Traction radiography for the diagnosis of scapholunate ligament tears: an experimental cadaver study

The aim of this experimental cadaver study was to verify that thumb traction radiography can be used to diagnose scapholunate interosseous ligament (SLIL) injury. Eight cadaver forearms were positioned vertically so that the thumb could be held in a Chinese finger trap and traction force applied using a 5 kg weight. Fluoroscopy was performed with the thumb unloaded and under traction, and then unloaded and under traction after division of the SLIL. The scapholunate joint gaps were measured electronically. The difference between the unloaded and loaded wrists with sectioned SLIL was not statistically significant. These results suggest that thumb traction radiography might not reliably detect acute, complete SLIL tears.     

Long-term Outcomes of Arthroscopic Debridement and Thermal Shrinkage for Isolated Partial Intercarpal Ligament Tears

A retrospective analysis was performed based on the medical records and imaging studies of 16 wrists (14 patients) with isolated partial intercarpal ligament tears (scapholunate ligament: 6 wrists, lunotriquetral ligament, 10 wrists) treated with arthroscopic debridement and thermal shrinkage. Three wrists had Geissler grade 1 tears and 13 wrists had grade 2 tears. Mean follow-up was 52.8 months. Overall pain visual analog scale scores improved significantly (P<.05) at rest and during activities of daily living and heavy manual work. Mean flexion-extension arc was 136.5°. Mean postoperative grip strength was 106 lb, which was significantly better than preoperative grip strength. Mean modified Mayo wrist score was 70 preoperatively and 94.7 postoperatively, a significant improvement. Overall functional outcomes according to the modified Mayo wrist score were rated as excellent in 13 wrists and good in 3. No patient had radiographic evidence of instability or arthritic changes. The scapholunate and lunotriquetral intervals in all patients were less than 3 mm on neutral and pronation grip radiographs. On lateral radiographs, no signs of intercalated segmental instability were seen, with a mean scapholunate angle of 55.3°.The results of this study suggest that arthroscopic debridement and thermal shrinkage provide symptomatic pain relief and prevention of intercarpal instability for a significant period of time in patients with partial intercarpal ligament tear.     

Distribution of posterior tibial displacement in knees with posterior cruciate ligament tears

BACKGROUND: While stress radiography has been used to objectively determine the limits of posterior tibial displacement in knees with posterior cruciate ligament tears, the magnitude and distribution of posterior tibial translation has not been defined in a large population of patients with this injury. METHODS: A retrospective diagnostic study of 1041 consecutive patients with posterior cruciate ligament tears was done. Posterior tibial displacement values that were obtained with use of instrumented stress radiography with the knee held in 90 degrees of flexion in the Telos device were evaluated and compared with the values from relevant cadaveric dissection studies. RESULTS: The mean amount of posterior tibial displacement on stress radiographs was -11.58 +/- 4.31 mm (range, -5 to -30 mm). There was a displacement peak in the range of -9 to -12 mm, with 37.9% of patients exhibiting posterior laxity within this range. Traffic-related injuries were associated with significantly greater displacement values than were sports-related injuries (p < 0.001). Grade-I or II instability (12 mm of posterior tibial displacement) occurred in association with 68.7% of the sports-related injuries, compared with 54.1% of the traffic-related injuries (p < 0.001). The mean amount of posterior tibial displacement on the intact side was -1.31 +/- 1.85 mm (range, -6 to 4 mm). CONCLUSIONS: Instrumented stress radiography is a useful testing method for objectively determining the amount of posterior tibial displacement of the knee in adults with a posterior cruciate ligament injury. Absolute posterior tibial displacement in excess of 8 mm is indicative of complete insufficiency of the posterior cruciate ligament. With tibial displacement exceeding 12 mm, additional injury of secondary restraining structures should be considered. We recommend the use of stress radiography to grade and classify posterior knee laxity.     

Dorsal intercarpal ligament capsulodesis for chronic,static scapholunate dissociation: clinical results

The purpose of this study was to review and report the results of using a new procedure, the dorsal intercarpal ligament capsulodesis (DILC), to treat a group of patients with chronic flexible scapholunate dissociation. This was a prospective study of 21 patients (22 wrists), ranging in age from 16 to 62 years followed up for 1 to 4 years. For this study all patients returned to complete a questionnaire and have a physical examination performed by physicians and therapists independent of the treating surgeons and to obtain standardized radiographs of the wrists. Patient demographics, mechanism of injury, range of motion, and grip strength were recorded. Patients completed the Mayo wrist, Short-Form (SF)-12, and Disabilities of Arm, Shoulder and Hand (DASH) questionnaires. Results showed there were significant improvements in scapholunate angle and scapholunate gap at final follow-up examination, with minor loss of range of motion and grip strength. Patients were satisfied with the outcomes, showing an average score of 17 on the DASH and 83 on the SF-12. The DILC procedure is a reasonable option for treating chronic scapholunate dissociation. The procedure has conceptual advantages to recommend it: it avoids a tether between radius and scaphoid and keeps the proximal carpal row linked as a functional unit. It reduces the scapholunate angle and gap. Overall the results to date are quite encouraging.     

Static scapholunate dissociation: a new reconstruction technique using a volar and dorsal approach in a cadaver model

We used 4 fresh-frozen cadaver arms to assess a method of reconstruction we designed for static scapholunate dissociation. The dorsal scapholunate ligament, scapholunate interosseous ligament, radioscapholunate, and radioscaphocapitate ligaments were sectioned. Radiographs were taken before sectioning, after sectioning, and after reconstruction. Passive motion was also measured before sectioning and after the repair. The dorsal scapholunate ligament was repaired directly; the palmar radioscapholunate and radioscaphocapitate ligaments were reconstructed using a free flexor carpi radialis tendon autograft and Mitek mini suture anchors (1.8-mm diameter and 5.4-mm length; Mitek Products, Norwood, MA) for anatomic fixation. An independent board-certified hand surgeon analyzed the radiographs of the wrists taken before and after sectioning and after reconstruction. Assessment of the unsectioned wrists revealed an average scapholunate angle of 45 degrees. After scapholunate dissociation was created the average scapholunate angle was 71 degrees. Repair of the dorsal scapholunate ligament alone did not improve the scapholunate angle. Average scapholunate angle after repair of the dorsal scapholunate ligament and reconstruction of the palmar ligaments was 43 degrees. Average range of motion on flexion, extension, and radial and ulnar deviation before ligament sectioning and after reconstruction was unchanged at 54 degrees, 59 degrees, 19 degrees, and 40 degrees respectively. This technique shows an improvement in scapholunate angle on lateral radiographs, and passive motion remained relatively unchanged.     

Carpal bone postures and motions are abnormal in both wrists of patients with unilateral scapholunate interosseous ligament tears

PURPOSE: The recent ability to measure 3-dimensional in vivo carpal kinematics has facilitated the noninvasive study of complex carpal bone motion. METHODS: In this study we examined the flexion/extension carpal kinematics of both wrists in 8 patients with unilateral scapholunate interosseous ligament (SLIL) tears by using computed tomographic (CT) imaging and a markerless bone registration technique. Carpal bone neutral posture and flexion/extension motion of both wrists of the injured patients were compared with the same parameters in wrists of 10 uninjured male and female volunteers (normals). RESULTS: The neutral posture of the injured scaphoid and lunate were significantly more extended than those of normals. In these patients, however, the postures of the scaphoid and lunate in the contralateral uninjured wrists also were abnormal and were similar to those of the injured wrist. In addition, extension of the lunate and flexion of the scaphoid in both the injured and uninjured wrist were significantly different from normal but not different from each other. CONCLUSIONS: This study was unable to attribute altered carpal posture and motion to SLIL tears because abnormalities were found in both wrists of patients with unilateral injury. The etiology of abnormal wrist kinematics in the asymptomatic wrist of patients with unilateral tears of the scapholunate ligament is not known.     

The prevalence of wrist ganglia in an asymptomatic population: magnetic resonance evaluation

Magnetic resonance imaging (MRI) was performed on the wrists of 103 asymptomatic volunteers. The images were evaluated independently by two musculoskeletal radiologists and one orthopaedic surgeon. Wrist ganglia were identified in 53 out of the 103 wrists. The average long and short axes measurements were 8 mm (range 3-22) and 3 mm (range 2-10), respectively. Seventy per cent of the ganglia originated from the palmar capsule in the region of the interval between the radioscaphocapitate ligament and the long radiolunate ligament. Fourteen per cent of the ganglia were dorsal and originated from the dorsal, distal fibres of the scapholunate ligament. Two ganglia had surrounding soft tissue oedema and one had an associated intraosseous component. Unlike previous surgical and pathological series, our study showed that palmar wrist ganglia are more common than dorsal wrist ganglia. The vast majority of these asymptomatic ganglia occur without associated ligamentous disruption, soft tissue oedema or intraosseous communication.     

Dorsal intercarpal ligament capsulodesis for scapholunate dissociation: biomechanical analysis in a cadaver model

The purpose of this study was to evaluate in cadavers a new method for treating scapholunate dissociations, dorsal intercarpal ligament capsulodesis (DILC), and to compare its performance with that of a previously described soft tissue reconstruction, Blatt capsulodesis (BC). A cadaver model was used to simulate normal and abnormal wrist motions. The positions of the scaphoid and lunate and their changes with wrist motion and ligament condition were recorded using biplanar radiographs taken posteroanteriorly and laterally. The scapholunate gap was measured on the posteroanterior radiographs and the scapholunate angle was measured on the lateral view radiographs. Following scapholunate interosseous ligament sectioning, a diastasis developed between the scaphoid and lunate that was maximum in the clenched fist position 2.1 +/- 0.33 mm (mean +/- SEM) with the ligament intact versus 8.0 +/- 1.74 mm after the ligament was sectioned. Dorsal intercarpal ligament capsulodesis reduced gap formation more than BC, including when the specimens were in the clenched fist position: increased gap versus intact specimens equals 1.0 mm for DILC versus 3.7 mm for BC. The differences in diastasis were statistically significant between BC and DILC when the wrist was in extension, radial deviation, and clenched fist positions. After the scapholunate interosseous ligament was divided, the scaphoid flexed relative to the lunate. Both capsulodeses improved scapholunate alignment and there was a trend for DILC to correct the scapholunate angle more than BC. The results demonstrate that DILC is an attractive alternative to BC ex vivo. Because DILC does not tether the scaphoid to the distal radius, as BC does, improved wrist motion, especially flexion, might be possible in vivo. The use of DILC in the treatment of scapholunate dissociation warrants further investigation and clinical trials.     

Prediction of soft-tissue injuries in Schatzker II tibial plateau fractures based on measurements of plain radiographs

BACKGROUND: Split-depression fractures of the lateral tibial plateau (Schatzker II) are associated with a significant risk of capsuloligamentous and meniscal injury. We hypothesized that the amount of fracture depression and widening on anteroposterior (AP) plain radiographs would correlate with the incidence of injury to these structures on magnetic resonance imaging (MRI). METHODS: Sixty-two consecutive patients with Schatzker II tibial plateau fractures had a knee x-ray series and MRI preoperatively. AP plain radiographs were measured for lateral joint line depression and condylar widening, and MRIs were evaluated for injury to soft-tissue structures around the knee. For each structure, the threshold of depression and widening that led to the greatest disparity in soft-tissue injury was determined. Multiple logistic regressions were applied to calculate whether depression and/or widening above the thresholds were predictive for injury to individual soft-tissue structures. RESULTS: When depression was greater than 6 mm and widening was greater than 5 mm, lateral meniscal injury occurred in 83% of fractures, compared with 50% of fractures with less displacement (p < 0.05). When either depression or widening was at least 8 mm, medial meniscal injury occurred more frequently (depression 53%, p < 0.05; widening 78%, p < 0.05; versus neither 15%). Lateral collateral ligament and posterior cruciate ligament tears were not seen with minimally displaced fractures (< 4 mm), but the incidence of injury approached 30% with increasing displacement. CONCLUSIONS: Due to the limited availability of MRI in some centers, correlation of lateral condylar depression and widening, as measured on plain radiographs, to injury of various soft-tissue structures may be extremely helpful in planning open or arthroscopic treatment methods. Using these guidelines, Schatzker II fractures with depression or widening approaching 5 mm deserve heightened vigilance in diagnosing and treating these concomitant soft-tissue injuries.     

Wrist kinetics after scapholunate dissociation: the effect of scapholunate interosseous ligament injury and persistent scapholunate gaps.

The purpose of this study was to investigate the effects of cutting of the scapholunate interosseous ligament (SLIL) and persistent widening of the scapholunate (SL) joint on changes in moment arms of the principal wrist motor tendons. In seven fresh frozen cadaveric upper extremities, excursions of the extensor carpi radialis longus (ECRL) and brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), and flexor carpi ulnaris (FCU) were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, then in the wrists with complete SLIL sectioning and in those with moderate or severe persistent SL joint widening. The data were converted to moment arms of the tendons. The results showed that moment arms of the ECRL and ECRB tendons after SLIL sectioning were, respectively, 110+/-6% and 105+/-3% of those in the intact wrist. In the wrists with moderate or severe SL joint widening, moment arms of the flexors significantly increased (P < 0.01 and P < 0.001, respectively). During radioulnar deviation, moment arms of the ECRL, ECRB, ECU, and FCU tendons decreased after SLIL sectioning and the SL joint widening. However, moment arms of the FCR tendon significantly increased 122+/-23% after the SLIL section, 133+/-28% after the moderate SL joint widening, and 138+/-24% after the severe SL joint widening compared with those of the intact wrists. This study demonstrated that integrity of the SLIL and appropriate SL joint space are important for mechanics of wrist motor tendons. Loss of integrity of the SLIL and persistent SL joint widening increase mechanical effects of the radial side wrist motor tendons, which may contribute to the pathomechanics of scaphoid malrotation, scapholunate advanced collapse, and early osteoarthritis in the radioscaphoid joint interface seen in SL dissociation. The results also suggest that reduction of the displaced SL joint is imperative to the recovery of wrist kinetics after SL dissociation.     

Scapholunate ligament injury occurring with scaphoid fracture--a rare coincidence?

In a retrospective study the results of a series 34 wrist arthroscopies in 189 acute scaphoid fractures were analysed. Scapholunate ligament tears were found in 13 cases. In 10 cases there was complete disruption of scapholunate interosseous ligament causing dynamic instability. Partial ligament tears without instability were seen in three cases. Despite the limitations of this series we conclude that occurrence of scapholunate ligament injury with a scaphoid fracture may be more common than generally thought.     

Arthoscopic diagnosis of partial scapholunate ligament tears as a cause of radial sided wrist pain in patients with inconclusive x-ray and MRI findings

To clarify the pathology of radial-sided wrist pain with inconclusive X-ray and MRI findings, we performed arthroscopic examinations of 11 wrists in 10 patients. Physical examination and various image investigations could not identify the cause of the pain. Arthroscopy revealed partial to complete tears of the scapho-lunate interosseous ligament and synovitis and/or chondral bone defects at the scaphotrapezio-trapezoidal joint in all 11 wrists. Surgical procedures consisted of eight simple synovectomies, two ligament reconstructions and one percutaneous pinning. Pain relief was achieved in 10 wrists. One wrist which had a simple synovectomy did not recover, so underwent secondary scaphotrapezio-trapezoidal fusion. In conclusion, we found that various degrees of scapholunate interosseous ligament tear and scaphotrapezio-trapezoidal joint osteoarthritis were the main causes of radial-sided wrist pain with inconclusive X-ray and simple MRI findings.     

Deltoid ligament integrity in lateral malleolar fractures: a comparative analysis of arthroscopic and radiographic assessments

Foot and ankle surgeons often rely on the medial clear space to evaluate competency of the deep deltoid ligament when evaluating ankle fractures. This investigation assesses the integrity of the deep deltoid ligament after lateral malleolar fracture by using direct arthroscopic visualization and medial clear-space separation on plain film radiographs. The objectives of this study were to test the reliability of medial clear-space separation and the Lauge-Hansen classification scheme in predicting deep deltoid rupture in displaced lateral malleolar fractures. The medial clear space was measured on injury radiographs of 40 patients with an isolated displaced lateral malleolar fracture who underwent open reduction and internal fixation. Injury radiographs were classified according to the Lauge-Hansen scheme. Direct arthroscopic visualization was used to evaluate the deep deltoid ligament under manual stress before fracture reduction. The mean preoperative medial clear space in patients with a deep deltoid rupture (n = 13) was 6.6 +/- 2.4 mm (range, 4 to 12 mm), and in patients without a deep deltoid rupture (n = 26), it was 4.0 +/- 1.0 mm (range, 2.5 to 6 mm) (P =.002, 2-sample t test). At an injury medial clear space > or =3 mm, the false positive rate for deltoid rupture was 88.5% (P =.54, Fisher's exact test). At > or =4 mm, the false positive rate was 53.6% (P =.007). All fractures were rotational injuries according to the Lauge-Hansen system. Three fractures were not classifiable; another 3 fractures showed deltoid ligament integrity opposite the expected finding. The results indicate that, in isolated displaced fractures of the lateral malleolus, radiographic widening of the medial clear space is not a reliable indicator for deep deltoid rupture. Some fractures considered stable by the Lauge-Hansen classification may require careful scrutiny to rule out deep deltoid injury.     

Soft tissue stabilization in the management of chronic scapholunate instability without osteoarthritis. A 15-year series

Management of chronic scapholunate instability without osteoarthritis remains controversial. Some surgeons favor partial wrist arthrodesis; others, soft tissue stabilization. Many techniques for soft tissue repair have been described but with few or unpredictable results. We reviewed all our cases of scapholunate instability without osteoarthritis treated by soft tissue stabilization. Since 1979, 37 soft tissue stabilization procedures have been performed to correct dynamic (25) or static (12) scapholunate instability without osteoarthritis. The average time from injury to surgical treatment was 7.2 mos. (range 0.25 to 36 mos.). Three cases were treated within the first month of injury. The choice of repair was determined intraoperatively. The scaphoid shift must be easily reducible to make the case eligible for soft tissue repair. The scapholunate ligament was usually disrupted from palmar to dorsal, and the average amount of disruption was 74%. When scapholunate ligament remnants were of sufficient quality, secondary repair was performed; but if not, ligament reconstruction using tendon grafts or capsulodesis was performed. The procedures used were secondary ligamentous repair in 16 (by direct suture, reinsertion using anchor and/or transosseous reattachment), ligament reconstruction using tendon grafts in 6, capsulodesis in 7 and a combination of these procedures in 8. The mean follow-up was 27 mos. (range 2 to 62 mos.). Postoperatively, there was an 83% decrease in pain. The average wrist motion was 60 degrees extension, 47 degrees flexion, 18 degrees radial deviation and 28 degrees ulnar deviation (92%, 84%, 106% and 88% of preoperative values and 88%, 75%, 78% and 76% of the uninvolved wrists, respectively), and the grip strength was 28 kg (117% of preoperative value and 78% of the uninvolved wrists). On roentgenograms, the mean static scapholunate distance was 4.2 mm (a 26% loss of reduction compared to the early postoperative gap), but scapholunate and radiolunate angles were within normal values (58 degrees and 9 degrees, respectively). At follow-up, one patient presenting a small zone of chondromalacia on the scaphoid at the time of secondary ligamentous repair developed severe radioscaphoid arthritis 15 months postoperatively. The results were further assessed according to the form of instability, delay before surgery, severity of disruption and type of repair. Patients with static instability showed worse clinical and radiological findings than those with dynamic instability. Surgical delay did not influence the outcome. The more severe the ligament disruption was, the poorer were the results. All types of repair had a comparable outcome except those treated by ligament reconstruction using tendon grafts. The results in the latter group were unsatisfactory in terms of motion, grip strength and radiological findings. This technique has been abandoned by the group. In conclusion, soft tissue stabilization is part of the armamentarium in the management of reducible chronic scapholunate instability without osteoarthritis. Ligament reconstruction using tendon grafts gave, in our hands, unsatisfactory results. Otherwise, all types of repair achieved a relatively pain-free wrist, with acceptable motion, grip strength, scapholunate and radiolunate angles but with a wider than normal static scapholunate distance. A longer follow-up is needed to assess the effect of this abnormal gap. Factors that favorably affected the outcome were: dynamic type of instability and partial disruption of the ligament.     

Arthroscopic electrothermal collagen shrinkage for symptomatic laxity of the scapholunate interosseous ligament

The medical records, radiographs and operative reports of ten consecutive patients of average age 37 (range 19-67) years with wrist pain secondary to structural disruption of the scapholunate interosseous ligament (Geissler Type 2 injuries) who were treated with wrist arthroscopy and electrothermal collagen shrinkage of the scapholunate interosseous ligament were reviewed. Functional outcomes were assessed using the DASH scoring system at an average follow-up of 28 (range 12-44) months. At latest follow-up, nine patients (90%) were asymptomatic and had returned to their pre-injury functional level. The mean score on the DASH questionnaire was 20 (range 11-48). One patient developed wrist discomfort and mechanical symptoms 7 months postoperatively and required revision surgery. Our preliminary findings suggest that this may be a viable treatment option in the management of patients with symptomatic scapholunate interosseous ligament laxity without complete ligament disruption. Additional study is needed to better understand the role of this treatment modality.     

A cause of painful clicking wrist: a case report

In a patient with symptomatic unilateral clicking of the wrist, a partial tear of the scapholunate ligament with subsequent scarring of the proximal third of the dorsal portion of the ligament had occurred. At operation the dorsomedial edge of the proximal pole of the scaphoid had snapped over the dorsal edge of the lunate as the palmar-flexed wrist was being returned to a neutral position. Release of the scarred portion of the scapholunate ligament was associated with widening of the scapholunate joint space to normal dimensions and cessation of the clicking phenomenon. Fourteen months after operation there was complete relief of symptoms, a full range of wrist motion and no radiographic evidence of widening of the scapholunate space, ligamentous instability, or rotatory subluxation of the scaphoid.     

Comparison of scapholunate distance measurements on plain radiography and computed tomography for the diagnosis of scapholunate instability associated with distal radius fracture

Purpose

To investigate radiographic criteria for scapholunate instability (SLI) in the setting of distal radius fracture (DRF) confirmed by arthroscopy.

Methods

Eighty-eight wrists with DRF treated by open reduction and internal fixation and assessed for SLI arthroscopically were evaluated. The scapholunate distance (SLD) was measured by preoperative posteroanterior wrist radiography and computed tomography (CT). SLD on radiographs was measured as the distance between the scaphoid cortex and the lunate cortex at the center of the scapholunate joint. SLDs were measured at the volar end (A1), center (A2), and dorsal end (A3) of the scapholunate joint on the central CT axial slice; and at the proximal end (C1), center (C2), and distal end (C3) of the scapholunate joint on the central CT coronal slice. Wrists were divided into three groups by arthroscopic assessments: stable (normal, Geissler grade 1 or 2), G3 (Geissler grade 3), and G4 (Geissler grade 4). SLD measurements on radiographs and CTs (A1–C3) were compared among the three groups. Receiver-operating characteristic (ROC) curve analyses were performed to evaluate the abilities of SLD measurements on radiographs and CTs to identify SLI in wrists with DRF. Interobserver and intraobserver reliabilities of SLD measurements on radiographs and CTs were analyzed by intraclass correlation coefficients (ICCs).

Results

SLDs of C3 differed significantly among the G3 and G4 groups, and among the stable and G4 groups. The area under the curve on ROC curve analysis was 0.855 for the SLD of C3, which was larger than that for SLD on radiographs. For C3, the intraobserver ICC was 0.832 and interobserver ICC was 0.73.

Conclusions

SLD at the distal end of the scapholunate joint on the central coronal CT slice was the most appropriate measurement for discrimination of Geissler grade 4 SLI in wrists with DRF.

Level of evidence

Level 2     

Bulge of the scapholunate ligament: an arthro-CT sign of traumatic scapholunate instability

Tears of the scapholunate ligament are usually diagnosed during an arthro-CT or arthro-MRI examination. Typically, the contrast agent passes from one joint to the other. In certain cases, fibrous scar tissue devoid of any mechanical effect may block the passage and lead to an erroneous interpretation of the images. We reviewed retrospectively patients who underwent arthroscopic treatment for scapholunate tears and who had normal arthro-CT images. We searched for specific aspects suggestive of ligament injury. Analysis of the arthro-CT images demonstrated that a bulge of the scapholunate ligament could be noted in patients whose diagnosis of scapholunate ligament injury was established arthroscopically. We propose that appropriate lecture of wrist images can identify scapholunate ligament injury in patients wrongly considered to be free of wrist injury, but who actually have an occult injury to the scapholunate ligament.     

The clinical implications of scaphotrapezium-trapezoidal arthritis with associated carpal instability

PURPOSE: Common causes of dorsal intercalated segment instability (DISI) include scapholunate dissociations and scaphoid fracture nonunions. Although less common than these, scaphotrapezium-trapezoidal (STT) osteoarthritis (OA) may also be associated with the development of a DISI deformity. The clinical implications of this form of carpal instability in cases of STT arthritis are still unknown. To study the radiographic progression and incidence of this entity, we reviewed our patients and report on 24 wrists with DISI in the presence of STT arthritis. METHODS: A retrospective chart and radiographic review was performed on all patients seen between 1994 and 2004, with the diagnosis of STT arthritis to identify a subgroup of patients with DISI deformity on the presenting radiographs. Patients' clinical and surgical courses were noted. Postoperative radiographic changes were recorded, as were clinical outcomes. RESULTS: Sixteen patients with 24 wrists having STT arthritis and DISI deformity on presenting radiographs were identified. The median STT arthritis grade was 3.0 based on a modified Eaton and Glickel grading system. The median radiolunate angle was -21 degrees of dorsal tilt. All patients had normal scapholunate angles. Abnormal scaphoid extension was seen in 19 of 24 wrists as measured by the radioscaphoid angle. Concomitant carpometacarpal arthritis was seen in 67% (n = 16) of the wrists, and midcarpal arthritis was identified in 50% (n = 8) of patients. Fifteen wrists required surgery for the symptoms and were followed up for a mean of 29 months after surgery. In the surgical group the radiolunate angles increased by mean of 6 degrees after surgery. Four of the 15 wrists required revisional surgery for persistent pain. CONCLUSIONS: Patients with STT arthritis may present with carpal instability that is not related to radiographic scapholunate instability. This instability is characterized by a normal scapholunate angle with an extension stance of the scaphoid and lunate. Midcarpal arthritis may be present. Surgical intervention for patients with STT arthritis and DISI deformity may lead to radiographic progression of midcarpal instability.