The Association of Sacral Table Angle Measurements With Spondylolytic and Spondylolisthetic Defects at the Lumbosacral Articulation: A Radiographic Analysis.

STUDY DESIGN: Retrospective radiographic study of 6 patients with L5 spondylolysis observed prospectively before the onset of lysis through adulthood. A radiographic analysis of 50 pediatric control subjects was compared with the study group. OBJECTIVE: To determine whether sacral table angle (STA) measurements bear etiologic association with the development of spondylolysis and/or subsequent spondylolisthesis. SUMMARY OF BACKGROUND DATA: Although radiographic parameters in association with spondylolysis and isthmic spondylolisthesis have been studied, no parameter has been shown to definitively have a role in development of this disease process. The STA is a recently described radiographic parameter useful in measuring anatomic changes across the lumbosacral articulation. This measurement's role as a predictor of pars lysis and subsequent slippage remains unknown. METHODS: The researchers examined the longitudinal plain radiographs of 6 patients observed from childhood, before the development of spondylolysis, through adulthood. Measurements of STA and percent slippage were performed. Fifty pediatric control subjects' radiographs were also examined with STA measurements. Statistical analysis was conducted on results. RESULTS: Mean STA of the study group before the development of spondylolysis was 95° ± 5.5°. Mean STA from the control group was 97.5° ± 4.3°. No statistical difference was found between groups (p > .05). No index patient had an abnormal STA before spondylolysis (less than 89°, defined as being outside 2 standard deviations from the control mean). Four of 6 index patients with spondylolysis developed spondylolisthesis. A negative correlation (r = .54) was seen for STA as a function of increasing percent slip when assessed longitudinally. CONCLUSIONS: Abnormal STA measurement was not seen before the development of spondylolysis in this study population. Decreasing STAs were seen secondarily in patients with L5 spondylolisthetic progression. This finding points to anatomic change and secondary remodeling of the upper sacrum as a result of slippage.

Relationship between near infrared spectroscopy and intra-compartmental pressures.

BACKGROUND: Near infrared spectroscopy (NIRS) has been suggested as a possible means for detecting perfusion deficits in patients with acute compartment syndrome (ACS). STUDY OBJECTIVES: To longitudinally examine NIRS in an ACS model to determine its responsiveness to decreasing perfusion pressure. METHODS: A NIRS sensor pad was placed under a tourniquet over the anterior compartment in the mid-tibia region on 20 volunteers. Initial perfusion pressures and NIRS values were recorded. The tourniquet pressure was sequentially raised by 10 mm Hg in 10-min intervals until systolic pressure was surpassed. NIRS values and perfusion pressure were determined at the end of each 10-min interval. RESULTS: There was no change in mean NIRS values from the initial baseline until 30 mm Hg of perfusion pressure was reached. Additionally, a statistically significant drop in mean NIRS values was observed as perfusion pressures dropped from 10 mm Hg to 0 mm Hg, and again with subsequent decreases of 10 mm Hg perfusion pressure until systolic pressure was surpassed. CONCLUSIONS: These results coincide with previously published studies using alternative methods of measuring blood flow or perfusion. NIRS values were responsive to decreasing perfusion pressures over a longitudinal period of time in an ACS model. These results suggest that NIRS may be useful for continuous, non-invasive monitoring of patients for whom ACS is a concern. Additional studies on traumatized patients are required.

The reliability of measurement of tissue pressure in compartment syndrome.

BACKGROUND: Although there is general agreement as to the pathophysiology and treatment of compartment syndrome and the importance of intramuscular pressure measurements, there are many methods described to obtain these measurements. Variations in experimental measurements using current electronic monitoring, needle, and catheter devices of 18 to 22 mmHg are reported and are enough to cause errors in clinical decision-making that could result in significant clinical consequences. Current unacceptable reliability has been reported with the use of bevel-tipped needles and the clinical Whitesides technique. Because this is contrary to the authors' cumulative clinical and research experience with various methods when properly used (with the small required saline flush to assure a fluid continuum between tissue and the pressure monitor), this study was designed to clarify these problems. Although the two Whitesides techniques (original and clinical) are not in current use where digital methods are available, the clinical method is still used in the Third World. METHODS: To eliminate comparative errors, a laboratory compartment syndrome model was devised to allow simultaneous testing of different devices in the same area of fusiform muscle against increasing intramuscular pressure using the same transducer and monitor. Slit catheters, side-ported bevel-tipped needles, and 18-gauge bevel-tipped needles were compared against each other. The two Whitesides methods using a capillary meniscus and a mercury manometer were compared against a current electronic transducer method using identical 18-gauge bevel-tipped needles and varying diameter capillary tubing. RESULTS: The side-ported needle, slit catheter, and 18-gauge bevel-tipped needle were found to measure equivalent pressure when compared statistically with each other in pairs. The original Whitesides method using a 1.25-mm capillary tube and the digital transducer method using 18-gauge bevel-tipped needles was also found to measure equivalent pressure. The clinical Whitesides method using current plastic intravenous tubing of 3.0-mm internal diameter fails to produce an obvious capillary meniscus, leading to diminished reliability in the measured pressure. CONCLUSIONS: The slit catheter, side-ported bevel-tipped needle, or an 18-gauge needle, when appropriately used with current electronic transducer monitoring, may be used clinically with confidence. When digital methods are not available, the original Whitesides method using 1.25-mm glass capillary tubing is an accurate alternative but requires preplanning. When only 3-mm tubing is available, this method is relatively useful when electronic means are not available by averaging several consecutive measurements.

Correlation between muscle oxygenation and compartment pressures in acute compartment syndrome of the leg.

BACKGROUND: Near-infrared spectroscopy estimates soft-tissue oxygenation approximately 2 to 3 cm below the skin. The purpose of the present study was to evaluate muscle oxygenation in the setting of an acute compartment syndrome of the leg and to determine if near-infrared spectroscopy is capable of detecting perfusion deficits. METHODS: Fourteen patients with unilateral lower extremity trauma were enrolled after the diagnosis of an acute compartment syndrome was made clinically and confirmed with intracompartmental pressure measurements. Lower extremity muscle compartments were evaluated with near-infrared spectroscopy, and near-infrared spectroscopy values of the uninjured, contralateral leg of each patient were used as internal reference values. The compartment perfusion gradient was calculated as the diastolic blood pressure minus the intracompartmental pressure. RESULTS: Intracompartmental pressures ranged from 21 to 176 mm Hg (mean, 79 mm Hg) and exceeded 30 mm Hg in all compartments but two (both in the same patient). Thirty-eight compartments had a perfusion gradient of < or = 10 mm Hg (indicating ischemia). Among ischemic compartments, near-infrared spectroscopy values in the anterior, lateral, deep posterior, and superficial posterior compartments of the injured limbs were decreased by an average 10.1%, 10.1%, 9.4%, and 16.3% in comparison with the corresponding compartments of the uninjured leg. Differences in near-infrared spectroscopy values (the near-infrared spectroscopy value for the injured leg minus the near-infrared spectroscopy value for the uninjured leg) were positively correlated with compartment perfusion gradient within each compartment (r = 0.82, 0.65, 0.67, and 0.62, for the anterior, lateral, deep posterior, and superficial posterior compartments, respectively; p < 0.05 for all). CONCLUSIONS: Normalized near-infrared spectroscopy values decrease significantly with decreasing lower limb perfusion pressures. Near-infrared spectroscopy may be capable of differentiating between injured patients with and without an acute compartment syndrome.

Spinal instrumentation for sacral-pelvic fixation: a biomechanical comparison between constructs ending with either S2 bicortical, bitriangulated screws or iliac screws.

STUDY DESIGN: A biomechanical study of 2 fixation techniques for lumbosacral fixation. OBJECTIVE: To evaluate 2 techniques, one using S1 screws combined with bicortical, bitriangulated (BCBT) S2 screws, and the other using S1 screws combined with iliac screws. SUMMARY OF BACKGROUND DATA: Common to the 2 techniques of sacral-pelvic fixation is S1 pedicle screws; the difference lies between S2 screws versus iliac screws. Iliac screws are clinically effective, yet present clinical disadvantages that S2 screws can potentially obviate, for example, wide dissection, soft tissue coverage, crossing the sacroiliac joint, and interference with bone graft harvesting. In an effort to optimize S2 fixation, we have used a BCBT S2 technique. METHODS: Eight fresh human sacral-pelvic specimens were harvested (average age 78.7 y; bone density 0.75 g/cm2). Screws were placed bilaterally: (1) at S1: 7.5 mm diameter screws were placed bicortical; (2) at S2: 7.5 mm diameter by 60 mm long screws were placed bicortical and bitriangulated; (3) the ilium received 7.5 mm diameter by 80-mm-long screws. Sacral-pelvic constructs were assembled and biomechanical stiffness testing was performed. The stiffness in each loading mode was calculated. After the stiffness tests were completed, each BCBT S2 screw and each iliac screw were individually loaded to determine fixation strength of each type of screw. RESULTS: There was no significant difference in stiffness between the 2 constructs, although S1 and the BCBT S2 construct tended to be stiffer in all modes. However, for the fixation strength of screws, the iliac screws loosened at loads that were significantly greater than those for BCBT S2 screws (c.f. 435.9 N with 144.7 N). CONCLUSIONS: Iliac screws maybe the better choice in cases with poor bone quality. However, the S1-BCBT-S2 screw construct is biomechanically an appropriate alternative to the S1-iliac screw construct and it presents clinical advantages.

Near-infrared spectroscopy in lower extremity trauma.

BACKGROUND: Near-infrared spectroscopy measures the percentage of hemoglobin oxygen saturation in the microcirculation of tissue up to 3 cm below the skin. The purpose of this study was to describe the measurable response of normal tissue oxygenation in the leg after acute trauma with use of this technique. METHODS: Twenty-six patients with acute unilateral tibial fractures and twenty-five uninjured volunteer control subjects were enrolled. Near-infrared spectroscopy measurements were obtained for both legs in all four compartments: anterior, lateral, deep posterior, and superficial posterior. The twenty-six injured legs were compared with twenty-five uninjured legs (randomly selected) of the volunteer control group, with the contralateral limb in each patient serving as an internal control. RESULTS: The mean tissue oxygenation for each compartment in the injured legs was 69% (anterior), 70% (lateral), 74% (deep posterior), and 70% (superficial posterior). In the control (uninjured) legs, the average tissue oxygenation percentage in each compartment was 54%, 55%, 60%, and 57%, respectively. Repeated-measures analysis revealed that near-infrared spectroscopy values averaged 15.4 percentage points (95% confidence interval, 12.2 to 18.6 percentage points) higher for injured legs than for uninjured legs, controlling for the value of the contralateral limb (p < 0.0001). CONCLUSIONS: Tibial fracture produces a predictable increase in tissue oxygenation as measured by near-infrared spectroscopy. The corresponding compartment of the contralateral leg can provide strong utility as an internal control value when evaluating the hyperemic response to injury.

Surgical treatment of destructive calcific lesions of the cervical spine in scleroderma: case series and review of the literature.

STUDY DESIGN: An independent retrospective chart review combined with a review of current literature. OBJECTIVES: To describe a series of destructive, calcific masses of the cervical spine causing pain, neurologic dysfunction, and instability in patients with scleroderma and detail the surgical interventions required. To review benign, calcific cervical spine lesions associated with scleroderma and collagen vascular disorders. SUMMARY OF BACKGROUND DATA: Little is know about the diagnosis and management of the destructive, calcific lesions of scleroderma in the cervical spine. METHODS: The medical and radiographic records of 3 patients with scleroderma lesions in the cervical spine were reviewed. A computer-based literature search of Ovid and PubMed databases was used to compile a comprehensive review of the topic. RESULTS: The perioperative and surgical management of 3 cases of scleroderma of the cervical spine are discussed in the context of a complete literature review on the topic. These complex lesions were found to require significant resources with regard to diagnosis and management. CONCLUSIONS: Destructive, calcific masses in the cervical spine associated with scleroderma and an indication for surgical treatment are rare. Treatment is complex and not without significant risk to the patient.

Spondylolytic spondylolisthesis: a study of pelvic and lumbosacral parameters of possible etiologic effect in two genetically and geographically distinct groups with high occurrence.

STUDY DESIGN: An anatomic and radiographic study of archeological skeletal remains from two genetically and geographically distinct groups with high occurrence rates of spondylolytic spondylolisthesis was done. Specimens were Aleut (27% known occurrence rate, n = 48) and Arikara Plains Indians (9% occurrence, n = 250+ of 1,062). OBJECTIVE: To evaluate three radiographic parameters highly correlated with spondylolisthesis (pelvic incidence [PI], sacral table angle [STA], and lumbar index [LI]) in genetically homogeneous populations to determine which may be etiologic or most predictive for lysis. SUMMARY OF BACKGROUND DATA: LI has been known to vary with the percentage of slip in lytic spondylolisthesis. Recent clinical studies have shown that PI is also significantly higher in high-grade slips, and a possible etiologic effect has been ascribed to this association. STA has also been shown to vary between normals, those with only lysis, and those with lysis and slip. The etiologic significance of STA is unknown. METHODS: Radiographic and direct morphologic measurement of PI, LI, and STA was done on L5 and reassembled sacra and ilia. Statistical analysis of these three parameters among all groups was done. RESULTS: 1) There is a genetically determined difference in the upper sacral tilt (STA) that may be etiologic. 2) Genetically homogeneous groups with a lower STA in normal specimens have an increased occurrence rate of spondylolysis. 3) When there has been pars lysis, changes in the STA occur as well as deformity more caudal in the sacrum. 4) These changes are likely related to remodeling with epiphyseal growth related to changed axial stresses secondary to pars lysis. 5) PI is not a primary etiologic factor in the process. CONCLUSIONS: The STA in the normal population for each genetic group varies and relates significantly to the occurrence rate and is thus probably etiologic. STA is more highly associated with the occurrence of pars defect than is PI. Upper sacral deformities appear due to the growth plate response to the changed pressure gradients across the epiphyseal plate rather than interosseous remodeling of the ilium and acetabular area. Thus, changes in PI would be secondary.