78-year-old man with acetabular bone defect after THA
A 78-year-old man presented to clinic with long-standing left groin and thigh pain.
He had previously undergone total hip arthroplasty via a posterior approach in 1996 and had a subsequent polyethylene component exchange in 2012 due to polyethylene wear and acetabular osteolysis. The patient recovered well from these surgeries, although he had experienced one posterior dislocation during the early postoperative period after his revision surgery, which was successfully managed with closed reduction. He had then returned to a highly active lifestyle that included long-distance cycling. Several months before his presentation, the patient reported worsening left groin pain with prolonged sitting and activity. He was evaluated by a local orthopedic surgeon who observed progressive acetabular and iliac osteolysis on radiographs (Figure 1).
The patient underwent a workup for potential causes of osteolysis, including infection and adverse local tissue response. Inflammatory markers, white blood cell count and left hip aspiration results were within normal limits. In addition, serum cobalt and chromium ion levels were within normal limits. A CT scan was obtained to better identify the degree of pelvic bone loss. This demonstrated extensive acetabular bone loss and an uncontained iliac bone defect. In addition, imaging indicated pseudocapsule-enclosed soft tissue and fluid collection that extended into the pelvis and exhibited a mass effect on the bladder (Figure 2).
Source: Nicolas A. Selemon, MD; Harold I. Salmons, MD; Niall H. Cochrane, MD; and Michael J. Taunton, MD
Revision of the acetabular component was recommended, and the patient was referred to our clinic for further evaluation and management. During the consultation, the patient was noted to have significant groin pain, which was exacerbated by prolonged sitting or walking and notably impeded the patient’s quality of life and desired activity level.
On physical examination, the patient ambulated with an antalgic gait on the left. Examination of the left hip showed neutral extension, flexion to 120°, abduction and adduction to 20°, and internal and external rotation to 20° and 30°, respectively. Leg lengths were equal. He was neurovascularly intact with a well-healed posterolateral hip incision.
Repeat inflammatory markers at the time of consultation were within normal limits, and repeated radiographs demonstrated stable acetabular and iliac osteolysis with no evidence of femoral component loosening.
What are the best next steps in the management of this patient?
See answer below.
Revision THA through posterior approach
After a discussion of nonoperative and operative options, the patient chose to proceed with a revision THA through the previous posterior approach. Given the apparently well-fixed femoral component, a revision involving only the acetabular component with structural allograft and impaction grafting was indicated.
Considering the expected size of the acetabular bone defect, several reconstructive options, including structural allograft, cup-cage constructs and acetabular component augments, were planned to be available at the time of surgery.
Revision THA, acetabular component
The patient was positioned in the left lateral decubitus position. The prior posterior hip incision was used to perform a standard revision posterolateral approach to the hip. The piriformis was tagged for future repair, and the short external rotators were removed from the femur. During the disimpaction of the femoral head, both the femoral head and femoral component trunnion were examined meticulously and showed evidence of mild corrosion.
The acetabulum was exposed using circumferential Hohmann retractors. The acetabular liner was removed, and the acetabular component was found to be well-fixed on the remaining anterosuperior pelvic bone stock. Therefore, an acetabular explant system was employed to carefully loosen the acetabular component and remove it with minimal additional bone loss.
Once removed, a significant amount of fluid under pressure was released, which appeared to consist of old blood and metal reaction products surrounding a pseudocapsule. After excising the pseudocapsule, the acetabular bone defect was found to be cavernous, with bone loss from 11 o’clock on the ilium, covering the ischium and extending inferiorly to 7 o’clock on the pubis (Figure 3). Overall, the patient exhibited a Paprosky 3B bone defect.
Acetabular bone grafting, revision
Given the extensive acetabular bony defect, the decision was made to reconstruct a neo-acetabulum using structural allograft and impaction bone grafting, as there was limited native bone stock to secure cup-cage or metal augment constructs. A femoral head allograft was prepared to address the posterosuperior bone defect. This was temporarily secured in place with two Steinmann pins in preparation for acetabular reaming (Figure 4).
After sequentially reaming a new acetabulum, an impaction grafting technique was utilized with cancellous bone graft reverse-reamed into the neoacetabulum to establish a suitable landing zone for a 60-mm trabecular metal acetabular component. Some supportive bone remained in the anterior column and some cortex of the ischium was present. This enabled us to ream a chamfer that provided initial stability and prevented the cup from migrating medially. Acetabular screws were used to provide additional support for the acetabular component, and secure the structural bone graft in place (Figure 4). We believed that the combination of the chamfer, the structural allograft and multiple screws constituted a durable construct.
A dual mobility and ceramic-on-polyethylene articulation was selected due to the multiple revised soft tissue envelope and a previous episode of instability. This ensured excellent intraoperative stability. The hip capsule and external rotators were repaired in the standard manner using #5 Ethibond suture (Ethicon) through the femoral bone. Subcutaneous and skin closure was carried out with 0 and 2-0 sutures and a Prineo dressing (Ethicon).
Postoperative protocol
The patient was placed on a standard rehabilitation protocol that included mobilization on postoperative day 0 and physical therapy. He was instructed to remain toe-touch-weight-bearing for the first 6 weeks postoperatively to facilitate the integration of the structural bone allograft. The patient received standard posterior hip dislocation precautions and was prescribed a 2-week course of doxycycline twice per day for surgical site infection prophylaxis.
At 6-week follow-up, the patient was ambulating well with crutches to aid weight-bearing restriction and had significantly improved groin pain. Postoperative radiographs demonstrated excellent acetabular component position with early ingrowth and bone graft incorporation (Figure 5).
Discussion
Large acetabular bone defects following THA can present challenging problems to treat. While mild and asymptomatic acetabular osteolytic lesions may be managed through observation, serial imaging and nonoperative measures, acetabular osteolysis often necessitates revision THA with acetabular component exchange. Prior to surgical management, it is essential to accurately identify the cause of osteolysis. Historically, first-generation ultra-high-molecular-weight polyethylene components produced microscopic polyethylene wear particles as it degraded. This degradation leads to macrophage-driven bone resorption. However, with the advent of highly cross-linked polyethylene, contemporary clinical presentations of osteolysis require investigation for alternative causes, including periprosthetic joint infection and metal reaction. In cases of suspected metal reaction or adverse local tissue response, obtaining synovial metal ion levels may be beneficial, particularly when serum metal ion levels are normal. In the case of our patient, it was likely that a combination of polyethylene wear and metal reaction contributed to significant osteolysis.
Surgical management of acetabular osteolysis often necessitates revision THA, with limited indications for cup retention and bone grafting. Careful planning is critical to effectively address the bony defect during surgery and to select a bone grafting and implant strategy that promotes long-term success. Preoperative advanced imaging with CT radiographs can be particularly advantageous in predicting the extent of bone loss at the time of surgery. The Paprosky acetabular bone loss classification depends on the integrity of four reproducible landmarks on plain radiographs (teardrop, hip center, Kohler line and ischium) and remains a widely used classification and guide for the surgical management of acetabular bone defects.
Several acetabular component grafting and reconstructive options have been successfully implanted, yielding good midterm clinical outcomes. These include structural allograft, impaction grafting and the use of a “jumbo” tantalum acetabular shell, as demonstrated in our case. Other acetabular reconstructive methods, such as cup-cage constructs, metal acetabular augments and custom triflange acetabular constructs, have shown reasonable midterm outcomes for massive acetabular defects or pelvic discontinuity. Ultimately, successfully treating Paprosky 3A and 3B acetabular defects requires excellent preoperative planning and familiarity with a variety of reconstructive options available to best address the pattern of bone defect encountered during surgery.
Key points:
- Workup of acetabular osteolysis includes serial radiographs, advanced imaging, evaluation of periprosthetic joint infection and metal reaction.
- Assessment of the acetabular bony defect can inform preoperative planning and allow for flexibility in acetabular reconstructive options during surgery.
- Surgeons have several acetabular reconstructive techniques available, including allograft and trabecular metal augments for massive acetabular bone loss.
- References:
- Chaudhry F, et al. J Arthroplasty. 2024;doi:10.1016/j.arth.2024.07.010.
- Houdek MT, et al. J Arthroplasty. 2021;doi:10.1016/j.arth.2021.04.034.
- Ingham E, et al. Biomaterials. 2005;doi:10.1016/j.biomaterials.2004.04.035.
- Paprosky WG, et al. J Arthroplasty. 1994;doi:10.1016/0883-5403(94)90135-x.
- Prieto HA, et al. J Arthroplasty. 2017;doi:10.1016/j.arth.2017.05.051.
- Sanghavi SA, et al. J Am Acad Orthop Surg. 2024;doi:10.5435/JAAOS-D-23-00645.
- Sheth NP, et al. J Am Acad Orthop Surg. 2019;doi:10.5435/JAAOS-D-16-00685.
- Tarabichi S, et al. J Arthroplasty. 2024;doi:10.1016/j.arth.2024.05.089.
- Taunton MJ, et al. Clin Orthop Relat Res. 2012;doi:10.1007/s11999-011-2126-1.
- For more information:
- Niall H. Cochrane, MD, is from Duke University School of Medicine in Durham, North Carolina. Harold I. Salmons, MD; Nicolas A. Selemon, MD; and Michael J. Taunton, MD, are from the Mayo Clinic in Rochester, Minnesota. Selemon’s email: selemon.nicolas@mayo.edu.
- Edited by Nicole Rynecki, MD, and Harold I. Salmons, MD. Rynecki is a chief resident in orthopedic surgery at NYU Langone. She will be pursuing a sports medicine fellowship at Hospital for Special Surgery following residency completion. Salmons is a chief orthopedic surgery resident at the Mayo Clinic. He will be pursuing an adult reconstruction fellowship at Hospital for Special Surgery following residency completion. For more information on submitting Orthopedics Today Grand Rounds cases, please email orthopedics@healio.com.
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