Introduction

Watanabe et al. described the first arthroscopy of the first metatarsophalangeal (MTP) joint in 1985. "The articulation between hallux and its metatarsal is entered at the point either lateral or medial to the extensor tendon. As this joint is extremely difficult to open with manual traction, a 2.7 mm outside diameter sheath must be used." Bartlett reported a case in 1988 in which successful arthroscopic debridement was performed on an osteochondral defect. The arthroscopic procedure has the advantage of less morbidity, outpatient treatment, and reduced risk of range of motion limitations that may be produced by the scarring that results from classic arthrotomy. Another advantage is a faster return to sports and work.

Anatomy

The first MTP joint is a chondroid joint composed of the metatarsal head and neck, the proximal phalanx, and the medial and lateral sesamoids. Minimal staibility is provided by the articulation because the ball (metatarsal head) and socket (proximal phalanx) are shallow. The sesamoid complex consists of two sesamoid bones, eight ligaments, and seven muscles. The sesamoids are contained within the tendon of the flexor hallucis brevis and articulate with the undersurface of the metatarsal head. Both sesamoids are attached on the plantar side through a fibrocartilaginous plate, which allows smooth gliding. The plantar plate also has attachements to the deep transverse intermetatarsal ligament, the flexor tendon sheaths, the plantar aponeurosis, and the transverse metatarsal ligaments, adductor hallucis. The intersesamoid ligament is strong and retains the relationship between the sesamoids. The extensor hallucis longus tendon divides the dorsal joint surface in half, and branches of the deep peroneal nerve innervate the lateral half of the hallux while branches of the superficial peroneal nerve innervate the medial half.

History & Physical Examination

A detailed physical examination should be performed to assess for swelling, joint-line tenderness, stiffness, and crepitus. Dorsiflexion and plantarflexion of the MTP and IP joints are checked in the neutral, resting position. Hypermobility of the first ray may be assessed by securing the metatarsal neck between the index finger and thumb, then stabilizing the lateral forefoot with the opposite hand. Instability is detected as increased motion in the sagittal and/or transverse planes. Pain at the end of the range of motion as compared with throughout mid-range may also be useful in deciding whether osteophyte excision, chondroplasty, or arthrodesis is best indicated.

Diagnostic imaging

CT scan shows a small osteochondral defect in the metatarsal head. 

Post-operative rehabilitation

The patient can be discharged the same day of surgery and weightbearing is allowed as tolerated. The patient is instructed to perform active dorsiflexion of the ankle. This exercise should be performed a few times per day. Active movements of the big toe can be performed as tolerated. The patient is instructed to elevate the foot when not walking to prevent edema. The dressing is removed 3 days post-operative. Normal walking without crutches at 4 - 5 days post surgery. Patients with limited range of motion are directed to a physiotherapist. Running can be started when range of motion is normal and in absence of swelling. This can on avarage be expected at 5-6 weeks post surgery. Sport resumption can on average be expected at 8-9 weeks post surgery. 

Recommended literature

Van Dijk CN, Veenstra KM, Nuesch BC. Arthroscopic surgery of the metatarsophalangeal first joint. Arthroscopy. 1998 Nov-Dec;14(8):851-5.

Frey C, van Dijk CN. Arthroscopy of the great toe. Instr Course Lect. 1999;48:343-6.