Defining trapezial dysplasia - analysis of trapezial inclination in a normal population

Assocation between trapezium size and failure of total trapeziometacarpal prosthesis. A survival analysis

AIMS

To assess the survival function of cementless total trapezium metacarpal prostheses (TTMPs) at 20 years, to compare survival functions by trapezium size, and to evaluate the association between the instantaneous risk of TTMP failure and small trapezium size using a multivariate Cox regression model.

METHODS

This observational cohort study included 221 consecutive patients with a mean follow-up after TTMP of 137.3 months (maximum of 246 months). Kaplan-Meier and actuarial life-table methods were used to evaluate the survival function of thecohort. Kaplan-Meier survival curves were compared by trapezium size. Multivariate Cox regression analysis was used to determine the effect of potential confounders on the association between small trapezium and the instantaneous risk of TTMP failure.

RESULTS

At the end of follow-up, there was a 89.01% chance of the TTMP surviving for 246 months or more. There was an association between TTMP survival time and trapezium size showing a significant trend such that the survival curves weresignificantly higher with larger trapezium size (Mantel-Cox test, p = 0.0001; WilcoxonBreslow test, p = 0.0002; Tarone-Ware test, p = 0.0001).The unadjusted Cox regression model showed a significant association between small trapezium size (smaller than 9 mm) and the instantaneous risk of TTPM failure (HR: 7.37, 95% CI: 2.46-22.07). In the multivariate Cox analysis, "age", "trapezium morphology", and "complications" were confounders in the association between small trapezium size and the hazard ratio of prosthetic failure (HR = 3.76; 95% CI 0.96 to 13.82).

CONCLUSION

These results confirm the long-term functional survival of TTMP prostheses and reveal a significant increase in trend of the survival curve with larger trapezium size. Patient age, trapezium morphology, and the presence of post-surgical complications are confounders in the association between small trapezium size and the hazard ratio of TTMP failure.

Analysis of trapeziometacarpal prosthesis cup position with respect to the trapezial anatomy

The purpose of this study was to analyse the anatomy of the trapezium with regard to cup position in trapeziometacarpal replacement and identify those trapeziums that are at risk of cup perforation through the trapezoid articular surface. The width of the proximal and distal articular surface and the height of the trapezium and second metacarpal facet were measured on 96 peritrapezial views reconstructed from computed tomography scans. The trapezoid articular surface of the trapezium (TRAST) angle was calculated, and four different cup designs were virtually positioned centrally in the trapezium and parallel to the proximal articular surface. Risk of perforation was defined as a cup that exceeds the ulnar border of the proximal articular surface. The mean TRAST angle in our study was 33°. Risk of perforation is higher when the second metacarpal facet is smaller than 5 mm and when the TRAST angle is 35° or more. In these cases, the position of the cup should be more radial or more distal.

Radiological imaging of the trapeziometacarpal joint: a historical and clinical perspective

The opposable thumb provides both stability and mobility and is needed to accomplish different prehensile tasks. The trapezium is a complex bone, with a distal articular surface that is convex in the sagittal plane of the thumb and concave in the coronal plane of the thumb. The numerous additional articulations with the carpus and the oblique orientation to the main plane of the hand makes it difficult to evaluate the trapeziometacarpal joint using standard hand or wrist radiographic views. This review gives an overview of the different radiological views that have been described for the thumb with an emphasis on their historical origin and positioning during radiography. We also describe different measurements and classifications that can be obtained using different thumb radiographs.

Bone morphological changes of the trapezium and first metacarpal with early thumb osteoarthritis progression

BACKGROUND

Thumb carpometacarpal osteoarthritis is characterized by osteophyte growth and changes in the curvature of the articular surfaces of the trapezium and first metacarpal. The aim of this longitudinal study was to quantify in-vivo bone morphology changes with osteoarthritis progression.

METHODS

The study analyzed an observational dataset of 86 subjects with early thumb osteoarthritis and 22 age-matched asymptomatic controls. CT scans of subjects' affected hands were acquired at enrollment (year 0), and at 1.5, 3, 4.5, and 6-year follow-up visits. Osteoarthritic subjects were classified into stable and progressive groups, as defined by osteophyte volume and the rate of osteophyte growth. Trapezium height, width, and volar facet recession, along with first metacarpal volar beak recession and recession angle, were quantified.

FINDINGS

Mean trapezium width increased 12% over six years in the progressive osteoarthritis group. Trapezium volar recession of the progressive osteoarthritis group was significantly greater than stable at enrollment (P < 0.0001) and year 6 (P < 0.0001). The first metacarpal volar beak of the progressive osteoarthritis group recessed significantly faster than stable (P = 0.0004) and control (P = 0.0003). In year 6, volar beak surfaces in subjects with progressive osteoarthritis were flatter with reduced curvature, measuring -8.7 ± 4.0 degrees, compared to the stable osteoarthritis (P < 0.0001) and control groups (P = 0.0003), which maintained nominal curvatures, measuring 0.7 ± 2.5 and 0.2 ± 3.2 degrees, respectively.

INTERPRETATION

Our results demonstrate significant recession and reduction in the angle of the first metacarpal volar beak in progressive osteoarthritis. Flattening of the first metacarpal volar beak may have important associations with carpometacarpal joint contact and loading migrations, further propagating osteophyte formation and bony remodeling. This work highlights the volar beak of the first metacarpal as a region of morphology change with disease.