The incidence of serious complication from lumbar manipulation is extremely low. A review of the “obtainable literature indicates that, on average, less than one case occurs per year.”82 Reported
complications have been classified by Terrett and Kleynhans82 and
are listed in Box 4-13. Loads measured during the application of lumbar and pelvic SP manipulation were comparable to those encountered by airline baggage handlers and deemed to be below an injury threshold.161
The most frequently described serious complications from SMT in the lumbar spine is compression of the cauda equina by a midline disc herniation at the level of the third, fourth, or fifth intervertebral disc (IVD).77,85,162,163 The resultant cauda equina
syndrome (CES) is characterized by paralysis, weakness, pain, reflex change, and bowel and bladder disturbances. Any patient who has bilateral radiculopathies with distal paralysis of the lower limbs, sensory loss in the sacral distribution, and sphincter paraly- sis may have CES and should be considered a nonmanipulable case and a surgical emergency.162
Estimating the rate of serious lumbar manipulation complica- tions is difficult because of the lack of prospective documentation of complications and the uncertainty as to the number of manipu- lations delivered. In a review of 80 years of literature, Haldeman and Rubinstein162 reported on 13 cases of CES that were appar-
ently the result of manipulative therapy. Their literature review identified 29 cases, but 16 of the cases were patients manipulated under anesthesia. Manipulation under anesthesia is an uncom- monly performed procedure, and including those cases does not accurately reflect the risk of lumbar manipulation. In many of the reported cases, both the chiropractic doctor and the emergency room physician failed to comprehend the nature of the problem and take appropriate action. This lack of prompt, appropriate
treatment likely increased the incidence of serious complication and residual impairment.
Shekelle and co-workers78 estimated the rate of post–lumbar
manipulation CES to be approximately 1 per 100 million manip- ulations. The rate was calculated by dividing the number of esti- mated lumbar manipulations delivered in the United States from 1967 to 1992 by the reported number (4) of postmanipulation cases of CES in the United States. A 2004 review on the safety of lumbar manipulation estimated that the risk of lumbar disc hernia- tion (LDH) and CES at 1 event per 3.72 million manipulations.85 side-posTure ManipulaTion and
inTerverTebral disC
Despite the extremely low rate of complication, controversy con- tinues to surround the question as to whether SP rotary adjust- ments can injure the lumbar IVDs. The debate is primarily a theoretic one, based on two opposing anatomic and biomechani- cal models. One position postulates that SP lumbar manipulation produces a torsional shear force that is damaging to the discs. The other postulates that the lumbar facets limit lumbar rotation and protect the discs by preventing undue torsional stress. The follow- ing discussion looks at the underlying information central to posi- tions presented by these opposing models.
Those advocating a position that lumbar SP rotary manipula- tion can potentially injure the disc often cite the biomechanical work and theories of Farfan. Farfan and associates were the first to advance the theory that repetitive rotational torsion and stress could be damaging to the lumbar IVDs.164 He estimated that
approximately 90% of the torsional strength of a lumbar motion segment is provided by the disc and facet joints, with the annu- lus providing the majority of the torsional resistance. His model postulates that repetitive end-range torsional loading can lead to tears in the annulus and disc degeneration. The injury process is hypothesized to begin with circumferential separation of the outer annular fibers, followed by the development of radial fissures, internal disruption of the disc, and possible production of disc protrusions and herniations.
A number of more recent studies bring into question the pure rotational model of disc failure and its relationship to SP lum- bar manipulation. These experiments support the position that the posterior elements of the spine, including the facet joints and ligaments, rather then the disc, are the key structures resisting tor- sion in the lumbar spine.165-167 The physiologic range of rotational
motion of the whole lumbar spine is approximately 10 to 15 degrees or approximately 2.5 degrees for each joint.139 The lumbar
joint space is small, and the articular cartilage must compress sig- nificantly (up to 60%) to allow up to 3 degrees of segmental move- ment. The primarily sagittally oriented lumbar facets provide an interlocking mechanism that minimizes rotational mobility and stress to the IVD. Movement must exceed 3 degrees of axial rota- tion (4% strain) before the annular fibers begin to demonstrate microscopic failure. Full macroscopic failure does not occur until 12 degrees.168 Therefore, impaction of the zygapophyseal joints
provides protection for the IVD by limiting tension to the annulus fibrosus to less than 4% strain.
Using a cadaveric model, Adams and Hutton165 demonstrated
that the torsion of the lumbar spine is resisted primarily by the
Disc-related complications Diagnostic error
Vascular complications from thrombosis Fracture in presence of osteoporosis
Manipulation in patient on anticoagulant therapy Rib fracture
Inguinal and abdominal hernia Unknown
BOX 4-13
reported Complications of lumbar Manipulationfacets and that the compressed facet is the first structure to yield at the limit of torsion. Significant injury to the articular cartilage and soft tissues was demonstrated before significant mechanical stress was transferred to the IVD.165,169 The capsular ligaments of
the tension facet (facet being distracted during rotation) and the supraspinous and intraspinous ligaments were found to be unin- volved or unimportant. This suggests that pure rotational damage to the IVD could occur only after significant disruption of the posterior joints. The same studies established that the disc was more vulnerable to flexion injuries.170 Flexion is not inhibited by
the articular facets, and distortion and disruption of the posterior annulus may occur with excessive flexion, especially when coupled with positions of lateral bending, loading, and rotation.
Bogduk,168 aware of the protective effects of the posterior
joints, has postulated a biomechanical model of injury to the disc that does not necessitate a preceding disruption of zygapophyseal joints. His model incorporates excessive rotation coupled with flexion. Flexion is presumed to tense the annular fibers, leaving less available stretch before their rotational limits are exceeded. Moreover, with the spine in a flexed position, the inferior and superior articular processes are less engaged, allowing for more segmental rotation. With excessive rotation, the normal axis of rotation is envisioned to shift from its central location in the pos- terior one third of the disc to the impacted facet (compression facet). The compression facet becomes the new axis of rotation, allowing for excessive pivoting of the superior vertebra, resulting in shear and torsion on contralateral facet and annular circumfer- ential discal tears (Figure 4-7).
Broberg171 studied the response to compression, shear, bend-
ing, and axial rotation of an IVD using a theoretic disc model. He reported that the stiffness of the IVD increases considerably with axial load. This finding implies that most experimental data obtained at zero axial load may reflect poorly on real situations involving weight bearing and axial loading. Within normal physi- ologic limits, bending, shear, or axial rotation does not seem to constitute a risk of fiber rupture, except in combination with very high axial loads. Moreover, with pure compression, the likelihood of fiber rupture is not very great because end-plate failure occurs earlier, before the rupture is manifest.172
It must be remembered that all of the previously described the- ories and speculations are based on studies conducted primarily on cadavers. Most of the studies examining the effects of torsion have been focused on the lumbar spine because of the high preva- lence of LBP in society, and many of the studies were performed on cadaver spine sections with the posterior elements removed. The effects of torsional forces on the cervical and thoracic seg- ments have not been adequately examined or studied. In the cervi- cal region, the facets do not interlock as in the lumbar spine, and greater axial rotation and torsion are available. The cervical spine is the most mobile region of the spine, yet the incidence of disc herniation here is much less frequently reported than in the lum- bar spine. Conclusions reached with these studies, especially any inference in their application to living human beings, must there- fore be viewed with caution. The IVD may respond very differ- ently to loads under normal physiologic loads or in circumstances in which there is associated disc degeneration or motion segment instability.
The clinical literature evaluating the potential risk of disc injury from lumbar manipulation reveals a very low incidence of reported manipulation-induced disc herniation. A review of the literature through 1993 by Assendelft, Bouter, and Kripschild revealed only 56 case reports of lumbar manipulation complications attributed to disc herniation.81 Nearly half (49%) of the cases occurred dur-
ing manipulation under anesthesia, and the majority of the cases (82%) progressed to CES. In addition, a number of the reported cases cannot be clearly cited as evidence of manipulation-induced disc herniation.163 In a number of the cases, the symptoms either
developed over time or at a point after treatment at which the patient was involved in other activities that may have triggered a worsening in his or her condition.162
Despite the very low level of documented postmanipulation disc herniations in the literature, disc problems account for the greatest percentage of malpractice claims filed against chiroprac- tors. NCMIC insures the overwhelming majority of chiroprac- tors, and the company paid claims on 1403 malpractice cases from 1991 through 1995.173 This results in an annual average
of 280 paid claims per year for this company. During this time, the percentage of filed claims for disc problems decreased slightly from 29% in 1991 to 26.8% in 1995. In 1995, the incidence was slightly higher in the lumbar spine (13.8%) than the cervical spine (12.2%).174 If the percentage of disc complications for filed claims
and claims that were settled are the same, the number of claims paid by NCMIC for disc-related problems in 1995 is approxi- mately 75. Of this number, approximately 37 resulted from lumbar manipulation. Axis Fracture, avulsion, capsular tear Fracture Annular tear Axis A B D C
Figure 4-7 Forced rotation beyond the normal range may shift the axis of rotation from its central location (a) to the impacted facet (b). Continued rotation may lead to fractures of the impacted facets or capsu- lar tears or avulsion fractures of the contralateral joint (C) and circumfer- ential tears of the annular fibers (d).
Although the total number of yearly claims paid for post–lum- bar manipulation disc-related problems is a very low percentage of patients receiving treatment, it is potentially an artificially ele- vated number. It is likely that the natural history of disc herniation has led to a mistaken connection of causation between manipula- tion and disc herniation. Patients with disc herniation often pres- ent initially with back pain that over time may progress to include leg pain. This often develops as associated NR inflammation and compression persist. If the initial evaluation of a patient is equivo- cal and the patient is not informed that he or she may be suffering from a disc herniation, subsequent progression of symptoms and the subsequent diagnosis of a disc herniation may lead the patient to erroneously assume that the manipulative treatment he or she received caused the disc herniation.
Although the debate on the risk of disc injury with lumbar manipulation has not been definitely resolved, the following ten- tative conclusions can be suggested:
1. The lumbar IVDs are protected from rotational stress and injury by the lumbar posterior joints.
2. Marked force would have to be applied to injure the disc with a rotational force.
3. Movement beyond normal range must be applied to injure the disc and likely would occur only after significant injury had been subjected to the posterior joints.
4. The disc is most vulnerable to flexion injuries. Loaded posi- tions combining flexion and rotation are probably the most risky.
5. The forces involved in skillfully delivered SP rotational manipulation are not sufficient to injure a healthy disc. 6. In patients with disc herniation, manipulative positions that
incorporate excessive flexion and rotation should be avoided. 7. Before applying adjustments in patients with disc herniations,
an evaluation of lumbar movements should be conducted. 8. Adjustments should not be delivered in positions and direc-
tions that implicate increased NR compromise (i.e., direc- tions that increase the intensity or distal distribution of the patient’s leg pain).174,175