Lumbar interbody fusion using the Brantigan I/F cage for posterior lumbar interbody fusion and the variable pedicle screw placement system: two-year results from a Food and Drug Administration investigational device exemption clinical trial.

STUDY DESIGN: A carbon fiber-reinforced polymer cage implant filled with autologous bone was designed to separate the mechanical and biologic functions of posterior lumbar interbody fusion. OBJECTIVES: To test the safety and efficacy of the carbon cage with pedicle screw fixation in a 2-year prospective study performed at six centers under a protocol approved by the Food and Drug Administration, and to present the data supporting the Food and Drug Administration approved indications. SUMMARY OF BACKGROUND DATA: The success of posterior lumbar interbody fusion has been limited by mechanical and biologic deficiencies of the donor bone. Some failures of pedicle screw fixation may be attributable to the absence of adequate load sharing through the anterior column. Combining an interbody fusion device with pedicle screw fixation may address some limitations of posterior lumbar interbody fusion or pedicle screw fixation in cases that are more complex mechanically. METHODS: This clinical study of posterior lumbar interbody fusion with pedicle screw fixation involved a prospective group of 221 patients. RESULTS: Fusion success was achieved in 176 (98.9%) of 178 patients. In the management of degenerative disc disease in patients with prior failed discectomy surgery, clinical success was achieved in 79 (86%) of 92 patients, and radiographic bony arthrodesis in 91 (100%) of 91 patients. Disc space height, averaging 7.9 mm before surgery, was increased to 12.3 mm at surgery and maintained at 11.7 mm at 2 years. Fusion success was notdiminished over multiple fusion levels. These results were significantly better than those reported in prior literature. Although significant surgical complications occurred, those attributable to the implant devices occurred less frequently and generally were minor. CONCLUSIONS: The Brantigan I/F Cage for posterior lumbar interbody fusion and the Variable Screw Placement System are safe and effective for the management of degenerative disc disease.

Evaluation of cold therapy in postoperative spine patients.

The use of cold therapy postoperatively in orthopaedics has been the topic of a long-standing discussion. How cold is applied, (i.e., ice vs. machine), the length of time of cold exposure, and frequency of appli- cation has been the subject of debate for years, and there is still no clear-cut answer or standard which isuniformly followed. The use of cold has been shown by both Cohn 1 and McCoy2to decrease the need for pain medication postoperatively. Masten3 used cold therapy in the laboratory to demonstrate that post-traumatic swelling was controlled with cold applications. McMaster and Liddle' showed a relationship with decreased edema and early application of ice.We attempted to look at the application of cold therapy in postoperative spine patients to see if there was significant benefit to our patients. In our study patients were randomly cho- sen to receive cold therapy postoperatively. Patient groups were normalized as to sex, age, and surgery. Both groups were homogenous when looked at overall. The Hot/Ice System™ (Incare Medical Products, Hollister Inc., Hollister, Calif.] was chosen as the method of cold delivery for three reasons: (1) ease of use, (2) limited need for nursing intervention, and (3) delivery of consistent cold temperatures (Fig. 1).

Seven-year follow-up of vertebral excision and reconstruction for malignant hemangioendothelioma of bone.

STUDY DESIGN: This study reports the 7-year follow-up of an L5 vertebral hemangioendothelioma treated with tumor excision and allograft reconstruction stabilized with transpedicular fixation. OBJECTIVES: A review of vertebral hemangioendotheliomas is provided to outline the rationale for surgical excision in such cases. SUMMARY OF BACKGROUND DATA: Radiation therapy has been the mainstay of therapy in surgically inaccessible lesions of the spine. The long-term follow-up of radical spinal tumor excision and reconstruction in previously surgically inaccessible areas has not been reported for vertebral hemangioendothelioma. METHODS: After embolizations, anterior L5 corpectomy and allograft femoral reconstruction was performed. Second-stage (same day) posterior element excision was followed by VSP stabilization of L4-S1 with artificial pedicles anchored into the femoral allograft at L5. Radiation therapy followed. RESULTS: Satisfactory long-term (7-year) segmental reconstruction using allograft and VSP was realized, even in the face of postoperative radiation therapy. CONCLUSION: Contemporary spinal reconstructive techniques have been developed that continue to limit the number of surgically inaccessible tumors in the spine. The present report shows these techniques to be durable and apparently effective in vertebral hemangioendothelioma.

Posterior transvertebral osteotomy for adult thoracolumbar kyphosis.

STUDY DESIGN: A retrospective case study was performed on the single-stage posterior transvertebral closing-wedge osteotomy for treatment of adult thoracolumbar kyphosis. SUMMARY OF BACKGROUND DATA: Forty-one consecutive cases in 38 patients available for follow-up, averaging 33 months (range 4-87 months), are included. All patients had severe pain and/or deformity; 51% of cases had previous fractures, and 49% had postlaminectomy failed back syndromes with kyphosis. A preoperative neurologic deficit was present in 34% of the cases including two with cauda equina syndrome. METHODS: Patient examination and interviews, subjective questionnaire, chart reviews, and radiographic measurements were performed independently. Complications, risks, benefits, results, and biomechanical considerations were evaluated and discussed as compared with other techniques. RESULTS: All cases had solid union at follow-up; 93% maintained correction averaging 35 degrees with three requiring revision for failure. Postoperatively, 19.5% of the cases had new neurologic deficits with five (12.2%) temporary or minor and three (7.3%) major, including one with unimproved paraplegia at follow-up. Eight of the 14 preoperative neurologic deficit cases improved postoperatively; 26 additional surgeries were performed on 18 patients most commonly for pain (x 11) and additional trauma (x 4). The subjective questionnaire results indicated significant patient satisfaction, with 76% stating they would repeat the surgery and 90% recommending it to another. CONCLUSION: This technically demanding high-risk procedure provides an effective and mechanically superior correction for acute angle thoracolumbar kyphosis in selected adult patients, with high subjective satisfaction.

Treatment of L5-S1 spondyloptosis by staged L5 resection with reduction and fusion of L4 onto S1 (Gaines procedure).

STUDY DESIGN AND OBJECTIVES: A retrospective study was performed on the two-stage Gaines procedure for the treatment of spondyloptosis, evaluating indications, techniques, results, and patient satisfaction. SUMMARY OF BACKGROUND DATA: Sixteen consecutive patients from two institutions were included. Their average age was 24 years. Average follow-up was 3.9 years, with 11 patients included in follow-up 2 or more years. Ten patients (63%) had a preoperative neurologic deficit--three with cauda equina syndrome, one with foot drop. All patients had severe back or radicular symptoms and significant disability or severe deformity. METHODS: Patient examinations, interviews, chart review, and radiographic measurements all were performed independently. A subjective questionnaire was administered to each patient comparing preoperative with postoperative changes in pain, function, and appearance, as well as their overall outcome assessment. RESULTS: Postoperatively, 12 patients (75%) had early neurologic deficits, with seven of these having had a preoperative deficit. Four of these seven had a persistent deficit at follow-up, one with a permanent foot drop and three with documented weakness that was still improving at follow-up. The patient with preoperative foot drop remained unchanged, and the remaining seven patients with early deficit all recovered within 1 year. All three patients with preoperative cauda equina syndrome recovered postoperatively. The subjective questionnaire results revealed extremely high patient satisfaction. They reported significant improvement in pain, function, and appearance. CONCLUSIONS: Despite the relatively high complication rate, with appropriate patient selection, planning, and surgical technique, this procedure appears to be a sound method for treating severe cases of spondyloptosis, yielding very high patient satisfaction.

Interbody fusion and instrumentation.

Fusion indications in adult degenerative disk disease of the lumbosacral spine include isolated disk resorption, primary and secondary instability, recurrent disk herniation, and pseudarthrosis. Common to these indications are variable proportions of biomechanical insufficiency of the motion segment, instability, deformity, and spinal stenosis. Apart from favorable psychosocial and work related variables, satisfactory outcome is dependent on treatment by a combination of diskectomy, decompression, and deformity correction, in addition to fusion. Isolated intertransverse or interbody fusions show variable fusion rates that are increased by concurrent instrumentation. Persistent pseudarthrosis rates and instrumentation failures have prompted circumferential fusion techniques. Posterior lumbar interbody fusion (PLIF) and segmental pedicle-based plate fixation overcome earlier problems with PLIF by allowing for wide decompression and increased exposure for disk space preparation, minimizing neural injury. Pedicle fixation restores segmental stability and minimizes graft retropulsion. Restoration of anterior column support prolongs instrumentation life, and increases fusion rates irrespective of the number of levels fused. Disk space distraction, with the use of instrumentation as a working tool, permits safer decompression of the intraforaminal zone, a common area of stenosis, and single or multilevel deformity correction to restore coronal, axial, and sagittal alignment and spinal balance. Even though the surgical technique is demanding, fusion rates up to 96% and clinical success up to 86% are achieved.

A carbon fiber implant to aid interbody lumbar fusion. Two-year clinical results in the first 26 patients.

The success of posterior lumbar interbody fusion (PLIF) has been limited by mechanical and biologic deficiencies of the donor bone. The authors have designed a carbon fiber-reinforced polymer implant that separates the mechanical and biologic functions of PLIF. The cagelike implant provides an actual device designed to meet the mechanical requirements of PLIF and replaces the donor bone with autologous bone, the best possible bone for healing. The authors report 2-year follow-up results for their first 26 consecutive patients, 18 of whom were postsurgical failed backs with a total of 37 previous surgeries. At 2 years, 28 of 28 PLIF cage fusion levels and 6 of 11 (54.5%) allograft levels exhibited radiographic fusion, a statistically significant difference at P = 0.0002. Clinical results were excellent in 11/26, good in 10/26, fair in 3/26, and poor in 2/26. Fair and poor results were attributable to objective identifiable problems unrelated to the carbon cage. The carbon implant achieved successful fusion in 6/6 (100%) of followed patients treated for a failed ETO allograft interbody fusion. A prospective controlled multi-centered study is being initiated.

The variable screw placement spinal fixation system. Report of a prospective study of 250 patients enrolled in Food and Drug Administration clinical trials.

The variable screw placement (VSP) system uses transpedicular screws and slotted plates to achieve constrained segmental fixation of the spine. A prospective multicenter study of 250 patients was performed under a Food and Drug Administration approved protocol to test the safety and effectiveness of this system. Complete 2-year follow-up data are reported for 169 of 223 (73%) patients who had fixation of three spinal levels or fewer. "Clinical success" was defined as an excellent or good result or improvement of two grades in a 10-point combined pain and function scale. "Fusion success" was defined by presence of continuous trabecular bone bridging the fusion area. For 86 patients with postsurgical failed back syndrome, clinical success was achieved in 69 (80.2%) and fusion success in 76 of 83 (91.6%) patients. These success rates were statistically higher than previous literature reports (P = 0.01 for clinical success and P = 0.02 for fusion success). For spondylolisthesis, clinical success was achieved in 44 of 57 patients (86.3%) and fusion success in 43 of 47 (91.5%) patients. For spinal stenosis, clinical success was achieved in 25 of 32 patients (78.1%) and fusion success in 30 of 31 (96.8%) patients. Overall fusion success was achieved in 186 of 200 (93%) patients with no statistical difference when comparing the numbers of levels fused. There were 21 device-related complications (8.4%) and 16 non-device-related complications (6.4%).

Compression strength of donor bone for posterior lumbar interbody fusion.

Forty-three blocks of allograft bone used clinically for posterior lumbar interbody fusion and twenty-three blocks of xenograft bone from goats and cows were tested in compression and compared with the clinical mechanical requirements of posterior lumbar interbody fusion. Variations in processing methods allowed evaluation of the effects of processing on mechanical strength. Fresh-frozen cancellous bone from Os Bone (Cleveland, OH) failed at an average load of 863 +/- 615 N. Fresh-frozen cancellous bone from the Mid American Tissue Center (Massilon, OH) failed at an average load of 3492 +/- 1720 N. Freeze-dried cancellous bone obtained from the American Red Cross failed at an average load of 1595 +/- 1031 N. Air-dried ethylene oxide sterilized cancellous bone from Os Bone failed at an average load of 1338 +/- 691 N. Air-dried ethylene oxide sterilized cancellous bone from Mid America failed at an average load of 1616 +/- 1157 N. Fresh-frozen tricortical bone from Mid America failed at an average load of 2257 +/- 1081 N. Air-dried ethylene oxide sterilized tricortical bone from Os Bone failed at an average load of 2474 +/- 1928 N. Air-dried ethylene oxide sterilized tricortical bone from Mid America failed at an average load of 2308 +/- 422 N. Bovine Surgibone from Unilab (Hillside, NJ) failed at an average load of 2967 +/- 399 N. Strength of bone in compression was not weakened by freeze drying, air drying, ethylene oxide sterilization, or by incubation at 37 degrees C for 1 week before testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical correlation between degenerative spine disease and dermatomal somatosensory-evoked potentials in humans.

The relationship between clinical status and preoperative and intraoperative dermatomal somatosensory-evoked potentials was investigated as a function of test site. Results indicated that the specificity and sensitivity of dermatomal somatosensory-evoked potentials varied with level of involvement: L5 demonstrated greatest agreement with equal correlation at L3, L4, and S1. Variables that influenced correlation included history of previous surgeries, type of anesthetic used, interpretation criteria, and whether the patient was awake or asleep. It was concluded that dermatomal somatosensory-evoked potentials can provide the surgeon with diagnostic and intraoperative information regarding the functional integrity of single nerve root function.

Lamina repair and replacement to control laminectomy membrane formation in dogs.

This study examined the efficacy of lamina repair by the use of various techniques to prevent postlaminectomy scar formation in a canine system. Five-level noncontiguous laminectomies were performed on six adult canines. The most caudal (Site 1) was left uncovered and served as the control. Exposed dura at each of the remaining four levels was covered with one of the following: Site 2, free autogenous laminar bone graft; Site 3, polymethylmethacrylate; Site 4, Teflon-Proplast composite; Site 5, collagen gel. The dogs used in the study were killed 16 weeks after surgery. Three specimens were examined by plain roentgenography and computerized tomography, two specimens were examined histologically, and the remaining four specimens were graded according to scar volume and scar adherence, as detected during gross dissection of the postlaminectomy scar. No repair technique interfered with roentgenography evaluation. The least scar and fewest adhesions were present under the free bone graft repair site. The Teflon-Proplast composite and polymethylmethacrylate both limited the amount and adherence of scar. Collagen gel and control sites were indistinguishable in this study. It is concluded that lamina repair with a solid material covering exposed dura significantly reduces the formation of postlaminectomy membrane and scar.

A carbon fiber implant to aid interbody lumbar fusion. Mechanical testing.

A carbon-fiber-reinforced polymer implant has been designed to aid interbody lumbar fusion. The cage-like implant has ridges or teeth to resist pullout or retropulsion, struts to support weight bearing, and a hollow center for packing of autologous bone graft. Because carbon is radiolucent, bony healing can be imaged by standard radiographic techniques. The device has been mechanically tested in cadaver spines and compared with posterior lumbar interbody fusion performed with donor bone. The carbon device required a pullout force of 353 N compared with 126 N for donor bone. In compression testing, posterior lumbar interbody fusion performed with the carbon device bore a load of 5,288 N before failure of the vertebral bone. Posterior lumbar interbody fusion performed with donor bone failed at 4,628 N, and unmodified motion segments failed at 6,043 N. The carbon fiber implant separates the mechanical and biologic functions of posterior lumbar interbody fusion.

Reduction of high-grade slips (grades III-V) with VSP instrumentation. Report of a series of 41 cases.

Records of 41 patients were reviewed for early complications resulting from reduction of high-grade spondylolisthesis. Blood loss averaged 1,427 ml. There were no cases of infection, dural tears, or bladder or bowel dysfunction. Two cases of transient foot drop and one case of permanent foot drop developed. A lumbar plexus stretch palsy occurred in one patient. Long-term results were evaluated in 20 patients followed up 2 or more years after surgery. Three of the 20 did not have interbody fusions and lost their reductions. All 20 patients went on to fuse with no pseudoarthrosis. One case of broken plate and two cases of broken screws occurred. Patient satisfaction ranged from good to excellent. Results suggest that reduction of high-grade slips with interbody fusion is a safe and effective procedure.

In vitro biocompatibility of polyetheretherketone and polysulfone composites.

Short carbon fiber reinforced composites could potentially replace some of the metal alloys used in orthopedic implants. In particular, polysulfone and, more recently, polyetheretherketone have been considered as the matrix material for carbon fiber reinforced composite implant materials. ASTM standards F813 and F619 for direct contact cell culture evaluation and extraction were employed to determine the in vitro biocompatibility of a carbon fiber composite of polyetheretherketone, PEEK, in comparison to a carbon fiber reinforced polysulfone composite. The cell cultures were assessed qualitatively by microscopy and quantitatively using an enzyme assay to determine cytotoxicity. Overall, the cellular response to the PEEK and polysulfone composites were negligible indicating that further in vivo studies with these materials are appropriate.

Transpedicular screw fixation.

Spinal fixation employing transpedicular screws has recently been the focus of increased attention at various institutions throughout the world, but concerns about the safety and efficacy of transpedicular screws linger. This study was undertaken to address some of these concerns. The study included evaluation of the internal and external morphology of the vertebral pedicles, which revealed that adequate bone stock is generally available at T2, T7, T12, and L1-L5 spinal levels to accept screws in the 4-7-mm diameter range. The pedicle was observed to be composed of abundant cancellous bone internally with relatively thick cortical walls. The method of pilot hole preparation for pedicle screws was also examined. Screws inserted in pilot holes prepared with a 3.4-mm blunt probe (ganglion knife) resulted in higher pullout forces in eight of 10 trials as compared with those with pilot holes prepared using a 3.2-mm drill. Furthermore, the probes afford greater control of hole depth and alignment. Fatigue studies on three screw designs revealed a graduation of strength between a 7.0-mm pedicle screw, a 5.5-mm pedicle screw, and a modified 6.5-mm cancellous lag screw. The modified cancellous lag screw has an inherent stress riser that affected fatigue life. It was noted that extreme care must be exercised to prevent bending of the pedicle screws during implantation. If bending occurs one can expect a 50% reduction in the number of cycles to failure.

Heparinized materials for control of the formation of the laminectomy membrane in experimental laminectomies in dogs.

This study examined the efficacy of heparinized biodegradable materials in the prevention of post-laminectomy scar formation using a canine system. Six-level noncontiguous laminectomies were performed on five adult canines. Exposed dura at each level was covered with the following: (1) nothing (control); (2) fat; (3) fat and autogeneic bone; (4) heparinized Avitene; (5) heparinized Surgicel; or (6) heparinized collagen gel. Canines were killed 16 weeks postoperatively and histologic specimens examined. Fibrous adhesions were abundant at Site 1 (control). Free fat grafts were well preserved and did not permit adhesions at Sites 2 and 3. None of the heparinized materials was as effective as fat in controlling scar formation. Overlying bone at Site 3 did not alter the quality of a free fat graft placed over the dura, a point possibly significant for laminectomies followed by fusion.

Reduction and stabilization of grade IV spondylolisthesis.

Virtually any degree of spondylolisthesis can be reduced and held using variable screw placement (VSP) slotted plates and transpedicular screws. All of the soft tissue holding the displaced vertebrae must be stretched prior to pulling the vertebrae back into normal alignment. Complete control of the displaced vertebrae is gained through the transpedicular screws, and fixation is accomplished by bolting the screws to the spine plates that have been bent to achieve the proper lumbar lordosis. Ultimate stability is gained by both a bilateral lateral and interbody fusion.

Posterior lumbar interbody fusion and plates.

Posterior lumbar interbody fusion (PLIF) is accepted by many authors as the surgical treatment for herniated discs, degenerative disc conditions, and Grades I and II spondylolistheses. PLIF is now used in conjunction with newly developed segmental spine plates by using transpedicular screw fixation to enhance the osteosynthesis and success rate of interbody fusion. To date, 104 fusions have been performed in 67 patients with no dislocations of any interbody grafts and no indication of absorption, pseudoarthrosis, or infections.

A morphometric study of human lumbar and selected thoracic vertebrae.

The results of a morphometric study of selected human vertebrae undertaken to provide data for implant design are presented in this report. Twenty-seven dimensions were measured from thoracic (T2, T7, T12) and lumbar (L1-L5) vertebrae using prepared spinal columns from 30 skeletons belonging to the Hamann-Todd Osteological Collection. Maximum and minimum pedicle dimensions indicated that the pedicles are less symmetric cephalad than they are caudal. Vertebral body height increases caudally except posteriorly where, after an initial increase, it decreases in the lower lumbar region. Major and minor body diameters and the major spinal canal diameter slightly increase caudally, whereas minor spinal canal diameter exhibits little or no change.

Trapeziometacarpal total joint replacement using the Steffee prosthesis.

The first forty-five Steffee trapeziometacarpal total joint replacements that were used to treat severe trapeziometacarpal arthritis in thirty-eight patients were analyzed retrospectively. The length of follow-up ranged from two through six and one-half years. Forty-two of the arthroplasties resulted in relief of pain, and the restoration of strength and motion was highly satisfactory. Although radiographs showed a high incidence of asymptomatic radiolucent lines at the bone-cement interface of the trapezial component, only three patients had symptomatic loosening. We concluded that trapeziometacarpal total joint replacement can provide good relief of pain and restore function of the thumb to patients with severe trapeziometacarpal arthritis, although further study is necessary to assess the long-term results of the procedure.