Approach to Genu Valgum
First thing: consider the differential diagnosis
– physiologic knock knees – should max out at around 12+/-8o at 3-4 years of age
– bony dysplasia – MED, SED, Morquio’s,.
– hypophosphatemic rickets – usually varus, but can be valgus
– proximal tibial fracture – often develop valgus deformity once healed
As always, do a full history.
– What’s the time course of the problem? How old is the patient? – valgus should be turning around at 3-4 yrs
– Family history? Hypophosphatemic rickets is an x-linked dominant trait
– Overall health, weight gain, motor milestones, growth and development – short stature (rickets or one of the bony dysplasias)
The key is to be looking for hints that this is something other than simple physiologic knock knees
– on the exam, you fuckin’ better be thinking that this is not simple physiologic knock knees!
Do a physical
– measure the deformity and do a knee exam looking for laxity, etc.
– note the height of the patient (rickets patients are short!)
– do a general physical to rule out any dysmorphic features and examine the hips
Get standing AP x-rays, and have low threshold for getting entire femur to see hips and entire tib/fib to see ankles.
If you’re not sure if this is part of a generalize skeletal dysplasia, get a skeletal survey!
– in general, gnu valgum is associated with more patellofemoral problems than genu varum
– if they are 30-36 months old and otherwise completely normal – observe; even if they are >20 degrees, they may resolve.
– non surgical management is not practical for these patients.
For physiologic knock knees
– wait until they’re 10 years of age, have > 10 cm intermalleolar distance, or >15-20 degrees of valgus – then consider a hemi-epiphyseodesis if you are confident you know how much length they are going to gain on that other side; or medial physeal stapling if unsure (you can take out the staple – but you are not guaranteed that it will continue to grow once you take out the staple)
– ie. use a hemi-epiphyseodesis when you’re fairly certain that overcorrection will not occur, but use staples when you aren’t sure or when the growth parameters are abit weird.
Note: in general, if you are operating on a genu varus – you want to correct them bigtime (basically OVERcorrect them.) But in genu valgum, you want to just get them about neutral, maybe slight valgus. Do not overcorrect the valgus knee.
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