Review of human supraspinatus tendon mechanics. Part I: fatigue damage accumulation and failure.

Repetitive stress injuries to the rotator cuff, and particularly the supraspinatus tendon (SST), are highly prevalent and debilitating. These injuries typically occur through the application of cyclic load below the threshold necessary to cause acute tears, leading to accumulation of incremental damage that exceeds the body's ability to heal, resulting in decreased mechanical strength and increased risk of frank rupture at lower loads. Consistent progression of fatigue damage across multiple model systems suggests a generalized tendon response to overuse. This finding may allow for interventions before gross injury of the SST occurs. Further research into the human SST response to fatigue loading is necessary to characterize the fatigue life of the tendon, which will help determine the frequency, duration, and magnitude of load spectra the SST may experience before injury. Future studies may allow in vivo SST strain analysis during specific activities, generation of a human SST stress-cycle curve, and characterization of damage and repair related to repetitive tasks.

Review of human supraspinatus tendon mechanics. Part II: tendon healing response and characterization of tendon health.

Overuse injuries of the rotator cuff, particularly of the supraspinatus tendon (SST), are highly prevalent and debilitating in work, sport, and daily activities. Despite the clinical significance of these injuries, there remains a large degree of uncertainty regarding the pathophysiology of injury, optimal methods of nonoperative and operative repair, and how to adequately assess tendon injury and healing. The tendon response to fatigue damage resulting from overuse is different from that of acute rupture and results in either an adaptive (healing) or a maladaptive (degenerative) response. Factors associated with the degenerative response include increasing age, smoking, hypercholesterolemia, biological sex (variable by tendon), diabetes mellitus, and excessive load post fatigue damage. After injury, the average healing rate of tendon is approximately 1% per day and may be significantly influenced by biologic sex (females have lower collagen synthesis rates) and excessive load after damage. Although magnetic resonance imaging (MRI) is considered the gold standard in assessing acute tears as well as tendinopathic change in the SST, ultrasonography has proven to be a valuable tool to measure tendinopathic change in real time. Ultrasonography can determine multiple mechanical and structural parameters of the SST that are altered in fatigue loading. Thus, ultrasonography may be utilized to understand how these parameters change in response to SST overuse, and may aid in determining the activity level that places the SST at greater risk of rupture.

Risk factors for failure of limb salvage among veterans with foot ulcers.

BACKGROUND: There is limited available information to guide early discussions involving limb salvage for patients with non-traumatic foot ulcers. We hypothesized patient, wound and treatment factors identifiable at initial operative treatment would be associated with failure of attempted limb salvage. METHODS: We retrospectively assessed United States military veterans treated operatively for non-traumatic foot ulcers at a Veteran's Administration (VA) hospital from 2008 to 2018. Cox proportional hazard analysis assessed for independent associations with eventual above ankle amputation. RESULTS: Limb salvage failed for 52 of 461 patients (11.0%). Univariable associations included initial wound area ≥1 cm (p < .001), immediate TMA (p < .001), diagnosis of PVD (p < .001) or diabetes (p = .005), nonpalpable pulse (p = .006), CKD (p = .023), creatine ≥ 1.5 (p = .004), and HgA1c ≥ 6.2 (p < .001). Independent associations consisted of initial wound area ≥1 cm (HR 6.0, 95% CI 1.4-25.1, p = .014), immediate TMA (HR 3.5, 95% CI 1.9-6.4, p < .001), and PVD (HR 3.5, 95% CI 1.6-7.5, p = .001). When <2 risk factors were present, 99.1% and 96.8% retained their hindfoot at 5 and 10 years, respectively. However, this decreased to 87.3% and 80.1% with two risk factors and fell to 63.3% and 43.3% with three risk factors. CONCLUSION: Failure of limb salvage was increasingly likely as the number of identified independent risk factors increased. These results may assist in prognostication and shared decision making between patients and providers. LEVEL OF EVIDENCE: Prognostic, Level III.

Evaluation for septic arthritis of the native adult knee is aided by multivariable assessment.

INTRODUCTION: Evaluation of suspected septic arthritis of the native adult knee is a common diagnostic dilemma. Pre-aspirate criteria predictive of septic arthritis do not exist for the adult knee and investigations of aspiration results (cell count, differential, gram stain and crystal analysis) have been limited to univariate analyses. Given numerous clinical variables inform the risk of septic arthritis, multivariable analysis that incorporates all clinically available information is critical to allowing accurate decision-making. METHODS: We retrospectively identified 455 cases of potential septic arthritis of a native adult knee at a tertiary health system from 2012 to 2017, of which 281 underwent aspiration. We recorded demographics, comorbidities, history, exam, laboratory, and radiographic data. Among aspirated cases, we performed univariate analyses of all variables for association with septic arthritis followed by multivariable logistic regression analysis. RESULTS: Septic arthritis was confirmed in 61 of 281 patients who underwent aspiration. Independent associations of risk for septic arthritis included synovial fluid WBC ≥ 30,000 (Odds Ratio 90.8, 95% Confidence Interval 26.6-310.1, p < 0.001), bacteria reported on synovial fluid gram stain (OR 21.5, 95% CI 3.9-119.2, p < 0.001), duration of pain >2 days (OR 6.9, 95% CI. 2.3-20.9, p < 0.001), history of septic arthritis at any joint (OR 5.0, 95% CI 1.1-23.4, p = 0.039), clinical effusion (OR 4.8, 95% CI 1.2-20.0, p = 0.030). Independent associations protective against septic arthritis included presence of synovial fluid crystals (OR 0.1, 95% CI 0.1-0.4, p < 0.001). The multivariable model was highly accurate in discriminating between septic and aseptic cases (AUC = 0.942). A web-based tool was created to aid clinical decision-making. CONCLUSION: When evaluating for septic arthritis of a native adult knee, several independent associations were identified for variables related and unrelated to joint aspiration. The associated multivariable model discriminated very well between patients with and without septic arthritis, outperforming previous univariate assessments. A web-based tool was created that estimates the probability of septic arthritis based on this model. This may aid decision-making in complex clinical scenarios.

AP pelvis radiograph is insufficient for diagnosis of U-type sacral fractures.

PURPOSE: We investigated the sensitivity of a screening test for pelvic ring disruption, the AP pelvis radiograph, for clinically serious U-type sacral fractures which merit consultation with an orthopedic trauma specialist and may require transfer to a higher level of care. METHODS: Retrospective clinical cohort of 63 consecutive patients presenting with U-type sacral fractures at one level 1 trauma referral center from January 2006 through December 2019. The sensitivity of the first AP pelvis radiograph obtained on admission, interpreted without reference to antecedent or concomitant pelvis computed tomography (CT) by a radiologist and a panel of three blinded orthopedic traumatologists, was determined against a reference diagnosis made from review of all pelvis radiographs, CT images, operative reports, and clinical documentation. RESULTS: Sensitivity of AP pelvis radiograph for U-type sacral fractures was 2% as interpreted by a radiologist and mean 12% (range 5-27%) as interpreted by orthopedic traumatologists with poor inter-rater agreement (Fleiss' κ = 0.11). 94% of sacra were at obscured by radiographic artifact. CONCLUSION: The sensitivity of an AP pelvis radiograph is poor for U-type sacral fractures, whether interpreted by radiologists or orthopedic traumatologists. Pelvis CT should be considered as a screening test to rule out sacral fracture when the patient reports posterior pelvic pain, even if plain radiography demonstrates no injury or a minimally displaced pelvic ring disruption. LEVEL OF EVIDENCE: Diagnostic level III.

For Surgically Treated Geriatric Acetabular Fractures, Longer Duration between Admission and Surgery Is Associated with an Increase in Post-operative Complications: A Study Using the National Trauma Data Bank.

INTRODUCTION: The purpose of this study was to determine whether time from hospital admission to surgery is associated with inpatient complications and mortality for geriatric patients undergoing surgical treatment of acetabular fractures. METHODS: This was a retrospective cohort study using the National Trauma Data Bank from 2016 to 2018 of patients presenting to level I through IV trauma centers in the United States. All patients aged 60 years or older with acetabular fractures requiring surgical treatment were included. The main outcome measurements were inpatient mortality and complication rates. RESULTS: There were 6,036 patients who met inclusion criteria. The median age was 69 years (interquartile range 64-76 years). The odds of a complication increased by 7% for each additional day between hospital admission and surgery (multivariable regression OR 1.07, 95% CI = 1.04 to 1.10; P < 0.001). Complications were also associated with patient age (OR 1.05, 95% CI = 1.03 to 1.06; P < 0.001) and mCCI ≥ 5 (OR 2.52, 95% CI = 1.4 to 4.2; P = 0.001). Inpatient mortality was not associated with time to surgery (OR 0.97, 95% CI = 0.92 to 1.02; P = 0.30), but was associated with patient age (OR 1.07, 95% CI = 1.05 to 1.10; P < 0.001; P < 0.001) and mCCI ≥ 5 (OR 4.62, 95% CI = 2.31 to 8.50; P < 0.001). DISCUSSION: In this database study, time from hospital admission to surgery was associated with a notable increase in inpatient complications but not inpatient mortality after adjusting for potentially confounding variables while age and mCCI were associated with both mortality and complications. Additional research is needed to determine the relationship between time to surgery with longer term mortality and complications and to assess causality. LEVEL OF EVIDENCE: Prognostic Level III.

Stable Lateral Compression Pelvic Ring Injury Requiring Operative Treatment due to Bladder Impingement: A Case Report.

CASE: A 25-year-old man sustained a stable lateral compression Type I (LC I) pelvic ring injury upon missing the landing of a downhill ski jump. He presented with painful voiding from a displaced bony fragment, partially impaling the bladder wall. With operative fixation of the fracture and urologic co-management, the patient had excellent outcomes at 1-year follow-up. CONCLUSION: We describe a rare urologic injury in the setting of an LC I pelvic ring injury. In the setting of an otherwise stable pelvic ring injury, careful review of imaging, detailed clinical history, and physical examination remain critical to optimizing patient outcomes.

Immediate Fixation of Acetabular Fractures Through an Anterior Approach Does Not Increase Morbidity or Mortality.

INTRODUCTION: Acetabular fractures requiring an anterior approach have historically been delayed, allowing a stable clot to form before creating large surgical exposures. The purpose of this study was to determine whether immediate fixation of acetabular fractures within 24 hours using an anterior approach demonstrates notable difference in blood loss, length of stay (LOS), complications, or mortality compared with acetabular fractures treated after 24 hours. METHODS: Ninety-three patients were optimized for surgery within 24 hours of injury. Thirty-two patients underwent fixation within 24 hours using an anterior approach to the acetabulum. Demographics, hours from injury to operating room, fracture classification, embolization, surgical approach, intraoperative cell salvage use, Charlson Comorbidity Index, American Society of Anesthesiologists class, Injury Severity Score, and Abbreviated Chest Injury Score were recorded. Estimated blood loss, transfusions, intensive care unit stay, total hospital LOS, complications, and mortality rates were compared. RESULTS: No statistically significant differences were observed in fracture classification, blood loss, or intraoperative transfusions between the immediate and delayed fixation groups. Six patients in the delayed group (9.8%) returned to the operating room for a complication compared with one patient (3.1%) in the immediate group ( P = 0.42). Three patients in the delayed group (4.9%) developed a surgical site infection compared with none (0%) in the immediate group ( P = 0.55). The immediate group had an average LOS of 7 days compared with 11 days in the delayed fixation group ( P = 0.01). No notable differences were observed in 30- or 90-day mortality rates. DISCUSSION: Medically optimized patients with acetabular fractures who undergo immediate fixation through an anterior approach do not seem to have an associated increase in blood loss, transfusions, or mortality. Prompt surgical management may also be associated with a shorter preoperative and postoperative LOS. LEVEL OF EVIDENCE: Therapeutic level III.

Sagittal deformity of Garden type I and II geriatric femoral neck fractures is frequently misclassified by lateral radiographs.

The objective of this study was to determine the validity and inter-rater reliability of radiographic assessment of sagittal deformity of femoral neck fractures. Design: This is a retrospective cohort study. Setting: Level 1 trauma center. Patients/Participants: Thirty-one patients 65 years or older who sustained low-energy, Garden type I/II femoral neck fractures imaged with biplanar radiographs and either computed tomography or magnetic resonance imaging were included. Main Outcome Measurements: Preoperative sagittal tilt was measured on lateral radiographs and compared with the tilt identified on advanced imaging. Fractures were defined as "high-risk" if posterior tilt was ≥20 degrees or anterior tilt was >10 degrees. Results: Of 31 Garden type I/II femoral neck fractures, advanced imaging identified 10 high-risk fractures including 8 (25.8%) with posterior tilt ≥20 degrees and 2 (6.5%) with anterior tilt >10 degrees. Overall, there was no significant difference between sagittal tilt measured using lateral radiographs and advanced imaging (P = 0.84), and the 3 raters had good agreement between their measurements of sagittal tilt on lateral radiographs (interclass correlation coefficient 0.79, 95% confidence interval [0.65, 0.88], P < 0.01). However, for high-risk fractures, radiographic measurements from lateral radiographs alone resulted in greater variability and underestimation of tilt by 5.2 degrees (95% confidence interval [-18.68, 8.28]) when compared with computed tomography/magnetic resonance imaging. Owing to this underestimation of sagittal tilt, the raters misclassified high-risk fractures as "low-risk" in most cases (averaging 6.3 of 10, 63%, range 6 - 7) when using lateral radiographs while low-risk fractures were rarely misclassified as high-risk (averaging 1.7 of 21, 7.9%, range 1 - 3, P = 0.01). Conclusions: Lateral radiographs frequently lead surgeons to misclassify high-risk sagittal tilt of low-energy femoral neck fractures as low-risk. Further research is necessary to improve the assessment of sagittal plane deformity for these injuries. Level of Evidence: Level IV diagnostic study.

Bridge Plate Fixation of Distal Femur Fractures: Defining Deficient Radiographic Callus Formation and Its Associations.

OBJECTIVE: To determine whether deficient early callus formation can be defined objectively based on the association with an eventual nonunion and specific patient, injury, and treatment factors. METHODS: Final healing outcomes were documented for 160 distal femur fractures treated with locked bridge plate fixation. Radiographic callus was measured on postoperative radiographs until union or nonunion had been declared by the treating surgeon. Deficient callus was defined at 6 and 12 weeks based on associations with eventual nonunion through receiver-operator characteristic analysis. A previously described computational model estimated fracture site motion based on the construct used. Univariable and multivariable analyses then examined the association of patient, injury, and treatment factors with deficient callus formation. RESULTS: There were 26 nonunions. The medial callus area at 6 weeks <24.8 mm 2 was associated with nonunion (12 of 39, 30.8%) versus (12 of 109, 11.0%), P = 0.010. This association strengthened at 12 weeks with medial callus area <44.2 mm 2 more closely associated with nonunion (13 of 28, 46.4%) versus (11 of 120, 9.2%), P <0.001. Multivariable logistic regression analysis found limited initial longitudinal motion (OR 2.713 (1.12-6.60), P = 0.028)) and Charlson Comorbidity Index (1.362 (1.11-1.67), P = 0.003) were independently associated with deficient callus at 12 weeks. Open fracture, mechanism of injury, smoking, diabetes, plate material, bridge span, and shear were not significantly associated with deficient callus. CONCLUSION: Deficient callus at 6 and 12 weeks is associated with eventual nonunion, and such assessments may aid future research into distal femur fracture healing. Deficient callus formation was independently associated with limited initial longitudinal fracture site motion derived through computational modeling of the surgical construct but not more routinely discussed parameters such as plate material and bridge span. Given this, improved methods of in vivo assessment of fracture site motion are necessary to further our ability to optimize the mechanical environment for healing. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Clinical and Radiographic Predictors of Nonunion in Open Tibial Shaft Fractures.

Open fracture is a risk factor for nonunion of diaphyseal tibia fractures. Compared with closed injuries, there is a relative lack of scientific knowledge regarding the healing of open tibia fractures. The objective of this study was to investigate which patient, injury, and surgeon-related factors predict nonunion in open tibial shaft fractures. A cohort of 98 patients with 104 extra-articular open tibial shaft fractures (OTA/AO 41A2-3, 42A-C, and 43A) were treated surgically between 2007 and 2018 at a single level 1 trauma center and were retrospectively reviewed. Patients underwent irrigation and debridement followed by definitive intramedullary nailing or plate fixation. Patient, injury, and perioperative prognostic factors were analyzed as predictors of nonunion based on anteroposterior and lateral radiographs. The nonunion rate was 27.9% (n=29). There were 12 occurrences of deep infection (11.5%). The median follow-up was 14 months. High-energy mechanism of injury (hazard ratio [HR], 5.76), Gustilo-Anderson class IIIA injury (HR, 3.66), postoperative cortical continuity of 0% to 25% (HR, 2.90), early postoperative complication (HR, 4.20), and deep infection (HR, 2.25) were significant predictors of nonunion on univariable analysis (P<.05). On multivariable assessment, only high-energy mechanism of injury, Gustilo-Anderson class IIIA injury, and early postoperative complication reached significance as predictors of nonunion. These data also indicate that lack of cortical continuity is a significant univariable radiographic predictor of nonunion. This is potentially modifiable, may guide surgeons in selecting patients for early bone grafting procedures, and should be assessed carefully in this high-risk population. [Orthopedics. 2021;44(3):142-147.].

Distal Nail Target and Alignment of Distal Tibia Fractures.

OBJECTIVES: To assess the relationship between the distal nail target and postoperative alignment for distal tibia fractures treated with intramedullary nailing. DESIGN: Retrospective cohort study. SETTING: A single level 1 trauma center. PATIENTS/PARTICIPANTS: One hundred thirty distal tibia fractures treated with intramedullary nailing over a 10-year period. MAIN OUTCOME MEASUREMENTS: Malalignment >5 degrees. RESULTS: Thirty-eight cases (29.2%) of malalignment >5 degrees included valgus (19 cases, 14.6%), procurvatum (13 cases, 10.0%), recurvatum (1 case, 0.8%), and combined valgus with procurvatum (5 cases, 3.8%). Medially directed nails demonstrated relative valgus (mean lateral distal tibia angle 86.4 vs. 89.4 degrees, P < 0.01) and more frequent coronal malalignment (24 of 78, 30.8% vs. 0 of 52, 0%, P < 0.01). Anteriorly directed nails demonstrated relative procurvatum (mean anterior distal tibia angle 82.8 vs. 80.9 degrees, P < 0.01) and more frequent sagittal malalignment (15 of 78, 19.2% vs. 3 of 52, 5.8%, P = 0.03). Malalignment was less common for nails targeting the central or slightly posterolateral plafond (0 of 30, 0% vs. 38 of 100, 38%), P < 0.01. Multivariate analysis demonstrated the distal nail target (P = 0.03), fracture within 5 cm of the plafond (P = 0.01), as well as night and weekend surgery (P = 0.03) were all independently associated with malalignment. CONCLUSIONS: Alignment of distal tibia fractures is sensitive to both injury and treatment factors. Nails should be targeted centrally or slightly posterolaterally to minimize malalignment. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Far Cortical Locking Fixation of Distal Femur Fractures is Dominated by Shear at Clinically Relevant Bridge Spans.

OBJECTIVES: Far cortical locking (FCL) constructs have been shown to increase axial interfragmentary displacement while limiting shear and have been specifically recommended in the treatment of distal femur fractures. However, there is no available data regarding their mechanical behavior within the range of bridge spans typically used for comminuted distal femur fractures. This biomechanical study of distal femur locked plate fixation assessed 4 methods of diaphyseal fixation for associated axial and shear displacement at bridge spans typically used in clinical practice. METHODS: Distal femur locking plates were used to bridge simulated fractures in femur surrogates with 4 different methods of diaphyseal fixation (bicortical locking, bicortical nonlocking, near cortical locking, and FCL). Axial and shear displacement were assessed at 5 different bridge spans for each fixation method. RESULTS: Diaphyseal fixation type was associated with the amount of shear (P = 0.04), but not the amount of axial displacement (P = 0.39). Specifically, FCL constructs demonstrated greater shear than bicortical locking (median 4.57 vs. 2.94 mm, P = 0.02) and bicortical nonlocking (median 4.57 vs. 3.41 mm, P = 0.02) constructs. CONCLUSIONS: Unexpectedly, FCL constructs demonstrated greater shear than bicortical locking and nonlocking constructs and similar axial displacement for all fixation methods. Bridge span had a dominant effect on displacement that interacted negatively with more flexible FCL diaphyseal fixation. Potentially interactive construct features are best studied in concert. Given the complexity of these relationships, computational modeling will likely play an integral role in future mechanotransduction research.

Long Bone Union Accurately Predicted by Cortical Bridging within 4 Months.

BACKGROUND: Previous retrospective research found that the presence or absence of bridging callus within 4 months postoperatively discriminated accurately between eventual union and nonunion of fractures of the tibial shaft. However, there remains no consensus regarding early prognostication of long bone nonunion. We prospectively assessed the accuracy and reliability of the presence of any bridging callus within 4 months in a cohort that was expanded to include both tibial and femoral shaft fractures. METHODS: We identified 194 consecutive fractures of the shaft of the tibia (OTA/AO type 42-A, B, or C) and femur (OTA/AO type 32-A, B, or C) that were treated with intramedullary nailing. Exclusions for inadequate follow-up (55), extended delay prior to nailing (10), and skeletal immaturity (3) resulted in a study population of 126 fractures (56 tibiae and 70 femora) in 115 patients. Digital radiographs made between 3 and 4 months postoperatively were independently assessed by 3 orthopaedic traumatologists. The accuracy of assessment of the presence of any bridging callus, bicortical bridging, and tricortical bridging to predict union or nonunion was assessed with chi-square analysis and by interobserver reliability (kappa statistic). RESULTS: The nonunion rate was 4% (5 of 126 fractures). The presence of any bridging callus by 4 months accurately predicted union (121 of 122 fractures) and its absence predicted nonunion (4 of 4 fractures). There was 1 incorrect prediction of union for a fracture that failed to unite (p < 0.001). Bicortical or greater bridging predicted union when present (116 of 116 fractures) and nonunion when absent (5 of 10 fractures), incorrectly predicting that 5 healing fractures would go on to nonunion (p < 0.001). Tricortical or greater bridging predicted union when present (103 of 103 fractures) and nonunion when absent (5 of 23 fractures), incorrectly predicting that 18 healing fractures would go on to nonunion (p < 0.001). Interobserver reliability was calculated for any bridging (kappa value, 0.91), bicortical bridging (kappa value, 0.79), tricortical bridging (kappa value, 0.71), and the exact number of cortices bridged (kappa value, 0.67). CONCLUSIONS: The presence of any bridging callus within 4 months accurately predicts the final healing outcome for tibial and femoral shaft fractures treated with intramedullary nailing. This criterion is simple and reliable, and only standard radiographs are needed to make the determination. Basing the prognosis on the bridging of additional cortices risks overestimation of the nonunion rate and is associated with relatively poor reliability.

Any Cortical Bridging Predicts Healing of Supracondylar Femur Fractures After Treatment With Locked Plating.

OBJECTIVES: To determine the accuracy and reliability of radiographic cortical bridging criteria in predicting the final healing of supracondylar femur fractures after treatment with locked plating. DESIGN: Retrospective review. SETTING: Two Level 1 trauma centers. PATIENTS/PARTICIPANTS: Patients who presented with supracondylar femur fractures (OTA/AO 33A, C) and were treated with locking plate fixation between January 1, 2004, and January 1, 2011. The final study population included 82 fractures after excluding patients with open physes (n = 4), nondisplaced fractures (n = 4), early revision for technical failure (n = 4), or inadequate follow-up (n = 42). INTERVENTION: Distal femur locking plate fixation. MAIN OUTCOME MEASUREMENTS: Postoperative radiographs until final follow-up were assessed for cortical bridging at each cortex on anterior-posterior and lateral views. Images were analyzed independently by 3 orthopaedic traumatologists to allow for assessment of reliability. Final determination of union required both radiographic and clinical confirmation. RESULTS: Assessment for any cortical bridging was the earliest accurate predictor of final union (95.1% accuracy at 4 months postoperatively), compared with criteria requiring bicortical bridging (93.9% accuracy at 6 months) and tricortical bridging (78% accuracy at 21 months). Any cortical bridging demonstrated a higher interobserver reliability (kappa = 0.73) relative to bicortical (kappa = 0.27) or tricortical bridging (kappa = 0.5). CONCLUSIONS: Our results for plate fixation of supracondylar distal femur fractures mirror those previously described for intramedullary nailing of tibia shaft fractures. Any radiographic cortical bridging by 4 months postoperatively is an accurate and reliable predictor of final healing outcome after locking plate fixation of supracondylar femur fractures. Assessment for bicortical or tricortical bridging is less reliable and inaccurate during the first postoperative year. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Effect of Tranexamic Acid on Transfusion: A Randomized Clinical Trial in Acetabular Fracture Surgery.

OBJECTIVES: Given the increasing evidence that minimizing blood loss and limiting allogeneic transfusion can improve patient outcome, we are performing a randomized controlled trial of the use of tranexamic acid (TXA) during acetabular fracture surgery. DESIGN: Prospective, multicenter, and randomized. SETTING: Two level I trauma centers. PARTICIPANTS: Eighty-eight patients underwent randomization, with 42 assigned to the TXA group and 46 assigned to the placebo group. INTERVENTION: The use of TXA during acetabular fracture surgery. MAIN OUTCOME MEASUREMENTS: The primary outcome was allogeneic blood transfusion. Secondary outcomes consisted of estimate blood loss (EBL) and venous thromboembolism (VTE). RESULTS: The overall transfusion rate was 40.9% (36 of 88), and the average estimated blood loss was 635 mL. There were no significant differences between groups for transfusion incidence, number of units transfused, EBL, or incidence of VTE. There was no difference in transfusion rate for the TXA group (0.097). Transfusion was significantly more likely in cases with low preoperative hemoglobin levels, higher rates of intraoperative blood loss, and longer surgical times. CONCLUSIONS: There was no significant difference in transfusion rate, EBL, or VTE for TXA versus placebo. Any potential benefit seems to be overwhelmed by other factors, specifically preoperative anemia and surgical time, which are highly variable in trauma surgery. These findings do not support the routine use of TXA in the setting of open reduction and internal fixation of acetabular fractures. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Defining the Lower Limit of a "Critical Bone Defect" in Open Diaphyseal Tibial Fractures.

OBJECTIVES: To determine healing outcomes of open diaphyseal tibial shaft fractures treated with reamed intramedullary nailing (IMN) with a bone gap of 10-50 mm on ≥50% of the cortical circumference and to better define a "critical bone defect" based on healing outcome. DESIGN: Retrospective cohort study. PATIENTS: Forty patients, age 18-65, with open diaphyseal tibial fractures with a bone gap of 10-50 mm on ≥50% of the circumference as measured on standard anteroposterior and lateral postoperative radiographs treated with IMN. INTERVENTION: IMN of an open diaphyseal tibial fracture with a bone gap. SETTING: Level-1 trauma center. MAIN OUTCOME MEASUREMENTS: Healing outcomes, union or nonunion. RESULTS: Forty patients were analyzed. Twenty-one (52.5%) went on to nonunion and nineteen (47.5%) achieved union. Radiographic apparent bone gap (RABG) and infection were the only 2 covariates predicting nonunion outcome (P = 0.046 for infection). The RABG was determined by measuring the bone gap on each cortex and averaging over 4 cortices. Fractures achieving union had a RABG of 12 ± 1 mm versus 20 ± 2 mm in those going on to nonunion (P < 0.01). This remained significant when patients with infection were removed. Receiver operator characteristic analysis demonstrated that RABG was predictive of outcome (area under the curve of 0.79). A RABG of 25 mm was the statistically optimal threshold for prediction of healing outcome. CONCLUSIONS: Patients with open diaphyseal tibial fractures treated with IMN and a <25 mm RABG have a reasonable probability of achieving union without additional intervention, whereas those with larger gaps have a higher probability of nonunion. Research investigating interventions for RABGs should use a predictive threshold for defining a critical bone defect that is associated with greater than 50% risk of nonunion without supplementary treatment. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.