Lecture 4-VCS 80630-Fall 2023-Bone Healing & Complications-Malek.pdf

BONE HEALING AND COMPLICATIONS https://boneresearchsociety.org Dr. Sarah Malek VCS 80630 – Small Animal Surgery Fall 2023 LEARNING OBJECTIVES • Describe different types of bone healing • Outline contributing factors to bone healing • List different types of ossification • List and describe the 4...

BONE HEALING AND COMPLICATIONS https://boneresearchsociety.org Dr. Sarah Malek VCS 80630 – Small Animal Surgery Fall 2023 LEARNING OBJECTIVES • Describe different types of bone healing • Outline contributing factors to bone healing • List different types of ossification • List and describe the 4A’s of radiographic bone healing • List and describe common complications of bone healing • List general treatment options for complications of bone healing • Describe types of bone grafts and their function BONE HEALING ESSENTIALS Local factors • Blood supply • Cellular interactions with local and systemic influences • Balanced function of osteoblast and osteoclasts • Stability at fracture site Systemic factors • Nutritional support • Systemic health • Age INTACT BONE BLOOD SUPPLY Endosteal blood flow • Inner 2/3 of cortex • Centrifugal • Afferent from nutrient artery • Proximal and distal metaphyseal arteries Periosteal arteries • Outer 1/3 of cortex FRACTURED BONE BLOOD SUPPLY Periosteal supply predominates early • Originates from overlying muscles Endosteal supply disrupted initially • Re-establishes as healing progresses Why does it matter? • Healthy surrounding soft tissues and periosteum are essential for bone healing!! TYPES OF BONE HEALING Primary (Direct) • Direct bone production • Minimal to no instability at fracture A. Gap healing gap <1mm B. Contact healing (no gap) Secondary (Indirect) • Minimal instability and gap >1mm • Requires formation of callus All types followed by bone remodeling PRIMARY (DIRECT) GAP HEALING PRIMARY (DIRECT) CONTACT HEALING SECONDARY (INDIRECT) BONE HEALING Involved tissues • Hematoma (immediate) • Granulation tissue (3-4 days) • Connective tissue • Fibrocartilage • Cartilage • Mineralized bone Tissue properties Elastic Stiff SECONDARY (INDIRECT) BONE HEALING TYPES OF OSSIFICATION Endochondral ossification • Bone forms from cartilage • Metaphyseal and epiphyseal growth plates • Secondary bone healing Intramembranous ossification • Bone forms directly from connective (fibrous) tissue • Primary gap bone healing • Distraction osteogenesis BONE REMODELING • Bone remodels along lines of stress (Wolff’s law) • Reduction of fracture callus size over time • Continuous osteoblast-osteoclast function GO TO THE POLLS! What do you think is the best type of bone healing? • Primary (direct) • Secondary (Indirect) • They are both good as long as the fracture heals without complications Respond at: PollEV.com/sarahmalek124 on app OR Text SARAHMALEK124 to 22333 once to join then text A,B, C for your response ASSESSMENT OF BONE HEALING Based on orthogonal radiographs 4A’s of fracture assessment 1.Apposition 2.Alignment 3.Apparatus 4.Activity S: Surrounding soft tissues and bones ASSESSMENT OF BONE HEALING IMAGE REQUIREMENTS Standard orthogonal views • • • • Optimal machine setting Optimal patient positioning Remove bandages Consistency in series overtime Additional views if • Implant superimposition on fracture site • Superimposed adjacent bones 4 A’S: APPOSITION Ideally > 50% contact of fractured surfaces • When possible or necessary Apposition assessment • Acceptable? • If changing overtime • Early phases of healing? • Instability? • Infection? 4 A’S: ALIGNMENT Joint above and below the fracture • Is there malalignment? Fracture fragments • Major and minor fragment alignment Requires consistency in imaging technique • Review existing previous images 4 A’S: ALIGNMENT Malalignments • • • • Valgus or varus External or internal rotation Procurvatum or recurvatum Translation in either plane Video available on Brightspace as supplementary material 4 A’s: Apparatus Evaluate all visible implants • Appropriateness • Size and position • Structural integrity • Implant loosening • Deformity • Breakage • Missing Immediate post op 6 weeks post op 4 A’S: ACTIVITY Immediate post op Preop Primary (P) bone healing • No callus formation • Initial radiolucency at fracture line Secondary (S) bone healing • • • • Limited resorption/rounding of fragments Peripheral callus Fracture line disappears Bone remodeling P 24wks post op 12wks post op S 4 A’S: ACTIVITY No activity is normal if • Immediately after sustaining fracture • Early postoperative assessment Fracture is radiographically healed if 1 • Continuity of cortex is restored • No visible fracture/gap Clinical union is different from biological union • Bridging callus or no fracture line • Across minimum of 3 of 4 cortices 2 3 4 BONE HEALING COMPLICATIONS Malunion • Fracture healed in malalignment Delayed union • Healing not progressing in the expected time frame Non-union • Failure of healing Osteomyelitis • Inflammation of bone, soft tissue elements of the marrow, endosteum, periosteum and vascular channels MALUNION Long-term impact on adjacent joints • Joint incongruity • Osteoarthritis • Direct impact: articular fracture • Indirect: abnormal loading of joints Limb function impairment • Variable based on severity MALUNION Treatment of severe cases • Corrective osteotomy/ostectomy • Acute • Delayed +/-limb lengthening* *Dogs and cats adapt relatively well to malunions that result in limb shortening • Compensation by adjacent joints CORRECTIVE OSTEOTOMIES Acute correction • Single stage osteotomy or ostectomy • Internal/external fixation methods CORRECTIVE OSTEOTOMIES Delayed correction • Staged procedures: complex deformities • Limb lengthening procedures • Distraction osteogenesis A. Gradual distraction • limb lengthening B. Gradual transport of bone segment • Large bony defects DELAYED CORRECTIVE OSTEOTOMY DISTRACTION OSTEOGENESIS A. Gradual distraction Start Finish DELAYED CORRECTIVE OSTEOTOMY DISTRACTION OSTEOGENESIS B. Gradual transport of bone segment Start Finish DELAYED UNION Why is it delayed? • Local factors • Instability at fracture site • Infection • Neurological deficits • Health of local soft tissues and periosteum • Initial trauma • Subsequent iatrogenic trauma DELAYED UNION Stability factors related to constructs • Too weak • Fracture instability • Implant failure: partial-complete • Too stiff (stress protection/shielding) • Osteopenia • Re-fracture of bone DELAYED UNION Why is it delayed? • Systemic factors • Systemic health • Extrinsic factors • Owner compliance • Patient compliance TREATMENT OF DELAYED UNION • Early detection • Identify cause(s) • Address underlying causes • Prevent from progressing to non-union • May or may not need surgical intervention NON-UNION • Vascular (Viable) • Inadequate healing response • Common causes • Instability • Infection • Avascular (Non-viable) • Biologically inactive • Limited or no callus formation • Usually occur as an end-stage version of vascular nonunion or when vascular supply is insufficient VASCULAR (VIABLE) NON-UNION Sub classification based on callus volume • Hypertrophic (elephant’s foot) • Moderately hypertrophic (horse’s foot) • Oligotrophic • No radiographic activity • Biologic activity at cellular level AVASCULAR (NONVIABLE) NON-UNION Sub classification • Dystrophic • Necrotic (e.g., sequestrum) • Defect (gap filled with fibrous tissue) • Atrophic (dead bone phagocytosed) Sequestrum: Isolated necrotic, non-viable bone fragment Involucrum: Viable layer of bone formed around a sequestrum TREATMENT OF NON-UNION Early surgical intervention • Curettage of fibrous tissue and necrotic bone • Opening of medullary cavity • Stabilization of the fracture • Remove and replace loose/broken implants • Bone grafting • If present, treat osteomyelitis (infection) Treatment is challenging, may require multiple surgeries, can take a long time, $$$, and may not be successful BONE GRAFT “Bone or bone substitute placed into spaces around a broken bone, or within defects in bone to aid bone healing” BONE GRAFT PROPERTIES Osteogenesis • New bone formation from transferred osteoblasts • Cancellous bone > bone marrow Osteoinduction • Promote progenitor migration and proliferation • Bone morphogenetic proteins (BMPs) Osteoconduction • Graft acts as a scaffold for new bone formation Osteopromotion • Enhancement of osteoinduction • Platelet rich plasma SOURCES OF BONE GRAFT Autograft • Donor and recipient are the same individual • Best osteogenic potential • Only 10% viable osteogenic properties Allograft • Donor and recipient are the same species • Commercially available Xenograft • Donor and recipient are different species • Clinically not very useful OSTEOMYELITIS • Significantly affects bone healing • Patient morbidity/mortality • Etiology – Bacteria (most common) – Others: fungi, viruses, foreign material/corroded implants • Implant associated osteomyelitis 1. Protein precipitation on implant surface 2. Surface colonization by bacteria 3. Biofilm formation (Slime): physical and chemical barrier IMPLANT ASSOCIATED OSTEOMYELITIS Radiographic signs • Can be hard to distinguish from normal healing – immature patients or large calluses • Bone lysis • Irregular periosteal reaction • Delayed healing/non-union/malunion • Implant failure • Sequestrum formation GO TO THE POLLS! Which scenario has a chance for the fracture to heal? • Uncontrolled infection and unstable implants • Controlled infection and stable implants • No infection and unstable implants Respond at: PollEV.com/sarahmalek124 on app OR Text SARAHMALEK124 to 22333 once to join then text A,B, C for your response TREATMENT OF OSTEOMYELITIS Address contributing factors • Instability • Focal abscess/draining tracts, devitalized tissue • Control infection • Culture-directed antibiotic therapy – Systemic +/- local • Continue antibiotics until bone is healed Remove implants after bone healing is completed • Biofilm on implants does not resolve IMPLANT ASSOCIATED OSTEOMYELITIS preop Immediate post op 2 months post op 3 months post op IMPLANT ASSOCIATED OSTEOMYELITIS 6 months so far REDUCING HEALING COMPLICATIONS Surgical strategies • Halsted’s principles • Achieve adequate stability at fracture site • +/-Bone grafting • Case follow up Non-surgical approach • Careful case selection • Technical expertise • Case follow up FACILITATING BONE HEALING Postoperative strategies • Meticulous follow up rechecks • Owner education on after care instructions • Activity restrictions • Implant care (e.g., external fixators) • Surgical incision care • Bandage care (e.g., casts and splints) TAKE HOME MESSAGES • Bone healing is complicated and is affected by intrinsic and extrinsic factors. • Different mechanisms of bone healing can produce different radiographic features. • Understanding complications of bone healing should guide our preventative and treatment strategies. • Bone grafts come in different forms with different properties to expedite bone healing when needed. • Facilitating healing in face of osteomyelitis requires controlling infection and maintaining stability at the fracture site with subsequent implant removal.