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

Ankle – Posterolateral Approach

Ankle – posterolateral approach

* position – prone with tourniquet

* incision – long. incision midway btw lat. malleolus & Achilles

* internervous plane – PB (SPN) & FHL (tibial n.)

* dissection
– mobilize skin flaps
– short saphenous vein & sural n. run just behind lat. malleolus
– incise deep fascia of leg in line with incision
– ID 2 peroneal tendons
– PB ant. to PL at level of ankle
– PB muscular down to level of ankle
– incise peroneal retinaculum to release tendons & retract lat.
– expose FHL
– incise lat. fibers of FHL as they arise from fibula
– retract FHL med.
– incise periosteum of distal tibia
– follow post. aspect of tibia down to post. ankle & incise capsule transversely

* dangers
– short saphenous vein & sural n.

Knee – Medial Approach

Knee – medial approach

* position – supine with affected knee flexed to 60 deg. & hip flexed & ER

* incision
– long, curved incision starting 2 cm prox. to add. tubercle
– curve ant. & inf. to point 6 cm below joint line on anteromed. aspect of tibia
– runs parallel to med. border of patella about 3 cm med. to it

* no internervous plane

* dissection
– raise skin flaps to expose fascia
– infrapatellar branch of saphenous n. crosses operative field transversely (usu cut)
– saphenous n. emerges from btw gracilis & sartorius
– long saphenous v. runs in posteromed. aspect of dissection

> ant. to superficial MCL
– incise fascia along ant. border of sartorius in line with muscle fibers from attachment to tibia to 5 cm above joint line
– flex knee to allow sartorius to retract post.
– ST & gracilis exposed behind & beneath sartorius
– retract all 3 muscles post.
– insertion of sup. MCL lies deep & distal to ant. edge of sartorius
– gentle traction to MCL will expose injury
– for intraart. exposure, incise joint capsule ant. to MCL

> post. to superficial MCL
– incise fascia along ant. border of sartorius
– retract 3 muscles of pes anserinus post.
– separate med. head of gastroc. from semimembranosus
– separate med. head of gastroc. from post. capsule
– exposes posteromed. corner
– incise capsule post. to MCL for intraart. exposure

* dangers
– infrapatellar branch of saphenous n. – usu cut
– saphenous n. – emerges btw sartorius & gracilis with long saphenous v.
– long saphenous v.
– med. inf. genicular art. – curves around upper end of tibia & may be damaged when med. head of gastroc. lifted off post. capsule
– popliteal art. – lies on post. capsule in midline & adj. to med. head of gastroc.

* special problems
– use drain — hematoma under skin flaps can cause skin necrosis

MCQs – Basic 4

MCQs-Basic 4
ankle anterior to knee anterior to hip (ant. to everything)
– Loading response posterior to ankle posterior to knee anterior to hip
– Midstance anterior to ankle anterior to knee posterior to hip
– Terminal stance anterior to ankle anterior to knee posterior to hip
– Preswing anterior to ankle posterior to knee posterior to hip

– hamstrings are most active at swing phase

– the hamstring functions to decelerate the thigh in late swing

– during walking, the center of gravity has an up/down motion of about an inch (2.5 cm) – may increase with walking faster.

– at heel strike the subtalar joint EVERTS – this unlocks the midfoot so that it can roll easily during midstance. The tib post tendon then activates to INVERT the subtalar joint during mid-terminal stance and this locks the midfoot so that push off is against a rigid lever.

– the axis of the calcaneocuboid and talonavicular joints are aligned when the subtalar joint is everted – this allows midfoot motion and the foot to accommodate the loading. As the subtalar joint is inverted by tib post, the axis of the calcaneocuboid and talonavicular joints are divergent, and thus the midfoot is locked

– a flexion moment of the hip exists during heelstrike (the joint reaction force passes anterior to the hip); there is a flexion moment only at the beginning of the stance phase – the joint reaction force then moves BEHIND the hip at midstance. There is a flexion moment to the hip during all of the swing phase.

– center of gravity is highest at midstance; probably lowest during loading response (all joints are flexed)

– at heelstrike, tib ant, EDL (not EHL), hamstrings, and quadriceps are all active. The hip flexors are not.

– increased energy consumption for 3 point crutch walking is about 50% (1.5 x normal)

– bone: 70% mineral/inorganic material – vast majority of this is hydroxyapatite
25-22% organic matrix (osteoid) – vast majority of this osteoid is collagen and other proteins (98%) The remaining 2% are cells.
5-8% water

– Approximately 90% of the organic matrix of bone is type I collagen – the remainder consists of noncollagenous matrix proteins. (some say 95%)

– bone is anisotropic

– matrix vesicles in bone contain phosphatases such as alkaline phosphatase and pyrophosphatase, which remove calcification inhibitors and provide the phosphate ions that allow mineral precipitation to take place. Pyrophosphatases therefore enhance mineralization.

– mineralization occurs in the gaps and pores within collagen fibers

– the function of alk phosphatase is not entirely clear – it may be required to provide PO4 and render the matrix calcifiable. It has some sort of role in mineralization.

– while osteoblasts/cytes have alk phosphatase to aid in mineralization, osteoclasts have acid phosphatase. The osteoclasts interact with bone at the CLEAR ZONE and RUFFLED BORDER. The clear zone is where the osteoclast attaches – it surrounds and seals off the area where the bone is to be resorbed. Intracellular carbonic anhydrase produces acid which is used to degrade bone underneat this area.

– osteons are 250 microns in diameter;

– volkmann canals connect the haversion canals which run up the center of the osteon.

– for blood flow in diaphyseal bone – inner 2/3 from intraosseous (centrifugal); outer 1/3 from periosteum (centripetal). All the vessels, including the cortical capillaries drain to intramedullary venous sinusoids inside the bone (centripetal)
– in experimental conditions, the average angle of a spiral fracture is approximately 30 degrees

– in the hypertrophic cartilage zone, the glycogen is consumed till depleted, and the condrocytes synthesize alk phosphatase – so you’d expect increase alk phosphatase, decreased glycogen.

– proteoglycan typically consists of a core protein and glycosaminoglycans such as chondroitan sulfate and keratin sulfate and dermatin sulfate. Hyaluronic acid is a glycosaminoglycan, but it is not part of the proteoglycan per se. Many of

Olecranon Fractures

Olecranon Fractures

(Colton ’73)
Type 1-undisplaced (

13 – Distal Humerus

13-Distal humerus

13-A-1 apophyseal avulsion(me
13-A-2 metaphyseal-simple
13-A-3 metaph.-comminuted
B-Partial articular
13-B-1 sagital lateral condyle
13-B-2 sagital medial condyle
13-B-3 frontal plane
C-Complete articular
13-C-1 simple articular + simple metaphysis
13-C-2 simple articular + comminuted metaphysis
13-C-3 comminuted articular