The purpose of this preliminary study was to evaluate the feasibility and accuracy of HipAlign (OrthAlign, Inc., USA) system for cup orientation in total hip arthroplasty (THA). The subjects of this study were 5 hips that underwent primary cementless THA via a posterior approach in the lateral decubitus position. Evaluation 1; after reaming acetabular bone, a trial cup was placed in the reamed acetabulum in an aimed alignment using HipAlign. Then, the trial cup alignment was measured using HipAlign and CT-based navigation system in the radiographic definition. Evaluation 2; a cementless cup was placed in the reamed acetabular in an aimed alignment using CT-based navigation and cup alignment was measured using both methods. After operation, we measured the cup alignment using postoperative CT in each patient. In the results, the average cup inclination measured with HipAlign was around 5 degrees of true cup inclination angles. The average cup anteversion with HipAlign tended to be larger than that with CT-based navigation or postoperative CT in both evaluations. That is because there is a difference in the pelvic sagittal tilt between the lateral position and supine position. In conclusion, this study suggests that guiding cup alignment with the use of HipAlign is feasible through a posterior approach and the mean cup inclination measured with HipAlign showed an acceptable level of accuracy, but the mean cup anteversion is not reliable. We need a further modification for pelvic registration to improve the accuracy of cup anteversion.

The purpose of this retrospective study was to estimate the outcome improvements after Total Hip Arthroplasty (THA) using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients who underwent THA with a navigation system in our institutions, and to compare them with those undergoing THA without a navigation system that had been reported in the literatures. The subjects in this study comprised 245 patients (39 males, 206 females; mean age, 59.9±12.0 years; mean BMI, 22.8±3.2 kg/m2) who underwent THA. All patients had adequate data to allow complete scoring of the WOMAC for a minimum one-year postoperative follow-up. CT-based navigation was used in all THAs. Postoperatively, no restrictions were imposed. A MEDLINE search was conducted using the search terms ‘Total hip’, ‘Quality of life (QOL)’, and ‘WOMAC’. 10 articles evaluated all WOMAC subscales one to two years after THA. The WOMAC subscale scores were compared statistically between our study and the results reported in the 10 articles using Welch's t-test. The present physical function subscale scores were the best of the 10 studies, and in 8 of the 10 studies, the differences were significant. WOMAC subscale results in our study were significantly better than those reported in most articles in which THA was performed without navigation. These results show that THA using navigation can improve patients' postoperative QOL.

The robotic-assisted system (ROBODOC) is the first active robot that was designed to reduce potential human errors in performing cementless total hip arthroplasty (THA). We have reported minimum five years follow-up clinical results. However, to our knowledge, there have been no longer follow-up reports. The purpose of this study was to prospectively compare the minimum ten years follow-up results of robotic-assisted and hand-rasping stem implantation techniques.

Between 2000 and 2002, we performed 146 THA on 130 patients who were undergoing primary THA. Robot assisted primary THA was performed on 75 hips and a hand-rasping technique was used on 71 hips. Among them, 112 hips (53 hips in the robotic milling group and 59 hips in the hand-rasping group) were followed more than 10 years. Follow-up periods ranged from 120–152 months (average 135). Preoperatively, we plan the position and the size of the stem three-dimensionally for both groups. At the operation, posterolateral approach was used. We evaluated survivorship and compared clinical results.

At the final follow-up, no stem was revised in either group. Plain radiographs showed bone ingrowth fixation for all the stems of both groups. There were no signs of mechanical loosening in any implant. Preoperatively, there were no significant differences in the Japanese Orthopedic Association (JOA) hip scores between the two groups. Ten years postoperatively, it was significantly better in the robotic milling group (98 points and 96 points, respectively) (Mann-Whitney U-test; p<0.05). The main difference was observed in the category of range of motion (19 points and 18 points, respectively) (p=0.01).

In the previous study, we have reported that the JOA hip score was significantly better in the robotic milling group up to three years postoperatively. In the present study, we found that it was still significantly better at ten years postoperatively. In conclusion, robotic milling THA was associated with better clinical scores until ten years postoperatively.

The occurrence of impingement can lead to instability, accelerated wear, and unexplained pain after THA. While implant and bony impingement were widely investigated, importance of soft tissue impingement was unclear. In the THA through posterior approach, it is known that posterior soft tissue repair can decrease the risk of dislocation. However, it is not known whether anterior soft tissue impingement by anterior hip capsule will influence hip ROM. The purpose of this study is to quantitatively measure the effect of anterior capsule resection on hip ROM in vivo during posterior approach THA using hip navigation system.

From June 2011, 26 hips (25 patients) that underwent primary THA using Stryker CT-based hip navigation system were the subjects. All were female osteoarthritis patients and the average age at the operation was 59 (47–76) years. Intraoperatively, acetabular cup and femoral stem placement were performed through posterior approach under the navigation system. After reduction of the joint, we measured hip ROM using the same navigation system. We measured them before and after the resection of anterior hip capsule and compared the difference.

After the resection of anterior hip capsule, the average increases of ROM were 0.7±3.5 degrees for flexion, 2.3±2.3 degrees for extension, 1.1±2.3 degrees for abduction and 2.1±2.9 degrees for external rotation at flexion 0 degree compared with ROM before the resection. However, it significantly increased 7.5±5.1 degrees for internal rotation at flexion 90 degree (range; −3–20, paired t-test p<0.001) and 6.1±5.5 degrees for internal rotation at flexion 45 degree (range; −4–18, p<0.001).

In this study, we used navigation system for assessment of soft tissue impingement. We found that during posterior approach THA, resection of anterior hip capsule brought about significant increase of ROM, especially in the direction of flexion with internal rotation. We also found that this procedure did not change ROM of flexion, extension, abduction and external rotation. These results indicated that, during THA through posterior approach, resection of anterior hip capsule could reduce the risk of posterior instability without increasing the risk of anterior instability.

We developed a custom-made template for corrective femoral osteotomy during THA in a patient with a previous Schanz osteotomy.

A seventy-year-old woman presented to our clinic with a chief complaint of right hip, left knee and left ankle pain with marked limp. She had undergone Schanz osteotomy of the left femur because of high dislocation of the left hip when she was 20 years old. After right THA was performed, we decided to perform left THA with corrective femoral osteotomy. A custom-made osteotomy template was designed and manufactured with use of CT data. During surgery, we placed the template on the bone surface, cut the bone through a slit on the template, and corrected the deformity as preoperatively simulated. Two years after surgery, she had no pain in any joints, could walk more than one hour without limp. Japanese Orthopedic Association hip score were 100 points for both hips.

THA in patients with previous Schanz osteotomy was reported to be technically demanding and the rate of complications was high. In 2008, Murase T et al. developed a system, including a 3D computer simulation program and a custom-made template to corrective osteotomy of malunited fractures of the upper extremity. We applied the system to corrective femoral osteotomy during THA in a patient with a previous Schanz osteotomy. The surgical procedure was technically easy and accurate osteotomy brought the patient to acquire good alignment of lower extremities with good clinical results.

Introduction

Current standard cups of metal on metal resurfacing hip arthroplasty (RHA) have no dome holes and it is very difficult for surgeons to confirm full seating of these cups. This sometimes results in gap formation between the cup and acetabular floor. Although the incidence of initial gaps using modular press-fit cups with dome screw holes has been reported to range from 20 to 35%, few studies have reported the incidence of gap formation with monoblock metal cups and its clinical consequences in RHA. The purpose of this study was to investigate retrospectively the incidence of initial gap formation and whether the initial gap influences the clinical results in RHA.