A case-control study of spontaneous patellar fractures following primary total knee replacement.
Peri-prosthetic patellar fracture following resurfacing as part of total knee replacement (TKR) is an infrequent yet challenging complication. This case-control study was performed to identify clinical, radiological and surgical factors that increase the risk of developing a spontaneous patellar fracture after TKR. Patellar fractures were identified in 74 patients (88 knees) from a series of 7866 consecutive TKRs conducted between 1998 and 2009. After excluding those with a previous history of extensor mechanism realignment or a clear traumatic event, a metal-backed patella, any uncemented component or subsequent infection, the remaining 64 fractures were compared with a matched group of TKRs with an excellent outcome defined by the Knee Society score. The mean age of patients with a fracture was 70 years (51 to 81) at the time of TKR. Patellar fractures were detected at a mean of 13.4 months (2 to 84) after surgery. The incidence of patellar fracture was found to be strongly associated with the number of previous knee operations, greater pre-operative mechanical malalignment, smaller post-operative patellar tendon length, thinner post-resection patellar thickness, and a lower post-operative Insall-Salvati ratio. An understanding of the risk factors associated with spontaneous patellar fracture following TKR provides a valuable insight into prevention of this challenging complication.
Samsung Medical Center, Department of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangsam-gu, Seoul 135-710, Korea.
J G
JG
Seo
Y W
YW
Moon
S H
SH
Park
J H
JH
Lee
H M
HM
Kang
S M
SM
Kim
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D005598:Fractures, Spontaneous / Q000209:etiology*; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000293:injuries* / Q000473:pathology; D057068:Periprosthetic Fractures / Q000209:etiology*; D011474:Prosthesis Design; D012307:Risk Factors