AOBOS Orthopedics key terms

An osteopathic concept describing impaired or altered function of interrelated components of the somatic system: skeletal, arthrodial, and myofascial structures plus their vascular, lymphatic, and neural elements. It is diagnosed by palpation for tissue texture change, asymmetry, restriction of motion, and tenderness (TART).

Rules describing coupled lumbar and thoracic spinal motion. Type I: with neutral mechanics, sidebending and rotation occur in opposite directions and are coupled. Type II: with a flexed or extended segment, rotation and sidebending occur in the same direction (non-neutral).

The principle that bone remodels along the lines of mechanical stress it experiences, adding mass where loads are high and resorbing where they are low. It explains stress shielding, cortical thickening with loading, and adaptive changes after fracture healing or implant placement.

The number of standard deviations a patient's areal bone mineral density lies above or below the mean of a young healthy reference population. A T-score at or below −2.5 defines osteoporosis; between −1.0 and −2.5 defines osteopenia.

A grading system for open fractures based on wound size, soft tissue injury, and contamination: type I is a clean wound under 1 cm; type II is 1–10 cm without extensive damage; type III (A, B, C) involves high-energy injury or vascular compromise.

Elevated pressure within a closed fascial compartment that compromises capillary perfusion and threatens muscle and nerve viability. Hallmarks are pain out of proportion, pain with passive stretch, tense compartments, and paresthesias; pulselessness and paralysis are late, unreliable findings.

Failure of a fracture to heal without further intervention, typically judged after six to nine months with no radiographic progression over three consecutive months. Causes include instability, infection, poor blood supply, and systemic factors such as smoking or diabetes.

A staged strategy for severely injured patients in which life-threatening hemorrhage and soft tissue contamination are addressed first with temporary stabilization, such as external fixation, and definitive fracture care is deferred until physiologic reserve recovers.

Progressive mechanical failure of implant fixation without infection, driven by particle debris, macrophage-mediated osteolysis, and cyclic micromotion. Radiographic signs include lucent lines, component migration, and cement mantle fracture, usually presenting with activity-related pain.

Infection involving a joint replacement and surrounding tissue, diagnosed using major criteria such as sinus tract communication or two positive cultures with the same organism, or minor criteria including elevated inflammatory markers, synovial cell count, and purulence.

A system for periprosthetic femur fractures around a total hip replacement. Type A is trochanteric, type B is around or just below the stem (B1 stable, B2 loose, B3 loose with poor bone stock), and type C is distal to the stem.

The hip-knee-ankle angle measured on a full-length standing radiograph, describing the line from femoral head center to ankle talus center. Neutral is approximately 180 degrees; varus or valgus deviation guides osteotomy and arthroplasty planning.

Detachment of the anterior labrum and capsule from the anteroinferior glenoid rim, typically after anterior shoulder dislocation. It is the most common structural cause of recurrent anterior instability and is repaired by capsulolabral reattachment.

A posterolateral humeral head impaction fracture created when the dislocated humeral head strikes the anterior glenoid. Large or engaging lesions contribute to recurrent anterior instability and may require remplissage or bony reconstruction.

A grading of fatty infiltration of the rotator cuff musculature on axial imaging, from stage 0 (no fat) to stage 4 (more fat than muscle). Higher stages predict poorer tendon healing after repair.

A dynamic examination for anterior cruciate ligament deficiency performed by extending the knee from flexion while applying valgus and internal rotation; the tibia reduces with a palpable clunk near 30 degrees of flexion.

A peripheral tear of the posterior horn of the medial meniscus at the meniscocapsular junction, often missed at arthroscopy and associated with chronic anterior cruciate ligament deficiency. It requires probing and stabilization to restore meniscal function.

A grading of spondylolisthesis based on the percentage of the superior vertebral body displaced over the inferior one on lateral radiograph: grade I is 0–25%, II 26–50%, III 51–75%, IV 76–100%, and grade V is spondyloptosis.

The standard radiographic measure of scoliotic curvature, taken between the end vertebrae with the greatest tilt: lines drawn along their endplates intersect, and the angle between perpendiculars to those lines defines curve severity.

A standardized grading of spinal cord injury from A to E, based on the sacral sparing examination: A is complete injury, B sensory incomplete, C and D motor incomplete, and E normal sensory and motor function.

New symptomatic degeneration, stenosis, or instability at the vertebral level next to a fused segment, attributed to altered load transfer and increased motion. Risk rises with longer constructs and pre-existing asymptomatic degeneration.

Failure of fracture healing in the scaphoid, most often at the proximal pole because blood supply enters distally and flows in retrograde fashion. Untreated it progresses to carpal collapse and arthritis, the scaphoid nonunion advanced collapse pattern.

Avascular necrosis of the lunate presenting with dorsal wrist pain and stiffness in young adults. Lichtman staging guides treatment, from radial shortening or vascularized grafting in early stages to salvage procedures such as proximal row carpectomy in advanced collapse.

Fibroproliferative thickening of the palmar fascia causing nodules and cords that progressively flex the metacarpophalangeal and proximal interphalangeal joints. Treatment options include needle aponeurotomy, collagenase injection, and limited or radical fasciectomy.

Injury to the triangular fibrocartilage complex, the ulnar-sided stabilizer of the distal radioulnar joint and ulnocarpal articulation. It presents with ulnar wrist pain and clicking; the Palmer classification separates traumatic from degenerative lesions.

Disruption of the terminal extensor tendon or its bony insertion at the distal interphalangeal joint, producing a fixed flexion deformity. Most cases are treated with continuous splinting of the distal joint in extension for six to eight weeks.

Disruption of the tarsometatarsal articulation, often with widening between the first and second metatarsal bases. It ranges from subtle ligamentous sprain to frank fracture-dislocation and may require weight-bearing or stress imaging for diagnosis.

Tearing of the tibiofibular syndesmotic ligaments above the ankle, causing pain, instability, and widening of the tibiofibular clear space on imaging. Treatment ranges from protected weight bearing to screw or suture-button fixation.

Lateral deviation of the great toe with medial prominence of the first metatarsal head and progressive attenuation of the medial capsule. The intermetatarsal angle helps classify severity and guide bunion correction procedures.

Progressive neuropathic joint destruction with fragmentation, dislocation, and collapse, most often in diabetic peripheral neuropathy. Acute management relies on immobilization and offloading rather than surgery, because impaired sensation and perfusion raise complication risk.

A grading of physeal fractures: type I through the physis, II through physis and metaphysis, III through physis and epiphysis, IV through metaphysis, physis, and epiphysis, and V a crush injury with poor prognosis.

Displacement of the capital femoral epiphysis through the physis in adolescents, presenting with hip, groin, or referred knee pain and limited internal rotation. Stable slips are treated with single screw fixation; unstable slips risk avascular necrosis.

Idiopathic avascular necrosis of the immature femoral head in children, causing hip pain and limp with lateralization and fragmentation over months. Treatment aims to contain the head within the acetabulum during reossification.

A primary malignant bone tumor producing osteoid, most common in the metaphysis of long bones in adolescents. Standard care is neoadjuvant chemotherapy, wide resection with limb salvage, and postoperative chemotherapy; percent tumor necrosis guides prognosis.

A benign cartilage-forming tumor within the medullary canal, often an incidental finding in the hand or long bones. It typically shows stippled calcification; multiple lesions suggest Ollier disease or Maffucci syndrome and require surveillance.