THA: 10 TO 14 YEAR FOLLOW-UP OF A TAPERED STRAIGHT TITANIUM PROXIMALLY POROUS STEM

Abstract

BACKGROUND: Historically results of cementless THA with a variety of porous material and design has been sporadic with 5–20% thigh pain. A simple straight tapered stem with anatomic features for proximal load transfer and excellent initial stability was developed in the early 90’s.

METHODS: 196 cementless collared Natural hip stems (Sulzer/ Zimmer) were implanted by a single surgeon using a posterior approach. They were entered into a database prospectively from 1992–95 and followed until 2006. Data was collected preoperatively and at intervals with last follow-up of 10–14 years. Physical exams, SF-36’s, hip assessments, patient satisfaction surveys and radiographs were performed. X-rays were analyzed for radiolucent zones and bone condensation/ remodeling.

RESULTS: 106 have 10 year data with 34 dead and 9 having moved out of state. One femoral component was removed for deep infection. Eight have had liner exchanges for polyethylene wear, 1 acetabulum was revised for recurrent dislocations.

There have been no femoral revisions for loosening and no complete radiolucencies involving the cancellous structured titanium (CSTi). 85% of x-rays show proximal bone condensation with maintenance of a strong calcar. Distal radiodense lines (halo) are present in 20% around the split smooth tip, with 30% showing an asymptomatic midstem cortical buildup.

Average Harris Hip scores at 10 years (including all Charnley classes) was 85. 90% of patients reported either no pain (65%) or slight (requiring no medication). 100% were satisfied with their outcomes. Anterior thigh pain was conspicuously absent occurring in one patient but disappearing the first year.

CONCLUSIONS: The design of the conical tapered stem which includes an anterior buildup proximal, proximal Cancellous Structured Titanium (CSTi), midstem anti-rotational flutes and a split/spread distal tip transmits force to the femur in a graduated load transfer keeping the proximal femur healthy without stress shielding. The split distal stem and decreasing radius provides a long zone of transition for stiffness and prevents thigh pain. The CSTi provides dependable bone ingrowth and seals the canal preventing osteolysis even in cases where there has been acetabular poly wear. X-rays, SF 36’s and clinical results document the success. As a straight stem ream/broach technique, excellent clinical results can be obtained by general community orthopedists using techniques they are comfortable with.