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Bone & Joint Research
Vol. 8, Issue 5 | Pages 207 - 215
1 May 2019
Key S Scott G Stammers JG Freeman MAR Pinskerova V Field RE Skinner J Banks SA

Objectives

The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities.

Methods

Using pulsed fluoroscopy and image matching, the coronal kinematics and articular surface separation of 16 well-functioning TKAs were studied during weight-bearing and non-weight-bearing, static, and dynamic activities. The closest distances between the modelled articular surfaces were examined with respect to knee position, and proportions of joint poses exhibiting separation were computed.


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_5 | Pages 86 - 86
1 Apr 2019
Al-Zibari M Everett SJ Afzal I Overschelde PV Skinner J Scott G Kader DF Field RE
Full Access

Background

In the late 1980's Michael Freeman conceived the idea that knee replacement would most closely replicate the natural knee joint, if the medial Tibio-Femoral articulation was configured as a “ball-in-socket”. Over the last three decades, medial rotation and medial pivot designs have proved successful in clinical use. Freeman's final iteration of the medial ball-in-socket concept was the Medial Sphere knee. We report the three-year survivorship, clinical outcomes, patient reported outcome measures (PROMs) and radiographic analysis of this implant in a multi-centre, multi-surgeon, prospective observational study.

Methods

Patients awaiting total knee replacement were recruited by four centres. They had no medical contraindication to surgery, were able to provide informed consent and were available for follow-up. Primary outcome was implant survival at six months, one, two, three and five years. Secondary outcomes were patient reported outcome measures: Oxford Knee Score (OKS), Euroqol (EQ-5D), International Knee Society Score (IKSS), IKSS Functional score and Health State score, complications and radiographic outcomes. Radiographic analysis was undertaken using the TraumaCad software and data analysis was undertaken using SPSS.


Bone & Joint Research
Vol. 5, Issue 3 | Pages 80 - 86
1 Mar 2016
Scott G Imam MA Eifert A Freeman MAR Pinskerova V Field RE Skinner J Banks SA

Objectives

Throughout the 20th Century, it has been postulated that the knee moves on the basis of a four-bar link mechanism composed of the cruciate ligaments, the femur and the tibia. As a consequence, the femur has been thought to roll back with flexion, and total knee arthroplasty (TKA) prostheses have been designed on this basis. Recent work, however, has proposed that at a position of between 0° and 120° the medial femoral condyle does not move anteroposteriorly whereas the lateral femoral condyle tends, but is not obliged, to roll back – a combination of movements which equates to tibial internal/ femoral external rotation with flexion. The aim of this paper was to assess if the articular geometry of the GMK Sphere TKA could recreate the natural knee movements in situ/in vivo.

Methods

The pattern of knee movement was studied in 15 patients (six male: nine female; one male with bilateral TKAs) with 16 GMK Sphere implants, at a mean age of 66 years (53 to 76) with a mean BMI of 30 kg/m2 (20 to 35). The motions of all 16 knees were observed using pulsed fluoroscopy during a number of weight-bearing and non-weight-bearing static and dynamic activities.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_1 | Pages 35 - 35
1 Jan 2016
Banks S Imam M Eifert A Field RE
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Introduction

Total knee arthroplasty (TKA) designs evolve as evidence accumulates on natural and prosthetic knee function. TKA designs based upon a medially conforming tibiofemoral articulation seek to reproduce essential aspects of normal knee stability and have enjoyed good clinical success and high patient satisfaction for over two decades. Fluoroscopic kinematic studies on several medially conforming knee designs show extremely stable knee function, but very small ranges of tibial axial rotation compared to healthy knees. The GMK Sphere TKA is a recent evolution in medially-conforming TKA designs that adopts a sagittally unconstrained lateral tibiofemoral articulation to allow more natural tibial rotation. This study was conducted to quantify motions in knees with this prosthesis to address two questions:

Does the medially conforming GMK Sphere design provide an AP-stable articulation that provides for tibiofemoral translations that are comparable to, but not larger than, translations measured in natural knees?

Does the medially conforming GMK Sphere design provide sufficient rotatory laxity to allow tibiofemoral rotations comparable to, but not larger than, rotations measured in natural knees?

Materials and Methods

Fifteen patients (9 females), mean age 65 years and mean BMI of 30 ±3, consented to participate. Sixteen knees received the GMK Sphere TKA. Mean Oxford Knee Score (OKS) improved significantly from 19±7 to 40±3 six months post surgery (P< 0.0001). On the day of the study, the mean OKS, Knee Society Score, EQ5D and Heath status scores were 40, 87, 0.83 and 85 respectively. Mean ROM from active maximum extension till maximum supine flexion was 108°±8°.

Motions in 16 knees were observed using pulsed-fluoroscopy during a range of activities. Subjects were observed in maximum flexion kneeling and lunging positions, and in stepping up/down on a 22cm step. Model-image registration methods were used to quantify three-dimensional knee motions from digitized fluoroscopic images.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 139 - 139
1 Dec 2013
Noble P Dwyer M Jones H Field RE McCarthy JC
Full Access

Introduction:

The sealing function of the acetabular labrum is central to the stability of the hip and the health of the joint. Disruption of the labrum has been shown to reduce intra-articular pressure and increase the rate of cartilage consolidation during static loading. Functional activities require movement of the hip through wide ranges of joint motion which disrupt joint congruency, and thus may alter the seal. This study was performed to test the hypothesis that the sealing function of the labrum varies with the position of the hip during functional activities.

Methods:

Six fresh cadaveric hip joint specimens were obtained from donors of average age 45.5 ± 16.1 years (range 25–63 years). Each specimen was dissected free of soft tissue, leaving the capsule and labrum intact, potted in mounting fixtures, and placed in a loading apparatus. Catheters were inserted into the central and peripheral compartments of each hip to allow infusion of fluid and monitoring of compartment pressures via miniature transducers (OMEGA Engineering, Inc). After application of a joint load of 0.50 BW, fluid was introduced into the central compartment at a constant rate until transport was indicated by a rise in pressure within the peripheral compartment. These measurements were performed with each hip placed in 10 functional positions ranging from −5 to 105 degrees of flexion, −5 to 13 degrees of abduction, and −25 to 35 degrees of external rotation simulating the sequential stages of gait, stooping, and pivoting. Motion analysis was performed via reflective marker arrays attached to the femur and pelvis to allow computer visualization of the position of the pelvis and femur using CT reconstructions. In each hip position, we measured the peak pressure (kPA) developed within the central compartment prior to fluid transfer to the peripheral compartment.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 458 - 458
1 Dec 2013
Noble P Dwyer M Jones H Field RE McCarthy JC
Full Access

Objectives:

Experimental disruption of the labrum has been shown to compromise its sealing function and alter cartilage lubrication. However, it is not known whether pathological changes to the labrum secondary to femoro-acetabular impingement (FAI) have a similar impact on labral function. This study was performed to determine the effect of natural labral damage secondary to abnormal femoral morphology on the labral seal.

Methods:

Ten intact hip specimens were obtained from male donors (47.8 ± 1.5 yrs) for use in this study. CT reconstructions demonstrated that 6 specimens were of normal morphology, while 4 displayed morphology typical of cam-FAI. Specimens were dissected free of the overlying soft tissue, leaving the capsule and labrum intact. Each specimen was potted and placed in a loading apparatus (0.5 BW). Pressures developed within the central and peripheral compartments were monitored with miniature pressure transducers. The sealing capacity of the labrum was measured by introducing fluid into the central compartment at a constant rate until transport was detected from the central to the peripheral compartment. These measurements were performed in 10 functional positions simulating sequential stages of gait, stooping, and pivoting. During testing, the 3D motion of the femoral head in the acetabulum was measured with motion analysis combined with computer visualization. Peak pressures were compared between specimens with and without labral damage for each of the three activities (p < 0.05).


Bone & Joint 360
Vol. 1, Issue 2 | Pages 7 - 10
1 Apr 2012
Field RE Shimmin A Cattani L

The need to demonstrate probity and fair market competition has increased scrutiny of the relationships between orthopaedic surgeons and the industry that supplies them with their tools and devices. Investigations and judgements from the US Department of Justice and the introduction of the AdvaMed and Eucomed codes have defined new boundaries for interactions between these groups. This article summarises the current interplay between orthopaedic surgeons and industry, and provides recommendations for the future.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 531 - 531
1 Aug 2008
Monoot P Eswaramoorthy V Kalairajah YE Field RE
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Introduction: Total hip replacements (THR) with the first generation metal-on-metal articulation were abandoned in 1970s in favour of metal-on-polyethylene articulation. Osteolysis due to polyethylene wear particles renewed the interest in metal-on-metal articulations. The second generation had improved clearance, metal hardness and reproducible surfaces. We describe the 10-year outcome of 63 THR with Metasul metal-on-metal articulation.

Methods: From 1995 to 1996, 86 patients (90 hips) underwent THR with Metasul articulation and cemented CF-30 femoral stem. Of these, 55 hips had a cemented Stuhmer-Weber-Allopro cup and 35 hips had an uncemented Allofit cup. Eleven patients (12 hips) died and five patients (6 hips) were not available for clinical evaluation. However all had been contacted and it was known that the hip was not painful and had not been revised. Nine patients were lost to follow up. Thirty nine hips in cemented group and 24 hips in uncemented group had clinical, radiological and Oxford hip score (OHS) at minimum of 10-years follow-up after the operation.

Results: The minimum length of follow up was 10-years with an average of 10.8 years. The average OHS at 10 years for the cemented group was 23 (range 12 – 42) and for the hybrid group was 20.3 (range 12 – 37). Five out of 63 (8%) hips had revision surgery. Two revisions (3%) were performed because of infection, 1 was revised (1.5%) because of unexplained pain and suspected metallosis and 2 were revised (3%) for suspected aseptic acetabular cup loosening.

Conclusion: In comparison with the outcome of first generation metal-on-metal bearing, the hips in our study had lower rate of revision due to acetabular wear and loosening. This is the first study to show that the Metasul articulation has good outcome over a 10-year period. The survivorship is 97% with aseptic loosening as the endpoint for revision surgery.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 560 - 560
1 Aug 2008
Kamat YD Aurakzai K Kalairajah Y Riordan J Field RE Adhikari AR
Full Access

Obesity [Body Mass Index (BMI) > 30kg/m2] is seen in a growing percentage of patients seeking joint replacement surgery. Operations in obese patients take longer and present certain technical difficulties. Computer navigation improves consistency of prosthetic component alignment but increases operation time.

Our aims were

to compare tourniquet times of non-obese with obese patients having knee replacement using standard instruments or computer navigation and

to evaluate the change in tourniquet time as the surgeon gained experience over a three year period.

A retrospective analysis of 232 total knee replacement (TKR) operations performed by a single knee surgeon over a three year period was carried out. Similar knee prostheses (Plus Orthopedics, UK) were used in all cases. Variables to be assessed were the operative technique (computer navigation assisted or standard instruments) and BMI of patients.

Of the 232 knees, 117 were performed using computer navigation and 115 with standard instruments. Each of the groups was subdivided as per BMI to differentiate obese patients (BMI > 30) from the non-obese. Tourniquet times of surgery were used for comparison amongst the subgroups.

There were 56 and 59 patients in the non-obese and obese subgroups respectively within the standard TKR group. The average tourniquet times for these were 79.3 and 86.3 minutes respectively. This was a significant difference (p=0.037). Correspondingly in the computer navigated group, there were 60 non-obese and 57 obese patients. Their tourniquet times were 105.4 and 100.5 minutes respectively. This difference was not significant (p=0.15)

The obese patients in each group were then studied separately and divided into three equally sized subgroups in chronological order. Each sub-group comprised 19 standard TKRs and 19 computer navigated TKRs. Tourniquet times of operations were compared within each sub-group. P values within the first subgroup showed a significant difference. There was no significant difference within the second and third subgroups.

We concluded that obesity significantly increased the operative time in the standard TKR group. However in computer navigated TKR there was no significant difference in operative time between non-obese and obese patients. As the surgeon acquired experience of computer navigation there was no difference in time taken for conventional and computer navigated TKR in obese patients. We hypothesize that in obese patients, computer assisted navigation helps the surgeon to overcome jig alignment uncertainty without any time penalty.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_III | Pages 261 - 261
1 Mar 2004
Field RE Singh PJ
Full Access

Aim: Analyse the outcome of primary and revision total hip replacement using the Oxford hip score. To determine any variation in outcome when analysing for age of patient. In addition, to compare the outcome in the National Health Service compared to the Private hospital. Method: We have used the Oxford Hip score to monitor the progress of 1441 primary and 173 revision hip replacements (THR) undertaken since the start of 1995 whose hips have been replaced, at St Helier Hospital, Carshalton and St Anthony’s Hospital, Cheam, over the last seven years. Our review programme was started in early 1999 and has generated 2286 Oxford assessments.). A subgroup of 634 National Health Service (NHS) and 322 private patients (PP), treated by the senior author, has provided 1277 Oxford assessments. Results: Mean preoperative scores were 39.06 and 39.48 for primary and revision THR respectively. The mean annual scores, for primary THR, from 12 to 84 months declined to 21 points at 1 year, 21 at 2 years, 21 at 3 years, 20 at 4 years, 22 at 6 years and 21 at 7 years. Conclusion: All postoperative reviews show a significant improvement (p ≤0.0001). The 50–60 year old group scored significantly better than the over 80 year patients up to 48 months, (p< 0.01) The mean preoperative score for the NHS patients was significantly higher than the PPs (p< 0.001). The PPs scored significantly better than the NHS group up to 36 months (p< 0.01).


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 76 - 76
1 Jan 2004
Singh PJ Marsh AJ Kerry SM Field RE
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Aim: To develop an accurate and reproducible validated digital technique for the two-dimensional measurement of longitudinal femoral stem migration on AP radiographs.

Method: Eight patients who underwent total hip replacement, under the care of the senior author, were randomly selected. In each case, three radio-opaque marker beads had been implanted into the greater trochanteric region at surgery. Using a standardised x-ray protocol, three consecutive AP standing hip x-rays were taken of each patient on the same day. The plain radiographs were digitised, and the vertical bead to stem tip distance measured by two orthopaedic trainees using Scion Image ‘freeware’ software package and standard computer equipment. Every patient had three different measurements on each of their three consecutive x-rays. The vertical bead to stem tip distance was averaged over the three beads.

Results: Statistical analysis was performed and the repeatability coefficient between x-rays was 0.61 (confidence interval 0.46 to 0.78). The limits of agreement for inter observer error for average bead to stem distance were −0.15 to 0.39.

Conclusion: Our results demonstrate the efficacy of our system for analysis of femoral stem migration in everyday clinical practice. This technique does require implantation of marker beads and a standardised protocol for patient positioning for radiographs.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 76 - 76
1 Jan 2004
Field RE Kavanagh TG Singh PJ
Full Access

Aim: Hip resurfacing is a bone conserving procedure with respect to proximal femoral resection. For previous generations of conservative hip replacement, preservation of the natural femoral head diameter necessitated additional sacrifice of acetabular bone in order to accommodate a sufficiently thick polyethylene acetabular component. We have investigated whether the BHR offers a bone conserving procedure with respect to the acetabular bone stock.

Method: We reviewed 284 Birmingham resurfacing hip replacements (BHR), and 479, primary hip replacements, in which an uncemented acetabular component (THUA) was used. The BHR and THUA group had mean age at surgery of 55 and 65 years respectively. In 32 BHR’s and 21 THUA, pre-operative templating measurements were available for subsequent comparison with size of component implanted.

Results: Comparison of component sizes, for both implant types, confirmed bi-modal distribution according to patient gender. BHR cups, implanted by the first author, in females, were significantly smaller than those implanted, by the same author, in THUA,(p< 0.0001). Pre-operative templating overestimated component size for all groups but the difference was only significant in male BHR cases;(p=0.03). BHR cups implanted by the first author were significantly smaller than the second author, for both male (p= 0.0001) and female patients;(p< 0.001).

Conclusion: In females, BHR is bone a conserving procedure for femoral and acetabular components. In males, the procedure is not bone sacrificing when compared to THUA. Pre-operative templating can overestimate size of acetabular component that will be used for men. A significant difference was found between size of acetabular components used by two surgeons for BHR.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 76 - 77
1 Jan 2004
Singh PJ Field RE Burtenshaw C Jaffer O
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Introduction: The acetabular cup comprises a 3mm thick bearing surface of UHMPE, a 1.5mm backing of 30% carbon fibre reinforced polybutyleneterephthalate (CFRPBT). Young’s modulus, of CFRPBT layer is similar to natural subchondral bony plate. The cup deforms, when loaded, with the surrounding acetabular bone so that micro-motion at the bone-prosthesis interface is reduced. We measured BMD in the periacetabulum

Method: BMD was analysed for 2 years (n=11 females) with Mean Barthel Index at 2 years 19. Regions of interest were defined according to De-Lee and Charnley (ROI I-III) for the acetabulum. BMD during follow-up was compared with immediate post-operative values. Mean precision error (CV%) was 1.8±0.87%.

Results: By 2 years the mean BMD in HA cup was 0.73gms/cm2 representing a decrease of 7% and 0.78gms/cm2, which representing a 4% decrease with the non-HA cup. With the HA cup at 2 years we measured an increase in ROI I of 3% and a reduction in ROI II and III of 3% and 20% respectively. With the non-HA cup at 2 years we measured an increase in ROI II of 7% and a reduction in ROI I and III of 3% and 16%. There was a significant difference (p< 0.05) in the BMD changes measured in non-weight bearing zone III and one of the weight bearing zones (zone II).

Conclusion: Changes in BMD measured reflect a pattern of maximally reduced stress in zone III followed by zone II and least in the load bearing axis of the acetabulum zone I.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 77 - 77
1 Jan 2004
Singh PJ Field RE
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Aim: A prospective study was undertaken to define the pattern of bone remodelling using DXA following implantation of our polished, tri-tapered, collarless, cannulated cemented femoral component.

Method: Our stem was implanted in 20 primary THRs. Our subjects comprised 7 male and 13 female patients. At the time of surgery the mean age was 73 (range 65 to 131). The mean weight at surgery was 75.4kg (range 47kg to 131.8kg) with a mean BMI of 28(range 22 to 40). All patients had a pre operative diagnosis of osteoarthritis. All the hips were implanted via the anterolateral approach. Pre-operative and sequential post-operative DXA evaluations were undertaken at 3 weeks, 6 and 12 months.

Results: The mean precision error was 0.78%(range 0.8–3.4% depending on region of interest). Statistical analysis revealed a significant increase in BMD measured in zones 1,2,4,5,6 (p< 0.05). In zones 3 and 7, the increase in BMD was not significant (p> 0.05). The real percentage increase in BMD at 12 months was 43% in zone 1, 20% in zone 2, 8% in zone 3, 31% in zone 4, 12% in zone 5, 24% in zone 6 and 7% in zone 7.

Conclusion: Peri-prosthetic bone remodelling has been observed within one year following total hip replacement (THR), which has been demonstrated by an increase in BMD in all zones. The implantation of our tri-tapered cannulated cemented femoral component, thus provides favourable proximal femoral loading at 12 months. Additional studies will determine whether stabilization of this bone turnover continues in the long term.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_I | Pages 77 - 77
1 Jan 2004
Field RE Singh PJ
Full Access

Aim: Analyse the outcome of primary and revision total hip replacement using the Oxford hip score. To determine any variation in outcome when analysing for age of patient. In addition, to compare the outcome in the National Health Service compared to the Private hospital.

Method: We have used the Oxford Hip score to monitor the progress of 1441 primary and 173 revision hip replacements (THR) undertaken since the start of 1995 whose hips have been replaced, at St Helier Hospital, Carshalton and St Anthony’s Hospital, Cheam, over the last seven years. Our review programme was started in early 1999 and has generated 2286 Oxford assessments. ). A subgroup of 634 National Health Service (NHS) and 322 private patients (PP), treated by the senior author, has provided 1277 Oxford assessments.

Results: Mean pre-operative scores were 39.06 and 39.48 for primary and revision THR respectively. The mean annual scores, for primary THR, from 12 to 84 months declined to 21 points at 1 year, 21 at 2 years, 21 at 3 years, 20 at 4 years, 22 at 6 years and 21 at 7 years.

Conclusion: All postoperative reviews show a significant improvement (p≤0.0001). The 50–60 year old group scored significantly better than the over 80 year patients up to 48 months, (p< 0.01) The mean pre-operative score for the NHS patients was significantly higher than the PPs (p< 0.001). The PPs scored significantly better than the NHS group up to 36 months (p< 0.01).