- Email: [email protected]
Single-strand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow
Single-strand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow Graham J. W. King, MD, MSc, FRCSC,a Cynthia E. Dunning, PhD,a Zane D. S. Zarzour, MD, FRCSC,a Stuart D. Patterson, MBChB, FRCSC,b and James A. Johnson, PhD,a London, Ontario, Canada, and Winter Haven, Fla
Because of a lack of biomechanical studies of lateral elbow ligament reconstruction in the literature, the initial stability afforded by 3 different techniques of lateral ulnar collateral ligament reconstruction was evaluated in 8 cadaveric elbows. The arm was mounted in a testing apparatus, and passive flexion was performed with the arm in varus and valgus orientations. A pivot shift test was performed with the arm in the vertical orientation. An electromagnetic tracking device was used to quantify motion pathways. After intact testing, each specimen underwent sectioning of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle. Reconstruction of the lateral ulnar collateral ligament was performed in a randomized sequence, consisting of proximal single-strand, distal single-strand, and double-strand tendon grafts. Division of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle caused a significant decrease in rotational stability when the pivot shift test was being performed (P < .0001). Varus-valgus stability also decreased after transection of the radial collateral and lateral ulnar collateral ligaments (P < .0001). Reconstruction of the lateral ulnar collateral ligament restored elbow stability to that of the intact state. There was no significant difference in stability between the single- and double-strand repair techniques (P > .05). This study demonstrates that both single- and double-strand reconstructions restore varus and posterolateral elbow stability and may be considered appropriate reconstructive From the Bioengineering Research Laboratory, Hand and Upper Limb Centre, St Joseph’s Health Centre, London, Ontario, Canada,a and Bond Clinic, Winter Haven, Fla.b Supported by funding from the Medical Research Council of Canada. Reprint requests: Graham J. W. King, MD, Hand and Upper Limb Centre, 268 Grosvenor St, London, Ontario, Canada N6A 4L6 (E-mail: [email protected]). Copyright © 2002 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2002/$35.00 + 0 32/1/118483 doi:10.1067/mse.2002.118483
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procedures in patients with symptomatic insufficiency of the lateral ligaments of the elbow. (J Shoulder Elbow Surg 2002;11:60-4.)
D
isruption of the lateral ligaments of the elbow at their humeral insertion usually occurs in patients with an elbow dislocation.6,16 Recurrent subluxation or dislocation is uncommon following closed reduction and early mobilization.1,6,8 Adequate ligamentous healing typically occurs with nonoperative treatment; however, patients occasionally will have with persistent symptoms of varus or posterolateral rotatory instability (PLRI) of the elbow (or both).3-5,13,17,20 The lateral ligaments of the elbow have been studied previously both anatomically2,11,14 and mechanically.10,12,16-19 The lateral ligaments consist of the radial collateral ligament (RCL), the annular ligament, and the lateral ulnar collateral ligament (LUCL).11,14 The LUCL has been shown to be an important stabilizer against PLRI.12-14,16 Reconstruction of the LUCL with a single heavy suture fixed to bone at the lateral epicondyle of the distal humerus and the crista supinatoris of the ulna has been shown to eliminate PLRI in the LUCL-deficient elbow.15 A double-strand tendon reconstruction has been recommended for the management of chronic PLRI, and good success has been documented in two clinical series.12,13 There have been no reported biomechanical studies that have documented the stabilizing effect of LUCL reconstruction with the use of tendon grafts. The purpose of this biomechanical study was to compare the stabilizing effect of 3 different methods of reconstruction of the LUCL. Our hypothesis was that reconstruction of the LUCL with any of these 3 techniques would be sufficient to restore elbow stability.
MATERIALS AND METHODS An in vitro testing apparatus incorporating a 2–degree of freedom hinge to allow testing of the upper extremity in varus, valgus, and vertical gravity-loading orientations was used.7 A humeral mounting clamp allowed rigid fixation of the mid shaft of the humerus, while providing sufficient clearance for unconstrained motion of the elbow and fore-
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arm. Joint kinematic data were collected by means of an electromagnetic tracking system that measures the 3 translations and 3 rotations of one or more receivers relative to the transmitter position (Flock of Birds; Ascension Technology, Burlington, Vt). The transmitter and receiver were positioned so that they constantly remained within the optimum operational range of the tracking device throughout the arc of motion.9 The receiver was rigidly fixed to the distalmedial edge of the ulna with care taken to ensure that the receiver did not impinge during forearm rotation. With the humerus in varus and valgus orientations, passive elbow flexion was performed with the forearm held in both pronation and supination. An experienced surgeon performed a pivot shift test (PST)13 with the cadaveric arm in vertical orientation. Valgus, axial, and supination forces were applied to the forearm with the elbow in extension and maintained as the elbow was flexed. Although the magnitude of these forces was not quantified, they were felt to be similar to that used in the clinical application of this test. The reproducibility of the PST as quantified by repeating the test 5 times was ±0.25° for the intact elbow and ±2.6° for the ligament-deficient elbow. Eight fresh-frozen upper extremities (mean age, 79 ± 14 years; range, 58-99 years) were mounted in the testing apparatus. After intact testing, the interval between the anconeus and extensor carpi ulnaris was identified and the lateral elbow ligaments were exposed by careful elevation of the common extensor muscles anteriorly and the anconeus posteriorly. The RCL and LUCL were divided from their attachment on the lateral epicondyle to mimic the common site of disruption seen clinically.6 The fascia between the extensor carpi ulnaris and the anconeus was repaired at each stage of testing with No. 1 braided absorbable suture. The skin incision used to expose the elbow was closed during testing, and the specimens were kept moist by irrigation with 0.9% normal saline solution. Testing was performed at 23°C ± 2°C. Because the palmaris longus was variably present in the cadaveric specimens, reconstruction of the LUCL was performed with the use of flexor digitorum superficialis tendons harvested from both the long and ring fingers (Figure 1). One drill hole (approximately 4 mm) was placed in the ulna at the level of the crista supinatoris, and a second (approximately 4 mm) was placed at the level of the proximal aspect of the lesser sigmoid notch, as has been described in the literature.12 A suture was passed through the drill holes, and the isometric point on the lateral epicondyle was identified. A drill hole large enough to accommodate the tendon grafts was placed at the point of isometry. To facilitate testing, specially developed tendon clamps were used to secure the reconstructions. After fixation of the graft to the ulna, the elbow was reduced and the graft was pre-tensioned to 20 N with a spring scale for 5 minutes prior to humeral fixation. Proximal single-strand, distal single-strand, and double-strand LUCL reconstructions were performed in random order, and the testing protocol was repeated at each stage. Kinematic data were transformed into the anatomic coordinate systems of the humerus and ulna through use of bony landmarks.7 Ulnar motion was expressed relative to the anatomic axes of the distal humerus. At each angle of elbow flexion, the varus-valgus laxity of the ulna was calculated by determining the difference in varus angulation
61
A
B
C Figure 1 Ligament reconstructions. Flexor digitorum superficialis tendons were used to reconstruct the LUCL. Each tendon strand was passed through a bone tunnel and secured with a specialized tendon clamp after appropriate pre-tensioning. Double-strand (A), proximal single-strand (B), and distal single-strand (C) reconstructions were used.
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Figure 2 PST. Sectioning of the RCL and LUCL caused a significant increase in external rotation of the ulna when the PST was performed (P < .0001). There was no significant difference in ulnar rotation between the intact elbow and any of the ligament reconstructions (P > .05).
(with the arm in varus orientation) from valgus angulation (with the arm in valgus orientation). The largest varus-valgus laxity measured throughout the arc of passive elbow flexion was defined as the maximum varus-valgus laxity. While the surgeon was performing the PST with the humerus in vertical orientation, rotational instability of the elbow was quantified by internal-external rotation of the ulna. Statistical comparisons were performed with 2-way repeated-measures analyses of variance and Student-Newman-Keuls multiple comparison procedures, and α was set at .05.
RESULTS Division of the RCL and LUCL from the lateral epicondyle caused a significant increase in rotational instability when the PST was performed at all angles of elbow flexion (P < .0001) (Figure 2). Division of the RCL and LUCL significantly increased maximum varusvalgus laxity of the elbow with the forearm in both pronation and supination (P < .0001) (Figure 3). Reconstruction of the LUCL with either a proximal singlestrand, a distal single-strand, or a double-strand tendon repair restored the rotational and varus-valgus stability of the elbow (Figures 2 and 3). There was no significant difference between any of the repairs and the intact elbow when the PST was performed (P > .05) (Figure 2). There was no significant difference in maximum varus-valgus laxity among the repairs and the intact elbow (P > .05) (Figure 3). DISCUSSION In this study the RCL and LUCL were shown to be important restraints against both rotational and varus instability. Our findings are similar to those reported by other investigators.10,16-19 We chose to divide the RCL and LUCL at their humeral insertions, as lateral ligament disruptions are usually seen at the lateral epicondyle.6
Patients with PLRI typically do not have radioulnar instability and have a competent annular ligament. The complete lateral ligament transection used in this experimental model induced gross instability similar to that seen after an acute elbow dislocation.6,16 In patients with chronic posterolateral rotational instability, the instability is often subtle, making the clinical diagnosis difficult, possibly because of incomplete healing of the lateral ligaments. This suggests that our model represents somewhat of a worst-case scenario. Because of the order of sectioning used in this study, we were unable to confirm the importance of the anconeus fascia and common extensor origin on the stability of the elbow as previously demonstrated by Cohen and Hastings.2 The common extensor muscles and anconeus were elevated off the lateral epicondyle to expose the underlying lateral ligaments of the elbow. Although this fascial interval was routinely repaired at each step of the testing protocol to keep the underlying tissues moist, it could not be anatomically repaired back to the lateral epicondyle. Although we believe that the common extensor origin should be repaired following lateral elbow surgery and when acute elbow instability is being surgically managed, its importance could not be evaluated in this study. In this in vitro investigation, we used specialized tendon clamps rather than suture anchors or other fixation methods that would be used clinically. Pilot studies with the commonly used clinical technique of tendon routing through drill holes with suture fixation12 have consistently demonstrated failure of the tendon-suture interface in this test system, necessitating the use of tendon clamps. Our goal was to evaluate the effect of strand number and position on the kinematics and stability of the elbow, rather than the absolute strength of the
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Figure 3 Maximum varus-valgus laxity. Division of the RCL and LUCL significantly decreased the varus-valgus stability of the elbow in both pronation and supination (P < .0001). Reconstruction of the LUCL with either a proximal single-strand, a distal single-strand, or a double-strand repair restored the varus-valgus rotational stability to that of the intact elbow (P > .05).
repairs. We used a provocative testing protocol, performing a PST and varus gravity loading to evaluate the ligament reconstructions at time zero. Given the more protective rehabilitation protocols typically used after reconstruction of the LUCL, it seems likely that grafts placed clinically are exposed to less initial loading than that used in this study. Reconstruction of the LUCL restored the rotational and varus stability of the elbow in this experimental model and supports the clinical practice of repair or reconstruction of the LUCL in patients who have lateral ligamentous insufficiency.12,13 O’Driscoll et al15 demonstrated that reconstruction of the LUCL with an “isometrically” placed, single heavy suture prevented PLRI when performing a PST. Our study supports the efficacy of the commonly used double-strand clinical reconstruction in controlling both varus and posterolateral rotational stability of the elbow. Furthermore, we have also demonstrated that a single-strand reconstruction fixed to the isometric point on the lateral epicondyle also restores elbow stability, at either of 2 sites of ulnar fixation. Reconstruction of the LUCL with a proximal or distal single-strand repair or with a double-strand repair reliably restored both varus and posterolateral rotational stability of the elbow in this in vitro testing system. With the sample size used, we could not detect a statistical difference between the 3 different repairs and the intact elbow. A power analysis demonstrated that a 3.5° difference in rotational laxity could be detected in this study with a β error of .8. This suggests that although small differences between the repairs and the intact
elbow may have been present, we had an adequate sample size to detect clinically relevant differences. A single-strand reconstruction may be useful in the clinical management of patients with PLRI because it simplifies the surgical procedure through the use of suture anchors or interference screws, as compared with the use of multiple bone tunnels, which make tendon routing and tensioning difficult. Fracture of the bone bridge between the tunnels, which occasionally occurs when a double-strand technique is used, can also be avoided. A single-strand reconstruction may also be useful in the situation of limited donor grafts, such as that which may occur when simultaneous medial and lateral collateral ligament reconstructions are performed. Although the strength of the LUCL has not been reported in the literature, on the basis of a previous mechanical study of the anterior band of the medial collateral ligament,21 it seems likely that a single-strand reconstruction of the LUCL should have sufficient strength. Multiple strands of the palmaris longus placed in a single-strand reconstruction could also be used if sufficient graft material was available and additional repair strength was desired, such as is commonly performed in reconstruction of the anterior cruciate ligament of the knee with hamstring tendon grafts. Clinical studies using a double-strand repair have reported good results.12,13 Similar studies are needed to evaluate the effectiveness of a single-strand reconstruction. We acknowledge Matt Danter, Matt Petrie, and Corrie Pillon, who provided technical assistance.
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REFERENCES 1. Borris LC, Lassen MR, Christensen CS. Elbow dislocation in children and adults. A long-term follow-up of conservatively treated patients. Acta Orthop Scand 1987;58:649-51. 2. Cohen MS, Hastings H. Rotatory instability of the elbow. The anatomy and role of the lateral stabilizers. J Bone Joint Surg Am 1997;79:225-31. 3. Doria A, Gil E, Delgado E, Alonso-Llames M. Recurrent dislocation of the elbow. Int Orthop 1990;14:41-5. 4. Dryer RF, Buckwalter JA, Sprague BL. Treatment of chronic elbow instability. Clin Orthop 1980;148:254-5. 5. Jacobs RL. Recurrent dislocation of the elbow joint. Clin Orthop 1971;74:151-4. 6. Josefsson O, Gentz CF, Johnell O, Wendeberg B. Surgical versus non-surgical treatment of ligamentous injuries following dislocation of the elbow joint. J Bone Joint Surg Am 1987;69:605-8. 7. King GJW, Zarzour ZDS, Rath DA, Dunning CE, Patterson SD, Johnson JA. Metallic radial head arthroplasty improves the valgus stability of the medial collateral deficient elbow. Clin Orthop 1999;368:114-25. 8. Lansinger O, Karlsson J, Korner L, Mare K. Dislocation of the elbow joint. Arch Orthop Trauma Surg 1984;102:183-6. 9. Milne AD, Chess DG, Johnson JA, King GJW. Accuracy of an electromagnetic tracking device: a study of the optimal operating range and metal interference. J Biomech 1996;29:791-3. 10. Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med 1983;11:315-9. 11. Morrey BF, An KN. Functional anatomy of the ligaments of the elbow. Clin Orthop 1985;201:84-90.
J Shoulder Elbow Surg January/February 2002
12. 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. 13. O’Driscoll SW, Bell DF, Morrey BF. Posterolateral rotatory instability of the elbow. J Bone Joint Surg Am 1991;73: 440-6. 14. O’Driscoll SW, Horii E, Morrey BF, Carmichael SW. Anatomy of the ulnar part of the lateral collateral ligament of the elbow. Clin Anat 1992;5:296-303. 15. O’Driscoll SW, Morrey BF, Korinek SL, An KN. The pathoanatomy and kinematics of posterolateral rotatory instability (pivot-shift) of the elbow [abstract]. Trans Orthop Res Soc 1990;15:6. 16. O’Driscoll SW, Morrey BF, Korinek SL, An KN. Elbow subluxation and dislocation. A spectrum of instability. Clin Orthop 1992;280:186-97. 17. Olsen BS, Søjbjerg JO, Dalstra M, Sneppen O. Kinematics of the lateral ligamentous constraints of the elbow joint. J Shoulder Elbow Surg 1996;5:333-41. 18. Olsen BS, Vaesel MT, Helmig P, Søjbjerg JO, Sneppen O. The lateral collateral ligament of the elbow joint: anatomy and kinematics. J Shoulder Elbow Surg 1996;5:103-12. 19. Olsen BS, Søjbjerg JO, Nielsen KK, Vaesel MT, Dalstra M, Sneppen O. Posterolateral elbow joint instability: the basic kinematics. J Shoulder Elbow Surg 1998;7:19-29. 20. Osborne G, Cotterill P. Recurrent dislocation of the elbow. J Bone Joint Surg Br 1966;48:340-6. 21. Regan WD, Korinek SL, Morrey BF, An KN. Biomechanical study of ligaments around the elbow joint. Clin Orthop 1991;271:170-9.
Because of a lack of biomechanical studies of lateral elbow ligament reconstruction in the literature, the initial stability afforded by 3 different techniques of lateral ulnar collateral ligament reconstruction was evaluated in 8 cadaveric elbows. The arm was mounted in a testing apparatus, and passive flexion was performed with the arm in varus and valgus orientations. A pivot shift test was performed with the arm in the vertical orientation. An electromagnetic tracking device was used to quantify motion pathways. After intact testing, each specimen underwent sectioning of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle. Reconstruction of the lateral ulnar collateral ligament was performed in a randomized sequence, consisting of proximal single-strand, distal single-strand, and double-strand tendon grafts. Division of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle caused a significant decrease in rotational stability when the pivot shift test was being performed (P < .0001). Varus-valgus stability also decreased after transection of the radial collateral and lateral ulnar collateral ligaments (P < .0001). Reconstruction of the lateral ulnar collateral ligament restored elbow stability to that of the intact state. There was no significant difference in stability between the single- and double-strand repair techniques (P > .05). This study demonstrates that both single- and double-strand reconstructions restore varus and posterolateral elbow stability and may be considered appropriate reconstructive From the Bioengineering Research Laboratory, Hand and Upper Limb Centre, St Joseph’s Health Centre, London, Ontario, Canada,a and Bond Clinic, Winter Haven, Fla.b Supported by funding from the Medical Research Council of Canada. Reprint requests: Graham J. W. King, MD, Hand and Upper Limb Centre, 268 Grosvenor St, London, Ontario, Canada N6A 4L6 (E-mail: [email protected]). Copyright © 2002 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2002/$35.00 + 0 32/1/118483 doi:10.1067/mse.2002.118483
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procedures in patients with symptomatic insufficiency of the lateral ligaments of the elbow. (J Shoulder Elbow Surg 2002;11:60-4.)
D
isruption of the lateral ligaments of the elbow at their humeral insertion usually occurs in patients with an elbow dislocation.6,16 Recurrent subluxation or dislocation is uncommon following closed reduction and early mobilization.1,6,8 Adequate ligamentous healing typically occurs with nonoperative treatment; however, patients occasionally will have with persistent symptoms of varus or posterolateral rotatory instability (PLRI) of the elbow (or both).3-5,13,17,20 The lateral ligaments of the elbow have been studied previously both anatomically2,11,14 and mechanically.10,12,16-19 The lateral ligaments consist of the radial collateral ligament (RCL), the annular ligament, and the lateral ulnar collateral ligament (LUCL).11,14 The LUCL has been shown to be an important stabilizer against PLRI.12-14,16 Reconstruction of the LUCL with a single heavy suture fixed to bone at the lateral epicondyle of the distal humerus and the crista supinatoris of the ulna has been shown to eliminate PLRI in the LUCL-deficient elbow.15 A double-strand tendon reconstruction has been recommended for the management of chronic PLRI, and good success has been documented in two clinical series.12,13 There have been no reported biomechanical studies that have documented the stabilizing effect of LUCL reconstruction with the use of tendon grafts. The purpose of this biomechanical study was to compare the stabilizing effect of 3 different methods of reconstruction of the LUCL. Our hypothesis was that reconstruction of the LUCL with any of these 3 techniques would be sufficient to restore elbow stability.
MATERIALS AND METHODS An in vitro testing apparatus incorporating a 2–degree of freedom hinge to allow testing of the upper extremity in varus, valgus, and vertical gravity-loading orientations was used.7 A humeral mounting clamp allowed rigid fixation of the mid shaft of the humerus, while providing sufficient clearance for unconstrained motion of the elbow and fore-
King et al
J Shoulder Elbow Surg Volume 11, Number 1
arm. Joint kinematic data were collected by means of an electromagnetic tracking system that measures the 3 translations and 3 rotations of one or more receivers relative to the transmitter position (Flock of Birds; Ascension Technology, Burlington, Vt). The transmitter and receiver were positioned so that they constantly remained within the optimum operational range of the tracking device throughout the arc of motion.9 The receiver was rigidly fixed to the distalmedial edge of the ulna with care taken to ensure that the receiver did not impinge during forearm rotation. With the humerus in varus and valgus orientations, passive elbow flexion was performed with the forearm held in both pronation and supination. An experienced surgeon performed a pivot shift test (PST)13 with the cadaveric arm in vertical orientation. Valgus, axial, and supination forces were applied to the forearm with the elbow in extension and maintained as the elbow was flexed. Although the magnitude of these forces was not quantified, they were felt to be similar to that used in the clinical application of this test. The reproducibility of the PST as quantified by repeating the test 5 times was ±0.25° for the intact elbow and ±2.6° for the ligament-deficient elbow. Eight fresh-frozen upper extremities (mean age, 79 ± 14 years; range, 58-99 years) were mounted in the testing apparatus. After intact testing, the interval between the anconeus and extensor carpi ulnaris was identified and the lateral elbow ligaments were exposed by careful elevation of the common extensor muscles anteriorly and the anconeus posteriorly. The RCL and LUCL were divided from their attachment on the lateral epicondyle to mimic the common site of disruption seen clinically.6 The fascia between the extensor carpi ulnaris and the anconeus was repaired at each stage of testing with No. 1 braided absorbable suture. The skin incision used to expose the elbow was closed during testing, and the specimens were kept moist by irrigation with 0.9% normal saline solution. Testing was performed at 23°C ± 2°C. Because the palmaris longus was variably present in the cadaveric specimens, reconstruction of the LUCL was performed with the use of flexor digitorum superficialis tendons harvested from both the long and ring fingers (Figure 1). One drill hole (approximately 4 mm) was placed in the ulna at the level of the crista supinatoris, and a second (approximately 4 mm) was placed at the level of the proximal aspect of the lesser sigmoid notch, as has been described in the literature.12 A suture was passed through the drill holes, and the isometric point on the lateral epicondyle was identified. A drill hole large enough to accommodate the tendon grafts was placed at the point of isometry. To facilitate testing, specially developed tendon clamps were used to secure the reconstructions. After fixation of the graft to the ulna, the elbow was reduced and the graft was pre-tensioned to 20 N with a spring scale for 5 minutes prior to humeral fixation. Proximal single-strand, distal single-strand, and double-strand LUCL reconstructions were performed in random order, and the testing protocol was repeated at each stage. Kinematic data were transformed into the anatomic coordinate systems of the humerus and ulna through use of bony landmarks.7 Ulnar motion was expressed relative to the anatomic axes of the distal humerus. At each angle of elbow flexion, the varus-valgus laxity of the ulna was calculated by determining the difference in varus angulation
61
A
B
C Figure 1 Ligament reconstructions. Flexor digitorum superficialis tendons were used to reconstruct the LUCL. Each tendon strand was passed through a bone tunnel and secured with a specialized tendon clamp after appropriate pre-tensioning. Double-strand (A), proximal single-strand (B), and distal single-strand (C) reconstructions were used.
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Figure 2 PST. Sectioning of the RCL and LUCL caused a significant increase in external rotation of the ulna when the PST was performed (P < .0001). There was no significant difference in ulnar rotation between the intact elbow and any of the ligament reconstructions (P > .05).
(with the arm in varus orientation) from valgus angulation (with the arm in valgus orientation). The largest varus-valgus laxity measured throughout the arc of passive elbow flexion was defined as the maximum varus-valgus laxity. While the surgeon was performing the PST with the humerus in vertical orientation, rotational instability of the elbow was quantified by internal-external rotation of the ulna. Statistical comparisons were performed with 2-way repeated-measures analyses of variance and Student-Newman-Keuls multiple comparison procedures, and α was set at .05.
RESULTS Division of the RCL and LUCL from the lateral epicondyle caused a significant increase in rotational instability when the PST was performed at all angles of elbow flexion (P < .0001) (Figure 2). Division of the RCL and LUCL significantly increased maximum varusvalgus laxity of the elbow with the forearm in both pronation and supination (P < .0001) (Figure 3). Reconstruction of the LUCL with either a proximal singlestrand, a distal single-strand, or a double-strand tendon repair restored the rotational and varus-valgus stability of the elbow (Figures 2 and 3). There was no significant difference between any of the repairs and the intact elbow when the PST was performed (P > .05) (Figure 2). There was no significant difference in maximum varus-valgus laxity among the repairs and the intact elbow (P > .05) (Figure 3). DISCUSSION In this study the RCL and LUCL were shown to be important restraints against both rotational and varus instability. Our findings are similar to those reported by other investigators.10,16-19 We chose to divide the RCL and LUCL at their humeral insertions, as lateral ligament disruptions are usually seen at the lateral epicondyle.6
Patients with PLRI typically do not have radioulnar instability and have a competent annular ligament. The complete lateral ligament transection used in this experimental model induced gross instability similar to that seen after an acute elbow dislocation.6,16 In patients with chronic posterolateral rotational instability, the instability is often subtle, making the clinical diagnosis difficult, possibly because of incomplete healing of the lateral ligaments. This suggests that our model represents somewhat of a worst-case scenario. Because of the order of sectioning used in this study, we were unable to confirm the importance of the anconeus fascia and common extensor origin on the stability of the elbow as previously demonstrated by Cohen and Hastings.2 The common extensor muscles and anconeus were elevated off the lateral epicondyle to expose the underlying lateral ligaments of the elbow. Although this fascial interval was routinely repaired at each step of the testing protocol to keep the underlying tissues moist, it could not be anatomically repaired back to the lateral epicondyle. Although we believe that the common extensor origin should be repaired following lateral elbow surgery and when acute elbow instability is being surgically managed, its importance could not be evaluated in this study. In this in vitro investigation, we used specialized tendon clamps rather than suture anchors or other fixation methods that would be used clinically. Pilot studies with the commonly used clinical technique of tendon routing through drill holes with suture fixation12 have consistently demonstrated failure of the tendon-suture interface in this test system, necessitating the use of tendon clamps. Our goal was to evaluate the effect of strand number and position on the kinematics and stability of the elbow, rather than the absolute strength of the
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Figure 3 Maximum varus-valgus laxity. Division of the RCL and LUCL significantly decreased the varus-valgus stability of the elbow in both pronation and supination (P < .0001). Reconstruction of the LUCL with either a proximal single-strand, a distal single-strand, or a double-strand repair restored the varus-valgus rotational stability to that of the intact elbow (P > .05).
repairs. We used a provocative testing protocol, performing a PST and varus gravity loading to evaluate the ligament reconstructions at time zero. Given the more protective rehabilitation protocols typically used after reconstruction of the LUCL, it seems likely that grafts placed clinically are exposed to less initial loading than that used in this study. Reconstruction of the LUCL restored the rotational and varus stability of the elbow in this experimental model and supports the clinical practice of repair or reconstruction of the LUCL in patients who have lateral ligamentous insufficiency.12,13 O’Driscoll et al15 demonstrated that reconstruction of the LUCL with an “isometrically” placed, single heavy suture prevented PLRI when performing a PST. Our study supports the efficacy of the commonly used double-strand clinical reconstruction in controlling both varus and posterolateral rotational stability of the elbow. Furthermore, we have also demonstrated that a single-strand reconstruction fixed to the isometric point on the lateral epicondyle also restores elbow stability, at either of 2 sites of ulnar fixation. Reconstruction of the LUCL with a proximal or distal single-strand repair or with a double-strand repair reliably restored both varus and posterolateral rotational stability of the elbow in this in vitro testing system. With the sample size used, we could not detect a statistical difference between the 3 different repairs and the intact elbow. A power analysis demonstrated that a 3.5° difference in rotational laxity could be detected in this study with a β error of .8. This suggests that although small differences between the repairs and the intact
elbow may have been present, we had an adequate sample size to detect clinically relevant differences. A single-strand reconstruction may be useful in the clinical management of patients with PLRI because it simplifies the surgical procedure through the use of suture anchors or interference screws, as compared with the use of multiple bone tunnels, which make tendon routing and tensioning difficult. Fracture of the bone bridge between the tunnels, which occasionally occurs when a double-strand technique is used, can also be avoided. A single-strand reconstruction may also be useful in the situation of limited donor grafts, such as that which may occur when simultaneous medial and lateral collateral ligament reconstructions are performed. Although the strength of the LUCL has not been reported in the literature, on the basis of a previous mechanical study of the anterior band of the medial collateral ligament,21 it seems likely that a single-strand reconstruction of the LUCL should have sufficient strength. Multiple strands of the palmaris longus placed in a single-strand reconstruction could also be used if sufficient graft material was available and additional repair strength was desired, such as is commonly performed in reconstruction of the anterior cruciate ligament of the knee with hamstring tendon grafts. Clinical studies using a double-strand repair have reported good results.12,13 Similar studies are needed to evaluate the effectiveness of a single-strand reconstruction. We acknowledge Matt Danter, Matt Petrie, and Corrie Pillon, who provided technical assistance.
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REFERENCES 1. Borris LC, Lassen MR, Christensen CS. Elbow dislocation in children and adults. A long-term follow-up of conservatively treated patients. Acta Orthop Scand 1987;58:649-51. 2. Cohen MS, Hastings H. Rotatory instability of the elbow. The anatomy and role of the lateral stabilizers. J Bone Joint Surg Am 1997;79:225-31. 3. Doria A, Gil E, Delgado E, Alonso-Llames M. Recurrent dislocation of the elbow. Int Orthop 1990;14:41-5. 4. Dryer RF, Buckwalter JA, Sprague BL. Treatment of chronic elbow instability. Clin Orthop 1980;148:254-5. 5. Jacobs RL. Recurrent dislocation of the elbow joint. Clin Orthop 1971;74:151-4. 6. Josefsson O, Gentz CF, Johnell O, Wendeberg B. Surgical versus non-surgical treatment of ligamentous injuries following dislocation of the elbow joint. J Bone Joint Surg Am 1987;69:605-8. 7. King GJW, Zarzour ZDS, Rath DA, Dunning CE, Patterson SD, Johnson JA. Metallic radial head arthroplasty improves the valgus stability of the medial collateral deficient elbow. Clin Orthop 1999;368:114-25. 8. Lansinger O, Karlsson J, Korner L, Mare K. Dislocation of the elbow joint. Arch Orthop Trauma Surg 1984;102:183-6. 9. Milne AD, Chess DG, Johnson JA, King GJW. Accuracy of an electromagnetic tracking device: a study of the optimal operating range and metal interference. J Biomech 1996;29:791-3. 10. Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med 1983;11:315-9. 11. Morrey BF, An KN. Functional anatomy of the ligaments of the elbow. Clin Orthop 1985;201:84-90.
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