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© 1997 The Journal of Bone and Joint Surgery, Inc. Functional Bracing for Rupture of the Achilles Tendon. Clinical Results and Analysis of Ground-Reaction Forces and Temporal Data*   , ROCHESTER, NEW YORKInvestigation performed at University of Rochester Medical Center and Ithaca College Department of Physical Therapy, Rochester
Fifteen patients who had sustained a rupture of the Achilles tendon were managed non-operatively with use of a functional bracing protocol, and clinical and functional performance measures were assessed after a mean duration of follow-up of thirty-one months (range, twenty-four to forty-five months). An age and gender-matched group of fifteen subjects was assessed to provide normative data for the comparison of side-to-side differences. Numerical scores were generated on the basis of subjective responses to a questionnaire, clinical measurements of the range of motion of the ankle and the circumference of the calf, and the results of the Thompson squeeze test and a single-limb heel-rise test. A 100-point scoring system was used to categorize the outcome as excellent, good, fair, or poor. In addition, ground-reaction forces and temporal data were assessed during functional dynamic activities that included walking, a single-limb power hop, and a thirty-second single-limb heel-rise endurance test. The result was graded as excellent for three patients, good for nine, fair for two, and poor for one. An increase in passive dorsiflexion of the treated ankle was the only clinical measure that was significantly different between the groups (p = 0.02). This increase in dorsiflexion was positively correlated with vertical force output between the mid-stance and terminal-stance phases of gait (r = 0.40, p = 0.05). With the numbers available, we could detect no significant differences between the groups with regard to the kinetic or temporal variables that were measured during functional dynamic activities. Patients who generated less peak vertical force and vertical height during the single-limb power-hop test tended to have poorer clinical scores. We believe that non-operative functional bracing may prove to be a viable alternative to operative intervention or use of a plaster cast for the treatment of acute ruptures of the Achilles tendon. The goals of treatment are to prevent the musculoskeletal changes that are associated with immobilization, to reduce the time needed for rehabilitation, and to facilitate an early return to work and to preinjury activities.
The reported prevalence of ruptures of the Achilles tendon has increased over the last few decades22,26. This increase may be related to improved clinical recognition of these injuries and to the growing number of individuals participating in recreational sports22,49. Public awareness of ruptures of the Achilles tendon also has been heightened in view of the recent injuries sustained by prominent athletes and political figures. A renewed interest in treatment strategies has accompanied the increased prevalence of these injuries. Traditionally, there have been two approaches to the treatment of ruptures of the Achilles tendon: operative intervention and non-operative treatment consisting of immobilization in a plaster cast6,10,12,15,16,19,20,27-29,31,32,46. Operative intervention has been associated with a lower rate of repeat rupture and an earlier return to preinjury activities when compared with non-operative treatment1-4,8,9,13,14,17,18,21,23,36,39-41,43,44,53. Proponents of operative treatment contend that the normal tension and length of the Achilles tendon complex can be restored only with an operation5. Another benefit of operative intervention has been the implementation of an early range of motion after postoperative removal of the cast36,43,53. Although operative intervention has been associated with a lower rate of repeat rupture, it also has distinct disadvantages, such as the risk of morbidity associated with an open procedure and higher cost35. These factors have prompted the pursuit of alternative, non-operative methods of treatment. One such alternative is the functional brace. This brace, which was developed by Fowler7 for the postoperative treatment of acute ruptures of the Achilles tendon, allows a patient to begin immediate weight-bearing and active plantar flexion of the ankle but limits dorsiflexion of the ankle. Two of us (G. P. McC. and K. E. DeH.), in a previous study of thirteen patients, investigated the use of a similar brace and a modified protocol for the primary non-operative treatment of a rupture of the Achilles tendon30. After a minimum duration of follow-up of one year, the result was graded as excellent for seven patients, good for five, and fair for one. Other authors also have reported good results with use of a similar program of functional bracing for the treatment of acute ruptures of the Achilles tendon42,47,48. Compared with immobilization in a plaster cast, functional bracing has been associated with an increased range of motion, an earlier return to the preinjury level of activity, and greater comfort42,48. Thermann et al.47, in a prospective, randomized study of fifty patients, detected no differences between functional bracing and operative treatment with regard to the progression of healing as documented with use of ultrasonography and clinical examination. The purpose of the present study was to assess functional performance in a group of patients who had been managed with a functional bracing protocol for the treatment of a rupture of the Achilles tendon. We focused on activities that place increased stress on the Achilles tendon, such as walking, rising onto the toes, and hopping. We hypothesized that our testing protocol would enable us to detect differences between the injured extremities of patients who had a rupture of the Achilles tendon and the uninjured extremities of an age and gender-matched group of individuals.
Patients and Matched Subjects All patients were managed with the non-operative functional bracing protocol that was adapted by the senior one of us (K. E. DeH.) from the postoperative protocol developed by Fowler7. Four of the nineteen patients were lost to follow-up: three could not be located, and one had moved out of state. The remaining fifteen patients (thirteen men and two women) were available for examination. The mean age of the patients at the time of the injury was forty-two years (range, thirty-three to sixty-two years), and the mean duration of follow-up after the injury was thirty-one months (range, twenty-four to forty-five months). Six patients had been injured while playing basketball; four, while playing racquet sports; three, while playing softball; one, while sailing; and one, while jumping rope. All patients were diagnosed as having an acute rupture of the Achilles tendon on the basis of a physical examination that revealed a positive result on the Thompson squeeze test49, the presence of a palpable gap, and the loss of active plantar flexion. An age and gender-matched group of subjects was recruited from the local community in order to provide normative data for the comparison of side-to-side differences in the kinetic and temporal variables that were assessed. The subjects included thirteen men and two women, and the mean age was forty-three years (range, thirty-two to sixty-seven years). All patients returned to the University of Rochester Medical Center for evaluation and were tested in the research laboratories at the Ithaca College Department of Physical Therapy at the University of Rochester campus facility. The study was approved by the Institutional Review Boards of both institutions.
Functional Bracing Protocol
At eight weeks, the patient is allowed to walk without crutches and begins a stretching program for plantar flexion, dorsiflexion, inversion, and eversion. The orthosis is not worn during the stretching exercises. The patient is taught how to perform seated heel-rises and progresses to standing double-limb heel-rises and then to standing heel-rises with five-pound (2.27-kilogram) handheld weights. The patient is instructed to wear the orthosis continuously (except during the stretching exercises) until the twelfth week after the injury. At sixteen weeks, the patient begins single-limb heel-rises and discontinues wearing the heel-lift. At twenty-six weeks, isokinetic strength-testing is performed. If the strength deficit is less than 30 per cent (as determined with the method described by Carter et al.7) when the injured extremity is compared with the uninjured extremity, the patient begins a progressive program of rehabilitation that includes running and jumping. If the deficit exceeds 30 per cent, the patient resumes the rehabilitation protocol at sixteen weeks and continues until the strength deficit is less than 30 per cent. The patient is seen every three months for one year and then every six months for another year. After two years, the patient is discharged from the program.
Follow-up Protocol
Equipment
Evaluation of Functional Performance Before each walking trial, the participant was given adequate time to reach a consistent, self-selected speed. Data were collected for five trials. A trial was considered to be acceptable if the participant maintained a consistent walking speed and landed naturally on the force platform. For the power-hop test, the participant was asked to step onto the force platform with the extremity to be tested and to jump as high as possible off the platform. The participant was instructed to jump off with only the extremity being tested but was permitted to land on both feet as the ground-reaction forces that were generated by landing were not evaluated in the present study. The arms could be used as needed in order to reach maximum vertical height as long as consistency was maintained between trials. Three trials were performed for each extremity, and an adequate rest period was allowed between trials. For the thirty-second single-limb heel-rise endurance test, the participant was instructed to step onto the force platform with the extremity to be tested and to perform single-limb heel-rises at a rate of forty-six per minute as synchronized to the beat of a metronome. The participant was allowed to maintain contact between the fingers and the undersurface of a stabilizing rod that had been placed in front of the force platform to assist with balance (Fig. 3). Two trials were performed for each extremity.
Analysis of the Data Dynamic ground-reaction forces in the vertical direction were determined as a percentage of body weight in order to allow for comparisons between participants. The difference between the minimum (F1) and maximum (F2) values of the vertical component of the resultant force between the foot and the floor (F2 - F1), the rate of peak force generation (slope) between F1 and F2, and the duration of the stance phase between heel-contact and toe-off were determined for each limb during the walking test (Fig. 4). The slope value and the difference between F1 and F2 were selected for analysis because these parameters directly reflect the major contribution of the triceps surae to the torque-generating capabilities of the ankle during the mid-stance and terminal-stance phases of gait24,38,54.
Peak vertical hop force and the rate of rise to peak vertical force (slope) were examined with use of the power-hop test. We also assessed vertical height, which represents the period between the unloaded and loaded conditions (Fig. 5). Vertical height was determined with the formula: vertical height (cm) = 9.8067 x (time/2)2.
The third measure of functional performance, the thirty-second single-limb heel-rise test, was used to assess the endurance capabilities of the triceps surae muscle group. The propulsive impulse and the braking impulse were measured as indicators of the concentric and eccentric phases of heel-rise activity, respectively. The propulsive impulse was represented by the positive area under the force-time curve, and the braking impulse was represented by the negative area under this curve. The peak propulsive force was the maximum vertical force achieved. All three parameters (the propulsive impulse, the braking impulse, and the peak propulsive force) were examined at five, fifteen, and twenty-five seconds during the timed heel-rise test (Fig. 6).
Each patient was paired with a matched normal subject. As we believed that it was important to account for whether the injured leg was the dominant leg, the contralateral leg was used as a control—that is, the analysis was based on the difference between the injured leg and the uninjured leg. If the dominant leg was injured, the value for the matched subject was calculated by subtracting the value for the non-dominant leg from that for the dominant leg; if the non-dominant leg was injured, the value for the matched subject was calculated by subtracting the value for the dominant leg from that for the non-dominant leg. Paired t tests were used to compare the mean differences between the groups with regard to the functional performance measures that were assessed during the walking and power-hop tests. All significance tests were two-sided. For the functional performance measures that were assessed during the single-limb heel-rise test, a repeated-measures analysis of variance was performed with use of the differences at each of the three time-points (five, fifteen, and twenty-five seconds). We report the results of a test for interaction, which indicates whether the difference between patients and matched subjects changed over time, as well as the results of a test for an overall difference between the two groups.
All patients tolerated the bracing protocol and the resistive exercises, and all demonstrated a strength deficit of less than 30 per cent on isokinetic testing at twenty-six weeks. One patient slipped while wearing the brace and sustained another rupture during the sixth week of treatment. The foot was placed back into full equinus, and the treatment program was begun again. The patient had a fair result at the time of the most recent follow-up. Five patients reported difficulties that may be considered indicative of deficits, such as uncertainty with regard to placement of the foot during stair-climbing and while walking on uneven terrain. Thirteen of the fifteen patients were pleased with the treatment and the outcome. On the basis of the scoring system developed by Thermann et al.47, the clinical result was graded as excellent for three patients, good for nine, fair for two, and poor for one. Ten patients had no change between the preinjury and postinjury levels of activity, four had a loss of one level, and one had a loss of two levels. Three patients who had a loss of one level reported a fear of another rupture, and one reported a change in lifestyle since the time of the injury. The patient who had a loss of two levels attributed the change in activity to a recent exacerbation of steroid-controlled asthma and an associated increase in weight. Passive dorsiflexion of the ankle was a mean of 2.6 degrees greater in the study group than in the matched group (p = 0.02). With the numbers available, we could detect no significant differences between the two groups with regard to circumference of the calf or plantar flexion of the ankle. The two groups selected similar speeds during the walking test: the mean walking speed was 1.36 ± 0.17 meters per second for the study group and 1.41 ± 0.17 meters per second for the matched group. Paired t tests did not demonstrate any significant differences between the groups with regard to the duration of the stance phase of gait or the dynamic ground-reaction force components that were assessed during either the walking test or the power-hop test (Table II).
Analysis of variance did not reveal any differences between the groups with regard to the three functional parameters (propulsive impulse, braking impulse, and peak propulsive force) that were evaluated during the single-limb heel-rise test. There was no indication of fatigue, as the peak propulsive force in each group remained consistent throughout the thirty-second test (Table III).
Non-parametric Kendall-tau correlations revealed no significant relationship, with the numbers available, between circumference of the calf and the ground-reaction force components that were assessed during the three functional performance tests. There was a weak but significant relationship between passive dorsiflexion of the ankle and vertical force output during gait (r = 0.40, p = 0.05); specifically, the magnitude of the difference in vertical force output between the mid-stance and terminal-stance phases of gait increased as the range of dorsiflexion increased. The magnitude of the differences between the injured and uninjured legs with regard to both peak vertical hop force and peak vertical height progressively increased as the clinical score worsened. However, because of the small number of patients in each group, the two patients who had a fair result and the one patient who had a poor result were combined into one category and the data were not subjected to statistical analysis. The mean cost of operative treatment (including hospital charges, the surgeon's fee, the cost of anesthesia, and the cost of physical therapy) was $5860 (range, $5790 to $5942). The mean cost of the functional bracing protocol (including the cost of the brace, the cost of the heel-lift, the surgeon's fee for office visits, and the cost of physical therapy) was $1570 (range, $1000 to $2500).
Traditional clinical parameters such as pain, limp, range of motion, circumference of the calf, and isokinetic strength have not been conclusively shown be associated with the functional outcome after a rupture of the Achilles tendon8,17,18. Although pain and a limp typically are associated with a poor outcome, these variables are not useful for the evaluation of most patients who have a healed rupture. Increased dorsiflexion has been associated with increased tendon-lengthening after a rupture33; however, its relationship to decreased force-generating capabilities of the ankle-joint complex has not been proved. Although dorsiflexion of the ankle in our study group was a mean of 2.6 degrees greater than dorsiflexion in the matched group, this increase was not associated with a loss of performance. One of the parameters that was used to determine the clinical outcome score was the difference between the injured side and the uninjured side with regard to the circumference of the calf (Table I). In the study group, the circumference of the calf was a mean (and standard error) of 11 ± 1.2 millimeters smaller on the injured side than it was on the uninjured side. However, there was a similar difference between the dominant side and the non-dominant side in the matched group of normal subjects (7 ± 0.8 millimeters). These findings suggest that the use of the difference in the circumference of the calf as a measure of clinical performance may bias the score toward a less favorable outcome. When circumference of the calf was eliminated from the scoring system, the clinical outcome scores improved: the result was categorized as excellent for eight patients, good for six, and fair for one. This finding should be considered when one uses a scoring system that employs circumference of the calf as an indicator of clinical outcome. In the present study, the side-to-side differences in the kinetic variables ranged from 7 to 13 per cent in the matched group (the so-called gold standard). Previous studies have shown side-to-side differences of 15 to 20 per cent to be within acceptable limits for a return to functional activities3,7,33. If we consider side-to-side differences of 20 per cent to be clinically relevant, the size of the present series (fifteen patients and fifteen matched subjects) has a minimum power of 0.80. We did not observe any substantial differences between the study group and the matched group with regard to the function of the lower limb during gait and during activities that place increased stress on the Achilles tendon. The slope value and the difference between the minimum (F1) and maximum (F2) vertical forces were selected for analysis because these parameters directly reflect the major contribution of the triceps surae to the torque-generating capabilities of the ankle during the mid-stance and terminal-stance phases of gait24,38,54. Kitaoka et al.24 found these variables to be indicators of functional performance in a previous study of gait patterns of patients who had calcaneal fracture. In that study, poorer clinical results were associated with changes in loading characteristics and with impairment of weight transmission to the forefoot during the terminal-stance phase of gait. These changes were reflected by smaller differences between the F1 and F2 ground-reaction forces. Such findings were not observed in the present study. However, we did observe a trend between the clinical score and the functional performance measures that were assessed with use of the power-hop test; specifically, the side-to-side differences in peak vertical force and peak vertical height increased as the clinical score worsened. We suggest that the analysis of these variables may allow for improved discrimination between patients who have a poor or fair result and those who have a good or excellent result. With the exception of increased dorsiflexion of the ankle in the study group, we detected no significant differences between the groups with regard to side-to-side variation in the clinical and functional performance measures that were assessed. The finding of increased dorsiflexion of the ankle on the side of the injury is consistent with the findings of previous follow-up reports on ruptures of the Achilles tendon and has been related to distraction of the ends of the tendon and healing in the lengthened position48. Such tendon-lengthening has been observed in association with both operative and non-operative treatment5,33. In studies of patients who have been managed non-operatively, the increased dorsiflexion that is associated with the lengthened tendon has been attributed to residual distraction or gapping of the ends of the tendon48. Thermann et al.48 recently demonstrated a significant relationship between the functional outcome (as indicated by the clinical score) and the amount of residual tendon-gapping (p = 0.1). Those authors observed better functional outcomes in patients who had closer tendon approximation as demonstrated with ultrasonography. Although increased dorsiflexion of the ankle suggests either passive tendon-lengthening or residual gapping, increased dorsiflexion was not found to have a significant effect on functional performance in the present study. Early return to work is a well known benefit of non-operative treatment. Previous reviews of the literature have revealed that the mean time lost from work has ranged from 10.5 to thirteen weeks after operative treatment and from 8.5 to nine weeks after non-operative treatment8,53. The patients in the present study were out of work for a mean of four days, and the longest time out of work was three weeks for one patient. The more rapid return to work may be due, in part, to the earlier weight-bearing allowed in the functional brace. It also may reflect the changes in medical practice in the managed health-care environment. The early range-of-motion and resistive exercises that are possible with the functional bracing protocol may minimize some of the changes that typically are associated with prolonged immobilization, such as cartilage atrophy, alterations in the properties of ligaments, and muscle atrophy25,34,45,52,55,56. Resistive exercises also may promote qualitative changes in the healing tendon, thereby facilitating a stronger anastomosis37,50-52. Non-operative functional bracing may prove to be a viable alternative to operative intervention or use of a plaster cast for the treatment of acute ruptures of the Achilles tendon in recreational athletes. The goals of treatment are to prevent the musculoskeletal changes that are associated with immobilization, to reduce the time needed for rehabilitation, and to facilitate an early return to work and to preinjury activities. Non-operative treatment with a functional brace also represents a feasible alternative for patients whose general condition precludes operative intervention. Additional investigations involving a larger population of patients, as well as comparison with a cohort of operatively treated patients, would strengthen decisions regarding the treatment of acute ruptures of the Achilles tendon.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
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