Pertrochanteric (Intertrochanteric) Fractures

Introduction

The pertrochanteric fracture — sometimes called the intertrochanteric fracture — is the extracapsular cousin of the femoral neck fracture and shares the epidemiology of the fragility hip fracture: elderly osteoporotic patient, low-energy mechanism, substantial mortality, and the requirement for prompt operative intervention to restore mobility. The two principal anatomical and clinical distinctions from femoral neck fractures are fundamental to management. First, the pertrochanteric fracture is extracapsular, with the fracture line outside the hip joint capsule; the blood supply to the femoral head is therefore largely preserved, and avascular necrosis is uncommon (in contrast to the high AVN rates of displaced femoral neck fractures). Second, the healing potential is favorable because the fracture is through cancellous trochanteric bone with abundant vascular supply, in contrast to the watershed neck region; nonunion is uncommon. The treatment is therefore almost always internal fixation rather than arthroplasty, with the central management question being the choice of construct rather than fixation versus replacement. This chapter, drawing principally on Rockwood and Green’s Fractures in Adults, AO Principles of Fracture Management, Apley & Solomon’s, and Miller’s Review of Orthopaedics, addresses the contemporary management of pertrochanteric fractures.

Surgical Anatomy

The pertrochanteric region extends from the femoral neck-shaft junction (the intertrochanteric line anteriorly and intertrochanteric crest posteriorly) to a horizontal level approximately 5 cm distal to the lesser trochanter. The region is bounded superiorly by the greater trochanter (insertion of the gluteus medius and minimus, with the piriformis fossa as the insertion of the piriformis posteriorly), inferiorly by the proximal femoral shaft, and includes the lesser trochanter medially (insertion of the iliopsoas tendon). The calcar femorale, a vertically oriented condensation of bone deep within the medial proximal femur extending from the medial cortex into the lesser trochanter region, is a critical structural element that determines fracture stability when intact. The blood supply to the proximal femur is principally through the medial and lateral femoral circumflex arteries, both branches of the deep femoral. The branches that contribute to the pertrochanteric region include direct branches into the cancellous trochanteric bone, with abundant supply that supports rapid healing. The principal deforming forces on the pertrochanteric fracture include the abductor pull on the greater trochanter (producing abduction and external rotation of the proximal fragment), the iliopsoas pull on the lesser trochanter fragment (medializing displacement of this fragment when separated, with consequent loss of medial cortical buttress), and the adductor pull on the femoral shaft (producing adduction of the shaft and varus angulation at the fracture).

Classification

Several classification systems are in widespread use. The two most clinically important are the AO/OTA classification and the Boyd-Griffin classification, with the Evans classification providing an additional historical reference. AO/OTA Classification (31-A) The AO/OTA classification (region 31-A) is the contemporary standard: 31-A1 (simple two-part): Two-part fracture with a single fracture line through the intertrochanteric region. - A1.1: Along the intertrochanteric line. - A1.2: Through the greater trochanter. - A1.3: Below the lesser trochanter. 31-A2 (multifragmentary with lesser trochanter involvement): Three-part fracture with a separate lesser trochanter fragment. - A2.1: With one intermediate fragment. - A2.2: With several intermediate fragments. - A2.3: With fracture extending more than 1 cm distal to the lesser trochanter. 31-A3 (reverse oblique and transverse): Fracture line running from medial proximal to lateral distal (the “reverse oblique” pattern) or transverse intertrochanteric pattern, or with subtrochanteric extension. - A3.1: Simple oblique. - A3.2: Simple transverse. - A3.3: Multifragmentary. The 31-A3 patterns are biomechanically distinct because the shearing forces on the fracture line are not reduced by axial weight bearing as they are in the typical intertrochanteric fracture; the choice of implant for these patterns is fundamentally different (favoring intramedullary nailing or fixed-angle plate fixation rather than dynamic compression).

Stability and the Boyd-Griffin / Evans Classifications The Boyd-Griffin classification (1949) and the Evans classification (1949, modified by Jensen 1980) organize fractures by stability. The principal determinant of stability is the integrity of the medial cortex (the medial buttress, including the lesser trochanter) and the presence of comminution. A stable fracture has an intact or reconstructible medial cortex after reduction; an unstable fracture has medial comminution that prevents direct cortical contact after reduction, with the result that load transmission occurs through the implant rather than through bone-to-bone contact. The Evans classification (modified Jensen) divides fractures into types I and II based on direction of fracture line, with subdivision by stability. The principal practical distinction remains stable versus unstable, with stability determined by the medial cortex integrity. The clinical importance of the stability assessment is that stable fractures can heal with substantial controlled collapse along the implant (the basis of sliding hip screw fixation, which permits controlled compression as the fracture site comes into apposition); unstable fractures cannot rely on bone-to-bone contact and require constructs that resist loading without excessive shortening or varus collapse.

Clinical Assessment

The clinical presentation closely resembles that of the femoral neck fracture: elderly patient with low-energy fall, hip pain, inability to bear weight, leg held in external rotation and shortening. The external rotation tends to be more pronounced in pertrochanteric fractures than in femoral neck fractures (often 90 degrees, “foot lying flat on the bed”) because the absence of capsular containment permits more rotation of the distal fragment. Ecchymosis over the greater trochanter, lateral thigh, and proximal thigh is more common than in capsular femoral neck fractures. The assessment otherwise parallels that of the femoral neck fracture: mechanism, comorbidities, functional baseline, cognitive status, and consideration of underlying medical contributors to the fall. Imaging is by AP pelvis and cross-table lateral radiographs of the affected hip. CT is occasionally useful for assessing fracture morphology in complex patterns being considered for atypical fixation.

Treatment Principles

Non-Operative Management Non-operative management of the pertrochanteric fracture is reserved for the non- ambulatory or terminally ill patient in whom operative intervention is contraindicated. The pain control allows bed-to-chair transfers and nursing care; the fracture heals in some position. Mortality in this group is very high because of the cascade of immobilization complications (pneumonia, decubitus ulcers, VTE). Operative Management — The General Principle Operative management is indicated in virtually all medically appropriate patients. The principles of operative fixation are: anatomical or near-anatomical reduction (with restoration of the neck-shaft angle and rotation), stable internal fixation with implant choice based on fracture pattern, early mobilization with weight bearing as tolerated, and prompt surgery within 24 to 48 hours of presentation (with evidence supporting this from multiple studies, including the NICE guidelines).

Sliding Hip Screw (Dynamic Hip Screw, DHS)

Principle and Construct The sliding hip screw (SHS, dynamic hip screw, DHS) is the historical workhorse construct for stable pertrochanteric fractures. The construct consists of a lag screw placed centrally in the femoral neck, engaging the femoral head, connected to a side plate along the lateral femoral cortex through a sliding mechanism. As axial load is applied through the femur, the lag screw slides within the side plate, allowing controlled compression of the fracture site as the lag screw advances laterally. This dynamic compression principle depends on intact medial buttress to oppose the medializing force on the screw; in unstable patterns with medial comminution, excessive sliding can occur with consequent shortening and medialization of the distal fragment.

Technical Considerations — The Tip-Apex Distance The most important technical consideration in SHS fixation is lag screw position, quantified by the tip-apex distance (TAD) described by Baumgaertner (1995). The TAD is the sum, measured in millimeters and corrected for radiographic magnification, of the distance from the tip of the lag screw to the apex of the femoral head on both AP and lateral radiographs. A TAD less than 25 mm is the goal; TAD greater than 25 mm is strongly associated with screw cut-out and fixation failure. The lag screw should be deep and central in the femoral head, with central position on both AP and lateral views, and with the tip approximately 5 to 10 mm from the subchondral surface. The calcar tip-apex distance (CalTAD) has been proposed as an alternative, measuring from the tip of the screw to the apex along a line through the inferior calcar; this measure may better predict cut-out in some patterns. Outcomes and Failure Modes SHS fixation produces reliable union in stable pertrochanteric fractures with appropriately positioned hardware. The principal failure modes include: Cut-out of the lag screw through the superior cortex of the femoral head — the most common failure mode, related to TAD greater than 25 mm, varus malreduction, and unstable fracture patterns. Excessive sliding with consequent limb shortening, lateral hardware prominence, and abductor weakness — related to medial comminution and the use of SHS in unstable patterns better treated with alternative constructs. Implant failure with breakage at the plate-barrel junction — uncommon with modern implants but described. The stable pertrochanteric fracture (AO 31-A1 and selected A2.1) remains an excellent indication for SHS fixation, with cost-effectiveness and reliable outcomes.

Cephalomedullary Nailing

Principle and Construct The cephalomedullary nail (CMN, also called proximal femoral nail or intramedullary hip screw) combines an intramedullary nail in the proximal femur with a lag screw (or helical blade) that engages the femoral head through the nail. Multiple designs exist (gamma nail, PFNA — proximal femoral nail antirotation, TFN — trochanteric fixation nail, Intertan, and others), with differences in lag-screw versus helical-blade design, in fastener trajectory, and in nail diameter and length. The mechanical advantage of the CMN over SHS is the shorter lever arm between the head fastener and the implant — the medial cortical buttress is provided by the nail itself rather than requiring intact medial bone — which makes the CMN superior in unstable fracture

patterns and reverse oblique (31-A3) patterns where lateral plate fixation is biomechanically inadequate. Technical Considerations The technique requires careful entry point selection (typically tip of greater trochanter or just medial, depending on nail design), appropriate reaming, anatomical reduction of the fracture before nail insertion (with attention to rotation, which can be more difficult to control than with open SHS technique), and appropriate positioning of the cephalic fastener with attention to the TAD principle (which applies similarly to nail-based constructs). The PFNA helical blade was designed to provide rotational stability and improved fixation in osteoporotic bone, with compaction of cancellous bone around the blade providing the holding force. Cut-out remains the principal failure mode, with the same predictors (TAD, malreduction). Short Versus Long Nails The choice between short (typically 240 mm or less, ending in the proximal femur above the diaphyseal isthmus) and long (typically 340 mm or longer, extending to the distal metaphysis) nails is a practical consideration. Short nails are easier to insert and produce fewer technical complications; long nails provide more comprehensive protection of the femur against subsequent fracture and are favored in patients at risk for atypical femoral fracture or with extension of the fracture line into the subtrochanteric region. The peri- implant fracture at the tip of a short nail — a recognized complication — has driven some advocacy for long nails in selected patients, though the routine use of long nails carries its own concerns (longer surgical time, more radiation exposure).

SHS Versus Cephalomedullary Nail — The Active Debate

The choice between SHS and CMN for pertrochanteric fractures has been the subject of extensive investigation, with the following broad consensus: Stable fractures (AO 31-A1 and selected A2.1): Both SHS and CMN produce reliable outcomes. The SHS has been the historical standard with cost-effectiveness and long track record; the CMN is increasingly used because of efficiency and applicability across pattern types. The Cochrane reviews and large registry studies generally show no significant difference in major outcomes for these stable patterns. Unstable fractures (AO 31-A2.2 and A2.3): The CMN has gained favor on the basis of biomechanical advantages, with several trials showing reduced sliding, reduced shortening, and better functional outcomes. The HEMI trial and other studies have provided supporting evidence, although results remain mixed in some series. Reverse oblique and transverse fractures (AO 31-A3): The CMN is the standard of care; SHS fixation in this pattern is biomechanically inadequate because the fracture line is essentially parallel to the screw, with shear force unable to be neutralized by the sliding mechanism. The use of SHS for A3 patterns is strongly discouraged.

Subtrochanteric extension: CMN with long nail is the standard; SHS is inadequate. The practical trend in many centers has been progressive shift toward CMN for all pertrochanteric fractures, with SHS reserved for stable simple patterns. The cost of CMN is higher, but the broader applicability and the avoidance of failures in unstable patterns have favored this transition.

Specific Considerations

Subtrochanteric Fractures The subtrochanteric fracture, traditionally defined as fracture in the region from the lesser trochanter to 5 cm distal, is biomechanically distinct because of the high stresses in this region. The fracture is exposed to compression on the medial cortex (the strongest cortical bone in the body at the medial calcar) and tension on the lateral cortex, with a marked tendency to varus and procurvatum (apex anterior) malalignment. Treatment is almost always with a cephalomedullary nail, typically long, with careful attention to reduction (often requiring open or percutaneous reduction techniques, the use of reduction clamps, cerclage cables, or “poke” techniques to achieve the medial cortical reduction that is essential for stability). The iliopsoas pull on the proximal fragment tends to produce flexion and external rotation that must be neutralized during reduction. Atypical Femoral Fractures Patients on long-term bisphosphonate therapy (or, less commonly, denosumab) are at risk for atypical femoral fractures — transverse subtrochanteric or femoral shaft fractures with characteristic radiographic features (lateral cortical thickening, transverse fracture line, medial spike at the fracture, beaking of the lateral cortex, generalized cortical thickening of the femur). Atypical fractures may be preceded by prodromal thigh pain, and an x-ray showing characteristic features without a complete fracture should prompt urgent CT or MRI for the incomplete atypical fracture (which often progresses if not stabilized). Treatment is prophylactic intramedullary nailing of the incomplete atypical fracture, or standard CMN for the complete atypical fracture. Management of the underlying osteoporosis (drug holiday or transition to anabolic agents such as teriparatide) is part of the overall approach. Bilateral Pertrochanteric Fractures Bilateral pertrochanteric fractures, like bilateral femoral neck fractures, are uncommon but occur in osteoporotic or seizure-prone patients. Bilateral fixation in one operation is performed if the patient’s physiology permits. Pertrochanteric Fractures in Younger Patients Pertrochanteric fractures in younger patients (under 50) are uncommon and typically follow high-energy mechanism. The principles are similar to those in the elderly — anatomical reduction and rigid internal fixation — but with the additional consideration of

preserving the longer-term functional outcome. CMN is typically used, with anatomical attention to neck-shaft angle and rotation. Outcomes are generally good in this population.

Summary and Take-Home Points

The pertrochanteric (intertrochanteric) fracture, the extracapsular counterpart of the femoral neck fracture, shares the epidemiology of the elderly fragility fracture but differs critically in that the blood supply to the femoral head is largely preserved (low AVN risk) and the healing potential through cancellous trochanteric bone is excellent (low nonunion risk). The treatment is therefore almost always internal fixation rather than arthroplasty, with the central management question being the choice of construct. The AO/OTA classification (31-A1 simple, A2 multifragmentary with lesser trochanter involvement, A3 reverse oblique/transverse) is the contemporary standard. Stability depends on the integrity of the medial cortex (the lesser trochanter and calcar femorale); unstable patterns require constructs that resist load without excessive sliding or varus collapse. The two principal constructs are the sliding hip screw (SHS) and the cephalomedullary nail (CMN). The SHS works through the dynamic compression principle, with the lag screw sliding within the side plate as axial load compresses the fracture; the SHS requires intact medial buttress and is appropriate for stable patterns. The CMN combines an intramedullary nail with a cephalic fastener; the shorter lever arm provided by the medial intramedullary position makes the CMN biomechanically superior in unstable patterns and the standard of care for reverse oblique (31-A3) patterns where SHS is inadequate. The tip- apex distance (TAD < 25 mm) is the key technical parameter for either construct, with cut-out being the principal failure mode and TAD greater than 25 mm being the principal predictor. The subtrochanteric fracture is biomechanically distinct because of the high stresses in this region and is treated almost universally with cephalomedullary nailing, often with attention to operative reduction techniques to achieve and maintain the medial cortical contact essential for stability. The atypical femoral fracture in patients on long-term bisphosphonates requires recognition of prodromal symptoms and characteristic radiographic features, with prophylactic nailing of incomplete fractures and standard CMN management of complete fractures, plus medical management of the underlying osteoporosis. The systemic management — prompt surgery, early mobilization, multidisciplinary geriatric co-management, VTE prophylaxis, and secondary fracture prevention — applies equally as discussed in the femoral neck chapter. The chapter that follows turns to the femoral shaft, where the principles of intramedullary nailing reach their classical and most refined application.