TRIAL REGISTRATION

This study is registered on ClinicalTrials.gov, NCT03189303.

Outcomes and complications of Total Hip Arthroplasty in patients with a pre-existing pathologic spine-hip relation. A systematic review of the literature

BACKGROUND

There has been a growing interest in pathologic spine-hip relations (PSHR) in current literature, with the aim of reducing the risk of prosthetic impingement, dislocation, and edge loading in total hip arthroplasty (THA). The primary objective of this review is to determine the effect of different PSHR on primary THA outcomes and complication profile. The secondary objective is to stratify the risk of different subgroups of PSHR patients.

METHODS

A systematic review of the literature was performed in accordance with PRISMA guidelines. Randomised controlled trials, comparative cohort studies and case-control studies comparing outcomes and complication rates of primary THA in patients with and without a PSHR (spinal fusion; degenerative spinal conditions determining stiff spine and/or spinal misalignment) were included. The quality of the included studies and the risk of bias were assessed. The revision rate, complications, and clinical and radiological data were analysed. Complications included: aseptic loosening (AL), periprosthetic joint infections (PJI), hip dislocations and periprosthetic fractures (PF).

RESULTS

Fifteen articles were included with 3.306.342 THAs. The mean follow-up (FU) was 31.4 ± 21.7 months. The population was divided into three subgroups: spinal fusion patients (48.315 THAs); non-fused patients with spinal stiffness (106.110 THAs); non-fused patients with normal spines (3.151.917 THAs). A statistically significant risk stratification was observed about dislocation rate (5.98 ± 6.9% SF, 3.0 ± 1.9% non-SF Stiff and 2.26 ± 1.4% non-SF; p = 0.028). Similarly, about THA revision rate, a statistically significant risk stratification was also observed (7.3 ± 6.8% SF, 6.4 ± 3.1% non-SF Stiff and 2.7 ± 1.7% non-SF; p = 0.020). No statistically significant difference was observed when analysing AL, PJI and PF.

CONCLUSION

A statistically significant risk stratification of dislocation and revision rate was observed in the different PHSR, as theorised by the Bordeaux classification. Fused patients present a higher risk, degenerated and/or stiff spine an intermediate risk and mobile spines a lower risk profile. A standardised approach to THA candidate patients must consider the possible PSHR to improve clinical outcomes and reduce adverse events of THA.

Hip-spine relationship: clinical evidence and biomechanical issues

The hip-spine relationship is a critical consideration in total hip arthroplasty (THA) procedures. While THA is generally successful in patient, complications such as instability and dislocation can arise. These issues are significantly influenced by the alignment of implant components and the overall balance of the spine and pelvis, known as spinopelvic balance. Patients with alteration of those parameters, in particular rigid spines, often due to fusion surgery, face a higher risk of THA complications, with an emphasis on complications in instability, impingement and dislocation. For these reasons, over the years, computer modelling and simulation techniques have been developed to support clinicians in the different steps of surgery. The aim of the current review is to present current knowledge on hip-spine relationship to serve as a common platform of discussion among clinicians and engineers. The offered overview aims to update the reader on the main critical aspects of the issue, from both a theoretical and practical perspective, and to be a valuable introductory tool for those approaching this problem for the first time.

Evaluation of changes in radiographic spinopelvic parameters after primary total hip arthroplasty and its relationship with short-term patient function

PURPOSE

Total hip arthroplasty (THA) is commonly used worldwide in pelvic osteoarthritis treatment. This surgery can change the spinopelvic parameters, which in turn affects the performance of the patients after surgery. However, the relationship between functional disability following THA and spinopelvic alignment is not completely understood. The limited available studies have also been conducted on the population with spinopelvic malalignments. This study aimed to examine the changes in spinopelvic parameters after primary THA in patients with normal preoperative spinopelvic characteristics and the association of these parameters with the performance, gender, and age of the patients after THA.

METHODS

Fifty-eight eligible patients with unilateral primary hip osteoarthritis (HOA) scheduled for total hip arthroplasty between February and September 2021 were studied. Spinopelvic parameters including pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured before surgery and three months after surgery, and the relationship between these parameters and patients' performance (Harris hip score) was assessed. Also, the relationship between the age and gender of the patients with these parameters was evaluated.

RESULTS

The mean age of study participants was 46.03 ± 14.25. Three months after THA, sacral slope decreased with the mean difference of 4.31 ± 10.26 degrees (p = 0.002) and Harris hip score (HHS) increased by 19.41 ± 26.55 points (p < 0.001). With increasing age in patients, the mean SS and PT decreased. Among the spinopelvic parameters, SS (β = 0.11) had a greater effect than PT on postoperative HHS changes and among the demographic parameters, age (β = -0.18) had a greater effect on HHS changes than gender.

CONCLUSION

Spinopelvic parameters are associated with age, gender, and patient's function after THA as sacral slope decreased and HHS increased after THA, and aging is accompanied by lowering of PT and SS.

Current Concepts in Diagnosis and Management of Patients Undergoing Total Hip Replacement with Concurrent Disorders of Spinopelvic Anatomy: A Narrative Review

Despite the high success rate of primary total hip replacement (THR), a significant early revision rate remains, which is largely attributed to instability and dislocations. Despite the implants being placed according to the safe zone philosophy of Lewinnek, occurrence of THR dislocation is not an uncommon complication. Large diagnostic and computational model studies have shown variability in patients' mobility based on the individual anatomic and functional relationship of the hip-pelvis-spine complex. The absolute and relative position of hip replacement components changes throughout motion of the patient's body. In the case of spinopelvic pathology such as spine stiffness, the system reaches abnormal positional states, as shown with computerized models. The clinical result of such pathologic hip positioning is edge loading, implant impingement, or even joint dislocation. To prevent such complications, surgeons must change the dogma of single correct implant positioning and take into account patients' individualized anatomy and function. It is essential to broaden the standard diagnostics and their anatomical interpretation, and correct the pre-operative surgical planning. The need for correct and personalized implant placement pushes forward the development and adaptation of novel technologies in THR, such as robotics. In this current concepts narrative review, we simplify the spinopelvic biomechanics and pathoanatomy, the relevant anatomical terminology, and the diagnosis and management algorithms most commonly used today.

Impact of previous lumbar spine surgery on total hip arthroplasty and vice versa: How long should we be concerned about mechanical failure?

INTRODUCTION

This registry study aims to assess the prevalence and demographic characteristics of patients with lumbar spine (LS) surgical procedures who undergo total hip arthroplasty (THA), to compare the long-term survival and causes of failure of THA in patients who previously underwent LS fusion and non-fusion surgical procedures, and to evaluate the risk of undergoing a revision LS surgery after THA.

MATERIALS AND METHODS

Patients who underwent LS surgery followed by THA were identified by cross-referencing data from the Orthopedic Prosthetic Implants Registry and the Regional Hospital Discharge Database. Three groups of THA patients were identified: patients who underwent previous lumbar surgery with fusion (LS fusion-THA), without fusion (LS non-fusion-THA), and a control group with only THA (No LS surgery-THA). Demographic data, THA survival, number and causes of failure, and data on revision procedures on THA and LS were collected.

RESULTS

Of the total of 79,984 THA, 2.2% of patients had a history of LS procedures. THA only patients showed better results, while patients in the LS fusion-THA group had worse implant survival at 5-year follow-up. In the LS fusion-THA and LS non-fusion-THA, mechanical THA failures were more frequent in the first two years after implantation. There were no differences between groups regarding the risk of undergoing LS revision surgery.

CONCLUSIONS

LS surgery negatively affects THA survivorship. In patients who previously underwent LS fusion and non-fusion surgical procedures, most THA failure occurs in the first two years after implant. The study contributes to the understanding of the relationship between the hip and the LS and provides useful guidance for clinical practice.

The radiation dose, clinical and anatomical implications of erect lumbar spine radiography: A single centre pre-post implementation evaluation

INTRODUCTION

Lumbar radiographs remain a common imaging examination despite strategies to reduce their use. Many authors have demonstrated benefits in changing from traditional supine and recumbent lateral projections to a prone and/or erect orientation. Despite evidence of clinical and radiation dose optimisation, widespread adoption of these strategies has stalled. This article describes the single-centre implementation and evaluation of erect PA and lateral projections.

METHOD

This was an observational study pre- and post-implementation of an erect imaging protocol. Patient BMI, image field size, source image and source object distances and DAP were collected together with assessment of radiographic spinal alignment and disc space demonstration. Effective dose was calculated with organ specific doses.

RESULTS

76 (53.5%) patients were imaged in the supine AP and recumbent lateral position, 66 (46.5%) had erect PA and lateral radiographs. Despite the larger BMI of the erect cohort and similar field sizes, effective dose was lower in the PA position by an average of 20% (p < 0.05), however, no significant difference in lateral dose. Anatomical improvements were evident with greater visualisation of intervertebral disc spaces in the PA erect (t = -9.03; p < .001) and lateral (t = -10.298; p < .001) orientations. Erect PA radiographs demonstrated a leg length discrepancy in 47.0% (0.3-4.7 cm) and a scoliosis in 21.2% of cases, with a significant link between these findings (r (64) = 0.44; p < .001).

CONCLUSION

Erect lumbar spine radiography provides information on clinical outcomes not available with recumbent projections. The improvements in anatomical visualisation and radiation dose reduction supports the local change in practice.

IMPLICATIONS FOR PRACTICE

- Erect imaging can reduce effective dose with an optimised acquisition protocol - additional pathological information can be revealed by the erect posture. - postural awareness is critical to interpret images accurately.

Evolution of Concepts: Can Personalized Hip Arthroplasty Improve Joint Stability?

Hip arthroplasty procedures are successful and reproducible. However, within the first two post-operative years, hip dislocations are the most common cause for revisions. This is despite the majority of the dislocations having the acetabular component within what is described as the 'safe zone'. The limitations of such boundaries do not take into account the variability of individual hip anatomy and functional pelvic orientation that exist. An alternative concept to address hip instability and improve overall outcomes is functional acetabular orientation. In this review article, we discuss the evolution of concepts, particularly the kinematic alignment technique for hip arthroplasty and the use of large-diameter heads to understand why total hip arthroplasty dislocations occur and how to prevent them.

Functional Component Positioning in Total Hip Arthroplasty and the Role of Robotic-Arm Assistance in Addressing Spinopelvic Pathology

Hip, spine, and pelvis function as a unified kinetic chain. Any spinal pathology, results in compensatory changes in the other components to accommodate for the reduced spinopelvic motion. The complex relationship between spinopelvic mobility and component positioning in total hip arthroplasty presents a challenge in achieving functional implant positioning. Patients with spinal pathology, especially those with stiff spines and little change in sacral slope, are at high instability risk. In this challenging subgroup, robotic-arm assistance enables the execution of a patient specific plan, avoiding impingement and maximizing range of motion; especially utilizing virtual range of motion to dynamically assess impingement.

Functional implant positioning in total hip arthroplasty and the role of robotic-arm assistance

INTRODUCTION

Accurate implant positioning, tailored to the phenotype and unique biomechanics of each patient is the single most important objective in achieving stability in THA and maximise range of motion. The spine-pelvis-hip construct functions as a single unit adapting to postural changes. It is widely accepted in the literature that no universaltarget exists and variations in spinopelvic mobility mandate adjustments to the surgical plan; thus bringing to the fore the concept of personalised, functional component positioning.

METHODS

This manuscript aims to outline the challenges posed by spinopelvic imbalance and present a reproducible, stepwise approach to achieve functional-component positioning. We also present the one-year functional outcomes and Patient Reported Outcome Measures of a prospective cohort operated with this technique.

RESULTS AND CONCLUSION

Robotic-arm assisted Total Hip Arthroplasty has facilitated enhanced planning based on the patient's phenotype and evidence suggests it results in more reproducible and accurate implant positioning. Preservation of offset, avoiding leg-length discrepancy, accurate restoration of the centre of rotation and accomplishing the combinedversion target are very important parameters in Total Hip Arthroplasty that affect post-operative implant longevity, patient satisfaction and clinical outcomes.

Total hip arthroplasty has higher complication rates in stiff spine patients: a systematic review and network meta-analysis

BACKGROUND

Ankylosing spondylitis (AS) and spinal fusion (SF) classified as stiff spines have been associated with the increased rate of complications following total hip arthroplasty (THA). However, the differences between the two cohorts have inconsistent evidence.

METHODS

We searched for studies comparing complications among stiff spine patients, including SF and AS, who underwent THA in PubMed/MEDLINE, Embase, Cochrane CENTRAL, Web of Science, and Scopus until March 2021. Studies detailing rates of mechanical complications, aseptic loosening, dislocation, infection, and revisions were included. We performed network meta-analyses using frequentist random-effects models to compare differences between cohorts. We used P-score to rank the better exposure with the lowest complications.

RESULTS

Fourteen studies were included in the final analysis. A total of 740,042 patients were included in the systematic review and network meta-analysis. Mechanical complications were highest among SF patients (OR 2.33, 95% CI 1.86, 2.92, p < 0.05), followed by AS patients (OR 1.18, 95% CI 0.87, 1.61, p = 0.82) compared to controls. Long Spinal Fusions had the highest aseptic loosening (OR 2.33, 95% CI 1.83, 2.95, p < 0.05), dislocations (OR 3.25, 95% CI 2.58, 4.10, p < 0.05), infections (OR 2.14, 95% CI 1.73, 2.65, p < 0.05), and revisions (OR 5.25, 95% CI 2.23, 12.32, p < 0.05) compared to AS and controls. Our results suggested that SF with longer constructs may be associated with higher complications in THA patients.

CONCLUSIONS

THAs following SFs have higher mechanical complications, aseptic loosening, dislocations, and infections, especially with longer constructs. AS patients may have fewer complications compared to this cohort.