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.