Michael Weaver, MD is an Orthopaedic Trauma Surgeon, at Brigham & Women’s Hospital.
The reduction and fixation of displaced femoral neck fractures has an unacceptably high rate of failure, particularly in the geriatric population. Reconstruction with either hemiarthroplasty or total hip arthroplasty (THA) is the accepted treatment for these fractures. In active patients reconstruction with a total hip has advantages in terms of pain relief, functional outcome, and prosthesis longevity (1).
While many surgeons are skilled in performing THA for degenerative conditions of the hip – including osteoarthritis and avascular necrosis – patients with femoral neck fractures present several unique challenges. Here are my experiences:
Femoral neck fractures are fragility fractures associated with poor bone quality, a marker of osteoporosis. The trend in arthroplasty has been toward press-fit femoral components that allow for bone ingrowth and long-term stability. Thus, I use ingrowth femoral stems with a more canal-filling geometry instead of taper-type stems to reduce hoop stresses and prevent fracture. A doubled up 16-gauge circlage wire should be placed prophylactically between the greater and lesser trochanters prior to broaching.
Care must also be taken with placement and impacting of the acetabular component. There is usually no subchondral sclerosis, and it can be easy to breach the medial wall with the acetabular reamers. Supplementing acetabular fixation with at least 2 screws can prove useful.
Pre-operative pelvic AP is the template to guide radiographic placement of the cup. Adjust the C-arm orientation to recreate this image.
The rate of dislocation is higher in fracture patients treated with THA than osteoarthritis patients treated with THA (2). An anterolateral approach is thus recommended to reduce the risk of dislocation, despite the higher incidence of Trendelenburg gait (3). Patients have an easier time complying with modified anterior hip precautions than posterior hip precautions – an important consideration for patients with mild cognitive deficits. The newer highly cross-linked polyethylene liners allow for larger femoral head sizes that improve stability.
Leg Length Discrepancy
Many arthroplasty surgeons use pre-operative leg lengths to guide component position and gauge leg lengths. This is more challenging in fracture patients as there is no one perfect guide. A combination of the following is helpful: visual inspection to ensure that the center of the new head is at the level of the tip of the greater trochanter; palpation of the contralateral knee through the drapes with the hip reduced; tissue tension; shuck; and c-arm guidance. Osteoarthritic patients have tighter tissues, while fracture patients typically have normal hip anatomy prior to injury leading to slightly looser tissue tension when limb length is restored.
Hip fractures are associated with increased morbidity and mortality. Mobilizing the patient early is critical. It is thus important to optimize patients quickly, so they may go to the operating room as soon as possible after injury. A close relationship with the medical and geriatric teams is essential to minimize post-operative complications. Particular attention should be paid to mobilization, nutrition, and adequate pain control.
Many elderly patients with hip fractures have friends or family who may have had a THA for osteoarthritis. Since fractures are injuries of the whole hip, they are often associated with contusion and injury to the surrounding musculature. It is thus important to counsel patients and families that recovery may be more challenging.
The C-arm improves reliability of cup position and accuracy in restoring normal leg lengths. Obtaining the correct view is critical to success. A few adjustments in the direction of the beam may be required before an appropriate view is obtained. Despite lateral positioning, the patient may slump forward or backwards in the bean-bag, causing over or under anteversion of the cup and adversely affecting stability. It is important to adjust the patient such that the x-ray is a true AP rather than an obturator or iliac oblique view. Positioning patients with the well leg flexed to ~ 40 degrees requires the beam to be adjusted to obtain a true AP of the pelvis. Displaying the pre-operative AP pelvis during the case and adjusting the patient or C-arm as needed to re-create that image prior to reaming helps placement of the acetabular component.
The C-arm is brought in twice: to confirm placement of final reamer and during impaction of the acetabular component; and again after the final broach is in place to confirm femoral fill and leg length equality.
After reaming, check the image to ensure adequate medialization of the cup. This also gives an idea of the proper cup position.
The actual component is then impacted.
Leg lengths are confirmed by taking an image of the well hip, and adjusting the rotation and abduction of the fractured hip with the broach in place until the same appearance of the lesser trochanter is obtained. The level of the lesser trochanters in relation to the ischium is used to gauge leg length.
The C-arm is a tool like any other. If something does not feel right, it probably is not. It is important to visually inspect the cup and test stability once the femoral broach is in place.
Post-operative films demonstrate appropriate acetabular component position and restoration of leg lengths.
The optimal care of femoral neck fractures has evolved. Many patients benefit from reconstruction with a total hip replacement to maximize pain relief, improve function and provide them with a durable result.
1. Hedbeck CJ, et al, Comparison of bipolar hemiarthroplasty with total hip arthroplasty for displaced femoral neck fractures: A concise four-year follow-up of a randomized trial. J Bone Joint Surg Am 2011; 93:445-50.
2. Hopley C, et al, Primary total hip arthroplasty versus hemiarthroplasty for displaced intracapsular hip fractures in older patients. BMJ 2010; 340:c2332.
3. Skoldenberg O, et al, Reduced dislocation rate after hip arthroplasty for femoral neck fractures when changing from posterolateral to anterolateral approach. Acta Orthop 2010; 81:583-7.