Clinical comparison of freeze-dried and fresh frozen patellar tendon allografts for anterior cruciate ligament reconstruction of the knee

Comparison of freeze-dried tibialis anterior allograft and four-strand hamstring autograft in anterior cruciate ligament reconstruction

PURPOSE

The aim of this retrospective study was to evaluate the clinical outcomes of the patients who underwent primary anterior cruciate ligament (ACL) reconstruction surgery with either hamstring autograft or freeze-dried tibialis anterior allograft, which performed by the same surgeon using the same fixation technique.

METHODS

In this retrospective study, patients who had primary ACL reconstruction using either four-strand hamstring autograft (FSH) or freeze-dried irradiated tibialis anterior allograft (FDT) between 2012 and 2015 were evaluated. Patients who were skeletally mature with a minimum follow-up of 24 months and who had no previous surgery from the affected knee were included; patients who had multiple ligament injuries or chondral lesions over Outerbridge grade 2 were excluded from the study. Patients were grouped according to the graft type used in ACL reconstruction. Tegner activity scale and Lysholm knee scoring scale were used to assess patients' activity levels and functional status preoperatively and at the final follow-up. KT-2000 arthrometer measurements were done at the final follow-up to evaluate anterior laxity.

RESULTS

There were 27 patients (mean age 27 ± 8.9 years) in the FSH group and 36 patients (mean age 27.1 ± 6.7 years) in the FDT group. The mean follow-up time was 38.2 ± 3.5 months for the FSH group and 41 ± 6.1 months for the FDT group. There were no statistically significant differences between the groups when preoperative and postoperative Tegner-Lysholm scores were compared (Tegner P = 0.583, 0.742; Lysholm P = 0.592, 0.249). The mean anteroposterior laxity and side-to-side differences measured by KT-2000 were 4.1 mm and 2.1 mm for the FSH group, respectively; 4.2 mm and 2.2 mm for the FDT group, respectively. There was not a statistically significant difference (P = 0.745, 0.562 respectively).

CONCLUSIONS

Primary ACL reconstruction with a single loop freeze-dried irradiated tibialis anterior allograft revealed comparable results with four-strand hamstring autograft in non-athlete patients.

LEVEL OF EVIDENCE

Level III, Therapeutic study.

Double-bundle PCL reconstruction using autologous hamstring tendons: outcome with a minimum 2-year follow-up

OBJECTIVE

To present the outcomes of posterior cruciate ligament (PCL) double-bundle reconstruction using autologous hamstring tendons, with a minimum follow-up of two years.

METHODS

Evaluation of 16 cases of PCL injury that underwent double-bundle reconstruction with autogenous hamstring tendons, between 2011 and 2013. The final sample consisted of 16 patients, 15 men and one woman, with a mean age of 31 years (21-49). The predominant mechanism was motorcycle accident in half of the cases. There was a mean interval of 15 months between the time of lesion and the surgery (three to 52 months). Five lesions were isolated and 11, associated. Clinical evaluation, application of validated scores, and measurements with use of the KT-1000 were performed.

RESULTS

The analysis showed a mean preoperative Lysholm score of 50 points (28-87), progressing to 94 points (85-100) postoperatively. The IKDC score also demonstrated improvement. In the preoperative evaluation, four and 12 patients were respectively classified as C (abnormal) and D (very unusual), and in the postoperative evaluation six as A (normal) and ten as B (close to normal). In the post-operative evaluation by KT1000 arthrometer, 13 patients showed difference between 0-2 mm and 3 between 3 and 5 mm, when compared with the contralateral side.

CONCLUSION

Autologous hamstring tendons are a viable option in double-bundle reconstruction of the PCL, with good clinical results in a minimum follow-up of two years.

Allografts in Anterior Cruciate Ligament Reconstruction

Usual allograft sources for anterior cruciate ligament (ACL) reconstruction are patellar ligament, Achilles tendon, tibialis anterior, and posterior. The advantages of the use of allograft include reduced donor-site morbidity, shorter operative time, smaller incisions, and no size restrictions. The disadvantages include increased cost, slower graft embodiment, and the risk of viral or bacterial infection, which may occur either by transmission from an infected donor or by contamination by the healthcare provider. Careful donor selection, aseptic graft procurement and processing, and tissue sterilization, by irradiation or proprietary chemical processing, are the three major steps of the graft preparation procedure. Successful allograft implantation depends on sterility, reduction of antigenicity, and preservation of the biomechanical properties of the graft. To date, reports on the clinical and functional outcomes of allograft compared to autograft ACL reconstruction are controversial. Overall, graft choice depends on surgeon and patient preference, since no graft can perfectly match the properties of the native ACL.

Failure rate of Achilles tendon allograft in primary anterior cruciate ligament reconstruction

PURPOSE

This study was performed to determine the failure rate of patients undergoing primary anterior cruciate ligament (ACL) reconstruction with an Achilles tendon allograft by a single surgeon with the same surgical technique, graft fixation, and postoperative rehabilitation. The Achilles tendon allograft was obtained from a single source.

METHODS

Of 158 patients who underwent primary ACL reconstruction with Achilles tendon allograft, 144 were followed up at a mean of 40 months. The mean age was 29.5 years at the time of surgery. Evaluation included a questionnaire at serial follow-up visits, physical examination, and return to play.

RESULTS

Of 144 patients, 8 (5.6%) sustained traumatic reruptures or had evidence of laxity failure. Patients were divided into 4 age groups: less than 18 years, 18 to 25 years, 26 to 40 years, and 41 years or greater. Failure rates of 8.7%, 8.8%, 5.7%, and 0%, respectively, were found. A chi(2) contingency test was performed comparing patients aged 25 years or younger and those aged over 25 years with a resulting P value of .5811. No statistically significant difference between the groups of failures was seen.

CONCLUSIONS

The results of our study show that the failure rate for freeze-dried Achilles tendon allograft in primary ACL reconstruction was 8 of 144 (5.6%). When these patients were followed up for a minimum of 24 months, we found failure rates of 8.7%, 8.8%, 5.7%, and 0% in those aged less than 18 years, 18 to 25 years, 26 to 40 years, and 41 years or older, respectively. No statistically significant difference between the groups of failures was seen.

LEVEL OF EVIDENCE

Level IV, case series.

What do we really know about allografts?

The use of allografts in sports medicine is becoming increasingly popular, and, therefore, this issue of Clinics in Sports Medicine is dedicated to the use of allografts in sports medicine. The majority of indications are related to the use of soft tissue grafts for ligament reconstruction, osteochondral (OC) allografts for articular surface reconstruction, and meniscal allografts for meniscal transplantation. There is an increasing amount of science and literature dealing with healing and outcomes, but many questions still remain. There are a number of issues, controversies, and lack of long-term outcomes to make definitive statements on what is really known about allograft use in sports medicine.

Tibial fixation of bone-patellar tendon-bone grafts in anterior cruciate ligament reconstruction: a cadaveric study of bovine bone screw and biodegradable interference screw

BACKGROUND

The use of interference screw fixation for bone-patellar tendon-bone grafts in anterior cruciate ligament fixation is well established. No previous study has compared bovine bone screws and biodegradable interference screws or demonstrated their efficacy for requirements associated with early rehabilitation.

HYPOTHESIS

There is no difference in tension loss and pull-out strength between bovine bone screws and biodegradable interference screws.

STUDY DESIGN

Controlled laboratory study.

METHODS

Anterior cruciate ligament reconstructions with bone-patellar tendon-bone allografts were performed in 40 human tibiae from 20 donors. A bovine bone screw and a polylevolactide interference screw were used for tibial fixation in each pair. A cyclic testing protocol with varying magnitude and orientation of the graft loading was developed. Cyclic tests were performed at 1 Hz for 5000 cycles with a peak force of 200 N applied to the graft. Survival rate and postcyclic-test pull-out strength were compared.

RESULTS

Fifteen of 20 reconstructions fixed with bovine bone screws and 17 of 20 fixed with biodegradable screws reached 5000 cycles. Graft tension drop after the 5000 cycles averaged 19.7 N ( +/- 12.9) for bovine bone screws and 18.9 N ( +/- 16.3) for biodegradable screws. There were no significant differences in tension loss and pull-out strength between the 2 types of screws.

CONCLUSION

Bovine bone screws are comparable to biodegradable interference screws in providing stable tibial fixation in anterior cruciate ligament reconstruction using bone-patellar tendon-bone allografts.

CLINICAL RELEVANCE

The use of bovine bone screws may be comparable to the popular biodegradable interference screws used for anterior cruciate ligament reconstruction in postsurgery rehabilitation.

Arthroscopic anterior cruciate ligament reconstruction using fresh-frozen bone plug-free allogeneic tendons: 10-year follow-up

PURPOSE

To evaluate the long-term outcomes following arthroscopic-assisted anterior cruciate ligament (ACL) reconstruction using fresh-frozen allogeneic tendon.

METHODS

Sixty-one athletically active patients (mean age at surgery, 20.9 years) who had arthroscopic-assisted ACL reconstruction using fresh-frozen free tendon allograft underwent physical examination, instrumented laxity measurement, radiographs, and thigh muscle strength at 10 to 14 years (mean, 11.5) postoperatively, and these data were compared with results of similar measurements obtained at 2 years postoperatively.

RESULTS

Lachman test and pivot shift test were maintained as negative in 53 (87%) and 52 (85%) patients at follow-up, respectively. Quantitative measurements using the KT-2000 knee arthrometer showed 1.6 +/- 1.3 (mean +/- SD) mm in the side-to-side difference, and no more than 3 mm in 56 patients (92%) at final follow-up. All but one was assessed as normal or nearly normal by International Knee Documentation Committee score. Patient activity level was decreased at the long-term follow-up, but this change was mainly associated with changes in social context (e.g., graduation from school) rather than with knee limitations. None of the patients experienced deep infection or graft rejection. Degenerative joint disease on radiographs was seen in 13 out of 15 patients (87%) whose menisci had been excised, whereas it was observed in 12 out of 46 (26%) whose menisci had been preserved.

CONCLUSIONS

A series of 61 patients with fresh-frozen bone plug-free tendon allografts using a 2-incision technique for arthroscopic ACL reconstruction results in long-term knee stabilization and functioning among young active individuals while simultaneously avoiding graft harvest site morbidity.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Clinical outcomes of allograft versus autograft in anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) injuries are the most common complete ligamentous injury to the knee. The optimal graft should be able to reproduce the anatomy and biomechanics of the ACL, be incorporated rapidly with strong initial fixation, and cause low graft-site morbidity. This article reviews the literature comparing the clinical outcomes following allograft and autograft ACL reconstruction and examines current issues regarding graft choice.

Nonirradiated versus irradiated Achilles allograft: in vivo failure comparison

BACKGROUND

Many studies suggest that gamma irradiation decreases allograft strength in a dose-dependent manner. No study has demonstrated that this decrease in strength translates into higher clinical failures.

HYPOTHESIS

Irradiation of allograft tissue will lead to higher early clinical failure in anterior cruciate ligament (ACL) reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Medical records were reviewed for 90 consecutive patients who had received Achilles allograft reconstruction for unilateral primary ACL injuries at one institution between July 2001 and June 2002. One half of patients received nonirradiated Achilles allograft and the other half received irradiated Achilles allograft at a dose range of 2.0 to 2.5 Mrad. The ACL allograft reconstructions were performed using the same surgical technique. The rehabilitation program was identical for both groups. All clinical failures were recorded.

RESULTS

At least 6 months' follow-up was available on 42 subjects in the nonirradiated group and 33 subjects in the irradiated group. A significant difference was noted in early failure rates between the groups (P <.01). The nonirradiated group had 1 in 42 (2.4%) catastrophic failure. In the irradiated group, 11 of 33 (33%) Achilles tendon grafts failed.

CONCLUSIONS

Less than satisfactory results led the senior authors to discontinue the use of irradiated allografts in ACL surgery. Continued research into alternatives to gamma irradiation is needed.

A literature review of autograft and allograft anterior cruciate ligament reconstruction

Knee anterior cruciate ligament reconstructive surgery has significantly evolved and now includes the option of using an allograft. This has resulted in numerous studies evaluating the advantages and disadvantages of allografts. The purpose of this literature review is to evaluate this research and present important findings to allow the selection of the most appropriate graft source when considering allograft versus autograft reconstruction.

Posterior cruciate ligament reconstruction: double-loop hamstring tendon autograft versus Achilles tendon allograft--clinical results of a minimum 2-year follow-up

PURPOSE

The purpose of this study was to compare clinical results of arthroscopic posterior cruciate ligament (PCL) reconstructions using double-loop hamstring tendon autograft and Achilles tendon allograft while preserving the original PCL remnant.

TYPE OF STUDY

Case-control study of results of treatment.

METHODS

From September 1997 to December 2000, 36 patients who received only PCL reconstruction were reviewed retrospectively. Of these, 18 patients received autogenous double-loop hamstring tendon reconstruction (group I) and 18 received Achilles tendon allograft reconstruction (group II). The same PCL reconstruction procedure was performed in both groups. At final follow-up at a minimum of 2 years, patients were evaluated by 4 measures: the International Knee Documentation Committee (IKDC) evaluation, Lysholm knee scores, the posterior draw test, and Telos stress radiography.

RESULTS

Between the 2 groups, preoperative demographic factors (age, gender, activity level, and mean duration to surgery) showed no statistically significant difference (P > .05). According to IKDC evaluation of group I, 16 of the 18 knees rated normal or nearly normal, whereas 2 fell into the abnormal category. By the same criteria, 14 of the 18 knees in group II were normal to nearly normal, 3 were abnormal, and 1 was severely abnormal. IKDC scores showed no statistical difference between the 2 groups (P = .98). Postoperative mean Lysholm knee scores were 90 points (range, 78-100) for group I and 85 (range, 70-95) for group II; improvements of 22 and 17 points, respectively. According to the Lysholm knee scores, group I showed slightly better results than did group II, with a statistical significance of P < .01. Telos stress radiography showed the mean difference in posterior translation between the injured and uninjured knees to be 2.2 mm (range, 0 to 7.0 mm) for group I and 2.9 mm (range, 1.0 to 7.0 mm) for group II. The Telos stress test showed no statistical difference between the 2 groups (P = .14).

CONCLUSIONS

The clinical outcome was the same for both groups. Despite its comparatively short length and small diameter, the double-loop hamstring tendon autograft was as good as Achilles tendon allograft in PCL reconstruction.

LEVEL OF EVIDENCE

Level III, case-control study.

Anterior cruciate ligament reconstruction using cryopreserved allografts

Primary ACL reconstruction historically has been done using autograft tissues whereas allografts have been limited to revision cases and patients who are older or with lower physical demands because some animal studies suggested a slower biologic incorporation rate. The purpose of the current study was to evaluate the effectiveness of the cryopreserved Achilles tendon allograft in primary ACL reconstruction in a consecutive series of athletes. Fifty consecutive patients with a strenuous or moderate preinjury activity level, as defined by the International Knee Documentation Committee (IKDC), had ACL reconstruction using cryopreserved Achilles tendon allografts secured with bioabsorbable interference screws. Five patients were professional athletes. The average age of the patients was 36 years (range, 17-50 years). A 3- to 5-year followup study was done in all of the patients using the IKDC form. Tunnel widening was measured in the lateral radiographs at the widest level. The overall outcome was normal or nearly normal in 94% of the patients. No failures were reported in this series. Forty-six patients (92%) returned to their same preinjury sport activity level. The average KT-1000 side-to-side difference was 2.3 mm. Average tibial tunnel widening was 2.7 mm (range, 0-6 mm); no significant correlation was observed between increased tunnel size and a fair or poor clinical outcome. This experience shows that favorable results can be obtained with cryopreserved Achilles tendon allografts in athletes in whom avoiding donor site morbidity may be an issue in terms of a prompt return to sport.

Effect of gamma irradiation on remodeling process of tendon allograft

Freeze-dried tendon allograft sterilized with gamma irradiation could be a reasonable option for ligament substitute. In the current study, the effects of freezing or freeze-drying followed by gamma irradiation on remodeling were analyzed biomechanically in a rat patellar tendon transplantation model at the time of harvest and during a 24-week healing period. The grafts were divided into four groups: fresh-freezing, freeze-drying, fresh-freezing followed by gamma irradiation, and freeze-drying followed by gamma irradiation. Before transplantation, the fresh-frozen grafts and the freeze-dried grafts showed significantly greater tensile strength than the gamma-irradiated grafts. However, at 4 weeks, the tensile strength of each group decreased to the equivalent level, which was approximately 20% of the tensile strength at Time 0, then increased gradually with time. At 24 weeks, the mean tensile strength of each transplanted graft achieved as much as 50% of the tensile strength at Time 0. The change in the tangent modulus with time followed a similar pattern as changes in the tensile strength. This study assumed that the extraarticular tendon transfer model was suitable for evaluating anterior cruciate ligament graft healing. These data suggest that the freeze-dried tendon allografts sterilized by gamma radiation could be a suitable substitute for anterior cruciate ligament reconstruction, if care is taken to protect the graft during the early stage after transplantation (< 4 weeks).

Arthroscopically assisted meniscal allograft transplantation with and without combined anterior cruciate ligament reconstruction

The menisci provide a vital role in load transmission across the knee joint as well as contribute to knee stability, particularly in the ACL-deficient knee. Loss of the meniscus, in part or in total, significantly alters joint function and predisposes the articular cartilage to degenerative changes, which has been well documented both clinically and radiographically. This study examined clinical and patient-reported outcomes following meniscal allograft transplantation with and without combined ACL reconstruction in a select group of 31 patients with complaints of pain and/or instability (34 meniscal allografts); 11 underwent isolated meniscal transplantation and 20 meniscal transplantation combined with ACL reconstruction. Bony fixation was performed with bone plugs for medial transplants and using a bone bridge for lateral transplants. All patients completed several knee-specific and general measures of health-related quality of life and underwent a comprehensive physical examination. Flexion weightbearing PA radiographs at latest follow-up were compared to those obtained preoperatively. Mean follow-up was 2.9 years (range 2-5.5 years). The Activities of Daily Living and Sports Activities Scale scores were 86+/-11 and 78+/-16, respectively, and the average Lysholm score was 84+/-14. There were no significant differences in these scores based upon which meniscus (medial or lateral) was transplanted, concurrent ACL reconstruction, or the degree of chondrosis at arthroscopy. SF-36 scores indicated that patients were functioning at a level similar to the age- and sex-matched population. Twenty-two patients stated they were greatly improved, 8 were somewhat improved, 1 was without change. All but one patient reported that knee function and level of activity were normal or nearly normal. The average loss of motion compared to the noninvolved side was 3 degrees for extension and 9 degrees for flexion. All but one patient had a negative or 1+ Lachman's test. The remaining patient had a 2+ Lachman's test. Assessment with the KT-1000 arthrometer revealed a side-to-side difference of 2 mm (range -2 mm to 7 mm). Average hop and vertical jump indices were both 85% of the contralateral extremity. No statistically significant joint space narrowing was observed by radiography over time. Meniscal allograft transplantation with and without combined ACL reconstruction in carefully selected patients with complaints of compartmental joint line pain and/or instability appears able to provide relief of symptoms and restore relatively high levels of function, particularly during activities of daily living.

Soft tissue allografts for knee reconstruction in sports medicine

Soft tissue allografts are an important substitute tissue for the reconstruction of deficient ligaments, torn menisci, and osteochondral defects during knee surgery. Interest in allografts for soft tissue reconstruction has arisen from the demand to obtain a stable knee with restoration of function and protection against additional injury. Use of allografts for soft tissue reconstruction is associated with less donor tissue site morbidity and reduced surgical time. Nevertheless, use of allografts has a potential for disease transmission, delayed graft incorporation, and host versus donor immunologic response to the graft. Experimental studies and animal models have provided information about the biologic aspects of graft incorporation and remodeling and have contributed to the development of methods of graft preparation and transplantation. Clinical studies of allograft transplantation in humans have helped to define surgical indications and techniques and have allowed for the assessment of clinical outcome. The current authors review the current literature concerning the basic and clinical principles of soft tissue allografts for knee reconstruction, and underscore the scientific basis for the clinical application of allograft tissue during knee surgery.

A biomechanical evaluation of anterior and posterior tibialis tendons as suitable single-loop anterior cruciate ligament grafts

PURPOSE

Because allograft tendons used to replace a torn anterior cruciate ligament are in short supply, it is useful to explore other possible graft sources. The purpose of this study was to determine whether a graft formed from a loop of either an anterior or posterior tibialis tendon has structural, material, and viscoelastic properties similar to those of a double-looped semitendinosus and gracilis (DLSTG) graft.

TYPE OF STUDY

Completely randomized design.

METHODS

Four structural and 3 material properties were determined for each type of graft (n = 10) by measuring the cross-sectional area, looping the tendon(s) over a post, gripping the free ends of the tendon(s) with a freeze clamp, and pulling the graft to failure by using a materials testing system. Two viscoelastic properties were determined for each type of graft (n = 10) by measuring the decrease in load under a constant displacement (i.e., stress relaxation test) and the increase in displacement under a constant load (i.e., creep test).

RESULTS

For grafts 95 mm in length, the ultimate load and ultimate displacement of a loop of anterior (4,122 N, 12.0 mm) and posterior tibialis (3,594 N, 12.5 mm) tendon were either similar to or significantly greater than those of the DLSTG graft (2,913 N, 8.4 mm) (P =.204 for the posterior tibialis ultimate load and P < or =.007 for the remaining quantities). The stiffness and cross-sectional area of the anterior (460 N/mm, 48.2 mm2) and posterior tibialis (379 N/mm, 41.9 mm2) grafts were similar to those of the DLSTG graft (418 N/mm, 44.4 mm2) (P > or =.283). The tensile modulus, stress at ultimate load, and strain at ultimate load of the anterior tibialis and posterior tibialis grafts were either similar to or significantly greater than those of the DLSTG graft. The decrease in load of the anterior tibialis and posterior tibialis grafts was either greater than or similar to that of the DLSTG graft for the relaxation test (P < or =.066). The increase in displacement of the anterior tibialis (0.3 mm) and posterior tibialis (0.4 mm) grafts was minimally but significantly greater than that of the DLSTG graft (0.2 mm) for the creep test (P < or =.004).

CONCLUSIONS

The structural, material, and viscoelastic properties of a single loop of anterior tibialis and posterior tibialis tendon are either better than or similar to those of a DLSTG graft. Consequently, single-loop grafts formed from tibialis tendons should function well as a replacement for a torn anterior cruciate ligament.

Radiographic and histologic analysis of the tibial tunnel after allograft anterior cruciate ligament reconstruction in goats

BACKGROUND

Several problems have been reported with use of allogenic grafts in anterior cruciate ligament reconstruction, including local immune response to allograft tendon within the synovial fluid, delayed maturation and ligamentization, and progressive tibial tunnel enlargement.

HYPOTHESIS

There is a correlation between the use of allograft and tibial tunnel enlargement.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty healthy adult female goats underwent allograft anterior cruciate ligament reconstruction and were followed with serial radiographs at 6-week intervals. Animals were randomly chosen for sacrifice between 18 and 36 weeks for histologic assessment.

RESULTS

Significant radiographic increases in tunnel size were noted within the first 6 weeks of healing and remained up to 36 weeks with no further remodeling noted. Histologic analysis showed progressive ligamentization of the allografts with tendon-to-tunnel wall biologic fixation with dense connective tissue. Remodeling and incorporation of the bone plug was seen in all cases. The allograft tendon underwent early fibrous attachment within the tunnel and remodeled toward ligament histologic structure. Remodeling and incorporation of the bone plug was seen by 18 weeks.

CONCLUSION

Tibial tunnel enlargement, consistent with that seen in humans after allograft anterior cruciate ligament reconstruction, did not appear to affect the ultimate incorporation of the allograft on a histologic level.

Preoperative anterior knee laxity did not influence postoperative stability restored by anterior cruciate ligament reconstruction

Eighty-six chronic anterior cruciate ligament (ACL)-injured patients were quantitatively measured for anterior knee stability preoperatively and at 2 years or later (mean, 30 months) postoperatively to examine the influence of preoperative knee laxity on the postoperative knee stability restored by the ACL reconstruction using multiplied hamstring tendon graft. The patients were divided into 3 groups according to the preoperative injured minus normal anterior laxity difference (AL-D) (group I [n = 27] <5 mm, group II [n = 48] 5 to 9 mm, group III [n = 11] >10 mm). The 3 groups were comparable in gender, age, meniscal status, graft excursion measured during operation, time from injury to operation, and activity level. The postoperative AL-D in group I was 0.8 +/- 1. 7 mm, that in group II was 1.1 +/- 1.6 mm, and in group III was 1.5 +/- 1.4 mm. There were no significant statistical differences among these 3 groups. With our surgical technique including postoperative rehabilitation, patients with severe instability could be treated successfully without needing any additional procedures such as extra-articular augmentation or specially designed postoperative rehabilitation programs.

Comparison of tibial tunnel enlargement after anterior cruciate ligament reconstruction using patellar tendon autograft or allograft

This retrospective study was designed to compare tibial tunnel enlargement in patients with autograft or allograft anterior cruciate ligament reconstructions. The changes were related to position of the tibial tunnel and clinical outcome. Twenty-six patients with autograft reconstructions and 41 with allograft reconstructions were studied at a mean follow-up of 59 months (range, 41 to 84) after surgery. The average tunnel enlargement on the anteroposterior view was 2.2 mm (SD, 2.5) for autografts and 2.8 mm (SD, 2.1) for allografts. On the lateral view, the tunnel enlargement was 2.6 mm (SD, 2.4) and 3.4 mm (SD, 2.6) for autografts and allografts, respectively. No significant differences were found between the autograft and allograft groups. A trend was found in the correlation between the position of the tibial tunnel and the tunnel enlargement: more anteriorly placed tunnels had more enlargement. The changes in tunnel diameter did not relate to knee functional score or laxity. There was a significant correlation between malposition of the tibial tunnel and poor clinical scores. A significant negative correlation was found between postoperative follow-up time and tunnel enlargement in both groups. We conclude that placement of the tibial tunnel is a determining factor in tibial tunnel enlargement and clinical knee scores after anterior cruciate ligament replacement with an autograft or allograft. Tunnel enlargement tends to be less at a longer postoperative follow-up.

Effect of freeze-drying or gamma-irradiation on remodeling of tendon allograft in a rat model

Freezing or freeze-drying and gamma-irradiation are techniques currently used for processing tendon allografts. However, it is still unknown how these processing methods affect graft remodeling. In this study, we used a rat patellar tendon transplantation model to investigate the effect of various processing methods on remodeling by quantifying loss of collagen labeled with a radioactive isotope. The grafts were divided into the following four groups according to the processing method: fresh-frozen, freeze-dried, fresh-frozen and gamma-irradiated, or freeze-dried and gamma-irradiated. The percentage of donor collagen, calculated from hydroxyproline content and radioactivity level, was used as an indicator of graft remodeling. At 2 weeks, the level of donor collagen in the fresh-frozen group was 62%; in the freeze-dried group, 59%; in the fresh-frozen and irradiated group, 57%; and in the freeze-dried and irradiated group, 44%. At 4 weeks, the percentage of donor collagen remaining in grafts decreased to 38% in the fresh-frozen group, 19% in the freeze-dried group, 27% in the fresh-frozen and irradiated group, and 12% in the freeze-dried and irradiated group. Finally, at 12 weeks, the levels were 19% in the fresh-frozen group, 20% in the freeze-dried group, 15% in the fresh-frozen and irradiated group, and 6% in the freeze-dried and irradiated group. The percentages of donor collagen in the freeze-dried and the fresh-frozen and irradiated groups were significantly lower than that in the fresh-frozen group at 4 weeks. The values for the freeze-dried and irradiated group were significantly lower than those for the fresh-frozen and irradiated group at 4 and 12 weeks. These data suggest that freeze-drying, freeze-drying followed by gamma-irradiation, and fresh-freezing followed by gamma-irradiation temporarily accelerate graft remodeling.

Comparison of anterior cruciate ligament reconstructions using patellar tendon autograft or allograft

Seventy-eight of 113 consecutive patellar tendon anterior cruciate ligament reconstructions (autograft, 47 of 66; allograft, 31 of 47) were evaluated at an average of 34 months. Reconstructions were compared with Lysholm and Tegner knee-rating scales, physical examination findings, instrumented laxity values, single-leg hop distances, and isokinetic strength results. Lysholm scores > or = 90 were achieved by 69% of autograft patients versus 67% of allograft patients. Desired Tegner activity scores were achieved by 80% of autograft patients versus 74% of allograft patients. Patellofemoral signs and symptoms were absent in 40% of autograft patients versus 44% of allograft patients. Side-to-side laxity differences < or = 3 mm were achieved in 80% of autograft patients versus 70% of allograft patients. Single-leg hop scores > or = 90% of the nonoperated leg were obtained in 76% of autograft patients versus 81% of allograft patients. Isokinetic results between groups were also similar. Traumatic ruptures were sustained by four allograft patients at an average of 11 months postoperatively compared with no traumatic ruptures in the autograft group (P = .011). This was the only difference of statistical significance.

Immune response to nonspecific and altered tissue antigens in soft tissue allografts

Soft tissue allografts have many uses in orthopaedic surgery, including knee ligament reconstruction, hand tendon surgery, shoulder instability, and rotator cuff reconstruction. The predictable biologic incorporation of soft tissue allografts without rejection or fear of disease transmission continues to be a goal of basic science researchers. A review of the current knowledge if the immune system response to donor specific, nonspecific, and altered tissue antigens in soft tissue or tendon allografts is presented. An in vitro study was done in an attempt to decrease immunogenicity of a frozen bone-ligament graft by adding irrigation with Betadine scrub solution and hydrogen peroxide to the conventional storage process of freezing. Although the irrigation with cytotoxic agents would undoubtedly further decrease immunogenicity, it also decreased stiffness and maximum load by 15%. Whether this decreased strength and stiffness would compromise the incorporation and long term success of soft tissue allografts would need to be studied by in vitro experiments.

Reconstruction of the anterior cruciate ligament with human allograft. Comparison of early and later results

Sixty-eight patients who had had reconstruction of an acute rupture of the anterior cruciate ligament with either a fascia lata or a bone-patellar ligament-bone allograft returned for two follow-up evaluations, at two to four years and at five to nine years (mean, seven years) postoperatively. The early (two to four-year) results in these patients have been reported previously. The mean time between the early and the later evaluation was fifty-six months (range, twenty to ninety-six months). At the early evaluation, fifty-two (78 per cent) of the sixty-seven patients who were tested with an arthrometer at eighty-nine newtons had less than three millimeters of increased anterior-posterior displacement compared with that of the contralateral limb; at the later evaluation, fifty-four (79 per cent) of the sixty-eight patients had this finding (p=0/97). With use of arthrometric and pivot-shift-test data, forty-eight (75 per cent) of sixty-four grafts were classified as functional at the early evaluation and fourteen (22 per cent), as partially functional; two (3 per cent) had failed. (Four grafts could not be classified because of incomplete data.) At the later examination, fifty (74 per cent) of the sixty-eight grafts were functional, thirteen (19 per cent) were partially functional, and five (7 per cent) had failed. At the early evaluation, sixty-two (93 percent) of sixty-seven patients had no palpable patellofemoral crepitus and five (7 per cent) had moderate crepitus. At the later evaluation, fifty-one (75 per cent) of the sixty-eight patients continued to have no crepitus, sixteen (24 per cent) had moderate crepitus, and on (1 per cent) had severe crepitus. An increase in crepitus between the early and the later evaluation was found in twelve (19 per cent) of the sixty-two patients who had normal crepitus at the early evaluation. With the numbers available, no factor, such as the type of graft, associated ligamentous injury, or meniscal repair, correlated significantly with the amount of patellofemoral crepitus at either follow-up evaluation. At the early evaluation, the result was rated excellent or good for thirty-eight (60 per cent) of sixty-three patients, fair for twenty-one (33 per cent), and poor for four (6 per cent). (The result could not be rated for four patients because of incomplete data.) At the later evaluation, the result was rated excellent or good for forty-five (66 per cent) of the sixty-eight patients, fair for eighteen (26 per cent), and poor for five (7 per cent). For nine patients (13 per cent), the over-all rating deteriorated from excellent or good at the early evaluation to fair or poor at the later examination. For six patients (9 per cent), the rating improved from fair at the early evaluation to excellent or good at the later evaluation. With the numbers available, we could detect no significant decrease in anterior-posterior displacement of the knee, patellofemoral crepitus, the pain or the jumping score, or the over-all knee rating over the time-period studied. While we currently recommend arthroscopically assisted reconstruction with a bone-patellar ligament-bone autogenous graft as the first choice for an acute rupture of the anterior cruciate ligament, our study shows that favorable results can be obtained with allografts and justifies their use when the surgeon and patient choose this approach.

Reconstruction of an Achilles tendon defect utilizing an Achilles tendon allograft

Acute ruptures of the Achilles tendon are common. Treatment for such ruptures is well documented. Treatment for chronic ruptures with a significant defect poses a surgical dilemma. The authors present the use of a tendon allograft to replace an Achilles tendon defect with a 2.5-year clinical follow-up inclusive of isokinetic testing.

Allograft versus autograft anterior cruciate ligament reconstruction: 3- to 5-year outcome

Sixty-four patients whose knees underwent anterior cruciate ligament reconstruction with nonirradiated allograft tissue were compared with 26 patients whose anterior cruciate ligaments were reconstructed using autograft tissue 3 to 5 years after their operation. Detailed symptoms, activity-level, and functional outcomes, physical examination, and instrumented knee testing were recorded. No statistically significant differences were found except a higher incidence of loss of terminal extension in the autograft group. These differences were small and not considered clinically significant. Laxity and knee scores were similar in both groups. According to International Knee Documentation Committee ratings, overall outcome was normal or nearly normal in 48% of the allograft patients and in 38% of the autograft patients. Overall subjective rating with the Cincinnati Knee Score was 85.8 for the allograft patients and 84.5 for the autograft patients. Allograft tissue provides an acceptable alternative to autograft tissue for reconstruction of the anterior cruciate ligament.

The remodelling process of allogeneic and autogenous patellar tendon grafts in rats: a radiochemical study

In order to study the remodelling of collagen fibres of transplanted tendons, one-half of the patellar tendon of the knee in 54 rats was replaced with a radioisotope (3H-proline)-labelled patellar tendon procured from a donor rat. Three transplantation models were used in this study: fresh-frozen allograft, fresh-frozen autograft (fresh-frozen isograft), and fresh autograft (fresh isograft). The percentage of old collagen was calculated as an indicator of collagen turnover from the amount of hydroxyproline and the radioactivity level of 3H-hydroxyproline in the transplanted tendons at 4, 12 and 24 weeks postoperatively. Histological evaluation was also performed at 2, 4, 12 and 24 weeks. At 4 weeks, the percentage of old collagen in the grafts from the fresh-frozen allograft group was significantly lower than in the autograft groups (20% vs. 48%). Although the percentage of old collagen in the fresh-frozen autograft group had decreased to the same level as in the fresh-frozen allograft group by 12 weeks (approximately 10%), the value was still high in the fresh autograft group at 12 weeks and remained higher (38%). Histologically, at 2 weeks, the cellularity in the fresh-frozen allograft was higher than in the fresh-frozen autograft. After 4 weeks, however, no significant difference was found between these two groups. In the fresh autograft group, the cellularity was lower than in the fresh-frozen groups at all times. In conclusion, the collagen turnover rate in the fresh-frozen allograft was the most rapid of the three transplantation models based on hydroxyproline turnover.

Anterior cruciate ligament reconstruction with fresh-frozen patellar tendon allografts: sixty cases with 2 years' minimum follow-up

A prospective study was performed on 101 patients who underwent an arthroscopic anterior cruciate ligament (ACL) reconstruction with fresh-frozen patellar tendon allograft (bone-patellar tendon-bone). We present the results of the first 60 patients with a minimum follow-up of 2 years. Thirty-four were men and 26 women with a mean age of 23. In 45 patients, a postoperative arthroscopy was performed, and tissue biopsies of the reconstructed ACL were obtained. Patients were evaluated according to the International Knee Documentation Committee evaluation form. After a mean follow-up of 47 months, the overall results were normal or nearly normal in 85%. Under postoperative arthroscopy, the macroscopic appearance of the implant was similar to that of a normal ligament. The ACL allograft was covered with a normal, well-vascularized synovium. There were no cases of infection, disease transmission or tissue rejection. We conclude that the use of fresh-frozen patellar tendon allografts is a good method of ACL reconstruction.

Dose-dependent response of gamma irradiation on mechanical properties and related biochemical composition of goat bone-patellar tendon-bone allografts

We studied the effects of gamma irradiation on the dimensions, mechanical and material properties, and mature hydroxypyridinium crosslink density of collagen in goat patellar tendon-bone specimens. Left and right patellar tendon-bone units were removed from 10 adult female goats and were bisected longitudinally. Each tendon half was frozen, and then the left halves were exposed to 4, 6, or 8 Mrad (40,000, 60,000, or 80,000 Gy) of gamma irradiation. The contralateral tendon halves served as controls (no irradiation). Each specimen then was loaded to failure in tension, and its soft-tissue midsubstance was processed to measure collagen content and hydroxypyridinium crosslink density. Dose-dependent reductions in the mechanical properties were found, including 46% (p < 0.01) and 18% (p < 0.05) reductions in maximum force and stiffness, respectively, at 4 Mrad. Similar reductions were noted in material properties, including 37% (p < 0.005) and 8% (p > 0.05) reductions in maximum stress and modulus, respectively, at 4 Mrad. These results are consistent with our previous report involving 2 and 3 Mrad (20,000 and 30,000 Gy) of exposure. We also found significant decreases in hydroxypyridinium crosslink density with 6 Mrad of irradiation (p < 0.05). However, since only one biomechanical parameter (modulus) correlated significantly with only one biochemical measure (hydroxypyridinium crosslink density) (p < 0.05), other possible mechanisms also are being explored to more fully explain these dose-dependent changes.

Mechanical properties of the human anterior cruciate ligament

The aim was to measure the stiffness and strength of the femur-anterior cruciate ligament-tibia complex tested in a physiological manner with a force exerted anteriorly on the tibia, at knee joint flexion angles of 0 degrees, 10 degrees and 30 degrees and at speeds of 50 and 500 mm/min. Ligaments were preconditioned by cycling five times, with data from the fifth cycle used to determine the stiffness of the ligament in a low-load range. The ligaments were then tested to failure with the knee at 30 degrees flexion. The specimens were divided into two groups, middle-aged (40-60) and old (>60). For each group no statistical difference was observed between stiffness of the ligament at different joint flexion angles or speeds. Seven of the 21 specimens in the older age group failed by avulsion at the bone-ligament interface. All the other specimens failed by tears in the substance of the ligament. Ultimate failure load was found to have a significant correlation with bodyweight. It was 1.6 and 1.3 times bodyweight for the middle-aged and older age groups respectively. This study has highlighted the importance of identifying different modes of failure, of making corrections for bodyweight and testing in a physiological manner. The results allow a better understanding of the mechanical behaviour of the anterior cruciate ligament and provide design data for anterior cruciate ligament grafts and prostheses. RELEVANCE:--Our clinical experience indicates that the anterior cruciate ligament is frequently ruptured during uncoordinated contraction of the quadriceps mechanism. The results of this study, in which the mechanical properties of the anterior cruciate ligament have been measured with force exerted anteriorly on the tibia, allow a more complete understanding of the mechanical behaviour of the anterior cruciate ligament and provide design data for anterior cruciate ligament grafts and prostheses.

Allograft reconstruction of the anterior and posterior cruciate ligaments after traumatic knee dislocation

Seven patients (average age, 26.3 years) with traumatic knee dislocations were retrospectively evaluated more than 2 years (average, 51 months) after having fresh-frozen allograft anterior and posterior cruciate ligament reconstructions. All patients were treated consecutively at an average of 9.6 days after injury. Two patients had arterial injuries and three patients had or developed common peroneal nerve palsy. Five patients had 20 additional injuries. All patients were enlisted in an early, aggressive physical therapy regimen with early protected weightbearing. Four patients required a manipulation under anesthesia for arthrofibrosis at an average of 16.8 weeks postoperatively (range, 6 to 33 weeks). At followup, only one patient had significant pain, three patients had rare or occasional giving way, and all seven were able to return to school or to the workplace. The functional grading was excellent in three patients, good in three patients, and fair in one patient. No patient had a significant flexion contracture; the average flexion arc was 118 degrees (range, 105 degrees to 135 degrees). Knee dislocation is a very traumatic injury, often resulting in a painful, dysfunctional knee. Anterior and posterior cruciate ligament reconstructions in young, active patients can minimize pain and optimize functional outcome. Arthrofibrosis is a common occurrence in these patients, and manipulation under anesthesia is frequently required.

Gamma irradiation: effects on biomechanical properties of human bone-patellar tendon-bone allografts

Sixty 10-mm bone-patellar tendon-bone allografts from young human donors were placed into four test groups, a control fresh-frozen group and three fresh-frozen irradiated groups. The irradiated groups were exposed to 2.0, 3.0, or 4.0 Mrad of gamma irradiation. The specimens were tested to tensile failure. The initial biomechanical strength of fresh-frozen allografts was reduced up to 15% when compared with fresh-frozen controls after 2.0 Mrad of irradiation. Maximum force, strain energy, modulus, and maximum stress demonstrated a statistically significant reduction after 2.0 Mrad of irradiation (P < 0.01). Stiffness, elongation, and strain were reduced but not with statistical significance. A 10% to 24% and 19% to 46% reduction in all biomechanical properties were found after 3.0 (P < 0.005) and 4.0 (P < 0.0005) Mrad of irradiation, respectively. After irradiation with a 4.0 Mrad dose, the ultimate load was below that of reported values for the human anterior cruciate ligament. It is clinically important to observe and document changes in human ligaments that result from currently used doses of gamma irradiation. The results from this study provide important information regarding the initial biomechanical properties of fresh-frozen human bone-patellar tendon-bone allografts after bacterial sterilization with gamma irradiation. The current accepted dose for sterilization is between 1.5 and 2.5 Mrad. There appeared to be a dose-dependent effect of irradiation on all the biomechanical parameters studied. Four of seven parameters were found to be reduced after 2.0 Mrad of irradiation. Reductions were found in all parameters after 3.0 and 4.0 Mrad of irradiation.

An unusual intrinsic complication of a patellar tendon allograft and recommendations for tissue banking

Complications of patellar-tendon allograft for anterior cruciate ligament (ACL) reconstruction in ACL-deficient patients have focused on disease transmission, strength, survivorship, technique, and processing to decrease antigenicity. Little has been described in regard to intrinsic complications of patellar-tendon allograft. This article discusses our experience with a damaged patellar-tendon allograft that was abnormally long and had a large osseous intratendinous mass. Based on this experience, we make recommendations on evaluating and procuring patellar-tendon allografts that will help orthopaedic surgeons avoid intrinsic patellar-tendon allograft complications.

Subcutaneous pretibial cyst formation associated with anterior cruciate ligament allografts: a report of four cases and literature review

Four clinical cases are described in which patients who had undergone anterior cruciate ligament reconstruction developed ganglion-like cysts at the external aparature of the tibial channel. All patients underwent operative treatment including curettage and bone grafting with the successful resolution of the cysts. A proposal, based on the incomplete incorporation of allograft tissues within bone tunnels, is given for the pathogenisis of these cysts, accompanied by a detailed description of the relevant literature.

Correlation of remaining patellar tendon width with quadriceps strength after autogenous bone-patellar tendon-bone anterior cruciate ligament reconstruction

One hundred twenty-one patients were prospectively studied to determine whether the different remaining patellar tendon widths after central 10-mm bone-patellar tendon-bone graft harvest influenced the rate and level of quadriceps strength achieved during rehabilitation. Size of the patellar tendon width, measured at the same location in each patient, ranged from 24 to 35 mm. For this study, patients were grouped according to their remaining tendon size into small (14 to 17 mm; mean, 15.8), medium (18 to 20 mm; mean, 19.2), and large (21 to 25 mm; mean, 22.5) widths. Postoperatively, the patient's isokinetic quadriceps scores were determined at 6 weeks, 3 months, 6 months, and 1 year. At 6 weeks, the small- and medium-width tendon groups were significantly weaker than the large-width tendon group. At 3 months, only the small-width tendon group continued to be significantly weaker than the large-width tendon group. At and beyond 6 months, no statistically significant differences were seen between remaining patellar tendon width groups and their isokinetic quadriceps scores. A constant-sized autogenous patellar tendon graft may be harvested for anterior cruciate ligament reconstruction without compromising ultimate postoperative quadriceps strength recovery.

Effects of gamma irradiation on the human immunodeficiency virus. A study in frozen human bone-patellar ligament-bone grafts obtained from infected cadavera

We studied the effects of several different doses of gamma radiation, ranging from 20,000 to 40,000 gray (2.0 to 4.0 megarad), with respect to the inactivation of the human immunodeficiency virus in fresh-frozen, whole bone-patellar ligament-bone grafts. Although the International Atomic Energy Agency has recommended the use of 25,000 gray of gamma radiation for the sterilization of medical products, the dose required for the inactivation of the human immunodeficiency virus in frozen allografts has not been established. Using one of the most sensitive and specific tests for the detection of the human immunodeficiency virus, the polymerase-chain-reaction test, we found that doses of 20,000 or 25,000 gray of gamma radiation did not destroy the genes of the human immunodeficiency virus effectively; DNA of the virus was detectable in the DNA of bone-marrow tissue obtained from grafts treated with these doses. However, DNA of the human immunodeficiency virus was not detectable in the grafts treated with 30,000 or 40,000 gray of gamma radiation. We conclude that a dose of 30,000 gray of gamma radiation or more is necessary for the sterilization of a fresh-frozen bone-patellar ligament-bone allograft, so that it can be used for reconstructive procedures without the risk of transmission of the virus to the recipient.

Bone tunnel enlargement after anterior cruciate ligament replacement

Radiographic increase in the size of tibial and femoral tunnels has been observed. This retrospective study compared tibial tunnel diameter in 56 autograft and 87 allograft patellar tendon bone-tendon-bone anterior cruciate ligament replacements whose observed tunnel changes were correlated with clinical results at 1 year postoperatively. Tibial tunnel sclerotic margins were measured approximately 1 cm below the joint line. Exact tunnel dimension was calculated by using a magnification factor determined by the interference screw of known diameter within the same tunnel. Average allograft tunnel enlargement was 1.2 mm (-2.5 to 6.0) compared with the autograft tunnel enlargement of 0.26 mm (-2.5 to 2.7); the difference was significant (P > 0.0002). No significant difference was seen in KT-1000 arthrometer measurements between autograft or allograft groups, and no correlation was seen between increased tunnel size and clinical outcome as determined by the modified Hughston knee evaluation system. Tunnel measurement reproducibility was confirmed by independent repeated measurements. The significance of this tunnel enlargement is unknown and does not appear to adversely affect clinical outcome of allograft utilization. Possible explanations include an immune response with resorption, stress shielding proximal to the interference screw resulting in resorption, or an inflammatory response by synovium in the tunnel.

Review on tension in the natural and reconstructed anterior cruciate ligament

This article reviews the methodology and results of published studies concerned with tension in the natural and reconstructed anterior cruciate ligament (ACL). This also includes studies of fiber length changes with knee motion and the relationships between graft tunnel placements and isometricity. Little work has been done in vivo: in humans, length changes of the anterior ACL fibers have been measured at operation, while animal longitudinal studies have been few and have given conflicting results. Work in vitro has used many methods to study ACL tension directly or indirectly, via length changes in fibers, but many authors have reported variable results, caused partly by inter-specimen differences and lack of control of forces or kinematics. It seems likely that different grafts require different peroperative tensions to restore normal stability when measured immediately after application at one knee position. But graft placement and the angle at which tensioning is performed also matter. Over-tensioning constrains knees under load cycling. Similarly, it is difficult to measure and therefore also to decide how tension should be distributed between an ACL graft and and augmentation to the graft. It was concluded that the published studies provide many guidelines for the effects of different graft placements or tensioning protocols but, overall, there is little firm evidence on which to recommend any particular ACL reconstruction protocol.