Patellofemoral Arthroplasty: Inlay vs. Onlay

A recent study, published in the KSSTA journal, compared two different implant types used in Patellofemoral Arthroplasty (PFA):

  • Group I consisted of an inlay (HemiCAP® Wave, Arthrosurface, Franklin, MA)
  • Group II was based on an onlay design (2nd generation, Journey™ PFJ, Smith & Nephew, Andover, MA)

snacAll patients were matched for age, gender, body mass index, and follow-up period with an independent observer evaluating the patients prospectively. Follow-up was 26 months for the inlay group and 25 months for the onlay cohort. No significant progression of tibiofemoral osteoarthritis (OA) was observed within the inlay group, whereas over half of the onlay group showed progression of knee OA (53%). While the mechanism of the disease progression was unclear, the authors hypothesized that the “onlay” device overstuffed the patellofemoral joint leading to chronic synovitis. The secretion of pro-inflammatory cytokines resulting from the synovitis is a known risk factor for OA. In addition, raising the height of the trochlea, which comes from using an onlay device, may have adverse effects on the extensor mechanism. This may increase the pressure in the femoral-tibial joint as the knee moves from extension to flexion. Based on this study, the inlay PF HemiCAP® design may improve long-term results and survival rates after isolated PFA.

Read the abstract here:

18 responses to “Patellofemoral Arthroplasty: Inlay vs. Onlay

  1. I have considerable arthritis in my joints. Are the hemicap Implants considered A partial replacement just for folks with minimal arthritis? Or can it be used as a substitute for a full joint replacement. I am very interested because I am a very active person and the full joint replacement implants that I have encountered are vulnerable to my activity.

  2. Hi Harlan – It’s possible that you could be a candidate! The best way to know is to consult with a surgeon who is trained and uses HemiCAP products.

  3. I am 52 years old and had a hemicap replacement in my left shoulder in April, 2016. Range of motion is normal, no pain and I am back to Powerlifting! I just wanted to say thank you Arthrosurface!

  4. Hi would like more information about this procedure.I am looking at doing surgery beginning of next year/total knee replacement.

  5. Hi val I live in the U.K. Just wondered if you had your knee done if so how you getting on I can’t seem to get any information on this surgery thanks. Pete swann

  6. Hi I live in the U.K. And wondering if there’s anyone that does the surgery in the uk or would I have to travel to the u.s both knees need surgery and wondered how much it would cost. My surgeon as said that the X-rays osteoarthritis is not too bad and can’t find any significant cartlidge deformity in the knees but could have diseased cartilage I’m 59 yrs old and 18 stone 5feet 10inches tall and fully fit just taking pain killers for the pain in my knees

  7. Hello, I live in southern Ontario in Canada and am interested in the HemiCAP for my big toe (1st metatarsal joint). Can someone put me in touch with a surgeon? Thank you.

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