Biomedical subjects

A C Stähelin

Publications and source records attributed to A C Stähelin.

5 recordsLinked to original sources

PubMed2001

Anatomic double-bundle posterior cruciate ligament reconstruction using hamstring tendons.

Recent biomechanical studies have shown that an anatomic double-bundle posterior cruciate ligament (PCL) reconstruction is superior in restoring normal knee laxity compared with the conventional single-bundle isometric reconstruction. We describe a modification of an endoscopic PCL reconstruction technique using a double-bundle Y-shaped hamstring tendon graft. A double- or triple-bundle semitendinosus-gracilis tendon graft is used and directly fixed with soft threaded biodegradable interference screws. In the medial femoral condyle, 2 femoral tunnels are created inside-out through a low anterolateral arthroscopic portal. First, in 80 degrees of flexion, the double-stranded gracilis graft is fixed with an interference screw inside the lower femoral socket, representing the insertion site of the posteromedial bundle. In full extension the combined semitendinosus-gracilis graft is pretensioned and fixed inside the posterior aspect of the single tibial tunnel. The double- or triple-stranded semitendinosus tendon is inserted in the higher femoral tunnel, presenting the insertion site of the anterolateral bundle. Finally, pretension is applied to the semitendinosus bundle in 70 degrees of flexion and a third screw is inserted. Using this technique, the stronger semitendinosus part of the double-bundle graft, which mimics the anterolateral bundle of the PCL, is fixed in flexion, whereas the smaller gracilis tendon part (posteromedial bundle) is fixed in full extension. Thus, a fully arthroscopic anatomic PCL reconstruction technique is available that may better restore normal knee kinematics as compared to the single-stranded isometric reconstruction.

Arthroscopy↗

PubMed2000

Biodegradable implants in sports medicine: the biological base.

Biodegradable implants are increasingly used in the field of operative sports medicine. Today, a tremendous variety of implants such as interference screws, staples, sutures, tacks, suture anchors, and devices for meniscal repair are available. These implants consist of different biodegradable polymers that have substantially different raw material characteristics such as in vivo degradation, host-tissue response, and osseous replacement. Because these devices have become the standard implant for several operative procedures, it is essential to understand their biological base. The purpose of this report is to provide a comprehensive insight into biodegradable implant biology for a better understanding of the advantages and risks associated with using these implants in the field of operative sports medicine. In particular, in vivo degradation, biocompatibility, and the osseous replacement of the implants are discussed. A standardized classification system to document and treat possible adverse tissue reactions is given, with special regard to extra-articular and intra-articular soft-tissue response and to osteolytic lesions.

Absorbable Implants↗

PubMed1997

All-inside anterior cruciate ligament reconstruction using semitendinosus tendon and soft threaded biodegradable interference screw fixation.

A modification of anterior cruciate ligament (ACL) reconstruction using a minimally invasive and endoscopic all-inside technique is presented. Both the femoral and tibial socket are approached through the joint so that there is no open tibial tunnel, which otherwise often causes significant pain and discomfort during early rehabilitation. The autologous semitendinosus tendon is harvested with a bone plug attached to its tibial insertion. The triple-stranded semitendinosus tendon is looped around the adjacent bone plug and fixed at the original tibial attachment site of the ACL using a soft threaded biodegradable poly-(D,L-lactide) interference screw. The screw is inserted endoscopically in an inside-out direction. In the femoral socket the graft is fixed without a bone plug directly to the tunnel wall using the biodegradable screw. The free part of the graft is thus not longer than the intra-articular distance, which may increase stiffness of the construct.

Absorption↗

PubMed1997

Clinical degradation and biocompatibility of different bioabsorbable interference screws: a report of six cases.

The clinical biocompatibility and degradation of bioabsorbable interference screws of different polymer composition is described in this report for six patients who underwent repeat arthroscopy after anterior cruciate ligament (ACL) reconstruction. Bioabsorbable interference screws were used for bone plug fixation of bone--patellar tendon--bone (BPTB) autografts. Poly (L-lactide) (PLLA) interference screws were used in one case, poly (D,L-lactide-co-glycolide) (PDLLA-co-PGA) in two cases and poly (D,L-lactide) (PDLLA) in three cases. The patients either underwent removal of the femoral screw or had a biopsy taken from the screw site during re-arthroscopy. Large fragments of the PLLA screw were still present 20 months postoperatively. In one case, the PDLLA-co-PGA screw was extruded spontaneously from the tibial bone tunnel 3 weeks after the operation. In the second PDLLA-co-PGA screw case, there was no evidence left of the screw material on biopsy 12 months after implantation. The PDLLA screw in one patient was removed 6 weeks after implantation without any signs of degradation. No traces of the PDLLA screws were found in the two other patients, 10 or 14 months postoperatively. There were no clinical signs of foreign-body reactions in all cases.

Adult↗

PubMedDate not supplied

Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone.

It has recently been shown that graft fixation close to the ACL insertion site is optimal in order to increase anterior knee stability. Hamstring tendon fixation using interference screws offers this possibility and a round threaded titanium interference screw has been previously developed. The use of a round threaded biodegradable interference screw may be equivalent. In addition, to increase initial fixation strength, graft harvest with a distally attached bone plug may be advantageous, but biomechanical data do not exist. This study compares the initial pullout force, stiffness of fixation, and failure modes of three strand semitendinosus grafts in 36 proximal calf tibiae using either biodegradable poly-(D,L-lactide) (Sysorb; Sulzer Orthopaedics Ltd, Münsingen, Switzerland) or round threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA) interference screws, harvested either without (biodegradable: group I, titanium III) or with (biodegradable: group II, titanium: group IV) attached tibial bone plugs. Maximum pullout force in group I (507 +/- 93 N) was significantly higher than in group III (419 +/- 77 N). Pullout force of bone plug fixation was significantly higher than that of direct tendon fixation (717 +/- 90 N in group II and 602 +/- 117 N in group IV). Pullout force of biodegradable fixation was significantly higher in both settings. These results indicate that initial pullout force of hamstring-tendon graft interference screw fixation can be increased by using a biodegradable interference screw. In addition, initial pullout force of hamstring-tendon graft fixation with an interference screw can be greatly increased by harvesting the graft with its distally attached tibial bone plug.

Absorption↗