The first metatarsophalangeal joint is a biaxial condylar articulation that relies on a synovial capsule, collateral ligaments, and a fibrous plantar plate to maintain joint stability. A medial sesamoid bone and a lateral sesamoid bone, encased in the tendons of the intrinsic muscles, lie beneath the head of the first metatarsal. In hallux valgus deformity, the tensile strength of the medial collateral ligament of the first metatarsophalangeal joint weakens and the hallux abducts laterally into valgus. Coincident with abduction of the hallux, the metatarsal shifts medially into adduction, potentially subluxating the sesamometatarsal articulation. The adductor hallucis and lateral capsule and metatarsal sesamoidal suspensory ligament become contracted.

Endoscopic distal soft tissue procedure², ⁴, ⁶ employs the same principles as the open procedure.

The lateral soft tissue release is performed through the toe web and plantar portals. The toe web portal is established by a stab incision over dorsum of the first toe web, the soft tissue is freed from the undersurface of the intermetatarsal ligament, and washboard feeling is felt with the hemostat. The arthroscopic cannula and trochar are passed through the toe web portal and advanced proximally underneath the ligament. The plantar aponeurosis is then reached and pierced by the trochar. The plantar portal should be just proximal to the plantar aponeurosis penetration point in order to maximize the “working length” of the portal tract.⁶ In order to have adequate working length, the plantar portal should be at the level of tarsometatarsal joint. The trochar is then passed through the toe web and exited through the plantar portal, and the arthroscopic cannula is then introduced through the plantar portal and exited through the toe web portal along the trochar. The trochar is then removed, and a 2.7-mm 30° arthroscope is introduced. The retrograde knife is then passed in from the toe web portal under arthroscopic guide until it reaches the proximal edge of the intermetatarsal ligament. This is easy to identify the edge by “probing” with the retrograde knife. The ligament is then released by the retrograde knife. After the ligament is released, the arthroscope is passed slightly dorsally through the cut ends of the ligament and is turned 90° toward the big
toe in order to see the adductor hallucis insertion. The insertion is released with the retrograde knife, and the fibular sesamoid bone can then been visualized. The lateral capsule is released proximal to the fibular sesamoid bone to the base of proximal phalanx and just dorsal to the fibular sesamoid bone. This can release the metatarsal sesamoidal suspensory ligament and preserve the metatarsophalangeal collateral ligament. In order to assure release of the phalangeal insertional band, the retrograde knife should be shifted slightly laterally when it hits the base of the proximal phalanx to finish the release of the band (Fig. 23-1). This is important for the reduction of the sesamoid apparatus. However, caution should be used as the sudden “loss of soft tissue resistance” after the release of the band may lead to accidental extension of the skin wound of the toe web portal.

There are three potential sites of nerve injury leading to three patterns of sensory loss. Firstly, the common digital nerve of the first intermetatarsal space can be injured close to the plantar portal. This will lead to sensory loss at both the medial side of the second toe and the lateral side of the big toe. In order to avoid it, the Wissinger technique should be used for the introduction of arthroscope through the plantar portal. This can assure correct positioning of the arthroscope and avoid multiple attempt of forceful insertion. Moreover, the introduction of the retrograde knife through the plantar portal should be avoided in order to prevent accidental cutting of the common digital nerve close to the plantar portal. Secondly, the medial digital nerve to the second toe can be injured just proximal to the intermetatarsal ligament. This will lead to sensory loss at the medial side of the second toe. The introduction of the trochar from the toe web portal should be gentle and should not encounter any resistance till the deep surface of the plantar aponeurosis is reached. This can reduce the risk of injury of the common digital nerve and the medial digital nerve of the second toe. The release of the ligament should be under direct arthroscopic visualization by the retrograde knife through the toe web portal, and any neural structure can be freed from the ligament before the release. Finally, the lateral digital nerve to the big toe can be injured during the release of the capsule, especially at the proximal end. This will lead to sensory loss at the lateral side of the big toe. The capsular release should be started a bit dorsal at the proximal border of the lateral capsule in order to avoid it.⁶

The medial exostectomy and medial capsular plication are performed through the proximal and distal bunion portals. The distal bunion portal is the same as the medial portal of first metatarsophalangeal arthroscopy, and the proximal portal is at the proximal pole of the bunion. The first metatarsophalangeal joint is examined through the distal bunion portal using a 1.9-mm 30° arthroscope. Arthroscopic synovectomy is performed through the dorsolateral portal if synovitis is present and the patient complains of first metatarsophalangeal joint pain with joint line tenderness.

The medial capsule is first stripped from the bony bunion by a small periosteal elevator through the proximal and distal portals. The bony prominence can be removed using arthroscopic burr under direct arthroscopic visualization. It should remove more at the dorsal side (Fig. 23-2). The adequacy of the exostectomy can be checked with image intensifier.

A bone tunnel of the neck of the first metatarsal is made with 2-mm drill through the proximal bunion portal. A long angiocath is passed through the bone tunnel, and the tip is caught by a hemostat through the toe web portal. The needle is removed, and the tip of the cannula is retrieved through the toe web portal (Fig. 23-3), and
a double-stranded PDS 1 suture can be passed from the proximal bunion portal to the toe web portal through the cannula to the toe web portal. The suture is then wrapped around the second metatarsal neck by means of an aneurysmal needle through the toe web portal. The suture is retrieved to the proximal bunion portal with a hemostat. The suture should be deep to the extensor tendons of both big toe and second toe and dorsal nerve and superficial to the dorsal capsule of the first metatarsophalangeal joint (Figs. 23-4 and 23-5).

PDS-1 suture with cutting-tip curve-eyed needle is prepared to plicate the medial capsule. The aim of medial capsular plication is to anchor the distal plantar corner of medial capsule to the proximal dorsal corner, in order to provide adduction and supination force to the proximal phalanx (Fig. 23-6). The needle is introduced through the distal bunion portal to pierce the plantar capsular flap and come out through the skin (inside out). Then, the skin is retracted with skin hook and the surface of the capsule is cleared with hemostat until the suture is seen. The suture is retrieved at the surface of the capsule and care must be taken to ensure that the digital nerve is not engaged. The suture is then passed through the plantar capsular flap again under direct visualization to avoid engaging the digital nerve, through the joint, and finally through the dorsal capsule and the skin (outside in). The suture is retrieved out from the joint through the distal bunion portal (Fig. 23-7). The suture is passed to proximal portal deep to the capsule. The needle is introduced through the proximal portal to pierce the dorsal capsular flap and come out through the skin (inside out) (Fig. 23-8). The sutures are retrieved at the surface of the capsule, as described above.

The first intermetatarsal space is closed up manually and held with a positioning screw (4.0-mm cannulated screw) bridging the bases of the two metatarsals (Fig. 23-9). The intermetatarsal sutures are then tied. Finally, the medial capsular suture is tied with the big toe held in reduced position.