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Hara Daisuke Last modified date:2024.06.03

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Department of Orthopaedic Surgery, Faculty of Medical Sciences, Kyushu University .
Academic Degree
M.D., Ph.D.
Country of degree conferring institution (Overseas)
Field of Specialization
Orthopaedic Surgery, Hip Surgery, Rheumatoid Arthritis
ORCID(Open Researcher and Contributor ID)
Research Interests
  • 3D kinematic analysis of normal hip, hip osteoarthritis, and replaced hip
    keyword: normal hip, hip osteoarthritis, total hip arthroplasty, 3D kinematic analysis

    Biomaterials for total hip arthroplasty
    keyword: polyethylene, electron beam-melting technique, bone ingrowth

    Sports activities after total hip arthroplasty and periacetabular osteotomy
    keyword: total hip arthroplasty, periacetabular osteotomy, sports activities

    Dynamic hip kinematics before and after periacetabular osteotomy in patients with dysplasia
    keyword : periacetabular osteotomy, kinematics

    Physical behaviour after total joint arthroplasties and osteotomies
    keyword : total joint arthroplasties, osteotomies, physical behaviour
    keyword : Hip joint, Total hip arthroplasty, kinematics, image-matching, sports
Academic Activities
1. Satoru Harada, Satoshi Hamai, Kyohei Shiomoto, Daisuke Hara, Goro Motomura, Satoshi Ikemura, Masanori Fujii, Yasuharu Nakashima, Wear analysis of the first-generation cross-linked polyethylene at minimum 10 years follow-up after THA: no significant effect of sports participation., Journal of artificial organs : the official journal of the Japanese Society for Artificial Organs, 10.1007/s10047-021-01297-x, 25, 2, 140-147, 2021.10, The impact of sports on long-term wear of highly cross-linked polyethylene (XLPE) after total hip arthroplasty (THA) is not fully understood. We investigated (1) the wear performance of the first-generation XLPE, and (2) whether sports participation influences the steady wear rate of XLPE. The femoral head penetration into the cup was measured digitally on radiographs of hips undergoing THA with XLPE. We retrospectively reviewed data that included age, gender, body mass index, follow-up period, preoperative diagnosis, types of XLPE, ball diameter, head material, inclination of the cup, physical function score, and sports participation. Statistical analyses were applied to determine whether sports affect the wear of XLPE and which factors were associated with the steady wear rate. Creep and steady wear rate were found to be 0.18 mm and 0.005 mm/year, respectively. Sports participation, regardless of impact, provided no significant difference in the steady wear rate. Multiple regression analysis demonstrated that sports did not increase the steady wear rate. Our findings showed excellent wear performance of the first-generation XLPE at a minimum of ten years after THA, without significant effect of sports participation on the liner wear..
2. Satoru Harada, Satoshi Hamai, Kyohei Shiomoto, Daisuke Hara, Masanori Fujii, Satoshi Ikemura, Goro Motomura, Yasuharu Nakashima, Patient-reported outcomes after primary or revision total hip arthroplasty: A propensity score-matched Asian cohort study, PLOS ONE, 10.1371/journal.pone.0252112, 16, 5, e0252112-e0252112, 2021.05,
Few studies have compared patient-reported outcome measures (PROMs) between primary and revision total hip arthroplasty (THA). We investigated and compared PROMs between propensity score-matched primary and revision THA in an Asian cohort.

The Oxford Hip Score (OHS) and University of California-Los Angeles (UCLA) activity score, satisfaction score, and Short Form-12 Health Survey (SF-12) were compared between 110 primary and 110 revision THAs after propensity score matching. Multivariate analyses were performed to determine which factors, including patients’ demographics, indication for revision, and pre-operative PROMs, were associated with post-operative PROMs in the revision THA cohort.

The revision THA cohort demonstrated significantly lower post-operative OHS, UCLA activity score, and satisfaction score (10% decrease on average) than those in the primary THA cohort (P .05). The difference in SF-12 mental component summary measure (MCS) between the two cohorts was statistically insignificant (P = .24). In multivariate analysis for the revision THA cohort, lower post-operative UCLA activity score was significantly associated with higher BMI and lower pre-operative UCLA activity score (P

Revision THA was associated with a modest but significant decrease in physical PROMs as compared with primary THA. Pre-operative UCLA activity score significantly affected the post-operative physical outcome measures in the revision THA cohort. However, post-operative SF-12 MCS was comparable between the primary and revision THA cohorts.

3. Daisuke Hara, Satoshi Hamai, Kyle R Miller, Goro Motomura, Kensei Yoshimoto, Keisuke Komiyama, Kyohei Shiomoto, Satoshi Ikemura, Yasuharu Nakashima, Scott A Banks, How does transtrochanteric anterior rotational osteotomy change the dynamic three-dimensional intact ratio in hips with osteonecrosis of the femoral head?, Clinical biomechanics (Bristol, Avon), 10.1016/j.clinbiomech.2021.105284, 82, 105284-105284, 2021.02, BACKGROUND: The intact ratio (the ratio of the intact area of the femoral head) on a two-dimensional anteroposterior radiograph is associated with the prognosis of hips with osteonecrosis of the femoral head after transtrochanteric anterior rotational osteotomy. However, changes of the three-dimensional intact ratio during dynamic weight-bearing activity and correlation of the three-dimensional intact ratio with clinical scores are still unknown. METHODS: Kinematics of eight hips with osteonecrosis of the femoral head that underwent anterior rotational osteotomy were analyzed using image-matching techniques during chair-rising and squatting preoperatively and postoperatively. Two types of dynamic three-dimensional intact ratios were examined, including the lunate covered area (IRLC) and in vivo peak contact force vector intersected area (IRFV). The static three-dimensional intact ratio in each octant of the femoral head was also examined. FINDINGS: The mean Harris hip score significantly improved from 67 preoperatively to 90 postoperatively. During chair-rising rising/squatting, the mean IRLC and IRFV significantly increased from 42%/41% and 7%/4% preoperatively, to 66%/65% and 79%/77% postoperatively, respectively. IRLC significantly changed during the motion whereas substantial postoperative IRFV was maintained throughout the motion. Additionally, Harris hip score and the static three-dimensional intact ratio in the superolateral regions had significant positive correlations with both IRLC and IRFV. INTERPRETATION: Hip kinematics affected IRLC but not IRFV, which suggests that substantial intact bone occupies the region in which peak contact forces are applied during deep hip flexion. Additionally, improving intact ratio in the superolateral region led to improvements in both IRLC and IRFV with favorable clinical scores..
4. Kyohei Shiomoto, Satoshi Hamai, Daisuke Hara, Hidehiko Higaki, Hirotaka Gondo, Yifeng Wang, Satoru Ikebe, Kensei Yoshimoto, Keisuke Komiyama, Satoru Harada, Yasuharu Nakashima, In vivo kinematics, component alignment and hardware variables influence on the liner-to-neck clearance during chair-rising after total hip arthroplasty., Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 10.1016/j.jos.2019.05.012, 25, 3, 452-459, 2020.05, BACKGROUND: There is an interest in quantifying dynamic hip kinematics before and after total hip arthroplasty (THA) during chair-rising: one of daily life activities. METHODS: The study consisted of 21 patients who underwent unilateral total hip arthroplasty for symptomatic osteoarthritis. We obtained continuous radiographs using a flat-panel X-ray detector while the participants rose from chair. We assessed the pre and postoperative hip joint's movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also measured minimum liner-to-neck distances at maximum hip flexion and extension as anterior and posterior liner-to-neck distances, respectively. Multivariate analyses were applied to determine which factors were associated with liner-to-neck distances. RESULTS: The cup inclination, cup anteversion, and stem anteversion averaged 37.4°, 23.1°, and 30.1°, respectively. Significantly larger maximum hip flexion angle (72°) was found during chair-rising after THA compared to that before THA (63°, P 
5. Kensei Yoshimoto, Satoshi Hamai, Hidehiko Higaki, Hirotaka Gondoh, Kyohei Shiomoto, Satoru Ikebe, Daisuke Hara, Keisuke Komiyama, Yasuharu Nakashima, Dynamic hip kinematics before and after periacetabular osteotomy in patients with dysplasia., Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 10.1016/j.jos.2019.03.019, 25, 2, 247-254, 2020.03, BACKGROUND: We prospectively analyzed the hip kinematics in patients with developmental dysplasia of the hip (DDH) before and after periacetabular osteotomy (PAO) and in healthy subjects while squatting to determine the influence of coverage of the femoral head on hip kinematics. METHODS: 14 hips in 14 patients with DDH and 10 hips in 10 volunteers were included. Continuous radiographs while squatting and computed tomography images were obtained to assess the in vivo kinematics of the hip and the rim-neck distance using density-based 3D-to-2D model-to-image registration techniques. RESULTS: The maximum hip flexion angles were 100.4° and 94.9° before and after PAO (p = 0.0863), respectively. The maximum hip flexion angles after PAO did not significantly differ from those of normal hips (102.2°; p = 0.2552). The hip abduction angles at maximum hip flexion were 31.7° and 26.2° before and after PAO (p = 0.1256), respectively. The rim-neck distance decreased from averaged 12.2 mm-8.9 mm (p = 0.0044) after PAO. The lateral center edge angle (LCEA) and anterior center edge angle (ACEA) significantly improved 14.7°-42.4° and 50.4°-54.0° after PAO (p 
6. Masato Kiyohara, Satoshi Hamai, Daisuke Hara, Daisuke Fujiyoshi, Satoru Harada, Kenichi Kawaguchi, Yasuharu Nakashima, Do component position and muscle strength affect the cup-head translation during gait after total hip arthroplasty?, European journal of orthopaedic surgery & traumatology : orthopedie traumatologie, 10.1007/s00590-019-02443-1, 29, 6, 1263-1269, 2019.08, INTRODUCTION: This study examined whether the component position or muscle strength affects the cup-head translation under in vivo weight-bearing conditions after total hip arthroplasty (THA). We hypothesized that there was a correlation between the hip offset or abductor strength and cup-head translation during gait. MATERIALS AND METHODS: We prospectively evaluated 31 patients undergoing unilateral cementless primary THA. The cup height, cup/stem offset, and limb length discrepancy were measured on anterior-posterior bilateral hip radiographic images. The isometric muscle strength of the lower limbs was quantified using a handheld dynamometer. Continuous radiographic images were recorded during gait, and cup-head translation was analysed using a computer-assisted method. RESULTS: The average cup height, cup/stem offset, and limb length discrepancy were - 3.8 ± 5.1 mm, 1.2 ± 5.2 mm/- 0.7 ± 7.7 mm, and - 2.1 ± 5.2 mm, respectively. The average hip abductor/flexor and knee extensor strength were 86% ± 18%/85% ± 17% and 88% ± 17% of the contralateral healthy hip, respectively. The average cup-head translation during swing phase of gait was - 0.003 ± 0.31 mm. Multiple regression analyses found no significant independent predictors of cup-head translation (p > 0.05). CONCLUSIONS: The component position or muscle strength did not significantly influence cup-head translation during gait after well-positioned primary THA..
7. Keisuke Komiyama, Satoshi Hamai, Satoru Ikebe, Kensei Yoshimoto, Hidehiko Higaki, Kyohei Shiomoto, Hirotaka Gondo, Daisuke Hara, Yifeng Wang, Yasuharu Nakashima, In vivo kinematic analysis of replaced hip during stationary cycling and computer simulation of optimal cup positioning against prosthetic impingement., Clinical biomechanics (Bristol, Avon), 10.1016/j.clinbiomech.2019.05.035, 68, 175-181, 2019.08, BACKGROUND: Dynamic hip kinematics during stationary cycling after total hip arthroplasty (THA) have been unclear. Furthermore, no computer simulation of optimal cup position based on in vivo kinematics has yet been assessed. METHODS: This study consisted of 7 patients who underwent unilateral primary THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, continuous radiographs were obtained during stationary cycling. We analyzed the three-dimensional replaced hip kinematics from the top to the bottom position of the crank using image-matching techniques and quantified minimum liner-to-stem neck distance. Simulation analyses with in vivo kinematics were performed to examine patient-specific optimal cup placement against prosthetic impingement. FINDINGS: During stationary cycling, pelvis showed 27.1° of posterior tilt on average without significant change. Hip flexed by 59.4° and 19.3° on average at the top and bottom positions, respectively. Minimum liner-to-neck distance was 8.8 mm on average at the bottom position. Liner-to-neck, bone-to-bone, or bone-to-component impingement was not observed at any positions in any hips. Simulation analysis of cup placement showed that larger cup anteversion, inclination, and use of elevated liner significantly decreased the minimum distance between posterior liner and stem neck. Cup anteversion of more than 30° with elevated liner could cause posterior liner-to-neck impingement at bottom position. INTERPRETATION: Stationary cycling after THA provides no excessive hip range of motion or liner-to-neck contact. Cup placement and use of elevated liner significantly influence the minimum liner-to-neck distance, in some cases simulating posterior prosthetic impingement..
8. Keisuke Komiyama, Satoshi Hamai, Daisuke Hara, Satoru Ikebe, Yifeng Wang, Hirotaka Gondo, Hidehiko Higaki, Yasuharu Nakashima, Dynamic hip kinematics during recreational classical ballet and hula dance after total hip arthroplasty: two case reports., Journal of medical case reports, 10.1186/s13256-018-1942-2, 13, 1, 11-11, 2019.01, BACKGROUND: The in vivo assessment of the three-dimensional kinematics of the hip during dance activities in patients after total hip arthroplasty has not been previously reported. We evaluated the replaced hip kinematics during recreational classical ballet and hula dance using radiographic-based image-matching techniques. CASE PRESENTATION: A 58-year-old Japanese woman (patient 1; height, 157 cm; weight, 74.5 kg) and a 73-year-old Japanese woman (patient 2; height, 153 cm; weight, 48 kg) were still doing classical ballet and hula dance, respectively, after primary total hip arthroplasty. For ballet, there were gradual three-dimensional hip movements with 48° flexion, 36° abduction, and 49° external rotation in développé and 34° flexion, 29° abduction, and 43° external rotation in plié. For hula, there were small three-dimensional hip movements with 31° flexion, 15° adduction, and 11° external rotation in kao and 17° flexion, 11° adduction, and 11° external rotation in kaholo. No liner-to-neck contact was found in any dance activities. CONCLUSION: Both classical ballet and hula dance produced complex ranges of hip movements and activity-dependent kinematics. These kinematic data could be useful for recommending each patient with total hip arthroplasty to continue recreational dance activities..
9. Satoshi Hamai, Yusuke Kohno, Daisuke Hara, Kyohei Shiomoto, Mio Akiyama, Jun-Ichi Fukushi, Goro Motomura, Satoshi Ikemura, Masanori Fujii, Yasuharu Nakashima, Minimum 10-Year Clinical Outcomes After Periacetabular Osteotomy for Advanced Osteoarthritis Due to Hip Dysplasia., Orthopedics, 10.3928/01477447-20180806-04, 41, 5, 300-305, 2018.09, The purpose of this study was to examine the minimum 10-year clinical outcomes, including patient-reported and functional outcomes, of periacetabular osteotomy in patients with advanced osteoarthritis. A total of 46 hips in 44 patients with advanced osteoarthritis who underwent periacetabular osteotomy between 1992 and 2006 were retrospectively reviewed. Mean age at surgery was 47.5 years, and mean follow-up was 16.9±4.7 years. Survivorship was determined using the Kaplan-Meier method, and the associated risk factors for the endpoint-conversion to total hip arthroplasty less than 15 years after surgery-were evaluated. The Oxford Hip Score and the University of California, Los Angeles activity score were evaluated at final follow-up. The survival rates at 15 and 20 years after surgery were 80% and 59%, respectively. Multivariate analysis indicated that body mass index greater than 24 kg/m2 (P=.034; odds ratio, 1.72) was significantly associated with the endpoint as an independent risk factor. For 32 hips of 31 patients with preserved native joints at final follow-up, the Oxford Hip Score and the University of California, Los Angeles score averaged 41±5 and 5.2±1.8, respectively, equivalent (P=.28 and P=.215, respectively) to the scores of 14 hips of 13 patients with conversion to total hip arthroplasty (38±8.7 and 5.8±1.4, respectively). The results of this mid-term study may be useful for surgical decision-making among patients with advanced osteoarthritis who want to preserve native hip joints. [Orthopedics. 2018; 41(5):300-305.]..
10. Keisuke Komiyama, Satoshi Hamai, Daisuke Hara, Satoru Ikebe, Hidehiko Higaki, Kensei Yoshimoto, Kyohei Shiomoto, Hirotaka Gondo, Yifeng Wang, Yasuharu Nakashima, Dynamic hip kinematics during squatting before and after total hip arthroplasty., Journal of orthopaedic surgery and research, 10.1186/s13018-018-0873-3, 13, 1, 162-162, 2018.07, BACKGROUND: The difference in in vivo kinematics before and after total hip arthroplasty (THA) for the same subjects and the clearance between the liner and neck during squatting have been unclear. The purpose of the present study was to clarify (1) the changes in the in vivo kinematics between prosthetic hips and osteoarthritis hips of the same subjects and (2) the extent of the liner-to-neck clearance during squatting under weight-bearing conditions. METHODS: This study consisted of 10 patients who underwent unilateral THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, we obtained continuous radiographs during squatting. We analyzed the hip joint's movements using three-dimensional-to-two-dimensional model-to-image registration techniques. We also quantified the minimum distance at maximum flexion and extension, and the minimum angle at maximum flexion between the liner and stem neck. RESULTS: The maximum hip flexion angles post-THA (80.7° [range, 69.4-98.6°]) changed significantly compared with the pre-THA values (71.7° [range, 55.2°-91.2°]). The pelvic tilt angle (posterior +, anterior-) at the maximum hip flexion post-THA (10.4° [range, - 6.7° to 26.9°]) was significantly smaller than that at pre-THA (16.6° [range, - 3° to 40.3°]). The minimum anterior and posterior liner-to-neck distances averaged 10.9 and 8.0 mm, respectively, which was a significant difference. The minimum liner-to-neck angle at maximum flexion averaged 34.7° (range, 20.7°-46.3°). No liner-to-neck contact occurred in any of the hips. CONCLUSION: THA increased the range of hip joint motion and the pelvis tilted anteriorly more after than before THA, with sufficient liner-to-neck clearance during squatting. These data may be beneficial for advising patients after THA regarding postoperative activity restrictions in daily life..
11. Kensei Yoshimoto, Yasuharu Nakashima, Miyo Wakiyama, Daisuke Hara, Akihiro Nakamura, Mikio Iwamoto, Initial stability of a highly porous titanium cup in an acetabular bone defect model., Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 10.1016/j.jos.2018.03.007, 23, 4, 665-670, 2018.07, BACKGROUNDS: The purpose of this study was to quantify the initial stability of a highly porous titanium cup using an acetabular bone defect model. METHODS: The maximum torque of a highly porous titanium cup, with a pore size of 640 μm and porosity of 60%, was measured using rotational and lever-out torque testing and compared to that of a titanium-sprayed cup. The bone models were prepared using a polyurethane foam block and had three levels of bone coverage: 100, 70, and 50%. RESULTS: The highly porous titanium cup demonstrated significantly higher maximum torque than the titanium-sprayed cups in the three levels of bone defects. On rotational torque testing, it was found to be 1.5, 1.3, and 1.3 times stronger than the titanium-sprayed cups with 100, 70 and 50% bone coverage, respectively. Furthermore, it was found to be 2.2, 2.3, and 1.5 times stronger on lever-out testing than the titanium-sprayed cup. No breakage in the porous layers was noted during the testing. CONCLUSION: This study provides additional evidence of the initial stability of highly porous titanium cup, even in the presence of acetabular bone defects..
12. Daisuke Hara, Satoshi Hamai, Keisuke Komiyama, Goro Motomura, Kyohei Shiomoto, Yasuharu Nakashima, Sports Participation in Patients After Total Hip Arthroplasty vs Periacetabular Osteotomy: A Propensity Score-Matched Asian Cohort Study., The Journal of arthroplasty, 10.1016/j.arth.2017.08.035, 33, 2, 423-430, 2018.02, BACKGROUND: No studies have compared sports participation between total hip arthroplasty (THA) and periacetabular osteotomy (PAO) in matched Asian cohorts. We investigated sports participation and activity levels in Asian THA cohort, and compared them between THA and PAO cohorts. METHODS: Multivariate analyses were applied to determine which factors were associated with postoperative sports participation and University of California-Los Angeles (UCLA) activity score in (1) 524 THA patients and (2) 487 acetabular dysplasia patients (295 THA patients and 192 PAO patients). In addition, postoperative sports participation and UCLA score were compared between 62 THA and 62 PAO patients after adjusting for baseline characteristics with propensity score matching. RESULTS: Sports participation and UCLA score significantly increased after THA (P
13. Daisuke Hara, Satoshi Hamai, Jun-Ichi Fukushi, Ken-Ichi Kawaguchi, Goro Motomura, Satoshi Ikemura, Keisuke Komiyama, Yasuharu Nakashima, Does Participation in Sports Affect Osteoarthritic Progression After Periacetabular Osteotomy?, The American journal of sports medicine, 10.1177/0363546517707942, 45, 11, 2468-2475, 2017.09, BACKGROUND: Periacetabular osteotomy (PAO) is an effective treatment for symptomatic acetabular dysplasia. However, whether postoperative participation in sports leads to progression of the Kellgren-Lawrence (KL) grade of osteoarthritis (OA) in these patients is unclear. PURPOSE: To investigate (1) participation in sports before and after PAO and (2) whether postoperative participation in sports leads to progression of the KL grade. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The authors retrospectively reviewed data on 161 patients (183 hips) who underwent PAO for symptomatic acetabular dysplasia with preoperative KL grade 1 or 2 between 1998 and 2011. The mean age at the time of surgery was 42.0 ± 10.9 years (range, 12-64 years), and the mean follow-up duration was 100 months (range, 13-180 months). Data included participation in sports, the University of California, Los Angeles (UCLA) activity scale score, age at the time of surgery, body mass index, follow-up duration, history of treatment for developmental hip dislocations, Merle d'Aubigné-Postel score, Oxford Hip Score, center-edge angle, and KL grade. Univariate and multivariate analyses were applied to determine which factors were associated with progression to KL grade 3 or 4 after PAO. RESULTS: The number of patients who participated in sports significantly increased from 50 (31.1%) preoperatively to 89 (55.3%) postoperatively. The mean UCLA score significantly increased from 4.7 ± 2.1 preoperatively to 5.5 ± 2.0 postoperatively. The KL grade progressed to grade 3 or 4 in 16 hips, including 4 hips that underwent conversion to total hip arthroplasty. No significant differences were found in postoperative participation in sports (89 hips [53.3%] vs 11 hips [68.8%], respectively; P = .24) and the UCLA score (5.6 ± 2.0 vs 5.1 ± 2.0, respectively; P = .30) between hips with KL grade 1 or 2 and KL grade 3 or 4. A multivariate analysis revealed that no factors, including postoperative participation in sports, were significantly associated with progression to KL grade 3 or 4. CONCLUSION: Postoperative participation in sports after PAO did not significantly and negatively influence progression of the KL grade at midterm follow-up..
14. Yasuharu Nakashima, Masanori Fujii, Yasuo Noguchi, Kenya Suenaga, Takuaki Yamamoto, Jun-Ichi Fukushi, Goro Motomura, Satoshi Hamai, Daisuke Hara, Yukihide Iwamoto, Arthroscopic validation of radiographic minimum joint space width associated with the subchondral bone exposure in symptomatic hip dysplasia., Modern rheumatology, 10.1080/14397595.2016.1222663, 27, 3, 524-528, 2017.05, OBJECTIVE: The purpose of this study was to clarify the minimum joint space width (MJSW) that leads to subchondral bone exposure (SBE) in patients with hip dysplasia. METHODS: We included 82 subjects (86 hips) who had hip dysplasia with center-edge angle less than 20° and who underwent periacetabular osteotomy combined with hip arthroscopy. The acetabular and femoral cartilages were divided into three regions: anterosuperior, superior, and posterosuperior; for each region, we analyzed the correlation between the incidence of SBE and the MJSW measured on plain radiographs. The disease stage was defined according to the Kellgren and Lawrence grades (KL grade). RESULTS: SBE was found in 51 hips (59.3%) in total, involved the acetabulum in 49 hips (57.0%), and involved the femoral head in 26 hips (30.2%). SBE was more frequent in the acetabulum, with the highest incidence in the anterosuperior region, followed by the superior region. SBE was present in six hips (22.2%), 17 hips (56.7%), and 28 hips (96.5%), at KL-1, KL-2, and KL-3, respectively. MJSW of hips with SBE was significantly smaller than those without SBE (2.3 vs 4.0 mm, p 
15. Keisuke Komiyama, Yasuharu Nakashima, Masanobu Hirata, Daisuke Hara, Yusuke Kohno, Yukihide Iwamoto, Does High Hip Center Decrease Range of Motion in Total Hip Arthroplasty? A Computer Simulation Study., The Journal of arthroplasty, 10.1016/j.arth.2016.03.014, 31, 10, 2342-7, 2016.10, BACKGROUND: High placement of a cementless acetabular cup is often required to have sufficient bone coverage in hip dysplasia. We examined whether a high hip center decreases the postoperative range of motion (ROM) in total hip arthroplasty. METHODS: Using a computer software, ROM and bone coverage were examined in 32 patients with unilateral osteoarthritis of the hip with Crowe type II or III hip dysplasia. The cup was placed at the anatomic hip center and moved vertically in 5-mm increments. Vertical center of rotation (V-COR) was defined as the distance from the head center to the interteardrop line. The required ROM was defined as flexion  ≥110°, internal rotation (IR) at 90° flexion ≥30°, extension ≥30°, and external rotation ≥30°. We determined the V-COR to satisfy the required ROM and cup center-edge angle (Cup-CE) ≥0°. RESULTS: Only 40.6% of the patients satisfied Cup-CE ≥0° at the anatomic hip center. Bone coverage increased with the peak at 30, 35 mm of V-COR (90.6% satisfied Cup-CE ≥0°) and decreased at ≥40 mm. Higher V-COR resulted in lower range of flexion and IR, but increased the range of extension and external rotation. The cutoff value from the receiver-operating characteristic curve for both flexion and IR was a V-COR of 35 mm. CONCLUSION: The higher hip center gained more bone coverage but decreased the range of hip flexion and IR. Acceptable V-COR in hip dysplasia was around 35 mm, about 20 mm above the true hip center, in terms of ROM..
16. Yusuke Kohno, Yasuharu Nakashima, Takashi Hatano, Mio Akiyama, Masanori Fujii, Daisuke Hara, Masayuki Kanazawa, Akihisa Haraguchi, Yukihide Iwamoto, High prevalence of cam deformity in dysplastic hips: A three-dimensional CT study., Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 10.1002/jor.23147, 34, 9, 1613-9, 2016.09, Cam deformity could lead to suboptimal articulation by causing secondary femoroacetabular impingement after periacetabular osteotomy; however, the inherent femoral head-neck morphology in dysplastic hips and the effect of an additional osteoarthritic deformity have not been well described. We compared femoral head-neck morphology using three-dimensional imaging of normal and dysplastic hips in pre/early (Tönnis grade 0 and 1) and advanced stage osteoarthritis (Tönnis grade 2). Using computed tomography, we measured the circumferential α-angle and head-neck offset ratio in 68 dysplastic hips and 24 normal hips. Locations of the head-neck junction were represented by the clock position. In the pre/early group, the α-angle was significantly larger at the anterosuperior and inferior aspects (1, 2, and 5-7 o'clock) and head-neck offset ratio was smaller at the anterosuperior aspect (2 o'clock) than in the control group. The α-angle was significantly larger at the anterior aspects (1-4 o'clock) in the advanced group than in the pre/early group. The maximum α-angle was most commonly found at 2 o'clock (60%, 41/68 hips) in dysplastic hips. The prevalence of cam deformity (maximum α-angle >55°) was 4.2% (1/24 hips) in the control group, 22% (11/50 hips) in the pre/early group, and 50% (9/18 hips) in the advanced group. Cam deformity, inherent in the pre/early group, was found with relatively high frequency. The higher prevalence in the advanced group reflected degeneration-modified changes. When performing periacetabular osteotomy, preoperative radiographic assessments should include the femoral head-neck junction to prevent secondary femoroacetabular impingement, especially in patients with advanced stage osteoarthritis. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1613-1619, 2016..
17. Masayuki Kanazawa, Yasuharu Nakashima, Takayuki Arai, Takahiro Ushijima, Masanobu Hirata, Daisuke Hara, Yukihide Iwamoto, Quantification of pelvic tilt and rotation by width/height ratio of obturator foramina on anteroposterior radiographs., Hip international : the journal of clinical and experimental research on hip pathology and therapy, 10.5301/hipint.5000374, 26, 5, 462-467, 2016.09, OBJECTIVE: Compared to sagittal pelvic tilt, only a few studies have examined axial rotation on anteroposterior radiographs. We therefore quantified 3-D pelvic rotation using the width and height ratio of the obturator foramina under the various pelvic tilts. METHODS: Using CT reconstructions of 10 healthy pelvises, anterior pelvic planes (APPs) were rotated by 20° in 5° increments on the axial plane with various degrees of sagittal pelvic tilt. The correlation between the pelvic rotation angle and the width ratio (WR) in the axial plane and the height/width ratio (H/W) in the sagittal plane were examined. RESULTS: Axial pelvic rotation and WR showed a high linear correlation regardless of the sagittal tilt, with the correlation coefficient ranging from 0.93 to 0.98 in males and 0.87 to 0.95 in females. The angle that resulted in a WR of 1:2 was approximately 13° in males and 18° in females. H/W also showed a linear regression with sagittal tilt. Axial rotation was determined by the following equation incorporating pelvic tilts; axial rotation (male:female) = (19.9:24.2) + (2.1:3.6) × Hright/Wright + (0.9:1.5) × Hleft/Wleft - (23.2:25.1) × WR. CONCLUSIONS: Pelvic tilt and rotation could be quantified by the equation using width and height ratios of the obturator foramina on a plain anteroposterior radiograph. Width and height ratios of the obturator foramina proved to be useful parameters in clinical practice for understanding pelvic rotation..
18. Daisuke Hara, Yasuharu Nakashima, Satoshi Hamai, Hidehiko Higaki, Satoru Ikebe, Takeshi Shimoto, Kensei Yoshimoto, Yukihide Iwamoto, Dynamic Hip Kinematics During the Golf Swing After Total Hip Arthroplasty., The American journal of sports medicine, 10.1177/0363546516637179, 44, 7, 1801-9, 2016.07, BACKGROUND: Although most surgeons allow their patients to play golf after total hip arthroplasty (THA), the effect on the implant during the golf swing is still unclear. PURPOSE: To evaluate hip kinematics during the golf swing after THA. STUDY DESIGN: Descriptive laboratory study. METHODS: Eleven hips in 9 patients who underwent primary THA were analyzed. All patients were right-handed recreational golfers, and these 11 hips included 6 right hips and 5 left hips. Periodic radiographic images of the golf swing were taken using a flat-panel x-ray detector. Movements of the hip joint and components were assessed using 3-dimensional-to-2-dimensional model-to-image registration techniques. Liner-to-neck contact and translation of the femoral head with respect to the acetabular cup (cup-head translation) were examined. Hip kinematics, orientation of components, and maximum cup-head translation were compared between patients with and without liner-to-neck contact. RESULTS: On average, the golf swing produced approximately 50° of axial rotation in both lead and trail hips. Liner-to-neck contact was observed in 4 hips with elevated rim liners (2 lead hips and 2 trail hips) at maximum external rotation. Neither bone-to-bone nor bone-to-implant contact was observed at any phases of the golf swing in any of the hips. Four hips with liner-to-neck contact had significantly larger maximum external rotation (37.9° ± 7.0° vs 20.6° ± 9.9°, respectively; P = .01) and more cup anteversion (26.5° ± 6.1° vs 10.8° ± 8.9°, respectively; P = .01) than hips without liner-to-neck contact. No significant differences between hips with and without contact were found for cup inclination (42.0° ± 2.5° vs 38.1° ± 5.5°, respectively; P = .22), combined anteversion (45.3° ± 8.9° vs 51.4° ± 7.9°, respectively; P = .26), or maximum cup-head translation (1.3 ± 0.3 mm vs 1.5 ± 0.4 mm, respectively; P = .61). CONCLUSION: In this analysis, the golf swing did not produce excessive hip rotation or cup-head translation in any hips. However, liner-to-neck contact during the golf swing was observed in 36% of the hips, with unknown effects on the long-term results. CLINICAL RELEVANCE: Golf is an admissible sport after THA because dynamic hip stability was observed. However, the implant position, especially cup anteversion and the use of elevated rim liners, promoted liner-to-neck contact..
19. Koji Murakami, Satoshi Hamai, Ken Okazaki, Satoru Ikebe, Takeshi Shimoto, Daisuke Hara, Hideki Mizu-uchi, Hidehiko Higaki, Yukihide Iwamoto, In vivo kinematics of healthy male knees during squat and golf swing using image-matching techniques., The Knee, 10.1016/j.knee.2015.08.004, 23, 2, 221-6, 2016.03, PURPOSE: Participation in specific activities requires complex ranges of knee movements and activity-dependent kinematics. The purpose of this study was to investigate dynamic knee kinematics during squat and golf swing using image-matching techniques. METHODS: Five healthy males performed squats and golf swings under periodic X-ray images at 10 frames per second. We analyzed the in vivo three-dimensional kinematic parameters of subjects' knees, namely the tibiofemoral flexion angle, anteroposterior (AP) translation, and internal-external rotation, using serial X-ray images and computed tomography-derived, digitally reconstructed radiographs. RESULTS: During squat from 0° to 140° of flexion, the femur moved about 25 mm posteriorly and rotated 19° externally relative to the tibia. Screw-home movement near extension, bicondylar rollback between 20° and 120° of flexion, and medial pivot motion at further flexion were observed. During golf swing, the leading and trailing knees (the left and right knees respectively in the right-handed golfer) showed approximately five millimeters and four millimeters of AP translation with 18° and 26° of axial rotation, respectively. A central pivot motion from set-up to top of the backswing, lateral pivot motion from top to ball impact, and medial pivot motion from impact to the end of follow-through were observed. CONCLUSIONS: The medial pivot motion was not always recognized during both activities, but a large range of axial rotation with bilateral condylar AP translations occurs during golf swing. This finding has important implications regarding the amount of acceptable AP translation and axial rotation at low flexion in replaced knees. LEVEL OF EVIDENCE: IV..
20. Yasuharu Nakashima, Masanobu Ohishi, Ken Okazaki, Jun-Ichi Fukushi, Akiko Oyamada, Daisuke Hara, Toshio Doi, Yukio Akasaki, Hisakata Yamada, Yukihide Iwamoto, Delayed diagnosis of ankylosing spondylitis in a Japanese population., Modern rheumatology, 10.3109/14397595.2015.1088679, 26, 3, 421-5, 2016.03, OBJECTIVES: This study was conducted to evaluate the period from symptom onset to diagnosis of ankylosing spondylitis (AS) in Japanese patients and to examine possible reasons for delayed diagnosis. METHODS: Seventy-two consecutive patients with AS were studied. Diagnostic delay was defined as the gap between the first spondyloarthropathic symptom and diagnosis of AS according to the modified New York criteria. RESULTS: The mean patient ages at disease onset and diagnosis were 25.6 ± 11.3 and 33.3 ± 13.2 years old, respectively, resulting in diagnostic delay of 6.7 years. The number of medical institutions to which patients were referred before diagnosis was 2.4, and orthopedic surgeons were most commonly visited (62%). Non-specific low back pain or lumbar spondylitis (33%) and degenerative arthritis (28%) were the primary diagnoses preceding that of AS. Absence of articular symptoms significantly correlated with diagnostic delay. The patients with disease onset on year 2000 or later had significantly shorter periods until diagnosis than those before 2000 (3.6 vs. 7.5 years). CONCLUSIONS: The present study showed a marked diagnostic delay among Japanese patients with AS. Although it has been improved, continuing medical education focusing on inflammatory back pain in adolescent is required for early diagnosis of AS..
21. Kanazawa, M., Nakashima, Y., Ohishi, M., Hamai, S., Motomura, G., Yamamoto, T., Fukushi, J.-I., Ushijima, T., Hara, D., Iwamoto, Y., Pelvic tilt and movement during total hip arthroplasty in the lateral decubitus position, Modern Rheumatology, 10.3109/14397595.2015.1092914, 26, 3, 435-40, 2016.03, OBJECTIVES: Total hip arthroplasty (THA) is often performed in the lateral decubitus (lateral) position. In this position, the pelvis may have various degrees of tilt leading to implant malposition. We sought to quantify the pelvic tilt in lateral position and further pelvic movement during surgery. METHODS: In 95 cases with primary THA, three-dimensional pelvic tilts were quantified by superimposing images reconstructed from CT data onto antero-posterior radiographs taken in lateral position at set-up and after cup placement. Pelvises were fixed with a device compressing anterior superior iliac spines and sacrum. RESULTS: Various degrees of pelvic tilt occurred compared to the supine position; sagittal: -3.1° (-25.5° to 10.2°), axial: 3.9° (-8.4° to 17°), coronal: 0.9° (-11.9° to 13.2°). Absolute changes more than 5° were observed 43%, 47%, and 12% in the sagittal, axial, and coronal planes, respectively. The more preoperative posterior pelvic tilt resulted in the more change in the sagittal plane. Further pelvic movement of about 3° in three planes were observed ranging from -11° to 20° after cup placement. CONCLUSION: This study showed various pelvic tilt and movement during THA. As pelvic tilt directly alters the cup orientation, its changes should be well understood. Improved tools for positioning and holding the pelvis are required..
22. Daisuke Hara, Yasuharu Nakashima, Taishi Sato, Masanobu Hirata, Masayuki Kanazawa, Yusuke Kohno, Kensei Yoshimoto, Yusuke Yoshihara, Akihiro Nakamura, Yumiko Nakao, Yukihide Iwamoto, Bone bonding strength of diamond-structured porous titanium-alloy implants manufactured using the electron beam-melting technique., Materials science & engineering. C, Materials for biological applications, 10.1016/j.msec.2015.11.025, 59, 1047-1052, 2016.02, The present study examined the bone bonding strength of diamond-structured porous titanium-alloy (Porous-Ti-alloy) manufactured using the electron beam-melting technique in comparison with fiber mesh-coated or rough-surfaced implants. Cylindrical implants with four different pore sizes (500, 640, 800, and 1000μm) of Porous-Ti-alloy, titanium fiber mesh (FM), and surfaces roughened by titanium arc spray (Ti-spray) were implanted into the distal femur of rabbits. Bone bonding strength and histological bone ingrowth were evaluated at 4 and 12weeks after implantation. The bone bonding strength of Porous-Ti-alloy implants (640μm pore size) increased over time from 541.4N at 4weeks to 704.6N at 12weeks and was comparable to that of FM and Ti-spray implants at both weeks. No breakage of the porous structure after mechanical testing was found with Porous-Ti-alloy implants. Histological bone ingrowth that increased with implantation time occurred along the inner structure of Porous-Ti-alloy implants. There was no difference in bone ingrowth in Porous-Ti-alloy implants with pore sizes among 500, 640, and 800μm; however, less bone ingrowth was observed with the 1000μm pore size. These results indicated Porous-Ti-alloy implants with pore size under 800μm provided biologically active and mechanically stable surface for implant fixation to bone, and had potential advantages for weight bearing orthopedic implants such as acetabular cups..
23. Daisuke Hara, Yasuharu Nakashima, Satoshi Hamai, Hidehiko Higaki, Satoru Ikebe, Takeshi Shimoto, Kensei Yoshimoto, Yukihide Iwamoto, Dynamic hip kinematics in patients with hip osteoarthritis during weight-bearing activities., Clinical biomechanics (Bristol, Avon), 10.1016/j.clinbiomech.2015.11.019, 32, 150-6, 2016.02, BACKGROUND: There is an interest in quantifying the hip kinematics of patients with end-stage hip disorders before total hip arthroplasty. The purpose of the present study was to obtain dynamic hip kinematics under four different conditions, including deep flexion and rotation, in patients with osteoarthritis of the hip. METHODS: Continuous X-ray images were obtained in 14 patients during gait, chair-rising, squatting, and twisting, using a flat panel X-ray detector. These patients received computed tomography scan to generate virtual digitally reconstructed radiographs. The density-based digitally reconstructed radiographs were then compared with the serial X-ray images acquired using image correlations. These 3D-to-2D model-to-image registration techniques determined the 3D positions and orientations of the pelvis and femur during the movement cycle of each activity. FINDINGS: For gait, chair-rising, and squatting, the maximum hip flexion angles averaged 22°, 64°, and 68°, respectively. The pelvis was tilted anteriorly by an average of around 7° during the full gait cycle. For chair-rising and squatting, the maximum absolute values of anterior/posterior pelvic tilt averaged 8°/17° and 6°/18°, respectively. Hip flexion showed maximum flexion angle on the way of movement due to further anterior pelvic tilt during both chair-rising and squatting. For twisting, the maximum absolute values of internal/external hip rotation averaged 3°/13°. INTERPRETATION: Patients with hip osteoarthritis prior to total hip arthroplasty demonstrated the limited ranges of coordinated motion of the pelvis, femur, and hip joint during each activity, especially in deeply flexed and rotated postures..
24. Yoshimoto, K., Nakashima, Y., Nakamura, A., Mawatari, T., Todo, M., Hara, D., Iwamoto, Y., Neck fracture of femoral stems with a sharp slot at the neck: biomechanical analysis, Journal of Orthopaedic Science, 10.1007/s00776-015-0745-1, 20, 5, 881-7, 2015.05, BACKGROUND: Fracture of the femoral stem in total hip arthroplasty (THA) is a rare complication. We have encountered 2 cases of neck fractures of the femoral stem occurring 9 and 12 years after THA. Morphological and biomechanical analysis were performed to investigate the mechanism of these fractures. METHOD: A titanium alloy femoral stem having a slot with sharp corners (R = 0.2 mm) at the neck had been implanted in both cases. Fracture surfaces were examined by use of scanning electron microscopy (SEM). Stress concentration was simulated by using a finite element method (FEM) to compare slots with sharp (R = 0.2 mm) and smooth (R = 2 mm) corners. RESULTS: Study of the retrieved stems revealed that neck fractures had occurred at the distal end of the slot in both cases. SEM revealed numerous fine fissures extending from the anterolateral edge, striations on the middle of the fracture surface, and dimples on the posteromedial surface, suggesting that the fractures had occurred from the anterolateral aspect toward the posteromedial aspect because of metallic fatigue. FEM analysis showed that mechanical stress was concentrated at the distal and anterolateral corners of the slot. Under 3500-N loading force, the stress at the sharp corner was 556 MPa, which was approximately twofold that at the smooth corner and exceeded the fatigue strength of titanium alloy. CONCLUSION: These findings showed that the sharp corner of slot increased stress concentrations at the anterolateral aspect and led to the neck fractures..
25. Hirata, M., Nakashima, Y., Hara, D., Kanazawa, M., Kohno, Y., Yoshimoto, K., Iwamoto, Y., Optimal anterior femoral offset for functional range of motion in total hip arthroplasty—a computer simulation study, International Orthopaedics, 10.1007/s00264-014-2538-0, 39, 4, 645-51, 2015.04, PURPOSE: Compared to medial femoral offset (MFO), the role of anterior femoral offset (AFO) on range of motion (ROM) in total hip arthroplasty (THA) has not been fully examined. We therefore defined AFO as the anterior distance from the centre of the femoral head to the proximal femoral axis in the sagittal plane and determined the optimal AFO required for ROM needed for activities of daily living using a computer-simulated THA model. METHODS: Various AFOs were obtained by changing stem anteversion (stem-AV) and stem tilt in the sagittal plane (stem-tilt) using a CT-based simulation software. The required ROM was defined as: flexion ≥ 110°, internal rotation at 90° flexion (IR) ≥ 30°, external rotation (ER) ≥ 30°, and extension ≥ 30°, and we determined AFO and MFO to satisfy required ROM. RESULTS: AFO was positively correlated with stem-AV and anterior stem-tilt. MFO was negatively correlated with stem-AV and not influenced by stem-tilt. Flexion and IR increased with both increased AFO and MFO, whereas extension and ER decreased with increased AFO. A smoothing spline curve showed the optimal AFO and MFO for required ROM to be from 15 mm to 25 mm on average and more than 32.1 mm, respectively. CONCLUSIONS: This is the first study to show that AFO directly influenced ROM in THA. Optimal AFO as well as MFO should be reconstructed to achieve sufficient ROM..
26. Hara, D., Nakashima, Y., Hamai, S., Higaki, H., Ikebe, S., Shimoto, T., Hirata, M., Kanazawa, M., Kohno, Y., Iwamoto, Y., Kinematic analysis of healthy hips during weight-bearing activities by 3D-to-2D model-to-image registration technique, BioMed Research International, 10.1155/2014/457573, 2014, 457573-457573, 2014.11, Dynamic hip kinematics during weight-bearing activities were analyzed for six healthy subjects. Continuous X-ray images of gait, chair-rising, squatting, and twisting were taken using a flat panel X-ray detector. Digitally reconstructed radiographic images were used for 3D-to-2D model-to-image registration technique. The root-mean-square errors associated with tracking the pelvis and femur were less than 0.3 mm and 0.3° for translations and rotations. For gait, chair-rising, and squatting, the maximum hip flexion angles averaged 29.6°, 81.3°, and 102.4°, respectively. The pelvis was tilted anteriorly around 4.4° on average during full gait cycle. For chair-rising and squatting, the maximum absolute value of anterior/posterior pelvic tilt averaged 12.4°/11.7° and 10.7°/10.8°, respectively. Hip flexion peaked on the way of movement due to further anterior pelvic tilt during both chair-rising and squatting. For twisting, the maximum absolute value of hip internal/external rotation averaged 29.2°/30.7°. This study revealed activity dependent kinematics of healthy hip joints with coordinated pelvic and femoral dynamic movements. Kinematics' data during activities of daily living may provide important insight as to the evaluating kinematics of pathological and reconstructed hips..
27. Hirata, M., Nakashima, Y., Itokawa, T., Ohishi, M., Sato, T., Akiyama, M., Hara, D., Iwamoto, Y., Influencing factors for the increased stem version compared to the native femur in cementless total hip arthroplasty, International Orthopaedics, 10.1007/s00264-014-2289-y, 38, 7, 1341-6, 2014.07, PURPOSE: Stem version is not always equivalent to femoral neck version (native version) in cementless total hip arthroplasty (THA). We therefore examined the discrepancy of version between the native femoral neck and stem using pre- and postoperative computed tomography (CT), the level of the femur where the canal version most closely fit the stem version, and the factors influencing version discrepancy between the native femoral neck and stem. METHODS: A total of 122 hips in 122 patients who underwent primary THA using a metaphyseal-fit stem through the postero-lateral approach were included. Pre- and postoperative CT images were utilized to measure native and stem version, and the version of the femoral canal at four levels relative to the lesser trochanter. RESULTS: The mean native and stem versions were 28.1 ± 11.0° and 38.0 ± 11.2°, respectively, revealing increased stem version with a mean difference of 9.8° (p
28. Kohno, Y., Nakashima, Y., Kitano, T., Nakamura, T., Takamura, K., Akiyama, M., Hara, D., Yamamoto, T., Motomura, G., Ohishi, M., Hamai, S., Yukihide, I., Subclinical bilateral involvement of the hip in patients with slipped capital femoral epiphysis - A multicentre study, International Orthopaedics, 10.1007/s00264-013-2131-y, 38, 3, 477-82, 2014.03, PURPOSE: This study was conducted to assess the posterior inclination of the contralateral femoral epiphysis in patients with unilateral slipped capital femoral epiphysis (SCFE). METHODS: The posterior sloping angle (PSA) was measured using lateral radiographs in 67 patients with a unilateral SCFE and in 41 age-matched normal controls. A symptomatic epiphyseal slip was defined as the development of SCFE. RESULTS: The contralateral PSA in SCFE patients was more widely distributed and significantly larger compared to controls (15.0° vs. 9.0°, p  19°) are likely to become symptomatic..
29. Akiyama, M., Nakashima, Y., Oishi, M., Sato, T., Hirata, M., Hara, D., Iwamoto, Y., Risk factors for acetabular retroversion in developmental dysplasia of the hip: Does the Pemberton osteotomy contribute?, Journal of Orthopaedic Science, 10.1007/s00776-013-0473-3, 19, 1, 90-6, 2014.01, BACKGROUND: The purpose of this study was to investigate residual acetabular retroversion after skeletal maturity in patients with Pemberton osteotomy. PATIENTS AND METHODS: We compared 40 hips in 36 patients treated with a Pemberton osteotomy (Pemberton group) and 30 hips in 26 patients treated only with a Pavlik harness (Rb group) for developmental dysplasia of the hip. The average age at operation in the Pemberton group was 94.5 months and the follow-up duration was 151.8 months. Radiographic parameters included the acetabular index (α angle) and the center-edge angle of Wiberg, preoperatively and at skeletal maturity. We examined the crossover sign (COS) at the latest follow-up as a sign of acetabular retroversion (AR). We compared the parameters between the two groups and examined the risk factors for acetabular retroversion using a multivariate Cox model. RESULT: A COS (+) was significantly more frequent in the Pemberton group compared to the Rb group [15 hips (37.5%) vs 3 hips (10%); p = 0.0077]. In the Pemberton group, the average age at operation in COS (+) hips was significantly older than that in COS (-) hips (126.9 vs 72.8 months; p = 0.0005). The preoperative α angle did not vary between hips with and without COS; however, the postoperative α angle was significantly smaller in COS (+) hips. A multiple logistic regression analysis for prediction of COS (+) showed that the age at operation and the amount change of α angle were significant predictors for COS (+) hips. The cut-off of the age at operation was 7 years and 9 months old. CONCLUSIONS: AR was present in 37.5% of the hips in the Pemberton group after skeletal maturity. Remodeling of acetabular version was observed in younger patients; however, hips in older patients (>8 years) at the time of operation and greater degrees of correction tended to result in AR..
30. Nakashima, Y., Sato, T., Yamamoto, T., Motomura, G., Ohishi, M., Hamai, S., Akiyama, M., Hirata, M., Hara, D., Iwamoto, Y., Results at a minimum of 10 years of follow-up for AMS and PerFix HA-coated cementless total hip arthroplasty: Impact of cross-linked polyethylene on implant longevity, Journal of Orthopaedic Science, 10.1007/s00776-013-0456-4, 18, 6, 962-8, 2013.11, PURPOSE: The purpose of this study was to report results at a minimum of 10 years for hydroxyapatite (HA) coating on the titanium arc-sprayed cementless total hip arthroplasty (THA) and to evaluate the impact of cross-linked polyethylene (XLPE) on implant longevity. METHODS: A total of 131 consecutive primary THAs in 123 patients using an AMS acetabular cup and a PerFix HA stem were retrospectively reviewed. Conventional PE was used for 62 hips (CPE group) and cross-linked PE for 69 hips (XLPE group), with mean follow-up periods of 13 and 11.5 years, respectively. These patients were reviewed using the Japanese Orthopaedic Association (JOA) Hip Score and evaluated in terms of PE wear, osteolysis, and implant survival. RESULTS: The JOA score improved from 42.6 to 83.9 points at the final follow-up. The mean wear rate of 0.12 mm/year in the CPE group was significantly greater than that of XLPE at 0.007 mm/year. In the CPE group, ten (16.1 %) and two (3.2 %) hips, respectively, underwent PE exchange due to severe wear and acetabular revision due to loosening associated with osteolysis. Three patients had revision in the XLPE group: one cup for aseptic loosening, one PE for recurrent dislocation, and one stem for neck fracture. No evident osteolysis was seen in the XLPE group. Kaplan-Meier survivorship with any revision as the end point shows that the 12-year survival rate was 97.7 % for cups, 93.8 % for PE liners, and 99.2 % for stems. Multivariate analysis revealed that the use of XLPE significantly reduced the risk of revision, with the odds ratio (OR) of 4.3. CONCLUSIONS: AMS and PerFix HA components in this series show excellent implant fixation; however, high rates of PE wear and subsequent osteolysis were limiting factors in long-term success. Low wear rates with XLPE suggest improved implant longevity..
31. Hirata, M., Nakashima, Y., Ohishi, M., Hamai, S., Hara, D., Iwamoto, Y., Surgeon error in performing intraoperative estimation of stem anteversion in cementless total hip arthroplasty, Journal of Arthroplasty, 10.1016/j.arth.2013.03.006, 28, 9, 1648-53, 2013.10, To examine the accuracy of intraoperative estimation of stem anteversion in total hip arthroplasty (THA), we compared the intraoperatively estimated stem anteversion (estimated prosthetic anteversion) to stem anteversion measured by postoperative computed tomography (true anteversion) in 73 hips in 73 patients. Estimated prosthetic anteversion was significantly greater than true anteversion by 5.8°, and the mean absolute value of surgeon error was 7.3° ranging from 11° underestimation to 25° overestimation. Surgeons tended to overestimate when the true anteversion was smaller. A multivariate analysis showed that advanced knee osteoarthritis significantly increased surgeon error. These results indicated that estimated prosthetic anteversion was generally larger than true anteversion and that the grade of knee osteoarthritis affected the degree of surgeon error..
32. Itokawa, T., Nakashima, Y., Yamamoto, T., Motomura, G., Ohishi, M., Hamai, S., Akiyama, M., Hirata, M., Hara, D., Iwamoto, Y., Late dislocation is associated with recurrence after total hip arthroplasty, International Orthopaedics, 10.1007/s00264-013-1921-6, 37, 8, 1457-63, 2013.08, PURPOSE: This study was conducted to examine the risk factors for recurrent dislocation after total hip arthroplasty (THA) and test the hypothesis that late dislocations are associated with recurrence. METHODS: A total of 1,250 hips in 1,017 patients were retrospectively reviewed. All operations were performed through the posterolateral approach with posterior soft tissue repair. An early or late dislocation was defined as a dislocation occurring before or after one year postoperatively, respectively. RESULTS: Dislocation occurred in 36 hips (2.9 %) and 20 of them experienced recurrence. Recurrent dislocations were observed in ten out of 25 hips (40.0 %) with early dislocation; however, ten out of 11 hips (90.9 %) with late dislocation experienced recurrence (p = 0.0046). Multivariate analysis revealed that late dislocation was significantly associated with recurrence with odds ratio of 5.94 per year. Seven in 20 hips with recurrent dislocation required surgical treatment. CONCLUSION: Late dislocation significantly contributed to the development of recurrent dislocations..
33. Hara, D., Nakashima, Y., Yamamoto, T., Higashihara, S., Todo, M., Hirata, M., Akiyama, M., Iwamoto, Y., Late failure of annealed highly cross-linked polyethylene acetabular liner, Journal of the Mechanical Behavior of Biomedical Materials, 10.1016/j.jmbbm.2013.08.003, 28, 206-12, 2013.08, Highly cross-linked polyethylene (HXPE) in total hip arthroplasty (THA) has been shown to significantly decrease wear rates compared with conventional polyethylene (CPE). However, crosslinking, thermal treatment and oxidation can decrease the mechanical properties of PE, and several cases of fracture of remelted HXPE liners were reported. We present, for the first time, unexpected failures of THA with the use of annealed HXPE liners in two patients occurring at 7 and 8 years after operation. Operative findings revealed dislocated liners from the metal shell and a fracture of the superior rim at the rim-dome junction in both liners. Scanning electron microscopy showed that the cracks initiated at the rim and propagated toward the articular surface. Both liners showed generally a low amount of oxidation (less than 1.00) at the articular surface and low wear rates; however, oxidation at the rim was relatively higher (mean 1.55). These findings suggested that decreased mechanical properties at the rim-dome junction due to cross-linking, annealing and oxidation might have been caused breakage of the HXPE liners after a long implantation time, although the annealed HXPE achieved low degree of wear..
Membership in Academic Society
  • Japan Society for Rheumatism and Joint Surgery
  • Japanese Orthopaedic Association
  • Japanese Orthopaedic Association West-Japanese Society of Orthopaedics & Traumatology
  • Japanese Hip Society
  • Japanese Society for Replacement Arthroplasty
  • Japan College of Rheumatology
  • Article award
  • Reviewer Certificate
  • Blue Ribbon Article Award
  • The Japanese Orthopaedic Association Academic Encouragement Award, 2018
  • The 32nd Academic Encouragement Award of Department of Orthopaedic Surgery, Kyushu University, 2016