Intact Wrist Research Articles

Biomechanics of the Trampoline Test in the Intact, Sectioned, and Repaired TFCC

Abstract Background Multiple techniques have been developed to detect a triangular fibrocartilage complex (TFCC) foveal detachment. One commonly used technique to evaluate TFCC integrity, the trampoline test, has had variable reliability. Questions/Purposes The purpose of this biomechanical experiment was to evaluate the suitability of the trampoline test in detecting TFCC foveal detachments. Methods In each of 10 cadaver arms, TFCC displacement near the ulnar fovea was measured using a plunger with increasing incremental loads in the intact wrist, after ulnar sectioning of the TFCC, and following TFCC repair. Results After the application of the eight incremental small weights, there was no significant difference in the relative displacement of the plunger between the intact case, after detachment of the ulnar aspect of the TFCC disc, and after repair (0.6 mm intact, 0.7 mm detached, and 0.7 repair). However, there were significant differences in the absolute ending point displacement referenced to the starting intact position (0.6 mm intact, 1.3 mm detached, and −0.9 mm after repair). Conclusion/Clinical Relevance This study suggests that the trampoline test may not be adequate to quantify displacement (bouncing) of the TFCC disc after injury.

O243: The effect of midcarpal fusions on dart thrower’s motion: a cadaveric study

Abstract Introduction Midcarpal osteoarthritis can be managed with several types of partial wrist fusion. Limited information is available regarding their effects on functional movement. Many daily activities require a coupled wrist movement, from radial extension to ulnar flexion, termed dart thrower’s motion (DTM). This study aimed to compare the effect of four different midcarpal fusions on DTM. Methods Twelve fresh-frozen cadaveric specimens were dissected. Sequential loading of tendons into radial extension and ulnar flexion enabled full DTM to be measured using goniometry. Specimens were tested at baseline and following each fusion, performed sequentially using Kirschner wires: (1) scaphocapitate fusion, (2) lunocapitate fusion with scaphoid excision, (3) four-corner fusion with scaphoid excision and (4) three-corner fusion with scaphoid and triquetral excision. A one-way ANOVA and Tukey test established the significance of differences in range of motion. Results Each procedure significantly decreased DTM compared with intact wrists. Scaphocapitate fusion resulted in the smallest mean reduction in movement from 78°–70° (p=0.0014). Four-corner fusion produced the greatest reduction in DTM from 78°–63° (p<0.0001). There was a significant difference in DTM between four-corner and scaphocapitate fusions (p=0.0338). There was no significant difference in the range of postoperative DTM between lunocapitate, three-corner, or four-corner fusions. Conclusion DTM was minimally affected by scaphocapitate fusion and maximally affected by four-corner fusion, with a significant difference seen between these two operations. However, as a 44°–87° range of DTM was maintained for four-corner fusions, this is felt to be adequate for function. These results could aid preoperative decision-making.

Excision of the Distal Pole of the Scaphoid and the Midcarpal Joint

Abstract Background Excision of the distal pole of the scaphoid is used to treat arthritis of the scaphotrapezial trapezoid (STT), radioscaphoid joint, and arthritis following scaphoid nonunion. Some patients develop midcarpal instability limiting utilization of this technique. Why some wrists develop postoperative instability while others do not, remains unclear. Questions/Purposes To identify the wrists prone to developing midcarpal joint instability we evaluated the effect of midcarpal joint structure on force transfer through the wrist, we hypothesized that the force transfer will be further altered when a distal pole excision is performed and that midcarpal joint structure will affect force transfer. Patients and Methods We used finite element analysis based on 19 computer tomography wrist scans. Nine type 1 (lunate has a facet with the capitate alone) and 10 type 2 (lunate has facets with both the capitate and hamate) models were prepared. A 200 N force was evenly split and applied to the dorsal crests of the trapezoid and capitate (100 N along each crest) to replicate the performance of a knuckle push-up. Displacement of the trapezoid, trapezium, scaphoid, capitate, and hamate was measured along each axis after the applied load. The simulation model was used to predict motion at the capitate and STT joint with excision of the distal pole. Results Excision of the distal pole of the scaphoid affected the transfer of forces significantly (∼200% all bones in all directions) in all wrists. There are significant differences in force transfer between type 1 and type 2 wrists in the amount of force transferred (type 1 > type 2), in the percent difference from an intact wrist (type 1 > type 2) and in the direction of displacement (type 1 the bones moved in different directions while type 2 wrists moved as one block). Conclusion This study suggests that midcarpal joint structure affects force transfer through the wrist and may predict wrist behavior following excision of the distal pole of the scaphoid. Specifically, type 1 wrists may be more prone to midcarpal joint collapse after excision. Level of evidence: 1.

A three degrees of freedom switchable impedance myoelectric prosthetic wrist

Wrist mobility contributes significantly to the execution of upper limb motor tasks. Despite this, current prosthetic wrists are far less advanced than other artificial joints. Typically, prosthetic wrists offer limited degrees of freedom, if any, which forces users to execute compensatory movements during task performance. This addition increases weight and complexity, two unwelcome factors in upper limb prostheses. This article presents the design of a 3-degree-of-freedom friction-lockable prosthetic wrist actuated by a single motor. The design features adaptable behavior when unlocked, promoting a gentle interaction with the environment, and enables users to adjust the hand configuration during pre-grasping phases. The proposed system was tested, combined with a hand prosthesis, and compared to a commercial rotational wrist during the execution of functional movements. Experiments involved nine able-bodied subjects and one prosthesis user. Participants also performed the experiments with their biological wrist (the intact wrist for the prosthesis user) as a control. Results showed that the lockable wrist was used actively 20% more often than the commercial solution without compromising users’ execution time. Interaction tests reveal that compensatory movements are reduced when using the proposed design, resulting in closer resemblance to the control wrist’s performance. The average satisfaction and usability scores were significantly higher for the proposed wrist, indicating its potential acceptance. Finally, the system was validated in a set of activities of daily living performed by the prosthesis user. The study contributes to the development of more intuitive and adaptable prostheses that can improve the quality of life of amputees.

Biomechanical Comparisons of Different Reconstructive Techniques for Scapholunate Dissociation: A Cadaveric Study.

There are many techniques for the treatment of chronic scapholunate dissociation. The three-ligament tenodesis (3LT) is used most widely, but reconstruction of the dorsal ligament alone may not provide sufficient stability. The Mark-Henry technique (MHT) compensates for the insufficient stability of 3LT by additional reconstruction of the volar ligament, but the procedure is complex. The SwiveLock technique (SWT), a recently introduced method, provides stability by using autologous tendons with synthetic tapes, but lacks long-term clinical results. To perform biomechanical comparisons of different reconstructive techniques for scapholunate dissociation using a controlled laboratory cadaveric model. Eleven fresh-frozen upper-extremity cadaveric specimens were prepared. The scapholunate distance, scaphoid rotation, and lunate rotation of the specimens were measured during continuous flexion-extension and ulnar-radial deviation movements. The data were collected using a wrist simulator with a linear guide rail system (tendon load/motion-controlled system) and a motion capture system. Results were compared in five conditions: (1) intact, (2) scapholunate dissociation, (3) SWT, (4) 3LT, and (5) MHT. Paired t-test was employed to compare the biomechanical characteristics of intact wrists to those of scapholunate dissociated wrists, and to those of wrists after each of the three reconstruction methods. SWT and MHT were effective solutions for reducing the widening in scapholunate distance. According to the radioscaphoid angle, all three reconstruction techniques were effective in addressing the flexion deformity of the scaphoid. According to the radiolunate angle, only SWT was effective in addressing the extension deformity of the lunate. In terms of scapholunate angle, only the results after SWT did not differ from those of the intact wrist. The SWT technique most effectively improved distraction intensity and rotational strength for the treatment of scapholunate dissociation. Taking into account the technical complexity of 3LT and MHT, SWT may be a more efficient technique to reduce operating time and minimize complications due to multiple incisions, transosseous tunnels, and complicated shuttling.

Evaluation of hand functions and distal radioulnar joint instability in elite wheelchair basketball athletes: a cross-sectional pilot study

BackgroundWrist injury affects wheelchair basketball players’ performance; however, the relationship between distal radioulnar joint (DRUJ) instability and hand functions is unclear. This cross-sectional pilot study investigated DRUJ instability in elite female wheelchair basketball athletes using force-monitor ultrasonography.MethodsNine elite female wheelchair basketball athletes (18 wrists) were included in the study. A triangular fibrocartilage complex (TFCC) injury was confirmed using magnetic resonance imaging (MRI). Hand functions were evaluated based on the range of motion (ROM) of wrist palmar flexion, dorsiflexion, radial deviation, and ulnar deviation; grip strength; arm circumference; forearm circumference; and DRUJ instability or pain using the ballottement test. The Mann–Whitney U test was used to compare parameters between the TFCC-injured and intact wrists. Radioulnar displacement was measured using force-monitor ultrasonography and pressure data, and the displacement-to-force ratio was used as an indicator of DRUJ instability. The correlation between the DRUJ displacement-to-force ratio and each hand function assessment was evaluated using Pearson correlation coefficient for the TFCC-injured and intact wrists. A generalized linear mixed model (GLMM) was used to estimate the relationship between hand functions and DRUJ instability.ResultsTFCC injuries in seven wrists were confirmed using MRI findings (38.9%). The ulnar deviation ROM values of the TFCC-injured wrist (n = 7) and intact (n = 11) groups were 38.6 ± 8.0° and 48.6 ± 7.8°, respectively. The ulnar deviation ROM was significantly smaller in the TFCC-injured wrists (p = 0.02, r = − 0.54). In the TFCC-injured wrists, no correlation was observed between the displacement-to-force ratio and the hand function assessment. In contrast, the displacement-to-force ratio negatively correlated with grip strength, arm circumference, and forearm circumference in the intact wrists (Pearson correlation coefficient r = − 0.78, − 0.61, and − 0.74, respectively). The GLMM showed that the displacement-to-force ratio significantly affected grip strength, arm circumference, and forearm circumference in the intact group.ConclusionsIn intact wrists, correlations were observed between hand functions such as upper arm/forearm strength and DRUJ stability evaluated using ultrasound. Maintaining and strengthening grip strength, forearm circumference, and arm circumference are associated with DRUJ stability and may be related to TFCC injury prevention in wheelchair basketball athletes.Trial registration: The protocol was registered with the UMIN Clinical Trials Registry (UMIN000043343) [Date of first registration: 16/02/2021].

THE BIOMECHANICAL ANALYSIS OF A NOVEL IMPLANT FOR SCAPHOLUNATE INTEROSSEOUS LIGAMENT RUPTURE REPAIR

There is currently no commercially available and clinically successful treatment for scapholunate interosseous ligament rupture, the latter leading to the development of hand-wrist osteoarthritis. We have created a novel biodegradable implant which fixed the dissociated scaphoid and lunate bones and encourages regeneration of the ruptured native ligament. To determine if scaphoid and lunate kinematics in cadaveric specimens were maintained during robotic manipulation, when comparing the native wrist with intact ligament and when the implant was installed.Ten cadaveric experiments were performed with identical conditions, except for implant geometry that was personalised to the anatomy of each cadaveric specimen. Each cadaveric arm was mounted upright in a six degrees of freedom robot using k-wires drilled through the radius, ulna, and metacarpals. Infrared markers were attached to scaphoid, lunate, radius, and 3rd metacarpal. Cadaveric specimens were robotically manipulated through flexion-extension and ulnar-radial deviation by ±40° and ±30°, respectively.The cadaveric scaphoid and lunate kinematics were examined with 1) intact native ligament, 2) severed ligament, 3) and installed implant.Digital wrist models were generated from computed tomography scans and included implant geometry, orientation, and location. Motion data were filtered and aligned relative to neutral wrist in the digital models of each specimen using anatomical landmarks. Implant insertion points in the scaphoid and lunate over time were then calculated using digital models, marker data, and inverse kinematics. Root mean squared distance was compared between severed and implant configurations, relative to intact.Preliminary data from five cadaveric specimens indicate that the implant reduced distance between scaphoid and lunate compared to severed configuration for all but three trials.Preliminary results indicate our novel implant reduced scapho-lunate gap caused by ligament transection. Future analysis will reveal if the implant can achieve wrist kinematics similar to the native intact wrist.

Pathomechanism of Triangular Fibrocartilage Complex Injuries in Patients with Distal-Radius Fractures: A Magnetic-Resonance Imaging Study.

Injury to the triangular fibrocartilage complex (TFCC) is one of the most common complications following a fracture of the distal radius. In this study, an examination of TFCC injuries in patients with distal-radius fractures was conducted using magnetic-resonance imaging (MRI); the aim of the study was to analyze the prevalence of TFCC injury as well as to suggest acceptable radiologic parameters for use in prediction of the injury pattern. Fifty-eight patients with distal-radius fractures who underwent MRI prior to undergoing open-reduction surgery between April 2020 and July 2021 were included in this study. An analysis of various radiologic parameters, the fracture type, and the MRI classification of TFCC injuries was performed. Radiologic parameters were used in the evaluation of distal radioulnar joint (DRUJ), radial shortening, and the dorsal angularity of the fracture. All of the patients in this study had definite traumatic TFCC injuries. A statistical relationship was observed between the radial length gap between the intact wrist and the injured wrist, which represents relative radial shortening, and the pattern of TFCC injury. In conclusion, the shortening of the distal radius, causing peripheral soft tissue of the ulnar side to become tauter, is highly relevant with regard to the pattern of TFCC injury. However, because no data on the clinical outcome were utilized in this study, it is lacking in clinical perspective. The conduct of further studies on patients’ clinical outcome will be necessary.

Load Distribution in Dorsally-Angulated Distal Radius Deformity Using Finite Element Analysis

The load axis of the carpals is located on the volar side of the normal distal radius. Avolar lunate facet fracture (VLFF) is exposed to volar-shearing stress, which can causevolar displacement of the carpus. A previous biomechanical study reported that the load at the scaphoid fossa was located more dorsally and the pressure at the lunate fossa decreased in a dorsally-angulated model. However, the distal radius load distribution for various volar tilts remains unclear. We speculate that if the volar tilt decreases, the load distribution moves dorsally and decreases the stress on the VLFF. Therefore, we analyzed a dorsally-angulated distal radius model to evaluate changes in the load distribution using finite element analysis. A 3-dimensional finite element wrist model was developed using computed tomography images. The ligaments were modeled as tension-only spring elements. We considered the intact wrist model for a volar tilt of 15° and created 5 additional models for volar tilts of 10°, 5°, 0°,-5°, and-10°. As the dorsal angulation increased, the stress distribution moved from volar to dorsal andfrom the lunate fossa toward the scaphoid fossa. The maximum stress on the volar lunate facetwas reduced as volar tilt decreased. The maximum stress was higher on the lunate fossa for volar tilts from 15° to 5°. In contrast, the maximum stress was higher on the scaphoid fossa for volar tilts of ≤0°. Load transmission moved from volar to dorsal and from the lunate fossa to the scaphoid fossa when the volar tilt decreased. Therefore, a decrease in the volar tilt would reduce the load on the VLFF. This study provides surgeons accurate knowledge regarding load distribution of the distal radius for various volar tilts that could be helpful in treating patients with VLFFs.

Conservative Approach is Safe for Perfused-Pulseless Hands Following Blunt Brachial Artery Injury in Children.

Blunt trauma of the brachial artery (BA) in pediatric age is often associated with neurological and orthopaedic injuries. Acute ischemic hands warrant immediate exploration, but the management of warm-pulseless hands following elbow trauma is controversial. This study evaluates the role of conservative treatment of blunt BA injuries in children with non-threatened hands. Eleven children with blunt trauma onto the BA having warm-pulseless hands were studied retrospectively. After a mean follow-up period of 2.5 ± 0.9 years, all cases had thorough clinical examination and duplex scan to assess the treatment outcomes. At the end of follow-up period, all subjects had well-perfused hands with intact wrist pulses. The duplex scan revealed those who had interposition grafts to be patent and one case had an aneurysmal dilatation. There was no statistical significance difference between affected and healthy forearms regarding the mean peak systolic velocity at the wrist, affected side was 62 ± 0.82 cm/s versus 68 ± 0.57 cm/s for opposite side ( p -value = 0.14). Patients with blunt BA trauma and warm-pulseless hands could be managed safely with conservative treatment, leaving surgical exploration for those who did not regain pulses after 48 hours. Duplex ultrasound can safely verify the patency of surgical repair and can be used for surveillance to detect future complications.

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

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. 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. 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. 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.

Biomechanical Comparison of Dart-Throw Motions after Partial Wrist Fusions.

Background Multiple partial wrist fusions exist for the management of arthritic disease. Limited information is available on their effect on wrist range of motion in the dart-throwing direction of wrist motion, even though it is used in most activities of daily living. Purpose The purpose of this study was to measure the retained motion for different orientations of dart-throwing motion for seven different partial wrist fusions and proximal row carpectomy (PRC). Methods Eight fresh frozen right cadavers were tested with the wrist intact and followed simulated fusions. Fusions were performed using an external fixation technique and included scaphocapitate, scapholunate (SL), capitolunate, radiolunate, radioscapholunate, scaphotrapeziotrapezoid, 4 corner fusion, and PRC. Results In the intact wrist, the average arc of wrist motion with the wrist oriented at 20 degrees away from the flexion-extension axis was significantly larger than at any other orientation of motion. All partial wrist fusions and the PRC had significantly smaller average dart-throw arc of motion compared with intact at an orientation 20 and 25 degrees away from flexion-extension. The SL fusion provided a significantly larger arc of motion than most of the other fusions at most orientations. Conclusion/Clinical Relevance This study provides a comprehensive compilation of the range of motion in a functional plane, "the dart-throw motion," for limited wrist fusions and PRC. These data provide the clinician with important information that can be used to educate patients regarding expectations after surgery.

The role of scapholunate interosseous, dorsal intercarpal, and radiolunate ligaments in wrist biomechanics

Rupture to wrist ligaments predisposes the joint to degenerative changes. Scapholunate interosseous ligament (SLIL) rupture, especially when compounded by dorsal intercarpal ligament (DIC) and long radiolunate ligament (LRL) disruption, can cause carpal bone kinematic abnormalities. It is essential to delineate the role of these ligaments and their constraints on wrist range-of-motion (ROM) and center of rotation (COR). Wrist ROM and COR location were determined in 9 specimens using a six degree-of-freedom robotic musculoskeletal simulator in 24 directions of wrist motion for four experimental conditions: intact, and after sequential sectioning of the SLIL, DIC, and LRL. Sectioning the SLIL alone did not change wrist ROM in any direction (p > 0.10), while sectioning the SLIL and both the DIC and LRL caused significant increases in radial deviation, radial-extension, and ulnar-flexion ROM (p < 0.05). The COR of the intact wrist was located between the proximal third and middle third of the capitate, depending on the direction of wrist motion. While SLIL sectioning alone did not affect the COR, subsequent DIC sectioning led to a distal shift of COR in motions involving ulnar-extension relative to the intact condition. Additional sectioning of the LRL caused a proximal shift of COR in motions involving radial-flexion. A proximal shift implies a more dominant role of the radiocarpal joint, while a distal shift of the COR implies an increased role for the midcarpal joint. Understanding the role of ligaments on overall wrist mechanics is critical to devising new treatment strategies to restore wrist function.

Kinematic analysis of two scapholunate ligament reconstruction techniques.

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). 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. 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. 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. 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.

Biomechanical comparison of arthroscopic and open lunate excisions in the cadaveric wrist

BackgroundIn advanced Kienböck disease, unreconstructible lunate should be excised as a salvage procedure. There is a lack of information about the biomechanical approaches evaluating the carpal kinematics after lunate excision. We hypothesized that arthroscopic lunate excision would not break the ring structure of the proximal carpal row, preventing carpal instability. We aimed to investigate changes in carpal kinematics following arthroscopic and open lunate excisions. MethodsWe used upper extremities from five fresh cadavers and simulated arthroscopic and open lunate excisions. Arthroscopic lunate excision was performed to preserve the attachment sites of intrinsic and extrinsic carpal ligaments to the lunate. Open lunate excision was conducted with sectioning of the intrinsic and extrinsic carpal ligaments. Using a three-dimensional space electromagnetic tracking device, rotation angles of the scaphoid and triquetrum and the change of scaphotriquetrum distance were measured under axial loading. We compared the rotation angles and the change of scaphotriquetrum distance among intact wrists, open, and arthroscopic lunate excisions. FindingsNo Significant differences in the rotation angle of the scaphoid and triquetrum or the change of scaphotriquetrum distance were found between intact wrist and arthroscopic lunate excision. The triquetrum significantly dorsiflexed and supinated in wrists with open lunate excisions compared with intact wrists. Significant differences in the change of scaphotriquetrum distance were found between intact and openly excised wrists and between arthroscopic and open excisions. InterpretationArthroscopic lunate excision potentially prevented kinematic change of the proximal carpal row under axial loading by maintaining the integrity of attachment sites of carpal ligaments.

Carpal Motion in Chronic Geissler IV Scapholunate Interosseous Ligament Wrists

Purpose This study evaluated the biomechanics of Geissler IV (G4) wrists in cadavers and compared them with intact specimens after multiple ligament sectioning to create scapholunate instability. It also evaluated carpal motion changes after sectioning of the lunotriquetral interosseous ligament (LTIL). Methods Eight cadaver wrists determined to be G4 arthroscopically were tested using a wrist joint motion simulator. The LTIL was then sectioned, and carpal motion was recorded again. Carpal motions were compared with 37 normal wrists after sectioning of the scapholunate interosseous ligament and other ligaments to create a G4 wrist. Results Carpal motion of the 37 normal wrists after ligamentous sectioning was similar to motion of the 8 specimens noted to be G4. These wrists did not demonstrate subluxation of the scaphoid that may occur after ligament sectioning. After sectioning of the LTIL, there were significant changes in lunate and triquetral motion. Conclusions These findings support the hypothesis that sectioning multiple ligaments in normal wrists to create scapholunate instability causes average motion comparable to that seen in G4 wrists. Ligamentous sectioning can cause a range of scaphoid instability. Lunotriquetral interosseous ligament sectioning in native G4 wrists caused greater changes in triquetral than scaphoid range of motion. Clinical relevance Patients with arthroscopically determined G4 lesions have an incompetent SLIL and scapholunate instability but do not necessarily have scapholunate dissociation and subluxation. Cadaver studies that evaluate instability by sectioning specific intact wrist ligaments are similar to the G4 specimens and thus are a good approximation of naturally occurring wrist instability. The functionality of secondary stabilizers not seen arthroscopically may explain the differences in motion. Geissler IV wrists and ligament-sectioned wrists are points on the spectrum of carpal instability, which is determined by the extent of damage to multiple ligamentous structures.

Shear Wave Elastography (SWE) Evaluation of Asymptomatic Flexor Pollicis Longus Tendon Condition After Volar Plate Fixation for Distal Radius Fracture.

ObjectiveThis study aimed to evaluate asymptomatic flexor pollicis longus (FPL) tendon condition after volar plate fixation for distal radius fracture using shear wave elastography (SWE).MethodsWe evaluated 36 distal radius fractures with shear wave elastography to evaluate the FPL tendon after volar plate fixation. Ultrasonography was used to measure the FPL distance to the volar plate in the involved wrists, and the thickness of the FPL tendon in the involved wrists was measured on SWE sonograms taken 12 months postoperatively. Measurements of the involved wrists were compared with those of the intact wrists. The radiographic parameters and Soong grade were collected to analyze the correlation between these indicators and the value of the Young’s modulus and asymptomatic tendon injury.ResultsThe mean values of the Young’s modulus for involved wrist were lower than for intact wrist tendons. The values of the Young’s modulus were correlated with the FPL distance, radial inclination, and Soong grade. FPL tendons of involved wrists exhibited in the majority a yellow (intermediate) SWE signal, compared to intact wrist tendons, which exhibited a red (hard) signal in the vast majority, and there were significant differences between the involved and intact wrist.ConclusionFPL tendon may develop asymptomatically changes after volar locking plate fixation of distal radius fractures, which can be detected by SWE effectively. FPL distance, radial accretion, and Soong grade may be the main causes of asymptomatic FPL tendon erosion.

Relationship between Fracture of the Ulnar Styloid Process and DRUJ Instability: A Biomechanical Study.

Background There has been clinical question in the treatment of ulnar styloid fracture with distal radius fracture, surgical fixation of the styloid fragment, or ignorance of the fragment. We examined relationship between size of the ulnar styloid fracture and distal radioulnar joint (DRUJ) stability biomechanically to answer the above clinical question. Methods Changes in the dorsopalmar stiffness of the DRUJ after experimentally simulating in four types of ulnar styloid fractures were examined in cadavers. After tip, middle, base-horizontal, and base-oblique type of styloid fractures were made sequentially, changes in dorsopalmar DRUJ stiffness were measured using the MTS machine in the intact wrist, for each fracture, at 60 degrees pronation, neutral, and 60 degrees supination, respectively. Additional cutting of the radioulnar ligament (RUL) at the fovea was also simulated with the base-horizontal fracture. Results The tip and middle type fractures did not demonstrate significant loss of stiffness compared with the intact. The base-horizontal fracture demonstrated only significant loss of stiffness in the dorsal direction (radius palmar; ulnar dorsal) with forearm in neutral rotation. The base-oblique fracture demonstrated significant loss of dorsopalmar stiffness of the DRUJ. Additional section of the RUL with the base-horizontal fracture induced significant loss of stiffness of the DRUJ compared with the intact. Conclusions Because the RUL originates from the fovea as well as from the base of the ulnar styloid, these results suggest that DRUJ instability closely correlates with how much of the bony fragment includes the originating portions of the RUL. The findings further suggest that larger base-oblique and base-horizontal fragments with resultant DRUJ instability must be reattached, but that even base-horizontal fragment as well as tip and middle ulnar styloid fragment can be ignored when there is no instability.

Stabilization of the distal radioulnar joint by reconstructing the interosseous membrane's distal oblique bundle: Cadaver study

IntroductionThe distal radioulnar (DRU) ligaments play a key role in stabilizing the DRU joint. Ligament reconstruction in this area is an accepted treatment. However, another structure may also be a significant DRUJ stabilizer–the distal oblique bundle (DOB) of the interosseous membrane (IOM). Recent studies have described DOB reconstruction methods, which should be compared to DRU ligament reconstruction. MethodsTwelve upper limbs were used. First, a descriptive anatomy study was done to determine the prevalence and features of the DOB (insertions, thickness, and relationship with DRU ligaments). Second, biomechanical testing was done with the wrist in neutral position, supination, and pronation. Distal radius translation was evaluated first on an intact wrist then evaluated again after creating bidirectional instability. Lastly, the same tests were repeated after DRU reconstruction using the Adams-Berger technique and DOB reconstruction using the Riggenbach technique. ResultsThe DOB was present in 50% of specimens and was bilateral. Reconstructing the DOB stabilized the wrist to the same degree as the Adams-Berger technique in neutral and pronation (8% residual major instability). Stability was harder to achieve in supination (25% major instability). It was better at controlling posterior radial translation than anterior translation (3% versus 14% major instability). ConclusionDOB reconstruction appears to be a reliable and less invasive treatment option for DRUJ instability since it is extra-articular. However, the wrist's position and the direction of radial translation seem to alter the stabilization's effectiveness. Level of evidenceIV; Cadaver study.

Distal radioulnar joint stability measured with radiostereometry during the piano key test.

Distal radioulnar joint instability is difficult to grade by clinical examination and interobserver reliability is low. This study used a new and precise radiostereometry method for measurement of distal radioulnar joint translation. Eight human donor arms were positioned in a custom-made fixture and a standardized piano key test was done with pressure on the ulnar head. Examination was done before and after dividing the styloid and foveal insertions of the triangular fibrocartilage complex. In the intact wrists, the piano key test induced a mean 1.36 mm translation of the ulnar head, which increased statistically significantly to 1.96 mm after a lesion of the styloid ligament insertion and to 2.3 mm after combined lesions of the styloid and foveal ligament insertions. This experimental cadaver study demonstrates a radiological method for precise quantification of distal radioulnar joint stability after different grades of triangular fibrocartilage complex injury.