RECONSTRUCTION OF SEVERE ACETABULAR BONE-DEFICIENCY WITH THE SPH BICOMPONENTE REVISION SYSTEM (LIMA-LTO, ITALY) IN REVISION TOTAL HIP ARTHROPLASTY.

Abstract

Introduction: Loosening of the acetabular Implant after Total Hip Replacement (THR) is often associated with massive bone loss. Many different solutions to this problem have been reported. The implant we used in our series is a cementless cup that consists of two different modular components: the outer shell, with a caudal hook and 3 iliac wings, and the inner module that can be placed in 20° angulation, where the liner is inserted. Non-structural bone graft was used.

Materials and Methods: From April 2002 to October 2004 24 patients were treated with this implant (age 70,7 years, 48–88). They had had zero to six prior surgeries. Indications were: Aseptic loosening (20), septic loosening (2), repetitive luxations(1), intraoperative acetabular fracture (1). Acetabular bone loss was intraoperatively graded using the DGOT classification. Paprosky Classification was used for preoperative radiological grading.

Harris Hip Score (HHS) was used for clinical evaluation (preoperative scores were retrospectively ascertained from patients’ charts). For radiological follow up plain X-rays of the pelvis a.p. and targeted views of the cup were used. Radiolucency, osteolysis (around cup, caudal hook, screws), migration (medial, cranial) and dumping was noted and the results divided into 3 groups: stable (no migration) at risk (cranial or medial migr.), loosened (cranial and medial migr.).

Results:18 Patients with implants in situ could be examined at an average follow up time of 18,3 months (3–30). (1died, 1 could not be reached, 2 did not want to come to fu, 2 explantations after infection). Average stay in hospital: 26 days, non weight bearing for av.: 9,8 weeks. Complications: 1 transient common peroneal nerve palsy, 1 luxation after 4 months (treated conservatively).

HHS improved from 36,4 to 69,3 points (max. 100). Pain: 15,5 to 36,8 pts (max. 44). Activity of daily living:14,3 to 36,8pts (max. 47). Walking distance 3,6–5,8 pts (max.11).

Radiological results (n=19, patient who died included in rad. FU): Radiolucency and osteolysis: Cup 5, hook 12, screws 10. Migration: medial:7 (all of those had medial bone defects), cranial:4, angulation > 4°:4 Outcome: stable: 11, at risk: 3, loosened 5 (1 died, 1 explanted, 3 control every 3 months)

Conclusion: In our series the SPH Bicomponente does not provide sufficient postoperative stability to facilitate good ingrowth of bone graft. Loosening occurs especially in cases with medial bone defects where the cup has too little contact to pelvic bone. In these cases cemented cups or structural grafts might give better stability. ‘At risk’ patients show better clinical performance than one would expect from the radiological findings.

A second follow up is starting recently with an average FU time of about 36 months.