Appropriate Distraction Strength for Metatarsophalangeal Joint Arthroscopy

Abstract

Background and Objectives: To investigate the natural metatasophalangeal (MTP) joint distance, we studied the appropriate degree of distraction for arthroscopy and the associated factors, including age, gender, and body mass index (BMI). Materials and Methods: Sixty-seven patients who underwent MTP joint arthroscopy or foot and ankle surgery from April 2013 to June 2020 were enrolled. Foot plain radiographs were taken using a mini-fluoroscan with no traction, manual traction, and traction of 5 pounds, 10 pounds, and 15 pounds to measure the MTP joint distance. Age, gender, and BMI were compared as associated factors. The minimum joint distance of MTP joint arthroscopy was defined as 2.8 mm, which was the sheath size of a 1.9 mm, 30° high-definition arthroscope. Results: Regarding natural MTP joint space sizes, the MTP-2 joint had the largest joint size (2.39 ± 0.37 mm). The MTP-5 joint had the smallest joint size (1.59 ± 0.34 mm). Traction of 10 lb was an appropriate distraction force for the MTP-1 joint (3.09 ± 0.03 mm) and MTP-4 joint (3.07± 0.47 mm) in arthroscopy. Traction of 5lb was an appropriate distraction force for the MTP-2 (3.32 ± 0.60 mm), MTP-3 (2.89 ± 0.50 mm), and MTP-5 (2.97 ± 0.49 mm) joints. For the MTP-1 and MTP-4 joints, males had significantly greater joint space sizes than females for no traction (p = 0.039), manual traction (p = 0.002), and traction of 5 pounds (p = 0.004), 10 pounds, (p = 0.013), and 15 pounds (p = 0.024). There was no statistically significant difference in joint space size according to age or BMI for any MTP joints (p > 0.05). Conclusions: Among natural joint spaces without traction, the MTP-2 joint had the largest joint size while the MTP-5 joint had the smallest joint size. In MTP joint arthroscopy, a traction power of 10 lb is sufficient for appropriate distraction of all MTP joints. Less distraction power is required for males than for females, especially for the MTP-1 and MTP-4 joints.

Keywords: MTP joint arthroscopy; distraction; foot ankle surgery.

Figure 1

Pictures showing a novel traction machine. (A) There are two joints that can adjust the angle and traction power (black arrow). (B) For effective traction, the new device for fixing legs to the bed was developed and straps (narrow black arrows) were used to fix legs. (C) A device for measuring the strength of distraction in real time.

Figure 2

Anterior–posterior foot plain radiographs taken using a mini-fluoroscan with manual traction: (A), 5 lb (B), 10 lb (C), and 15 lb (D) of traction. These plain radiographs were computerized and used to measure the MTP joint space with a PACS system. The lines in these plain radiographs are wire lines representing the distraction pounds.