Patellar Tendon Bearing Cast — Biomechanics, Clinical Uses and Advantages
DNB Orthopaedics • October 2023 • Paper I • Question 6 • 10 Marks [5+3+2]
Introduction
The Patellar Tendon Bearing (PTB) cast, also called the Sarmiento cast, is a functional below-knee cast designed to permit controlled weight bearing while reducing the load transmitted directly through the tibial fracture site.
It works by transferring a portion of axial load from the foot and distal tibia to pressure-tolerant soft-tissue and bony areas around the proximal leg, particularly the patellar tendon region and tibial condylar flares.
Core principle: Functional loading + soft-tissue compression + controlled fracture micromotion can maintain alignment and promote secondary bone healing.
Definition
A PTB cast is a well-molded below-knee functional cast that permits weight bearing by redistributing axial load away from the distal leg and fracture site toward proximal pressure-tolerant areas around the knee.
It is generally used after the acute swelling has settled and when the fracture has achieved sufficient stability for functional treatment.
Sarmiento Functional Bracing Concept
Augusto Sarmiento popularized functional treatment of tibial shaft fractures using a close-fitting cast or brace that allows early knee movement and controlled weight bearing.
The philosophy is…