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A 35-year-old man with an acute hand injury
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A 35-year-old, otherwise healthy, right-hand dominant man who works as a chef presented to the emergency department after a bicycle accident. He described falling from his bicycle and landing on his right hand. He reported acute pain in his right thumb and wrist with no other injuries. He had no numbness or tingling and no prior reports of hand trauma.
On initial evaluation, the patient was found to have swelling over the thenar eminence of the right hand. He also had tenderness to palpation around the anatomic snuffbox and pain with any axial loading of the thumb. His sensation was intact to light touch at both the ulnar and radial aspects of the thumb, and there was brisk capillary refill throughout the right thumb. The remainder of his physical examination confirmed there were no associated injuries and no evidence of other areas of trauma.
Three radiographic views of the right hand were obtained in the emergency department and are shown in Figure 1.
Images: Lee N
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Thumb carpometacarpal joint dislocation
Thumb carpometacarpal (CMC) joint dislocations make up approximately 1% of acute hand injuries. The most common variant is the Bennett fracture, which is a fracture-dislocation at the thumb CMC joint. The thumb CMC joint is a saddle joint comprised of the articulation between the trapezium and the base of the first metacarpal. The static stability of this joint is provided by four ligaments: the dorsoradial ligament; anterior oblique ligament; the posterior oblique ligament; and the intermetacarpal ligament. Thumb CMC dislocations occur in a dorsal direction as a result of axial loading with flexion of the first metacarpal. Persistent instability of the thumb CMC joint may cause pain, weakness and early degenerative changes. Stability of the thumb CMC joint is essential for key pinch and grasp strength.
Historically, there has been controversy regarding the injury pattern responsible for thumb CMC instability, with the anterior oblique ligament initially thought to be the primary stabilizer. Strauch and colleagues performed a cadaveric study to investigate the pathomechanics of thumb CMC dislocations. There were 33 specimens that were dissected with sequential sectioning of the ligamentous structures followed by evaluation of the stability of the thumb CMC articulation. The dorsoradial ligament was found to be the primary stabilizer to dorsal dislocation. Sectioning of the dorsoradial ligament allowed 41% subluxation in the neutral position, 53% subluxation in the flexed position and 13% subluxation in the extended position. This ligament also had the least joint subluxation when it was the only remaining ligament intact. In their experiments, dislocations never occurred when the dorsoradial ligament was intact.
In another study, Bettinger and colleagues described 16 ligaments that attach to the trapezium. The dorsoradial ligament was found to be shortest ligament that spanned the thumb CMC joint, and the thickest and widest ligament associated with the trapezium. A cadaveric study by van Brenk and colleagues demonstrated sectioning of the dorsoradial ligament resulted in the greatest amount of dorsal subluxation of the first metacarpal. This highlighted the importance of repairing or reconstructing this ligament when addressing thumb CMC joint instability.
Treatment of our patient
After the diagnosis of a thumb CMC dislocation was made for this patient in the emergency department, the patient underwent a closed reduction under local anesthesia. Post-reduction radiographs, shown in Figure 2, demonstrated improvement in the alignment of the thumb CMC joint, although the joint was not concentrically reduced.
When an anatomic reduction and stable joint is present following initial treatment, management options include: closed reduction and casting; closed or open reduction and percutaneous pinning; or early reconstruction of the thumb CMC ligament. The choice of ligament reconstruction is still subject to debate, as most of the literature is based on small case series. In our patient’s case, the CMC joint remained subluxated following the initial manipulation, prompting us to pursue surgical treatment.
There are multiple surgical options that have been described for patients with thumb CMC instability refractory to initial closed reduction, including open vs. closed reduction and stabilization with pins or ligamentous repair vs. reconstruction. Simonian and colleagues described a retrospective comparative study of eight patients treated with closed reduction and percutaneous pinning and nine patients treated with acute reconstruction of the volar oblique ligament with the flexor carpi radialis. Fifty percent of patients treated with closed reduction and percutaneous pinning had persistent instability at the thumb CMC joint and underwent subsequent surgical procedures. In the ligament reconstruction group, there were no patients with persistent instability.
Shah and colleagues reported a series of four patients who were treated operatively with either open reduction and casting or open reduction and percutaneous pinning. In this group of patients, the dorsal soft tissue was injured in all cases and the volar ligaments remained intact. Two of these four patients, both of whom were treated with reduction and pinning, went on to eventual dorsal subluxation of the first metacarpal. The observation that the dorsal capsule and ligamentous structures were injured is, however, in line with the cadaveric study on the function of the ligaments around the thumb CMC joint.
More recent attempts at surgical treatment of thumb CMC dislocation have focused more specifically on addressing the dorsoradial ligament. Okita and colleagues described one case involving direct repair of both the anterior oblique and dorsoradial ligaments with suture anchors. This patient had full function of the thumb at 1-year follow up. Fotiadis and colleagues also reported on repair of the dorsoradial ligament alone with a suture anchor. At 3 years following surgery, the patient was pain free and had no limitations with regard to the injured thumb.
For the case presented here, the patient was seen in the outpatient hand surgery clinic 2 days after his initial presentation. Given his persistent incongruency at the thumb CMC joint, surgical treatment was discussed with the patient and pursued. In the OR, the thumb CMC joint was examined under anesthesia and was noted to be grossly unstable. A dorsal approach to the thumb CMC joint was utilized. There was hemorrhage noted at the dorsal aspect of the first metacarpal. The dorsoradial ligament and capsular tissue was identified and had been avulsed off of its insertion on the trapezium. Using fluoroscopic imaging and direct visualization, a bio-absorbable suture anchor (Mini-Lock; DePuy Mitek) was placed into the trapezium. The thumb CMC joint was reduced, and with the joint held in its reduced position, sutures were placed through the robust dorsoradial ligament. With this secured, the stability of the joint was checked again and noted to be stable through a range of motion.
The patient was placed into a well-padded plaster splint for immobilization and kept non-weight-bearing on the operative hand in a thumb spica cast for 6 weeks, followed by active range of motion and limited weight-bearing restrictions for an additional 6 weeks. The patient self-advanced to full weight-bearing and full activity by 3 months, with no residual thumb pain or disability, and had returned to full activity and working as a chef by 3 months postoperatively. Two years following surgery, the patient continued to work as a chef and reported only episodic pain that did not interfere with his activities. Clinical pictures are shown in Figure 3. Radiographs, which are shown in Figure 4, demonstrate maintained reduction of the thumb CMC joint. Strength measurements were obtained at the two year post-operative follow-up visit, and there were no clinically meaningful differences between the operative and nonoperative hand with respect to pinch, grip strength and pincer grasp.
Conclusion
An isolated dislocation of the thumb CMC joint is a rare traumatic injury. The dorsoradial ligament has been shown to be the primary stabilizer of the joint. Although reports of treatment of this injury are not well-described in the literature due to the infrequency of this injury, there have been preliminary encouraging reports of successful treatment with suture anchor repair of the dorsoradial ligament.
- References:
- Betting PC, et al. J Hand Surg. 1999;24:786-798.
- Bosmans B, et al. J Hand Surg. 2008;doi:10.1016/j.jhsa.2007.11.022.
- Eaton RG, et al. J Bone Joint Surg. 1973;55:1655-1666.
- Fotiadis E, et al. J Orthop Surg Research. 2010;doi:10.1186/1749-799X-5-16.
- Okita G, et al. Arch Orthop Trauma Surg. 2011;doi:10.1007/s00402-010-1122-3.
- Shah J, et al. Clinic Orthop Rel Research. 1983;175:166-169.
- Simonian PT, et al. J Hand Surg. 1996;21:802-806.
- Strauch RJ, et al. J Hand Surg. 1994;19:93-98.
- Van Brenk B, et al. J Hand Surg. 1998;23:607-611.
- For more information:
- Drew A. Lansdown, MD; Musa Zaid, MD; and Nicolas Lee, MD; can be reached at the Department of Orthopaedic Surgery, University of California, San Francisco, 500 Parnassus Ave MU320W Box 0728, San Francisco, CA 94143-0728; Lansdown’s email: drew.lansdown@ucsf.edu. Zaid’s email: musa.zaid@ucsf.edu. Lee’s email: nicolas.lee@ucsf.edu.
Disclosures: Lansdown, Lee and Zaid report no relevant financial disclosures.