Consumption responses to COVID-19 payments: Evidence from a natural experiment and bank account data.

We document households' spending responses to a stimulus payment in Japan during the COVID-19 pandemic. In response to the pandemic, the Japanese government launched a universal cash entitlement program offering a sizable lump sum of money to all residents to alleviate the financial burden of the pandemic on households. The timings of cash deposits varied substantially across households due to unexpected delays in administrative procedures. Using a unique panel of 2.8 million bank accounts, we find an immediate jump in spending during the week of payments, followed by moderately elevated levels of spending that persist for more than one month after payments are received. We also document sizable heterogeneity in consumption responses by recipients' financial status and demographic characteristics. In particular, demand deposit balances play a more crucial role than other financial asset holdings, suggesting the importance of the wealthy hand-to-mouth.

The macroeconomics of COVID-19 exit strategy: the case of Japan.

In this paper, I use a simple SIR Macro model to examine Japan's soft lockdown policies in 2021 under the COVID-19 crisis. As real-time research, this paper consists of two parts written during two different research periods. The first part, which was originally reported in February 2021, studies the Japan's second soft lockdown policy (state of emergency declaration) from January to March 2021. After the model is calibrated using 2020 data, the results show that a long enough lockdown can avoid future lockdowns, improving both the infection and the economy. In addition, I propose the ICU targeting policy, which keeps the number of severe patients at a constant level, mimicking the monetary policy's inflation targeting. The model's prediction is evaluated from an ex-post perspective in the second part, written in July 2021. I find that the model broadly captures the realized consequences of the second soft lockdown and the subsequent paths. Furthermore, the simulation is projected to the end of the pandemic under a revised scenario, incorporating the proliferation of COVID-19 variants. Finally, I discuss the effectiveness of the inverse lockdown (economic stimulus) policy in the fall of 2021 under the dynamic infection externality.

Who spent their COVID-19 stimulus payment? Evidence from personal finance software in Japan.

In response to the COVID-19 crisis, governments worldwide have been formulating and implementing different strategies to mitigate its social and economic impacts. We study the household consumption responses to Japan's COVID-19 unconditional cash transfer program. Owing to frequent delays in local governments' administrative procedures, the timing of the payment to households varied unexpectedly. Using this natural experiment, we analyze households' consumption responses to cash transfers using high-frequency data from personal finance management software that links detailed information on expenditure, income, and wealth. We construct three consumption measures: one captures the baseline marginal propensity to consume (MPC), and the other two are for the lower and the upper bound of MPC. Additionally, we explore heterogeneity in MPCs by household income, wealth, and population characteristics, as well as consumption categories. Our results show that households exhibit immediate and non-negligible positive responses in household expenditure. There is significant heterogeneity depending on various household characteristics, with liquidity constraint status being the most crucial factor, in line with the standard consumption theory. Additionally, this study provides policymakers with insights regarding targeted cash transfer programs, conditioning on labor income, and liquidity constraints.

Evaluation of anterior inferior iliac spine impingement after hip arthroscopic osteochondroplasty using computer simulation analysis.

BACKGROUND: Anterior inferior iliac spine (AIIS) impingement is an important risk factor for revision hip arthroscopy. Although a morphological classification system is available, evaluating AIIS impingement with respect to joint kinematics remains a challenge. PURPOSE: To use computer simulation analysis to ascertain the prevalence of AIIS impingement before and after osteochondroplasty. METHODS: A total of 35 joints from 30 cases (20 males and 10 females; average age: 43.3 ± 13.7 years) were analyzed. All joints had cam morphology and underwent hip arthroscopic osteochondroplasty. A three-dimensional model of each joint was constructed pre- and postoperatively. Joint kinematic simulation software (ZedHip®, Lexi, Tokyo) was used to identify the impingement point on the acetabular side and the incidence (expressed as a percentage) of AIIS impingement calculated. Radiographic and clinical evaluation was performed pre- and postoperatively. RESULTS: AIIS impingement was observed postoperatively in six joints but preoperatively in only one joint. The rate of AIIS postoperative impingement was significantly higher than that of preoperative impingement. All impingement points were located on the inferior aspect of the AIIS apex. However, there were no significant differences between the AIIS impingement and non-impingement groups in terms of clinical outcome. CONCLUSION: The incidence of AIIS impingement after osteochondroplasty was 17% by computer simulation analysis. Osteochondroplasty may result in subsequent AIIS impingement.

Current risk factors for asymptomatic venous thromboembolism in patients undergoing total hip arthroplasty.

Objective: A history of venous thromboembolism (VTE) is a risk factor for newly formed VTE after total hip arthroplasty (THA). However, its morbidity and association with postoperative VTE are not clear and, therefore, were investigated in this study. Methods: Four-hundred and nineteen patients scheduled for primary THA were included. We preoperatively identified any VTE factors such as obesity, age, and history of VTE by interviewing and duplex ultrasonography for all patients, and the patients were assigned into 'high-' or 'low-risk' groups, that were the indication whether chemoprophylaxis was administered after surgery. Postoperative VTE was also examined on the day 7 by enhanced computed tomography (CT) for all patients. Results: Preoperative VTE were detected in 48 patients (11.4%), and postoperative VTE were found in 44 (10.5%). Linear and multivariate logistic regression analysis revealed osteonecrosis and preoperative VTE were the independent factors associated with postoperative VTE (Odds ratio (OR) 1.0 e-7 and 5.00, respectively). In the survey of each risk group, only preoperative VTE was recognized as a risk factor for high-risk group, and longer operation time for low-risk group. Conclusion: The present study confirmed high frequency of preoperative VTE which was still the strongest risk factor for postoperative asymptomatic VTE.

Computer-Assisted Hip Arthroscopic Surgery for Femoroacetabular Impingement.

Precise osteochondroplasty is key for success in hip arthroscopic surgery, especially for femoroacetabular impingement (FAI) caused by cam or pincer morphology. In this Technical Note, we present computer-assisted hip arthroscopic surgery for FAI, including preoperative planning by virtual osteochondroplasty and intraoperative computer navigation assistance. The important concept of this technique is that navigation assistance for osteochondroplasty is based on planning made by computer simulation analysis. The navigation assistance allows us to perform neither too much nor too little osteochondroplasty. Specifically, computer simulation was used to identify the impingement point. Virtual osteochondroplasty was then performed to determine the maneuvers that would improve range of motion. Thereafter, the planning data were transported to a computed tomography-based computer navigation system that directly provided intraoperative assistance. Thus, computer-assisted technology including preoperative simulation, virtual osteochondroplasty planning, and intraoperative navigation assistance may promote precise hip arthroscopic surgery for FAI.

Mechanical Strength of the Proximal Femur After Arthroscopic Osteochondroplasty for Femoroacetabular Impingement: Finite Element Analysis and 3-Dimensional Image Analysis.

PURPOSE: To examine the influence of femoral neck resection on the mechanical strength of the proximal femur in actual surgery. METHODS: Eighteen subjects who received arthroscopic cam resection for cam-type femoroacetabular impingement (FAI) were included. Finite element analyses (FEAs) were performed to calculate changes in simulative fracture load between pre- and postoperative femur models. The finite element femur models were constructed from computed tomographic images; thus, the models represented the shape of the original femur, including the bone resection site. Three-dimensional image analysis of the bone resection site was performed to identify morphometric factors that affect strength in the postoperative femur model. Four oblique sagittal planes running perpendicular to the femoral neck axis were used as reference planes to measure the bone resection site. RESULTS: At the transcervical reference plane, both the bone resection depth and the cross-sectional area at the resection site correlated strongly with postoperative changes in the simulated fracture load (R2 = 0.6, P = .0001). However, only resection depth was significantly correlated with the simulated fracture load at the reference plane for the head-neck junction. The resected bone volume did not correlate with the postoperative changes in the simulated fracture load. CONCLUSIONS: The results of our FEA suggest that the bone resection depth measured at the head-neck junction and transcervical reference plane correlates with fracture risk after osteochondroplasty. By contrast, bone resection at more proximal areas did not have a significant effect on the postoperative femur model strength in our FEA. The total volume of resected bone was also not significantly correlated with postoperative changes in femur model strength. CLINICAL RELEVANCE: This biomechanical study using FEA suggest that there is a risk of femoral neck fracture after arthroscopic cam resection, particularly when the resected lesion is located distally.

The Relationship Between the Location of Uptake on Positron Emission Tomography/Computed Tomography and the Impingement Point by Computer Simulation in Femoroacetabular Impingement Syndrome With Cam Morphology.

PURPOSE: To clarify the concordance rate of the location of uptake on positron emission tomography/computed tomography (PET/CT) and the impingement point demonstrated in computer simulation in femoroacetabular impingement (FAI) syndrome with cam morphology. METHODS: We included hip joints with FAI syndrome that underwent 18F-fluoride PET/CT. We also excluded hips with SUVmax <6. Each hip was evaluated for the region of the SUVmax point on PET/CT as well as the impingement point by computer simulation. We used ZedHip software (Lexi, Tokyo, Japan) for impingement simulation analysis based on CT data. Bony impingement is identified if there is a mesh in acetabular and femoral side contact in at least one unit. We investigated the rate of concordance between these 2 regions for each 10° flexion angle of the hip, ranging from 0° to 90°. RESULTS: Twenty-two hips of 22 patients were evaluated. The SUVmax region was most frequently distributed in the proximal middle region in 12 hips. In 18 of 22 hips (81.8%), the SUVmax region was concordant with the impingement region for at least one flexion angle. The concordance rates in 50° (P = .034), 60° (P = .007), 70° (P = .011), and 80° (P = .046) of flexion were significantly higher than in 90° of flexion. CONCLUSIONS: It was possible to visualize and clarify the detailed location of abnormal uptake in FAI syndrome patients with cam morphology by applying 18F-fluoride PET/CT. The concordance rates in 50°, 60°, 70°, and 80° of flexion were significantly higher than in 90° of flexion, which suggested that impingement may more frequently occur at less than 90° of flexion in FAI syndrome with cam morphology. LEVEL OF EVIDENCE: Level III, cross-sectional diagnostic study.

Reactive Osteochondromatous Lesion of the Femoral Neck in a Highly Active Preadolescent Patient: Is This the Pathogenesis of a Cam Deformity?

Here, we present a rare case of a preadolescent boy with a prominent bony bump on the femoral neck. The main histological feature was concordant with a reactive osteochondromatous lesion possibly induced by repetitive microtrauma, probably because of overtraining as a soccer goalkeeper. The nature of this pathological change is consistent with the growth of a cam deformity. Especially in the preadolescent age group, we should note that repetitive use of the same joint kinematics may induce a prominent cam deformity.

Comparison of improved range of motion between cam-type femoroacetabular impingement and borderline developmental dysplasia of the hip -evaluation by virtual osteochondroplasty using computer simulation.

BACKGROUND: While cam resection is essential to achieve a good clinical result with respect to femoroacetabular impingement (FAI), it is unclear whether it should also be performed in cases of borderline developmental dysplasia of the hip (DDH) with a cam deformity. The aim of this study was to evaluate improvements in range of motion (ROM) in cases of cam-type FAI and borderline DDH after virtual osteochondroplasty using a computer impingement simulation. METHODS: Thirty-eight symptomatic hips in 31 patients (11male and 20 female) diagnosed with cam-type FAI or borderline DDH were analyzed. There were divided into a cam-type FAI group (cam-FAI group: 15 hips), borderline DDH without cam group (DDH W/O cam group: 12 hips), and borderline DDH with cam group (DDH W/ cam group: 11 hips). The bony impingement point on the femoral head-neck junction at 90° flexion and maximum internal rotation of the hip joint was identified using ZedHip® software. Virtual osteochondroplasty of the impingement point was then performed in all cases. The maximum flexion angle and maximum internal rotation angle at 90° flexion were measured before and after virtual osteochondroplasty at two resection ranges (i.e., slight and sufficient). RESULTS: The mean improvement in the internal rotation angle in the DDH W/ cam group after slight resection was significantly greater than that in the DDH W/O cam group (P = 0.046). Furthermore, the mean improvement in the internal rotation angle in the DDH W/ cam and cam-FAI groups after sufficient resection was significantly greater than that in the DDH W/O cam group (DDH W/ cam vs DDH W/O cam: P = 0.002, cam-FAI vs DDH W/O cam: P = 0.043). CONCLUSION: Virtual osteochondroplasty resulted in a significant improvement in internal rotation angle in DDH W/ cam group but not in DDH W/O cam group. Thus, borderline DDH cases with cam deformity may be better to consider performing osteochondroplasty.

A new multiplex real-time polymerase chain reaction assay for the diagnosis of periprosthetic joint infection.

OBJECTIVES: A new multiplex real-time polymerase chain reaction (PCR) assay was developed to detect methicillin-resistant Staphylococcus (MRS) and to distinguish between gram-positive and gram-negative bacteria. In this study, we validated the sensitivity and specificity of this assay with periprosthetic joint infections (PJIs) and evaluated the utility of PCR for culture-negative PJI. METHODS: Forty-five samples from 23 infectious PJI cases and 106 samples from 64 non-infectious control cases were analyzed by real-time PCR using a LightCycler Nano® system. Twenty-eight clinical samples, comprising bacteria of known species isolated consecutively in the microbiological laboratory of our hospital, were used to determine the spectrum of bacterial species that could be detected using the new multiplex primers and probes. RESULTS: The sensitivity and specificity of the MRS- and universal-PCR assays were 92% and 99%, and 91% and 88%, respectively. Twenty-eight species of clinically isolated bacteria were detected using this method and the concordance rate for the identification of gram-positive or gram-negative organisms was 96%. Eight samples were identified as PCR-positive despite a culture-negative result. CONCLUSION: This novel multiplex real-time PCR system has acceptable sensitivity and specificity and several advantages; therefore, it has potential use for the diagnosis of PJIs, particularly in culture-negative cases.

Efficacy of Alendronate for the Prevention of Bone Loss in Calcar Region Following Total Hip Arthroplasty.

BACKGROUND: Bone mineral density (BMD) loss around femoral implants, particularly in the proximal femur, is a common outcome after total hip arthroplasty. Previous studies reported the prevention of postsurgical decrease in BMD with the use of osteoporosis drug therapy. This randomized study evaluated the efficacy of alendronate and alfacalcidol for preserving BMD over a long-term follow-up. METHODS: Sixty consecutive patients with hip osteoarthritis who had undergone primary cementless total hip arthroplasty were randomly assigned to an alendronate (n = 20), alfacalcidol (n = 18), or control (n = 22) group. Periprosthetic BMD was measured using dual-energy X-ray absorptiometry at 1 week, 1 year, and the current follow-up (minimum 9 years after surgery). Changes in BMD are reported as mean percentages relative to the values at 1 week (baseline reference). RESULTS: All groups showed a significant decrease in the BMD of the calcar at the current follow-up compared to the values at both 1 week and 1 year postoperatively (P < .001). The BMD values were significantly higher in the alendronate group than in the alfacalcidol and control groups (P < .05). The BMD values at the current follow-up were 76% ± 30% (alendronate group), 64% ± 22% (alfacalcidol group), and 59% ± 22% (control group) of the baseline values. CONCLUSION: Our findings demonstrate the efficacy of early administration of alendronate for the prevention of bone loss in the calcar region.

The Distribution of Impingement Region in Cam-Type Femoroacetabular Impingement and Borderline Dysplasia of the Hip With or Without Cam Deformity: A Computer Simulation Study.

PURPOSE: To identify the distribution of the impingement region in cam-type femoroacetabular impingement (FAI) or patients with borderline developmental dysplasia of the hip (DDH) using computer simulation analysis. METHODS: A total of 51 painful hip joints from 42 consecutive cases diagnosed as cam-type FAI (center edge [CE] angle ≥ 25°, alpha angle ≥ 55°) or borderline DDH (CE angle ≥ 20° and < 25°) with or without a cam deformity (alpha angle ≥ 55° or < 55°) were enrolled. ZedHip (Lexi, Tokyo, Japan) 3-dimensional computer simulation was used to identify impingement points. Computed tomography data were used for 3-dimensional modeling and impingement simulation. The maximum flexion angle and maximum internal rotation angle at 90° were evaluated. The impingement point was identified at a position of maximum internal rotation and 90° of flexion. Six impingement regions were defined. Differences in the distribution of the impingement region were evaluated between groups. RESULTS: There were significant differences in range of motion at maximum flexion and internal rotation among the 3 groups (P < .0001). There was no significant difference in the distribution of the impingement point in the cam-type FAI group (P = .71); similarly, there was no significant difference in the borderline DDH with a cam deformity group (P = .071). On the other hand, in terms of proximal or distal sites, there was a significant difference between the borderline DDH with and without a cam deformity group (P < .001). CONCLUSIONS: The impingement region in cases of cam-type FAI was variable. The coexistence of a cam deformity affected the distribution of the impingement region in cases of borderline DDH; the region tended to be distributed across proximal rather than distal regions. The site of cam osteochondroplasty should be based on the identified impingement point, particularly in cases of cam-type FAI and borderline DDH with a cam deformity. LEVEL OF EVIDENCE: Level IV, case control study.

Preoperative planning for implant placement with consideration of pelvic tilt in total hip arthroplasty: postoperative efficacy evaluation.

BACKGROUND: In total hip arthroplasty (THA), tilting of the pelvis alters the cup placement angles. Thus, the cup angles need to be planned with consideration of the effects of pelvic tilt. In the present study, we evaluated the efficacy of preoperative planning for implant placement with consideration of pelvic tilt in THA, and the accuracy of a CT-based computer navigation for implant positioning. METHODS: We examined 75 hips of 75 patients who underwent THA and were followed-up for one year postoperatively. The patients were divided into three groups (anterior, intermediate, posterior tilt) according to their preoperative pelvic tilt. Preoperative planning for implant placement was made with consideration of pelvic tilt and a CT-based navigation was used to execute the preoperative planning. Cup inclination, cup anteversion, and combined anteversion (CA) in supine and standing positions were examined 1 year after THA. The accuracy of the computer navigation was also examined. RESULTS: Mean CA was 35.0 ± 5.8° in supine position and 39.3 ± 5.7° in standing position. CA did not differ among the three subgroups (anterior, intermediate, posterior tilt) in either supine or standing position, indicating implant placements to be equally effective. The desired CA (37.3°) was midway between those in supine and standing positions for each subgroup. Respective mean absolute errors between preoperative planning and postoperative CT measurement was 5.3 ± 5.2° for CA. CONCLUSION: We obtained favorable THA results with preoperative planning with consideration of pelvic tilt by demonstrating supine and standing CA to be unaffected by preoperative pelvic tilt one year postoperatively. Mean absolute error of CA between preoperative planning and postoperative measurement was 5° with use of the CT-based navigation.

Difference in Postoperative Periprosthetic Bone Mineral Density Changes Between 3 Major Designs of Uncemented Stems: A 3-Year Follow-Up Study.

BACKGROUND: Although few studies have examined the direct effect of stress shielding on clinical outcomes, periprosthetic bone loss due to stress shielding is still an issue of concern, especially when physicians perform uncemented total hip arthroplasty (THA) in younger patients. Differences in femoral stem design may affect the degree of postoperative stress shielding. Therefore, the characteristics of the behavior for stress shielding of each type of femoral stem should be determined. This study compares differences in bone mineral density (BMD) change in the femur after primary THA between 3 major types of uncemented stems. METHODS: Among a total of 89 hips, 26 hips received THA with a fit-and-fill type stem (VerSys Fiber Metal MidCoat; Zimmer, Inc, Warsaw, IN), 32 hips received a tapered rectangular Zweymüller-type stem (SL-Plus; Smith & Nephew Inc, Memphis, TN), and 31 received a tapered wedge-type stem (Accolade TMZF; Stryker Orthopaedics, Mahwah, NJ). BMD measurements were performed with a HOLOGIC Discovery device (Hologic Inc, Waltham, MA). RESULTS: BMD in the medial-proximal femur was maintained for 3 years after THA in the group with the tapered wedge-type stem. BMD in the lateral-proximal femur was maintained for 3 years after THA in the group with the Zweymüller-type stem. There were no significant differences in the Harris Hip Score among the 3 stem groups preoperatively and 1, 2, and 3 years after surgery. CONCLUSION: There are clear differences in postoperative BMD loss of the proximal femur among these 3 commonly used uncemented stems.

Computer-Assisted Rotational Acetabular Osteotomy for Patients with Acetabular Dysplasia.

Rotational acetabular osteotomy (RAO) is a well-established surgical procedure for patients with acetabular dysplasia, and excellent long-term results have been reported. However, RAO is technically demanding and precise execution of this procedure requires experience with this surgery. The usefulness of computer navigation in RAO includes its ability to perform three-dimensional (3D) preoperative planning, enable safe osteotomy even with a poor visual field, reduce exposure to radiation from intraoperative fluoroscopy, and display the tip position of the chisel in real time, which is educationally useful as it allows staff other than the operator to follow the progress of the surgery. In our results comparing 23 hips that underwent RAO with navigation and 23 hips operated on without navigation, no significant difference in radiological assessment was observed. However, no perioperative complications were observed in the navigation group whereas one case of transient femoral nerve palsy was observed in non-navigation group. A more accurate and safer RAO can be performed using 3D preoperative planning and intraoperative assistance with a computed tomography-based navigation system.

The current status and future prospects of computer-assisted hip surgery.

The advances in computer assistance technology have allowed detailed three-dimensional preoperative planning and simulation of preoperative plans. The use of a navigation system as an intraoperative assistance tool allows more accurate execution of the preoperative plan, compared to manual operation without assistance of the navigation system. In total hip arthroplasty using CT-based navigation, three-dimensional preoperative planning with computer software allows the surgeon to determine the optimal angle of implant placement at which implant impingement is unlikely to occur in the range of hip joint motion necessary for daily activities of living, and to determine the amount of three-dimensional correction for leg length and offset. With the use of computer navigation for intraoperative assistance, the preoperative plan can be precisely executed. In hip osteotomy using CT-based navigation, the navigation allows three-dimensional preoperative planning, intraoperative confirmation of osteotomy sites, safe performance of osteotomy even under poor visual conditions, and a reduction in exposure doses from intraoperative fluoroscopy. Positions of the tips of chisels can be displayed on the computer monitor during surgery in real time, and staff other than the operator can also be aware of the progress of surgery. Thus, computer navigation also has an educational value. On the other hand, its limitations include the need for placement of trackers, increased radiation exposure from preoperative CT scans, and prolonged operative time. Moreover, because the position of a bone fragment cannot be traced after osteotomy, methods to find its precise position after its movement need to be developed. Despite the need to develop methods for the postoperative evaluation of accuracy for osteotomy, further application and development of these systems are expected in the future.

Evaluation of local bone turnover in painful hip by 18F-fluoride positron emission tomography.

OBJECTIVE: The diagnosis of painful hip without remarkable radiographic findings is still challenging. In recent years, femoroacetabular impingement (FAI) has been recognized as an important cause of painful hip. The hypothesis of this study was that local bone turnover may be accelerated in painful hip, especially in FAI lesions. To test this, patients with unilateral symptomatic hip underwent F-fluoride PET, which directly correlates with osteoblast activity and therefore bone turnover. PATIENTS AND METHODS: In total, 27 patients with unilateral symptomatic painful hip were enrolled. The diagnosis included 15 cam-type FAI cases, six labral tear cases, and six early-stage osteoarthritis cases. The region of interest for cam and pincer lesions was identified and the maximum standardized uptake value (SUVmax) in these regions and the contralateral asymptomatic regions were measured by F-fluoride PET. The SUVmax ratio was defined as symptomatic side SUVmax/asymptomatic side SUVmax. The α angle and center-edge angle were measured by plain radiograph. RESULTS: The SUVmax of both cam and pincer lesions were significantly higher than the SUVmax of the contralateral regions (P<0.0001). The cam SUVmax ratio correlated positively with the α angle (r=0.5, P=0.007). Patients with an α angle of more than or equal to 60° had a significantly higher cam SUVmax ratio than the less than 60° group (P=0.017). CONCLUSION: This study showed the accelerated local bone turnover in painful hip, partly in FAI cases. Accelerated bone turnover may play a significant role in FAI pathophysiology; therefore, its recognition by imaging modality may contribute toward a more sensitive diagnosis in painful hip.

Teriparatide Versus Alendronate for the Preservation of Bone Mineral Density After Total Hip Arthroplasty - A randomized Controlled Trial.

In this study, the effect of teriparatide for the prevention of bone mineral density (BMD) loss after THA was compared with alendronate in a randomized controlled trial. Forty-eight patients were assigned to three groups, namely, the teriparatide, alendronate, and no medication groups. Dual-energy x-ray absorptiometry (DEXA) was performed at 1 week post-surgery as a baseline reference, followed by subsequent measurements at 12, 24, and 48 weeks postoperatively. For periprosthetic BMD loss, a significant effect of teriparatide was demonstrated, though its effect was similar to alendronate. On the other hand, higher lumbar BMD was observed in the teriparatide group than in the alendronate group at 48 weeks post-surgery. Teriparatide administration may be one reasonable option for osteoporotic patient to preserve the periprosthetic BMD after THA.

Influence of Pelvic Tilt on Polyethylene Wear after Total Hip Arthroplasty.

We aimed to evaluate the effects of pelvic tilt on polyethylene wear after total hip arthroplasty (THA). A total of 105 joints treated with primary THA were included; conventional polyethylene (CPE) liners were used in 43 hips and highly cross-linked polyethylene (HXLPE) liners were used in the remaining 62 hips. The pelvis was tilted 6° posteriorly in the standing position as compared to the supine position, which resulted in significant increases of 1.7° and 2.8° in cup inclination in the CPE and HXLPE groups, respectively. Moreover, the change in pelvic tilt resulted in significant increases of 3.6° and 4.9° in cup anteversion in the CPE and HXLPE groups, respectively. For the CPE group, multiple regression analysis showed a significant association between the angle of pelvic tilt (PTA) and cup inclination and the polyethylene wear ratio. The adjusted R (2) of the regression model was larger for measures obtained in the standing position as compared to the supine position. For the HXLPE group, there was no significant relationship between radiographic parameters and polyethylene wear. Close observation of polyethylene wear is recommended for patients with severe posterior pelvic tilt who have undergone THA with conventional polyethylene.