Serious persistent problems after whiplash trauma to the neck, sometimes referred to as Whiplash Associated Disorders (WAD)1 is a common and costly condition; estimates indicate an incidence of over 250,000 in the United States, at an annual cost in 2002 of $2.7 billion or close to $10,000 per incident. 2 Although initial symptoms from acceleration-deceleration trauma to the neck may improve spontaneously or with physical therapy over the course of weeks-to-months, 1 chronic and potentially disabling symptoms persist in a significant percentage of all cases. 34 A complicating factor, which is also a reason for controversy, is the frequent failure of routine clinical laboratory investigative methods including MRI and electrodiagnostic studies, to objectively identify the cause of pain and other symptoms. 56

Although not a universal finding, stiffness of the neck and shoulders is a common sequela of whiplash. 5678910 Using 3D motion analysis techniques, Dall'Alba et al. 11 identified significant limitations with a particular pattern of cervical range of motion among patients with WAD, but also pointed out that their results do not provide an explanation for the loss of neck mobility. In a study where similar techniques were applied, Gargan et al found that cervical range of motion and psychological scores at three months were predictive of clinical outcomes at 2 years. 11 Their findings were confirmed by Tomlinson et al in a follow-up study on the same cohort, 7.5 years later. 9

Existing data suggest that neck stiffness in WAD may be an expression of pain inhibition from soft tissue injury and painful muscle spasm without pathology of the spine. Thus, injections of Botox^® to trigger points in superficial neck muscles have been shown to provide temporary but significant decrease in pain and increase in cervical ROM,8 with similar effect of short duration from injections of local anesthetic to myofascial trigger points in the neck. 12 While rarely a definitive solution to problems associated with the chronic whiplash syndrome, such injections may be helpful in identifying focal origin(s) of soft-tissue pain. 1213

3D motion analysis represents the diagnostic gold standard for conditions that affect the kinematics of the lower extremities, pelvis and trunk. Using this technology, several investigators have confirmed that deviations from normal gait mechanics also affect the compensatory movements of the head and neck. 1415 Other studies have demonstrated that temporal and spatial changes in gait are complimented in the neck through input from the vestibulo-ocular reflex (VOR) for stabilization of gaze during angular movements, 16 while head position is controlled by the cervicocollic reflex (CCR), vestibulocollic reflex (VCR) and optocollic reflexes (OCR) through proprioceptive, vestibular and ocular mechanisms. 1416 Whether variations in gait parameters are voluntary (due to changes in terrain, gait speed, direction, etc.) or represent deviations from "normal" kinematics (changes in temporal distance measures of walking or joint movement from disease, injury, or surgery), they will, through reflex mechanisms, result in adaptive changes in the kinematics of the cervical spine.

The effect of lower segment dysfunction on the upper body kinematics has been previously investigated in normal controls and in patient groups with musculoskeletal disorders. 171819 We have not, however, found any studies exploring if standard gait parameters are impaired as a result of upper body dysfunction, The present investigation was designed for that purpose and, secondly, to assess the usefulness of computerized 3D gait analysis to objectively monitor outcomes of treatment for neck pain.

Excellent reliability of the cervical spine measures were observed with ICC values consistently above 0.9 as detailed in Table 3.

The analysis of data confirmed statistically significant (p < 0.005) improvement in cervical range of motion in all six planes following treatment, with the greatest average improvements in flexion-extension (54%), followed by rotation (53.5%). Table 4.

At follow-up, walking speed had increased by an average of 13.9 centimeters/second, with a 5.2 centimeter average increase in step length. Table 5.

All patients gave postoperative neck pain ratings that were significantly lower than before surgery, both for daily pain, and for how much their pain increased during exertion. Table 6.

No major complications related to treatment were documented among the participants during surgery or the postoperative period.

Significant improvement in three gait parameters were documented after treatment for neck pain from whiplash, a condition that because of a purported lack of diagnostic laboratory findings has been described by some authors as a social or emotional disorder in need of no treatment. 232425

Pain-related neck stiffness is a cardinal component of the chronic whiplash syndrome, but reliable assessment of cervical range-of-motion is highly dependent on the subject's voluntary effort. Inclinometer- or observation based techniques, or even computer-guided three-dimensional measurement systems are therefore not ideal tools to objectively confirm or monitor chronic whiplash.26 In contrast, gait is a complex but highly automated function and therefore better suited for standardized analysis.

A clinically validated marker system 2728 was adopted for the purpose of this investigation, and the consistency of cervical range-of-motion was confirmed through repeated measurements in each participant since kinematic reproducibility has been established as a method to differentiate healthy subjects simulating neck pain from patients with true whiplash injuries.71229 With these precautions, we consider the present findings reliable and valid.

Various kinematic abnormalities have been reported in chronic whiplash syndrome, often without conclusive evidence of their underlying cause(s). Thus, even though imaging evidence of abnormal cervical 30 or craniocervical 31 motion patterns have lead to recommendations to fuse the cranio-cervical joint complex, 3233 it has not been shown that a causative relation exists between such radiological findings and the clinical whiplash syndrome. Other investigators have interpreted patterns of oculomotor dysfunction in whiplash patients as evidence of brainstem injury, or "disorganized neck proprioceptive activity" leading to distortion of the posture control system. 34353637 While none of the participants in this investigation had undergone specific diagnostic studies to assess brain stem function or cervical stability, the significant improvements in pain, cervical range-of-motion, and temporal-distance gait parameters illustrate that soft tissue surgery may alleviate considerable symptoms after whiplash in carefully selected patients. The findings also allow the following conclusions: (1) Upper segment pain, e.g. in chronic whiplash syndrome, may be expressed as gait and posture abnormalities;and (2) Computerized 3D gait analysis provides objective data for diagnosis or outcome studies in chronic whiplash.

The authors declare that they have no competing interests.

All authors participated in design and planning of the study, and read/approved the final manuscript. Patient selection and surgical interventions were performed by NAN. Data collection was performed by SDJ, and supervised by WS and GMG. Statistical analysis by WS.