United KingdomThe Main Issue of Large Diameter MoM Total Hip Arthroplasty: The Taper Junction PAPER NO. 562
Karren M. Takamura, BA, Los Angeles, CA
David Langton, Gateshead, United Kingdom
Jamshid N. Gandhi, MBBS, Coxhoe, Durham, United Kingdom
Antoni Nargol, FRCS, Yarm, United Kingdom
Thomas Joyce, PhD, Newcastle Upon Tyne, United Kingdom
James Lord, MSc, Newcastle Upon Tyne, United Kingdom
Raghavendra P. Sidaginamale, Shrewsbury, United Kingdom
INTRODUCTION: The modular junction of metal on metal (MoM) total hip replacements (THR) is an important source of metallic debris. This metallic debris can precipitate an immune response leading to potentially catastrophic soft tissue damage as well as osteolysis.
METHODS: We carried out a prospective study using custom techniques to analyze one of the largest collections of failed MoM THRs in the world. All explants from patients who had suffered adverse reactions to metal debris (ARMD) were included in this study. These explants included: 40 36mm THRs (one manufacturer), and 90 resurfacing head THRs from several manufacturers. Volumetric wear analysis of the bearing surfaces and taper junctions was carried out using a coordinate measuring machine. These values were compared to serum and whole blood prerevision metal ion concentrations from the corresponding patients. Scanning electron microscopy was used to assess the chemical composition of the wear debris.
RESULTS: All explants retrieved from ARMD patients were found to have abnormal areas of wear either at the bearing surface, the taper junction or both. Characteristic patterns of wear were identified on the internal surfaces of the tapers which appeared to reflect exactly the morphology of the mated stems. Taper wear depths reached in excess of 100 microns however rarely did taper material loss exceed a volume of 4mm3. In only 50% of patients with extensive taper damage were blood/serum metal ion concentrations greater than the threshold suggested by the MHRA.
DISCUSSION AND CONCLUSION: Taper wear is a major cause of concern for large head MoM THRs. It does not appear to be limited to specific designs.
Karren M. Takamura, BA, Los Angeles, CA
David Langton, Gateshead, United Kingdom
Jamshid N. Gandhi, MBBS, Coxhoe, Durham, United Kingdom
Antoni Nargol, FRCS, Yarm, United Kingdom
Thomas Joyce, PhD, Newcastle Upon Tyne, United Kingdom
James Lord, MSc, Newcastle Upon Tyne, United Kingdom
Raghavendra P. Sidaginamale, Shrewsbury, United Kingdom
INTRODUCTION: The modular junction of metal on metal (MoM) total hip replacements (THR) is an important source of metallic debris. This metallic debris can precipitate an immune response leading to potentially catastrophic soft tissue damage as well as osteolysis.
METHODS: We carried out a prospective study using custom techniques to analyze one of the largest collections of failed MoM THRs in the world. All explants from patients who had suffered adverse reactions to metal debris (ARMD) were included in this study. These explants included: 40 36mm THRs (one manufacturer), and 90 resurfacing head THRs from several manufacturers. Volumetric wear analysis of the bearing surfaces and taper junctions was carried out using a coordinate measuring machine. These values were compared to serum and whole blood prerevision metal ion concentrations from the corresponding patients. Scanning electron microscopy was used to assess the chemical composition of the wear debris.
RESULTS: All explants retrieved from ARMD patients were found to have abnormal areas of wear either at the bearing surface, the taper junction or both. Characteristic patterns of wear were identified on the internal surfaces of the tapers which appeared to reflect exactly the morphology of the mated stems. Taper wear depths reached in excess of 100 microns however rarely did taper material loss exceed a volume of 4mm3. In only 50% of patients with extensive taper damage were blood/serum metal ion concentrations greater than the threshold suggested by the MHRA.
DISCUSSION AND CONCLUSION: Taper wear is a major cause of concern for large head MoM THRs. It does not appear to be limited to specific designs.
