When Is It Appropriate For Arthrodiastasis Of The First MPJ?

   Multiple etiologies exist for painful conditions that involve the first metatarsophalangeal joint (MPJ). Hallux abducto valgus and hallux limitus are the most common pathologies of the first MPJ podiatrists see in most foot and ankle clinics. Other causes may include rheumatoid arthritis, trauma, connective tissue disorders, infection, iatrogenic and metabolic disorders. Historically, treatment has been geared to realigning structural abnormalities of bone as they affect the joint.1    Unfortunately, very little literature discusses specific treatment for maintaining the health of the cartilage at the first MPJ. In fact, the most recognized surgical procedures for problematic issues at the first MPJ are realignment osteotomies, implant arthroplasty and arthrodesis of the joint.    However, one may want to consider the new treatment modality of arthrodiastasis or joint distraction to help address certain pathological conditions of the first MPJ. Arthrodiastasis is a procedure whereby one distracts the first MPJ by applying an external fixator.2 There are three basic reasons why surgeons may employ arthrodiastasis to treat cartilage pathology. These reasons include:    • preventing mechanical contact within the joint;    • allowing weightbearing under distraction to promote pressure changes in the synovial fluid, which increases the proteoglycan metabolism essential for cartilage health; and    • removing stress to the subchondral bone, which allows a decrease in subchondral sclerosis.3    In a long-term, prospective, functional outcome study, VanRoermund, et. al., hypothesized the reduction of subchondral sclerosis as the major subjective finding correlating to improved clinical outcomes of 43 patients over four years.4 Clinical features, functional ability and improvement in pain were evident within the first year of follow-up examination. Interestingly, clinical outcome parameters improved over time and normalized between years three and four. Fifty percent of patients maintained increased joint space and 100 percent showed decreased subchondral sclerosis.

A Review Of Indications And Contraindications

   Indications for first MPJ arthrodiastasis include any joint with mild to moderate degenerative joint disease, with or without malalignment (transverse or sagittal plane) of the joint.    When it comes to severe degenerative joint disease, it may be beneficial to perform an arthrodesis or implant arthroplasty. However, one may still incorporate joint distraction when addressing joint malalignment issues via osteotomy correction.    Mild to moderate hallux abducto valgus with painful limitation of motion may also benefit from arthrodiastasis if one observes cartilage defects on preoperative testing/imaging or intraoperatively. Preoperative preparation of the patient is important when considering the use of external fixation for possible fixation of the osteotomy with distraction.    Contraindications for joint distraction include: ligamentous laxity (which may result in a more unstable joint); a severe loss of cartilage within the joint (end stage degenerative joint disease); vasospastic disorders and peripheral arterial disease; and active or sub-acute infections involving the joint. When it comes to joint distraction, proper evaluation and appropriate patient selection are essential for obtaining a predictable and satisfactory result.    Applying mini-external rail fixators is relatively simple but does require some experience. Ensuring proper placement of the transcutaneous pins is important in order to facilitate proper distraction as well as adequate and correct anatomic motion during the healing process. Inaccurate placement of pins will prevent movement about the first MPJ and cause mechanical abutment of the dorsal joint surfaces. Orienting the fixator in relationship to the joint to ensure motion is key to improving outcomes. The surgeon would usually perform and confirm all of these steps under fluoroscopy.    There are several manufacturers of small external fixators that one may use in joint distraction. In order to discuss the surgical technique, let us proceed to discuss proper mini-external fixator placement of the M-111 mini-rail (Orthofix, Inc.).

A Step-By-Step Approach To The Arthrodiastasis Procedure

   Prior to application and the appropriate osseous remodeling, one should perform joint debridement and subchondral drilling with standard closure. Be sure to inspect and mobilize the sesamoid apparatus for adhesions to the plantar aspect of the first metatarsal.    Insert a 2 mm Kirschner wire into the head of the first metatarsal from the medial side so it is in the center of the rotation of the joint. This point is slightly dorsal of the center point of an imaginary circle outlining the first metatarsal head. Orient the fixator so the body of the fixator with the distraction mechanism is facing the proximal phalanx. The hexagon at the center of the hinge should face outward.    Slide the articulating hinge over the Kirschner wire. Insert the 3 mm diameter bone screw through the distal seat of the distal clamp and insert the second screw into the proximal seat of the distal clamp. Manipulate the hallux, confirming that the movement is about the axis of the Kirschner wire. If not, remove and reset the Kirschner wire, adjusting the distraction mechanism as necessary.    After confirming motion about the axis of the first metatarsal, proceed to insert the 3 mm bone screws into the distal end of the first metatarsal.    Distract the joint 5 mm acutely (intraoperatively). Remove the Kirschner wire and tighten the articulated locking body screw. Be sure to lock the screw with the hallux in a neutral sagittal plane position.

What Does Post-Op Management Entail?

   Orthofix recommends waiting three days after surgery before begining gradual distraction. Distract the joint 0.5 mm per day until obtaining a joint space two or three times the normal width. One full clockwise turn of the threaded screw equals 1 mm of distraction.5 When the soft tissues have relaxed, loosen the articulated body locking screw to commence physical therapy. At the end of an exercise period, place the hallux in a neutral position and retighten the articulated body locking screw. Two weeks after completing the distraction, remove the fixator.    We frequently obtain 1 cm of distraction intraoperatively, hold static distraction for seven days and then proceed to disarticulate the hinge to allow daily passive range of motion activities. We maintain the presence of distraction for four to six weeks, allowing guarded weightbearing at week one before we remove the fixator. Recently, we have performed joint distraction of the first MPJ without disarticulating the hinge for movement. We have seen excellent results postoperatively with this approach.

Case Study: When A Runner Has A Chronically Painful First MPJ

   A 63-year-old female presented for surgical consultation with a history of a painful right first metatarsophalangeal joint. She had tried multiple conservative treatment modalities over the course of 18 months without successful relief of her symptoms. The patient was an active runner and walker but could not continue to participate in these activities.    Preoperative radiographs were significant for a dorsal medial enlargement of the metatarsal head, significant degenerative joint disease with subchondral sclerosis and widening of the first metatarsophalangeal articulation.    Intraoperatively, we found significant adaptation of the first MPJ, including periarticular spurs and loose bodies. We debrided the joint of all loose bodies and hypertrophic synovium, and drilled the cartilage defects. We aggressively mobilized the sesamoid apparatus with a McGlamry elevator and performed an aggressive dorsal metatarsal head remodeling. We proceeded to perform joint distraction.    The patient remained non-weightbearing for the first week. We loosened the articular hinge at seven days postoperatively and instituted range of motion and weightbearing. The distractor remained in place for five weeks. The patient currently is enjoying normal activities without pain at 18 months.

In Summary

   Arthrodiastasis is a new and exciting option for patients with painful motion secondary to cartilage defects in the first MPJ. Results are predictable with proper execution of the procedure to maintain a pain-free functional joint.    There are three key benefits to arthrodiastasis. It provides mechanical offloading. It facilitates early range of motion, which allows the synovial fluid to bathe the chondrocytes to maintain health. Lastly, distracting the joint helps the subchondral bone recover from abnormal stresses and decreases the amount of subchondral sclerosis on radiographs.    Indeed, joint distraction can be a valuable alternative to joint destructive procedures in otherwise healthy, active patients. Dr. Wilusz (left) is a Clinical and Surgical Instructor at the Foot and Ankle Clinic at the Southeast Michigan Surgical Hospital in Warren, Mich. He is an Associate of the American College of Foot and Ankle Surgeons. Dr. Pupp (right) is the Clinic Director of the Foot and Ankle Clinic at the Southeast Michigan Surgical Hospital in Warren, Mich. He is a Fellow of the American College of Foot and Ankle Surgeons, and is also the Clinic Director at the Sinai Grace Diabetic Foot Center in Detroit. Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.
 

References:

1. Chang TJ. Stepwise approach to hallux limitus: A surgical perspective. Clin Podiatr Surg. 13:449-459, 1996.
2. Magnan B, Bragantini A. Use of external minifixation in orthopedic deformities and diseases of the foot. In: Cziffer E, editor. Minifixation. External fixation of small boones. Budapest, Hungary: Szekszardi Nyomda; 1994. p187-96.
3. Buckwalter JA: Evaluating Methods of Restoring Cartilagenous Articular Surfaces. Clin Orthop 367(suppl):224-238, 1999.
4. Vanroermund, et al. Foot Ankle Clin N Am Sept 2002 and AAOS Annual Meeting 2001.
5. Orthofix, Inc. Applications by Anatomic Site. Richardson, TX:Orthofix p80-86.