Early migration of the new stem design was determined by Roentgen Stereophotogrammetric Analysis (RSA). Rapid early migration of a component relative to the bone, measured by RSA, is predictive of subsequent aseptic loosening for a number of femoral stems. As there was rapid early migration and rotation of the Charnley Elite stem, we predicted that the long-term results would be poor. An outcome assessment is required as stems of this type are still being implanted.
Preliminary clinical scores in the patients who had not undergone any subsequent surgery were adequate (Oxford Hip Score mean average of 23.9). Thirteen percent of radiographs analysed had evidence of loosening, giving an overall loosening rate of 14% at 8 years.
Joint Position Sense (JPS) &
sway were used as measures of proprioception performance. Both groups were assessed pre- and 6 months post-op. JPS was measured using an isokinetic dynamometer (KinCom, Chatanooga Ltd) as the error in actively and passively reproducing fi ve randomly ordered knee fl exion angles (30°, 40°, 50°, 60° and 70°). Sway (area, path and velocity) was measured during single leg stance using a Balance Performance Monitor (SMS Medical) for 30-second interval. Functional outcome was assessed using the Oxford Knee Score (OKS). Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups. Post-operatively, both groups had signifi cant improvement of JPS in the operated limb only (Mean ± standard deviation for UKA 4.64±1.44° and for TKA 5.18±1.35°). No changes in JPS were seen in the control side. Group 2 patients showed signifi cant improvement in both sway area and path (p<
.0001) for both limbs post-operatively. No signifi cant post-operative changes in sway occurred in either limb of Group 1 patients. The OKS improved post-operatively in both groups, rising from 21.4 to 35.5 for Group 1 patients and from 23.9 to 38 for Group 2 patients.
There has been a rapid uptake in the use of Resurfacing Hip Replacement (RHR) in the United Kingdom, and its use is likely to accelerate both in Europe and the USA. The current level of use of RHR is not accurately known. It was decided to audit the use of RHR amongst Consultant Orthopaedic Surgeons in the United Kingdom, and to identify the number of operations performed in the last twelve month period, and the specific training undertaken before offering this procedure. A questionnaire was sent to 1600 Consultant Orthopaedic Surgeons with 894 responding. 19% had performed RHR in the previous year. Excluding surgeons that do not perform Total Hip Replacement, 23.5% of surgeons had performed RHR. 29.5% of all orthopaedic surgeons had observed RHR surgery and 23% had been on an RHR course. 65% of all consultants who had attended a course were offering RHR surgery. 7.8% of those performing RHR had neither been on a course nor observed surgery. There was no relationship between years in practice and RHR surgery. There was a weak association with British Hip Society membership and with a previous fellowship in Hip Surgery. Of those performing RHR, 72% perform less than 20 cases per year. The majority of surgeons perform 6-10 RHRs per year. Although interest in RHR is increasing, it is currently performed by the minority of consultants. Given the steep learning curve, the lack of knowledge of long-term survival, and concerns regarding metal on metal bearing surfaces, RHR should be used by surgeons with a specialist interest in hip arthroplasty. We believe RHR should be used in accordance with the guidance given by the National Institute for Clinical Excellence.
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.
When the Oxford unicompartmental meniscal bearing arthroplasty (UCA) is used in the lateral compartment of the knee 10% of the bearings dislocate. An in-vitro cadaveric study was performed to investigate if the anatomy and joint geometry of the lateral compartment was a contributory factor in bearing dislocation. More specifically, the study investigated if the soft tissue tension of the lateral compartment, as determined by the length of the lateral collateral ligament (LCL), was related to bearing dislocation. A change in length of greater than 2 mm is sufficient to allow the bearing to dislocate. The Vicon Motion Analysis System (Oxford Metrics, Oxford, UK) was used to assess length changes in the LCL of seven cadaveric knees. Measurements were made of the LCL length through knee flexion and of the change in LCL length when a varus force was applied at a fixed flexion angle. Measurements were made in the normal knee and with the knee implanted with the Oxford prosthesis. In the intact knee the mean LCL change was 5.5mm (8%) over the flexion range. After implantation with the Oxford UCA the mean change in length was only 1 mm (1%). There was a significant difference in the LCL length at 90° (p=0.03) and 135° (p=0.01) of knee flexion compared to the intact knee. When a varus force was applied the LCL length change of the intact knee (5.4 mm) was significantly different (p=0.02) to that of the knee with the prosthesis implanted (2.7 mm) This study used a new method to dynamically measure LCL length. It found that after implantation of the Oxford lateral UCA the LCL remains isometric over the flexion range and does not slacken in flexion as it in the normal knee. This would suggest that the soft tissue tension was adequate to contain the bearing within the joint. However, when a varus force was applied the LCL did not sufficiently resist a displacing force producing an LCL length change greater than 2 mm. The evidence provided by this study is contradictory. The “lack of change in LCL length through flexion” suggests that the ligament remains tight through range and is unlikely to allow dislocation. However, the amount of distraction possible when an adducting moment is applied is sufficient to allow bearing dislocation. The length tension properties of the lateral structures are therefore implicated in the mechanism of dislocation.
The indications for unicompartmental knee arthroplasty (UKA) can be contentious. Concerns exist about implanting a UKA in younger individuals. It has been reported that it is contra-indicated in patients under the age of 60. The suggestion is that younger patients may compromise their outcome after surgery by their increased activity levels. However, the number of publications with data on UKA in young patients is minimal and the age/activity related criteria for UKA remains unknown. The aim of the study was 1) to confirm that younger UKA patients have higher activity levels than older patients, and 2) to test the hypothesis that younger, more active patients have inferior outcome when compared to older less active patients. Fifty consecutive patients undergoing UKA who were under 60 years (Group Y) and 50 patients over 60 years (Group O) were recruited. Indications were anteromedial arthritis with full thickness lateral compartment cartilage, a functioning ACL and a correctible varus. All patients underwent Oxford UKA using the minimally invasive technique. This device employs an unconstrained fully congruous meniscal bearing. Outcome was evaluated using Knee Society Scores. Activity level was documented using Tegner Activity Score. Average age of patients for group Y and O was 55 and 68 years respectively. Minimum follw-up was 2 years. pre-op. knee scores were comparable for each group. (y: 38.8, O: 35.8) and patients in both groups siginificantly improved after surgery. A significant difference in Tegner score was found between the two groups after surgery (y:4.1, O:2.6). More than 50% of younger patients regularly participated in high demand activities like skiing, tennis and manual labour. No statistically significant differences in any other post op. knee scores or complication rate were found despite adequate study power. Younger patients have increased activity levels after UKA when compared to an older age group. There is no evidence that the outcome of UKA in younger more active patients will be inferior to those who are older and more sedentary.
There are numerous ankle and hindfoot scores in existence, which have been devised and used to assess surgical interventions. All have in common that there has been little or no work done to demonstrate their validity, reliability or sensitivity to change. Which score one chooses to use for the assessment of outcome will at present depend largely on personal preference. We have undertaken a study to assess four of the most commonly used scores, those of Mazur (1978), Takakura (1990), AOFAS (1994) and Kofoed (1995) as well as a little used but well designed score, The Foot Function Index (1991). A cohort of twenty patients who had undergone a unilateral total ankle replacement (STAR) for rheumatoid or osteoarthritis were assessed by a single observer. The time following operation ranged from six to 48 months. All completed the above scores as well as a SF36 questionnaire. Using the SF36 as a “Gold standard” the scores were compared, both in terms of their overall results and also more specifically in terms of subsections such as pain and function. Our results, though not to be interpreted as validation, do give some rational basis for the choice of score to use in assessing total ankle replacements.
Injury to the dorsomedial cutaneous nerve has been identified as a potentially frequent occurrence after hallux valgus surgery. The existence of pre-operative pressure neuropathy is also described but remains largely unexplored. This study was performed to investigate the incidence of pre-operative sensory deficit in the hallux valgus toe, and to examine to what extent any deficit was related to the degree of joint angulation. A cohort of 43 patients (61 hallux toes) presenting for consideration of surgical correction had their sensation tested in pre-designated sensory zones using a five-filament set of Semmes-Weinstein monofilaments. These allowed good inter-observer reliability with an ICC (intra-class correlation coefficient) of 0.84 overall. Whilst sensory symptoms were self reported in only 21% of the feet, a measurable reduction in sensation by one monofilament grade or more was found in an additional 44% of the feet. No relationship was found between the degree of sensory loss and degree of angulation. Patients with symptomatic hallux valgus may have sensory loss of the toe despite not being aware of the deficit. Normal subjective sensation does not reliably predict normal sensory function. Given the potentially high rates of intra-operative nerve damage in hallux surgery we recommend objective sensory testing as part of routine pre-operative assessment.
The purpose of this study was to determine the rate of polyethylene wear in a fixed bearing knee replacement in order to establish a norm against which mobile bearing implants can be judged.
Linear wear was measured using an electronic micrometer and volumetric wear by creating a mould of the defect using dental wax, and subsequently weighing the wax. Results: All components developed dishing which varied in orientation but matched the alignment of the femoral component. A near congruous articulation was thus produced correctly aligned for that particular arthroplasty. The mean linear penetrative wear for the group was 0.33mm (0.09mm per year) and the volumetric wear 124mm³ (26mm³ per year). The rate of wear seemed greatest during the second year.