Measurement of ground reaction forces in cats 1 year after femoral head and neck ostectomy

The objective of this study was to compare ground reaction forces (GRFs) of a group of cats after femoral head and neck ostectomy (FHO) with those of a historical control group.

We searched the database of the Small Animal Clinic of the Veterinary University in Vienna for cats that had undergone unilateral FHO at least 1 year previously. Owners were telephoned and invited to the clinic with their cats for a re-examination. An in-house owner questionnaire-based evaluation, complete orthopaedic examination, hip radiography and gait analysis with a pressure-sensitive plate were performed, and results were compared within and between groups (FHO group and control group [CG]).

Seventeen cats that had undergone FHO (FHO group) at least 1 year previously and 15 healthy cats (CG) from a previous study were included. Measured GRFs (peak vertical force and vertical impulse [IFz] normalised to total force [%TF]) of the FHO legs were lower than those of the other legs of the FHO group and the legs of the CG. Results of the owner questionnaire were generally good and did not match the results of the GRF comparison. Furthermore, the gaits evaluated during the orthopaedic examination did not correlate with the measured GRFs where we identified a certain degree of lameness (reduced IFz, %TF) in all cats. Cats with limb shortening (dorsally displaced major trochanter major) were not revealed to have different GRF measurements.

This is the first study to assess GRFs in a large group of cats that had undergone FHO, comparing findings with those in healthy cats. Even if the differences are statistically significant, but rather small, our findings point to a long-term residual gait abnormality that could be detected using a pressure-sensitive plate but not always with an orthopaedic examination, in cats 1 year after FHO.