Fracture healing is a unique biological process where bone regenerates its original structure rather than forming a scar. Understanding the cellular biology, Perren's strain theoryand the Diamond Concept is essential for choosing the right orthopaedic fixation. In this comprehensive deep dive, we explore exactly how primary and secondary bone healing occur. ⏱ Chapters 0:00 Intro 0:10 Ch1 Card 0:58 Ch1 01 1:59 Ch1 02 2:49 Ch2 Card 3:26 Ch2 01 4:03 Ch2 02 4:37 Ch2 03 5:12 Ch3 Card 6:00 Ch3 01 6:46 Ch3 02 7:37 Ch3 03 8:21 Ch4 Card 9:02 Ch4 01 9:34 Ch4 02 10:09 Ch4 03 10:42 Ch4 04 11:15 Ch5 Card 12:01 Ch5 01 12:42 Ch5 02 13:25 Ch5 03 14:10 Ch6 Card 14:49 Ch6 01 15:27 Ch6 02 16:03 Ch6 03 16:35 Ch7 Card 17:15 Ch7 01 17:57 Ch7 02 18:33 Ch7 03 19:22 Ch8 Card 20:16 Ch8 01 21:10 Ch8 02 22:01 Closer This complete orthopaedic lecture covers the entire spectrum of fracture healing, from the basic science of bone matrix composition and cellular physiology to the biomechanics dictating clinical decision-making. We explore the three distinct healing pathways—primary, secondaryand distraction osteogenesis—alongside the four phases of indirect healing and the critical factors that influence bony union. Whether applying a compression plate for absolute stability or an intramedullary nail for relative stability, this video provides the foundational knowledge required to understand bone repair. 🦴 IN THIS VIDEO YOU'LL LEARN • The unique cellular physiology of osteoblasts, osteocytesand osteoclasts in bone regeneration • The difference between primary healing via cutting cones and secondary healing via enchondral ossification • How Perren's strain theory dictates whether granulation tissue, cartilageor bone can form in a fracture gap • The four sequential phases of secondary fracture healing: inflammation, soft callus, hard callusand remodelling • How the Diamond Concept (Cells, Scaffold, Signals, Mechanical Stability) defines the requirements for fracture union • Why absolute stability requires compression plating while relative stability utilises intramedullary nails and bridging fixation • The composition of the bone matrix, including hydroxyapatite, Type I collagenand key non-collagenous proteins • How blood supply changes from centrifugal to centripetal flow following medullary disruption • The key clinical and radiographic signs of fracture union, including the RUST score criteria ⏱️ CHAPTERS 📌 KEY TAKEAWAYS ✔️ Bone heals by true regeneration, restoring its original molecular and structural architecture without leaving scar tissue. ✔️ Primary healing requires absolute stability with less than 2% strain and leaves no callus, utilising Haversian cutting cones. ✔️ Secondary healing requires relative stability (2-10% strain) and progresses through a visible callus via enchondral ossification. ✔️ Soft callus is made of Type II collagen (cartilage), while hard callus is composed of Type I collagen (woven bone). ✔️ Nicotine, infectionand poor soft tissue envelopes are potent biological inhibitors that significantly increase non-union risk. 👩⚕️ WHO THIS IS FOR This video is designed for orthopaedic surgery trainees, junior doctorsand medical students seeking a rigorous understanding of bone physiology. It also serves as an excellent refresher for senior clinicians and provides highly detailed, accessible explanations for curious patients interested in orthopaedics. 📚 RELATED TOPICS: AO Principles of Fracture Fixation and Absolute vs Relative Stability · Perren's Strain Theory and Fracture Biomechanics · The Diamond Concept in Non-Union Management · Bone Grafting, BMPsand Osteoinductive Signals · Ilizarov Method and Distraction Osteogenesis Principles · RUST Score and Radiographic Assessment of Fracture Union 🔗 More free orthopaedic teaching at Orthovellum.com — subscribe for weekly videos. 🎨 CREDITS • Original Orthovellum production. ⚠️ DISCLAIMER: Educational only — not individual medical advice. Always consult a qualified clinician for diagnosis and treatment. #fracturehealing #orthopaedics #orthopedicsurgery #bonehealing #trauma #primaryhealing #secondaryhealing #bonescience #osteobiology #fracture #orthobullets #medicine