Effect of total contact cast immobilization on subtalar and talocrural joint motion in patients with diabetes mellitus.

Below-knee total contact casts (TCCs) are used in the treatment of neuropathic plantar ulceration.[1-5] Numerous studies, including a prospective, controlled clinical trial, have demonstrated favorable healing of neuropathic plantar ulcers with TCC.[1-5] The primary function of the TCC is to reduce pressure at the ulcer site by dispersing the load caused by body weight over the entire foot and leg surface that is in contact with the cast. In addition, the cast helps to control edema, protects the foot from external trauma, and immobilizes the foot and ankle.[1]

Factors contributing to neuropathic plantar ulceration in patients with diabetes include diminished plantar sensation; foot deformities; and limited mobility of the talocrural joint (TCJ), the subtalar joint (STJ), or the great toe metatarsophalangeal joint.[6-9] Limited joint mobility may decrease the flexibility of the foot and ankle and may increase susceptibility to ulceration.[8] Although TCC is effective in healing plantar ulcers, a potential negative side effect of immobilization may be loss of joint motion. A loss of motion may then contribute to skin breakdown.

A review of the literature reveals no articles pertaining to the effects of TCC on TCJ or STJ ROM in people with diabetes and plantar ulceration. There are some articles, however, that discuss the effect of cast immobilization on muscle, connective tissue, and joints.[10-15] Tabary et al,[10] for example, examined casting a cat's hind limb so that the soleus muscle was in a lengthened or shortened position. Various physiologic and structural changes were reported with respect to the soft tissue. Results indicated that casting in a shortened position decreased muscle extensibility and sarcomere number, whereas casting in a lengthened position increased sarcomere number.

The use of serial casting to help manage contractures in patients with head injuries or cerebral palsy is based on its known effects on muscle and connective tissue. The effect of "inhibitive casting" on passive dorsiflexion has been studied.[11] Passive ankle dorsiflexion was measured before and after inhibitive casting in children with cerebral palsy. Results indicated that passive ankle dorsiflexion ROM increased after cast treatment.

Other studies[12-15] examined the effect on ROM in the TCJ and STJ of cast immobilization for lower-extremity fractures. These studies demonstrated that joint mobility decreases following immobilization for lower-extremity fractures, but emphasized that early weight bearing is critical in minimizing losses of joint mobility. A TCC allows patients to bear weight while providing immobilization of the foot and ankle.

The effect of TCC on the joint mobility of patients with diabetes is unknown. Will TCC cause a decrease in ROM, as is typical after casting for orthopedic fracture cases, or will TCC cause ROM to improve, as is sometimes seen after use of serial casting? The purpose of this study was to determine whether, in patients with diabetes mellitus, differences in dorsiflexion and inversion/eversion ROM exist between extremities treated with TCC and those that were not casted. The null hypothesis was that there would be no significant difference in ROM between and within the casted and noncasted extremities before and after casting.

Method

Subjects

Inclusion criteria for admission to the study were that patients had to have unilateral plantar ulcers and a history of insulin- or non-insulin-dependent diabetes mellitus. Thirty-seven patients who met these criteria and who were referred to our clinic in consecutive order were the subjects. Table 1 contains descriptive data for the subjects. There were 29 male and 8 female subjects with a mean age of 54 years (SD = 11, range = 32-79). The mean age of the male subjects was 52 years (SD = 12, range = 32-72), and the mean age of the female subjects was 60 years (SD = 10, range = 47-79). Reported duration of diagnosis of diabetes mellitus was 16 years ( SD = 8, range = 3-34), with 13 subjects classified as having insulin-dependent diabetes mellitus and 24 subjects classified as having non-insulin-dependent diabetes mellitus. informed consent was obtained from all participants prior to treatment.

Table 1. Subject Descriptive Data (N = 37)
                                     X     SD   Range
Age (y)
 Overall                             54    11   32-79
 Males (n = 29)                      52    12   32-72
 Females (n = 8)                     60    10   47-79
Diagnosis
 IDDM(a)
  Males                              11
  Females                             2
 NIDDMI(b)
  Males                              18
  Females                             6
Duration of diabetes mellitus (y)
 Males                               16     8    2-34
 Females                             16    10    3-31
Ulcer duration (d)
 Males                              178   208    5-730
 Females                            321   616    7-300
Ulcer healing (d)
 Males                               38    25    6-119
 Females                             57    82    8-69
(a) IDDM = insulin-dependent diabetes mellitus.
(b) NIDDM = non-insulin-dependent diabetes mellitus.

Procedure

A below-knee TCC was used to treat the ulcers. Prior to casting, a diabetic foot evaluation was performed by one of two physical therapists (JED or MJM) as documented elsewhere.[16] Intrarater and interrater reliability had been established previously for all goniometric measurements used in the evaluation of a group of 31 patients with diabetes.[16] Intrarater/interrater intraclass correlation coefficients (ICC[2,1]) were .93/.81 for dorsiflexion, .96/.79 for eversion, and .94/.87 for inversion.

Goniometric measurements were taken with a 15.2-cm (6-in) plastic goniometer with a 2-degreeincrement scale. All measurements were done with the subject in the prone position. To measure passive STJ motion, a line was drawn that bisected the calcaneus and the lower third of the leg. Eversion and inversion measurements were obtained by aligning one arm of the goniometer with the line bisecting the calcaneus and the other arm with the line bisecting the lower third of the leg, passively inverting and everting the calcaneus, and measuring the angle in the frontal plane.[17] Active dorsiflexion was measured with subjects in the prone position, with the knee extended and the STJ in neutral alignment.[17]

A below-knee TCC was applied as described elsewhere.[5,18] The ulcer was covered with one thin layer of gauze. Cotton was placed between the toes to prevent maceration, and a stockinette was applied to the lower leg with 1/8-in felt pads applied to the malleoli and anterior tibia and a foam-rubber pad placed around the toes. The subject was positioned prone, and the leg was held by an assistant so the subject could remain relaxed with the TCJ held in neutral alignment. A total contact plaster shell was then molded around the lower leg. The shell was reinforced with plaster splints. A walking heel was mounted on a piece of 1/4-in plywood and attached to the plantar surface of the foot with plaster. A fiberglass roll was applied over the plaster for extra durability and to allow weight bearing sooner than would be possible with plaster alone. Subjects were given a written list of precautions and instructed to limit their walking to one third as much as they normally do and to use an assistive device (walker or crutch) provided to them to reduce weight bearing through the cast. Casts were removed after 5 to 7 days, and the ulcer and skin were then inspected. If there were no complications (ie, additional skin breakdown, deterioration of the ulcer, or patient refusing additional casting), the cast was reapplied and the subject was seen on a regular basis for cast changes (every 2-3 weeks) and for wound care until healing occurred. Wounds were considered healed when there was complete skin coverage with no drainage. At the time of cast changes, subjects were encouraged to move their foot and ankle. In general, the subjects moved their foot and ankle about 10 times in each plane of motion.

The TCC was discontinued when the ulcer was healed. A second evaluation was then conducted. The evaluating therapist was not allowed to know the precast ROM measurement.

Data Analysis

The measurements of dorsiflexion and inversion/eversion were analyzed with a two-way analysis of variance (ANOVA) using a mixed design (2 X 2). The factors of interest were (1) the repeated measures of pretreatment measurements versus posttreatment measurements of ROM and (2) the between-groups factor of noncasted foot (no ulcer) versus casted foot (ulcerated). We considered using a multivariate analysis of variance but did not because we considered each of the ROM measures separate dependent measures.[8] Results were considered significant at the .05 alpha level.

Results

Table 2 contains the means and standard deviations of all goniometric measures before and after casting, and those results are displayed graphically in Figures 1 through 4. Tables 3 through 6 contain the ANOVA results and indicate which of these findings were significantly different. The ANOVA results indicate the following: (1) a significant difference between precast and postcast measurements for dorsiflexion but not for any ST) motion (ie, dorsiflexion decreased by approximately 1 [degrees] on both sides [casted and noncasted], whereas STJ motion remained unchanged); (2) a significant difference between casted (ulcerated) and noncasted (nonulcerated) extremity for inversion, total ROM, and dorsiflexion (ie, the casted foot demonstrated less ROM than did the noncasted foot before and after casting); and (3) no significant interaction between the variables (ie, casting did not affect ROM of the casted leg differently than in the noncasted leg following treatment with TCC) (Tabs. 3-6).

[TABULAR DATA OMITTED]

Discussion

There was only a significant difference between pretreatment and posttreatment measures for dorsiflexion (Tab. 6). The casted and noncasted legs showed a slight decrease in dorsiflexion following treatment with TCC. Although the difference was statistically significant, the value (1 [degrees]) was quite small. There are several reasons why dorsiflexion decreased on the noncasted leg while the other leg was casted. Patients who received TCC were asked to limit their ambulation to one third their normal level. They were also instructed to decrease their step length and to use an assistive device to help decrease the pressure on their feet. These two gait modifications do not enable the TCJ to go through its normal excursion during the gait cycle. This may result in soft tissue changes similar to those that occur with an ankle that does not go through its entire ROM when a person is wearing footwear with a raised heel. Patients need to be instructed to stretch their noncasted ankle while the other is casted, and the casted ankle needs to be stretched during cast changes. We encourage a non-weight-bearing stretching program for both ankles. Weight-bearing stretching may result in increased pressure under the forefoot, thus contributing to skin breakdown. Additional research is needed to determine whether stretching exercises increase ROM in patients with diabetes and limited joint mobility.

There was no significant interaction between pretreatment/posttreatment measurements or between casted/ noncasted measurements for any ROM. Thus, TCC did not affect joint ROM in the casted extremity differently than in the noncasted extremity. We believe moving the foot and ankle at the time of cast changes and the weight-bearing[13-15] nature of the TCC are important in minimizing the effects of immobilization.

In agreement with previous reports, we found a significant difference between the ulcerated and nonulcerated extremities for inversion, total ROM, and dorsiflexion ROM prior to casting.[6-9] These findings support the hypothesis that decreased motion at the foot and ankle may contribute to plantar ulcer formation. There was no significant difference for eversion measures between the two sides. The ranges of values for dorsiflexion, inversion, and total ROM were greater than the truncated range for eversion (Tab. 2). The lack of statistical significance may be due to the fact that it is more difficult to find statistical differences between groups when the dependent measure has a narrow range of values (as seen for eversion).[19] Lack of statistical significance may also be due to the minimal difference in measures before and after casting.

Extremities with plantar ulcers had less mobility than did the extremities without ulcers (before and after casting). Additional research is needed to study limited joint motion in patients with diabetes and possible interventions to reduce the loss of motion. It remains to be seen whether medication, joint mobilization, or ROM exercises decrease limited joint motion and reduce the chance of subsequent ulceration. A preliminary study[20] described improvements in ROM of patients with limited joint motion and diabetes using an aldose reductase-inhibiting agent, but additional research is clearly needed.

Conclusions

Consistent with other reports in the literature, the ulcers of the subjects in this study healed after an average of 42 days of treatment with TCC. Subtalar joint motion was unchanged, but dorsiflexion was decreased slightly in the casted and noncasted extremities following casting. Treatment with TCC did not affect the casted leg differently than the noncasted leg (ie, there was no significant interaction between pretreatment/posttreatment ROM or between casted/noncasted extremity ROM). Inversion, eversion, and dorsiflexion ROMs were less in the ulcerated extremity than in the nonulcerated extremity. These findings support the hypothesis that limited joint motion may contribute to plantar ulceration. We believe the detrimental effects of TCC (ie, decreased dorsiflexion) may be minimized by an exercise program and are minor in view of the documented beneficial effects of TCC on ulcer healing.

References

[1] Mueller MJ, Diarnond JE, Sinacore DR, Delitto A. Total contact casting in treatment of diabetic plantar ulcers: controlled clinical trial. Diabetes Care. 1989;12:384-388. [2] Pollard JP, LeQuesne LP. Method of healing diabetic forefoot ulcers. Br Med J 1983;286: 436-437. [3] Helm PA, Walker SC, Pullium G. Total contact casting in diabetic patients with neuropathic foot ulcers. Arch Phys Med Rehabil. 1984;65:691-693. [4] Boulton AJM, Bonker JH, Gadiam M, et al. Use of plaster casts in the management of diabetic neuropathic foot ulcers. Diabetes Care. 1986;9:149-152. [5] Sinacore DR, Mueller Mj, Diamond JE, et al. Diabetic plantar ulcers treated by total contact casting: a clinical report. Phys Ther. 1987;67: 1543-1549. [6] Femando DJ, Masson EA, Veves A, et al. Relationship of limited joint mobility to abnormal foot pressures and diabetic foot ulceration. Diabetes Care. 1991;14:8-11. [7] Birke JA, Cornwall MW, Jackson M. Relationship between hallux limitus and ulceration of the great toe. Journal of orthopaedic and Sports Physical Therapy. 1988; 10: 172-176. [8] Mueller MJ, Diamond JE, Delitto A, Sinacore DR. Insensitivity, limited joint mobility, and plantar ulcers in patients with diabetes mellitus. Phys Ther. 1989;69:453-462. [9] Delbridge L, Perry P, Marr S, et al. Limited joint mobility in the diabetic foot: relationship to neuropathic ulceration. Diabetic Med. 1988; 5:333-337. [10] Tabary JC, Tabary C, Tardieu C, et al. Physiological and structural changes in the cat's soleus muscle due to immobilization at different lengths by plaster casts. J Physiol (Paris). 1972; 224:231-244, [11] Watt J, Sims D, Harchkham F, et al. A prospective study of inhibitive casting as an adjunct to physiotherapy for cerebral-palsied children. Dev Med Child Neurol 1986;28:480-488. [12] McMaster M. Disability of the hindfoot after fracture of the tibial shaft. J Bone Joint Surg [Br]. 1976;58:90-93. [13] Peter RE, Bachelin P, Fritschy D. Skiers' lower leg shaft fracture outcome in 91 cases treated conservatively with Sarmiento's brace. Journal of Orthopaedic and Sports Physical Therapy. 1988;16:486-491. [14] Pun WK, Orth MC, Chow SP, et al. A study of function and residual joint stiffness after functional bracing of tibial shaft fractures. Clin Orthop. 1991;267:157-163. [15] Ahl T, Dalen N, Selvik G. Mobilization after operation of ankle fractures: good results of early motion and weight bearing. Acta Orthop Scand. 1988;59:302-306. [16] Diamond JE, Mueller MJ, Delitto A, Sinacore DR. Reliability of a diabetic foot evaluation. Phys Ther. 1989;69:797-802. [17] McPoil TG, Brocato RS. The foot and ankle: biomechanical evaluation and treatment. In: Gould JA, Davies GJ, eds. orthopaedic and Sports Physical Therapy, St Louis, Mo: CV Mosby Co; 1990:293-322 [18] Coleman WC, Brand PW, Birke JA. The total contact cast: a therapy for plantar ulceration on insensitive feet. J Am Podiatr Med Assoc. 1984;74:548-552. [19] Lahey MA, Dowey RG, Saal FE. Intraclass correlations: There's more there than meets the eye. Psychol Bull. 1983;93:586-595 [20] Eaton RP, Sibbitt WL, Harsh A. The effect of an aldose reductase inhibiting agent on limited joint mobility in diabetic patients. Jama. 1985;253:1437-1440.

JE Diamond, PT, is Physical Therapy Orthopaedics Supervisor, Department of Physical Therapy, Irene Walter Johnson Rehabilitation Institute, Washington University Medical School, 509 S Euclid Ave, St Louis, MO 63110 (USA). Address all correspondence to Mr Diamond.

MJ Mueller, PhD, PT, is Instructor, Program in Physical Therapy, Washington Universitv School of Medicine.

A Delitto, PhD, PT, was Assistant Professor, Program in Physical Therapy, Washington University School of Medicine, when this study was conducted. He is now Assistant Professor, Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh Medical Center, 101 Pennsylvania Hall, Pittsburgh, PA 15261.