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Background: Anterior and posterior pelvic tilt appears to play a role in total hip arthroplasty (THA) stability. When changing from the standing to the sitting position, the pelvis typically rotates posteriorly while the hips flex and this affects the femoro-acetabular positions. This case-control study compares changes in 3-D acetabular cup orientation during functional pelvic tilt between posterior THA dislocations vs stable THAs. Methods: Standing and sitting 3-D cup orientation was compared between fifteen posterior dislocations vs 233 prospectively followed stable THAs. 3-D cup orientation was calculated using previously validated trigonometric algorithms on biplanar radiographs. Those algorithms combine the angles in the three anatomical planes (coronal inclination, transverse version, and sagittal ante-inclination) in the standing position with the change in sagittal pelvic tilt from standing to sitting to calculate the 3-D orientation in the sitting position. Results: The standing cup orientation of the dislocated THAs was only characterized by a lower coronal inclination (P =.039). Compared with the controls, from standing to sitting, they showed less posterior pelvic tilt (P

Sleep stage-specific intervention is widely used to elucidate the functions of sleep and their underlying mechanisms. For this intervention, it is imperative to accurately classify rapid-eye-movement (REM) sleep. However, the proof of fully automatic real-time REM sleep classification in vivo has not been obtained in mice. Here, we report the in vivo implementation of a system that classifies sleep stages in real-time from a single-channel electroencephalogram (EEG). It enabled REM sleep-specific intervention with 90 % sensitivity and 86 % precision without prior configuration to each mouse. We further derived systems capable of classification with higher frequency sampling and time resolution. This attach-and-go sleep staging system provides a fully automatic accurate and scalable tool for investigating the functions of sleep.

Serum immune markers can be useful in the diagnosis of periprosthetic joint infection (PJI) by detecting long-lasting abnormal immunological conditions. The purpose of this study was to examine whether serum immune markers can improve the diagnostic accuracy of PJI.We enrolled 51 PJI, 45 aseptic loosening, and 334 osteoarthritis patients for assessment of the discriminatory accuracy of serum markers including white blood cell count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and D-dimer, total protein, albumin (Alb), globulin (Glb), neutrophil-lymphocyte ratio, lymphocyte-monocyte ratio, platelet-lymphocyte ratio, albumin-globulin ratio (AGR), CRP-albumin ratio (CAR), and CRP-AGR ratio (CAGR). These diagnostic accuracies for low-grade PJI were also calculated in patients who had serum CRP levels10 mg/L.Among serum markers, Alb, Glb, AGR, CRP, ESR, CAR, and CAGR had highly accurate diagnostic accuracy for PJI, with area under the curve of 0.92, 0.90, 0.96, 0.97, 0.92, 0.97, and 0.98, respectively. In low-grade PJI patients, area under the curve of CRP, ESR, CAR, and CAGR (0.69, 0.80, 0.65, and 0.82, respectively) was decreased but that of Alb, Glb, and AGR (0.90, 0.88, and 0.95, respectively) remained high, indicating the diagnostic utility of these immune markers. The sensitivity and specificity of AGR with cutoff value of 1.1 were demonstrated as 0.92 and 0.89, respectively, and with cutoff value of 1.2, 1.00, and 0.79, respectively, in the diagnosis of low-grade infection.Our results demonstrate the potential value of Alb, Glb, AGR, and combination indices of these immune makers with CRP in improving preoperative serum diagnosis for PJI, especially in low-grade PJI.Diagnostic- Level II.

Background The functional anatomy of the osteoarthritic hip joint in the sagittal plane has not been defined. The purpose of this study was to define the functional anatomy of the hip using clinical and radiographic analyses. Methods 320 hips had preoperative standing and sitting lateral spine-pelvis-hip X-rays. Radiographic pelvic measurements were pelvic incidence (PI) and sacral slope (SS), and hip measurements were anteinclination (AI) and pelvic femoral angle (PFA). Pelvic tilt (PT) was calculated as PI-SS. A triangle model was created from the clinical data that illustrates the functional motion of the hip during postural changes from standing to sitting. Results Pelvic motion was coordinated with hip motion, even with spinopelvic imbalance and stiffness. Pelvic motion (ΔSS) varied for all 5 types of imbalance, but pelvic motion (ΔSS) and acetabular motion (ΔAI) changed with a 1:1 ratio and inversely with femoral motion (ΔPFA) with a 1:1 ratio. The triangle model showed similar results with ΔSS, ΔPT, and ΔAI changing in a 1:1:1 ratio, and femur motion inversely changing with a 1:1 ratio. Conclusion The functional anatomy of the hip joint can be visually illustrated using a triangle model. Pelvic angles SS, PT, and AI change in unison, whereas femoral motion (ΔPFA) changes inversely with pelvic motion (ΔSS) in a 1:1 ratio. This coordinated mobility explains the limitations of the Lewinnek safe zone, which include only the acetabulum.

Synovial fluid is important for the preoperative etiological diagnosis of suspected periprosthetic joint infection (PJI) or septic arthritis (SA). GENECUBE, an automated real-time polymerase chain reaction (PCR) assay, was used to detect bacterial mecA (methicillin resistance) and was compared with microbiological cultures for preoperatively diagnosing PJI and SA in 74 patients suspected of these infections and thus earmarked for surgery. PJI and SA were diagnosed in 21 and 6 cases, respectively, using modified ICM 2018 diagnostic criteria. Microbiological cultures determined methicillin-resistant staphylococcus (MRS) as the causative organism in six samples, which were all positive in the GENECUBE assay. Significantly also, the GENECUBE assay detected six MRS infections in culture-negative but infection-diagnosed patients, and in one inconclusive case, suggesting a higher sensitivity of this assay. Compared with microbiological culture, the sensitivity and specificity of the GENECUBE assay for mecAwas 100% and 92.2%, respectively. However, GENECUBE also produced invalid results in three cases, suggesting possible PCR inhibitors in the synovial fluid samples. We additionally validated the accuracy of pan-bacterial real-time PCR targeting 16S rRNA and other tests. Pan-bacterial real-time PCR was as effective as preoperative bacterial culture testing, although the α-defensin assay had the highest sensitivity at 100%. Hence, fully automated real-time PCR targeting of the bacterial mecA gene improves the etiological diagnosis of PJI and SA by reducing the testing time and lowering the false-positive detection rates. A screening approach for α-defensin followed by bacterial mecA gene testing in synovial fluids is therefore a more efficient method of preoperatively diagnosing PJI and SA.

Background: Although rotational changes in lower limb alignment after total hip arthroplasty (THA) affect functional stem anteversion, less is known about the effects of femoral rotational alignment in the standing position. This study investigated postoperative changes in femoral rotation and evaluated the association with whole-body alignment in patients who underwent THA. Methods: Sixty-five patients with unilateral hip osteoarthritis who underwent THA were enrolled. Preoperative and postoperative femoral rotation in the standing and supine positions were measured using EOS 2D/3D X-ray imaging system and computed tomography. Negative and positive changes in femoral rotation angle were indicative of internal and external rotation, respectively. The associations between femoral rotation and preoperative clinical and radiological factors were investigated. Results: Femoral rotation showed significant internal changes in both the standing (−4.7° ± 11.0°) and supine (−3.5°± 10.9°) positions after THA. The preoperative femoral rotation angle, knee flexion angle, sagittal vertical axis (SVA), lumbar lordosis, body mass index, age, and internal and external rotation angles of the hip range of motion on the contralateral side were significantly correlated with femoral rotation in the standing position after THA. Multiple regression analysis showed that preoperative femoral rotation (β = 0.416, P < .001) and SVA (β = 0.216, P = .040) were significant predictors of postoperative femoral rotation in the standing position. Conclusions: Femoral rotation had significant association with the patient-inherent posture represented by the SVA in the standing position. Because extensive external change of femoral rotation may increase the risk of hip impingement and dislocation, careful attention is required in patients with external femoral rotation and forward bent posture in the preoperative standing position.

A postoperative change in pelvic flexion following total hip arthroplasty (THA) is considered to be one of the causes of dislocation. This study aimed to predict the change of pelvic flexion after THA integrating preoperative and postoperative information with artificial intelligence.This study involved 415 hips which underwent primary THA. Pelvic flexion angle (PFA) is defined as the angle created by the anterior pelvic plane and the horizontal/vertical planes in the supine/standing positions, respectively. Changes in PFA from preoperative supine position to standing position at 5 years after THA were recorded and which were defined as a 5-year change in PFA. Machine learning analysis was performed to predict 5-year change in PFA less than -20° using demographic, blood biochemical, and radiographic data as explanatory variables. Decision trees were constructed based on the important predictors for 5-year change in PFA that can be handled by humans in clinical practice.Among several machine learning models, random forest showed the highest accuracy (area under the curve = 0.852). Lumbo-lordotic angle, femoral anteversion angle, body mass index, pelvic tilt, and sacral slope were most important random forest predictors. By integrating these preoperative predictors with those obtained 1 year after the surgery, we developed a clinically applicable decision tree model that can predict 5-year change in PFA with area under the curve = 0.914.A machine learning model to predict 5-year change in PFA after THA has been developed by integrating preoperative and postoperative patient information, which may have capabilities for preoperative planning of THA.

Background: Precise osteochondroplasty is important in arthroscopic hip surgery for cam-type femoroacetabular impingement (FAI). Although computer-assisted surgery with a navigation system may enhance the accuracy of arthroscopic osteochondroplasty, few clinical studies have assessed its accuracy. Purpose: To evaluate the accuracy of arthroscopic osteochondroplasty by a computed tomography (CT)–based navigation system for cam-type FAI, using 3-dimensional (3D) reconstruction with more detail compared with previous methods. Study design: Case series; Level of evidence, 4. Methods: Twenty patients (14 men and 6 women) who underwent navigation-assisted arthroscopic surgery for cam-type FAI were included. The preoperative 3D model of the femur was constructed from each patient’s CT data, and a planned model with virtual cam resection was generated. A femoral model was reconstructed from CT data postoperatively. The 3 models for each patient were overlaid using a 3D model registration method. Then, the contours of the bone resection area of each model were compared by measuring them. To measure the deviation between planned and actual bone resections, 4 cross-sectional images of the 3 femoral models were set at one-quarter intervals from the femoral head radius. All measurements were based on clockface lines set around the femoral neck axis at 30-minute intervals. Differences between the planned and postoperative contour lines were deemed resection deviations. Results: All cam resections were performed in the anterior half of the region of interest. Therefore, only the anterior half (48 points) of the 96 points per case were analyzed. In 876 (91.3%) points of the total measurement points (960 points/20 cases), the error in resection depth was within 3 mm. Overresection was observed at 35 (3.6%) points and underresection at 49 (5.1%) points. The observed maximum deviations from the planned models were 6.3 mm overresection and –7.1 mm underresection. The alpha angles of the postoperative model at the posterior 9- to 3-o’clock position were Conclusion: Navigation-assisted arthroscopic osteochondroplasty showed favorable accuracy. Underresection was more frequent than overresection on the anterosuperior side of the femur, despite assistance of the navigation system.

The severity of bone mineral density (BMD) loss after total hip arthroplasty (THA) depends on both implant- and patient-related factors. While implant fixation type is an important factor, but few studies have considered the effect of material composition on the same implant fixation type. In particular, differences in mechanical stiffness due to material composition are of great interest. Here, we compared changes in periprosthetic BMD after THA using proximal fixation concept stems comprising different titanium alloys, i.e., β titanium alloys stem and α + β titanium alloys stem.This retrospective cohort included 122 patients (β titanium alloys stem, 61 cases; α + β titanium alloys stem, 61 cases) who underwent primary THA between January 2009 and December 2019. The primary outcome was the change in periprosthetic BMD from base line. Age, body mass index, diagnosis, stem size, canal flare index, surgical approach, pre-operative lumbar BMD, and pre-operative activity scores were reviewed and changes in periprosthetic BMD between the two groups were compared using analysis of covariance. The secondary outcome was radiographic response after THA.There was significant difference in periprosthetic BMD in zone 6 and 7 at 2 years (p 0.05) between the two groups. There was no significant difference in other zones. A significant difference in radiographic response was noted only for the Engh classification.α + β titanium alloys stem resulted in a significantly higher rate of BMD loss in zones 6 and 7 compared with the β titanium alloys stem. These results may be due to differences in mechanical stiffness due to the different titanium alloy composition of the prosthetics.

The rapid detection of etiological agents is important for the successful treatment of iliopsoas abscess (IPA). The purpose of this study was to investigate the clinical utility of a real-time polymerase chain reaction (PCR) that targets the mecA gene for methicillin-resistant staphylococci (MRS) and the 16S rRNA gene for pan-bacteria. Our retrospective diagnostic study included 22 patients exhibiting IPAs and four patients with noninfectious iliopsoas mass regions who underwent computerized tomography or ultrasonography-guided biopsy and/or surgical treatment. Clinical symptoms, serum data, imaging analysis, and tissue microbiological culture were utilized for the diagnosis of IPA. The diagnostic accuracy of real-time PCR was determined based on the diagnosis of IPA and microbiological culture results. The microbiological culture was positive for 12 IPA cases that included 2 MRSA infections. Among 12 culture-positive IPA cases, 16S rRNA-PCR was positive in 12 and MRS-PCR in two. Among 10 culture-negative IPA cases, including 3 TB cases, 16S rRNA-PCR was positive in 8 and MRS-PCR in 2. In noninfectious iliopsoas mass patients, neither 16S rRNA nor MRS-PCR detected bacterial DNA. The sensitivity, specificity, positive predictive, and negative predictive values of 16S rRNA-PCR for diagnosing IPA were 0.91, 1.00, 1.00, and 0.67, respectively, while those for the diagnosis of MRS infection with MRS-PCR were 1.00, 0.92, 1.00, and 0.50, respectively. Real-time PCR targeting bacterial DNA can detect bacterial DNA in culture-negative cases and offer improved detectability of MRS infection in IPA patients.

Smjernice za prevenciju tromboembolijskih incidenata prilikom ortopedskih zahvata na kuku i koljenu.

Preoperative diagnosis of infection is important for appropriate surgical treatment of patients with rapid hip destruction (RHD). We investigated whether test results, including inflammatory and nutritional markers, could be used to accurately differentiate infectious and non-infectious RHD. Fifty patients with RHD who underwent total hip arthroplasty within a year of onset were observed. Infectious RHD was defined as ≥ 2 positive serological inflammatory, microbiological, or pathological evaluations. The albumin to globulin ratio (AGR), C-reactive protein (CRP)/albumin ratio (CAR), Glasgow prognostic score (GPS), modified GPS (mGPS), prognostic nutritional index (PNI), geriatric nutritional risk index (GNRI), and platelet to lymphocyte ratio (PLR) were calculated from the blood test results. In the infectious group, the white blood cell count, platelet count, CRP level, erythrocyte sedimentation rate, CAR, GPS, mGPS, and PLR were significantly higher, while the albumin level, AGR, PNI, and GNRI were significantly lower. The CRP and albumin levels showed the highest sensitivity (1.00 for both; specificity of 0.87 and 0.73, respectively) in diagnosing infectious RHD. Combining these measurements (CAR) increased the specificity to 0.92. The accuracy of other nutritional assessments was good. Thus, nutritional assessment as well as conventional assessment of the inflammatory response can improve the accuracy of preoperative diagnosis of infectious RHD.

Health screening is conducted in numerous countries to observe general health conditions. Machine learning has been applied to health screening records to predict asymptomatic patients' future medical states. However, for medical researchers and physicians, it is crucial to know why machine learning methods made such predictions to understand the underlying mechanism of the disease and prescribe treatments; therefore, predictions must be interpretable. We investigated the ability of an attentional neural network that processes tabular data, namely TabNet, to determine attributes that contribute to making predictions of the aggravation of type 2 diabetes. We used both model-agnostic and model-specific interpretation methods. For the former, we tested SHapley Additive exPlanations (SHAP). For the latter, we used model-specific feature importance and the mask in the attentive transformer of TabNet. We found that this mask provides useful information regarding which items in a biochemical analysis affect the aggravation of type 2 diabetes. The results from model-agnostic and model-specific methods were consistent.

The rapid detection of etiological agents is important for the successful treatment of iliopsoas abscess (IPA). The purpose of this study was to investigate the clinical utility of a real-time polymerase chain reaction (PCR) that targets the

Background Excessive external femoral rotation (FR) can functionally increase stem anteversion (SA) and is often observed at an early stage after surgery in revision total hip arthroplasty (THA). This study was conducted to investigate the prevalence of external FR, identify the factors associated with external FR, and determine the association of FR and other factors with hip dislocation in revision THA. Methods We enrolled 51 revision THA patients (55 hip cases). The patient background, angle of anatomical and functional SA, FR angle, sizes and densities of muscles around the hip joint, impingement distance, and consequence of postoperative hip dislocation were assessed by reviewing their medical history and imaging data that includes computed tomography (CT) scans before and after surgery. Results Forty-five hip cases (81.8%) showed external FR (mean 13.0°). External FR was significantly correlated with anatomical SA (r = − 0.54) and increase in functional SA (r = 0.36), which was significantly correlated with impingement distance (r = 0.46). The independent factors associated with external FR in multivariate analysis were the anatomical SA, CT densities of the psoas, gluteus medius and maximus muscles, and 2-stage revision (R2 = 0.559). During follow-up period, eight cases of revision THA showed hip dislocation. FR, functional SA, impingement distance, CT density of psoas and gluteus medius muscle, body mass index, number of past operation, and ratio of 2-stage revision THA were significantly different between cases with dislocation and non-dislocation. The odds ratio of FR and impingement distance for hip dislocation was identified as 1.061(95% confidence interval (CI): 1.011–1.114) and 0.901 (95% CI 0.820–0.991), respectively. Conclusions Revision THA frequently causes an external FR that functionally increases the SA and impingement risk, particularly in hips with 2-stage revision with psoas and gluteus medius muscle atrophy. Patients who have undergone revision THA and have an excessive external FR may require careful monitoring for possible hip dislocation due to hip joint instability and impingement.

BackgroundStress shielding after total hip arthroplasty (THA) can induce bone mineral density (BMD) loss around the femoral implant. Several studies using drug have described methods to prevent BMD loss around implants following THA. Switching from teriparatide to alendronate was reported to increase lumbar BMD; on the other hands, it is unclear whether switching from teriparatide to alendronate is effective around the implant. The aim of this study is that changes in BMD is compared in patients switched from teriparatide to alendronate, in patients treated with alendronate alone, and in control patients without medication after total hip arthroplasty.Patients and methodsPatients were randomized into three groups, those switched to alendronate after teriparatide (switch:n= 17), those receiving continuous alendronate (ALD:n= 15), and control untreated patients (control:n= 16) and followed up for 2 years after THA. Baseline periprosthetic BMD was measured by dual-energy X-ray absorptiometry (DEXA) 1 week after THA, followed by subsequent measurements at 1 and 2 years postoperatively. Lumbar BMD was also evaluated at preoperatively, 1 and 2 years postoperatively.ResultsTwo years after surgery, BMD (%) at zone 1 was significantly higher in the switch group than in the control group (P= 0.02). BMD (%) at zone 7 was significantly higher in the switch and ALD groups than in the control group (P= 0.01,P= 0.03). Lumbar BMD (%) anterior-posterior (AP) side was significantly higher in the switch group than in the ALD and control groups 2 years after surgery. On the other hand, lumbar BMD (%) lateral side was significantly higher in the switch and ALD groups than control group 2 years after surgery.ConclusionsSwitching therapy had a significant effect on BMD of the lumbar spine and zones 1 and 7 at 2 years postoperatively. At zone 1 in particular, it was found to be more effective than ALD alone.Trial registrationUMIN, registry numberUMIN000016158. Registered 8 January 2015

Objective: This study evaluated the effect of surgical intervention on disease activity and factors associated with postoperative disease activity in patients with rheumatoid arthritis (RA).Methods...

To evaluate radially reconstructed 3.0-Tesla 3-dimensional multiple-echo recombined gradient echo (MERGE) magnetic resonance imaging (MRI) without arthrography for the assessment of acetabular labrum tears, using arthroscopic evaluation as the reference standard.A total of 71 consecutive hips, including 29 with femoroacetabular impingement, 26 with borderline developmental dysplasia of the hip, and 16 with early-stage osteoarthritis, were evaluated in this retrospective study. MERGE MRI findings were evaluated according to the modified Czerny classification for 3 regions of interest: anterior region, anterolateral region, and lateral region. Cases with severe degeneration that was not concordant with any stage in the original Czerny classification were defined as stage Ⅳ. MERGE MRI findings were compared with arthroscopic findings, and the sensitivity, specificity, positive predictive value, and negative predictive value in terms of the existence of labrum tears were calculated.MERGE MRI findings revealed labrum tears more frequently in the anterolateral region than in the anterior and lateral regions (P.01). In cases of femoroacetabular impingement and borderline developmental dysplasia of the hip in particular, labrum tears were more frequently observed on MRI in the anterolateral region than in the lateral region (P.05). In comparison with MRI findings and arthroscopic findings, our newly defined stage IV in the modified Czerny classification was more frequently observed in cases with a Multicenter Arthroscopy of the Hip Outcomes Research Network (MAHORN) classification of degenerative or complex (P.01). The average sensitivity and specificity of all regions for the existence of labrum tears were 85% and 56%, respectively. Sensitivity and specificity were 79% and 50%, respectively, in the anterior region; 96% and 50%, respectively, in the anterolateral region; and 70% and 57%, respectively, in the lateral region.We validated the diagnostic performance of 3.0-Tesla 3-dimensional MERGE MRI for evaluating acetabular labrum tears and made comparisons with arthroscopic findings. Radially reconstructed MERGE magnetic resonance images showed excellent sensitivity for the diagnosis of labrum tears, particularly in the anterolateral region. The newly defined stage IV was distinctive of early-stage osteoarthritis cases with degeneration and/or complex arthroscopic findings. The noninvasive imaging modality of radially reconstructed MERGE MRI may be an alternative to magnetic resonance arthrography for evaluating labrum tears.Level Ⅱ, development of diagnostic criteria.

Background: Femoroacetabular impingement (FAI) is primarily caused by bony impingement between the acetabulum and femoral neck during hip motion. Increasing posterior pelvic tilt improves hip range of motion in patients with FAI. Purpose: To use computer simulation analysis to compare the effects of 3-dimensional (3D) changes in pelvic tilt (sagittal tilt [St], axial rotation, and coronal tilt) with changes in a single plane (St), with the aim of improving range of motion in patients with FAI. Study Design: Controlled laboratory study. Methods: We evaluated 43 patients with FAI treated by arthroscopic cam resection. A 3D simulation was used to construct the following pelvic models: a 5° and 10° increase posteriorly in St (St5° and St10°) and a combined 5° change in St, axial rotation, and coronal tilt (Complex5°) from the baseline of the anterior pelvic plane. Improvements in maximum internal rotation (MIR) at 45°, 70°, and 90° of hip flexion and improvements in maximum flexion with no internal rotation were compared among the St5°, St10°, and Complex5° models. The pelvic models of each single-plane change of 5° and 10° were evaluated in the same simulation. Results: At 90° and 70°, there was a significant difference between the Complex5° and St10° models with respect to improvement in MIR ( P = .004 at 90° of flexion; P = .017 at 70° of flexion). There was no significant difference in MIR at 45° of flexion ( P = .71) or in maximum flexion ( P = .42). Conclusion: At 70° and 90° of hip flexion, a combined change in 3D pelvic alignment of 5° (ie, St, axial rotation, and coronal tilt) was more effective in improving hip MIR than a 10° change in St only. Clinical Relevance: Effective physical therapy for FAI should address pelvic motion in all 3 planes rather than in a single plane.

Objectives To evaluate joint orientation angles of the coronal plane in patients with rheumatoid arthritis (RA) in comparison with osteoarthritis (OA). Methods In total, 72 patients with RA (90 knees) and 76 patients with OA (90 knees) who underwent total knee arthroplasty were enrolled. The hip–knee–ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and joint line convergence angle (JLCA) were measured on preoperative long-leg radiographs in the standing position. Student’s t-test was used to assess differences in radiographic data between patients with RA and OA. Results In knees with RA and OA, the mean HKA was −3.4 ± 9.4° and −10.6 ± 8.0°, the mean mLDFA was 86.6 ± 3.7° and 88.2 ± 2.7°, the mean mMPTA was 85.9 ± 4.0° and 84.3 ± 3.7°, and the mean JLCA was 2.7 ± 4.2° and 6.8 ± 4.1°. All parameters in the knees with RA were more valgus than those with OA. Conclusions Knees with RA had a great variability in joint orientation angles on the coronal plane; the whole lower limb alignment and the femur, tibia, and joint were more valgus in knees with RA than with OA.

Background Stress shielding after total hip arthroplasty (THA) leads to loss of bone mineral density (BMD) around the femoral implants, particularly in the proximal area. Loss of BMD around the implant is likely to occur within 1 year after THA; however, its severity depends on patient characteristics. This study evaluated preoperative factors correlated with the severity of zone 7 BMD loss after THA. Methods This retrospective cohort study included 48 patients who underwent primary THA from October 2011 to December 2015. All patients underwent implantation of a Zweymüller-type femoral component without any postoperative osteoporosis medications. The objective variable was a change in zone 7 BMD after 1 year. Factors evaluated included age, body mass index, Japanese Orthopaedic Association score, Harris Hip Score, Canal Flare Index (CFI), and lumbar BMD on the frontal and lateral sides. Univariate and multivariate regression analyses identified factors correlated with loss of zone 7 BMD. Results Univariate regression analysis identified CFI (P = 0.003) and preoperative lumbar BMD on the anterior-posterior (P = 0.003) and lateral (P P = 0.014) and lumbar BMD on the lateral side (P Conclusion Lower preoperative lumbar BMD on the lateral side and lower CFI were correlated with zone 7 BMD loss after THA. Patients with these characteristics should be monitored carefully for severe BMD loss after THA.