Coralline hydroxyapatite bone-graft substitutes in a canine diaphyseal defect model. Radiographic-histometric correlation.

Radiographic and histometric evaluation of a new form of bonegraft substitute derived from reef-building sea coral was performed in a canine diaphyseal defect model. Comparably sized blocks of this material and iliac crest autograft were placed into bilateral surgically created cortical windows in the distal radial diaphyses of 14 dogs. Representative graft specimens of both types underwent densitometric radiography and harvesting at 3, 6, 12, 24, and 48 months. Histometric analysis of implant specimens revealed satisfactory union and native osseous ingrowth at all time intervals. Graft specimens exhibited adequate union with scant host bone ingrowth at three months, but subsequent progressive appositional closure of cancellous spaces during the ensuing 45 months. Volume fraction and mean width of host bone remained stable in the implants but increased in the grafts due to neocortex formation. Stereologic distribution of bone was homogeneous in both implant and graft specimens, and no evidence for biodegradation of the former was observed. Corrected transmission density determinations accurately reflected these differences but correlated significantly with volume fractions and tissue widths of bone and soft tissue only in the autografts. These results support the successful early application of coralline hydroxyapatite bone graft substitutes as an alternative to autogenous grafting in the clinical setting and emphasize the potential role of noninvasive densitometric techniques in monitoring the incorporation of bone-graft materials.

Coralline hydroxyapatite bone-graft substitutes in a canine metaphyseal defect model. Radiographic-histometric correlation.

Radiographic and histometric evaluation of a new form of bone-graft substitute derived from reef-building sea coral was performed in a canine metaphyseal defect model. Blocks of this material were implanted into the proximal tibial metaphyses of eight dogs, with radiographic densitometry and harvesting performed at two, four, six, and 12 months. Histometric analysis demonstrated progressive apposition of host compact bone at the margins and trabecular bone at the interior of the implants with time following surgery. Corrected transmission density determinations correlated significantly with degree of osseous ingrowth (R = -0.78), void volume fraction (R = 0.88), and postoperative interval (R = 0.88). These results support the successful early application of coralline hydroxyapatite bone-graft substitutes as an alternative to autogenous grafting in the clinical setting, and indicate that the course of incorporation into host bone can be noninvasively monitored using densitometric techniques.

Comparative study of porous hydroxyapatite and tricalcium phosphate as bone substitute.

This study was performed to quantitate the bone ingrowth and biodegradability of porous calcium phosphate. Two kinds of coralline hydroxyapatite (CHA), along with sintered tricalcium phosphate (TCP), were evaluated. All implants had totally interconnecting pores. These pores measured 260-600 mu for CHA-Goniopora (CHAG), 190-230 microns for CHA-Porites (CHAP), and 100-300 microns for TCP. Cylindrical implants (3 mm in diameter by 8 mm in length) were implanted into the diaphyses of rabbit tibias for 3 to 24 weeks. The quantity of regenerated bone, remaining implant, nonmineralized space, and the middle two quarters of the cortical area were measured by a computerized operator-assisted analysis for bone histomorphometry. At 3 weeks after implantation, 17.3% of CHAG, 11.3% of CHAP, and 7.0% of TCP were infiltrated by regenerated bone. At 24 weeks, 56.1% of CHAG, 52.7% of CHAP, and 44.7% of TCP were occupied by lamellar-type bone. Implant degradation was noted to be 46.4% for TCP and 27.5% for CHAP. In contrast, CHAG did not show appreciable degradation until 24 weeks.

Experimental study on the repair of full thickness articular cartilage defects: effects of varying periods of continuous passive motion, cage activity, and immobilization.

In order to clarify the dose/response characteristics of continuous passive motion (CPM), the repair response of full thickness articular cartilage defects was studied in a rabbit model. The following combinations of CPM and immobilization (Imm) were utilized: CPM, 24 h/day; CPM, 8 h/day and Imm, 16 h/day; CPM, 2 h/day and Imm 22 h/day; Imm 24 h/day; and normal cage activity. These regimens were used only in the initial week and then all rabbits were permitted to move freely in their cages, except for a sixth Imm-CPM group that was kept immobilized in the initial week and then CPM 24 h/day for another week. The CPM 24 h/day and the CPM 8 h/day groups (groups 1 and 4, respectively) showed better repair than the other groups, i.e., better surface congruity, larger positive Safranin-O staining area, and greater number of chondrocytes in the repair tissue. The CPM 2 h/day group (group 3), however, showed only slightly better repair than the Imm group (group 4). The CPM following immobilization was not effective to overcome the harmful effect of immobilization. We conclude that in the present model, CPM for 8 or 24 h/day is effective for adequate cartilage repair even with some component of immobilization. Its application should be at least 8 h/day. On the contrary, if CPM is delayed for a week following immobilization, the effect of CPM on cartilage will be reduced.

Porous hydroxyapatite as a bone graft substitute in diaphyseal defects: a histometric study.

Porous hydroxyapatite (IP200), formed by conversion of the Poritidae porites exoskeleton, has pores averaging 230 microns and pore interconnections averaging 190 microns in diameter. In the distal radial diaphyses of 14 dogs, bilateral 7.5 X 20 mm cortical windows were created and fitted with 5 X 7.5 X 20 mm blocks of IP200 implants and iliac autografts. Both implanted and contralateral grafted radius specimens were retrieved at 3, 6, 12, 24, and 48 months. Unstained undecalcified sections were examined by microradiography and UV epi-illumination. Stained undecalcified sections were examined by light microscopy and quantitated by histometric methods. Implant specimens demonstrated good union and bone ingrowth at all time intervals. The implant specimens were composed of (mean +/- SE) 10.6% +/- 1.0% soft tissue, 51.2% +/- 1.3% bone, and 38.2% +/- 1.0% IP200. The graft specimens showed good union with little apparent ingrowth at 3 months, followed by progressive appositional closure of cancellous spaces. The graft specimens contained 21.9% +/- 0.9% bone at 3 months with increases at each time interval to 73.1% +/- 8.7% at 48 months. The volume fraction and mean width of IP200 did not change with time, confirming the absence of implant biodegradation. The volume fraction and mean width of bone remained stable in the implant but increased in the graft specimens, corresponding to graft neocortex formation. It is concluded that implants initially filled in with bone while grafts initially replaced much of their spongiosa and subsequently filled in with bone. Histometry of untreated defects and measurement of mechanical properties are suggested for further study.

Different effects of mechanical vibration on bone ingrowth into porous hydroxyapatite and fracture healing in a rabbit model.

The effects of mechanical vibration on bone ingrowth into porous hydroxyapatite implants and fracture healing were examined radiographically, histomorphometrically, and biomechanically in a rabbit model. Fifty-three female NZW rabbits were used in this study. These rabbits were divided into four separate studies to assess the effects of 20 and 60 min of vibration/day in both implant and osteotomy models as compared with the respective non-vibrated controls. For the implant model, coral hydroxyapatite goniopora rods were implanted bilaterally into tibiae and for the osteotomy model, bilateral fibulae were osteotomized. A resonant frequency of 25 Hz mechanical vibration was used. After periods of 2, 3, 4, and 6 weeks of vibration, the rabbits were killed and examined. For the implant model, there was no significant difference between control, 20, or 60 min of vibration/day with respect to the rate or amount of new bone ingrowth. For the fracture model, 60 min of vibration/day produced a significantly larger callus as compared with the non-vibrated controls (p less than 0.05), whereas 20 min of vibration/day did not. Although biomechanical testing demonstrated a general trend for increased strength in the vibrated animals, it failed to reach significance. These results suggest that the mechanical vibration used in the present study had a beneficial effect on callus volume, possibly due to the stimulation of secondary bone healing processes, but does not appear to promote bone ingrowth into a porous hydroxyapatite implant.

Bone ingrowth into porous calcium phosphate ceramics: influence of pulsing electromagnetic field.

The effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxyapatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF-treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3-4 weeks of PEMF stimulation.

Magnetic resonance imaging of the lumbar spine with CT correlation.

The results of magnetic resonance (MR) imaging and computed tomography (CT) in 18 patients with known degenerative disk disease of the lumbar spine were compared. In 60 intervertebral disk levels studied, there were 17 disks with degeneration and disk bulge, and 15 herniated disks. Final diagnoses were based on several factors, with surgical confirmation in five patients. There was good correlation between the two methods at 51 of the 60 levels studied. However, there were major discrepancies in interpretation at nine intervertebral disk levels. These included three false-positive MR imaging interpretations of a herniated disk and one false-negative herniated disk on MR imaging. MR imaging detected one case of disk herniation that was missed prospectively on CT. There were also four presumed degenerated disks seen on MR scans that appeared normal on CT. The conus medullaris was imaged in 16 of 18 patients. The sagittal view proved best for demonstrating both disk abnormality and the conus medullaris. The transaxial view was sometimes helpful in localizing a disk herniation, but partial-volume averaging in the 7-mm slice thickness limited its usefulness. There were five disk herniations that could not be accurately localized on the MR scan. MR imaging proved more sensitive than CT in detecting early disk disease, which appeared as decreased signal intensity within the disk. In three postoperative cases, MR imaging was better able to distinguish between recurrent disk herniation and postoperative scar formation. CT, on the other hand, was more specific in distinguishing herniated disk from disk bulge and proved far superior to MR imaging in localizing disk herniation.(ABSTRACT TRUNCATED AT 250 WORDS)

Automated percutaneous discectomy: a prospective multi-institutional study.

A prospective multi-institutional study was carried out to evaluate automated percutaneous discectomy in the treatment of lumbar disc herniations. Of the 327 patients who prospectively met the study criteria and were followed for longer than 1 year, 75.2% were successfully treated. When patients (n = 168) who prospectively did not meet the study criteria were treated, the success rate was 49.4%. One case of discitis was reported; otherwise, no other serious complications were noted, and specifically no vascular or nerve damage was encountered. This study indicates that automated percutaneous discectomy can be used successfully to treat lumbar disc herniations with minimal morbidity and emphasizes the need for proper patient selection.

Surgical experience following intervertebral discolysis with collagenase.

Of 410 patients with refractory herniated lumbar disc disease treated with intradiscal collagenase, 82 (20%) did not respond to enzyme treatment and subsequently underwent surgery. Failure to improve in 6 to 8 weeks was the predominant cause for surgical intervention (53 patients). Increased pain (18 patients), progressing neurological deficit (10 patients), and disc-space infection (one patient) were the other indications for surgery. At surgery, extrusions and/or sequestrations were found in 46 patients, undigested protrusions in 16 patients, and other causes of treatment failure in 14 patients. Six patients had normal findings. There was no evidence of adverse enzyme activity on the surrounding structures. Surgical results showed an overall success rate of 87%, and did not appear to be compromised by the previous enzyme therapy.

Cast-bracing for fractures of the femur. A preliminary report of a modified device.

The second-generation cast-brace system offers some advantages over previous systems of cast-brace treatment for fractures of the femur. Because the thigh section is adjustable, loosening of the cast-brace is not a problem. The device can be applied earlier and need not be reapplied when the girth of the thigh is reduced. Using a roller traction system, the cast-brace can also be used initially for traction and suspension without the complexity of traditional systems. With the use of commercially available plastic knee joints, special skills in alignment of the joints are not necessary, and no specially trained personnel need be on hand. The lightweight thigh section coupled to custom-fit plaster leg section, with the foot and ankle free, are less bulky than a totally plaster cast-brace with metal side joints. Walking may be begun earlier with the device, and in-patient hospital time is reduced. However, this system requires a high level of patient cooperation in that the patient is free to adjust the system himself and, therefore, the system may not be safe for application in all settings.

Porous hydroxyapatite as a bone-graft substitute in metaphyseal defects. A histometric study.

Porous hydroxyapatite (Interpore 500) formed by conversion of the Porites goniopora coral exoskeleton has pores averaging 600 micrometers and pore interconnections averaging 260 micrometers in diameter. In the proximal tibial metaphysis of eight dogs, a defect one cubic centimeter in size was created unilaterally and was fitted with a block of Interpore 500. Both proximal tibial metaphyses were retrieved at two, four, six, and twelve months. Stained undecalcified sections were examined by light microscopy and quantitated by histometric methods. The implant-side specimens contained compact bone along the external surface and trabecular bone interiorly. The interior of these specimens was composed of 51.9 +/- 1.3 per cent soft tissue, 13.0 +/- 1.2 per cent bone, and 35.1 +/- 1.2 per cent Interpore 500 (mean and standard error). The interior of the normal specimens was composed of 79.7 +/- 1.4 per cent soft tissue and 20.2 +/- 1.4 per cent bone. The allocation of implant pore space between bone and soft tissue was proportional to that of bone and soft tissue in the normal tibiae. The stereological distribution of regenerated bone in the porous hydroxyapatite was also the same as in the normal tibiae. The appositional process of incorporation of the implant was confirmed by the finding that 66.5 per cent of the surface of the Interpore 500 was covered with bone ingrowth at twelve months.

The below-the-knee amputation for vascular disease.

Of 190 consecutive patients with below-the-knee amputation done for diabetic or arteriosclerotic vascular disease, 167 were successfully fitted with a prosthesis and used the prosthesis in some or all of the activities of daily living. The surgical failure rate was 4.2 per cent; only eight patients required surgical revision to a higher level of amputation. The technique of rigid plaster dressing followed by delayed application of a plaster cast and pylon was not detrimental to wound healing and did not increase the interval between surgery and the use of the prosthesis, nor did it depress the eventual level of function. When compared with our own previous experience with other flaps, the long posterior flap offered a significant advantage in healing rate.

A randomized double-blind prospective study of the efficacy of pulsed electromagnetic fields for interbody lumbar fusions.

A randomized double-blind prospective study of pulsed electromagnetic fields for lumbar interbody fusions was performed on 195 subjects. There were 98 subjects in the active group and 97 subjects in the placebo group. A brace containing equipment to induce an electromagnetic field was applied to patients undergoing interbody fusion in the active group, and a sham brace was used in the control group. In the active group there was a 92% success rate, while the control group had a 65% success rate (P greater than 0.005). The effectiveness of bone graft stimulation with the device is thus established.

The value of the axial view in assessing discograms. An experimental study with cadavers.

The clinical value of discography is controversial. An axial view of a discogram such as could be obtained with CT scans should increase the structural information regarding disc pathology, and clarify the relationship to disease of the facet joints as well. To evaluate this concept, 103 intervertebral levels in 23 cadaver specimens were studied by anteroposterior, lateral, and axial roentgenographic views. From these three views, a new classification for interpreting discograms was developed. The correlations between the three different views were good, confirming the potential value of CT axial views. However, in one fourth of the discs there were pathologic anatomic findings that could be seen only in the axial views. There were more severe osteoarthritic changes in the right than the left facet joint, and a discrepancy between facet arthritis and disc disease was also noted.

Effect of smoking and pulsed electromagnetic fields on intradiscal pH in rabbits.

The adverse effect of cigarette smoking on human spines has been noted indirectly. There is correlation of increased back pain among individuals who smoke heavily. The hypothesis of this study was that an environment of cigarette smoking is an adverse event and will create a reduced pH in the rabbit intervertebral disc. Electromagnetic fields, however, can defend against this adverse event and reduce the tendency toward acidic pH. Rabbits were exposed to cigarette smoke for 2, 4, or 6 weeks and their intradiscal pH measured. Cigarette-smoke-exposed discs demonstrated a consistently lower pH than did the discs of the machine control rabbits. The second group of rabbits were exposed to cigarette smoke and pulsed electromagnetic fields. The cigarette-smoke-exposed rabbits that were exposed to the pulsed electromagnetic fields for 4 hr/day demonstrated no change in their intradiscal pH, in contrast to those who were exposed to smoke alone. In conclusion, cigarette smoke exposure in rabbits consistently produces a lower intradiscal pH and pulsed electromagnetic fields can defend against this adverse effect.

Spinal pain rehabilitation: inpatient and outpatient treatment results and development of predictors for outcome.

Multidisciplinary treatment outcomes with a 1-year follow-up is reported for 100 chronic low-back pain patients participating in inpatient rehabilitation and 100 patients participating in outpatient rehabilitation. Treatment for both groups of patients was based on principles of operant conditioning and consisted of increasing structured exercise activities and educational classes for instruction in techniques of pain management. Results are presented in terms of patient reports of decreased pain, increased activity, decreased medication, need for further treatment, and return to work. A method for predicting return to work was developed by way of a computerized discriminate analysis with the formulas presented for consideration by those interested in similar patient groups.

Trunk strength testing in patient evaluation and treatment.

A wide variety of trunk strength testing devices has been developed, the goal being to quantify back strength, patient effort, and spinal function or dysfunction. Although the idea of applying quantitative values to spine function is appealing, controversy exists regarding the reliability and validity of these testing systems. In this issue, two experienced investigators give their opinions as to the values and pitfalls of lumbar trunk strength testing, and provide insight into the most appropriate applications of these often costly systems.

Development of the Hispanic Low Back Pain Symptom Check List.

STUDY DESIGN: The Low Back Pain Symptom Check List identifies psychological disturbance in patients with low back pain. This report traces the development of a translation for Hispanic populations. OBJECTIVE: The study explores the reliability and assesses the equivalence of the translation in providing pain and psychological information. SUMMARY OF BACKGROUND DATA: A number of psychometric measures appear suitable for routinely assessing psychological disturbance among back injured patients. Unfortunately, there are few measures with language translations that can be applied to Hispanic populations. METHODS: In study 1, the English form was translated by two bilingual physicians. In study 2, reliability was examined using Cronbach's measure of internal consistency. In study 3, the equivalence of the Hispanic and English forms in predicting treatment outcome was examined. RESULTS: Coefficient alphas and mean pain scores were similar for the English and Hispanic forms. Overall agreement between the two forms in tracking psychological disturbance was 91%. The Hispanic form was equally accurate in predicting treatment outcome. CONCLUSIONS: The Hispanic form is reliable and provides pain and psychological information much like the English form.