Radiolunate joint congruency test

1. Arc center distance
as a novel quantitative radiographic parameter
for volar Barton fractures
Department of Orthopedic Surgery,
Seoul National University Hospital
김민범, 이정현, 이영호
2022년 대한골절학회 춘계학술대회

2. Introduction – Volar Barton fracture
Benis et al. 2020 OTSR

3. Introduction
• Radiolunate joint: hinge joint at saggital plane of CT images
cf. radioscaphoid joint: ellipsoid joint
Axial
load

4. Introduction
• Arc Center Distance (ACD)
• for hinge joints
• Tibio-talar joint
• Elbow joint
• etc
Arc center distance
(mm)

6. Introduction
• Old Radiographic parameters
to evaluate incongruence of
the lunate facet in volar
Barton fracture
Volar tilt angle (VTA)
Anteroposterior distance (APD)
Tear drop angle (TDA)
Capitate-to-axis-of-radius distance (CARD)

7. Introduction: purpose
• To investigate conventional radiographic parameters (VTA, APD, TDA, and
radio-carpal alignment) in volar Barton fractures
• To introduce the ACD as a new parameter.

8. Methods
• Patients who underwent surgery for a volar Barton-type distal radius fracture
between June 2013 and February 2021 were reviewed.
• Skeletally mature patients who underwent a preoperative computed
tomography (CT) scan of the wrist were included.
• Patients with underlying deformities of the wrist were excluded.
• Twenty-four cases were included. Postoperative CT images were not
available in three cases.

9. Results
[Table 1] Change of parameters before & after the surgery (N=24)

10. Results
[Table 2] Comparison of conventional parameters
(fractured wrist versus normal contralateral wrist) (N=24)

11. • The AUC & reliability of the ACD
Results- ROC curve (pre, post op results)
3 observers,
Interobserver interclas:
coefficient 0.92
(95% CI 0.837-0.964, N=3)
Intraobserver interclass
coefficient 0.958
(95% CI 0.901-0.982)
Cut-off: 1.02mm
Sensitivity 100%
Specificity 80.95%

12. • Comparison of ROC curves
Results (pre, post op. results)
[Table 3] AUC of the ROC curve and 95% confidence
interval (CI) of the parameters (N=24 (21 for ACD))

13. Results
[Table 4] Pairwise comparison of ROC curves by DeLong method (N=21)

14. Discussion
• joint congruency 반영에 좋은 지표: 수술 전 후 변화 평가
• PACS 'multiple circle tool' and short learning curve
• ACD 와 장기적 예후 반영과의 상관 관계 평가 연구 필요
• A cutoff value of 1.02 mm → unstable nature of volar Barton fractures
• 일반적인 acceptable reduction value 2mm 보다 작은 값!

15. Discussion - Limitations
• The study was retrospective, and the number of cases was small.
• This study did not investigate long-term radiographic changes or clinical
outcomes.
• The measurement of the ACD requires the acquisition of CT images.
• Exposure of radiation:
• effective dose for CT of wrist and hand: 0.03 mSv
• (effective dose for conventional chest radiograph: =0.08 mSv)
• average dose length product of wrist CT: 154.8 mGy-cm (range 114.4–234.3) which was
comparable to the reported dose length product (136.7 mGy-cm)

16. Conclusion
• ACD is a useful parameter to assess radiolunate joint
congruency in volar Barton fracture quantitatively

18. Thank you for your attention
* This study has been submitted to Archives of Orthopaedic and Trauma Surgery and under minor revision.