Range of motion after 1, 2, and 3 level cervical disc arthroplasty.

Background: Motion of a solid body involves translation and rotation. Few investigations examine the isolated translational and rotational components associated with disc arthroplasty devices. This study investigates single- and multi-level cervical disc arthroplasty with respect to index and adjacent level range of motion. The investigators hypothesized that single- and multilevel cervical disc replacement will lead to comparable or improved motion at implanted and adjacent levels. Methods: Seven human cervical spines from C2 to C7 were subjected to displacement-controlled loading in flexion, extension, and lateral bending under intact, 1-Level (C5-C6), 2-Level (C5-C6, C6-C7) and 3-Level (C5-C6, C6-C7, C4-C5) conditions. 3D motions sensors were mounted at C4, C5, and C6. Motion data for translations and rotations at each level for each surgical condition and loading mode were compared to intact conditions. Results: 1-Level: The index surgery resulted in statistically increased translations in extension and lateral bending at all levels with statistically increased translation observed in flexion in the superior and inferior levels. In rotation, the index surgeries decreased rotation under flexion, with remaining levels not statistically different to intact conditions. 2-Level: A device placed inferiorly resulted in statistically increased translations at all levels in extension with statistically increased translations superior and inferior to the index level in flexion. Lateral bending resulted in increased nonsignificant translations. Rotations were elevated or comparable to the intact level for all loading. 3-Level: Translations were statistically increased for all levels in all loading modes while rotations were elevated or were comparable to the intact level for all loading modes and levels. Conclusions: Micromotion sensors permitted monitoring and recording of small magnitude angulations and translations using a loading mechanism that did not over constrain cervical segmental motion. Multilevel cervical disc arthroplasty yielded comparable or increased overall motion at the index and adjacent levels compared to intact conditions.

Transfixation of the Sacroiliac Joint: Biomechanical Stability of a Dual-Implant Minimally Invasive Procedure.

BACKGROUND: Despite minimally invasive techniques for sacroiliac joint fixation, clinical challenges remain. The investigators hypothesized the studied technique will transfix the sacroiliac joint to a level comparable to the intact sacroiliac joint. OBJECTIVES: The study objective was to determine the dynamic stability of a square inter-joint implant using a triangular notch in opposing bone segments spanning the joint space. STUDY DESIGN: Stability was assessed by measuring micromotion using contralaterally placed transducers spanning the sacroiliac joint of a specimen during cyclic loading. SETTING: A porcine in-vitro model was equipped with micromotion transducers on the intact and surgically implanted sacroiliac joint. Cyclic loading was applied on the L4 vertebra and the recorded micromotion data at each sacroiliac joint was analyzed. METHODS: Porcine specimens from L3 to the sacrum including the pelvic ring were used to biomechanically evaluate the implantation technique. A novel technique consisting of a square inter-joint implant was placed so as to create a triangular stabilization notch within adjacent boney components of the sacroiliac joint. Displacement transducers were placed across implanted and contralateral porcine sacroiliac joint. Specimens were subjected to compressive loading between -10N and -100N followed by bending/rotation between 0.4Nm and 4.0Nm. Tests were conducted at 0.5Hz for 200 cycles. For each loading mode, transducer deflections (or rotations) were averaged at five-cycle intervals. Student's t-tests were used to compare fitted parameters between implanted and intact sacroiliac joint. RESULTS: In compression, implanted SIJ displayed reduced deflection compared to intact sacroiliac joint (P < 0.0001). In bending/rotation, initial rotation for the intact sacroiliac joint was increased compared to implanted sacroiliac joint (P < 0.0001). The computed Half-Life parameter represents the number of cycles at which the initial rotation decreases by 50% and was found to be statistically reduced for implanted sacroiliac joint as compared to intact sacroiliac joint. LIMITATIONS: The use of porcine specimens resulted in uniform and good quality bone purchase. Further study may be required to evaluate the technique in older patients where bone quality is reduced. CONCLUSIONS: Compared to the intact sacroiliac joint, the implant and procedure in this study demonstrated decreased motion under cyclic compression. Under rotation, the implanted sacroiliac joint displayed increased initial stability that subsequently normalized to intact sacroiliac joint values.

Endplate Deformation Due to Open and Strutted Intervertebral Devices.

BACKGROUND: There is an absence of work on vertebral endplate response to peripheral loading following disc removal and interbody placement. Endplate deflection into the interbody space may impart beneficial strain on the developing fusion mass, influencing bone formation and remodeling. The aim of this study was to verify endplate deformation due to peripheral loading using a custom transducer and to investigate whether endplate motion is inhibited by implant design. METHODS: A total of 14 porcine (L4, L5) vertebrae were assigned to open or strutted implant designs. A custom transducer was placed on the endplate while 500 N was applied to the implant at 1 Hz for 500 cycles. Endplate motion was acquired for each time point and averaged among specimens of the same design. The rates and magnitudes of endplate deformation were compared between implant designs using unpaired t tests. RESULTS: Peripheral loading of both implant designs resulted in endplate deflection into the interbody space. The open implant design demonstrated an increased rate and magnitude of endplate deformation when compared with strutted implants. CONCLUSION: Interbody cage design directly influences the dynamic motion of the vertebral endplate during cyclic loading. A larger, faster deflection of the endplate could increase the strain rate, duration, and magnitude on the developing interbody fusion mass. These parameters of dynamic strain have been correlated with increased bone formation and remodeling. CLINICAL RELEVANCE: Unimpeded endplate deformation in an open cage design could impart a strain pattern on the developing fusion mass that increases bone formation and remodeling, ultimately leading to a faster and stronger fusion.

Differences in femoral morphology among the Orientals and Caucasians: a comparative study using plain radiographs.

The purpose of this study was to identify the differences in femoral dimensions among Caucasian and Oriental populations. A total of 268 femora were collected from China, Japan, Korea, Taiwan and the United States. Firstly, the dimensional parameters for measuring femur were identified. These were initially measured on bone specimens to determine the methodology, followed by measuring the same parameter on plane radiographs of the same bone specimen using a board, and digitized with the aim of verifying the repeatability and reliability of the data. Data were analyzed using ANOVA, paired students t test and Pearson's correlation analysis. The results revealed that Caucasian femora are significantly larger in maximum bone length (BL), head-neck length (HNL), lesser trochanter width and the total width of the distal epiphysis (Wdf). The Beijing femora were found to be the longest and the Japanese femora constituted the shortest bone lengths and smallest angle alpha among the Oriental populations. A strong correlation was observed between Wdf and HD, HNL, Wmc and Wlc in all the populations; however, correlation between Wdf and BL was mild. The angle alpha showed no correlation with BL. This study generated a large database of femoral geometry, which may help pharmaceutical companies to design orthopedic implants for Oriental populations.

Segmental bone replacement via patient-specific, three-dimensional printed bioresorbable graft substitutes and their use as templates for the culture of mesenchymal stem cells under mechanical stimulation at various frequencies.

The treatment of large segmental bone defects remains a challenge as infection, delayed union, and nonunion are common postoperative complications. A three-dimensional printed bioresorbable and physiologically load-sustaining graft substitute was developed to mimic native bone tissue for segmental bone repair. Fabricated from polylactic acid, this graft substitute is novel as it is readily customizable to accommodate the particular size and location of the segmental bone of the patient to be replaced. Inspired by the structure of the native bone tissue, the graft substitute exhibits a gradient in porosity and pore size in the radial direction and exhibit mechanical properties similar to those of the native bone tissue. The graft substitute can serve as a template for tissue constructs via seeding with stem cells. The biocompatibility of such templates was tested under in vitro conditions using a dynamic culture of human mesenchymal stem cells. The effects of the mechanical loading of cell-seeded templates under in vitro conditions were assessed via subjecting the tissue constructs to 28 days of daily mechanical stimulation. The frequency of loading was found to have a significant effect on the rate of mineralization, as the alkaline phosphatase activity and calcium deposition were determined to be particularly high at the typical walking frequency of 2 Hz, suggesting that mechanical stimulation plays a significant role in facilitating the healing process of bone defects. Utilization of such patient-specific and biocompatible graft substitutes, coupled with patient's bone marrow cells seeded and exposed to mechanical stimulation of 2 Hz have the potential of reducing significant volumes of cadaveric tissue required, improving long-term graft stability and incorporation, and alleviating financial burdens associated with delayed or failed fusions of long bone defects.

Substrate effects on cell-envelope deformation during early-stage Staphylococcus aureus biofilm formation.

Bacterial adhesion to a surface is the first step in biofilm formation, and adhesive forces between the surface and a bacterium are believed to give rise to planktonic-to-biofilm phenotypic changes. Here we use Focused-Ion-Beam (FIB) tomography with backscattered scanning electron microscopy (SEM) to image Staphyolococcus aureus (S. aureus) biofilms grown on Au-coated polystyrene (PS) and Au-coated PS modified by mixed thiols of triethylene glycol mono-11-mercaptoundecyl ether (EG3) and 1-dodecanethiol (CH3). The FIB-SEM technique enables a direct measurement of the contact area between individual bacteria and the substrate. The area of adhesion is effectively zero on the EG3 substrate. It is nonzero on all of the other substrates and increases with increasing hydrophobicity. The fact that the contact area is highest on the unmodified gold, however, indicates that other forces beyond hydrophobicity are significant. The magnitude of bacterial deformation suggests that the adhesive forces are on the order of a few nN, consistent with AFM force measurements reported in the literature. The resolution afforded by electron microscopy furthermore enables us to probe changes in the cell-envelope thickness, which decreases within and near the contact area relative to other parts of the same bacterium. This finding supports the idea that mechanosensing due to stress-induced membrane thinning plays a role in the planktonic-to-biofilm transition associated with bacterial adhesion.

Disease severity and treatment in adolescent idiopathic scoliosis: the impact of race and economic status.

BACKGROUND CONTEXT: Ethnic disparities have been documented in the incidence and treatment of many diseases. Additionally, race and socioeconomic status (SES) have been shown to affect disease severity and access to care in the recent orthopedic literature. PURPOSE: To assess the role, if any, that race, SES, and health insurance type play in disease severity and treatment decisions in patients with adolescent idiopathic scoliosis. STUDY DESIGN: Retrospective chart review. PATIENT SAMPLE: Pediatric patients seen in a single surgeon's practice over 6 years (2004-2009). OUTCOME MEASURES: Treatment modality (observation, bracing, or surgery). METHODS: Data were obtained from 403 patients seen over 6 years (2004-2009). A patient-reported questionnaire was used to collect race, age, family income, and parent marital status data. Race was self-reported as "Asian," "black or African American," "Hispanic or Latino," "white or Caucasian," or "Other." Socioeconomic status was determined using family income and type of health insurance as indicators. Major curve magnitude and prescribed initial treatment (observation, brace, or surgery) were assessed from physician records. An independent sample t test was used to detect differences in curve magnitude of the different racial groups. A Pearson chi-square analysis was used to detect group differences for curves in surgical patients, defined as curves greater than 40°, and their initial treatment. RESULTS: Patients self-identified with one of the following racial groups: white (N=219), black (N=86), Hispanic (N=44), Asian (N=37), or Other (N=17). Mean curve magnitude was greater in black than in white patients (33° vs. 28°, p<.05). Black patients were more likely to present with curves in the surgical range (34% vs. 24%, p<.05) and were more likely to have surgery as their initial treatment than white patients (34% vs. 19%, p<.05). Black patients had more limited health care plans and lower incomes compared with whites (p<.001). Patients with higher access insurance plans presented at a younger age than patients with more limited access plans, irrespective of race (13.6 vs. 14.1, p<.05). There was no difference in Cobb angle at presentation by income or type of insurance. CONCLUSIONS: Curve magnitude and percentage of patients with curves in the surgical range were greater in black than in white patients. There was no difference in age on presentation or treatment offered across all racial groups. Black patients were more likely to have surgery as their initial treatment than white patients. While race did have an impact on disease severity in this single surgeon's practice, SES did not.

Predicting operative blood loss during spinal fusion for adolescent idiopathic scoliosis.

BACKGROUND: Patient and surgical factors are known to influence operative blood loss in spinal fusion for adolescent idiopathic scoliosis (AIS), but have only been loosely identified. To date, there are no established recommendations to guide decisions to predonate autologous blood, and the current practice is based primarily on surgeon preference. This study is designed to determine which patient and surgical factors are correlated with, and predictive of, blood loss during spinal fusion for AIS. METHODS: Retrospective analysis of 340 (81 males, 259 females; mean age, 15.2 y) consecutive AIS patients treated by a single surgeon from 2000 to 2008. Demographic (sex, age, height, weight, and associated comorbidities), laboratory (hematocrit, platelet, PT/PTT/INR), standard radiographic, and perioperative data including complications were analyzed with a linear stepwise regression to develop a predictive model of blood loss. RESULTS: Estimated blood loss was 907±775 mL for posterior spinal fusion (PSF, n=188), 323±171 mL for anterior spinal fusion (ASF, n=124), and 1277±821 mL for combined procedures (n=28). For patients undergoing PSF, stepwise analysis identified sex, preoperative kyphosis, and operative time to be the most important predictors of increased blood loss (P<0.05). For ASF, the mean arterial pressure at incision and the operative time were predictive (P<0.05). The following formula was developed to estimate blood loss in PSF: blood loss (mL)=C+Op-time (min)×(6.4)-pre-op T2-T12 kyphosis (degrees)×(8.7), C=233 if male and -270 if female. CONCLUSION: We find sex, operative time, and preoperative kyphosis to be the most important predictors of increased blood loss in PSF for AIS. Mean arterial pressure and operative time were predictive of estimated blood loss in ASF. For posterior fusions, we also present a model that estimates blood loss preoperatively and can be used to guide decisions regarding predonation of blood and the use of antifibrinolytic agents. LEVEL OF EVIDENCE: Retrospective study: Level II.

Radially and axially graded multizonal bone graft substitutes targeting critical-sized bone defects from polycaprolactone/hydroxyapatite/tricalcium phosphate.

Repair and regeneration of critical sized defects via the utilization of polymeric bone graft substitutes are challenges. Here, we introduce radially and axially graded multizonal bone graft substitutes fabricated from polycaprolactone (PCL), and PCL biocomposites with osteoconductive particles, that is, hydroxyapatite (HA), and ß-tricalcium phosphate (TCP). The novel bone graft substitutes should provide a greater degree of freedom to the orthopedic surgeon especially for repair of critically sized bone defects. The modulus of the graft substitute could be tailored in the axial direction upon the systematic variation of the HA/TCP concentration, while in the radial direction the bone graft substitute consisted of an outer layer with high stiffness, encapsulating a softer core with greater porosity. The biocompatibility of the bone graft substitutes was investigated using in vitro culturing of human bone marrow-derived stromal cells followed by the analysis of cell proliferation and differentiation rates. The characterization of the tissue constructs included the enzymatic alkaline phosphates (ALP) activity, microcomputed tomography imaging, and polymerase chain reaction analysis involving the expressions of bone markers, that is, Runx2, ALP, collagen type I, osteopontin, and osteocalcin, overall demonstrating the differentiation of bone marrow derived stem cells (BMSCs) via osteogenic lineage and formation of mineralized bone tissue.

Unitary bioresorbable cage/core bone graft substitutes for spinal arthrodesis coextruded from polycaprolactone biocomposites.

A unitary bioresorbable cage/core bone graft substitute consisting of a stiff cage and a softer core with interconnected porosity is offered for spinal arthrodesis. Polycaprolactone, PCL, was used as the matrix and hydroxyapatite, HA, and ß-tricalcium phosphate, TCP, were used in the formulation of the cage layer to impart modulus increase and osteoconductivity while the core consisted solely of PCL. The crystallinity, biodegradation rate (under accelerated conditions) and mechanical properties, i.e., the uniaxial compression, relaxation modulus upon step compression and cyclic compressive fatigue properties, of the co-extruded cage/core bone graft substitutes could be manipulated by changes in the concentration of HA/TCP in the cage layer. The cyclic fatigue behavior of the cage/core bone graft substitutes were also compared to the behavior of bovine vertebral cancellous bone characterized under similar testing conditions. The biocompatibility of the cage/core bone graft substitutes were assessed via in vitro culturing of human bone marrow derived stromal cells, BMSCs. The cell proliferation rates, time dependencies of the alkaline phosphates (ALP) activity and the expressions of bone markers, i.e., Runx2, ALP, collagen type I, osteopontin and osteocalcin, and the collected µ-CT images demonstrated the differentiation of BMSCs via osteogenic lineage and formation of mineralized bone tissue to indicate the biocompatibility of the cage/core bone graft substitutes.

In vitro analysis and mechanical properties of twin screw extruded single-layered and coextruded multilayered poly(caprolactone) scaffolds seeded with human fetal osteoblasts for bone tissue engineering.

In vitro culturing and mechanical properties of three types of three-dimensional poly(caprolactone) scaffolds with interconnecting open-foam networks are reported. The scaffolds targeted bone tissue regeneration and were fabricated using twin screw extrusion and coextrusion techniques, for continuous mixing/shaping and formation of single or multilayers with distinct and tailorable porosities and pore sizes. Human fetal preosteoblastic cells, hFOB, were cultured on the extruded and coextruded scaffolds under osteogenic supplements and the samples of the resulting tissue constructs were removed and characterized for cell viability and proliferation using the MTS assay, differentiation, and mineralized matrix synthesis via the alkaline phosphatase, ALP, activity and Alizarin Red staining and cell migration using confocal microscopy and scanning electron microscopy. The hFOB cells formed a confluent lining on scaffold surfaces, migrated to the interior and generated abundant extracellular matrix after 2 weeks of culturing, indicative of the promise of such scaffolds for utilization in tissue engineering. The scaffolds and tissue constructs exhibited compressive fatigue behavior that was similar to that of cancellous bone, suggesting the suitability of their use as bone graft substitutes especially for repair of critical-sized defects or nonunion fractures.

Maximal pulmonary recovery after spinal fusion for adolescent idiopathic scoliosis: how do anterior approaches compare?

STUDY DESIGN: Retrospective analysis of prospectively collected data. OBJECTIVE: To compare the relative rates of pulmonary recovery and maximal pulmonary function with surgical approach. SUMMARY OF BACKGROUND DATA: Anterior versus posterior spinal fusion (ASF, PSF) for the treatment of adolescent idiopathic scoliosis (AIS) has been debated. Although procedures that violate the chest wall may compromise pulmonary function, lung function continues to improve after surgery at variable rates depending upon surgical approach. METHODS: We reviewed the medical records from one hundred fifty nine AIS patients (age 15.6±2.2; 113 women; 46 men) treated with spinal fusion from 2003 to 2007 by a single surgeon. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and radiographic measurements were evaluated before surgery and at 1, 3, 6, 12, and 24-months follow-up on average. Four surgical groups were compared: PSF, ASF (open thoracoabdominal approach for thoracolumbar curvature), video-assisted thoracoscopic surgical release with instrumentation (VATS-I), and VATS with PSF. FEV1 and FVC were fitted to model to evaluate the immediate postoperative pulmonary function (Yo), maximal recovery (Plateau), and rate (K) of pulmonary improvement. RESULTS: Patients in each surgical subgroup were as follows: PSF (Lenke 1: n=50, Lenke 2,3: n=20), ASF (Lenke 5, n=35), VATS-I (Lenke 1=31, Lenke 3=1), and VATS+PSF (Lenke1: n=9, Lenke 2-6: n=13). Early postoperative pulmonary function was higher with ASF and PSF as compared to both VATS groups (P<0.05). Comparing all curve types, VATS-I showed a small decline of absolute FEV1 compared to PSF at 2-years follow-up. Comparing thoracic curves, however, no differences in FEV1 or FVC were noted at 6 to 12 months until 2-years follow-up. The rate of recovery (K) was equivalent for all surgical approaches and curve types. CONCLUSION: Compared to ASF or PSF, VATS procedures showed an initial decline in pulmonary function, which resolved fully by 6- to 12-months follow-up. Modest declines in maximal pulmonary function with VATS-I were seen when comparing all curve types together but not when comparing Lenke 1 curves alone. VATS procedures for thoracic scoliosis and open approaches for thoracolumbar curve types were associated with minimal to no permanent deficits.

The treatment of vertebral and chest wall deformities with expandable thoracoplasty and a prosthetic expandable implant.

BACKGROUND: Expansion thoracoplasty is a temporary solution to allow complete pulomonary development in the setting of vertebral and rib cage deformities. After thoracoplasty, an expandable implant is needed to maintain the correction. The Growing Spine Profiler (GSP) is a new type of readjustable rib distracter. The purpose of this study was to evaluate the experiences of surgeons in Europe with the implantation of the GSP. METHODS: We retrospectively reviewed 44 patients that underwent placement of the GSP at 15 sites throughout Europe. The mean age at the time of surgery was 6.24 years. Basic demographic data and postoperative management were reviewed. All patients received an opening-wedge thoracostomy with device implantation and expansion thoracoplasty. Retrospectively, the original indications for implantation were determined. Digital images of the radiographs were used to measure coronal and sagittal parameters. RESULTS: The most common diagnoses for implantation were hemivertebrae (9), hemivertebrae with chest wall deformity (10), and unilateral bar (8). Outcomes were available for 43 patients with a mean follow-up period of 3.07 years. There were 23 patients that had an adverse event. Rib fractures were the most common adverse event, with 8 incidents in 7 patients. Radiographically, coronal curve magnitudes were maintained, whereas sagittal kyphosis gradually increased. CONCLUSIONS: The GSP was effective in the maintenance of deformity, while providing a moderate complication rate. Further studies need to be performed to determine the safety and efficacy of this implant.

Biomechanical analysis of a disc prosthesis distal to a scoliosis model.

STUDY DESIGN: Biomechanical study of bovine spines. OBJECTIVE: The purpose of this study was to perform a biomechanical test to analyze intervertebral deflections following placement of both 1 and 2 semiconstrained TDRs in the subjacent segments of a long fusion. SUMMARY OF BACKGROUND DATA: Long-term sequela of long lumbar fusion for scoliosis include adjacent segment disease and flatback syndrome. Total disc replacement (TDR) is a viable option for the treatment of these conditions. Little data has been published regarding the placement of a TDR distal to a scoliosis fusion. METHODS: Six thoracolumbar bovine spines (T12-S1) were instrumented from T12 to L5, with bilateral pedicle screw fixation at each level. L5-L6 and L6-S1 served as the test levels. One TDR (FlexiCore, Stryker Spine, Allendale, NJ) was initially performed adjacent to the fusion, followed by a subsequent TDR insertion at the last spinal segment. The applied load, total specimen deflection, and local transducer deflections were recorded before and after a TDR at both levels. The results were expressed as a percentage of the intact specimen. Flexion, extension, lateral bending, and torsional deflections were recorded. RESULTS: There were no significant differences (P > 0.05) in sensor deflection observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact spines specimens. A similar effect was observed at the L5-L6 and L6-S1 levels in the anterior and lateral transducers when compared to intact or prior L5-L6 and intact L6-S1 constructs. CONCLUSION: This study has shown that using the FlexiCore system at 1 and/or 2 intervertebral disc spaces caudal to a scoliosis fusion model did not significantly change the sensor deflection at the 2 segments adjacent to a scoliosis fusion construct. Future research will continue to define the clinical setting and patients best suited for management by TDR systems.

Torsional stability of cross-link configurations: a biomechanical analysis.

BACKGROUND CONTEXT: Cross-link systems have been used to augment segmental spinal instrumentation since the earliest introduction of these fixation systems. Although transverse cross-links have little impact on sagittal motion of spinal constructs, cross-linkage does affect torsional rigidity. Despite the wide variety of cross-link designs, almost all have been configured as transverse devices. The relative mechanical benefit of different cross-link configurations is not known. PURPOSE: The purpose of this study was to compare the torsional stability of three different cross-link configurations. STUDY DESIGN: Biomechanical analysis of segmental instrumentation constructs using porcine spines. METHODS: Thoracic porcine spines (T4 to T10) were instrumented with 6.5-mm conical pedicle screws and 7.0-mm connecting rods from T5 to T9. Terminal vertebrae were embedded in polymethylmethacrylate (PMMA) after a T7 corpectomy. Four cross-link configurations were tested in a randomized manner: Un-cross-linked Control (CONT); Transverse Rod-Rod (RR); Transverse Screw-Screw (SS); and Diagonal Screw-Screw (DX) Cross-links. The specimens were rotated to 3 Nm at a rate of 0.2 degrees/s and cycled six times with data acquisition over the final two cycles. Stiffness, rotation, and energy data were normalized to each control. A Newman-Keuls repeated measures analysis of variance was used to infer significant differences. RESULTS: Diagonal cross-link configurations provided the most rigid construct. Transverse cross-links did not significantly change torsional behavior compared with the unlinked control. Rotation and energy expended were not significantly greater torsional stiffness compared with other constructs tested (p<.01). CONCLUSIONS: The diagonal cross-link configuration provided increased torsional stiffness as compared with unlinked or transverse configurations. This observation should be considered in future cross-link designs.

The use of outcomes instruments in the assessment of patients with idiopathic scoliosis.

Outcomes research is becoming an increasingly vital aspect of modern medicine. With current cost containment measures, the need for effective and reproducible treatment options is essential. The methodology associated with these outcomes studies is varied. Studies involving radiographic assessment can be effective with respect to instrumentation performance. However, studies that use physical parameters for outcomes do not include the patient's perception of outcome. For surgical outcome to be considered successful, patient satisfaction must be taken into account. The tools and methods used to assess patient satisfaction are complicated, as these outcomes measures must stratify the various aspects of daily living, personal perception, and overall well-being. The interpretation and analysis of these patient-perceived data can prove challenging because the variability within a group can be large based on human factors. Nonetheless, patient satisfaction should be of prime importance and should be addressed in any outcome study. An overview of the parameters and terms associated with outcomes research in the assessment of patients with scoliosis is important in order to improve existing care or aid in the evaluation of new standards of care.

A biomechanical comparison of posterior cruciate ligament reconstructions using single- and double-bundle tibial inlay techniques.

BACKGROUND: The efficacy of using a double-bundle versus single-bundle graft for posterior cruciate ligament reconstruction has not been demonstrated. HYPOTHESIS: A double-bundle graft restores knee kinematics better than a single-bundle graft does in tibial inlay PCL reconstructions. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric knees were subjected to 6 cycles from a 40-N anterior reference point to a 100-N posterior translational force at 10 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. Testing was performed for the intact and posterior cruciate deficient knee as well as for both reconstructed conditions. Achilles tendons, divided into 2 equal sections, were prepared as both single-bundle and double-bundle grafts. Both grafts were employed in the same knee, and the order of graft reconstruction was randomized. RESULTS: There were no statistical differences in translation between the intact state and either of the reconstructions (P > .05) or between either of the reconstructions at any flexion angle (P > .05). CONCLUSION: No differences in translation between the 2 graft options were identified. CLINICAL RELEVANCE: The use of a double-bundle graft may not offer any advantages over a single-bundle graft for tibial inlay posterior cruciate reconstructions.

The effect of humeral component anteversion on shoulder stability with glenoid component retroversion.

BACKGROUND: Posterior glenoid bone loss is often seen in association with glenohumeral osteoarthritis. This posterior asymmetric wear can lead to retroversion of the glenoid component and posterior instability after total shoulder arthroplasty. Options for the treatment of this asymmetric wear include eccentric reaming of the so-called high side, bone-grafting, and/or anteverting the humeral component. Although anteverting the humeral component has been advocated by many, it has not been substantiated on the basis of biomechanical data. The purpose of the present study was to determine whether anteverting the humeral component increases the stability of a total shoulder replacement with a retroverted glenoid component. METHODS: A total shoulder arthroplasty was performed in eight human cadaveric shoulders. The glenoid component was placed in 15 degrees of retroversion. Two humeral versions were tested for each specimen: anatomic version and 15 degrees of anteversion relative to anatomic version. The specimens were mounted supine in a custom fixture on a servohydraulic testing system. The humerus was translated posteriorly by one-half of the width of the glenoid. Three positions of humeral rotation were tested for each position of humeral version. Both the energy and the peak load were analyzed as measures of joint stability. RESULTS: There was no significant difference in either energy or peak load between the tests performed with the humeral component in 15 degrees of anteversion and those performed with the component in anatomic version in any of the three rotational positions (p > 0.05). CONCLUSIONS: Although anteverting the humeral component during total shoulder arthroplasty to compensate for glenoid retroversion has been advocated, these data suggest that compensatory anteversion of the humeral component does not increase the stability of a shoulder replacement with a retroverted glenoid component.

Selective retention of bone marrow-derived cells to enhance spinal fusion.

Connective tissue progenitors can be concentrated rapidly from fresh bone marrow aspirates using some porous matrices as a surface for cell attachment and selective retention, and for creating a cellular graft that is enriched with respect to the number of progenitor cells. We evaluated the potential value of this method using demineralized cortical bone powder as the matrix. Matrix alone, matrix plus marrow, and matrix enriched with marrow cells were compared in an established canine spinal fusion model. Fusions were compared based on union score, fusion mass, fusion volume, and by mechanical testing. Enriched matrix grafts delivered a mean of 2.3 times more cells and approximately 5.6 times more progenitors than matrix mixed with bone marrow. The union score with enriched matrix was superior to matrix alone and matrix plus marrow. Fusion volume and fusion area also were greater with the enriched matrix. These data suggest that the strategy of selective retention provides a rapid, simple, and effective method for concentration and delivery of marrow-derived cells and connective tissue progenitors that may improve the outcome of bone grafting procedures in various clinical settings.

Evaluation of the biological response of wear debris.

STUDY DESIGN: An animal study was conducted to evaluate the biological response to titanium particles from an artificial intervertebral disc in terms of serology and histologic changes. OBJECTIVES: To determine the biological response to wear debris in the retroperitoneal and epidural space. SUMMARY OF BACKGROUND DATA: Few wear studies exist about mechanical artificial discs. METHODS: Twenty-three New Zealand white rabbits were used for two approaches of the lumbar spine. In a retroperitoneal group (10 rabbits), lateral flank approach at the L2-L3 area was used. In an epidural group (13 rabbits), a dorsal laminotomy of L2 was performed. The wear debris was obtained from mechanical test cycling of the implantable intervertebral disc. At 4 and 12 weeks postoperatively, five or six animals from each group were killed. The tissues, including deposition site, regional lymph nodes and major organs, were evaluated with hematoxylin and eosin staining. RESULTS: At death all rabbits were found to be healthy. Blood results from the predeath samples were found to be consistent with the preoperative blood work values. Scar tissue was minimal with good healing. All organs were found to be normal in appearance. On histopathology sections, adverse reactions such as fibrosis, granuloma formation or necrosis were not found in any tissues. Free particles were found sparingly in all tissue sections with minimal cellular response. No remarkable difference was found according to groups or time intervals. Smaller particles were found to be engulfed in macrophages without adverse biological consequences. CONCLUSION: Titanium particles traveled from the sites of deposition but elicited no to minimal biological response.