This meta analysis address the relationship between infection developing after total hip arthroplasty (THA) and heterotopic ossification (HO). To identify the gaps in available knowledge, we screened for full-length peer-reviewed research articles listed in PubMed, Embase, and Web of Science over the past 20 years. The following search terms and Boolean operators were used: heterotopic ossification AND infection AND (hip replacement OR hip arthroplasty). The search resulted in the identification of as few as 14 articles describing periprosthetic joint infection (PJI) and HO after THA. Data summarized from 6 studies suitable for further meta-analysis yielded a cumulative sample size of 753 observations, with 186 recorded events of HO. The pooled RR was estimated at 2.22 (95% CI: 1.00 to 4.91, p = 0.0497), suggesting a more than twofold risk of HO compared to the group without PJI. In conclusion, there is a clear association between a higher risk of HO and PJI. Basic research findings support the hypothesis that bacterial pathogen-associated molecular patterns (PAMPs) can lead to osteogenesis through a toll-like receptor (TLR) and nuclear factor kappa B (NF-κB) pathway in the course of HO development. Together, these results suggest that HO prophylaxis should always be prescribed in PJI after THA. Moreover, during revisions following THA for presumed non-septic reasons, the presence of HO warrants consideration for infection, as there is a potential heightened risk of pathologic ossification induced by PAMPs.

Keywords: heterotopic ossification; total hip arthroplasty; total hip replacement; periprosthetic joint infection; bacteria

Authors Ł. Pulik and P. Łęgosz contributed equally to this work.

Aims

The use of a porous metal shell supported by two augments with the ‘footing’ technique is one solution to manage Paprosky IIIB acetabular defects in revision total hip arthroplasty. The aim of this study was to assess the medium-term implant survival and radiological and clinical outcomes of this technique.

The use of trabecular metal (TM.) shells supported by two TM augments in the footing technique has been described as a potential option for the treatment of Paprosky 3B acetabular defects. The aim of this study was to assess the mid implant survivorship and radiological and clinical outcomes after acetabular revision using this technique.

We undertook a retrospective, double-centre series of 39 hips in 39 patients (15 male, 24 female) treated with the footing technique using a TM shell supported by two TM augments, for severe acetabular bone loss between 2007 and 2020. The mean age at the time of surgery was 62,9 (28 to 86) years. The mean follow-up was 5,4 (1,5 to 15) years.

The cumulative mid survivorship of the implant with revision for any cause was 89%. 3 hips (7,6%) required further revision due to aseptic loosening, and 1 (2,8%) required revision for infection. The mean Harris Hip Score improved significantly from 48 (29 to 65) preoperatively to 79 points (62 to 98) at the latest follow-up (p < 0.001).

The reconstruction of Paprosky 3B acetabular defects with TM shells and two augments in footing-technique showed excellent mid-term results. This technique appears to be a viable option for treating these defects.

In recent years, there has been increasing interest in the use of simultaneous hip arthroplasty compared to staged procedures in patients with bilateral pathology. The aim of this study was to compare simultaneous and staged hip arthroplasty in patients with bilateral pathology by assessing the transfusion rate, postoperative hemoglobin drop, length of stay (LOS), in-hospital complications, 30-days readmissions, leg length difference and early functional outcome.

We conducted a retrospective cohort study that included all patients who were undergoing primary total hip arthroplasty (THA) by a single surgeon in a high-volume arthroplasty center between 2015 and 2020 as simultaneous or staged procedures. Staged bilateral arthroplasties were performed within 12 months and were stratified by the time between procedures. Data was acquired through the electronic files at the Orthopädische Chirurgie München (OCM). For functional outcome we compared the ability of the patients to walk independently on the ward and the ability to walk a set of stairs alone which was recorded daily by the attending physiotherapist.

In total n=290 patients were assessed for eligibility and included in this study. One hundred and thirty eight patients were allocated to the staged arthroplasty group. The second staged procedure was performed within 12 months of the first procedure. One hundred and fifty two patients were allocated to the simultaneous arthroplasty group. No statistical difference was found between the two groups regarding demographic data. Primary outcome measurements: There was no significant difference in transfusion rate or complication rate (p=0.1147). In both groups the transfusion rate was actually 0%. Secondarily, no statistically significant difference was found between the postoperative hemoglobin drop (p=0.1147) and the functional outcome (p=0.7249), nor the length of stay (LOS) (p=: 0.6415), as well as the 30 days readmission rate between both groups. No difference was found in leg length in the simultaneous group. The OR time in the simultaneous group ranged from 62min to 111min with an average of 77min. No surgery exceeded a 120min window.

We observed no significant differences in transfusion rate, in hospital complications, as well as readmission rate between both groups. The early functional outcome showed no significant difference in mobility. Simultaneous hip arthroplasty is as safe as a staged procedure, with no higher risk for the patient, in a specialized high volume center with a specialized surgeon and an adequate team. Level of evidence: Level IV

Orientation of the native acetabular plane as defined by the transverse acetabular ligament (TAL) and the posterior labrum was measured intra-operatively using computer-assisted navigation in 39 hips. In order to assess the influence of alignment on impingement, the range of movement was calculated for that defined by the TAL and the posterior labrum and compared with a standard acetabular component position (abduction 45°/anteversion 15°).

With respect to the registration of the plane defined by the TAL and the posterior labrum, there was moderate interobserver agreement (r = 0.64, p < 0.001) and intra-observer reproducibility (r = 0.73, p < 0.001). The mean acetabular component orientation achieved was abduction of 41° (32° to 51°) and anteversion of 18° (−1° to 36°). With respect to the Lewinnek safe zone (abduction 40° ±10°, anteversion 15° ±10°), 35 of the 39 acetabular components were within this zone. However, there was no improvement in the range of movement (p = 0.94) and no significant difference in impingement (p = 0.085).

Alignment of the acetabular component with the TAL and the posterior labrum might reduce the variability of acetabular component placement in total hip replacement. However, there is only a moderate interobserver agreement and intra-observer reliability in the alignment of the acetabular component using the TAL and the posterior labrum. No reduction in impingement was found when the acetabular component was aligned with the TAL and the posterior labrum, compared with a standard acetabular component position.

Aim: The LPS Mobile Flex was designed to adress a physiological range of motion after TKA. Methods: We compared 40 LPS and 40 LPS Flex knees in a prospective randomized study. The average age was 64.9 (60–70) years in the LPS group (26 female/14 male) and 63.6 (54–70) years in the LPS Mobile Flex group (27 female/14 male. The surgeries were performed by two surgeons. Same approaches and techniques were used to adress the ßexion capacities. No patient was lost to the follow up. The outcome was clinical and radiological investigated and comprised after 3 month. For the clinical comparison the American knee society score was used. Results: The average range of motion in the LPS group was 110û (90–150û) after 3 month (preop. ßexion was 111û (85–140û). At the same time the average range of motion in the LPS Flex group was 125û (95–150) (preop. ßexion was 108û (80–130). After 3 month the ßexion ability was signiþcantly improved by 15û using the LPS ßex. According the knee score there were no significant differences between the groups besides the range of motion. Also radiologically there were no differences between the groups. 92,5% of the patients in each group showed central tracking in the patellofemoral groove in the sunrise view. Conclusions: The LPS Mobile Flex is an alternative to improve knee function and make the knee more physiological after TKA. To take advantage of the design features it requires a proper surgical technique and a proper patient selection.