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The anatomical configuration and clinical implications of the peroneal tubercle
Y&Foot (1996) 6, 138-142 0 1996 Pearson Professmnal Ltd
The anatomical configuration and clinical implications of the peroneal tubercle E. I? Hofmeister, I? Juliano, F. Lippert Department of Orthopedics, Nutional Naval Medical Center; Bethesda, MD, and The U~~f#~~ed Services University of the Health Sciences, Bethesda, MD
Many dis~r~pa~lcies and convicting data have been published on the anatomical identification, location, incidence and size of the peroneal tubercle. All such studies have been performed on freeze-dried bone, and no studies have measured the size of the peroneal tubercle in cadavers. Using 35 cadaver specimens, we found that the incidence of a peroneal tubercle was 94%, which is greater than previously reported. The average length was 10.3 mm, width 5.6 mm, height 4.0 mm: and average distance to the cal~allealcuboid joint was 17.2 mm. The incidence of hypertrophy of the peroneal tubercle was 3%. We also review the literature on the incidence and size of the peroneal tubercle, function of the peroneal tubercle, related structures, pathology associated with the peroneal tubercle, and treatment of these abnormalities. ~~~~ARY.
INTRODUCTION
Anatomy The peroneal tubercle is a structure projected from the anterior third of the lateral border of the calcaneus. It is bound superiorly by the peroneus brevis tendon and inferiorly by the peroneus longus tendon (Fig. 1) The peroneal tubercle is obliquely inclined with the long axis, running posterior~superior to anterior-inferior, with a glide facet for the peroneus longus tendon. The angle of this axis with reference to a horizontal reference line has been reported between a range of 35-50°.5*6 The reported dimensions of the peroneal tubercle have varied. The length of the peroneal tubercle has been reported as 2-20 mm with an average of 9.8 mm,’ 10mm,‘” and 13mrn5 The width has been reported as 0.2-10mm with an average of 1mm’O and 6mm.7 The height has been reported as O-9mm with an average of 4mm. 7~10The distance from the most anterior portion of the peroneal tubercle to the calcanealcuboid joint has been reported as lo-21mm with an average of 15 and 16mm.7,*0 Laidlaw classified the inte~~iate form of the peroneal tubercle into three groups. The first group was ‘oval form and well isolated,’ and the incidence was 60% of the well marked forms. The remainder of the well marked forms were classified as ‘ridge forms,’ in which the peroneal tubercle was narrow and long. A third group was classified as ‘imperfectly developed forms, in which the trochlea and retrotrochlear eminence were not clearly defined. This group occurred 6”/ of the time.
Incidence The peroneal tubercle is a structure projecting off the lateral border of the anterior third of the calcaneus. Numerous authors have reported the incidence of a peroneal tube&e with confusing and convicting data likely due to different genetic populations. In the late lSOOs,Grub& found that the presence of the peroneal tubercle was 39.1% and in 1889, Stieda” found an incidence of 33%. Pfitzner3 reported an overall incidence of a peroneal tubercle to be 39.9%. However, he found a difference in gender: the incidence in women was 42% compared to 39% in men. Since the turn of the 20th century, numerous other authors have reported the incidence as 32%,4 35.5%,5 44%” and 68%.7 In 1984, AgarwaP examined 14 10 Indian calcaneal specimens and found a 57.5% incidence of a peroneal tubercle in 480 specimens taken from the Agra region, and a 97.6% incidence in 930 specimens from the Lucknow region. He attributed the difference of occurrences to the genetic difference of the two Indian populations. Penteado et al9 examined skeletons and reported a bilateral asymmetry of the patient; the incidence in specimens from the right foot was 38.0% versus 76.1% in the left foot.
Correspondence to: LT Eric Hofmeister, Department of Orthopedics, 44-391 Nilu St #5, Kaneohe Bay, Hawaii 96744. 138
The peroneal tubercle 139
Fig.
l-Gross
dissection
showing
the peroneus
longus
tendon
(PL),
A second classification was reported by Edwards.(j He described type A as a prominent, well developed peroneal tubercle, and 24% of his specimens were in this group. Type B were those with a definite but less marked process, and occurred 20% of the time. Type C consisted of a low ridge above the groove for the peroneal longus tendon, and was present 14% of the time. Lastly, type D was an absence of a peroneal tubercle. This occurred in 44% of his samples. In a third attempt at classifying the peroneal tubercle, Agarwal et al* used four groupings recording data from two different geographic regions. Type I was a single peroneal tubercle found anterior and inferior to the tuberculum ligamenti calcaneofibularis. This group made up 31% from region 1 and 60”! from region 2. Type II peroneal tubercle was again a single tubercle, but incompletely divided into an anterior and posterior portion by a smooth, shallow groove. The incidence was 19% in region 1,24% in region 2. Type III consisted of tubercles completely separated by a roughened area, and had an incidence of 8% and 14% in regions 1 and 2 respectfully. In type IV, the peroneal tubercle was absent. As stated previously. the incidence was 42.5% in region 1 compared to that of 2.4% in region 2. Function
There are three functions of the peroneal tubercle. First, it serves as the insertion site of the inferior peroneal retinaculum. Second, it physically separates the common peroneal tendon sheath into separate sheaths for the peroneus longus and brevis tendons
peroneus
brevis
tendon
(PB) and the peroneal
tubercle
(PT).
(Fig. 2). Third, it assists with first ray planterflexion by serving as another fulcrum or pulley for the peroneus longus tendon, the other pulleys being the retromalleolar groove of the fibula and the groove around the cuboid.‘“J’ Related structures
There are several other structures near the lateral calcaneus that can be easily confused with the peroneal tubercle, to include the retrotrochlear eminence, the OS peroneum, the calcaneus accessorius, and the OS subfibulare. The retrotrochlear eminence is posterior to the peroneal tubercle and more centrally located on the calcaneus. Superior and posterior to the retrotrochlear eminence is the tuberculum ligamenti calcaneofibulars (peroneal spine) which serves as the distal attachment for the calcaneofibular ligament, Anteriorly located, a tuberculum ligamenti talocalcanei, which serves as the distal attachment for the lateral talocalcaneal ligament, may be present.s The incidence of the retrotrochlear eminence is 98% and therefore is considered the most constant structure of the lateral surface of the calcaneus.5*6 The OSperoneum, when present, is a sesamoid in the peroneus longus tendon located as the tendon passes inferior to the plantar aspect of the cuboid. If a fracture occurs through the OSperoneum causing the peroneus longus tendon to rupture, a portion of this sesamoid can migrate posterior and superior to its original position, closely resembling the peroneal tubercle.‘?-l4 In these cases, it is important to look for
140 The Foot
Inferior Peroneal Retinaculum
Fig. Z-Cross-sectional view of peroneal tuber& (PT). Note the insertion of the inferior r~tinacul~ on the tubercle.
a second segment of the sesamoid at the level of the cuboid tunneLI The OS subfibulare, originally thought to be a sesamoid within the peroneus longus tendonI is an ununited apophysis located inferior to the tip of the fibula.” Tt recently has been reported of having an incidence of 6.7%,16 and there have been reported symptomatic cases of this structure.17 It is differentiated by its rounded, even appearance with well defined cortical margins. “,” The calcaneus accessorius is an accessory bone approximating with the peroneal tubercle just distal to the fibular malleolus.18.“9 It is very seldom present, and no larger than 5 mm in diameter.‘l It is differentiated from the peroneal tubercle by its articulation with the calcaneus rather than arising from it. Pathology Since it may cause pathology when h~ertrophied~ the peroneal tubercle’s normal measurements are important to quantify. In cases where it was present, the peroneal tubercle has been reported as prominent or hypertrophied as high as 20.5-24%.5%6 The etiology of the hypertrophied peroneal tubercle appears to be multifacto~al, and can occur in a planus type” and a cavus type foot.21 The peroneus longus tendon plantar flexes the first ray. If excessive force is placed on the peroneal tubercle by the peroneus longus tendon, such as in a cavovarus foot, peroneal hypertrophy may occur. Bonnett2’ reported on such a case. His case of unilateral peroneal tubercle hypertrophy was in a patient with paralytic foot drop. He believed that peroneus longus tendon spasms were
the causative factor for peroneal tubercle enlargement. He suggested that the peroneal tubercle adapts to excessive force from the peroneus longus tendon, causing an enlargement. Burman 23 also reported a case in which an enlarged peroneal tubercle was thought to be due to the forces and tension from the peroneus longus tendon. The peroneus quartus muscle, when present, inserts on the peroneal tubercle. One report demonstrates that in cases that this muscle was present, all showed radiographic signs of hypertrophy of the peroneal tubercleZ4 In none of these cases was an enlarged or hypertrophied peroneal tubercle defined. Symptoms of an enlarged peroneal tubercle include pain, a clicking sensation with ambulation21 and can be so painful as to limit ~bulation of a patient.“2 Pierson & Inglisz5 believed a case of peroneal tubercle hypertrophy caused localized tenosynovitis of the peroneal longus tendon that mimicked subtalar instability. There is also a case report of an enlarged peroneal tubercle being the causative reason for a peroneus longus tendon rupture during an inversion movement.= The hypertrophied tubercle can usually be seen on radiographs that include the calcaneus. The peroneal tubercle is also subject to trauma. Burman26 reported a fracture of the anterior portion of the peroneal tubercle believed to be secondary to an inversion ankle sprain. Treatment Treatment for an enlarged peroneal tubercle consists of conservative therapy and surgical intervention. Conservative treatment includes stretching the peroneus longus muscle, change in shoe gear, accommodative footwear, padding, and orthotics.27,28 If conservative treatment fails, surgical reduction of the hypertrophy may be required. The easiest way to perform reduction is to divide the peroneal tendons and excise the tubercle.21 The author has had successful results by leaving enough of the tubercle to preserve its function. Trerrino et a12gdeveloped and used a technique to maintain the integrity of the tendon sheath. They strengthened the retillaculum by using the deep fascia, and then reinforced the sheath with the retinaculum. Berenter & GoldmanZ8 created a thin osteochondral flap before resecting the remainder of the peroneal tubercle, thus preserving the cartilaginous gliding facet of the peroneal tubercle and the gliding capacity of the tendon.
MATERIALS
AND METHODS
Thirty-five fresh frozen and fixed dissected and the peroneal tnbercle exposed. The specimens consisted and female, right and left feet. The
cadavers were identified and of both male height, width,
The Deroneal tubercle 14 1 Table l--
Results
Specimen
1 2 3 4 5 6 I 8 9 10
11 12 13 14 1.5 16 17 18 19 20 21 22 23 24 '5 26 27 28 29 30 31 32 33 34
35
--.____ Foot”
L L R L R L R R L R R R L L R R
L L R
R R L L R L L L R R L R L R L
Length
(mm)
S.8 1.1 10.7 9.8 6 7.5 7.9
12 10 8 11.7 9 11.7 13.7 13.3 13 15.3 13 8 12.8 8.1
11.8 12.7 16.8 0 12.5 0 7.2
9.1 12.9 16.8 7.1 8.4 11.9 13.8
Peroneal (mm)
Width -
4.1
tube&e Thickness
(mm)
3.9 4 55 3.4 4.6 6.9 3.9 7.9 2.6 4.7 3 5.7 4.3 7.3 2.7 3 3.1 3.7 4 1
4.2 6.5 6.1 4.5 4.3 5.1
6.9 4.7 8.1 5 I I 8 6.3 7 9 7 6 5 4.5 8.4 5.3 0 5.7 0 4 5.1 6.1 6.1 3.9 3.9
5.1
.I. -~ Distance**(mm)
16.3
14 23 22.7 21.3 17.8 0 19.2 0 22.8 21.8 17.4 19.2 23.7 16.2 13.3 14.1
19.7 9.3 25.1 23.7 22.2 25.9 20.9 15.1 15.7 21.4 25.6 23.5 17.3 14.8 24.4 26.1 18.6 21.7 19.4 12.5 19.9 21.6 24.2 21.1 23.8 18.6 21.4 19.6 20.4 18.4 21.9 19.8 22.1 19.8 20.46
13.2 13.1 23.3 21.3 20 22 16 18.5 14 13
11 24.7 15.7 25.7 16.3
13.9 19
7.1
5.2 3.2 0 4 0 2.5 4.2 5.4 4.5 2 2 4.8 5.2 4.00 1-7
17.16
8.6
16.8
8.1
Average Range
10.33 6-17
5.59 4-P
R
15.6
8.1
-__- _ ._---.______
Peroneus longus tendon Area (mm2)
1 l-25 31.3
*Denotes right or left foot of specimen **Distance from the peroneal tube&e to the calcanealcuboid joint. Also note that specimen number 3.5was considered lly~rtrophied and was not included in the cafculatlons.
length, and distance to the calcaneocuboid joint were measured 3 times using calipers and then averaged, The results were then tabulated using descriptive statistics. In a similar fashion, the average of 3 measurements of the width and thickness of the peroneus longus tendon was made at the superior aspect of the inferior retinaculum. Using these measurements, the area of the tendon was calculated using a standard elliptical area equation: area = 3.142 (length) (width)/4. The foot type (planovalgus vs cavovarus) of each specimen could not be determined due to the fixed state of the post-mortem specimens.
average distance to the calcanealcuboid joint was 17.2 mm. The incidence of h~rtrophy of the peroneal tendon was 3% (1135). This 1 case, which was not included in Table 1, had a peroneal tubercle measuring 15.6 mm in length, 8.1 mm in width and 8.6 mm in thickness. These values were not included in our results as the thickness was more than double the average size. This was the only case in which hypertrophy was present. The average area of the peroneus longus tendon was 20.46 mm2 compared to 31.3 mm2 in the hypertrophied specimen.
DISCUSSION RESULTS
(FIG. 3)
Using 35 cadaver specimens, we found that the incidence of a peroneal tubercle was 94%, the average length was 10.3 mm, width 5.6 mm, height 4.0 mm, and
We took measurements from cadaver specimens rather than freeze-dried bone, as these measurements would be more easily compared to operative measurements when locating, determining hypertrophy, and accessing size after surgical reduction of a hype~rophied
142 The Foot peroneal tubercle. Although our sizes did not vary much from recent literature, the incidence of the peroneal tubercle was much greater and the incidence of hypertrophy was much less than previously reported in the literature. Additionally, we attempted to demonstrate that the peroneus longus tendon enIarges in the cavovarus foot type, causing hypertrophy of the peroneal tubercle. Although our specimen of peroneal tubercle hypertrophy has an enlarged tendon, foot type could not be determined. Further human observations and studies are required and are currently being investigated.
6.
I. 8. 9.
10. 11, 12.
13.
CONCLUSION
14.
We found the peroneal tubercle present in 94% of the specimens, with the average size being 10.3 mm long, 5.6 mm. wide, 4.0 mm thick, and being 17.2 mm from the calcanealcuboid joint. The incidence of hypertrophy was only 3% and was associated with an increased tendon size. It is important to be familiar with this structure as pedal pathology can be secondary to an abnormal size, and by knowing the normal size and orientation, one can determine if hypertrophy is present.
15.
1993:505,513. 16.
17. 18. 19.
20.
RETRENCH 1. Gruber W Ueber den eme Thierbildun Reprasenttrenden Normalen, und unber den Exostotisch Gewordenen Processus Trochlearis Calcanei. Virchows Arch 1877: 70: 128.-132. 2. Steida L. Cited by: Burman M. Stenosing tendovaginitis of the foot and ankle. Studies with special reference to the stenosing tendovaginitls of the peroneal tendons at the peroned tube&e. Arch Surg 1953: 67: 686698. 3. Pfitzner W. Die Variationen im Aufbau der Fussskelets. Morph01 Arbeiten 1896; 6: 2455527. 4. Sarrafian S K. Anatomv of the Foot and Ankle. Philadelohia. I Lippincott, 1983: 63-64. 5. Laidlaw P P. The varieties of the OScalcis. J Anat Physiol 1904; 38: 133-143.
Bowlus T, Korman S, Desilvio M, Climo R, Accessory OS fibulare avulsion secondary to the mversion ankle injury. JAPMA 1980; 70: 302-303. Griffiths J. Menelaus M. Symptomatic ossciles of the latera malleolus in children. J Bone Joint Sure 1987: 69B: 317-319. Hirschtick A. An anomalous tarsal bone. J Bone Joint Surg 1951; 33A: 907-910. Mercer. Cited by Mann R A, Coughlin M J. Surgery of the foot and ankle, 6th ed. St Louis: Mosby, 1993: 505, 513. Budde M. Zur Pathologie des Processus Trochlearia Calcanei, Arch Klin Chir 1924; 133: 64-65. Bisceglia G, Sirota A, Dull D. An unusual case of hypertrophied peroneal tubercles. JAPA 1983; 9: 481-482. Bonnet P. Synovite des peroniers lateraux en relation avec un tubercle externe du calcaneum exuberan. Lyon Chir 1931; 28: 476480. From A. Ruiz J, Christman R, Hillstrom H. Anatomical considerations of the peroneal tubercle. JAPMA w
ACKNOWLEDGEMENTS
The Chief, Navy Bureau of Medicine and Surgery, Washington DC, Clinical Investigation Program sponsored the study, #B094-048. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, nor the US Government.
Edwards M E. The relattons of the peroneal tendons to the fibula, calcaneus, and cuboidenum. Am J Anat 1928; 42: 213-242. Oertel 0. Beitrag zur anatomie und vergl: anatomie des process trochiearis calcanei als grudnlage fur seine pathologie. Arch Path01 Anat 1923; 247: 5633579. Agarwal A K. Jeyasingh S C, Gupta S C, Gupta C D. Ashok S. Peroneal Tubercle and its variation in the Indian calcanei. Anat Anz 1984; 156: 241-244. Penteado C, Duarte E, Filho J, Stabille S. Non-metric traits of the infracranial skelton. Anat Anz 1986; 162: 47-50. Ruiz .I, Christman R, Hillstrom H. Anatomical considerations of the peroneal tubercle. JAPMA 1993; 83: 5633575. Mann R A, Cough& M J. Surgery of the foot and ankle, 6th ed. St Louis: Mosby, 1993: 505.513. Tehranzadeh J, Stoll D, Gabriele 0. Case report 271: Posterior migration of the OSperoneum indication a tear of the peroneal tendon. Skel Radio1 1984; 12: 4447. Thompson F, Patterson A. Rupture of the peroneus longus tendon. J Bone Joint Sum 1989: 71A: 2933295. Peacock K, Resnick E, coder J. Fracture of the OSperoneum with rupture of the peroneus longus tendon. Clin Orthop 1986; 202: 223-226. Trolle D. Accessory bones of the foot. Copenhagen: Munskgrad, 1948. Cited in: Mann R A, Coughlin M J. Surgery of the foot and ankle, 6th cd. Louis: Mosby, St
21. 22.
1993;83:563-575.
Burman M. Subcutaneous tear of the tendon of the peroneus longus. Its relationship to the giant peroneal tubercle. Arch Surg 1956; 73: 216-219. 24. Sobel L, Walther B. Congenital variations of the peroneus quartus muscle: an anatomic study. Foot Ankle 1991; 11: 81-89. 35. Pierson J, Inglis A, Stenosing tenosynovitis of the peroneus longus tendon associated with hypertrophy of the peroneal tubercle and an OSperoneum. J Bone Joint Surg 1992: 74A: 440442. 26. Burman M. Stenosing tendovaginitis of the foot and ankle. Studies with special reference to the stenosing tendovaginitis of the peroneal tendons at the peroneal tube&e. Arch Surg 23.
1953;67:686-698.
27. Wachter S, Beekman S. Peroneus quartus. A case report. JAPA 1983; 73: 523-524. 28. Berenter J, Goldman F. Surgical approach for enlarged peroneal tubercles. JAPMA 1989; 79: 451-454. 29. Trevino S, Gould N, Korson R. Surgical treatment of stenosing tenosynovitis at the ankle. Foot Ankle 1981: 2: 3745.
The anatomical configuration and clinical implications of the peroneal tubercle E. I? Hofmeister, I? Juliano, F. Lippert Department of Orthopedics, Nutional Naval Medical Center; Bethesda, MD, and The U~~f#~~ed Services University of the Health Sciences, Bethesda, MD
Many dis~r~pa~lcies and convicting data have been published on the anatomical identification, location, incidence and size of the peroneal tubercle. All such studies have been performed on freeze-dried bone, and no studies have measured the size of the peroneal tubercle in cadavers. Using 35 cadaver specimens, we found that the incidence of a peroneal tubercle was 94%, which is greater than previously reported. The average length was 10.3 mm, width 5.6 mm, height 4.0 mm: and average distance to the cal~allealcuboid joint was 17.2 mm. The incidence of hypertrophy of the peroneal tubercle was 3%. We also review the literature on the incidence and size of the peroneal tubercle, function of the peroneal tubercle, related structures, pathology associated with the peroneal tubercle, and treatment of these abnormalities. ~~~~ARY.
INTRODUCTION
Anatomy The peroneal tubercle is a structure projected from the anterior third of the lateral border of the calcaneus. It is bound superiorly by the peroneus brevis tendon and inferiorly by the peroneus longus tendon (Fig. 1) The peroneal tubercle is obliquely inclined with the long axis, running posterior~superior to anterior-inferior, with a glide facet for the peroneus longus tendon. The angle of this axis with reference to a horizontal reference line has been reported between a range of 35-50°.5*6 The reported dimensions of the peroneal tubercle have varied. The length of the peroneal tubercle has been reported as 2-20 mm with an average of 9.8 mm,’ 10mm,‘” and 13mrn5 The width has been reported as 0.2-10mm with an average of 1mm’O and 6mm.7 The height has been reported as O-9mm with an average of 4mm. 7~10The distance from the most anterior portion of the peroneal tubercle to the calcanealcuboid joint has been reported as lo-21mm with an average of 15 and 16mm.7,*0 Laidlaw classified the inte~~iate form of the peroneal tubercle into three groups. The first group was ‘oval form and well isolated,’ and the incidence was 60% of the well marked forms. The remainder of the well marked forms were classified as ‘ridge forms,’ in which the peroneal tubercle was narrow and long. A third group was classified as ‘imperfectly developed forms, in which the trochlea and retrotrochlear eminence were not clearly defined. This group occurred 6”/ of the time.
Incidence The peroneal tubercle is a structure projecting off the lateral border of the anterior third of the calcaneus. Numerous authors have reported the incidence of a peroneal tube&e with confusing and convicting data likely due to different genetic populations. In the late lSOOs,Grub& found that the presence of the peroneal tubercle was 39.1% and in 1889, Stieda” found an incidence of 33%. Pfitzner3 reported an overall incidence of a peroneal tubercle to be 39.9%. However, he found a difference in gender: the incidence in women was 42% compared to 39% in men. Since the turn of the 20th century, numerous other authors have reported the incidence as 32%,4 35.5%,5 44%” and 68%.7 In 1984, AgarwaP examined 14 10 Indian calcaneal specimens and found a 57.5% incidence of a peroneal tubercle in 480 specimens taken from the Agra region, and a 97.6% incidence in 930 specimens from the Lucknow region. He attributed the difference of occurrences to the genetic difference of the two Indian populations. Penteado et al9 examined skeletons and reported a bilateral asymmetry of the patient; the incidence in specimens from the right foot was 38.0% versus 76.1% in the left foot.
Correspondence to: LT Eric Hofmeister, Department of Orthopedics, 44-391 Nilu St #5, Kaneohe Bay, Hawaii 96744. 138
The peroneal tubercle 139
Fig.
l-Gross
dissection
showing
the peroneus
longus
tendon
(PL),
A second classification was reported by Edwards.(j He described type A as a prominent, well developed peroneal tubercle, and 24% of his specimens were in this group. Type B were those with a definite but less marked process, and occurred 20% of the time. Type C consisted of a low ridge above the groove for the peroneal longus tendon, and was present 14% of the time. Lastly, type D was an absence of a peroneal tubercle. This occurred in 44% of his samples. In a third attempt at classifying the peroneal tubercle, Agarwal et al* used four groupings recording data from two different geographic regions. Type I was a single peroneal tubercle found anterior and inferior to the tuberculum ligamenti calcaneofibularis. This group made up 31% from region 1 and 60”! from region 2. Type II peroneal tubercle was again a single tubercle, but incompletely divided into an anterior and posterior portion by a smooth, shallow groove. The incidence was 19% in region 1,24% in region 2. Type III consisted of tubercles completely separated by a roughened area, and had an incidence of 8% and 14% in regions 1 and 2 respectfully. In type IV, the peroneal tubercle was absent. As stated previously. the incidence was 42.5% in region 1 compared to that of 2.4% in region 2. Function
There are three functions of the peroneal tubercle. First, it serves as the insertion site of the inferior peroneal retinaculum. Second, it physically separates the common peroneal tendon sheath into separate sheaths for the peroneus longus and brevis tendons
peroneus
brevis
tendon
(PB) and the peroneal
tubercle
(PT).
(Fig. 2). Third, it assists with first ray planterflexion by serving as another fulcrum or pulley for the peroneus longus tendon, the other pulleys being the retromalleolar groove of the fibula and the groove around the cuboid.‘“J’ Related structures
There are several other structures near the lateral calcaneus that can be easily confused with the peroneal tubercle, to include the retrotrochlear eminence, the OS peroneum, the calcaneus accessorius, and the OS subfibulare. The retrotrochlear eminence is posterior to the peroneal tubercle and more centrally located on the calcaneus. Superior and posterior to the retrotrochlear eminence is the tuberculum ligamenti calcaneofibulars (peroneal spine) which serves as the distal attachment for the calcaneofibular ligament, Anteriorly located, a tuberculum ligamenti talocalcanei, which serves as the distal attachment for the lateral talocalcaneal ligament, may be present.s The incidence of the retrotrochlear eminence is 98% and therefore is considered the most constant structure of the lateral surface of the calcaneus.5*6 The OSperoneum, when present, is a sesamoid in the peroneus longus tendon located as the tendon passes inferior to the plantar aspect of the cuboid. If a fracture occurs through the OSperoneum causing the peroneus longus tendon to rupture, a portion of this sesamoid can migrate posterior and superior to its original position, closely resembling the peroneal tubercle.‘?-l4 In these cases, it is important to look for
140 The Foot
Inferior Peroneal Retinaculum
Fig. Z-Cross-sectional view of peroneal tuber& (PT). Note the insertion of the inferior r~tinacul~ on the tubercle.
a second segment of the sesamoid at the level of the cuboid tunneLI The OS subfibulare, originally thought to be a sesamoid within the peroneus longus tendonI is an ununited apophysis located inferior to the tip of the fibula.” Tt recently has been reported of having an incidence of 6.7%,16 and there have been reported symptomatic cases of this structure.17 It is differentiated by its rounded, even appearance with well defined cortical margins. “,” The calcaneus accessorius is an accessory bone approximating with the peroneal tubercle just distal to the fibular malleolus.18.“9 It is very seldom present, and no larger than 5 mm in diameter.‘l It is differentiated from the peroneal tubercle by its articulation with the calcaneus rather than arising from it. Pathology Since it may cause pathology when h~ertrophied~ the peroneal tubercle’s normal measurements are important to quantify. In cases where it was present, the peroneal tubercle has been reported as prominent or hypertrophied as high as 20.5-24%.5%6 The etiology of the hypertrophied peroneal tubercle appears to be multifacto~al, and can occur in a planus type” and a cavus type foot.21 The peroneus longus tendon plantar flexes the first ray. If excessive force is placed on the peroneal tubercle by the peroneus longus tendon, such as in a cavovarus foot, peroneal hypertrophy may occur. Bonnett2’ reported on such a case. His case of unilateral peroneal tubercle hypertrophy was in a patient with paralytic foot drop. He believed that peroneus longus tendon spasms were
the causative factor for peroneal tubercle enlargement. He suggested that the peroneal tubercle adapts to excessive force from the peroneus longus tendon, causing an enlargement. Burman 23 also reported a case in which an enlarged peroneal tubercle was thought to be due to the forces and tension from the peroneus longus tendon. The peroneus quartus muscle, when present, inserts on the peroneal tubercle. One report demonstrates that in cases that this muscle was present, all showed radiographic signs of hypertrophy of the peroneal tubercleZ4 In none of these cases was an enlarged or hypertrophied peroneal tubercle defined. Symptoms of an enlarged peroneal tubercle include pain, a clicking sensation with ambulation21 and can be so painful as to limit ~bulation of a patient.“2 Pierson & Inglisz5 believed a case of peroneal tubercle hypertrophy caused localized tenosynovitis of the peroneal longus tendon that mimicked subtalar instability. There is also a case report of an enlarged peroneal tubercle being the causative reason for a peroneus longus tendon rupture during an inversion movement.= The hypertrophied tubercle can usually be seen on radiographs that include the calcaneus. The peroneal tubercle is also subject to trauma. Burman26 reported a fracture of the anterior portion of the peroneal tubercle believed to be secondary to an inversion ankle sprain. Treatment Treatment for an enlarged peroneal tubercle consists of conservative therapy and surgical intervention. Conservative treatment includes stretching the peroneus longus muscle, change in shoe gear, accommodative footwear, padding, and orthotics.27,28 If conservative treatment fails, surgical reduction of the hypertrophy may be required. The easiest way to perform reduction is to divide the peroneal tendons and excise the tubercle.21 The author has had successful results by leaving enough of the tubercle to preserve its function. Trerrino et a12gdeveloped and used a technique to maintain the integrity of the tendon sheath. They strengthened the retillaculum by using the deep fascia, and then reinforced the sheath with the retinaculum. Berenter & GoldmanZ8 created a thin osteochondral flap before resecting the remainder of the peroneal tubercle, thus preserving the cartilaginous gliding facet of the peroneal tubercle and the gliding capacity of the tendon.
MATERIALS
AND METHODS
Thirty-five fresh frozen and fixed dissected and the peroneal tnbercle exposed. The specimens consisted and female, right and left feet. The
cadavers were identified and of both male height, width,
The Deroneal tubercle 14 1 Table l--
Results
Specimen
1 2 3 4 5 6 I 8 9 10
11 12 13 14 1.5 16 17 18 19 20 21 22 23 24 '5 26 27 28 29 30 31 32 33 34
35
--.____ Foot”
L L R L R L R R L R R R L L R R
L L R
R R L L R L L L R R L R L R L
Length
(mm)
S.8 1.1 10.7 9.8 6 7.5 7.9
12 10 8 11.7 9 11.7 13.7 13.3 13 15.3 13 8 12.8 8.1
11.8 12.7 16.8 0 12.5 0 7.2
9.1 12.9 16.8 7.1 8.4 11.9 13.8
Peroneal (mm)
Width -
4.1
tube&e Thickness
(mm)
3.9 4 55 3.4 4.6 6.9 3.9 7.9 2.6 4.7 3 5.7 4.3 7.3 2.7 3 3.1 3.7 4 1
4.2 6.5 6.1 4.5 4.3 5.1
6.9 4.7 8.1 5 I I 8 6.3 7 9 7 6 5 4.5 8.4 5.3 0 5.7 0 4 5.1 6.1 6.1 3.9 3.9
5.1
.I. -~ Distance**(mm)
16.3
14 23 22.7 21.3 17.8 0 19.2 0 22.8 21.8 17.4 19.2 23.7 16.2 13.3 14.1
19.7 9.3 25.1 23.7 22.2 25.9 20.9 15.1 15.7 21.4 25.6 23.5 17.3 14.8 24.4 26.1 18.6 21.7 19.4 12.5 19.9 21.6 24.2 21.1 23.8 18.6 21.4 19.6 20.4 18.4 21.9 19.8 22.1 19.8 20.46
13.2 13.1 23.3 21.3 20 22 16 18.5 14 13
11 24.7 15.7 25.7 16.3
13.9 19
7.1
5.2 3.2 0 4 0 2.5 4.2 5.4 4.5 2 2 4.8 5.2 4.00 1-7
17.16
8.6
16.8
8.1
Average Range
10.33 6-17
5.59 4-P
R
15.6
8.1
-__- _ ._---.______
Peroneus longus tendon Area (mm2)
1 l-25 31.3
*Denotes right or left foot of specimen **Distance from the peroneal tube&e to the calcanealcuboid joint. Also note that specimen number 3.5was considered lly~rtrophied and was not included in the cafculatlons.
length, and distance to the calcaneocuboid joint were measured 3 times using calipers and then averaged, The results were then tabulated using descriptive statistics. In a similar fashion, the average of 3 measurements of the width and thickness of the peroneus longus tendon was made at the superior aspect of the inferior retinaculum. Using these measurements, the area of the tendon was calculated using a standard elliptical area equation: area = 3.142 (length) (width)/4. The foot type (planovalgus vs cavovarus) of each specimen could not be determined due to the fixed state of the post-mortem specimens.
average distance to the calcanealcuboid joint was 17.2 mm. The incidence of h~rtrophy of the peroneal tendon was 3% (1135). This 1 case, which was not included in Table 1, had a peroneal tubercle measuring 15.6 mm in length, 8.1 mm in width and 8.6 mm in thickness. These values were not included in our results as the thickness was more than double the average size. This was the only case in which hypertrophy was present. The average area of the peroneus longus tendon was 20.46 mm2 compared to 31.3 mm2 in the hypertrophied specimen.
DISCUSSION RESULTS
(FIG. 3)
Using 35 cadaver specimens, we found that the incidence of a peroneal tubercle was 94%, the average length was 10.3 mm, width 5.6 mm, height 4.0 mm, and
We took measurements from cadaver specimens rather than freeze-dried bone, as these measurements would be more easily compared to operative measurements when locating, determining hypertrophy, and accessing size after surgical reduction of a hype~rophied
142 The Foot peroneal tubercle. Although our sizes did not vary much from recent literature, the incidence of the peroneal tubercle was much greater and the incidence of hypertrophy was much less than previously reported in the literature. Additionally, we attempted to demonstrate that the peroneus longus tendon enIarges in the cavovarus foot type, causing hypertrophy of the peroneal tubercle. Although our specimen of peroneal tubercle hypertrophy has an enlarged tendon, foot type could not be determined. Further human observations and studies are required and are currently being investigated.
6.
I. 8. 9.
10. 11, 12.
13.
CONCLUSION
14.
We found the peroneal tubercle present in 94% of the specimens, with the average size being 10.3 mm long, 5.6 mm. wide, 4.0 mm thick, and being 17.2 mm from the calcanealcuboid joint. The incidence of hypertrophy was only 3% and was associated with an increased tendon size. It is important to be familiar with this structure as pedal pathology can be secondary to an abnormal size, and by knowing the normal size and orientation, one can determine if hypertrophy is present.
15.
1993:505,513. 16.
17. 18. 19.
20.
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ACKNOWLEDGEMENTS
The Chief, Navy Bureau of Medicine and Surgery, Washington DC, Clinical Investigation Program sponsored the study, #B094-048. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, nor the US Government.
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