Graft selection for posterior cruciate ligament surgery

GRAFT SELECTION FOR POSTERIOR CRUCIATE LIGAMENT SURGERY BERNARD R. BACH, JR, MD

The indications for posterior cruciate ligament (PCL) surgery are not well established. PCL injuries occur much less frequently than anterior cruciate ligament (ACL) injuries. Conflicting data suggest on one hand that PCL-deficient patients may function well despite their clinical laxity, yet a time-related correlation between injury interval and extent of articular cartilage injury also has been reported. A myriad of factors, including graft selection, placement, fixation, position of the knee at the time of fixation, position of immobilization, rehabilitation, and the surgeon's inexperience, contribute to the less predictable results of PCL surgery. Graft selection issues are discussed in this article, and a survey of leading ligament surgeons regarding the PCL is presented. KEY WORDS: posterior cruciate ligament, graft selection

During the past decade marked advances have occurred in the surgical treatment and rehabilitation of patients after reconstruction for the anterior cruciate ligament (ACL)-deficient knee. A decade ago nonanatomic extra-articular reconstructions were performed, meniscal repairs infrequently performed, and motion often delayed. In 1992 intra-articular reconstructions without extra-articular augmentation, early weight bearing, and accelerated rehabilitation programs yielded negative pivot shift rates of less than 10%, minimal motion problems if complete extension is achieved early postoperatively, and a high likelihood of returning to sports unbraced, with an extremely satisfied patient population. Our understanding of the posterior cruciate ligament (PCL)-deficient knee lags behind and perhaps parallels our understanding of the ACL-deficient knee 10 years ago. A number of factors contribute to this dichotomy. The incidence of PCL injuries is far less; perhaps lout of every 10 to lout of every 20 of ACL injuries. Natural history studies reported by Parolie and Bergfeld! and Fowler have suggested that in short-term and intermediate follow-up periods, athletes with PCL-deficient knees functioned well despite obvious clinical laxities. Clancy et al reported on the surgical results of PCL deficiency and observed a time-related relationship between the interval to surgery and articular injuries, particularly of the medial femoral condyle.P" They reported greater than 90% good-to-excellent results using an open technique with middle-third patellar tendon reconstruction. Clancy'S extensive experience treating PCL-deficient knees is shared by only a handful of surgeons in the

From the Sports Medicine Section, Department of Orthopaedic Surgery, Rush Medical College, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL. Address reprint requests to Bernard R. Bach, Jr, MD, Sports Medicine Section, Department of Orthopaedic Surgery, Rush Medical College, Rush-Presbyterian-St. Luke's Medical Center, 1725 W Harrison St, Suite 439, Chicago, IL 60612. Copyright © 1993 by W. B. Saunders Company 1060-1872/93/0102-0004$05.00/0

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United States, and a shared observation of many has been that it is difficult to improve on a grade 1 (1 to 5 mm) posterior translation after reconstruction. Additionally, observations at the National Football League "combine" have noted anywhere from a 2% to 5% incidence of unrecognized posterior cruciate deficiencies in elite-level college football players. 1 Graft selection, placement, fixation, position of knee flexion at the time of fixation, period of immobilization, position of immobilization, and rehabilitation are among the myriad of factors that contribute to the variables affecting PCL surgical results as well as the relative inexperience of most knee ligament surgeons, many of whom perform more than 100 ACL reconstructions annually. This article deals with the topic of graft selection for PCL surgery. A review of the literature demonstrates a relative paucity of PCL studies, particularly when compared with those of the ACL.1-75 In an attempt to stabilize the PCL-deficient knee, authors have recommended primary multiple suture repair with and without augmentation; hamstring repairs with and without ligament augmentation device (LAD) augmentation; free middle-third patellar tendon reconstruction; sandwiched double middle-third patellar tendon; allograft fascia lata; patellar tendon or Achilles tendon; menisca! substitution; use of the popliteus tendon; and medial head gastrocnemius. 3,5,9-11,16, [9,35,38,41,43,46,49,57,62,67,68,75 Graft selection may be influenced by several factors including biomechanical strength characteristics, graft fixation, graft site access, ease or difficulty passing the graft through bone tunnels, and rehabilitation factors. What are the advantages and disadvantages of various grafts and these factors? Autogenous patellar tendon is a high-strength graft that allows bone-to-bone fixation (Fig 1). Butler et al in their classic biomechanical strength study demonstrated that the ultimate tensile strength of a 14-mm patellar tendon graft was 1730 Nand 159% to 168% that of the native ACL. 13 More recently, Cooper et al repeated Noyes' study using different fixation devices in 2 young cadavers and noted that ultimate failure rates of 2,238 ± 316

Operative Techniques in Sports Medicine, Vol 1, No 2 (April), 1993: pp 104-109

Fig 1. Photograph of prepared autogenous middle-third patellar tendon.

N (7 mm), 2,977 ± 516 N (10 mm), and 4,389 ± 708 N (15 mm).17 One concern regarding the use of the patellar tendon is that of an inadequate width of tissue for PCL surgery. Clancy in the mid-1980s to late 1980s recommended the use of ipsilateral and contralateral patellar tendon tissue sandwiched together to provide a large bulk of tissue approximately the size of the PCL. Currently he recommends a lO-mm ipsilateral middle-third autogenous patellar tendon graft. He acknowledged that better placement of the tibial tunnel (Figs 2 and 3) has yielded improved results. Cooper's data appears to substantiate the opinion that a 10- to 12-mm middle-third graft should be sufficient graft material for reconstruction purposes. Patellofemoral pain, extensor mechanism morbidity, residual thigh girth atrophy, and isokinetic evidence of residual quadriceps weakness are acknowledged problems associated with ACL knee ligament surgery in general and the use of a patellar tendon autograft, specifically. Because patients with a PCL-deficient knee have a posterior sag and drop back resulting in increased patellofemoral contact pressures and patellofemoral symptoms, this factor must be addressed when considering an autogenous patellar tendon graft. In contrast to ACL reconstruction using patellar tendon, graft passage can be quite difficult. The graft must be passed through longer bone tunnels, and the path traversed is in a zigzag direction. Inadequate tissue debridement on the posterior tibia may contribute to the difficulties of graft passage, although graft passers (DePuy Co, Warsaw, IN) facilitate the process. The length of the bone-tendonbone construct results in the bone plug residing deep within the tibial tunnel (Fig4). An interference screw can be used on the femoral side for fixation; an interference screw on the tibial side would place the screw deep within the tibial tunnel, and fixation could not be reliably predictable. Although some surgeons use interference screws for fixation on both femoral and tibial sides, I am concerned about placing a screw deep within'an intraosseous tunnel because subsequent surgery such as a high tibial osteotomy would necessitate its removal. An alternative for interference fixation would be a long 32mm threaded 6.5-mm AO cancellous screw or securing the graft over an obliquely oriented screw and post over a screw and post. The use of the hamstring tendons (semitendinosisgracilis) are, like the patellar tendon, readily accessible. An 18- to 20-cm graft can be harvested through a small incision over the pes anserine region using a variety of PCl GRAFT SELECTION

Fig 2. Intraoperative radiograph demonstrating Inaccurate placement of tibial pin. Note that the pin is directed toward the proximal upslope of the pel insertion site.

tendon strippers. When the hamstring tendons are used for knee ligament reconstructions, I prefer the O'BrienWarren tendon stripper (Concept Inc, Largo, FL). The issue of the relative strengths of the hamstring tendon has been raised. Noyes'P study on the relative strengths of tissues suggested that the semitendinosis (70% of ACL) combined with the gracilis (49% of ACL) has an ultimate tensile strength approximating that of the ACL. Proponents of the hamstring tendon graft for ACL surgery rationalize that the additive strengths of these tissues are as strong as, or when doubled, tripled, or quadrupled, surpass that of a patellar tendon autograft. To my knowledge this has not been proven unequivocally, although the cross-sectional area of a rounded tendon is comparable to the rectangular or ribbon-shaped crosssectional area of the patellar tendon graft. In a patient with significant pre-existing patellofemoral symptoms, the use of the hamstrings or an allograft may be more appealing; however, graft fixation is an important issue to

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Fig 3. Intraoperative photograph demonstrating appropriate placement of tibial pin. This site is more distally located on the tibial Insertion upslope.

consider because a screw and post, staple, and/or ligament button is required. Allograft patellar tendon is an alternative graft source. The advantage of avoiding donor site morbidity and using a larger width graft is unique to this graft selection. Graft preparation by an assistant may reduce surgical time. Issues of fixation and passage are identical to those of autograft patellar tendon. The major disadvantage of allograft tissue is the potential transmission of the human immunodeficiency virus (HIV) virus. Buck et al conducted epidemiologic modeling studies and concluded that the likelihood of contracting HIV from an allograft is less than 1 in 1,000,000 when rigorous donor selection, exclusion screening for the HIV antigen and antibody,

Fig 4. Intraoperative radiograph demonstrating bone plug of patellar tendon graft. Note how recessed within the tibial tunnel the graft Is. A longer graft will make passage of the graft construct more difficult. I do not use an interference screw In the tibial Intraosseous tunnel. Instead, I prefer a screw-andpost fixation. The screw head Is countersunk into the tibial defect where the patellar tendon graft was harvested, thus reducing the likelihood of prominent hardware.

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and histopathological studies of donor tissues are conducted. 76 Bone graft healing and incorporation, collagen cell repopulation and ligamentization, recovery of mechanical strength, and antigenicity are not completely understood. Use of the patellar tendon allograft is preferred for chronic PCL deficiency by approximately 10% of nationally recognized knee ligament surgeons recently surveyed. The major advantages of the Achilles tendon allograft are the large cross-sectional area of collagen, adequate length, ability to obtain rigid bone fixation on one end of the graft, and ease of graft passage. Lack of donor site morbidity and preparation time are additional advantages. The Achilles tendon allograft has the same potential issues of disease transmission and healing as the allograft patellar tendon. Furthermore, Achilles tendon allograft reconstruction requires soft tissue fixation rather than rigid bone-bone fixation on the tibial side. The Achilles tendon allograft was preferred by approximately 10% of surgeons in a recently conducted suryey. Some knee ligament surgeons have recommended incorporation of the Kennedy LAD (3M Co, Minneapolis-St Paul, MN) to strengthen any of these graft tissues. Fowler has extensive experience with this device using LAD augmentation of the quadriceps tendon or semi tendinosis tendons for ACL surgery. 77 Stress protection mayor may not be desirable for PCL grafts, and the amount and duration of stress protection is not known. The device is made of a synthetic material, and its longterm effects are unknown. Also, the device is expensive. Use of the GoreTex graft (Gore Co, Flagstaff, AZ) is not recommended for index ACL ligament surgery or for PCL surgery. A survey of 55 active sports medicine surgeons, nearly all of whom treat intercollegiate or professional teams or are sports medicine fellowship directors, was recently conducted (Herodicus Society, Acapulco, Mexico, July 1 to 4, 1992). Fifty-five of 58 members surveyed returned their questionnaire. The 18 questions that were asked for our respondents are given in Table 1. Twenty-two of 55 respondents (40%) performed more than 100 ACL reconstructions annually; 13% performed more than 80 reconstructions; 18% performed between 60 and 79 reconstructions; and 9% performed between 50 and 60 reconstructions. In contrast to the high volume of ACL surgery performed by this group of sports surgeons, 31 surgeons (56%) performed fewer than 5 PCL reconstructions annually. Twelve surgeons (22%) performed between 5 and 10 PCL reconstructions; only 11 surgeons (20%) performed between 10 and 20 reconstructions annually. Only 1 surgeon performed more then 20 PCL repairs and! or reconstructions annually. When independently compared, the ratio of PCL to ACL reconstructions was between 1% and 10% annually. Respondents indicated that 96% and 88% would not consider performing PCL repair or reconstruction for an acute isolated PCL grade 1 or 2 injury, respectively. Grade 3 acute isolated injuries were considered as potential surgical lesions by nearly 60% of the surgeons. However, when performed, patients were carefully selected. Similarly, 90% of the respondents would not consider PCL reconstruction for a chronic grade 1 injury, 74% for BERNARD R. BACH

TABLE 1. pel Survey of Herodicus Society Members 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14.

15.

16. 17. 18. 19. 20. 21. 22.

How many PCl repairs/reconstructions do you perform annually? <5 5·10 10-20 20-30 30-40 >50 How many ACl repairs/reconstructions do you perform annually? <25 26-35 36-45 46·60 61·80 81-100 >100 What percentage of your isolated PCl surgeries are performed acutely «4 wk)? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of your isolated PCl sur.geries are performed >4 wk post injury? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated grade 1 PCl injuries do you repair/reconstruct acutely? o 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated grade 2 PCl injuries do you repair reconstruct acutely? o 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated grade 3 PCl injuries do you repair/reconstruct acutely? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated chronic grade 1 PCl injuries do you repair/reconstruct? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated chronic grade 2 PCl injuries do you repair/reconstruct? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of isolated chronic grade 3 PCl injuries do you repair/reconstruct? o 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of your acutely injured isolated PCl injuries will you treat conservatively initially? o 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What percentage of your acutely injured isolated PCl patients will you obtain MRls on? 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% What is your graft selection for acutely injured isolated PCls requiring surgery? A. Primary repair/unaugmented B. Primary repair/augmented with hamstring tendon(s) C. Primary reconstruction with autogenous mid-third patellar tendon O. Primary reconstruction with allograft mid-third patellar tendon E. Primary reconstruction with allograft Achilles tendon F. Primary reconstruction with autogenous doubled mid-third patellar tendon using ipsilateral and contralateral patellar tendons G. Hamstring tendons H. Any of the above (indicate letter ) with LAD I. Other _

o o

o o o

o

What is your graft selection for chronic isolated PCls requiring surgery? A. Primary repair/unaugmented B. Primary repair/augmented with hamstring tendon(s) C. Primary reconstruction with autogenous mid-third patellar tendon O. Reconstruction with allograft mid-third patellar tendon E. Reconstruction with allograft Achilles tendon F. Reconstruction with autogenous doubled mid-third patellar tendon using ipsilateral and contralateral patellar tendons G. Reconstruction with hamstring tendons H. Any of the above (indicate letter ) with LAD I. Other Your graft preference is based on: (Please rank in order of importance _ A. Biomechanical strength considerations of graft B. Siomechanical strength considerations of fixation C. Ease/difficulty of graft passage O. length of bone tunnels E. Graft tissue access F. Rehabilitation considerations Does your graft selection allow for early ROM? Yes No Do you tension your graft in A. extension B. 30° flexion C. 45° flexion O. 60° flexion E. other Do you allow early weight bearing (WB) after isolated pel reconstruction within the first 6 weeks? A. Yes B. No If weight bearing is allowed. do you A. we in extension B. WB as tolerated C. TOWS O. PWB 30 pounds What is your preference for graft fixation on the femoral side? A. interference screw B. button C. staple D. screw/post What is your preference for graft fixation on the tibial side? A. interference screw B. bullon C. staple O. screw/post What percentage of your PCl reconstructions do you perform arthroscopically assisted? o 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Abbreviations: TOWS. touch·down weight bearing; PWB. partial weight bearing.

a chronic grade 2 injury, and 13% for a chronic grade 3 isolated injury. The majority of respondents favored rehabilitation and observation for most acute or chronic isolated injuries. Graft selection in the acute and chronic PCL-deficient knee varied. Autogenous middle-third patellar tendon was the most commonly preferred graft in both acute and PCl GRAFT SELECTION

chronic knees. One factor that affects graft selection in an isolated PCL-deficient knee is whether the injury is acute or chronic. In our survey 34% used the same graft and 66% used different grafts depending on the time interval from injury. In certain situations an individual might select between two graft sources. In this survey 10% would consider an unaugrnented primary repair

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acutely, 18% preferred primary repair with hamstring augmentation, 30% preferred autogenous patellar tendon, 4% preferred allograft patellar tendon, and 10% preferred allograft Achilles tendon reconstruction. With surgical reconstruction recommended for chronic PCL insufficiency, 2% preferred hamstrings, 54% preferred autogenous patellar tendon, 10% preferred allograft patellar tendon, and 12% preferred allograft Achilles tendon reconstruction. However, in the acute setting approximately 25% of the surgeons listed more than one graft choice. Several surgeons specifically indicated that the location of the tear and quality of tissue affected their intraoperative decision. Most of these surgeons (8 of 13) listed the patellar tendon as one of their multiple graft choices. Four of these surgeons considered augmenting autogenous or allograft tissue with an LAD device. In the chronic setting, autogenous patellar tendon graft was clearly the most commonly preferred tissue. It was more than five times more commonly preferred than any other tissue (54%). Allograft patellar tendon (10%) and allograft Achilles tendon (12%) also were commonly used. The hamstring tendons were infrequently used in the chronic setting. Nine surgeons (18%) preferred more than one graft tissue depending on the situation. Six of these nine surgeons preferred autogenous patellar tendon, three preferred allograft patellar tendon, and six incorporated an LAD stent with either autogenous patellar tendon, allograft Achilles, or patellar tendon as one of their graft choices. In our survey 78% of surgeons listed graft strength characteristics as the most important issue governing their decision regarding graft selection. Seventy percent used an interference screw on either the femoral or tibial side, and a screw-and-post fixation was used on one or both sides by 51 %. Graft fixation was ranked as the second most important factor. The survey dealt with the isolated PCL-deficient knee without displaced bone avulsion. Graft selection may be altered with a multiple ligament insufficiency is encountered. For example, if a patient has a grade 2 to 3 PCL deficiency with a posterolateral rotatary instability characterized by a posterolateral spin or asymmetric thighfoot angles greater at 90° than at 30°, it would be unwise to use the hamstring tendon for PCL repair and/or reconstruction if the surgeon planned a Clancy biceps tenodesis for the posterolateral pathology.3,29 Multiple ligament involvement may require a compromise in graft selection if one cannot use allograft tissues. For example, a combined ACL-PCL deficiency might require use of the hamstrings for one ligament and the patellar tendon for another. Some authors have advocated use of the ipsilateral and contralateral patellar tendon grafts to reconstruct both the ACL and PCL. Others have suggested that the middle-third patellar tendon could be used for one graft, and a strip of the proximal quadriceps tendon and a bone block from the proximal pole of the patella could be used for another graft. Shelbourne has preferred to reconstruct the PCL initially in the patient with a knee dislocation and perform a delayed ACL reconstruction if required (personal communication). The ipsilateral patellar tendon may be used for one graft, and the ipsilateral

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quadriceps tendon harvested with a proximal pole patellar bone plug may be used for another graft. These cases should be cared for by experienced knee ligament surgeons because preoperative evaluation, intraoperative technique execution, and postoperative rehabilitation of these multiply injured patients is extremely challenging.

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