Re-Implantation of Total Hip Replacement (THR) with Burch-Schneider (BS) plate in 2003–2007 – Midterm Results at Our Institution

Materials and Methods: Five hundred and forty-nine total hip re-replacement surgeries were performed at our institution, the Orthopaedic Clinic of the Bulovka Hospital, between 2003 – 2007. Follow-up ranged from 5 to 10 years. 243 of the surgeries involved acetabular cup re-implantations, with 77 (31.6%) of those having used the BS cage. In all cases, the acetabular bone loss was assessed according to Paprosky classification. Preoperative procedures included anteroposterior pelvis x-ray pelvis, with determination of the proximalization of the center of rotation, osteolysis of the os ischii and teardrop, and position of the implant in relation to Köhler’s line. During the operations, the remaining bone stock and pelvis discontinuity was defined.


Introduction
The Burch-Schneider (BS) plate ( Figure 1) has been in constant use since its introduction in 1974. In 1987, however, the material was switched from steel to titanium, with the aim of improving its utility and long-term outcome. Our institution commonly uses the BS plate for pelvis reconstructions. In the preoperative planning stage, we routinely perform anteroposterior (AP) x-ray of the pelvis to determine the pelvic defects, proximalization of the center of rotation, osteolysis of the os ischii and teardrop, and the position of implants with respect to the Köhlers ilioischial line. All of these parameters can influence re-implantation of the acetabular component, particularly as they help to determine the underlying acetabular defects. We also routinely use the Paprosky classification system [1] when assessing which spherical acetabular components to use for re-implantation ( Figure 2), considering every degree for its effect on the stability of the spherical component to be implanted. Most of our cases were IIIa than IIIb as defect of the acetabulum. For patients with Paprosky defect IIIa-defined as a proximolateral defect without pelvic discontinuity -the plate is better implanted into pelvis, as it will overcome the loss integrity in the posterior wall due to the defect. Considering the literature, wall acetabulum and that the defect can effect more than 50% of resting bone. Scott et al. [3] also reported that excessive defects of the acetabulum, without healing potential, are indicators for use of bone grafts in the reconstruction procedure. On the other hand, Hur et al. [4] reported on a mechanical aspect, in that osteosystesis of the pelvis occurs due to pelvic discontinuity with press-fit acetabulum when the BS cage is used, even when the BS cage did not present any superficial results (i.e. functional outcomes).  Finally, Peters et al. [5] had earlier noted poor long-term results for the BS plate in resolving pelvic discontinuity. The stability of the BS plate can be assessed by x-ray, and the imaging findings can help to predict its duration over the long-term. To this end, Gill et al. [6] showed plate instability as being indicated on x-ray by fracture of the proximal screws in the plate, together with proximal-migration of more than 5 mm, and with progression of radiolucent lines.
Moreover, Van den Linde and Tonino [7] showed that fracture of the proximal screws without subsequent migration of the plate or change of inclination on x-ray does not equate to plate loosening.
Our x-ray analyses agreed with these reported parameters ( Figure   3). In addition, Gross et al. [8] showed that resorption of the bone grafts implanted into the pelvis upon re-implantation served as a marker of plate stability, as evidenced by x-ray imaging. This study was designed to Gross et al. [8].

Figure 3:
Representative case of fracture located proximally in the BS plate but without loosening. The three x-ray images were taken over a 6-year period, as indicated. The fractured screws are indicated by yellow arrows. perform re-implantation for subsequent defects, which tend to be larger, and especially so with the acetabular component ( Figure 4).

Materials and Methods
All patients with BS plate re-implantation were assessed by x-ray of the pelvis to identify cases of asymptomatic loosening; only 5 cases (7%) were found. In follow-up, the patients were re-operated (two times in total for 4.2% of the cases to address complete loosening or  and luxation (2012). In the same year (2012), we re-admitted the patient for re-reimplantation and implanted a hemispheric modulus with excenter and larger revision stem. In Figure 6, a case of mechanical loosening of the BS plate is presented. This event does not, generally, lead to positional plate loosening. Instead, the plate protrudes into the pelvis slightly, though it is still capable of full-weight bearing.

Bone Cement
The use of bone cement is not supported in the literature.    We had performed operations only from the lateral pelvic approach, and revision with pelvic approach was not necessary; this approach is even recommended for revision of pelvic vessels [9,10]. We performed preoperative angiography in cases with suspected vessel damage and subsequent likelihood of difficulty in operation; as such, this procedure was not performed routinely. We preferred to perform a preoperative computed tomography scan with filtration of the steel scatter. This technique helped us to assess the key feature of good, long-lasting duration, that being good integration of allografts, deep into the acetabulum. Good position and firm osteointegration of the plate are also essential, as they will promote creation of the bony layer inside the pelvis (Figure 9).
Additional results are presented in Figures 9-14 and Tables 1-3.