Study Design

An in vitro biomechanical study.

Purpose

To evaluate the biomechanics of a novel posterior integrated clamp (IC) that extends on an already implanted construct in comparison to single long continuous bilateral pedicle screw (BPS) and rod stabilization system.

Overview of Literature

Revision surgery in the thoracolumbar spine often necessitates further instrumentation following a failed previous back surgery. Stability of these reconstructed constructs is not known.

Methods

Six osteoligamentous T12-L5 calf spines were tested on a spine motion simulator in the following configurations: intact, four level constructs (T13-L4), three level constructs (L1-L4), and two level constructs (L2-L4), by varying the ratio between BPS and IC. A load control protocol of 8 Nm moments was applied at a rate of 1°/sec to establish the range of motion value for each construct in flexion-extension, lateral bending, and axial rotation. Statistical analysis was performed on raw data using repeated measures analysis of variance and significance was set at p<0.05.

Results

On an average, the reduction in motion for the four level continuous pedicle screw and rod construct (67%) was similar to those extended with integrated clamps (64%). Furthermore, for three level and two level constructs, no significant difference was observed between continuous pedicle screw constructs and those revised with the integrated clamps (regardless of the ratio between BPS and IC).

Conclusions

The novel posterior IC showed equivalent biomechanical rigidity to continuous pedicle screw rod constructs in revision scenarios. Clinical studies on posterior rod adjunct systems are necessary to confirm these results.

Study Design

Retrospective study.

Purpose

The objective of the study is to evaluate the relationship between the detection rate of lumbar disc herniation and socioeconomic status.

Overview of Literature

Income is one important determinant of public health. Yet, there are no reports about the relationship between socioeconomic status and the detective rate of disc herniation.

Methods

In this study, 443 cases were checked for lumbar computed tomography for lumbar disc herniation, and they reviewed questionnaires about their socioeconomic status, the presence of back pain or radiating pain and the presence of a medical certificate (to check the medical or surgical treatment for the pain) during the Korean conscription.

Results

Without the consideration for the presence of a medical certificate, there was no difference in spinal physical grade according to socioeconomic status (p=0.290). But, with the consideration of the presence of a medical certificate, the significant statistical differences were observed according to socioeconomic status in 249 cases in the presence of a medical certificate (p=0.028). There was a lower detection rate in low economic status individuals than those in the high economic class. The common reason for not submitting a medical certificate is that it is neither necessary for the people of lower socioeconomic status nor is it financially affordable.

Conclusions

The prevalence of lumbar disc herniation is not different according to socioeconomic status, but the detective rate was affected by socioeconomic status. Socioeconomic status is an important factor for detecting lumbar disc herniation.

Study Design

Retrospective study.

Purpose

The goal of care for paraplegic people is the enhancement of their "well-being". However, despite the frequent use of the term "well-being", its definition remains unclear and there is little information in the literature concerning the paraplegic's own perspective. The study was conducted to explore the Pakistani paraplegia's perspective of well-being.

Overview of Literature

Studies have shown that paraplegia changes not only physical and psychological, but also socioeconomic, states, which have significant impact on an individual's "subjective well-being", however there is no clear definition of well-being and the methods of measuring the phenomena.

Methods

Fifty paraplegic adults from different rehabilitation centers of Pakistan participated in an in-depth interview using natural inquiry method. The interviews were audio-taped, transcribed, and analyzed.

Results

Three commonly used meanings of well-being and eight components were identified and included in the definition. The results indicated that the meaning of well-being is an individual's perception, which includes both objective and subjective values and experiences.

Conclusions

The study provides information that was used to develop specific rehabilitation program for the paraplegic Pakistani adults to enhance their well-being.

Study Design

A cross-sectional imaging study.

Purpose

The objective was to assess the degree of degeneration and the associated factors through imaging studies of the lesion segment and the adjacent superior and inferior segments of isthmic and degenerative spondylolisthesis.

Overview of Literature

Few articles existed for degeneration and related factors in isthmic and degenerative spondylolisthesis.

Methods

The subjects were 95 patients diagnosed with spondylolisthesis. Simple plain radiographs including flexion and extension and magnetic resonance imaging were used to investigate the degree of translation, disc degeneration, high intensity zone (HIZ) lesion, Schmorl's node (SN) and Modic changes.

Results

Advanced disc degeneration, grade 5, was shown to be significant in the index segment of the isthmic type (p=0.034). Overall, type 2 Modic change was most common in both groups and also, it was observed more in the isthmus group, specifically, the index segment compared to the degenerative group (p=0.03). For the SN, compared to the degenerative type, the isthmus type had a significantly high occurrence in the index segment (p=0.04). For the HIZ lesions, the isthmus type had a higher occurrence than the degenerative type, especially in the upper segment (p=0.03).

Conclusions

Most advanced disc degeneration, fifth degree, SN and Modic change occurred more frequently in the lesions of the isthmus type. HIZ lesions were observed more in the isthmus type, especially in the segment superior to the lesion.

Study Design

Retrospective analysis.

Purpose

To evaluate the effectiveness of anterior cervical discectomy with fusion for degenerative cervical disc disease.

Overview of Literature

Anterior spinal surgery originated in the mid-1950s and graft for fusion was also employed. Currently anterior cervical microdiscectomy and fusion with an intervertebral cage is a widely accepted procedure for treatment of cervical disc hernia. Artificial grafts and cages for fusion are preferred because of their lower morbidity, reduced operating time and acceptable fusion rate.

Methods

The study involved retrospective analysis and investigation of long-term results for 41 consecutive patients who had undergone anterior cervical discectomy and fusion with an intervertebral cage for cervical disc hernia. The angle of lordosis, segmental height and range of motion were evaluated preoperatively and postoperatively at 1 month and 2 years. The clinical outcome was assessed by the visual analog scale and Odom's criteria.

Results

The angle of lordosis increased by 2.62° and the range of motion angle increased by 5.14° after the operation. The segmental height did not change. The visual analog scale and Odom's criteria scores decreased significantly after the operation.

Conclusions

Using a cage in anterior cervical discectomy prevents segmental collapse, so the segmental height and the angle of lordosis are preserved and newly-developed pain does not occur.

Spinal hydatid cyst is a rare occurrence in non endemic countries. We present a case of recurrent lumbar hydatid disease in a 21-year-old male who following initial treatment had a good functional outcome and healing for 8 years, following which he came back with complaints of low back ache and neurological deficit. Patient underwent a second surgery with global debridement of L3-L5 vertebrae followed by medical management for two years. He had a good surgical outcome with recovery from the neurological deficit. Patient has returned to his routine activities and is being reviewed every year; there is no evidence of recurrence in the past 3 years. To the best of our knowledge recurrence after 8 years of initial treatment, followed by good clinical and radiological outcome for 3 years after surgery and treatment of the recurrence has not been reported in literature.

Gunshot wounds to the spine account for 13% to 17% of all gunshot injuries and occur predominantly in the thoracic region. Minimally invasive spine surgery procedures implementing serial muscle dilation and the use of a tubular retracting system with a working channel minimize soft tissue trauma, facilitate less bony and soft tissue resection, decrease blood loss, minimize scarring and improve cosmesis, decrease hospitalization, and reduce postoperative pain and narcotic usage in comparison to more open, traditional approaches. Although minimally invasive spine surgery techniques and instrumentation have gained considerable attention, their application in the management of gunshot injuries to the sacrum has not been reported. The following is a brief case report of a 21-year-old male who sustained a gunshot injury to the sacrum who was managed operatively via minimally invasive spine surgery techniques and instrumentation.

Spinal dermoid tumors are rare, benign, slow growing tumors. These tumors may become acutely symptomatic after rupture or infection. Excision of the lesion with long term close follow-up studies is required for the management of these lesions. We present a very rare case of ruptured conus medullaris dermoid cyst in a 22-year-old male presented with urinary retention and low back pain. Magnetic resonance imaging scan with contrast reveals a lesion in the cauda equina inseparable from conus medullaris with fat droplets within the central spinal canal extending up to the medulla. Patient was operated with laminectomy and near complete excision of the lesion was done. Patient's low back pain was relieved following surgery. However patient had persistent urinary incontinence and on clean intermittent self-catheterization. Histopathology was suggestive of dermoid cyst.

Proximal junctional disease is a well-recognized postoperative phenomenon in adults who are undergoing long thoracolumbar fusion and instrumentation, and is attributed to increased a junctional stress concentration. In general, the onset of symptoms in these patients is insidious and the disease progresses slowly. We report on a contrary case of rapidly progressing paraplegia secondary to acute disc herniation at the proximal adjacent segment after long posterior thoracolumbar fusion with cement augmentation at the upper instrumented vertebra and the supra-adjacent vertebra. The patient was treated with a discectomy through the costo-transverse approach combined with extension of the posterior instrumentation. The patient's neurological status improved markedly. Stress concentration at the proximal junction disc space may have caused accelerated disc degeneration which in turn lead to this complication.

Lumbar disc herniation (LDH) associated with a contralateral neurological deficit is sometimes encountered by surgeons. Compression against the opposite pedicle in case of a large discal herniation and prominent stenotic changes of contralateral side are held responsible for contralateral symptoms and findings. In this study, we report a case of LDH associated with a painless contralateral neurological deficit. Prominent venous engorgement and congestion at the contralateral side of discal herniation were detected during the operation. It's treatment with bipolar coagulation and significant improvement was seen after the operation.

Patient safety regarding wrong site surgery has been one of the priority issues in surgical fields including that of spine care. Since the wrong-side surgery in the DM foot patient was reported on a public mass media in 1996, the wrong-site surgery issue has attracted wide public interest as regarding patient safety. Despite the many wrong-site surgery prevention campaigns in spine care such as the operate through your initial program by the Canadian Orthopaedic Association, the sign your site program by the American Academy of Orthopedic Surgeon, the sign, mark and X-ray program by the North American Spine Society, and the Universal Protocol program by the Joint Commission, the incidence of wrong-site surgery has not decreased. To prevent wrong-site surgery in spine surgeries, the spine surgeons must put patient safety first, complying with the hospital policies regarding patient safety. In the operating rooms, the surgeons need to do their best to level the hierarchy, enabling all to speak up if any patient safety concerns are noted. Changing the operating room culture is the essential part of the patient safety concerning spine surgery.

Study Design

Prospective experimental study.

Purpose

To evaluate bacterial contamination during surgery.

Overview of Literature

The participants of surgery and ventilation system have been known as the most significant sources of contamination.

Methods

Two pairs of air culture blood agar plate for G(+) bacteria and MacConkey agar plate for G(-) bacteria were placed at 3 different locations in a conventional operation room: in the surgical field, under the airflow of local air conditioner, and pathway to door while performing spine surgeries. One pair of culture plates was retrieved after one hour and the other pair was retrieved after 3 hours. The cultured bacteria were identified and number of colonies was counted.

Results

There was no G(-) bacteria identified. G(+) bacteria grew on all 90 air culture blood agar plates. The colony count of one hour group was 14.5±5.4 in the surgical field, 11.3±6.6 under the local air conditioner, and 13.1±8.7 at the pathway to the door. There was no difference among the 3 locations. The colony count of 3 hours group was 46.4±19.5, 30.3±12.9, and 39.7±15.2, respectively. It was more at the surgical field than under the air conditioner (p=0.03). The number of colonies of one hour group was 13.0±7.0 and 3 hours group was 38.8±17.1. There was positive correlation between the time and the number of colonies (r=0.76, p=0.000).

Conclusions

Conventional operation room was contaminated by G(+) bacteria. The degree of contamination was most high at the surgical field. The number of bacteria increased right proportionally to the time.

Study Design

Retrospective chart review.

Purpose

To assess whether spontaneous reduction of spondylolisthesis, as seen on magnetic resonance imaging (MRI), is related to the degree of segmental instability and low back pain.

Overview of Literature

The flexion-extension radiographs obtained in the sagittal plane are frequently used when segmental instability of spondylolisthesis is evaluated.

Methods

We retrospectively reviewed 137 patients and measured the differences of the percentage of sagittal translation and sagittal angulation to determine the segmental instability between the flexion and extension radiographs, and the spontaneous reduction on MRI. We then compared the degrees of segmental instability and the degrees of spontaneous reduction. To assess the effect of low back pain on segmental motion in regards to the flexion-extension radiographs, we compared the preoperative visual analogue scales (VAS) score for low back pain between the more and the less spontaneous reduction groups.

Results

The mean degree of spontaneous reduction was 5.2%. A statistically significant correlation was found between the sagittal translation on the flexion-extension radiographs and the degree of spontaneous reduction (r = 0.557, p < 0.001) and between the sagittal angulation on the flexion-extension radiographs and the degree of spontaneous reduction (r = 0.215, p = 0.012). The preoperative VAS scores for low back pain of the more spontaneous reduction group and the less spontaneous reduction group were 4.6 and 3.6 points, respectively, and this difference was statistically significant (p = 0.002).

Conclusions

Spontaneous reduction of spondylolisthesis on MRI was found to be closely related to segmental instability, and the degree of spontaneous reduction seen on MRI could be useful for the evaluation of segmental instability in patients with spondylolisthesis, especially with severe low back pain.

Study Design

Retrospective study.

Objectives

To investigate the outcomes of fluoroscopically guided selective nerve root block as a nonsurgical treatment for cervical radiculopathy.

Overview of Literature

Only a few studies have addressed the efficacy and persistence of cervical nerve root block.

Methods

This retrospective study was conducted on 28 consecutive patients with radicular pain due to cervical disc disease or cervical spondylosis. Myelopathy was excluded. Cervical nerve root blocks were administered every 2 weeks, up to 3 times. Outcomes were measured by comparing visual analogue scale (VAS) scores, patient satisfaction, and medication usage before the procedure and at 1 week and 3, 6, and 12 months after the procedure. In addition, complications associated with the procedure and need for other treatments were evaluated.

Results

The average preoperative VAS score was 7.8 (range, 5 to 10), and this changed to 2.9 (range, 1 to 7) at 3 months and 4.6 (range, 2 to 7) at 12 months. Patient satisfaction was 71% at 3 months and 50% at 12 months. Five patients used medication at 3 months, whereas 13 used medication at 12 months. Average symptom free duration after the procedure was 7.8 months (range, 1 to 12 months). Two patients were treated surgically. Only two minor complications were noted; transient ptosis with Horner's syndrome and transient causalgia.

Conclusions

Although selective nerve root block for cervical radiculopathy is limited as a definitive treatment, it appears to be useful in terms of providing relief from radicular pain in about 50% of patients at 12 months.

Study Design

Retrospective.

Purpose

To determine the effect of severity of cervical spondylotic myelopathy (CSM) on gait parameters according to the number of involved spinal cord segments.

Overview of Literature

Although there are a large number of studies on CSM, almost all studies have focused on hand function and only a few studies have examined the gait function in patients with CSM.

Methods

Twenty-three patients with CSM underwent magnetic resonance imaging and gait analysis. The subjects were divided into 2 groups; group I consisted of 9 patients with a single-level stenotic lesion and group II comprised 14 patients with multi-level stenotic lesions. Gait parameters were compared between the 2 groups and the normal control group.

Results

There was no significant difference in the Japanese Orthopaedic Association score between the 2 groups. Cadence, walking speed, stride length, and step length were decreased in group II compared to group I and normal control group. Peak ankle plantar flexion moments during the stance phase and peak knee flexion angle during the swing phase were decreased in group II. Peak ankle, knee, and hi p power generation during the stance phase were decreased in group II; in addition, the peak ankle power generation was decreased in group II than in the normal control group.

Conclusions

Patients with multi-level stenotic lesions had decreased gait ability compared to that in patients with a single-level stenotic lesion. The number of involved spinal cord segments can be one cause of gait deterioration in patients with CSM. Performing a gait analysis is useful for accurate evaluation of the patient.

Study Design

A retrospective study.

Purpose

To evaluate the surgical results of cervical pedicle screw (CPS) fixation combined with laminoplasty for treating cervical spondylotic myelopathy (CSM) with instability.

Overview of Literature

Cervical fixation and spinal cord decompression are required for CSM patients with instability. However, only a few studies have reported on CPS fixation combined with posterior decompression for unstable CSM patients.

Methods

Thirteen patients that underwent CPS fixation combined with laminoplasty for CSM with instability were evaluated in this study. We assessed the clinical and radiological results of the surgical procedures. The Japanese Orthopedic Association (JOA) scoring system was used to evaluate the clinical results. The percentages of sli p, difference in sli p angle between maximum flexion and maximum extension of unstable intervertebrae, and perforation rate of CPS were evaluated.

Results

The mean JOA scores before surgery, immediately after surgery, and at final follow-up were 9.1, 13.3, and 12.6, respectively. The mean percentages of sli p before surgery, immediately after surgery, and at final follow-up were 9.1%, 3.2%, and 3.5%, respectively; there were significant improvements immediately after surgery and at final follow-up. The difference in sli p angle between the maximum flexion and maximum extension of the unstable intervertebrae changed from 9.0° before surgery to 1.6° at the final follow-up. The perforation rate of CPS was 10.9%.

Conclusions

The results suggest that CPS fixation combined with laminoplasty is an effective surgical procedure for treating CSM with instability.

Study Design

A prospective study.

Purpose

To Investigate the prevalence of magnetic resonance imaging (MRI) changes of the lumbar spine in low back pain (LBP) and the associated risk factors in young Arab population.

Overview of Literature

Studies on the prevalence of MRI findings and their relationship with LBP have been conducted; these have occurred in adult populations in developed countries. The prevalence of MRI changes in the young Arab population with LBP is not known.

Methods

Two hundred and fourteen patients of Arab origin in the 16 to 29 year age group with LBP symptoms underwent MRI examinations. The prevalence of MRI changes in the lumbar spine and associated risk factors were determined and compared to age, race, and gender-matched controls.

Results

A majority (64%) of the patients with LBP (138 out of 214) were found to have MRI evidence of degenerative disc disease (DD) compared to 10% (22 out of 214) in the control group. The majority (61%) of patients had multiple level disease, most commonly involving the lowest 2 disc levels. Reduced signal of the disc followed by disc bulge was the most common MRI features seen in the symptomatic subjects. Obesity correlated with MRI prevalence of abnormalities, while activity demonstrated a positive trend.

Conclusions

The MRI prevalence of DD among the young Arab patients with LBP is high when compared to other reports in literature. Obesity correlated with MRI prevalence of abnormalities while activity demonstrated a positive trend.

Study Design

Retrospective study.

Purpose

To evaluate the incidence and risk factors of complications following posterior vertebral resection (PVR) for spinal deformity.

Methods

A review of 233 patients treated with PVR at one institution over a nine-year period (1997 to 2005) was performed. The average age was 33.5 years. Complications were assessed in terms of surgical techniques (posterior vertebral column resection [PVCR] and decancellation osteotomy) and etiologies of deformity.

Results

Local kyphosis was corrected from 51.4° to 2.7°, thoracic scoliosis 63.9° to 24.5° (62.6% correction), and thoracolumbar or lumbar scoliosis 50.1° to 17.1° (67.6%). The overall incidence of complications was 40.3%. There was no significant difference between PVCR and decancellation osteotomy in the incidence of complications. There were more complications in the older patients (>35 years) than the younger (p < 0.05). Hig her than 3,000 ml of blood loss and 200 minutes of operation time increased the incidence of complications, with significant difference (p < 0.05). More than 5 levels of fusion significantly increased the total number of complications and postoperative neurologic deficit (p < 0.05). Most of the postoperative paraplegia cases had preoperative neurologic deficit. Preoperative kyphosis, especially in tuberculous sequela, had hig her incidences of complications and postoperative neurologic deficit (p < 0.05). More than 40° of kyphosis correction had the tendency to increase complications and postoperative neurologic deficit without statistical significance (p > 0.05). There was 1 mortality case by heart failure. Revision surgery was performed in 15 patients for metal failure or progressing curve.

Conclusions

The overall incidence of complications of PVR was 40.3%. Older age, abundant blood loss, preoperative kyphosis, and long fusion were risk factors for complications.

Study Design

A retrospective analysis of 7 patients with traumatic rotatory atlanto-axial subluxation.

Overview of Literature

Cases of traumatic rotatory atlantoaxial subluxation in children are difficult to be stabilized. Surgical challenges include: narrow pedicles, medial vertebral arteries, vertebral artery anomalies, fractured pedicles or lateral masses, and fixed subluxation. The use of O-arm and computer-assisted navigation are still tested as aiding tools in such operative modalities.

Purpose

Report of clinical series for evaluation of the safety of use of the O-arm and computed assisted-navigation in screw fixation in children with traumatic rotatory atlantoaxial subluxation.

Methods

In the present study, 7 cases of rotatory atlantoaxial traumatic subluxation were operated between December 2009 and March 2011. All patient-cases had undergone open reduction and instrumentation using atlas lateral mass and axis pedicle screws with intraoperative O-arm with computer-assisted navigation.

Results

All hardware was safely placed in the planned trajectories in all the 7 cases. Intraoperative O-arm and computer assisted-navigation were useful in securing neural and vascular tissues safety with tough-bony purchases of the hardware from the first and only trial of application with sufficient reduction of the subluxation.

Conclusions

Successful surgery is possible with using the intraoperative O-arm and computer-assisted navigation in safe and proper placement of difficult atlas lateral mass and axis pedicle screws for rotatory atlantoaxial subluxation in children.

The purpose of this case report was to report a rare case of pyogenic spondylodiscitis caused by Campylobacter fetus. A 37-year-old male presented with fever and low back pain. By lumbar magnetic resonance imaging (MRI), no abnormal finding was observed at the first presentation. However, low back pain was aggravated, and fever did not improve. Thus, lumbar MRI was repeated on the 26 day after the onset of symptoms, showing abnormal signals at vertebrae and disc spaces, and pyogenic spondylitis was diagnosed. The possibility of pyogenic spondylodiscitis should be taken into account if a patient presents with low back pain and fever, and areas of low signal intensity on a T1-weighted MRI should be carefully examined. When initial MRI does not reveal abnormal findings, repeated MRI after one or two weeks or, more favorably, immediate gadolinium enhancement MRI, are important for patients who have persistent low back pain and fever.

Chondrosarcomas are malignant cartilage forming tumours. They form the second most common primary malignant tumour involving the vertebral axis. We present a rare presentation of a secondary chondrosarcoma from the spinous process of lumbar vertebra and discussed its management. The main emphasis is on the rare presentation and the need for awareness and suspicion of the pathology.

Cervical stenosis, especially of the upper cervical spine, is quite rare which can be developmental or acquired. Clefts or aplasias of anterior and posterior arches of atlas, ossification of the transverse atlantal ligament, hypertrophy of the dens and os odontoideum are rare conditions causing cervical myelopathy reported either singly or in combination. Hypertrophy of the posterior arch of atlas in the absence of any ring hypoplasia as a cause of cervical myelopathy has not been reported earlier. The authors report a case of cervical myelopathy in a 26-year-old female due to hypertrophied posterior arch of atlas which was preoperatively diagnosed as a bony tumor. Being aware of such an entity may avoid diagnostic surprises and facilitate patient prognostication and management.

A 38-year-old man was operated with posterior spinal decompression and pedicle screw instrumentation for his L2 fracture with incomplete neurological deficit. In the recovery, he complained of blindness in both eyes after twelve hours. Computed tomographic scan and magnetic resonance angiography revealed bilateral occipital lobe infarcts. He remained permanently blind even after three years follow-up. Though rare, perioperative vision loss is a potential complication following spine surgery in prone position. We report a rare occurrence of cortical blindness following lumbar spine surgery.

A 54-year-old female patient had a 6-year history of backache and left sciatica. Five years earlier, she had undergone surgery in another hospital for left L4-5 disc herniation. Computed tomography revealed the ossified wall that enclosed the left L5 nerve root. There were also osteophytic changes in the left L5-S zygapophyseal joint. These osteophytes developed rostrally, along the left L5 nerve root, throug h the intervertebral foramina. We performed decompression surgery for the left L5 nerve root, and surgery resulted in symptomatic relief. We experienced a rare clinical presentation of osteophytic formation, with a specific configuration in relation to the nerve root. Surgeons should be aware of entrapment of the lumbar spinal nerve by advanced osteophytic changes occurring in the zygapophyseal joint after lumbar surgery.

The spinal column is involved in less than 1% of all cases of tuberculosis (TB). Spinal TB is a very dangerous type of skeletal TB as it can be associated with neurologic deficit due to compression of adjacent neural structures and significant spinal deformity. Therefore, early diagnosis and management of spinal TB has special importance in preventing these serious complications. In order to extract current trends in diagnosis and medical or surgical treatment of spinal TB we performed a narrative review with analysis of all the articles available for us which were published between 1990 and 2011. Althoug h the development of more accurate imaging modalities such as magnetic resonance imaging and advanced surgical techniques have made the early diagnosis and management of spinal TB much easier, these are still very challenging topics. In this review we aim to discuss the diagnosis and management of spinal TB based on studies with acceptable design, clearly explained results and justifiable conclusions.