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Anomalous flexor superficialis indicis: Two case reports and literature review
Anomalous flexor superficialis indicis: Two case reports and literature review Derived from postmortem dissections, early descriptions of a muscle belly in the palm that served the index finger in the manner of the flexor digitorum superficialis were published by MacAlister (1868), Graper (1917), and Mainland (1927). In the English literature, we have found reports on only 15 clinical cases that involved the palm. Based on available information regarding sex, 12 patients were female and one was male. The anomaly involved the right hand in all cases and was bilateral in four of the female patients. We report two additional cases, of which one is considered the first bilateral case in a man with symptoms on the left side. (J HAND SURG 10A:296·99, 1985.)
Louis S. Elias, M.D., F.A.C.S., and Frances P. Schulter-Ellis, Ph.D., Baltimore, Md.
Derived from postmortem dissections, early descriptions of a muscle belly that lies medial to the thenar eminence in the human hand and is attached to the index finger in the manner of the flexor digitorum superficialis (FDS) muscle were published by MacAlister,l Graper,2 and Mainland. 3 In a search of the literature, we have found records of 15 clinical cases of this anomaly4-15 and have summarized pertinent information from these in Table I. Two additional clinical cases of an aberrant FDS belly of the index finger have been reported. 16- 17 One was bilateral in a male patient and caused carpal tunnel syndrome on both sides. However, in both of these cases, no portion of the fleshy mass rested in the palm distal to the carpal tunnel. They represented a different expression of variance than is the subject of this article. The same holds true for the
complex variation reported by Fromont,18 in which muscle bellies to both the second and fifth digits originated from the transverse carpal ligament. Variations in hand musculature per se are not uncommon. Many probably go unnoticed since the onset of symptoms frequently coincides with strain or increased exercise of the digits. However, given the paucity of reports in the literature, a muscle belly in the palm that serves as a flexor of the proximal interphalangeal (PIP) joint of the index finger is apparently a From the Raymond M. Curtis Hand Center, Union Memorial Hospital, the Department of Orthopedic Surgery, Johns Hopkins School of Medicine, and the Department of Anatomy, University of Maryland School of Medicine, Baltimore, Md. Received for publication Feb. 6, 1984; accepted in revised form July 5, 1984.
Reprint requests: Louis S. Elias, MD, 1103 North Point Blvd., Suite 401, Baltimore, MD 21224. 296
THE JOURNAL OF HAND SURGERY
rare occurrence. When symptoms are present, the physician is confronted with a diagnostic challenge. The following are reports of two symptomatic cases. The first patient presented for treatment with a painful mass and the second with a carpal tunnel syndrome. The second case was bilateral but symptomatic only in the left hand. To our knowledge, it is the first such case to be reported in a male subject.
Case reports Case 1. An I8-year-old white, right-handed, female student presented in 1976 with a painful mass along the ulnar side of the thenar eminence of her right hand. Pain was aggravated by gripping objects such as a doorknob or a tennis racket. Two months earlier, another surgeon had operated on the same hand and had found an "hypertrophied muscle" that he did not excise. Examination revealed a healed scar along the ulnar side of the thenar eminence and a longitudinal soft mass of 5 by 2.5 cm that could be easily palpated and moved from side to side. The mass became firm and less mobile on resistive flexion of the PIP joint of the index finger (Fig. 1, A). Radiography, arteriography, and a scan of the hand were normal. At operation, a muscle belly with one tendon at each end was found. The proximal tendon extended underneath the flexor retinaculum and traction on it suggested continuity with the bellies of the superficial digital flexor in the forearm. The distal tendon was inserted on the middle phalanx of the index finger as a normal FDS tendon does. Innervation was provided by the median nerve through its branch to the first lumbrical muscle. Electrical stimulation of the nerve supply or the muscle belly itself caused flexion of the PIP joint of the index finger (Fig. I, B). The profundus tendon to this finger and the first lumbrical muscle were normal. The aberrant muscle belly with its tendons was excised. Examination 2 years later showed good functional recovery with only a slight limitation of active flexion of the finger.
Vol. lOA, No.2 March 1985
Anomalous flexor superjicialis indicis 297
Table I. Pertinent infonnation from the reports of 15 clinical cases involving an anomalous muscle belly in the palm that served as the FDS of the index finger Case No.
Author
Symptoms
1966 1969 1970 1971 1972 1972 1973
14
Case' Wesser et aI.' Vichare6 Smith' Spinner' Spinner' Still and Kleinert" Still and Kleinert" Still and Kleinert" Hayes'" Das and Brown" Probst and Hunter" Tountas and Halikman" Christensen 14
15
Martelo-Villar"
I
2 3 4 5 6 7 8 9 IO II
12 13
16 II
F M
19 18
F
38
F
1973
28
1973
Treatment
Involved hand
Mass, pain Mass* Mass, pain CTS CTS CTS CTS
Partial excision Exploration Exploration Excision Decompression Decompression Excision
Right Rightt Right
F
CTS
Excision
Bilateral
33
F
CTS*
Excision
Right
1974 1975
29 17
F F
Typist Typist
Excision Excision
Bilateral Right
1975
49
F
Plaster finisher
Excision
Rightt
1976
14
F
Mass Mass (occasional pain) Mass, pain, inability to make a fist Mass. pain
Excision
Right
1977
20
F
Mass (slight pain)
Exploration
Bilateral
1980
14
F
Mass* (slight pain)
Exploration
Bilateral
F
Typist Housewife
Telephone operator
(Played piano) Student
FH
Right
No
Yes
CTS. carpal tunnel syndrome; FH. family history. 'Proximal attachment to transverse carpal ligament or the base of thenar eminence. tReported as right-handed.
Case 2. An 18-year-old white, right-handed, male student presented in 1979 with numbness and tingling of the fingers of his left hand, which had begun 2 months earlier. Just before that, he had attempted suicide by cutting both wrists. The cuts were very superficial and were treated with dressings. Examination of the left hand revealed a 5 by 2.5 cm, soft, mobile mass along the ulnar side of the thenar eminence. Resistive flexion of the PIP joint increased its prominence and tingling in the fingers. Hypoesthesia existed in the median nerve distribution. Otherwise, the hand was normal. An identical but smaller mass in the patient's right palm was asymptomatic. Nerve conduction studies of both median nerves were normal. A preoperative diagnosis was made based on experience with the first case. The patient was counseled about the nature of the mass, and decompression of the left median nerve was recommended. At surgery, the variant muscle was observed to have a distal tendon that inserted into the middle phalanx of the index finger and through which a normal profundus tendon passed. The muscle belly extended proximally under the flexor retinaculum. It received its nerve supply in the palm in common with the first lumbrical muscle (Fig. 2). Stimulation of this nerve produced flexion of the PIP joint of the index finger. The flexor retinaculum was released. The mass was not excised, and its nerve supply was left intact. The attachment of its proximal tendon was not determined since surgical exploration into the forearm was not justified. The pa-
tient made an uneventful recovery and lost his preoperative symptoms.
Discussion
Probst and Hunter12 and Christensen 14 have pointed out that there appear to be three types of anomalies of the functional unit of the FDS that serves the index finger. They grade one into the other. In some instances, the proximal tendon of the muscle (belly) attaches either to the transverse carpal ligament5 •
9
or to
the' 'base of the thenar eminence, , '15 thereby rendering the entire functional unit intrinsic to the hand. That is, the muscle and its tendons are contained wholly within the hand. Second, there is a digastric fonn with continuity existing by way of a tendon between the palmar and forearm bellies. 9 • 12. 13 A third type involves a muscle belly that occupies a position in the forearm from which it extends distally into the carpal tunnel, but not further into the palmY Clinically, in the first instance, patients present a palmar mass that mayor may not be painful. Those in whom the digastric fonn exists may present a palmar mass or carpal tunnel syndrome. The latter may develop symptoms because the palmar belly is sometimes elongated and passes proximally under the transverse carpal ligament.
298
Elias and Schulter-Ellis
Fig. 1. The right hand of an 18-year-old woman. A, Arrows indicate a palmar mass as it appears with resistive flexion of the index finger. B, Exploration of the hand revealed: A, an aberrant muscle belly, which on stimulation, caused flexion of the index finger; B, tendons of A; C, the flexor digitorum profundus tendon to the index finger; and D, the first lumbrical muscle.
Diagnosing a painful palmar mass presents some difficulties. In the cases cited, preoperative diagnoses have included tendon sheath tumors, lipoma, palmar ganglion, vascular malformation, and hamartoma. A presumptive diagnosis of an aberrant muscle belly depends on a high degree of suspicion, which should be entertained if the mass is soft, but becomes firm with resistive flexion of the PIP joint. A bilateral condition may also be an indicator since pathologic masses are rarely symmetrical. A final diagnosis rests on exploration. Reported treatments for a painful muscle mass have included simple exploration without excision, partial excision, and complete excision (Table I). Reflecting on our first case, which involved the digastric form, it now appears that neurectomy might have been a feasible alternative to complete excision of the palmar belly. Our rationale is that ensuing atrophy of
The Journal of HAND SURGERY
Fig. 2. A, The left hand of an 18-year-old man: A, an aberrant muscle with its tendon to the index finger; B, the nerve supply emerging from the belly of C, the first lumbrical muscle. Broken lines enclose the area shown in B. B, The structures of A, B, and C within the dotted lines of A.
the muscle tissue would have relieved the patient of symptoms, and flexion of the index finger would have suffered no embarrassment because the continuity of the distal tendon with the forearm belly would not have been interrupted. Unfortunately, this is hindsight, and determining the therapeutic value of such a procedure must await a new case. Little is known about inheritance factors. Only two authors have tried to establish family histories. n , 14 Interestingly, the female sex is affected far more frequently than the male. In addition, one half of the clinical cases were reported to involve the right side (side was not recorded in four cases), and only 25% of the cases were bilateral. Although the three postmortem cases l - 3 involved the left hand, our second case is apparently the first bilateral one of a man with symptoms on the left side. The authors are grateful to Spencer P. Ellis for preparing the illustrations, including the original drawing for Fig. 2, B.
Vol. lOA, No.2 March 1985
REFERENCES I. MacAlister A: Further notes on muscular abnormalities in human anatomy and their bearing upon homotypical myology. Proc R Irish Acad 10:121-64, 1866-1869 2. Graper L: Eine zehr seltene Varietiit des M. flexor digitorum sublimis. Anat Anz 50:80-4, 1917 3. Mainland D: An uncommon abnormality of the flexor digitorum sublimis muscle. J Anat 62:86-9, 1927 4. Case DB: A pseudotumor of the hand. Postgrad Med J 42:574-5, 1966 5. Wesser DR, Calostypis F, Hoffman S: The evolutionary significance of an aberrant flexor superficialis muscle in the human palm. J Bone Joint Surg [Am] 51 :396-8, 1969 6. Vichare NA: Anomalous muscle belly of the flexor digitorum superficialis. J Bone Joint Surg [Br] 52:757-9, 1970 7. Smith RJ: Anomalous muscle belly of the flexor digitorum superficialis causing carpal tunnel syndrome. J Bone Joint Surg [Am] 53:1215-6, 1971 8. Spinner M: Injuries of the major branches of peripheral nerves of the forearm. Philadelphia, 1972, WB Saunders Co, p 100 9. Still JM, Kleinert HE: Anomalous muscles and nerve entrapment in the wrist and hand. Plast Reconstr Surg 52:394-400, 1973
Anomalous flexor superficialis indicis
10. Hayes CW: Anomalous flexor sublimis muscle with incipient carpal tunnel syndrome. Plast Reconstr Surg 53:479-83, 1974 II. Das SK, Brown HG: An anomalous flexor digitorum sublimis to index finger with absent lumbrical. Br J Plast Surg 28:299-300, 1975 12. Probst CE, Hunter JM: A digastric flexor digitorum superficialis. Bull Hosp Jt Dis Orthop Inst 36:52-7, 1975 13. Tountas CP, Halikman LA: An anomalous flexor digitorum sublimis muscle. Clin Orthop 76:230-3, 1976 14. Christensen S: Anomalous muscle belly of the flexor digitorum superficialis in two generations. Hand 9: 162-4, 1977 15. Martelo- Villar FJ: Bilateral anomalous flexor sublimis muscle to the index finger. Br J Plast Surg 33:80-2, 1980 16. Tanzer RC: The carpal tunnel syndrome-a clinical and anatomical study. J Bone Joint Surg [Am] 41:626-34, 1959 17. Neviaser RJ: Flexor digitorum superficialis indicis and carpal tunnel syndrome. Hand 6:155-6, 1974 18. Fromont Dr: Anomalies musculaires multiples de la main. Absence du flechisseur propre du pouce. Absence des muscles de l'eminence thenar. Lombricaux supplementaires. Bull Soc Anat Paris 70:395-401, 1895
Pathologic anatomy of the forearm: Intersection syndrome Intersection syndrome of the forearm is a common painful condition that is infrequently diagnosed. It presents with pain and swelling in the area where the muscle bellies of the abductor pollicis longus and extensor pollicis brevis cross the common wrist extensors. The etiology is not well understood, but operative treatment of 13 patients has shown that the basic pathologic abnormality is stenosing tenosynovitis of the sheath of the common radial wrist extensors. (J HAND SURG 10A:299-302, 1985.)
Amis B. Grundberg, M.D., and Douglas S. Reagan, M.D., Des Moines, Iowa
Intersection syndrome presents with symptoms and signs in the area where the muscle bellies of the abductor pollicis longus (APL) and the extensor From the Iowa Methodist Medical Center, Des Moines, Iowa. Received for publication April 26, 1984; accepted in revised form July 31, 1984. Reprint requests: Amis B. Grundberg, M.D., 1440 Pleasant, Des Moines, IA 50314.
pollicis brevis (EPB) intersect the extensor carpi radialis longus and brevis (ECRL and ECRB) tendons (Fig. 1). This area is about 4 em proximal to the wrist. The syndrome manifests as pain and swelling and, in severe cases, as redness and crepitus (Fig. 2). The diagnosis is easily made because the patient points to this area as the origin of his pain. It should be noted that the area naturally presents swelling because of the muscle bellies of the EPB and APL. The THE JOURNAL OF HAND SURGERY
299
Louis S. Elias, M.D., F.A.C.S., and Frances P. Schulter-Ellis, Ph.D., Baltimore, Md.
Derived from postmortem dissections, early descriptions of a muscle belly that lies medial to the thenar eminence in the human hand and is attached to the index finger in the manner of the flexor digitorum superficialis (FDS) muscle were published by MacAlister,l Graper,2 and Mainland. 3 In a search of the literature, we have found records of 15 clinical cases of this anomaly4-15 and have summarized pertinent information from these in Table I. Two additional clinical cases of an aberrant FDS belly of the index finger have been reported. 16- 17 One was bilateral in a male patient and caused carpal tunnel syndrome on both sides. However, in both of these cases, no portion of the fleshy mass rested in the palm distal to the carpal tunnel. They represented a different expression of variance than is the subject of this article. The same holds true for the
complex variation reported by Fromont,18 in which muscle bellies to both the second and fifth digits originated from the transverse carpal ligament. Variations in hand musculature per se are not uncommon. Many probably go unnoticed since the onset of symptoms frequently coincides with strain or increased exercise of the digits. However, given the paucity of reports in the literature, a muscle belly in the palm that serves as a flexor of the proximal interphalangeal (PIP) joint of the index finger is apparently a From the Raymond M. Curtis Hand Center, Union Memorial Hospital, the Department of Orthopedic Surgery, Johns Hopkins School of Medicine, and the Department of Anatomy, University of Maryland School of Medicine, Baltimore, Md. Received for publication Feb. 6, 1984; accepted in revised form July 5, 1984.
Reprint requests: Louis S. Elias, MD, 1103 North Point Blvd., Suite 401, Baltimore, MD 21224. 296
THE JOURNAL OF HAND SURGERY
rare occurrence. When symptoms are present, the physician is confronted with a diagnostic challenge. The following are reports of two symptomatic cases. The first patient presented for treatment with a painful mass and the second with a carpal tunnel syndrome. The second case was bilateral but symptomatic only in the left hand. To our knowledge, it is the first such case to be reported in a male subject.
Case reports Case 1. An I8-year-old white, right-handed, female student presented in 1976 with a painful mass along the ulnar side of the thenar eminence of her right hand. Pain was aggravated by gripping objects such as a doorknob or a tennis racket. Two months earlier, another surgeon had operated on the same hand and had found an "hypertrophied muscle" that he did not excise. Examination revealed a healed scar along the ulnar side of the thenar eminence and a longitudinal soft mass of 5 by 2.5 cm that could be easily palpated and moved from side to side. The mass became firm and less mobile on resistive flexion of the PIP joint of the index finger (Fig. 1, A). Radiography, arteriography, and a scan of the hand were normal. At operation, a muscle belly with one tendon at each end was found. The proximal tendon extended underneath the flexor retinaculum and traction on it suggested continuity with the bellies of the superficial digital flexor in the forearm. The distal tendon was inserted on the middle phalanx of the index finger as a normal FDS tendon does. Innervation was provided by the median nerve through its branch to the first lumbrical muscle. Electrical stimulation of the nerve supply or the muscle belly itself caused flexion of the PIP joint of the index finger (Fig. I, B). The profundus tendon to this finger and the first lumbrical muscle were normal. The aberrant muscle belly with its tendons was excised. Examination 2 years later showed good functional recovery with only a slight limitation of active flexion of the finger.
Vol. lOA, No.2 March 1985
Anomalous flexor superjicialis indicis 297
Table I. Pertinent infonnation from the reports of 15 clinical cases involving an anomalous muscle belly in the palm that served as the FDS of the index finger Case No.
Author
Symptoms
1966 1969 1970 1971 1972 1972 1973
14
Case' Wesser et aI.' Vichare6 Smith' Spinner' Spinner' Still and Kleinert" Still and Kleinert" Still and Kleinert" Hayes'" Das and Brown" Probst and Hunter" Tountas and Halikman" Christensen 14
15
Martelo-Villar"
I
2 3 4 5 6 7 8 9 IO II
12 13
16 II
F M
19 18
F
38
F
1973
28
1973
Treatment
Involved hand
Mass, pain Mass* Mass, pain CTS CTS CTS CTS
Partial excision Exploration Exploration Excision Decompression Decompression Excision
Right Rightt Right
F
CTS
Excision
Bilateral
33
F
CTS*
Excision
Right
1974 1975
29 17
F F
Typist Typist
Excision Excision
Bilateral Right
1975
49
F
Plaster finisher
Excision
Rightt
1976
14
F
Mass Mass (occasional pain) Mass, pain, inability to make a fist Mass. pain
Excision
Right
1977
20
F
Mass (slight pain)
Exploration
Bilateral
1980
14
F
Mass* (slight pain)
Exploration
Bilateral
F
Typist Housewife
Telephone operator
(Played piano) Student
FH
Right
No
Yes
CTS. carpal tunnel syndrome; FH. family history. 'Proximal attachment to transverse carpal ligament or the base of thenar eminence. tReported as right-handed.
Case 2. An 18-year-old white, right-handed, male student presented in 1979 with numbness and tingling of the fingers of his left hand, which had begun 2 months earlier. Just before that, he had attempted suicide by cutting both wrists. The cuts were very superficial and were treated with dressings. Examination of the left hand revealed a 5 by 2.5 cm, soft, mobile mass along the ulnar side of the thenar eminence. Resistive flexion of the PIP joint increased its prominence and tingling in the fingers. Hypoesthesia existed in the median nerve distribution. Otherwise, the hand was normal. An identical but smaller mass in the patient's right palm was asymptomatic. Nerve conduction studies of both median nerves were normal. A preoperative diagnosis was made based on experience with the first case. The patient was counseled about the nature of the mass, and decompression of the left median nerve was recommended. At surgery, the variant muscle was observed to have a distal tendon that inserted into the middle phalanx of the index finger and through which a normal profundus tendon passed. The muscle belly extended proximally under the flexor retinaculum. It received its nerve supply in the palm in common with the first lumbrical muscle (Fig. 2). Stimulation of this nerve produced flexion of the PIP joint of the index finger. The flexor retinaculum was released. The mass was not excised, and its nerve supply was left intact. The attachment of its proximal tendon was not determined since surgical exploration into the forearm was not justified. The pa-
tient made an uneventful recovery and lost his preoperative symptoms.
Discussion
Probst and Hunter12 and Christensen 14 have pointed out that there appear to be three types of anomalies of the functional unit of the FDS that serves the index finger. They grade one into the other. In some instances, the proximal tendon of the muscle (belly) attaches either to the transverse carpal ligament5 •
9
or to
the' 'base of the thenar eminence, , '15 thereby rendering the entire functional unit intrinsic to the hand. That is, the muscle and its tendons are contained wholly within the hand. Second, there is a digastric fonn with continuity existing by way of a tendon between the palmar and forearm bellies. 9 • 12. 13 A third type involves a muscle belly that occupies a position in the forearm from which it extends distally into the carpal tunnel, but not further into the palmY Clinically, in the first instance, patients present a palmar mass that mayor may not be painful. Those in whom the digastric fonn exists may present a palmar mass or carpal tunnel syndrome. The latter may develop symptoms because the palmar belly is sometimes elongated and passes proximally under the transverse carpal ligament.
298
Elias and Schulter-Ellis
Fig. 1. The right hand of an 18-year-old woman. A, Arrows indicate a palmar mass as it appears with resistive flexion of the index finger. B, Exploration of the hand revealed: A, an aberrant muscle belly, which on stimulation, caused flexion of the index finger; B, tendons of A; C, the flexor digitorum profundus tendon to the index finger; and D, the first lumbrical muscle.
Diagnosing a painful palmar mass presents some difficulties. In the cases cited, preoperative diagnoses have included tendon sheath tumors, lipoma, palmar ganglion, vascular malformation, and hamartoma. A presumptive diagnosis of an aberrant muscle belly depends on a high degree of suspicion, which should be entertained if the mass is soft, but becomes firm with resistive flexion of the PIP joint. A bilateral condition may also be an indicator since pathologic masses are rarely symmetrical. A final diagnosis rests on exploration. Reported treatments for a painful muscle mass have included simple exploration without excision, partial excision, and complete excision (Table I). Reflecting on our first case, which involved the digastric form, it now appears that neurectomy might have been a feasible alternative to complete excision of the palmar belly. Our rationale is that ensuing atrophy of
The Journal of HAND SURGERY
Fig. 2. A, The left hand of an 18-year-old man: A, an aberrant muscle with its tendon to the index finger; B, the nerve supply emerging from the belly of C, the first lumbrical muscle. Broken lines enclose the area shown in B. B, The structures of A, B, and C within the dotted lines of A.
the muscle tissue would have relieved the patient of symptoms, and flexion of the index finger would have suffered no embarrassment because the continuity of the distal tendon with the forearm belly would not have been interrupted. Unfortunately, this is hindsight, and determining the therapeutic value of such a procedure must await a new case. Little is known about inheritance factors. Only two authors have tried to establish family histories. n , 14 Interestingly, the female sex is affected far more frequently than the male. In addition, one half of the clinical cases were reported to involve the right side (side was not recorded in four cases), and only 25% of the cases were bilateral. Although the three postmortem cases l - 3 involved the left hand, our second case is apparently the first bilateral one of a man with symptoms on the left side. The authors are grateful to Spencer P. Ellis for preparing the illustrations, including the original drawing for Fig. 2, B.
Vol. lOA, No.2 March 1985
REFERENCES I. MacAlister A: Further notes on muscular abnormalities in human anatomy and their bearing upon homotypical myology. Proc R Irish Acad 10:121-64, 1866-1869 2. Graper L: Eine zehr seltene Varietiit des M. flexor digitorum sublimis. Anat Anz 50:80-4, 1917 3. Mainland D: An uncommon abnormality of the flexor digitorum sublimis muscle. J Anat 62:86-9, 1927 4. Case DB: A pseudotumor of the hand. Postgrad Med J 42:574-5, 1966 5. Wesser DR, Calostypis F, Hoffman S: The evolutionary significance of an aberrant flexor superficialis muscle in the human palm. J Bone Joint Surg [Am] 51 :396-8, 1969 6. Vichare NA: Anomalous muscle belly of the flexor digitorum superficialis. J Bone Joint Surg [Br] 52:757-9, 1970 7. Smith RJ: Anomalous muscle belly of the flexor digitorum superficialis causing carpal tunnel syndrome. J Bone Joint Surg [Am] 53:1215-6, 1971 8. Spinner M: Injuries of the major branches of peripheral nerves of the forearm. Philadelphia, 1972, WB Saunders Co, p 100 9. Still JM, Kleinert HE: Anomalous muscles and nerve entrapment in the wrist and hand. Plast Reconstr Surg 52:394-400, 1973
Anomalous flexor superficialis indicis
10. Hayes CW: Anomalous flexor sublimis muscle with incipient carpal tunnel syndrome. Plast Reconstr Surg 53:479-83, 1974 II. Das SK, Brown HG: An anomalous flexor digitorum sublimis to index finger with absent lumbrical. Br J Plast Surg 28:299-300, 1975 12. Probst CE, Hunter JM: A digastric flexor digitorum superficialis. Bull Hosp Jt Dis Orthop Inst 36:52-7, 1975 13. Tountas CP, Halikman LA: An anomalous flexor digitorum sublimis muscle. Clin Orthop 76:230-3, 1976 14. Christensen S: Anomalous muscle belly of the flexor digitorum superficialis in two generations. Hand 9: 162-4, 1977 15. Martelo- Villar FJ: Bilateral anomalous flexor sublimis muscle to the index finger. Br J Plast Surg 33:80-2, 1980 16. Tanzer RC: The carpal tunnel syndrome-a clinical and anatomical study. J Bone Joint Surg [Am] 41:626-34, 1959 17. Neviaser RJ: Flexor digitorum superficialis indicis and carpal tunnel syndrome. Hand 6:155-6, 1974 18. Fromont Dr: Anomalies musculaires multiples de la main. Absence du flechisseur propre du pouce. Absence des muscles de l'eminence thenar. Lombricaux supplementaires. Bull Soc Anat Paris 70:395-401, 1895
Pathologic anatomy of the forearm: Intersection syndrome Intersection syndrome of the forearm is a common painful condition that is infrequently diagnosed. It presents with pain and swelling in the area where the muscle bellies of the abductor pollicis longus and extensor pollicis brevis cross the common wrist extensors. The etiology is not well understood, but operative treatment of 13 patients has shown that the basic pathologic abnormality is stenosing tenosynovitis of the sheath of the common radial wrist extensors. (J HAND SURG 10A:299-302, 1985.)
Amis B. Grundberg, M.D., and Douglas S. Reagan, M.D., Des Moines, Iowa
Intersection syndrome presents with symptoms and signs in the area where the muscle bellies of the abductor pollicis longus (APL) and the extensor From the Iowa Methodist Medical Center, Des Moines, Iowa. Received for publication April 26, 1984; accepted in revised form July 31, 1984. Reprint requests: Amis B. Grundberg, M.D., 1440 Pleasant, Des Moines, IA 50314.
pollicis brevis (EPB) intersect the extensor carpi radialis longus and brevis (ECRL and ECRB) tendons (Fig. 1). This area is about 4 em proximal to the wrist. The syndrome manifests as pain and swelling and, in severe cases, as redness and crepitus (Fig. 2). The diagnosis is easily made because the patient points to this area as the origin of his pain. It should be noted that the area naturally presents swelling because of the muscle bellies of the EPB and APL. The THE JOURNAL OF HAND SURGERY
299