Preoperative Electrodiagnostic Study Findings Differ Between Patients With Double-crush Syndrome and Carpal Tunnel Syndrome: A Propensity Matched Analysis.

INTRODUCTION: Double-crush syndrome (DCS) represents a condition that involves peripheral nerve compression in combination with spinal nerve root impingement. The purpose of this study was to compare electrodiagnostic study (EDS) results in patients undergoing carpal tunnel release (CTR) for carpal tunnel syndrome with those undergoing both CTR and anterior cervical diskectomy and fusion for DCS. METHODS: Patients receiving an isolated CTR were compared with those undergoing CTR and anterior cervical diskectomy and fusion within two years of CTR. The latter group was defined as our DCS cohort. Electrodiagnostic study results were collected which included sensory and motor nerve conduction data as well as electromyogram (EMG) findings. All electrodiagnostic studies were done before CTR in both sets of patients. RESULTS: Fifty-four patients with DCS and 137 CTR-only patients were included. Patients with DCS were found to have decreased sensory onset latency (3.51 vs 4.01; P = 0.015) and peak latency (4.25 vs 5.17; P = 0.004) compared with the CTR-only patients. Patients with DCS had slower wrist motor velocity (30.5 vs 47.7; P = 0.012), decreased elbow motor latency (9.62 vs 10.6; P = 0.015), and faster elbow motor velocity (56.0 vs 49.4; P = 0.031). EMG results showed that patients with DCS were more likely to have positive findings in the biceps (31.9% vs 1.96%; P < 0.001) and triceps (24.4% vs 2.97%; P < 0.001), but not abductor pollicis brevis (APB) (45.7% vs 37.9%; P = 0.459). CONCLUSION: We identified changes on EDS between patients with and without DCS. In patients with DCS, sensory nerve studies showed shorter peak and onset latency than in CTR-only patients. Interestingly, DCS and CTR-only patients had different patterns of wrist and elbow motor nerve conduction. Providers observing positive EMG findings proximal to the APB should raise their suspicion for possible cervical radiculopathy and when present with carpal tunnel syndrome-like symptoms, should also consider DCS in their diagnostic differential.

Reimbursement of Lumbar Fusion at an Orthopaedic Specialty Hospital Versus Tertiary Referral Center.

STUDY DESIGN: Retrospective Cohort Study. OBJECTIVE: To explore the differences in Medicare reimbursement for lumbar fusion performed at an orthopaedic specialty hospital (OSH) and a tertiary referral center and to elucidate drivers of Medicare reimbursement differences. SUMMARY OF BACKGROUND DATA: To provide more cost-efficient care, appropriately selected patients are increasingly being transitioned to OSHs for lumbar fusion procedures. There are no studies directly comparing reimbursement of lumbar fusion between tertiary referral centers (TRC) and OSHs. METHODS: Reimbursement data for a tertiary referral center and an orthopaedic specialty hospital were compiled through the Centers for Medicare and Medicaid Services. Any patient with lumbar fusions between January 2014 and December 2018 were identified. OSH patients were matched to TRC patients by demographic and surgical variables. Outcomes analyzed were reimbursement data, procedure data, 90-day complications and readmissions, operating room times, and length of stay (LOS). RESULTS: A total of 114 patients were included in the final cohort. The tertiary referral center had higher post-trigger ($13,554 vs. $8,541, P<0.001) and total episode ($49,973 vs. $43,512, P<0.010) reimbursements. Lumbar fusion performed at an OSH was predictive of shorter OR time (ß=0.77, P<0.001), shorter procedure time (ß=0.71, P<0.001), and shorter LOS (ß=0.53, P<0.001). There were no significant differences in complications (9.21% vs. 15.8%, P=0.353) or readmission rates (3.95% vs. 7.89%, P=0.374) between the 2 hospitals; however, our study is underpowered for complications and readmissions. CONCLUSION: Lumbar fusion performed at an OSH, compared with a tertiary referral center, is associated with significant Medicare cost savings, shorter perioperative times, decreased LOS, and decreased utilization of post-acute resources. LEVEL OF EVIDENCE: 3.

The Impact of Physical Therapy After Lumbar Fusion Surgery.

STUDY DESIGN: Retrospective Cohort. OBJECTIVE: To determine if outcomes varied between patients based on physical therapy (PT) attendance after lumbar fusion surgery. SUMMARY OF BACKGROUND DATA: The literature has been mixed regarding the efficacy of postoperative PT to improve disability and back pain, as measured by patient-reported outcome measures. Given the prevalence of PT referrals and lack of high-quality evidence, there is a need for additional studies investigating the efficacy of PT after lumbar fusion surgery to aid in developing robust clinical guidelines. METHODS: We retrospectively identified patients receiving lumbar fusion surgery by current procedural terminology codes and separated them into 2 groups based on whether PT was prescribed. Electronic medical records were reviewed for patient and surgical characteristics, PT utilization, and surgical outcomes. Patient-reported outcome measures (PROMs) were identified and compared preoperatively, at 90 days postoperatively and one year postoperatively. RESULTS: The two groups had similar patient characteristics and comorbidities and demonstrated no significant differences between readmission, complication, and revision rates after surgery. Patients that attended PT had significantly more fused levels (1.41 ± 0.64 vs. 1.32 ± 0.54, P =0.027), longer operative durations (234 ± 96.4 vs. 215 ± 86.1 min, P =0.012), and longer postoperative hospital stays (3.35 ± 1.68 vs. 3.00 ± 1.49 days, P =0.004). All groups improved similarly by Oswestry Disability Index, short form-12 physical and mental health subsets, and back and leg pain by Visual Analog Scale at 90-day and 1-year follow-up. CONCLUSION: Our data suggest that physical therapy does not significantly impact PROMs after lumbar fusion surgery. Given the lack of data suggesting clear benefit of PT after lumbar fusion, surgeons should consider more strict criteria when recommending physical therapy to their patients after lumbar fusion surgery. LEVEL OF EVIDENCE: Level-Ⅲ.

Cellular Bone Matrix Leading to Disseminated Tuberculosis After Spinal Fusion: A Report of 2 Cases.

CASE: Although implanted tuberculosis (TB) is rare, a single lot of cellular bone matrix was found to be infected with TB, leading to devastating outcomes. We present 2 cases referred to our institution because of instrumentation failure caused by TB inoculation of cellular bone matrix. CONCLUSION: Irrespective of spinal region of implanted TB infection, excision of infected bone, extensive irrigation and debridement, and instrumented stabilization are of primary importance to ensure TB eradication and adequate stabilization.

Risk Factors and Characteristics of Recalcitrant Osteomyelitis After Initial Surgical and Antibiotic Treatment.

OBJECTIVES: To evaluate the injury, patient, and microbiological characteristics that place patients at risk for recalcitrant fracture-related infection and osteomyelitis despite appropriate initial treatment. DESIGN: Retrospective chart review. SETTING: Three level I trauma centers. PATIENTS AND PARTICIPANTS: Two hundred and fifty-seven patients undergoing surgical debridement and antibiotic therapy for osteomyelitis from 2003 to 2019. MAIN OUTCOME MEASUREMENTS: Patients were categorized as having undergone serial bone debridement if they had 2 separate procedures a minimum of 6 weeks apart with a full course of appropriate antibiotics in between. Patient records were reviewed for age, injury location, body mass index, smoking status, comorbidities, and culture results including the presence of multidrug-resistant organisms and culture-negative osteomyelitis. RESULTS: A total of 257 patients were identified; 49% (n = 125) had a successful single course of treatment, and 51% (n = 132) required repeat debridement for recalcitrant osteomyelitis. At the index treatment for osteomyelitis, the most common organisms in both groups were methicillin-resistant (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). There was no significant difference in incidence of polymicrobial infection between the 2 groups (25% vs. 20%, P = 0.49). The most common organisms cultured at the time of repeat saucerization remained MRSA and MSSA; however, the same organism was cultured from both the index and repeat procedures in only 28% (n = 37) of cases. Diabetic patients, intravenous drug use status, delay to diagnosis, and open fractures of the lower leg are independent risk factors for failure of initial treatment of posttraumatic osteomyelitis. CONCLUSIONS: Successful eradication of fracture-related infection and posttraumatic osteomyelitis is difficult and fails 51% of the time despite standard surgical and antimicrobial therapy. Although MRSA and MSSA remain the most common organisms cultured, patients who fail initial treatment for osteomyelitis often do not culture the same organisms as those obtained at the index procedure. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Facet Distraction and Dysphagia: A Prospective Evaluation of This Common Postoperative Issue Following Anterior Cervical Spine Surgery.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: Our primary study was to investigate whether the degree of postoperative facet and disk space distraction following anterior cervical discectomy and fusion (ACDF) affects the rate of postoperative dysphagia. SUMMARY OF BACKGROUND DATA: Although ACDF is safe and well tolerated, postoperative dysphagia remains a common complication. Intervertebral disk space distraction is necessary in ACDF to visualize the operative field, prepare the endplates for fusion, and facilitate graft insertion. However, the degree of distraction tolerated, before onset of dysphagia, is not well characterized ACDF. MATERIALS AND METHODS: A prospective cohort study was conducted of 70 patients who underwent ACDF between June 2018 and January 2019. Two independent reviewers measured all preoperative and postoperative radiographs measured for interfacet distraction distance and intervertebral distraction distance, with intrareviewer reproducibility measurements after one month. For multilevel surgery, the level with the greatest distraction was measured. Primary outcomes were numerical dysphagia (0-10), Eating Assessment Tool 10, and Dysphagia Symptom Questionnaire score collected at initial visit and two, six, 12, and 24 weeks postoperatively. RESULTS: A total of 70 patients were prospectively enrolled, 59 of whom had adequate radiographs. An average of 1.71 (SD: 0.70) levels were included in the ACDF construct. Preoperatively, 13.4% of patients reported symptoms of dysphagia, which subsequently increased in the postoperative period at through 12 weeks postoperatively, before returning to baseline at 24 weeks. Intrareviewer and interreviewer reliability analysis demonstrated strong agreement. There was no relationship between interfacet distraction distance/intervertebral distraction distance and dysphagia prevalence, numerical rating, Eating Assessment Tool 10, or Dysphagia Symptom Questionnaire. CONCLUSIONS: Patients who had an ACDF have an increased risk of dysphagia in the short term, however, this resolved without intervention by six months. Our data suggests increased facet and intervertebral disk distraction does not influence postoperative dysphagia rates. LEVEL OF EVIDENCE: 3.

Preoperative epidural steroid injections do not increase the risk of postoperative infection in patients undergoing lumbar decompression or fusion: a systematic review and meta-analysis.

PURPOSE: Epidural corticosteroid injections (ESI) are a mainstay of nonoperative treatment for patients with lumbar spine pathology. Recent literature evaluating infection risk following ESI after elective orthopedic surgery has produced conflicting evidence. Our primary objective was to review the literature and provide a larger meta-analysis analyzing the temporal effects of steroid injections on the risk of infection following lumbar spine surgery. METHODS: We conducted a query of the PubMed, Embase, and Scopus databases from inception until April 1, 2022 for studies evaluating the risk of infection in the setting of prior spinal steroid injections in patients undergoing lumbar spine decompression or fusion. Three meta-analyses were conducted, (1) comparing ESI within 30-days of surgery to control, (2) comparing ESI within 30-days to ESI between 1 and 3 months preoperatively, and (3) comparing any history of ESI prior to surgery to control. Tests of proportions were utilized for all comparisons between groups. Study heterogeneity was assessed via forest plots, and publication bias was assessed quantiatively via funnel plots and qualitatively with the Newcastle-Ottawa Scale. RESULTS: Nine total studies were included, five of which demonstrated an association between ESI and postoperative infection, while four found no association. Comparison of weighted means demonstrated no significant difference in infection rates between the 30-days ESI group and control group (2.67% vs. 1.69%, p = 0.144), 30-days ESI group and the > 30-days ESI group (2.34% vs. 1.66%, p = 0.1655), or total ESI group and the control group (1.99% vs. 1.70%, p = 0.544). Heterogeneity was low for all comparisons following sensitivity analyses. CONCLUSION: Current evidence does not implicate preoperative ESI in postoperative infection rates following lumbar fusion or decompression. Operative treatment should not be delayed due to preoperative steroid injections based on current evidence. There remains a paucity of high-quality data in the literature evaluating the impact of preoperative ESI on postoperative infection rates. LEVEL OF EVIDENCE: II.

How does spinopelvic alignment influence short-term clinical outcomes after lumbar fusion in patients with single-level degenerative spondylolisthesis?

Context: Studies on adult spinal deformity have shown spinopelvic malalignment results in worse outcomes. However, it is unclear if this relationship exists in patients with single-level degenerative spondylolisthesis (DS) receiving short-segment fusions. Aims: To determine if spinopelvic alignment affects patient-reported outcome measures (PROMs) after posterior lumbar decompression and fusion (PLDF) with or without a transforaminal lumbar interbody fusion in patients with L4-5 DS. Settings and Design: A retrospective cohort analysis was conducted on patients who underwent PLDF for L4-5 DS at a single tertiary referral academic medical center. Materials and Methods: Patients were divided into groups based on preoperative cutoff values of 20° for pelvic tilt (PT) and 11° for pelvic incidence-lumbar lordosis mismatch (PI-LL) with subsequent reclassification based on correction to <20° PT or 11° PI-LL. Radiographic outcomes and PROMs were compared between the groups. Statistical Analysis Used: Multiple linear regression analyses were performed to determine whether radiographic cutoff values served as the independent predictors of change in PROMs. Statistical significance was set at P < 0.05. Results: A total of 188 patients with completed PROMs were included for the analysis. Preoperative PT >20° was associated with significantly greater reduction in PI-LL (-2.41° vs. 1.21°, P = 0.004) and increase in sacral slope (SS) (1.06° vs. -1.86°, P = 0.005) compared to patients with preoperative PT <20°. On univariate analysis, no significant differences were observed between any groups with regard to PROMs. Preoperative sagittal alignment measures and postoperative correction were not found to be independent predictors of improvement in clinical outcomes. Conclusion: A preoperative PT >20° is associated with improved PI-LL reduction and an increase in SS. However, no differences in clinical outcomes were found 1 year postoperatively for patients with preoperative PT >20° and PI-LL ≥11° compared to patients below this threshold.

Demographics and Medical Comorbidities as Risk Factors for Increased Episode of Care Costs Following Lumbar Fusion in Medicare Patients.

The objective was to evaluate medical comorbidities and surgical variables as independent risk factors for increased health care costs in Medicare patients undergoing lumbar fusion. Care episodes limited to lumbar fusions were retrospectively reviewed on the Centers of Medicare and Medicaid Innovation (CMMI) Bundled Payment for Care Improvement (BPCI) reimbursement database at a single academic institution. Total episode of care cost was also collected. A multivariable linear regression model was developed to identify independent risk factors for increased total episode of care cost, and logistic models for surgical complications and readmission. A total of 500 Medicare patients were included. Risk factors associated with increased total episode of care cost included transforaminal interbody fusion (TLIF) and anterior lumbar interbody fusion (ALIF) (ß = $5,399, P < 0.001) and ALIF+PLF (AP) fusions (ß = $24,488, P < 0.001), levels fused (ß = $3,989, P < 0.001), congestive heart failure (ß = $6,161, P = 0.022), hypertension with end-organ damage (ß = $10,138, P < 0.001), liver disease (ß = $16,682, P < 0.001), inpatient complications (ß = $4,548, P = 0.001), 90-day complications (ß = $10,012, P = 0.001), and 90-day readmissions (ß = $15,677, P < 0.001). The most common surgical complication was postoperative anemia, which was associated with significantly increased costs (ß = $18,478, P < 0.001). Female sex (OR = 2.27, P = 0.001), AP fusion (OR = 2.59, P = 0.002), levels fused (OR = 1.45, P = 0.005), cerebrovascular disease (OR = 4.19, P = 0.003), cardiac arrhythmias (OR = 2.32, P = 0.002), and fluid electrolyte disorders (OR = 4.24, P = 0.002) were independent predictors of surgical complications. Body mass index (OR = 1.07, P = 0.029) and AP fusions (OR = 2.87, P = 0.049) were independent predictors of surgical readmission. Among medical comorbidities, congestive heart failure, hypertension with end-organ damage, and liver disease were independently associated with a significant increase in total episode of care cost. Interbody devices were associated with increased admission cost.

Management and Scheduling of Spine Surgery in a Level 1 Trauma Center in the Setting of the COVID-19 Pandemic: Feasibility and Considerations for Reimplementation of Elective Spine Surgery.

Introduction: Determination of what constitutes necessary surgery in the setting of acute hospital resource strain during the COVID-19 pandemic is an unprecedented challenge for healthcare systems. Over the past two years during the COVID-19 pandemic, there have been many changes in reviews of medically necessary spine surgery. There continues to be no clear guidelines on recommendations and further discussion is necessary to continue to provide appropriate and high-level care during future pandemics. Significance: This review critically appraises and evaluates current barriers to medically necessary spine surgery during the COVID-19 pandemic and evaluates future decision making to maintain spine surgery during future pandemics or limitations in medical care. Results: Multiple studies included in this review have shown that while various orthopaedic surgeries may be considered elective, medically necessary spine surgery will need to continue during settings of limited medical care. This review discussed multiple methods and recommendations to limit transmission of virus from patients to providers and providers to patients. Conclusion: Continued medically necessary spine surgery in the setting of the COVID-19 pandemic and future pandemics should continue while limiting risk of transmission to continue providing high-level medical care and allowing hospitals to maintain financial responsibility.

Intradiscal Therapies for Lumbar Degenerative Disk Disease.

Discogenic low back pain is a common musculoskeletal complaint in patients presenting to orthopaedic surgeons. In addition to surgical options, there are several nonsurgical intradiscal treatments that have gained interest, ranging from biologic, nonbiologic, cell-based, and molecular therapies. However, there is limited evidence for many of these techniques, and some are still in the clinical trial stage. We describe a broad overview of these intradiscal therapies, the mechanism of action, and the evidence behind them.

Does displacement of cervical and thoracolumbar dislocation-translation injuries predict spinal cord injury or recovery?

OBJECTIVE: For patients with cervical and thoracolumbar AO Spine type C injuries, the authors sought to 1) identify whether preoperative vertebral column translation is predictive of a complete spinal cord injury (SCI) and 2) identify whether preoperative or postoperative vertebral column translation is predictive of neurological improvement after surgical decompression. METHODS: All patients who underwent operative treatment for cervical and thoracolumbar AO Spine type C injuries at the authors' institution between 2006 and 2021 were identified. CT and MRI were utilized to measure vertebral column translation in millimeters prior to and after surgery. A receiver operating characteristic (ROC) curve was generated to predict the probability of sustaining a complete SCI on the basis of the amount of preoperative vertebral column translation. ROC curves were then used to predict the probability of neurological recovery on the basis of preoperative and postoperative vertebral column translation. RESULTS: ROC analysis of 67 patients identified 6.10 mm (area under the curve [AUC] 0.77, 95% CI 0.650-0.892) of preoperative vertebral column translation as predictive of complete SCI. Additionally, ROC curve analysis found that 10.4 mm (AUC 0.654, 95% CI 0.421-0.887) of preoperative vertebral column translation was strongly predictive of no postoperative neurological improvement. Residual postoperative vertebral column translation after fracture reduction and instrumentation had no predictive value on neurological recovery (AUC 0.408, 95% CI 0.195-0.622). CONCLUSIONS: For patients with cervical and thoracolumbar AO Spine type C injuries, the amount of preoperative vertebral column translation is highly predictive of complete SCI and the likelihood of postoperative neurological recovery.

The Effect of Tranexamic Acid on Operative and Postoperative Blood Loss in Transforaminal Lumbar Interbody Fusions.

OBJECTIVE: The purpose of this retrospective cohort study was to evaluate the effect of tranexamic acid (TXA) on reducing perioperative blood loss and length of stay after transforaminal lumbar interbody fusion (TLIF). Spine surgery is associated with the potential for significant blood loss, and adequate hemostasis is essential to visualizing crucial structures during the approach and procedure. Although TXA use has been extensively studied in the pediatric and adult spinal deformity literature, there is a dearth of literature on its efficacy in reducing blood loss for patients who undergo 1- to 3-level TLIF. METHODS: All patients requiring 1- to 3-level TLIF who received a preoperative loading dose of TXA were grouped and compared with patients who didn't receive TXA. Demographic, surgical, and laboratory values were collected and analyzed. Continuous and categorical variables were analyzed with χ2, Kruskal-Wallis, or analysis of variance tests, depending on normality and data type. Multiple linear regressions were developed to determine independent predictors of the estimated blood loss (EBL), total blood loss, drain output, and length of stay. Statistical significance was set at P < 0.05. RESULTS: Patients who received preoperative TXA had more comorbidities (P = 0.006), longer surgery length (P < 0.001), and longer length of stay (P = 0.004). TXA was independently associated with a decreased day 0, 1, 2, and total drain output (P < 0.001, P = 0.001, P = 0.007, P < 0.001, respectively), but was not associated with a change in EBL, total blood loss, or length of stay. CONCLUSIONS: The application of preoperative TXA for patients undergoing 1- to 3-level TLIF reduced drain output in the first 2 postoperative days, but it did not affect hospital length of stay, total blood loss, or EBL.

Effect of the COVID-19 Pandemic on Sports-Related Injuries Evaluated in US Emergency Departments.

BACKGROUND: Organized athletics are undergoing a gradual resumption after a prolonged hiatus in 2020 because of the coronavirus disease 2019 (COVID-19) pandemic. PURPOSE/HYPOTHESIS: The purpose of this study was to evaluate the effect of the 2020 COVID-19 period on emergency department (ED) visits for sports-related injuries in the United States. It was hypothesized that such visits decreased in response to the pandemic conditions. STUDY DESIGN: Descriptive epidemiology study. METHODS: A selection of sports (baseball, basketball, softball, soccer, American football, weightlifting, track and field, martial arts, boxing, golf, personal fitness, cycling, tennis, and ice hockey) were classified as being an organized team, organized individual, or nonorganized sport. The National Electronic Injury Surveillance System database was then queried for ED visits for sports-related injuries between January 1, 2018, and December 31, 2020, and we compared weighted national injury estimates and injury characteristics from athletes presenting to EDs in 2018 and 2019 versus those from the 2020 COVID-19 pandemic period and between March 1 and May 31, 2020 (government-imposed lockdown period). Bivariate comparisons between variables were conducted using chi-square analysis, with strength of association assessed using odds ratios. RESULTS: The 164,151 unweighted cases obtained from the query resulted in a weighted national estimate of 5,664,795 sports-related injuries during the study period. Overall, there was a 34.6% decrease in sports-related ED visits in 2020 compared with the yearly average between 2018 and 2019 (baseline). The number of ED visits in 2020 decreased by 53.9% versus baseline for injuries incurred by participation in an organized team sport and by 34.9% for injuries incurred by participation in an organized individual sport. The number of ED visits during the 2020 lockdown period decreased by 76.9% versus baseline for injuries incurred by participation in an organized team sport and by 65.8% for injuries incurred by participation in an organized individual sport. Injuries sustained while participating in a nonorganized sport remained relatively unaffected and decreased by only 8.1% in 2020. CONCLUSION: ED visits in the United States for injuries sustained while participating in an organized team or individual sport underwent a decrease after the beginning of the COVID-19 pandemic in 2020, especially during the lockdown period.

The epidemiology of indoor and outdoor rock climbing injuries presenting to USA emergency departments.

BACKGROUND: The popularity of both indoor and outdoor rock climbing has dramatically increased over the last decade. The purpose of this study is to evaluate trends in USA climbing injury rates as well as assess specific injury characteristics, especially in the context of indoor and outdoor climbing. METHODS: The National Electronic Injury Surveillance System database was queried (2010-2019) to compare national weighted injury estimates and compare various injury characteristics from climbers presenting to USA emergency departments. RESULTS: The annual national estimates of rock climbing-related injuries presenting to USA emergency rooms increased significantly (P=0.030) from 2010 (N.=2381; CI 1085-3676) to 2019 (N.=4596; CI 492-8699). About 58.7% of the injuries in this study that could be classified by location occurred climbing outdoors. Ankle injuries were 2.25 times more likely (CI 1.03-3.08) to occur indoors than outdoors. Outdoor climbers were 2.25 times more likely to sustain an injury via falling and 13.8 times more likely to be injured by being struck by an object than indoor climbers (CI 1.05-2.42 and CI 10.67-17.78, respectively). CONCLUSIONS: Indoor and outdoor rock climbing are associated with different injury characteristics and risks. Therefore proper safety precautions, equipment, and training specific to terrain should be observed by all climbers in order to help decrease the rising trend of rock climbing-related injuries in the USA.