INTRODUCTION
Intertrochanteric fracture (IT) is one of the most common fractures around the hip especially in the elderly due to trivial trauma.[12] According to location, configuration and stability, IT fractures have been classified.[3] As per the location it can be peritrochantric, intertrochanteric or subtrochanteric fracture. Depending upon the stability, it can be stable or unstable fractures. These fractures are further divided into subtypes. It is important for a treating orthopaedic surgeon to have in depth knowledge of relevant anatomy and classification of such fractures for better management. This article will highlight the relevant anatomy of intertrochanteric area and will provide an overview of various classifications.
RELEVANT ANATOMY
Bony Anatomy[4]
Bony configuration of proximal femur with hip joint is to be considered while dealing with IT Fractures. One must know various anthropometric parameters and other notable points which are (i) The neck shaft angle is 130 (+/- 7) degrees (ii) Anteversion 10 (+/- 7) degrees (iii) Intertrochanteric area exists between greater and lesser trochanters (iv) Average radius of curvature of femur is 114–120 cm which decreases with age and is major cause of increased bowing in elderly (v) Calcar femorale is vertical wall of dense bone that extends from posteromedial aspect of femoral shaft to posterior portion of femoral neck. Bony anatomy helps to know the level of involvement of intertrochanteric fracture which ultimately helps to determine stable versus unstable fracture patterns [Figure 1].
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Figure 1: Bony anatomy of proximal femur on which the pertrochanteric (Blue line)and intertrochanteric (Red line) fracture lines are shown
Muscular Anatomy[45]
One must remember the deforming forces acting on proximal and distal segment of IT fracture. On proximal segment flexion, external rotation and abduction are noted due to deforming forces of flexors (iliopsoas, sartorius, rectus femoris and pectineus), external rotators (piriformis, superior gemellus, obturator internus, inferior gemellus and quadratus femoris) and abdutors (gluteus maximus, gluteus medius, gluteus minimus and tensor fascia lata) of hip. Main deforming forces on distal segment is adduction and shortening due to pulling effect of adductors (adductor longus, adductor brevis, adductor magnus and gracilis) leading to overall varus alignment.[4]
Blood supply[45]
Intertrochanteric area has rich collateral circulation which reduces risk of non-union. It receives supply from 3 sources (i) trochanteric anastomosis (ascending branch of medial circumflex femoral artery (MFCA), ascending branch of lateral circumflex femoral artery (LFCA), deep branch of superior gluteal artery and inferior gluteal artery) (ii) transverse branch of LFCA and MFCA and (iii) periosteum and surrounding muscles
Biomechanics[6]
Ward’s triangle is area of lowest Bone mineral density (BMD) in femoral neck bordered by 3 main compressive/tensile trabeculae (i) primary compressive trabeculae which extends from medial femoral head along calcar and excellent support to proximal femur. It is vertically oriented with a triangular configuration(ii) Principal tensile trabeculae which forms an arc through the superior cortex of the femoral head and neck. It extends from greater trochanter to inferior aspect of femoral head below fovea (iii) Secondary compressive trabeculae WHICH HAS fan-like configuration crossing from greater trochanter to lesser and also comprises calcar.
CLASSIFICATION
There are several classification system for trochanteric fractures proposed by authors over last 7 decades but most popular is AO / OTA (Muller) Classification (1990).[7] According to their evolution we can divide them in two groups (i) Older Classifications (i.e. before AO / OTA) e.g. Evans classification (1949), Bohler’s Classification (1936), Boyd and Griffin Classification (1949), Kyle and Gustilo Classification (1979), Tronzo Classification (1973), J.C. Scott’s Classification, Murray And Frew (1949), Jensen and Michaelson Classification (1975), Hafner’s Classification, W.K. Massie’s Classification (1963) (ii) Modern Classification i.e. A.O. and O.T.A. (Muller) Classification (1990) and G.S. Kulkarni et al. All these classifications have their own importance. Out of all we will discuss some popular classifications with their clinical relevance.
Evans classification
In 1949, Evans[8] published his classification on intertrochanteric (IT) fractures [Table 1] according to which IT fractures are classified into Stable and Unstable fractures [Figure 2a]. Stable fractures have intact or minimally communited posteriomedial cortex, while Unstable fracture has greater communition of posteriomedial cortex. Unstable fractures after reduction can be converted to stable fracture if the posteriomedial cortex opposition can be achieved. Reverse oblique pattern was considered inheritably unstable fracture as distal femur has tendency to drift medially due adductor pull.
Table 1: Boyd and Griffin (1949) classification with clinical relevance
Figure 2: Diagrammatic representation of Evan’s classification [a], it’s Jensen’s modification [b] and Kyle’s classification [c]
Jensen’s modification of the evans classification
Jansen (1975)[9] later modified Evans classification into three groups depending upon the number of fragments [Table 1]. This classification reduced the number of types from 6 to 5 by including the extremely rare fracture with a reversed oblique fracture line and large greater trochanter fragment into Type 3. Modification of the Evans system offers the best prediction of the possibility of obtaining reliable anatomical reduction and the risk of secondary fracture dislocation [Figure 2b].
Kyle’s classification
Kyle’s[10] classified IT Fractures into 4 types [Figure 2c]. Type IV is the most difficult type of fracture to fix because of the great forces imposed by muscle forces and weight bearing on the subtrochanteric region of the femur. Addition of new variant [Table 2] i.e. extension of intertrochanteric fracture in neck has clinical Importance:
Table 2: Tronzo’s classification with clinical relevance
Boyd and griffin classification
Boyd and Griffin (1949)[11] were first to mention instability in both coronal and sagittal plane. This classification, included fractures from the extracapsular part of the neck to a point 5 cm distal to the lesser trochanter [Figure 3a]. It is classified into 4 groups and each group has clinical relevance [Table 3].
Figure 3: Diagrammatic representation of Boyd and Graffin classification [a], Tranzo’s classification [b] and AO / OTA classification [c]
Table 3: Evan’s classification showing its types, stability character and description. Also showing Jensen’s modification of Evan’s classification
Tronzo’s classification
Tronzo’s (1973)[12] incorporated Boyds and Griffin two plane instability in classification [Figure 3b]. It is classified into 4 groups and each group has clinical relevance [Table 4].
Table 4: Kyle’s classification showing its types, stability character and description
Other older classifications
The Ramadier’s (1966),[13] Decoulx and Lavarde’s (1969),[14] Ender’s (1970)[15] and the Briot (1980)[16] classification are other older classification system for Trochanteric Fractures. They were very important at times but with evolution of AO/OTA Classification, they are hardly been used.
A.O. / OTA (Muller) classification
The classification system devised by Muller and the A.O. group is extremely comprehensive and complete.[7] Each region of the skeleton is assigned an alpha- numerical value and is further classified into a type and a sub group.
Types and subtypes of AO / OTA Classification
According to AO/OTA alphanumeric classification intertrochanteric fractures have been assigned as ‘Type 31A’ (Bone = femur = 3, Segment = proximal = 1, Site = trochanter = A which has 3 types = A1, A2, A3). Type - A1 is simple (two-part) fractures, with the typical oblique fracture line extending from the greater trochanter to the medial cortex; the lateral cortex of the greater trochanter remains intact. Type - A2 fractures are comminuted with a posteromedial fragment; the lateral cortex of the greater trochanter, however, remains intact. Fractures in this group are generally unstable, depending on the size of the medial fragment. Type - A3 fractures are those in which the fracture line extends across both the medial and lateral cortices; this group includes the reverse obliquity pattern or subtrochanteric extensions. Each type (A1, A2, A3) is then further classified into three subgroups [Table 5] [Figure 3c].
Table 5: AO / OTA classification showing its types, stability character and description
Clinical importance AO/OTA Classification
This helps in predicting prognosis and suggests treatment for the entire spectrum of IT fractures. Fractures A1.1 through A2.1 are commonly described as stable, and fractures A2.2 through A3.3 usually are unstable. Generally, the Evans-Jensen type I fracture is represented by the 31-A1 group. Evans-Jensen type II fractures are in the 31-A2 group. The so-called reverse obliquity intertrochanteric fracture is in group 31-A3. It’s alphanumeric and standardized format make this system useful, particularly for research and documentation. As per this classification, those who has criteria of instability (see introduction) needs special attention.
Dr G. S. Kulkarni et al. classification
Dr G.S. Kulkarni et al. published his new classification in 2006 for intertrochanteric fractures.[17] His classification is based on AO / OTA and Evan-Jansen classification and added new varieties of intertrochanteric fractures described by Gotfried and Kyle.[78101718] This classification is very helpful while deciding the implant for fixation. according to the fracture type. It is classified into 3 types (with 3 more subtypes in each types) each types has impact on decision making on choice of implant [Table 6] [Figure 4].
Table 6: Classification by Kulkarni et.al. showing its types, stability character and description
Figure 4: Diagrammatic representation of Classification proposed by Kulkarni et al. showing different types of stable [a], unstable [b] and very unstable [c] trochanteric fractures
CONCLUSION
Intertrochanteric fractures are challenging to manage not only because of its peculiar anatomy but due to varieties of fracture patterns also. Majority of older classifications (e.g. Tronzo’s classification) are found to be less reliable and have hardly any use in clinical practice. The modern classification proposed by AO/OTA group has good reliability but subgroup assessment has poor reliability. In spite, it is very useful in deciding management, record keeping and research. The latest classification proposed by Dr G.S. Kulkarni et al. is found to be simple and easy to apply in practice as it describes about not only the character and stability of about fracture but also the preferred implant to fix them. Since there is no consensus on the best classification of intertrochanteric fractures, it is important for a treating orthopaedic surgeon to have in depth knowledge of relevant anatomy and various classification.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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