Total knee arthroplasty (TKA) disturbs patellar blood flow, an unintended accompaniment to TKA that may be a cause for postoperative anterior knee pain. We compared patellar blood flow before and after medial parapatellar arthrotomy to pre- and postoperative anterior knee pain scores to ascertain whether disrupted patellar blood flow correlates with anterior knee pain following TKA. Blood flow measurements were performed at full extension and at 30°, 60°, 90° and 110° of flexion prior to and after medial arthrotomy in 50 patients (21 male, 29 female; mean age 73.1±8.6 years) undergoing TKA. Anterior knee pain was assessed using the pain intensity numeric rating scale. A significant decrease in blood flow was detected at 60°, 90°, and 110° of flexion (p values: 0.00314,< 0.0001,< 0.0001 respectively). The medial arthrotomy did not have a statistically significant influence on patellar blood flow in the Students’ t-test (margin of significance p& #61603;0.05) Nineteen patients exhibited an average 14% (range 1%–54%) increase in patellar blood perfusion at knee flexions of 90° and 110° after medial arthrotomy (p value: 0.32) Prior to TKA, 16 of the 50 patients (32%) complained of anterior knee pain (average NRS 7.12, range 5–10). At 6-month follow up, 4 of the 16 patients (25%) complained of moderate anterior pain (average NRS 5.7, range 5–6), while 8 of 16 (50%) patients reported discomfort (average NRS 3.5, range 2–4) around the patella. No statistically significant correlation was found between intraoperative findings on patellar blood flow and the presence of anterior knee pain

Introduction: Ruptured anterior cruciate ligaments (ACL) are generally thought not to heal after treatment so that the ligament must be replaced by a graft. We developed and evaluated a surgical technique that restores knee stability using the self-healing capacity of the ruptured ACL.

Methods: The ACL was cut close to the femoral insertion in 14 sheep. The contralateral, nonoperated side served as the control. After microfracturing at the femoral foot print, the ACL was stabilized using the dynamic intraligamentary stabilization (DIS) technique. A strong intraligamentary suture was attached on the femoral side with a button and on the tibial side by means of an intraosseous spring-loaded screw with a preload of 85 N. In 7 of 14 sheep the ruptured ligament was covered with a collagen membrane. The joint was not immobilized postoperatively. Histological evaluation, magnetic resonance imaging (MRI) and biomechanical testing were performed after 3 months.

Results: Three days postoperative all animals showed no lameness and regularly used the operated leg. Macroscopically, all repaired ACLs appeared healed. Histological and MRI examinations confirmed the healing response of the ACL after DIS. The collagen membrane exhibited a more hypertrophic scare tissue reaction. Biomechanical testing showed an average increase of the operated anterior drawer 2.4 mm (range 0 mm – 4.5 mm) greater than on the control side. No lesions of the meniscus and cartilage were detected.

Conclusions: A ruptured ACL has the biological potential to heal after DIS in a sheep model. The surgical technique achieved a stable knee joint with free range of motion and full weight bearing during the healing period without signs of osteoarthritis or other intraarticular damage at follow up.