Treatment of swan neck deformity in cerebral palsy.

Swan neck deformity in patients with cerebral palsy can result from hand intrinsic muscle spasticity or overpull of the digital extensors. After accurate identification of the etiology of the deformity, surgical treatment is directed at correcting the underlying muscle imbalance. Intrinsic lengthening can be used to treat intrinsic muscle spasticity, whereas central slip tenotomy is employed when digital extensor overpull is the deforming force. Accurate diagnosis and application of the proper surgical technique are essential when treating swan neck deformity in patients with cerebral palsy.

Attrition or rupture of digital extensor tendons due to carpal boss: report of 2 cases.

We present 2 cases that demonstrate the potential for tendon involvement in the presence of a carpal boss. In the first, a patient presented with tendon rupture without antecedent pain. In the second, pain and tendon irritation prompted magnetic resonance imaging that revealed tendon fraying, which was confirmed at surgery. These cases illustrate the potential for tendinous sequelae of a carpal boss. Advanced imaging may be considered when tendon irritation is clinically suspected. Attention to the possibility of tendon rupture in the setting of an otherwise asymptomatic carpal boss is advised.

Postanesthesia care unit imaging is unnecessary when intraoperative imaging is used during anterior cervical decompression and fusion procedures.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To characterize the clinical utility of imaging in the postanesthesia care unit (PACU) after anterior cervical decompression and fusion (ACDF) procedures. SUMMARY OF BACKGROUND DATA: Two sets of imaging are often taken at the end of ACDF procedures: one intraoperatively and the other in the PACU. The latter may have low clinical utility. MATERIALS AND METHODS: One hundred four patients who underwent ACDF procedures with anterior plate/screw constructs were identified. A panel assessed intraoperative and PACU series for adequacy of images to detect potential issues with placement of the surgical construct and for any actual visible issues with placement of the surgical construct. RESULTS: Intraoperative series were adequate to detect potential issues with construct placement for 78.8% of cases, whereas PACU series were adequate for only 58.7% of cases (significant difference, P<0.001). For both series, nearly all inadequacies were because of the shoulders obstructing the lateral view. Accordingly, cases with lower inferior operative levels were much more likely to have inadequate intraoperative and PACU series than cases with higher inferior operative levels (significant differences, P<0.001 for both). In no case was an issue with construct placement visible on a PACU series that was not also visible on an intraoperative series. CONCLUSIONS: This study demonstrates that PACU images are inferior to intraoperative images and offer little or no incremental clinical utility for detecting issues with surgical construct placement after ACDF procedures. PACU imaging after ACDF procedures might be discontinued to realize savings in time, cost, and radiation exposure.

Whiplash causes increased laxity of cervical capsular ligament.

BACKGROUND: Previous clinical studies have identified the cervical facet joint, including the capsular ligaments, as sources of pain in whiplash patients. The goal of this study was to determine whether whiplash caused increased capsular ligament laxity by applying quasi-static loading to whiplash-exposed and control capsular ligaments. METHODS: A total of 66 capsular ligament specimens (C2/3 to C7/T1) were prepared from 12 cervical spines (6 whiplash-exposed and 6 control). The whiplash-exposed spines had been previously rear impacted at a maximum peak T1 horizontal acceleration of 8 g. Capsular ligaments were elongated at 1mm/s in increments of 0.05 mm until a tensile force of 5 N was achieved and subsequently returned to neutral position. Four pre-conditioning cycles were performed and data from the load phase of the fifth cycle were used for subsequent analyses. Ligament elongation was computed at tensile forces of 0, 0.25, 0.5, 0.75, 1.0, 2.5, and 5.0 N. Two factor, non-repeated measures ANOVA (P<0.05) was performed to determine significant differences in the average ligament elongation at tensile forces of 0 and 5 N between the whiplash-exposed and control groups and between spinal levels. FINDINGS: Average elongation of the whiplash-exposed capsular ligaments was significantly greater than that of the control ligaments at tensile forces of 0 and 5 N. No significant differences between spinal levels were observed. INTERPRETATION: Capsular ligament injuries, in the form of increased laxity, may be one component perpetuating chronic pain and clinical instability in whiplash patients.

Dynamic vertebral artery elongation during frontal and side impacts.

BACKGROUND CONTEXT: Elongation-induced vertebral artery (VA) injury has been hypothesized to occur during nonphysiological coupled head motions during automobile impacts. Although previous work has investigated VA elongation during head-turned and head-forward rear impacts, no studies have performed similar investigations for frontal or side impacts. PURPOSE: The present study quantified dynamic VA elongations during simulated frontal and side automotive collisions, and compared these data with corresponding physiological limits. STUDY DESIGN/SETTING: In vitro biomechanical study of dynamic VA elongation during simulated impacts. METHODS: A biofidelic whole cervical spine model with muscle force replication and surrogate head underwent simulated frontal impacts (n=6) of 4, 6, 8, and 10 g or left side impacts (n=6) of 3.5, 5, 6.5, and 8 g. RESULTS: Average (SD) maximum physiological VA elongation was 7.1 (3.2) mm, measured during intact flexibility testing. Average peak dynamic elongation of right VA during left side impact, up to 17.4 (2.6) mm, was significantly greater (p<.05) than physiological beginning at 6.5 g, whereas the highest average peak VA elongation during frontal impact was 2.5 (2.4) mm, which did not exceed the physiological limit. Side impact, as compared with frontal impact, caused earlier occurrence of average peak VA elongation, 113.8 (13.5) ms versus 155.0 (46.2) ms, and higher average peak VA elongation rate, 608.8 (99.0) mm/s versus 130.0 (62.9) mm/s. CONCLUSIONS: Elongation-induced VA injury is more likely to occur during side impact as compared with frontal impact.

Dynamic mechanical properties of intact human cervical spine ligaments.

BACKGROUND CONTEXT: Most previous studies have investigated ligament mechanical properties at slow elongation rates of less than 25 mm/s. PURPOSE: To determine the tensile mechanical properties, at a fast elongation rate, of intact human cervical anterior and posterior longitudinal, capsular, and interspinous and supraspinous ligaments, middle-third disc, and ligamentum flavum. STUDY DESIGN/SETTING: In vitro biomechanical study. METHODS: A total of 97 intact bone-ligament-bone specimens (C2-C3 to C7-T1) were prepared from six cervical spines (average age: 80.6 years, range, 71 to 92 years) and were elongated to complete rupture at an average (SD) peak rate of 723 (106) mm/s using a custom-built apparatus. Nonlinear force versus elongation curves were plotted and peak force, peak elongation, peak energy, and stiffness were statistically compared (p<.05) among ligaments. A mathematical model was developed to determine the quasi-static physiological ligament elongation. RESULTS: Highest average peak force, up to 244.4 and 220.0 N in the ligamentum flavum and capsular ligament, respectively, were significantly greater than in the anterior longitudinal ligament and middle-third disc. Highest peak elongation reached 5.9 mm in the intraspinous and supraspinous ligaments, significantly greater than in the middle-third disc. Highest peak energy of 0.57 J was attained in the capsular ligament, significantly greater than in the anterior longitudinal ligament and middle-third disc. Average stiffness was generally greatest in the ligamentum flavum and least in the intraspinous and supraspinous ligaments. For all ligaments, peak elongation was greater than average physiological elongation computed using the mathematical model. CONCLUSIONS: Comparison of the present results with previously reported data indicated that high-speed elongation may cause cervical ligaments to fail at a higher peak force and smaller peak elongation and they may be stiffer and absorb less energy, as compared with a slow elongation rate. These comparisons may be useful to clinicians for diagnosing cervical ligament injuries based upon the specific trauma.

Effect of rotated head posture on dynamic vertebral artery elongation during simulated rear impact.

BACKGROUND: Elongation-induced vertebral artery injury has been hypothesized to occur during non-physiological coupled axial rotation and extension of head. No studies have quantified dynamic vertebral artery elongation during head-turned rear impacts. Therefore, we evaluated effect of rotated head posture vs. forward head posture at the time of impact on dynamic vertebral artery elongation during simulated rear impacts. METHODS: A whole cervical spine model with surrogate head and muscle force replication underwent either simulated head-turned (n = 6) or head-forward (n = 6) rear impacts of 3.5, 5, 6.5 and 8 g. Continuous dynamic vertebral artery elongation was recorded using custom transducer and compared to physiological values obtained during intact flexibility testing. FINDINGS: Average (SD) peak dynamic vertebral artery elongation of up to 30.5 (2.6) mm during head-turned rear-impact significantly exceeded (P < 0.05) the physiological beginning at 5 g. Highest peak elongation of 5.8 (2.1) mm during head-forward rear impact did not exceed physiological limit. Head-turned rear impact caused earlier occurrence of average peak vertebral artery elongation, 84.5 (4.2) ms vs. 161.0 (43.8) ms, and higher average peak vertebral artery elongation rate, 1336.7 (74.5) mm/s vs. 211.5 (97.4) mm/s, as compared to head-forward rear impact. INTERPRETATION: Elongation-induced vertebral artery injury is more likely to occur in those with rotated head posture at the time of rear impact, as compared to head-forward.

Low-intensity pulsed ultrasound treatment for scaphoid fracture nonunions in adolescents.

Background Treatment of scaphoid nonunion is challenging, leading clinicians to pursue innovation in surgical technique and adjunctive therapies to improve union rates. Purpose The purpose of this study was to investigate the use of low-intensity pulsed ultrasound as an adjunctive treatment modality following surgical treatment of scaphoid nonunion in adolescent patients, for whom this therapy has not yet been FDA-approved. Patients and Methods We performed a retrospective review of adolescent patients with scaphoid nonunion treated surgically followed by adjunctive low-intensity pulsed ultrasound therapy. All patients underwent 20 minutes of daily ultrasound therapy postoperatively until there was evidence of bony healing, based on both clinical and radiographic criteria. Final healing was confirmed by > 50% bone bridging on CT scan. Results Thirteen of fourteen (93%) patients healed at a mean interval of 113 days (range 61-217 days). There were no surgical or postoperative complications. One patient developed heterotopic bone formation about the scaphoid. Conclusions Our study suggests that low-intensity pulsed ultrasound therapy can safely be utilized as an adjunctive modality in adolescents to augment scaphoid healing following surgical intervention. Level of Evidence Level IV, Case series.

Scaphoid interfragmentary motions due to simulated transverse fracture and volar wedge osteotomy.

BACKGROUND: Our goal was to determine 3-dimensional interfragmentary motions due to simulated transverse fracture and volar wedge osteotomy of the scaphoid during physiologic flexion-extension of a cadaveric wrist model. METHODS: The model consisted of a cadaveric wrist (n = 8) from the metacarpals through the distal radius and ulna with load applied through the major flexor-extensor tendons. Flexibility tests in flexion-extension were performed in the following 3 test conditions: intact and following transverse fracture and wedge osteotomy of the scaphoid. Scaphoid interfragmentary motions were measured using optoelectronic motion tracking markers. Average peak scaphoid interfragmentary motions due to transverse fracture and wedge osteotomy were statistically compared (P<0.05) to intact. FINDINGS: The accuracy of our computed interfragmentary motions was ± 0.24 mm for translation and ± 0.54° for rotation. Average peak interfragmentary motions due to fracture ranged between 0.9 mm to 1.9 mm for translation and 5.3° to 10.8° for rotation. Significant increases in interfragmentary motions were observed in volar/dorsal translations and flexion/extension due to transverse fracture and in separation and rotations in all 3 motion planes due to wedge osteotomy. INTERPRETATION: Comparison of our results with data from previous in vitro and in vivo biomechanical studies indicates a wide range of peak interfragmentary rotations due to scaphoid fracture, from 4.6° up to 30°, with peak interfragmentary translations on the order of several millimeters. Significant interfragmentary motions, indicating clinical instability, likely occur due to physiologic flexion-extension of the wrist in those with transverse scaphoid fracture with or without volar bone loss.