Aims

To review the evidence and reach consensus on recommendations for follow-up after total hip and knee arthroplasty.

Aims

The aim of this study was to conduct a cross-sectional, observational cohort study of patients presenting for revision of a total hip, or total or unicompartmental knee arthroplasty, to understand current routes to revision surgery and explore differences in symptoms, healthcare use, reason for revision, and the revision surgery (surgical time, components, length of stay) between patients having regular follow-up and those without.

Introduction: Aseptic loosening is the leading cause of failure in total hip arthroplasty. We present our long-term results of cemented revision of failed total hip replacements.

Materials And Methods: All patients requiring revision for aseptic loosening were prospectively followed up to assess the patterns of failure as well as the clinical and radiological outcomes of revision. There were 102 cases between 1992 and 2000. The mean age at revision was 67.4 (36–88). There were 60 male and 42 female patients. At the time of the final follow-up 26 patients had died and 10 had further surgery. Of the remainder, 64 patients attended the final assessment and 2 could not be traced.

Results: The mean time to follow-up was 6.8 years (5–13 years).

53 patients required revision of both components. There were 49 stem only revisions.

4 patients were re-revised for recurrent loosening and 2 for infection.

There were 14 dislocations. Of these, 4 required secondary stabilisation and 2 underwent Girdlestone’s excision arthroplasty for recurrent dislocation.

46 of the 64 patients who attended final follow-up had no changes in their X-ray appearances compared to the immediately post-operative films. 9 of the stems and 9 of the cups had signs of progressive lucent lines around the cement mantle.

This gives a survivorship of 89% at ten years with reoperation for any cause as the end-point.

Discussion: Initial reported results of cemented revisions were variable. These have been improving with more recent publications including those from the Scandinavian hip registries. Our results confirm the latter findings of excellent survivorship in cemented revisions.

Purpose: We report the 10 to 13 year results of the PFC knee system at our institution.

Method/Results: Between 1992 and 1995 97 PFC primary knee arthroplasties were performed consecutively in 82 patients. 32 patients have subsequently died (37 knees) and four (4 knees) are lost to follow-up. Clinical and radiological review of 46 patients (56 knees) was performed at a mean of 11.1 years post-operatively. Outcome was assessed using the Charnley modification of the Merle D’Aubigne score, with a median of 5 for pain and 4 for function. Radiological failure was defined as progressive radiolucency (1 case), lysis (1 case) or subsidence (1 case). Polyethylene wear was detectable in 10 cases, with > 50% in two. There was 100% survivorship with revision for aseptic loosening as an endpoint. There has been one revision for infection and one patella resurfacing, giving a 98% survivorship with no re-operation. In addition one periprosthetic fracture above a well fixed femoral component, required a supracondylar nail.

Conclusions: The PFC gives excellent outcome and survivorship at 13 years, regardless of the experience of the operating surgeon. This demonstrates that with careful training the PFC is a reliable knee replacement in the long-term for trainers and trainees alike.

Considerable differences in kinematics between different designs of knee prostheses and compared to the natural knee have been seen in vivo. Most noticeably, lift off of the femoral condyles from the tibial insert has been observed in many patients. The aim of this study was to simulate lateral femoral condylar lift off in vitro and to compare the wear of fixed bearing knee prostheses with and without lift off.

Twelve PFC Sigma cruciate retaining fixed bearing knees (DePuy, Leeds, UK) were tested using six station simulators (Prosim, Manchester, UK). The kinematic input conditions were femoral axis loading (maximum 2.6 kN), flexion-extension (0–58°), internal/external rotation (±5°) and anterior/posterior displacement (0–5 mm). Six knees were tested under these standard conditions for 4 million cycles. Six knees were tested under these conditions with the addition of lateral femoral condylar lift off, for 5 million cycles. The lubricant used was 25% newborn calf serum. Wear of the inserts was determined gravimetrically.

Under the standard kinematic conditions the mean wear rate with 95% confidence limits was 8.8 ± 4.8 mm 3/million cycles. When femoral condylar lift off was simulated the mean wear rate increased to 16.4 ± 2.9mm 3/million cycles, which was statistically significantly higher (p < 0.01, Students t-test). The wear patterns on the femoral articulating surface of all the inserts showed more burnishing wear on the medial condyle than the lateral. However, in the simulation of lift off the medial condyle was more aggressively worn with evidence of adhesion and surface defects.

The presence of lateral femoral condylar lift off accelerated the wear of PFC Sigma cruciate retaining fixed bearing knees. The lateral lift off produced uneven loading of the bearing, resulting in elevated contact stresses and hence more wear damage to the medial side of the insert. The implications of condylar lift off include increased wear of the polyethylene and possible osteolysis.

There is currently much interest in the wear of metal-on-metal THRs and potential concerns about elevated metal ion levels. Generally, wear of metal-on-metal THR’s has been low in simulator studies. Slightly higher and more variable wear has been found clinically. Variations in surgical approach, technique and fixation method may influence the level of force applied across the prosthesis during gait. It is hypothesised that increased joint tensioning may increase loading of THR’s during the swing-phase; leading to elevated wear and friction due to depleted fluid film lubrication. This study aimed to assess the effect of swing-phase load on the friction, lubrication and wear of metal-on-metal THR’s.

Cobalt-chrome 28mm metal-on-metal THR’s were tested in a physiological hip simulator, loading was modified to provide; (1) ISO swing-phase load (280N, as per ISO 14242-1) and (2) low swing-phase load (< 100N). Friction testing was conducted using a pendulum friction simulator, with 280N and 100N swing-phase loads. Theoretical lubrication modelling was carried out using elastohydrodynamic lubrication theory.

The overall mean volumetric wear rates was 10-times greater in THR’s tested with an ISO swing-phase load in comparison to THR’s tested with low swing-phase loads (0.58±0.49 compared to 0.06±0.039mm³/million cycles). The friction factors were 0.129 and 0.173 respectively under low and ISO swing-phase conditions. A decrease in the predicted lubricant film thickness when the swing-phase load was increased was observed; at the start of stance phase this was 0.12microns and 0.07microns under low and ISO swing-phase conditions respectively.

The results demonstrate that the performance of metal-on-metal THR’s is highly dependent on swing-phase load conditions. It is postulated that fixation method and surgical technique can affect the swing-phase load. This study has demonstrated that over-tensioning of the tissues may also accelerate wear. These observations may explain some of the variations reported clinically.

Introduction: Reduction of ultra high molecular weight polyethylene (UHMWPE) wear in total knee replacement (TKR) bearings may delay the onset of osteolysis and subsequent loosening of components. This study used finite element (FE) modelling and in vitro simulator testing to investigate the effect of wear path geometry on UHMWPE surface wear.

Methods: The wear of PFC Sigma fixed bearing TKRs (DePuy) was investigated using a six-station force/ displacement controlled knee simulator (frequency 1 Hz) using previously developed methods [1]. High, intermediate and low kinematic inputs were simulated for up to five million cycles (Table 1) with identical flexion-extension and axial loading for all components. This kinematic data was also applied to a FE model of the PFC Sigma TKR and run using PAM-CRASH-SAFE software. The anterior-posterior (AP), medial-lateral (ML) and inferior-superior data were recorded and the resulting wear paths generated by selecting nodes from the contacting surface of the polyethylene relative to the femoral.

Results and Discussion: The mean wear rates with 95% confidence limits on the simulator when subjected to high, intermediate and low kinematics were 22.75 ± 5.95, 9.85 ± 3.7 and 5.2 ± 3.77 mm3 per million cycles, respectively. All FE models exhibited looped wear paths. An example wear path for the first 60% of the gait cycle for a lateral node is displayed in Figure I. The high kinematics model generated the greatest ML displacement and similar AP displacement to the intermediate kinematics model. The low kinematics model showed least ML and AP displacements. The AP displacements for medial wear paths differed little when subjected to the different kinematics. A looped wear path on the surface of UHMWPE results in greater cross shear transverse to the principal direction of motion, which is parallel to AP displacement in TKR and is the axis along which strain hardening occurs. This study revealed that increased AP displacement and tibial rotation kinematics generate more looped wear paths, increase ML and AP displacements on the surface of fixed bearing TKR and result in greater cross shear which ultimately increases UHMWPE surface wear.

The management of leg-length inequality following total hip replacement remains controversial. Many leg length discrepancies are well tolerated and need no treatment. Some patients require only a heel raise, but some patients remain dissatisfied after their hip replacement surgery.

A recent report has suggested that leg-lengthening following total hip replacement does not correlate with patient satisfaction nor joint-specific or generic health scores[1]. This is not our experience. While many patients find leg lengthening an inconvenience, others have major disability following this complication. We report 4 patients who experienced unremitting pain and functional limitation following leg-lengthening as a result of primary hip arthroplasty.

All 4 patients underwent revision surgery which equalised leg length and resulted in immediate and complete resolution of their symptoms. We discuss the clinical findings, x-ray appearances and surgical technique employed to correct this problem. We have never had to revise a hip because of a shortened leg on the operated side.

From February 1992 to December 1997, 379 total hip arthroplasties in 342 patients were performed. 13 patients were lost to follow up, with 33 unrelated deaths. All arthroplasties were performed via the posterior approach in the lateral position. All patients were enrolled in an arthroplasty register at the time of surgery by the operating surgeon. Patients underwent clinical and radiological follow up. Kaplan-Meier survivorship analysis was used to determine the failure rate of the prosthesis, with revision surgery or decision to revise as the end-point.

The overall survivorship from all causes of failure at 5–10 years was 99.4%.

There were two stem revisions. One stem was revised for aseptic loosening at 4 years and one revised for recurrent dislocation. The stem aseptic loosening rate was 0.26%.

The cup aseptic loosening rate was 0%. The dislocation rate was 0.53% (2 from 379).

The superficial infection rate was 0.53% (2 from 379). There were no deep infections in this series.

At 12 months 71.2% had no pain (270 from 379), and 53.8% (204 from 379) had normal function. 94.5% said the procedure was worthwhile or very good. At 12 months radiological follow-up revealed progressive radioluceny in 7.65% (29 from 379) acetabuli, and progressive radiolucency in 2.90% (11 from 379) femora (one progressing to revision for aseptic loosening). No acetabular cups required revision.

In patients aged 65 years or younger at the time of surgery the survivorship was 100% for both components. Attention to meticulous and consistent operative technique in acetabular and femoral preparation, in particular a complete cement mantle with good zone 7 cement and osseointegrated cement bone interfaces, enables these results to be achieved.

In 2004 the Charnely Hip replacement remains the Gold Standard hip replacement.

An audit of a group of dislocations (7 out of 66 hip replacements) revealed a problem with the Charnley Golf Ball cup when used with the posterior approach.

Sixty-six consecutive Charnley hip replacements in one institution by one surgeon using the posterior approach over a one year period are presented. The dislocation rate prior to the introduction of the Golf Ball cup was less than 1%. The overall dislocation rate after the introduction of the Golf Ball socket rose to 10.6%.

Four patients suffered one dislocation, 2 patients suffered two dislocations and 1 patient suffered a dislocation and spontaneous reduction. Five patients were revisions hip replacements and 61 primary hip replacements. Two of the revisions dislocated.

A study of the type of acetabular component type in this series showed there were 17 Wroblewski Angle Bore Sockets (WAB), 11 ogee long posterior wall sockets (OGLPW) and 38 golf ball (GB) sockets making a total of 66 hip replacements.

Of the 17 patients with the WAB the dislocation rate was 0 %. Of the 11 OGLPW patients the dislocation rate was 0 %. However in the 38 patients with golf ball sockets the dislocation rate was 18% (7/38). All the dislocations were anterior.

The acetabular component position was flexion 15–30 degrees (mode 30 degrees) and anteversion 0–10 degrees (mode 0 degrees). The numbers were not large enough to produce any statistical correlation. All femoral stems were set to 0 degrees anteversion.

Following this audit we discontinued the use of the golf ball socket with the posterior approach and have had no further dislocations in primary hip replacement using either the OGLPW or the WAB sockets.

Surgeons who use the posterior approach should be warned about the problems of a high anterior dislocation rate when using the Golf Ball cup.

In vivo and in vitro studies of ceramic on ceramic (COC) bearings have demonstrated that swing phase microseparation followed by the impact of the femoral head on the superior acetabular insert rim leads to accelerated wear. However, resultant wear remained low. The wear of ceramic on polyethylene (COP) and metal on metal (MOM) couples under swing phase microseparation is unknown, this study aimed to compare the wear of these total hip replacements under standard and microseparation conditions.

A physiological hip simulator was used, loads and motions were applied to approximate in vivo conditions. Microseparation was achieved by displacing the femoral head inferiorly during swing phase, the head contacted the inferior cup rim and was laterally displaced. On heel strike the head contacted the superior cup rim prior to relocation. Components (as shown in table 1) were tested for 5 million cycles, at a frequency of 1 hertz in 25% (v/v) new born calf serum. Under standard conditions, wear of COC and MOM bearings was significantly lower than wear of COP couples. Under microseparation conditions the COC and MOM wear increased by 4 and 25 times respectively. Microseparation conditions reduced wear of COP couples by a factor of 4. Creep deformation and damage to the UHMWPE cup rim was observed, however, wear remained low. It is postulated that this reduction in polyethylene wear is due to the separation of the components in swing phase improving the entrapment of lubricant, hence wear is reduced via a squeeze film lubrication mechanism.