Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings.

Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens.

Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or convex shape, the perfect AP angle aligned with a tangent to the subchondral surface extending from center to posterior plateau on CT. Phase Three: Based on the CT protocol created in Phase Two, mean medial slope (5.2°+/-2.3° posterior) was significantly less than lateral slope (7.5°+/-3.0° posterior) in 54 knees (p<0.001). In individual specimens, the difference between medial and lateral slopes was variable, ranging from 6.8° more laterally to 3.1° more medially. In a paired comparison of right and left knees from the same cadaver, no differences were noted between sides (medial p=0.43; lateral p=0.62).

On average there is slightly more tibial slope in the lateral plateau than medial plateau (2° greater). However, individual patients may have substantially more lateral slope (up to 6.8°) or even more medial slope (up to 3.1°). Since tibial slope was similar between contralateral limbs, evaluating slope on the uninjured side provides a template for sagittal plane reduction of tibial plateau fractures.

Introduction

Conventional screws achieve sufficient insertion torque in healthy bone. In poor bone screw stripping can occur prior to sufficient torque generation. It was hypothesized that a screw with a larger major/minor diameter ratio would provide improved purchase in poor bone as compared to conventional screws. We evaluated the mechanical characteristics of such a screw using multiple poor bone quality models.

Purpose: Bone grafting of subchondral voids during ORIF of tibial plateau fractures is commonly performed. The efficacy of various graft materials to resist post-operative articular displacement and stimulate bone regeneration in the grafted zone, remains largely unstudied. Studies in animals with a new composite material have shown that this composite material leads to greater bone formation and stronger bone versus autograft at 13 and 26 weeks. This study was designed to determine whether this material helps resist articular fragment displacement and leads to stronger bone regeneration and better functional outcome in the treatment of tibial plateau fractures.

Methods: Thirty four patients with unilateral tibial plateau fractures (OTA 41A-B), were enrolled in a prospective multicenter single cohort study. The treatment protocol included ORIF and defect augmentation with a composite bone graft substitute (PRODENSE®, Wright Medical Technology). Reduction and bone formation was evaluated and followed with both plain radiographs and CT scans obtained immediately postop and at 12 and 24 weeks. Functional outcome was assessed using the SMFA scores. CT analysis was performed by an independent musculoskeletal radiologist who quantified maintenance of reduction of the articular surface and bone density within the grafted area.

Results: Eighteen of the 34 enrolled patients were eligible for follow-up at 24 weeks (sixteen were not yet eligible for the 24 week time point). Mean change in articular reduction was 0.75mm, Density measures in the region of the initial subchondral void decreased from a mean of 1400 Hounsfield units at baseline (immediately post-op) to 600 at 24 weeks, suggesting bone regeneration and normal remodeling. Short form Musculoskeletal Function Assessment activity scores improved from 55.15 (SD=42.8) at baseline to 20.92 (SD=18.09) at 24 weeks. Complications include 1 DVT, 3 infections and 1 cellulitis, all of which resolved. There was an additional infection that required revision of the ORIF.

Conclusions and Significance: Serial CT evaluations revealed maintenance of post-operative reduction with displacement of less than 1mm. Bone density, in the region of the grafted area was near normal and confirms that the composite graft material promotes strong bone regeneration. Functional outcomes improved with time from surgery and approached that of uninjured cohorts.

Purpose: Locked plating has become a commonly used technique in complex fracture and nonunion work. The combination of locked and unlocked screws in the same construct has been referred to as “hybrid” fixation. Little work is available to direct the specifics of this fixation method. The purpose of this study was to determine the relative contribution of the number and location of locked screws on the properties of hybrid plate constructs in an osteoporotic bone model.

Method: A prefabricated osteoporotic model was used for reproducibility (composite cylinders 35 mm in diameter and consisting of a 2.5 mm fiberglass shell filled with 10 lb/ft3 polyurethane). A 5mm gap model was used, and fixed with a 12 hole plate. Six different constructs were tested including 2 unlocked and 4 hybrid configurations. All screws were bicortical and placed with 4Nm of torque. Baseline removal (loosening) torque was recorded for each screw for comparison with removal torque after cyclic loading. Testing was performed with ±8Nm of torsional load and run to 100,000 cycles. Stiffness of each construct was measured at 10,000 cycle increments and the removal torque of each screw was recorded at the conclusion of the 100,000 cycles.

Results: Stiffness of the constructs was most affected by the number of screws. No effect was seen with the replacement of one or two unlocked screws with locked screws on each side of the gap. Replacement of three unlocked screws with locked screws increased the stiffness of the construct (p< 0.001).

Conclusion: At least three bicortical locked screws on each side of a construct are needed to increase the stiffness and decrease the loss of stiffness over 100,000 cycles of torsional stress in an osteoporotic surrogate model. Locked screws placed between the fracture and unlocked screws protect the unlocked screws from loosening and may have some clinical utility in fatigue of the construct.

Purpose: Many lateral malleolar fractures in patients with osteoporotic bone are rotationally unstable, requiring fixation stable in torsion with good fatigue properties, but without bulk due to the soft tissue constraints. The purpose of this study was to evaluate the torsional performance of a thin (1.5mm) plate with locked and non-locked constructs in a simulated osteoporotic lateral malleolus fracture.

Method: A transverse fracture gap to mimic comminution was created in (15 lb/ft3) density foam. 3 bicortical unlocked screws were used proximal to the fracture in a 5 hole thin (1.5mm) plate for both constructs. Distally, two screws that did not breach the far cortex (12mm) were placed as locked in one group and unlocked in the other. The constructs were loaded in torsion at 1 Hz at 7.5/0.75 in-lbf (0.85/0.08 N-m) of torque. A torsional fatigue failure was defined as either a fracture of the plate, screw pull-out, or construct rotation 10 degrees beyond the maximum initial rotational displacement. Testing was conducted until construct failure or run-out of 300,000 cycles.

Results: The thin plate constructs with locked distal screws showed significantly improved fatigue properties (p< 0.00001). None of the locking plate constructs failed prior to the 300,000 cycle end point. In stark contradistinction, all of the non-locked contructs failed at an average cycle count of only 9,541 (range 1,000 – 23,000 cycles). The failure mode for each of the non-locked constructs was pull-out of the distal screws.

Conclusion: These results indicate that the use of a thin plate with locking capability provides a significant advantage over non-locked constructs in fatigue performance in areas of poor bone density subjected to torsional loads, such as the lateral malleolus.

Antegrade femoral nailing through the greater trochanter, using nails designed for piriformis entry, is associated with varus and iatrogenic comminution. Nails designed for greater trochanter insertion theoretically reduce these complications, but clinical outcomes comparing these to piriformis entry remain unknown. We compared femoral shaft fracture repair with a nail designed for trochanteric entry to an identical nail without a trochanteric bend inserted through the piriformis fossa.

The trochanteric nail was easier to insert with decreased operative and fluoroscopy time. It resulted in equally high union rates, low complication rates, and functional results similar to conventional nailing through the piriformis fossa.

Trochanteric antegrade nailing of the femur is thought to be advantageous over conventional antegrade nailing due to improved ease of insertion, but is unproven. This study compares results of femoral shaft fracture treatment using a nail designed specifically for trochanteric entry, Trigen TAN, to results using an identical nail without a trochanteric bend inserted through the piriformis fossa, Trigen FAN.

A femoral nail specially designed for trochanteric insertion resulted in equally high union rates, equally low complication rates, and functional results similar to conventional antegrade femoral nailing through the piriformis fossa. As a result of increased ease of insertion, decreased operative time and decreased fluoroscopy time, the greater trochanter entry portal, coupled with an appropriately designed nail, represents a rational alternative for antegrade femoral nailing.

Insertion of a specially designed femoral nail though the trochanter is faster, easier, and requires less fluoroscopy time than conventional antegrade nailing through the piriformis fossa.

Overall, there was < 10° malalignment and no iatrogenic fracture comminution. The average operative time was 21% greater using the FAN nail than using the TAN nail, (p=.08). The average fluoroscopy time was 61% greater for the FAN group than for the TAN group, (p< .05). Trends in functional outcome (Lower Extremity Measure) were similar for both groups.

One hundred and eight patients treated for a femoral shaft fracture were included in this study. Ninety-eight patients were treated with either a Trigen TAN nail (n=38) or Trigen FAN nail (n=53); seventeen patients with insufficient follow-up were excluded from analysis.

Funding:Smith & Nephew, Memphis TN

Reducing exposure to radiation is a concern to physicians and supporting staff. Little is known about the factors leading to increased exposure in intramedullary nailing of long bone fractures. This study examines antegrade and retrograde nailing of femur and tibia fractures. Factors that increased radiation exposure were obesity, severely comminuted fractures, nails inserted through the piriformis fossa, and insertion of more locking bolts in femoral nails. In addition, femoral nails required more radiation exposure than tibial nails.

Exposure to radiation is a concern to physicians. The purpose of this study was to determine factors associated with increased radiation exposure with intramedullary nailing of long bone fractures.

Femoral nailing through the piriformis fossa, highly comminuted fractures, insertion of more locking bolts (femur), and obesity are each associated with the higher radiation exposure.

Factors associated with increased radiation exposure are identified for tibial and femoral nailing.

Radiation exposure was higher for nailing of femur fractures (ninety-two seconds) compared to nailing of tibia fractures (sixty seconds). Exposure was greatest for insertion through the piriformis fossa (one hundred and twenty-one seconds) and least for retrograde insertion (seventy-four seconds) and intermediate for insertion through the trochanter (eighty-seven seconds). Obese patients (BMI > 30) had higher exposure times for both femoral (obese-one hundred and sixty seconds, non-obese-eighty-five seconds) and tibial nailing (obese-seventy-nine seconds, non-obese-fifty-five seconds). Only the most severely comminuted fracture patterns (Winquist IV) were associated with increased fluoroscopy time. Increasing number of interlocking bolts was associated with higher exposure for the femur but not the tibia.

One hundred and thirty-nine consecutive patients treated with intramedullary nailing for either a femoral shaft (OTA 32, n=71) or tibial shaft (OTA 42, n=68) fracture were prospectively evaluated in this IRB approved study. Radiation exposure (c-arm fluoroscopy time) was measured. Femur fractures were treated with either a retrograde nail (n=24), an antegrade nail inserted through the piriformis fossa (n=20), or an antegrade nail inserted through the tip of the greater trochanter (n=27).

Funding: Smith & Nephew