The Effects of Noninvasive Traction on SSEPs During Ankle Arthroscopy.

BACKGROUND: The purpose of this study was to evaluate the effects of noninvasive ankle distraction on intraoperative somatosensory evoked potentials (SSEPs) and peripheral nerve sensibility of the foot during ankle arthroscopy. METHODS: Twenty patients undergoing ankle arthroscopy were prospectively evaluated using noninvasive ankle traction. All had preoperative clinical examination with baseline neurologic evaluation and static 2-point discrimination (2PD) test. Intraoperative SSEPs were monitored continuously throughout surgery. Thirty pounds of traction was applied using noninvasive traction. A 50% decrease in amplitude or a 10% increase in latency was considered significant. At 2 weeks postoperatively, the 2PD test was repeated. Pre- and postoperative 2PD was compared and subsequently correlated with intraoperative SSEPs. RESULTS: Three patients sustained significant SSEP signal alterations during surgery. The changes were transient and directly related to application of traction but returned to baseline without traction release. Abnormal postoperative 2PD testing was found in the operative extremity in 12 patients but resolved by the second postoperative visit. Only 2 of 12 had intraoperative SSEP changes. Eleven patients had abnormal postoperative 2PD testing in the nonoperative limb. Nine had changes in both limbs. Routine history and clinical examination did not suggest any neurologic injury. There was no statistically significant correlation between intraoperative SSEP alterations and subsequent development of abnormal postoperative 2PD testing. CONCLUSION: Transient intraoperative SSEP changes occurred with noninvasive distraction but were reversible when using 30 pounds of traction. 2PD testing changes were common postoperatively but not correlated to changes in SSEP. Patients with increased 2PD did not have sensory changes detectable on clinical exam or subjective patient history. LEVEL OF EVIDENCE: Experimental level II, prospective comparative study.

Allograft swelling after preparation during ACL reconstruction: do we need to upsize tunnels?

The purpose of this study was to determine whether the pull-through force of soft-tissue allografts increases over time after being hydrated with saline-soaked sponges. Eighteen aseptic soft-tissue, fresh-frozen anterior tibialis allograft specimens were thawed and sized using standard sizing guides. After sizing, initial pull-through force was measured using an Instron Model 5865 machine. Grafts were randomized to soak in saline sponges for 20, 40, or 60 min. After soaking, pull-through force was again assessed. Pre- and post-soaking pull-through forces were compared using a paired t test. The effect of time on pull-through force was evaluated using an ANOVA and Tukey post hoc test. Two allografts had initial pull-through forces outside the inclusion criteria and were excluded. The average pull-through force for the remaining 16 allografts pre-soaking was 43.0 N and post-soaking was 81.7 N, for an increase of 90 % (P < 0.001). Longer hydration time in the saline soaked sponges was not correlated with higher pull-through force (P = 0.724). Pull-through force post-hydration was not related to the allograft diameter (P = 0.641). Post-hydration, 33 % of grafts that had soaked for 20 min and 40 % of grafts that had soaked for 40 or 60 min required greater than 100 N pull-through force. Our data supports the hypothesis that soft-tissue allografts swell as a result of being stored in saline-soaked sponges, resulting in greater pull-through forces during graft passage. Surgeons should bear in mind that allografts swell when stored in saline-soaked gauze and should size their tunnels accordingly.