Mini-incision THA yields long-term stability similar to conventional techniques

No cases showed clinical or radiographic signs of aseptic loosening at 10 years' follow-up.

Total hip arthroplasty performed using a mini-incision approach appears to provide long-term stability and durability similar to conventional open procedures, according to a study.

Markus Flören, MD, and D. Kevin Lester, MD, evaluated the 10-year clinical and radiographic outcomes for THA patients treated using a mini-incision posterior technique between 1988 and 1991. The researchers then compared the results to those of published reports involving the same femoral prosthesis implanted with conventional surgical techniques.

The data analysis included 90 hips in 79 patients followed for a mean 10.9 ± 1.1 years postop. Patients had a mean age of 62.1 years at the time of their index operation and 73 years at final follow-up.

In all cases, the surgeon implanted a cementless press-fit Zweymüller Alloclassic prosthesis (Zimmer) and a cementless Perfecta RS stem (Wright Medical Technology), according to the study, published in the Journal of Arthroplasty.

Overall, eight acetabular components were revised an average of 6.8 years after the initial surgery due to early polyethylene wear. For seven of these cases, the acetabular component remained stable and surgeons exchanged only the inlay. The remaining one case had all components exchanged because of suspected infection, the study authors said.

No patients showed either clinical or radiographic signs of aseptic loosening, the authors noted.

At final follow-up, Harris Hip Score averaged 92.3 ± 7.9, with a mean pain subscale score of 43.2 ± 2.7. Excellent scores were reported for 65 patients (72%), good for 18 patients (20%), fair for six (7%) and poor for only one (1%), according to the study.

Additionally, most patients maintained good function, with 66 hips (73%) unrestricted regarding maximum walking distance and only 14 hip (16%) limited to a distance of just 2 to 3 blocks.

"No patients were nonambulatory, nor was any restricted to indoor activities," the authors said.

Radiographic studies were available for 70 of the 90 (78%) hips included in the study. Of these, the researchers found no detectable radiographic changes in 26 femurs (37%), and no hips showed stem subsidence.

The researchers found atrophic bone changes around 40 stems (57%), with 31 stems (44%) having such changes in at least four of 14 zones reviewed, usually the proximal zones. "In only one case were atrophic changes seen in the distal zones: 4, 5, 10 and 11," the authors said.

Of the 70 hips with available radiographs, 62 hip (89%) showed no evidence of osteolysis. Only 10 prostheses (14%) showed radiolucent lines 2 mm or less, and only 10 acetabular implants showed both radiolucent lines and osteolysis (14%), according to the study.

"Overall, our clinical and radiographic results show that the implants achieved stable, functional and durable fixation in a high proportion of patients when the mini-incision technique was used," the study authors said.

"These clinical and radiographic results fall within the same range reported in other studies when the same type of prosthesis was inserted with traditional surgical approaches to the hip. The mini-incision technique did not compromise long-term implant survival," they said.

For more information:
Flören M, Lester DK. Durability of implant fixation after less-invasive total hip arthroplasty. J Arthroplasty. 2006;21:783-790.