Trabecular metal acetabular components show high survivorship in revision cases

At 5-year follow-up, a study into revising failed acetabular components showed a high survival rate for the tantalum trabecular metal implants used.

Further results from a study on trabecular metal acetabular components used in hip revision surgery suggest the use of these porous tantalum implants may lead to high component survival rates.

One patient’s TM revision cup is shown.

One of the patients with a TM modular augment. Images: Torres A

“The excellent osteoconductive porous tantalum trabecular metal may enable faster, wider and stronger biological fixation, even when limited viable host bone is present,” Ana Torres, MD, PhD, of Gijón, Spain, said in presenting these results at the 12th EFORT Congress 2011.

One patient after a revision surgery A) Preop B) 2 years follow-up C) 5 years follow-up.

Torres and colleagues analyzed clinical and radiographic outcomes for 263 patients to determine the stability and function of tantalum acetabular implants used in revision hip surgeries performed between 2000 and 2002. Patients were operated on at five hospitals using either posterolateral or anterolateral approaches with 8.9 years, mean, between their initial and revision surgeries, the first of which was performed after 198 cases. The group had a mean age of 69.5 years, and included 150 women and 113 men.

Prior implant instability

Torres and colleagues evaluated implant and screw position, polyethelene wear, radiolucent lines, gaps and osteolysis. To determine implant effectiveness, they used CT scans preoperatively, clinical exams, and radiographic imaging done preoperatively and then postoperatively at 3 months, 6 months and annually thereafter.

One patient after a primary THR A) Preop B) Postop C) 1 year follow-up.

Investigators found aseptic loosening was the reason for 71% of revisions, while polyethylene wear with and without osteolysis in stable components comprised 23.5% of them. Femoroacetabular impingement or instability constituted 5.7% of hips revised. Femoral components were revised in 64.6% of cases.

Revisions

In 29.6% of revisions, an extended trochanteric osteotomy was performed. To repair bone defects, surgeons used morsellized bone allograft in 47.9% of cases. Revision implant success was determined using the Harris Hip score (HHS), WOMAC, UCLA and quality of life scores, with Morbidity assessed via the Charnley classification. Most of the patients (42.2%) were Charnley class B2.

Surgeons implanted the TM (trabecular metal) Monoblock Acetabular Cup (Zimmer; Warsaw, U.SA.) in 78 patients and the TM Revision cup and TM modular augment in select cases.

Study strengths

Revision to tantalum implants was successful in 87% of cases and 49% of patients were satisfied with their results. Implant survivorship was 99.2% through 5 years follow-up. At the latest follow-up there were no signs of component migration or progressive radiolucent lines, according to Torres.

Mean clinical outcome scores increased by the 1-year follow-up with the preoperative HSS of 43.6 improving to 82.1 points. The WOMAC improved from 42.9 to 80 points and pre-revision UCLA scores of 3 increased to 6. At final follow-up, investigators observed full radiographic implant/peripheral bone contact in 86.3% of cases.

The study’s strengths included the large cohort, reproducible surgical techniques, readily available implants, long follow-up and outcomes measures used, Torres said, but noted the large number of hospitals and surgeons that participated may be a weakness. However, she said, there are no differences in outcomes based on those factors. — by Jeff Craven

Reference:

• Torres A, Fairen M, Mazon A, et al. Tantalum cups on hip revision surgery. Our study results with at least 5-years follow-up. Paper #3060. Presented at the 12th EFORT Congress 2011. June 1-4. Copenhagen, Denmark.

• Ana Torres, MD, PhD, can be reached at the Orthopaedic Surgery and Trauma Department, Santa Lucia Hospital, Cartagena, Murcia, Spain; + 34-605302700; email: anatp10@msn.com.
• Disclosure: Torres has no relevant financial disclosures.

Trabecular metal implants are a very strong tool in the orthopaedic surgeon’s armamentarium: they have excellent initial stability due to their high degree of friction co-efficiency, up to 80% surface porosity and elasticity similar to subchondral and cancellous bone. Due to those properties, this material is bone-friendly with a high capacity for bone over- and in-growth leading to excellent implant fixation to the bone. In revision surgery, the bone quality is compromised; therefore, the need is imperative for a bone friendly material such as trabecular metal which has the potential for initial stability and quick and reliable bone in-growth. Even in cases without good and reliable initial stability, the possibility to use bone screws with the ilium enhancing the stability is of great use to surgeons. This study provides good feedback and experience from the use of this material offering promising results and a good and reliable solution to the management of difficult cases with severe bone defects in the acetabular side. I would prefer if the investigators gave some more details on the management of huge bone defects such as Paprosky IIIb and usefulness of the trabecular metal augments. Nevertheless this is a multicenter study with a large number of patients and I would like to see it published.

— George Macheras, MD
Session moderator
4th Department of Orthopaedics, KAT General Hospital
Athens
Disclosure: Macheras has no relevant financial disclosures.