Cortical hypertrophy in total hip arthroplasty with cementless stem

Case contributed by Dr Domenico Nicoletti

Presentation

Incidental finding on postoperative control radiography.

Patient Data

Age: 60 years
Gender: Female

Postoperative radiograph in right hip prosthesis. Normal cortical thickness with no signs of stress shielding. There is large subchondral bone cyst in the right acetabulum.
 

X-ray

Two years post-operative

Two-year post-operative radiograph demonstrating distal cortical hypertrophy and proximal stress shielding.  There is a focal-type cortical hypertrophy to distal femoral, in Gruen zones 3-5. There is also stress shielding with loss of the medial cortex density below the minor trochanter (Gruen zone 7) and greater trochanter (Gruen zone 1) with calcar resorption as different parts of reactive bone remodeling. Unchanged the subchondral cyst of the right acetabulum.

Case Discussion

Cortical hypertrophy is a fusiform enlargements of the cortical bone in the bone-implant region, which appeared in Gruen zones 3 or 5, ‘the focal type,’ whereas if cortical hypertrophy appear in zones 2, 3, 4, 5, and 6 as ‘the diffuse type’. Unloading of the proximal medial femoral cortex is usually associated with an increased bone strain at the distal part of the prosthesis, which may cause distal femoral cortical hypertrophy and then this pattern of abnormal loading might cause proximal osteopenia (Wolff’s law “where the bone is stressed it hypertrophies, where it is discharged it is reabsorbed”).

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Case information

rID: 87298
Published: 26th Feb 2021
Last edited: 2nd Mar 2021
Inclusion in quiz mode: Included

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