Search

Few studies investigate the influence of inflammatory bowel disease (IBD) on complications following total knee arthroplasty (TKA). Therefore, we compared complications and readmissions frequencies after TKA in patients with Crohn's disease (CD) and ulcerative colitis (UC) to patients without IBD.A large administrative claims database was used to identify patients who underwent primary TKAs from 2010 to 2019 and had a diagnosis of IBD before TKA. Patients were stratified into two groups: those with CD (n = 8,369) and those with UC (n = 11,347). These patients were compared a control of 1.3 million patients without an IBD diagnosis. Chi-square and unadjusted odds ratios (OR) with 95% confidence intervals (CI) were used to compare complication frequencies. Multivariable logistic regression was used to evaluate independent risk factors for 90-day complications.Compared to patients without IBD, patients with IBD were associated with higher unadjusted 90-day odds for Clostridium difficile infection (CDI) (CD: OR 2.81 [95% CI 2.17 to 3.63]; p 0.001; UC: OR 3.01 [95% CI 2.43 to 3.72]; p 0.001) and two-year periprosthetic joint infection (CD: OR 1.34 [95% CI 1.18 to 1.52]; p 0.001; UC: OR 1.26 [95% CI 1.13 to 1.41]; p 0.001). After controlling for risk factors like obesity, tobacco use, and diabetes, both types of IBD were associated with higher 90-day odds for CDI and PJI (p 0.001 for all).IBD is associated with higher 90-day postoperative CDI and PJI compared with patients without IBD. Providers should consider discussing these risks with patients who have a diagnosis of IBD.

Mechanical knee symptoms secondary to knee osteoarthritis (OA) may warrant knee arthroscopy (KA). Degenerative changes may progress and require a subsequent total knee arthroplasty (TKA). Recent studies have evaluated the timing of KA prior to TKA, associated a narrow interval with increased post-TKA complications. However, an updated analysis is required. We compared surgical outcomes in recipients of KA prior to TKA as stratified by four, time-dependent cohorts (< 12, 12 to 16, 16 to 20, and 20 to 24 weeks prior to TKA). We specifically compared: 90-day (1) manipulations under anesthesia (MUAs); (2) septic revisions at 90 days, 1 year, and 2 years; as well as (3) how various independent risk factors influenced the manipulations or revisions. We queried a national database for patients undergoing TKA. Patients who underwent KA with the following intervals: 0.476). The adjusted analyses showed an increased risk for 90-day MUA among all TKA cohorts (p

No consensus exists regarding the appropriate timing of bariatric surgery (BS) or the complication profiles between Roux-en-Y Gastric Bypass (RYGB) and sleeve gastrectomy (SG) prior to total knee arthroplasty (TKA). We sought to compare 90-day medical and up to two-year surgical complications and revisions among (1) BS performed 6 months and 1 year prior to TKA; (2) between BS types (RYGB and SG) prior to TKA; and (3) with comparison to 2 non-BS cohorts of morbidly and nonmorbidly obese patients.We queried a national database to identify patients undergoing BS (RYGB and SG) prior to TKA from 2010 to 2020. Timing (six-month and one-year intervals) and type of BS (RYGB and SG) were identified. Cohorts without prior BS served as comparators: BMI, kg/mThe timing of BS (6 months and 1 year) had similar incidences of medical/surgical complications and revisions, with both lower than the BMI40 cohort (P.001). Differences between types of BS were also lower than the BMI40 cohort (P.001). The BMI 20-35 had lower complications and revisions among all cohorts. No differences were observed between BS timing or type as risk-factors for PJIs and revisions.Timing (6 months or 1 year prior to TKA) and type of BS shared similar complication profiles, lower than BMI40 and higher than BMI 20-35. These findings support a surgeon's decision to proceed with TKA at six months post-BS if indicated.

Over 25% of patients with rheumatoid arthritis (RA) are expected to undergo a joint replacement during their lifetime. Current practice guidelines recommend withholding biologic therapy 1 week prior to total hip arthroplasty, given its immunosuppressive effects. Most patients are on a regimen including biologic and nonbiologic therapy; however, the individual influences of these therapies are not well understood in the setting of total knee arthroplasty (TKA). Therefore, we sought to compare biologic, nonbiologic, and recipients of both types of therapy in patients with RA undergoing TKA. We specifically assessed (1) medical complications at 90 days; (2) surgical complications up to 1 year; and (3) independent risk factors for prosthetic joint infections (PJIs).A retrospective review was conducted using a national, all-payer database for patients undergoing primary TKA from January 2010 to April 2020 (n = 1.97 million). Patients diagnosed with RA were then separated into at least 1-year users of biologic (n = 3,092), nonbiologic (28,299), or dual (n = 10,949) therapy. Bivariate analyses were utilized to assess for 90-day medical and up to 1-year surgical outcomes. Additionally, multivariate regression models were utilized to assess for independent risk factors.The incidence and odds ratio for medical/surgical outcomes were equivocal among the biologic, nonbiologic, and recipients receiving both types of therapy (p > 0.061). No differences were observed between the type of therapy as additional risk factors for infection (p > 0.505). However, glucocorticoids at 90 days and alcohol abuse, diabetes mellitus, obesity, as well as tobacco use were identified as additional risk factors for PJI(p No appreciable differences in medical or surgical outcomes were associated with the independent use of biologic, nonbiologic, or recipients of both types of therapy in patients with RA. Additionally, alcohol abuse, diabetes mellitus, glucocorticoids, obesity, and tobacco use conferred an increased risk of PJI. These results can serve as an adjunct to current practice guidelines.

Poor metaphyseal fixation secondary to bone loss in revision total knee arthroplasty (TKA) continues to be challenging. One technique to increase implant stability is the use of novel three-dimensional (3D) printed titanium metaphyseal cones with adjunctive stems for added fixation. However, the survival of these novel constructs is poorly understood. Therefore, we sought to examine 3D-printed titanium metaphyseal cone components in revision TKA for aseptic as well as septic reasons and aimed to evaluate: (1) revision-free survivorships; (2) patient-reported outcomes measures (PROMs); (3) postoperative medical complications; and (4) radiographic outcomes. A consecutive series of 62 patients who underwent revision TKA with use of a titanium metaphyseal cone at a single institution between September 1, 2015 and May 31, 2021 were examined. The patients had a minimum follow-up period of 2 years (mean, 40 months, range, 24–72 months). PROMS included Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS-JR) scores at baseline and last clinical follow-up. Overall, when excluding infections, the combined implant survivorship was 96% (52 out of 54), while it was 95% (35 out of 57) for aseptic revisions and 100% (17 out of 17) for septic revisions. Reasons for revisions within the aseptic revision cohort included loosening (5%) as well as periprosthetic joint infections (PJIs) (7.5%). All failures following an index septic revision were due to PJI. Mean KOOS scores at baseline as well as at final follow-up was 43 points (range, 16–80) and 70 points (range, 34–100), respectively. None of the patients had medical complications. Other than the loosening reported (only femoral component), of the surviving patients no patients had evidence of progressive radiolucencies. The use of titanium cones in revision TKA provides good revision-free survivorship at 2 years. Further research is warranted on the longer-term survivorship of 3D-printed titanium cones. The current study has found that 3D-printed titanium cones can be incorporated as part of the revision knee surgeon's armamentarium.

Introduction: Revision total hip arthroplasty (THA) can be challenging in the face of proximal femoral bone loss, catastrophic implant failure, or recurrent hip instability. Tapered modular femoral stems have shown substantial success at short follow up for aseptic revisions. The purpose of this study was to report mid-term revision THA outcomes of a tapered modular femoral stem at a tertiary referral center used to treat both aseptic as well as periprosthetic joint infections (PJIs). We specifically sought to assess: (1) revision-free implant survivorship; (2) patient-reported outcome measurements (i.e., Hip Disability and Osteoarthritis Outcome Score, Joint Replacement [HOOS JR]); (3) postoperative surgical complications and 30-day readmissions; as well as (4) radiographic outcomes. Materials and Methods: We reviewed a consecutive series of 92 patients who underwent revision THA between 2009 and 2013 with a tapered modular femoral stem. After accounting for mortality (n=7) and loss to follow up (n=13), a total of 72 implants in 66 patients who had eight years of mean follow up (range, 2 to 11) were included. PJI (46%) was the predominant preoperative indication for revision THA, followed by aseptic loosening (25%), periprosthetic fracture (18%), and symptomatic hardware (10%). Outcomes of interest included all-cause revision-free survivorship, postoperative complications, and HOOS JR, as well as SF-12 scores. Radiographically, they were evaluated for subsidence, radiolucencies, and loosening. Results: Aseptic revision-free survivorship of the femoral component was 95.8% (69 out of 72). Including septic cases, revision-free survivorship was 87.5% (63 cases), and 60 implants (83.3%) had an all-cause revision-free survivorship. For those patients who underwent septic revisions, eight out of nine remained infection free, while one underwent a resection arthroplasty. Furthermore, the cause for femoral aseptic revisions were subsidence (1.4%) and aseptic loosening (2.8%). Functional score improvements for HOOS JR, SF-12 PCS, as well as MCS were 29, 13, and 2, respectively (all p

Arthrofibrosis is an abnormal histopathologic response, is debilitating for patients, and poses a substantial unsolved clinical challenge. This study characterizes molecular biomarkers and regulatory pathways associated with arthrofibrosis by comparing fibrotic and non-fibrotic human knee tissue. The fibrotic group encompasses 4 patients undergoing a revision total knee arthroplasty (TKA) for arthrofibrosis (RTKA-A) while the non-fibrotic group includes 4 patients undergoing primary TKA for osteoarthritis (PTKA) and 4 patients undergoing revision TKA for non-arthrofibrotic and non-infectious etiologies (RTKA-NA). RNA-sequencing of posterior capsule specimens revealed differences in gene expression between each patient group by hierarchical clustering, principal component analysis, and correlation analyses. Multiple differentially expressed genes (DEGs) were defined in RTKA-A versus PTKA patients (i.e., 2059 up-regulated and 1795 down-regulated genes) and RTKA-A versus RTKA-NA patients (i.e., 3255 up-regulated and 3683 down-regulated genes). Our findings define molecular and pathological markers of arthrofibrosis, as well as novel potential targets for risk profiling, early diagnosis and pharmacological treatment of patients.

Aims Arthrofibrosis is a relatively common complication after joint injuries and surgery, particularly in the knee. The present study used a previously described and validated rabbit model to assess the biomechanical, histopathological, and molecular effects of the mast cell stabilizer ketotifen on surgically induced knee joint contractures in female rabbits. Methods A group of 12 skeletally mature rabbits were randomly divided into two groups. One group received subcutaneous (SQ) saline, and a second group received SQ ketotifen injections. Biomechanical data were collected at eight, ten, 16, and 24 weeks. At the time of necropsy, posterior capsule tissue was collected for histopathological and gene expression analyses (messenger RNA (mRNA) and protein). Results At the 24-week timepoint, there was a statistically significant increase in passive extension among rabbits treated with ketotifen compared to those treated with saline (p = 0.03). However, no difference in capsular stiffness was detected. Histopathological data failed to demonstrate a decrease in the density of fibrous tissue or a decrease in α-smooth muscle actin (α-SMA) staining with ketotifen treatment. In contrast, tryptase and α-SMA protein expression in the ketotifen group were decreased when compared to saline controls (p = 0.007 and p = 0.01, respectively). Furthermore, there was a significant decrease in α-SMA (ACTA2) gene expression in the ketotifen group compared to the control group (p < 0.001). Conclusion Collectively, these data suggest that ketotifen mitigates the severity of contracture formation in a rabbit model of arthrofibrosis. Cite this article: Bone Joint Res 2020;9(6):302–310.

Introduction: Over ⅓ of the population in the United State is obese (body mass index [BMI] >30 kg/m2), with an increasing proportion being morbidly obese (BMI >40 kg/m2). As the obesity rate climbs, an increasing number have entered the super-obese category (BMI >50 kg/m2), theoretically increasing risk for complications after total hip arthroplasty (THA). This study compared complications in non-obese, obese, morbidly obese, and super-obese patients undergoing THA. We specifically assessed: (1) 1- and 2-year peri-prosthetic joint infection (PJI) rates; (2) complication rates; as well as (3) 1- and 2-year revision rates. Methods: A database review identified patients undergoing primary THA from 01 January 2010 to 31 December 2019. Patients were stratified based on the presence of International Classification of Diseases, 9th and 10th revision diagnosis codes of non-obese (BMI 2) ( n = 8680), obese (BMI 2) ( n = 12,443), morbidly obese (BMI 2) ( n = 5250), and super-obese (BMI >50 kg/m2) ( n = 814) prior to THA. Complication rates at 90 days, 1 year, and 2 years were compared across groups. Results: At all time points, super-obese patients were associated with higher rates of PJI, even when compared to morbidly obese patients. Complications such as sepsis, venous thrombo-embolism, and revision surgeries were found in higher numbers in super-obese as well as morbidly obese patients, compared to obese and non-obese patients. Conclusions: This study provides large-scale analyses demonstrating the association between super-obese and morbidly obese patients and higher infection rates, as well as complications, following THA. Importantly, the association of PJI is highest among super-obese patients, even when compared to morbidly obese patients. Attaining a BMI 2 prior to surgery may be an important goal discussed with patients to lower the chance of postoperative infections.

Background Total knee arthroplasties (TKAs) with cementless fixation have been studied in multiple series with varying success. The aim of this study was to prepare a systematic review of the literature to evaluate clinical outcomes and revtpdelision rates of patients undergoing contemporary cementless TKA. Methods A search of PubMed and MEDLINE was conducted for English-language articles published between 2005 and 2018 to identify studies examining survivorship and clinical outcomes of cementless TKAs. Studies that reported clinical and/or radiographic outcomes were included. Data collected included the number of TKAs, implant utilized, primary diagnosis, mean age and follow-up, implant survivorship, complications, revisions, and clinical outcome scores. All hybrid constructs and revision TKAs were excluded. Poisson regression analysis was used to determine the revision incidence rates per 1,000 person-years. Results Forty-three studies with 10,447 TKAs met inclusion criteria, of which 8,187 were primary cementless TKAs. The mean follow-up was 7 years. The revision incidence per 1,000 person-years was 4.8 for all cementless designs. The complication rate for all cementless TKAs was 6%, with deep venous thrombosis being the most common complication. The mean postoperative Knee Society Score and Functional Score were 92 and 83, respectively. Conclusions While newer-generation cementless designs have shown improved survivorship and clinical outcomes compared with earlier-generation cementless designs, the literature for cementless designs remains limited when compared with cemented designs. Further studies are needed to determine if cementless TKA can achieve the same benefits that have been realized with cementless total hip arthroplasty. Level of evidence Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Introduction: The inflammatory cascade and production of prostaglandins may play a role in the pathogenesis of arthrofibrosis, a debilitating condition after joint replacement and other orthopedic procedures. Cyclooxygenase 2 (COX-2) inhibitors may mitigate the inflammatory response and formation of arthrofibrosis, but oral delivery is associated with risk of systemic side effects in many patients. The nonsteroidal anti-inflammatory drug, celecoxib, may have therapeutic benefits for arthrofibrosis, but current methods for its local delivery (e.g., biologically derived microspheres) are not translatable to immediate clinical use. Therefore, we investigated the use of a drug scaffold for sustainable intra-articular delivery of therapeutic doses of celecoxib. Materials and Methods: Celecoxib was eluted from clinically approved biodegradable collagen membranes over 7 days as measured by UV spectroscopy and high-performance liquid chromatography/mass spectroscopy. Eluted concentrations of celecoxib were examined for toxicity (live/dead staining) and profibrotic gene expression (real-time-quantitative polymerase chain reaction) in rabbit knee capsular fibroblasts in vitro. Results: Sustained concentrations of celecoxib eluted from the membrane over 7 days from both a wet and dry scaffold, with a burst release (30–45%) of celecoxib in the first 2 h. Rabbit cells treated with eluted concentrations experienced a toxic response to the burst release doses, and inhibitory effects on profibrotic genes were seen in response to the sustained doses eluted from the scaffold. Conclusions: This study characterized the novel use of collagen scaffolds for intra-articular drug delivery to treat arthrofibrosis. Scaffolds exhibit celecoxib release through an initial burst release followed by sustained release of antifibrotic doses over 7 days. Thus, collagen scaffolds are promising for clinician-directed treatment of arthrofibrosis. IMPACT STATEMENT: This study introduces a biodegradable drug scaffold for the treatment of arthrofibrosis. This scaffold elutes a sustained concentration of COX-2 inhibiting drug at anti-fibrotic doses over seven days. Placement of this scaffold in the intra-articular space may attenuate the arthrofibrotic disease process.

The diagnosis of a periprosthetic joint infection (PJI) remains a clinical challenge, as there is no uniformly accepted gold standard. In 2011, the Musculoskeletal Infection Society (MSIS) convened a work group to create a standardized definition for a PJI that could be universally adopted. Based on the MSIS criteria, the diagnosis of a PJI can be made with 1 of the 2 major criteria, or 3 of the 5 minor criteria. The purpose of this study was to determine the likelihood of having a PJI based on the number of positive minor criteria and thereby develop a prediction algorithm for differentiating between a chronic PJI and a non-PJI based on the number of positive MSIS minor criteria.We retrospectively reviewed 297 patients who presented to a tertiary care center between 2004 and 2014 with a failed total joint arthroplasty and subsequently underwent a PJI workup to exclude chronic PJI. Patients were divided into 2 groups: (1) PJI group and (2) non-PJI group. Patients who had a positive PJI workup and subsequently underwent a 2-stage revision for infection were included in the PJI group. Patients who had a negative clinical and diagnostic workup were included in the non-PJI group. One hundred eighty-two patients met the criteria for inclusion in the study, 91 in each group. Univariate and multiple logistic regression analyses were used to evaluate 21 independent variables in each of the 2 groups. A prediction algorithm for differentiating between a chronic PJI and a non-PJI based on independent multivariate variables was created.Patients who had a PJI differed significantly (P.05) from those who did not have a PJI with regard to 10 independent variables, which included all the MSIS minor criteria we evaluated. Five independent multivariate variables were identified to differentiate between the 2 groups: positive cultures, elevated synovial white blood cell count, elevated synovial polymorphonuclear neutrophil percentage, elevated erythrocyte sedimentation rate, and elevated C-reactive protein. The predictive probability of a PJI for all 32 combinations of these 5 variables was: 3.6% for 1 positive variable, 19.3% for 2, 58.7% for 3, 83.8% for 4, and 97.8% for 5. The chi-squared test for trend and the area under the receiver-operating characteristic curve (0.977) suggest that the model is highly predictive, with an excellent diagnostic performance in identifying a PJI.Diagnosing a PJI remains a clinical challenge as there is no gold standard for diagnosis. The development of the MSIS criteria, which is based on a consensus of over 400 of the world's experts in musculoskeletal infection, was a major step forward in defining the diagnosis of a PJI. However, to our knowledge, the likelihood of having a PJI based on the number of positive minor criteria has yet to be validated or quantified. Of the 20 independent variables that were evaluated, 10 were found to be significantly associated with a PJI, including all the MSIS minor criteria evaluated. In addition, a diagnostic prediction algorithm was constructed to determine the likelihood of a PJI based on 5 binary independent multivariate variables. The relationship was also examined with a receiver-operating characteristic curve analysis. The area under the curve was 0.98, indicating excellent diagnostic performance for the MSIS minor criteria in identifying a PJI.III.

The current method of measuring arthrofibrosis in live rabbits is critically limited. Specifically, this method involves radioactive fluoroscopy, error-prone goniometric measurements, and static joint angle outcomes that fail to approximate the compliance of tissues surrounding the joint. This study aims to validate a novel method of capturing the compliance of contracted tissues surrounding the joint without the use of fluoroscopy or animal sacrifice. Surgically induced contractures of one-hundred and eight rabbits were measured using the current standard of contracture measurement (a pulley system) as well as a newly designed dynamic load cell (DLC) device. The DLC device was highly reliable when compared to the pulley system (r = 0.907, p < 0.001). Finally, the DLC device produced joint stiffness hysteresis curves capable of approximating the compliance of stiff joint tissues, ultimately calculating a mean joint stiffness of 1.57 ± 1.31 N · m · rad-1 (range, 0.33-6.37 N · m · rad-1 ). In conclusion, the DLC device represents a valid method for measuring joint contractures. Further, the DLC device notably improves current techniques by introducing the capacity to approximate the compliance of contracted tissues in living rabbits. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Substance P (SP), a neurotransmitter released after injury, has been linked to deregulated tissue repair and fibrosis in musculoskeletal tissues and other organs. Although SP inhibition is an effective treatment for nausea, it has not been previously considered as an anti-fibrotic therapy. Although there are extensive medical records of individuals who have used SP antagonists, our analysis of human registry data revealed that patients receiving these antagonists and arthroplasty are exceedingly rare, thus precluding a clinical evaluation of their potential effects in the context of arthrofibrosis. Therefore, we pursued in vivo studies to assess the effect of SP inhibition early after injury on pro-fibrotic gene expression and contractures in an animal model of post-traumatic joint stiffening. Skeletally mature rabbits (n = 24) underwent surgically induced severe joint contracture, while injected with either fosaprepitant (a selective SP antagonist) or saline (control) early after surgery (3, 6, 12, and 24 hours). Biomechanical testing revealed that differences in mean contracture angles between the groups were not statistically significant (p = 0.27), suggesting that the drug neither mitigates nor exacerbates joint contracture. However, microarray gene expression analysis revealed that mRNA levels for proteins related to cell signaling, pro-angiogenic, pro-inflammatory and collagen matrix production were significantly different between control and fosaprepitant treated rabbits (p

Post-traumatic joint contractures reduce range of motion and require surgical intervention. Repeated surgical interventions can also cause recurrent contractures, leading to a paradox that highlights the need for alternative treatment strategies. Gene expression analysis by next generation sequencing of RNA (RNA-seq) from joint tissues revealed that Wnt ligands are actively expressed in joint capsules. Therefore, we investigated the intra-articular surgical implantation of an inhibitor of fibrotic cell differentiation as a possible strategy for treating post-traumatic joint contracture. Wnt/β-catenin signaling pathway inhibitor Dickkopf 1 (DKK1) was administered into rabbit knees using oligo[(poly(ethylene glycol) fumarate)] hydrogels (OPF). In vitro experiments were used to determine the cytotoxicity of DKK1 and appropriate dosing. Contractures were induced in skeletally mature female rabbits ( n = 12) by disrupting knee joint capsules and immobilizing the joint by internal k-wire fixation. Surgical release was performed at 8 weeks when OPF containing DKK1 (or vehicle) was administered. In vitro results indicated that > 90% of DKK1 was released from OPF after 4 days, and rabbit fibroblasts remained viable at 200 nM (DKK1). Although not statistically significant, joint stiffness measurements were different ( p

We evaluated recently published articles relevant to the biological effects of titanium dioxide (TiO2) particles on local endogenous cells required for normal bone homeostasis, repair, and implant osseointegration. Structural characteristics, size, stability, and agglomeration of TiO2 particles alter the viability and behavior of multiple bone-related cell types. Resulting shifts in bone homeostasis may increase bone resorption and lead to clinical incidents of osteolysis, implant loosening, and joint pain. TiO2 particles that enter cells (through endocytosis or Trojan horse mechanism) may further disrupt implant retention. We propose that cellular responses to titanium-based nanoparticles contribute to pathological mechanisms underlying the aseptic loosening of titanium-based metal implants.

Background: Periprosthetic joint infections (PJIs) are devastating complications. Excessive anticoagulation with warfarin is an independent risk factor for PJIs. The use of a dedicated anticoagulation clinic to improve warfarin management has not been proven. Methods: Between 2006 and 2014, we identified 92 patients who were placed on postoperative warfarin, and later developed PJI. These patients were compared to 313 patients who underwent total joint arthroplasty placed on warfarin without developing PJI. Patients were included if they had no history of a venous thromboembolic event, were warfarin naive, and enrolled in the anticoagulation clinic. A univariate analysis compared independent variables, and statistical analysis was performed using Student's t-test and Pearson chi-square test for continuous and categorical variables. Results: Thirty-six PJI patients and 297 control patients met the inclusion criteria. The venous thromboembolism rate was 2.1%. At discharge, 82% of all patients were subtherapeutic. Patients were within their target international normalized ratio (INR) range 26.7% of the time. The mean INR in the initial postoperative period for the PJI group was 1.46 and 1.29 in the control group (P < .001). In the acute postoperative period, 13.3% of the knee PJI group were therapeutic or supratherapeutic compared with 3.5% in the knee control group (P = .002). Conclusions: Despite utilization of a dedicated anticoagulation clinic, patients were only within their target INR range 27% of the time. Total knee arthroplasty patients who developed a PJI were more likely to be therapeutic or supratherapeutic in the initial postoperative period. Consequently, the risks associated with warfarin as a venous thromboembolism prophylaxis may outweigh the potential benefits. Keywords: Total joint arthroplasty (TJA), Periprosthetic joint infection (PJI), International normalized ratio (INR), Warfarin, Venous thromboembolism (VTE), Pulmonary emboli (PE)

The dense formation of abnormal scar tissue after total knee arthroplasty results in arthrofibrosis, an unfortunate sequela of inflammation. The purpose of this study was to use a validated rabbit model to assess the effects on surgically-induced knee joint contractures of two combined pharmacological interventions: celecoxib (CXB) loaded on an implanted collagen membrane, and subcutaneously (SQ) injected ketotifen. Thirty rabbits were randomly divided into five groups. The first group received no intervention after the index surgery. The remaining four groups underwent intra-articular implantation of collagen membranes loaded with or without CXB at the time of the index surgery; two of which were also treated with SQ ketotifen. Biomechanical joint contracture data were collected at 8, 10, 16, and 24 weeks. At the time of necropsy (24 weeks), posterior capsule tissue was collected for messenger RNA and histopathologic analyses. At 24 weeks, there was a statistically significant increase in passive extension among rabbits in all groups treated with CXB and/or ketotifen compared to those in the contracture control group. There was a statistically significant decrease in COL3A1, COL6A1, and ACTA2 gene expression in the treatment groups compared to the contracture control group (P < .001). Histopathologic data also demonstrated a trend towards decreased fibrous tissue density in the CXB membrane group compared to the vehicle membrane group. The present data suggest that intra-articular placement of a treated collagen membrane blunts the severity of contracture development in a rabbit model of arthrofibrosis, and that ketotifen and CXB may independently contribute to the prevention of arthrofibrosis. Statement of clinical significance: Current literature has demonstrated that arthrofibrosis may affect up to 5% of primary total knee arthroplasty patients. For that reason, novel pharmacologic prophylaxis and treatment modalities are critical to mitigating reoperations and revisions while improving the quality of life for patients with this debilitating condition.

Background Varus-valgus constrained (VVC) implants are used for compromised ligamentous stability in revision total knee arthroplasties (TKAs). Mobile-bearing VVC implants may reduce rotational forces; yet, limited clinical data exist. The purpose of this study is to report mid-term risk of re-revision, complications, and clinical outcomes with a mobile-bearing VVC implant. Methods Three hundred thirty-seven patients (367 TKAs) who underwent revision TKA with a mobile-bearing VVC implant between 1999 and 2013 at a single institution were reviewed. Mean age at revision was 67 years. Mean follow-up was 4 years. The main indications for revision were aseptic loosening in 158 cases (43%), reimplantation after 2-stage exchange arthroplasty in 120 (33%), instability in 61 (17%), and other in 28 (7%). Clinical outcomes were assessed by Knee Society Scores, and survivorship was analyzed with death as the competing risk. Results The 5-year cumulative incidences of any re-revision or re-revision for aseptic loosening were 9% and 3%, respectively. Twenty-six knees (7%) were re-revised: 15 for infection, 6 for aseptic loosening, and 5 for other causes. There were 17 cases of irrigation and debridement, 10 cases of manipulations under anesthesia, and 9 cases of periprosthetic fractures. There were no bearing “spin-outs.” The mean Knee Society Scores improved from 45 preoperatively to 77 at most recent follow-up (P Conclusion The functional improvement and 5-year cumulative incidence of revision of a mobile-bearing VVC implant demonstrated acceptable outcomes with no unique complications related to the mobile-bearing construct. Additional follow-up will be needed to determine long-term implant survivorship.

BACKGROUND: Stiffness is a common reason for suboptimal clinical outcomes after primary total knee arthroplasty (pTKA). There is a lack of consensus regarding its definition, which is often conflated with its histopathologic subcategory—i.e., arthrofibrosis. There is value in refining the definition of acquired idiopathic stiffness in an effort to select for patients with arthrofibrosis. We conducted a systematic review and meta-analysis to establish a consensus definition of acquired idiopathic stiffness, determine its prevalence after pTKA, and identify potential risk factors for its development. METHODS: MEDLINE, Embase, Cochrane Controlled Register of Trials (CENTRAL), and Scopus databases were searched from 2002 to 2017. Studies that included patients with stiffness after pTKA were screened with strict inclusion and exclusion criteria to isolate the subset of patients with acquired idiopathic stiffness unrelated to known extrinsic or surgical causes. Three authors independently assessed study eligibility and risk of bias and collected data. Outcomes of interest were then analyzed according to age, sex, and body mass index (BMI). RESULTS: In the 35 included studies (48,873 pTKAs), the mean patient age was 66 years. In 63% of the studies, stiffness was defined as a range of motion of 5° at 6 to 12 weeks postoperatively. The prevalence of acquired idiopathic stiffness after pTKA was 4%, and this did not differ according to age (4%, I(2) = 95%, among patients 12 weeks after pTKA in patients in the absence of complicating factors including preexisting stiffness. The mean prevalence of acquired idiopathic stiffness after pTKA was 4%; females and obese patients were at increased risk. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Melorheostosis, a rare mesenchymal dysplasia of bone, generally affects about 0.001% of people globally with about 400 cases total being reported. Melorheostosis of the hand, especially in the pediatric population, has been seldom reported. Previous studies have investigated potential genetic mutations associated with melorheostosis however, questions still remain regarding effective treatment options for this disease. This case report describes a unique case of pediatric melorheostosis of the hand and further clarifies current theories on melorheostosis with regards to pathogenesis, best treatment practices, and future research.

Background: Leg-length discrepancy (LLD) is a frequent and recurring issue after total hip arthroplasty (THA). It can lead to discomfort and litigation due to the patient’s perception of this inequality. Purpose: The aim of this study was to evaluate the functional impact of postoperative LLD and length correction in patients after primary THA. We hypothesised that clinical outcomes are inversely correlated to length correction and residual discrepancy. Methods: In a prospective cohort, we included 121 patients undergoing unilateral primary THA. Patients were categorised into 3 groups based on their residual LLD using routine EOS imaging; Shorter (+5 mm). Delta of Correction (DC) was defined as the difference between pre- and postoperative discrepancy measured on EOS imaging. Functional scores (HHS, Postel Merle d’Aubigné, and WOMAC) were measured preoperatively and at last follow-up. The average follow-up was 24 months. We evaluated the clinical and radiographic outcomes regarding the residual LLD and DC. Results: All patients had improvement in their functional scores at last follow-up. There was no difference in clinical outcomes, regardless of preoperative or residual LLD. The highest scores were found in the population with the smallest variations (DC -5 to +5 mm, HHS 96). Conversely, poorer results were found in shortened patients (DC 15 mm, with HHS of 83, p < 0.005. Patient perception of postoperative LLD correlated with the DC ( p = 0.004). Conclusion: The DC measurement is a more effective assessment than arthroplasty.

Introduction Current diagnostic criteria for arthrofibrosis are limited. Since many patients will be aspirated during their clinical course, synovial fluid analysis may supplement current diagnostic criteria for arthrofibrosis. The goal of this study was to determine a unique synovial fluid and inflammatory marker profile for diagnosing arthrofibrosis. Hypothesis Patients with arthrofibrosis following total knee arthroplasty will have a unique synovial fluid aspirate profile compared to control patients to aid in diagnosis. Materials and methods Between 2013 and 2017, 32 patients (32 total knee arthroplasties [TKAs]) underwent revision TKAs for arthrofibrosis. Fourteen patients had pre-revision aspirations. They were 2:1 matched based on age, sex, body mass index (BMI), and year of revision to 28 patients who underwent aseptic revision TKAs for reasons other than arthrofibrosis (control group). Mean age at revision was 66 years, with 64% males. Results In TKAs revised for arthrofibrosis, mean total cell count was 828 cells/uL. These aspirates contained a mean distribution of 46% macrophages (range: 4–76%), 31% lymphocytes (range: 11–68%), 21% neutrophils (range: 0–75%), 1% other cells (mainly synovial cells; range: 0–11%), and 1% eosinophils (range: 0–7%). There was no significant difference in mean total cell count (p = 0.8) or mean distribution of macrophages (p = 0.6), lymphocytes (p = 0.1), neutrophils (p = 0.2), eosinophils (p > 0.9), or serum inflammatory markers (p > 0.7) when compared to controls. All aspirations were culture negative for infection. Discussion The profile of arthrofibrotic synovial fluid aspirates and serum inflammatory marker values were similar to patients revised for non-arthrofibrotic aseptic etiologies. This suggests synovial fluid and serum inflammatory markers in non-infected knees with arthrofibrosis should expect to have characteristics similar to synovial fluid and inflammatory marker profiles in other aseptic diagnoses. Level of evidence III; retrospective case-control study.

Introduction Current diagnostic criteria for arthrofibrosis are limited. Since many patients will be aspirated during their clinical course, synovial fluid analysis may supplement current diagnostic criteria for arthrofibrosis. The goal of this study was to determine a unique synovial fluid and inflammatory marker profile for diagnosing arthrofibrosis. Hypothesis Patients with arthrofibrosis following total knee arthroplasty will have a unique synovial fluid aspirate profile compared to control patients to aid in diagnosis. Materials and methods Between 2013 and 2017, 32 patients (32 total knee arthroplasties [TKAs]) underwent revision TKAs for arthrofibrosis. Fourteen patients had pre-revision aspirations. They were 2:1 matched based on age, sex, body mass index (BMI), and year of revision to 28 patients who underwent aseptic revision TKAs for reasons other than arthrofibrosis (control group). Mean age at revision was 66 years, with 64% males. Results In TKAs revised for arthrofibrosis, mean total cell count was 828 cells/uL. These aspirates contained a mean distribution of 46% macrophages (range, 4–76%), 31% lymphocytes (range, 11–68%), 21% neutrophils (range, 0–75%), 1% other cells (mainly synovial cells; range, 0–11%), and 1% eosinophils (range, 0–7%). There was no significant difference in mean total cell count (p = 0.8) or mean distribution of macrophages (p = 0.6), lymphocytes (p = 0.1), neutrophils (p = 0.2), eosinophils (p > 0.9), or serum inflammatory markers (p > 0.7) when compared to controls. All aspirations were culture negative for infection. Discussion The profile of arthrofibrotic synovial fluid aspirates and serum inflammatory marker values were similar to patients revised for non-arthrofibrotic aseptic etiologies. This suggests synovial fluid and serum inflammatory markers in non-infected knees with arthrofibrosis should expect to have characteristics similar to synovial fluid and inflammatory marker profiles in other aseptic diagnoses. Level of evidence III; Retrospective case-control study.

Aims Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA. Patients and Methods We identified 84 patients (97 THAs) between 1998 and 2015 who had undergone spinal fusion prior to primary THA. Patients were stratified into three groups depending on the length of lumbar fusion and whether or not the sacrum was involved. Mean age was 71 years (40 to 87) and 54 patients (56%) were female. The mean body mass index (BMI) was 30 kg/m2 (19 to 45). Mean follow-up was six years (2 to 17). Patients were 1:2 matched to patients with primary THAs without spine fusion. Hazard ratios (HR) were calculated. Results Dislocation in the fusion group was 5.2% at one year versus 1.7% in controls but this did not reach statistical significance (HR 1.9; p = 0.33). Compared with controls, there was no significant difference in rate of dislocation in patients without a sacral fusion. When the sacrum was involved, the rate of dislocation was significantly higher than in controls (HR 4.5; p = 0.03), with a trend to more dislocations in longer lumbosacral fusions. Patient demographics and surgical characteristics of THA (i.e. surgical approach and femoral head diameter) did not significantly impact risk of dislocation (p > 0.05). Significant radiological differences were measured in mean anterior pelvic tilt between the one-level lumbar fusion group (22°), the multiple-level fusion group (27°), and the sacral fusion group (32°; p < 0.01). Ten-year survival was 93% in the fusion group and 95% in controls (HR 1.2; p = 0.8). Conclusion Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months. Fusions involving the sacrum with multiple levels of lumbar involvement notably increased the risk of postoperative dislocation compared with a control group and other lumbar fusions. Surgeons should take care with component positioning and may consider higher stability implants in this high-risk cohort.

Total hip arthroplasty (THA) alleviates hip pain and improves joint function. Current implant design permits long-term survivorship of THAs, but certain metal-on-metal (MoM) articulations can portend catastrophic failure due to adverse local tissue reactions (ALTR). Here, we identified biological and molecular differences between periacetabular synovial tissues of patients with MoM THA failure undergoing revision THA compared to patients undergoing primary THA for routine osteoarthritis (OA). Analysis of tissue biopsies by RNA-sequencing (RNA-seq) revealed that MoM patient samples exhibit significantly increased expression of immune response genes but decreased expression of genes related to extracellular matrix (ECM) remodeling. Thus, interplay between local tissue inflammation and ECM degradation may account for the pathology and compromised clinical outcomes in select patients with MoM implants. We conclude that adverse responses of host tissues to implant materials result in transcriptomic modifications in patients with MoM implants that permit consideration of strategies that could mitigate ECM damage.

Background Proper component positioning in total hip arthroplasty (THA) is crucial for implant fixation and hip stability. The purpose of this study is to assess if neutral coronal stem alignment (0° ± 3°) improved long-term survivorship in uncemented femoral components. Methods Between 2005 and 2010, 1028 primary THAs were performed with 2 contemporary dual-tapered, proximally coated uncemented stem types. Alignment was measured immediately postoperatively and at most recent follow-up. In total, 978 femoral stems (95%) were within 0° ± 3° of the neutral anatomic coronal axis, and the 50 stems (5%) outside that range were considered outliers (3.1° of valgus to 4.8° of varus). Outcomes analyzed included implant survivorship, Harris Hip Scores, and incidence of dislocation. Mean follow-up was 5 years. Results Survivorship free of aseptic femoral component loosening was 99.3% and 98.2% at 5 and 8 years in the neutral group vs 100% at 5 and 8 years in the outlier group (P = .98). Survivorship free of femoral component revision for any reason was 99.1% and 97.3% at 5 and 8 years vs 100% at 5 and 8 years, respectively (P = .80). Harris Hip Scores were similar (89 in both groups; P = .84) at most recent follow-up. The incidence of mild to moderate thigh pain was also similar in both groups (6.1% vs 6%, P = .85). The incidence of dislocation was 1.5% at 8 years, and similar between both groups (P = .77). Conclusion Slight malalignment of contemporary dual-tapered uncemented THA femoral components does not appear to negatively impact survivorship or clinical outcomes, which is in contrast to cemented femoral components. Level of evidence III Case-control study.

BACKGROUND Periprosthetic joint infection (PJI) of the knee with concurrent disruption of the extensor mechanism is a devastating complication. Historically, knees with such complications have been salvaged with use of an arthrodesis or amputation. The purpose of this study was to assess the survival and functional outcomes of a 2-stage exchange arthroplasty combined with knitted monofilament polypropylene (Marlex; C.R. Bard) mesh reconstruction of the extensor mechanism. METHODS From 2000 to 2015, 16 patients underwent a 2-stage exchange arthroplasty and Marlex-mesh reconstruction for PJI with an extensor mechanism disruption. The study included 9 male patients and 7 female patients with a mean age at the time of reimplantation and mesh reconstruction of 64 years. The mean follow-up was 4 years. PJI was diagnosed on the basis of the Musculoskeletal Infection Society criteria. Clinical outcomes, including survivorship, Knee Society Score (KSS) results, and complications, were assessed. RESULTS Of 16 reconstructions, 13 were in place at the time of the latest follow-up. At 2 years, survivorship free of mesh failure was 86%, survivorship free of PJI was 87%, and survivorship free of PJI or mesh failure was 75%. The mean KSS improved from 48 prior to resection to 74 after mesh reconstruction and reimplantation. The mean extensor lag improved from 31° prior to resection to 3° after mesh reconstruction. Two patients required mesh revision, 1 patient required an above-the-knee amputation for complex wound complications related to reinfection, 1 patient developed a reinfection requiring irrigation and debridement, and 1 patient developed a superficial infection that required debridement. CONCLUSIONS Two-stage exchange arthroplasty combined with Marlex-mesh reconstruction of the extensor mechanism is a viable alternative to knee arthrodesis or amputation. At 2 years, 75% of mesh reconstructions were in place and without evidence of PJI. Moreover, the functional outcomes were improved, with a negligible extensor lag. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Trauma, surgery, and other inflammatory conditions can lead to debilitating joint contractures. Adjunct pharmacologic modalities may permit clinical prevention and treatment of recalcitrant joint contractures. We investigated the therapeutic potential of rosiglitazone by intra-articular delivery via oligo[poly(ethylene glycol)fumarate] (OPF) hydrogels in an established rabbit model of arthrofibrosis. OPF hydrogels loaded with rosiglitazone were characterized for drug elution properties upon soaking in minimum essential media (MEM) with 10% fetal bovine serum and measurements of drug concentrations via High Performance Liquid Chromatography (HPLC). Drug-loaded scaffolds were surgically implanted into 24 skeletally mature female New Zealand White rabbits that were divided into equal groups receiving OPF hydrogels loaded with rosiglitazone (1.67 mg), or vehicle control (10 µl DMSO). After 8 weeks of joint immobilization, rabbits were allowed unrestricted cage activity for 16 weeks. Contracture angles of rabbit limbs treated with rosiglitazone showed statistically significant improvements in flexion compared to control animals (mean angles, respectively, 64.4° vs. 53.3°, p

AimsReconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes.Patients and MethodsA search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction.ResultsA total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing’s sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34).ConclusionBoth the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes. Cite this article: Bone Joint J 2018;100-B(1 Supple A):22–30.

Background Quadriceps snips (QSs) are commonly used to gain enhanced exposure during revision total knee arthroplasties (TKAs). The goals of this study were to evaluate the longer-term clinical outcomes and complications in a contemporary cohort of patients treated with QS and to compare them to a matched cohort treated with standard exposure during revision TKAs. Methods We retrospectively identified 3107 revision TKAs performed at our institution between 2002 and 2012. QS was performed in 321 of these knees. Each QS revision TKA was 1:1 matched to a control (standard exposure) based on age, gender, body mass index, surgery date, and reason for revision. Clinical outcomes studied included Knee Society Score, range of motion, and extensor lag. Other outcomes assessed were complications (especially extensor mechanism disruption) and survivorship. Mean follow-up was 5 years. Results The mean Knee Society Score improvement was not significantly different between groups (P = .9). At latest follow-up, the mean range of motion was 93° in the QS group and was slightly higher at 100° in the control group (P = .002). Postoperative extensor lag of 10 degrees or more was present in 21 (6.7%) QS knees versus 19 (6.8%) control knees (P = .95). Complication rates were similar in both groups with extensor mechanism disruption occurring in 3 in the QS group (0.7% at 10 years) versus 4 in the control group (0.8% at 10 years; P = .91). Kaplan-Meier survivorships free of revision for aseptic loosening, free of any revision, and free of any reoperation were similar at 10 years (85%, 71%, and 61%, respectively, in the QS group vs 89%, 70% and 60%, respectively, in the control group). Conclusion This matched cohort study is the largest to report the results of QS and also the largest to report results compared with patients treated with standard exposure. Building on the results of smaller historical series, this study demonstrates QS was a facile technique in complex revision TKAs allowing for safe exposure with few complications. Level of Evidence III (case-control study).

Background Delayed wound dehiscence (DWD) typically occurs 2 to 7 weeks postoperatively and is characterized by wound gapping and drainage at a surgical site which has initial normal wound healing. This wound problem clinically mimics deep surgical site infection and, after eventual skin healing, leaves a cosmetically unattractive widened, atrophic surgical scar. Methods A single-center, retrospective analysis was completed of 252 knees, over a 13-year period, in 194 patients (average age, 14.9 y) undergoing patellar realignment surgery. All knees in this study were treated through an anterior midline knee incision from mid-patella to the tibial tubercle. At wound closure either a 2-0 polyglactin 910 (Vicryl) group (V) or polydioxane (PDS) group (P) suture was used for subcutaneous reapproximation and then the skin was closed with a 4-0 subcuticular Poliglecaprone 25 and IRGACARE (Monocryl) suture. Wound complications were recorded and analyzed by subcutaneous suture type, severity, size of involvement, duration, and treatment type. Results Of the 252 knees, there were 132 knees in the V group and 120 in the P group. A total of 195 surgeries were primary surgeries and 57 knees were through previous surgical scars. Eleven patients had surgeries in which 1 knee was in each study group. Overall there were 6.1% (8/132) of the V group and 1.7% (2/120) of the P group with DWD (P=0.11); hence there was a trend toward more DWD with Vicryl than PDS, but this did not meet statistical significance. Mean time to resolution of wound dehiscence was 26 days for V group and 46 days for the P group. The length of incision was demonstrated to be a statistically significant independent risk factor for the development of DWD, irrespective of suture type. Conclusions The frequency of DWD in anterior knee incisions in our study population was 6.1% in the polyglactin 910 (Vicryl) group and 1.7% in the polydioxane (PDS) group. Although this analysis did not achieve statistical significance, a 3.5 times decrease in DWD when PDS was used is considered by the authors to be clinically significant. The authors have definitively switched from Vicryl to PDS for the subcutaneous skin closure at the knee in patients aged 20 years and younger in the push to make wound complications a nonevent. Level of evidence Level IV.

Background The management of femoral and tibial shaft fractures has long been among the simplest in orthopaedic trauma. Little data exist on the predictors of complications associated with these fractures. The evolving healthcare system is creating a focus on quality metrics and changing payment models. It is critical that traumatologists develop a better understanding of complication rates associated with these injuries so that they may continue to improve patient care while also reducing overall medical costs. Methods Using the ACS-NSQIP database, we evaluated patient demographics, comorbidities and 30-day complications of femoral and tibial fractures. A bivariate analysis was then used to compare rates of minor and major post-operative complications within 30 days. A multivariate logistic regression was performed, assessing the odds of developing a minor and/or major complication up to 30 days post-surgery. Results 2891 patients were identified. For femoral fractures, intramedullary nailing (IMN) demonstrated an overall complication rate of 14.9% ( n = 151) whereas open reduction and internal fixation (ORIF) with plating showed an overall complication rate of 15.6% ( n = 70). Patients undergoing plating of the femur or tibia were 2 times more likely than the IMN patients to demonstrate postoperative complications. Conclusion Our study is the first to demonstrate that plating of femoral and tibial fractures doubles the odds of developing a complication. As our healthcare system shifts to bundled payment plans, it is impertinent for the orthopaedic surgeon to understand the risk factors associated with fracture treatments in order to assess the best treatment plan.

Background Context: Hybrid spinal implants that combine cobalt-chrome rods with titanium screws have been introduced with the goal of reducing the profile of implants used for lumbar fusion. 4.5mm and 4.75mm cobalt-chrome rods have been reported by the manufacturers as having similar results in biomechanical testing to conventional 5.5mm titanium rods, however little is known about the long-term clinical performance of these implants. This report discusses an interesting radiographic finding routinely encountered in our practice following use of these implants. Purpose: To describe the occurrence of radiographic lucency surrounding pedicle screws following the use of low-profile hybrid spinal implants for instrumented posterior lumbar fusion. Study Design: Case report. Methods: This is an observational case series of 14 patients undergoing lumbar fusion instrumented with hybrid cobalt/chrome – titanium implants. All cases involved instrumented posterior lumbar fusion for the treatment of degenerative spondylolisthesis. Patients were followed for one year with radiographic evaluation of both screw lucency and bony fusion as well as subjective outcomes including visual analog scale (VAS) pain score and Oswestry disability index (ODI). Results: At one year post-operative, all 14 patients had radiographic lucency around at least two pedicle screws in the construct despite radiographic bony fusion. All patients reported subjective improvement in VAS score and ODI, and all patients returned to work within 3 months post-operative. Conclusion: We note a 100% rate of pedicle screw lucency in our series of patients undergoing posterior spinal fusion instrumented with hybrid lowprofile cobalt-chrome implants. Lucency around pedicle screws has been previously associated in the literature with screw loosening, micro motion, and pseudo arthrosis. Despite this observation, the patients in our series subjectively report favorable outcomes. The significance and cause of lucency around pedicle screws with these low-profile implants is unknown, but may be due to decreased construct stiffness related to smaller rod diameter. Long-term experience with these implants is lacking and further studies are warranted.