Healing of tibial bone tunnels after bone grafting for staged revision anterior cruciate ligament surgery: A prospective computed tomography analysis

Satisfactory outcomes after one-stage revision anterior cruciate ligament reconstruction using rectangular tunnel technique

PURPOSE

One-stage revision anterior cruciate ligament reconstruction (ACLR) with the anatomic rectangular tunnel (RT) technique using bone-patellar tendon-bone (BTB) grafts results in anatomically precise tunnel placement and secure graft fixation. This study evaluated knee joint laxity and clinical outcomes in terms of femoral tunnel overlap. It was hypothesised that there would be no significant differences in knee joint laxity or clinical outcomes regardless of femoral tunnel overlap.

METHODS

Between 2012 and 2021, a single surgeon conducted 196 one-stage revision ACLRs with the RT technique using BTB grafts. Patients were divided based on the presence of femoral tunnel overlap. Knee joint laxity was evaluated using the Lachman test, pivot shift test, and side-to-side difference measured with a KT-1000 arthrometer. Clinical outcomes were assessed using the Lysholm score, Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) Knee Examination Form 2000. Knee joint laxity and clinical outcomes were compared between groups after a median follow-up of 2.5 years (range 2.0-8.0).

RESULTS

The study included 30 and 73 patients in the overlap and non-overlap groups, respectively. No significant differences were observed in the results of the Lachman test, pivot shift test, or KT-1000 arthrometer as well as in the Lysholm, KOOS, or IKDC scores between the two groups. Based on the IKDC scores, all patients were graded as normal or nearly normal.

CONCLUSION

One-stage revision ACLR with the RT technique using BTB grafts improved knee joint laxity and had favourable clinical outcomes regardless of femoral tunnel overlap. To achieve optimal results in one-stage revision ACLR, it is crucial to create a tunnel within the anatomical attachment area and ensure proper graft fixation and tensioning.

LEVEL OF EVIDENCE

III.

Consistent Indications and Good Outcomes Despite High Variability in Techniques for Two-Stage Revision Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To systematically review the current literature regarding the indications, techniques, and outcomes after 2-stage revision anterior cruciate ligament reconstruction (ACLR).

METHODS

A literature search was performed using SCOPUS, PubMed, Medline, and the Cochrane Central Register for Controlled Trials according to the 2020 Preferred Reporting Items for Systematic Reviews and Meta Analyses statement. Inclusion criteria was limited to Level I-IV human studies reporting on indications, surgical techniques, imaging, and/or clinical outcomes of 2-stage revision ACLR.

RESULTS

Thirteen studies with 355 patients treated with 2-stage revision ACLR were identified. The most commonly reported indications were tunnel malposition and tunnel widening, with knee instability being the most common symptomatic indication. Tunnel diameter threshold for 2-stage reconstruction ranged from 10 to 14 mm. The most common grafts used for primary ACLR were bone-patellar tendon-bone (BPTB) autograft, hamstring graft, and LARS (polyethylene terephthalate) synthetic graft. The time elapsed from primary ACLR to the first stage surgery ranged from 1.7 years to 9.7 years, whereas the time elapsed between the first and second stage ranged from 21 weeks to 13.6 months. Six different bone grafting options were reported, with the most common being iliac crest autograft, allograft bone dowels, and allograft bone chips. During definitive reconstruction, hamstring autograft and BPTB autograft were the most commonly used grafts. Studies reporting patient-reported outcome measures showed improvement from preoperative to postoperative levels in Lysholm, Tegner, and objective International Knee and Documentation Committee scores.

CONCLUSIONS

Tunnel malpositioning and widening remain the most common indications for 2-stage revision ACLR. Bone grafting is commonly reported using iliac crest autograft and allograft bone chips and dowels, whereas hamstring autograft and BPTB autograft were the most used grafts during the second-stage definitive reconstruction. Studies showed improvements from preoperative to postoperative levels in commonly used patient reported outcomes measures.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I, III, and IV studies.

Tunnel Management in Revision Anterior Cruciate Ligament Reconstruction: Current Concepts

Bone tunnel-related complications are frequently encountered during revision anterior cruciate ligament reconstruction (ACLR). Issues with tunnel positioning, enlargement, containment, and hardware interference may complicate surgery and compromise outcomes. As a result, several strategies have emerged to address these issues and optimize results. However, a systematic, unified approach to tunnel pathology in revision ACLR is lacking. The purpose of this review is to highlight the current state of the literature on bone tunnel complications and, although extensive literature on the subject is lacking, present an updated approach to the evaluation and management of tunnel-related issues in revision ACLR.

Arthroscopic Bone Graft Technique for Two-Stage Revision Anterior Cruciate Ligament Reconstruction

Revision anterior cruciate ligament reconstruction is an increasingly common procedure, with 2-stage surgery often required to address large bone defects and malpositioned tunnels. The arthroscopic bone grafting technique described herein uses morselized allograft bone to provide reproducible fill of asymmetrical bone defects without autograft harvest or additional loss of native bone. The second stage of the anterior cruciate ligament reconstruction can typically proceed 6 months following bone grafting.

Allograft Bone Dowels Show Better Incorporation in Femoral Versus Tibial Tunnels in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Computed Tomography-Based Analysis

PURPOSE

The purpose of this study was to quantitatively evaluate the radiographic outcomes of allograft dowels used in 2-stage revision anterior cruciate ligament reconstruction (ACLR) and to compare the incorporation rates of dowels placed in tibial and femoral tunnels.

METHODS

Prospective review of patients who underwent 2-stage revision ACLR with allograft bone dowels. Inclusion criteria were tibial/femoral tunnel diameter of ≥14 mm on preoperative computed tomography (CT) or overlapping of prior tunnels with planned tunnels. Second-stage timing was determined based on qualitative dowel integration on CT obtained at ∼3 months after the first stage. Quantitative analysis of incorporation rates was performed with the union ratio (UR) and occupying ratio (OR) on postoperative CT scans.

RESULTS

Twenty-one patients, with a mean (SD) age of 32.1 (11.4; range, 18-50) years, were included. Second-stage procedures were performed at a mean (SD) of 6.5 (2.1; range, 2.4-11.5) months after first-stage revision. All dowels showed no signs of degradation at the host bone/graft junction at the second-stage procedure. The mean (SD) diameter of the dowels placed in tibial tunnels was greater than those placed in femoral tunnels (16.1 [2.3] mm vs 12.4 [1.6] mm; P < .05). CT was obtained at a mean (SD) of 121 (28; range, 59-192) days after the first-stage surgery. There was no difference between the OR of femoral and tibial tunnels (mean [SD], 87.6% [4.8%] vs 85.7% [10.1%]; P = .484), but the UR was significantly higher in femoral tunnels (mean [SD], 83% [6.2%] vs 74% [10.5%], P = .005). The intraclass correlation coefficients of OR and UR measurements indicated good reliability.

CONCLUSIONS

Allograft bone dowels are a viable graft choice to replenish bone stock in the setting of a staged revision ACL reconstruction. Allograft dowels placed in femoral tunnels had a higher healing union ratio than tibial tunnel allografts and no evidence of degradation at the bone/graft junction, with no difference seen in occupying ratio.

LEVEL OF EVIDENCE

Level IV, case series.

Tunnel Enlargement Correlates With Postoperative Posterior Laxity After Double-Bundle Posterior Cruciate Ligament Reconstruction

Background:

There exists little information in the relevant literature regarding tunnel enlargement after posterior cruciate ligament (PCL) reconstruction (PCLR).

Purpose:

To sequentially evaluate tunnel enlargement and radiographic posterior laxity through double-bundle PCLR using autologous hamstring tendon grafts.

Study Design:

Case series; Level of evidence, 4.

Methods:

We prospectively analyzed 13 patients who underwent double-bundle PCLR for an isolated PCL injury. Three-dimensional computed tomography images were obtained at 3 weeks, 6 months, and 1 year postoperatively, and the tunnel enlargement was calculated by sequentially comparing the cross-sectional areas of the bone tunnels. We also sequentially measured radiographic posterior laxity. The correlation between the tunnel enlargement ratio and the postoperative increase in posterior laxity was evaluated.

Results:

The cross-sectional area at the aperture in each tunnel significantly increased from 3 weeks to 6 months (P < .003), but it did not continue doing so thereafter. The 6-month tunnel enlargement ratios of the femoral anterolateral tunnel, the femoral posteromedial tunnel, the tibial anterolateral tunnel, and the tibial posteromedial tunnel were 31.6% ± 23.5%, 90.3% ± 54.7%, 30.5% ± 26.8%, and 49.6% ± 37.0%, respectively, while the corresponding ratios at 1 year were 28.1% ± 19.8%, 83.1% ± 56.9%, 26.8% ± 32.8%, and 47.6% ± 39.0%, respectively. The posterior laxity was 9.0 ± 4.0 mm, −1.5 ± 2.3 mm, 3.4 ± 2.0 mm, and 3.9 ± 1.9 mm, preoperatively, immediately after surgery, 6 months and 1 year postoperatively, respectively. From the immediate postoperative period, the posterior laxity significantly increased at 6 months postoperatively (P < .001), but it did not thereafter. The postoperative increase in posterior laxity had a significant positive correlation with the anterolateral tunnel enlargement ratio in both femoral and tibial tunnels at 6 months (ρ = 0.571-0.699; P = .011-.041) and 1 year (ρ = 0.582-0.615; P = .033-.037).

Conclusion:

Tunnel enlargement after PCLR mainly occurred within 6 months, with no progression thereafter. The anterolateral tunnel enlargement positively correlated with postoperative increase in posterior laxity.

Economic Reliable Technique for Tunnel Grafting Using Iliac Crest Bone Graft in Two-Staged Revision Anterior Cruciate Ligament Surgery

Revision anterior cruciate ligament surgery is a technically demanding procedure. Mal-positioned tunnels together with bone loss and its management are some of the difficulties and challenges faced. Two-staged procedures have successfully been used to tackle those challenges. We present a technique that is safe, reliable, reproducible, and economic in the management of bone defects faced in anterior cruciate ligament revision surgery by using iliac crest bone graft. Preoperative assessment of tunnel position and size is done by computed tomography. Tri-cortical iliac crest bone graft is harvested through a trap door. It is then shaped to fit the tunnels to be filled. It is tapered at the advancing end to facilitate introduction. Mounted on a passing pin and a drill bit, the graft is arthroscopically introduced into the femoral and tibial tunnels. The second stage is performed after the graft has incorporated, as seen on postoperative computed tomography, done at approximately 3 months after the first stage. Iliac crest provides a natural abundant reservoir for bone graft and has all the advantages of being an autograft. With good meticulous technique, complications can be avoided with less donor-site morbidity. This technique is safe, reliable, and reproducible. It provides an ample amount of graft and harvest does not rely on implants; hence, it is economic.

Anterior Cruciate Ligament Re-tear and Revision Reconstruction in the Skeletally Immature Athlete

PURPOSE OF REVIEW

With an increase in high-demand sporting activity, the rate of pediatric and adolescent anterior cruciate ligament (ACL) reconstruction is increasing. Yet, the failure rates after reconstruction are much higher than the adult population. The purpose of this paper is to understand failure rates, reasons for graft failure, and strategies for successful revision surgery.

RECENT FINDINGS

A complete understanding of the failure etiology is essential for the clinician treating this population prior to revision. This begins with an assessment of post-operative patient compliance and sporting activity. Surgical technique must then be scrutinized for non-anatomic tunnel placement and poor graft size/type. Concurrent bony deformity must also be addressed including lower extremity valgus alignment and tibial slope abnormalities. Meniscus and chondral injury must be aggressively treated. Furthermore, imaging must be examined to look for missed posterolateral corner injury. Lateral extra-articular tenodesis (in the setting of ligamentous laxity or rotational instability) may be also indicated as well. The surgeon can then choose a graft type and surgical technique that optimizes outcome and respects skeletal growth. Prior to surgical intervention, the clinician must also counsel patients in regard to the guarded prognosis and outcomes in this setting. Prolonged rehabilitation protocols/return-to-play timing as well as sporting activity modification in the post-operative period after revision are critical. There is limited literature on revision ACL reconstruction in the skeletally immature athlete. An understanding of all the risk factors for failure is essential in order to achieve treatment success.

Two-stage revision anterior cruciate ligament reconstruction: Our experience using allograft bone dowels

The incidence of anterior cruciate ligament reconstruction (ACLR) is continuously increasing. As a result so has the need for revision ACLR, which unfortunately has worse functional outcomes and rate of return to sport. Revision ACLR can be performed as a single stage or in two stages. The latter is recommended in the presence of enlarged and/or malpositioned tunnels. We describe our surgical technique, experience and outcome of our first 19 patients in whom we used allograft bone dowels in the first stage of revision ACLR.

Two-Stage Revision Anterior Cruciate Ligament Reconstruction: A Systematic Review of Bone Graft Options for Tunnel Augmentation

BACKGROUND

No consensus is available regarding the optimal choice of bone graft material for bone tunnel augmentation in revision anterior cruciate ligament (ACL) surgery.

PURPOSE

To compare the outcomes of different bone graft materials for staged revision ACL reconstruction.

STUDY DESIGN

Systematic review.

METHODS

A systematic review using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was performed. PubMed, EMBASE, and the Cochrane Library were queried through use of the terms anterior cruciate ligament and revision to identify all studies reporting outcomes of bone tunnel grafting in 2-stage revision ACL reconstruction. Data extracted included indications for 2-stage surgery, surgical technique, graft material, time between surgeries, rehabilitation protocols, physical examination findings, patient-reported outcomes, and radiographic and histologic findings.

RESULTS

The analysis included 7 studies with a total of 234 patients. The primary outcome in 2 studies was graft incorporation (mean follow-up, 8.8 months), whereas the other 5 studies reported clinical outcomes with follow-up mean ± SD of 4.2 ± 2.1 years. The indication for bone grafting and between-stage protocol varied among studies. Autograft was used in 4 studies: iliac crest bone autograft (ICBG, n = 3) and tibial bone autograft (TBA, n = 1). In 2 studies, the authors investigated the outcomes of allograft: allograft bone matrix (ABM) and allograft bone chips (AC). Finally, 1 study compared ICBG to a synthetic bone substitute. Radiographic evaluation of bone graft integration after the first stage was reported in 4 studies, with an average duration of 4.9 months. In 4 studies, the authors reported the time interval between first and second surgeries, with an average of 6.1 months for ICBG compared with 8.7 months for allogenic and synthetic grafts. Revision ACL graft failure rates were reported by 5 studies, including 1 study with ABM (6.1%), 1 study with AC (8.3%), 1 study with TBA (0%), and 2 studies with ICBG (0% and 2%).

CONCLUSION

The indications for staged ACL reconstruction and the rehabilitation protocol between stages need to be clearly established. The available data indicate that autograft for bone tunnel grafting in 2-stage ACL revision may be associated with a lower risk of revision ACL reconstruction graft failure compared with allograft bone.

Two-Stage Anterior Cruciate Ligament Reconstruction Revision Surgery for Severe Bone Defects With Anterolateral Ligament Reconstruction Technique

Anterior cruciate ligament revision surgery poses a number of specific difficulties. These include the lack of bone mass to enable effective fixation of the reconstruction, morbidity of the donor area when bone autograft is used to fill the tunnels, and absence of the semitendinosus and gracilis homolateral tendons in cases in which they have already been used in the primary surgical procedure. To address all these problems, we describe a 2-stage revision technique that uses bone allograft for tunnel filling and Achilles allograft for ligament reconstruction. In addition, the intervention includes an extra-articular phase in which the anterolateral ligament is reinforced to increase the rotational stability of the knee, thus improving the prognosis of operation.

Cancellous allogenic and autologous bone grafting ensure comparable tunnel filling results in two-staged revision ACL surgery

OBJECTIVES

Patients with recurrent instability after anterior cruciate ligament (ACL) reconstruction often present with enlarged or misplaced tunnels and bone grafting is required prior to the actual revision reconstruction. Autologous bone grafting features limited quantity and donor site morbidity. These problems may be eliminated utilizing cancellous bone allografts, but their efficiency and reliability have not been investigated systematically. The aim of the present study was to compare tunnel filling rates attained by utilizing either allogenic or autologous cancellous bone grafts.

MATERIALS AND METHODS

A total of 103 consecutive patients were enrolled retrospectively. All patients suffered from recurrent instability and underwent either allogenic or autologous cancellous bone grafting. Computed tomography (CT) was carried out before and after the bone grafting procedure. Based on preoperative CT scans, positioning and maximum diameter of the femoral and tibial tunnels were determined. Tunnel filling rates were calculated as a ratio of pre- and postoperative tunnel volumes. Primary outcome was the tibial tunnel filling rate. Femoral filling rates and density of the grafted bone were assessed secondarily.

RESULTS

Preoperative CT scans revealed no significant differences between the two groups regarding distribution of misplacement and widening of the femoral or tibial tunnel. Postoperative CT scans were conducted after an interval of 5.2 months. Tunnel filling rates of 74.5% (± 14.3) femoral and 85.3% (± 10.3) tibial were achieved in the allogenic compared to 74.3% (± 15.9) femoral and 84.9% (± 9.4) tibial in the autologous group. With p values of 0.85 at the femur and 0.83 at the tibia, there were no significant differences between the groups. The density of the grafted bone revealed significantly higher values in the allogenic group.

CONCLUSIONS

Utilizing cancellous bone allografts in two-staged revision ACL surgery provides for sufficient and reproducible filling of enlarged or misplaced tunnels. The filling rates are comparable to those achieved with autologous bone grafting. Advantages of allografts are the unrestricted quantity and the absence of any harvesting procedure.

Two-stage revision anterior cruciate ligament reconstruction

With the rising number of anterior cruciate ligament (ACL) reconstructions, revision ACL reconstructions are becoming increasingly common. A revision procedure may be performed to improved knee function, correct instability, and facilitate a return to normal activities. When performing a revision reconstruction, the surgeon decides between a single-stage or a two-stage revision. Two-stage revisions are rarely performed, but are particularly useful when addressing substantial tunnel-widening, active infection, and concomitant knee pathology (e.g., malalignment, other ligamentous injuries, meniscal or chondral lesions). Among these potential scenarios requiring a two-stage revision, tunnel-widening is the most common cause; the first stage involves graft removal, tunnel curettage, and bone grafting, followed by revision ACL reconstruction in the second stage. The purpose of this article is to review the preoperative planning, surgical considerations, rehabilitation, and outcomes of two-stage revision ACL reconstructions and summarize the recent literature outlining treatment results.

Relationship between bone plug position and morphological changes of tunnel aperture in anatomic rectangular tunnel ACL reconstruction

PURPOSE

In animal studies after ACL reconstruction (ACL-R) using the bone-patellar tendon-bone (BTB), the graft-healing pattern was found to depend on the relationship between bone plug and the tunnel wall. This difference of graft-healing pattern could influence the postoperative morphological changes of the tunnel. However, no study has assessed the relationship between bone plug position and the change of tunnel morphology. Therefore, the main purpose of this study was to investigate the relationship between the bone plug position within femoral or tibial tunnel and morphological changes of each tunnel aperture in ACL-R using computed tomography.

METHODS

Subjects were 30 consecutive patients (six females and 24 males; mean age, 20.4 ± 5.4 years) who underwent primary ACL-R using BTB. The distance from the tunnel aperture to the tendon-bone junction (TBJ) at 2 weeks postoperatively, and tunnel aperture enlargement and tunnel wall migration from 2 weeks to 6 months postoperatively, were evaluated.

RESULTS

The distance from the femoral tunnel aperture to the TBJ in most cases was less than 2 mm, whereas the TBJ was located within the tibial tunnel. Femoral tunnel aperture was significantly enlarged (17.0 ± 11.7%) distally, and the tibial tunnel aperture was significantly enlarged (19.6 ± 12.5%) posterolaterally. Only the position at distal portion of femoral bone plug was correlated with femoral tunnel aperture enlargement (r = 0.454, p = 0.0015).

CONCLUSION

Both femoral and tibial tunnel aperture were significantly enlarged distally and posterolaterally 6 months postoperatively. Only correlation between the position at distal portion of femoral bone plug and femoral tunnel enlargement were found, suggesting the deep plug position in the tunnel is a risk factor for femoral tunnel enlargement, highlighting the importance of accurately locating the TBJ just at the femoral tunnel aperture. Another option is to deviate the harvest site in the patellar tendon to match the shape of the TBJ and the tunnel aperture.

LEVEL OF EVIDENCE

4 (case series).

Excellent bone plug–socket integration at 8 weeks after anterior cruciate ligament reconstruction using an adjustable-length loop cortical fixation device

Objectives

Recently, adjustable-length loop cortical fixation devices (ALCFDs) have been developed. However, they are not frequently used for bone–patellar tendon–bone (BTB) grafting, mainly because it is uncertain whether an ALCFD enables sufficient integration of the bone plug. Thus, the purpose of this study was to evaluate bone plug–socket integration in anterior cruciate ligament reconstruction (ACL-R) with an ALCFD.

Methods

Twenty consecutive patients with a mean age of 25±10 years underwent primary anatomic rectangular tunnel (ART) ACL-R with a BTB graft using BTB TightRope. The operated knees were evaluated by CT at 4 weeks and 8 weeks postoperatively. Union between the bone plug and the socket wall were assessed on 30 evaluation planes. No border between the plug and the socket wall, or trabecular continuity, were defined as complete union and a visible gap of >1 mm as incomplete union. When complete union was observed on >20, 11–20, 5–10 or <5 of the evaluation planes, bone integration was graded as excellent, good, fair or poor, respectively. In addition, the interface area between the plug and the socket wall was assessed by CT value index. Clinical evaluation was performed at 2 years postoperatively using the International Knee Documentation Committee (IKDC) form.

Results

The proportion of patients with excellent bone integration was 20% at 4 weeks and 85% at 8 weeks, showing a significant difference (p=0.00015). Moreover, the CT value index of the interface area at 4 weeks was 25.8%±11.8% and that at 8 weeks was 15.3%±9.0%, again showing a significant difference (p=0.005). These suggest that bone integration of the interface area progresses over time and adequate at 8 weeks. Clinically, all 16 patients examined directly were rated their knees as normal or nearly normal with a mean side-to-side difference in anterior laxity at manual maximum force by KT-2000 of 0.2±0.3 mm.

Conclusion

Excellent bone plug–socket integration was observed at 8 weeks after ART ACL-R using an ALCFD with satisfactory clinical results. An ALCFD could be safely applied for ART ACL-R.

Level of evidence

4 (case series).

Outcomes of revision anterior cruciate ligament reconstruction secondary to reamer-irrigator-aspirator harvested bone grafting

INTRODUCTION

Patients with widened or misplaced tunnels may require bone grafting prior to revision anterior cruciate ligament (ACL) reconstruction. Utilising reamer-irrigator-aspirator (RIA) harvested bone from the femur showed promising filling rates. Nevertheless, the procedure has neither been validated in a larger population nor been assessed with regards to radiological and clinical outcome of the subsequently conducted revision ACL reconstruction. Therefore, the aim of this study was to evaluate tunnel filling rates, positioning of the revision tunnels and outcome parameters of such two-staged revision ACL reconstructions.

MATERIAL AND METHODS

A total of 15 consecutive patients were prospectively enrolled in this case series. CT scans were analysed before and after autologous RIA harvested bone grafting. Tunnel volumes and filling rates were calculated based on manual segmentation of axial CT scans. Revision ACL reconstruction was carried out after a mean interval of 6.2 months (±3.7) and positioning of the revision tunnels was assessed by plane radiographs. The mean follow-up was 19.8 months (±8.4) for objective evaluation and 37.1 months (±15.4) for patient reported outcomes. The clinical outcome was assessed by the quantification of the anterior tibial translation, the IKDC objective score, the Tegner activity scale and the Lysholm score.

RESULTS

Initial CT scans revealed mean tunnel volumes of 3.8cm³ (±2.7) femoral and 6.1cm³ (±2.4) tibial. Filling rates of 76.1% (±12.4) femoral and 87.4% (±5.9) tibial were achieved. Postoperative radiographs revealed significantly improved tunnel positioning with anatomical placement in all but one case at the femur and in all cases at the tibia. At follow up, patients showed significantly improved anterior tibial translations with residual side-to-side differences of 1.7 mm (±0.8) and significantly improved IKDC objective scores. Furthermore, significantly higher values were achieved on the Tegner activity scale (5.3 ± 1.4 vs. 2.8 ± 0.5) and the Lysholm score (85.4 ± 7.9 vs. 62.5 ± 10.5) compared to the preoperative status.

CONCLUSION

Autologous RIA harvested bone grafting ensures sufficient bone stock consolidation allowing for anatomical tunnel placement of the subsequently conducted revision ACL reconstruction. The two-staged procedure reliably restores stability and provides satisfying subjective and objective outcomes. Thus, RIA harvested bone grafting is an eligible alternative to autologous iliac crest or allogenic bone grafting.

Femoral tunnel enlargement after anatomic anterior cruciate ligament reconstruction: Bone-patellar tendon-bone /single rectangular tunnel versus hamstring tendon / double tunnels

PURPOSE

This study aimed to prospectively compare the femoral tunnel enlargement at the aperture as well as inside the tunnel after anatomic anterior cruciate ligament (ACL) reconstruction with bone-patellar tendon-bone (BTB) graft to that with hamstring tendon (HST) graft.

METHODS

This study included 24 patients with unilateral ACL rupture. Twelve patients underwent anatomic rectangular tunnel (ART) ACL reconstruction with BTB graft and the remaining 12 underwent anatomic triple-bundle (ATB) ACL reconstruction with HST graft. Three-dimensional computer models of femur and bone tunnels were reconstructed from computed tomography images obtained at 3 weeks and 1 year postoperatively. The femoral tunnel enlargement from 3 weeks to 1 year was evaluated by comparing the cross-sectional area (CSA), and compared between the two groups.

RESULTS

The CSA in the ART group at 1 year decreased at the aperture as well as inside the tunnel comparing that at 3 weeks. The CSAs of both tunnels in the ATB group at 1 year significantly increased at the aperture in comparison to those at 3 weeks, and gradually decreased toward the inside of the tunnel. The enlargement rate at the aperture in the ART group was -12.9%, which was significantly smaller than that of anteromedial graft (27.9%; P = 0.006) and posterolateral graft (31.3%; P = 0.003) in the ATB group. The tunnel enlargement rate at 5 mm from the aperture in the ART group was also significantly smaller than that in the ATB group. At 10 mm from the aperture, there was no significant difference between the tunnel enlargement rate in the ART group and that of anteromedial tunnel.

CONCLUSIONS

The tunnel enlargement rate around the aperture was significantly smaller after the ART procedure than that after the ATB procedure. Thus, BTB graft might be preferable as a graft material to HST graft in the femoral tunnel enlargement.

Supercritical Carbon Dioxide-Sterilized Bone Allograft in the Treatment of Tunnel Defects in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic Evaluation

PURPOSE

To examine the histologic properties of supercritical carbon dioxide (sCO₂)-sterilized bone allograft for tunnel grafting and determine in vivo graft quality, as well as graft incorporation and remodeling, in 2-stage revision anterior cruciate ligament (ACL) surgery.

METHODS

Histologic evaluation was performed in 12 subjects undergoing 2-stage revision ACL reconstruction. In the first stage, the femoral and tibial tunnels were debrided, tunnel dimensions were measured, and tunnels were grafted with sCO₂-sterilized bone allograft. In the second stage, revision ACL reconstruction was performed and bone biopsy specimens were taken from the tibia. Tissue, bone, and graft volumes were measured, and histomorphometric analysis was performed.

RESULTS

The mean time between the 2 stages was 8.8 months (range, 5.6-21.3 months). In the second stage, bone graft material was easily identified by its necrotic appearance comprising mature lamellar bone devoid of osteocyte nuclei within osteocyte lacunae. In all tissue samples, host-bone apposition of predominantly mature lamellar bone was noted on the surface of graft fragments in keeping with "creeping substitution." In several regions in 3 cases, osteoblastic and osteoclastic activity was evident in keeping with ongoing creeping substitution and remodeling. The mean bone volume over tissue volume was 68% (range, 33%-92%), and the mean graft volume over bone volume was 41% (range, 19%-70%). The mean graft volume (8 cases) harvested at less than 7 months (44%; 95% confidence interval, 31.4%-56.8%) was not significantly different than the mean graft volume (4 cases) harvested at greater than 10 months (34%; 95% confidence interval, 14.3%-54.2%; P = .214).

CONCLUSIONS

The sCO₂-sterilized bone allograft showed graft incorporation and remodeling through creeping substitution.

CLINICAL RELEVANCE

The initial bone apposition and graft fragment bridging appear to provide a strong environment for ACL graft fixation resulting in technically successful 2-stage revision ACL reconstruction.

Arthroscopic Delivery of Injectable Bone Graft for Staged Revision Anterior Cruciate Ligament Reconstruction

Bone defects caused by femoral and tibial tunnel enlargement can pose a significant technical challenge when planning to perform revision anterior cruciate ligament reconstruction. A number of options have been described for managing osseous deficiencies, including the use of large autograft or allograft bone dowels to provide sufficient tunnel fill and subsequent structural support for revision surgery. These techniques can be time-consuming and technically demanding to ensure proper tunnel fill and press-fit stability of the bone graft. We describe our preferred technique for arthroscopic bone grafting using a mixture of demineralized cortical bone graft augmented with platelet-rich plasma delivered through a simple delivery system.