This is a 10-year old male who was throwing a 
football with his friends in the morning while at a youth 
camp.  He noted some shoulder pain following this 
which worsened through the afternoon.  The pain was 
not of sudden onset and it did not feel like his shoulder 
popped out.   He did not fall onto his shoulder and he 
was not struck in the shoulder by anyone.  He was  
brought to the emergency department because of 
persistent pain and limited movement of his shoulder.  
He denied any numbness or tingling.
     His past history is unremarkable.  Specifically, it is 
negative for any fractures.
     Exam:  VS T37.3, P80, R18, BP 120/70.   He is alert 
and comfortable in no distress.  His anterior left 
shoulder is swollen.  The head of the humerus is 
prominent anteriorly.  There is severe tenderness in this 
region.  There is tenderness along the entire humerus.  
His clavicle is non-tender.  He is not tender over the 
elbow.  Supination and pronation are intact.  There is 
no visible deformity other than the shoulder.  Pulses, 
perfusion, sensation and finger movement are all intact 
distally.  The remainder of his physical exam is 
unremarkable.
     What is his diagnosis clinically?  Should we attempt 
to reduce a possible shoulder dislocation without 
obtaining radiographs?  This does not appear to be a 
shoulder dislocation since there is no sudden event 
causing the dislocation.  While throwing can cause a 
dislocation, his history is not consistent with this.  
Additionally, shoulder dislocations in young children are 
not very common, while fractures are fairly common.  It 
would  be best to obtain radiographs first.
     What would radiographs reveal in such a patient?  Is 
a fracture possible?  According to his history, his 
shoulder does not appear to have sustained enough 
trauma to cause a fracture and the gradual onset and 
progression of his pain does not appear to be 
consistent with a fracture.  We often make such 
assumptions, but we are often assuming that every 
patient has normal bones.  Patients occasionally have 
bone abnormalities such as metastatic tumor, bone 
cysts or occult primary bone diseases which make the 
patient's bone highly fracture prone.  Without 
radiographs, we would not be able to tell if there is an 
abnormality of the bone.  In addition to this uncertainty, 
the history given to us may be incorrect.  Histories are 
frequently fabricated as a cover-up for child abuse.
     Radiographs of his shoulder are obtained. 

View shoulder radiographs.


     These radiographs demonstrate a pathologic 
fracture through a bone cyst of the proximal humerus.  
The fracture extends distally through the humerus.  The 
bone cyst's margins are well defined and slightly 
sclerotic.

View pointers.


     The black arrows point out the fractures around the 
cyst.  The white outline arrows point out the fractures in 
the mid humerus.
     If the clinician assumes that a fracture is not 
possible and attempts to reduce a dislocated shoulder, 
this would worsen a fracture injury and cause 
unnecessary pain.  You may decide to assume that 
your patient has normal bones, but this is not always 
true.

     In another case, a 9 year old boy presents with 
severe shoulder pain after bumping his shoulder 
against a door as the door was closing.  Radiographs 
are obtained.

View shoulder radiographs.




     These radiographs show a large bone cyst in the 
proximal humerus with a pathologic fracture involving 
the cyst.   This is another case where the history of the 
trauma is minor, but a fracture is present because of 
abnormal bone.  We cannot always assume that our 
patients have normal bones.
     Pathologic fractures occur with minimal trauma that 
would not ordinarily be expected to cause a fracture.  
Basically, these are fractures through weak bones.  
Conditions causing weak bones can be divided into two 
types:  1) conditions which cause focal weakness and 
2) generalized conditions causing all the bones to be 
weak.
     Focal conditions include benign tumors or tumor-like 
conditions, malignant bone tumors, metastatic lesions, 
infectious or inflammatory conditions (osteomyelitis, 
eosinophillic granuloma) and iatrogenically weakened  
areas of bone (screw holes, bone graft harvest sites, 
etc.).  While an incompletely healed fracture may be 
weaker than normal bone, a new fracture through a 
healing fracture is generally not considered to be a 
pathologic fracture.
     Generalized conditions resulting in weak bones 
include osteogenesis imperfecta, osteopetrosis, 
neurofibromatosis, fibrous dysplasia, rickets, renal 
osteodystrophy, scurvy, hyperparathyroidism, Cushing's 
syndrome, cytotoxic drugs and disuse atrophy due to 
neurological or other disabling conditions resulting in 
generalized demineralization.

     Unicameral bone cysts are one of the most common 
types of benign bone cysts.  These cysts contain 
serous fluid and are lined by a thin connective tissue 
membrane.  Most of these are located in the 
metaphysis of the proximal humerus or femur.  These 
usually heal spontaneously during the teen years unless 
a pathologic fracture occurs.  Large cysts at risk for 
recurrent pathologic fracture require treatment, while 
smaller lesions generally regress on their own.
     Aneurysmal bone cysts are also benign bone cysts, 
but are not as common as unicameral bone cysts. 
Common locations include the spine and the same 
areas as unicameral bone cysts.  These are 
eccentrically placed within the metaphysis.  The lesion 
resorbs cortex and elevates the periosteum resulting in 
an aneurysm-like appearance.  These are more difficult 
to distinguish from malignant tumors and CT may be 
helpful in determining this.
     Non-ossifying fibromas, non-osteogenic fibromas 
and fibrous cortical defects are different terms for the 
same histologic process (synonyms).  The names differ 
because of the different radiographic appearances.  
Small lesions are called fibrous cortical defects.  Larger 
lesions, referred to as non-ossifying fibromas, cause 
bulging of the bone and bony reaction over the lesion. 
     Fibrous  dysplasia is a developmental anomaly of 
the bone that results in focal lesions of the bone where 
fibrous tissue replaces the medullary canal.  The 
majority of patients have a single focal lesion and a few 
patients have multiple lesions.

References:
     Poitras B, Rivard CH.  Pathologic Fractures 
(Chapter 56).  In:  Letts RM (ed).  Management of 
Pediatric Fractures,  New York, New York, Churchill 
Livingstone, 1994, pp. 1027-1048.