Unstable trochanteric femoral fractures: extramedullary or intramedullary fixation

Abstract

For operative treatment of unstable trochanteric fractures two options exist: extramedullary or intramedullary stabilisation. A review of 18 international papers that compared two different treatment methods for trochanteric fractures, in prospective randomised clinical trials, is presented. In view of the overall results, routine use of intramedullary fixation devices is not to be recommended for stable trochanteric fractures. For these fractures one of the sliding hip screw systems provides a safe and simple alternative. For unstable fractures intramedullary implants are (biomechanically) superior. The review shows that clinical advantages of both treatment methods are suggested and advocated, but still remain to be demonstrated on evidence base.

Introduction

Trochanteric fractures pose a challenge to the trauma surgeon in many ways: the nomenclature is often confusing, uniform classification is difficult because of the use of different classification systems, and the various treatment options are diverse, not evidence based and without consensus. An unstable trochanteric fracture adds to this, the challenge of a biomechanically very unfavourable fracture. A good treatment plan therefore starts with proper fracture classification.

Several trochanteric fracture classifications exist:21., 27., 33., 39., 40. the most basic and rational is to divide trochanteric fractures into stable or unstable fracture patterns.21., 27., 45., 55. In general, instability is determined by the presence of a zone of comminution of the medial cortex30., 34., 38., 39., 47., 50. and posterolateral instability.⁵³ Nowadays, the most commonly used classification is that of the AO/ASIF group (Fig. 1).⁴⁰ This classification has a good reproducibility⁴⁸ as it basically divides the trochanteric fractures (type 31A) into three groups: A1 fractures (stable pertrochanteric fractures), A2 fractures (unstable pertrochanteric fractures with medial comminution including a fractured lesser trochanter) and A3 fractures (unstable intertrochanteric fractures with or without medial comminution). The instability of A2 and A3 fractures is created when one, or both, of the cortices is comminuted in a way that progressive (varus) displacement will follow unless intrinsic stability is provided by means of a stabilising implant. The forces that tend to displace the fracture must be neutralised by the implant. Theoretically, these forces are best transmitted through an implant close to the centre of axial loading, resulting in a shorter lever arm and a lower bending moment. The implant should, together with the fracture fragments, be able to bear full load. It should allow controlled fracture impaction (a gliding mechanism) in order to facilitate impaction and compression, therewith increasing stability. The risk of the implant cutting out in osteoporotic bone should be as small as possible and the periosteal blood supply should be disturbed as little as possible.⁵⁷ Together, these demands stress the importance of an adequate interpretation of what may be expected (biomechanically) from a fracture–implant construct. The choice of implant depends on the degree of instability: the more unstable the fracture, the more stability is required of the method of fixation.

In general, for treatment of unstable trochanteric fractures two options exist: extramedullary or intramedullary stabilisation. The extramedullary option (Fig. 2) comprises any kind of sliding hip screw (SHS) connected to a plate at the lateral cortex: for instance the Dynamic Hip Screw^® (DHS; Mathys Medical) or the Compression Hip Screw^® (CHS; Smith and Nephew). The indicated advantages consist of the possibility of direct open fracture reduction and a relatively simple surgical technique, which is safe and very forgiving. The intramedullary method basically exists of a percutaneously inserted nail connected to one or more neck screws sliding through the nail. Examples of the intramedullary devices are the Gamma Nail^® (Stryker Howmedica), the Intramedullary Hip Screw^® (IMHS; Smith and Nephew) and the Proximal Femoral Nail^® (PFN; Synthes), as shown in Fig. 3. The minimally invasive intramedullary technique is said to be associated with less blood loss and a lower infection rate, and the implant construction should allow direct full weight bearing because of its favourable biomechanical properties. Results of randomised clinical studies comparing the results of intramedullary and extramedullary fixation techniques for unstable trochanteric fractures are inconsistent and rare. Most comparative studies focus on treatment of stable trochanteric fracture types.3., 8., 31., 32., 41., 42., 44. We performed a literature review in an attempt to find consensus about the best treatment strategy for unstable trochanteric femoral fractures.