Firoz Miyanji

The mechanical properties of the ligamentum teres: a pilot study to assess its potential for improving stability in children's hip surgery.

The anatomic and histological characteristics of the ligamentum teres and its vascular contributions to the femoral head have been well described. The function of the ligamentum teres remains poorly understood. Although excision is the current standard in treating complete developmental hip dysplasia, we developed an interest in maintaining, shortening, and reattaching the ligament to assure early postoperative stability in developmental hip dysplasia. To analyze its potential for providing hip joint stability, we investigated the biomechanical properties of the ligamentum teres in an in vitro porcine model. Six immature porcine hips were dissected, with the proximal femur and acetabular anatomy kept intact, isolating the ligamentum teres. Specimens were loaded in tension using custom fixation rigs at 0.5 mm/s in line with the fibers. Data for displacement and force were collected and sampled at 10 Hz for duration of each test. The ligamentum teres failed in a stepwise fashion. The mean ultimate load to failure was 882 ± 168 N. Mean stiffness and failure stress were calculated as 86 ± 25 N/mm and 10 ± 2 MPa, respectively. The biomechanical function of the ligamentum teres is not inconsequential. We found the ultimate load of the ligamentum teres in the porcine model to be similar to those reported for the human anterior cruciate ligament. The strength of the ligamentum teres may confirm its potential for providing early stability in childhood hip reconstructions. In the setting of dysplasia, the preservation and the transfer of the ligamentum teres to augment stability should be considered as an adjunct to open reduction.

Ligamentum teres maintenance and transfer as a stabilizer in open reduction for pediatric hip dislocation: surgical technique and early clinical results

PurposeThe ligamentum teres has primarily been considered as an obstruction to reduction in children with developmental dislocation of the hip (DDH). In the early surgical descriptions of both the medial (Ludloff) approach and the anterior (Salter) approach to the hip, it was generally accepted that the ligamentum teres was an obstruction to reduction and was excised (similar to the discarding of menisci for knee surgery in our orthopedic history). Because of the known propensity for early re-dislocation following open reduction, we developed surgical methods for maintaining the ligamentum teres when performing open reduction for hip dislocation in young children. This study presents the surgical methods developed for ligament maintenance and transfer, and analyzes the early clinical and radiographic results in a study group.MethodsThe techniques for open reduction by both the medial Ludloff approach and the anterior open reduction were developed and refined. Twenty-one children (23 hips) had ligamentum teres shortening and transfer performed as part of either a medial Ludloff or anterior open reduction for hip dislocation. Complete pre-operative and post-operative clinical and radiographic analysis was performed.ResultsAll patients had stable hips at follow-up. The transferred ligamentum teres appeared to provide additional stability to prevent repeat dislocation. We noted no apparent loss of hip motion or other adverse events. One patient had avascular necrosis (AVN).ConclusionsIn this series of 23 hips, in which ligamentum teres transfer/tenodesis was utilized, we found no residual subluxation or dislocation in either the medial Ludloff or the anterior open reduction groups. Based on these early positive results, we recommend the method for children treated with the Ludloff open reduction procedure. Although we have less experience with it, the technique presented for ligamentum maintenance and transfer in anterior open reduction may provide similar added stability. This is an early follow-up study, and long-term follow-up will be required to confirm the ultimate femoral head and acetabular development.

Postoperative segmental motion of the unfused spine distal to the fusion in 100 patients with adolescent idiopathic scoliosis.

Study Design. A cross-sectional study. Objective. The purpose of this study was to assess intervertebral segmental and cumulative motion in the distal unfused segments of the spine in patients with adolescent idiopathic scoliosis after instrumentation as a function of the lowest instrumented level. Summary of Background Data. The implications of hyper- or hypomobility in the unfused segments of the spine after instrumentation are poorly understood. There is little research on changes in functional movement capabilities of the spine after thoracolumbar spinal fusion. Methods. Patients were prospectively offered inclusion into this institutional review board–approved cross-sectional study at their routine 2-, 3-, 4-, or 5-year postoperative visits at 1 of the 5 participating centers. Motion was assessed by standardized radiographs acquired in maximum right, left and forwarding bending positions. The intervertebral angles were measured via digital radiographic measuring software at each level from T12 to S1. The relationship of the vertebral segmental motion for each interspace to the lowest instrumented vertebrae was evaluated with an analysis of variance. The relationship between the cumulative preserved motion and each domain of the Scoliosis Research Society questionnaire were evaluated using a Pearson correlation coefficient. Results. The data for 100 patients are included. The lowest instrumented vertebrae ranged from T10 to L4. In lateral bending, an association was detected between the lowest fused vertebral level and the degree of motion at the distal unfused segments. With a more distal instrumented vertebrae, there was significantly greater L2–L3, L3–L4, and L4–L5 segment motion (P = 0.002, 0.009, and 0.001, respectively). A similar trend was noticed at L5–S1 level. In addition, the summed motion from L3 to S1 also increased with a more distal fusion (P = 0.001). Similar results were not found in forward bending. None of the domains of the Scoliosis Research Society questionnaire correlated with the preserved L3–S1 motion. Conclusion. In a group of postoperative patients with adolescent idiopathic scoliosis, evaluation of the distal unfused intervertebral motion showed that preservation of vertebral motion segments allowed greater distribution of functional motion across more levels. With each distal fusion level, motion was significantly increased at the L2–L3, L3–L4, and L4–L5 segmental levels in lateral bending. The relationship between the increased motion and subsequent disc degeneration with a more distal fusion is unknown, but suspected.

Publication of abstracts submitted to the annual meeting of the Pediatric Orthopaedic Society of North America: is there a difference between accepted versus rejected abstracts?

Purpose The purpose of this study was to determine publication rates of all abstracts submitted for presentation at the annual conference of the Pediatric Orthopaedic Society of North America (POSNA) comparing papers accepted for presentation with those that were not accepted and to determine the median times to publication and the mean impact factor of journals that published papers from the 2 groups. Methods The titles and authors of all abstracts submitted for presentation to the POSNA for the years 2003 to 2005 were identified. To determine publication status, we conducted a computerized Pubmed search using the first authors name. If multiple publications were identified, the Boolean search operator AND was used to combine author names with key words. The title of each located published article was compared with the title of the abstract. If differences were noted, the abstract content was compared with the final publication. The journals, impact factor was determined using the journal citation report. The median time from conference presentation to publication was determined using a Kaplan-Meier survival analysis. Results Of 1191 abstracts submitted to the annual meetings of POSNA from the years 2003 through 2005, 440 (37%) were accepted for presentation. Acceptance of submitted abstracts increased from 30% in 2003 to 40% in 2005. Of the 1191 abstracts 599 (50%) were subsequently published by August 2009. The mean publication rate for abstracts accepted for presentation was 58.9% (259 of 440) compared with 45% (339 of 751) for rejected abstracts. The median time to publication of accepted abstracts was not significantly different when compared with that of rejected abstracts. The mean journal impact factor for accepted articles was 2.2 compared with 1.5 for rejected abstracts. Conclusions The publication rates of abstracts submitted to POSNA is high compared with those of other international orthopaedic associations. The mean publication rate for accepted abstracts and rejected abstracts has increased substantially from 45% and 38% in 1991 to 1994 to 58.9% and 45% in 2003 to 2005, respectively. The journal in which most of the abstracts are ultimately published is the Journal of Pediatric Orthopaedics Mobility. Significance A significant proportion of abstracts not accepted for presentation at POSNA meetings are published in peer-reviewed journals. Nonacceptance of a study for presentation should not be a hindering factor for researchers in attempting to publish their study in peer-reviewed journals. Level of Evidence Not applicable.

Biomechanical Comparison of Fully and Partially Threaded Screws for Fixation of Slipped Capital Femoral Epiphysis

Background: Previous data have shown that an equal number of threads on each side of the physis maximizes stability for slipped capital femoral epiphysis (SCFE) fixation. The purpose of the current study was to determine if a fully threaded cancellous screw provides greater stability compared with a partially threaded screw in a porcine model. Methods: Twenty skeletally immature porcine femurs were sectioned, and a 30-degree angular wedge was resected from the femoral neck to simulate SCFE. Femora were randomly assigned to partially threaded (16 mm) or fully threaded screw groups (n = 10/group). Kirschner wires were inserted in a retrograde fashion to stabilize the proximal fragment. Each 7.3-mm-diameter screw was placed using fluoroscopic guidance to obtain 3 threads crossing the physis. Specimens were fixed in custom fixation rigs, and the epiphyseal fragment was loaded at 0.5 mm/s in a posterior-inferior direction to simulate slip progression. Data for displacement (in millimeters) and force (in newtons) were collected for the entire test. Forces at 2, 4, 6, and 8 mm of fragment displacement were compared between groups using a 1-way analysis of variance (p < 0.05). Results: Increasing epiphyseal displacements were associated with incremental increases in loading. There were no significant differences between fully threaded or partially threaded screws for loads at each displacement. Each stepwise increase in displacement was associated with approximately 325 N of force. Conclusion: There was no biomechanical benefit when using a fully threaded screw for stabilization of an in vitro SCFE model. Clinical Relevance: Although there were no differences between screw types in an in vitro model, bone healing around the fully threaded screw may eventually provide greater stability. The use of fully threaded screw remains a reasonable option in the treatment of SCFE, and implant removal may be easier with such a system. Further studies are warranted to verify these 2 points.

Is the lumbar modifier useful in surgical decision making?: defining two distinct Lenke 1A curve patterns.

Study Design. Retrospective review of adolescent idiopathic scoliosis (AIS) patients. Objective. To investigate the clinical deformity and radiographic features of Lenke 1A and 1B curves to determine if the “A” and “B” lumbar modifiers actually describe 2 distinct curve patterns. Summary of Background Data. The Lenke classification system attempts to address some of the shortcomings of the King-Moe classification system by providing a more comprehensive, reliable, and treatment-based categorization of all AIS deformities. Although this classification is useful in determining which regions of the spine should be fused, it does not necessarily divide AIS curves into distinct patterns. Methods. A critical analysis of the clinical deformity, radiographic features, and surgical treatment of AIS patients with Lenke 1A and 1B right thoracic curves was performed. Lenke 1A curves were differentiated according to the L4 coronal plane tilt. Analysis of variance and Pearson &khgr;2 analysis were used to perform statistical comparisons between the individual curve patterns (P ≤ 0.05). Results. Ninety-three patients with preoperative and 2-year postoperative data were included in this analysis (65 Lenke 1A, and 28 Lenke 1B). Thirty-three patients were subdivided as 1A-L (L4 tilted to the left) and 32 patients were subdivided as 1A-R (L4 tilted to the right). The interobserver reliability for determining the direction of L4 tilt was excellent (&kgr; = 0.94, P ≤ 0.001). Patients with 1A-L curves were similar to patients with 1B curves with respect to the L4 tilt and the location of the stable vertebra (most often in the thoracolumbar junction). In contrast, patients with 1A-R curves had a more distal stable verte bra (most often L3 or L4). The surgical treatment also differed between these 2 groups with regards to the lowest instrumented vertebra (LIV). 1A-L and 1B curves were similar with a median LIV of T12, whereas the 1A-R curves had a more distal median LIV of L2 (P = 0.01). Conclusion. Two Lenke 1A curve patterns can be described based on the direction of the L4 tilt. This distinction has ramifications regarding selection of fusion levels and assessing surgical outcomes. The A and B lumbar modifiers do not describe 2 distinct curve types within the Lenke 1 group; however, the tilt direction of L4 does allow subdivision of the Lenke 1A curves into 2 distinguishable patterns (1A-R and 1A-L). The 1A-L curves are similar to 1B curves and different in form and treatment from the 1A-R pattern.

Is larger scoliosis curve magnitude associated with increased perioperative health-care resource utilization?: a multicenter analysis of 325 adolescent idiopathic scoliosis curves.

BACKGROUND The treatment of patients with large adolescent idiopathic scoliosis curves has been associated with increased surgical complexity. The purpose of this study was to determine whether surgical correction of larger adolescent idiopathic scoliosis curves increased the utilization of health-care resources and to identify potential predictors associated with increased perioperative health-care resource utilization. METHODS A nested cohort of patients with adolescent idiopathic scoliosis with Lenke type 1A and 1B curves were identified from a prospective longitudinal multicenter database. Four perioperative outcomes were selected as the primary health-care resource utilization outcomes of interest: operative time, number of vertebral levels instrumented, duration of hospitalization, and allogeneic blood transfusion. The effect of curve magnitude on these outcomes was assessed with use of univariate and multivariate regression. RESULTS Three hundred and twenty-five patients with a mean age of 15 ± 2 years were included. The mean main thoracic curve was 54.4° ± 7.8°. Larger curves were associated with longer operative time (p = 0.03), a greater number of vertebral levels instrumented (p = 0.0005), and the need for blood transfusion (with every 10° increase associated with 1.5 times higher odds of receiving a transfusion). In addition to curve magnitude, surgical center, bone graft method, and upper and lower instrumented levels were strong predictors of operative time (R2 = 0.76). The duration of hospitalization was influenced by the surgical center and intraoperative blood loss (R2 < 0.4), whereas the number of levels instrumented was influenced by the curve magnitude, curve correction percentage, upper instrumented vertebra, and surgical center (R2 = 0.64). CONCLUSIONS Correction of larger curves was associated with increased utilization of perioperative health-care resources, specifically longer operative time, a greater number of vertebral levels instrumented, and higher odds of receiving a blood transfusion.

Direct vertebral body derotation, thoracoplasty, or both: which is better with respect to inclinometer and scoliosis research society-22 scores?

Study Design. Prospective, longitudinal cohort (nonrandomized). Objective. To compare thoracoplasty (Th), direct vertebral body derotation (DVBD), and Th and DVBD with respect to correction of the rib prominence and Scoliosis Research Society (SRS) self-image scores in patients undergoing surgery for adolescent idiopathic scoliosis (AIS). Summary of Background Data. Rib prominence correction is one of the main goals of AIS surgery. Th and DVBD are powerful tools for correction of the rib prominence; however, a paucity of literature exists comparing Th, DVBD, and Th and DVBD. Methods. A prospective longitudinal database was queried to identify patients with AIS who underwent a posterior spinal fusion with pedicle screws and 2 years of follow-up. A total of 326 patients were identified and divided into 3 groups: (1) Th alone (N = 47), (2) DVBD alone (N = 196), and (3) both Th and DVBD (N = 83). Patients were subdivided into categories on the basis of their preoperative inclinometer reading: (1) ⩽9° (mild), (2) 10 to 15° (moderate), and (3) ≥16° (severe). Pre- and postoperative inclinometer readings and SRS self-image scores were compared using analysis of variance. Results. Overall, the groups were similar preoperatively except for the DVBD group having higher percentage of thoracic flexibility. The preoperative rib prominence values were Th = 13.2, DVBD = 14.0, and Th and DVBD = 12.9 (P = 0.27). Taken collectively, the postoperative 2-year inclinometer readings were similar for all 3 groups (Th = 5.2, DVBD = 7.0, Th and DVBD = 5.6; P = 0.66). However, the SRS-22 self-image scores were significantly better for patients having both Th and DVBD (Th = 3.37, DVBD = 3.44, Th and DVBD = 3.76; P < 0.01). When patients were stratified by severity of preoperative rib prominence, all patients with mild prominences achieved similar corrections, although SRS self-image scores were highest in the Th and DVBD group. In patients with larger rib prominences, the addition of Th was necessary for optimal rib prominence correction, but there was no difference in SRS-22 self-image scores. Conclusion. Our results suggest that Th alone, DVBD alone, or both Th and DVBD provide equivalent inclinometer results in patients with mild preoperative rib prominences (⩽9°), but higher SRS-22 self-image scores are achieved using both Th and DVBD. For larger rib prominences, better inclinometer readings are achieved with Th, although SRS-22 self-image scores are comparable.

Biomechanical differences between transfacet and lateral mass screw-rod constructs for multilevel posterior cervical spine stabilization.

Study Design. In vitro biomechanical investigation using human cadaveric cervical spines. Objective. Evaluate differences in biomechanical stability between typical lateral mass screw + rod constructs compared to transfacet screw fixation with and without rods. Summary of Background Data. Lateral mass screw + rod constructs have reported efficacious arthrodesis rates/quality but risk damaging the lateral neurovascular structures. Transfacet screw fixation has been studied in the lumbar spine, but little data exists regarding its potential utility in the cervical spine. Methods. Sixteen human cadaveric cervical spines were stripped of soft tissue leaving the occiput and ligamentous structures intact. Spines were randomized to lateral mass or transfacet groups (n = 8/group). Spines were prepared in typical surgical fashion and instrumented with the appropriate devices. In the case of the transfacet constructs, the occiput was left intact to simulate the potential surgical difficulty of screw insertion. The transfacet screw group was initially instrumented with rods. Once instrumented (C3–C6) for each group, spines were further dissected to isolate the instrumented levels. End vertebral bodies were rigidly fixed and constructs biomechanically tested in flexion/extension, lateral bending, and axial torsion between ±2 Nm. After testing for the transfacet screw + rod group, rods were removed and spines retested. All instrumentation was then removed and spines tested in their destabilized state as would occur with surgical preparation. Stiffness data were calculated for each test direction for all groups. Raw and normalized data were each compared across techniques with a 1-way ANOVA (P < 0.05). Results. The transfacet screw groups (with and without rods) were found to have statistically similar biomechanical stability to lateral mass screw + rod constructs for each test direction. Conclusion. Transfacet screws (without rods) were found to have similar biomechanical stability compared to typical lateral mass screw + rod constructs. However, transfacet fixation eliminates the risk to the neurovascular structures and lowers the overall implant profile.

Unplanned return to the operating room in patients with adolescent idiopathic scoliosis: are we doing better with pedicle screws?

Study Design. Prospective, longitudinal cohort. Objective. To evaluate the incidence, timing, and risk factors for reoperation in patients with adolescent idiopathic scoliosis (AIS) treated with pedicle screws (PSs) compared with hybrid (Hb) constructs. Summary of Background Data. Rates of return to the operating room (OR) after definitive fusion for AIS vary, with a paucity of data on PS constructs. Methods. A prospective multicenter database was retrospectively queried to identify consecutive patients with AIS who underwent posterior spinal fusion with either PS or Hb constructs with a minimum 2-year follow-up. All reoperations were stratified into an early group (<60 d) or a late group (>60 d). Univariate and multivariate logistical analyses were performed to identify potential risk factors related to reoperation. Results. A total of 627 patients met the inclusion criteria (PS = 540, Hb = 87). There was a statistically significant difference in the rate of reoperations between the PS (3.5%) and Hb groups (12.6%), P < 0.001. Early return to the OR occurred in 2.0% of the patients with PS compared with 3.4% in the Hb group, P = 0.43. Late returns to the OR occurred in 1.5% of PS group versus 9.2% of the Hb group, P < 0.001. Multivariate analysis revealed longer operating time as an independent risk factor for an unplanned return to the OR in patients treated with PSs (P < 0.05). Conclusion. Our results suggest that patients with AIS treated with PS have decreased rates of unplanned return to the OR when compared with patients with Hb constructs. The majority of returns to the OR were early (<60 d) for the PS group compared with late (>60 d) for the Hb group. Longer operative times increased the risk of unplanned reoperation for the PS group. Level of Evidence: 3