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Author:  Alejandro Badia, MD and Alexis Jiménez, MD

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Abstract
A case of bilateral Stage III thumb CMC joint osteoarthritis in a patient with Ehlers-Danlos syndrome is reported. Bilateral arthroscopic tendon interposition arthroplasty using a slip of palmaris longus tendon after limited trapezial hemiresection was performed. Following surgery and brief rehabilitation, the patient was able to return to all previous activities, remained pain free and demonstrated increases in pinch strength bilaterally.
The Ehlers-Danlos syndrome is an inherited group of disorders that is characterized by abnormal collagen synthesis. While the overall prevalence of the Ehlers-Danlos syndrome is not known, it is believed to affect approximately 1 in 20,000 people in the U.S., making it the most common of connective tissue disorders. Currently, there are eleven forms of the disease identified, recently organized into six categories. Each form is differentiated based on the pattern of inheritence, clinical symptoms and organs affected. And while some forms of the syndrome appear in diverse organs, the three cardinal manifestations of Ehlers-Danlos syndrome are skin extensibility, joint hypermobility, and skin fragility.

Beighton et al. was the first to describe a scale to assess Ehlers-Danlos patients degree of joint hypermobility in 1969. They scored patients on a 0-5 scale on their ability to perform the follwing maneuvers: 1) passive dorsiflexion of the metacarpophalangeal joint past 90 degrees, 2) passive opposition of the thumb to the volar aspect of the forearm, 3) hyperextension of the elbow >10 degrees, 4) hyperextension of the knee >10 degrees, 5) forward flexion of the trunk until the palms can rest easily on the floor. In the same paper, Beighton noted that laxity was demonstrated in all joints, particularly those of the digits. Five of the patients had osteoarthritis of the hands, especially of the thumbs. Overall, they noted that “the incidence of osteoarthritis was directly related to the hypermobility index” score of the patients.

Pain in arthritic thumbs has long been an indication for surgery. Many earlier authors (Carroll and Stark) advocated arthrodesis of the thumb CMC joint as a means of decreasing pain and enhancing stability. Disadvantages of this technique included decreased range of motion and a lenghty period of immobilization required. Others (Murley and Gervis) endorsed excision of the trapezuim as a means of treatment, which afforded pain relief but sacrificed strength at the joint. Froimson had success with using a rolled slip of the FCR tendon as a spacer after excision of the trapezuim. Swanson advocated the use of a silicone spacer for similar such operations. Eaton, however, advanced a proceedure of tendon interposition arthroplasty for degenerative thumb CMC arthritis in which much of the trapezuim was left intact, believing that trapezium excision effectively represented overtreatment of arthritis limited solely to the thumb CMC joint. Subsequent descriptions of arthroscopic techniques in thumb CMC arthroplasty operations was provided by Menon, Berger, and Braun, among others. Braun et al. state that the indications of arthroscopic tendon interposition arthroplasty are for pinch or grasp strength weakness due to a painful thumb base, particularly if radiographic evidence supporting this presentation is scant. Herein, we describe bilateral arthroscopic tendon interposition arthroplasty of the thumb CMC joints using a slip of the palmaris longus tendon as a spacer, in a patient with Ehlers-Danlos syndrome.

Case Report A 56 year old right hand dominant man with a history of Ehlers-Danlos syndrome presented with over one year of steadily increasing pain at both thumb bases, worse on the right side. On examination, the patient displayed visibly prominent basal joints, particularly on the right side, with tenderness. Extreme skin and ligamentous laxity was noted. The grind test was positive with pain present. Pinch strength testing showed a right-sided déficit, with a value of 16 lbs., compared to 20 lbs. on the left. Radiographs showed evidence of bilateral basal joint subluxation, more pronounced on the right, as well as narrowing of the joint space and some early marginal osteophytes. There was a slight Tinel’s sign over the median nerve. Subchondral sclerosis was evident, with no cyst being present. A nerve conduction study showed increased motor latency bilaterally, indicating the presence of Carpal Tunnel syndrome.

Based on the findings, the patient appeared to have bilateral late Stage II basal joint artritis secondary to Ehlers-Danlos syndrome and ligamentous laxity. Arthroscopy of the right thumb CMC joint however, revealed more extensive synovitis and advanced osteoarthritis with extensive cartilage loss, indicating Stage III arthritis. The decision was therefore made to proceed with arthroscopic tendon interposition arthroplasty using the palmaris longus tendon. An endoscopic Carpal Tunnel release was also performed.

At one week post-op, a thumb spica cast was applied for a 3 week period followed by hand therapy. At two months post-op, right-sided pinch strength was 10lbs. and x-rays showed good positioning of the right basal joint. During this time, however, deterioration of the left thumb was noted, with the patient reporting increasing pain. Radiographic examination of the left thumb basal joint showed bone-to-bone contact with large marginal osteophytes and sclerosis. The patient underwent the same arthroscopic thumb CMC joint interposition arthroplasty and endoscopic carpal tunnel release as had been performed previously on the right side. Additionally, the first extensor compartment was released. At eight weeks follow-up on the left side, excellent pain relief was noted, with good functional range of motion. One year after the right side and four months after the left, there was total absence of pain with the patient returning to all of his normal activities. Right sided grip strength was 112 lbs., and 120lbs. on the left. Right and left pinch strength were 18 and 22 lbs., respectively.

Discussion

This is the first report of bilateral thumb CMC joint arthroscopic interposition arthroplasty in an Ehlers-Danlos patient in the literature. However, the evidence for substantial hand problems in EDS patients is very well established. Ainsworth et al. surveyed 151 Ehlers-Danlos patients and found that 27% with the type III disorder reported hand pain, with 77% having hand hypermobility. Gamble et al. studied 24 EDS patients and found that not only did all have increased finger joint range of motion, but tip pinch strength was particularly affected as it caused trapeziometacarpal subluxation and pain in most. Stanitski assessed functional orthopedic problems in EDS patients and found that 73% claimed less than normal upper extremity function. Sixty-four percent said they easily dropped objects, implying functional hand strength problems. Kornberg and Aulicino presented four EDS patients who displayed hand and wrist joint prolems which were directly attributable to laxity of the joint capsules and ligaments. One patient showed degenerative changes in several joints of the hand and another had degenerative arthritic changes in the right thumb CMC joint as well as subluxation.
Moore studied two fraternal twins with EDS and noted that the thumb CMC joint appeared particularly susceptible to painful subluxation due to its heavy reliance on ligamentous support that becomes weakened in Ehlers-Danlos syndrome. Cooney and Chao found that the thumb is in adduction for many functional activities, an essentially unstable position which could contribute to subluxation of this joint. Gamble et al. similarly found that activities of daily living seemed to cause joint subluxation, possible dislocation and eventual degenerative changes often seen in EDS. Eaton and associates agree that the ensuing arthrosis of the thumb CMC joint is “a predictable sequelae of ligamentous laxity whether post-traumatic or idiopathic” in origin. They also caution that frank degenerative joint disease with cartilage erosion, sclerosis and osteophyte formation may all result from chronic, untreated thumb CMC hypermobility. While the long-term success rates for thumb CMC tendon interposition arthroplasty have been encouraging, there is as yet no data on how this proceedure will fare in Ehlers-Danlos patients. Eaton reported finding good-to-excellent results in 74% of stage III-IV (non-EDS) patients an average of seven years after a simliar open proceedure. While the open technique has proven effective in treating thumb basal joint arthritis, the advantages of arthroscopic versus an open technique are intuitive including fewer complications, minimal capsular and soft-tissue disruption, less post-operative pain and a generally shorter recovery time.

It is reasonable to wonder if the ligamentous laxity inherent to Ehlers-Danlos syndrome would compromise this patients reconstructed thumb CMC joints at some point in the future. But should this occur, previous tendon interposition arthroplasty would not preclude revision surgery via an open excisional arthroplasty. However, the outcome sought for the tendon interposition arthroplasty in this patient was to stabilize the thumb CMC joints in order to relieve pain and restore strength and function, all of which are evident after preliminary follow-up. The patient’s insistence upon having the opposite side similarly reconstructed is further testament to the success of this particular technique.We therefore recommend this proceedure as a treatment for arthritic thumb basal joints in patients with Ehlers-Danlos syndrome, and strengthen our conviction in using this technique for the routine surgical management of advanced basal joint osteoarthritis.

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