A Review on CMC Joint Arthritis
Dr. Gregory Rubin
With the increasing popularity of cell phone use, there is a corresponding increase in thumb-related pathology. Osteoarthritis represents one such overuse syndrome. The second most common location in the hand where patients develop osteoarthritis is their thumb trapeziometacarpal joint (Glyka Martou, 2004). Unfortunately for those suffering, the CMC joint is involved with flexion, extension, adduction, abduction, and opposition of the thumb (David Melville, 2015).
Etiology. Upwards of 25% of women over the age of 50 will develop thumb carpometacarpal joint arthritis (Frank Yuan, 20178). The CMC joint is a bicon-cavoconvex joint (reciprocal saddle) that relies on capsular ligaments, intrinsic, and extrinsic hand muscles as the primary joint restraints (Glyka Martou, 2004; SW Song, 2019). This differs from most joints that typically have more bony constraint. In 1994 Pellegrini, et. al hypothesized that ligamentous laxity leads to the development of shearing forces in the joint leading to degeneration of the articular cartilage (Glyka Martou, 2004). The main culprit is weakness of the anterior oblique ligament of the joint (Marie-Lyne Grenier, 2016). Patient’s with Ehler-Danlos were found to have arthritic changes in their CMC joint as early as age 15 (Ann Van Heest, 2008).
Physical Exam. A patient with pain at the base of the thumb that is worsened with pinching will clue a physician in on the CMC joint (SW Song, 2019). Other common complaints are pain with opening jars, weakness in pinch strength, and cramping in the hand (Kristofer Matullo, 2007). On examination, the physician may find soft tissue swelling on inspection of the joint and patients typically have pain with palpation over the joint (SW Song, 2019). Pain at the CMC can also be exacerbated with the grind test (Kristofer Matullo, 2007).
Imaging. The primary target when imaging for CMC arthritis is the trapeziometacarpal joint (David Melville, 2015). Radiographs of the carpometacarpal joint include a true AP, lateral, and oblique view (David Melville, 2015). A true AP of the CMC joint is known as the Robert’s view and the patient’s forearm is positioned in max pronation for the xray (David Melville, 2015). One specialty view to better visualize the trapezial articulation is the basal joint stress view (Figure 1), which has the patient press both thumbs together. This image allows for a better view of the trapeziometacarpal articulation (David Melville, 2015). Classification of the stage of arthritis is known as the Eaton-Little staging (David Melville, 2015). Stage I involves widening of the joint without any joint space narrowing, stage II has mild joint space narrowing and osteophyte formation, stage III has pronounced narrowing of the joint, subchondral sclerosis and cyst formation and osteophytes, and Stage IV is similar to stage III but with even more narrowing and sclerosis/cyst formation (David Melville, 2015).
Treatment. Nonsurgical treatment is first line for patients with thumb carpometacarpal arthritis. Orthoses are typically used as part of a nonsurgical treatment. A study in 2016 looked at three thumb orthoses and looked at their effect on pinch strength since the decrease in pinch strength is one of the biggest functional limitations of CMC arthritis (Marie-Lyne Grenier, 2016). Another purpose of an orthotic is to decrease motion at the CMC joint with the aim that this will decrease pain by decreasing further cartilage wearing (Marie-Lyne Grenier, 2016). The studied found improvements in pinch strength in all groups wearing an orthotic (Marie-Lyne Grenier, 2016).
An orthopedic group in Sweden had long wait times for surgery, so they created a program that involved making custom splints for patients awaiting CMC surgery to help with pain and function (Magnus Berggren, 2001). Interestingly, they found that when the patients who initially were wanting surgery came back for re-evaluation, they declined surgery (Magnus Berggren, 2001). As a result, they created a prospective study that randomized patients to three groups with one receiving hand therapy and two other groups being given splints (Magnus Berggren, 2001). What they found was that of 33 patients who had initially wanted surgery, only 10 at 7 months follow up still wanted surgery (Magnus Berggren, 2001). Over the next 7 years, only 2 patients from the group who did not want surgery eventually wanted surgery (Magnus Berggren, 2001).
In order to better guide physicians in prescribing orthotics, a review published in Hand proposed that patients wear a short thumb stabilizing splint while at work and a thumb spica splint when off of work for 3-4 weeks (Kristofer Matullo, 2007).
Physical therapy is also a component of first line therapy. As mentioned above, the etiology of CMC arthritis is thought to be secondary to ligament laxity leading to joint instability and irregular loading of the joint causing articular cartilage wearing. Based on this principle, one of the first goals of PT is to strengthen the joint stability by working on strengthening the surrounding hand musculature including the thenar musculature, thumb extensors, and thumb abductors (Kristin Valdes, 2012). The other tenant of hand therapy should involve thumb flexibility to help increase joint range of motion (Kristin Valdes, 2012).
Intra-articular injections can also be considered for CMC joint arthritis. A study in 2006 in Osteoarthritis and Cartilage looked at hyaluronic acid verse corticosteroid injections for patients with CMC joint arthritis (S. Fuchs, 2006). They found that over 79% of the patients who received a steroid injection or hyaluronic acid injection had pain relief at 26 weeks after their first treatment (S. Fuchs, 2006). There are no current studies looking at the role of PRP for CMC arthritis. However, many providers are doing this injection based on extrapolated data from other studies showing an improvement in pain following intra-articular PRP injections.
If the nonsurgical attempts to manage pain and function of CMC arthritis fail then patients are typically referred to our hand surgery colleagues. One of the first surgeries that was initially done for CMC arthritis is a Trapeziometacarpal arthrodesis. However, this procedure fell out of favor due to high rates of nonunion and loss of mobility of the CMC joint (AM Gay, 2016).
Due to the theory that OA of the CMC joint occurs due to ligament laxity, physicians started offering ligament reconstruction as a treatment for early Stage I and II CMC arthritis (SW Song, 2019). The flexor carpi radialis is typically used, as it can reconstruct both the anterior oblique and dorsoradial ligaments, which are the two main stabilizers of the CMC joint (SW Song, 2019).
A study published in the Journal of Hand Surgery evaluated Medicare claims in patients with CMC arthritis to see what procedures physicians were doing (Frank Yuan, 20178). What they found was that over 90% of the time, a partial or complete trapeziectomy with ligament reconstruction and tendon interposition (LRTI) was being done (Frank Yuan, 20178). The other procedures that were done less than 10% of the time were a simple complete trapeziectomy, thumb carpometacarpal arthrodesis, and thumb carpometacarpal prosthetic arthroplasty (Frank Yuan, 20178).
There is a lack of good quality evidence regarding whether a trapeziectomy or trapeziectomy with LRTI would be indicated (Frank Yuan, 20178). A review published in the Plastic and Reconstructive Surgery journal in 2004 aimed to compare the two procedures and failed to find objective outcome measurements that were in favor of LRTI verse arthrodesis and trapeziectomy alone (Glyka Martou, 2004).
Due to some of the side effects of trapeziectomy, such as post operative weakness with pinching, there has been interest in developing an implant as a surgical alternative (Maria Jorheim, 2009). In 2009 in the Journal of Hand Surgery, Dr. Jorheim looked at outcomes in patients receiving an Artelon implant, which is a spacer designed to increase joint space, and compared them to patients receiving a trapeziectomy and APL arthroplasty. (Maria Jorheim, 2009). They did not find a statistically significant difference in pinch strength between the two procedures or differences in pain scores (Maria Jorheim, 2009). Also of note is that the Artelon implant will degrade after a couple of years, making the long term outcomes unknown (Maria Jorheim, 2009).
Other trapeziometacarpal joint replacements exist similar to the ball and socket joint of the hip (AM Gay, 2016). Despite these joint replacements leading to pain relief, they have multiple complications including joint dislocation and hardware loosening (AM Gay, 2016).
Conclusion. The main take away from this article is that CMC arthritis is a common condition in our patient population over the age of 50 and that physicians should attempt a gradual step up from conservative measures to a myriad of surgical options. When evaluating surgical options, there is no trial or study that places one surgery in favor over all the others (SW Song, 2019). However, amongst a recent survey for physicians in the American Society for Surgery of the Hand, a trapeziectomy with LRTI is the most commonly done (SW Song, 2019).
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