Aims

To establish the survivorship, function, and metal ion levels in an unselected series of metal-on-metal hip resurfacing arthroplasties (HRAs) performed by a non-designer surgeon.

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.

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.

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.

Introduction

There are conflicting reports in the literature regarding the migration of femoral stems in revision hip arthroplasty following the use of impaction allografting with or without cement. In some cemented series distal migration of the prosthesis within the cement mantle has been recorded, as well as migration of the whole cement/prosthesis construct into the graft.

An attempt to analyse whether impaction allografting without cement is more or less satisfactory than the technique with the addition of cement is compromised by conflicting reports of where the migration actually occurs. In some cemented series distal migration of the prosthesis within the cement mantle has been recorded as well as migration of the whole cement/prosthesis construct into the graft.

Two prospective consecutive series of revision hip arthroplasties by a single surgeon:- Group 1; Uncemented impaction grafting revision hip replacement in a series of 30 patients (33 hips). Group 2; Cemented impaction grafting revision hip replacement in a series of 30 patients (31 hips). Group demographics were similar. Each case used the same design of hip implant with the only difference in design being a proximal hydroxyapatite coating used on the uncemented implants.

Follow-up ranged from 2 to 17 years for the uncemented group and from 1 to 11 years for the cemented group. A validated hip scoring system was employed at regular follow up incorporating pain and functional assessment.

Migration rates for the uncemented group were 0 to 15 mm for 30 hips; however 3 hips were revised early due to excessive migration. 3 hips sustained early complications (1 fracture, 1 dislocation, 1 varus malposition of stem). Migration rates for the cemented group were 0 to 9 mm for 29 hips, however the remaining 3 hips were revised due to excessive migration (up to 33mm). Although similar results were obtained in terms of success and also pain and function scores, marginal improvement in results did occur with the cemented series overall. Statistical significance was not reached however. More sinkage occurred in the uncemented group overall, the majority occurring in the first 6 post-operative months. Part of the improvement with the cemented series results may be explained by the improved techniques achieved whilst performing the uncemented series.

These results from a single surgeon demonstrate that the method is highly technique dependent and relies on adequate graft impaction. With sufficient graft and an appropriate prosthetic design, cement is not essential to the early success of this method. However, the extent of the initial migration did not accurately predict a successful outcome for the procedure. The absence of cement removes any confusion as to the location of any migration.

The proximally hydroxyapatite coated neck retaining Freeman hip stem (Finsbury Orthopaedics, Leather-head, United Kingdom.) was first implanted in 1989. The outcome of the first 100 stems, in 52 men (6 bilateral) and 40 women (2 bilateral) has been reported to ten years, we have extended the follow-up of this series to 17 years.

The mean age was 58.9 years (19 to 84). The diagnosis was osteoarthritis for 70 hips, rheumatoid arthritis for seven hips, post-traumatic arthritis for 14 hips and either avascular necrosis, septic arthritis or developmental hip disorder in nine hips.

The total hip replacements implanted during the period of study (January 1989 to March 1992) were all secured without cement for either component. The acetabular components comprised press-fitted screw-in Rotalok implants (Corin Medical, Cirencester, United Kingdom) or SLF components (Finsbury). All operations were performed using an anterolateral approach with retention of the femoral neck. Three patients have been lost to follow-up, but are included up to their last clinical follow-up.

There have been 40 re-operations for revision of the acetabular component due to aseptic loosening. However, in all but four of these cases the stem was not revised. In two of these the stem revisions were for damage to the trunion following fracture of the modular ceramic head producing fretting against the ceramic debris and acetabular component. In the other two, revision was due to surgeon preference and in both cases well fixed femoral components were extracted at the time of acetabular revision. Osteointegration of these two stems was evidenced by the adherent bone at the time of removal. There has been only one case of aseptic loosening occurring at 14 years. This was found to be rotationally loose at revision and in hindsight was undersized having migrated distally 7.6mm in the first year before stabilising. The survivorship for the stem at 17 years is 98.5% (95% CI; 94.6% to 100%) with 52 patients at risk, all of whom have satisfactory clinical and radiological outcomes. The Freeman uncemented neck retaining proximally hydroxyapatite coated stem has excellent survival results to 17 years.

In order to eliminate the “conflict” that can occur with physiological roll back of the femur on the tibia, most modern knee arthroplasty prostheses are designed to have little conformity between the femoral and tibial surfaces. However, a consequence of this design is paradoxical anterior sliding of the femur on tibia, which can result in clinically significant gait abnormalities. Recent studies show that during movement of the knee, the medial side remains very nearly stable like a ball-in-socket joint, whilst the lateral side moves front to back, rotating around the centre of the medial side. A total knee joint prosthesis designed with these same kinematics may therefore be advantageous. The objective of this study was to investigate the hypothesis that the increased constraint of a medial pivot knee promotes earlier loosening of the prosthesis.

METHODS: This was a retrospective radiographic cohort study. Using our unit’s knee arthroplasty database, all patients with a Freeman-Samuelson 1000 knee arthroplasty (medial pivot design) or a Freeman-Samuelson Modular knee arthroplasty with a minimum follow-up of 2 years were identified, and matched as closely as possible for age, length of follow-up and pre-operative diagnosis (Osteoarthritis, Rheumatoid arthritis or Post-traumatic arthritis). This was a single surgeon series using a standard surgical approach with a posterior cruciate sacrificing technique. Standardised anteroposterior and lateral radiographs taken postoperatively, at 6 months, 1 year and then at yearly intervals, were examined systematically and independently of the senior surgeon (GS). Component migration and radiolucent line scores were allocated as recommended by the Knee Society.

RESULTS: Group 1 (n=55),–Freeman Samuelson Modular design, mean age–70.3 years, mean length of follow-up–4.5 years. Group 2 (n=48),–Freeman Samuelson 1000 design (Medial pivot), mean age–70.4 years, mean length of follow-up–4.3 years. There were no failures in group 1. There was one failure requiring revision of the femoral component in group 2. Radiolucent lines were more prominent and frequent in the tibia, particularly under the medial and lateral plateau’s (KSS zone 1 and 6). There was no significant difference in the overall radiolucent line scores between the two groups (p=0.39, Mann Whitney U test). Similarly we found no difference between radiolucent line progression in the specific tibial zones (1–6 KSS system). Radiolucent lines in the femur were infrequent and insignificant.

CONCLUSION: We found no statistically significant difference between the two designs of knee prosthesis in terms of either total radiolucent line score or rate of radiolucent line progression. The increased constraint of the medial pivot knee prosthesis does not appear to result in an increased incidence of radiographic loosening.

Introduction: Aseptic loosening due to polyethylene wear is a mode of failure in knee arthroplasty. No study has evaluated the roughness of the articulating surface of retrieved femoral components & its role in creation of polyethylene wear. AIM The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components. Our hypothesis was that the surface finish of the femoral components, articulating with the polyethylene inserts deteriorated in accordance with the duration of implantation.

Materials and Methods: 22 femoral components, all Freeman-Samuelson prostheses, were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. Firstly, the surfaces of femoral components & polyethylene inserts were visually inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a contact stylus profilometer with a 2-mm-radius stylus tip and a cut-off length of 0.8mm. The surface roughness was characterised by measuring Ra(mm), which is the arithmetic mean of the absolute values of the measured height deviations taken within the evaluation area and measured from the main line or surface. Both condyles were examined as separate areas articulating with the tibial components from 0° to 60° and 61° to 120° of knee flexion. Surface roughness (Ra) measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK).

Results: The mean CAK was 7.2° ± 1°. Dull edged parallel scratching and burnishing were the main modes of damage identified on the surface in the articulating areas. Visual analysis of polyethylene inserts failed to identify embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components. The mean Ra values recorded were: Control: Mean-0.0230 mm, SD- 0.00821. Medial Femoral condyle (0° – 60°) – 0.0225 mm, SD – 0.00797, P=0.832 Medial Femoral Condyle (61° – 120°) – 0.0244 mm, SD – 0.00532, P= 0.189 Lateral Femoral condyle (0° – 60°) – 0.0263 mm, SD – 0.00694, P= 0.078 Lateral Femoral Condyle (61° – 120°) – 0.0253 mm, SD – 0.00758, P= 0.286 No statistically significant difference was seen in the mean roughness (Ra) of the articulating areas when compared to that of the control (P< 0.05).

Conclusion: This study showed that the surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis even if the femoral component has fine scratching or burnishing on its surface.

Aim: The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components.

Our hypothesis was that the surface finish of the femoral components deteriorated in accordance with the duration of implantation

Materials and method: 22 femoral components (all Freeman-Samuelson prostheses) were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. The surfaces of femoral components & polyethylene inserts were inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a stylus profilometer. The surface roughness was characterised by measuring Ra (micron-meter), which is the mean of the measured height deviations within the evaluation area. The articulating surface on both condyles was examined seperately. Ra measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK)

Results: The mean CAK was 7.2° ± 1°. Parallel scratching and burnishing were the main modes of damage on the surface in the articulating areas. Inspection of polyethylene inserts failed to find embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components.

The mean Ra values were:

Control: Mean-0.0230 mm, SD- 0.00821.

Medial Femoral condyle (0 – 60) = 0.0225 mm, SD – 0.00797

Medial Femoral Condyle (61 – 120) = 0.0244 mm, SD – 0.00532

Lateral Femoral condyle (0 – 60) = 0.0263 mm, SD – 0.00694

Lateral Femoral Condyle (61 – 120) = 0.0253 mm, SD – 0.00758

No statistically significant difference was seen in the mean-Ra of the femoral condyles compared to that of the control (P less than 0.05).

Conclusion: The surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis.

Aims: To demonstrate that tranexamic acid reduces the blood loss incurred as a result of lower limb arthroplasty. Methods: We prospectively studied 30 primary hip and knee arthroplasty patients. Entry criteria were primary joint replacement, exclusion criteria were: a history of bleeding disorders, previous thromboembolic disease or renal insufþciency. The senior author (GS) performed all the operations. Surgical technique and postoperative mobilisation was standardised for both hip and knee arthroplasty cohorts. Tranexamic acid was administered at the time of surgery. The patients had haemoglobin levels assessed preoperatively and a haemoglobin level three days post operatively to allow its stabilisation following surgery. Any blood transfused was noted. Blood was transfused on a case-by-case basis the indications were a haemoglobin less than 8 g/dl or symptoms of anaemia. The results were then compared with a matched population from the bone and joint research unit database. Results: The mean fall in haemoglobin in hip arthroplasty with tranexamic acid was 2.8 ± 0.33 g/dl (95% Conþdence Interval) and 3.85 ± 0.44 g/dl (95% Conþdence Interval) without tranexamic acid this was statistically signiþcant p< 0.05. The mean fall in haemoglobin in knee arthroplasty with tranexamic acid was 1.67± 0.36 g/dl (95% Conþdence Interval) and 2.84 ± 0.35 g/dl (95% Conþdence Interval) without tranexamic acid this was statistically signiþcant p< 0.05. Transfusion requirements were reduced. Conclusions: Tranexamic acid is an inexpensive and effective way of reducing blood loss following hip and knee arthroplasty.

Aims: To compare the in vivo wear rates of the polyethylene inserts of different thicknesses in Freeman-Samuelson (F/S) total knee arthroplasties. Methods: Radiographs of 17 patients with F/S modular prostheses and 6mm thick inserts, 19 patients with 8mm inserts, and 6 patients with F/S1000 (more conformed medial femoral condyle) with 8mm inserts were studied. The distance (polyethylene thickness) between femoral and tibial components was measured from A-P radiographs at 6 months, 3 years and 5 years with correction for magnification and antero-posterior tilting of the tibial tray. Wear rates were calculated. Comparisons were made between the medial and lateral sides of the inserts, between the different thicknesses and between the two types of prostheses. Results: The difference in the wear rate between the medial and lateral side in the 3 groups of polyethylene inserts was shown to be 0.229, 0.054, and −0.044 mm/yr (p> 0.2 in all 3 groups). Between the two thicknesses in the F/SM group, the 6mm group had a higher wear rate than the 8mm group (diff = 0.072 mm/yr, p< 0.05) over 5 years, with the majority of wear occurring in the first 3 years (Diff = 0.098mm/yr, p< 0.05). Between the two types of prostheses used, the wear rate over 5 years was shown to be 0.006mm/yr (p> 0.5). Conclusions: The study showed that the 6mm polyethylene components had a significantly higher rate of wear than the 8mm ones, but there was no significant difference shown between the medial and lateral sides of the inserts and two versions of the prosthesis.

Twenty-nine patients (30 hips) with uncemented acetabular impaction allografting contained behind a metal backed component screwed to the pelvis at revision hip arthroplasty were reviewed at 12 to17 years (average 15.3 years) follow up. Five patients had died with the prosthesis in situ, 4 patients were lost to follow up, 13 patients had failed requiring further revision (only one failed prior to 5 years) and 9 survivors were minimally asymptomatic. The mean time to failure warranting further surgery was 9 years.

Analysis of available serial radiographs (24 cases) demonstrated signs of loosening (migration, progressive radiolucent lines, screw breakage) in 54% of the latest radiographs of all cases. Removing those lost to follow up or deceased, 72% were radiologically loose (in the intact asymptomatic group 57% could be defined as loose). Additionally, in 70% of the cases the acetabular component tended to fail in a varus manner as the medial wall remodelled.

These results indicate as previously published, short term results for this technique are satisfactory but in the long term they are not. Factors associated with this include the pressfit nature of the polyethylene liner which has been implicated in disappointing long term results for this prosthesis in primary applications, but not of the level of failure encountered in the current series. This experience suggests that the reliance on screw fixation over a bed of allograft in the absence of cement supplementation does not provide sufficient stability for reliable bone graft incorporation.

The method reported above should be abandoned.

This report concerns an operative technique using inexpensive pre-polymerised cement discs as a means of addressing the bone loss from the posterior femoral condyles found during revision total knee replacement.

Bone lost from the posterior condyles in the loosened femoral component of a total knee replacement enlarges the flexion gap at revision. Downsizing the femoral component to fit the remaining bone requires a thicker tibial insert and a proximalised new femoral component to maintain balanced gaps in flexion and extension. Patella infera results from this proximalisation of the joint line and interferes with the extensor apparatus.

Some knee systems offer customised components with thickened posterior femoral condyles or provide the surgeon with the option of adding metal augments to the femoral component to manage the posterior femoral bone loss.

This technique has been applied to ten cases (follow- up ranging from 15 to 46 months) in which inexpensive pre-polymerised cement spacers were incorporated into the posterior femoral cement mass. This allowed the use of primary stemmed components with preservation of the original joint line position.

No case has resulted in loosening although two cases have required further revision due to recurrence of their original infection. At revision of these cases the cement discs remained firmly incorporated in the cement mass.

We conclude that this technique is reliable, inexpensive and could be applied to other prosthetic varieties.