Bradford L. Currier

Biodegradable polymer scaffolds for cartilage tissue engineering

Cartilage defects are common, painful conditions and none of the currently available treatment options are satisfactory. Tissue engineering techniques involving scaffolds made from biodegradable synthetic polymers hold great promise for the future. These materials can be manufactured in an injectable form for minimally invasive procedures or in a preformed state to treat large irreparable lesions including arthritis. The mechanical and biologic properties of synthetic polymers can be tailored to different clinical applications and engineering strategies. The scaffold serves as a mechanical substrate for cells and bioactive factors and can help direct and organize the process of regeneration. The ultimate goal of tissue engineering is to recapitulate normal organogenesis to create histologically and functionally normal tissue. A review of the characteristics and potential of synthetic polymers shows that these substances will play a major role in treating cartilage disorders.

Charnley low-friction arthroplasty of the hip: Twenty-year results with cement

The first 333 Charnley (Thackray, United Kingdom) total hip arthroplasties performed at the Mayo Clinic between 1969 and 1970 have been followed since that time. One hundred twelve patients (112 hips) remain alive at 20 years. Clinical results remain excellent. The Mayo clinical and roentgenographic hip scoring system rates the results as good to excellent in 39 of 69 hips (with all necessary data to calculate the entire score), fair in 13 hips, and poor in 17 hips. The clinical score alone showed satisfactory results in 77 of 112 hips. Some clinical deterioration was attributed to the advancing age of the patients (mean age at final follow-up evaluation, 84 years). Probable roentgenographic loosening (component migration, complete bone-cement interface, radiolucent line greater than 1 mm, cement fracture) was noted in 12 of 69 acetabular components (17%) and 28 of 69 femoral components (36%). Two patients had required revision since the last report at 15 years for a total of 38 patients (32 revised, 4 Girdlestone arthroplasties, 2 stem fractures not yet revised). The probability of surviving 20 years without revision of the components was 84% (83% for men, 85% for women). The rates of loosening, revision, and failure (revision, Girdlestone, or symptomatic loosening) remain linear over 20 years of follow-up evaluation. If the probability of revision is based on patient age at the time of the initial total hip arthroplasty, there is a significantly increased probability of revision in those patients less than 59 years of age (27%) compared to those 59-65 years of age (13%), 65-70 years (7.5%), and over 70 years (12%).

A system for surgical staging and management of spine tumors: A clinical outcome study of giant cell tumors of the spine

Study Design. This study developed and independently applied a spine tumor classification system, referred to as the Weinstein‐Boriani‐Biagini system, in a retrospective analysis of a series of patients with spinal giant cell tumors from three institutions. Objective. To evaluate factors of potential prognostic significance for recurrence of spinal giant cell tumors. Summary of Background Data. No prior reviews of patients treated with modern surgical techniques are available. Methods. Charts and radiographs for 36 cases of spinal giant cell tumors were reviewed by an independent investigator. All patients had had recent clinical follow‐up examinations. All patients were classified according to the Enneking system. A subgroup of 24 patients for whom preoperative computed tomography scans were available were classified using the Weinstein‐Boriani‐Biagini staging system. Outcome measures included pain, neurologic status, and tumor recurrence. Results. Recurrence rates were substantially higher among patients treated with attempted surgical excision before referral to a tertiary care center (83% vs. 18%). There was a higher recurrence rate for tumors that involved the vertebral body and posterior elements in comparison with lesions residing in only anterior elements (24% vs. 0%). Tumors that had extra‐osseous extension into the canal and into the paraspinous musculature had a higher recurrence rate than tumors either confined to the osseous compartment or with extension either into the spinal canal or externally into paraspinous planes, but not both (21% vs. 10%). Conclusions. These results indicate that the Weinstein‐Boriani‐Biagini system may prove useful in developing treatment algorithms and in assessing outcome for these rare and difficult lesions. At least in the case of giant cell tumors, the musculoskeletal tumor staging system as developed by Enneking for long bones suggests the ideal surgical margin and may provide information relevant to tumor recurrence rates. Additional aspects of tumor extent and location, however, may berelevant to primary tumor recurrence rates when theselesions occur in the spine.

Aneurysmal Bone Cyst of the Spine: Management and Outcome

Study Design. The clinical records, radiographs, histologic sections, and operative reports of 52 consecutive patients with an aneurysmal bone cyst of the spine were reviewed to evaluate diagnostic and therapeutic options and to correlate treatment and outcome. Objectives. To define the incidence, clinical presentation, diagnostic and therapeutic options, and prognosis of patients with aneurysmal bone cyst of the spine. Summary of Background Data. There are special considerations in the management of spinal lesions: relative inaccessibility of the lesions, associated intraoperative bleeding, necessity of removing the entire lesion to avoid the possibility of recurrence, proximity of the lesion to the spinal cord and nerve roots, and potential postoperative bony spinal instability. Methods. Fifty‐two consecutive patients with an aneurysmal bone cyst of the spine were treated from 1910 to 1993. Forty patients initially treated for a primary lesion had operative treatment (19 intralesional excision and bone grafting and 21 intralesional excision); four also had adjuvant radiation therapy. Preoperative arterial embolization was performed in two. Results. There was a recurrence rate of 10% within 10 years. All recurrences were noted less than 6 months after surgery. Of 12 patients treated for a recurrent lesion, two had a subsequent recurrence (16.7%) within 9 years. At last follow‐up examination, 50 patients (96%) were free of the disease. One patient died of postradiation osteosarcoma, and one died of intraoperative bleeding. Conclusions. Current treatment recommendations involve preoperative selective arterial embolization, intralesional excision curettage, bone grafting, and fusion of the affected area if instability is present.

C-Reactive Protein, Erythrocyte Sedimentation Rate and Orthopedic Implant Infection

Background C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been shown to be useful for diagnosis of prosthetic hip and knee infection. Little information is available on CRP and ESR in patients undergoing revision or resection of shoulder arthroplasties or spine implants. Methods/Results We analyzed preoperative CRP and ESR in 636 subjects who underwent knee (n = 297), hip (n = 221) or shoulder (n = 64) arthroplasty, or spine implant (n = 54) removal. A standardized definition of orthopedic implant-associated infection was applied. Receiver operating curve analysis was used to determine ideal cutoff values for differentiating infected from non-infected cases. ESR was significantly different in subjects with aseptic failure infection of knee (median 11 and 53.5 mm/h, respectively, p = <0.0001) and hip (median 11 and 30 mm/h, respectively, p = <0.0001) arthroplasties and spine implants (median 10 and 48.5 mm/h, respectively, p = 0.0033), but not shoulder arthroplasties (median 10 and 9 mm/h, respectively, p = 0.9883). Optimized ESR cutoffs for knee, hip and shoulder arthroplasties and spine implants were 19, 13, 26, and 45 mm/h, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 89 and 74% for knee, 82 and 60% for hip, and 32 and 93% for shoulder arthroplasties, and 57 and 90% for spine implants. CRP was significantly different in subjects with aseptic failure and infection of knee (median 4 and 51 mg/l, respectively, p<0.0001), hip (median 3 and 18 mg/l, respectively, p<0.0001), and shoulder (median 3 and 10 mg/l, respectively, p = 0.01) arthroplasties, and spine implants (median 3 and 20 mg/l, respectively, p = 0.0011). Optimized CRP cutoffs for knee, hip, and shoulder arthroplasties, and spine implants were 14.5, 10.3, 7, and 4.6 mg/l, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 79 and 88% for knee, 74 and 79% for hip, and 63 and 73% for shoulder arthroplasties, and 79 and 68% for spine implants. Conclusion CRP and ESR have poor sensitivity for the diagnosis of shoulder implant infection. A CRP of 4.6 mg/l had a sensitivity of 79 and a specificity of 68% to detect infection of spine implants.

Biomechanical Evaluation of Anterior Cervical Spine Stabilization

Study Design. An in vitro biomechanical study. Objectives. To simulate a severe compressive flexion injury for determination of the relative stability of different anterior instrumentation systems in a porcine model and to validate this model in human cadaveric specimens. Summary of Background Data. Anterior plate fixation is useful for high‐grade mechanical insufficiency of the cervical spine and may prevent the need for a second procedure. Methods. The cervical spines of 45 porcine and 12 cadaveric specimens were subjected to nondestructive flexion, lateral bending, and torsional testing on a modified universal testing machine. A corpectomy was performed with release of the posterior ligamentous structures. The specimens were stabilized with one of three anterior plate constructs. The nondestructive testing was repeated to evaluate structural stability (stiffness and neutral zone). Finally, destructive testing examined failure moment, energy to failure, and mechanism of failure. Results. The instrumented specimens had flexural and lateral bending and torsional stiffness values that were similar to or greater than those of their paired intact specimens. The cervical spine locking plate had a significantly higher flexural stiffness ratio (plated:intact), torsional stiffness ratio, lower flexural neutral zone ratio, higher failure moment, and higher energy to failure than did the Caspar plate. Conclusions. The cervical spine locking plate is theoretically safer than the Caspar system because the posterior vertebral body cortex is not breached by the fixation screws, and the screws are less likely to back out anteriorly and irritate the esophagus. According to these results, the cervical spine locking plate system is biomechanically equivalent to and in some cases more stable than the Caspar system for fixation of a severe compressive flexion injury.

Primary Ewing's sarcoma of the spine

Thirty-six patients with primary Ewings sarcoma of the spine were diagnosed at the Mayo Clinic between 1951 and 1988. The mean age was 17 years (range, 5-40 years). Neurologic symptoms and signs were seen in 58% of the patients. Forty-seven percent of all patients had an open biopsy of the lesion and underwent a decompressive laminectomy. Three of the four patients with thoracic or thoracolumbar involvement had progressive kyphosis after laminectomy. All patients received radiation therapy in various dosages. Sixteen of the patients were registered in the Intergroup Ewings Sarcoma Study. Intensive combination chemotherapy was administered to 32 of the patients. Nine patients were free of disease at the final follow-up examination (follow-up ranged from 6 to 184 months). The 5-year survival rate was 33%. The mean survival time was 2.9 years. No significant correlation was found between the location of the tumor in the spine and the length of disease-free survival, overall survival, or incidence of metastatic disease. Patients enrolled in the Intergroup Ewings Sarcoma Study had significantly better rates of disease-free survival and overall survival.

Degenerative Cervical Spondylosis: Clinical Syndromes, Pathogenesis, and Management

Degenerative changes in the cervical spinal column are ubiquitous in the adult population, but infrequently symptomatic. The evaluation of patients with symptoms is facilitated by classifying the resulting clinical syndromes into axial neck pain, cervical radiculopathy, cervical myelopathy, or a combination of these conditions. Although most patients with axial neck pain, cervical radiculopathy, or mild cervical myelopathy respond well to initial nonsurgical treatment, those who continue to have symptoms or patients with clinically evident myelopathy are candidates for surgical intervention.

Relationship between surgical margins and local recurrence in sarcomas of the spine.

The combination of improved resection, stabilization, and fusion techniques allows for more aggressive removal of malignant spinal tumors with acceptable mortality and morbidity. Thirty consecutive patients with primary sarcomas of the mobile spine, who were operated on at the authors’ institution from January 1970 to December 2000, were included in the current study. Demographic information, tumor location, type of resection, resection margins, local recurrence, and overall survival data were retrieved and analyzed. Treatment consisted of en bloc resection in 12 patients (40%) and piecemeal resections in 18 patients (60%). The resection was classified as wide in seven patients (23.3%), marginal in three patients (10%), and intralesional in 20 patients (66.7%). Pathology reports showed tumor-free resection margins in 12 patients (40%). In the remaining 18 patients (60%), resection margins were positive and resulted in a fivefold increase in the risk of a local recurrence. Ninety-two percent of the patients with local recurrence died of sequelae associated with the local recurrence. Primary sarcomas of the mobile spine in certain cases, can be removed completely with tumor-free resection margins. En bloc resection with tumor-free margins provides substantial improvement in overall survival.

Bowel and bladder function after major sacral resection

Major sacral resection generally is reserved for patients with malignant lesions. Because of the uncommon nature of these diseases, little is known about outcomes of surgical treatment. The current authors describe the retrospective analysis of bowel and bladder function in patients having major sacral resection at their institution during a 10-year period. Fifty-three patients were identified. In patients who had unilateral sacrectomy, in whom the contralateral sacral nerves were preserved, normal bowel and bladder function was retained in 87% and 89%, respectively. In patients who had bilateral S2-S5 nerve roots sacrificed, all had abnormal bowel and bladder function. In patients who had bilateral S3-S5 resection, normal bowel and bladder function was retained in 40% and 25%, respectively. In patients who had bilateral S4-S5 resection, with preservation of the S3 nerves bilaterally, normal bowel and bladder function was retained in 100% and 69%, respectively. In patients who had asymmetric sacral resections, with preservation of at least one S3 nerve root, normal bowel and bladder function was retained in 67% and 60%, respectively. These results show that unilateral resection of sacral roots or preservation of at least one S3 root in bilateral resection preserves bowel and bladder function in the majority of patients.