Influence of intra-articular injectate volume on joint surface coverage and leakage following canine elbow...

To determine whether reduced intra-articular (IA) injection volumes provide complete synovial surface coverage while minimizing leakage following canine elbow arthroscopy.

Randomized cadaveric study.

Forty elbow joints from 20 canine cadavers weighing >15 kg.

Standard medial elbow arthroscopy was performed with portals placed under arthroscopic guidance. The egress portal was created along the caudal margin of the medial epicondylar ridge, directed toward the anconeal process. A third, craniomedial instrument portal was created approximately 1 cm cranial to the camera portal. Following arthroscopy, India ink-volume-matched to whole, half, or quarter of a 0.5 mg/kg ropivacaine dose (0.75% concentration)-was injected via the egress portal. Each joint underwent 10 passive flexion-extension cycles before dissection. A masked investigator (ES) qualitatively assessed synovial surface coverage (100%, 75%-99%, 50%-74%, 25%-49%, 0%-24%) and leakage severity (mild, moderate, severe). Portal placement attempts, cadaver age, and bodyweight were recorded.

Mean cadaver age was 9.3 years (range: 1-16 years), and mean weight was 29.9 kg (range: 17.9-43.6 kg). Complete (100%) synovial surface coverage was observed in all 40 elbows, including those receiving quarter-dose injections. Leakage occurred in every dose group, with a similar distribution of mild, moderate, and severe categories. Portal placement was successful on the first attempt in 32 elbows (80%) and the second attempt in eight elbows (20%).

Reduced IA injection volumes achieved complete synovial surface coverage but did not reduce leakage severity.

Reduced intra-articular injection volumes were sufficient to achieve complete synovial surface coverage in this model, suggesting potential flexibility in clinical dosing strategies. Nonetheless, extravasation occurred at all tested volumes, reinforcing that some leakage should be expected in practice.