title: Mobile bearing vs fixed bearing prostheses for posterior cruciate retaining total knee arthroplasty for postoperative functional status in patients with osteoarthritis and rheumatoid arthritis.
abstract: BACKGROUND
  It is unclear whether there are differences in benefits and harms between mobile and fixed prostheses for total knee arthroplasty (TKA). The previous Cochrane review published in 2004 included two articles. Many more trials have been performed since then; therefore an update is needed.
  
  
  OBJECTIVE
  To assess the benefits and harms of mobile bearing compared with fixed bearing cruciate retaining total knee arthroplasty for functional and clinical outcomes in patients with osteoarthritis (OA) or rheumatoid arthritis (RA).
  
  
  METHODS
  We searched The Cochrane Library, PubMed, EMBASE, CINAHL and Web of Science up to 27 February 2014, and the trial registers ClinicalTrials.gov, Multiregister, Current Controlled Trials and the World Health Organization (WHO) International Clinical Trials Registry Platform for data from unpublished trials, up to 11 February 2014. We also screened the reference lists of selected articles.
  
  
  METHODS
  We selected randomised controlled trials comparing mobile bearing with fixed bearing prostheses in cruciate retaining TKA among patients with osteoarthritis or rheumatoid arthritis, using functional or clinical outcome measures and follow-up of at least six months.
  
  
  METHODS
  We used standard methodological procedures as expected by The Cochrane Collaboration.
  
  
  RESULTS
  We found 19 studies with 1641 participants (1616 with OA (98.5%) and 25 with RA (1.5%)) and 2247 knees. Seventeen new studies were included in this update.Quality of the evidence ranged from moderate (knee pain) to low (other outcomes). Most studies had unclear risk of bias for allocation concealment, blinding of participants and personnel, blinding of outcome assessment and selective reporting, and high risk of bias for incomplete outcome data and other bias. Knee painWe calculated the standardised mean difference (SMD) for pain, using the Knee Society Score (KSS) and visual analogue scale (VAS) in 11 studies (58%) and 1531 knees (68%). No statistically significant differences between groups were reported (SMD 0.09, 95% confidence interval (CI) -0.03 to 0.22, P value 0.15). This represents an absolute risk difference of 2.4% points higher (95% CI 0.8% lower to 5.9% higher) on the KSS pain scale and a relative percent change of 0.22% (95% CI 0.07% lower to 0.53% higher). The results were homogeneous. Clinical and functional scores The KSS clinical score did not differ statistically significantly between groups (14 studies (74%) and 1845 knees (82%)) with a mean difference (MD) of -1.06 points (95% CI -2.87 to 0.74, P value 0.25) and heterogeneous results. KSS function was reported in 14 studies (74%) with 1845 knees (82%) as an MD of -0.10 point (95% CI -1.93 to 1.73, P value 0.91) and homogeneous results. In two studies (11%), the KSS total score was favourable for mobile bearing (159 vs 132 for fixed bearing), with MD of -26.52 points (95% CI -45.03 to -8.01, P value 0.005), but with a wide 95% confidence interval indicating uncertainty about the estimate.Other reported scoring systems did not show statistically significant differences: Hospital for Special Surgery (HSS) score (seven studies (37%) in 1021 knees (45%)) with an MD of -1.36 (95% CI -4.18 to 1.46, P value 0.35); Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score (two studies (11%), 167 knees (7%)) with an MD of -4.46 (95% CI -16.26 to 7.34, P value 0.46); and Oxford total (five studies (26%), 647 knees (29%) with an MD of -0.25 (95% CI -1.41 to 0.91, P value 0.67). Health-related quality of lifeThree studies (16%) with 498 knees (22%) reported on health-related quality of life, and no statistically significant differences were noted between the mobile bearing and fixed bearing groups. The Short Form (SF)-12 Physical Component Summary had an MD of -1.96 (95% CI -4.55 to 0.63, P value 0.14) and heterogeneous results. Revision surgeryTwenty seven revisions (1.3%) were performed in 17 studies (89%) with 2065 knees (92%). In all, 13 knees were revised in the fixed bearing group and 14 knees in the mobile bearing group. No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.58), and homogeneous results were reported. MortalityIn seven out of 19 studies, 13 participants (37%) died. Two of these participants had undergone bilateral surgery, and for seven participants, it was unclear which prosthesis they had received; therefore they were excluded from the analyses. Thus our analysis included four out of 191 participants (2.1%) who had died: one in the fixed bearing group and three in the mobile bearing group. No statistically significant differences were found. The risk difference was -0.02 (95% CI -0.06 to 0.03, P value 0.49) and results were homogeneous. Reoperation ratesThirty reoperations were performed in 17 studies (89%) with 2065 knees (92%): 18 knees in the fixed bearing group (of the 1031 knees) and 12 knees in the mobile group (of the 1034 knees). No statistically significant differences were found. The risk difference was -0.01 (95% CI -0.01 to 0.01, P value 0.99) with homogeneous results. Other serious adverse eventsSixteen studies (84%) reported nine other serious adverse events in 1735 knees (77%): four in the fixed bearing group (of the 862 knees) and five in the mobile bearing group (of the 873 knees). No statistically significant differences were found (risk difference 0.00, 95% CI -0.01 to 0.01, P value 0.88), and results were homogeneous.
  
  
  CONCLUSIONS
  Moderate- to low-quality evidence suggests that mobile bearing prostheses may have similar effects on knee pain, clinical and functional scores, health-related quality of life, revision surgery, mortality, reoperation rate and other serious adverse events compared with fixed bearing prostheses in posterior cruciate retaining TKA. Therefore we cannot draw firm conclusions. Most (98.5%) participants had OA, so the findings primarily reflect results reported in participants with OA. Future studies should report in greater detail outcomes such as those presented in this systematic review, with sufficient follow-up time to allow gathering of high-quality evidence and to inform clinical practice. Large registry-based studies may have added value, but they are subject to treatment-by-indication bias. Therefore, this systematic review of RCTs can be viewed as the best available evidence.
authors: Department of Medical Decision Making, Leiden University Medical Center, Postzone J10-s, room J10-88, P.O. Box 9600, Leiden, Netherlands, 2300 RC. s.n.hofstede@lumc.nl.
authors: Stefanie N
authors: SN
authors: Hofstede
authors: Klaas Auke
authors: KA
authors: Nouta
authors: Wilco
authors: W
authors: Jacobs
authors: Miranda L
authors: ML
authors: van Hooff
authors: Ate B
authors: AB
authors: Wymenga
authors: Bart G
authors: BG
authors: Pijls
authors: Rob G H H
authors: RG
authors: Nelissen
authors: Perla J
authors: PJ
authors: Marang-van de Mheen
mesh_terms: D001172:Arthritis, Rheumatoid / Q000601:surgery*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation* / Q000401:mortality; D015982:Bias; D006304:Health Status; D006801:Humans; D007719:Knee Joint; D007720:Knee Prosthesis; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011474:Prosthesis Design / Q000379:methods; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D016059:Range of Motion, Articular; D012086:Reoperation / Q000706:statistics & numerical data
references: Knee Surg Sports Traumatol Arthrosc. 2010 Mar;18(3):367-74
references: 19876616
references: Osteoarthritis Cartilage. 2011 Nov;19(11):1270-85
references: 21907813
references: Knee Surg Sports Traumatol Arthrosc. 2010 Jul;18(7):879-88
references: 19946671
references: Exp Ther Med. 2013 Jul;6(1):45-51
references: 23935716
references: J Arthroplasty. 2011 Dec;26(8):1219-23
references: 21397453
references: Int Orthop. 2005 Jun;29(3):179-81
references: 15809873
references: Int Orthop. 2010 Mar;34(3):349-54
references: 19898821
references: Clin Orthop Relat Res. 2005 Mar;(432):204-9
references: 15738823
references: J Arthroplasty. 2009 Sep;24(6):932-40
references: 18835693
references: J Bone Joint Surg Br. 2003 Jan;85(1):62-7
references: 12585579
references: Cochrane Database Syst Rev. 2004;(2):CD003130
references: 15106190
references: Knee Surg Sports Traumatol Arthrosc. 2011 Dec;19(12):2052-9
references: 21562841
references: Acta Orthop Belg. 2008 Dec;74(6):801-8
references: 19205328
references: J Bone Joint Surg Br. 2007 Oct;89(10):1317-23
references: 17957070
references: Z Orthop Ihre Grenzgeb. 2004 Jan-Feb;142(1):40-5
references: 14968383
references: J Orthop Surg (Hong Kong). 2009 Aug;17(2):179-82
references: 19721147
references: Knee Surg Sports Traumatol Arthrosc. 2010 Oct;18(10):1311-6
references: 20407753
references: Knee Surg Sports Traumatol Arthrosc. 2012 Aug;20(8):1450-5
references: 21946980
references: J Arthroplasty. 2011 Jun;26(4):531-6
references: 20932706
references: J Bone Joint Surg Am. 2005 Oct;87(10):2290-6
references: 16203896
references: J Bone Joint Surg Am. 2001 Dec;83(12):1779-81
references: 11741053
references: J Arthroplasty. 2010 Sep;25(6):998-1003
references: 19775858
references: Knee Surg Sports Traumatol Arthrosc. 2011 Sep;19(9):1488-95
references: 21431376
references: Rev Chir Orthop Reparatrice Appar Mot. 2008 May;94(3):247-51
references: 18456059
references: Arch Orthop Trauma Surg. 2012 Jun;132(6):875-81
references: 22526193
references: J Bone Joint Surg Am. 2012 May 16;94(10):866-73
references: 22617913
references: J Arthroplasty. 1996 Dec;11(8):952-63
references: 8986574
references: J Bone Joint Surg Br. 2007 Jul;89(7):904-10
references: 17673583
references: Knee. 2014 Mar;21(2):374-81
references: 24380804
references: J Orthop Surg (Hong Kong). 2001 Jun;9(1):45-50
references: 12468843
references: J Arthroplasty. 1998 Sep;13(6):699-706
references: 9741449
references: Knee Surg Sports Traumatol Arthrosc. 2014 Jul;22(7):1626-31
references: 23269476
references: Knee Surg Sports Traumatol Arthrosc. 2012 Feb;20(2):337-45
references: 22057385
references: Knee Surg Sports Traumatol Arthrosc. 2012 Dec;20(12):2519-27
references: 22419265
references: Clin Orthop Relat Res. 2009 Feb;467(2):493-503
references: 18465188
references: Clin Orthop Relat Res. 2011 Jan;469(1):48-54
references: 20568026
references: Bone Joint J. 2013 Sep;95-B(9):1209-16
references: 23997134
references: J Bone Joint Surg Am. 2009 Sep;91(9):2104-12
references: 19723986
references: J Arthroplasty. 2012 Feb;27(2):207-12
references: 21752586
references: J Bone Joint Surg Br. 2012 May;94(5):648-55
references: 22529085
references: Clin Orthop Relat Res. 2001 Nov;(392):101-15
references: 11716371
references: Z Orthop Ihre Grenzgeb. 2005 Sep-Oct;143(5):567-72
references: 16224678
references: J Bone Joint Surg Br. 2008 Sep;90(9):1172-9
references: 18757956
references: J Med Assoc Thai. 2012 Oct;95 Suppl 10:S77-86
references: 23451443
references: Open Orthop J. 2011;5:201-8
references: 21687563
references: J Arthroplasty. 2005 Feb;20(2):145-53
references: 15902852
references: J Knee Surg. 2007 Jan;20(1):20-6
references: 17288084
references: Knee. 2005 Dec;12(6):414-8
references: 16125941
references: Bone Joint J. 2013 Apr;95-B(4):486-92
references: 23539700
references: J Arthroplasty. 2011 Dec;26(8):1205-13
references: 21295940
references: Int Orthop. 2009 Aug;33(4):997-1000
references: 19399499
references: Orthop Surg. 2013 May;5(2):112-7
references: 23658046
references: J Bone Joint Surg Am. 1992 Mar;74(3):383-9
references: 1548265
references: Clin Orthop Relat Res. 2004 Nov;(428):221-7
references: 15534546
references: J Bone Joint Surg Am. 2007 Apr;89(4):780-5
references: 17403800
references: J Bone Joint Surg Am. 2011 Dec 21;93 Suppl 3:55-61
references: 22262425
references: Knee. 2007 Dec;14(6):448-51
references: 17920887
references: Knee Surg Sports Traumatol Arthrosc. 2015 Jun;23(6):1653-9
references: 24509880
references: Clin Orthop Relat Res. 2008 Aug;466(8):1959-65
references: 18523833
references: J Arthroplasty. 2004 Feb;19(2):135-40
references: 14973854
references: J Arthroplasty. 2009 Sep;24(6):873-84
references: 18701243
references: Clin Orthop Relat Res. 2003 May;(410):235-47
references: 12771835
references: Arch Orthop Trauma Surg. 2011 Oct;131(10):1341-50
references: 21655969
references: Zhonghua Yi Xue Za Zhi. 2011 Mar 22;91(11):752-6
references: 21600100
references: J Bone Joint Surg Am. 2009 Jan;91(1):134-41
references: 19122088
references: J Arthroplasty. 2009 Sep;24(6 Suppl):24-7
references: 19553072
references: J Long Term Eff Med Implants. 2011;21(3):197-203
references: 22150352
references: J Bone Joint Surg Br. 2012 Oct;94(10):1366-71
references: 23015562
references: J Arthroplasty. 2010 Dec;25(8):1201-8
references: 20022460
references: Clin Orthop Relat Res. 2010 Mar;468(3):775-81
references: 19322618
references: Clin Orthop Relat Res. 2006 Jul;448:114-21
references: 16826105
references: Z Orthop Ihre Grenzgeb. 2001 Sep-Oct;139(5):393-6
references: 11605289