Systematic Postoperative Assessment of a Minimally-Invasive Sheep Model for the Treatment of Osteochondral Defects

To assess the clinical course of a sheep stifle joint model for osteochondral (OC) defects, medial femoral condyles (MFC) were exposed without patella luxation using medial parapatellar skin (3–4 cm) and deep incisions (2–3 cm). Two defects (7 mm diameter; 10 mm depth; OC punch) were left empty or refilled with osteochondral autologous transplantation cylinders (OATS) and explanted after six weeks. Incision-to-suture time, anesthesia time, and postoperative wound or impairment scores were compared to those in sham-operated animals. Implant performance was assessed by X-ray, micro-computed tomography, histology, and immunohistology (collagens 1, 2; aggrecan). There were no surgery-related infections or patellar luxations. Operation, anesthesia, and time to complete stand were short (0.5, 1.4, and 1.5 h, respectively). The wound trauma score was low (0.4 of maximally 4; day 7). Empty-defect and OATS animals reached an impairment score of 0 significantly later than sham animals (7.4 and 4.0 days, respectively, versus 1.5 days). Empty defects showed incomplete healing and dedifferentiation/heterotopic differentiation; OATS-filled defects displayed advanced bone healing with remaining cartilage gaps and orthotopic expression of bone and cartilage markers. Minimally-invasive, medial parapatellar surgery of OC defects on the sheep MFC allows rapid and low-trauma recovery and appears well-suited for implant testing.

A Closer Look is necessary: Traumatic luxation of the patella as a co-injury of an acl-rupture

Aims and Objectives: The rupture of the acl is considered to be one of the most common knee injuries in sports traumatology. Many patients report that they felt the sensation of a luxated patella during their knee distorsion. In many cases patients patients with the suspicion of a traumatic patella luxation showed in the mri a complete rupture of the acl. Materials and Methods: We report about 10 patients consulting our department within the last year after a significant knee trauma. In the mri as well as during the arthroscopic evaluation they showed a complete rupture of the acl as well as the findings of a fresh, traumatic patella luxation. We evaluated and analysed the preoperative and intraoperative pictures (mri and arthrosopy). Results: All patients showed in the posttraumatic mri a complete rupture of the acl as well as an at least partial rupture of the mpfl and a rupture of the medial retinaculum. 4 patients showed a persistent subluxation of the patella, 8 patients showed also a rupture of the medial collateral ligament. During the operation we verified a significant instability of the patella in 8 patients so that a stabilization of the patella was performed (open medial stabilization or mpfl reconstruction) in the same operation the acl was reconstructed (semi-t). Eventhough the patients were treated with only one operation and the regaining of motion was prolonged compared with isolated acl-reconstruction, after 12 months postoperatively all patients had a satisfactory range of motion. Conclusion: The typical trauma mechanism for an acl rupture is a valgus position of the knee in combination with an external rotation of the tibia, which leads to an enlargement of the q-angle which is considered a predisposition for a patella luxation. If an acl rupture occurs, the patella can luxate within the same trauma. In the posttraumatic mri the rupture of the mpfl is often misinterpreted as a rupture of the medial collateral ligament, particularly if the patella is, as in most cases, in full reposition. Within an acl-rupture a luxation of the patella can occur simultaneously, leading to a significant instability which needs to be treated (medial stabilization or mpfl-reconstruction). Our data shows that a single stage treatment with acl-reconstruction and medial stabilization is technical practicable and mid-term investigation shows good clinical results without a higher risk of an arthrofibrosis.