Hugh U. Cameron

The 3-6-Year Results of a Modular Noncemented Low-bending Stiffness Hip Implant A Preliminary Study

A review of the 3-6-year clinical and radiographic results of a modular noncemented stem has been carried out. This is a three-part stem consisting of a head, stem, and proximal sleeve. The stems are split distally like a clothespin in the coronal plane to reduce bending stiffness. No mechanical failures have occurred, including no bead separation from the single-layer porous-coated taper lock sleeves. Of the 48 cases, 13 had smooth stems distally while the rest were fluted. Five of the fluted stems were solid, that is, nonsplit. Clinical results are 93.7% excellent, 4.2% good, and 2.1% poor with the Harris hip rating. There have been no revisions. Thigh pain incidence with the distal split stem was 4.4%. Radiographic follow-up evaluations revealed nonprogressive radiolucency around one of the ingrowth sleeves. When inserted in varus the smooth stems developed some radiolucency around the distal end. Fluting of the stem appeared to prevent this.

Patella baja complicating total knee arthroplasty: A report of two cases

Severe noniatrogenic patella baja is a rare condition. Two cases were seen accompanying severe osteoarthritis of the knee. In both cases, following total knee arthroplasty the patella failed to make contact with the femoral component. The tibial tubercle had to be shifted proximally 2 cm to restore the normal joint mechanics. In one case, dislocation of the patella to gain access to the knee could be achieved only with osteotomy of the tibial tubercle. The technique of tibial tubercle elevation adopted was to raise a long bone flap. This allowed the tibial tubercle to be moved proximally and anchored securely.

Design rationale in early clinical trials with a hemispherical threaded acetabular component

Ninety-eight cases of a titanium hemispherical screw cup were followed for 1-3 years (average, 2 years). To differentiate stem problems from acetabular problems, as and because the early results of the cemented stem are well known, the authors studied only those uncemented screw cups with a cemented stem. Of five cases with acetabular pain, one was definitely loose and two were probably loose and require revision. With increasing experience, the selection criteria for the use of an uncemented screw cup have become increasingly rigid; today, the loose cases would probably be handled with a bipolar implant. In most cases initial radiolucency decreased with time, and on clinical radiographs the vast majority showed no radiolucency. The overall Harris rating was 91% (excellent). The early results for this component are quite promising, but further longitudinal studies are required.

Cementless fixation in total knee arthroplasty

In this study we present our experience with four generations of uncemented total knee arthroplasty (TKA) from Smith & Nephew: Tricon M, Tricon LS, Tricon II and Profix, focusing on the failure rates correlating with each design change. Beginning in 1984, 380 Tricon M, 435 Tricon LS, 305 Tricon 2 and 588 Profix were implanted by the senior author. The rate of revision for loosening was 1.1% for the Tricon M, 1.1% for the Tricon LS, 0.5% for the Tricon 2 with a HA coated tibial component, and 1.3% for the Profix TKA. No loosening of the femoral component was seen with the Tricon M, Tricon LS or Tricon 2, with no loosening seen of the tibial component with the Profix TKA. Regarding revision for wear, the incidence was 13.1% for the Tricon M, 6.6% for the Tricon LS, 2.3% for the Tricon 2, and 0% for the Profix. These results demonstrate that improvements in the design of uncemented components, including increased polyethylene thickness, improved polyethylene quality, and the introduction of hydroxyapatite coating, has improved the outcomes of uncemented TKA over time.

Nineteen year results of THA using modular 9 mm S-ROM femoral component in patients with small femoral canals.

A retrospective analysis was undertaken of 30 consecutive THA performed in 25 patients with hypoplastic proximal femurs, who had received a 9-mm uncemented modular S-ROM stem. The mean patient age was 42 years (17-69 years), mean height was 152.5 cm (130-170.5 cm), mean weight was 63 kg (39-90 kg), and mean follow-up period was 19 years (range, 12-23 years). Subsidence was seen in 2 hips, with asymptomatic femoral osteolysis present in 11 hips; overall survival of the femoral stem was 93.3%, with two revisions of the femoral component required for aseptic loosening. After a mean follow-up of 19 years, the use of the S-ROM 9 mm femoral stem in the patient with the small femur was associated with a low revision rate due to aseptic loosening of the stem.

Long-Term Comparison of Porous Versus Hydroxyapatite Coated Sleeve of a Modular Cementless Femoral Stem (SROM) in Primary Total Hip Arthroplasty

UNLABELLED Hydroxyapatite (HA) is commonly used on femoral stems to assist in osseous integration but there is limited evidence of the benefit it provides. We report a prospective comparison of 117 and 102 patients receiving either porous or HA coated sleeves respectively. Patients were evaluated at mean of 12.5 years in the porous and 13.7 years in the HA groups. The mean Harris Hip Score was 94.7 and 94.5 in the porous and HA groups respectively. One porous and 2 HA stems required revision. This study demonstrates that there is no long-term advantage to using an HA coating on the sleeve of this modular stem and confirms excellent long-term results for the SROM stem in a primary arthroplasty setting. LEVEL OF EVIDENCE II (prospective cohort study).