Older man with hip dislocation, fracture of femoral head and posterior wall

The patient is a 74-year-old man with a past medical history of hypertension who initially presented to an urgent care facility with left knee pain after falling directly onto his knee.

At the urgent care facility, knee radiographs were negative and the patient was discharged home with crutches and NSAIDs. The patient continued to have difficulty ambulating, requiring use of a rolling walker despite previously being a community ambulator without assistive devices.

Approximately 6 weeks later, he presented at the ED due to dark stools and was found to have a gastric ulcer induced from NSAID usage, along with new-onset atrial fibrillation, congestive heart failure and left lower extremity cellulitis. A duplex ultrasound of his bilateral legs was negative. Pelvic and hip radiographs demonstrated a left posterior hip dislocation with an associated femoral head and posterior wall fracture (Pipkin type 4). The morphology of the fracture was further assessed through a CT scan (Figure 1).

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Given his newly diagnosed medical comorbidities and the chronicity of this injury, operative intervention was delayed until the patient was medically optimized and his cellulitis was treated to help reduce perioperative complication rates.

The decision was made to proceed with THA and posterior wall open reduction and internal fixation (ORIF). Once medically optimized, the patient was taken to the OR.

The decision was made to proceed with THA instead of ORIF given the patient's age, bone quality, delayed presentation and higher risk for failure with ORIF.

Repeat radiographic evaluation prior to the patient's definitive surgery again demonstrated a chronic left posterior wall fracture with associated femoral head fracture/dislocation with signs of progressive femoral head collapse and posterior wall resorption (Figure 2). Given these findings, fixation of the posterior wall through a posterior approach was planned with available multihole acetabular cups, augments and a cage to ensure adequate shell fixation.

The patient was positioned in the right lateral decubitus position and prepped in the usual sterile fashion. A posterolateral Kocher incision was made and taken sharply down to the iliotibial band, which was then incised. The greater trochanteric bursa was taken down and the gluteus maximus was released along its proximal insertion to aid in mobilization. The piriformis was identified and taken down with the capsule as one contiguous sleeve.

The dislocated femoral head was identified along with the thin posterior wall fragment. The femoral neck cut was then templated and cut to the desired preoperative plan. An anterior acetabular retractor was placed. The sciatic nerve was found and protected with a lesser notch retractor.

Intraoperatively, the decision was made to excise the nearly fully resorbed posterior wall fragment, along with all the fibrotic soft tissue surrounding this fragment. With the acetabulum exposed, the posterior/superior wall defect was evaluated and found to be about 40% of the surface of the acetabulum. Acetabular augments were then trialed, but found to have an inappropriate fit. At this juncture, a screw rebar and cement technique was pursued. Sequential reaming to 53 mm was performed until an appropriate acetabular fit was obtained. The reamer was left in place in the appropriate version and inclination. An eight-hole pelvic reconstruction plate was custom contoured around the acetabular reamer to correspond to the patient's anatomy to recreate the posterior wall because the prefabricated acetabular augments did not appropriately fit a posterior wall defect. Cortical screws were placed proximally and distally to secure the plate. The reamer was removed and a size 54 multihole cup was then impacted in the planned inclination and version with three 5-mm cancellous screws placed in the cup.

Next, four 3.5-mm cortical screws were placed along the remaining acetabular rim and along the ilium to act as rebar. Bone cement was then applied over the cortical screws and along the posterior cup where bone loss had occurred to strengthen the construct. An additional seven-hole reconstruction plate was then positioned over the rebar screws and cement, while drying, for additional reinforcement (Figure 3).

Femoral broaching was then done and a size 8, high-offset press-fit stem was placed. Femoral head trialing ensued to ensure a desireable hip range of motion without signs of impingement or instability. A 22-mm (+7 mm) head with a modular dual mobility liner was used. Fluoroscopic imaging confirmed appropriate implant positioning and plate/screw positioning (Figure 4). Standard layered closure with the repair of the capsule and short external rotators was performed. Postoperatively, pelvic and Judet radiographic views were obtained (Figure 5). The patient was made weight-bearing as tolerated with posterior hip precautions for 6 weeks postoperatively.

The decision was made to perform arthroplasty instead of ORIF given the patient's age, bone quality, delayed presentation and higher risk for failure ORIF. A better candidate for ORIF of a femoral head fracture with an associated posterior wall is a young patient who presents acutely. Garrett Pipkin classified a femoral head fracture associated with hip dislocations based on the location of the fracture relative to the fovea capitis femoris and based on a concomitant femoral neck or acetabular rim fracture. Patients with Pipkin type 4 fractures, as is the case with our patient, are associated with an increased risk of avascular necrosis and early conversion to THA within 1 year of ORIF. Kyle H. Cichos, MD, and colleagues also described an especially higher rate of conversion to THA in the oldest of patients, which supports the decision for primary arthroplasty.

Our patient also presented a significant challenge with regard to acetabular shell fixation given the acetabular bone loss encountered. Wayne G. Paprosky, MD, FACS, and colleagues, classified acetabular defects based on the location of bone loss affecting the teardrop, ischium and direction of component migration in conjunction with the ability to provide rigid support for an acetabular component. Based on the degree of support, Paprosky and colleagues proposed the type and amount of graft required to mitigate instability. Since these guidelines were introduced by Paprosky, both cemented and noncemented techniques have been described. The cemented techniques involving impaction bone grafting or bulk allograft with cemented acetabular component or reconstruction rings have acceptable results, but early failures with allograft resorption are described. Noncemented fixation techniques utilizing porous shells, which have shown good results in primary and revision scenarios, can be used in the form of a jumbo cup, augment-cup, cup-in-cup, bilobed cup or reconstruction cages. Despite the changes in technology, challenges still exist relating to the quality of host bone to achieve ingrowth and filling of large or segmental bone defects as in Paprosky type 3A and 3B defects while restoring the appropriate hip center.

Achieving cup-bone stability is particularly important when acetabular wall/rim defects are present, as is frequently encountered during revision-type scenarios. It has been reported that less than 50% bone-acetabular cup contact may be a contraindication to use of an uncemented cup alone. Previous studies have proposed the need for a reconstruction cage spanning the ilium to ischium when a structural graft is supporting more than 50% of the acetabular component as these fractures have a propensity to be unstable, as indicated by midterm to long-term complication rates as high as 21.2%. However, with second-generation enhanced porous surface shells, this standard has been challenged as was done by Amir Sternheim and colleagues who reported a rate of mechanical failure of 7.5% (four of 53) with trabecular metal revision shells in hips with less than 50% acetabular bleeding host-bone contact. Despite these findings, no failures were reported in 49 hips with greater than 50% contact at a mean follow-up of 6 years.

While porous-coated hemispherical cups with screws have been successfully used in scenarios that involve upward of 50% contact loss, acetabular augments can be effectively used in unique scenarios. Paprosky types 2B, C and 3A and 3B defects have been successfully treated with acetabular augments with excellent midterm results. As in the case presented, the final decision to use an augment is often made intraoperatively based on the defect location and morphology. Based on the location, size and morphology of our patient's posterior wall being nearly 40% deficient, the cement-rebar interface construct offered a custom alternative to reinforce the posterior wall/rim defect that was not as well addressed by prefabricated acetabular augments.

The cement-rebar technique, as described by Frank A. Liporace, MD, and colleagues aims to improve the mechanical stability of the acetabular component when bone loss exists allowing for adequate joint mobility and early weight-bearing. The screws are positioned proudly within the defect to act as a rebar to reinforce the surrounding cement which can be custom molded to fit the defect morphology. This unitized construct functions to augment structural support along the acetabular defect and, in turn, provides additional cup stability to minimize mechanical failure. A recent biomechanical cadaveric study evaluating primary cup stability in THA with acetabular defect augmentation through a rebar technique, resulted in favorable redistribution of von Mises stress with most peak stresses directed away from the reconstructed site. While long-term outcomes are still unknown, midterm results from Liporace and associates have shown no mechanical failures. A cement-rebar technique can be considered in unique cases of acetabular bone loss when additional acetabular cup fixation is required.