Ulnolunate Impaction Syndrome

Fig. 4. Ulnar TFCC tear. Coronal fat-suppressed T1-weighted image from an MR arthrogram (radiocarpal joint injection only) demonstrates contrast extravasating into the DRUJ (asterisk) and through the ulnar aspect of the TFCC (arrows), consistent with an ulnar-sided TFCC tear. Contrast is also noted extending into the midcarpal joint through a torn lunotriquetral ligament (curved black arrow).

Tears of the LTL are much less common than scapholunate ligament (SLL) tears, occurring only about one sixth as often [27]. Viegas and colleagues [11] studied 393 cadaveric wrists and found that 36% had disruption of the LTL. Therefore, a finding of LTL disruption is not significant unless it corresponds to the patient's symptoms.

LTL tears can be traumatic or degenerative. Traumatic tears typically result from a fall on a dorsiflexed wrist, forcing the forearm into pronation [28]. Clinically, the patients have point tenderness and experience a painful snap with radial and ulnar deviation. Ballottement and shear tests may be performed to determine whether LT joint instability is present. Both tests involve exerting pressure in opposite directions on adjacent carpal bones [27,29].

The spectrum of LT injury includes partial tear, complete tear, dynamic instability, and static instability. A complete tear of the LTL is not sufficient to cause a VISI deformity. There must also be disruption of one of the secondary restraints of the LT joint (the radiolunotriquetral ligament or the radiocarpal ligament) [22,27]. Viegas and colleagues [30,31] proposed a staging system for ulnar-sided perilunate instability, which covers the spectrum of LT injury:

Stage I: partial or complete LTL disruption (no VISI) Stage II: complete LTL tear plus disruption of palmar LTLs (dynamic VISI) Stage III: complete LTL tear plus disruption of palmar LTLs plus disruption of dorsal radiocarpal ligaments (static VISI)

Degenerative tears of the LTL typically occur in association with ulnolunate impaction syndrome (UIS), which is discussed in detail later [32]. Most degenerative perforations occur in the membranous portion of the ligament, while the volar and dorsal portions remain intact.

It is crucial to distinguish whether a torn LTL is traumatic or is part of the ulnolunate impaction syndrome, because the treatments are different (LT joint stabilization or ulnar shortening, respectively) [33,34]. Conventional radiographs are most often normal in stable injuries (partial or complete LTL tears in isolation). Widening of the LT interval is not seen, even in advanced cases. When one or both of the secondary restraints are disrupted in addition to the LTL, there may be a step-off at the LT joint, as well as a VISI deformity (Fig. 5). Conventional radiographs can also demonstrate ulnar variance, which may help differentiate whether the tear is traumatic or is part of the ulnolunate impaction syndrome. Conventional arthrography can demonstrate a communicating defect between the radiocarpal and midcarpal joints. Arthrography can also demonstrate the presence of a TFCC tear. However, TFCC disruption may be seen with both traumatic LTL tears and LTL tears associated with UIS. MRI and MR arthrography have been used for evaluation of the LTL, with great variability in sensitivity and specificity. In 1989, Zlatkin and colleagues [16] proposed three criteria for MR diagnosis of interosseous ligament tears: nonvisualization of the ligament, fluid signal traversing the ligament on T2-weighted images, and morphologic distortion of the ligament. Because non-visualization of the ligament is a relatively rare manifestation of an LTL tear [15], other findings, such as complete ligamentous disruption or a discrete linear area of high signal traversing the ligament on T2*- or fat-suppressed T2-weighted images, are believed to be more useful signs of LTL disruption (Fig. 6) [18,35-37]. Great variation has been reported in sensitivity and specificity for detection of LTL disruption on MRI compared with arthroscopy, ranging from 40% to 100% and from 33% to 100%, respectively [38]. MR ar-thrography permits better evaluation of LTL tears, because contrast material

Fig. 5. Traumatic LTL tear with VISI deformity. Frontal radiograph (A) in this trauma patient demonstrates a step-off at the lunotriquetral joint (arrow). Lateral view (B) demonstrates volar tilt of the lunate (curved arrow), with a markedly decreased scapholunate angle: findings of a VISI deformity, indicating that the LTL, as well as one or both of the secondary restraints, has been disrupted.

Visi Lunate

Fig. 5. Traumatic LTL tear with VISI deformity. Frontal radiograph (A) in this trauma patient demonstrates a step-off at the lunotriquetral joint (arrow). Lateral view (B) demonstrates volar tilt of the lunate (curved arrow), with a markedly decreased scapholunate angle: findings of a VISI deformity, indicating that the LTL, as well as one or both of the secondary restraints, has been disrupted.

Fig. 6. Degenerative LTL tear. Coronal T2* gradient echo image demonstrates a discrete linear area of high signal traversing the expected location of the LTL (arrow). The ligament itself is not visualized. Also noted is cystic change in the ulnar aspect of the lunate (arrowhead], indicating a degenerative LTL tear as part of the ulnolunate impaction syndrome.

may be seen crossing the defect from the radiocarpal to the midcarpal joint (Fig. 7) [22,35,39].

DISTAL RADIOULNAR JOINT

The DRUJ is a diarthodial joint consisting of the articulation of the sigmoid notch of the radius with a portion of the distal ulna termed the ulnar seat. The mechanics of the DRUJ allow the distal radius to rotate approximately 150° around a relatively fixed ulnar head [8,40,41]. The contact between the

Fig. 7. LTL tear—MR arthrogram. Coronal fat-suppressed Tl-weighted image from an MR ar-throgram (radiocarpal joint injection only] in the same patient as depicted in Fig. 4 demonstrates gadolinium extending into the midcarpal joint (arrowheads] between the lunate and triquetrum (arrow). The LTL is not visualized. The scapholunate ligament remains intact. Gadolinium is also seen in the DRUJ (asterisk), indicating a TFCC tear.

articular surfaces of the sigmoid notch and the ulnar seat is maximal (approximately 60%) in neutral forearm rotation. In full supination and pronation, the contact decreases to less than or equal to 10% [42]. Therefore, ligamentous joint support is crucial. Stabilizers of the DRUJ include the joint capsule, the interosseous membrane, the TFCC, the floor of the ECU tendon sheath, and the pronator quadratus muscle [43]. The TFCC provides intrinsic support, with the dorsal and volar RU ligaments providing the most stability. The other structures listed provide extrinsic support [44].

Causes of DRUJ pain include osteoarthritis, inflammatory arthritis, infection, chronic instability, and ligamentous laxity. Patients who have DRUJ pathology typically experience pain when the distal ulna and distal radius are pressed together. They may also have crepitus on forearm rotation [8]. Conventional radiographs are of limited use in evaluating the DRUJ. Os-teophytes, subchondral changes, and joint space narrowing can be seen in advanced osteoarthritis (Fig. 8). MRI is useful in excluding some causes, such as infection and inflammatory arthritis. However, MRI is suboptimal for evaluation of DRUJ subluxation, because the patient positioning necessary to achieve neutral forearm rotation is difficult in an MR scanner. Therefore, CT is the most useful method for evaluating DRUJ subluxation. Both the symptomatic and asymptomatic wrist should be scanned in neutral rotation, full pronation, and full supination [44]. Three different methods have been proposed for evaluation of DRUJ instability: Mino's criteria, the epicenter method, and the congru-ity method.

Mino's criteria involve drawing a line through the dorsal ulnar and radial borders of the distal radius and a line through the volar ulnar and radial borders of the distal radius. If the distal ulna moves above or below the lines drawn, there is dorsal or volar incongruity, respectively [45]. Wechsler and colleagues [46] proposed the congruity and epicenter methods [46]. The congruity

Radial Sigmoid Notch
Fig. 8. DRUJ arthritis. Frontal view of the wrist demonstrates joint space narrowing and osteophyte formation involving the DRUJ (arrow).

method involves reconstructing the arcs of the ulnar head and sigmoid notch and comparing the congruity of these arcs. The epicenter method involves designating the center of rotation of the DRUJ as a point halfway between the center of the ulnar styloid and the center of the ulnar head. The chord of the sigmoid notch is denoted by drawing a line connecting the dorsal and volar aspects of the medial border of the sigmoid notch. A perpendicular line is then drawn from the epicenter to the chord. If the line intersects the middle half of the chord, the DRUJ position is considered normal. If the line intersects the outer half, there is mild subluxation. If the line is outside the sigmoid chord, there is severe subluxation (Fig. 9) [46].

Chiang and colleagues [44] examined CT scans of 80 wrists in 40 patients who had suspected DRUJ subluxation. CT was performed in neutral rotation, active pronation, and active supination. The authors found the epicenter method to be the most accurate of the three methods, presumably because it takes into account normal translation of the joint in pronation and supination.

Distal Radioulnar Subluxation Mri

Fig. 9. Methods for evaluating DRUJ subluxation. Three identical axial CT images of the DRUJ in pronation demonstrate the three criteria for evaluating subluxation of the DRUJ. (A) Mino's criteria show the distal ulna dorsal to the RDL (radiodorsal line), indicating dorsal incongruity of the DRUJ. RPL, radiopalmar line. (B) Congruity method shows incongruity of the distal radial and carpal arcs (C, arc of the sigmoid notch of the radius; C1, arc of the ulnar seat), indicating an incongruous DRUJ. (C) Epicenter method. A perpendicular line drawn from the center of rotation of the DRUJ to the sigmoid chord intersects the middle half of the chord, indicating normal DRUJ position. Although (A) and (B) show incongruity of the DRUJ, (C) does not, illustrating the increased specificity of the epicenter method, which takes into account the normal translation of the DRUJ in supination and pronation.

Fig. 9. Methods for evaluating DRUJ subluxation. Three identical axial CT images of the DRUJ in pronation demonstrate the three criteria for evaluating subluxation of the DRUJ. (A) Mino's criteria show the distal ulna dorsal to the RDL (radiodorsal line), indicating dorsal incongruity of the DRUJ. RPL, radiopalmar line. (B) Congruity method shows incongruity of the distal radial and carpal arcs (C, arc of the sigmoid notch of the radius; C1, arc of the ulnar seat), indicating an incongruous DRUJ. (C) Epicenter method. A perpendicular line drawn from the center of rotation of the DRUJ to the sigmoid chord intersects the middle half of the chord, indicating normal DRUJ position. Although (A) and (B) show incongruity of the DRUJ, (C) does not, illustrating the increased specificity of the epicenter method, which takes into account the normal translation of the DRUJ in supination and pronation.

EXTENSOR CARPI ULNARIS TENDON

Disorders of the ECU tendon include subluxation, dislocation, tendinopathy, tenosynovitis, and rupture. The tendon courses through the sixth dorsal compartment, contained within a fixed fibrous tunnel, or subsheath, which extends from the base of the ulnar styloid to the triquetrum. This tunnel is covered by but not adherent to the extensor retinaculum and provides a straight approach to the carpus for the tendon, regardless of the degree of pronation or supination [47]. The mechanism for ECU subluxation or dislocation is typically forearm supination and ulnar deviation of the hand [47]. The subsheath tears, and the patient feels a painful soft snap. MRI shows malposition of the tendon and may show inflammation of the tendon sheath (Fig. 10). Tendinopathy, tenosynovitis, and tendon rupture are all well evaluated on MRI. In tendinopathy, the tendon is typically thickened and may have increased signal intensity on T1- or T2-weighted images [15]. In tenosynovitis, fluid signal intensity is seen within the tendon sheath (Fig. 11). The sixth dorsal compartment is the second most common location of stenosing tenosynovitis in the upper extremity; this is most commonly related to sports requiring repetitive wrist motion [48]. Discontinuity of tendon fibers on MRI is seen with complete rupture of the tendon.

PISOTRIQUETRAL JOINT

Disorders that can affect the pisotriquetral joint (PTJ) include osteoarthritis, inflammatory arthritis, and joint instability. Seven separate structures insert on the pisiform. These are the flexor carpi ulnaris, the flexor retinaculum, the pi-sohamate ligament, the pisometacarpal ligaments, the abductor digiti minimi muscle, the extensor retinaculum, and the meniscus homolog [49-51]. The pisiform is connected to the triquetrum by a loose fibrous capsule, and disruption of any one of the seven structures listed could lead to PTJ instability [52]. In addition, some surgeries, such as carpal tunnel release and ulnar shortening, predispose to PTJ instability. Clinically, patients who have PTJ disorders present with pain in the hypothenar area, which is reproduced by ''rocking'' the

Abductor Digiti Minimi Pain
Fig. 10. ECU subluxation. Axial fat-suppressed T2-weighted image demonstrates subluxation of the ECU from its normal position in the dorsal groove of the distal ulna (curved arrow). A large amount of associated soft tissue swelling is seen.

VflfN*

Fig. 11. ECU tendinopathy, tenosynovitis. Axial fat-suppressed T2-weighted image (A) demonstrates thickening and abnormal high T2 signal within the ECU (arrow). There is also fluid signal surrounding the tendon. Coronal Tl-weighted image (B) in the same patient demonstrates fusiform swelling of the ECU (arrowheads).

pisiform on the triquetrum [47]. Diagnosis is confirmed by direct injection of anesthetic into the PTJ [53].

Conventional radiographs taken in 30° supination may demonstrate joint space narrowing, erosions, or osteophytes. MRI can detect earlier changes, such as subchondral edema and chondromalacia. If the patient's pain is determined to arise from the PTJ, excision of the pisiform has been found to be highly successful in relieving symptoms [47].

THE IMPACTION AND IMPINGEMENT SYNDROMES

Ulnolunate Impaction Syndrome

UIS, also called ulnar impaction syndrome or ulnocarpal abutment, is a degenerative condition related to excessive load-bearing across the ulnar aspect of the wrist. Chronic impaction between the distal ulna and the ulnar carpus leads to a continuum of changes, usually beginning with a degenerative tear of the TFCC, followed by chondromalacia of the lunate, triquetrum, and distal ulna, then a degenerative tear of the LTL, and, finally, osteoarthritis of the ul-nocarpal and distal RU joints (Fig. 12) [54-57]. Factors that predispose to UIS are congenital positive ulnar variance, malunion of a distal radial fracture, previous radial head resection (after Essex-Lopresti fracture), and daily activities that cause excessive loading of the ulnar carpus [58].

The normal load distribution across the wrist is 80% across the radial aspect and 20% across the ulnar aspect [1,5,59]. Palmer and colleagues [60] found that minimal changes in ulnar variance changed the normal load distribution drastically. A 2.5-mm increase in ulnar variance increased the ulnar load to 42%, and a 2.5-mm decrease in ulnar variance decreased the ulnar load to 4.3%. Patients who have UIS present with subacute or chronic pain that is worse with activity and is exacerbated by maneuvers that increase ulnar variance, such as forearm pronation, power grip, and ulnar deviation [54,55].

Arthroscopic Tfcc

Fig. 12. Ulnolunate impaction syndrome coronal view illustration. Demonstrates the findings in UIS, including central TFCC tear (asterisk), chondromalacia of the distal ulna, proximal ulnar aspect of the lunate, proximal radial aspect of the triquetrum (arrowheads), and a tear of the LTL (curved arrow).

Fig. 12. Ulnolunate impaction syndrome coronal view illustration. Demonstrates the findings in UIS, including central TFCC tear (asterisk), chondromalacia of the distal ulna, proximal ulnar aspect of the lunate, proximal radial aspect of the triquetrum (arrowheads), and a tear of the LTL (curved arrow).

When assessing the distal forearm and wrist for ulnar variance, it is especially important that frontal radiographs be performed with the wrist in neutral forearm rotation, the elbow flexed at 90°, and the shoulder abducted 90° [43]. Radiographs may show positive or neutral ulnar variance as well as subchondral cystic change or sclerosis involving the ulnar head, ulnar aspect of the lunate, or the proximal radial aspect of the triquetrum (Fig. 13). However, conventional radiographs can be normal in early UIS. On MRI, subtle early changes such as cartilage fibrillation, marrow edema, subchondral cystic change, and ligamentous integrity may be visualized (Fig. 14). Ulnar variance cannot be accurately diagnosed on MRI, because the position for a standard frontal view is difficult to duplicate. MR arthrography demonstrates the same changes seen on MRI and can also help to clarify the Palmer classification of a lesion preoperatively. For example, the presence of a TFC perforation can differentiate between a class 2B and a class 2C lesion, and the presence of an LTL or ulnocarpal ligament tear can differentiate between a class 2C and a class 2D lesion [3].

The goal of treatment for UIS is to decrease the load across the ulnar side of the wrist, which can be accomplished using many different surgical procedures. Most procedures focus on ulnar shortening (open or arthroscopic) and attempt to preserve the insertion site of the TFCC onto the base of the ulnar styloid, as well as the integrity of the DRUJ [54]. The choice of surgical procedure depends on the age of the patient, the integrity of the DRUJ, and the cause of the UIS. For example, in patients in whom the cause of the UIS is a malunited distal radial fracture, corrective radial osteotomy may be performed [8]. In patients who have positive or neutral ulnar variance without DRUJ incongruity,

Ulnolunate Impaction Syndrome
Fig. 13. Ulnolunate impaction syndrome. Frontal radiograph of the wrist demonstrates neutral ulnar variance, subchondral cystic change at the ulnar aspect of the lunate (arrow), and early degenerative change of the DRUJ, some of the plain film findings in UIS.

an ulnar shortening osteotomy or a wafer procedure could be performed. Ulnar shortening osteotomy involves resecting bone from the distal ulnar shaft, followed by plate and screw fixation. Wafer procedures (open or arthroscopic) involve excision of the distal 2 to 4 mm of the ulnar head, preserving the ulnar styloid and TFCC attachments. In patients who have UIS and DRUJ

Tfcc Sion Palmer

Fig. 14. Ulnolunate impaction syndrome. Coronal fat-suppressed T1-weighted (A) and fat-suppressed T2-weighted (B) images from an MR arthrogram (radiocarpal joint injection only) demonstrate the full spectrum of MR changes of UIS, including a degenerative tear of the TFCC (curved arrow), chondromalacia of the lunate and triquetrum, chondromalacia and cystic change in the distal ulna (arrowheads), a degenerative tear of the LTL (arrow), and osteoarthritis of the ulnocarpal and distal RU joints.

Fig. 14. Ulnolunate impaction syndrome. Coronal fat-suppressed T1-weighted (A) and fat-suppressed T2-weighted (B) images from an MR arthrogram (radiocarpal joint injection only) demonstrate the full spectrum of MR changes of UIS, including a degenerative tear of the TFCC (curved arrow), chondromalacia of the lunate and triquetrum, chondromalacia and cystic change in the distal ulna (arrowheads), a degenerative tear of the LTL (arrow), and osteoarthritis of the ulnocarpal and distal RU joints.

incongruity, surgical procedures include excision of the distal ulna (Darrach procedure); resection of the ulnar seat, leaving the ulnar shaft and styloid undisturbed (hemiresection-interposition); and DRUJ arthrodesis with creation of a pseudarthrosis proximal to the fusion (Sauve-Kapandji procedure). Potential complications vary by procedure but include nonunion, instability of the ulnar stump, and DRUJ incongruity [8].

Ulnar Styloid Impaction

Ulnar styloid impaction is due to either a long ulnar styloid process or a nonunited styloid process fracture impacting on the proximal triquetrum [38]. Styloid impaction from a long or ''parrot-beaked'' styloid process can result in chondromalacia of the ulnar styloid and the proximal triquetrum and can lead to LT joint instability (Fig. 15). An ulnar styloid is considered long when its overall length is greater than 6 mm or when the ulnar styloid process index (USPI) is greater than 0.21 ± 0.07 [61]. The USPI is defined as (styloid length — ulnar variance)/ width of the ulnar head [62]. Conventional radiographs demonstrate a long styloid or one with a volar or radial curve (Fig. 16) [38]. MRI demonstrates chondromalacia and subchondral changes of the proximal triquetrum and ulnar styloid (Fig. 17). MR arthrography can aid in better evaluation of the TFCC and its ulnar attachments [3]. Therapy for this condition involves resection of all but the proximal 2 mm of the ulnar styloid. The proximal 2 mm is kept intact to preserve the integrity of the TFCC attachments [61].

Ulnar styloid impaction due to ulnar styloid fracture nonunion can result from several different mechanisms, including impaction, DRUJ instability, TFCC injury, irritative loose body, or partial rupture of the ECU tendon

Fig. 15. Ulnar styloid impaction. Coronal view illustration demonstrates chondromalacia and subchondral change involving the tip of a long ulnar styloid and the proximal ulnar aspect of the triquetrum (arrowheads).

Ulnar Styloid Abutment Syndrome

Fig. 15. Ulnar styloid impaction. Coronal view illustration demonstrates chondromalacia and subchondral change involving the tip of a long ulnar styloid and the proximal ulnar aspect of the triquetrum (arrowheads).

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Cure Tennis Elbow Without Surgery

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