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.

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.

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.

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.

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.