Background

The anterior approach for total hip arthroplasty has recently been hypothesized to result in less muscle damage. While clinical outcome studies are essential, they are subject to patient and surgeon bias. We prospectively analyzed biochemical markers of muscle damage and inflammation in patients receiving anterior and posterior minimally-invasive total hip arthroplasty to provide objective evidence of the surgical insult.

A monobloc porous tantalum acetabular cup with a 28mm internal diameter was employed in 397 primary total hip replacements between August 1997 and December 2003. All patients were personally examined at yearly intervals for 3 years following surgery and at 2 year intervals thereafter. Thirty-one patients were known to have died and 69 hips were lost to follow up less than three years following implantation, leaving 297 hips (81%) available for review up to 10 years following implantation.

The mean age at surgery was 66.2 years, with 12% of patients aged 80 years or older. 58% of the patients were female and 42% male. 82% of the patients had osteoarthritis. Clinical and radiographic data were analyzed for patients followed for a minimum of 3 years. Mean follow up was 5.4 years. The mean preoperative Harris hip score was 31, increasing to 89 at last follow up.

The most common complication was dislocation. Eleven patients had dislocations in the early postoperative period: 4 required closed and 2 open reduction, and five required revision of the acetabular component for recurrent instability. Three patients (4 hips) with severe rheumatoid arthritis developed late instability and required acetabular revision. Four patients had a femoral fracture, 2 of which healed with slight settling and 1 of which required open reduction, subsequently became infected and required removal of the prosthesis. There was 1 superficial and 2 additional deep infections, one of which required component removal. Two patients had a fracture of the greater trochanter and required internal fixation. Four femoral components loosened, of which 3 were revised, all without involvement of the acetabular component.

There were 3 transient sciatic nerve palsies; one resolved completely and two partially, although all 3 were lost to follow before 3 years.

The porous tantalum monobloc acetabular components performed remarkably well at up to ten years following implantation. There were no instances of clinical or radiographic loosening, no osteolysis and no measurable wear visible on postoperative radiographs. The highly porous tantalum achieved reliable bony ingrowth in all cases. We hypothesize that the direct compression molding of the polyethylene into the porous tantalum substrate eliminated the backside wear and the flexion of the polyethylene liner that occurs in modular cups.

The purpose of this study was to evaluate a high flex porous tantalum metal monoblock component system implanted through a MIS technique.

A fellowship trained surgeon proficient in MIS surgery performed 109 consecutive TKAs in 95 patients. Patients were implanted with a tantalum monoblock tibia and a fiber-metal cruciate-retaining high flex femur through a MIS midvastus approach. Ninety uncemented porous tantulum monoblock patellae and 19 cemented all polyethylene patellae were implanted.

Knee Society scores and Knee Society radiographic scores were calculated in all patients. Follow-up for a minimum of 2 years was performed in 109 knees. The average follow up was 39 months. Sixty-six percent of the patients were female and 34% male. The average age was 66 years. The average preoperative Knee Society Knee score was 36. The average preop Knee Society Functional Score was 46. Osteoarthritis was the primary diagnosis in 104 knees. Rheumatoid arthritis and Hemophilia was the diagnosis in two knees each.

The average Knee Society Knee Score improved to 89. The average Knee Society Function score improved to 86. 106 of the knees were rated good or excellent and three knees were rated poor. Two patellar revisions were performed for loose components and one for patellar misalignment. One patella fracture occurred that required ORIF. One femoral component was revised for loosening. There were nonprogressive radiographic lucencies demonstrated on 4 tibial components. One tibial component was rated loose. There were radiographic lucencies on 5 femoral components, all nonprogressive. There were two uncemented tantalum patellar components with stable radiolucencies.

Early results in 109 consecutive porous tantalum metal tibial and high flex cruciate-retaining femoral components implanted through an MIS midvastus approach have a high rate of success at a minimum followup of two years.