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 – Anterior Approach

Ankle – anterior approach

* position – supine with tourniquet

* incision – long. incision over ant. ankle halfway btw malleoli

* no internervous plane – use intermuscular plane btw EHL & EDL

* dissection
– incise fascia in line with skin
– ID interval btw EHL & EDL
– find nv bundle just med. to EHL
– follow nv bundle distally to ankle until it crosses behind EHL
– mobilize nv bundle
– incise remaining soft tissue on ant. tibia to expose tibia & ankle joint
– subperiosteal dissection of distal tibia

* dangers
– SPN – run close to line of incision just under skin
> above ankle – btw EHL & TA
> distal to ankle – btw EHL & EDL
> crosses post. to EHL at level of ankle

Hip – Medial Approach

Hip – medial approach

* position – supine with affected hip flexed, abducted & ER

* incision – long. incision on med. side of thigh starting 3 cm below pubic tubercle over add. longus

* internervous plane
– add. longus & gracilis (both innervated by ant. branch of obturator n. but receive nerve supply prox. to dissection)
– add. brevis & magnus
– add. magnus – 2 nerve supplies (post. division of obturator n. & tibial portion of sciatic n.)

* dissection
– incise subcut. tissue
– develop plane btw add. longus & gracilis
– develop plane btw add. brevis & magnus
– place retractor above & below LT to isolate psoas tendon

* dangers
– ant. div. of obturator n.
> lies on top of obturator ext. & runs down med. side of thigh btw add. longus & add. brevis
> supplies add. longus, gracilis, add. brevis

– post. div. of obturator n.
> lies in substance of obturator ext. & runs down thigh on add. magnus & under add. brevis
> supplies obturator ext. & add. portion of add. magnus

– med. fem. circumflex art. – passes around med. side of distal part of psoas

Ulnar Nerve – Volar Approach

Ulnar nerve – volar approach

* position – supine with tourniquet

* incision
– curved incision following radial border of hypothenar eminence
– cross wrist joint obliquely at 60 deg
– extend incision onto volar aspect of distal forearm

* no internervous plane

* dissection
– identify FCU tendon
– incise fascia of tendon on radial border
– retract FCU ulnarly to expose ulnar n. & art.
– follow NV bundle distally & incise volar carpal ligament – decompresses Guyon’s canal

* dangers
– ulnar n.
> use care when incising fascia on radial side of FCU
> use care when incising volar carpal lig. distally

Glenoid Fractures

Glenoid Fractures

Type I-glenoid rim (often assoc. with shoulder dislocation)
Type II-separation of segment of inferior glenoid (obligue or transverse)
Type III-Assoc. With AC Joint injury
Type IV-fracture traverses glenoid and body to exit through medial border of scapula
Type V-combination of II and IV

43 – Tibia/Fibula Malleoli

43-Tibia/Fibula Malleoli

A-Infrasyndesmotic lesion
44-A-1 isolated
44-A-2 # medial malleolus
44-A-3 postero-medial #
B-Transsyndesmotic fibular fracture
44-B-1 isolated
44-B-2 with medial lesion
44-B-3 with medial lesion
C-Suprasyndesmotic lesion
44-C-1 fibular diaphyseal simple
44-C-2 fibular diaphyseal comminuted
44-C-3 proximal fibular lesion