Intact Wrist Research Articles

The effect of surgery for basal osteoarthritis of the thumb on dart thrower's motion.

This study aimed to identify the effects of basal thumb surgery on the range of dart thrower's motion. Thirteen fresh-frozen cadaveric specimens were placed in a customized jig. Simulated scaphotrapeziotrapezoid joint fusion was carried out on all specimens. Half the specimens then underwent trapeziectomy and the rest had excision of the distal pole of the scaphoid. Simulated scaphotrapeziotrapezoid fusion reduced the range of dart thrower's motion to 89% of the range in the intact wrists, from a mean of 117° to 104°. Although this reduction is not large, it was statistically significant. Simulated trapeziectomy caused a very small increase in dart thrower's motion range compared with the range in the intact wrists. Simulated distal pole of scaphoid excision did not change the range of dart thrower's motion. These results may inform preoperative decisions for surgical management of basal osteoarthritis of the thumb.

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

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. 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. 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. Our findings support the theory that there is a relationship between scapholunate kinematics and laxity at the level of the interosseous ligaments. 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.

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.

The Effect of Surgical Treatments for Trapeziometacarpal Osteoarthritis on Wrist Biomechanics: A Cadaver Study

PurposeStudies have shown the effects of surgical treatments for trapeziometacarpal osteoarthritis on thumb biomechanics; however, the biomechanical effects on the wrist have not been reported. This study aimed to quantify alterations in wrist muscle forces following trapeziectomy with or without ligament reconstruction and replacement.MethodsA validated physiological wrist simulator replicated cyclic wrist motions in cadaveric specimens by applying tensile loads to 6 muscles. Muscle forces required to move the intact wrist were compared with those required after performing trapeziectomy, suture suspension arthroplasty, prosthetic replacement, and ligament reconstruction with tendon interposition (LRTI).ResultsTrapeziectomy required higher abductor pollicis longus forces in flexion and higher flexor carpi radialis forces coupled with lower extensor carpi ulnaris forces in radial deviation. Of the 3 surgical reconstructions tested post-trapeziectomy, wrist muscle forces following LRTI were closest to those observed in the intact case throughout the range of all simulated motions.ConclusionsThis study shows that wrist biomechanics were significantly altered following trapeziectomy, and of the reconstructions tested, LRTI most closely resembled the intact biomechanics in this cadaveric model.Clinical relevanceTrapeziectomy, as a standalone procedure in the treatment of trapeziometacarpal osteoarthritis, may result in the formation of a potentially unfilled trapezial gap, leading to higher wrist muscle forces. This biomechanical alteration could be associated with clinically important outcomes, such as pain and/or joint instability.

MRI Study on the Distance between the Distal Radius and the Flexor and Extensor Tendons: Is There Any Room for Error/Hardware?

Purpose This study aims to quantify the distances between the cortex of the distal radius and flexor and extensor tendons. Methods We analyzed 50 magnetic resonance images (MRI) of intact wrist without pathology. The distances between the volar cortex and the flexor pollicis longs (FPL), index flexor digitorum profunduns (FDPi), flexor digitorum profundus (FDP), and flexor digitorum superficialis (FDS) were measured at the level of the watershed line and 3- and 6-mm proximal to this level. The distances between the dorsal cortex and the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor pollicis longus (EPL), extensor indicis proprius (EIP), and the extensor digitorum communis (EDC) were measured at the level of Lister's tubercle and 5-mm distal to this level. Analysis was descriptive. Results At the watershed line, the FPL, FDPi, FDP, and FDS were located at an average of 3.1, 2.4, 3.6, and 5.1 mm, respectively, volar to the volar cortex. The distances of the FDP and FDS increased at 3-mm proximal to the watershed line and increased for all four tendons at 6-mm proximal to the watershed line. Dorsally, at Listers' tubercle the ECRL, ECRB, EPL, EIP, and EDC were identified at an average of 0.7, 0.5, 0.5, 2.6, and 3.2 mm, respectively, dorsal to the dorsal cortex of the distal radius. At 5-mm more distal, these tendons were located on average 1.2, 1.0, 0.7, 1.9, and 1.8 mm, respectively, dorsal to the dorsal cortex. Conclusion On the volar side, on average there is enough room for a volar plate when staying proximal to the watershed line. On the dorsal side, there is virtually no room for protruding screws as physical anatomical space is limited to a maximum of 0.7 mm from cortex to the closest tendon (the FDP), with screw increments being 2 mm. Level of Evidence This is a Level II Study.

Dorsal Wrist Extrinsic Carpal Ligament Injury Exacerbates Volar Radiocarpal Instability After Intra-Articular Distal Radius Fracture.

Background: Volar radiocarpal instability is often seen after loss of fixation of volar lunate facet fragments. The pathogenesis of post-traumatic volar radiocarpal instability is poorly understood. The purpose of this study was to determine if injury to the dorsal wrist extrinsic carpal ligaments contributes to volar radiocarpal instability. Methods: Six matched pairs of cadaveric upper extremities were tested using a dynamic hand testing system. In group 1, the intact wrist, the wrist with a volar lunate facet fracture, and the fractured wrist after 500 cycles of grip were tested. In group 2, in addition to the intact and fractured wrist, the fractured wrist with the dorsal extrinsic carpal ligaments cut and the fractured wrist with the dorsal extrinsic carpal ligaments cut after 500 cycles of grip were also tested. Volar-dorsal displacement of the lunate was measured from 45° wrist flexion to 45° wrist extension in 22.5° increments with the wrist flexors/extensors loaded for each condition. Results: Volar lunate translation did not significantly increase after the volar lunate facet fracture alone, and was not evident to a significant extent until the dorsal wrist extrinsic carpal ligaments were cut. Further instability of the lunate occurred after grip cycling only with the dorsal extrinsic capsular ligaments cut. Conclusions: Injury to the dorsal wrist extrinsic carpal ligaments exacerbates volar radiocarpal instability. Unrecognized dorsal sided injury may be a contributing factor to why stable fixation of volar lunate facet fragments remains problematic after volar plating of intra-articular distal radius fractures with displaced volar lunate facet fragments.

Wrist kinetics after scaphoidectomy

BackgroundThe scaphoid cannot be excised without generating substantial carpal dysfunction. The extent and nature of such a destabilizing procedure, however, has never been properly studied in the laboratory. MethodsWe used a six-degrees-of-freedom motion tracking device to quantify the changes in carpal alignment produced by isometric simultaneous loading of five wrist motor tendons in 12 fresh normal cadaver arms, before and after excising the entire scaphoid. FindingsIn the intact wrist, tendon loading consistently extended and supinated the capitate while flexing the triquetrum. After scaphoidectomy, the opposite rotations were always found: the capitate collapsed into flexion and pronation, whereas the triquetrum migrated proximally, while extending and radial deviating. All these changes were statistically significant. InterpretationUnless it is supplemented by some sort of midcarpal stabilization, scaphoidectomy alone is much too aggressive as a procedure to be considered a treatment option for wrist osteoarthritis. Level of evidenceLaboratory study. Not applicable.

The Role of Triangular Fibrocartilage Complex in Axial Stability of the Forearm.

Background The triangular fibrocartilage complex (TFCC) provides stability to the wrist and disruption of this complex can result in axial instability which can lead to ulnocarpal abutment. Purpose This article determines the individual contributions of the volar radioulnar ligament (VRUL), dorsal radioulnar ligament (DRUL), and foveal attachment of the TFCC to longitudinal stability of the forearm under axial load. Materials and Methods Eighteen cadaveric specimens were randomly assigned into three groups representing the component of the TFCC to be initially transected: VRUL, DRUL, and foveal attachment. Prior to transection, posterioranterior radiographs of the wrist were obtained at 0, 44.5, and 90 N of axial load. Serial transection of the TFCC components were performed with radiographs obtained at each of the aforementioned loads. Ulnar variance was assessed with two-way repeated measures analysis of variance and paired t -tests. Results Transection of the foveal attachment demonstrated a significant change in ulnar variance of 1.5 and 0.6 mm under 45 and 90 N of load, respectively. At 0 N of load, there was no significant change in ulnar variance between an intact wrist and a wrist with all three ligaments transected; however, a significant change in ulnar variance, 1.0 mm, was observed under 90 N of load. Conclusion The foveal attachment of the TFCC provides the largest contribution to axial stability. Clinical Relevance The TFCC provides axial stability to the wrist and disruption of the TFCC may result in change in ulnar variance observed on an axial loaded wrist radiograph.

Effect of Push-Up Position on Wrist Joint Pressures in the Intact Wrist and Following Scapholunate Interosseous Ligament Sectioning.

To determine the contact pressures between the scaphoid and lunate and the distal radius during 2 wrist push-up positions before and following scapholunate interosseous ligament (SLIL) sectioning. Eight fresh cadaveric wrists were tested in a neutral flexion-extension (knuckle) push-up position and in an extended push-up position. Pressure measurements were acquired as each wrist was loaded with the wrist in extension and with the wrist in a neutral position. Data were acquired with the SLIL intact and following sectioning of its dorsal, volar, and proximal components. The wrist was disarticulated and a map drawn on each sensor to identify each joint fossa. A push-up performed with the wrist in extension caused a significantly greater peak pressure in the radioscaphoid fossa but not in the radiolunate fossa. Moving the wrist into extension caused a significant dorsal movement of the pressure centroid an average of 2.9 mm in the radiolunate fossa and an average of 5.7 mm in the radioscaphoid fossa. Sectioning the SLIL caused the centroid of pressure in the radioscaphoid fossa to significantly move an average 1.4 mm radially. A push-up with the wrist in extension causes a significant increase in the pressure in the radioscaphoid fossa but not in the radiolunate. This finding may help explain why degenerative arthritis first develops in the radioscaphoid fossa before involving the radiolunate fossa. As expected, gapping that occurs with SLIL injury was observed here as a radial translation of the scaphoid and not as a movement of the lunate. The new location of scaphoid contact may be an additional reason for the development of radioscaphoid arthritis occurring before radiolunate arthritis. This study provides a possible explanation as to why degenerative arthritis may first occur in the radioscaphoid fossa.

Relative Contributions of the Midcarpal and Radiocarpal Joints to Dart-Thrower's Motion at the Wrist.

To identify the relative contributions of the radiocarpal (RC) and midcarpal (MC) joints to dart-thrower's motion (DTM) of the wrist. Six cadaveric upper extremities were fixed to a custom-designed loading jig allowing for pure moment-rotation analysis in 24 different directions of wrist motion. Each specimen was tested in 3 states: intact, simulated radiocarpal fusion (sRCF) and simulated pancarpal fusion (sPCF). Moments of ± 1.5 Nm were applied at each of 24 directions for each state and the resulting wrist rotation recorded. Data from each specimen were reduced to compute the range of motion (ROM) envelopes and the orientation of the ROM for the 3 different states. The ROM was significantly decreased in the sRCF and sPCF groups compared withthe intact group in the directions of the pure extension, radial extension, ulnar flexion, and ulnar deviation. No significant difference in ROM was detected between the sRCF and sPCF groups in any direction. The ROM envelopes for the intact, sRCF, and sPCF groups were all oriented obliquely to the axis of pure wrist flexion-extension near a path of ulnar flexion-radial extension, consistent with prior reports on DTM. Although both simulated fusion types decreased ROM compared with the intact wrist, the principal direction of wrist motion along the path of DTM was not significantly altered by simulated RCF or PCF. These findings suggest that the RC and MC joints can each contribute to asimilar mechanical axis of motion located along the path of DTM when the other jointhas been eliminated via fusion. Surgical options such as partial wrist fusions maymaintain the native wrist's mechanical axis if either the RC or the MC joint ispreserved, despite significant reduction in overall ROM.

Analysis of tenodesis techniques for treatment of scapholunate instability using the finite element method

Chronic scapholunate ligament (SL) injury is a common disorder affecting the wrist. Despite advances in surgical techniques used to treat this injury, SL gap re-emergence may occur postoperatively. This paper presents an investigation into the performance of the Corella, schapolunate axis (SLAM), and modified Brunelli tenodesis (MBT) surgical reconstruction techniques used to treat scapholunate instability. Finite element (FE) models were used to undertake virtual surgery, and the resulting scapholunate (SL) gap and angle obtained using the 3 techniques were compared. The Corella technique was found to achieve the SL gap and angle closest to the intact (ligament) wrist, restoring SL gap and angle to within 5.6% and 0.6%, respectively. The MBT method resulted in an SL gap least close to the intact. The results of our study indicate that the contribution of volar scapholunate interosseous ligament to scapholunate stability could be important.

Flexor tendon complications in comminuted distal radius fractures treated with anatomic volar rim locking plates

ObjectiveAnatomic volar rim locking plates are designed with the aim of treating intraarticular distal radius fractures. When used to treat comminuted distal radius fractures, these plates can damage the flexor tendons.In this study, we sought to determine the radiological and functional results and rate of complications of these plates. MethodsWe retrospectively reviewed the records of 36 patients (28 males, 8 females; mean age: 46.4 years) with AO/OTA Type C2-C3 distal radius fractures treated with anatomic volar rim distal radius plates between January 2011 and December 2014. Radial length, radial inclination and palmar tilt were compared with the intact wrist. Results were evaluated with the Mayo wrist and Lidstrom scores. Complications were documented throughout the follow-up period of 23.8 (range: 12 to 48) months. ResultsPostoperative measurements of the radial length, inclination and palmar tilt did not differ significantly. Mayo wrist and Lidstrom scores were good and excellent in 27 and 32 patients, respectively. Flexor tenosynovitis was symptomatic in 15 patients and asymptomatic (localized swelling only) in 21. Plates were removed from 15 patients due to symptomatic tenosynovitis and from six patients due to partial rupture of the flexor pollicis longus tendon. The flexor digitorum profundus tendon of the second finger was also partially ruptured in three patients. ConclusionAnatomic volar rim locking plates provide satisfying radiological and functional results in treating AO/OTA Type C2-C3 comminuted distal radius fractures. However, if these plates interfere with the union of the fracture, they should be removed to avoid potential tendon problems caused by their placement in the rim region.Level of Evidence: Level IV, Therapeutic study

Ultrasonic Evaluation of the Flexor Pollicis Longus Tendon Following Volar Plate Fixation for Distal Radius Fractures

To evaluate with ultrasound the thickness of the flexor pollicis longus (FPL) tendon andits relationship to the volar locking plate after the fixation of distal radius fractures. We evaluated 27 type C2 and C3 distal radius fractures with ultrasound to evaluate damage to the FPL tendon after volar plate fixation. The thickness of the FPL tendon and its distance to the volar plate in the involved wrists and to the volar rim in the contralateral uninjured wrist were measured on sonograms taken 12 months postoperatively. Measurements of the involved wrists were compared with those of the intact wrists. The mean plate-tendon distance in the involved wrist was considerably shorter than the mean volar rim-tendon distance in the intact wrist, and the FPL tendon was considerably thicker in the involved wrist than in the intact wrist. In distal radial fractures treated with volar locking plates, increases in the thickness of the FPL tendon and a consequent decrease in the distance between the tendon and the plate can be determined with ultrasonography. This finding is a warning that asymptomatic tenosynovitis may eventually cause tendon ruptures. Diagnostic IV.

Retraction Note to: Carpal tunnel syndrome in patients who are receiving long-term renal hemodialysis

The development of a carpal tunnel syndrome has become an increasingly recognized problem in patients who are treated by long-term hemodialysis. Arteriovenous fistula has been identified as one of the possible cause for the development of carpal tunnel syndrome. Wrists of 558 hemodialysis patients who had fistula at least 1 year served as the case group and the other intact wrists of the same patients served as the control group. Carpal tunnel syndrome was diagnosed clinically; however, 232 random patients underwent electrodiagnostic studies the day after hemodialysis. In 170 (30.5%) wrists with arteriovenous fistula developed carpal tunnel syndrome versus 68 (12.2%) in the contralateral wrist. Three patients had a concurrent diagnosed radial steal syndrome. In all three wrists that had radial steal syndrome developed carpal tunnel syndrome. There was a correlation, however, between the development of the carpal tunnel syndrome, and the side of the longest vascular access. Contrary to the clinical assessment, electrodiagnostic studies did not indicate any significant association between the frequency of carpal tunnel syndrome and arteriovenous fistula or its duration. Hemodialysis patients are at considerable risk of developing carpal tunnel syndrome in the wrist with an arteriovenous fistula. Close observation and routine clinical examination is mandatory to prevent further problems.

Effect of wrist position on distal radioulnar joint stability: a biomechanical study.

We investigated distal radioulnar joint (DRUJ) stability in different wrist positions and examined the relative contribution of each ligamentous component of the triangular fibrocartilage complex (TFCC) to DRUJ stability. We used nine fresh-frozen cadavers. The humerus and ulna were fixed at 90° elbow flexion. The radiocarpal unit was translated relative to the ulna in dorsopalmar directions with the wrist in five positions. Displacement of the unit was measured by an electromagnetic tracking device. Magnitudes of displacement were compared between different wrist positions in various sectioning stages: ulnocarpal ligament (UCL) sectioning, radioulnar ligaments (RUL) sectioning, and extensor carpi ulnaris (ECU) floor sectioning. Wrist position and sectioning stage significantly influenced the displacement. In intact wrists, the displacement in wrist extension was significantly lower than that in neutral. However, after UCL sectioning, there were no longer any significant differences. After RUL sectioning, the displacement in radial deviation was significantly lower than that in neutral. Following ECU floor sectioning, there were no longer any significant differences. Thus, in intact wrists, DRUJ stability in wrist extension is likely due to tightening of the UCL. After complete RUL sectioning, DRUJ is stabilized in radial deviation due to tightening of the ECU floor.

Effect of Pisiform Excision or Pisotriquetral Arthrodesis as a Treatment for Pisotriquetral Arthritis: A Biomechanical Study

To determine whether flexor carpi ulnaris (FCU) forces and tendon displacements change after pisotriquetral arthrodesis or after pisiform excision. Nine cadaver wrists were moved through 4 variations of a dart throw motion, each having an oblique plane of motion, but with different ranges of motion and different antagonistic forces. The FCU tendon force and movement were measured in the intact wrist, following pisotriquetral arthrodesis, and following pisiform excision. Changes in force and tendon movement were compared using a repeated measures analysis of variance. After excision of the pisiform, a significantly greater FCU force was required during the 2 variations of the dart throw motion having a larger range of motion and during the smaller motion having a larger antagonistic force. Pisotriquetral arthrodesis did not cause a significant increase in the peak FCU force. Excision of the pisiform caused the FCU tendon to significantly retract during all wrist motions as compared to the intact wrist or after pisotriquetral arthrodesis. Greater FCU forces are required to move the wrist when the pisiform with its moment arm function has been removed. This occurs during large oblique plane wrist motions and also in a smaller motion when greater antagonistic forces are applied. Excision of the pisiform also allows the FCU to move proximally, again because its moment arm function has been eliminated. Excision of the pisiform requires greater FCU forces during large wrist motions and during motions that include large gripping forces such that excision may be a concern in high-demand patients with pisotriquetral arthritis. Although pisotriquetral arthrodesis does not alter the mechanical advantage of the FCU, its use in high-demand patients with pisotriquetral osteoarthritis cannot yet be recommended until the effects of that arthrodesis on midcarpal kinematics are further clarified.

4-Corner Arthrodesis and Proximal Row Carpectomy: A Biomechanical Comparison of Wrist Motion and Tendon Forces

Controversy exists as to whether a proximal row carpectomy (PRC) is a better procedure than scaphoid excision with 4-corner arthrodesis for preserving motion in the painful posttraumatic arthritic wrist. The purpose of this study was to determine how the kinematics and tendon forces of the wrist are altered after PRC and 4-corner arthrodesis. We tested 6 fresh cadaver forearms for the extremes of wrist motion and then used a wrist simulator to move them through 4 cyclic dynamic wrist motions, during which time we continuously recorded the tendon forces. We repeated the extremes of wrist motion measurements and the dynamic motions after scaphoid excision with 4-corner arthrodesis, and then again after PRC. We analyzed extremes of wrist motion and the peak tendon forces required for each dynamic motion using a repeated measures analysis of variance. Wrist extremes of motion significantly decreased after both the PRC and 4-corner arthrodesis compared with the intact wrist. Wrist flexion decreased on average 13° after 4-corner arthrodesis and 12° after PRC. Extension decreased 20° after 4-corner arthrodesis and 12° after PRC. Four-corner arthrodesis significantly decreased wrist ulnar deviation from the intact wrist. Four-corner arthrodesis allowed more radial deviation but less ulnar deviation than the PRC. The average peak tendon force was significantly greater after 4-corner arthrodesis than after PRC for the extensor carpi ulnaris during wrist flexion-extension, circumduction, and dart throw motions. The peak forces were significantly greater after 4-corner arthrodesis than in the intact wrist for the extensor carpi ulnaris during the dart throw motion and for the flexor carpi ulnaris during the circumduction motion. The peak extensor carpi radialis brevis force after PRC was significantly less than in the intact wrist. The measured wrist extremes of motion decreased after both 4-corner arthrodesis and PRC. Larger peak tendon forces were required to achieve identical wrist motions with the 4-corner arthrodesis compared with the intact wrist. We observed smaller forces for the PRC. These results may help explain why PRC shows early clinical improvement, yet may lead to degenerative arthritis.

Radioscapholunate Arthrodesis With Excision of the Distal Scaphoid: Comparison of Contact Characteristics to the Intact Wrist

To evaluate the midcarpal contact characteristics at the lunocapitate (LC) and scaphotrapezio-trapezoidal (STT) joints in 3 wrist conditions: intact, after simulating a radioscapholunate (RSL) arthrodesis, and after an RSL arthrodesis with distal scaphoid excision (DSE). Eight fresh-frozen cadaveric specimens were tested using a custom jig with the wrist in neutral, 15° and 30° flexion and extension, 10° radial deviation, and 20° ulnar deviation. The RSL arthrodesis was performed using 2.4-mm distal radius plates with locking screws. Using a pressure sensor, contact force, average pressure, peak pressure, and contact area at the STT and LC joints were measured for 3 conditions: intact wrist, RSL arthrodesis, and RSL arthrodesis with DSE. Following RSL arthrodesis, average and peak pressure at the LC joint increased significantly compared to the intact wrist. In the STT joint, the average and peak contact pressure increased significantly compared to the intact wrist. Following DSE, average and peak pressure at the LC joint increased further compared to the RSL arthrodesis condition. Our findings showed increased contact pressures in the STT and LC joint following RSL arthrodesis, which may explain the clinical findings of midcarpal arthritis. Also, although DSE may improve short-term range of motion and clinical incidence of midcarpal arthritis, our findings showed that this comes at a cost, as the remaining portions of the midcarpal joint are subject to higher forces and pressures following DSE. Radioscapholunate arthrodesis results in increased midcarpal contact pressures that may explain the clinical incidence of midcarpal arthritis. Excision of the distal scaphoid further increases contact pressures in the remaining midcarpal joint and may further increase the incidence of midcarpal arthritis. These alterations in contact characteristics of the midcarpal joint should be considered when excising the distal scaphoid for improved range of motion.

Scaphoid Excision and Midcarpal Arthrodesis: The Effect of Triquetral Excision—A Biomechanical Study

To evaluate the biomechanical alterations that occur after traditional scaphoid excision and midcarpal arthrodesis with and without excision of the triquetrum. The hypothesis of this study was that removal of the triquetrum increases the radiolunate contact pressure. We cyclically moved 10 fresh cadaver wrists using a wrist joint motion simulator while measuring the contact pressures between the proximal carpal row and the distal radius and ulna using a dynamic pressure sensor. We acquired data in the intact wrist, after a midcarpal arthrodesis with the scaphoid excised, and then again with the triquetrum removed, which is also known as a capitolunate arthrodesis. The peak pressures in the radiolunate fossa significantly increased with either of the midcarpal arthrodeses compared with the intact wrist during each of the 3 dynamic wrist motions. In comparing the 2 midcarpal arthrodeses, the peak pressure in the ulnocarpal fossa significantly decreased after the triquetrum was removed during wrist radioulnar deviation and in the static ulnarly deviated position. After arthrodesis, we could identify no differences during any motion or static wrist position in the peak radiolunate pressures with or without the triquetrum. We found that scaphoid excision and 4-corner arthrodesis shifts loads to the radiolunate joint. Isolated capitolunate arthrodesis with excision of the scaphoid and triquetrum further alters carpal kinematics and loading patterns. These findings raise concern about routine excision of the triquetrum when performing a midcarpal arthrodesis.

Arthroscopic gap distance can predict the degree of scapholunate ligament tears: a cadaver study

BackgroundMidcarpal joint arthroscopy is essential for diagnosing scapholunate (SL) instability, but a discrepancy may exist between the grade of arthroscopic evaluation and the extent of SL ligament tears. This study aimed to investigate whether the magnitude of arthroscopic SL gap distance could predict the extent of ligamentous disruptions in a simulated SL dissociation model. MethodsEight upper extremities of fresh cadavers were analyzed. Static and dynamic SL gap distances were measured with using custom-made probes via midcarpal arthroscopy in intact wrists following sequential sectioning of the SL stabilizing ligaments. Comparisons of static and dynamic SL gaps between stages were conducted using analysis of variance followed by the Games–Howell test. Receiver operating characteristic (ROC) curves were constructed to assess the diagnostic performance of the SL gap distance in identifying simulated ligament tears. ResultsThere were no significant differences between stages in the static SL gap distance. Dynamic SL gap distance increased significantly following SL interosseous ligament (SLIL) sectioning. According to the ROC curve for dynamic SL gap distance, the area under the curve was 0.94 for the assessment of the diagnostic performances in identifying complete SLIL sectioning. A cut-off value of 1.4mm for the dynamic SL gap showed the highest diagnostic accuracy rate (91%). The dynamic SL gap distance showed a high diagnostic performance in the detection of dorsal intercarpal ligament (DICL) sectioning. The highest accuracy rate (85%) was noted when the threshold value was set at 2.8mm. ConclusionThe SLIL is the primary stabilizer of the SL joint in the viewpoint of arthroscopic measurement. Dynamic SL joint widening of more than 1.4mm showed the best predictive ability for complete SLIL tears, while 2.8mm widening made it possible to predict both DICL and SLIL tears.