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The Curtis Hand Injury Matrix Score: Determining the Need for Specialized Upper Extremity Care

Published:September 21, 2021DOI:https://doi.org/10.1016/j.jhsa.2021.07.034

      Purpose

      Given the limited impact of transfer guidelines and the lack of comparative metrics for upper extremity trauma, we introduced the Curtis Hand Injury Matrix (CHIM) score to evaluate upper extremity injury acuity from the specialist perspective. Our goal was to evaluate the CHIM score as an indicator of complexity and specialist need by correlating the score with arrival mode, length of stay (LOS), discharge disposition, and procedure location.

      Methods

      We identified all hand and upper extremity emergency room visits at our institution in 2018 and 2019. On initial evaluation, our institution’s hand surgery team assigned each patient an alphanumeric score with a number (1–5) and letter (A–H) corresponding to injury severity and pathology, respectively. Patients were divided into 5 groups (1–5) with lower scores indicating greater severity. We compared age, LOS, discharge disposition, procedure location, transfer status, and arrival mode between groups and assessed the relationships between matrix scores and discharge disposition, procedure performed, and LOS.

      Results

      There were 3,822 patients that accounted for 4,026 upper extremity evaluations. There were significant differences in LOS, discharge dispositions, procedure locations, transfer status, and arrival modes between groups. Patients with more severe scores had higher rates of admission and more operating room procedures. Higher percentages of patients who arrived via helicopter, ambulance, or transfer had more severe scores. Patients with more severe scores were significantly more likely to have a procedure, hospital admission, and longer hospital stay.

      Conclusions

      The CHIM score provides a framework to catalog the care and resources required when covering specialized hand and upper extremity calls and accepting transfers. This clinical validation supports considering broader use.

      Type of study/level of evidence

      Prognostic IV.

      Key words

      The introduction of regional trauma centers and inter-hospital transfers have reshaped upper extremity injury care in the United States. Although the factors associated with upper extremity transfers have been well studied, there is no system in place for receiving institutions to grade their accepted transfers and demonstrate the associated burden of inappropriate transfers on their regional centers.
      • Friebe I.
      • Isaacs J.
      • Mallu S.
      • Kurdin A.
      • Mounasamy V.
      • Dhindsa H.
      Evaluation of appropriateness of patient transfers for hand and microsurgery to a Level I Trauma Center.
      • Hartzell T.L.
      • Kuo P.
      • Eberlin K.R.
      • Winograd J.M.
      • Day C.S.
      The overutilization of resources in patients with acute upper extremity trauma and infection.
      • Bauer A.S.
      • Blazar P.E.
      • Earp B.E.
      • Louie D.L.
      • Pallin D.J.
      Characteristics of emergency department transfers for hand surgery consultation.
      • Petkovic D.
      • Wongworawat M.D.
      • Anderson S.R.
      Factors affecting appropriateness of interfacility transfer for hand injuries.
      • Eberlin K.R.
      • Hartzell T.L.
      • Kuo P.
      • Winograd J.
      • Day C.
      Patients transferred for emergency upper extremity evaluation: does insurance status matter?.
      • Daly C.A.
      • Cho B.H.
      • Desale S.
      • Aliu O.
      • Mete M.
      • Giladi A.M.
      The effects of Medicaid expansion on triage and regional transfer after upper-extremity trauma.
      • Crichlow R.J.
      • Zeni A.
      • Reveal G.
      • et al.
      Appropriateness of patient transfer with associated orthopaedic injuries to a Level I Trauma Center.
      • Goldfarb C.A.
      • Borrelli Jr., J.
      • Lu M.
      • Ricci W.M.
      A prospective evaluation of patients with isolated orthopedic injuries transferred to a Level I Trauma Center.
      • Patterson J.M.
      • Boyer M.I.
      • Ricci W.M.
      • Goldfarb C.A.
      Hand trauma: a prospective evaluation of patients transferred to a Level I Trauma Center.
      • Vallier H.A.
      • Parker N.A.
      • Beddow M.E.
      Reasons for transfer to a level 1 trauma center and barriers to timely definitive fracture fixation.
      • Maroukis B.L.
      • Chung K.C.
      • MacEachern M.
      • Mahmoudi E.
      Hand trauma care in the United States: a literature review.
      While some have retrospectively evaluated transfer appropriateness with an expert review panel, others have based it on the highest level of physician care required.
      • Friebe I.
      • Isaacs J.
      • Mallu S.
      • Kurdin A.
      • Mounasamy V.
      • Dhindsa H.
      Evaluation of appropriateness of patient transfers for hand and microsurgery to a Level I Trauma Center.
      • Hartzell T.L.
      • Kuo P.
      • Eberlin K.R.
      • Winograd J.M.
      • Day C.S.
      The overutilization of resources in patients with acute upper extremity trauma and infection.
      • Bauer A.S.
      • Blazar P.E.
      • Earp B.E.
      • Louie D.L.
      • Pallin D.J.
      Characteristics of emergency department transfers for hand surgery consultation.
      • Petkovic D.
      • Wongworawat M.D.
      • Anderson S.R.
      Factors affecting appropriateness of interfacility transfer for hand injuries.
      Recently, there has been an increased focus on finding criteria to grade transfer quality on the receiving end.
      • Eberlin K.R.
      • Hartzell T.L.
      • Kuo P.
      • Winograd J.
      • Day C.
      Patients transferred for emergency upper extremity evaluation: does insurance status matter?.
      This will allow upper extremity trauma centers that accept all transfers to catalog their consultations and demonstrate the associated burden, particularly with less severe injuries that do not require specialized care. However, doing so requires a reliable metric.
      Although severity scales and scoring systems have long been used in other fields to measure and categorize injured patients, upper extremity trauma lacks a well-established scoring system.
      • Champion H.R.
      Trauma scoring.
      • Lefering R.
      Trauma scoring systems.
      • Russell R.J.
      • Hodgetts T.J.
      • McLeod J.
      • et al.
      The role of trauma scoring in developing trauma clinical governance in the Defence Medical Services.
      • Mehmood A.
      • Hung Y.W.
      • He H.
      • Ali S.
      • Bachani A.M.
      Performance of injury severity measures in trauma research: a literature review and validation analysis of studies from low-income and middle-income countries.
      Upper extremity metrics include a “Tic-Tac-Toe” classification system, mangled extremity severity score, and the hand injury severity score.
      • Slauterbeck J.R.
      • Britton C.
      • Moneim M.S.
      • Clevenger F.W.
      Mangled extremity severity score: an accurate guide to treatment of the severely injured upper extremity.
      • Weinzweig J.
      • Weinzweig N.
      The “Tic-Tac-Toe” classification system for mutilating injuries of the hand.
      • Campbell D.A.
      • Kay S.P.
      The hand injury severity scoring system.
      Others have applied the visual analog scale to determine hand injury complexity and rate transfer appropriateness. Limitations in each metric have prevented widespread use.
      • Crichlow R.J.
      • Zeni A.
      • Reveal G.
      • et al.
      Appropriateness of patient transfer with associated orthopaedic injuries to a Level I Trauma Center.
      • Goldfarb C.A.
      • Borrelli Jr., J.
      • Lu M.
      • Ricci W.M.
      A prospective evaluation of patients with isolated orthopedic injuries transferred to a Level I Trauma Center.
      • Patterson J.M.
      • Boyer M.I.
      • Ricci W.M.
      • Goldfarb C.A.
      Hand trauma: a prospective evaluation of patients transferred to a Level I Trauma Center.
      ,
      • Slauterbeck J.R.
      • Britton C.
      • Moneim M.S.
      • Clevenger F.W.
      Mangled extremity severity score: an accurate guide to treatment of the severely injured upper extremity.
      • Weinzweig J.
      • Weinzweig N.
      The “Tic-Tac-Toe” classification system for mutilating injuries of the hand.
      • Campbell D.A.
      • Kay S.P.
      The hand injury severity scoring system.
      • Saxena P.
      • Cutler L.
      • Feldberg L.
      Assessment of the severity of hand injuries using “hand injury severity score”, and its correlation with the functional outcome.
      • Matsuzaki H.
      • Narisawa H.
      • Miwa H.
      • Toishi S.
      Predicting functional recovery and return to work after mutilating hand injuries: usefulness of Campbell’s Hand Injury Severity Score.
      • Mink van der Molen A.B.
      • Ettema A.M.
      • Hovius S.E.
      Outcome of hand trauma: the hand injury severity scoring system (HISS) and subsequent impairment and disability.
      • van der Molen A.B.
      • Matloub H.S.
      • Dzwierzynski W.
      • Sanger J.R.
      The hand injury severity scoring system and workers’ compensation cases in Wisconsin, USA.
      • Urso-Baiarda F.
      • Lyons R.A.
      • Laing J.H.
      • Brophy S.
      • Wareham K.
      • Camp D.
      A prospective evaluation of the Modified Hand Injury Severity Score in predicting return to work.
      Infections are also not included in most of these systems, and because hand and upper extremity infections are increasing in incidence and severity they must be included as well.
      • Ovalle Jr., F.
      • Dembinski D.
      • Yalamanchili S.
      • Minkara A.
      • Stern P.J.
      Hand and upper extremity infections in intravenous drug users: epidemiology and predictors of outcomes.
      • Luginbuhl J.
      • Solarz M.K.
      Complications of hand infections.
      • Gundlach B.K.
      • Sasor S.E.
      • Chung K.C.
      Hand infections: epidemiology and public health burden.
      Given the lack of standardized upper extremity injury scoring, the Maryland Institute for Emergency Medical Services Systems implemented the Curtis Hand Injury Matrix (CHIM) score classification system. The matrix was designed by hand surgeons at the Curtis National Hand Center in conjunction with the Maryland Institute for Emergency Medical Services Systems physician leadership, and it was reviewed and approved by outside hand surgery specialists before implementation. The system is straightforward and can be used to classify patients during triage. It offers detailed descriptions of each injury pattern to facilitate score selection. The CHIM score is also comprehensive because it extends beyond the hand and categorizes the upper extremity condition based on both pathology and severity. Overall, the score indicates the level of need for acute, specialized care. Although a previous study has shown that the matrix score corresponds with discharge disposition, the CHIM score has not yet been fully validated.
      • Daly C.A.
      • Cho B.H.
      • Desale S.
      • Aliu O.
      • Mete M.
      • Giladi A.M.
      The effects of Medicaid expansion on triage and regional transfer after upper-extremity trauma.
      Our institution uses the CHIM score as a categorization tool for all upper extremity patients seen by our on-call hand surgery team in our emergency department (ED). We aimed to evaluate the matrix by correlating the score with other factors, including length of stay (LOS), discharge disposition, procedure and procedure location, transfer status, and arrival mode. We hypothesized that if the CHIM score is valid, patients with more severe scores will be more likely to stay longer, have a procedure, and be admitted than patients with less severe scores.

      Materials And Methods

      Study sample

      After obtaining institutional review board approval, we performed a retrospective review of all hand and upper extremity patients seen in the Curtis National Hand Center/MedStar Union Memorial Hospital ED between January 1, 2018, and December 31, 2019. Per state protocol, every patient seen by the hand surgery team in the ED must receive a score and be properly logged. As such, we included all patients with a hand or upper extremity injury or pathology, whether single or multiple, seen and evaluated through our ED. We excluded 6 visits that had missing scores. As the only state-designated center for isolated hand and upper extremity injuries, we accept all patients with hand and upper extremity injuries, as well as transfers from the surrounding region.
      Maryland Institute for Emergency Medical Services Systems. 2019–2020 Annual Report.
      The institution is located in Baltimore, Maryland, but also draws acutely injured patients from a broad region, including Washington, DC; Virginia; Pennsylvania; Delaware; and West Virginia.
      Maryland Institute for Emergency Medical Services Systems. 2019–2020 Annual Report.

      Measures of explanatory and outcome variables

      At the time of initial evaluation, each patient was assigned an alphanumeric CHIM score (Fig. 1). The numerical component of the score ranges from 1 to 5, indicating severity. Scores of 1 or 2 denote a condition deemed to be an absolute indication for specialized hand surgical care, a score of 3 denotes a relative indication, and scores of 4 or 5 indicate that urgent evaluation at an established hand center is not warranted. The score is also broken down by letters A to H, depending on the following: (A) Hand and Wrist Fracture, (B) Forearm and Elbow Fracture, (C) Complete/Partial Amputation, (D) Nerve/Vessel Injury, (E) Soft Tissue Trauma, (F) Infection, (G) Thermal Injury, and (H) Pressure Pathology. Detailed descriptions are provided for each category to facilitate score determinations (Fig. 1; Table E1 [available online on the Journal’s website at www.jhandsurg.org]). During the initial emergency room evaluation, the treating resident physician or hand surgery midlevel provider assigned a matrix score based on the patient’s presentation. The score was then reviewed and verified by a single hand surgery fellow or an attending hand surgeon who could modify the score as needed. This final score was used for our analyses. Patients with multiple injury types were classified based on the hand surgeon’s determination of the most severe injury pattern. However, the hand specialist takes the entirety of the patient presentation into account by factoring in all injuries when determining case complexity and assigning the score. For example, a hand & wrist fracture (A) may not warrant specialist consultation in the ED (eg, level 4), but concurrent nerve injury symptoms (D) or soft tissue trauma (E) could increase the case severity as judged by the hand surgeon (eg, level 2). The score would still be classified as a hand and wrist fracture (A) if that was determined to be the most severe injury, even if the other associated problems are what indicated a need for more urgent specialist involvement.
      Figure thumbnail gr1
      Figure 1Curtis Hand Injury Matrix Score classifications based on the referral index and pathology portfolio, as well as indication for referral.
      Outcome variables used to evaluate the CHIM score included patient transfer status, arrival mode, discharge disposition, LOS, and procedure details. Demographic covariates reported across groups included age, sex, and race. Discharge disposition was coded as discharged, admitted, or left against medical advice. The “admitted” group included patients who were admitted to the hospital, held for observation, or sent directly to the operating room or catheterization laboratory because several factors influence the decision details after ruling out discharge. Procedure location was categorized as no procedure, ED, or operating room. Length of stay was recorded as time in hours. Transfer status was coded as transfer or no transfer. Arrival mode was categorized as helicopter, ambulance, private vehicle, walk-in, or unknown.

      Statistical analysis

      Patients were divided into 5 groups (1–5) based on their score, with 1 indicating the highest severity. We summarized the distribution of categorical and continuous variables using frequencies and medians with interquartile ranges or means with standard deviations, respectively. We compared differences in patient age and LOS using quantile regression tests. Differences in discharge disposition, procedure location, transfer status, and arrival mode were evaluated using chi-square analyses. Since transfer status and arrival mode were determined prior to the matrix score, we analyzed the distribution of referral groups within each category of these variables to assess whether patient presentation affected their scores. We then conducted bivariate linear regression analyses with the matrix score as the independent variable and LOS as the outcome variable. Finally, we conducted bivariate logistic regression analyses with matrix score as the independent variable, discharge disposition (discharged/not discharged) as the outcome in 1 model, and procedure performed (yes/no) in a separate model. The significance level was set at a P value of .05.

      Results

      The final cohort included 3,822 patients. These patients accounted for 4,026 upper extremity–focused visits, since some patients had multiple emergency room visits during the study period. A post hoc power calculation demonstrated that a total sample size of 4,026 achieves >99% power to detect a moderate effect size of 0.40 using a 4 degrees of freedom chi-square test with a significance level of .05. Patients were predominantly male (68%), were predominately White (50%) or African-American (38%), and had a mean age of 44 years (Table 1). Of the 4,026 visits, 2% were the most severe category (category 1), 10% were category 2, 36% were category 3, 39% were category 4, and 14% were the least severe category (category 5). Most patients presented with soft tissue trauma (32%), hand and wrist fractures (26%), infection (20%), or complete/partial amputation (13%; Table 2). Of the visits, 35% led to admission, whereas 64% were discharged. Ultimately, 46% of visits required an ED procedure and 19% an operating room procedure. In terms of arrival at our institution, most patients arrived by private vehicle (45%) or walk-in (30%), and 30% of visits were transferred from another hospital.
      Table 1Summary Characteristics for All Upper Extremity Injury Patients and Hospital Visits∗
      Characteristicsn (%)Mean (SD)Median (IQR)
      Total patients3,822 (100)
      Sex
       Male2,589 (67.7)
       Female1,233 (32.3)
      Race
       White1,890 (49.5)
       African-American1,480 (37.7)
       Asian39 (1.0)
       American Indian/Alaskan Native4 (0.1)
       Other342 (9.0)
       Declined to answer64 (1.7)
      Age, y43.9 (18.7)43 (29–58)
      Total hospital visits4,026 (100)
      Referral Index Category (1–5)
       Category 170 (1.7)
       Category 2391 (9.7)
       Category 31,441 (35.7)
       Category 41,565 (38.8)
       Category 5559 (13.9)
      ED disposition
       Discharged2,568 (63.8)
       Admitted1,420 (35.3)
       Left against medical advice37 (0.9)
      Procedure location
       No procedure1,433 (35.6)
       ED1,837 (45.6)
       Operating room756 (18.8)
      Transfer status
       Transfer1,210 (30.1)
       No transfer2,807 (69.9)
      Arrival mode
       Helicopter66 (1.6)
       Ambulance815 (20.2)
       Private vehicle1,807 (44.9)
       Walk-in1,217 (30.2)
       Unknown121 (3.0)
      Length of stay, h3.9 (2.3)3.5 (2.5–4.8)
      IQR, interquartile range.
      Table 2Distribution of Curtis Hand Injury Matrix Scores for All Upper Extremity Injury Patients
      CHIM ScoreABCDEFGHN/ATotal
      Hand and Wrist FractureForearm and Elbow FractureComplete/Partial AmputationNerve/ Vessel InjurySoft Tissue TraumaInfectionThermal InjuryPressure Pathology
      12042567402270
      22041164194345041391
      332358179903354461361,441
      439776221545952076361,565
      5102181512295104742559
      Total1,0461675041811,2758061416174,026
      CHIM, Curtis Hand Injury Matrix; NA, not applicable.
      There were statistically significant differences in LOSs, discharge dispositions, and procedure locations between the 5 groups (P < .05; Table 3). Of the patients assigned the most severe category (category 1), 84% were admitted, compared to 79% in category 2, 59% in category 3, 11% in category 4, and 6% in category 5 (Fig. 2). The rates of operating room procedures were higher in categories 1 (73%) and 2 (62%) compared to categories 3 (30%), 4 (2%), and 5 (1%). The rates of ED procedures were 9%, 23%, 37%, 64%, and 39% in categories 1 through 5, respectively.
      Table 3Demographics and Care Variables by CHIM Score
      VariablesReferral CategoryP Value
      12345
      Age, y, median (IQR)39 (26–57)47 (30–59)43 (30–58)42 (28–58)40 (28–58)<.05
      Length of stay, h, median (IQR)2.7 (2.0–3.5)3.8 (2.9–5.1)3.9 (2.9–5.3)3.3 (2.4-4.5)2.7 (1.8–3.9)<.05
      Discharge disposition, n (%)<.05
       Discharged11 (15.7)79 (20.2)580 (40.3)1380 (88.2)518 (92.7)
       Admitted59 (84.3)310 (79.3)845 (58.6)170 (10.9)36 (6.4)
       Left AMA0 (0.0)2 (0.5)16 (1.1)15 (0.9)5 (0.9)
       Total70 (100)391 (100)1,441 (100)1,565 (100)559 (100)
      Procedure location, n (%)<.05
       No procedure13 (18.6)58 (14.8)482 (33.5)540 (34.5)340 (60.8)
       Emergency room6 (8.6)89 (22.8)526 (36.5)998 (63.8)218 (39.0)
       Operating room51 (72.8)244 (62.4)433 (30.0)27 (1.7)1 (0.2)
       Total70 (100)391 (100)1,441 (100)1,565 (100)559 (100)
      AMA, against medical advice; CHIM, Curtis Hand Injury Matrix; IQR, interquartile range.
      Figure thumbnail gr2
      Figure 2Differences in ED disposition and procedure location based on referral category. AMA, against medical advice.
      There were also statistically significant differences in transfer arrival status and method of arrival based on referral category (P < .05; Table 4). Of the patients who arrived via transfer, 21% were determined to be an absolute indication for referral (categories 1 and 2), 44% were considered a relative indication (category 3), and 35% had no indication for specialist referral (categories 4 and 5). In addition, patients who arrived via helicopter and ambulance had a higher percentage of visits classified as absolute or relative indications for referral (categories 1–3; Fig. 3).
      Table 4Emergency Department Arrival Details by CHIM Score
      Arrival DetailsReferral CategoryTotalP Value
      12345
      Arrival mode, n (%)<.05
       Helicopter8 (12.1)19 (28.8)24 (36.4)13 (19.7)2 (3.0)66 (100)
       Ambulance28 (3.4)149 (18.3)326 (40.0)278 (34.1)34 (4.2)815 (100)
       Private vehicle25 (1.4)177 (9.8)638 (35.3)738 (40.8)229 (12.7)1,807 (100)
       Walk-in5 (0.4)35 (2.9)418 (34.3)483 (39.7)276 (22.7)1,217 (100)
       Unknown4 (3.3)11 (9.1)35 (28.9)53 (43.8)18 (14.9)121 (100)
      Transfer arrival status, n (%)<.05
       Transfer40 (3.3)211 (17.4)532 (44.0)360 (29.8)67 (5.5)1,210 (100)
       No transfer30 (1.1)180 (6.4)908 (32.3)1,198 (42.7)491 (17.5)2,807 (100)
      CHIM, Curtis Hand Injury Matrix.
      Figure thumbnail gr3
      Figure 3Transfer status and arrival mode for all patients broken down by assigned referral category.
      Bivariate regression analyses found that patients assigned more severe matrix scores corresponding to absolute or relative indications for referral were significantly more likely to be admitted, to need a procedure, and to have a longer hospital stay, compared to patients with less severe matrix scores (Table 5).
      Table 5Associations Between CHIM Score and Care Required
      Care VariableOR/Coefficient (95% CI)P Value
      Hospital admission, OR (95% CI)
       Category 5Ref
       Category 41.8 (1.2–2.6)<.05
       Category 320.9 (14.7–29.9)<.05
       Category 256.5 (37.2–85.8)<.05
       Category 177.2 (37.3–159.7)<.05
      Procedure performed, OR (95% CI)
       Category 5Ref
       Category 42.9 (2.4–3.6)<.05
       Category 33.1 (2.5–3.8)<.05
       Category 28.9 (6.4–12.4)<.05
       Category 16.8 (3.6–12.7)<.05
      Length of stay, coefficient (95% CI)
       Category 5Ref
       Category 436.4 (22.7–50.0)<.05
       Category 374.9 (61.1–88.7)<.05
       Category 270.7 (52.5–88.9)<.05
       Category 1−5.9 (−39.8 to 28.0).73
      CHIM, Curtis Hand Injury Matrix; OR, odds ratio; Ref, reference.

      Discussion

      Patients with more severe matrix scores had greater odds of being admitted, needing a procedure, and staying longer than patients with less severe scores. However, the majority of patients with less severe scores still required emergency room procedures, supporting the importance of having well-trained emergency room providers with access to specialist consultation. In addition, patients who arrived at our center via transfer or who arrived in a helicopter or ambulance were more often assigned more severe scores corresponding to absolute or relative indications for referral. These results support the validity of the scoring system and allow us to consider a broader role for it in evaluating upper extremity injury acuity from the specialist perspective.
      Injury scoring systems are an important aspect of regionalized trauma care. They facilitate inter-hospital communication, decision-making, and outcome comparisons.
      • Champion H.R.
      Trauma scoring.
      ,
      • Lefering R.
      Trauma scoring systems.
      Primary care and emergency practitioners also rely on scoring systems to make appropriate transfer and triage decisions. Yet, up to this point, hand pathology has lacked a widely accepted and reliable scoring system to guide transfer decision-making or to properly classify injury severity. As a result, regional trauma centers have difficulty assessing the quality of their own transfer arrivals, limiting understanding of the system burden, resource needs, and quality of the trauma/triage process locally and regionally. We use the CHIM score to provide an assessment and insights from the specialist perspective.
      Other metrics are available, but not widely used. The Tic-Tac-Toe system is qualitative and limited to mutilating injuries and the mangled extremity severity score is not designed specifically for hand injuries.
      • Slauterbeck J.R.
      • Britton C.
      • Moneim M.S.
      • Clevenger F.W.
      Mangled extremity severity score: an accurate guide to treatment of the severely injured upper extremity.
      ,
      • Weinzweig J.
      • Weinzweig N.
      The “Tic-Tac-Toe” classification system for mutilating injuries of the hand.
      ,
      • Saxena P.
      • Cutler L.
      • Feldberg L.
      Assessment of the severity of hand injuries using “hand injury severity score”, and its correlation with the functional outcome.
      Although the hand injury severity score is correlated with returns to work, functional outcomes, and long-term disabilities, the score is difficult to calculate and must often be assigned retrospectively, limiting utility in acute trauma evaluations.
      • Campbell D.A.
      • Kay S.P.
      The hand injury severity scoring system.
      • Saxena P.
      • Cutler L.
      • Feldberg L.
      Assessment of the severity of hand injuries using “hand injury severity score”, and its correlation with the functional outcome.
      • Matsuzaki H.
      • Narisawa H.
      • Miwa H.
      • Toishi S.
      Predicting functional recovery and return to work after mutilating hand injuries: usefulness of Campbell’s Hand Injury Severity Score.
      • Mink van der Molen A.B.
      • Ettema A.M.
      • Hovius S.E.
      Outcome of hand trauma: the hand injury severity scoring system (HISS) and subsequent impairment and disability.
      • van der Molen A.B.
      • Matloub H.S.
      • Dzwierzynski W.
      • Sanger J.R.
      The hand injury severity scoring system and workers’ compensation cases in Wisconsin, USA.
      • Urso-Baiarda F.
      • Lyons R.A.
      • Laing J.H.
      • Brophy S.
      • Wareham K.
      • Camp D.
      A prospective evaluation of the Modified Hand Injury Severity Score in predicting return to work.
      The visual analog scale is over-simplified, lacks clear scoring criteria, and has not been validated.
      • Crichlow R.J.
      • Zeni A.
      • Reveal G.
      • et al.
      Appropriateness of patient transfer with associated orthopaedic injuries to a Level I Trauma Center.
      • Goldfarb C.A.
      • Borrelli Jr., J.
      • Lu M.
      • Ricci W.M.
      A prospective evaluation of patients with isolated orthopedic injuries transferred to a Level I Trauma Center.
      • Patterson J.M.
      • Boyer M.I.
      • Ricci W.M.
      • Goldfarb C.A.
      Hand trauma: a prospective evaluation of patients transferred to a Level I Trauma Center.
      Considering these limitations, we introduced the CHIM score to classify upper extremity injuries. The CHIM score is specifically designed for upper extremities and is assigned during the initial emergency room evaluation. The CHIM score also features 8 pathology categories that account for most hand consultations and compares severity within each injury category.
      Clinically validating an upper extremity metric poses unique challenges. While injury severity scales used in polytrauma are often assessed based on endpoints like mortality, morbidity, and disability, scoring systems for extremity injuries are more often used to determine viability, salvage potential, and functional status.
      • Champion H.R.
      Trauma scoring.
      ,
      • Lefering R.
      Trauma scoring systems.
      ,
      • Slauterbeck J.R.
      • Britton C.
      • Moneim M.S.
      • Clevenger F.W.
      Mangled extremity severity score: an accurate guide to treatment of the severely injured upper extremity.
      • Weinzweig J.
      • Weinzweig N.
      The “Tic-Tac-Toe” classification system for mutilating injuries of the hand.
      • Campbell D.A.
      • Kay S.P.
      The hand injury severity scoring system.
      • Saxena P.
      • Cutler L.
      • Feldberg L.
      Assessment of the severity of hand injuries using “hand injury severity score”, and its correlation with the functional outcome.
      ,
      • Copes W.S.
      • Champion H.R.
      • Sacco W.J.
      • Lawnick M.M.
      • Keast S.L.
      • Bain L.W.
      The Injury Severity Score revisited.
      Upper extremity pathologies are unique because the outcomes are often less severe than those associated with polytrauma and are less clearly comparable, especially in terms of long-term function. Therefore, we attempted to evaluate the CHIM score by correlating it with metrics that have an impact on provider and hospital burdens and overall care needs, including emergency room disposition, need for procedure, LOS, arrival mode, and transfer status.
      Given our institution’s status as a designated upper extremity referral and trauma center that accepts all patients, we can use these results to grade the acuity of patient presentation on a large scale.
      Maryland Institute for Emergency Medical Services Systems. 2019–2020 Annual Report.
      The score does not influence transfer decision-making, but it does allow us to better characterize the appropriateness of the transfer, as well as the level of care and resources required. Our results showed that patients with more severe scores had greater odds of having a procedure, staying longer, and being admitted. It is important for hand surgery specialists receiving transfers to have a categorization tool that catalogs the acuity of their consults. This scoring system allows specialists to communicate the associated care and resource requirements for each particular injury pattern. Therefore, future conversations about resource allocation and specialist utilization can be better informed, be more accurate, and have more impact.
      As the state’s designated center for isolated upper extremity injuries, we are in a unique position, as the receiving institution of transfers, to evaluate the quality of our transfer arrivals. Of all the patients who arrived via transfer from another institution, >35% were assigned a matrix score indicating that a transfer was unnecessary or inappropriate. The factors influencing transfer decisions have been widely studied. Although injury complexity is believed to be the primary reason, many studies have found that inappropriate transfers are also driven by reimbursement concerns or insurance status.
      • Bauer A.S.
      • Blazar P.E.
      • Earp B.E.
      • Louie D.L.
      • Pallin D.J.
      Characteristics of emergency department transfers for hand surgery consultation.
      • Petkovic D.
      • Wongworawat M.D.
      • Anderson S.R.
      Factors affecting appropriateness of interfacility transfer for hand injuries.
      • Eberlin K.R.
      • Hartzell T.L.
      • Kuo P.
      • Winograd J.
      • Day C.
      Patients transferred for emergency upper extremity evaluation: does insurance status matter?.
      • Daly C.A.
      • Cho B.H.
      • Desale S.
      • Aliu O.
      • Mete M.
      • Giladi A.M.
      The effects of Medicaid expansion on triage and regional transfer after upper-extremity trauma.
      • Crichlow R.J.
      • Zeni A.
      • Reveal G.
      • et al.
      Appropriateness of patient transfer with associated orthopaedic injuries to a Level I Trauma Center.
      • Goldfarb C.A.
      • Borrelli Jr., J.
      • Lu M.
      • Ricci W.M.
      A prospective evaluation of patients with isolated orthopedic injuries transferred to a Level I Trauma Center.
      ,
      • Vallier H.A.
      • Parker N.A.
      • Beddow M.E.
      Reasons for transfer to a level 1 trauma center and barriers to timely definitive fracture fixation.
      ,
      • Maroukis B.L.
      • Chung K.C.
      • MacEachern M.
      • Mahmoudi E.
      Hand trauma care in the United States: a literature review.
      The CHIM scoring system is not intended to standardize transfer protocols and does not account for the complexity of a transfer decision. For example, a category 4 patient (can likely be managed by an experienced emergency medicine physician) may still require transfer if someone with the required skill set is not available at an outside facility. Such a transfer would be clinically reasonable even if the injury is of lower severity and, in an ideal care setting, could have been treated without involving a hand specialist. Hand specialists can use the data from CHIM scoring to classify the care they provide, including patients that required a specialist and those that did not. The score has potential as a broader communication tool that can ultimately facilitate future planning and organizational discussions about triage protocols, resource allocation, and appropriate indications for specialist consultation. However, that would require validation of the system with less experienced providers, as well as evaluation of the reliability of the scoring system, which was not performed as part of the work presented here.
      Additionally, the CHIM score has not yet undergone a rigorous prospective validation. Instead, this study established value by clinically validating the score in a second subset of patient data.
      • Daly C.A.
      • Cho B.H.
      • Desale S.
      • Aliu O.
      • Mete M.
      • Giladi A.M.
      The effects of Medicaid expansion on triage and regional transfer after upper-extremity trauma.
      The results validate the CHIM score because it is significantly correlated with important metrics of provider and hospital burdens including LOS, admission, and need for a procedure. By demonstrating the clinical applicability across 2 different studies, the score can be more confidently used by call providers to categorize the various consults they manage.
      • Daly C.A.
      • Cho B.H.
      • Desale S.
      • Aliu O.
      • Mete M.
      • Giladi A.M.
      The effects of Medicaid expansion on triage and regional transfer after upper-extremity trauma.
      Further studies are needed to determine reliability of the scoring system across hand specialists and with nonspecialist providers before using it for broader triage or transfer purposes. It is this reliability aspect that will be critical to any broader system implementation or any future use in decision-making, rather than a decision analysis as we have performed here.
      As a preliminary study of a new scoring system, there are a number of inherent limitations. Despite the large sample size, the generalizability of our findings could be limited because most patients came from the same region and presented to 1 institution. Our findings may not be applicable to other hospitals or reproducible in other settings because we always have access to an in-house team of hand surgery specialists to assign scores. Because patients are scored by the providers who make clinical decisions, this could introduce bias as well. This classification system by necessity relies on human evaluation, so it has a degree of subjectivity and inter-observer variation. The score is ultimately verified by fellowship-trained hand surgeons who are best suited to make distinctions. However, we do not know whether the score was changed by the hand specialist or whether there were differences between specialists. Future work is needed to evaluate the interrater reliability of the scoring system. In addition, since the score is logged according to the most severe injury, rather than creating a composite score, the hand surgeon determines how to classify patients who present with multiple injury components, taking the entirety of the patient presentation into account when determining case complexity. The retrospective nature of the study design can only establish associations between the CHIM score and the care required. Finally, the current study evaluated the initial hospital episode but did not include long-term functional outcomes. Whether linking the CHIM score to severity provides unique insights into long-term outcomes is an area of future study.
      Regionalized trauma centers report overall better care outcomes, but it is unclear whether the transfer system is as effective for patients with isolated upper extremity pathologies.
      • MacKenzie E.J.
      • Rivara F.P.
      • Jurkovich G.J.
      • et al.
      A national evaluation of the effect of trauma-center care on mortality.
      ,
      • MacKenzie E.J.
      • Weir S.
      • Rivara F.P.
      • et al.
      The value of trauma center care.
      In addition, inappropriate transfers can place an undue burden on the patient, specialist, and institution. Given the lack of comparative metrics for upper extremity injuries, we introduced the CHIM score to evaluate upper extremity injury acuity from the specialist perspective. The scoring system allows hand specialists to catalog their consults, demonstrate the degree to which the care they are being asked to provide might be distributed elsewhere in a health system, and communicate the associated resource requirements. Through future prospective validation studies and reliability studies, the CHIM score could ultimately have broader impacts on triage and transfer protocols, resource allocation, hand surgery service line support, and overall quality of patient care.

      Appendix A

      Table E1CHIM Score Anatomy Locations and Severity Descriptions
      Anatomy Classification12345
      AHand and wrist fractureComplex fractures of the hand and wrist, including but not limited to: open fractures, multiple adjacent fractures or dislocations of the digits, carpal fracture or fracture-dislocation patterns, fractures with bone loss.Moderately complex fractures of the hand and wrist, including but not limited to: complicated fractures or “complex” dislocations, reducible but unstable wrist or hand fractures, comminuted fractures, and most open fractures.Cases of sufficient complexity that would be expected to have enhanced outcomes when treated by specialists, including but not limited to: displaced fractures or challenging dislocations of the metacarpals or phalanges, scaphoid fractures, isolated but potentially destabilizing injuries of the wrist ligaments.Relatively straightforward hand and wrist fractures or dislocations, including but not limited to: reducible PIP or MP dislocations that remain stable, minimally angulated fractures of the tubular bones of the hand.Hand and wrist fractures of a minor complexity that require only orthosis fabrication or observation: incomplete or minimally displaced fractures of the tubular bones, triquetral avulsion fractures, minor tuft fractures of the P3 associated with distal tip injuries.
      BForearm and elbow fractureComplex fractures of the forearm and elbow, including but not limited to: open fractures with tissue loss, irreducible fracture dislocations about the wrist or elbow, fractures and dislocations associated with nerve or vessel injury, fractures associated with evolving compartment syndrome.Moderately complex fractures of the forearm and wrist, including but not limited to: complicated fractures of the distal radius, forearm, and elbow. Multiple fractures of the forearm and wrist in combination. Irreducible fractures of the elbow, elbow dislocations associated with the radial head and coronoid fractures, some open injuries, or those fractures associated with possible compartment syndrome. Galeazzi and Monteggia–type fractures of the forearm.Cases of sufficient complexity that would be expected to have enhanced outcomes when treated by specialists, including but not limited to: displaced fractures of the distal radius or radial head, almost any fracture of the ulna with the exception of the styloid, fractures and dislocations affecting the DRUJ, challenging elbow dislocations that have been reduced but remain only provisionally stable when splinted.Relatively straightforward forearm and elbow fractures or dislocations, including but not limited to: reducible distal radius fractures that remain stable in an orthosis, suspected elbow subluxation/dislocation that remains stable with no decrement in range of motion or mechanical symptoms.Forearm and elbow fractures of a minor complexity that require only orthosis fabrication or observation: incomplete or minimally displaced fractures of the radial head or distal radius, “torus” fractures of the radius in a child.
      CComplete/ partial amputationMost patients with multiple amputations of the finger or amputations of the hand, forearm, or arm sustained as an isolated injury.Most patients with isolated amputations of the finger or amputations of the hand, forearm, or arm sustained as an isolated injury.Most patients with multiple amputations of at least 1 salvageable part. Soft tissue injuries in which perfusion of the distal tissue is questionable or believed to be inadequate to sustain viability. Most amputations in the child in which either replantation/revascularization or advanced techniques in soft tissue management may enhance the long-term outcome.Relatively straightforward injuries in which the patient has sustained tissue loss. Typically, these will be distal injuries, like a tip crush or amputation where minimal shortening and closure would be indicated. Even many single-digit amputations that may not be candidates for replantation may not require transport to a hand surgery specialty center.Injuries associated with minor tissue loss that would not be candidates for replantation of the amputated part. Examples include tangential or distal skin loss from the finger tip.
      DNerve/vessel injuryMost patients with open injuries in regions in which major arterial or nerve injuries are highly suspected and are accompanied by loss of perfusion and/or nerve function. Limb-threatening injuries in which isolated or multiple injuries to the vascular tree have been sustained or those conditions in which a profound change in perfusion has been observed and documented.Most patients with open injuries associated with difficult-to-control arterial bleeding that fails to cease with pressure-dressing application. Open injuries that are associated with a change in perfusion status. Lacerations which are thought to affect the brachial artery or both the radial and ulnar arteries. Lacerations of 1 of the 3 major nerves of the upper extremity with predictable sensory and motor loss.Open injuries in the region of digital vessels or radial or ulnar nerves with associated bleeding that is difficult to control, but is associated with good distal perfusion. Likewise, open injuries that present with an equivocal sensory examination or frank anesthesia in an identifiable nerve distribution.Relatively straightforward injuries in which the patient has sustained a laceration with associated arterial or venous bleeding that ceases with brief application of pressure. Additionally, any laceration or crushing injury in the region of a vessel or nerve that still presents with unequivocal distal perfusion, even with temporary or equivocal nerve embarrassment.Almost any closed injury with suspected nerve or vessel dysfunction in a patient with adequate perfusion of the distal parts.
      ESoft tissue traumaComplex soft tissue injuries that may present with extensive, multiple, or circumferential tissue losses of the muscle, nerve, and vessel. Perfusion is likely compromised and the need for sophisticated handling of the deep tissues is required. Skin coverage would likely require distant coverage strategies or delayed/staged coverage approaches. Even in cases in which the distal elements are relatively spared, the extent of a forearm soft tissue injury may cause the surgeon to contemplate amputation.Moderately complex soft tissue injuries of either the flexor or extensor surfaces that present with more extensive damage to tissues below the level of the muscle fascia, and likely includes direct injury to nerves and vessels, although perfusion is still thought to be adequate. The extent of the wounds may require primary or secondary reconstruction of the motor units and skin coverage may require either regional or distant coverage strategies.Injuries of sufficient complexity that present with tissue injury beneath the level of the muscle fascia. Although perfusion is adequate, motor function is compromised by either nerve embarrassment or mechanical injury to motor units. Primary wound closure may be challenging. Regional coverage strategies or skin grafting may need to be employed.Relatively straightforward soft tissue injuries of the extensor or flexor surfaces that still present with adequate perfusion and intact nerve function. The size of the wound or its orientation make the surgical handling more challenging, but primary closure or healing by secondary intention is thought to be compatible with a good result.Minor soft tissue injuries of the extensor, or even flexor surfaces of the hand and/or forearm that are not associated with obvious nerve and vessel trauma and that can be closed primarily after minor debridement of the wound edges.
      FInfectionComplex soft tissue, intra-articular, or bone infections that are associated with significant soft tissue destruction. Suspected or evolving cases of necrotizing fasciitis.Established infections of the hand, wrist, or forearm that present with significant collections of purulent material that may compromise adjacent or distal tissues. Intra-articular infections of the wrist joint. Ascending, fulminating, or rapidly spreading infections about the hand or forearm. Unusual infections like those suspected to be the result of marine exposures.Infections of sufficient complexity that present with abscesses beneath the level of muscle fascia. Suppurative flexor tenosynovitis that has progressed to a significant extent or become associated with embarrassment of the perfusion or sensation to the finger.Relatively straightforward soft tissue infections about the nail bed or distal tuft (felons) that are isolated and contained. Minor infections at the site of open injuries that do not spread deeper than the muscle fascia. Some recognizable abscess development patterns like “collar button” abscesses.Minor soft tissue infections that are mainly or solely confined to superficial tissues, like cellulitis. Most distal infections, like paronychia.
      GThermal injuryComplex burn injuries that may involve all upper extremity tissue, including tendon and bone. Depth and/or surface area burned is extensive, yet burns remain isolated to the hand and upper extremity. Burn injury is extensive enough that amputation is a possible or likely outcome.Isolated upper extremity burns that require immediate operative intervention in the form of tangential excision and grafting escharotomy, compartment release, joint pinning, etc. Possible involvement of nerves and vessels can complicate treatment, but viability of the hand/forearm is not necessarily in question.Burns of the hand and/or forearm that are of significant depth and/or surface area as to potentially require early operative intervention. Burns remain isolated to the upper extremity and do not cause significant systemic compromise.Moderate burns or frostbite injuries requiring more extensive local care, but typically not requiring formal operative intervention (larger superficial second-degree or some small third-degree burns). The extent of the injury is expanded, but is still small enough as to not cause significant systemic problems.Minor burns or frostbite injuries requiring only local care (first-degree or superficial second-degree burns). Extent of the injury is isolated to a focal location and is a small percentage of the total body surface area.
      HPressure pathologyClinically manifested compartment syndrome, with either/both clinically suspected and/or documented pressure elevations. The compartment pressure elevation may be accompanied by either nerve or vessel compromise. High-pressure injection injuries with agents that have additional chemical irritation or toxicity. High-pressure injection injuries >7,000 psi. Chemotherapeutic agents that cause increased pressure or local tissue reactions.Symptoms consistent with compartment syndrome of the hand and/or forearm, even without specific changes in perfusion or nerve function. High-pressure injection injuries <7,000 psi. Selected chemotherapeutic agents that cause increased pressure or local tissue reactions.Relatively severe crush injuries that result in significant swelling and “tenseness” of the tissues of the hand and forearm. Pain out of proportion to magnitude of trauma. Compartment pressure measurements in the “borderline” high range or may be evolving. Most high-pressure injection injuries.Moderate crush injuries or trauma that are associated with modest to moderate swelling. Pain not out of proportion to the magnitude of trauma. No evolving nerve deficits or escalation of discomfort. Can be managed with orthosis fabrication and pain medication.Minor crush injuries that do not appear to be associated with initial or evolving swelling or compromise of the tissue or alteration in the compartment pressures or nerve function.
      CHIM, Curtis Hand Injury Matrix; DRUJ, distal radioulnar joint; MP, metacarpophalangeal; PIP, proximal interphalangeal.

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