A Review of the Effect of Lower-Extremity Pathology on Automobile Driving Function

Abstract

The effect of lower-extremity pathology and surgical intervention on automobile driving function has been a topic of contemporary interest in the medical literature. The objective of this review was to summarize the topic of driving function in the setting of lower-extremity impairment. Included studies involved lower-extremity immobilization devices, elective and traumatic lower-limb surgery, chronic musculoskeletal pathology, and diabetes as it relates to the foot and ankle, focusing on the effect each may have on driving function. We also discuss the basic US state regulations with respect to impaired driving and changes to automobile structure that can be made in the setting of lower-extremity pathology.

The effect of lower-extremity pathology and surgical intervention on automobile driving function has been a topic of contemporary interest in the medical literature. Several authors have studied the effects of lower-extremity immobilization[1,2,3,4,5,6,7] and chronic musculoskeletal pathology[8,9,10] on driving outcomes, produced original data on the return to driving after lower-extremity surgery,[11,12,13,14,15,16,17,18,19,20,21] and offered general guidelines on driving in the setting of these and other medical conditions affecting the lower extremity.[22,23,24,25,26,27,28,29,30,31,32,33,34] The objective of this review was to provide readers with a summary of this literature on the topic of driving function in the setting of lower-extremity impairment. Studies included in this review involved lower-extremity immobilization devices, elective and traumatic lower-limb surgery, chronic musculoskeletal pathology, and diabetes as it relates to the foot and ankle, focusing on the effect that each may have on driving function. We also discuss the basic US state regulations regarding impaired driving and changes to automobile structure that can be made in the setting of lower-extremity pathology.

Methods

It would be inaccurate to consider this a systematic review given the breadth and scope of the topic, but we did attempt to perform comprehensive literature searches that at least contained all prospective clinical trials, retrospective clinical cohort analyses, retrospective case series, consensus statements, and US federal documentation specifically involving foot and ankle pathology on the respective topics. This included searches in PubMed, Ovid, Embase, and the Cochrane Database of Systematic Reviews, as well as manual searches of the Journal of the American Podiatric Medical Association, The Journal of Foot and Ankle Surgery, and Foot and Ankle International. The resultant manuscripts were analyzed for their content and were included in this report if they provided information that we considered to be of value to physicians working in the field of foot and ankle medicine.

Discussion

Lower-Extremity Immobilization

Immobilization devices used in the treatment of lower-extremity conditions are designed to splint and protect joints with the intention to limit the available motion. These may be broadly categorized as either removable (ie, surgical shoes, removable walking boots, molded ankle-foot orthoses, ankle braces, and knee braces) or irremovable (plaster or fiberglass splints and casts). Specific to the ankle joint, limitation of motion could be hypothesized to affect the depression of and transition between an automobile’s accelerator and brake pedals. The knee and hip may also play an important role, particularly when transitioning between pedals. Two common braking strategies involve 1) keeping the right heel in a stationary position on the floor board of the automobile and pivoting between the accelerator and the brake with dorsiflexion and plantarflexion of the ankle, respectively, or 2) keeping the ankle joint in a relatively immobile position with flexion and extension of the hip and knee, respectively, to get between the accelerator and brake pedals.[1,15,35,36]

Several studies have investigated driving function with an immobilized ankle. Tremblay et al[2] investigated braking performance with the use of a driving simulator specifically testing individuals in a running shoe, a removable walking boot, and a below-the-knee fiberglass cast. They found that there was a significantly longer mean braking reaction time while wearing the fiberglass cast or walking boot relative to the running shoe and that a significantly lower mean braking force was applied with the cast. Murray et al[4] conducted a similar trial involving the same immobilizers in an on-the-road study in an actual automobile, which yielded results consistent with those cited previously herein. It is important to note in both of these studies, however, that although mean braking times were statistically significantly delayed relative to those with the sneaker, the braking responses were still faster than reported safety standards.

This brings up the important concept of semantics with respect to outcome measures in the driving literature. An emergency brake response represents a complex process involving the central and peripheral nervous systems and a chain of musculoskeletal events.[35,36] With an automatic transmission car, the driver has to first recognize some sort of visual or auditory stimulus alerting him or her to initiate braking, physically remove the right foot/leg from an active plantarflexory force on the accelerator pedal, transition the foot/leg effectively from the accelerator pedal to the brake pedal, and then reapply an effective plantarflexory force to the brake pedal. Although it is possible to measure ‘‘reaction time’’ of the central nervous system to the stimulus, or ‘‘foot transfer time’’ between the accelerator and brake pedals, or ‘‘braking force’’ of the plantarflexory energy applied to the brake pedal, most studies use a more basic definition of ‘‘brake response time,’’ which measures the time between initiation of the stimulus and effective depression of the brake pedal. Although there are a variety of reports with respect to normal and abnormal brake response times, several investigators and government sources have established a cutoff threshold for potentially unsafe brake response times at 0.700 sec.[8,18,35] In other words, brake response times less than approximately 0.700 sec are classified as normal and brake response times greater than approximately 0.700 sec are classified as abnormally delayed.

Hofmann et al[1] tested emergency braking in 30 young volunteers wearing 4 different types of commonly prescribed ankle braces and found that reaction times and foot transfer times were statistically increased in most trials. Another study evaluated driving with varying degrees of ankle and knee immobilization. Waton and colleagues[3] investigated the effects of immobilization of these joints with a below-the-knee plaster cast, a knee immobilization brace, and an above-the-knee plaster cast. As in other studies, an increased brake response time was noted as the degree of limb immobilization increased. Specifically, the increase in brake response time seen with an above-the-knee cast was found to increase the stopping distance of a car traveling at 30 mph by approximately 3 m (~10 feet).

Our group has previously investigated driving function in another common form of lower-extremity immobilization device: a stiff-soled surgical shoe.[37] We compared mean brake response times with use of a driving simulator among a control shoe, a surgical shoe, and a removable walking boot and found statistically and clinically significant increased brake response times for both the surgical shoe and the walking boot compared with the control shoe. We also introduced a new driving outcome measure in the form of an ‘‘inaccurate brake response,’’ which we defined as inadvertent simultaneous depression of both the brake and accelerator pedals during an emergency braking response. We had noted during pilot testing that the relative width of the walking boot and surgical shoe seemed to contribute to an increased incidence of pedal ‘‘misapplications,’’ and evidence has demonstrated that this represents a common cause of automobile accidents.[38] We found an increased incidence of ‘‘inaccurate brake responses’’ with the walking boot in our study, accounting for 18% of all braking trials involving the walking boot.

Despite the increasing amount of literature on the effects of lower-extremity immobilization on brake response times, there is no general consensus regarding the overall safety or legality of driving with these devices.[22,23,24,25,26,27,28,29,30,31,32,33,34,39] It is reasonable to conclude that studies have consistently demonstrated an increased mean brake response time in the presence of immobilization devices compared with regular shoes, but it is unclear whether this constitutes an increase into an unsafe zone regarding established safety thresholds. Based on a review of the literature, we conclude that these devices have at least the potential to lead to unsafe driving, and we recommend to our patients that they drive only while in regular shoes. Although we specifically attempt to educate patients with respect to the risk of delayed response times and pedal misapplications, it is up to the individual treating physician to advise the patients on the risks and safety issues that come with wearing immobilization devices because there are no universal US state or federal regulations regarding the use of these devices while operating a vehicle.

Elective Lower-Extremity Surgery

There is also no literature available that provides definitive recommendations for the return to driving in the postoperative setting. Typically a surgeon uses the specific procedure to guide a specific postoperative course. For example, a patient who undergoes an arthrodesis is generally nonweightbearing for several weeks to 3 months depending on the joint involved. And most surgeons agree that driving constitutes a weightbearing activity. Once the patient is out of the immobilization device and is permitted to bear weight as tolerated, it might be reasonable to assume that most activities, including driving, can be resumed without implications.

A prospective observational study conducted by Holt et al[11] analyzed total brake response time, reaction time, and braking time in patients undergoing a right foot first metatarsal osteotomy for the correction of hallux abducto valgus deformity. A driving trial with a simulator was performed on each patient preoperatively and at 2 and 6 weeks postoperatively. The study group was compared with a matched control group not undergoing surgery. Despite the relatively small study cohort (n = 28 in the experimental group), the authors concluded that by 6 weeks, braking responses were comparable with those of the control group. It is interesting to note, however, that 75% of patients were unable to complete testing 2 weeks postoperatively secondary to pain.

In the only other study we identified specifically examining elective foot and ankle surgery, Jeng et al[9] sought to compare brake response times between patients with and without right ankle fusion well after the postoperative recovery period. In addition to a driving simulator, pedobarographic measurements were obtained. Not only were mean brake response times significantly increased in the surgical cohort, but those with ankle fusions maintained the center of force in the forefoot during driving, whereas the control group had an evenly distributed center of force about the forefoot and midfoot. There were no significant differences noted regarding brake force, peak pressure, or contact area. This study is another example where it is important to note, however, that despite the statistically significant difference observed between the two groups, the arthrodesis group’s mean brake response time was still below the previously described safety threshold of 0.700 sec, potentially limiting the clinical significance of these findings.

Similar investigations have also been undertaken for patients after other elective extremity orthopedic surgeries ranging from the knee to the lumbar spine.[14,15,16,17,18] In a study by Liebensteiner and colleagues,[18] driving reaction time was evaluated in patients undergoing lumbar spine fusion. Responses were significantly increased immediately postoperatively but decreased to below preoperative values at the final 3-month follow-up visit. Interestingly, the authors additionally identified a positive correlation between extremity pain and driving reaction times. The authors concluded that it is safe for patients undergoing lumbar fusion to drive after the procedure, noting a positive effect of the procedure on driving performance. MacDonald and Owen[17] investigated delay and force of brake application in patients undergoing total hip arthroplasty. It is interesting to note in this study that most patients had higher preoperative values secondary to disease at the hip, which decreased in the postoperative setting (from 0.704 sec to 0.591 sec at 32 weeks after right hip replacement). Given the significant differences in the preoperative and postoperative measurements, the authors deemed 8 weeks as the appropriate time for return to driving activity after this procedure.

Moving distally, Liebensteiner and colleagues[14] looked at patients undergoing total knee arthroplasty and its effect on brake response times. They did not find a significant increase in brake response time beyond 2 weeks in the postoperative setting compared with the control group. Gotlin et al[16] performed a similar study of patients with anterior cruciate ligament reconstructions. The patients were evaluated before and after surgery, noting significant improvement in brake response time from weeks 2 to 4. Based on the results of this study, the authors propose that brake response times matched those of the control population 4 to 6 weeks postoperatively.

Given the previous results, it is evident that return to safe driving after orthopedic limb surgery is likely procedure dependent. A general theme of the literature that we observed, however, is that there is a negative short-term effect of surgery on driving parameters, but that generally does return to at least baseline in line with recovery from the procedure. We conclude that it is unlikely that there are definitive benchmarks for return to driving after elective lower-extremity surgery, but rather each patient should be evaluated on an individual basis.

Lower-Extremity Trauma

Lower-extremity trauma could also be hypothesized to negatively affect driving function and may limit an individual’s ability to safely operate a vehicle. Haverkamp et al[24] performed a survey of orthopedic surgeons regarding their practices for the treatment of lower-extremity trauma and their postoperative decision making regarding resumption of driving. Although up to one-third of surgeons did not discuss driving with their patients, full weightbearing was the most frequent criteria used to determine ability to resume driving. Most surgeons were not aware of the presence or absence of rules governing driving in the setting of lower-extremity pathology, and most indicated that guidelines would be useful to help surgeons advise their patients.

Egol and colleagues[12] published a study to help evaluate when patients were able to drive after surgery for lower-extremity trauma (including intraarticular and extra-articular foot, ankle, and leg fractures). The authors noted that outcomes were significantly affected until 6 weeks after initiation of weightbearing in the setting of long bone and articular lower-extremity fractures.

These authors also performed a separate investigation specifically focused on driving after ankle fracture operative repair.[13] A control group was established to obtain normal mean braking times. The fracture group was tested at 6, 9, and 12 weeks postoperatively. At 6 weeks, mean brake time was 1.33 sec compared with the control group’s 1.079 sec. To put things into perspective, at 6 weeks, the delayed mean brake response time equates to an increase in distance traveled before braking of 22 feet at 60 mph. No correlation was noted between brake times and improvement in functional scores. The authors concluded that by 9 weeks, brake times had normalized to baseline values.

We have now discussed immobilization, surgery, and trauma to the lower extremity and the implications of each on driving, but it is important to note that these scenarios often occur simultaneously. Those who have had trauma or surgery are often immobilized; therefore, one might consider a potential additive effect.

Chronic Musculoskeletal Pathology

We identified two studies that evaluated driving outcomes in the setting of chronic lower-extremity musculoskeletal pathology in the absence of surgery. Talusan et al[8] identified 37 patients with chronic foot musculoskeletal pathology, such as arthritis, and evaluated driving outcomes before and after local anesthetic administration to the area. Interestingly, they found increased brake response times greater than those of a control group and the recommended safety threshold of 0.70 sec both before and after the injection. They concluded that the presence of chronic foot and ankle pathology and pain contributed to impaired brake response times. Similarly, Hofmann et al[10] performed a crosssectional analysis concluding that symptomatic knee and hip osteoarthritis correlated with negative driving performances. These two add to the group of studies that we identified with a positive association between lower-extremity pain (whether chronic or acute postoperative pain) and poorer driving outcomes[8,10,14,17,18]

Diabetes

Various chronic systemic disease states, notably diabetes, may also have a substantial effect on driving function. Outside of the risk of a hypoglycemic episode, two of the primary complications of diabetes—retinopathy and neuropathy—might lead to compromised vision, hearing, lower-extremity sensation, and articular proprioception.[40,41,42,43,44,45] In fact, a study by Muhil and colleagues[46] examined auditory and visual reaction times in two groups of diabetic patients with a hemoglobin A_1c level of greater or less than 7.0%. Although both groups showed an increase relative to the control group, those with a hemoglobin A_1c level greater than 7.0% had a statistically significant increase in reaction time, indicating that a more chronic, uncontrolled disease process with a higher hemoglobin A_1c level leads to longer reaction times. Other studies by Mohan et al[47] and Sanchez-Marin and Padilla-Medina[48] arrived at similar conclusions regarding diabetes increasing reaction times. Sanchez-Marin et al[48] specifically cited an average 33% longer distance traveled before brake pedal depression. It would not be difficult to envision how these factors might have the potential to increase the risk of being in an automobile accident. Indeed, one study reported that the risk of a motor vehicle accident was 12% to 19% higher in diabetic individuals, although it did not identify specific causative factors.[33]

Another major complication of diabetes is amputation and limb loss. Authors such as Engkasan[19] and Boulias[20] and their colleagues have examined return to driving after major limb amputation, noting a 45.6% to 80.5% rate of return to driving. Of those returning with a right-sided major limb amputation, up to half used their prosthetic device to control one or both pedals. Meikle et al[21] hypothesized that this might negatively affect driving function whether it is with respect to pedal pressure, pedal transfer, or reaction time. They studied patients who had previously undergone right-sided below-the-knee amputations and found that the total response times were slowest using a two-footed technique.[21] Similar response times were noted using the prosthesis alone compared with using the left foot alone.

Given the relative overall lack of data regarding response times in diabetic drivers, our group endeavored to examine several hypotheses to evaluate the effect that diabetes, specifically with neuropathy or associated foot pathologies, can have on driving function. For part I of this investigation we compared a control group of 25 active drivers with neither diabetes nor neuropathy with an experimental group of 25 active diabetic drivers with lower-extremity sensorimotor neuropathy. The experimental group demonstrated a 37.89% slower mean brake response time (0.76 versus 0.55 sec; P < .001), with abnormally slow brake responses occurring at a greater frequency (57.5% versus 35.0%; P < .001).[49] For part II of this investigation we compared a control group of 25 active diabetic drivers without neuropathy with an experimental group of 25 active diabetic drivers with neuropathy. The experimental group again demonstrated a slower mean brake response time (0.76 versus 0.68 sec; P < .001), with abnormally slow brake response times occurring at a greater frequency (57.5% versus 35.0%; P < .001).[50]

For part III of this investigation we compared a control group of 20 active diabetic drivers with neuropathy but no history of specific diabetic foot pathology (defined as ulceration, partial foot amputation, or Charcot’s neuroarthropathy) with an experimental group of 20 active diabetic drivers with neuropathy with a history of specific diabetic foot pathology. The control group actually demonstrated an 11.11% slower mean brake response time (0.79 versus 0.71 sec; P < .001), with abnormally slow brake response times occurring at similar frequency (58.13% versus 48.13%; P = .0927).[51] The observed mean in both groups was slower than the suggested safety threshold of 0.700 sec, indicating that any lower-extremity neuropathy, regardless of the presence of specific foot pathology, had a negative effect on brake response time. The results of these investigations provided original data regarding abnormally delayed brake response times in diabetic patients with lower-extremity neuropathy, and may raise the potential that this population has impaired driving function.

US Laws and Regulations

Given the data reviewed previously herein, a reasonable question faced in clinical lower-extremity medical practice could be exactly what constitutes safe driving and a return to safe driving. For better or for worse, this is often a decision made based on the patient’s and the doctor’s judgment alone. Recognizing this potential for subjectivity, we attempted to organize the individual US state laws and regulations regarding driving that might be related to patients presenting for care with podiatric physicians.[39] We found that most states had no explicit or specific regulations regarding driving in a lower-extremity cast, with lower-extremity immobilization devices, or after foot or ankle surgery. The state with the most specific regulations was Maine, where a document from the Department of the Secretary of State and the Bureau of Motor Vehicles titled ‘‘Physical, Emotional, and Mental Competence to Operate a Motor Vehicle’’ stated that ‘‘driving may need to be temporarily prohibited due to an immobilizing cast...if it impedes safe operation of a motor vehicle.’’[52](p16) Even this, the most specific information we found documented, contains the words may and if. We also found that most states had vague definitions for ‘‘careless,’’ ‘‘reckless,’’ and ‘‘negligent’’ driving. For example, Nebraska defines negligent driving as ‘‘indifferent, offhand, neglectful’’; careless driving as ‘‘inattentive, forgetful, inconsiderate’’; reckless driving as ‘‘rash, heedless, dangerous’’; and willful reckless driving as ‘‘deliberate and intentional.’’[53] Although none of these definitions specifically refer to driving in a cast, brace, or postoperative bandage, we do not believe that it would be a stretch to imagine someone making this argument. This lack of formal regulations puts a tremendous burden on the physician to determine the feasibility of operating a vehicle.

There is some literature published by surgeons regarding this important issue. Giddins and Hammerton[25] echo some of the preceding points in their review article, which examined the published documents on driving, licensing, and insurance in the United Kingdom. They specifically outline the duty of the patient, the insurer, and the physician. In the United Kingdom it is the patient’s responsibility to inform the proper authorities of any condition that may affect their driving, especially if the duration exceeds 3 months. In fact, insurers may refuse to cover accidents that may have been caused by a condition resulting from an injury or operation unless documented by the physician that the patient was safe to drive. Physicians are required only to report their patients to the proper authorities if they feel that they will be a danger to the public. One of the concluding points of this article was centered on the physician’s role in this decision-making process, ultimately stating that education of patients regarding their condition and solid documentation of recommendations were essential.

Von Arx and colleagues,[29] also of the United Kingdom, performed a survey-based investigation in which they sent specific clinical scenarios to physicians, insurers, and the local authorities to establish a consensus on driving safety. Although the scenarios encompassed both upper- and lower-extremity pathology, there was a 90% consensus among responding physicians that patients in a below-the-knee cast were unsafe to drive. When asked whether they gave specific advice to their patient regarding driving, 97% responded in the affirmative. Most insurance companies did not respond to the survey, but those that did indicated that it is up to the patient to follow the instructions of the treating physician. The local authorities interestingly responded by discouraging physicians from giving advice to patients regarding driving and that the burden falls to patients to decide whether they are fit to drive.

Regarding US-based policy for driving safety on a national level, the American Association of Motor Vehicle Administrators, in conjunction with the National Highway Traffic Safety Administration, has issued a Driver Fitness Medical Guidelines statement.[54] In this briefing, several medical conditions are highlighted, including vision problems, dementia, seizure disorders, brain injury, musculoskeletal disease, and, relevant to this particular article, diabetes and extremity impairment. Their focus on diabetes is purely from a hypoglycemia standpoint, indicating that drivers must carry the proper medications or have a passenger accompanying them who would be able to assist them if an episode were to arise. Although retinopathy is mentioned, no focus is given to neuropathy and its potential deleterious effects on driving. Regarding lower-extremity injury or surgery, the only specific literature-based recommendation made was for anterior cruciate ligament surgery, in which it was deemed safe for return to driving 4 to 6 weeks after surgery. In looking at other fractures, hip or knee arthroplasties, and other orthopedic conditions, there was no consensus in the literature that supported a statement from these boards regarding a designated time for return to driving, only relaying that the situation must be addressed on a case-bycase basis.

Automobile Modifications

In the setting of permanent lower-extremity impairment, several automobile modifications are available to those who still qualify to operate a vehicle. These modifications include left-sided accelerator and brake pedals, hand-controlled accelerators and brakes, and handpieces to turn the steering wheel. With these alterations, especially the hand or leftsided accelerator and brake, comes a relearning process to accustom oneself to the equipment. Because these modifications are not second nature, one could propose that there would still be somewhat of an impaired driving function, especially in the early stages of use. ‘‘Human Factors Analysis of Automotive Adaptive Equipment for Disabled Drivers,’’ a document compiled by the Texas Transportation Institute for the US Department of Transportation, compiled the results of several studies regarding the effects of automobile modifications on driving function. One of these studies was ‘‘Significant Differences in Brake Reaction Time Performance with Three Mechanical Hand Controls and the Stock Configuration."[55] The authors sought to examine differences in brake response times between the conventional brake apparatus and three different mechanical hand controls: push-pull, push–right angle pull, and rotary. Test participants were all healthy volunteers with no noted limitations. The experimental setup was similar to that of the brake response studies previously mentioned. The three mechanical hand controls had significantly faster response times compared with the traditional brake pedal system, with the greatest significance noted with the pushpull mechanism (0.37 sec versus 0.55 sec with a brake pedal). They also noted a statistically significant difference between male and female participants, with males having faster reaction times. Based on these study results, it seems that the mechanical hand controls, given the faster break reaction times, produce braking performance at least as good as the standard configuration.

In another study by Richter and Hyman,[56] brake reaction times with use of adaptive controls were examined. Comparisons were made among the normal pedal system, a hand control system, and a simulated trigger switch. Fifteen participants were tested in all three scenarios and demonstrated statistically significant decreases in brake reaction time with use of the hand control and trigger switch (0.50 sec for the foot, 0.37 sec for the hand, and 0.20 sec for the trigger). The authors make an important assertion that this difference is likely attributable to the fact that the hand control eliminates the need for movement to the brake because the hand is already on the control. Another important factor to consider is that all of the participants in these studies were healthy volunteers who did not have the disabilities that most of the drivers using these devices are burdened with; therefore, further studies are warranted to better appreciate the potential effects of those disabilities. However, because all of these brake response times were less than the 0.700-sec threshold, it seems that the nontraditional brake systems may be viable alternatives for those with disability.

Conclusions

Driving function in the setting of lower-extremity pathology and surgical intervention is likely decreased from baseline. The intention of this literature review was to highlight the effect of immobilization, surgery, trauma, and diabetes on driving function, demonstrating most notably a trend toward increased brake response times. Despite the literature illustrating these potential negative effects on driving, there are no universal or explicit US laws or policies that regulate driving in any of these scenarios. This means that in most situations, the physician is primarily tasked with deciding when it is appropriate for each patient to return to driving activities. We hope that this information is educational for readers and is useful in the development of future investigations that focus on the driving characteristics of drivers with lower-extremity dysfunction.

Financial Disclosure

None reported.