There is little information available to surgeons regarding how the lateral soft-tissue structures prevent instability in knees implanted with total knee arthroplasty (TKA). The aim of this study was to quantify the lateral soft-tissue contributions to stability following cruciate retaining (CR) TKA. Nine cadaveric knees with CR TKA implants (PFC Sigma; DePuy Synthes Joint Reconstruction) were tested in a robotic system (Fig. 1) at full extension, 30°, 60°, and 90° flexion angles. ±90 N anterior-posterior force, ±8 Nm varus-valgus and ±5 Nm internal-external torque were applied at each flexion angle. The anterolateral structures (ALS, including the iliotibial band, anterolateral ligament and anterolateral capsule), the lateral collateral ligament (LCL), the popliteus tendon complex (Pop T) and the posterior cruciate ligament (PCL) were then sequentially transected. After each transection the kinematics obtained from the original loads were replayed, and the decrease in force / moment equated to the relative contributions of each soft-tissue to stabilising the applied loads.Introduction
Methods
The advent of double bundle ACL (Anterior Cruciate Ligament) reconstruction had been hailed as potentially allowing for more anatomically and physiologically functioning graft, however until recently there had been little evidence of enhanced functional outcomes. The aim of this study is to explore whether the dimensions of hamstring two strand single bundle grafts, are predictive of the combined four strand single bundle graft that results from combining the single bundle grafts, as well as the impact of double bundle grafts upon the available healing and attachment area within the bony tunnels. Grafts of all likely two strand single bundle graft sizes, measured to the nearest 0.5mm in diameter using unslotted sizing block, were prepared using porcine flexor tendons,. These two strand single bundles were then systematically combined, and re-measured. By geometrical calculation, the sum of the circumferences of the two, two strand double bundle grafts were compared to the combined four strand single bundle graft formed by combining the two smaller bundles.Introduction
Methods
Subtalar dislocation of the hindfoot is a rare injury and can be associated with poor functional outcomes. We report a case of an irreducible subtalar dislocation in an elite athlete, who returned to elite sport. A 28 year old competitor in the world mountain bike championships was injured in a high speed fall from his mountain bike during a competitive downhill run in July 2007. He had an obvious deformity at the scene and a fracture dislocation of the ankle was suspected. The injury was closed and neuro-vascular status was intact. Radiographs revealed the ankle mortise was intact with the talus anatomical, but a subtalar dislocation was present which proved irreducible in the emergency department. The patient was taken to the operating theatre and the dislocation was reduced through a short antero-medial arthrotomy using a blunt lever and traction. Post- reduction, the joint was stable and was supported in a below knee cast. He was kept partial weight bearing for 6 weeks and then had an intensive physiotherapy rehabilitation regime. Serial radiology showed no evidence of avascular necrosis or other skeletal abnormalities. Our patient has since returned to elite Mountain Biking and won the British National Championships in 2008 and the World Championships in Canberra in 2009.
The aim of this study was to assess the increase in the anterior diameter of the knee and the impact of this increase on the range of motion and function of the knee. Twenty-eight patients (34 knees) who underwent Patello-femoral replacement with FPV (Wright Medical) prosthesis between 2005 and 2009 who were identified retrospectively and analyzed using chart and radiological review. Oxford and AKSS knee-scores were gathered prospectively pre-operative and at follow-up. Trochlear height was measured using lateral radiograph. Trochlear height was compared pre and postoperatively. Patellar height was also measured in preoperative and postoperative skyline view and was compared. The range of movement at six weeks and the Oxford and American knee society knee scores at six months postoperatively were noted. Association between increased anterior height and improved range of motion was studied. All but three-knees regained full knee extension. Postoperative mean range of flexion of the knee joint was 116 degrees. The mean Oxford knee and the mean American Knee Society Knee Scores significantly improved post-operatively The trochlear height was increased by 4mms. Patellar height was also increased by 3 mms resulting in average total increase of 7 mms in the anterior-posterior diameter of the knee. We found no relationship between range of motion of the knee and the increase in the anterior-posterior diameter. We found a negative correlation between increase in the antero-posterior and preoperative trochlear and patellar height. We conclude that FPV Patello-femoral replacement results in correct anatomical reconstruction of the trochlear height rather than ‘overstuffing’ of the patellofemoral joint which can lead to stiffness and failure of resolution of pain post-operatively. This should in turn result in durable improvements in pain and function.
Patellofemoral unicompartmental joint replacement is a controversial subject with a relatively small evidence base. Of the 50,000 total knee arthroplasties performed each year in the UK, approximately 10% are performed for predominantly patellofemoral arthritis. There are several patellofemoral unicompartmental prostheses on the market with the National Joint Registry recording 745 such prostheses used in 2007. Most evidence in favour of this procedure comes from experience with the Avon prosthesis (Stryker) predominantly from designer-surgeons. The FPV patellofemoral joint replacement (Wright Medical) has been in use in Europe for several years. The instruments have recently been redesigned and the device marketed in the UK. In 2007 the FPV had 5.9% market share (n=44). We present our early experience with the FPV patellofemoral joint replacement, which to our knowledge, is the first clinical outcome series for this prosthesis. 33 consecutive FPV joint replacements in 29 patients were performed between April 2007 and September 2009 for unicompartmental patellofemoral OA. All cases were performed or directly supervised by the senior author. Results are presented with a minimum follow-up of six months. Oxford and American Knee Society scores (AKSS) were obtained on all patients preoperatively and at subsequent outpatient visits. Mean preoperative AKSS knee score was 49.7 points and postoperative scores at 6 months and 1 year were 82.5 and 86.4 respectively. Mean Oxford score preoperatively was 30.4 (37%) and at 6 months and 1 year were 21.3 (56%) and 11.2 (77%) respectively. There were no complications related to the implant. One knee required a secondary open lateral release due to inadequate balancing at the index procedure. Further medium to long-term follow up data are required, but our initial experience with this device is encouraging.
