Ulnar Styloid Triquetral Impaction: Diagnosis and Treatment

RATIONALE AND BASIC SCIENCE

Ulnar styloid triquetral impaction (USTI) is often unrecognized, yet it is a relatively common condition in which the ulnar styloid, or fragments of the ulnar styloid, impact into the triquetrum and produce localized pain and dysfunction. The syndrome occurs in supination. To achieve supination, the carpus and radius rotate around the ulnar head, placing the ulnar styloid more radial (more central) and therefore closer to the triquetrum) ( Figs. 49-1and 49-2 ). As seen on the lateral radiograph, the carpus is volar to the ulnar styloid ( Fig. 49-3 ). Dorsiflexion brings the triquetrum closer to the ulnar styloid. Therefore, combining these two positions means that the most likely position to produce impaction is dorsiflexion and supination. The provocative test, described by Topper and associates, consists of wrist dorsiflexion and pronation followed by rotation of the forearm into full supination while maintaining dorsiflexion ( Fig. 49-4 ). A similar position also occurs when one places the hand on the back pocket, repetitively turns pages, or forces the lower hand position in the “slap-shot,” as in ice hockey. Typically, pain is increased by direct palpation precisely over the tip of the ulnar styloid. This is best felt deep and volar to the extensor carpi ulnaris (ECU) tendon. Pain is not in the dorsal ulnocarpal interval unless ulnocarpal impaction (UCI) is also present.

The diagnosis of USTI may be confused with that of UCI, which also presents as ulnar-sided pain. UCI is a consequence of ulnar head and lunate impaction. In the latter instance, the pain is ulnar and dorsal, increased by local palpation over the proximal ulnar aspect of lunate. The tenderness is not over the ulnar styloid. The provocative test, performed with the forearm in pronation and the wrist ulnarly deviated ( Fig. 49-5 ), is different from that carried out in USTI. Radiographic signs suggestive of USTI include ulnar styloid sclerosis, growth, flattening, small “kissing” cysts, and occasional loose bodies. A bone scan may show increased uptake about the styloid process. Magnetic resonance imaging (MRI) may show signal changes in the triquetrum, suggesting altered marrow vascularity and cystic reactive changes in the ulnar styloid. This is different from the MRI findings in UCI ( Fig. 49-6 ).

Multiple pathologic processes can produce USTI. It is often present along with UCI. Successful treatment is therefore dependent on the cause of the USTI and whether UCI and distal radioulnar joint (DRUJ) arthritis are also present, since all the syndromes must be treated. The causes of USTI relate to anatomic and kinematic aspects that diminish the distance between the ulnar styloid and the triquetrum. There are four basic etiologic categories for USTI. Each category has subcategories in which different anatomic factors, pathologic causes, and carpal kinematics result in USTI. These categories relate to whatever aspect of the forearm-wrist complex is involved in the inappropriate motion or growth.

Category 1: Movement of Ulnar Styloid to Triquetrum

An example of a category 1 USTI can be seen in Figure 49-7 (blue arrow). The following are examples of involvements that can cause a category 1 USTI:

Congenitally long ulnar styloid . Not all styloids mature to the same length or shape ( Fig. 49-8 ). Lengths of the ulnar styloid vary considerably, ranging from 0 to 14.8 mm with an average length of 6.3 mm. A long ulnar styloid predisposes to USTI.

FIGURE 49-8

These previously untreated, uninjured ulnae show markedly different sizes of the ulnar styloid ( arrows ).
Growth of the ulnar styloid . After trauma, the ulnar styloid may increase in both length and width ( Fig. 49-9 A and B). In addition avulsed ulnar styloid fragments, which occur frequently, remain attached to the collateral ligament and adjacent soft tissues and increase in size ( Fig. 49-10 ). They are not free within the joint and frequently produce symptoms of impaction.

FIGURE 49-9

A, Both forearms show growth of the ulnar styloid on the left ( red arrows ). White arrow shows evidence of past trauma. B, Both forearms in supination show ulnar styloid triquetral impaction on the left ( arrow ).

FIGURE 49-10

Growth of an avulsed ulnar styloid fragment ( arrow ).
Longitudinal growth of the ulna . This is uncommon but was seen in a rare pagetoid involvement of the ulna and in the mosaic bone hypertrophy of Proteus syndrome. UCI was the main diagnosis, but USTI was also present.
Radial physeal growth arrest . In whole physis involvement, the distal radial physis slows in growth as a result of trauma, and the continuing normal distal ulnar physis growth produces a positive ulnar variance. This usually results in UCI or UCI plus USTI. Associated with the positive ulnar variance are a decrease in the inclination of the radius and—most important—a change in slope of the sigmoid notch. The sigmoid notch slopes so that the proximal end is closer to the ulna ( Fig. 49-11 ). In partial physis involvement, the volar ulnar-sided growth arrest in Madelung’s deformity results in a complex clinical situation in which both UCI and USTI coexist ( Fig. 49-12 ).

FIGURE 49-11

Both forearms show radial physeal growth arrest on the left with a positive ulnar variance, a change in sigmoid notch slope, and a decreased radial inclination.

FIGURE 49-12

Madelung’s deformity with ulnocarpal impaction and ulnar styloid triquetral impaction.

Category 2: Movement of Triquetrum to Ulnar Styloid

An example of a category 2 USTI can be seen in Figure 49-7 (yellow arrow). This impaction occurs when the carpus moves proximally (as in collapse of the proximal carpal row), the radius moves proximally (as in distal radius malunions with a loss of radial length), the carpus ulnarly translocates, or the hand-wrist-radius complex moves ulnarly as one intact unit, which occurs after full or partial ulnar head excision ( Fig. 49-13 ). The following are possible causes of category 2 USTI:

Wrist arthrodesis . By removing articular cartilage and subchondral bone, this operation brings the triquetrum closer to the ulnar styloid, which may produce USTI that may be apparent only in supination ( Fig. 49-14 ).

FIGURE 49-14

Wrist arthrodesis with ulnar styloid triquetral impaction.
Kienböck’s disease . With collapse of the lunate, USTI may be present as a minor complaint along with symptoms related to Kienböck’s disease ( Fig. 49-15 ).

FIGURE 49-15

Kienböck’s disease with lunate collapse and ulnar styloid triquetral impaction. Red arrow points to larger space than yellow arrow.
Distal radius fractures (see Fig. 49-7 , white arrow). Radial shortening brings the carpus proximal and produces UCI and frequently USTI ( Fig. 49-16 ).

FIGURE 49-16

Both wrists with left post-distal radius fracture show shortening with ulnocarpal impaction and ulnar styloid triquetral impaction.
Ulnar translocation (see Fig. 49-7 , green arrow). This can occur with carpal translocation, in which translocation of the carpus ulnarly brings the lunate closer to the ulnar head and brings the triquetrum closer to the ulnar styloid. This rarely occurs with traumatic extrinsic wrist ligament insufficiency. It is common in patients with rheumatoid arthritis in which articular cartilage loss and resultant pseudoligamentous laxity allow the carpus to slide ulnarly ( Fig. 49-17 ). USTI can and often does occur, but in these situations it is rarely the patient’s major complaint. In addition, the carpus and radius may converge toward the ulna. If one excises the ulnar head transversely (Darrach procedure) or obliquely (matched hemiarthroplasty), the carpus and radius move toward the ulna. The latter procedure must incorporate a distal shortening of the ulna to prevent iatrogenic USTI from occurring (see Fig. 49-13 ).

FIGURE 49-17

Both wrists with rheumatoid involvement on the right show ulnocarpal impaction and ulnar styloid triquetral impaction with multiple vector causation.
Essex-Lopresti lesion (see Fig. 49-7 , white arrow). A radial head fracture, treated with excision and not replacement, may be associated with disruption of the DRUJ and radial shortening. This brings the carpus closer to the ulnar head and brings the triquetrum closer to the ulnar styloid. The syndromes of UCI and USTI may then coexist. Here, a radial head implant may be the treatment for USTI.
Rheumatoid arthritis . Diseases that produce loss of articular cartilage at both the radiocarpal and radiocapitellar joints result in the both radius and carpus moving proximally (see Fig. 49-17 ).
Radial growth abnormalities .

May be related to trauma, infection, and other rare causes such as enchondroma.

Category 3: Combination of Categories 1, 2, and 4

Multiple vectors may contribute to produce USTI (see Fig. 49-7 ). Frequently, an individual has more than one factor producing USTI. Figure 49-17 , already described, demonstrates all four vectors. The carpus has moved proximally. It has also moved ulnarly. There has been growth at the tip of the ulnar styloid. The radius has moved proximally. In this person, radiocarpal and UCI symptoms were much more troublesome than USTI symptoms; yet the USTI symptom complex was also present.

Category 4: Dynamic Impaction (with and without Predisposing Factors)

Occasionally, USTI may be present with no obvious predisposing factors. For instance, the ulnar styloid is not long, the ulnar variance is negative, and the radial head has not been excised ( Fig. 49-18 ). Patients may have experienced a single severe episode or repetitive episodes of trauma with the wrist positioned in supination and dorsiflexion.

CLINICAL STUDY

From the general film library, radiographs of a control group of 1000 patients showing no evidence of bony trauma were assessed for the average length of the ulnar styloid and the average projection of the styloid distal to the radius. Ulnar styloid length, measured from the base of the ulnar styloid to the tip in a line parallel with the long axis of the ulna, ranged from 0.0 to 14.80 mm with a mean of 6.31 mm and a standard deviation of 1.82 mm (n = 1000).

A prospective study of 56 patients with the clinical findings of USTI was completed in one surgeon’s (AAG) practice. Inclusion criteria required all three of the following: a history of ulnar wrist pain and a physical examination with both a positive USTI provocative test and tenderness localized precisely over the tip of the ulnar styloid. Frequently, USTI was not the major complaint, and more than one diagnosis was present. The additional diagnoses were based on clinical and radiographic findings. All patients underwent plain radiographic studies of the wrist. The radiographs were assessed for features that would cause a dynamic decrease in the ulnar styloid–triquetral interval.

In the latter group of 56 patients, other data included patient demographics and causative factors. The distribution of males and females was almost even (54% male, 46% female). Ages ranged from 15 to 69 years (mean 37 years). The patient’s dominant side was more often involved. One case was bilateral. Symptom duration ranged from 1.5 months to 6 years. A traumatic event was recalled in 38 of the 56 patients, 23 of which were fractures. Twenty-one (91%) of the fractures involved the distal radius, and most were associated with an ulnar styloid fracture. Twenty-four patients had an operative procedure to correct their problem. Seventeen operations consisted of ulnar styloid excision. Since USTI was often not the only diagnosis present, the other procedures performed included two radial osteotomies, one ulnar shortening, three matched hemiarthroplasties, and one Sauvé-Kapandji procedure. See Table 49-1 for patient demographics.

TABLE 49-1

Demographics of Patients with Ulnar Styloid Triquetral Impaction

Age (years)	Gender	Occupation	Dominant Side	Duration of Symptoms	Traumatic Event/Cause	Surgical Procedure/Treatment	Classification
33	Male	Laborer	Yes	1 yr	None	Ulnar styloid resection	1A
47	Male	Office job	Yes	8 mo	Forced twisting injury	Ulnar styloid resection	1A
40	Male	Restaurant worker	—	10 mo	Fall	None	1A
38	Female	Dental hygienist	—	—	None	None	4
48	Male	Bus driver	Yes	6 mo	Tennis related	Ulnar styloid resection	4
46	Female	—	Yes	10 mo	Colles’ fracture	Ulnar shortening	2C + 1B = 3
29	Female	Police officer	Yes	1 yr	Injury on punching bag	Ulnar styloid resection	1A
27	Male	Contractor	Yes	—	AVN of lunate 5 yr before	None	1A + 2B = 3
40	Male	Sheet metal worker	No	7 mo	Injury lifting weights	Ulnar styloid resection	1A
21	Male	Student	Yes	—	Throwing a ball	Excision of ulnar styloid and matched hemiarthroplasty	1B
22	Male	Hockey player	Yes	2.5 mo	Hockey—wrist shot	None	4
49	Male	Forklift driver	—	—	Injured arm driving forklift	Ulnar styloid resection	2C + 1B = 3
32	Female	Phys. ed. teacher	Yes	1 yr	Fracture of distal radius	None	2C + 1B = 3
33	Female	Homemaker	No	3 mo	Surgery as a child, volleyball injury	None	2C + 1D = 3
56	Female	Office worker	Yes	6 mo	Colles’ fracture	Ulnar styloid resection	2C + 1B = 3
35	Male	—	No	5 mo	Distal radius fracture	None	1A + 2C = 3
45	Female	Nurse	Yes	5 mo	Lifting bed rail	None	4
64	Female	—	Yes	1 yr	Distal radius fracture	Distal radial osteotomy	2C
45	Male	Laborer	—	3 mo	Injury lifting a window	None	1B
52	Female	Homemaker	—	2 mo	Distal radius fracture	None	2C
31	Female	—	Yes	8 mo	None	Ulnar styloid resection	4
17	Male	Student	No	—	SH II of distal radius	None	1D + 1B = 3
17	Male	Student	—	7 mo	Fracture of distal radius	None	2C
26	Male	—	—	3 yr	Radial head excision for fracture	Excision of ulnar styloid with TFCC repair; Sauvé-Kapandji procedure	2E
32	Female	Office clerk	Yes	3 mo	MVC	Ulnar styloid resection	1A
62	Female	Nurse	Yes	1 yr	None	None	2F + 2D = 3
28	Male	—	—	3 yr	Perilunate dislocation with subsequent fusion	Excision of ulnar styloid	2A
46	Female		—	1 yr	Fracture of distal radius	Matched hemiarthroplasty	2D
52	Male	Construction	Yes	—	Fracture of distal radius and ulnar styloid	None	2C
31	Female	Typist	No	1 yr	Fracture of distal radius 4 yr before. Reinjury with twisting force	None	1B + 2C = 3
40	Male	Home renovator	Yes	11 mo	MVC	None	4
19	Male	Hockey player	—	A few months	None	None	4
69	Male	Retired engineer	—	1 yr	Wrist injury at 13 yr of age	None	1B
45	Female	—	No	2 yr	Fracture of distal radius	None	2C
47	Female	—	Yes	6 mo	Osteotomy and excision of ulnar head 15 yr earlier	Planned Sauvé-Kapandji	1D + 2G = 3
15	Male	Student	No	—	SH II fracture of distal radius 2 yr earlier	None	1D
46	Female	Lab. technician	Yes	1.5 mo	None	None	4
46	Female	Hospital worker	—	4 mo	Fracture of distal radius and ulnar styloid	None	1B + 2C = 3
50	Female	—	Yes	—	Fracture of distal radius and ulnar styloid	None	1B + 2C = 3
28	Female	Scrub nurse	Yes	—	Previous fracture of ulnar styloid	Ulnar styloid resection, arthrotomy of wrist with loose body excision	1B
36	Male	Technologist	Yes	2 yr	Wrist fracture with closed management	None	1B
45	Male	Mechanic	Yes	—	Wrist fracture 20 yr earlier, followed by excision of lunate 19 yr earlier, followed by arthrodesis	None	2A
63	Female	Not working	No	2 yr	Previous undisplaced fracture of distal radius	None	2C
41	Female	Nurse	—	—	Injury with patient transfer	Excision of ulnar styloid	1B
17	Male	Student	No	—	Football injury	Excision of ulnar styloid	1B
17	Female	Student	Bilateral	2 yr	None	None	1D
32	Male	Carpenter	Yes	—	MVC with Galeazzi fracture and avulsion of ulnar styloid	Excision of ulnar styloid	1B
33	Male	Unemployed	No	—	Distal radius fracture	Radial osteotomy	2C
34	Female	—	—	6 yr	Fall from horse	None	4
22	Male	Construction	Yes	2 yr	Distal radius fracture	None	1B
16	Male	Student	No	1 yr	Hockey—lower hand	Injection	1A + 4
30	Female	Mechanic	Yes	2 yr	Distal radius fracture	Excision	1B
56	Female	Secretary	No	1.5 yr	Distal radius fracture	Matched hemiarthroplasty	2C
33	Male	Physical therapist	No	2 yr	Forced dorsiflexion in supination	None	4
23	Male	Hockey player	Yes	2 yr	Forced dorsiflexion in supination	Excision	4
54	Male	Cook	No	2 yr	—	None	1A