Pre-operative bone mineral density is a predictive factor for excellent early patient-reported outcome measures in cementless total hip arthroplasty using a proximally fixed anatomic stem. A prospective study at two year minimum follow-up

Combined assessment of acetabular coverage and femoral head-neck shapes predicts osteoarthritis progression after periacetabular osteotomy

INTRODUCTION

Postoperative osteoarthritis (OA) progression is a major determinant of failure after curved periacetabular osteotomy (CPO). A large postoperative combination angle, i.e., the combination of computed tomography-based anterior center edge and alpha angles, is associated with femoroacetabular impingement after CPO, but its association with postoperative OA progression is unclear. We aimed to identify the anatomical parameters that can lead to OA progression after CPO and the impact of the combination angle on the same.

MATERIALS AND METHODS

We included 90 hips that were subjected to CPO at our center between March 2013 and March 2018. Seventeen hips showed OA progression with an increase in the Tönnis classification after surgery; 73 hips showed no progression. Radiographic anatomical parameters, including the lateral and anterior center edge angles, femoral and acetabular anteversion, and combination angle, and clinical outcomes, including modified Harris Hip Scores (mHHSs), postoperative anterior impingement, and range of motion, were compared between the two groups. Statistical significance was set at P < 0.05.

RESULTS

Postoperative OA progression was significantly affected by preoperative OA evidence (P = 0.017), acetabular anteversion < 5.0° (P = 0.003), and a combination angle > 107.0° (P = 0.025). Patients with radiographic OA progression were associated with poor mHHSs (P = 0.017) and high frequencies of anterior impingement with a limited hip flexion and internal rotation angle.

CONCLUSIONS

OA progression after CPO may be associated with preoperative evidence of OA and postoperative acetabular retroversion as well as a large combination angle. Surgeons should focus on the potential effects of preoperative OA grades, postoperative reduction in acetabular anteversion, and postoperative combination angle.

Bone Quality Assessment Before Total Hip Arthroplasty: The Role of Densitometry

Background Total hip arthroplasty (THA) is effective in the treatment of hip osteoarthritis. Radiographic evaluation, standard in THA planning, is sufficient in examining hip anatomy, although it may not precisely assess bone quality. A routinely implemented method in bone quality assessment is densitometry. The technique allows for a measurement of bone mineral density (BMD). Methodology In the study, we included 26 participants who qualified for THA. All the patients were preoperatively examined with radiographs and densitometry of the affected hip. On the preoperative anteroposterior radiograph, we measured the canal-to-calcar isthmus ratio (CC ratio) and the cortical index (CI). Intraoperatively, during the THA procedure, we measured the thickness of the cortical bone and the diameter of the femoral neck in the line of neck resection. Results The examination with Pearson's correlation coefficient revealed that BMD significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.5, P = 0.009), and with the measured thickness of the cortical bone (r = 0.47, P = 0.015), CI significantly positively correlates with the intraoperatively measured diameter of the femoral neck (r = 0.6, P = 0.001), and with the CC ratio (r = 0.44, P = 0.024), the intraoperatively measured diameter of the femoral neck significantly positively correlates with the intraoperatively measured thickness of the cortical bone (r = 0.59, P = 0.001). All of the other correlations were not statistically significant. Conclusions BMD measurements can be used in THA planning as they positively correlate with intraoperative measurements. The radiological parameters (CC ratio and CI) may not be as precise in bone quality assessment.

Does the bone mineral density measured on a preoperative CT scan before total hip arthroplasty reflect the bone's mechanical properties?

INTRODUCTION

No method exists to quantify the bone quality and factors that will ensure osteointegration of total hip arthroplasty (THA) implants. A preoperative CT scan can be used to evaluate the bone mineral density (BMD) when planning a THA procedure. The aim of this study was to validate BMD measurement as a marker of bone quality based on a preoperative CT scan.

HYPOTHESIS

BMD reflects the bone's mechanical properties for the purposes of preoperative THA planning.

METHODS

Patients who underwent primary THA for hip osteoarthritis or dysplasia with cementless implants and 3D preoperative plan were enrolled prospectively. The cortical BMD was calculated on CT scans used in the preoperative planning process. During the surgical procedure, the femoral head and neck were collected. These bone samples were subsequently scanned with a calibrated micro-CT scanner. The BMD was derived from the micro-CT scan and used as input for a finite element model to determine the bone's mechanical properties. Correlations between BMD, apparent moduli of elasticity and porosity were calculated.

RESULTS

The values of cortical BMD measured on the micro-CT and CT scan were significantly correlated (cc=0.52). The mean angular cortical BMD measured with the micro-CT scan was 1472.33mg/cm³ (SD: 357.53mg/cm³, 980.64-2830.6mg/cm³). There was no significant correlation between cortical BMD and the various apparent moduli of elasticity, except for E_yy and G_zy. Cortical BMD and porosity were inversely correlated with a Spearman coefficient of -0.41 (CI₉₅: [-0.71; -0.02], p=0.03). There was also an inverse correlation between the apparent moduli of elasticity (independent of their orientation) and porosity (p<0.01).

DISCUSSION

BMD provides information about porosity, which is a major factor when evaluating the bone's mechanical properties before THA.

LEVEL OF EVIDENCE

IV.

A combination of acetabular coverage and femoral head-neck measurements can help diagnose femoroacetabular impingement

This study aimed to evaluate the relationship between the radiographical features of combination of the acetabular coverage and the femoral head-neck shape and the occurrence of femoroacetabular impingement (FAI). In this study, 114 patients who had FAI with or without labral tear and mild osteoarthritis were analyzed. Plain radiographs and computed tomography (CT) were taken for evaluation of acetabular coverage and femoral head-neck measurements. The relationship between the combination angle of acetabular coverage and femoral head-neck measurements and the occurrence of FAI was evaluated. The prevalence of FAI patients with the combination angle of CT-anterior CE + α angle ≥100° was 6.1% (7/114 patients). Receiver operator characteristic curve analysis demonstrated a higher area under the curve for combination of CT-anterior center edge angle (ACEA) with the α angle at 0.94 (CT-ACEA +α angle). A threshold for the occurrence of FAI was determined using the combination CT-ACEA + α angle at 100°. The frequency of FAI surgery was significantly higher in patients with a combination angle ≥100° than in those with a smaller angle. The average modified Harris hip score was significantly lower in patients with a combination angle ≥100° than in those with a smaller angle. We suggest that the combination of lateral center edge angle ≥40°, α angle ≥50° and combined angles of CT-ACEA and α angle ≥100° may help diagnosis of FAI. Level of evidence III: retrospective cohort study.

Anterior acetabular coverage and femoral head-neck measurements predict postoperative anterior impingement: A simulation study

The aim of this simulation study was to evaluate the relationship of elements of anterior acetabular coverage and femoral head-neck shape with the occurrence of postoperative anterior impingement after curved periacetabular osteotomy (PAO). Sixty-two patients with symptomatic developmental dysplasia of the hip who had undergone curved PAO were selected. The likelihood of developing postoperative anterior impingement was explored through simulations of the range of motion by collision detection of the pelvis and femur. Postoperative anterior impingement was defined as impingement that occurred during postoperative bone flexion <105° or postoperative internal rotation <20° at 90° flexion. The three-dimensional center-edge (CE) angles, acetabular and femoral versions, radiographic alpha angles of the femoral head, combination angles of anterior CE and alpha angles, and combined anteversions of acetabular and femoral versions were compared between patients with postoperative anterior impingement and nonimpingement. A receiver operator characteristic (ROC) analysis was conducted to determine thresholds of the examined radiographic parameters and calculate their accuracy for predicting postoperative anterior impingement. A multivariate analysis was performed to test whether combined anteversion, anterior CE angle, and combination angle are associated with excellent modified Harris Hip Scores (mHHSs). ROC analysis demonstrated a combination angle ≥108° was predictive of the occurrence of postoperative anterior impingement after curved PAO, which can lead to impaired clinical outcomes. Conversely, a combination angle <108° was significantly associated with mHHS ≥ 90 points. To avoid postoperative anterior impingement, osteochondroplasty of the femoral head or anterior CE angle control should be performed for patients with preoperative combination angles ≥90°.

Short-Term Analysis of the Changes in the Bone Mineral Density of the Proximal Femur After Uncemented Total Hip Arthroplasty: A Prospective Study of 110 Patients

Introduction

Mechanical loading continuously exposes the bone to remodeling processes. Increased load leads to a gain in bone mass, and reduced load results in a loss. After inserting a prosthesis, the proximal femur is bypassed in loading as the bodyweight shifts distally. This lack of load induces bone resorption according to Wolff’s law. To avoid this bone resorption, the implant's bending stiffness should be less than the femoral bone. Dual-energy X-ray absorptiometry (DEXA) is a well-accepted method to measure periprosthetic bone mineral density (BMD) after total hip arthroplasty (THA). Since the strength and durability of the fixation of a femoral prosthesis in cementless hip arthroplasty depend largely on the quantity and quality of the surrounding bone, preoperative and postoperative evaluation of the quantity and quality of the femoral bone is very important in the long-term prognosis of hip arthroplasty.

Materials and methods

A prospective study of 110 patients in the age group of 25-60 years who underwent uncemented total hip arthroplasty in our tertiary healthcare institution was performed. An uncemented, fully hydroxyapatite-coated implant from a single manufacturer was used in all the patients. All the patients were mobilized on the first post-operative day. The BMD was measured at the proximal femur and the distal tip using a DEXA scan. Gruen zones were used for calculating BMD at different anatomical locations in the femur, with particular importance to zones 1, 4, and 7.

Results

The pre-operative BMD in all zones measured, viz. zones 1, 4, and zone 7 of the affected side, was found to be significantly lower as compared to the BMD values on the control side (P< 0.05). The mean change in the mean BMD was calculated for all the zones and compared with each other using an unpaired t-test. The mean BMD changes were found to be significantly higher in zone 7 in comparison to both zones 1 and 4 (p<0.05).

Conclusion

Significant periprosthetic bone loss after uncemented THA in the femur was noted in Gruen zones 1, 4, and 7 during the first six months after THA, with the greatest bone loss in the femoral calcar area (zone 7). The lower the preoperative BMD of the patient, the greater the postoperative bone loss.

Combination of Anterior Acetabular Coverage and Femoral Head Shape Predicts Femoroacetabular Impingement After Periacetabular Osteotomy

BACKGROUND

Femoroacetabular impingement (FAI) after periacetabular osteotomy (PAO) may be affected by both anterior acetabular coverage and femoral head shape. This study aimed to radiographically evaluate the relationship of the combination of acetabular coverage and femoral head shape with the occurrence of FAI after curved PAO.

METHODS

In this study, 76 hip joints from patients with symptomatic developmental dysplasia of the hip underwent curved PAO. The relationship between the combined postoperative anterior center-edge and alpha angles (ie, the combination angle) and the occurrence of postoperative FAI was evaluated. Clinical factors and the preoperative and postoperative 3-dimensional center-edge angles, acetabular versions, femoral versions, radiographic alpha angles of the femoral head, and the combination angle were measured and compared to clinical outcomes.

RESULTS

The modified Harris Hip Scores, University of California, Los Angeles activity scores, and acetabular coverage angles were significantly improved following curved PAO. Receiver operator characteristic curve analysis demonstrated that the combination angle over 108° may be a predictive factor for the occurrence of FAI after curved PAO. Multivariate analysis demonstrated that an age <40 years (odds ratio 6.6, 95% confidence interval 1.2-36.4, P = .037) and a combination angle <108° (odds ratio 9.2, 95% confidence interval 1.7-50.0, P = .010) were significantly associated with modified Harris Hip Scores ≧90 points.

CONCLUSION

A combination angle >108° may be a predictive factor for the occurrence of FAI after curved PAO and impaired clinical outcomes. To avoid postoperative FAI, we propose that osteochondroplasty of the femoral head should be performed for patients with preoperative combination angles >90°.