Classification and biomechanics of cuff tears
Classification is important to enable comparison of results Sofar no uniform classification of cuff tears is accepted as well as validated. Classification is either anatomical (gross inspection), arthroscopic or by imaging.
First description of classification by Codman, 1934, on supraspinatus tears:
- full thickness tears (FTRCT)
- partial thickness tears (PTRCT)
o bursal side
o articular side (rim rent)
o vertical, with connection from joint to bursa, not
o involving the whole breadth (width?) of the tendon
Articular side tears are more common than the other types (Fakuda, 1996, Itoi, 1992, Gartsman 1990, Ellman, 1990, Weber, 1997). Codman¡¦s assertion, that partial cuff tears can heal was not substantiated by Fukuda and Hamada (1996). Yamanaka (1994) observed healing of 10% of the PTRCT¡¦s proven with arthrography.
The footprint of the supraspinatus is 25 x 11-22 mm (Nottage 2003). The surface of the footprint supraspinatus and Infraspinatus is 8 cmƒU (Bassett 1990). The Infraspinatus is partly covering the supraspinatus. In the supraspinatus area there is hardly bare bone between the cartilage of the head and insertion of the supraspinatus tendon (Nottage 2003). In the Infraspinatus area in nearly all shoulders a bare bone is present. The tendon length in the anterior part of the supraspinatus muscle is longer (mean 5, 4 cm) than in the posterior part (mean 2, 8 cm, Volk 2001).
FULL THICKNESS ROTATOR CUFF TEARS:
Patte (1990) described full thickness tears in 2 dimensions: he measured in sagittal direction as well as in frontal direction (table 1). DeOrio and Cofield (1984) described FTRCT¡¦s as:
Small: less than 2 cm in diameter (from stump to cartilage)
Medium: 1-3 cm diameter
Large: 3-5 cm diameter
Massive: more than 5 cm diameter (nearly always with involvement of Infraspinatus).
This classification only refers to frontal measurement, can be used for arthroscopy and is most frequently used.
CT arthro as well as MR arthro can give proper information on the extent of the tear as well as the vitality of the cuff muscle.
Retraction of the tendon is measured according to Patte:
Stage 1: stump at level at footprint
Stage 2: stump at level of humeral head
Stage 3: stump at level of glenoid
Vitality of the muscle (fatty infiltration) is recorded on either the CT or MRI according to the classification of Goutallier (1994).
Stage 0: absence of fat
Stage 1: several fine fat lines
Stage 2: fat less than muscle
Stage 3: fat equivalent to muscle
Stage 4: fat greater than muscle
Ultrasound is sensitive and specific for full thickness tears (Swen, 1999), but less effective in partial tears.
PARTIAL THICKNESS ROTATOR CUFF TEARS:
Following the description of Codman, Elmann (1990) subdivided the partial tears according to the depth of the tear (less than 3 mm, 3-6 mm and more than 6 mm) Snyder (1993) considers the width of the tear.
The Upper Extremity Committee (Meeting, Paris, 2003) proposes the following classification, which however has to be validated yet: during arthroscopy an evaluation is performed, measuring the
Depth: < 5 mm: D1 > 5 mm: D2
AP extension: in mm; 0 is the level of the LHB
Delamination: yes or no
Frontal extension: amount of the footprint involved (medial to lateral), largest part
Tirman (1994) showed that the ABER view in the MR Arthro is the most effective view to visualize undersurface cuff tears.
Lee and Lee (2002) made a classification of 3 groups:
Type A: horizontal or intrasubstance component, no abnormalities on articular surface
Type B: irregularity of the articular surface
Type C: flap lesion along the surface
CT Arthro is less effective in diagnosing partial cuff tears, as well as ultrasound.
Other cuff muscles
The Infraspinatus muscle is often included in massive tears.
The Subscapularis muscle is less frequently involved, either isolated (mostly traumatic) or in combination with the large tears of supra and Infraspinatus.
Fox and Romeo (2003) defined the following subgroups:
Type 1: fraying
Type 2: compete tear upper 25%
Type 3: compete tear upper 50%
Type 4: complete tear with retraction