Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee. Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20).Introduction
Methods
The heat produced by drills, saws and PMMA cement in the handling of bone can cause thermal necrosis. Thermal necrosis could be a factor in the formation of a fibrous tissue membrane and impaired bony ingrowth into porous prostheses. This has been proposed to lead to non-union of osteotomies and fractures, the failure of the bone-cement interface and the failure of resurfacing arthroplasty. We compared three proprietary blades (the De Soutter, the Stryker Dual Cut and the Stryker Precision) in an in-vitro setting with porcine tibiae, using thermocouples embedded in the bone below the cutting surface to measure the increases in bone temperature. There was a significant (p=0.001) difference in the change in temperature (δT) between the blade types. The mean increase in temperature was highest for the De Soutter, 2.84°C (SD: 1.83°C, range 0.48°C to 9.30°C); mean δT was 1.81°C (SD: 1.00°C, range 0.18°C to 4.85°C) for the Precision and 1.68°C (SD: 0.95°C, range 0.24°C to 5.67°C). Performing paired tests, there was no significant difference in δT between the Precision and Dual Cut blades (p=0.340), but both these blades had significantly (p=0.003 for Precision vs De Soutter, p<0.001 for Dual Cut vs De Soutter) lower values for δT than the Dual Cut.
It is established good practice that hip and knee replacements should have regular follow-up and for the past seven years at the North Hampshire Hospital a local joint register has been used for this purpose and we compare this with results of the Swedish and UK national and the Trent Regional registries. Since March 1999, all primary and revision hip and knee arthroplasties performed at North Hampshire Hospital, Basingstoke have been prospectively recorded onto a database set up by one of the senior authors (JMB). Data from patients entered in the first five years of the register were analysed. All patients have at least one year clinical and radiological review then a minimum of yearly postal follow-up. 3266 operations (1524 hips and 1742 knees) were performed under the care of 13 consultants. Osteoarthritis was the most common primary diagnosis in over 75% of hips and knees. Our revision burden was 7.5% (10.2% hips and 3.5% knees). As of 31/12/2006 6.2% of patients had died and 5.5% were lost to follow-up. Revision rates were 1.5% and 1.4% for primary total hip and knee replacements respectively. Our data analysis of revisions and patello-femoral replacements has allowed us to change our practice following local audit which is ongoing. Oxford scores at 2 years had improved from a mean of 19 and 21 pre-operatively to 40 and 39 for primary hips and knees respectively. Our costs are estimated at approximately £35 per patient for their lifetime on the register. Compared to other registries: Our dataset is more complete and comprehensive Our costs are less All patients have a unique identifier (the UKNJR has at least 26% of data which is anonymous) Our audit loops have been closed.
Our aim was to determine the effects of tibial component malrotation and posterior slope on knee kinematics following Scorpio cruciate retaining total knee replacement in cadaver specimens. The movements of the hip, thigh and lower leg were monitored in 3D using a validated infra-red Computer Navigation System via bone implanted trackers. Ten normal comparable cadaver specimens were mounted in a custom rig allowing 3D assessment of kinematics under various loading conditions. The specimens then underwent Navigated TKR as per normal operating surgical protocols however an augmented tibial component was implanted. This allowed the researchers to precisely modify the rotation of the tibial component around its predetermined central axis, as well as to alter the posterior slope of the component. A pneumatic cylinder was used to provide a simulated quadriceps extension force while the knee was tested with a variety of applied loads including anterior and posterior draw, abduction and adduction, internal and external rotation. TKR kinematics are significantly different from those of the native knee (p<
0.05). Increasing tibial posterior slope resulted in an incremental posterior position of the femur (p<
0.05), deviation of the neutral path of motion (p<
0.05) and alteration of the normal AP envelope of laxity (p<
0.05). Tibial component malrotations over 10 degrees resulted in increasing deviations of the neutral movement path of motion (p<
0.05) without significantly affecting the envelope of laxity. Tibial component malrotations of more than 10 degrees, when combined with a posterior slope of six degrees or more, resulted in prosthetic subluxation under certain loading conditions. This study has demonstrated significant differences in knee kinematics before and after total knee implantation. Increasing values of internal and external rotation, as well as posterior slope of the tibial tray resulted in further deviations of total knee kinematics from normal by altering the neutral path of motion and the soft tissue envelope, with combined misalignments resulting in the greatest deviations from normal with prosthetic subluxation in some cases. Deviations from normal kinematics may result in increased ligament tension and incongruence or dysfunction of the component articulations, with the generation of sheer forces in the gait cycle. These may contribute to premature wear and loosening. Surgeons should be aware of this when considering the addition of posterior slope or assessing tibial component positioning in TKR.
Kinematics were different after TKR. Increasing posterior slope resulted in increasing posterior position of the femur, particularly at maximum flexion. Posterior slope also resulted in a deviation of the neutral path of motion and alteration of the normal envelope of laxity. Tibial component malrotations over 5 degrees resulted in deviations of the neutral path of motion without affecting the envelope of laxity. Combined malrotations over 10 degrees with posterior slopes over 6 degrees resulting in prosthetic subluxation under certain loading conditions.
The ligament was then repaired using a suture and the tensile strength of this determined. The ligament was then reconstructed in three ways including: Biodegradable corkscrew anchors and two tendon techniques with interference screws. One method used a blind tunnel into the MFC, while the other passed through a tunnel in the femoral condyles. Both methods passed through tunnels in the patella.
The mean strength of the suture repair was 36.7 (SD 26.5) Newton. The biodegradable bone anchor gave a mean strength of 142.3 (SD 38.5) Newton. The blind tunnel hamstring reconstruction’s had a mean strength of 126 (SD 20.8) Newton. The double tunnel hamstring reconstruction’s failed at a mean of 195.0 (SD 65.6) Newton.
The kinematic profile of single axis design TKR was closer to normal especially near extension. During mid-flexion, abnormal anterior femoral translation was noticed with the polyradial design. No significant difference was noted between CR and CS designs.
Four types of prosthetic replacement for the anterior cruciate ligament (carbon fibre, carbon fibre and Dacron composite, Dacron alone and bovine xenograft) were assessed at three, six and 12 months after implantation in the knees of New Zealand white rabbits. The synovium and both intra-articular and intra-osseous portions of the ligaments were examined macroscopically, by light microscopy and by scanning electron microscopy. All the knees showed mild synovitis, and there was no significant growth into the intra-articular part of any ligament. Carbon fibre and xenograft did not appear to be suitable materials in this animal model. The composite ligament showed short-term ingrowth of fibrous tissue only into the periphery of the sheath in its intra-osseous portion, whereas the Dacron ligament showed progressive fibrous tissue ingrowth with some bony incorporation of its outer fibres.
Rigid posterior fixation of the skull to the third, fourth and fifth cervical vertebrae was achieved in three patients who, as a result of operation, had gross instability of the craniocervical junction. An anatomically contoured steel loop was secured to the occiput via small burr holes and to the vertebrae by sublaminar wiring. This technique has the advantage over bone grafting, either alone or with cement, in that it affords rigid stabilisation, allows early mobilisation and may contribute to eventual bony fusion.
We reviewed 230 patients an average of 34 months after they had undergone partial or total meniscectomy by surgeons of different experience in a busy unit. Open and arthroscopic meniscectomies were compared. Arthroscopic partial meniscectomy resulted in a significant reduction of inpatient stay and earlier return to work and sport. Analysis of the type of meniscal damage showed that arthroscopic removal of "bucket handles" achieved better results than open techniques. Comparatively poor results were found for lateral meniscectomy.