Introduction: History and Rationale
In recent decades there have been tremendous advances in techniques and results of anterior cruciate ligament reconstruction using arthroscopically-assisted techniques. The rationale supporting the current philosophy of anterior cruciate ligament reconstruction is based on prospective randomized studies, which have shown the following. First, Sandberg et al 36 documented no difference between primary anterior cruciate ligament repair versus nonoperative treatment. Second, two prospective randomized studies done in the 1990s showed at 2- and 5-year followup that patients with anterior cruciate ligament reconstructions with patellar tendon had significantly more stability and higher activity level than patients with primary anterior cruciate ligament repair and ligament augmentation. 16,19 Finally, the most compelling reason to reconstruct is the result of a study by Andersson et al 6 in which anterior cruciate ligament reconstruction lowered the meniscus tear rate and surgery at 2 years from 27% to 3%. However, there are no studies to date either suggesting or documenting that anterior cruciate ligament reconstruction prevents or delays degenerative changes. The goal of the current study was to review anterior cruciate ligament reconstructions in which a patellar tendon autograft was used, looking at outcomes to compare patellar tendon autograft with hamstring autograft, and compare surgical techniques.
Outcome Studies of Patellar Tendon Autograft
A literature review was conducted to study the results of two-incision arthroscopic-assisted and endoscopic anterior cruciate ligament reconstructions using a central third patellar tendon autograft without extraarticular augmentation. Only studies with a minimum followup of 2 years were included after an extensive Medline search (written communication, D Nedeff, MD, and B Bach, MD, 2000). This comprehensive analysis identified 19 articles 1,2,7–10,13,16,19,21,23,26,28,30–32,37,39,41 that used an arthroscopically-assisted technique using patellar tendon autograft. These articles comprised less than 1% of the articles related to the anterior cruciate ligament identified in the Medline database retrieval.
Table 1 summarizes the 19 articles. There were 1282 patients in the 19 articles. There were eight prospective and 11 retrospective studies. The average patient age was 26.1 years with a range of 22 to 29 years. One study was an outlier with a mean of 45.1 years 23 because the study only evaluated patients older than 40 years. Men comprised 65% of all the subjects who were studied. The followup was greater than 80% in all but two articles. 10,20 The patient’s ability to return to his or her original level of sport participation before anterior cruciate ligament reconstruction only was addressed in 13 of the 19 studies. Forty-one percent to 92% of the patients resumed participating in their preoperative sporting activities. The time for return to sports was 6 months or greater for all studies, except for one study 9 in which the mean time for return to sports was 4 to 6 months.
The percentage of patients with meniscal tears at the time of anterior cruciate ligament reconstruction ranged from 28% to 94%. The overall mean manual maximum side-to-side difference of KT-1000™ (MEDmetric, San Diego, CA) testing with a side-to-side difference of 3 mm or less ranged from a low of 48% to a high of 98% in the studies included in this evaluation. Of the nine authors who used a less than 3-mm cut-off as a measure of stability, 70% to 90% of their patients at followup had a KT-1000™ of less than 3 mm.
Sixteen of 19 authors reported complications. Reoperation rates varied from 2% to 31% within each study. In a majority of the series, the most common reason for reoperation was a lack of full range of motion (ROM) for which the patient required arthroscopic lysis of adhesions. This ranged from 1% to 31% for the entire patient population. Overall, 7% of all patients studied required surgery for lysis of adhesions. Fourteen studies (14 of 16 that reported complications) observed that fewer than 10% of patients required a secondary surgery for arthroscopic lysis of adhesions and 12 of 16 (75% of the studies) had a reoperation rate of less than 5% for lysis of adhesions. As a consequence, attention has been directed toward the timing of surgery, toward motion and quadriceps recovery, and toward possibly staging meniscal repair before anterior cruciate ligament reconstruction. These are thought to be the key contributing factors to the development of arthrofibrosis. Meniscal repair or partial meniscectomy resulted in 3% of patients requiring a secondary procedure. Seven studies (44%) had no patients requiring repeat meniscal surgery. Reoperation for graft failure was uncommon ranging from 0% to 4% with 11 of 17 (65%) studies reporting no reoperations for graft failure. Less than 0.4% of patients had an infection. Approximately 4% of patients had hardware removed, and less than 1% had a second surgery for patellar trauma.
A major criticism of the patellar tendon autograft is the potential for major extensor mechanism complications (patellar fracture or patellar tendon rupture). Fourteen of 16 studies (88%) reported no such complications. Patellar pain is a major preoperative and postoperative concern. Overall in the current review, there were three of 13 studies that reported a patellar pain incidence greater than 20%. 13,26,28 Of the 13 studies published since 1995, eight authors reported an incidence of patellar pain ranging from 3% to 17% in seven studies 2,9,10,19,32,37,39 and 50% in one study. 26 Patellar pain is thought to be less today than it was in the late 1980s (verbal communication, BR Bach, MD, 2001). The potential reasons include an accelerated rehabilitation program, which emphasizes early weightbearing, early quadriceps function, recovery of knee extension, and no postoperative immobilization. Only a prospective randomized design between patellar tendon and hamstring can evaluate one graft choice over another with reference to patellar pain. The current authors will address patellar pain syndrome in several prospective randomized studies comparing patellar tendon with hamstring anterior cruciate ligament reconstructions.
Postoperative rating scales provide an overview of results. The Tegner and Lysholm 40 and Lysholm and Gillquist 27 scores can be obtained via a telephone interview, whereas the other rating scales require a personal evaluation. The Tegner and Lysholm scoring system 40 was used in four studies. Lysholm and Gillquist 27 scores were used in 12 studies, with a mean score of 91 (range, 85–96). The postoperative knee activity rating score of Noyes 29 was used in four studies with a mean of 86 (range, 84–88). The modified Hospital for Special Surgery knee evaluation scale 24,42 had a mean of 89 points (range, 88–90 points) in the four studies using this scale. Eight studies used the International Knee Documentation Committee scale as reported by Anderson 5 with a mean score of 76%. Thirty-nine percent to 96% of the patients were rated as “normal or nearly normal” after anterior cruciate ligament reconstruction using the International Knee Documentation Committee score. One study used the subjective rating score of Zarins and Rowe. 43 Two studies did not record such postoperative scales. 1,39 Subjective patient satisfaction is an additional means of evaluation. Unfortunately, in the current review, 11 of 19 (58%) studies did not report a measure of subjective satisfaction. In those studies that assessed patient satisfaction, 91% to 98% of patients were subjectively satisfied with their outcome. Currently, the newer validated outcome measures should be used when reporting the results of knee treatments. These questionnaires are completed by patients thereby reducing bias and include Short Form-36 4,22,25,38 Western Ontario and McMaster University Osteoarthritis Index. 11 Knee Injury and Osteoarthritis Outcome Score, 35 Lysholm and Gillquist, 27 and International Knee Documentation Committee scale. 5
Only four of the 19 studies, which met the inclusionary criteria, reported a followup at least 5 years postoperatively. 1,2,10,32 Currently, there are no reported series in the North American literature evaluating minimum 10-year followup of contemporary arthroscopically-assisted patellar tendon autograft reconstruction. Three studies included patients with previously failed anterior cruciate ligament reconstructions (revisions) in their study group. 1,28,30 It would be advisable to exclude this subgroup to provide a more accurate assessment of index anterior cruciate ligament reconstruction.
The methods of fixation and major postoperative rehabilitation protocols were evaluated. Thirteen studies (68%) used femoral interference screw fixation. 7–10,16,19,26,30–32,37,39,41 Three studies used ligament buttons 1,2,13; two of these studies were reported in 1992 and 1993, respectively. 1,13 Only two authors 22,25 used screw or post fixation techniques. The patterns of tibial fixation were similar with 16 of 19 studies (84%) using tibial interference screw fixation. Various postoperative weightbearing protocols were used. After 1995, most studies used immediate weightbearing protocols (progressive weightbearing). Only one author reported a nonweightbearing protocol after 1995, 32 whereas five of six studies published before 1995 used nonweightbearing protocols, which varied from 2 to 8 weeks postoperatively. 1,8,13,16,31 Within the postoperative protocols, seven studies used a continuous passive motion machine and the remaining 12 studies did not.
The current review provides details on a predictable arthroscopic technique of anterior cruciate ligament reconstruction with a high short-term stability rate, extremely high patient subjective satisfaction level, and low postoperative complication rate. Patellar tendon autograft continues to be the most popular technique used by a majority of surgeons, especially at the collegiate and professional level. A need exists for long-term (5–10 year) postoperative outcomes analysis of these patient populations including the use of newer validated outcomes measures.
Autograft Choice: Patellar Tendon Versus Hamstring
Despite the plethora of publications on techniques and results of arthroscopic anterior cruciate ligament reconstruction in the past 2 decades, there are few scientifically valid studies comparing autograft patellar tendon versus hamstring reconstructions. 3,15,28,30 The percentage of patellar tendon versus hamstring anterior cruciate ligament reconstructions has cycled despite few valid data to support shifts in choice. To scientifically choose between two treatments, in this case patellar tendon versus hamstring autograft anterior cruciate ligament reconstruction, a prospective randomized or comparative design is required. Each group must have an identical patient population, timing of surgery, equal associated injuries, same rehabilitation, and outcome or results measured identically. The only difference should be the primary variable being investigated, in this case the anterior cruciate ligament graft (patellar tendon versus hamstring). Given these scientific criteria, only four studies 3,15,28,30 published to date provide a comparison between autograft patellar tendon versus hamstring. Table 2 and Table 3 outline aspects of the design, surgical technique, rehabilitation, outcomes, and results. The first three studies 3,28,30 were prospective and randomized by either alternating each patient or by month of birth. Both techniques were done by one surgeon during the same period. The study design by Corry et al 15 is prospective and comparative because the patellar tendon reconstructions were done during the first period followed by hamstring in a later time, but not concurrently. This sequential study cannot control the variables between patellar tendon and hamstring and does not allow for a prospective randomized design. However, the four studies documented statistically that the groups being compared were equal preoperatively.
Marder et al 28 and Aglietti et al 3 studied chronic anterior cruciate ligament tears; however, O’Neill 30 and Corry et al 15 evaluated chronic and acute anterior cruciate ligament tears. The only study that reviewed isolated anterior cruciate ligament injuries was done by Corry et al. 15Table 2 summarizes the technical aspects of each study. The size of patellar tendon graft, single or doubled hamstring, method of fixation, and technique are shown in Table 2. Regarding rehabilitation (Table 3), full weightbearing was allowed at 1 to 6 weeks. Jogging was allowed at 1.5 to 7 months. The patients in the study of Marder et al 28 used a hinged brace for ROM during the first 4 weeks, and the patients in the study of Aglietti et al 3 used a splint for the first 4 weeks except when working on ROM. The patients in the other two studies did not use braces. A continuous passive motion machine was not used postoperatively in any of the studies. Based on today’s rehabilitation standards, these techniques are conservative with only one study allowing return to sports at 6 months, but based on the time when the reconstructions were done, are all relatively aggressive.
The results of these studies are summarized in Table 4. All studies have relatively short-term followups with a minimum of 2 years. A large number of variables were evaluated in the four studies, yet only seven statistically significant differences were shown. Marder et al 28 showed a significant weakness in hamstring strength in the hamstring group when peak hamstring torque at 60° per second was measured. Aglietti et al 3 and O’Neill 30 did not reproduce this. Range of motion was significantly less in the patellar tendon group in the study by Aglietti et al 3 but the other three studies also did not reproduce this finding. Only Corry et al 15 showed significantly more laxity in the hamstring group, which was stratified to females only with hamstring reconstruction. Again, the other three studies did not show any instrumented differences at 20 lb or maximum, but did not specifically evaluate by gender. Only Corry et al 15 examined and showed significantly more pain with kneeling in patients with patellar tendon. The only consistent result reported in all three studies that used similar scoring scales was activity level. The patients in the patellar tendon group had a significantly higher overall activity in the studies of Aglietti et al 3 and O’Neill, 30 and a significantly greater percentage of patients attained Level I activity (Level I, strenuous; Level II, moderate; Level III, light; and Level IV, sedentary) in the study of Corry et al. 15 The patients in study of O’Neill 30 who had a two-incision patellar tendon returned to a significantly greater level of activity than the patients who had endoscopic patellar tendon or the two-incision hamstring. There were consistent findings where differences did not exist including physician’s ligament examination (Lachman grade and pivot shift), patellofemoral pain, and graft failure. There was a 10% reoperation rate in the study of Marder et al 28 for the removal of screw and washer. Finally, the timing of surgery was not a significant variable in the study of O’Neill. 30
The differences between patellar tendon and hamstring can be described best as subtle based on the aforementioned scientific evaluations. Except for the consistent finding of an increased activity level in the patellar tendon group, all patients had comparable results. At this point, surgeons should focus their attention to the details of each technique including tunnel position, method of fixation and tension, and adoption of rational rehabilitation protocols rather than the type of graft. They should be confident each graft should yield excellent results in the majority of their patients. Questions yet unanswered include ideal graft in the professional or National College Athletic Association Division I athlete, long-term results between patellar tendon and hamstring, and whether accelerated rehabilitation protocols produce similar results with patellar tendon versus hamstring. Clearly more scientific studies, especially long-term, are needed to address these questions to further advance the field of anterior cruciate ligament reconstruction.
Prospective Randomized Studies on Operative Techniques
There are several basic approaches to a patellar tendon anterior cruciate ligament reconstruction. The proposed advantages of arthroscopy are better observation of tunnel position reflected by more predictable stability, less pain postoperatively, and more rapid rehabilitation. However, few studies have evaluated the different operative techniques of patellar tendon anterior cruciate ligament reconstruction with a rigorous scientific method. In a prospective, randomized, blinded study, Raab et al 33 compared arthroscopic and miniopen reconstruction with an ipsilateral patellar tendon autograft. The miniopen group consisted of a limited open approach, which did not remove the patella from the trochlear groove. The arthroscopic procedure on the average took 13 minutes longer (p < 0.001). There were no statistical differences in the amount of postoperative pain medication required, ROM, KT-1000 arthrometer results, or any other relationship between the two groups in any of the variables measured. In a prospective randomized comparison, Cameron et al 14 looked at early rehabilitation benefits of doing anterior cruciate ligament reconstruction with arthroscopic assistance versus the miniopen technique. The followup was short-term at 6 months. There was no statistical difference in the operative time, estimated blood loss, total milligrams of meperidine used, and the 3-day postoperative pain scores. At 6 months, stability tests done by the physician showed no statistical difference. With Cybex dynamometer (Lumex, Inc, Ronkonkoma, NY) muscle strength testing at 6 months, the quadriceps strength at the slow arc (60°/second) was greater for the arthroscopic group. There also was a significant difference at 6 months with the patients in the miniopen group having greater thigh musculature atrophy. These two studies show there are few differences between arthroscopic and miniopen anterior cruciate ligament reconstructions provided tunnel placement, graft fixation, and rehabilitation are done well. There are no prospective randomized studies that compare an open technique (arthrotomy with disarticulation of patella from the trochlear groove) with the arthroscopic technique or miniopen technique.
Arthroscopically-assisted anterior cruciate ligament reconstruction began with a two-incision technique. However, the endoscopic technique now is equally popular with the potential benefits of improved cosmesis (avoiding an additional incision on the lateral side of the knee), less postoperative pain, less likelihood of tethering the extensor mechanism or iliotibial band and hopefully accelerated rehabilitation.
There are several scientific studies evaluating the difference between endoscopic and two-incision technique. In a prospective randomized study, Brandsson et al 12 compared endoscopic versus two-incision technique. There were no significant differences found in the KT-1000 arthrometer values, patellofemoral pain, or International Knee Documentation Committee score at 24 months. This study showed that the two techniques yield identical functional results and knee stability after anterior cruciate ligament reconstruction. In a prospective randomized study, Reat and Lintner 34 compared the early functional outcomes of anterior cruciate ligament reconstruction using a one-incision endoscopic technique versus a two-incision technique. This was a small study (N = 30) that showed no statistically significant difference between the outcomes when evaluating operative time, subjective postoperative pain, ROM at Weeks 1, 3, 6 and final followup, International Knee Documentation Committee activity-related anterior knee pain, and KT-1000 results. Garfinkel et al 17 prospectively studied patients with endoscopic patellar tendon anterior cruciate ligament reconstruction versus two-incision reconstruction. At 1 year after surgery, there was no significant difference in ROM, thigh girth, isokinetic strength, or subjective evaluation. In one arm of a prospective randomized study comparing endoscopic to two-incision technique, O’Neill 30 found the patients in the two-incision group returned to a greater level of athletic activity. He also reported that a higher percentage of the patients who had the two-incision technique had a difference of 3 mm or less on testing stability with the KT-2000 (MEDmetric, San Diego, CA) arthrometer. There was no difference in the overall outcome, with 90% of the knees having normal or nearly normal function. Gerich et al 18 compared one-incision versus two-incision technique in a prospective randomized trial. They found the single-incision technique did not differ from the two-incision technique in terms of postoperative pain medication, incidence of effusion, postoperative ROM, or any rehabilitation parameters.
Scientific data in these six studies all show that there is no major difference, except stability in favor of the two-incision technique, between endoscopic and two-incision anterior cruciate ligament reconstruction. They essentially are interchangeable. One should make the decision on which to do based on training and expertise. The surgeon should focus on attention to detail on proper tunnel placement, graft fixation, and avoidance of complications of each technique.
In this evaluation, a minimum 2-year followup on patellar tendon anterior cruciate ligament reconstruction was reviewed. The current authors identified prospective randomized studies on nonoperative treatment versus repair, reconstruction versus nonoperative treatment, graft choice of patellar tendon versus hamstring, operative technique miniopen versus arthroscopic, and endoscopic versus two-incision. The results of this review show several important points. Patellar tendon autograft anterior cruciate ligament reconstruction results in predictable short-term results with few complications. The differences between patellar tendon and hamstring can best be described as subtle based on scientific studies. Except for consistent finding of an increased activity level in the patellar tendon group they have comparable outcomes. There is no advantage in using an arthroscopic technique versus miniopen technique. Finally, there is no advantage in an endoscopic technique versus arthroscopic two-incision technique.
If the primary principles of anterior cruciate ligament reconstruction are followed, one can expect consistent results with patellar tendon reconstruction. This would entail proper anatomic position of the femoral and tibial tunnels and secure fixation of the graft, which allows for a rational accelerated rehabilitation protocol. However, there is a clear need for prospective long-term (5 to 10 years) followup studies with validated outcome data by questionnaire coupled with objective measures of stability, function, and arthritis. This is important to scientifically investigate continued results of patellar tendon anterior cruciate ligament reconstruction with a focus on risk factors associated with poor function and development of arthritis.
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Kurt P. Spindler, MD; and Edward M. Wojtys, MD—Guest Editors© 2002 Lippincott Williams & Wilkins, Inc.