PATIENT SPECIFIC CUTTING BLOCKS: OF UNPROVEN VALUE – AFFIRMS

Introduction Proposed advantages of patient-specific instrumentation in total knee arthroplasty (TKA) include enhanced accuracy for component positioning, reduced operative time, and increased OR efficiency leading to potential cost savings. However, various studies with relatively small sample sizes have evaluated the impact of these custom cutting guides and were unable to detect any significant differences compared to conventional surgical technique. Therefore, the purpose of this study is to improve the sensitivity of investigation through meta-analysis and compare patient-specific versus standard TKA instrumentation with regard to: (1) coronal alignment, (2) sagittal alignment, (3) operative time, (4) blood loss, (5) transfusion requirement, and (6) peri-operative costs. Methods A systematic review of the peer-reviewed literature indexed on Medline and/or Embase was performed in search of Level I, II, or III studies comparing the results of patient-specific versus standard TKA instrumentation. Nine studies remained following the screening process. The data published in these studies were extracted and aggregated for the purpose of comparing the two treatment groups with regard to coronal alignment, sagittal alignment, operative time, blood loss, transfusion requirement, and peri-operative costs. Using previously published data, it was determined that a sample size of 80 patients per group would have sufficient power (0.80) to detect a significant difference (α = 0.05) in all primary outcomes. Results The nine component studies described a total of 957 total knee arthroplasties (529 performed with patient-specific instrumentation and 428 with standard instrumentation). While patient-specific instrumentation demonstrated improved accuracy in coronal alignment as measured by femorotibial angle (FTA) (p = 0.0003), standard instrumentation demonstrated improved accuracy in coronal alignment as measured by hip-knee-ankle (HKA) (p = 0.02). Importantly, there were no significant differences in the ability of either technique to avoid outliers (+ or – 3 degrees of target alignment) in either FTA or HKA. Measures of sagittal alignment accuracy were equivalent between the two groups for both the femoral component (p = 0.5) and the tibial component (p = 0.9). Operative time (92.5 minutes vs. 104.1 minutes, p = 0.1), blood loss (371 mL vs. 384 mL, p = 0.2), and transfusion requirement (10.1% vs. 14.1%, p = 0.1) were also similar between treatment groups. The three studies that compared costs (307 TKAs) found decreased peri-operative costs associated with patient-specific instrumentation as a result of increased OR efficiency, but these costs were offset by the expenditures related to producing the custom instrumentation. Discussion and Conclusion Patient-specific instrumentation does not demonstrate superiority over standard instrumentation with regard to coronal or sagittal alignment. In addition, operative time, blood loss, and transfusion requirement are similar between techniques. Finally, while patient-specific instrumentation can lead to cost savings through improved OR efficiencies, these costs are often offset by the cost of generating the custom instrumentation. Therefore, current data does not support routine use of patient-specific instrumentation during primary TKA.