The Journal of Foot & Ankle Surgery xxx (2015) 1–4
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Original Research
Prevalence and Role of a Low-Lying Peroneus Brevis Muscle Belly in Patients With Peroneal Tendon Pathologic Features: A Potential Source of Tendon Subluxation Roya Mirmiran, DPM, FACFAS 1, Chad Squire, DPM 2, Daniel Wassell, DPM 2 1
Chief, Department of Podiatric Surgery, New Mexico Veterans Affairs Health Care System, Albuquerque, NM Former Resident, Podiatric Medicine and Surgery Residency, New Mexico Veterans Affairs Health Care Systems and Kaiser Foundation Hospital, Albuquerque, NM 2
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 3
A peroneus brevis low-lying muscle belly (LLMB) is a rare anomaly. A few published studies have supported the presence of this anomaly as an etiology for a peroneal tendon tear. However, the association between a peroneus brevis LLMB and tendon subluxation has not been well explored. In the present retrospective study, the magnetic resonance imaging (MRI) and intraoperative findings of 50 consecutive patients undergoing primary peroneal tendon surgery during a 5-year period were assessed. The sensitivity and specificity of MRI compared with the intraoperative findings for identifying peroneal tendon disease were investigated. The presence of associated peroneal tendon pathologic features in patients with and without a peroneus brevis LLMB was also compared. The sensitivity of MRI was high for identifying peroneal tenosynovitis (81.58%) and tear (85.71%). Although the sensitivity of MRI for detecting a peroneus brevis LLMB (3.23%) and tendon subluxation (10.00%) was low, MRI had high specificity at 94.74% and 100%, respectively. Intraoperatively, a peroneus brevis LLMB was seen in 62.00% of the patients with chronic lateral ankle pain and was associated with 64.52% of the patients with tenosynovitis, 29.03% of those with tendon subluxation, and 80.65% of those with a peroneus brevis tendon tear. Although the presence of a peroneus brevis LLMB did not show any statistically significant association with peroneus brevis tendon subluxation, of the 10 patients with intraoperatively observed tendon subluxation, 9 had a concomitant peroneus brevis LLMB. More studies with larger patient populations are needed to better investigate the role of a peroneus brevis LLMB as a mass-occupying lesion resulting in peroneal tendon subluxation. Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle anomaly fibula lateral malleolus magnetic resonance image muscle tear tenosynovitis
Peroneal tendon injuries as a result of lower extremity trauma have been well recognized and studied. Advances in magnetic resonance imaging (MRI) have enhanced our ability to diagnose soft tissue pathologic entities such as tenosynovitis and tendon tears. A lowlying muscle belly (LLMB) (Fig) is a rare anomaly, most commonly associated with the peroneus brevis tendon (1–3). A LLMB is defined as a muscle extending beyond its normal length. In the case of the peroneus brevis muscle, it is expected that the muscle would end an average of 1.6 to 2.0 cm above the distal tip of the fibula (4). Cases of a Financial Disclosure: This project was supported in part by the National Center for Research Resources and National Center for Advancing Translational Sciences of the National Institutes of Health (grant 8UL1TR000041) and the University of New Mexico Clinical and Translational Science Center. Conflict of Interest: None reported. Address correspondence to: Roya Mirmiran, DPM, FACFAS, Department of Surgery (112), New Mexico Veterans Affairs Health Care System, 1501 San Pedro, Southeast, Albuquerque, NM 87108. E-mail address: [email protected] (R. Mirmiran).
peroneus brevis LLMB have been documented in published studies (1,3,5–9). However, to our knowledge, the association between a peroneus brevis LLMB and tendon subluxation has not been well studied. The 3 primary peroneal tendon disorders are tenosynovitis, tendon subluxation, and tendon tears (10,11). Peroneal tendon synovitis and tears are common findings, especially as a result of ankle sprains. Previous studies have addressed peroneal tendon tears, highlighting the need for appropriate diagnosis and surgical treatment (10–14). It is well recognized that MRI can be a useful tool to assess peroneal tendon tears. However, in the published data, concerns have been reported regarding the false reading of a tendon tear when relying on MRI studies as the only imaging source. Khoury et al (15) evaluated the accuracy of MRI findings for surgically proven peroneal tendon tears. They found 2 false-positive results (16.67%) and 1 false-negative result (8.33%) among 12 patients who had undergone surgery for a suspected peroneal tendon tear. In another retrospective study by Lamm et al (7), the MRI findings of peroneal
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R. Mirmiran et al. / The Journal of Foot & Ankle Surgery xxx (2015) 1–4
association existed between a peroneus brevis LLMB and tendon subluxation. We hypothesized that a peroneus brevis LLMB could be a contributing factor to peroneal tendon subluxation secondary to its mass effect. Our secondary aim was to determine the prevalence of peroneal tendon pathologic entities, more specifically a LLMB, in our patient population. The sensitivity and specificity of MRI in identifying surgically proven tendon pathologic entities were also studied. We undertook a retrospective study of patients who had undergone lateral ankle surgery to assess the reliability of MRI, determine the prevalence of peroneal tendon pathologic features, and compare the presence of tenosynovitis, tendon tear, and subluxation in patients with and without a peroneus brevis LLMB.
Patients and Methods
Fig. An intraoperative photograph of a peroneus brevis tendon with a low-lying muscle belly. In our study, a low-lying muscle belly was defined as an extension of the muscle belly within the fibular groove. As noted in this patient, the muscle belly extended beyond the tip of fibula.
tendon tears were compared with the intraoperative findings in 32 patients. The MRI diagnosis of a peroneus brevis tendon tear had a sensitivity and specificity of 83% and 75%, respectively. In their study, they reported 2 false-positive (6.25%) and 4 false-negative (12.50%) cases of a peroneus brevis tendon tear using MRI. Although the investigators included patients with LLMB, it is unclear how many cases of LLMB were identified from the imaging studies or intraoperatively (7). In addition, the investigators did not clearly discuss the relation of LLMB to any observed peroneal tendon pathologic entity. The association between tears of the peroneus brevis tendon and the distal extent of its muscle belly was reported by Freccero and Berkowitz (5). The average distance between the musculotendinous junction to the distal fibula measured 33.1 mm on MRI in 29 patients with a surgically confirmed peroneus brevis tendon tear. However, this distance was reported to be 41.2 mm for 30 patients with a surgically confirmed intact peroneus brevis tendon (5). Although the investigators discussed the association between peroneus brevis tears and the extent of the muscle belly, they did not report any tendon subluxation relative to the presence of a peroneus brevis LLMB. Geller et al (1) also discussed the crucial effect of a peroneus brevis LLMB on peroneal tendon tears. Using 30 cadaver legs, they reported the influence of the presence of a lower musculotendinous junction on an increased prevalence of peroneal tendon tears. The musculotendinous junction was significantly more distal in the torn specimens than in those without a tear (1). That study, however, included a small number of specimens with tendon tears (n ¼ 4). The association between a peroneus brevis LLMB and tendon subluxation was not studied in their cadaveric study (1). In another study, Pollack et al (2) reported 1 case of a peroneal tendon tear that was missed on MRI. On exploration of the tendon, a peroneus brevis LLMB was noted and thought to be the possible source of the tendon tear. (2). The published studies on the relationship between peroneal tendon subluxation and a peroneus brevis LLMB are very limited. To our knowledge, only a single case study has reported on the presence of a peroneus brevis LLMB in the setting of peroneal tendon subluxation (6). In another study, peroneal tendon subluxation was seen as a result of a bifid peroneus brevis tendon, rather than a LLMB (16). Although the presence of a peroneus brevis LLMB in cases of peroneal tendon tears has been documented in several studies (1–3), the prevalence of a peroneus brevis LLMB and its association with peroneal tendon subluxation has not been adequately studied. In the present study, our primary goal was to determine whether any
A sample size power analysis was completed, and it was determined that 50 patients were adequate to provide 80% power (a ¼ 0.05). The human research review committee at the University of New Mexico, which served as the institutional review board of record for the New Mexico Veterans Affairs Health Care System, approved the present study. We performed a review of the medical records of 50 consecutive patients who had undergone peroneal tendon repair. A database of those patients who had undergone peroneal tendon repair during a 5-year period from November 2008 to November 2013, in the practice of the senior author (R.M.), was generated using the Common Procedural Terminology (CPTÒ) codes from the surgical package of the New Mexico Veterans Affairs Health Care System. The CPTÒ codes used to identify patients with peroneal tendon surgery were 27659 and 27658. Using the keywords “peroneal” and “peroneus,” the list of operations for these patients was then further narrowed to specifically identify those patients who had undergone peroneal tendon repair surgery. Only those patients who had undergone primary peroneal tendon repair with preoperative MRI studies of the affected ankle completed were included. Patients who had undergone revision peroneal tendon surgery, had the peroneal tendon or tendons used for lateral ankle ligament reconstruction, had a history of ankle fracture requiring open reduction internal fixation, or had incomplete medical records (including preoperative MRI studies) were excluded from the present study. Each patient’s medical records, including progress notes, MRI findings, and operative reports, were reviewed by all authors to record the documented clinical, imaging, and intraoperative findings of peroneal tendon tenosynovitis, subluxation, and tear and the presence of a peroneus brevis LLMB. A clinical finding was defined as patient having 1 symptoms of peroneal tenderness, subluxation, snapping, or pain at the posterolateral ankle on physical examination. All MRI scans were reviewed by 2 musculoskeletal fellowship-trained radiologists. The operations were performed by 2 surgeons at the senior author’s (R.M.) practice. Peroneal tenosynovitis was defined as the presence of a fluid collection within the peroneal tendon sheath or hypertrophy of the tendon on the MRI scans or evidenced intraoperatively (11). Subluxation of the peroneal tendon was defined as displacement of the tendon, within the tendon sheath, lateral to the retromalleolar groove. Peroneal tendon tear was defined as the documented presence of a longitudinal tear within the tendon seen on MRI or intraoperatively (11). A LLMB was defined as extension of the muscle belly within the fibular groove. The intraoperative findings were considered the reference standard for identifying the noted tendon pathologic entities, and the results were compared with the imaging findings. The present study was designed to primarily investigate whether the presence of a peroneus brevis LLMB was associated with peroneal tendon tenosynovitis, subluxation, and tear. We also aimed to determine the prevalence of common peroneal tendon diseases in our patient population. Using the intraoperative findings, the sensitivity and specificity of MRI in identifying surgically proven tendon pathologic entities were also studied. The sensitivity and specificity of MRI in detecting peroneal tendon disease was calculated using the Clopper-Pearson (exact) test, with the 95% confidence level. Because of the small size of the samples, Fisher’s exact test was used to compare the significance for tenosynovitis, tendon tear, and subluxation in patients with or without a peroneus brevis LLMB. A 2-sided p value of .05 was considered statistically significant.
Results The medical records of 50 consecutive patients who had undergone primary peroneal tendon surgery in a 5-year period, from November 2008 to November 2013, and met the study criteria were reviewed. Of the 50 patients, 8 were female and 42 were male, with mean age of 50.05 (range 24 to 68) years.
R. Mirmiran et al. / The Journal of Foot & Ankle Surgery xxx (2015) 1–4
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Table 1 Number of tendon pathologic entities identified using magnetic resonance imaging versus intraoperatively (N ¼ 50 patients)
Table 3 Intraoperatively observed peroneal tendon pathologic entities stratified by the presence of a peroneus brevis LLMB
Pathologic Entity
MRI Finding (n)
Intraoperative Finding (n)
Prevalence (%)
LLMB
Tenosynovitis
Subluxation
PBT Tear
Tenosynovitis PBT tear Subluxation LLMB
34 39 1 2
38 42 10 31
76.00 84.00 20.00 62.00
Present (n ¼ 31) Absent (n ¼ 19) p Value
20 (64.52) 18 (94.74) .0182
9 (29.03) 1 (5.26) .067
25 (80.65) 17 (89.47) .693
Abbreviations: LLMB, low-lying muscle belly; MRI, magnetic resonance imaging; PBT, peroneus brevis tendon. Using the intraoperative findings, our patient population had a high prevalence of tenosynovitis, PBT tear, and LLMB.
The most common pathologic entities observed intraoperatively were tenosynovitis (38 cases in 50 patients) and peroneus brevis tendon tear (42 cases in 50 patients; Table 1). We noted 31 cases of a peroneus brevis LLMB intraoperatively, 2 of which were also identified using MRI. The prevalence for peroneus brevis tendon tear, tenosynovitis, and a LLMB was 84.00%, 76.00%, and 62.00%, respectively. Peroneal tendon subluxation was seen in 20.00% of the patients (Table 1). Using the intraoperative findings, the sensitivity and specificity of MRI in identifying peroneal tendon pathologic features were investigated. The sensitivity of MRI in identifying peroneal tenosynovitis and peroneus brevis tendon tear was high at 81.58% and 85.71%, with a specificity of 75.00% and 62.50%, respectively (Table 2). MRI had low sensitivity but high specificity in detecting peroneal tendon subluxation (10% sensitive, 100.00% specific; Table 2). Of the 50 patients who had undergone peroneal tendon surgery, 2 (4.00%) had preoperative MRI findings for the presence of a peroneus brevis LLMB. In contrast, 31 cases (62.00%) of LLMB were identified intraoperatively (Table 1). MRI was not a sensitive test in diagnosing a LLMB because 29 cases (93.55%) were missed using MRI. The diagnosis of a LLMB had a low sensitivity of 3.23% but a high specificity of 94.74% using MRI. Using Fisher’s exact test, the absence of a LLMB was significantly (p ¼ .0182) associated with the presence of tenosynovitis (Table 3). However, no statistically significant association was found between a peroneus brevis LLMB and a peroneus brevis tendon tear (p ¼ .693) or subluxation (p ¼ .067). Tendon subluxation, however, was noted in 10 patients, 9 of whom had a concomitant peroneus brevis LLMB (Table 3). Discussion Adequate studies focusing on the relationship between a peroneus brevis LLMB and peroneus brevis tendon pathologic entities are lacking. We completed a retrospective study of 50 patients who had undergone peroneus brevis tendon surgery. The prevalence for peroneal tendon disease, more specifically of a peroneus brevis LLMB, was investigated in our patient population. The most common peroneal tendon disease seen in our patient population was peroneal tenosynovitis and peroneus brevis tendon tear. Our findings are similar to those reported in published studies. In a study of 40 patients
Table 2 Sensitivity and specificity of MRI for each tendon disease using the intraoperative findings as the reference standard (N ¼ 50 patients overall)
Tenosynovitis PBT tear Subluxation LLMB
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
81.58 (n ¼ 31/38) 85.71 (n ¼ 36/42) 10.00 (n ¼ 1/10) 3.23 (n ¼ 1/31)
75.00 (n ¼ 9/12) 62.50 (n ¼ 5/8) 100.00 (n ¼ 40/40) 94.74 (n ¼ 18/19)
91.18 92.31 100.00 50.00
56.25 45.45 81.63 37.50
Abbreviations: LLMB, low-lying muscle belly; MRI, magnetic resonance imaging; NPV, negative predictive value; PBT, peroneus brevis tendon; PPV, positive predictive value.
Abbreviations: LLMB, low-lying muscle belly; PBT, peroneus brevis tendon. Data presented as n (%).
who had undergone surgery for chronic pain along the peroneal tendons, Dombek et al (17) noted 88% cases of peroneus brevis tendon tear, 33% of a peroneus brevis LLMB, and 20% of tendon subluxation. Of the 50 patients in our study, the prevalence for a peroneus brevis tendon tear and subluxation was 84% and 20%, respectively. However, in our patient population, we had a greater number of patients (62%) with a peroneus brevis LLMB, despite using the same definition for the LLMB. In a study by Giza et al (18), the relationship between peroneus brevis tendon tears identified using MRI was compared with the clinical findings. A clinical finding of a tendon tear was defined as the patient having one of the following symptoms or presentation: peroneal tenderness, weakness, subluxation, snapping, or pain on the posterolateral ankle. Of the 56 patients with positive findings on MRI, only 27 had associated symptoms on clinical examination. They concluded that MRI has a positive predictive value of 48% for the presence of a true tendon tear (18). In our patient population, the positive predictive value for a peroneus brevis tendon tear using MRI was 92.31% (Table 2). Our study design was different than that of the study by Giza et al (18), because we compared the actual intraoperative observations rather than the clinical examination findings with what was discerned using MRI. In addition, in a study by Park et al (19), MRI was noted to be 83.9% sensitive and 74.5% specific for identifying peroneal tendon pathologic entities. More specifically, the sensitivity for MRI in diagnosing peroneus brevis tenosynovitis, tendon tear, and a LLMB was reported at 25%, 54.5%, and 91.7%, respectively. Park et al (19) concluded that MRI alone should not be relied on as a source to determine the necessity for surgical intervention. Our results differed from their findings, because we found MRI to be a less sensitive test, missing >90% of the LLMBs seen intraoperatively. Our reported sensitivity for MRI in detecting peroneus brevis tenosynovitis and tendon tear was greater at 81.58%, and 85.71%, respectively. This might have been because of the heightened education and recent advances in MRI technology and availability of a higher resolution image resulting in increased detection of tendon tears and tenosynovitis. Although in the study by Park et al (19), 12 cases of LLMB were encountered intraoperatively, they did not explore the effect or association of a peroneus brevis LLMB on the occurrence of a tendon tear or tenosynovitis. Our study showed that MRI, although a sensitive test for diagnosing tenosynovitis and tendon tears, remains a poor imaging study for the presence of a LLMB or tendon subluxation. MRI is considered a static imaging tool. This might explain why peroneus tendon subluxation, which is usually a dynamic finding, is not easily demonstrated using MRI. A LLMB for the peroneus brevis muscle can be missed owing to the imaging protocol and the presence of the “magic angle” because of the oblique course of the peroneal tendon. Freccero and Berkowitz (5) reported a retrospective study of surgically explored peroneus brevis tendons from 1999 to 2004. Their study focused on MRI measurement of the distance from the distal fibular tip to the end of the peroneus brevis musculotendinous junction in patients who had had intraoperative findings of a peroneus brevis tendon tear. A positive correlation was noted for the occurrence of a tendon tear among those with a lower lying muscle
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belly (5). Freccero and Berkowitz (5) reported that the incidence of confirmed tears with associated LLMB warranted additional study. In a cadaveric study of 115 ankles, Unlu et al (20) reported that their findings contradicted the findings of Freccero and Berkowitz (5) and that an increased distance from the distal tip actually increased the probability of a peroneus brevis tendon tear. In their study, they reported 15 cases of a peroneus brevis tendon tear among the 115 specimens. No LLMBs were reported in their study (20). Although there are few citations in published studies on the presence of LLMB placing patients at greater risk of developing a tendon tear, the data on an association between a LLMB and peroneus brevis tendon subluxation are inadequate. In our study, we hypothesized that the distal extension of the muscle belly within the fibular groove might result in a mass-occupying phenomenon. With an excessive tissue mass, the peroneal tendons could be at a greater risk of tenosynovitis, tendon subluxation, and eventual attritional tear. Although no statistically significant difference was found in the presence or absence of a LLMB on peroneus brevis tendon subluxation, in our patient population, 90% of the patients with peroneus brevis tendon subluxation had a concomitant LLMB. We also did not find a significant difference in the presence of a peroneus brevis tendon tear among the patients with or without a LLMB. A LLMB was less likely to be associated with the presence of tenosynovitis. The reason for this is unclear (Table 3). Larger prospective studies are needed to better study the relationship between a LLMB and peroneus brevis tendon synovitis. To the best of our knowledge, our study is the first reported series to examine the association between a peroneus brevis LLMB and tendon subluxation. The present retrospective study had several limitations. Owing to the retrospective nature of our study, we used the CPTÒ codes 27659 and 27658 to identify patients who had undergone peroneus brevis tendon repair. We might have not identified all the patients at our facility who had undergone peroneus brevis surgical correction because no CPTÒ code is specific to peroneal tendon repair. We had a small number of patients with a subluxing peroneus brevis tendon, making it difficult to perform an accurate analysis. In addition, the operations were performed by 2 separate surgeons, and the operative records and clinical findings were documented by multiple residents. In conclusion, we believe that MRI alone should not be used as a diagnostic tool for peroneus tendon pathologic entities, because MRI might not be the most reliable method to accurately detect all types of tendon pathologic disorders. As presented in our study, MRI can miss cases of a peroneus brevis LLMB and tendon subluxation. The clinical findings and ultrasound imaging should be considered as adjuncts to the MRI findings if concern exists for the presence of tendon subluxation. Despite the small number of patients in the present study, our findings reinforce the need for an increased clinical suspicion of a peroneus brevis LLMB in patients with lateral ankle pain and peroneal tendinopathy, more specifically tendon subluxation. We believe that a LLMB could have a direct relationship with the presence of tendon
subluxation. Peroneus brevis tendon subluxation was identified in 10 patients intraoperatively, 9 of whom had a concomitant peroneus brevis LLMB. The results of our study can be used in the development of future cohort prospective studies focusing on the role of the presence of a LLMB in tendon subluxation. Acknowledgment The authors acknowledge and appreciate the work of Cliff Qualls, PhD, in the statistical analysis of the collected data. References 1. Geller J, Lin S, Cordas D, Vieira P. Relationships of a low-lying muscle belly to tears of the peroneus brevis tendon. Am J Orthop (Belle Mead NJ) 32:541–544, 2003. 2. Pollack D, Khaimov G, Guberman R. Limitation of magnetic resonance imaging in diagnosing longitudinal peroneal tendon tears. J Am Podiatr Med Assoc 104:90– 94, 2014. 3. Zhenbo Z, Jin W, Haifeng G, Huanting L, Feng C, Ming L. Sliding fibular graft repair for the treatment of recurrent peroneal subluxation. Foot Ankle Int 35:496–503, 2014. 4. Edwards ME. The relations of the peroneal tendons the fibula, calcaneus, and cuboideum. Am J Anat 42:213–253, 1928. 5. Freccero DM, Berkowitz MJ. The relationship between tears of the peroneus brevis tendon and the distal extent of its muscle belly: an MRI study. Foot Ankle Int 27:236–239, 2006. 6. Sobel M, Bohne WH, O’Brien SJ. Peroneal tendon subluxation in a case of anomalous peroneus brevis muscle. Acta Orthop Scand 63:682–684, 1992. 7. Lamm BM, Myers DT, Dombek M, Mendicino RW, Catanzariti AR, Saltrick K. Magnetic resonance imaging and surgical correlation of peroneus brevis tears. J Foot Ankle Surg 43:30–36, 2004. 8. Lui TH. Tendoscopic resection of low-lying muscle belly of peroneus brevis or quartus. Foot Ankle Int 33:912–914, 2012. 9. Saupe N, Mengiardi B, Pfirrmann CW, Vienne P, Seifert B, Zanetti M. Anatomic variants associated with peroneal tendon disorders: MR imaging findings in volunteers with asymptomatic ankles. Radiology 242:509–517, 2007. 10. Heckman DS, Reddy S, Pedowitz D, Wapner KL, Parekh SG. Operative treatment for peroneal tendon disorders. J Bone Joint Surg Am 90:404–418, 2008. 11. Wang XT, Rosenberg ZS, Mechlin MB, Schweitzer ME. Normal variants and diseases of the peroneal tendons and superior peroneal retinaculum: MR imaging features. Radiographics 25:587–602, 2005. 12. Mendeszoon M, McVey JT, MacEvoy A. Surgical correction of subluxing peroneal tendons utilizing a lateral slip of the achilles tendon: a case report. Foot Ankle Online J 2:3–7, 2009. 13. Krause JO, Brodsky JW. Peroneus brevis tendon tears: pathophysiology, surgical reconstruction, and clinical results. Foot Ankle Int 19:271–279, 1998. 14. Sammarco GJ. Peroneal tendon injuries. Ortho Clinic North Am 25:135–145, 1994. 15. Khoury NJ, El-Khoury GY, Saltzman CK, Kathol MH. Peroneus longus and brevis tendon tears: MR imaging evaluation. Radiology 200:833–841, 1996. 16. Hammerschlag WA, Goldner JL. Chronic peroneal tendon subluxation produced by an anomalous peroneus brevis: case report and literature review. Foot Ankle 10:45–47, 1989. 17. Dombek MF, Lamm BM, Saltrick K, Mendicino RW, Catanzariti AR. Peroneal tendon tears: a retrospective review. J Foot Ankle Surg 42:250–258, 2003. 18. Giza E, Mak W, Wong SE, Roper G, Campanelli V, Hunter JC. A clinical and radiological study of peroneal tendon pathology. Foot Ankle Spec 6:417–421, 2013. 19. Park HJ, Cha SD, Kim HS, Chung ST, Park NH, Yoo JH, Park JH, Kim JH, Lee TW, Lee CH, Oh SM. Reliability of MRI findings of peroneal tendinopathy in patients with lateral chronic ankle instability. Clin Orthop Surg 2:237–243, 2010. 20. Unlu MC, Bilgili M, Akgun I, Kaynak G, Ogut T, Uzun I. Abnormal proximal musculotendinous junction of the peroneus brevis muscle as a cause of peroneus brevis tendon tears: a cadaveric study. J Foot Ankle Surg 49:537–540, 2010.
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Original Research
Prevalence and Role of a Low-Lying Peroneus Brevis Muscle Belly in Patients With Peroneal Tendon Pathologic Features: A Potential Source of Tendon Subluxation Roya Mirmiran, DPM, FACFAS 1, Chad Squire, DPM 2, Daniel Wassell, DPM 2 1
Chief, Department of Podiatric Surgery, New Mexico Veterans Affairs Health Care System, Albuquerque, NM Former Resident, Podiatric Medicine and Surgery Residency, New Mexico Veterans Affairs Health Care Systems and Kaiser Foundation Hospital, Albuquerque, NM 2
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 3
A peroneus brevis low-lying muscle belly (LLMB) is a rare anomaly. A few published studies have supported the presence of this anomaly as an etiology for a peroneal tendon tear. However, the association between a peroneus brevis LLMB and tendon subluxation has not been well explored. In the present retrospective study, the magnetic resonance imaging (MRI) and intraoperative findings of 50 consecutive patients undergoing primary peroneal tendon surgery during a 5-year period were assessed. The sensitivity and specificity of MRI compared with the intraoperative findings for identifying peroneal tendon disease were investigated. The presence of associated peroneal tendon pathologic features in patients with and without a peroneus brevis LLMB was also compared. The sensitivity of MRI was high for identifying peroneal tenosynovitis (81.58%) and tear (85.71%). Although the sensitivity of MRI for detecting a peroneus brevis LLMB (3.23%) and tendon subluxation (10.00%) was low, MRI had high specificity at 94.74% and 100%, respectively. Intraoperatively, a peroneus brevis LLMB was seen in 62.00% of the patients with chronic lateral ankle pain and was associated with 64.52% of the patients with tenosynovitis, 29.03% of those with tendon subluxation, and 80.65% of those with a peroneus brevis tendon tear. Although the presence of a peroneus brevis LLMB did not show any statistically significant association with peroneus brevis tendon subluxation, of the 10 patients with intraoperatively observed tendon subluxation, 9 had a concomitant peroneus brevis LLMB. More studies with larger patient populations are needed to better investigate the role of a peroneus brevis LLMB as a mass-occupying lesion resulting in peroneal tendon subluxation. Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle anomaly fibula lateral malleolus magnetic resonance image muscle tear tenosynovitis
Peroneal tendon injuries as a result of lower extremity trauma have been well recognized and studied. Advances in magnetic resonance imaging (MRI) have enhanced our ability to diagnose soft tissue pathologic entities such as tenosynovitis and tendon tears. A lowlying muscle belly (LLMB) (Fig) is a rare anomaly, most commonly associated with the peroneus brevis tendon (1–3). A LLMB is defined as a muscle extending beyond its normal length. In the case of the peroneus brevis muscle, it is expected that the muscle would end an average of 1.6 to 2.0 cm above the distal tip of the fibula (4). Cases of a Financial Disclosure: This project was supported in part by the National Center for Research Resources and National Center for Advancing Translational Sciences of the National Institutes of Health (grant 8UL1TR000041) and the University of New Mexico Clinical and Translational Science Center. Conflict of Interest: None reported. Address correspondence to: Roya Mirmiran, DPM, FACFAS, Department of Surgery (112), New Mexico Veterans Affairs Health Care System, 1501 San Pedro, Southeast, Albuquerque, NM 87108. E-mail address: [email protected] (R. Mirmiran).
peroneus brevis LLMB have been documented in published studies (1,3,5–9). However, to our knowledge, the association between a peroneus brevis LLMB and tendon subluxation has not been well studied. The 3 primary peroneal tendon disorders are tenosynovitis, tendon subluxation, and tendon tears (10,11). Peroneal tendon synovitis and tears are common findings, especially as a result of ankle sprains. Previous studies have addressed peroneal tendon tears, highlighting the need for appropriate diagnosis and surgical treatment (10–14). It is well recognized that MRI can be a useful tool to assess peroneal tendon tears. However, in the published data, concerns have been reported regarding the false reading of a tendon tear when relying on MRI studies as the only imaging source. Khoury et al (15) evaluated the accuracy of MRI findings for surgically proven peroneal tendon tears. They found 2 false-positive results (16.67%) and 1 false-negative result (8.33%) among 12 patients who had undergone surgery for a suspected peroneal tendon tear. In another retrospective study by Lamm et al (7), the MRI findings of peroneal
1067-2516/$ - see front matter Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2015.02.012
2
R. Mirmiran et al. / The Journal of Foot & Ankle Surgery xxx (2015) 1–4
association existed between a peroneus brevis LLMB and tendon subluxation. We hypothesized that a peroneus brevis LLMB could be a contributing factor to peroneal tendon subluxation secondary to its mass effect. Our secondary aim was to determine the prevalence of peroneal tendon pathologic entities, more specifically a LLMB, in our patient population. The sensitivity and specificity of MRI in identifying surgically proven tendon pathologic entities were also studied. We undertook a retrospective study of patients who had undergone lateral ankle surgery to assess the reliability of MRI, determine the prevalence of peroneal tendon pathologic features, and compare the presence of tenosynovitis, tendon tear, and subluxation in patients with and without a peroneus brevis LLMB.
Patients and Methods
Fig. An intraoperative photograph of a peroneus brevis tendon with a low-lying muscle belly. In our study, a low-lying muscle belly was defined as an extension of the muscle belly within the fibular groove. As noted in this patient, the muscle belly extended beyond the tip of fibula.
tendon tears were compared with the intraoperative findings in 32 patients. The MRI diagnosis of a peroneus brevis tendon tear had a sensitivity and specificity of 83% and 75%, respectively. In their study, they reported 2 false-positive (6.25%) and 4 false-negative (12.50%) cases of a peroneus brevis tendon tear using MRI. Although the investigators included patients with LLMB, it is unclear how many cases of LLMB were identified from the imaging studies or intraoperatively (7). In addition, the investigators did not clearly discuss the relation of LLMB to any observed peroneal tendon pathologic entity. The association between tears of the peroneus brevis tendon and the distal extent of its muscle belly was reported by Freccero and Berkowitz (5). The average distance between the musculotendinous junction to the distal fibula measured 33.1 mm on MRI in 29 patients with a surgically confirmed peroneus brevis tendon tear. However, this distance was reported to be 41.2 mm for 30 patients with a surgically confirmed intact peroneus brevis tendon (5). Although the investigators discussed the association between peroneus brevis tears and the extent of the muscle belly, they did not report any tendon subluxation relative to the presence of a peroneus brevis LLMB. Geller et al (1) also discussed the crucial effect of a peroneus brevis LLMB on peroneal tendon tears. Using 30 cadaver legs, they reported the influence of the presence of a lower musculotendinous junction on an increased prevalence of peroneal tendon tears. The musculotendinous junction was significantly more distal in the torn specimens than in those without a tear (1). That study, however, included a small number of specimens with tendon tears (n ¼ 4). The association between a peroneus brevis LLMB and tendon subluxation was not studied in their cadaveric study (1). In another study, Pollack et al (2) reported 1 case of a peroneal tendon tear that was missed on MRI. On exploration of the tendon, a peroneus brevis LLMB was noted and thought to be the possible source of the tendon tear. (2). The published studies on the relationship between peroneal tendon subluxation and a peroneus brevis LLMB are very limited. To our knowledge, only a single case study has reported on the presence of a peroneus brevis LLMB in the setting of peroneal tendon subluxation (6). In another study, peroneal tendon subluxation was seen as a result of a bifid peroneus brevis tendon, rather than a LLMB (16). Although the presence of a peroneus brevis LLMB in cases of peroneal tendon tears has been documented in several studies (1–3), the prevalence of a peroneus brevis LLMB and its association with peroneal tendon subluxation has not been adequately studied. In the present study, our primary goal was to determine whether any
A sample size power analysis was completed, and it was determined that 50 patients were adequate to provide 80% power (a ¼ 0.05). The human research review committee at the University of New Mexico, which served as the institutional review board of record for the New Mexico Veterans Affairs Health Care System, approved the present study. We performed a review of the medical records of 50 consecutive patients who had undergone peroneal tendon repair. A database of those patients who had undergone peroneal tendon repair during a 5-year period from November 2008 to November 2013, in the practice of the senior author (R.M.), was generated using the Common Procedural Terminology (CPTÒ) codes from the surgical package of the New Mexico Veterans Affairs Health Care System. The CPTÒ codes used to identify patients with peroneal tendon surgery were 27659 and 27658. Using the keywords “peroneal” and “peroneus,” the list of operations for these patients was then further narrowed to specifically identify those patients who had undergone peroneal tendon repair surgery. Only those patients who had undergone primary peroneal tendon repair with preoperative MRI studies of the affected ankle completed were included. Patients who had undergone revision peroneal tendon surgery, had the peroneal tendon or tendons used for lateral ankle ligament reconstruction, had a history of ankle fracture requiring open reduction internal fixation, or had incomplete medical records (including preoperative MRI studies) were excluded from the present study. Each patient’s medical records, including progress notes, MRI findings, and operative reports, were reviewed by all authors to record the documented clinical, imaging, and intraoperative findings of peroneal tendon tenosynovitis, subluxation, and tear and the presence of a peroneus brevis LLMB. A clinical finding was defined as patient having 1 symptoms of peroneal tenderness, subluxation, snapping, or pain at the posterolateral ankle on physical examination. All MRI scans were reviewed by 2 musculoskeletal fellowship-trained radiologists. The operations were performed by 2 surgeons at the senior author’s (R.M.) practice. Peroneal tenosynovitis was defined as the presence of a fluid collection within the peroneal tendon sheath or hypertrophy of the tendon on the MRI scans or evidenced intraoperatively (11). Subluxation of the peroneal tendon was defined as displacement of the tendon, within the tendon sheath, lateral to the retromalleolar groove. Peroneal tendon tear was defined as the documented presence of a longitudinal tear within the tendon seen on MRI or intraoperatively (11). A LLMB was defined as extension of the muscle belly within the fibular groove. The intraoperative findings were considered the reference standard for identifying the noted tendon pathologic entities, and the results were compared with the imaging findings. The present study was designed to primarily investigate whether the presence of a peroneus brevis LLMB was associated with peroneal tendon tenosynovitis, subluxation, and tear. We also aimed to determine the prevalence of common peroneal tendon diseases in our patient population. Using the intraoperative findings, the sensitivity and specificity of MRI in identifying surgically proven tendon pathologic entities were also studied. The sensitivity and specificity of MRI in detecting peroneal tendon disease was calculated using the Clopper-Pearson (exact) test, with the 95% confidence level. Because of the small size of the samples, Fisher’s exact test was used to compare the significance for tenosynovitis, tendon tear, and subluxation in patients with or without a peroneus brevis LLMB. A 2-sided p value of .05 was considered statistically significant.
Results The medical records of 50 consecutive patients who had undergone primary peroneal tendon surgery in a 5-year period, from November 2008 to November 2013, and met the study criteria were reviewed. Of the 50 patients, 8 were female and 42 were male, with mean age of 50.05 (range 24 to 68) years.
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Table 1 Number of tendon pathologic entities identified using magnetic resonance imaging versus intraoperatively (N ¼ 50 patients)
Table 3 Intraoperatively observed peroneal tendon pathologic entities stratified by the presence of a peroneus brevis LLMB
Pathologic Entity
MRI Finding (n)
Intraoperative Finding (n)
Prevalence (%)
LLMB
Tenosynovitis
Subluxation
PBT Tear
Tenosynovitis PBT tear Subluxation LLMB
34 39 1 2
38 42 10 31
76.00 84.00 20.00 62.00
Present (n ¼ 31) Absent (n ¼ 19) p Value
20 (64.52) 18 (94.74) .0182
9 (29.03) 1 (5.26) .067
25 (80.65) 17 (89.47) .693
Abbreviations: LLMB, low-lying muscle belly; MRI, magnetic resonance imaging; PBT, peroneus brevis tendon. Using the intraoperative findings, our patient population had a high prevalence of tenosynovitis, PBT tear, and LLMB.
The most common pathologic entities observed intraoperatively were tenosynovitis (38 cases in 50 patients) and peroneus brevis tendon tear (42 cases in 50 patients; Table 1). We noted 31 cases of a peroneus brevis LLMB intraoperatively, 2 of which were also identified using MRI. The prevalence for peroneus brevis tendon tear, tenosynovitis, and a LLMB was 84.00%, 76.00%, and 62.00%, respectively. Peroneal tendon subluxation was seen in 20.00% of the patients (Table 1). Using the intraoperative findings, the sensitivity and specificity of MRI in identifying peroneal tendon pathologic features were investigated. The sensitivity of MRI in identifying peroneal tenosynovitis and peroneus brevis tendon tear was high at 81.58% and 85.71%, with a specificity of 75.00% and 62.50%, respectively (Table 2). MRI had low sensitivity but high specificity in detecting peroneal tendon subluxation (10% sensitive, 100.00% specific; Table 2). Of the 50 patients who had undergone peroneal tendon surgery, 2 (4.00%) had preoperative MRI findings for the presence of a peroneus brevis LLMB. In contrast, 31 cases (62.00%) of LLMB were identified intraoperatively (Table 1). MRI was not a sensitive test in diagnosing a LLMB because 29 cases (93.55%) were missed using MRI. The diagnosis of a LLMB had a low sensitivity of 3.23% but a high specificity of 94.74% using MRI. Using Fisher’s exact test, the absence of a LLMB was significantly (p ¼ .0182) associated with the presence of tenosynovitis (Table 3). However, no statistically significant association was found between a peroneus brevis LLMB and a peroneus brevis tendon tear (p ¼ .693) or subluxation (p ¼ .067). Tendon subluxation, however, was noted in 10 patients, 9 of whom had a concomitant peroneus brevis LLMB (Table 3). Discussion Adequate studies focusing on the relationship between a peroneus brevis LLMB and peroneus brevis tendon pathologic entities are lacking. We completed a retrospective study of 50 patients who had undergone peroneus brevis tendon surgery. The prevalence for peroneal tendon disease, more specifically of a peroneus brevis LLMB, was investigated in our patient population. The most common peroneal tendon disease seen in our patient population was peroneal tenosynovitis and peroneus brevis tendon tear. Our findings are similar to those reported in published studies. In a study of 40 patients
Table 2 Sensitivity and specificity of MRI for each tendon disease using the intraoperative findings as the reference standard (N ¼ 50 patients overall)
Tenosynovitis PBT tear Subluxation LLMB
Sensitivity (%)
Specificity (%)
PPV (%)
NPV (%)
81.58 (n ¼ 31/38) 85.71 (n ¼ 36/42) 10.00 (n ¼ 1/10) 3.23 (n ¼ 1/31)
75.00 (n ¼ 9/12) 62.50 (n ¼ 5/8) 100.00 (n ¼ 40/40) 94.74 (n ¼ 18/19)
91.18 92.31 100.00 50.00
56.25 45.45 81.63 37.50
Abbreviations: LLMB, low-lying muscle belly; MRI, magnetic resonance imaging; NPV, negative predictive value; PBT, peroneus brevis tendon; PPV, positive predictive value.
Abbreviations: LLMB, low-lying muscle belly; PBT, peroneus brevis tendon. Data presented as n (%).
who had undergone surgery for chronic pain along the peroneal tendons, Dombek et al (17) noted 88% cases of peroneus brevis tendon tear, 33% of a peroneus brevis LLMB, and 20% of tendon subluxation. Of the 50 patients in our study, the prevalence for a peroneus brevis tendon tear and subluxation was 84% and 20%, respectively. However, in our patient population, we had a greater number of patients (62%) with a peroneus brevis LLMB, despite using the same definition for the LLMB. In a study by Giza et al (18), the relationship between peroneus brevis tendon tears identified using MRI was compared with the clinical findings. A clinical finding of a tendon tear was defined as the patient having one of the following symptoms or presentation: peroneal tenderness, weakness, subluxation, snapping, or pain on the posterolateral ankle. Of the 56 patients with positive findings on MRI, only 27 had associated symptoms on clinical examination. They concluded that MRI has a positive predictive value of 48% for the presence of a true tendon tear (18). In our patient population, the positive predictive value for a peroneus brevis tendon tear using MRI was 92.31% (Table 2). Our study design was different than that of the study by Giza et al (18), because we compared the actual intraoperative observations rather than the clinical examination findings with what was discerned using MRI. In addition, in a study by Park et al (19), MRI was noted to be 83.9% sensitive and 74.5% specific for identifying peroneal tendon pathologic entities. More specifically, the sensitivity for MRI in diagnosing peroneus brevis tenosynovitis, tendon tear, and a LLMB was reported at 25%, 54.5%, and 91.7%, respectively. Park et al (19) concluded that MRI alone should not be relied on as a source to determine the necessity for surgical intervention. Our results differed from their findings, because we found MRI to be a less sensitive test, missing >90% of the LLMBs seen intraoperatively. Our reported sensitivity for MRI in detecting peroneus brevis tenosynovitis and tendon tear was greater at 81.58%, and 85.71%, respectively. This might have been because of the heightened education and recent advances in MRI technology and availability of a higher resolution image resulting in increased detection of tendon tears and tenosynovitis. Although in the study by Park et al (19), 12 cases of LLMB were encountered intraoperatively, they did not explore the effect or association of a peroneus brevis LLMB on the occurrence of a tendon tear or tenosynovitis. Our study showed that MRI, although a sensitive test for diagnosing tenosynovitis and tendon tears, remains a poor imaging study for the presence of a LLMB or tendon subluxation. MRI is considered a static imaging tool. This might explain why peroneus tendon subluxation, which is usually a dynamic finding, is not easily demonstrated using MRI. A LLMB for the peroneus brevis muscle can be missed owing to the imaging protocol and the presence of the “magic angle” because of the oblique course of the peroneal tendon. Freccero and Berkowitz (5) reported a retrospective study of surgically explored peroneus brevis tendons from 1999 to 2004. Their study focused on MRI measurement of the distance from the distal fibular tip to the end of the peroneus brevis musculotendinous junction in patients who had had intraoperative findings of a peroneus brevis tendon tear. A positive correlation was noted for the occurrence of a tendon tear among those with a lower lying muscle
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belly (5). Freccero and Berkowitz (5) reported that the incidence of confirmed tears with associated LLMB warranted additional study. In a cadaveric study of 115 ankles, Unlu et al (20) reported that their findings contradicted the findings of Freccero and Berkowitz (5) and that an increased distance from the distal tip actually increased the probability of a peroneus brevis tendon tear. In their study, they reported 15 cases of a peroneus brevis tendon tear among the 115 specimens. No LLMBs were reported in their study (20). Although there are few citations in published studies on the presence of LLMB placing patients at greater risk of developing a tendon tear, the data on an association between a LLMB and peroneus brevis tendon subluxation are inadequate. In our study, we hypothesized that the distal extension of the muscle belly within the fibular groove might result in a mass-occupying phenomenon. With an excessive tissue mass, the peroneal tendons could be at a greater risk of tenosynovitis, tendon subluxation, and eventual attritional tear. Although no statistically significant difference was found in the presence or absence of a LLMB on peroneus brevis tendon subluxation, in our patient population, 90% of the patients with peroneus brevis tendon subluxation had a concomitant LLMB. We also did not find a significant difference in the presence of a peroneus brevis tendon tear among the patients with or without a LLMB. A LLMB was less likely to be associated with the presence of tenosynovitis. The reason for this is unclear (Table 3). Larger prospective studies are needed to better study the relationship between a LLMB and peroneus brevis tendon synovitis. To the best of our knowledge, our study is the first reported series to examine the association between a peroneus brevis LLMB and tendon subluxation. The present retrospective study had several limitations. Owing to the retrospective nature of our study, we used the CPTÒ codes 27659 and 27658 to identify patients who had undergone peroneus brevis tendon repair. We might have not identified all the patients at our facility who had undergone peroneus brevis surgical correction because no CPTÒ code is specific to peroneal tendon repair. We had a small number of patients with a subluxing peroneus brevis tendon, making it difficult to perform an accurate analysis. In addition, the operations were performed by 2 separate surgeons, and the operative records and clinical findings were documented by multiple residents. In conclusion, we believe that MRI alone should not be used as a diagnostic tool for peroneus tendon pathologic entities, because MRI might not be the most reliable method to accurately detect all types of tendon pathologic disorders. As presented in our study, MRI can miss cases of a peroneus brevis LLMB and tendon subluxation. The clinical findings and ultrasound imaging should be considered as adjuncts to the MRI findings if concern exists for the presence of tendon subluxation. Despite the small number of patients in the present study, our findings reinforce the need for an increased clinical suspicion of a peroneus brevis LLMB in patients with lateral ankle pain and peroneal tendinopathy, more specifically tendon subluxation. We believe that a LLMB could have a direct relationship with the presence of tendon
subluxation. Peroneus brevis tendon subluxation was identified in 10 patients intraoperatively, 9 of whom had a concomitant peroneus brevis LLMB. The results of our study can be used in the development of future cohort prospective studies focusing on the role of the presence of a LLMB in tendon subluxation. Acknowledgment The authors acknowledge and appreciate the work of Cliff Qualls, PhD, in the statistical analysis of the collected data. References 1. Geller J, Lin S, Cordas D, Vieira P. Relationships of a low-lying muscle belly to tears of the peroneus brevis tendon. Am J Orthop (Belle Mead NJ) 32:541–544, 2003. 2. Pollack D, Khaimov G, Guberman R. Limitation of magnetic resonance imaging in diagnosing longitudinal peroneal tendon tears. J Am Podiatr Med Assoc 104:90– 94, 2014. 3. Zhenbo Z, Jin W, Haifeng G, Huanting L, Feng C, Ming L. Sliding fibular graft repair for the treatment of recurrent peroneal subluxation. Foot Ankle Int 35:496–503, 2014. 4. Edwards ME. The relations of the peroneal tendons the fibula, calcaneus, and cuboideum. Am J Anat 42:213–253, 1928. 5. Freccero DM, Berkowitz MJ. The relationship between tears of the peroneus brevis tendon and the distal extent of its muscle belly: an MRI study. Foot Ankle Int 27:236–239, 2006. 6. Sobel M, Bohne WH, O’Brien SJ. Peroneal tendon subluxation in a case of anomalous peroneus brevis muscle. Acta Orthop Scand 63:682–684, 1992. 7. Lamm BM, Myers DT, Dombek M, Mendicino RW, Catanzariti AR, Saltrick K. Magnetic resonance imaging and surgical correlation of peroneus brevis tears. J Foot Ankle Surg 43:30–36, 2004. 8. Lui TH. Tendoscopic resection of low-lying muscle belly of peroneus brevis or quartus. Foot Ankle Int 33:912–914, 2012. 9. Saupe N, Mengiardi B, Pfirrmann CW, Vienne P, Seifert B, Zanetti M. Anatomic variants associated with peroneal tendon disorders: MR imaging findings in volunteers with asymptomatic ankles. Radiology 242:509–517, 2007. 10. Heckman DS, Reddy S, Pedowitz D, Wapner KL, Parekh SG. Operative treatment for peroneal tendon disorders. J Bone Joint Surg Am 90:404–418, 2008. 11. Wang XT, Rosenberg ZS, Mechlin MB, Schweitzer ME. Normal variants and diseases of the peroneal tendons and superior peroneal retinaculum: MR imaging features. Radiographics 25:587–602, 2005. 12. Mendeszoon M, McVey JT, MacEvoy A. Surgical correction of subluxing peroneal tendons utilizing a lateral slip of the achilles tendon: a case report. Foot Ankle Online J 2:3–7, 2009. 13. Krause JO, Brodsky JW. Peroneus brevis tendon tears: pathophysiology, surgical reconstruction, and clinical results. Foot Ankle Int 19:271–279, 1998. 14. Sammarco GJ. Peroneal tendon injuries. Ortho Clinic North Am 25:135–145, 1994. 15. Khoury NJ, El-Khoury GY, Saltzman CK, Kathol MH. Peroneus longus and brevis tendon tears: MR imaging evaluation. Radiology 200:833–841, 1996. 16. Hammerschlag WA, Goldner JL. Chronic peroneal tendon subluxation produced by an anomalous peroneus brevis: case report and literature review. Foot Ankle 10:45–47, 1989. 17. Dombek MF, Lamm BM, Saltrick K, Mendicino RW, Catanzariti AR. Peroneal tendon tears: a retrospective review. J Foot Ankle Surg 42:250–258, 2003. 18. Giza E, Mak W, Wong SE, Roper G, Campanelli V, Hunter JC. A clinical and radiological study of peroneal tendon pathology. Foot Ankle Spec 6:417–421, 2013. 19. Park HJ, Cha SD, Kim HS, Chung ST, Park NH, Yoo JH, Park JH, Kim JH, Lee TW, Lee CH, Oh SM. Reliability of MRI findings of peroneal tendinopathy in patients with lateral chronic ankle instability. Clin Orthop Surg 2:237–243, 2010. 20. Unlu MC, Bilgili M, Akgun I, Kaynak G, Ogut T, Uzun I. Abnormal proximal musculotendinous junction of the peroneus brevis muscle as a cause of peroneus brevis tendon tears: a cadaveric study. J Foot Ankle Surg 49:537–540, 2010.
