Measurement of the tendon of the biceps brachii after tenotomy: study on cadavers.

OBJECTIVE: To evaluate the influence of elbow and forearm range of motion on the distal excursion of the long head of the biceps (LHB).
METHODS: The distal excursion of the LHB after tenotomy of the shoulders of eight cadavers was ascertained by measuring the distance between a point marked out on the LHB, 3 cm from the anterolateral border of the acromion, and its position at different degrees of elbow flexion, using a digital pachymeter. The measurements at elbow flexion of 135°, 90°, 45° and 0° were noted: these angles were established using a goniometer. The measurements were made with the forearm in neutral, supination and pronation positions.
RESULTS: Differences between the mean measurements of the distal excursion of the LHB (total sample) were observed between the degrees of elbow flexion (p < 0.01). However, no statistical differences were observed between the different forearm positions, between the sides, genders and ages of the cadavers studied.
CONCLUSION: Progressive extension of the elbow caused progressive distal excursion of the LHB, but without interference in the forearm position, gender, side or age of the cadavers studied.

Introduction

The long head of the tendon of the biceps brachii muscle (LHB) is developed at around the seventh to eighth week of gestation and it becomes differentiated starting from the mesoderm. It is described as continuous with the labrum of the glenoid and the supraglenoid tubercle, and it passes anteriorly and superiorly to the head of the humerus before entering the bicipital groove.1, 2 It is intra-articular and extrasynovial and slides passively over the head of humerus during abduction or rotation. Its length is 9 cm and its diameter is 5–6 mm. It innervation is through a network of sensory fibers of the sympathetic nervous system.3, 4, 5

The biceps extends from the scapula to the forearm and has functions relating to the shoulder and elbow. Its function relating to the elbow has been well established and includes both flexion and supination. On the other hand, in relation to the shoulder, although several functions have been attributed, the exact role of the LHB remains a matter of controversy. Electromyographic analyses have shown that the LHB serves as a stabilizer in unstable joints, but not in stable shoulders. Biomechanical studies have demonstrated that the tendon acts as a dynamic depressor of the head of the humerus, but this has not been proven clinically.8, 9 Kuhn et al. demonstrated its importance as a restrictor of external rotation of the abducted arm.

Lesions of the superior glenoid that involve the LHB are called SLAP lesions (superior labrum, anterior and posterior). They were first described at the beginning of the 1990s by Snyder et al. The conservative or surgical treatment for these lesions has been well established, but there has never been a consensus regarding the postoperative rehabilitation treatment. There are protocols described in the current literature,12, 13 in which early mobility of the extended elbow is avoided because of doubts regarding the consequent tensioning of the proximal LHB and superior glenoid labrum, which were reinserted during the operation. These actions could cause failure of healing and a new injury.12, 13

The objective of this study was to evaluate the influence of the range of motion of the elbow and forearm on the distal excursion of the LHB.

Methods

This study was approved by our institution's research ethics committee (number: CAAE 19893114.6.0000.5463). Sixteen shoulders of eight cadavers obtained from the Death Verification Service of the University of São Paulo (SVOC-USP) were dissected. None of these cadavers presented any fractures of the upper limbs, local deformities or scarring. The dissections were performed by means of an anterolateral access measuring 10 cm (Fig. 1A), followed by dissection between the anterior and lateral deltoid muscle (Fig. 1B) so as to approach and dissect the LHB (Fig. 1C).

Fig. 1

Tenotomy procedure on a cadaver. (A) Marking out the bone anatomical parameters and access route; (B) access via anterolateral route; (C) dissection of the LHB from its groove to its origin in the glenoid; (D) measurement of the excursion of the LHB after proximal tenotomy, with elbow flexion at 135°, 90°, 45° and 0°.

Using a surgical pen, a line perpendicular to the LHB was marked out, 3 cm distally to the anterolateral border of the acromion. Tenotomy of the LHB was performed at its origin in the supraglenoid tubercle, with the elbow at maximum flexion. The distal excursion of the LHB was verified by measuring the distance between the line marked out on the bicipital tendon and needles placed at the edge of the line previously established on the LHB, using a digital pachymeter (Lee Tools, Houston, USA) (Fig. 1D), as the elbow was extended. Measurements were noted at the following degrees of elbow flexion: 135°, 90°, 45° and 0°, which were established using a goniometer. The measurements were made with the forearm in the neutral, supination and pronation positions.

Statistical analysis

To compare the results from the measurements on the distal excursion of the LHB, the Friedman test was used. To determine the measurements between which statistically significant differences occurred, the Wilcoxon test was used. For all the tests, the rejection level for the hypothesis of nullity was 0.05 (significance level of 95%).

The Friedman and Wilcoxon tests were also used to compare the results from the measurements on the excursion of the LHB separately and on the entire sample. To compare the results from the measurements according to sex and side studied, the Mann–Whitney test was used. To evaluate the relationship between age and the results from the measurements made, the Spearman correlation was used.

Results

Among the eight cadavers dissected, five were female and three were male. There were eight right shoulders and eight left shoulders (Table 1). The mean value for the distal excursion of the LHB with the forearm in the neutral position and at 135° of elbow flexion was 1.41 mm; at 90°, 13.97 mm; at 45°, 18.01 mm; and at 0°, 22.53 mm (Table 2). When these measurements were made with the forearm moved into pronation and supination positions, there were no differences in relation to the above measurements.

Table 1

Measurements (in mm, using a digital pachymeter) of the distal excursion at elbow flexions of 135°, 90°, 45° and 0° (angles obtained by means of a goniometer).

Cadaver	Age	Sex	Side	Excursion at 135°	Excursion at 90°	Excursion at 45°	Excursion at 0°
1	76	F	R	1.51	17.59	19.08	25.62
			L	1.45	15.16	21.16	25.76
2	72	F	R	1.88	12.15	17.53	21.13
			L	0.99	12.84	18.32	21.06
3	64	M	R	1.25	13.13	19.06	23.07
			L	1.66	14.25	20.15	23.99
4	75	F	R	1.58	12.88	16.5	22.54
			L	1.57	11.98	15.84	21.4
5	58	M	L	1.48	14.85	16.41	21.63
			R	1.52	14.23	17.02	20.73
6	72	F	R	1.6	17.9	19.76	26.43
			L	1.51	16.9	19.6	26.12
7	69	M	R	1.27	12.14	17.16	21.19
			L	1.5	13.13	18	21.77
8	88	F	R	1.15	13	16.49	19.18
			L	1.16	11.31	16.02	18.85

Table 2

Statistical analysis on the measurements of the distal excursion of the LHB in relation to the total sample.

Total sample	General
	135°	90°	45°	0°
Mean	1.44	13.97	18.01	22.53
Median	1.51	13.13	17.77	21.70
Standard deviation	0.22	2.03	1.64	2.41
Q1	1.27	12.67	16.50	21.11
Q3	1.57	14.93	19.21	24.40
N	16	16	16	16
IC	0.11	1.00	0.80	1.18
p value	<0.001

Comparisons between the measurements on the distal excursion of the LHB showed significant differences (p < 0.001), considering the entire sample, at all degrees of elbow flexion (Table 2). On the other hand, there were no statistical differences between the right and left sides (Table 3), between the male and female sexes (Table 4) or between the ages (Table 5), among the cadavers studied.

Table 3

Statistical analysis on the measurements of the distal excursion of the LHB in relation to the sides.

Side	Mean	Median	Standard deviation	Q1	Q3	N	IC	p value
Excursion at 135°
Right	1.47	1.52	0.24	1.27	1.59	8	0.16	0.495
Left	1.42	1.49	0.22	1.38	1.53	8	0.16
Excursion at 90°
Right	14.13	13.07	2.33	12.70	15.07	8	1.61	0.875
Left	13.80	13.69	1.84	12.63	14.93	8	1.27
Excursion at 45°
Right	17.83	17.35	1.29	16.89	19.07	8	0.89	0.916
Left	18.19	18.16	2.00	16.31	19.74	8	1.39
Excursion at 0°
Right	22.49	21.87	2.49	21.03	23.71	8	1.72	0.834
Left	22.57	21.70	2.50	21.32	24.43	8	1.73

Table 4

Statistical analysis on the measurements of the distal excursion of the LHB in relation to sex.

Sex	Mean	Median	Standard deviation	Q1	Q3	N	IC	p value
Excursion at 135°
Female	1.44	1.51	0.26	1.23	1.58	10	0.16	0.914
Male	1.45	1.49	0.16	1.32	1.52	6	0.13
Excursion at 90°
Female	14.17	12.94	2.49	12.32	16.47	10	1.54	0.828
Male	13.62	13.68	1.00	13.13	14.25	6	0.80
Excursion at 45°
Female	18.03	17.93	1.83	16.49	19.47	10	1.14	1.000
Male	17.97	17.58	1.41	17.06	18.80	6	1.13
Excursion at 0°
Female	22.81	21.97	2.93	21.08	25.73	10	1.82	0.828
Male	22.06	21.70	1.23	21.30	22.75	6	0.98

Table 5

Statistical analysis on the measurements of the distal excursion of the LHB in relation to age.

	Age
	Corr	p value
Excursion at 135°	−21.6%	0.422
Excursion at 90°	−19.7%	0.466
Excursion at 45°	−12.2%	0.653
Excursion at 0°	−8.9%	0.742

Discussion

This study is in agreement with the study conducted by Gramstad et al., with evidence of increasing distal excursion of the LHB as the elbow is extended. On the other hand, according to those authors, not only elbow extension but also pronation of the forearm was associated with increased tension on the LHB, and on the superior labrum of the glenoid. In our observations, no differences in distal excursion of the LHB were seen with regard to the positioning of the forearm (pronation or supination). This difference in results can possibly be explained by the fact that those authors made their measurements with the shoulder abducted at 60°, whereas in our study, the measurements were made with the shoulder adducted against the body.

According to Wilk et al., in postoperative treatment for SLAP lesions, active and passive elbow extension exercises are indicated starting in the first ten days after the operation, only for patients who underwent simple debridement (types I and III of Snyder's classification). However, among patients who underwent repairs to SLAP lesions (types II and IV of Snyder's classification), early complete extension of the elbow and the consequent proximal bicipital tensioning should be avoided. This guidance is concordant with the findings from our study, since greater distal excursion of the LHB after tenotomy at its origin was demonstrated as the elbow was progressively extended.

Conclusions

After tenotomy at the origin of the LHB, progressive extension of the elbow caused progressive distal excursion of the LHB, but without interference from the position of the forearm or from the sex, side or age of the cadavers studied.

Conflicts of interest

The authors declare no conflicts of interest.