Accuracy of cup placement compared with preoperative surgeon targets in primary total hip arthroplasty using standard instrumentation and techniques: a global, multicenter study.

BACKGROUND: Acetabular cup positioning in total hip arthroplasty (THA) is closely related to outcomes. The literature has suggested cup parameters defined by the Lewinnek safe zone; however, the validity of such measures is in question. Several studies have raised concerns about the benefits of using the Lewinnek safe zone as a predictor of success. In this study we elected to use prospective surgeon targets as the basis for comparison to see how successful surgeons are positioning their cup using standard instruments and techniques. METHODS: A prospective, global, multicenter study was conducted. Cup positioning success was defined as a composite endpoint. Both cup inclination and version needed to be within 10° of the surgeon target to be considered a success. Radiographic analysis was conducted by a third-party reviewer. RESULTS: In 170 subjects, inclination, target versus actual, was 44.8° [standard deviation (SD 0.9°)] and 43.1° (SD 7.6°), respectively (p = 0.0029). Inclination was considered successful in 84.1% of cases. Mean version, target versus actual, was 19.4° (SD 3.9°) and 27.2° (SD 5.6°), respectively (p < 0.0001). Version was considered successful in 63.4% of cases, and combined position (inclination and version) was considered successful in 53.1%. CONCLUSION: This study shows that with traditional methods of placing the cup intraoperatively, surgeons are only accurate 53.1% of the time compared with a predicted preoperative plan. This study suggests that the inconsistency in cup positioning based on the surgeon's planned target is potentially another important variable to consider while using a mechanical guide or in freehand techniques for cup placement in THA. TRIAL REGISTRATION: This study is registered on ClinicalTrials.gov, NCT03189303.

Sex-based differences in neck selectivity in total hip arthroplasty using a modular femoral neck system.

BACKGROUND: Dislocation is a major complication of total hip arthroplasty (THA). The modular femoral neck system provides practical advantages by allowing adjustment of neck version and length in the presence of intraoperative instability. Anatomical studies have identified morphological differences in the hip joint between men and women. Despite sex-based differences in hip morphology, it remains unclear whether such differences affect neck selectivity in THA using a modular neck system and whether this approach achieves anatomical reconstruction, thereby reducing complications such as dislocation. This study aimed to investigate gender differences in neck selectivity in THA with the modular neck system and assess the clinical impact of the modular neck system. METHODS: A total of 163 THAs using a modular neck system were included in this study. Data on the type of modular neck and intraoperative range of motion (ROM) were retrieved from patient records. Pre- and post-operative leg length differences (LLD) were examined as part of the radiographic assessment. Dislocation was investigated as a postoperative complication. RESULTS: Neck selectivity did not significantly differ between men and women. The comparison of pre- and post-operative LLD revealed a tendency for varus necks to improve LLD more than version-controlled necks. Furthermore, no significant correlation was found between intraoperative ROM and neck selectivity, or postoperative dislocation and neck selectivity. CONCLUSIONS: This study on THA with a modular neck system provided valuable insights into sex-based differences in neck selectivity and highlighted the potential benefits of the modular neck system in addressing LLD and preventing postoperative dislocation.

Equivalent revision rates and patient reported outcomes with routine use of a short (125mm) cemented stem for total hip arthroplasty compared to a standard length (150mm) cemented stem. A two surgeon series of 1335 patients.

BACKGROUND: Routine total hip arthroplasty (THA) using a short cemented stem as compared with a standard length cemented stem may have benefits in terms of stress distribution, bone preservation, stem subsidence and ease of revision surgery. Two senior arthroplasty surgeons transitioned their routine femoral implant from a standard 150 mm Exeter V40 cemented stem to a short 125 mm Exeter V40 cemented stem for all patients over the course of several years. We analysed revision rates, adjusted survival, and PROMS scores for patients who received a standard stem and a short stem in routine THA. METHODS: All THAs performed by the two surgeons between January 2011 and December 2021 were included. All procedures were performed using either a 150 mm or 125 mm Exeter V40 stem. Demographic data, acetabular implant type, and outcome data including implant survival, reason for revision, and post-operative Oxford Hip Scores were obtained from the New Zealand Joint Registry (NZJR), and detailed survival analyses were performed. Primary outcome was revision for any reason. Reason for revision, including femoral or acetabular failure, and time to revision were also recorded. RESULTS: 1335 THAs were included. 516 using the 150 mm stem and 819 using the 125 mm stem. There were 4055.5 and 3227.8 component years analysed in the standard stem and short stem groups respectively due to a longer mean follow up in the 150 mm group. Patient reported outcomes were comparable across all groups. Revision rates were comparable between the standard 150 mm stem (0.44 revisions/100 component years) and the short 125 mm stem (0.56 revisions/100 component years) with no statistically significant difference found (p = 0.240). CONCLUSION: Routine use of a short 125 mm stem had no statistically significant impact on revision rate or PROMS scores when compared to a standard 150 mm stem. There may be benefits to routine use of a short cemented femoral implant.

Is AI 3D-printed PSI an accurate option for patients with developmental dysplasia of the hip undergoing THA?

BACKGROUND: In traditional surgical procedures, significant discrepancies are often observed between the pre-planned templated implant sizes and the actual sizes used, particularly in patients with congenital hip dysplasia. These discrepancies arise not only in preoperative planning but also in the precision of implant placement, especially concerning the acetabular component. Our study aims to enhance the accuracy of implant placement during Total Hip Arthroplasty (THA) by integrating AI-enhanced preoperative planning with Patient-Specific Instrumentation (PSI). We also seek to assess the accuracy and clinical outcomes of the AI-PSI (AIPSI) group in comparison to a manual control group. METHODS: This study included 60 patients diagnosed with congenital hip dysplasia, randomly assigned to either the AIPSI or manual group, with 30 patients in each. No significant demographic differences between were noted the two groups. A direct anterior surgical approach was employed. Postoperative assessments included X-rays and CT scans to measure parameters such as the acetabular cup anteversion angle, acetabular cup inclination angle, femoral stem anteversion angle, femoral offset, and leg length discrepancy. Functional scores were recorded at 3 days, 1 week, 4 weeks, and 12 weeks post-surgery. Data analysis was conducted using SPSS version 22.0, with the significance level was set at α = 0.05. RESULTS AND CONCLUSION: The AIPSI group demonstrated greater prosthesis placement accuracy. With the aid of PSI, AI-planned THA surgery provides surgeons with enhanced precision in prosthesis positioning. This approach potentially offers greater insights and guidelines for managing more complex anatomical variations or cases.

Accuracy of portable navigation during THA in patients with severe developmental dysplasia of hip.

INTRODUCTION: Correct cup placement in total hip arthroplasty (THA) for patients with developmental dysplasia of the hip (DDH) is considerably difficult. This study aimed to analyze the orientation accuracy of cup insertion during THA using a portable navigation system in patients with DDH. MATERIALS AND METHODS: In this retrospective cohort study, we analyzed data from 64 patients who underwent THA using infrared stereo camera-matching portable navigation. Patients underwent THA via the anterolateral approach in the lateral decubitus position. Navigation records for intraoperative cup angles, postoperative cup angles measured on computed tomography (CT) images, and cup angle measurement differences were measured and compared between patients with non-DDH/mild DDH and severe DDH. Furthermore, the predictive factors for outliers of accurate acetabular cup placement were analyzed. RESULTS: The average measurement absolute abduction differences (postoperative CT-navigation record) were 3.9 ± 3.5° (severe DDH) and 3.3 ± 2.6° (non-DDH/ mild DDH), and the anteversion differences were 4.7 ± 3.4° (severe DDH) and 2.3 ± 2.1° (non-DDH/ mild DDH). The anteversion difference was different between the two groups. Multivariate analysis showed that the navigation difference (absolute difference in anteversion between postoperative CT and navigation records of > 5°) was significantly associated with severe DDH (odds ratio [OR]: 3.3; p = 0.049, 95% confidence interval [CI]: 1.0-11.1) and posterior pelvic tilt (OR: 1.1; p = 0.042, 95% CI: 1.0-1.27). CONCLUSIONS: In patients with severe DDH, it is important to pay close attention during THA using portable navigation. However, the average difference was < 5º even in patients with severe DDH, and the accuracy may be acceptable in a clinical setting when the cost is considered.

15-year survivorship of a unique dual-modular femoral stem in primary hip arthroplasty.

BACKGROUND: Hip offset, version, and length are interdependent femoral variables which determine stability and leg length. Balancing these competing variables remains a core challenge in hip arthroplasty. The potential benefits of modular femoral stems have been overshadowed by higher rates of failure. The objective of this study was to assess the survivorship of a unique dual-modular femoral stem at an average 15-year follow-up period. METHODS: The records of all patients with osteoarthritis who underwent primary total hip arthroplasty with this device between 2004-2009 were reviewed. There were no exclusions for BMI or other factors. We examined the data with Kaplan-Meier survival analysis. The primary endpoint for survival was mechanical failure of the modular neck-body junction. RESULTS: The survivorship of this device in 172 subjects was 100% with none experiencing mechanical failure of the modular junction at an average of 15 years. 60 patients died of causes unrelated to their THA and 9 patients were lost to follow-up. There were three early (≤ 12 months) dislocations (1.7%), and seven total dislocations (4.1%). 16 patients underwent reoperations during the follow-up period, none for any complication of the modular junction. Radiographic results showed well-fixed femoral stems in all cases. There were no leg length discrepancies of greater than 10 mm, and 85% were within 5 mm. CONCLUSION: There were no mechanical failures of the modular junction in any of the subjects over the average 15-year period, demonstrating that this dual-modular design is not associated with increased failure rates. We achieved a 1.7% early dislocation rate and a 4.1% total dislocation rate without any clinically significant leg length discrepancies.

Excellent survival of two anatomically adapted hydroxyapatite coated cementless Total Hip Arthroplasties. A mean follow-up of 11.3 years.

There are many different types of cementless anatomically adapted Total Hip Arthroplasties (THAs) on the market, the Anatomic Benoist Gerard (ABG) I and II are such types of cementless THAs. In this retrospective single-centre study we evaluated the overall survival with revision for any reason and aseptic loosening as endpoint at more than 11 years follow-up. Between 2000 and 2004, 244 cementless THAs were performed in 230 patients in a primary care hospital. At a mean of 11.3 years follow-up (range 9.8 - 12.8 years) clinical examination, plain radiography and Patient Reported Outcome Measures (PROMs) were obtained and analysed. The PROMs consisted of the Oxford Hip Score (OHS) and the Western Ontario and McMaster University Index (WOMAC). At a mean of 11.3 years follow-up 32 patients (13.1%) had died of unrelated causes. Of the remaining cohort all 198 patients (212 THAs) have been reached for evaluation. There were no patients considered as lost to follow-up. At a mean of 11.3 years 11 patients (11 THAs) have had a revision of either the femoral implant or acetabular component resulting in an overall survival of 95.5%. There was no statistically significant difference (p=0.564) in survival between the ABG I and II THAs. Radiographic there were no changes between the ABG I and II last follow up. The ABG II performed statistically significant better in PROMs. We concluded that both anatomically adapted hydroxyapatite coated cementless THAs show excellent survival at more than 11 years follow-up.

Lower Risk of Revision With 32- and 36-Millimeter Femoral Heads Compared With 28-mm Heads in Primary Total Hip Arthroplasty: A Comparative Single-Center Study (10,104 Hips).

BACKGROUND: We aimed to compare the clinical outcomes of different head sizes (28-, 32-, and 36- millimeter) in primary total hip arthroplasty (THA) at mean 6 years follow-up (range, 1 to 17.5 years). METHODS: This was a retrospective consecutive study of primary THA at our institution (2003 to 2019). Demographic and surgical data were collected. The primary outcome measures were all-cause revision, revision for dislocation, and all-cause revision excluding dislocation. Continuous descriptive statistics used means, median values, ranges, and 95% confidence intervals, where appropriate. Kaplan-Meier survival curves were used to estimate time to revision. Cox proportional hazard regression analyses were used to compare revision rates between the femoral head size groups. Adjustments were made for age at surgery, sex, primary diagnosis, American Society of Anesthesiologists score, articulation type, and fixation methods. There were 10,104 primary THAs included; median age was 69 years (range, 13 to 101) with 61.5% women. A posterior approach was performed in 71.6%. There were 3,295 hips with 28-mm heads (32.6%), 4,858 (48.1%) with 32-mm heads, and 1,951 (19.3%) with 36-mm heads. RESULTS: Overall rate of revision was 1.7% with the lowest rate recorded for the 36-mm group (2.7 versus 1.3 versus 1.1%). Cox regression analyses showed a decreased risk of all-cause revision for 32 and 36-mm head sizes as compared to 28-mm; this was statistically significant for the 32-mm group (P = .01). Risk of revision for dislocation was significantly reduced in both 32-mm (P = .03) and 36-mm (P = .03) head sizes. Analysis of all cause revision excluding dislocation showed no significant differences between head sizes. CONCLUSIONS: We found a significantly reduced risk of revision for all causes, but particularly revision for dislocation with larger head sizes. Concerns regarding increased risk of early revision for aseptic loosening, polyethylene wear, or taper corrosion with larger heads appear to be unfounded in this cohort of 10,104 patients with up to 17 years follow-up.

A novel design of hip-stem with reduced strain-shielding.

The use of uncemented stems in hip arthroplasty has been increasing, even in osteoporotic patients. The major concerns of uncemented hip-stems, however, are peri-prosthetic fracture, thigh pain, and proximal femoral stress-/strain-shielding. In this study, a novel design of uncemented hip-stem is proposed that will reduce such concerns, improve osseointegration, and benefit both osteoporotic and arthritic patients. The stem has a central titanium alloy core surrounded by a set of radial buttresses that are partly porous titanium, as is the stem tip. The aim of the study was to investigate the mechanical behaviour of the proposed partly-porous design, examining load transfer in the short-term, and comparing its strain-shielding behaviour with a solid metal implant. The long-term effect of implant-induced bone remodelling was also simulated. Computed tomography based three-dimensional finite element models of an intact proximal femur, and the same femur implanted with the proposed design, were developed. Peak hip contact and major muscle forces corresponding to level-walking and stair climbing were applied. The proposed partly-porous design had approximately 50% lower strain-shielding than the solid-metal counterpart. Results of bone remodelling simulation indicated that only 16% of the total bone volume is subjected to reduction of bone density. Strain concentrations were observed in the bone around the stem-tip for both solid and porous implants; however, it was less prominent for the porous design. Lower strain-shielding and reduced bone resorption are advantageous for long-term fixation, and the reduced strain concentration around the stem-tip indicates a lower risk of peri-prosthetic fracture.

A prospective randomized study of Refobacin Bone Cement R versus Palacos R + G.

Aims: Refobacin Bone Cement R and Palacos R + G bone cement were introduced to replace the original cement Refobacin Palacos R in 2005. Both cements were assumed to behave in a biomechanically similar fashion to the original cement. The primary aim of this study was to compare the migration of a polished triple-tapered femoral stem fixed with either Refobacin Bone Cement R or Palacos R + G bone cement. Repeated radiostereometric analysis was used to measure migration of the femoral head centre. The secondary aims were evaluation of cement mantle, stem positioning, and patient-reported outcome measures. Methods: Overall, 75 patients were included in the study and 71 were available at two years postoperatively. Prior to surgery, they were randomized to one of the three combinations studied: Palacos cement with use of the Optivac mixing system, Refobacin with use of the Optivac system, and Refobacin with use of the Optipac system. Cemented MS30 stems and cemented Exceed acetabular components were used in all hips. Postoperative radiographs were used to assess the quality of the cement mantle according to Barrack et al, and the position and migration of the femoral stem. Harris Hip Score, Oxford Hip Score, Forgotten Joint Score, and University of California, Los Angeles Activity Scale were collected. Results: Median distal migration (y-axis) at two years for the Refobacin-Optivac system was -0.79 mm (-2.01 to -0.09), for the Refobacin-Optipac system was -0.75 mm (-2.16 to 0.20), and for the Palacos-Optivac system was -1.01 mm (-4.31 to -0.29). No statistically significant differences were found between the groups. Secondary outcomes did not differ statistically between the groups at the two-year follow-up. Conclusion: At two years, we found no significant differences in distal migration or clinical outcomes between the three groups. Our data indicate that Refobacin Bone Cement R and Palacos R + G are comparable in terms of stable fixation and early clinical outcomes.

Cup-cage constructs in revision total hip arthroplasty for pelvic discontinuity.

Aims: Pelvic discontinuity is a challenging acetabular defect without a consensus on surgical management. Cup-cage reconstruction is an increasingly used treatment strategy. The present study evaluated implant survival, clinical and radiological outcomes, and complications associated with the cup-cage construct. Methods: We included 53 cup-cage construct (51 patients) implants used for hip revision procedures for pelvic discontinuity between January 2003 and January 2022 in this retrospective review. Mean age at surgery was 71.8 years (50.0 to 92.0; SD 10.3), 43/53 (81.1%) were female, and mean follow-up was 6.4 years (0.02 to 20.0; SD 4.6). Patients were implanted with a Trabecular Metal Revision Shell with either a ZCA cage (n = 12) or a TMARS cage (n = 40, all Zimmer Biomet). Pelvic discontinuity was diagnosed on preoperative radiographs and/or intraoperatively. Kaplan-Meier survival analysis was performed, with failure defined as revision of the cup-cage reconstruction. Results: The five-year all-cause survival for cup-cage reconstruction was 73.4% (95% confidence interval (CI) 61.4 to 85.4), while the ten- and 15-year survival was 63.7% (95% CI 46.8 to 80.6). Survival due to aseptic loosening was 93.4% (95% CI 86.2 to 100.0) at five, ten, and 15 years. The rate of revision for aseptic loosening, infection, and dislocation was 3/53 (5.7%), 7/53 (13.2%), and 6/53 (11.3%), respectively. The mean leg length discrepancy improved (p < 0.001) preoperatively from a mean of 18.2 mm (0 to 80; SD 15.8) to 7.0 mm (0 to 35; SD 9.8) at latest follow-up. The horizontal and vertical hip centres improved (p < 0.001) preoperatively from a mean of 9.2 cm (5.6 to 17.5; SD 2.3) to 10.1 cm (6.2 to 13.4; SD 2.1) and 9.3 cm (4.7 to 15.8; SD 2.5) to 8.0 cm (3.7 to 12.3; SD 1.7), respectively. Conclusion: Cup-cage reconstruction provides acceptable outcomes in the management of pelvic discontinuity. One in four constructs undergo revision within five years, most commonly for periprosthetic joint infection, dislocation, or aseptic loosening.

Acetabular component liner exchange with highly crosslinked polyethylene for wear and osteolysis.

Aims: Isolated acetabular liner exchange with a highly crosslinked polyethylene (HXLPE) component is an option to address polyethylene wear and osteolysis following total hip arthroplasty (THA) in the presence of a well-fixed acetabular shell. The liner can be fixed either with the original locking mechanism or by being cemented within the acetabular component. Whether the method used for fixation of the HXLPE liner has any bearing on the long-term outcomes is still unclear. Methods: Data were retrieved for all patients who underwent isolated acetabular component liner exchange surgery with a HXLPE component in our institute between August 2000 and January 2015. Patients were classified according to the fixation method used (original locking mechanism (n = 36) or cemented (n = 50)). Survival and revision rates were compared. A total of 86 revisions were performed and the mean duration of follow-up was 13 years. Results: A total of 20 patients (23.3%) had complications, with dislocation alone being the most common (8.1%; 7/86). Ten patients (11.6%) required re-revision surgery. Cementing the HXLPE liner (8.0%; 4/50) had a higher incidence of re-revision due to acetabular component liner-related complications than using the original locking mechanism (0%; 0/36; p = 0.082). Fixation using the original locking mechanism was associated with re-revision due to acetabular component loosening (8.3%; 3/36), compared to cementing (0%; 0/50; p = 0.038). Overall estimated mean survival was 19.2 years. There was no significant difference in the re-revision rate between the original locking mechanism (11.1%; 4/36) and cementing (12.0%; 6/50; p = 0.899). Using Kaplan-Meier survival analysis, the revision-free survival of HXLPE fixed with the original locking mechanism and cementing was 94.1% and 93.2%, respectively, at ten years, and 84.7% and 81.3%, respectively, at 20 years (p = 0.840). Conclusion: The re-revision rate and the revision-free survival following acetabular component liner exchange revision surgery using the HXLPE liner were not influenced by the fixation technique used. Both techniques were associated with good survival at a mean follow-up of 13 years. Careful patient selection is necessary for isolated acetabular component liner exchange revision surgery in order to achieve the best outcomes.

Virtual biomechanical assessment of porous tantalum and custom triflange components in the treatment of patients with acetabular defects and pelvic discontinuity.

Aims: The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) - the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) - using virtual modelling. Methods: Pre- and postoperative CT scans from ten patients who underwent revision with the TMARS for a Paprosky IIIB acetabular defect with pelvic discontinuity were retrospectively collated. Computer models of a CTAC implant were designed from the preoperative CT scans of these patients. Computer models of the TMARS reconstruction were segmented from postoperative CT scans using a semi-automated method. The amount of bone removed, the implant-bone apposition that was achieved, and the restoration of the centre of rotation of the hip were compared between all the actual TMARS and the virtual CTAC implants. Results: The median amount of bone removed for TMARS reconstructions was significantly greater than for CTAC implants (9.07 cm3 (interquartile range (IQR) 5.86 to 21.42) vs 1.16 cm3 (IQR 0.42 to 3.53) (p = 0.004). There was no significant difference between the median overall implant-bone apposition between TMARS reconstructions and CTAC implants (54.8 cm2 (IQR 28.2 to 82.3) vs 56.6 cm2 (IQR 40.6 to 69.7) (p = 0.683). However, there was significantly more implant-bone apposition within the residual acetabulum (45.2 cm2 (IQR 28.2 to 72.4) vs 25.5 cm2 (IQR 12.8 to 44.1) (p = 0.001) and conversely significantly less apposition with the outer cortex of the pelvis for TMARS implants compared with CTAC reconstructions (0 cm2 (IQR 0 to 13.1) vs 23.2 cm2 (IQR 16.4 to 30.6) (p = 0.009). The mean centre of rotation of the hip of TMARS reconstructions differed by a mean of 11.1 mm (3 to 28) compared with CTAC implants. Conclusion: In using TMARS, more bone is removed, thus achieving more implant-bone apposition within the residual acetabular bone. In CTAC implants, the amount of bone removed is minimal, while the implant-bone apposition is more evenly distributed between the residual acetabulum and the outer cortex of the pelvis. The differences suggest that these implants used to treat pelvic discontinuity might achieve short- and long-term stability through different biomechanical mechanisms.

Long-term outcomes of revision total hip arthroplasty with the Zimmer Modular Revision hip system.

Aims: There are limited long-term studies reporting on outcomes of the Zimmer Modular Revision (ZMR) stem, and concerns remain regarding failure. Our primary aim was to determine long-term survival free from all-cause revision and stem-related failure for this modular revision stem in revision total hip arthroplasty (THA). Secondary aims included evaluating radiological and functional outcomes. Methods: We retrospectively identified all patients in our institutional database who underwent revision THA using the ZMR system from January 2000 to December 2007. We included 106 patients (108 hips) with a mean follow-up of 14.5 years (2.3 to 22.3). Mean patient age was 69.2 years (37.0 to 89.4), and 51.9% were female (n = 55). Indications for index revision included aseptic loosening (73.1%), infection (16.7%), fracture (9.3%), and stem fracture (0.9%). Kaplan-Meier analysis was used to determine the all-cause and stem-related failure revision-free survival. At most recent follow-up, Oxford Hip Scores (OHS) were collected, and radiological stem stability was determined using the Engh classification. Results: A total of 17 hips (15.7%) underwent re-revision of any component. Indications for re-revision were stem failure (35.3%; n = 6), infection (29.4%; n = 5), instability (29.4%; n = 5), and acetabular aseptic loosening (5.9%; n = 1). The five- and 15-year all-cause survival was 89.7% (95% confidence interval (CI) 86.7 to 92.7) and 83.3% (95% CI 79.6 to 87.0), respectively. There were six re-revisions (5.6%) for stem failure; five for stem fracture and one for aseptic loosening. The five- and 15-year survival free from stem-related failure was 97.2% (95% CI 95.6 to 98.8) and 94.0% (95% CI 91.6 to 96.4), respectively. At final follow-up, the mean OHS was 36.9 (8.0 to 48.0) and 95.7% (n = 66) of surviving modular revision stems were well-fixed in available radiographs. Conclusion: Femoral revision with the ZMR offers satisfactory long-term all-cause revision-free survival, good survival free of stem-related failure, and favourable clinical outcomes. Stem fracture was the most common reason for stem-related failure and occurred both early and late. This highlights the importance of both early and long-term surveillance for stem-related failure.

Reconstruction of Paprosky IIIB acetabular defects with porous tantalum shells and augments using the footing technique.

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. Methods: We undertook a retrospective, two-centre series of 39 hips in 39 patients (15 male, 24 female) treated with the 'footing' technique for Paprosky IIIB acetabular defects between 2007 and 2020. The median age at the time of surgery was 64.4 years (interquartile range (IQR) 54.4 to 71.0). The median follow-up was 3.9 years (IQR 3.1 to 7.0). Results: The cumulative medium-term survival of the acetabular construct was 89%. Two hips (5.1%) required further revision due to shell loosening, one hip (2.6%) due to shell dislocation, and one hip (2.6%) due to infection. The median Harris Hip Score improved significantly from 47 points (IQR 41.5 to 54.9) preoperatively to 80 points (IQR 73.5 to 88.6) at the latest follow-up (p < 0.001). Conclusion: The reconstruction of Paprosky IIIB acetabular defects with porous tantalum shells and two augments using the 'footing' technique showed excellent medium-term results. It is a viable option for treating these challenging defects.

Hip Reconstruction In Situ with Screws and Cement (HiRISC) construct to treat large acetabular bone defects.

Aims: Large bone defects resulting from osteolysis, fractures, osteomyelitis, or metastases pose significant challenges in acetabular reconstruction for total hip arthroplasty. This study aimed to evaluate the survival and radiological outcomes of an acetabular reconstruction technique in patients at high risk of reconstruction failure (i.e. periprosthetic joint infection (PJI), poor bone stock, immunosuppressed patients), referred to as Hip Reconstruction In Situ with Screws and Cement (HiRISC). This involves a polyethylene liner embedded in cement-filled bone defects reinforced with screws and/or plates for enhanced fixation. Methods: A retrospective chart review of 59 consecutive acetabular reconstructions was performed by four surgeons in a single institution from 18 October 2018 to 5 January 2023. Cases were classified based on the Paprosky classification, excluding type 1 cases (n = 26) and including types 2 or 3 for analysis (n = 33). Radiological loosening was evaluated by an orthopaedic surgeon who was not the operating surgeon, by comparing the immediate postoperative radiographs with the ones at latest follow-up. Mean follow-up was 557 days (SD 441; 31 to 1,707). Results: Out of the 33 cases analyzed, six (18.2%) constructs required revision, with four revisions due to uncontrolled infection, one for dislocation, and one for aseptic loosening. Among the 27 non-revised constructs, only one showed wider radiolucencies compared to immediate postoperative radiographs, indicating potential loosening. Patients who underwent revision (n = 6) were significantly younger and had a higher BMI compared to those with non-revised constructs (p = 0.016 and p = 0.026, respectively). Sex, race, ethnicity, American Society of Anesthesiologists grade, infection status (patients with postoperative PJI diagnosis (septic) vs patients without such diagnosis (aseptic)), and mean follow-up did not significantly differ between revised and non-revised groups. Conclusion: The HiRISC technique may serve as a feasible short-term (about one to two years) alternative in patients with large acetabular defects, particularly in cases of PJI. Longer follow-up is necessary to establish the long-term survival of this technique.

Modular fluted tapered stems in two-stage reimplantation of previously infected total hip arthroplasties.

Aims: Uncemented implants are now commonly used at reimplantation of a two-stage revision total hip arthoplasty (THA) following periprosthetic joint infection (PJI). However, there is a paucity of data on the performance of the most commonly used uncemented femoral implants - modular fluted tapered (MFT) femoral components - in this setting. This study evaluated implant survival, radiological results, and clinical outcomes in a large cohort of reimplantation THAs using MFT components. Methods: We identified 236 reimplantation THAs from a single tertiary care academic institution from September 2000 to September 2020. Two designs of MFT femoral components were used as part of an established two-stage exchange protocol for the treatment of PJI. Mean age at reimplantation was 65 years (SD 11), mean BMI was 32 kg/m2 (SD 7), and 46% (n = 109) were female. Mean follow-up was seven years (SD 4). A competing risk model accounting for death was used. Results: The 15-year cumulative incidence of any revision was 24%. There were 48 revisions, with the most common reasons being dislocation (n = 25) and infection (n = 16). The 15-year cumulative incidence of any reoperation was 28%. Only 13 revisions involved the fluted tapered component (FTC), for a 15-year cumulative incidence of any FTC revision of 8%. Only two FTCs were revised for aseptic loosening, resulting in a 15-year cumulative incidence of FTC revision for aseptic loosening of 1%. Stem subsidence ≥ 5 mm occurred in 2% of unrevised cases. All stems were radiologically stable at most recent follow-up. Mean Harris Hip Score was 69 (SD 20) at most recent follow-up. Conclusion: This series demonstrated that MFT components were durable and reliable in the setting of two-stage reimplantation THA for infection. While the incidence of aseptic loosening was very low, the incidence of any revision was 24% at 15 years, primarily due to dislocation and recurrent PJI.

The learning curve of a novel seven-axis robot-assisted total hip arthroplasty system: a randomized controlled trial.

BACGROUND: The aim of this study was to assess the learning curve of a novel seven-axis robot-assisted total hip arthroplasty (RaTHA) system. METHODS: A total of 59 patients who underwent unilateral total hip arthroplasty at our institution from June 2022 to September 2022 were prospectively included in the study. In this randomized controlled clinical trial, robot-assisted THA (RaTHA) and Conventional THA (CoTHA) were performed using cumulative sum (CUSUM) analysis to evaluate the learning curve of the RaTHA system. The demographic data, preopera1tive clinical data, duration of operation, postoperative Harris Hip Score (HHS), postoperative Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and duration of operation between the learning stage and the proficiency stage of the RaTHA group were compared between the two groups. RESULTS: The average duration of operation of the RaTHA group was increased by 34.73 min compared with the CoTHA group (104.26 ± 19.33 vs. 69.53 ± 18.38 min, p < 0.01). The learning curve of the RaTHA system can be divided into learning stage and proficiency stage, and the former consists of the first 13 cases by CUSUM analysis. In the RaTHA group, the duration of operation decreased by 29.75 min in the proficiency stage compared to the learning stage (121.12 ± 12.84 vs.91.37 ± 12.92, p < 0.01). CONCLUSIONS: This study demonstrated that the surgical team required a learning curve of 13 cases to become proficient using the RaTHA system. The duration of operation, total blood loss, and drainage gradually shortened (decreased) with the learning curve stage, and the differences were statistically significant. TRIAL REGISTRATION: Number: ChiCTR2200061630, Date: 29/06/2022.

Are silver-coated megaprostheses superior to uncoated megaprostheses in managing chronic end-stage periprosthetic hip and knee infection?

INTRODUCTION: Outcomes for silver coated megaprostheses (SC-MP) used in cases of end-stage periprosthetic joint infection (PJI) have not been clearly defined. Although attractive, concerns over implant longevity and the risk of infection relapse exist among the scientific community. Therefore, we sought to investigate the effect of silver coating in lower-extremity MPs used in such difficult-to-treat scenarios. The study's primary hypothesis was that the periprosthetic infection control rate would be higher in patients with silver-coated implants. MATERIALS AND METHODS: Non-interventional retrospective study with a historical comparison group. We identified all consecutive end-stage hip and knee PJI cases at our center managed with exchange arthroplasty using a silver-coated megaprosthesis from January 2016 to March 2021, these cases were compared with a historical cohort of end-stage PJI cases managed with uncoated megaprostheses. The main outcome studied was infection control rate. Secondarily, we analyzed the short-to-medium-term survivorship of this type of silver-coated implant. RESULTS: Fifty-nine megaprostheses used in cases of end-stage PJI were included in this study. We identified 30 cases of chronic hip or knee PJI in which a silver-coated modular megaprosthesis was implanted. Our non-coated megaprosthesis (NC-MP) historical group included 29 patients. Both groups had similar demographic characteristics. We found no statistically significant differences in infection control rate (80% vs. 82.8%, p = 0.47) or implant survivorship (90% vs. 89.65%, p = 1) after a mean follow-up for SC-MP of 46.43 months, and 48 months for the non-coated MP group. In relapsed cases, there were no differences in infection eradication after DAIR (66% SC-MP vs. 60% NC-MP success rate, p = 1). During the follow-up we observed one case of skin argyria without further repercussion. CONCLUSION: We were unable to confirm our initial hypothesis that use of silver-coated implants in end-stage PJI scenarios may be associated with better outcomes in terms of infection control or implant survivorship.

Accuracy of cup placement and pelvic motion in total hip arthroplasty in the lateral decubitus position using a new computed tomography-based navigation system with augmented reality technology.

INTRODUCTION: This study aimed to investigate the accuracy of cup position and assess the changes in pelvic tilt during primary total hip arthroplasty (THA) in the lateral decubitus position using a new computed tomography (CT)-based navigation system with augmented reality (AR) technology. MATERIALS AND METHODS: There were 37 cementless THAs performed using a CT-based navigation system with AR technology in the lateral decubitus position and 63 cementless THAs performed using manual implant techniques in the lateral decubitus position in this retrospective study. Postoperative cup radiographic inclination and anteversion were measured using postoperative CT, and the proportion of hips within Lewinnek's safe zone was analyzed and compared between the two groups. The mean absolute values of navigation error were assessed. Intraoperative pelvic tilt angles were also recorded using navigation system. RESULTS: The percentage of cups inside Lewinnek's safe zone was 100% in the navigation group and 35% in the control group (p < 0.001). The mean absolute values of navigation error in inclination and anteversion were 2.9° ± 2.1° and 3.3° ± 2.4°, respectively. The mean abduction angle of the pelvis was 5.1° ± 4.8° after placing the patients in the lateral decubitus position and 4.1° ± 6.0° after cup placement. The mean posterior tilt angle was 6.8° ± 5.1° after placing the patients in the lateral decubitus position and 9.3° ± 5.9° after cup placement. The mean internal rotation angle was 14.8° ± 7.4° after cup placement. There were no correlations between the navigation error in inclination or anteversion and the absolute values of changes of the pelvic tilt angle at any phase. CONCLUSIONS: Although progressive pelvic motion occurred in THA in the lateral decubitus position, especially during cup placement, the CT-based navigation system with AR technology improved cup placement accuracy.