Orthopedics Syllabus

Differentiate a sprain from a strain.

A sprain is an injury to a ligament (bone-to-bone), graded I (stretch), II (partial tear), III (complete tear). A strain is an injury to a muscle or musculotendinous unit.

How are ligament sprains graded and what is the clinical hallmark of each grade?

Grade I: microscopic stretch, no laxity, mild pain. Grade II: partial tear, mild-moderate laxity with firm endpoint. Grade III: complete rupture, gross laxity with no endpoint. Function loss increases with grade.

What is the initial management acronym for acute soft tissue injuries?

RICE (Rest, Ice, Compression, Elevation), often expanded to PRICE (Protection added) or POLICE (Protection, Optimal Loading, Ice, Compression, Elevation) emphasizing early controlled loading over strict rest.

What are the three phases of tendon healing?

Inflammatory phase (days 0–7, cellular infiltration), proliferative/fibroblastic phase (weeks, type III collagen deposition), and remodeling/maturation phase (months, type III replaced by stronger organized type I collagen).

Define polytrauma and the ISS threshold commonly used.

Polytrauma is injury to multiple body regions/systems where at least one injury (or the combination) is life-threatening. It is commonly defined by an Injury Severity Score $\text{ISS} \geq 16$ (Berlin definition adds physiological derangement).

How is the Injury Severity Score (ISS) calculated?

The body is divided into 6 regions scored by the Abbreviated Injury Scale (AIS 0–6). The ISS is the sum of the squares of the three highest AIS scores from different regions: $\text{ISS} = A^{2} + B^{2} + C^{2}$, ranging 0–75. Any AIS of 6 automatically makes ISS = 75.

Contrast 'Early Total Care' (ETC) with 'Damage Control Orthopedics' (DCO).

ETC involves definitive fixation of major fractures within 24 hours in stable patients. DCO involves temporary stabilization (external fixation), hemorrhage/contamination control, and delayed definitive surgery in physiologically unstable ('borderline') polytrauma patients to avoid a second hit.

List the ATLS primary survey sequence.

ABCDE: Airway with cervical spine protection, Breathing/ventilation, Circulation with hemorrhage control, Disability (neurologic/GCS), and Exposure/Environment control (undress, prevent hypothermia).

What is the 'lethal triad' (trauma triad of death)?

Hypothermia, acidosis (metabolic), and coagulopathy — a self-perpetuating cycle in severe trauma that damage control resuscitation aims to interrupt.

What are the key risk factors for Developmental Dysplasia of the Hip (DDH)?

The '6 Fs' / classic factors: Female sex, Firstborn, Family history, Frank breech presentation, oligohydramnios, and left hip predominance. Mnemonic aids include 'the 4 Ps': positive family history, primiparity, podalic (breech) presentation, and packaging problems.

Name the two provocative clinical tests for neonatal DDH and what they detect.

Ortolani test (reduction — abduction with anterior lift, positive 'clunk' as dislocated hip relocates) and Barlow test (dislocation — adduction with posterior pressure, positive if reducible hip dislocates). Both are most reliable in the first weeks of life.

What is the imaging modality of choice for DDH by age, and why the age cutoff?

Ultrasound is used before ~4–6 months of age because the femoral head is largely cartilaginous. After ~4–6 months, when the ossific nucleus appears, plain radiographs (AP pelvis) become the modality of choice.

What is the first-line treatment for DDH in an infant under 6 months?

A Pavlik harness, which holds the hips in flexion and abduction to encourage concentric reduction. It is typically avoided/less effective after 6 months or in irreducible/teratologic dislocations.

What is the significance of the greenstick and torus (buckle) fractures unique to children?

Pediatric bone is more porous and has a thick periosteum. A torus/buckle fracture is a compression of one cortex; a greenstick fracture is an incomplete fracture where one cortex breaks and the other bends — both reflect the plasticity of immature bone.

Why do pediatric fractures remodel and heal faster than adult fractures?

Children have thick, metabolically active periosteum, open physes providing growth-driven remodeling potential, and greater osteogenic capacity. Remodeling is best for fractures near the physis, in the plane of joint motion, and in younger children with more growth remaining.

What is a supracondylar humerus fracture and its key associated complication?

A common pediatric elbow fracture (often extension-type from fall on outstretched hand). Key risks include neurovascular injury — the anterior interosseous nerve (median) is most commonly injured, and brachial artery injury can occur; malunion causes cubitus varus (gunstock deformity).

What is amelia versus meromelia in congenital limb deficiency?

Amelia is the complete absence of a limb. Meromelia is partial absence of a limb (e.g., hemimelia — absence of the distal half; phocomelia — hands/feet attached directly to the trunk with absent intermediate segments).

Contrast fibular hemimelia and tibial hemimelia in terms of inheritance and stability.

Fibular hemimelia is the most common long-bone deficiency, usually sporadic, causing limb shortening and foot deformity. Tibial hemimelia is rarer, often autosomal dominant/associated with syndromes, and produces an unstable knee since the tibia is the main weight-bearing bone.

What are the main bearing surface options for Total Hip Arthroplasty and a key drawback of each?

Metal-on-polyethylene (wear debris → osteolysis, improved with highly cross-linked PE), ceramic-on-ceramic (excellent wear but risk of squeaking/fracture), ceramic-on-polyethylene (low wear), and metal-on-metal (largely abandoned due to metallosis and adverse local tissue reactions/pseudotumors).

What are the two main modes of THA fixation and how do they achieve stability?

Cemented fixation uses polymethylmethacrylate (PMMA) as a grout for immediate stability. Cementless (press-fit) fixation relies on bone ingrowth/ongrowth into a porous-coated implant for biological fixation over time.

What is the most common complication after primary THA and a key modifiable risk factor?

Dislocation is among the most common early complications; risk is influenced by surgical approach (posterior approach historically higher unless capsule repaired), component malposition (outside the Lewinnek safe zone), and patient factors. The posterior approach classically restricts flexion/adduction/internal rotation.

What is the target acetabular cup orientation ('Lewinnek safe zone') in THA?

Approximately $40^{\circ} \pm 10^{\circ}$ of inclination (abduction) and $15^{\circ} \pm 10^{\circ}$ of anteversion, aiming to minimize dislocation and impingement (though the concept has limitations with spinopelvic mobility).

What is the most common long-term reason for revision Total Knee Arthroplasty?

Aseptic loosening is a leading cause of late revision, along with instability, polyethylene wear/osteolysis, and infection (the leading cause of early revision). Malalignment and stiffness also contribute.

What are the alignment goals in Total Knee Arthroplasty (mechanical axis)?

Traditional mechanical alignment aims to restore a neutral hip-knee-ankle axis ($0^{\circ} \pm 3^{\circ}$), with the femoral component perpendicular to the femoral mechanical axis and tibial component perpendicular to the tibial mechanical axis, balancing flexion and extension gaps.

Differentiate cruciate-retaining (CR) from posterior-stabilized (PS) TKA designs.

CR designs preserve the posterior cruciate ligament for femoral rollback. PS designs sacrifice the PCL and use a tibial post-and-cam mechanism to substitute for it, providing rollback and preventing posterior tibial subluxation.

What is the gold-standard diagnosis of periprosthetic joint infection component (synovial fluid criteria)?

Diagnosis uses major criteria (sinus tract communicating with prosthesis, or two positive periprosthetic cultures of the same organism) plus minor criteria including elevated serum CRP/ESR, elevated synovial WBC count, elevated synovial polymorphonuclear percentage, positive alpha-defensin, and elevated synovial CRP (MSIS/ICM criteria).

What is the two-stage revision protocol for infected arthroplasty?

Stage 1: remove implants, debride, and place an antibiotic-loaded cement spacer, followed by IV antibiotics (typically ~6 weeks). Stage 2: after infection clearance is confirmed, reimplant a definitive prosthesis. It remains the gold standard for chronic periprosthetic joint infection.

What are the three columns of the spine (Denis classification) and their significance?

Anterior column (anterior longitudinal ligament, anterior half of vertebral body/disc), middle column (posterior half of body/disc, posterior longitudinal ligament), and posterior column (pedicles, facets, posterior ligamentous complex). Involvement of $\geq 2$ columns generally indicates instability.

What defines spinal shock versus neurogenic shock?

Spinal shock is the transient loss of all reflexes/sensory-motor function below the injury level (resolution marked by return of the bulbocavernosus reflex). Neurogenic shock is hemodynamic — hypotension with bradycardia from loss of sympathetic tone in injuries above T6.

What distinguishes a complete from an incomplete spinal cord injury (ASIA)?

A complete injury (ASIA A) has no motor or sensory function preserved in the lowest sacral segments (S4–S5), including no sacral sparing. Incomplete injuries (ASIA B–D) have some preserved function below the neurologic level, including sacral sparing, and carry better prognosis.

Compare central cord syndrome and anterior cord syndrome.

Central cord syndrome (often hyperextension in older patients with cervical spondylosis): upper limb weakness > lower limb, variable sensory loss; best prognosis of incomplete injuries. Anterior cord syndrome (anterior spinal artery/flexion): loss of motor and pain/temperature below the lesion with preserved proprioception/vibration; worst prognosis.

What are the pathological features distinguishing lumbar disc herniation from spinal stenosis symptoms?

Disc herniation causes radicular pain (sciatica) from nerve root compression, worse with sitting/flexion and Valsalva, positive straight leg raise. Central lumbar stenosis causes neurogenic claudication — bilateral leg pain worse with standing/extension/walking, relieved by sitting/flexion ('shopping cart sign').

What are the cardinal features of degenerative cervical/lumbar spondylosis on imaging?

Disc space narrowing, osteophyte formation, facet joint hypertrophy/arthrosis, endplate sclerosis (Modic changes), and ligamentum flavum hypertrophy, which together can narrow the canal and foramina.

Define scoliosis and the Cobb angle threshold for diagnosis.

Scoliosis is a lateral curvature of the spine with rotation, defined as a Cobb angle $> 10^{\circ}$ in the coronal plane. The Cobb angle is measured between lines drawn along the endplates of the most tilted (end) vertebrae of the curve.

What are the treatment thresholds for adolescent idiopathic scoliosis by Cobb angle?

Curves $< 25^{\circ}$: observation. Curves $25^{\circ}$–$45^{\circ}$ in a skeletally immature patient: bracing (e.g., to prevent progression). Curves $> 45^{\circ}$–$50^{\circ}$: surgical correction (fusion) is generally considered.

Differentiate scoliosis, kyphosis, and lordosis.

Scoliosis is abnormal lateral (coronal) curvature with rotation. Kyphosis is excessive posterior convex (sagittal) curvature (e.g., thoracic hyperkyphosis, Scheuermann disease). Lordosis is excessive anterior concave (sagittal) curvature, typically lumbar (hyperlordosis).

What is the classic mechanism of an ACL injury and the associated 'unhappy triad'?

A non-contact pivoting injury — sudden deceleration with valgus and internal rotation (or hyperextension). The O'Donoghue 'unhappy/terrible triad' classically involves ACL tear, medial collateral ligament tear, and medial meniscus tear (though lateral meniscus involvement is now recognized as common).

Name the primary clinical tests for ACL insufficiency and which is most sensitive/specific.

Lachman test (30° flexion — most sensitive), anterior drawer test (90° flexion), and the pivot-shift test (most specific for functional instability, reproduces the giving-way). A soft/absent endpoint indicates ACL rupture.

What is the primary blood supply pattern of the meniscus and its clinical relevance?

Only the peripheral ~10–30% is vascular (the red-red and red-white zones) supplied by the perimeniscal capillary plexus; the inner white-white zone is avascular. Peripheral (red zone) tears can heal/be repaired, whereas central avascular tears usually require debridement.

What clinical test and classic symptom suggest a meniscal tear?

McMurray test (pain/click with knee flexion-extension under rotation), joint-line tenderness, and Apley grind test. Classic symptoms are mechanical locking, catching, and effusion following a twisting injury.

What are the functions of the ACL and PCL respectively?

The ACL is the primary restraint to anterior translation of the tibia on the femur (and secondary restraint to rotation). The PCL is the primary restraint to posterior translation of the tibia on the femur.

Which rotator cuff muscle is most commonly torn and what is its innervation and action?

The supraspinatus is most commonly torn. It is innervated by the suprascapular nerve and initiates the first ~15–30° of shoulder abduction (and depresses/stabilizes the humeral head in the glenoid).

Name the four rotator cuff muscles (SITS) and their main actions.

Supraspinatus (initiates abduction), Infraspinatus (external rotation), Teres minor (external rotation), and Subscapularis (internal rotation). Together they dynamically stabilize the glenohumeral joint by centering the humeral head.

What are the key special tests for rotator cuff pathology?

Jobe's empty can test (supraspinatus), external rotation lag/Patte test (infraspinatus/teres minor), lift-off and belly-press tests (subscapularis), and the Neer and Hawkins-Kennedy tests for subacromial impingement.