Evaluation of pisotriquetral motion pattern using four-dimensional CT: initial clinical experience in asymptomatic wrists

Clinical Radiology 70 (2015) 1362e1369

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Evaluation of pisotriquetral motion pattern using four-dimensional CT: initial clinical experience in asymptomatic wrists S. Demehri a, *, N. Hafezi-Nejad a, U. Thakur a, J.N. Morelli a, S.D. Lifchez b, K.R. Means c, J.T. Shores b a

Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, USA Department of Plastic and Reconstructive Surgery, Johns Hopkins University, Baltimore, MD, USA c The Curtis National Hand Center at MedStar Union Memorial Hospital, Baltimore, MD, USA b

article in formation Article history: Received 13 April 2015 Received in revised form 9 July 2015 Accepted 22 July 2015

AIM: To characterise the normal motion pattern of the pisotriquetral (PT) joint during wrist extension and flexion, as well as observer performance of measurements using fourdimensional (4D)-computed tomography (CT) acquisitions and double-oblique multiplanar reconstruction (MPR) technique in asymptomatic contralateral joints of patients with unilateral wrist pain. MATERIALS AND METHODS: In this Health Insurance Portability and Accountability Act (HIPAA)-compliant institutional review board-approved study, 4D-CT was performed on the asymptomatic contralateral wrists of 10 patients (mean age: 46 years; M/F: 6/4) for comparison to the symptomatic side. Two independent observers defined the “obliqueesagittal” plane for PT joint measurements. Measurements were obtained for the anteroposterior (AP) interval and craniocaudal (CC) excursion during the extensioneflexion arc of wrist motion. RESULTS: The median (interquartile range) of the AP interval was 0.65 mm (0.55e1 mm) in extension, 1.1 mm (0.8e1.82 mm) in the neutral position, and 4.65 mm (2.07e5.87 mm) in flexion. Likewise, the median of the CC excursions in asymptomatic wrists were 0 mm in extension, 0.27 mm (0e0.37 mm) in the neutral position, and 0.28 mm (0.18e0.31 mm) in flexion. The AP interval measurements obtained at wrist flexion were larger than measurements obtained at wrist extension. There was a strong consistency in AP interval difference measurements between the two observers (ICC¼0.80; p<0.01); however, CC excursion difference measurements did not reach the significance threshold between the two observers (ICC¼0.40; p¼0.11). CONCLUSION: PT joint kinematics in asymptomatic wrists demonstrates an increase in AP interval and CC excursion during wrist flexion. MPR techniques provide good interobserver agreements for AP interval measurements. The reported intervals for asymptomatic joints can be used as a reference for asymptomatic wrists. Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

* Guarantor and correspondent: S. Demehri, Department of Radiology, Johns Hopkins University School of Medicine, Musculoskeletal Radiology, Russell H. Morgan Department of Radiology and Radiological Science, 601 N. Caroline Street, JHOC 5165, Baltimore, MD 21287, USA. Tel.: þ1 (410) 955 6500. E-mail address: [email protected] (S. Demehri). http://dx.doi.org/10.1016/j.crad.2015.07.007 0009-9260/Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

S. Demehri et al. / Clinical Radiology 70 (2015) 1362e1369

Introduction Pisotriquetral (PT) joint instability is considered in the differential diagnosis for ulnar-sided wrist symptoms, such as pain and clicking. PT instability is also associated with PT osteoarthritis (OA) and adjacent flexor carpi ulnaris (FCU) tendon injuries, which are the most common pathologies involving the PT joint1,2 and can be readily detected using static computed tomography (CT) or magnetic resonance imaging (MRI); however, detection of subtle PT instabilities is challenging using static cross-sectional imaging.3 Traditionally, cine radiography has been used to investigate certain carpal instabilities and abnormalities, such as scapholunate dissociation4,5; however, the accuracy and reproducibility for detection and characterisation of subtle carpal instability can be challenging due to the complex three-dimensional (3D) structure of carpal bones and the difficulty in discerning their contour using twodimensional (2D) cine radiography. Accurate PT measurements using cine radiography can be challenging due to the inconsistent visualisation of the articular surfaces of the pisiform and triquetrum, especially in the postero-anterior (PA) projection.6 Previous studies have characterised PT kinematics using spiral CT for image acquisition of the wrist in extension and flexion using a special positioning platform7; however, no prior imaging study has been performed to test the feasibility of PT kinematic evaluation in clinical practice. Using spiral CT examinations, 3D registration matching techniques, and an anatomical reference coordinate system, in vivo PT kinematics, have been previously investigated; however, this technique is very complicated and cumbersome and not easily performed and interpreted in routine clinical practice.7 Using 320-row multidetector CT with 16 cm craniocaudal (CC) coverage and consecutive gantry rotations with high temporal resolution, acquisition of four-dimensional CT (4D-CT) images of the carpus is now feasible in clinical practice. It can be used for certain patients with wrist symptoms and inconclusive findings in static imaging, such as plain radiography and MRI.8,9 The clinical application of 4D-CT has also been recently demonstrated in other joints, such as wrist,5,8,10 elbow,11 and knee.12 Recently, two reported cases of PT instability were diagnosed using 4D-CT.8 The definition of carpal bone axis and orientation, as well as the determination of alignment using anatomical landmarks, is critical for accurate and reproducible determination of PT motion abnormalities. Using 4D-CT with isotropic voxel enables novel methods for image post-processing. A double-oblique multiplanar reconstruction (MPR) technique was implemented in the present study, which is currently used widely in clinical practice to detect and grade coronary artery stenosis.13e15 Using MPR, PT alignment changes during the extensioneflexion arc of wrist motion was defined in different planes. The purpose of the present study was to characterise the normal motion pattern of the PT joint during wrist extension and flexion, as well as observer performance of measurements using 4D-

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CT acquisitions and double-oblique MPR technique, in asymptomatic contralateral joints of patients with unilateral wrist pain.

Materials and methods Study population The present study was approved by the institutional review board and was compliant with the Health Insurance Portability and Accountability Act. Informed consent was waived because this was a retrospective cross-sectional study. 4D-CT examinations of bilateral wrists were performed in 10 patients (mean age: 46 years, male/female: 6/ 4) with unilateral wrist symptoms who presented with unilateral wrist pain and clicking. Bilateral wrists simultaneously underwent 4D-CT examinations. The asymptomatic contralateral wrists were imaged for comparison and to aid in the detection of subtle motion abnormalities in the symptomatic wrist. The asymptomatic contralateral wrists were examined by an experienced hand surgeon to exclude any abnormalities before scan acquisition.

4D-CT acquisition All CT examinations were acquired using a 320-row detector CT system (Aquilion one, Toshiba, Tokyo, Japan). A dedicated custom-designed wrist platform was used for 4DCT acquisition, which was designed to allow for in-scanner unconstrained wrist motion while immobilising the forearm (Fig 1). A musculoskeletal radiologist trained the patients for each wrist motion evaluated, and each motion was performed during 5-second intervals of image acquisition. All 4D-CT examinations included the extensioneflexion arc of motion for PT motion analysis. The temporal resolution of the 4D-CT acquisition was 250 milliseconds and using half reconstruction mode with a CT gantry speed of two rotations per second, the frame rate for acquisitions was 0.5 per second. Therefore, 11 (first acquisition at 0 seconds, 11th acquisition at 5th second) volumes of kinematic CT acquisition were obtained for each wrist motion. Fig 2 demonstrates four selected 3D volume-rendered CT images (of 11 volumes of 4D-CT acquisition) in one patient’s symptomatic wrist with increased PT AP interval (from 1 mm in extension to greater than 12 mm in flexion), which was reported previously.8 The subjects’ torso and thyroid gland were shielded using a lead apron during the CT acquisition. The effective radiation dose (mSv) was calculated by multiplying the doseelength product (DLP) reported from the CT system by the conversion factor of 0.0001 (k) for distal extremities.16 The method of Leng et al.17 was followed in which images were acquired using a 100 mAs current but with similar qualities to the conventional 200 mAs. This modification significantly reduced the skin dose to 33 mGy (effective dose: 0.79 mSv), much lower than 2000 mGy, which is the threshold dose for induction of radiationinduced skin erythema.17,18

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Figure 1 Dedicated custom-designed wrist platform for 4D-CT acquisition that immobilises the forearm while allowing in-scanner unconstrained wrist motion.

Figure 2 Oblique sagittal plane images obtained from 11 consecutively acquired CT volumes in a symptomatic wrist with PT instability,8 which demonstrates abnormal increase in PT AP interval from 1 mm in extension to greater than 12 mm in flexion.

4D-CT interpretation The PT distance measurements were performed using commercial image post-processing software (Vitrea fX, Vital Images, Toshiba Medical Systems Company, Minnetonka, MN, USA). The imaging findings were interpreted and reported by two independent observers who are fellowship-trained musculoskeletal radiologists. Observer 1 performed all PT distance measurements at all 11 CT volumes to determine the PT motion pattern during wrist extensioneflexion (Fig 2). Observer 2 performed the

measurements only at extension (CT volume 1) and flexion (CT volume 11). These were compared to determine interobserver agreement. A double-oblique MPR technique was used to determine the PT distance measurements. Using MPR, the observers predefined oblique planes passing through specific anatomical landmarks of the carpal bones to perform independent measurements. PT distances were determined during the wrist extensioneflexion arc using similar measurements obtained from radiographic analysis of the PT joint.6 In order to perform the measurements, the observers

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Figure 3 (a) Primary axial plane of the distal radius, perpendicular to the radial and ulnar diaphysis. Using the axial plane, the primary sagittal plane is defined as a line crossing the anterior and posterior margins of the ulnar sigmoid notch (blue line) and perpendicular coronal plane is defined as a line crossing through ulnar and radial styloid process (green line). (b) Oblique sagittal planes in using the MPR technique that were used for PT interval measurements. P, pisiform; T, triquetrum; R, radius; U, ulna; L, lunate.

initially defined “primary” axial, coronal, and sagittal planes. The “primary” axial plane was defined as a plane perpendicular to the imaged distal radial and ulnar metaphyses. Using the “primary” axial plane, the “primary” sagittal plane was subsequently defined using the anterior and posterior margins of the sigmoid notch (Fig 3a; blue line). The perpendicular “primary” coronal plane was defined using the ulnar and radial styloid process (Fig 3a; green line). Subsequently, the centreline of the “oblique” sagittal plane (through the PT joint) was defined at the triquetrum’s maximum diameter in the “primary” coronal plane. All PT measurements were performed using the “oblique” sagittal plane (Fig 3b). Details of the planes and measurements have been previously described8 and are summarised in Fig 4.

PT measurements Measurements were obtained for the PT joint anteroposterior (AP) interval and the CC excursion throughout the extensioneflexion arc. For AP interval measurements using sagittaleoblique MPR images, the observers determined the minimum AP interval between the triquetrum and pisiform. For the measurement of the CC excursion, the distance between the distal poles of the triquetrum and pisiform was measured during the extensioneflexion arc.

Statistical analysis All kinematic measurements are presented in millimetres and the median values (interquartile range). The PT

Figure 4 Measurements of the PT AP interval and CC excursion in one wrist during extension and flexion. (a) PT interval in flexion is 5.1 mm. (b) PT interval in the extension is 1.8 mm. (ced) CC excursion is w0 in both flexion and extension.

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Table 1 Asymptomatic pisotriquetral joint kinematic measurements obtained by observer 1 throughout all 11 CT volumes. Volume

1: Extension 2 3 4 5 6: Neutral 7 8 9 10 11: Flexion

Pisotriquetral AP interval (mm)

Pisotriquetral CC excursion

Median

Lower interquartile

Upper interquartile

Median

Lower interquartile

Upper interquartile

0.65 0.75 1.10 0.85 0.85 1.10 1.90 3.40 3.90 4.30 4.65

0.55 0.55 0.60 0.60 0.77 0.80 1.20 1.27 1.52 1.82 2.07

1.00 0.95 1.40 1.32 1.30 1.82 2.52 3.92 4.60 5.35 5.87

0.00 0.00 0.00 0.00 0.09 0.27 0.29 0.29 0.25 0.23 0.28

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.19 0.18 0.14 0.18

0.00 0.16 0.24 0.31 0.32 0.37 0.39 0.37 0.42 0.46 0.31

Extension: CT volume 1; flexion: CT volume 11. Values are presented as median (interquartile range). AP, anteroposterior; CC, craniocaudal.

AP interval and CC excursion in extension and flexion volumes were compared using Wilcoxon’s non-parametric test. The interclass correlation coefficient (ICC) was used to derive the consistency in measurements between the two observers. SPSS (version 18, Chicago, IL, USA) was used for the analysis. A p-value of less than 5% (0.05) was considered significant.

of the PT CC excursions in asymptomatic wrists were 0 mm in extension, 0.27 mm (0e0.37 mm) in the neutral position and 0.28 mm (0.18e0.31 mm) in flexion. Table 1 demonstrates the median and interquartile ranges in all 11 volumes. Fig 5 shows the changing pattern of PT interval and CC excursion measurements from extension to flexion of the wrist.

Extensioneflexion differences

Results Data from 10 asymptomatic wrists were included in the study. CT images demonstrated no imaging features of PT OA in asymptomatic wrists. The study population consisted of four women and six men, with a mean age of 45.816.2 years (range: 24e72 years). Using the observer 1 measurements, the median and interquartile ranges of the PT AP interval among asymptomatic wrists was 0.65 mm (0.55e1 mm) in extension, 1.1 mm (0.8e1.82 mm) in the neutral position and 4.65 mm (2.07e5.87 mm) in flexion, respectively. Likewise, the median and interquartile ranges

The PT joint AP interval measurements obtained at wrist flexion (observer 1: 4.65 mm, range 2.07e5.87 mm; observer 2: 4.40 mm, range 2.97e6.50 mm) were larger than measurements obtained at wrist extension (observer 1: 0.65 mm, range 0.55e1 mm; observer 2: 0.85 mm, range 0.6e0.97 mm; observer 1: p¼0.008; observer 2: p¼0.008). PT joint CC excursion measurements obtained at wrist flexion (observer 1: 0.25 mm, range 0.2e0.32 mm; observer 2: 0.27 mm, range 0.18e0.31 mm) were also larger than measurements obtained at extension (observer 1: 0 mm; observer 2: 0.05 mm, range 0e0.32 mm; observer 1:

Figure 5 Increasing pattern of PT AP interval (PTI) and CC excursion (CCE) in extension/flexion of the wrist obtained from observer 1 measurements.

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Table 2 Asymptomatic pisotriquetral joint kinematic measurements of the two observers. Pisotriquetral AP interval (mm)

Observer 1 Observer 2

Pisotriquetral CC excursion

Flexion

Extension

Difference

Flexion

Extension

Difference

4.65 (2.07e5.87) 4.40 (2.97e6.50)

0.65 (0.55e1.00) 0.85 (0.60e0.97)

3.85 (1.45e5.10) 3.90 (2.07e5.60)

0.27 (0.18e0.31) 0.25 (0.20e0.32)

0.00 (0.00e0.00) 0.05 (0.00e0.32)

0.26 (0.09e0.31) 0.15 (0.04e0.30)

Values are presented as median (interquartile range). AP, anteroposterior; CC, craniocaudal.

p¼0.015, observer 2: p¼0.15). Thus, both PT interval and CC excursion increased in flexion (versus extension), although the differences in values for PT CC excursion were not statistically significant (Table 2).

Interobserver reliability PT AP interval measurements were highly consistent between the two observers both in flexion and extension states (for flexion: ICC¼0.77, range 0.33e0.94, p< 0.01; for extension: ICC¼0.54, range 0.09e0.86, p¼0.04). The PT CC excursion measurements had positive consistency between the two observers, but did not reach statistical significance for extension (for flexion: ICC¼0.75, range 0.27e0.93, p<0.01; for extension: ICC¼0.46, range 0.20e0.83, p¼0.08). Similarly, there was a strong consistency in PT AP interval difference measurements between the two observers (ICC¼0.80, range 0.38e0.95, p< 0.01); however, PT CC excursion difference measurements did not reach the significance threshold between the two observers (ICC¼0.40, range 0.26e0.81, p¼0.11). Unlike PT CC excursion measurements, PT AP intervals of consecutive motion volumes had an increasing trend while moving from full extension to full flexion (Fig 5).

Discussion Abnormal carpal and inter-carpal motion can be evaluated using 4D-CT. This innovative technique can be helpful in certain cases where static cross-sectional imaging and cine radiography are inconclusive. The 4D-CT acquisition includes the isotropic volume of an entire wrist with a temporal resolution to dynamically demonstrate wrist kinetics over various pre-defined arcs of motion.11 Recent advances in commercially available post-processing tools, such as MPR, may aid in the detection of subtle motion abnormalities of the carpus in routine clinical practice.8,13,14 The present study provides evidence for the applicability of 4D-CT, using the defined measurements of PT interval and excursion, by different observers. Subjects with ulnar-sided wrist symptoms (including pain and clicking) who are suspected of having PT instability on physical examination may benefit from advanced imaging techniques such as MRI19,20; however, in many cases, conventional and advance imaging techniques, including MRI, may be inconclusive.19,20 In such instances, and if the surgeon has a high clinical suspicion for PT instability, 4D-CT can provide a clinically feasible dynamic

assessment of the PT joint.8 The present study provides further evidence for the reliability of the measurements that are performed using 4D-CT examination. The complex arrangement of tendons and biomechanics of the PT joint explains the rarity of pisiform dislocation, which is usually caused by a hyperextension force at the wrist that is translated to the pisiform via the FCU tendon. It has been reported that ulnar neuropraxia from pisiform dislocation can improve after surgery.2,21 Given the low prevalence of PT instability, only a limited number of investigators have evaluated its corresponding radiological changes.19 Some authors have proposed that PT instability is accompanied by alterations in PT kinematic measures.20,22 This finding was confirmed in a recent report.8 To the authors’ knowledge, no previous study has evaluated the normal kinematic indices in asymptomatic wrists. In the current study, the normal kinematics of the PT joint were evaluated in 10 asymptomatic wrists to develop suggested ranges of PT indices in asymptomatic wrists. The present results demonstrates that PT AP interval measurements increase during wrist flexion up to 5e6 mm (upper quartile of measurement differences by the two observers) in asymptomatic joints, which was determined by a relatively high interobserver agreement. Therefore, in patients with ulnar wrist symptoms, interval widening of the PT AP interval more than 5e6 mm during flexion may represent AP instability. Although there were also differences in PT CC excursion measurements during wrist extensioneflexion, the difference was not significant, and the agreement was not high between the measurements of the two observers. This may be due to small sample size in the present study or the complexity of the protocol used for PT CC excursion measurements. Nevertheless, as shown in Table 2, one of the trained observers did not identify the alterations in CC excursion measures (in many cases) that had been identified by the other observer. Thus, PT CC excursion measurements did not have the interobserver reliability that was present in PT interval assessments. The present data also suggest that during static CT or MRI examination of the wrist, if the image acquisition is obtained with the patient’s wrist in a neutral position, a PT AP interval measurement >2 mm may represent abnormal widening of the PT joint, and this can be further evaluated with 4D CT or cine fluoroscopy examinations. Radiological evaluation of the PT joint during active motion can be challenging, and cine radiography is the most commonly used method. Cine radiography is an established technique for evaluation of carpal motion.6 It likely requires less radiation exposure compared to 4D-CT acquisition23;

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however, in cine radiography, unlike 4D-CT acquisition, the operator is usually exposed to scattered ionising radiation during wrist manipulation for the examination. Moreover, 2D cine radiography has limited applicability in routine clinical practice for diagnosing subtle carpal motion abnormalities. 4D-CT provides enhanced accuracy and simplicity in visualising the complex 3D carpal bone structures.8,19 In comparison with 4D-CT, cine radiography is typically performed in an anaesthetised patient and the motion is created passively by the operator rather than actively by the patient. Passive motion may not accurately reflect the exact motion that provokes the patient’s symptoms and cannot initiate the active motion forces upon the carpal bones (such as the flexor carpi ulnaris actively pulling the pisiform) that most accurately reproduce the motion and symptoms in question. Therefore, wrist examination using cine radiography under general anaesthesia may not reproduce subtle carpal instability occurring as a result of an active motion, as opposed to 4D-CT that is acquired during active motion. For practical 4D-CT interpretation, prior knowledge of normal PT kinematics is necessary. Using knowledge of the normal PT interval and excursion movements during active extensioneflexion, 4D-CT comparisons in symptomatic joints may be made which are clinically relevant. In the present study, a reliable PT interval metric and the appropriate values to expect in asymptomatic wrists are provided (Table 1). Clinically, standard active arcs of motion including extensioneflexion, pronationesupination, radialeulnar deviation, and even relaxed to clenched fist (axially loading) can be examined by 4D-CT acquisition. Alternatively, the specific wrist motion or position that provokes a patient’s symptoms can be simulated as well. Despite the fact that 4D-CT is not “real-time” imaging, it can precisely address a specific complaint (including restricted range of motion, clunk/click, or pain) to the corresponding 4D-CT images. In the future, with more knowledge of carpal motion patterns using 4D-CT, more focused examinations can be performed with fewer carpal motions, thereby reducing further radiation exposure. 4D-CT examinations are currently acquired using a tube current of 80e100 mAs by the present authors. Previous investigators have shown that using “simulated” CT acquisition protocols with tube currents as low as 67 mAs can allow for adequate interpretation of CT imaging of small osseous structures such as the paranasal sinuses.24 With a further description of various carpal bone motion patterns and their normal range, the need for imaging the contralateral wrist may also be obviated to avoid additional radiation exposure. The present study has a number of limitations. Due to the limited number of study participants, meaningful conclusions could not be derived from the sub-group analyses (including any potential gender differences). Future studies with larger numbers of participants may further delineate PT motion patterns among different age and gender subgroups, if they exist. This study also did not evaluate the measurement of the PT angle on lateral wrist radiograph or 4D-CT. In a future study, the authors plan to evaluate the PT angle to determine whether changes in it associate with

abnormal carpal bone motion. As this was the authors’ first experience measuring asymptomatic wrists, the PT interval changes were not measured in any motion arcs except extensioneflexion. Nevertheless, future works will include three standard motions (extensioneflexion, radialeulnar deviation and relaxedeclenched fist). These data may be a useful reference for other researchers and clinicians who may utilise other (possibly simpler) imaging techniques. Nevertheless, 4D-CT may have other advantages, including 3D reconstructions and enhanced accuracy. Future studies will evaluate the PT interval difference among symptomatic wrists in a larger sample of participants. According to the present limited, but expanding, experience in the 4D-CT imaging of symptomatic wrists, it is hypothesised that there will be a considerably larger PT interval for symptomatic wrists. In the previously reported 4D-CT examination of a symptomatic wrist with PT instability, a 12.2 mm PT interval was measured in wrist flexion.8 Lastly, all of the measurements in the wrists reported in the current study are from asymptomatic wrists of patients with one symptomatic wrist. Thus, they may not be a true representative of “normal” wrists as at least one of the subjects’ wrists has demonstrated susceptibility to dysfunction. The authors’ recent experience shows that 4D-CT may be a useful tool for evaluation of patients with wrist symptoms without definite diagnosis using static CT or MRI examinations. Further studies are planned to delineate the technical efficacy of 4D-CT in the determination of carpal motion abnormalities and its added diagnostic impact when compared to static imaging.

Acknowledgements S.D. has grants from GERRAF 2014e2016; Carestream Health Inc. 2013e2015 for Cone-Beam CT clinical trial; Toshiba Medical Systems as a consultant. Other authors declare no conflicts of interest.

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