The Role of Imageless Computer-Assisted Navigation During Total Knee Arthroplasty on Femoral Component Sagittal Alignment and Outcomes.

Background: While total knee arthroplasty (TKA) is highly successful, 15%-20% of patients are not satisfied postoperatively, which may be due to alignment of the TKA components. Imageless computer navigation was developed to increase implant alignment accuracy and precision, but controversy surrounds the patient benefit of this technology. The target of femoral sagittal alignment and its role in patient-reported outcomes (PROMs) after TKA using assistive technology has not been well-defined. Methods: Femoral sagittal alignment, 30-day complications, and PROMs through 1 year were collected retrospectively from unilateral elective TKA patients who underwent surgery between July 2020 and February 2023. Two surgeons equally versed in conventional and imageless navigation techniques participated in patient record identification. Students t-tests and chi-square tests of proportion were used to compare outcomes, 30-day complications, and alignment. Results: Completed PROMs were available for 387 patients; 181 in the computer navigation group and 206 in the conventional arthroplasty group. PROMs were statistically significantly different between groups, favoring computer navigation (P = .014 at 12 months). Lateral femoral angle measurements were greater in females who underwent TKA with computer navigation (P < .001). Of note, 14 patients in the conventional technique group returned to the emergency department within 30 days, as compared to 4 in the navigation group (P = .033). Conclusions: PROMs are improved in the navigation group compared to the conventional technique group. Fewer patients in the navigation group returned to the emergency department. Navigation appeared to provide a small benefit compared to conventional techniques, though final lateral femoral angle was not predictive of outcomes. Additional surgical characteristics may need to be examined to determine the reasons for the differences in outcomes between these techniques.

Tranexamic Acid Reduces the Amount of Blood Transfused in Revision Total Hip Arthroplasty for Vancouver B2/B3 Periprosthetic Femur Fractures.

BACKGROUND: Periprosthetic fractures around total hip arthroplasty (THA) represent a significant source of morbidity and mortality. The use of tranexamic acid (TXA) in arthroplasty is well described, yet little literature supports its role in periprosthetic femur fractures (PFFs). This study investigated the effect of preoperative TXA administration on transfusion rate and volume, length of stay, and 90-day complication rates in patients undergoing revision THA for PFF. MATERIALS AND METHODS: All patients undergoing revision THA for PFF (Vancouver B2/B3) at our institution from August 2016 to June 2022 were identified. Routine TXA administration at surgical start was introduced in 2018. Patient demographics, operative time, blood product use, length of stay, and 90-day complications were collected. Patients were divided into those who received TXA preoperatively and those who did not. RESULTS: A total of 56 patients were included. There was no difference in age, sex, anesthetic type, fracture classification, or preoperative blood values between cohorts. TXA significantly lowered the amount of blood product required (2.3 units vs 3.2 units, P=.023). Preoperative TXA did not independently reduce length of stay; however, blood transfusion was associated with increased length of stay (7 days vs 4.7 days, P=.003). There were no differences in 90-day complications. CONCLUSION: Among patients who underwent revision THA for Vancouver B2/B3 PFF, TXA did not affect transfusion rates but did result in the use of fewer blood products without an increase in complications. We support routine use of TXA in this patient population. Future studies should assess earlier administration of TXA in the emergency department or once patients' conditions have been medically optimized. [Orthopedics. 2024;47(5):e261-e267.].

Increasing Body Mass Index Not Associated With Worse Patient-Reported Outcomes After Primary THA or TKA.

INTRODUCTION: As the US obesity epidemic continues to grow, so too does comorbid hip and knee arthritis. Strict body mass index (BMI) cutoffs for total hip and knee arthroplasty (THA and TKA) in the morbidly obese have been proposed and remain controversial, although current American Academy of Orthopaedic Surgeons guidelines recommend a BMI of less than 40 m/kg2 before surgery. This study sought to compare patient-reported outcomes and 30-day complication, readmission, and revision surgery rates after THA or TKA between morbidly obese patients and nonmorbidly obese control subjects. METHODS: All patients undergoing primary THA and TKA at our institution from May 2020 to July 2022 were identified. Patient demographics, surgical time, length of stay and 30-day readmission, revision surgery, and complication rates were prospectively collected. Preoperative and postoperative Hip and Knee Society (Hip Osteoarthritis Outcome Score [HOOS] and Knee Osteoarthritis Outcome Score [KOOS]) were collected. Patients were stratified by BMI as ideal weight (20 to 24.9), overweight (25 to 29.9), class I obese (30 to 34.9), class II obese (35 to 39.9), and morbidly obese (>40 m/kg2). RESULTS: A total of 1,423 patients were included for final analysis. No difference was observed in 30-day unplanned return to emergency department, readmission, or revision surgery in the morbidly obese cohort. Morbidly obese patients undergoing THA had lower preoperative HOOS (49.5 versus 54.5, P = 0.004); however, there was no difference in postoperative HOOS or KOOS at 12 months across all cohorts. DISCUSSION: No difference was observed in 30-day return to emergency department, readmission, or revision surgery in the morbidly obese cohort. Despite a lower preoperative HOOS, there was no difference in 12-month HOOS or KOOS when stratified by BMI. These findings suggest that such patients may achieve similar benefit from arthroplasty as their ideal weight counterparts.

Preoperative Bladder Scanning Can Predict Postoperative Urinary Retention Following Total Joint Arthroplasty.

BACKGROUND: As total joint arthroplasty (TJA) moves to the outpatient setting, it is becoming clear that postoperative urinary retention (POUR) is a potential impediment to same-day discharge. Although risk factors for POUR have been widely studied, the lack of their clinical utility warrants investigation of specific preoperative factors that can assist in surgical planning and patient optimization. The purpose of the current study was to determine whether preoperative symptom surveys and bladder scanning are useful tools in identifying POUR risk. METHODS: We performed a prospective analysis of patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) at a high-volume orthopaedic hospital between December 1, 2020, and September 30, 2021. A total of 507 patients (324 female and 183 male) undergoing TJA completed the American Urological Association (AUA) symptom index preoperatively and then again at 14 and 64 days postoperatively. Post-void bladder scans were obtained in the immediate preoperative setting. POUR was defined as a bladder volume of >500 mL that required catheterization. Chi-square and quintile analysis were used to compare bladder scanning volumes, and Student t tests were used to compare AUA scores. RESULTS: The rate of POUR was 37% (66 female and 34 male) and 23% (37 female and 19 male) in the TKA and THA groups, respectively. Increasing post-void residual volume (PVRV) measured on preoperative bladder scanning was found to be predictive of POUR. Among the TKA cohort, younger age and lower body mass index were also associated with increased catheterization, although age was not statistically significant. The AUA symptom survey was not found to correlate with POUR in either population. CONCLUSIONS: There was a predictable and exponential increase in the rate of catheterization as preoperative PVRV increased from 50 to 200 mL. The AUA symptom score showed no utility in predicting POUR in our study population. We propose that preoperative bladder ultrasonography become standard practice in TJA, especially among patients scheduled for same-day discharge. LEVEL OF EVIDENCE: Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Multimodal analgesia is superior to opiates alone after tibial fracture in patients with substance abuse history.

Objectives: To evaluate the effectiveness of multimodal analgesia in patients with a tibial shaft fracture. Design: Retrospective review. Setting: Large, urban, academic center. Patients: One hundred thirty-eight patients were evaluated before implementation of multimodal analgesia. Thirty-four patients were evaluated after implementation. All patients were treated operatively with internal fixation for their tibial shaft fracture. Patients with polytrauma were excluded. Intervention: Multimodal analgesia. Main Outcome Measures: Pain levels at rest and with movement were assessed. Morphine milligram equivalents (MMEs) dosed per patient were calculated each day. Length of stay was also documented. Results: After implementation of a multimodal analgesic program, there was a statistically significant decrease in pain score at rest (4.7-4.0, P = 0.034) and with movement (5.8-4.8, P = 0.007). MMEs dosed in the multimodal analgesic program correlated with pain score (R2 = 0.5), whereas before implementation of the program, MMEs dosed were not dependent on pain score (R2 = 0.007). Patients with a history of substance abuse had the most profound effect from this paradigm change. For those with a history of substance abuse, treatment of pain using a multimodal approach reduces MMEs dosed and length of stay (5.7-3.1 days, P = 0.016). Conclusions: Multimodal analgesia improves patient pain scores both at rest and during movement. In patients with a history of substance abuse, multimodal analgesia not only decreases pain but also decreases length of stay and MMEs dosed to levels consistent with someone who does not have a substance abuse history. Level of Evidence: Therapeutic Level III.

Preoperative Factors to Assess Risk for Postoperative Urinary Retention in Total Joint Arthroplasty: A Retrospective Analysis.

BACKGROUND: Postoperative urinary retention (POUR) is a significant problem in total joint arthroplasty (TJA). Although risk factors for POUR have been well documented, they are ubiquitous in an aging total joint population, which makes risk stratification difficult. The purpose of this study was to determine if a high preoperative post-void bladder scan identifies patients at risk for POUR. METHODS: A retrospective analysis was conducted on all TJAs performed at a high-volume orthopedic center between December 2019 and February 2020. A total of 585 elective TJA patients received post-void bladder scans before surgery. Bladder scan volumes were correlated with catheterization via Chi-squared tests. RESULTS: A high post-void residual volume (PVRV > 50 ml) was associated with an increased risk of catheterization (23% vs 34%, chi-squared statistic = 6.2638, P value = .013), as was intravenous fluid volume (>1000 ml in knee, >2000 ml in hip). Catheterization rates were higher among total knee arthroplasty patients younger than 60 years (37% vs 24%, chi-squared statistic = 4.284, P value = .0385) and total hip arthroplasty (THA) patients older than 65 years (30% vs 18%, chi-squared statistic = 3.292, P value = .0695). Multiple risk factors were additive. CONCLUSIONS: Higher PVRV and intravenous fluids were independently associated with catheterization after TJA. Younger age was associated with greater risk in total knee arthroplasty, while older age increased risk in THA. We propose that a preoperative bladder scan to detect a high PVRV may provide clinical utility to identify patients likely to develop POUR.

Does the Use of an Intra-Articular Local Anesthetic Injection During Total Hip Arthroplasty Reduce Patient Reported Pain Scores or Patient Opioid Consumption?

BACKGROUND: During primary total hip arthroplasty (THA), some surgeons use an intra-articular injection (IAI) containing 200 mg ropivacaine to target postoperative pain. There is no clear consensus on the efficacy of an IAI alone. The purpose of this study is to evaluate the effect of a 200 mg ropivacaine IAI on pain scores, opioid consumption, and mobility for primary THA patients. METHODS: We retrospectively reviewed 571 patients who underwent primary THA at a single institution. Patients were grouped according to those who received a 200 mg ropivacaine IAI and those who did not. Primary outcome measures for this study included pain scores, morphine milligram equivalents (MMEs) dosed, distance of ambulation achieved, and time to ambulation. RESULTS: The intervention group reported higher average pain scores with activity than the control group (P = .024). The intervention group also required higher MMEs. When striated by hour, a statistically significant uptick in pain started at 16 hours (P = .0009) and persisted to 28 hours (P = .032) in patients receiving a 200 mg ropivacaine IAI. This correlated with an increase in MMEs seen at hour 24 through 32 (P = .003 to P = .012). Level of ambulation, time to ambulation, and distance ambulated did not differ between groups. An IAI of 200 mg ropivacaine also appeared to lead to higher pain scores and higher opioid doses in males. CONCLUSION: The IAI does not appear to reduce postoperative pain scores or MMEs dosed for THA patients. More research is needed to look at the utilization and efficacy of intra-articular ropivacaine, especially focusing on functional outcomes and gender differences.

Osterix-mCherry Expression Allows for Early Bone Detection in a Calvarial Defect Model.

The process of new bone formation following trauma requires the temporal recruitment of cells to the site, including mesenchymal stem cells, preosteoblasts, and osteoblasts, the latter of which deposit minerals. Hence, bone repair, a process that is assessed by the extent of mineralization within the defect, can take months before it is possible to determine if a treatment is successful. Here, a fluorescently tagged Osterix, an early key gene in the bone formation cascade, is used as a predictive measure of bone formation. Using a calvarial defect model in mice, the ability to noninvasively track the Osterix transcription factor in an Osterix-mCherry mouse model is evaluated as a measure for bone formation following treatment with recombinant human Bone-Morphogenetic-Protein 2 (rhBMP-2). Two distinct delivery materials are utilized, an injectable nanocomposite hydrogel and a collagen sponge, that afford distinct release kinetics and it is found that cherry-fluorescent protein can be detected as early as 2 weeks following treatment. Osterix intensity correlates with subsequent bone formation and hence can serve as a rapid screening tool for osteogenic drugs or for the evaluation and optimization of delivery platforms.

Hydrogel Nanocomposites with Independently Tunable Rheology and Mechanics.

Hydrogels are an attractive class of biomaterials for minimally invasive local drug delivery given their injectability, tunability, high water content, and biocompatibility. Broad applicability though is challenged: relatively modest mechanical properties restrict use to soft tissues, while flow properties necessary for injectability limit implantation to dried, enclosed tissues to minimize material migration during gelation. To address these dual concerns, we designed an injectable nanocomposite hydrogel based on dextran aldehyde and a poly(amido amine) dendrimer doped with phyllosilicate nanoplatelet fillers. Balance of components allows for exfoliation of nanoplatelets, significantly changing macromer solution flow, facilitating injection and manipulation in a wide variety of implantation contexts while enhancing compressive modulus of hydrogels at low loading. Importantly, rheological and mechanical effects were dependent on aspect ratio, with high aspect ratio nanoplatelets having much stronger effects on mechanics and low aspect ratio nanoplatelets having stronger effects on rheology, enabling nearly independent control of rheological and mechanical properties. Nanoplatelets enhanced hydrogel properties at a filler loading substantially lower than that of comparably sized nanoparticles. We present a model to explain the role that aspect ratio plays in control of rheology and mechanics in nanoplatelet-containing hydrogels, with lessons for further nanocomposite hydrogel development. This low-cost biocompatible material may be useful as a drug delivery platform in challenging implantation environments.

Connective Tissue Growth Factor reporter mice label a subpopulation of mesenchymal progenitor cells that reside in the trabecular bone region.

Few gene markers selectively identify mesenchymal progenitor cells inside the bone marrow. We have investigated a cell population located in the mouse bone marrow labeled by Connective Tissue Growth Factor reporter expression (CTGF-EGFP). Bone marrow flushed from CTGF reporter mice yielded an EGFP+ stromal cell population. Interestingly, the percentage of stromal cells retaining CTGF reporter expression decreased with age in vivo and was half the frequency in females compared to males. In culture, CTGF reporter expression and endogenous CTGF expression marked the same cell types as those labeled using Twist2-Cre and Osterix-Cre fate mapping approaches, which previously had been shown to identify mesenchymal progenitors in vitro. Consistent with this past work, sorted CTGF+ cells displayed an ability to differentiate into osteoblasts, chondrocytes, and adipocytes in vitro and into osteoblast, adipocyte, and stromal cell lineages after transplantation into a parietal bone defect. In vivo examination of CTGF reporter expression in bone tissue sections revealed that it marked cells highly localized to the trabecular bone region and was not expressed in the perichondrium or periosteum. Mesenchymal cells retaining high CTGF reporter expression were adjacent to, but distinct from mature osteoblasts lining bone surfaces and endothelial cells forming the vascular sinuses. Comparison of CTGF and Osterix reporter expression in bone tissue sections indicated an inverse correlation between the strength of CTGF expression and osteoblast maturation. Down-regulation of CTGF reporter expression also occurred during in vitro osteogenic differentiation. Collectively, our studies indicate that CTGF reporter mice selectively identify a subpopulation of bone marrow mesenchymal progenitor cells that reside in the trabecular bone region.

Osterix-cre labeled progenitor cells contribute to the formation and maintenance of the bone marrow stroma.

We have carried out fate mapping studies using Osterix-EGFPCre and Osterix-CreERt animal models and found Cre reporter expression in many different cell types that make up the bone marrow stroma. Constitutive fate mapping resulted in the labeling of different cellular components located throughout the bone marrow, whereas temporal fate mapping at E14.5 resulted in the labeling of cells within a region of the bone marrow. The identity of cell types marked by constitutive and temporal fate mapping included osteoblasts, adipocytes, vascular smooth muscle, perineural, and stromal cells. Prolonged tracing of embryonic precursors labeled at E14.5dpc revealed the continued existence of their progeny up to 10 months of age, suggesting that fate mapped, labeled embryonic precursors gave rise to long lived bone marrow progenitor cells. To provide further evidence for the marking of bone marrow progenitors, bone marrow cultures derived from Osterix-EGFPCre/Ai9 mice showed that stromal cells retained Cre reporter expression and yielded a FACS sorted population that was able to differentiate into osteoblasts, adipocytes, and chondrocytes in vitro and into osteoblasts, adipocytes, and perivascular stromal cells after transplantation. Collectively, our studies reveal the developmental process by which Osterix-Cre labeled embryonic progenitors give rise to adult bone marrow progenitors which establish and maintain the bone marrow stroma.

Generation and characterization of Osterix-Cherry reporter mice.

Osterix is a zinc finger containing transcription factor, which functions as a key regulator of osteoblast differentiation. To better understand the temporal and spatial expression of Osterix during embryonic development and in the adult skeleton, we generated Osterix-Cherry reporter mice. Bacterial recombination techniques were employed to engineer a transgenic construct, which consisted of a ∼39 kb DNA fragment encompassing the Osterix/Sp7 gene, but excluding adjacent gene sequences. Osterix reporter expression was characterized at embryonic, neonatal, and adult ages both by itself and in the context of a cross with Bone Sialoprotein (BSP)-Topaz reporter mice. Relative to Osterix, BSP is a more mature marker of osteoblast differentiation. In agreement with osteoblast lineage maturation, Osterix reporter expression preceded BSP reporter expression during embryonic development and spatially appeared in a much broader cell population. Strong Osterix reporter expression was observed in mature osteoblasts and osteocytes. However, weaker Osterix-Cherry positive cells were also observed in the bone marrow, possibly identifying an early osteoprogenitor cell population. Evaluation of Osterix reporter expression in male femur tissue sections from 10 days to 12 weeks of age revealed persistent expression in cells of the osteoblast lineage and a surprising increase in maturing chondrocytes of the growth plate. Also, Osterix reporter expression was transiently detected in the kidney after birth.

Introduction of a Phe377del mutation in ANK creates a mouse model for craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a monogenic human disorder characterized by thickening of craniofacial bones and flaring metaphyses of long bones. Mutations for autosomal dominant CMD have been identified in the progressive ankylosis gene ANKH. Previous studies of Ank loss-of-function models, Ank(null/null) and Ank(ank/ank) mice, suggest that Ank plays a role in the regulation of bone mineralization. However, the mechanism for Ank mutations leading to CMD remains unknown. We generated the first knockin (KI) mouse model for CMD expressing a human mutation (Phe377 deletion) in ANK. Homozygous Ank knockin mice (Ank(KI/KI)) replicate many typical features of human CMD including hyperostosis of craniofacial bones, massive jawbones, decreased diameters of cranial foramina, obliteration of nasal sinuses, fusion of middle ear bones, and club-shaped femurs. In addition, Ank(KI/KI) mice have increased serum alkaline phosphatase and TRACP5b, as reported in CMD patients. Biochemical markers of bone formation and bone resorption, N-terminal propeptide of type I procollagen and type I collagen cross-linked C-terminal telopeptide, are significantly increased in Ank(KI/KI) mice, suggesting increased bone turnover. Interestingly, Ank(KI/KI) bone marrow-derived macrophage cultures show decreased osteoclastogenesis. Despite the hyperostotic phenotype, bone matrix in Ank(KI/KI) mice is hypomineralized and less mature, indicating that biomechanical properties of bones may be compromised by the Ank mutation. We believe this new mouse model will facilitate studies of skeletal abnormalities in CMD at cellular and molecular levels.