Total Wrist Arthroplasty: An International Perspective.

Concerns about implant durability and technical difficulty continue to make total wrist arthroplasties a specialized procedure with a narrow scope of indications. As a result, more routinely performed total or partial wrist arthrodesis continues to maintain popularity over arthroplasty. However, wrist motion preservation is undoubtedly preferable for patients and current literature is trending to more favorable outcomes for total wrist arthroplasties. In the setting of the evolving role of wrist arthroplasties in clinical practice, it is important to focus on providing hand surgeons a practical approach to incorporating total wrist arthroplasty into the treatment toolbox available to them when treating patients with painful wrist arthritis.

A Changing Landscape in the Surgical Management of Wrist Arthritis: An Analysis of National Trends From 2009 to 2019.

PURPOSE: The purpose of this study was to analyze the trends in the annual volume and incidence of proximal row carpectomy (PRC), four-corner fusion (4CF), total wrist arthrodesis (TWF), and total wrist arthroplasty (TWA) from 2009 to 2019 in the United States. METHODS: The IBM Watson Health MarketScan databases were queried to identify annual case volumes for PRC, 4CF, TWF, and TWA from 2009 to 2019. The annual incidence of these procedures was then calculated based on the population estimates from the US Census Bureau. Trends in annual volume and incidence over the study period were evaluated using regression line analysis. Further subgroup analysis was conducted based on age and region. RESULTS: From 2009 to 2019, the total case volumes for the four procedures increased by 3.4%, but the incidence decreased by 2.8%. However, PRC case volume and incidence trends significantly increased (38.2% and 29.7%, respectively), whereas 4CF remained constant. Conversely, the case volume and incidence of TWA significantly decreased (-52.2% and -54.5%, respectively), whereas TWF remained constant. When stratified by age, all four procedures decreased in the <45-year-old cohort (combined -35.1%) significantly for 4CF, TWF, and TWA. TWA decreased significantly in the <45-year-old and 45- to 65-year-old cohorts (53.6% and 63.2%, respectively). For age >65 years, the total case incidence increased by 98.9%, including a significant positive trend in TWF (175%). CONCLUSIONS: Surgical management of wrist arthritis remains a controversial issue. However, PRC has gained recent support in the literature, and our results reflect this shift, even for the <45-year-old cohort. Furthermore, TWA declined, despite reports of positive early outcomes for fourth-generation implants. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic II.

Determining the Optimal Intramedullary Screw Canal Fill Ratio in Length Unstable Metacarpal Fractures: A Biomechanical Investigation.

PURPOSE: Intramedullary (IM) screw fixation is gaining popularity in the treatment of metacarpal fractures. Despite its rapid adoption, there is a paucity of evidence regarding parameters to optimize effectiveness. This study aimed to quantify the relationship between stability, IM screw size, and canal fill using a cadaveric model. METHODS: Thirty cadaveric metacarpals (14 index, 13 middle, and three ring fingers; mean age: 58.3 years, range: 48-70) were selected to allow for canal fill ratios of 0.7-1.1 for screws sized 3.0, 3.5, and 4.5 mm. Metacarpals underwent a 45° volar-dorsal osteotomy at the midpoint before fixation with an IM screw. Specimens were subjected to 100 cycles of loading at 10 N, 20 N, and 30 N before load-to-failure testing. Correlation coefficients for angular displacement on the final cycle at each load, peak load to failure, and average stiffness were assessed. RESULTS: Correlation coefficients for the angular displacement on the 100th cycle were as follows: 10 N, R = 0.62, 20 N, R = 0.57, and 30N, R = 0.58. Correlation values for peak load to failure as a function of canal fit were as follows: 3.0 mm, R = 0.5, 3.5 mm, R = 0.17, and 4.5 mm, R = 0.44. The canal fill ratio that intersected the line-of-best fit at an angular deformity of 10° was 0.74. Average peak forces for 3.0-, 3.5-, and 4.5-mm screws were 79.5, 136.5, and 179.6 N, respectively. Average stiffness for each caliber was 14.8, 33.4, and 52.3 N/mm. CONCLUSIONS: Increasing screw diameter and IM fill resulted in more stable fixation, but marginal gains were seen in ratios >0.9. A minimum fill ratio of 0.74 was sufficient to withstand forces of early active motion with angular deformity <10°. CLINICAL RELEVANCE: An understanding of the relationship of IM fill ratio of metacarpal screws to fracture stability may provide a framework for clinicians to optimally size these implants.

Dupuytren Disease: Surgical Tips, Optimizing Outcomes, and Cost Considerations.

Dupuytren disease is associated with benign fibroproliferative changes to the palmar fascia of the hand sometimes resulting in progressive contractures of the fingers. The earliest descriptions of these contractures date back to the 18th century. Much has been learned about the condition since the clawing condition was first described; however, optimal treatment still poses significant challenges to modern-day surgeons. It is important to examine the treatment options for Dupuytren disease and highlight the current evidence, techniques, and cost considerations of open fasciectomy, needle aponeurotomy, and recently described minimally invasive treatment.

A Kinematic Analysis of Wrist and Carpal Function Using Four-Dimensional Computed Tomography Technology: A Dynamic Perspective.

PURPOSE: An emerging imaging modality, four-dimensional computed tomography, can provide dynamic evaluation of carpal motion, which allows for a better understanding of how the carpals work together to achieve range of motion. The objective of this work was to examine kinematic motion of the carpus through a flexion/extension arc of motion using four-dimensional computed tomography. METHODS: A convenience sample of 20 uninjured participants underwent a four-dimensional computed tomography scanning protocol through a complete arc of flexion/extension motion. Kinematic changes in motion were quantified using helical axes motion data for each carpal. Rotation angles were compared between bones to identify differences in kinematic motion between bones. RESULTS: The bones within the proximal carpal row, the lunate, scaphoid, and triquetrum, rotate significantly to differing magnitudes at the ends of motion (40° of flexion and 40° of extension). The scaphoid rotates to the highest magnitude, followed by the triquetrum, and lastly, the lunate. The distal carpal row bones rotate to similar magnitudes throughout the entire range of motion. CONCLUSIONS: This work describes the kinematics of the carpals throughout dynamic in vivo flexion and extension. CLINICAL RELEVANCE: This study adds to an understanding of wrist mechanics and the possible clinical implications of pathological deviation from baseline kinematics.

Intramedullary Metacarpal Fracture Fixation: A Biomechanical Study of Screw Diameter and Comparison With Intramedullary Wire Stabilization.

PURPOSE: Interest in intramedullary metacarpal fracture fixation (IMFF) with screws is increasing. However, the optimal screw diameter for fracture fixation is not yet established. In theory, larger screws should be more stable, but there is concern about long-term sequelae of larger metacarpal head defects and extensor mechanism injury created during insertion as well as implant cost. Therefore, the purpose of this study was to compare different diameter screws for IMFF to a popular and more cost-effective alternative of intramedullary wiring. METHODS: Thirty-two cadaveric metacarpals were used in a transverse metacarpal shaft fracture model. Treatment groups consisted of IMFF with 3.0 × 60 mm, 3.5 x 60 mm, and 4.5 x 60 mm screws as well as 4 1.1-mm intramedullary wires. Cyclic cantilever bending was performed with the metacarpals mounted at 45° to simulate physiologic loading. Cyclical loading at 10, 20, and 30 N was performed to determine fracture displacement, stiffness, and ultimate force. RESULTS: At 10, 20, and 30 N of cyclical loading, all screw diameters tested provided similar stability as measured by fracture displacement and were superior to the wire group. However, ultimate force under load to failure testing was similar between the 3.5- and 4.5-mm screws and superior to 3.0-mm screws and wires. CONCLUSIONS: For IMFF, 3.0, 3.5, and 4.5-mm diameter screws provide adequate stability for early active motion and are superior to wires. When comparing the different screw diameters, 3.5- and 4.5-mm diameter screws offer similar construct stability and strength superior to the 3.0-mm diameter screw. Therefore, to minimize metacarpal head morbidity, smaller screw diameters may be preferable. CLINICAL RELEVANCE: This study suggests that IMFF with screws is biomechanically superior to wires in cantilever bending strength in the transverse fracture model. However, smaller screws may be sufficient to permit early active motion while minimizing metacarpal head morbidity.

Volar versus dorsal approach for supinator to posterior interosseous nerve transfer: An anatomical study in cadavers.

INTRODUCTION: Supinator to posterior interosseous nerve (SPIN) transfer allows reconstruction of finger/thumb extension and thumb abduction for low radial nerve palsy, incomplete C6 tetraplegia, and brachial plexus injury affecting C7-T1. No study has compared dorsal versus volar approach to perform SPIN transfer. This comparison is studied in the present work, assessing supinator motor branch length and ability to achieve nerve transfer from either approach. METHODS: Ten fresh frozen cadavers were randomly allocated to receive either a dorsal or volar approach to PIN and supinator radial and ulnar branches (RB = radial, UB = ulnar). Supinator head innervation patterns were documented. RB and UB lengths, forearm lengths measured from ulnar styloid to olecranon, visualization of extensor carpi radialis brevis (ECRB) motor nerve without additional dissection, and ability to perform tension-free nerve transfer were assessed. RESULTS: Nine of 10 specimens had supinator branches innervating both heads. The ECRB nerve was visualized in all volar but only one dorsal approach. No significant differences in forearm length were found. Volar with elbow extended: mean RB length was 35 ± 7.8 mm and UB was 37.8 ± 9.3 mm. Dorsal with elbow extended: mean RB length was 30 ± 4.1 mm and UB was 38.8 ± 7.3 mm. Dorsal with elbow flexed 90°: RB was 25.6 ± 3.8 mm and UB was 34.8 ± 4.8 mm. No significant differences were found in branch lengths between approaches (dorsal vs. volar UB, p = .339; dorsal vs. volar RB, p = .117). All limbs achieved tension-free coaptation. CONCLUSION: Neither approach demonstrated superiority in achieving tension-free nerve transfer. Volar permitted immediate identification of ECRB nerve whereas this was only visualized in one dorsal specimen without additional dissection. Overall, the volar approach allows direct coaptation in elbow extension, mimicking maximal physiologic tension for neurorrhaphy. It simultaneously permits additional procedures for pinch reconstruction via single exposure, circumventing limb/microscope maneuvering, dorsal dissection, and increased operative time. Ultimate choice of approach should depend on surgeon familiarity and potential need for additional simultaneous transfers.

The Utility of Quantitative Computed Tomography to Detect Differences in Subchondral Bone Mineral Density Between Healthy People and People With Pain Following Wrist Trauma.

The mechanisms underlying chronic pain development following musculoskeletal trauma are complex and multifactorial. In their search, some researchers are turning to the subchondral bone as a potential contributor to pain due to its vascularity, using a depth-specific imaging technique. However, this technique has been mainly used in the knee. We propose the use of a quantitative computed tomography (QCT) depth-specific analysis to measure subchondral bone following wrist trauma. Ten participants (n = 5 post-trauma; n = 5 healthy) underwent bilateral computed tomography scans of their wrist accompanied by a calibration phantom with known densities. Average subchondral volumetric bone mineral density (vBMD) was studied at three depths from the subchondral surface (0-2.5, 2.5-5, 5-7.5 mm) according to radial articular surface contact in both wrists of each participant. Percentage differences and Cohen's d effect sizes were calculated to analyze bilateral vBMD and vBMD differences between groups. This image-based tool demonstrated subject-specific, depth-specific, and joint-specific measures of vBMD within the wrist. This methodology highlighted the differences between depth-specific vBMD in healthy people and people who have experienced wrist trauma. Overall, the healthy cohort demonstrated higher vBMD across all three depths and both articular surfaces. This imaging technique further distinguished between subchondral cortical and trabecular bones, wherein clinical implications can be drawn from these distinctions in future work. Our study therefore supports the utility of a QCT imaging technique in detecting differences in depth-specific vBMD in the wrist.

How Is the Probability of Reporting Various Levels of Pain 12 Months After Noncatastrophic Injuries Associated with the Level of Peritraumatic Distress?

BACKGROUND: Psychological factors have been shown to be consistent predictors of chronic pain in people with musculoskeletal injuries. However, few prognostic studies have considered multiple risk factors including peritraumatic distress. In addition, previous research has not considered that the associations between peritraumatic distress and pain levels can vary across pain outcomes. QUESTION/PURPOSE: To determine whether an easily measurable level of baseline distress is associated with pain levels 1 year after noncatastrophic traumatic injuries when the outcome to be assessed is not normally distributed. METHODS: This was a prospective cohort study. The data were captured from two cohorts in London, Ontario, Canada, and Chicago, IL, USA. Participants were adults with acute noncatastrophic (that is, not treated with surgery or hospitalization) musculoskeletal injuries of any etiology with various injury locations (60% [145 of 241] spinal and 40% [96 of 241] peripheral) that presented to local urgent care centers. Other inclusion criteria included English/French speakers and having no other disorder that would affect their pain levels. In total, between the years 2015 and 2018, 241 participants were recruited based on the inclusion criteria. Ninety-three percent (225 of 241) of participants provided baseline data, and of these, 48% (109 of 225) were lost to follow-up in 1 year. Based on a complete case approach, this study included 116 participants who ranged in age from 18 to 66 years and 69% (80) of whom were women. The Traumatic Injuries Distress Scale (TIDS) was used to evaluate distress at baseline (within 4 weeks of injury). The TIDS is a validated, reliable 12-item risk prognosis screening tool that takes less than 3 minutes to complete with questions regarding uncontrolled pain, negative affect, and intrusion/hyperarousal. The minimum and maximum possible scores are 0 and 24, with higher scores indicating higher levels of distress. The Numeric Pain Rating Scale (NPRS) was used to assess the pain level at baseline and again 12 months postinjury. To complete the NPRS, participants rate the severity of their pain on a scale of 0 to 10, with 0 indicating no pain and 10 indicating the worst pain imaginable. NPRS scores of 1 to 3 indicate mild pain, 4 to 6 indicate moderate pain and 7 or higher indicate severe pain. As a preliminary analysis, to assess whether the participants as a group experienced recovery, a paired samples t-test was used to compare NPRS scores at baseline and 12 months. In all, 52% (60 of 116) of participants reported no pain (NPRS = 0), and mean pain intensity scores improved from 4.8 ± 2.1 at baseline to 1.6 ± 1.6 at 12-month follow-up (p < 0.001). Quantile regression was used to describe the association between baseline distress and pain levels 1 year after the injury. This technique was used because it reveals the relationships at different quantiles of the pain outcome distribution. RESULTS: The results indicate some people (52% [60 of 116]) recovered regardless of their baseline level of distress (30th quantile of the NPRS: ß = 0). However, in those with persisting pain, higher levels of baseline distress are associated with greater levels of pain 12 months after the injury (50th quantile of the NPRS: ß = 0.11; p = 0.01; 70th quantile of the NPRS: ß = 0.27; p < 0.001; 90th quantile of the NPRS: ß = 0.31; p = 0.01). According to this model, with a baseline TIDS score of 5, there is 10% probability that patients will report moderate or greater levels of pain (4 or higher of 10) 12 months later. This probability then increases as the TIDS score increases. For instance, at a score of 13 on the TIDS, the probability of a patient reporting moderate or higher levels of pain increases to 30%, and the probability of reporting severe pain (higher than 6 of 10) is 10%. CONCLUSION: Clinicians and surgeons in orthopaedic settings can screen for the presence of peritraumatic distress using the TIDS, which is an easily administered tool that does not require extensive knowledge of psychology, and by using it they can identify those with higher levels of distress who are more likely to have persistent, long-term pain. A score of 4 or less indicates a low risk of persistent pain, a score between 5 and 12 (endpoints included) indicates moderate risk, and a score of 13 or higher indicates high risk. Future studies should investigate whether certain immediate interventions for peritraumatic distress in the aftermath of trauma can decrease the likelihood that a patient will develop chronic pain after injury. As an analysis technique, quantile regression is useful to assess complex associations in many orthopaedic settings in which a certain outcome is expected to occur in most patients leading to non-normally distributed data. LEVEL OF EVIDENCE: Level II, therapeutic study.

The Evaluation of a Flexor Digitorum Profundus-to-Volar Plate Zone I Repair Versus Button Repair: An In vitro Biomechanics Study.

PURPOSE: The purpose of the study was to evaluate joint kinematics and tendon work of flexion (WOF) following a flexor digitorum profundus (FDP)-to-volar plate (VP) repair technique relative to a pullout button for zone I flexor tendon injuries. METHODS: Fourteen digits were tested using an in vitro active finger motion simulator under 3 repaired conditions following a simulated zone I avulsion: button, FDP-VP, and "no slack" FDP-VP (corrected for additional VP length). Outcome metrics included active joint range of motion (ROM), fingertip strength, FDP and flexor digitorum superficialis tensile loads, and WOF. RESULTS: The button and FDP-VP techniques restored WOF to the intact condition for FDP and flexor digitorum superficialis. All repairs restored distal interphalangeal joint ROM and kinematics to the intact condition. Similarly, all repairs restored WOF; however, the "no slack" FDP-VP significantly increased WOF by 10% to 12% over the simple FDP-VP repair. The button technique had similar fingertip strength to the intact condition, whereas the FDP-VP repairs significantly reduced peak fingertip strength from intact, albeit only 1-2 N compared with the button repair. CONCLUSION: In this in vitro cadaveric model, the button and FDP-VP techniques restored WOF and ROM to within intact levels, with no difference between these repairs in all measured outcome metrics. CLINICAL RELEVANCE: Based on its initial strength and its equal biomechanical performance compared with the button repair, the FDP-VP technique may be a viable option for treating FDP avulsions.

Evaluation of Four-Dimensional Computed Tomography as a Technique for Quantifying Carpal Motion.

Delayed diagnosis of dynamic carpal instability often occurs because early changes in bone alignment and movement are difficult to detect and manifest mainly during a dynamic/functional task. Current diagnostic tools are only able to examine the carpal bones under static or sequential-static conditions. Four-dimensional (three dimensions + time) computed tomography (4DCT) enables quantification of carpal mechanics through 3D volume sequences of the wrist in motion. A comprehensive understanding of carpal mechanics is needed to define normal function and structure and provide targets for treatment of carpal injuries. In this study, measurements of scaphoid translation and joint congruency were taken by creating models from the CT scans of the carpals in extreme frames of motion, registering those models to the neutral position, transforming the models into a local coordinate system, and using software to calculate the joint surface areas (JSA). Results indicated that the centroid of the scaphoid translated 6.4 ± 1.3 mm and extended from extreme radial to extreme ulnar deviation. Results are consistent with the literature. An additional study was performed to measure the responsiveness of the 4DCT technique presented. Bone models from each frame of motion for radio ulnar deviation (RUD) and flexion extension (FE) were created and distinct differences between their JSA were measured qualitatively and quantitatively. The results show that there was statistically significantly different JSA within carpal joints between RUD and FE. These studies provide the first step in developing the methodology when using 4DCT scanning to measure subtle abnormalities in the wrist.

Use of Thermoplastic Rings Following Venting of Flexor Tendon Pulleys: A Biomechanical Analysis.

PURPOSE: Normal digital flexion relies on flexor tendon pulleys to convert linear muscular force to angular digital motion. However, there is a growing trend to vent them partially during flexor tendon repair. The objective of this study was to examine the effects of a thermoplastic ring, acting as an external pulley, on flexor tendon biomechanics and finger range of motion (ROM) after pulley venting. METHODS: We tested 15 cadaveric digits using an in vitro active finger motion simulator. We measured loads induced by flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) as well as joint ROM with sequential sectioning of the A2, A3, and A4 pulleys compared with an intact pulley condition. At each stage, external thermoplastic pulley rings were applied snugly over the proximal and middle phalanges to recreate A2 and A4 function, respectively. RESULTS: After complete venting of the A2, A3, and A4 pulleys, proximal interphalangeal joint ROM significantly decreased by 13.4° ± 2.7° and distal interphalangeal joint ROM decreased by 15.8° ± 2.1°. Application of external rings over the proximal and middle phalanx resulted in a residual ROM decrease of 8.3° ± 1.9° at the proximal interphalangeal joint and 7.9° ± 2.1° at the distal interphalangeal joint, nearly restoring ROM. Similarly, complete pulley venting resulted in reduced FDS load by 37% and FDP load by 50% compared with intact pulleys. After application of external rings, loads were restored almost to normal, with a 9% reduction for FDS load and 9% reduction for FDP load compared with intact pulleys. CONCLUSIONS: The application of thermoplastic rings acting as external pulleys is an effective, noninvasive, and reproducible approach to restore flexor tendon biomechanics and digit ROM after pulley venting. CLINICAL RELEVANCE: Thermoplastic rings may be a useful therapeutic adjunct in restoring joint ROM and flexor tendon loads after surgical venting of the pulleys.

The Effect of Malunited Scaphoid Fractures on Joint Congruency.

PURPOSE: Although the consequences of scaphoid nonunion have been well-established, the implications of malunions are not well-known. To date, malunions have mainly been studied with 2-dimensional imaging. The objective of this study was to employ 3-dimensional computed tomography (CT) imaging and inter-bone distance mapping to determine the implications of a scaphoid malunion on 3-dimensional joint surface area (JSA) (a measure of joint contact area) at an average of 7 ± 2 years (range, 4-12 years) after fracture. METHODS: In 14 subjects with previous unilateral, malunited scaphoid fractures, we measured the 3-dimensional JSA using reconstructed CT bone models of the carpus. The JSA was compared within each individual, comparing images of the wrist collected at the time of fracture (baseline) and 7 years later (follow-up CT scans). RESULTS: There was a significant increase in the measured JSA (reduced joint space) at the scaphotrapezial (23% increase) and scaphocapitate (13% increase) joints when the baseline and follow-up scans of the wrist were compared. An increased JSA indicates that the 2 opposing surfaces are closer in contact and have a reduced joint spacing reflective of degenerative changes. However, participants in this study showed no radiographic signs of degenerative changes in the wrists at midterm follow-up. CONCLUSIONS: An increase in JSA was found in patients with a malunited scaphoid in the scaphotrapezial and scaphocapitate joints of the wrist an average of 7 years after injury, but these joint changes were not evident in measured radiographic signs of arthritis. CLINICAL RELEVANCE: As early as 4 years after injury, the 3-dimensional JSA is significantly increased at the scaphocapitate and scaphotrapezial joints. Future work is needed to determine the implication of this increased in 3-dimensional JSA on the underlying subchondral bone, and to observe these patients for longer to determine whether degenerative changes develop.

The Effect of Forearm Position on Wrist Joint Biomechanics.

PURPOSE: All active motion wrist joint simulators have been designed to simulate physiologic wrist motion; however, a main difference among them is the orientation of the forearm (horizontal or vertical with respect to gravity). Moreover, the effect of forearm orientation on experimental results has yet to be quantified, but it may be an important variable. Thus, the purpose of this study was to determine the effect of forearm orientation on wrist kinematics and contact mechanics. METHODS: Eight cadaveric upper limbs were cycled through a flexion-extension motion using an active motion wrist simulator. Motion trials were performed in 3 forearm orientations (gravity-neutral, gravity-flexion, and gravity-extension). A computed tomography-based joint congruency technique was used to examine radiocarpal joint contact and joint contact centroid translation in the 3 tested orientations. RESULTS: At full wrist extension and wrist flexion, radioscaphoid contact area was greatest in the gravity-extension orientation. Radiolunate contact area was similar among all 3 forearm orientations. The radioscaphoid contact centroid was consistent among the 3 tested positions with the wrist in neutral wrist position. In contrast, the radioscaphoid contact centroid translated radially in the gravity-neutral position relative to the gravity-flexion position in extreme extension. There were no differences in radiolunate centroid contact position in the 3 forearm orientations. CONCLUSIONS: This study demonstrates that forearm orientation affects contact mechanics and end-range carpal kinematics. Future biomechanical studies should report forearm orientation and discuss the implication of the forearm orientation used on the experimental results. CLINICAL RELEVANCE: This study provides evidence that the wrist joint is sensitive to forearm positions consistent with activities of daily living and rehabilitation protocols.

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.

The Impact of Scaphoid Malunion on Radioscaphoid Joint Contact: A Computational Analysis.

PURPOSE: The clinical relevance of scaphoid malunion is controversial because the biomechanical sequelae remain poorly understood. In this computational study, the effect of increasing scaphoid malunion on radioscaphoid joint contact was assessed. METHODS: Six computational wrist models of active wrist flexion-extension were used to examine 6 scaphoid malunions of varying severities. The malunions were computationally created using 3-dimensional imaging software. Each scaphoid was shortened at the waist by 2 mm to simulate fracture comminution and the distal pole was angulated volarly from 15° to 55° in 10° intervals to create a total of 6 scaphoid malunion models per specimen. Each malunion model was then assessed at 3 wrist positions: neutral, 40° flexion, and 40° extension. The radioscaphoid contact area, as well as the contact centroid, was calculated. RESULTS: There was a statistically significant association between malunion severity and a wider area of contact at the radiocar: pal joint. The centroid of this radioscaphoid contact area also moved in an ulnar direction for all tested wrist positions. In the extended wrist position, the centroid also moved volarly. CONCLUSIONS: In this computational model, the amount of radioscaphoid joint contact was significantly increased with progressive scaphoid malunion severity. Furthermore, the position of the contact centroid had a significant change in position in the ulnar direction in all wrist positions with increasing scaphoid malunion. The clinical importance of this contact is yet to be elucidated, but this computational model serves as a basis for understanding the biomechanical consequences of scaphoid humpback deformities. CLINICAL RELEVANCE: This study provides a computational analysis examining changes at the radioscaphoid joint that may occur within the wrist with the scaphoid malunited.

Scaphoid Malunion Clinical and Radiographic Outcomes at a Minimum of 4 Years Follow-Up.

PURPOSE: To evaluate the radiographic and clinical outcomes of patients with scaphoid malunion after acute fracture at a mean of 7 years after injury. METHODS: Patients with scaphoid malunion were identified from a departmental database of acute scaphoid fractures. Patients with a scaphoid height-to-length ratio greater than 0.6 on final follow-up computed tomography (CT) scan were considered malunited. These patients were contacted to return for CT imaging and clinical assessment. A total of 22 patients were included (4 females and 18 males). Average age of the group was 41 years (range, 16-64 years) and average length of follow-up was 7.4 years (range, 4.4-11.8 years) after injury. RESULTS: Ten patients who underwent CT imaging demonstrated arthritic changes at the radial styloid, scaphoid fossa, or scaphotrapeziotrapezoid joint(s). Despite this, patients had good clinical function that was not significantly different compared with the uninjured side. Patients reported minimal pain and disability based on patient-reported outcome measures, and there was a moderate correlation between passive range of motion and height-to-length ratio. CONCLUSIONS: Nearly half of all patients with malunited acute scaphoid fractures demonstrated radiographic findings of early arthritis on CT imaging but overall good clinical results on midterm follow-up. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic IV.

A New Surface Landmark for Thumb Digital Nerve Bifurcation: A Cadaveric Study.

PURPOSE: The radial and ulnar thumb digital nerves are critical for tactile sensation and dexterity in the hand. This cadaveric study sought to validate a surface landmark for the bifurcation of the thumb radial digital nerve (RDN) and ulnar digital nerve (UDN). METHODS: We used 24 fresh-frozen cadaveric specimens for dissections. With the thumb placed in the plane of the palm and fully radially abducted, the index finger metacarpophalangeal joint was flexed to 90°. Then, while keeping the distal interphalangeal joint straight, the proximal interphalangeal joint was flexed until the fingertip contacted the thenar eminence to identify the point of bifurcation. We made a U-shaped incision and identified the bifurcation of the thumb RDN and UDN. The point of bifurcation was measured from the ulnar- and proximal-most aspects of the incision. RESULTS: The bifurcation of the thumb RDN and UDN was consistently identified within the U in 22 of 24 specimens (92%). In 16 specimens, the index RDN was also identified either trifurcating with the thumb RDN and UDN or branching from a common digital nerve of index RDN and thumb UDN. Most bifurcation points were found directly along the ulnar and proximal edge of the incision. Two specimens contained a bifurcation point 2 mm ulnar to the ulnar limb of the U. CONCLUSIONS: The bifurcation U is a consistent landmark for the thumb RDN and UDN point of bifurcation. The variable branching patterns in this region confirms the importance of thorough clinical examination with penetrating injuries to the thenar eminence. CLINICAL RELEVANCE: This surface anatomic landmark for the thumb RDN and UDN bifurcation may aid in preventing iatrogenic injuries during elective procedures and identifying at-risk structures during penetrating injuries to the palm.

An Anthropometric Assessment of the Proximal Hamate Autograft for Scaphoid Proximal Pole Reconstruction.

PURPOSE: Fragmentation of the scaphoid proximal pole secondary to avascular necrosis presents a difficult reconstructive problem. This anthropometric study assesses the utility of the ipsilateral proximal hamate for complete osteochondral scaphoid proximal pole reconstruction. METHODS: Twenty-nine cadaveric specimens underwent computed tomography scanning and 3-dimensional reconstruction of the carpus and distal radius. Scaphoid height was measured and a third of its height was used to simulate resection of the proximal scaphoid pole and extent of hamate autograft required. The proximal scaphoid and hamate were divided into 6 sections, and compared using an iterative point-to-point distance algorithm. Average distance between the scaphoid and the hamate surfaces was determined. An interbone algorithm was used to assess radioscaphoid joint congruency and articular contact surface of the native scaphoid compared with the scaphoid reconstructed with hamate autograft. RESULTS: The mean height of scaphoid proximal pole excision and proximal hamate autograft height was 9.3 mm. Comparing the morphology of the native scaphoid and hamate autografts, the absolute distances were the largest in the volar radioscaphoid, dorsal radioscaphoid, and dorsal scaphocapitate segments. Without osteotomy, the hamate autograft may cause impaction in the dorsal-radial aspect of the distal radius. The hamate autograft also shifted the articular contact point of the radioscaphoid joint toward the dorsal-radial position. Nine hamate autografts were classified as poor-fitting. Poor-fitting specimens had a greater radial styloid to distal radioulnar joint distance. These specimens also had wider hamates and scaphoids in the radial-ulnar dimension and wider scaphoids in the volar-dorsal dimension. Lunate type did not correspond to anthropometric fit. CONCLUSIONS: The proximal hamate osteochondral graft was poor fitting in 31% of cases (9 of 29 specimens). Wrists with radial-ulnar hamate width less than 10 mm, radial-ulnar scaphoid width less than 10 mm, and volar-dorsal scaphoid width less than 16 mm demonstrate better anthropometric fit. CLINICAL RELEVANCE: This study provides an anthropometric assessment of the recently described proximal hamate autograft, a new bone graft option for proximal scaphoid pole reconstruction.

Image-Based Comparison Between the Bilateral Symmetry of the Distal Radii Through Established Measures.

PURPOSE: Anthropometric assessment of bony structures in the body is important for preoperative computer-aided surgery, implant design, finite element modeling, and biomechanical studies investigating joint structure and function. The use of the contralateral limb in surgery and clinical practice relies on the assumption that the right and left limbs of an individual are symmetric. Therefore, the purpose of this study was to quantify the bilateral symmetry of the bony structures of the distal radius using 3-dimensional (3D) computed tomography. METHODS: We collected computed tomography images of 37 paired, fresh-frozen, healthy cadaveric male upper limbs (aged 75.4 ± 8.3 years). Three-dimensional reconstructed models were created using semiautomatic segmentation. Using the 3D models, we measured 3D radial inclination, 3D volar tilt, 3D radial height, medial volar cortical angle, middle volar cortical angle, and lateral volar cortical angle and compared them between sides. RESULTS: There were no statistically significant differences measured between right and left distal radius in 37 paired wrists. Mean radial height was 12.81 mm (SD, 1.74 mm) on the left and 12.88 mm (SD, 1.72 mm) on the right. Mean volar tilt was 10.74° (SD, 3.74°) and 10.77° (SD, 3.19°) and radial inclination was 24.05° (SD, 2.63°) and 24.18° (SD, 3.41°) on the left and right, respectively. Mean volar cortical angle across the radius was 140.9° (SD, 7.9°) on the left and 140.1° (SD, 7.9°) on the right. CONCLUSIONS: Direct bilateral comparison of the distal radius and wrist joints is useful to predict normal anatomy of the injured radius, because bilateral similarities exist. CLINICAL RELEVANCE: This article provides a comprehensive list of measurements of the distal radius compared bilaterally using a 3D model. From this study, we found that the contralateral radius can be used as a benchmark with which to compare fracture reduction and to manage malunions during the preoperative planning of corrective osteotomies. It can also be used to define normal anatomy.