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A study of the dynamic relationship of the lumbrical muscles and the carpal tunnel
A STUDY OF THE DYNAMIC RELATIONSHIP LUMBRICAL MUSCLES AND THE CARPAL
OF THE TUNNEL
N. W. YII and D. ELLIOT From the North-East
Thames Regional Plastic Surgery Unit, St. Andrew’s Hospital, Billericay, Essex, UK
The dynamic relationship of the lumbrical muscles to the carpal tunnel was studied in 35 hands in 32 patients and their movement into the tunnel on finger flexion was examined with a view to its use as a diagnostic provocation test in carpal tunnel syndrome.
The Journal of Hand Surgery (British and European Volume, 1994) 19B: 4: 439-443 Two patients with telescoping of their fingers as a result of rheumatoid arthritis who presented with carpal tunnel syndrome and were found at operation to have their lumbrical muscles resting in the carpal tunnel were the impetus to this study. Anomalous variants of the lumbrical muscles have been found occupying the carpal tunnel previously and are assumed to have caused carpal tunnel syndrome (Touborg-Jensen, 1970; Butler and Bigley, 1971; Still and Kleinert, 1973; Schultz et al, 1973; Eriksen, 1973; Jabaley, 1978; Nather and Pho, 1981). As the origins of the lumbrical muscles lie close to the distal border of the flexor retinaculum (Mehta and Gardner, 1961), it seems likely that they move into the tunnel during finger flexion and that, in so doing, they may exacerbate carpal tunnel syndrome. That they move into the carpal tunnel during finger flexion was noted by Kaplan (1953) but we were unable to find any subsequent study confirming his observation. This study was undertaken to investigate the dynamic relationship of the lumbrical muscles and the carpal tunnel and the possibility that their movement into the carpal tunnel in finger flexion might exacerbate carpal tunnel syndrome, providing a basis for a diagnostic provocation test. PATIENTS
nerve compression which were confirmed by nerve conduction studies. She also had telescoping of the fingers, volar subluxation of the MP joints and fixed flexion deformities of the PIP joints. As in the previous case, there was very little synovium in the carpal tunnel, and a minimal synovectomy was performed. The lumbrical muscle bellies had also migrated proximally to fill the carpal tunnel. Post-operative recovery was uneventful and she remained symptom free after division of the flexor retinaculum, although the lumbricals remained within the carpal tunnel.
AND METHOD
Case 1
A 66-year-old housewife with a 25-year history of rheumatoid arthritis developed pain and paraesthesiae in the sensory distribution of the right median nerve. Clinical examination of her right hand revealed severe rheumatoid disease with telescoping of the fingers (Fig 1). Nerve conduction studies confirmed compression of the median nerve in the carpal tunnel. At surgery, the carpal tunnel contained very little synovial proliferation but the lumbrical muscles had migrated proximally as a result of the shortening of the finger and volar subluxation of the MP joints. The carpal tunnel was filled with lumbrical muscles (Fig 2). A limited synovectomy was performed. She was relieved of the symptoms by division of the flexor retinaculum, although the lumbrical muscle bellies remained within the carpal tunnel. Case 2 Fig 1
A 74-year-old housewife with a 20-year history of rheumatoid arthritis developed symptoms of left median 439
Hand of Case 1 showing telescoping of the fingers largely a result of volar subluxation of the metacarpophalangeal joints.
as
THE JOURNAL OF HAND SURGERY VOL. 19B No. 4 AUGUST 1994
Fig2
Intra-operative carpal tunnel.
view of Case
1 showing
lumbricals
in the
35 hands in 32 consecutive patients undergoing decompression of idiopathic carpal tunnel syndrome were studied. 29 were females and three were male, with a mean age of 56.0 years (age range 27-87 years; standard deviation 17.2 years). Most of the patients in the study were referred late for surgery, with a mean duration of symptoms of 25.1 months (range 6-48 months). 24 patients (82.8%) had had symptoms for 1 year or more. Surgery was performed under brachial block anaesthesia with exsanguination and an arm tourniquet in place. The wrist remained in the neutral position throughout the investigation and surgery. An incision was made in the line of the third web space from just distal to the distal border of the flexor retinaculum to approximately 1 cm distal to the distal wrist crease. After division of the palmar aponeurosis, the distal edge of the flexor retinaculum was marked. Where the proximal edge of each lumbrical muscle was not visible at or proximal to the distal edge of the flexor retinaculum, the lumbrical was not sought more distally in the palm. This was recorded as zero lumbrical within the carpal tunnel. By traction on the tendons of FDP within the
carpal canal, the fingers were drawn into full flexion and the position of the most proximal part of each lumbrical relative to the distal edge of the flexor retinaculum was recorded in millimetres with each finger in full flexion. In those patients in whom the median nerve showed either obvious narrowing, erythema or both, indicating the site of nerve compression, the distance between the distal edge of the nerve compression and the distal edge of the flexor retinaculum was also recorded. After the first three patients had been investigated as above, and all had exhibited proximal movement of the lumbrical muscles into the carpal tunnel on finger flexion, the possibility that making a clenched fist might provoke symptoms in patients with carpal tunnel syndrome was considered. All subsequent patients (29 patients with 3 1 carpal tunnel decompressions; 26 female and 3 male with a mean age of 56.1 years and age range of 27-87 years) were also investigated pre-operatively. Each patient was asked immediately before surgery to make a fist of the hand and the time until the onset of paraesthesiae recorded; this test will subsequently be referred to as the “lumbrical provocation test”. After 1 minute’s rest, Phalen’s test was carried out (Phalen, 1966). After a further minute’s rest, compression of the median at the wrist was carried out until paraesthesiae were elicited (Paley and McMurtry, 1985). In the above three tests, a positive result was recorded when the symptoms were reproduced within 60 seconds. Finally, Tinel’s test was carried out over the median nerve at the wrist (Tinel, 1915). One patient, who was already suffering continuous paraesthesiae at the time of surgery, was excluded from these tests. These four tests were also carried out on both hands in a control group of patients. This group consisted of 30 asymptomatic individuals, who had no complaint of numbness, tingling, pain or clumsiness in the hands. The control group was matched to the study group for age and sex, and included 26 females and 4 males with a mean age of 55.8 years (range 27-86 years; 18.8 years standard deviation). The Chi-square test was used to examine the difference in the number of positive lumbrical provocation tests between the study and control groups. The paired t-test was used to compare the mean response time between the lumbrical provocation test and the Phalen’s test. RESULTS
The excursions of the lumbrical muscles into the carpal tunnel in the 35 hands (32 patients) studied are shown in Figures 3 to 6. In only six patients out of 32 (18.8%) were the proximal ends of one or more lumbricals in the tunnel with the fingers fully extended. Only eight lumbricals out of 140 (5.7%) entered the carpal tunnel in this finger position. In all 32 patients ( lOOoh)studied, three or more lumbricals moved into the carpal canal on finger flexion. Furthermore all lumbricals, except two
LUMBRICALS
441
IN CT
50 45 40 Excursion into the Carpal Canal (mm)
2;;;
35 30
carpal
25
Consecutive Hands Examined
edge of lumbrical attachment in full finger flexion 0 Proximal edge of lumbrical attachment in full finger extension -S Distal edge of carpal ligament
*Proximal
Fig 3
Excursion of the index finger lumbrical carpal tunnel.
to FDP
tendon
to FDP
tendon
a ??
if(lumbrical
I) in the
50 45 40 1 35 Excursion 30 I into the 25 Carpal canal 20 1 (~1 15 : 10
b
+Proximal edge of lumbrical attachment in full finger flexion ?? Proximal edge of lumbrical attachment in full finger extension + Distal edge of flexor retinaculum Fig 4
Excursion of the middle finger lumbrical carpal tunnel.
to FDP tendon to FDP
(lumbrical
tendon
II) in the
50 45 40 35 Excursion 30 into the 25 Carpal 20
Fig 6
Proximal edge of lumbrical attachment in full finger flexion Proximal edge of lumbrical attachment in full finger extension Distal edge of flexor retinaculum
Excursion of the little finger lumbrical carpal tunnel.
to FDP tendon to FDP
(lumbrical
tendon
IV) in the
lumbricals to little fingers, moved into the carpal tunnel when the fingers were fully flexed. Most lumbricals had an excursion of more than 1 cm into the carpal tunnel on fully flexing the fingers, the middle finger lumbricals having the greatest excursions and the little finger lumbricals having the least. These observations are summarized in Table 1. Table 2 summarizes the results of the pre-operative testing in the last 29 patients (32 hands). It can be seen that the lumbrical provocation test is the most sensitive test with 97% sensitivity. It also has a high specificity of 93% and a positive predictive value of 88%. A significant difference was seen in the proportions of positive lumbrical provocation tests between the study and control groups (P~O.001). Figure 7 records the mean response time for each provocative test. The mean time for a positive lumbrical provocation test was 16.1 seconds compared to 25.1 seconds with the Phalen’s test. This difference was found to be significant (P < 0.01). There was no significant difference in the response time between the lumbrical provocation test and the manual compression test. In 22 hands (63%) the median nerve showed an obvious site of compression. In 19 of these 22 hands Table 1-Lumbrical
excursion into the carpal tunnel
15 10
Lumbricals
G+ ??
+zFig 5
Proximal edge of lumbrical attachment in full finger flexion Proximal edge of lumbrical attachment in full finger extension Distal edge of flexor retinaculum
Excursion of the ring tinger lumbrical carpal tunnel.
to FDP
tendon
to FDP
tendon
(lumbrical
III) in the
Mean excursion into carpal tunnel (cm) Range of excursion into carpal tunnel (cm) Percentage of lumbricals that showed excursion of more than 1 cm into the carpal tunnel
Index
Middle
Ring
Little
1.7
2.1
1.6
1.1
0.5-4.8
18
0.5-4.3
93
0.5-3.5
85
O-2.8
34
442
THE JOURNAL
Table 2-Test
P&den’s test
Pressure provocation test
Tinel’s sign
30/31 (97%) 4160 (6.7%) 97% 93%
2713 1 (87%) 4/60 (6.7%) 87% 93%
25/31 (81%) O/60 (0%) 81% 100%
13/31 (42%) O/60 (0%) 42% 100%
of positive
tests/total
60
0 LUUhiCal
Positive
response
VOL. 19B No. 4 AUGUST
Lumbrical provocation test
*The results are expressed as the number
Fig 7
SURGERY
1994
results
Carpal tunnel group* Control group* Sensitivity Specificity
prmGdim
OF HAND
test
Manual compression
Pbalen’s test.
test.
time for provocative
tests.
(86.4%) one or more lumbricals moved to, or proximal to, the distal edge of the visible nerve compression during full finger flexion. DISCUSSION Although it is impossible to relate carpal tunnel syndrome directly to the presence of any space-occupying lesion in the tunnel, it is usually assumed that nerve compression is due to an obvious space-occupying lesion when one is present. Nerve compression has been associated with muscle variants of palmaris longus (Ashby, 1964; Backhouse and Churchill-Davidson, 1975; Brones and Wilgis, 1978), of the flexor superficialis (Tanzer, 1959; Gardner, 1970; Baruch and Hass, 1977; Smith, 1971; Still and Kleinert, 1973) and of the lumbrical muscles (Touborg-Jensen 1970; Butler and Bigley, 1971; Schultz et al, 1973; Still and Kleinert, 1973; Eriksen, 1973; Jabaley, 1978; Nather and Pho, 1981). Although carpal tunnel syndrome in patients with rheumatoid arthritis is generally attributed to synovial proliferation, this was minimal in the two cases described above, and the lumbricals occupied a considerable volume of the carpal tunnel. The change in the resting position of the normal lumbrical muscles in the two cases had resulted in a persistent abnormal space-occupying lesion in the tunnel. It seems likely that the lumbricals caused, or contributed significantly to, the nerve compression in these cases and that retraction of the tendons of FDP following a change of finger length, MP joint volar subluxation and PIP joint flexion into the boutonni&e
number
of hands tested.
position, or a combination of these common deformities of rheumatoid disease, may contribute to median nerve compression in this condition more commonly than has been previously realized. Simple division of the flexor retinaculum appears to be sufficient to decompress the nerve in these cases, as with carpal tunnel syndrome in the presence of muscle anomalies. We were unable to find any previous study describing the dynamic relationship of the lumbrical muscles to the carpal tunnel. This study shows that in over 80% of individuals examined, the lumbricals do not lie within the carpal tunnel when the fingers are extended and in all of them three or more lumbricals move into the tunnel in the clenched fist position. In other words, a considerable bulk of lumbrical muscles moves into the carpal tunnel when the hand makes a fist. This may explain the fact that many patients with carpal tunnel syndrome complain of paraesthesiae when gripping, writing, cycling and driving, although the latter two activities also extend the wrist into the position of a reverse Phalen’s test. This study suggests that the lumbrical movement into the tunnel may be used to provoke symptoms in carpal tunnel syndrome. Clenching the fist was sufficient in our patients with well-established carpal tunnel syndrome to induce paraesthesiae in 97% of the cases, while Phalen’s test was positive in 87%. The sensitivity of Phalen’s test has been reported to range from 48% (Loong, 1977) to 93% (Grundberg, 1983), with most authors reported results in between (Phalen, 1966; Heller et al, 1986; Gellman et al, 1986; Seror, 1988; DeKrom et al, 1990; Durkan, 1991; Novak et al, 1992; Williams et al, 1992). The specificity of Phalen’s test also varies from 59% (Heller et al, 1986) to 100% (Williams et al, 1992) with intermediate results reported by others (Gellman et al, 1986; Durkan, 199 1). The relatively high sensitivity of Phalen’s test and of the lumbrical provocation test in our series may be related to the fact that most of our patients presented late with well-established symptoms, the likelihood of a positive Phalen’s test having been correlated with the severity of the carpal tunnel syndrome in previous studies (Spindler and Dellon, 1982; Seror, 1988). The sensitivity and specificity of the pressure provocative test in this series are similar to those in previous studies (Gellman et al, 1986; Durkan, 1991; Williams
LUMBRICALS
443
IN CT
et al, 1992), as are these measures with respect to Tinel’s sign, which also has a poorer sensitivity in other studies (Phalen, 1966; Loong, 1977; Bowles et al, 1983; Gellman et al, 1986; Durkan, 1991; Novak et al, 1992; Williams et al, 1992). Acknowledgements The authors wish to thank Dr M. Reilly, PhD, epidemiologist, Green, BSc, statistician, for their advice.
and MS Sandra
References ASHBY, B. S. (1964). Hypertrophy of the palmaris longus muscle. Journal of Bone and Joint Surgery, 46B: 2: 230-232. BACKHOUSE, K. M. and CHURCHILL-DAVIDSON, D. (1975). Anomalous pahnaris longus muscle producing carpal tunnel-like compression. Hand, 7: 1: 22-24. BARUCH, A. and HASS, A. (1977). Anomaly of the median nerve (letter). Journal of Hand Surgery, 2: 4: 331-332. BOWLES, A. P., ASHER, S. W. and PICKETT, J. B. (1983). Use of Tinel’s sign in carpal tunnel syndrome. Annals of Neurology, 13: 689-690. BRONES, M. F. and WILGIS, E. F. S. (1978). Anatomical variations of the palmaris longus, causing carpal tunnel syndrome: Case Reports. Plastic and Reconstructive Surgery, 62: 5: 798-800. BUTLER, B., and BIGLEY, E. C. (1971). Aberrant index (first) lumbrical tendinous origin associated with carpal-tunnel syndrome: A case report. Journal of Bone and Joint Surgery. 53A: 1: 160-162. DEKROM, M. C. T. F. M., KNIPSCHILD, P. G., KESTER, A. D. M. and SPAANS, S. (1990). Efficacy of provocative tests for diagnosis of carpal tunnel syndrome. Lancet, 335: 393-395. DURKAN, J. A. (1991). A new diagnostic test for carpal tunnel syndrome. The Journal of Bone and Joint Surgery, 73A: 4: 535-538. ERIKSEN, J. (1973). A case of carpal tunnel syndrome on the basis of an abnormally long lumbrical muscle. Acta Orthopaedica Scandinavia, 44: 275-277. GARDNER, R. C. (1970). Confirmed case and diagnosis of pseudocarpal-tunnel (sublimis) syndrome. New England Journal of Medicine, 282: 15: 858. GELLMAN, H., GELBERMAN, R. H., TAN, A. M. and BOTTE, M. J. (1986). Carpal tunnel syndrome: An evaluation of the provocative diagnostic tests. The Journal of Bone and Joint Surgery, 68A: 5: 735-737. GRUNDBERG, A. B. (1983). Carpal tunnel decompression in spite of normal electromyography. Journal of Hand Surgery, 8: 3: 348-349. HELLER, L., RING, H., COSTEFF, H. and SOLZI, P. (1986). Evaluation of Tinel’s and Phalen’s signs in diagnosis of the carpal tunnel syndrome. European Neurology, 25: 40-42. JABALEY, M. E. (1978). Personal observations on the role of the lumbrical muscles in carpal tunnel syndrome. Journal of Hand Surgery, 3: 1: 82-84.
KAPLAN, E. B. Functional and Surgical Anatomy of the Hand. Philadelphia, Lippincott, 1953: 77-79. LOONG, S. C. (1977). The carpal-tunnel syndrome: A clinical and electrophysiological study in 250 patients. Clinical and Experimental Neurology, 14: 51-65. MEHTA, H. .I. and GARDNER, W. U. (1961). A study of lnmbrical muscles in the human hand. American Journal of Anatomy, 109: 227-238. NATHER, A. and PHO, R. W. H. (1981). Carpal-tunnel syndrome produced by an organizing haematoma within the anomalous second lmnbrical muscle. The Hand, 13: 1: 87-91. NOVAK, C. B., MACKINNON, S. E., BROWNLEE, R. and KELLY, L. (1992). Provocative sensory testing in carpal tunnel syndrome. Journal of Hand Surgery, 17B: 2: 204-208. PALEY, D. and MCMURTRY, R. Y. (1985). Median nerve compression test in carpal tunnel syndrome diagnosis reproduces signs and symptoms in affected wrist. Orthopaedic Review, 14: 7: 41-45. PHALEN, G. S. (1966). The carpal-tunnel syndrome. 17 years’ experience in diagnosis and treatment of 654 hands. Journal of Bone and Joint Surgery, 48A: 2: 211-288. SCHULTZ, R. J., ENDLER, P. M. and HUDDLESTON, H. D. (1973). Anomalous median nerve and an anomalous muscle belly of the first lmnbrical associated with carpal-tunnel syndrome. Journal of Bone and Joint Surgery, 55A: 8: 1744-1746. SEROR, P. (1988). Phalen’s test in the diagnosis of carpal tunnel syndrome. Journal of Hand Surgery, 13B: 4: 383-385. SPINDLER, H. A. and DELLON, A. L. (1982). Nerve conduction studies and sensibility testing in carpal tunnel syndrome. Journal of Hand Surgery, 7: 3: 260-263. SMITH, R. I. (1971). Anomalous muscle belly of the flexor digitomm superficialis causing carpal tunnel syndrome: Report of a case. Journal of Bone and Joint Surgery, 53A: 6: 1215-1216. STILL, J. M. and KLEINERT, H. E. (1973). Anomalous muscles and nerve entrapment in the wrist and hand. Plastic and Reconstructive Surgery, 52: 4: 394-400. TANZER, R. C. (1959). The carpal-tunnel syndrome: A clinical and anatomical study. Journal of Bone and Joint Surgery, 41A: 4: 626-634. TINEL, J. (1915). Le signe du “fourmillement” dam les lesions des nerfs periphtriques. La Presse Mtdicale, 47: 388-389. TOUBORG-JENSEN, A. (1970). Carpal-tunnel syndrome caused by an abnormal distribution of the lmnbrical muscles. Scandinavian Journal of Plastic and Reconstructive Surgery, 4: 72-74. WILLIAMS, T. M., MACKINNON, S. E., NOVAK, C. B., MCCABE, S. and KELLY, L. (1992). Verification of the pressure provocative test in carpal tunnel syndrome. Annals of Plastic Surgery, 29: 1: 8-l 1.
Accepted: 2 March 1994 David Essex,
Elliot UK.
MA,
FRCS,
Consultant
Plastic
Surgeon,
0 1994 The British
Society
for Surgery
of the Hand
St Andrew’s
Hospital,
Billericay,
OF THE TUNNEL
N. W. YII and D. ELLIOT From the North-East
Thames Regional Plastic Surgery Unit, St. Andrew’s Hospital, Billericay, Essex, UK
The dynamic relationship of the lumbrical muscles to the carpal tunnel was studied in 35 hands in 32 patients and their movement into the tunnel on finger flexion was examined with a view to its use as a diagnostic provocation test in carpal tunnel syndrome.
The Journal of Hand Surgery (British and European Volume, 1994) 19B: 4: 439-443 Two patients with telescoping of their fingers as a result of rheumatoid arthritis who presented with carpal tunnel syndrome and were found at operation to have their lumbrical muscles resting in the carpal tunnel were the impetus to this study. Anomalous variants of the lumbrical muscles have been found occupying the carpal tunnel previously and are assumed to have caused carpal tunnel syndrome (Touborg-Jensen, 1970; Butler and Bigley, 1971; Still and Kleinert, 1973; Schultz et al, 1973; Eriksen, 1973; Jabaley, 1978; Nather and Pho, 1981). As the origins of the lumbrical muscles lie close to the distal border of the flexor retinaculum (Mehta and Gardner, 1961), it seems likely that they move into the tunnel during finger flexion and that, in so doing, they may exacerbate carpal tunnel syndrome. That they move into the carpal tunnel during finger flexion was noted by Kaplan (1953) but we were unable to find any subsequent study confirming his observation. This study was undertaken to investigate the dynamic relationship of the lumbrical muscles and the carpal tunnel and the possibility that their movement into the carpal tunnel in finger flexion might exacerbate carpal tunnel syndrome, providing a basis for a diagnostic provocation test. PATIENTS
nerve compression which were confirmed by nerve conduction studies. She also had telescoping of the fingers, volar subluxation of the MP joints and fixed flexion deformities of the PIP joints. As in the previous case, there was very little synovium in the carpal tunnel, and a minimal synovectomy was performed. The lumbrical muscle bellies had also migrated proximally to fill the carpal tunnel. Post-operative recovery was uneventful and she remained symptom free after division of the flexor retinaculum, although the lumbricals remained within the carpal tunnel.
AND METHOD
Case 1
A 66-year-old housewife with a 25-year history of rheumatoid arthritis developed pain and paraesthesiae in the sensory distribution of the right median nerve. Clinical examination of her right hand revealed severe rheumatoid disease with telescoping of the fingers (Fig 1). Nerve conduction studies confirmed compression of the median nerve in the carpal tunnel. At surgery, the carpal tunnel contained very little synovial proliferation but the lumbrical muscles had migrated proximally as a result of the shortening of the finger and volar subluxation of the MP joints. The carpal tunnel was filled with lumbrical muscles (Fig 2). A limited synovectomy was performed. She was relieved of the symptoms by division of the flexor retinaculum, although the lumbrical muscle bellies remained within the carpal tunnel. Case 2 Fig 1
A 74-year-old housewife with a 20-year history of rheumatoid arthritis developed symptoms of left median 439
Hand of Case 1 showing telescoping of the fingers largely a result of volar subluxation of the metacarpophalangeal joints.
as
THE JOURNAL OF HAND SURGERY VOL. 19B No. 4 AUGUST 1994
Fig2
Intra-operative carpal tunnel.
view of Case
1 showing
lumbricals
in the
35 hands in 32 consecutive patients undergoing decompression of idiopathic carpal tunnel syndrome were studied. 29 were females and three were male, with a mean age of 56.0 years (age range 27-87 years; standard deviation 17.2 years). Most of the patients in the study were referred late for surgery, with a mean duration of symptoms of 25.1 months (range 6-48 months). 24 patients (82.8%) had had symptoms for 1 year or more. Surgery was performed under brachial block anaesthesia with exsanguination and an arm tourniquet in place. The wrist remained in the neutral position throughout the investigation and surgery. An incision was made in the line of the third web space from just distal to the distal border of the flexor retinaculum to approximately 1 cm distal to the distal wrist crease. After division of the palmar aponeurosis, the distal edge of the flexor retinaculum was marked. Where the proximal edge of each lumbrical muscle was not visible at or proximal to the distal edge of the flexor retinaculum, the lumbrical was not sought more distally in the palm. This was recorded as zero lumbrical within the carpal tunnel. By traction on the tendons of FDP within the
carpal canal, the fingers were drawn into full flexion and the position of the most proximal part of each lumbrical relative to the distal edge of the flexor retinaculum was recorded in millimetres with each finger in full flexion. In those patients in whom the median nerve showed either obvious narrowing, erythema or both, indicating the site of nerve compression, the distance between the distal edge of the nerve compression and the distal edge of the flexor retinaculum was also recorded. After the first three patients had been investigated as above, and all had exhibited proximal movement of the lumbrical muscles into the carpal tunnel on finger flexion, the possibility that making a clenched fist might provoke symptoms in patients with carpal tunnel syndrome was considered. All subsequent patients (29 patients with 3 1 carpal tunnel decompressions; 26 female and 3 male with a mean age of 56.1 years and age range of 27-87 years) were also investigated pre-operatively. Each patient was asked immediately before surgery to make a fist of the hand and the time until the onset of paraesthesiae recorded; this test will subsequently be referred to as the “lumbrical provocation test”. After 1 minute’s rest, Phalen’s test was carried out (Phalen, 1966). After a further minute’s rest, compression of the median at the wrist was carried out until paraesthesiae were elicited (Paley and McMurtry, 1985). In the above three tests, a positive result was recorded when the symptoms were reproduced within 60 seconds. Finally, Tinel’s test was carried out over the median nerve at the wrist (Tinel, 1915). One patient, who was already suffering continuous paraesthesiae at the time of surgery, was excluded from these tests. These four tests were also carried out on both hands in a control group of patients. This group consisted of 30 asymptomatic individuals, who had no complaint of numbness, tingling, pain or clumsiness in the hands. The control group was matched to the study group for age and sex, and included 26 females and 4 males with a mean age of 55.8 years (range 27-86 years; 18.8 years standard deviation). The Chi-square test was used to examine the difference in the number of positive lumbrical provocation tests between the study and control groups. The paired t-test was used to compare the mean response time between the lumbrical provocation test and the Phalen’s test. RESULTS
The excursions of the lumbrical muscles into the carpal tunnel in the 35 hands (32 patients) studied are shown in Figures 3 to 6. In only six patients out of 32 (18.8%) were the proximal ends of one or more lumbricals in the tunnel with the fingers fully extended. Only eight lumbricals out of 140 (5.7%) entered the carpal tunnel in this finger position. In all 32 patients ( lOOoh)studied, three or more lumbricals moved into the carpal canal on finger flexion. Furthermore all lumbricals, except two
LUMBRICALS
441
IN CT
50 45 40 Excursion into the Carpal Canal (mm)
2;;;
35 30
carpal
25
Consecutive Hands Examined
edge of lumbrical attachment in full finger flexion 0 Proximal edge of lumbrical attachment in full finger extension -S Distal edge of carpal ligament
*Proximal
Fig 3
Excursion of the index finger lumbrical carpal tunnel.
to FDP
tendon
to FDP
tendon
a ??
if(lumbrical
I) in the
50 45 40 1 35 Excursion 30 I into the 25 Carpal canal 20 1 (~1 15 : 10
b
+Proximal edge of lumbrical attachment in full finger flexion ?? Proximal edge of lumbrical attachment in full finger extension + Distal edge of flexor retinaculum Fig 4
Excursion of the middle finger lumbrical carpal tunnel.
to FDP tendon to FDP
(lumbrical
tendon
II) in the
50 45 40 35 Excursion 30 into the 25 Carpal 20
Fig 6
Proximal edge of lumbrical attachment in full finger flexion Proximal edge of lumbrical attachment in full finger extension Distal edge of flexor retinaculum
Excursion of the little finger lumbrical carpal tunnel.
to FDP tendon to FDP
(lumbrical
tendon
IV) in the
lumbricals to little fingers, moved into the carpal tunnel when the fingers were fully flexed. Most lumbricals had an excursion of more than 1 cm into the carpal tunnel on fully flexing the fingers, the middle finger lumbricals having the greatest excursions and the little finger lumbricals having the least. These observations are summarized in Table 1. Table 2 summarizes the results of the pre-operative testing in the last 29 patients (32 hands). It can be seen that the lumbrical provocation test is the most sensitive test with 97% sensitivity. It also has a high specificity of 93% and a positive predictive value of 88%. A significant difference was seen in the proportions of positive lumbrical provocation tests between the study and control groups (P~O.001). Figure 7 records the mean response time for each provocative test. The mean time for a positive lumbrical provocation test was 16.1 seconds compared to 25.1 seconds with the Phalen’s test. This difference was found to be significant (P < 0.01). There was no significant difference in the response time between the lumbrical provocation test and the manual compression test. In 22 hands (63%) the median nerve showed an obvious site of compression. In 19 of these 22 hands Table 1-Lumbrical
excursion into the carpal tunnel
15 10
Lumbricals
G+ ??
+zFig 5
Proximal edge of lumbrical attachment in full finger flexion Proximal edge of lumbrical attachment in full finger extension Distal edge of flexor retinaculum
Excursion of the ring tinger lumbrical carpal tunnel.
to FDP
tendon
to FDP
tendon
(lumbrical
III) in the
Mean excursion into carpal tunnel (cm) Range of excursion into carpal tunnel (cm) Percentage of lumbricals that showed excursion of more than 1 cm into the carpal tunnel
Index
Middle
Ring
Little
1.7
2.1
1.6
1.1
0.5-4.8
18
0.5-4.3
93
0.5-3.5
85
O-2.8
34
442
THE JOURNAL
Table 2-Test
P&den’s test
Pressure provocation test
Tinel’s sign
30/31 (97%) 4160 (6.7%) 97% 93%
2713 1 (87%) 4/60 (6.7%) 87% 93%
25/31 (81%) O/60 (0%) 81% 100%
13/31 (42%) O/60 (0%) 42% 100%
of positive
tests/total
60
0 LUUhiCal
Positive
response
VOL. 19B No. 4 AUGUST
Lumbrical provocation test
*The results are expressed as the number
Fig 7
SURGERY
1994
results
Carpal tunnel group* Control group* Sensitivity Specificity
prmGdim
OF HAND
test
Manual compression
Pbalen’s test.
test.
time for provocative
tests.
(86.4%) one or more lumbricals moved to, or proximal to, the distal edge of the visible nerve compression during full finger flexion. DISCUSSION Although it is impossible to relate carpal tunnel syndrome directly to the presence of any space-occupying lesion in the tunnel, it is usually assumed that nerve compression is due to an obvious space-occupying lesion when one is present. Nerve compression has been associated with muscle variants of palmaris longus (Ashby, 1964; Backhouse and Churchill-Davidson, 1975; Brones and Wilgis, 1978), of the flexor superficialis (Tanzer, 1959; Gardner, 1970; Baruch and Hass, 1977; Smith, 1971; Still and Kleinert, 1973) and of the lumbrical muscles (Touborg-Jensen 1970; Butler and Bigley, 1971; Schultz et al, 1973; Still and Kleinert, 1973; Eriksen, 1973; Jabaley, 1978; Nather and Pho, 1981). Although carpal tunnel syndrome in patients with rheumatoid arthritis is generally attributed to synovial proliferation, this was minimal in the two cases described above, and the lumbricals occupied a considerable volume of the carpal tunnel. The change in the resting position of the normal lumbrical muscles in the two cases had resulted in a persistent abnormal space-occupying lesion in the tunnel. It seems likely that the lumbricals caused, or contributed significantly to, the nerve compression in these cases and that retraction of the tendons of FDP following a change of finger length, MP joint volar subluxation and PIP joint flexion into the boutonni&e
number
of hands tested.
position, or a combination of these common deformities of rheumatoid disease, may contribute to median nerve compression in this condition more commonly than has been previously realized. Simple division of the flexor retinaculum appears to be sufficient to decompress the nerve in these cases, as with carpal tunnel syndrome in the presence of muscle anomalies. We were unable to find any previous study describing the dynamic relationship of the lumbrical muscles to the carpal tunnel. This study shows that in over 80% of individuals examined, the lumbricals do not lie within the carpal tunnel when the fingers are extended and in all of them three or more lumbricals move into the tunnel in the clenched fist position. In other words, a considerable bulk of lumbrical muscles moves into the carpal tunnel when the hand makes a fist. This may explain the fact that many patients with carpal tunnel syndrome complain of paraesthesiae when gripping, writing, cycling and driving, although the latter two activities also extend the wrist into the position of a reverse Phalen’s test. This study suggests that the lumbrical movement into the tunnel may be used to provoke symptoms in carpal tunnel syndrome. Clenching the fist was sufficient in our patients with well-established carpal tunnel syndrome to induce paraesthesiae in 97% of the cases, while Phalen’s test was positive in 87%. The sensitivity of Phalen’s test has been reported to range from 48% (Loong, 1977) to 93% (Grundberg, 1983), with most authors reported results in between (Phalen, 1966; Heller et al, 1986; Gellman et al, 1986; Seror, 1988; DeKrom et al, 1990; Durkan, 1991; Novak et al, 1992; Williams et al, 1992). The specificity of Phalen’s test also varies from 59% (Heller et al, 1986) to 100% (Williams et al, 1992) with intermediate results reported by others (Gellman et al, 1986; Durkan, 199 1). The relatively high sensitivity of Phalen’s test and of the lumbrical provocation test in our series may be related to the fact that most of our patients presented late with well-established symptoms, the likelihood of a positive Phalen’s test having been correlated with the severity of the carpal tunnel syndrome in previous studies (Spindler and Dellon, 1982; Seror, 1988). The sensitivity and specificity of the pressure provocative test in this series are similar to those in previous studies (Gellman et al, 1986; Durkan, 1991; Williams
LUMBRICALS
443
IN CT
et al, 1992), as are these measures with respect to Tinel’s sign, which also has a poorer sensitivity in other studies (Phalen, 1966; Loong, 1977; Bowles et al, 1983; Gellman et al, 1986; Durkan, 1991; Novak et al, 1992; Williams et al, 1992). Acknowledgements The authors wish to thank Dr M. Reilly, PhD, epidemiologist, Green, BSc, statistician, for their advice.
and MS Sandra
References ASHBY, B. S. (1964). Hypertrophy of the palmaris longus muscle. Journal of Bone and Joint Surgery, 46B: 2: 230-232. BACKHOUSE, K. M. and CHURCHILL-DAVIDSON, D. (1975). Anomalous pahnaris longus muscle producing carpal tunnel-like compression. Hand, 7: 1: 22-24. BARUCH, A. and HASS, A. (1977). Anomaly of the median nerve (letter). Journal of Hand Surgery, 2: 4: 331-332. BOWLES, A. P., ASHER, S. W. and PICKETT, J. B. (1983). Use of Tinel’s sign in carpal tunnel syndrome. Annals of Neurology, 13: 689-690. BRONES, M. F. and WILGIS, E. F. S. (1978). Anatomical variations of the palmaris longus, causing carpal tunnel syndrome: Case Reports. Plastic and Reconstructive Surgery, 62: 5: 798-800. BUTLER, B., and BIGLEY, E. C. (1971). Aberrant index (first) lumbrical tendinous origin associated with carpal-tunnel syndrome: A case report. Journal of Bone and Joint Surgery. 53A: 1: 160-162. DEKROM, M. C. T. F. M., KNIPSCHILD, P. G., KESTER, A. D. M. and SPAANS, S. (1990). Efficacy of provocative tests for diagnosis of carpal tunnel syndrome. Lancet, 335: 393-395. DURKAN, J. A. (1991). A new diagnostic test for carpal tunnel syndrome. The Journal of Bone and Joint Surgery, 73A: 4: 535-538. ERIKSEN, J. (1973). A case of carpal tunnel syndrome on the basis of an abnormally long lumbrical muscle. Acta Orthopaedica Scandinavia, 44: 275-277. GARDNER, R. C. (1970). Confirmed case and diagnosis of pseudocarpal-tunnel (sublimis) syndrome. New England Journal of Medicine, 282: 15: 858. GELLMAN, H., GELBERMAN, R. H., TAN, A. M. and BOTTE, M. J. (1986). Carpal tunnel syndrome: An evaluation of the provocative diagnostic tests. The Journal of Bone and Joint Surgery, 68A: 5: 735-737. GRUNDBERG, A. B. (1983). Carpal tunnel decompression in spite of normal electromyography. Journal of Hand Surgery, 8: 3: 348-349. HELLER, L., RING, H., COSTEFF, H. and SOLZI, P. (1986). Evaluation of Tinel’s and Phalen’s signs in diagnosis of the carpal tunnel syndrome. European Neurology, 25: 40-42. JABALEY, M. E. (1978). Personal observations on the role of the lumbrical muscles in carpal tunnel syndrome. Journal of Hand Surgery, 3: 1: 82-84.
KAPLAN, E. B. Functional and Surgical Anatomy of the Hand. Philadelphia, Lippincott, 1953: 77-79. LOONG, S. C. (1977). The carpal-tunnel syndrome: A clinical and electrophysiological study in 250 patients. Clinical and Experimental Neurology, 14: 51-65. MEHTA, H. .I. and GARDNER, W. U. (1961). A study of lnmbrical muscles in the human hand. American Journal of Anatomy, 109: 227-238. NATHER, A. and PHO, R. W. H. (1981). Carpal-tunnel syndrome produced by an organizing haematoma within the anomalous second lmnbrical muscle. The Hand, 13: 1: 87-91. NOVAK, C. B., MACKINNON, S. E., BROWNLEE, R. and KELLY, L. (1992). Provocative sensory testing in carpal tunnel syndrome. Journal of Hand Surgery, 17B: 2: 204-208. PALEY, D. and MCMURTRY, R. Y. (1985). Median nerve compression test in carpal tunnel syndrome diagnosis reproduces signs and symptoms in affected wrist. Orthopaedic Review, 14: 7: 41-45. PHALEN, G. S. (1966). The carpal-tunnel syndrome. 17 years’ experience in diagnosis and treatment of 654 hands. Journal of Bone and Joint Surgery, 48A: 2: 211-288. SCHULTZ, R. J., ENDLER, P. M. and HUDDLESTON, H. D. (1973). Anomalous median nerve and an anomalous muscle belly of the first lmnbrical associated with carpal-tunnel syndrome. Journal of Bone and Joint Surgery, 55A: 8: 1744-1746. SEROR, P. (1988). Phalen’s test in the diagnosis of carpal tunnel syndrome. Journal of Hand Surgery, 13B: 4: 383-385. SPINDLER, H. A. and DELLON, A. L. (1982). Nerve conduction studies and sensibility testing in carpal tunnel syndrome. Journal of Hand Surgery, 7: 3: 260-263. SMITH, R. I. (1971). Anomalous muscle belly of the flexor digitomm superficialis causing carpal tunnel syndrome: Report of a case. Journal of Bone and Joint Surgery, 53A: 6: 1215-1216. STILL, J. M. and KLEINERT, H. E. (1973). Anomalous muscles and nerve entrapment in the wrist and hand. Plastic and Reconstructive Surgery, 52: 4: 394-400. TANZER, R. C. (1959). The carpal-tunnel syndrome: A clinical and anatomical study. Journal of Bone and Joint Surgery, 41A: 4: 626-634. TINEL, J. (1915). Le signe du “fourmillement” dam les lesions des nerfs periphtriques. La Presse Mtdicale, 47: 388-389. TOUBORG-JENSEN, A. (1970). Carpal-tunnel syndrome caused by an abnormal distribution of the lmnbrical muscles. Scandinavian Journal of Plastic and Reconstructive Surgery, 4: 72-74. WILLIAMS, T. M., MACKINNON, S. E., NOVAK, C. B., MCCABE, S. and KELLY, L. (1992). Verification of the pressure provocative test in carpal tunnel syndrome. Annals of Plastic Surgery, 29: 1: 8-l 1.
Accepted: 2 March 1994 David Essex,
Elliot UK.
MA,
FRCS,
Consultant
Plastic
Surgeon,
0 1994 The British
Society
for Surgery
of the Hand
St Andrew’s
Hospital,
Billericay,