Hirofumi Oshima

Long-term hip simulator testing of the artificial hip joint bearing surface grafted with biocompatible phospholipid polymer

To prevent periprosthetic osteolysis and subsequent aseptic loosening of artificial hip joints, we recently developed a novel acetabular highly cross‐linked polyethylene (CLPE) liner with graft polymerization of 2‐methacryloyloxyethyl phosphorylcholine (MPC) on its surface. We investigated the wear resistance of the poly(MPC) (PMPC)‐grafted CLPE liner during 20 million cycles in a hip joint simulator. We extended the simulator test of one liner to 70 million cycles to investigate the long‐term durability of the grafting. Gravimetric, surface, and wear particle analyses revealed that PMPC grafting onto the CLPE liner surface markedly decreased the production of wear particles and showed that the effect of PMPC grafting was maintained through 70 million cycles. We believe that PMPC grafting can significantly improve the wear resistance of artificial hip joints.

Wear resistance of the biocompatible phospholipid polymer-grafted highly cross-linked polyethylene liner against larger femoral head.

The use of larger femoral heads to prevent the dislocation of artificial hip joints has recently become more common. However, concerns about the subsequent use of thinner polyethylene liners and their effects on wear rate have arisen. Previously, we prepared and evaluated the biological and mechanical effects of a novel highly cross‐linked polyethylene (CLPE) liner with a nanometer‐scaled graft layer of poly(2‐methacryloyloxyethyl phosphorylcholine) (PMPC). Our findings showed that the PMPC‐grafted particles were biologically inert and caused no subsequent bone resorptive responses and that the PMPC‐grafting markedly decreased wear in a hip joint simulator. However, the metal or ceramic femoral heads used in this previous study had a diameter of 26 mm. Here, we investigated the wear‐resistance of the PMPC‐grafted CLPE liner with a 40‐mm femoral head during 10 × 106 cycles of loading in the hip joint simulator. The results provide preliminary evidence that the grafting markedly decreased gravimetric wear rate and the volume of wear particles, even when coupled with larger femoral heads. Thus, we believe the PMPC‐grafting will prolong artificial hip joint longevity both by preventing aseptic loosening and by improving the stability of articular surface.

Total Hip Arthroplasty After Rotational Acetabular Osteotomy

In this study, we aimed to determine whether the outcomes of total hip arthroplasty (THA) after rotational acetabular osteotomy (RAO) are equal to those of primary THA, and to elucidate the characteristics of THA after RAO. The clinical and radiographic findings of THA after RAO (44 hips), with minimum 24 months of follow-up, were compared with a matched control group of 58 hips without prior RAO. We found that the outcomes in terms of functional scores and complication rates did not differ between THA after RAO and THA without previous pelvic osteotomy, indicating that the results of THA after RAO are equivalent to those of primary THA. Although THA after RAO requires technical considerations, similar clinical outcomes to primary THA can be expected.

Grafting of poly(2-methacryloyloxyethyl phosphorylcholine) on polyethylene liner in artificial hip joints reduces production of wear particles.

Despite improvements in the techniques, materials, and fixation of total hip arthroplasty, periprosthetic osteolysis, a complication that arises from this clinical procedure and causes aseptic loosening, is considered to be a major clinical problem associated with total hip arthroplasty. With the objective of reducing the production of wear particles and eliminating periprosthetic osteolysis, we prepared a novel hip polyethylene (PE) liner whose surface graft was made of a biocompatible phospholipid polymer-poly(2-methacryloyloxyethyl phosphorylcholine (MPC)). This study investigated the wear resistance of the poly(MPC)-grafted cross-linked PE (CLPE; MPC-CLPE) liner during 15×10(6) cycles of loading in a hip joint simulator. The gravimetric analysis showed that the wear of the acetabular liner was dramatically suppressed in the MPC-CLPE liner, as compared to that in the non-treated CLPE liner. Analyses of the MPC-CLPE liner surface revealed that it suffered from no or very little wear even after the simulator test, whereas the CLPE liners suffered from substantial wears. The scanning electron microscope (SEM) analysis of the wear particles isolated from the lubricants showed that poly(MPC) grafting dramatically decreased the total number, area, and volume of the wear particles. However, there was no significant difference in the particle size distributions, and, in particular, from the SEM image, it was observed that particles with diameters less than 0.50μm were present in the range of the highest frequency. In addition, there were no significant differences in the particle size descriptors and particle shape descriptors. The results obtained in this study show that poly(MPC) grafting markedly reduces the production of wear particles from CLPE liners, without affecting the size of the particles. These results suggest that poly(MPC) grafting is a promising technique for increasing the longevity of artificial hip joints.

Hand-Held Bone Cutting Tool With Autonomous Penetration Detection for Spinal Surgery

In spinal surgery, a surgeon often needs to remove some parts of the spine to relieve the pressure on the spinal cord or other nerves. In this procedure, the surgeon needs to cut and drill some holes in the spine. This operation is very risky because there are some nerves beneath the target bones, and this procedure therefore requires a skilled and experienced surgeon. However, if the cutting tool could detect penetration of the bone autonomously, the safety of the procedure would be improved drastically. This study presents a hand-held bone cutting tool system that detects the penetration of the workpiece. The system learns the cutting states and motion states from demonstrations by a surgeon, and it autonomously detects the penetration of the workpiece and stops the actuation of the cutting tool immediately before total penetration. The proposed scheme for penetration detection does not require knowledge of the shape and the position of the workpiece and, therefore, it does not require any costly systems, such as robotic arms and position sensor systems. In addition, the proposed scheme can be easily applied to various shapes of the cutting tool, such as drills and saws. The developed system was evaluated through experiments. The results showed that the performance of the developed system was satisfactory in both a motorized and a hand-held setup.

Development of the Japanese Version of the Leeds Assessment of the Neuropathic Symptoms and Signs Pain Scale: Diagnostic Utility in a Clinical Setting.

We aimed to assess the diagnostic utility of the linguistically validated Japanese version of the Leeds Assessment of Neuropathic Symptoms and Signs Pain Scale (LANSS‐J) as a screening tool for neuropathic pain in the clinical setting.

A Patient-Specific Instrument for Femoral Stem Placement During Total Hip Arthroplasty

To ensure that the femoral stem is placed in the proper position during total hip arthroplasty, the authors developed a patient-specific instrument. A total of 10 total hip arthroplasties were performed with the assistance of the patient-specific instrument during this study. The mean accuracy of stem tilt, varus/valgus, and anteversion was 2.1°±4.1°, 1.0°±0.7°, and 4.7°±1.2°, respectively. No complications were observed and no reoperations were required for any of the patients who underwent surgery included in this study. The results support the feasibility of this patient-specific instrument for use during stem placement in total hip arthroplasty. [Orthopedics. 2017; 40(2):e374-e377.].

Clinical safety and wear resistance of the phospholipid polymer-grafted highly cross-linked polyethylene liner

To reduce the production of wear particles and subsequent aseptic loosening, we created a human articular cartilage‐mimicked surface for a highly cross‐linked polyethylene liner, whose surface grafted layer consisted of a biocompatible phospholipid polymer, poly(2‐methacryloyloxyethyl phosphorylcholine). Although our previous in vitro findings showed that poly(2‐methacryloyloxyethyl phosphorylcholine)‐grafted particles were biologically inert and caused no subsequent bone resorptive responses, and poly(2‐methacryloyloxyethyl phosphorylcholine) grafting markedly decreased wear in hip joint simulator tests, the clinical safety, and in vivo wear resistance of poly(2‐methacryloyloxyethyl phosphorylcholine)‐grafted highly cross‐linked polyethylene liners remained open to question. Therefore, in the present study, we evaluated clinical and radiographic outcomes of poly(2‐methacryloyloxyethyl phosphorylcholine)‐grafted highly cross‐linked polyethylene liners 5 years subsequent to total hip replacement in 68 consecutive patients. No reoperation was required for any reason, and no adverse events were associated with the implanted liners. The average Harris Hip Score increased from 38.6 preoperatively to 96.5 5 years postoperatively, and health‐related quality of life, as indicated by the Short Form 36 Health Survey, improved. Radiographic analyses showed no periprosthetic osteolysis or implant migration. Between 1 and 5 years postoperatively, the mean steady‐state wear rate was 0.002 mm/year, which represented a marked reduction relative to other highly cross‐linked polyethylene liners, and appeared to be unaffected by patient‐related or surgical factors. Although longer follow up is required, poly(2‐methacryloyloxyethyl phosphorylcholine)‐grafted highly cross‐linked polyethylene liners improved mid‐term clinical outcomes. The clinical safety and wear‐resistance results are encouraging with respect to the improvement of long‐term clinical outcomes with poly(2‐methacryloyloxyethyl phosphorylcholine)‐grafted highly cross‐linked polyethylene liners.

Evaluation of the three-dimensional bony coverage before and after rotational acetabular osteotomy

PurposeRotational acetabular osteotomy is a type of pelvic osteotomy that involves rotation of the acetabular bone to improve the bony coverage of the femoral head for patients with acetabular dysplasia. Favourable post-operative long-term outcomes have been reported in previous studies. However, there is a paucity of published data regarding three-dimensional bony coverage. The present study investigated the three-dimensional bony coverage of the acetabulum covering the femoral head in hips before and after rotational acetabular osteotomy and in normal hips.MethodsThe computed tomography data of 40 hip joints (12 joints before and after rotational acetabular osteotomy; 16 normal joints) were analyzed. The three-dimensional bony coverage of each joint was evaluated using original software.ResultsThe post-operative bony coverage improved significantly compared with pre-operative values. In particular, the anterolateral aspect of the acetabulum tended to be dysplastic in patients with acetabular dysplasia compared to those with normal hip joints. However, greater bony coverage at the anterolateral aspect was obtained after rotational acetabular osteotomy. Meanwhile, the results of the present study may indicate that the bony coverage in the anterior aspect may be excessive.ConclusionThree-dimensional analysis indicated that rotational acetabular osteotomy achieved favorable bony coverage. Further investigations are necessary to determine the ideal bony coverage after rotational acetabular osteotomy.

Total Hip Arthroplasty in a Patient with Oto-Spondylo-Megaepiphyseal Dysplasia Planned by Three-Dimensional Motion Analyses and Full-Scale Three-Dimensional Plaster Model of Bones

We present the case of a 28-year-old woman with oto-spondylo-megaepiphyseal dysplasia, which is a rare skeletal disorder, who underwent bilateral total hip arthroplasty. Full-scale three-dimensional plaster model of the acetabulum and the femur provided us with a feasible preoperative plan. Pre- and postoperative three-dimensional motion analyses proved a significant improvement in her ambulation and confirmed the efficacy of total hip arthroplasty. In conclusion, full-scale three-dimensional plaster models of the bone and three-dimensional motion analyses were useful for total hip arthroplasty in patients with skeletal dysplasia.