CHAPTER SYNOPSIS:
Proximal interphalangeal (PIP) joint arthritis can lead to pain, instability, and impairment of hand function. Arthrodesis provides excellent pain relief and stability to affected joints at the expense of mobility. Arthroplasty preserves mobility and relieves pain in a suitable subset of patients.
IMPORTANT POINTS:
Arthrodesis remains the gold standard for pain relief and stability in proximal interphalangeal joint arthritis.
Consideration of patient’s vocation, avocations, and needs should weigh heavily in selection of treatment.
Arthrodesis may have greater longevity than arthroplasty in younger, more active patients.
Lateral stresses are poorly tolerated by arthroplasty, although newer surface-replacement designs promise better stability than older spacer designs.
Meticulous surgical technique is necessary to ensure success of arthrodesis or arthroplasty.
CLINICAL/SURGICAL PEARLS:
Fixation hardware for arthrodesis includes Kirschner wires (or K-wires), tension band wires, headless compression screws, and plates. Successful arthrodesis requires rigid fixation.
Kirschner wires are quick and easy to use but provide poor stability.
Tension band wires provide excellent stability and great flexibility in selection of position of arthrodesis.
Headless compression screws provide excellent stability but limit fixation angle.
Plates are generally used in salvage/repeat arthrodeses.
Bone carpentry must be meticulous.
Location of the drill hole in the proximal phalanx is critical to successful placement of headless compression screws.
Options for arthroplasty include flexible silicone prostheses or surface-replacement arthroplasty.
Flexible silicone prostheses have stood the test of time. Stability is provided by retained or reconstructed collateral ligaments.
The prosthesis is designed as a spacer, and it may piston in the proximal or middle phalangeal medullary canal.
Either a dorsal or volar approach to the PIP joint may be used.
Range of motion after silicone arthroplasty is variable; some authors report net loss, whereas others report net gain. Pain relief is reliable.
Surface-replacement arthroplasty simulates the anatomy of the native PIP joint, which helps impart greater lateral stability, combined with intact collateral ligaments, than silicone arthroplasty.
Technique is very demanding; each manufacturer has its own technique specific to the implant.
Materials are cobalt chrome on ultra-high molecular weight polyethylene or pyrocarbon.
CLINICAL/SURGICAL PITFALLS:
Successful arthrodesis depends on large apposing cancellous surfaces and rigid fixation.
Whether prepared with a rongeur, bone mills, or a saw, apposing surfaces must be free of cartilage and congruent.
Tension band wiring or headless compression screws provide rigid fixation.
Even tension on the tension band wire is possible by placing a second twisting loop opposite the primary twisting loop.
The transverse drill hole in the middle phalanx must be dorsal to the midaxial line of the phalanx.
The proximal hole for the compression screw must be at least 6 or 7 mm proximal to the arthrodesis site to prevent cortical fragmentation.
The proximal hole for the compression screw must be sufficiently enlarged to allow passage of the trailing thread without fracture.
The assistant should hold the phalanges in close apposition in appropriate position while the surgeon inserts the screw or tension band wires.
Arthroplasty requires adequate soft tissues at the joint, including collateral ligaments and soft tissue coverage.
Varied approaches to the joint may be used for silicone replacement arthroplasty. If collateral ligaments must be removed, they must be carefully replaced through drill holes. Machining of the medullary cavity with a burr or prosthesis-specific rasp must ensure that the cross section of the hole corresponds to the rectangular profile of the prosthetic stem.
If the silicone prosthesis size is too small, it will be unstable; if it is too big, it will restrict motion.
If the central slip is inadvertently detached, carefully reattach through drill holes on the dorsum of the middle phalanx.
For surface-replacement arthroplasty, follow the manufacturer’s technique carefully. The location and angles of the bone cuts are critical to ensure stable prosthetic seating. Carefully use the jigs provided.
Incision into the dorsal apparatus in a Chamay configuration allows adjustment of tension in the extensor apparatus on closure.
INTRODUCTION/SCOPE OF PROBLEM
Arthritis at the proximal interphalangeal (PIP) joint of the fingers can be debilitating. Although it is less common than arthritis at the basilar joint of the thumb, pain, deformity, swelling, and stiffness can result from joints afflicted with posttraumatic arthritis, inflammatory arthritis, or osteoarthritis. As in other arthritic joints, treatment should be directed toward pain relief and functional improvement.
The PIP joint is essentially a hinge joint. Disease in the ring or small finger PIP joints affects gripping activities significantly, whereas disease in the index finger PIP joint largely affects pinch. Conservative treatment measures include splints, buddy tape, therapy (including various modalities such as heat, iontophoresis, and hot wax), nonsteroidal anti-inflammatory medications, and intraarticular steroid injections. It is noteworthy that because of the anatomy of the PIP capsular structures, injection can be easily accomplished by retrograde insertion of a 25-gauge needle just distal to the dorsal surface of the proximal phalangeal head between the condyles in a digit with the PIP flexed approximately 20 to 30 degrees. One cc or less of steroid medication can be injected, and the examiner’s palpating fingers on the radial and ulnar sides of the joint will detect insufflation of the joint if the needle is correctly placed.
If conservative treatment measures fail to provide relief, surgical treatment should be offered. The gold standard for achieving pain relief and stability in arthritic PIP joints has been for many years and remains arthrodesis. It is a straightforward procedure that reliably provides pain relief and improvement in function. However, the loss of motion can cause considerable morbidity. For this reason, the search continues for a reliable and durable arthroplasty solution for the PIP joint. Although considerable improvements have been made since arthroplasty was first performed at the PIP joint, the ideal solution—restoring motion and providing the longevity and pain relief of a well-done arthrodesis—remains at bay.
PIP ARTHRODESIS
History/Introduction
In 1960, Moberg professed that “the prime requisite of a good digital arthrodesis is a painless and stable union in proper position occurring in a reasonable space of time.” Despite advances in motion-preserving procedures at the PIP joint, arthrodesis remains a basic and frequently used technique for relief of pain and disability in the fingers.
As in all techniques of bone fixation, those that provide structural rigidity and compression are likely to have the highest success rates in achieving solid fusion. Fixation with Kirschner wires has been performed for years, although Kirschner wires alone lack structural rigidity. Complex methods of bone carpentry, including tenon methods and bone peg techniques, were used to achieve stability prior to the advent of modern headless compression screws. More recently, tension band wiring and headless compression screw fixation of interphalangeal joint fusions have demonstrated consistent success with relatively low complication rates. At the present time, they represent the product of three decades of investigations to increase the rigidity of interphalangeal arthrodesis while simplifying the associated surgical techniques.
Indications/Contraindications
Arthrodesis of the proximal interphalangeal joint is indicated to relieve pain and instability in an arthritic, painful joint. It is more commonly indicated in index and middle fingers where arthroplasty is more likely to fail as a result of high coronal plane loads on the joint, especially during pinch. Individual assessment of the anatomy and of the patient will help decide whether arthrodesis or arthroplasty is more suitable in each patient. Consideration of vocational and avocational activities is needed to determine if they can reasonably be performed with an arthrodesed joint or if motion is needed. The surgeon must decide with the patient how much lateral coronal plane stress and force is imparted to the patient’s joints on a daily basis. Those of a manual laborer must sustain more stress than those of a seamstress. The more coronal plane stress is encountered, the more likely an arthroplasty is to fail and the more likely an arthrodesis will provide the best long-term stability.
Patients with weakened soft tissues, as in rheumatoid arthritis, may be more prone to instability with arthroplasty, and arthrodesis should be considered. Those with severe coronal plane angulation preoperatively also will likely do better with arthrodesis than arthroplasty.
Contraindications to arthrodesis include a requirement for motion, active infection, irreparable soft tissue defect over the joint, or severe systemic disease. A relative contraindication is heavy smoking because of its known adverse effect on bone healing. At the very least, heavy smokers should be warned of the increased risk of nonunion.
Surgical Technique
Regardless of the method of fixation for arthrodesis, I prefer a dorsal approach to the joint ( Fig. 13-1 ). A curvilinear incision is made around the joint dorsally. Dorsal veins are preserved, and the extensor tendon covered by a thin filmy epitenon is encountered. There is no macroscopically defined separation between the extensor tendon and the joint capsule at the PIP level. The combined structure of tendon and capsule is divided in the midline to enter the joint. The central slip insertion into the dorsal base of the middle phalanx should be carefully peeled off the bone, but the distal insertion fibers should be left intact. In this way, the central slip can reattach after closure, which helps maintain the length-tension relationships of the extensor apparatus. The lateral bands are left undisturbed so that they may continue to extend the distal interphalangeal joint.
Because the joint is to be fused, the collateral ligaments are sacrificed to allow unfettered exposure of the joint surfaces. They can be either peeled off the condyles subperiostally, or simply sectioned. In either case, any redundant tissue after sectioning or recession should be excised so that it does not interfere with bony apposition. Attention must be paid to the location of the neurovascular bundles on both sides of the finger, keeping them out of harm’s way.
After removal of the collateral ligaments, the joint is hyperflexed. The volar plate remains attached to both proximal and middle phalanges. At this point, as much of the volar plate as is accessible should be excised. If it remains in place, it will prevent apposition of the proximal to the middle phalanx after the obligatory bone shortening that occurs with preparation of the opposing surfaces.
The appropriate angle for arthrodesis must be determined preoperatively in consultation with the patient. Patient activities must weigh heavily on the decision; a guitar player in his fretting hand may want the joints more flexed than a secretary who spends much of the day on a keyboard. Asking the patient to wear custom-fabricated orthoplast splints prior to surgery, in varying amounts of flexion at the PIP joint, is a good way for them to assess the adequacy of the arthrodesis angle prior to surgery. Index and middle fingers are usually fused in 15 to 30 degrees of flexion. The ring and small fingers are more functional when fused at 30 to 45 degrees because they are more involved in grip.
When the desired fusion angle is determined, implementation must be planned depending on the carpentry method chosen. If saw cuts are to be used, both cuts should be angled. The sum of the angles on each bone equals the total amount of joint flexion obtained ( Fig. 13-2 ). This produces the largest surface area of bone apposition for the arthrodesis. Coronal plane alignment, however, is completely determined by the saw cuts; no further adjustment can be made without recutting the bone, which further shortens the digital skeleton. A microsagittal saw can be carefully used to perform the cuts, protecting the adjacent soft tissues.
Alternatively, a rongeur may be used to create cup and cone or convex–concave opposing surfaces on the two bone ends ( Fig. 13-3 ). This technique is more forgiving with respect to the final angle of arthrodesis because small adjustments in the flexion/extension angle, and rotation, can be made without reshaping the bones. Bone mills are available to create reproducible convex and concave surfaces on the bone ends, although I find their use cumbersome in the digital skeleton. I prefer the careful use of a rongeur.
Prior to hardware insertion, there must be tight bony apposition between the proximal and middle phalanges. If there is not, or if there is any resistance to close apposition, the most common cause is a retained volar plate. A sufficient width of the volar plate must be removed so that it is no longer an impediment to snug apposition of the bony surfaces. Small rongeurs can also be used to remove any marginal osteophytes that lead to an unsightly enlargement of the joints in osteoarthritis. Patients can remain unhappy even after a stable and painless arthrodesis if their joints remain visibly enlarged, particularly if it prevents wearing of their rings.
Hardware Insertion
Kirschner Wires
The PIP joint can be fixed by Kirschner wires inserted from proximal to distal or distal to proximal. After machining of the joint surfaces, the proximal and middle phalanges are held in the appropriate position and two wires, usually 0.035 inches or 0.045 inches in diameter, are driven across the arthrodesis site. I prefer parallel wires. With crossed wires there is a risk that they cross at the arthrodesis site, which results in a loss of rotational control. They are usually left protruding through the skin and capped. Fixation is simple but not very secure.
Tension Band Wires
Use of a tension band technique is more complex than Kirschner wires alone but far more secure. Fixation begins by placement of two parallel Kirschner wires, usually 0.035 inches in diameter, from proximal to distal across the arthrodesis site. They must extend at least one third of the length into the middle phalanx. I then use another 0.035-inch Kirschner wire to drill a hole transversely across the middle phalanx, dorsal to the intramedullary Kirschner wires already placed. Through this hole one threads a stainless steel wire, usually 22 or 24 gauge transversely across the phalanx. Both ends of this wire are then crossed dorsally over the arthrodesis site.
To ensure even distribution of tension in the tension band wire it is important to have a means to tighten both limbs of the tension band. One limb will be tightened by twisting together the two ends of the wire. The second limb should have a twisting loop placed in it, at the same level in the digit as the first loop. After forming this second twisting loop with a small needle holder, the crossed end of the tension band wire is looped around the volar side of the proximal ends of the Kirschner wires and then brought to the other end of the tension band wire. Here, the first tightening loop is made. Then, using two needle holders simultaneously, both loops are tightened while pulling up on the wire twists. The needle holders must hold the wires to be twisted some distance away from the base of the wire twist. This results in a more uniform distribution of tension in adjacent wire twists. Tension in the twisted loops must be “just right” to ensure sufficient tightness but no wire breakage. This technique results in a tension band loop with tension evenly distributed throughout its length ( Fig. 13-4 ).
Finally, the protruding Kirschner wires are cut as flush as possible with the bone. Use of the appropriate wire cutters here is essential. It is absolutely impossible to cut these Kirschner wires flush with the dorsal bone surface of the proximal phalanx with a blunt nose end cutting wire cutter. Rather, an electrician’s diagonal cutter style of wire cutter is needed ( Fig. 13-5 ). Sufficient protrusion of the Kirschner wires always remains to prevent the looped tension band from sliding off.
Headless Compression Screw
Headless compression screws are made by numerous manufacturers and include the TwinFix (Stryker-Leibinger, Kalamazoo, MI), Herbert or Herbert/Whipple (Zimmer, Warsaw, IN), HBS (Orthosurgical, Miami, FL), Millennium (Millennium Medical, Santa Fe, NM), and Acutrak (Acumed, Hillsboro, OR). Planning and execution of screw insertion must be meticulous. The screw is inserted antegrade at the PIP joint from the dorsal surface of the proximal phalanx. The dorsal entry site must be made at least 6 to 7 mm proximal to the joint surface to prevent fragmentation of the dorsal cortex. I start the hole with a 0.045-inch Kirschner wire for the Herbert or Mini-Herbert screw or the included Kirschner wire from the screw set when using the TwinFix or Acutrak screws. The direction of the wire must be at the angle, in the sagittal plane, of the desired arthrodesis.
After the hole has been made with the Kirschner wire, the drill(s) from the screw set are used in the appropriate sequence. For the Herbert or Mini-Herbert screws, the “long, skinny” drill is used first to drill through the proximal phalanx into the medullary canal of the middle phalanx ( Fig. 13-6 ). This is followed by the “short, fat” drill for the trailing threads in the proximal phalanx only. The TwinFix and Acutrak screws have a single cannulated drill that can follow the Kirschner wire through the proximal and into the distal phalanx. It is important that the drill pass the cortical isthmus of the middle phalanx.
After drilling, a 1.1-mm rongeur must be used to enlarge the cortical hole in the proximal phalanx. Small bites can be taken circumferentially around the dorsal proximal phalangeal hole. This process is essential to prevent fragmentation of the dorsal cortex on screw insertion. The hole must be enlarged to almost the diameter of the trailing threads of the screw. If the screw being used requires a tap, it is used at this point.
Screw length is determined either by direct measurement or by estimate. A Kirschner wire can be placed down the screw canal and observed on fluoroscopy. The leading edge of the screw should reach the isthmus of the middle phalanx at its narrowest point. It is then withdrawn and the length is measured. Length need not be precise because the trailing threads may engage anywhere along the hole in the proximal phalanx; usually screws of 16 to 22 mm in length are used for adults.
The assistant then aligns and holds the joint in compression and the screw is carefully inserted until it is buried in the dorsal cortex of the proximal phalanx. Final rotational alignment can be completed during screw insertion ( Fig. 13-7 ).
