Potential risk of thermal damage to cervical nerve roots by a high-speed drill

Can postoperative deltoid weakness after cervical laminoplasty be prevented by using intraoperative neurophysiological monitoring?

Laminoplasty, frequently performed in patients with cervical myelopathy, is safe and provides relatively good results. However, motor palsy of the upper extremities, which occurs after decompression surgery for cervical myelopathy, often reduces muscle strength of the deltoid muscle, mainly in the C5 myotome. The aim of this study was to investigate prospectively whether postoperative deltoid weakness (DW) can be predicted by performing intraoperative neurophysiological monitoring (IONM) during cervical laminoplasty and to clarify whether it is possible to prevent palsy using IONM. We evaluated the 278 consecutive patients (175 males and 103 females) who underwent French-door cervical laminoplasty for cervical myelopathy under IONM between November 2008 and December 2016 at our hospital. IONM was performed using muscle evoked potential after electrical stimulation to the brain [Br(E)-MsEP] from the deltoid muscle. Seven patients (2.5%) developed DW after surgery (2 with acute and 5 with delayed onset). In all patients, deltoid muscle strength recovered to ≥ 4 on manual muscle testing 3-6 months after surgery. Persistent IONM alerts occurred in 2 patients with acute-onset DW. To predict the acute onset of DW, Br(E)-MsEP alerts in the deltoid muscle had both a sensitivity and specificity of 100%. The PPV of persistent Br(E)-MsEP alerts had both a sensitivity and specificity of 100% for acute-onset DW. There was no change in Br(E)-MsEP in patients with delayed-onset palsy. The incidence of deltoid palsy was relatively low. Persistent Br(E)-MsEP alerts of the deltoid muscle had a 100% sensitivity and specificity for predicting a postoperative acute deficit. IONM was unable to predict delayed-onset DW. In only 1 patient were we able to prevent postoperative DW by performing a foraminotomy.

Heat generation by ultrasonic bone curette comparing with high-speed drill

BACKGROUND

Ultrasonic bone curettes have been used as with high-speed drills. However, the amount of heat generated by the ultrasonic bone curette is not well known. This study quantitatively assessed the heat generated by an ultrasonic bone curette and compared it to that by a high-speed drill.

METHODS

The thermal change in a swine skull during bone curetting using an ultrasonic device and a high-speed drill were assessed. The investigation focused on the type of surgical manipulation (brush-like strokes vs. pushing motion) and irrigation (room temperature vs. cold water; low-volume irrigation vs. high-volume irrigation).

RESULTS

The thermal elevation during drill use was suppressed when using brush-like strokes compared to pushing motion (brush-like strokes, 44.7 °C; pushing motion, 69.2 °C; p < 0.01). Cold-water irrigation while drilling had a small effect compared to room temperature (RT) water (RT, 44.7 °C; cold, 35.2 °C; p = 0.12). The temperature generated by the curette was higher than that generated by the drill (curette, 72.5 °C; drill, 44.7 °C; p < 0.01). High-volume irrigation was required to reduce the heat generated by the curette (no irrigation, 88.6 °C; low-volume, 72.5 °C; high-volume, 60.5 °C; p < 0.01).

CONCLUSIONS

The ultrasonic bone curate generated more heat than the high-speed drill. During surgical manipulation, the use of brush-like strokes by both the high-speed drill and the ultrasonic bone curette is necessary to avoid excess thermal elevation. Irrigation with RT water is sufficient to avoid heat generation. High-volume irrigation is required to reduce the heat generated by the curette.

Narrow width of muscle-preserving selective laminectomy demonstrated sufficient surgical outcomes and reduced surgical invasiveness

Sufficient width of laminectomy or laminoplasty is considered a criterion for successful surgical outcomes following posterior cervical decompression. No previous study has focused on surgical outcomes achieved by wide versus narrow decompression. This study examined whether narrow laminectomy width (LW) affected surgical outcomes in cervical compressive myelopathy (CCM). Between 2005 and 2010, we performed muscle-preserving selective laminectomy (SL) with decompression between the bilateral medial margin of the facet joints (wide SL). After 2010, we began to perform narrow SL, in which the LW was no more than 2-3 mm wider than the spinal cord width (SW). Clinical features and radiological findings from 97 CCM patients in whom SL was performed at two consecutive levels, including the C4/5 level, were examined in this study. The relationship between LW and patients' functional outcomes was analyzed. Mean blood loss was lower in the narrow SL group than in the wide SL group. The length of hospital stay was also shorter in the narrow SL group. The wide SL group showed greater posterior spinal cord shift. The incidence of C5 palsy correlated with LW and LW minus SW (LW-SW). The recovery rate (RR) of Japanese Orthopaedic Association score was comparable between the two groups. The RR was not correlated with LW and LW-SW. Sufficient functional recovery can be achieved by narrow SL, and it offers advantages over wide posterior decompression, including reduced surgical invasiveness and complications. Wide decompression width is not always necessary for CCM patients.

Use of Ultrasonic Device in Cervical and Thoracic Laminectomy: a Retrospective Comparative Study and Technical Note

Multilevel severe compressive myelopathy is a challenging disorder for the surgeons, the aim of this study is to assess the efficacy and safety of a newly designed ultrasonic burr as an assistant tool to the ultrasonic scalpel in laminectomy for this disease. This is a retrospective comparative study, the included subjects were patients who received cervical and thoracic laminectomy using ultrasonic device (LUD, n = 9, 10 surgeries) and controls with the high-speed burr (LHB, n = 16). Fifteen patients (60.0%) showed severe cord occupancy and the average number of laminae operated was 3.5. Ultrasonic devices caused less blood loss (P = 0.02) and quicker operative time per level (P < 0.001) than LHB, and was associated with more operated laminae (P = 0.04). Preoperative JOA scores (P = 0.51), improvement rate (P = 0.47), and dural injury (P = 0.51) were not related to LUD. Our experience indicates ultrasonic devices are safe and effective for laminectomy treating multilevel and severe compressive myelopathy, the instrument could be used with ease especially for cases with ossified posterior longitudinal ligament and ossification of the ligamentum flavum, proper utility of the instrument is crucial to prevent complications.

Analysis of C5 palsy in cervical myelopathy with massive anterior compression following laminoplasty

BACKGROUND

Little data is available about comparison of the incidence and clinical characteristics of the C5 palsy between patients of cervical myelopathy with occupying ratio greater than 50% and those with occupying ratio less than 50% following laminoplasty.

METHODS

One-hundred eighteen patients with cervical myelopathy who underwent open door laminoplasty were reviewed in this study. The patients were divided into two groups: group A comprising 55 patients with an anterior occupying ratio greater than 50% and group B comprising 63 patients with an anterior occupying less than 50%. Clinical and radiological outcomes were assessed between two groups.

RESULTS

No statistically difference was found in preoperative Japanese Orthopedic Association (JOA) score of both groups (10.7 ± 1.7 in group A vs 10.9 ± 1.1 in group B, P > 0.05). Improvements in postoperative JOA score were achieved, and there was a statistical difference (14.0 ± 1.4 in group A vs 14.8 ± 0.9 in group B, P < 0.05). Group A had a lower rate of recovery than group B (P < 0.05). Totally, 12 of 118 (10.2%) patients developed the C5 palsy postoperatively. C5 palsy occurred in 3 of 63 patients in the group B compared with 9 of 55 in the group A. Statistically significant difference was found in the incidence of C5 palsy between the two groups (P < 0.05). Furthermore, patients in group A required significantly longer recovery periods than group B. Both preoperative and postoperative MRI presented more levels of T2 high-signal lesion in group A than group B. The degree of posterior shift of the cord after posterior decompression in group A was less than group B (P < 0.05).

CONCLUSIONS

Patients with a high degree of anterior compression have higher risk of C5 palsy than those with a relative low degree of anterior compression.

Anatomical analysis of human ligamentum flavum in the cervical spine: Special consideration to the attachments, coverage, and lateral extent

BACKGROUND

Posterior decompression surgeries of cervical spine such as laminoplasty and laminoforaminotomy are well established and increasing in aging population. The anatomical knowledge of cervical ligamentum flavum (LF) is critical to perform posterior spinal surgeries, however, few studies have evaluated it, especially the relation of LF and neural foramen.

METHODS

The whole spine was removed en bloc from 15 formalin-embalmed human cadavers and then divided into two segments along the pedicle bases. A total of 90 LFs from C2-C3 to C7-T1 were measured manually from the ventral side before being painted with iron powder containing contrast agent and scanned by computed tomography. We recorded dimensions, coverage of adjacent laminae, and the relationships between LF and neural foramen or facet joints. Three-dimensional CT data was used to evaluate manually limited areas and make reconstructed images.

RESULTS

LF height gradually increased from C2-C3 to C7-T1, and gradually decreased from medial to lateral within each level. LF width and thickness were relatively constant from cranial to caudal. The laminar surface covered by LF gradually increased from 33% in para midline and 30% laterally at C2, and increased to 70% in para midline and 47% laterally at C6, this trend was not completed at C7. The empty zone of the laminar surface (without LF coverage) was located at the upper half of each lamina; this zone gradually decreased from cranial to caudal. The craniomedial side of the cervical facet joint was covered by a mean 4.6 ± 0.7 mm of LF, however, LF did not enter the cervical neural foramen.

CONCLUSIONS

LF did not enter the neural foramen in cervical spine unlike lumbar spine. This information might be critical to avoid neurological deterioration after cervical laminoplasty or laminoforaminotomy. Surgeons would imagine the attachments and coverage of LF and its relation to posterior bony structures to perform safe posterior cervical surgeries.

Type II sciatic nerve variant: an unexpected interventional hazard

A 12-year-old girl presented with a 1-week history of right hip pain. MRI revealed a lesion in the incompletely fused posterior triradiate cartilage of the right acetabulum with imaging characteristics of an osteoid osteoma. The surgeon requested guidewire placement under CT guidance for lesion drilling. The CT approach was planned to avoid the usual course of the sciatic nerve, and the lesion was successfully removed and confirmed at histology to be an osteoid osteoma. At a follow-up visit, MRI showed no recurrence but demonstrated an abnormal common peroneal nerve from the sciatic notch to the popliteal fossa with denervation oedema in the tibias anterior and peroneal musculature. Review of the imaging showed a bifid piriformis muscle and type II sciatic nerve variant, with the common peroneal nerve component exiting the sciatic notch between the muscle bellies. The nerve's unexpected superolateral position placed it adjacent to the course of the guidewire, resulting in a presumed thermal injury at the time of drilling. This unusual case highlights the importance of the pre-procedural documentation of sciatic nerve variants in the planning of pelvic intervention.

Factors associated with postoperative C5 palsy after expansive open-door laminoplasty: retrospective cohort study using multivariable analysis

PURPOSE

The aim of the present study was to investigate the factors associated with C5 palsy by focusing on radiological parameters using multivariable analysis.

METHODS

The authors retrospectively assessed 190 patients with cervical spondylotic myelopathy treated by open-door laminoplasty. Four radiographic parameters-the number of expanded lamina, C3-C7 angle, lamina open angle and space anterior to the spinal cord-were evaluated to clarify the factors associated with C5 palsy.

RESULTS

Of the 190 patients, 11 developed C5 palsy, giving an overall incidence of 5.8%. Although the number of expanded lamina, lamina open angle and space anterior to the spinal cord were significantly larger in C5 palsy group than those in non-palsy group, a multiple logistic regression analysis revealed that only the space anterior to the spinal cord (odds ratio 2.60) was a significant independent factor associated with C5 palsy. A multiple linear regression analysis indicated that the lamina open angle was associated with the space anterior to the spinal cord and the analysis identified the following equation: space anterior to the spinal cord (mm) = 1.54 + 0.09 × lamina open angle (degree). A cut-off value of 53.5° for the lamina open angle predicted the development of C5 palsy with a sensitivity of 72.7% and a specificity of 83.2%.

CONCLUSIONS

The larger postoperative space anterior to the spinal cord, which was associated with the lamina open angle, was positively correlated with the higher incidence of C5 palsy.

The incidence of nerve root injury by high-speed drill can be reduced by chilled saline irrigation in a rabbit model

Aims

We aimed to evaluate the temperature around the nerve root during drilling of the lamina and to determine whether irrigation during drilling can reduce the chance of nerve root injury.

Materials and Methods

Lumbar nerve roots were exposed to frictional heat by high-speed drilling of the lamina in a live rabbit model, with saline (room temperature (RT) or chilled saline) or without saline (control) irrigation. We measured temperatures surrounding the nerve root and made histological evaluations.

Results

In the control group, the mean temperature around the nerve root was 52.0°C (38.0°C to 75.5°C) after 60 seconds of drilling, and nerve root injuries were found in one out of 13 (7.7%) immediately, three out of 14 (21.4%) at three days, and 11 out of 25 (44.0%) at seven days post-operatively. While the RT group showed a significantly lower temperature around the nerve root compared with the control group (mean 46.5°C; 34.5°C to 66.9°C, p < 0.001), RT saline failed to significantly reduce the incidence of nerve root injury (ten out of 26; 38.5%; odds ratio (OR) 0.96; 95% confidence interval (CI) 0.516 to 1.785; p = 0.563). However, chilled saline irrigation resulted in a significantly lower temperature than the control group (mean 39.0°C; 35.3°C to 52.3°C; p < 0.001) and a lower rate of nerve root injury (two out of 21; 9.5%, OR 0.13; 95% CI 0.02 to 0.703, p = 0.010).

Conclusion

Frictional heat caused by a high-speed drill can cause histological nerve root injury. Chilled saline irrigation had a more prominent effect than RT in reducing the incidence of the thermal injury during extended drilling. Cite this article: Bone Joint J 2017;99-B:554–60.

Differences in the time of onset of postoperative upper limb palsy among surgical procedures: a meta-analysis

BACKGROUND CONTEXT

The time of onset of postoperative upper limb palsy (ULP), also referred to as C5 palsy, varies among patients. Although some studies addressed the relationship between the time of onset of ULP and the potential etiologies, no meta-analysis has been conducted regarding the association between the time of onset of ULP and other factors such as surgical procedure type and treated diseases.

PURPOSE

This study aimed to elucidate differences in the time of onset of ULP among spinal surgical procedures and treated diseases to understand its etiology.

STUDY DESIGN

This is a meta-analysis.

OUTCOME MEASURES

The time of onset of ULP after cervical decompression surgery.

METHODS

We conducted a meta-analysis via searches of the PubMed, EMBASE, and Cochrane Library databases. Upper limb palsy within 2 days postoperatively or at 3 days or more postoperatively was defined as early- and late-onset, respectively. We calculated the pooled prevalence of early- and late-onset ULP with regard to surgical procedures and diseases using a random effects model. The proportion of early-onset ULP relative to all ULP was also determined. Surgical procedures were categorized into four procedures: (1) anterior cervical discectomy and fusion (ACDF); (2) anterior cervical corpectomy and fusion (ACCF); (3) laminoplasty or laminectomy (LPN); and (4) posterior spinal fusion with decompression (PSF). Treated diseases were classified as ossification of the posterior longitudinal ligament (OPLL) and non-OPLL.

RESULTS

The pooled prevalence of early-onset ULP was significantly stratified across three groups of surgical procedures (PSF [9.0%]>ACCF [3.7%] and LPN [2.5%]>ACDF [0.6%]). In the pooled analysis of late-onset ULP prevalence, three procedures (PSF [4.3%], ACCF [2.8%], and LPN [2.9%]) were similar, but ACDF (1.0%) was associated with a significantly lower prevalence than LPN. The prevalence of both early- and late-onset ULP was significantly higher with OPLL than without OPLL. However, the proportion of early-onset ULP relative to all ULP was similar between non-OPLL and OPLL (50.8% vs. 49.5%).

CONCLUSIONS

The high prevalence of early-onset ULP in PSF is attributable to a lag correction effect, which is triggered by posterior correction and fusion through comparison with LPN. The combination of our meta-analysis results and previous knowledge facilitates our understanding of the etiology of ULP.

Significant reduction in the incidence of C5 palsy after cervical laminoplasty using chilled irrigation water

Aims

The aim of this study was to determine whether chilled irrigation saline decreases the incidence of clinical upper limb palsy (ULP; a reduction of one grade or more on manual muscle testing; MMT), based on the idea that ULP results from thermal damage to the nerve roots by heat generated by friction during bone drilling.

Methods

Irrigation saline for drilling was used at room temperature (RT, 25.6°C) in open-door laminoplasty in 400 patients (RT group) and chilled to a mean temperature of 12.1°C during operations for 400 patients (low-temperature (LT) group). We assessed deltoid, biceps, and triceps brachii muscle strength by MMT. ULP occurring within two days post-operatively was categorised as early-onset palsy.

Results

The incidence of ULP (4.0% vs 9.5%, p = 0.003), especially early-onset palsy (1.0% vs 5.5%, p < 0.001), was significantly lower for the LT group than for the RT group. Multivariate analysis indicated that RT irrigation saline use, concomitant foraminotomy, and opened side were significant predictors for ULP.

Discussion

Using chilled irrigation saline during bone drilling significantly decreased the ULP incidence, particularly the early-onset type, and shortened the recovery period for ULP. Chilled irrigation saline can thus be recommended as a simple method for preventing ULP. Take home message: Chilled irrigation during laminoplasty reduces C5 palsy. Cite this article: Bone Joint J 2016;98-B:117–24.

How Safe Is High-Speed Burring in Spine Surgery? An In Vitro Study on the Effect of Rotational Speed and Heat Generation in the Bovine Spine

STUDY DESIGN

In vitro animal cadaveric study.

OBJECTIVE

To identify the appropriate rotational speed and safe bone distance from neural tissue during bone burring in spinal surgery.

SUMMARY OF BACKGROUND DATA

Bone burring is a common step in spinal surgery. Unwanted frictional heat produced during bone burring may result in thermal injury to the bone and adjacent neural structure. One of the important parameters influencing the bone temperature rise during bone burring is rotational speed.

METHODS

This laboratory-based animal study used bovine spine bones, and the tests were conducted using a steel round burr. The bone temperature was measured simultaneously with thermocouple at the distances of 1 mm, 3 mm, and 5 mm from the burring site during the burring process. The bone burring was done with 4 different rotational speeds of 35,000 revolutions per minute (rpm), 45,000 rpm, 65,000 rpm, and 75,000 rpm.

RESULTS

This study showed that increasing the rotational speed significantly elevated bone temperature. The threshold temperature of 47°C was reached when bone was burred for 10 seconds, with a rotational speed of 45,000 rpm. The mean bone temperature measured at a distance 1 mm from the burring site for all 4 rotational speeds was always higher than that measured at a distance of 3 mm and 5 mm and this difference was statistically significant (P < 0.001). There was no significant difference between the mean bone temperature measured at a distance of 3 mm and 5 mm (P > 0.05).

CONCLUSION

Taking 47°C as the threshold temperature for causing significant impairment to the regenerative capacity of bone, a rotational speed of lower than 45,000 rpm is preferable so as to minimize thermal injury to bone tissue. We also concluded that a 3-mm distance between the site of burring and the neural tissue is a safe distance.

LEVEL OF EVIDENCE

N/A.

Development of postoperative C5 palsy is associated with wider posterior decompressions: an analysis of 41 patients

BACKGROUND CONTEXT

C5 palsy is a postoperative complication, characterized by deltoid weakness. The pathogenesis of C5 palsy after laminoforaminotomies in patients with degenerative spinal disease is poorly understood. We hypothesize that the spinal cord fallback is associated with postoperative C5 palsy.

PURPOSE

We investigate radiographic parameters associated with the development of postoperative C5 palsy.

STUDY DESIGN/SETTING

This is a retrospective single-institutional clinical study.

PATIENT SAMPLE

The source population was all patients undergoing a C4-C5 posterior laminoforaminotomy plus instrumented fusion for the management of degenerative spinal disease at a single institution over a 7-year period. The study population was 41 patients who had both preoperative and postoperative imaging.

OUTCOME MEASURE

The outcome measure was postoperative C5 palsy, defined as transient motor decline of the deltoid function.

METHODS

Of those patients with both preoperative and postoperative radiographic studies, we measured cord position, Cobb angle, width of the C5 foramen, and width of the dura.

RESULTS

Nine patients with C5 palsy and 32 patients without C5 palsy fit the inclusion criteria for this study. In comparison with the non-C5 palsy group, the C5 palsy group had a statistically greater widening of the C5 foramen (p<.001), dural expansion (p<.001), and posterior cord shift (p<.001). Change in lordosis did not differ (p=.985). Lordotic correction was not correlated with the posterior cord shift in linear regression analysis (p=.67) or C5 palsy in univariate analysis (p=.627). Conversely, widening of the C5 foramen was correlated with greater cord displacement (p=.002), and both of these factors statistically predicted C5 palsy after the multivariate regression analysis.

CONCLUSION

Our findings suggest that wider decompressions at C4-C5 are correlated with greater fallback of the spinal cord, which statistically increases the risk of C5 palsy.

Delayed cervical palsy following cervical spine fusion leads to an increase in hospital-related costs

OBJECT

Delayed cervical palsy (DCP) is a known complication following cervical spine surgery. While most DCPs eventually improve, they can result in significant temporary disability. Postoperative complications affect hospital length of stay (LOS) as well as overall hospital cost. The authors sought to determine the hospital cost of DCP after cervical spine fusion operations.

METHODS

A retrospective review of patients undergoing cervical fusion for degenerative disease at the Mayo Clinic from 2008 to 2012 was performed. Patients who developed DCPs not attributable to intraoperative trauma were included. All nonoperative-related costs were compared with similar costs in a control group matched according to age, sex, and surgical approach. All costs and services were reflective of the standard costs for the current year. Raw cost data were presented using ratios due to institutional policy against publishing cost data.

RESULTS

There were 27 patients (18 men, 9 women) who underwent fusion and developed a DCP over the study period. These patients were compared with 24 controls (15 men, 9 women) undergoing fusion in the same time period. There was no difference between patients and controls in mean age (62.4 ± 3.1 years vs. 63.8 ± 2.5 years, respectively; p = 0.74), LOS (4.2 ± 3.3 days vs 3.8 ± 4.5 days, respectively; p = 0.43), or operating room-related costs (1.08 ± 0.09 vs. 1.0 ± 0.07, respectively; p = 0.58). There was a significant difference in nonoperative hospital-related costs between patients and controls (1.67 ± 0.15 vs 1.0 ± 0.09, respectively; p = 0.04). There was a significantly higher utilization of postoperative imaging (CT or MRI) in the DCP group (14/27, 52%) when compared with the matched cohort (4/24, 17%; p = 0.018), and a significantly higher utilization of physiatry services (24/27 [89%] vs 15/24 [63%], respectively; p = 0.046).

CONCLUSIONS

While DCPs did not significantly prolong the length of hospitalization, they did increase hospital-related costs. This method could be further extrapolated to model costs of other complications as well.

Predicting C5 palsy via the use of preoperative anatomic measurements

BACKGROUND CONTEXT

C5 nerve root palsy (C5P) is a relatively rare complication after anterior and posterior cervical decompression surgery that leads to a variety of debilitating symptoms. The precise etiology remains obscure, and a clear understanding of preoperative risk factors for C5P development does not exist.

PURPOSE

To determine whether postoperative C5P can be predicted from preoperative anteroposterior diameter (APD), foraminal diameter (FD), and/or cord-lamina angle (CLA).

STUDY DESIGN

Retrospective review.

PATIENT SAMPLE

Consecutive patients who underwent either anterior or posterior decompression surgery at C4-C5 for cervical spondylotic myelopathy.

OUTCOME MEASURES

Development of C5P.

METHODS

Blinded reviewers retrospectively assessed magnetic resonance images for each included patient's C4-C5 interspace, including the midline APD, the left and right FDs, and the left and right CLA. Multivariable logistic regression was used to model the probability of palsy on the basis of one or more predictors. A jackknife validation was performed to internally validate the model and assess its generalizability.

RESULTS

A total of 98 patients fit the inclusion criteria; 12% had developed symptoms of C5 palsy postoperatively. Using the three variables in a predictor-model, we found that the odds ratio of having palsy for APD, FD, and CLA was 0.3, 0.02, and 1.4, respectively. For every 1-mm increase in APD and FD, the odds of developing palsy decrease 69% (p<.0001) and decrease 98% (p<.0003), respectively. In contrast, for every 1-degree increase in CLA, the odds of developing palsy increase by 43% (p<.0001). The receiver-operating characteristic curve for this three-variable model predicting development of palsy has an area under the curve (concordance index) of 0.97. After implementing a jackknife validation, the area under the curve was 95%.

CONCLUSIONS

This study is the first to use the combination of APD, FD, and CLA to predict development of postoperative C5 palsy after decompression surgery for patients with spondylotic myelopathy. This prediction formula may allow for better patient selection and to prepare patients that have an increased probability of developing this complication.

Morphological distinction of cervical nerve roots associated with motor function in 219 healthy volunteers: a multicenter prospective study

STUDY DESIGN

A prospective study.

OBJECTIVE

To examine the diameter (mm), transverse diameter (mm), and cross-sectional area (mm²) of the C5, C6, and C7 nerve roots using ultrasonography.

SUMMARY OF BACKGROUND DATA

Each of the cervical nerve roots affected a different motor or sensory area. Although there were several studies that performed a detailed assessment of cervical nerve root anatomy in cadavers, only a few studies on the thickness of cervical nerve roots in living specimens have been performed. We examined whether the thickness of the C5, C6, and C7 nerve roots, as well as the area supplied by each of the roots, varied.

METHODS

All 219 subjects (99 males and 120 females; mean age, 47 ± 15 yr) were healthy volunteers. The diameter and the transverse diameter were measured via ultrasonography, and the cross-sectional area was calculated for each of the C5-C7 nerve roots.

RESULTS

The following diameter measurements (right and left, respectively) were obtained: C5, 2.8 and 2.9 mm; C6, 3.6 and 3.8 mm; and C7, 3.3 and 3.4 mm. The following transverse diameter measurements were obtained (right and left, respectively): C5, 2.8 and 3.0 mm; C6, 3.7 and 3.8 mm; and C7, 3.5 and 3.4 mm. The following cross-sectional area measurements (right and left, respectively) were obtained: C5, 6.3 and 6.4 mm²; C6, 10.7 and 11.0 mm²; and C7, 8.8 and 8.8 mm². Based on the 3 measurement methods, the C5 nerve root was significantly thinner than the other 2 nerve roots (P < 0.001), and the C7 nerve root was smaller than the C6 nerve root (P = 0.001).

CONCLUSION

The C5 nerve root was significantly thinner than the C6 and C7 cervical nerve roots. The fact that the C5 nerve is thinner may render it more susceptible to damage during cervical surgery.

Bone temperature elevation by drilling friction and neurological outcome in the cervical spino-laminoplasty

BACKGROUND

Drill-induced heat has been suspected as a cause of tissue injury, and there are ample experimental data to substantiate the implication. However, no clinical results have been presented with measurement of temperature in the vicinity of neural structures during the actual spinal procedures.

METHODS

Using a thermocouple, temperature in the gutters drilled in the midline and the lateral margins of the lamina was monitored closely in 61 patients, who underwent the French-door style of cervical spino-laminoplasty. The drilling was performed intermittently for a duration of 5 or 10 seconds, using 3- or 5-mm diamond burrs with sufficient continuous cooling irrigation. The correlations between bone temperature elevation and postoperative sensorimotor symptoms were then analyzed.

RESULTS

In the lateral gutters at the most cephalad level (typically C3), where the drilling was performed underneath an overlying bundle of muscle attached to C2's spinous process, the temperature rose significantly. This occurred even with 5-second drilling sessions. The average peak temperature was 44 °C at this level. At all other sites, the temperature was maintained below 40 °C. In three patients, transient neurological deficit developed postoperatively, which did not correlate with the incidence of bone temperature elevation.

CONCLUSIONS

Intermittent drilling with sufficient irrigation can prevent thermal neuronal damage generated by high-speed drills. Drilling with small diamond burrs in deep and narrow spaces covered by overlying muscles predisposes to inadequate irrigation and thermal elevation. Continuous, protracted drilling without frequent irrigation may result in excessive heat generation and nerve injury.

The use of cooled saline during bone drilling to reduce the incidence of upper-limb palsy after cervical laminoplasty

Object

No previous hypothesis has attempted to fully account for the occurrence of upper-limb palsy (ULP) after cervical laminoplasty. The authors propose that friction-generated heat from a high-speed drill may cause thermal injury to the nerve roots close to the drilled bone, which may then lead to ULP. The authors investigated the effect of cooling the saline used for irrigation during the drilling on the incidence of upper-limb (C-5) palsy following cervical laminoplasty.

Methods

The irrigation saline for drilling was used at room temperature (RT, average temperature of 25.6°C) in operations of 79 patients (the RT group) and cooled to an average of 12.1°C in operations of 80 patients (the low-temperature [LT] group). The authors used a hand-held dynamometer to precisely assess muscle strength presurgery and 2 weeks postsurgery.

Results

There was a 7.6% and 1.9% decrease in the strength of the deltoid muscle, a 10.1% and 4.4% decrease in the strength of the biceps brachii, a 1.3% and 0.6% decrease in the strength of the triceps brachii, and a 7.6% and 3.1% decrease in grip strength in the RT and LT groups, respectively. Multivariate analysis revealed that a significant predictor for decreased deltoid muscle strength was the use of irrigation saline at RT.

Conclusions

Using cooled irrigation saline during bone drilling significantly decreased the incidence of ULP and can thus be recommended as a simple method for the prevention of ULP.

Temperature prediction in high speed bone grinding using motor PWM signal

This research explores the feasibility of using motor electrical feedback to estimate temperature rise during a surgical bone grinding procedure. High-speed bone grinding is often used during skull base neurosurgery to remove cranial bone and approach skull base tumors through the nasal corridor. Grinding-induced heat could propagate and potentially injure surrounding nerves and arteries, and therefore, predicting the temperature in the grinding region would benefit neurosurgeons during the operation. High-speed electric motors are controlled by pulse-width-modulation (PWM) to alter the current input and thus maintain the rotational speed. Assuming full mechanical to thermal power conversion in the grinding process, PWM can be used as feedback for heat generation and temperature prediction. In this study, the conversion model was established from experiments under a variety of grinding conditions and an inverse heat transfer method to determine heat flux. Given a constant rotational speed, the heat conversion was represented by a linear function, and could predict temperature from the experimental data with less than 20% errors. Such results support the advance of this technology for practical application.

Thermal model to investigate the temperature in bone grinding for skull base neurosurgery

This study develops a thermal model utilizing the inverse heat transfer method (IHTM) to investigate the bone grinding temperature created by a spherical diamond tool used for skull base neurosurgery. Bone grinding is a critical procedure in the expanded endonasal approach to remove the cranial bone and access to the skull base tumor via nasal corridor. The heat is generated during grinding and could damage the nerve or coagulate the blood in the carotid artery adjacent to the bone. The finite element analysis is adopted to investigate the grinding-induced bone temperature rise. The heat source distribution is defined by the thermal model, and the temperature distribution is solved using the IHTM with experimental inputs. Grinding experiments were conducted on a bovine cortical bone with embedded thermocouples. Results show significant temperature rise in bone grinding. Using 50°C as the threshold, the thermal injury can propagate about 3mm in the traverse direction, and 3mm below the ground surface under the dry grinding condition. The presented methodology demonstrated the capability of being a thermal analysis tool for bone grinding study.

Use of an ultrasonic osteotome device in spine surgery: experience from the first 128 patients

INTRODUCTION

The ultrasonic BoneScalpel is a tissue-specific device that allows the surgeon to make precise osteotomies while protecting collateral or adjacent soft tissue structures. The device is comprised of a blunt ultrasonic blade that oscillates at over 22,500 cycles/s with an imperceptible microscopic amplitude. The recurring impacts pulverize the noncompliant crystalline structure resulting in a precise cut. The more compliant adjacent soft tissue is not affected by the ultrasonic oscillation. The purpose of this study is to report the experience and safety of using this ultrasonic osteotome device in a variety of spine surgeries.

METHODS

Data were retrospectively collected from medical charts and surgical reports for each surgery in which the ultrasonic scalpel was used to perform any type of osteotomy (facetectomy, laminotomy, laminectomy, en bloc resection, Smith Petersen osteotomy, pedicle subtraction osteotomy, etc.). The majority of patients had spinal stenosis, degenerative or adolescent scoliosis, pseudoarthrosis, adjacent segment degeneration, and spondylolisthesis et al. Intra-operative complications were also recorded.

RESULTS

A total of 128 consecutive patients (73 female, 55 male) beginning with our first case experience were included in this study. The mean age of the patients was 58 years (range 12-85 years). Eighty patients (62.5 %) had previous spine surgery and/or spinal deformity. The ultrasonic scalpel was used at all levels of the spine and the average levels operated on each patient were 5. The mean operation time (skin to skin) was 4.3 h and the mean blood loss was 425.4 ml. In all cases, the ultrasonic scalpel was used to create the needed osteotomies to facilitate the surgical procedure without any percussion on the spinal column or injury to the underlying nerves. There was a noticeable absence of bleeding from the cut end of the bone consistent with the ultrasonic application. There were 11 instances of dural injuries (8.6 %) and two of which were directly associated with the use of ultrasonic device. In no procedure was the use of the ultrasonic scalpel abandoned for use of another instrument due to difficulty in using the device or failure to achieve the desired osteotomy.

CONCLUSIONS

Overall, the ultrasonic scalpel was safe and performed as desired when used as a bone cutting device to facilitate osteotomies in a variety of spine surgeries. However, caution should be taken to avoid potential thermal injury and dural tear. If used properly, this device may decrease the risk of soft tissue injury associated with the use of high speed burrs and oscillating saws during spine surgery.

Evaluation of drill-induced heat transmission in an orbital model

PURPOSE

To evaluate the influence of saline irrigation on temperature rise in orbit bones and the optic canal during high-speed drilling.

METHODS

An experimental study measuring temperature rise in an orbit during high-speed drilling was conducted. The orbital rims, sphenoid bone, and optic canals of 6 unpreserved caprine orbits were drilled with a 3.1-mm diamond drill bit at 35,000 rpm. Each orbit was divided into groups receiving no irrigation, continuous or intermittent external irrigation at 5-second intervals during the procedures. The temperature rise of each site was compared among the groups, along with the duration of drilling.

RESULTS

The mean (± SD) temperature elevation in the optic canal without irrigation was 2.38 °C (± 0.30 °C). This was significantly higher than in the canals receiving intermittent irrigation (0.90 °C ± 0.40 °C; p < 0.001) and continuous irrigation (0.66 °C ± 0.40 °C; p < 0.001). Mean temperature rise in the orbital rim without irrigation was significantly higher (3.51 °C ± 1.30 °C) than with intermittent (1.05 °C ± 0.31 °C; p < 0.001) and continuous (0.98 °C ± 0.61 °C; p < 0.001) irrigation. Mean temperature rise in the sphenoid was significantly higher (3.68 °C ± 1.66 °C) without irrigation than with intermittent (1.36 °C ± 1.17 °C; p = 0.005) and continuous (0.90 °C ± 0.33 °C; p < 0.001) irrigation. There were no statistically significant differences between any of the intermittent and continuous irrigation groups.

CONCLUSIONS

The presence of either continuous or intermittent irrigation during orbital drilling procedures significantly decreases the temperature rise in the region adjacent to the surgical site. This has important implications for surgical technique when operating near the optic canal. Further studies regarding potential effects on the optic nerve are warranted.

Can prophylactic bilateral C4/C5 foraminotomy prevent postoperative C5 palsy after open-door laminoplasty?: a prospective study

STUDY DESIGN

A prospective study.

OBJECTIVE

To evaluate the effectiveness of prophylactic C4/C5 microforaminotomy with open-door laminoplasty for cervical myelopathy in preventing postoperative C5 palsy.

SUMMARY OF BACKGROUND DATA

Postoperative C5 palsy is a common complication of cervical laminoplasty. Although the etiology of C5 palsy and preventive measures remain unclear, we hypothesize that C5 palsy is caused by C5 nerve root impairment induced by potential C4/C5 foraminal stenosis and posterior shifting of the spinal cord after laminoplasty.

METHODS

The study included 141 consecutive patients with cervical myelopathy (103 men and 38 women) who underwent open-door laminoplasty with prophylactic bilateral C4/C5 foraminotomy between 2009 and 2010. These were designated as the foraminotomy group (FG). One hundred forty-one consecutive patients (100 men and 41 women) who underwent open-door laminoplasty without prophylactic foraminotomy during 2006 to 2008 served as a control group. This was the nonforaminotomy group (NFG). The incidence of C5 palsy, operation time, blood loss, and the number of decompressed disc levels were recorded.

RESULTS

The incidence of C5 palsy was 1.4% (2 of 141 cases) in the FG, and 6.4% (9 of 141 cases) in the NFG. The mean operation times were 129 and 102 minutes, respectively. There were significant differences in the incidence of C5 palsy and operation time (both comparisons, P < 0.05). There were no significant differences in blood loss or the number of decompressed disc levels (both comparisons, P > 0.05).

CONCLUSION

Prophylactic bilateral C4/C5 microforaminotomy significantly decreased the incidence of postoperative C5 palsy. These results suggest that the main etiology of C5 palsy was C5 root impairment. However, 2 patients experienced C5 palsy despite undergoing prophylactic foraminotomy, which indicated that other factors including spinal cord impairment after acute decompression against cervical canal stenosis may also be considered as minor etiologies of C5 palsy. We conclude that prophylactic C4/C5 foraminotomy was an effective preventive measure against postoperative C5 palsy after laminoplasty.

Neurological complications of cervical spine surgery: C5 palsy and intraoperative monitoring

STUDY DESIGN

Review article.

OBJECTIVE

To review the epidemiology, etiology, risk factors, prevention, and treatment of neurological complications associated with cervical spine surgery. The article focuses on C5 palsy and intraoperative neurophysiological monitoring.

SUMMARY OF BACKGROUND DATA

Neurological problems are the complications most feared by patients and surgeons alike, but, fortunately, spinal cord injury is uncommon. C5 palsy is a less severe but much more common and perplexing problem. Intraoperative monitoring is widely used in cervical spine surgery, but it is unclear how effective it is at preventing spinal cord or nerve root injury.

METHODS

Narrative and review of the literature.

RESULTS

The incidence of new, severe motor weakness in 2 or more extremities occurring within 12 hours of surgery is 0.18%. The rate in the cervical spine is 3 of 1000. The incidence of isolated C5 palsy is much greater; the rate varies between 0% and 30%, depending on how the condition is defined and which patient group is being analyzed. Numerous theories have been postulated to explain the pathogenesis of C5 palsy, and preventative strategies are discussed. Approximately 70% of patients recover completely without treatment. The mean time to full recovery is 4 to 5 months. Recovery is spontaneous; no treatment has been shown to shorten the time to recovery or improve the recovery rate. A systematic review of the literature found a high level of evidence that multimodal intraoperative monitoring is effective at detecting intraoperative neurological injury. The evidence that intraoperative monitoring reduces the rate of new or worsened perioperative neurological deficits is not as strong. Algorithms help surgeons respond to monitoring alerts and manage neurological deficits that are identified postoperatively.

CONCLUSION

The keys to managing neurological complications in cervical spine surgery are prevention through careful planning, appropriate multimodal monitoring, meticulous surgical technique, and decisive action when a problem is identified.

Does milling one-piece titanium dental implants induce osteocyte and osteoclast changes?

One-piece dental implants avoid adverse effects sometimes associated with the traditional implant-abutment interface and may provide a suitable alternative to two-piece implants; however, one-piece implants often need in situ milling, which may exacerbate cell apoptosis from excessive heat at the bone-implant interface and induce secondary crestal bone loss. Twelve implants were placed in the metaphyses of two sheep under general anesthesia. Six implants were milled with a diamond bur while the other six implants remained intact. Animals were euthanized after four days, and bone blocks were harvested. Bone samples were studied without decalcification. Osteocytes were stained with Hoechst 33342 and osteoclasts by the TRAcP reaction. Both cell types, in the cortical and trabecular bone around the implant's cervical region, were counted utilizing morphometric methods. Values were compared to areas at a distance from the cervical region. No difference was observed between milled and unmilled implants, which suggested that the amount of generated heat did not provoke osteocyte loss or induce osteoclastogenesis. Intraoral abutment preparations did not increase cellular apoptosis at the bone-implant interface after four days in the ovine model.

C5 palsy after cervical laminoplasty

We have reviewed 1858 patients who had undergone a cervical laminoplasty and identified 43 (2.3%) who had developed a C5 palsy with a MMT (MRC) grade of 0 to 2 in the deltoid, with or without involvement of the biceps, but with no loss of muscular strength in any other muscles. The clinical features and radiological findings of patients with (group P; 43 patients) and without (group C; 100 patients) C5 palsy were compared. CT scanning of group P revealed a significant narrowing of the intervertebral foramen of C5 (p < 0.005) and a larger superior articular process (p < 0.05). On MRI, the posterior shift of the spinal cord at C4–5 was significantly greater in group P, than in group C (p < 0.01).

This study is the first to correlate impairment of the C5 nerve root with a C5 palsy. It may be that early foraminotomy in susceptible individuals and the avoidance of tethering of the cord by excessive laminoplasty may prevent a post-operative palsy of the C5 nerve root.