IntroductionSubtrochanteric fractures are fractures that occur in a zone extending from the lesser trochanter to 5cmdistal to the lesser trochanter, however extension into the intertrochanteric region is common. Thesefractures are more difficult to treat as compared to intertrochanteric fractures due to the powerfulmuscle forces acting on the fragments as well as the tremendous stress that is normally placed throughthis region. When seen in young patients, they are due to high-energy trauma or pathologic fracturewith 10% of high-energy fractures due to gun shot wounds. In the elderly, they are often low energyinjuries involving osteoporotic bone. Pathologic fractures account for 17-35% of all subtrochantericfractures¹. Fracture may also occur at the site of screw placement for a previous femoral neck fracture ifthe inferior screw is placed too low (below the lesser trochanter), as this creates a cortical defect andstress riser.AnatomySubtrochanteric fractures are fractures that occur in a zone extending from the lesser trochanter to 5cmdistal to the lesser trochanter. The medial and posteromedial cortices of the subtrochanteric femurexperience the highest compressive stresses in the body. The lateral cortex is under a high degree oftensile stress. These fractures occur at the cortico-cancellous junction. The high composition of corticalbone and subsequently the decreased vascularity impairs the capacity for healing of these fractureswhen compared to the abundant cancellous bone of the intertrochanteric region of the hip.The proximal fragment is usually flexed and externally rotated by the pull of the iliopsoas and shortexternal rotators, and abducted by the pull of the gluteus medius and minimus. The distal fragment isadducted and shortened by the pull of the adductors leading to a varus and procurvatum fracturealignment. These factors should be considered when attempting reduction.ClassificationFielding Classification - This is an anatomic classification based on location of the fracture and is rarelyusedType I - at level of lesser trochanterType II - <2.5 cm below lesser trochanterType III - 2.5-5cm below lesser trochanter
Seinsheimer Classification - This system incorporates factors affecting stability and offers managementguidelines.Type I - nondisplacedType II - two part fracturesSubtypes based on fracture pattern and displacementType III - three part spiral fractureSubtypes based on type of fracture fragmentsType IV - comminutedType V - intertrochanteric extensionRussell-Taylor Classification - This classification is based on integrity of the piriformis fossa. It wasdesigned to guide treatment of intramedullary nails using a piriformis fossa starting point. This systemmay not be as important as it used to be, due to changes in entry point techniques and improvedimplant designs¹.Type I - intact piriformis fossaA - lesser trochanter attached to proximal fragmentB - lesser trochanter detached from proximal fragmentType II - fracture extends into piriformis fossaA - stable posterior-medial buttressB - comminution of lesser trochanterOrthopaedic Trauma Association Classification - Based on degree of comminution and mainly used forresearch purposes.PresentationPatients typically present in significant pain unable to ambulate with deformity of the proximal thigh.High energy mechanisms should receive a full trauma evaluation and careful inspection for openfracture. A detailed neurovascular exam of the extremity should be performed. Due to the size of thethigh compartment, hypovolemic shock is possible secondary to this fracture.
Subtrochanteric Fractures and Long-Term Alendronate UseA relationship between long-term Alendronate use and subtrochanteric fractures has been establishedand is hypothesized to result from long-term suppression of bone remodeling. A retrospective case-control study of postmenopausal women presenting with low-energy femoral fractures reportedbisphosphonate use in 15/41 subtrochanteric/shaft fractures vs. 9/82 age-, race-, and BMI-matchedfemoral neck and intertrochanteric fractures (odds ratio = 4.44, 95%CI = 1.77-11.35; p = 0.002). Acommon radiographic pattern consisting of a simple oblique fracture with cortical thickening andbeaking of the cortex on one side was highly associated with bisphosphonate use. Patients with thisfracture pattern had an average duration of alendronate use of 7.3 years, vs. 2.8 years for those withoutthe pattern 1 . Up to 76% of these patients may have prodromal pain 2 . Patients with low-energyfractures who have been on long-term bisphosphonate therapy should have imaging of the contralateralfemur. Prophylactic fixation should be considered if a contralateral stress fracture is found 3 .Consideration should also be given to discontinuing alendronate, in consultation with an endocrinologist3.DiagnosisFor all hip fractures, an AP pelvis, internal rotation AP and cross-table lateral of the affected hip shouldbe obtained. An MRI may also be required for pathologic fractures to evaluate the proximal femur forsoft tissue extension of an underlying bone tumor. It is helpful to obtain a contralateral femur x-raytaken with a radio-opaque ruler or scanogram for patients with highly comminuted fractures as a meansto measure the native femur length so that it may be reproduced during ORIF of the affected extremity.Patients with low-energy fractures who have been on long-term bisphosphonate therapy should havecontralateral femur imaging to rule out impending fractures.TreatmentInitially, the limb should be stabilized with Hare traction, Bucks traction or skeletal traction. If there willlikely be a delay in surgical stabilization, femoral or tibial skeletal traction should likely be employed.Nonoperative treatment in 90-90 skeletal traction followed by hip spica casting should only beemployed in those whom surgery is deemed very high risk. 90-90 traction attempts to counteract thedeforming muscular forces. Traction usually is required for 12-16 weeks.Surgical stabilization is the standard of care. The treatment option include:
Intramedullary nail fixation is the preferred treatment. In general, intramedullary devices have beenfound to be almost twice as strong as extramedullary implants. First generation interlocking nails(centromedullary) are indicated when both trochanters are intact as the oblique locking screw is able toobtain adequate purchase. Second generation interlocking nails with a locking screw that extends intothe femoral neck (cephalomedullary) offer more stable fixation and are indicated when the lessertrochanter is displaced or comminuted. Advantages of intramedullary fixation include 1) Potential forclosed treatment with preservation of fracture hematoma and blood supply to fracture fragments, 2)Decreased the moment arm on the implant compared to a lateral plate and thus decreases the tensilestress on the implant, 3) Reaming the canal in preparation of the implant provides internal bone graft, 4)intramedullary implants have been found to be twice as strong as traditional extramedullary implants.Disadvantages include 1) the implant cannot be used to help facilitate reduction and the fracture sitemay need to be opened to affect a reduction and guide pin insertion, thus lessening benefits of closedintramedullary fixation. It is nonetheless critical to achieve reduction and to maintain this reduction(using instruments, an incision or both as needed) while the nail is being placed. Failure to do so willresult in varus displacement during implantation. Obtainment of proper nail starting point can be easedby lateral/lazy lateral patient positioning or the use of a trochanteric starting nail. If a trochanteric nail ischosen, it is imperative that a very medial starting point is chosen, again to avoid varus deformity.Russell et al have reported decreased rates of malalignment using the Minimally Invasive Nail InsertionTechnique (MINIT) 4 .Ninety-five degree fixed-angle devicesHistorically this was the most common device used for operative fixation. This is a fixed angle constructthat provides rigid fixation. Advantages include 1) Offers a treatment option for fractures withcomminution of the trochanters that may make intramedullary implant insertion difficult, 2) Provides formultiple points of proximal fixation. Disadvantages include 1) Technically very demanding, 2) Extensivesoft-tissue dissection, 3) High risk of implant failure due to tremendous stress applied to the platelaterally.Sliding hip screwThis device is indicated only for very proximal fractures. The sliding of the screw allows medialization ofthe distal fragment, which reduces bending moment on fracture and implant. The sliding mechanismmust cross the fracture site to lessen the risk of implant failure and the posteromedial cortex must bereconstructed to decrease the stress on the device.Post-Operative Care
Rehab: Weight bearing is guided by fracture pattern. Protected weight bearing can be started early infractures with posteromedial bony contact¹. Most patients should not fully bear weight for the first 6-8weeks.ComplicationsNonunion. Incidence of 0-8% 5 . Presents with continued inability to bear weight at 4-6 months andcontinued pain. Varusmalreduction is an important predictor of nonunion accompanied by implantfailure.Malunion:Coxavarus: Caused by uncorrected abduction deformity, nail entry point that is too lateral, andmigration of hardware proximally in the femoral head and neck.Shortening: Due to uncorrected shortening intraoperatively and premature dynamization. Rotational deformity: Do to uncorrected external rotation of proximal fragment. This can be assessedintraoperatively with visualization of the lesser trochanter.Fixation failure: Most common in osteoporotic bone. Screw cutout in the femoral head; backing out oflocking screws.Failure of implant: Excessive motion at fracture site leads to implant fatigue.Infection:Red Flags and controversies
Plate vs. intramedullary fixation.Role of locked plating and navigation.Fracture may also occur at the site of screw placement for a femoral neck fracture if the inferior screw isplaced too low as this creates a cortical defect and stress riser.OutcomesCurrently, most subtrochanteric fractures in which the piriformis fossa or greater trochanter are intactcan be successfully treated with a cephalomedullary device. Care must be taken to avoid varus duringplacement of the device. Comminutedsubtrochanteric fractures may be treated with a longintramedullary device or a fixed angled plate. Sliding hip screws should generally be avoided as theyhave higher failure rates.References:1. Bucholz RW, Heckman JD, Court-Brown CM, Tornetta P, Koval KJ. Rockwood and Greens Fractures inAdults: Rockwood, Green, and Wilkins Fractures, 2 Volume Set. Sixth Edition. Lippincott Williams &Wilkins; 2005Sun Nov 27 04:47:04 PST 20111Lenart BA, Neviaser AS, Lyman S, Chang CC, Edobor-Osula F, Steele B, van der Meulen MC, Lorich DG,Lane JM, 2009. "Association of low-energy femoral fractures with prolonged bisphosphonate use: a casecontrol study." OsteoporosInt 20 (8): 1353-62 [PubMed]2Kwek EB, Goh SK, Koh JS, Png MA, Howe TS, 2008. "An emerging pattern of subtrochanteric stressfractures: a long-term complication of alendronate therapy?" Injury 39 (2): 224-31 [PubMed]3Capeci CM, Tejwani NC, 2009."Bilateral low-energy simultaneous or sequential femoral fractures inpatients on long-term alendronate therapy." J Bone Joint Surg Am 91 (11): 2556-61 [PubMed]
[ab]4Russell TA, Mir HR, Stoneback J, Cohen J, Downs B, 2008. "Avoidance of malreduction of proximalfemoral shaft fractures with the use of a minimally invasive nail insertion technique (MINIT)." J OrthopTrauma 22 (6): 391-8 [PubMed]5Lundy DW, 2007. "Subtrochanteric femoral fractures." J Am AcadOrthopSurg 15 (11): 663-71 [PubMed]CORR Articles