Technique for arthroscopic arthroplasty for TCM joint with severe dorsal subluxation

 We have been performing partial resection of the trapezium under arthroscopic surgery and ligament plasty using mini Tight Rope (mini-TR) since 2015, Most cases that required operation had TCM dorsal subluxation even though the Eaton classification was 2 degrees. In addition, since many cases have a steep angle between the metacarpal bone axis and the articular surface on the lateral view, there were occasional cases where TCM was difficult to abduct and extend, even if the trapezium was resected in the usual manner, and there were occasional cases where the MP was overextended, or the MP joint was painful. There were also cases where the dorsal subluxation progressed.

 Since 2020, we have been resecting mainly dorsal side of the trapezium to make it nearly perpendicular to the metacarpal bone axis, and thoroughly resecting the beak osteophyte and scar tissue on the ulnar side to make it easier to reduce the subluxation. Therefore, in cases where reduction was stable, the mini-TR was placed laterally, centered on the thumb metacarpal bone, and in cases where subluxation was still present, it was placed slightly dorsally and the index metacarpal bone was placed at 1/3 of the way. The results of these cases (Group A) that had been treated more than 6 months after surgery were compared with the results of the previous cases (Group B) from 2015 to 2019.

Cases and Results: Group A had 151 cases, and Group B had 65 cases. These were evaluated for postoperative range of motion, VAS improvement, and degree of dorsal subluxation progression using XP.

In Group A, VAS improved from 72.3 to 20.1 (p<0.05), taking an average of 4.5 months. In Group B, VAS improved from 74.5 to 16 (P<0.001), taking an average of 3.8 months, which was slightly shorter. The thumb palmar abduction angle was 110% compared to preoperative levels in Group A and 125% in Group B, which was better in Group B. Pulp pinch was good, from 2.8 before surgery to 3.6 after surgery in group A, and from 2.5 to 4.2 in group B. In the XP evaluation, dorsal subluxation progressed by an average of 1.8 mm in group A and 0.8 mm in group B compared to immediately after surgery.

Most patients who undergo surgery for CM joint arthropathy of the thumb have dorsal subluxation, and in particularly severe cases, MP hyperextension occurs, and MP joint pain may be complained of for a while even after partial trapezoid resection under arthroscopic surgery. However, with the surgical innovations of this case, the recovery time for range of motion and postoperative pain was shortened, and the progression of dorsal subluxation after surgery was less.

Keywords: Thumb CM Arthroscope Arthroplasty