Loudon and Charnley (1980) describe a radiographic method for measuring femoral prosthesis subsidence after cemented total hip arthroplasty, then apply it to compare 100 conventional-stem hips against 75 hips with the Charnley flanged (Cobra) stem to determine whether stem geometry influences implant stability.
When reviewing serial post-op hip radiographs, use a fixed bony landmark (e.g., trochanteric wire or cortical reference) to track stem-tip position — changes under ~1.5 mm are within measurement noise, but progressive descent or a transverse lucency at the stem tip signals cement fracture and mechanical failure of the cement-stem interface.
This paper established that stem geometry, not just cement technique or metallurgy, is a primary determinant of subsidence risk in cemented THA.
Loudon and Charnley (1980) describe a radiographic method for measuring femoral prosthesis subsidence after cemented total hip arthroplasty, then apply it to compare 100 conventional-stem hips against 75 hips with the Charnley flanged (Cobra) stem to determine whether stem geometry influences implant stability.
When reviewing serial post-op hip radiographs, use a fixed bony landmark (e.g., trochanteric wire or cortical reference) to track stem-tip position — changes under ~1.5 mm are within measurement noise, but progressive descent or a transverse lucency at the stem tip signals cement fracture and mechanical failure of the cement-stem interface.
This paper established that stem geometry, not just cement technique or metallurgy, is a primary determinant of subsidence risk in cemented THA.