Assessing hand ligaments and tendons lesions using MRI

Assessing hand ligaments and tendons lesions using MRI Award: Certificate of Merit Poster No.: C-0691 Congress: ECR 2017 Type: Educational Exhibit Authors: A. M. Benitez Vazquez, M. I. Rossi Prieto, C. L. Peñalver Paolini, J. Carrascoso Arranz, V. Martinez de la Vega; Madrid/ES Keywords: Trauma, Diagnostic procedure, MR, Musculoskeletal system, Musculoskeletal soft tissue, Extremities DOI: 10.1594/ecr2017/C-0691 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 92

Learning objectives 1- Review the normal anatomy of the finger 2- Technical considerations, including proper positioning and specific protocols based on the suspected pathology 3- Review and illustrate the various tendon pathologies Background Familiarity with the anatomy of the normal finger is essential to identify pathologic entities. MRI is a fundamental tool in the anatomic assessment, detection and management of fingers soft-tissue traumas. We will review this technique, focusing on the aspects and specific protocols that can be most helpful to evaluate the suspected patologies. Findings and procedure details MRI PROTOCOL The patient is positioned prone with the arm raised above the head, which places the hand close to de isocenter of the gantry. The imaging planes for axial, coronal, and sagittal acquisitions must be prescribed with respect to the finger rather than the hand (Fig. 1). Page 2 of 92

Fig. 1: A) Axial T1-weighted MRI shows scan lineas for coronal imaging lane (doubleended arrow). B) Coronal T1-weighted MRI shows scan lines for sagittal imaging plane (double-ended arrow). References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES An adjacent finger should be included within the FOV to allow internal comparison. On MRI, normal flexor tendons have low T1 and low T2 signal. Flexor tendons are thicker than extensor tendons. T1-weighted imaging provide better anatomical detail, whereas T2-weighted sequences better assess the pathology, which is seen as a pathological increase in the signal. It is usual to perform sequences in T1-weighted and T2 or DPweighted fat-suppressed. FLEXOR TENDONS The flexor mechanism of the index, middle, ring, and small fingers consists of the flexor digitorum profundus (FDP), which inserts on the volar base of the distal phalanx and the flexor digitorum superficialis (FDS), which inserts on the mid portion of the middle phalanx (Fig 2). Page 3 of 92

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Fig. 2: A) Midsagittal density-weighted fat-suppresed MR image shows the FDP tendon (arrows) and its insertion on the base of the distal phalanx (arrowhead). B) Parasagittal density-weigthed fat-suppresed MR image shows the inserion of the FDS tendon on the middle phalanx (arrowhead) References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Within the wrist and hand, the FDS tendons are located superficially (volar) to the FDP tendons. Within the fingers, the FDS tendons split at the level of the mid diaphysis of the proximal phalanges to allow the FDP tendons to pass superficially. At the level of de PIP joint, the two splits of each FDS tendon reunite deep to the FD tendon to form the Camper chiasm (Fig 3). Fig. 3: Anatomy of the flexor tendos. A) Figure (lateral view) shows de FDP (orange) and FDS (yellow) tendons and their points of insertions. B) Figuere of chiasm of the FDS tendon. Note the joining of the two slips (arrows) before their final individual insertions on the middle phalanx. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Each FDS tendon inserts on the volar surface of the mid diaphysis as two separate slips (Fig 4). Page 5 of 92

Fig. 4: Normal flexor tendon. A) Saggital T1-weighted MRI shows flexor digitorum superficialis (FDS) tendon (star) and flexor digitorum profundus (FDP) tendon (triangle). Lines a and b correspond to level of axial images in B and C, respectively. B) Axial T1-weighted MRI at level of base of middel phalanx (reference line b depicted in A)shows split tendon of FDS (stars) and overlying split of FDP tendon (triangles). C) Axial T1-weighted MRI at level of head of metacarpal (reference line a deplicted in A) shows FDS tendon (star) superficial to FDP tendon (triangle). References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES The relationship of the FDS and FDP tendons is best revealed by following the tendons on contiguous axial images. The insertion of the flexor tendons is best seen on sagittal images. Page 6 of 92

MR OF FLEXOR TENDON INJURIES We can divide the lesions into two groups: open injuries (lacerations) and closed injuries (avulsions). CLOSED INJURIES OR AVULSIONS The FDP tendon is avulsed more commonly than the FDS tendon. FDP tendon avulsions are especially common among rugby or foot-ball players who grab the jersey of an opponent (also called jersey finger). The injury results from forced hyperextension at the DIP joint during active finger flexion. This injury is often missed in the acute phase. There is no classic deformity, and swelling and pain may mask the pathognomonic sign of loss of active flexion at the DIP joint. The FDP avulsion injuries were originally classified by Leddy and Packer into three types according to the level of the lesion, the degree of retraction, and the absence or presence of a bone fragment: Type I lesions: Are characterized by retraction of the tendon into the palm. Type II lesions: The tendon retracts to the PIP joint. Occasionally, a small bone fleck is avulsed, and this can be seen at the level of the PIP joint. Type III lesions: There is avulsion of a large bone fragment, which stays in place by the A4 pulley. Three additional avulsion types have been described since the original work of Leddy and Packer: Type IV lesions: Avulsion fractures of the FDP in which the avulsed fracture fragment does not remain attached to the torn FDP tendon. Type V lesions: Avulsion fractures of the FDP with an extra articular (type Va) or intra articular (type Vb) fracture of the proximal phalanx. Type VI lesions: Open avulsion fractures of the FDP with a lost fracture fragment. In T2-weighted fat-suppressed or density-weighted fat-suppressed sequences, tendon tears are seen as fluid signal at the site of the tear. On T1-weighted sequences, tendon tears are seen as intermediate or low signal, although associated haemorrhage may show increased signal. In case doubts arise, or a better evaluation is needed, post contrast T1-weighted fat suppression sequences can be performed. Page 7 of 92

(Fig 5) Fig. 5: Axial T1-weighted (A) and axial T2-weighted fat-suppresed MR images show a thickening of the long flexor tendon of the thumb, with signal increase on T2-weighted fat-suppressed image and isointense signal in T1-weighted image. Tendon tear was suspected but not clearly visualized, so it was decided to use intravenous constrast (see figure 6). References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES (Fig 6) Page 8 of 92

Fig. 6: Same patient as in figure 5. Axial post IV contrast T1-weighted fat-suppresed MR image (A, B and C) and sagittal post IV contrast T1-weighted fat-suppressed MR image (D, E and F). Thumb's long flexor tendon thickening, fluid and synovium enhancement indicative of tenosynovitis, and partial tear (arrows in A, B, E and F) at the metacarpal level. C and F show the normal tendon. E and F show inflammatory changes in the metacarpophalangeal joint. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Avulsion fractures are seen as focal areas of cortical discontinuity at the site of the tendon insertion and associated edema in the underlying bone marrow. (Fig 7) Fig. 7: Index FDS's radial margin partial tear, coronal (A) and axial (B and C) post IV contrast T1-weighted fat-suppressed MR images. A) The green arrow points to the FDS radial margin partial tear. B) Fluid in the tendon sheath and peritendinous inflammatory component at the metacarpal level, with tendon integrity. C) Radial margin tendon tear and deviation at the metacarpal joint level. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES (Fig 8) Page 9 of 92

Fig. 8: FDP's radial margin tendon partial tear, at 6 mm from the distal interphalangeal joint. A) Axial T2-weighted fat-suppressed. The ruptured fibers are indicated by an arrow. Tenosynovitis signs. B) Sagittal post IV contrast T1 fat-suppressed in the FDP's radial margin. Increased signal in the injured region. Distal insertion is preserved. C) Sagittal post IV contrast T1 fat-suppressed in the FDP's ulnar margin, with fiber integrity and preserved distal insertion. D) Axial post IV contrast T1 fat-suppressed at the tear level. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES (Fig 9) Page 10 of 92

Fig. 9: Complete FDP rupture of the ring finger following recent Dupuytren treatmen. A) Sagittal T2-wighted fat-suppressed MRI. B and D) Axial T2-wighted fat-suppressed MRI. C) Axial post contrast T1-wighted fat-suppresed MRI. The green arrow points to the distal end of the FDP and de yellow arrow points to the inflammatory changes en the ventral region secundary to Dupuytren treatmen. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES (Fig 10) Page 11 of 92

Fig. 10: FDP tendon distal avulsion (Leddy and Parker type II). A Sagittal T2-weighted fat-suppressed MRI. B, C and D axial T2-weighted fat-suppressed MRI. A) Torn and retracted FDP tendon at the proximal interphalangeal joint (arrow). Lines a, b and c mark axial level at B, C and D images. B) FDP tendon insertion at distal phalanx avulsion, with soft tissue edema. C) FDP absence (arrow) with soft tissue edema. D) Retracted FDP tendon and peripheral edema. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES (Fig 11) Page 12 of 92

Fig. 11: Index finger complete FDP and FDS tendons rupture at proximal interphalangeal joint level (Leddy and Parker type II), marked with green arrow and increased soft tissue signal. A) Sagittal post IV contrast T1-weighted fat-suppressed image. B) Axial T2-weighted fat-suppressed image. C) Axial post IV contrast T1weighted fat-suppressed image. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Flexor tendon tears may have associated tenosynovitis. When it is chronic, flexor tenosynovitis may lead to thickening of the digital sheath and pulleys (more frequently A1) and present with clinical findings of trigger finger. OPEN INJURIES OR LACERATIONS Page 13 of 92

Flexor tendon lacerations are open injuries usually resulting from lacerations of the volar aspect of the hand. Flexor tendon lacerations are classified into five zones: Zone I: Extends from the distal insertion of the FDP tendon to the distal insertion of the FDS tendon. Zone II (the so-called no-man's-land): Extends from the distal insertion of the FDS tendon to the distal palmar fold, with de FDP and FDS tendons in direct contact. Lacerations en zone II are the most frequent and carry the worst prognosis. Zone III: Extends from the proximal part of the A1 pulley to the distal part of the flexor retinaculum. Zone IV: Consist of the carpal tunnel. Zone V: Extends from forearm proximal to the flexor retinaculum. (Fig 12) Page 14 of 92

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Fig. 12: The flexor tendons are divided into five zones: Zone I extends from the distal insertion of the FDP tendon to the distal insertion of the FDS tendon. Zone II (no-man's land) extends from the distal insertion of the FDS tendon to the distal palmar fold, with the FDP and FDS tendons in direct contact. Zone III extends from the proximal part of the A1 pulley to the distal part of the flexor retinaculum. Zone IV consist of the carpal tunnel. Zone V consist of the forearm proximal to the flexor retinaculum. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Zone I injuries are isolated lacerations of the FDP and manifest clinically as loss of active flexion of the distal phalanx. Trauma in the four proximal zones is associated with lesions of both tendons and implies the loss of active flexion of the PIP and DIP joints. PULLEY SYSTEM From the neck of the metacarpal to the DIP joint, the flexor tendons run along osteofibrous canals lined by a synovial sheath that provide nutrition and lubrication to the tendons. The floor of the fibrous-osseous canal is the volar aspect of the phalanges and the volar plates of the MCP and interphalangeal joints. The fibrous portion of the canal consists of five annular pulleys (A1-A5), which are transverse well-defined areas of thickening of the tendon sheath, and three cruciform pulleys (C1-C3), which are formed by crisscrossing fibers of the components of the annular pulley (Fig 13). Page 16 of 92

Fig. 13: Pulley sistem: A) Sagittal T1-weighted MRI shows location of annular pulleys (A1-A5) and cruciate cruciate pulleys (C1-C3). B) Axial T2-weighted fat-suppressed image at level of fourth metacarpophalangeal joint shows A1 pulley (arrrows). C) Axial T2-weighted fat-suppressed image at level of mid diaphysis of proximal phalanx shows A2 pulley (arrows) References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES The A2 and A4 pulleys are the largest and thickest and also have the most constant morphology and prevalence. The cruciform pulleys are the most variable in shape and prevalence. The main function of the annular pulleys is to fix the tendon sheaths to the bony skeleton, thus stabilizing the tendon during finger flexion. The cruciform pulleys are Page 17 of 92

designed to permit deformation of the tendon sheath during flexion without impingement of the tendon itself. PULLEY INJURIES Pulley injuries are most commonly seen in rock climbers. Rock climbing commonly involves flexion of the metacarpophalangeal and PIP joints and extension of the DIP joints, which places high stress on the pulleys and can result in complete or partial tears. The A2 pulley of the ring finger is the most commonly injured pulley. Usually injury of the pulley system begins at the distal part of the A2 pulley, the most important component in flexor tendon function, and progresses from partial to complete rupture, which is followed by involvement of the A3, A4, and rarely A1 pulleys. Lesions of the pulley system can be diagnosed directly as a focal discontinuity of the pulley fibers or indirectly by detection of a gap between the flexor tendon and the bone on sagittal images obtained during forced flexion, a finding referred to as the "bowstringing sign". It is important to recognize that partial pulley tears may not result in bowstringing. Additional indirect findings of pulley injuries include edema superficial and deep to the pulley and fluid within the tendon sheath. (Fig 14 and Fig 15) Fig. 14: A and B: A3 pulley rupture. A) Sagittal T1-weighted MR image showing Boutonnière deformity and increased gap between the flexor tendons and the bone Page 18 of 92

(bowstringing sign) at level of proximal interphalangeal. B) Axial T2-weighted fatsuppressed MR image. A3 pulley rupture (arrows) and bowstringing sing (dashed line). A' and B': A4 pulley rupture (arrows). A') Sagittal T1-weighted MR image. B') Axial T2weighted fat-suppressed MR image. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Fig. 15: A) A2-A3 and C1-C2 pulley rupture. Sagittal and axial T1-weighted MR images. Increased gap between flexor tendons and the bone (bowstringing sign). B) A1-A4 and C1-C2 pulley rupture. On the left side, sagittal T1-weighted MR image. Note the bowstringing sign, subluxation of the proximal interphalangeal joint and pulling of the volar plate (arrow). On the right side, axial T1-weighted MR images show the bowstringing sign. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES EXTENSOR MECHANISM Digit extension involves simultaneous action of both extrinsic and intrinsic extensor muscles. The extrinsic tendons originate within the forearm and there is considerable anatomic variation. Their function is primarily extension of the MCP joint but also extension of the PIP and DIP joints. Page 19 of 92

The intrinsic muscles are the interosseous and lumbrical muscles, which originate and insert in the hand. Their function is extension of the PIP and DIP joints and flexion of the MCP joint. At the MCP joint, these extrinsic tendons are stabilized over the dorsum of the metacarpal head by the extensor hood. The sagittal bands are the main component of the extensor hood, which starts mainly at the volar plate and has a dorsal tendinous point of insertion, gliding with the extensor system as the digit moves. Distal to the sagittal bands, the transverse fibers of the intrinsic tendons contribute to the anatomy of the extensor hood (fig 16). Fig. 16: Anatomy of the extensor apparatus at the MCP joint. A) Axial T1-weighted MRI. B) Axial T1-weighted MRI slightly more distal. Arrows: Saggital bands, a: Extensor extrinsic tendon, b: Volar plate, c: Flexor tendons, d: interosseous muscle, e: lumbrical muscle, *: Deeptransverse metacarpal ligament, III: Third metacarpal. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Distal to the MCP joint, the extrinsic and intrinsic tendons blend into the dorsal apparatus and are circumferentially distributed over the dorsum of the fingers. The extrinsic extensor tendon continues in the central and the lateral slips or bands. The central slip inserts on the base of the middle phalanx. The intrinsic tendons contribute to form the lateral slips. Page 20 of 92

Once the lateral slips receive the contribution of the intrinsic muscles, they are called conjoint tendons (fig 17). Fig. 17: A) Sagittal T1-weighted MRI shows the inserteion of the central slip on the base of the middle phalanx (arrow). B) Axial T1-weighted MRI at the proximal phalanx, near the PIP. Arrows: Central slip. Triangles: Lateral slips. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Conjoint tendons converge distally to form the terminal tendon, which inserts on the base of the distal phalanx (fig 18 and fig 19). Page 21 of 92

Fig. 18: Axial T1-weighted MRI obtained at the middle phalanx of the third finger (III). Tringles: Conjoint tendons. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 22 of 92

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Fig. 19: Sagittal T1-weighted MR image shows the insertion of the terminal tendon on the base of the distal phalanx (arrow). References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES The triangular ligament connects the conjoint tendons over the dorsum of the middle phalanx to prevent palmar subluxation during PIP joint flexion. Thin retinacular ligaments attach the conjoint lateral tendon to the flexor tendon sheath and prevent dorsal subluxation during PIP joint extension. The triangular and retinacular ligaments are not well visualized on MRI (Fig 20). Page 24 of 92

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Fig. 20: Figure of the extensor apparatus. Ext: Extensor tendon. In: Interosseous muscle. L: Lumbrical muscle. Bs: Sagittal band. Ft: Transverse fibers. Bc: Central band or central slip. Bl: Lateral band or lateral slip. Tc: Conjoint tendon. Lr: Retinacular ligaments. Lt: Triangular ligament. Tt: Terminal tendon. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES On MR images, the normal extensor tendons appear as thin structures of very low signal intensity. The axial and sagittal planes are the most useful for tendon identification. Stabilizing fibrous structures, especially the sagittal bands, are best seen in axial planes. EXTENSOR MECHANISM INJURIES Injuries to the extensor mechanism of the finger are common because it consists of thin, superficially located structures. These anatomic structures predispose tendons to lacerations and also to closed tendon injuries. The concept of anatomic zones is based on the characteristic anatomic features of the extensor tendon system and the specific findings at each lesion topography. The Verdan classification is the most widely accepted. This includes eight zones from the DIP joint to extrinsic extensor muscles in the forearm. Some authors include two further zones: Zone I: DIP joint. Zone II: Middle phalanx. Zone III: PIP joint. Zone IV: Proximal phalanx. Zone V: MCP joint. Zone VI: Dorsum of hand. Zone VII: Wrist extensor compartment. Zone VIII: Extrinsic extensor muscles. (fig 21 ) Page 26 of 92

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Fig. 21: Verdan's zones: Zone I: DIP joint. Zone II: Middle phlanx. Zone III: PIP joint. Zone IV: Proximal phalanx. Zone V: MCP joint. Zone VI: Dorsum of hand. Zone VII: Wrist extensor compartment. Zone VIII: Extrinsic extensor muscles. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES ZONE I INJURIES (DIP JOINT) Forced flexion at the DIP joint, while the PIP is extended, produces an avulsion injury of the terminal extensor tendon, with or without a small avulsion fracture, with incomplete extension of the DIP joint, leading to deformity of the distal phalanx in flexion, also known as mallet finger. This is the most common closed tendon injury seen in sports. It requires surgical treatment. If left untreated, mallet deformity will frequently progress to a swan neck deformity (flexion deformity of the DIP joint and hyperextension of the PIP joint), which is cause by retraction of the extensor mechanism (Fig 22). Page 28 of 92

Fig. 22: Mallet finger. Avulsion injury of the terminal extensor tendon, with or without avulsion fracture produces an incomplete extension of the DIP joint. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES ZONE II INJURIES (MIDDLE PHALANX) Injuries which occur at the level of the middle phalanx, result in injuries to the triangular ligament and/or conjoint tendons. If only one conjoint tendon is injured, treatment is usually conservative, because DIP extension can still be achieved; however, if the triangular ligament and both conjoint tendons are torn, surgical repair is often required (fig 23). Fig. 23: Extensor indicis tendon's conjoint radial tendon rupture (arrow). A) Axial T2weighted fat-suppressed MR image. B) Axial T1-weighted MR image. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES ZONE III INJURIES ( PIP JOINT) Injuries which occur at the level of de PIP joint, result in tears of the central slip or near its point of insertion on the base of the middle phalanx. Rupture of the central slip may be caused by a blow to the dorsum of the middle phalanx, acute violent flexion of the PIP joint or volar dislocation of the PIP joint. In the early acute phase, the results of physical examination ma be misleading because the lateral bands may still be in their proper anatomic position and still extend the PIP joint. Page 29 of 92

If the injury goes unrecognized, the lateral bands move volarly to the axis of rotation of the PIP joint. This induces flexion of the PIP joint and an increase in the force on the intact terminal extensor insertion, with subsequent extension of the DIP joint. The deformity is not apparent during the first 7-14 days. (Fig 24 and Fig 25). Fig. 24: Boutonnière deformity. Sagittal T1-weighted MRI shows a classic deformity with flexion of the PIP joint and extension of the DIP joint References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 30 of 92

Fig. 25: Extensor digiti minimi tendon's central slip tear (arrow) and imflamatory changes (arrow). A) Saggital T1-weighted MR image. B) Sagittal T2-weighted fatsuppressed image. C) Axial T1-weighted image. D) Axial T2-weighted fat-suppressed image. There is no Boutonnière deformity, which is not apparent during first 7-14 days. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES ZONE IV (PROXIMAL PHALANX) Injuries at the level of the proximal phalanx can result in injuries to the central slip, the lateral slips, the medial bands, and the extensor hood. Most commonly, these are caused by dorsal lacerations and are usually associated with partial tendon tears. Page 31 of 92

ZONE V ( MCP JOINT) Injuries at the level of the MCP joint involve the sagittal band and extrinsic extensor tendon. Most commonly, these are caused by human bite wounds an usually involve the dominant second MCP joint. These injuries are often open injuries and can result in partial or complete tendon tears. These are usually associated with tear of the MCP joint capsule and may eventually lead to a septic arthritis at the MCP joint. Sagittal band injuries are usually closed injuries resulting from resisting finger extension or direct trauma. Sagittal bands injuries most commonly involve the radial sagittal band of the middle or the ring finger. It usually requires surgical treatment (Fig 26 and fig 27). Fig. 26: Partial tear of the extensor digitorum communis tendon at the MCP joint (green arrows) and radial sagittal band (yellow arrows). Note the inflamatory changes Page 32 of 92

in soft tissues and fluid in the MCF joint. Trabecular fracture of the metacarpal head with bone edema (triangles). A and C) Axial T2-weighted fat-suppressed images. B and D) Post contrast T1- weighted fat-suppressed. E) Sagittal T2-weighted fat-suppressed. Lines a and b correspond to level of axial images in A-B and C-D, respectively. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Fig. 27: Small partial rupture of pollicis longus flexor tendon (arrows) at metacarpophalangeal joint level (zone V). A) Sagittal T1- weighted MR image. B) Sagittal T2-weighted fat-suppressed. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES ZONE VI (DORSUM OF THE HAND) The dorsum of the hand features greater anatomic variability because of tendinous multiplicity and the presence of connections between the different tendons. In most cases, there is more than one tendon for each finger between the wrist and the MCP joints. Page 33 of 92

Near the MCP joint, the extensor tendons are interconnected in the dorsum of the hand by intertendinous connections (connexus intertendineus) (Fig 28 and fig 29). Fig. 28: Axial T1-wighted MR image obtained at the dorsum of the hand show the extensor digitorum tendons (arrows). References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 34 of 92

Fig. 29: Small finger distal diaphysis fracture with significant angulation, ventral displacement of the distal fragment (green arrow) and dorsal displacement of the proximal fragment, which has caused a complete rupture of the extensor tendon with important inflammatory changes of soft tissues (white arrows). A) Sagittal T1-weighted MR image. B) Axial T1-weighted MR image. C) Axial T2-weighted fat suppressed. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES FINGER LIGAMENTS The most important ligamentous structures of the index, middle, ring and small finger are the collateral ligaments, the volar plates and the sagittal bands. Page 35 of 92

COLLATERAL LIGAMENTS Collateral ligaments are the main stabilizers of the MCP, PIP and DIP joints. There are two proper collateral ligaments (radial and ulnar collateral ligaments) and two accessory collateral ligaments per joint. Collateral ligaments are seen along the radial and ulnar margins of the joints. Proper collateral ligaments of the MCP, PIP and DIP joints course distally in a slightly oblique course to attach to the volar one third of the base of the proximal, middle, and distal phalanx, respectively. Distal attachment is slightly broader than proximal attachment. The proximal attachment of accessory collateral ligaments of the MCP, PIP and DIP joints is volar to the respective proper collateral ligament. The accessory collateral ligaments fan out distally and volarly and attach to the volar plate (Fig 30). Page 36 of 92

Fig. 30: Proper collateral ligaments (oranges) and accessory collateral ligaments (white translucent) of the MCP, PIP and DIP joints. Proper collateral ligaments of the MCP, PIP and DIP joints course distally in a slightly oblique course to attach to the volar one third of the base of the proximal, middle, and distal phalanx, respectively. Distal attachment is slightly broader than proximal attachment. The proximal attachment of accessory collateral ligaments of the MCP, PIP and DIP joints is volar to the respective proper collateral ligament. The accessory Page 37 of 92

collateral ligaments fan out distally and volarly and attach to the volar plate. Yellow lines: Volar plates. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES The proper collateral ligaments are taut in flexion, and accessory collateral ligaments are taut in extension. VOLAR PLATES The volar plate is a thick fibrocartilaginous structure that constitutes the palmar aspect of the MCP, PIP and DIP joints capsule. Distally, it is firmly attached to the volar lip of the base of the proximal, middle and distal phalanges. Proximally it is attached to the volar metacarpal head, distal PIP and distal DIP. The volar plate prevents hyperextension of the PIP joint. On MR images, normal collateral ligaments appear as sharply defined low-signalintensity bands. They are best visualized in the coronal projection. The volar plate is a low-signal-intensity structure that is best seen in a sagittal plane (Fig 31). Page 38 of 92

Fig. 31: Normal collateral ligaments and volar plates. A) PIP joint collateral ligaments (arrows) at coronal T1-weighted RM image. B) MCP joint collateral ligaments (arrows) at coronal T1-weighted RM image. C and D) MCP joint volar plate (arrow) at sagittal T2-weighted fat-suppressed and sagittal T1-weighted MR images, respectively. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES FINGER LIGAMENTS INJURIES The most common ligament injuries of the finger occur at the PIP joint. COLLATERAL LIGAMENTS INJURIES Page 39 of 92

When an abducting or adducting force is applied to the joint while the finger is extended, three main injuries may occur: Ligamentous sprain with no loss of articular stability. Partial ligamentous tear with lateral articular instability. Complete ligamentous rupture with major instability and articular luxation. (Fig 32) Fig. 32: Middle finger radial collateral ligament complete rupture (arrow). A) Coronal DP-weighted fat-suppressed MR image. B) Axial T2-weighted fat-suppressed MR image at DIP joint level. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES VOLAR PLATES INJURIES Volar plates injuries are caused by hyperextension of the interphalangeal joint or rotational longitudinal compression. Lesions include different degrees of dorsal articular displacement, which are divided into three types: Type I lesions: Hyperextension results in avulsion of the volar plate from its distal insertion or, less frequently from its proximal insertion. With no treatment, the natural evolution of distal disruption of the volar plate is from the middle phalanx is hyperextension of the PIP joint, which causes a swanneck deformity due to articular injury (fig 33). Conversely, the natural evolution of proximal disruption of the volar plate from the proximal phalanx causes a flexion deformity of the PIP joint, the so-called pseudoboutonnière deformity, with an intact extensor mechanism. Page 40 of 92

Fig. 33: Swan-neck deformity. It consist of hyperextension of the PIP joint, due to an untreated volar plate avulsion from its distal insertion. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Type II lesions: Consist of volar plate avulsion, extensive involvement of the periarticular soft tissues even middle phalanx luxation. Type III lesions: Fracture-dislocation of the volar base of the middle phalanx. An unstable injury involves mare than 40% of the articular surface with the volar plate and collateral ligaments attached to the volar fragment. The treatment is conservative in all cases except for the unstable type III injury (fracturedislocation), which needs open reduction and internal fixation. Dislocation of the MCP joint is uncommon, but when it occurs it is usually dorsal and follows the forced hyperextension of the finger. Simple dislocation: Volar plate is not interposed in the joint. Treatment is conservative. Complex MCP dislocations Volar plate is interposed in the joint. Surgical reduction is necessary. ANATOMY OF THUMB LIGAMENT COMPLEX OF THE METACARPOPHALANGEAL JOINT The ligamentous structures include the proper collateral ligaments on the ulnar (ulnar collateral ligament) and radial (radial collateral ligament) sides, as well as the more volarly located accessory collateral ligaments (accessory radial collateral ligament and accessory ulnar collateral ligament). Page 41 of 92

The ulnar collateral ligament originates dorsally from the tubercle of the metacarpal condyle and passes obliquely distal and volar to insert at the base of the proximal phalanx. The ulnar collateral ligament is strengthened by the aponeurosis of the adductor pollicis muscle. This aponeurosis is a thin layer superficial to the ulnar collateral ligament joining dorsally with fibers of the extensor hood. The radial collateral ligament arises dorsally from the condyle of the metacarpal head, courses obliquely, and inserts distally and volarly at the tubercle of the proximal phalanx. The accessory collateral ligaments are contiguous to the volar aspect of the proper collateral ligaments and the volar plate (Fig. 34 and Fig. 35). Fig. 34: A) Coronal T2-weighted fat-suppressed MRI. B) Coronal T2 fat-suppressed, slightly ventran than A. C) Eschematic figure. At MCP joint: Green arrow: Ulnar collateral ligament. Green arrow heads: Aponeurosis of the adductor pollicis tendon. Red arrow: Radial collateral ligament. Red arrow heads: Aponeurosis of abductor pollicis brevis tendon. At IP joint: Red fine arrow: Radial collateral ligament. Green fine arrow: Ulnar collateral ligament. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 42 of 92

Fig. 35: Axial T2-weighted fat-suppressed MRI of first metacarpophalangeal joint at level of metacarpal head. Green arrows: Ulnar collateral ligament. Yellow arrow: Accessory ulnar collateral ligament. Arrow heads: Aponeurosis of the adductor pollicis tendon. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES The accessory collateral ligaments are contiguous to the volar aspect of the proper collateral ligaments and the volar plate (Fig 36). Page 43 of 92

Fig. 36: Axial T1-weighted MRI of first metacarpophalangeal joint at level of metacarpal head (I). Green arrow: Ulnar collateral ligament. Fine green arrow: Accessory ulnar collateral ligament. Red arrow: Radial collateral ligament. Fine red arrow: Accessory radial collateral ligament. S: Sesamoids. Yellow arrow heads: Volar plate. TF: Flexor pollicis longus tendon. B) Shematic figuere: LC: Collateral ligaments. LCa: Accessory collateral ligaments. PV: Volar plate. TF: Flexor pollicis longus tendon. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Volar plate is a wedge-shaped fibrocartilage plate that surrounds the joint and strengthens the joint capsule. This plate is mainly prominent on the volar and the dorsal side. The plate is distally attached to the base of the proximal phalanx, along the distal insertion of the extensor pollicis brevis tendon. Two sesamoids are located within the lateral margins of the volar plate (fig 37). Page 44 of 92

Fig. 37: A) Sagittal T2-weighted fat-suppressed MRI. B) Sagittal T1-weighted MRI. C) Schematic figure. Yellow arrow heads: Volar plates. Blue arrow heads: Dorsal plates. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES LIGAMENT COMPLEX OF THE INTERPHALANGEAL JOINT The proper and accessory collateral ligaments of the interphalangeal joint run in an equal fashion as at the metacarpophalangeal joint. The volar and dorsal aspects of the interphalangeal joint are encapsulated by the volar and dorsal plates (Fig 37). The extensor pollicis longus tendon inserts with the attachment of the dorsal plate at the base of the distal phalanx. The flexor pollicis longus tendon attaches more distally at the volar aspect of the distal phalanx. ANNULAR PULLEY SYSTEM Page 45 of 92

The annular pulley system of the thumb consists of three to four pulleys: two annular pulleys are located at the level of the joints. The first annular pulley (A1) is at the level of the metacarpophalangeal joint, and the second annular pulley (A2) is at the level of the interphalangeal joint. The oblique annular pulley (Ao) is located at the level of the proximal phalanx, and a variable annular pulley (Av) is located at the base of the proximal phalanx (fig 38). Fig. 38: Annular pulley system of thumb: A1: First annular pulley at level of metacarpophalangeal joint. Av: Variable annular pulley at level of base of proximal Page 46 of 92

phalanx. A2: Second annular pulley, at level of interphalangeal joint. Note asymmetric variable annular pulley on axial image, with shorter ulnar than radial limb, leading to marked ulnar position of the flexor pollicis longus tendon. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES RM CONSIDERATIONS Recent study on healthy volunteers (Hirschmann et al.) demonstrate that ulnar collateral ligament and the adductor pollicis aponeurosis commonly have a striated appearance in T2-weighted fat-suppressed, whereas the radial collateral ligament has a low signal. The accessory collateral ligaments show variable signal. Knowledge of the variable SI is fundamental in diagnosing chronic ligamentous lesions of the metacarpophalangeal joint, because these conditions may not be accompanied by edema. This study also found a small amount of fluid around the adductor pollicis aponeurosis in up to one fourth of their volunteers. This finding is usually attributed to a trauma genesis of the collateral ligament complex in the literature. Up to now, normal values for the thickness of the collateral ligament have not been established for MRI. Compared with the ulnar collateral ligament, the radial collateral ligament is mostly thinner and of low SI. The normal appearance of the plates can be associated with an intermediate SI or can bi striated on intermediate-weighted fat-saturated MRI. A synovial recess between the base of the proximal phalanx and the plate was constantly visible and of full thickness in all volunteers on the dorsal side of the joint. On the volar side, the recess was evident in only a minority of volunteers and differed in length. An intermediate SI was observed in all volunteers for the oblique annular and the second annular pulleys and in the majority of volunteers for the first annular pulley, whereas the variable annular pulley was mainly of low. The thickness of the first annular pulley is 0,5 mm. A thickened first annular pulley may lead to inflammation and irritation of the flexor pollicis longus tendon, which is called "trigger finger". GAMEKEKEPER'S THUMB OR SKIER'S THUMB. This injury is very commonly caused by skiing accidents. Page 47 of 92

It occurs after violent hyper abduction of the thumb, which leads to a total or partial rupture of the ulnar collateral ligament (UCL), and usually takes place at its distal point of insertion. It might be accompanied by bone avulsion. In total rupture of the UCL, retraction may be mild (with the torn UCL beneath the adductor aponeurosis) or severe and associated with interposition of the adductor aponeurosis (with the torn UCL lying superficially at the proximal end of the aponeurosis). The latter condition, which is called a Stener lesion, requires surgical treatment because conservative treatment would lead to chronic instability. A torn UCL appears on MR images as a gap in the otherwise normally located UCL. The ligament usually appears to be thickened beneath the adductor aponeurosis (Fig 39). Fig. 39: UCL rupture:retracted ligament (red arrow) and soft tissue edema. The adductor aponeurosis (green arrow)covers the ligament throughout its path. A and B) Coronal T2-weighted fat-suppressed MRI. Note the bone edema in the proximal phalanx and metacarpian, due to trabecular fracture. C and D) Axial T2-weighted fat-suppressed MRI, D) obtained at the retracted ligament level and C) obtained millimeters above it. Note the absence of ligament below de adductor aponeurosis at this level. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 48 of 92

In the Stener lesion, the adductor aponeurosis appears below the UCL and usually shows surrounding hyper intense effusion on T2-weighted MR images (Fig 40). Fig. 40: Stener lesion. a) Coronal T2-weighted fat-suppressed MRI. B) Coronal T2weighted fat-suppressed MRI slightly more ventral than A. Green arrow: Torn and Page 49 of 92

retracted UCL. Yellow arrow: Adductor aponeurosis below the UCL. Note the soft tissues edema and bruises at the base ot the proximal phalanx and metacarpal head. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES RADIAL COLLATERAL LIGAMENT INJURIES Radial collateral ligament lesions are less frequent than ulnar collateral ligament lesions. RCL lesions result from adduction forces on the metacarpophalangeal joint. Recent literature seems to advocate the surgical treatment for complete acute ruptures of the radial collateral ligament because there is no risk of Stener lesion (Fig 41). Page 50 of 92

Fig. 41: UCR rupture at his proximal attachment (arrows): A) Coronal T2-weighted fatsuppressed MRI. B) Sagittal R2-weighted fat-suppressed MRI. References: Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Images for this section: Page 51 of 92

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Fig. 4: Normal flexor tendon. A) Saggital T1-weighted MRI shows flexor digitorum superficialis (FDS) tendon (star) and flexor digitorum profundus (FDP) tendon (triangle). Lines a and b correspond to level of axial images in B and C, respectively. B) Axial T1weighted MRI at level of base of middel phalanx (reference line b depicted in A)shows split tendon of FDS (stars) and overlying split of FDP tendon (triangles). C) Axial T1weighted MRI at level of head of metacarpal (reference line a deplicted in A) shows FDS tendon (star) superficial to FDP tendon (triangle). Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 55 of 92

Fig. 5: Axial T1-weighted (A) and axial T2-weighted fat-suppresed MR images show a thickening of the long flexor tendon of the thumb, with signal increase on T2-weighted fat-suppressed image and isointense signal in T1-weighted image. Tendon tear was suspected but not clearly visualized, so it was decided to use intravenous constrast (see figure 6). Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Fig. 6: Same patient as in figure 5. Axial post IV contrast T1-weighted fat-suppresed MR image (A, B and C) and sagittal post IV contrast T1-weighted fat-suppressed MR image (D, E and F). Thumb's long flexor tendon thickening, fluid and synovium enhancement Page 56 of 92

indicative of tenosynovitis, and partial tear (arrows in A, B, E and F) at the metacarpal level. C and F show the normal tendon. E and F show inflammatory changes in the metacarpophalangeal joint. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Fig. 7: Index FDS's radial margin partial tear, coronal (A) and axial (B and C) post IV contrast T1-weighted fat-suppressed MR images. A) The green arrow points to the FDS radial margin partial tear. B) Fluid in the tendon sheath and peritendinous inflammatory component at the metacarpal level, with tendon integrity. C) Radial margin tendon tear and deviation at the metacarpal joint level. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 57 of 92

Fig. 8: FDP's radial margin tendon partial tear, at 6 mm from the distal interphalangeal joint. A) Axial T2-weighted fat-suppressed. The ruptured fibers are indicated by an arrow. Tenosynovitis signs. B) Sagittal post IV contrast T1 fat-suppressed in the FDP's radial margin. Increased signal in the injured region. Distal insertion is preserved. C) Sagittal post IV contrast T1 fat-suppressed in the FDP's ulnar margin, with fiber integrity and preserved distal insertion. D) Axial post IV contrast T1 fat-suppressed at the tear level. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 58 of 92

Fig. 9: Complete FDP rupture of the ring finger following recent Dupuytren treatmen. A) Sagittal T2-wighted fat-suppressed MRI. B and D) Axial T2-wighted fat-suppressed MRI. C) Axial post contrast T1-wighted fat-suppresed MRI. The green arrow points to the distal end of the FDP and de yellow arrow points to the inflammatory changes en the ventral region secundary to Dupuytren treatmen. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 59 of 92

Fig. 10: FDP tendon distal avulsion (Leddy and Parker type II). A Sagittal T2-weighted fat-suppressed MRI. B, C and D axial T2-weighted fat-suppressed MRI. A) Torn and retracted FDP tendon at the proximal interphalangeal joint (arrow). Lines a, b and c mark axial level at B, C and D images. B) FDP tendon insertion at distal phalanx avulsion, with soft tissue edema. C) FDP absence (arrow) with soft tissue edema. D) Retracted FDP tendon and peripheral edema. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 60 of 92

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fat-suppressed image at level of mid diaphysis of proximal phalanx shows A2 pulley (arrows) Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Fig. 14: A and B: A3 pulley rupture. A) Sagittal T1-weighted MR image showing Boutonnière deformity and increased gap between the flexor tendons and the bone (bowstringing sign) at level of proximal interphalangeal. B) Axial T2-weighted fatsuppressed MR image. A3 pulley rupture (arrows) and bowstringing sing (dashed line). A' and B': A4 pulley rupture (arrows). A') Sagittal T1-weighted MR image. B') Axial T2weighted fat-suppressed MR image. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 64 of 92

Fig. 15: A) A2-A3 and C1-C2 pulley rupture. Sagittal and axial T1-weighted MR images. Increased gap between flexor tendons and the bone (bowstringing sign). B) A1-A4 and C1-C2 pulley rupture. On the left side, sagittal T1-weighted MR image. Note the bowstringing sign, subluxation of the proximal interphalangeal joint and pulling of the volar plate (arrow). On the right side, axial T1-weighted MR images show the bowstringing sign. Radiodiagnostico, RUBER, Hospital Ruber Juan Bravo - Madrid/ES Page 65 of 92