Mark A. Lee

Operative stabilization of supracondylar femur fractures above total knee arthroplasty ☆: A comparison of four treatment methods

Periprosthetic fractures of the distal femur above a total knee arthroplasty present a challenging surgical problem for orthopedic surgeons. Numerous operative and nonoperative treatment options exist including casting, Rush rods, supracondylar nails, and plate fixation. Potentially significant complications are associated with all current treatment alternatives. Plate or nail constructs frequently achieve limited distal fixation, leading to loss of fixation and varus angulation. This complication was not observed with the Less Invasive Stabilization System (LISS). In addition, our early results demonstrate the superiority of LISS treatment with low infection rates, no requirement for acute bone grafting, and secure fixation allowing for immediate postoperative mobilization. LISS fixation may offer a superior surgical treatment option for periprosthetic distal femur fractures.

Nonunions and the Potential of Stem Cells in Fracture-Healing

Recent progress in human embryonic and adult stem cell research is a cause for much enthusiasm in bone and joint surgery. Stem cells have therapeutic potential in the realm of orthopaedic surgery because of their capacity to self-renew and differentiate into various types of mature cells and tissues, including bone. Because nonunions remain a clinically important problem, there is interest in the use of cell-based strategies to augment fracture repair. Such strategies are being investigated with variations in the model systems, sources of stem cells, and methods for the application and enhancement of osseous healing, including genetic modifications and tissue-engineering. This review highlights the recent progress in the utilization of stem cells and cell-based gene therapy in promoting fracture-healing and its potential utility in the clinical setting.

Polyaxial locking plate fixation in distal femur fractures: a biomechanical comparison.

Objectives: Uniaxial, first-generation locking plates have become increasingly popular for fixation of supracondylar femur fractures. Polyaxial plates are currently available, which allow for variable-angle screw insertion; however, the biomechanical integrity of these new locking constructs is yet unproven. This study compares the mechanical stability of a conventional locking plate with that of a new polyaxial design. Methods: A comminuted supracondylar femur fracture (AO/OTA33-A3) gap model was created in fourth-generation synthetic composite bones. Fixation was obtained with 2 different plate constructs: (1) a conventional locking plate (uniaxial screw heads threading directly into plate) and (2) a polyaxial locking plate (screw heads are captured and “locked” into a fixed angle using locking caps). Eight specimens of each type were then tested in axial, torsional, and cyclic axial modes on a material testing machine. Results: The mean axial stiffness for the polyaxial locking plate was 24.4% greater than the conventional locking plate (168.2 vs 127.1 N/mm; P < 0.0001). The mean torsional stiffness was also greater for the polyaxial plate (2.78 vs 2.57 Nm/degree; P = 0.0226). Cyclic axial loading caused significantly less (P = 0.0034) mean irreversible deformation in the polyaxial plate (5.6 mm) than in the conventional plate (8.8 mm). The mean ultimate load to failure was significantly higher (P = 0.0005) for the polyaxial plate (1560 N) than for the conventional plate (1337 N). Conclusions: The tested plate construct with its polyaxial locking screw mechanism provides a biomechanically sound fixation option for supracondylar femur fractures. The frictional locking mechanism allows maintenance of angular stability while affording the option of variable screw placement.

Retropatellar technique for intramedullary nailing of proximal tibia fractures: A cadaveric assessment

Objective: To investigate if the radiographically correct and anatomically safe starting point and the appropriate sagittal plane vector could be obtained using a retropatellar technique for proximal tibia fractures treated with an intramedullary device. Methods: We performed a cadaveric and radiographic study utilizing 16 limbs. We performed a retropatellar approach via longitudinal quadriceps split, passed a specialized trocar through the patellofemoral joint and onto the superior aspect of the tibia, and inserted Kirschner wires into the anatomic safe zone of the tibial plateau at 0, 10, 20, 30, 40, and 50 degrees of knee flexion utilizing biplanar fluoroscopy. We recorded knee flexion with a goniometer and the entrance vector of the Kirschner wire in relation to the anterior tibial cortex. Setting: University-affiliated cadaver and anatomy laboratory. Results: There was a progressive increase in the ability to obtain the correct anatomical start site from 1 of 16 (6.25%) at full extension to 12 of 16 (75%) at 50 degrees of knee flexion (P = 0.00098). A statistically significant decrease in the average sagittal plane entrance vector in relation to the anterior tibial cortex was found from 23.1 degrees at full extension to −0.41 degrees at 50 degrees of knee flexion (P < 0.0001). Conclusions: The retropatellar technique allows the radiographically defined correct start site to be localized, particularly at higher degrees of knee flexion. More favorable intramedullary nail insertion angles were possible with the retropatellar technique, particularly with knee flexion angles greater than 20 degrees. The retropatellar technique demands further investigations to further delineate its advantages, limitations, and possible risks to local anatomy.

The distal approach for anterolateral plate fixation of the tibia: An anatomic study

Objectives: To determine what anatomic structures are at risk when placing plates from distal to proximal along the anterolateral border of the tibia. Design: Cadaveric dissection study. Setting: The Zimmer Institute, Warsaw, Indiana. Methods: A laboratory investigation was performed using 10 matched limbs (5 right and 5 left) of 5 fresh, frozen, nonpreserved cadaveric specimens. Dissections were carried out to identify the relationships between the plate/screw contructs and (1) the superficial peroneal nerve (SPN) and the pedicle containing the deep peroneal nerve and the anterior tibial vessels (DPN/ATV). Results: The SPN was always visualized in the subcutaneous tissues of the distal incision. The DPN/ATV courses along the posterior half of the tibial shaft proximally and crosses the distal third of the plate as it transitions to an anterior position The pedicle crosses and covers the tibia in a consistent region 40 to 110 mm proximal to the ankle joint. Conclusions: The distal anterolateral approach can be used to place plates along the anterolateral border of the tibia. The SPN is always seen in the distal incision and is not at risk. The structures at risk are the deep peroneal nerve and the anterior tibial vessels as they course from a posterior position proximally to a more anterior position distally.

The retropatellar portal as an alternative site for tibial nail insertion: a cadaveric study.

Objective: To define spatial relationships between major intra-articular structures of the knee and the entry site of a tibial nail inserted using a retropatellar portal. Design: Cadaveric study using 16 fresh-frozen limbs. Setting: University-affiliated cadaver and anatomy laboratory. Results: The mean distance of the nail entry site and the medial and lateral menisci were 6.6 ± 3.2 mm and 6.4 ± 4.4 mm, respectively. The distance to the medial and lateral articular surfaces were 5.6 ± 3.6 mm and 7.4 ± 4.2 mm, respectively. The mean distance to the anterior cruciate ligament footprint was 7.5 ± 3.5 mm. The lateral meniscus was never injured during the procedure. The anterior cruciate ligament was undisturbed in all specimens. The medial meniscus was injured 1 to 2 mm in 12.5% of specimens. The intermeniscal ligament was injured 1 to 2 mm in 81.2% of the specimens. Conclusion: The intermeniscal ligament and medial meniscus are at the most risk during intramedullary nailing of the tibia using the retropatellar technique. This may be corrected by avoiding an excessively medial start point. Damage to the intermeniscal ligament and medial meniscus occurs more commonly with the retropatellar portal, but this damage was never more than 1 to 2 mm. This risk, however, appears similar to the pattern and incidence of injury that occurred in prior studies investigating tibial nail insertion through a standard patellar tendon approach. The retropatellar technique demands clinical investigation to further define both its safety and its use.

Scapulothoracic dissociation: diagnosis and treatment.

Scapulothoracic dissociation is an important and increasingly common clinical condition resulting from massive traction injury to the anterolateral shoulder girdle with disruption of scapulothoracic articulation. It frequently is accompanied by an acromioclavicular separation, displaced clavicular fracture, or sternoclavicular disruption. Vascular lesions have been reported in 88% of patients and severe neurologic injuries occur in 94% of patients. Many patients have a poor outcome with a flail extremity in 52%, early amputation in 21%, and death in 10%. Early recognition of this injury combined with a logical treatment protocol can help to decrease the substantial morbidity and mortality associated with this condition.

Influence of prior fasciotomy on infection after open reduction and internal fixation of tibial plateau fractures.

BACKGROUND High-energy tibial plateau fractures may present with an acute or impending compartment syndrome requiring emergent fasciotomy. There is little information regarding the optimal management of the fasciotomy wound with respect to the subsequent definitive internal fixation of the tibial plateau fracture. The purpose of this study was to compare the rate of infection complication after internal fixation of tibial plateau fractures in patients requiring fasciotomy for compartment syndrome with patients in whom a fasciotomy was not required. METHODS We retrospectively reviewed all tibial plateau fractures presenting over a 55-month period. Fourteen patients who presented with an associated compartment syndrome requiring fasciotomy and 128 patients in whom a fasciotomy was not performed met inclusion criteria. Patients age, sex, mechanism of injury, management of their fasciotomy, operative treatment of their plateau fracture, follow-up surgical procedures, follow-up complications, and length of follow-up were reviewed. Infection complications were defined as cellulitis requiring treatment with intravenous or oral antibiotics, patients requiring operative debridement after definitive fixation, and documentation of osteomyelitis. RESULTS In the fasciotomy group, two patients developed cellulitis that was treated with a short course on oral antibiotics. There were no documented deep infections. In the no fasciotomy group, eight patients (6.25%) had a documented culture-positive deep infection. Additionally, six patients had documented occurrences of cellulitis managed with oral or intravenous antibiotics. CONCLUSIONS Definitive internal fixation of tibial plateau fractures in the presence of open fasciotomy wounds does not seem to be associated with an increased infection risk.

Biomechanical comparison of polyaxial and uniaxial locking plate fixation in a proximal tibial gap model.

Objectives: Lateral locked plating for proximal tibial fractures with metaphyseal disruption provides a biomechanically stable and biologically favorable alternative to conventional medial/lateral plate fixation. New polyaxial screw technology incorporates expanding screw bushings, allowing variable angle screw placement, while providing angular stability. We hypothesize that polyaxial locking plates will exhibit comparable stiffness, strength to failure, and resistance to plastic deformation to conventional locking plates in a proximal tibial gap model. Methods: We stabilized extra-articular metaphyseal gap osteotomies in synthetic composite tibiae with dual medial and lateral plating, Less Invasive Stabilization System (LISS) plates, 4.5-mm proximal tibial lateral locking plates with (LP+) and without (LP−) angled screws, and 4.5-mm polyaxial locking plates with (PA+) and without (PA−) angled screws. All were tested with cyclic, ramped, and axial loading to failure. Results: No plates demonstrated screw failure before plate failure. Dual-plate constructs did not fail. All lateral plates failed at the osteotomy. LP− failed at low load. PA+ was significantly stiffer (165 ± 17 N/mm) with greater load to failure (711 ± 23 N) than all other constructs (PA−: 56 ± 6 N/mm, 617 ± 33 N; LP+: 137 ± 23 N/mm, 488 ± 39 N; LISS: 76 ± 5 N/mm, 656 ± 39 N). PA+ had significantly less plastic deformation (12.1 ± 0.8 mm) than LP+ (13.4 ± 3.7 mm), but more than PA− (5.8 ± 1.2 mm) and LISS (3.9 ± 0.6 mm). PA− did not differ significantly from LISS in any parameter. Conclusions: This study demonstrates that this unique polyaxial locking plate mechanism, when tested in various constructs, exhibits similar biomechanical performance regarding stiffness, strength to failure, and resistance to plastic deformation when compared with uniaxial locking plates. The polyaxial locking plate with an angled screw was stiffest and had the greatest load to failure. The polyaxial locking plate alone tested similar to the LISS. In addition, the benefit of the angled screw for biomechanical stability is demonstrated.

The effect of C-arm malrotation on iliosacral screw placement.

Objectives: We sought to determine whether inaccurate C-arm positioning could create images that lead to inaccurate interpretation of iliosacral screw positions. Design: Cadaveric dissection study. Setting: The learning institute of Zimmer Inc. in Warsaw, Indiana. Methods: A laboratory investigation was performed using 3 nonpreserved cadaveric specimens. Several anatomic landmarks of the pelvis were outlined using radiographic markers and guide wires placed in several positions within the pelvis in each specimen. Using C-arm images we inserted the following: a “good” wire (GW), an out-the-front (OTF) wire, an out-the-back (OTB) wire placed into the sacral canal, an “in-out-in” (IOI) wire, and a wire in the S1 foramen (S1). The C-arm was then canted in 2-degree increments toward the head and then toward the feet starting from the optimum position. Results: Properly positioned wires always appear to be contained within bone regardless of the amount of malrotation of the C-arm from the optimum inlet and outlet views. Conclusions: Improper malrotated fluoroscopic inlet and outlet views of the pelvis will distort the anatomic landmarks of the pelvis before improperly placed guide wires appear to be correctly placed. Properly placed guide wires will always appear correctly positioned regardless of the malrotation of the C-arm. “Malrotated” views, however, can be used to rule out certain incorrect screw positions.