Roentgen Stereophotogrammetric Analysis (RSA) is the gold standard for measuring implant micromotion thereby predicting implant loosening. Early migration has been associated with the risk of long-term clinical failure. We used RSA to assess the stability of the Australian designed cementless hip stem (Paragon TM) and now report our 5-year results.

Fifty-three patients were prospectively and consecutively enrolled to receive a Paragon hip replacement. Tantalum beads were inserted into the bone as per RSA protocol and in the implant. RSA x-rays were taken at baseline 1–4 days post-surgery, at 6 weeks, 6 months, 12 months, 2 years, and 5 years. RSA was completed by an experienced, independent assessor.

We reported the 2-year results on 46 hips (ANZJS 91 (3) March 2021 p398) and now present the 5-year results on 27 hips. From the 2-year cohort 5 patients had died, 8 patients were uncontactable, 1 patient was too unwell to attend, 5 patients had relocated too far away and declined. At 5 years the mean axial subsidence of the stem was 0.66mm (0.05 to 2.96); the mean rotation into retroversion was 0.49˚ (−0.78˚ to 2.09˚), rotation of the stem into valgus was −0.23˚ (−0.627˚ to 1.56˚). There was no detectable increase in subsidence or rotation between 6 weeks and 5 years. We compared our data to that published for the Corail cementless stem and a similar pattern of migration was noted, however greater rotational stability was achieved with the Paragon stem over a comparable follow-up period.

The RSA results confirm that any minor motion of the Paragon cementless stem occurs in the first 6 weeks after which there is sustained stability for the next 5 years. The combination of a bi-planar wedge and transverse rectangular geometry provide excellent implant stability that is comparable to or better than other leading cementless stems.

Introduction & aims

The magnitude and pattern of acceptable migration in clinically successful cementless stems is not well understood. Radiostereometric analysis (RSA) is a well-recognised method of assessing implant migration.

Previous studies have reported long term RSA results for cemented stems. The aim of this study was to assess the long-term migration characteristics of the Corail hydroxyapatite-coated cementless stem at 10 years using RSA.

Introduction

To evaluate the clinical success and hip pain and function of patients with infected hip replacement treated by two-stage exchange using a temporary implant with high dose vancomycin added to the antibiotic cement at the first stage revision.

Introduction

There has been almost universal adoption of highly cross-linked polyethylene as the polyethylene of choice in metal-on-polyethylene articulations in total hip replacement (THR). Although wear of conventional polyethylene has been shown to be related to periprosthetic osteolysis, the relationship between wear of highly cross-linked polyethylene and osteolysis remains uncertain. Our aim was to determine the incidence and volume of periacetabular osteolysis at a minimum of seven years following primary THR with metal on highly cross-linked polyethylene articulations.

Anterior lumbar inter-body fusion (ALIF) is a surgical procedure that is available to chronic lower back pain patients who fail to respond to conservative treatments. Failure to achieve fusion may result in persistence of pain. Fusion of the lumber vertebral segment is more accurately assessed using fine-cut helical Computed tomography (CT) scans (0.25 mm thickness slices). Unfortunately this technique exposes the body to high radiation dose with hazard of increase risk of late malignancy. An alternative imaging tool is radiostereometry (RSA) which developed as a means to determine the magnitude of relative motion between two rigid bodies. In this study we used RSA to detect movement at the fused lumbar segment (ALIF site) during flexion and extension and compare the results obtained with fine-cut helical CT scan using histopathology as final gold standard assessment tool.

ALIF of three levels of lumbar spine (L1-L2, L3-L4, and L5-L6) was done in 9 sheep. The sheep divided into three groups (3sheep each). The first group had RSA assessment immediately, 3, and 6 months after surgery. The second group had RSA immediately, 3, 6, 9 months after surgery. The third group had an RSA immediately, 3, 6, 9, 12 months after surgery All the animals were humanly killed immediately after having the last scheduled RSA (group1, group2, and group 3 sheep were killed 6 month, 9month and 12 months after surgery respectively). This followed by in vitro fine cut CT and histopathology after the animals are scarified. Micro CT scan has been also used to identify the area where histopathology slide should be made to pick up fusion. Fine cut CT scan assessment for all sheep were done. The CT scan has been reported by two independent radiologists. Histopathology has been started and will finish in 2 weeks

RSA showed there was significant increasing stiffness of the spine though the fused segments as the time pass on compare to immediate postoperative assessment. CT scan were done and showed variable fusion though out the spinal segments. Histopathology of all sheep has been started and the results will be available in 2 weeks which will be followed by statistical assessment to decide how accurate RSA compare to CT scan in assessment of fusion.

This study aimed to compare the early clinical results and stem subsidence between three consecutive series of revision hip replacement cases with femoral impaction bone grafting to evaluate the effects of developments in technique. In the original series 1 (n=23), bone graft was irradiated at 25kG. I n series 2 (n=12) non-irradiated double washed graft and long stems were used as required.

In series 3 (n=21) modular tamps were used. Sensitive radiographic analysis techniques, EBRA and RSA, were used to measure stem subsidence. Major stem re-revision was required in five hips in series one, one hip in series two and no hips in series three. Two periprosthetic fractures occurred in series one. There was a statistically significant reduction in stem subsidence at the cement-bone interface at 12 months between series one and series two and three (p<0.05). In series three there was negligible stem subsidence at the cement-bone interface.

Technique developments in femoral impaction grafting, including the use of modular tamps designed to simply the procedure, yields excellent early clinical and radiographic results. Using RSA, we have shown that the fixation of the stems in bone is comparable to that achieved in primary hip replacement.