Fri., 10/15/10 Geriatrics, Paper #39, 10:00 am OTA-2010
Radiographic Evaluation of Intertrochanteric Hip Fractures Treated With or Without Distal Interlocking in a Cephalomedullary Construct
George Karl Van Osten, III, MD1; Mark A. Lee, MD2;
1North Mississippi Medical Center, Tupelo, Mississippi, USA
2University of California, Davis, Sacramento, California, USA
Purpose: This study was designed to identify any difference with regard to classically accepted radiographic parameters for construct failure between intertrochanteric (IT) fractures treated with or without distal interlocking in a long cephalomedullary (CM) component. The hypothesis was that fractures treated without distal interlocking would show radiographic evidence of proximal cutout and construct failure.
Methods: This study is an IRB-approved, single institution, retrospective radiographic review. 150 total patients with IT hip fractures (OTA 31A) treated with a CM construct were identified in a previously compiled institutional database. Inclusion criteria were OTA 31 A1, A2, A3 fracture; treatment with long CM construct ± distal interlocking bolt; adequate radiographic documentation; and absence of ipsilateral injury. 104 total cases were selected as meeting these criteria, with 57 distally unlocked and 47 distally locked. Fractures were further subclassified as stable or unstable by the principal investigator using the OTA classification scheme and original injury radiographs. Three separate categories were analyzed: overall (N = 104), locked (N = 47) versus nonlocked (N = 57); stable (N = 28), locked (N = 12) versus nonlocked (N = 16); and unstable (N = 76), locked (N = 35) versus nonlocked (N = 41). All radiographic measurements were made by the principal investigator using a digital radiography system, and a conversion factor based upon known implant diameter was used for neutralization of magnification error. Measured radiographic parameters for implant failure were calculated based on an AP hip or pelvis view and included: (1) lag screw to femoral head medial distance (Δm), (2) lag screw to femoral head vertical distance (Δh), and (3) construct neck-shaft angle (Δa). Mean differences (Δm, Δh, Δa) from immediate postoperative radiograph to final follow-up radiograph between locked and unlocked CM constructs were calculated for each group (overall, stable, unstable). Statistical analysis was performed using a Student t test technique for identification of significance.
Results: In the overall group (N = 104), locked (N = 47) exhibited Δm 0.231, Δh 0.493, and Δa 3.32; unlocked (N = 57) had Δm 0.386, Δh 0.296, and Δa 1.97. In the stable group (N = 28), locked (N = 12) had Δm –0.452 (increased mean distance), Δh 0.450, and Δa 2.25; unlocked (N = 16) exhibited Δm 0.458, Δh 0.631, and Δa 0.31. In the unstable group (N = 76), locked (N = 35) showed Δm 0.467, Δh 0.508, and Δa 3.69; unlocked (N = 41) data were Δm 0.358, Δh 0.166, and Δa 2.61. The stable group showed a mathematically significant difference (P = 0.0286) with regard to medial distance, yet this represents a trend counterintuitive to predicted failure mechanisms. There was no other significant difference calculated.
Conclusion: There is no evidence of an increased incidence of failure, with regard to classically designed radiographic parameters, between IT fractures treated with or without distal interlocking in a long CM construct.
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• The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an “off label” use). ◆FDA information not available at time of printing. Δ OTA Grant.