CT- versus MRI-based patient-specific instrumentation for total knee arthroplasty: A systematic review and meta-analysis.

BACKGROUND: To determine whether computed tomography (CT) or magnetic resonance imaging (MRI) is more suitable for the patient-specific instrumentation (PSI) systems for total knee arthroplasty (TKA). METHODS: PubMed, Embase, and the Cochrane Library were searched from inception to June 2016 for prospective comparative trials that compared CT- versus MRI-based PSI systems for TKA. Our predefined primary outcome was the outliers incidence of coronal overall limb alignment. RESULTS: Six studies with a total of 336 knees meeting the eligibility criteria, and four trials were included in the meta-analysis. Compared with MRI-based PSI systems, CT-based PSI systems were associated with a higher outliers incidence of coronal overall limb alignment (risk ratio: 1.67; 95% confidence interval (CI): 1.03-2.72; P = 0.04), more angular errors of coronal overall limb alignment (mean difference (MD): 1.01°; 95% CI: 0.47-1.56; P = 0.0003), and longer operation time (MD: 5.02 min; 95% CI: 1.26-8.79; P = 0.009). While no significant differences in the coronal/sagittal alignment of the femoral/tibial component outliers, the angular errors of coronal overall limb alignment, the angular errors of the femoral/tibial component in coronal plane, or incidence of change of implant size of the femoral/tibial component were observed. CONCLUSIONS: The current limited evidence suggests that MRI-based PSI systems exhibit higher accuracy for TKA regarding the coronal limb axis than CT-based PSI systems. However, well-designed studies comparing CT-versus MRI-based PSI systems for TKA are warrant to confirm these results before widespread use of this technique can be recommended.

Three-dimensional color map: a novel tool to locate the surgical transepicondylar axis.

BACKGROUND: Accurate localization of the surgical transepicondylar axis (sTEA) in total knee arthroplasty (TKA), the most reliable anatomical reference for femoral rotation, has long been a challenge, primarily because it is intractable to locate the center of the sulcus of the medial epicondyle. This study aimed to introduce and verify a novel method to locate the sTEA more precisely. METHODS: This study included 26 adult femoral specimens and 80 adult patients with computed tomography (CT) scan data. Three dimensions (3D) models based on CT scans of the distal femurs were reconstructed with Mimics and imported into Geomagic Studio. The 3D color map method was applied to locate the sTEA. To further verify the accuracy of the method, the identified sTEA was transferred to the femoral specimens and compared with the points identified by the total station machine. We further compared the recognition rate of sTEA between 3D color map method and two-dimensional (2D) CT slices method. The repeatability of this novel method was also evaluated. RESULTS: The 3D color map method located the centers of the sulcus of the medial epicondyle and the most prominent point of the lateral epicondyle of all the femoral specimens, which were further identified and confirmed by patient-specific guide plates and total station machine on femoral specimens. The 3D color map method achieved a recognition rate of up to 96.23%, while the recognition rate of the 2D CT slices method was only 68.87%. The repeatability of this objective method was excellent. CONCLUSIONS: The results of this study indicated that the 3D color map method could be used to accurately and objectively locate the sTEA, with high repeatability and recognition rate. However, the proposed novel method requires further validation in clinical applications.

Body mass index and the risk of low bone mass-related fractures in women compared with men: A PRISMA-compliant meta-analysis of prospective cohort studies.

BACKGROUND: Body mass index (BMI) is inconsistently associated with the progression of low bone mass-related fractures. We conducted a systematic review and meta-analysis to summarize the evidence regarding the relationship between BMI and the risk of fracture in men and women separately. Furthermore, we analyzed the association between BMI and fracture risk in women compared with men. METHODS: PubMed, EmBase, and the Cochrane Library were searched up to November 2015 to identify prospective cohort studies of low bone mass-related fractures. Prospective cohort studies that reported effect estimates of fracture risk for different BMI categories compared to normal weight were included. Relative risk (RR) and the ratio of relative risk (RRR) were calculated using a random-effect model to measure the relationship between BMI and fracture risk. RESULTS: We analyzed 37 cohorts (32 articles), which included a total of 506,004 women and 118,372 men; overall, 38,200 incident cases were reported. Overall, a lower BMI was not associated with fracture risk in men (RR: 1.50, 95% confidence interval [CI]: 1.00-2.26; P = 0.051) or women (RR: 1.25, 95% CI: 0.97-1.62; P = 0.083). Although a higher BMI might play a beneficial impact in men (RR: 0.80, 95% CI: 0.69-0.93; P = 0.003), it has little effect in women (RR: 0.91, 95% CI: 0.74-1.11; P = 0.343). In addition, an increase in BMI by 5 kg/m decreased the risk of fractures in men (RR: 0.90, 95% CI: 0.83-0.98; P = 0.017) and women (RR: 0.85, 95% CI: 0.81-0.89; P < 0.001). Finally, there was no evidence of a sex difference in the RR for fractures between participants with different BMI categories compared with those with normal BMI. Finally, gender did not affect the risk of fracture for any category of BMI values. CONCLUSION: Higher BMI may affect the risk of fractures regardless of the sex. This association may be due to the interaction between the participants' BMI and their bone mass density.