Radiolucent lines: a question of nomenclature

Mid-term clinical radiological results of the constrained condylar knee prosthesis in total knee revision

INTRODUCTION

The aim of the present study is to analyze the clinical-radiological outcomes of patients undergoing knee prosthesis revision surgery using constrained condylar prosthesis (LCCK; Zimmer-Biomet).

MATERIAL AND METHODS

Retrospective study of 89 patients operated on between the years 2008 and 2020 with a minimum of 2 years of follow-up. Clinical outcomes were evaluated using the WOMAC Index score and KOOS scales. Radiological results (radiolucent lines, osteolysis, and cortical hypertrophy) were evaluated by two independent observers. Implant survival was analyzed using the Kaplan-Meier method.

RESULTS

At the end of follow-up, a mean WOMAC Index score of 78.67 and KOOS score of 68.8 were obtained. Radiolucent lines (both non-progressive and progressive) were detected in 83.3% of the patients in the sample. Areas of osteolysis > 5 mm around the components were present in 6.75%. Cortical hypertrophy was seen around the femoral stem in 20.3% of cases, around the tibial stem in 20.3% and around both components in 6.76%. No statistically significant relationship was found between the presence of radiolucent lines, osteolysis or cortical hypertrophy with functional results. Implant survival was 88.1% at 13 years.

CONCLUSION

The present study shows high survival of LCCK prosthesis in revision surgery. The progressive radiolucencies, were associated with worst clinical outcome.

Early appearance of radiolucent lines around total knee arthroplasty in rheumatoid arthritis patients. How does it impact the aseptic failure rate and functional outcomes at 13 years of follow-up?

INTRODUCTION

Aseptic total knee arthroplasty (TKA) failure has been associated with radiolucent lines. This study aimed to determine the impact of the early appearance of radiolucent lines (linear images of 1, 2, or >2mm at the cement-bone interface) around the TKA on prosthetic survival and functional outcomes in rheumatoid arthritis (RA) patients during a 2-20 years follow-up.

METHODS

We retrospectively analyzed a consecutive series of RA patients treated with TKA between 2000 and 2011. We comparatively analyzed patients with and without radiolucent lines around implants. Clinical outcomes were assessed with the knee society score (KSS) collected before surgery, at years 2, 5, and 10, and at the last postoperative follow-up. The knee society roentgenographic evaluation system was used to analyze the impact of radiolucent lines around the implants at 1, 2, 5, and more than ten years of follow-up. The reoperation and prosthetic survival rates were calculated at the end of the follow-up.

RESULTS

The study series included 72 TKAs with a median follow-up of 13.2 years (range: 4.0-21.0), of which 16 (22.2%) had radiolucent lines. We did not observe aseptic failure, and prosthetic survival at the end of the study was 94.4% (n=68). The KSS improved significantly (p<0.001) between preoperative values at 2, 5, and 10 years and the end of follow-up, with no differences between patients with and without radiolucent lines.

CONCLUSIONS

Our study demonstrates that the early appearance of radiolucent lines around a TKA in RA patients does not significantly impact prosthetic survival or long-term functional outcomes at 13 years of follow-up.

Early appearance of radiolucent lines around total knee arthroplasty in rheumatoid arthritis patients. How does it impact the aseptic failure rate and functional outcomes at 13 years of follow-up?

INTRODUCTION

Aseptic total knee arthroplasty (TKA) failure has been associated with radiolucent lines. This study aimed to determine the impact of the early appearance of radiolucent lines (linear images of 1, 2, or > 2mm at the cement-bone interface) around the TKA on prosthetic survival and functional outcomes in rheumatoid arthritis (RA) patients during a 2-20 years follow-up.

METHODS

We retrospectively analyzed a consecutive series of RA patients treated with TKA between 2000 and 2011. We comparatively analyzed patients with and without radiolucent lines around implants. Clinical outcomes were assessed with the knee society score (KSS) collected before surgery, at years 2, 5, and 10, and at the last postoperative follow-up. The knee society roentgenographic evaluation system was used to analyze the impact of radiolucent lines around the implants at 1, 2, 5, and more than ten years of follow-up. The reoperation and prosthetic survival rates were calculated at the end of the follow-up.

RESULTS

The study series included 72 TKAs with a median follow-up of 13.2 years (range: 4.0-21.0), of which 16 (22.2%) had radiolucent lines. We did not observe aseptic failure, and prosthetic survival at the end of the study was 94.4% (n=68). The KSS improved significantly (p<0.001) between preoperative values at 2, 5, and 10 years and the end of follow-up, with no differences between patients with and without radiolucent lines.

CONCLUSIONS

Our study demonstrates that the early appearance of radiolucent lines around a TKA in RA patients does not significantly impact prosthetic survival or long-term functional outcomes at 13 years of follow-up.

Beneficial effect of a zirconium-nitride-coated implant in total knee arthroplasty revision for suspected metal hypersensitivity

INTRODUCTION

Revision of total knee arthroplasty (rTKA) for suspicion of metal hypersensitivity (MHS) may require hypoallergenic implants. Results for coated implants have not been reported. The aim of the present study was to assess short-term results and survival of rTKA for MHS using a multilayer implant coating.

HYPOTHESIS

Multilayer implant coating improves functional results in rTKA, with survival comparable to primary coated implants.

MATERIAL AND METHODS

A single-center retrospective observational study included 28 patients (30 knees) undergoing rTKA for MHS using a coated implant between May 2011 and November 2016. Exclusion criteria comprised implant malpositioning and history of infection in the affected knee. Clinical and radiological results were assessed on the International Knee Society (IKS) and SF-36 functional scores and Ewald radiological score. Survival was calculated on Kaplan-Meier estimation.

RESULTS

Mean follow-up was 3.8 years. Mean IKS score increased by 40.2 points (40%) [range, 28.1-52.3] (p<0.05). Mean range of motion increased by 17° [range, 9.5-24.5°] (p<0.05). Mean physical and mental SF-36 components were respectively 44.7 and 46.1. Survivorship was 93%.

DISCUSSION

There was significant functional improvement after rTKA for MHS. There were no short-term complications related to the zirconium nitrate coating. However, studies with longer follow-up will be needed for confirmation.

LEVEL OF EVIDENCE

IV; retrospective study.

The lexicon for periprosthetic bone loss versus osteolysis after cervical disc arthroplasty: a systematic review

BACKGROUND

Periprosthetic bone loss is a common observation following arthroplasty. Recognizing and understanding the nature of bone loss is vital as it determines the subsequent performance of the device and the overall outcome. Despite its significance, the term "bone loss" is often misused to describe inflammatory osteolysis, a complication with vastly different clinical outcomes and treatment plans. Therefore, the goal of this review was to report major findings related to vertebral radiographic bone changes around cervical disc replacements, mitigate discrepancies in clinical reports by introducing uniform terminology to the field, and establish a precedence that can be used to identify the important nuances between these distinct complications.

METHODS

A systematic review of the literature was conducted following PRISMA guidelines, using the keywords "cervical," "disc replacement," "osteolysis," "bone loss," "radiograph," and "complications." A total of 23 articles met the inclusion criteria with the majority being retrospective or case reports.

RESULTS

Fourteen studies reported periprosthetic osteolysis in a total of 46 patients with onset ranging from 15-96 months after the index procedure. Reported causes included: metal hypersensitivity, infection, mechanical failure, and wear debris. Osteolysis was generally progressive and led to reoperation. Nine articles reported non-inflammatory bone loss in 527 patients (52.5%), typically within 3-6 months following implantation. The reported causes included: micromotion, stress shielding, and interrupted blood supply. With one exception, bone loss was reported to be non-progressive and had no effect on clinical outcome measures.

CONCLUSIONS

Non-progressive, early onset bone loss is a common finding after CDA and typically does not affect the reported short-term pain scores or lead to early revision. By contrast, osteolysis was less common, presenting more than a year post-operative and often accompanied by additional complications, leading to revision surgery. A greater understanding of the clinical significance is limited by the lack of long-term studies, inconsistent terminology, and infrequent use of histology and explant analyses. Uniform reporting and adoption of consistent terminology can mitigate some of these limitations. Executing these actionable items is critical to assess device performance and the risk of revision.

LEVEL OF EVIDENCE IV

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Clinical and Radiological Outcomes Following Medial Pivot Total Knee Arthroplasty: A Retrospective Chart Review Study

Medial pivot total knee arthroplasty (MP-TKA) is a relatively new design that simulates normal knee mechanics with the aim of enhancing postoperative recovery. Furthermore, it reduces postoperative complications in patients with end-stage osteoarthritis of the knee. No study has been done regarding this topic in Saudi Arabia yet, so we aimed to study the post-operative clinical and radiological outcomes of MP-TKA, as well as the postoperative complications. A retrospective cohort chart review study was conducted on 46 patients and 70 knees after applying our inclusion/exclusion criteria. The patients were followed up for an average period of two years. Clinical outcomes were assessed pre- and postoperatively by the validated Saudi Arabian version of the Knee Injury and Osteoarthritis Outcome Score (KOOS), as well as radiological outcomes and postoperative complications gathered from patients’ charts. The postoperative KOOS score showed a statistically significant improvement in pain, symptoms, and activities of daily living in comparison with the preoperative score (P-value < 0.0001). The mean time until ambulation and length of hospital stay were five and 14 days, respectively. Four patients (8.7%) showed radiological complications. Deep vein thrombosis was observed in only two knees (4.3%), and there were no revision cases. Thus, MP-TKA has been shown to improve pain, symptoms, and activities of daily living with a relatively short time until ambulation and length of hospital stay, in addition to a low incidence of postoperative and radiological complications.

Vitamin E-enriched polyethylene bearings are not inferior to Arcom bearings in primary total knee arthroplasty at medium-term follow-up

INTRODUCTION

The release of wear particles can be responsible for periprosthetic osteolysis, which can in turn, lead to aseptic loosening. Vitamin E-infused polyethylene (HXLPE Vit-E) has been shown, in vitro, to be more resistant to wear than conventional polyethylene (UHMWPE) by its crosslinking (HXLPE) and its higher resistance to oxidation. After reading a case report of a fracture of a vitamin E-enriched HXLPE bearing, the aim of this retrospective study was to evaluate fracture risk and clinical inferiority or not of vitamin-E HXLPE compared to conventional polyethylene in total knee arthroplasty (TKA).

MATERIALS AND METHODS

Three hundred and forty-nine patients (403 TKAs) were contacted, to find out whether they had undergone revision surgery for any reason after a mean (SD) of 7 (1.5) years. Follow-up control radiographs were analyzed for periprosthetic radiolucent lines (RLL) and loosening. Two different Patient Reported Outcome Measurements Scores (PROMS), KOOS and FJS-12, were utilized to assess the daily functionality and identify potential problems.

RESULTS

No statistically significant difference in revision rate, occurrence of aseptic loosening or RLL nor outcome as measured with PROMS was observed.

CONCLUSIONS

No bearing fractures or clinical inferiority was observed for vitamin E-enriched HXLPE at medium-term follow-up (7 years) compared to conventional Arcom polyethylene.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Total knee arthroplasty with the Medial-Pivot knee system: Clinical and radiological outcomes at 9.5 years' mean follow-up

INTRODUCTION

The "ball-in-socket" design of the Medial-Pivot knee system (MicroPort Orthopedics, Arlington, Tennessee, USA) aims to reproduce normal knee kinematics by medializing its rotational axis. The goal of this study was to measure knee range of motion (ROM) with this implant after a mean follow-up of 10 years and to report the survivorship and long-term clinical and radiological outcomes. We hypothesized the prosthetic knee would have at least 120° flexion at 10 years.

MATERIAL AND METHODS

This was retrospective, single-centre study of 74 Medial-Pivot knees implanted in 71 patients (average age of 69 years) between May 2005 and November 2007. All patients who received a Medial-Pivot knee were included consecutively. The mean follow-up was 10 years. Clinical and radiological assessments were performed using the Knee Society Score (KSS) and Ewald's score. Kaplan-Meir survival analysis was used to calculate survivorship.

RESULTS

Seven percent of cases were lost to follow-up. The knee ROM was 110° at 10 years. The survivorship was 93% for all revision causes and 95.9% when revisions due to trauma or infection were excluded. The mean KSS score was 195. Stable radiolucent lines were found in 14% of cases. No aseptic loosening was observed.

CONCLUSION

Our hypothesis was not confirmed. Knee flexion at the final follow-up was comparable to other semi-constrained implant designs but was not as large as expected. The survival of the Medial-Pivot knee at 10 years is good. Its radiological and clinical outcomes are satisfactory.

LEVEL OF EVIDENCE

IV (retrospective cohort study).

Radiolucent lines are decreased at 3 years following total knee arthroplasty using trabecular metal tibial components

Objective To analyse location and frequency, and change over time, of radiolucent lines (RLLs) around trabecular metal tibial components in total knee arthroplasty (TKA). Methods Osteoarthritic knees in patients who had undergone TKA were retrospectively evaluated via analysis of RLLs on anteroposterior and lateral X-rays obtained at 2 and 6 months, and 1, 2 and 3 years following TKA. Results In 125 osteoarthritic knees from 90 patients (mean age, 75.0 ± 6.2; 21 male/69 female), frequency of RLLs around trabecular metal tibial components was generally highest at 2 and 6 months, and 1 year following TKA, then gradually decreased over the 3-year follow-up. Frequency of RLLs around trabecular metal tibial components was greater at the tip of the two pegs, particularly the medial peg, and around the pegs, versus other zones. No postoperative revisions were performed for loosening. Conclusions Over 3 years following TKA, RLLs were most frequently observed up to 1 year, then gradually decreased. RLLs were significantly more frequent in the medial peg zone and zones close to the medial peg than in other zones.

A long term clinical outcome of the Medial Pivot Knee Arthroplasty System

BACKGROUND

The ideal total knee arthroplasty (TKA) should provide maximum range of motion and functional stability for all desired daily activities and, if possible, to replicate normal knee kinematics and function. The ADVANCE® Medial Pivot (AMP) Knee System was designed with a highly congruent medial compartment and a less conforming lateral compartment to more closely mimic the kinematics of the normal knee and to offer more stability through out of range of motion (ROM). The purpose of this study was to evaluate the long-term clinical and radiographic outcomes of this TKA system.

METHODS

Three hundred and twenty-five (325) patients (347 knees) with knee osteoarthritis underwent a TKA using the AMP prosthesis in our Department. For evaluation, objective and subjective clinical rating systems along with radiograph series were used. The average follow-up was 15.2years.

RESULTS

All patients showed a statistically significant improvement (p<0.0005) in the Knee Society clinical rating system, Western Ontario and McMaster Universities Osteoarthritis Index questionnaire, SF-12® questionnaire, and Oxford knee score. The majority of patients (94%) were able to perform age-appropriate activities with a mean knee flexion of 120° (range, 105°-135°) at final follow-up. Survival analysis showed a cumulative success rate of 98.8% at 17years.

CONCLUSION

The obtained results demonstrate excellent long-term clinical outcome for this knee design.

Total knee arthroplasty with an oxidised zirconium femoral component: a 5-year follow-up study

PURPOSE

To report the early results of the Oxinium Genesis II prosthesis with an oxidised zirconium femoral component in 55 patients.

METHODS

71 knees in 21 men and 34 women aged 32 to 75 (mean, 55) years were evaluated; 16 of the patients had bilateral staged total knee replacements with a mean interval of 9 (range, 6-16) months between surgeries. The indications for surgery included osteoarthritis (n=57), rheumatoid arthritis (n=13) and revision from a unicompartmental knee replacement for osteoarthritis (n=1). Postoperatively, patients were evaluated using the Knee Society score (KSS), the modified Oxford Knee Score, and the SF-12 health survey, as were component position, leg and knee alignment, and prosthesis-bone interface or fixation on radiographs.

RESULTS

The mean follow-up was 62 (range, 51-88) months. The mean KSS, Oxford Knee Score, and SF-12 physical component score improved significantly. Radiolucent lines (<2 mm) were noted in the tibial cement-bone interface in 17 knees (most commonly in zones 4 and 1) and in the femoral cement-bone interface in one knee. The alignment of the knees and positioning of the components were acceptable. There were no revisions for septic or aseptic loosening.

CONCLUSION

Early results of the Oxinium Genesis II prosthesis are comparable to the standard total knee prostheses.

Clinical and radiologic outcomes of total knee arthroplasty using the Advance Medial Pivot prosthesis. A mean 7 years follow-up

BACKGROUND

Medial Pivot total knee prosthesis has been designed according to studies on normal knee kinematics aiming to replicate physiological knee movement. The purpose of this study was to evaluate clinical and radiologic results of the Advance Medial Pivot Total Knee Arthroplasty, at a mean follow-up of seven years.

METHODS

One hundred seventy two Medial Pivot total knee arthroplasties in 160 consecutive patients have been evaluated using the American Knee Society Score and the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System. Statistical analysis was performed using the Student's t-test and the Wilcoxon matched-pairs signed-rank (Mann-Whitney) test in order to evaluate the significance of differences within the groups of patients. Patients compliance was 93.75% thus only six patients (3.75%) lost to follow-up and four patients (2.5%) died for reasons unrelated to the surgery.

RESULTS

The mean Knee Society score and range of motion was improved from 77.6 points and 97.7° to 152.8 points and 112.5° respectively (p<.001). In total 85.8% and 82.4% of the knees had an excellent (≥ 80) or good (70-79) functional and knee scores respectively. Relief of pain was satisfactory in 88.9% of the patients, while 96% of the patients return to age-related daily life activities. Stability and comfort during walking was subjectively judged by the patients as satisfactory in about 90%. Anterior knee pain was observed in eight patients (5.4%). The Kaplan-Meier survivorship analysis showed a cumulative success rate of 98.6%.

CONCLUSIONS

The results are encouraging but longer follow-up of this cohort is necessary in the study of this specific design. Level of evidence IV.

Do capsular pressure and implant motion interact to cause high pressure in the periprosthetic bone in total hip replacement?

When there is a debonding at the bone-implant interface, the difference in stiffness between the implant and the bone can result in micromotion, allowing existing gaps to open further or new gaps to be created during physiological loading. It has been suggested that periprosthetic fluid flow and high pressure may play an important role in osteolysis development in the proximity of these gaps. To explain this phenomenon, the concepts of "effective joint space" and "pumping stem" have been cited in many studies. However, there is no clear understanding of the factors causing, or contributing to, these mechanisms. It is likely that capsular pressure, gap dimensions, and micromotion of the gap during cyclic loading of an implant can play a defining role in inducing periprosthetic flow. In order to obtain a better understanding of the main influences on periprosthetic flows and the development of osteolysis, steady state and transient 2D computational fluid dynamic simulations were performed for the joint capsule of the lateral side of a stem-femur system, and a gap in communication with the capsule and the surrounding bone. It was shown that high capsular pressure may be the main driving force for high fluid pressure and flow in the bone surrounding the gap, while micromotion of only very long and narrow gaps can cause significant pressure and flow in the bone. At low capsular pressure, micromotion induced large flows in the gap region; however, the flow in the bone tissue was almost unaffected. The results also revealed the existence of high velocity spikes in the bone region at the bottom of the gap. These velocity spikes can exert excessive fluid shear stress on the bone cells and disturb the local biological balance of the surrounding interstitial fluid which can result in osteolysis development. High capsular pressure was observed to be the main cause of these velocity spikes whereas, at low capsular pressure, gap micromotion of only very long and narrow gaps generated significant velocity spikes in the bone at the bottom of the gaps.

Cementless revision TKA with bone grafting of osseous defects restores bone stock with a low revision rate at 4 to 10 years

BACKGROUND

Addressing bone loss in revision TKA is challenging despite the array of options to reconstruct the deficient bone. Biologic reconstruction using morselized loosely-packed bone graft potentially allows for augmentation of residual bone stock while offering physiologic load transfer. However it is unclear whether the reconstructions are durable.

QUESTIONS/PURPOSES

We therefore sought to determine (1) survivorship and complications, (2) function, and (3) radiographic findings of cementless revision TKA in combination with loosely-packed morselized bone graft to reconstruct osseous defects at revision TKA.

PATIENTS AND METHODS

We retrospectively reviewed 56 patients who had undergone revision TKAs using cementless long-stemmed components in combination with morselized loose bone graft at our institution. There were 26 men and 30 women with a mean age of 68.3 years (range, 56-89 years). Patients were followed to assess symptoms and function and to detect radiographic loosening, component migration, and graft incorporation. The minimum followup was 4 years (mean, 7.3 years; range, 4-10 years).

RESULTS

Cumulative prosthesis survival, with revision as an end point, was 98% at 10 years. The mean Oxford Knee Scores improved from 21 (36%) preoperatively to 41 (68%) at final followup. Five patients (9%) had reoperations for complications.

CONCLUSIONS

Our observations suggest this technique is reproducible and obviates the need for excessive bone resection, use of large metal augments, mass allografts, or custom prostheses. It allows for bone stock to be reconstructed reliably with durable midterm component fixation.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Radiolucent lines in low-contact-stress mobile-bearing total knee arthroplasty: a blinded and matched case control study

Background

Low-contact-stress (LCS) mobile-bearing total knee arthroplasty (TKA) (Johnson & Johnson, New Brunswick, NJ; previously: DePuy, Warsawa, USA) provides excellent functional results and wear rates in long-term follow-up analyses. Radiological analysis shows radiolucent lines (RLL) appearing immediately or two years after primary implantation, indicative of poor seat. Investigations proved RLL to be more frequent in uncemented TKA, resulting in a consensus to cement the tibial plateau, but their association with clinical findings and patients discomfort and knee pain is still unknown.

Methods

553 patients with 566 low-contact-stress (LCS) total knee prostheses were screened for continuous moderate knee pain. We compared tibial stress shielding classified by Ewald in patients suffering from pain with a matched, pain-free control group on blinded X-rays. We hypothesized a positive correlation between pain and radiolucency and higher frequency of such radiolucent lines in the most medial and most lateral zones of the tibial plateau.

Results

Twenty-eight patients suffered from knee pain in total. Radiolucencies were detected in 27 of these cases and in six out of 28 matched controls without knee pain. We could demonstrate a significant correlation of knee pain and radiolucencies, which appeared significantly more frequently in the outermost zones of the tibial plateau.

Conclusion

Our findings suggest that radiolucent lines, representing poor implant seat, about the tibial plateau are associated with knee pain in LCS patients. Radiolucencies are observed more often in noncemented LCS, and cementing the tibial plateau might improve implant seat and reduce both radiolucent lines and associated knee pain.

The Freeman femoral component with hydroxyapatite coating and retention of the neck: an update with a minimum follow-up of 17 years

The outcome at ten years of 100 Freeman hip stems (Finsbury Orthopaedics, Leatherhead, United Kingdom) retaining the neck with a proximal hydroxyapatite coating in a series of 52 men (six bilateral) and 40 women (two bilateral), has been described previously. None required revision for aseptic loosening. We have extended the follow-up to 20 years with a minimum of 17 years. The mean age of the patients at total hip replacement was 58.9 years (19 to 84). Six patients were lost to follow-up, but were included up to their last clinical review. A total of 22 patients (22 hips) had died, all from causes unrelated to their surgery. There have been 43 re-operations for failure of the acetabular component. However, in 38 of these the stem was not revised since it remained stable and there was no associated osteolysis. Two of the revisions were for damage to the trunnion after fracture of a modular ceramic head, and in another two, removal of the femoral component was because of the preference of the surgeon. In all cases the femoral component was well fixed, but could be extracted at the time of acetabular revision. In one case both components were revised for deep infection. There has been one case of aseptic loosening of the stem which occurred at 14 years. This stem had migrated distally by 7.6 mm in ten years and 8.4 mm at the time of revision at which stage it was found to be rotationally loose. With hindsight this component had been undersized at implantation. The survivorship for the stem at 17 years with aseptic loosening as the endpoint was 98.6% (95% confidence interval 95.9 to 100) when 62 hips were at risk. All remaining stems had a satisfactory clinical and radiological outcome. The Freeman proximally hydroxyapatite-coated femoral component is therefore a dependable implant and its continued use can be recommended.

The Medial Rotation total knee replacement: a clinical and radiological review at a mean follow-up of six years

We describe the survivorship of the Medial Rotation total knee replacement (TKR) at ten years in 228 cemented primary replacements implanted between October 1994 and October 2006, with their clinical and radiological outcome. This implant has a highly congruent medial compartment, with the femoral component represented by a portion of a sphere which articulates with a matched concave surface on the medial side of the tibial insert. There were 78 men (17 bilateral TKRs) and 111 women (22 bilateral TKRs) with a mean age of 67.9 years (28 to 90). All the patients were assessed clinically and radiologically using the American Knee Society scoring systems. The mean follow-up was for six years (1 to 13) with only two patients lost to follow-up and 34 dying during the period of study, one of whom had required revision for infection. There were 11 revisions performed in total, three for aseptic loosening, six for infection, one for a periprosthetic fracture and one for a painful but well-fixed replacement performed at another centre. With revision for any cause as the endpoint, the survival at ten years was 94.5% (95% CI 85.1 to 100), and with aseptic loosening as the endpoint 98.4% (95% CI 93 to 100). The mean American Knee Society score improved from 47.6 (0 to 88) to 72.2 (26 to 100) and for function from 45.1 (0 to 100) to 93.1 (45 to 100). Radiological review failed to detect migration in any of the surviving knees. The clinical and radiological results of the Medial Rotation TKR are satisfactory at ten years. The increased congruence of the medial compartment has not led to an increased rate of loosening and continued use can be supported.

The shortcomings of computer-aided measurement of migration for the prediction of failure of three forms of acetabular fixation by survival analysis and migration study to ten years

We studied, to ten years, migration by vertical displacement and angular change using a digitizer and standard radiographs and survival of three methods of acetabular fixation in primary hip replacement. Two implants were uncemented metal-backed components, one version of which was hydroxyapatite-coated. Both types had 28 mm polyethylene inserts. The third type was a cemented all-polyethylene cup with a 28 mm internal diameter. All cups articulated with a Freeman neck-retaining stem. The purpose was to see if the early migration data predicted the long-term outcome and could be used to forecast implants that would fail for the purpose of pre-market assessment. No statistical differences were found between the groups in the parameters studied. At the threshold accuracies of our migration measurements (three millimetres and three degrees) at three years, we could not identify components that would subsequently fail. However, migration less than these threshold values and the absence of radiolucent lines were strongly associated with implant survival at ten years. Our system was insufficiently accurate for pre-market surveillance.;

The correlation between immediate radiolucent lines and early implant migration in cemented acetabular components

Periacetabular radiolucent lines (RLLs) on postoperative radiographs have been associated with early loosening of the acetabular component. It has also been shown that excessive migration of an implant corresponds to an increased incidence of later clinical failure. This study relates RLLs on anterior-posterior hip radiographs taken 10 days and 6 months postoperatively to implant migration detected by roentgen stereophotogrammetric analysis. We have shown that RLLs in DeLee and Charnley zone III in the first week postoperatively as well as at 6 months are positively and significantly (P < .05) associated with migration detected by roentgen stereophotogrammetric analysis. No significant association was found for zone I or II at either 10 days or at 6 months. Considering the limitations in observing RLLs, their presence in zone III appears to reflect on the mechanical stability of the acetabular cup from the beginning. This indicates that zone III, which represents the inferomedial aspect of the acetabulum, might have to receive special attention when preparing the acetabulum and implanting the acetabular cup.

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.

Progression of radiolucent lines in cementless twin-bearing low-contact-stress knee prostheses: a retrospective study

A total of 134 low-contact-stress (LCS) total knee arthroplasties (TKAs) with mobile meniscal bearings were implanted in 121 patients with a mean age of 74 years (range, 49-91 years) at the time of surgery. The radiographic results obtained from 91 prostheses at an average follow-up of 7.5 years (range, 4.8-9.6 years) showed that radiolucent lines (RLL) appeared most frequently near the tibial plateau (97%) and that most RLL were present immediately postoperatively (67%) or appeared within the first year (96%). RLL were predominantly nonprogressive (99%). Progressive RLL did not affect the fixation or stability of the prosthesis. There were no revisions for aseptic loosening. Cementless LCS TKA achieves excellent radiologic and clinical midterm results.

Acetabular reconstruction in developmental hip dysplasia using reinforcement ring with a hook

We followed prospectively 27 patients with severe acetabular bone-stock deficiencies due to developmental dysplasia of the hip. Mean preoperative patient age was 56 (34-78) years, mean Harris hip score was 31 (16-66) points and pre-operative mean acetabular angle of Sharp was 47 degrees (34 degrees - 61 degrees). Operative acetabular reconstruction was performed in 28 hips using reinforcement ring with a hook placed in the true acetabulum and autologous bone grafting. A 2-year clinical and radiological follow-up was available in 27 hips. Mean Harris hip score improved to 91 (70-100) points. There were no clinical or radiological signs of aseptic loosening in 25 hips, and the bone graft was radiologically incorporated in all hips. In 24 hips, a radiostereometric analysis showed low rates of non-progressive translation and rotation in 21 reinforcement rings. Three rings showed progressive translation and/or rotation at the 2-year follow-up and were rated probably loose.

Osteodensitometry after total hip replacement with uncemented taper-design stem

We followed 24 patients (26 hips) with uncemented total hip replacement for a minimum of 3 years. Patient mean age was 52 (40-69) years. The aim was to evaluate femoral periprosthetic bone mineral density (BMD) using quantitative computed tomography osteodensitometry. At 3-years' follow-up, 25 hips were clinically rated good or excellent. The mean Harris hip score rose from 58 (49-68) pre-operatively to 94 (81-98) at the last follow-up. All hips were radiologically stable. Mean decrease of the overall BMD in the femoral metaphysis was 14.3%, and mean decrease of cortical BMD was 17.3%. In the diaphysis, mean decrease of overall BMD was 5.5% and mean decrease of cortical BMD was 4.5%. Observed loss was markedly lower than in comparable series with uncemented stems.

Clinical outcome and periprosthetic bone remodelling of an uncemented femoral component with taper design

We followed 48 consecutive patients (50 hips) with osteoarthritis who received a primary total hip replacement using a tapered stem with hydroxylapatite coating (Cerafit Multicone H-A.C.) and a press-fit cup. Mean follow-up was 3 years, mean patient age was 54.7 years, and mean preoperative Harris hip score was 57. Quantitative evaluation of periprosthetic bone remodelling was assessed 1 year after the index operation using computed tomography (CT). Clinical and radiological follow-up was obtained in all hips. The mean Harris hip score at follow-up was 96. Forty-nine hips were clinically rated good or excellent. No thigh pain was reported. Radiographs showed stable fixation by bone ingrowth in all hips. Fifteen hips were eligible for CT. Three years after operation, mean decrease of overall bone mineral density (BMD) was 14.2% and mean decrease of cortical BMD 15.5% in the metaphyseal portion. In the diaphyseal portion, mean decrease of overall BMD was 10.0% and mean decrease of cortical BMD 7.7%. Minimal changes were observed at the level of the tip of the stem. Clinical and radiological outcome using a tapered femoral stem with hydroxylapatite coating compares favourably with other reports. Osteodensitometry shows limited proximal femoral bone resorption.

Uncemented acetabular components with polyethylene or alumina liners

Sixty consecutive patients (60 hips) were allocated in two matched-pair groups. Patients were matched for age, gender, body mass index, level of activity, and bone stock. Both groups received an uncemented total hip arthroplasty with a modular press-fit cup and an alumina femoral head. In the first group, an acetabular liner made of polyethylene was used; in the second group, an alumina liner. Both groups were followed for a minimum of 5 years. No hip required revision, and there was no radiographic evidence of aseptic loosening in either group. Mean Harris hip score was 94.7 (87.1-99) points in the polyethylene group and 93 (88.5-100) points in the alumina group.

A study of polyethylene and modularity issues in >1000 posterior cruciate-retaining knees at 5 to 11 years

Polyethylene quality and production technique and monoblock versus modular design of tibial components affect the polyethylene wear of total knee arthroplasties (TKAs). We reviewed >1000 TKAs performed with the AGC prosthesis (Biomet, Warsaw, IN) using a uniform surgical technique with a 5- to 11-year follow-up. Of tibial components, 698 were of compression-molded monoblock design and 353 were of ram-extruded modular assembly design. The effect of the differences in tibial component design on the 5- to 11-year clinical and radiologic outcomes was studied. Higher rates of osteolysis, radiolucent lines, and revision were found with the ram-extruded modular design. This modular design is similar to most tibial component designs currently used in TKA, yet osteolysis in completely cemented components is described rarely. The TKAs done with a compression-molded monoblock design gave better clinical and radiologic results. The improved results may be due to polyethylene quality, assembly design, or a combination of these factors.

Fixation of the tibial component using CMW-1 or Palacos bone cement with gentamicin: similar outcome in a randomized radiostereometric study of 51 total knee arthroplasties

We studied CMW-1 bone cement with gentamicin in the laboratory and in a randomized clinical study. Palacos bone cement containing gentamicin was used as the control. In the preclinical evaluation, the CMW cement had slightly less mechanical strength. In the clinical study, 51 patients (51 knees) operated on with total knee arthroplasty were studied for 2 years. We used radiostereometric analysis to measure migration of the tibial components, randomized to fixation with either of the two types of cement. The extent and pattern of migration were similar in both groups, and we found no differences in the number, size and extent of radiolucent lines or clinical outcome. No complications occurred. Our findings suggest a need for more studies of CMW-1 bone cement containing gentamicin in a larger cohort of patients.

A retrospective clinical and radiographic review of 173 hydroxyapatite-coated screw cups with 5- to 10-year follow-up, showing low revision rates for fixation failure

We reviewed the midterm results of 173 hydroxyapatite-coated screw cups. The average follow-up was 6.5 years (range, 5-9 years). The follow-up rate was 93%. Patients were assessed using the Merle D'Aubigne-Postel clinical scoring scale and by radiographic review. Two patients had revision surgery for recurrent dislocation (1.2%), 3 patients were revised for aseptic loosening (1.7%), 1 patient underwent revision surgery because of deep prosthetic infection (0.6%), and 2 patients were revised for polyethylene wear without loosening (1.2%), which gave a total revision rate of 4.7%. The average postoperative Merle D'Aubigne-Postel scores were 5.7 for pain, 5.5 for range of motion, and 5.4 for function.