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Effect of ulnar tunnel location on elbow stability in double-strand lateral collateral ligament reconstruction
ARTICLE IN PRESS J Shoulder Elbow Surg (2016) ■■, ■■–■■
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ORIGINAL ARTICLE
Effect of ulnar tunnel location on elbow stability in double-strand lateral collateral ligament reconstruction H. Mike Kim, MD*, Colin R. Andrews, BS, Evan P. Roush, BS, Gregory I. Pace, MD, Gregory S. Lewis, PhD Department of Orthopaedics and Rehabilitation, Penn State College of Medicine Milton S. Hershey Medical Center, Hershey, PA, USA Background: Double-strand lateral ulnar collateral ligament (LUCL) reconstruction is an effective treatment for posterolateral rotatory instability (PLRI) of the elbow, but anatomic landmarks for ulnar tunnel placement are often difficult to identify intraoperatively, which potentially can result in a nonanatomic LUCL reconstruction. This study investigated the effect of ulnar tunnel location on joint stability in doublestrand LUCL reconstruction. Methods: PLRI was artificially created in 7 cadaveric elbows, and double-strand LUCL reconstruction was performed. Five different ulnar tunnels were made along the length of the ulna. In each specimen, each possible pair of 2 tunnels (10 total) were used for graft passage. Varus and posterolateral joint gapping was measured after joint loading using a 3-dimensional digitizer system and X-ray image intensifier. Results: No significant gapping was observed at the posterolateral ulnohumeral joint regardless of the location of the ulnar tunnels (P > .05). In contrast, the lateral radiocapitellar joint showed statistically significant varus gapping when both ulnar tunnels were placed proximal to the radial head-neck junction (P < .05). Discussion: This findings of study suggest that the location of the ulnar tunnels may not be as critical as that of the humeral tunnel during double-strand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial head-neck junction level. Level of evidence: Basic Science Study; Biomechanics © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Lateral ulnar collateral ligament reconstruction; ulnar tunnels; elbow stability; posterolateral rotatory instability; double-strand; docking technique
The lateral collateral ligament complex consists of the lateral ulnar collateral ligament (LUCL), radial collateral ligNo Institutional Review Board or Ethical Committee review was needed for this cadaveric biomechanical study. *Reprint requests: H. Mike Kim, MD, 30 Hope Dr, P.O. Box 859, EC089, Hershey, PA 17033, USA. E-mail address: [email protected] (H.M. Kim).
ament, and annular ligament.12-14 Disruption of these ligaments at the humeral attachment site usually occurs in patients with elbow dislocation.20 Although most patients achieve adequate healing of the ligaments and regain a stable joint, persistent instability in the form of posterolateral rotatory instability (PLRI) does occur in some patients.17,18,20 The LUCL has been known to be a primary stabilizer of the elbow against PLRI,15-17,20 and reconstruction of the LUCL has been shown
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ARTICLE IN PRESS 2 to reliably restore the elbow stability in patients with PLRI.7,8,16,17,22 A number of studies have reported various LUCL reconstruction techniques with respect to the graft fixation method, the source of the graft, graft configuration, the number of graft strands, and the location of graft attachment sites.2,5,7,9,10,16,21,22 Double-strand tendon LUCL reconstruction has been used commonly with successful clinical results.7,16,17 One of the theoretical advantages of a double-strand LUCL reconstruction technique is that varus and posterolateral rotational stability of the elbow can both be achieved by having 2 separate strands of graft tendon.8 For successful LUCL reconstruction, identifying the anatomic landmarks and reconstructing the ligament at the anatomic location is critical. Ideal humeral tunnel placement for LUCL reconstruction has been well studied because it is directly related to the isometry of the ligament.15,16,19,23 In contrast, the literature is somewhat unclear on the ideal location of the ulnar tunnel, simply suggesting that the tunnel be placed close to the tubercle of the supinator crest of the proximal ulna. The supinator tubercle is often not prominent enough to be identified in many individuals,1 and the supinator crest extends from a level proximal to the radial head to a level distal to the radial neck.1,6 This makes it challenging to place the ulnar tunnels at an anatomic location during a LUCL reconstruction, potentially leading to inadvertent nonanatomic placement of the tunnels. This study investigated the effect on elbow joint stability of placing the ulnar tunnels at various locations in double-strand LUCL reconstruction. We hypothesized that ulnar tunnel location would significantly affect elbow stability.
Materials and methods Specimen preparation and LUCL reconstruction Seven nonpaired fresh frozen elbow cadaveric specimens from seven donors (5 men; mean age, 50 ± 12; range, 35-63 years) with no evidence of previous surgery, trauma, or arthritis were dissected using the Kocher lateral approach. The lateral collateral ligament complex and anconeus were detached from the proximal and distal attachment sites (Fig. 1, A). Part of the extensor origin and part of the flexor digitorum profundus origin were detached from the lateral epicondyle and the medial aspect of the proximal ulna, respectively. The entire lateral aspect of the capitellum, lateral epicondyle, radial head, and the proximal ulna were exposed, resulting in obvious posterolateral rotatory instability of the elbow. A docking technique, as described by Jones et al,7 was used for LUCL reconstruction. A 1.5-cm-deep humeral docking tunnel was made at the isometric point of the LUCL on the lateral epicondyle using a 4.5-mm drill bit (tunnel H in Fig. 1). The isometric point was determined at the center of the rotation of the capitellum and usually fell on the base of the lateral epicondyle where the epicondyle flattens onto the lateral aspect of the capitellum, as previously described by Cohen and Hastings.3 Two suture retrieval tunnels were made on either side of the supracondylar ridge toward the docking tunnel using a 2.0-mm drill bit.
H.M. Kim et al.
Figure 1 (A) Preparation of cadaveric elbow specimen for lateral ulnar collateral ligament reconstruction. A humeral tunnel was made at the isometric point on the lateral epicondyle (H). Two suture retrieval tunnels were made on the either side of the supracondylar ridge (yellow arrows). Five transosseous ulnar tunnels (A, B, C, D, and E) were created along the lateral aspect of the proximal ulna. Tunnel D was made at the level of the radial head-neck junction (large white arrow), representing the ideal location of the distal ulnar tunnel. The tunnels were separated by a 5-mm bone bridge. (B) Depiction of the graft directions for the 5 ulnar tunnels. Two tunnels were randomly chosen for graft passage at a time for a total of 10 combinations of ulnar tunnels. The testing protocol was repeated for each combination of ulnar tunnels
To test the effect of ulnar tunnel locations on the posterolateral rotatory stability of the elbow, 5 transosseous ulnar tunnels were created along the lateral aspect of the proximal ulna using a 3.2mm drill bit. These tunnels were made along the line bisecting the anteroposterior width of the proximal ulna. The first tunnel was made at the level of the radial head-neck junction (tunnel D), which represented the anatomic location of the distal ulnar tunnel. The tubercle of the supinator crest was not clearly identifiable in 5 of the 7 specimens, so the radial head-neck junction was used as the reference, as previously described in the literature.1,6,8 The second tunnel (tunnel E) was made distal to tunnel D with a 5-mm bone bridge between the 2 tunnels. The third (tunnel C), fourth (tunnel B), and fifth tunnels (tunnel A) were made proximal to tunnel D with a 5-mm bone bridge between each of them. Double-strand LUCL reconstruction was simulated using 2 nonabsorbable 2-mm-wide tapes (FiberTape; Arthrex, Naples, FL, USA), instead of using an actual tendon graft, to maintain consistent mechanical properties of the ligament substitute across the testing conditions and specimens (Fig. 1, B). This was based on our pilot experiment where the mechanical properties of tendon grafts substantially changed after only a few repetitions of the testing protocol.
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
Figure 2 Locations of distance measuring points for 3-dimensional digitizer (circled number 1, 2, 3, and 4) and for the X-ray image intensifier (circled number 5 and 6). A 7-mm metal bead was attached to the posterior aspect of the capitellum to be used as a reference for later calibration of fluoroscopic images. The letters A, B, C, D, and E indicate the 5 transosseous ulnar tunnels. Two tapes were first passed through the humeral docking tunnel and then through the suture retrieval tunnels. The tapes were tied over the bony bridge of the supracondylar ridge (Fig. 2). The free ends of the tapes were passed through a pair of 2 ulnar tunnels chosen among the 5 ulnar tunnels (a total of 10 possible combinations). The combinations and testing order were randomly chosen to eliminate testing bias. The tapes were tensioned through the tunnel with constant manual tensioning, and a Kelly clamp was used to secure the tape against the medial cortex of the ulna while the elbow was held at an anatomically reduced position (Fig. 2). The humerus was mounted horizontally using a clamp with the lateral aspect of the elbow facing directly upward (Fig. 3). The entire forearm distal to the elbow joint was hung free, with the weight of each specimen’s forearm applying a gravitational varus stress to the elbow, which would normally occur clinically in patients upon arm abduction. A 2.0-mm Kirschner (K) wire was inserted through the distal radius and ulna approximately 3 cm proximal to the wrist joint in a fully supinated position. A nylon rope was applied to the radial side of the K-wire, and 5 N of force was applied to this rope parallel to the floor using a pulley and a hanging weight to exert a supination and extension force on the distal forearm (Fig. 3). The elbow flexion-extension angle was kept constant at 10° or 45° with use of a metal bar that was placed against the ulna. All elbow specimens readily dislocated posterolaterally with this positioning when they were not held by a reconstructed LUCL. The elbow joint was first reduced and held in the anatomic position, and baseline measurement of the joint using MicroScribe (Revware, Raleigh, NC, USA) and fluoroscopy was performed as described below.
Gapping measurement using MicroScribe Gapping of the radiocapitellar and posterolateral ulnohumeral joints was measured in 3 dimensions with use of the MicroScribe G digitizer. Four points on the bony structures were selected for distance measurement: (1) 1 immediately anterior to the isometric point of the LUCL on the lateral epicondyle of the distal humerus (circled number 1 in Fig. 2), (2) 1 on the equator of the radial head with the forearm fully supinated (circled number 2), (3) 1 immediately
3
Figure 3 Testing setup. The humerus was mounted horizontally with the lateral aspect of the elbow facing directly upward. The entire forearm distal to the elbow joint was hung free, with the weight of each specimen’s forearm applying a gravitational varus stress to the elbow. A nylon rope (white arrow) was applied to a Kirschner wire that had been inserted through the distal radius and ulna at full supination. A 5 N force was applied to this rope parallel to the floor, using a pulley and a hanging weight to exert a supination and extension force on the distal forearm. The elbow flexion-extension angle was kept constant at 10° or 45° with use of a metal bar (yellow arrow). proximal to the supinator crest between the ulnar tunnel C and D (circled number 3), and (4) 1 on the proximal ulna between the ulnar tunnel A and B (circled number 4). The cortex at each point was gently drilled with a 1.6-mm K-wire to make a small pit, which ensured a secure and reliable positioning of the MicroScribe tip across testing. Direct distance was measured between point 1 and each of the other 3 points (2, 3, and 4) at baseline and after loading with the elbow flexed at 10° and 45°. Testretest reliability of this method was examined by repeating the reconstruction and measurement on the first 2 specimens. The Cronbach α was 0.999, indicating excellent reliability. The rest of the specimens underwent a single measurement of each distance.
Gapping measurement using fluoroscopic images As an adjunctive method of gapping measurement, fluoroscopic examinations were performed using a portable X-ray image intensifier. A metal bead with a diameter of 1.5 mm was attached to the capitellum just proximal to the articular cartilage (circled number 5 in Fig. 2) and to the proximal ulna just distal to the greater sigmoid notch (circled number 6). A separate metal bead with a 7-mm diameter was attached to the posterior aspect of the capitellum and served as a reference for calibration (Fig. 2). True lateral elbow view X-ray images were obtained at baseline and after loading with the elbow flexed at 10° and 45°. The X-ray images were saved in a computer for later measurement of the distance between the two 1.5-mm metal beads. The distance was measured with use of image binarization and marker center detection in ImageJ (National Institutes of Health, Bethesda, MD, USA) with the 7-mm bead used as the reference for
ARTICLE IN PRESS 4 calibration. Test-retest reliability of this method was examined by repeating the reconstruction and measurement on the first two specimens. The Cronbach α was 0.956, indicating excellent reliability. The rest of the specimens underwent a single measurement.
H.M. Kim et al. Table I Summary of MicroScribe data presented as the distance differences† from baseline after elbow joint loading Ulnar tunnel combination
Statistical methods For the MicroScribe method, the elbow joint gapping after loading was measured by obtaining the distance between the lateral epicondyle (point 1) and each of the other points (points 2, 3, and 4). For the fluoroscopic method, the joint gapping was measured by obtaining the distance between the capitellum (point 5) and the proximal ulna (point 6). The distances after loading were compared with the distances at baseline using a one-sample t test for each of the 10 combinations of ulnar tunnels. The data were also compared among the 10 ulnar tunnel combinations using repeated-measures analysis of variance (ANOVA). Statistical significance was set at P < .05. The data are presented as mean ± standard deviation.
Results Gapping measurement using MicroScribe The MicroScribe data for gapping measurement are presented in Table I as distance differences from the baseline. The distance from point 1 to point 2 that represents the gapping of the lateral radiocapitellar joint was significantly increased after loading compared with the baseline when the graft was passed through 2 of the proximal ulnar tunnels (tunnel A-B, A-C, A-D, and B-C with 10° elbow flexion; tunnel A-B and A-C with 45° elbow flexion, P < .05; Figs. 4 and 5). In contrast, the distance from point 1 to 3 and the distance from point 1 to 4 did not show significant differences after loading in either elbow flexion angle. Repeatedmeasures ANOVA comparisons among the ulnar tunnel combinations showed that the distance from point 1 to point 3 was significantly greater when tunnel A-B was used than when tunnel C-E or tunnel D-E was used at 10° elbow flexion (P < .05).
Gapping measurement using fluoroscopic images The fluoroscopic data for gapping measurement are presented in Table II as distance differences from the baseline. The differences in the distances between at baseline and after loading, regardless of the ulnar tunnel combinations in either elbow flexion angle, were not significant (P > .05). Repeatedmeasures ANOVA comparisons showed no significant differences among the ulnar tunnel combinations (P > .05).
Discussion Anatomic reconstruction of the LUCL requires accurate identification of the bony attachment sites of the ligament. Humeral tunnel placement for anatomic LUCL reconstruction has been studied well enough to render a consensus that the isomet-
Point 1-2 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E Point 1-3 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E Point 1-4 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E
10° elbow flexion
45° elbow flexion
Mean SD P value* Mean SD P value* (mm) (mm) 1.4 0.8 0.6 0.4 0.9 0.6 0.4 0.4 0.1 0.3
0.8 0.5 0.7 0.6 0.8 0.9 0.7 0.7 0.7 0.8
.003 .006 .048 .124 .036 .104 .207 .165 .668 .398
1.1 0.8 0.6 0.3 0.4 0.3 0.4 0.4 0.6 0.5
0.8 0.8 0.7 0.6 0.7 0.5 0.5 0.5 0.7 0.6
.009 .038 .056 .267 .162 .195 .100 .073 .052 .080
0.3 0 −0.2 −0.2 0 −0.2 −0.3 −0.1 −0.4 −0.4
0.7 .260 0.8 1.000 0.7 .523 0.8 .508 0.8 1.000 0.4 .224 0.7 .330 0.8 .824 0.5 .083 0.7 .205
0.5 0.2 0.1 −0.1 0 −0.3 0 −0.2 0.2 0.1
0.8 0.4 0.8 0.5 0.6 0.6 0.5 0.5 0.6 0.7
.108 .180 .815 .639 .850 .260 .829 .310 .382 .626
−0.4 −0.6 −0.7 −0.7 −0.6 −0.7 −0.6 −0.6 −0.7 −0.6
1.0 1.0 1.0 1.0 0.9 0.8 1.0 1.0 0.9 0.9
−0.1 −0.2 −0.2 −0.3 −0.3 −0.4 −0.2 −0.3 −0.1 0
0.6 0.4 0.5 0.4 0.6 0.5 0.4 0.5 0.5 0.5
.775 .292 .380 .097 .178 .056 .203 .164 .783 .827
.294 .180 .116 .121 .128 .052 .151 .157 .095 .109
SD, standard deviation. Microscribe; Revware, Raleigh, NC, USA. * P values were derived from 1-sample t-test (baseline = 0). † Difference = distance after loading – distance at baseline. Baseline refers to the status when the elbow joint was held in anatomic reduction.
ric point on the lateral epicondyle should be made at the geometric center of the capitellar articular surface,2,11,15 which corresponds to the base of the lateral epicondyle where the epicondyle flattens onto the lateral aspect of the capitellum.2 A significant part of the capitellum and lateral epicondyle can be visualized intraoperatively, which helps locate the humeral tunnel precisely. In contrast, anatomic guidelines for the ulnar tunnel placement have been somewhat unclear, and identifying the landmarks intraoperatively is often challenging. The current literature recommends creating the ulnar tunnels at or close to the supinator tubercle of the supinator crest.7,15,16 The supinator crest is a relatively well-defined ridge-like structure on the ulna, but it extends from a level proximal to the
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
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Figure 4 At 10° elbow flexion, the distance between point 1 and 2 (spanning the lateral radiocapitellar joint) showed a significant increase from the baseline after loading when both ulnar tunnels were made at or proximal to the radial head-neck junction (combination A-B, A-C, A-D, and B-C). The error bars indicate the standard deviation. *P < .05.
Figure 5 At 45° elbow flexion, the distance between point 1 and 2 (spanning the lateral radiocapitellar joint) showed a significant increase from the baseline after loading when both ulnar tunnels were made proximal to the radial head-neck junction (combination A-B and A-C). The error bars indicate the standard deviation. *P < .05.
radial head to a level distal to the radial neck.1,6 Therefore, simply identifying the crest is not sufficient for the exact location of the ulnar tunnels. Furthermore, identifying the supinator tubercle intraoperatively is often difficult because the tubercle is not prominent in every individual. A recent study by Anakwenze et al1 reported that the supinator tubercle was prominent in only 50% of their cadaveric specimens and suggested that a significant number of LUCL reconstructions might be nonanatomic at the ulnar attachment site. Little is known about the biomechanical consequence of nonanatomic placement of the ulnar attachment site. The present study investigated the effect of ulnar tunnel location on the stability of the posterolateral elbow joint in double-strand LUCL reconstruction. The study found that the stability of the posterolateral ulnohumeral joint could be re-
liably obtained regardless of the location of the ulnar tunnels. There was no significant gapping of the posterolateral ulnohumeral joint (distance from point 1 to 3 and distance from point 1 to 4) on varus-supination loading regardless of location of the ulnar tunnels. However, statistically significant gapping at the lateral radiocapitellar joint (distance from point 1 to 2) did occur when both ulnar tunnels were placed proximal to the radial head-neck junction level. Whether this amount of gapping is clinically significant or would lead to clinical signs of varus instability is unknown. We observed that when both ulnar tunnels were located proximal to the radial head-neck junction, the course of the graft strands was in more of an anterior-to-posterior direction than of a proximalto-distal direction. This rather anterior-to-posterior course of the graft might have led to insufficient stability against varus
ARTICLE IN PRESS 6
H.M. Kim et al. Table II Summary of fluoroscopic data presented as distance differences from baseline after elbow joint loading* Ulnar tunnel combination
10° elbow flexion Mean (mm)
SD
P value
A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E
0.2 −0.2 −0.2 −0.1 −0.3 −0.6 −0.6 −0.4 −0.5 −0.6
1.1 1.2 0.9 1.1 0.8 0.9 1.0 0.8 0.9 0.8
.58 .60 .51 .90 .41 .12 .18 .18 .18 .13
45° elbow flexion †
Mean (mm)
SD
P value†
−0.1 0 0 −0.1 −0.2 −0.3 −0.4 −0.3 −0.3 −0.5
0.4 0.4 0.4 0.6 0.4 0.5 0.5 0.5 0.6 0.5
.57 1.00 .94 .54 .30 .20 .07 .23 .26 .06
SD, standard deviation. * Difference = distance after loading—distance at baseline. Baseline refers to the status when the elbow joint was held in anatomic reduction. † P values were derived from 1 sample t-test (baseline = 0).
stress while providing sufficient stability against posterolateral rotational stress. However, placement of the ulnar tunnels at or distal to the radial head-neck junction level did not result in significant gapping of the posterolateral ulnohumeral joint. This finding suggests that the location of the ulnar tunnels may not be as critical as the location of the humeral tunnel during doublestrand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial neck level. It should be noted though that the radiocapitellar joint can gap if both strands of the graft tendon are passed through ulnar tunnels placed proximal to the radial head-neck junction level. In their cadaveric biomechanical study, King et al8 compared the elbow stability between a single-strand and a doublestrand LUCL reconstruction techniques and reported no significant difference in varus and posterolateral rotational stability between the 2 techniques. They placed the proximal ulnar tunnel at the level of the proximal aspect of the lesser sigmoid notch (ie, the proximal margin of the radial head) and placed the distal ulnar tunnel at the level of the crista supinatoris (or supinator crest). Exactly where in the crista supinatoris they made the distal tunnel is unclear, but their figure showed that the tunnel was located at the level of the radial head-neck junction. The graft configuration of their double-strand technique is similar to our ulnar tunnel combination B-D. The study of Goren et al6 used 13 cadaveric elbows to investigate the isometric points on the lateral epicondyle and proximal ulna for LUCL reconstruction. They reported that there was substantial individual variability in ulnar tunnel isometry with no truly isometric point and that isometry was not as sensitive to ulnar tunnel placement as humeral tunnel placement. They did note that the position of most isometric tunnel
placement was on the supinator crest 16 to 20 mm distal to the proximal margin of the radial head for the proximal wall of the ulnar tunnel. The effect of tunnel placement on joint stability was not investigated in this study. Dargel et al4 compared the posterolateral rotational stability among 3 different LUCL reconstruction techniques: single-bundle LUCL reconstruction, single-bundle LUCL reconstruction with radial collateral ligament augmentation, and dual-reconstruction of both LUCL and radial collateral ligament. They found no significant differences among the techniques. The study stated that a single ulnar tunnel was created at the supinator crest but provided no further details on the exact tunnel location. In this in vitro study, we used nonabsorbable synthetic tapes instead of actual tendon grafts for LUCL reconstruction. This was because of the repeated-measures design of the study, where each graft had to undergo more than 20 repetitions of the testing protocol in each specimen. During a pilot experiment that used digital extensor tendon grafts, substantial deformation of the grafts was observed after only a few repetitions of the testing protocol, which prompted us to seek a replacement material that would experience less permanent deformation upon mechanical stress and less graft wear upon repeated graft passage and clamping. The synthetic tapes used in the study showed no changes in the mechanical properties throughout the testing. Our study goal was to evaluate the relative effects of the graft position on the stability of the elbow rather than the absolute strength of the reconstructions. We used a gravitational stress to load the elbow joint rather than a fixed amount of stress across the specimens to simulate the immediate postoperative period after a LUCL reconstruction where the elbow is frequently subject to gravitational varus stress whenever the arm is abducted from the body. Therefore, the varus stress varied depending on the weight of the forearm of each specimen. This study has several important limitations. First, the testing was static in nature in loads and at certain elbow flexion angles, not dynamic with varying muscle forces and elbow positions. Only 2 elbow flexion angles were tested in this study, which might have failed to reflect the joint stability at other elbow angles. Second, each strand of the tape grafts was tensioned and clamped manually, which might have introduced bias. The reliability of this manual tensioning and clamping was examined for the first 2 specimens and was shown to be excellent. Third, elbow stability was examined only at time 0 with synthetic tape grafts. The natural chronological changes of normal tendon grafts caused by force-deformation were not considered. Fourth, some of the data showed negative values for differences between at baseline and after loading, indicating that the elbow was over-reduced after reconstruction in some of the testing conditions. Although these values were small, the study findings might possibly have been affected by the overreduction in some of the specimens.
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
7
Conclusions 7.
In this in vitro study, we investigated the effect of various ulnar tunnel locations during LUCL reconstruction on elbow joint stability. Our study findings suggest that the location of the ulnar tunnels may not be as critical as the location of the humeral tunnel during double-strand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial head-neck junction level. That the radiocapitellar joint can gap if both strands of the graft tendon are passed through ulnar tunnels placed proximal to the radial head-neck junction level should be noted. This finding can be especially useful in situations where the exact location of the tubercle of the supinator crest is difficult to identify intraoperatively.
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Disclaimer
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The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
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References 1. Anakwenze OA, Khanna K, Levine WN, Ahmad CS. Characterization of the supinator tubercle for lateral ulnar collateral ligament reconstruction. Orthop J Sports Med 2014;2:1-4. http://dx.doi.org/ 10.1177/2325967114530969 2. Cohen MS. Lateral collateral ligament instability of the elbow. In: Trumble T, Budoff J, editors. Wrist and elbow reconstruction & arthroscopy. Rosemont, IL: American Society for Surgery of the Hand; 2006. p. 453-60 ISBN-13: 9780974001821. 3. Cohen MS, Hastings H. Rotatory instability of the elbow. The anatomy and role of the lateral stabilizers. J Bone Joint Surg Am 1997;79:225-33. 4. Dargel J, Boomkamp E, Wegmann K, Eysel P, Müller LP, Hackl M. Reconstruction of the lateral ulnar collateral ligament of the elbow: a comparative biomechanical study. Knee Surg Sports Traumatol Arthrosc 2015. [Epub May 10, 2015]. http://dx.doi.org/10.1007/s00167-015-3627-3 5. Eygendaal D. Ligamentous reconstruction around the elbow using triceps tendon. Acta Orthop Scand 2004;75:516-23. 6. Goren D, Budoff JE, Hipp JA. Isometric placement of lateral ulnar collateral ligament reconstructions: a biomechanical study. Am J
18. 19.
20.
21.
22.
23.
Sports Med 2010;38:153-9. http://dx.doi.org/10.1177/036354650934 6049 Jones KJ, Dodson CC, Osbahr DC, Parisien RL, Weiland AJ, Altchek DW, et al. The docking technique for lateral ulnar collateral ligament reconstruction: surgical technique and clinical outcomes. J Shoulder Elbow Surg 2012;21:389-95. http://dx.doi.org/10.1016/j.jse.2011.04.033 King GJ, Dunning CE, Zarzour ZD, Patterson SD, Johnson JA. Singlestrand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow. J Shoulder Elbow Surg 2002;11:60-4. http://dx.doi.org/10.1067/mse.2002.118483 Lee B, Teo LHY. Surgical reconstruction for posterolateral rotatory instability of the elbow. J Shoulder Elbow Surg 2003;12:476-9. http://dx.doi.org/10.1016/S1058-2746(03)00091-0 Lin KY, Shen PH, Lee CH, Pan RY, Lin LC, Shen HC. Functional outcomes of surgical reconstruction for posterolateral rotatory instability of the elbow. Injury 2012;43:1657-61. http://dx.doi.org/10.1016/ j.injury.2012.04.023 Moritomo H, Murase T, Arimitsu S, Oka K, Yoshikawa H, Sugamoto K. The in vivo isometric point of the lateral ligament of the elbow. J Bone Joint Surg Am 2007;89:2011-7. http://dx.doi.org/10.2106/ JBJS.F.00868 Morrey BF. Anatomy of the elbow joint. In: Morrey BF, editor. The elbow and its disorders. Philadelphia: Saunders Elsevier; 2009. p. 11-38 ISBN-13: 9781416029021. Morrey BF, An KN. Functional anatomy of the ligaments of the elbow. Clin Orthop Relat Res 1985;201:84-90. Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med 1983;11:315-9. Morrey BF, O’Driscoll SW. Lateral collateral ligament injury. In: Morrey BF, editor. The elbow and its disorders. Philadelphia: WB Saunders; 2000. p. 556-62 ISBN-13: 9780721677521. Nestor BJ, O’Driscoll SW, Morrey BF. Ligamentous reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1992;74:1235-41. O’Driscoll SW, Bell DF, Morrey BF. Posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1991;73:440-6. O’Driscoll SW, Jupiter JB, King GJW, Hotchkiss RN, Morrey BF. The unstable elbow. J Bone Joint Surg Am 2000;82:724. O’Driscoll SW, Morrey BF. Surgical reconstruction of the lateral collateral ligament. In: Morrey BF, editor. Master techniques in orthopaedic surgery: the elbow. Philadelphia: Lippincott Williams and Wilkins; 2002. p. 249-63 ISBN-13: 9780781719919. O’Driscoll SW, Morrey BF, Korinek S, An KN. Elbow subluxation and dislocation. A spectrum of instability. Clin Orthop Relat Res 1992;280:186-97. Olsen BS, Søjbjerg JO. The treatment of recurrent posterolateral instability of the elbow. J Bone Joint Surg Br 2003;85:342-6. http://dx.doi.org/10.1302/0301-620x.85b3.13669 Sanchez-Sotelo J, Morrey BF, O’Driscoll SW. Ligamentous repair and reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint Surg Br 2005;87:54-61. http://dx.doi.org/10.1302/0301-620X .87B1.15096 Yadao MA, Savoie FH 3rd, Field LD. Posterolateral rotatory instability of the elbow. In: Instructional course lectures. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2004. p. 607-14 ISBN-13: 9780892033089.
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ORIGINAL ARTICLE
Effect of ulnar tunnel location on elbow stability in double-strand lateral collateral ligament reconstruction H. Mike Kim, MD*, Colin R. Andrews, BS, Evan P. Roush, BS, Gregory I. Pace, MD, Gregory S. Lewis, PhD Department of Orthopaedics and Rehabilitation, Penn State College of Medicine Milton S. Hershey Medical Center, Hershey, PA, USA Background: Double-strand lateral ulnar collateral ligament (LUCL) reconstruction is an effective treatment for posterolateral rotatory instability (PLRI) of the elbow, but anatomic landmarks for ulnar tunnel placement are often difficult to identify intraoperatively, which potentially can result in a nonanatomic LUCL reconstruction. This study investigated the effect of ulnar tunnel location on joint stability in doublestrand LUCL reconstruction. Methods: PLRI was artificially created in 7 cadaveric elbows, and double-strand LUCL reconstruction was performed. Five different ulnar tunnels were made along the length of the ulna. In each specimen, each possible pair of 2 tunnels (10 total) were used for graft passage. Varus and posterolateral joint gapping was measured after joint loading using a 3-dimensional digitizer system and X-ray image intensifier. Results: No significant gapping was observed at the posterolateral ulnohumeral joint regardless of the location of the ulnar tunnels (P > .05). In contrast, the lateral radiocapitellar joint showed statistically significant varus gapping when both ulnar tunnels were placed proximal to the radial head-neck junction (P < .05). Discussion: This findings of study suggest that the location of the ulnar tunnels may not be as critical as that of the humeral tunnel during double-strand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial head-neck junction level. Level of evidence: Basic Science Study; Biomechanics © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Lateral ulnar collateral ligament reconstruction; ulnar tunnels; elbow stability; posterolateral rotatory instability; double-strand; docking technique
The lateral collateral ligament complex consists of the lateral ulnar collateral ligament (LUCL), radial collateral ligNo Institutional Review Board or Ethical Committee review was needed for this cadaveric biomechanical study. *Reprint requests: H. Mike Kim, MD, 30 Hope Dr, P.O. Box 859, EC089, Hershey, PA 17033, USA. E-mail address: [email protected] (H.M. Kim).
ament, and annular ligament.12-14 Disruption of these ligaments at the humeral attachment site usually occurs in patients with elbow dislocation.20 Although most patients achieve adequate healing of the ligaments and regain a stable joint, persistent instability in the form of posterolateral rotatory instability (PLRI) does occur in some patients.17,18,20 The LUCL has been known to be a primary stabilizer of the elbow against PLRI,15-17,20 and reconstruction of the LUCL has been shown
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ARTICLE IN PRESS 2 to reliably restore the elbow stability in patients with PLRI.7,8,16,17,22 A number of studies have reported various LUCL reconstruction techniques with respect to the graft fixation method, the source of the graft, graft configuration, the number of graft strands, and the location of graft attachment sites.2,5,7,9,10,16,21,22 Double-strand tendon LUCL reconstruction has been used commonly with successful clinical results.7,16,17 One of the theoretical advantages of a double-strand LUCL reconstruction technique is that varus and posterolateral rotational stability of the elbow can both be achieved by having 2 separate strands of graft tendon.8 For successful LUCL reconstruction, identifying the anatomic landmarks and reconstructing the ligament at the anatomic location is critical. Ideal humeral tunnel placement for LUCL reconstruction has been well studied because it is directly related to the isometry of the ligament.15,16,19,23 In contrast, the literature is somewhat unclear on the ideal location of the ulnar tunnel, simply suggesting that the tunnel be placed close to the tubercle of the supinator crest of the proximal ulna. The supinator tubercle is often not prominent enough to be identified in many individuals,1 and the supinator crest extends from a level proximal to the radial head to a level distal to the radial neck.1,6 This makes it challenging to place the ulnar tunnels at an anatomic location during a LUCL reconstruction, potentially leading to inadvertent nonanatomic placement of the tunnels. This study investigated the effect on elbow joint stability of placing the ulnar tunnels at various locations in double-strand LUCL reconstruction. We hypothesized that ulnar tunnel location would significantly affect elbow stability.
Materials and methods Specimen preparation and LUCL reconstruction Seven nonpaired fresh frozen elbow cadaveric specimens from seven donors (5 men; mean age, 50 ± 12; range, 35-63 years) with no evidence of previous surgery, trauma, or arthritis were dissected using the Kocher lateral approach. The lateral collateral ligament complex and anconeus were detached from the proximal and distal attachment sites (Fig. 1, A). Part of the extensor origin and part of the flexor digitorum profundus origin were detached from the lateral epicondyle and the medial aspect of the proximal ulna, respectively. The entire lateral aspect of the capitellum, lateral epicondyle, radial head, and the proximal ulna were exposed, resulting in obvious posterolateral rotatory instability of the elbow. A docking technique, as described by Jones et al,7 was used for LUCL reconstruction. A 1.5-cm-deep humeral docking tunnel was made at the isometric point of the LUCL on the lateral epicondyle using a 4.5-mm drill bit (tunnel H in Fig. 1). The isometric point was determined at the center of the rotation of the capitellum and usually fell on the base of the lateral epicondyle where the epicondyle flattens onto the lateral aspect of the capitellum, as previously described by Cohen and Hastings.3 Two suture retrieval tunnels were made on either side of the supracondylar ridge toward the docking tunnel using a 2.0-mm drill bit.
H.M. Kim et al.
Figure 1 (A) Preparation of cadaveric elbow specimen for lateral ulnar collateral ligament reconstruction. A humeral tunnel was made at the isometric point on the lateral epicondyle (H). Two suture retrieval tunnels were made on the either side of the supracondylar ridge (yellow arrows). Five transosseous ulnar tunnels (A, B, C, D, and E) were created along the lateral aspect of the proximal ulna. Tunnel D was made at the level of the radial head-neck junction (large white arrow), representing the ideal location of the distal ulnar tunnel. The tunnels were separated by a 5-mm bone bridge. (B) Depiction of the graft directions for the 5 ulnar tunnels. Two tunnels were randomly chosen for graft passage at a time for a total of 10 combinations of ulnar tunnels. The testing protocol was repeated for each combination of ulnar tunnels
To test the effect of ulnar tunnel locations on the posterolateral rotatory stability of the elbow, 5 transosseous ulnar tunnels were created along the lateral aspect of the proximal ulna using a 3.2mm drill bit. These tunnels were made along the line bisecting the anteroposterior width of the proximal ulna. The first tunnel was made at the level of the radial head-neck junction (tunnel D), which represented the anatomic location of the distal ulnar tunnel. The tubercle of the supinator crest was not clearly identifiable in 5 of the 7 specimens, so the radial head-neck junction was used as the reference, as previously described in the literature.1,6,8 The second tunnel (tunnel E) was made distal to tunnel D with a 5-mm bone bridge between the 2 tunnels. The third (tunnel C), fourth (tunnel B), and fifth tunnels (tunnel A) were made proximal to tunnel D with a 5-mm bone bridge between each of them. Double-strand LUCL reconstruction was simulated using 2 nonabsorbable 2-mm-wide tapes (FiberTape; Arthrex, Naples, FL, USA), instead of using an actual tendon graft, to maintain consistent mechanical properties of the ligament substitute across the testing conditions and specimens (Fig. 1, B). This was based on our pilot experiment where the mechanical properties of tendon grafts substantially changed after only a few repetitions of the testing protocol.
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
Figure 2 Locations of distance measuring points for 3-dimensional digitizer (circled number 1, 2, 3, and 4) and for the X-ray image intensifier (circled number 5 and 6). A 7-mm metal bead was attached to the posterior aspect of the capitellum to be used as a reference for later calibration of fluoroscopic images. The letters A, B, C, D, and E indicate the 5 transosseous ulnar tunnels. Two tapes were first passed through the humeral docking tunnel and then through the suture retrieval tunnels. The tapes were tied over the bony bridge of the supracondylar ridge (Fig. 2). The free ends of the tapes were passed through a pair of 2 ulnar tunnels chosen among the 5 ulnar tunnels (a total of 10 possible combinations). The combinations and testing order were randomly chosen to eliminate testing bias. The tapes were tensioned through the tunnel with constant manual tensioning, and a Kelly clamp was used to secure the tape against the medial cortex of the ulna while the elbow was held at an anatomically reduced position (Fig. 2). The humerus was mounted horizontally using a clamp with the lateral aspect of the elbow facing directly upward (Fig. 3). The entire forearm distal to the elbow joint was hung free, with the weight of each specimen’s forearm applying a gravitational varus stress to the elbow, which would normally occur clinically in patients upon arm abduction. A 2.0-mm Kirschner (K) wire was inserted through the distal radius and ulna approximately 3 cm proximal to the wrist joint in a fully supinated position. A nylon rope was applied to the radial side of the K-wire, and 5 N of force was applied to this rope parallel to the floor using a pulley and a hanging weight to exert a supination and extension force on the distal forearm (Fig. 3). The elbow flexion-extension angle was kept constant at 10° or 45° with use of a metal bar that was placed against the ulna. All elbow specimens readily dislocated posterolaterally with this positioning when they were not held by a reconstructed LUCL. The elbow joint was first reduced and held in the anatomic position, and baseline measurement of the joint using MicroScribe (Revware, Raleigh, NC, USA) and fluoroscopy was performed as described below.
Gapping measurement using MicroScribe Gapping of the radiocapitellar and posterolateral ulnohumeral joints was measured in 3 dimensions with use of the MicroScribe G digitizer. Four points on the bony structures were selected for distance measurement: (1) 1 immediately anterior to the isometric point of the LUCL on the lateral epicondyle of the distal humerus (circled number 1 in Fig. 2), (2) 1 on the equator of the radial head with the forearm fully supinated (circled number 2), (3) 1 immediately
3
Figure 3 Testing setup. The humerus was mounted horizontally with the lateral aspect of the elbow facing directly upward. The entire forearm distal to the elbow joint was hung free, with the weight of each specimen’s forearm applying a gravitational varus stress to the elbow. A nylon rope (white arrow) was applied to a Kirschner wire that had been inserted through the distal radius and ulna at full supination. A 5 N force was applied to this rope parallel to the floor, using a pulley and a hanging weight to exert a supination and extension force on the distal forearm. The elbow flexion-extension angle was kept constant at 10° or 45° with use of a metal bar (yellow arrow). proximal to the supinator crest between the ulnar tunnel C and D (circled number 3), and (4) 1 on the proximal ulna between the ulnar tunnel A and B (circled number 4). The cortex at each point was gently drilled with a 1.6-mm K-wire to make a small pit, which ensured a secure and reliable positioning of the MicroScribe tip across testing. Direct distance was measured between point 1 and each of the other 3 points (2, 3, and 4) at baseline and after loading with the elbow flexed at 10° and 45°. Testretest reliability of this method was examined by repeating the reconstruction and measurement on the first 2 specimens. The Cronbach α was 0.999, indicating excellent reliability. The rest of the specimens underwent a single measurement of each distance.
Gapping measurement using fluoroscopic images As an adjunctive method of gapping measurement, fluoroscopic examinations were performed using a portable X-ray image intensifier. A metal bead with a diameter of 1.5 mm was attached to the capitellum just proximal to the articular cartilage (circled number 5 in Fig. 2) and to the proximal ulna just distal to the greater sigmoid notch (circled number 6). A separate metal bead with a 7-mm diameter was attached to the posterior aspect of the capitellum and served as a reference for calibration (Fig. 2). True lateral elbow view X-ray images were obtained at baseline and after loading with the elbow flexed at 10° and 45°. The X-ray images were saved in a computer for later measurement of the distance between the two 1.5-mm metal beads. The distance was measured with use of image binarization and marker center detection in ImageJ (National Institutes of Health, Bethesda, MD, USA) with the 7-mm bead used as the reference for
ARTICLE IN PRESS 4 calibration. Test-retest reliability of this method was examined by repeating the reconstruction and measurement on the first two specimens. The Cronbach α was 0.956, indicating excellent reliability. The rest of the specimens underwent a single measurement.
H.M. Kim et al. Table I Summary of MicroScribe data presented as the distance differences† from baseline after elbow joint loading Ulnar tunnel combination
Statistical methods For the MicroScribe method, the elbow joint gapping after loading was measured by obtaining the distance between the lateral epicondyle (point 1) and each of the other points (points 2, 3, and 4). For the fluoroscopic method, the joint gapping was measured by obtaining the distance between the capitellum (point 5) and the proximal ulna (point 6). The distances after loading were compared with the distances at baseline using a one-sample t test for each of the 10 combinations of ulnar tunnels. The data were also compared among the 10 ulnar tunnel combinations using repeated-measures analysis of variance (ANOVA). Statistical significance was set at P < .05. The data are presented as mean ± standard deviation.
Results Gapping measurement using MicroScribe The MicroScribe data for gapping measurement are presented in Table I as distance differences from the baseline. The distance from point 1 to point 2 that represents the gapping of the lateral radiocapitellar joint was significantly increased after loading compared with the baseline when the graft was passed through 2 of the proximal ulnar tunnels (tunnel A-B, A-C, A-D, and B-C with 10° elbow flexion; tunnel A-B and A-C with 45° elbow flexion, P < .05; Figs. 4 and 5). In contrast, the distance from point 1 to 3 and the distance from point 1 to 4 did not show significant differences after loading in either elbow flexion angle. Repeatedmeasures ANOVA comparisons among the ulnar tunnel combinations showed that the distance from point 1 to point 3 was significantly greater when tunnel A-B was used than when tunnel C-E or tunnel D-E was used at 10° elbow flexion (P < .05).
Gapping measurement using fluoroscopic images The fluoroscopic data for gapping measurement are presented in Table II as distance differences from the baseline. The differences in the distances between at baseline and after loading, regardless of the ulnar tunnel combinations in either elbow flexion angle, were not significant (P > .05). Repeatedmeasures ANOVA comparisons showed no significant differences among the ulnar tunnel combinations (P > .05).
Discussion Anatomic reconstruction of the LUCL requires accurate identification of the bony attachment sites of the ligament. Humeral tunnel placement for anatomic LUCL reconstruction has been studied well enough to render a consensus that the isomet-
Point 1-2 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E Point 1-3 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E Point 1-4 distance A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E
10° elbow flexion
45° elbow flexion
Mean SD P value* Mean SD P value* (mm) (mm) 1.4 0.8 0.6 0.4 0.9 0.6 0.4 0.4 0.1 0.3
0.8 0.5 0.7 0.6 0.8 0.9 0.7 0.7 0.7 0.8
.003 .006 .048 .124 .036 .104 .207 .165 .668 .398
1.1 0.8 0.6 0.3 0.4 0.3 0.4 0.4 0.6 0.5
0.8 0.8 0.7 0.6 0.7 0.5 0.5 0.5 0.7 0.6
.009 .038 .056 .267 .162 .195 .100 .073 .052 .080
0.3 0 −0.2 −0.2 0 −0.2 −0.3 −0.1 −0.4 −0.4
0.7 .260 0.8 1.000 0.7 .523 0.8 .508 0.8 1.000 0.4 .224 0.7 .330 0.8 .824 0.5 .083 0.7 .205
0.5 0.2 0.1 −0.1 0 −0.3 0 −0.2 0.2 0.1
0.8 0.4 0.8 0.5 0.6 0.6 0.5 0.5 0.6 0.7
.108 .180 .815 .639 .850 .260 .829 .310 .382 .626
−0.4 −0.6 −0.7 −0.7 −0.6 −0.7 −0.6 −0.6 −0.7 −0.6
1.0 1.0 1.0 1.0 0.9 0.8 1.0 1.0 0.9 0.9
−0.1 −0.2 −0.2 −0.3 −0.3 −0.4 −0.2 −0.3 −0.1 0
0.6 0.4 0.5 0.4 0.6 0.5 0.4 0.5 0.5 0.5
.775 .292 .380 .097 .178 .056 .203 .164 .783 .827
.294 .180 .116 .121 .128 .052 .151 .157 .095 .109
SD, standard deviation. Microscribe; Revware, Raleigh, NC, USA. * P values were derived from 1-sample t-test (baseline = 0). † Difference = distance after loading – distance at baseline. Baseline refers to the status when the elbow joint was held in anatomic reduction.
ric point on the lateral epicondyle should be made at the geometric center of the capitellar articular surface,2,11,15 which corresponds to the base of the lateral epicondyle where the epicondyle flattens onto the lateral aspect of the capitellum.2 A significant part of the capitellum and lateral epicondyle can be visualized intraoperatively, which helps locate the humeral tunnel precisely. In contrast, anatomic guidelines for the ulnar tunnel placement have been somewhat unclear, and identifying the landmarks intraoperatively is often challenging. The current literature recommends creating the ulnar tunnels at or close to the supinator tubercle of the supinator crest.7,15,16 The supinator crest is a relatively well-defined ridge-like structure on the ulna, but it extends from a level proximal to the
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
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Figure 4 At 10° elbow flexion, the distance between point 1 and 2 (spanning the lateral radiocapitellar joint) showed a significant increase from the baseline after loading when both ulnar tunnels were made at or proximal to the radial head-neck junction (combination A-B, A-C, A-D, and B-C). The error bars indicate the standard deviation. *P < .05.
Figure 5 At 45° elbow flexion, the distance between point 1 and 2 (spanning the lateral radiocapitellar joint) showed a significant increase from the baseline after loading when both ulnar tunnels were made proximal to the radial head-neck junction (combination A-B and A-C). The error bars indicate the standard deviation. *P < .05.
radial head to a level distal to the radial neck.1,6 Therefore, simply identifying the crest is not sufficient for the exact location of the ulnar tunnels. Furthermore, identifying the supinator tubercle intraoperatively is often difficult because the tubercle is not prominent in every individual. A recent study by Anakwenze et al1 reported that the supinator tubercle was prominent in only 50% of their cadaveric specimens and suggested that a significant number of LUCL reconstructions might be nonanatomic at the ulnar attachment site. Little is known about the biomechanical consequence of nonanatomic placement of the ulnar attachment site. The present study investigated the effect of ulnar tunnel location on the stability of the posterolateral elbow joint in double-strand LUCL reconstruction. The study found that the stability of the posterolateral ulnohumeral joint could be re-
liably obtained regardless of the location of the ulnar tunnels. There was no significant gapping of the posterolateral ulnohumeral joint (distance from point 1 to 3 and distance from point 1 to 4) on varus-supination loading regardless of location of the ulnar tunnels. However, statistically significant gapping at the lateral radiocapitellar joint (distance from point 1 to 2) did occur when both ulnar tunnels were placed proximal to the radial head-neck junction level. Whether this amount of gapping is clinically significant or would lead to clinical signs of varus instability is unknown. We observed that when both ulnar tunnels were located proximal to the radial head-neck junction, the course of the graft strands was in more of an anterior-to-posterior direction than of a proximalto-distal direction. This rather anterior-to-posterior course of the graft might have led to insufficient stability against varus
ARTICLE IN PRESS 6
H.M. Kim et al. Table II Summary of fluoroscopic data presented as distance differences from baseline after elbow joint loading* Ulnar tunnel combination
10° elbow flexion Mean (mm)
SD
P value
A-B A-C A-D A-E B-C B-D B-E C-D C-E D-E
0.2 −0.2 −0.2 −0.1 −0.3 −0.6 −0.6 −0.4 −0.5 −0.6
1.1 1.2 0.9 1.1 0.8 0.9 1.0 0.8 0.9 0.8
.58 .60 .51 .90 .41 .12 .18 .18 .18 .13
45° elbow flexion †
Mean (mm)
SD
P value†
−0.1 0 0 −0.1 −0.2 −0.3 −0.4 −0.3 −0.3 −0.5
0.4 0.4 0.4 0.6 0.4 0.5 0.5 0.5 0.6 0.5
.57 1.00 .94 .54 .30 .20 .07 .23 .26 .06
SD, standard deviation. * Difference = distance after loading—distance at baseline. Baseline refers to the status when the elbow joint was held in anatomic reduction. † P values were derived from 1 sample t-test (baseline = 0).
stress while providing sufficient stability against posterolateral rotational stress. However, placement of the ulnar tunnels at or distal to the radial head-neck junction level did not result in significant gapping of the posterolateral ulnohumeral joint. This finding suggests that the location of the ulnar tunnels may not be as critical as the location of the humeral tunnel during doublestrand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial neck level. It should be noted though that the radiocapitellar joint can gap if both strands of the graft tendon are passed through ulnar tunnels placed proximal to the radial head-neck junction level. In their cadaveric biomechanical study, King et al8 compared the elbow stability between a single-strand and a doublestrand LUCL reconstruction techniques and reported no significant difference in varus and posterolateral rotational stability between the 2 techniques. They placed the proximal ulnar tunnel at the level of the proximal aspect of the lesser sigmoid notch (ie, the proximal margin of the radial head) and placed the distal ulnar tunnel at the level of the crista supinatoris (or supinator crest). Exactly where in the crista supinatoris they made the distal tunnel is unclear, but their figure showed that the tunnel was located at the level of the radial head-neck junction. The graft configuration of their double-strand technique is similar to our ulnar tunnel combination B-D. The study of Goren et al6 used 13 cadaveric elbows to investigate the isometric points on the lateral epicondyle and proximal ulna for LUCL reconstruction. They reported that there was substantial individual variability in ulnar tunnel isometry with no truly isometric point and that isometry was not as sensitive to ulnar tunnel placement as humeral tunnel placement. They did note that the position of most isometric tunnel
placement was on the supinator crest 16 to 20 mm distal to the proximal margin of the radial head for the proximal wall of the ulnar tunnel. The effect of tunnel placement on joint stability was not investigated in this study. Dargel et al4 compared the posterolateral rotational stability among 3 different LUCL reconstruction techniques: single-bundle LUCL reconstruction, single-bundle LUCL reconstruction with radial collateral ligament augmentation, and dual-reconstruction of both LUCL and radial collateral ligament. They found no significant differences among the techniques. The study stated that a single ulnar tunnel was created at the supinator crest but provided no further details on the exact tunnel location. In this in vitro study, we used nonabsorbable synthetic tapes instead of actual tendon grafts for LUCL reconstruction. This was because of the repeated-measures design of the study, where each graft had to undergo more than 20 repetitions of the testing protocol in each specimen. During a pilot experiment that used digital extensor tendon grafts, substantial deformation of the grafts was observed after only a few repetitions of the testing protocol, which prompted us to seek a replacement material that would experience less permanent deformation upon mechanical stress and less graft wear upon repeated graft passage and clamping. The synthetic tapes used in the study showed no changes in the mechanical properties throughout the testing. Our study goal was to evaluate the relative effects of the graft position on the stability of the elbow rather than the absolute strength of the reconstructions. We used a gravitational stress to load the elbow joint rather than a fixed amount of stress across the specimens to simulate the immediate postoperative period after a LUCL reconstruction where the elbow is frequently subject to gravitational varus stress whenever the arm is abducted from the body. Therefore, the varus stress varied depending on the weight of the forearm of each specimen. This study has several important limitations. First, the testing was static in nature in loads and at certain elbow flexion angles, not dynamic with varying muscle forces and elbow positions. Only 2 elbow flexion angles were tested in this study, which might have failed to reflect the joint stability at other elbow angles. Second, each strand of the tape grafts was tensioned and clamped manually, which might have introduced bias. The reliability of this manual tensioning and clamping was examined for the first 2 specimens and was shown to be excellent. Third, elbow stability was examined only at time 0 with synthetic tape grafts. The natural chronological changes of normal tendon grafts caused by force-deformation were not considered. Fourth, some of the data showed negative values for differences between at baseline and after loading, indicating that the elbow was over-reduced after reconstruction in some of the testing conditions. Although these values were small, the study findings might possibly have been affected by the overreduction in some of the specimens.
ARTICLE IN PRESS Tunnel location in LUCL reconstruction
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Conclusions 7.
In this in vitro study, we investigated the effect of various ulnar tunnel locations during LUCL reconstruction on elbow joint stability. Our study findings suggest that the location of the ulnar tunnels may not be as critical as the location of the humeral tunnel during double-strand LUCL reconstruction and that posterolateral rotatory elbow stability can be achieved reasonably well as long as at least 1 of the 2 ulnar tunnels is located at or distal to the radial head-neck junction level. That the radiocapitellar joint can gap if both strands of the graft tendon are passed through ulnar tunnels placed proximal to the radial head-neck junction level should be noted. This finding can be especially useful in situations where the exact location of the tubercle of the supinator crest is difficult to identify intraoperatively.
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Disclaimer
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The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
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References 1. Anakwenze OA, Khanna K, Levine WN, Ahmad CS. Characterization of the supinator tubercle for lateral ulnar collateral ligament reconstruction. Orthop J Sports Med 2014;2:1-4. http://dx.doi.org/ 10.1177/2325967114530969 2. Cohen MS. Lateral collateral ligament instability of the elbow. In: Trumble T, Budoff J, editors. Wrist and elbow reconstruction & arthroscopy. Rosemont, IL: American Society for Surgery of the Hand; 2006. p. 453-60 ISBN-13: 9780974001821. 3. Cohen MS, Hastings H. Rotatory instability of the elbow. The anatomy and role of the lateral stabilizers. J Bone Joint Surg Am 1997;79:225-33. 4. Dargel J, Boomkamp E, Wegmann K, Eysel P, Müller LP, Hackl M. Reconstruction of the lateral ulnar collateral ligament of the elbow: a comparative biomechanical study. Knee Surg Sports Traumatol Arthrosc 2015. [Epub May 10, 2015]. http://dx.doi.org/10.1007/s00167-015-3627-3 5. Eygendaal D. Ligamentous reconstruction around the elbow using triceps tendon. Acta Orthop Scand 2004;75:516-23. 6. Goren D, Budoff JE, Hipp JA. Isometric placement of lateral ulnar collateral ligament reconstructions: a biomechanical study. Am J
18. 19.
20.
21.
22.
23.
Sports Med 2010;38:153-9. http://dx.doi.org/10.1177/036354650934 6049 Jones KJ, Dodson CC, Osbahr DC, Parisien RL, Weiland AJ, Altchek DW, et al. The docking technique for lateral ulnar collateral ligament reconstruction: surgical technique and clinical outcomes. J Shoulder Elbow Surg 2012;21:389-95. http://dx.doi.org/10.1016/j.jse.2011.04.033 King GJ, Dunning CE, Zarzour ZD, Patterson SD, Johnson JA. Singlestrand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow. J Shoulder Elbow Surg 2002;11:60-4. http://dx.doi.org/10.1067/mse.2002.118483 Lee B, Teo LHY. Surgical reconstruction for posterolateral rotatory instability of the elbow. J Shoulder Elbow Surg 2003;12:476-9. http://dx.doi.org/10.1016/S1058-2746(03)00091-0 Lin KY, Shen PH, Lee CH, Pan RY, Lin LC, Shen HC. Functional outcomes of surgical reconstruction for posterolateral rotatory instability of the elbow. Injury 2012;43:1657-61. http://dx.doi.org/10.1016/ j.injury.2012.04.023 Moritomo H, Murase T, Arimitsu S, Oka K, Yoshikawa H, Sugamoto K. The in vivo isometric point of the lateral ligament of the elbow. J Bone Joint Surg Am 2007;89:2011-7. http://dx.doi.org/10.2106/ JBJS.F.00868 Morrey BF. Anatomy of the elbow joint. In: Morrey BF, editor. The elbow and its disorders. Philadelphia: Saunders Elsevier; 2009. p. 11-38 ISBN-13: 9781416029021. Morrey BF, An KN. Functional anatomy of the ligaments of the elbow. Clin Orthop Relat Res 1985;201:84-90. Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med 1983;11:315-9. Morrey BF, O’Driscoll SW. Lateral collateral ligament injury. In: Morrey BF, editor. The elbow and its disorders. Philadelphia: WB Saunders; 2000. p. 556-62 ISBN-13: 9780721677521. Nestor BJ, O’Driscoll SW, Morrey BF. Ligamentous reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1992;74:1235-41. O’Driscoll SW, Bell DF, Morrey BF. Posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1991;73:440-6. O’Driscoll SW, Jupiter JB, King GJW, Hotchkiss RN, Morrey BF. The unstable elbow. J Bone Joint Surg Am 2000;82:724. O’Driscoll SW, Morrey BF. Surgical reconstruction of the lateral collateral ligament. In: Morrey BF, editor. Master techniques in orthopaedic surgery: the elbow. Philadelphia: Lippincott Williams and Wilkins; 2002. p. 249-63 ISBN-13: 9780781719919. O’Driscoll SW, Morrey BF, Korinek S, An KN. Elbow subluxation and dislocation. A spectrum of instability. Clin Orthop Relat Res 1992;280:186-97. Olsen BS, Søjbjerg JO. The treatment of recurrent posterolateral instability of the elbow. J Bone Joint Surg Br 2003;85:342-6. http://dx.doi.org/10.1302/0301-620x.85b3.13669 Sanchez-Sotelo J, Morrey BF, O’Driscoll SW. Ligamentous repair and reconstruction for posterolateral rotatory instability of the elbow. J Bone Joint Surg Br 2005;87:54-61. http://dx.doi.org/10.1302/0301-620X .87B1.15096 Yadao MA, Savoie FH 3rd, Field LD. Posterolateral rotatory instability of the elbow. In: Instructional course lectures. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2004. p. 607-14 ISBN-13: 9780892033089.