Limb Rotation in Lower Extremity Fractures.

Fractures of the tibia and femur are common. Rotation of the limb can affect the outcome of the injury, both in the immediate term and the long term. Because plain radiographs are two dimensional, rotation is hard to assess radiographically. As a result, rotational malalignment is common. It is important to provide technical tips on the assessment of rotation preoperatively, intraoperatively, and postoperatively. The goal is to better assess rotation so that deformity can be minimized. This applies to fractures of the tibia and femur. Even after careful treatment, rotational deformities can occur. When they are symptomatic, correction should be considered. Techniques for correction of malrotation of both tibial and femoral fractures are presented.

Axial Plane Deformity: How to Avoid It and How to Correct It.

Malreductions in the axial plane (ie, length and rotation) are common when managing long bone fractures. Careful attention to detail during the initial treatment can prevent these malreductions. Various fluoroscopy-based techniques exist for the prevention of malrotation and limb-length discrepancy during surgery for fracture. If malreductions do occur, a systematic clinical and radiographic evaluation can provide the necessary information to correct rotational malreduction and limb-length discrepancy.

Antibiotic administration for open reduction internal fixation of closed ankle fractures: Is one preoperative dose enough?

Although preoperative antibiotics are used routinely in ankle fracture surgery, there is considerable variability in postoperative antibiotic dosing regimens amongst surgeons. The aim of this study is to compare the rate of surgical site infection (SSI) in patients receiving one dose of preoperative antibiotics to patients who received more than one dose of antibiotics. A single-center Level I Trauma Center retrospective review of patients with isolated closed ankle fractures who underwent open reduction internal fixation over a 10-year period was performed. Demographics data and risk factors were obtained from the electronic medical record. SSI was detected using a text-mining algorithm on all postoperative clinic notes. Factors associated with the development of SSI or increased antibiotic dosing were evaluated. Eight-hundred and twenty-six patients were included in the analysis. There was no correlation between infection rate and any of the potential risk factors evaluated. Two-hundred and ninety-two patients received only one dose of antibiotics preoperatively and 534 patients received more than one antibiotic dose. The rate of SSI was not significantly different between the single-dose cohort (5.8 %) and the multi-dose cohort (3.9 %) (p=0.215). Routine use of postoperative antibiotics in open reduction internal fixation of closed ankle fractures did not decrease the rate of SSI, regardless of associated comorbidities. LEVEL OF EVIDENCE: : Level III (therapeutic retrospective cohort study).

Outcomes of Nonoperatively Treated Vancouver B1 Fractures: Is Failure Common?

BACKGROUND: Periprosthetic fractures (PPFx) are a severe complication of total hip and hemiarthroplasty. Surgical treatment is typically performed but can result in major morbidity. Nonoperative PPFx management may provide a successful treatment alternative in select patients. METHODS: Vancouver B1 PPFx patients treated over a 10-year period were identified. Patient demographic data were retrospectively recorded. Injury and postoperative radiographs were reviewed. There were 48 patients who met the study criteria. Patients were divided into operative and nonoperative comparative cohorts. Outcome comparisons between the 2 cohorts included 1-year mortality, unplanned surgery within 24 months of injury, fracture union rate, and return to preinjury ambulation status. RESULTS: There was no difference in 1-year mortality between the nonoperative and operative cohorts (17 versus 8%; P = .32). We found no significant difference in unplanned surgery between the nonoperative and operative groups (8.7 versus 12%; P = .71), fracture union (100 versus 96%, P = .34), or return to ambulation status (86 versus 91%; P = .86). Nonoperative fractures were minimally displaced and within the metaphyseal region of the proximal femur without stem subsidence. Nonoperative fractures with subsequent treatment failure had initial fracture extension closer to the tip of the stem compared to successfully treated nonoperative fractures (5.5 versus 10.2 centimeters; P = .02). CONCLUSION: Select nonoperatively treated patients had infrequent need for unplanned surgery, high union rate, and return to their preinjury ambulation status. Nonoperative management is not appropriate for all Vancouver B1 PPFx, but those patients who have minimally displaced meta-diaphyseal fractures and partial remaining distal fixation can be successfully treated.

Iliac dysmorphism: defining radiographic characteristics and association with pelvic osseous corridor size.

INTRODUCTION: Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor. METHODS: Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured. RESULTS: The IOTC is an elliptical area measuring 22.3 cm2. All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001). DISCUSSION: All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants. CONCLUSION: This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.

Biomechanical comparison of a novel tensioned cable construct versus tension band wiring for transverse patella fracture fixation.

PURPOSE: Tension band wiring (TBW) is the most widely accepted method for patella fracture fixation. The purpose of our study was to compare the biomechanical efficacy of a novel cable construct to TBW for the fixation of transverse patella fractures. The tensioned cable construct was hypothesized to have less fracture gapping after cyclic flexion-extension loading and greater ultimate load to failure as compared to TBW. METHODS: Transverse patellar osteotomies (AO/OTA 34C1.1) were performed on nine pairs of fresh-frozen human cadaveric whole legs (mean age 82.2 years, range 71-101). Treatment with TBW or tensioned cable construct was randomized within each specimen pair. Fracture site displacement was measured after 5000 flexion-extension cycles from 0° to 90° at 0.5 Hz. In load to failure testing, the knee was fixed at 45° of flexion and the quadriceps tendon was pulled proximally at 0.5 mm/sec until patella fixation failure. Comparisons were made using paired t-tests with alpha values of 0.05. RESULTS: Eight paired specimens completed the cyclic loading. The tensioned cable construct had significantly less fracture gapping than TBW (2.9 vs 10.9 mm; p = 0.020). Seven paired limbs underwent load to failure testing, which revealed no significant difference between the tensioned cable construct and TBW (1551.6 N vs 1664.0 N; p = 0.26). CONCLUSION: In this study of transverse patella fracture fixation, a tensioned cable construct demonstrated significantly less fracture gapping compared to TBW in response to cyclic loading with no significant difference in load at failure.

Supraacetabular osseous corridor: defining dimensions, sex differences, and alternatives.

INTRODUCTION: The supraacetabular (SA) corridor extends from the anterior inferior iliac spine to the posterior ilium and can safely accommodate implants to stabilize pelvic and acetabular fractures. However, quantitative analysis of its dimensions and characteristics have not been thoroughly described. This study seeks to define the dimensions, common constriction points, and any alternative trajectories that would maximize the corridor diameter. METHODS: Computed tomography of 100 male and 100 female hemipelves without osseous trauma were evaluated. The corridor boundaries were determined through manual best-fit analysis. The largest intercortical cylinder within the pathway was created and measured. Alternative trajectories were tested within the SA boundaries to identify another orientation that maximized the diameter of the intercortical cylinder. RESULTS: The traditional SA corridor had a mean diameter of 8.3 mm in men and 6.2 mm in women. This difference in diameter is due to a more S-shaped ilium in women. A larger alternative SA corridor was found that had a less limited path through the ilium and measured 11.3 mm in men and 9.9 mm in women. These dimensions are significantly different compared to those of the traditional SA corridor in both men and women. CONCLUSIONS: In men, the SA corridor allows for the safe passage of most hardware used in pelvic and acetabular fractures. However, in women, the SA corridor is restricted by a more S-shaped ilium. An alternative trajectory was found that has a significantly larger mean diameter in both sexes. Ultimately, the trajectory of hardware will be dictated by the clinical scenario. When large implants are needed, especially in women, we recommend considering the alternative SA corridor.

Defining the iliac wing osseous fixation pathways: anatomy and implant constriction points.

INTRODUCTION: Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor. METHODS: Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured. RESULTS: The IOTC is an elliptical area measuring 22.3 cm2. All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001). DISCUSSION: All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants. CONCLUSION: This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.

MRI-only occult geriatric hip fractures: is displacement common with nonoperative treatment?

INTRODUCTION: Although surgical fixation is routinely recommended for geriatric hip fractures, nonoperative treatment may be an option for certain stable fracture patterns. Occult hip fractures are nondisplaced fractures not evident on radiographs, but display intraosseous edema on MRI. Our aim is to report the rate of nonoperative treatment failure in patients with occult geriatric hip fractures. METHODS: All nonoperatively treated femoral neck or intertrochanteric femur fractures (AO/OTA 31A and 31B) from 2003 to 2018 were identified. Patients older than 65 years with negative radiographs but a hip fracture evident on MRI were included. Patients who died prior to fracture displacement or union were excluded. Charts and imaging were reviewed for demographic data, fracture type, clinical course, displacement, and whether corrective surgery was performed. RESULTS: Of 15 final study patients, there were 6 femoral neck and 9 intertrochanteric fractures. Two fractures displaced, both requiring surgery (2/15; 13.3%). Both displacements occurred in the femoral neck group (2/6; 33%) compared to none in the intertrochanteric cohort (0/9; 0%). This trend did not reach statistical significance (p = 0.14). CONCLUSION: Thirty-three percent (2/6, 33%) of femoral neck fractures displaced and required surgery. The remainder of the cohort (13/15, 87%) healed without complication, including all of the intertrochanteric fractures (9/9, 100%). Although this difference did not reach statistical significance, the results may better inform treatment discussions for geriatric patients with occult hip fractures diagnosed by MRI. LEVEL OF EVIDENCE: Level III.

The effect of antegrade femoral nailing on femoral head perfusion: a comparison of piriformis fossa and trochanteric entry points.

INTRODUCTION: Piriformis fossa entry antegrade femoral nailing is a common method for stabilizing diaphyseal femur fractures. However, clinically significant complications such as chronic hip pain, hip abductor weakness, heterotopic ossification and femoral head osteonecrosis have been reported. A recent cadaveric study found that piriformis entry nailing damaged either the deep branch of the medial femoral circumflex artery (MFCA) or its distal superior retinacular artery branches in 100% of specimens and therefore recommended against its use. However, no study has quantitatively assessed the effect of different femoral entry points on femoral head perfusion. MATERIALS AND METHODS: Twelve fresh-frozen cadaveric lower extremity specimens were randomly allocated to either piriformis fossa or trochanteric entry nailing using a 13-mm reamer. The contralateral hip served as an internal matched control. All specimens subsequently underwent gadolinium-enhanced fat-suppressed gradient-echo sequence MRI to assess femoral head perfusion. Gross dissection was also performed to assess MFCA integrity and distance to the opening reamer path. RESULTS: MRI quantification analysis revealed near full femoral head perfusion with no significant difference between the piriformis and trochanteric starting points (95 vs. 97%, p = 0.94). There was no observed damage to the deep MFCA in either group. The mean distance from the reamer path to the deep MFCA was 3.2 mm in the piriformis group compared to 18.5 mm in the trochanteric group (p = 0.001). Additionally, there was a significantly greater number of mean terminal superior retinacular vessels damaged by the opening reamer in the piriformis cohort (1 vs. 0; p = 0.007). CONCLUSIONS: No statistically significant difference in femoral head perfusion was found between the two groups. Therefore, we cannot recommend against the use of piriformis entry femoral nails. However, we caution against multiple errant starting point attempts and recommend meticulous soft tissue protection during the procedure.

Manual Stress Ankle Radiography Has Poor Ability to Predict Deep Deltoid Ligament Integrity in a Supination External Rotation Fracture Cohort.

Stress ankle radiographs are routinely performed to determine deep deltoid ligament integrity in supination external rotation (SER) ankle fractures. However, variability is present in the published data regarding what medial clear space (MCS) value constitutes a positive result. The purposes of the present study were to evaluate the diagnostic accuracy of different MCS cutoff values and determine whether this clinical test could accurately discriminate between patients with and without a deep deltoid ligament disruption. MCS measurements were recorded for stress ankle injury radiographs in an SER ankle fracture cohort. Preoperative ankle magnetic resonance imaging studies, obtained for all patients, were then read independently by 2 musculoskeletal attending radiologists to determine deep deltoid ligament integrity. The MCS measurements were compared with the magnetic resonance imaging diagnosis using receiver operating characteristic analyses to determine the sensitivity, specificity, and optimal data-driven cutoff values. SER II-III patients demonstrated a mean stress MCS distance of 4.3 ± 0.98 mm compared with 5.8 ± 1.76 mm in the SER IV cohort (p < .001). An analysis of differing MCS positive cutoff thresholds revealed that a stress MCS of 5.0 mm maximized the combined sensitivity and specificity of the external rotation test: 65.8% sensitive and 76.5% specific. Using the receiver operating characteristic curve analysis of the MCS measurement, the calculated area under the curve was 0.77, indicating inadequate discriminative ability for diagnosing SER pattern fractures with or without a deep deltoid ligament tear. Judicious use of additional diagnostic testing in patients with a stress MCS result between 4.0 mm and 5.5 mm is warranted.

Ankle injuries in distal tibial spiral shaft fractures: results from an institutional change in imaging protocol.

INTRODUCTION: Posterior malleolus and other articular ankle injuries are known to concomitantly occur with tibial shaft fractures, especially spiral fractures of the distal one-third diaphysis. Due to our heightened awareness of this combined injury, our department instituted a new preoperative ankle imaging protocol for all distal one-third spiral tibia shaft fractures. The purpose of this study was to evaluate the effectiveness of an imaging protocol involving radiographs, CT and magnetic resonance imaging (MRI) in a distal one-third spiral tibia fracture cohort. MATERIALS AND METHODS: All operatively treated patients with a spiral distal one-third tibial shaft fracture from February 2012 to March 2013 underwent a standardized ankle imaging protocol. Patients had preoperative orthogonal ankle radiographs as well as a CT scan of the tibia that included the ankle. All ankle imaging was scrutinized for evidence of an ankle injury. If no ankle fracture was identified, patients would then undergo an ankle MRI. RESULTS: Twenty-five patients met the inclusion and exclusion criteria for this study. Concomitant osseous ankle injuries were identified by radiograph and CT in 56 % (14/25) of cases. The remaining 44 % (11/25) of patients had no evidence of a combined injury by radiograph or CT and therefore underwent an MRI. Of the MRI cohort, 64 % (7/11) were found to have an occult ankle fracture. The overall incidence of a combined injury using our protocol was 84 % (21/25). Identification of an occult injury led to a change in management for all of these patients. CONCLUSIONS: Concomitant ipsilateral ankle and distal one-third spiral tibial shaft fractures are more common than previously reported. Utilizing a new imaging protocol, we found that the incidence of this combined injury was 84 %. Recognition of the ankle fracture component in this tibial shaft cohort can be important as it may alter the surgical plan and postoperative management.

Evaluation of Lauge-Hansen designation of Weber C fractures.

Associations between Weber C ankle fractures and pronation external rotation (PER) injuries of the Lauge-Hansen classification have often been incorrectly correlated. The purpose of the present study was to evaluate the Lauge-Hansen designation of Weber C fractures by establishing the proportion of Weber C fractures that are supination external rotation (SER), supination adduction (SA), pronation abduction (PA), PER, and hyperplantarflexion variant fractures. A clinical database of operative ankle fractures treated by the senior author (D.G.L.) was reviewed. The inclusion criteria were patient age older than 16 years, preoperative ankle radiographs, and Weber C fracture designation. A total of 132 patients met the inclusion criteria, and the proportion of PA, PER, SER, SA, and variant fractures among the Weber C fractures was analyzed. PA fractures accounted for 0.8% (n = 1), PER fractures 56.8% (n = 75), SER fractures 35.6% (n = 47), and hyperplantarflexion variant fractures 6.8% (n = 9) of the 132 Weber C fractures. Patients with Weber C-PER fractures were more commonly male (p = .005) and younger (p = .003) and demonstrated a greater fibular fracture height (p < .001) than those with Weber C-SER and Weber C-variant fractures. Our study quantitatively demonstrated that not all Weber C fractures occur secondary to pronation injuries. This distinction is important, because all pronation injuries will demonstrate medial ankle injury, but SER and variant fractures might not. We therefore recommend careful evaluation of the fibular fracture characteristics, including the direction of fracture propagation and the distance from the tibial plafond, when classifying Weber C fractures using the Lauge-Hansen system, because correct classification is vital in preparation for appropriate operative treatment.

The Intermalleolar Method for Intraoperative Rotational Assessment of the Tibia-A Prospective Clinical Validation Study.

OBJECTIVES: To determine the accuracy of the intermalleolar method, an intraoperative fluoroscopic method for assessing tibial rotation in patients undergoing intramedullary nail fixation for tibial shaft fractures, by comparing it with the gold standard computed tomography (CT). DESIGN: Prospective cohort study. SETTING: Academic Level 1 trauma center. PATIENT SELECTION CRITERIA: Consecutive patients, aged 18 years and older, with unilateral tibial shaft fractures who underwent intramedullary fixation from September 2021 to January 2023. OUTCOME MEASURES AND COMPARISONS: Intraoperatively, tibial rotation measurements were obtained using the intermalleolar method on both the uninjured and injured limbs. Postoperatively, patients underwent bilateral low-dose lower extremity rotational CT scans. CT measurements were made by 4 blinded observers. Mean absolute rotational differences and standard errors were calculated to compare the injured and uninjured limbs. Subgroup analysis was performed assessing accuracy relating to injured versus uninjured limbs, body mass index, OTA/AO fracture pattern, tibial and fibular fracture location, and distal articular fracture extension requiring fixation. RESULTS: Of the 20 tibia fractures, the mean patient age was 43.4 years. The intermalleolar method had a mean absolute rotational difference of 5.1 degrees (standard error 0.6, range 0-13.7) compared with CT. Sixty percent (24/40) of the measurements were within 5 degrees, 90% (36/40) of the measurements were within 10 degrees, and 100% (40/40) were within 15 degrees of the CT. No patients were revised for malrotation postoperatively. CONCLUSIONS: The intermalleolar method is accurate and consistently provides intraoperative tibial rotation measurements within 10 degrees of the mean CT measurement for adult patients undergoing intramedullary nail fixation for unilateral tibial shaft fractures. This method may be employed in the operating room to accurately quantify tibial rotation and assist with intraoperative rotational corrections. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

The crippling effects of a cyberattack at an academic level 1 trauma center: An orthopedic perspective.

INTRODUCTION: Malicious cyberattacks are increasing in frequency and severity with healthcare institutions spending an average of over 10 million dollars to resolve the consequences of healthcare data breaches. This cost does not include the effect of a downtime event should a healthcare system electronic medical record (EMR) lose functionality. An Academic Level 1 trauma center suffered a cyberattack resulting in a total EMR downtime of 25 days. Orthopedic operative time was used as a surrogate for OR functionality during the event and a framework with specific examples is presented to promote rapid adaptation during downtime events. METHODS: Operative time losses were identified by calculating a running average of weekday total in room operative time during a total downtime event secondary to a cyberattack. This data was compared to week-of-the-year matched data from the year prior and the year after the attack. A framework for creating adaptations to a total downtime event was created by repeatedly interviewing different provider groups and identifying how they adjusted care to the challenges faced. RESULTS: Total weekday in room operative time during the attack decreased by 53.4% ± 12.2% and 53.2% ± 14.9% when comparing the matched period one year prior and one year after, respectively. Immediate challenges to patient care were identified by small groups of highly motivated individuals, with self-assigned agile teams formed. These teams sequenced system processes, identified failure points, and created real-time solutions. A frequently updated EMR backup mirror and hospital disaster insurance were crucial for mitigating the impact of the cyberattack. CONCLUSIONS: Cyberattacks are expensive and their downstream effects, including downtime events, can be crippling. Agile team formation, process sequencing, and understanding EMR backup times are tactics used to combat the challenges of a prolonged total downtime event. LEVEL OF EVIDENCE: Level III retrospective cohort.

Treatment of Lisfranc fracture-dislocations with primary partial arthrodesis.

BACKGROUND: The optimal method of treatment for Lisfranc fracture-dislocations remains controversial, and the role of primary partial arthrodesis for combined osseous-ligamentous Lisfranc injuries is unclear. This study reviewed the outcomes of Lisfranc injuries treated by primary partial arthrodesis. METHODS: Patients who underwent primary partial arthrodesis for a primarily ligamentous or combined osseous and ligamentous Lisfranc fracture-dislocation were reviewed retrospectively and assessed at followup according to radiographic, clinical and standardized patient-based outcomes. Twenty-five patients (12 ligamentous, 13 combined), median age of 46 (range, 20 to 73) years, were followed for an average of 42 (range, 24 to 96) months. RESULTS: The average American Orthopedic Foot and Ankle Society (AOFAS) score was 81 points (scale 0 to 100), with patients in general losing points for mild pain, limitations of recreational activities, and fashionable footwear requirements. There was no statistical difference between ligamentous and combined injuries with regard to the physical or mental component scores on the SF-36. At latest followup, patients reported an average return to 85% of their preinjury activity level (range, 50% to 100%). Twenty-one patients (84%) expressed satisfaction with their outcome and at latest followup, the mean visual analog pain scale (VAS) score was 1.8 out of 10 (range, 0 to 8). Three patients showed radiographic signs of post-traumatic arthritis of adjacent joints. CONCLUSION: Treatment of both primarily ligamentous and combined osseous and ligamentous lisfranc injuries with primary partial arthrodesis produced good clinical and patient-based outcomes.

Intraoperative Comparative Femoral Rotation Imaging: Do not Overlook Parallax.

OBJECTIVE: To investigate the degree of error due to parallax during intraoperative rotational imaging involving the distal femur. METHODS: Twelve, fresh-frozen, lower-extremity cadaveric specimens were studied. The limbs were positioned supine and rotated until the posterior femoral condyles were superimposed using a C-arm. The C-arm was then repositioned to place the femoral condyles at the anterior and posterior margins of the image intensifier. The rotation necessary to resuperimpose the femoral condyles due to parallax was recorded. A second C-arm was then used from the contralateral side to simulate the rotational imaging technique to determine the magnitude and directionality of combined parallax. RESULTS: All 12 specimens demonstrated parallax, resulting in rotational discrepancies. Compared with central field of view alignment, the mean rotational discrepancy was 5.6 and 5.5 degrees for anterior and posterior positions, respectively. Contralateral imaging resulted in an additive effect with rotational differences of 9.0 and 12.6 degrees for bilateral anterior and posterior positions, respectively. CONCLUSIONS: Parallax causes rotational discrepancies with fluoroscopic imaging of the distal femur when the posterior femoral condyles are off-center in the imaging field of view. If femoral condyles are not centered when obtaining intraoperative rotational imaging of the uninjured and injured femurs, parallax can result in potentially clinically significant rotational deformity even if the femurs seem perfectly matched at the conclusion of surgery. We recommend perfectly centering of the posterior femoral condyles in the imaging field of view when obtaining lateral images of the distal femur to prevent this potentially overlooked contribution to malrotation.

A Novel Fluoroscopic Method for Assessing Rotational Malalignment of the Tibia.

OBJECTIVE: To evaluate the accuracy and reliability of a novel fluoroscopic technique for assessing tibial rotation and compare it with a previously described fluoroscopic method. METHODS: A multiplanar circular ring external fixator was secured to the tibial diaphysis of 5 cadaveric lower extremity specimens. Using deformity correction software, the frame and tibia were programed to randomly rotate 5, 10, 15, 20, 25, and 30 degrees of internal and external rotation. After each rotation, 2 blinded, independent observers measured the degree of tibial rotation using 2 different fluoroscopic methods: the previously described "mortise" method and the novel "intermalleolar" method. A total of 65 measurements were made by each observer. Accuracy and interobserver reliability were calculated. RESULTS: Both intermalleolar and mortise methods had a mean absolute rotational difference from the true torsion of 3 degrees (standard error 1; range, 0-10 degrees intermalleolar vs. 0-18 degrees mortise). We found that 98.5% (128/130) of measurements using the intermalleolar method were less than 10 degrees from the true rotation compared with 93.8% (122/130) using the mortise method. Both the intermalleolar and the mortise methods had excellent interobserver reliability (intraclass correlation coefficient 0.99 and 0.96, respectively). CONCLUSION: Measuring tibial rotation fluoroscopically using the intermalleolar method is both accurate and reliable. Compared with the previously described mortise method, it has similar accuracy and provides a value that approximates the true tibial rotation. Also, it can be used reliably and effectively intraoperatively to identify tibial malrotation and assist in intraoperative rotational corrections.

Important Factors for Retrograde Nailing Through Total Knee Arthroplasty: A Cadaveric Study.

OBJECTIVES: Evaluate how total knee arthroplasty (TKA) implant design, femoral component size, and preoperative knee range of motion affect retrograde femoral nailing. METHODS: Cadaveric specimens were prepared for TKA with a single radius (SR) or medial pivot (MP) design and tested with cruciate retaining (CR), cruciate substituting (CS), and posterior stabilizing (PS) 9-mm liners. Knee extension identified the minimum flexion required to pass an opening reamer without impinging on TKA components. The angle between the reamer path and the femoral shaft was calculated from lateral fluoroscopic images. RESULTS: In SR TKA, the average flexion required was 70, 71, and 82 degrees for CR, CS, and PS, respectively. The required flexion in PS was significantly greater (P = 0.03). In MP TKA, the average flexion required was 74, 84, and 123 degrees for CR, CS, and PS, respectively. The required flexion was significantly greater in CS and PS designs (P < 0.0001). Femoral component size did not affect the minimum flexion required. The entry reamer resulted in 9.2 (SR) and 12.5 (MP) degrees of apex anterior deviation. CONCLUSIONS: When performing retrograde nailing through either of these TKA designs with a 12-mm opening reamer, at least 70 degrees of knee flexion is required to avoid damage to the polyethylene liner or femoral component. PS implants require significantly more flexion with both TKA designs. Femoral component size did not affect the flexion requirement. Approximately a 10-degree deviation exists between the reamer path and femoral shaft.