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Corresponding author: Abbas Peymani, MD, MS, Department of Plastic, Reconstructive and Hand Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Meibergdreef 9, Amsterdam, The Netherlands.
Department of Biomedical Engineering and PhysicsDepartment of Radiology and Nuclear Medicine, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
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.
Previous studies have established a spectrum of skeletal abnormalities, particularly in the distal radius, which have been quantified for use in diagnosis.
Furthermore, imaging studies have revealed various soft tissue abnormalities, including the volar radiolunate ligament known as Vickers ligament and the anomalous volar radiotriquetral ligament.
These anatomical changes are thought to play a causal role in the progressive symptomatology of the condition, with the purpose of surgery being to restore the anatomical configuration and normalize the anatomy in order to improve wrist biomechanics.
no in vitro or in vivo biomechanical studies have been performed for Madelung deformity.
The objective of this study was to investigate the wrist biomechanics of Madelung deformity patients, using 4-dimensional computed tomography (CT) imaging during flexion-extension motion and radioulnar deviation, and comparing those biomechanical features with wrists of healthy volunteers.
Methods
Setting and study population
For this study, we retrospectively included patients with Madelung deformity, for whom 4-dimensional CT scans of 1 or both wrists were available. All Madelung deformity patients visiting our clinic undergo 4-dimensional CT imaging to visualize carpal bone kinematics based on a previously developed protocol, independent of the severity of the deformity.
have previously hypothesized the deformity to be true Madelung deformity in the presence of a Vickers ligament or if a patient is bilaterally affected with an underlying diagnosis of Leri-Weill dyschondrosteosis,
although there is no consensus on this definition. Patient charts were reviewed to determine any underlying genetic disorders and surgical notes were reviewed to assess the presence of Vickers ligament. For patients who did not undergo surgical treatment, we reviewed preoperative x-ray and CT imaging instead to identify the ligamentous origin.
We excluded patients with a posttraumatic Madelung deformity and wrists that had previously undergone surgical correction. A total of 5 patients were eligible for inclusion; all with bilateral Madelung deformity. After excluding 1 wrist (previous corrective osteotomy of the radius), this resulted in a total of 9 included wrists. In addition, previously acquired 4-dimensional CT scans of 9 healthy female volunteers (18 wrists) were included in the kinematic analysis for comparison. None of the healthy volunteers had a medical history of skeletal disorders or a surgical history of wrist interventions. Volunteers with hypermobility, assessed using the Beighton score,
were excluded. This study was approved by our medical center institutional review board.
Image acquisition
The 4-dimensional CT scans were acquired using a Philips Brilliance 64 CT scanner (Philips, Cleveland, OH). First, a static CT scan was performed of the wrist in neutral position (120 kV, 75 mAs). Next, the participant gripped the handle of a custom-made positioning device (Fig. 1), limiting wrist movement to either flexion-extension or radioulnar deviation. Participants performed each motion over 12 seconds while dynamic 4-dimensional CT scans were acquired (120 kV, 30 mAs; collimation, 64 × 0.625 mm; axial field of view, 4 cm; rotation time, 0.4 s), resulting in a total of 30 reconstructions per motion. The static high-quality CT scan was used for segmentation; the dynamic low-quality CT scans were used for position detection. Participants received a total dose of 0.3 mSv.
Figure 1Wrist positioning device to keep the carpus in the field of view during 4-dimensional imaging. The patient can move the wrist about either the flexion-extension axis or the radioulnar deviation axis.
to obtain virtual 3-dimensional models of the radius, ulna, scaphoid, lunate, triquetrum, and capitate bones. The scaphoid, lunate, and triquetrum were used to assess radiocarpal motion; the capitate was used to assess overall wrist motion. The virtual bone models were aligned with the dynamic 4-dimensional CT scans (30 per motion) to quantify the position of each carpal bone during movement using 2 parameters: translation (x, y, and z coordinates of the virtual bone models’ centroid), and rotation (φ, θ, and ψ angles relative to the neutral position). Total translation was calculated using the formula and total rotation was calculated using the formula .
Image processing and computation
The virtual 3-dimensional models and corresponding kinematics parameters were exported and further processed using software programmed in MATLAB R2018b (MathWorks Inc., Natick, MA). This software performed the following functions automatically: wrist alignment, detection of radial and ulnar landmarks (eg, radial styloid process, ulnar styloid process), visualization of the wrist during motion (Fig. 2), and the computations described later.
Figure 2Visualizing movement of virtually segmented wrist models. Colors indicate different positions during motion (blue, first position; orange, last position).
To quantify the position of the wrist during motion in flexion-extension or radioulnar deviation angles, we first determined the longitudinal axis of the capitate bone in neutral position. Next, we calculated the angle in degrees between this neutral axis and the dynamic longitudinal axis of the capitate bone during each of the 30 positions per motion. To visualize a full motion in a graph, flexion and radial deviation angles were represented as negative values; extension and ulnar deviation angles were represented as positive values.
Articular surface area and joint space thickness (Fig. 3) were calculated using a previously described method.
Briefly, for each of the 30 positions during a motion, we calculate for each point on the radius the nearest point to the scaphoid or lunate. Next, these points are filtered using 2 pragmatically chosen constraints: (1) a maximum distance of 4 mm between opposing points; (2) a maximum angle difference of 15° between the normal lines of opposing points. The articular surface area per motion is acquired by merging the points of 30 positions; a combined version is calculated by merging the points of all 60 positions from 2 motions (flexion-extension and radio-ulnar deviation). For each position within the motion trajectory, the minimum distance to the opposing point is taken for each point in the articular surface area. The mean of these minimum distances provides the joint space thickness, defined as the articular cartilage thickness between the radius and the scaphoid (radioscaphoid joint space thickness) or between the radius and the lunate (radiolunate joint space thickness).
Figure 3Articular surface area and joint space thickness.
Python v3.7.2 (Python Software Foundation. Python Language Reference, version 3.7.2) was used to process MATLAB data files and to perform statistical analyses and graphical data visualization using the SciPy, StatsModels, and Seaborn packages.
For ROM, articular surface area, and joint space thickness, we compared the means of the calculated parameters between Madelung deformity wrists and healthy wrists. Data normality was determined using the Shapiro-Wilk test. If a variable was normally distributed in both groups, an independent samples t test (variances equal) or Welch t test (variances not equal) was performed. Equality of variances was assessed using the Levene test. If a variable was not normally distributed, the Mann-Whitney U test was performed.
To compare carpal bone kinematics while adjusting for ROM (flexion-extension and radioulnar deviation angles), we developed mixed-effects models for each combination of 3 proximal carpal bones (scaphoid, lunate, and triquetrum), 2 distinct motions (flexion-extension and radioulnar deviation), and 2 outcomes of interest (total translation and total rotation); this resulted in a total of 12 models. As fixed-effects, we entered angle (ROM) and wrist type (healthy or Madelung). In addition, to account for possible size differences between Madelung patients and healthy volunteers, we added wrist size as a fixed effect, defined as the absolute distance between the centroids of capitate and the lunate. Lastly, to optimally fit each model, we added angle2 and angle3 as fixed effects, depending on the outcome curve being quadratic- or cubic-shaped, respectively. Intercepts for different wrists were added as random effects. The P values were obtained by likelihood ratio tests of the full model including wrist type and the model without wrist type. To determine which specific parameters were responsible for an altered total translation or rotation, we performed separate subanalyses for translation over x, y, and z coordinates (Table E1), and for rotation over φ, θ, and ψ angles (Table E2).
Results
Patients with Madelung deformity (n = 5) had a mean age of 23.7 ± 4.9 years; healthy volunteers (n = 9) had a mean age of 28.0 ± 2.6 years. All participants were women. Study characteristics are described in Table 1. Wrists of Madelung deformity patients had a significantly lower maximum angle of flexion (47.9° ± 16.5° versus 72.8° ± 7.2°; P < .05) and radial deviation (12.5° ± 8.5° versus 23.3° ± 5.5°; P < .05) compared with wrists of healthy volunteers (Table 2). No significant differences were found for maximum extension and maximum ulnar deviation.
During flexion-extension motion (Table 3), a significantly decreased rotation was seen in both the lunate bone (difference, –4.6°; 95% confidence interval [95% CI], –7.1 to –2.2; P < .05) and the triquetrum bone (difference, –4.8°; 95% CI, –6.7 to –3.0; P < .05) for Madelung deformity wrists. Carpal kinematics during radioulnar deviation (Table 4) showed significant decreases in lunate bone translation (difference, –0.7 mm; 95% CI, –1.0 to –0.4; P < .05), >triquetrum bone translation (difference, –0.6 mm; 95% CI, –0.9 to –0.3; P < .05), and triquetrum bone rotation (difference, –1.9; 95% CI, –3.7 to –0.1; P < .05). There were no significant differences found for scaphoid bone translation and rotation during flexion-extension motion or radioulnar deviation.
Table 3Carpal Kinematics During Flexion-Extension Motion
Table 5 describes the articular surface area and joint space thickness of the distal radius during motion. Patients with Madelung deformity had significantly decreased articulating surface areas of the scaphoid (1.4 ± 0.2 cm2 versus 1.6 ± 0.2 cm2; P < .05) and lunate fossa (1.2 ± 0.4 cm2 versus 1.5 ± 0.3 cm2; P<0.05), and significantly increased radioscaphoid (1.3 ± 0.1 mm versus 1.2 ± 0. mm; P < .05) and radiolunate joint space thickness (1.6 ± 0.2 mm versus 1.3 ± 0.3 mm; P < .05).
Table 5Articular Surface Area and Joint Space Thickness
In this study, we imaged patients’ wrist bones during flexion-extension motion and radioulnar deviation through a previously developed 4-dimensional CT protocol. In comparison with wrists of healthy volunteers, wrists of Madelung deformity patients have decreased mobility of the lunate and triquetrum bones. The articular surface areas of the scaphoid and lunate fossa are decreased, and radiocarpal cartilage thickness does not significantly differ from healthy wrists.
A major strength of this in vivo study is that all measurements were performed automatically through self-developed software algorithms
leading to an objective assessment in a dynamic setup. Another strength is that the mixed-model analysis of 4-dimensional CT data allows for the quantification of individual carpal bone mobility, while considering the differences in wrist ROM between patients and volunteers. Because wrist ROM is intrinsically linked to carpal bone mobility, correcting for this parameter in our analyses shows that the reported differences in mobility occur despite, and not because of, differences in ROM. A limitation of this study is the small number of wrists (n = 9) and corresponding limited statistical power because most of the patients in our database could not be included owing to having previously undergone surgical procedures to correct the deformity. Another limitation was that 2 patients received growth hormone therapy, shown to be effective in the treatment of short stature associated with SHOX gene deficiency,
Effectiveness of the combined recombinant human growth hormone and gonadotropin-releasing hormone analog therapy in pubertal patients with short stature due to SHOX deficiency.
possibly influencing wrist kinematics owing to altered skeletal growth. Lastly, the investigative scope of this study was limited to flexion-extension motion and radioulnar deviation (radiocarpal articulation), yet multiple studies have shown decreased mobility to be particularly prominent in forearm pronation and supination (radioulnar articulation).
Furthermore, we found patients to have lower maximum angles of flexion with no significant differences for extension. Previous studies that performed preoperative goniometer measurements in a clinical setting found decreases to be primarily in wrist extension rather than flexion,
This discrepancy is likely a result of our automatic 3-dimensional measurements, in which our 0-point is defined by the orientation of the capitate with the wrist in a neutral position. One of the clinically visible features of Madelung deformity is the palmar displacement of the carpus.
This is also visible in the configuration of the virtual bones in 3-dimensional space, in which the capitate is palmarly rotated in a neutral wrist position. Therefore, this shift of the 0-point toward flexion translates into relatively higher degrees of extension and, thus, relatively lower degrees of flexion in our 3-dimensional measurements.
Clinically measured decreases of ROM have been extensively quantified,
but it is still unknown whether these are caused by pain, intrinsic mechanical properties, or other reasons. In our study, the lunate and triquetrum show decreased mobility during flexion-extension motion and radioulnar deviation, yet scaphoid bone mobility remains normal. We hypothesize that scaphoid and lunate kinematics should be closely intertwined owing to the ligamentous connections of the scapholunate joint.
However, it has been demonstrated in vivo that these interosseous ligaments allow for the occurrence of considerable multiplanar motion between the 2 bones,
resulting in comparable, yet distinct, motion patterns. Interestingly, the lunate and the triquetrum are the only carpal bones for which anomalous ligaments have been identified.
identified the radiotriquetral ligament, extending from the radius to the volar aspect of the triquetrum. Although their occurrence has not been reported consistently,
imaging studies have confirmed their presence in true bilateral Madelung deformity, and their absence in acquired Madelung-type or pseudo–Madelung deformity.
have previously hypothesized the deformity to be true in the presence of a Vickers ligament or if a patient is bilaterally affected with an underlying diagnosis of Leri-Weill dyschondrosteosis.
We confirmed ligamentous anomalies in 1 patient during surgery. Three other patients exhibited the characteristic radiolucent flame-shaped notch on imaging, revealed to represent the ligament origin.
However, we did not assess each patient using appropriate imaging techniques such as magnetic resonance imaging, which is better suited to confirm ligamentous anomalies.
Whereas retrospectively searching for this abnormality could hypothetically bias our objectivity, the ligament origin is quite distinguishable from any normal anatomical variations.
Furthermore, the causative mechanism could be the abnormal skeletal configuration instead of the anomalous ligamentous bands. Because the spectrum of skeletal abnormalities has been shown to vary widely, this could limit the generalizability of conclusions regarding carpal kinematics in a subset of patients.
Prospective studies could reveal the effects of different skeletal configurations by assessing the associations between kinematics and parameters that quantify the skeletal deformity, such as ulnar tilt and lunate fossa angle.
The impact of Madelung deformity on the radiocarpal joints has not been previously investigated. Previous studies reported a decreased radiolunate surface area in Madelung deformity patients by quantifying the percentage of the lunate that is in contact with the articular radial surface on static x-ray imaging
In addition to quantifying carpal kinematics, 4-dimensional CT imaging allows a dynamic determination of the articular surface areas and cartilage thickness of the radioscaphoid and radiolunate joints.
Both joints showed significantly smaller surface areas in patients, especially the lunate fossa. Given the decreased ROM during flexion-extension and radioulnar deviation, it is expected that a smaller contact area is being utilized. Also, it has been hypothesized that a subset of patients experience pain due to osteoarthritis.
Despite the abnormal carpal kinematics seen in this study, radiocarpal cartilage remained intact; our patient group was relatively young (mean age, 23.7 ± 4.9 years) and wrist joint osteoarthritis in the general population has been seen mainly in older individuals.
Age-sex specific prevalence of radiographic abnormalities of the joints of the hands, wrists and cervical spine of adult residents of the Tecumseh, Michigan, Community Health Study area, 1962–1965.
However, a more plausible explanation could be that, because the deformity slowly progresses until becoming clinically apparent in early adolescence, the wrist can fully utilize its adaptive capacity,
These parameters should be investigated in a larger postsurgical patient group with long-term follow-up.
In conclusion, radiocarpal kinematics in Madelung deformity are abnormal, showing a decreased mobility of the lunate and triquetrum bones. It remains unknown whether this is caused by the anomalous radiolunate and radiotriquetral ligaments or by the distorted skeletal configuration. Prospective studies could use the 4-dimensional CT analysis to investigate the biomechanical effects of surgical ligament release.
Effectiveness of the combined recombinant human growth hormone and gonadotropin-releasing hormone analog therapy in pubertal patients with short stature due to SHOX deficiency.
Age-sex specific prevalence of radiographic abnormalities of the joints of the hands, wrists and cervical spine of adult residents of the Tecumseh, Michigan, Community Health Study area, 1962–1965.
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