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.

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

Ankle & Hindfoot – Anterolateral Approach

Ankle & hindfoot – anterolateral approach

* position – supine with sandbag under buttock

* incision
– curved incision on anterolat. aspect of ankle
– start 5 cm prox. to ankle joint & 2 cm ant. to ant. border of fibula
– curve distally crossing ankle joint 2 cm med. to tip of lat. malleolus
– end 2 cm med. to 5th MT base over base of 4th MT

* internervous plane – peroneal muscles (SPN) & extensor muscles (DPN)

* dissection
– incise fascia in line with skin thru sup. & inf. extensor retinacula
– ID & preserve any dorsal branches of SPN
– ID peroneus tertius & EDL
– in upper half of wound, incise down to bone lat. to these muscles
– retract extensors med.
– distally ID EDB at origin from calcaneus & detach
– branches of lat. tarsal art. need to be cauterized
– reflect EDB distally & med.
– ID dorsal capsule of calcaneocuboid & talonavicular joints
– ID fat in sinus tarsi & clear to expose talocalcaneal joint
– incise joint capsules

* dangers
– DPN & ATA – cross front of ankle joint btw EHL & EDL

Acetabulum – Anterior Approach

Acetabulum – anterior approach
(extended iliofemoral approach)

* position
– supine +/- sandbag under affected hip

* incision
– long icision following iliac crest to ASIS
– curve incision 8-15cm to run vertically down thigh towards lat. aspect of patella

* internervous plane
– sartorius (fem. n.) & TFL (sup. gluteal n.)
– rectus femoris (fem. n.) & gluteus medius (sup. gluteal n.)

* dissection
– ER leg to stretch sartorius
– ID gap btw TFL & sartorius usu 2-3 in below ASIS
– dissect down thru subcut. fat along intermuscular interval avoiding lat. fem. cut. n. –> pierces deep fascia of thigh close to interval
– incise deep fascia on med. side of TFL
– detach origin of TFL to develop plane
– ascending branch of lat. fem. circumflex art. crosses btw TFL & sartorius
– detach gluteus medius from origin with gluteus minimus
– for exposure of post. column, detach glutei from GT via osteotomy
– detach rectus from both origins (AIIS & sup. lip of acetabulum)
– to gain access to med. aspect of iliac wing, detach abd. musculature from iliac crest
– subperiosteal dissection under iliacus

* dangers
– lat. fem. cut. n.
> reches thigh by passing over, behind or thru sartorius 2.5 cm below ASIS
> beware of nerve when incising fascia btw TFL & sartorius

– femoral n. – lies directly ant. to hip joint in fem. triangle & well med. to rectus femoris

– ascending branch of lat. fem. circumflex art. – crossed field prox. btw TFL & sartorius

– superior gluteal art.
> form nv bundle that supplies gluteus min. & med.
> at risk with detachment of both origin & insertion of these 2 muscles

Acetabulum – Ilioinguinal Approach

Acetabulum – ilioinguinal approach

• position – supine with GT @ edge of table
– need catheter

• incision – curved ant. Incision starting 5cm above ASIS
– 1cm above pubic tubercle to midline

* no internervous plane

* dissection
– incise subcut. fat
– expose aponeuroses of ext. oblique
– lat. fem. cut. n. in lat. edge of dissection
– divide ext. oblique from superficial inguinal ring to ASIS
– ID round lig. or spermatic cord = med. bundle
– divide ant. part of rectus sheath to expose underlying rectus
– strip iliacus from inside of wing of ilium –> can expose SI joint
– divide rectus transversely 1cm prox. to insertion
– develop plane btw back of symphysis & bladder = space of Retzius)
– peel fibers of int. oblique & transversus from inguinal lig. –> avoids inf. epigastric art. & deep inguinal ring
– push peritoneum upwards to expose ext. iliac vessels
– isolate ext. iliac vessels = middle bundle
– isolate iliopsoas & fem. n. = lat. bundle
– expose med. surface of acetabulum & sup. pubic ramus

* dangers
– fem. n. – runs beneath inguinal lig. lying on iliopsoas; avoid excessive retraction

– inf. epigastric art. – passes med. to deep inguinal lig.

– spermatic cord – contains vas deferens & testicular art.

– bladder – easily mobilized off back of symphsis

– corona mortis
> anastomosis of branch of obturator art. & ext. iliac art.
> occurs in 25-30% of patients
> on undersurface of ext. iliac art.