Wataru Ando

The long-term course of periprosthetic bone mineral density (BMD) after cementless total hip arthroplasty (THA) and BMD changes during late osteoporosis treatment remain unclear. Fifty-eight hips in 44 patients underwent dual-energy X-ray absorptiometry (DXA) > 15 years after cementless THA using a proximally coated tapered stem. Longitudinal changes were assessed in 18 hips (12 patients) with serial DXA obtained within three months, at one year, and at a mean of 17.2 years postoperatively. For therapeutic analysis, ten hips (7 patients) with osteoporosis received zoledronic acid annually, together with daily eldecalcitol and calcium, for two years with serial DXA before treatment and during follow-up. At a mean of 17.2 years, lumbar spine BMD declined to 74.9% of baseline (P < 0.001 vs 1 year). Zones 3-5 showed similar reductions (all P > 0.05, vs lumbar spine). In contrast, proximal zones 1, 2, 6, and 7 showed significantly greater reductions (60.0%, 61.8%, 54.0%, and 30.8%, respectively; all P < 0.001 vs lumbar spine), with zone 7 demonstrating the greatest decrease. During osteoporosis treatment, lumbar spine BMD increased to 107.8% of pretreatment values at two years (P = 0.004). No statistically significant change in periprosthetic BMD was detected, although only zone 5 showed a significant increase (P = 0.014). Proximal periprosthetic bone loss was evident beyond 15 years after cementless THA, with the greatest reduction in Zone 7. Late osteoporosis treatment was associated with no significant further decline in periprosthetic BMD but did not reverse severe proximal bone loss.

Introduction: SONIALVISION G4 is a fluoroscopic imaging system equipped with a bone densitometry function calibrated against GE Healthcare dual-energy X-ray absorptiometry (DXA) measurements. However, evidence supporting the validity of in vivo bone mineral density (BMD) measurements remains limited. This study compared BMD measurements obtained using SONIALVISION G4 with GE DXA reference data and evaluated their validity using quantitative computed tomography (CT). Materials and Methods: A total of 887 BMD examinations performed with SONIALVISION G4 in women aged ≥45 years were compared with published Japanese reference data obtained using GE DXA. CT-derived BMD was quantified using a validated deep learning–based method and compared with measurements obtained using SONIALVISION G4 in 30 patients. To validate the CT method against GE DXA, 697 patients from four additional institutions underwent GE DXA and CT. Analyses were conducted for both the femoral neck and total hip. Results: Femoral neck BMD generally showed small differences from the reference values, whereas total hip BMD was consistently higher in women aged ≥55 years. CT-derived BMD correlated with SONIALVISION G4 measurements (r = 0.762 and 0.842 for the femoral neck and total hip, respectively), with median absolute differences of 0.022 and 0.133 g/cm ² . In contrast, CT-derived BMD showed very strong correlations with GE DXA (r = 0.913 and 0.959) and smaller absolute differences (0.043 and 0.033 g/cm ² ). Conclusion: SONIALVISION G4 showed small differences in femoral neck BMD measurements compared with CT-derived measurements but may systematically overestimate total hip BMD. Further validation studies are warranted.

Purpose: To review Japan’s major contributions to hip joint preservation and reconstruction, spanning joint-preservingosteotomy, biomaterials innovation, and computer-assisted precision arthroplasty. Methods: A narrative review was performed to summarize landmark clinical and scientific advances originating from Japan in the management of osteonecrosis of the femoral head (ONFH), developmental dysplasia of the hip (DDH), total hiparthroplasty (THA), bearing surface technology, and computer-assisted surgery. Results: Japanese research has advanced the understanding and treatment of ONFH through nationwide epidemiological studies, development of classification systems, clarification of steroid-associated pathophysiology, and long-term validation of joint-preserving procedures, particularly transtrochanteric rotational osteotomy. In DDH, Japanese surgeons refined reconstructive osteotomies and established surgical strategies for complex primary and high-dislocation THA. Early clinical adoption of highly cross-linked polyethylene and advances in ceramic bearing technology improved implant longevity by reducing wear and osteolysis. Japan also pioneered CT-based navigation for both acetabular and femoral component placement and introduced the functional pelvic plane concept, shifting implant alignment from fixed safe zones toward individualized functional positioning that incorporates stem anteversion and spinopelvic dynamics. These innovations have subsequently expanded to robotic-assisted surgery and advanced three-dimensional reconstruction. Conclusion: Japan has made substantial contributions to modern hip surgery, from biological joint preservation to precision arthroplasty. This integrated approach—emphasizing anatomical accuracy, biomechanical restoration, and long-term durability—continues to influence contemporary practice and provides a foundation for future advances in robotics, artificial intelligence, and personalized hip reconstruction.

Introduction: Dual mobility cups (DMCs) were developed to enhance stability and reduce dislocation after total hip arthroplasty (THA). The uncemented monoblock M2a-Magnum cup combined with the Active Articulation E1 DMC (Zimmer Biomet) accommodates a femoral head 6 mm smaller than the cup diameter, theoretically improving dislocation resistance. This study evaluated the mid-term outcomes of this construct in primary THA. Methods: Between June 2014 and April 2020, 210 hips in 188 patients underwent primary THA using this implant across two institutions. Of these, 168 hips (148 patients; follow-up rate: 78%) were reviewed ≥5 years postoperatively (mean 7.2 years, range 5.0–10.4). The mean age was 68.7 years (33–90), with 61 men and 96 women; the mean BMI was 23.5 ± 3.5 kg/m ² . Diagnoses included osteoarthritis (120), osteonecrosis of the femoral head (29), traumatic osteonecrosis (6), rapidly destructive coxopathy (5), rheumatoid arthritis (4), and fractures (13). Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) hip score. Kaplan-Meier survival analysis was performed with dislocation as the endpoint. Radiographic evaluation included cup orientation and radiolucent lines (RLLs). Dislocation cases were further examined with range-of-motion (ROM) simulation using Zed Hip software. Results: The mean JOA score improved from 54.6 preoperatively to 88.9 at final follow-up. No implant loosening or significant RLLs were detected, although 11.9% of cups were oriented outside the Lewinnek safe zone. Complications included one intraprosthetic dislocation at 4.5 years requiring revision and one dislocation at 2.7 years, successfully managed with closed reductions, though a 7 mm offset discrepancy was noted. ROM simulation demonstrated implant-to-implant and bone-to-bone impingement, respectively. Dislocation-free rate was 98.8% at final follow-up. Conclusion: The M2a-Magnum with Active Articulation DMC demonstrated excellent mid-term outcomes and a low dislocation rate. However, malpositioning contributed to instability, emphasizing the importance of precise implant positioning to maximize the stability benefits of DMCs. Key words: dual mobility cups (DMCs), total hip arthroplasty (THA), dislocation, implant positioning

Purpose The cumulative probability of a first-time dislocation (CPD) after total hip arthroplasties (THAs) with a 22-mm head was reported in 2004 to rise steadily to 7% at 25 years. Later reports employing larger heads indicated that dislocations were concentrated in shorter periods after THA. Therefore, dislocations may occur differently over time depending on head sizes, which has not been clearly demonstrated. The purpose was to examine this hypothesis. Methods With first-time dislocation as the endpoint, the Cox proportional-hazards regression model and the Kaplan–Meier analyses were applied to 6,339 THAs performed for nontraumatic osteonecrosis of the femoral head, considering all possible influencing variables. Follow-up was 6.5 years on average (range, 0 to 27). Results First-time dislocations occurred in 289 THAs (4.6%) at a mean of 2.9 years (range, 0 to 19) following THA, with head sizes of 22, 26, 28, 32, and ≧ 36 mm in 33, 76, 86, 58, and 36 THAs, respectively (dislocation rate: 13.5, 8.2, 5.7, 2.5, and 2.7%, respectively; p < 0.001 in χ2 test). CPD increased linearly after THA in the 22-mm group, while larger-head groups showed a steep early rise followed by a decline. Conclusion First-time dislocations occurred differently over time with different head sizes.

Objectives: Alcohol consumption is a recognized risk factor for osteonecrosis of the femoral head (ONFH), as well as hypertension, and malignant tumors. Aldehyde dehydrogenase 2 (ALDH2) activity influences alcohol-associated risks by modulating acetaldehyde metabolism; however, its role in ONFH remains unclear. This study aimed to investigate whether the alcohol flushing response, a proxy for ALDH2, modifies the relationship between alcohol consumption and ONFH. Methods: A hospital-based case–control study was conducted on newly diagnosed patients with ONFH and controls recruited. Information on alcohol flushing responses was collected using a self-administered questionnaire and categorized into current/former flushers (inactive ALDH2) and never flushers (active ALDH2). Odds ratios (OR) and their 95% confidence intervals (CI) of various levels of alcohol consumption (habitual drinking, heavy drinking, and drinking of ≥320 g/week) were assessed for ONFH using a logistic regression model. Stratified analysis and multiplicative interaction were used to investigate the effect modification by the alcohol flushing response on the association between alcohol consumption and ONFH. Results: A total of 118 cases with ONFH and 213 controls were included (mean age, 45 years; 197 men and 134 women). The adjusted ORs of alcohol consumption for the development of ONFH were 1.5 (95% CI: 0.4–6.0) and 3.7 (0.3–41.3) for habitual drinking, 1.6 (0.4–5.6) and 2.0 (0.1–24.2) for heavy drinking, and 3.8 (0.8–17.6) and 4.5 (0.4–49.2) for drinking of ≥320 g/week among current/former and never flushers, respectively. No significant multiplicative interactions were observed. Conclusions: Alcohol flushing response may not modify the relationship between alcohol consumption and the risk of ONFH.

A nationwide multicenter follow-up cohort study of hip-replacement arthroplasties performed for nontraumatic osteonecrosis of the femoral head (ONFH) was conducted to clarify factors associated with need for reoperation. We analyzed 7393 arthroplasties including 6284 total hip arthroplasties (THAs), 886 bipolar hemiarthroplasties (BPs), 188 total resurfacing arthroplasties, and 35 hemi-resurfacing arthroplasties (hRSs). The identified risk factors were combined systemic steroid use and excessive alcohol consumption (both ONFH-associated factors), a lateral approach, alumina BPs (aBPs), and hRSs, which were reported previously. The present study performed further analyses separately for THAs and BPs to clarify risk factors in each surgical group. A Cox proportional-hazard model identified the following risk factors: the acetabular-articulating materials of conventional polyethylene (cPE) and metal in the THAs and both ONFH-associated factors, minimum-incision surgery (MIS), and aBPs in the BPs. The risk factors were specific to each surgical group. In the ONFH patients, when performing THA, cPE and metal are not recommended as the acetabular-articulating material. When performing BP, patients with both ONFH-associated factors should be treated carefully, and the employment of MIS and use of aBP are not good strategies.