OTA 2002 Posters

Basocervical Compared with Intertrochanteric Fractures: An Analysis of Radiographic and Functional Outcomes

Brian W. Su, BSE; Themistocles S. Protopsaltis, MD; Marshall A. Kuremsky, BA; C. B. Chapman; S. M. Sinicropi; Melvin P. Rosenwasser, MD; Columbia Presbyterian Medical Center and the New York Orthopaedic Hospital, New York, New York, USA

Purpose: There are few studies that address basocervical fractures as separate entities because of their inclusion in the broader category of either high intertrochanteric (IT) fractures or low neck fractures. Biomechanical studies of intertrochanteric fractures have shown that increasing the fracture angle increases the force absorbed by the implanted hardware. The fracture angle and subsequent varus moment is greater in basocervical fractures than IT fractures, therefore predisposing the implant and fracture sites to a higher load of force. The treatment of basocervical fractures is similar to that of intertrochanteric fractures, namely rigid internal fixation with a sliding hip screw (SHS). Some authors advocate use of an additional derotational screw (DRS) with the intention of gaining rotational control of the proximal fragment during hip screw insertion. However, biomechanical studies have failed to show a difference between the SHS plus cancellous screw and the SHS alone in resisting either axial load or torsional stresses. We examined the results of the treatment of basocervical fractures with radiographic parameters (compression of SHS) and clinical outcomes. The use of a DRS and the outcomes of basocervical fractures compared with IT fractures were considered.

Methods: The records of 69 patients with an average age of 80 years were reviewed (38 basocervical and 31 IT fractures). Intertrochanteric fractures were divided into unstable and stable based on a CT grading system developed at our institution. Baseline pre-fracture ambulatory status was obtained from the patient or from the medical record. Thirty months after surgery, SF-36 scores were collected from 55 patients. Fracture Recovery Scores (FRS) were collected from 35 of the patients at an average of 28 months after surgery. In the majority of patients, a SHS was used to reduce the fracture. Collapse of the SHS was measured radiographically as the distance of screw protrusion past the screw barrel and reported as a percent of total screw length. Patients were grouped according to the severity of lag screw collapse, stratified as greater or less than 10% collapse. A Student's t-test was used to compare the clinical outcomes (SF-36 and FRS) among the following groups: basocervical to IT fractures, basocervical to stable IT fractures, basocervical to unstable IT fractures, and basocervical fractures with and without a DRS. A chi-square test was used to compare collapse severity between groups. Pearson's correlation coefficient was used to correlate percent of collapse with clinical outcome.

Results: Patients with basocervical fractures had a greater SF-36 pain score (less pain) than those who had unstable IT fractures (P = 0.03). There were no other statistically significant differences in SF-36 scores between basocervical and IT fractures. FRS scores were generally lower in the basocervical group when compared with IT (54.6 vs. 63.4, P = 0.04); however, this difference was not statistically significant. The average FRS score for basocervical patients was 54.6 and the average for all IT patients was 63.4 (P = 0.4). The number of patients with greater than 10% collapse of the SHS was statistically larger in the basocervical group when compared with all IT patients (P = 0.034) and to IT patients with stable fractures (P = 0.006). Among basocervical patients, 67.7% had greater than 10% collapse as opposed to 52.1% of all IT patients and 28.6 % of patients with stable IT fractures. There was no difference in collapse severity when basocervical patients were compared with the subset of IT patients with unstable fractures (P = 0.54). There were no differences in either collapse (P = 0.33) or clinical outcomes (SF-36 and FRS) when basocervical fractures treated with SHS alone were compared with those treated with the addition of a DRS.

Conclusions: The results of this study demonstrate that basocervical fractures tend to collapse more than do stable IT fractures. The significantly greater magnitude of collapse supports the biomechanical premise that basocervical fractures are inherently more unstable than IT fractures. However, there were no differences in functional outcome between basocervical and IT fractures. In fact, the sliding in basocervical fractures was not statistically different from that of unstable IT fractures; in addition, both of these groups had similar clinical outcomes. The data in this study support the conclusion that the biomechanical instability of basocervical fractures does not lend itself to a clinically significant reduction in functional outcome. The use of an additional DRS does not affect lag screw collapse or functional outcome. This finding supports those of the biomechanical studies that show that the addition of a cancellous screw does not improve the loads supported by the implant. On the basis of the results of this study, the DRS may be used to stabilize the proximal fragment during placement of the SHS but serves no function in improving stability or clinical outcome after placement of the SHS.