Substantial Improvement in Self-Reported Mental Health Following Total Hip Arthroplasty Occurs Independent of Anesthetic Technique.

BACKGROUND: The influence of anesthetic type on mental health after total hip arthroplasty (THA) is poorly understood. Adverse effects of general anesthesia (GA) on cognition following major non-cardiac surgery are well known, but mental health following THA is less well-studied. We hypothesized that neuraxial anesthesia (NA) would provide favorable mental health profiles compared with GA after THA. METHODS: Prospectively collected Patient-Reported Outcomes Measurement Information System-10 (PROMIS) Global Mental Health (GMH) scores at preoperative baseline, and 1, 3, and 6 months after THA were accessed on 4,353 patients in the Pulmonary Embolism Prevention After HiP and KneE Replacement (PEPPER) Trial (ClinicalTrials.gov: NCT02810704). Anesthesia was categorized as: general (GA), neuraxial (NA), and neuraxial with peripheral block (NAP). The GMH was assessed longitudinally and compared between groups. RESULTS: Postoperative GMH improved (P < .05) over preoperative in every anesthetic group. Groups receiving NA had higher baseline GMH scores. Improvement in GMH was diminished after GA alone and plateaued after 1 month. Adding NA or peripheral nerve block to GA conferred additional benefit to GMH improvement. CONCLUSIONS: Patient-perceived mental health improves significantly after THA regardless of anesthetic type. Patients who have higher baseline GMH scores more commonly received NA, likely due to nonsurgical care determinants; these differences in mental wellness persisted at follow-up. Adjunctive NA or peripheral nerve block favored GMH improvement, whereas solitary GA diminished GMH improvement, which plateaued after 1 month. Substantial mental health benefits of THA may overshadow subtle differences in GMH attributable to anesthetic type.

Patient-reported outcomes following cemented versus cementless primary total knee arthroplasty: a comparative analysis based on propensity score matching.

BACKGROUND: Existing studies of patient-reported outcomes (PRO) following total knee arthroplasty (TKA) based on fixation methods (cemented vs cementless) are limited to single centers with small sample sizes. Using multicentered data,, we compared baseline and early post-operative global and condition-specific PROs between patients undergoing cemented versus cementless TKA. METHODS: With PROs prospectively collected through Comparative Effectiveness Pulmonary Embolism Prevention After Hip and Knee Replacement (PEPPER) trial (ClinicalTrials.gov: NCT02810704), we examined pre- and post-operative (1, 3, and 6-months) outcomes in 5,961 patients undergoing primary TKA enrolled by 28 medical centers between December 2016 and August 2021. Outcomes included the short-form of the Knee Injury and Osteoarthritis Outcome Score (KOOS-Jr.), the Patient-Reported Outcomes Measurement Information System Physical Health (PROMIS-PH), and the Numeric Pain Rating Scale (NPRS). To minimize selection bias, we performed a 1-to-1 propensity score matched analysis to assess relative pre- to post-operative change in outcomes within and between cemented and cementless TKA groups. RESULTS: With greater than 90% follow-up, significant pre to- post-operative improvements were observed in both groups. At 6 months, the cemented TKA group achieved a 3.3 point (55% of the Minimum Clinically Important Difference) greater improvement in the mean KOOS-Jr. (95%CI: 0.36, 6.30; P = 0.028) than did the cementless group with no significant between-group differences in PROMIS-PH and NPRS. CONCLUSIONS: In a large cohort of primary TKAs, patients with cemented fixation reported early incremental benefit in KOOS-Jr. over those with cementless TKA. Future studies are warranted to capture longer follow-up of PROs.

The Fate of Morbidly Obese Patients With Joint Pain: A Retrospective Study of Patient Outcomes.

BACKGROUND: The number of obese patients seeking a total joint arthroplasty (TJA) continues to increase. Weight loss is often recommended to treat joint pain and reduce risks associated with TJA. We sought to determine the effectiveness of an orthopedic surgeon's recommendation to lose weight. METHODS: We identified morbidly obese (body mass index (BMI) 40-49.9 kg/m2) and super obese (BMI ≥50 kg/m2) patients with hip or knee osteoarthritis. Patients with less than 3-month follow-up were excluded. Patient characteristics (age, gender, BMI, comorbidities), disease characteristics (joint affected, radiographic osteoarthritis grading), and treatments were recorded. Clinically meaningful weight loss was defined as weight loss greater than 5%. RESULTS: Two hundred thirty morbid and 50 super obese patients were identified. Super obese patients were more likely to be referred to weight management (52.0% vs 21.7%, P < .001) and were less likely to receive TJA (20.0% vs 41.7%, P = .004). Each 1 kg/m2 increase in BMI decreased the odds of TJA by 10.9% (odds ratio = 0.891, 95% confidence interval: 0.833-0.953, P = .001). Forty (23.0%) of the nonoperatively treated patients achieved clinically meaningful weight loss, and 19 (17.9%) patients who underwent TJA lost weight before surgery. After surgery, the number of patients who achieved a clinically meaningful weight loss grew to 32 (30.2%). CONCLUSION: In morbid and super obese patients, increasing BMI reduces the likelihood that a patient will receive TJA, and when counseled by their orthopedic surgeon, few patients participate in weight-loss programs or are otherwise able to lose weight. Weight loss is an inconsistently modifiable risk factor for joint replacement surgery.

Patient-Reported Outcomes Following Total Hip Arthroplasty: A Multicenter Comparison Based on Surgical Approaches.

BACKGROUND: Comparisons of patient-reported outcomes (PROs) based on surgical approach for total hip arthroplasty (THA) in the United States are limited to series from single surgeons or institutions. Using prospective data from a large, multicenter study, we compare preoperative to postoperative changes in PROs between posterior, transgluteal, and anterior surgical approaches to THA. METHODS: Patient-reported function, global health, and pain were systematically collected preoperatively and at 1, 3, and 6 months postoperatively from patients undergoing primary THA at 26 sites participating in the Comparative Effectiveness of Pulmonary Embolism Prevention After Hip and Knee Replacement (ClinicalTrials.gov: NCT02810704). Outcomes consisted of the brief Hip disability and Osteoarthritis Outcome Score, the Patient-Reported Outcomes Measurement Information System Physical Health score, and the Numeric Pain Rating Scale. Operative approaches were grouped by surgical plane relative to the abductor musculature as being either anterior, transgluteal, or posterior. RESULTS: Between 12/12/2016 and 08/31/2019, outcomes from 3018 eligible participants were examined. At 1 month, the transgluteal cohort had a 2.2-point lower improvement in Hip disability and Osteoarthritis Outcomes Score (95% confidence interval, 0.40-4.06; P = .017) and a 1.3-point lower improvement in Patient-Reported Outcomes Measurement Information System Physical Health score (95% confidence interval, 0.48-2.04; P = .002) compared to posterior approaches. There was no significant difference in improvement between anterior and posterior approaches. At 3 and 6 months, no clinically significant differences in PRO improvement were observed between groups. CONCLUSION: PROs 6 months following THA dramatically improved regardless of the plane of surgical approach, suggesting that choice of surgical approach can be left to the discretion of surgeons and patients without fear of differential early outcomes.

Optimal Length of Stay Following Total Joint Arthroplasty to Reduce Readmission Rates.

BACKGROUND: Length of stay (LOS) following total joint arthroplasty (TJA) continues to decrease. The effects of this trend on readmission risk and total cost are unclear. We hypothesize that optimal LOS following TJA minimizes index hospitalization, early readmission risk, and total cost. METHODS: Retrospective data from the South Carolina Department of Revenue and Fiscal Affairs was reviewed for patients who underwent primary TJA in South Carolina from 2000 to 2015 (n = 172,760). Data for readmissions within 90 days were included. Severity of illness was estimated by Elixhauser score (EH). Index LOS is defined as the surgery and the subsequent hospital stay. RESULTS: Patients with more significant medical comorbidities (EH ≥ 4) had significantly longer LOS than healthier patients (4.0 vs 3.4 days, P < .001). Independent of EH, readmitted patients had a significantly longer index LOS than those never readmitted (4.3 vs 3.6 days, P < .001). For healthier patients (EH ≤ 3), each additional inpatient day increased readmission risk, while among sicker patients, staying 2 days vs 1 day was protective against readmission risk. Since 2000, the total index cost of TJA has doubled and average cost per inpatient day has tripled, but readmission rates remain essentially unchanged (7.4% to 7.0%). CONCLUSION: Increased LOS was associated with increased readmission risk. Patients with greater medical comorbidities stay longer to protect against readmission. Optimal LOS after TJA is highly influenced by the patient's overall health. Despite a 300% increase in TJA daily cost, readmission rate has changed minimally over the last 15 years.

The Effects of Bundled Payment Programs for Hip and Knee Arthroplasty on Patient-Reported Outcomes.

BACKGROUND: Patient-reported outcomes are essential to demonstrate the value of hip and knee arthroplasty, a common target for payment reforms. We compare patient-reported global and condition-specific outcomes after hip and knee arthroplasty based on hospital participation in Medicare's bundled payment programs. METHODS: We performed a prospective observational study using the Comparative Effectiveness of Pulmonary Embolism Prevention after Hip and Knee Replacement trial. Differences in patient-reported outcomes through 6 months were compared between bundle and nonbundle hospitals using mixed-effects regression, controlling for baseline patient characteristics. Outcomes were the brief Knee Injury and Osteoarthritis Outcomes Score or the brief Hip Disability and Osteoarthritis Outcomes Score, the Patient-Reported Outcomes Measurement Information System Physical Health Score, and the Numeric Pain Rating Scale, measures of joint function, overall health, and pain, respectively. RESULTS: Relative to nonbundled hospitals, arthroplasty patients at bundled hospitals had slightly lower improvement in Knee Injury and Osteoarthritis Outcomes Score (-1.8 point relative difference at 6 months; 95% confidence interval -3.2 to -0.4; P = .011) and Hip Disability and Osteoarthritis Outcomes Score (-2.3 point relative difference at 6 months; 95% confidence interval -4.0 to -0.5; P = .010). However, these effects were small, and the proportions of patients who achieved a minimum clinically important difference were similar. Preoperative to postoperative change in the Patient-Reported Outcomes Measurement Information System Physical Health Score and Numeric Pain Rating Scale demonstrated a similar pattern of slightly worse outcomes at bundled hospitals with similar rates of achieving a minimum clinically important difference. CONCLUSIONS: Patients receiving care at hospitals participating in Medicare's bundled payment programs do not have meaningfully worse improvements in patient-reported measures of function, health, or pain after hip or knee arthroplasty.

Preoperative Smoking Cessation as a Durable Form of Long-Term Smoking Cessation.

Smokers who undergo total joint arthroplasty (TJA) face increased rates of medical and surgical complications that can be reduced by preoperative smoking cessation. We investigated the long-term durability of preoperative smoking cessation among TJA patients. Twenty-seven TJA patients who were identified as having an active history of smoking at the preoperative appointment before TJA consented to telephone survey about their perioperative and current smoking status. Average time from operation to survey was 3.7 years. Of the 27 patients, 21 (77.8%) were identified as having quit smoking prior to surgery. Of these 21 patients, 10 (47.6%) self-reported continued abstinence from smoking at the time of survey. Our cessation rate was significantly lower than reported long-term smoking cessation rates with standard therapies (p < 0.001). Our results suggest that preoperative counseling and a requirement for smoking-cessation prior to elective TJA may have long-term durability that exceeds that of popular reported methods. (Journal of Surgical Orthopaedic Advances 29(2):103-105, 2020).

In vivo model of human post-traumatic heterotopic ossification demonstrates early fibroproliferative signature.

BACKGROUND: The relationship between the tissue injury healing response and development of heterotopic ossification (HO) is poorly understood. Here we compare a rat blast model and human traumatized muscle from a blast injury to study the early signatures of osteogenesis and fibrosis during the formation of HO. METHODS: Rat and human tissues were characterized using histology, scanning electron microscopy, immunohistochemistry, as well as gene and protein expression analysis. Additionally, animals and humans were assessed radiographically for HO formation following injury. RESULTS: Markers of bone formation were dramatically increased in tissue samples from both humans and rats, and both displayed increased fibroproliferative regions within the injured tissues and elevated expression of markers of tissue fibrosis such as TGF-ß1, Fibronectin, SMAD3 and PAI-1. Markers of inflammation and fibrosis (ACTA, TNFα, BMP1 and BMP3) were elevated at the RNA level in both rat and human samples. By day 42, bone formation in the rat blast model appeared similar in radiographs compared to human patients who progressed to develop post-traumatic HO. CONCLUSIONS: Our data demonstrates that a similar early fibrotic response is evident in both the rat blast model and the human tissues following a traumatic injury and demonstrates the relevance of this animal model for future translational studies.

Failure of Indomethacin and Radiation to Prevent Blast-induced Heterotopic Ossification in a Sprague-Dawley Rat Model.

BACKGROUND: Although use of nonsteroidal antiinflammatory drugs and low-dose irradiation has demonstrated efficacy in preventing heterotopic ossification (HO) after THA and surgical treatment of acetabular fractures, these modalities have not been assessed after traumatic blast amputations where HO is a common complication that can arise in the residual limb. QUESTIONS/PURPOSES: The purpose of this study was to investigate the effectiveness of indomethacin and irradiation in preventing HO induced by high-energy blast trauma in a rat model. METHODS: Thirty-six Sprague-Dawley rats underwent hind limb blast amputation with a submerged explosive under water followed by irrigation and primary wound closure. One group (n = 12) received oral indomethacin for 10 days starting on postoperative Day 1. Another group (n = 12) received a single dose of 8 Gy irradiation to the residual limb on postoperative Day 3. A control group (n = 12) did not receive either. Wound healing and clinical course were monitored in all animals until euthanasia at 24 weeks. Serial radiographs were taken immediately postoperatively, at 10 days, and every 4 weeks thereafter to monitor the time course of ectopic bone formation until euthanasia. Five independent graders evaluated the 24-week radiographs to quantitatively assess severity and qualitatively assess the pattern of HO using a modified Potter scale from 0 to 3. Assessment of grading reproducibility yielded a Fleiss statistic of 0.41 and 0.37 for severity and type, respectively. By extrapolation from human clinical trials, a minimum clinically important difference in HO severity was empirically determined to be two full grades or progression of absolute grade to the most severe. RESULTS: We found no differences in mean HO severity scores among the three study groups (indomethacin 0.90 ± 0.46 [95% confidence interval {CI}, 0.60-1.19]; radiation 1.34 ± 0.59 [95% CI, 0.95-1.74]; control 0.95 ± 0.55 [95% CI, 0.60-1.30]; p = 0.100). For qualitative HO type scores, the radiation group had a higher HO type than both indomethacin and controls, but indomethacin was no different than controls (indomethacin 1.08 ± 0.66 [95% CI, 0.67-1.50]; radiation 1.89 ± 0.76 [95% CI, 1.38-2.40]; control 1.10 ± 0.62 [95% CI, 0.70-1.50]; p = 0.013). The lower bound of the 95% CI on mean severity in the indomethacin group and the upper bound of the radiation group barely spanned a full grade and involved only numeric grades < 2, suggesting that even if a small difference in severity could be detected, it would be less than our a priori-defined minimum clinically important difference and any differences that might be present are unlikely to be clinically meaningful. CONCLUSIONS: This work unexpectedly demonstrated that, compared with controls, indomethacin and irradiation provide no effective prophylaxis against HO in the residual limb after high-energy blast amputation in a rat model. Such an observation is contrary to the civilian experience and may be potentially explained by either a different pathogenesis for blast-induced HO or a stimulus that overwhelms conventional regimens used to prevent HO in the civilian population. CLINICAL RELEVANCE: HO in the residual limb after high-energy traumatic blast amputation will likely require novel approaches for prevention and management.

Identification of circulating murine CD34+OCN+ cells.

BACKGROUND AIMS: Previous studies identified a circulating human osteoblastic population that expressed osteocalcin (OCN), increased following fracture and pubertal growth, and formed mineralized colonies in vitro and bone in vivo. A subpopulation expressed CD34, a hematopoietic/endothelial marker. These findings led to our hypothesis that hematopoietic-derived CD34+OCN+ cells exist in the circulation of mice and are modulated after fracture. METHODS: Flow cytometry was used to identify CD34+OCN+ cells in male B6.SJL-PtprcaPepcb/BoyJ and Vav-Cre/mTmG (VavR) mice. Non-stabilized tibial fractures were created by three-point bend. Fractures were longitudinally imaged by micro-computed tomography, and immunofluorescent staining was used to evaluate CD34+OCN+ cells within fracture callus. AMD3100 (10 mg/kg) was injected subcutaneously for 3 days and the CD34+OCN+ population was evaluated by flow cytometry. RESULTS: Circulating CD34+OCN+ cells were identified in mice and confirmed to be of hematopoietic origin (CD45+; Vav1+) using two mouse models. Both circulating and bone marrow-derived CD34+OCN+ cells peaked three weeks post-non-stabilized tibial fracture, suggesting association with cartilage callus transition to bone and early mineralization. Co-expression of CD34 and OCN in the fracture callus at two weeks post-fracture was observed. By three weeks, there was 2.1-fold increase in number of CD34+OCN+ cells, and these were observed throughout the fracture callus. AMD3100 altered CD34+OCN+ cell levels in peripheral blood and bone marrow. DISCUSSION: Together, these data demonstrate a murine CD34+OCN+ circulating population that may be directly involved in fracture repair. Future studies will molecularly characterize CD34+OCN+ cells, determine mechanisms regulating their contribution, and examine if their number correlates with improved fracture healing outcomes.

External Beam Irradiation Preferentially Inhibits the Endochondral Pathway of Fracture Healing: A Rat Model.

BACKGROUND: External beam irradiation is an accepted treatment for skeletal malignancies. Radiation acts on both cancerous and normal cells and, depending on the balance of these effects, may promote or impair bone healing after pathologic fracture. Previous studies suggest an adverse effect of radiation on endochondral ossification, but the existence of differential effects of radiation on the two distinct bone healing pathways is unknown. QUESTIONS/PURPOSES: The purpose of this study was to investigate the differential effects of external beam irradiation on endochondral compared with intramembranous ossification with intramedullary nail and plate fixation of fractures inducing the two respective osseous healing pathways through assessment of (1) bone biology by histomorphometric analysis of cartilage area and micro-CT volumetric assessment of the calcified callus; and (2) mechanical properties of the healing fracture by four-point bending failure analysis of bending stiffness and strength. METHODS: Thirty-six male Sprague-Dawley rats underwent bilateral iatrogenic femur fracture: one side was repaired with an intramedullary nail and the other with compression plating. Three days postoperatively, half (n = 18) received 8-Gray external beam irradiation to each fracture. Rodents were euthanized at 1, 2, and 4 weeks postoperatively (n = 3/group) for quantitative histomorphometry of cartilage area and micro-CT assessment of callus volume. The remaining rodents were euthanized at 3 months (n = 9/group) and subjected to four-point bending tests to assess stiffness and maximum strength. RESULTS: Nailed femurs that were irradiated exhibited a reduction in cartilage area at both 2 weeks (1.08 ± 1.13 mm versus 37.32 ± 19.88 mm; 95% confidence interval [CI] of the difference, 4.32-68.16 mm; p = 0.034) and 4 weeks (4.60 ± 3.97 mm versus 39.10 ± 16.28 mm; 95% CI of the difference, 7.64-61.36 mm; p = 0.023) compared with nonirradiated fractures. There was also a decrease in the volume ratio of calcified callus at 4 weeks (0.35 ± 0.08 versus 0.51 ± 0.05; 95% CI of the difference, 0.01-0.31; p = 0.042) compared with nonirradiated fractures. By contrast, there was no difference in cartilage area or calcified callus between irradiated and nonirradiated plated femurs. The stiffness (128.84 ± 76.60 N/mm versus 26.99 ± 26.07 N/mm; 95% CI of the difference, 44.67-159.03 N/mm; p = 0.012) and maximum strength (41.44 ± 22.06 N versus 23.75 ± 11.00 N; 95% CI of the difference, 0.27-35.11 N; p = 0.047) of irradiated plated femurs was greater than the irradiated nailed femurs. However, for nonirradiated femurs, the maximum strength of nailed fractures (36.05 ± 17.34 N versus 15.63 ± 5.19 N; 95% CI of the difference, 3.96-36.88 N; p = 0.022) was greater than plated fractures, and there was no difference in stiffness between the nailed and plated fractures. CONCLUSIONS: In this model, external beam irradiation was found to preferentially inhibit endochondral over intramembranous ossification with the greatest impairment in healing of radiated fractures repaired with intramedullary nails compared with those fixed with plates. Future work with larger sample sizes might focus on further elucidating the observed differences in mechanical properties. CLINICAL RELEVANCE: This work suggests that there may be a rationale for compression plating rather than intramedullary nailing of long bone fractures in select circumstances where bony union is desirable, adjunctive radiation treatment is required, and bone stock is sufficient for plate and screw fixation.

Process Improvement Project Using Tranexamic Acid Is Cost-Effective in Reducing Blood Loss and Transfusions After Total Hip and Total Knee Arthroplasty.

BACKGROUND: Tranexamic acid (TXA) has been associated with decreased blood loss and transfusion after total hip arthroplasty (THA) and total knee arthroplasty (TKA). The purpose of this study was to examine both transfusion utilization and the economic impact of a Process Improvement Project implementing TXA for THA and TKA. METHODS: After standardization of TXA administration in THA and TKA patients, retrospective data were compared from 12 consecutive months before (group A, n = 336 procedures) and after (group B, n = 436 procedures) project initiation. RESULTS: TXA administration increased with project implementation (group A = 3.57%, group B = 86.01%) and was associated with reductions in perioperative hemoglobin decrement (20.2%), patients transfused (45%), and number of units transfused per patient (61.9%). Cost savings were notable per patient ($128) and annually program wide ($55,884) with the primary THA subgroup contributing the most to the savings. No increase in adverse effects was observed. CONCLUSION: Standardized administration of TXA is an effective and economically favorable blood-reduction strategy for patients undergoing elective THA or TKA. Although reduction in transfusions with TXA may be greater after TKA, the economic and clinical impact of transfusion reduction is more substantial in THA patients.

Complications of Total Hip Arthroplasty: Standardized List, Definitions, and Stratification Developed by The Hip Society.

BACKGROUND: Reporting of complications after total hip arthroplasty (THA) is not standardized, and it is done inconsistently across various studies on the topic. Advantages of standardizing complications include improved patient safety and outcomes and better reporting in comparative studies. QUESTIONS/PURPOSES: The purpose of this project was to develop a standardized list of complications and adverse events associated with THA, develop standardized definitions for each complication, and stratify the complications. A further purpose was to validate these standardized THA complications. METHODS: The Hip Society THA Complications Workgroup proposed a list of THA complications, definitions for each complication, and a stratification scheme for the complications. The stratification system was developed from a previously validated grading system for complications of hip preservation surgery. The proposed complications, definitions, and stratification were validated with an expert opinion survey of members of The Hip Society, a case study evaluation, and analysis of a large administrative hospital system database with a focus on readmissions. RESULTS: One hundred five clinical members (100%) of The Hip Society responded to the THA complications survey. Initially, 21 THA complications were proposed. The validation process reduced the 21 proposed complications to 19 THA complications with definitions and stratification that were endorsed by The Hip Society (bleeding, wound complication, thromboembolic disease, neural deficit, vascular injury, dislocation/instability, periprosthetic fracture, abductor muscle disruption, deep periprosthetic joint infection, heterotopic ossification, bearing surface wear, osteolysis, implant loosening, cup-liner dissociation, implant fracture, reoperation, revision, readmission, death). CONCLUSIONS: Acceptance and use of these standardized, stratified, and validated THA complications and adverse events could advance reporting of outcomes of THA and improve assessment of THA by clinical investigators. LEVEL OF EVIDENCE: Level V, therapeutic study.

Preventing Hospital Readmissions and Limiting the Complications Associated With Total Joint Arthroplasty.

Total joint arthroplasty is a highly successful surgical procedure for patients who have painful arthritic joints. The increasing prevalence of total joint arthroplasty is generating substantial expenditures in the American healthcare system. Healthcare payers, specifically the Centers for Medicare and Medicaid Services, currently target total joint arthroplasty as an area for healthcare cost-savings initiatives, which has resulted in increased scrutiny surrounding orthopaedic care, health resource utilization, and hospital readmissions. Identifying the complications associated with total hip and total knee arthroplasty that result in readmissions will be critically important for predictive modeling and to decrease the number of readmissions after total joint arthroplasty. In addition, improving perioperative optimization, providing seamless episodic care, and intensifying posthospital coordination of care may decrease the number of unnecessary hospital readmissions. Identified modifiable risk factors that substantially contribute to poor clinical outcomes after total joint arthroplasty include morbid obesity; poorly controlled diabetes and nutritional deficiencies; Staphylococcus aureus colonization; tobacco use; venous thromboembolic disease; cardiovascular disease; neurocognitive, psychological, and behavioral problems; and physical deconditioning and fall risk. Both clinical practice and research will be enhanced if defined total joint arthroplasty complications are standardized and stratification schemes are used to identify high-risk patients. Subsequently, clinical intervention will be warranted to address modifiable risk factors before proceeding with total joint arthroplasty.

Does Blast Medium Affect Heterotopic Ossification in a Blast-amputation Model?

BACKGROUND: Heterotopic ossification (HO) develops after nearly 2/3 of traumatic blast amputations in the contemporary battlefield. This phenomenon has potentially devastating consequences for servicemen and women and its pathophysiology warrants further investigation using a previously developed animal blast model. QUESTIONS/PURPOSES: We asked, what is the (1) severity (quantity) and (2) type (location) of HO bone formation after a hindlimb blast amputation with two distinct blast media. We hypothesized that a more "war-relevant" blast medium could be a more accurate model and potentially intensify the development of HO. METHODS: Using a Sprague-Dawley rat model, the pathophysiology of ectopic bone formation in a traumatic hindlimb blast amputation was evaluated. Twenty-four animals underwent blast amputations and closure based on a previously established experimental model. Half the amputations were subjected to blasted sand and the other 1/2 to blasted water. Serial orthogonal radiography was performed on each animal until euthanasia at 24 weeks to track the development of HO. Heterotopic bone severity and type were assessed by three independent graders at each time using a novel grading scale to assess quantity and quality of HO. RESULTS: All animals had radiographic evidence of HO develop. No differences were observed in ectopic bone development between sand and water blasting regarding severity or type at any time. Animals that received water and sand blasting had moderate HO develop at 24 weeks (median, 2.0 and 2.5 weeks, respectively; range, 1-3 weeks; difference of medians, 0.5; p=0.67). At the time of euthanasia, 10 animals that were water blasted had Type 3 HO compared with 11 in the sand-blasted group (p=1.00). CONCLUSIONS: Our study showed a clear development of HO after hindlimb blast amputation in a Sprague-Dawley rat model; however, no difference was observed in HO development based on the type of blast media. This suggests it is the blast mechanism that induces ectopic bone development, regardless of the blasted medium. The grading scale we developed for our animal-model study provided a reliable means of assessing HO severity and type. CLINICAL RELEVANCE: We anticipate that future investigations will elucidate similarities between service members' wartime extremity injuries and the animal model used in our study, and with focused future research this model may have beneficial therapeutic implications as the pathophysiology of HO development is further understood.

How do I get out of this jam? Early postoperative problems of primary total hip arthroplasty.

Acute postoperative problems associated with total hip arthroplasty typically require prompt attention. Because the circumstances surrounding these problems provide limited time for consultation or literature review, effective management depends on the surgeon being aware of treatment options and favored treatment methods and executing the best treatments. Surgeons should be aware of management strategies for the most common and difficult early postoperative complications after primary total hip arthroplasty, including wound problems, periprosthetic femur fractures, nerve dysfunction, and venous thromboembolism. State-of-the-art knowledge will help the treating surgeon successfully manage complications.

How is forearm compliance affected by various circumferential dressings?

BACKGROUND: The forearm is the second most common location for extremity compartment syndrome. Compliance is a physical property that describes a material's ability to expand with an increasing internal volume. The effect of circumferential dressings on extremity pressures has been investigated in various animal models and in some nonphysiologic mechanical models, but the importance of this effect has not been fully investigated in the human upper extremity. In addition, the physical property of compliance has not been reported in the analysis of compartment volume-pressure relationships. QUESTIONS/PURPOSES: We created a physiologic cadaver model for acute compartment syndrome in the human forearm to determine (1) how much volume is required to reach the pressure threshold of 50 mm Hg in forearms, undressed and dressed with various circumferential dressings, (2) differences in forearm compliances that result from dressings, and (3) whether univalving or bivalving of those dressings adequately reduces compartment pressures. METHODS: A sealed inflatable bladder was placed deep in the volar compartment of seven fresh-frozen cadaveric forearms and overlying fascia and skin were closed. Compartment pressures were measured as saline was infused in the bladder, and compliance was calculated from pressure versus volume curves. This was repeated for each specimen using five external wraps, splints, and casts. At a baseline of 50 mm Hg, each dressing then was univalved (and bivalved, when appropriate for the material) and the decrease in compartment pressure was measured. For each of the seven cadaver forearms, one test was performed without dressings and then for each of five dressing conditions. RESULTS: Forearms in fiberglass casts accommodated only a mean of 19 mL (SD, 11 mL; 95% CI, 9-28 mL) before reaching the 50 mm Hg pressure threshold, which was much less than in undressed forearms (mean, 77 mL; SD, 25 mL; 95% CI, 55-98 mL; p < 0.001). Mean compliances were as follows: ACE™ wrap (1.75 mL/mm Hg; SD, 0.41 mL/mm Hg), Webril™ (1.54 mL/mm Hg; SD, 0.56 mL/mm Hg), Kling(®) (1.23 mL/mm Hg; SD, 0.52 mL/mm Hg), sugar tong splint (1.05 mL/mm Hg; SD, 0.52 mL/mm Hg), and fiberglass cast (0.38 mL/mm Hg; SD, 0.27 mL/mm Hg). Univalving of all circumferential wraps dropped the mean compartment pressure from the 50 mm Hg starting point: ACE™ (46%; SD, 14%), Webril™ (52%; SD, 20%), Kling(®) (70%; SD, 18%), sugar tong splint (52%; SD, 19%), and fiberglass cast (58%; SD, 7%), with p less than 0.001 for all dressings. CONCLUSIONS: We observed the compressive effect of various commonly used upper-extremity splints and wraps, finding the least amount of accommodation afforded by fiberglass casts. Univalve release resulted in reduction in forearm compartment pressures, even in fiberglass casts. CLINICAL RELEVANCE: A rigid circumferential dressing can have a dramatic effect on extremity compartment compliance. Contrary to common clinical teaching, univalving of forearm circumferential dressings effectively reduced compartment pressures, as shown in this physiologic model.

Heterotopic bone formation about the hip undergoes endochondral ossification: a rabbit model.

BACKGROUND: Heterotopic ossification (HO) occurs most commonly after trauma and surgery about the hip and may compromise subsequent function. Currently available animal models describing the cellular progression of HO are based on exogenous osteogenic induction agents and may not reflect the processes following trauma. QUESTIONS/PURPOSES: We therefore sought to characterize the histologic progression of heterotopic bone formation in an animal model that recapitulates the human condition without the addition of exogenous osteogenic material. METHODS: We used a rabbit model that included intramedullary instrumentation of the upper femur and ischemic crush injury of the gluteal muscle. Bilateral surgical induction procedures were performed on 30 animals with the intention of inciting the process of HO; no supplemental osteogenic stimulants were used. Three animals were sacrificed at each of 10 predetermined times between 1 day and 26 weeks postoperatively and the progression of tissue maturation was graded histologically using a five-item scale. RESULTS: Heterotopic bone reliably formed de novo and consistently followed a pathway of endochondral ossification. Chondroid elements were found in juxtaposition with immature woven bone in all sections that contained mature osseous elements. CONCLUSIONS: These results establish that HO occurs in an animal model mimicking the human condition following surgical trauma about the hip; it is predictable in its histologic progression and follows a pathway of endochondral bone formation. CLINICAL RELEVANCE: By showing a consistent pathway of endochondral ossification leading to ectopic bone formation, this study provides a basis for understanding the mechanisms by which HO might be mitigated by interventions.

Special topics.

Concerning the past decade of war, three special topics were examined at the Extremity War Injuries VII Symposium. These topics included the implementation of tourniquets and their effect on decreasing mortality and the possibility of transitioning the lessons gained to the civilian sector. In addition, the training of surgeons for war as well as residents in a wartime environment was reviewed.