Donald J. Prolo

Toward uniformity in evaluating results of lumbar spine operations. A paradigm applied to posterior lumbar interbody fusions.

Criteria for evaluating the results of treating lumbar spinal disorders vary widely. Comparative analyses of outcome among different therapy protocols are compromised by the diversity among the groups studied, as well as by the varying methods of measuring success. A rating scale is proposed based on the economic and functional status of the patient before and after treatment; anatomic results can be correlated. Application of this method to 34 patients who had undergone posterior lumbar interbody fusion showed a favorable response in 85% with a fusion incidence of 94%. This rating scale is easily applicable and can delineate pre- and postoperative conditions of patients on a semiquantitative basis. A more universal acceptance of common criteria for judging the outcome of lumbar spinal operations will facilitate comparisons among various methods of treatment.

Ethylene Oxide Sterilization of Bone, Dura Mater, and Fascia Lata for Human Transplantation

The use of allogeneic human bone, dura, and fascia has achieved an enduring and accelerating role in the augmentation of spinal fusions and the repair of skeletal and dural defects. Primary sterilization of these nonviable cadaveric tissues magnifies the potential sources and ensures the microbiological sterility of the implant. Subsequent lyophilization facilitates preservation and distribution and reduces the immunogenicity of the graft. The evaluation of gaseous ethylene oxide (EO) as a sterilant was suggested by the delerious effects of alternative methods. Through a series of experiments, the following properties of EO sterilization were studied: (a) surface and interstitial sterilization; (b) the diffusion of EO into tissue, the formation of the reaction products ethylene chlorohydrin (EC) and ethylene glycol (EG), and the desorption of all three from tissues; (c) lyophilization and aeration in the removal of residues; and (d) minimization of residues through pretreatment. Gaseous EO is a very effective surface sterilant of wet bone, dura, and fascia and does not grossly alter these tissues. Its partial penetration through compact bone renders it less reliable for an interstitial antimicrobial effect, unless access to the interior is provided by serial openings. The toxicity of EO, EC, and EG mandates the desorption through lyophilization of these compounds (EC and EG are formed during sterilization with EO). Before sterilization, bone must be rid of marrow by vigorous irrigation with deionized water. The resultant reduction of the number of cells and of the available chloride decreases antigenicity and the formation of EC. Freeze-drying for more than 72 hours, in some cases augmented by prolonged aeration at room temperature, reduces EO, EC, and EG to acceptable levels. The accurate assay of residues in tissue requires acetone extraction for gas chromatography on rehydrated tissues because extraction of dry tissues gives falsely low results. Rigorous adherence to a protocol incorporating these findings justifies the acceptance of gaseous EO as a safe, relatively rapid, and inexpensive sterilant of bone and soft tissues.

Quantitative Comparisons of Healing in Cranial Fresh Autografts, Frozen Autografts and Processed Autografts, and Allografts in Canine Skull Defects

Adult dog skull defects larger than 17 mm do not spontaneously heal. A quest for a potentially viable, cosmetically, mechanically, and technically acceptable template for human cranial reconstruction prompted a comparison of processed autogeneic and allogeneic bone implants with a fresh autograft control in the dog. Quantitative reproducible observations demonstrated that fresh calvarial bone autografts were superior to the nonviable implants in volume percent defect filled, mm2 new cortical bone, mm2 new and old cortical bone, and cortical bone porosity. Frozen autografts achieved 75%, antigen-extracted, autolyzed, partially demineralized auto- and allografts, 50% of the overall efficiency of fresh autografts. Fresh cancellous bone added to allografts did not improve long-term repair. Remodeling of all grafts appeared consistent with osteoconductive invasion by peripheral host endosteal and diploic elements; host external periosteum and dura contributed less. Central osteoinductive recruitment of mesenchymal cells from muscle or dura seemed not to occur in the adult dog. Partially demineralized dog calvarial grafts were resorbed without acting as a template for new bone formation. Surface demineralization, antigen extraction, and autolytic digestion of autografts and allografts, with or without fresh iliac bone, did not improve calvarial bone regeneration in adult dogs.

Autogenous skull cranioplasty: fresh and preserved (frozen), with consideration of the cellular response.

Every craniotomy requires immediate replacement of a fresh autograft of skull or, in the presence of cerebral swelling, delayed reimplantation of preserved autogenous skull. Resumption of osteogenesis, the index of viability, determines the effectiveness of these segments of calvaria in protecting the brain and restoring skull conformity. The cellular response in skull replaced either at the end of craniotomy or after frozen preservation was studied by light and fluorescence microscopy, skull roentgenograms, and radionuclide scintigraphy. In 5 patients eventual total remodeling of skull was found at the time of a second craniotomy performed from 1 to 19 years after the first. In 12 patients skull sections removed aseptically at craniotomy were frozen and stored for 1 to 35 months at -20 degrees C in bacitracin. This cytotoxic preservative method fixed the tissue, which appeared unchanged on light microscopy and was sterile on bacteriological and fungal cultures. In 53 patients who underwent autogenous cranioplasty with skull stored frozen for 3 weeks to 19 months, 48 operations were totally successful. Complications included infections in 2 patients, resorption in 2 infants, and incomplete restoration in 1 adult. In 10 patients the sequential dynamics of skull revitalization were found to be: revascularization, resorption, and accretion. The repair of membranous skull is similar to that of endochondral bone of the skeleton. Skull is metabolically intensely active after reimplantation and is the ideal material for cranioplasty.

Invasion of the brain by a cellular blue nevus of the scalp.A case report with light and electron microscopic studies

Repeated biopsies of a large pigmented lesion of the scalp of a young boy over a six‐year period showed the characteristic features of a cellular blue nevus. Recent severe neurologic symptoms necessitated more radical surgical intervention. This disclosed focal invasion of the underlying skull, meninges, and brain. Apart from focal necrosis and multiple nucleoli in the most recent surgical specimen, the histologic features of the lesion have remained constant, despite its locally aggressive behavior. Electron microscopic studies demonstrated distinctive nucleolar configurations not previously reported.

Superior Osteogenesis in Transplanted Allogeneic Canine Skull Following Chemical Sterilization

Sterilization of allogeneic bone increases the availability of this tissue for supplanting skeletal defects and effecting fusions. The optimal sterilant destroys micro-organisms, preserves the physical and chemical integrity of bone and possibly even reduces immunogenicity. Cortical bone of skull heals slowly and is variably resorbed. Of 36 dogs, spontaneous regeneration in 72 paired 20 mm defects was constant but always incomplete, and restored only about one third of the cross-sectional area of the defect at six months. The repair in defects replaced with canine allogeneic bony disc, sterilized with ethylene oxide (n = 9), gamma irradiation (n = 7), or methanol/chloroform/iodoacetic acid (n = 7) and then lyophilizedd, was compared with repair in defects filled with aseptically procured lyophilized only (n = 23) discs from the same donor. Criteria for evaluation of implants at six months included volume of defect filled, radiodensity, extent of fusion around circumference, revascularization, and remodeling. Bony discs sterilized with methanol/chloroform/iodoacetic acid remodeled at a superior rate (p less than 0.01). Radiation sterilization resulted in diminished density and inferentially reduced protection of the brain (p less than 0.025). Ethylene oxide, lyophilized implants, and implants lyophilized only produced comparable repair. Whereas an acceptable cranioplasty was achieved in 86% of methanol/chloroform/iodoacetic acid, lyophilize implants, all other alloimplants served an osteoconductive function with a successful repair occurring in 56% to 58%.

Composite autogeneic human cranioplasty: frozen skull supplemented with fresh iliac corticocancellous bone.

Skull totally exteriorized during craniotomy becomes nonviable. Resorption of the reimplanted cranial section occurs variably according to its treatment, the properties of the recipient bed, and the metabolic conditions of the host. Neurosurgeons commonly deep freeze autogeneic skull for preservation before delayed autogeneic cranioplasty. Aseptic necrosis commonly follows replacement of the autograft in its former cranial bed. This clinical study of six patients represents an attempt to block this destructive resorption by supplementing the frozen autograft with fresh corticocancellous autogeneic ilium. Observations of these patients ranging in age from 12 to 52 years support the following conclusions: (a) Osteogenesis was not enhanced by the addition of fresh corticocancellous bone to the frozen autoimplant. (b) The period of time that the autoimplant was frozen did not influence its subsequent biological behavior after cranioplasty. (c) Sterilization with ethylene oxide and in one case additional gamma irradiation did not impair the quality of the implant compared to those not sterilized. (d) Resorption occurred in both frozen and fresh but devitalized autogeneic skull. (e) Autogeneic skull is repaired by osteoconduction rather than by inducing competent perivascular stem cells to become osteogenic. (f) Freezing of autogeneic skull for preservation is practical, acceptable, but suboptimal from the perspectives of cerebral protection and cosmetic reconstruction. (g) The supplementation of the frozen autoimplant with fresh corticocancellous bone increases operating time and patient discomfort without affording additional benefit.