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INTRINSIC TIGHTNESS (INTRINSIC CONTRACTURES)

Introduction

The intrinsic muscles, located in the deep compartments of the hand, comprise five groups: the thenars, hypothenars, palmar and dorsal interossei, and the lumbricals. These muscles are of great functional importance and, in balance with the extrinsic muscles, allow performance of fine motor tasks as well as grasping of heavy objects and performing intricate fine motor activities such as playing a musical instruments.  The intrinsic muscles account for 85% of pinch strength and 53% of grip strength.2  The intrinsic muscles can be negatively affected by a variety of conditions, including burns, trauma, or inflammation. Intrinsic contractures are relatively common sequelae of crush injuries to the hand and acute hand compartment syndrome, even if the compartments are released properly.  The resulting rare condition is called intrinsic tightness, intrinsic plus hand, hyper-intrinsic hand, or intrinsic contracture, Intrinsic tightness manifests as difficulty flexing the fingers.

Related Anatomy

  • Median and ulnar nerves
  • Thenar muscles: abductor pollicis brevis (APB), flexor pollicis brevis (FPB), opponens pollicis (OP), adductor pollicis (AP), and first palmar and dorsal interossei
  • Hypothenar muscles: abductor digiti minimi (ADM), flexor digiti minimi brevis (FDMB), and opponens digiti minimi (ODM).
  • Palmar volar interossei lie on the palmar surfaces of the metacarpals.  The palmar interossei adduct the fingers in reference to the middle finger.   
  • Dorsal interossei are between the metacarpals and abduct the fingers in reference to the long finger.  Usually the dorsal interossei have two heads except the third dorsal interosseous and volar interossei have one head.  However, abnormalities do occur.
  • Lumbricals:  The lumbricals have their origin on the palmar portion of the flexor digitorum profundus (FDP).

Incidence and Related Conditions

  • Intrinsic muscle contracture is rare.
  • Patients with tetraplegia and cerebral palsy regularly experience intrinsic tightness due to spasticity or tight lumbricals; however, diagnosis can be difficult in these patients because extrinsic flexor spasticity hides the intrinsic tightness.
  • Eating disorders (eg, anorexia nervosa) also may lead to intrinsic muscle dysfunction in the hand, due to atrophy.
  • Intrinsic muscles are often affected in patients with rheumatoid arthritis (RA).
  • In RA patients, subluxation of the metacarpophalangeal (MP) joint and extensor tendon mechanism can contract the ulnar intrinsic tendon, which may lead to swan-neck deformity

Differential Diagnosis

  • CNS lesions
  • Edema
  • Hematoma
  • Immobilization, excessive
  • Inflammation
  • Ischemia
  • Spasticity
  • Trauma
ICD-10 Codes

  • INTRINSIC TIGHTNESS

    Diagnostic Guide Name

    INTRINSIC TIGHTNESS

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    INTRINSIC TIGHTNESS M24.542M24.541 

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
  • Limited active finger flexion right hand after a distal radius fracture with marked initial swelling.
    Limited active finger flexion right hand after a distal radius fracture with marked initial swelling.
  • This patient has a intrinsic contracture. When the MP join is extended the PIP joint can not flexion normally.
    This patient has a intrinsic contracture. When the MP join is extended the PIP joint can not flexion normally.
  • This patient has a intrinsic contracture. When the MP join is flexed the PIP joint can flexion normally.
    This patient has a intrinsic contracture. When the MP join is flexed the PIP joint can flexion normally.
Pathoanatomy Photos and Related Diagrams
Intrinsic and Extrinsic Tendon Anatomy
  • Finger extensor tendon anatomy lateral view: A. Extensor tendon; B. Central slip; C. Oblique fibers of dorsal aponeurosis; D. Lateral slip; E. Conjoined lateral band; F. Triangular ligament; G. Terminal extensor tendon; H. Flexor digitorum profundus; I. Volar plate; J. A-2 & A-4 pulleys; K. Flexor digitorum superficialis; L. Transverse retinaculum; M. Accessory collateral ligament; N. Proper collateral ligament
    Finger extensor tendon anatomy lateral view: A. Extensor tendon; B. Central slip; C. Oblique fibers of dorsal aponeurosis; D. Lateral slip; E. Conjoined lateral band; F. Triangular ligament; G. Terminal extensor tendon; H. Flexor digitorum profundus; I. Volar plate; J. A-2 & A-4 pulleys; K. Flexor digitorum superficialis; L. Transverse retinaculum; M. Accessory collateral ligament; N. Proper collateral ligament
  • Finger extensor tendon anatomy dorsal view: A. Extensor tendon; B. Central slip; C. Oblique fibers of the dorsal aponeurosis; D. Lateral slip; E. Conjoined lateral band; F. Triangular ligament; G. Terminal extensor tendon
    Finger extensor tendon anatomy dorsal view: A. Extensor tendon; B. Central slip; C. Oblique fibers of the dorsal aponeurosis; D. Lateral slip; E. Conjoined lateral band; F. Triangular ligament; G. Terminal extensor tendon
Dorsal and Volar Interosseous
  • Dorsal interossei are between the metacarpals and abduct the fingers in reference to the long finger.  Usually the dorsal interossei have two heads except the third dorsal interosseous.
    Dorsal interossei are between the metacarpals and abduct the fingers in reference to the long finger.  Usually the dorsal interossei have two heads except the third dorsal interosseous.
  • There are three volar interossei and each has one head.
    There are three volar interossei and each has one head.
Symptoms
Pain especially with passive finger flexion
Stiffness of index, long, ring, and little fingers
Weakness of grip
Marked limitation of PIP flexion when the MP joints are extended
Typical History

Intrinsic muscle tightness occurs irrespective of age, gender, and occupation.  There is no typical patient. If there is one commonality, it is that symptoms of pain, stiffness, and weakness in the hand are ill defined. The patient may have experienced trauma or burns; have a condition such as RA that causes inflammation; already be in treatment for tetraplegia or cerebral palsy; or have an eating disorder. In milder cases, flexing the finger joints and grasping a tool are difficult. In patients with severe tightness, opening the hand can be challenging. 

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Conservative
  • Hand therapy and anti-claw splint
  • Therapy trial recommended for three months before surgical treatment
  • Dynamic splinting (reverse knuckle bender), if MP is locked 
  • Evaluate the fingers for co-existing joint contractures, especially MP extension contractures
Operative
  • Distal intrinsic release procedure: performed on both the ulnar and radial sides of the extensor hood.  Ideally, releases are performed under local so the effectiveness of each release can be judged immediately.
  • More complex cases may require fractional lengthening or interosseous muscle slide, proximal tenotomy, and ulnar motor branch neurectomy.2
  • Active motion the day after the operation
  • Resting splint between training sessions, for 4 weeks
  • Should not be performed in patients relying on the intrinsic muscles to flex the MP joints; these patients have weak finger flexion
  • Followed by early range-of-motion exercises with or without supervision
  • Palm-based splint for those having difficulty with MP extension
  • Associated swan neck deformities and PIP volar plate laxity may require separate procedures directed at these specific deformities
  • Note also the related sections for swan neck secondary to rheumatoid arthritis, cerebral palsy, tetraplegia, etc.
Treatment Photos and Diagrams
  • Littler Intrinsic Releases - Triangle of lateral band is removed radially and ulnarly.
    Littler Intrinsic Releases - Triangle of lateral band is removed radially and ulnarly.
  • Littler Intrinsic Releases
    Littler Intrinsic Releases
  • Littler Intrinsic Releases - Improved flexion post release.
    Littler Intrinsic Releases - Improved flexion post release.
CPT Codes for Treatment Options

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Common Procedure Name
Tenotomy intrinsic muscles
CPT Description
Release intrinsic muscles or hand, each muscle
CPT Code Number
26593
CPT Code References

The American Medical Association (AMA) and Hand Surgery Resource, LLC have entered into a royalty free agreement which allows Hand Surgery Resource to provide our users with 75 commonly used hand surgery related CPT Codes for educational promises. For procedures associated with this Diagnostic Guide the CPT Codes are provided above. Reference materials for these codes is provided below. If the CPT Codes for the for the procedures associated with this Diagnostic Guide are not listed, then Hand Surgery Resource recommends using the references below to identify the proper CPT Codes.

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Complications
  • Adhesions
  • Inadvertent excision of transverse fibers (may result in extensor tendon dysfunction)
  • Recurrence of swan-neck deformity
  • Weakened grip
Outcomes
  • Depend on severity of deformity
  • Co-existing MP extension contractures will make outcomes less predictable
  • Improvement in range of motion (ROM) occurs more quickly in patients with mild preoperative intrinsic tightness (1 mo) than in those with severe disorder (3 mo)
  • Overall, improvements are often significant in terms of gripping ability and control
Video
Bunnell's Intrinsic Tightness Test
YouTube Video
Intrinsic and Extrinsic Tightness of the Hand
Key Educational Points
  • The optimal amount of extensor hood to excise in the distal intrinsic release procedure is a subject of differing opinion. Suggestions include:  
    • For index, ring, and small fingers, excise a minimum of 60%, 39%, and 31%, respectively, of the distance from the PIP joint center to the start of the transverse fibers.
    • For the middle finger, excise a minimum of 65% of the distance from the PIP joint center to the transverse fibers.1
  • The incidence of eating disorders is growing, and therefore hand surgeons are more frequently seeing related atrophy of the intrinsic muscles. 
  • The intrinsic muscles allow the hand to grasp large objects.  Without intrinsics, the flexor tendons would tend to flex the interphalangeal joints (cause a hooked fist) and push large objects out of the hand rather than wrapping the figers around the larger object.
  • To assess the relative tightness of the radial vs. the ulnar lateral band, deviate the finger during the Bunnell test.  For example, radial deviation will assess the ulnar lateral band.
  • Always examine the patient for associated joint contractures and extrinsic tightness.
References

New Articles

  1. Carlson EJ, Carlson MG. Treatment of swan neck deformity in cerebral palsy. J Hand Surg Am 2014;39(4):768-72. PMID: 24613587
  2. Takai H, Hamada Y, Tonogai I, Hibino N. Locking of the metacarpophalangeal joint caused by idiopathic intrinsic muscle atrophy of the hand: report of three cases. Hand (NY) 2012;7(4):431-4. PMID: 24294165
  3. Espirit MT, Kuxhaus L, Kaufmann RA, et al. Quantifying the effect of the distal intrinsic release procedure on proximal interphalangeal joint flexion: a cadaveric study. J Hand Surg Am 2005;30:1032-38. PMID: 16182064
  4. Reinholdt C, Fridén J. Selective release of the digital extensor hood to reduce intrinsic tightness in tetraplegia. J Plast Surg Hand Surg 2011;45(2):83-9. PMID: 21504278

Review

  1. Chung KC, Pushman AG. Current concepts in the management of the rheumatoid hand. J Hand Surg Am 2011;36(4):736-47. PMID: 21463736
  2. Tosti R, Thoder JJ, Ilyas AM.  Intrinsic contracture of the hand: diagnosis and management.  J Am Acad Orthop Surg 2013; 21:581-591

Classic

  1. Swezey RL, Fiegenberg DS. Inappropriate intrinsic muscle action in the rheumatoid hand. Ann Rheum Dis 1971;30(6):619-25. PMID: 5130142
  2. Kozin SH, Porter S, Clark P, Thoder JJ.  The contribution of the intrinsic muscles to grip and pinch strength.  J Hand Surg Am 1999;24(1):64.72
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