Primary total hip arthroplasty with Asian-type AML total hip prosthesis: follow-up for more than 10 years

Failure rates of Asian-type anatomic medullary locking stemmed metal-on-metal total hip replacement: A cause for adverse tissue reactions to metal debris (ARMD)

BACKGROUND

Adverse tissue reaction to metal debris (ARMD) as a secondary complication of Metal-on-metal total hip replacement (MoM THR) has been of concern. We have been performing cementless MoM THR using an Asian-type anatomic medullary locking (AML) stem. The purpose of this study is to examine the incident rate of ARMD, and the implant survival rate.

METHODS

The study included 187 patients (211 hip joints) who underwent MoM THR between February 2007 and November 2009 at our hospital and who were followed up for a minimum of 6 years. The cases included 174 female joints and 37 male joints. The average age at the time of surgery was 68.4 years. The average postoperative follow-up period was 87.5 months.

RESULTS

ARMD was observed in 23 joints postoperatively, and the incidence rate was 10.9%. Most of the instances occurred within the first 30 months postoperatively. Revision surgery was performed for 14 joints after conservative treatment failed, and we changed the bearing surface. During the intraoperative observation, black-colored deposition of metal debris on the head-neck junction was observed in 13 cases. Kaplan-Meier analysis using the replacement surgery as the end point showed that this implant has a survival rate of 93.8% 7 years after the primary surgery.

CONCLUSIONS

We conclude that the major cause of failure of Asian-type AML stemmed MoM THR is likely the breakage of the fixation between the taper neck and metal head at the head-neck junction.

Cementless Total Hip Arthroplasty in Hip Dysplasia with an Extensively Porous-Coated Cylindrical Stem Modified for Asians: A 12-Year Follow-Up Study

Long-term outcomes of primary cementless total hip arthroplasty were examined for 198 hips of Asian patients with developmental dysplasia of the hip. AML stems were modified for patients' relatively small physique. Stable fixation was achieved despite various proximal femoral deformities. At follow up (mean 12.1 years), radiographs demonstrated fixation in all hips, with 100% stem survivorship. Radiographic changes revealed that the severity of stress-shielding was mild in 55% of hips, moderate in 26%, and severe in 19%. Longer follow up is needed to determine whether these changes will develop into clinical manifestations. A distal fixation stem can be a useful reconstruction option when application of a proximal fixation stem in primary total hip arthroplasty is difficult for various reasons.

Design process of cementless femoral stem using a nonlinear three dimensional finite element analysis

BACKGROUND

Minimal available information concerning hip morphology is the motivation for several researchers to study the difference between Asian and Western populations. Current use of a universal hip stem of variable size is not the best option for all femur types. This present study proposed a new design process of the cementless femoral stem using a three dimensional model which provided more information and accurate analysis compared to conventional methods.

METHODS

This complete design cycle began with morphological analysis, followed by femoral stem design, fit and fill analysis, and nonlinear finite element analysis (FEA). Various femur parameters for periosteal and endosteal canal diameters are measured from the osteotomy level to 150 mm below to determine the isthmus position.

RESULTS

The results showed better total fit (53.7%) and fill (76.7%) canal, with more load distributed proximally to prevent stress shielding at calcar region. The stem demonstrated lower displacement and micromotion (less than 40 μm) promoting osseointegration between the stem-bone and providing primary fixation stability.

CONCLUSION

This new design process could be used as a preclinical assessment tool and will shorten the design cycle by identifying the major steps which must be taken while designing the femoral stem.

Midterm results of hybrid total hip arthroplasty for treatment of osteoarthritis secondary to developmental dysplasia of the hip-Chinese experience

This study was designed to evaluate the midterm results of hybrid total hip arthroplasty in a consecutive series of 45 Chinese patients with osteoarthritis secondary to dysplastic hip. The average follow-up was 6.6 years. A total of 24 hips were classified as dysplasia, 20 hips as low dislocation, and 13 hips as high dislocation. The preoperative Harris score was 46.19 +/- 18.01, which improved to 91.78 +/- 3.52 at the final follow-up. The rate of polyethylene liner wear was 0.27 mm/y. Osteolysis was identified around 5 acetabular components and 13 femoral components. With the use of loosening or revision as the end point for failure, the survival rate was 1.0. We suggest that hybrid total hip arthroplasty in Chinese developmental dysplasia of hip patients has favorable results at midterm follow-up, even though their lifestyle includes more deep flexion of the hip. There is no significant difference of postoperative Harris score with increasing severity of dysplasia.