Abstract
Introduction: Tapered proximally porous-coated stems have many advantages, including no diaphyseal reaming, proximal fixation, and less thigh pain. Conventional rehabilitation suggests that touch-down weight-bearing (TDWB) is required for bone ingrowth and soft-tissue healing to occur. Immediate weight-bearing as tolerated (WBAT) could provide rapid mobilization and quicker recovery and faster return to functionality. This study examines early results with WBAT after implantation of a tapered stem.
Materials and methods: During 1999 and 2000, all THAs were performed with a fiber-metal taper (FMT) component and WBAT was allowed immediately. No cemented or hybrid THAs were performed during this time-period. Radiographs were obtained in the recovery room, and then at 6, 12 and 52 weeks postoperatively. Patients with a minimum 12-week follow-up were included to answer five study questions: Does immediate WBAT affect ingrowth of the stem? Does immediate WBAT lead to more subsidence and/or instability? Does immediate WBAT affect the acetabular component? Does immediate WBAT affect Harris Hip Score? Is there an age limitation? Forty-one cases performed had a minimum 12-week follow-up. Four intraoperative fractures occurred (4.8%), and these patients were excluded as they were made TDWB for 6 weeks. Thus, 37 cases remained and comprised the study group.
Results: Of the 37 patients, 21 were perfomed for OA, 14 for AVN and two for post-acetabular fracture DJD. The average age was 57 (range, 16–78). The average follow-up was 6 months (range, 3–20 months). Radiographically, all 37 stems were ingrown by the 12-week radiograph. Seven patients (17%) had subsidence of the stem, with an average of 0.9 mm (range, 0–7 mm). There were no dislocations. Thirty-six acetabular components (97%) achieved bony ingrowth by the 12-week radiograph. No cups had measurable migration and 9 had nonprogressive radiolucent lines present in one zone. The average HHS was 88 (range, 64–100). Among patients older than age 70, 5/5 stems were ingrown with one stem showing subsidence prior to ingrowth. Two patients (5.4%) had minimal thigh pain.
Discussion and conclusions: This study demonstrates that immediate WBAT does not preclude bony fixation of the stem or acetabulum after Cementless THA. Clearly, longer follow-up will determine whether issues regarding fixation arise at later dates. However, it would be expected that since bony ingrowth occurs, reliably, fixation should remain stable for long periods of time. One immediate advantage of WBAT is that rehabilitation can be facilitated.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
