Deep Transverse Metatarsal Ligament Transection in Morton's Neuroma Excision: A Cadaveric Study Examining Effects on Metatarsal Alignment.

BACKGROUND

In the dorsal incisional approach for Morton's neuroma, it is required to transect the deep transverse metatarsal ligament (DTML) that lies in the interspace between the third and fourth metatarsal heads. The purpose of this study was to evaluate the relationship between transection of the DTML in the third intermetatarsal space and the metatarsal alignment.

METHODS

Nine human cadaveric lower extremity limbs were used for this study. Each limb was mounted to the MTS 858 Mini Bionix biomechanical test system and loaded to 120% of the donor's documented body weight at a rate of 15 lbf/s, in order to simulate peak weightbearing ground reactive forces on the forefoot. Preoperative and immediate postoperative radiographs were obtained. Cyclic loading was then performed to simulate 1 month of full weightbearing. Radiographs were repeated and metatarsal alignment was analyzed.

RESULTS

A statistically significant difference was noted with intermetatarsal angle (IMA) 1-2 and IMA 1-4. The IMA 1-2 after 1 month cycling time showed statistical significant difference from those found immediately postoperatively (P < .05). Average increase in IMA 1-2 from preoperative to 1 month cycling time was 2.18°. The power of the analyses for IMA 1-2 was 0.992. Regarding the IMA 1-4, data recorded at 1 week and 1 month cycling times showed a statistically significant difference compared to the preoperative IMA 1-4 (P < .05). Average increase in IM 1-4 angles from preoperative to 1 month cycling time was an increase of 1.79°. The power of the analyses for IM 1-4 angles was 0.953.

CONCLUSION

Technically, 2.18° increase in IMA 1-2 or 1.79° increase in IM 1-4 would be considered an abnormal widening of the forefoot, but clinically, these values could not be detected; nor should they deter a surgeon or patient from undergoing a Morton's neurectomy via a dorsal incisional approach.

LEVELS OF EVIDENCE: Level V: Cadaveric study.