First Metatarsophalangeal Joint Space Area Decreases Within 1 Month After Implantation of a Polyvinyl Alcohol Hydrogel Implant: A Retrospective Radiographic Case Series.

In 2016, the U.S. Food and Drug Administration approved the first and only polyvinyl alcohol hydrogel implant for the treatment of hallux rigidus. The implant functions as a bumper to maintain first metatarsophalangeal joint space to prevent contact of the phalangeal base with the first metatarsal head. Short-term and intermediate outcomes with this implant have reported positive outcomes with no radiographic outcomes of implant wear or subsidence. We performed a retrospective radiographic review of 27 consecutive patients who received the implant and measured preoperative and postoperative joint space area (JSA). We found a significant improvement in JSA (p < .001) between the preoperative JSA and JSA at the first postoperative visit at 1 to 2 weeks. We also found a significant decrease in JSA (p < .001) between the first postoperative visit and the second postoperative visit at 5 to 12 weeks. This information could have further implications for implant design as well as how we can better achieve functional improvements in the first metatarsophalangeal joint in patients with hallux rigidus.

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.