Subsidence remains a concern when utilizing modern tapered fluted titanium (TFT) femoral stems and may lead to leg length discrepancy, impingement, instability and failure to obtain stem osseointegration. This study aims to compare stem subsidence across three modern TFT stems. Our secondary aim was to investigate the influence of bicortical contact or ‘scratch fit’ on subsidence, as well as the role of intraoperative imaging in maximizing this bicortical contact and preventing stem subsidence.

A retrospective review of 271 hip arthroplasties utilizing modern TFT stems in a single institution was performed. Three stem designs were included in the analysis: one monoblock TFT stem (n=91) and two modular TFT stems (Modular A [n=90]; Modular B [n=90]). Patient demographics, Paprosky femoral bone loss classification, bi-cortical contact, utilization of intra-operative imaging and stem subsidence (comparison of initial post-operative radiograph to the latest follow up radiograph - minimum three months) were recorded.

There was no statistically significant difference in the amount of subsidence between the three stems (Monoblock: 2.33mm, Modular A: 3.43mm, Modular B: 3.02mm; p=0.191). There was no statistical difference in subsidence >5mm between stems (Monoblock: 9.9%, Modular A: 22.2%, Modular B: 16.7%). Subgroup analysis based on femoral bone loss grading showed no difference in subsidence between stems. Increased bicortical contact was strongly associated with reduced subsidence (p=0.004). Intra-operative imaging was used in 46.5% (126/271) of cases; this was not correlated with bicortical contact (p=0.673) or subsidence (p=0.521). Across all groups, only two stems were revised for subsidence (0.7%).

All three modern TFT stems were highly successful and associated with low rates of subsidence, regardless of modular or monoblock design. Surgeons should select the stem that they feel is most clinically appropriate.

The purpose of this study was to precisely measure the 10-year polyethylene wear rate of primary total hips using Radiostereometric analysis (RSA) comparing Oxidized Zirconium (OxZi) to cobalt chrome (CoCr) femoral heads articulating with highly cross-linked polyethylene (XLPE).

RSA was performed on 46 patients who underwent total hip arthroplasty − 23 who received OxZi femoral heads and 23 who received CoCr heads in combination with XLPE at a minimum of 10 years follow-up. All patients had identical THR systems implanted except for the femoral head utilized. The Centre Index method was utilised to assess total wear rates (from index surgery until final evaluation) using a dedicated RSA Software program (UmRSA Digital Measure v.2.2.1). In addition, the Martell technique was used to subtract head penetration occurring in the first 1–2 years (i.e. bedding-in phase) to allow calculation of the ‘steady state’ wear rates.

There were no significant differences in demographics (i.e age, BMI, gender) between the groups. The average time from surgery of the RSA examinations was 11.7 and 12.6 years for the CoCr and OxZi groups respectively. Using the Centre Index Method to calculate total head penetration, wear rates were slightly higher in the OxZi group (0.048 +/− 0.021mm/year) compared to the CoCr group (0.035 +/− 0.017mm/year) with no statistical difference between the groups (p= 0.02). After correction for the bedding-in period, there was no statistically significant difference in mean ‘steady-state’ wear rate between OxZi (0.031 +/− 0.021mm/year) and CoCr (0.024 +/− 0.019mm/year) at 10 year follow up (p= 0.24). A comparison of preoperative and postoperative SF12, HHS, and WOMAC scores showed no statistical difference between the groups.

RSA demonstrated the 10 year in-vivo wear rates of both bearing combinations to be well below the threshold for osteolysis. There was no significant difference between either the total or ‘steady-state’ wear rates of the OxZi and CoCr groups at 10 years.

The infection rate after total joint arthroplasty (TJA) has been shown to be 1–2% in multiple series and registry data. Irrigation, debridement, and polyethylene exchange (IDPE) is a common first line treatment in many cases of acute prosthetic joint infection (PJI). The reinfection rate in open IDPE procedures is variable with studies showing reinfection rates of 10–70% depending on various patient and microbial factors. Our pilot study aimed to determine if the bacterial load in infected total joints was sufficiently reduced by IDPE to allow for the use of post-debridement cultures as an independent marker of procedural success.

46 prosthetic joint infections underwent irrigation and debridement using 6L of normal saline and 3L of a normal saline and bacitracin mixture prior to the insertion of a new polyethylene liner. This protocol utilized a single equipment setup with all surgical members donning new gloves prior to polyethylene exchange. Between 3 and 5 intraoperative cultures were obtained both prior to and after debridement as per the surgeon's standard protocol. A two-tailed student's t-test was used to evaluate for any differences in the rate of positive culture between these two groups.

Of all pre- and post-debridement cultures sampled 66.5% and 60.7% of cultures were positive respectively. No significant difference in the rate of positive intraoperative culture was found between pre-debridement and post-debridement groups (p = 0.52). In 32 of 46 (69%) cases there was no difference in the total number of positive cultures despite a thorough debridement.

Our data shows that open debridement of PJI does not provide a sterile environment, and post-debridement cultures should not be used as an independent marker of procedural success. The role of an irrigation and debridement to reduce the bacterial burden and potentiate the clearance of an infection is established but its efficacy is unclear, and the inability to create a post-debridement sterile environment is a concern.

The purpose of this study is to compare 90-day costs and outcomes for primary total hip arthroplasty (THA) patients between a non-obese (BMI 18.5–24.9) versus overweight (25–29.9), obese (30–34.9), severely-obese (35–39.9), morbidly-obese (40–44.9), and super-obese (45+) cohorts.

We conducted a retrospective review of a prospective institutional database of primary THA patients from 2006–2013, including patients with a minimum of three-year follow-up. Thirty-three super-obese patients were identified, and the other five cohorts were randomly selected in a 2:1 ratio (total n = 363). Demographics, 90-day outcomes (costs, reoperations, and readmissions), and outcomes after three years (revisions and change scores for SF12, HHS, and WOMAC) were collected. Costs were determined using unit costs from our institutional administrative data for all in-hospital resource utilization. Comparisons between the non-obese and other groups were made with Kruskal-Wallis tests for non-normal data and chi-square and Fisher's exact test for categorical data.

The 90-day costs in the morbidly-obese ($13,134 ± 7,250 mean ± standard deviation, p <0.01) and super-obese ($15,604 ± 6,783, p <0.01) cohorts were statistically significantly greater than the non-obese cohorts ($10,315 ± 1,848). Only the super-obese cohort had statistically greater 90-day reoperation and readmission rates than the non-obese cohort (18.2% vs 0%, p <0.01 and 21.2% vs 4.5%, p=0.02, respectively). In addition, reoperations and septic revisions after 3 years were greater in the super-obese cohort compared to the non-obese cohort 21.2% vs 3.0% (p = 0.01), and 18.2% vs 1.5% (p= 0.01), respectively. There were no other statistical differences between the other cohorts with the non-obese cohort at 90-days or after 3 years. Improvements in SF12, HHS, and WOMAC were comparable in all cohorts.

The 90-day costs of a primary total hip arthroplasty for morbidly-obese (BMI 40–44.9) and super-obese (BMI>45) are significantly greater than for non-obese patients, yet these patients have comparable improvements in outcome scores. Health care policies, when based purely on the economic impact of health care delivery, may place morbidly-obese and super-obese patients at risk of losing arthroplasty care, thereby denying them access to the comparable quality of life improvements.

Lewinnek's safe zone recommendation to minimise dislocations was a target of 5–25° for anteversion angle and 30–50° for inclination angle. Subsequently, it was demonstrated that mal-positioning of the acetabular cup can also lead to edge loading, liner fracture, and greater conventional polyethylene wear. The purpose of this study was to measure the effect of acetabular cup position on highly crosslinked polyethylene wear in total hip arthroplasty (THA) at long-term follow-up.

We identified all patients that underwent primary THA with a minimum of 10 years follow-up using an institutional database in London, Ontario, Canada. Patients with a single implant design consisting of a 28 mm cobalt chromium head and highly crosslinked polyethylene liner (ram extruded, GUR 1050, 100 kGy gamma irradiated, remelted, ethylene oxide sterilised) were selected for inclusion. In total, 85 hips from 79 recruited patients were analysed. Patients underwent a supine radiostereometric analysis (RSA) exam in which the x-ray sources and detectors were positioned to obtain an anterior-posterior and cross-table lateral radiograph. Acetabular cup anteversion angle, inclination angle, and 3D penetration rate (including wear and creep) were measured from the stereo radiograph pairs.

At a mean follow-up of 13 years (range, 10–17 years) the mean penetration rate was 0.059 mm/year (95% CI: 0.045 to 0.073 mm/year). Mean anteversion angle was 18.2° (range, −14 to 40°) and mean inclination angle was 43.6° (range, 27 to 61°). With respect to the Lewinnek safe zone, 67% hips met the target for anteversion angle, 77% met the target for inclination angle, and 51% met the target for both. There was no correlation between anteversion angle and penetration rate (r = −0.14, p = 0.72) or between inclination angle and penetration rate (r = 0.11, p = 0.35). There was also no difference (p = 0.07) in penetration rate between hips located within the Lewinnek safe zone for both anteversion angle and inclination angle (mean 0.057 mm/year, 95% CI: 0.036 to 0.079 mm/year) and those outside the safe zone (mean 0.062 mm/year, 95% CI: 0.042 to 0.083 mm/year).

Acetabular cup position had no effect on the wear rate of highly crosslinked polyethylene at long-term follow-up. Although care should still be taken to correctly position the acetabular cup for stability, highly crosslinked polyethylene is a forgiving bearing material that can withstand a wide range of cup positions without negatively impacting longevity due to wear.