In this BoardsCast episode, we finish Tobias Chapter 44 — Bandaging, External Coaptation, and External Devices for Companion Animals with the concept that determines whether even the most advanced prosthetic device succeeds or fails: The interface determines whether the prosthesis works. A prosthesis is not just a replacement for missing limb length. It is a load-transfer system. Force has to move from the patient’s body, through the residual limb, across the skin-device interface, into the prosthesis, and finally into the ground—then back up the same chain. If that handoff fails, function fails. We break down the three dimensions of prosthetic stability: Axial stability — controls traction and compressionAngular stability — controls bendingRotational stability — controls twisting, pronation, and supinationAnd the corresponding failure modes: Pistoning = axial instabilityRocking = angular instabilityTwisting = rotational instability The key mechanical warning: Stable in one direction does not mean stable. A socket may resist axial traction perfectly and still rotate around the residual limb when torque is applied. We also break down: Why longer residual limbs generally provide better prosthetic stabilityWhy preserving useful bony landmarks can improve rotational controlWhy a longer prosthesis creates a larger lever arm and increases interface loadWhy socket fit must be snug, not tightWhy too loose causes motion and frictionWhy too tight creates pressure, ischemia, and tissue injuryWhy excessive skin mobility in dogs and cats can make socket prostheses mechanically difficultWhy hair loss, redness, licking, chewing, abrasions, and ulceration are warning signs of interface failureHow passive hinges may actually improve axial and rotational stability by letting the device move with the patient instead of fighting normal joint motionWhy prosthetic integration requires progressive functional training—from tolerance at rest to standing, walking, trotting, and normal activity Then we contrast the socket-based exoprosthesis with transdermal osseointegrated prostheses. Osseointegration bypasses the external socket and anchors directly to bone, eliminating many problems of pistoning, rocking, and skin sliding. But it creates a completely different weak link: The skin-implant barrier. You trade socket instability for the risk of chronic infection at a permanent transcutaneous interface. The clinical question becomes: “Where is the handoff failing?” For a socket prosthesis, ask whether you can control axial, angular, and rotational motion while protecting the skin. For a transdermal implant, ask whether bone fixation is stable and whether the soft tissue and skin interface can remain biologically integrated and infection-resistant. — 🎁 Simini Bonus Claim your free sample of Simini Protect Lavage (just cover shipping): https://www.simini.com/evaluation-kit Listen On: Spotify | Apple Podcasts | Amazon Music
