Mach v. Wells Concrete Products Co., 866 N.W.2d 921

David J. Mach injured his left leg at work in 2010; he alleged resulting CRPS and sought workers’ compensation for medical expenses and disability.
In the 2010 proceeding Mach sought payment for a spinal cord neurostimulator; the compensation judge found he did not prove CRPS and denied compensation for the neurostimulator, though awarded some past medical bills. The WCCA affirmed.
Mach later had his neurostimulator replaced in 2012 and filed a 2013 claim seeking reimbursement for replacement and related care; he submitted a new treating-physician letter diagnosing ongoing CRPS.
Wells moved to dismiss the 2013 claim as barred by res judicata and collateral estoppel because the 2010 adjudication rejected neurostimulator treatment; the compensation judge granted dismissal.
The WCCA reversed, reasoning the 2010 decision covered only expenses through January 5, 2011 and did not preclude later medical expenses; this Court granted review.
The Supreme Court held res judicata did not apply to the 2013 claim but remanded because whether collateral estoppel bars the claim depends on whether Mach’s condition materially changed since the 2010 adjudication.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Does res judicata bar Mach’s 2013 claim for later medical expenses?	Res judicata should not bar later-incurred treatment because it was not ripe in 2010.	The neurostimulator issue was already litigated and decided against Mach.	Res judicata does not bar the 2013 claim because the later treatment and expenses arose after the 2010 judgment.
Does collateral estoppel (issue preclusion) bar relitigation of whether a neurostimulator is reasonable treatment?	Not if Mach’s condition changed or new evidence exists showing treatment became reasonable after 2010.	Yes — the earlier adjudication necessarily decided that neurostimulator treatment was not reasonable.	Collateral estoppel may apply unless Mach proves a material change in condition or new facts; remanded to determine if condition changed.
Who bears burden of proving collateral estoppel defense in this context?	N/A (plaintiff must prove entitlement to benefits).	Employer asserts estoppel and must prove affirmative defense.	Employer (Wells) has burden to establish collateral estoppel.
Does ongoing employer liability for medical treatment affect preclusion analysis?	Ongoing statutory duty means later treatments can be new claims and not precluded.	N/A (employer’s argument focused on prior adjudication).	The court emphasized employer’s continuing liability under Minn. Stat. § 176.135 means preclusion is limited when condition changes.

Hauschildt v. Beckingham, 686 N.W.2d 829 (Minn. 2004) (distinguishes res judicata and collateral estoppel and discusses issue preclusion principles)
Nelson v. Am. Family Ins. Grp., 651 N.W.2d 499 (Minn. 2002) (elements for claim preclusion and collateral estoppel)
Care Inst., Inc.-Roseville v. Cty. of Ramsey, 612 N.W.2d 443 (Minn. 2000) (standard of review for application of preclusion doctrines)
Westendorf v. Campbell Soup Co., 243 N.W.2d 157 (Minn. 1976) (application of res judicata principles to workers’ compensation)
Saenger v. Liberty Carton Co., 316 N.W.2d 737 (Minn. 1982) (prior adjudication of disability does not preclude later showing of changed condition)
Hauser v. Mealey, 263 N.W.2d 803 (Minn. 1978) (definition and scope of claim preclusion)