Muller describes the University of Berne total hip replacement system used from 1966 to 1970. The construct pairs a polyethylene acetabular cup with a 32 mm chromium-cobalt-molybdenum femoral head on a cemented standard stem. The paper walks through the full surgical technique, instrumentation, and a detailed catalog of complications.
This paper captures the reasoning behind one of the foundational design choices in modern hip arthroplasty: why we articulate a metal head against polyethylene rather than metal against metal.
Muller's argument is mechanical. Metal-to-metal makes 3-point contact and generates friction that loosened cups within the first 6 months. Polyethylene deforms slightly to spread load across the whole surface and has a low friction coefficient, so cup loosening became almost unknown.
The orientation targets are still testable today. Commit the cup to 45 degrees inclination with 10-15 degrees anteversion and the head to 10 degrees antetorsion. Understand the failure modes: too little cup anteversion dislocates posteriorly, too much dislocates anteriorly.
Note the approach-dependent nerve risk. The anterolateral approach spares the sciatic nerve, while the posterior (dorsal) approach carries frequent peroneal palsies. Finally, the cement pearl: never pressurize cement until it no longer sticks to the glove, because forcing liquid monomer under pressure can cause fatal embolic and toxic effects.
Muller describes the University of Berne total hip replacement system used from 1966 to 1970. The construct pairs a polyethylene acetabular cup with a 32 mm chromium-cobalt-molybdenum femoral head on a cemented standard stem. The paper walks through the full surgical technique, instrumentation, and a detailed catalog of complications.
This paper captures the reasoning behind one of the foundational design choices in modern hip arthroplasty: why we articulate a metal head against polyethylene rather than metal against metal.
Muller's argument is mechanical. Metal-to-metal makes 3-point contact and generates friction that loosened cups within the first 6 months. Polyethylene deforms slightly to spread load across the whole surface and has a low friction coefficient, so cup loosening became almost unknown.
The orientation targets are still testable today. Commit the cup to 45 degrees inclination with 10-15 degrees anteversion and the head to 10 degrees antetorsion. Understand the failure modes: too little cup anteversion dislocates posteriorly, too much dislocates anteriorly.
Note the approach-dependent nerve risk. The anterolateral approach spares the sciatic nerve, while the posterior (dorsal) approach carries frequent peroneal palsies. Finally, the cement pearl: never pressurize cement until it no longer sticks to the glove, because forcing liquid monomer under pressure can cause fatal embolic and toxic effects.