Arthritis of the first metatarsophalangeal joint, commonly called hallux rigidus, may occur for a variety of reasons: trauma, hallux valgus (bunion), and an elevated first metatarsal are the most typical. Hallux rigidus is also seen in inflammatory disorders including rheumatoid arthritis and gout.
The decision to fuse the first metatarsal and the proximal phalanx depends on the stage of the disease. The stage (or grade) of hallux rigidus is determined according to the Clinical-Radiographic System for Grading Hallux Rigidus developed by Coughlin and Shurnas [1]. Arthrodesis is indicated primarily in grades III and IV, in which the clinical examination demonstrates significant crepitus and pain at the mid-range of motion, and radiolographic evaluation shows substantial joint space narrowing. By contrast, cheilectomy is recommended if osteophytes are present, pain only occurs at maximum dorsiflexion and plantarflexion, and if radiographic evaluation shows less severe joint space narrowing.
Because arthrodesis restricts joint motion, interpositional arthroplasty may be indicated in patients who wish to preserve some joint motion [2]. A similar procedure, the Keller resection arthroplasty, is less invasive than arthrodesis and more suited to elderly patients susceptible to surgical complications [3].
Conservative treatment to reduce pain includes activity modification, footwear modification, or steroid injections. Patients are counseled to wear rocker-bottom shoes or use carbon shoe inserts equipped with a Morton’s extension (which minimizes plantar loading of the hallux) [3].
Contraindications for surgical treatment are active infection and severe, peripheral vascular disease. Arthrodesis can also be difficult in female patients based on shoewear preferences and possibly less tolerated in patients with pre-existing interphalangeal joint arthritis or first tarsometatarsal arthritis.
Preoperative Planning
Weight-bearing AP and lateral radiographs are obtained [Figure 1]. The first tarsometatarsal joint, the interphalangeal joint, and the first metatarsophalangeal joint are assessed.
At the author’s institution, the surgery is commonly performed under sedation in conjunction with regional anesthesia (typically a spinal block and either an ankle or popliteal block for post-operative pain).
After positioning, the leg is prepped and draped in the usual sterile fashion. At this time intravenous antibiotics are administered. An Esmarch bandage is used to exsanguinate the entire limb and a thigh tourniquet is inflated to between 250 to 275 mmHg. The tourniquet is released before closure of the wound at the end of the surgery.
The author commonly introduces a mixture of autologous bone marrow aspirate concentrate (BMAC) and demineralized bone matrix into the joint space to potentially increase the rate of fusion.
The patient is placed supine on the operating table with a bump under the ipsilateral hip and a wedge pillow under the ipsilateral leg. The table may be titled downward slightly to place the leg parallel to the floor and to facilitate the approach towards the dorsal aspect of the joint.
Approach
An incision is made on the dorsal aspect of the foot, centered at the first metatarsophalangeal joint [Figure 2]. It is carried down through skin and subcutaneous tissue. With caution, the extensor hallucis longus is protected laterally. The dorsal cutaneous nerve may be seen and protected medially. The entire joint is freed by performing a capsulotomy and removing any soft tissue or collateral ligaments directly off bone until the articular surface of the proximal phalanx is exposed.
Figure 2. The dorsal incision
Technique
Large osteophytes on the first metatarsal or the proximal phalanx are first removed with a rongeur. The authors used one of a variety of commercially available reaming systems to prepare the joint surfaces. A 1.6 guide wire is placed into the canal of the first metatarsal. It should start in the center of the metatarsal head and pass along the center of the metatarsal shaft. The correct placement of the guide wire is checked with intra-operative fluoroscopy [Figure 3].
Figure 3. Guide wire placement
The largest concave (or “cup”) reamer, commonly 24 mm in diameter, is selected and placed over the guide wire. The metatarsal surface is sequentially reamed with progressively smaller reamers until no cartilage remains and the contours of the metatarsal head are well-matched by the reamer. The guide wire in the first metatarsal is then removed and placed in the center and down the canal of the proximal phalanx. The correct placement of the guide wire is again verified with intra-operative fluoroscopy.
A convex (or “cone”) reamer is placed over this guide wire and the proximal phalanx is sequentially reamed beginning with the smallest size reamer, gradually stepping up to the size that matches the final cup reamer previously used on the metatarsal head. This is essential for matching the surfaces of the metatarsal head and the base of the proximal phalanx. If necessary, the dorsal aspect of the proximal phalanx is smoothed with a rongeur. The ability to place the joint into appropriate alignment is confirmed. Any surrounding debris is removed with a rongeur, and the entire joint space is irrigated with sterile saline.
A 1.6 K-wire is then used to fenestrate the articular surfaces of both the first metatarsal and the proximal phalanx. A small Hoke osteotome is then used to fish scale both articular surfaces [Figure 4].
Figure 4. The prepared articular surface
Demineralized bone matrix mixed with autologous BMAC is then placed in a small amount in the joint. The joint is now re-positioned and provisionally fixed with two crossing 1.6 K-wires at an appropriate valgus angle about 15 degrees [4].
The position of the joint is checked with intra-operative fluoroscopy [Figure 5]. The position can also be checked by placing a flat plate against the plantar aspect of the foot. Stephens and McKeown suggest the following: With the interphalangeal joint in full extension, the tip of the hallux must clear the surface of the foot plate; when the interphalangeal joint is plantarflexed to roughly 60 degrees, the tip of the hallux should touch the foot plate [4]. Alternatively, Bayomy et. al suggest an optimal maximum dorsiflexion angle of 20 to 25 degrees [5].
Figure 5. Provisional joint fixation and positioning
One of a variety of commercially available dorsal plates for first metatarsophalangeal arthrodesis is placed across the top of the first metatarsophalangeal joint. The plate used by the authors in this procedure requires six screws, up to two of which can be placed in compression.
The plate is bent to match the contours of the dorsal surface of the joint and to prevent excess extension. A 5.0 mm burr is commonly used to smooth the surface of both the proximal phalanx and the first metatarsal to allow the plate to sit smoothly on the bone. The plate is held in place with proximal and distal olive wires while the two distal holes are drilled first with a 2.0 mm drill, and two 2.7 mm screws are inserted. The proximal oblong hole of the plate is drilled in compression mode and a 2.7 mm screw is inserted. Then the two more proximal holes are drilled and two additional 2.7 mm screws are inserted. The distal oblong hole is drilled in non-compression mode and a 2.7 mm is inserted.
A 3.5 mm compression screw is then inserted across the joint from distal medial to proximal lateral (i.e. the medial aspect of the proximal phalanx to the lateral aspect of the first metatarsal). This can be done with a cannulated drill and implant. Alternatively, the holes can be made with a cannulated drill and then filled with a solid screw. Solid screws drilled with compression are stronger than smaller cannulated screws, but must be of similar make to the plate (i.e. stainless steel or titanium). Care must be taken to avoid the screws previously placed. The position and dorsiflexion of the hallux is again verified by placing a flat plate against the plantar aspect of the foot [Figure 6]. If everything is to satisfaction, the wound is then irrigated. The remaining mixture of demineralized bone matrix and BMAC is applied along either side of the joint.
Figure 6. Dorsiflexion range is verified after fixation
Each layer of the wound is closed with the appropriate gauge and type of suture. The capsule is closed with a 2.0 vicryl suture in an interrupted fashion. The subcutaneous layer is closed with a 4.0 vicryl suture also in an interrupted fashion. The skin is closed with a 4.0 nylon suture in a continuous fashion. A sterile dressing is wrapped around the limb and a below knee splint is placed to ensure that the joint is kept immobile during healing.
The entire technique is summarized in the following video produced by the authors:
Pearls and Pitfalls
While some shortening of the proximal phalanx and the first metatarsal is needed, avoid any excessive shortening to prevent transfer metatarsalgia.
Flat cuts must be extremely accurate for good positioning, thus they are not recommended. Cup- and cone-shaped reamers ensure more effective joint positioning.
Correctly match the size of the reamers to ensure good bony apposition at the site of arthrodesis.
The initial compression across the fusion site can either be obtained with the plate or the cross screw.
Postoperative Care
The patient is transferred to a designated recovery area and is prescribed medication for DVT prophylaxis upon discharge. The patient is seen at 2 weeks, 6 weeks, 3 months, and 6 months after surgery. Radiographs are obtained at each of the aforementioned follow-up visits [Figure 7].
The patient is advised to remain non-weight bearing on the operative foot for the first 6 weeks after surgery. At the 2 week follow-up appointment, the below knee splint is removed and the foot is placed in a tall CAM walker boot. Six weeks after surgery, the patient begins progressively weight bearing over the next 4 weeks.
Figure 7. Post-operative radiographs
Outcomes
Coughlin reports union rates of 94%, and Stephens and McKeown state that union rates for arthrodesis commonly quoted in the literature range from 80% upward [1,4]. Those studies utilized a similar construct, a dorsal plate with a cross screw. Brodsky reports improvements in the load bearing function of the foot and improvements in gait after arthrodesis, most likely due to pain relief following surgery [6].
Complications
Common complications following first metatarsophalangeal arthrodesis include nonunion, infection, and interphalangeal joint stiffness. If nonunion is asymptomatic, it does not require revision surgery. Extensive scarring can potentially cause tenodesis of the extensor hallucis longus.
References
Coughlin MJ, Shurnas PS. Hallux rigidus: Grading and long-term results of operative treatment. J Bone Joint Surg Am. 2003; 85-A:2072-88
Berlet GC, Hyer CF, Lee TH, Philbin TM, Hartman JF, Wright ML. Interpositional arthroplasty of the first MTP joint using a regenerative tissue matrix for the treatment of advanced hallux rigidus. Foot Ankle Int. 2008; 1:10-21.
Deland JT, Williams BR. Surgical Management of Hallux Rigidus. J Am Acad Orthop Surg. 2012; 20:347-58.
Stephens MM, McKeown R. First metatarsophalangeal joint arthrodesis: Perspective 1. In:Operative techniques in foot and ankle surgery. 1st ed. Philadelphia: Lippincott, Williams & Wilkins; 2011. p 147-51.
Bayomy AF, Aubin PM, Sangeorzan BJ, Ledoux WR. Arthrodesis of the first metatarsophalangeal joint: A robotic cadaver study of the dorsiflexion angle. J Bone Joint Surg Am. 2010; 92:1754-64.
Brodsky JW, Baum BS, Pollo FE, Mehta H. Prospective gait analysis in patients with first metatarsophalangeal arthrodesis for hallux rigidus. Foot Ankle Int. 2007; 28:162-5.
Smith BW, Coughlin MJ. First metatarsophalangeal joint arthrodesis: Perspective 2. In: Operative techniques in foot and ankle surgery. 1st ed. Philadelphia: Lippincott, Williams & Wilkins; 2011. p 152-62.
Campbell JT, Kirk KL. First metatarsophalangeal joint arthrodesis: Perspective 3. In: Operative techniques in foot and ankle surgery. 1st ed. Philadelphia: Lippincott, Williams & Wilkins; 2011. p 163-8.
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