Anteroposterior Group Research Articles

A comparative cohort study of surgical approaches for adult spinal deformity at a minimum 2-year follow-up.

This study was a retrospective multi-center comparative cohort study. A retrospective institutional database of operative adult spinal deformity patients was utilized. All fusions > 5 vertebral levels and including the sacrum/pelvis were eligible for inclusion. Revisions, 3 column osteotomies, and patients with < 2-year clinical follow-up were excluded. Patients were separated into 3 groups based on surgical approach: 1) posterior spinal fusion without interbody (PSF), 2) PSF with interbody (PSF-IB), and 3) anteroposterior (AP) fusion (anterior lumbar interbody fusion or lateral lumbar interbody fusion with posterior screw fixation). Intraoperative, radiographic, and clinical outcomes, as well as complications, were compared between groups with ANOVA and χ2 tests. One-hundred and thirty-eight patients were included for study (PSF, n = 37; PSF-IB, n = 44; AP, n = 57). Intraoperatively, estimated blood loss was similar between groups (p = 0.171). However, the AP group had longer operative times (547.5min) compared to PSF (385.1) and PSF-IB (370.7) (p < 0.001). Additionally, fusion length was shorter in PSF-IB (11.4) compared to AP (13.6) and PSF (12.9) (p = 0.004). There were no differences between the groups in terms of change in alignment from preoperative to 2years postoperative. There were no differences in clinical outcomes. While postoperative complications were largely similar between groups, operative complications were higher in the AP group (31.6%) compared to the PSF (5.4%) and PSF-IB (9.1) groups (p < 0.001). While there were differences in intraoperative outcomes (operative time and fusion length), there were no differences in postoperative clinical or radiographic outcomes. AP fusion was associated with a higher rate of operative complications.

Optimal screw orientation for fixation of coronal shear fractures: a biomechanical comparison

Coronal shear fractures of the capitellum are rare injuries which can be challenging to treat. The aim of this study was to compare the biomechanical properties of different internal screw fixation techniques for Dubberley type IA fractures of the capitellum. In this biomechanical study, Dubberley type IA fractures of the capitellum were created in 30 human fresh-frozen humeri. The specimens were then divided into 3 groups: fixation was either performed with 3×3.0mm headless cannulated compression screws (HCCSs) in anteroposterior (AP) orientation (AP group), 3×3.0mm HCCSs in posteroanterior (PA) orientation (PA group) or with 2×3.0mm HCCSs in PA orientation and 1×3.0mm HCCS in lateral orientation (LAT) group. Displacement under cyclic loading and ultimate load-to-failure were evaluated in all specimens. There was no significant difference in fragment displacement after 2000 cycles between AP and PA groups (0.8±0.5mm vs. 0.8±0.6mm; P=.987) or PA and LAT groups (0.8±0.6mm vs. 0.8±0.3mm; P=.966). LAT group showed the highest load-to-failure (548±250N) without reaching statistically significant difference to AP group (388±173N; P=.101). There was also no significant difference between AP and PA groups (388±173N vs. 422±114N; P=.649). Variations in screw placement had no statistically significant influence on cyclic displacement or load-to-failure in Dubberley Type IA fractures. However, fracture fixation in 2 planes-both the coronal and the sagittal plane-by adding a screw in a lateral to medial direction may be beneficial to increase primary stability.

Biomechanical Comparison of a Closed-Loop Double Endobutton to a Lag Screw in Fixation of Posterior Malleolar Fractures

Anteroposterior (AP) lag screw, posteroanterior (PA) lag screw, or posterior buttress plate are usually performed for posterior malleolar fixation, but the biomechanically strongest technique is unclear. The aim of our study was to biomechanically compare 3 different fixation methods for posterior malleolar fractures; AP lag screw, PA lag screw, and closed-loop double endobutton. Fracture models were created using a thin blade power saw after drawing the fracture line. The resultant fracture involved 30% of the joint on the distal tibial joint surface and extends with an angulation of approximately 50 degrees using 15 tibia composite bone samples. After anatomical reduction, fixation was achieved with 3.5 mm cortical screw in PA direction and in AP direction for group PA and AP, respectively. In Group DL, fixation was achieved with a closed-loop double endobutton (double lift loop, Orthomed, Turkey). The highest compression force to generate all displacement amounts was required for the double loop group (Group DL). The strongest fixation against compression was a double loop. The PA group was the second strongest fixation, and the AP group was the biomechanically weakest among these 3 fixation techniques. The closed-loop double endobutton technique was found biomechanically superior to anterior to posterior or posterior to anterior screw fixation techniques for posterior malleolar fracture.

Posterior fragment in ankle fractures: anteroposterior vs posteroanterior fixation

IntroductionThe aim of this study was to compare reduction quality and functional outcome of posterior malleolus fractures treated with indirect reduction and anteroposterior (AP) fixation or with direct reduction via a posterolateral approach and posteroanterior (PA) fixation. MethodsForty-eight patients with trimalleolar fracture were enrolled in the study. Patients were randomised in two groups: indirect reduction and AP fixation (AP group) and direct reduction and PA fixation (PA group). Inclusion criteria were: posterior fragment involving more than 25% of the articular surface, displacement over 2mm and ankle instability. The quality of reduction was evaluated using postoperative plain radiographs. Residual displacement of the posterior fragment, articular step-off and/or articular surface gap were analysed. The reduction was considered excellent (<1mm), good (1–2mm) or poor (>2mm). Range of motion (ROM) was measured bilaterally, and the difference in dorsiflexion between the injured and uninjured side was considered as dorsiflexion restriction. Demographic data (age, sex), type of fracture (AO/ASIF classification) and complications were noted. ResultsForty-six patients completed all follow-up examinations. There was no statistically significant difference in age (p = 0.41), sex (p = 0.29) or specific type of fracture (p = 0.83) distribution between the AP and PA groups. All fractures completely healed within 3 months. The overall complication rate was 8.7%. There was no statistically significant difference in complication rate between the two groups (p = 0.71). Radiological evaluation of the ankle showed there was significantly better quality of reduction with direct reduction via a posterolateral approach in the PA group. Excellent reduction was achieved in 79.2% and 45.5% of the PA and AP groups, respectively. The quality of reduction was significantly higher in the PA group compared with the AP group (p = 0.04). The mean restriction of dorsiflexion was lower in the PA group (5.96 ± 0.65°) compared with the AP group (6.45 ± 1.06°), but this difference did not reach statistical significance (p = 0.07). ConclusionsThe direct reduction technique via a posterolateral approach and PA fixation enables higher quality of reduction and better functional outcome in the management of the posterior fragment compared with indirect reduction and percutaneous AP fixation.

Factors Affecting Survival in Patients Undergoing Palliative Spine Surgery for Metastatic Lung and Hepatocellular Cancer: Dose the Type of Surgery Influence the Surgical Results for Metastatic Spine Disease?

BackgroundSurgical treatment for metastatic spine disease has been becoming more prominent with the help of technological advances and a few favorable reports on the surgery. In cases of this peculiar condition, it is necessary to establish the role of surgery and analyze the factors affecting survival.MethodsFrom January 2011 to April 2015, 119 patients were surgically treated for metastatic spine lesions. To reduce the bias along the heterogeneous cancers, the primary cancer was confined to either the lung (n = 25) or the liver (n = 18). Forty-three patients (male, 32; female, 11; mean age, 57.5 years) who had undergone palliative surgery were enrolled in this study. Posterior decompression and fusion was performed in 30 patients (P group), and anteroposterior (AP) reconstruction was performed in 13 patients (AP group) for palliative surgery. Pre- and postoperative (3 months) pain (visual analogue scale, VAS), performance status (Karnofsky performance score), neurologic status (American Spinal Injury Association [ASIA] grade), and spinal instability neoplastic score (SINS) were compared. The survival period and related hazard factors were also assessed by Kaplan-Meier and Cox regression analysis.ResultsMost patients experienced improvements in pain and performance status (12.3% ± 17.2%) at 3 months postoperatively. In terms of neurologic recovery, 9 patients (20.9%) graded ASIA D experienced neurological improvement to ASIA E while the remainder was status quo. In an analysis according to operation type, there was no significant difference in patient demographics. At 12 months postoperatively, cumulative survival rates were 31.5% and 38.7% for the P group and the AP group, respectively (p > 0.05). Survival was not affected by the pre- and postoperative pain scale, Tokuhashi score, neurologic status, SINS, or operation type. Preoperative Karnofsky performance score (hazard ratio, 0.93; 95% confidence interval [CI], 0.89 to 0.96) and improvement of performance status after surgery (hazard ratio, 0.95; 95% CI, 0.92 to 0.97) significantly affected survival after operation.ConclusionsThere was no significant difference in surgical outcomes and survival rates between posterior and AP surgery for metastatic lesions resulting from lung and hepatocellular cancer. Preoperative Karnofsky score and improvement of performance status had a significant impact on the survival rate following surgical treatment for these metastatic spine lesions.

Hemivertebra Resection for Congenital Scoliosis in Young Children

A retrospective comparative study of prospectively collected data. To compare clinical, radiographic, and health-related quality of life (Scoliosis Research Society [SRS]-24) outcomes in patients undergoing hemivertebra excision by simultaneous anteroposterior (AP) or posterolateral only approach (PL). AP hemivertebra resection for congenital scoliosis has provided reliable and safe long-term outcomes with respect to clinical and radiographic findings. Recently, PL excision has been described with rather high implant failure and revision rates. There are no studies comparing outcomes of AP and PL hemivertebra excision in 1 center. In addition, studies reporting health-related quality of life after surgery for congenital scoliosis are few. Between 2001 and 2008, 12 AP and 11 PL hemivertebra excisions were conducted in 21 patients (16 males) with congenital scoliosis or kyphoscoliosis due to unbalanced hemivertebrae in our hospital. The average age at surgery was 4.0 years (range, 1.2-11.4) and the mean follow-up time 2.5 years (range, 1-7 years). Before surgery, the mean Cobb angle of the main curve was 33° (range, 25°-45°) in the AP group and 43° (range, 26°-87°) in the PL group. At the final follow-up visit, the main curve had been corrected to a mean of 12° (range, 2°-27°) and 15° (range, 6°-28°), respectively (P = NS). The Scoliosis Research Society-24 total scores were similar, 101 (range, 89-109) for the AP and 100 (range, 85-106) for the PL group at the final follow-up visit. Any complication was observed in 8% (1/12) of patients in the AP group and, whereas the PL group had 40% (4/10) complication rate with 2 temporary neurologic deficits, no implant failures were observed. All patients underwent spinal fusion during follow-up. PL resection is technically more demanding and slightly faster method for hemivertebral resection. It has nearly as good correction rate as the AP-method but more minor complications. Hemivertebrectomy seems to provide a controllable untethering effect in patients with a symptomatic tethered cord.

A Concomitant Posterior Approach Improves Fusion Rates but not Overall Reoperation Rates in Multilevel Cervical Fusion for Spondylosis

Retrospective comparative study of 2 approaches to multilevel fusion for cervical spondylosis in consecutive patients at a single institution. To provide justification for a concomitant posterior approach in multilevel cervical fusion for spondylosis by demonstrating decreased pseudarthrosis and reoperation rates. Among the factors that affect cervical rates is the number of levels, such that increasing the number of levels leads to lower fusion rates. Because of this, modifications have been sought to improve union in multilevel procedures. One option is an antero-posterior (AP) approach or circumferential arthrodesis. Seventy-eight consecutive patients who underwent multilevel cervical fusion at a single institution and with minimum 2-year follow-up data were divided into an anterior-only group (anterior: n=55), and an AP group (AP: n=23). Union was assessed by surgical exploration, computerized tomography scan, and flexion-extension radiographs. The groups were compared in terms of pseudarthrosis rates and reoperation rates. Using chi(2) analysis, there was a significant difference in pseudarthrosis rates (anterior 38% vs. AP 0%; P<0.001), and reoperation rate for pseudarthrosis (anterior 22% vs. AP 0%; P=0.01). There were no differences in overall (anterior 36% vs. AP 30%; P=0.62) and early (anterior 15% vs. AP 26%; P=0.13) reoperation rates, but late reoperations were increased in the anterior group (24% vs. AP 4%; P=0.043). A concomitant posterior fusion significantly reduced the incidence of pseudarthrosis (0% vs. 38%) and pseudarthrosis-related reoperations (0% vs. 22%) compared with traditional anterior-only fusion. However, this did not translate to a difference in overall reoperation rates. The majority of reoperations in the AP group (86%) were performed within 6 months, whereas those in the anterior-only group (65%) were performed later, which was generally when a pseudarthrosis became evident.

The Mechanical Behavior of Locking Compression Plates Compared With Dynamic Compression Plates in a Cadaver Radius Model

The purpose of this cadaveric study was to compare the mechanical behavior of a locked compression plate, which uses threaded screw heads to create a fixed angle construct, with a dynamic compression plate construct in a cadaver radius model. Mechanical study with cyclic testing and high-speed optical motion analysis. Biomechanics laboratory at an academic institution. Eighteen pairs of fresh-frozen human cadaver radii were divided into 3 groups of 6 to be tested as a group in each of the following force applications: anteroposterior (AP) bending, mediolateral bending, or torsion. Each bone was osteotomized leaving a 5-mm fracture gap and then fixed with a plate. For each pair, 1 radius received a standard plate (limited-contact dynamic compression plates; LC-DCP), the contralateral radius was fixed with a locking compression plate (LCP), and specimens underwent cyclic loading. Normalized stiffness, average energy absorbed, and Newton-cycles to failure were calculated. In addition, a 3-dimensional, high-speed, infrared motion analysis system was used to evaluate motion at the fracture site. Construct stiffness, fracture site motion, cycles to failure, and energy absorption. Repeated measures ANOVA were used to detect differences between groups with time. In the torsion group, LCP specimens failed at 60% greater Newton-cycles than the LC-DCP (1473 vs. 918; P < 0.05). In the AP group, the LC-DCP absorbed significantly greater energy during 10,000 cycles compared with the LCP group (P < 0.05). The 2 constructs demonstrated different biomechanical behavior with time. As cycling progressed in the LC-DCP specimens under torsion testing, stiffness (measured at the actuator at the bone ends) did not change significantly; however, fracture motion (measured at the fracture surfaces) decreased significantly (P = 0.04). The LCP specimens did not display similar behavior. Our findings indicated that LCP constructs may demonstrate subtle mechanical superiority compared with the LC-DCP. The LCP specimens had less energy absorption in the AP group and survived longer in the torsion group. Discordance of motion between measurement regions was observed only in the LC-DCP torsion group, and may have been caused by plate-bone slippage or bone-screw subcatastrophic failure. However, many other compared parameters were found to be similar, and the clinical significance of the few differences found between constructs mandates further investigation.

Revision lumbar arthrodesis for the treatment of cylindrical cage pseudarthrosis: perioperative complications and pitfalls

James D. Schwender, MD, Francis Denis, MD, Timothy A. Garvey, MD, John E. Lohnstein, MD, James W. Ogilvie, MD, Joseph H. Perra, MD, Manuel R. Pinto, MD, Ensor E. Transfeldt, MD, Robert B. Wood, MD, Minneapolis, MN, USAIntroduction: The revision of symptomatic cage pseudarthrosis can be performed by either posterior stabilization alone or circumferential revision including anterior cage removal and anteroposterior (AP) stabilization. Inherent risks associated with revision anterior surgery are numerous. However, posterior surgery alone does not directly address the pseudarthrosis, and pain may remain in spite of solid posterior arthrodesis if the fibrous nonunion does not heal. Although an anterior bony pseudarthrosis has predictable healing with posterior stabilization, there is no information to date concerning what of this study is to identify and describe the perioperative complications associated with revision surgery for the treatment of cage pseudarthrosis.Methods: The current study addresses perioperative complications in 29 consecutive patients who underwent revision surgery for lumbar interbody cage pseudarthrosis.Results: The primary diagnosis for the index surgery was disc degeneration (86%) or spondylolisthesis (14%). Placement of the cages was originally achieved by means of anterior open technique in 85% of the cases. Time interval between the index surgery and the revision ranged from 6 to 81 months (median, 20 months). AP revision was performed in 17 patients (59%), 11 patients (38%) underwent posterior stabilization alone and 1 patient underwent an anterior alone approach. Pedicle screw instrumentation was used for posterior stabilization in all patients. Pseudarthrosis was confirmed intraoperatively in all patients. Twenty-nine cages were removed in 17 patients (20 from L5–S1; 4 from L4–L5; 1 each from L1–2, L2–3, L3–4). Two-thirds (8 of 12) of the cages encountered at L4–L5 were deemed impossible to remove because of the risk of vascular injury, whereas only 20% (5 of 25) at L5–S1 were not removed.Typically, it was found to be more difficult to remove the right-sided cage at L4–5 (three left, five right not removed), whereas at L5–S1 the left side was found to be more difficult (four left, one right not removed). Three of the AP patients (18%), all with anterior cage placement at L5–S1, had iliac vein lacerations requiring repair. All three patients remained hemodynamically stable, and surgery was completed with estimated blood loss of 600 cc, 1,400 cc and 2,300 cc. A fourth patient had a ureter injury requiring subsequent nephrectomy. No neurologic sequelae were encountered with anterior cage removal in those cases where cage placement was originally from the posterior approach. No other intraoperative complications were identified in the AP group, and no intraoperative complications were identified in the posterior only group. Three AP patients (18%) and two posterior alone patients (17%) had postoperative complications, including two infections (one AP, one posterior alone), one radiculopathy (posterior alone) and two patients with prolonged ilius (both AP). As expected, AP revision compared with the one-sided revisions resulted in increased operative time (477 minutes and 222 minutes, respectively), blood loss (1,070 cc and 477 cc, respectively) and days of hospitalization (6 and 4, respectively).Conclusions: Circumferential revision, including cage removal and posterior stabilization, is associated with increased perioperative complications. Great trepidation should be used when planning cage removal from the L4–5 level, because of our finding that 80% of such cages were impossible to remove without excessive risk. Operative time, hospitalization and blood loss are all increased with circumferential revisions. It remains to be answered by this ongoing prospective study if there exists a difference in clinical and patient outcome measures between these two groups that will justify the increased perioperative morbidity associated with attempted cage removal.

Sutural complexity in artificially deformed human (Homo sapiens) crania

The pattern of complexity of cranial sutures is highly variable both among and within species. Intentional cranial vault deformation in human populations provides a controlled natural experiment by which we were able to quantify aspects of sutural complexity and examine the relationship between sutural patterns and mechanical loading. Measures of sutural complexity (interdigitation, number, and size of sutural bones) were quantified from digitized tracings of 13 sutures and compared among three groups of crania (n = 70) from pre-European contact Peru. These groups represent sample populations deformed in 1) anteroposterior (AP) and 2) circumferential (C) directions and 3) an undeformed population. Intergroup comparisons show few differences in degree or asymmetry of sutural interdigitation. In the few comparisons which show differences, the C group is always more interdigitated than the other two while the AP group has more sutural bones. The sutures surrounding the temporal bone (sphenotemporal, occipitotemporal, and temporoparietal) most frequently show significant differences among groups. These differences are related to the more extreme binding of C type deformation and are consistent with hypothesized increases in tension at coronally oriented sutures in this group. The larger number of sutural bones in the AP group is consistent with the general broadening of the cranium in this group and with experimental evidence indicating the development of ossicles in areas of tension. We suggest that so few changes in sutural complexity occurred either because the magnitude of the growth vectors, unlike their direction, is not substantially altered or because mechanisms other than sutural growth modification are responsible for producing the altered vault shapes. In addition, the presence of fontanelles in the infant skulls during binding and the static nature of the binding may have contributed to the similarity in complexity among groups.