Achilles Tendon After Percutaneous Surgical Repair: Serial MRI Observation of Uncomplicated Healing

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1 MRI of Achilles Tendon Musculoskeletal Imaging Original Research Akira Fujikawa 1 Yukishige Kyoto 1 Masahisa Kawaguchi 2 Yutaka Naoi 1 Yo Ukegawa 2 Fujikawa A, Kyoto Y, Kawaguchi M, Naoi Y, Ukegawa Y Keywords: Achilles tendon, MRI, orthopedic surgery DOI:1.2214/AJR Received March 16, 27; accepted after revision May 19, Department of Radiology, Japan Self-Defense Forces Central Hospital, , Ikejiri, Setagaya, Tokyo , Japan. Address correspondence to A. Fujikawa. 2 Department of Orthopedic Surgery, Japan Self-Defense Forces Central Hospital, Tokyo, Japan. AJR 27; 189: X/7/ American Roentgen Ray Society Achilles Tendon After Percutaneous Surgical Repair: Serial MRI Observation of Uncomplicated Healing OBJECTIVE. The purpose of this study was to prospectively explore the MRI features of normal healing of the expected residual tendon gap in the Achilles tendon after percutaneous surgical repair. SUBJECTS AND METHODS. MR images of the Achilles tendon were obtained approximately 4, 8, and 12 weeks after surgery. Assessment of MR images was focused on the presence of residual tendon gap and gap length, Achilles tendon contour, and contrast enhancement in the ruptured area. Cases of open surgical repair were used for comparison. We attempted to statistically compare the timing of tendon gap disappearance within the percutaneous surgical repair group and between the percutaneous and open surgical repair groups. RESULTS. A total of 3 tendons repaired with percutaneous surgical technique and 1 repaired with open surgical technique were evaluated. At the first, second, and third MRI sessions of the percutaneous surgical repair group, a residual gap was found in 1%, 8%, and none of the tendons on T1-weighted images and in 87%, 63%, and none of the tendons on T2- weighted images. Achilles tendon contour was visualized in 3%, 9%, and 1% of the tendons on T1-weighted images and 9%, 1%, and 1% of the tendons on T2-weighted images. Intratendinous enhancement was present in 1%, 73%, and 7% of the tendons in the percutaneous surgical repair group. Ring-shaped peritendinous enhancement was recognized at the third session in all subjects. A significantly longer time was required for tendon gap disappearance after percutaneous than after open surgical repair. CONCLUSION. The time course of the MR findings in the ruptured Achilles tendon after percutaneous surgical repair appears to reflect regular healing. reatments of patients with acute T Achilles tendon rupture include open surgical repair, conservative therapy, and percutaneous surgical repair [1]. Percutaneous surgical repair is aimed at fusion of the ruptured area by suturing the Achilles tendon and pulling the ruptured tendon ends toward each other, inducing fixation of the tendon ends [2, 3] (Fig. 1). Compared with open surgical repair, percutaneous surgical repair is simpler to perform, yields cosmetically more favorable outcome, and causes postoperative infection less frequently. Percutaneous repair, however, carries higher risk of postoperative rerupture and sural nerve injury [3]. Because the optimal management after percutaneous surgical repair is controversial at our institution, we needed a means of objective investigation of Achilles tendons repaired with percutaneous surgical technique. For postoperative management of a ruptured Achilles tendon, knowledge of the baseline MRI features of the surgically treated tendon is useful for evaluating postoperative complications and rehabilitation protocols. Most previous studies [4, 5] of postoperative MRI of ruptured Achilles tendons, however, have pertained mostly to open surgical repair. When a ruptured Achilles tendon is repaired with percutaneous technique, the contact between the two ends of the ruptured tendon is incomplete, and, theoretically, a residual gap persists postoperatively. Using MRI, we examined how the inevitable gap in the tendon after percutaneous surgical repair improves over time and when the gap eventually disappears. Subjects and Methods Patients The medical ethics committee at our institution approved the study. The subjects were patients whose condition had been diagnosed as acute complete Achilles tendon rupture on the basis AJR:189, November

2 Fig. 1 Diagram shows percutaneous surgical repair of Achilles tendon rupture. Six stab incisions, three on medial and three on lateral aspect of tendon, are placed at levels proximal and distal to rupture. Needles and sutures (dashed line) are passed so that sutures are pulled to firmly appose ruptured tendon ends. Contact between two ends of ruptured tendon is incomplete. of physical examination findings including a positive result of a Thompson test and a palpable tendon defect and findings on low-voltage radiography of the Achilles tendon. All patients had undergone percutaneous surgical repair or open surgical repair within 1 week of the diagnosis. Before enrollment, each patient was informed about the design of the study and provided written consent. Selection of the treatment method was based on talks between the orthopedic surgeons and each patient. For 2 weeks after surgery, the treated leg was kept in a cast in the equinus position with no weight bearing. From the third to sixth weeks after surgery, the degree of dorsiflexion of the ankle of the cast-immobilized leg was gradually decreased, and partial weight bearing was started. Seven weeks after surgery, the cast was removed, and full weight bearing was begun. Patients underwent follow-up at an outpatient orthopedic surgical clinic for approximately 3 months after surgery. MRI Schedule MRI of the Achilles tendon was performed approximately 4 weeks (3 5 weeks) (Figs. 2A 2D), 8 weeks (7 9 weeks) (Figs. 2E 2H), and 12 weeks (11 13 weeks) (Figs. 2I 2L) after surgery. Imaging Protocol We used a 1.5-T MRI system (Signa Horizon, GE Yokogawa Medical Systems) with a commercially available quadrature cervical spinal coil or knee coil. During MRI, the patient remained in the supine position with the affected Achilles tendon placed on the coil. The affected leg was positioned so that the ruptured site on the Achilles tendon was covered on the sagittal scout-view image. The protocols were axial fat-suppressed spin-echo T1-weighted images (TR/ TE, 66/17), axial and sagittal fast spin-echo T2- weighted images (3,5/84), and contrast-enhanced axial fat-suppressed spin-echo T1-weighted images (66/17). Axial images were obtained with a 4-mm section thickness, 2-mm gap, cm field of view, matrix, and 2 signals averaged. Sagittal images were obtained with a 3-mm section thickness, 1-mm gap, cm field of view, matrix, and 2 signals averaged. For contrast-enhanced MRI, gadopentetate dimeglumine (.1 mmol/kg body weight, Magnevist, Schering [now Bayer Schering Pharma AG]) or gadodiamide hydrate (.1 mmol/kg body weight, Omniscan, Daiichi [now GE Healthcare]) was administered IV. Assessment Images were evaluated by two radiologists, both blinded to the clinical data. The assessments were based on consensus between the radiologists. Presence or absence of tendon gap and gap length Sagittal images were not used because measuring the gap length was difficult owing to the brushlike appearance of the ends of ruptured tendon (Figs. 2D, 2H, and 2L). Therefore, only axial images were used for tendon gap evaluation. According to the definition of tendon gap used in this study, a tendon gap was judged present in cases in which no area of hypointensity comparable with that of the neighboring tendon was visible in the space that had probably been occupied by the Achilles tendon before rupture (Figs. 2A 2C). Even when the contour of the Achilles tendon was visible on axial images and some hypointensity was visible within this area, a tendon gap was judged present if the hypointense area within the contour was macroscopically smaller than approximately one fourth of the contour or if the areas of hypointensity had a dotted distribution (Figs. 2E 2G). Gap length was calculated by multiplying 6 mm (the sum of the slice thickness of 4 mm and the slice gap of 2 mm) by the number of axial images showing a tendon gap. Gap lengths thus were in multiples of 6 ± 2 mm, considering error in the first and last slices. Because the cast was removed 7 weeks after surgery, the findings at Achilles tendon palpation conducted by orthopedic surgeons on the days of the second and third MRI sessions were analyzed in relation to the presence or absence of a tendon gap on MR images. Presence or absence of the contour of the Achilles tendon at the rupture site If an area showing the contour of the Achilles tendon was visible on all axial images at the rupture site, this area was referred to as the compartment of the Achilles tendon, whether or not the signal intensity within this area was low enough to indicate the presence of Achilles tendon fibers (Figs. 2A 2C). Presence or absence of contrast enhancement at the rupture site The finding of contrast enhancement within the ruptured part of the tendon or within the incompletely repaired tendon was deemed to indicate the presence of intratendinous enhancement whether or not enhancement was homogeneous or inhomogeneous (Figs. 2C, 2G, and 2K). The finding of contrast enhancement around the compartment of the Achilles tendon or around the incompletely repaired Achilles tendon was deemed to indicate peritendinous enhancement (Figs. 2G and 2K). Statistical Analysis Comparison within the percutaneous surgical repair group To analyze the time course of the gap after percutaneous surgical repair, the data from the first MRI session were compared with those from the second and third sessions by use of the Wilcoxon s signed rank test. Rather than using the test designed for assessing the independence of the two groups to compare the tendon gap disappearance rate between T1-weighted and T2-weighted images, because our results were paired data obtained from the same patients, the results were subjected to the McNemar test for paired data. Comparison between the percutaneous and open surgical repair groups For comparison between the percutaneous and open surgical repair groups, T1-weighted images and T2-weighted images were separately analyzed for statistically significant differences. The timing of tendon gap disappearance in the two groups was compared by use of the Mann-Whitney U test. The percentage of tendons exhibiting gap disappearance was compared between the two groups for each MRI session by use of Fisher s exact test. The cumulative gap disappearance rate was calculated with the Kaplan-Meier method, and gap disappearance thereby was deemed an event. During this calculation, cases of rerupture and cases in which the patient did not complete the study protocol were excluded from the population serving as the denominator. The log-rank test was used for comparison of the cumulative gap disappearance rate between the two groups. Data processing and statistical analyses were performed with the computer program SAS release 8.2 TS2M (SAS Institute). 117 AJR:189, November 27

3 MRI of Achilles Tendon A B C D E F G H I J K L Fig year-old man with ruptured Achilles tendon after percutaneous surgical repair. A L, Serial MR images obtained 28 days (A D), 57 days (E H), and 87 days (I L) after surgery. Disappearance of tendon gap appears earlier on T2-weighted images (A, E, and I) than on T1-weighted images (B, F, and J). Contrast-enhanced T1-weighted images (C, G, and K) show decrease in intratendon enhancement and increase in peritendon enhancement as ring-shaped appearance over time. Sagittal images (D, H, and L) were not used for measurement of gap length because of difficulty measuring precise length. Results Patients Between January 2 and June 24, 49 patients who had undergone surgical treatment of Achilles tendon rupture were enrolled in this study. Two patients had bilateral Achilles tendon ruptures, the timing of the rupture differing between the two sides. In total, 51 surgically treated Achilles tendons were studied. Forty of the 51 tendons were treated with percutaneous surgical repair and 11 with open surgical repair. Seven tendons were not included in follow-up because the patients had changed workplaces. Four tendons treated with percutaneous surgical repair were excluded from the statistical analysis because rerupture was clinically suspected, but the patients completed the study protocol. Rerupture developed 7 8 AJR:189, November

4 6 (±2) 35 (±2) 5 3 Gap Length (mm) st 2nd Postoperative MRI Study p <.1 weeks after surgery. In all four cases, conservative treatment was started immediately after detection of rerupture. Finally, an analysis was conducted of 3 Achilles tendons in 29 patients treated with percutaneous surgical repair (26 men, three women; age range, years; mean age, 39.4 years; affected side, right in 1 cases, left in 2 cases) and 1 tendons in 1 patients treated with open surgical repair (1 men; age range, years; mean age, 41.8 years; affected side, right in seven cases, left in three cases). MRI Schedule The timing of MRI varied depending on the patient s convenience and the availability of the MRI facility. The first session was conducted days (mean, 25.8 days), the second, days (mean, 52.3 days), and the third, 7 91 days (mean, 82.7 days) after surgery. Assessment The postoperative MRI appearance of the rupture site after percutaneous surgical repair was not significantly different from that after open surgical repair. Persistent Achilles tendon gap and gap length During the first MRI session, T1- weighted images depicted a tendon gap in all 3 tendons in the percutaneous and all 1 p <.1 3rd A Fig. 3 Changes in gap length after percutaneous suture. Dashed line represents gap length changes in cases of rerupture of Achilles tendon during period of observation. Four cases of rerupture of Achilles tendon were excluded from statistical analysis. A, Graph shows findings on T1-weighted images over time. B, Graph shows findings on T2-weighted images over time. Gap Length (mm) tendons in the open surgical repair group. T2-weighted images showed a tendon gap in 26 (87%) of the tendons in the percutaneous and in six (6%) of the tendons in the open surgical repair group (Figs. 2A 2C). The length of the tendon gap during the first MRI session varied. In the percutaneous surgical repair group, the length ranged from 6 to 48 ± 2 mm on T1-weighted images and from to 3 ± 2 mm on T2- weighted images. In the open surgical repair group, the length ranged from 6 to 3 ± 2 mm on T1-weighed images and from to 12 ± 2 mm on T2-weighted images. During the second MRI session, a tendon gap was found on T1-weighted images in 24 (8%) of the tendons in the percutaneous and one (1%) of the tendons in the open surgical repair group. T2-weighted images showed a tendon gap in 19 (63%) of the tendons in the percutaneous but in none of the tendons in the open surgical repair group (Figs. 2E 2G). During the third MRI session, neither T1-weighted nor T2-weighted images showed a tendon gap in any case in either group (Figs. 2I 2K). Palpation of the surgically treated Achilles tendons on the days of the second and third MRI sessions revealed no tendon gap except in the cases of rerupture st 2nd Postoperative MRI Study p <.1 p <.1 3rd Compartment of the Achilles tendon at the ruptured site In the percutaneous surgical repair group, the percentages of cases of Achilles tendon compartment at the first, second, and third MRI sessions were 3%, 9%, and 1% on T1-weighted images and 9%, 1%, and 1% on T2-weighted images. In the open surgical repair group, the values were 6%, 8%, and 1% on T1-weighted images and 9%, 1%, and 1% on T2- weighted images. Contrast enhancement at the rupture site Intratendinous enhancement at the first, second, and third MRI sessions was present in 1%, 73%, and 7% of the tendons in the percutaneous and 1%, 6%, and 1% of the tendons in the open surgical repair group (Figs. 2C and 2G). Peritendinous enhancement was visualized as ring-shaped enhancement in all tendons in both groups during the second MRI session, and it remained visible during the third MRI session (Figs. 2G and 2K). Statistical Analysis Comparison within the percutaneous surgical repair group Tendon gap length during the second and third MRI sessions was significantly less than that during the first session (p <.1, Wilcoxon s signed rank test) (Fig. 3). Gap disappearance occurred signifi- B 1172 AJR:189, November 27

5 MRI of Achilles Tendon Proportion of Cumulative Gap Disappearance Postoperative Period (wk) cantly earlier on T2-weighted than on T1- weighted images (p =.63; significance level of p <.1, McNemar test). Comparison between the percutaneous surgical repair and open surgical repair groups In the percutaneous surgical repair group, the time from surgery to tendon gap disappearance was 11.6 ± 1.5 weeks on T1- weighted images and 1.4 ± 3. weeks on T2- weighted images. In the open surgical repair group, this period was 8.6 ± 1.1 weeks on T1- weighted images and 6.5 ± 2.3 weeks on T2- weighted images. A significantly longer time was required for tendon gap disappearance after percutaneous surgical repair than after open surgical repair (p =.1, Mann-Whitney U test). The tendon gap disappearance rate was significantly lower in the percutaneous than in the open surgical repair group (p <.1, Fisher s exact test) only at the second MRI session. A log-rank test comparison of cumulative gap disappearance rates between the two groups revealed a significant delay in tendon gap disappearance on both T1- and T2- weighted images in the percutaneous compared with the open surgical repair group (p <.1, log-rank test) (Fig. 4). Discussion In this study, we confirmed the presence of a residual tendon gap on MR images after percutaneous surgical repair. We estimate that the tendon gap on MR images may represent a mixture of the inevitable gap associated with this operative procedure and tendinous degeneration before fusion. Using a.1-t MRI unit, A Fig. 4 Proportion of postoperative cases in which gap disappearance was observed after percutaneous suture (n =4) (solid line) and open suture (n =11) (dashed line). Difference between two groups is statistically significant (p <.1, log-rank test). A, Kaplan-Meier graph shows findings on T1-weighted images. B, Kaplan-Meier graph shows findings on T2-weighted images. Proportion of Cumulative Gap Disappearance Postoperative Period (wk) Karjalainen et al. [4] visualized an area of hyperintensity at the rupture site on T2-weighted images 3 weeks after open surgical repair and considered the hyperintense area within the tendon to represent active scar tissue. We also found a tendon gap at the first session even after open surgical repair. We speculate that the tendon gap consists of a physical gap and tendinous degeneration for remodeling at the rupture site before fusion, although we had no histologic support [1, 4, 6 8]. A similar healing process appears to occur in the ruptured part after percutaneous surgical repair. It therefore seems probable that the size of the Achilles tendon gap after percutaneous surgical repair may be overestimated on MRI compared with the anatomic size of the tendon gap immediately after surgery. The tendon gap at the first MRI session after percutaneous surgical repair had disappeared weeks after surgery irrespective of the gap length determined on MR images (Fig. 3). This observation suggests that tendon continuity may be restored rapidly in the advanced stage of healing because repair takes place over the entire tendon gap simultaneously. In the early postoperative period, however, the speed of repair may be affected by the time for replacement of the actual tendon gap with granulation tissue. During the second MR session after percutaneous surgical repair, palpation did not confirm the presence of a tendon defect despite the tendon gap seen on MR images obtained on the same day. This discrepancy in findings between MR images and palpation may be explained as follows. The part visible as a tendon gap on MR images might already have been filled with granulation tissue, whereas mature fibrous tissue may still be absent. At palpation, the gap filled with such granulation tissue may not be perceived as a defect in the tendon. The result suggests, therefore, that palpation of the Achilles tendon after surgical repair should not be used as the reference standard for assessing tendon fusion. An adequate blood supply is indispensable for healing of a ruptured Achilles tendon because the flow of fibroblasts into the ruptured area is facilitated by the blood supply [1, 6, 7]. Fibroblasts migrate into the ruptured part and initiate replacement of the reactive immature granulation tissue with fibrous scar tissue. Intratendinous contrast enhancement during the first half of the observation period is likely to be from a combination of granulation tissue and fibrovascular scar. Postoperative MRI of the Achilles tendon revealed a tendency for earlier disappearance of the tendon gap on T2-weighted than on T1- weighted images. This finding together with the change in frequency of intratendinous enhancement suggests that T2-weighted imaging may be more sensitive for perceiving the transition of blood-rich immature granulation tissue to fibrous scar tissue. Care therefore is needed in regard to possible differences in tendon gap findings related to MRI sequence. The Achilles tendon has no synovial sheath, but the paratenon around this tendon prevents friction between the tendon and the overlying skin. The paratenon, a loosely arranged, thin, B AJR:189, November

6 clear areolar connective tissue in the peritendinous area, plays an important role in repair of the Achilles tendon because of its involvement in the blood supply [9, 1]. Blood is supplied to the Achilles tendon not only in the form of intrinsic blood flow from the musculotendinous junction but also in the form of extrinsic blood flow through the paratenon [8, 11]. Orthopedic surgeons are aware of two roles of the paratenon during Achilles tendon repair: prevention of adhesion to the skin and blood supply during healing. In this study, restoration of the compartment of the Achilles tendon preceded disappearance of the tendon gap. Furthermore, ring-shaped contrast enhancement around the tendon was visible after restoration of the continuity of the tendon. These findings may suggest that the peritendinous area, possibly representing the paratenon, is crucial for repair of a ruptured Achilles tendon. Because the study was designed to explore MRI features of healing after surgery, four cases of rerupture were excluded from the statistical analysis, but the study was continued even in these four cases. The site of rerupture in the four cases was identical to the site of the first rupture, suggesting that the initially ruptured part of the tendon had been fragile. A finding common to all four cases was that the tendon gap had not disappeared by the third MRI session. In two of the four cases, cystic changes were found at the rupture site, but this finding cannot be considered specific to rerupture. The number of rerupture cases in the study was not large enough for a conclusion, and rerupture is expected to assume varying patterns, such as complete and incomplete. Furthermore, rerupture occurred 7 8 weeks after surgery, a period identical to that during which a tendon gap continued to be visualized on MR images in many cases. In cases in which it is difficult to make a clinical diagnosis of rerupture, delayed tendon gap disappearance may serve as an MRI sign of rerupture. A major weakness of this study was a lack of reference standard for assessing the integrity of the Achilles tendon. Histologic correlation of the tendon gap seen on MR images would have clarified healing of the ruptured Achilles tendon. However, invasive study would have been ethically unacceptable. We believe that MRI is the best noninvasive method for evaluating postoperative changes in the Achilles tendon. A minor limitation was that repair after the 13th postoperative week was not studied. However, the presence of incomplete replacement of the tendon gap with mature tendinous tissue and the presence of persistent peritendinous enhancement both suggest ongoing repair of the tendon. It was difficult to define an end point of complete fusion in the ruptured Achilles tendon. A second minor limitation was that because of volume averaging within each slice, the measurement we used would seem to provide greater potential measurement error than ± 2 mm. We conclude that the tendon gap visible on MR images after percutaneous surgical repair is expected to disappear approximately 12 weeks after surgery. The time course of the MRI features of the Achilles tendon after percutaneous surgical repair can be considered to reflect normal healing. References 1. Maffulli N. Rupture of the Achilles tendon. J Bone Joint Surg Am 1999; 81: Ma GW, Griffith TG. Percutaneous repair of acute closed ruptured Achilles tendon: a new technique. Clin Orthop Relat Res 1977; 128: Bradley JP, Tibone JE. Percutaneous and open surgical repairs of Achilles tendon ruptures: a comparative study. Am J Sports Med 199; 18: Karjalainen PT, Aronen HJ, Pihlajamaki HK, Soila K, Paavonen T, Bostman OM. Magnetic resonance imaging during healing of surgically repaired Achilles tendon ruptures. Am J Sports Med 1997; 25: Maffulli N, Thorpe AP, Smith EW. Magnetic resonance imaging after operative repair of Achilles tendon rupture. Scand J Med Sci Sports 21; 11: Dykyj D, Jules KT. The clinical anatomy of tendons. J Am Podiatr Med Assoc 1991; 81: Evans NA, Stanish WD. The basic science of tendon injuries. Curr Orthop 2; 14: Karjalainen PT, Soila K, Aronen HJ, et al. MR imaging of overuse injuries of the Achilles tendon. AJR 2; 175: Hollenberg GM, Adams MJ, Weinberg EP. Sonographic appearance of nonoperatively treated Achilles tendon rupture. Skeletal Radiol 2; 29: Soila K, Karjalainen PT, Aronen HJ, Pihlajamaki HK, Tirman PJ. High-resolution MR imaging of the asymptomatic Achilles tendon: new observations. AJR 1999; 173: Kvist M, Jozsa L, Jarvinen M. Vascular changes in the ruptured Achilles tendon and paratenon. Int Orthop 1992; 16: AJR:189, November 27