A Porteous

Does the joint line matter in revision total knee replacement

We identified 148 patients who had undergone a revision total knee replacement using a single implant system between 1990 and 2000. Of these 18 patients had died, six had developed a peri-prosthetic fracture and ten had incomplete records or radiographs. This left 114 with prospectively-collected radiographs and Bristol knee scores available for study. The height of the joint line before and after revision total knee replacement was measured and classified as either restored to within 5 mm of the pre-operative height or elevated if it was positioned more than 5 mm above the pre-operative height. The joint line was elevated in 41 knees (36%) and restored in 73 (64%). Revision surgery significantly improved the mean Bristol knee score from 41.1 (SD 15.9) pre-operatively to 80.5 (SD 15) post-operatively (p < 0.001). At one year post-operatively both the total Bristol knee score and its functional component were significantly better in the restored group than in the elevated group (p < 0.01). Overall, revision from a unicondylar knee replacement required less use of bone graft, fewer component augments, restored the joint line more often and gave a significantly better total Bristol knee score (p < 0.02) and functional score (p < 0.01) than revision from total knee replacement. Our findings show that restoration of the joint line at revision total knee replacement gives a significantly better result than leaving it unrestored by more than 5 mm. We recommend the greater use of distal femoral augments to help to achieve this goal.

Observed kneeling ability after total, unicompartmental and patellofemoral knee arthroplasty: perception versus reality.

Kneeling is an important function of the knee, but little information is available on ability to kneel after different knee arthroplasty procedures. Previous work has asked patients about their kneeling ability; in this study it was objectively assessed. One hundred and twenty two patients — 38 having had total knee replacement (TKR), 53 unicompartmental knee replacement (UKR), 31 patello-femoral replacement (PFR) — were observed trying to kneel at 90° on a chair, at 90° on the floor, and at 120° on the floor. Only 37% of patients thought they could kneel, whereas 81% were actually able to kneel (p <0.001). Ability to kneel on the chair and on the floor at 90°was significantly better than perceived ability for all prosthesis types (p <0.001). Kneeling at 120° showed no difference between perception and reality except for the PFR group (p <0.05). In all positions, increased range of movement significantly improved kneeling ability (p <0.001). Kneeling ability in men was significantly better than in women (p <0.001). Patient-centred questionnaires do not accurately document kneeling ability after knee arthroplasty.

The Posterior Condylar Offset Ratio.

INTRODUCTION Posterior Condylar Offset is an area of interest in knee arthroplasty research and clinical outcome. The aim of the study is to define a quantifiable Posterior Condylar Offset Ratio, a normal value for this ratio and to confirm its reproducibility on pre-operative radiographs. METHOD We propose a new Posterior Condylar Offset Ratio which is defined as the maximal thickness of the posterior condyle projecting posteriorly to a straight line drawn as the extension of the posterior femoral shaft cortex, divided by the maximal thickness of the posterior condyle projecting posterior to a straight line drawn as the extension of the anterior femoral shaft cortex on a true lateral radiograph of the distal quarter of the femur. We have measured this on 100 true lateral radiographs (50 females, 50 males, and mean age 65 years). RESULTS The mean ratio was 0.44 (SD 0.02) and was shown to have good reproducibility (intra-observer error 0.899 and inter-observer error 0.882. The ratio was also very consistent between male and female patients (0.44 (SD 0.02) for the males and 0.45 (SD 0.02) for the females). Adjusting the ratio for reported posterior condyle articular cartilage thickness increased the ratio to 0.47 (SD 0.02). CONCLUSION We suggest our Posterior Condylar Offset Ratio is a useful tool to aid further research in this area of knee arthroplasty and propose a normal value of 0.44 on radiographs and 0.47 on post-operative knee arthroplasty radiographs.

Measurements of in vivo intra-articular gentamicin levels from antibiotic loaded articulating spacers in revision total knee replacement

Previous in vitro studies have found high levels of antibiotic release in the days immediately following implantation of antibiotic loaded articulating spacers. However there are relatively few data describing the elution profile beyond this immediate period. This study was designed to measure if gentamicin levels continue to be clinically therapeutic after an extended period following in vivo implantation. Twelve patients received a gentamicin loaded articulating spacer between a 1st and 2nd stage revision total knee arthroplasty. At the 2nd stage procedure synovial fluid and blood samples were collected and assayed for the presence of gentamicin. The second stage revision occurred at a median of 99 days following spacer insertion. The median intra-articular gentamicin levels were 0.46 mg/L (0.24 to 2.36 mg/L) which would be considered therapeutic. There were no cases of reinfection. In this study, preformed articulating spacers containing gentamicin provided therapeutic concentrations in the synovial fluid surrounding the joint throughout the period of implantation. These data confirm the observations from in vitro studies, where a prolonged elution profile was observed for such spacers.

Long-term (ten- to 15-year) outcome of arthroscopically assisted Elmslie-Trillat tibial tubercle osteotomy

We present the ten- to 15-year follow-up of 31 patients (34 knees), who underwent an Elmslie-Trillat tibial tubercle osteotomy for chronic, severe patellar instability, unresponsive to non-operative treatment. The mean age of the patients at the time of surgery was 31 years (18 to 46) and they were reviewed post-operatively, at four years (2 to 8) and then at 12 years (10 to 15). All patients had pre-operative knee radiographs and Cox and Insall knee scores. Superolateral portal arthroscopy was performed per-operatively to document chondral damage and after the osteotomy to assess the stability of the patellofemoral joint. A total of 28 knees (82%) had a varying degree of damage to the articular surface. At final follow-up 25 patients (28 knees) were available for review and underwent clinical examination, radiographs of the knee, and Cox and Insall scoring. Six patients who had no arthroscopic chondral abnormality showed no or only early signs of osteoarthritis on final radiographs; while 12 patients with lower grade chondral damage (grade 1 to 2) showed early to moderate signs of osteoarthritis and six out of ten knees with higher grade chondral damage (grade 3 to 4) showed marked evidence of osteoarthritis; four of these had undergone a knee replacement. In the 22 patients (24 knees) with complete follow-up, 19 knees (79.2%) were reported to have a good or excellent outcome at four years, while 15 knees (62.5%) were reported to have the same at long-term follow-up. The functional and radiological results show that the extent of pre-operatively sustained chondral damage is directly related to the subsequent development of patellofemoral osteoarthritis.

Do long leg supine CT scanograms correlate with weight-bearing full-length radiographs to measure lower limb coronal alignment?

INTRODUCTION The gold standard for measuring knee alignment is the lower limb mechanical axis (MA) using weight-bearing lower limb full-length x-ray (FLX). However, CT scanograms (CTS) are becoming increasingly popular in view of lower radiation exposure, speed of data acquisition and supine positioning. We compared the correlation and degree of agreement of knee joint coronal alignment using these two imaging modalities. METHOD From our series of complex primary and revision knee arthroplasty patients, we selected those with both FLX and CTS recorded onto digital PACS. The coronal alignments were assessed in 24 knees and the valgus/varus angles relative to the MA were measured. Results were analysed statistically using the paired samples t-test, Pearsons correlation coefficient, intra-class correlation coefficient, Cohens kappa and Passing and Bablok regression to assess potential equality of methods. RESULTS The mean MA was 180.5° (165°-200°) for the CTS and 181° (164°-202°) for the FLX. The CTS MA angle data between the assessors were highly correlated (r=0.971, p <0.001) as were FLX MA angle measurements (r=0.988, p <0.001). 41.7% of the CTS and 37.5% of the FLX were in varus alignment, while 50% of the CTS and 43.8% of the FLX were in valgus alignment. Malalignment >5° was revealed by 18.8% of the CTS and 35.4% of the FLX. CONCLUSION Overall, good agreement was observed in MA angle data between the two imaging modalities, but reproducibility may be problematic. In the malaligned limb, weight-bearing FLX still remains a vital imaging modality. CTS should be used with caution in view of the under-detection of malalignment.

Fixed bearing lateral unicompartmental knee arthroplasty—Short to midterm survivorship and knee scores for 101 prostheses

BACKGROUND Isolated unicompartmental knee arthritis is less common laterally than medially. Lateral unicompartmental knee arthroplasty (UKA) constitutes only 1% of all knee arthroplasty performed. Use of medial UKA is supported by several published series showing good long-term survivorship and patient satisfaction, in large patient cohorts. Results of lateral UKA however have been mixed. We present the short and mid-term survivorship and 5-year clinical outcome of 101 lateral UKAs using a single prosthesis. METHODS Over a 9 year period, 100 patients who satisfied inclusion criteria underwent a lateral fixed-bearing unicompartmental arthroplasty. American Knee Society (AKSS), Oxford Knee (OKS) and modified Western Ontario McMaster Universities Arthritis Index (WOMAC) scores were completed preoperatively and at 1, 2 and 5 years postoperatively. Kaplan-Meier survival analysis was used to determine the 2-year and 5-year survivorship, using revision for any cause as end point. RESULTS Survivorship was 98.7% and 95.5% at 2 and 5 years respectively. 1 knee was revised for subsidence of the tibial component and 1 knee for progression of medial compartment osteoarthritis. Of a possible 35 knees in situ at 5 year follow-up, 33 knees were fully scored. Median AKSS, OKS and modified WOMAC scores were 182, 41, and 16 respectively. CONCLUSIONS The mid-term survivorship and outcome scores at 5-years suggest that lateral unicompartmental knee arthroplasty provides a valuable alternative to total joint replacement in selected patients with isolated lateral tibio-femoral arthritis at mid-term follow-up. Level II evidence.

A comparison of patient based outcome following knee arthrodesis for failed total knee arthroplasty and revision knee arthroplasty

Arthrodesis of the knee is an infrequently performed operation perceived by both patient and surgeon to have a poor outcome. This study compares functional outcome of knee arthrodesis following failed primary arthroplasty with that of revision knee arthroplasty in a matched patient group. Outcome was measured using the SF12 and Oxford Knee Score. Twelve patients underwent arthrodesis, of which eight were available for functional review at a mean of 53 months. No significant difference was found between the outcome scores of the two groups, although it is recognised that the numbers involved were low. Arthrodesis of the knee may be considered as a surgical option following failed arthroplasty when factors are present that may mitigate against an optimal result following revision knee arthroplasty.

Minimally invasive total knee arthroplasty; a pragmatic randomised controlled trial reporting outcomes up to 2 year follow up.

BACKGROUND We present a prospective, randomised, multi-surgeon, controlled trial comparing minimally invasive (MIS) and standard approach total knee arthroplasty (TKA). METHODS Participants underwent unilateral TKA. Patients were randomised to Bristol, quadriceps sparing MIS or standard medial parapatellar approaches. Length of stay with secondary outcome measures including knee range of movement, Oxford Knee Score (OKS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and American Knee Society Score (KSS) up to 2 years. Radiographic and post operative assessment was blinded. RESULTS 86 patients (92 knees) participated in the study. Mean operative time between MIS and control groups was 95.5 (95% CI 90.0-101.0) and 94.8 (95% CI 88.2-101.4) minutes respectively. Mean readiness for discharge was shorter in the MIS group 4.5±1.5 (95% CI, 4.1-4.9) days versus 5.9±2.7 (95% CI, 5.1-6.7) days amongst controls (p=0.004). Patients in the MIS group had fewer complications (p=0.003). One patient developed a deep vein thrombosis (DVT) and one required revision surgery, both in the control group. 83 patients completed follow up to 2 years (40 MIS, 43 controls). Range of movement and other outcome measures improved up to 1 year post-operatively with no statistically significant differences between MIS and controls. We found no evidence of radiographic loosening in either group at the 2 year follow up. CONCLUSIONS MIS offers reduced length of stay and fewer complications for patients following TKR without evidence of component mal-alignment. Our findings of fewer systemic complications in MIS TKR patients warrant further future study. LEVEL OF EVIDENCE Level 1.

Revision of isolated patellofemoral arthroplasty to total knee replacement

Background Patellofemoral arthroplasty is becoming an established treatment for isolated patellofemoral arthritis. Revision to total knee replacement occasionally is required. Lessons learned from patients requiring revision surgery and their subsequent post-revision outcomes are described. Method This study reviewed 49 patellofemoral arthroplasties in 43 patients who had revision to a total knee replacement. These cases were obtained from a cohort of 487 patellofemoral arthroplasties prospectively reviewed between 1989 and 2006. Results The most common reason for revision was progression of arthritis in the tibiofemoral joint (30 knees in 26 patients). Persistent pain from technical error was found in 11 knees (10 patients), and 4 knees in 4 patients had unexplained persistent pain. The revision procedure was straightforward with no technical difficulties. All patients had a primary cemented total knee replacement without requiring bone grafting or prosthetic augmentation. The patients reported significant improvements in the Oxford Knee Score (26/48 points) P = 0.003 and the Bristol Pain Score (25/40 points) P = 0.0001 compared with the scores before patellofemoral arthroplasty. The outcomes were less favorable than expected and were worse than those seen after a successful primary patellofemoral arthroplasty. Conclusion Reasons for patellofemoral arthroplasty failure were identified. Patellofemoral arthroplasty was easy to revise to a primary knee arthroplasty; however, good clinical results could not be guaranteed. These results emphasize the need for careful patient selection and precise surgical technique during the primary operation.