Is DISI Deformity Related to Presence of a Medial Lunate Facet in Patients with Scapholunate Dissociation?

Background Lunate morphology has been suggested to influence carpal kinematics. Purpose We investigate a possible relation between presence of a medial lunate facet and dorsal intercalated segment instability (DISI) of the wrist in patients with a scapholunate (SL) dissociation. Methods We retrospectively reviewed patients diagnosed with SL dissociation between 2000 and 2017. Lunate morphology was categorized based on radiographs and magnetic resonance imaging (MRI), as type I or II according to Viegas and Galley. DISI was defined as radiolunate angle > 15 degrees and SL instability as SL angle > 60 degrees. SL distance > 3 mm was considered as widening and carpal height ratio < 0.5 was considered as carpal collapse. We used descriptive statistics to report on SL instability and DISI in patients with Viegas type I and type II lunates. We calculated kappa to determine agreement between radiographs and MRI and to determine inter- and intraobserver agreement. Results Of 119 patient files, 79 wrists met the inclusion criteria of which 25 were type I lunates and 54 type II. Similar spreading of the data of both groups was found regarding DISI, SL instability, and SL widening based on radiographic classification of the lunate, even after adding MRI findings. In the presence of carpal collapse, capitate-to-triquetrum distance was higher. We found a substantial inter- and intraobserver agreement for lunate classification. Conclusion Our results suggest a similar prevalence of DISI deformity or enlarged SL angle in patients with type I or II lunate in presence of SL dissociation. The Viegas classification is a reliable and reproducible classification system. Level of evidence This is a Level III, cross-sectional study design.

Posttraumatic Carpal Instability Nondissociative

Background Posttraumatic midcarpal instability nondissociative (CIND) is an exceptional rare condition, therefore the outcome after different treatment options remains unknown. Questions The purpose of this study was to investigate the different treatment options for posttraumatic CIND. We also describe the different radiological and magnetic resonance imaging (MRI) findings in this patient cohort. Patients and Methods We present outcomes of 10 patients who developed CIND following acute wrist trauma between 2007 and 2018, 3 with dorsal intercalated segment instability pattern (CIND-DISI) and 7 with volar intercalated segment instability (CIND-VISI) radiographically. Results Three patients with CIND-VISI had satisfactory outcomes with conservative treatment. Two patients with irreducible CIND-DISI and one with CIND-VISI underwent proximal row carpectomy (PRC), two with reducible CIND-VISI had radiolunate fusion, and two with secondary osteoarthritis had total wrist fusion. All patients with CIND-DISI needed surgery, whereas only four of the seven patients with CIND-VISI needed surgery. On MRI, all three patients with CIND-DISI had rupture of the radiolunate ligament. Conclusions The data collected in this study may provide the first step toward better understanding of the pathology for this exceptionally rare finding. In CIND-VISI, we have not seen any ligament injury in four patients. Therefore, conservative therapy is more likely to be the first step. In CIND-DISI, we recommend an operative procedure: if detected early, with ligament suture, otherwise by radiolunate fusion, PRC, or total wrist fusion. Level of Evidence This is a Level IV study.

Four-Dimensional CT Analysis of Dorsal Intercalated Segment Instability in patients with Suspected Scapholunate Instability

Background In this study we sought to evaluate the contribution of dynamic four-dimensional computed tomography (4DCT) relative to the standard imaging work-up for the identification of the dorsal intercalated segment instability (DISI) in patients with suspected chronic scapholunate instability (SLI). Methods Forty patients (22 men, 18 women; mean age 46.5 ± 13.1 years) with suspected SLI were evaluated prospectively with radiographs, arthrography, and 4DCT. Based on radiographs and CT arthrography, three groups were defined: positive SLI (n = 16), negative SLI (n = 19), and questionable SLI (n = 5). Two independent readers used 4DCT to evaluate the lunocapitate angle (LCA) (mean, max, coefficient of variation [CV], and range values) during radioulnar deviation. Results The interobserver variability of the 4DCT variables was deemed excellent (intraclass correlation coefficient = 0.79 to 0.96). Between the three groups, there was no identifiable difference for the LCAmean. The LCAmax values were lower in the positive SLI group (88 degrees) than the negative SLI group (102 degrees). The positive SLI group had significantly lower LCAcv (7% vs. 12%, p = 0.02) and LCArange (18 vs. 27 degrees, p = 0.01) values than the negative SLI group. The difference in all the LCA parameters between the positive SLI group and the questionable SLI group was not statistically significant. When comparing the negative SLI and questionable SLI groups, the LCAcv (p = 0.03) and LCArange (p = 0.02) values were also significantly different. The best differentiation between patients with and without SLI was obtained with a LCAcv and LCArange threshold values of 9% (specificity of 63% and sensitivity of 62%) and 20 degrees (specificity of 71% and sensitivity of 63%), respectively. Conclusion In this study, 4DCT appeared as a quantitative and reproducible relevant tool for the evaluation of DISI deformity in cases of SLI, including for patients presenting with questionable initial radiography findings. Level of evidence This is a Level III study.

Correction of humpback and DISI deformities by vascularized bone grafting in patients with scaphoid nonunion

Introduction: Although vascularized bone grafting (VBG) using 1, 2 intercompartmental supraretinacular artery (1, 2 ICSRA) is effective for scaphoid nonunion, dorsal intercalated segment instability (DISI) deformity persists even after correction of humpback deformity (HD). The purpose of this retrospective study was to evaluate the correction of HD and DISI deformity after 1, 2 ICSRA VBG for scaphoid nonunion. Methods: We treated 18 patients (mean age: 25.8, 16 males and 2 females) with scaphoid nonunion using a 1, 2-ICSRA VBG between January 2010 and December 2018. The average time from injury to surgery was 20.0 (3–120) months. The nonunions were located at the waist in all patients. The correction of HD and DISI deformity was investigated on the preoperative images and images at the last examination. Results: In all patients, the correction of HD was positively correlated with that of DISI deformity. Moreover, we focused on the time from injury to surgery and evaluated changes in HD and DISI deformity according to the time to surgery. As a result, changes in HD and DISI deformity were positively correlated in patients with a shorter time to surgery but were not correlated when the time to surgery exceeded 5 months. Conclusions: These results suggest that DISI deformity can be corrected by correcting HD when the time from injury to surgery is short, but that correction is difficult if the time to surgery is prolonged.

How Much Scaphoid Can be Safely Resected? A Biomechanical Analysis of the Effects of Distal Scaphoid Resection

Background: Resection of the distal pole of the scaphoid has been advocated as a simple alternative to other wrist salvage procedures for scaphoid nonunion advanced collapse and scaphotrapezio-trapezoid arthritis. However, the extent of scaphoid that may be resected without adversely affecting carpal kinematics has never been clearly defined. Methods: Seven cadaveric upper extremities were tested in a custom motion wrist simulator. A 3-stage sequential sectioning of the distal scaphoid protocol was performed in 25% increments then cyclic active wrist flexion-extension and dart thrower’s motion trials were recorded. Results: The extent of distal scaphoid resection had no effect on overall wrist range of motion. The lunate assumed a more extended position following resection of the distal scaphoid compared to intact. At 25%, 50%, and 75% of distal scaphoid resection, the lunate extended to 13.32° ± 9.4°, 23.43° ± 7.5°, and 15.81° ± 16.9°, respectively. The capitate migrated proximally with 25% and 50% distal scaphoidectomy, and proximally and radially with 75% of the scaphoid resected. Resection of 75% of the scaphoid resulted in unstable wrist kinematics. Conclusions: Resection of up to 25% of the distal scaphoid did not significantly influence carpal kinematics and induced mild lunate extension deformity. Resection of 50% of the scaphoid induced further and potentially clinically significant lunate extension and dorsal intercalated segment instability. Further removal of 75% of the distal scaphoid induced capitate migration radially and unpredictable wrist kinematics. Consequently, removal of over 25% of the scaphoid should be avoided or supplemented with partial wrist fusion.

Vascularized Bone Grafting for Scaphoid Nonunion with Humpback Deformity: The Surgical Technique

Background Scaphoid nonunion with humpback deformity and avascular necrosis (AVN) is a challenging problem. Correction of dorsal intercalated segment instability (DISI) requires grafting of a large and hard vascularized bone segment onto the volar side of the scaphoid. Purposes We have been treating the patients with one-incision vascularized bone grafting technique for scaphoid nonunion to improve blood supply and correct humpback deformity. We evaluated these cases retrospectively to the surgical efficacy of our procedure. Methods We harvested vascularized bone from the dorsal side of the radius using the method by Zaidemberg et al and inserted the cortical aspect into the scaphoid volar side using a direct lateral approach. Totally, 11 patients (nine males andtwo females) with a mean age of 40 years were recruited for this study. The mean time from fracture to treatment was 6 years and 3 months. The mean preoperative radiolunate angle was 25 degrees. All the patients showed AVN of the proximal scaphoid on T1-weighted images. An averaged follow-up period was 2 years and 3 months. Results Postoperative computed tomography revealed bony union in 10 patients (91% of union rate) with a mean modified Mayo'swrist score of 88 points (range, 75–100 points) and a mean disabilities of arm, shoulder, and hand (DASH) score of 4 points (range, 0–20 points). The mean radiolunate angle was corrected from 25 to 5 degrees. No adverse events were observed, except temporary mild paresthesia of the radial nerve territory in two patients. Conclusion This technique effectively corrected DISI in patients with scaphoid nonunion accompanied by humpback deformity and AVN.

Effect of Trapeziectomy on Carpal Stability

Background: The scaphoid-trapezoid-trapezium (STT) articulation stabilizes the scaphoid and links the proximal and distal carpal rows. The purpose of the study was to determine whether trapezium excision in the treatment of trapeziometacarpal (TM) arthritis affects carpal stability. Methods: A retrospective chart and radiographic review was performed on all wrists that underwent trapeziectomy with suspensionplasty or ligament reconstruction, and tendon interposition for TM arthritis between 2004 and 2016. Radiographic outcome measures included the modified carpal height ratio (MCHR) and radioscaphoid (RS), radiolunate (RL), and scapholunate (SL) angles. Degenerative change at the TM and STT joints was classified according to the Eaton-Littler, and Knirk and Jupiter classification systems. Radiographic parameters were compared between preoperative and final follow-up time points. Results: A total of 122 wrists were included in the study with a mean follow-up of 3.5 years (range: 1.0-13.0 years). The mean RL (range: −2.2° ± 11.8° to −10.7° ± 16.5°) and RS angles (range: 52.6° ± 13.8° to 44.4° ± 17.8°) decreased significantly (<.001) without significant change in SL angle, indicating progressive lunate and scaphoid extension after trapeziectomy. The mean MCHR decreased significantly (range: 1.6 ± 0.1 to 1.5 ± 0.1) following trapeziectomy, indicating progressive carpal collapse. Progressive scaphoid-trapezoid arthrosis was observed following trapeziectomy. No other preoperative radiographic factors investigated were associated with significant differences in preoperative and postoperative values for radiographic outcome measures. Conclusions: Trapeziectomy can lead to loss of carpal height, coordinated extension of both the lunate and scaphoid, and progressive scaphotrapezoid arthrosis. As such, in wrists with dynamic or static carpal instability, trapeziectomy should be performed with caution due to the risk of carpal collapse with a nondissociative pattern of dorsal intercalated segment instability.

Scapholunate Ligament Injury and the Effect of Scaphoid Lengthening

Objective We hypothesized that lengthening the scaphoid in a model of scapholunate ligament injury (SLI) will result in correction of radiographic markers of dorsal intercalated segment instability (DISI) deformity. Materials and Methods An SLI with DISI deformity was created by sectioning the SL ligament, the palmar radiocarpal ligaments, and scapho-trapezio-trapezoid ligaments of a cadaveric upper extremity (n = 5). The wrist was radiographed in both anteroposterior and lateral planes to confirm creation of SLI and DISI. The scaphoid was then osteotomized at its waist. A series of grafts (1–8 mm) were then placed at the osteotomy site. Radiographs were completed at each length. The main outcome measures were scapholunate interval (SL, mm), scapholunate angle (SLA, degrees), and radiolunate angle (RLA, degrees). These values, measured following the insertion of varying graft lengths, were compared with baseline measurements taken “post-injury” status. Results The ability to create an SLI with DISI was confirmed in the postinjury group with a statistically significant change in RLA, SLA, and SL compared with preinjury. With osteotomy and progressive insertion of spacers, the values improved into the accepted normal ranges for RLA (6 mm) and SLA (4 mm) with scaphoid lengthening. Conclusions In this cadaveric model of SL injury, radiographic markers of DISI were returned to within normal ranges with scaphoid osteotomy and lengthening. Clinical Relevance The results of this study add insight into wrist kinematics in our injury model and may represent a potential future direction for surgical treatment of SLI.

The Effects of Capitate Height Alteration on Dorsal Intercalated Segment Instability

Question/Purpose Carpal kinematics may be influenced by the manipulation of carpal dimensions. This may provide a surgical alternative to unpredictable soft tissue reconstruction for scapholunate dissociation. The purpose of this study was to determine if altering capitate height can correct dorsal intercalated segment instability (DISI). Materials and Methods Five cadaveric wrists had baseline radiolunate (RL) angles and scapholunate (SL) intervals measured fluoroscopically, confirming no baseline DISI. We simulated open- and clenched-fist testing via a constant load of the wrist extensors and sequential loading of the digital flexors. We confirmed no baseline static/dynamic DISI. The SL ligament and secondary stabilizers (scapho-trapezio-trapezoid [STT] and dorsal intercarpal ligaments) were transected. Repeat loading and fluoroscopic measurements confirmed creation of static DISI. Capitate height was altered in three interventions: 2 mm shortening osteotomy of capitate waist, 7 mm shortening osteotomy of capitate waist, and 2 mm lengthening of original capitate height by insertion of a spacer at capitate waist. The osteotomized capitate was stabilized with a Kirschner wire; RL angles and SL intervals were measured via fluoroscopy during open- and clenched-fist testing. Primary and secondary outcomes were change in RL angle and SL interval, from the DISI stage to each capitate shortening and lengthening stage. Results SL ligament and secondary stabilizers sectioning created a DISI pattern, with abnormal RL angles (>15°) and widened SL intervals. Neither capitate shortening nor overexpansion corrected RL angles or SL intervals in any DISI-induced wrists. Conclusions Under the conditions studied, isolated capitate shortening or lengthening did not correct radiographic DISI posturing of the lunate following sectioning of the SL and STT interosseous ligaments. Further study of carpal kinematics with more substantial bone changes and loading of adjacent joints may be beneficial. Clinical relevance Surgeons performing capitate shortening osteotomy in isolation should not expect to improve DISI.