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Shoulder Injuries
C H A P T E R
Shoulder Injuries
188
CAROL L. GILLIS
SOFT TISSUE INJURIES OF THE SHOULDER History and Clinical Signs
Because of its prominent location on the point of the shoulder, the biceps brachii tendon is the most commonly injured structure of the shoulder soft tissues. Unlike most tendons and ligaments, the biceps tendon is often injured as a result of direct trauma rather than cumulative overload. The medical history often includes the horse being kicked while breeding or being ridden, or hitting a fence or other solid object with the affected shoulder. Athletic use overload also occurs. Rarely, the biceps tendon is injured, or bicipital synovitis develops secondarily to developmental orthopedic disease of the humeral tubercles. Synovitis of the bicipital bursa may occur alone or in conjunction with damage to the biceps tendon. Horses with bicipital bursitis or biceps tendonitis resent palpation of the tendon and pressure applied to the front of the shoulder. If the horse is asked to walk and then halt, it often prefers to stand with the affected limb placed slightly caudal to the unaffected one. The supraspinatus muscle is also prominently placed on the humeral tubercles, and injury of this muscle also should be suspected with the previously described injury history. Clinical signs are similar to those seen with biceps tendon injury. The infraspinatus muscle and its bursa are often injured when the lower limb is abruptly or excessively adducted, such as when a Western event horse or a polo pony suddenly changes direction while traveling at high speed. Pain on palpation of the muscle and on limb adduction or abduction are the usual clinical signs.
Diagnosis The primary imaging modality for diagnosis of muscle, tendon, and bursa injuries is ultrasonography. A highfrequency linear transducer (7 to 12 MHz) is ideal for the examination. The shoulder area should be clipped (except for very short-haired horses) and washed with mild soap and water, after which ultrasound gel is applied. The tendinous origin of the bicipital muscle is located on the craniodistal aspect of the distal part of the scapula, and it is important to begin the exam at this location (Figure 188-1). The tendon is evaluated in long- and short-axis planes as it traverses the humeral tubercles and joins the muscle distally. At the level of the humeral tubercles, the most common site of injury, the tendon is bilobed; each lobe may need to be evaluated separately because of size. The usual ultrasonographic parameters of size, echogenicity, and fiber pattern should be used to determine whether injury has occurred. The deep edge of the tendon is normally hypoechoic as it undergoes compression by the humeral tubercle, which results in it having a fibrocartilaginous component. This creates two diagnostic challenges. The first is to determine whether the hypoechoic region is normal, either through practice in the use of ultrasound or by comparison with the
opposite tendon. The second is to differentiate the hypoechoic tendon from the fluid contents of the bicipital bursa. This can best be achieved by changing the transducer angle slightly until the bursa sheath can be detected. The bursa normally contains less than 3 mm depth of hypoechoic to anechoic fluid (Figure 188-2). With inflammation, the bursa initially distends with effusion, with first synovial prolif eration and finally adhesions developing over time in the absence of treatment. The bursa may be injected under ultrasound guidance, with a 11 2-inch, 19-gauge needle used to access either the shallow part of the sheath lateral to midline or the lateral part of the bursa between the lateral lobe of the biceps tendon and the axial border of the cranial greater humeral tubercle. A volume of 15 to 20 mL of local anesthetic should be injected to sufficiently anesthetize the structure and confirm that it is the source of pain. In less than 20% of horses, the bursa communicates with the shoulder joint, so the response to anesthesia must be interpreted in conjunction with ultrasonographic findings. Distal to the humeral tubercles, the muscular portion of the biceps tendon is examined in both planes to the point of its short tendinous insertion. The supraspinatus muscle is examined in short- and longaxis views from its origin in the supraspinous fossa to its tendinous portion, which bifurcates to insert on the humeral tubercles medial and lateral to the biceps tendon. The infraspinatus muscle is examined from its origin in the infraspinous fossa to its tendinous portion, which splits into deep (short) and shallow (long) insertions on the lateral aspect of the humerus. The infraspinous bursa is evaluated for volume and character of fluid (Figure 188-3). The deltoideus muscle is fairly well protected from direct trauma because of its caudolateral location and is not often injured from overuse. It is most commonly injured in conjunction with deltoid tuberosity fractures. Muscle damage and fracture fragments can be identified ultrasonographically. Any open wound in the shoulder area should be an indication for ultrasonographic evaluation of associated soft and hard tissues. Air or gas in the wound can interfere with diagnostic images; therefore ultrasound should be performed after cleaning but before probing the wound.
Treatment and Rehabilitation Bicipital or infraspinatus bursa inflammation without concomitant muscle or tendon injury is treated with systemic nonsteroidal antiinflammatory drug administration, ultrasound-guided injection of polysulfated glycosaminoglycan, a steroid or steroid and hyaluronic acid combination, cold therapy for 15 minutes twice daily, and walking exercise for 4 days. The horse should be reevaluated before returning to work to ensure effectiveness of treatment. Infectious bursitis is treated with lavage, appropriate antimicrobials, and antiinflammatories. It is important to treat inflammation
805
806
SECTION
XVII Musculoskeletal
L biceps OR
A
Figure 188-1 A, Sonogram showing long- (left) and short-axis (right) views of a normal biceps tendon at the origin. Notice the strong parallel linear fiber pattern and evenly bright echogenicity of the tendon. B, Long- and short-axis views of an injured biceps tendon at the origin. Notice the central gap in the fiber pattern on the longaxis view (left) and the hypoechoic core lesion on the short-axis view (right), in addition to the tendon enlargement.
A
A A:1.33 cm2 C:5.87 cm
6.0
R biceps OR
A
B
A
B
B A A = 1.34 cm, B = 0.45 cm
A = 2.23 cm2, B = 0.48 cm2
B
T LA523 5.6 mm
A Biceps lat
R infraspinatus and bursa
1
A
Bicip bursa C C B
Figure 188-3 Sonogram of the long-axis view of an infraspinatus bursa that is distended with hypoechoic fluid and fibrin after recent traumatic injury.
B
A 0.13 cm
B 0.13 cm
mm
C 0.08 cm
Figure 188-2 Sonogram of the short-axis view of the lateral lobe of a normal biceps tendon and the surrounding bursa. Notice that the bursa, which might more accurately be termed a sheath, extends shallow to the tendon as well as deep to it, attaching only at dorsal midline. Fluid depth on all three measurements is within normal limits. Also notice the hypoechoic deep portion of the biceps tendon; this area represents the fibrocartilaginous tissue that is a result of compression in the portion of the tendon where it glides over the humeral tubercles.
aggressively; otherwise, synovial proliferation and adhesions may cause long-term lameness and loss of normal tendon gliding long after the infection has resolved. Injury to the tendinous portion of the biceps, supraspinatus, or infraspinatus muscles is treated initially with anti inflammatory therapy, either with systemic nonsteroidal antiinflammatory drugs at an appropriate dose for 3 weeks or with topical application of 1% diclofenac cream twice daily for 3 weeks, applied before exercise. Oral administration of methocarbamol for 3 weeks is also helpful to relieve muscle spasm and pain. Physical therapy, including massage and cold therapy, for 15 minutes twice daily after exercise for 3 weeks will assist in mobilizing edema and in pain relief.
Controlled exercise is the essential requirement for heal ing. Pasture turnout yields a 25% or less chance for return to work without reinjury because the horse exercises randomly and intermittently, resulting in partial healing followed by reinjury in a cycle that can continue for years. The horse should therefore be confined to an area in which it may only walk, generally an area with maximum dimensions of 12 by 24 feet. Controlled exercise is initiated immediately, with 15 minutes of hand walking twice daily; this is increased by 5 minutes every 2 weeks. The horse is reexamined clinically and with diagnostic ultrasound every 6 to 8 weeks, depending on the initial severity of the lesion, with mild lesions requiring shorter time intervals between examinations and potential increases in exercise level. At the first recheck exam, the horse should be free of pain on examination at the walk and on shoulder palpation or manipulation. Ultrasonographic findings are evaluated as good, fair, or poor. Good healing progress includes resolution of swelling, decrease in size of any discrete core lesion, and improvement in overall echogenicity for generalized tears or increase in echogenicity of discrete core lesions. Good or fair progress indicates that the tendon has healed sufficiently for riding exercise at the walk to begin. The horse remains confined in an area in which it may only walk, except for riding exercise and a second exercise period of hand walking of 15 to 20 minutes. On average, riding time begins at 25 minutes and increases every 2 weeks. Poor tendon healing indicates either inappropriate rehabilitation or lameness elsewhere; these complicating factors must be identified and corrected for normal healing to proceed. At the second recheck examination, the horse should be free of pain on examination at the walk and trot and on shoulder palpation or manipulation. Good healing progress includes resolution of any discrete core lesion or improvement in overall echogenicity, stable or decreasing crosssectional area of the tendon, and stable or slightly improved fiber pattern. Good or fair progress indicates sufficient healing for trot exercise to begin. Amount of trot work varies with age and intended use of the horse, but in general is initiated as a 5-minute set after a 20-minute walk warm-up 5 days per week. Additional 5-minute sets are added at 2- to 3-week intervals. The horse remains confined in an area in which it only walks except for riding exercise and a second exercise period of hand walking of 15 to 20 minutes. At the third recheck examination, the horse should be clinically sound and free from pain on palpation or manip ulation. Evidence of progress in healing on ultrasound examination includes stable cross-sectional area of the tendon, good echogenicity, and improving fiber pattern. An increase of more than 12% in cross-sectional area is an indication of overload of the healing tendon, either from inappropriate rehabilitation, including excessive controlled or uncontrolled exercise, or from lameness originating elsewhere. These factors must be identified and corrected at this time for a successful outcome. Good or fair progress indicates that sufficient healing has occurred for cantering to be added to the current exercise schedule, 5 days per week. Work is increasingly adjusted to the horse’s future job; generally, cantering is added in 5-minute sets in the same manner in which trotting was added. After 1 week of cantering, the horse can be turned out. At the fourth recheck examination, the horse should be clinically sound and free of pain on palpation or manipulation. Good healing progress on ultrasound examination includes normal tendon cross-sectional area, normal echogenicity, and parallel linear fiber pattern. Good progress
CHAPTER
188 Shoulder Injuries
807
indicates that sufficient tendon healing has occurred for the horse to begin 4 to 6 weeks of training for its sport, followed by return to competition. Muscle injuries are less common than injury to the tendinous portion of these structures. If muscle injury is detected, a similar rehabilitation program is initiated; however, muscle heals much more rapidly than tendon, and each exercise level is generally maintained for a 4-week interval rather than for 6 to 8 weeks. Wounds ranging from punctures to open lacerations in the shoulder region should be treated with removal of any bone fragments or foreign bodies under ultrasound guidance, followed by debridement of contaminated tissue, lavage, and appropriate antibiotic therapy. Healing of damaged muscle or tendon is monitored with ultrasound.
Prognosis The percentage of horses that return to intended use without reinjury from shoulder injuries is 80% to 85% if a controlled exercise protocol is successfully completed. Muscle and tendon tissues possess intrinsic stem cells, which will repair damaged tissue provided that an appropriate environment for healing (i.e., initial antiinflammatory treatment followed by stimulation through a correct level of loading) is provided. The author has seen no difference between horses following such a protocol alone and horses in which regenerative therapy was used. This may be partly a result of our limited knowledge of the appropriate cells or cellular products to use and how to employ them; however, improvement over the current good prognosis may be difficult to obtain. Conversely, regenerative treatments undertaken without a controlled exercise program of the same duration yields results in the range of 25% to 45% for return to work without reinjury.
INJURIES OF THE SCAPULA AND HUMERUS History and Clinical Signs
Lameness associated with the scapula or humerus is rare in the adult horse and is often associated with a fall or direct blow that results in acute lameness. In young equine athletes, stress fractures of the scapula and developmental orthopedic disease manifestation are more common. Osseous cyst–like lesions of the humeral tubercles are rare; they may be developmental or arise subsequent to bone trauma. Lameness from bone lesions is generally acute and significant. The horse will likely resent palpation or manipulation of the affected structure; however, swelling is often difficult to detect because of the overlying heavy musculature.
Diagnosis Pain should be localized to the shoulder region by means of a careful clinical exam that includes diagnostic nerve blocks of the distal limb if needed, because acute distal limb lameness (as from a severe foot abscess) may cause reluctance to bear weight and trembling and flaccidity in the shoulder musculature, an appearance that may easily be mistaken for a shoulder region injury. Diagnostic ultrasound is useful for imaging bony lesions that extend to the surface, such as fractures of the scapular spine and deltoid tuberosity. Communicating cyst–like lesions of the humeral tubercles are readily seen on ultrasound examination. Ultrasound is also useful for evaluating the lateral aspect of the articular surface of the humeral head. Special radiographic views, including the flexed skyline view and oblique views of the humeral tubercles, may be helpful for evaluating bony lesions of the shoulder joint. Nuclear
808
SECTION
XVII Musculoskeletal
scintigraphy and magnetic resonance imaging are also indicated to define deeper bone lesions.
Treatment and Rehabilitation Stress fractures of the scapula respond well to rest and confinement, requiring about 4 months to heal per sonographic appearance. A careful training program before return to competition is required to allow the horse as well as the scapula to return to full strength. Fractures of the scapular spine are often associated with wounds; removal of fragments is usually necessary for wound healing to proceed. Treatment of deltoid tuberosity fractures and concomitant deltoideus muscle injury necessitates wound care, rest, and rehabilitation of the muscle injury. Cystlike lesions of the humeral tubercles respond well to treatment of the associated bursitis and, if tendon damage is also present, the controlled exercise program described for soft tissue injury.
Prognosis Horses with a fracture of the scapular spine, a fracture of the deltoid tuberosity, or cystlike lesions of the humeral tubercles have a good prognosis for return to athletic use. Fractures of the humeral tubercles, humeral head, or neck of the scapula carry a poor prognosis for return to athletic use. Developmental orthopedic disease lesions of the articular surfaces of the humeral head and scapula have a guarded prognosis for return to athletic use.
Suggested Readings Coudry V, Allen AK, Denoix JM. Congenital abnormalities of the bicipital apparatus in four mature horses. Equine Vet J 2005;37:272-275.
Davidson EJ, Martin BB Jr. Stress fracture of the scapula in two horses. Vet Radiol Ultrasound 2004;45:407-410. Fiske-Jackson AR, Crawford AL, Archer RM, et al. Diagnosis, management, and outcome in 19 horses with deltoid tuberosity fractures. Vet Surg 2010;39: 1005-1110. Gillis CL. Soft tissue injuries: tendinitis and desmitis. In: Hinchcliff KW, Kaneps AJ, eds. Equine Sports Medicine and Surgery. 1st ed. St. Louis: Elsevier, 2004:412-431. Jenner F, Ross MW, Martin BB, et al. Scapulohumeral osteochondrosis: a retrospective study of 32 horses. Vet Comp Orthop Traumatol 2008;21:406-412. Lawson SE, Marlin DJ. Preliminary report into the function of the shoulder using a novel imaging and motion capture approach. Equine Vet J Suppl 2010;38:552-555. Little D, Redding WR, Gerard MP. Osseous cyst-like lesions of the lateral intertubercular groove of the proximal humerus: a report of 5 cases. Equine Vet Ed 2009;21:60-66. Mez JC, Dabareiner RM, Cole RC, et al. Fractures of the greater tubercle of the humerus in horses: 15 cases (1986-2004). J Am Vet Med Assoc 2007;230:1350-1355. Parth RA, Svalbe LS, Hazard GH, et al. Suspected primary scapulohumeral osteoarthritis in two Miniature ponies. Aust Vet J 2008;86:153-156. Redding WR, Pease AP. Imaging of the shoulder. Equine Vet Educ 2010:199-209. Schneeweiss W, Puggioni A, David F. Comparison of ultrasound-guided vs. “blind” techniques for intra-synovial injections of the shoulder area in horses: scapulohumeral joint, bicipital and infraspinatus bursae. Equine Vet J 2012;44:674-678. Whitcomb MB, le Jeune SS, Macdonald MM, et al. Disorders of the infraspinatus tendon and bursa in three horses. J Am Vet Med Assoc 2006;229:549-556.
Shoulder Injuries
188
CAROL L. GILLIS
SOFT TISSUE INJURIES OF THE SHOULDER History and Clinical Signs
Because of its prominent location on the point of the shoulder, the biceps brachii tendon is the most commonly injured structure of the shoulder soft tissues. Unlike most tendons and ligaments, the biceps tendon is often injured as a result of direct trauma rather than cumulative overload. The medical history often includes the horse being kicked while breeding or being ridden, or hitting a fence or other solid object with the affected shoulder. Athletic use overload also occurs. Rarely, the biceps tendon is injured, or bicipital synovitis develops secondarily to developmental orthopedic disease of the humeral tubercles. Synovitis of the bicipital bursa may occur alone or in conjunction with damage to the biceps tendon. Horses with bicipital bursitis or biceps tendonitis resent palpation of the tendon and pressure applied to the front of the shoulder. If the horse is asked to walk and then halt, it often prefers to stand with the affected limb placed slightly caudal to the unaffected one. The supraspinatus muscle is also prominently placed on the humeral tubercles, and injury of this muscle also should be suspected with the previously described injury history. Clinical signs are similar to those seen with biceps tendon injury. The infraspinatus muscle and its bursa are often injured when the lower limb is abruptly or excessively adducted, such as when a Western event horse or a polo pony suddenly changes direction while traveling at high speed. Pain on palpation of the muscle and on limb adduction or abduction are the usual clinical signs.
Diagnosis The primary imaging modality for diagnosis of muscle, tendon, and bursa injuries is ultrasonography. A highfrequency linear transducer (7 to 12 MHz) is ideal for the examination. The shoulder area should be clipped (except for very short-haired horses) and washed with mild soap and water, after which ultrasound gel is applied. The tendinous origin of the bicipital muscle is located on the craniodistal aspect of the distal part of the scapula, and it is important to begin the exam at this location (Figure 188-1). The tendon is evaluated in long- and short-axis planes as it traverses the humeral tubercles and joins the muscle distally. At the level of the humeral tubercles, the most common site of injury, the tendon is bilobed; each lobe may need to be evaluated separately because of size. The usual ultrasonographic parameters of size, echogenicity, and fiber pattern should be used to determine whether injury has occurred. The deep edge of the tendon is normally hypoechoic as it undergoes compression by the humeral tubercle, which results in it having a fibrocartilaginous component. This creates two diagnostic challenges. The first is to determine whether the hypoechoic region is normal, either through practice in the use of ultrasound or by comparison with the
opposite tendon. The second is to differentiate the hypoechoic tendon from the fluid contents of the bicipital bursa. This can best be achieved by changing the transducer angle slightly until the bursa sheath can be detected. The bursa normally contains less than 3 mm depth of hypoechoic to anechoic fluid (Figure 188-2). With inflammation, the bursa initially distends with effusion, with first synovial prolif eration and finally adhesions developing over time in the absence of treatment. The bursa may be injected under ultrasound guidance, with a 11 2-inch, 19-gauge needle used to access either the shallow part of the sheath lateral to midline or the lateral part of the bursa between the lateral lobe of the biceps tendon and the axial border of the cranial greater humeral tubercle. A volume of 15 to 20 mL of local anesthetic should be injected to sufficiently anesthetize the structure and confirm that it is the source of pain. In less than 20% of horses, the bursa communicates with the shoulder joint, so the response to anesthesia must be interpreted in conjunction with ultrasonographic findings. Distal to the humeral tubercles, the muscular portion of the biceps tendon is examined in both planes to the point of its short tendinous insertion. The supraspinatus muscle is examined in short- and longaxis views from its origin in the supraspinous fossa to its tendinous portion, which bifurcates to insert on the humeral tubercles medial and lateral to the biceps tendon. The infraspinatus muscle is examined from its origin in the infraspinous fossa to its tendinous portion, which splits into deep (short) and shallow (long) insertions on the lateral aspect of the humerus. The infraspinous bursa is evaluated for volume and character of fluid (Figure 188-3). The deltoideus muscle is fairly well protected from direct trauma because of its caudolateral location and is not often injured from overuse. It is most commonly injured in conjunction with deltoid tuberosity fractures. Muscle damage and fracture fragments can be identified ultrasonographically. Any open wound in the shoulder area should be an indication for ultrasonographic evaluation of associated soft and hard tissues. Air or gas in the wound can interfere with diagnostic images; therefore ultrasound should be performed after cleaning but before probing the wound.
Treatment and Rehabilitation Bicipital or infraspinatus bursa inflammation without concomitant muscle or tendon injury is treated with systemic nonsteroidal antiinflammatory drug administration, ultrasound-guided injection of polysulfated glycosaminoglycan, a steroid or steroid and hyaluronic acid combination, cold therapy for 15 minutes twice daily, and walking exercise for 4 days. The horse should be reevaluated before returning to work to ensure effectiveness of treatment. Infectious bursitis is treated with lavage, appropriate antimicrobials, and antiinflammatories. It is important to treat inflammation
805
806
SECTION
XVII Musculoskeletal
L biceps OR
A
Figure 188-1 A, Sonogram showing long- (left) and short-axis (right) views of a normal biceps tendon at the origin. Notice the strong parallel linear fiber pattern and evenly bright echogenicity of the tendon. B, Long- and short-axis views of an injured biceps tendon at the origin. Notice the central gap in the fiber pattern on the longaxis view (left) and the hypoechoic core lesion on the short-axis view (right), in addition to the tendon enlargement.
A
A A:1.33 cm2 C:5.87 cm
6.0
R biceps OR
A
B
A
B
B A A = 1.34 cm, B = 0.45 cm
A = 2.23 cm2, B = 0.48 cm2
B
T LA523 5.6 mm
A Biceps lat
R infraspinatus and bursa
1
A
Bicip bursa C C B
Figure 188-3 Sonogram of the long-axis view of an infraspinatus bursa that is distended with hypoechoic fluid and fibrin after recent traumatic injury.
B
A 0.13 cm
B 0.13 cm
mm
C 0.08 cm
Figure 188-2 Sonogram of the short-axis view of the lateral lobe of a normal biceps tendon and the surrounding bursa. Notice that the bursa, which might more accurately be termed a sheath, extends shallow to the tendon as well as deep to it, attaching only at dorsal midline. Fluid depth on all three measurements is within normal limits. Also notice the hypoechoic deep portion of the biceps tendon; this area represents the fibrocartilaginous tissue that is a result of compression in the portion of the tendon where it glides over the humeral tubercles.
aggressively; otherwise, synovial proliferation and adhesions may cause long-term lameness and loss of normal tendon gliding long after the infection has resolved. Injury to the tendinous portion of the biceps, supraspinatus, or infraspinatus muscles is treated initially with anti inflammatory therapy, either with systemic nonsteroidal antiinflammatory drugs at an appropriate dose for 3 weeks or with topical application of 1% diclofenac cream twice daily for 3 weeks, applied before exercise. Oral administration of methocarbamol for 3 weeks is also helpful to relieve muscle spasm and pain. Physical therapy, including massage and cold therapy, for 15 minutes twice daily after exercise for 3 weeks will assist in mobilizing edema and in pain relief.
Controlled exercise is the essential requirement for heal ing. Pasture turnout yields a 25% or less chance for return to work without reinjury because the horse exercises randomly and intermittently, resulting in partial healing followed by reinjury in a cycle that can continue for years. The horse should therefore be confined to an area in which it may only walk, generally an area with maximum dimensions of 12 by 24 feet. Controlled exercise is initiated immediately, with 15 minutes of hand walking twice daily; this is increased by 5 minutes every 2 weeks. The horse is reexamined clinically and with diagnostic ultrasound every 6 to 8 weeks, depending on the initial severity of the lesion, with mild lesions requiring shorter time intervals between examinations and potential increases in exercise level. At the first recheck exam, the horse should be free of pain on examination at the walk and on shoulder palpation or manipulation. Ultrasonographic findings are evaluated as good, fair, or poor. Good healing progress includes resolution of swelling, decrease in size of any discrete core lesion, and improvement in overall echogenicity for generalized tears or increase in echogenicity of discrete core lesions. Good or fair progress indicates that the tendon has healed sufficiently for riding exercise at the walk to begin. The horse remains confined in an area in which it may only walk, except for riding exercise and a second exercise period of hand walking of 15 to 20 minutes. On average, riding time begins at 25 minutes and increases every 2 weeks. Poor tendon healing indicates either inappropriate rehabilitation or lameness elsewhere; these complicating factors must be identified and corrected for normal healing to proceed. At the second recheck examination, the horse should be free of pain on examination at the walk and trot and on shoulder palpation or manipulation. Good healing progress includes resolution of any discrete core lesion or improvement in overall echogenicity, stable or decreasing crosssectional area of the tendon, and stable or slightly improved fiber pattern. Good or fair progress indicates sufficient healing for trot exercise to begin. Amount of trot work varies with age and intended use of the horse, but in general is initiated as a 5-minute set after a 20-minute walk warm-up 5 days per week. Additional 5-minute sets are added at 2- to 3-week intervals. The horse remains confined in an area in which it only walks except for riding exercise and a second exercise period of hand walking of 15 to 20 minutes. At the third recheck examination, the horse should be clinically sound and free from pain on palpation or manip ulation. Evidence of progress in healing on ultrasound examination includes stable cross-sectional area of the tendon, good echogenicity, and improving fiber pattern. An increase of more than 12% in cross-sectional area is an indication of overload of the healing tendon, either from inappropriate rehabilitation, including excessive controlled or uncontrolled exercise, or from lameness originating elsewhere. These factors must be identified and corrected at this time for a successful outcome. Good or fair progress indicates that sufficient healing has occurred for cantering to be added to the current exercise schedule, 5 days per week. Work is increasingly adjusted to the horse’s future job; generally, cantering is added in 5-minute sets in the same manner in which trotting was added. After 1 week of cantering, the horse can be turned out. At the fourth recheck examination, the horse should be clinically sound and free of pain on palpation or manipulation. Good healing progress on ultrasound examination includes normal tendon cross-sectional area, normal echogenicity, and parallel linear fiber pattern. Good progress
CHAPTER
188 Shoulder Injuries
807
indicates that sufficient tendon healing has occurred for the horse to begin 4 to 6 weeks of training for its sport, followed by return to competition. Muscle injuries are less common than injury to the tendinous portion of these structures. If muscle injury is detected, a similar rehabilitation program is initiated; however, muscle heals much more rapidly than tendon, and each exercise level is generally maintained for a 4-week interval rather than for 6 to 8 weeks. Wounds ranging from punctures to open lacerations in the shoulder region should be treated with removal of any bone fragments or foreign bodies under ultrasound guidance, followed by debridement of contaminated tissue, lavage, and appropriate antibiotic therapy. Healing of damaged muscle or tendon is monitored with ultrasound.
Prognosis The percentage of horses that return to intended use without reinjury from shoulder injuries is 80% to 85% if a controlled exercise protocol is successfully completed. Muscle and tendon tissues possess intrinsic stem cells, which will repair damaged tissue provided that an appropriate environment for healing (i.e., initial antiinflammatory treatment followed by stimulation through a correct level of loading) is provided. The author has seen no difference between horses following such a protocol alone and horses in which regenerative therapy was used. This may be partly a result of our limited knowledge of the appropriate cells or cellular products to use and how to employ them; however, improvement over the current good prognosis may be difficult to obtain. Conversely, regenerative treatments undertaken without a controlled exercise program of the same duration yields results in the range of 25% to 45% for return to work without reinjury.
INJURIES OF THE SCAPULA AND HUMERUS History and Clinical Signs
Lameness associated with the scapula or humerus is rare in the adult horse and is often associated with a fall or direct blow that results in acute lameness. In young equine athletes, stress fractures of the scapula and developmental orthopedic disease manifestation are more common. Osseous cyst–like lesions of the humeral tubercles are rare; they may be developmental or arise subsequent to bone trauma. Lameness from bone lesions is generally acute and significant. The horse will likely resent palpation or manipulation of the affected structure; however, swelling is often difficult to detect because of the overlying heavy musculature.
Diagnosis Pain should be localized to the shoulder region by means of a careful clinical exam that includes diagnostic nerve blocks of the distal limb if needed, because acute distal limb lameness (as from a severe foot abscess) may cause reluctance to bear weight and trembling and flaccidity in the shoulder musculature, an appearance that may easily be mistaken for a shoulder region injury. Diagnostic ultrasound is useful for imaging bony lesions that extend to the surface, such as fractures of the scapular spine and deltoid tuberosity. Communicating cyst–like lesions of the humeral tubercles are readily seen on ultrasound examination. Ultrasound is also useful for evaluating the lateral aspect of the articular surface of the humeral head. Special radiographic views, including the flexed skyline view and oblique views of the humeral tubercles, may be helpful for evaluating bony lesions of the shoulder joint. Nuclear
808
SECTION
XVII Musculoskeletal
scintigraphy and magnetic resonance imaging are also indicated to define deeper bone lesions.
Treatment and Rehabilitation Stress fractures of the scapula respond well to rest and confinement, requiring about 4 months to heal per sonographic appearance. A careful training program before return to competition is required to allow the horse as well as the scapula to return to full strength. Fractures of the scapular spine are often associated with wounds; removal of fragments is usually necessary for wound healing to proceed. Treatment of deltoid tuberosity fractures and concomitant deltoideus muscle injury necessitates wound care, rest, and rehabilitation of the muscle injury. Cystlike lesions of the humeral tubercles respond well to treatment of the associated bursitis and, if tendon damage is also present, the controlled exercise program described for soft tissue injury.
Prognosis Horses with a fracture of the scapular spine, a fracture of the deltoid tuberosity, or cystlike lesions of the humeral tubercles have a good prognosis for return to athletic use. Fractures of the humeral tubercles, humeral head, or neck of the scapula carry a poor prognosis for return to athletic use. Developmental orthopedic disease lesions of the articular surfaces of the humeral head and scapula have a guarded prognosis for return to athletic use.
Suggested Readings Coudry V, Allen AK, Denoix JM. Congenital abnormalities of the bicipital apparatus in four mature horses. Equine Vet J 2005;37:272-275.
Davidson EJ, Martin BB Jr. Stress fracture of the scapula in two horses. Vet Radiol Ultrasound 2004;45:407-410. Fiske-Jackson AR, Crawford AL, Archer RM, et al. Diagnosis, management, and outcome in 19 horses with deltoid tuberosity fractures. Vet Surg 2010;39: 1005-1110. Gillis CL. Soft tissue injuries: tendinitis and desmitis. In: Hinchcliff KW, Kaneps AJ, eds. Equine Sports Medicine and Surgery. 1st ed. St. Louis: Elsevier, 2004:412-431. Jenner F, Ross MW, Martin BB, et al. Scapulohumeral osteochondrosis: a retrospective study of 32 horses. Vet Comp Orthop Traumatol 2008;21:406-412. Lawson SE, Marlin DJ. Preliminary report into the function of the shoulder using a novel imaging and motion capture approach. Equine Vet J Suppl 2010;38:552-555. Little D, Redding WR, Gerard MP. Osseous cyst-like lesions of the lateral intertubercular groove of the proximal humerus: a report of 5 cases. Equine Vet Ed 2009;21:60-66. Mez JC, Dabareiner RM, Cole RC, et al. Fractures of the greater tubercle of the humerus in horses: 15 cases (1986-2004). J Am Vet Med Assoc 2007;230:1350-1355. Parth RA, Svalbe LS, Hazard GH, et al. Suspected primary scapulohumeral osteoarthritis in two Miniature ponies. Aust Vet J 2008;86:153-156. Redding WR, Pease AP. Imaging of the shoulder. Equine Vet Educ 2010:199-209. Schneeweiss W, Puggioni A, David F. Comparison of ultrasound-guided vs. “blind” techniques for intra-synovial injections of the shoulder area in horses: scapulohumeral joint, bicipital and infraspinatus bursae. Equine Vet J 2012;44:674-678. Whitcomb MB, le Jeune SS, Macdonald MM, et al. Disorders of the infraspinatus tendon and bursa in three horses. J Am Vet Med Assoc 2006;229:549-556.