- Email: [email protected]
Acromioclavicular reconstructions with hamstring tendon grafts: A comparative biomechanical study
Acromioclavicular reconstructions with hamstring tendon grafts: A comparative biomechanical study Sani Erak, FRACS,b Matthew H Pelletier, MBiomedE,a Kevin R Woods, FRACS,b Paul N Smith, FRACS,c and William R Walsh, PhD,a Sydney, New South Wales and Canberra, Australia
The surgical treatment of chronic acromioclavicular injuries remains controversial. There is increasing use of autogenous tendon grafts to perform these reconstructions. This study examined the mechanical properties of differing configurations of these grafts. Mechanical testing of acromioclavicular joint reconstructions was performed with a screw and soft tissue washer for tendon fixation, a simple loop of tendon tied to itself, and a bio-interference screw for tendon fixation, with and without a loop of nonabsorbable suture for reinforcement. The bio-interference screw fixation, with reinforcement by a loop of nonabsorbable suture, gave the highest load to failure among the group (502N 6 177), which was not significantly different from the intact ligaments (705 N 6 132), although it was significantly less stiff than the intact group (57.2 N/mm 6 12.6 and 109.7 N/mm 6 32.6, respectively). All other reconstructions had an ultimate load and stiffness which were significantly less than that of the intact specimens. (J Shoulder Elbow Surg 2008;17:772-778.)
Acromioclavicular joint injuries are common around
the shoulder, and most can be treated nonoperatively. Grade III injuries, according to Rockwood’s classification, are a controversial area, with a number of studies suggesting that they may function satisfactorily without operative intervention in most patients.16 However, a number of these injuries will continue to cause signif-
From the aSurgical & Orthopaedic Research Laboratory, Prince of Wales Hospital, Sydney, New South Wales; bCanberra Orthopaedic Group, Canberra; cAustralian National University Medical School, Canberra. This work study was performed with financial support from an educational grant from the Trauma and Orthopaedic Research Unit, The Canberra Hospital, Canberra, Australian Capital Territory, Australia. Arthrex Australia supplied the bio-intereference (Biotenodesis) screws and FibreWire suture used in this study. Reprint requests: Sani Erak, Canberra Orthopaedic Group, Clinical Services Building, John James Memorial Hospital, Strickland Crescent, Deakin, ACT, Australia 2600 (E-mail: sanierak@iinet. net.au). Copyright ª 2008 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2008/$34.00 doi:10.1016/j.jse.2008.01.143
772
icant pain and functional limitation. Grade IV to VI injuries generally require operative intervention.16 The optimum method of reconstruction of acromioclavicular joint injuries remains unclear. Some of the methods described for treating both acute and chronic injuries include coracoclavicular screws, suture anchors, coracoclavicular slings with sutures or tapes, transfer of the coracoacromial ligament with or without augmentation, dynamic muscle transfers, stabilization of the acromioclavicular joint with pins or with hook plates, and direct repair of the coracoclavicular ligaments.16 Recently, there has been increasing interest in the use of tendon grafts to reconstruct the torn coracoclavicular ligaments.1,6,7,11-13,17,19-21 A number of case reports on the use of this method exist,11,12 in addition to a number of biomechanical studies1,7,13,17 and 2 recent clinical series.19,21 Each of these has used a different method of reconstruction, including coracoclavicular slings through a drill hole in the clavicle,11,13 a coracoclavicular sling through drill holes in the clavicle and coracoid,12 and a number of anatomic reconstructions, where the drill holes were made in the clavicle approximating the normal insertion points of the coracoclavicular ligaments and ligaments passed in varying configurations.1,7,17 In the current study, we looked at the current method used by one of the authors, in addition to a simple loop of tendon, and a number of variations of an anatomic method described by Mazzocca, involving the use of bio-interference screws.15 MATERIALS AND METHODS Eleven shoulder specimens were harvested from fresh frozen cadavers. The mean age was 71 years (range, 61-80). The specimens were disarticulated at the glenohumeral and sternoclavicular joints and cleared of all soft tissue, except for the acromioclavicular joint and coracoclavicular ligaments. None of the shoulder specimens had identifiable disease at the acromioclavicular joint or coracoclavicular ligament complex. Semitendinosus and gracilis tendons were obtained from 11 separate cadavers using a tendon stripper and were prepared by removing remnant muscle tissue. Each tendon was whipstitched at both free ends. The doubled over tendon was then sized for diameter. Prior to testing, the specimens were thawed to room temperature. The body of the scapula was mounted in an open
J Shoulder Elbow Surg Volume 17, Number 5
Erak et al
773
Figure 1 Photograph of embedded specimen with jig attached.
top steel box filled with a low melting point (66 C), metallic alloy. The clavicle was secured to a custom-made jig with multiple loading points on either side of the coracoclavicular ligament complex or reconstruction. Care was taken to ensure that the scapula and clavicle were kept in appropriate anatomic alignment for the testing procedure (Figure 1). Testing was performed on a MTS 858 MiniBionix machine (MTS Corporation, Minneapolis, MN). The scapula box was secured to the load sensor and the clavicle and jig were attached to the actuator. Uniaxial tensile loading was then applied in a superior direction at a rate of 25 mm/min until specimen failure. Testing to failure was first performed on 8 intact shoulder specimens to document the structural properties of the intact coracoclavicular ligament complex. The coracoclavicular ligament complex was sectioned on the remaining 3 specimens. The acromioclavicular joint was sectioned on all specimens prior to testing. After failure, reconstructions were performed with either gracilis or semitendinosus tendons, which were randomly allocated among the reconstructions. Specimens were kept appropriately hydrated during testing. Each reconstruction was mounted on the testing jig and loaded to failure, as described for the intact state. The failure mode was characterized. Multiple reconstructions were performed on each specimen (Figures 2-6).
Screw and soft tissue washer (SSTW) reconstruction (n ¼ 9) A drill hole was made in the lateral portion of the clavicle of sufficient diameter to allow free passage of the graft. The tendon was looped through this hole, and then both free ends were passed underneath the coracoid and back up to the clavicle on the medial side. One strand was passed from the anterior side of the clavicle and the other end from the posterior side to the superior aspect of the clavicle.
Figure 2 SSTW Reconstruction. The tendon is passed through a lateral drill hole, and looped over the anterior aspect of the clavicle. The graft is the looped underneath the coracoid, and one strand brought anteriorly over the clavicle, and the other strand posteriorly over the clavicle. The 2 graft ends are then secured to the superior aspect of the clavicle with a 4.5 mm cortical screw and soft tissue washer.
The ends of the tendon were then fixed with a 4.5 mm cortical screw with a soft tissue washer, after predrilling with a 3.2 mm drill through both cortices.
MA screw lateral (n ¼ 4) (¼’’Modified Anatomic,’’ named for modification of the anatomic technique described by Mazzocca et al18) A drill hole was made in the lateral aspect of the clavicle, close to the normal insertion point of the trapezoid ligament. Another drill hole was placed in the postero-medial aspect of the clavicle close to the insertion of the conoid ligament. The diameter of the drill hole was appropriate for graft size to allow the free passage of the loop of the graft. One limb of the graft was passed through this hole and the other behind the clavicle. Both ends of the graft were then passed underneath the coracoid and through the lateral drill hole in the clavicle from an inferior to superior direction. A BioTenodenesis screw (Arthrex Inc, Naples, FL) was then used to fix the graft after applying tension to it with the acromioclavicular joint held in an anatomical position. The size of the drill hole in the lateral aspect of the clavicle was made in accordance with the technique guide for the BioTenodenesis screws.18
MMA (n¼4) (¼’’Modification of the Modified Anatomic’’) This was similar to MA screw lateral, except that the 2 free ends of the tendon were passed anterior and posterior
774
Erak et al
Figure 3 Modified anatomic (MA) screw lateral. The tendon graft is looped through a drill hole in the postero-medial aspect of the clavicle, close to the insertion point of the native conoid ligament. The two strands of the graft are looped underneath the coracoid, and brought up from inferior to superior through a lateral drill hole in the clavicle. Here, the graft is fixed to the clavicle with a BioTenodesis screw. This is the same configuration used in the FibreWire group, except with the addition of a loop of FibreWire through the clavicular drill holes, and underneath the coracoid.
to the clavicle, then passed through the lateral drill hole from superior to inferior and secured with a BioTenodesis screw, as described above.
MA screw medial (n¼4) In an attempt to improve the pullout strength of the fixed end of the reconstruction, the directions of the closed loop of tendon and fixed end were reversed. The closed loop of tendon was now passed through the hole in the lateral clavicle and looped over the anterior aspect. The free ends of the tendon were passed under the coracoid to the medial aspect of the clavicle and passed through a hole from inferior to superior. After reduction of the acromioclavicular joint to an anatomic alignment, the graft was fixed with a BioTenodesis screw passed from the superior aspect of the clavicle.
Simple loop (n ¼ 3) As described by Lee et al,16 the graft was passed around the coracoid and through a drill hole in the clavicle as a single strand. The graft was secured to itself by tying the tendon ends in a double surgical knot, with additional sutures using a heavy nonabsorbable suture material adjacent to the knot.
FiberWire plus MA screw lateral group (‘‘Fibrewire group,’’ n ¼ 4) This replicates the MA screw lateral group, except that, in addition to the tendon graft, a loop of 2-FibreWire
J Shoulder Elbow Surg September/October 2008
Figure 4 Modification of modified anatomic (MMA). The graft is looped through the postero-medial drill hole as before, and both strands are looped underneath the coracoid. The 2 strands are brought up separately anterior and posterior to the clavicle, and then passed from superior to inferior through the lateral drill hole in the clavicle. A BioTenodesis screw fixes the graft in this position.
(Arthrex Inc, Naples, FL) was passed alongside the graft through the medial drill hole, under the coracoid, through the inner core of the BioTenodesis screw laterally, and then tied in a surgical knot. Results from the individual tests were analyzed using Microsoft Excel (Microsoft Corp, Redmond, WA) to construct load-displacement curves and generate results for load to failure, elongation at failure, and stiffness. One way analysis of variance was used to determine if there was any difference among the groups, followed by a post hoc multiple comparison test (Duncan’s multiple range test) to determine which groups were significantly different. A student t test was used to compare results between 2 groups. Statistical significance was set at .05.
RESULTS The results of the mechanical testing for each group of reconstruction are presented in Table I. The FiberWire group had the highest load to failure among the reconstructions, and the MA screw lateral group the lowest failure to load. All reconstructed groups were significantly lower compared to the intact state, except for the FiberWire group (P < .05). The MA screw lateral and MA screw medial combined group had a lower load to failure (309N 6108) than the FibreWire group (P ¼ .039). The FiberWire group had the highest stiffness and was significantly more stiff than the loop and MMA
Erak et al
J Shoulder Elbow Surg Volume 17, Number 5
Figure 5 Modified anatomic (MA) screw medial. The graft is looped through a lateral drill hole in the clavicle, underneath the coracoid, and brought up from inferior to superior on the medial aspect of the clavicle. Here it is fixed with a BioTenodesis screw.
groups (P < .05). The loop and MMA groups had the lowest stiffness. All reconstructions were significantly different from the intact ligaments (P < .05). The MA lateral, MA medial, and FiberWire groups had the lowest elongation to failure among the reconstructions, while the loop and MMA groups had the highest. The loop and MMA groups were significantly different from the MA lateral, MA medial, FiberWire, SSTW, and intact groups (P < .05). The intact group was only statistically different from the loop and MMA groups (P < .05). Intact ligaments failed by rupture of the ligament’s midsubstance (n ¼ 5), avulsion of the insertion of the ligaments from the coracoid (n ¼ 1) or clavicle (n ¼ 1), or by fracture of the coracoid (n ¼ 1). Although there was 1 coracoid fracture, the SSTW reconstructions failed by failure of the tendons from under the soft tissue washer. The MA screw lateral and MA screw medial groups failed at the insertion of the tendon to bone around the BioTenodesis screw. The MMA group failed similarly at the insertion site of the tendon to the bone around the BioTenodesis screw, although there was 1 fractured coracoid in this group. Two of the loop reconstructions failed by fracturing the coracoid and the 3rd by failure of the knot. Three of the 4 FiberWire reconstructions failed by fracture of the coracoid, and 1 failed by breakage of the FiberWire and pullout of the tendons from the fixation point on the clavicle.
775
Figure 6 Simple loop. The graft is passed through a drill hole directly above the coracoid, and the graft looped through this hole, and underneath the coracoid. The graft is used as a single strand, and the free ends are tied to each other in a surgical knot, and the knot reinforced with heavy nonabsorbable sutures.
Overall, 14 gracilis tendons and 14 semitendinosus tendons were used in the reconstructions. There was no statistical difference for any properties investigated between the type of tendon used (P > .05). DISCUSSION Use of autogenous tissue, such as hamstring grafts or transfer of the coracoacromial ligament, in reconstruction of the acromioclavicular joint is appealing, as it may offer a biological solution to deficiency of the coracoclavicular ligaments. While transfer of the coracoacromial ligament remains a widely used technique, some of the potential disadvantages include relatively poor biomechanical performance when used without augmentation9,13 and the loss of the normal stabilizing function of that ligament.14 In the results published by Harris et al,9 the coracoacromial ligament transfer failed at 145 N and had a relatively low stiffness (8 N/mm). This low failure load has also been reported by other authors.3,13 The results of this reconstruction appear to fall short of those achieved by any of the hamstring reconstruction groups. In that study, the coracoacromial ligament transfer was not augmented by an additional cerclage suture. Biomechanical studies, which have looked at coracoacromial ligament transfer with augmentation, do show improved load to failure results.7,17 Other
776
Erak et al
J Shoulder Elbow Surg September/October 2008
Table I Structural properties of the coracoclavicular reconstruction (means 6 SD) Method
Tensile strength (N)
Tensile stiffness (N/mm)
SSTW reconstruction (n ¼ 9) MA screw lateral (n ¼ 4) MA screw medial (n ¼ 4) MMA (n ¼ 4) Simple loop (n ¼ 3) FibreWire (n ¼ 4) Intact (n ¼ 8)
379 (6 113)a 289 (6 65) a
36.5 (6 8.2) a 40.6 (6 18.2) a
15.0 (6 5.2) 10.5 (6 3.8)
328 (6 149) a
45.2 (6 21.7) a
11.7 (6 3.1)
320 (6 168) a 366 (6 208) a
22.6 (6 12.6) a,b 19.7 (6 9.2) a,b
23.0 (6 2.2) a,b,c 27.9 (6 10.6) a,b,c
502 (6177) 705 (6132)
57.2 (6 12.6) a 109.7 (6 32.6)
Elongation at failure (mm)
12.0 (6 2.7) 11.7 (6 3.2)
SSTW, screw and soft tissue washer; MA, modified anatomic; MMA, modified modified anatomic. a Significantly different from intact coracoclavicular complex at P<0.05. b Significantly different from FibreWire group at P<0.05. c Significantly different from SSTW reconstruction, MA screw lateral, MA screw medial groups at P<0.05.
reconstructions of the acromioclavicular joint, which do not utilize autogenous tissue, either rely on primary healing of the coracoclavicular ligaments, which is unlikely to occur in chronic dislocations, or on prosthetic material to maintain reduction. The latter could lead to problems with fatigue of the material over time or of the coracoid, in addition to the possible disadvantage of having prosthetic material in situ. Coracoclavicular screws, especially if used with bicortical fixation on the coracoid, can have impressive structural properties but do not offer a lasting biologic solution for the reconstruction; can over-constrain the acromioclavicular joint;10 routinely require removal, and are associated with a number of complications.5,8 In testing of the intact ligaments, load to failure in our study was higher than that noted by Harris et al9 (705 N vs 500 N) but more closely approximates that in other studies.7,13,18 The reason for this is not clear but may be related to less initial dissection around the coracoclavicular ligament complex. The values obtained for stiffness and elongation at failure are similar between the 2 studies. Among the reconstructions, the FiberWire group performed the best. The load to failure was highest of the reconstructions, although not statistically reaching significance unless directly compared to the combined MA screw lateral and MA screw medial groups. This was not unexpected, as the weak point in any of the hamstring reconstructions is predominantly the fixation method of the tendon to bone. The addition of a reinforcing suture with strong mechanical properties, such as FiberWire, may protect the tendon/bone interface. The stiffness of the FiberWire reconstruction was significantly different than that of the MMA and loop groups, as was the elongation to failure. This reconstruction is essentially a modification of that described by Mazzocca,15 which places the insertion points of the tendon graft on the clavicle in more anatomically correct positions. In our modifica-
tion, we used a closed loop on the more medial aspect of the reconstruction, which was thought to help place the insertion point more posteriorly, as the insertion of the conoid ligament is on the posterior aspect of the clavicle. A closed loop here also eliminates the need for a screw in this position and hence a potential weak point in fixation of the graft. The other modification to the described technique is that the tendon graft is doubled over rather than used as a single strand. It is unclear from the present study to what degree the addition of the tendon graft added to the mechanical properties of the FiberWire plus tendon group. The mechanical properties may have only reflected that of the FiberWire, with the tendon not being loaded in the test. There was no clear discernable second point of failure in the testing of the specimens used for the FiberWire group that may have been attributed to failure of the tendon, as the coracoid fractured in 3 specimens. In the remaining specimen, there was rapid failure of the tendon to bone interface after failure of the FiberWire suture. Whether the BioTenodesis screw was placed lateral or medial in the modified anatomic reconstructions (without FibreWire) did not appear to make a difference to the load to failure of these reconstructions. It was hypothesized that the screw may have better fixation in the more medial bone. As placing the screw laterally and the closed loop medially and posteriorly more closely replicates the normal anatomy, we would recommend this configuration be used for further testing or development. There was no difference in stiffness or elongation to failure. The MMA group was an attempt to alter the line of force on the tendon, so that it was not being pulled out from directly beneath the clavicle. While load to failure did not improve, there appeared to be a decrease in the stiffness of the construct and an increase in the elongation at failure, the latter of which was statistically significant compared to the MA screw lateral
Erak et al
J Shoulder Elbow Surg Volume 17, Number 5
and MA screw medial groups (in addition to the SSTW and FibreWire groups). We would not recommend further testing or development of this type of configuration. Lee et al13 reported failure loads for a simple loop of tendon tied into a knot of approximately 500 N for the gracilis and 700 N for the semitendinosus, which is higher than that which we could achieve in this study. Two of our 3 loop configurations fractured the coracoid, so it is possible that, after repeat testing on our specimens and in elderly specimens, the coracoid was weakened and failed earlier than in their study. Of their tendon reconstructions, it appears 26 of their 28 failed in the midsubstance of the tendon and only 2 fractured the coracoid. In our testing, the stiffness of the loop reconstruction was significantly less that that of the FiberWire group, and elongation to failure was higher than all of the other reconstructions, except for the MMA group. The results for stiffness were less that what was reported by Lee et al13 (19.7 N/mm vs approx 40 N/mm). It appears that we were unable to replicate their results achieved for this reconstruction, which may be related to technical factors, such as the strength of the knot or how many reinforcing sutures are placed in around the knot. The same group has published a recent clinical series with excellent results utilizing the loop configuration of a tendon graft and also incorporating a mersilene tape cerclage suture.19 Our numbers in this group were low, but we did not persevere with testing of this configuration because of the low stiffness and high elongation at failure of this reconstruction when performed in our hands. The SSTW reconstruction performed satisfactorily overall in terms of load to failure, stiffness, and elongation at failure. However, the concern with this type of reconstruction is that the fixation points of the graft onto the clavicle are in nonanatomic positions, thus leading to evaluation of more anatomic reconstruction configurations. Furthermore, the screw can be prominent in some patients and require a second procedure to remove it. In our study, there was no difference in mechanical properties of the reconstructions using either gracilis or semitendinosus. Lee et al13 reported similar results among the use of gracilis, semitendinosus, and long toe extensor tendon grafts. The importance of antero-posterior stability is becoming increasingly recognized. The acromioclavicular joint capsule is a significant stabilizer of the acromioclavicular joint, particularly in an antero-posterior plane.2,4 In higher grade injuries of the acromioclavicular joint, where this stabilizing influence is lost, it may become important to reproduce the anatomy of the native coracoclavicular ligaments more closely, to reduce antero-posterior laxity. Our study did not address this stability plane, and future work with the Fi-
777
berWire group or modified anatomic reconstructions would do well to investigate this issue. There were a number of limitations to this present study. Testing was performed in a superior plane and not in the antero-posterior direction. Noncyclic testing was performed, so that no information is given about the creep behavior of the reconstructions. Multiple tests were performed on most specimens and alterations in the position of fixation points of the graft to the clavicle may have affected results. The effects on the multiple tests and testing failure of the intact state on 8 of the specimens also may have had an effect on results, although it has been shown that repeated testing of the scapula-clavicle complex does not change the properties of the coracoid.1 Fracture of the coracoid, as a failure mechanism, may be more common in our testing, as the specimens used were derived from an older population, where bone density may be reduced compared to a younger population who normally undergo these types of reconstructions. A separate FiberWire suture alone group (without the addition of a tendon graft) would have documented to what degree the properties of the combined suture plus tendon group could solely be attributed to the FiberWire suture. Despite these limitations, we believe the present study does show that the modified anatomic reconstructions may hold a place in reconstructions of the acromioclavicular joint. They are certainly appealing from a biologic point of view in providing autogenous tissue to replace or augment the coracoclavicular ligaments. The addition of a loop of FiberWire appears to give an advantage in ultimate load and stiffness of the reconstruction. This may protect the graft during a revascularization phase in situ. In the acute phase, reconstructions performed without suture reinforcement have mechanical properties inferior to that of the intact coracoclavicular complex and should be protected. Recent clinical series utilizing tendon grafts have incorporated a reinforcing suture or wire in their constructs.19,21 Further work to delineate the antero-posterior laxity of these reconstructions—particularly comparing them to methods where the graft is fixed to or passed through a drill hole in the coracoid, rather than looped underneath it—would be warranted. REFERENCES
1. Costic RS, Labriola JE, Rodosky MW, et al. Biomechanical rationale for development of anatomical reconstructions of coracoclavicular ligaments after complete acromioclavicular joint dislocations. Am J Sports Med 2004;32:1929-36. 2. Debski RE, Parsons IMt, Woo SL, et al. Effect of capsular injury on acromioclavicular joint mechanics. J Bone Joint Surg Am 2001; 83-A:1344-51. 3. Deshmukh AV, Wilson DR, Zilberfarb JL, et al. Stability of acromioclavicular joint reconstruction: biomechanical testing of various
778
4. 5. 6. 7.
8. 9. 10. 11.
Erak et al
surgical techniques in a cadaveric model. Am J Sports Med 2004; 32:1492-8. Fukuda K, Craig EV, An KN, et al. Biomechanical study of the ligamentous system of the acromioclavicular joint. J Bone Joint Surg Am 1986;68:434-40. Galpin RD, Hawkins RJ, Grainger RW. A comparative analysis of operative versus nonoperative treatment of grade III acromioclavicular separations. Clin Orthop Relat Res 1985;193:150-5. Gonzalez R, Damacen H, Nyland J, et al. Acromioclavicular joint reconstruction using peroneus brevis tendon allograft. Arthroscopy 2007;23:788. e1-4. Grutter PW, Petersen SA. Anatomical acromioclavicular ligament reconstruction: a biomechanical comparison of reconstructive techniques of the acromioclavicular joint. Am J Sports Med 2005;33:1723-8. Guy DK, Wirth MA, Griffin JL, et al. Reconstruction of chronic and complete dislocations of the acromioclavicular joint. Clin Orthop Relat Res 1998;347:138-49. Harris RI, Wallace AL, Harper GD, et al. Structural properties of the intact and the reconstructed coracoclavicular ligament complex. Am J Sports Med 2000;28:103-8. Jari R, Costic RS, Rodosky MW, et al. Biomechanical function of surgical procedures for acromioclavicular joint dislocations. Arthroscopy 2004;20:237-45. Jones HP, Lemos MJ, Schepsis AA. Salvage of failed acromioclavicular joint reconstruction using autogenous semitendinosus tendon from the knee. Surgical technique and case report. Am J Sports Med 2001;29:234-7.
J Shoulder Elbow Surg September/October 2008
12. LaPrade RF, Hilger B. Coracoclavicular ligament reconstruction using a semitendinosus graft for failed acromioclavicular separation surgery. Arthroscopy 2005;21:1277. 13. Lee SJ, Nicholas SJ, Akizuki KH, et al. Reconstruction of the coracoclavicular ligaments with tendon grafts: a comparative biomechanical study. Am J Sports Med 2003;31:648-55. 14. Lee TQ, Black AD, Tibone JE, et al. Release of the coracoacromial ligament can lead to glenohumeral laxity: a biomechanical study. J Shoulder Elbow Surg 2001;10:68-72. 15. Mazzocca AD. Anatomic coracoclavicular reconstruction – surgical technique. Arthrex Product Literature 2005. 16. Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med 2007;35: 316-29. 17. Mazzocca AD, Santangelo SA, Johnson ST, et al. A biomechanical evaluation of an anatomical coracoclavicular ligament reconstruction. Am J Sports Med 2006;34:236-46. 18. Motamedi AR, Blevins FT, Willis MC, et al. Biomechanics of the coracoclavicular ligament complex and augmentations used in its repair and reconstruction. Am J Sports Med 2000;28:380-4. 19. Nicholas SJ, Lee SJ, Mullaney MJ, et al. Clinical outcomes of coracoclavicular ligament reconstructions using tendon grafts. Am J Sports Med 2007;35:1912-7. 20. Pennington WT, Hergan DJ, Bartz BA. Arthroscopic coracoclavicular ligament reconstruction using biologic and suture fixation. Arthroscopy 2007;23:785. e1-7. 21. Tauber M, Eppel M, Resch H. Acromioclavicular reconstruction using autogenous semitendinosus tendon graft: results of revision surgery in chronic cases. J Shoulder Elbow Surg 2007;16:429-33.
The surgical treatment of chronic acromioclavicular injuries remains controversial. There is increasing use of autogenous tendon grafts to perform these reconstructions. This study examined the mechanical properties of differing configurations of these grafts. Mechanical testing of acromioclavicular joint reconstructions was performed with a screw and soft tissue washer for tendon fixation, a simple loop of tendon tied to itself, and a bio-interference screw for tendon fixation, with and without a loop of nonabsorbable suture for reinforcement. The bio-interference screw fixation, with reinforcement by a loop of nonabsorbable suture, gave the highest load to failure among the group (502N 6 177), which was not significantly different from the intact ligaments (705 N 6 132), although it was significantly less stiff than the intact group (57.2 N/mm 6 12.6 and 109.7 N/mm 6 32.6, respectively). All other reconstructions had an ultimate load and stiffness which were significantly less than that of the intact specimens. (J Shoulder Elbow Surg 2008;17:772-778.)
Acromioclavicular joint injuries are common around
the shoulder, and most can be treated nonoperatively. Grade III injuries, according to Rockwood’s classification, are a controversial area, with a number of studies suggesting that they may function satisfactorily without operative intervention in most patients.16 However, a number of these injuries will continue to cause signif-
From the aSurgical & Orthopaedic Research Laboratory, Prince of Wales Hospital, Sydney, New South Wales; bCanberra Orthopaedic Group, Canberra; cAustralian National University Medical School, Canberra. This work study was performed with financial support from an educational grant from the Trauma and Orthopaedic Research Unit, The Canberra Hospital, Canberra, Australian Capital Territory, Australia. Arthrex Australia supplied the bio-intereference (Biotenodesis) screws and FibreWire suture used in this study. Reprint requests: Sani Erak, Canberra Orthopaedic Group, Clinical Services Building, John James Memorial Hospital, Strickland Crescent, Deakin, ACT, Australia 2600 (E-mail: sanierak@iinet. net.au). Copyright ª 2008 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2008/$34.00 doi:10.1016/j.jse.2008.01.143
772
icant pain and functional limitation. Grade IV to VI injuries generally require operative intervention.16 The optimum method of reconstruction of acromioclavicular joint injuries remains unclear. Some of the methods described for treating both acute and chronic injuries include coracoclavicular screws, suture anchors, coracoclavicular slings with sutures or tapes, transfer of the coracoacromial ligament with or without augmentation, dynamic muscle transfers, stabilization of the acromioclavicular joint with pins or with hook plates, and direct repair of the coracoclavicular ligaments.16 Recently, there has been increasing interest in the use of tendon grafts to reconstruct the torn coracoclavicular ligaments.1,6,7,11-13,17,19-21 A number of case reports on the use of this method exist,11,12 in addition to a number of biomechanical studies1,7,13,17 and 2 recent clinical series.19,21 Each of these has used a different method of reconstruction, including coracoclavicular slings through a drill hole in the clavicle,11,13 a coracoclavicular sling through drill holes in the clavicle and coracoid,12 and a number of anatomic reconstructions, where the drill holes were made in the clavicle approximating the normal insertion points of the coracoclavicular ligaments and ligaments passed in varying configurations.1,7,17 In the current study, we looked at the current method used by one of the authors, in addition to a simple loop of tendon, and a number of variations of an anatomic method described by Mazzocca, involving the use of bio-interference screws.15 MATERIALS AND METHODS Eleven shoulder specimens were harvested from fresh frozen cadavers. The mean age was 71 years (range, 61-80). The specimens were disarticulated at the glenohumeral and sternoclavicular joints and cleared of all soft tissue, except for the acromioclavicular joint and coracoclavicular ligaments. None of the shoulder specimens had identifiable disease at the acromioclavicular joint or coracoclavicular ligament complex. Semitendinosus and gracilis tendons were obtained from 11 separate cadavers using a tendon stripper and were prepared by removing remnant muscle tissue. Each tendon was whipstitched at both free ends. The doubled over tendon was then sized for diameter. Prior to testing, the specimens were thawed to room temperature. The body of the scapula was mounted in an open
J Shoulder Elbow Surg Volume 17, Number 5
Erak et al
773
Figure 1 Photograph of embedded specimen with jig attached.
top steel box filled with a low melting point (66 C), metallic alloy. The clavicle was secured to a custom-made jig with multiple loading points on either side of the coracoclavicular ligament complex or reconstruction. Care was taken to ensure that the scapula and clavicle were kept in appropriate anatomic alignment for the testing procedure (Figure 1). Testing was performed on a MTS 858 MiniBionix machine (MTS Corporation, Minneapolis, MN). The scapula box was secured to the load sensor and the clavicle and jig were attached to the actuator. Uniaxial tensile loading was then applied in a superior direction at a rate of 25 mm/min until specimen failure. Testing to failure was first performed on 8 intact shoulder specimens to document the structural properties of the intact coracoclavicular ligament complex. The coracoclavicular ligament complex was sectioned on the remaining 3 specimens. The acromioclavicular joint was sectioned on all specimens prior to testing. After failure, reconstructions were performed with either gracilis or semitendinosus tendons, which were randomly allocated among the reconstructions. Specimens were kept appropriately hydrated during testing. Each reconstruction was mounted on the testing jig and loaded to failure, as described for the intact state. The failure mode was characterized. Multiple reconstructions were performed on each specimen (Figures 2-6).
Screw and soft tissue washer (SSTW) reconstruction (n ¼ 9) A drill hole was made in the lateral portion of the clavicle of sufficient diameter to allow free passage of the graft. The tendon was looped through this hole, and then both free ends were passed underneath the coracoid and back up to the clavicle on the medial side. One strand was passed from the anterior side of the clavicle and the other end from the posterior side to the superior aspect of the clavicle.
Figure 2 SSTW Reconstruction. The tendon is passed through a lateral drill hole, and looped over the anterior aspect of the clavicle. The graft is the looped underneath the coracoid, and one strand brought anteriorly over the clavicle, and the other strand posteriorly over the clavicle. The 2 graft ends are then secured to the superior aspect of the clavicle with a 4.5 mm cortical screw and soft tissue washer.
The ends of the tendon were then fixed with a 4.5 mm cortical screw with a soft tissue washer, after predrilling with a 3.2 mm drill through both cortices.
MA screw lateral (n ¼ 4) (¼’’Modified Anatomic,’’ named for modification of the anatomic technique described by Mazzocca et al18) A drill hole was made in the lateral aspect of the clavicle, close to the normal insertion point of the trapezoid ligament. Another drill hole was placed in the postero-medial aspect of the clavicle close to the insertion of the conoid ligament. The diameter of the drill hole was appropriate for graft size to allow the free passage of the loop of the graft. One limb of the graft was passed through this hole and the other behind the clavicle. Both ends of the graft were then passed underneath the coracoid and through the lateral drill hole in the clavicle from an inferior to superior direction. A BioTenodenesis screw (Arthrex Inc, Naples, FL) was then used to fix the graft after applying tension to it with the acromioclavicular joint held in an anatomical position. The size of the drill hole in the lateral aspect of the clavicle was made in accordance with the technique guide for the BioTenodenesis screws.18
MMA (n¼4) (¼’’Modification of the Modified Anatomic’’) This was similar to MA screw lateral, except that the 2 free ends of the tendon were passed anterior and posterior
774
Erak et al
Figure 3 Modified anatomic (MA) screw lateral. The tendon graft is looped through a drill hole in the postero-medial aspect of the clavicle, close to the insertion point of the native conoid ligament. The two strands of the graft are looped underneath the coracoid, and brought up from inferior to superior through a lateral drill hole in the clavicle. Here, the graft is fixed to the clavicle with a BioTenodesis screw. This is the same configuration used in the FibreWire group, except with the addition of a loop of FibreWire through the clavicular drill holes, and underneath the coracoid.
to the clavicle, then passed through the lateral drill hole from superior to inferior and secured with a BioTenodesis screw, as described above.
MA screw medial (n¼4) In an attempt to improve the pullout strength of the fixed end of the reconstruction, the directions of the closed loop of tendon and fixed end were reversed. The closed loop of tendon was now passed through the hole in the lateral clavicle and looped over the anterior aspect. The free ends of the tendon were passed under the coracoid to the medial aspect of the clavicle and passed through a hole from inferior to superior. After reduction of the acromioclavicular joint to an anatomic alignment, the graft was fixed with a BioTenodesis screw passed from the superior aspect of the clavicle.
Simple loop (n ¼ 3) As described by Lee et al,16 the graft was passed around the coracoid and through a drill hole in the clavicle as a single strand. The graft was secured to itself by tying the tendon ends in a double surgical knot, with additional sutures using a heavy nonabsorbable suture material adjacent to the knot.
FiberWire plus MA screw lateral group (‘‘Fibrewire group,’’ n ¼ 4) This replicates the MA screw lateral group, except that, in addition to the tendon graft, a loop of 2-FibreWire
J Shoulder Elbow Surg September/October 2008
Figure 4 Modification of modified anatomic (MMA). The graft is looped through the postero-medial drill hole as before, and both strands are looped underneath the coracoid. The 2 strands are brought up separately anterior and posterior to the clavicle, and then passed from superior to inferior through the lateral drill hole in the clavicle. A BioTenodesis screw fixes the graft in this position.
(Arthrex Inc, Naples, FL) was passed alongside the graft through the medial drill hole, under the coracoid, through the inner core of the BioTenodesis screw laterally, and then tied in a surgical knot. Results from the individual tests were analyzed using Microsoft Excel (Microsoft Corp, Redmond, WA) to construct load-displacement curves and generate results for load to failure, elongation at failure, and stiffness. One way analysis of variance was used to determine if there was any difference among the groups, followed by a post hoc multiple comparison test (Duncan’s multiple range test) to determine which groups were significantly different. A student t test was used to compare results between 2 groups. Statistical significance was set at .05.
RESULTS The results of the mechanical testing for each group of reconstruction are presented in Table I. The FiberWire group had the highest load to failure among the reconstructions, and the MA screw lateral group the lowest failure to load. All reconstructed groups were significantly lower compared to the intact state, except for the FiberWire group (P < .05). The MA screw lateral and MA screw medial combined group had a lower load to failure (309N 6108) than the FibreWire group (P ¼ .039). The FiberWire group had the highest stiffness and was significantly more stiff than the loop and MMA
Erak et al
J Shoulder Elbow Surg Volume 17, Number 5
Figure 5 Modified anatomic (MA) screw medial. The graft is looped through a lateral drill hole in the clavicle, underneath the coracoid, and brought up from inferior to superior on the medial aspect of the clavicle. Here it is fixed with a BioTenodesis screw.
groups (P < .05). The loop and MMA groups had the lowest stiffness. All reconstructions were significantly different from the intact ligaments (P < .05). The MA lateral, MA medial, and FiberWire groups had the lowest elongation to failure among the reconstructions, while the loop and MMA groups had the highest. The loop and MMA groups were significantly different from the MA lateral, MA medial, FiberWire, SSTW, and intact groups (P < .05). The intact group was only statistically different from the loop and MMA groups (P < .05). Intact ligaments failed by rupture of the ligament’s midsubstance (n ¼ 5), avulsion of the insertion of the ligaments from the coracoid (n ¼ 1) or clavicle (n ¼ 1), or by fracture of the coracoid (n ¼ 1). Although there was 1 coracoid fracture, the SSTW reconstructions failed by failure of the tendons from under the soft tissue washer. The MA screw lateral and MA screw medial groups failed at the insertion of the tendon to bone around the BioTenodesis screw. The MMA group failed similarly at the insertion site of the tendon to the bone around the BioTenodesis screw, although there was 1 fractured coracoid in this group. Two of the loop reconstructions failed by fracturing the coracoid and the 3rd by failure of the knot. Three of the 4 FiberWire reconstructions failed by fracture of the coracoid, and 1 failed by breakage of the FiberWire and pullout of the tendons from the fixation point on the clavicle.
775
Figure 6 Simple loop. The graft is passed through a drill hole directly above the coracoid, and the graft looped through this hole, and underneath the coracoid. The graft is used as a single strand, and the free ends are tied to each other in a surgical knot, and the knot reinforced with heavy nonabsorbable sutures.
Overall, 14 gracilis tendons and 14 semitendinosus tendons were used in the reconstructions. There was no statistical difference for any properties investigated between the type of tendon used (P > .05). DISCUSSION Use of autogenous tissue, such as hamstring grafts or transfer of the coracoacromial ligament, in reconstruction of the acromioclavicular joint is appealing, as it may offer a biological solution to deficiency of the coracoclavicular ligaments. While transfer of the coracoacromial ligament remains a widely used technique, some of the potential disadvantages include relatively poor biomechanical performance when used without augmentation9,13 and the loss of the normal stabilizing function of that ligament.14 In the results published by Harris et al,9 the coracoacromial ligament transfer failed at 145 N and had a relatively low stiffness (8 N/mm). This low failure load has also been reported by other authors.3,13 The results of this reconstruction appear to fall short of those achieved by any of the hamstring reconstruction groups. In that study, the coracoacromial ligament transfer was not augmented by an additional cerclage suture. Biomechanical studies, which have looked at coracoacromial ligament transfer with augmentation, do show improved load to failure results.7,17 Other
776
Erak et al
J Shoulder Elbow Surg September/October 2008
Table I Structural properties of the coracoclavicular reconstruction (means 6 SD) Method
Tensile strength (N)
Tensile stiffness (N/mm)
SSTW reconstruction (n ¼ 9) MA screw lateral (n ¼ 4) MA screw medial (n ¼ 4) MMA (n ¼ 4) Simple loop (n ¼ 3) FibreWire (n ¼ 4) Intact (n ¼ 8)
379 (6 113)a 289 (6 65) a
36.5 (6 8.2) a 40.6 (6 18.2) a
15.0 (6 5.2) 10.5 (6 3.8)
328 (6 149) a
45.2 (6 21.7) a
11.7 (6 3.1)
320 (6 168) a 366 (6 208) a
22.6 (6 12.6) a,b 19.7 (6 9.2) a,b
23.0 (6 2.2) a,b,c 27.9 (6 10.6) a,b,c
502 (6177) 705 (6132)
57.2 (6 12.6) a 109.7 (6 32.6)
Elongation at failure (mm)
12.0 (6 2.7) 11.7 (6 3.2)
SSTW, screw and soft tissue washer; MA, modified anatomic; MMA, modified modified anatomic. a Significantly different from intact coracoclavicular complex at P<0.05. b Significantly different from FibreWire group at P<0.05. c Significantly different from SSTW reconstruction, MA screw lateral, MA screw medial groups at P<0.05.
reconstructions of the acromioclavicular joint, which do not utilize autogenous tissue, either rely on primary healing of the coracoclavicular ligaments, which is unlikely to occur in chronic dislocations, or on prosthetic material to maintain reduction. The latter could lead to problems with fatigue of the material over time or of the coracoid, in addition to the possible disadvantage of having prosthetic material in situ. Coracoclavicular screws, especially if used with bicortical fixation on the coracoid, can have impressive structural properties but do not offer a lasting biologic solution for the reconstruction; can over-constrain the acromioclavicular joint;10 routinely require removal, and are associated with a number of complications.5,8 In testing of the intact ligaments, load to failure in our study was higher than that noted by Harris et al9 (705 N vs 500 N) but more closely approximates that in other studies.7,13,18 The reason for this is not clear but may be related to less initial dissection around the coracoclavicular ligament complex. The values obtained for stiffness and elongation at failure are similar between the 2 studies. Among the reconstructions, the FiberWire group performed the best. The load to failure was highest of the reconstructions, although not statistically reaching significance unless directly compared to the combined MA screw lateral and MA screw medial groups. This was not unexpected, as the weak point in any of the hamstring reconstructions is predominantly the fixation method of the tendon to bone. The addition of a reinforcing suture with strong mechanical properties, such as FiberWire, may protect the tendon/bone interface. The stiffness of the FiberWire reconstruction was significantly different than that of the MMA and loop groups, as was the elongation to failure. This reconstruction is essentially a modification of that described by Mazzocca,15 which places the insertion points of the tendon graft on the clavicle in more anatomically correct positions. In our modifica-
tion, we used a closed loop on the more medial aspect of the reconstruction, which was thought to help place the insertion point more posteriorly, as the insertion of the conoid ligament is on the posterior aspect of the clavicle. A closed loop here also eliminates the need for a screw in this position and hence a potential weak point in fixation of the graft. The other modification to the described technique is that the tendon graft is doubled over rather than used as a single strand. It is unclear from the present study to what degree the addition of the tendon graft added to the mechanical properties of the FiberWire plus tendon group. The mechanical properties may have only reflected that of the FiberWire, with the tendon not being loaded in the test. There was no clear discernable second point of failure in the testing of the specimens used for the FiberWire group that may have been attributed to failure of the tendon, as the coracoid fractured in 3 specimens. In the remaining specimen, there was rapid failure of the tendon to bone interface after failure of the FiberWire suture. Whether the BioTenodesis screw was placed lateral or medial in the modified anatomic reconstructions (without FibreWire) did not appear to make a difference to the load to failure of these reconstructions. It was hypothesized that the screw may have better fixation in the more medial bone. As placing the screw laterally and the closed loop medially and posteriorly more closely replicates the normal anatomy, we would recommend this configuration be used for further testing or development. There was no difference in stiffness or elongation to failure. The MMA group was an attempt to alter the line of force on the tendon, so that it was not being pulled out from directly beneath the clavicle. While load to failure did not improve, there appeared to be a decrease in the stiffness of the construct and an increase in the elongation at failure, the latter of which was statistically significant compared to the MA screw lateral
Erak et al
J Shoulder Elbow Surg Volume 17, Number 5
and MA screw medial groups (in addition to the SSTW and FibreWire groups). We would not recommend further testing or development of this type of configuration. Lee et al13 reported failure loads for a simple loop of tendon tied into a knot of approximately 500 N for the gracilis and 700 N for the semitendinosus, which is higher than that which we could achieve in this study. Two of our 3 loop configurations fractured the coracoid, so it is possible that, after repeat testing on our specimens and in elderly specimens, the coracoid was weakened and failed earlier than in their study. Of their tendon reconstructions, it appears 26 of their 28 failed in the midsubstance of the tendon and only 2 fractured the coracoid. In our testing, the stiffness of the loop reconstruction was significantly less that that of the FiberWire group, and elongation to failure was higher than all of the other reconstructions, except for the MMA group. The results for stiffness were less that what was reported by Lee et al13 (19.7 N/mm vs approx 40 N/mm). It appears that we were unable to replicate their results achieved for this reconstruction, which may be related to technical factors, such as the strength of the knot or how many reinforcing sutures are placed in around the knot. The same group has published a recent clinical series with excellent results utilizing the loop configuration of a tendon graft and also incorporating a mersilene tape cerclage suture.19 Our numbers in this group were low, but we did not persevere with testing of this configuration because of the low stiffness and high elongation at failure of this reconstruction when performed in our hands. The SSTW reconstruction performed satisfactorily overall in terms of load to failure, stiffness, and elongation at failure. However, the concern with this type of reconstruction is that the fixation points of the graft onto the clavicle are in nonanatomic positions, thus leading to evaluation of more anatomic reconstruction configurations. Furthermore, the screw can be prominent in some patients and require a second procedure to remove it. In our study, there was no difference in mechanical properties of the reconstructions using either gracilis or semitendinosus. Lee et al13 reported similar results among the use of gracilis, semitendinosus, and long toe extensor tendon grafts. The importance of antero-posterior stability is becoming increasingly recognized. The acromioclavicular joint capsule is a significant stabilizer of the acromioclavicular joint, particularly in an antero-posterior plane.2,4 In higher grade injuries of the acromioclavicular joint, where this stabilizing influence is lost, it may become important to reproduce the anatomy of the native coracoclavicular ligaments more closely, to reduce antero-posterior laxity. Our study did not address this stability plane, and future work with the Fi-
777
berWire group or modified anatomic reconstructions would do well to investigate this issue. There were a number of limitations to this present study. Testing was performed in a superior plane and not in the antero-posterior direction. Noncyclic testing was performed, so that no information is given about the creep behavior of the reconstructions. Multiple tests were performed on most specimens and alterations in the position of fixation points of the graft to the clavicle may have affected results. The effects on the multiple tests and testing failure of the intact state on 8 of the specimens also may have had an effect on results, although it has been shown that repeated testing of the scapula-clavicle complex does not change the properties of the coracoid.1 Fracture of the coracoid, as a failure mechanism, may be more common in our testing, as the specimens used were derived from an older population, where bone density may be reduced compared to a younger population who normally undergo these types of reconstructions. A separate FiberWire suture alone group (without the addition of a tendon graft) would have documented to what degree the properties of the combined suture plus tendon group could solely be attributed to the FiberWire suture. Despite these limitations, we believe the present study does show that the modified anatomic reconstructions may hold a place in reconstructions of the acromioclavicular joint. They are certainly appealing from a biologic point of view in providing autogenous tissue to replace or augment the coracoclavicular ligaments. The addition of a loop of FiberWire appears to give an advantage in ultimate load and stiffness of the reconstruction. This may protect the graft during a revascularization phase in situ. In the acute phase, reconstructions performed without suture reinforcement have mechanical properties inferior to that of the intact coracoclavicular complex and should be protected. Recent clinical series utilizing tendon grafts have incorporated a reinforcing suture or wire in their constructs.19,21 Further work to delineate the antero-posterior laxity of these reconstructions—particularly comparing them to methods where the graft is fixed to or passed through a drill hole in the coracoid, rather than looped underneath it—would be warranted. REFERENCES
1. Costic RS, Labriola JE, Rodosky MW, et al. Biomechanical rationale for development of anatomical reconstructions of coracoclavicular ligaments after complete acromioclavicular joint dislocations. Am J Sports Med 2004;32:1929-36. 2. Debski RE, Parsons IMt, Woo SL, et al. Effect of capsular injury on acromioclavicular joint mechanics. J Bone Joint Surg Am 2001; 83-A:1344-51. 3. Deshmukh AV, Wilson DR, Zilberfarb JL, et al. Stability of acromioclavicular joint reconstruction: biomechanical testing of various
778
4. 5. 6. 7.
8. 9. 10. 11.
Erak et al
surgical techniques in a cadaveric model. Am J Sports Med 2004; 32:1492-8. Fukuda K, Craig EV, An KN, et al. Biomechanical study of the ligamentous system of the acromioclavicular joint. J Bone Joint Surg Am 1986;68:434-40. Galpin RD, Hawkins RJ, Grainger RW. A comparative analysis of operative versus nonoperative treatment of grade III acromioclavicular separations. Clin Orthop Relat Res 1985;193:150-5. Gonzalez R, Damacen H, Nyland J, et al. Acromioclavicular joint reconstruction using peroneus brevis tendon allograft. Arthroscopy 2007;23:788. e1-4. Grutter PW, Petersen SA. Anatomical acromioclavicular ligament reconstruction: a biomechanical comparison of reconstructive techniques of the acromioclavicular joint. Am J Sports Med 2005;33:1723-8. Guy DK, Wirth MA, Griffin JL, et al. Reconstruction of chronic and complete dislocations of the acromioclavicular joint. Clin Orthop Relat Res 1998;347:138-49. Harris RI, Wallace AL, Harper GD, et al. Structural properties of the intact and the reconstructed coracoclavicular ligament complex. Am J Sports Med 2000;28:103-8. Jari R, Costic RS, Rodosky MW, et al. Biomechanical function of surgical procedures for acromioclavicular joint dislocations. Arthroscopy 2004;20:237-45. Jones HP, Lemos MJ, Schepsis AA. Salvage of failed acromioclavicular joint reconstruction using autogenous semitendinosus tendon from the knee. Surgical technique and case report. Am J Sports Med 2001;29:234-7.
J Shoulder Elbow Surg September/October 2008
12. LaPrade RF, Hilger B. Coracoclavicular ligament reconstruction using a semitendinosus graft for failed acromioclavicular separation surgery. Arthroscopy 2005;21:1277. 13. Lee SJ, Nicholas SJ, Akizuki KH, et al. Reconstruction of the coracoclavicular ligaments with tendon grafts: a comparative biomechanical study. Am J Sports Med 2003;31:648-55. 14. Lee TQ, Black AD, Tibone JE, et al. Release of the coracoacromial ligament can lead to glenohumeral laxity: a biomechanical study. J Shoulder Elbow Surg 2001;10:68-72. 15. Mazzocca AD. Anatomic coracoclavicular reconstruction – surgical technique. Arthrex Product Literature 2005. 16. Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med 2007;35: 316-29. 17. Mazzocca AD, Santangelo SA, Johnson ST, et al. A biomechanical evaluation of an anatomical coracoclavicular ligament reconstruction. Am J Sports Med 2006;34:236-46. 18. Motamedi AR, Blevins FT, Willis MC, et al. Biomechanics of the coracoclavicular ligament complex and augmentations used in its repair and reconstruction. Am J Sports Med 2000;28:380-4. 19. Nicholas SJ, Lee SJ, Mullaney MJ, et al. Clinical outcomes of coracoclavicular ligament reconstructions using tendon grafts. Am J Sports Med 2007;35:1912-7. 20. Pennington WT, Hergan DJ, Bartz BA. Arthroscopic coracoclavicular ligament reconstruction using biologic and suture fixation. Arthroscopy 2007;23:785. e1-7. 21. Tauber M, Eppel M, Resch H. Acromioclavicular reconstruction using autogenous semitendinosus tendon graft: results of revision surgery in chronic cases. J Shoulder Elbow Surg 2007;16:429-33.