Joint Preparation and Ray Shortening in Arthroscopic Versus Open First Metatarsophalangeal Fusion: A Cadaver Study

Abstract

Purpose This study compares the amount of joint preparation and first ray shortening following first metatarsophalangeal (MTP) joint fusion utilizing open conical reaming versus arthroscopic technique. Methods Ten below-knee cadaver specimens were randomly assigned to undergo either open or arthroscopic first MTP fusion. Following fixation, first ray length measurements were obtained from pre-operative and post-operative radiographs and were used to determine first ray shortening. Additionally, the ratio of first ray length to second ray length was calculated both pre-operatively and post-operatively and compared between the two approaches. All ankles were then completely dissected, and prepared surface areas were demarcated. ImageJ photo analysis software (National Institutes of Health, Bethesda, MD, USA) was used to calculate the percentage of prepared and unprepared cartilage of each articular surface of each specimen. Results Overall, the open approach resulted in 99.3% ± 1.6% joint surface preparation, whereas the arthroscopic approach yielded 92.9% ± 7.2% (p = 0.089). On average, the head of the first metatarsal was significantly more prepared with the use of the open approach (99.5% ± 1.1%) than with the arthroscopic approach (96.6% ± 1.5%) (p = 0.008). However, with respect to the base of the phalanx, the average difference in preparation between the arthroscopic approach and the open approach was not statistically significant (90.0% ± 12.8% vs. 99.0% ± 2.2%; p = 0.160). The average amount of first ray shortening in the arthroscopic approach was 2.2 ± 1.8 mm compared to 2.1 ± 3.2 mm in the open approach (p = 0.934). The average change in the first to second ray length ratio was 0.02 for both approaches (p = 0.891). Conclusion Arthroscopic first MTP fusion can be used to achieve joint preparation comparable to open technique while maintaining first ray length.

Keywords: arthroscopic; joint preparation; mtp fusion; ray shortening.

Figure 1. First Ray Plain Film

Pre- and post-operative measurement of the first ray length using ImageJ software analysis of fluoroscopic images.

Figure 2. MT Head Preparation

Measurement of total prepared fusion contact surface area using ImageJ software for (a) the most incomplete arthroscopically prepared MT head, (b) the most complete arthroscopically prepared MT head, (c) the most incomplete open technique prepared MT head, and (d) the most complete open technique prepared MT head. The blue circle represents the estimated fusion contact surface area. Red outlines represent areas of remaining articular cartilage. MT, metatarsal