Long-term results of the metal-cancellous cementless Lübeck total hip arthroplasty: a critical review at 12.8 years.

INTRODUCTION

The influence of a spongy metal surface total hip arthroplasty (THA) (S&G, ESKA, Lübeck, Germany) on the clinical, psychometric, and radiograhic long-term results were examined.

MATERIAL AND METHODS

An amount of 137 THA with the cementless spongy metal Lübeck hip prosthesis were evaluated long-term, radiographically and clinically, with a mean follow-up time of 12.8 years (range 10.1-14.9 years). The MOS SF-36 was used to assess the health-related quality of life (HRQL).

RESULTS

Cumulative survival rates were 90% (+/-8%) for the cups and 86% (+/-5%) for the stems at 14.9 years. Four stems fractured at the middle part (3%) without major trauma. In the remaining patients the clinical results expressed as Harris Hip Score (HHS) averaged 88 (range 34-100). Patients above 60 years undergoing THA had no significant difference in HRQL (MOS SF-36) in comparison to the age-matched healthy population (P>0.05). Patients younger than 60 years had scores lower than normal in the physical function domains (P<0.01), but were comparable in the mental health domains (P>0.05). Radiolucent lines and bone atrophy related to stress shielding by distal fixation were found in the periprosthetic Gruen Zone I (19.8, 16.8%) and VII (10.3, 27.1%) of the proximal femur.

DISCUSSION

Whereas the rate of aseptic cup failures of the cementless spongy metal Lübeck hip prosthesis is among the best, the failure rate of the stems is attributable to osteolysis of the proximal femur. The fractures of the stem may be attributed to the combination of the lack of proximal support, the fully porous stem made of a cast cobalt-chrome-molybdenum alloy, and the narrow dimension of the stem core. The long-term results of the spongy metal cup are good, whereas the high loosening and fracture rate of fully coated stem are a source of concern especially with regard to the difficult revision scenario with frequent massive bone loss.