Distal Ulnar Resection Arthroplasty (Darrach Procedure): An Intraoperative Masterclass

Introduction and Epidemiology

The surgical management of distal radioulnar joint (DRUJ) pathology has undergone profound evolution over the centuries, transitioning from complete osseous ablation of the distal ulna to highly nuanced, anatomically preserving resection arthroplasties that respect forearm kinematics. The distal ulna resection, universally recognized as the Darrach procedure, was initially described in the early surgical literature by Severinus in 1644, Rognetta in 1834, and Dupuytren in 1839. Subsequent morphological modifications and clinical descriptions were provided by Malgaine in 1855 and Moore in 1880. Dr. William Darrach formally detailed the distal ulna resection that bears his name in 1912 and 1913, originally advocating the technique for the treatment of irreducible posttraumatic volar DRUJ dislocations. Over a century later, this foundational operation continues to maintain a definitive role in the reconstructive armamentarium for a variety of afflictions affecting the DRUJ, particularly in low-demand, elderly, or rheumatoid patient populations.

Pathologic conditions that precipitate DRUJ degenerative change or disrupt inherent joint mechanics inevitably lead to debilitating ulnar-sided wrist pain, profound decrements in grip strength, and severe dysfunction of forearm pronosupination. Historically, the classic Darrach procedure was applied broadly across diverse patient demographics; however, the complete excision of the ulnar head fundamentally removes the critical osseous fulcrum against which the radius rotates. In higher-demand patients, this frequently results in painful radioulnar convergence (impingement) under load and symptomatic ulnar stump instability. In an effort to mitigate these biomechanical derangements and preserve the critical stabilizing soft tissue elements of the distal ulna, alternative treatments to complete ablation were developed.

Bowers published his seminal results on the hemiresection interposition technique (HIT), which fundamentally differs from the Darrach procedure in its preservation of longitudinal and transverse stabilizers. In the HIT, only the weight-bearing "seat" and "pole" of the ulnar head are resected, intentionally preserving the ulnar styloid and the vital foveal soft tissue attachments of the triangular fibrocartilage complex (TFCC). Concurrently, Watson and Gabuzda advocated for the matched resection procedure. The essential element of the matched resection is meticulously contouring the profile of the resected distal ulna to match the convex geometry of the medial side of the radius, thereby distributing forces evenly and minimizing point-loading impingement throughout the entire arc of rotation.

Epidemiologically, resection arthroplasties of the DRUJ are most frequently indicated and performed in patients with inflammatory arthropathies, primarily rheumatoid arthritis. In this demographic, the classic "caput ulnae" syndrome presents with dorsal subluxation of the distal ulna, volar subluxation and supination of the carpus, and impending attritional extensor tendon rupture (Vaughan-Jackson syndrome). Post-traumatic osteoarthritis secondary to distal radius fractures with intra-articular extension into the sigmoid notch represents the second most common demographic. Primary osteoarthritis of the DRUJ is relatively rare; its presence should prompt a thorough investigation into underlying morphological variants, such as Madelung deformity, or subtle, chronic instability patterns.

Surgical Anatomy and Biomechanics

A profound understanding of the DRUJ anatomy and its complex biomechanical relationships is an absolute prerequisite for executing a successful resection arthroplasty and avoiding iatrogenic instability. The DRUJ is a diarthrodial trochoid joint that functions in obligate concert with the proximal radioulnar joint (PRUJ) to facilitate pronation and supination of the forearm around a fixed longitudinal axis.

The articulation is constrained loosely by its osseous architecture, relying heavily on extrinsic and intrinsic soft tissue stabilizers. This inherently loose constraint allows forearm rotation through a functional 150-degree arc while simultaneously permitting necessary proximal and distal migration, as well as dorsal and palmar translation of the ulna relative to the radius during the rotational arc. During pronation, the radius crosses over the ulna, and the ulnar head translates dorsally and distally relative to the sigmoid notch.

The articular cartilage-covered "cap" of the distal ulna can be conceptually and functionally divided into two distinct anatomical regions: the seat and the pole. The seat of the ulna is the convex portion that articulates directly with the concave sigmoid notch of the distal radius. The arc of curvature of the sigmoid notch ranges between 90 and 135 degrees, with an average radius of curvature of 8 to 13 mm. Because the radius of curvature of the sigmoid notch is substantially greater than that of the ulnar head, the joint is inherently incongruent, allowing for translational glide rather than simple rotation. The seat is covered by articular cartilage around approximately 270 degrees of its surface. This region supports the compressive loads of the distal radius during most activities of daily living and acts as the primary fulcrum for load support across the forearm axis.

The pole is the distal-most portion of the ulna that lies deep to the cartilaginous articular disc of the TFCC. This region supports the centrum of the TFCC as compressive loads pass from the ulnar carpus (lunate and triquetrum) to the bony elements of the forearm. During power grip, relative ulnar variance increases dynamically, and the pole absorbs a significantly higher proportion of ulnocarpal load (up to 20% of total axial load).

The medial distal portion of the ulna projects as the ulnar styloid. The base of the styloid (the fovea) contains the critical isometric attachment of the deep layer of the TFCC, known as the ligamentum subcruentum. Distal to this foveal attachment, in a more peripheral and apical location, lies the attachment of the superficial layer of the TFCC. The dorsal and volar portions of the TFCC are thickened, forming the limbi of the complex, which function as the volar and dorsal radioulnar ligaments. These ligaments play the most critical role in stabilizing the DRUJ. Biomechanically, during pronation, the dorsal radioulnar ligament tightens; during supination, the volar radioulnar ligament tightens.

Secondary stabilizers include the extensor carpi ulnaris (ECU) tendon subsheath, the dynamic tension of the pronator quadratus (PQ), and the interosseous membrane (IOM). The distal oblique bundle (DOB) of the interosseous membrane is of particular biomechanical importance. When the ulnar head is resected, the interosseous membrane must resist the converging forces of the radius and ulna. If the interosseous membrane is attenuated or previously injured, resection arthroplasty frequently leads to dynamic, painful radioulnar impingement.

Indications and Contraindications

Rigorous patient selection is the most critical determinant of clinical success in DRUJ resection arthroplasty. The decision to proceed with a Darrach, hemiresection interposition technique, or matched resection depends heavily on the patient's physiological age, functional occupational demands, underlying pathology, and the structural integrity of the longitudinal forearm stabilizers.

The classic Darrach procedure remains highly effective in the elderly, low-demand patient with rheumatoid arthritis presenting with a destroyed DRUJ and caput ulnae syndrome. In these highly selected patients, the procedure not only reliably relieves pain but also prevents attritional rupture of the extensor tendons over the prominent ulnar head. Conversely, the Darrach procedure is generally contraindicated in young, high-demand laborers due to the unacceptably high risk of symptomatic ulnar stump instability, loss of grip strength, and radioulnar convergence under load.

For higher-demand patients requiring a resection arthroplasty, the hemiresection interposition technique (HIT) or Watson matched resection is preferred, provided the foveal attachments of the TFCC are intact or anatomically reconstructable. If longitudinal instability exists (e.g., an unrecognized Essex-Lopresti injury with previous radial head excision or severe IOM disruption), any form of distal ulna resection is strictly contraindicated. Resecting the distal ulna in the setting of longitudinal radioulnar dissociation will result in uninhibited proximal migration of the radius, leading to severe ulnocarpal impingement, altered elbow mechanics, and catastrophic whole-arm dysfunction.

Operative vs Non Operative Management

Pre Operative Planning and Patient Positioning

Thorough preoperative clinical and radiographic evaluation is mandatory to rule out subtle instability patterns that would contraindicate a simple resection. Clinical examination must carefully assess the presence of a "piano key" sign (ballottement of the distal ulna indicating gross instability), ECU tendon subluxation during supination, and the precise arc of painful pronosupination. The examiner must also evaluate the proximal radioulnar joint, the radial head, and the elbow to rule out longitudinal forearm instability.

Standard posteroanterior (PA) and lateral radiographs of the wrist are obtained. The lateral radiograph must be a true, zero-rotation lateral, defined strictly by the collinearity of the palmar cortices of the pisiform and the scaphoid pole, to accurately assess dorsal or volar subluxation of the ulnar head relative to the radius. Grip-loaded PA views can demonstrate dynamic ulnar positive variance, highlighting incompetence of the longitudinal stabilizers.

Advanced imaging, specifically computed tomography (CT), is the gold standard for evaluating the cross-sectional morphology of the sigmoid notch, the version of the joint, and the absolute degree of radioulnar subluxation. Axial cuts obtained in neutral, full pronation, and full supination can definitively map the kinematics of the joint, identify the primary zone of impingement, and quantify arthritic change.

The patient is positioned supine on the operating table with the operative extremity extended on a radiolucent hand table. A well-padded proximal arm tourniquet is applied. Intravenous regional anesthesia (Bier block), regional brachial plexus block, or general anesthesia may be utilized depending on patient comorbidities and anticipated surgical duration. The arm is prepped and draped in standard sterile fashion. Intraoperative fluoroscopy must be available and positioned to allow dynamic, real-time assessment of the radioulnar relationship and impingement following resection.

Detailed Surgical Approach and Technique

The surgical approach to the DRUJ is typically performed via a dorsal longitudinal incision. The incision is centered directly over the DRUJ, extending from the mid-carpus proximally along the ulnar shaft for approximately 5 to 7 centimeters.

Dorsal Surgical Approach

The extensor retinaculum is exposed. The fifth extensor compartment, containing the extensor digiti minimi (EDM), is identified and opened longitudinally. The EDM is retracted radially. Alternatively, the approach can be performed through the interval between the fifth and sixth extensor compartments. The floor of the fifth compartment is incised to expose the DRUJ capsule. Extreme care must be taken to preserve the dorsal radioulnar ligament of the TFCC if a hemiresection is planned. The ECU subsheath is inspected; if attenuated or ruptured, it should be marked for later plication or formal reconstruction to prevent postoperative ECU snapping.

The Darrach Procedure Technique

For the classic Darrach procedure, a meticulous subperiosteal dissection of the distal ulna is performed. It is critical to elevate the periosteum sharply and cleanly to create a robust, continuous sleeve for subsequent closure. This periosteal sleeve acts to tether the ulnar stump and is the primary defense against postoperative dorsal stump subluxation.

An oscillating saw is used to perform a transverse osteotomy of the distal ulna. The level of resection is of paramount importance; it should be just proximal to the proximal margin of the sigmoid notch. Resecting excessive ulna (greater than 1.5 to 2.0 cm) completely detaches the pronator quadratus and severely destabilizes the interosseous membrane, exponentially increasing the risk of severe ulnar stump instability and radioulnar convergence.

Following the osteotomy, the distal fragment is excised by sharply releasing its attachments to the TFCC and the ulnar collateral ligament. The ulnar stump is then meticulously contoured with a rongeur and rasp to remove any sharp cortical edges that could abrade the surrounding soft tissues or the radius during rotation. The periosteal sleeve is closed securely over the stump. If the stump is highly unstable intraoperatively, a pronator quadratus interposition or an ECU tenodesis may be performed concurrently to provide dynamic stabilization.

Hemiresection Interposition Technique

The Bowers hemiresection interposition technique is designed to selectively resect only the articulating portion of the ulnar head while preserving the ulnar styloid and the critical foveal attachments of the TFCC.

Following capsulotomy, an osteotome or a high-speed burr is used to resect the radial articular surface (the seat) of the ulnar head. The resection is carried ulnarly until the subchondral bone of the seat is completely removed, leaving a functional shell of bone consisting of the ulnar styloid and the medial cortex.

The dead space created between the resected ulna and the sigmoid notch must be filled to prevent bony contact during transverse compression. An "anchovy" is fashioned, typically utilizing a distally based strip of the ECU tendon, the palmaris longus tendon, or a rolled flap of local joint capsule and extensor retinaculum. This soft tissue interposition is sutured securely into the defect, often anchoring it via drill holes to the dorsal and volar margins of the sigmoid notch.

Matched Resection Arthroplasty

The Watson matched resection procedure focuses on the precise geometric contouring of the distal ulna rather than relying on soft tissue interposition. The goal is to create a long, tapering resection that matches the concavity of the distal radius across the entire arc of pronation and supination.

The distal ulna is exposed, and an oscillating saw is used to make a long, oblique cut starting proximally on the radial aspect of the ulna and exiting distally near the base of the ulnar styloid. The resulting surface is meticulously smoothed with a rasp to eliminate any focal prominences.

The arm is then taken through a full, dynamic range of motion under direct visualization and fluoroscopy. The surgeon must palpate the radioulnar interval to ensure no point-loading or impingement occurs at any extreme of rotation. If impingement is noted, further contouring of the ulnar stump is performed iteratively until smooth, frictionless tracking is achieved.

Complications and Management

Despite meticulous surgical technique, resection arthroplasties of the DRUJ are associated with a distinct and challenging profile of postoperative complications. The most notorious and functionally limiting complication is radioulnar impingement, also known clinically as painful radioulnar convergence.

Radioulnar impingement occurs when the radius and the ulnar stump converge under load, leading to painful bony contact. This is particularly prevalent in the classic Darrach procedure when performed in high-demand patients, or when excessive bone (greater than 2 cm) is resected, which completely detaches the pronator quadratus and destabilizes the interosseous membrane. Over time, this chronic convergence can lead to erosive scalloping of the medial cortex of the radius.

Ulnar stump instability is another frequent complication, characterized by symptomatic dorsal subluxation of the distal ulna during pronation. This is often due to failure to adequately reconstruct the periosteal sleeve, incompetence of the ECU subsheath, or preexisting unrecognized longitudinal instability.

Complications and Salvage Strategies

Management of the failed Darrach or hemiresection is a complex reconstructive challenge. If the patient develops painful convergence, conversion to an ulnar head arthroplasty may be considered to restore the radioulnar fulcrum, provided the sigmoid notch is relatively preserved and the soft tissue envelope is robust. Alternatively, a salvage procedure such as the Sauvé-Kapandji procedure (radioulnar arthrodesis with proximal ulnar pseudoarthrosis) can be employed, though this is technically difficult in the setting of a previous resection due to the profound lack of distal ulnar bone stock.

Post Operative Rehabilitation Protocols

Postoperative rehabilitation is carefully tailored to the specific procedure performed and the intraoperative assessment of the soft tissue reconstruction's quality. The primary goal in the initial postoperative phase is to protect the soft tissue repairs, particularly the periosteal sleeve closure in a Darrach or the capsular/retinacular interposition in a hemiresection, while preventing stiffness.

Immediately postoperatively, the patient is placed in a bulky dressing reinforced with a well-molded sugar-tong splint or a Muenster splint. The forearm is immobilized in neutral rotation to minimize tension on both the dorsal and volar soft tissue structures. Strict elevation and active digital range of motion are initiated immediately to prevent dependent edema and digital stiffness.

At 2 to 3 weeks postoperatively, the splint and sutures are removed. If the intraoperative stability of the ulnar stump was deemed excellent, the patient may be transitioned to a removable short-arm splint, and active-assisted forearm pronation and supination are initiated. If the stump was tenuous, or if a formal ECU tenodesis was performed, immobilization in a Muenster splint