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Currently, there is no surgical assistance system that can perform a three-dimensional (3D) planned total hip arthroplasty (THA) by methods other than surgical assistance navigation or robots. However, they are expensive, cumbersome, and subject to additional invasiveness, so there is a need for a simpler and less expensive 3D surgical support system. In this study, THA was performed using the anterolateral approach (Watson-Jones) in the supine position in 23 subjects to examine the efficacy and safety of a patient-specific femoral guide linked to 3D surgery support software. In 48% of the subjects, the difference in anterior torsion angle from the preoperative plan was within ±5 degrees, while in 83% of the subjects, the difference was within ±10 degrees. The 95% confidence interval (4.61-8.70) of the absolute difference did not fall below the pre-defined threshold of 7.2 degrees (p = 0.293). No adverse events were observed other than 2 cases (8.7%) of hemorrhage that required a blood transfusion. We confirmed the efficacy and safety of the patient-specific femoral guide in anterolateral supine approach THA.

Background: Differences in proximal femoral morphology between ethnicities may have implications on the design of cementless tapered wedge stems. This study analyses the differences in Asian and Caucasian bone morphology as well as the related fit of various cementless tapered wedge stem designs., Methods: A computed tomography database and modelling software was used to retrospectively analyse a total of 1345 femora. Ethnicity related comparisons as well as the fit of the stem designs were analysed., Results: Statistically significant differences between canal shape of Caucasian and Japanese as well as non-Japanese Asians were observed. The fit of the stems within the femoral canal was highly dependent on the respective stem shape., Conclusions: The shape differences in stem designs had a larger influence on the fit within the femoral canal than the differences in ethnicity related to bone morphology.

Total hip arthroplasty (THA) is performed for pain relief in patients with osteoarthritis of the hip joint. After THA, patients may recover muscle mass and physical function. Muscle quality is the main parameter used to indicate intramuscular fat content, and it is related with muscle function in older individuals. However, how THA affects muscle quality, as determined by echo intensity (EI), is not well understood. The purpose of this study was to determine the long-term characteristics of EI, muscle quantity, muscle function, and physical functions in the patients with THA surgery. In order to achieve the purpose, we performed two comparison. First, we compared muscle EI, quantity and function in operated leg with unoperated legs in the same patients and with the legs of healthy adults (i.e., both unoperated legs). Second, we compared physical functional tests between THA patient and age and body composition matched controls. Twenty-two older individuals (age: 67.1 ± 5.3 years, height: 160.9 ± 7.1 cm, body mass: 62.6 ± 16.1 kg) who underwent unilateral THA several (5.2 ± 3.1) years ago (THA group) and 22 healthy controls with matching age and body composition (age: 68.3 ± 4.4 years, height: 160.3 ± 7.9 cm, body mass: 61.7 ± 7.8 kg) (CON group) participated in this case-control study. EI, an index of muscle quality, and muscle thickness (MT), an index of muscle quantity, were measured from B-mode transverse images of the rectus femoris obtained through ultrasound. The maximal isometric knee extension torque was measured in both the operated and unoperated legs in the THA group and in the right leg in the CON group (control leg); physical function tests, such as sit-to-stand, walking speed, hip adduction, and abduction torque assessments, were performed in both groups. MT and maximal isometric knee extension torque in operated leg were not different with unoperated, and control legs; the EI in the operated leg was significantly higher than that in the control leg (106.9 ± 16.9 vs. 92.4 ± 21.0 a.u., P < 0.05). The THA group demonstrated slower walking speed and lower hip abduction torque than the CON group (walking speed: 1.3 ± 0.2 vs. 1.5 ± 0.2 m/s; hip abduction torque 1.2 ± 0.3 vs. 1.5 ± 0.5 Nm/kg, P < 0.05). Several years after THA, the operated legs completely recovered the same level of muscle quantity as that in healthy participants but with lower muscle quality and hip joint function. These defects may be associated with locomotive dysfunction in older THA patients., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: We developed an augmented reality (AR)-based portable navigation system in which the surgeon can view the pelvic plane and placement angle of an acetabular cup on the display of a smartphone during THA., Questions/purposes: (1) Is acetabular component placement more accurate using the AR-based portable navigation system compared with the conventional freehand technique? (2) Is intraoperative measurement of placement angle more accurate when using the AR-based portable navigation system compared with a goniometer?, Methods: Forty-six patients were randomly assigned to undergo acetabular cup placement during THA using the AR-based portable navigation system (AR navigation group) or placement of a mechanical alignment guide (conventional group). All surgeries were performed with the patient in the lateral decubitus position. We compared the absolute value of the difference between the targeted placement angle and postoperative measured placement angle between the groups using two types of imaging (radiography and CT)., Results: In terms of radiographic inclination, the mean differences between the targeted placement angle and postoperative measured angle were smaller in the AR navigation group than in the conventional group for both radiographs and CT images (2.3° ± 1.4° versus 3.9° ± 2.4°, respectively; p = 0.009 and 1.9° ± 1.3° versus 3.4° ± 2.6°, respectively; p = 0.02). There were no differences in radiographic anteversion between the two groups. No complications were associated with the use of the AR-based portable navigation system., Conclusions: This system yielded no differences in acetabular anteversion accuracy, and no clinically important differences in acetabular inclination. Therefore, at this time we cannot recommend this device as its costs and risks cannot be justified based on the absence of a clinically meaningful difference in cup placement accuracy. Although we detected no complications, this was a small series, and this approach adds both surgical time and pins in the ilium., Level of Evidence: Level I, therapeutic study.

Background: There have been several reports regarding airport security checks using arched metal detectors in patients with orthopedic implants and/or joint replacement surgery. Implants of different sizes and/or materials are used in total hip arthroplasty (THA), but there have been no reports regarding differences in detection rates between different types of THA implants and materials. We examined detection rates by airport metal detectors among THA patients with different implants., Methods: We selected 1684 patients from regular outpatients at our hospital from June to December 2016. A questionnaire elicited responses regarding usage of airplanes, flight type (domestic/international), and detection by airport metal detectors. Data were investigated according to unilateral/bilateral THA, femoral stem type, acetabular shell component diameter, femoral head diameter, and femoral head material type., Results: Among 671 patients selected from those who used airplanes, 346 patients reported detection by metal detectors. Detection rates for patients with unilateral THA/domestic flights, unilateral THA/international flights, bilateral THA/domestic flights, and bilateral THA/international flights were 23% (81 of 351 patients), 56% (114 of 186 patients), 75% (140 of 204 patients), and 86% (118 of 138 patients), respectively. Logistic regression analysis indicated that the most effective explanatory variables were cup size and material type of femoral head for domestic flights, and cup size for unilateral THA/international flights., Conclusion: Detection rate was lowest for patients with unilateral THA/domestic flights (23%), and highest for bilateral THA/international flights (86%). Statistical analyses of implant data indicated that cup size was the most significant explanatory variable., (Copyright © 2019 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)

Background: Modular stems are useful for total hip arthroplasty (THA) in anatomically difficult dysplasia. Here, we present mean 6.8-year outcomes of cementless primary THA using S-ROM-A (modified modular stem for Asian patients) femoral prosthesis in anatomically difficult cases., Methods: Charts of 373 patients (461 hips) undergoing THA (mean age, 58 years) were reviewed for clinical evaluation of modified Merle d'Aubigné-Postel score and Kaplan-Meier survivorship with revision for any reason as the end point. For radiographic analysis, 331 patients (412 hips) followed up for ≥5 years were included. Bearing couples were metal-on-metal (n = 145), metal-on-polyethylene (n = 120), and ceramic-on-polyethylene (n = 147). Radiography and multiplanar computed tomography were performed., Results: No postoperative dislocation or deep infection occurred. Mean modified Merle d'Aubigné-Postel score improved significantly (10.9 points preoperatively, 16.7 points at last follow-up; P < .001). Cumulative 5- and 10-year stem survival rates were 100% and 84%, respectively (95% confidence interval, 75%-93%). All stems were classified as bone ingrown fixation. Osteolysis occurred in metal-on-metal (42.8%) and metal-on-polyethylene (15.8%) groups. Mean time to osteolysis was ~3 years, with no significant difference between 3 groups (P = .264). In logistic regression, lower cup inclination angle was significantly associated with osteolysis (odds ratio, 0.914; 95% confidence interval, 0.84-0.99; P = .029)., Conclusion: S-ROM-A femoral prosthesis achieved excellent midterm fixation, and the modular system was useful in primary THA with severe deformity. Bearing couples are potentially associated with adverse reactions to metal debris. S-ROM-A with ceramic-on-polyethylene bearing couples may be an option for anatomically difficult THA., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Periarticular analgesic injection (PAI) is being used more commonly for pain relief after orthopaedic surgeries. However, there is conflicting evidence regarding the effectiveness of PAI for post-THA pain relief., Questions/purposes: In a double-blind, randomized, controlled trial among patients undergoing same-day bilateral THA, with each patient serving as his or her own control, we asked: (1) Did the pain score as measured on a 100-mm VAS differ between the hips that received PAI versus placebo? (2) Were there differences in complications between the treatment and control hips in these patients?, Methods: Over a 1-year period at one center, 45 patients underwent same-day bilateral THA; three were excluded for prespecified reasons, and two declined participation in this randomized, controlled trial, leaving 40 patients (80 THAs) in the study. Patients randomly received PAI in one hip and placebo in the contralateral hip; patients, surgeons, and nurses were blinded in terms of which hip received the PAI and which hip received a placebo saline injection. The PAI solution included ropivacaine, morphine hydrochloride hydrate, methylprednisolone, ketoprofen, and epinephrine. The primary outcome was the VAS for pain at rest 24 hours after THA, measured using a 100-mm horizontal VAS. The VAS score was compared between two groups and assessed to reach the reported threshold values for the minimum clinically important difference (MCID) of 20 mm for the postoperative VAS score. No patients were lost to followup, and there were no missing data for the primary outcome. Complications that occurred during the trial were recorded prospectively with emphasis on infection, wound complications, nerve palsy and allergic reactions to the injections., Results: There were no clinically important differences between hips treated with the PAI and those treated with the placebo injection at any point. The hips that received PAI had less pain than those receiving placebo 24 hours after THA (16 ± 17 mm versus 22 ± 20 mm; mean difference, 6 mm; 95% confidence interval [CI], 2-9 mm; p = 0.006), but this effect size was below the MCID of 20 mm and thus is unlikely to be clinically important. The hips that received PAI also had better VAS scores in the recovery room (38 ± 29 mm versus 52 ± 33 mm; mean difference 14 mm; 95% CI, 5-23 mm; p = 0.004) and 3 hours after THA than placebo controls (28 ± 22 mm versus 37 ± 24 mm; mean difference 9 mm; 95% CI, 2-16 mm; p = 0.010). Neither of these differences exceeded the MCID and likewise were unlikely to be clinically important. No complications, including surgical site infections, were observed in either group., Conclusions: Periarticular analgesic injection for pain control after THA did not result in a clinically important reduction in pain at any point examined. Given the expense associated with this PAI mixture and the lack of effectiveness outside this timeframe, we cannot recommend its use. Other mixtures or concentrations of drugs may be helpful in short-stay admissions for THA, but this will require further research., Level of Evidence: Level I, therapeutic study.

Background: We developed an acetabular cup placement device, the AR-HIP system, using augmented reality (AR). The AR-HIP system allows the surgeon to view an acetabular cup image superimposed in the surgical field through a smartphone. The smartphone also shows the placement angle of the acetabular cup. This preliminary study was performed to assess the accuracy of the AR-HIP system for acetabular cup placement during total hip arthroplasty (THA)., Methods: We prospectively measured the placement angles using both a goniometer and AR-HIP system in 56 hips of 54 patients undergoing primary THA. We randomly determined the order of intraoperative measurement using the 2 devices. At 3 months after THA, the placement angle of the acetabular cup was measured on computed tomography images. The primary outcome was the absolute value of the difference between intraoperative and postoperative computed tomography measurements., Results: The measurement angle using AR-HIP was significantly more accurate in terms of radiographic anteversion than that using a goniometer (2.7° vs 6.8°, respectively; mean difference 4.1°; 95% confidence interval, 3.0-5.2; P < .0001). There was no statistically significant difference in terms of radiographic inclination (2.1° vs 2.6°; mean difference 0.5°; 95% confidence interval, -1.1 to 0.1; P = .13)., Conclusion: In this pilot study, the AR-HIP system provided more accurate information regarding acetabular cup placement angle than the conventional method. Further studies are required to confirm the utility of the AR-HIP system as a navigation tool., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Simultaneous bilateral total hip arthroplasty (THA) can offer a potential benefit of greater postoperative hip motion without the negative influence of contralateral hip disabilities, compared to two-stage THA. However, postoperative changes in hip motion after simultaneous bilateral THA have rarely been reported. The purpose of this study was to clarify the efficacy of simultaneous procedures on postoperative hip motion and functional recovery., Methods: We retrospectively compared hip motion in 27 patients treated with simultaneous bilateral THA to those in 11 patients with two-stage bilateral THA, 35 patients with unilateral THA for unilateral disease, and 15 patients with unilateral THA for bilateral disease. We also evaluated the clinical manifestations according to the Japanese Orthopaedic Association (JOA) hip scores and compared the outcomes among the groups. All of the THA surgeries were primarily performed through a posterolateral approach using cement-less prostheses. The diagnosis at surgery was dysplastic osteoarthritis in all patients, and the patients were followed up for at least 4 years., Results: The postoperative improvement of motion in hip flexion was significantly greater in patients treated with simultaneous procedures compared to patients with two-stage THA and unilateral THA for bilateral disease. The differences in improvement of motion in hip abduction were less marked than the improvement in hip flexion among the groups. Although there were no significant differences in pain scores among the groups, the values for activity of daily living were significantly greater in patients treated with simultaneous bilateral THA and patients with unilateral THA for unilateral disease than in patients with unilateral and two-stage bilateral THA for bilateral disease., Conclusions: The simultaneous procedure was considered to be more effective in patients with bilateral hip osteoarthritis and demonstrated a substantial improvement in hip motion and functional recovery after THA.

This study evaluated the internal rotation limit prior to bony impingement of the proximal femur on the pelvis after total hip arthroplasty (THA). Reconstructed computed tomography (CT) images of 90 degrees hip flexion were used to simulate the internal rotation limit against safety limits measured intraoperatively. Ninety joints in 86 subjects (12 men and 74 women) underwent THA for the treatment of secondary coxarthrosis. The correlation between the internal rotation limit prior to the bony impingement intraoperatively and the simulated internal rotation angle on the reconstructed CT image was statistically significant. We provide a new method to simulate the internal rotation limit prior to bony impingement based on postoperative CT.