Evaluation of Patients’ Posture and Gait Profile After Lumbar Fusion Surgery by Video Rasterstereography and Treadmill Gait Analysis

Here, we present a protocol to analyze the posture and the gait of patients after lumbar fusion surgery by means of high-resolution video rasterstereography and a treadmill equipped with an integrated sensor mat. Allowing critical functional postoperative evaluation on a less subjective level may enhance accuracy and reliability of indication for surgery.

With this technique, we are finally able to analyze the gait and posture of patients after spinal surgery in a more objective way, compared with the typical, widely used questionnaires. The technique is completely free of radiation and once implemented feasible with moderate effort. Furthermore, the good validity and high intra and interrater reliability are great advantages of this method.

The functional aspect of the data that can be obtained with this technique is not only relevant for spinal surgeries but also interesting for general disabilities of the lower extremities. We would advise a first-time user to focus on the relevant parameters needed for the main question and help keep the patient relaxed during the rasterstereographic and treadmill measurements. The methodical setup of this technique is complex with several potential pitfalls.

Therefore, we believe that visual demonstration of this method is helpful for everyone who wants to implement it. Before initiating the procedure, hang a two point five by two meter piece of plain black cloth or similar that entirely covers the background of the image to be taken to improve the contrast. Recruit a subject aged more than 18 years who suffers from lumbar back pain and degenerative disc disease.

Gather all of the relevant data for the back pain related patient history, results from X-ray and magnetic resonance imagery, current pain medication, and history of physiotherapy. Perform an orthopedic physical examination to identify the origin of the lumbar back pain and to locate tender pressure points. Test the lateral flexion and trunk inclination and extension and have the patient perform the straight leg raise.

For differential diagnosis, also test the hip joint, for example, for flexion, extension, and rotation. Examine each of the key muscles to rule out that the patient has a neurologic deficit of the lower limbs that requires immediate surgery. And schedule measurement dates for one day before and for seven days, three months, and one year after the surgery.

At each measurement session, ask the patient to complete the Oswestry Disability Index Questionnaire and to indicate their usual value on the numeric pain rating scale. Begin the measurement process by asking the patient to undress from head down to the waist to expose all four of the necessary anatomical landmarks. The neck with the vertebrae prominence, the two lumbar dimples, and the sacrum point as the cranial end of the rima ani.

Confirm that the caudal landmarks are also visible. Have the patient stand freely and barefoot in a relaxed, standard anatomical position with the feet shoulder-width apart and position the patient facing the black background with the back toward the camera device. Using measuring tape, confirm that the distance from the back surface of the patient to the camera device is 200 centimeters and click the automatic landmark detection software button to begin the measurement.

In the case of a scanning error, manually re-adjust the landmark positions according to the manufacturer's instructions provided with the software so that the landmarks match their actual anatomic positions. Set the system to a measurement time of 30 seconds. Due to the 15 Hertz rate of the camera device, about 450 images will be captured.

Then click generate and wait for the results. The software will calculate the average terminal values needed for further analysis. Let the patient rest for 120 seconds after the rasterstereographic measurements.

During the rest period, set the slope of an instrumented treadmill with an integrated system containing capacitive pressure sensors under the belt to register gait parameters to zero percent and connect the treadmill and video camera to a computer equipped with the manufacturer's measurement software. Then ask the patient to stand on the treadmill barefoot with their pants rolled up to their knees. Attach a safety plug to the patient's shirt and instruct the patient to use the two lateral rail bars attached to the sides of the treadmill to prevent the patient from falling off the treadmill in case of stumbling.

To register the total load distribution on each foot, ask the patient to stand freely on the treadmill sensors three times for 10 seconds per measurement while the treadmill is not moving. After the third measurement, instruct the patient to walk between the markers on the treadmill to make sure every step is recorded. Also, instruct the patient to walk at a normal gait without holding the handrails.

Then have the patient walk between two adhesive markers along the surface of the treadmill at a normal gait without using the handrails, if possible, to define the limits of the integrated sensor mat. Increase the speed in small increments of 0.1 kilometers per hour, starting from 0.5 kilometers per hour until the patient's individual maximum well-tolerated walking speed is reached. Then film the patient's gait from behind with the video camera to allow visual correlation between the actual gait profile and the assessed parameters.

After two 20-second trials, with a 60-second rest between trials, print the results in a report through the software interface. In this representative study, perioperative rasterstereographic analysis of patients who suffered from chronic lumbar back pain and who were treated with lumbar fusion surgery revealed no significant changes in trunk length at the three-month follow up compared to preoperative measurements. However, a significantly reduced lordotic angle was observed at the first post-operative measurement compared to the pre-operative values.

No differences for the measurements of trunk inclination or lateral tilt were detected at any time point. Treadmill gait measurements of the same patient cohort showed a significant reduction in cadence from pre-operative to three months post-operative assessments. Over the three post-operative months, significant changes were also detected for the spatiotemporal swing phase, stance phase, and foot rotation parameters.

For high accuracy, correct landmark detection is essential. Make sure that all of the anatomical landmarks are clearly visible and correctly detected by the software. The combination of the posture, gait, and foot pressure measurements can be used for various disabilities of the lower extremities or as a control for neurologic condition therapies.

While adjusting the treadmill speed, it is important that the patient walks without stress or imbalances to ensure the closest possible resemblance to their everyday gait.