Session I - Hip Fractures

*Does Intraoperative Tip-Apex Distance (TAD) Estimation Reduce the Rate of Cut Out of Intertrochanteric Hip Fracture Fixation?

Michael R. Baumgaertner, MD, Brian D. Solberg, MD, Carl Rykoski

Yale University School of Medicine, New Haven, CT

In the Spring of 1993, we presented to our institution a new way to describe the position of the screw in the femoral head (TAD) that was highly predictive for cut out [1]. The purpose of this follow up study was to see if awareness of this technique would lead to a reduction of cut out failures at our institution.

Methods: From a prospective evaluation of 146 consecutive intertrochanteric hip fractures treated between April, 1993 and February, 1995 we included 118 patients with complete records and a three month minimum follow up (study group). These patients were compared to the original TAD study group (198 cases) that was drawn from consecutive patients treated from 1988 through 1992 (control group ). Variables considered included the patient's age, the stability of the fracture, the quality of the reduction achieved, the type and angle of implant used, and the position of the screw measured by the tip-apex distance as well as the zone technique, and the presence or absence of cut out of the implant from the proximal femur.

Results: The TAD for the control group averaged 25 (range 9-63) millimeters and the rate of cut out was 8%. The study group had an average TAD of 20 (range 6-40) millimeters and there were no cut outs (0%). Both differences were statistically significant (p=0.0001 and p=0.0015, respectively). Central/central zone position increased from 44% in the control group to 65% in the study group (p=0.0002). Although there was no significant difference in the frequency of unstable fractures between groups, the study group patients were five years older, on average, than the control group (81 versus 76 years, p=0.001). There was a significantly reduced use of 150° implants in the study group (12% vs 1%, p=0.0003).

Discussion: Studies that rely on a historical control can be confounded by many variables. Although this control group was nearly contemporary with the study group, the results could have been influenced by a shift away from 150° devices and the effects of surgeon "turnover" at our institution. Additionally, the "Hawthorne" effect of improved performance when the subject knows that he/she is being monitored might have had some effect.

Conclusion: A significant reduction of the cut out rate of fixation for intertrochanteric fractures occurred at our institution after surgeons were made aware of the local failure rate and were introduced to the Tip-Apex Distance. In an era of product driven research where many studies compare different devices, this report demonstrates that improved surgical technique remains perhaps the most important variable in surgical outcome.

1. Baumgaertner, M.R., et al. The Value of the Tip-Apex Distance in Predicting Failure of Fixation of Peritrochanteric Fractures of the Hip. Journal of Bone & Joint Surgery - American Volume, 1995. 77(7) p. 1058-64.