The total number of keywords used in the 424 original articles published over the past 15 years was 1,703, of which the 20 most used keywords are shown in Table 1. “Total knee arthroplasty (TKA)”, a keyword indicating the type of surgery, was most frequently used, except for “knee”, a keyword indicating affected joints, followed by “osteoarthritis (OA)”, a keyword indicating diagnosis.
Rank 2 “TKA”
Excluding the keyword “knee”, there were 885 keywords used with the most used keyword “TKA”. Among them, the 10 most used keywords after excluding the keyword “knee” and the keyword “OA (used 19 times)” are shown in Table 2. Among the 10 keywords, the keywords related to the surgical technique that can be controlled were “navigation”, “posterior cruciate retaining (CR) or substituting (PS)”, “posterior tibial slope (PTS)”, “tourniquet”, and “minimal invasive surgery (MIS)”. Keywords related to the perioperative situation that cannot be controlled were “infection”, “transfusion”, “revision”, “blood loss”, and “range of motion (ROM)”.
Rank 4 “anterior cruciate ligament (ACL) reconstruction”
Of the 96 keywords used with “ACL reconstruction”, which is the 4th ranked keyword in the overall ranking, 17 were keywords related to graft used during surgery, and 16 were keywords related to evaluation tool after surgery. After that, keywords for techniques related to femoral tunnel drilling were used 14 times. Among them, "trans-tibial (TT) technique", "outside-in (OI) technique", and "anteromedial (AM) portal technique” were used 7 times, 5 times, and 2 times, respectively. The keyword “three-dimensional computed tomography (3D-CT)”, which means imaging modality for the location of the femoral tunnel, was used a total of 4times. A research article using the two keywords "TT technique” and “OT technique” at the same time was first published in 2013. Since then, the use of "TT technique", "OI technique", "AM portal technique", and "3D-CT” as keywords has steadily increased, and in some articles, two or more keywords have been used simultaneously (Figure 2).
Rank 5 “navigation”
The keyword “navigation” was used in studies related to TKA in 92% (23 times), and the other two were used in studies on closed tibial osteotomy and anterior cruciate ligament, respectively. Analyzing the number of uses of the keyword “navigation” according to the 5-year-phase, it was found that it was used 8 times in phase I, 9 times in phase II, and 6 times in phase III.
Rank 7 “osteotomy”
The keyword ranked 7th in the frequency of use was used 28 times. 85.7% of the total was used to represent high tibial osteotomy (HTO) – the treatment of medial OA – and according to the surgical technique, open wedge (OW) and closed wedge (CW) accounted for 64.3% (18 times) and 21.4% (6 times), respectively. The remaining 14.3% (4 times) was used to represent the bone resection technique used during TKA or revision TKA surgery. Because of analyzing the number of uses of "osteotomy”, which means HTO by 5-year-phase, it was found that OW-HTO was used 1, 3, and 14 times in phase I, II, and III, respectively, and CW-HTO was used 3, 1, and 2 times, respectively (Figure 3). In addition, since 2013, the cumulative number of uses of OW-HTO as a keyword overcome the cumulative number of uses of CW-HTO (Figure 4).
Rank 11 “unicompartmental knee arthroplasty (UKA)”
The keyword “UKA” as a type of surgery has been used 18 times, and has been used 8 times in the last 5 years (phase III), accounting for 44.4% of the total. Among the keywords used with “UKA”, there were three types of surgery. “osteotomy”’ and “TKA” were used in a comparative study with UKA surgery, and “revision arthroplasty” was used to mean TKA performed as a treatment modality for complications that occurred after UKA surgery.
Rank 17 “ROM”
The keyword “ROM” was used 14 times, of which 11 times were used in TKA-related studies. The remaining 3 times were used in studies related to revision TKA, UKA, and arthrofibrosis, respectively.
Rank 17 “PTS”
The keyword “PTS” was used 14 times, among them, 11 times were used in TKA-related studies, 2 times were used in ACL-related studies, and 1 time was used in meniscus-related study.
Rank 9, 14, 19
95% of the keyword “infection” and 88% of the keyword “revision” were used in TKA-related studies, and the entire of the keyword “blood loss” was used in TKA-related studies.