The performance of artificial intelligence chatbot large language models to address skeletal biology and bone health queries.

Artificial intelligence (AI) chatbots utilizing large language models (LLMs) have recently garnered significant interest due to their ability to generate humanlike responses to user inquiries in an interactive dialog format. While these models are being increasingly utilized to obtain medical information by patients, scientific and medical providers, and trainees to address biomedical questions, their performance may vary from field to field. The opportunities and risks these chatbots pose to the widespread understanding of skeletal health and science are unknown. Here we assess the performance of 3 high-profile LLM chatbots, Chat Generative Pre-Trained Transformer (ChatGPT) 4.0, BingAI, and Bard, to address 30 questions in 3 categories: basic and translational skeletal biology, clinical practitioner management of skeletal disorders, and patient queries to assess the accuracy and quality of the responses. Thirty questions in each of these categories were posed, and responses were independently graded for their degree of accuracy by four reviewers. While each of the chatbots was often able to provide relevant information about skeletal disorders, the quality and relevance of these responses varied widely, and ChatGPT 4.0 had the highest overall median score in each of the categories. Each of these chatbots displayed distinct limitations that included inconsistent, incomplete, or irrelevant responses, inappropriate utilization of lay sources in a professional context, a failure to take patient demographics or clinical context into account when providing recommendations, and an inability to consistently identify areas of uncertainty in the relevant literature. Careful consideration of both the opportunities and risks of current AI chatbots is needed to formulate guidelines for best practices for their use as source of information about skeletal health and biology.

Artificial intelligence chatbots are increasingly used as a source of information in health care and research settings due to their accessibility and ability to summarize complex topics using conversational language. However, it is still unclear whether they can provide accurate information for questions related to the medicine and biology of the skeleton. Here, we tested the performance of three prominent chatbots­ChatGPT, Bard, and BingAI­by tasking them with a series of prompts based on well-established skeletal biology concepts, realistic physician­patient scenarios, and potential patient questions. Despite their similarities in function, differences in the accuracy of responses were observed across the three different chatbot services. While in some contexts, chatbots performed well, and in other cases, strong limitations were observed, including inconsistent consideration of clinical context and patient demographics, occasionally providing incorrect or out-of-date information, and citation of inappropriate sources. With careful consideration of their current weaknesses, artificial intelligence chatbots offer the potential to transform education on skeletal health and science.

Chat Generative Pretraining Transformer Answers Patient-focused Questions in Cervical Spine Surgery.

STUDY DESIGN: Review of Chat Generative Pretraining Transformer (ChatGPT) outputs to select patient-focused questions. OBJECTIVE: We aimed to examine the quality of ChatGPT responses to cervical spine questions. BACKGROUND: Artificial intelligence and its utilization to improve patient experience across medicine is seeing remarkable growth. One such usage is patient education. For the first time on a large scale, patients can ask targeted questions and receive similarly targeted answers. Although patients may use these resources to assist in decision-making, there still exists little data regarding their accuracy, especially within orthopedic surgery and more specifically spine surgery. METHODS: We compiled 9 frequently asked questions cervical spine surgeons receive in the clinic to test ChatGPT's version 3.5 ability to answer a nuanced topic. Responses were reviewed by 2 independent reviewers on a Likert Scale for the accuracy of information presented (0-5 points), appropriateness in giving a specific answer (0-3 points), and readability for a layperson (0-2 points). Readability was assessed through the Flesh-Kincaid grade level analysis for the original prompt and for a second prompt asking for rephrasing at the sixth-grade reading level. RESULTS: On average, ChatGPT's responses scored a 7.1/10. Accuracy was rated on average a 4.1/5. Appropriateness was 1.8/3. Readability was a 1.2/2. Readability was determined to be at the 13.5 grade level originally and at the 11.2 grade level after prompting. CONCLUSIONS: ChatGPT has the capacity to be a powerful means for patients to gain important and specific information regarding their pathologies and surgical options. These responses are limited in their accuracy, and we, in addition, noted readability is not optimal for the average patient. Despite these limitations in ChatGPT's capability to answer these nuanced questions, the technology is impressive, and surgeons should be aware patients will likely increasingly rely on it.

Capacity for large language model chatbots to aid in orthopedic management, research, and patient queries.

Large language model (LLM) chatbots possess a remarkable capacity to synthesize complex information into concise, digestible summaries across a wide range of orthopedic subject matter. As LLM chatbots become widely available they will serve as a powerful, accessible resource that patients, clinicians, and researchers may reference to obtain information about orthopedic science and clinical management. Here, we examined the performance of three well-known and easily accessible chatbots-ChatGPT, Bard, and Bing AI-in responding to inquiries relating to clinical management and orthopedic concepts. Although all three chatbots were found to be capable of generating relevant responses, ChatGPT outperformed Bard and BingAI in each category due to its ability to provide accurate and complete responses to orthopedic queries. Despite their promising applications in clinical management, shortcomings observed included incomplete responses, lack of context, and outdated information. Nonetheless, the ability for these LLM chatbots to address these inquires has largely yet to be evaluated and will be critical for understanding the risks and opportunities of LLM chatbots in orthopedics.

A multi-stem cell basis for craniosynostosis and calvarial mineralization.

Craniosynostosis is a group of disorders of premature calvarial suture fusion. The identity of the calvarial stem cells (CSCs) that produce fusion-driving osteoblasts in craniosynostosis remains poorly understood. Here we show that both physiologic calvarial mineralization and pathologic calvarial fusion in craniosynostosis reflect the interaction of two separate stem cell lineages; a previously identified cathepsin K (CTSK) lineage CSC1 (CTSK+ CSC) and a separate discoidin domain-containing receptor 2 (DDR2) lineage stem cell (DDR2+ CSC) that we identified in this study. Deletion of Twist1, a gene associated with craniosynostosis in humans2,3, solely in CTSK+ CSCs is sufficient to drive craniosynostosis in mice, but the sites that are destined to fuse exhibit an unexpected depletion of CTSK+ CSCs and a corresponding expansion of DDR2+ CSCs, with DDR2+ CSC expansion being a direct maladaptive response to CTSK+ CSC depletion. DDR2+ CSCs display full stemness features, and our results establish the presence of two distinct stem cell lineages in the sutures, with both populations contributing to physiologic calvarial mineralization. DDR2+ CSCs mediate a distinct form of endochondral ossification without the typical haematopoietic marrow formation. Implantation of DDR2+ CSCs into suture sites is sufficient to induce fusion, and this phenotype was prevented by co-transplantation of CTSK+ CSCs. Finally, the human counterparts of DDR2+ CSCs and CTSK+ CSCs display conserved functional properties in xenograft assays. The interaction between these two stem cell populations provides a new biologic interface for the modulation of calvarial mineralization and suture patency.

Characterization and Potential Relevance of Randomized Controlled Trial Patient Populations in Total Joint Arthroplasty in the United States: A Systematic Review.

BACKGROUND: A substantial number of randomized controlled trial (RCT) studies in total joint arthroplasty (TJA) are published each year in the United States (US). However, it is unknown how closely the demographic and clinical characteristics of these cohorts resemble that of the US patient population undergoing TJA. Thus, the purpose of this systematic review was to evaluate the patient characteristics of published RCTs in TJA in the US and to compare these characteristics against patient cohorts from national patient databases. METHODS: RCT studies regarding primary TJA conducted in the US were selected. Key patient demographics were aggregated and compared against demographics characteristics of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality National Inpatient Sample (NIS) and American College of Surgeons National Surgical Quality Improvement Program patient cohorts. RESULTS: One hundred and fifty-three RCTs fulfilled the inclusion criteria and were included. The total number of patients in the 153 RCTs was 24,135 patients. The average age of patients in the TJA RCT cohort was 65 years (53-80) while the NIS cohort was 67 years (18-90) (d = 0.21, effect size = small). The average body mass index of the TJA RCT cohort was 30.8 (18.2-37.6) while the National Surgical Quality Improvement Program cohort was 31.9 (14.1-59.6) (d = 0.18, effect size = small). For TJA, effect sizes for age, body mass index BMI, sex, ethnicity, smoking, and diabetes were all small or very small. CONCLUSION: Overall, the US RCT patient cohort for TJA does not differ substantially from the general patient population undergoing TJA in the United States. Differences in demographic and clinical characteristics between the TJA RCT cohort and database cohorts ranged from minimal to small, suggesting that these differences are unlikely to impact clinical outcomes.

Intermittent parathyroid hormone increases stability and improves osseointegration of initially unstable implants.

AIMS: To develop an early implant instability murine model and explore the use of intermittent parathyroid hormone (iPTH) treatment for initially unstable implants. METHODS: 3D-printed titanium implants were inserted into an oversized drill-hole in the tibiae of C57Bl/6 mice (n = 54). After implantation, the mice were randomly divided into three treatment groups (phosphate buffered saline (PBS)-control, iPTH, and delayed iPTH). Radiological analysis, micro-CT (µCT), and biomechanical pull-out testing were performed to assess implant loosening, bone formation, and osseointegration. Peri-implant tissue formation and cellular composition were evaluated by histology. RESULTS: iPTH reduced radiological signs of loosening and led to an increase in peri-implant bone formation over the course of four weeks (timepoints: one week, two weeks, and four weeks). Observational histological analysis shows that iPTH prohibits the progression of fibrosis. Delaying iPTH treatment until after onset of peri-implant fibrosis still resulted in enhanced osseointegration and implant stability. Despite initial instability, iPTH increased the mean pull-out strength of the implant from 8.41 N (SD 8.15) in the PBS-control group to 21.49 N (SD 10.45) and 23.68 N (SD 8.99) in the immediate and delayed iPTH groups, respectively. Immediate and delayed iPTH increased mean peri-implant bone volume fraction (BV/TV) to 0.46 (SD 0.07) and 0.34 (SD 0.10), respectively, compared to PBS-control mean BV/TV of 0.23 (SD 0.03) (PBS-control vs immediate iPTH, p < 0.001; PBS-control vs delayed iPTH, p = 0.048; immediate iPTH vs delayed iPTH, p = 0.111). CONCLUSION: iPTH treatment mediated successful osseointegration and increased bone mechanical strength, despite initial implant instability. Clinically, this suggests that initially unstable implants may be osseointegrated with iPTH treatment. Cite this article: Bone Joint Res 2022;11(5):260-269.

A Subset of Osteosarcoma Bears Markers of CXCL12-Abundant Reticular Cells.

Currently, the cell of origin for osteosarcoma or other primary skeletal tumors is largely unknown. Recent reports identifying specific cell types comprising bone now newly enable investigation of this topic. Specifically, CXC motif chemokine 12 (CXCL12)-abundant reticular (CAR) cells are a specific skeletal stromal cell type that orchestrate the bone marrow microenvironment through cross-talk with hematopoietic and endothelial cells and a likely candidate cell of origin for at least a subset of primary skeletal tumors. Here, we analyze osteosarcomas via immunohistochemistry for known markers of CAR cells such as leptin receptor (LEPR), B-cell factor 3 (EBF3), CXCL12, and platelet-derived growth factor receptor alpha (PDGFRA). A large proportion of high-grade tumors expressed LEPR, PDGFRA, and EBF3 but not CXCL12. These data raise the hypothesis that CAR cells are the cell of origin of this osteoblastic osteosarcoma subset, a finding with implications for the cellular oncogenesis of primary osteosarcoma and the development of effective targeted therapies. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Immune Response to Persistent Staphyloccocus Aureus Periprosthetic Joint Infection in a Mouse Tibial Implant Model.

Staphyloccocus aureus is one of the major pathogens in orthopedic periprosthetic joint infection (PJI), a devastating complication of total joint arthroplasty that often results in chronic and persistent infections that are refractory to antibiotics and require surgical interventions. Biofilm formation has been extensively investigated as a reason for persistent infection. The cellular composition, activation status, cytokine profile, and role of the immune response during persistent S. aureus PJI are incompletely understood. In this study, we used histology, multiparametric flow cytometry, and gene expression analysis to characterize the immune response in a clinically relevant orthopedic PJI model. We tested the hypothesis that persistent S. aureus infection induces feedback mechanisms that suppress immune cell activation, thereby affecting the course of infection. Surprisingly, persistent infection was characterized by strikingly high cytokine gene expression indicative of robust activation of multiple components of innate and adaptive immunity, along with ongoing severe neutrophil-dominated inflammation, in infected joint and bone tissues. Activation and expansion of draining lymph nodes and a bone marrow stress granulopoiesis reaction were also maintained during late phase infection. In parallel, feedback mechanisms involving T-cell inhibitory receptors and exhaustion markers, suppressive cytokines, and regulatory T cells were activated and associated with decreased T-cell proliferation and tissue infiltration during the persistent phase of infection. These results identify the cellular and molecular components of the mouse immune response to persistent S. aureus PJI and indicate that neutrophil infiltration, inflammatory cytokine responses, and ongoing lymph node and bone marrow reactions are insufficient to clear infection and that immune effector mechanisms are suppressed by feedback inhibitory pathways. These immune-suppressive mechanisms are associated with diminished T-cell proliferation and tissue infiltration and can be targeted as part of adjuvant immunotherapeutic strategies in combination with debridement of biofilm, antibiotics, and other therapeutic modalities to promote eradication of infection. © 2021 American Society for Bone and Mineral Research (ASBMR).

Inhibition of PAD4 mediated neutrophil extracellular traps prevents fibrotic osseointegration failure in a tibial implant murine model : an animal study.

AIMS: Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system's response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Pad4-/- mice that display defects in peptidyl arginine deiminase 4 (PAD4), an essential protein required for NETs) or resolution (via DNase 1 treatment, an enzyme that degrades the cytotoxic DNA matrix) of NETs can prevent osseointegration failure and formation of peri-implant fibrotic tissue. METHODS: Patient peri-implant fibrotic tissue was analyzed for NETs biomarkers. To enhance osseointegration in loose implant conditions, an innate immune system pathway (NETs) was either inhibited (Pad4-/- mice) or resolved with a pharmacological agent (DNase 1) in a murine model of osseointegration failure. RESULTS: NETs biomarkers were identified in peri-implant fibrotic tissue collected from aseptic loosening patients and at the bone-implant interface in a murine model of osseointegration failure. Inhibition (Pad4-/- ) or resolution (DNase 1) of NETs improved osseointegration and reduced fibrotic tissue despite loose implant conditions in mice. CONCLUSION: This study identifies a biological target (NETs) for potential noninvasive treatments of aseptic loosening by discovering a novel connection between the innate immune system and post-injury bone remodelling caused by implant loosening. By inhibiting or resolving NETs in an osseointegration failure murine model, fibrotic tissue encapsulation around an implant is reduced and osseointegration is enhanced, despite loose implant conditions. Cite this article: Bone Joint J 2021;103-B(7 Supple B):135-144.

Tmem100- and Acta2-Lineage Cells Contribute to Implant Osseointegration in a Mouse Model.

Metal implants are commonly used in orthopedic surgery. The mechanical stability and longevity of implants depend on adequate bone deposition along the implant surface. The cellular and molecular mechanisms underlying peri-implant bone formation (ie, osseointegration) are incompletely understood. Herein, our goal was to determine the specific bone marrow stromal cell populations that contribute to bone formation around metal implants. To do this, we utilized a mouse tibial implant model that is clinically representative of human joint replacement procedures. Using a lineage-tracing approach, we found that both Acta2.creERT2 and Tmem100.creERT2 lineage cells are involved in peri-implant bone formation, and Pdgfra- and Ly6a/Sca1-expressing stromal cells (PαS cells) are highly enriched in both lineages. Single-cell RNA-seq analysis indicated that PαS cells are quiescent in uninjured bone tissue; however, they express markers of proliferation and osteogenic differentiation shortly after implantation surgery. Our findings indicate that PαS cells are mobilized to repair bone tissue and participate in implant osseointegration after surgery. Biologic therapies targeting PαS cells might improve osseointegration in patients undergoing orthopedic procedures. © 2021 American Society for Bone and Mineral Research (ASBMR).

Alendronate enhances osseointegration in a murine implant model.

Administration of bisphosphonates following total joint arthroplasty might be beneficial to reduce aseptic loosening. However, their effects on peri-implant bone formation and bone-implant interface strength have not been investigated yet. We used a physiologically loaded mouse implant model to investigate the short-term effects of postoperative systemic alendronate on osseointegration. A titanium implant with a rough surface was inserted in the proximal tibiae of 17-week-old female C57BL/6 mice (n = 44). Postimplantation mice were given alendronate (73 µg/kg/days, n = 22) or vehicle (n = 22) 5 days/week. At 7- and 14-day postimplantation, histology and histomorphometry were conducted. At 28 days, microcomputed tomography and biomechanical testing were performed (n = 10/group). Postoperative alendronate treatment enhanced osseointegration, increasing maximum pullout load by 45% (p < .001) from 19.1 ± 4.5 N in the control mice to 27.6 ± 4.9 N in the treated mice, at day 28 postimplantation. Alendronate treatment increased the bone volume fraction by 139% (p < .001) in the region distal to the implant and 60% (p < .05) in the peri-implant region. At 14-day postimplantation, alendronate treatment decreased the number of osteoclasts per bone perimeter (p < .05) and increased bone volume fraction (p < .01) when compared with the control group. Postimplantation, short-term alendronate treatment enhanced osseointegration as demonstrated by increased bone mass, trabecular bone thickness, and maximum pullout load. Alendronate decreased peri-implant osteoclasts while preserving peri-implant osteoblasts and endothelial cells, in turn, increasing bone volume fraction. This data supports the postoperative clinical use of bisphosphonates, especially in patients with high risks of aseptic loosening.

2020 John Charnley Award: The antimicrobial potential of bacteriophage-derived lysin in a murine debridement, antibiotics, and implant retention model of prosthetic joint infection.

AIMS: Current treatments of prosthetic joint infection (PJI) are minimally effective against Staphylococcus aureus biofilm. A murine PJI model of debridement, antibiotics, and implant retention (DAIR) was used to test the hypothesis that PlySs2, a bacteriophage-derived lysin, can target S. aureus biofilm and address the unique challenges presented in this periprosthetic environment. METHODS: The ability of PlySs2 and vancomycin to kill biofilm and colony-forming units (CFUs) on orthopaedic implants were compared using in vitro models. An in vivo murine PJI model of DAIR was used to assess the efficacy of a combination of PlySs2 and vancomycin on periprosthetic bacterial load. RESULTS: PlySs2 treatment reduced 99% more CFUs and 75% more biofilm compared with vancomycin in vitro. A combination of PlySs2 and vancomycin in vivo reduced the number of CFUs on the surface of implants by 92% and in the periprosthetic tissue by 88%. CONCLUSION: PlySs2 lysin was able to reduce biofilm, target planktonic bacteria, and work synergistically with vancomycin in our in vitro models. A combination of PlySs2 and vancomycin also reduced bacterial load in periprosthetic tissue and on the surface of implants in a murine model of DAIR treatment for established PJI. Cite this article: Bone Joint J 2020;102-B(7 Supple B):3-10.

Does a Competing Risk Analysis Show Differences in the Cumulative Incidence of Revision Surgery Between Patients with Oncologic and Non-oncologic Conditions After Distal Femur Replacement?

BACKGROUND: Distal femur replacement is frequently used for limb salvage after bone tumor resections. It is also used in patients with severe bone loss because of traumatic conditions or revision TKA. Some studies on distal femur replacement reported on revision-free survival without distinguishing between patients with oncologic diagnoses and those without, although these patients might be incomparable because of their differences in important patient- and disease-specific characteristics. This may lead to an inaccurate and undifferentiated interpretation of the results of survival analyses. QUESTIONS/PURPOSES: (1) What is the overall cumulative incidence of revision surgery after cemented and cementless distal femoral replacement, as determined with a competing risk analysis? (2) Does the cumulative incidence of revision surgery change over time? (3) Are there differences in the cumulative incidence of revision surgery between patients with oncologic conditions and those without who are treated with cemented or cementless distal femoral replacement? METHODS: A total of 403 patients were possible candidates for distal femoral replacement. Of these, 56 patients elected to undergo different procedures, 83 were excluded because an expendable growing prosthesis was implanted, and 28 were lost to follow-up. Therefore, 229 patients who underwent distal femoral replacement for oncologic or non-oncologic reasons between 1983 and 2016 were retrospectively included in this study. The type of fixation method (cemented or cementless) was obtained from the patients' medical records, operation reports, and radiographic analyses from plain radiographs. All radiographs were standardized and obtained at standard time intervals in our institution. No algorithm regarding the fixation approach was followed. According to our data, patients receiving cementless fixation were younger and therefore likely to be more active than those receiving cemented fixation. The median follow-up duration of the overall cohort was 85 months (range 0.1-391 months). Patients who died or had revision surgery before the 2-year minimum follow-up interval were adequately considered using competing risk calculation. The reasons for revision surgery were classified using the classification system proposed by the International Society for Limb Salvage. A competing risk analysis was performed to estimate the cumulative incidence function of revision, accounting for death as a competing event. To evaluate the influence of potential prognostic factors, including diagnosis (oncologic versus non-oncologic), fixation (cemented versus cementless), year of distal femoral replacement, age, and sex on the occurrence of revision surgery, univariate and multivariable Fine and Gray models were applied. RESULTS: The competing risks analysis revealed cumulative incidences of revision surgery for any cause (Types 1 to 5) of 26% (95% CI, 20.3%-31.9%) at 12 months, 37.9% (95% CI, 31.3%-44.4%) at 24 months, 52.6% (95% CI, 45.1%-59.5%) at 5 years, and 58.2% (95% CI, 50.1%-65.4%) at 10 years for all patients. Rotating hinge-type prostheses showed a lower cumulative incidence of revision surgery (41.6%; 95% CI, 31.8%-51%) than fixed-hinge prostheses did (64%; 95% CI, 50.5%-74.5% ) at 5 years (Gray's test: p = 0.01). According to the multivariate Fine and Gray model, the year of surgery did not have any effect on the risk of revision surgery (1994 to 2003: hazard ratio 0.70; 95% CI, 0.46-1.07); 2004 to 2016: HR 0.83; 95% CI, 0.52-1.34; p = 0.26). The multivariate analysis, adjusted for disease, sex, age, cementation, and year of surgery, revealed a difference in the risk of revision surgery between patients with oncologic disease and those with non-oncologic disease (HR 0.44 for oncologic versus non-oncologic; 95% CI, 0.22-0.87; p = 0.02) and a reduction in the risk of overall revision with cemented fixation in patients with oncologic disease (HR 0.53; 95% CI, 0.29-0.98; p = 0.03). CONCLUSION: This study indicates that even with newer implants, there was a high incidence of revision surgery after distal femoral replacement. According to our analysis, patients with oncologic diagnoses have a lower likelihood of revision when the stem is cemented whereas the type of fixation did not impact patients with non-oncologic diagnoses. Because of differences in patient demographics (age, etiology of disease, and use of chemotherapy) and outcomes of fixation, oncologic and non-oncologic patients should be analyzed separately in survival studies about distal femoral replacement. LEVEL OF EVIDENCE: Level III, therapeutic study.

Vancomycin-laden calcium phosphate-calcium sulfate composite allows bone formation in a rat infection model.

OBJECTIVE: Local antibiotic delivery systems with differing chemical and mechanical properties have been developed to assist in the management of osteomyelitis. We investigated the bone conductive and resorptive capabilities of a calcium phosphate-calcium sulfate (CaP/CaS) composite compared with commercially available polymethylmethacrylate (PMMA). In addition, we compared the in vivo preventative and treatment efficacies of both biomaterials in a proven osteomyelitis model. METHODS: Sixty-four, male Sprague-Dawley rats were inoculated with 10 µl of 1.5 x 108 CFU/ml of Staphylococcus aureus in a surgically drilled defect in the right proximal tibia. Infected animals were randomly allocated into prevention and treatment groups with 32 rats each. In the prevention group, the defect was filled with a plug containing either PMMA or CaP/CaS immediately after the inoculation. In the treatment group, the infected defects were irrigated, debrided, and filled with either a PMMA or CaP/CaS plug. Both CaP/CaS and PMMA were impregnated with 10% weight of vancomycin. Rats were sacrificed 6 weeks after cement insertion. Infection was detected by bacterial culture and histological analysis. Bone formation in the defect was assessed with micro-computed tomography and histology. RESULTS: No bacteria were detected in any group. Both the prevention and treatment groups using CaP/CaS had significantly more bone volume fraction, bone area, and cartilage area than the PMMA groups. CONCLUSIONS: When loaded with 10% of vancomycin, CaP/CaS and PMMA have the same efficacy for treatment and prevention of osteomyelitis. CaP/CaS enhances bone defect healing through improved bone remodeling in our osteomyelitis rat model.

Femoral Derotation Osteotomy in Adults for Version Abnormalities.

BACKGROUND: Version abnormalities of the femur can cause pain and hip joint damage due to impingement or instability. A retrospective clinical review was conducted on patients undergoing a subtrochanteric derotation osteotomy for either excessive anteversion or retroversion of the femur. METHODS: A total of 55 derotation osteotomies were performed in 43 patients: 36 females and 7 males. The average age was 29 years (range, 14 to 59 years). The osteotomies were performed closed with an intramedullary saw. Fixation was performed with a variety of intramedullary nails. Twenty-nine percent of patients had a retroversion deformity (average, -9° of retroversion; range, +2° to -23°) and 71% had excessive anteversion of the femur (average, +37° of anteversion; range, +22° to +53°). The etiology was posttraumatic in 5 patients (12%), diplegic cerebral palsy in 2 patients (5%), Prader-Willi syndrome in 1 patient (2%), and idiopathic in 35 patients (81%). Forty-nine percent underwent concomitant surgery with the index femoral derotation osteotomy, including hip arthroscopy in 40%, tibial derotation osteotomy in 13%, and a periacetabular osteotomy in 5%. Tibial osteotomies were performed to correct a compensatory excessive external tibial torsion that would be exacerbated in the correction of excessive femoral anteversion. RESULTS: No patient was lost to follow-up. Failures occurred in three hips in three patients (5%): two hip arthroplasties and one nonunion that healed after rerodding. There was one late infection treated successfully with implant removal and antibiotics with an excellent final clinical outcome. At an average follow-up of 6.5 years (range, 2 to 19.7 years), the modified Harris Hip Score improved by 29 points in the remaining 52 cases (P < 0.001, Wilcoxon signed-rank test). The results were rated as excellent in 75%, good in 23%, and fair in 2%. Subsequent surgery was required in 78% of hips, 91% of which were implant removals. CONCLUSIONS: A closed, subtrochanteric derotation osteotomy of the femur is a safe and effective procedure to treat either femoral retroversion or excessive anteversion. Excellent or good results were obtained in 93%, despite the need for subsequent implant removal in more than two-thirds of the patients.