With a compelling case study, this author illustrates how the biomechanical needs of a patient can change postoperatively. Accordingly, he emphasizes the importance of a sound biomechanical assessment and gait analysis after surgery, and how these findings will influence conservative management postoperatively.
Orthotic devices are prescribed for a variety of reasons by many different practitioners. Simply increasing the support for many of our patients’ feet provides relief. However, there is a segment of our patient population that needs even more attention. Ensuring appropriate attention to the details of how the foot functions from heel strike to propulsion is sometimes vital in keeping our patients ambulatory. For those patients who undergo reconstructive procedures, this attention to detail is sometimes as important as the surgery itself.
The foot will heal and the responsibilities of the surgeon may conclude, but if ambulation remains difficult or painful, focus on function is critical. With podiatric surgical expertise increasing steadily, we can not forget the importance of conservative biomechanical care for our patients, our practices and our profession.
Fabricating orthotic devices for our patients is something most of us do routinely. It is often a part of conservative care leading up to a surgical procedure and, in many instances, may even prevent the need for surgery. After surgery, the foot can change, sometimes in structure, sometimes in function, or both. For this reason, the pre-operative needs of our patients are often different than the postoperative needs. If it is a unilateral surgery, then only one foot may change. If it is a reconstructive surgery, there may be additional components such as leg length differences that one needs to assess. For this very reason, podiatrists need to repeat the thorough pre-operative biomechanical examination after the surgery as well. This may result in having to fabricate a new orthotic device for just the operated foot or a new pair if function has caused enough of a change to require something totally different. The following case study illustrates these key points.
A 56-year-old healthy female was diagnosed with tibialis posterior tendonitis. She had pain for a few months and it was unresponsive to physical therapy, ice, and anti-inflammatory medication. The examination revealed tenderness following the course of the tibialis posterior tendon from its insertion on the navicular proximal to the level of the medial malleolus. She had difficulty performing a single toe raise on this affected left lower extremity. The patient was able to rise up on the toes of both feet but clearly with weakness and pain. Additionally, she had been wearing shoes that were inappropriate in that they offered no support and were slip on shoes.
The X-rays exhibited an abducted forefoot with an increase in the talar declination angle and decrease in the calcaneal inclination angle. She also had a moderate bunion deformity with an intermetatarsal angle of 16 degrees. The appearance of her feet was asymmetric. The symptomatic foot had a lower longitudinal arch and the forefoot was more abducted. She had developed a limp and most days, she had to find time to get off of her feet in order to escape the pain.
Initial treatment consisted of taping for temporary support, footwear recommendations and an over-the-counter support. Her initial response was positive. Therefore, the treating physician prescribed custom orthotic devices. These devices were made from neutral suspension casts of both feet. The orthotics were semi-rigid devices made of polypropylene 5/32" with a deep heel cup for the left foot. Footwear recommendations included a motion control shoe that would accommodate the orthotic devices.
The patient was definitely more comfortable and functioned better with the orthotic devices than without, but the pain continued. Over the course of a few months, her situation gradually deteriorated further. At this point, the treating physician considered a custom AFO but obtained a MRI first. The MRI indicated partial tearing of the tibialis posterior tendon with extensive tenosynovitis. Due to the progressive nature of her deformity, the pain and the lack of improvement with conservative care, the patient was eager to pursue surgical intervention.
Surgery consisted of tendon repair, a calcaneal osteotomy as well as an osteotomy of the medial cuneiform. Since the bunion was an issue at times as well, the surgeon performed a first metatarsal head osteotomy as well and there were no complications.
The patient proceeded to undergo physical therapy following the surgery and had a typical course of nonweightbearing with gradual return to activity. Unfortunately, while she was recovering from surgery, she continued to have left foot pain and continued to have a limp. She had difficulty making it through the day without severe pain, In addition, she started to complain of low back and hip pain on the left side. The surgery was over. The foot had healed. The next step was biomechanical assessment.
Her postoperative examination revealed very little subtalar joint range of motion within the frontal plane. She exhibited a resting varus position to the foot. In addition, the first MTP joint exhibited very little movement within the sagittal plane with approximately equal dorsiflexion and plantarflexion. In relaxed stance, the hallux did not purchase the ground effectively. All of these changes indicated a significant difference between her preoperative and postoperative foot. Prior to surgery she had functional orthotic devices with the main purpose being to control the excessive pronation of the left foot. Now with the mechanics of her foot surgically altered, her needs were much different. She could no longer tolerate the same semi-rigid orthotic on either foot.
The treating physician performed video/computer gait analysis in order to better identify the issues at hand. This included F-Scan analysis and digital video analysis from four different camera views while the patient walked upon the gait platform. By integrating the two, one can correlate body function and position with foot function and position. It is often the foot that is the chief complaint but the foot can affect the rest of the body or the body can affect the foot. We need to be in the habit of looking at the entire body when assessing foot function.
Gait analysis findings included a very short center of force traveling through the operated left foot. This indicated difficulties with active and passive propulsion. She was apropulsive primarily because of the lack of motion from the first MTP joint as well as the fact that she was having difficulty with pronating at heel strike. The patient exhibited inversion at heel strike mainly because of the inverted attitude of the entire foot. This finding was unchanged from the preoperative assessment. This was also the position the foot assumes just prior to heel strike. Since the ground is flat, there was a large pronatory force being placed on the subtalar joint. With lack of motion at the subtalar joint, compensation was forced to occur elsewhere such as the midtarsal joint and the first ray.
Taking all of these considerations into account, the clinician needed to fabricate a new device for the left foot. Given that the patient now has less motion in the foot, she would no longer be able to tolerate the semi-rigid material. Softer and more flexible devices would be better tolerated. As is often the case, feet with restricted motion do better with softer devices and feet with hypermobility do better with more rigid devices. Her right foot did not change but since the clinician was selecting new orthotic material, a new pair of devices was necessary. If the clinician did not replace the right orthotic, there would be different thicknesses that would present other issues.
The device included a neutral heel cup with 0° of motion in order to try and balance the heel at contact. Cushioning was also important at heel strike because of the lack of the subtalar joint motion. Total contact of the foot was important during midstance in order to try and distribute the weight more evenly across the foot. First ray accommodations were necessary for the propulsive phase of gait. The purpose of this was to try to allow the first ray to plantarflex and promote propulsion from the first ray.
The asymmetry in the function between her feet was also indicative of another factor, namely a leg length discrepancy. With the feet now being structurally and functionally different after the surgery, one must at least check for a leg length discrepancy. The operated foot had been collapsed prior to the surgery, perhaps making it function as though it was the shorter side. Now that there has been reconstruction of this foot, it could go from being on the short side to being on the long side. Complaints of back and hip pain are the clues that one may need to assess more closely for leg length discrepancy. Gait analysis is also an excellent way to elucidate issues like this.
Regardless of how successful new orthotic devices are, you cannot ignore the shoes. First of all, one need to ensure proper measurement of the size of her feet is necessary. It is possible that foot size or width can change after certain procedures. Also bear in mind that the foot can feel different to the patient, causing a change in how it feels inside of a shoe and leading to a different size. This is often a subjective issue but patients become much more aware of their feet following surgery as they may notice details and sensations they did not preoperatively. The shoe should have the toe break in the proper location. The ball of the foot should fit into the widest part of the forefoot of the shoe. The shank of the shoe should be stable in the frontal as well as the sagittal planes.
Proceeding through these steps of care and allowing for time to see how the patient adapts and responds is important. This enables you to carefully assess the impact of the changes. Changing too many things at one time not only can make it difficult to determine the success of the treatment but it may also introduce other problems or complaints. Documenting each step of the care, even when the changes are small, will help you later on if initial attempts have been unsuccessful. You can then see a map of where you started and gain some ideas as to what might be worth trying next.
Despite the efforts with the shoes and orthotic devices, sometimes it is still not enough as was the case with this patient. Since she was still having difficulty with propulsion, the clinician added forefoot rocker soles to the shoes the patient wore most of the time. These modifications assisted the patient’s forward progression once her center of weight moved into the forefoot of the shoe. This is unlike some of the new shoes on the market now that exhibit rocker soles. Many of these shoes have rocker soles that are in the rearfoot. The rearfoot type of rocker makes the foot unstable and may actually hinder propulsion. Also, with some individuals, one needs to take the angle and base of gait in to account when adding rocker soles, which is obviously impossible with some of the shoes that are available now.
Orthotic devices have been an integral part of conservative treatment for foot and related complaints for over a century. Initially, the purpose of orthotic devices was to provide more support for the foot. As the field of biomechanics evolved, it was more than support that orthotic devices could offer. Controlling the motion of the foot became an important consideration as well as alleviating areas of pressure. In certain situations, a combination of support, controlling motion and distributing pressure is necessary. One can accomplish this with a variety of designs made from a wide array of materials. Sometimes, it is necessary to combine the purposes of an orthotic device.
The aforementioned case study was just one example of a patient who had postoperative needs that were different than her pre-operative needs. There are many more examples like this that we face every day in our practices. There are minor cases in which a single toe or metatarsal might change in position all the way to a major case involving Charcot reconstruction in a patient who is neuropathic.
We can not afford to forget how important biomechanics is prior to surgery, during surgery and even after surgery. With more and more emphasis on surgical training within our profession, we can not lose sight of the podiatric fundamentals.
Dr. Levine is a Fellow of the American Academy of Podiatric Sports Medicine. He is in private practice and is the director and owner of the Frederick, Md.-based Walkright and Physician‘s Footwear, a fully accredited pedorthic facility.