United States Court of Appeals
                           FOR THE EIGHTH CIRCUIT
                                   ___________

                                   No. 98-2324
                                   ___________

Michael A. Bone; Ramona Bone,       *
                                    *
     Plaintiffs - Appellants,       *
                                    * Appeal from the United States
     v.                             * District Court for the
                                    * Eastern District of Missouri.
Ames Taping Tool Systems, Inc.      *
                                    *
     Defendant - Appellee.          *
                               ___________

                             Submitted: January 15, 1999

                                  Filed: June 8, 1999
                                   ___________

Before LOKEN, HANSEN, and MORRIS SHEPPARD ARNOLD, Circuit Judges.
                           ___________

LOKEN, Circuit Judge.

       Michael Bone worked as a drywall taper for many years, using an automated
taping gun known as the “Bazooka.” In late 1990, Bone began experiencing
numbness and burning in his arms and hands. He has since been treated for
cumulative injuries to his shoulders, elbows, and wrists. Bone and his wife sued the
Bazooka’s manufacturer, Ames Taping Tool Systems, Inc., in Missouri state court,
asserting product liability and loss of consortium claims. Ames removed, invoking
the district court’s diversity jurisdiction. The Bones now appeal the district court’s
grant of summary judgment for Ames on the question of causation. We review the
grant of summary judgment de novo, viewing the evidence most favorably to the non-
moving party. See Mullins v. Tyson Foods, Inc., 

, 1158 (8th Cir.
1998). Concluding that the deposition testimony of plaintiffs’ medical experts is
sufficient evidence that use of the Bazooka directly caused or contributed to cause
Michael Bone’s injuries, we reverse and remand.

      Michael Bone taped drywall from 1980-1992, operating the Bazooka several
hours each workday. The Bazooka weighed seventeen pounds when full of taping
compound. It required repetitive wrist motions and considerable pressure to apply
compound. With no convenient hand holds, it was awkward to support and
maneuver, particularly while doing overhead work. Bone developed carpal tunnel
syndrome in both wrists, rotator cuff damage to both shoulders, thoracic outlet
syndrome affecting his neck and shoulders, and cubital tunnel syndrome in his
elbows. When months of therapy and four surgeries failed to alleviate his discomfort,
Bone quit taping because he could not work without severe pain and numbness.

       Under Missouri law, to prevail on a claim of strict liability, negligence, or
breach of warranty, Bone must prove that his use of the Bazooka directly caused or
contributed to cause some or all of his injuries. Missouri uses the “but-for” causation
test; use of the Bazooka was a legal cause of Bone’s injuries if they would not have
occurred “but for” that conduct. See Callahan v. Cardinal Glennon Hosp., 

, 860-63 (Mo. banc 1993); Tenbarge v. Ames Taping Tool Sys., Inc., 

, 659 n.3 (8th Cir. 1997). In a case involving multiple possible causes, a
plaintiff must “exclude other causes by presenting substantial evidence that a
particular cause for which defendant is liable is responsible for plaintiff’s injuries.”
Kircher v. Purina Mills, Inc., 

, 117 (Mo. banc 1989).

      The Bones rely on the deposition testimony of four treating physicians to prove
causation. Dr. S. Vic Glogovac treated Michael Bone’s wrists for carpal tunnel
syndrome. He opined that the forceful, repetitive flexion and extension of Bone’s

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wrists created pressure on the carpal tunnel, causing nerve damage over an extended
period of time. He attributed the pressure to Bone’s use of his hands at work,
specifically to his operating the heavy Bazooka for several hours a day. The district
court dismissed Dr. Glogovac’s opinion as not being stated “to a reasonable degree
of medical certainty.”1 However, Dr. Glogovac testified:

           Q Doctor, is your opinion in that regard based upon reasonable
      medical certainty?

             A Yes.

Dr. Glogovac’s deposition testimony is sufficient evidence to raise a genuine issue
of material fact whether the Bazooka caused Michael Bone’s wrist injuries.
“Absolute certainty is not required.” Lemm v. Gould, 

, 200 (Mo.
1968).

      Dr. Susan Mackinnon treated Michael Bone’s shoulder problems. She testified
that his “use of that Bazooka gun definitely contributed to the development of
thoracic outlet syndrome.” She also opined that his thoracic outlet syndrome would
aggravate cubital tunnel syndrome, the elbow injuries Michael developed. She
acknowledged that other overhead activities would be aggravating factors but found
Bone’s use of the Bazooka most significant because it involved supporting a heavy
object while working overhead. The district court dismissed this testimony because



      1
        Many Missouri cases state that a medical expert’s opinions must be expressed
to a reasonable degree of medical certainty. When the issue is causation, this requires
the expert to have a “reasonable certainty in his mind” that “the result in question
most probably came from the cause assigned.” “[O]pinions of experts that a certain
occurrence or condition might or could produce a certain result . . . does not alone
constitute substantial evidence that such occurrence or condition did cause it.”
Kinealy v. Southwestern Bell Tel. Co., 

, 404-05 (Mo. 1963).

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it was not stated to a reasonable degree of medical certainty. Again, that issue was
sufficiently covered in Dr. Mackinnon’s deposition:

            Q Doctor, have all the opinions that you’ve given here . . . been
      based upon your education, training, experience, your treatment of Mike
      Bone to a reasonable medical certainty?

             A Yes.

We conclude Dr. Mackinnon’s deposition testimony is sufficient evidence to raise a
genuine issue of material fact whether the Bazooka caused or contributed to Michael
Bone’s shoulder and elbow injuries.

      We agree with the district court that the deposition testimony of plaintiffs’
other treating physicians did not create a genuine issue of material fact as to
causation. Dr. Robert Markenson discussed generally how overhead work can cause
or contribute to rotator cuff tendinitis in the shoulders, but he did not attribute
Michael’s shoulder injuries specifically to his use of the Bazooka. Dr. Richard
Lehmann testified that Bone’s use of the Bazooka “probably” caused his shoulder
problems, but he did not have sufficient knowledge of Bone’s work activities to
provide a foundation for that rather hesitant opinion. Nevertheless, giving the Bones
the benefit of all reasonable inferences, the testimony of Dr. Glogovac and Dr.
Mackinnon provide sufficient evidence of causation under Missouri law to defeat
Ames’s motion for summary judgment on this issue.

      The Bones also seek review of the district court’s pretrial ruling that the
opinion testimony of their design engineer and ergonomics expert on the issue of the
Bazooka’s alleged defective design must be excluded under Daubert v. Merrell Dow
Pharmaceuticals, Inc., 

(1993). The Supreme Court recently emphasized
that district courts must screen the reliability of all expert testimony but have
substantial discretion in deciding how to test an expert’s reliability and whether the

                                         -4-
expert’s relevant testimony is reliable. See Kumho Tire Co. v. Carmichael, 

, 1174-76 (1999). We decline to consider this pretrial evidentiary ruling at this
point in the lawsuit, particularly since it is not at all clear what impact the ruling will
have on the ultimate disposition of plaintiffs’ claims, whether by summary judgment
or after trial. See Newman v. Ford Motor Co., 

, 152-54 (Mo. banc
1998); Tune v. Synergy Gas Corp., 

, 14 (Mo. banc 1994).

      The judgment of the district court is reversed and the case is remanded for
further proceedings not inconsistent with this opinion.

       A true copy.

              Attest:

                 CLERK, U. S. COURT OF APPEALS, EIGHTH CIRCUIT.




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