What’s New in Hip Surgery

As surgical technology continues to expand at a rapid pace, it is essential that today’s literature keep up with evidence that either supports or refutes this trend. This includes developments in component design, perioperative antibiotic administration, surgical approach, perioperative pain control, and hip preservation techniques. Component Design and Technology Bearing Surface in Total Hip Arthroplasty (THA) Despite improved wear rates, squeaking and noise have long been associated with ceramic-on-ceramic THA bearing surfaces and is considered a multifactorial phenomenon. In a single-blinded randomized controlled trial (RCT) of 2 different ceramic-on-ceramic bearing designs, Paulsen et al. examined the prevalence of squeaking. One group (n = 91) consisted of a Trident acetabular component with a metal-backed Biolox Forte liner and an associated V40 ceramic head on an ABG stem (Stryker), and another group (n = 92) consisted of a Trilogy acetabular component with a non-metal-backed Biolox delta ceramic liner and an associated 12/14-taper Biolox delta ceramic head on a CLS Spotorno stem (Zimmer Biomet)1. After 12 months, 17 (19%) of 91 patients in the Trident group and 13 (14%) of 92 patients in the Trilogy group reported some form of noise; the difference was not significant (p = 0.41). Vitamin E-impregnated cross-linked polyethylene (VEPE) liners are thought to reduce wear because of their antioxidant properties. In an RCT, Tsikandylakis et al. examined the performance of large metal heads and VEPE liners2. The acetabular shells (G7; Zimmer Biomet) implanted ranged from 50 to 64 mm, with all patients receiving a neutral E1 VEPE liner and cobalt-chromium femoral head. The intervention group received the largest possible head (36 to 44 mm) that utilized the thinnest liner (range, 4.7 to 5.7 mm), whereas the control group received a standard 32-mm head and a liner ranging from 6.7 to 11.3 mm. After radiostereometric analysis (RSA) at 5 years, the median proximal penetration of the liner was not significantly different (p = 0.691) between the treatment group (−0.04 mm) and the control group (−0.03 mm), there was no difference in peri-acetabular lucencies (p = 0.197), and no pseudotumors were reported. The authors acknowledged that a low level of measurements exceeded the RSA precision limit of 0.15 mm, which precluded the reporting of volumetric wear. It may be that, with a longer duration, these values would permit further analysis of linear wear differences and analysis of volumetric wear. Furthermore, longer follow-up is required to assess the risk of pseudotumor development with the use of large cobalt-chromium heads. Femoral and Acetabular Component Design Hydroxyapatite-coated stems make up the majority of uncemented stems implanted in North America. Kim et al. performed a meta-analysis comparing hydroxyapatite-coated and non-hydroxyapatite-coated uncemented femoral stems in primary THA3. They included 2,309 patients across 24 RCTs and reported a significant difference in femoral revisions between patients who had hydroxyapatite-coated stems (6 [1%] of 605) and patients who had non-hydroxyapatite-coated stems (15 [4%] of 371) (relative risk [RR], 0.29 [95% confidence interval (CI), 0.13 to 0.68], p = 0.004), with low heterogeneity (p = 0.38). Thigh pain was reported less often in patients with hydroxyapatite-coated stems (RR, 0.56 [95% CI, 0.33 to 0.93], p = 0.03; heterogeneity, p = 0.69), although only 3 studies reported this outcome. Although these results suggest that hydroxyapatite-coated stems are superior, caution must be applied for overall generalization given the many different stem types assessed in this study and the numerous versions available in today’s market. The morphology of uncemented stems continues to evolve, with numerous different available types. In a 3-arm clinical trial that sought to determine how different uncemented stem morphologies may impact bone mineral density (BMD), Hooper et al. randomized 119 patients to receive a collarless dual-wedge taper stem, an anatomic stem, or a triple-taper stem. Bone density was measured with dual x-ray absorptiometry (DXA) scans preoperatively and at 6 weeks, 1 year, and 2 years postoperatively. Averaged across all stems, Gruen zones 1, 2, 3, 5, and 6 showed increased density at 2 years, with slightly varying patterns. Furthermore, the patients with double-taper and anatomic stems showed greater BMD in proximal femoral Gruen zones 1, 2, 4, and 5 compared with patients with the triple-taper design. Greater preservation of BMD was observed in zone 2 in patients with the dual-wedge and anatomic stems (p = 0.019). In Gruen zone 7, BMD was preserved in patients with the dual-wedge stem, whereas BMD decreased in patients with the triple-taper stem, although this did not reach significance (p = 0.059). In Gruen zone 4, BMD decreased in patients with all stems. No stems were loose at the final follow-up. As the use of triple-taper stems increases, studies should focus on the possible impacts on BMD over time, particularly in the proximal femur, given the BMD impacts of the fully coated predecessor stems in this region. However, the mean age of the included patients was 65 years of age and this study included younger patients with presumably better bone density. This may have limited the generalizability of this study to the older population, which is arguably where lower BMD is likely to have bigger impacts. Also, collared triple-tapered stems are becoming much more popular than the studied collarless designs, which was another limitation. Finally, a longer follow-up time is needed to assess these results, given the longevity of the modern implants. Acetabular porous coating design is another common innovation, with new designs manufactured for supposed superior cementless fixation. In an RCT, van der Lelij et al. examined 38 patients and compared their treatment with a hydroxyapatite-coated, plasma-sprayed, cluster-hole Trident acetabular shell (Stryker) versus the newer Trident II version, with an arch-deposited, commercially pure titanium ultraporous surface, also with a hydroxyapatite coating5, in 40 patients. Utilizing RSA, the authors showed that, at 12 and 24 months, there was no difference in mean proximal migration (p = 0.875). The authors cautioned against extrapolation to other newer Trident II designs as well as patients requiring screw fixation for stability, as those cases were excluded. This study brings into question whether the higher costs of newer implants are justified, if performance is similar, at least in straightforward cases in which no screw fixation is required. The reader is cautioned to not translate these findings to revision cases. New Technology and THA Robotics in THA has been increasingly studied, particularly with its application to achieving improved accuracy in the execution of a preoperative plan. In an RCT of 60 patients, Fontalis et al. compared conventional THA with robotic-assisted THA with respect to the achievement of the preplanned center of rotation6. Both groups underwent computed tomographic (CT) preoperative planning regarding the center of rotation, and the authors found that the center-of-rotation median error was 1.4 mm (interquartile range [IQR], 0.87 to 3.42 mm) for robotic THA and 4.3 mm (IQR, 3 to 6.8 mm) for conventional THA (p < 0.001). The authors also found statistically improved accuracy for offset (median absolute error, 2 compared with 3.9 mm; p = 0.019) and leg-length discrepancy (mean, 0.6 compared with 1.4 mm; p < 0.001) favoring robotic-assisted THA. As with most robotic studies, the authors concluded that the improved accuracy does not necessarily translate into improved survivorship and functional outcomes, with more high-quality studies required. Antibiotics and THA Perioperative Prophylaxis The debate about antibiotic prophylaxis in total joint arthroplasty (TJA) continues. In an RCT, Peel et al. examined >4,000 patients undergoing THA and total knee arthroplasty (TKA) and found that the addition of 1.5 g of vancomycin to standard cefazolin prophylaxis did not demonstrate superiority in reduced surgical site infections when compared with cefazolin-only prophylaxis (RR, 1.28 [95% CI, 0.94 to 1.73]; p = 0.11). The addition of vancomycin was also associated with an increased risk of hypersensitivity reactions (1.2% compared with 0.5%; RR, 2.20 [95% CI, 1.08 to 4.49])7. More evidence is also emerging for the use of single-antibiotic cement (0.5-g gentamicin per 40-g mix [Palacos R+G cement; Heraeus Medical]) compared with high-dose, dual-antibiotic cement (1-g gentamicin and 1-g clindamycin per 40-g mix [Copal G+C cement; Heraeus Medical]) intraoperatively. In an RCT, Png et al. showed that high-dose, dual-antibiotic cement is less cost-effective than single-antibiotic cement8. In older patients with displaced femoral neck fractures managed with hemiarthroplasty performed with cement, dual antibiotics were associated with a significantly higher mean cost without significant improvements in quality-adjusted life-years. Although the authors included a large sample size within the context of a randomized trial, interpretation should be cautiously approached, as the outcomes were only measured at 120 days postoperatively, which may not have captured the effect of any periprosthetic joint infections (PJIs) diagnosed after that point, and there was no formal power analysis reported. Porto et al. advocated for more preoperative testing of patients with a reported penicillin allergy. Their systematic review of 11 studies including 1,276,663 patients found that the prevalence of patients with a true penicillin allergy is lower than that reported by patients (0.7% to 3.0%)9. Although the implications of this are not conclusive in the literature, the authors suggested that there may be a higher rate of infection associated with the administration of second-line antibiotics (for patients with a purported penicillin allergy). The authors cautioned about the interpretation of these results, as many studies had a risk of bias as well as heterogeneity. Many patients will claim a childhood allergy to penicillin but will have vague, if any, documentation of an actual allergic reaction. Unless there is a documented serious allergic response, many modern centers are successfully administering cephalosporin antibiotic prophylaxis in the absence of formal testing. A history of to penicillin is not a to the use of cefazolin at which has had over a of without any In a meta-analysis of studies including patients who underwent primary THA or and revision et al. showed that, antibiotic prophylaxis in reduce the risk of infections when compared with standard prophylaxis (RR, [95% CI, to p = heterogeneity, This into a reduced risk of in the antibiotic prophylaxis with a needed to of patients. only the primary THA and patients with antibiotic prophylaxis were less likely to a after overall (p = and less likely to a after THA (p = was no significant difference after primary (p = antibiotic prophylaxis to a in the of a after revision overall (p = and a in the of a after revision (p = with no difference after revision THA (p = However, there was much heterogeneity in the of and antibiotic between included studies, as the authors cautioned regarding the interpretation and generalization of these More to be with to this a and et al. reported on their of a with an antibiotic in with the standard cement control The group received and vancomycin an for by The control group received a with vancomycin and which was implanted for a mean of 120 were no of antibiotic measured in either group and no However, this study did not the of further is required to assess its this study is an to the of this One must keep in that is not a and was in the because of the risk of infection from an The more question in is whether this is more at infection than a which has been emerging as the new standard of Perioperative Although the for in primary THA is the is not necessarily true for revision THA. In a systematic review and et al. examined the for in revision They included a total of studies that compared the rate of in with and without They found that of the patients receiving and of the patients managed without required [95% CI, to p < to a However, the authors cautioned that, although the results should be with given that preoperative and were not analysis to the revision was not and some included studies had Finally, a heterogeneity was not which may have further limited the continues to be debate on whether or is the more particularly with respect to analysis of the trial comparing and to this Despite the trial that was significantly superior to in within days after primary THA and the reduced cost of did not the increased cost of The authors that the trial was not for a cost which may have the the overall on the on compared with the prophylaxis which may have in other In the and cost implications of a are different from those of a not in this The continues to be to the femoral is a common associated with this and is often et al. compared conventional with in the approach, reporting that, although may be associated with a slightly lower of of compared with of p = there were no significant differences in in patients with or without a femoral This should not be considered as have a effect and are not to this with to the the and the to the hip a of Although there has been evidence to suggest that the is associated with in a study of patients, et al. that, although there are some functional differences between the and a approach, these not to clinical differences at years Perioperative Perioperative pain control with after THA continues to be studied, particularly as it to The group is often utilized in the with a hip and is thought to without has been reported. 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