Core Topics

Core topics in orthopaedics

AO Classification

The AO group has developed a comprehensive classification of fractures. The classification is arranged in order of increasing severity according to the complexities of the fracture, difficulty of treatment and worsening prognosis.

More detailed information about the classification can be obtained from AO Foundation


Unicameral Bone Cyst (UBC)

Unicameral Bone Cyst (UBC)

– solitary, fluid-filled cystic lesions located in metaphysis of long bones near physis in kids & adolescents
– predominantly proximal femur & proximal humerus

Signs & Symptoms:
– usu asymptomatic
– pathologic # associated with minimal trauma

– radiolucent, trabeculated lesion with well-defined borders surrounding by sclerotic margin
– ‘fallen leaf’ sign in pathologic #

– lined with loose connective tissue membrane containing small numbers of fibroblasts, giant cells & hemosiderin-laden macrophages

– 15% will heal after # with observation alone
– treat # as you would for most #s of that region
– once # healed, aspiration & steroid injections (x 3)
– curettage & bone grafting improves healing rate & provides mechanical support



– 1o bone tumor with predilection for tibial diaphysis presenting during early adulthood

Signs & Symptoms:
– painful masses with variable symptom duration ranging from few months to few years

– well-circumscribed, eccentric, lytic lesions of tibial diaphysis
– may be multicystic lesion with surrounding sclerosis
– expansion of bone +/- intact cortex but no periosteal reaction

– wide variety of histologic appearances
– basaloid pattern composed of groups of cells which peripherally have palisading epithelial cells
– hypocellular, poorly organized, fibrous connective tissue between islands of epithelial cells

– wide excision (limb salvage vs amputation)
– 20-25% metastasize to lungs

Aneurysmal Bone Cyst (ABC)

Aneurysmal Bone Cyst (ABC)

– solitary expansile lesion located in metaphysis of long bones, flat bones & vertebrae
– presents in 2nd decade
– cysts filled with blood

Signs & Symptoms:
– pain with tenderness & swelling at the site of the lesion

– expansile eccentric lesion surrounded by a thinned cortex with periosteal new bone formation
– CT/MRI – characteristic ‘fluid-fluid’ level
– beware of telangiectatic osteosarcoma – has fluid-fluid levels but far more aggressive looking

– blood spaces separated by cellular septa lacking an endothelial cell lining & containing a variety of cells such as fibroblasts, multinucleated giant cells & histiocytes & metaplastic bone
– large solid cellular areas may be seen

– excision, curettage & bone grafting
– cryosurgery or chemical ablation may be used

Hip – Posterior Approach

Hip – posterior approach

* position – lateral decubitus

* incision – 15cm curved incision centered on post. edge of GT
– curve towards PSIS or @ 30 deg. angle

* no internervous plane

* dissection
– incise fascia latae to expose vastus lateralis
– split fibers of GMax in line with fibers
– retract fibers of spit GMax
– ID short ER
– ID sciatic nerve
– IR hip to put short ER on stretch & pull operative field farther from sciatic n.
– stay sutures in piriformis & obturator internus tendons
– detach short ER from femur (piriformis, sup. gem., obt. int., inf. gem)
– may need to detach sup. border of quad. fem.
– reflect muscles backward to protect sciatic n.
– incise capsule
– dislocate hip

* dangers
– sciatic n. – always ID & protect

– IGA – leaves pelvis beneath piriformis & heads cephalad to supply deep surface of GMax
– branches cut with splitting of GMax

– cruciate anastomosis
> at lower border of QF
> anastomosis of ascending branch of 1st perforator, descending branch of inf. epigastric art., med. & lat. fem. circumflex art.

Forearm – Volar Approach (Henry’s)

Forearm – volar approach (Henry’s)

* position – supine with tourniquet


Thoracic Spine – Anterior Approach

Thoracic spine – anterior approach

* position – lat. with bean bag

* incision
– usu R sided approach
– 1/2way btw spine & scapula –> ant. axillary line
– 2 ribs above level wanting to be accessed

* dissection
– divide lat. dorsi in line with skin
– divide serratus ant. in line with skin down to rib
– expose rib subperiosteally
– resect rib as far post. as possible
– nick pleura with knife
– enter pleura bluntly
– deflate lung & retract ant.
– identify esphagus
– incise pleura over lat. sid of esophagus & retract
– tie off intercostal vessels (avoid if possible due to blood supply to SC)

* dangers
– intercostal vessels
> during rib resection
> during exposure of vert. body
– lung

41 – Tibia/Fibula Proximal

41-Tibia/Fibula Proximal

41-A-1 avulsion
41-A-2 metaphyseal-simple
41-A-3 metaph.-comminuted
B-Partial articular
41-B-1 pure split
41-B-2 pure depression
41-B-3 split-depression
C-Complete articular
41-C-1 simple articular + simple metaphysis
41-C-2 simple articular + comminuted metaphysis
41-C-3 comminuted articular

Distal Humerus – Intracondylar

Distal Humerus-Intracondylar

(Riseborough and Radin)
Type 1-non-displaced
Type 2-trochlea and capitellum displaced but not rotated
Type 3-trochlea and capitellum both displaced and rotated
Type 4-type 3 with sig. comminution