The effect of sectioning the dorsal radiocarpal ligament and insertion of a pressure sensor into the radiocarpal joint on scaphoid and lunate kinematics

Arthroscopic scapholunate ligament repair and dorsal capsulodesis with suture anchor in acute and subacute scapholunate dissociation

PURPOSE

The objective of this study was to investigate the potential of arthroscopic scapholunate ligament repair and dorsal capsulodesis with suture anchor as a treatment option for patients experiencing symptomatic acute and subacute (< 3 months) scapholunate instability.

METHODS

From Jan. 2017 to Jan 2020, 19 wrists with acute or subacute tears of the SL ligament with symptomatic instability were treated with arthroscopic SL repair and dorsal capsulodesis with a suture anchor. The average time from injury to operation was 8.8 weeks (range, 4-11 weeks) and the regular follow-up mean duration at our clinic was 26.5 months (range, 24-32 months). The pain score according to the visual analog scale, wrist range of motion, grip strength, radiographic outcomes and functional outcomes according to the Modified Mayo Wrist Score (MMWS) were evaluated preoperatively and postoperatively during the follow-up period.

RESULTS

All 19 patients had rupture and dissociation of the SL ligament in the radiocarpal joint. The total arc of wrist motion in the flexion-extension plane loss averaged 5.1° (P > .01).The Wilcoxon signed-rank test was used to compare the results: grip force improved significantly with 14.7% improvement of that on the normal side (P < .01); the postoperative MMWS was significantly better than the preoperative scores (P < .01). Of 19 patients of the series, 18 patients (94.7%) achieved good or excellent results according to the MMWS and 16 patients (84.2%) resumed their previous activities. Only one patient (5.3%) had residual laxity of the scapholunate ligament joint at 15 months of follow-up.

CONCLUSIONS

At a minimum of two years of follow-up, patients with acute or subacute symptomatic dissociation of scapholunate ligament instability who underwent arthroscopic scapholunate ligament repair and dorsal capsulodesis with suture anchor treatment had satisfactory results.

LEVEL OF EVIDENCE

Level IV, case series.

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.

Motion and Strength Analysis of 2-Tine Staple and K-Wire Fixation in Scapholunate Ligament Stabilization in a Cadaver Model

Purpose

Previous studies have demonstrated the benefits of 2- and 4-tine staple fixation in scapholunate interosseous ligament (SLIL) reconstruction, including improved rotational control and avoidance of the articular surface. This study compared scaphoid and lunate kinematics after SLIL fixation with traditional Kirschner wire (K-wire) fixation or 2-tine staple fixation.

Methods

Eight fresh frozen cadaver arms with normal scapholunate (SL) intervals were included. Infrared motion capture was used to assess kinematics between the scaphoid and lunate as the wrists were moved through a simulated dart-throw motion. Kinematic data were recorded for each wrist in 4 states: SLIL intact, SLIL sectioned, K-wire fixation across SL interval and scaphocapitate joint, and 2-tine Nitinol staple fixation across SL interval. Strength of the SL staple fixation was evaluated using an axial load machine to assess load to failure of the staple construct.

Results

Range of motion of the scaphoid and lunate with SLIL intact and SLIL sectioned were similar. K-wire fixation across the SL interval significantly decreased the overall wrist range of motion as well as scaphoid and lunate motion in all planes except for scaphoid flexion. Conversely, scaphoid and lunate motion after staple fixation was similar to that in normal wrists, except for a significant decrease in scaphoid extension. Under axial load simulating a ground-level fall, 3 of 8 arms demonstrated no failure, and none of the failures was due to direct failure of the 2-tine staple.

Conclusions

This study demonstrates 2-tine staple fixation across the SL interval is effective in providing initial stability and maintaining physiologic motion of the scaphoid and lunate compared with K-wire fixation after SLIL injury.

Clinical relevance

This study demonstrates an alternate technique for the stabilization of the SL interval in repair of acute SLIL injuries using 2-tine staple fixation, which maintains near physiologic motion of the scaphoid and lunate after SLIL injury.

An Approach to Robotic Testing of the Wrist Using Three-Dimensional Imaging and a Hybrid Testing Methodology

Robotic technology is increasingly used for sophisticated in vitro testing designed to understand the subtleties of joint biomechanics. Typically, the joint coordinate systems in these studies are established via palpation and digitization of anatomic landmarks. We are interested in wrist mechanics in which overlying soft tissues and indistinct bony features can introduce considerable variation in landmark localization, leading to descriptions of kinematics and kinetics that may not appropriately align with the bony anatomy. In the wrist, testing is often performed using either load or displacement control with standard material testers. However, these control modes either do not consider all six degrees-of-freedom (DOF) or reflect the nonlinear mechanical properties of the wrist joint. The development of an appropriate protocol to investigate complexities of wrist mechanics would potentially advance our understanding of normal, pathological, and artificial wrist function. In this study, we report a novel methodology for using CT imaging to generate anatomically aligned coordinate systems and a new methodology for robotic testing of wrist. The methodology is demonstrated with the testing of 9 intact cadaver specimens in 24 unique directions of wrist motion to a resultant torque of 2.0 N·m. The mean orientation of the major principal axis of range of motion (ROM) envelope was oriented 12.1 ± 2.7 deg toward ulnar flexion, which was significantly different (p < 0.001) from the anatomical flexion/extension axis. The largest wrist ROM was 98 ± 9.3 deg in the direction of ulnar flexion, 15 deg ulnar from pure flexion, consistent with previous studies [1,2]. Interestingly, the radial and ulnar components of the resultant torque were the most dominant across all directions of wrist motion. The results of this study showed that we can efficiently register anatomical coordinate systems from CT imaging space to robotic test space adaptable to any cadaveric joint experiments and demonstrated a combined load-position strategy for robotic testing of wrist.

Carpal Pronation and Supination Changes in the Unstable Wrist

Background  Little is known about changes in scaphoid and lunate supination and pronation following scapholunate interosseous ligament (SLIL) injury. Information on these changes may help explain why some SLIL reconstructions have failed and help in the development of new techniques. Purpose  To determine if following simulated SLIL injury there was an increase in scaphoid pronation and lunate supination and to determine if concurrently there was an increase in the extensor carpi ulnaris (ECU) force. Materials and Methods  Scaphoid and lunate motion were measured before and after sectioning of the SLIL and two volar ligaments in 22 cadaver wrists, and before and after sectioning of the SLIL and two dorsal ligaments in 15 additional wrists. Each wrist was dynamically moved through wrist flexion/extension, radioulnar deviation, and a dart-throwing motion. Changes in the ECU force were recorded during each wrist motion. Results  Scaphoid pronation and lunate supination significantly increased following ligamentous sectioning during each motion. There were significant differences in the amount of change in lunate motion, but not in scaphoid motion, between the two groups of sectioned ligaments. Greater percentage ECU force was required following ligamentous sectioning to achieve the same wrist motions. Conclusion  Carpal supination/pronation changed with simulated damage to the scapholunate stabilizers. This may be associated with the required increases in the ECU force. Clinical Relevance  In reconstructing the SLIL, one should be aware of the possible need to correct scaphoid pronation and lunate supination that occur following injury. This may be more of a concern when the dorsal stabilizers are injured.

Optimal detection of scapholunate ligament tears with MRI

Background Scapholunate interosseous ligament (SLIL) injuries can often be difficult to detect using magnetic resonance imaging (MRI), especially with older 1.0 and 1.5 Tesla magnets. Wrist arthroscopy is the gold standard for diagnosis of SLIL injuries, but is an invasive procedure with associated risks. Purpose To assess whether SLIL injuries can be more accurately detected using axial MRI sequences instead of coronal sequences. Material and Methods An institutional review board approved retrospective analysis of arthroscopic wrist surgeries performed at our institution. Patients that had a preoperative MRI performed at our university center using a 1.5 Tesla scanner with a dedicated wrist coil were included in the study. Three fellowship-trained musculoskeletal radiologists reviewed the axial sequences and coronal sequences independently. The accuracy of the coronal and axial sequences was compared with the arthroscopic/surgical findings. Result Twenty-six patients met the inclusion criteria. The sensitivity for SLIL tears was 79% and 65% for the axial and coronal sequences, respectively. The specificity was 82% for the axial and 69% for the coronal sequences, respectively. The positive and negative predictive values for the axial sequences were 76% and 84% respectively, compared to 68% and 71% for the coronal sequences, a statistically significant difference. Conclusion SLIL tears are more readily detectable on axial MRI sequences than coronal. Clinically, patients with radial-sided wrist pain and suspicion for SLIL tears should have the axial sequences scrutinized carefully. An otherwise normal study with the axial sequence being degraded by motion or other MRI artifacts might need repeat imaging.

Arthroscopic Classification of the Lesions of the Dorsal Capsulo-Scapholunate Septum (DCSS) of the Wrist

The dorsal capsulo-scapholunate septum (DCSS) is an anatomic structure linking the scapholunate ligament and the dorsal capsule of the wrist. It should be a predynamic scapholunate stabilizer. The authors, using their experience for the extrinsic ligaments testing, suggest an arthroscopic testing of the DCSS. The status could be graded in 4 stages according to the trampoline aspect and to the fiber attachment. They report a preliminary study on a series of 53 arthroscopies made between January 2014 and December 2015 with evaluation of scapholunate ligament instability and DCSS laxity. There is a significant correlation between the lesional stage of the DCSS and the arthroscopic predynamic scapholunate instability stage (P<0.01).

A biomechanical model of the wrist joint for patient-specific model guided surgical therapy: Part 2

An enhanced musculoskeletal biomechanical model of the wrist joint is presented in this article. The computational model is based on the multi-body simulation software AnyBody. Multi body dynamic musculoskeletal models capable of predicting muscle forces and joint contact pressures simultaneously would be valuable for studying clinical issues related to wrist joint degeneration and restoration. In this study, the simulation model of the wrist joint was used for investigating deeper the biomechanical function of the wrist joint. In representative physiological scenarios, the joint behavior and muscle forces were computed. Furthermore, the load transmission of the proximal wrist joint was investigated. The model was able to calculate the parameters of interest that are not easily obtainable experimentally, such as muscle forces and proximal wrist joint forces. In the case of muscle force investigation, the computational model was able to accurately predict the computational outcome for flexion and extension motion. In the case of force distribution of the proximal wrist joint, the model was able to predict accurately the computational outcome for an axial load of 140 N. The presented model and approach of using a multi-body simulation model are anticipated to have value as a predictive clinical tool including effect of injuries or anatomical variations and initial outcome of surgical procedures for patient-specific planning and custom implant design. Therefore, patient-specific multi-body simulation models are potentially valuable tools for surgeons in pre- and intraoperative planning of implant placement and orientation.

Scaphoid tuberosity excursion is minimized during a dart-throwing motion: A biomechanical study

PURPOSE

The purpose of this study was to determine whether the excursion of the scaphoid tuberosity and therefore scaphoid motion is minimized during a dart-throwing motion.

METHODS

Scaphoid tuberosity excursion was studied as an indicator of scaphoid motion in 29 cadaver wrists as they were moved through wrist flexion-extension, radioulnar deviation, and a dart-throwing motion.

RESULTS

Study results demonstrate that excursion was significantly less during the dart-throwing motion than during either wrist flexion-extension or radioulnar deviation.

CONCLUSION

If the goal of early wrist motion after carpal ligament or distal radius injury and reconstruction is to minimize loading of the healing structures, a wrist motion in which scaphoid motion is minimal should reduce length changes in associated ligamentous structures. Therefore, during rehabilitation, if a patient uses a dart-throwing motion that minimizes his or her scaphoid tuberosity excursion, there should be minimal changes in ligament loading while still allowing wrist motion.

STUDY DESIGN

Bench research, biomechanics, and cross-sectional.

LEVEL OF EVIDENCE

Not applicable. The study was laboratory based.

Effect of pisiform excision or pisotriquetral arthrodesis as a treatment for pisotriquetral arthritis: a biomechanical study

PURPOSE

To determine whether flexor carpi ulnaris (FCU) forces and tendon displacements change after pisotriquetral arthrodesis or after pisiform excision.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CLINICAL RELEVANCE

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.

Anatomical Description of the Dorsal Capsulo-Scapholunate Septum (DCSS)-Arthroscopic Staging of Scapholunate Instability after DCSS Sectioning

Background The dorsal capsuloligamentous scapholunate septum (DCSS) is a confluence of the dorsal capsule, the dorsal intercarpal ligament (DIC), and the scapholunate interosseous ligament (SLIOL). It appears to play a role in the stability of the scapholunate articulation. The purpose of this study was to describe the anatomical basis for this structure and to investigate its role in scapholunate instability through sectioning of this structure followed by an arthroscopic and fluoroscopic analysis. Material and Methods In the anatomical part of the study we dissected 3 fresh cadaver wrists to examine the anatomy of the DCSS. In the arthroscopic part of the study we assessed the EWAS grade of SL instability before and after sectioning the DCSS and measured the scapholunate and radiolunate angles fluoroscopically. Results Sectioning the DCSS increased the EWAS grade of SL instability but did not affect the scapholunate gap, the scapholunate angle or radiolunate angle. Conclusion We have demonstrated that there is a distinct structure that is separate from the dorsal capsule, which we have labeled the Dorsal Capsuloligamentous Scapholunate Septum. We believe that the DCSS is a previously unreported secondary stabilizer of the SL joint which may have therapeutic and prognostic implications.

Dorsal wrist capsular tears in association with scapholunate instability: results of an arthroscopic dorsal capsuloplasty

Purpose The purpose of this study is to report the association of dorsal wrist capsular avulsion with scapholunate ligament instability and to evaluate the results of an arthroscopy-assisted repair. Methods We retrospectively reviewed 10 patients with a mean age of 39.1 years suffering from chronic dorsal wrist pain. They underwent a wrist arthroscopy with an evaluation of the scapholunate ligament complex from the radiocarpal and midcarpal compartments. An avulsion of the dorsal intercarpal ligament (DICL) from the scapholunate interosseous ligament (SLIL) was visible from the radiocarpal compartment in all cases, while the SLIL was intact. The DICL tear was repaired with an arthroscopy-assisted dorsal capsuloplasty. Patients were assessed preoperatively and postoperatively by the QuickDASH (Disabilities of the Arm, Shoulder, and Hand) questionnaire, by the Visual Analog Scale (VAS) for pain, and by a clinical and radiological examination. Results Preoperatively, all patients had reduced flexion and radial deviation of the affected wrist. On the lateral radiograph, 5 of the 10 patients showed an increase of the scapholunate angle (60 to 85°). The scapholunate instability was graded as Messina-European Wrist Arthroscopy Society (EWAS) II in five cases and as grade IIIB in five cases. A tear of the ulnar part of the triangular fibrocartilage complex (TFCC) was found in seven cases. At a mean followup of 16 months, the wrist range of motion (ROM), the grip strength, the QuickDASH, and the VAS of pain improved significatively. The scapholunate angle was normalized in all cases. Discussion Isolated tears of the DICL at its insertion from the dorsal part of the SLIL can be associated with scapholunate instability in the absence of an injury to the SLIL. The diagnosis is made arthroscopically. The arthroscopic dorsal capsuloplasty is a minimally invasive technique that provides short-term satisfactory results. Further studies are needed to determine whether repair of the DICL tear could prevent secondary destabilization of the scapholunate ligament complex. Level of evidence IV (case series) Diagnosis.

The biomechanical effects of a deepened articular cavity during dynamic motion of the wrist joint

BACKGROUND

A deepened articular cavity of the distal radius due to a metaphyseal comminution zone is associated with early osteoarthritis and reduced joint motion. As this deformity has not been investigated biomechanically, the purpose of this study was to evaluate the effects of a deepened articular cavity on contact biomechanics and motion range in a dynamic biomechanical setting.

METHODS

Six fresh frozen cadaver forearms were tested in a force controlled test bench during dynamic flexion and extension and intact mean contact pressure and contact area as well as range of motion were evaluated. Malunion was then simulated and intraarticular as well as motion data were obtained. Intact and malunion data were compared for the scaphoid and lunate facet and the total radial joint surface.

FINDINGS

Due to malunion simulation, cavity depth increased significantly. Motion decreased significantly to 54-69% when compared to the intact state. Malunion simulation led to a significant decrease of contact area in maximum extension for all locations (by ~50%). In maximum flexion and neutral position, contact area decrease was significant for the scaphoid fossa (by 51-54%) and the total radial joint surface (by 47-50%). Contact pressure showed a significant increase in maximum extension in the scaphoid fossa (by 129%).

INTERPRETATION

Already a small cavity increase led to significant alterations in contact biomechanics of the radiocarpal joint and to a significant range of motion decrease. This could be the biomechanical cause for degenerative changes after the investigated type of malunion. We think that restoration of the normal distal radius shape can minimize osteoarthritis risk post trauma and improve radiocarpal motion.

Exploring the anatomy of dorsal radiocarpal ligament of the wrist and its ulnar part: a cadaveric study

The current study aimed to explore the anatomy of the dorsal radio-carpal ligament (DRC ligament) and to investigate the presence and histological structure of ulnar part of the DRC ligament. Twenty cadaveric wrist joints were dissected and attachments of the DRC ligament and the newly described ulnar part of the DRC ligament were identified and noted. Samples of both ligaments were sent for histological examination. The DRC ligament was identified in all 20 specimens with type I Mizuseki arrangement of fibres seen in 60% of wrists. The ulnar part of the DRC ligament was successfully identified in 18 of the 20 wrists. The histological observation of the ulnar part of the DRC ligament showed the highly uniform arrangement of collagen bundles typical of ligaments. This study explores the anatomy of the DRC ligament and confirms the presence of the ulnar part of DRC ligament through histological analysis not undertaken in previous studies.

DORSAL CAPSULODESIS AND LIGAMENTOPLASTY FOR CHRONIC PRE-DYNAMIC AND DYNAMIC SCAPHOLUNATE DISSOCIATION

Scapholunate (SL) instability is the most common cause of carpal instability. Pre-dynamic and dynamic type SL instability is difficult to diagnose and treat. This series reviews 17 soldiers with pre-dynamic or dynamic SL instability diagnosed by midcarpal arthroscopy and treated with dorsal capsulodesis and augmentation ligamentoplasty with partial dorsal radiocarpal (DRC) ligament procedure between 1997 and 2000. The sample included 14 males and three females. The dominant hand was involved in 15 patients. Moreover, the average patient age was 29.3 years (range 19–36 years). The diagnosis was based on clinical and arthroscopic criteria. Fifteen patients were followed up at our clinic regularly, with the follow-up period ranging from 12 to 39 months (mean 25.2 months). Fourteen patients had excellent or good results, and one patient had poor result based on Mayo Modified Wrist Score. Wrist motion in the flexion-extension plane loss averaged 18.4°. Grip force increased significantly following treatment, with improvement totaling 15% of normal side. No complications were found in this series. Consequently, dorsal capsulodesis and ligamentoplasty with partial DRC ligament is considered a valuable therapeutic option for cases of pre-dynamic and dynamic SL instability.

Measurement of intraarticular wrist joint biomechanics with a force controlled system

Pathologies of the wrist, such as fractures or instabilities, can lead to alterations in joint biomechanics. Accurate treatment of these pathologies is a frequent challenge for the surgeon. For biomechanical investigations, a test-setup that applies physiological loading of the wrist joint is necessary. A force controlled test-bench with agonistic and antagonistic muscle forces was built to move six fresh frozen human upper extremities through flexion and extension of the wrist joint. Tendon forces, range of motion, intraarticular contact area and contact pressure of the lunate and scaphoid facet as well as tendon excursion were investigated and compared with the current literature. During wrist motion the extensors exerted double the force of the flexors. Capsulotomy and sensor insertion decreased the range of motion from 63.4° (SD 14.1) to 45.9° (SD 23.7). The ratio of force transmitted through the radius and ulna was 77:23 and pressure distribution between the scaphoid and lunate facet showed a 70:30 relationship. The obtained data indicate a good agreement with the available literature. Therefore, the force controlled test-bench in combination with intraarticular radiocarpal measurements can be used to investigate the influence of wrist pathologies on joint biomechanics.

The use of thermal shrinkage for scapholunate instability

Scapholunate interosseous ligament (SLIL) instability is the most common form of carpal instability. There is a lack of consensus among hand surgeons as to the appropriate treatment of various stages. This article reviews the background and results of thermal treatment of predynamic instability of the SLIL. Case examples are discussed as well as a series of patients treated with our protocol for this injury.

Association between lunate morphology and carpal collapse in cases of scapholunate dissociation

PURPOSE

Type II lunate morphology has recently been shown to decrease the incidence of dorsal intercalated segment instability (DISI) deformity in patients with scaphoid nonunions. A similar association has been suggested for scapholunate dissociation, but a formal comparison has yet to be performed. The purpose of this study was to determine if an association exists between lunate morphology and DISI in cases of scapholunate dissociation.

METHODS

A retrospective review was performed on 58 patients with the diagnosis of scapholunate dissociation as determined by use of radiographs, magnetic resonance imaging, arthrotomy, and arthroscopy. Posteroanterior radiographs were used to assess the presence of a medial facet on the lunate and to determine the distance between the capitate and the triquetrum. A DISI deformity was defined as a radiolunate angle >15 degrees, and scapholunate instability was defined as a scapholunate angle >60 degrees using the tangential method. Statistical analysis was performed with a chi-squared test and kappa test.

RESULTS

Twenty-five patients had a type I lunate, and 33 patients had a type II lunate. A total of 15 patients had DISI deformity on preoperative radiographs; of these, 10 patients with a type I lunate and 5 patients with a type II lunate had DISI deformity. This difference was found to be significant.

CONCLUSIONS

In cases of scapholunate dissociation, type II lunates were associated with a significantly lower incidence of DISI despite having radiographic or arthroscopic evidence of a complete scapholunate interosseous ligament tear. Osseous morphology may play a role in the development of a radiographic DISI deformity. Further research is required to assess the clinical importance of this finding and the biomechanical cause of this phenomenon.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

Incidence of dorsal radiocarpal ligament tears in the presence of other intercarpal derangements

PURPOSE

The aim of this study was to examine the incidence of dorsal radiocarpal ligament (DRCL) tears in patients who underwent wrist arthroscopy for chronic pain.

METHODS

A chart review was performed of 64 patients who underwent diagnostic wrist arthroscopy for wrist pain. Interosseous ligament instability/tears were graded according to the Geissler classification. Tears of the triangular fibrocartilage complex (TFCC) and other intracarpal pathology were documented. Any DRCL tears were noted.

RESULTS

The average duration of wrist pain before arthroscopy was 20 months. There were 35 of 64 patients with DRCL tears. The average duration of wrist pain before treatment was 20 months (range, 4 to 60 months). There were 5 patients who had an isolated DRCL tear. Thirteen patients in this series had a scapholunate interosseous ligament (SLIL) derangement; 7 of 13 also had a DRCL tear. Seven patients had a lunotriquetral interosseous ligament (LTIL) derangement; 2 of 7 also had a DRCL tear. Two patients had a capitohamate ligament tear; 1 of these patients also had a DRCL tear. There were 7 patients with a solitary TFCC tear; 6 of 7 were in association with a DRCL tear. One patient had a chronic ulnar styloid nonunion and a DRCL tear. Two or more lesions were present in 23 patients; DRCL tears were present in 12 of 23 patients. Three patients had generalized arthrofibrosis; 1 had a volar ganglion and 2 had a normal examination. None of these were associated with DRCL tears.

CONCLUSIONS

DRCL tears are commonly seen with injuries to the SLIL, the LTIL, and the TFCC. Isolated DRCL tears should be treated with an arthroscopic repair. DRCL repairs in the presence of other intracarpal pathologies requires further study.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The incidence of dorsal radiocarpal ligament tears in patients having diagnostic wrist arthroscopy for wrist pain

PURPOSE

The goal of this study was to examine the incidence of dorsal radiocarpal ligament (DRCL) tears in patients having diagnostic arthroscopy for chronic wrist pain.

METHODS

A chart review was performed of 64 patients who had diagnostic wrist arthroscopy for chronic wrist pain that was refractory to conservative measures. For each case, interosseous ligament instability/tears were graded according to the Geissler classification. Tears of the triangular fibrocartilage complex and the presence or absence of a DRCL tear were noted.

RESULTS

There were 35 of 64 wrists (in 64 patients) with DRCL tears. The average duration of wrist pain prior to treatment was 20 months. Only 10 patients could recall a specific injury. Five patients had an isolated DRCL tear. A scapholunate interosseous ligament injury was identified in 13 patients, of whom 7 had a concomitant DRCL tear. A lunotriquetral interosseous ligament injury was present in 7 patients, of whom 2 had a concomitant DRCL tear. Two patients had a capitohamate ligament tear: 1 of these patients had a DRCL tear. There were 7 patients with a solitary triangular fibrocartilage complex tear: 6 of 7 were in association with a DRCL tear. One patient had a chronic ulnar styloid nonunion and a DRCL tear. Two or more lesions were present in 23 patients; DRCL tears were present in 12.

CONCLUSIONS

DRCL tears are commonly seen with injuries to the primary wrist stabilizers. Recognition of this condition and further research into treatment methods are needed.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.

Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part III

PURPOSE

This study continued our previous investigations of the ligaments stabilizing the scaphoid and lunate in which we examined the scapholunate interosseous ligament, the radioscaphocapitate, and the scaphotrapezial ligament. In this current study, we examined the effects of sectioning the dorsal radiocarpal ligament, dorsal intercarpal ligament, scapholunate interosseous ligament, radioscaphocapitate, and scaphotrapezial ligaments. In the current study, the scapholunate interosseous ligament, radioscaphocapitate, and scaphotrapezial ligaments were sectioned in a different order than performed previously.

METHODS

Three sets of 8 cadaver wrists were tested in a wrist joint motion simulator. In each set of wrists, only 3 of the 5 ligaments were cut in specific sequences. Each wrist was moved in continuous cycles of flexion-extension and radial-ulnar deviation. Kinematic data for the scaphoid and lunate were recorded for each wrist in the intact state, after the 3 ligaments were sectioned in various sequences and after the wrist was moved through 1,000 cycles of motion.

RESULTS

Dividing the dorsal intercarpal or scaphotrapezial ligaments did not alter the motion of the scaphoid or lunate. Dividing the dorsal radiocarpal ligament alone caused a slight statistical increase in lunate radial deviation. Dividing the scapholunate interosseous ligament after first dividing the dorsal intercarpal, dorsal radiocarpal, or scaphotrapezial ligaments caused large increases in scaphoid flexion and lunate extension.

CONCLUSIONS

Based on these findings, we concluded that the scapholunate interosseous ligament is the primary stabilizer and that the other ligaments are secondary stabilizers of the scapholunate articulation. Dividing the dorsal radiocarpal, dorsal intercarpal, or scaphotrapezial ligaments after cutting the scapholunate interosseous ligament produces further changes in scapholunate instability or results in changes in the kinematics for a larger portion of the wrist motion cycle.

Severity of scapholunate instability is related to joint anatomy and congruency

PURPOSE

To determine whether the bony architecture of the distal radius and proximal scaphoid have a role in stabilizing the scaphoid, and to determine whether a relationship between the bony geometry measurements and the amount of wrist constraint could be determined.

METHODS

Eight cadaver wrists were tested in a wrist joint motion simulator. The level of scapholunate instability after sectioning the scapholunate interosseous, radioscaphocapitate, and the scaphotrapezium ligaments was determined and related to radiographic measurements of volar tilt, lateral tilt (ulnar tilt of the radioscaphoid fossa), the depth of the radioscaphoid fossa, and 6 radii of curvature measurements of the proximal scaphoid and distal radius. The force to dorsally dislocate the scaphoid out of the radioscaphoid fossa was computed.

RESULTS

The radioscaphoid fossa and scaphoid curvatures were larger in those wrists that did not show gross instability after ligamentous sectioning in the wrist simulator. Similarly, those wrists with a deeper radioscaphoid fossa and greater volar tilt were also more stable. The force required to dislocate these wrists was greater than in those wrists that showed gross carpal instability.

CONCLUSIONS

This study suggests that the bony anatomy of the radius and scaphoid have a role in stabilizing the carpus after ligament injury. The effect of ligament sectioning on producing carpal instability may be moderated by the bone geometry of the radiocarpal joint. This may explain why some people may have a tear of the scapholunate interosseous ligament but not present with clinical symptoms.

Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study

PURPOSE

To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model.

METHODS

Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension.

RESULTS

Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion.

CONCLUSIONS

The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.

Clinical applications of volar portals in wrist arthroscopy

Volar portals for wrist arthroscopy have certain advantages over the standard dorsal portals for visualizing dorsal capsular structures as well as the palmar aspects of the carpal ligaments. The volar radial portal is relatively easy to use and is an ideal portal for evaluation of the dorsal radiocarpal ligament and the palmar aspect of the scapholunate interosseous ligament. The volar midcarpal portal may be considered as an occasional accessory portal for visualizing the palmar aspects of the capitate and hamate in cases of avascular necrosis or osteochondral fractures. The volar ulnar portal is especially useful for the viewing and debridement of palmar tears of the lunotriquetral ligament.

The two parts of the dorsal radiocarpal (radiolunotriquetral) ligament

An anatomical study was performed to identify the configuration of the dorsal radiocarpal ligament. Fourteen fresh frozen wrists from seven cadavers (mean age 65 years) were dissected under loupe magnification. The study demonstrates that the dorsal radiocarpal ligament had, in every case examined, an additional superficial component which has not been previously described. It arises from the distal part of the interosseous border of the radius. It runs obliquely, distally and ulnarward, over the distal ulna to attach to the lunate and triquetrum. The dorsal radiocarpal ligament blends with the underlying dorsal radioulnar ligament which runs transversely, at a deeper plane, between the radius and ulna. The paper discusses the clinical implications of this finding.

The hysteresis effect in carpal kinematics

PURPOSE

Carpal bones show hysteresis that is dependent on the direction of wrist motion during a continuous active loading protocol. We describe an accurate methodology for analyzing the hysteresis effect and we apply this model to analyze the effect of sequential ligament sectioning on scapholunate instability.

METHODS

In 8 fresh cadaver forearms scaphoid, lunate, and third metacarpal motions were recorded while each wrist was moved in continuous cycles of active motion in flexion-extension and radioulnar deviation. Motions were analyzed for the intact state and after sequential sectioning of the scapholunate interosseous, scaphotrapezium, and radioscaphocapitate ligaments. Carpal motion was curve-fitted with respect to the third metacarpal motion using optimization criteria. The area between the 2 curves that represents opposite directions of wrist motion was measured to give the total hysteresis area. Repeated-measures analysis of variance was used to determine significance.

RESULTS

In the flexion-extension trials the scaphoid and lunate total hysteresis area was significantly greater than the intact state only after all 3 ligaments were sectioned. In the radioulnar deviation trials the scaphoid total hysteresis area was significantly greater than the intact after just scapholunate interosseous ligament sectioning; however, the lunate total hysteresis area decreased with additional sequential sectionings in 4 of the 8 specimens as compared with the intact state. These 4 specimens started with a significantly greater intact total hysteresis area than the other 4 specimens.

CONCLUSIONS

The computation of the total hysteresis area from the hysteresis effect was found to be a sensitive technique to determine the subtle onset of abnormal carpal motion. By using this technique in a ligament sectioning study significant increases in the total hysteresis area were seen after just scapholunate interosseous ligament sectioning during wrist radioulnar deviation. This subtle change may signify the onset of dynamic scapholunate instability. The total hysteresis area of the lunate in a subset of lax specimens did not increase after ligament sectioning. This divergent behavior may explain why some patients with scapholunate instability do not develop dorsal intercalated segmental instability.

Arthroscopic dorsal radiocarpal ligament repair

PURPOSE

The goal of this study was to determine if arthroscopic repair of a dorsal radiocarpal ligament (DRCL) tear is effective in ameliorating wrist pain.

TYPE OF STUDY

Retrospective study.

METHODS

A chart review was performed of 53 patients (56 wrists) who underwent wrist arthroscopy with use of a volar radial portal. There were 21 patients with DRCL tears. Mean follow-up was 16 months. Thirteen patients underwent arthroscopic DRCL repair and/or thermal shrinkage (5 repairs, 6 repair plus shrinkage, and 2 shrinkage). Lunotriquetral tears were treated with debridement and pinning. Triangular fibrocartilage (TFC) tears were debrided or repaired. Scapholunate ligament tears/instability were treated with capsulodesis.

RESULTS

The 4 patients who underwent repair of an isolated DRCL tear had excellent results with no or mild pain. All returned to their previous occupation. Dorsal capsulodesis was performed in 7 patients with 4 fair/poor results. Nine DRCL repairs/shrinkage were in association with other procedures for ulnar-sided pathology with 6 fair/poor results.

CONCLUSIONS

Tears of the DRCL are more common than previously suspected. They are best seen through a volar radial portal and are amenable to arthroscopic repair. DRCL tears appear to be part of a spectrum of radial and ulnar-sided carpal instability as evidenced by the frequent association with scapholunate ligament tears/instability or ulnar-sided pathology. Isolated DRCL tears can be solely responsible for wrist pain. Good results are obtained with arthroscopic repair of isolated DRCL tears. The presence of a DRCL tear when seen in combination with a scapholunate, lunotriquetral, or TFC tear connotes a greater degree and/or duration of carpal instability, and portends a poorer prognosis following treatment. Recognition of this condition and further research into treatment methods is needed.

LEVEL OF EVIDENCE

Level IV.

Changes in patterns of scaphoid and lunate motion during functional arcs of wrist motion induced by ligament division

PURPOSE

To determine the in vitro motion of the scaphoid and lunate during wrist circumduction and wrist dart-throw motions and to see how these motions change after the ligamentous stabilizers of the scaphoid and lunate are sectioned in a manner simulating scapholunate instability.

METHODS

Twenty-one fresh-frozen cadaver forearms were moved through a dart-throw motion and a circumduction motion using a wrist joint simulator. Scaphoid and lunate motion were measured with the wrist ligaments intact and after sectioning of the scapholunate interosseous ligament, the scaphotrapezium ligament, and the radioscaphocapitate ligament.

RESULTS

In the intact wrist the scaphoid and lunate moved more during circumduction than during the dart-throw motion. With ligamentous sectioning the scaphoid flexed more and the lunate extended more during both the circumduction and dart-throw motions. During the circumduction motion both before and after sectioning the global motion of the scaphoid was greater than that of the lunate. After sectioning the scaphoid motion increased and the lunate motion decreased.

CONCLUSIONS

The scaphoid and lunate motions were observed to change remarkably after ligamentous sectioning. The observed changes in carpal motion correlate with the clinical observation that after ligamentous injury arthritic changes occur in the radioscaphoid joint and not in the radiolunate joint. Analysis of the injured wrist in positions that combine flexion-extension and radial-ulnar deviation may allow noninvasive diagnosis of specific wrist ligament injuries.

Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study

PURPOSE

Carpal kinematics have been studied widely yet remain difficult to understand fully. The noninvasive measurement of carpal kinematics through medical imaging has become popular. Studies have shown that with radial deviation the scaphoid and lunate flex whereas the capitate moves radiodorsally relative to the lunate. This study investigated the midcarpal and radiocarpal contributions to radial and ulnar deviation of the wrist. This was accomplished through noninvasive characterization of the scaphoid, lunate, and capitate using 3-dimensional medical imaging of the wrist in radial and ulnar deviation.

METHODS

Eight fresh-frozen and thawed cadaveric wrists were used in an experimental set-up that positioned the wrist through spring-scale actuation of the 4 wrist flexor and extensor tendon groups. The wrists were scanned by computed tomography in neutral and full radial and ulnar deviation. Body mass-based local coordinate systems were used to track the motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion and Euler angles were calculated from neutral to radial and ulnar deviation for the capitate relative to the radius, lunate, and scaphoid and for the lunate and scaphoid relative to the radius.

RESULTS

The capitate, scaphoid, and lunate moved in a characteristic manner relative to the radius and to one another. Radial and ulnar deviation occurred primarily in the midcarpal joint. Midcarpal motion accounted for 60% of radial deviation and 86% of ulnar deviation. In radial deviation the proximal row flexed and the capitate extended; the converse was true in ulnar deviation.

CONCLUSIONS

Radioulnar deviation (in-plane motion) occurred mostly through the midcarpal joint, with a lesser contribution from the radiocarpal joint. The results of our study agree with previous investigations that found the scaphoid and lunate flex in radial deviation (out-of-plane motion) relative to the radius whereas the capitate extends (out-of-plane motion) relative to the scaphoid/lunate (with the converse occurring in ulnar deviation). Our study shows how these out-of-plane motions combine to produce in-plane wrist radioulnar deviation. The use of 3-dimensional visualization greatly aids in the understanding of these motions. The results of our study may be useful clinically in understanding the consequences of isolated midcarpal fusions in the treatment of wrist instability.

Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: Part II

PURPOSE

This study is a continuation of our previous investigation of the ligaments stabilizing the scaphoid and lunate. We evaluated the effects of sectioning the scapholunate interosseous ligament, radioscaphocapitate ligament, and scaphotrapezial ligament in 3 sequences.

METHODS

Three sets of 8 cadaver forearms were placed in a wrist simulator and moved in continuous cycles of flexion-extension and radial-ulnar deviation. Kinematic data for the scaphoid and lunate were recorded for each wrist in the intact state, after the 3 ligaments were sectioned in various sequences and after the wrist was moved through 1,000 cycles of motion.

RESULTS

Sectioning only the scaphotrapezium ligament (ST) or the radioscaphocapitate ligament (RSC) resulted in minimal angular changes to the motion of the scaphoid and lunate. Sectioning of the scapholunate interosseous ligament (SLIL) or 1,000 cycles of repetitive wrist motion after ligament sectioning altered scaphoid and lunate kinematics.

CONCLUSIONS

Based on these findings it was concluded that the SLIL is the primary stabilizer and the RSC and ST are secondary stabilizers of the scapholunate articulation. Repetitive motion after ligament injury probably results in further carpal instability.

Three-dimensional modeling and animation of two carpal bones: a technique

The objectives of this study were to (a). create 3D reconstructions of two carpal bones from single CT data sets and animate these bones with experimental in vitro motion data collected during dynamic loading of the wrist joint, (b). develop a technique to calculate the minimum interbone distance between the two carpal bones, and (c). validate the interbone distance calculation process. This method utilized commercial software to create the animations and an in-house program to interface with three-dimensional CAD software to calculate the minimum distance between the irregular geometries of the bones. This interbone minimum distance provides quantitative information regarding the motion of the bones studied and may help to understand and quantify the effects of ligamentous injury.

Arthroscopic resection of arthrosis of the proximal hamate: a clinical and biomechanical study

PURPOSE

The purpose of this study was to present a series of patients with arthrosis of the proximal hamate treated by arthroscopic resection. To further investigate this condition a biomechanical study also was undertaken to document the effect this proximal hamate resection has on carpal loading.

METHODS

Between 1991 and 2001 there were 23 patients who had arthroscopic proximal hamate resection for the treatment of proximal hamate arthrosis. Twenty-one patients were available for final follow-up evaluation (average, 4.7 y). Patients were evaluated by using a modified wrist score that examined pain relief, patient satisfaction, range of motion, and grip strength. Six cadaver wrists had resection of the proximal hamate. Loads across the carpal and midcarpal joints were documented with pressure-sensitive film before and after proximal hamate resection.

RESULTS

Ninety-five percent of the patients had a type II lunate. Twenty-one of 23 wrists had lunotriquetral tears confirmed on arthroscopic examination. Follow-up evaluation revealed 14 excellent, 4 good, 1 fair, and 2 poor results. Biomechanical studies revealed that resection of 2.4 mm of the proximal hamate unloads the hamatolunate articulation without changing the load at the triquetrohamate joint.

CONCLUSIONS

Arthrosis of the proximal pole of the hamate seems to be associated closely with tears of the lunotriquetral joint and may be part of the spectrum of ulnar-sided wrist degeneration. Arthroscopic resection of the proximal pole of the hamate appears to be a useful treatment in patients with symptomatic hamate arthrosis, even in those patients with lunotriquetral laxity.

Scaphoid and lunate motion during a wrist dart throw motion

PURPOSE

The primary purpose of this study was to measure the in vitro scaphoid and lunate motion during 9 different variations of a wrist dart throw motion. Another goal was to determine the specific dart throw motion that minimized scaphoid and lunate motion.

METHODS

Scaphoid and lunate motion were recorded in 7 cadaver forearms during various combinations of wrist dart throw motions caused by a wrist joint motion simulator.

RESULTS

During wrist flexion and extension the scaphoid and lunate motions follow the wrist motion. During wrist radial and ulnar deviation the scaphoid and lunate correspondingly flex and extend. During intermediate motions the scaphoid and lunate move as little as 26% of the total third metacarpal motion and do not necessarily follow a planar motion.

CONCLUSIONS

These findings suggest that there may be a dart throw motion during which there may be minimal scaphoid and lunate motion. If a subject's wrist motion could be clinically restricted to this dart throw motion, early hand mobility might be possible after surgery on the scaphoid and lunate.

Scaphoid kinematics in vivo

The purpose of this study was to quantify 3-dimensional (3-D) in vivo scaphoid kinematics during flexion-extension motion (FEM) and radial-ulnar deviation (RUD) of the hand. The right wrists of 11 healthy volunteers were imaged by spiral computed tomography during RUD and 5 of those wrists also during FEM. With a matching technique, relative translations and rotations of the scaphoids were traced. Our results showed a broad spectrum of kinematic patterns of the scaphoid during RUD, with small intercarpal motions within the proximal carpal row. Some scaphoids rotated basically around the flexion-extension axis only whereas others rotated almost entirely around the deviation axis during RUD. During FEM we found highly uniform scaphoid motion patterns with large intercarpal motions within the proximal carpal row. These findings suggest that current theories cannot sufficiently explain wrist kinematics and stress the need for more in vivo studies on 3-D carpal kinematics.

Biomechanical evaluation of ligamentous stabilizers of the scaphoid and lunate

This study evaluated the effects of sectioning the scapholunate interosseous ligament, radioscaphocapitate ligament, and scaphotrapezial ligament on the kinematics of the scaphoid and lunate. Eight cadaver upper extremities were placed in a wrist joint simulator and moved in continuous cycles of flexion-extension and radial-ulnar deviation. Positional data of the scaphoid and lunate were obtained in the intact state, after the scapholunate ligament was cut; after the scapholunate and scaphotrapezial ligaments were cut; after the scapholunate, scaphotrapezial, and radioscaphocapitate ligaments were cut; and after all 3 ligaments were cut and the specimen was placed through an additional 1,000 cycles of flexion-extension. Cutting the scapholunate ligament caused changes in scaphoid and lunate motion during flexion-extension, but not radial-ulnar deviation. Additional sectioning of the scaphotrapezial ligament followed by the radioscaphocapitate ligament caused further kinematic changes in these carpal bones. One thousand cycles of motion after all 3 ligaments were sectioned caused additional kinematic changes in the scaphoid and lunate. The scapholunate ligament appears to be the primary stabilizer between the scaphoid and lunate. The radioscaphocapitate and scaphotrapezial ligaments are secondary restraints. Repetitive cyclic motion after ligament sectioning appears to have additional deleterious effects on carpal kinematics.

Biomechanical analysis of two ulnar head prostheses

The biomechanical effectiveness of 2 ulnar head prostheses was evaluated in 5 fresh-frozen cadaver arms. By using electromagnetic sensors, the amount of forearm rotation, diastasis, and dorsal/palmar subluxation of the radius at the level of the sigmoid notch was measured with the forearm in neutral rotation, pronation, and supination with and without dorsal/palmar loading. Testing was done in the intact specimens and after insertion of 2 types of ulnar head prostheses. Dynamic forearm rotation was also achieved by applying loads in the line of action of the appropriate pronator or supinator muscles to obtain a centroidal path of the radius relative to the ulna. Overall after ulnar head replacement forearm rotation lessened in pronation, diastasis decreased in most forearm positions, and subluxation increased in supination compared with the intact specimen. Despite these changes, both prostheses maintained near-normal biomechanics of the distal radioulnar joint when compared with the irregular behavior occurring after distal ulna resection. Therefore these prostheses are suggested for restoration of distal radioulnar joint function.