The Relationship Between the Tensile and the Torsional Properties of the Native Scapholunate Ligament and Carpal Kinematics.

PURPOSE: The purpose of this exploratory study was to examine the relationship between the tensile and the torsional properties of the native scapholunate interosseous ligament (SLIL) and kinematics of the scaphoid and lunate of an intact wrist during passive radioulnar deviation. METHODS: Eight fresh-frozen cadaveric specimens were transected at the elbow joint and loaded into a custom jig. Kinematic data of the scaphoid and lunate were acquired in a simulated resting condition for 3 wrist positions-neutral, 10° radial deviation, and 30° ulnar deviation-using infrared-emitting rigid body trackers. The SLIL bone-ligament-bone complex was then resected and loaded on a materials testing machine. Specimens underwent cyclic torsional and tensile testing and SLIL tensile and torsional laxity were evaluated. Correlations between scaphoid and lunate rotations and SLIL tensile and torsional properties were determined using Pearson correlation coefficients. RESULTS: Ulnar deviation of both the scaphoid and the lunate were found to decrease as the laxity of SLIL in torsion increased. In addition, the ratio of lunate flexion-extension to radial-ulnar deviation was found to increase with increased SLIL torsional rotation. CONCLUSIONS: Our findings support the theory that there is a relationship between scapholunate kinematics and laxity at the level of the interosseous ligaments. CLINICAL RELEVANCE: Laxity and, specifically, the tensile and torsional properties of an individual's native SLIL should guide reconstruction using a graft material that more closely replicates the individual's native SLIL properties.

Ankle joint contact loads and displacement in syndesmosis injuries repaired with Tightropes compared to screw fixation in a static model.

BACKGROUND: The effect of syndesmotic fixation on restoration of pressure mechanics in the setting of a syndesmotic injury is largely unknown. The purpose of this study is to examine the contact mechanics of the tibiotalar joint following syndesmosis fixation with screws versus a flexible fixation device for complete syndesmotic injury. METHODS: Six matched pairs of cadaveric below knee specimens were dissected and motion capture trackers were fixed to the tibia, fibula, and talus and a pressure sensor was placed in the tibiotalar joint. Each specimen was first tested intact with axial compressive load followed by external rotation while maintaining axial compression. Next, syndesmotic ligaments were sectioned and randomly assigned to repair with either two TightRopes® or two 3.5 mm cortical screws and the protocol was repeated. Mean contact pressure, peak pressure, reduction in contact area, translation of the center of pressure, and relative talar and fibular motion were calculated. Specimens were then cyclically loaded in external rotation and surviving specimens were loaded in external rotation to failure. RESULTS: No differences in pressure measurements were observed between the intact and instrumented states during axial load. Mean contact presure relative to intact testing was increased in the screw group at 5 Nm and 7.5 Nm torque. Likewise, peak pressure was increased in the TightRope group at 7.5 Nm torque. There was no change in center of pressure in the TightRope group at any threshold; however, at every threshold tested there was significant medial and anterior translation in the screw group relative to the intact state. CONCLUSION: Either screws or TightRope fixation is adequate with AL alone. With lower amounts of torque, the TightRope group appears to have contact and pressure mechanics that more closely match native mechanics.

Assessment of Open Syndesmosis Reduction Techniques in an Unbroken Fibula Model: Visualization Versus Palpation.

OBJECTIVES: This cadaveric study sought to evaluate the accuracy of syndesmotic reduction using direct visualization via an anterolateral approach compared with palpation of the syndesmosis through a laterally based incision. METHODS: Ten cadaveric specimens were obtained and underwent baseline computed tomography (CT) scans. Subsequently, a complete syndesmotic injury was simulated by transecting the anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, transverse ligament, interosseous membrane, and deltoid ligament. Three orthopaedic trauma surgeons were then asked to reduce each syndesmosis using direct visualization via an anterolateral approach. Specimens were then stabilized and underwent postreduction CT scans. Fixation was then removed, the anterolateral exposure was closed, and the surgeons were then asked to reduce the syndesmosis using palpation only via a direct lateral approach. Specimens were again instrumented and underwent postreduction CT scans. Two-tailed paired t tests were used to compare reductions with baseline scans with significance set at P < 0.05. RESULTS: There was no statistically significant difference between reduction via direct visualization or palpation via lateral approach when compared with baseline scans. Although measurements did not reach significance, there was a tendency toward external rotation, and anteromedial translation with direct visualization, and a trend toward fibular external rotation and posterolateral translation with palpation. CONCLUSIONS: There is no difference in reduction quality using direct visualization or palpation to assess the syndesmosis. Surgeons may therefore choose either technique when reducing syndesmotic injures based on personal preference and other injury factors.

Anatomy and Biomechanics of the Finger Proximal Interphalangeal Joint.

A complete understanding of the normal anatomy and biomechanics of the proximal interphalangeal joint is critical when treating pathology of the joint as well as in the design of new reconstructive treatments. The osseous anatomy dictates the principles of motion at the proximal interphalangeal joint. Subsequently, the joint is stabilized throughout its motion by the surrounding proximal collateral ligament, accessory collateral ligament, and volar plate. The goal of this article is to review the normal anatomy and biomechanics of the proximal interphalangeal joint and its associated structures, most importantly the proper collateral ligament, accessory collateral ligament, and volar plate.

Tensile and Torsional Structural Properties of the Native Scapholunate Ligament.

PURPOSE: The ideal material for reconstruction of the scapholunate interosseous ligament (SLIL) should replicate the mechanical properties of the native SLIL to recreate normal kinematics and prevent posttraumatic arthritis. The purpose of our study was to evaluate the cyclic torsional and tensile properties of the native SLIL and load to failure tensile properties of the dorsal SLIL. METHODS: The SLIL bone complex was resected from 10 fresh-frozen cadavers. The scaphoid and lunate were secured in polymethylmethacrylate and mounted on a test machine that incorporated an x-y stage and universal joint, which permitted translations perpendicular to the rotation/pull axis as well as nonaxial angulations. After a 1 N preload, specimens underwent cyclic torsional testing (±0.45 N m flexion/extension at 0.5 Hz) and tensile testing (1-50 N at 1 Hz) for 500 cycles. Lastly, the dorsal 10 mm of the SLIL was isolated and displaced at 10 mm/min until failure. RESULTS: During intact SLIL cyclic torsional testing, the neutral zone was 29.7° ± 6.6° and the range of rotation 46.6° ± 7.1°. Stiffness in flexion and extension were 0.11 ± 0.02 and 0.12 ± 0.02 N m/deg, respectively. During cyclic tensile testing, the engagement length was 0.2 ± 0.1 mm, the mean stiffness was 276 ± 67 N/mm, and the range of displacement was 0.4 ± 0.1 mm. The dorsal SLIL displayed a 0.3 ± 0.2 mm engagement length, 240 ± 65 N/mm stiffness, peak load of 270 ± 91 N, and displacement at peak load of 1.8 ± 0.3 mm. CONCLUSIONS: We report the torsional properties of the SLIL. Our novel test setup allows for free rotation and translation, which reduces out-of-plane force application. This may explain our observation of greater dorsal SLIL load to failure than previous reports. CLINICAL RELEVANCE: By matching the natural ligament with respect to its tensile and torsional properties, we believe that reconstructions will better restore the natural kinematics of the wrist and lead to improved outcomes. Future clinical studies should aim to investigate this further.

Association of Lunate Morphology With Carpal Instability in Scapholunate Ligament Injury.

BACKGROUND: We examined the relationship between lunate morphology (type 1 without a medial facet; type II with a medial facet) and dorsal intercalated segmental instability (DISI) in patients with scapholunate ligament injuries. We tested the primary null hypothesis that there is no relationship between lunate morphology and development of DISI. Secondary analysis compared the agreement of classifying lunate morphology based on the presence of a medial lunate facet, capitate-to-triquetrum (CT) distance, and magnetic resonance imaging (MRI). METHODS: We performed a retrospective chart review of patients with known scapholunate ligament injuries from 2001 to 2016. Posterior-anterior radiographs and MRI, when available, were evaluated. CT distances were measured as a secondary classification method. DISI and scapholunate instability were determined as radiolunate angle >15° and scapholunate angle >60°, respectively. Differences between groups were determined using chi-square analysis with significance set at P < .05. Agreement between plain radiographs, MRI, and CT distance was calculated using the kappa statistic. RESULTS: Our search found 58 of 417 patients who met inclusion criteria; 41 of 58 had type II and 17 of 58 had type I lunates. There was no significant difference between groups in regard to DISI or scapholunate instability. Subanalysis using MRI alone or correcting any discrepancy between plain film and MRI classification, using MRI as the standard, found no difference between groups in regard to DISI or scapholunate instability. CONCLUSIONS: In patients with scapholunate ligament injuries, there are no differences in the development of DISI or scapholunate instability between patients with type I and type II lunates.

Treatment Trends in Older Adults With Midshaft Clavicle Fractures.

PURPOSE: We present a retrospective administrative claims database review examining the effect of recent literature supporting surgical clavicle fixation in a primarily young male population, on the treatment of midshaft clavicle fractures in patients older than 65 years. We tested the null hypothesis that there is no change in trends in surgical fixation of midshaft clavicle fractures in patients older than 65 years. Secondary analysis examined overall trends and trends based on sex. METHODS: Data from 2007 to 2012 were extracted using the Medicare Standard Analytic File and Humana administrative claim databases contained within the PearlDiver Patient Records Database. Patients with clavicle shaft fractures and their treatments were identified by International Classification of Disease, Ninth Revision, and Current Procedural Terminology codes. The primary response variable was the proportion of surgical to nonsurgical cases per year, and explanatory variables included age and sex. Data were analyzed using a trend in proportions test with significance set at P less than .05. RESULTS: A total of 32,929 patients with clavicle shaft fractures were identified. During the study period, the proportion of clavicle shaft fractures treated surgically in patients older than 65 years (2.4%-4.6%) and younger than 65 years (11.2%-16.4%) showed a significant increasing trend. When analyzed by both sex and age, there was also an increasing trend in the proportion of surgically treated males in the older than 65 years (3.3%-6.2%) and the younger than 65 years groups (10.9%-19.5%). Lastly, there was an increase in the proportion of surgically treated females older than 65 years (1.7%-3.4%) and younger than 65 years (12.1%-14.3%). CONCLUSIONS: Our analysis demonstrates an overall increase in the proportion of surgically treated clavicle shaft fractures, including in the male and female population older than 65 years. In the setting of an aging population, future research evaluating possible benefits of surgical intervention in this population is needed prior to adopting this practice pattern. TYPE OF STUDY/LEVEL OF EVIDENCE: II.

Cost Minimization Analysis of Ganglion Cyst Excision.

PURPOSE: Cost minimization analysis can be employed to determine the least costly option when multiple treatments lead to equivalent outcomes. We present a cost minimization analysis from the payers' perspective, of the direct per patient cost of arthroscopic versus open ganglion cyst excision. We tested the null hypothesis that there is no difference in cost between the 2 procedures from the payer perspective. METHODS: We utilized data from a private payer administrative claims database comprising 16 million individuals from 2007 to 2015. Using Current Procedural Terminology codes to identify open and arthroscopic ganglion excisions, we extracted demographic data and fees paid to providers and facilities for the procedure. RESULTS: We identified 5,119 patients undergoing open ganglion cyst excision and 20 patients undergoing arthroscopic ganglion excision. The average cost of an open excision was significantly lower than an arthroscopic excision ($1,821 vs $3,668). CONCLUSIONS: Surgical costs from arthroscopic ganglion excision are significantly more than open excision. This data can inform health systems participating in value-based models. TYPE OF STUDY/LEVEL OF EVIDENCE: Economic and Decision Analysis IV.

Ulnar-sided wrist pain in the athlete (TFCC/DRUJ/ECU).

PURPOSE OF REVIEW: The goal of this manuscript is to review key historic and recent literature regarding extensor carpi ulnaris (ECU), triangular fibrocartilage complex (TFCC) and distal radioulnar joint (DRUJ) injuries, particularly in athletes. RECENT FINDINGS: Many recent studies examining the ECU focus on clinical and radiographic diagnosis. Several physical exam findings are described in addition to the use of MRI and US. Imaging studies must be clinically correlated due to high incidence of findings in asymptomatic patients. In regard to the TFCC/DRUJ, there are numerous recent studies that support the use of MRA as an adjunctive diagnostic study. There are also a number of repair constructs that are described for the various different kinds of TFCC pathology reviewed here. In summary, there are a number of options for the diagnosis and treatment of ulnar-sided wrist pain. Patient factors, especially in the athletic population, must be taken into account when approaching any patient with these pathologies.