Introduction

Radiostereometric Analysis (RSA) is an imaging method that is increasingly being utilized for monitoring fixation of orthopaedic implants in randomized clinical trials. Extensive RSA research has been conducted over the last 35+ years using standard clinical x-ray acquisition modalities that irradiate screen/film media or Computed Radiography (CR) plates. The precision of RSA can depend on a number of factors including modality image quality.

Purpose: The purpose of this study is to measure in vivo linear head penetration of a newer generation highly crosslinked liner (X3, Stryker Orthopedics) using Radiostereometric Analysis (RSA).

Method: The 12 hips (11 patients) included in this study are a subset from a larger randomized controlled trial comparing Exeter stem migration in cement mantles with and without Tobramycin. Criteria for inclusion in this subset were the use of an uncemented Trident acetabular component containing X3 polyethylene in combination with a 32 mm stainless steel femoral head. The average age was 72.7 years (range 65 to 80), and there was an equal gender distribution. RSA examinations were taken with patients lying supine at six weeks, six months, one year, and two years postoperatively. The six week examinations were used as the reference examinations for measuring head penetration. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Head penetration was determined via edge-detection measurements of the femoral head and acetabular cup.

Results: The mean cumulative femoral head penetration at 6 months was 0.23 mm; this remained statistically unchanged both at 1 year: 0.20mm (p=0.69, 95% UCL of the difference: +0.15mm) and 2 years: 0.25mm (p=0.77, 95% UCL of the difference: +0.10mm).

Conclusion: It is generally recognized that femoral head penetration of more than 0.1 mm per year can result in osteolysis. The purpose of cross linking polyethylene is to reduce wear to below this level. The results of this study show that after an initial bedding in of approximately 0.2 mm, femoral head penetration is not detectable over the subsequent 18 months. Further follow-up is underway to confirm that this promising reduction in wear is maintained.

Purpose: While it is generally accepted that the results of revision total knee replacement (TKR) are inferior to those of primary TKR, there is little published information documenting this. The purpose of this study is to compare patient-reported functional outcomes following primary and revision total knee arthroplasty patients using standardized, validated outcome metrics.

Method: Using data from an academic arthroplasty database, we undertook a review of health related quality of life (SF-12) and disease specific measures (WOMAC) of patients undergoing either primary or revision TKR. The sample included 39 patients who had undergone revision TKR for reasons other than infection, and 39 patients who had undergone primary TKR matched by gender, age, modified Charnley classification, and number of years of follow-up. Student’s t-test was used to compare both groups. Average length of follow up was 2 years.

Results: The mean age was 65 years. Sixty percent (67%) of the patients were female.

Despite being matched by age, gender and modified Charnley classification, there were significant differences in post-operative functional scores. The revision TKR group’s mean WOMAC score was 73 (SD 17), compared to the primary group’s mean score of 84 (SD 14), p=0.002. Similarly, the revision group’s mean SF-12 PCS score was 35 (SD 8) compared to the primary group’s superior score of 44 (SD 10), p< 0.0001. There was no differences detected in post-operative SF-12 mental component scores; 49 (SD 12) for the revision group compared to 53 (SD 10) for the primary group, p=0.11.

Conclusion: This study confirms the general clinical impression that the functional results of revision TKR are inferior to primary TKR, as measured by both the WOMAC and SF-12 tools.

Purpose: The purpose of this study is to determine if the addition of Tobramycin antibiotic powder to cement for primary hip replacement surgery increases the risk of long term aseptic loosening. This was accomplished by measurement of implant micromotion with Radiostereometric Analysis (RSA).

Method: Exeter femoral stems and Trident acetabular components were implanted into 33 patients. Stems were cemented in a randomized manner with either Simplex P or Simplex T. Tantalum beads were injected into the femur to serve as reference points for RSA measurements. RSA examinations were taken with supine positioning at six weeks, six months, one year, and two years post-operatively. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Distal migration of the stem centroid was measured at each follow-up period and the mean migration rates for both groups were determined. Non-inferiority testing of stem migration in Simplex T compared to Simplex P was accomplished using a one sided t-test, with the significance level set at 0.05. A clinically inferior additional amount of distal migration was set at 0.4mm/yr.

Results: Eleven patients were excluded from the study: seven patients either dropped out of the study or missed the six week and/or two year follow-up examinations, two patients had radiographic image quality issues, and two patients had loosening of their tantalum markers in subsequent follow-ups. Of the remaining 22 patients, eight were male and 14 were female, with an average age at time of surgery of 71.2 (range, 63–81) years. The mean total distal migrations for the Tobramycin and non-Tobramycin cement groups at two years were 0.891 and 0.732 mm, respectively; the mean stem migration rates were 0.263 and 0.179 mm/yr, respectively. The differences in total distal migration and stem migration rate were not statistically significant (P = 0.06 and UCL = 0.173, respectively).

Conclusion: The addition of Tobramycin to Simplex cement does not appear to impact the distal migration pattern for a polished tapered cemented hip stem at two years. This finding suggests that Tobramycin does not have any clinically relevant deleterious effects on the in vivo mechanical properties of Simplex cement.

Purpose: Implant retrieval analysis provides valuable information to researchers, clinicians and manufactures about the in vivo wear characteristics. Wear analysis can quantify visible damage on retrieved UHMWPE bearing surfaces used in total knee arthroplasty (TKA). Various researchers have developed wear scores to help provide insight into the modes of prosthetic failure. Four scoring methods are compared in order to determine their inter-rater reliability.

Method: A cohort of 60 retrieved G2, Smith & Nephew/Richards, TKA implants were analyzed by two observers using four scoring techniques. The scoring methods used had been developed by Hood, Wasielewski, Currier, and Brandt. The intraclass correlation coefficient (ICC) was used in assessing the inter-rater reliability.

Results: The ICC demonstrated significant correlation between raters (P< 0.05). Hood’s method produced a correlation of 0.89, Wasielewski’s method 0.83, Currier’s method 0.58, and Brandt’s method 0.82. All but Currier’s method had excellent correlation between raters.

Conclusion: The analysis techniques for articular surface wear for total knee bearings by Hood, Brandt, and Wasielewski showed excellent inter rater reliability; however currier’s method was only fair. One common issue among all these methods is that the scoring systems do not identify or assign differentiating weights to clinically relevant wear modalities to capture inferior implants designs. A new wear analysis technique that is efficient and assigns clinical severity weights to wear modes in TKA bearings should be investigated.

Introduction: Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis, which appears to be caused by a melatonin signalling dysfunction proved recently in osteoblasts. This pathology occurs and progresses during the time of pre-puberty and puberty growth. This period is known to be under the hormonal control and coincides with many biological changes related to the secretion of estrogens, of which estradiol (E2) is the most active. The female prevalence of AIS disease is clearly evident. Indeed, in Quebec the spine deformities considered clinically significant (at least 11° of deformity) are found in a girl:boy ratio of approximately 2:1 for reduced scoliosis, and this ratio increases to 10:1 for scoliosis of more than 30o of deformation. However, the reason for this female prevalence as well as the role of estrogens and estrogen receptors in AIS is not clear despite the fact that these hormones are known for their impact on bone and bone growth, including the spine.

The purpose of the present study was to investigate the role of E2 on the responsiveness of the AIS cells to the melatonin, to determine the expression of estrogens receptors (ERα and ERβ) in AIS tissues and to clarify the impact of estrogen receptor gene polymorphisms in the pathogenesis of AIS.

Methodology: The effects of oestrogen on the AIS osteoblasts (n=10) response to the melatonin was determined by measuring the reduction of forskolin-induced cAMP accumulation. The forskolin treated osteoblasts were incubated in the presence of increasing amounts of melatonin (10–11 to 10-5 M) with or without physiological concentrations (10-10 M) of 17-β-estradiol for 16 hours, and the intracellular cAMP measured by radio-immunoassay using Biotrak Kit. Using RT-PCR, we determined ERα and ERβ mRNA expression in osteoblasts from AIS patients (n=14). Polymorphisms of the first intron of the ERα gene, which contains the XbaI and PvuII polymorphisms, were investigated by PCR following digestion with restriction enzyme and using the genomic DNA from lymphocytes isolated from scoliotic patients (n=33). Using the restriction enzymes XbaI and PvuII, the allelic variants XX, Xx, xx, PP, Pp, and pp were identified in 33 AIS patients (uppercase letters represent absence, and lowercase letters represent presence of restriction sites).

Results: The intracellular level of cAMP was significantly increased (p< 0.01) in the presence of a physiological concentration of 17-β-estradiol (10-10 M) when compared to the level observed in the presence of melatonin alone (10-9 M) (melatonin + estradiol: 109.46 ± 20.07; melatonin 76.09 ± 12.32 (mean ± SD)). As previously described by Dr Moreau’s team, the same pattern (three type of response to melatonin) takes place in the presence of 17-β-estradiol. We observed the loss of ERβ gene expression in 8/ 14 AIS patients contrasting with ERα gene expression that was found in all AIS patients. The XbaI and PvuII polymorphisms were found in 70% (23/33) and 80% (26/33) of the cases respectively. Of the 33 cases, 21 presented both digestion sites, 24 presented PvuII digestion site (6 homozygote, 18 heterozygote) and 23 (8 homozygote, 15 heterozygote) presented XbaI digestion site. The allelic variants were found as follows: XX: n=8, Xx: n=15, xx: n=8, PP: n=6, Pp: n=18 and pp: n=6. Classified by their location in the spine, seven right thoracic, one left thoracic, one right thoracolumbar, three left thoracolumbar and nine right thoracic-left lumbar were found among the patients presenting PvuII positive polymorphism. Among the patients with XbaI positive polymorphism, six right thoracic, one left thoracic, one right thoracolumbar, three left thoracolumbar and eight right thoracic left lumbar were found.

Conclusion: These results show the antagonistic effects of the 17-β-estradiol on AIS osteoblasts response to the melatonin. Thus estrogens interference with melatonin signalling activity would act as a triggering or aggravating factor in the pathogenesis of AIS. At the molecular level, it is possible that estrogens attenuate the response of AIS cells to melatonin through the desensitization of melatonin receptors. The loss of ERβ expression in a significant number of AIS patients appears to be important for the change of the ERα/ERβ receptors ratio that consequently may perhaps alter estrogens signalling pathways. The XbaI and PvuII polymorphisms are present in a significant number of AIS patients but this was not dependant of the curve pattern. These results clearly support the interplays and crosstalk between estrogens and melatonin signalling pathways in AIS aetiopathogenesis.

Supported by the Fondation Yves Cotrel, Institut de France

The twelve matte and twelve polished surfaces of hemi-arthroplasties were contaminated with Staph. epidermidis and then irrigated with bulb or pulse irrigation. The surfaces were then quantitatively cultured using a standardized swabbing technique. Results are expressed as the percentage of contaminant bacteria recovered. The matte finish groups showed median values of 1.46 and 2.88x10⁻² while the polished finish groups showed 1.49x10⁻³ and 2.83x10⁻⁶ with bulb and pulse irrigation, respectively. The difference between irrigation types was significant (p=0.002) for both matte and polished surfaces. Pulse irrigation was more effective than bulb irrigation in removing contaminant bacteria from the prosthetic surfaces studied.

Tremendous suffering is associated with infection following total joint arthroplasty. To reduce infection risk, some surgeons use pulse irrigation prior to wound closure. This practice is based on the assumption that pulse irrigation will more effectively remove adherent bacteria. However, there has been no study of the effectiveness of pulse irrigation in clearing bacteria from prosthetic surfaces. The hypothesis of this study is that pulse irrigation is more effective than bulb irrigation in removing intra-operative bacterial contaminants from prosthetic surfaces.

The matte and polished surfaces of hemiarthroplasties were studied separately. Each surface was contaminated with Staph. epidermidis and then irrigated with pulse or bulb irrigation. A third group without irrigation was also studied. The surface was then swabbed three times using a standardized technique. The swab tips were quantitatively cultured.

Twelve matte and twelve polished surfaces were examined using both irrigation types with corresponding non-irrigation reference values. Results are expressed as the percentage of contaminant bacteria recovered. The matte finish groups showed median values of 1.46 and 2.88x10⁻² while the polished finish groups showed 1.49x10⁻³ and 2.83x10⁻⁶ with bulb and pulse irrigation, respectively. The difference between irrigation types is significant (p=0.002) for both matte and polished surfaces.

Pulse irrigation was more effective than bulb irrigation in removing contaminant bacteria from the prosthetic surfaces studied.

Funding: Hip Hip Hooray, Zimmer-Sadler

Allogenic blood transfusions are frequent sequellae of hip and knee arthroplasty with potentially deleterious consequences. A prospective collection of a comprehensive data set of 1,185 knee and 1,064 hip arthroplasty patients including primary and revision surgeries was completed with analysis of allogenic and predonated blood usage, blood salvage systems and costs. The most effective strategy in reducing allogenic blood transfusion is the use of a blood salvage system. The most expensive strategy is the use of blood salvage systems with predonation. The least expensive and least effective strategy is no predonation of blood and no blood salvaging system.

The purpose of this study is to evaluate the usage, effectiveness and cost of blood salvage technologies in total hip and knee arthroplasty.

The most effective strategy in reducing allogenic blood transfusion is the use of a blood salvage system. The most expensive strategy is the use of blood salvage systems with predonation. The least expensive and least effective strategy is no predonation of blood and no blood salvaging system. More than half of the predo-nated blood collected was never used.

Blood loss in total hip and knee arthroplasty can have significant deleterious physiologic effects on patients. There are potential health risks with allogenic blood transfusion as well as patient anxiety toward allogenic transfusion. Recent advances in blood management provide additional options that need further evaluation.

The lowest cost strategy was no predonation and no blood salvage system at an average of $30 per patient, but with a 14% incidence of allogenic transfusion. Pre-donation alone had a cost of $330 with a 12% transfusion rate. Predonated blood was wasted in 60% of knee arthroplasties and 48% of hip arthroplasties. The Consta Vac and OrthoPAT blood salvage systems had a cost of $110 and $365 with 5% and 7% transfusion rate, respectively.

A prospective collection of a two-year comprehensive data set of 1,185 knee and 1,064 hip arthroplasty patients including both primary and revision surgeries was completed. Analysis of blood counts, allogenic and predonated blood usage, blood salvage systems, length of stay, demographics and costs were performed.

Purpose: Recently, we highlighted a dysfunction in the melatonin signalling pathway in the osteoblasts from adolescent idiopathic scoliosis patients (AIS). The objective of this project is to verify if in the cells coming from the SIA patients, estrogens interfere with melatonin signalling pathways and to identify mechanisms through which these effects are carried out.

Methods: The effects of estrogens on the melatonin signalling pathway, in osteoblasts from AIS patients (n=7), were determined by measuring the capacity of the Gi proteins to inhibit the accumulation of cAMP. The osteoblasts were incubated in the presence of increasing amounts of melatonin (10–11 to 10–5 M) with or without 17-& #946;-estradiol in physiological concentrations (10–10 M) (n=7). Moreover, coimmunoprecipitations using anti-phosphoserine antibodies were carried out and then followed with a Western blot in order to detect melatonin receptors (MT1 and MT2).

Results: The intracellular level of cAMP is higher in the presence of a physiological concentration of 17-& #946;-estradiol among scoliotic patients compared to the level observed in the presence of melatonin alone. Moreover, the preliminary results of the coimmunoprecipitations seem to show an increase in the phosphorylation of proteins interacting with MT1 and MT2 receptors. The precise nature of these proteins remains to be identified.

Conclusions: These results seem to show the antagonistic effects of the 17-& #946;-estradiol on the melatonin signalling pathway in the osteoblasts from AIS patients. However, more cAMP dosages in the presence and absence of 17-& #946;-estradiol are underway so as to increase the number of patients. The results of this study could contribute to the development of the first molecular screening tests as well as the development of new therapeutic approaches.

Allogenic blood transfusions are frequent sequellae of hip and knee arthroplasty with potentially deleterious consequences. A prospective collection of a comprehensive data set of 1,185 knee and 1,064 hip arthroplasty patients including primary and revision surgeries was completed with analysis of allogenic and predonated blood usage, blood salvage systems and costs. The most effective strategy in reducing allogenic blood transfusion is the use of a blood salvage system. The most expensive strategy is the use of blood salvage systems with predonation. The least expensive and least effective strategy is no predonation of blood and no blood salvaging system.

The purpose of this study is to evaluate the usage, effectiveness and cost of blood salvage technologies in total hip and knee arthroplasty.

The most effective strategy in reducing allogenic blood transfusion is the use of a blood salvage system. The most expensive strategy is the use of blood salvage systems with predonation. The least expensive and least effective strategy is no predonation of blood and no blood salvaging system. More than half of the predonated blood collected was never used.

Blood loss in total hip and knee arthroplasty can have significant deleterious physiologic effects on patients. There are potential health risks with allogenic blood transfusion as well as patient anxiety toward allogenic transfusion. Recent advances in blood management provide additional options that need further evaluation.

The lowest cost strategy was no predonation and no blood salvage system at an average of $30 per patient, but with a 14% incidence of allogenic transfusion. Pre-donation alone had a cost of $330 with a 12% transfusion rate. Predonated blood was wasted in 60% of knee arthroplasties and 48% of hip arthroplasties. The Consta Vac and OrthoPAT blood salvage systems had a cost of $110 and $365 with 5% and 7% transfusion rate, respectively.

A prospective collection of a two-year comprehensive data set of 1,185 knee and 1,064 hip arthroplasty patients including both primary and revision surgeries was completed. Analysis of blood counts, allogenic and predonated blood usage, blood salvage systems, length of stay, demographics and costs were performed.

Surgical treatment of recurrent dislocation after total hip arthroplasty (THA) is challenging with often disappointing results. The influence of the posterior hip capsule is important, and restoration of its function is a major goal of treatment. We describe our experience using an Achilles tendon allograft as a checkrein to limit hip internal rotation and to prevent posterior instability. Twenty unstable THAs were treated using this technique, eliminating instability in fifteen. At an average follow-up of 3.6 years, Achilles tendon allograft augmentation has proven a useful adjunct for the treatment of recurrent posterior dislocation after THA in selected patients.

The purpose of this study is to review our results with a novel treatment for recurrent dislocation after total hip arthroplasty (THA) using an Achilles tendon allograft as a checkrein to prevent instability.

Achilles tendon allograft augmentation has proved to be a useful adjunct for the treatment of recurrent posterior dislocation after THA in selected patients.

Surgical treatment of recurrent dislocation after total hip arthroplasty (THA) is challenging with often disappointing results. Among possible causes of dislocation, the influence of the static soft tissue restraint provided by the hip capsule is important, and restoration of its integrity and function is a major goal of treatment. We describe a new technique in which an Achilles tendon allograft is employed as a checkrein to limit hip internal rotation and to prevent posterior instability.

Twenty unstable THAs with recurrent instability were treated using this technique, eliminating instability in fifteen at an average follow-up of 3.6 (0.5 to 6.6) years.

Prospective data was collected and reviewed on the first twenty patients with recurrent THA instability stabilized with an Achilles tendon allograft. Head and liner exchanges accompanied the allograft. Use of a constrained cup was considered a failure.

Instability was successfully controlled in 75% of patients with use of the Achilles allograft. The technique is an important addition to the treatment arsenal of this difficult problem.