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BMJ Case Rep. 2015; 2015: bcr2015212837.
Published online 2015 December 16. doi:  10.1136/bcr-2015-212837
PMCID: PMC4691900
Case Report

Bilateral closed flexor pollicis longus musculotendinous junction ruptures


We present a case of bilateral closed flexor pollicis longus musculotendinous junction ruptures. Our case suggests multifactorial aetiology and provides further evidence for genetic influences in musculotendinous junction injuries.


Closed flexor tendon ruptures of the hand are uncommon. They usually occur at the flexor digitorum profundus (FDP) bony insertion1 and less commonly at the musculotendinous junction.

Closed musculotendinous junction ruptures in the absence of underlying disease or direct trauma are very rare with limited literature on the subject.2 Furthermore, the pathogenesis of such injuries is incompletely understood.

Case presentation

A fit and well 34-year-old male laundry worker presented with a 2-week history of inability to flex his non-dominant left thumb at the interphalangeal joint. He was a non-smoker with no previous steroid use or drug abuse. There was no history of injury or previous fractures, and he did not participate in regular sporting activities.


Ultrasound scan showed a flexor pollicis longus (FPL) musculotendinous junction rupture. When the interphalangeal joint of the thumb was moved the tendon could be seen moving in the forearm confirming continuity (figures 1 and and2).2). The FPL muscle was, however, atrophied, suggesting a rupture at the musculotendinous junction. Doppler ultrasound scan and nerve conduction studies were normal.

Figure 1
Ultrasound scan showing continuity of left flexor pollicis longus tendon at the first metacarpal. Right to left is distal to proximal.
Figure 2
Ultrasound scan showing continuity of left flexor pollicis longus tendon in the distal forearm. Right to left is distal to proximal.


Intraoperatively, there was complete rupture at the FPL musculotendinous junction. On gross examination there was no evidence of attrition or other pathology. The patient was surgically treated with a ring finger flexor digitorum superficialis (FDS) tendon transfer. His thumb was placed in a resting splint postoperatively and he was started on an early active mobilisation regime a week later.

Outcome and follow-up

The patient had full return of thumb flexion and hand function. He returned to work, but 2.5 years later presented with a similar history affecting his dominant thumb, again with no obvious aetiology. Ultrasound scan confirmed another FPL musculotendinous junction rupture and he was offered another tendon transfer but declined surgery due to personal reasons.


The weakest points along the muscle-tendon unit are known to be the bony insertion of the tendon and, less commonly, the musculotendinous junction.3 Clinically, ruptures are uncommon and typically seen in the context of trauma or underlying pathology.

Closed musculotendinous junction ruptures are proposed to occur from longitudinal traction on contracted muscles4 or attrition of the musculotendinous junction by nearby structures from pre-existing pathology or following trauma.5 In the upper limb, closed musculotendinous injuries frequently involve the rotator cuff, long extensor and long flexor muscles.6 In the lower limb, the Achilles tendon is the most frequently injured tendon, especially in athletic individuals or during recreational activity. The incidence of Achilles tendon rupture in the general population is known to be around 7/100 000.7 Several case series have reported under 10% of these ruptures to occur at the musculotendinous junction.7 8

Closed flexor tendon ruptures usually occur at their bony insertion secondary to trauma or underlying pathology, such as rheumatoid arthritis.2 In the upper limb, the FDP tendon is most commonly involved in closed flexor tendon ruptures. FDP tendon avulsion injuries are relatively common due to stress concentration at the hard–soft tissue interface.9 These injuries are also called ‘jersey fingers’, due to their association with sports, where the flexed distal interphalangeal joint is hyperextended or forcefully flexed against passive extension.10 The ring finger accounts for 75% of FDP tendon avulsions. FDS tendon ruptures are less common and most commonly affect the ring and middle fingers.11

Closed FPL tendon ruptures are rare with only around 10 reported cases in the English literature.1 2 All these cases were as a result of trauma or underlying pathology.12 Reported mechanisms included crush injuries, hyperextension injuries and after treatment of other pathologies, for example, Bennett's fracture13 or distal radius fractures.14

Spontaneous tendon ruptures describe a group of rare closed injuries where ‘no intrinsic or extrinsic pathological processes can be macroscopically identified’.1 A review of the current English literature shows around 60 spontaneous flexor tendon ruptures to date.2 These are most commonly reported to involve the FDP tendon with no predisposing factors, but have occasionally been linked to variations in tendon anatomy such as fusion of the ring and little finger FDP tendons side to side until the mid-palmar level.6 The mechanisms involved in spontaneous flexor tendon injuries are incompletely understood. They have been speculated to involve repetitive movements with microtrauma, or increased stress loading, especially when carrying out tasks involving flexion against resistance.15

We present a case of bilateral closed FPL musculotendinous junction ruptures in the absence of any obvious underlying pathological process or direct trauma. Our patient’s work predominantly required repeated folding of clothes and manual transfer with no excessive force. Imbriglia and Goldstein15 have reported 10 cases of spontaneous FDP tendon ruptures of the little finger with all patients having jobs requiring repetitive motion with power grip on a routine basis. Boyes et al1 found that the force producing the flexor tendon ruptures was often slight, and suggested that some underlying factors may already predispose the muscle tendon unit to rupture. Although our patient had no relevant family history and declined genetic tests, the bilateral nature of our case suggests a role for genetic influences.

It is known that there is a spectrum of genetic influences on the strength of connective tissue. Disorders of connective tissue, such as Ehlers-Danlos syndrome (EDS), have highlighted genetic mutations in two of the three chains constituting ubiquitous collagen type V α 1 (COL5A1)16 and collagen type V α 2 (COL5A2).17 Numerous mutations have been identified in rarer variants of EDS, of particular note is the tenascin-X deficient EDS caused by mutations in the TNXB gene18 coding for tenascin glycoprotein. This decreases the messenger RNA expression of several collagen type VI genes such as COL6A1, COL6A2 and COL6A3.19

Studies suggest that various genes, such as tenascin-C (TNC), COL5A1 and matrix metallopeptidase 3 (MMP3), may be involved with musculotendinous injuries. The TNC gene encodes a glycoprotein found in tendons thought to be concerned with cell–matrix interactions.20 TNC expression is regulated at the musculotendinous junction in a dose-dependent manner based on mechanical loading in tendons.21 The COL5A1 gene encodes the α1 chain of the low abundance type V fibrillar collagen found in tendons. It has been widely implicated as a polymorphic association with tendon integrity in white individuals.22 The MMP3 gene codes for a protein involved in the homoeostatic processes in tendons and regulates their mechanical properties. An interaction of MMP3 with COL5A1 has been proposed with regard to tendinopathy.23

Our case presentation suggests multifactorial aetiology including repetitive microtrauma and genetic influences. Musculotendinous junction ruptures are difficult to repair directly and tendon transfer remains the best surgical option.

Learning points

  • Closed musculotendinous junction ruptures in the absence of underlying pathology or direct trauma are rare and difficult to repair. Tendon transfer remains the best surgical option to restore function.
  • Musculotendinous junction injuries may have multifactorial aetiology.
  • Genes such as TNC, COL5A1 and MMP3, may contribute to musculotendinous junction injury susceptibility.


Contributions: AQ and KYW contributed equally.

Competing interests: None declared.

Patient consent: Obtained.

Provenance and peer review: Not commissioned; externally peer reviewed.


1. Boyes JH, Wilson JN, Smith JW Flexor tendon ruptures in the forearm and hand. J Bone Joint Surg Am 1960;42:637–46. [PubMed]
2. Bois A, Johnston G, Classen D Spontaneous flexor tendon ruptures of the hand: case series and review of the literature. J Hand Surg 2007;32:1061–71. doi:10.1016/j.jhsa.2007.06.012 [PubMed]
3. McMaster PE. Tendon and muscle ruptures: clinical and experimental studies on the causes and location of subcutaneous ruptures. J Bone Joint Surg Am 1933;15:705–22.
4. Takami H, Takahashi S, Ando M et al. Rupture of the flexor pollicis longus tendon at the musculotendinous junction in a bowler. Arch Orthop Trauma Surg 1998;117:277–8. doi:10.1007/s004020050246 [PubMed]
5. Lepage D, Tatu L, Loisel F et al. Cadaver study of the topography of the musculotendinous junction of the finger extensor muscles: applicability to tendon rupture following closed wrist trauma. Surg Radiol Anat 2015;37:853–8. doi:10.1007/s00276-015-1417-8 [PubMed]
6. de Roos WK, Zeeman RJ A flexor tendon rupture in the palm of the hand. J Hand Surg 1991;16:663–5. doi:10.1016/0363-5023(91)90191-D [PubMed]
7. Leppilahti J, Orava S Total Achilles tendon rupture: a review. Sports Med 1998;25:79 doi:10.2165/00007256-199825020-00002 [PubMed]
8. Motta P, Errichiello C, Pontini I Achilles tendon rupture. A new technique for easy surgical repair and immediate movement of the ankle and foot. Am J Sports Med 1997;25:172–6. doi:10.1177/036354659702500205 [PubMed]
9. Benjamin M, Toumi H, Ralphs JR et al. Where tendons and ligaments meet bone: attachment sites (‘entheses’) in relation to exercise and/or mechanical load. J Anat 2006;208:471–90. doi:10.1111/j.1469-7580.2006.00540.x [PubMed]
10. Leddy JP. Avulsions of the flexor digitorum profundus. Hand Clin 1985;1:77–83. [PubMed]
11. Tos P, Catalano F Spontaneous rupture of the flexor superficialis tendon of ring finger: a case report and review of literature. Musculoskelet Surg 2011;95:245–6. doi:10.1007/s12306-011-0109-8 [PubMed]
12. Uekubo K, Itoh S, Yoshioka T Closed traumatic rupture of the flexor pollicis longus tendon in zone TI: a case report. Hand Surg 2015;20:145 doi:10.1142/S021881041572003X [PubMed]
13. Rae PS, Finlayson D Closed rupture of flexor pollicis longus tendon associated with treatment of Bennett's fracture. J Hand Surg Br 1984;9:129–30. doi:10.1016/S0266-7681(84)80008-X [PubMed]
14. Bell JSP, Wollstein R, Citron ND Rupture of flexor pollicis longus tendon. J Bone Joint Surg 1998;80:225–6. doi:10.1302/0301-620X.80B2.8351 [PubMed]
15. Imbriglia JE, Goldstein SA Intratendinous ruptures of the flexor digitorum profundus tendon of the small finger. J Hand Surg 1987;12:985–91. doi:10.1016/S0363-5023(87)80095-3 [PubMed]
16. De Paepe A, Nuytinck L, Hausser I et al. Mutations in the COL5A1 gene are causal in the Ehlers-Danlos Syndromes I and II. Am J Hum Genet 1997;60:547–54. [PubMed]
17. Symoens S, Syx D, Malfait F et al. Comprehensive molecular analysis demonstrates type V collagen mutations in over 90% of patients with classic EDS and allows to refine diagnostic criteria. Hum Mutat 2012;33:1485–93. doi:10.1002/humu.22137 [PubMed]
18. Burch GH, Gong Y, Liu W et al. Tenascin-X deficiency is associated with Ehlers-Danlos syndrome. Nat Genet 1997;17:104–8. doi:10.1038/ng0997-104 [PubMed]
19. Minamitani T, Ariga H, Matsumoto KI Deficiency of tenascin-X causes a decrease in the level of expression of type VI collagen. Exp Cell Res 2004;297:49–60. doi:10.1016/j.yexcr.2004.03.002 [PubMed]
20. Jarvinen TA, Kannus P, Jarvinen TL et al. Tenascin-C in the pathobiology and healing process of musculoskeletal tissue injury. Scand J Med Sci Sports 2000;10:376–82. doi:10.1034/j.1600-0838.2000.010006376.x [PubMed]
21. Jarvinen TA, Jozsa L, Kannus P et al. Mechanical loading regulates the expression of tenascin-C in the myotendinous junction and tendon but does not induce de novo synthesis in the skeletal muscle. J Cell Sci 2003;116:857–66. doi:10.1242/jcs.00303 [PubMed]
22. September AV, Cook J, Handley CJ et al. Variants within the COL5A1 gene are associated with Achilles tendinopathy in two populations. Br J Sports Med 2009;43:357–65. doi:10.1136/bjsm.2008.048793 [PubMed]
23. Raleigh SM, van der Merwe L, Ribbans WJ et al. Variants within the MMP3 gene are associated with Achilles tendinopathy: possible interaction with the COL5A1 gene. Br J Sport Med 2009;43:514–20. doi:10.1136/bjsm.2008.053892 [PubMed]

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