The Language of Studies Lecture 8 Secs. 3.1 – 3.3 Wed, Jan 26, 2005

Observation vs. Experimentation Observational study – A study in which the subjects are not manipulated or controlled in any way, but simply observed. Observational study – A study in which the subjects are not manipulated or controlled in any way, but simply observed. Designed experiment – A study in which the researchers actively impose some treatment on the subjects and observe the response. Designed experiment – A study in which the researchers actively impose some treatment on the subjects and observe the response.

Think About It Think About It, p Think About It, p. 131.

Explanatory and Response Variables Response variable – The variable that measures the outcome. It is believed to be affected by the explanatory variable. Response variable – The variable that measures the outcome. It is believed to be affected by the explanatory variable. Explanatory variable – The variable or factor that is thought to explain the observed outcome. It is believed to affect the response variable. Explanatory variable – The variable or factor that is thought to explain the observed outcome. It is believed to affect the response variable.

Let’s Do It! Example 3.1, p. 132 – Explanatory Variable and Response Variable. Example 3.1, p. 132 – Explanatory Variable and Response Variable. Let’s do it! 3.1, p. 134 – Explanatory Variable versus Response Variable. Let’s do it! 3.1, p. 134 – Explanatory Variable versus Response Variable. Let’s do it! 3.2, p. 134 – Food Myths. Let’s do it! 3.2, p. 134 – Food Myths.

Levels and Treatments The explanatory variable is typically denoted X. The explanatory variable is typically denoted X. The response variable is typically denoted Y. The response variable is typically denoted Y. Values of the explanatory variable are called levels. Values of the explanatory variable are called levels. If there is more than one explanatory variable, then combinations of their values are called treatments. If there is more than one explanatory variable, then combinations of their values are called treatments.

Confound It! Confounding variable – A variable whose effect cannot be separated from the effect of the explanatory variable. Confounding variable – A variable whose effect cannot be separated from the effect of the explanatory variable. If a study has one or more confounding variables, then the researchers cannot attribute changes in the response variable to any one explanatory variable. If a study has one or more confounding variables, then the researchers cannot attribute changes in the response variable to any one explanatory variable. Normally, researchers try to control for all confounding variable (that they can think of). Normally, researchers try to control for all confounding variable (that they can think of).

Example Example 3.3, p. 135 – Treating Multiple Sclerosis with Protein. Example 3.3, p. 135 – Treating Multiple Sclerosis with Protein. Let’s Do It! 3.3, p. 136 – Invasive versus noninvasive Cancer Treatments. Let’s Do It! 3.3, p. 136 – Invasive versus noninvasive Cancer Treatments. The Role of Cyclooxygenase-2 Inhibitors in Fusion Rates of Hindfoot Arthrodesis The Role of Cyclooxygenase-2 Inhibitors in Fusion Rates of Hindfoot Arthrodesis The Role of Cyclooxygenase-2 Inhibitors in Fusion Rates of Hindfoot Arthrodesis The Role of Cyclooxygenase-2 Inhibitors in Fusion Rates of Hindfoot Arthrodesis

The Role of Cyclooxygenase-2 Hypotheses/Purpose: Recent research demonstrates the effectiveness of cyclooxygenase-2 (COX-2) inhibitors in controlling postoperative pain. These reports have shown that COX-2 inhibitors delay bone fracture healing in animal models. Our hypothesis states that short-term use of COX-2 inhibitors can be utilized for postoperative pain management without impact on fusion rates in patients undergoing subtalar and ankle arthrodesis. Hypotheses/Purpose: Recent research demonstrates the effectiveness of cyclooxygenase-2 (COX-2) inhibitors in controlling postoperative pain. These reports have shown that COX-2 inhibitors delay bone fracture healing in animal models. Our hypothesis states that short-term use of COX-2 inhibitors can be utilized for postoperative pain management without impact on fusion rates in patients undergoing subtalar and ankle arthrodesis.

The Role of Cyclooxygenase-2 Conclusions/Significance: The use of COX-2 inhibitors for postoperative pain control has no affect on the rate of fusion for patients undergoing subtalar and ankle arthrodesis. The overall nonunion rate does not appear to be affected by use of COX-2 inhibitor drugs. In addition, the time to union for patients who received COX-2 inhibitors was less than those who did not receive COX-2 inhibitors, but this was not statistically significant. Conclusions/Significance: The use of COX-2 inhibitors for postoperative pain control has no affect on the rate of fusion for patients undergoing subtalar and ankle arthrodesis. The overall nonunion rate does not appear to be affected by use of COX-2 inhibitor drugs. In addition, the time to union for patients who received COX-2 inhibitors was less than those who did not receive COX-2 inhibitors, but this was not statistically significant.

The Role of Cyclooxygenase-2 This study suggests that despite evidence that COX-2 inhibitors may inhibit bone healing at the cellular level, their use in the short-term postoperative setting does not affect overall ankle arthrodesis rates. Short-term use of these medications appears to not cause significant clinical difficulties and is therefore not contraindicated in orthopedic procedures. This study suggests that despite evidence that COX-2 inhibitors may inhibit bone healing at the cellular level, their use in the short-term postoperative setting does not affect overall ankle arthrodesis rates. Short-term use of these medications appears to not cause significant clinical difficulties and is therefore not contraindicated in orthopedic procedures.

The Role of Cyclooxygenase-2 Summary of Methods/Results: 200 consecutive patients undergoing subtalar and ankle arthrodesis were reviewed. Patients underwent the procedure by either of the senior two authors between 1999 and The surgical techniques were performed in similar manner minimizing variability. One group of patients received COX-2 inhibitor medications postoperatively. This group received the recommended dose for post- operative pain control for five days after surgery. The other group did not receive this medication. Summary of Methods/Results: 200 consecutive patients undergoing subtalar and ankle arthrodesis were reviewed. Patients underwent the procedure by either of the senior two authors between 1999 and The surgical techniques were performed in similar manner minimizing variability. One group of patients received COX-2 inhibitor medications postoperatively. This group received the recommended dose for post- operative pain control for five days after surgery. The other group did not receive this medication.

The Role of Cyclooxygenase-2 Records were reviewed to evaluate for time immobilized, time to full weight bearing, time to radiographic fusion and clinical union. Radiographs were reviewed to evaluate for radiographic union. Reviewers were blinded as to which group did and did not receive COX- 2 inhibitor medications. Records were reviewed to evaluate for time immobilized, time to full weight bearing, time to radiographic fusion and clinical union. Radiographs were reviewed to evaluate for radiographic union. Reviewers were blinded as to which group did and did not receive COX- 2 inhibitor medications.

The Role of Cyclooxygenase-2 Time to union and nonunion rates were established for each group to determine if there was a significant difference between groups receiving COX-2 inhibitor medications for acute pain indications. A nonunion was determined if patients were clinically symptomatic with pain or motion at the attempted arthrodesis site. A nonunion was also determined if bridging trabeculae were not apparent across the arthrodesis site on plain radiographs. Time to union and nonunion rates were established for each group to determine if there was a significant difference between groups receiving COX-2 inhibitor medications for acute pain indications. A nonunion was determined if patients were clinically symptomatic with pain or motion at the attempted arthrodesis site. A nonunion was also determined if bridging trabeculae were not apparent across the arthrodesis site on plain radiographs.

The Role of Cyclooxygenase-2 The group that received the COX-2 inhibitor medication had an overall nonunion rate of 11.2%. For all patients that achieved arthrodesis, average time to union was 89.8 days for this group. When separated by arthrodesis site, the majority of nonunions were failed ankle arthrodesis (96%). In the group that did not receive a COX-2 inhibitor postoperatively, the overall nonunion rate was 12.4%, again with failed ankle arthrodesis accounting for the majority of the nonunions (97%). Time to union in this group averaged 93.4 days. The group that received the COX-2 inhibitor medication had an overall nonunion rate of 11.2%. For all patients that achieved arthrodesis, average time to union was 89.8 days for this group. When separated by arthrodesis site, the majority of nonunions were failed ankle arthrodesis (96%). In the group that did not receive a COX-2 inhibitor postoperatively, the overall nonunion rate was 12.4%, again with failed ankle arthrodesis accounting for the majority of the nonunions (97%). Time to union in this group averaged 93.4 days.

The Role of Cyclooxygenase-2 The time to union was shorter in the group that received COX-2 inhibitors, but this was not statistically significant. The overall nonunion rate was lower in the group that received COX-2 inhibitors, but this, too, was not statistically significant. The time to union was shorter in the group that received COX-2 inhibitors, but this was not statistically significant. The overall nonunion rate was lower in the group that received COX-2 inhibitors, but this, too, was not statistically significant.

Do Explanatory Variables Explain? A study cannot prove that variations in the explanatory variable really were the cause of variations in the response variable. A study cannot prove that variations in the explanatory variable really were the cause of variations in the response variable. The study can only give evidence supporting that belief. The study can only give evidence supporting that belief. It may be the case that there is a third variable that is affecting both the explanatory and response variables. It may be the case that there is a third variable that is affecting both the explanatory and response variables. It may be conceivable that the “response” variable affected the “explanatory” variable! It may be conceivable that the “response” variable affected the “explanatory” variable!