Early Wear of Highly Cross-linked Polyethylene Following THA
An active 58-year-old male patient presents with a continuously squeaking hip 3 years after a total hip arthroplasty. Radiographs show eccentric wear to the polyethylene liner. What went wrong and how will the issue be resolved?
Alexander J. Rondon, MD, and James J. Purtill, MD
Polyethylene is the most common material utilized for acetabular liners. Although a titanium acetabular cup achieves stability from bony ingrowth, a polyethylene liner achieves stability via a locking mechanism within the acetabular cup.
First generations of polyethylene had higher wear rates (approximately 0.2 mm/year), often resulting in osteolysis and subsequent component loosening. Advances in manufacturing, both sterilization and cross-linking, have led to the manufacturing of ultra-high-molecular-weight (UHMW) polyethylene, drastically reducing the annual wear rate 10-fold (<0.02 mm/year). [1,2]
In this article, we present the case of an early catastrophic wear with UHMW polyethylene at 3 years post-total hip arthroplasty (THA).
A 58-year-old male patient presents with a “squeaky” hip and polyethylene failure approximately 3 years after a right THA. He had undergone the procedure for post-traumatic arthritis following a motorcycle accident 20 years ago. Of note, the patient is active, owns a gym, and participates in high-function gym activities such as box jumps.
This is the patient’s second visit for a complaint of squeaking: One week prior to the current visit, he presented following 3 instances of squeaking. Radiographs at the time showed no wear and no signs of component loosening, subsidence, or fracture. Now, 1 week later, he presents with continuous squeaking. Radiographs show catastrophic wear.
The index THA was performed with a 52-mm Pinnacle Titanium cup, 32-mm lipped AltrX cross-linked polyethylene liner, 32-mm ceramic ball with +5 mm neck length, and size 7 standard Tri-Lock stem (DePuy Synthes; Warsaw, Indiana).
- Height: 5 feet, 10 inches; weight: 162 pounds; BMI: 23.3
- Well-healed lateral incision
- Hip range of motion full and pain free
- Normal distal lower extremity neurovascular exam
- Serum erythrocyte sedimentation rate: 13 mm/hour
- Serum C-reactive protein: 3.0 mg/L
Figure 1. Anteroposterior radiograph of the pelvis immediate postoperatively following the index procedure.
Figure 2: Anteroposterior radiograph of the pelvis following initial audible sweaking, 1 week prior to presentation with wear and approximately 3 years postoperatively.
Figure 3. Anteroposterior radiograph of the pelvis at the time of presentation to the office with audible squeaking on ambulation. There is eccentric wear.
- Early catastrophic wear of an UHMW polyethylene liner
There were several considerations for the management of this patient:
- Is the polyethylene liner fractured?
- Is the acetabular component well fixed?
- Is the femoral stem well fixed?
- Should cement be utilized to lateralize the liner?
We discussed with the patient the need for revision surgery to address the eccentric polyethylene wear and he agreed to the procedure. Given the patient’s active lifestyle, repeat catastrophic wear was a significant concern for the revision THA, which we also discussed with the patient.
We elected to proceed with a head and liner exchange, as the acetabular component was well fixed, but we were prepared for a full acetabular or femoral revision if necessary.
- Utilizing the prior incision, dissection was taken down and deep to the fascia.
- Severe and very focal wear of the inner polyethylene liner was identified posteromedially (Figure 4). This suggested that catastrophic wear ultimately resulted in the liner becoming disengaged from the locking mechanisms of the acetabular cup.
Figure 4. The UHMW polyethylene lipped liner shows focal damage and posteromedial wear. Additional strip wear was noted on the ceramic head.
- The acetabular screws were then removed. The titanium cup was well fixed and well positioned. The femoral stem was also noted to be well fixed.
- A ceramic head and polyethylene exchange was performed with a 32-mm lipped AltrX cross-linked polyethylene liner and a 32-mm ceramic ball with +5 mm neck length (DePuy Synthes). The 52-mm Pinnacle Titanium cup and size 7 standard Tri-Lock stem were retained.
- The immediate postoperative radiograph is shown in Figure 5.
Figure 5. Immediate postoperative radiograph following head and liner exchange to a ceramic–on–polyethylene articulation.
The patient was made weight-bearing as tolerated immediately postoperatively. No hip precautions were instituted.
We describe early (less than 4 years) catastrophic wear of an AltrX highly cross-liked polyethylene lipped liner following primary THA, with intraoperative findings confirming disengagement of the liner as well as acetabular cup and posteromedial wear of the liner.
The position of the acetabular component has been described as a factor associated with increased polyethylene wear. For this case, the abduction cup inclination was measured to be 43° and was found to be well fixed and well positioned. Patil et al  have reported increased mean linear wear when abduction cup inclination is greater than 45°. Hill et al  reported early catastrophic wear of a Pinnacle Marathon polyethylene liner, concluding that their acetabular cup was malpositioned, with cup inclination of 70°.
Another potential cause of early catastrophic wear is fracture of the polyethylene liner. A case report by Waewsawangwong et el  noted vertical cup position and a fracture along the superior rim of the liner’s locking mechanism as a cause of early failure at 20 months.
Another early failure (less than 3 years) reported by Moore et al  cited abnormal loading of the liner due to improper initial seating of the liner in the acetabular cup at the time of the index procedure. Yun et al  reported on a series of 23 patients with early catastrophic wear due to polyethylene liner dissociation utilizing the Pinnacle acetabular component. They noted that 9 of 23 liners were malpositioned and said that precautions must be taken to ensure that the liner is properly seated in the locking mechanism during initial implantation.
Our case adds to the current literature and serves to reiterate the importance of proper acetabular cup position as well as judicious confirmation of proper seating of the liner within the acetabular cup during the initial procedure.
Alexander J. Rondon, MD, is an orthopaedic surgery resident at the Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania. James J. Purtill, MD, is the Residency Program Director at the Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania. He specializes in hip and knee replacement at The Rothman Institute, Philadelphia, Pennsylvania.
Adult Reconstruction Section Editor, Rothman Institute Grand Rounds
Disclosures: The authors have no disclosures relevant to this article.
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