Revision anterior cruciate ligament reconstruction with hamstring tendon autograft: 5- to 9-year follow-up

BACKGROUND: The results of revision anterior cruciate ligament reconstruction are limited in the current literature, and no studies have previously documented the outcome of revision anterior cruciate ligament reconstruction using solely hamstring tendon grafts. HYPOTHESIS: Revision anterior cruciate ligament reconstruction with 4-strand hamstring tendon graft affords acceptable results and is comparable to reported outcomes with the bone-patellar tendon-bone graft. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty-seven consecutive revision anterior cruciate ligament reconstructions with the hamstring tendon graft and interference screw fixation were assessed a mean time of 89 months (range, 60-109 months) after surgery. Assessment included the International Knee Documentation Committee knee ligament evaluation, instrumented laxity testing, and radiologic examination. RESULTS: Of the 50 knees reviewed, 5 (10%) had objective failure of the revision anterior cruciate ligament reconstruction. Of the 45 patients with functional grafts, knee function was normal or nearly normal in 33 patients (73%). An overall grade of normal or nearly normal was found in 56% of patients. The mean side-to-side difference on manual maximum testing was 2.5 mm (range, -1 to 4 mm). Degenerative changes on radiographs were identified in 23% of patients at the time of surgery, increasing to 56% of patients at review. The status of the articular cartilage at the time of revision surgery was the most significant contributor to successful outcome. CONCLUSION: Revision anterior cruciate ligament reconstruction with hamstring tendon graft and interference screw fixation affords acceptable results at a minimum of 5 years' follow-up. Good objective results can be obtained, but subjectively, the results appear inferior to those of primary anterior cruciate ligament reconstruction in the literature, which may be related to the high incidence of articular surface damage in this patient population. We recommend that, when available, hamstring tendon autografts should be considered for revision anterior cruciate ligament reconstruction.     

A prospective randomized study of patellar versus hamstring tendon autografts for anterior cruciate ligament reconstruction

BACKGROUND: Bone-patellar tendon-bone graft has been the most commonly used graft material in anterior cruciate reconstructions, but there has been increasing use of hamstring tendon grafts. However, no existing clinical studies show adequate support for the choice of one graft over the other. HYPOTHESIS: Hamstring tendons are equally as good as patellar tendon in anterior cruciate ligament reconstructions. STUDY DESIGN: Prospective randomized clinical trial. METHODS: Ninety-nine patients with laxity caused by a torn anterior cruciate ligament underwent arthroscopically assisted reconstruction with graft randomization according to their birth year. Grafts were either bone-patellar tendon-bone with metal interference screw fixation or double-looped hamstring tendons with metal plate fixation. There were no significant differences between the two groups preoperatively or at operation. Standard rehabilitation included immediate postoperative mobilization without a knee brace, protected weightbearing for 2 weeks, and return to full activity at 6 to 12 months. RESULTS: Forty-three patients in the patellar tendon group and 46 patients in the hamstring tendon group were available for clinical evaluation at a minimum of 21 months after surgery. No statistically significant differences were seen with respect to clinical and instrumented laxity testing, International Knee Documentation Committee Score ratings, isokinetic muscle torque measurements, and Kujala patellofemoral, Lysholm, and Tegner scores. CONCLUSION: Equal results were seen for patellar and hamstring tendon autograft anterior cruciate ligament reconstructions at 2 years after surgery. Both techniques seem to improve patients' performance.     

Mechanical evaluation of a soft tissue interference screw in free tendon anterior cruciate ligament graft fixation

In this study of bioabsorbable screw fixation of free tendon grafts used in anterior cruciate ligament reconstruction, we performed load-to-failure and cyclic loading of tendon fixation in porcine bone. Bone density measurements from dual photon absorptometry scans were obtained to correlate bone density with fixation failure. The average density of porcine bone (1.42 g/cm2) was similar to that of young human bone (1.30 g/cm2) and significantly higher than that of elderly human cadaveric bone specimens (0.30 g/cm2). Cyclic loading was performed on free tendon grafts fixed with a bioabsorbable screw alone and on grafts fixed with a bioabsorbable screw and an anchor (polylactic acid ball or cortical bone disk). Stiffness of fixation increased substantially with the addition of a cortical bone disk anchor or polylactic acid ball compared with the interference screw alone. Tensile fixation strength of central quadriceps free tendon and hamstring tendon grafts were significantly superior in porcine bone of density similar to young human bone than in elderly human cadaveric bone. The bioabsorbable interference screw yielded loads at failure comparable with traditional bone-tendon-bone and hamstring tendon fixation when controlled for bone density. The addition of a cortical bone disk anchor provided the most optimal fixation of free tendon with the bioabsorbable screw and reduced slippage with cyclic loading to a very low level.     

Gender differences in outcome after anterior cruciate ligament reconstruction with hamstring tendon autograft

BACKGROUND: It is now well documented that women are more likely to suffer anterior cruciate ligament injuries than are men. A few studies have examined gender differences in the outcome of anterior cruciate ligament reconstruction with patellar tendon graft and hamstring tendon with EndoButton fixation, but no well-controlled studies have specifically compared men and women after anterior cruciate ligament reconstruction with hamstring tendon graft and interference screw fixation. HYPOTHESIS: There is no difference in outcome between men and women after anterior cruciate ligament reconstruction with hamstring tendon autograft and interference screw fixation. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: There were 100 men and 100 women who underwent isolated anterior cruciate ligament reconstruction by a single surgeon. Patients were assessed preoperatively and at 1, 2, and 7 years after surgery. Variables were compared between female and male patients. RESULTS: Laxity on physical evaluation was greater in women than in men on Lachman (P = .04), pivot-shift (P = .05), and mean manual maximum testing (P = .05) at 7 years. However, the magnitude of this difference was small. No patient had a greater than grade 1 Lachman or pivot-shift test result, and the mean difference between men and women was 0.6 mm on instrumented testing. Anterior cruciate ligament graft rupture occurred in 11 men and 10 women. There was no difference between male and female patients for self-reported knee function or symptoms of instability or radiologic examination. CONCLUSION: Anterior cruciate ligament reconstruction using hamstring tendon autograft affords excellent self-reported and objective results in both men and women after 7 years. Although significantly greater laxity on physical examination was present in female patients than in male patients, the magnitude of this difference was small and had no effect on activity level, graft failure, or subjective or functional assessment.     

The influence of supplementary tibial fixation on laxity measurements after anterior cruciate ligament reconstruction with hamstring tendons in female patients

BACKGROUND: Female patients undergoing arthroscopic anterior cruciate ligament reconstruction with a hamstring tendon graft developed increased postoperative laxity compared to male and female patients who had reconstruction using a patellar tendon graft. This difference may be due to graft slippage in less dense female tibial bone. HYPOTHESIS: Reinforcement of tibial fixation of the hamstring tendon graft in women by supplementary methods may reduce laxity. STUDY DESIGN: Randomized controlled clinical trial; Level of evidence, 2. METHODS: Fifty-six female patients divided into 2 groups (standard tibial fixation with 7 x 25-mm metal interference screw versus metal interference screw with supplementary staple fixation) were followed for 2 years. RESULTS: After 2 years, the mean side-to-side difference using KT-1000 arthrometer manual maximum measurements was 1.8 mm (standard group) and 1.1 mm (staple group) (P=.05). The percentage of patients with a side-to-side difference of <3 mm did not differ significantly between the 2 groups (P=.66): 88.8% of the standard group versus 90.5% of the staple group. A grade 0 Lachman test result was present in 63% of the standard group and 86% of the staple group (P=.04). Kneeling pain was experienced by 7% of the standard group and 29% of the staple group (P=.05). CONCLUSIONS: Supplementary tibial fixation in female patients undergoing anterior cruciate ligament reconstruction with hamstring tendon graft in addition to a single-size screw significantly improves laxity measurements and clinical stability assessment 2 years after surgery. However, this improvement is at the cost of increased kneeling pain.     

Femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction: biomechanical evaluation of different fixation techniques: is there an acute angle effect?

BACKGROUND: The literature provides little biomechanical data about femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction. HYPOTHESIS: A hybrid fixation technique with use of an undersized screw has sufficient strength to provide secure fixation of posterior cruciate ligament grafts. Additional aperture fixation with a biodegradable interference screw can prevent graft damage that might be caused by an acute angle on the edge of the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: In part 1, extracortical fixation of posterior cruciate ligament reconstructions with quadrupled porcine flexor digitorum grafts to simulate human hamstring grafts was compared with hybrid fixation methods using 6-, 7-, and 8-mm screws. Groups were tested in cycling loading with the load applied in line with the bone tunnel. In part 2, extracortical fixation was compared with hybrid fixation using a 1-mm undersized screw anterior and posterior to the graft. Structural properties and graft abrasion were evaluated after cyclic loading with the load applied at 90 degrees to the tunnel. In each group, 8 porcine knees were tested. RESULTS: In part 1, stiffness, maximum load, and yield load were significantly higher for hybrid fixation than for extracortical fixation. Hybrid fixation with an 8-mm screw resulted in higher yield load than with a 7-mm screw. In part 2, graft laceration was more pronounced in specimens with extracortical fixation than with hybrid fixation. Posterior screw placement was superior to the anterior position. CONCLUSION: For all parameters, hybrid fixation with an interference screw provided superior structural results. No relevant disadvantages of undersized screws could be found. Graft damage due to abrasion at the edge of the femoral bone tunnel was reduced by use of an interference screw. The posterior screw placement seems favorable. CLINICAL RELEVANCE: Hybrid fixation of hamstring grafts in posterior cruciate ligament reconstruction is superior to extracortical fixation alone with no relevant disadvantages of undersized screws. The results raise the suspicion of an acute angle effect of the femoral bone tunnel.     

Patellar tendon or semitendinosus tendon autografts for anterior cruciate ligament reconstruction? A prospective randomized study with a two-year follow-up

BACKGROUND: There are well-known problems with the use of bone-patellar tendon-bone autografts for anterior cruciate ligament reconstruction, especially in terms of donor site morbidity. Hamstring tendon grafts have been increasingly used as an alternative, but there are very few controlled studies comparing the methods. HYPOTHESIS: Use of semitendinosus tendon grafts will cause less donor site morbidity and result in better knee-walking ability. STUDY DESIGN: Prospective randomized clinical trial. METHODS: Seventy-one patients who had a unilateral anterior cruciate ligament rupture underwent arthroscopic reconstruction with interference screw fixation and use of either bone-patellar tendon-bone or semitendinosus tendon graft. Outcome assessment was performed by physiotherapists not involved in the patients' care. RESULTS: At the 2-year follow-up, no differences were found in terms of the Lysholm score, Tegner activity level, KT-1000 arthrometer side-to-side laxity measurement, single-legged hop test, or International Knee Documentation Committee classification results. The knee-walking test was rated difficult or impossible to perform by 53% of the bone-patellar tendon-bone group and by only 23% of the semitendinosus graft patients, a significant difference. CONCLUSIONS: The semitendinosus tendon graft is at least an equivalent option to the bone-patellar tendon-bone graft for anterior cruciate ligament reconstruction, and we recommend its use.     

Biomechanical properties of quadruple tendon and patellar tendon femoral fixation techniques

Two femoral fixation techniques for quadruple hamstring tendon grafts were compared under cyclic loading with the patellar tendon: the rectangular inserted pin (TransFix) and biodegradable interference screw fixation of the quadruple tendon and titanium interference screw fixation of the middle third of the patellar tendon. Porcine specimens were mounted onto a tension load machine, and the tendon-fixation-femur-complex was tested for stiffness, displacement during 800 cycles of loading between 50 and 250 N and ultimate tension load. TransFix fixation showed the greatest stiffness at 183.6 N/mm ( P<0.05). The least displacement under cyclic loading was observed for the titanium interference screw followed by the TransFix and biodegradable interference screw ( P<0.01). The ultimate tension load was greatest for the TransFix fixation at 1303+/-282 N, followed by patellar tendon fixation with 763+/-103 N and the biodegradable interference screw fixation with 480+/-133 N ( P<0.001). To reduce initial elongation of the graft and displacement at the fixation site, preconditioning of both the tendon and tendon-fixation complex is especially important when using quadruple tendons. TransFix fixation provides better stability and greater stiffness and pull-out strength than the other techniques. This finding is of clinical relevance to surgeons of the anterior cruciate ligament.     

Biomechanical comparison of posterior cruciate ligament reconstruction techniques using cyclic loading tests

Posterior tibial translation (PTT) of the posterior cruciate ligament (PCL) reconstructed-knee under cyclic loading of 1,000 cycles with a 100-N load was compared between four different procedures, including two reconstructions with patellar tendon graft (transtunnel and inlay techniques) and two reconstructions with hamstring tendon graft (Endobutton and EndoPearl techniques) in twelve fresh-frozen human knees. The EndoPearl technique is a direct tendon fixation using biodegradable interference screws and an anchoring device, while the Endobutton technique is an indirect tendon fixation using a titanium button and surgical tape. The change of PTT after cyclic loading in the Endobutton technique was significantly greater than in the other reconstruction technique. No graft rupture at the killer turn or complete pullout from the bone tunnel was found. The advantage of the inlay technique compared to the transtunnel technique with respect to the posterior stability could not be shown in the current study. Posterior laxity of PCL reconstructed-knees with hamstring tendon graft using the Endobutton technique increased more easily than that with patellar tendon graft. For PCL reconstruction using the hamstring tendon graft, anatomical fixation may be preferable to prevent excessive posterior laxity in the early phase of the rehabilitation protocol.     

Cyclic pull-out strength of hamstring tendon graft fixation with soft tissue interference screws. Influence of screw length

Blunt-threaded interference screws used for fixation of hamstring tendons in anterior cruciate ligament reconstructions provide aperture fixation and may provide a biomechanically more stable graft than a graft fixed further from the articular surface. It is unknown if soft tissue fixation strength using interference screws is affected by screw length. We compared the cyclic and time-zero pull-out forces of 7 x 25 mm and 7 x 40 mm blunt-threaded metal interference screws for hamstring graft tibial fixation in eight paired human cadaveric specimens. A four-stranded autologous hamstring tendon graft was secured by a blunt-threaded interference screw into a proximal tibial tunnel with a diameter corresponding to the graft width. Eight grafts were secured with a 25-mm length screw while the other eight paired grafts were secured with a 40-mm length screw. During cyclic testing, slippage of the graft occurred as the force of pull became greater with each cycle until the graft-screw complex ultimately failed. All grafts failed at the fixation site, with the tendon being pulled past the screw. There were no measurable differences in the mean cyclic failure strength, pull-out strength, or stiffness between the two sizes of screws. Although use of the longer screw would make removal technically easier should revision surgery be necessary, it did not provide stronger fixation strength than the shorter, standard screw as had been postulated.     

Clinical outcome of anterior cruciate ligament reconstruction with quadrupled hamstring tendon graft and bioabsorbable interference screw fixation

BACKGROUND: To date, there has been no publication of clinical follow-up data on patients who have undergone quadrupled hamstring tendon autograft anterior cruciate ligament reconstruction with bioabsorbable screw fixation. PURPOSE: To report the results of quadrupled hamstring tendon autograft anterior cruciate ligament reconstruction with bioabsorbable interference screw fixation. STUDY DESIGN: Retrospective review. METHODS: Sixty-five patients (66 knees) were retrospectively identified by chart review as having undergone quadrupled hamstring tendon autograft anterior cruciate ligament reconstruction with bioabsorbable interference screw fixation with a minimum 2-year follow-up. RESULTS: Data were collected on 48 knees in 47 patients (73%) at an average 30.2 months (range, 24 to 43) after surgery. Thirty-six patients (37 knees) returned for clinical evaluation (56% return) and subjective follow-up only was obtained in 11 patients (17%). The mean Lysolm knee score was 91 (range, 45 to 98), with a mean of 97 for the uninvolved knee. The mean Tegner activity score was 5.7 (range, 3 to 7). The KT-1000 arthrometer mean side-to-side difference for manual maximum displacement was 2.03 mm (range, -1 to 8). The mean International Knee Documentation Committee knee score was 83 (range, 47 to 100). Patients who underwent associated partial meniscectomy or meniscal repair had significantly lower International Knee Documentation Committee scores than patients without associated procedures (P < 0.01). CONCLUSIONS: Quadrupled hamstring tendon autograft anterior cruciate ligament reconstruction with bioabsorbable interference screw fixation is comparable with other methods of anterior cruciate ligament reconstruction in terms of patient satisfaction, knee stability, and function.     

A prospective, randomized comparison of semitendinosus and gracilis tendon versus patellar tendon autografts for anterior cruciate ligament reconstruction: five-year follow-up

BACKGROUND: There are still controversies about graft selection for primary anterior cruciate ligament reconstruction. Prospective randomized long-term studies are needed to determine the differences between the materials. HYPOTHESIS: Five years after anterior cruciate ligament reconstruction, there is a difference between hamstring and patellar tendon grafts in development of degenerative knee joint disease. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: From June 1999 to March 2000, 64 patients were included in this prospective study. A single surgeon performed primary arthroscopically assisted anterior cruciate ligament reconstruction in an alternating sequence. In 32 patients, anterior cruciate ligament reconstruction was performed with hamstring tendon autograft, whereas in the other 32 patients, anterior cruciate ligament reconstruction was performed with patellar tendon autograft. RESULTS: At the 5-year follow-up, no statistically significant differences were seen with respect to the Lysholm score, clinical and KT-2000 arthrometer laxity testing, anterior knee pain, single-legged hop test, or International Knee Documentation Committee classification results; 23 patients (82%) in the hamstring tendon group and 23 patients (88%) in the patellar tendon group returned to their preinjury activity levels. Graft rupture occurred in 2 patients from the hamstring tendon group (7%) and in 2 patients from the patellar tendon group (8%). Grade B abnormal radiographic findings were seen in 50% (13/26) of patients in the patellar tendon group and in 17% (5/28) of patients in the hamstring tendon group (P = .012). CONCLUSION: Both hamstring and patellar tendon grafts provided good subjective outcomes and objective stability at 5 years. No significant differences in the rate of graft failure were identified. Patients with patellar tendon grafts had a greater prevalence of osteoarthritis at 5 years after surgery.     

Biomechanical analysis of femoral tunnel pull-out angles for anterior cruciate ligament reconstruction with bioabsorbable and metal interference screws

BACKGROUND: Fixation strength of metal and bioabsorbable interference screws has not been evaluated while varying the anterior cruciate ligament graft tension angle. HYPOTHESIS: There is no difference in fixation strength between 2 types of interference screws for anterior cruciate ligament graft fixation while the graft tension angle is varied relative to the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight anterior cruciate ligament reconstructions were performed using immature porcine femurs stripped of soft tissue and doubled-over porcine flexor digitorum profundus tendon grafts. Specimens were randomized to bioabsorbable or titanium interference screw fixation. Specimens were randomized to one of three pull angles (0 degrees , 30 degrees , 60 degrees ) representing loading at different knee flexion angles (n = 8/group). Reconstructed ligaments were tensioned to 10 N followed by 200 loading cycles between 10 and 150 N and a final failure test. Construct elongation (mm) at 100 and 200 cycles and failure load (N) were analyzed using a 2-way analysis of variance (P < .05). RESULTS: Screw material interacted significantly with graft tension angle, as the bioabsorbable screw specimens demonstrated significantly greater fixation strength when tensioned at greater angles. Specimens fixed with bioabsorbable screws showed significantly less elongation at both 100 and 200 cycles and significantly greater failure load compared with titanium screws. CONCLUSION: Bioabsorbable interference screws acutely have increased fixation strength compared with titanium interference screws for anterior cruciate ligament grafts loaded at greater tension angles. CLINICAL RELEVANCE: The strength of anterior cruciate ligament reconstruction fixation increases with increasing divergence between the tension angle and femoral tunnel, a condition seen when the knee approaches full extension.     

Twisting and braiding reduces the tensile strength and stiffness of human hamstring tendon grafts used for anterior cruciate ligament reconstruction

BACKGROUND: Twisting and braiding of four-strand hamstring tendon grafts used for anterior cruciate ligament reconstruction has been proposed, but not proven, as a method of improving tensile properties. HYPOTHESIS: Twisting and braiding four-strand human hamstring tendon grafts will have no significant effect on initial graft strength or stiffness. STUDY DESIGN: Paired in vitro biomechanical study. METHODS: In 12 matched cadaveric pairs, a doubled gracilis and semitendinosus tendon graft from one knee was twisted 180 degrees over a 30-mm length, while the doubled tendon graft from the contralateral knee was prepared for biomechanical testing with the graft strands in a parallel orientation. For an additional 12 matched pairs, a doubled graft was braided into a weave while the contralateral graft was prepared for testing in a parallel orientation. All four strands of each doubled tendon graft were equally tensioned with weights before being clamped in a tendon-freezing grip. Tensile testing was then performed. RESULTS: Twisting decreased graft strength by 26% (P < 0.01) and stiffness by 43% (P < 0.01), while braiding reduced strength by 46% (P < 0.01) and stiffness by 54% (P < 0.01), compared with parallel-oriented grafts. CONCLUSIONS: Equally tensioned, parallel four-strand human hamstring tendon grafts were significantly stronger and stiffer than twisted or braided four-strand hamstring tendon grafts. Clinical Relevance: We caution against the use of twisted or braided four-strand hamstring tendon grafts for anterior cruciate ligament reconstruction.     

Close-looped graft suturing improves mechanical properties of interference screw fixation in ACL reconstruction

Purpose

In anterior cruciate ligament reconstruction with looped soft-tissue grafts, an interference screw is frequently used for tibial fixation. This study compared three alternatives thought to improve the initial mechanical properties of direct bioabsorbable interference screw fixation: suturing the graft to close the loop, adding a supplementary staple, or increasing the oversize of the screw diameter relative to the bone tunnel from 1 to 2 mm.

Methods

Twenty-eight porcine tibiae and porcine flexor digitorum profundus tendons were randomized into four testing groups: a base fixation using 10-mm-diameter screw with open-looped graft, base fixation supplemented by an extracortical staple, base fixation but closing the looped graft by suturing its ends, and base fixation but using an 11-mm screw. Graft and bone tunnel diameters were 9 mm in all specimens. Constructs were subjected to cyclic tensile load and finally pulled to failure to determine their structural properties.

Results

The main mode of failure in all groups was pull-out of tendon strands after slippage past the screw. The sutured graft group displayed significantly lower residual displacement (mean value reduction: 47–67 %) and higher yield load (mean value increase: 38–54 %) than any alternative tested. No other statistical differences were found.

Conclusions

Suturing a soft-tissue graft to form a closed loop enhanced the initial mechanical properties of tibial fixation with a bioabsorbable interference screw in anterior cruciate ligament reconstructions using a porcine model, and thus, this may be an efficient means to help in reducing post-operative laxity and early clinical failure. No mechanical improvement was observed for an open-looped tendon graft by adding an extracortical staple to supplement the screw fixation or by increasing the oversize of the screw to tunnel diameter from 1 to 2 mm.     

The influence of reverse-thread screw femoral fixation on laxity measurements after anterior cruciate ligament reconstruction with hamstring tendon

In arthroscopically assisted anterior cruciate ligament reconstruction using hamstring tendon graft, the graft rotates slightly as the femoral screw is inserted. Its final position tends to be in the anterior half of the tunnel in right knees, resulting in clinical laxity. To perform identical procedures on left and right knees, a reverse-thread screw was designed for femoral fixation in right knees. We prospectively studied 80 patients undergoing right-knee anterior cruciate ligament reconstruction with hamstring tendon autograft. Thirty-six patients underwent reconstruction with a standard screw and 44 underwent reconstruction with a reverse-thread screw. The same technique, performed by the same surgeon, was used on all patients. At 12 months' follow-up, the average side-to-side differences on arthrometry testing were 2.00 mm for the standard screw group and 0.95 mm for the reverse-thread screw group using a manual maximum test, and 1.66 mm and 1.00 mm, respectively, using the 20-pound test. Both differences were statistically significant. Of the standard group, 23% had a manual maximum difference of 3 mm or more, compared with 8% of the reverse-thread group. A significant difference was found between these two groups for Lachman test (77% with grade 0 for the standard group compared with 92% for the reverse group) but pivot shift and Lysholm knee score were not significantly different. The use of a reverse-thread screw for femoral fixation in right-knee anterior cruciate ligament reconstructions in men significantly decreased laxity at 12 months after surgery compared with standard screw fixation.     

Interference screw fixation of soft tissue grafts in anterior cruciate ligament reconstruction: part 2: effect of preconditioning on graft tension during and after screw insertion

BACKGROUND: Preconditioning of tendon grafts is believed to eliminate natural viscoelasticity of the tendons and prevent knee laxity after anterior cruciate ligament (ACL) reconstruction. HYPOTHESIS: Preconditioned ACL grafts maintain their initially set tension. STUDY DESIGN: Randomized experimental study. METHODS: Forty-two human anterior tibialis (AT) tendon grafts were subjected to either no preconditioning (group 1), cyclic preconditioning (group 2), or isometric preconditioning (group 3). The residual graft tension was then recorded immediately after the application of an initial graft tension of 80 N and fixation into tibia with an interference screw, as well as 10 minutes later. In another experiment, the residual graft tension was recorded 1, 10, and 60 minutes after 10 AT and quadrupled hamstring tendon (HT) grafts alone (no fixation) had been subjected to isometric preconditioning (80 N). RESULTS: Immediately after screw insertion, the residual (AT) graft tensions were 79 +/- 19 N, 100 +/- 17 N, and 102 +/- 15 N in groups 1 through 3, respectively. Ten minutes later, the corresponding values were 49 +/- 16 N, 60 +/- 11 N, and 64 +/- 12 N. For the AT and HT grafts alone, the residual graft tensions were 67 +/- 2 N and 67 +/- 2 N, 45 +/- 2 N and 46 +/- 4 N, and 29 +/- 3 N and 34 +/- 5 N at 1, 10, and 60 minutes, respectively. CONCLUSIONS: A steady decrease (-60% within 60 minutes after initial tensioning) occurs in the initially set tension of the soft tissue ACL grafts. Clinical Relevance: Clinically applicable preconditioning protocols cannot eliminate the intrinsic viscoelasticity from ACL soft tissue grafts, and thus, the reasonableness of preconditioning per se is questioned in ACL reconstruction.     

The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction. Part I: femoral site

BACKGROUND: Strength of graft fixation is the weakest link in anterior cruciate ligament reconstruction. HYPOTHESIS: There is no difference in initial fixation strength between different hamstring tendon graft femoral fixation devices. STUDY DESIGN: Randomized experimental study. METHODS: Each of six devices was used in the fixation of 10 quadrupled human semitendinosus-gracilis tendon grafts in tunnels drilled in porcine femora and tested 10 times with a single-cycle load-to-failure test at a rate of 50 mm/min and 10 times with a 1500-cycle loading test between 50 and 200 N at one cycle every 2 seconds. The specimens that survived the cyclic loading were subjected to a single-cycle load-to-failure test. RESULTS: The Bone Mulch Screw (1112 N) was strongest in the single-cycle load-to-failure test, followed by EndoButton CL (1086 N), RigidFix (868 N), SmartScrew ACL (794 N), BioScrew (589 N), and RCI screw (546 N). It also showed the lowest residual displacement (2.2 mm) and was strongest in the single-cycle load-to-failure test after cyclic loading. CONCLUSIONS: The Bone Mulch Screw was superior to all other devices. Clinical Relevance: Caution may be warranted in employing aggressive rehabilitation after reconstruction with these devices. Preconditioning of the graft-implant complex before fixation is important.     

A randomized comparison of patellar tendon and hamstring tendon anterior cruciate ligament reconstruction

BACKGROUND: Patellar and hamstring tendon autografts are the most frequently used graft types for anterior cruciate ligament reconstruction, but few direct comparisons of outcomes have been published. HYPOTHESIS: There is no difference in outcome between the two types of reconstruction. STUDY DESIGN: Prospective randomized clinical trial. METHODS: After isolated anterior cruciate ligament rupture, 65 patients were randomized to receive either a patellar tendon or a four-strand hamstring tendon graft reconstruction, and results were reviewed at 4, 8, 12, 24, and 36 months. RESULTS: Pain on kneeling was more common and extension deficits were greater in the patellar tendon group. There were greater quadriceps peak torque deficits in the patellar tendon group at 4 and 8 months but not thereafter. In the hamstring tendon group, active flexion deficits were greater from 8 to 24 months, and KT-1000 arthrometer side-to-side differences in anterior knee laxity at 134 N were greater. Cincinnati knee scores, International Knee Documentation Committee ratings, and rates of return to preinjury activity levels were not significantly different between the two groups. CONCLUSIONS: Both grafts resulted in satisfactory functional outcomes but with increased morbidity in the patellar tendon group and increased knee laxity and radiographic femoral tunnel widening in the hamstring tendon group.     

How four weeks of implantation affect the strength and stiffness of a tendon graft in a bone tunnel: a study of two fixation devices in an extraarticular model in ovine

BACKGROUND: For a tendon graft to function as an anterior cruciate ligament, the tendon must heal to the bone tunnel. We studied the effect of 4 weeks of implantation on the strength and stiffness of a tendon in a bone tunnel using two different fixation devices in an ovine model. HYPOTHESIS: The type of fixation device in anterior cruciate ligament reconstruction may affect early healing, which can be measured as the strength and stiffness of a tendon in a bone tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: An extraarticular tendon graft reconstruction was performed in ovine tibias. The graft was fixed with either a bioresorbable interference screw or a WasherLoc. After 4 weeks of implantation the strength and stiffness of the complex and the tendon graft-bone tunnel interface were determined by incrementally loading specimens to failure. RESULTS: For the interference screw, the strength deteriorated 63% and the stiffness deteriorated 40%. For the WasherLoc, the strength was similar and the stiffness improved 136%. CONCLUSIONS: The type of fixation device determines whether the strength and stiffness of a tendon in a bone tunnel increases or decreases after implantation. Clinical Relevance: The pace of rehabilitation may need to be adjusted based on the type of fixation device used to secure a soft tissue graft.