Survivorship of the KUDO total elbow prosthesis--comparative study of cemented and uncemented ulnar components: 89 cases followed for an average of 6 years

Background The Kudo total elbow prosthesis (TEP) is a well-established implant with good mid-term results. The ulnar component can be placed with or without cement, and the humeral component is normally placed without cement.

Methods 89 Kudo type-5 total elbow prostheses were evaluated after a mean follow-up of 6 (1.7-11) years. The indication for joint replacement was rheumatoid arthritis in all cases. 49 prostheses were placed without cement. In 40 cases, the ulnar component was cemented and the humeral component was uncemented.

Results In the uncemented group, 7 revisions had taken place. 3 of these ulnar components were shortstemmed and 4 were long-stemmed. No revisions had been performed in the hybrid group. In the uncemented group another 7 patients showed progressive radiolucencies, while 3 patients in the hybrid group showed progressive radiolucencies.

Interpretation In this group of RA patients, the survivorship of the cemented ulnar component was better than that of the uncemented ulnar component.     

Limited influence of prosthetic position on aseptic loosening of elbow replacements: 125 elbows followed for an average period of 5.6 years

Background Aseptic loosening of elbow replacements, seen in long-term follow-up, remains a problem. In this study, we attempted to determine the influence of cementing technique, prosthetic position, different component sizes, use of a bone plug, and intraoperative fractures on the development and progression of radiolucent lines and aseptic loosening.

Methods We studied standard radiographs of 125 primary Souter-Strathclyde total elbow prostheses using the Wrightington method. Additionally, 104 preoperative radiographs were available for analysis. We used a Markow statistical model to detect relationships between all factors described above.

Results After a mean follow-up time of 5.5 (2-19) years, 21 (17%) prostheses had loosened radiographically (10-year survival: 65%). When the humeral component was tilted more medially or more anteriorly, we found development of radiolucent lines at the medial condyle and at the posterior side of the humeral component. However, the progression of these lines was not influenced by these positions. No other prognostic factors for radiolucent lines or aseptic loosening were found.

Interpretation Despite the small number of elbows studied, the weak influence of prosthetic position on aseptic loosening gives more ground for a multifactorial cause for aseptic loosening of the Souter-Strathclyde total elbow prosthesis.     

High-precision measurements of cementless acetabular components using model-based RSA: an experimental study

Background In RSA, tantalum markers attached to metal-backed acetabular cups are often difficult to detect on stereo radiographs due to the high density of the metal shell. This results in occlusion of the prosthesis markers and may lead to inconclusive migration results. Within the last few years, new software systems have been developed to solve this problem. We compared the precision of 3 RSA systems in migration analysis of the acetabular component.

Material and methods A hemispherical and a nonhemispherical acetabular component were mounted in a phantom. Both acetabular components underwent migration analyses with 3 different RSA systems: conventional RSA using tantalum markers, an RSA system using a hemispherical cup algorithm, and a novel modelbased RSA system.

Results We found narrow confidence intervals, indicating high precision of the conventional marker system and model-based RSA with regard to migration and rotation. The confidence intervals of conventional RSA and model-based RSA were narrower than those of the hemispherical cup algorithm-based system regarding cup migration and rotation.

Interpretation The model-based RSA software combines the precision of the conventional RSA software with the convenience of the hemispherical cup algo-rithm-based system. Based on our findings, we believe that these new tools offer an improvement in the measurement of acetabular component migration.     

Local peroperative treatment with a bisphosphonate improves the fixation of total knee prostheses: a randomized, double-blind radiostereometric study of 50 patients

Background Postoperative migration of a joint prosthesis is related to the risk of late loosening. We have previously reported that oral treatment with clodronate reduced migration of the cemented NexGen total knee prosthesis during the first postoperative year, as measured by radiostereometry (RSA). Oral bisphosphonate treatment is sometimes unpleasant, and local treatment will enable higher local concentrations. We now report the results of local peroperative treatment with another bisphosphonate, ibandronate, with the same prosthesis.

Methods This is a double-blind, randomized study of 50 patients using RSA with maximal total point motion (MTPM) as primary effect variable. 1 mg ibandronate (1 mL) or 1 mL saline was applied to the tibial bone surface 1 min before cementation. RSA examination was done on the first postoperative day, and at 6, 12, and 24 months.

Results One ibandronate-treated patient died of unrelated causes, and 1 control patient refused to come for follow-up, leaving 24 patients in each group for analysis. There were no cases of aseptic loosening. By repeated measures ANOVA, migration (MTPM) was reduced by local application of ibandronate (p = 0.006). The effect was most pronounced at 6 months, with a reduction from 0.45 to 0.32 mm (95% CI for reduction: 0.04-0.21 mm). At 12 months, the migration from the postoperative examination was reduced from 0.47 to 0.36 mm (95% CI for reduction: 0.02-0.20 mm). At 24 months, the reduction was from 0.47 to 0.40 mm (95% CI: -0.01-0.16 mm).

Interpretation This is the first study to show improvement of prosthesis fixation by local pharmacological treatment in humans. The treatment appears to be safe, cheap, and easy to perform. However, the improvement in postoperative stability was not greater than with systemic clodronate treatment.     

High long-term loosening rate of conical screw cups

Background Acetabular screw cups seem to give high primary stability. We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up.

Patients and methods We examined 92 uncemented titanium alloy conical screw cups prospectively. Implant migration was assessed with a digital high-precision method (EBRA) with an accuracy of 1.0 mm.

Results After mean 11 (0.5-18) years, 87 patients were available for examination and 5 patients had died. 32 implants had been revised and 7 cases showed radiographic evidence of loosening. The 10-year survival rate was 71%. Migration of more than 1 mm occurred in 53 hips. Implant survival was strongly associated with an annual migration of greater than 0.2 mm.

Interpretation The long-term behavior of this cup is not satisfactory. In spite of extraordinarily high primary implant stability, secondary osseointegration of this cup often fails. The annual migration rate represents a valid parameter for prediction of implant survival.     

Acetabular reconstruction with the Burch-Schneider ring: an EBRA analysis of 40 cup revisions

Background Reconstruction of the bone stock and fixation of the implant remain challenging problems in revision surgery. In this retrospective study, we wanted to gain information on initial stability and wear after revision with the Burch-Schneider ring.

Patients and methods Between 1994 and 1998, we performed 70 reconstructions of the acetabulum with a Burch-Schneider ring in revision arthroplasty. 63 patients could be followed up clinically and radiographically. 40 cups were suitable for EBRA measurements whereas migration and wear could not be assessed by this method in 23 cases due to lack of comparability of pelvic radiographs. The mean follow-up time was 4.7 years.

Results 2 cups were re-revised and 14 cups had breakage or changes of position of the screws. 30 cups showed detectable migration and 18 cups detectable wear. The mean migration was 2.8 mm and the mean wear rate was 0.12 mm/year. 16 cups had detectable migration after 1 year; 11 of these 16 continued to migrate and 9 of them had screw breakage. Both re-revisions showed early migration. Early migration correlated with later screw breakage and the overall migration correlated with wear. The only risk factor found for early migration was the wear rate.

Interpretation The Burch-Schneider ring is an established and reliable implant for cup revision with good clinical results, but it seems to be difficult to maintain intraoperative stability. The implants with continuous migration may lead to late clinical failure and require further observation. Wear may contribute to migration and resorption of the bone graft. ▪     

Structural allografts for bone stock reconstruction in two-stage revision for infected total hip arthroplasty: good outcome in 16 of 18 patients followed for 5-14 years

Background The use of massive bone allografts in cases of revision of failed total hip arthroplasties (THAs) due to infection is controversial.

Patients and methods 18 patients presented with infection at the site of a THA and were treated with a two-stage protocol. In the first stage, the prosthesis was removed together with all necrotic tissues and cement material if present. A custom-made mold of Palacos R cement containing 1 g of gentamicin was then inserted in 17 of the 18 patients. Systemic antibiotics were used during the interval period. In the second stage, the patients had either acetabular or femoral reconstruction using bulk allograft bone.

Results Mean follow-up was 9 (5-14) years. 1 patient presented with recurrent infection and underwent a Girdlestone resection arthroplasty as definitive treatment. Another patient had a mechanical failure of the acetabular component, which was revised 10 years after the second stage of the reconstruction. The mean Harris Hip Score improved from 34 points preoperatively to 71 points at the last review. By our definition, 16/18 of the patients had a successful outcome.

Interpretation Our results support the use of massive allografts in staged reconstructions of infected THAs complicated by considerable bone loss. ▪     

Selective COX-2 inhibitor versus indomethacin for the prevention of heterotopic ossification after hip replacement: a double-blind randomized trial of 100 patients with 1-year follow-up

Introduction Recent reports have suggested that selective COX-2 inhibition may be sufficient for the prevention of heterotopic ossification.

Methods We performed a randomized controlled study to evaluate the effect of the selective COX-2 inhibitor rofecoxib compared to that of indomethacin on the incidence and extent of heterotopic ossification in patients who had undergone hip replacement surgery. 50 patients received a daily dose of 25 mg rofecoxib and 50 patients received a daily dose of 100 mg indomethacin (25, 25, and 50 mg).

Results No ossifications were found in 48 patients. Grade-II ossifications were seen in 5/46 patients in the rofecoxib group and in 6/50 patients in the indomethacin group. Grade-III and grade-IV ossifications were seen in 3/46 patients in the rofecoxib group only. The differences were not statistically significant. The study medication had to be discontinued in 2 patients in the indomethacin group, due to dyspepsia.

Interpretation After short-term administration, the selective COX-2 inhibitor rofecoxib was effective in preventing heterotopic ossification after total hip arthroplasty.     

Comparison of two types of ulnar component in type-5 Kudo total elbow arthroplasty in patients with rheumatoid arthritis: a long-term follow-up

The purpose of this study was to assess the long-term results (more than ten years) of two types of cemented ulnar component with type-5 Kudo total elbow arthroplasty in a consecutive series of 56 patients (60 elbows) with rheumatoid arthritis, and to compare the results in elbows above and below a Larsen grade IV. There was no radiolucency around the humeral component. Patients in whom a metal-backed ulnar component and a porous-coated stem were used had better clinical results and significantly less progression of radiolucent line formation around the ulnar component. They also had a significantly better long-term survival than patients with an all-polyethylene ulnar component. The clinical results of arthroplasty using all-polyethylene ulnar components were inferior, regardless of the degree of joint destruction. We conclude that the type-5 Kudo total elbow arthroplasty with cementless fixation of the porous-coated humeral component and cemented fixation of a metal-backed ulnar component is acceptable and well-tolerated by rheumatoid patients.     

Very low wear of non-remelted highly cross-linked polyethylene cups: an RSA study lasting up to 6 years

Background and purpose Highly cross-linked polyethylenes (PEs) all appear to reduce wear dramatically in laboratory studies, although there is substantial variation in this respect between manufacturers. Nonremelted cross-linked PE is almost as tough as unirradiated PE, but is not completely stable and can oxidize in vivo, as has been shown in recent retrievals studies.

We had reported low wear and good clinical performance after 2 years for 10 non-remelted highly crosslinked PE cups compared to 16 conventional PE cups sterilized by gamma-in-air.

Method Because of possible degradation by free radicals, we followed up both cohorts for 5 years (conventional PE) and 6 years (highly cross-linked PE).

Result Mean (CI) proximal head penetration over the observation time was linear and measured 0.08 (0.02-0.13) mm for cross-linked PE and 0.42 (0.23-0.62) mm for conventional PE, and total penetration was 0.23 (0.1-0.35) mm and 0.75 (0.05-1.4) mm respectively. After subtracting creep, the annual wear for non-remelted highly cross-linked PE was below 6 µm. The cups had equally low migration and few radiolucencies.

Interpretation The theoretical possibility of oxidation in non-remelted highly cross-linked PE may not show clinically. However, it may be that cemented cups with their thicker PE are more forgiving than metal-backed cups with thin PE moving in the locking mechanism. So far, we can conclude that the Crossfire highly crosslinked polyethylene cups performed very well clinically, with extremely low wear even after almost 6 years. This is reassuring, but care should be taken in extrapolating these results to other cross-linked PEs or uncemented cups where toughness of PE is more of an issue.     

Effect of bone marrow grafting on the titanium porous-coated implant in bilateral total knee arthroplasty

Background and purpose Poor bone ingrowth into the porous coating of tibial components has been reported. We hypothesized that iliac marrow grafting might be useful to enhance bone ingrowth into a porous-coated implant. The first part of this study was to examine the presence of fibroblast colony-forming units (CFUF) containing osteogenic precursor cells in tibial bone marrow and iliac bone marrow. The second aim was to compare the clinical and radiographic results after bilateral total knee arthroplasty (TKA) with and without autologous bone marrow transplantation to the bone-implant interface.

Methods Simultaneous bilateral TKA was performed in 21 patients with osteoarthritis. Aspirated iliac bone marrow was transplanted to the interface of one randomly selected porous-coated tibial component in each patient, and contralateral knees served as controls. All of the 21 patients were followed for 5 years.

Results The average number of CFU-F was significantly lower in tibial marrow than in iliac marrow (p = 0.008). The final fluoroscopically-guided radiographs revealed a decrease in the number of knees with radiolucent lines after marrow grafting compared to those without grafting (p = 0.004).

Interpretation Iliac bone marrow is useful as a bone grafting material to enhance the biological fixation in porous-coated implants.     

Postoperative clodronate decreases prosthetic migration: 4-year follow-up of a randomized radiostereometric study of 50 total knee patients

Background We have previously reported that 6 months of oral treatment with clodronate reduced the migration of the NexGen total knee prosthesis during the first postoperative year, as measured by radiostereometry (RSA). We now report the 4-year results.

Methods This was a double-blind randomized study, using RSA with maximal total point motion (MTPM).

Results With analysis according to the “intention to treat” principle, the only remaining difference between the groups at 4 years was reduced rotation around the transverse axis (a secondary variable) in the clodronate group. However, 3 patients (all clodronate) did not take any tablet after surgery. If they are excluded, there was an almost statistically significant difference between the groups at 4 years regarding MTPM from baseline, with the clodronate group showing 25% less migration. From 1 to 4 years, there was no difference in migration rate by MTPM, but there was a continuous increase in rotation around the transverse axis in the controls, which differed from the clodronate group. There were no cases of aseptic loosening. 2 patients had migration of more than 1.3 mm from baseline to 4 years; neither of them had taken clodronate. The others had migration of less than 0.9 mm.

Interpretation Because migration was clearly reduced by clodronate during the first postoperative year, and there was still a difference at 4 years when analyzed per protocol, it appears likely that this treatment can diminish the risk of loosening. The difference in the number of outliers also points in this direction, and may be more relevant than mean migration values.     

5-year experience of highly cross-linked polyethylene in cemented and uncemented sockets: two randomized studies using radiostereometric analysis

Background Laboratory tests and early clinical studies have shown that highly cross-linked polyethylene (PE) markedly improves wear resistance compared to conventional PE. We evaluated this type of PE in two randomized clinical studies using radiostereometric analysis (RSA). The 2- and 3-year follow-up of these studies have already been reported. We found a lower penetration rate for the highly cross-linked PE than for conventional PE. We now report the outcome after 5 years.

Patients and methods 60 patients (61 hips) with a median age of 55 years were randomized to receive either highly cross-linked PE (Durasul) or conventional cemented all-polyethylene sockets of the same design. 55 patients (56 hips) were followed for 5 years. In the second study, 32 patients (64 hips) with a median age of 48 years and with bilateral primary or secondary osteoarthritis of the hip had hybrid total hip arthroplasty with liners made of highly cross-linked PE (Longevity) on one side and conventional PE on the other. 23 patients in this study have passed the 5-year follow-up.

Results Bedding-in and creep for the Durasul all-PE was reached by 2 years, and by 1 year for the Longevity liners. In both control groups with conventional PE, this was reached by 6 months. The steady-state wear rate was close to zero in the two study groups and 0.06 mm/ year for the conventional PE in the two control groups.

Interpretation We found that use of highly crosslinked PE instead of conventional PE reduced the wear by more than 95%, which supports continued use of this type of PE in young, active patients.     

Socket wall addition device in the treatment of recurrent hip prosthesis dislocation: good outcome in 12 patients followed for 4.5 (1-9) years

Background Recurrent dislocation in total hip replacement is difficult to treat and causes severe morbidity.

Patients and methods 12 patients suffering dislocations were reoperated with a socket wall addition device (anti-luxation ring) for the Lubinus SPII prosthesis, and were followed up after a mean of 4.5 (1-9) years with regard to redislocation, function and radiographic loos-ening.

Results 1 of the patients suffered a redislocation after almost 7 years of use. There was no loosening during the follow-up time. A Harris hip score of 87 (60-100), a health-related quality of life (EQ-5D) index of 0.8 (0.6-1.0) and total range of motion of 145° (125-165) indicate that the patients had a level of function comparable to that of age-matched hip surgery patients with no com-plications.

Interpretation The anti-luxation ring shows promising mid-term results and seems to provide an alternative to more extensive revision surgery for selected patients. ▪     

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 2. Completely cemented components: MB not superior to AP components

Background Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2).

Patients and methods In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8 mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score.

Results We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point.

Interpretation Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem.

  ▪     

Forearm bone-anchored amputation prosthesis: a case study on the osseointegration

Background and purpose Bone-anchored titanium implants have been used for anchorage of amputation prostheses for more than one and a half decades. Histo-logical and ultrastructural analyses were performed on a forearm amputation prosthesis after being in use for more than 11 years.

Material, methods and results The implant was retrieved from the ulnar bone after a fatigue fracture of the titanium implant, and was clinically stable at the time of removal. The histological findings showed a large amount of bone within the threads and a high degree of apposition of mineralized bone to the implant surface. Ultrastructural analysis of thin samples prepared by focused ion-beam microscopy revealed an electron-dense layer at the interface and direct apposition of crystalline hydroxyapatite at the implant surface.

Interpretation Our observations in this retrieval study provide a structural correlate to the functional properties and clinical results of amputation prostheses.     

Surgical treatment of posttraumatic stiffness of the elbow: 2-year outcome in 21 patients after a column procedure

Background and purpose Posttraumatic stiffness is a common complication of elbow injury and can result in considerable impairment in daily life. We assessed the outcome in 21 patients treated by a column procedure.

Patients and methods We followed 21 patients (average age 40 (10-76) years, 11 women) for 2 years after surgery for a stiff elbow. Range of motion (ROM) and function (EFA score) were measured preoperatively and at 3,12, and 24 months postoperatively.

Results Before surgery, the mean ROM was 69° (SD 24) and the mean EFA score was 74 (SD 13), which improved significantly to 104° (17) and 91 (6), respectively, after release. There were no significant differences between the postoperative measurements at 3,12, and 24 months. No neurovascular complications were noted; 2 patients developed periarticular ossifications postoperatively.

Interpretation A column procedure results in an increase in motion and functional scores at 2-year follow-up. Outcome at 3 months after treatment is the same as after 2 years.     

Micromotion of the Souter-Strathclyde total elbow prosthesis in patients with rheumatoid arthritis

21 elbows in 18 patients with rheumatoid arthritis were treated with a Souter-Strathclyde total elbow prosthesis. 18 elbows were included in a radiostereometry (RSA) study. The aim of this clinical RSA study was to assess the three-dimensional micromotion pattern of the Souter-Strathclyde prosthesis, and thereby gain insight in the aseptic loosening process of this prosthesis. Implants were defined as at risk of aseptic loosening when the translation rate during the second postoperative year was more than 0.4 mm along one or more coordinate axes and/or the rate of rotation was more than 1° about one or more coordinate axes. Clinical examination revealed an increase in the range of motion and a marked reduction in pain. The RSA showed that 8 of 18 humeral components were at risk of aseptic loosening, although no signs of such loosening - defined as a complete radiolucent line of 2 mm or more - were found on the plain radiographs. In 7 humeral components, an anterior tilt about the transverse axis was seen that resulted in an anterior translation of the proximal tip and a posterior translation of the component's trochlea. Long-term studies of the Souter-Strathclyde prosthesis, have shown that this rotation is a specific pattern of failure in some implants. None of the ulnar components was at risk for aseptic loosening. Improvements in fixation of the Souter-Strathclyde total elbow arthroplasty should focus on the humeral component. At present, the lateral flange of the implant is enlarged to improve rotational stability about the transverse and longitudinal axes. The effect of this change in design on micromotion of the Souter-Strathclyde total elbow prosthesis will be studied in a randomized RSA study comparing the new design to the existing one.     

Inter- and intra-batch variability in the handling characteristics and viscosity of commonly used antibiotic-loaded bone cements

Background Several factors can affect the viscosity of a cement and therefore its handling characteristics. We performed an in vitro study to ascertain whether anecdotal observations of differences in handling between batches of the same brand of cement actually existed.

Methods 3 batches of Simplex P Tobramycin (SPT), Refobacin Bone Cement (RBC), SmartSet GHV (SSG) and Palacos R+G (PRG) were tested. 6 replicates of each batch were vacuum-mixed and their viscosity in relation to time was measured under laboratory conditions using a rheometer. We examined the handling characteristsics of 6 replicates of each batch after they were hand-mixed under theater conditions.

Results Inter- and intra-batch variability was seen in the viscosity of all brands of cement tested. Interbatch calculations were influenced by high intra-batch variability in viscosity. The viscosity of RBC cement was similar to that of SSG, but different to that of PRG (p = 0.01 at 5 N and p = 0.009 at 40 N).

Interpretation Our results suggest that in clinical practice, extrinsic factors such as preparation conditions and methods probably play a more important role than the intrinsic variability of cements. However, variability in handling and viscosity will exist in all brands of cement prepared under theater conditions and the surgeon must be aware of why they may act differently.     

Outcome of isolated tibial polyethylene insert exchange after uncemented total knee arthroplasty: 27 patients followed for 8-71 months

Background The outcome of performing isolated tibial polyethylene insert exchange (ITPIE) after total knee arthroplasty (TKA) is under debate. We evaluated the survival probability of ITPE after uncemented TKA.

Method 27 patients (27 knees) with an ITPIE performed mean 9 (0.9-17) years after the initial TKA were included in the study (22 patients also had the patellar component replaced simultaneously). All patients had their exchange performed at our department between 1997 and 2001 and had their latest follow-up examination mean 40 (8-71) months after the exchange.

Results During the follow-up, 2 patients had total knee revision because of aseptic loosening and 2 patients had isolated patella component exchange (in 1 of the patients, combined with a new ITPIE). Kaplan-Meier survival analysis gave a survival probability of 80% at 34 months of follow-up.

Interpretation The short-term survival after an ITPIE was similar to that of a total knee revision with exchange of all components. Since the ITPIE is a much smaller operation with fast rehabilitation, we recommend it in elderly patients with a well-fixed and wellaligned prosthesis without surface damage of the components.