Subtalar Joint Neutral Positions and Drop Test

Transcription

1 A R C H S T U D Y.. Reliability of Open and Closed Kinetic Chain Subtalar Joint Neutral Positions and Drop Test Ann Marie Picciano, MS, PT, ATC' Megan S. Rowlands, MS, PT2 Teddy Worrell, EdD, PT, SCS, ATC3 T he subtalar joint is described as a single-axis joint with triplanar motions that traverse all three cardinal planes (9). These triplanar motions are called pronation and supination and can be described in both the open kinetic chain (OKC)(non- weight-bearing position) and the closed kinetic chain (CKC) (weightbearing position). Pronation in the OKC is described as simultaneous calcaneal eversion with foot abduction and dorsiflexion. Closed kinetic chain pronation occurs with calcaneal eversion, but the foot remains fixed, causing the talus to move into adduction and plantarflexion (8). Open kinetic chain supination occurs with calcaneal inversion with foot adduction and plantarflexion and changes to calcaneal inversion with talar abduction and dorsiflexion in the CKC (8). In OKC pronation and supination, the motions occur at the subtalar joint with the calcaneus moving on a relatively still talus. The difference in CKC movement occurs because the calcaneus and foot are fixed, ground reaction forces come into play, and the talus becomes a moving structure. Closed kinetic chain movement occurs not only at the subtalar joint but also at the forefoot, midtarsal joint, and talocrural joint (9). JOSPT Volume 18 Number 4 October 1993 Subtalar joint (ST/) measurements are commonly made in the clinic to assess foot and ankle positions because of the high incidence of lower extremity dysfunctions. The purposes of this study were to investigate the intratester and intertester reliability of the open kinetic chain subtalar joint neutral (OKC STIN) and closed kinetic chain subtalar joint neutral (CKC STIN) positions and the navicular drop test (NDT). Two inexperienced testers performed repeated measurements on 15 subjects (N = 30 feet) during two testing sessions. lntratester and intertester reliability (ICC 1,I) and standard error of measurement (SEMI were determined for each dependent variable. For OKC STIN, the intratester ICC values were.06 and.27, and the intertester ICC value was.00. The intratester SEM values were 1.81 and 2.29; and the intertester was '. The CKC STIN intratester ICC values were.14 and. 18, with SEM values of 2.46 and 2.40'. The intertester CKC ICC value was.is, with an SEM of 2.43'. For the NDT, the intratester ICC values were.6 1 and.79, and the SEM values were 1.92 mm and 2.57 mm. The intertester ICC value was.57 and the SEM was 2.72 mm. The results reveal that both OKC and CKC STIN yield poor intratester and intertester reliability and the NDT yields poor to moderate intratester reliability and poor intertester reliability. We conclude that these foot and ankle measurements are not reliable when performed by inexperienced testers. Therefore, clinicians should practice these measurement techniques and determine their measurement error. Key Words: reliability, subtalar, navicular ' Associate Physical Therapist/Athletic Trainer, The PT Center for Sports Medicine and Family Physical Therapy, Akron, OH. Ms. Picciano was formerly a graduate student at the University of Indianapolis Krannert Craduate School of Physical Therapy, Indianapolis, IN. Contract Therapist, Wisconsin. Ms. Rowlands was formerly a graduate student at the University of Indianapolis Krannert Craduate School of Physical Therapy, Indianapolis, IN. Assistant Professor of Physical Therapy, University of Indianapolis, Krannert Graduate School of Physical Theraov East Hanna Ave.. Indianamlis. IN It is often necessary to evaluate the OKC and CKC subtalar joint function in patients with various lower extremity and back dysfunctions in the OKC and CKC (1 8). An evaluation of this joint commonly includes measuring the position of subtalar joint neutral (STJN), the position where neither pronation nor supination occurs (1 3). One accepted method for measuring STJN was described by Root et a1 (1 3) and later modified in detail by Elveru et a1 (5). The method for measuring STJN, as described by Elveru et a1 (5), requires that the subject is positioned prone in the OKC, and the head of the talus is palpated for bilateral congruency while the forefoot is passively pronated, and the ankle is dorsiflexed until a soft end feel is reached. The position of the calcaneus in relation to the lower third of the leg is then measured with a goniometer. Elveru et a1 (4) used this method

2 and reported the intratester and intertester reliability of 14 inexperienced testers who measured 50 feet. They determined that the intratester reliability for OKC STJN was.77 (ICC 1.1). and the intertester reliability was.25. These researchers concluded that their methods were moderately reliable when performed by one tester. They further reported that their methods had limited clinical usefulness due to the low intertester reliability (4). Diamond et al (3) examined the interrater and intrarater reliability of various foot and ankle measurements common to a diabetic foot evaluation. The two testers in this study participated over an 18-month period in 20 training sessions which provided instruction on the specific measurements to be investigated. Both feet of 31 volunteers were measured. The intratester reliabilities (ICC 2,l) for OKC STJN were.74 for right feet and.96 for left feet, and the intertester reliabilities were.62 and.79, respectively. The authors concluded that therapists who train extensively can take many clinical foot and ankle measurements reliably in the diabetic population. Smith-Oricchio and Harris (1 5) also investigated measuring OKC STJN; however, they only reported the intertester reliability (ICC 3,l). They used three experienced testers and 20 subjects recently diagnosed with ankle pathologies. They reported a.60 reliability for OKC STJN. The researchers then performed several calcaneal measurements in both OKC and CKC. They concluded that the OKC STJN method had moderate intertester reliability. They further concluded that intertester reliability for CKC measurements (ICC =.75 and.95) was superior to that of OKC measurements because the error of passive foot positioning was eliminated in the CKC (1 5). Lattanza et al (7) measured and compared the amount of calcaneal eversion in OKC vs. CKC and re- ported that subtalar joint eversion was significantly greater in the CKC. They suggest that OKC evaluation may not provide accurate information about subtalar joint motion and function; therefore, they strongly encourage CKC subtalar joint evaluation. One method of CKC subtalar evaluation (1 5) involves measuring calcaneal eversion in a standing position, which only addresses the coronal plane component of the subtalar triplanar motion (1 1). Pronation in the CKC also includes plantarflexion, a sagittal plane motion, and adduction, a transverse plane motion (8.12). Pronation is a normal component of gait. However, if the amount Motion at the midtarsal joint is dependent upon the position of the subtalar join t. of pronation is great enough, it will cause the medial longitudinal arch to drop (1 0). Because of this effect on the medial longitudinal arch, excessive subtalar pronation has been linked to various lower extremity dysfunctions, such as metatarsalgia, plantar fascitis, medial knee pain, and stress fractures (1 8). Therefore, assessment of talar motions is important when evaluating the subtalar joint. It is not addressed by the methods that only measure calcaneal eversion in the CKC. Brody (2) described an alternate method, the navicular drop test (NDT), which addresses the plantarflexion component of talar motion and can be used to assess the amount of subtalar pronation. The NDT en- tails marking the navicular tuberosity and measuring the distance it drops from CKC STJN to a position of relaxed bilateral stance, also described as the resting calcaneal stance position (13). Brody (2) reports that a difference greater than 15 mm (5h in) is considered to be an abnormal amount of pronation; however, he does not provide data to support this statement. The navicular and the cuboid articulate with the talus and calcaneus to form the midtarsal joint. Motion at the midtarsal joint is dependent upon the position of the subtalar joint (9,17). Subotnick (17) reports that there is an intimate relationship between these two joints and that they are interdependent upon each other for proper functioning. Because of this relationship, Brody (2) suggests that the NDT can be used to assess subtalar joint function in the CKC. The OKC STJN literature reports that reliability using a single tester varies from moderate (4) to high (3) based on the tester's experience. The reliability between testers decreases to moderate for experienced testers (3,15) and poor for inexperienced testers (4). The literature further states that reliability improves when applied to the CKC (15) and that CKC measurement values differ from OKC values (7). In addition, the CKC evaluation provides more accurate information regarding STJ position and movement in weight bearing-the position of most activities (7). After reviewing the literature on CKC STJ evaluation, the two studies found have reported STJ range of motion (ROM) and calcaneal position measurement reliability (7,15). We have been unable to locate any studies that assess CKC STJN reliability. The purposes of this study were to use inexperienced testers to investigate the intratester and intertester reliabilities of the following: I) OKC STJN, 2) CKC STJN, and 3) the NDT. Volume 18 Number 4 October 1993 JOSPT

3 METHODS Subjects Fifteen subjects volunteered to participate in this study ( x age = years, height = cm, x weight = 65.9 kg). All subjects denied any neurological or orthopaedic pathology that may have affected their lower extremities. Prior to participation, each subject was informed of the purpose and procedure of the study and signed a consent form which was approved by the Univer- Reasons for the low reliability of the open and closed kinetic chain methods may be attributed to the inexperience of the testers and to the difficulty of drawing accurate bisections of the lower leg and calcaneus. sity Committee on Research Involving Human Subjects. Each foot was treated independently, therefore, the data were collected on 30 feet (N = 30 feet). Testers All measurements were made by two inexperienced physical therapy students. The two testers (MSR and AMP) were instructed in the three measurements used in this study by a physical therapist with 5 years of experience and who uses these measurements in clinical practice. One 2- hour training session was held. JOSPT Volume 18 Number 4 October 1993 Instrumentation One 6-in universal plastic goniometer with 1 " increments was used with the scale facing the tester, covered by opaque tape to prevent any bias from previous readings. The goniometer was accurate to 1 ". To record the measurements, the other tester read the reverse side of the goniometer. A caliper was used to bisect the lower one-third of the leg (14), and a flexible ruler was used for bisecting the calcaneus. An elevated wooden box measuring 14W X 14L X 15H in was used as a platform for the CKC measurements. MEASUREMENT PROCEDURES Open Kinetic Chain Subtalar Joint Neutral The procedure for this measurement was based upon the methods described by Elveru et al (5) and Smith-Oricchio and Harris (1 5). The subject assumed a prone position, with the foot and ankle to be measured extended approximately 6 in off the plinth and the opposite lower extremity placed in a position of hip flexion, external rotation, abduction, and knee flexion (5,15). No specific randomization was established for measuring the right or left foot first. Each subject was asked to assume the measuring position without specifying which foot would be measured first. Tester 1 began by using a caliper (15) to bisect the lower one-third of the leg (Figure 1). The caliper was positioned at the medial and lateral borders of the lower leg approximately 8 in above the calcaneus, and a mark was placed at the midpoint with a water soluble marker. The caliper placement was repeated approximately 6 in above the calcaneus, and another mark was placed at the midpoint. A vertical line was drawn with a straight - ed, me to create the bisection line. The next step was to bisect the calcaneus. Elveru et al (5) chose to visually bisect the calcaneus because they found that a calcaneal bisection line did not accurately represent calcaneal position during STJ ROM measurements secondary to skin movement when the joint was moved. During the literature review and practice sessions prior to initiation of this study, the authors determined that objectively bisecting the calcaneus (13.1 5,18,) was a more utilized and accurate method of measuring STJN. Thus, we chose to draw a calcaneal bisection line. Midpoints at both the superior and inferior as- FIGURE 1. A caliper is used to find two midpoints for bisecting the lower third of the leg. This line is used for both the open kinetic chain subtalar joint neutral (OKC STIN) and closed kinetic chain subtalar joint neutral (CKC STIN) measurements.

4 pects of the calcaneus were found by palpating the medial and lateral borders of the calcaneus and drawing a dot at each midpoint located by using a flexible ruler. Connecting these points created the bisection line. Tester 1 then placed the subject's foot in STJN by palpating the medial and lateral aspects of the head of the talus with the thumb and index finger of the medial hand. The thumb of the lateral hand was placed on the plantar surface of the fourth and fifth metatarsal heads and was used to pronate and supinate the subtalar joint until the medial and lateral heads of the talus were equally positioned between the tester's fingers. The foot was then pushed into slight dorsiflexion with the lateral hand in order to hold the STJN position. Using the medial hand, Tester 1 aligned the goniometer with the bisection lines of the leg and calcaneus with the axis located between the malleoli. The angle was read and recorded by the other tester. The foot was then released and allowed to return to resting position and the OKC STJN measurement was repeated by Tester 1 to establish two values for this measurement. Closed Kinetic Chain Subtalar Joint Neutral The subject was asked to stand on the wooden box. Tester 1 instructed the subject to place one foot in front of the other without extending off the box to create a unilateral stance position with the weight on the foot to be measured. Each subject held onto a rack mounted on the wall in front of them for balance. Unilateral stance was used to simulate the midstance position of gait in which the STJ should be in the neutral position (8.9.12). Tester 1 used the palpation technique to feel for talar dome congruency, placed the subject's foot in STJN if necessary, and aligned the goniometer in the same manner as for the OKC meas- urement (5). Again, the angle was read and recorded by the other tester (Figure 2). The measured foot was released, and the subject was allowed to return to bilateral resting stance position. Then the CKC STJN measurement was repeated by Tester 1 to obtain two values. Navicular Drop Test While performing the OKC measurements, a dot was drawn over the most prominent aspect of the navicular tuberosity in preparation for this measurement (2). The location of the mark was determined by palpating the tuberosity, holding the thumb just beneath the most prominent point, and then drawing the dot just above the thumb. For the NDT, subjects remained on the box in a bilateral stance position (2) and were instructed to place most of their weight on the opposite lower extremity but to keep the foot FIGURE 2. For measuring closed kinetic chain subtalar joint neutral (CKC STIN), the subtalar joint (ST/) is placed in neutral and a goniometer is aligned with the lower leg and calcaneal bisection lines. being measured in contact with the box. Tester 1 placed the foot in STJN, then aligned an index card perpendicular to the medial side of the foot and placed a mark on the index card at the level of the dot on the navicular tuberosity. The subject was then asked to stand with both feet bearing equal weight, and another mark was placed on the card at the level of the navicular tuberosity. The distance between the two marks on the card (measured in mm) represented the distance the navicular tuberosity dropped from the STJN position to a position of relaxed bilateral stance. This method was repeated to obtain a second value for the NDT. All marks were removed from the subject's lower legs and feet and the entire procedure was repeated with Tester 2 performing all the measurements and Tester 1 recording. One week later, the subjects returned and another interview guaranteed that no injury or pathology had occurred between testings. The entire procedure for both testers was repeated. Data Analysis The two values for each measurement were averaged and the mean values were obtained. With this sample of subjects, all OKC calcaneal measurements were either zero or a varus position, and all CKC measurements were either zero or a valgus position. The intratester reliability was determined by comparing Tester 1's 30 mean values from the first testing session with the 30 mean values from the second testing session. The same procedure was followed for the mean values of Tester 2. The intraclass correlation coefficient (ICC 1,l) described by Shrout and Fleiss (14) was utilized to describe the degree of reliability of the 30 measurements for each tester. The intertester reliability was determined by combining the two sessions into one and comparing the Volume 18 Number 4 October 1993 JOSPT

5 60 mean values of Tester 1 with the 60 mean values of Tester 2. Again the intertester reliability was obtained by using the intraclass correlation coefficient (ICC 1.1) (1 4) to describe the reliability. The standard error of measurement (SEM) was obtained to determine the actual number of degrees or mm the measurement values differed (1). A 95% confidence interval (1.96 SEM) was determined for all variables and testers. ICC [I, I ] = lntraclass correlation coeiiicient. SEM = Standard error of the measurement. OKC SJ/N = Open kinetic chain subtalar joint CKC SJ/N = Closed kinetic chain subtalar joint NDT = Navicular drop test. TABLE 2. lntratester and intertester reliability and standard error of measurement. RESULTS The means, standard deviations, and ranges for each measurement are summarized in Table 1. Open kinetic chain STJN intratester reliability and SEM were.27 and " for Tester 1 and.06 and 2.29" for Tester 2. Open kinetic chain STJN intertester reliability was 0.00, with a SEM of 2.51 ". Closed kinetic chain STJN intratester reliability and SEM values were.14 and 2.46" for Tester 1 and.18 and 2.40" for Tester 2. Closed kinetic chain STJN intertester reliability and SEM were.15 and 2.43", respectively. Navicular drop test measurements revealed an intratester reliability of.61 and.79, with SEM values of 2.57 mm and 1.92 mm. Navicular drop test intertester reliability was.57, and the SEM was 2.72 mm (Table 2). The 95% confidence intervals are reported in Table 3. OKC STJN* CKC STJN* NDTt Degrees. t Millimeters. OKC STIN = Open kinetic chain subtalar joint CKC STIN = Closed kinetic chain subtalar joint NDT = Navicular drop test. TABLE 1. Descriptive statistics of the dependent variables. JOSPT Volume 18 Number 4 October 1993 lntratester Tester 1 Tester 2 Intertester OKC STJN' CKC STJN* NDTt ' Degrees. t Millimeters. OKC STIN = Open kinetic chain subtalar joint CKC STIN = Closed kinetic chain subtalar joint NDT = Navicular drop test. TABLE 3.95% confidence intervals. DISCUSSION The results indicate a reliability far lower than what the literature reports for OKC STJN. These results do, however, support Elveru et al (4) and indicate that the OKC STJN method of evaluation yields poor intertester reliability when performed by inexperienced testers and has limited clinical usefulness. The results do not support the findings of Smith-Oricchio and Harris (1 5), who used one tester with 1 year of experience and two testers who each had 2 years of experience in an orthotic clinic. They reported moderate reliability for OKC STJN. These ICC values are considerably lower than those reported by Diamond et al (3), who reported that testers who trained extensively in the methods had good OKC STJN reliability. The reliability for the CKC STJN measurement in this study is also poor and does not support the claim by Smith-Oricchio and Harris (1 5) that reliability improves when applied to the CKC. The intertester reliability was higher for CKC (ICC =.15) than for OKC (ICC = 0.00), however, not high enough to make this method a reliable clinical tool as performed by these two testers. Reasons for the low reliability of the open and closed kinetic chain methods may be attributed to the inexperience of the testers and to the difficulty of drawing accurate bisections of the lower leg and calcaneus. Due to the bony configurations and the rotation that existed between the leg and foot of many subjects, the bisection lines did not coincide exactly. Therefore, instead of aligning the goniometer on both lines, it was necessary to align the goniometer exactly on one bisection line and parallel to the other bisection line for some subjects (1 3). The NDT yields poor to moderate intratester reliability ( ) and poor intertester reliability (.57). The supposition by Brody that arch height could be used to categorize foot types has been questioned in recent literature based on the anatomical variability among individuals (6). Placing the STJ in the neutral position is the primary source of error for this measurement as well as marking the navicular tuberosity for repeated measurements. Elveru et al (4) and Smith-Oric-

6 chi0 and Harris (1 5) reported ICC as their index of reliability and did not report the SEM. Stratford (1 6) demonstrated that the SEM and ICC reveal different information concerning measurement consistency. Stratford (16) states that because the ICC is a numerical representation of classical test theory's version of reliability, it does not directly portray consistency, whereas consistency between repetitions is represented by the SEM because it is reported in the same units as the actual measurement. He recommends that both the ICC and the SEM be reported for reliability studies. The SEM was used to further evaluate the reliability for the NDT which when using the ICC values yielded moderate intratester reliability. The mean value for the NDT was 9.0 mm (Table 1). and the intratester SEM values (Table 2) were 2.57 mm and 1.92 mm. The 95% confidence intervals for Tester 1 and 2 were mm and mm, respectively. These data indicate that when the NDT is performed by a single tester, the value should fall within these ranges 95% of the time. Because these ranges are so large, we feel that the NDT is not a reliable clinical measurement. The same analysis of the SEM and mean holds true for the intratester OKC and CKC STJN. The SEM values are large (OKC = 1.81 and 2.2g0, CKC = 2.46 and 2.40") when compared to the means (OKC = 4.0, CKC = 4.0"). This in conjunction with the large confidence intervals further reinforces that these measurements, as performed in this study, are not reliable in the clinic. This analysis is also true for the intertester values for all measurements. Although the results of this study indicate that the STJ measurements commonly used in a clinical foot evaluation are unreliable, the study by Diamond et al (3) provides additional insight. These researchers studied OKC STJN and many other footlankle measurements, including inversion, eversion, dorsiflexion, calcaneal stance position, tibia1 varum, and forefoot and rearfoot relationship in STJN, and found these measurements to be reliable when the testers had undergone extensive training in the specific methods studied. The results of this study indicate that OKC STJN, CKC STJN, and NDT cannot be performed reliably in the clinic by inexperienced testers. Physical therapists who perform foot and ankle evaluations should practice taking specific ankle and subtalar measurements and perform repeated measures to determine their own reliability and SEM. CONCLUSIONS Data from the subtalar joint neutral measurements described in this study of inexperienced testers reveal that both open kinetic chain and closed kinetic chain methods yielded poor intratester and intertester reliability and that the navicular drop test yielded poor to moderate intratester and poor intertester reliability. Additional studies are needed to report the intratester and intertester ICC, SEM, and confidence intervals for experienced testers as well as the optimum frequency, duration, and content of a training session for inexperienced testers to improve their reliability while taking foot and ankle measurements. JOSPT REFERENCES I. Baumgartner TA: Norm-referenced measurement: Reliability. In: Safrit, Woods (eds), Measurement Concepts in Physical Education and Exercise Science, pp Champaign, IL: Human Kinetics Publishers, Brody D: Techniques in evaluation and treatment of the injured runner. 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I Orthop Sports Phys Ther 7(2):69-72, Moore KL: Clinically Oriented Anatomy, Baltimore: Williams & Wilkins, 1980 I 1. Oatis CA: Biomechanics of the foot andankle under static conditions. Phys Ther 68(12): , Root M, Orien W, Weed I, Hughes R: Biomechanical Examination of the Foot (Vol I), Los Angeles: Clinical Biomechanics Corporation, Root M, Orien W, Weed I: Clinical Biomechanics (Vol2): Normal and Abnormal Functions of the Foot, Los Angeles: Clinical Biomechanics Corporation, Shrout PE, Fleiss jl: lntraclass correlations: Uses in assessing rater reliability. Psycho1 Bull 86(2): , Smith-Oricchio K, Harris BA: lnterrater reliability of subtalar neutral, calcaneal inversion and eversion. I Orthop Sports Phys Ther 12(1): 10-15, Stratford P: Reliability: Consistency of differentiating among subjects! Phys Ther 69(4): , Subotnick 51: Biomechanics of the subtala and midtarsal joints. I Am Podiatr Med Assoc 65(8): , Vogelbach WD, Combs LC: A biomechanical approach to the management of chronic lower extremity pathologies as they relate to excessive pronation. Athl Train 22:6-16, Volume 18 Number 4 October 1993 JOSPT