Use of a Spacer Block Tool for Assessment of Joint Line Position during Revision Total Knee Arthroplasty

There is a tendency of orthopaedic surgeons to elevate joint line (JL) in revision total knee arthroplasty (RTKA). Here, we ascertain the use of the spacer block tool (SBT) to determine JL more accurately for less experienced RTKA surgeons. To perform more precise restoration of JL, an SBT with markers was developed and produced using computer software and three-dimensional printers. The study was planned prospectively to include patients who received either condylar constrained or rotating hinge RTKA between January 2016 and December 2019. To determine JL, distance from fibular head (FH), adductor tubercle (AT), and medial epicondyle (ME) were measured on contralateral knee preoperative radiographs and on operated knee postoperative radiographs. Patients were randomized and grouped according to the technique of JL reconstruction. In Group 1, conventional methods by evaluating aforementioned landmarks and preoperative contralateral knee measurements were used to determine JL, whereas in Group 2, the SBT was used. The main outcome measure was the JL change in revised knee postoperatively in contrast to contralateral knee to compare effective restoration of JL between the groups. Twenty-five patients in Group 1 (3 males, 22 females, 72 years, body mass index [BMI] 32.04 +/- 4.45) and 20 patients (7 males, 13 females, 74 years, BMI 30.12 +/- 5.02) in Group 2 were included in the study. JL measurements for the whole group were FH-JL=18.3 +/- 3.8mm, AT-JL=45.8 +/- 4.6mm, and ME-JL=27.1 +/- 2.8mm preoperatively, and FH-JL=20.7 +/- 4.2mm, AT-JL=43.4 +/- 5.2mm, and ME-JL=24.7 +/- 3.1mm postoperatively. JL level differences in reference to FH, AT, and ME in Group 1 were 3.6 +/- 3.1, 3.6 +/- 3.5, and 3.4 +/- 3.1mm, respectively, and in Group 2 were 1.0 +/-.0.9, 1.3 +/- 1.3, and 1.1 +/- 1.3mm, respectively. There were statistically significant differences between the two groups in JL changes referenced to all of the specific landmarks (p<0.05). The use of the SBT helped restore JL effectively in our cohort of RTKA patients. Therefore, this tool may become a useful and inexpensive gadget for less experienced and low-volume RTKA surgeons.

Automated summary

The study confirmed the use of the spacer block tool (SBT) for more accurate determination of joint line (JL) in revision total knee arthroplasty (RTKA), especially beneficial for less experienced surgeons. It provides a useful and inexpensive gadget for effective restoration of JL in RTKA patients, showing statistically significant differences in JL changes compared to conventional methods.