Evaluation of depth gauge accuracy in a canine tibial plateau leveling osteotomy model.

Objective: To evaluate the accuracy of six depth gauges used in three tibial plateau leveling osteotomy (TPLO) plate holes.

Study Design: Ex vivo experimental study.

Animals And Sample Population: Cadaveric canine limbs (n = 10), one 25-mm-thick wood board, and one 33.8-mm-diameter polyvinyl chloride (PVC) pipe.

Methods: A TPLO was performed on 10 canine cadaveric pelvic limbs. Three 3.5-mm plate holes were filled with screws. The remaining three plate holes: a compression hole, a combination compression-locking hole, and a stacked combination compression-locking hole were measured by three observers using six commercial depth gauges and using a micrometer as gold standard. The process was repeated on one wood board and one PVC pipe.

Results: Bone measurements collected using two depth gauges with base diameter < 5 mm were smaller than measurements collected using the four depth gauges with base diameter > 5.5 mm (p ranging from < .001 to .038). Mean depth gauge measurements were smaller than micrometer measurements by 2.20 mm for the compression hole, 0.82 mm for the combination hole, and 3.57 mm for the stacked combination hole. Measurement differences among depth gauges were also present for wood board and PVC pipe measurements. Bone measurement variability between depth gauges was less for the combination and compression holes than for the stacked combination hole.

Conclusion: Depth gauges lacked accuracy. Measurements differed among gauges and measurement variability varied based on plate hole geometry.

Clinical Relevance: Depth gauge measurement accuracy varies based on measuring devices and on 3.5-mm plate hole geometry.