gms | German Medical Science

Introduction: Calcium pyrophosphate dihydrate crystal deposition disease (CPPD) is known to affect fibrocartilaginous tissue in the large and smaller peripheral joints. The affection of the axial skeleton is unclear. We assessed the frequency and severity of structural changes in the lower spine in patients with established CPPD in comparison to degenerative disc disease (DDD).

Methods: In a retrospective study, patients with CPPD or DDD as a main diagnosis with available spinal conventional radiographs (CR) performed during 2014–2020 were included. Other inflammatory conditions affecting the spine were excluded. The segments T7/8-L5/S1 were evaluated for the occurrence of disc-calcification, intradiscal vacuum-phenomenon, disc height (normal/narrowing/complete loss), endplate erosion, osteophytes and spondylolisthesis. When lumbar spine MRIs of the same time point were available, discovertebral units were evaluated for the occurrence of vacuum phenomena, endplate erosion, Modic changes and disc dehydration (Pfirrmann). Follow-up CRs were assessed if available. All available images were evaluated by 2 independent readers.

Results: CR of 140 CPPD patients (1.171 discovertebral units) and 99 DDD (803 discovertebral units) were evaluated (mean age 74.4±9.9 and 71±6.2, 20% vs. 20.2% males, respectively). Spine-MRIs were available from 48 CPPD and 44 DDD patients. Vacuum phenomena, disc calcification, osteophytes and erosion were significantly more frequently seen in CPPD patients compared to DDD (Table 1 [Tab. 1]) with no differences between the thoracic and the lumbar spine. Follow-up CR were available for 29 CPPD patients and 46 DDD. Both groups presented statistically significant progression of endplate erosions and osteophytes (p 0.001 - 0.02). Notably, even though CR follow-up times in the CPPD group were, compared to DDD (median (IQR) 1.9 (2.4) vs 3.0 (3.1) years, p=0.033, respectively), shorter, radiographic progression was noted more frequently in CPPD vs. DDD for erosive changes (6.8% vs. 0.6%, p=0.018) and disc calcification (5.8% vs. 0.6%, p=0.007). When comparing MRIs, a higher number of discovertebral units was affected by vacuum phenomena (34 vs 13, p=0.04) and endplate erosions (L4/5 (45.5% vs 24.4%, p=0.04), L5/S1(40.4% vs 19.5%, p=0.03) in CPPD patients vs. DDD, respectively.

Conclusion: CPPD patients showed more severe and progressive degenerative findings in the lower spine as assessed by both, CR and MRI, in comparison to established DDD. This data shows that CPPD manifestations in the axial skeleton are clinically relevant.