Articular cartilage of the posterior condyle can affect rotational alignment in total knee arthroplasty

Purpose

Rotational alignment is important for patellar tracking, ligament balance, and tibiofemoral congruity after total knee arthroplasty (TKA). The posterior condylar axis is often referred to as a rotational alignment landmark. However, articular cartilage wear localized only in the medial condyle might affect the accuracy of rotation, because surgical planning based on CT does not consider the cartilage thickness. The purpose of this study was to clarify whether the cartilage thickness of the posterior condyle affects rotational alignment after TKA.

Methods

A total of 40 osteoarthritis patients waiting for TKA were recruited. MRI of axial sections was performed preoperatively. Scans were controlled to make the cross section perpendicular to the mechanical axis of the femur on the coronal plane and to the tangent line of the distal femur on the sagittal plane, so that the surgical section of the actual femur could be simulated. The condylar twist angle (CTA) was measured with and without articular cartilage. The cartilage thickness on the medial and lateral posterior condyles was surveyed in both MRI images and surgical specimens.

Results

The CTA without cartilage (6.8?±?2.0°) was significantly larger than the CTA with cartilage (5.2?±?2.0°) (P?Conclusions Surgical planning for TKA not considering articular cartilage might lead to the externally rotated malposition of the femoral implant.

Level of evidence

II.     

Patella baja after unicompartmental knee arthroplasty

Purpose

The literature data on patellar height following unicompartmental knee arthroplasty (UKA) are scarce.

Methods

A total of 41 knee joints in 37 patients after UKA were prospectively evaluated for patellar height by using the Insall–Salvati and modified Insall–Salvati ratio. Patellar height was measured preoperatively, postoperatively, at 6, 12?weeks, and, at 1?year postoperatively. Patients were categorized according to age, gender, operated side, and rehabilitation program.

Results

Regarding all the patients, the Insall–Salvati ratio demonstrated a significant decrease only for the time period “postoperatively–1?year postoperatively”, whereas the modified Insall–Salvati ratio showed a significant decrease only for the period “preoperatively–postoperatively”. The Insall–Salvati ratio showed a significant decrease in the patellar height of men and left knees, whereas the modified Insall–Salvati ratio revealed a significant decrease in patients older than 65?years and those who followed a specific rehabilitation program.

Conclusions

The decrease in the patellar height after UKA occurs within the first postoperative year. Women, right knees, patients younger than 65?years and those who do not follow a specific rehabilitation program are less prone to decrease in the patellar height; ratio-specific differences are evident for each subgroup.

Level of evidence

Diagnostic study, Level III.     

Severe metallosis after unicompartmental knee arthroplasty

We report on a case of a patient who had femoral osteolysis and severe metallosis of the knee joint resulting from the secondary abrasive wear of the metal-backed tibial component of a unicompartmental knee arthroplasty due to massive wear of tibial polyethylene. The failure was diagnosed 11 years after implantation. This metallosis affected the intra-articular tissues and the subchondral bone.     

Proprioception after bicruciate-retaining total knee arthroplasty is comparable to unicompartmental knee arthroplasty

Purpose

Rising expectations in functional performance of total knee joints are inciting further improvement of knee arthroplasty implants. From a patient-centred view, bicruciate-retaining models provide a more natural feeling knee. However, there is no evidence of functional advantage for these implants. The aim of this study was to evaluate balance ability as a measure of proprioception in patients with a bicruciate-retaining total knee arthroplasty.

Methods

A prospective, controlled trial was conducted to compare balance ability in 60 patients after arthroplasty of the knee for osteoarthritis. We compared patients with a bicruciate-retaining knee arthroplasty (BCR group) to a control group of patients with a medial unicompartmental knee arthroplasty (UKA group) and another control group of patients with a posterior stabilized total knee arthroplasty (PS group). The patient population comprised 30 women (50.0 %) and 30 men in three cohorts of 20 each. The mean age was 62.1 ± 8.0 years (range 43–78). Patients were evaluated preoperatively and 9 months post-operatively. The evaluation included clinical, radiological, and balance testing—a single-leg stance with eyes closed compared to eyes open. The difference in area of sway between eyes closed and eyes open represents static balance ability after knee arthroplasty.

Results

Perioperative data showed that there was no intra-operative fracture of the intercondylar eminence. There was a decreased post-operative knee extension 9 months post-operative in the BCR group, which was not clinically relevant in any case. We recorded a lower difference in the area of sway between eyes closed and eyes open (ΔA _(ec–eo)) for the BCR group (p = 0.01) and the UKA group (p = 0.04) compared to the PS group.

Conclusions

This study found superior static balance ability after preservation of both cruciate ligaments in arthroplasty of the knee, indicating superior proprioceptive function. Hence, BCR implants could provide improved functional properties. Superior proprioceptive function of bicruciate-retaining implants can be an important factor in implant selection. Further prospective, randomized studies to investigate kinematics and long-term survivorship of bicruciate-retaining implants are needed.

Level of evidence

II.

     

Anterior cruciate ligament reconstruction after unicompartmental knee arthroplasty

Purpose  

ACL deficiency may cause abnormal knee kinematics and is associated with a tenfold increase in surgical failures after unicompartmental knee arthroplasty, such as aseptic loosening of the tibial compartment and medial bearing instability. The current investigators hypothesized that in a knee with UKA, single-bundle ACL reconstruction would restore tibiofemoral translation to levels similar to those of the intact ACL.     

Overstuffed medial compartment after mobile-bearing unicompartmental knee arthroplasty

Overstuffing of the medial compartment in medial compartmental knee arthroplasty is a known pitfall. Attention to the flexion-extension gap should be addressed. If, however, overstuffing is found it can be corrected by revising the femoral component only.     

Magnetic resonance imaging of the knee after medial unicompartmental arthroplasty

Objective

We evaluated safety and potential diagnostic value of magnetic resonance (MR) imaging of the knee treated with medial unicompartmental arthroplasty (MUA).

Methods

The treated knee of 8 patients who underwent MUA was studied with four different 1.5-T MR sequences. Two radiologists independently evaluated eleven anatomical items using a score from 0 (not assessable) to 3 (completely assessable). The sum of the scores for each sequence was divided by the potential maximal sum, obtaining a percentage visibility index (PVI) for each item.

Results

No adverse effect was reported during or within 30 min after the exam. Posterior cruciate ligament was unseen in all patients by both observers. The following PVIs were reported for the remaining ten items: femoral–patellar relationship 83–100%; femoral–patellar cartilage 92–100%; Hoffa's fat pad 75–92%; patellar ligament 79–100%; lateral meniscus 100%; femoral–tibial lateral joint 100%; lateral collateral ligament 96–100%; anterior cruciate ligament 54–83%; femoral–tibial lateral cartilages 92–100%; posterolateral corner 100%. Agreement between readers was found in 331/352 (94%) evaluations (k = 0.74–0.78).

Conclusions

MR imaging after MUA offers a safe and reproducible evaluation of residual knee anatomy except for cruciate ligament, and can be used to follow-up these patients.     

Medial femoral head border is a reliable and reproducible reference for axis determination for femoral component of unicompartmental knee arthroplasty

Purpose

The femoral component should be implanted parallel to the mechanical axis in unicompartmental knee arthroplasty. It was hypothesised that a line between medial femoral condyle centres and medial border of femoral head will be parallel to the mechanical axis; this study set out to examine this hypothesis.

Methods

One hundred X-rays in fifty patients were included for this study. Long-leg standing X-rays including hip and ankle with patellae facing forwards were obtained. On these films, we measured the angle, α, between mechanical axis and the line between the femoral head centre and knee centre (medial mechanical axis), and the angle, β, between the medial mechanical axis and a line between medial femoral condyle and femoral head centre.

Results

The average value of α was 0.1 ± 0.5° and the average value of β 3.0° ± 0.3°. These data indicate that mechanical axis and medial mechanical axis are virtually parallel to each other.

Conclusion

As medial femoral head border is easily identified fluoroscopically, it is a reliable landmark for orientating the femoral component of medial UKA.

Level of evidence

Case series with no comparison group, Level IV.     

Large osteochondral defects of the femoral condyle: press-fit transplantation of the posterior femoral condyle (MEGA-OATS)

BACKGROUND AND AIMS: Large osteochondral defects in the weight-bearing zone of the knee remain a challenging therapeutic problem. Surgical options include drilling, microfracturing, and transplantation of osteochondral plugs but are often insufficient for the treatment of large defects of the femoral condyle. PATIENTS AND METHODS: Large osteochondral defects of the femoral condyle (mean defect size 7.2 cm(2) range 3-20) were treated by transplantation of the autologous posterior femoral condyle. Between 1984 and 2000, 29 patients were operated on: in 22 the medial, in 6 the lateral femoral condyle, and in one the trochlear groove was grafted. Thirteen patients underwent simultaneous high tibial valgus osteotomy. In the first series (1984-1999) the graft was temporarily fixed with a screw ( n=12), but from 1999 we used a newly developed press-fit technique ( n=17) avoiding screw fixation of the graft. The operative technique comprising graft harvest, defect preparation, transplantation, and fixation is described. Patients were clinically evaluated using the Lysholm score, and magnetic resonance imaging with intravenous contrast was performed 6 and 12 weeks after surgery (mean follow-up 17.7 months (range 3-46). RESULTS: Pain and swelling were reduced in 26 patients. Three patients of the first series reported persistent problems and were subjectively not satisfied. The mean Lysholm score rose from preoperatively 52 to 77 points after 3 months, 74 after 6, 88 after 12, and 95 after 18. Magnetic resonance imaging showed good graft viability in all cases. We saw one arthrofibrosis after 6 months but noted no problems related to the loss of the missing posterior condyle. CONCLUSION: Large osteochondral defects of the femoral condyle can be treated by transplantation of the autologous posterior femoral condyle. The use of only one osteochondral piece renders better approximation of the femoral cartilage curvature and thus joint congruence than in mosaic plasty. However, whether loss of the posterior condyle has a long-term negative impact on the knee joint remains to be elucidated.     

Combined unicompartmental knee arthroplasty and anterior cruciate ligament reconstruction

Purpose  

Patients presenting anterior cruciate ligament (ACL) deficiency and isolated osteoarthritis of the medial compartment are treated either with biplanar osteotomy or with total knee arthroplasty (TKA). However, these patients between the forties and fifties are often very active in daily life and feel limited due to their knee. In order to follow the idea of preserving as much as possible from the joint, the concept of unicondylar joint replacement in conjunction with ACL reconstruction has been followed. There seems to be a limited experience with this concept. The purpose of the follow-up study was to evaluate the midterm clinical and functional outcome.     

Osteoarthritis of the patella, lateral femoral condyle and posterior medial femoral condyle correlate with range of motion

Purpose

The type of osteoarthritis and the degree of severity which causes restriction of knee range of motion (ROM) is still largely unknown. The objective of this study was to analyse the location and the degree of cartilage degeneration that affect knee range of motion and the connection, if any, between femorotibial angle (FTA) and knee ROM restriction.

Methods

Four hundreds and fifty-six knees in 230 subjects with knee osteoarthritis undergoing knee arthroplasty were included. Articular surface was divided into eight sections, and cartilage degeneration was evaluated macroscopically during the operation. Cartilage degeneration was classified into four grades based on the degree of exposure of subchondral bone. A Pearson correlation was conducted between FTA and knee flexion angle to determine whether high a degree of FTA caused knee flexion restriction. A logistic regression analysis was also conducted to detect the locations and levels of cartilage degeneration causing knee flexion restriction.

Results

No correlation was found between FTA and flexion angle (r = ?0.08). Flexion angle was not restricted with increasing FTA. Logistic regression analysis showed significant correlation between restricted knee ROM and levels of knee cartilage degeneration in the patella (odds ratio (OR) = 1.77; P = 0.01), the lateral femoral condyle (OR = 1.62; P = 0.03) and the posterior medial femoral condyle (OR = 1.80; P = 0.03).

Conclusion

For clinical relevance, soft tissue release and osteophyte resection around the patella, lateral femoral condyle and posterior medial femoral condyle might be indicated to obtain a higher degree of knee flexion angle.

Level of evidence

Case–control study, Level III.     

The Oxford unicompartmental knee arthroplasty: a radiological perspective

Unicompartmental knee arthroplasty (UKA) is increasingly being performed in both specialist centres as well as district hospitals. The radiologists should be aware of the required preoperative imaging, the normal appearance, and complications of this procedure. Unfortunately, very little is available in the radiology literature. This review aims to provide a radiological perspective to an already widely used procedure.     

Changes in femoral posterior condylar offset and knee flexion after PCL-substituting total knee arthroplasty: comparison of anterior and posterior referencing systems

Purpose

Anterior referencing and posterior referencing are two major techniques for positioning femoral components and balancing the sagittal plane during total knee arthroplasty (TKA). The purpose of this study was to evaluate the changes in medial and lateral posterior condylar offset (PCO) after bilateral TKA using anterior referencing (AR) or posterior referencing (PR) systems and compare the effect of the PCO changes on knee flexion.

Methods

Twenty female patients (mean age, 68.6 years) underwent bilateral TKA using the AR technique in one knee and the PR technique in the contralateral knee. Three-dimensional reconstructed computed tomographic images from the sagittal plane were used to evaluate PCO before and after arthroplasty. Knee Society scores and range of motion were evaluated postoperatively at a mean of 2.9 years.

Results

Postoperative medial and lateral PCOs were significantly greater (p < 0.001 and p = 0.048, respectively) in the AR group (30.9 ± 2.2 and 29.1 ± 1.5 mm, respectively) than those in the PR group (29.1 ± 2.7 and 27.3 ± 2.3 mm, respectively). In addition, the degree of change in the PCO after TKA was greater in the AR group than in the PR group. On the final follow-up, no differences in the degree of knee flexion were observed between the two groups (124.7° for AR and 124.5° for PR). Knee Society scores were similar in the two groups both preoperatively and postoperatively. On the final follow-up, individual changes in the medial and lateral PCO were not associated with changes in the knee flexion angle.

Conclusions

Restoration of PCO after TKA was more accurate with the PR technique than with the AR technique. However, the postoperative differences in PCO showed no correlation with changes in knee flexion 2 years after PCL-substituting TKA.

Level of evidence

Therapeutic study, Level I.

     

Causes of revision following Oxford phase 3 unicompartmental knee arthroplasty

Purpose

Revision of unicompartmental knee arthroplasty (UKA) is relatively rare, but there is concern that the minimally invasive approach might result in more complications and a higher rate of revision. Current data regarding the revision of UKA using the Oxford phase 3 prosthesis are confined to a few reviews of single-institution experience. The purpose of this study was to provide an evidence-based summarisation of the revision of UKA with a pooled analysis of the reported cases.

Methods

A systematic review of published studies that evaluated the causes that required further surgical intervention after UKA using the Oxford phase 3 prosthesis was performed. A structured literature review of multiple databases referenced articles from 1998 to 2012. The revision rates between Asian population and western population were compared.

Results

A total of 2,683 patients (3,138 knees) from 17 published studies were assessed. The median age of the patients was 62.5 (range 32–93) years. The median follow-up period was 5.6 (range 0.1–11) years. Postoperative revision was necessary in 146 knees with a pooled percentage of 4.6 %. Bearing dislocation was found to be the single most important predisposing cause of revision, with a pooled percentage of 1.5 % (47/3,138 knees). The rate of bearing dislocation was significantly higher in Asian population than that in western population (p < 0.001).

Conclusions

Mobile bearing UKA seems to be less appropriate for the Asian population as extreme knee flexion is required for cultural purposes.

Level of evidence

Retrospective case series, Level IV.     

Intraoperative assessment of resected condyle thickness in total knee arthroplasty

Purpose

The purpose of this study was to assess the use of resected condyle thickness measurement, obtained with caliper, when verifying the accuracy of distal femoral bone resection in total knee arthroplasty.

Methods

Fifty-two total knee arthroplasties were performed to treat osteoarthritis with varus knee. The difference of caliper-measured thickness of resected medial and lateral femoral condyles after removal of cartilage from the lateral condyle was compared with radiographically measured values. The preoperative planned valgus cut angles and the postoperative femoral component valgus angles were compared.

Results

The difference of radiograph-measured thickness averaged 2.4 ± 2.2 mm and the difference of caliper-measured thickness averaged 2.0 ± 2.1 mm (r = 0.735, P < 0.001). The postoperative femoral component valgus angle averaged 4.8° ± 1.6° (range, 2.0°–7.6°). The difference between the valgus cut angle and femoral component valgus angle averaged ?0.3° ± 1.5°.

Conclusions

The confirmation of correspondence between the caliper-measured and radiographically measured thickness of resected condyles could verify the accuracy of distal femoral bone resection in total knee arthroplasty.

Level of evidence

III.     

Outpatient surgery for unicompartmental knee arthroplasty is effective and safe

Purpose

There has been increasing interest in accelerated programs for knee arthroplasty. We examined the efficacy and safety of an outpatient surgery (OS) pathway in patients undergoing unicompartmental knee arthroplasty (UKA).

Methods

This case–controlled study evaluates patients operated for UKA in an OS pathway (n = 20) compared to rapid recovery (RR), the current standard (n = 20). We investigated whether patients could be discharged on the day of surgery, resulting in comparable or better outcome by means of adverse events (AEs) in terms of pain (numerical rating scale, NRS), incidences of postoperative nausea and vomiting (PONV) and opiate use (<48 h postoperatively), complication and readmission rates (<3 months postoperatively). Patient-reported outcome measures (PROMS) were obtained preoperatively and 3 months postoperatively.

Results

Postoperative pain (NRS > 5) was the most common reason for prolonged hospital stay in the OS pathway. Eighty-five per cent of the patients were discharged on the day of surgery, whereas 95 % of the patients were discharged on postoperative day 3 in the RR pathway. Overall, median pain scores in both pathways did not exceed a NRS score of 5, without significant differences (RR vs. OS) in the number of patients with PONV (4 vs. 2) and opiate use (11 vs. 9) <48 h postoperatively. At 3 months postoperatively, no significant differences were found for AEs and PROMS between both pathways.

Conclusion

The results of this study illustrates that an OS pathway for UKA is effective and safe with acceptable clinical outcome. Well-established and adequate standardized protocols, inclusion and exclusion criteria and a change in mindset for both the patient and the multidisciplinary team are the key factors for the implementation of an OS pathway.

Level of evidence

Case–control study, Level III.