Ability of near infrared spectroscopy to measure oxygenation in isolated upper extremity muscle compartments.

PURPOSE: Near infrared spectroscopy (NIRS), a noninvasive means for monitoring muscle oxygenation, may be useful in the diagnosis of acute compartment syndrome, a condition characterized by poor tissue perfusion. This study used the decrease in muscle oxygenation caused by exercise to investigate the ability of anatomic placement of NIRS sensor pads over compartments of the forearm to isolate perfusion values of a specific compartment. METHODS: We recruited 63 uninjured volunteers from a private clinic-based setting and placed NIRS sensor pads over the dorsal, volar, and mobile wad compartments of 1 forearm. A total of 49 participants also had the contralateral forearm monitored, which served as an internal control. Participants performed a series of 3 exercises designed to sequentially activate the muscles of each compartment. A washout period separated each exercise to allow perfusion to return to baseline. We compared NIRS values of each compartment recorded during muscle contraction with baseline values. RESULTS: Mean NIRS values decreased significantly from baseline during muscle contraction for all compartments, whereas mean NIRS values of muscle compartments that remained at rest showed little or no change. We observed no changes in NIRS values of the contralateral arm, which remained at rest during the entire data collection period. CONCLUSIONS: Although lack of an existing method for quantifying muscle perfusion precludes validation of this technique against a reference standard, this study suggests that NIRS can provide oxygenation values that are both sensitive and specific to muscle compartments of the forearm. Future studies should investigate NIRS among patients with upper extremity injuries. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.

Cadaveric Study of Appropriate Screw Length for Distal Radius Stabilization Using Volar Plate Fixation.

We conducted a study to highlight areas of risk with distal radius fixation to prevent occurrence of extensor tendon injury without compromising the security and stability of the fixation. Twelve cadaveric forearms were used. The volar locking plate was placed to best anatomical and radiologic fit on the distal radius of each arm. All 7 holes in the plate were drilled, and bicortical length was measured using a depth gauge under fluoroscopy to estimate screw lengths. Screws were secured into place, and dorsal prominence was measured. The central screw positions had the least dorsal screw prominence, mean (SD) of 0.50 (1.06) mm, and were considered low-risk. The radial and ulnar screw positions had more dorsal screw prominence, 3.38 (1.38) mm and 1.03 (1.30) mm, respectively. Although only radial prominence was statistically significant, both radial and ulnar screw positions were considered high-risk and in need of screw length adjustments. The data suggest that screw length for this plate should be decreased by about 3 mm for the radial positions and by 1 mm for the ulnar positions to decrease the risk for tendon rupture and irritation secondary to dorsal screw prominence.