Recognize DIP arthritis in management of mucous cysts.
For optimal result:
Ensure proper patient selection
Consider the position of DIP joint after fusion
Pay careful attention to surgical preparation of the bone
Use familiar/appropriate fixation technique
Major and minor complications in most large series are not negligible—even for this simple-appearing procedure. Make certain to discuss this preoperatively with patients.
Careful consideration of DIP position with patient preoperatively
Use of familiar and reproducible techniques (no fixation technique has proved superior)
Meticulous preparation of bone ends
Care with tissues, particularly dorsal skin
Being aware of lack of bone stock
Consideration of K-wires for thumb interphalangeal (IP) fusion
Intraoperative imaging to confirm placement of fixation
Selection of improper fixation for desired position of joint (i.e., Herbert screw for DIP at 20 degrees)
Motion before clinical/radiographic union
Improper fixation for poor bone stock (i.e., Accutrak with very small bones)
Poor preparation of bone ends for fusion
Hastily executed straight cuts creating improper angle or deviation
Fixation with separation of bone ends
The distal interphalangeal (DIP) joint is one of the most prone areas of the body to be affected by osteoarthritis. More common in females, the incidence clearly increases with age, and although certain activities may exacerbate symptoms, specific behaviors have not been shown to actually cause the disease process. Presentation and functional deficits can range widely and often do not correlate with radiographs or physical appearance. Treatment options, as with other types of arthritis, should be tailored to the patient.
The diagnosis is based on symptoms, physical findings, and radiographic appearance of the joint. Many patients present with only cosmetic complaints related to the classic insidious enlargement of the arthritic DIP joint referred to as Heberden’s nodes ( Fig. 12-1 ) and related to osteophyte formation and chronic joint swelling. Others may complain of severe, disabling pain despite minimal or no significant physical findings. The classic presentation includes morning stiffness, pain with stressful or repetitive activities (which could include typing or holding a pencil), and improvement with rest. A previously asymptomatic joint can become inflamed and profoundly symptomatic after an inciting event such as jamming the finger. In more advanced stages, lateral instability is not uncommon and is occasionally the primary functional deficit. Mucoid cysts are small, firm nodules appearing near the DIP joint that can be found in all stages of the arthritic process and, perhaps as a result of an emotional response to their appearance, will often provoke the initial physician visit.
On physical examination, enlargement of the DIP joints, if present, should be readily apparent. Range of motion is typically affected and in severe cases can be quite compromised. Deviation (usually in a lateral direction) is common later in the disease process, but more subtle instability can be detected by stressing the joint. The joint itself is often tender to palpation, and pain with motion, especially at the extremes of flexion and extension, is common. A small cyst (mucoid) may be present just proximal or distal to the joint. When located distal enough to compress the germinal matrix, a corresponding groove can be seen in the nail plate. The skin over the cyst may be thin and the skin directly surrounding the cyst is often erythematous. Cysts may be cosmetically displeasing but painless, or they may be uncomfortable.
The most sophisticated diagnostic testing routinely needed should be an x-ray. Findings compatible with a diagnosis of osteoarthritis include joint narrowing, subchondral thickening and sclerosis, and osteophyte formation. In more advanced cases, joint deviation or subluxation may be associated with bone loss. A dorsal osteophyte should be seen radiographically to correspond with a physical suspicion of mucoid cyst. If this is not the case, the diagnosis of cyst should be questioned. Magnetic resonance imaging (MRI) may be appropriate for more detailed soft tissue analysis if no radiographic markers for osteoarthritis are present and the dorsal mass is clinically not obviously a cyst.
Initial treatment should be conservative and can range from patient education and counseling (for minimally symptomatic patients or for primarily cosmetic concern) to steroid injections. Anti-inflammatory medications are often helpful as long as they are tolerated. Finger splints, however, are almost never well tolerated. Cortisone mixed with lidocaine (usually 0.5 cc total) can be injected into the joint using a 25- or 27-gauge needle and introducing it parallel and under the extensor tendon at the dorsal aspect of the joint. Although this may be helpful in alleviating discomfort, the skin in this area is usually thin and prone to atrophic changes. Because of this, no more than one or two injections over time (several months apart) should be administered. Mucoid cysts, even when minimally symptomatic, may require treatment. As the overlying skin thins with the pressure from the cyst, rupture and subsequent bacterial contamination and sepsis of the DIP joint can result. Prophylactic treatment can avoid this rare but significant complication. If skin integrity appears adequate, a needle can be introduced subcutaneously from several millimeters away to aspirate the cyst. Efforts should be made to not violate the skin overlying the cyst itself, and if corticosteroid is to be introduced, the needle should be repositioned into the joint itself and injection into the fragile skin should be avoided. If this is unsuccessful or if rupture is eminent, then surgical excision is recommended. Multiple dorsal incisions have been described but a longitudinal or Y -shaped incisions seem to work well. After carefully undermining the skin (keep the fat with the skin) to identify and excise the cyst and pedicle going to the joint, a small longitudinal opening in the extensor tendon and capsule allows identification and excision of dorsal osteophytes, which is an important component of successful surgical treatment. A small rongeur or curette works well for this. If more than 50% of the extensor tendon is released, a temporary (4 to 6 weeks) K-wire across the DIP joint may avoid the development of an iatrogenic mallet finger. Patients should not only be warned of this possibility but also that dorsal incisions over the DIP joint tend to look “angry” for several weeks but usually end up doing fine. Local or rotational flap closure should be planned for if the skin overlying the cyst appears too thin, although others have reported no problems with secondary healing only. Removal of the cyst, osteophytes, or both will not generally alleviate pain and swelling associated with activity (symptoms of arthritis) and, if unresponsive to conservative measures, more definite surgical steps will be necessary.
“The prime requisite of a good digital arthrodesis is a painless and stable union in proper position occurring in a reasonable space of time.”
Arthrodesis, with the goal of painless and stable union, is a reasonable alternative for the patient who experiences pain or embarrassment of function as a result of deformity, collapse, or appearance. Only a few alternate reconstructions are available to afford stability and symptom relief at the DIP joint. Chondral arthroplasty and vascularized joint transfer have been attempted for the proximal interphalangeal (PIP) and the metacarpophalangeal (MCP) joints with limited success but have found little application in the DIP joint. Likewise, interposition arthroplasty with silicone (and more recently pyrocarbon and other component devices) has been used and investigated extensively for the MCP and the PIP joints; however, this has not been routinely used for the DIP joint. Implant arthroplasty at the DIP is limited in part by the force generated with tip pinch and key pinch requiring great resistance by the collateral ligament at the DIP (and PIP) joint to prevent deformity. Wilgis, however, has reported on the use of silicone arthroplasty for DIP arthritis in 38 patients. Three required removal for fracture, infection, and bone resorption, but stability was not a major issue. Average range of motion was 33°.
Functionally, the DIP has been assigned 15% of the total intrinsic digital flexion arc and 3% of the overall arc of the finger. This small number in comparison to the PIP (85% of intrinsic digital function) belies the importance of this joint, as any patient with significant disease will attest, but generally supports the minimal functional deficit associated with fusion. Numerous reports in the literature advocate the DIP arthrodesis as a predictable method of achieving painless function. The goal of stable union, even with numerous published techniques, may still be “difficult to achieve.”
Volar plate arthroplasty of the DIP joint is one procedure that has been advocated for treatment of posttraumatic arthritis and chronic subluxation of the DIP joint. Fractures and dislocations of the DIP joint frequently involve avulsion of the FDP or the EDC. Articular impaction fracture is much more rare and leads to a pattern of dorsal subluxation and arthritis similar to the more commonplace PIP injury. Thus the technique of treating both of these ginglymus joints similarly has been described. Rettig and colleagues describe 10 patients treated for this condition with a mean time from injury of 8 weeks. The operative technique consists of a volar approach with reflection of the flexor tendon and elevation of the collateral ligaments to facilitate reduction. After removal of any fracture fragments the volar plate is secured by means of polyglactin suture and Keith needles passed through drill holes. They reported 8 out of 10 patients with no pain and average arc of motion in fingers of 42 degrees and the thumb IP joint of 51 degrees.
SURGICAL TECHNIQUE OF ARTHRODESIS
As with all surgical arthrodesis procedures, the keys to success are preservation of soft tissue, proper bone preparation, and adequate compression and stabilization of the fusion site. The proximity of the germinal matrix to the DIP joint and the thickness of overlying skin warrant careful consideration when designing surgical approach. Damage to the nail matrix or eponychium/perionychium may lead to permanent nail deformity. Elevation of thin skin flaps or overzealous use of cautery may lead to necrosis, wound healing problems, or infection. Most authors advocate a Y -shaped or H -type incision centrally over the DIP ( Fig. 12-2 ). After cutting through the skin, flap creation should be minimal and kept thick. Dorsal veins usually require bipolar electrocautery. Incision with scalpel directly to the periosteal surface is performed and the terminal extensor tendon is cut right over the joint. “Shotgun” exposure of the joint requires complete division of the collateral ligaments on both sides of the DIP joint. Instead of “releasing” the ligaments from the middle phalanx head, the ligaments can be cut midsubstance, but care should be taken during this maneuver to avoid injury to the soft tissue envelope and the deep neurovascular structures lying in the fatty volar pad. Dissection and identification of the nerve and artery are unnecessary if division of the collateral ligaments is limited to the volar-most extent of the joint surface in the coronal plane.
Proper exposure will greatly facilitate bone preparation. Usually, identification and removal of osteophytes using a curette or rongeur will further aid the exposure and allow proper alignment of joint surfaces. These surfaces can then be prepared using either an oscillating saw, a rongeur, or Coughlin cup and cone reamers. Straight saw cuts are quick and, if done well, offer excellent surface contact to aid in bone healing (although care must be taken to avoid thermal injury to the osteocytes). The main disadvantage is that adjustments to alignment once initial cuts are made can be difficult and result in additional and unwanted shortening of the digits as extra “corrective” cuts are made. The cup and cone technique avoids this problem ( Fig. 12-3 ). Although more exacting to create with a rongeur (or requiring additional equipment if using reamers), such a convex–concave approximation allows the surgeon to change the flexion angle, and radial and ulnar deviation prior to fixation, slightly. Preparation of the head can be done in basically five bites: (1) removal of the tip of the phalanx, (2 and 3) removal of the radial and ulna condyles, and (4 and 5) removal of remaining dorsal cartilage and volar condyles (plus some fine tuning with the rongeur to make sure the “cone” fits nicely into the “cup”). The base of the distal phalanx can be prepared by carefully creating a central hole and then using the edge of this hole to bite away the subchondral bone and cartilage like the petals of a flower. When making this center hole, be careful not to “plunge” into the medullary canal, which creates a defect in the cancellous bone. In especially hard bone, a large K-wire or small drill can help get the center hole started. A burr can also be used in select situations. Regardless of which technique is used, complete removal of subchondral bone on both sides of the joint and good approximation of the underlying cancellous bone are musts. In situations of bone loss from longstanding deformity or in cases of redo fusions, cancellous bone graft can be easily obtained from the distal radius. After making a small incision over Lister’s tubercle, dorsal cortex can be exposed by cutting directly down on to the prominence and carefully lifting up the periosteum and overlying soft tissue. The EPL runs intimately close to this bone so recognition of its presence is necessary to avoid an embarrassing injury to this important tendon. A rongeur can remove the tubercle and expose the underlying cancellous bone, which can be easily removed with a curette for placement into the arthrodesis site. Afterward, bone wax is placed into the radial defect to decrease postoperative bleeding.