Introduction

Autologous Chondrocyte Implantation (ACI) is an effective surgical treatment for chondral defects. ACI involves arthrotomy for cell implantation. We describe the development of an intra-articular injection of cultured MSC, progressing from in-vitro analysis, through animal model, clinical and radiological outcome at five years follow up

Aim:

To simplify sagittal plane spinal assessment by describing a single novel angle in the lumbar spine equivalent to the difference between pelvic incidence (PI) and lumbar lordosis (LL) and evaluate its reliability.

Dual energy X-ray absorptiometry (DXA) is a precise tool for measuring bone mineral density (BMD) around total joint prostheses. The Hologic ‘metal-removal hip’ analysis package (Hologic Inc, Waltham, Massachusetts) is a DOS-based analysis platform that has been previously validated for measurement of pelvic and proximal BMD after total hip arthroplasty (THA). This software has undergone a change in the operating platform to a Windows-based system that has also incorporated changes to DXA image manipulation on-screen. These changes may affect the magnitude of random error (precision) and systematic error (bias) when compared with measurements made using the previously validated DOS-based system. These factors could influence interpretation of longitudinal studies commenced using the DOS system and later completed using the Windows system. The aims of this study were to compare the precision and bias of pelvic and femoral periprosthetic BMD measurements made using the Windows versus the DOS analysis platform of the Hologic ‘metal-removal hip’ software. A total of 29 subjects (17 men and 12 women) with a mean age of 51years (SD±10), who had undergone hybrid THA using a cemented stem and uncemented cup. Subjects underwent duplicate DXA scans of the hemipelvis and proximal femur taken on the same day after a period for repositioning.. Scans were obtained with the patient lying supine in the scanner with the legs in extension and the foot in a neutral position. Scans were carried out using the same Hologic QDR 4500-A fan-beam densitometer in ‘metal-removal hip’ scanning mode. The DXA scan acquisitions were analysed using both the DOS and the Windows versions of the analysis software. The same observer made all analyses (NRS). Pelvic scans were analysed using a four region of interest model and femoral scans were analysed using a seven region of interest model. Precision was expressed as coefficient of variation (CV%) and compared between methods using the F-test. Systematic bias was examined using the Bland and Altman method and paired t-test. The CV% for the pelvic regions of interest (n=4) varied from 3.92 to 8.54 and from 2.36 to 5.96 for the Windows and DOS systems, respectively. The CV% for the net pelvic region was 3.04 and 2.36 for Windows versus DOS, respectively (F- test, p> 0.05). The CV% for the femoral regions of interest (n=7) varied from 1.58 to 4.14 and from 1.84 to 4.65 for the Windows and DOS systems, respectively. The CV% for the net femoral region was 1.75 and 1.51 for Windows versus DOS, respectively (F- test, p> 0.05). Absolute BMD values for the net pelvic region were similar (Bland-Altman, Windows minus DOS value mean = -1.0%, 95% CI −7.5 to 5.6; t-test p.0.05). Absolute BMD values for the net femoral region were also similar (Bland-Altman, Windows minus DOS value mean = 1.3%, 95% CI −8.3 to 10.8; t-test p.0.05). In summary precision of the measurements using the 2 operating systems was similar and there was no systematic bias between methods. These data suggest that scans analysed using each platform may be used interchangeably within the same study subjects, without the need of a calibration correction.

Peri-prosthetic bone loss may contribute to aseptic loosening after THA. The aims of this randomised controlled trial extension study were to study the effect of pamidronate therapy on Peri-prosthetic bone mineral density (BMD) and Peri-prosthetic osteolysis over 5 years after primary THA.

50 patients were enrolled in the study in 1998. All received a hybrid THA (Ultima-TPS stem, Plasmacup) for osteoarthritis. Subjects were randomised to receive either 90mg of pamidronate or placebo by intravenous infusion on the 5^th post-operative day. At 5 years 36 patients (41 Hips: placebo n=21, pamidronate n=20) returned for measurement of BMD and clinical and plain radiographic assessment. Five patients had died and nine had withdrawn from the study.

The effect of pamidronate in maintaining femoral bone mass in the region of the calcar previously reported at 2 years was maintained at 5 years (Gruen zone 6 pamidronate versus placebo ANOVA P=0.038; Gruen zone 7 ANOVA P=0.048). No differences in pelvic BMD were found between treatment groups at 5 years. Harris hip scores used to evaluate clinical outcome did not show any significant difference between the 2 groups over the 5-year period. (Mann Whitney p> 0.05). Isolated expansile osteolytic lesions were identified on AP radiographs of the hip at 5 years in 4 patients (2 placebo, 2 pamidronate; P> 0.05). One patient had a 5x9mm lytic lesion in the region of the femoral calcar, and 3 patients had pelvic lytic lesions in the region of the acetabular dome (largest measuring 20x10mm).

Single-dose peri-operative pamidronate therapy preserves femoral calcar bone mass over a 5 year period after THA. However, although the number of subjects with osteolysis is small, we have seen no difference in the rate of osteolytic lesions between treatment groups. Long term study of this patient group is required to examine the rate of aseptic loosening between the treatment groups.

The pattern and magnitude of pelvic periprosthetic bone loss around cementless metal-backed acetabular implants have previously been described. The pattern of periprosthetic BMD change around cemented all-polyethylene acetabular implants is unreported. The aims of this study were to determine the precision of pelvic BMD measurements around the Charnley cup and to examine the longitudinal pattern of BMD change over the first 2 years after surgery.

19 subjects who had previously received a Charnley cup for osteoarthritis underwent duplicate measurements of pelvic BMD after repositioning using an Hologic QDR 4500A densitometer. Scan analysis was carried out using a 4-region of interest model according to a protocol previously described. In-vivo precision was expressed as coefficient of variation (CV%) for each region of interest. The precision of pelvic periprosthetic BMD measurements were 7.7%, 9.8%, 10.8%, and 9.9% for regions 1 to 4, respectively.

Longitudinal BMD changes were measured over a 2 year period in 32 patients (mean age 74 years; 22 women) undergoing cemented THA for unilateral osteoarthritis (17 right-sided). Transient decreases in BMD were observed in regions 2 and 3 (behind the dome of the implant) at 3 months (−9.0% and −13.2%, respectively; P< 0.05) and at 1 year (−8.1% and −9.3%; P< 0.05). By 2 years there had been some recovery in bone mass (BMD−6.9% and −2.6% respectively). No significant changes in BMD for regions 1 and 4 (located at the rim of the implant) were found.

The precision of pelvic periprosthetic BMD measurements for the cemented Charnley cup are poorer than those we have previously reported for cementless cups and may be due, in part, to cement artifact. The pattern of BMD change observed for the Charnley implant suggests that load transfer between the implant and the pelvis occurs principally at the implant rim. The magnitude of bone loss is similar to that we have previously reported for cementless metal-backed acetabular implants.

The Exeter (Howmedica Ltd) and Ultima-TPS (Depuy Ltd) implants are both collarless, polished, double-tapered, cemented femoral implants. The Exeter is manufactured in stainless steel and has an excellent long-term survivorship. The Ultima-TPS is manufactured in cobalt-chrome and has been recently introduced. The aim of this study was to compare the early performance of these implants in a 2-year randomised clinical trial.

65 patients with unilateral hip osteoarthritis were randomised to receive either the Exeter or TPS stem. All received a Charnley Cup. Outcome measures included the Oxford Hip Questionnaire, proximal femoral bone mineral density (BMD) measured by dual energy x-ray absorptiometry, and implant subsidence measured using EBRA. At 2 years 43 patients (66%) were reviewed. 22 patients (mean age 70 years, 16 female, BMI 27.9Kg/m²) received the TPS implant, and 21 patients (mean age 70 years, 15 female, BMI 28.9Kg/m²) received the Exeter implant. 19 patients withdrew for reasons unrelated to the study, 2 died, and 1 was withdrawn after deep wound infection.

Complete Oxford hip scores were available pre-operatively and at 2 years in 37 patients (n=20 TPS). Median (IQR) pre-operative hip scores were 51 (43 to 54) and 48 (36 to 53) for the TPS and Exeter implants, respectively. At 2 years the hip scores improved to 24 (18 to 31) and 22 (16 to 31), respectively. There were no differences in scores between groups at each time-point. There were no differences in BMD between groups at pre-operative baseline, 3 months, 1 and 2 years (Gruen zones 1–7, all time-points; n=19 TPS, n=13 Exeter implants: P> 0.05). Maximum bone loss was seen in Gruen zone 7 at 2 years for bone implants (TPS-11%, Exeter -14%, P> 0.05). Measurement of subsidence over 2 years using EBRA was possible in 20 patients (n=7 TPS, n=13 Exeter). Mean subsidence at 2 years was 1.62mm for the TPS implant and 1.60mm for the Exeter implant (P> 0.05). There was no plain radiographic evidence of osteolysis in either group.

These data suggest that the early performance of the two implants studied is similar. However, long-term survivorship data is required to confirm their equivalency.