Trochanteric Femoral Fracture Classification: Relevance of the Fracture Line Angle, a Radiological Study
Daphne van Embden, Mark S Gaston, Lucy A Bailey, A Hamish RW Simpson
Daphne van Embden, Mark S Gaston, Lucy A Bailey, A Hamish RW Simpson, Department of Orthopaedics, University of Edinburgh, Royal Infirmary of Edinburgh, Little France, United Kingdom
Daphne van Embden, Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands
Correspondence to: D. van Embden, MD, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA Leiden, Postbus 9600, 2300 RC Leiden, The Netherlands
Received: November 21, 2014
Revised: December 24, 2014
Accepted: December 28, 2014
Published online: April 23, 2015
AIM: The aim of this study was to evaluate the trochanteric fracture line in terms of the fracture line angle and anatomical location.
METHODS: The preoperative AP radiographs of 164 randomly selected patients with trochanteric fractures were obtained. Measurements were made of: (1) the angle between the mid-shaft femoral axis and the fracture line, (2) the intersection point of the fracture line with the greater trochanter.
RESULTS: An increase in comminution correlated with an increased fracture line angle. The angle of the fracture line relative to the femoral shaft showed a mean of 43º (SD 10), but a range from 19º to 146º.
CONCLUSIONS: This study provides information on the fracture line properties of trochanteric fractures and demonstrates a massive range in fracture line inclination and fragment size. Theoretical Engineering modelling studies have indicated that the measurements described in this study will have a major bearing on fracture stability. These findings can be applied to improve classifications for stable and unstable trochanteric fractures.
© 2015 The Authors. Published by ACT Publishing Group Ltd.
Key Words: Hip fracture classification; Trochanteric fractures; Stability; Hip fracture treatment; Patho-anatomy
van Embden D, Gaston MS, Bailey LA, Simpson AHRW. Trochanteric Femoral Fracture Classification: Relevance of the Fracture Line Angle, A Radiological Study. International Journal of Orthopaedics 2015; 2(2): 250-255 Available from: URL: http://www.ghrnet.org/index.php/ijo/article/view/1146
The trochanteric femoral fracture is still regarded as a major orthopaedic challenge as high rates of failure of fixation occur[1-4].
To optimise fracture fixation, the fracture pattern needs to be understood. A number of classification systems have been developed for trochanteric hip fractures. In 1949 Evans described an anatomical classification based on the number of fragments and whether or not the lesser trochanter is split off as a separate fragment. The AO-classification of Müller is comprehensive but is difficult to apply in detail in the clinical setting. Currently, no single classification system for trochanteric fractures is unanimously accepted because most show low inter- and intra-observer agreement and are therefore considered unreliable[8-11]. Moreover, classification of trochanteric fractures is often considered of low clinical relevance because classifying the fracture does not indicate a prognosis or guide treatment, since both stable and unstable fractures are fixated with a sliding hip screw (SHS) or an intramedullary device (IM). Studies assessing new implants or comparing existing implant types rarely use fracture classification systems despite their possible value.
Reverse type trochanteric fractures with a reversed oblique fracture line have been shown to be a biomechanically different type of fracture and are for this sub type intramedullary nailing has been recommended. In addition, clinical studies suggest that the integrity of the lateral wall is a factor in trochanteric fracture stability which indicates that the site where the fracture line breeches the lateral cortex is important. Therefore, the aim of this study was to evaluate the variation in anatomy of the trochanteric fracture line, in particular its inclination and the integrity of the lateral wall was assessed.
All pre-operative antero-posterior (AP) radiographs of the hip and pelvis and post-operative AP hip radiographs of femoral trochanteric fracture patients treated by SHS at the Royal Infirmary of Edinburgh over a 6 month period were analyzed. The radiographs were not standardized, but the images were obtained in routine clinical practice and therefore the ones available to the treating orthopaedic surgeon.
The radiographs were digitized with a high-resolution flat-bed scanner especially designed to scan radiographs (UMAX™ Powerlook 2100XL). The images were imported into Image J™, a Java image processing program, and parameters were recorded by 2 orthopaedic residents and confirmed by two orthopaedic consultants.
Each image was corrected for magnification error by recording the barrel width of the SHS on the post-operative image. (Dynamic Hip System, DePuy Synthes, Switzerland) The real width of this was known and was not affected by rotation on the radiographs, as it was a cylinder. The use of known SHS dimensions to correct for magnification has been reported previously. Magnification was then corrected for the pre-operative image by measuring the smallest femoral neck width on the post-operative radiographs and the smallest femoral neck width on the preoperative radiograph. Any difference in the preoperative film was corrected throughout all measurements made on this image. Data that needed correction for magnification from eight fractures were excluded from analysis because of poor postoperative radiograph quality.
All fractures were classified according the AO/ASIF classification and Jensen’s modification of the Evans classification(Figure 1). Fractures that showed a sub-trochanteric extension (fracture extending distally outside trochanteric area as defined in the AO/ASIF classification) were excluded.
Measurements of the fractured femur were taken from the pre-operative AP scanned radiograph (Figure 2A and Figure 2B). In particular, the greater trochanter was scrutinized to determine whether the lateral wall was intact and the greater trochanter was measured to assess whether the, fracture line was in the proximal, middle or distal one-third of the greater trochanter (Figure 3). If the fracture was displaced or communited, the fracture line was ascertained from the proximal end of the distal fragment of the fractured femur. If the height of the greater trochanter was difficult to assess due to it being fractured, its height was estimated from the contra-lateral femur on the pelvic radiograph. The area of the greater and lesser trochanter fragments was measured using a pixilation technique (Image J™).
The AP area of the lesser trochanter fragment was calculated and the percentage of the width of the bone that this fracture fragment extended across the femur (the intrusion distance) was measured.
Accuracy was assessed using repeat measurements (N=10), yielding a 3.5 % RSD (relative standard deviation) for the linear measures, 2.2 % RSD for the angular measures and 10.1% for the area measurements.
Data was collected and analysed using statistical computer software SPSS version 14. Statistical significance accepted at p