Constraint and material properties of the subregions of the scapholunate interosseous ligament

Partial Scapholunate Interosseous Ligament Injuries: A Systematic Review of Treatment Options

Purpose  This systematic review summarizes the existing evidence on treatment options and outcomes for partial scapholunate interosseous ligament (pSLIL) injuries. Methods  A systematic electronic search of Medline, Embase, and CINAHL was performed from inception through to February 13, 2022. All primary research articles addressing the treatment of pSLIL tears were eligible for inclusion regardless of timing of surgery, surgical technique, or rehabilitation. The PRISMA Checklist guided the reporting and data abstraction. Descriptive statistics and forest plots are presented. Results  A total of 14 studies with 342 patients were included for analysis. Treatments were categorized into four groups: electrothermal shrinkage (ES), arthroscopic capsuloplasty (AC), open capsulodesis (OC), and no treatment (NT). There were five studies in the ES group ( N  = 69, mean age = 34.3 ± 3.3 years), three studies in the AC group ( N  = 138, mean age = 32.2 ± 3.8 years), five studies in the OC group ( N  = 123, mean age of 30.7 ± 7.8 years), and one study in the NT group ( N  = 12, mean age = 43 years, range = 28-67 years). The average postintervention visual analog scale pain score for the ES group was 1.4 ± 0.5 (from 5.7 ± 1.8), for the AC group was 3.2 ± 1.3 (from 6.6 ± 0), for the OC group was 2.3 ± 2.1 (from 5.6 ± 1.6), and for the NT group was 3.2 (from 7.6). The wrist extension range of motion improved postoperatively for all intervention groups (ES = 66.3°-70.7°; AC = 67°-74.5°; and OC = 48.9°-63.5°), whereas it remained unchanged for the NT group (46°-45°). Grip strength also improved in all intervention groups (ES = 17.9-29.9 kg; AC = 24.0-32.2 kg; and OC = 15.8-26.6 kg), while the NT group remained unchanged (25-24 kg). The radiographic scapholunate gap improved postoperatively in all groups that reported pre- and postintervention (ES = 2.2-1.9 mm; OC = 2.5-1.8 mm) and slightly worsened in the NT group (2.5-2.7 mm). In the ES group, there were three complications (11.5%, no major complications), in the AC group there was one major complication (0.9%, complex regional pain syndrome [CRPS]), and in the OC group there were six complications (15.4%, four major complications-CRPS). Conclusion  All interventional treatment options (ES, AC, and OC) provided significant improvements in patient-reported pain, range of motion, grip strength, and radiographic parameters, with low complication rates. In comparison, no improvement in range of motion or grip strength was noted in the NT group. Therefore, surgical management of pSLIL injuries is an effective and relatively safe treatment option. Further studies comparing the outcomes of specific surgical treatments are warranted to further elucidate the optimal management option for pSLIL tears. Level of Evidence  Level III, systematic review of Level III-IV studies.

Comparing Patient-Reported Outcomes on Three-Ligament Tenodesis Between Partial and Complete Scapholunate Ligament Injuries: A Cohort Study

PURPOSE

Multiple studies report outcomes after 3-ligament tenodesis (3-LT) in treating traumatic scapholunate interosseous ligament injury (SLIL). However, investigators do not differentiate between patients with partial or complete SLIL injury. The relation between the extent of SLIL disruption and surgical outcomes and if this should be considered when treating a patient with SLIL injury remains unknown. We aimed to evaluate differences in patient-rated wrist evaluation (PRWE) scores, satisfaction and return to work between patients with partial or complete chronic traumatic SLIL injury treated with 3 ligament tenodesis at 12 months after surgery.

METHODS

All patients with chronic SLIL injury (partial and complete) who were treated with 3-LT at our clinic and received the same postoperative management between December 2011 and December 2019 were studied. Only patients who had completed the PRWE and return to work questionnaires preoperatively and 12 months after surgery were included. Patients were allocated to the partial (classified as Geissler 2 or 3) or complete SLIL injury group (classified as Geissler 4) by retrospectively assessing wrist arthroscopy reports.

RESULTS

Thirty-nine patients with partial and 90 with complete SLIL injuries were included. At 1-year follow-up, PRWE scores had significantly improved in both groups. When adjusting for clinical baseline characteristics, there was no statistically significant difference between patients with partial or complete SLIL injury. Patients with complete SLIL injury had a 70% higher return to work within the first 12 months after 3-LT; however, satisfaction with the treatment result was similar for both study groups 1 year after surgery.

CONCLUSIONS

Patients with complete and partial traumatic SLIL injury report better PRWE total scores at 12 months after 3-LT, but there was no statistically significant difference between the groups in PRWE scores or satisfaction with the treatment result.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Measurement of Scapholunate Joint Space Width on Real-Time MRI-A Feasibility Study

INTRODUCTION

The scapholunate interosseous ligament is pivotal for wrist stability, and its impairment can result in instability and joint degeneration. This study explores the application of real-time MRI for dynamic assessment of the scapholunate joint during wrist motion with the objective of determining its diagnostic value in efficacy in contrast to static imaging modalities.

MATERIALS AND METHODS

Ten healthy participants underwent real-time MRI scans during wrist ab/adduction and fist-clenching maneuvers. Measurements were obtained at proximal, medial, and distal landmarks on both dynamic and static images with statistical analyses conducted to evaluate the reliability of measurements at each landmark and the concordance between dynamic measurements and established static images. Additionally, inter- and intraobserver variabilities were evaluated.

RESULTS

Measurements of the medial landmarks demonstrated the closest agreement with static images and exhibited the least scatter. Distal landmark measurements showed a similar level of agreement but with increased scatter. Proximal landmark measurements displayed substantial deviation, which was accompanied by an even greater degree of scatter. Although no significant differences were observed between the ab/adduction and fist-clenching maneuvers, both inter- and intraobserver variabilities were significant across all measurements.

CONCLUSIONS

This study highlights the potential of real-time MRI in the dynamic assessment of the scapholunate joint particularly at the medial landmark. Despite promising results, challenges such as measurement variability need to be addressed. Standardization and integration with advanced image processing methods could significantly enhance the accuracy and reliability of real-time MRI, paving the way for its clinical implementation in dynamic wrist imaging studies.

Scapholunate Ligament Injuries

Injuries to the scapholunate interosseous ligament (SLIL) complex can result in a predictable cascade of incongruous motion in the carpus that leads to radiocarpal degeneration. Both acute traumatic impact and repetitive motion can render the SLIL insufficient. A thorough understanding of SLIL anatomy is required for appropriate diagnosis and treatment. Here, we review scapholunate ligament anatomy, prevention strategies, methods of diagnosis, nonoperative and operative treatments, and outcomes. A myriad of treatment options exist for each stage of the SLIL injury, and management should be an open discussion between the patient and physician.

One-Year Outcomes of the Anatomical Front and Back Reconstruction for Scapholunate Dissociation

PURPOSE

Anatomical front and back (ANAFAB) reconstruction addresses the critical volar and dorsal ligaments associated with scapholunate dissociation. We hypothesized that patients with symptomatic, chronic, late-stage scapholunate dissociation would demonstrate improvements in all radiographic parameters and patient-reported outcomes (PROMs) after ANAFAB reconstruction.

METHODS

From 2018 to 2021, 21 ANAFAB reconstructions performed by a single surgeon were followed prospectively, with 20 patients having a minimum follow-up of 12 months. In total, 17 men and four women were included, with an average age of 49 years. Three patients had modified Garcia-Elias stage 3 disease, eight stage 4, seven stage 5, and three stage 7. ANAFAB reconstruction of intrinsic and extrinsic ligament stabilizers was performed using a hybrid synthetic tape/tendon graft in a transosseous reconstruction. Pre- and postoperative radiographic parameters, grip, pinch strength, the Patient-Rated Wrist Evaluation, PROMIS Upper Extremity Function, and PROMIS Pain Interference outcome measures were compared.

RESULTS

Mean follow-up was 17.9 months (range: 12-38). Radiographic parameters were improved at follow-up, including the following: scapholunate angle (mean 75.3° preoperatively to 69.2°), scapholunate gap (5.9-4.2 mm), dorsal scaphoid translation (1.2-0.2 mm), and radiolunate angle (13.5° to 1.8°). Mean Patient-Rated Wrist Evaluation scores for pain and function decreased from 40.6 before surgery to 10.4. We were unable to detect a significant difference in grip or pinch strength or radioscaphoid angle with the numbers tested. There were two minor complications, and two complications required re-operations, one patient who was converted to a proximal row carpectomy for failure of fixation, and one who required tenolysis/arthrolysis for arthrofibrosis.

CONCLUSIONS

At 17.9-month average follow-up, radiographic and patient-reported outcome parameters improved after reconstruction of the critical dorsal and volar ligament stabilizers of the proximal carpal row with the ANAFAB technique.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Ligamentoplasty in scapholunate instability: short-term results of the "all dorsal scapholunate repair" technique

Injury to the scapholunate complex is the cause of scapholunate instability which can lead to radiocarpal and medio-carpal osteoarthritis. Several ligamentoplasty techniques have been reported for the treatment of chronic scapholunate instability before the osteoarthritis stage. The objective of this study was to assess the short-term results of an "all dorsal scapholunate repair" ligamentoplasty. We report the clinical, radiological and functional results of a retrospective study including 21 patients, operated between June 2019 and December 2020 for a stage 3 or 4 scapholunate instability according to the Garcia Elias classification. With a follow-up of 14.2 months, the pain was 0.1/10 according to the VAS at rest and 4/10 during exercise. Wrist strength was measured at 65% of the opposite side. The flexion-extension range of motion was 105°. Radiologically, there was a reduction of the diastasis and scapholunate angle. Osteolysis areas around the anchors were described in 47% of patients. The mean QuickDASH was 29.2/100, PRWE 24/100 and Mayo wrist score 67.8/100. Eighty-one percent of patients were satisfied. Seventeen patients had returned to work 5.2 months postoperatively. In the case of work-related injury, the functional scores were poorer, with a delayed return to work. This technique provides encouraging results in the short term. Most patients were improved compared to preoperative state. The work-related injury appears to be a poor prognostic factor. A longer-term study is imperative to confirm the maintenance over time of the correction of carpal malalignment and the evolution of the osteolysis areas.Level of evidence: Level IV Retrospective study.

Correlation between dorsal capsulo-scapholunate septum (DCSS) lesion and predynamic scapholunate instability

OBJECTIVE

Scapholunate instability is the most common ligament injury of the wrist. In case of predynamic instability, diagnosis can be difficult, even under arthroscopy. Scapholunate instability is not the result of an isolated injury to the scapholunate interosseous ligament. Scapholunate stability is dependent not only on the scapholunate ligament, but on a complex that is comprising intrinsic and extrinsic ligaments. The dorsal capsule-scapholunate septum (DCSS) is one of the secondary stabilizers of the scapholunate complex. The objective of the present study was to investigate the correlation between DCSS lesion and predynamic scapholunate instability.

METHOD

A prospective multicenter study included patients who underwent wrist arthroscopy for traumatic wrist. Arthroscopic DCSS lesion stage and instability according to European Wrist Arthroscopy Society stage were assessed.

RESULTS

Twenty-seven subjects were included. We found a significant correlation between pathological DCSS and predynamic scapholunate instability and a correlation between DCSS lesion severity and instability level.

CONCLUSION

Isolated DCSS lesion should be considered a predictive factor for predynamic instability.

Scapholunate Instability: Diagnosis and Management - Anatomy, Kinematics, and Clinical Assessment - Part I

Injuries to the scapholunate joint are the most frequent cause of carpal instability. The sequelae of these injuries account for considerable morbidity, and if left untreated, may lead to scapholunate advanced collapse and progressive deterioration of the carpus. Rupture of the scapholunate interosseous ligament and its critical stabilizers causes dyssynchronous motion between the scaphoid and lunate. Additional ligament injury or attenuation leads to rotary subluxation of the scaphoid and increased scapholunate gap. Intervention for scapholunate instability is aimed at halting the degenerative process by restoring ligament integrity and normalizing carpal kinematics. In the first section of this review, we discuss the anatomy, kinematics, and biomechanical properties of the scapholunate ligament as well as its critical ligament stabilizers. We provide a foundation for understanding the spectrum of scapholunate ligament instability and incorporate meaningful new anatomical insights that influence treatment considerations. The purpose is to provide an update regarding the anatomy of the scapholunate ligament complex, importance of the critical ligament stabilizers of the proximal carpal row, introduction of safe technique to surgically expose the scaphoid and lunate, as well as pathoanatomy as it pertains to the treatment of scapholunate dissociation. In the second section of this review, we propose a novel ligament-based treatment algorithm based on the stage of injury, degree and nature of ligament damage, and presence of arthritic changes.

Clinical Outcomes of Arthroscopic-Assisted Volar Scapholunate Capsulodesis: A Case Series

Purpose  We have previously described arthroscopic-assisted volar scapholunate (SL) capsulodesis as an alternative technique for addressing volar SL interosseous ligament (SLIL) injuries. In this article, we report the outcomes of this procedure in a cohort of patients. Methods  Postoperative outcomes including range of motion, grip strength, visual analog scale (VAS) pain score, Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), and Mayo Wrist Score were assessed through a prospective review of six patients in a single center who underwent this procedure. Results  Six patients (four male and two female) with a mean age of 43 ± 14 years were evaluated in the study. The mean duration of follow-up was 41 ± 17 weeks. Postoperative outcomes noted a reduction in VAS pain score from 8 before surgery to 0.7 postoperatively ( p  = 0.00004) and improvement in Mayo Wrist Score (42 preoperatively to 80 postoperatively; p  = 0.001), grip strength (86% of contralateral side; p  = 0.20), and flexion arc (81% of contralateral side; p  = 0.08). QuickDASH was 20 ± 8 and Patient-Rated Wrist Evaluation score was 13 ± 2 at the last clinical follow-up. There was an improvement in SL gap ( p  = 0.03), SL angle ( p  = 0.11), and radiolunate angle ( p  = 0.15) measurements postoperatively. Conclusions  The described arthroscopic-assisted volar SL capsulodesis in this study presents an alternative method to address volar SLIL pathology with positive short-term clinical outcomes. Clinical Relevance  Arthroscopic-assisted volar SL capsulodesis may be considered in the treatment algorithm for volar SLIL injuries.

Assessing carpal kinematics following scapholunate interosseous ligament injury ex vivo using four-dimensional dynamic computed tomography

BACKGROUND

Scapholunate interosseous ligament injuries are prevalent and often challenging to diagnose radiographically. Four-dimensional CT allows visualization of carpal bones during motion. We present a cadaveric model of sequential ligamentous sectionings ("injuries") to quantify their effects on interosseous proximities at the radioscaphoid joint and scapholunate interval. We hypothesized that injury, wrist position, and their interaction affect carpal arthrokinematics.

METHODS

Eight cadaveric wrists were moved through flexion-extension and radioulnar deviation after injuries. Dynamic CT images of each motion were acquired in each injury condition using a second-generation dual-source CT scanner. Carpal osteokinematics were used to calculate arthrokinematic interosseous proximity distributions during motion. Median interosseous proximities were normalized and categorized by wrist position. Linear mixed-effects models and marginal means tests were used to compare distributions of median interosseous proximities.

FINDINGS

The effect of wrist position was significant for both flexion-extension and radioulnar deviation at the radioscaphoid joint; the effect of injury was significant for flexion-extension at the scapholunate interval; and the effect of their interaction was significant for radioulnar deviation at the scapholunate interval. Across wrist positions, radioscaphoid median interosseous proximities were less able to distinguish injury conditions versus scapholunate proximities. Median interosseous proximities at the scapholunate interval are majoritively able to detect differences between less (Geissler I-III) versus more (Geissler IV) severe injuries when the wrist is flexed, extended, and ulnarly-deviated.

INTERPRETATION

Dynamic CT enhances our understanding of carpal arthrokinematics in a cadaveric model of SLIL injury. Scapholunate median interosseous proximities in flexion, extension, and ulnar deviation best demonstrate ligamentous integrity.

Evaluation of Scapholunate Injury and Repair with Dynamic (4D) CT: A Preliminary Report of Two Cases

Background  In predynamic or dynamic scapholunate (SL) instability, standard diagnostic imaging may not identify SL interosseous ligament (SLIL) injury, leading to delayed detection and intervention. This study describes the use of four-dimensional computed tomography (4DCT) in identifying early SLIL injury and following injured wrists to 1-year postoperatively. Description of Technique  4DCT acquires a series of three-dimensional volume data with high temporal resolution (66 ms). 4DCT-derived arthrokinematic data can be used as biomarkers of ligament integrity. Patients and Methods  This study presents the use of 4DCT in a two-participant case series to assess changes in arthrokinematics following unilateral SLIL injury preoperatively and 1-year postoperatively. Patients were treated with volar ligament repair with volar capsulodesis and arthroscopic dorsal capsulodesis. Arthrokinematics were compared between uninjured, preoperative injured, and postoperative injured (repaired) wrists. Results  4DCT detected changes in interosseous distances during flexion-extension and radioulnar deviation. Generally, radioscaphoid joint distances were greatest in the uninjured wrist during flexion-extension and radioulnar deviation, and SL interval distances were smallest in the uninjured wrist during flexion-extension and radioulnar deviation. Conclusion  4DCT provides insight into carpal arthrokinematics during motion. Distances between the radioscaphoid joint and SL interval can be displayed as proximity maps or as simplified descriptive statistics to facilitate comparisons between wrists and time points. These data offer insight into areas of concern for decreased interosseous distance and increased intercarpal diastasis. This method may allow surgeons to assess whether (1) injury can be visualized during motion, (2) surgery repaired the injury, and (3) surgery restored normal carpal motion. Level of Evidence  Level IV, Case series.

Biomechanical Analysis of Three Different Reconstruction Techniques for Scapholunate Instability: A Cadaveric Study

BACKGROUND

This study aimed to compare the biomechanical strength of 360° scapholunate interosseous ligament (SLIL) reconstruction only using an artificial material (AM), double dorsal limb (DDL) SLIL reconstruction only using AM, and the modified Brunelli technique (MBT) with ligament.

METHODS

Eight cadaver wrists were used for this study. The SL interval, SL angle, and radiolunate (RL) angle were recorded with MicroScribe. The SL distance was measured after dividing the volar and dorsal aspects. We utilized four different wrist postures (neutral, flexion, extension, and clenched fist) to compare five conditions: intact wrist, SLIL resection, 360° SLIL reconstruction using AM, DDL SLIL reconstruction using AM, and MBT SLIL reconstruction with ligament.

RESULTS

The dorsal SL distance in the SLIL resection was widened in all wrist positions. The dorsal SL distance was restored with all three techniques and in all wrist positions. The volar SL distance in the wrist extension position was widened in the SLIL resection condition. The volar SL distance was restored in the extension position after 360° SLIL reconstruction using AM condition. There were no statistically significant differences in SL and RL angles among the conditions.

CONCLUSIONS

All three reconstruction techniques could restore the dorsal SL distance. However, only the 360° SLIL reconstruction using AM restored the volar SL distance in the wrist extension position. DDL SLIL reconstruction using AM tended to overcorrect, whereas 360° SLIL reconstruction using AM effectively stopped volar SL interval widening.

Arthroscopic-Assisted Volar Scapholunate Capsulodesis: A New Technique

Most current surgical techniques for scapholunate interosseous ligament injuries address the dorsal component only. Previously, volar capsulodesis has been described either as an open approach or an "all-inside" technique. In this article, we report an alternative arthroscopic technique to address volar scapholunate interosseous ligament injuries. Arthroscopic-assisted volar scapholunate capsulodesis may be considered in the treatment algorithm for volar scapholunate interosseous ligament injuries.

A fluid-structure interaction investigation of intra-articular pressure and ligament in wrist joint

Understanding the stresses on the scapholunate interosseous ligament (SLIL) and its interaction with synovial fluid pressure could be vital to improve wrist treatment for various wrist conditions such as arthritis, sprains and tendonitis. This study investigated the interaction between the intra-articular pressure, specifically the synovial fluid pressure change and the SLIL stresses in a computational model during wrist radioulnar deviation (RUD). Magnetic resonance imaging (MRI) scans were used to acquire the anatomical model of the carpal bones and ligament, while the kinematics of scaphoid and lunate were obtained through dynamic computerized tomography (CT) scans. A two-way fluid-structure interaction (FSI) was used to model the dynamics between the scaphoid and lunate, the SLIL, and the synovial fluid. The synovial fluid pressure change was found to be small (-4.86 to 3.23 Pa) and close to that simulated in a previous work without the SLIL (-1.68 to 2.64 Pa). Furthermore, peaks of maximum fluid pressure were found to trail the peaks of ligament stress. Therefore, it is suggested that the influence of synovial fluid pressure on the ligament in the SLIL model is negligible and simulations of the scapholunate joint could forego fluid-structure interactions. Future studies can instead explore other structures in the carpus that can possibly contribute to the ligament stresses. Clinically, treatments can be targeted at these areas to help prevent or slow the progression of ligament injuries into serious consequences like the degenerative joint disease.

Biomechanical Finite Element Method Model of the Proximal Carpal Row and Experimental Validation

The Finite Element Method (FEM) models are valuable tools to create an idea of the behavior of any structure. The complexity of the joints, materials, attachment areas, and boundary conditions is an open issue in biomechanics that needs to be addressed. Scapholunate instability is the leading cause of wrist pain and disability among patients of all ages. It is needed a better understanding of pathomechanics to develop new effective treatments. Previous models have emulated joints like the ankle or the knee but there are few about the wrist joint. The elaboration of realistic computational models of the carpus can give critical information to biomedical research and surgery to develop new surgical reconstructions. Hence, a 3D model of the proximal carpal row has been created through DICOM images, making a reduced wrist model. The materials, contacts, and ligaments definition were made via open-source software to extract results and carry on a reference comparison. Thus, considering the limitations that a reduced model could carry on (unbalanced forces and torques), the stresses that result in the scapholunate interosseous ligament (SLIL) lead us to a bones relative displacement, which support the kinematics hypothesis in the literature as the distal carpal row moves as a rigid solid with the capitate bone. Also, experimental testing is performed, successfully validating the linear strength values of the scapholunate ligament from the literature.

Design Requirements for Scapholunate Interosseous Ligament Reconstruction

Background  As numerous repairs, reconstructions, and replacements have been used following scapholunate interosseous ligament (SLIL) injury, there is a need to define the structural requirements for any reconstruction or replacement. Methods  Research has been conducted on the force needed to keep the scaphoid and lunate reduced following simulated injury, the failure force of the native SLIL and various replacements, the stiffness of the SLIL and replacements, and the torsional resistance of the scaphoid relative to the lunate. Results  Forces on the order of 50 N are needed to keep the scaphoid and lunate reduced during simple wrist motions in the chronically injured wrist. Even greater forces (up to 110 N) are needed to keep the bones reduced during strenuous activities, such as pushups. The failure force of the entire SLIL has been reported to be as high as 350 N and the failure force of just the dorsal component of the SLIL to be 270 N. Conclusions  The design requirements for a reconstruction or repair may vary depending upon the demands of the patient. In a high demand patient, a reconstruction needs to support the above-mentioned forces during cyclic loading (50 N), when performing strenuous activities (110 N), or during a fall (at least 350 N). Any artificial replacement must undergo careful biocompatibility testing.

Histomorphology of the Subregions of the Scapholunate Interosseous Ligament and Its Enthesis

Background  The scapholunate interosseous ligament (SLIL) has three subregions: dorsal, proximal, and volar. The SLIL enthesis has not previously been studied despite its important mechanical function in wrist joint biomechanics. Questions/Purposes  This study aims to compare the histomorphological differences between the SLIL subregions, including at their entheses. Three questions are explored: Do the gross dimensions differ between SLIL subregions? Does the enthesis qualitatively, and its calcified fibrocartilage (CF) quantitatively, differ between (a) SLIL subregions and (b) scaphoid and lunate attachments? Methods  Twelve fresh-frozen human cadaveric wrists were dissected and the gross dimensions of the SLIL subregions measured. Subregions were histologically processed for morphological and compositional analyses, including quantification of enthesis CF area. Results  The dorsal subregion was the thickest. The dorsal and volar subregions had fibrocartilaginous entheses, while the proximal subregion was attached to articular cartilage. The dorsal subregion had significantly more CF than the volar subregion. There was no significant difference in the enthesis CF between scaphoid and lunate attachments in the three subregions. Conclusions  There are significant morphological differences between the SLIL subregions. The dorsal subregion has the largest amount of CF, which is consistent with the greater biomechanical force subjected to this subregion. The similar histomorphology of the ligament at the scaphoid and lunate entheses suggests that similar biomechanical forces are applied to both attachments. Clinical Relevance  The histomorphological results confirm that the dorsal subregion is the strongest of the three subregions. The results from the entheseal region may have important implications in the study of graft incorporation during SLIL reconstruction.

Ligamentization and Remnant Integration: Review and Analysis of Current Evidence and Implications for Scapholunate Reconstruction

Background  Scapholunate interosseous ligament injuries are common but remain a therapeutic challenge. Current treatment modalities prioritize restoration of normal anatomy with reconstruction where appropriate. To date no reconstructive technique has been described that discusses the potential benefit of preservation of the scapholunate ligament remnant. Little is known about the "ligamentization" of grafts within the wrist. However, a growing body of knee literature suggests that remnant sparing may confer some benefit. In the absence of wrist specific studies, this literature must guide areas for potential augmentation of current surgical practices. Objective  The purpose of this study was to perform a review of the process of ligamentization and a systematic review of the current literature on the possible role of ligament sparring and its effect on ligamentization. Methods  A systematic search of the literature was performed to identify all the studies related to remnant sparing and the ligamentization of reconstructed tendons, regardless of graft type or joint involved from MEDLINE, EMBASE, and PubMed until February 1, 2016 using the following keywords: ligamentization, graft, remodelling, reconstruction, biomechan*, histolo∗, scapholunate ligament. Each selected study was evaluated for methodological quality and risk of bias according to a modified Systematic Review Center for Laboratory Animal Experimentation criteria. Conclusions  The available literature suggests that ligament sparring demonstrated a trend toward improvements in vascularity, mechanoreceptors, and biomechanics that lessens in significance over time. Clinical Relevance  This review suggests that remnant sparing may be one way to improve outcomes of scapholunate ligament reconstructive surgery. Level of Evidence  This is a level I/II, review study.

Finite element analysis of the performance of additively manufactured scaffolds for scapholunate ligament reconstruction

Rupture of the scapholunate interosseous ligament can cause the dissociation of scaphoid and lunate bones, resulting in impaired wrist function. Current treatments (e.g., tendon-based surgical reconstruction, screw-based fixation, fusion, or carpectomy) may restore wrist stability, but do not address regeneration of the ruptured ligament, and may result in wrist functional limitations and osteoarthritis. Recently a novel multiphasic bone-ligament-bone scaffold was proposed, which aims to reconstruct the ruptured ligament, and which can be 3D-printed using medical-grade polycaprolactone. This scaffold is composed of a central ligament-scaffold section and features a bone attachment terminal at either end. Since the ligament-scaffold is the primary load bearing structure during physiological wrist motion, its geometry, mechanical properties, and the surgical placement of the scaffold are critical for performance optimisation. This study presents a patient-specific computational biomechanical evaluation of the effect of scaffold length, and positioning of the bone attachment sites. Through segmentation and image processing of medical image data for natural wrist motion, detailed 3D geometries as well as patient-specific physiological wrist motion could be derived. This data formed the input for detailed finite element analysis, enabling computational of scaffold stress and strain distributions, which are key predictors of scaffold structural integrity. The computational analysis demonstrated that longer scaffolds present reduced peak scaffold stresses and a more homogeneous stress state compared to shorter scaffolds. Furthermore, it was found that scaffolds attached at proximal sites experience lower stresses than those attached at distal sites. However, scaffold length, rather than bone terminal location, most strongly influences peak stress. For each scaffold terminal placement configuration, a basic metric was computed indicative of bone fracture risk. This metric was the minimum distance from the bone surface to the internal scaffold bone terminal. Analysis of this minimum bone thickness data confirmed further optimisation of terminal locations is warranted.

Autologous Osteoligamentous Reconstruction of Scaphoid Proximal Pole With Metatarsal Head and Collateral Ligament: Cadaver Anatomic Description of Novel Surgical Technique

Background: Historically, scaphoid nonunion has been surgically treated with vascularized bone graft taken from multiple different anatomic sites. However, none of these grafts fully recapitulate the unique osteoligamentous anatomy of the proximal pole of the scaphoid and the attachment of the scapholunate ligament (SLIL). We studied the anatomy of the vascularized second metatarsal head with its lateral collateral ligament as a potential novel treatment of proximal pole scaphoid nonunion with collapse. Methods: Scaphoids and second metatarsal heads were harvested from bilateral upper and lower extremities of 18 fresh frozen cadavers (10 male, 8 female) for a total of 36 scaphoids and 36 second metatarsal heads. The ipsilateral second metatarsal head was harvested with its lateral collateral ligament and its blood supply from the second dorsal metatarsal artery (SDMA). Measurements of the scaphoid, the SLIL, the second metatarsal head, and lateral collateral ligaments were compared to matched limbs from the same cadaver. Results: The anatomic dimensions of the second metatarsal head with its lateral collateral ligament are similar to the scaphoid proximal pole and the SLIL in matched cadaveric specimen. Conclusions: This anatomic cadaver study reveals that the second metatarsal head with its associated lateral collateral ligament is a well-matched donor to reconstruct the proximal pole of the scaphoid and SLIL. This anatomic similarity may be well suited to treat nonunion of the scaphoid proximal pole with or without avascular necrosis with simultaneous reconstruction of the SLIL. The authors describe a technique of vascularized reconstruction of the osteoligamentous proximal pole of the scaphoid with its attached SLIL utilizing autologous second metatarsal head with its attached lateral collateral ligament. Based on this cadaver study, this technique merits consideration.

Kinematic analysis of two scapholunate ligament reconstruction techniques

PURPOSE

This study compares the kinematic changes after the procedures for scapholunate interosseous ligament (SLIL) reconstruction-the modified Brunelli technique (MBT) and Mark Henry's technique (MHT).

METHODS

Ten cadaveric wrists were used. The scapholunate (SL) interval and angle and radiolunate (RL) angle were recorded using the MicroScribe system. The SL interval was measured by dividing the volar and dorsal portions. Four motions of the wrist were performed-neutral, flexion, extension, and clenched fist (CF) positions-and compared among five conditions: (1) intact wrist, (2) volar SLIL resection, (3) whole SLIL resection, (4) MBT reconstruction, and (5) MHT reconstruction.

RESULTS

Under the whole SLIL resection condition, the dorsal SL intervals were widened in all positions. In all positions, the dorsal SL intervals were restored after MBT and MHT. The volar SL interval widened in the extension position after volar SLIL resection. The volar SL interval was not restored in the extension position after MBT and MHT. The SL angle increased in the neutral and CF positions under the whole SLIL resection condition. The SL angle was not restored in the neutral and CF positions after MBT and MHT. The RL angle increased in the neutral and CF positions under the whole SLIL resection condition. The RL angle was not restored in the neutral and CF positions after MBT and MHT.

CONCLUSION

The MBT and MHT may restore the dorsal SL interval. No significant differences in restoration of the SL interval between MBT and MHT were found in the cadaveric models.

CLINICAL RELEVANCE

No significant differences between MBT and MHT were found in the cadaveric models for SLIL reconstruction. When considering the complications due to volar incision and additional procedures in MHT, MBT may be a more efficient technique in terms of operative time and injury of the anterior structures during surgery, but further research is needed.

Scapholunate and lunotriquetral interosseous ligament augmentation with internal bracing in perilunate dislocation: Case reports

RATIONALE

The goals of surgical treatment of the perilunate dislocation (PLD) are confirmation of reduction, ligament repair, and supplemental fixation of the bony architecture. Open reduction and direct repair of the torn ligament are recommended for acute PLD. However, repair of the scapholunate interosseous ligament (SLIL) and lunotriquetral interosseous ligament (LTIL) is often unreliable, and secure repair is challenging. Internal bracing (IB) is an augmentation method that uses high-strength non-absorbable tape and enhances strength and support during the critical period of ligamentous healing. However, there is a paucity of data on the application of IB for PLD in the wrist. We report 3 cases of PLD that were augmented with IB after SLIL and LTIL repair.

PATIENT CONCERNS

All 3 cases were men who visited our emergency department with wrist after falling off a ladder.

DIAGNOSES

Initial radiographs revealed a dorsal PLD.

INTERVENTIONS

Surgically, complete rupture of the SLIL and LTIL were confirmed. K-wires were placed into the scaphoid and lunate and used as joysticks to correct the intercalated segment instability pattern. This usually requires correcting scaphoid flexion and lunate extension and closing the scapholunate interval. Prior to SLIL and LTIL repair, temporary intercarpal fixation was performed with K-wires to maintain the carpal relationship. The dorsal SLIL and LTIL were carefully repaired using suture anchors. However, ligament repair was unreliable, and insecure. In view of the likelihood of insufficient repair, we performed IB augmentation using synthetic tape.

OUTCOMES

At the last follow-up, all cases were pain-free and had returned to all activities. The last follow-up radiographs showed good alignment of the carpal bones and no arthritic changes.

LESSONS

IB augmentation can reduce the period of K-wire fixation and cast immobilization and can enable early joint motion. We believe that interosseous ligament augmentation using IB is a reasonable treatment option for PLD.

Carpal Instability: II. Imaging

Beyond clinical examination, the various forms of carpal instability are assessed with radiologic methods and arthroscopy. For this purpose, the imaging demand for spatial and contrast resolution is particularly high because of the small ligamentous structures involved. The entities of carpal instability are classified into degrees of severity. Early (dynamic) forms of instability can either be indirectly detected with X-ray stress views and cineradiography or by direct visualization of ruptured ligaments in high-resolution magnetic resonance (MR) imaging and MR or computed tomography (CT) arthrography, with the latter the standard of reference in imaging. Advanced (static) forms of carpal instability are sufficiently well detected on radiographs; visualization of early carpal osteoarthritis is superior on CT. To prevent disability of the hand, the radiologist has to provide an early and precise diagnosis. This case-based review highlights the imaging procedures suitable for detection and classification of carpal instability.

Multiphasic scaffold for scapholunate interosseous ligament reconstruction: A study in the rabbit knee

Scapholunate interosseous ligament tears are a common wrist injury in young and active patients that can lead to suboptimal outcomes after repair. This research aims to assess a multiphasic scaffold using 3D-printing for reconstruction of the dorsal scapholunate interosseous ligament. The scaffold was surgically implanted in vivo in the position of the native rabbit medial collateral ligament. Two branches of treatment were implemented in the study. In the first group, the rabbits (n = 8) had the knee joint fixed in flexion for 4 weeks using 1.4 mm K-wires prior to sample harvesting. The second group (n = 8) had the rabbit knee joint immobilized for 4 weeks prior to K-wire removal and mobilization for an additional 4 weeks prior to sample harvesting. Overall, samples were harvested at 4 weeks post-surgery (immobilized group) and eight weeks post-surgery (mobilized group). Mechanical tensile testing (n = 5/group) and histology (n = 3/group) of the constructs were conducted. Tissue integration and maturation were observed resulting in increased mechanical strength of the operated joint at 8 weeks (P < .05). Bone and ligament tissues were regenerated in their respective compartments with structural and mechanical properties approaching those reported for the human dorsal SLIL ligament. Clinical Significance: This proof of concept study has demonstrated that the synthetic multiphasic scaffold was capable of regenerating both bone and ligament while also withstanding the physiological load once implanted in the rabbit knee. The artificial scaffold may provide an alternative to current techniques for reconstruction of scapholunate instability or other ligament injuries in the hand and wrist.

Carpal Instability: I. Pathoanatomy

The pathoanatomy of carpal instability is multifactorial and usually complex. A thorough medical history and clinical examination are essential, as well as profound knowledge of the specific instability patterns. The stability of the wrist is ensured by the carpal joint surfaces, by intact intra-articular (particularly the scapholunate interosseous ligament) and intracapsular ligaments, and by crossing extensor and flexor tendons, the latter making the proximal carpal row an "intercalated segment." An important classification feature is the distinction between dissociative and nondissociative forms of carpal instability. Among others, scapholunate dissociation, lunotriquetral dissociation, midcarpal instability, and ulnar translocation are the most common entities. Early forms of instability are considered dynamic. In the natural course, static instability of the wrist and osteoarthritis will develop. This review focuses on the pathoanatomical fundamentals of the various forms of carpal instability.

Innervation of the wrist joint: Literature review and clinical implications

The aim of this study was to review the literature on the innervation of the wrist with an emphasis on pathological and therapeutic aspects. The nerves involved in wrist innervation and their mechanoreceptor endings are described. The literature over the past 30 years includes several topics that are still subjects of discussion and debate and require further research.

Comparison of Three Different Internal Brace Augmentation Techniques for Scapholunate Dissociation: A Cadaveric Biomechanical Study

Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. However, there is no detailed information about the direction, location, or number of IBs required for scapholunate interosseous ligament (SLIL) injury repair. Thus, this study compared the biomechanical characteristics of short-transverse IB, long-oblique IB, and the combination of short-transverse and long-oblique (Combo) IB for SLIL injury in a biomechanical cadaveric model. We prepared nine fresh-frozen full upper extremity cadaveric specimens for this study. The scapholunate distance, scapholunate angle, and radioscaphoid angle were measured using the MicroScribe digitizing system with the SLIL intact, after scapholunate dissociation and the three different reconstructions. Three-dimensional digital records were obtained in six wrist positions in each experimental condition. Short-transverse IB had a similar effect compared with long-oblique IB in addressing the widening of the scapholunate distance. However, both were less effective than Combo IB. For scaphoid flexion deformity, short-transverse IB had minimal effect, while long-oblique IB had a similar effect compared to Combo IB. Combo IB was the most effective for improving distraction intensity and rotational strength. This study provides important information about the biomechanical characteristics of three different IB methods for SLIL injury and may be useful to clinicians in treating scapholunate dissociation.

A Biomechanical Evaluation of the ECRL Tenodesis for Reconstruction of the Scapholunate Ligament

PURPOSE

Reconstruction of the scapholunate ligament (SLL) in the setting of dynamic instability remains a surgical challenge, with lack of consensus on the best reconstructive procedure. Reconstruction of only the dorsal component may lead to volar gapping and abnormal wrist kinematics. This cadaveric active motion simulation study determined whether scapholunate (SL) motion, angulation, and contact are restored following open reconstruction using the extensor carpi radialis longus (ECRL) tenodesis, which reconstructs both the volar and the dorsal SLL components.

METHODS

Seven fresh-frozen cadaveric upper limbs (mean age, 68 ± 10.1 years) underwent a 4-stage protocol of cyclic dart-throw motion and flexion-extension motion (utilizing an active wrist motion simulator that used tendon load/motion-controlled actuation. Scaphoid and lunate motion, relative scaphoid translation, SL angle, and dorsal-volar SL diastasis were measured with (1) wrist ligaments intact, (2) following complete sectioning of the SLL, and (3) following SL reconstruction using the ECRL tenodesis technique.

RESULTS

Complete SLL sectioning resulted in a typical pattern of SL instability. Following the ECRL tenodesis, lunate extension was not corrected. Scaphoid flexion, however, was not significantly different from the native state in FEM but remained significantly flexed during dart-throw motion. Differential dorsal and volar gapping did not significantly improve following ECRL tenodesis (dorsal, 1.2-2.3 mm; volar, 1.1-1.7 mm).

CONCLUSIONS

This biomechanical study demonstrates that the ECRL tenodesis did not fully restore native carpal kinematics, despite dorsal and volar SLL, and scaphotrapeziotrapezoid reconstruction.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Narrative Review of Ligamentous Wrist Injuries

Ligamentous wrist injuries are common occurrences that require complex anatomical mastery and extensive understanding of diagnostic and treatment modalities. The purpose of this educational review article is to delve into the most clinically relevant wrist ligaments in an organized manner to provide the reader with an overview of relevant anatomy, function, clinical examination findings, imaging modalities, and options for management. Emphasis is placed on elucidating reported diagnostic accuracies and treatment outcomes to encourage evidence-based practice.

Suture Tape Augmentation for Scapholunate Ligament Repair: A Biomechanical Study

PURPOSE

Scapholunate (SL) ligament tears in the acute setting can be treated by primary repair through various techniques. The purpose of this study was to compare repair of the SL ligament with suture anchors alone versus repair of the SL ligament augmented with suture tape.

METHODS

Twelve fresh-frozen cadavers (6 matched pairs) underwent a dorsal approach to the wrist and the SL ligament was sharply dissected off of its scaphoid attachment. Six cadavers underwent direct repair of the SL ligament using 2 suture anchors. The other 6 underwent repair of the SL ligament, which was then augmented with suture tape. All specimens then underwent load to failure testing using tensile distraction forces applied by a universal testing system. Maximum load to failure and mode of failure were recorded.

RESULTS

Maximum load to failure (135 N; SD, 44.94 N) for specimens that were repaired and augmented with the internal brace was higher than that for specimens in the repair-only group (68 N; SD, 14.69 N).

CONCLUSIONS

Biomechanical testing demonstrated a higher maximum load to failure in SL ligament repairs augmented with suture tape compared with a repair-only technique in this cadaveric model.

CLINICAL RELEVANCE

Acute SL ligament injuries may benefit from suture tape augmentation by increasing the stability of the primary repair. This may prove to be beneficial in higher-demand patients.

Internal Bracing Augmentation for Scapholunate Interosseous Ligament Repair: A Cadaveric Biomechanical Study

PURPOSE

Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. This study compared scapholunate interosseous ligament (SLIL) repair alone, SLIL repair with IB augmentation (RIBA), and native intact SLIL (NIS) in a biomechanical cadaveric model.

METHODS

We used 21 specimens of fresh-frozen wrists in this study (7 matched pairs, SLIL repair-only and SLIL RIBA groups; and 7 independent fresh-frozen wrists, NIS group). In the SLIL RIBA group, augmentation using IB was performed after the repair. The specimens were preloaded and cyclically loaded in tension. Maximum extension and hysteresis were measured in all specimens. The specimens were subsequently tested for load to failure. Failure load (yield point load, mean ultimate load, and load at clinical failure) and linear stiffness were calculated.

RESULTS

In cyclic tensile testing, RIBA showed lower maximum extension and lower hysteresis than repair alone. In load to failure testing, the yield point load was statistically higher in the RIBA (59.3 N) group than in the repair-only (30.4 N) group but showed no significant difference compared with the NIS (90.7 N) groups. Moreover, the RIBA (98.5 N) group showed higher and lower mean ultimate loads than the repair-only (37.7 N) and NIS (211.8 N) groups, respectively. Load at clinical failure was higher with RIBA than with repair alone (3-mm extension: 70.0 vs 26.4 N; 4-mm extension: 84.1 vs 33.4 N). Repair alone and RIBA had comparable linear stiffness (38.2 vs 44.1 N/mm).

CONCLUSIONS

Although SLIL RIBA did not recreate biomechanical properties equivalent to those of NIS, it demonstrated a significantly higher strength than repair alone.

CLINICAL RELEVANCE

Repair with IB augmentation could serve as a novel surgical technique that enhances SLIL direct repair through biomechanical support.

Difference in Carpal Alignment between Scapholunate Dissociation and Kienbock Disease: A Retrospective Study

Introduction Scapholunate dissociation is the most frequent type of wrist instability and, if untreated, can lead to wrist osteoarthritis, known as scapholunate advanced collapse. Kienbock disease can also lead to wrist osteoarthritis. Both involve carpal instability; however, the possibility of completely different mechanisms underlying each ligamentous state and carpal malalignment must be considered.

Materials and Methods We retrospectively reviewed 17 patients with scapholunate dissociation and 14 patients with Kienbock disease. All arthroscopic findings for scapholunate dissociation were classified as Geissler grade 4. All cases of Kienbock disease were treated by lunate resection and vascularized pisiform transfer without interosseous ligament reconstruction. Carpal alignments were evaluated from pre- and postoperative radiographs.

Results Scapholunate dissociation showed greater lunate dorsiflexion and more dorsal locations of the scaphoid and capitate compared with Kienbock disease, but preoperative scaphoid flexion was similar in both groups. Eleven of 17 cases of scapholunate dissociation and no cases of Kienbock disease showed dorsal subluxation of the scaphoid preoperatively. Postoperative radiographs revealed no progression of carpal collapse in either groups.

Conclusion This study revealed the sacrifice of the scapholunate/lunotriquetral interosseous ligament do not incur static scapholunate dissociation, and that the secondary stabilizers may preserve carpal alignment.

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.

Dorsal Intercarpal Ligament Preserving Arthrotomy and Capsulodesis for Scapholunate Dissociation

Carpal instability secondary to scapholunate (SL) ligament tears can lead to a significant disability of the wrist. Different surgical procedures have been proposed to treat SL instability. A variety of dorsal capsulodesis techniques tethering the scaphoid have been used in patients with SL dissociation. We report a novel technique of modified dorsal intercarpal ligament (DICL) capsulodesis for the treatment of SL dissociation. The surgical indication for this procedure is complete SL ligament tear with a reducible carpal malalignment and no secondary osteoarthritis. This procedure is indicated when the remnant of torn ligament in the dorsal SL interosseous space is available for repair. First, carpal malalignment is corrected and the scaphoid and the lunate are temporarily fixed with a transosseous screw or Kirschner wires. Using a dorsal approach, the DICL is then exposed, which originates from the triquetrum and attaches to the scaphoid, trapezium, and trapezoid. The distal and proximal borders of the ligament are identified and elevated without detaching the attachment sites. The DICL is transferred proximally to reinforce the dorsal SL interosseous ligament. The wrist joint is immobilized for 3 weeks postoperatively, and dart-throwing motion is permitted until temporary SL fixation is removed at 2 to 3 months after surgery. A wrist brace is recommended until 3 to 6 months after the first surgery depending on the patient's occupation and sports activity.

Performance evaluation of surgical techniques for treatment of scapholunate instability in a type II wrist

We investigated the performance of three tenodesis techniques, modified Brunelli, Corella, and scapholunate axis (SLAM) methods in repairing scapholunate interosseous ligament (SLIL) disruption for a type II wrist using finite element-based virtual surgery and compared the results with those of a previous investigation for a type I wrist. In addition, a comparison of the carpal mechanics of type I and type II wrists was undertaken in order to elucidate the difference between the two types. For the type II wrist, following simulated SLIL disruption, the Corella reconstruction technique provided a superior outcome, restoring dorsal gap, volar gap, and SL angle to within 3.5%, 7.1%, and 8.4%, respectively, of the intact wrist. Moreover, application of the ligament reconstruction techniques did not significantly alter the motion pattern of the type II and type I wrists. For the type I wrist, SLIL disruption resulted in no contact between scaphoid-lunate cartilage articulation, whereas for the type II wrist, some contact was maintained. We conclude that the Corella ligamentous reconstruction technique is best able to restore SL gap, angle, and stability following SL ligament injury for both type II and type I wrists and is able to do so without altering wrist kinematics. Our findings also support the view that type I wrists exhibit row behaviour and type II wrists column behaviour. In addition, our analysis suggests that the extra articulation between the lunate and hamate in a type II wrist may help improve stability following SL ligament injury.

Scapholunate kinematics after flexible anchor repair

The scapholunate joint is one of the keystones of the wrist kinematics, and its study is difficult due to the carpal bones size and the richness of surrounding ligaments. We propose a new method of quantitative assessment of scapholunate kinematics through bone motion tracking in order to investigate scapholunate ligament lesion as well as repair techniques. On 6 intact wrists, steel beads were inserted into the bones of interest to track their motions. Experimental set up allowed wrist flexion extension and radio-ulnar deviation motions. Low-dose bi-planar radiographs were performed each 10° of movement for different configurations: 1) intact wrist, 2) scapholunate ligament division, 3) repair by soft anchors at the posterior then 4) anterior part. Beads' 3D coordinates were computed at each position from biplanar X-Rays, allowing accurate registration of each wrist bone. The Monte Carlo sensitivity study showed accuracy between 0.2° and 1.6 ° for the scaphoid and the lunate in motions studied. The maximum flexion-extension range of motion of the scaphoid significantly decreased after anterior repair from 73° in injured wrist to 62.7°. The proposed protocol appears robust, and the tracking allowed to quantify the anchor's influence on the wrist kinematics.

Additively Manufactured Multiphasic Bone-Ligament-Bone Scaffold for Scapholunate Interosseous Ligament Reconstruction

The scapholunate interosseous ligament (SLIL) is a frequently torn wrist ligament, and current surgical options for SLIL tears are suboptimal. This research aims to develop a novel multiphasic bone-ligament-bone scaffold (BLB) with a porous interface using 3D-printing and cell sheet technology for the reconstruction of the dorsal scapholunate interosseous ligament. The BLB comprises two bone compartments bridged by aligned polycaprolactone fibers mimicking the architecture of the native tissue. Mechanical testing of the BLBs shows their ability to withstand physiological forces. Combination of the BLB with human bone marrow mesenchymal stem cell sheet demonstrates that the harvesting did not compromise cell viability, while allowing homogeneous distribution in the ligament compartment. The BLBs are loaded with cell sheets and bone morphogenetic protein-2 in the ligament and bone compartment respectively prior to ectopic implantation into athymic rats. The histology demonstrates rapid tissue infiltration, high vascularization, and more importantly the maintenance of the compartmentalization as bone formation remains localized to the bone compartment despite the porous interface. The cells in the ligament compartment become preferentially aligned, and this proof-of-concept study demonstrates that the BLB can provide sufficient compartmentalization and fiber guiding properties necessary for the regeneration of the dorsal SLIL.

Scapholunate Ligament Internal Brace 360 Tenodesis (SLITT) Procedure: A Biomechanical Study

Background  Twelve paired fresh frozen cadaveric wrists were randomized to a 360-degree tenodesis repair group or the 360-degree tenodesis repair with an internal brace (suture tape) construct. Case Description  The specimens were preloaded to 5 N and subsequently biomechanically loaded to failure, at a rate of 0.1 mm/s on a jig that allowed for axial load. The maximum load and mode of failure were recorded. Load to failure in the 360 tenodesis group with internal brace was 283.47 ± 100.25 N, compared with the 360 tenodesis group only, whose yield strength was 143.61 ± 90.54 N. The mode of failure within the internal brace construct was either through knot slippage, graft disruption, or bone separation from strength testing construct. The 360 tenodesis group tended to fail via graft slippage or graft rupture. Literature Review  The management of scapholunate instability can be a difficult problem to treat. Traditionally, many of the surgical reconstructions have focused upon dorsal ligament reconstruction with Kirschner (K) wire fixation. This results in prolonged immobilization of the wrist with varied outcomes, in part due to the multiaxial instability that may persist due to concomitant volar ligament disruption. To address this instability, surgical techniques have been devised that address both the volar and dorsal ligament injuries. Clinical Relevance  Scapholunate reconstruction with a 360-degree tenodesis and internal brace augmentation (SLITT procedure) provided superior biomechanical stability than tenodesis alone.

Carpal Kinematics following Sequential Scapholunate Ligament Sectioning

Background  The scapholunate ligament (SLL) is the most commonly injured intercarpal ligament of the wrist. It is the primary stabilizer of the scapholunate (SL) joint, but the scaphotrapeziotrapezoid (STT) and radioscaphocapitate (RSC) ligaments may also contribute to SL stability. The contributions of SL joint stabilizers have been reported previously; however, this study aims to examine their contributions to SL stability using a different methodology than previous studies. Purpose  The purpose of this in vitro biomechanical study was to quantify changes in SL kinematics during wrist flexion and extension following a previously untested sequential sectioning series of the SL ligament and secondary stabilizers. Methods  Eight cadaveric upper extremities underwent active wrist flexion and extension in a custom motion wrist simulator. SL kinematics were captured with respect to the distal radius. A five-stage sequential sectioning protocol was performed, with data analyzed from 45-degree wrist flexion to 45-degree wrist extension. Results  Wrist flexion and extension caused the lunate to adopt a more extended posture following sectioning of the SLL and secondary stabilizers compared with the intact state ( p  < 0.009). The isolated disruption to the dorsal portion of the SLL did not result in significant change in lunate kinematics compared with the intact state ( p  > 0.05). Scaphoid kinematics were altered in wrist flexion following sequential sectioning ( p  = 0.013). Additionally, disruption of the primary and secondary stabilizers caused significant change to SL motion in both wrist flexion and wrist extension ( p  < 0.03). Conclusions  The SLL is the primary stabilizer of the SL articulation, with the STT and RSC ligaments playing secondary stabilization roles. Clinical Relevance  Understanding the role primary and secondary SL joint stabilizers may assist in the development of more effective treatment strategies and patient outcomes following SLL injuries.

Yoga-Induced Myositis Ossificans Traumatica of the Scapholunate Ligament

Background  Myositis ossificans traumatica (MOT) involves the heterotopic development of lamellar bone after a traumatic injury. Despite being termed "myositis," MOT is not limited to muscle but rather can involve tendons, fat, and fascia. "Traumatica" reflects that lesions are usually associated with a history of significant trauma, that is, fractures or surgery; however, many reports suggest they can also be linked to repetitive low-energy insults. In both cases, the inflammatory response secondary to tissue injury generates a proliferative osteoblastic cascade. Case Description  We present a case of persistent wrist pain in a 43-year-old woman associated with yoga activities. Her radiographic studies demonstrated partial scapholunate (SL) ligament tear and an associated mass lesion. Surgical pathology revealed MOT involving the SL ligament. Literature Review  MOT lesions in the upper extremity are usually localized around the elbow, and cases in the hand are relatively rare. There are no prior reports of occurrences within the wrist joint or in association with the SL ligament. However, biomechanical studies have quantified significant mechanical strains across the SL interval during various yoga poses. This pattern of microtrauma is capable of generating MOT. Clinical Relevance  Upper extremity weight-bearing positions are common in yoga and subject the wrist, especially the SL interval, to high mechanical strains. This pattern of microtrauma should lead the clinician to suspect MOT when encountering a mass in the wrist, but malignancy and infection must be ruled out.

The Quantitative Anatomy of the Dorsal Scapholunate Interosseous Ligament

BACKGROUND

The anatomy of the scapholunate interosseous ligament (SLIL) has been described qualitatively in great detail, with recognition of the dorsal component's importance for carpal stability. The purpose of this study was to define the quantitative anatomy of the dorsal SLIL and to assess the use of high-frequency ultrasound to image the dorsal SLIL.

METHODS

We used high-frequency ultrasound imaging to evaluate 40 wrists in 20 volunteers and recorded the radial-ulnar (length) and dorsal-volar (thickness) dimensions of the dorsal SLIL and the dimensions of the scapholunate interval. We assessed the use of high-frequency ultrasound by comparing the length and thickness of the dorsal SLIL on ultrasound evaluation and open dissection of 12 cadaveric wrists. Student's t test was used to assess the relationship between measurements obtained on cadaver ultrasound and open dissection.

RESULTS

In the volunteer wrists, the mean dorsal SLIL length was 7.5 ± 1.4 mm and thickness was 1.8 ± 0.4 mm; the mean scapholunate interval was 5.0 mm dorsally and 2.5 mm centrally. In the cadaver wrists, there was no difference in dorsal SLIL length or thickness between ultrasound and open dissection.

CONCLUSIONS

The dorsal SLIL is approximately 7.5 mm long and 1.8 mm thick. These parameters may be useful in treatment of SLIL injuries to restore the native anatomy. High-frequency ultrasound is a useful imaging technique to assess the dorsal SLIL, although further study is needed to assess the use of high-frequency ultrasound in detection of SLIL pathology.

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.

Scapholunate Ligament Internal Brace 360-Degree Tenodesis (SLITT) Procedure

Background  Scapholunate (SL) joint instability is one of the most common injuries of the wrist and may result from a fall or high-energy mechanism on the outstretched hand. The purpose of this case report is to describe the outcome of a 360-degree tenodesis to the SL joint with an internal brace (SLITT) for the treatment of SL instability. Case Description  A 42-year-old male patient underwent SL ligament reconstruction with the SLITT procedure 12 months after injury. Given the intrinsic stability of the reconstruction, Kirschner (K) wires were not used and an early range of motion protocol was initiated. Thirteen months after his reconstruction, he was back at work with maintenance of his carpal alignment. Discussion  Since its initial description, a myriad of different surgical techniques for SL instability have been devised with varied success. These include capsular shrinkage, dorsal capsulodesis, reduction-association with a screw of the scapholunate joint (RASL), scapholunate axis method (SLAM), bone ligament bone grafts, and a variety of tendon reconstructions. Possible explanations for this varied outcome may be related to the use of soft tissue reconstructions for irreducible injuries and reconstruction of only the dorsal SL ligament. In addition, many of these techniques involve prolonged immobilization with the use of K-wires. Clinical Relevance  The SLITT procedure reconstructs both the volar and dorsal SL ligament. Given the added stability afforded by intrinsic bracing, we feel that this reconstruction may permit earlier range of motion without the need for K-wire stabilization.

Arthroscopic Dorsal Capsuloplasty in Scapholunate Tears EWAS 3: Preliminary Results after a Minimum Follow-up of 1 Year

Purpose  We retrospectively evaluated the results of all arthroscopic dorsal scapholunate (SL) capsuloplasty without pinning in patients presenting predynamic instability and dorsal capsuloscapholunate septum lesions on arthro-computed tomography scan after failed medical treatment. Materials and Methods  Fifteen patients, mean age 34.3 years, underwent all arthroscopically assisted dorsal capsuloplasty. Patients were assessed preoperatively and postoperatively by a clinical (pain, Watson's test, range of motion, and strength), functional (quick disabilities of the arm, shoulder, and hand), patient-rated wrist evaluation, and Mayo wrist score scores), and radiological (SL gap and dorsal intercalated segmental instability [DISI]) examination. SL tears were evaluated during surgery by European Wrist Arthroscopy Society (EWAS) classification. Results  The mean follow-up period was 20.2 months (range, 12-41). Preoperatively, positive Watson's test was noted in all cases. DISI deformity was noted in three cases without any SL gap. The SL instability was graded EWAS IIIB ( n  = 8) or EWAS IIIC ( n  = 7). Postoperatively, positive Watson's test was noted in only one case. Activity pain decreased from 7.8 preoperatively to 2.4 postoperatively. Range of motion in flexion-extension increased from 92.9 degrees preoperatively to 126.2 degrees postoperatively. Grip strength increased from 24.2 preoperatively to 38.2 postoperatively. At final follow-up, range of motion in flexion-extension and grip strength were estimated at 87 and 91% compared with contralateral side, respectively. All functional scores were significantly improved at the last follow-up. No radiographic SL gapping in grip views or DISI deformity was noted. Discussion  Cadaveric studies demonstrated that the dorsal portion of SL ligament is critical for the stability of the SL complex. The entire arthroscopic SL capsuloplasty technique provides reliable results for pain relief, avoiding postoperative stiffness associated with open procedures. It is an alternative technique for patients with predynamic SL instability after failure of medical management and shall not prelude the resort to any further open procedure. Level of Evidence  This is a level IV, case series.

Optimal management of scapholunate ligament injuries

Scapholunate ligament (SLL) injuries are a common cause of wrist pain and instability. Treatment of SLL injuries requires intricate understanding of wrist anatomy and biomechanics. Mindful physical exam and appropriate diagnostic studies can orient the surgeon to the defined stage of injury. Review of the literature on each treatment by stage can prepare the upper extremity surgeon to provide the best evidence-based care. The optimal management of SLL injuries should result in a stable, painless wrist.

Length Changes in Scapholunate Interosseous Ligament With Resisted Wrist Radial and Ulnar Inclination

PURPOSE

To investigate the changes in length of the scapholunate interosseous ligament (SLIL) when the wrist is resisting horizontal lateral load and the forearm is in full pronation in vivo.

METHODS

We obtained computed tomography scans of the wrists of 6 volunteers in 3 situations: 0° position (0° extension and 0° ulnar inclination) and full forearm pronation without force, and in the same position but with resisted ulnar and radial deviation. Nine zones of 3 subregions of the SLIL were measured and analyzed with computer modeling.

RESULTS

Changes in length of the palmar SLIL with resisted ulnar deviation were significantly greater than those without an applied lateral load. In contrast, the changes in length of the dorsal SLIL with resisted radial deviation were statistically greater than those in the 0° position without loading. However, no significant differences in the changes in length of the proximal SLIL were found in any of 3 situations, except the dorsal zone with resisted radial deviation.

CONCLUSIONS

Application of lateral load has an effect on the separation of the palmar and dorsal insertions of the SLIL. The palmar subregion of the SLIL was more highly strained with wrist-resisted ulnar deviation. Conversely, the dorsal subregion of the SLIL was under greater tension with wrist-resisted radial deviation.

CLINICAL RELEVANCE

For patients undergoing nonsurgical treatment of SLIL tears, a sudden contraction of ulnar or radial deviation agonist muscles may be harmful and contribute to SL instability.