The incidence of deep venous thrombosis after arthroscopically assisted anterior cruciate ligament reconstruction

Independent Risk Factors Associated With Venous Thromboembolism After Knee Arthroscopy: A Retrospective Study of 222 Patients

Background

A serious complication after knee arthroscopy is venous thromboembolism (VTE), which includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). However, asymptomatic VTE is frequently undetected.

Purpose

To (1) report the incidence of VTE after knee arthroscopy using ultrasound examination and computed tomography pulmonary angiography (CTPA) and (2) discover the independent risk factors of VTE after knee arthroscopy and determine the corresponding cutoff values of these indicators.

Study Design

Case-control study; Level of evidence, 3.

Methods

Included were 222 patients (115 male) who underwent arthroscopic knee procedures between October 2022 and January 2023. Baseline characteristics, blood test results, and VTE assessments were collected. During the 2-week follow-up, routine lower extremity vascular ultrasound was applied for DVT measurement, with CTPA evaluation for suspected PE. Patients were allocated into VTE and no-VTE groups, and descriptive statistics were used to analyze baseline data. Logistic regression analysis was used to determine the correlation between binary variables and the presence of postoperative VTE. Multivariate logistic regression analysis was further performed to determine the independent risk factors of VTE.

Results

Of the 222 patients, 37 (16.7%) had DVT and 1 (0.5%) had both DVT and PE. Compared to the no-VTE group, the VTE group was significantly older, with more female patients; higher body mass index (BMI) and postoperative D-dimer level; and higher rates of hypertension, hyperlipidemia, varicose veins of the lower extremity, and abnormal postoperative fibrin degradation product level (P≤ .043 for all). Notably, operative time >20 minutes was not significantly associated with postoperative VTE (P = .513). The independent risk factors for VTE included age >32 years (odds ratio [OR], 20.71 [95% CI, 4.40-97.47]; P < .001), BMI >23 kg/m2 (OR, 3.52 [95% CI, 1.11-11.14]; P = .032), hyperlipidemia (OR, 6.81 [95% CI, 1.86-24.88]; P = .004), and postoperative D-dimer level >0.63 mg/L (OR, 34.01 [95% CI, 7.36-157.07]; P < .001).

Conclusion

The incidence of VTE after knee arthroscopy was 16.7% at the 2-week follow-up. Age >32 years, BMI >23 kg/m2, hyperlipidemia, and postoperative D-dimer >0.63 mg/L were independent risk factors of postoperative VTE within 2 weeks after knee arthroscopy. For patients with knee arthroscopy, the cutoff value of postoperative D-dimer for VTE was found to be 0.63 mg/L for timely intervention.

Factors associated with perioperative deep vein thrombosis in arthroscopic anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) is reportedly associated with a higher incidence of deep vein thrombosis (DVT) incidence than other arthroscopic surgical procedures. The aim of this study is to retrospectively investigate the incidence and type of DVT and evaluate the relationship between DVT and risk factors among all patients who underwent ACLR under uniform conditions consisting of mechanical prophylaxis, no medical prophylaxis, and preoperative and postoperative lower extremity venous ultrasonography.

METHODS

Of the 114 patients who underwent arthroscopic primary ACLR at our hospital who did not have a compound ligament injury or revision surgery, 112 patients were included. Two patients were not examined. DVT evaluation consisted of whole-leg ultrasonography at 1 week after surgery. We evaluated age, sex, body mass index, comorbidities, operative time, tourniquet time, presence of concurrent surgery (meniscus repair/resection or osteochondral column grafting), and non-weight-bearing status at 1 week after surgery as risk factors for DVT.

RESULTS

DVT was found in 33 (29.5%) of 112 patients. Of these, 22 (19.6%) had distal DVT and 11 (9.8%) had proximal DVT. Non-weight-bearing status at 1 week after surgery was a statistically significant risk factor for proximal DVT (P = .034).

CONCLUSIONS

Non-weight-bearing status is an independent risk factor for DVT, suggesting that early weight bearing may reduce the occurrence of DVT.

The Effect of Lower Limb Position on Anterior Cruciate Ligament Reconstruction on Uncommon Complications after Surgery

Background

To reduce the complications of orthopedic surgery, the desire for less invasive procedures, such as, knee arthroscopy to repair the anterior cruciate ligament, has increased. There are, currently, two common positions for limbs that are used during surgery depending on the surgeon's experience. Therefore, our aim was to investigate the effect of limb position on complications after anterior cruciate ligament reconstruction surgery.

Materials and Methods

From April 2016 to July 2020 at our orthopedic-sports trauma center, 688 patients between the ages of 18 and 50 with anterior cruciate ligament rupture underwent reconstruction surgery with a hamstring graft. Patients were divided into two groups in terms of limb position at the time of surgery. For three months, patients were evaluated for surgical complications, basic demographic information, and information during surgery.

Results

There was no statistically significant difference between the two groups in terms of demographic information, side of injury, preparation time, tourniquet time, operation time, and duration of hospitalization. At quarterly follow-up, there was no significant difference between the two groups in terms of postoperative complications (P = 0.976).

Conclusions

There is no difference between compartment syndrome and deep vein thrombosis in different situations, therefore, the surgeon should operate in any position he is skilled in. Also, surgeons should always pay special attention to these complications and provide necessary training to patients in order to prevent them.

Postoperative D-dimer levels predict venous thromboembolisms detected with contrast-enhanced computerized tomography in patients undergoing anterior cruciate ligament reconstruction

BACKGROUND

In the literature, factors associated with postoperative venous thromboembolisms (VTEs) after anterior cruciate ligament reconstruction (ACLR) are limited. This study aimed to investigate the incidence of venous thromboembolisms (VTEs) after anterior cruciate ligament reconstruction (ACLR) and to identify risk and predictive factors for VTEs.

METHODS

This retrospective study included 136 patients who underwent arthroscopic ACLR with mechanical prophylaxis between April 2012 and July 2022. Contrast-enhanced computed tomography (CT) was applied to detect VTEs comprising deep venous thromboses and pulmonary embolisms 7 days after surgery. Data including age, sex, body mass index, concomitant treatments, graft types, smoking status, operative and tourniquet times, postoperative D-dimer levels, and other laboratory test results, were collected for analyses. The incidence of radiographically confirmed VTEs and the associated risk factors, such as age, sex, body mass index, concomitant treatments, graft types, smoking status, operative and tourniquet times, postoperative D-dimer levels, and other laboratory test results, were analyzed.

RESULTS

The overall incidence of radiographic VTEs was 11.0% (15 cases) in 136 patients. There was one symptomatic patient who had Homan's sign. Multivariable analysis indicated that postoperative D-dimer level was an independent factor related to a radiographic VTE after ACLR, although there was no association between radiographic VTEs and preoperative status or operation status. The optimal cutoff value for postoperative D-dimer level was 2.8 μg/ml according to the receiver operating characteristic curve analysis, with a sensitivity of 80.0% and specificity of 83.5%.

CONCLUSION

The incidence of ACLR-associated radiographical VTEs (deep venous thrombosis and pulmonary embolism) under mechanical prophylaxis was 11.0% in this study. An elevated D-dimer level at 7 days after surgery is an independent predictor of VTE in patients undergoing ACLR. The postoperative D-dimer level is a more reliable marker for identifying VTE in patients who underwent ACLR.

Anterior cruciate ligament tear increases the risk of venous thromboembolism: a population-based cohort study

PURPOSE

Previous studies highlighted an increased risk of venous thromboembolism (VTE) among patients with anterior cruciate ligament reconstruction (ACLR); however, the risk for those with ACL tear but without undergoing ACLR has not been reported yet. The aim of this study was to evaluate the risk of VTE among ACL tear individuals with or without ACLR derived from the general population.

METHODS

A cohort study was conducted using data from the IQVIA Medical Research Database of the United Kingdom. Up to five non-ACL tear individuals (n = 22,235) were matched to each case of ACL tear (n = 4474) by age, sex, body mass index and entry-time. The relation of ACL tear to VTE [pulmonary embolism (PE) and deep vein thrombosis (DVT)] was examined using a multivariable Cox proportional hazard model. A sub-cohort analysis, in which the ACL tear individuals were stratified into those with ACLR and those without ACLR, was also conducted.

RESULTS

VTE developed in 13 individuals with ACL tear and nine individuals without ACL tear (incidence rates: 3.1 vs. 0.4/1000 person-years), with multivariable-adjusted hazard ratio (HR) being 6.59 (95% CI 2.28-19.08) in 1-year follow-up. For ACL tear individuals with ACLR, the HR was 11.44 (95% CI 2.71-48.28), and for those without ACLR, the HR was 6.02 (95% CI 1.44-24.25), compared with individuals without ACL tear.

CONCLUSION

This large-sample population-based cohort study provides the first evidence on an increased risk of VTE in ACL tear individuals regardless of subsequent ACLR, which supports the necessity for monitoring venous-thromboembolic complications in the target population, including those without ACLR.

LEVEL OF EVIDENCE

III.

Incidence and risk factors for symptomatic venous thromboembolism following anterior cruciate ligament reconstruction

PURPOSE

To determine the incidence of symptomatic venous thromboembolism (VTE) following anterior cruciate ligament (ACL) reconstruction using a large national database and to identify corresponding independent risk factors.

METHODS

The Humana administrative claims database was reviewed for patients undergoing ACL reconstruction from 2007 to 2017. Patient demographics, medical comorbidities, as well as concurrent procedures were recorded. Postoperative incidence of VTE was measured by identifying symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE) at 30 days, 90 days, and 1 year postoperatively. Univariate analysis and binary logistic regression were performed to determine independent risk factors for VTE following surgery.

RESULTS

A total of 11,977 patients were included in the study. The incidence of VTE was 1.01% (n = 120) and 1.22% (n = 146) at 30 and 90 days, respectively. Analysis of VTE events within the first postoperative year revealed that 69.6% and 84.3% of VTEs occurred within 30 and 90 days of surgery, respectively. Logistic regression identified age ≥ 45 (odds ratio [OR] = 1.88; 95% confidence interval [CI] 1.32-2.68; p < 0.001), inpatient surgery (OR = 2.07; 95% CI 1.01-4.24; p = 0.045), COPD (OR = 1.51; 95% CI 1.02-2.24; p = 0.041), and tobacco use (OR = 1.75; 95% CI 1.17-2.62; p = 0.007), as well as concurrent PCL reconstruction (OR = 3.85; 95% CI 1.71-8.67; p = 0.001), meniscal transplant (OR = 17.68; 95% CI 3.63-85.97; p < 0.001) or osteochondral allograft (OR = 15.73; 95% CI 1.79-138.43; p = 0.013) as independent risk factors for VTE after ACL reconstruction.

CONCLUSIONS

The incidence of symptomatic postoperative VTE is low following ACL reconstruction, with the majority of cases occurring within 90 days of surgery. Risk factors include age ≥ 45, inpatient surgery, COPD, tobacco use and concurrent PCL reconstruction, meniscal transplant or osteochondral allograft.

LEVEL OF EVIDENCE

III.

Does anterior cruciate ligament reconstruction increase venous thromboembolism risk compared with knee meniscectomy under arthroscopy?

Background

This study compared the incidence of postoperative venous thromboembolism (VTE) between meniscectomy and anterior cruciate ligament reconstruction (ACLR) under arthroscopy and assessed whether ACLR increases the VTE risk compared with meniscectomy.

Methods

A retrospective study of prospectively collected clinical data, including data on 436 patients ranging in age from 18 to 60 years who underwent ACLR or meniscectomy surgery, was performed between October 2018 and October 2019 in our hospital. All patients underwent routine VTE screening by venous ultrasonography in postoperative week 2 and then clinical follow-up at 4 and 6 weeks post-surgery. The incidence of VTE was calculated, and clinical factors such as age, sex, body mass index (BMI), smoking, concomitant procedure, Caprini score, and duration of tourniquet use were evaluated in relation to the risk factors for VTE.

Results

A total of 320 patients who underwent arthroscopic ACLR or meniscectomy were available for analysis. Of these patients, 130 (40.6%) underwent ACLR, and 190 (59.4%) underwent meniscectomy. No cases of pulmonary embolism (PE) or femoral deep vein thrombosis (DVT) were reported in either group. Fourteen patients (10.8%) developed VTE in the ACLR group compared with 10 (5.3%) in the meniscectomy group, with no significant difference (p = 0.066). Among these patients, 4 (3.1%) patients in the ACL reconstruction group and 2 (1.1%) patients in the meniscectomy group had DVT confirmed by Doppler ultrasound (p > 0.05). ACLR, age, and BMI (OR = 3.129; 1.061; 1.435) tended to increase the risk of VTE, but the results were not statistically significant (p = 0.056, 0.059, 0.054).

Conclusions

The incidence of VTE after ACLR and meniscectomy within 6 weeks post-surgery was 10.8 and 5.3%, respectively. ACLR, age, and BMI had a tendency to increase the risk of VTE.

Clinical Study of Neuromuscular Electrical Stimulation in the Prevention of Deep Venous Thrombosis of Lower Extremities after Anterior Cruciate Ligament Reconstruction

This paper is written to observe the clinical effects of "neuromuscular electrical stimulation in the prevention of deep venous thrombosis of lower extremities after anterior cruciate ligament reconstruction" in our department. Data from March 2018 to March 2021 was selected including 187 males and 91 females. They were randomly divided into experimental groups and control groups. The experimental group adopted DVT general prevention + basic physical prevention + NMES and the control group adopted DVT general prevention + basic physical prevention. The VAS score, the content of blood D-dimer, the circumference of the affected knee, and results of DVT color ultrasound screening were studied in each group on the first day before operation and the fourth day after the operation. Results obtained showed that there were no significant differences in the baseline characteristics of the two groups of patients, such as gender composition, age, and so on (P > 0.05). The VAS scores, blood D-dimer content, and knee circumference of each group on the day before and on the fourth day after surgery were observed. Diameter and DVT color Doppler ultrasound screening results were superior to the control group in the test group and the difference was statistically significant (P < 0.05). It was concluded that NMES can effectively reduce the pain, knee swelling, and incidence of DVT in patients after ACL reconstruction. It is a simple and effective intervention therapy to prevent the occurrence of DVT.

Use of Batroxobin in Central and Peripheral Ischemic Vascular Diseases: A Systematic Review

Background and Purpose: The mechanism of action of Batroxobin included the decomposition of the fibrinogen to fibrin degradation products (FDPs) and D-dimer and mobilization of endothelial cells to release endogenous nt-PA and to promote thrombolysis. This review aims to summarize current study findings about batroxobin on correcting cerebral arterial, venous, and peripheral vascular diseases, to explore the mechanism of batroxobin on anti-thrombosis process.

Methods: A thorough literature search was conducted utilizing the PubMed Central (PMC) and EMBASE databases to identify studies up to June 2021. Data from clinical studies and animal experiments about batroxobin were extracted, integrated and analyzed based on Cochrane handbook for systematic reviews of interventions approach and the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P), including the condition of subjects, the usage and dosage, research observation index and main findings.

Results: A total of 62 studies were enrolled in this systematic review, including 26 clinical studies and 36 animal experiments. The 26 clinical studies involved 873 patients with arterial ischemic events, 92 cases with cerebral venous thrombosis, 13 cases with cerebral cortical vein thrombosis, and 1,049 cases with peripheral vascular diseases. These patients included 452 males and 392 females aged 65.6 ± 5.53 years. The results revealed that batroxobin had broad effects, including improving clinical prognosis (n = 12), preventing thrombosis (n = 7), promoting thrombolysis (n = 6), and improving vascular cognitive dysfunction (n = 1). The effects of batroxobin on reducing neuronal apoptosis (n = 8),relieving cellular edema (n = 4), improving spatial memory (n = 3), and promoting thrombolysis (n = 13) were concluded in animal experiments. The predominant mechanisms explored in animal experiments involved promoting depolymerization of fibrinogen polymers (n = 6), regulating the expression of related molecules (n = 9); such as intercellular adhesion molecule, heat shock proteins, tumor necrosis factor), reducing oxidative stress (n = 5), and reducing inflammation response (n = 4).

Conclusion: Batroxobin can correct both arterial and venous ischemic diseases by promoting depolymerization of fibrinogen polymers, regulating the expression of related molecules, reducing oxidative stress, and reducing the inflammation response.

Not Using a Tourniquet May Reduce the Incidence of Asymptomatic Deep Venous Thrombosis After ACL Reconstruction: An Observational Study

Background

Deep venous thrombosis (DVT) and pulmonary embolism are serious potential complications after anterior cruciate ligament reconstruction (ACLR). Little is known about the influence of tourniquet use on the incidence of DVT after ACLR.

Purpose

To compare the incidence of DVT after ACLR with and without the use of a tourniquet.

Study Design

Cohort study; Level of evidence, 3.

Methods

Between November 2018 and May 2020, a total of 60 consecutive ACLRs in 60 patients, including 7 revision surgeries, were performed without tourniquet use at our hospital and were enrolled in this study (T- group). In addition, 55 consecutive ACLRs in 55 patients, including 10 revision surgeries, were performed with tourniquet use between April 2017 and September 2018 and were enrolled as the control group (T+ group). DVT was diagnosed using ultrasonography of both legs performed preoperatively and at postoperative week 1. The incidence of postoperative DVT was compared between the T- and T+ groups. Logistic regression analysis was performed to evaluate the effect of older age (≥40 vs <40 years) and tourniquet use on the occurrence of DVT.

Results

No DVTs were detected preoperatively. The incidence of postoperative DVT was significantly lower in the T- group compared with the T+ group (1 patient [1.7%] vs 9 patients [16.4%]; P = .005). All patients with DVT were asymptomatic. Although the mean operative time was not significantly different (80.8 minutes in the T+ group vs 78.5 minutes in the T- group; P = .461), the mean blood loss from the drain was significantly lower in the T- group than in the T+ group (149.9 vs 201.9 mL; P < .001). Age ≥40 years and tourniquet use were significantly related to the occurrence of DVT (odds ratio, 8.3 [95% CI, 1.9-36.8]; P = .005; and odds ratio, 8.8 [95% CI, 1.0-75.3]; P = .047, respectively).

Conclusion

ACLRs performed without tourniquet resulted in a significantly lower incidence of DVT after ACLR and significantly less bleeding from drains. If adequate visibility of the surgical field is obtained, ACLR without tourniquet use may reduce the incidence of DVT.

Postoperative thromboprophylaxis does not reduce the incidence of thromboembolic events after ACL reconstruction

INTRODUCTION

Anterior cruciate ligament (ACL) reconstructive surgery is one of the most common ligament-related surgeries performed in France. The French Society of Anesthesia & Intensive Care Medicine (SFAR) recommends the systematic use of low-molecular weight heparin postoperatively to prevent venous thromboembolisms (VTE). However, these recommendations differ from one country to another; several national societies do not recommend them. To specify the benefits of such a treatment, we did a retrospective case-control study to evaluate the incidence of symptomatic VTE after ACL reconstruction. Hypothesis We hypothesized that the rate of symptomatic VTE would be the same, whether a course of postoperative anticoagulants is prescribed or not.

METHODS

This was a retrospective, multicenter, multi-surgeon study. Of the four participating surgeons, two never prescribed thromboprophylaxis after surgery while the other two always prescribed a 10-day course of low-molecular weight heparin. All patients who underwent primary ACL reconstruction using an autologous graft between the 1st of January 2019 and the 15th of February 2020 were included. The 535 patients who had undergone ACL reconstruction were divided into two groups: (Group 1) 279 patients in the group without anticoagulants; 96% received a four-strand semi-tendinosus graft (ST4) and 4% received a quadriceps tendon (QT) graft; the mean age of these patients was 30 years (14-58); 41% of them were women and 22% of them were smokers; the mean body mass index was 24.4 (18-37); the mean tourniquet time was 37minutes. (Group 2) 256 patients in the group with anticoagulants; 81% received a semi-tendinosus/gracilis graft, 15% received a ST4 and 4% a QT; the mean age of these patients was 29 years (14-60); 38% of them were women and 21% of them were smokers; the mean body mass index was 25.0 (18-38); the mean tourniquet time was 34minutes. The two groups were comparable in all respects except for the type of graft used. All patients were contacted at a minimum interval of 3 months after their surgery, by telephone. Doppler ultrasonography was done solely when a VTE was suspected.

RESULTS

In the group without anticoagulants, 249 of 279 patients were contacted, while in the group with anticoagulants, 221 of 256 were contacted. The two groups were comparable in terms of age, gender ratio, tourniquet time, body mass index and proportion of smokers. Two cases of deep vein thrombosis (all in the calf region) were found in each group with no associated pulmonary embolism. There was no difference between groups in the VTE rate.

DISCUSSION

Our hypothesis was confirmed since the incidence of symptomatic VTE was the same whether postoperative anticoagulants were prescribed or not. The incidence of symptomatic VTE after ACL reconstruction was identical whether thromboprophylaxis was used or not. This casts doubt on the need for postoperative thromboprophylaxis, especially in younger patients who do not have risk factors, and brings into question whether the recommendations in France should be changed.

LEVEL OF EVIDENCE

III (retrospective case-control study).

The incidence and risk factor of deep venous thrombosis after arthroscopically assisted anterior cruciate ligament reconstruction

PURPOSE

To retrospectively analyze the incidence and risk factors of deep venous thrombosis (DVT) detected by ultrasonography after arthroscopically assisted Anterior Cruciate Ligament Reconstruction (ACLR).

METHODS

We retrospectively reviewed medical records of arthroscopically assisted ACLR surgery performed at our institution between 2012 and 2015. Revision ACLR, bone patella tendon bone (BTB) graft reconstruction, and concomitant multiple ligament reconstructions were excluded. We performed a standardized double-bundle reconstruction procedure using hamstrings graft for ACLR. All patients routinely received DVT screening by using venous ultrasonography on postoperative day 7 from 2012 to 2013, and postoperative days 7 and 14 from 2014 to 2015. The prevalence of DVT was calculated and clinical factors such as age, gender, Body Mass Index (BMI), operative time, and duration of tourniquet application were evaluated in relation to the risk factor of DVT.

RESULTS

Two hundred and fifty-six patients (129 men and 127 women) with a mean age of 28.9 were enrolled. Sixteen patients (6.6%) were detected with DVT on postoperative day 7. Among 146 patients who received venous ultrasonography on both postoperative days 7 and 14, DVT were detected in five additional patients on postoperative day 14. In a total of 21 patients who were diagnosed with DVT, two were proximal, the remaining 19 were distal, and no patient had progressed to pulmonary embolism (PE). In terms of predisposing factors for developing DVT on postoperative day 7, only age ≥30 showed a statistically significant higher risk of DVT (P = 0.03).

CONCLUSION

Incidence of DVT after ACLR detected by ultrasonography on postoperative day 7 was 6.6%. Patients aged ≥30 years have a potentially higher risk for developing DVT. Great care for DVT should be taken if prolonged immobilization is applied after ACLR surgery.

LEVEL OF EVIDENCE

Level Ⅳ.

Incidence of Deep Venous Thrombosis Associated With Proximal Hamstring Rupture

Background:

Rates of deep venous thrombosis (DVT) have been studied for most common orthopaedic injuries. However, rates and risk factors have not been published for proximal hamstring injuries.

Purpose:

To determine the incidence of symptomatic DVT associated with proximal hamstring rupture and associations with prophylactic anticoagulation.

Study Design:

Case series; Level of evidence, 4.

Methods:

Inclusion criteria included all complete and, in a separate cohort, partial proximal hamstring ruptures treated by the senior author from 2007 through 2018 with at least 8 weeks of follow-up. Tendinopathy without tear was excluded. No DVT screening was performed. Charts of patients with symptomatic DVT were reviewed for the treatment method, the presence of imaging-confirmed DVT or pulmonary embolism, and risk factors for DVT. No patients received postinjury DVT prophylaxis. Surgical patients were routinely instructed to take aspirin (325 mg bid) or apixaban (2.5 mg bid) for 4 weeks. Patients with risk factors for DVT received enoxaparin (40 mg daily) for 2 weeks followed by aspirin (325 mg bid) for 2 weeks.

Results:

A total of 144 complete proximal hamstring ruptures were included: 132 treated operatively and 12 treated nonoperatively. There were 10 DVTs associated with the injury, for an overall rate of 6.9%. Five of the DVTs were diagnosed preoperatively in patients who had not received DVT prophylaxis; the other 5 were diagnosed postoperatively in patients on DVT prophylaxis. Six of the 10 DVTs had identifiable risk factors. All patients with postoperatively diagnosed DVTs were on prophylactic aspirin or enoxaparin. In the partial proximal hamstring rupture cohort of 114 ruptures, there were no DVTs.

Conclusion:

There is a high incidence of DVT associated with complete proximal hamstring ruptures (6.9%) despite many patients receiving DVT prophylaxis. This is substantially higher than that in other lower extremity injuries. Clinicians should have a high index of suspicion for DVT after these injuries, and postinjury DVT prophylaxis may be warranted.

The Importance of a Standardized Screening Tool to Identify Thromboembolic Risk Factors in Pediatric Lower Extremity Arthroscopy Patients

INTRODUCTION

Deep vein thrombosis and pulmonary embolism are major complications that can occur in common orthopaedic procedures such as knee arthroscopy. The purpose of this study is to determine the incidence of venous thromboembolism (VTE) risk factors in adolescent patients undergoing elective lower extremity arthroscopy. A second objective is to determine whether a targeted, standardized screening tool is both cost- and clinically effective in the identification of VTE risk factors in adolescents.

METHODS

A standardized VTE screening tool was prospectively administered to all elective arthroscopic procedures in a pediatric sports medicine practice. A comparison cohort that did not complete the screening tool was isolated through a retrospective chart review identifying VTE risk factors. The incidence and cost between the two cohorts were compared.

RESULTS

Of 332 subjects who did not receive a targeted screening (TS) tool, 103 risk factors were noted. One pulmonary embolism case was identified with a total incidence of 0.15% over 3 years. With TS, we identified 325 subjects with 134 identifiable risk factors. Six patients (1.8%) were noted to be very high risk, requiring consultation with hematology. No VTEs were reported. When compared with the retrospective review, TS identified 30% more risk factors. A significant increase in the identification of family history of blood clots (P < 0.001), history of previous blood clot (P = 0.059), recurrent miscarriages in the family (P = 0.010), and smoking exposure (P = 0.062) was found. Additionally, the total cost of screening was less than the cost of prophylaxis treatment with no screening ($20.98 versus $23.51 per person, respectively).

DISCUSSION

Risk factors for VTE may be present in 32.5% of elective adolescent arthroscopic patients. A TS model for VTE identified 30% more risk factors, especially a significant family history, and was shown to be a cost-effective way to safely implement a VTE prevention program.

LEVEL OF EVIDENCE

Level II.

Deep venous thrombosis and pulmonary embolism after anterior cruciate ligament reconstruction: incidence, outcome, and risk factors

AIMS

The aim of this study was to investigate the incidence, risk factors, and outcome of venous thromboembolism (VTE) following anterior cruciate ligament (ACL) reconstruction in a nationwide cohort.

PATIENTS AND METHODS

All ACL reconstructions, primary and revision, that were recorded in the Swedish Knee Ligament Register (SKLR) between 2006 and 2013 were linked with data from the Swedish National Board of Health and Welfare. The incidence of VTE was determined by entries between the day of surgery until 90 days postoperatively based on diagnosis codes and the prescription of anticoagulants. Risk factors, outcome, and the use of thromboprophylaxis were analyzed. Descriptive statistics with multivariate analysis were used to describe the findings.

RESULTS

The cohort consisted of 26 014 primary and revision ACL reconstructions. There were 89 deep venous thromboses (DVTs) and 12 pulmonary emboli (PEs) with a total of 95 VTEs (0.4 %). Six patients with a PE had a simultaneous DVT. The only independent risk factor for VTE was age greater than or equal to 40 years (odds ratio 2.31, 95% confidence interval 1.45 to 3.70; p < 0.001). Thromboprophylaxis was prescribed to 9461 patients (36%) and was equally distributed between those with and those without a VTE (37.9% vs 36.4%). All patient-reported outcome measures (PROMs) one and two years postoperatively were significantly lower in those with VTE.

CONCLUSION

The incidence of VTE following ACL reconstruction is 0.4%, and the only significant risk factor is age. Patients with VTE had worse postoperative clinical outcome than patients without VTE. We recommend against the routine use of thromboprophylaxis, but it should be considered in older patients.

Characteristics, treatment patterns and outcomes of patients presenting with venous thromboembolic events after knee arthroscopy in the RIETE Registry

Knee arthroscopy is the most common orthopedic procedure worldwide. While incidence of post-arthroscopy venous thromboembolic events (VTE) is low, treatment patterns and patient outcomes have not been described. Patients from the "Registro Informatizado Enfermedad TromboEmbolica" who had confirmed post-arthroscopy VTE were compared to patients with provoked, post bone-fracture, and to patients with unprovoked VTE. Baseline characteristics, presenting signs and symptoms, treatment and outcomes including recurrent VTE, bleeds or death were compared. A total of 101 patients with post-arthroscopy VTE and 19,218 patients with unprovoked VTE were identified. Post-arthroscopy patients were younger (49.5 vs. 66 years, P < 0.0001) and had less history of VTE [5.9% vs. 20%, OR 0.26 (0.11-0.59)]. Among patients with isolated DVT, there were fewer proximal DVT in the post-arthroscopy group [40% vs. 86%, OR 0.11 (0.06-0.19)]. Treatment duration was shorter in the post-arthroscopy group (174 ± 140 vs. 311 ± 340 days, P < 0.0001) and more often with DOAC [OR 3.67 (1.95-6.89)]. Recurrent VTE occurred in 6.18 (1.96-14.9) and 11.9 (11.0-12.8) per 100 patient years [HR 0.52 (0.16-1.26)] after treatment in the post-arthroscopy and unprovoked groups, respectively. Recurrent VTE occurred in 5.17 (1.31-14.1) per 100 patient years in a separate post bone-fracture group (n = 147), also not statistically different than the post-arthroscopy recurrence rate. After anticoagulation cessation, some patients post-knee arthroscopy develop VTE. While our small sample size precludes drawing firm conclusions, this signal should warrant further research into the optimal treatment duration for these patients, as some patients may be at increased risk for long-term recurrence.

Risk Factors for Deep Vein Thrombosis or Pulmonary Embolus Following Anterior Cruciate Ligament Reconstruction

Background:

Nearly 350,000 Americans develop a deep venous thromboembolism (DVT) or pulmonary embolism (PE) annually, and nearly 100,000 Americans die from these events. To date, little research has investigated patient-specific risk factors that increase the rate of DVT/PE following anterior cruciate ligament reconstruction (ACLR).

Purpose:

To determine relevant patient risk factors for the development of DVT/PE following ACLR.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

All instances of ACLR from 2005 to 2014 within the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) prospective database were analyzed. Both univariate analysis and binary logistic regression were performed to determine which patient demographics and surgical factors were associated with DVT or PE following surgery.

Results:

Of the 9146 patients who underwent ACLR, 46 (0.5%) developed postoperative DVT, 8 (0.1%) developed PE, and 5 (0.05%) developed both. The following variables were associated with the development of DVT or PE on univariate analysis: increased age, a high tibial osteotomy (HTO) performed at the time of ACLR, microfracture performed, the presence of hypertension requiring medical therapy, and the presence of an active wound infection. Independent predictors of DVT or PE on multivariate analysis included HTO (odds ratio [OR], 22.7), the presence of an active wound infection (OR, 11.0), or hypertension requiring medication (OR, 2.2). Meniscal repair was not a risk factor for DVT or PE on univariate or multivariate analysis.

Conclusion:

In a review of 9146 patients undergoing ACLR, 46 (0.5%) developed DVT in the 30-day postoperative period. Increasing age over 30 years, concomitant HTO or microfracture, hypertension requiring medication, and presence of wound infection were all associated with an increased risk of DVT. The annual incidence of DVT/PE following ACLR reconstruction is low (<1%) and has not changed over time.

Incidence and risk factors of deep venous thrombosis following arthroscopic posterior cruciate ligament reconstruction

The objective of this study was to identify the incidence and associated risk factors for deep venous thrombosis (DVT) after arthroscopic posterior cruciate ligament (PCL) reconstruction.This study included 128 patients who underwent arthroscopic PCL reconstruction. Venography was performed on the operated leg 3 days postoperatively. The patients were divided into 2 groups based on whether they had DVT. A correlation analysis was performed to determine the factors associated with DVT.Of all the 128 patients, 28 patients (21.9%) developed DVT, with 4 (3.1%) in a proximal location. Significant differences were found in the mean age, time of application of tourniquet, mean VAS scores, mean D-dimer level, mean cholesterol level, and various surgical procedures in patients with DVT compared with those without DVT. DVT is difficult to diagnose solely based on clinical symptoms.The incidence of DVT was 21.9% in patients who underwent arthroscopic PCL reconstruction. The rate of asymptomatic clots in the calf region was rather high after PCL reconstruction, and the rate of proximal clots was 4%. Older age, longer durations of tourniquet application, higher VAS scores and D-dimer levels, and complex surgical procedures were all substantial risk factors for DVT after PCL reconstruction. The treatment of DVT with batroxobin and anticoagulants was effective and safe.

Thromboembolic Events After Arthroscopic Knee Surgery: Increased Risk at High Elevation

PURPOSE

To evaluate the incidence of thromboembolic events in patients undergoing arthroscopic surgery of the knee in centers located at elevations near sea level and compare those rates with the patients undergoing the same operations in centers at high elevation.

METHODS

A retrospective review was conducted using a database of a major health care system with surgery centers located throughout the United States. More than 115 centers located in 15 different states were analyzed for any reported thromboembolic events including deep vein thromboses and pulmonary embolism (PE) in patients who had undergone knee arthroscopy over a 2-year period. The centers located at elevations lower than 1,000 ft were considered sea level centers. Centers located at elevations above 4,000 ft were considered high-elevation centers. Centers located between 1,000 ft and 4,000 ft elevation were excluded.

RESULTS

A total of 35,877 patients underwent a knee arthroscopy at a low-elevation center and 10,181 patients underwent a knee arthroscopy at a high-elevation center between 2011 and 2012. During that same time period, 45 total venous thromboembolic events (VTEs) including 12 PEs occurred at centers considered low elevation, whereas 50 VTEs including 4 PEs occurred at centers considered high elevation. The incidence of VTE at low-elevation centers was 0.13%. The incidence of VTE at high-elevation centers was 0.49%. The difference was statistically significant, P < .0001. The relative risk of developing a VTE was 3.8 times higher at high elevation. There was no difference in PE incidence between high- and low-elevation centers (0.04% vs 0.03%, respectively; P = .78).

CONCLUSIONS

Patients undergoing arthroscopic procedures of the knee in centers at high elevation are at 3.8 times higher risk of developing a VTE than those undergoing the same procedures in centers at low elevations. There was no observed increased risk of PE.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Editorial Commentary: Should the Virchow Triad Have Been a Quartet? Is High Altitude a Risk Factor for Deep Venous Thrombosis After Knee Arthroscopy?

The Virchow triad includes stasis of blood flow, endothelial injury, and hypercoagulability. It forms the physiological foundation for the development of one of our most dreaded complications: deep venous thrombosis. Although the complication rate after knee arthroscopy remains low, significant morbidity may be associated with thromboembolic events. Tyson et al. report an increased incidence of venous thromboembolism in knee operations performed at higher altitudes versus those conducted closer to sea level. Multiple acquired conditions and inherited traits have been identified as risk factors for the development of venous thromboembolism. Geographic altitude should be included within this list.

Arterial complications, venous thromboembolism and deep venous thrombosis prophylaxis after anterior cruciate ligament reconstruction: A systematic review

AIM

To summarize the current knowledge on vascular complications and deep venous thrombosis (DVT) prophylaxis after anterior cruciate ligament (ACL) reconstruction.

METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement. MEDLINE, EMBASE, Cochrane, Web of Science, CINAHL, PubMed publisher, and Google scholar medical literature databases were searched up to November 10, 2015. Any arthroscopic surgical method of primary or revision intra-articular ACL reconstruction of all graft types in humans was included. A risk of bias assessment was determined.

RESULTS

Fourty-seven studies were included in the review. Pseudaneurysms were the most frequently reported arterial complication after ACL reconstruction, irrespective of graft type or method of graft fixation with an incidence of 0.3%. The time to diagnosis of arterial complications after ACL reconstruction varied from days to mostly weeks but even years. After ACL reconstruction without thromboprophylaxis, the incidence of DVT was 9.7%, of which 2.1% was symptomatic. The incidence of pulmonary embolism was 0.1%. Tourniquet time > 2 h was related to venous thromboembolism. Thromboprophylaxis is indicated in patients with risk factors for venous thromboembolism.

CONCLUSION

After ACL reconstruction, the incidence of arterial complications, symptomatic DVT and pulmonary embolism was 0.3%, 2.1% and 0.1% respectively. Arterial complications may occur with all types of arthroscopic ACL reconstruction, methods of graft fixation as well as any type of graft. Patients considered to be at moderate or high risk of venous thromboembolism should routinely receive thromboprophylaxis after ACL reconstruction.

Snake venom toxins: toxicity and medicinal applications

Snake venoms are complex mixtures of small molecules and peptides/proteins, and most of them display certain kinds of bioactivities. They include neurotoxic, cytotoxic, cardiotoxic, myotoxic, and many different enzymatic activities. Snake envenomation is a significant health issue as millions of snakebites are reported annually. A large number of people are injured and die due to snake venom poisoning. However, several fatal snake venom toxins have found potential uses as diagnostic tools, therapeutic agent, or drug leads. In this review, different non-enzymatically active snake venom toxins which have potential therapeutic properties such as antitumor, antimicrobial, anticoagulating, and analgesic activities will be discussed.

Risk Factors for Short-term Complications of Anterior Cruciate Ligament Reconstruction in the United States

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) is a commonly performed procedure that is highly successful in restoring knee stability and function. The incidence of early ACLR complications and the risk factors for these complications are not well defined.

PURPOSE

To determine the incidence of 30-day complications and patient and surgical risk factors for complications after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent ACLR between 2005 and 2013 were identified in the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database using Current Procedural Terminology billing codes. Postoperative complications in the 30-day period after surgery were identified. Potential patient and surgical risk factors for 30-day complications after ACLR were analyzed using univariate and multivariate analyses.

RESULTS

A total of 4933 patients were identified. Major complications occurred in 27 patients (0.55%), and minor complications occurred in 43 patients (0.87%), with overall complications occurring in 66 patients (1.34%). The most common complications were symptomatic deep venous thrombosis requiring treatment (n = 27; 0.55%), return to the operating room (n = 18; 0.36%), superficial infections (n = 10; 0.20%), deep infections (n = 7; 0.14%), and pulmonary embolism (n = 6; 0.12%). A single mortality (0.02%) occurred. Multivariate analyses demonstrated that smoking, dyspnea, a history of chronic obstructive pulmonary disease, and recent weight loss were all risk factors for the development of overall complications, although in combination, these factors accounted for only 3% of the variance in the complication rate.

CONCLUSION

ACLR has a low incidence of complications (1.34%) in the early postoperative period, with the most common being symptomatic venous thromboembolic disease requiring treatment, return to the operating room, and infections. Because ACLR is an elective procedure, surgeons should use this information to counsel patients on risks and to guide their decision making about patient selection.

The Prevalence of Symptomatic Deep Venous Thrombosis and Pulmonary Embolism After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Arthroscopically assisted anterior cruciate ligament (ACL) reconstruction is a common orthopaedic procedure. The incidence and risk factors of venous thromboembolism (VTE) after ACL reconstruction remain unclear.

PURPOSE

To define the incidence of VTE after ACL reconstruction and identify associated risk factors in a large cohort of patients.

STUDY DESIGN

Descriptive epidemiological study.

METHODS

All patients aged ≥18 years who underwent ACL reconstruction between 2005 and 2011 were identified from the Department of Defense Medical Data Repository. The prevalence of VTE, including deep venous thrombosis (DVT) and pulmonary embolism (PE), within 3 months of ACL reconstruction was queried. Univariate analyses were performed to define odds ratios (ORs) for demographic, medication use, and procedural-related risk factors.

RESULTS

A total of 87 VTE events (0.53% [95% CI, 0.42%-0.65%]) occurred after 16,558 ACL reconstructions performed on 15,767 patients. DVT was documented after 55 procedures and PE after 35 procedures. Three patients were documented to have both DVT and PE within the study period. The odds of VTE increased in patients aged ≥35 years (OR, 1.96 [95% CI, 1.27-3.04]; P = .003). Nicotine history increased the odds of DVT (OR, 1.99 [95% CI, 1.15-3.43]; P = .014). Concomitant high tibial osteotomy (HTO) increased the odds of PE (OR, 18.31 [95% CI, 2.4-139.6]; P = .005), whereas concomitant posterior cruciate ligament (PCL) reconstruction increased the odds of both VTE (OR, 3.43 [95% CI, 1.07-11.2]; P = .38) and DVT (OR, 5.57 [95% CI, 1.71-18.14]; P = .004). Nonsteroidal drug use was associated with decreased odds for VTE and DVT (OR, 0.44 [95% CI, 0.28-0.70]; P < .001 and OR, 0.38 [95% CI, 0.22-0.69]; P < .001, respectively). Anticoagulants were associated with increased odds for VTE, DVT, and PE (OR, 98.32 [95% CI, 61.63-156.86]; P < .001; OR, 111.93 [95% CI, 63.95-195.92]; P < .001; and OR, 47.84 [95% CI, 22.55-101.52]; P < .001, respectively). No detectible difference in odds was found for sex, body mass index, or aspirin or cyclooxygenase-2 inhibitor use.

CONCLUSION

The incidence of VTE after ACL reconstruction in this large population was low. Increased odds of VTE was identified in patients aged ≥35 years with a history of nicotine use, anticoagulant use, concomitant HTO, or concomitant PCL reconstruction. Controlled studies are necessary to determine the efficacy of chemoprophylaxis and to develop evidence-based clinical practice guidelines to minimize VTE after ACL reconstruction.

Rates of Deep Venous Thrombosis and Pulmonary Embolus After Anterior Cruciate Ligament Reconstruction: A Systematic Review

Context:

Venous thromboembolic (VTE) disease is thought to be an uncommon but serious problem after anterior cruciate ligament (ACL) reconstruction. Rates of VTE after ACL reconstruction are not well documented.

Objective:

To determine the rates of deep vein thrombosis (DVT) and symptomatic pulmonary emboli (PE) after ACL reconstruction.

Data Sources:

Five publicly available databases (PubMed, Cochrane Database of Systematic Reviews, Scopus, Embase, and CINAHL Complete) were utilized.

Study Selection:

All studies that screened patients for DVT and reported rates of DVT and PE after ACL reconstruction were eligible for inclusion. Level 5 evidence, cadaver, biomechanical, and basic science studies; studies reporting only multiligament reconstruction outcomes; studies where rates of DVT and PE could not be separated out from patients undergoing other types of arthroscopic knee procedures; and classification studies were excluded.

Study Design:

Systematic review.

Level of Evidence:

Level 4.

Data Extraction:

All study, subject, and surgical data were analyzed. Descriptive statistics were calculated.

Results:

Six studies met the inclusion criteria, with a mean Modified Colman Methodology Score of 30 ± 8.22. A total of 692 patients (488 men [70.5%]; mean age, 31.6 ± 2.82 years; mean follow-up, 7 ± 18.4 months) underwent ACL reconstruction using either semitendinosus-gracilis autograft (77.6%), bone–patellar tendon–bone (BTB) autograft (22%), or allograft (0.4%). No patient received postoperative pharmacological anticoagulation. Fifty-eight patients (8.4%) had a DVT (81% below knee and 19% above knee), while only 1 patient (0.2%) had a symptomatic PE. When reported, 27% of DVT episodes were symptomatic.

Conclusion:

The rate of DVT after ACL reconstruction in patients who did not receive postoperative pharmacological anticoagulation is 8.4%, while the rate of symptomatic PE is 0.2%. Of the DVT episodes that occurred, 73% were asymptomatic.

Extensive Lower-Extremity Deep Venous Thrombosis Following Arthroscopic Anterior Cruciate Ligament Reconstruction Related to May-Thurner Syndrome: A Case Report

CASE

An extensive iliofemoral-popliteal deep venous thrombosis following arthroscopic anterior cruciate ligament reconstruction presented on the ninth postoperative day as the result of underlying May-Thurner syndrome. The patient was managed with therapeutic anticoagulation and mechanical disruption of the thrombus. The focal stenosis of the left common iliac vein was addressed with angioplasty and stent placement. Repeat venography demonstrated no residual stenosis of the vein.

CONCLUSION

A multidisciplinary approach remains necessary for treating and reducing the risk of post-thrombotic syndrome. The present case further emphasizes the need for aggressive workup and response when a patient presents with left-sided deep venous thrombosis associated with underlying May-Thurner syndrome.

Low frequency of symptomatic venous thromboembolism after multiligamentous knee reconstruction with thromboprophylaxis

BACKGROUND

Reconstruction of the multiligament-injured knee often involves extended surgical and tourniquet use times and often is performed in patients who have sustained concomitant fractures as well as vascular injuries, all of which would appear to predispose the patient to the potentially serious complications of deep vein thrombosis and perhaps pulmonary embolism, yet little is known about the frequency of venous thromboembolic (VTE) events after multiligamentous knee reconstruction.

QUESTIONS/PURPOSES

The purposes of this study were to (1) determine the frequency of symptomatic VTE after multiligamentous knee reconstruction at a single institution; and (2) to determine associated risk factors for VTE in these patients.

METHODS

The records of 134 (63% of the 213 consented individuals in our longitudinal database) patients who underwent primary (129 [96%]) or revision (five [4%]) multiligamentous knee reconstruction at a single institution between 1992 and 2013 were retrospectively reviewed. With two patients undergoing procedures bilaterally, this resulted in a total of 136 multiligamentous knee reconstructions. VTE for which clinical symptoms were evident and confirmed by imaging within 3 months after the reconstructive procedure was noted. Pre- and perioperative data were collected with respect to demographics, associated injuries, medical history, smoking status, and surgical data. Standard rehabilitation and thromboprophylaxis protocols were used in all patients.

RESULTS

Three cases of symptomatic VTE (three deep vein thromboses) occurred after the 136 reconstructions (2%; 95% confidence interval, 0.53%-7.3%). Two of the three patients were obese and the remaining patient smoked and abused alcohol. However, as a result of a low frequency of VTE, no risk factors could be identified in this series.

CONCLUSIONS

Symptomatic VTE occurred in 2% of multiligamentous knee reconstructions at our institution while receiving thromboprophylaxis. This is similar to rates documented after anterior cruciate ligament reconstruction without thromboprophylaxis. Further multicenter research is required to identify the true frequency of and risk factors for developing VTE in patients undergoing multiligamentous knee reconstruction after knee dislocation.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Incidence of symptomatic and asymptomatic venous thromboembolism after elective knee arthroscopic surgery: a retrospective study with routinely applied venography

PURPOSE

The purpose of this study was to assess the incidence of total venous thromboembolism (VTE) after knee arthroscopy with routinely applied venography.

METHODS

We reviewed 537 consecutive patients undergoing arthroscopic knee surgery from March 2012 to July 2013. The surgical procedure was categorized as simple anterior cruciate ligament reconstruction (ACLR), posterior cruciate ligament reconstruction (PCLR), or reconstruction of both cruciate ligaments. All patients having arthroscopy in our institution were routinely examined with venography on the third postoperative day. Clinical signs of DVT were checked and recorded before venography.

RESULTS

Eighty (14.9%) of 537 patients were diagnosed with VTE by venography. Of the 80 detected cases of VTE, only 20 (3.7%) patients presented with clinical signs of DVT, indicating that there were 60 (11.2%) asymptomatic cases. No patient died or presented with a clinically suspected pulmonary embolism (PE). Sex, body mass index (BMI), operative time, and duration of tourniquet application were not significant risk factors for DVT. Patient age (P < .0001) is a strongly significant risk factor for deep venous thrombosis (DVT). Compared with patients who underwent simple arthroscopic procedures, complex procedures-the reconstruction of 1 (P < .005) or both knee cruciate ligaments (P < .0005)-led to a significantly higher postoperative incidence of DVT.

CONCLUSIONS

The total incidence of VTE diagnosed with venography after arthroscopic knee surgery was 14.9%, of which only 3.7% of cases were symptomatic, indicating 11.2% cases of silent VTE. Advanced age and complex arthroscopic surgery are strongly associated with VTE.

LEVEL OF EVIDENCE

Level IV, prognostic case series.