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

Carpal Kinematics in Madelung Deformity

PURPOSE

Various skeletal and soft tissue abnormalities have been identified in Madelung deformity and have been hypothesized to play a causal role in its progressive symptomatology; however, our pathological understanding of these changes remains limited. In this study, we biomechanically assessed the Madelung deformity wrist, using 4-dimensional computed tomography imaging.

METHODS

Nine Madelung deformity wrists (5 patients; age, 24 ± 5 y) and 18 healthy wrists (9 volunteers; age, 28 ± 3 y) underwent 4-dimensional imaging during flexion-extension motion and radioulnar deviation. Carpal kinematics and radiocarpal joint parameters were quantified and compared.

RESULTS

In Madelung deformity wrists, significantly decreased rotation was seen in the lunate (-4.6°) and the triquetrum (-4.8°) during flexion-extension motion. During radioulnar deviation, significant decreases were visible in lunate bone translation (-0.7 mm), triquetrum bone translation (-0.6 mm), and triquetrum bone rotation (-1.9°). Patients had significantly decreased articulating surface areas of the scaphoid (1.4 ± 0.2 cm² versus 1.6 ± 0.2 cm²) and lunate (1.2 ± 0.4 cm² versus 1.5 ± 0.3 cm²) fossa, and significantly increased radioscaphoid (1.3 ± 0.1 mm versus 1.2 ± 0.1 mm) and radiolunate (1.6 ± 0.2 mm versus 1.3 ± 0.3 mm) joint space thicknesses.

CONCLUSIONS

There is a decreased mobility of the lunate and triquetrum bones in Madelung deformity.

CLINICAL RELEVANCE

Four-dimensional imaging could be used in future studies that investigate the effect of surgical ligament release on carpal kinematics and subsequent wrist mobility.

The Use of Contact Biomechanics to Study the Intact, Proximal Row Carpectomy and Scaphoid Excision, Four Bone Fusion Wrist

The study of contact biomechanics of the wrist is a challenge. This is partly due to the relatively small size of the joint as well as the lack of space in the radiocarpal joint which makes the delivery of investigative materials such as pressure sensitive film without causing artifact, difficult. Fortunately, a number of authors have studied the intact wrist, the scapholunate ligament injured wrist, the proximal row carpectomy and the scaphoid excision, four bone fusion. Despite some contrasting findings, there are some general concepts that we understand about wrist mechanics.

Accuracy of manual and automatic placement of an anatomical coordinate system for the full or partial radius in 3D space

Accurate placement of a coordinate system on the radius is important to quantitatively report 3D surgical planning parameters or joint kinematics using 4D imaging techniques. In clinical practice, the scanned length of the radial shaft varies among scanning protocols and scientific studies. The error in positioning a radial coordinate system using a partially scanned radius is unknown. This study investigates whether the imaged length of the radius significantly affects the positioning of the coordinate system. For different lengths of the radius, the error of positioning a coordinate system was determined when placed automatically or manually. A total of 85 healthy radii were systematically shortened until 10% of the distal radius remained. Coordinate systems were placed automatically and manually at each shortening step. A linear mixed model was used to associate the positioning error with the length of the radial shaft. The accuracy and precision of radial coordinate system placement were compared between automatic and manual placement. For automatic placement of the radial coordinate system, an increasing positioning error was associated with an increased shortening of the radius (P = < 0.001). Automatic placement is superior to manual placement; however, if less than 20% of the radial shaft length remains, manual placement is more accurate.

Scapholunate instability: improved detection with semi-automated kinematic CT analysis during stress maneuvers

OBJECTIVES

To evaluate the diagnostic performance of radioulnar deviation (RUD) and clenching fist (CF) maneuvers for the evaluation of scapholunate dissociation (SLD) using quantitative kinematic CT.

METHODS

Thirty-seven patients with suspected scapholunate instability were prospectively evaluated with kinematic CT. Two radiologists independently evaluated the SLD during RUD and CF maneuvers. Various dynamic parameters describing SLD were compared (maximal value, variation coefficient and range) in patients with and without scapholunate ligament ruptures confirmed by CT arthrography.

RESULTS

SLD in CF varied from 3.17 ± 0.38 to 3.24 ± 0.80 mm in controls and from 4.11 ± 0.77 and 4.01 ± 0.85 mm in patients with scapholunate ligament ruptures for reader 1 and 2 (p < 0.009). SLD in RUD varied from 3.35 ± 0.51 and 3.01 ± 0.78 mm in controls and from 4.51 ± 1.26 to 4.42 ± 1.75 mm in patients with scapholunate ligament ruptures for reader 1 and 2 (p varied from 0.001 to 0.002). The inter-observer variability was better for RUD (ICC = 0.85 versus 0.6 for RUD and CF respectively).

CONCLUSION

Analysis of SLD using kinematic CT has shown significant measurement differences between the groups with or without scapholunate instability with good diagnostic performance.

KEY POINTS

• Kinematic CT can quantitatively assess scapholunate dissociation. • SLD analysis on kinematic CT has excellent reproducibility with radioulnar deviation maneuver. • Scapholunate dissociation was significantly different in patients with and without instability. • Diagnostic performance for scapholunate instability identification was better with radioulnar deviation.

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.