Outpatient Bryant's Overhead Traction Does Not Affect the Rate of Open Reduction or Avascular Necrosis in Developmental Dislocation of the Hip

BACKGROUND

The efficacy of preliminary traction to increase the likelihood of closed reduction and/or decrease the incidence of avascular necrosis in the management of developmental dysplasia of the hip (DDH) is controversial. We sought to document compliance with and effectiveness of Bryant's outpatient traction in patients with idiopathic DDH.

METHODS

Patients presenting between 6 and 24 months of age with idiopathic irreducible DDH were prospectively enrolled in the study. Prereduction outpatient traction was prescribed at participating surgeons' preference and parents' expressed willingness to comply with a traction protocol of at least 14 hours/day for 4 weeks. Traction hours were documented using a validated monitor; parents also reported average daily usage. Rate of successful closed reduction and evidence of capital epiphyseal growth disturbance 1 year' and 2 years' postreduction were documented.

RESULTS

Ninety-six patients with 115 affected hips were enrolled. Reliable recorded traction hours were obtained in 31 patients with 36 affected hips. Defining compliance as 14 hours/day average use, 14 of 31 patients (45.2%) were compliant, 2 (6.5%) admitted noncompliance, while 15 (48.2%) claimed to be compliant, but were not. Overall, 68/115 hips (59.0%) were closed reduced. Age at treatment was the only demographic characteristic associated with an increased incidence of closed reduction (11.7 vs. 14.6 mo, P<0.01). Successful closed reduction was achieved in 10/16 hips (62.5%) of compliant patients, 12/20 (60.0%) of noncompliant patients, and 43/72 (59.7%) of no-traction patients. Irregular ossific nucleus development was noted 1-year postindex reduction in 5/16 (31.3%) of complaint-patient hips and 25/92 (27.2%) of noncomplaint and no-traction hips. Distorted proximal femoral epiphysis was noted at 2 years postreduction in 2/15 hips (13.3%) of compliant patients and 15/52 hips (28.8%) in noncompliant and no-traction patients. None of these differences was statistically significant.

CONCLUSIONS

Parent-reported use of outpatient traction is unreliable. Four weeks of outpatient overhead Bryant's traction did not affect the rate of closed reduction or avascular necrosis in late-presenting DDH in this cohort.

LEVEL OF EVIDENCE

Level II-prospective cohort.

Effect of Lateral Column Lengthening on Subtalar Motion in a Cadaveric Model

BACKGROUND

Although lengthening of the lateral column through a calcaneal neck osteotomy is an integral component of flatfoot reconstruction in younger patients with flexible planovalgus deformities, concern exists as to the effect of this intra-articular osteotomy on subtalar motion. The purpose of this study was to quantify the alterations in subtalar motion following lateral column lengthening (LCL).

METHODS

The subtalar motion of 14 fresh-frozen cadaveric feet was assessed using a 3-dimensional motion capture system and materials testing system (MTS). Following potting of the tibia and calcaneus, optic markers were placed into the tibia, calcaneus, and talus. The MTS was used to apply a rotational force across the subtalar joint to a torque of 5 Nm. Abduction/adduction, supination/pronation, and plantarflexion/dorsiflexion about the talus were recorded. Specimens then underwent LCL via a calcaneal neck osteotomy, which was maintained with a 12-mm porous titanium wedge. Repeat subtalar motion analysis was performed and compared to pre-LCL motion using a paired t test.

RESULTS

No statistically significant differences in subtalar abduction/adduction (10.9 vs 11.8 degrees, P = .48), supination/pronation (3.5 vs 2.7 degrees, P = .31), or plantarflexion/dorsiflexion (1.6 vs 1.0 degrees, P = .10) were identified following LCL.

CONCLUSION

No significant changes in subtalar motion were observed following lateral column lengthening in this biomechanical cadaveric study.

CLINICAL RELEVANCE

Although these findings do not obviate concerns of clinical subtalar stiffness following lateral column lengthening for planovalgus deformity correction, they suggest that diminished postoperative subtalar motion, when it occurs, may be due to soft tissue scarring rather than alterations of joint anatomy.

The point of epiphyseal penetration affects rotational stability of screw fixation in slipped capital femoral epiphysis: A biomechanical study

The epiphyseal tubercle, a posterosuperior projection of the epiphysis into the metaphysis, serves as the axis of rotation in slipped capital femoral epiphysis (SCFE) and a source of physeal stability. We hypothesized that in a biomechanical model of single screw fixation of stable SCFE, a screw passing through the epiphyseal tubercle (the axis of rotation) would confer less rotational stability than a centrally placed screw. Three femurs were selected from a sample population of 8- to 15-year-old healthy hips to represent three stages of maturation: a "young" femur with a prominent epiphyseal tubercle and decreased epiphyseal cupping around the metaphysis, a "median" femur with a subsiding tubercle, and a "mature" femur with a subsided epiphyseal tubercle and increased peripheral epiphyseal cupping. Specimens were three-dimensional printed with one of two screw trajectories: passing centrally in the epiphysis or directly through the epiphyseal tubercle. Resistance to rotational displacement was measured through stiffness and maximum torque over 30° degrees of displacement. In the "young" model, epiphyseal tubercle screw position conferred less rotational stiffness and required less maximum torque during rotational displacement when compared to a centrally placed screw (P < .001). In the "median" and "mature" models where the tubercle has subsided and is replaced by peripheral epiphyseal cupping, screw position through the tubercle was associated with equal or greater rotational stiffness and maximum torque during displacement as a centrally placed screw.

Biomechanical Considerations in Foot and Ankle Circular External Fixation: Maintenance of Wire Tension

Initial tensioning of the forefoot wires to 130 kg followed by simultaneous tensioning of the calcaneal wires to 90 kg and using the rigid double-row foot plate closed anteriorly via threaded rods produce maximum preservation of the initial wire tension during foot circular external fixation.

Abstract 128: Interleukin-17 Mediates Hypertension, Intrauterine Growth Restriction, Cytolytic Natural Killer Cells and Vascular Dysfunction in Pregnant Rats

Preeclampsia is a hypertensive disorder of pregnancy characterized by intrauterine growth restriction (IUGR), vascular dysfunction, and chronic immune activation including increased T H 17s and cytolytic NK cells (NK C ). We recently developed a novel model of preeclampsia in which placental ischemia (PI)-induced T H 17s cause a preeclampsia-like phenotype in pregnant rats characterized by hypertension, IUGR, oxidative stress (ROS), and increased cytolytic NK cells (NK C ). In the current study we investigated a novel role for IL-17, the main cytokine secreted from T H 17s, to directly induce IUGR, NK C activation, and vascular dysfunction in pregnancy. IL-17 (150 pg/day) was chronically infused into a subset of normal pregnant (NP) rats from gestation day (GD) 12-19 (NP+IL-17) via i.p. minipump. On GD 18 carotid catheters were implanted and on GD 19 MAP, fetal weight, placental weight, placental NK C , and NK C -associated proteins were measured and vascular reactivity of uterine arteries was assessed. Data are expressed as mean±SEM. MAP significantly increased from 100±3 mmHg in NP (n=9) to 115±1 mmHg in NP+IL-17 (n=12). Fetal weight significantly decreased from 2.5±0.04 g in NP to 2.3±0.03 g in NP+IL-17 (p<0.05). Placental weight significantly decreased from 0.62±0.02 g in NP to 0.55±0.01 g in NP+IL-17 (p<0.05). Placental ROS significantly increased 1353±337 RLU/min/mg in NP to 2210±180 RLU/min/mg in NP+IL-17 (p<0.05). Placental NK C increased from 2.6±1.6% of the total NK population in NP to 11.3±2.2% in NP+IL-17 (p<0.05). Placental granzyme B increased from 22.7±1.6 pg/mg in NP to 30.2±2 pg/mg in NP+IL-17 (p<0.05). Placental granzyme A increased from 3067±225 pg/mg in NP to 3926±210 pg/mg (p<0.05). Additionally, placental levels of VEGF, an important pro-angiogenic factor secreted by non-cytolytic uterine NK cells significantly decreased from 77.6±6.5 pg/mg in NP to 54.2±3.2 pg/mg in NP+IL-17 (p<0.05). We also observed impaired relaxation of uterine arteries in response to acetylcholine. These data suggest a shift from non-cytolytic NK to NK C cells in the placentas of NP+IL17. In addition to hypertension and ROS, this study demonstrates novel roles for IL-17 to directly mediate IUGR, NK C activation, and endothelial vascular dysfunction during pregnancy.

Impact of tunnels and tenodesis screws on clavicle fracture: a biomechanical study of varying coracoclavicular ligament reconstruction techniques

PURPOSE

The purpose of this study was to compare the load to fracture of distal clavicles with no tunnels, one tunnel, or 2 tunnels and to evaluate the effect of inserting tenodesis screws in the tunnels on load to fracture of the distal clavicle.

METHODS

Fifty right sawbone clavicles were obtained and divided into 5 groups (n = 10): group 1, normal clavicle; group 2, one tunnel, no tenodesis screw; group 3, 2 tunnels, no tenodesis screws; group 4, one tunnel with tenodesis screw; and group 5, 2 tunnels with 2 tenodesis screws. Tunnels were created using a 5-mm-diameter reamer, and 5.5 × 10 mm polyethyl ethyl ketone tenodesis screws were used. A 4-point bending load was applied to the distal clavicles. Load to failure was noted for each specimen.

RESULTS

Load to failure in clavicles without tunnels was significantly higher (1,157.18 ± 147.10 N) than in all other groups (P < .0005). No statistical differences were noted between groups 2, 3, 4, and 5. Load to failure was not statistically different in clavicles with one versus 2 tunnels. In addition, the use of tenodesis screws in the tunnels did not affect the load required to fracture.

CONCLUSIONS

The use of tunnels in the clavicle for coracoclavicular (CC) ligament reconstruction significantly reduces the load required to fracture the distal clavicle. The addition of tenodesis screws does not appear to significantly increase the strength of the clavicle in this construct.

CLINICAL RELEVANCE

CC ligament reconstruction techniques commonly use tunnels in the distal clavicle, which may render the clavicle more susceptible to fracture. This study helps quantify the effect of these tunnels on the strength of the distal clavicle.

A novel double-row rotator cuff repair exceeds strengths of conventional repairs

Double-row rotator cuff repairs are becoming popular because of their ability to improve initial ultimate failure load for full-thickness rotator cuff tears, especially in middle-aged to elderly patients. We hypothesized a quasi-double-row repair using a combination of transosseous sutures, anchors, and double knots (TOAK technique) would exceed the clinically relevant 250-N load threshold and the initial mean ultimate failure loads of anchor-only and transosseous suture-only fixation. In simulated full-thickness supraspinatus tears in cadavers (mean age, 62 years; range, 50-77 years), failure loads of two repair techniques were compared with a TOAK repair using sutures and bioabsorbable anchors. Radiographic densitometry was conducted on all humeral heads. Testing was performed at 6 mm per minute in 18 bones in the following three groups (n = 6 per group): (1) transosseous suture-only with weave-type stitch and single-knot fixation; (2) anchor-only with horizontal mattress stitch and single-knot fixation; and (3) TOAK. The mean ultimate failure load was 238 N for the transosseous suture-only group and 215 N for the anchor-only group. Although the bones had lower density, TOAK specimens failed at 55% to 67% higher loads (mean, 404 N) than the other groups. These data support further evaluation of the TOAK technique for full-thickness supraspinatus tears in middle-aged to elderly patients.

New rod-plate anterior instrumentation for thoracolumbar/lumbar scoliosis: biomechanical evaluation compared with dual-rod and single-rod with structural interbody support

STUDY DESIGN

A new rod-plate anterior implant was designed to provide plate fixation at the cephalad and caudal-end segments of a 5-level anterior spine construct. Biomechanical testing was performed on calf spines instrumented with 5-segment anterior scoliosis constructs. OBJECTIVES.: To analyze the initial and post-fatigue biomechanical performance of the new implant, and compare it to an anterior dual-rod construct and a single-rod construct with interbody cages.

SUMMARY OF BACKGROUND DATA

Using single-rod anterior instrumentation for thoracolumbar and lumbar scoliosis, an unacceptable incidence of loss of correction, segmental kyphosis, and pseudarthrosis has been reported. Inadequate construct stiffness due to early postoperative bone-screw interface failure, especially at cephalad and caudal-end vertebrae, has been implicated as the cause of these complications.

METHODS

Thirty calf spines were instrumented over 5 segments with: (1) single-rod augmented with rod-plate implants, (2) dual-rod construct, and (3) single-rod with titanium mesh cages. Stiffness in flexion-extension and lateral bending modes was determined initially and post-cyclical loading by measuring segmental range of motion (ROM). Post-fatigue screw pullout tests were also performed.

RESULTS

In lateral bending, the caudal-end segmental ROM for rod-plate construct was 54% less than single-rod with cages construct (P < 0.05), with no difference between rod-plate and dual-rod constructs. In flexion-extension, the rod-plate construct showed 45% to 91% (initial test) and 84% to 90% (post-fatigue) less ROM than the single-rod with cages construct (P < 0.001). Again, there was no difference between rod-plate and dual-rod constructs at the cephalad and caudal-end segments. Post-fatigue screw pullout strengths of the rod-plate construct were significantly greater than those of the dual-rod and single-rod with cages constructs (P < 0.05).

CONCLUSIONS

The rod-plate construct was significantly stiffer and provided greater stability of bone-screw interface than the single-rod with cages construct. It achieved similar stiffness and improved bone-screw interface stability compared to dual-rod construct.

Recombinant human bone morphogenetic protein-2 enhances anterior spinal fusion in a thoracoscopically instrumented animal model

BACKGROUND

Thoracoscopically assisted anterior spinal arthrodesis and instrumentation is being used more widely to treat idiopathic scoliosis. However, harvesting autologous bone increases operative time and morbidity. The purpose of this study was to compare autologous iliac crest and rib graft with recombinant human bone morphogenetic protein-2 (rhBMP-2) in thoracoscopically assisted anterior spinal arthrodesis and instrumentation in an animal model.

METHODS

Twenty-two pigs underwent thoracoscopically assisted anterior spinal arthrodesis. Each animal had five contiguous thoracic discectomies followed by anterior instrumentation. The animals were randomly assigned to five treatment groups. Group I consisted of control animals that received no graft material; group II, animals treated with autologous rib graft; group III, animals treated with autologous iliac crest graft; group IV, animals treated with an rhBMP-2-composite sponge (collagen-hydroxyapatite-tricalcium phosphate carrier); and group V, animals treated with a composite sponge carrier alone. The animals were killed four months after the procedure, and the spines were harvested. The fusion mass was assessed with use of axial and sagittal computed tomography scans. The spines were tested biomechanically with incremental loads applied in the frontal and axial planes to achieve bending moments of up to 6.0 N-m. Angular motion at each segment was recorded with use of a three-dimensional motion analysis system. Histomorphometric analysis of each undecalcified disc segment was also performed.

RESULTS

The fusion grades, according to computed tomography analysis with use of a 4-point grading system in which scores of 3 and 4 indicated a solid fusion, were 0.6 point for group I, 2.1 points for group II, 2.3 points for group III, 3.8 points for group IV, and 0.4 point for group V. Group IV (the rhBMP-2-treated animals) had a higher grade than all of the other groups. Group II (rib graft) and group III (iliac crest) had similar grades, and both were greater than group I (the untreated controls) and group V (composite sponge alone) (p < 0.05). In axial rotation, lateral bending, and flexion-extension, the spines in group IV were stiffer than those in the four other groups (p < 0.05); the spines in groups II and III were similar, and the spines in both of those groups were stiffer than those in groups I and V (the control groups). Histologic analysis demonstrated that the total new-bone area, expressed as a percentage of the total disc space area, was 23.2% in group I, 37.1% in group II, 37.2% in group III, 48.5% in group IV, and 5.9% in group V. Group IV had significantly greater bone formation than all of the other groups (p < 0.001). The animals treated with rib graft (group II) and iliac crest (group III) had a similar amount of bone formation, and it was greater than that in both control groups (p < 0.001).

CONCLUSIONS

The rhBMP-2 significantly increased the prevalence and quality of the spinal fusion after thoracoscopically assisted anterior arthrodesis and instrumentation in an animal model compared with that in the other treatment groups and in the controls.

Effect of displacement of ulna-shaft fractures on forearm rotation: a cadaveric model

Nonoperative treatment of ulna-shaft fractures may result in healing with residual displacement. In the study reported here, we used a cadaveric model to try to determine whether displacement significantly reduces forearm supination and pronation. Transverse osteotomies were made one third, one half, and two thirds of the distance from the proximal end to the distal end of each of 7 fresh cadaveric forearms. Displacements of 50% and 100% were tested at each osteotomy site. Specimens were mounted on a material-testing machine, and forearm rotation was determined. Supination loss was less than 15 degrees for all directions of displacement at all osteotomy sites. Pronation loss was less than 10 degrees at the distal osteotomy site; at the middle osteotomy site, pronation loss was 19 degrees with 100% radial displacement (P < .05) and 20 degrees with 100% ulnar displacement (P< .05); and, at the proximal osteotomy site, pronation loss was 19 degrees with 50% radial displacement (P < .01), 41 degrees with 100% radial displacement (P < .0005), and 33 degrees with 100% ulnar displacement (P < .005). We conclude that large residual displacement in distal fractures and moderate residual displacement in midshaft fractures do not significantly compromise forearm rotation. Proximal displacement was less tolerated in this model and resulted in significantly reduced forearm rotation.

External fixation of the lumbar spine in a canine model

OBJECTIVE

To compare the mechanical properties of two types of external skeletal fixation of the lumbar spine with polymethylmethacrylate (PMMA)/Steinmann pin fixation in a canine unstable spine model.

STUDY DESIGN

Cadaver study.

SAMPLE POPULATION

Lumbar spines of 17 mature large-breed dogs.

METHODS

Spine stiffness (N-m/deg) in flexion, extension, and rotation under physiological loading conditions and spine strength (N-m) in flexion were determined. Spines were destabilized at L3-L4, instrumented and retested. Fixation techniques included four-pin PMMA (PMMA4), eight-pin PMMA (PMMA8), eight-pin biplanar type I external skeletal fixator (ESF) (SK), and eight-pin spinal arch ESF (ARCHES).

RESULTS

All fixation groups were as stiff as intact spines in extension and rotation and were significantly stiffer in flexion. In flexion, both PMMA8 and ARCHES were significantly stiffer than SK, and PMMA8 was significantly stiffer than PMMA4. In rotation, PMMA8 and ARCHES were significantly stiffer than SK, and in flexion to failure, PMMA8 and ARCHES were significantly stiffer than PMMA4.

CONCLUSIONS

External skeletal spinal fixation (ESSF) has mechanical properties comparable to more commonly used PMMA/pin internal fixation techniques.

CLINICAL RELEVANCE

External fixation of the canine spine has several potential advantages over internal fixation including minimal dissection for pin placement, the ability to span affected vertebrae with placement of implants distant from the site of injury, postoperative adjustability, and complete removal of implants after healing. This study supports the biomechanical stability ESSF of the canine lumbar spine. Further studies are indicated to evaluate zones of consistently safe and secure placement of pins and clinical efficacy.

In vitro strength comparison of hydroxyapatite cement and polymethylmethacrylate in subchondral defects in caprine femora

Hydroxyapatite cement was investigated in situ for the reconstruction of juxta-articular defects. Polymethylmethacrylate is currently the most commonly used material for the reconstruction of bone defects following the exteriorization and curettage of aggressive benign tumors. In vitro, we compared the effects of hydroxyapatite cement and polymethylmethacrylate in restoring the stiffness of the subchondral plate in a caprine femoral defect model. Ten matched pairs of caprine femora underwent nondestructive compression testing normal to the load-bearing surface. A standardized subchondral defect 12 mm in diameter was created in the medial femoral condyle. Compression testing was repeated to determine the reduction in stiffness caused by the defect. Each femur from each pair was randomly assigned to one of two groups (n=9), and the defects were augmented with either polymethylmethacrylate or hydroxyapatite cement. After 12 hours, compression testing was repeated to determine the subchondral stiffness after augmentation. Compared with intact femora, the defect specimens that were later treated with either polymethylmethacrylate or hydroxyapatite cement exhibited stiffness values of 70 (386+/-107 N/mm) and 59% (343+/-94 N/mm) respectively, which represented a significant reduction in stiffness (p=0.05). Augmentation with polymethylmethacrylate or hydroxyapatite cement restored stiffness by 81 (450+/-111 N/mm) and 71% (413+/-115 N/mm), respectively, of the values of intact specimens. Hydroxyapatite cement restored stiffness significantly (p=0.05) over the stiffness of the nonaugmented defect compared with the stiffness after augmentation with polymethylmethacrylate (p=0.12). Neither polymethylmethacrylate nor hydroxyapatite cement restored stiffness to that of intact femora (p=0.05). In the current detect model, hydroxyapatite cement was comparable with polymethylmethacrylate in restoring subchondral stiffness. Unlike polymethylmethacrylate, however, hydroxyapatite cement has the following advantages: it is osteoconductive, is replaced by host bone, and avoids the potential for thermal necrosis. Hydroxyapatite cement may therefore provide a viable alternative to polymethylmethacrylate for augmentation of juxta-articular and other bone defects.

Effect of recombinant human bone morphogenetic protein-2 on fracture healing in a goat tibial fracture model

Bone morphogenetic proteins (BMPs) are considered to have important regulatory roles in skeletal embryogenesis and bone healing. Recombinant human BMPs (rhBMPs) have been shown to heal critical size defects and promote spinal fusion. We studied the effects of rhBMP-2 in an absorbable collagen sponge (ACS) on bone healing in a large animal tibial fracture model. Bilateral closed tibial fractures were created in 16 skeletally mature goats and reduced and stabilized using external fixation. In each animal, one tibia received the study device (0.86 mg of rhBMP-2/ACS or buffer/ACS), and the contralateral fracture served as control. The device was implanted as a folded onlay or wrapped circumferentially around the fracture. Six weeks following fracture, the animals were sacrificed and the tibiae harvested for torsional testing and histomorphologic evaluation. Radiographs indicated increased callus at 3 weeks in the rhBMP-2/ACS treated tibiae. At 6 weeks, the rhBMP-2/ACS wrapped fractures had superior radiographic healing scores compared with buffer groups and controls. The rhBMP-2/ACS produced a significant increase in torsional toughness (p = 0.02), and trends of increased torsional strength and stiffness (p = 0.09) compared with fracture controls. The device placed in a wrapped fashion around the fracture produced significantly tougher callus (p = 0.02) compared with the onlay application. Total callus new bone volume was significantly increased (p = 0.02) in the rhBMP-2/ACS fractures compared with buffer groups and controls regardless of the method of device application. The rhBMP-2/ACS did not alter the timing of onset of periosteal/endosteal callus formation compared with controls. Neither the mineral apposition rates nor bone formation rates were affected by rhBMP-2/ACS treatment. The increased callus volume associated with rhBMP-2 treatment produced only moderate increases in strength and stiffness.

Effects of pneumolysin on human polymorphonuclear leukocytes and platelets

Pneumolysin was bound by human polymorphonuclear leukocytes in a reaction which occurred very rapidly at 0 degrees C. Low concentrations of pneumolysin were found to stimulate leukocyte migration and lysosomal enzyme secretion. At increasing lysin levels, inhibition of spontaneous migration and chemotaxis, cell death, and lysis were observed. Pneumolysin was also found to lyse platelets and to activate serum to become chemotactic.

Additional evidence that a new virulence-associated antigen of Neisseria gonorrhoeae is not of pilus origin

Triton-X-100-treated pilus suspensions prepared from Neisseria gonorrhoeae produced a single line of precipitate in immunodiffusion tests. This line was distinct from that of the virulence-associated antigen.

Strain-specific virulence-associated antigen of Neisseria gonorrhoeae

A strain-specific virulence-associated antigen has been found in Neisseria gonorrhoeae strain F-62. Using immunodiffusion in agar gel, it has been shown that the antigen is distinguishable from endotoxin and the virulence-associated toxic protein. It does not appear to be derived from pili. The antigen was not detected in T1 and/or T2 colony type cultures of 10 other isolates. It exhibited a possible partial immunological relationship with an antigen found in one additional strain. It was susceptible to digestion with Pronase and trypsin.