Bone formation near direct current electrodes with and without motion.

The osteogenesis induced in the medullary canal of rabbits by the implantation of moving and stationary wire electrodes was studied with and without the simultaneous application of 20-microA constant direct cathodic current. After 3 weeks, the formation of new trabecular bone in the canal was studied and measured microscopically. Electrically stimulated osteogenesis was not observed at stationary electrodes. As in previous studies with this model, a movable electrode alone stimulated new bone formation whose area was 7-10% of the canal area. The amount of this bone was not statistically increased by the addition of cathode current. Movable, electrically active cathodes were associated, however, with fluid-filled spaces incorporated within the new trabecular bone. When mechanical stimuli were controlled, we were not able to demonstrate that the direct current stainless steel cathode acts either as an inducer or a substantial enhancer of medullary osteogenesis.

Electromagnetic effects on bone formation at implants in the medullary canal in rabbits.

This experiment was aimed at illuminating the relationship between electromagnetic and mechanical stimuli of bone formation when present simultaneously. Movable and stationary intramedullary wire implants were studied in rabbits treated with a pulsing electromagnetic field (PEMF) 4 h/day for 3 weeks, and were compared with identical control animals without PEMF. Trabecular bone formed routinely at spontaneously movable implants, but not at stationary ones. On average, PEMF-treated movable implants in the femur induced 44% more bone than untreated movable implants. Also, in the PEMF-treated femora, a 22% enlargement of the area of the medullary canal was observed compared with no-field controls. In the tibia, these effects were weak or nonexistent. The PEMF used did not induce bone at stationary implants, suggesting that under these conditions it is not a primary trigger in vivo.

Bone growth after osteotomy and internal fixation in young rabbits.

The factors leading to overgrowth following fixation of long-bone fractures in children have never been clearly understood. The amount of trauma and the type of fixation may play a role. A rabbit model was used to investigate the influence of a femoral osteotomy and plate fixation on subsequent growth. Unilateral midshaft femoral osteotomy was performed in 6-week-old rabbits, and the bone was fixed internally with a plate and screws. End-to-end reduction was performed either at full length or with a segment removed. Bone length measurements at the end of growth revealed no significant difference in growth between the control femur and the femur that had undergone osteotomy and plate fixation. Shortened plated femora also showed no tendency to grow longer or faster than full-length fixed femora or controls. Interestingly, in the ipsilateral tibia a small but statistically significant length increase, equivalent to about 2% increase in additional growth, was observed, whereas technetium-99 methylene diphosphonate uptake was reduced in the tibial physes. In the context of the rabbit experimental model chosen, these results suggest that significant femoral over-growth does not occur following femoral osteotomy and plate fixation.

Application of low-intensity ultrasound to growing bone in rats.

Low-intensity pulsed ultrasound recently has been shown to accelerate long bone fracture healing, but its effect on bone growth and development is unknown. The longitudinal growth and bone density of the femur and tibia in young rats was measured after application of an ultrasound transducer emitting 1.5-MHz pulsed ultrasound (30 mW/cm2, SATA) for 20 min/day. After 28 days, no length difference was detected (< or = 2%) compared to the sham-treated leg or to unexposed controls. Also, no significant difference in bone mineral density (BMD) of the femur or tibia was found (< or = 6%). In a repeated experiment in which a periosteal trauma stimulus was created in the femoral diaphysis, the ultrasound also had no effect on growth or BMD. This results suggests that physeal bone growth is far less sensitive to this level of ultrasound application than is fracture repair. This may be related to the cascade of cellular events and regulatory factors that are present after a fracture.

Somatosensory cortical evoked potential changes after deformity correction.

The somatosensory cortical evoked potentials recorded during posterior spine fusion and instrumentation for 99 consecutive patients with idiopathic scoliosis, 18 years of age or younger, were retrospectively reviewed. The potentials were recorded from scalp electrodes while synchronously stimulating both tibial nerves near the ankles. Signal changes observed during consecutive 30-minute time intervals after deformity correction were analyzed. No changes in neurologic status were observed postoperatively. Latency values tended to remain constant on average. A small, but statistically significant, decrease in the first two interpeak amplitudes was observed during the first 30-minute interval after deformity correction. The first interpeak amplitude recovered, while the second remained statistically significantly decreased. No patient had a decrease of greater than 50% in both of the first two amplitudes, which persisted throughout the 60-minute interval immediately after deformity correction. This study demonstrated a tendency for somatosensory cortical evoked potential interpeak amplitudes to decrease during the first 30 minutes after deformity correction. There was a great deal of individual variation, including amplitude increases in many patients. There was no evidence supporting an association between dramatic, sustained amplitude decreases and uncomplicated deformity correction. The value of thoroughly evaluating somatosensory cortical evoked potential signal trends while making intraoperative decisions is emphasized.

Return to play after cervical spine injury.

STUDY DESIGN: A questionnaire survey was mailed to members of the Cervical Spine Research Society, the Herodiuus Sports Medicine Society, and to members of the authors' Department of Orthopaedics. OBJECTIVES: The purpose of our study was to evaluate what influence, if any, factors such as published guidelines, type of sport of the patient, number of years in practice, subspecialty interest, and sports participation of the respondent held in the "return to play" decision-making process after a cervical spine injury. SUMMARY OF BACKGROUND DATA: The consequences of cervical spine injury are potentially catastrophic, and return to play decisions in athletes with a history of neck injury can be agonizing. Although recent publications have addressed some of the concerns regarding cervical spine injuries in the athletic population, many questions remain unanswered. Factors such as published guidelines, type of sport of the patient, number of years in practice, subspecialty interest, and sports participation of the respondent have all been suggested as having a possible role in return to play decisions. METHODS: Representative radiographs and case histories of 10 athletes who had sustained neck injury were mailed to 346 physicians. For each case physicians selected every type of play (of six categories) that they felt comfortable recommending. Type of play was divided into six categories: Type 1, collision sports; Type 2, contact sports; Type 3, noncontact, high velocity sports; Type 4, noncontact, repetitive load sports (e.g., running); Type 5, noncontact, low impact sports; Type 6, no sports. In addition, demographic data regarding board certification, subspecialty interest, number of years in practice, use of guidelines in return to play decisions, and personal participation in sports were queried from all respondents. Statistical analysis was completed with Statview (Berkeley, CA). Basic descriptive statistics, chi2, and ANOVA were used where appropriate. RESULTS: Three hundred forty-six questionnaires were mailed and 113 were returned (response rate 32.7%). One hundred ten (97%) of the respondents who completed the questionnaire were board certified. Seventy-five were subspecialists in spine, 22 were subspecialists in sportsmedicine, and 13 reported interests in both sports medicine and spine. Use of Published Guidelines. Although 49% of respondents reported using guidelines in decision-making, the use of guidelines was statistically significant in only one case (P = 0.04). Hierarchy of Risk. In general, those physicians who participated in the study followed the hierarchy of risk that we established in this study (Type 1 [collision sports; highest level of risk] through Type 6 [no sports; lowest level of risk]). Twelve (10.6%) respondents, however, deviated from it in one or more cases. Years in Practice. In three cases there was a statistically significant association between the number of years a physician was in practice and the type of play selected (P < 0.05). In each case a lower level of play tended to be recommended by more senior physicians. Subspecialty Interest. In three cases those respondents with a spine subspecialty interest recommended returned to a higher level of play (P < 0.05). CONCLUSIONS: There is no consensus on the postinjury management of many cervical spine-injured patients. Further research, education, and discussion on this topic are needed.

Early clinical experience with the Syracuse I-Plate: an anterior spinal fixation device.

Sixteen patients were treated with a new anterior internal fixation device after thoracolumbar or lumbar decompression, and fusion with bone grafting. Ten patients had acute burst fractures, four had metastatic tumors, and two had old, healed fractures with deformity. In the acute fracture group, eight patients had neurologic deficits and seven patients experienced improvement. Six patients had lesions of the conus medullaris, all of which improved. The four patients with metastatic tumors underwent surgery for back and leg pain and all gained significant relief. Two patients had correction of old fracture deformity with satisfactory outcome. Complications were minimal. The new anterior stabilization device provided early stability, allowed early patient mobilization, was easy to insert, and has a low profile. Late collapse, non-union, and kyphotic deformity have not been noted thusfar.

MR of post traumatic spinal cord lesions. Unexpected improvement of hemorrhagic lesions.

Fifteen patients who sustained spinal cord trauma were evaluated by MR within 72 hours of injury. Nine patients had hemorrhagic and six had nonhemorrhagic traumatic spinal cord lesions. Three patients with hemorrhagic and all six patients with nonhemorrhagic lesions showed some degree of neurological improvement on follow-up examinations. In two of the three patients with hemorrhagic lesions who improved, the hemorrhage was extensive. This supports the observation that hemorrhagic lesions are not always associated with a poor clinical outcome.

Spine deformity in familial dysautonomia (Riley-Day syndrome).

Familial dysautonomia spanning a 30-year period reviewed retrospectively. The 16 patients identified included nine with spine deformities. Serious general medical problems were common. Spine deformities included kyphosis, scoliosis, or a combination of both. Brace treatment was attempted and was unsuccessful in three patients. Seven underwent surgical stabilization. Although all seven patients tolerated the surgical procedures, at least one postoperative complication was noted in each case. Follow-up ranged from 1 1/2 to 16 1/2 years. We recommend close observation of the deformities, early stabilization when disorders are progressive, and a high level of awareness of potential complications.

The effects of fat interposition for central-physeal defects. A histologic study in rabbits.

The effects of autogeneic fat interposition in a central cylindrical physeal defect were observed in rabbits. A 3.6-mm longitudinal drill hole was made across the physis of the distal femur, bilaterally, in four- to six-week-old New Zealand rabbits. One side was filled with an autogeneic fat graft and the contralateral defect was left as a control. The rabbits were killed at intervals during the remaining growth period, and the defects were examined histologically. Although fat grafts reduced the rate of osseous bridging across the physis and allowed more longitudinal growth than controls, transverse regeneration of the physis did not occur in the eight-week period preceding closure. The lack of physeal regeneration across the gap may reflect an important difference between central and peripheral defects.

Wrist pain and distal growth plate closure of the radius in gymnasts.

Three cases in which wrist pain developed in skeletally immature competitive gymnasts are presented. In all three cases there is radiographic evidence of premature growth plate closure, resulting in shortening of the radius and alterations in the normal distal radioulnar articulation. Repetitive compressive loading of the distal growth plate of the radius is proposed as a potential etiology of this condition. Treatment goals, including an example of successful ulnar shortening, are reviewed. The authors suggest activity limitation with the onset of symptoms, in order to avoid the permanent structural changes observed in our patients.

Knee extensor mechanics after subtotal excision of the patella.

Two sets of six fresh frozen autopsy specimens were used to test the quadriceps force requirements for knee extension after sequential distal-to-proximal and proximal-to-distal excisions of the patella. The quadriceps force as a function of knee flexion angle was recorded for varying amounts of excision and compared with the results for total patellectomy. Excision of the proximal one half or less resulted in lower force requirements when compared with total patellectomy. The effects of removal of the proximal three-fourths length of patella were inconsistent and actually increased the force requirements in three knees. The effects of distal to proximal excisions indicate a biomechanical advantage to maintaining a fragment equal to at least three fourths the length of the proximal patella. Retaining a fragment of adequate size preserves at least some of the mechanical advantage provided by the intact patella.

Ultrasonography for urinary tract evaluation in patients with congenital spine anomalies.

Outpatient pediatric orthopedic records were reviewed retrospectively in an attempt to identify all patients with congenital spine and urinary tract anomalies. All patients with a positive intravenous pyelogram (IVP) were asked to return for ultrasonographic evaluation. Urinary tract abnormalities were identified in seven (26%) of the 27 patients with documented IVPs. An additional patient was later added to the series, making a total of seven patients who returned for an ultrasonogram, which was then compared with the IVP. Observations and a review of the literature suggest that ultrasonography combined with urinalysis and serum creatinine is the screening protocol of choice in this patient population.