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Updated: Oct 4, 2026
Automated Joint Space Detection Improves Bone Segmentation Accuracy
Published on: November 28, 2025
Radiographic joint space in rheumatoid elbow joints. A 15-year prospective follow-up study in 74 patients
J T Lehtinen1, K Kaarela, E A Belt
1Rheumatism Foundation Hospital, Heinola, Finland.
Objective:
To evaluate radiographically the humeroulnar (HU) and humeroradial (HR) joint spaces in patients with long-term rheumatoid arthritis (RA).
Methods:
An inception cohort of 74 patients with RA were followed for 15 yr. At the end-point, 148 elbows were radiographed by a standard method. The HU and HR joint spaces were examined from the anteroposterior radiographs by measuring the shortest tangential distance in the middle of the joints. Destruction of the elbow joints, assessed with the Larsen method on a scale of 0-5, was studied in relation to the joint-space measurements.
Results:
Mean (s.d.) HU joint space (n=148) in RA patients was 2.5 (1.1) mm, range 0-4 mm [2.9 (0.8) mm in men and 2.4 (1.1) mm in women]. Mean (s.d.) HR joint space (n=140) was 2.3 (0.9) mm, range 0-4 mm [2.5 (0.8) mm in men and 2.3 (1.0) mm in women]. HU and HR spaces of the affected joints (Larsen grades 2-5) [1.9 (s.d. 1.1) and 1.8 (0.9) mm respectively] were notably narrower than those of the unaffected (Larsen grades 0-1) joints [3.1 (0.7) and 2.9 (0.6) mm]. All the joints graded as Larsen 4 or 5 (n=13) had a value of 0 mm for both joint spaces. Both the HU and the HR joint-space narrowing was associated with increasing destruction (Larsen grading) of the joint. [r= -0.69 (95% CI -0.77 to -0.60) and r= -0.70 (-0.78 to -0.60)]. The monotonic narrowing was significantly increasing from unaffected (Larsen 0, 1), slightly (2), moderately (3) to severely (4, 5) affected joints (P<0.001). A step in this process occurred between Larsen grades 3 and 4, when the mean joint space diminished from 1.4 and 1.5 respectively to 0 mm.
Conclusions:
Joint-space narrowing is a frequent consequence of rheumatoid affection of the elbow joint. HR joint space decreases together with HU joint space; however, the HR joint space is already slightly narrower at the start. The narrowing is a rather late phenomenon, occurring only after erosive destruction. This should be borne in mind when using the Larsen method to evaluate changes in the elbow joint.
