Faculty Bibliography

We report a case of a patient who underwent two-level lumbar total disc replacement at L4-L5 and L5-S1 with the ProDisc II prosthesis, who was diagnosed with early anterior migration of the caudally placed device with partial occlusion of the left common iliac vein. The device was explanted and revised to an anterior lumbar interbody fusion with posterior instrumented fusion. Despite the substantial experience with lumbar disc arthroplasty in Europe and the United States, there exist few reports of device explantation or revision. To our knowledge, early postoperative vascular complications, while discussed hypothetically, have not been reported. With implantation of the total disc replacement in proximity to the great vessels, the potential for vascular complications is clearly substantial. The technical aspects of the device explantation are discussed as well as issues pertinent to early failure. A literature review of device complications associated with lumbar total disc replacement is also presented

BACKGROUND CONTEXT: Outpatient cervical spine surgery has previously been described for posterior laminoforaminotomy and anterior microdiscectomy with allograft fusion. Anterior cervical discectomy and fusion (ACDF) with plate fixation has not, to our knowledge, been described as an outpatient procedure. PURPOSE: The objective of this study was to evaluate the safety and feasibility of ACDF with instrumentation when performed as an outpatient in a free-standing ambulatory surgical center. Additionally, the authors sought to determine any patient selection bias and its effect on outcome. STUDY DESIGN: This study is a retrospective medical record review. PATIENT SAMPLE: The sample included all patients who underwent one or two level ACDF with plate fixation at levels C4-5 or below as an adjunct to autogenous iliac crest bone graft or structural allograft from 1998 to 2002 by the two senior authors. OUTCOME MEASURES: Complications were assessed clinically with special attention to dysphagia and respiratory complications. Inpatient lengths of stay and postoperative hospital admission or readmission were also measured. METHODS: Thirty consecutive patients were treated at a free-standing ambulatory surgery center, whereas two control groups, each of 30 consecutive patients, had surgery performed in the hospital and were admitted overnight for observation. The first control group consisted of admitted patients before the commencement of patient selection for the outpatient group; the second control group was comprised of admitted patients who had surgery performed concurrently with the outpatient group. The study group was evaluated on the first postoperative day and 3 weeks after surgery. RESULTS: Ninety patients underwent ACDF plate fixation at 140 different levels. Forty patients were treated at one level, and 50 were treated at two levels. The three groups were comparable in age, sex, and body mass index. There were no major complications. Seven patients (13%) had minor postoperative complications among the controls: transient dysphagia in three (5%) and graft donor site pain in four (14%). Three patients (10%) in the outpatient group had minor complications (all had dysphagia). Among the controls, four patients (7%) had increased length of stay owing to complications. Four patients (7%) in the combined control group were readmitted for early complications; no patient was admitted for a complication after outpatient surgery. CONCLUSIONS: In the present study, selection criteria for outpatient surgery included one or two level involvement C4-5 or lower, absence of myelopathy, subjective neck size, and estimated operative time. The data did not otherwise suggest a difference in the surgical populations. The outpatient group had a lower complication rate compared with the controls. This was likely the result of selection bias. Transient dysphagia was the most prevalent complication in the outpatient group

BACKGROUND: Discography has been widely used in the lumbar and cervical spine as a diagnostic tool to identify sources of discogenic pain that may be amenable to surgical treatment. Discography in the cervical spine is currently performed without the benefit of pressure monitoring, and corresponding pressure parameters have not been determined. OBJECTIVE: The purpose of this study was to develop the framework for intradiscal pressure monitoring in the cervical spine and the basis for a pressure curve that will reflect clinically significant cervical internal disc disruption. We also sought to determine whether there is any pressure increase in adjacent discs during cervical discography that might result in false-positive diagnosis during in-vivo discography. An additional goal was to establish safe upper parameters for infusion volume and intradiscal pressure in the cervical spine. DESIGN: Investigation of fresh-frozen discs in the cervical spine. METHODS: Investigated were 26 discs in 5 fresh-frozen cadaveric cervical spines aged 45 to 68 with no prior history of cervical spine disease. A T2 MRI was performed on each specimen and radiographically abnormal discs were noted. Pressure-controlled, fluoroscopically guided discography was performed on each level using a right lateral approach. Opening pressure, rupture pressure, volume infused, and location of rupture were recorded. Pressures were simultaneously recorded at each adjacent disc level using additional pressure monitors and identical needle placement. Immediately following discography, CT was performed on each specimen according to the discography protocol. RESULTS: Twenty-six discs C2-3 to C7-T1 were grossly intact for evaluation. The median opening pressure was 30 psi (range 14-101 psi). Two discs did not rupture and were pressurized to 367 psi. In 24 discs, the median intradiscal rupture pressure was 40 psi (range 14-171 psi). The median volume infused at rupture was 0.5 ml (range 0.25-1.0 ml). When grouped, the median intradiscal rupture pressure in the C2-3, C3-4, and C7-T1 discs was 53 psi (range 16-171 psi) compared to 36.5 psi (range 14-150 psi) in the C4-5, C5-6, and C6-7 discs (p=0.18). There was no measurable pressure change in any of the 30 adjacent disc levels evaluated. CONCLUSION: In the cervical spine, iatrogenic disc injury may be caused at significantly lower pressures and volumes infused than in the lumbar spine. There was no measurable pressure change in any of the adjacent disc levels evaluated at maximum intradiscal pressurization. Further cadaveric testing will be necessary to develop parameters for intradiscal pressure monitoring in the cervical spine

The solitary osteochondroma, a common pediatric bone tumor, is a cartilage-capped exostosis. Hereditary multiple exostosis is an autosomal dominant disorder manifested by the presence of multiple osteochondromas. Linkage analysis has implicated mutations in the EXT gene family, resulting in an error in the regulation of normal chondrocyte proliferation and maturation that leads to abnormal bone growth. Although exostoses are benign lesions, they are often associated with characteristic progressive skeletal deformities and may cause clinical symptoms. The most common deformities include short stature, limb-length discrepancies, valgus deformities of the knee and ankle, asymmetry of the pectoral and pelvic girdles, bowing of the radius with ulnar deviation of the wrist, and subluxation of the radiocapitellar joint. For certain deformities, surgery can prevent progression and provide correction. Patients with hereditary multiple exostosis have a slight risk of sarcomatous transformation of the cartilaginous portion of the exostosis

Anterior-posterior surgery is indicated for the treatment of lumbar instability in the presence of simultaneous compromise of both the anterior and the posterior spinal elements or to augment the stability and rigidity of a fusion construct. The addition of an anterior interbody fusion to a posterior instrumented fusion serves to more successfully restore sagittal balance, effect indirect neural decompression, and to decrease pedicle screw strain by reconstituting the load-sharing ability of the anterior column. A variety of posterior fixation and minimally invasive techniques has been demonstrated to increase circumferential construct stiffness and rates of fusion

Hereditary multiple exostosis is a genetic disorder characterized by multiple osteochondromas that can cause pain, deformity, and potential malignant degeneration. Linkage analysis has identified a family of EXT genes which, if mutated, can lose heterozygosity and potentially cause osteochondromas. A database was established of 43 patients with hereditary multiple exostoses treated at a tertiary pediatric healthcare system. Twenty patients had a known family history of the disorder. All patients were diagnosed between birth and 13 years. Symptoms or deformity were observed in the forearms of 29 patients, the knees of 37 patients, and the ankles of 28 patients. Valgus knee deformity related to hereditary multiple exostoses, previously reported to be attributable to proximal tibial changes alone, resulted from proximal tibial or distal femoral valgus deformities in this series. Twenty-seven patients required between one and five surgeries to address their lesions. No patient had malignant degeneration of an osteochondroma; however, three patients had first-degree relatives with transformation of an osteochondroma to chondrosarcoma. This database now may be a resource for additional analysis. By correlating specific genetic mutations with clinical manifestations, it may be possible to stratify patients into subtypes of hereditary multiple exostoses and identify genetic markers associated with malignant degeneration