The measurement of patellar height: a review of the methods of imaging

Many radiographic techniques have been described for measuring patellar height. They can be divided into two groups: those that relate the position of the patella to the femur (direct) and those that relate it to the tibia (indirect). This article looks at the methods that have been described, the logic behind their conception and the critical analyses that have been performed to test them.

The management of patients with painful total knee replacement

The management of patients with a painful total knee replacement requires careful assessment and a stepwise approach in order to diagnose the underlying pathology accurately. The management should include a multidisciplinary approach to the patient's pain as well as addressing the underlying aetiology. Pain should be treated with appropriate analgesia, according to the analgesic ladder of the World Health Organisation. Special measures should be taken to identify and to treat any neuropathic pain. There are a number of intrinsic and extrinsic causes of a painful knee replacement which should be identified and treated early. Patients with unexplained pain and without any recognised pathology should be treated conservatively since they may improve over a period of time and rarely do so after a revision operation.

Evaluation of patients with a painful total knee replacement

Evaluation of patients with painful total knee replacement requires a thorough clinical examination and relevant investigations in order to reach a diagnosis. Awareness of the common and uncommon problems leading to painful total knee replacement is useful in the diagnostic approach. This review article aims to act as a guide to the evaluation of patients with painful total knee replacement.

Bone bruising of the knee

Bone bruising demonstrated by MRI is discussed with histological findings and proposed classifications. The effects of the mechanism of injury on bone bruising at the knee and the natural history of the process are reviewed. The relationship of bone bruising to osteochondral sequelae and to osteoarthritis are considered.

Patellar height measurement in trochlear dysplasia

A number of measurements of patellar height are in clinical use all of which reference from the tibia. The patellotrochlear index (PTI) has been proposed recently as a more accurate reflection of the functional height of the patella and described in normal knees. We compared patellar height measurements in patients with patellofemoral dysplasia. In a retrospective analysis of the MRI scans of 33 knees in 29 patients with patellofemoral dysplasia we assessed the inter- and intraobserver reliability of four patellar height measurements: the recently described PTI, Insall-Salvati (IS), Blackburne-Peel (BP) and Caton-Deschamps (CD) ratios. We also assessed the correlation between the different measurements in predicting patella alta. Three blinded observers on two separate occasions performed the measurements. There were 21 females and 8 males with a median age of 21 years (range 13-33). Statistical analysis revealed good inter-observer reliability for all measurements (0.78 for PTI, 0.78 for IS, 0.73 for BP and 0.77 for CD). Intra-observer reliability was also good (0.80, 0.83, 0.75 and 0.78, respectively). There was weak correlation between the PTI and the other ratios for patella alta. There was a strong correlation between the CD and BP ratios (0.96) and a moderate correlation between IS and CD and IS and BP ratios (0.594 and 0.539, respectively). We propose the PTI as a more clinically relevant measure than the IS, CD and BP ratios.

Adolescent patellar instability

Patellar instability most frequently presents during adolescence. Congenital and infantile dislocation of the patella is a distinct entity from adolescent instability and measurable abnormalities may be present at birth. In the normal patellofemoral joint an increase in quadriceps angle and patellar height are matched by an increase in trochlear depth as the joint matures. Adolescent instability may herald a lifelong condition leading to chronic disability and arthritis.

Restoring normal anatomy by trochleoplasty, tibial tubercle transfer or medial patellofemoral ligament (MPFL) reconstruction in the young adult prevents further instability. Although these techniques are proven in the young adult, they may cause growth arrest and deformity where the physis is open. A vigorous non-operative strategy may permit delay of surgery until growth is complete. Where non-operative treatment has failed a modified MPFL reconstruction may be performed to maintain stability until physeal closure permits anatomical reconstruction. If significant growth remains an extraosseous reconstruction of the MPFL may impart the lowest risk to the physis. If minor growth remains image intensifier guided placement of femoral intraosseous fixation may impart a small, but acceptable, risk to the physis.

This paper presents and discusses the literature relating to adolescent instability and provides a framework for management of these patients.

Cite this article: Bone Joint J 2017;99-B:159–70.

The outcome of all-inside meniscal repair with relation to previous anterior cruciate ligament reconstruction

BACKGROUND

Arthroscopically assisted all-inside meniscal repair has become a popular treatment for meniscal tears. Previous studies have suggested a beneficial effect of concomitant anterior cruciate ligament reconstruction on meniscal repair outcomes. The effect of prior cruciate ligament reconstruction (predating the meniscal injury) on meniscal repair success is unreported. The aim of this study was to assess the success of meniscal repair in our practice. Further aims were to analyze the effect of concomitant- and past-anterior cruciate ligament reconstruction on meniscal repair outcomes.

METHODS

Retrospective review of all patients undergoing arthroscopic meniscal repair during a 53 month period was performed. Mean followup was 13.5 months (mean 6-50). The primary outcome measure was meniscal reoperation.

RESULTS

Sixteen of 104 patients required reoperation, giving an overall meniscal repair success rate of 85%. Patients undergoing concomitant anterior cruciate ligament reconstruction enjoyed significantly improved outcomes (91%, p=0.049), while those with a past history of anterior cruciate ligament reconstruction had significantly worse meniscal repair success rates (63%, p=0.016).

CONCLUSIONS

Arthroscopic meniscal repair in a selected patient group offers good success rates, especially when performed with concomitant anterior cruciate ligament reconstruction. We have identified a subgroup of patients, those with a past history of anterior cruciate ligament reconstruction predating the meniscal injury, who appear to have relatively poor outcomes from meniscal repair. Potential reasons for this finding are discussed.

LEVEL OF EVIDENCE

Level IV, case series.

Reliability of radiographic measurements of knee motion following knee arthroplasty for use in a virtual knee clinic

INTRODUCTION

We sought to validate radiographic measurements of range of motion of the knee after arthroplasty as part of a new system of virtual clinics.

METHODS

The range of motion of 52 knees in 45 patients was obtained by 2 clinicians using standardised techniques and goniometers. Inter-rater reliability and intraclass correlation coefficients (ICCs) were calculated. Radiographs of these patients' knees in full active flexion and extension were also used to calculate intra and inter-rater reliability compared with clinical measurements using four different methods for plotting angles on the radiographs.

RESULTS

The ICC for inter-rater reliability using the goniometer was very high. The ICC was 0.91 in extension and 0.85 in flexion while repeatability was 8.49° (-8.03-8.99°) in extension and 5.23° (-4.54-5.74°) in flexion. The best ICC for radiographic measurement in extension was 0.86, indicating 'near perfect' agreement, and repeatability was 5.43° (-4.04- 6.12°). The best ICC in flexion was 0.95 and repeatability was 5.82° (-3.38-6.55°). The ICC for intrarater reliability was 0.98 for extension and 0.99 for flexion on radiographic measurements.

CONCLUSIONS

Validating the use of radiographs to reliably measure range of motion following knee arthroplasty has allowed us to set up a 'virtual knee clinic'. Combining validated questionnaires and radiographic measurement of range of motion, we aim to maintain high quality patient surveillance following knee arthroplasty, reduce our ratio for new to follow-up patients in line with Department of Health guidelines and improve patient satisfaction through reduced travel to hospital outpatients.