[Show abstract][Hide abstract] ABSTRACT: PURPOSE: Insights into the complexity of active in vivo carpal motion have recently been gained using 3-dimensional imaging; however, kinematics during extremes of motion has not been elucidated. The purpose of this study was to determine motion of the carpus during extremes of wrist flexion and extension. METHODS: We obtained computed tomography scans of 12 healthy wrists in neutral grip, extreme loaded flexion, and extreme loaded extension. We obtained 3-dimensional bone surfaces and 6-degree-of-freedom kinematics for the radius and carpals. The flexion and extension rotation from neutral grip to extreme flexion and extreme extension of the scaphoid and lunate was expressed as a percentage of capitate flexion and extension and then compared with previous studies of active wrist flexion and extension. We also tested the hypothesis that the capitate and third metacarpal function as a single rigid body. Finally, we used joint space metrics at the radiocarpal and midcarpal joints to describe arthrokinematics. RESULTS: In extreme flexion, the scaphoid and lunate flexed 70% and 46% of the amount the capitate flexed, respectively. In extreme extension, the scaphoid extended 74% and the lunate extended 42% of the amount the capitates extended, respectively. The third metacarpal extended 4° farther than the capitate in extreme extension. The joint contact area decreased at the radiocarpal joint during extreme flexion. The radioscaphoid joint contact center moved onto the radial styloid and volar ridge of the radius in extreme flexion from a more proximal and ulnar location in neutral. CONCLUSIONS: The contributions of the scaphoid and lunate to capitate rotation were approximately 25% less in extreme extension compared with wrist motion through an active range of motion. More than half the motion of the carpus when the wrist was loaded in extension occurred at the midcarpal joint. CLINICAL RELEVANCE: These findings highlight the difference in kinematics of the carpus at the extremes of wrist motion, which occur during activities and injuries, and give insight into the possible etiologies of the scaphoid fractures, interosseous ligament injuries, and carpometacarpal bossing.
Full-text · Article · Dec 2012 · The Journal of hand surgery
[Show abstract][Hide abstract] ABSTRACT: Hammering is a functional task in which the wrist generally follows a path of motion from a position of combined radial deviation and extension to combined ulnar deviation and flexion, colloquially referred to as a dart thrower's motion. The purpose of this study was to measure wrist and forearm motion and scaphoid and lunate kinematics during a simulated hammering task. We hypothesized that the wrist follows an oblique path from radial extension to ulnar flexion and that there would be minimal radiocarpal motion during the hammering task.
Thirteen healthy volunteers consented to have their wrist and distal forearm imaged with computed tomography at 5 positions while performing a simulated hammering task. The kinematics of the carpus and distal radioulnar joint were calculated using established markerless bone registration methods. The path of wrist motion was described relative to the sagittal plane. Forearm rotation and radioscaphoid and radiolunate motion were computed as a function of wrist position.
All volunteers performed the simulated hammering task using a path of wrist motion from radial extension to ulnar flexion that was oriented an average of 41 degrees +/- 3 degrees from the sagittal plane. These paths did not pass through the anatomic neutral wrist position; rather, they passed through a neutral hammering position, which was offset by 36 degrees +/- 8 degrees in extension. Rotations of the scaphoid and lunate were not minimal but averaged 40% and 41%, respectively, of total wrist motion. The range of forearm pronation-supination during the task averaged 12 degrees +/- 8 degrees .
The simulated hammering task was performed using a wrist motion that followed a coupled path of motion, from extension and radial deviation to flexion and ulnar deviation. Scaphoid and lunate rotations were greatly reduced, but not minimized, compared with rotations during pure wrist flexion/extension. This is likely because an extended wrist position was maintained throughout the entire task studied.
Full-text · Article · Jul 2010 · The Journal of hand surgery
[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Apr 2010 · The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology
[Show abstract][Hide abstract] ABSTRACT: Wrist distraction is a common treatment maneuver used clinically for the reduction of distal radial fractures and midcarpal dislocations. Wrist distraction is also required during wrist arthroscopy to access the radiocarpal joint and has been used as a test for scapholunate ligament injury. However, the effect of a distraction load on the normal wrist has not been well studied. The purpose of this study was to measure the three-dimensional conformational changes of the carpal bones in the normal wrist as a result of a static distractive load.
Using computed tomography, the dominant wrists of 14 healthy volunteers were scanned at rest and during application of 98 N of distraction. Load was applied using finger traps, and volunteers were encouraged to relax their forearm muscles and to allow distraction of the wrist. The motions of the bones in the wrist were tracked between the unloaded and loaded trial using markerless bone registration. The average displacement vector of each bone relative to the radius was calculated, as were the interbone distances for 20 bone-bone interactions. Joint separation was estimated at the radiocarpal, midcarpal, and carpometacarpal joints in the direction of loading using the radius, lunate, capitate, and third metacarpal.
With loading, the distance between the radius and third metacarpal increased an average of 3.3 mm +/- 3.1 in the direction of loading. This separation was primarily in the axial direction at the radiocarpal (1.0 mm +/- 1.0) and midcarpal (2.0 mm +/- 1.7) joints. There were minimal changes in the transverse direction within the distal row, although the proximal row narrowed by 0.98 mm +/- 0.7. Distraction between the radius and scaphoid (2.5 mm +/- 2.2) was 2.4 times greater than that between the radius and lunate (1.0 mm +/- 1.0).
Carpal distraction has a significant (p < .01) effect on the conformation of the carpus, especially at the radiocarpal and midcarpal joints. In the normal wrist, external traction causes twice as much distraction at the lunocapitate joint than at the radiolunate joint.
Full-text · Article · Feb 2010 · The Journal of hand surgery
[Show abstract][Hide abstract] ABSTRACT: The combination of three-dimensional (3-D) models with dual fluoroscopy is increasingly popular for evaluating joint function in vivo. Applying these modalities to study knee motion with high accuracy requires reliable anatomical coordinate systems (ACSs) for the femur and tibia. Therefore, a robust method for creating ACSs from 3-D models of the femur and tibia is required. We present and evaluate an automated method for constructing ACSs for the distal femur and proximal tibia based solely on 3-D bone models. The algorithm requires no observer interactions and uses model cross-sectional area, center of mass, principal axes of inertia, and cylindrical surface fitting to construct the ACSs. The algorithm was applied to the femur and tibia of 10 (unpaired) human cadaveric knees. Due to the automated nature of the algorithm, the within specimen variability is zero for a given bone model. The algorithm's repeatability was evaluated by calculating variability in ACS location and orientation across specimens. Differences in ACS location and orientation between specimens were low (<1.5mm and <2.5 degrees). Variability arose primarily from natural anatomical and morphological differences between specimens. The presented algorithm provides an alternative method for automatically determining subject-specific ACSs from the distal femur and proximal tibia.
Full-text · Article · Feb 2010 · Journal of Biomechanics
[Show abstract][Hide abstract] ABSTRACT: The development of small cannulated screws permitted minimally invasive percutaneous fixation of acute scaphoid fractures. There are known mechanical advantages to increased screw length and central screw placement, as well as documented deleterious effects of screw malposition, including articular protrusion, proximal pole fracture, and nonunion. The purpose of this study was to compare 2 methods of calculating a screw axis accessible via a volar surgical approach.
To prevent screw protrusion through the surface of the scaphoid, we required the central screw axis to be contained completely within a "safe zone," defined as a 3-dimensional region located a fixed distance from the inner cortical surface. Safe zones were calculated based on computed tomography-generated models of the right scaphoid from 10 healthy subjects. Two methods for screw axis calculation were compared: (1) maximum screw length (MSL) within the safe zone and (2) a cylinder best-fit (CYL) to the safe zone. The volar approach was defined as percutaneous screw placement through the scaphoid tubercle without violation of the trapezium. Resultant screw axes were compared between the 2 methods for volar accessibility, screw length, and location of the screw axis.
The MSL axes were completely accessible without violating the trapezium in all but 2 subjects. The average MSL axes were 11% longer than the CYL axes and passed significantly closer to the scaphoid tubercle than did the CYL axes (1.8 mm vs 6.4 mm). The MSL axes passed significantly farther (1.6 mm) from the bone centroid than did the CYL axes (0.4 mm). All 10 MSL axes were located in the central one-third of the proximal pole.
Without violation of the trapezium, MSL axis can be attained via the volar percutaneous approach to the scaphoid. Using this approach, the ideal starting point for maximal screw length was located 1.7 mm dorsal and 0.2 mm radial to the apex of the scaphoid tubercle.
No preview · Article · May 2009 · The Journal of hand surgery
[Show abstract][Hide abstract] ABSTRACT: Scaphoid nonunions are a common complication of scaphoid fractures and frequently progress to degenerative arthritis. This study evaluated the effect of scaphoid nonunion on the in vivo kinematics of the radioscaphocapitate articulation.
Computed tomography with a markerless registration technique was used to quantify motion of the scaphoid, lunate, and capitate in vivo, in 6 patients with unilateral scaphoid nonunion. The 3-dimensional helical axis of motion rotations of each bone were measured as a function of wrist flexion-extension and compared with those of the uninjured contralateral wrist. Mixed linear modeling was used to compare flexion-extension of the injured scaphoid fragments with those of the uninjured scaphoid, and the lunate of the injured wrist with the lunate of the uninjured wrist. Interfragmentary motion in the injured scaphoid was assessed by calculating rotation of the distal fragment relative to the proximal fragment, as well as the linear displacement between the 2 fragments at the fracture site.
Flexion and extension of the distal scaphoid fragment was similar to that of the uninjured scaphoid. Extension of the proximal fragment was significantly decreased by 38%, compared with the uninjured scaphoid. Similarly, extension of the lunate in the injured wrist was significantly decreased, by 40%. Interfragmentary rotation was 33% of wrist motion in flexion and 35% of wrist motion in extension. Maximum interfragmentary displacement was on the order of 1 mm.
Scaphoid nonunions have a dramatic impact on carpal kinematics, partially uncoupling the proximal and distal carpal rows. Although the results of this in vivo study differ from past in vitro studies, the increase in lunocapitate motion we identified is consistent with the current theory that the scaphoid acts as a fundamental link between the proximal and distal carpal rows.
Full-text · Article · Oct 2008 · The Journal of hand surgery
[Show abstract][Hide abstract] ABSTRACT: This study determined the effect of tear size on gap formation of single-row simple-suture arthroscopic rotator cuff repair (ARCR) vs transosseous Mason-Allen suture open RCR (ORCR) in 13 pairs of human cadaveric shoulders. A massive tear was created in 6 pairs and a large tear in 7. Repairs were cyclically tested in low-load and high-load conditions, with no significant difference in gap formation. Under low-load, gapping was greater in massive tears. Under high-load, there was a trend toward increased gap with ARCR for large tears. All repairs of massive tears failed in high-load. Gapping was greater posteriorly in massive tears for both techniques. Gap formation of a modeled RCR depends upon the tear size. ARCR of larger tears may have higher failure rates than ORCR, and the posterior aspect appears to be the site of maximum gapping. Specific attention should be directed toward maximizing initial fixation of larger rotator cuff tears, especially at the posterior aspect.
No preview · Article · Jul 2008 · Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.]
[Show abstract][Hide abstract] ABSTRACT: To assess the effects of interference screws, which are commonly used to surgically fix an anterior cruciate ligament (ACL) graft in the ACL-deficient knee, and magnetic field strength on cartilage volume and thickness measurements with quantitative magnetic resonance imaging (qMRI).
Five cadaver knees were imaged using a cartilage-sensitive sequence (T1-weighted water-excitation, three-dimensional (3D) fast low-angle shot) on 1.5T and 3T scanners with and without interference screws implanted. The tibiofemoral articular cartilage was segmented and reconstructed from the magnetic resonance images, and volume and thickness measurements were made on the resulting 3D models.
Although several load-bearing regions showed significant differences in volume and thickness between magnet strengths, most showed no significant difference between screw conditions. The medial tibial cartilage showed a mean decrease in volume of 5.9% and 8.0% in the presence of interference screws at 3T and 1.5T, respectively. At 3T and 1.5T, the medial tibial cartilage showed a mean decrease in thickness of 7.0% and 12.0%, respectively, in the presence of interference screws.
Caution should be used when interpreting thickness and volume of cartilage at 3T in the presence of interference screws, particularly in the medial tibial compartment. Additionally, 3T and 1.5T qMRI should not be used interchangeably to assess structural changes in tibiofemoral articular cartilage during longitudinal studies.
Full-text · Article · Jun 2008 · Osteoarthritis and Cartilage
[Show abstract][Hide abstract] ABSTRACT: Midcarpal degeneration is well documented after radioscapholunate fusion. This study tested the hypothesis that radioscapholunate fusion alters the kinematic behavior of the remaining lunotriquetral and midcarpal joints, with specific focus on the dart-thrower's motion.
Simulated radioscapholunate fusions were performed on 6 cadaveric wrists in an anatomically neutral posture. Two 0.060-in. carbon fiber pins were placed from proximal to distal across the radiolunate and radioscaphoid joints, respectively. The wrists were passively positioned in a custom jig toward a full range of motion along the orthogonal axes as well as oblique motions, with additional intermediate positions along the dart-thrower's path. Using a computed tomography-based markerless bone registration technique, each carpal bone's three-dimensional rotation was defined as a function of wrist flexion/extension from the pinned neutral position. Kinematic data was analyzed against data collected on the same wrist prior to fixation using hierarchical linear regression analysis and paired Student's t-tests.
After simulated fusion, wrist motion was restricted to an average flexion-extension arc of 48 degrees , reduced from 77 degrees , and radial-ulnar deviation arc of 19 degrees , reduced from 33 degrees . The remaining motion was maximally preserved along the dart-thrower's path from radial-extension toward ulnar-flexion. The simulated fusion significantly increased rotation through the scaphotrapezial joint, scaphocapitate joint, triquetrohamate joint, and lunotriquetral joint. For example, in the pinned wrist, the rotation of the hamate relative to the triquetrum increased 85%. Therefore, during every 10 degrees of total wrist motion, the hamate rotated an average of nearly 8 degrees relative to the triquetrum after pinning versus 4 degrees in the normal state.
Simulated radioscapholunate fusion altered midcarpal and lunotriquetral kinematics. The increased rotations across these remaining joints provide one potential explanation for midcarpal degeneration after radioscapholunate fusion. Additionally, this fusion model confirms the dart-thrower's hypothesis, as wrist motion after simulated radioscapholunate fusion was primarily preserved from radial-extension toward ulnar-flexion.
Full-text · Article · May 2008 · The Journal Of Hand Surgery
[Show abstract][Hide abstract] ABSTRACT: The skeletal wrist consists of eight small, intricately shaped carpal bones. The motion of these bones is complex, occurs in three dimensions, and remains incompletely defined. Our previous efforts have been focused on determining the in vivo three-dimensional (3-D) kinematics of the normal and abnormal carpus. In so doing we have developed an extensive database of carpal bone anatomy and kinematics from a large number of healthy subjects. The purpose of this paper is to describe that database and to make it available to other researchers. CT volume images of both wrists from 30 healthy volunteers (15 males and 15 females) were acquired in multiple wrist positions throughout the normal range of wrist motion. The outer cortical surfaces of the carpal bones, radius and ulna, and proximal metacarpals were segmented and the 3-D motion of each bone was calculated for each wrist position. The database was constructed to include high-resolution surface models, measures of bone volume and shape, and the 3-D kinematics of each segmented bone. The database does not include soft tissues of the wrist. While there are numerous digital anatomical databases, this one is unique in that it includes a large number of subjects and it contains in vivo kinematic data as well as the bony anatomy.
No preview · Article · Feb 2007 · Journal of Biomechanics