Single and Multilevel Lumbar Total Disc Replacement Adjacent to L5-S1 ALIF (Lumbar Hybrid): 6 Years of Follow-up.

BACKGROUND: Single and multilevel lumbar arthroplasty has had excellent results, but the L5-S1 level frequently has pathology that precludes arthroplasty. This study evaluated clinical outcomes and sagittal range of motion (ROM) of operated levels and adjacent motion segments in single- and multiple-level ProDisc-L above a simultaneous L5-S1 fusion (hybrid) after a 2- to 6-year follow-up. METHODS: In this prospective cohort study, 46 patients underwent simultaneous lumbar total disc replacement (TDR) at one to three levels and anterior lumbar interbody fusion (ALIF) at L5-S1. Twenty-three patients had L5-S1 ALIF + L4-5 TDR, 19 patients had L5-S1 ALIF + two-level TDR, and 4 patients had L5-S1 ALIF + three-level TDR. Oswestry disability index (ODI) and visual analog scores (VAS) of patient satisfaction (VAS-S) and pain (VAS-P) were recorded. Sagittal motion on pre- and postoperative lumbar radiographs at each operative segment and adjacent segment was acquired. Patients were evaluated preoperatively and at 6 weeks, 3 months, 6 months, and annually for 24 to 72 months postoperatively. RESULTS: For clinical results, there were no differences among the groups for age, gender, body mass index, tobacco use, or worker's compensation status. At 2-6 years postoperation, all patients had significant reductions in ODI and VAS scores. For radiographic results, at the nonsurgical level adjacent to the TDR + ALIF constructs, the mean preoperative ROM was 9.40 ± 1.80° compared with 10.50 ± 2.25° postoperatively. The mean preoperative ROM at levels undergoing TDR was 10.4 ± 2.71° versus 12.6 ± 2.25° postoperatively. There was no statistically significant difference in ROM at each prosthetic motion segment between patients receiving one-, two-, or three-level TDR. The mean preoperative ROM at the L5-S1 segment to undergo fusion was 2.4 ± 2.44°, with all patients having a postoperative ROM of 0.00°. CONCLUSIONS: Multilevel TDR above an L5-S1 ALIF (hybrid procedure) preserves ROM at the individual TDR levels and does not reduce the fusion rate of the L5-S1 fused level. Most significantly, the nonoperative adjacent level maintains its preoperative ROM at 2-6 years postoperatively.

Outpatient Versus Inpatient Anterior Lumbar Spine Surgery: A Multisite, Comparative Analysis of Patient Safety Measures.

BACKGROUND: The frequency and complexity of spinal surgery performed in an ambulatory surgery center (ASC) is increasing. However, safety and efficacy data of most spinal procedures adapted to the ASC are sparse and have focused on anterior cervical surgery. The purpose of this study was to compare the 90-day complication and readmission rates of anterior lumbar spine surgery performed in an ASC or inpatient setting. METHODS: We performed a retrospective comparative analysis of 226 consecutive anterior lumbar surgeries (283 levels treated) completed in an ASC (n = 124) or in an inpatient tertiary care hospital (n = 102) over a 3-year period. These included anterior lumbar interbody fusion (ALIF), artificial disc replacement (ADR), and hybrids. Patients undergoing simultaneous or staged posterior procedures within 3 months were excluded. Patient demographics and surgical parameters between the two surgical settings were compared. Ninety-day medical complications and readmission rates were assessed. One-way analysis of variance and Chi-square analysis were used. A P value of less than .05 was considered statistically significant. RESULTS: The two study groups had similar baseline characteristics. While there was a trend toward fewer complications, reoperations, and readmissions for the ASC cohort, the differences were not statistically significant. There were 7 intraoperative complications (5.6% minor vascular injury) in the inpatient cohort and 0 in the ASC cohort. The overall 90-day postoperative complication rate was 5.6% for the inpatient cohort and 0.9% for the ASC cohort. The 90-day readmission rate was 1.9% in the ASC cohort and 1.6% in the inpatient cohort. The 90-day reoperation rate was 0.8% for the inpatient cohort and 0% in the ASC cohort. The average hospital stay was 2.3 ± 1.5 days for the inpatient cohort. CONCLUSION: The 90-day readmission rates were lower for outpatients than for inpatients, while the complication and reoperation rates were similar. Our results demonstrate that anterior lumbar procedures, including single-level and multilevel ALIF, ADR, and hybrid procedures, can be performed safely in an ASC. This has significant cost savings implications for the ASC setting.

Low Complication Rate of Anterior Lumbar Spine Surgery in an Ambulatory Surgery Center.

BACKGROUND: As healthcare costs rise, attempts are being made to perform an increasing proportion of spine surgery in ambulatory surgery centers (ASCs). ASCs are more efficient, both economically and functionally. There remains uncertainty regarding the safety of performing anterior lumbar procedures requiring vascular access, as little has been published on this subset of patients. METHODS: This is a consecutive case series analysis of anterior lumbar spine surgeries that were performed in a free-standing ASC in a private-practice setting over a 1-year period, including anterior lumbar interbody fusion, artificial disc replacement, and hybrid procedures. The preoperative, intraoperative, and postoperative data recorded included age, gender, body mass index, tobacco use, and the presence of diabetes; level and procedure, operating room time, estimated blood loss, complications; discharge site, occurrence of reoperation, hospital admission, or any medical complication or infection over a 90-day period. RESULTS: Fifty-one patients underwent 63 treated levels (34 artificial disc replacement, 29 anterior lumbar interbody fusion): 40 single-level, 10 two-level, one three-level. Average age was 45 years; 27 female, 24 males. None of the patients were diabetics, three were current smokers, seven were former smokers. Average body mass index was 27 ± 4 (range 16-36). Average total anesthesia time was 100 minutes (range 57-187 minutes). Average estimated blood loss was 23 mL (range 5-250 mL). Seventy-one percent of patients were discharged directly home, 29% to an aftercare facility. In the 30-day postoperative period there were no deaths, one hospital admission for pain, and no significant medical complications or surgical site infections. CONCLUSION: In this consecutive case series artificial disc replacement or anterior lumbar interbody fusion was performed at 63 levels in 51 patients in the ASC setting with an observed major complication rate of zero and hospital unplanned admission rate of 2% (1/51). This provides some evidence that these procedures are safe to perform in the ASC setting. However, a highly experienced vascular surgeon and efficient surgical team, and strict patient selection criteria are all critical in making this possible.

The Safety of Single and Multilevel Cervical Total Disc Replacement in Ambulatory Surgery Centers.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: Evaluate the safety profile of single- and multilevel cervical artificial disc replacement (ADR) performed in an outpatient setting. SUMMARY OF BACKGROUND DATA: As healthcare costs rise, attempts are made to perform an increasing proportion of spine surgery in ambulatory surgery centers (ASCs). ASCs are more efficient, economically and functionally. Few studies have published on the safety profile of multilevel cervical ADR. METHODS: We have performed an analysis of all consecutive cervical ADR surgeries that we performed in an ASC over a 9-month period, including multilevel and revision surgery. The pre-, intra-, and postoperative data recorded included age, sex, body mass index, tobacco use, and diabetes; level and procedure, operating room time, estimated blood loss (EBL), and complications; and discharge site, occurrence of reoperation, hospital admission, or any medical complication or infection over a 90-day period. RESULTS: A total of 147 patients underwent 231 treated levels: 71 single-level, 76 multilevel: 69 two-level, 6 three-level, and 1 four-level. Average age was 50 ±â€Š10 years; 71 women, 76 men. None of the patients had insulin-dependent diabetes, 4 were current smokers, and 16 were former smokers. Average body mass index was 26.8 ±â€Š4.6 (range 18-40). Average total anesthesia time was 88 minutes (range 39-168 min). Average EBL was 15 mL (range 5-100 mL). Approximately 90.3% of patients were discharged directly home, 9.7% to an aftercare facility. In the 90-day postoperative period there were zero deaths and two hospital admissions (1.4%)-one for medical complication (0.7%) and one for a surgical site infection (0.7%). CONCLUSION: In this consecutive case series we performed 231 ADRs in 147 patients in the outpatient setting, including multilevel and revision procedures, with 2 minor postoperative complications resulting in hospital unplanned admissions within 90 days. We believe that these procedures are safe to perform in an ASC. An efficient surgical team and careful patient selection criteria are critical in making this possible. LEVEL OF EVIDENCE: 3.

Biomechanical Analysis of Cortical Versus Pedicle Screw Fixation Stability in TLIF, PLIF, and XLIF Applications.

STUDY DESIGN: Cadaveric biomechanical study. OBJECTIVES: Medial-to-lateral trajectory cortical screws are of clinical interest due to the ability to place them through a less disruptive, medialized exposure compared with conventional pedicle screws. In this study, cortical and pedicle screw trajectory stability was investigated in single-level transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and extreme lateral interbody fusion (XLIF) constructs. METHODS: Eight lumbar spinal units were used for each interbody/screw trajectory combination. The following constructs were tested: TLIF + unilateral facetectomy (UF) + bilateral pedicle screws (BPS), TLIF + UF + bilateral cortical screws (BCS), PLIF + medial facetectomy (MF) + BPS, PLIF + bilateral facetectomy (BF) + BPS, PLIF + MF + BCS, PLIF + BF + BCS, XLIF + BPS, XLIF + BCS, and XLIF + bilateral laminotomy + BCS. Range of motion (ROM) in flexion-extension, lateral bending, and axial rotation was assessed using pure moments. RESULTS: All instrumented constructs were significantly more rigid than intact (P < .05) in all test directions except TLIF + UF + BCS, PLIF + MF + BCS, and PLIF + BF + BCS in axial rotation. In general, XLIF and PLIF + MF constructs were more rigid (lowest ROM) than TLIF + UF and PLIF + BF constructs. In the presence of substantial iatrogenic destabilization (TLIF + UF and PLIF + BF), cortical screw constructs tended to be less rigid (higher ROM) than the same pedicle screw constructs in lateral bending and axial rotation; however, no statistically significant differences were found when comparing pedicle and cortical fixation for the same interbody procedures. CONCLUSIONS: Both cortical and pedicle trajectory screw fixation provided stability to the 1-level interbody constructs. Constructs with the least iatrogenic destabilization were most rigid. The more destabilized constructs showed less lateral bending and axial rotation rigidity with cortical screws compared with pedicle screws. Further investigation is warranted to understand the clinical implications of differences between constructs.

Multiple-Level Lumbar Total Disk Replacement: A Prospective Clinical and Radiographic Analysis of Motion Preservation at 24-72 Months.

BACKGROUND: Recent studies demonstrate the efficacy of lumbar arthroplasty using the ProDisc-L. Patients frequently present with multilevel pathology and may be candidates for multilevel disk replacement. PURPOSE: To evaluate clinical outcomes and sagittal range of motion of operated levels and adjacent lumbar motion segments in multiple-level ProDisc-L constructs after 2-6 years follow-up. PATIENT SAMPLE: A total of 159 patients underwent adjacent 2-level (n=114), 3-level (n=41), or 4-level (n=4) lumbar total disk replacement (TDR). STUDY-DESIGN: This is a prospective cohort. OUTCOME MEASURES: Clinical measures: Oswestry Disability Index and Visual Analog Score of patient satisfaction (VAS-S) and pain (VAS-P) data were collected. Radiographic measures: sagittal motion on preoperative and postoperative lumbar radiographs at each operative segment and adjacent segment. METHODS: Patients were evaluated with radiographic and clinical outcomes measures preoperatively, at 6 weeks, 3 months, 6 months, and annually for 24-72 months postoperatively. RESULTS: Radiographic: at the motion segment adjacent to the TDR, mean preoperative range of motion (ROM) was 8.20±2.88 degrees, compared with 8.40±2.4 degrees postoperatively at last follow-up (P>0.05). Between the 3 TDR groups, there were no significant differences in ROM at any time point except at L5-S1. Across both groups for TDR motion segments, the mean preoperative ROM was 10.15±2.71 versus 12.30±2.25 degrees postoperatively (P=0.011) at last follow-up. At L5-S1 mean preoperative motion was 7.60±3.90 versus 5.81±3.1 degrees postoperatively (P=0.60). Clinical: at 24-72 months postoperatively, all patients had significant reductions in Oswestry Disability Index, VAS-P, and VAS-S scores (P<0.05). At up to 72 months of follow-up, no patient underwent adjacent-level surgery but there were 3 cases of index-level revision surgery. CONCLUSIONS: Multilevel TDR preserves ROM at the individual TDR levels. Most significantly, the nonoperative adjacent level maintains its preoperative ROM at 2-6 years postoperatively. At up to 6 years of follow-up, there has been no need for revision or adjacent-segment surgery. Patients also demonstrate significant improvement in pain and disability at latest follow-up.

Femoral Neurogram Before Transpsoas Spinal Access at L4-5 Intervertebral Disk Space: A Proposed Screening Tool.

STUDY DESIGN: Observational study. OBJECTIVE: To illustrate the variability of the course of the femoral nerve across the L4-5 disk space, and to present a novel application of transforaminal epidural steroid injections (TFESI) in the visualization of femoral nerve roots. SUMMARY OF BACKGROUND DATA: A concern regarding the lateral retroperitoneal transpsoas approach is the proximity of the lumbar plexus. Current techniques of assessing the proximity of neural tissue to the L4-5 disk space have limited capabilities. METHODS: A total of 100 patients were selected for L4-5 TFESI (L4 selective nerve root blocks) because of lumbar radiculopathy. L4 neurograms were obtained while performing L4-5 TFESI under flouroscopic guidance, using a retroneural technique. The course of the L4 root/femoral nerve was then evaluated under fluoroscopy in the anteroposterior and lateral planes. Images were then reviewed by a radiologist, physiatrist, and 2 orthopedic spine surgeons. RESULTS: Fluoroscopic evaluation revealed that the pattern of location of the femoral nerve was highly variable. In males, it was located 4.7% in zone 2, 32.5% in zone 3, 53.5% in zone 4, and 9.3% in zone P. In female patients, it was located 7.0% in zone 2, 14% in zone 3, 54.4% in zone 4, and 24.6% in zone P. CONCLUSIONS: An L4 neurogram will provide an accurate trajectory of L4 root/femoral nerve as it crosses the L4-5 intervertebral disk space. An accurate assessment is essential to help minimize the increasing frequency of thigh pain, paresthesias, and weakness associated with the lateral access to the L4-5 intervertebral disk space. Femoral nerves that fall within zones 2 and 3 will require more manipulation during retraction and may be better suited with a different surgical approach.

Lumbar plexus anatomy within the psoas muscle: implications for the transpsoas lateral approach to the L4-L5 disc.

BACKGROUND: The transpsoas lateral surgical approach has been advocated as an alternative to direct anterior approaches for less invasive or minimally invasive access to the spine. Postoperative thigh pain, paresthesia, and/or weakness have been described after the use of this surgical approach. The purpose of this cadaveric anatomic study is to provide a description of the lumbar plexus as it relates to the transpsoas lateral surgical approach. METHODS: Dissection of the lumbar plexus was performed in eighteen cadaveric specimens. Needle markers were placed in the L2-L3, L3-L4, and L4-L5 discs in the midcoronal plane. The anatomic structures were surveyed, and the proximity of the needle to the neural structures was observed. RESULTS: In thirteen of the eighteen specimens, the femoral nerve received its contributions from the L2 to L4 nerve roots and was formed at the L4-L5 disc space. In all specimens, the femoral nerve passed dorsal to or directly at the midpoint of the disc. In three specimens, the needle displaced or was immediately adjacent to the femoral nerve. The femoral nerve was found between the needle and the posterior aspect of the L4-L5 disc space in thirteen of the eighteen specimens. CONCLUSIONS: Because of the proximity of the neural elements, in particular the femoral nerve, to the center of the disc space, the transpsoas lateral surgical approach to the L4-L5 disc space will likely cause intraoperative displacement of neural structures from their anatomic course during retractor dilation. Careful attention should be paid to retractor placement and dilation time during transpsoas lateral access surgery, particularly at the L4-L5 disc.

Direct surgical repair of spondylolysis in athletes: indications, techniques, and outcomes.

OBJECT: Athletes present with back pain as a common symptom. Various sports involve repetitive hyperextension of the spine along with axial loading and appear to predispose athletes to the spinal pathology spondylolysis. Many athletes with acute back pain require nonsurgical treatment methods; however, persistent recurrent back pain may indicate degenerative disc disease or spondylolysis. Young athletes have a greater incidence of spondylolysis. Surgical solutions are many, and yet there are relatively few data in the literature on both the techniques and outcomes of spondylolytic repair in athletes. In this study, the authors undertook a review of the surgical techniques and outcomes in the treatment of symptomatic spondylolysis in athletes. METHODS: A systematic review of the MEDLINE and PubMed databases was performed using the following key words to identify articles published between 1950 and 2011: "spondylolysis," "pars fracture," "repair," "athlete," and/or "sport." Papers on both athletes and nonathletes were included in the review. Articles were read for data on methodology (retrospective vs prospective), type of treatment, number of patients, mean patient age, and mean follow-up. RESULTS: Eighteen articles were included in the review. Eighty-four athletes and 279 nonathletes with a mean age of 20 and 21 years, respectively, composed the population under review. Most of the fractures occurred at L-5 in both patient groups, specifically 96% and 92%, respectively. The average follow-up period was 26 months for athletes and 86 months for nonathletes. According to the modified Henderson criteria, 84% (71 of 84) of the athletes returned to their sports activities. The time intervals until their return ranged from 5 to 12 months. CONCLUSIONS: For a young athlete with a symptomatic pars defect, any of the described techniques of repair would probably produce acceptable results. An appropriate preoperative workup is important. The ideal candidate is younger than 20 years with minimal or no listhesis and no degenerative changes of the disc. Limited participation in sports can be expected from 5 to 12 months postoperatively.

Use of all-pedicle-screw constructs in the treatment of adolescent idiopathic scoliosis.

All-pedicle-screw constructs are safe and biomechanically advantageous in the management of adolescent idiopathic scoliosis. Safe and reproducible placement of thoracic pedicle screws is dependent on a thorough understanding of normal and abnormal anatomy, meticulous technique, and the use of neuromonitoring and fluoroscopy. Improvement in the biomechanical properties secondary to the use of pedicle screw fixation has led to shorter fusions with improved deformity correction. Coronal, sagittal, and rotational correction is superior to that obtained with hook instrumentation. Improved derotation may decrease the need for thoracoplasty, thus eliminating the risk of associated morbidity. Superior control of the deformity with all-pedicle-screw fixation, as well as the use of adjunctive posterior releases, often obviates the need for an anterior approach, even in severe curves measuring 70 degrees to 100 degrees . Improved correction, shorter fusion, and the lower morbidity associated with posterior-only approaches may compensate for higher implant costs.

Resection of glial scar following spinal cord injury.

While many studies have focused on modulating the immune response and enhancing axonal regeneration after spinal cord injury (SCI), there is limited work being performed on evaluating the role of glial scar in SCI. We sought to evaluate the effects of glial scar resection in contusion models and dorsal hemisection models of SCI. At 1-week postinjury, 2 mm of glial scar was excised from specimens in one of the two groups from each injury model. Functional outcome was measured weekly using the Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale along with histologic evaluation of spinal cord tracts to determine axonal regeneration. Within the dorsal hemisection model, there was no significant difference in recovery for animals that underwent glial scar excision versus animals that did not have scar excision (p = 0.61). Animals subjected to the contusion model, however, demonstrated lower BBB scores in the glial resection group during the earlier postoperative periods (< 4 weeks; p < 0.05). Histological analysis revealed no axons within the glial resection contusion model, and moderate axonal growth within the nonresection contusion group and both hemisection groups (p > 0.05 for differences among the three groups). While glial scar may serve to stabilize the preserved axonal tracts and thereby permit modest recovery in a contusion model of SCI, it may be of less importance with a dorsal hemisection model. These experiments highlight that basic biologic processes following SCI may vary tremendously based on the injury mechanism and that the role of glial scar in spinal cord regeneration must be elucidated.

Transplantation of preconditioned Schwann cells following hemisection spinal cord injury.

STUDY DESIGN: Chronically compressed sciatic nerve segments were transplanted to hemisected spinal cord injured rats. Histologic evaluation and behavior functional outcomes were tested after 6 weeks following surgery. OBJECTIVE: To evaluate the outcome of preconditioned peripheral nerves as a permissive environment in axonal regeneration of the injured spinal cord. SUMMARY OF BACKGROUND DATA: Schwann cells have been used to facilitate a permissive environment for the injured spinal cord to regenerate. Previous experiments have shown compressive mechanical stress to be important in stimulating the regenerative behavior of Schwann cells. Transplantation of highly permissive Schwann cell-enriched peripheral nerve grafts may enhance regeneration in spinal cord injury. METHODS: Adult Sprague-Dawley rats (n = 24) were used to create a hemisection injury of the spinal cord. At 1-week postinjury creation, the spinal cords were reexposed for all animals. Peripheral nerve grafts were obtained from rat sciatic nerve, either untreated or subjected to mechanical compression for 2 weeks with nonconstrictive tubing. Transplantation of grafts was performed after a resection of the glial scar. Functional outcome was measured using the Basso, Beattie, Bresnahan Locomotor Rating Score and footprint analysis. Tract tracing of descending and ascending spinal cord tracts was performed at 6 weeks after surgery for histologic evaluation of axonal regeneration. RESULTS: Preconditioned transplants had significantly higher Basso, Beattie, Bresnahan Scores versus hemisection alone in the late postoperative period (P < 0.05). They also had significantly less foot exorotation and base of support when compared to nonconditioned transplants. Histologic analysis showed increased regeneration at lesional sites for preconditioned transplants versus control group (P < 0.05). CONCLUSIONS: Functional recovery after hemisection injury improved significantly in the late postoperative period with transplantation of preconditioned peripheral nerve. Preconditioned grafts also exhibit sustained axonal regeneration at and past the lesional site in histologic analysis. Further investigation with later time points is warranted.

Transplantation of preconditioned schwann cells in peripheral nerve grafts after contusion in the adult spinal cord. Improvement of recovery in a rat model.

BACKGROUND: Recovery after injury to the peripheral nervous system is based on the pro-regenerative relationship between axons and the extracellular matrix, a relationship established by Schwann cells. As mechanical conditioning of Schwann cells has been shown to stimulate their regenerative behavior, we sought to determine whether transplantation of these cells to the central nervous system (i.e., the spinal cord), with its limited regenerative capacity after injury, would improve axonal regeneration and functional recovery. METHODS: A moderate contusion injury of the spinal cord was created with a force-directed impactor in forty-eight adult Sprague-Dawley rats, and, at one week postinjury, the spinal cords were reexposed in all animals. In twenty-four of these animals, peripheral nerve grafts with Schwann cells that had been obtained from the sciatic nerves of donor animals, and had been either untreated or subjected to mechanical conditioning, were transplanted to the contused area of the cords following resection of the glial scar. Another group of animals was treated with glial scar excision only, and a fourth group had the contusion injury but neither glial excision nor transplantation. Scores according to the Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale were assigned preoperatively and weekly thereafter. Tract tracing of descending and ascending spinal cord tracts was performed at six weeks postoperatively for quantitative histological evaluation of axonal regeneration. RESULTS: While the recovery following glial scar excision without peripheral nerve transplantation was significantly worse than the recovery in the other groups, both transplantation groups had significantly higher BBB scores than the controls (no transplantation) in the early postoperative period (p < 0.05). Moreover, histological analysis showed markedly increased axonal regeneration at the lesional sites in the animals treated with the mechanically conditioned grafts than in the other groups (p < 0.05). CONCLUSIONS: Functional recovery after spinal cord contusion improved following glial scar excision with transplantation of Schwann cells in peripheral nerve grafts to the contusion areas. Although recovery did not differ significantly between the transplantation groups, only the preconditioned grafts led to axonal regeneration at and past the lesional site. These grafts may further enhance functional recovery as the descending tracts eventually reach their target end-organs.

Radiofrequency cartilage reshaping: efficacy, biophysical measurements, and tissue viability.

OBJECTIVES: To assess the feasibility of reshaping cartilage using radiofrequency (RF) heating, and to examine the effects of this process on tissue biophysical properties (optical and thermal) and cellular viability. METHODS: Mechanically deformed porcine septal cartilage was reshaped using 2 RF-generating devices. We performed dynamic measurements of tissue thermal and optical properties while heating cartilage with one of these devices. Cellular viability was assessed immediately and 7 days after treatment. RESULTS: A characteristic change in the diffuse transmittance of light through the cartilage occurred during heating. Change in transmittance has been shown to accompany the onset of stress relaxation in cartilage. Peak radiometric surface temperature during heating was 88.6 degrees C. Specimens retained their user-specified curved shape for the observed period of 14 days. Chondrocyte viability in RF-heated tissue was 19% and 14% of that in untreated control specimens at days 0 and 7 after treatment, respectively. CONCLUSIONS: Radiofrequency heating has been shown to effectively reshape cartilage while maintaining cellular viability, illustrating a novel application for a widely used technology.

Quantitative assessment of chondrocyte viability after laser mediated reshaping: a novel application of flow cytometry.

BACKGROUND AND OBJECTIVES: Lasers can be used to reshape cartilage by accelerating mechanical stress relaxation. In this study, fluorescent differential cell viability staining and flow cytometry were used to determine chondrocyte viability following laser heating. STUDY DESIGN/MATERIALS AND METHODS: Porcine septal cartilages were irradiated with an Nd:YAG laser (lambda = 1.32 microm, 25 W/cm(2)) while surface temperature, stress relaxation, and diffuse reflectance were recorded. Each slab received one, two, or three laser exposures (respective exposure times of 6.7, 7.2, 10 seconds). Irradiated samples were then divided into two groups analyzed immediately and at 5 days following laser exposure. Chondrocytes were isolated following serial enzymatic digestion, and stained using SYTO/DEAD Red (Molecular Probes, Eugene, OR). A flow cytometer was then used to detect differential cell fluorescence; size; granularity; and the number of live cells, dead cells, and post-irradiation debris in each treatment population. RESULTS: Nearly 60% of chondrocytes from reshaped cartilage samples isolated shortly after one irradiation, were viable while non-irradiated controls were 100% viable. Specimens irradiated two or three times demonstrated increasing amounts of cellular debris along with a reduction in chondrocyte viability: 31 and 16% after two and three exposures, respectively. In those samples maintained in culture medium and assayed 5 days after irradiation, viability was reduced by 28-88%, with the least amount of deterioration in untreated and singly irradiated samples. CONCLUSIONS: Functional fluorescent dyes combined with flow cytometric analysis successfully determines the effect of laser irradiation on the viability of reshaped cartilage.