Orthopedics

Feature Article 

Incidence of and Risk Factors for Knee Collateral Ligament Injuries With Proximal Tibia Fractures: A Study of 32,441 Patients

Andre M. Samuel, MD; Pablo J. Diaz-Collado, MD; Lauren K. Szolomayer, MD; Daniel H. Wiznia, MD; Wayne W. Chan, MD; Adam M. Lukasiewicz, MD, MSc; Bryce A. Basques, MD, MHS; Daniel D. Bohl, MD, MPH; Jonathan N. Grauer, MD

Abstract

Proximal tibia fractures are associated with concurrent collateral ligament injuries. Failure to recognize these injuries may lead to chronic knee instability. The purpose of this study was to identify risk factors for concurrent collateral ligament injuries with proximal tibia fractures and their association with inpatient outcomes. A total of 32,441 patients with proximal tibia fractures were identified in the 2011–2012 National Trauma Data Bank. A total of 1445 (4.5%) had collateral ligament injuries, 794 (2.4%) had injuries to both collateral ligaments, 456 (1.4%) had a medial collateral ligament injury only, and 195 (0.6%) had a lateral collateral ligament injury only. On multivariate analysis, risk factors found to be associated with collateral ligament injuries included distal femur fracture (odds ratio, 2.1), pedestrian struck by motor vehicle (odds ratio, 2.0), obesity (odds ratio, 1.6), young age (odds ratio, 1.9 for 18 to 29 years vs 40 to 49 years), motorcycle accident (odds ratio, 1.5), and Injury Severity Score of 20 or higher (odds ratio, 1.4). In addition, patients with simultaneous injuries to both collateral ligaments had higher odds of inpatient adverse events (odds ratio, 1.51) and longer hospital stay (mean, 2.27 days longer). The risk factors reported by this study can be used to identify patients with proximal tibia fractures who may warrant more careful and thorough evaluation and imaging of their knee collateral ligaments. [Orthopedics. 2018; 41(2):e268–e276.]

Abstract

Proximal tibia fractures are associated with concurrent collateral ligament injuries. Failure to recognize these injuries may lead to chronic knee instability. The purpose of this study was to identify risk factors for concurrent collateral ligament injuries with proximal tibia fractures and their association with inpatient outcomes. A total of 32,441 patients with proximal tibia fractures were identified in the 2011–2012 National Trauma Data Bank. A total of 1445 (4.5%) had collateral ligament injuries, 794 (2.4%) had injuries to both collateral ligaments, 456 (1.4%) had a medial collateral ligament injury only, and 195 (0.6%) had a lateral collateral ligament injury only. On multivariate analysis, risk factors found to be associated with collateral ligament injuries included distal femur fracture (odds ratio, 2.1), pedestrian struck by motor vehicle (odds ratio, 2.0), obesity (odds ratio, 1.6), young age (odds ratio, 1.9 for 18 to 29 years vs 40 to 49 years), motorcycle accident (odds ratio, 1.5), and Injury Severity Score of 20 or higher (odds ratio, 1.4). In addition, patients with simultaneous injuries to both collateral ligaments had higher odds of inpatient adverse events (odds ratio, 1.51) and longer hospital stay (mean, 2.27 days longer). The risk factors reported by this study can be used to identify patients with proximal tibia fractures who may warrant more careful and thorough evaluation and imaging of their knee collateral ligaments. [Orthopedics. 2018; 41(2):e268–e276.]

Proximal tibia fractures are common, typically high-energy injuries that are associated with significant damage to the local soft tissue structures of the knee.1–4 Previous studies have had mixed results regarding the rate of concurrent collateral ligament injuries, with reports of medial collateral ligament (MCL) injuries ranging from 3% to 25% and lateral collateral ligament (LCL) injuries ranging from 3% to 10%.1,5,6 One study reported rates of concurrent collateral ligament injuries as high as 70% when including partial tears.7 The wide range of percentages reported is due to the relatively small sample in each study. In addition, most of these studies used a sample of traumatic tibial plateau fractures that met operative indications and then further evaluated with magnetic resonance imaging2,4,5,7 or arthroscopic examination,1,7 so they identified many injuries that would be routinely missed. Thus, in the current study, the authors examined a large national cohort of patients to identify the incidence of proximal tibia fractures with concurrent collateral ligament injuries. Doing so enables a determination of the incidence of collateral ligament injuries with tibial plateau fractures and better identifies the risk factors for sustaining these injuries. These risk factors should help in determining which patients may benefit from additional physical examination or imaging to elucidate the extent of soft tissue injuries with the proximal tibia fracture.

Collateral ligament insufficiency may be easily missed in the acute trauma setting,8 as more emergent injuries often take priority, and fractures make ligamentous examination difficult. However, delayed or missed treatment of collateral ligament injuries may lead to long-term knee instability and poor patient-reported outcomes.9–11 This long-term effect makes the identification of risk factors for concurrent collateral ligament injuries in patients with proximal tibia fractures important. Clinicians should be able to recognize patients for whom further evaluation of ligamentous damage may be warranted via physical examination or imaging or during surgery.

It is unknown whether patients who sustain proximal tibia fractures with concurrent collateral ligament injuries differ in terms of patient and injury characteristics from patients without associated collateral ligament injuries. Given these gaps in current knowledge, this study used a national cohort of patients from the American College of Surgeons National Trauma Data Bank (NTDB) to compare proximal tibia fracture patients with and without collateral ligament injury. Because this significant injury combination is relatively rare, in-depth study is difficult for the individual practitioner, the individual institution, or even the multi-institution study group. Therefore, studying a large national cohort is an ideal approach to quantifying these injuries and assessing the patient groups who sustain them.

The purpose of this study was to identify the incidence, injury characteristics, risk factors, and inpatient outcomes of patients with proximal tibia fractures and concurrent collateral ligament injuries. The authors hypothesized that concurrent collateral ligament injuries in patients with proximal tibia fractures are not as common as some previous studies reported, but that they are likely more frequent in severely and multiply injured patients. This patient population may be more at risk of having these injuries missed. Instability as a result of collateral ligament injury has been identified as a cause of poor outcomes in proximal tibia fractures.10

Materials and Methods

The NTDB Research Data Set for admission years 2011 and 2012 was used for this study. The NTDB is the largest national database of trauma patients, containing more than 1.6 million cases from more than 900 level I to IV trauma centers during years 2011 and 2012.12 Although all data in the NTDB are de-identified, the authors obtained a waiver for this study from the human investigations committee of their institution.

All patients with proximal tibia fractures were identified in the NTDB using International Classification of Diseases, Ninth Revision (ICD-9) diagnosis codes 823.00, 823.01, 823.10, and 823.12, representing closed fractures of the proximal tibia. Open fractures were excluded from this study because they may inaccurately skew the data for length of stay (LOS) and in-house complications, given that patients may need multiple trips to the operating room for serial debridement, wound coverage, or infections. The status of patients' collateral ligaments was then determined using the presence vs absence of ICD-9 diagnosis codes (844.1—MCL; 844.0—LCL; 836.50–836.69—complete knee dislocation). Pediatric patients (younger than 18 years) were also excluded from the study population.

Associations of collateral ligament injures with sex, age, Charlson Comorbidity Index (CCI), and 8 specific comorbidities (alcoholism, cancer, chronic respiratory disease, congestive heart failure, coronary artery disease, diabetes mellitus, hypertension requiring medication, and obesity) were analyzed in this study. These comorbidities were identified using NTDB-specific data elements, obtained via chart abstraction by local trauma data registrars. Mechanism of injury was determined using ICD-9 e-codes reported in the NTDB. Injury Severity Score (ISS) is directly reported in the NTDB. Associated injuries were also determined based on ICD-9 codes (Table 1).

Codesa Used for Characterization of Associated Injuries and Mechanisms of Injuries

Table 1:

Codes Used for Characterization of Associated Injuries and Mechanisms of Injuries

A modified CCI13 was calculated to summarize patient comorbidities; however, this was not used in the multivariate analysis because it correlated with age and the individual comorbidities being studied in this analysis. Computation of the modified CCI is detailed in Table 2.

Comparison of Modified Charlson Comorbidity Index With Original

Table 2:

Comparison of Modified Charlson Comorbidity Index With Original

Inpatient adverse events are reported in the NTDB using specific chart-reviewed variables. Aggregate surrogate variables of serious inpatient adverse events (SAEs), minor inpatient adverse events (MAEs), and any inpatient adverse events (AAEs) were then created. Serious inpatient adverse events include acute respiratory distress syndrome, cardiac arrest, death, myocardial infarction, severe sepsis, stroke, thromboembolic events, and unplanned return to the operating room. Minor inpatient adverse events include acute kidney injury, alcohol or drug withdrawal, bloodstream infection, compartment syndrome, decubitus ulcer, osteomyelitis, pneumonia, surgical site infection, unplanned intubation, unplanned return to the intensive care unit, and urinary tract infection. Total hospital LOS was also analyzed as an outcome variable.

Sex, age, CCI, comorbidities, mechanism of injury, ISS, and associated injuries were compared between patients with and patients without MCL or LCL injuries using Pearson's chi-square test. Multivariate logistic regression was used to identify associated patient characteristics for those with collateral ligament injury and proximal tibia fractures. Obesity was the only comorbidity associated with collateral ligament injuries on bivariate analysis. The following variables were included in the multivariate analysis: sex, age, obesity, mechanism of injury, ISS, and specific other lower extremity fractures, including proximal, midshaft, and distal femur fractures; midshaft tibia/fibula fractures; and distal tibia/fibula fractures. Continuous variables, age and ISS, were converted into discrete categorical variables for this analysis. Finally, multivariate logistic regression was used to determine the association of collateral ligament injury with SAEs, MAEs, AAEs, and hospital LOS after controlling for both CCI and ISS.

All statistical analyses were conducted using Stata version 13.0 statistical software (StataCorp LP, College Station, Texas). All tests were 2-tailed, and the Bonferroni correction was used to account for the multiple statistical tests performed. Based on 18 different hypotheses tested, the level of statistical significance was set at α=0.005.

Results

A total of 32,441 patients with proximal tibia fractures were identified and met inclusion criteria. Of the included patients, 1445 (4.5%) had collateral ligament injuries recorded (Table 3). Injuries to both the MCL and the LCL were most common (2.4%), followed by MCL only (1.4%) and LCL only (0.6%). Of the patients with plateau fractures, 2.2% had documented knee dislocation diagnoses. Of the 1445 patients with collateral ligament injuries, 21% underwent a collateral ligament repair during their initial hospitalization. Although ICD-9 coding does not allow for anterior cruciate ligament injuries to be distinguished from posterior cruciate ligament injuries, as a comparison, the authors found that 3.2% of all tibial plateau fractures had a cruciate ligament injury; 1.8% of the patients without collateral ligament injuries and 30.5% of those with collateral ligament injuries also sustained a cruciate ligament injury.

Incidence of Collateral Ligament Injuries With Proximal Tibia Fractures (n=32,441)

Table 3:

Incidence of Collateral Ligament Injuries With Proximal Tibia Fractures (n=32,441)

Characteristics differed between patients with and patients without collateral ligament injuries (Table 4). Specifically, patients with collateral ligament injuries were more likely to be male, younger (mean age, 41 vs 50 years), and obese. They also had a lower CCI (1.1 vs 2.0). The difference between 1.1 and 2.0 on the CCI scale is nearly equivalent to a single additional comorbidity such as congestive heart failure, myocardial infarction, or chronic obstructive pulmonary disease or 10 years in age. This is clinically relevant in this study, where approximately two-thirds of the population had a CCI of 0 to 2. With increasing age, patients were less likely to suffer collateral ligament injury.

Comparison of Patient Demographics and Comorbidities

Table 4:

Comparison of Patient Demographics and Comorbidities

Injury characteristics also differed between patients with and patients without collateral ligament injuries (Table 5). Patients with collateral ligament injuries were more likely to have higher-energy mechanisms of injury (P<.001). The most common mechanism of injury for both patients with and patients without collateral ligament injuries was motor vehicle accident. Patients with collateral ligament injuries were also more likely to have a higher overall ISS (mean, 14 vs 11; P<.001) and higher rates of all broad categories of associated injuries (P<.001).

Comparison of Injury Characteristics

Table 5:

Comparison of Injury Characteristics

On multivariate analysis, increasing age was associated with decreasing risk of collateral ligament injury (P≤.001; Table 6). Obesity (odds ratio, 1.6; 95% confidence interval, 1.3–1.9) and ISS of 20 or higher (odds ratio, 1.4; 95% confidence interval, 1.2–1.7) were associated with increased risk of collateral ligament injury. Of the associated lower extremity fractures analyzed, only distal femur fracture was significantly associated with greater risk of collateral ligament injury (odds ratio, 2.1; 95% confidence interval, 1.8–2.5). Pedestrians struck by a motor vehicle (odds ratio, 2.0; 95% confidence interval, 1.7–2.3) and motorcycle accidents (odds ratio, 1.5; 95% confidence interval, 1.3–1.8) were more likely to have collateral ligament injuries.

Multivariate Analysis of Risk Factors for Collateral Ligament Injuries With Proximal Tibia Fracture

Table 6:

Multivariate Analysis of Risk Factors for Collateral Ligament Injuries With Proximal Tibia Fracture

Inpatient outcomes were different between patients with and patients without collateral ligament injuries (Table 7). After controlling for CCI and ISS, simultaneous injury to both collateral ligaments was associated with increased odds of SAEs (odds ratio, 1.38; P=.015), MAEs (odds ratio, 1.58; P<.001), and AAEs (odds ratio, 1.51; P<.001) and an increased inpatient LOS of 2.27 days (P<.001). Isolated LCL injury was associated with a mean increased inpatient LOS of 1.95 days (P=.009). Isolated MCL injury was associated with lower odds of AAEs (odds ratio, 0.66; P=.007).

Association of Collateral Ligament Injuries With Short-term Outcomes

Table 7:

Association of Collateral Ligament Injuries With Short-term Outcomes

Discussion

Proximal tibia fractures are common high-energy injuries that have been associated with significant damage to local soft tissue structures, including the collateral ligaments of the knee.1,5,6 These ligament injuries are sometimes repaired or reconstructed in the acute setting.14 Early operative repair can improve patient-reported outcomes and may reduce the chance of subsequent knee instability.12 These injuries can often also be missed in the acute setting, as it is difficult to perform an effective ligamentous examination on a patient in pain, and they may not be identified in complex polytrauma patients. When these injuries are missed, patients may require additional surgical intervention at a later date because of knee instability.9,10 Therefore, identification of patients at greatest risk for collateral ligament injuries with proximal tibia fractures is necessary in the acute setting. The current authors identified the incidence, injury characteristics, risk factors, and inpatient outcomes of patients with proximal tibia fractures and concurrent collateral ligament injuries.

Of the 32,441 patients diagnosed with proximal tibia fractures, 1445 had concurrent collateral ligament injuries. This incidence of 4.5% measured in a large patient cohort is similar to some previously reported rates of collateral ligament injury.1,5,6,15,16 Other studies that have reported significantly higher rates of collateral ligament injury, up to 70%, have either included partial ligament tears7 or investigated smaller cohorts.1,5 This finding may indicate that a significant number of ligamentous injuries are missed in the initial hospitalization, as many of the studies with significantly higher rates of collateral ligament injuries also performed magnetic resonance imaging for every patient.

Two high-energy mechanisms of injury were identified as significant risk factors for collateral ligament injury: motorcycle accidents and pedestrians struck by motor vehicles. This analysis also identified obese patients as being more likely to have concurrent collateral ligament injuries with proximal tibia fractures. Low-energy falls in the obese have previously been described as a unique mechanism of knee dislocation.17 One study reported 15 of 17 patients with complete disruption of one or both collateral ligaments.17 Higher mechanical loading of the joint at baseline and during injury likely contributes to the increased deforming forces on the ligaments. In addition, systemic inflammation, as seen in obesity and metabolic syndrome,18–20 may also result in weakened ligaments predisposed to rupture.

Even after controlling for ISS and mechanism of injury, increasing age was associated with decreased risk of collateral ligament injury. One previous study reported that the tensile strength of bone decreases with age in comparison with the soft tissues, shifting the injury sequelae to bony structures rather than the ligaments.8

The finding that concurrent proximal tibia with distal femur fractures were associated with collateral ligament injuries was surprising. To the authors' knowledge, this relationship has not been described in previous studies. With more than twice the odds of a collateral ligament injury, patients with concurrent proximal tibia and distal femur fractures would benefit from a thorough evaluation of collateral ligaments in the acute setting. In terms of physical examination for collateral ligament injuries with proximal tibia fractures, the authors suggest that the bony injuries be fixed first in order to perform a ligamentous examination once the bony structures are out to length and stable. In the emergency department, physical examination of the collateral ligaments is often limited by bony instability and pain. Physical examination may be performed intraoperatively under fluoroscopic guidance when the patient is under anesthesia and pain is no longer an issue. Varus and valgus stress examinations at 0° and 30° of knee flexion are the most accurate way to test the collateral ligaments and can be compared with examinations of the contralateral side.21 Patients should also be reexamined 6 weeks postoperatively to assess stability of cruciate and collateral knee ligaments.4

Patients who had injury to both collateral ligaments were found to have increased rates of inpatient adverse events and a longer LOS, even after controlling for injury severity and comorbidities. Patients with LCL-only injuries, which are often repaired or reconstructed acutely, were at increased risk of longer LOS, whereas those with MCL-only injuries, which are often managed nonoperatively, did not have longer LOS. Twenty-one percent of patients with any collateral ligament injury received surgery. The LOS may be driven, in part, by the need for operative treatment. It also may be affected by the ability to mobilize patients, the need for rehabilitation placement, and pain control.

The current study had several strengths compared with previous studies of the concurrence of collateral ligament injuries and proximal tibia fractures. This study represents the largest cohort of proximal tibia fracture patients with concurrent collateral ligament injuries reported. Previous studies included cohorts of up to 100 patients with concurrent tibial plateau and collateral ligament injuries by performing magnetic resonance imaging on a series of plateau injuries.4 Another study identified risk factors such as young age, obesity, concurrent distal femur fracture, and high-energy mechanism of injury (motorcycle accident, pedestrian struck by motor vehicle) for concurrent collateral ligament injuries with proximal tibia fractures.7 This can help guide providers in the acute setting in making sure that these patients are evaluated for potential collateral ligament injuries and avoiding missing these injuries, which can lead to poor outcomes later on.

A limitation of this study was the limited specificity of ICD-9 diagnosis codes. Within the ICD-9 system, further detail regarding the specific proximal tibia fracture types (eg, Schatzker or Moore classifications) cannot be described.22 Gardner et al2 showed that partial collateral ligament tears are more common than complete tears in tibial plateau fractures, except for the MCL in Schatzker IV, V, and VI fractures. In addition, LCL tears rarely occur in isolation from injuries to the other posterolateral corner structures of the knee, such as the popliteus tendon, popliteofibular ligament, iliotibial band, and biceps femoris tendon.23 However, injuries to these other structures are not identified through ICD-9 codes. Because of the association between LCL injury and posterolateral corner injuries, the authors can assume that identifying the LCL injury includes these other injuries as well, although this might not always be the case. There is also no record of whether ligamentous injuries were diagnosed through magnetic resonance imaging or examination under anesthesia; thus, there is no reference to grade and degree of ligament injury. A prospective study with a larger sample of proximal tibia fractures including the grade and degree of ligamentous injuries and the types of fractures would help elucidate injury patterns and their incidence, risk factors for the different patterns, surgical interventions, and, ultimately, outcomes. Although a prospective study like this is warranted to better characterize proximal tibia fractures with concurrent collateral ligament injuries, the current study provides a large retrospective analysis of these injuries on which prospective studies can be based. Finally, the authors did not include cruciate ligament injuries, as these are often managed in a delayed fashion and not in the acute setting. Additionally, it is not possible to distinguish between anterior cruciate ligament injuries and posterior cruciate ligament injuries in the database. The number of generic cruciate ligament injuries for plateau fracture with collateral vs without collateral was discussed as a general comparison.

Conclusion

Risk factors such as younger age, obesity, concurrent distal femur fracture, and high-energy mechanism (pedestrian struck by motor vehicle, motorcycle accident) can be used to identify patients with proximal tibia fractures who may warrant more careful and thorough evaluation of their knee collateral ligaments. Collateral ligament injuries, particularly LCL injury with proximal tibia fractures, are associated with increased LOS when controlling for other variables such as ISS, CCI, and age. Many collateral ligament injuries may be missed during initial hospitalization, as the authors' incidence was lower than that of some studies that included routine magnetic resonance imaging. Additional work is needed to determine the best method of evaluation and the best method of treatment of proximal tibia fractures to ensure that concurrent collateral ligament injury is identified and treated appropriately.

References

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  15. Scheerlinck T, Ng CS, Handelberg F, Casteleyn PP. Medium-term results of percutaneous, arthroscopically-assisted osteosynthesis of fractures of the tibial plateau. J Bone Joint Surg Br. 1998; 80(6):959–964. doi:10.1302/0301-620X.80B6.8687 [CrossRef]
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Codesa Used for Characterization of Associated Injuries and Mechanisms of Injuries

Associated InjuryCode
Head injury800.00–804.99, 850.00–854.19
Spinal injury805.00–805.59, 806.00–806.59, 952.00–952.29
Pelvic fracture808.00–808.99
Upper extremity fracture810.00–819.99, 828.0–828.1
Other lower extremity fracture820.00–828.1 (except 823.00–823.19)
  Proximal femur fracture820.00–820.99
  Femoral shaft fracture821.01, 821.11
  Distal femur fracture821.20–821.39
  Tibial/fibular shaft fracture823.20–823.39
  Distal tibia/fibula fracture824.00–824.99
Thoracic organ injury860.00–862.99
Abdominal organ injury863.00–868.99
External cause of injury
  MVA (motor vehicle occupant)800–809 (except 8XX.2), 810–825 (except 8XX.2, 8XX.3, 8XX.7), 829.0–829.9, 840.0–844.9, 929.0, 958.5, 988.5
  MVA (motorcyclist)810–825 (only 8XX.2 and 8XX.3)
  MVA (pedestrian)800–809 (only 8XX.2), 810–825 (only 8XX.7)

Comparison of Modified Charlson Comorbidity Index With Original

ComorbidityOriginal ScoringModified NTDB ScoringRationale
Myocardial infarction11
Congestive heart failure11
Peripheral vascular disease11
Cerebrovasular accident11
Dementia11
COPD1Not reported in NTDB
Respiratory disease1In lieu of COPD
Connective tissue disease1Not reported in NTDB
Pelvic ulcer disease1Not reported in NTDB
Diabetes uncomplicated11
Diabetes, end organ damage2Not reported in NTDB
Chronic kidney disease22
Hemiplegia2Not reported in NTDB
Functionally dependent status2In lieu of hemiplegia
Leukemia2Not reported in NTDB
Lymphoma2Not reported in NTDB
Solid tumor2Not reported in NTDB
Chemotherapy within 30 days2In lieu of other cancers
Malignant tumor66
Mild liver disease1Not reported in NTDB
Ascites1In lieu of mild liver disease
Severe liver disease3Not reported in NTDB
Esophageal varices3In lieu of severe liver disease
Cirrhosis3In lieu of severe liver disease
AIDS6Not reported in NTDB
Age >40 y11
Age >50 y11
Age >60 y11
Age >70 y11

Incidence of Collateral Ligament Injuries With Proximal Tibia Fractures (n=32,441)

InjuryNo.Percent of All Proximal Tibia Fractures
Proximal tibia fracture only30,99695.5
Proximal tibia fracture + collateral ligament injury14454.5
  Both collateral ligaments7942.4
  Medial collateral ligament only4561.4
  Lateral collateral ligament only1950.6
Knee dislocation7152.2

Comparison of Patient Demographics and Comorbidities

Characteristic (N=32,441 Patients)Proximal Tibia Fracture Only (N=30,996)Proximal Tibia Fracture + Collateral Ligament Injury (N=1445)


No.PercentNo.PercentP
Sex<.001a
  Male18,67260101971
  Female12,3244042629
Age, yMean=50Mean=41<.001a
  18–2944251441629
  30–3943181429220
  40–4958941929620
  50–5973102327119
  60–694818161118
  70–7925148453
  80+17176141
Charlson Comorbidity IndexMean=2.0Mean=1.1<.001a
  085322869148
  156911830121
  262092022916
  34314141148
  4370012785
  5+25508322
Comorbidity
  Hypertension85822825918<.001a
  Diabetes4001131047<.001a
  Alcoholism38471221415.007
  Chronic respiratory disease23388876.032
  Obesity218571319.004a
  Congestive heart failure729281<.001a
  Coronary artery disease4241151.289
  Cancer183140.124

Comparison of Injury Characteristics

Characteristic (N=32,441 Patients)Proximal Tibia Fracture Only (N=30,996)Proximal Tibia Fracture + Collateral Ligament Injury (N=1445)


No.PercentNo.PercentP
Mechanism of injury<.001a
  Fall97793225618
  Motor vehicle accident17,68057105373
    Motor vehicle driver87322842529
    Motorcyclist45511530121
    Pedestrian43971432723
    Other3537111369
Injury Severity ScoreMean=11Mean=14<.001a
  0–919,3816369748
  10–1966732141429
  20+49421633423
Associated injury
  Other lower extremity fracture12,2644066946<.001a
    Proximal femur fracture11624493.483
    Femoral shaft fracture15005785.335
    Distal femur fracture2203722616<.001a
    Tibial/fibular shaft fracture47191521915.943
    Distal tibia/fibula fracture287891188.151
  Upper extremity fracture66682236725<.001a
  Head injury57741938327<.001a
  Spinal injury44791427619<.001a
  Thoracic organ injury39871326919<.001a
  Pelvic fracture32821122816<.001a
  Abdominal organ injury2670919614<.001a

Multivariate Analysis of Risk Factors for Collateral Ligament Injuries With Proximal Tibia Fracture

Risk Factor for Collateral Ligament InjuryRate of Collateral Ligament Injury (4.5% Overall)Multivariate Odds Ratio (95% Confidence Interval)P
Sex
  Female3.3%Reference
  Male5.2%1.2 (1.0–1.3).020a
Age
  18–29 y8.6%1.9 (1.6–2.2)<.001a
  30–39 y6.3%1.4 (1.2–1.6)<.001a
  40–49 y4.8%Reference
  50–59 y3.6%0.7 (0.6–0.9).001a
  60–69 y2.3%0.5 (0.4–0.6)<.001a
  70–79 y1.8%0.4 (0.3–0.6)<.001a
  80+ y0.8%0.2 (0.1–0.3)<.001a
Comorbidity
  Obesity5.7%1.6 (1.3–1.9)<.001a
Mechanism of injury
  Non-MVA3.0%Reference
  MVA (motor vehicle occupant)4.6%1.1 (1.0–1.3).112
  MVA (motorcyclist)6.2%1.5 (1.3–1.8)<.001a
  MVA (pedestrian)6.9%2.0 (1.7–2.3)<.001a
Injury Severity Score
  0–93.5%Reference
  10–195.8%1.3 (1.2–1.5)<.001a
  20+6.3%1.4 (1.2–1.7)<.001a
Associated lower extremity injuries
  Proximal femur fracture4.1%0.8 (0.6–1.0).093
  Femoral shaft fracture4.9%0.7 (0.6–0.9).009
  Distal femur fracture9.3%2.1 (1.8–2.5)<.001a
  Tibial/fibular shaft fracture4.4%0.9 (0.7–1.0).063
  Distal tibia/fibula fracture3.9%0.8 (0.7–1.0).020

Association of Collateral Ligament Injuries With Short-term Outcomes

Collateral Ligament InjuriesMultivariate Effect Size (95% Confidence Interval)P
Length of stay (additional days)
  No collateral ligament injury0.00 (Reference)
  Medial collateral ligament0.09 (−0.88 to 1.06).859
  Lateral collateral ligament1.95 (0.48 to 3.42).009a
  Both collateral ligaments2.27 (1.53 to 3.01)<.001a
Serious adverse eventsb (odds ratio)
  No collateral ligament injury1.00 (Reference)
  Medial collateral ligament0.68 (0.45 to 1.03).068
  Lateral collateral ligament0.67 (0.35 to 1.25).207
  Both collateral ligaments1.38 (1.06 to 1.79).015a
Minor adverse eventsc (odds ratio)
  No collateral ligament injury1.00 (Reference)
  Medial collateral ligament0.89 (0.65 to 1.22).471
  Lateral collateral ligament1.32 (0.86 to 2.03).202
  Both collateral ligaments1.58 (1.28 to 1.95)<.001a
Any adverse events (odds ratio)
  No collateral ligament injury1.00 (Reference)
  Medial collateral ligament0.66 (0.48 to 0.89).007a
  Lateral collateral ligament1.16 (0.77 to 1.74).477
  Both collateral ligaments1.51 (1.24 to 1.83)<.001a
Authors

The authors are from the Department of Orthopaedic Surgery (AMS), Hospital for Special Surgery, New York, New York; the Department of Orthopaedics and Rehabilitation (PJD, LKS, DHW, WWC, AML, JNG), Yale School of Medicine, New Haven, Connecticut; and the Department of Orthopaedic Surgery (BAB, DDB), Rush University Medical Center, Chicago, Illinois.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Jonathan N. Grauer, MD, Department of Orthopaedics and Rehabilitation, Yale School of Medicine, 47 College St, New Haven, CT 06510 ( jonathan.grauer@yale.edu).

Received: May 22, 2017
Accepted: December 15, 2017
Posted Online: February 19, 2018

10.3928/01477447-20180213-03

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