Tomonori Shigemura1, Yasuaki Murata2, Yohei Yamamoto2, Norichika Mizuki2, Yasunori Toki2, Yuichi Wada2. 1. Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, 3426-3 Anesaki, 299-0111 Ichihara, Chiba, Japan. Electronic address: tshigepon@yahoo.co.jp. 2. Department of Orthopaedic Surgery, Teikyo University Chiba Medical Center, 3426-3 Anesaki, 299-0111 Ichihara, Chiba, Japan.
Abstract
BACKGROUND: Precise implant alignment is a crucial prognostic factor in total knee arthroplasty (TKA). Portable navigation systems (PN-TKA) were reported to be better than the conventional technique (CON-TKA). We hypothesized that PN-TKA offered greater radiologic precision than CON-TKA in mechanically aligning components. We investigated whether (1) it improved global mechanical alignment, and (2) optimized component placement with respect to the tibial and femoral mechanical axes. PATIENTS AND METHODS: A systematic literature review compared PN-TKA versus CON-TKA. PubMed, Web of Science and Cochrane Library search retrieved ten studies. Their data were pooled using RevMan 5.3. Odds ratios (OR) for dichotomous data were calculated with 95% confidence intervals (CIs) for each outcome. Statistical heterogeneity was assessed as I2 using a standard χ2 test. I2>50% denoted significant heterogeneity requiring a random effects model; otherwise, a fixed effects model was applied. RESULTS: There were significantly fewer outliers for mechanical axis (I2=24%, OR=0.62, 95% CI=0.42-0.91, p=0.02) and coronal femoral component angle (I2=58%, OR=0.31, 95% CI=0.13-0.73, p=0.007) using PN-TKA; however, no significant difference was observed for coronal tibial component angle outliers (I2=0%, OR=0.66, 95% CI=0.38-1.15, p=0.14). DISCUSSION: Although PN-TKA appeared to improve global alignment, it had no effect on coronal tibial alignment, which is a key factor in predicting the long-term success of component fixation. There thus appeared to be no definite advantage of PN-TKA over CON-TKA. LEVEL OF EVIDENCE: III.
BACKGROUND: Precise implant alignment is a crucial prognostic factor in total knee arthroplasty (TKA). Portable navigation systems (PN-TKA) were reported to be better than the conventional technique (CON-TKA). We hypothesized that PN-TKA offered greater radiologic precision than CON-TKA in mechanically aligning components. We investigated whether (1) it improved global mechanical alignment, and (2) optimized component placement with respect to the tibial and femoral mechanical axes. PATIENTS AND METHODS: A systematic literature review compared PN-TKA versus CON-TKA. PubMed, Web of Science and Cochrane Library search retrieved ten studies. Their data were pooled using RevMan 5.3. Odds ratios (OR) for dichotomous data were calculated with 95% confidence intervals (CIs) for each outcome. Statistical heterogeneity was assessed as I2 using a standard χ2 test. I2>50% denoted significant heterogeneity requiring a random effects model; otherwise, a fixed effects model was applied. RESULTS: There were significantly fewer outliers for mechanical axis (I2=24%, OR=0.62, 95% CI=0.42-0.91, p=0.02) and coronal femoral component angle (I2=58%, OR=0.31, 95% CI=0.13-0.73, p=0.007) using PN-TKA; however, no significant difference was observed for coronal tibial component angle outliers (I2=0%, OR=0.66, 95% CI=0.38-1.15, p=0.14). DISCUSSION: Although PN-TKA appeared to improve global alignment, it had no effect on coronal tibial alignment, which is a key factor in predicting the long-term success of component fixation. There thus appeared to be no definite advantage of PN-TKA over CON-TKA. LEVEL OF EVIDENCE: III.