Aims

The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function.

When the Birmingham Hip Resurfacing (BHR) metal-on-metal implant system was approved by the United States Food and Drug Administration in 2006, a multicenter, prospective, post-approval study (PAS) was required. This study uses data from the PAS to investigate metal level and glomerular filtration rate (GFR) trends over the first decade in vivo.

Between October 2006 and March 2011, 290 primary BHR procedures were performed among 262 patients at 5 sites. Whole blood samples were sent to a single specialized laboratory to determine GFR, cobalt (Co) and chromium (Cr) levels. The population for this study consists of 117 unrevised unilateral patients with a mean age at surgery of 51.3±6.5 years who had pre-operative, 1-year, 4-year, 5-year and 10-year laboratory data. The mean follow-up for these patients that included 36 females was 10.1±0.2 years.

Median metal levels at 1-year increased relative to pre-operative values for Co (by a factor of 9.7 from 0.13 to 1.26 ppb, p<0.001) and Cr (by a factor of 2.5 from 0. 60 to 1.50 ppb, p<0.001). Metal levels subsequently remained relatively constant over time with a median 10-year value of 1.12 ppb for Co and 1.29 ppb for Cr. Based on 585 blood samples from all 117 patients, there was no relationship between GFR and Co (_→=−0.06, p=0.14) or Cr (_→=0.05, p=0.27) levels. However, lower pre-operative GFR values were associated with larger increases in Co at 1-year relative to the pre-operative level (_→=−0.26, p=0.005). There was no relationship between pre-operative GFR values and changes in Cr at 1 year (_→=−0.13, p=0.15).

Through the first decade in vivo, elevated whole blood metal levels for unilateral BHR patients do not appear to adversely affect GFR. However, patients with lower pre-operative GFR values tend to have larger increases in their Co level at 1-year.

Introduction

The BIRMINGHAM HIP^◊ Resurfacing is a metal-on-metal (MOM) hip implant system approved by the US FDA in 2006. The approval required a multicenter, prospective, post-approval study (PAS). Our purpose is to report the current minimum 10-year results.

In the United Kingdom's National Joint Registry 2018 Annual Report, the combination of a POLARSTEM hip stem and R3 acetabular component has the lowest revision rate of any total hip arthroplasty (THA) construct combination at 7 years. Although revision rates remain a crucial measure of an implant combination's performance, there is increasingly more attention being given to patient-reported outcome measures (PROMs), which often reflect the endpoints that patients’ themselves consider of paramount importance in choosing to undergo THA. Therefore, the current analysis was undertaken to better understand the PROMs-based performance of this combination. Bespoke implant reports were requested for the POLARSTEM/R3 combination with OXINIUM™ heads and highly cross-linked polyethylene (XLPE) bearing. Reports used data from the National Health Service PROMs programme, which collected the Oxford Hip Score (OHS), EQ-5D and EQ-VAS. Health gain scores, calculated as differences between preoperative and 6-month post-operative scores, were adjusted to account for any differences in patient demographics between comparative groups. The mean OHS adjusted health gain score for the construct combination was 22.8 (95% confidence interval [CI]: 22.4 – 23.1; n = 1799 patients) compared to 21.2 (95% CI: 21.2 – 21.3; n = 111,055). For EQ-5D, the scores were 0.462 (95% CI: 0.451 – 0.473; n = 1685) for the construct and 0.434 (95% CI: 0.433 – 0.436; n = 102,448) for the class average. For EQ-VAS, the construct had adjusted scores of 14.2 (95% CI: 13.4 – 14.9; n = 1605) compared to the class average of 11.4 (95% CI: 11.3 – 11.5; n = 98,610). There were also more patients who rated their satisfaction as ‘excellent’ in the specific construct group. Comparisons were statistically significant in all cases (p < 0.001). In conclusion, in addition to excellent mid-term survivorship, the POLARSTEM/R3 construct combination has demonstrated superior PROMs that may improve patient outcomes.

Surgical site infections (SSIs) are associated with significant consequences in orthopaedic surgery, where their presence can lead to ultimate revision of the implant. Furthermore, infections and impaired wound healing can prolong length of hospital stay following orthopaedic surgery, which can place additional financial burdens on healthcare systems. The current analysis was conducted to determine whether the use of the PICO single-use negative pressure wound therapy (sNPWT) system after orthopaedic surgery reduced the incidence of SSIs and length of hospital stay compared with using conventional dressings. A systematic literature review (SLR) was performed using the PubMed, Embase and Cochrane Library databases. English-language studies comparing PICO sNPWT to conventional dressings published from 2011 to August 2018 with ≥10 patients in each treatment arm were included. Reference lists of included studies were searched for further relevant studies. Meta-analyses were performed using a fixed effect (I² < 50%) or random effects model (I² ≥ 50%). The SLR identified 6,197 studies, of which 5 relevant studies (607 patients) were included. The odds of an SSI were reduced by 57% (odds ratio [OR]: 0.43; 95% confidence interval [CI]: 0.21–0.86; p = 0.02) and there was consistency between studies (I² = 0%). Three studies reported on length of hospital stay. The mean difference between patient groups indicated that PICO sNPWT was associated with a 1-day reduction in hospital stay (mean difference [MD]: −0.99; 95% CI: −1.32 to −0.65; p < 0.00001) and there was again consistency between studies (I² = 0%). These results suggest that the use of PICO sNPWT system after closed surgical incisions can reduce the incidence of SSIs and shorten the duration of hospital stay when used in orthopaedic patient populations.