You are in: eMedicine Specialties > Orthopedic Surgery > HAND AND UPPER EXTREMITY Swan-Neck DeformityArticle Last Updated: Nov 2, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Roberto Sandoval, MD, Consulting Staff, Department of Emergency Medicine, Anaheim Memorial Medical Center, La Palma Intercommunity Hospital Roberto Sandoval is a member of the following medical societies: American College of Emergency Physicians and American Medical Association Coauthor(s): John A Kare, MD, Assistant Professor of Emergency Medicine, Charles R Drew University of Medicine and Science/UCLA, Director of Research, Department of Emergency Medicine, Martin Luther King Jr/Charles R Drew Medical Center; Eleby R Washington III, MD, FACS, Associate Professor, Department of Surgery, Division of Orthopedics, Charles R Drew University of Medicine and Science; Roman V Voytsekhovskiy, MD, Fellow in Hand Surgery, Department of Orthopedic Surgery, Rush University Medical Center; Robert R Schenck, MD, Associate Professor, Departments of Plastic and Orthopedic Surgery, Rush Medical College; Director, Section of Hand Surgery, Department of Plastic and Orthopedic Surgery, Rush University Medical Center Editors: Joseph E Sheppard, MD, Director of Hand and Upper Extremity, Associate Professor, Department of Orthopedic Surgery, University of Arizona; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Robert J Nowinski, DO, Clinical Assistant Professor of Orthopaedic Surgery, Ohio University College of Osteopathic Medicine; Private Practice, Orthopedic Specialists and Sports Medicine, Newark, Ohio; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Harris Gellman, MD, Consulting Surgeon, Broward Hand Center, Voluntary Clinical Professor of Orthopedic Surgery and Plastic Surgery, Departments of Orthopedic Surgery and Surgery, University of Miami School of Medicine Author and Editor Disclosure Synonyms and related keywords: volar plate synovitis, synovitis of capsule, collateral ligament synovitis, finger deformity, arthritis, rheumatoid arthritis, hand deformity, finger deformity, rheumatoid factor, rheumatoid hand, RA, tenosynovitis, swan neck deformity, boutonniere deformity INTRODUCTIONSection 2 of 10
  Structural deformities of the digits of the hand are common in patients with rheumatoid arthritis (RA). A swan-neck deformity, typically defined as proximal interphalangeal (PIP) joint hyperextension with concurrent distal interphalangeal (DIP) joint flexion, occurs in approximately 50% of patients with RA. However, swan-neck deformity is not unique to RA, because it may also be congenital or traumatic in nature. Multiple surgical procedures are available for the correction of this digital abnormality. The deformity of the finger or fingers must be staged accurately to use the most appropriate surgical technique. The staging of the deformed finger is based on the condition of the articular cartilage—which is determined by radiography—and on the flexibility of the PIP joint. ProblemSwan-neck deformity is common in persons with RA. It occurs as the end result of rheumatoid synovitis of the metacarpophalangeal (MP), PIP, and/or DIP joints, which disrupts the balance of flexion and extension forces acting across a joint. (See also the eMedicine article Hand, Rheumatoid Hand.) Nalebuff classifies swan-neck deformities into the following 4 types1:
The above classification aids in the choice of surgical treatment for this complex condition. An alternative classification was proposed by Welsh and Hastings, who classified swan-neck deformity as mobile, snapping, or fixed, on the basis of the condition of the digital intrinsic muscles.2 Welsh and Hastings subdivided swan-neck deformity into 2 types:
The Nalebuff classification is the more widely accepted one. FrequencyApproximately 50% of patients with RA develop a swan-neck deformity. EtiologyThe primary cause of RA is unclear. The inflammation is believed to be a T-cell–mediated immune response against soft tissue and cartilage, leading to synovitis, chondrolysis, and periarticular bone absorption. The disease may be triggered by a combination of factors, including viral infection and a genetic predisposition in patients with the major histocompatibility complex (MHC) class II alleles DR4 and DR1. The molecular and cellular aspects of RA are better understood. Neutrophils and macrophages accumulate in the synovial fluid because of many chemotactic substances produced by the activation of the inflammatory cascades. Rheumatoid synovium is produced by fibroblastlike stromal cells and angiogenesis. The destruction of cartilage occurs by enzymatic digestion (chondrolysis) and by the inhibition of chondrocyte collagen and proteoglycan synthesis. PathophysiologyThe pathophysiology of the swan-neck deformity begins with flexor synovitis, which increases the flexor pull on the MP joint. Constant efforts to extend the finger against this pull lead to stretching of the collateral ligaments and the volar plate at the PIP joint. In a normal finger, intrinsic muscles (interosseous and lumbrical) insert into the lateral bands and serve as flexors of the MP joint and extensors of the PIP and DIP joints by being located volar to the MP joint axis and dorsal to the PIP and DIP joint axes. In a rheumatoid finger, the lateral bands are constrained in their dorsal position, upsetting the flexor-extensor balance. In this position, the lateral bands increase the pull of the long extensor tendon's central slip, which attaches to the dorsal base of the middle phalanx. The increase of flexor profundus tension resulting from hyperextension of the PIP joint leads to a reciprocal flexion of the DIP joint. Progressive disease causes joint destruction and fixed contracture. ClinicalEvaluation of the patient with complaints attributable to a joint begins with taking a careful history of the current problem. Although patients occasionally present with point tenderness, individuals with arthrosis often complain of diffuse, dull joint pain. The proliferation of synovium around a joint can be detected by observing fluctuant swelling beneath the examiner's fingers when the joint is held in 45º of flexion. The active and passive ranges of motion of each joint should be measured with a goniometer. Hyperextension is recorded as a negative value. The lateral stability of each joint should be tested by applying 3-point pressure, with the finger in extension. The finger in question should also be tested for intrinsic (interosseous and lumbrical) muscle tightness. The examiner should hold the MP joint in full, passive extension and flexion and then gently flex the PIP joint with the other hand. In the normal finger, full PIP joint flexion is possible in extension and flexion of the MP joint. In contrast, in the presence of intrinsic tightness, resistance to PIP joint flexion is encountered when the MP joint is in extension (and the intrinsics are already passively stretched), although when the MP joint is in flexion, passive PIP flexion is possible. The angle of passive PIP flexion is determined with a goniometer and recorded. INDICATIONSSection 3 of 10
When a patient with RA develops joint deformities that are unresponsive to medical management, surgical intervention is often necessary. These deformities lead to loss of the ability to grip, grasp, and pinch, often leaving the patient unable to perform the activities of daily living. Appropriately timed surgical intervention helps patients return to a greater activity level, which improves the individual's overall medical condition and avoids further deconditioning; independence is greater and self-image is improved. Patients with RA should be referred to a hand surgery specialist early in the disease's course. Surgical intervention for the swan-neck deformity is advised when active flexion of the PIP joint from its hyperextended position is not possible or occurs with a bothersome snap. RELEVANT ANATOMYSection 4 of 10
See Surgical Therapy. WORKUPSection 5 of 10
Lab Studies
Imaging Studies
TREATMENTSection 6 of 10
Medical TherapySee Surgical Therapy. Surgical TherapyType I deformity Swan-neck deformity can arise at the PIP or DIP joint; in either case, it can lead to the classic appearance of PIP joint hyperextension with DIP joint flexion. Patients with type I deformity maintain the ability to actively flex the PIP joint. When the deformity originates at the PIP joint, it is caused by stretching of the capsule secondary to active synovitis or rupture of the flexor digitorum superficialis tendon, removing the restraint to PIP joint hyperextension. If the synovitis involves the DIP joint, the deformity begins with stretching or rupture of the terminal tendon attachment of the extensor mechanism to the distal phalanx, resulting in a mallet deformity. (See also the eMedicine article Mallet Finger.) This subsequently causes extensor mechanism imbalance, with relative overpull of the central slip; these problems, together with laxity of the PIP joint's volar plate, resultinPIP joint hyperextension. The treatment of type I deformity is focused on correcting PIP joint hyperextension and restoring DIP joint extension. Conservative treatment can be used, with Silver Ring splints (Silver Ring Splint Co., Charlottesville, Va) being employed to permit active PIP flexion and limit hyperextension of the PIP joint. Alternatively, an inexpensive figure-8 thermoplastic splint can be fashioned by a hand therapist. These splints can be useful in the early stages of the disease. If splints are not tolerated, several procedures can be considered, including DIP joint fusion (soft-tissue procedures at the DIP joint are unsuccessful) and PIP joint flexor tenodesis, in which a volar zigzag incision is made over the PIP joint to expose the flexor tendon sheath; the sheath is opened proximally to the A1 pulley, and the flexor digitorum superficialis is separated from the sheath, creating a slight flexion contracture of the PIP joint. Another option is retinacular ligament reconstruction and dermodesis, in which an elliptic wedge of skin is removed from the volar aspect of the PIP joint, and the skin defect is closed with the digit in flexion. However, this procedure is usually only of temporary value, because the skin stretches out with time. Type II deformity A type II deformity has an appearance similar to that of the type I deformity; however, PIP joint flexion is influenced by the position of the MP joints. When the MP joints are extended or radially deviated, passive PIP joint flexion is limited; when the MP joints are flexed or ulnarly deviated, a greater degree of PIP joint flexion is possible. As the patient's RA continues to progress, radial deviation of the metacarpals and volar subluxation of the MP joints increase secondary to increased tightness of the intrinsic muscles. Consequently, a swan-neck deformity develops. The treatment of a type II deformity centers on the relief of intrinsic tightness, which is accomplished using intrinsic release. In this procedure, a dorsal longitudinal incision is made over the proximal phalanx, exposing the extensor mechanism. A rhomboid portion of the ulnar extensor aponeurosis is then resected (radial as well, if the tightness is severe). The surgeon resects the lateral band(s) through which the abnormally tight intrinsics have produced MP flexion and PIP hyperextension. In patients with severe involvement of the MP joints, silicone-implant arthroplasty is performed, combined with the rebalancing of the intrinsics and the long extensor tendons.3 Type III deformity A type III deformity is characterized by a significant reduction of PIP joint motion, as well as by well-preserved joint spaces, as depicted on radiographs. The stiffness is caused by contracture of the extensor mechanism, collateral ligaments, and skin. The initial goal of the surgical reconstruction of a type III deformity is the restoration of passive motion to the PIP joint. This may be accomplished by using 1 or more procedures, including the following:
Once passive motion has been restored, the deformity may be corrected with the previously mentioned procedures. Postoperative splinting and exercises are implemented by a hand therapist, under the supervision of the surgeon, to maintain the gains that were achieved surgically. Type IV deformity Patients with a type IV deformity have stiff PIP joints and associated radiographic changes consistent with advanced intra-articular disease. These deformities require a salvage-type procedure—namely, arthrodesis or arthroplasty. In deciding which of these procedures to perform, it is important to consider the status of adjacent joints, flexor tendons, and ligaments. It is also important to assess the function of the adjacent fingers. Fusion is particularly useful for the index and middle fingers, because these digits need lateral stability when opposed to the thumb during pinch. Arthroplasty is recommended for the ring and small fingers, where mobility aids grasp. If the MP joints require arthroplasty, PIP joint fusion is recommended, although it has been suggested that arthroplasty can be performed. Proximal joint fusion involves a curved dorsal skin incision. A longitudinal incision is made through the tendon over the joint, resecting the collateral ligaments. Two Kirschner wires (K-wires) are then passed obliquely across the joint to provide stable fixation, usually at 25° of flexion for the index finger and slightly more for the third digit. Postoperative care consists of cast immobilization for 6-8 weeks. Arthroplasty can be performed if the surrounding soft tissues are adequate. A dorsal incision is made to expose the extensor mechanism and is split longitudinally. The articular surfaces of the opposing proximal and middle phalanges are removed, and the medullary canals are prepared for the insertion of the implant. The skin is closed with the joint in slight flexion. A palmar incision is then made to release any flexor tendon adhesions. Postoperative care includes splinting the PIP joints in 10° or 20° of flexion and instituting passive and active exercises with a dynamic extension/flexion splint. Follow-upSee Surgical Therapy. COMPLICATIONSSection 7 of 10
The complications following swan-neck reconstruction include stiffness, infection, and a recurrence of the deformity. If prostheses are used, there may be early or late prosthetic dislocation, breakage, or both. On average, there is less functional improvement in swan-neck deformities caused by RA than in those resulting from trauma. OUTCOME AND PROGNOSISSection 8 of 10
Early swan-neck deformity can be corrected by intrinsic release, flexor synovectomy, the correction of PIP joint hyperextension with capsulodesis or tenodesis, or a combination thereof. Patients have reported significant pain relief after PIP joint synovectomy. At 5-year follow-up, 60% of patients who underwent PIP joint synovectomy maintained their improved grip strength. Soft-tissue reconstruction is not advisable in cases of advanced swan-neck deformity if lateral instability exists or if the patient has suffered articular changes or joint destruction. Kiefhaber and Strickland were disappointed in the results of soft-tissue reconstruction of boutonnière and swan-neck deformities.4 They recommended arthrodesis for most PIP joints with significant extensor deficit and for all rigid boutonniere deformities. (See also the eMedicine article Boutonniere Deformity.) FUTURE AND CONTROVERSIESSection 9 of 10
As with many hand problems, the treatment for swan-neck deformity is much more likely to be successful if it is implemented early in the course of the deformity. If there is not timely referral to a hand surgeon, the resultant function of the hand may be severely compromised. It is important, therefore, that a correct diagnosis of RA is made, that medical treatment is instituted, and that hand surgery evaluation is performed before severe and possibly permanent deformities occur. It is the responsibility of the emergency physician to be cognizant of the treatments available for swan-neck deformity and to work closely with the patient in obtaining an early referral to a hand surgeon. REFERENCESSection 10 of 10
Article Last Updated: Nov 2, 2007 |
