Capitate-based kinematics of the midcarpal joint during wrist radioulnar deviation: an in vivo three-dimensional motion analysis

Radiocarpal and midcarpal kinematics in scapholunate instability: a four-dimensional CT study in vivo

The distribution of motion between the radiocarpal and midcarpal joints in scapholunate instability is poorly understood. This has potential implications in predicting degenerative changes and in selecting salvage procedures. We studied 19 healthy wrists and 19 wrists with scapholunate instability using dynamic computed tomography during wrist extension to flexion and ulnar to radial deviation. Radiocarpal and midcarpal kinematics of the scaphoid and the lunate were computed. In scapholunate instability, in the radial column, there was increased motion in the radiocarpal joint when the wrist was radially deviating beyond 10° or moving from 70° to 40° extension. In both groups, the capitolunate joint was the dominant articulation in the central column. In scapholunate instability, there was significantly more capitolunate motion during 70° to 30° extension. These changes may predict the development of radioscaphoid arthritis and enable identifying a kinematically abnormal wrist. The motion distribution in scapholunate instability was abnormal beyond 10° of radial deviation and between 70° and 40° of wrist extension.Level of evidence: III.

Carpal kinematics and morphological correlates of wrist ulnar deviation mobility in nonhuman anthropoid primates

OBJECTIVES

Primates employ wrist ulnar deviation during a variety of locomotor and manipulative behaviors. Extant hominoids share a derived condition in which the ulnar styloid process has limited articulation or is completely separated from the proximal carpals, which is often hypothesized to increase ulnar deviation range of motion. Acute angulation of the hamate's triquetral facet is also hypothesized to facilitate ulnar deviation mobility and mechanics. In this study, we test these longstanding ideas.

METHODS

Three-dimensional (3D) carpal kinematics were examined using a cadaveric sample of Pan troglodytes, Pongo sp., and five monkey species. Ulnar styloid projection and orientation of the hamate's triquetral facet were quantified using 3D models.

RESULTS

Although carpal rotation patterns in Pan and Pongo were uniquely similar in some respects, P. troglodytes exhibited overall kinematic similarity with large terrestrial cercopithecoids (Papio and Mandrillus). Pongo, Macaca, and Ateles had high wrist ulnar deviation ranges of motion, but Pongo did this via a unique mechanism. In Pongo, the triquetrum functions as a distal carpal rather than part of the proximal row. Ulnar styloid projection and wrist ulnar deviation range of motion were not correlated but ulnar deviation range of motion and the triquetrohamate facet orientation were correlated.

CONCLUSIONS

Increased ulnar deviation mobility is not the function of ulnar styloid withdrawal in hominoids. Instead, this feature probably reduces stress on the ulnar side wrist or is a byproduct of adaptations that increase supination. Orientation of the hamate's triquetral facet offers some potential to reconstruct ulnar deviation mobility in extinct primates.

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

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

Wrist Bone Motion during Flexion-Extension and Radial-Ulnar Deviation: An MRI Study

The wrist joint plays a vital role in activities of daily living. Clinical applications, e.g., therapeutic planning, prosthesis design, and wrist biomechanical analysis, require a detailed understanding of wrist maneuvers and motion. The lack of soft tissue information, motion analysis on limited carpal bones, etc., restrain the investigation of wrist kinematics. In this study, we established 3D models of carpal bones with their cartilages, and revealed the helical axes (HA) of all eight carpal bones for the first time. Both left and right hands at different positions of flexion-extension (FE) and radial-ulnar deviation (RUD) from five subjects were in-vivo imaged through a magnetic resonance imaging device. We segmented all of the bones, including cartilage information in the wrist joint, after which we explored the kinematics of all carpal bones with the HA method. The results showed that the HA of all carpal bones for FE bounded tightly and was mainly located slightly above the radius. During the RUD, carpal bones in the distal row rotated along with wrist movement while the scaphoid, lunate, and triquetrum primarily flexed and extended. Further results reported that the carpal bones translated greater in RUD than in FE. With the generation of more delicate wrist models and thorough investigations of carpal motion, a better understanding of wrist kinematics was obtained for further pathologic assessment and surgical treatment.

Perilunate Dislocations: Current Treatment Options

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Approximately 25% of all patients who sustain perilunate dislocations present in a delayed fashion.

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While management of acute injuries is relatively well-described, treatment of chronic injuries can be complex and there is a paucity of scientific evidence to guide management.

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Treatment options include open reduction internal fixation, proximal row carpectomy, scaphoid or lunate excision with or without arthrodesis, and total wrist arthrodesis, although indications vary based on chronicity of injury and patient factors.

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The purpose of this article was to determine the quality of evidence supporting surgical options for the treatment of these injuries.

Anatomy, Biomechanics, and Loads of the Wrist Joint

The wrist is by far the most differentiated section of the musculoskeletal system. The spectrum of wrist injuries ranges from minor injuries to complex traumas with simultaneous loss of functions, resulting in enormous economic costs. A proper understanding of the anatomy and biomechanics is essential for effective treatment, whether conservative or surgical; this applies to the wrist no less than to other parts of the human body. Here; information on the wrist anatomy; kinematics; and biomechanical behavior is presented, commencing with a brief explanation of the structure of its hard and soft tissues. Eight carpal bones in combination with two forearm bones (radius and ulna) construct the wrist joint. The motion of the wrist joint is initiated by the muscles of the forearm, and strong and short ligaments ensure the stability of the wrist. All of these components are essential to bringing functions to the wrist joint because these structures allow wrist mobility and sustainability. In addition, the kinematics of the wrist joint is presented and different biomechanical model approaches. The therapeutic (surgical) restoration of the balance between the load–bearing capacity and the actual stress on a joint is the prerequisite for a lifelong and trouble-free function of a joint. Regarding the complex clinical problems, however, a valid biomechanical wrist joint model would be necessary as assistance, to improve the success of systematized therapies based on computer–aided model–based planning and intervention.

Quantifying wrist angular excursion on impact for Jab and Hook lead arm shots in boxing

The hand region is reported as the most common injury site in boxing, with more observed time loss than any other area in this sport. The amount of wrist motion, specifically flexion, has been described as contributing to these injuries, yet no literature is available to quantify wrist kinematics in boxing. This is the first paper describing wrist motion on impact in boxing. Utilising an electromagnetic tracking system, two types of shots were assessed, Jab (straight arm) and Hook (bent arm), during in-vivo testing procedures with 29 elite boxers. For both shots, flexion and ulnar deviation occurred concurrent on impact, with an M and SD of 9.3 ± 1.9° and 4.7 ± 1.2° respectively for Jab shots, and 5.5 ± 1.1° and 3.3 ± 1.1° respectively for Hook shots, supporting dart throwing motion at the wrist. For both Jab & Hook, wrist motion on impact occurred within >30% and >20% respectively of total available active range of motion, with wrist angles greater in both flexion (t = 9.0, p < 0.001, d = 1.7) and ulnar deviation (t = 8.4, p < 0.001, d = 1.6) for Jab compared to Hook shots. The study provides novel and quantifiable information regarding wrist kinematics during the impact phase of punching and potentially an improved understanding of injury mechanisms in boxing.

Partial Trapeziotrapezoid Resection and Thumb Range of Movement After Trapeziometacarpal Joint Fusion-A Biomechanical Study

PURPOSE

Trapeziometacarpal (TMC) joint arthrodesis is an effective treatment for stage III osteoarthritis. Although this procedure alleviates thumb pain and restores grip power and pinch strength, persistent limitation of thumb movement is inevitable. This biomechanical study aimed to investigate the altered kinematics of thumb circumduction motion after TMC joint arthrodesis and subsequent excision of the trapeziotrapezoid (TT) and trapezio-second metacarpal (T-2MC) joint spaces.

METHODS

Eight cadaver upper extremities were mounted on a custom testing apparatus. The hand and carpal bones were fixed to the apparatus, except for the first metacarpal bone, trapezium, and trapezoid. A 50-g load was applied at the tip of the first metacarpal head to generate passive thumb circumduction. An electromagnetic tracking system measured the angular and rotational displacement of the first metacarpal. All specimens were tested in 4 conditions: intact, after simulated TMC joint fusion, after subsequent excision of 3 mm of bone at the TT joint space, and after additional 3 mm resection at the T-2MC joint space.

RESULTS

After simulated TMC arthrodesis, the range of angular motion of thumb circumduction decreased to 25% that of the intact thumb. Subsequent resections at the TT and T-2MC joint spaces increased circumduction ranges to 49% (TT joint) and 73% (TT plus T-2MC joints) that of the intact thumb. The range of thumb rotational motion showed a similar trend.

CONCLUSIONS

Trapeziometacarpal arthrodesis decreased the range of both angular and rotational motion during thumb circumduction. Subsequent resections at the paratrapezial space increased the range of thumb motion, suggesting that hypermobility of the paratrapezial joints increases thumb mobility after TMC joint fusion.

CLINICAL RELEVANCE

Patients with hypermobile paratrapezial joints may have larger thumb movement after TMC joint fusion. Additional resections of the TT and T-2MC joint spaces may further mobilize the thumb in patients who complain of stiffness after TMC fusion.

A Minimum 5-Year Longitudinal Study of a New Total Wrist Arthroplasty in Patients With Rheumatoid Arthritis

PURPOSE

To evaluate the longitudinal clinical outcomes using a new semiconstrained wrist prosthesis for the treatment of severe rheumatoid arthritis of the wrist.

METHODS

Twenty patients with rheumatoid arthritis (20 wrists) underwent total wrist arthroplasty with the prosthesis in a clinical trial. The preoperative Larsen classification was grade IV in 16 wrists and grade V in 4 wrists. Assessments were performed before surgery, 1.5 years after surgery, and at final follow-up (≥ 5 years after surgery) using the visual analog scale for pain, Figgie wrist score, Japanese version of the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, and plain radiographs.

RESULTS

At final follow-up, no patient had wrist pain. The preoperative flexion-extension arc at final follow-up was similar to the preoperative range. The mean 1.5-year postoperative Figgie score was significantly improved and was unchanged at final follow-up. The DASH score significantly improved from before surgery to 1.5 years after surgery; the DASH score was improved further at final follow-up, but not significantly. Five of the 19 wrists evaluated had radiographic findings indicating carpal component loosening at final follow-up; however, all patients with the loosening were asymptomatic and had not undergone revision surgery.

CONCLUSIONS

Total wrist arthroplasty using this wrist prosthesis leads to favorable clinical outcomes regarding pain relief and retained range of wrist motion.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Qualification of Wrist Functional Performance During Dart Thrower's Movement

Recently, numerous comprehensive studies have been concentrating on the intricate kinematics of the wrist joint functionality captured with dart thrower's movement. It is envisaged that the wrist capability in performing daily activities can be more accurately characterized or encapsulated in the dart thrower's movement. This study examines the characteristic function of wrist movements during dart-throwing motion using only gyroscopic data measured from inertial sensors. A multi-dimensional form of dart throwing trajectory is described using quaternion representation associated with distance metric to quantitatively validate the functional wrist performance between two cohorts; healthy controls and patients. Eight normal subjects and eight patients engaged in a series of clinical trials conducted after undergoing post-surgical reconstructive procedures of the wrist joint. The discriminative results in terms of silhouette clustering evaluation show that the use of distance metric values based quaternion trajectory is well-matched consistently with subjective expert assessments. Our proposed approach captures the relative motions underpinning the wrist joint instead of relying on the traditional measure based on the range of motion measure. Therefore, this paper proposes a reliable approach to dynamically capture the wrist functionality during dart thrower's movement; a movement envisaged to describe the ability to engage in daily life activities. These quantitative outcomes in terms of measurement consistency will provide insightful information in understanding the significant changes in wrist joint signatures associated with various scenarios.

A composite 3D printed model of the midcarpal joint

Three-dimensional (3D) printing has recently been developed as a resource for teaching human anatomy through the accurate reproduction of anatomical specimens. Using a composite 3D printed model with the incorporation of metal and magnets, we were able to demonstrate and analyse movements at the midcarpal joint during the 'dart thrower's motion', which is an important motion in daily activities involving the use of the hand. The hand component with the distal row of carpal bones was subjected to flexion and extension at the midcarpal joint and observed for simultaneous abduction/adduction. Notable adduction was observed in the flexed position as compared to the extended position. Moreover, while the primary movements at the midcarpal joint were taking place in the medial part of the joint, the lateral part of the joint (which is ellipsoid) served to accommodate the arc of movement. We suggest that such composite 3D printed models are useful teaching tools for enhancing the understanding of complex joint movements.

Patellar instability can be classified into four types based on patellar movement with knee flexion: a three-dimensional computer model analysis

Objective

Patellar instability (PI) represents various underlying pathologies, including patellar malalignment. Continuous patellar alignment develops to patellar tracking and is regarded as the end product of combined predisposing factors. We quantitatively investigated the inhomogeneity of patellar tracking in PI.

Methods

Sixty knees of 56 patients with PI and 15 knees of 10 healthy volunteers (HVs) were studied. Three-dimensional (3D) computer models were created based on MRIs at 10° intervals over 0°–50° of flexion, and patellar tracking was quantitatively analysed using patellar 3D shift. Classification was performed according to the maximum 3D shift (max-shift), indicating the extent of lateral deviation, and the change of 3D shift from 0° to 50° (change0–50), indicating movement direction. First, the cut-off value (COV) of the max-shift was defined based on the data from HVs. When a value was greater than the COV, it was defined as a major subluxation, and when the value was smaller it was defined as a minor subluxation. Next, the two COVs of change0–50 were similarly defined. When a value was greater than the upper COV, it was defined as a major-lateral type, laterally moving the patella with flexion, and when smaller than the lower COV it was defined as a major-medial type, medially moving the patella with flexion. When a value fell between the two COVs, it was defined as a major-straight type.

Results

Fifty-three patellae (88%) with values larger than the COV of the max-shift (mean +1 SD of HV) were defined as major subluxations and seven (12%) showing smaller values as minor subluxations. Among the major subluxations, 25 (42%) showing a smaller value than the lower COV of change0–50 (mean –2 SD of HV) were defined as major-medial type, while 7 (12%) showing a larger value than the upper COV of change0–50 (mean +2 SD) were defined as major-lateral type. Twenty-one (35%) were defined as major-straight type. No further analysis was performed on the seven minor subluxations (the minor type).

Conclusion

PI was quantitatively classified into four types according to the extent of lateral deviation and the movement direction of the patellae with flexion, showing inhomogeneity of patellar tracking.

Radiocarpal fusion and midcarpal resection interposition arthroplasty: long-term results in severely destroyed rheumatoid wrists

BACKGROUND

The aim of this retrospective study is to evaluate distal resection interposition arthroplasty of the wrist as a tool to restore mobility as well as to restore stability in severely destroyed wrist joints.

METHODS

Thirty-four wrists in 28 rheumatoid arthritis patients were included. The mean follow-up time was 9 years after surgical treatment with clinical and radiological examination. The results were accessed based on a modification of Clayton ́s scoring system as well as a functional questionnaire.

RESULTS

71% patients were satisfied with pain, function and activities of daily life. Better results were reported by patients with a young age, early surgical intervention, a shorter duration of the disease, and lesser involvement of other joints.

CONCLUSIONS

The results for radiocarpal arthrodesis were comparable to those of synovectomy or arthrodesis of the wrist. The results after total wrist joint arthroplasty varies probably as the result of different patient groups, implant types and evolution of prosthetic designs, and are not comparable with the present study.

Reliability and responsiveness of a goniometric device for measuring the range of motion in the dart-throwing motion plane

Background: Dart-throwing motion (DTM) is an important component of wrist function and, consequently, has the potential to become an evaluation tool in rehabilitation. However, no measurement method is currently available to reliably measure range of motion (ROM) of the wrist in the DTM plane. Objectives: To determine the reliability and responsiveness of a goniometric device to measure wrist ROM in the DTM plane. Methods: ROM of the wrist in the DTM plane was measured in 70 healthy participants. The intra-class correlation coefficient (ICC) was used to evaluate the relative reliability of measurement, and a Bland-Altman analysis conducted to establish its absolute reliability, including the 95% limits of agreement (95% LOA). The standard error of the measurement (SEM) and minimal detectable change at the 95% confidence level (MDC₉₅) were calculated as measures of responsiveness. Results: The intra-rater ICC was 0.87, and an inter-rater ICC of 0.71. There was no evidence of a fixed or proportional bias. For intra- and inter-rater reliability, 95% LOA ranged from -13.83 to 11.12 and from -17.75 to 16.19, respectively. The SEM and MDC₉₅ were 4.5° and 12.4°, respectively, for intra-rater reliability, and 6.0° and 16.6°, respectively, for inter-rater reliability. Conclusion: The ROM of the wrist in the DTM plane was measured with fair-to-good reliability and responsiveness and, therefore, has the potential to become an evaluation tool for rehabilitation.

Impact of scapholunate dissociation on human wrist kinematics

Neither the complex motions of the scapholunate joint, nor the kinematic changes that occur as a result of injury to it, are fully understood. We used electromagnetic tracking within affected bones to evaluate the physiologic motions in the planes of flexion and extension, and of radial and ulnar deviation of human cadaver wrists, before and after complete transection of the scapholunate ligaments. Despite individual variance between each wrist, we were able to establish a pattern in the changes that occurred after scapholunate ligament injury. During the motions examined, the scaphoid showed an increase in translational deviation in almost all motion axes. In contrast, the movement of the lunate seemed to be impaired, especially in radial-ulnar deviation.

Kinematics of the anthropoid os centrale and the functional consequences of scaphoid-centrale fusion in African apes and hominins

In most primates, the os centrale is interposed between the scaphoid, trapezoid, trapezium, and head of the capitate, thus constituting a component of the wrist's midcarpal complex. Scaphoid-centrale fusion is among the clearest morphological synapomorphies of African apes and hominins. Although it might facilitate knuckle-walking by increasing the rigidity and stability of the radial side of the wrist, the exact functional significance of scaphoid-centrale fusion is unclear. If fusion acts to produce a more rigid radial wrist that stabilizes the hand and limits shearing stresses, then in taxa with a free centrale, it should anchor ligaments that check extension and radial deviation, but exhibit motion independent of the scaphoid. Moreover, because the centrale sits between the scaphoid and capitate (a major stabilizing articulation), scaphoid-centrale mobility should correlate with scaphocapitate mobility in extension and radial deviation. To test these hypotheses, the centrale's ligamentous binding was investigated via dissection in Pongo and Papio, and the kinematics of the centrale were quantified in a cadaveric sample of anthropoids (Pongo sp., Ateles geoffroyi, Colobus guereza, Macaca mulatta, and Papio anubis) using a computed-tomography-based method to track wrist-bone motion. Results indicate that the centrale rotates freely relative to the scaphoid in all taxa. However, centrale mobility is only correlated with scaphocapitate mobility during extension in Pongo-possibly due to differences in overall wrist configuration between apes and monkeys. If an extant ape-like wrist characterized early ancestors of African apes and hominins, then scaphoid-centrale fusion would have increased midcarpal rigidity in extension relative to the primitive condition. Although biomechanically consistent with a knuckle-walking hominin ancestor, this assumes that the trait evolved specifically for that biological role, which must be squared with contradictory interpretations of extant and fossil hominoid morphology. Regardless of its original adaptive significance, scaphoid-centrale fusion likely presented a constraint on early hominin midcarpal mobility.

Correlation of 3D Shift and 3D Tilt of the Patella in Patients With Recurrent Dislocation of the Patella and Healthy Volunteers: An In Vivo Analysis Based on 3-Dimensional Computer Models

BACKGROUND

The concepts of lateral deviation and lateral inclination of the patella, characterized as shift and tilt, have been applied in combination to evaluate patellar malalignment in patients with patellar dislocation. It is not reasonable, however, to describe the 3-dimensional (3D) positional relation between the patella and the femur according to measurements made on 2-dimensional (2D) images.

PURPOSE

The current study sought to clarify the relation between lateral deviation and inclination of the patella in patients with recurrent dislocation of the patella (RDP) by redefining them via 3D computer models as 3D shift and 3D tilt.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Altogether, 60 knees from 56 patients with RDP and 15 knees from 10 healthy volunteers were evaluated. 3D shift and tilt of the patella were analyzed with 3D computer models created by magnetic resonance imaging scans obtained at 10° intervals of knee flexion (0°-50°). 3D shift was defined as the spatial distance between the patellar reference point and the midsagittal plane of the femur; it is expressed as a percentage of the interepicondylar width. 3D tilt was defined as the spatial angle between the patellar reference plane and the transepicondylar axis. Correlations between the 2 parameters were assessed with the Pearson correlation coefficient.

RESULTS

The patients' mean Pearson correlation coefficient was 0.895 ± 0.186 (range, -0.073 to 0.997; median, 0.965). In all, 56 knees (93%) had coefficients >0.7 (strong correlation); 1 knee (2%), >0.4 (moderate correlation); 2 knees (3%), >0.2 (weak correlation); and 1 knee (2%), <0.2 (no correlation). The mean correlation coefficient of the healthy volunteers was 0.645 ± 0.448 (range, -0.445 to 0.982; median, 0.834). A statistically significant difference was found in the distribution of the correlation coefficients between the patients and the healthy volunteers ( P = .0034). When distribution of the correlation coefficients obtained by the 3D analyses was compared with that by the 2D (conventional) analyses, based on the bisect offset index and patellar tilt angle, the 3D analyses showed statistically higher correlations between the lateral deviation and inclination of the patella ( P < .01).

CONCLUSION

3D shift and 3D tilt of the patella were moderately or strongly correlated in 95% of patients with RDP at 0° to 50° of knee flexion.

CLINICAL RELEVANCE

It is not always necessary to use both parameters when evaluating patellar alignment, at least for knees with RDP at 0° to 50° of flexion. Such a description may enable surgeons to describe patellar alignment more simply, leading to a better, easier understanding of the characteristics of each patient with RDP.

Biomechanical Evaluation of Carpal Kinematics during Simulated Wrist Motion

Background Flexion and extension of the wrist is achieved primarily at the radiocarpal and midcarpal joints. Carpal kinematics have been investigated, although there remains no consensus regarding the relative contribution of each bone to wrist motion. Purpose To determine the kinematics of the scaphoid, lunate, and capitate during unconstrained simulated wrist flexion/extension and to examine the effect of motion direction on the contribution of each bone. Materials and Methods Seven cadaveric upper extremities were tested in a passive wrist simulator with 10N tone loads applied to the wrist flexors/extensors. Scaphoid, lunate, and capitate kinematics were captured using optical tracking and analyzed with respect to the radius. Results Scaphoid and lunate motion correlated linearly with wrist motion (R² = 0.99, 0.97). In extension, the scaphoid and lunate extended 83 ± 19% and 37 ± 18% relative to total wrist extension (p = 0.03, 0.001), respectively. In flexion, the scaphoid and lunate flexed 95 ± 20% and 70 ± 12% relative to total wrist flexion (p = 1.0,0.01) , respectively. The lunate rotated 46 ± 25% less than the capitate and 35 ± 31% less than the scaphoid. The intercarpal motion between the scaphoid and lunate was 25 ± 17% of wrist flexion. Conclusion The scaphoid, lunate, and capitate move synergistically throughout planar wrist motion. The scaphoid and lunate contributed at a greater degree during flexion, suggesting that the radiocarpal joint plays a more critical role in wrist flexion. Clinical Relevance The large magnitude of differential rotation between the scaphoid and lunate may be responsible for the high incidence of scapholunate ligament injuries. An understanding of normal carpal kinematics may assist in positioning carpal bones during partial wrist fusions and in developing more durable wrist arthroplasty designs.

Decoupling the Wrist: A Cadaveric Experiment Examining Wrist Kinematics Following Midcarpal Fusion and Scaphoid Excision

At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.

The effect of wrist surgery on the kinematic consistency of joint axis reconstruction in a static posture

Three-dimensional analysis of wrist motion is a growing focus in orthopedic research, however, our understanding of its validity (accuracy and reliability) remains limited. Nine human cadavers were tested to estimate wrist joint axes alignment in a postural static pose. The objective was to investigate a rater's ability to reliably align three skin- tracked wrist joint coordinate system (WJCS) definitions across baseline and reconstructive wrist states (intact, mid-carpal arthrodesis, and proximal-row carpectomy). Two WJCSs (legacy, anatomic) were based on palpated bony landmarks and the third (functional) was based on both landmarks and passive flexion-extension motion. A coordinate frame based on the anatomic definition was tracked with bone pins and served as a reference. Each WJCS was tested in each wrist state and in three forearm position (45° pronation, neutral, 45° supination). The angular offset about each axis of the WJCS frames were calculated with respect to the reference in flexion-extension, radial-ulnar deviation, and pronation-supination for every iteration. Reliability and root mean square deviation values were analyzed across wrist states. Our data suggest that no WJCS is uniformly more reliable than another. The functional WJCS definition was most consistent across intact and post-operative states for pronation-supination offset, but this was dependent on rater interpretation. It still however offers the practical benefit of requiring fewer landmarks.

Surgical Treatments for Scapholunate Advanced Collapse Wrist: Kinematics and Functional Performance

PURPOSE

The purpose of this investigation was to compare kinematic motion and functional performance during 2 tasks in patients following 4-corner fusion (4CF) or proximal row carpectomy (PRC) and to compare these data with those from healthy asymptomatic individuals.

METHODS

Twenty men (10 4CFs and 10 PRCs, ages, 43-82 y) were recruited for 3-dimensional wrist motion analysis testing. Kinematic coupling (the ratio of wrist flexion/extension to radial-ulnar deviation), kinematic path length (a measure of total angle distance), clinical measures, and performance measures were collected during 2 tasks: dart throwing and hammering. For each outcome, between-group comparisons employed a 1-way analysis of variance with post hoc analysis using the Fisher least significant difference test.

RESULTS

All clinical measures (flexion-extension, radial-ulnar deviation, and grip strength) were decreased for 4CF and PRC patients compared with healthy subjects. Coupling, kinematic path length, and performance were all significantly reduced in 4CF and PRC patients compared with healthy subjects during both tasks. Reduced coupling and a shorter kinematic path length are indicative of less global and combined wrist motion. There were no differences identified in coupling patterns or performance between the surgical groups for the dart-throwing task. However, in hammering, the kinematic path length and performance (time and total strikes) were worse in 4CF than in PRC.

CONCLUSIONS

Differences in wrist kinematics and performance were identified between the groups. PRC subjects performed better on kinematic and performance variables. As expected, both groups demonstrated decreased wrist kinematic motion and functional performance compared with individuals with normal wrists. These results require confirmation and while they cannot be used to determine the benefits of one procedure over the other, they are an important step in quantifying differences in motion and function between procedures.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

A technique for quantifying wrist motion using four-dimensional computed tomography: approach and validation

Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucial for diagnosis and prescription of the most effective interventions for preventing progression to osteoarthritis. Current imaging techniques are unable to detect injuries reliably and are static in nature, thereby capturing bone position information rather than motion which is indicative of ligament injury. A recently developed technique, 4D (three dimensions + time) computed tomography (CT) enables three-dimensional volume sequences to be obtained during wrist motion. The next step in successful clinical implementation of the tool is quantification and validation of imaging biomarkers obtained from the four-dimensional computed tomography (4DCT) image sequences. Measures of bone motion and joint proximities are obtained by: segmenting bone volumes in each frame of the dynamic sequence, registering their positions relative to a known static posture, and generating surface polygonal meshes from which minimum distance (proximity) measures can be quantified. Method accuracy was assessed during in vitro simulated wrist movement by comparing a fiducial bead-based determination of bone orientation to a bone-based approach. The reported errors for the 4DCT technique were: 0.00-0.68 deg in rotation; 0.02-0.30 mm in translation. Results are on the order of the reported accuracy of other image-based kinematic techniques.

Dynamic in vivo evaluation of radiocarpal contact after a 4-corner arthrodesis

PURPOSE

To understand the mechanisms that preserve joint integrity after 4-corner arthrodesis (FCA).

METHODS

We investigated the long-term changes of the radiolunate articulation after an FCA for different motions of the wrist in a cross-sectional study that included wrists of 10 healthy participants and both operated and nonoperated wrists of 8 individuals who had undergone FCA on 1 side. The average postoperative follow-up period of the FCA group was 5.7 years. The radiolunate articulation was assessed from dynamic 3-dimensional distance maps during wrist motion. Contact surface area, centroid position of the articular area, and distance between radiolunate articular surfaces were measured and compared between healthy subjects and operated and nonoperated wrists of FCA patients.

RESULTS

The total radiolunate articulation area was larger in patients with FCA. The average radiolunate joint space thickness was preserved in the operated FCA wrists. The centroid of the articulation area was shifted radially and dorsally in FCA wrists.

CONCLUSIONS

Changes of the motion pattern of the lunate during radioulnar deviation and flexion-extension of the wrist after FCA can explain the shift of the centroid radially and dorsally.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.

International Federation of Societies for Surgery of the Hand 2013 Committee's report on wrist dart-throwing motion

This report updates information on wrist dart-throwing (DT) motion, based on the most recent research published on the kinematics, kinetics, and clinical applications of DT motion. A wide range of DT planes exists. "Pure" DT motion is done along an oblique plane that intercepts the coronal and sagittal planes at the zero position, and occurs almost exclusively at the midcarpal joint with near zero scaphoid and lunate motion. "Functional" DT motion such as a hammering is done along an oblique plane that is almost parallel to the pure DT plane, but that has an offset toward the dorsal side. Functional DT rotation has greater scaphoid and lunate motion compared with pure DT motion. Midcarpal arthrodesis adversely affects DT motion compared with radiocarpal arthrodesis. During a DT motion, the mean and peak tendon forces of the flexor carpi ulnaris and the extensor carpi radialis longus were the greatest among wrist motors. By performing a task along the plane of DT motion, the scapholunate (SL) joint was stable and SL ligament elongation was minimal in healthy subjects. However, a more recent study of patients with SL dissociation revealed that DT exercises applied tensile forces on the SL ligament and induced an SL gap.

Unifying model of carpal mechanics based on computationally derived isometric constraints and rules-based motion - the stable central column theory

This study was part of a larger project to develop a (kinetic) theory of carpal motion based on computationally derived isometric constraints. Three-dimensional models were created from computed tomography scans of the wrists of ten normal subjects and carpal spatial relationships at physiological motion extremes were assessed. Specific points on the surface of the various carpal bones and the radius that remained isometric through range of movement were identified. Analysis of the isometric constraints and intercarpal motion suggests that the carpus functions as a stable central column (lunate-capitate-hamate-trapezoid-trapezium) with a supporting lateral column (scaphoid), which behaves as a 'two gear four bar linkage'. The triquetrum functions as an ulnar translation restraint, as well as controlling lunate flexion. The 'trapezoid'-shaped trapezoid places the trapezium anterior to the transverse plane of the radius and ulna, and thus rotates the principal axis of the central column to correspond to that used in the 'dart thrower's motion'. This study presents a forward kinematic analysis of the carpus that provides the basis for the development of a unifying kinetic theory of wrist motion based on isometric constraints and rules-based motion.

Dynamic motion analysis of dart throwers motion visualized through computerized tomography and calculation of the axis of rotation

We used a dynamic three-dimensional (3D) mapping method to model the wrist in dynamic unrestricted dart throwers motion in three men and four women. With the aid of precision landmark identification, a 3D coordinate system was applied to the distal radius and the movement of the carpus was described. Subsequently, with dynamic 3D reconstructions and freedom to position the camera viewpoint anywhere in space, we observed the motion pathways of all carpal bones in dart throwers motion and calculated its axis of rotation. This was calculated to lie in 27° of anteversion from the coronal plane and 44° of varus angulation relative to the transverse plane. This technique is a safe and a feasible carpal imaging method to gain key information for decision making in future hand surgical and rehabilitative practices.

Wrist kinematic coupling and performance during functional tasks: effects of constrained motion

PURPOSE

To quantify the coupled motion of the wrist during selected functional tasks and to determine the effects of constraining this coupled motion using a radial-ulnar deviation blocking splint on performance of these tasks.

METHODS

Ten healthy, right-handed men performed 15 trials during selected functional tasks with and without a splint, blocking radial and ulnar deviation. The following tasks were performed: dart throwing, hammering, basketball free-throw, overhand baseball and football throwing, clubbing, and pouring. Kinematic coupling parameters (coupling, kinematic path length, flexion-extension range of motion, radial-ulnar deviation range of motion, flexion-extension offset, and radial-ulnar deviation offset) and performance were determined for each functional task. A generalized estimation equation model was used to determine whether each kinematic coupling parameter was significantly different across tasks. A repeated-measures generalized estimation equation model was used to test for differences in performance and kinematic coupling parameters between the free and splinted conditions.

RESULTS

Wrist motion exhibited linear coupling between flexion-extension and radial-ulnar deviation, demonstrated by R(2) values from 0.70 to 0.99. Average wrist coupling and kinematic path lengths were significantly different among tasks. Coupling means and kinematic path lengths were different between free and splinted conditions across all tasks other than pouring. Performance was different between wrist conditions for dart throwing, hammering, basketball shooting, and pouring.

CONCLUSIONS

Wrist kinematic coupling parameters are task specific in healthy individuals. Functional performance is decreased when wrist coupling is constrained by an external splint.

CLINICAL RELEVANCE

Surgical procedures that restrict wrist coupling may have a detrimental effect on functional performance as defined in the study. Patients may benefit from surgical reconstructive procedures and wrist rehabilitation protocols designed to restore kinematic coupling.

In vivo changes in contact regions of the radiocarpal joint during wrist hyperextension

PURPOSE

Distal radius and scaphoid fractures commonly occur after a fall with the hand outstretched and wrist hyperextended. We investigated contact characteristics of the radiocarpal joint in neutral position, hyperextension, and hyperextension combined with radial deviation in vivo.

METHODS

Eight volunteers without a known history of wrist injury were enrolled. We obtained computed tomography scans with 3-dimensional reconstructions of the subjects' right wrists in neutral, hyperextension, and hyperextension with 10° of radial deviation. The contact regions of the radiocarpal joint were mapped. The direction and distance of changes in the contact region centers were recorded and analyzed.

RESULTS

From neutral position to hyperextension, the contact of the scaphoid substantially shifted from the middle to the dorsal part of the articular surface of the radius in 5 of the 8 wrists. With these wrists further deviated radially, the contact shifted to the surface over the radial styloid. In the other wrists, the contact of the scaphoid remained in the center of the radial articular surface. In all wrists, the contact of the radius on the scaphoid shifted from the proximal lateral surface of the scaphoid to the proximal dorsal surface of the scaphoid, and the contact of the radius on the lunate shifted dorsally.

CONCLUSIONS

During wrist hyperextension, the contact of the scaphoid on the distal radius exhibited 2 possible types of changes: either shifting from the mid-portion to the dorsal ridge of the articular surface of the radius or remaining at the center of the articular surface. Combined wrist hyperextension with radial deviation caused the scaphoid to contact the radius over the radial styloid. The contact of the radius on the scaphoid shifted from proximal lateral to proximal dorsal scaphoid, and that on the lunate shifted dorsally.

CLINICAL RELEVANCE

This study provided in vivo mechanical findings to improve our understanding of the mechanism of hyperextension injuries of carpus.

In vivo length and changes of ligaments stabilizing the thumb carpometacarpal joint

PURPOSE

To investigate the lengths and changes of selected ligaments stabilizing the thumb carpometacarpal (CMC) joint during thumb motion in vivo.

METHODS

We obtained serial computed tomography scans of the thumb CMC joints of 6 healthy volunteers during thumb flexion, abduction, and opposition. We reconstructed the 3-dimensional structures of the bones of the thumb CMC joint using customized software and modeled the paths of fibers of 5 principal ligaments--deep anterior oblique (beak), dorsoradial, posterior oblique, intermetacarpal, and dorsal intermetacarpal--at each of the CMC joint positions studied. We estimated the virtual lengths of these ligaments in neutral position, flexion, abduction, and opposition of the CMC joint by measuring the distances between the origin and the insertion of individual ligaments, and statistically analyzed the length changes.

RESULTS

The estimated length of the CMC joint ligaments underwent significant changes during thumb motion in vivo. Thumb flexion led to the greatest changes in ligament lengths. During flexion, all the ligaments lengthened significantly (p < .05 or p < .01), except for the beak ligament, which shortened significantly (p < .001). The lengths of the ligaments changed similarly during thumb abduction and opposition, except for the dorsoradial ligament. In both motions, the posterior oblique and dorsal intermetacarpal ligaments lengthened and the beak ligament shortened significantly (p < .05 or p < .01). During the 3 thumb motions, the beak ligament underwent marked shortening, while the other measured ligaments lengthened to varied extent.

CONCLUSIONS

The estimated lengths of principal ligaments stabilizing the CMC joint change substantially during thumb motions in vivo. Thumb flexion causes the greatest changes of the ligament lengths; abduction and opposition result in similar changes in the ligament lengths. The beak ligaments shorten while the other ligaments lengthen. This in vivo study suggests that thumb motions expose the CMC joint ligaments to different tensions at these thumb positions, and that the ligaments are under lower tension during thumb opposition and abduction than during flexion.

In vivo length changes of carpal ligaments of the wrist during dart-throwing motion

PURPOSE

The dart-throwing motion is an important movement pattern during most wrist actions. The aim of this study was to investigate length changes in the wrist ligaments in different positions of the dart-throw motion in vivo.

METHODS

We obtained computed tomography scans of the wrists of 6 volunteers at 5 positions of the wrist during the dart-throw motion: 20° of radial deviation with 60° of extension; 10° of radial deviation with 30° of extension; the neutral position of the carpus; 20° of ulnar deviation with 30° of flexion; and 40° of ulnar deviation with 60° of flexion. We reconstructed the 3-dimensional carpal and distal radioulnar joint structures with customized software and computed changes in length of 8 palmar and dorsal wrist ligaments.

RESULTS

From wrist radial deviation with extension to ulnar deviation with flexion, the radioscaphocapitate, long radiolunate, ulnocapitate, and ulnotriquetral ligaments decreased significantly in length but the dorsal radiocarpal ligament and the dorsal intercarpal (DIC) ligament inserting on the trapezoid lengthened significantly; the ulnolunate ligament and the DIC ligament inserting on the scaphoid were shortest in neutral position.

CONCLUSIONS

At wrist radial extension, the radioscaphocapitate, long radiolunate, ulnocapitate, and ulnotriquetral ligaments are lengthened and under increased tension. At wrist ulnar flexion, the dorsal radiocarpal ligament and the DIC ligament inserting on the trapezoid are lengthened and under increased tension. The ulnolunate ligament and the DIC ligament inserting on the scaphoid are the shortest and under the least tension in neutral position. These findings will help us understand the biomechanics of the carpus during the dart-throwing motion.

Scaphoid and lunate translation in the intact wrist and following ligament resection: a cadaver study

PURPOSE

To determine the amount of scaphoid and lunate translation that occurs in normal cadaver wrists during wrist motion, and to quantify the change in ulnar translation when specific dorsal and volar wrist ligaments were sectioned.

METHODS

We measured the scaphoid and lunate motion of 37 cadaver wrists during wrist radioulnar deviation and flexion-extension motions using a wrist joint motion simulator. We quantified the location of the centroids of the bones during each motion in the intact wrists and after sectioning either 2 dorsal ligaments along with the scapholunate interosseous ligament or 2 volar ligaments and the scapholunate interosseous ligament.

RESULTS

In the intact wrist, the scaphoid and lunate statistically translated radially with wrist ulnar deviation. With wrist flexion, the scaphoid moved volarly and the lunate dorsally. After sectioning either the dorsal or volar ligaments, the scaphoid moved radially. After sectioning the dorsal or volar ligaments, the lunate statistically moved ulnarly and volarly.

CONCLUSIONS

Measurable changes in the scaphoid and lunate translation occur with wrist motion and change with ligament sectioning. However, for the ligaments that were sectioned, these changes are small and an attempt to clinically measure these translations of the scaphoid and lunate radiographically may be limited. The results support the conclusion that ulnar translocation does not occur unless multiple ligaments are sectioned. Injury of more than the scapholunate interosseous ligament along with either the dorsal intercarpal and dorsal radiocarpal or the radioscaphocapitate and scaphotrapezial ligaments is needed to have large amounts of volar and ulnar translation.

The effect of radioscapholunate fusion on wrist movement and the subsequent effects of distal scaphoidectomy and triquetrectomy

Radioscapholunate arthrodesis is a salvage procedure indicated for osteoarthritis of the radiocarpal joint involving the lunate facet of the radius. This cadaver study examines changes in wrist motion resulting from radioscapholunate arthrodesis, and the effects of surgical techniques to improve the range of motion. Simulated radioscapholunate arthrodesis, distal scaphoidectomy and triquetrectomy were carried out sequentially on six cadaver forearms and measurements (maximum flexion/extension and radial/ulnar deviation) were taken in the intact situation and after each surgical step using a magnetic tracking device. Radioscapholunate arthrodesis diminishes the amplitudes of movements of the wrist in all directions, but range of motion in the radioscapholunate fused wrist improves after scaphoidectomy and improves further after triquetrectomy (88% of original flexion/extension and 98% of original radial/ulnar deviation). Radioscapholunate arthrodesis causes a significant change in kinematics between the hamate and the triquetrum in flexion/extension.

Studying primate carpal kinematics in three dimensions using a computed-tomography-based markerless registration method

The functional morphology of the wrist pertains to a number of important questions in primate evolutionary biology, including that of hominins. Reconstructing locomotor and manipulative capabilities of the wrist in extinct species requires a detailed understanding of wrist biomechanics in extant primates and the relationship between carpal form and function. The kinematics of carpal movement, and the role individual joints play in providing mobility and stability of the wrist, is central to such efforts. However, there have been few detailed biomechanical studies of the nonhuman primate wrist. This is largely because of the complexity of wrist morphology and the considerable technical challenges involved in tracking the movements of the many small bones that compose the carpus. The purpose of this article is to introduce and outline a method adapted from human clinical studies of three-dimensional (3D) carpal kinematics for use in a comparative context. The method employs computed tomography of primate cadaver forelimbs in increments throughout the wrist's range of motion, coupled with markerless registration of 3D polygon models based on inertial properties of each bone. The 3D kinematic principles involved in extracting motion axis parameters that describe bone movement are reviewed. In addition, a set of anatomically based coordinate systems embedded in the radius, capitate, hamate, lunate, and scaphoid is presented for the benefit of other primate functional morphologists interested in studying carpal kinematics. Finally, a brief demonstration of how the application of these methods can elucidate the mechanics of the wrist in primates illustrates the closer-packing of carpals in chimpanzees than in orangutans, which may help to stabilize the midcarpus and produce a more rigid wrist beneficial for efficient hand posturing during knuckle-walking locomotion.

The advantage of throwing the first stone: how understanding the evolutionary demands of Homo sapiens is helping us understand carpal motion

Unlike any other diarthrodial joint in the human body, the "wrist joint" is composed of numerous articulations between eight carpal bones, the distal radius, the distal ulna, and five metacarpal bones. The carpal bones articulate with each other as well as with the distal radius, distal ulna, and the metacarpal bases. Multiple theories explaining intercarpal motion have been proposed; however, controversy exists concerning the degree and direction of motion of the individual carpal bones within the two carpal rows during different planes of motion. Recent investigations have suggested that traditional explanations of carpal bone motion may not entirely account for carpal motion in all planes. Better understanding of the complexities of carpal motion through the use of advanced imaging techniques and simultaneous appreciation of human anatomic and functional evolution have led to the hypothesis that the "dart thrower's motion" of the wrist is uniquely human. Carpal kinematic research and current developments in both orthopaedic surgery and anthropology underscore the importance of the dart thrower's motion in human functional activities and the clinical implications of these concepts for orthopaedic surgery and rehabilitation.

Three-dimensional kinematics of the rheumatoid wrist after partial arthrodesis

BACKGROUND

Partial arthrodesis of the wrist, such as radiolunate and radioscapholunate arthrodesis, is intuitively more appealing for the treatment of the rheumatoid wrist than total arthrodesis is because it preserves some motion. However, wrist kinematics after partial arthrodesis are incompletely understood. The purpose of the present study was to evaluate the kinematics of the radiocarpal and midcarpal joints of rheumatoid wrists with use of three-dimensional computed tomography before and after partial arthrodesis.

METHODS

We selected ten wrists that were affected by rheumatoid arthritis in which the radiolunate joint was severely damaged but the midcarpal joint congruities were relatively well preserved. Six radiolunate and four radioscapholunate arthrodeses were then performed, with preservation of the joint congruity between the scaphoid, lunate, and capitate. We acquired in vivo three-dimensional kinematic data during wrist flexion-extension preoperatively and postoperatively with use of computed tomography and a markerless bone-registration technique. Postoperative midcarpal joint congruity and range of motion were compared with preoperative values.

RESULTS

The mean range of global wrist motion was 48 degrees +/- 21 degrees after radiolunate arthrodesis and 47 degrees +/- 14 degrees after radioscapholunate arthrodesis. Midcarpal joint congruities and motion between the scaphoid, lunate, and capitate were well preserved in all ten wrists. The postoperative range of capitate motion relative to the lunate was 109% of the preoperative value after radiolunate arthrodesis and 88% after radioscapholunate arthrodesis. The directions of capitate motion relative to the lunate after both types of partial arthrodesis were significantly more oblique than before the arthrodeses, changing from radiodorsal to ulnopalmar along the so-called dart-throwing motion plane (p < 0.05).

CONCLUSIONS

The results of this kinematic analysis, which showed that midcarpal motion occurred in the dart-throwing motion plane, may support the use of radiolunate and radioscapholunate arthrodeses as an alternative to total wrist arthrodesis in patients with symptomatic rheumatoid arthritis of the wrist.

Three-dimensional in vivo kinematics of the subtalar joint during dorsi-plantarflexion and inversion-eversion

BACKGROUND

It is difficult to determine the kinematics of the subtalar joint because of its anatomical and functional complexity. The purpose of the study was to clarify the 3D kinematics of the subtalar joint in vivo.

MATERIALS AND METHODS

Subjects were four healthy female volunteers. Magnetic resonance imaging (MRI) sequences were acquired in seven positions during dorsi-plantarflexion (DPF) and in 10 positions during inversion-eversion (IE) at intervals of 10 degrees. MRI data of the talus and calcaneus in the neutral position were superimposed on images of the other positions using voxel-based registration, and relative motions and axes of rotation were visualized and quantitatively calculated.

RESULTS

The calcaneus always rotated from dorsolateral to medioplantar during DPF and IE, and the motion plane was very similar to that of the entire foot in IE. The axes of rotation of the calcaneus relative to the talus during DPF and IE had a very close spatial relationship, running obliquely from antero-dorso-medial to postero-planto-lateral and penetrating the talar neck. The rotation angle around each of these calcaneal axes tended to be greater in IE (20 degrees +/- 2 degrees) than in DPF (16 degrees +/- 3 degrees). In DPF, motion of the calcaneus relative to the talus occurred predominantly around maximum dorsiflexion and plantarflexion, with little movement observed at intermediate positions. During IE, the calcaneus exhibited uninterrupted motion related to foot movement.

CONCLUSION

The subtalar joint is essentially a uniaxial joint with a motion plane almost identical to that of IE of the entire foot.

CLINICAL RELEVANCE

Knowledge of normal subtalar kinematics may be helpful when evaluating pathologic conditions.

Range of motion effects of distal pole scaphoid excision and triquetral excision after radioscapholunate fusion: a cadaver study

PURPOSE

Radioscapholunate (RSL) fusion is an effective surgical procedure for the treatment of isolated radiocarpal arthritis. Although functional wrist motion is typically preserved through the midcarpal joint, many patients are still frustrated by postoperative limitations. The purpose of this study was to evaluate motion of cadaver wrists after simulated RSL fusion with excision of the distal pole of the scaphoid and the triquetrum.

METHODS

Ten fresh-frozen cadaver upper extremities were mounted on a custom testing apparatus after isolation of the flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis longus, and extensor carpi ulnaris tendons. Sequential loading of these tendons resulted in flexion, extension, radial, and ulnar deviation. We subsequently measured range of motion with the use of digital photography. All specimens were tested in 4 states: intact (normal), RSL fusion (simulated), RSL fusion with distal scaphoid pole excision, and RSL fusion with distal scaphoid pole and triquetrum excision. The results were statistically analyzed using a repeated measures analysis of variance.

RESULTS

Range of motion decreased to 39% to 46% of normal for flexion and extension and 65% to 71% of normal for radial and ulnar deviation after simulated RSL fusion. The addition of distal pole of scaphoid excision resulted in flexion and extension returning to 72% to 79% of normal, and radial and ulnar deviation returning to 84% to 89% of normal. Excision of the triquetrum further increased flexion and extension to 87% to 97% of normal, and radial and ulnar deviation to 119% to 137% of normal.

CONCLUSIONS

The combination of triquetral and distal scaphoid pole excision after RSL fusion improves wrist motion to levels close to normal in the cadaver model.

In vivo length changes of selected carpal ligaments during wrist radioulnar deviation

PURPOSE

To investigate changes in the lengths of selected carpal ligaments during wrist radioulnar deviation in vivo.

METHODS

We studied in vivo changes in the lengths of fibers of 5 palmar and dorsal intracapsular ligaments of the wrist during radioulnar deviation in 6 wrists of healthy volunteers using a noninvasive approach. Using serial computed tomography scans and volume registration techniques, the carpal kinematics were examined at 4 positions, from 40 degrees ulnar deviation to 20 degrees radial deviation, in 20 degrees increments. The 3-dimensional structures of the carpal bones, distal radius and ulna, and metacarpal bones were reconstructed using customized software. We modeled the paths of fibers of 5 palmar and dorsal carpal ligaments: radioscaphocapitate (RSC), long radiolunate (LRL), ulnocapitate (UC), dorsal intercarpal (DIC), and dorsal radiocarpal (DRC) ligaments. We analyzed changes in the lengths of these ligaments during wrist radioulnar deviation.

RESULTS

During wrist ulnar deviation, the RSC, LRL, and DIC ligaments lengthened significantly. During radial deviation, the UC and DRC ligaments lengthened significantly. Compared with their lengths at the neutral position of the carpus, the LRL ligament showed the greatest elongation rate at wrist ulnar deviation, and the DRC ligament showed the greatest elongation rate at wrist radial deviation among the 5 ligaments studied.

CONCLUSIONS

Among ligaments measured, the RSC, LRL, and DIC ligaments are tensed during wrist ulnar deviation. The UC and DRC ligaments are tensed during wrist radial deviation. Results of this in vivo study suggest that radial or ulnar deviation may predispose some carpal ligaments to excessive tensile load. The finding that the ligaments undergo different elongation rates during wrist motion may also indicate their roles in maintaining normal wrist kinematics.

In vivo changes in lengths of the ligaments stabilizing the distal radioulnar joint

PURPOSE

To investigate changes in lengths of the ligaments stabilizing the distal radioulnar joint during forearm pronation and supination in vivo.

METHODS

We studied in vivo kinematics of the distal radioulnar joint by measuring the length changes of the ligaments of the distal radioulnar joint in 6 wrists of normal volunteers. Using serial computed tomography scans and volume registration techniques, the distal radioulnar joints were examined at 7 positions from 90 degrees pronation to 90 degrees supination in 30 degrees increments. The 3-dimensional structures of the joint were reconstructed with customized software. The paths of palmar and dorsal superficial and deep fibers of the radioulnar ligaments were modeled, and changes in their lengths were computed and analyzed statistically.

RESULTS

The lengths of the palmar superficial radioulnar ligaments decreased significantly during forearm pronation from 90 degrees to 30 degrees compared with those at the other positions. During pronation from 90 degrees to neutral rotation, lengths of the dorsal deep radioulnar ligaments decreased significantly. The lengths of the dorsal superficial radioulnar ligament decreased significantly during forearm supination from neutral rotation to 90 degrees , as did the lengths of the palmar deep radioulnar ligaments. The palmar and dorsal superficial radioulnar ligaments showed greater length changes than did the palmar and dorsal deep radioulnar ligaments during forearm pronation-supination. The dorsal superficial radioulnar ligament had the greatest length changes during pronation-supination among the studied ligaments.

CONCLUSIONS

These in vivo measurements validate that in forearm pronation, the dorsal superficial radioulnar ligament and palmar deep radioulnar ligament tighten, serving as restraints for the distal radioulnar joint instability. In forearm supination, the palmar superficial radioulnar ligament and dorsal deep radioulnar ligament tighten, maintaining stability of the distal radioulnar joint.

Detection of in vivo dynamic 3-D motion patterns in the wrist joint

We present a method for measurement dynamic in vivo carpal motion patterns. The method consists of a 4-D rotational X-ray (RX) with improved image quality and image processing for accurate detection in vivo wrist motion measurements. Dynamic 3-D imaging yields a number of volume reconstructions of the wrist at different phases of its cyclic motion. Next, the carpal reconstructions are registered to their static acquired and segmented counterpart in all phases. With this information, the relation between the applied motion and carpal kinematic behavior is acquired, i.e., the motion patterns. We investigated the precision of the image acquisition and processing and tested it on three healthy subjects. The precision of the image acquisition and image processing is in the range of submillimeters and subdegrees, respectively, which is better than existing systems and sufficient for clinical investigations. Reproducibility measurements show some more deviation ( > 1 degrees). This method was tested on four human volunteers and agrees for the greater part with previously done invasive and nondynamic measurements. In vivo motion pattern measurement with 4-D-RX imaging and processing is accurate and noninvasive. The motion patterns can reveal disorders that could not have been detected in either video fluoroscopy, computed tomography, or MRI.

The non-dissociative clunking wrist: a personal view

Clunking of the wrist is often the result of a combined radiocarpal and midcarpal ligament insufficiency, coupled with inadequate neuromuscular coordination. When symptomatic, these wrists may benefit from splinting, isometric exercising of specific muscles and advice on activity modification. Failing this, different surgical strategies have been proposed, depending on the location of dysfunction. When the clunking derives from an isolated injury of one joint, reconstruction of its inadequate ligaments may be an effective solution. However, soft tissue procedures tend to fail when clunking results from multilevel instability. In these cases, partial carpal arthrodesis is an alternative. Although effective in eliminating the clunking, midcarpal fusion is associated with alteration of the so-called "dart-throwing" motion, the most common rotation in daily activities, and hence is not recommended. Radiolunate fusion, by contrast, appears to be a less morbid alternative, with the benefit of eliminating the painful clunking while preserving a good range of dart-throwing motion.

Gender differences in capitate kinematics are eliminated after accounting for variation in carpal size

Previous studies have found gender differences in carpal kinematics, and there are discrepancies in the literature on the location of the flexionextension and radio-ulnar deviation rotation axes of the wrist. It has been postulated that these differences are due to carpal bone size differences rather than gender and that they may be resolved by normalizing the kinematics by carpal size. The purpose of this study was to determine if differences in radio-capitate kinematics are a function of size or gender. We also sought to determine if a best-fit pivot point (PvP) describes the radio-capitate joint as a ball-and-socket articulation. By using an in vivo markerless bone registration technique applied to computed tomography scans of 26 male and 28 female wrists, we applied scaling derived from capitate length to radio-capitate kinematics, characterized by a best-fit PvP. We determined if radio-capitate kinematics behave as a ball-and-socket articulation by examining the error in the best-fit PvP. Scaling PvP location completely removed gender differences (P=0.3). This verifies that differences in radio-capitate kinematics are due to size and not gender. The radio-capitate joint did not behave as a perfect ball and socket because helical axes representing anatomical motions such as flexion-extension, radio-ulnar deviation, dart throwers, and antidart throwers, were located at distances up to 4.5 mm from the PvP. Although the best-fit PvP did not yield a single center of rotation, it was still consistently found within the proximal pole of the capitate, and rms errors of the best-fit PvP calculation were on the order of 2 mm. Therefore, the ball-and-socket model of the wrist joint center using the best-fit PvP is appropriate when considering gross motion of the hand with respect to the forearm such as in optical motion capture models. However, the ball-and-socket model of the wrist is an insufficient description of the complex motion of the capitate with respect to the radius. These findings may aid in the design of wrist external fixation and orthotics.