Table 1.

Factors potentially associated with aseptic failure of patella implants and outcomes of cases

Mechanism of failure				Outcome
Evidence of AVN	Fracture	Superior rim present?	Mechanism of failure	Treatment	Time to revision (years)	Revision of femoral and/or tibial component	Followup from time of primary surgery (years)	Presence of anterior knee pain	Pain component of Knee Society score (of 50)
Yes	Transverse	Yes	AVN; fracture	Observed			15	Yes weekly 8/10	45
Yes	Fragmentation	Yes	AVN	Observed			14	No	50
No	No	Yes	?Poorly supported on lateral and shear force form tilt	Observed			13	No	45
No	No	Yes	Unclear	Observed			13	No	50
No	No	No	No rim	Revised	6		11	No	45
Yes	Longitudinal fracture, then fragments	No	AVN; fracture; no rim	Patellectomy	1		5 (deceased)	Not recorded	“Ongoing pain”
No	No	No	Revised for patella subluxation	Revised (and realignment)	6		6 (demented)	Unknown	Unknown (patient demented, no further followup)
No	No	No	No rim	Revised	4		6 (deceased)	Not recorded	45
Yes	Fragmentation	Unable to assess	AVN; fracture	Removed	5		12	No	45
No	Longitudinal	Yes	Fracture	Removed; subsequent patellectomy 2 years later	5	Revised	5 (deceased)	Not recorded	20
No	Longitudinal	Unable to assess	Fracture	Removed	12	Revised	13 (deceased)	Not recorded	45
No	No	No	No rim	Revised	10	Revised (then further revision 1 year later)	11	Not recorded	50
No	No	Yes	Unclear	Revised	14	Revised	14	Recent revision	Recent revision
No earlier radiographs	No earlier radiographs	No earlier radiographs	Aseptic loosening, cause unclear	Removed	5	Revised for instability	6 (deceased)	No	50

AVN = avascular necrosis.