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David Shakespeare

Publications and source records attributed to David Shakespeare.

At least 19 recordsLinked to original sources
PubMed2006

Flexion after total knee replacement. A comparison between the Medial Pivot knee and a posterior stabilised implant.

A comparison was made between 261 knees replaced with the Medial Pivot arthroplasty and 288 replaced with the 913 posterior stabilised arthroplasty (PS knee). There was no significant difference in the flexion obtained at 12 months after surgery (111 degrees and 109 degrees , respectively). When the knees were grouped into preoperative flexion ranges, there was no significant difference between the two implants. Those knees with preoperative flexion up to 90 degrees gained most (mean 22.6 degrees and 19 degrees for the PS knee and Medial Pivot, respectively). Knees with a preoperative flexion of 125 degrees or greater lost flexion. Regression analysis of individual knees revealed a small (average 2.9 degrees ), but significant greater loss of flexion at 12 months after surgery in the Medial Pivot group, with increasing preoperative flexion (beta coefficient = 2.923, P = 0.007). Some knees in both groups which had less than average preoperative flexion lost rather than gained flexion. We attributed this to patient factors such as pain, swelling and poor compliance with rehabilitation. Although the Medial Pivot knee may have advantages in terms of contact area and kinematics we found no advantage in terms of postoperative flexion over our posterior stabilised knee.

Aged↗
PubMed2005

Accuracy of implantation of components in the Oxford knee using the minimally invasive approach.

Screened postoperative X-rays of 224 Oxford knees implanted through the minimally invasive approach were analysed using 16 criteria. The technique was as recommended by the Oxford Group except that the femoral intramedullary rod was used only as a guide to flexion/extension of the femoral component. All femoral components were within the recommended range for varus/valgus and mediolateral position. Eighteen femoral components were either too flexed or extended, but by a maximum of only 10 degrees . Tibial components were inserted in slight varus (mean 1.8 degrees , S.D. 8.8, range 10 to -10). All were within the range for posterior slope in spite of difficulty in establishing objective landmarks. Tibial coverage was imprecise with the phase 3 implants which were short and broad relative to the cut surface. In 36% of knees the tibial tray was implanted too anterior resulting in posterior under hang. There have been no clinical signs to indicate tipping of the meniscus in deep flexion. The depth of cement penetration under the keel was excessive in three cases, resulting from porotic bone rather than technical error in the depth of the cut. There has been one case of femoral component loosening following a fall and no tibial loosening in spite of imprecise alignment of some components.

Arthrography↗
PubMed2005

Achieving ligament stability and correct rotational alignment of the femur in knee arthroplasty: a study using the Medial Pivot knee.

In a series of 90 Medial Pivot arthroplasties rotational alignment of the femur was achieved by provisionally reconstructing the lateral side of the joint and tensioning the medial side with feeler gauges. Axial CT scans were employed to measure the rotational alignment relative to surgical epicondylar axis. In valgus knees the cutting block was externally rotated to adjust for posterolateral bone loss. The mean rotational alignment of the femur was 0.6 degrees of external rotation (S.D. 1.3, range 3 degrees of ER to 4 degrees of IR). The mean laxity of the medial ligament was 1 mm in flexion (SD 1, range 0-5 mm) and 0.5 mm in flexion (S.D. 0.5, range 0-2 mm) In those knees in which the medial ligament had been released the CT alignment was perfect, but when internally rotated against the hip 3-4 mm of gapping was noted. In valgus knees the mean rotation of the femoral component was 0.8 degrees of internal rotation (S.D. 1.5, range 1 degrees of IR to 4 degrees of ER). In spite of externally rotating the cutting block there was still a tendency to internally rotate the femur in some knees. This simple technique achieves the two goals of ligament stability and correct rotational alignment in a high proportion of cases. It may be applicable to any instrument system which employs posterior referencing.

Arthroplasty, Replacement, Knee↗
PubMed2005

Patellar instability-can the TT-TG distance be measured clinically?

The horizontal distance between the tibial tubercle and the centre of the groove (TT-TG) is an important determinant in the treatment of patellar instability. We set out investigate whether it could be measured in the outpatient setting using a length of string lined up between a proximal reference point, the centre of the patello-femoral groove and the tibial tubercle. The technique was employed in 24 knees of patients awaiting patellar realignment and the results compared with linked MRI slices through the trochlear and tibial tubercle. With the knee at 90 degrees of flexion, the centre of the trochlear groove lines up with tibial tubercle in patients with both objective and potential instability, making visual inspection of the knee in this position unhelpful in deciding whether to transfer the tibial tubercle. In the extended knee, the technique failed to detect the large TT-TG distance demonstrated on the MRI in the objectively unstable group. Visual inspection of the leg is unreliable in assessment of the position of the tibial tubercle relative to the trochlear groove. The knee should be scanned before a decision is taken to transfer the tibial tubercle medially.

Ambulatory Care↗
PubMed2005

Accuracy of patellar resection in total knee replacement. A study using the medial pivot knee.

A series of 80 patellae were randomly allocated to osteotomy by sawing or milling while implanting the medial pivot knee. Three landmarks were used to control the plane of the cut in the coronal plane. The lateral edge of the patellar tendon distally, and both medial and lateral edges of the quadriceps tendon proximally. A line drawn across the widest points if the patella (the patellar horizon) was used to analyse the slope of the cut (P angle) and the orientation of the patella relative to the trochlear groove both pre- and post-operatively (PF angle) on 45 degrees skyline views. No patellae were under resected. The mean thickness of the remnant was 16 mm (range 14-19). There was no difference between sawing and milling, but the former was technically preferable. No patellae were found to be subluxed. The mean P angle was 2 degrees (S.D. 3.2). The maximum P angle was 10 degrees , but in no cases did obliquity of cut with under resection of the medial patellar facet lead to lateral tilt of the patellar horizon. The mean post-operative PF angle was 2.3 degrees (S.D. 2.6). The majority of patellae retained a similar orientation to the patellar groove post-operatively. In three patients, the patella tilted laterally with respect to the groove. One resulted from under resection of the lateral patellar facet and two in which the slope of the cut was good, probably resulted from an error in femoral rotation. In all 80 knees, the patellar dome remained in full contact with the groove. Use of three fixed landmarks provides consistent patellar resection in terms of depth and slope. Errors in slope of up to 10 degrees do not cause patellar tilt but may lead to medial overload due to increasing thickness of the patella. Errors in femoral sizing and rotation are more potent causes of lateral tilt and overload.

Arthroplasty, Replacement, Knee↗
PubMed2005

The effect of aprotinin on blood loss in bilateral total knee arthroplasty.

Twenty-five patients undergoing bilateral total knee arthroplasty were given aprotinin (1-2 million units) in doses adjusted for weight, infused at the end of the first arthroplasty. Blood management was compared with our previous series of 68 patients who were not treated with aprotinin. Blood drained and re-transfused in the first 6 h was significantly less in the aprotinin group (323 ml, S.D. 320) than the untreated group (1033 ml, S.D. 539, p<0.0005). The total blood drained was also less in the aprotinin group (713 ml compared to 1613 ml, p<0.0005) but this was accounted for soley by the difference in early blood loss. The use of other blood products was less in the aprotinin group (360 ml, S.D. 357 compared to 827 ml, S.D. 434, p<0.0005). The mean postoperative haemoglobin on the day following surgery was similar at around 10 g. There were no complications or adverse reactions to the use of aprotinin. We conclude that aprotinin significantly reduces early blood loss after bilateral knee arthroplasty. In our hands, we have found it to be safe. Further work is required to determine whether postoperative use may further reduce the need for blood transfusion.

Aged↗
PubMed2005

The influence of the tibial sagittal cut on component position in the Oxford knee.

The alignment of the components of the Oxford knee replacement were analysed before and after modification of technique for performing the sagittal cut. In the 126 knees prior to the change, there was wide variation in the apparent femoral rotation on screened X-rays centred on the tibial component. In the 40 knees after the change, the variability was markedly reduced (traditional technique, mean femoral rotation 7.86 degrees, range -5 degrees to 30 degrees, compared with 3.18 degrees, range 0 degrees to 15 degrees in the modified group, p=0.0001.). We conclude that the apparent rotation of the femur is largely due to variation in position of the sagittal cut. The mean meniscal displacement was not reduced in the modified group but the range was smaller in that no menisci were displaced more than 3.5 mm from the tibial upright compared with 15% in the traditional group. Menisci which were displaced tended to rotate. The mean rotation and range were greater in the unmodified group (5.92 degrees ER range, 20 degrees ER to 25 degrees IR, traditional group, compared with 0.39 degrees ER, range 10 degrees ER to 12.5 degrees IR in the modified group, p=0.001). A simple technique for controlling the direction of the sagittal cut using intra articular landmarks gives reproducible results. The apparent femoral rotation on screened views in extension is reduced as is the range of meniscal displacement and rotation. Application of this technique may be helpful in lateral resurfacing where soft tissue support is less likely to resist meniscal dislocation.

Arthroplasty, Replacement, Knee↗
PubMed2004

Can the epicondylar axis be defined accurately in total knee arthroplasty?

As part of a study on rotational alignment of the femoral component in knee replacement, the surgical epicondylar axis was identified in 74 knees and marked with pins. An alternative technique was employed to achieve rotational alignment and in each case the distance between the pins and the cut surface of the posterior condyles was measured. The alignment of the femoral component was measured postoperatively by axial CT scans of the distal femur, allowing an assessment to be made of what would have been achieved if the epicondylar pins had been used for guidance. Only 75% of knees would have been within 3 degrees of the true epicondylar axis using the epicondyles to control rotation. The error range was large (range 6 degrees ER to 11 degrees IR). Our conclusion is that even in experienced hands clinical estimation of the epicondylar axis is inaccurate and should not be relied upon as the sole determinant of femoral rotation.

Aged↗
PubMed2004

Patellar subsidence in heavy patients undergoing bilateral knee arthroplasty.

A retrospective review of 40 patients undergoing simultaneous bilateral total knee replacement was undertaken to investigate the link between patient body weight and patellar subsidence. Of the 40 patients, three (five knees) had collapse or fracture of the patellar bone and four (five knees) had developed radiolucent lines around the patellar implant. None of these patients were symptomatic and their Knee Society and Oxford functional scores were satisfactory. All of the seven patients had body weights significantly greater than the average for the series.

Arthroplasty, Replacement, Knee↗
PubMed2004

Varus/valgus alignment of the femur in total knee arthroplasty. Can accuracy be improved by pre-operative CT scanning?

In a series of 80 consecutive knee replacements, pre-operative scout scans of the femur were taken and the angle between the slope of the worn femur and the mechanical axis was measured. At surgery the angle of the distal femoral cut was adjusted to make it perpendicular to the mechanical axis. Post-operative scans revealed that 97.5% of femoral components were implanted within 2 degrees of the target. The angle between a perfectly positioned virtual intra-medullary rod on the pre-operative films and the mechanical axis showed marked variations between individuals indicating that the use of a fixed angular correction from an intra-medullary rod is unreliable even under perfect circumstances. In practice it is subject to further inaccuracy due to variability in the anatomy of the femur and rod placement. With the advent of robotically assisted surgery, the technical limits of conventional instruments need to be explored in terms of improving accuracy for each individual patient. In terms of the coronal alignment of the femur, this involves some degree of preplanning rather than relying on arbitrary targets based on incorrect assumptions.

Arthroplasty, Replacement, Knee↗
PubMed2003

Suction technique to improve cement penetration under the tibial component in total knee arthroplasty.

Improving the longevity and reliability of cemented total knee arthroplasty remains an important part of orthopaedic research. This paper examines the recently described method of preparation of the cancellous surface of the tibia using suction cannulae in the proximal tibia and stem recess during pulsatile lavage and component fixation. The technique provides a surface clear of debris, fat, blood and marrow, and prevents backflow of blood. A retrospective analysis of post-operative radiographs shows significant improvement in the penetration of cement into the tibial plateau, and improved cement profile towards the periphery. Techniques of stem cementation are also compared, and it is recommended that for this particular design implant, cement should be applied into the cut stem recess in the tibia rather than to the stem of the implant itself. This technique of preparation of the cut surface of the tibia is a simple and, to-date, complication-free method of reliably providing satisfactory cement penetration during total knee arthroplasty.

Aged↗
PubMed2003

Varus/valgus alignment of the femoral component in total knee arthroplasty.

The position of the femoral component in 362 total knee replacements was assessed radiologically. A subgroup of 32 knees, 18 of which had perfect alignment and 14 with imperfect alignment underwent CT scout scans of the femur from which the mechanical axis of the femur could be measured. Radiologically 92% of all components were implanted within 3 degrees of the target value. There was close correlation between the CT and X-ray measurements in the subgroup. Deviation from the mechanical axis was 1.16 degrees (range -2.5 to +2) in the perfectly aligned knees, validating both surgical technique and radiological assessment. Causes for inaccuracy in femoral placement and future likely developments are discussed.

Arthroplasty, Replacement, Knee↗
PubMed2003

Varus/valgus alignment of the tibial component in total knee arthroplasty.

The varus/valgus alignment of the tibial components of 350 total knee arthroplasties was assessed radiologically. All the tibial components were implanted using an extramedullary guide under the supervision of the senior author. Of components, 96.3% were implanted within 2 degrees of the perpendicular to the longitudinal axis of the tibia. In order to validate our X-ray assessment, a subgroup of 40 knees was re-assessed using a CT scanogram. Analysis of this subgroup showed a close correlation between the results using the two different methods (mean difference 0.88 degrees, S.D. 0.75). We believe that with anticipated future advances in robotic and computer assisted surgery it is important to set the benchmark for what can be achieved with current technology.

Arthroplasty, Replacement, Knee↗
PubMed2003

Fixed flexion deformity and flexion after knee arthroplasty. What happens in the first 12 months after surgery and can a poor outcome be predicted?

Fixed flexion deformity and flexion of 284 knee replacements were recorded pre-operatively at 6 weeks and 12 months after surgery. Eighteen knees (6.3%) achieved unsatisfactory movements at 12 months. Seven knees (2.4%) had a fixed flexion greater than 10 degrees, six (2.1%) had flexion less than 90 degrees and five (1.8%) had both. The only pre-operative variable of predictive value for a poor outcome was a high fixed flexion deformity (10 out of 52 knees P<0.001). Only one out of 15 knees with limited pre-operative flexion was restricted afterwards. Seven knees (2.4%) with good pre-operative movements developed either limited flexion or a fixed flexion greater than 10 degrees, none had both. There were no post-operative events which contributed to this. Eight knees (2.8%) achieved very poor movements. In each case there was a significant post-operative event which contributed to this. Overall, the flexion achieved at 12 months was directly related to the pre-operative flexion. Those knees with <90 degrees of flexion gained 29.3 degrees (S.D. 18). Those with 130 degrees or greater flexion lost 15.2 degrees (S.D. 13.6). The mean pre-operative fixed flexion was reduced by 50% at 6 weeks and again at 12 months. Knees with a high fixed flexion deformity alone pre-operatively have an increased risk of developing stiffness afterwards even if the deformity is corrected at surgery. In most cases significant post-operative events play a major role in this outcome. A small percentage of knees develop stiffness without any obvious explanation.

Arthroplasty, Replacement, Knee↗