Facts
The dispute concerns the insured [A.] , born in 1984, who on 9 July 2017 was the victim of a road traffic accident on the motorway, which resulted in pain in the left shoulder. The initial diagnosis made at the hospital was a grade I acromioclavicular sprain, without fracture. Compulsorily insured against accidents as an unemployed person, the insured was covered by the Swiss National Accident Insurance Fund (CNA).
Persistence of pain: an MRI of 19 October 2017 revealed a significant acromioclavicular arthropathy, of degenerative origin in the first place. Doctor [D.] , orthopaedic surgeon, diagnosed a Tossy II type instability and post-traumatic arthrosis. The CNA's district physician, Doctor [E.] , acknowledged a temporary aggravation of a pre-existing degenerative condition, without impact or structural traumatic injury, and considered that the accident had ceased to produce its effects three months after it occurred.
By decision of 3 May 2018, confirmed on objection on 27 August 2018, the CNA closed the case as of 9 April 2018 and terminated benefits. The medical adviser of the insured's health insurer, Doctor [F.] , concluded that there was a natural causal link to the degree of probability prevailing. Doctor [D.] recommended resection of the distal end of the clavicle.
By judgment of 6 June 2019, the Public Law Court of the Cantonal Court of the Canton of Neuchâtel upheld the insured's appeal, annulled the decision and remitted the matter to the CNA for a new decision, considering that the exclusively degenerative nature of the lesions had not been established.
The CNA lodged an appeal with the Federal Supreme Court, principally seeking reinstatement of the decision on objection, in the alternative termination of benefits solely for the consequences of the arthrosis, and in the further alternative annulment of the judgment and remittal for supplementary investigation. The respondent seeks dismissal of the appeal.
Considerations
On admissibility, the Federal Supreme Court notes that a remittal decision in principle does not terminate the proceedings and does not cause irreparable harm. However, where the remittal ruling leaves the administration no latitude for judgment, it is treated as a final decision. In this case, the cantonal judgment obliges the CNA to grant benefits beyond 9 April 2018 without any margin of assessment, so it is treated as a final decision and the appeal is admissible (art. 90, 93 FSCA).
On the merits, the Federal Supreme Court observes that a Tossy II type dislocation is among the injuries treated as equivalent to an accident (art. 6 para. 2 AIA), but that the case must be examined under the angle of art. 6 para. 1 AIA, since the CNA has acknowledged the existence of an accident in the legal sense. To establish the right to benefits, a natural causal link is required, the accident being a sine qua non condition of the health impairment, established to the degree of probability prevailing. Where a pre-existing condition is aggravated, the duty to provide benefits ceases only when the impairment results exclusively from causes unrelated to the accident, namely the statu quo ante or sine. The burden of proving the disappearance of the causal link lies with the insurer.
As regards the probative value of medical opinions, where the case is settled without an external expert opinion, strict requirements apply: even a minimal…