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

MCQs – Anatomy 2

MCQs-Anatomy 2
(deltoid); then technically internervous between infraspinatus (suprascapular) and teres minor (axillary).

– the posterior approach to the humerus – dissection is between lateral and medial heads of triceps (radial nerve and profundus running between). Remember: the posterior approach is good for more distal humeral fractures, because the distal 1/3 of the humerus at the front is covered by the brachialis which at this level is hard to move out of the way. The posterior approach is limited superiorly by radial nerve – you can always slip the plate underneath it.

– the radial nerve is found between medial and lateral heads of triceps, and at the elbow, between brachialis and brachioradialis

– Musculocutaneous nerve: (C4), C5,6,7
– Axillary nerve: C5,6
– Radial nerve: C5, 6, 7, 8, T1
– Median nerve: (C5), C6,7,8, T1
– Ulnar nerve: (C7), C8, T1

– the ulnar nerve pierces the IM septum about 8-10 cm above the medial epicondyle to run in the posterior compartment, just on the ANTERIOR surface of the medial head of triceps. It then pierces the two heads of FCU to run deep to flexor digitorum superficialis and flexor carpi ulnaris, but superficial to FDP.

– like the ulnar nerve, the median nerve also passes under the fibrous arch of FDS and runs between FDS and FDP

– the last muscle to recover from radial nerve injury is extensor indicis proprius. It is actually distal to EPL.

– for high radial nerve injury: order of re-innervation. Complicated question. The brachioradialis and ECRL obvious return first. The PIN goes through supinator and emerges (often giving off ECRB before going through supinator, or ECRB gets it from the superficial branch). As it emerges from the distal end of supinator, there are two main distributions of the PIN – one superficial to the EDC, EDMinimi, and ECU; and one that travels more deep to innervate APL, EPL, EPB, and finally most distally, Ext Indices Proprius. Notice that it looks like EPL might get innervated before EPB. Arguable. In any event, index finger extension will return before thumb retropulsion because EDC is reinnervated before EPL.

– so the order: EDC, EDMinimi, ECU (all the superficial ones); then APL, EPL, EPB, Eindicis (the deep ones)
– note that EDMinimi is innervated quite high

– posterior branch of obturator artery – this is what comes through the ligamentum teres

– the medial Ludloff approach to the hip: superficial exposure goes under adductor longus (between adductor longus and gracilis). Pectineus is more medial, and lies about at the same level as adductor (though it inserts just anterior to longus on the femur). This interval then gets you onto adductor brevis. The deep dissection then goes UNDER brevis between adductor brevis and adductor magnus which is an internervous plane between the anterior branch of obturator nerve (supplying brevis) and the posterior branch (supplying magnus). By lifting up on brevis and pulling down on magnus, you will see the lesser trochanter with the iliopsoas tendon attachment.. Note that the brevis is sorta “sandwhiched” between the anterior and posterior divisions of the obturator nerve (but is supplied by the anterior)

– the profunda femoris lies on pectineus then curves posteriorly – it gives off the medial circumflex artery, which passes posterior to pectineus and then curls behind the iliopsoas tendon (in close proximity to the tendon!) – YOU HAVE TO WATCH OUT FOR THIS ARTERY WHEN YOU DO THE DEEP DISSECTION. After the superficial dissection, you get between longus and brevis – the artery is in this plane as it heads under iliopsoas. You avoid it here by going deep to brevis (between brevis and magnus), but then you end up exposing iliopsoas tendon in the deep dissection – and the artery is RIGHT THERE!

– therefore, during the medial Ludloff approach, the most endangered structure is the medial circumflex femoral artery. Also exposed are both the anterior branch of the obturator nerve (during superficial exposure) and the posterior branch

Forearm – Dorsal Approach (Thompson)

Forearm – dorsal approach (Thompson)

* position – supine with tourniquet

* incision – straight incision from just anterior to lat. epicondyle –> ulnar side of Lister’s tubercle

* internervous plane:
– prox – ECRB (radial n.) & EDC (PIN)
– distal – ECRB (radial n.) & EPL (PIN)

* superficial dissection
– incise fascia
– interval btw ECRB & EDC
– start midshaft
– interval btw ECRB & EPL

* deep dissection
– proximal 1/3
> identify supinator
> locate PIN as it emerges 1 cm from distal end of muscle btw deep & superficial heads
> dissect nerve out of supinator
> fully supinate forearm
> detach supinator at insertion from ant. aspect of radius

– middle 1/3
> APL & EPB cross dorsal aspect of radius
> retract off bone & make incision along their sup. & inf. borders

– distal 1/3
> separating ECRB & EPL exposes lat. border of radius

* dangers – PIN – identify carefully b/c in 25% it touches the dorsal aspect of radius at level of biceps tuberosity

Thoracic Spine – Posterolateral Approach

Thoracic spine – posterolateral approach

* position – prone with bolsters positioned long.

* incision – curved linear incison about 8 cm lat. to appropriate spinous process

* no internervous plane

* dissection
– incise subcut. fat & fascia in line with skin incision
– cut thru trapezius in line with fibers close to transverse processes
– cut down to post. aspect of rib to be resected
– separate all muscle attachments from rib subperiosteally
– dissect lat. along sup. border of rib & med. along inf. border
– divide rib about 6-8 cm from midline
– detach any remaining muscle & twist rib’s med. end to complete resection
– remove muscle from TP
– remove TP at jxn with lamina & pedicle
– enter retropleural space by digital palpation
– remove parietal pleura from vert. body

* dangers
– dura – if dissection is extensive around vert. body & central canal entered
– intercostal art. – safe with subperiosteal dissection
– pleura – initially use blunt dissection

ACJ Dislocations

AC Dislocations

(originally Tossy and Allman-3 types)
Type I-AC ligament sprain
Type II-AC ligs torn,C/T intact
Type III-AC,C/T all torn
Type IV-AC,C/T all torn and distal clavicle buttonholes postero-superior into trapezius-marked/fixed dislocation
Type V-IV + deltoid and trapezius tear thus v.v.displaced
Type VI-AC,C/T all torn and distal clavicle goes inferior and trapped under coracoid process
Type VII-Total clavicular dislocation (AC and SC dislocation)

Monteggia Fractures

Monteggia Fractures

(Bado, 1967)
ulna fracture with radial head dislocation
Type 1-anterior
Type 2-posterior
Type 3-lateral
Type 4-#radius and ulna with ant. radial head