Degenerative cervical spondylosis: clinical syndromes, pathogenesis, and management

Degenerative changes in the cervical spinal column are ubiquitous in the adult population, but infrequently symptomatic. The evaluation of patients with symptoms is facilitated by classifying the resulting clinical syndromes into axial neck pain, cervical radiculopathy, cervical myelopathy, or a combination of these conditions. Although most patients with axial neck pain, cervical radiculopathy, or mild cervical myelopathy respond well to initial nonsurgical treatment, those who continue to have symptoms or patients with clinically evident myelopathy are candidates for surgical intervention.

Changes in the lumbar foramen following anterior interbody fusion with tapered or cylindrical cages

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) using both cylindrical and tapered threaded interbody cages has been shown to restore disc height, reduce segmental motion, and relieve low back pain. The effectiveness of these stand-alone cage designs in restoration and maintenance of intervertebral foraminal dimensions has received little attention.

PURPOSE

To investigate the effects of anterior implantation of cylindrical and tapered interbody cages on morphologic changes of the lumbar neuroforamen and maintenance of foraminal dimensions under dynamic loading.

STUDY DESIGN/SETTING

A biomechanical study using bovine calf spine model to compare the deformation of foraminal space after ALIF with either tapered cages or cylindrical cages.

METHODS

Sixteen fresh calf spines were randomly assigned to undergo ALIF at the L3-L4 level using either two threaded cylindrical or two tapered cages. Lumbar spines were subjected to unconstrained loading in flexion, extension, and lateral bending. Rotation of the L3-L4 segment and dynamic deformation in foraminal height were obtained through a motion analysis system, and compared between the two cage groups. Foraminal dimensions were assessed before and after tapered or cylindrical cage implantation with digitized measurement of bilateral foraminal molds.

RESULTS

Regardless of cage design, anterior implantation of cages increased neuroforaminal area by 17% (p=.0005) and increased the foraminal height by 9% (p=.0004) in the neutral unloaded position. In dynamic loading conditions, foraminal height was significantly stabilized in all loading directions by the cylindrical cages (p=.01) and on both sides during lateral bending by the tapered cages (p<.03). Foraminal stabilization provided by either cage was most prominent in the direction of lateral bending (26-37% of the intact values), while cylindrical cages also provided substantial stabilization in flexion (26% of the intact value). Significant linear relationships were found between foraminal height and residual fusion segment motion under dynamic loading conditions.

CONCLUSION

Results from this bovine model biomechanical study indicate that stand-alone anterior interbody fusion cages with either tapered or cylindrical design are effective in restoring neuroforaminal height and stabilize the spine to withstand foraminal deformation during daily loading. The degree of stabilization was influenced substantially by the loading direction, to a lesser degree by the cage type, and was strongly dependent on the segment mobility. Although bovine lumbar spine is widely accepted for comparative studies, direct clinical interpretation should be made with caution owing to the anatomical differences from human.

Posterolateral intertransverse lumbar fusion in a mouse model: surgical anatomy and operative technique

BACKGROUND CONTEXT

Animal models are frequently used for studying the effect of bone graft substitutes or allogeneic materials on osterolateral lumbar fusion. Transgenic technology in the mouse provides a unique opportunity to further understand the biology of spine fusion.

PURPOSE

To describe pertinent lumbar spine anatomy and formulate a surgical protocol for posterolateral fusion in the mouse model.

STUDY DESIGN

Diagnostic model: development of an animal model for biologic evaluation of posterolateral spine fusion.

METHOD

Ten mice were killed to study relevant lumbar spine anatomy and develop a protocol for lumbar spine fusion. The L4-L6 fusion protocol was validated in 46 mice for ease of exposure, preparation of the posterolateral fusion bed, introduction of bone inductive agents, and perioperative care.

RESULTS

Anatomy and surgical technique for posterolateral intertransverse lumbar fusion in the mouse model are described. A paraspinal approach allows exposure of the transverse processes, decortication, and graft placement at the L4-L6 intertransverse fusion site. Decortication alone did not result in fusion, whereas the use of bone graft resulted in satisfactory fusion rates. Perioperative morbidity and mortality rates were low.

CONCLUSION

The mouse posterolateral lumbar spine fusion model is reproducible, inexpensive, and has low complication rates. Knowledge of the relevant anatomy and adherence to a well-defined surgical protocol provides a reliable and reproducible experimental spine fusion model.

Bilateral C5 motor paralysis following anterior cervical surgery—a case report

Numerous authors have reported C5 root palsies following posterior cervical surgery, and several mechanisms of injury have been proposed. Similar deficits after anterior cervical procedures are considered to occur less commonly. We report on a 48-year-old male who underwent multi-level anterior discectomy and fusion for cervical spondylotic myelopathy. Bilateral C5 nerve root deficits were noticed in the immediate postoperative period, and treated non-operatively. A postoperative magnetic resonance imaging (MRI) scan showed an increase in cervical lordosis accompanied by a posterior shifting of the spinal cord. Potential mechanisms of nerve root injury in this situation are discussed, and the literature on postoperative C5 root deficits is reviewed. The patient returned to his preoperative occupation as an operating room nurse 6 months following surgery, with complete neurologic recovery occurring over an 11-month period. C5 deficits following anterior cervical surgery occur more frequently than generally assumed. Improved lordosis and longitudinal lengthening of the cervical spinal column in multilevel anterior decompression and interbody fusion can paradoxically result in a traction injury to the spinal cord and C5 nerve roots.

Anterior longitudinal ligament injuries in whiplash may lead to cervical instability

Although whiplash injuries account for a significant annual cost to society, the exact mechanism of injury and affected tissues remain unknown. Previous investigations documented injuries to the cervical anterior longitudinal ligament in whiplash. The present investigation implemented a comprehensively validated computational model to quantify level-dependent distraction magnitudes of this structure in whiplash. Maximum ligament distractions approached failure levels, particularly in middle to lower cervical levels, and occurred during the initial phase of head-neck kinematics. In particular, the C5-C6 anterior longitudinal ligament sustained distraction magnitudes as high as 2.6mm during the retraction phase, corresponding to 56% of distraction necessary to result in ligament failure. Present results demonstrated that anterior structures in the lower cervical spine may be susceptible to injury through excess distraction during the retraction phase of whiplash, which likely occurs prior to head restraint contact. Susceptibility of these structures is likely due to non-physiologic loading placed on the cervical spinal column as the head translates posteriorly relative to the thorax. Injury to anterior spinal structures can result in clinical indications including cervical instability in extension, axial rotation, and lateral bending modes. Mitigation of whiplash injury may be achieved by minimizing head retraction during initial stages of whiplash.

Reflex muscle contraction in the unaware occupant in whiplash injury

STUDY DESIGN

Computer modeling and parametric analysis were used to determine the effect of reflex contraction of the neck muscles in the unaware occupant in whiplash.

OBJECTIVE

To delineate effects of reflex contraction on spinal segmental kinematics during the retraction phase.

SUMMARY OF BACKGROUND DATA

The ability of reflex neck muscle contraction to mitigate whiplash injury in the unaware occupant remains unclear. Analyzing relative timing between electromyographic and head-neck kinematics, previous investigators theorized that muscle contraction alters spinal kinematics, decreasing injury likelihood. Other investigators suggested that injury occurs during the initial (retraction) phase of head-neck kinematics, before significant muscle force generation.

METHODS

Computer modeling was used to determine reflex contraction effects on segmental angulations, implementing parametric analysis techniques to vary reflex delay and impact severity.

RESULTS

Shorter reflex delays had a greater effect on segmental angulations later in the event and at lower impact severities. However, the magnitude of this effect, particularly at higher impact severities and during maximum cervical S-curvature (factors implicated in the whiplash injury mechanism) was minimal, altering segmental angulations by a maximum of 19%.

CONCLUSIONS

Because reflex contraction did not substantially alter spinal kinematics, muscle contraction likely does not initiate in sufficient time to mitigate whiplash injuries that may occur during the retraction phase.

Biomechanical changes at adjacent segments following anterior lumbar interbody fusion using tapered cages

STUDY DESIGN

A biomechanical evaluation of anterior cages in a calf lumbar spine model.

OBJECTIVES

To determine changes in spinal motion and intradiscal pressures at immediately adjacent lumbar motion segments following anterior insertion of tapered cages.

SUMMARY OF BACKGROUND DATA

Stand-alone anterior lumbar interbody fusion (ALIF) is an effective approach in the treatment of discogenic low back pain. A tapered lumbar (LT) cage design attempts to restore physiologic lordosis and sagittal balance. We are not aware of any previous biomechanical evaluation of the effects of LT cages on adjacent motion segments.

METHODS

Nine fresh calf spines (L2-L5) were procured for the study. Pure moments (up to 8.5 Nm) in flexion, extension, and lateral bending were applied to the L2 vertebra in five steps through a nonconstrained loading system. With each step of loading, three-dimensional rotation at three intervertebral disc levels was obtained through a three-camera motion analysis system, and intradiscal pressures within the nucleus pulposus of the two nonoperated discs were measured with miniature transducers. The spines were tested initially intact and following paired anterior LT cage insertion.

RESULTS

Following ALIF, small to moderate increase in motion was found at both adjacent segments in flexion (superior: 12.5%, P < 0.05; inferior: 11.3%, P < 0.02) and lateral bending (superior: 7.8%, P < 0.02; inferior: 6.6%, P < 0.02). An increase in intradiscal pressure was noted at the superior adjacent segment under flexion (21%, P < 0.01) and lateral bending (16%, P < 0.03). Intradiscal pressure changes at the inferior adjacent level were not significant.

CONCLUSIONS

Statistically significant changes in intradiscal pressures and motion were found at the adjacent levels following a single-level stand-alone ALIF procedure using paired LT cages.

Does anterior plating of the cervical spine predispose to adjacent segment changes?

STUDY DESIGN

In a human cadaveric model, the effects of plate supplementation on the mechanical behaviors of adjacent segments were investigated.

OBJECTIVES

The objective was to determine the effects of anterior cervical fusion and plating on the adjacent segments.

SUMMARY OF BACKGROUND DATA

Increases in intradiscal pressure and intervertebral motion at adjacent segments have been reported in the lumbar spine following an instrumented fusion. It is unclear if the same phenomenon presents in the cervical spine.

METHODS

Seven human cadaveric cervical spines (C2-T1) were used, and fusion of the C5-C6 segment was chosen for the purpose of this study. Two miniature pressure transducers were implanted within each adjacent disc. Flexion, extension, lateral bending, and torsion loads up to 2.5 Nm were applied to the intact spine, and following each of the two procedures, anterior discectomy and grafted fusion, and anterior plating of the C5-C6 motion segment.

RESULTS

At the surgical level, a significant increase in segmental stiffness was observed after plating in all directions. Following the grafted fusion, there were no statistically significant changes at the superior adjacent segment, and there was a 13.7% increase in axial rotation in the inferior adjacent segment. Once anterior plating was applied, slight increase (<12%) over the intact spines was noted in lateral bending in both adjacent segments. However, there was no significant difference between the grafted fusion and anterior plated fusion at either adjacent segment. At both adjacent disc levels, the differences in intradiscal pressures between grafted fusion and plated fusion were less than 30% in all directions, and none of these differences was statistically significant.

CONCLUSIONS

Intradiscal pressures and intervertebral motion at the adjacent levels are not significantly affected by the instrumented anterior fusion. The clinically observed degenerative change at adjacent segments in the cervical spine is more likely to be attributed to natural progression of the spondylotic process as opposed to biomechanical effect of the instrumentation or fusion.

Influence of thoracic ramping on whiplash kinematics

BACKGROUND

Some experimental whiplash investigations using human volunteers and full-body cadavers reported thoracic ramping, characterized by superior translation and extension rotation of the cervico-thoracic junction. The effect of this phenomenon on cervical spinal kinematics has not been quantitatively determined.

METHODS

A comprehensively validated computational model exercised in 2.7 m/s rear impact was used to determine effects of superior translation and extension rotation of T1 on cervical segmental kinematics during the retraction phase.

FINDINGS

In general, thoracic ramping had a minimal effect on cervical intervertebral kinematics during retraction.

INTERPRETATION

Results of the present study demonstrated that magnitude of thoracic ramping plays a minimal role in the whiplash injury mechanism due to decreased effect on cervical segmental kinematics.

Mechanical evaluation of posterior wiring as a supplement to anterior cervical plate fixation

STUDY DESIGN

An in vitro experimental study was performed to examine 3-dimensional biomechanical stability of cervical fixations.

OBJECTIVES

To determine whether posterior interspinous wiring contributes to the rigidity of a single-level motion segment that has been plated anteriorly, and to determine the effects of this combined fixation on intradiscal pressure and spinal motion at the adjacent segments.

SUMMARY OF BACKGROUND DATA

Combined anterior and posterior column fixation is being increasingly used in a variety of clinical situations that do not involve complete disruption of the motion segment. The biomechanical validity of combined anterior posterior fixation in the absence of overt posterior ligamentous disruption has not been studied.

METHODS

Six human fresh-frozen cadaveric cervical spines (C3-T1) were used. Three-dimensional intersegmental motion and intradiscal pressure were measured while the spine was loaded in flexion, extension, lateral bending, and torsion (up to 2.5 Nm). Fixation stability at the operative level (C5-C6) and influence of the fixation on adjacent segments were evaluated after an anterior plating procedure and combined anterior plating and posterior wiring.

RESULTS

Comparing the combined approach with anterior plating alone, significant reductions in C5-C6 motion was noted: 49% in flexion (P <0.05), 48% in extension (P <0.003), and 33% and 39%, respectively, in left and right torsion (P <0.05). Reduction in the left and right lateral bending was not significant (18% and 12%, respectively). The improved fixation had minimal influence on the adjacent segments.

CONCLUSIONS

Combined anterior posterior fixation further reduces the segmental motion by almost 50% in flexion and extension, 33% and 39% in torsion, and does not significantly alter intradiscal pressure and spinal motion at adjacent segments.

Changes in galactose and lactic acid content of sweet whey during storage

Whey is often stored or transported for a period of time prior to processing. During this time period, galactose and lactic acid concentrations may accumulate, reducing the quality of spray-dried whey powders in regard to stickiness and agglomeration. This study surveyed industry samples of Cheddar and mozzarella cheese whey streams to determine how galactose and lactic acid concentrations changed with storage at appropriate (4 degrees C) and abuse (37.8 degrees C) temperatures. Samples stored at 4 degrees C did not exhibit significant increases in levels of lactic acid or galactose. Mozzarella whey accumulated the greatest amount of galactose and lactic acid with storage at 37.8 degrees C. Whey samples derived from cheese made from single strains of starter culture were also evaluated to determine each culture's contribution to galactose and lactic acid production. Starter cultures evaluated included Streptococcus salivarius ssp. thermophilus. Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. cremoris, and Lactococcus lactis ssp. lactis. Whey derived from L. helveticus accumulated a significantly greater amount of lactic acid upon storage at 37.8 degrees C as compared with the other cultures. Galactose accumulation was significantly decreased in whey from L. lactis ssp. lactis stored at 37.8 degrees C in comparison with the other cultures. Results from this study indicate that proper storage conditions (4 degrees C) for whey prevent accumulation of galactose and lactic acid while the extent of accumulation during storage at 37.8 degrees C varies depending on the culture(s) used in cheese production.

Aerosol therapy for malignancy involving the lungs

The lungs are common sites of involvement by primary and metastatic malignant disease. Patients with malignancies in the lung have limited treatment options and are usually not curable. Numerous investigators have studied the potential of delivering various therapeutic agents directly to the lungs and pulmonary lymphatics by nebulization. Most of the research involves the use of immunomodulatory strategies; a few aerosol studies of chemotherapy and gene therapy have also been conducted. Most of these studies have been conducted in animal models. A few human trials have also been completed. Results suggest that aerosol therapies have the potential to shrink pulmonary metastases of selected histologies, and that survival in selected patients with metastatic renal cell cancer may be prolonged. The approach to therapy of cancer in the lungs holds promise as a means to avoid systemic toxicity and obtain an improved therapeutic effect. Research is currently underway to address issues of local versus systemic toxicity, optimal drug delivery and selection of optimal drugs and schedules including outpatient aerosol therapy. Future issues in design of aerosol cancer treatment include identifying effective combinations of agents, schedules, and use of aerosol therapy at home as adjuvant therapy.

Intradiscal pressure and kinematic behavior of lumbar spine after bilateral laminotomy and laminectomy

BACKGROUND CONTEXT

Bilateral laminotomy has been proposed as an alternative to laminectomy for decompression of lumbar spinal stenosis. Preservation of the posterior midline ligaments with laminotomy is presumed to maintain spinal segment stability. There have been no previous studies that directly compare the amount of destabilization and increase in disc pressures between the two procedures.

PURPOSE

To quantify spinal segmental instability caused by bilateral laminotomy and laminectomy, and to compare the central and peripheral intradiscal pressures after the two procedures.

STUDY DESIGN/SETTING

Mechanical testing of the lumbar motion segments of calf spines.

METHODS

Nine fresh calf spines were tested under flexion, extension, lateral bending and axial rotation, intact first, then after laminotomy and laminectomy at the level of L4-L5. Four miniature pressure transducers were implanted in the central and peripheral disc at L4-L5 to measure intradiscal pressures. Three-dimensional motion was measured with motion analysis system.

RESULTS

Comparing with bilateral laminotomy, laminectomy showed significant increase in segmental motion at the surgical level in flexion (16%, p<.05), extension (14%, p<.04) and right axial rotation (23%, p<.03). In flexion, the stress at the anterior annulus increased a nonsignificant 20% after laminotomy, but significant 130% after laminectomy (p<.02). In the intact spine, the posterolateral annulus experienced the highest stress with lateral bending to the same side when compared with other loading directions. This stress remained unchanged after laminotomy but increased 9% after laminectomy (p<.06). In rotation, axial intradiscal stresses were evenly distributed and unchanged after each procedure.

CONCLUSIONS

Laminectomy causes more destabilization of a spinal motion segment than laminotomy and significantly increases disc stress in the anterior annulus.

Late recurrence of a primitive neuro-ectodermal tumor

Late recurrences after therapy are rare in primitive neuro-ectodermal tumor (PNET). Most recurrences occur within the first 2 years after therapy, although a small number of recurrences may occur up to 5 years after therapy. We present a rare case of a recurrence of PNET in a 31-year-old woman 17 years after her initial presentation. The potential biological implications of this late recurrence as well as responses to subsequent therapy, including temozolomide, are discussed.

Whiplash injury determination with conventional spine imaging and cryomicrotomy

STUDY DESIGN

Soft tissue-related injuries to the cervical spine structures were produced by use of intact entire human cadavers undergoing rear-end impacts. Radiography, computed tomography, and cryomicrotomy techniques were used to evaluate the injury.

OBJECTIVES

To replicate soft tissue injuries resulting from single input of whiplash acceleration to whole human cadavers simulating vehicular rear impacts, and to assess the ability of different modes of imaging to visualize soft tissue cervical lesions.

SUMMARY OF BACKGROUND DATA

Whiplash-associated disorders such as headache and neck pain are implicated with soft tissue abnormalities to structures of the cervical spine. To the authors' best knowledge, no previous studies have been conducted to determine whether single cycle whiplash acceleration input to intact entire human cadavers can result in these soft tissue alterations. There is also a scarcity of data on the efficacy of radiography and computed tomography in assessing these injuries.

METHODS

Four intact entire human cadavers underwent single whiplash acceleration (3.3 g or 4.5 g) loading by use of a whole-body sled. Pretest and posttest radiographs, computed tomography images, and sequential anatomic sections using a cryomicrotome were obtained to determine the extent of trauma to the cervical spine structures.

RESULTS

Routine radiography identified the least number of lesions (one lesion in two specimens). Although computed tomography was more effective (three lesions in two specimens), trauma was not readily apparent to all soft tissues of the cervical spine. Cryomicrotome sections identified structural alterations in all four specimens to lower cervical spine components that included stretch and tear of the ligamentum flavum, anulus disruption, anterior longitudinal ligament rupture, and zygopophysial joint compromise with tear of the capsular ligaments.

CONCLUSIONS

These results clearly indicate that a single application of whiplash acceleration pulse can induce soft tissue-related and ligament-related alterations to cervical spine structures. The pathologic changes identified in this study support previous observations from human volunteers observations with regard to the location of whiplash injury and may assist in the explanation of pain arising from this injury. Although computed tomography is a better imaging modality than radiography, subtle but clinically relevant injuries may be left undiagnosed with this technique. The cryomicrotome technique offers a unique procedure to understand and compare soft tissue-related injuries to the cervical anatomy caused by whiplash loading. Recognition of these injuries may advance the general knowledge of the whiplash disorder.

Interleukin-6 and nerve growth factor levels in peripheral nerve and brainstem after trigeminal nerve injury in the rat

Earlier studies have demonstrated that inflammation plays a role in the development of evoked pain following partial nerve injury. In this report, we demonstrate bilateral changes in interleukin-6 (IL-6) and nerve growth factor (nerve growth factor) levels following unilateral infraorbital nerve (infraorbital nerve) constriction. infraorbital nerve constriction resulted in an initial period of decreased mechanical sensitivity (1 and 3 days), followed by recovery (7 days) and then a marked bilateral mechanical hypersensitivity (10 and 28 days). nerve growth factor levels in the injured infraorbital nerve were elevated on all days, but peak concentrations of nerve growth factor were observed on day 3. A smaller increase was also observed on days 1, 3, and 7 in the uninjured nerve. A bilateral elevation of IL-6 was also seen on days 3 and 10 in the infraorbital nerve, and in the brainstem on days 3, 7 and 10 after constriction. No changes in mechanical sensitivity were found after a sham-injury, but there was a small increase in brainstem IL-6 ipsilaterally at 7 days. We conclude from these data that increases in IL-6 and nerve growth factor may contribute to the development of mechanical allodynia after trigeminal nerve injury, but they are not specifically correlated with the onset or duration of pain behaviors.

Sequence information, distinction and quantitation of C-terminal leucine and isoleucine in ternary complexes of tripeptides with Cu(II) and 2,2'-bipyridine

Tripeptides form ternary complexes with Cu(2+) and 2,2'-bipyridine (bpy) that self-assemble upon mixing the components in aqueous methanol solution. Electrospray ionization (ESI) of the complex solutions provides abundant singly charged [Cu(peptide -- H)bpy](+) and doubly charged [Cu(peptide)bpy](2+) ions. Collision-induced dissociation (CID) at low ion kinetic energies of several tripeptides, AGG, GGA, LGG, GGL, GGI, FGG, GGF, LGF, GLF, GFL, GYA and GAY, showed fragments that were indicative of the amino acid sequence in the peptide. In addition, CID of single and doubly charged complexes of isomeric tripeptides GGL and GGI provided unambiguous distinction of the isomeric leucine and isoleucine residues. Leucine peptides eliminated C(3)H(7) radicals from the amino acid side-chain whereas isoleucine eliminated C(2)H(5) radicals. CID of gas-phase doubly charged peptide complexes in a quadrupole ion trap produced a series of singly charged sequence fragments that following isolation and further CID furnished distinct fragments that allowed quantitation of leucine and isoleucine-containing peptides in mixtures.

Non-Hodgkin's tumor and Pancoast's syndrome

A 60-year old man presented with Horner's syndrome, and acute right hand and lower extremity weakness. Chest X-ray and MRI revealed a right apical lung tumor (presumed to be a primary lung cancer), with brachial plexus infiltration and spinal cord compression. Emergent radiotherapy was initiated for spinal cord compression and a biopsy was obtained 24 h later. A careful review of pathology demonstrated a non-Hodgkin's lymphoma. The patient subsequently received chemotherapy, and is now in remission. This case illustrates the importance of a tissue diagnosis before initiating therapy for a Pancoast's tumor.

Holmium:YAG percutaneous nephrolithotomy: the laser incident angle matters

PURPOSE

Laser physics dictate that maximal radiant exposure occurs when the laser strikes the target at a normal incidence. Since the renal collecting system often limits nephroscope movements during percutaneous nephrolithotomy, the laser-calculus incidence angle may vary. We have observed during holmium:YAG percutaneous nephrolithotomy that the side firing fiber more easily approaches a normal incidence compared to the end firing fiber. We test the hypothesis that holmium:YAG percutaneous nephrolithotomy is faster with a side firing fiber compared to an end firing fiber.

MATERIALS AND METHODS

Consecutive holmium:YAG percutaneous nephrolithotomy cases were studied retrospectively. The calculus size and composition, surgical time, fragmentation speed (size/time) and stone-free rates were compared between 11 patients treated with end and 8 treated with side firing fibers.

RESULTS

When the end and side firing groups were compared, calculus sizes (mean plus or minus standard deviation) were 22 +/- 13 versus 48 +/- 17 mm. (p = 0.004), calcium oxalate monohydrate incidence was 55 versus 75% (p = 0.3), surgical times were 168 +/- 87 versus 124 +/- 51 minutes, computed fragmentation speeds were 0.15 +/- 0.09 versus 0.43 +/- 0.15 mm. per minute (p = 0.0009) and stone-free rates were 73 versus 88% (p = 0.4), respectively.

CONCLUSIONS

The side firing fiber is faster than the end firing fiber for holmium:YAG percutaneous nephrolithotomy. These results are consistent with principles of laser physics.

Ureteroscopic management of ureteral calculi: electrohydraulic versus holmium:YAG lithotripsy

PURPOSE

This study compared electrohydraulic and holmium:YAG lithotripsy for ureteral calculi.

MATERIALS AND METHODS

Two cohorts of consecutive patients with ureteral calculi treated with ureteroscopic electrohydraulic or holmium:YAG lithotripsy were retrospectively compared. Electrohydraulic lithotripsy was done using a 1.9F fiber at energy settings between 50 and 100 v. Holmium:YAG lithotripsy was done using a 365 microm. fiber at energy settings of 0.6 to 1.5 J.

RESULTS

A total of 23 and 47 consecutive patients underwent electrohydraulic and holmium:YAG lithotripsy, respectively. For preoperative calculi less than 15 mm. mean stone size plus or minus standard deviation was 9 +/- 3 versus 9 +/- 3 mm. (p = 0.5), mean operative time was 72 +/- 21 versus 102 +/- 38 minutes (p = 0.004), stone-free rate at the end of ureteroscopy was 65 versus 97 (p < 0.01) and 3-month stone-free rate was 94 versus 97% (p = 0.4) for electrohydraulic versus holmium:YAG lithotripsy. For preoperative calculi 15 mm. or greater stone size was 19 +/- 5 versus 19 +/- 4 mm. (p = 0.9), operative time was 159 +/- 61 versus 108 +/- 27 minutes (p = 0.01), stone-free rate at the end of ureteroscopy was 33 versus 87% (p = 0.001) and 3-month stone-free rate was 67 versus 100% (p = 0.02). Complications were not significantly different in either comparison.

CONCLUSIONS

The overall likelihood that a patient would be rendered stone-free at ureteroscopy and 3 months after ureteroscopy favored holmium:YAG over electrohydraulic lithotripsy. For ureteral calculi less than 15 mm. electrohydraulic lithotripsy was more rapid than the holmium:YAG procedure but for ureteral calculi 15 mm. or greater the holmium:YAG technique was more rapid than electrohydraulic lithotripsy. The outcomes differences may have resulted from the different mechanisms of electrohydraulic and holmium:YAG lithotripsy.