False magnetic resonance imaging persistence of a biodegradable anterior cruciate ligament interference screw with chronic inflammation after 4 years in vivo

Tibial and Femoral Tunnel Changes After ACL Reconstruction: A Prospective 2-Year Longitudinal MRI Study

BACKGROUND

Tunnel widening after anterior cruciate ligament reconstruction (ACL-R) is a well-accepted and frequent phenomenon, yet little is known regarding its origin or natural history.

PURPOSE

To prospectively evaluate the cross-sectional area (CSA) changes in tibial and femoral bone tunnels after ACL-R with serial MRI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients underwent arthroscopic ACL-R with the same surgeon, surgical technique, and rehabilitation protocol. Each patient underwent preoperative dual-energy x-ray absorptiometry and clinical evaluation, as well as postoperative time zero MRI followed by subsequent MRI and clinical examination, including functional and subjective outcome tests, at 6, 12, 24, 52, and 104 weeks. Tibial and femoral tunnel CSA was measured on each MRI at tunnel aperture (ttA and ftA), midsection (ttM and ftM), and exit (ttE and ftE). Logistic regression modeling was used to examine the predictive value of demographic data and preoperative bone quality (as measured by dual-energy x-ray absorptiometry) on functional outcome scores, manual and instrumented laxity measurements, and changes in tunnel area over time.

RESULTS

Eighteen patients (including 12 men), mean age 35.5±8.7 years, underwent ACL-R. There was significant tunnel expansion at ttA and ftA sites 6 weeks postoperatively (P=.024 and .0045, respectively). Expansion continued for 24 weeks, with progressive tunnel narrowing thereafter. Average ttA CSA was significantly larger than ftA CSA at all times. The ttM significantly expanded after 6 weeks (P=.06); continued expansion to week 12 was followed by 21 months of reduction in tunnel diameter. The ftM and both ttE and ftE sites decreased in CSA over the 2 years. Median Lysholm and International Knee Documentation Committee scores significantly improved at final follow-up (P=.0083 and <.0001, respectively), and patients returned to preoperative activity levels. Pivot shift significantly decreased (P<.0001). Younger age (<30 years), male sex, and delayed ACL-R (>1 year from time of injury) predicted increased tunnel widening and accelerated expansion in CSA (P<.005).

CONCLUSION

Tunnel expansion after ACL-R occurs early and primarily at the tunnel apertures. Expansion may not affect clinical outcome. Younger age, male sex, and delay from injury to ACL-R may be potential risks for enlargement.

The degradation outcome of biocomposite suture anchors made from poly L-lactide-co-glycolide and β-tricalcium phosphate

PURPOSE

The purpose of this study was to evaluate the long-term in vivo degradation of biocomposite suture anchors made of poly L-lactide-co-glycolide (PLLA/PGA) and β-tricalcium phosphate (β-TCP).

METHODS

Starting in 2008, the in vivo biological behavior of a biocomposite suture anchor was studied in a consecutive series of rotator cuff tendon repairs. Twenty patients undergoing rotator cuff repair secured with biocomposite PLLA/PGA-β-TCP suture anchors with at least a 36-month follow-up were evaluated by physical, radiographic, and computed tomographic (CT) evaluations of the operated shoulder. American Shoulder and Elbow Surgeons (ASES), Rowe, Simple Shoulder Test (SST), Constant, and Single Assessment Numeric Evaluation (SANE) scores were also obtained. CT scan data measured in Hounsfield units (HU) evaluated the material density at the anchor sites. Soft tissue and cancellous bone readings were also taken. Osteoconductivity scores were determined at the screw sites using an ossification quality score (range, 1 to 4).

RESULTS

Fifteen men and 5 women were evaluated an average of 37 months after surgery (range, 36 to 40). CT scans and radiographs showed no PLLA/PGA-β-TCP anchor material remaining. A total of 28 anchors were implanted in the 20 patients. The anchors were usually replaced with calcified, nontrabecular material. Osteoconductivity was present in 20 of 28 (71%) of the anchor sites and was nearly complete or complete (type 3 or 4 ossification) in 14 of 28 (50%). Mean anchor site density (94 HU) was not different from the mean cancellous bone density (99.8 HU). ASES, Rowe, SST, Constant, and SANE scores improved from 57.3, 64.5, 6.0, 51.7, and 45 preoperatively to 89.6, 86.5, 10.8, 78.6, and 84.3 at follow-up, respectively. All postoperative clinical outcome measures were statistically greater than the preoperative scores.

CONCLUSIONS

The PLLA/PGA-β-TCP (Healix BR, DePuy Mitek, Raynham, MA) suture anchor completely degraded and no remnant was present 3 years after implantation. Osteoconductivity was confirmed in 20 of 28 (71%) anchor sites and was nearly complete or complete in 14 of 28 (50%). The PLLA/PGA-β-TCP biocomposite suture anchor is osteoconductive.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Long-term degradation of a poly-lactide co-glycolide/β-tricalcium phosphate biocomposite interference screw

PURPOSE

To evaluate the long-term in vivo degradation of biodegradable interference screws made of poly-L-lactide co-glycolide (poly-L-lactic acid [PLLA]/polyglycolic acid [PGA]) and β-tricalcium phosphate (β-TCP).

METHODS

To study in vivo the biological behavior of a PLLA/PGA/β-TCP biocomposite screw (Milagro; DePuy Mitek, Raynham, MA), an institutional review board-approved program using anterior cruciate ligament (ACL) interference fixation screws was initiated in 2005. Thirteen patients who had bone-patellar tendon-bone ACL reconstruction fixed at both the femur and tibia with PLLA/PGA/β-TCP screws at least 24 months earlier were evaluated by physical, radiographic, and computed tomography (CT) evaluations. Lysholm, Tegner, Cincinnati, and International Knee Documentation Committee scores were also obtained. Radiographs and CT scans of the operated knee were obtained. CT scan data measured in Hounsfield units (HU) evaluated the material density at the screw and bone plug sites. Soft-tissue and cancellous and cortical bone site readings were also taken. Osteoconductivity scores were determined at the screw sites by use of an ossification quality score (range, 1 to 4).

RESULTS

Eleven men and two women were evaluated at a mean of 38 months after surgery (range, 24 to 49 months). CT scans and radiographs showed the bone plug fused to the tunnel wall with no PLLA/PGA/β-TCP screw remaining. The screws were replaced with material that was calcified and non-trabecular. Osteoconductivity was present in 21 of 26 tunnels (81%) and complete (type 4 ossification) in 5 of 26 (19%). Mean screw site densities (femoral, 159 HU; tibial, 157 HU) were not different from the mean cancellous bone density (femoral, 146 HU; tibial, 140 HU). No positive pivot-shift tests were found. Lysholm, Tegner, and Cincinnati scores improved from 44, 3.7, and 37 preoperatively to 93, 6, and 87 at follow-up, respectively. The mean KT arthrometer (MEDmetric, San Diego, CA) difference was 0.8 mm.

CONCLUSIONS

The PLLA/PGA/β-TCP interference screw completely degraded, and no remnant was present 3 years after implantation for a bone-patellar tendon-bone graft ACL reconstruction. Osteoconductivity was confirmed in 21 of 26 screw sites (81%) and completely filled the site in 5 of 26 (19%). The PLLA/PGA/β-TCP biocomposite interference screw is osteoconductive.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

A prospective randomized study of ACL-reconstructions using bone-patellar tendon-bone grafts fixed with bioabsorbable or metal interference screws

INTRODUCTION

Bioabsorbable screws are, at the expense of metal screws, increasingly used as fixation device in ACL-reconstructions. The possible advantages with bioabsorbable screws are better postoperative MRI evaluations and easier revision surgery.

PURPOSE

The aim of this study was to compare the clinical outcome after ACL-reconstructions with BPTB-grafts fixed with metal interference screws or bioabsorbable screws 7 years postoperatively. The resorption of the bioabsorbable screws was also analyzed.

METHODS

Between 2000 and 2001, 41 patients with ACL deficient knees were randomized for the use of BPTB-graft fixed with either metal interference screws or bioabsorbable poly-L: -lactic acid screws. This is a 7-year follow-up with clinical examinations of both groups and, MRI of the patients with bioabsorbable screws.

RESULTS

The clinical and functional results were satisfactory in both groups. There were no significant differences between the groups in any parameter measured, except for better Pivot shift results in the bioscrew group (P = 0.04). The MRI evaluation showed degradation of the bioscrews. A residual screw tract which appeared threaded was seen in the tibia in 11 of the 16 patients. There was no sign of bony ingrowth in the previous screw site in the tibia in any of the patients.

CONCLUSION

The potential advantages of using PLLA-screws compared to metal screws are not sufficient to warrant the routine use of PLLA-screws in ACL-reconstructions.

LEVEL OF EVIDENCE

I.

Painful knee joint after ACL reconstruction using biodegradable interference screws- SPECT/CT a valuable diagnostic tool? A case report

With the presented case we strive to introduce combined single photon emission computerized tomography and conventional computer tomography (SPECT/CT) as new diagnostic imaging modality and illustrate the possible clinical value in patients after ACL reconstruction. We report the case of a painful knee due to a foreign body reaction and delayed degradation of the biodegradable interference screws after ACL reconstruction. The MRI showed an intact ACL graft, a possible tibial cyclops lesion and a patella infera. There was no increased fluid collection within the bone tunnels. The 99mTc-HDP-SPECT/CT clearly identified a highly increased tracer uptake around and within the tibial and femoral tunnels and the patellofemoral joint. On 3D-CT out of the SPECT/CT data the femoral graft attachment was shallow (50% along the Blumensaat's line) and high in the notch. At revision arthroscopy a diffuse hypertrophy of the synovium, scarring of the Hoffa fat pad and a cyclops lesion of the former ACL graft was found. The interference screws were partially degraded and under palpation and pressure a grey fluid-like substance drained into the joint. The interference screws and the ACL graft were removed and an arthrolysis performed.

In the case presented it was most likely a combination of improper graft placement, delayed degradation of the interference screws and unknown biological factors. The too shallow and high ACL graft placement might have led to roof impingement, chronic intraarticular inflammation and hence the delayed degradation of the screws.

SPECT/CT has facilitated the establishment of diagnosis, process of decision making and further treatment in patients with knee pain after ACL reconstruction. From the combination of structural (tunnel position in 3D-CT) and metabolic information (tracer uptake in SPECT/CT) the patient's cause of the pain was established.

Polymer-hydroxyapatite composite versus polymer interference screws in anterior cruciate ligament reconstruction in a large animal model

The aim of the study was to assess the hard tissue response of a composite hydroxyapatite/poly L-lactic acid (HA/PLLA) interference screw for anterior cruciate ligament (ACL) reconstruction compared to a standard PLLA screw. Twelve skeletally mature rams underwent unilateral ACL reconstruction using an autologous bone-patellar tendon graft. Each animal received either two test HA/PLLA interference screws or two control PLLA interference screws. Animals were sacrificed at 6 and 12 months post-implantation and the operated knees excised. Undecalcified sections of the screw and surrounding tissues were cut from resin embedded samples and stained; sections were approximately parallel to the longitudinal axis of the screws. A quantitative assessment of bone formation between each screw type (PLLA vs. HA/PLLA) and adjacent tissue in both the tibia and femur was undertaken using automated image analysis (KS400, Zeiss, UK). The inflammatory response of each screw type was assessed by histological evaluation. New bone formation along the perimeter of the screw threads was statistically significantly higher with the HA/PLLA than the PLLA alone. The inflammatory response as assessed semi-quantitatively by histologically determining the number of inflammatory cells present in the tissue adjacent to the implant, was higher for PLLA than HA/PLLA. Significantly increased new bone formation and decreased inflammatory cells were observed in vivo with the composite screw in comparison with the standard polymer. A novel HA/PLLA composite biomaterial in the form of an interference screw demonstrated an improved hard-tissue response compared to PLLA in a large animal ACL reconstruction. This study determined the differences in the tissue response between PLLA and a composite material of HA/PLLA. The improved tissue related outcomes observed in vivo, may be of benefit clinically in ACL reconstruction.

Bilok interference screws for anterior cruciate ligament reconstruction: clinical and radiographic outcomes

PURPOSE

The purpose of this study was to evaluate the clinical effectiveness and radiographic response of a poly-L-lactide (PLLA)/beta-tricalcium phosphate (TCP) interference screw for anterior cruciate ligament (ACL) reconstruction.

METHODS

In a consecutive series of patellar tendon autograft ACL reconstructions, all patients had both ends fixed with PLLA/beta-TCP screws. Inclusion criteria were positive Lachman and pivot-shift tests and closed or nearly closed growth plates. Exclusionary criteria were posterior cruciate ligament tears and bilateral ACL or multiple ligament injuries. Tegner, Lysholm, Cincinnati, and International Knee Documentation Committee activity scores; Lachman and pivot-shift data; radiographic examinations; and KT measurements (MEDmetric, San Diego, CA) were obtained.

RESULTS

In this study 41 patients met the criteria (31 male and 10 female patients), at a mean follow-up of 34 months (range, 24 to 44 months). Of these patients, 40 were available for follow-up (1 had died). Postoperatively, the mean Cincinnati score was 83 (64 preoperatively), the mean Tegner score was 5.5 (3.2 preoperatively), the mean Lysholm score was 88 (59 preoperatively), and the mean International Knee Documentation Committee activity score was 3.0 out of 4 (1.8 preoperatively). No patients had positive postoperative Lachman or pivot-shift tests. The maximum difference based on KT manual examinations 3 mm or less. Adverse events included screw breakage during insertion. Postoperative radiographs showed rapid bone plug incorporation. Radiographic tunnel obliteration with bony ingrowth was shown at 2 and 3 years' follow-up.

CONCLUSIONS

The PLLA/beta-TCP interference screw performed well clinically based on both subjective and objective results. Radiographic screw incorporation into the adjacent bone was apparent at 3 years.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.