Issue: July 2021
Source: Berstock JR, et al. Bone Joint J. 2018;doi:10.1302/0301-620X.100B1.BJJ-2017-0569.R1.
Disclosures: Matthews reports he has stock in Johnson & Johnson, which owns DePuy Synthes and manufactures the Pinnacle cup. Langfitt and Scholten report no relevant financial disclosures.
July 15, 2021
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68-year-old man with right hip pain, inability to bear weight after a golf swing

Issue: July 2021
Source: Berstock JR, et al. Bone Joint J. 2018;doi:10.1302/0301-620X.100B1.BJJ-2017-0569.R1.
Disclosures: Matthews reports he has stock in Johnson & Johnson, which owns DePuy Synthes and manufactures the Pinnacle cup. Langfitt and Scholten report no relevant financial disclosures.
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A 68-year-old man presented to the ED after he fell following a hard swing on the golf course and felt a pop in his right hip. He was unable to bear weight after the fall and had to use a walker to leave the golf course.

The patient reported mild discomfort in the right hip but no significant pain. His medical comorbidities included hypertension, hyperlipidemia, chronic low back pain, stage 3 chronic kidney disease and a BMI of 35 kg/m2. He reported he was active and on his feet for extended periods of time for his work as a plumber.

Steven D. Jones Jr.
Steven D. Jones Jr.
Donald (DJ) Scholten
Donald (DJ) Scholten

The patient had bilateral metal-on-metal total hip arthroplasties performed in 2005. In 2019, the patient had revisions of the bilateral acetabular liners and femoral head balls to ceramic-on-polyethylene on the right hip and cobalt chrome-on-polyethylene on the left hip due to concerns of metallosis. He since had no reported issues with either hip until this golfing incident. The components of his original right THA included a DePuy Tri-Lock stem with a Pinnacle cup.

On exam in the ED, his right leg was slightly shortened, he had pain with motion of the right hip, but his right lower extremity was otherwise neurovascularly intact.

What injuries would be suspected in this older patient with a previous right THA?

Common injuries of the hip in a patient with previous arthroplasty include prosthetic hip dislocation, liner dissociation from the cup, as well as periprosthetic fracture. X-ray images of the right hip revealed a broken femoral stem trunion (Figure 1).

THA with a broken trunion
1. Anteroposterior radiograph of the patient’s right hip THA with a broken trunion is shown.

Source: Maxwell K. Langfitt, MD

What is the best next step in management of this patient?

See answer below.

One-stage femoral stem revision, polyethylene liner exchange, antibiotic bead placement

The patient was taken to surgery for one-stage exchange of the femoral component of the right hip with polyethylene liner exchange and placement of antibiotic beads.

A standard posterior approach to the hip was performed. The implant was removed using custom osteotomes that are designed for use with various stems and stem sizes (Figure 2). This allows for extraction of the implant with minimal bone loss and without the need for an extended trochanteric osteotomy, which is a longer and more morbid procedure with a slower recovery time. When using these osteotomes, it is important to meticulously clear the lateral shoulder of the implant. This allows for passage of the osteotome and reduces the risk of greater trochanter fracture upon extraction, as well for threading-in an extraction tool into the shoulder of the implant.

hip femoral stem with a broken trunion
2. Intraoperative photographs show the hip femoral stem with a broken trunion.

Modular stem, cone body

Once the implant was removed, the bone was prepared for new implants. A Restoration Modular Stem System (Stryker) conical stem and cone body were used to replace the femoral component and a new Pinnacle ALTRX (DePuy Synthes) polyethylene liner was inserted into the cup before replacing the head ball with a new ceramic head. No metallosis was encountered, and cultures obtained during the case were negative. The acetabular component was stable without evidence of damage and the hip was stable upon reduction without impingement (Figure 3).

Postoperative radiographs
3. Postoperative radiographs of the revision femoral stem are shown.

The patient was made toe-touch weight-bearing for 6 weeks due to the stem being diaphyseal engaging and the potential for subsidence with immediate weight-bearing as tolerated with these implants. He was also given posterior hip precautions because of the approach used. The patient worked with physical therapy and was cleared for discharge on postoperative day 1. Cultures from samples taken intraoperatively were negative at final result. At his most recent clinic visit, he was recovering well and managing with his restrictions on weight-bearing.

Discussion

Fracture of the femoral neck component (trunion) in THA is an uncommon complication. A retrospective review by David A. Heck, MD, and colleagues, which looked at the membership of the American Association of Hip and Knee Surgeons during a 5-year period, found the rate of prosthetic femoral neck fracture was 0.27% within their cohort. Aasis Unnanuntana, MD, and colleagues published a case report of two cases of trunion fracture which both happened within 7 years of the index procedure. In these cases, the trunion diameter was small and failure occurred in the area of the component that had an intentional manufactured groove as part of the design. They reported there was also evidence of corrosion which may have contributed to the failure. Another case report by E.W. Lee and colleagues looked at two cases of early fatigue failure of the femoral component. In both cases, the fracture occurred at the neck-shoulder junction, an area that experiences considerable stress during loading. They found a major contributor to the failure of these implants was laser etching on the implant in the region of failure.

Multifactorial failure

Many factors may contribute to trunion failure in THA. Patient factors, such as high BMI and high activity levels, lead to increased loads on the component. Other things, like varus positioning of the implant, as well as implant design, can contribute to increased loads and decreased resistance to stress. Combined malpositioning of the acetabular and femoral components can lead to impingement of the trunion on the acetabular shell, leading to notching of the trunion over time and eventual failure. Corrosion or trunionosis also may contribute to failure. This is especially seen in implants that contain a metal as opposed to a ceramic head ball. In many of the case reports of trunion fracture currently published, there are manufactured etchings or grooves around the area of failure. However, this is not always the case. The implant in our case was a Tri-Lock stem (J&J Medical Devices). The failure in this case occurred at the neck-shoulder junction, which does not have any manufactured groove or laser etching. It is difficult to know what the ultimate cause of failure was in our patient. Most likely, it was a combination of trunionosis from the original metal head ball, the revision to a ceramic head ball 14 years after the initial implantation, as well as patient factors, such as his elevated BMI and heavy activity levels.

In summary, although trunion fractures are uncommon, these almost universally require revision of the femoral component. No matter the cause of the failure, it is important to consider material type, size and manufacturing specifics of the component, as well as patient factors and final position of the implant in these revision cases.