Naohiko Mashima

Outcomes of surgical treatment for cervical myelopathy in patients more than 75 years of age.

STUDY DESIGN Retrospective study on the results of surgical treatment of compressive cervical myelopathy in patients more than 75 years of age. OBJECTIVES To investigate clinical features and surgical outcomes of compressive cervical myelopathy in aged patients and to discuss the role of surgical treatment. SUMMARY OF BACKGROUND DATA There are few data focused on the outcomes of surgery in patients with cervical myelopathy who are more than 75 years of age. METHODS Seventeen patients with compressive cervical myelopathy who underwent surgery were reviewed. The average age at the time of surgery was 77.2 years. Posterior decompression in 15 patients and anterior decompression in 2 patients were performed. Neurologic deficits before and after surgery were assessed using a scoring system proposed by the Japanese Orthopaedic Association (JOA score). Independence of daily living was evaluated. Radiologic features were examined with radiographs and magnetic resonance imaging. Clinical results were compared with those of patients less than 65 years old as a control. RESULTS The preoperative mean JOA score was 6.1, the postoperative maximum JOA scores averaged 11.4, and the recovery rate was 48.4%. These were significantly inferior to scores in those less than 65 years of age. All seven of the patients who could not walk even with aids before surgery became independent in daily activities after surgery. At the final follow-up, the mean JOA score had decreased to 10.7 and the recovery rate to 39.1%. Five of nine patients whose follow-up periods were more than 5 years showed decreases in JOA score, although all patients were still ambulatory. CONCLUSIONS Surgical decompression for cervical myelopathy appears to be beneficial, even in patients more than 75 years of age, in improving neurologic function and ability to engage in activities of daily living.

Mid-term clinical and radiographic outcomes of porous tantalum modular acetabular components for hip dysplasia.

It is still challenging to perform successful cementless cup fixation during total hip arthroplasty for hip dysplasia. In this multicenter study we evaluated the clinical results of porous tantalum modular acetabular cups (TM cups) in 45 dysplastic hips with a mean follow-up period of 9.8 years. The mean Japanese Orthopaedic Association hip score improved from 48.2 preoperatively to 92.1 at the most recent follow-up. All of the cups were radiographically stable with no evidence of progressive radiolucencies or osteolysis regardless of bone grafting. Sixteen hips with bone grafts showed the integration of grafted bone without any radiolucencies. There were no revisions of TM cups. The use of TM cups for dysplastic hips provided satisfactory 10-year clinical and radiographic results.

Clinical and Laboratory Wear Studies of Zirconia-on-UHMWPE Combination in Cementless THA

We investigated the wear performance of zirconia femoral heads in vivo and in vitro. The in vivo wear rate of polyethylene against the conventional zirconia heads in cementless THA was 0.139 mm/year, which is relatively satisfactory as compared to the reported wear rates of metal-backed polyethylene against metal heads. However, there still exist some problems concerning the degradation of zirconia. Therefore, the present manufacturer has improved the conventional zirconia. The results of hip simulator testing using the improved zirconia heads were satisfactory. Thus, the current improved zirconia which is more resistant to the degradation would contribute to the polyethylene wear reduction over the extended periods. Introduction Zirconia ceramics (Y-TZP) possess high mechanical strength and excellent wear properties, which have been confirmed in numerous in vitro studies [1]. In 1985, zirconia ceramics were successfully introduced into clinical use as femoral heads in articulation with ultrahigh molecular weight polyethylene components in THA. On the other hand, there have been some concerns about the low temperature degradation associated with the long-term implantation. Therefore, zirconia ceramics have been improved by several manufacturers to eliminate such degradation. There still are only a few studies about the clinical wear behavior of zirconia-on-polyethylene bearing combination. In the present study, we measured the clinical wear of polyethylene against the conventional zirconia. In addition, we investigated the wear properties of the improved zirconia especially when articulated with crosslinked polyethylene (CPE) in the hip simulator wear tests, because CPE has recently been expected to reduce wear debris dramatically. Based on these data, we discussed the effectiveness of zirconia as one of alternate bearing materials. Materials and Methods Clinical wear measurement: Between 1992 and 1994, as a multicenter clinical trial in Japan, a total of 94 hips undergone cementless THA using a Kobelco H-5 system (Kobe Steel Ltd., Kobe, Japan), in which a 22 or 26mm modular zirconia head was used. The mechanical properties of zirconia are shown in Table 1. Among these cases, we investigated 74 hips radiographically as to the linear wear of polyethylene liner. Zirconia heads were sterilized by EtO and polyethylene liners and metal implants were sterilized with gamma irradiation. Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 823-826 doi:10.4028/www.scientific.net/KEM.240-242.823

The Relationship Between Increased Hip Range of Motion, Wear, and Locking Mechanism Failure in the Harris-Galante Acetabular Component

We performed both clinical and radiographic evaluations of 178 patients (190 hips) who had undergone cementless total hip arthroplasties using Harris-Galante I/II porous cups after an average 12-year follow-up period (range, 8-18 years). We revised 15 Harris-Galante I/II porous cups (7.8%), and the locking mechanism was broken in 10 revised cups (67%). There was a significant association between locking mechanism failure and linear polyethylene wear. We observed a significant positive correlation between linear polyethylene wear and increased ranges of motion such as flexion, adduction, and external rotation at the last follow-up visit after the primary operation. Increased ranges of motion seen in Asians induced higher linear polyethylene wear and locking mechanism failure due to impingement of the neck and cup.

A three-dimensional computed tomography study of distal femoral morphology in Japanese patients: Gender differences and component fit

BACKGROUND Previous anthropometric studies have reported gender differences in distal femoral morphology. However, to date, very few studies have investigated the knee morphology of Japanese adults and possible gender differences. The purpose of this study was to examine the distal femoral morphology of Japanese patients, to characterize anatomical differences between male and female, and to evaluate the need to create gender-specific knee prostheses. MATERIAL AND METHODS We evaluated 80 knees in 40 male and 40 female Japanese patients scheduled for total knee arthroplasty (TKA). The mediolateral (ML) and anteroposterior (AP) dimensions of the knees at different levels were measured preoperatively using three-dimensional computed tomography, and ML/AP aspect ratios were calculated. RESULTS On the distal femoral cut surface, the mean ML widths were 74.9 mm for male and 65.1mm for female, and the mean AP lengths were 63.4mm for male and 58.9 mm for female. Such values were generally smaller compared to data from European and North American studies. In this study, the mean ML/AP aspect ratios were 1.31 for male and 1.25 for female, higher than those from non-Asian regions. The ML/AP ratios of Japanese patients were negatively correlated with distal femoral AP length. CONCLUSIONS Japanese female had a relatively narrower femoral width for a given AP length than male. Our study suggests the utility of Japanese-specific implants and provides useful insights for manufacturers to design components of appropriate sizes and aspect ratios for Japanese TKA patients.

Correction of hallux valgus deformity using the center of rotation of angulation method

BackgroundTo correct a hallux valgus (HV) deformity quantitatively and prevent unexpected postoperative deformity, the center of rotation of angulation (CORA) method was applied during HV surgery.To correct a hallux valgus (HV) deformity quantitatively and prevent unexpected postoperative deformity, the center of rotation of angulation (CORA) method was applied during HV surgery.MethodsTo create a normal foot model, radiographs of 64 normal female feet were measured. Points A and B were defined as the intersection of the intermetatarsal angle and the HV angle. CORA1 and CORA2 were defined as the intersection of the axes of the first metatarsal and the first proximal phalanx in the normal and HV models, respectively. Procedures to correct HV deformity using the CORA method were devised and were applied to HV feet, which underwent a focal dome osteotomy or medial wedge osteotomy.ResultsPoint A was 2.3 times the length of the second metatarsal proximally from the top of the second metatarsal head, and point B was 0.17 times the length of the first metatarsal proximally from the top of the first metatarsal head. Two methods were used to correct the deformity. With one method, a focal dome osteotomy was performed at the first metatarsal on the circle at the CORA1 and the distal fragment was moved to the standard first metatarsal axis. The first proximal phalanx was then moved around the metatarsal head to the standard axis of the first proximal phalanx at the CORA2. With the other method, a medial wedge osteotomy was performed on or proximal to the CORA2, and the distal fragment was moved to the first standard metatarsal axis.ConclusionsWe propose a preoperative plan to use the CORA method to correct deformities that prevent translation of the axis or an angulation deformity. HV deformity can be corrected effectively using the CORA method.

Long Term Results With the Interlocking Uncemented Long Stem in Revision Hip Arthroplasty: A Mean 15-Year Follow-Up

Stem fixation is difficult to achieve in severe proximal bone loss in revision hip surgery. In this study, we sought to present the results of distally-locked stem with screws (HUCKESTEP HIP stem) in 21 revision hips with mean follow-up period of 15 years. The preoperative mean Japanese Orthopaedic Association hip score had improved from 54 to 75 points. Further revisions were required for 2 stems, in one because of infection and the other because of screws fracture and subsidence. With removal of the stem for any reason as an end-point, the cumulative survival at 15 years was 90.4%. While this study had small number, the use of this interlocking stem for revision hips with extensive proximal bone defects provided satisfactory 15-year clinical and radiographic results.