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Cast wedging and fracture nonunion

Cast wedging to correct alignment, and the causes, investigation and management of nonunion.

15 questions 2 source pages

Images appear with the first question taken from each source page — tap a question to open it.

Q1What is the indication and timing for cast wedging?▸

Q2Describe the open wedging technique.▸

Half-circumferential cut with a 1cm bridge
Wedge applied on the concave side
Cuts perpendicular to the plane of angulation; bridge lies on the axis of rotation
Cork keeps the wedge open; fresh POP bandaging ~5cm distal and proximal

Q3Where is the wedge placed relative to the deformity?▸

Q4What is the FDA definition of non union and the definition of delayed union?▸

FDA: fracture at least 9 months old with no signs of healing for 3 consecutive months
Delayed union: bone unable to achieve union in the expected time frame (6 months)

Q5How is delayed union treated?▸

Conservative: shock wave USG (early, 2-3 months), vibration (train muscle mass, proprioception, promote union)
Electrical stimulation - increased expression of BMP2,7 and osteoblast proliferation (direct current, pulsed electromagnetic field)
Operative: dynamization, bone graft, bone marrow

Q6Describe the Paley and descriptive classifications of non union.▸

Paley type 1: <1cm defect (then lax/stiff/deformity)
Paley type 2: >1cm defect (shortening/gap/both)
Descriptive: atrophic, oligotrophic, hypertrophic (horse hoof/elephant foot), pseudarthrosis
Also infective non union

Q7What are the causes of non union according to the diamond concept?▸

Diamond concept: inductive, conductive, osteogenic, host and vascular factors
Mechanical instability: inadequate fixation, bone loss, poor bone quality
Inadequate vascularity: severe soft tissue injury with periosteal stripping, malalignment, bone loss, distraction
Poor bone contact: soft tissue interposition, malalignment, bone loss, distraction

Q8Describe the X-ray findings and postulated causes in this subtrochanteric non union.▸

Previous subtrochanteric fracture fixed with a long cephalomedullary device + 1 cerclage wire
No healing, bone defect, varus alignment, no broken implant
Atrophic non union
Biology: watershed area; mechanical: wide medullary canal, large deforming force; varus increases the bending moment, leading to increase in fracture strain per unit length; the region experiences the highest tensile stress according to Koch's diagram

Q9How is this subtrochanteric non union managed?▸

Q10How is non union assessed?▸

Rule out infection (initial open injury, wound infection, erythema/sinus, blood tests)
Delineate the cause: atrophic vs hypertrophic non union
Atrophic: biological +/- mechanical causes; consider periosteal/endosteal blood supply
r/o complication due to non union (broken implant, AVN, arthritis)

Q11What are the management principles in non union?▸

Alignment, stability, bone potential to heal, +/- adjacent joint stiffness
Rule out infection
Address patient/systemic factors: DM, nutrition, smoking, compliance
Formulate a plan: bring in blood supply, optimal reduction, stable fixation, +/- manage bone defect

Q12What are the local causes of atrophic versus hypertrophic non union?▸

Atrophic - bone factors: vulnerable blood supply, minimal bone contact, high stress, no periosteum
Atrophic - fracture factors: open injury, butterfly fragment with no blood supply
Atrophic - surgeon factors: diminished blood supply (distruption of endosteum + periosteum blood supply) - disruption of endosteal/periosteal supply, non-optimal fixation method
Hypertrophic - bone factors: minimal bone contact, high stress, no periosteum
Hypertrophic - fracture factors: degree of initial comminution --> poor initial stability if fixed with load sharing device
Hypertrophic - surgeon factors: wrong implant, poor reduction, poor fixation skill

Q13Describe the X-ray findings and management in the distal radius non union.▸

Fracture shaft of distal radius fixed with 6-hole DCP with compression
Positive callus, fracture gap still seen; need proper AP + lateral X-ray to delineate alignment; no ulnar fracture
One distal screw very near the fracture gap
Hypertrophic/oligotrophic non union
Management: rule out infection, delineate cause (initial malreduction, unstable fixation), whole forearm X-ray, revision plating + bone graft

Q14How are bone defects managed?▸

Further management depends on size of defect and integrity of soft tissue coverage, vascularity of tissue bed
Small <6cm: acute shortening, non-vascularised bone graft, Papineau technique
Intermediate up to 12cm: vascularised bone graft (e.g. fibular), can also provide soft tissue coverage in same flap
Large >6cm: acute shortening + distraction osteogenesis, bone transport, Masquelet technique
Amputation for significant bone/soft tissue/NV defect or patients unfit for multiple surgery

Q15Why is exchange nailing used for non union and what are the results?▸

Largest series by group in Edinburgh, published in 2016 BJJ: union 75% after 1st exchange, rising to 95% after 2nd exchange
In infected non union: 35% after 1st, 65% after second
Works by 3 mechanisms: larger nail improves mechanical stability; Reaming increases periosteal blood flow – stimulate the formation of periosteal new bone; reaming products are osteoinductive
Simple JBJS 2016: the strongest predictor of failure of exchange nailing was infection and suggested other treatment options such as ilizarov treatment should be preferred

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