Gruen and colleagues used serial radiographs to identify the mechanical patterns by which cemented stem‑type femoral components loosen, as a basis for classifying that loosening.
Retrospective serial radiographic review of 389 cemented total hip replacements in 301 patients, followed 6 months to 6 years (mean about 3).
Methods
Design
Retrospective serial radiographic review
Patients
350 consecutive patients with 454 hips screened
389 hips in 301 patients analyzed
65 hips excluded for sepsis, radiolucent cement or follow‑up under 6 months
Charnley and Trapezoidal‑28 stems
Follow‑up 6 months to 6 years (mean about 3)
Basis
Seven zones around the stem on the AP radiograph
Looseness defined as cement fracture or lucency between stem and cement or between cement and bone
Loosening defined as progressive change on serial films
Key Findings
Serial films showed progressive loosening in 56 of the 389 hips (14.4%), and all 56 were classified into the four mechanical failure modes.
At least one radiographic sign of looseness was present in 76 of 389 hips (19.5%).
Lucency at the stem‑cement interface appeared in 40 hips, and in 16 of these it was already visible on the immediate postoperative film, which the authors linked to surgical technique.
Only 7 of the 56 progressively loosening stems needed revision for pain and restricted function, 2% of all hips studied.
The authors stressed that a failure mode meant loss of radiographic fixation or cement integrity, not necessarily a symptomatic hip.
Board pearl
Both stem fractures in this series had failed in Mode IV (bending cantilever), and the authors noted that such fractures were preceded by loss of proximal cement support.
Authors' conclusion
The 4 modes of failure characterizing stem-type component progressive loosening mechanisms consisted of stem pistoning within the acrylic (3.3%), cement-embedded stem pistoning with the femur (5.1%), medial midstem pivot (2.5%), calcar pivot (0.7%) and bending (fatigue) cantilever (3.3%).
Gruen and colleagues used serial radiographs to identify the mechanical patterns by which cemented stem‑type femoral components loosen, as a basis for classifying that loosening.
Retrospective serial radiographic review of 389 cemented total hip replacements in 301 patients, followed 6 months to 6 years (mean about 3).
Methods
Design
Retrospective serial radiographic review
Patients
350 consecutive patients with 454 hips screened
389 hips in 301 patients analyzed
65 hips excluded for sepsis, radiolucent cement or follow‑up under 6 months
Charnley and Trapezoidal‑28 stems
Follow‑up 6 months to 6 years (mean about 3)
Basis
Seven zones around the stem on the AP radiograph
Looseness defined as cement fracture or lucency between stem and cement or between cement and bone
Loosening defined as progressive change on serial films
Key Findings
Serial films showed progressive loosening in 56 of the 389 hips (14.4%), and all 56 were classified into the four mechanical failure modes.
At least one radiographic sign of looseness was present in 76 of 389 hips (19.5%).
Lucency at the stem‑cement interface appeared in 40 hips, and in 16 of these it was already visible on the immediate postoperative film, which the authors linked to surgical technique.
Only 7 of the 56 progressively loosening stems needed revision for pain and restricted function, 2% of all hips studied.
The authors stressed that a failure mode meant loss of radiographic fixation or cement integrity, not necessarily a symptomatic hip.
Board pearl
Both stem fractures in this series had failed in Mode IV (bending cantilever), and the authors noted that such fractures were preceded by loss of proximal cement support.
Authors' conclusion
The 4 modes of failure characterizing stem-type component progressive loosening mechanisms consisted of stem pistoning within the acrylic (3.3%), cement-embedded stem pistoning with the femur (5.1%), medial midstem pivot (2.5%), calcar pivot (0.7%) and bending (fatigue) cantilever (3.3%).