M. Foumani

In-vivo three-dimensional carpal bone kinematics during flexion-extension and radio-ulnar deviation of the wrist: Dynamic motion versus step-wise static wrist positions

An in-vivo approach to the measurement of three-dimensional motion patterns of carpal bones in the wrist may have future diagnostic applications, particularly for ligament injuries of the wrist. Static methods to measure carpal kinematics in-vivo only provide an approximation of the true kinematics of the carpal bones. This study is aimed at finding the difference between dynamically and statically acquired carpal kinematics. For eight healthy subjects, static and a dynamic measurements of the carpal kinematics were performed for a flexion-extension and a radio-ulnar deviation movement. Dynamic scans were acquired by using a four-dimensional X-ray imaging system during an imposed cyclic motion. To assess static kinematics of the wrists, three-dimensional rotational X-ray scans were acquired during step-wise flexion-extension and radio-ulnar deviation. The helical axis rotations and the rotation components. i.e. flexion-extension, radio-ulnar deviation and pro-supination were the primary parameters. Linear mixed model statistical analysis was used to determine the significance of the difference between the dynamically and statically acquired rotations of the carpal bones. Small and in most cases negligible differences were observed between the dynamic motion and the step-wise static motion of the carpal bones. The conclusion is that in the case of individuals without any pathology of the wrist, carpal kinematics can be studied either dynamically or statically. Further research is required to investigate the dynamic in-vivo carpal kinematics in patients with dynamic wrist problems.

Statistical descriptions of scaphoid and lunate bone shapes

Diagnosing of injuries of the wrist bones is problematic due to a highly complex and variable geometry. knowledge of variations of healthy bone shapes is essential to detect wrist pathologies, developing prosthetics and investigating biomechanical properties of the wrist joint. In previous literature various methods have been proposed to classify different scaphoid and lunate types. These classifications were mainly qualitative or were based on a limited number of manually determined surface points. The purposes of this study are to develop a quantitative, standardized description of the variations in the scaphoid and lunate and to investigate whether it is feasible to divide carpal bones in isolated shape categories based on statistical grounds. The shape variations of the scaphoid and lunate were described by constructing a statistical shape model (SSM) of healthy bones. SSM shape parameters were determined that describe the deviation of each shape from the mean shape. The first five modes of variation in the SSMs describe 60% of the total variance of the scaphoid and 57% of the lunate. Higher modes describe less than 5% of the variance per mode. The distributions of the parameters that characterize the bone shape variations along the modes do not significantly differ from a normal distribution. The SSM provides a description of possible shape variations and the distribution of scaphoid and lunate shapes in our population at an accuracy of approximately the voxel size (0.3x0.3x0.3mm(3)). The developed statistical shape model represents the previously qualitatively described variations of scaphoid and lunate. However, strict classifications based on shape differences are not feasible on statistical grounds.

A 4D Statistical Model of Wrist Bone Motion Patterns

Direct imaging of ligament damage in the wrist remains a challenge. Still, such damage can be assessed indirectly through the analysis of changes in wrist pose and motion pattern. For this purpose we built a statistical reference model that describes healthy motion patterns. We show that such a model can also be used to detect and quantify pathologies. A model that only describes the global translations and rotations of the carpal bones is insufficiently accurate due to size and shape variations of the bones. We present a local statistical motion model that minimizes the influence of size and shape differences by analyzing the coordinate differences of pairs of points on adjacent bone surfaces. These differences are determined in a set of 14 healthy example wrists imaged in a range of poses by means of 4D-RX imaging. The distribution of the differences as a function of the pose form the local statistical motion model (LSMM). Translations of 2 mm and rotations of 20 with respect to the healthy example wrists are detected as outliers in the point pair distributions. An evaluation involving wrists with a damaged ligament between scaphoid and lunate shows that not only joint space widenings can be detected, but also shifts of congruent bone surfaces. The LSMM is also used to perform a virtual reconstruction of the most likely healthy wrist after a simulated perturbation of bones. The reconstruction precision is shown to be about 1 mm. Therefore, the presented 4D statistical model of wrist bone movement may become a valuable clinical tool for diagnosis and surgical planning.

The effect of tendon loading on in-vitro carpal kinematics of the wrist joint

Measurements of in-vitro carpal kinematics of the wrist provide valuable biomechanical data. Tendon loading is often applied during cadaver experiments to simulate natural stabilizing joint compression in the wrist joint. The purpose of this study was to investigate the effect of tendon loading on carpal kinematics in-vitro. A cyclic movement was imposed on 7 cadaveric forearms while the carpal kinematics were acquired by a 4-dimensional rotational X-ray imaging system. The extensor- and flexor tendons were loaded with constant force springs of 50 N, respectively. The measurements were repeated without a load on the tendons. The effect of loading on the kinematics was tested statistically by using a linear mixed model. During flexion and extension, the proximal carpal bones were more extended with tendon loading. The lunate was on the average 2.0 degrees (p=0.012) more extended. With tendon loading the distal carpal bones were more ulnary deviated at each angle of wrist motion. The capitate was on the average 2.4 degrees (p=0.004) more ulnary deviated. During radioulnar deviation, the proximal carpal bones were more radially deviated with the lunate 0.7 degrees more into radial deviation with tendon loading (p<0.001). Conversely, the bones of distal row were more flexed and supinated with the capitate 1.5 degrees more into flexion (p=0.025) and 1.0 degrees more into supination (p=0.011). In conclusion, the application of a constant load onto the flexor and extensor tendons in cadaver experiments has a small but statistically significant effect on the carpal kinematics during flexion-extension and radioulnar deviation.

In-vivo dynamic and static three-dimensional joint space distance maps for assessment of cartilage thickness in the radiocarpal joint

BACKGROUND The assessment of the joint space thickness is an important clinical parameter for diagnosing osteoarthritis. The accuracy of joint space thickness evaluation from radiographs is limited due to anatomical complexity of the wrist. We propose using distance maps estimated from 3-dimensional and 4-dimensional images reflecting joint space thickness distribution over the relevant part of the articular surface. METHODS In this paper we investigate the difference between joint space thicknesses acquired from dynamic distance maps to static distance maps. A dynamic distance map gives for every point on a subchondral bone surface the shortest distance to the opposing subchondral bone surface during wrist motion. We hypothesize that the joint space thickness calculated from dynamic distance maps provide a better reflection of the functional joint space thickness. The diagnostic potential of the dynamic joint space thickness measurement is illustrated by comparing data from distance maps of osteoarthritic wrists with normal wrists. FINDINGS In 10 healthy wrists which are examined, dynamic joint space thickness is smaller than static acquired joint space thickness suggesting that dynamic distance maps provide a better estimate of the measured joint space thickness than joint space thickness based on a static joint space thickness. In 3 examined osteoarthritic wrists the joint space thickness is smaller than in healthy individuals. Moreover, the difference between dynamic and static joint space thickness is smaller in pathological joint parts. INTERPRETATION The method presented in this paper demonstrates the feasibility of in vivo dynamic distance maps to detect joint space thickness in the radiocarpal joint of healthy individuals.

Quantitative detection of cartilage surfaces and ligament geometry of the wrist using an imaging cryomicrotome system

Biomechanical models may aid in improving diagnosis and treatment of wrist joint disorders. As input, geometrical information is required for model development. Previous studies acquired some elements of the average wrist joint geometry. However, there is a close geometric functional match between articulating surfaces and ligament geometry. Therefore, biomechanical models need to be fed with the geometric data of individual joints. This study is aimed at acquiring geometric data of cartilage surfaces and ligaments from individual wrist joints by using a cryomicrotome imaging system and the evaluation of inter- and intra-observer variability of the data. The 3D geometry of 30 cartilage surfaces and 15 ligaments in three cadaver wrists was manually detected and quantitatively reconstructed. The inter- and intra-observer variability of the cartilage surface detection was 0.14 and 0.19 mm, respectively. For the position of the radius attachment of the dorsal radiocarpal ligament (DRC), the observer variations were 0.12 and 0.65 mm, for intra-/inter-observer, respectively. For the DRC attachment on the triquetrum, the observer variations were 0.22 and 1.19 mm. Anatomic reconstruction from 3D cryomicrotome images offer a method to obtain unique geometry data of the entire wrist joint for modeling purposes.

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.

Four-dimensional rotational radiographic scanning of the wrist in patients after proximal row carpectomy

We measured cartilage thickness, contact surface area, volume of the capitate and shape of the capitate during motion in the operated and unaffected wrists of 11 patients with a mean follow-up of 7.3 years after proximal row carpectomy. Radiocapitate cartilage thickness in the operated wrists did not differ significantly from radiolunate cartilage thickness in the unaffected wrists. The radiolunate surface area was significantly less than the radiocapitate surface area. The volume of the capitate was significantly increased in the operated wrists. The shape of the capitate changed significantly in two of three orthogonal directions. The combination of remodelling of the capitate, increase in its surface area and intact cartilage thickness could help to explain the clinical success of proximal row carpectomy.

Carpal intraosseous cyst formation following scaphoid nonunion

Scaphoid cysts are often observed around sites of fracture nonunion, indicating a declining healing potential (Slade and Dodds, 2006). We often see cysts in carpal bones surrounding scaphoid nonunions. These cysts are classified as subchondral degenerative cysts if they are secondary to joint degeneration (Schrank et al., 2003). Their presence is not typically taken into account when staging scaphoid nonunion advanced collapse wrist (Vishwanathan et al., 2013). The aim of this study was to report the sites and incidence of intra-osseous cysts shown on computed tomography (CT) or magnetic resonance imaging (MRI) scans following scaphoid nonunion. We reviewed the CT or MRI scans of 73 patients with 74 scaphoid nonunions. There were 66 men and seven women with a mean age of 32 years (range 14–66). There were six unilateral and 58 bilateral pre-operative CT-scans and 17 unilateral preoperative MRIscans. The opposite uninjured wrists in the bilateral scans served as controls. Cysts were measured with an onscreen measurement tool by two observers. Only relative large cysts (>3 mm) (Schrank et al., 2003), which were clearly distinguishable, were included for analysis. This study was approved by our Ethical Committee. In 21 (28%) patients, bone cysts were only visible in the scaphoid. In 15 (20%) patients there was cystic development in other bones in the wrist (Table 1). There were nine (12%) trapezoid, six (8%) capitate, four (5%) hamate, two (3%) lunate and two (3%) triquetral cysts. There were no trapezium or pisiform cysts. Based on the Mann–Whitney U test, older nonunions were associated with cystic development more widely in the wrist (P = 0.008). All cysts outside the scaphoid showed cortical penetration to the joint space. Most trapezoid cysts were eccentrically on the ulnar side (Figure 1). In the capitate bone, besides cysts facing the trapezoid/distal scaphoid fragment, there were also cysts facing the hamate bone ulnarly and lunate proximally. In the healthy wrists we saw eight cysts (14%): four in the capitate; two in the lunate; one in the scaphoid bone; and one in the trapezium (Table 1). The exact pathogenesis of subchondral degenerative cysts in osteoarthritic joints is unclear (Schrank et al., 2003). One theory suggests that elevated intraarticular pressure may cause intraosseous herniation of synovium. The other suggests that mechanical stress results in micro-fractures and vascular insufficiency causing cystic necrosis (Li et al., 2013). It is difficult to differentiate between degenerative cysts and pre-existing intraosseous ganglia. Our finding that scaphoid nonunions of longer duration were associated with cysts in multiple carpal bones, except for the trapezium and pisiform, suggests that at least some of the cysts have formed after scaphoid injury. Furthermore, the incidence of carpal cysts varies considerably when comparing healthy wrists to injured wrists. Schrank et al. evaluated intraosseous ganglia in 208 cadaveric wrists without scaphoid injury using radiographs and MRI scans (Schrank Letters to the Editor Short Report Letters 600147 JHS0010.1177/1753193415600147Journal of Hand Surgery (European Volume)Short report letters research-article2015

A Rare Case of Bilateral Lunotriquetral Coalition and Bilateral Scaphoid Nonunion.

To the Editor: Carpal coalition is rare in Caucasians, with a prevalence of 0.1%, but it is more prevalent in WestAfrican populations. Lunotriquetral (LT) coalitions are most common and can be classified into 4 Minnaar types. Type 1 includes a fibrocartilage coalition resembling pseudoarthrosis, type 2 is incomplete osseous fusion with a distal notch, type 3 is complete osseous fusion, and type 4 is complete fusion with other abnormalities. We wish to report a rare case of bilateral LT coalition with bilateral scaphoid nonunion, which to our knowledge has not been reported previously in the Englishliterature. A 16-year-old African boy playing American football presented with right-sided wrist pain 2 months after a fall. Radiographs showed no acute osseous pathology. Half a year later, the patient had a similar injury to the opposite wrist. After a delay of 3 months, he presented with persisting pain of both wrists. A bilateral computed tomography scan showed a bilateral scaphoid nonunion and left-sided Minnaar type 1 and right-sided Minnaar type 3 coalitions (Fig. 1). The left-sided nonunion was successfully treated with screw fixation. The right-sided nonunion was initially treated with screw fixation in conjunction with cancellous bone grafting. However, because of persistent nonunion and additional fracturing of the proximal pole postoperatively, a subsequent salvage procedure was performed including styloidectomy, proximal scaphoid excision, and pyrocarbon implant insertion (APSI; Tornier, Montbonnot-SaintMartin, France). Lunotriquetral coalition is often an asymptomatic and incidental finding. Some patients present with pain resulting from fracturing of the fused part of the joint after trauma. One French article evaluated 32 wrists