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Andriano K. P.; Pohjonen T.; and Törmälä P.: Processing and characterization of absorbable polylactide polymers for use in surgical implant. J. for Applied Biomaterials, 5: 133-140, 1994.
Absorbable fibers of linear poly-alpha-hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly L-lactide (PLA) fibers may degrade too slowly for optimal function. Polymers produced by co-polymerization of L-lactide with varying amounts of D-lactide may offer an alternative choice for absorbable fiber based implants. Poly (L/D-lactide) stereo-copolymers with L/D lactide molar rations of 95/5, 90/10, and 85/15 were considered. Melt-spun / hotdrawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x-ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37°C. Fabrication was reproducible and results indicated that tensile strength, modulus, and birefringe all increased with increasing draw ratios up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide copolymer fibers when compared to reported values for PGA and PLLA fibers, suggest these materials may be useful in absorbable surgical implants for tissue repair and regeneration.
Because semi-crystalline absorbable polymers such as PGA or PLLA degrade much faster in the amorphous than in the crystalline phase, these polymers degrade inhomogenously losing mechanical strength as the amorphous phase degrades, followed by mass loss of slowly degrading insoluble crystallites that may give rise to a tissue reaction, and possibly accumulate in the lymph nodes. Therefore, absorbable polymers with a low to moderate degree of crystallinity should be favored for medical applications.
Barber F. A.; Elrod B. F.; McGuire D. A.; and Paulos L. E.: Preliminary
results of an absorbable interference screw. Arthroscopy, 11: 573-548, 1995.
A randomized, prospective multicenter comparison was done of a bioabsorbable interference screw (Bioscrew; Linvatec Corp, Largo, FL) made from poly L-lactic acid and a metal interference screw produced by the same company. Assignment was randomized by sealed envelopes. A total of 110 patients underwent arthroscopic patellar tendon autografts. A minimum follow-up is available on 85 patients (mean 19 months, range 12 to 33) including 42 patients with Bioscrews and 43 with metal screws. There were 56 male and 29 female patients. The average age was 29 years (16 to 50 years). Tourniquet times and associated surgical findings were similar for the two groups. Postoperative Tegner and Lysholm scores were not statistically different between the two groups. KT tests at 1 year showed an average 20-lb laxity for 1.8 mm and 1.2 mm for the metal screw groups. The average 1-year KT maximum manual side-to-side difference was 1.6 mm for the Bioscrews and 1.6 mm for the metal screws. A pivot shift was absent in 83% of Bioscrews and 90% of metal screws at follow-up.
Six of 85 Bioscrews inserted (7%) broke on insertion (all were 7-mm diameter screws at the femoral site). No additional fixation was required in four cases. In two, the broken screw was replaced. No lytic bone changes or tunnel widening were found with any Bioscrew. One metal screw had tibial tunnel widening. No statistical difference was found between Bioscrew and the metal screw groups. Short-term data support the conclusion that the Bioscrew is a reasonable alternative to metal interference screws.
Black J.: Does corrosion matter? J. Bone Joint Surg., 70-B(4): 517-520, 1988.
It is known, from both animal studies and the epidemiology of human workplace exposure, that metal-bearing chemical carcinogens typically have long latencies, with a five to 10 year minimum exposure required and a typical 20 year delay to mean tumour expression in man. Until recently, there was no significant human population with implants of greater than ten years' duration. Thus, present reports of tumours at implant sites and at remote sites in patients with implants may be harbingers of future problems. The benefits of metallic implants in orthopaedic surgery are clear and cannot be denied by even the greatest pessimist. However, we are living in an increasingly risk-aversive society; we are asked daily to balance benefit with risk in decisions affecting ourselves, our family, the environment and, in the practice of orthopaedic surgery, the patient. It is becoming clear that there are real risks associated with the use of metals as chronic implants. Prudence suggests that steps should be taken to limit risk by minimising the exposure of patients to corrosion products.
Yes, corrosion does matter. All metallic implants corrode. The corrosion products are biologically active. Patients do exhibit symptoms relative to corrosion products from implants. The magnitude and clinical significance of these symptoms remains to be seen. However, all orthopaedic surgeons should reflect that, as they wait for further intelligence, corrosion continues. Second by second, minute by minute, day by day, week by week, month after month, year piled upon year, metal is released and permeates every tissue of the bodies of patients with metallic implants.
Böstman O.; Pihlajamäki H. K.; Partio E. K.; and Rokkanen P. U.: Clinical biocompatibility and degradation of polylevolactide screws in the ankle. Clin. Orthop., 320, 101-109, 1995.
The clinical biocompatibility and degradation behaviour of absorbable fracture fixation devices are still unknown in humans. Fifty one patients with displaced fracture of the ankle treated by open reduction and internal fixation with absorbable screws made of polylevolactide were seen in follow-up for at least three years. The mean duration of follow-up time was 52 months. The tissue tolerance and the degradation of the devices were studied clinically and radiographically using computed tomographic scans. In addition, biopsy specimens for histologic examination were taken in five patients. The screws were clinically effective: An accurate position of the fragments was maintained until union in 50 patients. A mild transient subcutaneous late foreign body reaction occurred in one patient 22 months after fixation of the fracture. Despite radiographic evidence of an advancing degradation of the implants, biopsy specimens taken 45 months after the original operation still showed consistent areas of polylactide in the tissues. In three patients, a disturbing palpable subcutaneous screw had to be removed.
The incidence of foreign body reactions to polylevolactides screws in the ankle seems to be low, but the duration of the degradation process of the polymer in human tissues is considerably longer than has been anticipated.
Brown G.; Pena F.; Grontvedt T.; Aune A.; and Engebretsen L. : Comparison of fixation strength between metallic and bioabsorbable interference screws. Procs. AAOSM, 1995.
Because of the superior initial fixation strength of interference screws in anterior cruciate ligament (ACL) reconstruction, metallic interference screws have become the standard implant for fixation of bone-patellar tendon- bone grafts. Complications connected with the use of metallic interference screws are rare, but include adverse reactions to metal, cold intolerance, loosening and need for removal, and interference with revision surgery and MRI knee imaging. These complications led to the development of a bioabsorbable alternative. In order to test the hypothesis that metallic and bioabsorbable interference screws have equal failure strength in bone-patellar tendon-bone ACL reconstruction, a failure analysis of interference screw fixation in young human cadaver models was performed.
Eighteen bone-patellar tendon-bone specimens were harvested from nine human cadaver knees from five donors (age range 32-57 years) Under completely open technique, the patellar bone block was inserted into the lateral femoral condyle tunnel and the bone block-tunnel gap was measured. A 7 mm metallic or bioabsorbable interference screw (Bioscrew; Linvatec Corp, Largo, FL) was inserted over a guide pin in an inside-out direction and insertion torque was measured during insertion. A ramp displacement was applied to failure at a velocity of 50 mm/min in line with the axis of the femoral tunnel. The load-displacement curve was recorded and failure mode was recorded. A new parameter, interference, is defined as the screw outer thread diameter minus the tunnel-block gap. This definition of interference is equivalent to the amount of screw thread engagement in the bone.
Statistically significant differences in insertion torque and failure load were noted using a Student's t-test for individual comparisons. The insertion torque for the metallic interference screw (mean 1.6 N-m, standard deviation 0.7 N-m) was significantly greater than for the bioabsorbable interference screw (mean 0.6 N-m, standard deviation 0.3 N-m) the failure load for the metallic interference screw (mean 640 N, standard deviation 201 N) was significantly greater than for the bioabsorbable interference screw (mean 331 N, standard deviation 130 N). No statistically significant differences in bone block-tunnel gap, interference, or bone mineral density were noted.
The failure load of the metallic interference screw is significantly greater than the bioabsorbable interference screw in young human cadaver models. Preliminary reports on the clinical use of bioabsorbable screws stated that screw breakage was the main intra-operative complication. This is consistent with our results of screw fracture during insertion and thread damage following bone block pullout.
The bioabsorbable screw mean failure strength is below the estimated 450 N ACL load imposed during routine activities. We recommend conservative rehabilitation activities in the early post-operative period when this particular bioabsorbable screw (Bioscrew; Linvatec Corp, Largo, FL) is used.
Guanche C. A. Tourniquet-induced tibial nerve palsy complicating anterior cruciate ligament reconstruction. Arthroscopy, 11, 5: 620-622, 1995.
In this case report, an unremarkable anterior cruciate ligament reconstruction is complicated by a tourniquet-incuced tibial nerve palsy. The case underscores the necessity of being aware of the potential for complications associated with tourniquets, despite following recommended guidelines of tourniquet time and pressure.
Gutin B.; Warren R.; Wieckiewicz T.; O'Brien S.; Altchek D.; and Kroll M.: Does tourniquet use during anterior cruciate ligament surgery interfere with postoperative recovery? A review of the literature. Arthroscopy, 7: 52-56, 1991.
This article explores the issue of whether use of a tourniquet during arthroscopically assisted repair of the anterior cruciate ligament (ACL) slows the postoperative recovery of function. A tourniquet is customarily used to provide a bloodless field, thus enabling the surgeon to visualize the joint clearly. However, there is increasing evidence that tourniquets cause muscle and nerve damage that can have long-term consequences for the recovery of function following surgery. The two randomized trials that investigated tourniquet use during meniscectomy reached contradictory conclusions about the effects of the tourniquet. There have been no randomized trials of tourniquet use during the longer and more complex ACL surgery. This article reviews the pertinent literature and suggests some clinical implications of the available information.
Johnson L. L. and Van Dyk G.E.: Arthroscopically monitored ACL reconstruction: compaction drilling and compression screw fixation. In the crucial ligaments: Diagnosis and treatment of ligamentous injuries about the knee, edited by J.A. Feagin, Jr. Ed. 2, pp. 555-593. New York, Churchill Livingstone, 1994.
The purpose of this chapter is to report a new method of arthroscopically monitored bone-patellar tendon-bone graft reconstruction of the anterior cruciate ligament (ACL). This method introduces the new concept of compaction drilling and axial compression screw fixation, and draws attention to new surgical methodology and instrumentation. This method, which uses an interference screw of unique design, emphasizes basic surgical principles and attention to surgical details.
Johnson L. L.: Comparison of bioabsorbable and metal interference screws in anterior cruciate ligament reconstruction: a clinical trial. Procs. AAOSM, San Franzisco, 1995.
The purpose of this study was to determine if a biodegradable interference screw was as safe and effective as a metal screw of the same design used for the same purpose; anterior cruciate ligament reconstruction.
Method: Experienced orthopedic surgeons were recruited to participate in one of two groups for this study. No financial incentive was offered to either the institution, surgeon or the patient for participation. The surgeons and their patients were devided into two groups; Group I (Biodegradable screw), Group II (Metal screw). The qualified patient had to have functional instability due to anterior cruciate ligament instability of the knee, but without severe degenerative arthritis. The success criteria included the restoration of functional stability supported by clinical examination measurement. Failure criteria included continued functional instability , presence of clinical signs of inflammation, x-ray evidence of bone cyst formation, or migration of the tendon graft bone blocks. The surgery was performed using both arthroscopic and open techniques. The substitute donor graft tissue was patellar bone tendon bone in all cases. Group I (Biodegradable screw): There were four centers and four surgeons recruited for this trial. There were 57 patients in this group. There were 43 autogenous and 14 allografts utilized. Group II (Metal screw): There were two centers and two surgeons recruited for this trial. There were 34 patients in this group. All 34 patients had an autogenous graft utilized. Follow-up clinical evaluations were conducted at six months and again at one year.
Results: The results showed restoration of anterior cruciate ligament functional stability in all patients. There were no infections, no neurovascular injury, nor thromboembolic complications. Three patients in the biodegradable group underwent re-operations for reasons unrelated to the device. Two were for ankylosis and one for subsequent injury. There were no re-operations in the metal group. There was no evidence for inflammation to the bioabsorbable material noted by clinical examination or by x-ray review. The lack of inflammation was supported by biopsy of the screw site of the three re-operated patients. Both the bioabsorbable and the metal groups showed same statistical results.
Conclusion: This bioabsorbable screw was both safe and effective for the intended purpose and comparable to the metal screw of the same design.
Kousa P.; Järvinen T. L. N.; Pohjonen T.; Kannus P.; Kotikoski M.; and Järvinen M.: Fixation strength of a biodegradable screw in anterior cruciate ligament reconstruction. J. Bone Joint Surg., 77-B(6): 901-905, 1995.
We compared the strength of fixation of a biodegradable screw with that of two metal screws in a bone-patellar-tendon-bone (BPTB) graft in the bovine knee. We used 33 fresh BPTB specimens with a circular tibial bone plug of 9 mm in diameter which were anchored in the tibial metaphyseal bone tunnel with either an interference screw (n=11), an AO cancellous screw (n=11) or a fibrillated, self-reinforced biodegradable poly-L-lactide screw (n=11). The mean force to failure in the three groups was 1358 +/- 348 N, 1081 +/- 331 N and 1211 +/- 362 N, respectively. There was no significant difference in the groups with regards to the linear load or the elastic moduli of fixation.
We conclude that the biodegradable screw is as good as either of the two metal screws in the fixation of a BPTB graft in the bovine knee and can be recommended for ACL reconstruction using this type of graft.
Kurosaka M.; Yashiysa S.; and Andrish J. T.: A biomechanical comparison of different surgical techniques of graft fixation for anterior cruciate ligament reconstruction. Am. J. Sports Med., 15: 225-229, 1987.
Different surgical methods of graft fixation in ACL reconstruction were examined to determine the effects on mechanical properties of the reconstructed ACL. Ten human cadavers were used in this study. Six different types of grafts were studied. The tendon grafts were removed from each cadaver and fixed to femurs and tibias as ACL substitutes with different surgical fixation methods, leaving femur-reconstructed graft-tibia preparations. The surgical techniques used were staple fixation, tying sutures over buttons, and screw fixation. In the latter, the screws were introduced through femoral and tibial drill holes from the outside in order to achieve interference fit as described by Lambert. Tensile testing demonstrated that the original ACL is significantly stronger than the graft used for reconstruction in linear load, stiffness, and maximum tensile strength. All of the failures of the reconstructed ACL grafts occurred at the fixation site, indicating that the mechanically weak link of the reconstructed graft is located at the fixation site. Among the different methods of fixation, one-third of the patellar tendon secured with a cancellous screw, especially with a custom designed large diameter screw, showed significantly higher values. Although many other factors affect the success of ACL reconstruction, our study indicates that the method of surgical fixation is the major factor influencing the graft's mechanical properties in the immediate postoperative period.
Mishra A. K. Fanton G. S., Dillinham M.F., and Carver T. J.: Patellar tendon graft harvesting using horizontal incisions for anterior cruciate ligament reconstruction. Arthroscopy, 11, 6: 749-752, 1995.
Autograft endoscopic anterior cruciate ligament (ACL) reconstruction traditionally has been performed via standard arthroscopy portals and a single longitudinal anterior incision. This vertical incision is used for harvesting the central third of the patellar tendon with patellar and tibial bone blocks. From 1992 to 1995, more than 400 cases have been done with a new technique of graft procurement. This new method employs two transverse incisions that are more cosmetic and are less likely to become a source of pain or flexion limitation.
Morgan C. D.; Kalman, D.O.; and Grawl D. M.: Definitive landmarks for reproducible tibial tunnel placement in anterior cruciate ligament reconstruction. Arthroscopy, 11, 3: 275-288, 1995.
The purpose of this prospective study was to define constant anatomic intraarticular and extra-articular landmarks that can be used as definitive reference points to reproducibly create a tibial tunnel for anterior cruciate ligament (ACL) reconstruction that (1) results in an impingement-free graft in full extension without an intercondylar roofplasty; (2) positions the tibial tunnel's intraarticular orifice sagittally central in the original ACL insertion without guessing; (3) positions the tibial tunnel such that the sagittal tunnel-plateau angle is parallel with the intercondylar roof-plateau angle in full extension to minimize shear seen by the graft at the tibial tunnel inlet, and by doing so; (4) maximises tunnel length to avoid patellar tendon graft-tunnel mismatch allowing for endosteal interference fixation on both sides of the joint. Anatomic dissections in 50 knees showed the ACL sagittal central insertion point on the intercondylar floor averages 7 mm (range 7 to 8 mm) sagittally anterior to the anterior margin of the posterior cruciate ligament (PCL) with the knee flexed 90° such that the PCL may be used as a reliable reference landmark for locating the ACL sagittal central insertion. This constant relationship was found to be independent of knee size. Extraarticularly, beginning the tibial tunnel sagittally 1 cm above the superior (sartorial) border of the pes anserinus insertion and coronally 1.5 cm posteromedial from the medial margin of the tibial tubercle along the superior surface of the pes, directed toward the sagittal central ACL insertion, led to a sagittal tunnel-plateau angle that averaged 68° (range 64° to 72°) with a corresponding tunnel length that averaged 58 mm (range 50 to 65 mm) in 23 knees. This data correlated well with data obtained clinically in a series of 50 consecutive ACL reconstructions using intraarticular PCL and extra-articular pes anserine-medial tibial tubercle referenced tibial tunnels in which postoperative full extension lateral radiographs confirmed a sagittal tunnel-plateau angle parallel or near parallel with the intercondylar roof-plateau angle in all cases averaging 68° +/- 3.8°. Tibial tunnel length averaged 60 mm (range 52 to 66 mm) in no case was there patellar tendon autograft-tunnel length mismatch.
O'Donnell J. B. and Scerpella T. A.: Endoscopic anterior cruciate ligament Reconstruction: modified technique and radiographic review. Arthroscopy, 11, 5: 577-584, 1995.
The original technique for endoscopic anterior cruciate ligament reconstruction has several potential complications because of constraints imposed by working through the tibial tunnel: improper femoral tunnel placement, violation of the femoral tunnel posterior wall, femoral interference screw divergence, graft laceration during insertion, and distal tibial bone block protrusion. We performed 100 consecutive endoscopic anterior cruciate ligament reconstructions with bone-tendon-bone autograft using a modified technique that minimizes each of these problems through the use of an accessory medial parapatellar portal. Postoperative radiographic review showed femoral screw divergence in only 9% of cases (average angle, 6.9°), all in the anteroposterior plane. The tibial tunnel was drilled at an average of 66° to the plateau and averaged 52 mm in length. There was no graft damage during screw insertion or protrusion of the bone blocks.
We conclude that this modified technique allows simplified, reproducible tunnel and screw placement.
Shapiro J.; Cohn T. B.; Jackson D. W .; Postzak P.;D.; Parker R. D.; and Greenwald A. S.: The biomechanical effects of geometric configuration of bone-tendon-bone autografts in anterior cruciate ligament reconstruction. Arthroscopy, 8: 453-458, 1992.
This study provides biomechanical support for a new technique of autograft anterior cruciate ligament reconstruction featuring circular bone plugs and endosteal interference fit fixation. Six matched pairs of fresh frozen human knees were utilized. Femoral interference fit pull-out strength was determined from material-testing-machine-generated oscillograph recordings at a strain rate of 100%/s. Circular bone plugs, obtained with a circular oscillating saw, provided 19.9% greater interference fit pull-out strength compared with identically fixed trapezoidal bone plugs. Different geometric defects were compared in three- and four-point bending on an Instron machine with frozen patellae and an artificial bone composite. Circular defects have 107% greater strength than matched trapezoidal patellar defects in three-point bending. In a bone composite, circular defects are 53% stronger than triangular and 25% stronger in four-point bending than trapezoidal defects.
A new technique of harvesting bone plugs with endosteal interference fit fixation is described and biomechanically supported. To date, this technique has been performed on over 500 cases clinically without evidence of patellar fracture or fixation failure. This study demonstrates the efficacy of this simple and reproducible technique compared with previously reported procedures.
Shelbourne K. D., and Nitz P.: Accelerated rehabilitation after anterior cruciate ligament reconstruction. Am. J. Sports Med., 18: 292-299, 1990.
To overcome many of the complications after ACL reconstruction (prolonged knee stiffness, limitation of complete extension, delay in strength recovery, anterior knee pain), yet still maintain knee stability, we developed a rehabilitation protocol that emphasizes full knee extension on the first postoperative day and immediate weight-bearing according to the patient's tolerance. Of 800 patients who underwent intraarticular ACL patellar tendon-bone graft reconstruction, performed by the same surgeon, the last 450 patients have followed the accelerated rehabilitation schedule as outlined in the protocol. A longer than 2 year follow-up is recorded for 73 of the patients in the accelerated rehabilitation group. On the 1st postoperative day, we encouraged these patients to walk with full weight-bearing and full knee extension. By the 2nd postoperative week, the patients with a 100 degrees range of motion participated in a guided exercise and strengthening program. By the 4th week, patients were permitted unlimited activities of daily living and were allowed to return to light sports activities as early as the 8th week if the Cybex strength scores of the involved extremity exceeded 70% of the scores of the noninvolved extremity and the patient had completed a sport-specific functional/agility program. The patient database was compiled from frequent clinical examinations, periodic knee questionnaires, and objective information, such as range of motion measurements, KT-1000 values, and Cybex strength scores. A series of graft biopsies obtained at various times have revealed no adverse histologic reaction. The evidence indicates that in this population, the accelerated rehabilitation program has been more effective than our initial program in reducing limitations of motion (particularly knee extension) and loss of strength while maintaining stability and preventing anterior knee pain.
Shellock F. G.; Mink J.H.; Curtin S.; and Friedman F. J.: Mr imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact. J. magn. Reson. Imaging 2. 225-228, 1992.
Magnetic resonance (MR) imaging is contraindicated for patients with certain ferromagnetic implants, primarily because of potential risks related to movement or dislodgment of the devices. An additional problem with metallic implants is the potential image distortion that may affect the interpretation of the MR study. Since MR imaging is frequently useful for the evaluation of postoperative anterior cruciate ligament (ACL) reconstruction, the ferromagnetic qualities and artifacts associated with MR imaging were determined for five metallic orthopedic implants commonly used for this surgery. Only the Perfix interference screw displayed a substantial deflection force and caused extensive signal loss. Images of the knee of one patient with two Perfix screws in place were not interpretable because of the image distortion caused by these implants. Therefore, alternative nonferromagnetic implants should be considered for reconstruction of the ACL.
Stahelin A.C.; and Feinstein R.: Bioabsorbable interference screws for ACL reconstruction: two years of clinical experience. Proc. Sports medicine 2000, Stockolm, Sweden, June 1995.
Metal screws, which are commonly used for endoscopic interference fixation of the bone plugs, carry the risk of immediate or late postoperative complications, such as tendon-graft lacerations or difficulties during hardware removal resulting in excessive bone loss. In addition, radiological follow-up studies are often distorted. In many cases a second operation is indicated for the hardware removal. Non-metallic means of fixation would therefore be preferable. Since 1992 we have used bioabsorbable interference screws for the fixation of B-Pt-B grafts in nearly 200 patients undergoing anterior cruciate ligament reconstruction. For the first 16 patients we used poly-lactic-glycolic, for the remainder poly-lactic acid screws. Current studies with a newly designed bioabsorbable screw and screwdriver are underway and show promising results.
From 1992 to 1993 we inserted a total of 37 lactide-glycolide and 28 polylactide bioabsorbable screws in our first 36 patients with arthroscopically assisted ACL-reconstruction procedures. The mean follow-up time of the pilot study patients was one year (range 12-26 months). There were no drop-outs. 10/36 patients have now been followed postoperatively for over two years. All patients were examined (clinical examinations, questionnaires, KT-1000), by an orthopedic surgeon of the Department of Orthopedics, University Hospital Basel who was neither involved in the original operation nor in the postoperative follow-up. In addition CT scans, MRIs and in five cases bone-biopsies were performed between 2 and 104 weeks postoperatively. Using the criteria's of the International Knee Documentation Committee the results were normal in 32/36 of the patients and not normal in 4/36 of the patients. Three patients with lactide-glycolide screws developed postoperative sinus tracts at the tibial incision site. They all healed uneventfully.
To date there has been no fixation failure nor have there been signs which might be indicative of an adverse reaction to the lactic-glycolic acid. Sequential MRI studies show uneventful incorporation of the autograft as well as disappearance of the bioabsorbable screws. There was one common "complication" when the lactic-glycolic acid screw was used: because of the brittleness of this interference screw the outermost part of the femoral screw broke off at the bone level before the screw was fully inserted in two thirds of the cases. In all these cases however, this complication did not adversely affect the outcome and no graft fixations had to be revised.
The breakage of the screws before full insertion must also be seen in connection with our technique of tibial tunnel and femoral socket hole preparation. Rather than drilling the holes we use a compaction tool to prepare the plug sites. This results in a harder cancellous bone wall and might thus favour breakage of the screws. Furthermore because it provides a stronger seat, we like to use the screws in a self-tapping way.
Stahelin A.C.; Feinstein R.; and Friederich N.: Clinical
experience using a bioabsorbable interference screw for ACL reconstruction. Proc.
AAOS, Orlando, 1995 and Orthopaedic Transactions, J. Bone Joint Surg 19, 2: 287-288, 1995.
The use of conventional metallic hardware for fixation of the Bone-Patellar tendon-Bone (B-Pt-B) graft in anterior cruciate ligament (ACL) reconstruction carries the risk of immediate or late postoperative complications. In addition, radiological follow-up studies are often distorted. Other non-metallic means of fixation would therefore be preferable. This study evaluated the clinical efficacy of a bioabsorbable interference screw for fixation of the B-PT-B graft in ACL reconstruction.
From 1992 to 1993 we inserted 37 lactide-glycolide and 28 polylactide bioabsorbable screws for fixation of B-PT-B grafts in 36 arthroscopically assisted ACL reconstruction procedures. The mean follow-up time was 1 year (range 6-26 months). There were no drop-outs. 10/36 patients have been followed postoperatively for over two years. Clinical examinations (questionnaires, KT-1000), CT scans, MRIs and bone-biopsies were performed 2, 6, 12, 54 and 104 weeks postoperatively.
Using the criteria's of the International Knee Documentation Committee the results were normal in 32/36 of the patients and not normal in 4/36 of the patients. Three patients with lactide-glycolide screws developed postoperative sinus tracts at the tibial incision site. They all healed uneventfully. There has been no fixation failure nor have there been signs which might be indicative of an adverse reaction to the lactic-glycolic acid. Sequential MRI studies showed uneventful incorporation of the autograft as well as disappearance of the bioabsorbable screws. There was one "common" complication: because of the brittleness of lactide-glycolide interference screws the outermost part of the screw broke in two thirds of the cases during insertion of the femoral screw, so that it was as not possible to countersink the screw all the way. This complication did not adversely affect the outcome and no graft fixations had to be revised.
Lactide-glycolide and polylactide bioabsorbable interference screws are a promising alternative for B-PT-B graft fixation in ACL reconstruction. Certain drawbacks associated with the use of metallic devices may be avoided with the use of a non-metallic bioabsorbable interference screw.
Disadvantages of bioabsorbable versus metallic interference screws are at present their inferior handling characteristics which may often require the use of an additional bone tap. These problems could be solved using a properly designed screw-screwdriver system and a not too quickly degrading noncristalline polymer.
A new design of the bioabsorbable screw and its screwdriver mechanism improved the handling characteristics and breakage of the screw does not occur. Our experience has convinced us that the advantages of bioabsorbable screws in ACL-reconstruction are such, that in most cases they will supersede the use of metallic screws.
SYSORB is a registered trademark of Sulzer Orthopedics:
Technical information about the SYSORB Screw and about the associated instruments can be obtained from: Sulzer Orthopedics Ltd., Grabenstrasse 25, 6341 Baar, Switzerland Phone: ++41 (41) 768 32 32, Fax: ++41(41) 761 92 00 Mail: Monica Fucentese Sulzer medica
. (Abstract)
Toljan M. A..; and Orthner E.:. Bioabsorbable interference screws in ACL surgery Procs. AAOSM, San Francisco, 1995.
Investigations part of a prospective, randomized study comparing the outcome after femoral rear entry and all inside techniques.
Materials and Methods Between April 1st 1993 and March 25th 1994, 60 patients were randomly allocated to the study group. The Bioscrew group consists of 30 patients mean age 23 years, no patient was lost for follow-up. All Bioscrews were inserted by one surgeon (A.A.T). With the all inside technique, the femoral tunnel was created by first drilling a 4.5 mm pilot hole which was then dilated up to 10 mm. MRI-scans were obtained 6 weeks, 3 months, 6 months and 1 year postop.
Results: 3 months postop, the screw showed high signal intensity in T2 caused by liquidisation, the bone plug remained at the original position, we saw no migration. 6 months postop, there were local reactions in 41% of the cases, ranging from edema to defined cysts. 12 months postop. (10 cases up to now:) as the lesions had become smaller, but were still visible. Three main types of reaction were identified, ranging from bony edema to clearly defined cysts.
Conclusions: Interference fixation of bone-tendon-bone transplants with a biodegradable screw is an elegant method with sufficient immediate and long term fixation strength. No migration was seen in MRI follow ups. In 41% of the cases local reactions ranging from bony edema to defined cysts were seen in T2 and fat sat sequences. Clinically, no febrile episodes or sterile effusions occurred. This particular screw (Instrument Makkar, East Lansing, MI, USA) cannot be recommended for routine use until long term follow-ups have proven its clinical safety.-
Verheyen C. C. P. M.; de Winjn J. R.; Van Blitterwijk C. A.; Rozing P. M.; and de Grott K.: Examination of afferent lymph nodes after 2 years of transcortical implantation of poly(L-lactide) containing plugs: A case report. J. Biomed. Mat. Res. 27, 115-118, 1993.
Since the introduction of polyglycolide, poly (L-lactide), and their composites as materials for the internal fixation for fractures in humans they have been increasingly used clinically. A set-back in the development and general acceptance of these resorbable poly (alpha-hydroxy acids) in reconstructive surgery is the occurence of sinus formation through local nonbacterial inflammatory reactions with a considerable tissue swelling weeks or months after implantation (reported incidences: 5.9 - 22.5%). Review reports of these inflammatory lesions describe the characteristics of nonspecific foreign body reaction that often necessitates aspiration or a second operation. Also similar problems with the crystalline degradation products of poly (L-lactide) fixating zygomatic bone have been encountered 2-3 years after implantation.
Here we report the results 2 years after transcortical implantation of poly (L-lactide) and hydroxylapatite containing plugs in the femora of one goat. Special interest was focused on the histologic evaluation of the efferent lymph nodes.
Please send questions or comments to: kruzlifix@staehelin.ch
Copyright © 1996 Andreas C. Staehelin
Most recent update May, 28, 1996