Day-case laparoscopic ventral rectopexy: an achievable reality.

AIM: Laparoscopic ventral rectopexy (LVR) is a non-resectional technique for selected patients with full-thickness rectal prolapse and obstructed defaecation syndrome. Despite its challenges, LVR can be performed with relatively minimal patient trauma thus creating the potential for same-day discharge. Our aim was to assess the safety of day-case LVR and identify factors associated with same-day discharge. METHOD: Data were prospectively collected on all patients (n = 120) from June 2008 to October 2011. Variables included demographics, perioperative details and postoperative course. Primary outcome was length of stay and secondary outcome was symptom improvement at the latest outpatient follow-up. Patients discharged the same day after LVR were compared with those who stayed overnight or longer. RESULTS: Indications included rectocele and internal prolapse (47%), full-thickness rectal prolapse (44%) and other (9%). Mean operative time was 97 min, same-day discharge occurred with 23% (n = 27) and 67% (n = 80) were discharged on postoperative day 1. In terms of complications, 89% had none, 8% minor and 3% major, including one 24-h readmission for pain. Logistic regression identified younger age (P = 0.054) and private insurance status (P < 0.001) as being significantly associated with same-day discharge. Although surgical indication (P < 0.001), no prior hysterectomy (P = 0.012) and use of biological mesh (P = 0.012) had significant association they were probably confounded by age. CONCLUSION: In selected patients with rectal prolapse or obstructed defaecation, same-day discharge after LVR is feasible and safe. Our analysis identified quicker discharge in the private system with younger patients. Nevertheless, in unselected patients 90% were discharged by the first operative day.

Multidisciplinary management of Hunter syndrome.

Hunter syndrome is a rare, X-linked disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase. In the absence of sufficient enzyme activity, glycosaminoglycans accumulate in the lysosomes of many tissues and organs and contribute to the multisystem, progressive pathologies seen in Hunter syndrome. The nervous, cardiovascular, respiratory, and musculoskeletal systems can be involved in individuals with Hunter syndrome. Although the management of some clinical problems associated with the disease may seem routine, the management is typically complex and requires the physician to be aware of the special issues surrounding the patient with Hunter syndrome, and a multidisciplinary approach should be taken. Subspecialties such as otorhinolaryngology, neurosurgery, orthopedics, cardiology, anesthesiology, pulmonology, and neurodevelopment will all have a role in management, as will specialty areas such as physiotherapy, audiology, and others. The important management topics are discussed in this review, and the use of enzyme-replacement therapy with recombinant human iduronate-2-sulfatase as a specific treatment for Hunter syndrome is presented.

Female sexual dysfunction after ileal pouch-anal anastomosis.

BACKGROUND: The aim was to measure female sexual function after total proctocolectomy with ileal pouch-anal anastomosis for ulcerative colitis using a validated scoring system and to determine the impact of pouch function on sexual function. METHODS: A cross-sectional survey was performed using a modified version of the Female Sexual Function Index (FSFI-m). Measures of pouch function, including the Faecal Incontinence Severity Index, were also evaluated. RESULTS: Of 166 women eligible for inclusion, 90 responded to the questionnaires and 83 of these reported sexual activity. The mean age of the 83 women was 38.4 years and the mean time since pouch formation was 6.2 years. Thirty-nine women (47.0 per cent) had an FSFI-m score of 26 or less, indicating sexual dysfunction. The association between sexual dysfunction and stool leakage interfering with the ability to enjoy sexual activity tended toward significance (P = 0.071), but other measures of pouch function were not associated with sexual dysfunction. Some 55-80 per cent of respondents perceived no change or improved performance in the six domains of sexual function. CONCLUSION: Almost half of the respondents reported having sexual dysfunction. Although poor pouch function was not identified as an important predictor of sexual dysfunction in this series, larger studies may be required to identify associated prognostic factors clearly.

Postoperative deep wound infections in adults after spinal fusion: management with vacuum-assisted wound closure.

OBJECTIVE: Vacuum-assisted wound closure (VAC) exposes the wound bed to negative pressure, resulting in removal of edema fluid, improvement of blood supply, and stimulation of cellular proliferation of reparative granulation tissue. It has been used to treat open wounds in the extremities, open sternal wounds, pressure ulcers, and abdominal wall wounds. This study retrospectively reviewed instrumented spine fusions complicated by surgical wound infection and managed by a protocol including the use of VAC in order to evaluate the efficacy of applying vacuum therapy on patients with deep spine infections and exposed instrumentation. METHODS: Twenty consecutive patients with deep wound infections after undergoing spinal fusion procedures were studied. There were 12 men and 8 women with an average age of 55 years (31-81 years). Eight patients had undergone concomitant anterior and posterior arthrodesis, nine patients had a posterior spinal fusion, and three patients had a transforaminal lumbar interbody fusion. Seven patients had a decompression with exposed dura. Sixteen patients presented with a draining wound within the first 6 weeks postoperatively (average 24 days). There were four patients who presented with back pain and temperature after 1 year postoperatively (average 3 years). All patients were taken to the operating room for irrigation and debridement followed by placement of the VAC with subsequent delayed closure of the wound. RESULTS: There was an average of 1.8 (1-8) irrigation and debridement procedures prior to placement of the VAC. Once the VAC was initiated, there was an average of 2.2 (2-3) procedures until and including closure of the wound. The wound was closed an average of 7 days (5-14 days) after the placement of the initial VAC in the wound. All patients tolerated the VAC without adverse effects. All patients were kept on a 6-week course of intravenous antibiotic therapy. The average follow-up was 10 months (6-24 months). There were no cases of uncontrolled sepsis once the VAC was initiated. All patients achieved a clean closed wound without removal of instrumentation at a minimum follow-up of 6 months. CONCLUSION: VAC therapy is an effective adjunct in closing complex deep spinal wounds with exposed instrumentation.

Human angiotensin II type 1 receptor isoforms encoded by messenger RNA splice variants are functionally distinct.

Human tissues that express the angiotensin II (Ang II) type 1 receptor (hAT(1)R) can synthesize four distinct alternatively spliced hAT(1)R mRNA transcripts. In this study, we show that the relative abundance of these mRNA transcripts varies widely in human tissues, suggesting that each splice variant is functionally distinct. Here we demonstrate, for the first time, that the hAT(1)R-B mRNA splice variant encodes a novel long hAT(1)R isoform in vivo that has significantly diminished affinity for Ang II (i.e. >3-fold) when compared with the short hAT(1)R isoform (encoded by hAT(1)R-A mRNA splice variant). This reduced agonist affinity caused a significant shift to the right in the dose-response curve for Ang II-induced inositol trisphosphate production and Ca(2+) mobilization of the long hAT(1)R when compared with that of the short hAT(1)R. The functional differences between these isoforms allows Ang II responsiveness to be fine-tuned by regulating the relative abundance of the long and short hAT(1)R isoform expressed in a given human tissue.

Extension of fusions to the pelvis in idiopathic scoliosis.

STUDY DESIGN: Retrospective study of patients after extension of previous scoliosis fusions to the pelvis. OBJECTIVE: To determine whether modern instrumentation and surgical techniques provide for increased fusion rates with fewer complications. SUMMARY OF BACKGROUND DATA: Traditionally, long fusions to the pelvis in adults with idiopathic scoliosis have resulted in high complication rates, including pseudarthrosis. METHODS: The hospital and clinic charts of 41 patients (40 female, 1 male) were reviewed 41 months (range: 24-116) after surgery for extension to the pelvis of previous scoliosis fusions. Thirty-nine of 41 had a combined anteroposterior fusion extension; two had posterior extension only. In 37 of 41 patients, Cotrel-Dubousset (CD) instrumentation was used; in two, Isola (Acromed Corp., Cleveland, OH), in one, TSRH; (Sofamor-Danek, Memphis, TN), and in one, Synergy (Cross Medical Products, Columbus, OH). Parameters analyzed were fusion rate, sagittal and coronal balance, lumbar lordosis, length of fusion extension, and distal fixation method. RESULTS: Complications were seen in 30 of 41 patients. The pseudarthrosis rate was 37% (15/41) and was significantly related to the method of distal posterior fixation. With sacral fixation only, the rate was 53% (8/15), with iliac fixation only 42% (3/7), and with both iliac and sacral fixation 21% (4/19; P < 0.05). This was not correlated with fusion rate, and the length of fusion extension did not affect the pseudarthrosis rate or sagittal balance. CONCLUSION: When fixed to the ilium and sacrum, modern instrumentation appears capable of maintaining sagittal balance with lower rates of pseudarthrosis when previous scoliosis fusions are extended to the pelvis. The complication rate remains significant.

Fibronectin and its fragments increase with degeneration in the human intervertebral disc.

STUDY DESIGN: This laboratory-based experiment correlates fibronectin content of intervertebral disc with a morphologic grade of degeneration. OBJECTIVES: To correlate the fibronectin content of the anulus fibrosus and nucleus pulposus with a gross morphologic grade of disc degeneration, and to determine the molecular size of the extractable fibronectin. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration increases with age and can lead to low back pain. Fibronectin helps to organize the extracellular matrix and provides environmental cues by interaction with cell surface integrins. In other tissues, its synthesis is elevated in response to injury. Fibronectin fragments can stimulate cells to produce metalloproteases and cytokines and inhibit matrix synthesis. METHODS: In this study, 17 anuli fibrosis and 18 nuclei pulposus from 11 spines were graded by Thompson's gross morphologic scale. Fibronectin was sequentially extracted with 4 mol/L guanidine hydrochloride and trypsin, and then quantitated by enzyme-linked immunoassay. The size of extractable fibronectin was determined by Western blot analyses. RESULTS: The fibronectin content of the disc increased with grade and was significantly elevated between Grades 3 and 4. The percentage of extractable fibronectin varied widely, but it was more extractable from the nucleus. In both the nucleus and anulus, 30% to 40% of the extractable fibronectin existed as fragments. Many of the fragments contained functional heparin or collagen-binding sites. CONCLUSIONS: Fibronectin is elevated in degenerated discs and frequently present as fragments. Elevated levels of fibronectin suggest that disc cells are responding to the altered environment. Fibronectin fragments resulting from normal or enhanced proteolytic activity could be a mechanism that induces the cell to degrade the matrix further.

Torsional rigidity of scoliosis constructs.

STUDY DESIGN: A biomechanical study of the rigidity of various scoliosis constructs instrumented with and without caudal pedicle screw anchors and with none, one, or two cross-link devices. OBJECTIVES: To determine whether the increased torsional rigidity provided by distal pedicle screw fixation might make cross-linking unnecessary. SUMMARY OF BACKGROUND DATA: Pedicle screws and cross-linking devices have been shown to increase the structural rigidity of spinal constructs. Their relative contributions to scoliosis construct rigidity has not been determined. METHODS: "Short" (T2-T11) and "long" (T2-L3) scoliosis constructs were mounted on an industrially fabricated spine model and tested in a hydraulic testing machine. Four different short and four different long constructs were tested: hooks only, hooks with concave side thoracic sublaminar wires, hooks with distal pedicle screw anchors, and hooks, distal pedicle screw anchors, and concave thoracic sublaminar wires. There were four iterations for each construct tested: no cross-links, one superior cross-link at T4-T5, one inferior cross-link at T9-T10, and two cross-links. Torsional rigidity was tested by applying a rotational torque at T2. Vertebral body motion was recorded with a three-dimensional video analysis system. RESULTS: Constructs with distal pedicle screws were statistically more rigid in torsion than those with hooks as distal anchors. The additional torsional rigidity from one or more cross-links was negligible compared with that provided by pedicle screws. CONCLUSIONS: With pedicle screws as distal anchors in scoliosis constructs, cross-linking with one or two devices adds very little additional rotational stiffness and may be unnecessary in many cases.

Lumbar fusion results related to diagnosis.

STUDY DESIGN: Pain outcome and functional outcome after primary lumbar fusion surgery were determined by a self-assessment questionnaire. The responses were correlated with various clinical parameters. OBJECTIVES: To determine the result of fusion surgery among patients in various diagnostic groups using semiquantitative outcome scales. SUMMARY OF BACKGROUND DATA: Most previous studies on the results of primary lumbar fusion have reported the presence of pain, but few have addressed function outcomes. Results of a literature review were inconclusive as to whether a patient's diagnosis is a predictor of improved results. METHODS: During the 3-year period from 1988 to 1990, 165 patients underwent a primary lumbar fusion procedure. They had a chart and radiograph review and were categorized into five major diagnostic groups: 1) pediatric, 2) grade I-II spondylolisthesis (low-slip), 3) grade III-IV spondylolisthesis (high-slip), 4) degenerative disc disease, and 5) postdiscectomy. At a follow-up period of 5 years (mean) after the fusion, patients were mailed a questionnaire in which they described their pain and functional status before and after their lumbar fusion surgery. Questionnaires were returned by 92% of the patients. The questionnaire scores, complications, and revision procedures were grouped by patient diagnosis and analyzed. RESULTS: Patient satisfaction with the results of primary lumbar fusion ranged from 69% (for the postdiscectomy group) to 100% (for the pediatric and high-slip groups). For all diagnostic groups, lumbar fusion resulted in a significant decrease in back pain and leg pain (visual analog scale), which was maintained throughout the follow-up period. For back pain, the pediatric and high-slip groups showed significantly more improvement than the degenerative disc disease or postdiscectomy groups. Leg pain among patients in the pediatric and high-slip groups was significantly more improved than leg pain among patients in the low-slip, degenerative disc disease, or postdiscectomy groups. There was no deterioration of pain scores during the follow-up period. After fusion, all groups had a significant decrease in Oswestry disability scores; patients in the pediatric and high-slip group had significantly more improvement than patients in the degenerative disc disease or postdiscectomy groups. High- and low-slip groups had a significant improvement in their pain drawing score. Medication use was substantially reduced in all groups. After fusion, a lack of improvement in back pain score or disability score was significantly correlated with pseudarthrosis. CONCLUSIONS: The outcome of primary lumbar fusion surgery was decreased pain and increased function for the majority of patients in all five diagnostic categories. The amount of improvement varied by diagnostic group. Patients with developmental conditions showed greater improvement than patients with degenerative conditions.

Does scoliosis have a psychological impact and does gender make a difference?

STUDY DESIGN: A population-based case-control study, we identified adolescents with and without scoliosis in Minnesota who were 12 through 18 years of age. Matched control subjects were randomly selected from school children who did not have scoliosis or any other condition. Information on scoliosis was obtained by a self-administered questionnaire, the Adolescent Health Survey. Collected on more than 75,000 school age adolescents, with established validity and reliability, a secondary analysis of adolescents with scoliosis was performed as compared with a normative peer group. OBJECTIVE: To describe and characterize the psychosocial impact of scoliosis on the areas of peer relations, body image, and health-compromising behavior, such as suicidal thought and alcohol consumption. SUMMARY OF BACKGROUND DATA: The impact of adolescent idiopathic scoliosis has not been assessed using generic health status measures appropriate for adolescents. Previous studies have concentrated on the health status of adults by measuring work status, marriage status, and other adult measures. The purpose of this study was to study the health status of patients with adolescent idiopathic scoliosis, using the Adolescent Health Survey, a generic health status measure with established validity and reliability. METHODS: Body image, peer relations, social and high-risk behavior, and comparative health were assessed to determine if scoliosis was an independent risk factor and to determine if scoliosis was associated with these psychosocial issues. RESULTS: Six hundred eighty-five cases of scoliosis were identified from the 34,706 adolescents. The prevalence was 1.97%. Of the 685 adolescents with scoliosis and their control subjects, the adjusted odds ratio for having suicidal thought among adolescent with scoliosis, compared to adolescents without scoliosis, was 1.40 (P value of 0.04) after adjustment for race, gender, socioeconomic status, and age. The adjusted odds ratio for having feelings about poor body development among adolescents with scoliosis was 1.82 (P value 0.001) compared with adolescents without scoliosis after adjustment for race, gender, socioeconomic status, and age. Scoliosis was an independent risk factor for suicidal thought, worry and concern over body development, and peer interactions after adjustment. CONCLUSION: Scoliosis is a significant risk factor for psychosocial issues and health-compromising behavior. Gender differences exist in male and female adolescents with scoliosis.

Vertebral body MRI related to lumbar fusion results.

The evaluation of continued pain after a technically successful posterolateral lumbar spine fusion is often challenging. Although the intervertebral disc is often a source of low back pain, abnormal endplates may also be a focus of pain, and possibly a source of continued pain after a posterolateral fusion. MRI allows noninvasive evaluation for disc degeneration, as well as for abnormal endplates and adjacent vertebral body marrow. Previous studies have found inflammatory marrow changes, adjacent to abnormal endplates, associated with disc degeneration in low back pain patients. In this study, preoperative MRI scans in 89 posterolateral lumbar fusion patients were reviewed, by an independent radiologist, to determine whether vertebral body marrow changes adjacent to the endplates were related to continued pain. Independent chart review and follow-up telephone interview of all patients at a 4-year follow-up (mean) formed the basis for the clinical results. Vertebral body MRI signals consistent with inflammatory or fatty changes were found in 38% of patients, and always occurred adjacent to a degenerated disc. Inflammatory MRI vertebral body changes were significantly related to continued low back pain at P = 0.03. We conclude that posterolateral lumber fusion has a less predictable result for the subset of degenerative disc patients with abnormal endplates and associated marrow inflammation. More research is needed to determine the biological and biomechanical effects of posterolateral fusion upon the endplate within the fused segments. If indeed further study supports the hypothesis that abnormal endplates associated with inflammation are a source of pain, then treating the endplates directly by anterior fusion may be a preferred treatment for this subset of degenerative patients.

Magnetic resonance imaging and biological changes in injured intervertebral discs under normal and increased mechanical demands.

STUDY DESIGN: An animal model was used to examine the short-term tissue response to changes in the mechanical environment after the structure (disc) is mechanically injured. OBJECTIVES: To observe changes in an injured intervertebral disc and the corresponding motion segment when the mechanical demands of the disc were increased by fusion of the adjacent motion segments. SUMMARY OF BACKGROUND DATA: Disc degeneration has been modeled in animals by producing a tear in the anulus via laminectomy, laparotomy, or posterolaterally. Methods of altering and quantifying the mechanics of the intervertebral joint by use of internal fixation and fusion in the canine have been developed. METHODS: Eight dogs divided into two groups (a study and a control group) had anular stab wounds (L2-L3). The study group was surgically instrumented posteriorly from L3 to L7. Magnetic resonance imaging studies were conducted for all animals before and periodically after the surgical procedures. At the end of the study, the segments were processed histologically and biochemically. RESULTS: Anular bulging was seen on magnetic resonance imaging in all control animals 4 months after injury and did not progress out until 6 months after injury. Similar changes were seen in study animals, but 75% were herniated by 6 months. Histologic changes correlated with magnetic resonance imaging changes. No significant difference in water or proteoglycan content of the disc tissue between groups was found. CONCLUSIONS: Progression from the bulging of the anulus to herniation was not evident in damaged discs not subjected to adjacent fusions. No change in water or proteoglycan content as a function of altered mechanical state was found, suggesting the short-term effect of the altered mechanics is on the mechanical structure and not on the cells or extracellular matrix.

Back pain in children and adolescents.

Back pain in children is a common problem that is infrequently reported to physicians. Persistent back pain in children is serious, and most conditions can be diagnosed with relatively simple tests, including diagnostic plain radiographs and bone scans. Many cases, including strains and sprains, are relieved with rest and decreased activity. If persistent back pain, increasing pain, fever, or neurologic deficit is present, referral to the orthopedic surgeon should be swift until a specific cause can be found and treated.

Pelvic fractures after long lumbosacral spine fusions.

STUDY DESIGN: A retrospective review of late pelvic ring fractures after long spine fusions to the lumbosacral spine. OBJECTIVES: To review the clinical course and predisposing features of late fractures of the pelvic ring, usually atraumatic, in patients with long fusions to the lumbosacral spine. SUMMARY OF BACKGROUND DATA: Fractures of the pelvic ring after long fusions to the lumbosacral spine is a heretofore rarely reported complication. METHODS: Records from the authors' institution from 1985 to 1994 were reviewed retrospectively. Two hundred sixty-eight patients with long fusions to the lumbosacrum were identified. RESULTS: Between 1985-1994, five patients suffered late atraumatic fractures of the pelvic ring after long instrumented fusions to L5 or the sacrum. All fractures were on the left side of the pelvic ring, primarily the public rami. All patients were women, and at the time of fracture, all were aged 50 years or older. Fractures occurred from 4 months to 7 years after the last surgery (mean, 28 months). All were treated with protected weightbearing until comfortable. At average 27 months' follow-up evaluation, four patients reported no pain; the fifth had become pain-free at 31 months, but 2 months later, the patient spontaneously fractured the contralateral public rami. CONCLUSION: Stress-type fractures of the pelvic ring are a potential source of late pain after long fusions to the lumbosacral spine. Orthopedic surgeons should be aware of this possibility, especially in older, potentially osteoporotic women. Early treatment with simple protected weightbearing appears satisfactory and can prevent significant morbidity.

Effect of sacral and iliac instrumentation on strains in the pelvis. A biomechanical study.

STUDY DESIGN: This study is a biomechanical study on human cadaver pelves using strain gauges to measure strains at different locations in response to different load states. OBJECTIVES: To examine the changes in strains, at different sites on the pelvis, and after instrumentation of the lumbosacral joint and the lumbosacroiliac joint. SUMMARY OF BACKGROUND DATA: Pelvic girdle pain after long instrumented fusions to the sacrum has been described and studied along with sacroiliac and pubic instability. Fractures of the pelvic rami or the iliac wing have been reported in patients after surgical fusions that incorporated the sacrum and sacroiliac joint. METHODS: Pelves with lumbar spine attached had three axis rosette strain gauges cemented to specific sites on the pelves (ilium [correction of ileum] and rami). Specimens were tested in different configurations involving lumbosacral and sacroiliac instrumentation. Iliac bone harvest was also tested. Strain values were computed and compared for each configuration. RESULTS: The "Galveston" and "sacral" instrumentation configurations caused significant stress shielding in pelves under all compression loads applied. Axial rotations on the instrumented specimens caused higher strains at all sites. Harvesting of bone from the ilium did not alter the strains seen at the different sites. CONCLUSIONS: This study suggests significant stress shielding provided by sacro and sacroiliac instrumentation systems, supporting the possibility of development of device-related osteopenia that may predispose patients to late, insufficiency-type fractures as their activity increases. The rigid instrumentation of the lumbosacral spine was found to increase the stress during torsion, which may lead to failure during activity.

Kinematics of the canine lumbar intervertebral joint. An in vivo study before and after adjacent instrumentation.

STUDY DESIGN: In vivo, canine lumbar spine intervertebral motion was measured before and after instrumentation of caudal segments. The three-dimensional kinematics of the intervertebral joint were described using helical axes and Fourier series. OBJECTIVE: The in vivo three-dimensional kinematics of the intervertebral joint were measured and described. An animal model where intervertebral motion could be repeatedly changed was developed. SUMMARY OF BACKGROUND DATA: The kinematics of intervertebral joints have been described from results of extensive in vitro testing, some limited in vivo testing, and clinically by evaluation of flexion/extension films. In the canine, in vivo intervertebral motion has been described previously, but the method possessed some measurement artifact. METHODS: In vivo, four canines had motion data collected (L2-L3) while the animals walked on a treadmill. L3 To L7 were instrumented in all of the animals and motion testing was repeated 1 and 12 weeks later. Helical axes of motion were determined for each gait cycle. Fourier series were fit to the motion data, helical axis parameters, and Fourier coefficients were all statistically compared (pre- and postinstrumentation). RESULTS: Vertebral rotations (coronal plane) and excursion of the L2/3 facet increased significantly (P < 0.01) after caudal instrumentation. Helical axes were oriented in a ventral direction and only the angle of rotation about the axis changed significantly (P < 0.05) after instrumentation of caudal segments. The Fourier coefficients (amplitudes) showed a significant (P < 0.05) increase in the coronal plane rotations only, after adjacent instrumentation. CONCLUSION: The in vivo kinematics of the intervertebral joint have been completely defined in this study. Some motion characteristics compare very well to human motion. Since motion at an intervertebral joint now can be repeatedly altered, this animal model shows promise as a useful tool for investigation of tissue response to changes in motion at a joint.

An improved technique for measuring in vivo intervertebral motion in the canine.

STUDY DESIGN: An experimental animal study using an established technique for measuring in vivo motion in canines was designed to improve measurement techniques and to eliminate the effects of the instrument mounting technique on the tissue and subsequently on the motion being measured. OBJECTIVES: The purpose of this study was to improve a technique for measuring in vivo intervertebral motion in canines, so that the measuring technique did not affect the motion being measured. SUMMARY OF BACKGROUND DATA: Biplanar radiography has been used to measure in vivo intervertebral motion, but involves radiation exposure and expensive equipment. Electromechanical devices have been used more recently but have had significant effects on the motion over extended time periods. METHODS: Intervertebral motion was measured using an instrumented spatial linkage in eight adult canines divided into two groups that differed regarding the method of "mounting pin" placement. Group I had open surgical placement of the pins and Group II had pins placed into the spinous processes. After pin implantation, the instrumented spatial linkage was attached and motion data were recorded during walking. This testing sequence was repeated 3 weeks later. Animals were killed and intervertebral and facet motion were calculated from the experimental data and compared statistically. RESULTS: Facet motion decreased 1 to 3 weeks after pin implantation for animals of group I (3.4 +/- 0.2 mm to 1.1 +/- 0.3 mm), whereas the facet excursion of animals in Group II showed no change (3.0 +/- 0.2 mm and 3.1 +/- 0.3 mm). CONCLUSIONS: A new method of measuring in vivo intervertebral motion in canines has been developed and shown to have no significant affect on the segment mechanics.

Comparison of in vivo and in vitro adjacent segment motion after lumbar fusion.

STUDY DESIGN: For in vitro studies, there is no basis for choosing a "load control study" over a "displacement control" study. This study qualitatively compared results from in vitro and in vivo tests, allowing the authors to address the experimental assumptions that in vitro testing contributes to the understanding of the in vivo condition. OBJECTIVES: To compare motion changes at segments adjacent to fusions for in vitro and in vivo tests. SUMMARY OF BACKGROUND DATA: Investigators have measured the effects of spinal fusions on the adjacent segment in a human cadaver model and found greater adjacent facet joint load after fusions. Others have found significant increases in motion and facet loads at segments adjacent to in vitro lumbosacral and long fusions, when the same range of motion was repeated before and after immobilization of lumbar segments. METHODS: L2-L3 motion was measured in vitro by an instrumented spatial linkage under load and displacement control before and after immobilization of segments (L3-L7). In vivo, L2-L3 motion was measured while animals walked on a treadmill. L3-L7 was fused and the L2-L3 motion testing was repeated. The change in in vivo adjacent segment motion was qualitatively compared with the in vitro change under "load" and "displacement" control. RESULTS: Under "load" control, in vitro facet motion did not significantly change after immobilization, whereas under "displacement" control, the facet motion significantly increased from 2.2 +/- 0.4 mm to 4.1 +/- 0.6 mm. Post-instrumentation, in vivo L2-L3 facet motion increased significantly. This change in vivo related better to the changes seen in the in vitro "displacement" control test than to the in vitro "load" control test.