Introduction: Early non progressive horizontal RLLs (< 2mm) under the tibial component following cemented TKR have been noted to be due to poor cement injection into cancellous bone. They may facilitate the entry of joint fluid and wear debris into the interface, which may proceed to ballooning osteolysis. At present, there is no consensus on the preferred cementing technique (single mix versus dual mix cementation) in TKR.

Purposes of the study: To assess RLLs in immediate postoperative radiographs in cemented TKRs at the cement-bone and cement-implant interface.

To compare the RLLs following single mix and dual mix cementation techniques.

Study Design: Prospective, consecutive radiographic analysis.

Material and Methods: 53 consecutive cemented TKRs in 39 patients (12: 27, F: M) with mean age of 72.5 years (range 50–90 y) who were operated on between 2001 to 2004 by the senior author (NMG). 27 had single mix and 26 had double mix cementation. Immediate postoperative radiographic assessment (AP and LAT standing view) was blinded for single mix versus dual mix cementation. All the radiographs were independently assessed by two of the authors for the presence of RLLs using the zonal pattern of the Knee Society scoring system. We have evaluated the RLLs in the cement-implant interface in a similar manner as described for the bone-cement interface.

Results: Most common TKR used was the Maxim (31) followed by the PFC (9). 29(54.7%) TKRs had RLLs (11in single mix : 18 in dual mix). There were more RLLs at the Cement-implant interface (29), than the bone-cement interface (10). In AP view, Zones 1(medial) and 4 (lateral) were the common sites for RLLs in both groups (< 2mm). In Lateral view, Zone 1 (Anterior) followed by Zone 2 (Posterior) were the common sites of RLLs (< 2mm). In AP view, there was no significant difference in the number of RLLs (Zone 4) between the two groups. The total number of RLLs in all zones (Zone 1–4) was significantly low in the single mix group (p< 0.05). There was no difference between the two groups in the lateral view.

Conclusions: Single mix cementation technique reduces the incidence of RLLs in the immediate postoperative radiographs following cemented TKRs.

Introduction The Zweymuller tapered cementless titanium femoral stem has been in widespread use since 1986.1 Stress shielding of the proximal femur has been a concern with pressfit cementless femoral stems. Radiolucent lines (RLLs) are signs of stress shielding and possibly over time, may lead to aseptic loosening.2

Aim To evaluate the longterm radiographic bone response in the femur following Zweimuller total hip replacements.

Study Design Consecutive case study (serial radiographic analysis)

Material and Methods 49 Total Hip Replacements in 42 patients (M:F=25:17) with a mean age of 59 years (range 49–70 years), were included in the study. All patients were operated on by the senior surgeon (JRW). 28 Alloclassic and 21 Endoplus stems were implanted. AP and Lateral radiographs were assessed. A gap of 1mm or more at the bone prosthesis interface was recorded as positive for RLLs in the Gruen zones. The mean duration of follow-up was 46 months (range 24–140 months). 17 patients had follow up of more than 5 years. Other measurements included subsidence, bone remodelling and heterotropic ossification.

Results After 2 years there were distinct radiological changes (RLLs), mainly in Gruen zones 1 and 7, in 18/49(36%) femora. Though there was evidence of RLLs in zones 2 and 6, the numbers were insignificant. Subsidence of more than 3mm was noted in 16 stems (33%). Heterotropic ossification was found in 4 patients (8%), one of whom required excision. Persistent pain due to trochanteric bursitis was noted in 10 patients. 4 patients needed revision due to reasons other than aseptic loosening. There were two dislocations, which needed revision of the acetabular component.

RLLs were more common in the Endoplus group (10/21) compared to the Alloclassic group (8/28). There was no clinical compromise (all had pain free mobility) in these patients and no progression of RLLs was noted.

Conclusion Proximal femoral stress shielding following Zweimuller femoral stem implantation is observed in significant number of patients. The RLLs do not correlate with symptoms and patient satisfaction.