Pediatric Bone — Epiphysiolyses, Plastic Deformation, and Greenstick Fractures
Introduction
The pediatric skeleton differs from the adult skeleton in fundamental ways that produce distinct fracture patterns, distinct healing characteristics, and distinct management considerations. The presence of the physis (growth plate) at the ends of long bones — the cartilaginous zone of longitudinal growth — creates a unique anatomical structure that is at once the source of the remarkable healing and remodeling potential of the growing skeleton and a vulnerable region prone to specific injury patterns. The periosteum of the immature skeleton is thicker, more cellular, more vascular, and more biologically active than its adult counterpart, contributing to the unique fracture patterns and the favorable healing properties. The bone itself is more porous, more elastic, and less stiff than adult bone, producing plastic deformation without complete fracture and the characteristic greenstick fracture pattern. This final chapter of the compendium addresses the surgical anatomy and biology of pediatric bone, the Salter-Harris classification of physeal injuries, the plastic deformation and greenstick fracture patterns, and the principles of pediatric fracture management distinct from adult care. The chapter draws on Tachdjian’s Pediatric Orthopaedics, Rockwood and Green’s Fractures in Adults, Apley & Solomon’s, and Netter’s Concise Orthopaedic Anatomy.
The Physis (Growth Plate) — Anatomy and Biology
The physis is the cartilaginous plate at the metaphyseal-epiphyseal junction of growing long bones, responsible for the longitudinal growth of the skeleton. The physis is organized into characteristic zones from epiphyseal to metaphyseal side: Reserve zone: Adjacent to the epiphysis; contains chondrocytes at rest, providing the cellular source for the growth plate. Proliferative zone: Where chondrocytes actively divide in characteristic columnar arrangements, producing the cellular substrate for growth. Hypertrophic zone: Subdivided into: - Zone of maturation: Chondrocytes enlarge and produce extracellular matrix. - Zone of degeneration: Chondrocytes degenerate as the matrix calcifies. - Zone of provisional calcification: The most distal portion of the hypertrophic zone, where the matrix calcifies and provides a substrate for new bone formation. Metaphysis: The bony region adjacent to the physis, where the calcified matrix is replaced by woven bone, then by trabecular bone. The physeal failure typically occurs in the zone of provisional calcification or the zone of hypertrophy — the weakest layer of the physis — producing the characteristic Salter-Harris fracture patterns.
The vascular supply to the physis is unique: separate vessels supply the epiphyseal and metaphyseal sides, with no vessels crossing the physis itself. This vascular pattern explains why physeal fracture displacement may disrupt the epiphyseal blood supply (with consequent avascular necrosis of the epiphysis) while the metaphyseal supply remains intact. The perichondrial ring (groove of Ranvier) surrounds the physis peripherally, contributing to circumferential growth (widening) of the physis and the metaphysis. Injuries to the perichondrial ring can produce localized growth arrest.
Salter-Harris Classification of Physeal Injuries
The Salter and Harris classification (1963) divides physeal fractures into five types by the relationship of the fracture line to the physis: Type I: Fracture through the physis only, with separation of the epiphysis from the metaphysis. The fracture line passes through the zone of provisional calcification. Typically caused by shearing forces. The epiphysis displaces relative to the metaphysis. Examples: birth-related humeral or femoral physeal separations; SCFE (which is essentially a Salter- Harris I of the proximal femur — Topic Orth-19). Growth disturbance is uncommon if reduction is anatomical. Type II: Fracture through the physis with extension into the metaphysis (the “Thurston- Holland fragment” being the small metaphyseal triangle attached to the epiphysis). The most common Salter-Harris type. The fracture line passes through the zone of provisional calcification and exits through the metaphysis. Growth disturbance is uncommon with appropriate reduction. Type III: Fracture through the physis with extension into the epiphysis, crossing the joint surface. The fracture line passes through the zone of provisional calcification proximally and through the epiphyseal cartilage to the joint surface. Anatomical reduction is required because of the articular involvement; growth disturbance can occur with malreduction. Type IV: Fracture crossing the physis, the metaphysis, AND the epiphysis. The fracture line crosses all three structures. Anatomical reduction is essential; the fracture has a high risk of growth arrest because of bony bridging across the physis if not adequately reduced. Type V: Crush injury of the physis without displacement of bony fragments. The fracture is often radiographically subtle initially, with growth arrest manifesting weeks to months later. The diagnosis is often retrospective. Treatment is observation and management of the consequences if growth arrest develops. The Rang modification adds: Type VI: Injury to the perichondrial ring or periosteum producing peripheral growth arrest. Type VII: Isolated injury to the epiphysis without physeal involvement.
Type VIII: Injury to the metaphysis with potential to disrupt the blood supply to the physis. Type IX: Injury to the periosteum with potential to affect appositional growth. The classification predicts both immediate management (anatomical reduction required for types III and IV) and the risk of long-term growth disturbance (highest for types IV and V).
Plastic Deformation
The pediatric bone, with its higher porosity, lower stiffness, and more elastic behavior, can deform without complete fracture under bending forces. Plastic deformation is the persistent angular deformity of a bone without a discrete fracture line, produced by forces sufficient to exceed the elastic limit of the bone but insufficient to produce complete fracture. The most common sites of plastic deformation are the ulna and fibula (the thinner of the paired bones in the forearm and leg), often in association with a frank fracture of the other bone. The classical setting is the pediatric both-bone forearm fracture with frank radial fracture and plastic deformation of the ulna; the “missed” plastic deformation may obstruct subsequent reduction of the radial fracture. Recognition of plastic deformation requires careful inspection of the radiographs with comparison to the contralateral side. The bone shows the characteristic bowing without a fracture line. Treatment of plastic deformation depends on the magnitude of angulation. Less than 10 degrees of angulation generally does not require treatment in young children because of remodeling potential. Greater angulation (more than 10 to 20 degrees in younger children, less in older children) requires reduction; reduction may require deliberate over- correction under anesthesia, with the bone forced past the deformity into a slight opposite angulation that then relaxes back to a corrected position. Persistent angulation that does not respond to closed reduction may require completion of the deformation to a complete fracture through controlled osteotomy, with subsequent reduction.
Greenstick Fractures
The greenstick fracture is the classical pediatric incomplete fracture pattern, named after the analogy of bending a green tree branch — the bone breaks on one cortex (the tension side) while the opposite cortex (the compression side) remains intact but plastically deformed and bowed. The mechanism is a bending force that exceeds the failure strength of one cortex but not the other. The intact cortex provides residual stability and tends to spring back toward the original position when the deforming force is released, although typically not to full anatomical alignment.
Locations: The greenstick fracture is most common in the forearm (both-bone or isolated), but can occur in any bone. The clavicle, tibia, fibula, humerus, and femur are all common sites in childhood. Treatment of greenstick fractures depends on the magnitude of the deformity: Minimally angulated fractures (less than 10 to 15 degrees) are managed by cast immobilization alone, with the remodeling potential of the growing skeleton resolving any residual deformity over months to years. Significantly angulated fractures require closed reduction, often with completion of the fracture (deliberately fracturing the intact cortex to allow full anatomical reduction). The fracture is then immobilized in a cast in the corrected position. The risk of recurrence of the angulation in the cast is a recognized concern, particularly if the fracture has not been completed. Serial radiographic monitoring is essential, with re- reduction or operative management for redisplacement.
Other Pediatric Fracture Patterns
Buckle (Torus) Fracture The buckle (torus) fracture is a compression fracture of the metaphyseal cortex without a complete fracture line, producing a characteristic “buckling” of the cortex. The fracture is most common at the distal radius and is typically a stable injury treated in a short-arm cast or removable splint for 3 to 4 weeks with good healing and no concerns about deformity. Bowing Deformity The bowing deformity is a more severe variant of plastic deformation with substantial angulation; the management is as for plastic deformation.
Avulsion Fractures Avulsion fractures at apophyseal sites (where tendons or ligaments attach to ossifying secondary growth centers) are particularly common in adolescents during the period of apophyseal development. The classical examples include the anterior superior iliac spine (sartorius avulsion), the anterior inferior iliac spine (rectus femoris avulsion), the ischial tuberosity (hamstring avulsion), and the tibial tubercle (patellar tendon avulsion). Treatment is typically non-operative for minimally displaced fractures (rest, NSAIDs, protected weight bearing) and operative for severely displaced fractures (ORIF with screws). Apophyseal Avulsions in Specific Locations Tibial tubercle avulsion (Ogden classification) occurs during the closing phase of the tibial tubercle apophysis in adolescents. The classification (types I, II, III) is based on the involvement of the tibial tubercle, the proximal tibial physis, and the joint surface. Type III with intra-articular extension requires anatomical reduction.
Tillaux fracture and Triplane fracture at the distal tibia are addressed in Topic Trauma- 28.
Specific Pediatric Considerations
Periosteum The pediatric periosteum is substantially thicker, more cellular, and more biologically active than in adults. The periosteum often remains intact on one side of a pediatric fracture, providing a hinge that facilitates reduction and contributing to the rapid healing characteristic of childhood. The periosteal sleeve fracture is the classical lateral clavicle pediatric pattern (Neer type IV) where the periosteum remains intact while the clavicular bone fragments.
Healing Potential Pediatric bones heal substantially faster than adult bones — typical adult tibial shaft fractures may take 16 weeks to heal, while a similar fracture in a young child may heal in 6 weeks. The healing time generally correlates with age, with the youngest children healing most rapidly. Remodeling Potential The remodeling potential of the pediatric bone is substantial and is a critical consideration in management. The factors favoring remodeling include: Younger age: More years of growth remaining. Proximity to a physis: Bones close to active physes remodel more reliably. Deformity in the plane of motion of the adjacent joint: Angulation in the sagittal plane (matching knee flexion-extension) remodels better than angulation in the coronal plane (which does not match the principal axis of joint motion at the knee). Rotational malalignment does NOT remodel and must be corrected. The acceptable deformity for non-operative management increases with younger age and with proximity to an active physis. For instance, a femoral shaft fracture in a 3-year-old can accept substantially more angulation, shortening, and malposition than the same fracture in a 12-year-old.
Growth Arrest and Its Management
Growth arrest following physeal injury occurs when bony bridges form across the physis, tethering the epiphysis to the metaphysis and preventing further growth. The incidence of growth arrest varies by fracture type and location: Salter-Harris I and II: Less than 10 percent risk. Salter-Harris III: 20 to 30 percent risk depending on location and quality of reduction.
Salter-Harris IV: 30 to 50 percent risk. Salter-Harris V: Essentially 100 percent risk. Distal femur and proximal tibia physeal injuries have the highest risk of clinically significant growth arrest because of the substantial contribution of these physes to lower extremity length (the distal femur contributes approximately 9 mm/year of growth; the proximal tibia approximately 6 mm/year). Management of growth arrest depends on the location, the size of the bony bridge, and the remaining growth potential: Observation with serial radiographic follow-up for at least the first year after injury, with attention to leg-length discrepancy and angular deformity. Bar excision (Langenskiöld procedure): Removal of the bony bridge between the epiphysis and metaphysis with interposition of fat or other material to prevent reformation. Indicated for small (<50 percent of the physis) bridges in patients with significant remaining growth potential. Success rates are approximately 50 to 70 percent. Limb lengthening or shortening procedures for established leg-length discrepancy. Corrective osteotomy for established angular deformity. Contralateral epiphysiodesis to equalize leg lengths by stopping growth of the unaffected side at the appropriate time.
Principles of Pediatric Fracture Management
Closed Reduction Closed reduction is the cornerstone of pediatric fracture management for the great majority of fractures. The combination of strong periosteum (which provides a guide for reduction), favorable remodeling, and rapid healing means that many fractures can be managed by closed reduction and cast immobilization, with substantial residual deformity acceptable. Cast Application Cast application in pediatric fractures requires attention to growth (avoiding cast restriction of an actively growing limb that may produce ischemia or pressure injury), to the mechanical principles of three-point fixation, and to the activity level of children (with appropriate strength of materials and protection of vulnerable areas). Operative Indications The specific indications for operative pediatric fracture management include: Open fractures requiring debridement and fixation. Irreducible fractures that cannot be maintained in acceptable position by closed means.
Articular fractures (Salter-Harris III and IV) requiring anatomical reduction. Fractures with associated neurovascular injury requiring direct surgical management. Polytrauma in adolescents requiring stable fixation for nursing care and mobilization. Pathological fractures through bone cysts, fibrous dysplasia, or other lesions. Selected fractures in older adolescents approaching skeletal maturity where remodeling potential is limited and adult-style anatomical reduction is preferred. Specific Pediatric Fixation Techniques Flexible intramedullary nailing (TENS — titanium elastic nailing system, Métaizeau): The principal operative technique for pediatric long-bone diaphyseal fractures (forearm, femur, humerus). Uses two flexible nails inserted retrograde or antegrade through small metaphyseal incisions, providing three-point fixation across the fracture. Avoids the physes and the principal vascular supply, with reliable union and excellent functional outcomes. K-wire (Kirschner wire) fixation: For smaller fractures, particularly hand and foot fractures, distal radius and supracondylar humerus fractures. Wires are removed at 4 to 8 weeks. Plate fixation: Reserved for older adolescents and for fractures not amenable to flexible nailing or K-wires. External fixation: For severely open fractures, polytrauma, and selected complex injuries. Submuscular plating: For pediatric femoral shaft fractures in selected indications. Specific Approaches Modified for Children Surgical approaches in children must respect the physes (avoiding crossing of the physis with hardware when possible, or using smooth wires across the physis if necessary), the smaller anatomical scale (requiring appropriately sized instruments and gentler tissue handling), and the specific pediatric variants of common conditions (such as the supracondylar humerus fracture in children — the most common pediatric elbow fracture — with its specific management considerations).
Summary and Take-Home Points
The pediatric skeleton differs fundamentally from the adult skeleton in the presence of the physis (growth plate), the thicker and more biologically active periosteum, and the more porous and elastic bone material, producing distinct fracture patterns and management considerations. The Salter-Harris classification organizes physeal fractures into five principal types: I (through the physis only), II (through the physis and metaphysis — the most common), III (through the physis and into the epiphysis — articular involvement), IV (crossing all three layers — physis, metaphysis, epiphysis), and V (crush of the physis without displacement). The Rang modifications add types VI through IX for additional patterns. The classification predicts both immediate management (anatomical
reduction required for types III and IV) and the risk of long-term growth disturbance (highest for types IV and V; essentially 100 percent for type V). Plastic deformation is the persistent angular deformity without complete fracture, most common in the ulna and fibula, often in association with frank fracture of the other paired bone. Recognition requires careful radiographic assessment; treatment may require deliberate over-correction or completion of the deformation to a complete fracture for adequate reduction. Greenstick fractures are incomplete fractures with one cortex broken (tension side) and the opposite cortex intact (compression side), classically in the forearm. Treatment is by cast immobilization for minimally angulated fractures and by closed reduction with completion of the fracture for significantly angulated patterns. The remodeling potential of the growing skeleton is substantial, with younger age, proximity to active physes, and deformity in the plane of joint motion all favoring remodeling. Rotational malalignment does NOT remodel and must be corrected. The acceptable deformity for non-operative management is therefore substantially more generous than in adults. Growth arrest following physeal injury can produce leg-length discrepancy or angular deformity, with management options including observation, bar excision (Langenskiöld), limb lengthening or shortening, corrective osteotomy, and contralateral epiphysiodesis. The distal femur and proximal tibia physes have the highest clinical impact because of their substantial contribution to lower extremity length. Pediatric fracture management principles include closed reduction as the cornerstone, with operative management reserved for specific indications (open fractures, irreducible fractures, articular fractures, polytrauma, fractures in older adolescents). The flexible intramedullary nailing (TENS) technique is the principal operative approach for pediatric long-bone diaphyseal fractures.
This chapter concludes the 74-topic Bulgarian state board curriculum in Orthopedics and Traumatology covered in this compendium. The work has progressed from the 30 orthopedic topics addressing congenital, developmental, degenerative, neoplastic, inflammatory, and metabolic conditions, through the 32 trauma topics addressing the principles of fracture management and the specific regional fracture patterns from the spine to the foot, and finally through the 12 anatomy and surgical approaches topics addressing the regional anatomy and operative access from the cervical spine to the pediatric skeleton. The thematic continuities — the classification systems (AO/OTA, Salter-Harris, Schatzker, Letournel, and many others), the named eponymous lesions and procedures (Hill-Sachs, Bankart, Pavlik, Ponseti, Smith-Petersen, Kocher, Henry, and many others), the recurring decision frameworks (operative versus non-operative, fixation versus replacement, salvage versus amputation), and the underlying principles of biology (fracture healing, the
diamond concept, the blood supply to the femoral head and the talus, the physeal anatomy) — provide the conceptual scaffolding on which the specific clinical management decisions rest. The candidate preparing for the state board examination is encouraged to use this compendium as a structured review covering the breadth of the syllabus, supplementing the specific topic chapters with the recommended primary references (AO Principles, Rockwood and Green’s, Apley & Solomon’s, Miller’s, Tachdjian’s, Rothman-Simeone, and others) for the depth of understanding required for the examination and for clinical practice. Good luck with the preparation and the examination.