Neural interfacing architecture enables enhanced motor control and residual limb functionality postamputation.

Despite advancements in prosthetic technologies, patients with amputation today suffer great diminution in mobility and quality of life. We have developed a modified below-knee amputation (BKA) procedure that incorporates agonist-antagonist myoneural interfaces (AMIs), which surgically preserve and couple agonist-antagonist muscle pairs for the subtalar and ankle joints. AMIs are designed to restore physiological neuromuscular dynamics, enable bidirectional neural signaling, and offer greater neuroprosthetic controllability compared to traditional amputation techniques. In this prospective, nonrandomized, unmasked study design, 15 subjects with AMI below-knee amputation (AB) were matched with 7 subjects who underwent a traditional below-knee amputation (TB). AB subjects demonstrated significantly greater control of their residual limb musculature, production of more differentiable efferent control signals, and greater precision of movement compared to TB subjects (P < 0.008). This may be due to the presence of greater proprioceptive inputs facilitated by the significantly higher fascicle strains resulting from coordinated muscle excursion in AB subjects (P < 0.05). AB subjects reported significantly greater phantom range of motion postamputation (AB: 12.47 ± 2.41, TB: 10.14 ± 1.45 degrees) when compared to TB subjects (P < 0.05). Furthermore, AB subjects also reported less pain (12.25 ± 5.37) than TB subjects (17.29 ± 10.22) and a significant reduction when compared to their preoperative baseline (P < 0.05). Compared with traditional amputation, the construction of AMIs during amputation confers the benefits of enhanced physiological neuromuscular dynamics, proprioception, and phantom limb perception. Subjects' activation of the AMIs produces more differentiable electromyography (EMG) for myoelectric prosthesis control and demonstrates more positive clinical outcomes.

Degenerative subtalar joints complicated by medial plantar intraneural cysts : cutting the cystic articular branch prevents recurrence.

AIMS: The pathogenesis of intraneural ganglion cysts is controversial. Recent reports in the literature described medial plantar intraneural ganglion cysts (mIGC) with articular branches to subtalar joints. The aim of the current study was to provide further support for the principles underlying the articular theory, and to explain the successes and failures of treatment of mICGs. PATIENTS AND METHODS: Between 2006 and 2017, five patients with five mICGs were retrospectively reviewed. There were five men with a mean age of 50.2 years (33 to 68) and a mean follow-up of 3.8 years (0.8 to 6). Case history, physical examination, imaging, and intraoperative findings were reviewed. The outcomes of interest were ultrasound and/or MRI features of mICG, as well as the clinical outcomes. RESULTS: The five intraneural cysts followed the principles of the unifying articular theory. Connection to the posterior subtalar joint (pSTJ) was identified or suspected in four patients. Re-evaluation of preoperative MRI demonstrated a degenerative pSTJ and denervation changes in the abductor hallucis in all patients. Cyst excision with resection of the articular branch (four), cyst incision and drainage (one), and percutaneous aspiration/steroid injection (two) were performed. Removing the connection to the pSTJ prevented recurrence of mIGC, whereas medial plantar nerves remained cystic and symptomatic when resection of the communicating articular branch was not performed. CONCLUSION: Our findings support a standardized treatment algorithm for mIGC in the presence of degenerative disease at the pSTJ. By understanding the pathoanatomic mechanism for every cyst, we can improve treatment that must address the articular branch to avoid the recurrence of intraneural ganglion cysts, as well as the degenerative pSTJ to avoid extraneural cyst formation or recurrence. Cite this article: Bone Joint J 2018;100-B:183-9.

Portal safety and efficacy of anterior subtalar arthroscopy: a cadaveric study.

Anterior subtalar arthroscopy was performed in 14 feet of 7 cadaveric bodies using the primary visualization and working portals. The cartilage of the anterior/middle calcaneal facet that can be reached was marked. The feet were dissected and the distances between the portals and surrounding cutaneous nerves were measured. Any damage to the ligaments of the sinus tarsi was noted. The percentage area of the articular cartilage that was marked was measured. In all specimens, the primary visualization portal tract passed through the lateral root of the inferior extensor retinaculum. The primary working portal tract passed through the lateral root in nine specimens (64%). Cervical ligament was intact in all specimens. In three specimens (21%), the primary visualization portal tract passed through the posterior edge of the intermediate root of the inferior extensor retinaculum. The interosseous talocalcaneal ligament was intact in all specimens. The primary visualization portal tract passed through the medial root of the inferior extensor retinaculum in eight specimens (57%). The primary working portal tract passed through the medial root of the inferior extensor retinaculum in one specimen. The average working area on the calcaneal facet was 95% +/- 4% of the total articular surface. There was no case of nerve injury in all specimens. In conclusion, anterior subtalar arthroscopy is a minimally invasive approach to deal with pathologies of this joint without the need of extensive resection of the ligamentous structures of the sinus tarsi.

The communicating branches between the sural and superficial peroneal nerves in the foot: a review of 55 cases.

The rich sensory innervation of the ankle and foot is manifest through the numerous communicating branches linking the neural trunks, particularly the superficial peroneal and sural nerves on the anterolateral aspect of the hindfoot. The 35 communicating branches seen in 55 dissections (58%) were proximal in half of the cases, lying in the malleolar and lateral tarsal regions, and distal in the other half, in the metatarsal region. The communicating branch was straight in 25 cases and curved in 11. The average distances of the communicating branch from the crest of the lateral malleolus and the tubercle of the 5th metatarsal was 4.7 and 4.1 cm, but there was a wide range of values. We believe that stretching of the proximal communicating branch during forced inversion of the ankle and/or foot or during fractures of the calcaneus or direct injury in surgical approaches or arthroscopy of the ankle may lead to unexplained pre- and submalleolar pain. Advances in modern imaging may allow recognition of these branches and guidance of infiltration and even neurolysis in cases of failure of conservative treatment.

Innervation of the sinus tarsi and implications for treating anterolateral ankle pain.

Anterolateral ankle pain can persist despite the best care of sprains or fractures. It is possible that this pain is related to stretch or traction injuries to the nerves that innervate the subtalar joint. If this were true, identification of these nerve branches by local anesthetic block would provide an indication that surgical interruption of the function of these nerves may provide pain relief. In 28 feet of 14 cadavers (7 male/7 female), investigation of the deep peroneal nerve demonstrated a consistent pattern whereby a series of 2 to 4 (mean, 2.9 +/- 0.6) branches innervated the anterolateral part of the subtalar joint. All these nerve branches originated from the lateral terminal branch of the deep peroneal nerve on the dorsum of the foot. The mean distance between the exit of the first articular branch and the exit of the terminal motor branch both originating from the lateral terminal branch was 3.8 +/- 1.1 cm. The motor branch passed under the extensor digitorum brevis muscle at a mean distance of 5.3 +/- 0.6 cm from the tip of the lateral malleolus. The presented anatomy provides a basis for the diagnosis and treatment of persistent anterolateral ankle pain of neural origin.