Traditional total knee arthoplasty techniques have involved implantation of diaphyseal stems to aid in fixation expecially when using constrained polyethylene inserts. While the debate over cemented vs uncemented stems continues, the actual use of stems is considered routine. The authors' experience with cemented stemmed knee revisions in older patients with osteoporotic bone has been favorable. Our younger patients with press-fit stems from varying manufacturers have been plagued with a relatively high incidence of component loosening and stem tip pain in the tibia and occasionally thigh. We report the early results of the first 20 total knee revisions using press-fit metaphyseal filling sleeved stemless implants with constrained bearings. Twenty three patients with failed primary or revision total knees were assigned to receive stemless sleeved revision knee designs using the DePuy MBT/TC3 system. Reasons for revision included loosening, implant fracture, stiffness, instability, and stem pain. Twenty patients (ages ranging from 42–73) were successfully reconstructed without stems. Six knees with significant uncontained cavitary defects were included. Three patients with unexpectedly osteoporotic metaphyseal bone were revised with cemented stemmed implants and excluded. All cases used cement for initial fixation on the cut bone surface and fully constrained mobile bearing inserts.Purpose
Methods
The use of tapered titanium femoral stems has gained in popularity for primary total hip arthroplasty. One of the basic stem designs is a fully grit blast square tapered stem with distal fixation (Zweymuller-type). Another stem design (Muller-type), a proximally porous coated flat wedge stem with proximal fixation is associated with a low but significant perioperative femoral fracture risk. Both of these implant types are inserted with a broach-only technique. We theorize that the Zweymuller-type implant can be inserted safely with pneumatic broaching with a very low fracture risk even when broached by rotating residents with no prior experience. We prospectively reviewed 300 consecutive hip arthroplasty cases using Zweymuller-type stems from eight different manufacturers implanted using the Woodpecker TM pneumatic broaching system. The series included both THA and hemiarthroplasty cases with a wide range of cortical/canal indexes. Patient age ranged from 14 to 98 (avg. 68). Half of the hip stems were inserted through a posterolateral modified Kocher-Gibson approach, and half through an anterolateral Hardinge approach. Approximately 25 rotating residents who were initially unfamiliar with this broaching technique and stem implant type performed the majority of the procedures. We routinely obtained an intra-operative AP pelvis x-ray to confirm trial implant size, alignment, and adjust the leg lengths. The overall technique/implant-related perioperative complication rate was 2% (6/300). These included intra-operative femoral fractures(2), post-operative femoral fractures (1), dislocations(3), and deep infections(2). There were no cases of nerve palsy or leg length inequality >
1cm. Rates of post-op blood transfusions and venous thromboembolism were not reviewed for the purposes of this study. Only one of the complications (one deep infection) required exchange of the original femoral component. There was no significant difference in complication rates between type of surgical approach, brand of square tapered stem manufacturer, or experience of the operating surgeon. We conclude that hip arthroplasty using pneumatically broached, square tapered, cementless distal fixation (Zweymuller-type) hip stems has a low learning curve and can be implanted safely even in very osteoporotic bone. This technique/implant gives the surgeon control of stem anteversion for stability and leg length inequality correction. The incidence of certain perioperative complications can be reduced by using Zweymuller-type stems using pneumatic broaching regardless of approach, implant manufacturer, or surgeon experience. These patients will continue to be followed clinically for implant survivorship.
