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D J Beard

Publications and source records attributed to D J Beard.

At least 19 recordsLinked to original sources
PubMed2006

No deterioration of kinematics and cruciate function 10 years after medial unicompartmental arthroplasty.

The mechanisms of failure for unicompartmental arthroplasty are poorly understood. There is some suggestion that long term ligament degeneration, particularly of the anterior cruciate ligament (ACL), may affect long term survivorship. This study evaluated whether the cruciate mechanism remained functional in the long term (10 years) following UKA. Two separate cohorts of patients who had undergone St Georg Sled medial compartmental arthroplasty had knee kinematics assessed using an established fluoroscopic technique. One group (early) was assessed at a mean of 46 months (3.8 years) since surgery, whilst the other (late) was assessed at a mean of 125 months (10.4) following surgery. No significant difference was found in the sagittal plane kinematics between the two groups or in comparison to the control normal knee. The results suggest that after fixed bearing UKA the cruciate mechanism remains intact over time and the ligaments continue to function similarly to those of the normal knee.

Aged↗
PubMed2006

A convex lateral tibial plateau for knee replacement.

Unicompartmental knee replacements have not performed as well in the lateral compartment as in the medial. This may be because the tibial components have flat or slightly concave surfaces which match the medial plateau but not the convex lateral plateau. The aim of this study was to find the optimal radius for a convex lateral tibial component. Twelve normal lateral tibial plateau were retrieved at knee replacement, and their surface contour in their mid sagittal plane was determined. The optimal circle was fitted and its radius measured. A series of different shaped tibial components were superimposed. From published information about the position of the femoral condyle relative to the tibia in different degrees of flexion, the flexion gap at these angles was determined. The average radius of the lateral tibial plateau was 40 mm. However, as the surface was polyradial it was not clear if this average radius would be optimal. In full flexion, a flat tibial plateau distracted the knee by 8 mm (p<0.001). A 75 mm radius spherical tibial plateau did not alter the knee kinematics significantly and gave rise to a change in joint distraction of 1.5 mm. Spherical tibial plateau of 50 mm and 25 mm radii significantly altered knee kinematics (p<0.001) and resulted in changes in distraction of 3 mm and 4 mm respectively. The optimal shape for a unicompartmental lateral tibial plateau is likely to be a spherical dome with radius of about 75 mm. The incorporation of this shape in the lateral side of a total knee replacement might improve its flexion.

Femur↗
PubMed2006

The premature failure of the Charnley Elite-Plus stem: a confirmation of RSA predictions.

We performed a clinical and radiological study to determine the rate of failure of the Charnley Elite-Plus femoral component. Our aim was to confirm or refute the predictions of a previous roentgen stereophotogrammetric analysis study in which 20% of the Charnley Elite-Plus stems had shown rapid posterior head migration. It was predicted that this device would have a high early rate of failure.We examined 118 patients at a mean of nine years after hip replacement, including the 19 patients from the original roentgen stereophotogrammetric study. The number of revision procedures was recorded and clinical and radiological examinations were performed. The rate of survival of the femoral stems at ten years was 83% when revision alone was considered to be a failure. It decreased to 59% when a radiologically loose stem was also considered to be a failure. All the patients previously shown in the roentgen stereophotogrammetric study to have high posterior head migration went on to failure. There was a highly significant difference (p = 0.002) in posterior head migration measured at two years after operation between failed and non-failed femoral stems, but there was no significant difference in subsidence between these two groups. Our study has shown that the Charnley Elite-Plus femoral component has an unacceptably high rate of failure. It confirms that early evaluation of new components is important and that roentgen stereophotogrammetric is a good tool for this. Our findings have also shown that rapid posterior head migration is predictive of premature loosening and a better predictor than subsidence.

Adult↗
PubMed2006

Combined anterior cruciate reconstruction and Oxford unicompartmental knee arthroplasty.

The options for treatment of the young active patient with isolated symptomatic osteoarthritis of the medial compartment and pre-existing deficiency of the anterior cruciate ligament are limited. The potential longevity of the implant and levels of activity of the patient may preclude total knee replacement, and tibial osteotomy and unicompartmental knee arthroplasty are unreliable because of the ligamentous instability. Unicompartmental knee arthroplasties tend to fail because of wear or tibial loosening resulting from eccentric loading. Therefore, we combined reconstruction of the anterior cruciate ligament with unicompartmental arthroplasty of the knee in 15 patients (ACLR group), and matched them with 15 patients who had undergone Oxford unicompartmental knee arthroplasty with an intact anterior cruciate ligament (ACLI group). The clinical and radiological data at a minimum of 2.5 years were compared for both groups. The groups were well matched for age, gender and length of follow-up and had no significant differences in their pre-operative scores. At the last follow-up, the mean outcome scores for both the ACLR and ACLI groups were high (Oxford knee scores of 46 (37 to 48) and 43 (38 to 46), respectively, objective Knee Society scores of 99 (95 to 100) and 94 (82 to 100), and functional Knee Society scores of 96 and 96 (both 85 to 100). One patient in the ACLR group needed revision to a total knee replacement because of infection. No patient in either group had radiological evidence of component loosening. The radiological study showed no difference in the pattern of tibial loading between the groups. The short-term clinical results of combined anterior cruciate ligament reconstruction and unicompartmental knee arthroplasty are excellent. The previous shortcomings of unicompartmental knee arthroplasty in the presence of deficiency of the anterior cruciate ligament appear to have been addressed with the combined procedure. This operation seems to be a viable treatment option for young active patients with symptomatic arthritis of the medial compartment, in whom the anterior cruciate ligament has been ruptured.

Adult↗
PubMed2005

In vivo kinematics of the ACL-deficient limb during running and cutting.

Anterior cruciate ligament-deficient (ACLD) knee kinematics during high-demand activities are poorly understood. We have devised a new method, using gait analysis, to more accurately assess 3-D in vivo kinematics of the knee. This has enabled us to report on how knee kinematics are altered after ACL rupture, during running and cutting. Fifteen unilaterally ACLD subjects were assessed using a 12-camera 100 Hz VICON motion analysis system. Simultaneous electromyographical (EMG) recordings were used to assess the role of the sensorimotor system in knee joint stability. All subjects were able to perform demanding cutting activities without experiencing symptoms of instability. We found that running produces fundamentally different kinematic patterns to those seen during walking. Tibiofemoral translation in the anteroposterior plane is controlled to within normal limits. Conversely, coronal translation and rotation are poorly controlled. We found that the injured leg was maintained in greater extension during the stance phase of all running activities studied and that the quadriceps muscle was active for longer during this period. We believe that low-demand activities, such as walking, do not reproduce kinematics relevant to ACLD instability and that future investigations into functional instability in the ACLD knee should focus on coronal and rotational displacements.

Adolescent↗
PubMed2005

In-vivo sagittal plane knee kinematics: ACL intact, deficient and reconstructed knees.

Sagittal plane video fluoroscopy was used to analyse the bilateral knee kinematics of patients with unilateral ACL deficiency (ACLD) before, and 4 months after, hamstrings graft ACL reconstruction. Kinematics were studied during weight resisted knee extension, passive knee extension, and a step up. Thigh EMG records were also obtained from five subjects. In addition, six uninjured control subjects were analysed to establish normal kinematics. Kinematics were analysed by calculating the angle between the long axis of the tibia and the patella tendon through the range of knee flexion. Shear forces were calculated using a model of knee extension and force plate data. A maximum anterior TT of 7.3 (S.D. 2.1) mm was recorded in ACL intact (ACLI) knees during the weightbearing activity. Hamstrings activity was able to control ATT in the ACLD tibia to within the normal range of translation of the ACLI knee. Despite clinical improvements, ATT increased postoperatively in the reconstructed knees to 11.6 (S.D. 3.8) mm (P<0.048). The findings suggest that the ACL has only a minor role in the control of ATT during activity, and that the extent of ATT is more closely related to the level of quadriceps-generated shear force. A reduction in hamstrings force is proposed as the most likely cause for increased ATT post reconstruction. These findings have implications for the development of ACL rehabilitation regimes, and also may modify graft choice and the surgical aims of the procedure.

Adult↗
PubMed2005

Efficacy of an accelerated recovery protocol for Oxford unicompartmental knee arthroplasty--a randomised controlled trial.

Unicompartmental knee arthroplasty (UKA) is appropriate for one in four patients with osteoarthritic knees. This study was performed to compare the safety, effectiveness and economic viability of a new accelerated protocol with current standard care in a state healthcare system. A single blind RCT design was used. Eligible patients were screened for NSAID tolerance, social circumstances and geographical location before allocation to an accelerated recovery group (A) or standard care group (S). Primary outcome was the Oxford Knee Assessment at 6 months post operation, compared using independent Mann-Whitney U-tests. A simple difference in costs incurred was calculated. The study power was sufficient to avoid type 2 errors. Forty-one patients were included. The average stay for Group A was 1.5 days. Group S averaged 4.3 days. No significant difference in outcomes was found between groups. The new protocol achieved cost savings of 27% and significantly reduced hospital bed occupancy. In addition, patient satisfaction was assessed as greater with the accelerated discharge than with the routine discharge time. The strict inclusion criteria meant that 75% of eligible patients were excluded. However, a large percentage of these were due to the distances patients lived from the hospital.

Arthroplasty, Replacement, Knee↗
PubMed2005

Real in vivo kinematic differences between mobile-bearing and fixed-bearing total knee arthroplasties.

We did an in vivo fluoroscopic study comparing the sagittal plane kinematics of mobile-bearing and fixed-bearing total knee arthroplasties in a unique group of patients. These patients were part of a larger bilateral randomized controlled outcome trial with each patient having received both types of total knee arthroplasties. Invited patients did three exercises with each of their different knee replacements; extension against gravity, flexion against gravity, and a step-up. These exercises were recorded using video fluoroscopy, and a series of still digital images over the flexion range were retrieved. The relationship of patella tendon angle to knee flexion angle for each patient was derived. The patella tendon angle to knee flexion angle of the mobile-bearing knee behaved in a linear manner more closely replicating the normal knee, whereas the fixed-bearing knee behaved in a nonlinear, more variable manner. This pattern of results was similar for all three exercises with each patient having one knee replacement that behaved differently in the sagittal plane when compared with their other knee replacement. These kinematic differences may explain the clinical differences observed in the randomized controlled trials that compared these two total knee arthroplasties.

Adult↗
PubMed2005

The effect of hip resurfacing on oxygen concentration in the femoral head.

We inserted an electrode up the femoral neck into the femoral head of ten patients undergoing a metal-on-metal hip resurfacing arthroplasty through a posterior surgical approach and measured the oxygen concentration during the operation. In every patient the blood flow was compromised during surgery, but the extent varied. In three patients, the oxygen concentration was zero at the end of the procedure. The surgical approach caused a mean 60% drop (p < 0.005) in oxygen concentration while component insertion led to a further 20% drop (p < 0.04). The oxygen concentration did not improve significantly on wound closure. This study demonstrates that during hip resurfacing arthroplasty, patients experience some compromise to their femoral head blood supply and some have complete disruption.

Adult↗
PubMed2005

Influence of surface geometry and the cam-post mechanism on the kinematics of total knee replacement.

Abnormal sagittal kinematics after total knee replacement (TKR) can adversely affect functional outcome. Two important determinants of knee kinematics are component geometry and the presence or absence of a posterior-stabilising mechanism (cam-post). We investigated the influence of these variables by comparing the kinematics of a TKR with a polyradial femur with a single radius design, both with and without a cam-post mechanism. We assessed 55 patients, subdivided into four groups, who had undergone a TKR one year earlier by using an established fluoroscopy protocol in order to examine their kinematics in vivo. The kinematic profile was obtained by measuring the patellar tendon angle through the functional knee flexion range (0 degrees to 90 degrees ) and the results compared with 14 normal knees. All designs of TKR had abnormal sagittal kinematics compared with the normal knee. There was a significant (p < 0.05) difference between those of the two TKRs near to full extension. The presence of the cam-post mechanism did not influence the kinematics for either TKR design. These differences suggest that surface geometry is a stronger determinant of kinematics than the presence or absence of a cam-post mechanism for these two designs. This may be because the cam-post mechanism is ineffective.

Aged↗
PubMed2005

Influence of stem geometry on the stability of polished tapered cemented femoral stems.

Polished, tapered stems are now widely used for cemented total hip replacement and many such designs have been introduced. However, a change in stem geometry may have a profound influence on stability. Stems with a wide, rectangular proximal section may be more stable than those which are narrower proximally. We examined the influence of proximal geometry on stability by comparing the two-year migration of the Exeter stem with a more recent design, the CPS-Plus, which has a wider shoulder and a more rectangular cross-section. The hypothesis was that these design features would increase rotational stability. Both stems subsided approximately 1 mm relative to the femur during the first two years after implantation. The Exeter stem was found to rotate into valgus (mean 0.2 degrees , sd 0.42 degrees ) and internally rotate (mean 1.28 degrees , sd 0.99 degrees ). The CPS-Plus showed no significant valgus rotation (mean 0.07 [correction] degrees, sd 0.29 [correction] degrees ) or internal rotation (mean -0.03 degrees , sd 0.75 degrees ). A wider, more rectangular cross-section improves rotational stability and may have a better long-term outcome.

Aged↗
PubMed2004

Minimally invasive Oxford unicompartmental knee arthroplasty: functional results at 1 year and the effect of surgical inexperience.

Oxford medial unicompartmental arthroplasty (UCA) is now routinely performed through a short incision without dislocation of the patella. We present the 1 year results of the first 104 knees operated in Oxford using this technique and the learning curve associated with it. The patient's average age at surgery was 68 years. The average American Knee Society 'knee score' improved from 37 to 94 points and the average 'functional score' from 50 to 92 points. Average maximum flexion improved from 117 to 131 degrees. The average knee score during a surgeon's first 10 cases was 88 points, which was significantly less (P<0.03) than the score achieved for subsequent cases after the first 10 (95 points). These data suggest for the first time that a learning curve exists with worse results being achieved during a surgeon's first 10 cases. However, the results during the learning curve are still similar to that achieved after total knee arthroplasty.

Aged↗
PubMed2003

Symmetrical vs asymmetrical total knee replacement--a medium term comparative analysis.

Modifications of established implants can result in deleterious effects, as with the Capitol and the matt coated Exeter hips. In 1991 the Kinemax plus modification of the Kinematic knee was introduced in Bristol, the design changes having been made to reduce patello-femoral complications. We carried out a comparative analysis of the prospective recorded data on a consecutive series of 182 total knee replacements (95 Kinematic and 87 Kinemax plus knees) performed between 1991 and 1993. The same instrumentation and surgical technique was used. Since the design had introduced a broader trochlear, offset patella and had changed from an asymmetrical to a symmetrical femoral component, particular attention was paid to tracking and range of movement. All patients were reviewed at 5 years using the Bristol knee score and radiographs. There was no difference in the overall score (both prosthesis scoring 85-86) but the Kinemax plus group with a symmetrical trochlear had a significantly greater improvement in the range of movement (14 degrees as opposed to 4 degrees; P<0.05). In addition, secondary intervention for mal-tracking was significantly less in the Kinemax group. No deleterious effect of the changed geometry was observed. It is concluded that the introduction of a symmetrical femoral component with an offset patella reduced patello-femoral complications without detectable disadvantages.

Aged↗
PubMed2002

Defining the femoral axis on lateral knee fluoroscopy.

The methodological detail about determining the femoral axis on lateral fluoroscopic images of the knee is lacking. This paper reports on the use of the posterior border of the lower femoral diaphysis to represent the axis. This method is accurate, simple, reliable and can be used by researchers studying knee joint kinematics using dynamic video fluoroscopy. It is also useful in the outpatient clinic to assess the flexion/extension position of femoral components after knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed2002

Accelerated recovery for unicompartmental knee replacement--a feasibility study.

A pilot study assessed the feasibility of discharging NHS patients undergoing knee replacement within a day of surgery. Seven patients with medial compartment osteoarthritis were recruited after fulfilling strict exclusion criteria. Pre-operative assessment revealed that all patients had significant dysfunction and pain before operation. They had medial unicompartmental replacement through a short incision without dislocation of the patella. Each patient underwent an accelerated recovery program that included pain control, physiotherapy and self-assessment. Patients were mobilised immediately after operation. Follow-up assessment was performed at 1, 2 and 6 weeks after surgery. All patients, except one (who failed to go home because of an administrative error), returned home the day after surgery. The average pain score for the first 2 weeks after surgery was 2/10. At 6 weeks, knee flexion averaged 125 degrees and all patients were walking independently and painfree. The new protocol allows for early, safe discharge of patients undergoing unicompartmental knee replacement.

Aged↗
PubMed2002

A kinematic study of lateral unicompartmental arthroplasty.

When the Oxford unicompartmental meniscal bearing arthroplasty (UCA) is used in the lateral compartment 10% of the bearings dislocate. A fluoroscopic study was performed to investigate if abnormal mid-sagittal plane kinematics was related to bearing dislocation. Video fluoroscopy is an accepted means of determining in-vivo knee kinematics in the sagittal plane. Video fluoroscopy was obtained of 5 Oxford lateral UCAs 10 years post-operatively and of five normal knees. Patellar tendon angle (PTA), derived from dynamic fluoroscopic images, was used to describe the joint kinematics. This in-vivo experiment demonstrated that the PTA/knee relationship for the Oxford lateral UCA is similar to the normal knee. Both the normal knee (r(2)=0.99) and the Oxford lateral UCA (r(2)=0.98) demonstrated a linear relationship between flexion angle and PTA. No significant difference in PTA was found between the normal knee and the Oxford lateral UCA. This study demonstrated normal kinematics, as indicated by PTA, ten years after implantation of the Oxford lateral UCA. It is therefore reasonable to suggest that abnormal kinematics is not a significant factor relating to meniscal bearing dislocation in the lateral compartment.

Adult↗
PubMed2002

Dislocation of the bearing of the Oxford lateral unicompartmental arthroplasty. A radiological assessment.

When the Oxford unicompartmental meniscal bearing arthroplasty is used in the lateral compartment of the knee, 10% of the bearings dislocate. A radiological review was carried out to establish if dislocation was related to surgical technique. The postoperative radiographs of 46 lateral unicompartmental arthroplasties were analysed. Five variables which related to the position and alignment of the components were measured. Dislocations occurred in six knees. Only one of the five variables, the proximal tibial varus angle, had a statistically significant relationship to dislocation. This variable quantifies the height of the lateral joint line. The mean proximal tibial varus angle for knees the bearings of which had dislocated was 9 degrees and for those which had not it was 5 degrees. In both groups it was greater than would be expected in the normal knee (3 degrees). Our study suggests that a high proximal tibial varus angle is associated with dislocation. The surgical technique should be modified to account for this, with care being taken to avoid damage to or overdistraction of the lateral soft tissues.

Aged↗