Anatomical Study of Osborne's Ligament Elongation in Relation To

日大医誌 72 (3): 154Ð158 (2013) 154

Original

Anatomical Study of Osborne’s Ligament Elongation in Relation to Elbow Flexion

Kei YAMADA1), Masahiro NAGAOKA1), Soya NAGAO1), Takako NAGAI1), Taihei YAMAGUCHI1), Junnosuke RYU2) and Yasuaki TOKUHASHI2) 1)Department of Orthopedic Surgery, Surugadai Nihon University Hospital 2)Department of Orthopedic Surgery, Nihon University School of Medicine To study the elongation of Osborne’s ligament due to elbow flexion, 19 cadavers were dissected. The length of Osborne’s ligament from its point of attachment to the humerus to its point of attachment to the ulna was measured in 10° increments of elbow flexion angle from 20° to 140°. Up to 40° 3, the length decreased slightly, and then increased almost linearly to an average of 7.62 mm or 52.3%. Osborne’s ligament had a tendency to gradually elongate at a flexion angle of more than 90°. However, this distance was shortened in four elbows due to variations in the sites of attachment of Osborne’s ligament. Key wards: Osborne’s ligament, elongation, elbow, cubital tunnel, cadaver (J. Nihon Univ. Med. Ass., 2013; 72 (3): 154Ð158)

Of the various entrapment neuropathies of the upper Introduction extremity, cubital tunnel syndrome is the second most The term cubital tunnel was first used by Feindel common after carpal tunnel syndrome3). Many studies and Stratford in 19581). They defined that cubital tun- have been conducted to clarify the pathogenesis of cu- nel is the space beginning from the point just distal to bital tunnel syndrome5Ð17). the medial epicondyle to the point at which the ulnar In many cases, entrapment of Osborne’s ligament is nerve dips from a superficial to a deep submuscular associated with the onset of cubital tunnel syndrome. course. The roof of the cubital tunnel is formed by the Upon flexion, the cubital tunnel narrows. Studies have aponeurotic arch and this is called Osborne’s liga- shown the increased cubital tunnel pressure due to el- ment1Ð3). On the other hand, the floor is formed by the bow flexion. Changes in a cross-sectional area of the medial ligaments of the elbow joint1). cubital tunnel can be observed. Ulnar nerve strain has Osborne’s ligament is sometimes called the cubital been reported as a factor for cubital tunnel syndrome. tunnel retinaculum or has simply called the fibrous To clarify the pathogenesis of cubital tunnel syn- band or fibrous arch in recent years. It is about 4 mm drome, we anatomically observed the morphology of wide, and extends from the medial to the tip of the ole- Osborne’s ligament and assessed the dynamics of cranon. In this study, we call the apneurotic arch Osborne’s ligament stretching during elbow flexion at Osborne’s ligament because it is the most classical 10° intervals. In this study, we attempted to examine term. the relationship between elbow flexion angle and the According to O’Driscall et al, the roof of the cubital degree of elongation of Osborne’s ligament in greater tunnel is formed by the cubital tunnel retinaculum detail than in previous studies. We also examined the (CTR) and flexor carpi ulnaris aponeurosis. The vari- degree of elongation in relation to the point of attach- ous forms of CTR are classified into four categories. In ment of the ligament to the medial epicondyle. type 0, the CTR is absent and the ulnar nerve is dislo- cated. In type Ia, the ‘normal’ retinaculum is thin and Materials and Methods becomes taut in full flexion but does not compress the A total of 19 elbows of 19 cadavers (10 male and 9 nerve. In type Ib, it is pathologically thick, and female) were used. All of them were for medical stu- becomes taut between 90° and 120° of flexion. This dents studying anatomy at Nihon University School of type is associated with obvious evidence of chronic Medicine. The ages of the cadavers ranged from 60 to nerve compression. In type II, the CTR is replaced by a 97 years (average, 80.7 years). There were 11 right muscle, anconeus epitrochlearis. In the previous study, elbows and 8 left elbows. The specimens were chosen CTR was found in 26 out of 27 elbows examined after the anatomical practice of sutudents. The exami- (96.3%)4). nation performed in the anatomical training room at

Received: February 6, Accepted: April 12, 2013 72 (3) 2013 Anatomical Study of Osborne’s Ligament 155

45 40 35 30 25 20

Length (mm) 15 10 5 0

20 40 60 80 100 120 140 Fig. 1 The Osbone’s ligament of O’driscoll classification type Elbow Flexion (degrees) Ib The left elbow. Ol: the olecranon, ME: the medial epicondyle Fig. 2 The degree of lengthening of Osborne’s ligament dur- ing elbow flexion (19 elbows)

Table 1 The average and median length of Osborne’s ligament

Angle of elbow Median Average ± S.D. (mm) joint (°) (mm) 20 19.34 ± 5.40 20.13 30 19.40 ± 5.45 19.97 40 19.80 ± 5.61 19.63 50 20.24 ± 5.27 20.06 60 21.02 ± 5.00 21.46 70 21.83 ± 5.25 21.76 80 22.52 ± 4.71 22.54 90 23.45 ± 4.44 22.82 100 24.35 ± 4.46 23.54 110 25.04 ± 4.39 24.26 Fig. 3 The degree of shortening of Osborne’s ligament during 120 25.71 ± 4.44 24.41 elbow flexion (4 elbows) 130 26.43 ± 4.57 24.88 140 26.96 ± 4.57 25.16 from the medial side of each wire. This distance was measured using digital calipers at 10° increments of Nihon University School of Medicine in November elbow flexion angle from 20° to 140°. A non-paramet- 2007. ric Wilcoxon’s signed rank test was used to assess To accurately measure flexion angle, soft tissue was Osborne’s ligament elongation. removed circumferentially to expose the humeral shaft. The carrying angle and the range of motion were Results measured using the following markers: humerus In all elbows, the ulnar nerve did not dislocate due to (proximal), ulna (distal), and the tip of the medial epi- elbow flexion. The carrying angles ranged from 20° to condyle of the humerus (hinge). The medial side of the Ð14° (average, 7.2°). On the basis of O’Driscoll’s clas- elbow was opened, and Osborne’s ligament was iden- sification, two Osborne’s ligaments were classified tified on the basis of O’Driscoll’s classification. The into Type 0, 11 into Type Ia, five into Type Ib, and one attachment site of the flexor carpi ulnaris (FCU) to the into Type II. The average and median lengths of humerus and ulna was identified. When Osborne’s Osborne’s ligament (distance between the two heads ligament was present, both ends of the ligament closest of the FCU) measured at each flexion angle are shown to the elbow joint were analyzed by two investigators, in Table 1. At elbow flexions from 20° to 40°, the and a 1.2 mm Kirschner wire was inserted at each length gradually decreased, and at elbow flexions from point (Fig. 1). When Osborne’s ligament was not 40° to 140°, Osborne’s ligament length increased present, the area of the elbow joint closest to the at- gradually to 7.62 mm on average (Fig. 2). However, in tachment site of the two heads of the FCU was marked. four of the 19 elbows, Osborne’s ligament length The distance between the two wires was measured decreased at elbow flexion angles from 20° to 140°. In 156 Kei YAMADA et al. 日大医誌

45 40 35 30 25 20

Length (mm) 15 10 5 0

20 40 60 80 100 120 140 Elbow Flexion (degrees) Fig. 6 Plots of attachment site of Osborne’s ligament, length- Fig. 4 The degree of lengthening of Osborne’s ligament dur- ened less than 2 mm. ing elbow flexion (15 elbows) M: Medial epicondyle

ment sites were plotted, and the attachment site on the humerus was found to be posterior to the medial epi- condyle in many cases (Fig. 5). In contrast, among the cases in which Osborne’s ligament lengthened by less than 2 mm between elbow extension and flexion, the attachment site on the humerus was found to be ante- rior to the medial epicondyle in many cases (Fig 6). However, no correlation existed between O’Driscoll type and extension length. Discussion Cubital tunnel syndrome is the second most com- mon entrapment neuropathy following carpal tunnel syndrome, and it is caused by the entrapment of the ulnar nerve in the cubital region. In previous studies Osborne’s ligament morphology, cubital tunnel nar- Fig. 5 Plots of attachment site of Osborne’s ligament, elon- rowing due to elbow flexion, Osborne’s ligament gated more than 12 mm. stretching, and ulnar nerve straining were studied. M: Medial epicondyle The above-mentioned factors are considered to be involved in the development of cubital tunnel syn- these four elbows, the degrees of decrease in length drome. Elbow flexion increases the internal pressure were 0.76, 0.53, 0.38, and 3.38 mm, and except for one of the cubital tunnel owing to the collateral ligament case, the shortening was slight (Fig. 3). Excluding bulging on the floor of the cubital tunnel. One of the these four elbows, the degrees of lengthening and factors for the development of cubital tunnel syndrome shortening of Osborne’s ligament during elbow flex- is that Osborne’s ligament compresses the nerve on the ion exhibit a more consistent pattern. However, it roof of the cubital tunnel as the elbow flexes. seemed that the degree of increase was smaller at In 1958, Findel and Stratford were the first to report elbow flexion angles greater than 90° than at angles on Osborne’s ligament stretching due to elbow flex- smaller than 90°, particularly at angles from 130° to ion1). Vanderpool et al. examined 18 cadaver limbs 140° (Fig. 4). and reported that Osborne’s ligament stretched by 5 We were able to measure all flexion angles from 20° mm every 45°, and from extension to full flexion to 140° in 19 elbows. The average increase was 9.99 (135°), the ligament lengthened by 40%18). Apfelberg mm, and in cases in which a decrease was measured, et al. studied 15 cadavers and reported that elbow flex- the average decrease was 1.26 mm. Among the cases ion increased the distance between the medial epi- in which Osborne’s ligament lengthened by at least 12 condyle and the olecranon by about 1 cm5). Schuind et mm between elbow extension and flexion, the attach- al. anatomically analyzed five elbows and measured 72 (3) 2013 Anatomical Study of Osborne’s Ligament 157 the length of Osborne’s ligament at angles of 0°, 45°, attachment sites, because Osborne’s ligament is not a 90°, and 135°. The results showed a ligament length true ligament but an aponeurosis. Furthermore, be- increase of 45% from full extension to full flexion19). cause the cadavers had been dissected to reveal the None of these studies provided clear numerical values. insertions, the true rotation center could not be pre- In the present study, we measured elbow flexion served. Therefore, the medial epicondyle was chosen angle and the length of Osborne’s ligament (between as the rotation center of the elbow for our study. the heads of the FCU) at different angles to investigate the change in length of the ligament with elbow flex- Conclusions ion. A total of 19 elbows of 19 cadavers were dissected. The results showed that Osborne’s ligament length The length of Osborne’s ligament was measured at 10° increased to 7.62 mm on average or by 52.3% at elbow increments of elbow flexion. The degree of elongation flexion angles from 20° (shortest length) to 140° was greater when the ligament was attached posterior (longest length). This value of 52.3% was higher than to the medial epicondyle and smaller when the liga- the 45% reported by Schuind et al.19), and the 40% ment was attached anterior to the medial epicondyle. reported by Vanderpool et al.18). Elbow flexion short- The elongation of Osborne’s ligament had a tendency ened Osborne’s ligament in four elbows (21.1%). to increase more gradually after 90° flexion than When excluding these cases, the ligament length before 90° flexion, which indicates that the increase increased at elbow flexion angles from 20° to 140° by in internal pressure may involve other factors. 9.99 mm or 67.7%. These results demonstrated that the length of Osborne’s ligament or the distance between Acknowledgements the heads of the FCU increases significantly with el- I wish to thank Professor Ryu and Professor bow flexion angle, but, as reported previously, the de- Nagaoka of Nihon University for their encouragement gree of increase is not necessarily constant in all cases. during this study, and Professor Aizawa of the Depart- The reason for this is individual variations in the at- ment of Anatomy, Nihon University for his permission tachment site of Osborne’s ligament to the humerus to use the cadavers in this study. and ulna. Our results showed that the degree of elonga- tion was greater when the ligament was attached pos- References terior to the medial epicondyle and smaller when the ligament was attached anterior to the medial epi- 1) Feindel W, Stratford J. The role of the cubital tunnel in condyle. Ochi et al.20) measured the length of the tardy ulnar palsy. Can J Surg 1958; 1: 287Ð300. 2) Osborne G. Ulnar neuritis. Postgrad Med J 1959; 35: 392Ð medial collateral ligament at different elbow flexion 396. angles. The posterior oblique ligament (POL) length 3) Robertson C, Saratsiotis J. A review of compressive ulnar was the smallest at 30° flexion, increasing with flexion neuropathy at the elbow. J Manipulative Physiol Ther 2005; angle, and peaking at full flexion. These changes 28: 345. e1Ð345. e18. resemble the changes in the length of Osborne’s liga- 4) O’driscoll SW, Horii E, Carmichael SW et al. The cubital ment. The POL is aligned in the same direction as tunnel and ulnar neuropathy. J Bone Joint Surg [Br] 1991; Osborne’s ligament, and attached posterior to the rota- 73-B: 613Ð617. 5) Apfelberg DB, Larson SJ. Dynamic anatomy of the ulnar tion center of the elbow, resulting in the above-men- nerve at the elbow. Plast Reconstr Surg 1973; 51: 79Ð81. tioned pattern. This agrees with the high lengthening 6) Dellon AL, Chang E, Coert JH, et al. Intraneural ulnar nerve rate for Osborne’s ligament attached posterior to the pressure changes related to operative techniques for cubital medial epicondyle. tunnel decompression. J Hand Surg [Am] 1994; 19: 923Ð Macnicol and Gelberman et al. used cadavers to 930. measure the changes in internal pressure with respect 7) Gelberman RH, Yamaguchi K, Hollstien SB, et al. Changes to elbow flexion angle. The results showed that the in interstitial pressure and cross-sectional area of the cu- bital tunnel and of the ulnar nerve with flexion of the el- degree of increase in internal pressure was higher at a bow. An experimental study in human cadavera. J Bone flexion angle of 90° or greater than at a flexion angle Joint Surg [Am] 1998; 80: 492Ð501. 7, 8) of less than 90° . In the present study, Osborne’s 8) Macnicol MF. Extraneural pressures affecting the ulnar ligament elongation became rather slight after 90° nerve at the elbow. Hand 1982; 14: 5Ð11. flexion. Taken together, an increase in internal pres- 9) Green JR, Jr., Rayan GM. The cubital tunnel: anatomic, sure may involve other factors, such as nerve strain or histologic, and biomechanical study. J Shoulder Elbow bulging of the medial collateral ligament on the floor Surg 1999; 8: 466Ð470. 10) Iba K, Wada T, Aoki M, et al. The relationship between the of the cubital tunnel at a flexion angle greater than 90°. pressure adjacent to the ulnar nerve and the disease causing One limitation of the present study was that it was cubital tunnel syndrome. J Shoulder Elbow Surg 2008; 17: difficult to identify the attachment sites of Osborne’s 585Ð588. ligament, although two investigators determined the 11) Wilgis EF, Murphy R. The significance of longitudinal ex- 158 Kei YAMADA et al. 日大医誌

cursion in peripheral nerves. Hand Clin 1986; 2: 761Ð766. 16) Byl C, Puttlitz C, Byl N, et al. Strain in the median and ulnar 12) Wright TW, Glowczewskie F, Jr., Cowin D, et al. Ulnar nerves during upper-extremity positioning. J Hand Surg nerve excursion and strain at the elbow and wrist associated [Am] 2002; 27: 1032Ð1040. with upper extremity motion. J Hand Surg [Am] 2001; 26: 17) Toby EB, Hanesworth D. Ulnar nerve strains at the elbow. J 655Ð662. Hand Surg [Am] 1998; 23: 992Ð997. 13) Aoki M, Takasaki H, Muraki T, et al. Strain on the ulnar 18) Vanderpool DW, Chalmers J, Lamb DW, et al. Peripheral nerve at the elbow and wrist during throwing motion. J compression lesions of the ulnar nerve. J Bone Joint Surg Bone Joint Surg [Am] 2005; 87: 2508Ð2514. [Br] 1968; 50: 792Ð803. 14) Grewal R, Varitimidis SE, Vardakas DG, et al. Ulnar nerve 19) Schuind FA, Goldschmidt D, Bastin C, et al. A biomechani- elongation and excursion in the cubital tunnel after decom- cal study of the ulnar nerve at the elbow. J Hand Surg [Br] pression and anterior transposition. J Hand Surg [Br] 2000; 1995; 20: 623Ð627. 25: 457Ð460. 20) Ochi N, Ogura T, Hashizume H, et al. Anatomic relation 15) Hicks D, Toby EB. Ulnar nerve strains at the elbow: the between the medial collateral ligament of the elbow and the effect of in situ decompression and medial epicondylec- humero-ulnar joint axis. J Shoulder Elbow Surg 1999; 8: 6Ð tomy. J Hand Surg [Am] 2002; 27: 1026Ð1031. 10.