Introduction The aim of this study was to examine the flexion stability of posterior stabilised (PS) compared with deep dished (DD) tibial inserts in PCL sacrificing total knee arthroplasty using posterior stress radiography.

Methods Kneeling posterior stress radiographs at 90° of flexion were taken pre and post-operatively in 36 knees undergoing primary arthroplasty with PCL resection (26 DD and 10 PS implants). Sagittal plane tibial translation was measured.

Results The deep dish inserts all showed posterior displacement (mean: −5.1 mm, range: −2 to −12 mm). The posterior stabilised implants were all displaced anteriorly (mean: +6.7 mm, range: +3 to +12 mm). The difference in translation was highly significant (P< 0.0001). There was a strong correlation between implant and position of the tibia (R = 0.86). In seven patients comparison was possible between a DD component in one knee and a PS implant in the other. There was a mean post-operative side to side difference of 11 mm (range: 5 to 21 mm).

Conclusions This study discriminates between two implant types on stress x-rays. The posterior tibial displacement in the DD group suggests that this implant does not provide enough posterior flexion stability to compensate for the PCL resection. The anterior translation in the PS group has implications for the design and wear of the post as well as advice to patients about possibly avoiding kneeling in this PS design.

Introduction The aim of the study was to investigate the incidence, in Australia, of popliteal artery injury during knee surgery; to assess the distance from the popliteal artery to the posterior tibia in flexion and extension; and to investigate the influence of major trauma or surgery on the anatomy.

Methods A questionnaire was sent to Australian members of the ANZ Society of Vascular Surgeons. Duplex ultrasound studies were obtained through the Vascular Laboratory University of Melbourne. Studies in extension and 90° of flexion assessed the distance from the popliteal artery to the posterior tibia. Twelve persons with normal knees were assessed bilaterally. Eight patients with a posterior cruciate ligament deficient knee were assessed bilaterally. Seventy vascular surgeons responded documenting 115 popliteal artery injuries occurring during knee surgery. There were 69 lacerations, 27 thromboses, 13 AV fistula and 19 false aneurysms. In 12 normal people (24 knees) the popliteal artery was 5.5 mm (2.9 to 9.9) from the tibia in extension and 5.7 mm (2.9 to 10.0) in 90° of flexion. In ten of 24 knees the artery moved closer in flexion. In the eight posterior cruciate ligament deficient knees the artery was 4.7 mm (2.7 to 6.9) from the tibia in extension and 3.8 mm (2.6 to 4.5) at 90° of flexion. In all eight PCL knees the artery moved closer in flexion. In normal knees the popliteal artery may move closer to the tibia in flexion, the average distance being about 5.5 mm.

Conclusions The popliteal artery is closer to the knee joint following trauma or surgery and specifically closer in flex-ion than in extension. Risks of injury are significant.