Modified hybrid stem fixation in revision TKA is durable at 2 to 10 years.
BACKGROUND
Hybrid revision knee component fixation, in which cement is placed in the metaphysis combined with a cementless diaphyseal engaging stem, provides ease of insertion, possibly improved component alignment, and easier removal if required, compared with fully cemented prostheses. The literature suggests the technique has a 2 to 5 year survivorship ranging from 81% to 94%.


OBJECTIVE
To confirm the literature we asked whether (1) a modified hybrid fixation technique is durable and reliable at an average 5-year followup, (2) this method of fixation provides clinical improvements as assessed by knee scores, (3) there are radiographic findings unique to this fixation technique, (4) the degree of knee constraint influences clinical performance or radiographic findings, and (5) end-of-stem pain is associated with this fixation method?


METHODS
We retrospectively reviewed all 83 patients who had 88 both-component revision TKAs using our modified hybrid fixation technique. We assessed the Knee Society scores and evaluated radiographs for radiolucent and radiosclerotic lines. The minimum followup was 24 months (average, 65 months; range, 24-126 months).


RESULTS
Kaplan-Meier survivorship free of aseptic loosening was 100% at 5 years and 90% at 10 years. Postoperatively, the mean Knee Society pain and function scores both improved. Partial radiolucent lines were rare; two components were loose. We commonly observed radiosclerotic lines adjacent to stem extensions but these did not affect clinical scores or implant stability at last followup. Neither knee scores nor radiographic findings differed based on knee constraint. End-of-stem pain occurred rarely and was transient.


CONCLUSIONS
Modified hybrid fixation of revision knee arthroplasty using a diaphyseal engaging stem and cementation only in the metaphysis is durable at a mean 5 years followup.


METHODS
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Sah
Alexander P
AP
Department of Orthopedics, Washington Hospital Healthcare System, 2000 Mowry Avenue, Fremont, CA 94536, USA. asah07@gmail.com
Shukla
Sanjai
S
Della Valle
Craig J
CJ
Rosenberg
Aaron G
AG
Paprosky
Wayne G
WG
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D002484:Cementation; D019544:Equipment Failure Analysis; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D053208:Kaplan-Meier Estimate; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular; D012086:Reoperation; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome