Question:
In women having total knee replacement, does a gender-specific total knee prosthesis produce better functional outcomes than a standard prosthesis produces?
Design:
Randomized (allocation concealed), blinded (patients, physiotherapists, and other outcome assessors) controlled trial with mean follow-up of 3.25 years.
Setting:
A university hospital in Seoul, South Korea.
Patients:
146 women who had grade-III to grade-V bilateral osteoarthritis of the knee with a varus deformity between 1° and 26°. Patients with a diagnosis of rheumatoid arthritis were excluded. 138 patients (95%, 276 knees) (mean age, 71.2 y; mean body-mass index, 27.3) completed follow-up.
Intervention:
Patients’ knees were allocated to a gender-specific or a standard NexGen CR-flex prosthesis (Zimmer, Warsaw, Indiana). Each patient had both types of prostheses. The surgical technique was the same in all knees. The femoral component was introduced in 3° of external rotation in relation to the posterior femoral condyles or perpendicular to the so-called Whiteside line or parallel to the transepicondylar axis. Patellae were resurfaced with use of a polyethylene prosthesis, and the implants were cemented after pulsed lavage, drying, and pressurization of the cement. On the second postoperative day, patients began active and passive range-of-movement exercises and began standing at the bedside or walking with assistance twice daily for thirty minutes under the supervision of a physiotherapist.
Main outcome measures:
The primary outcomes were the Knee Society knee and function scores (maximum, 100 points for each; higher scores = better outcome). Other outcomes were range of movement, complication rates, radiographic assessment, and patient satisfaction (a visual analog scale of 0 to 10, with higher scores indicating greater satisfaction).
Main results:
Eighty-eight knees per group were required for the study to have 80% power to accept the hypothesis that satisfaction would be similar between the two groups when the difference in mean satisfaction score was <3.0 points. The Knee Society knee and function scores and patient satisfaction were not different in the gender-specific and standard-prosthesis groups (Table). Complication rates were low in both groups, and no differences were observed in radiographic parameters.
Conclusion:
In women having total knee replacement, a gender-specific total knee prosthesis did not confer any benefit in functional outcome or patient satisfaction when compared with a standard prosthesis.
The introduction of gender-specific knee arthroplasties to accommodate anatomical differences between women and men has stimulated spirited debate. Interestingly, several different knee arthroplasties have qualified, with use of FDA-approved criteria, as being gender-specific without any changes being made in their designs, presumably due to the fact that, in most systems, smaller implant sizes were developed to accommodate smaller female anatomy.
The need for gender-specific knee arthroplasties is based on the assumption that women have results that are inferior to those of men following total knee replacement. However, this claim is not substantiated in the literature1,2. Furthermore, the 2010 Annual Report of the Australian National Joint Replacement Registry reported that 127,847 female patients with a diagnosis of osteoarthritis had lower cumulative revision rates at nine years following total knee arthroplasty compared with 96,825 male patients3.
In this excellent randomized controlled trial by Kim and colleagues, no significant differences were observed between one gender-specific knee arthroplasty and its matching standard knee arthroplasty equivalent in terms of disease-specific outcomes (Knee Society scores) or patient satisfaction at a mean follow-up of 3.25 years.
In conclusion, gender-specific total knee implants do not seem to confer any benefit in terms of clinical outcome, satisfaction, or survivorship.
References
Bourne
RB;
McCalden
RW;
MacDonald
SJ;
Mokete
L;
Guerin
J. Influence of patient factors on TKA outcomes at 5 to 11 years followup. Clin Orthop Relat Res.
2007;464:27-31.[PubMed]
MacDonald
SJ;
Charron
KD;
Bourne
RB;
Naudie
DD;
McCalden
RW;
Rorabeck
CH. The John Insall Award: gender-specific total knee replacement: prospectively collected clinical outcomes. Clin Orthop Relat Res.
2008;466:2612-6.[PubMed] [CrossRef]
Australian Orthopaedic Association National Joint Replacement Registry. Annual Report. Adelaide: AOA; 2010, p 111.