HAUGH, PE

JOHNSTON, AF

Kernohan, George

MOLLAN, RAB

TRAINOR, BP

English

Hip dislocation remains the most significant childhood orthopaedic abnormality despite the efforts of neonatal screening, first described in 1910. A new method of enhancing the performance of screening, the Belfast hip screener, is a non-invasive device developed to detect and interpret the vibrations (''clicks'' and ``clunks'') which are emitted as the hips are physically tested A progress report is presented covering ten years' work from early records made with tape recorders to modern methods of digital signal processing

Ulster University's Research Portal

The Ulster Medical Journal, Volume 61, No. 2, pp. 151 - 156, October 1992.The Belfast hip screener:from infancy to maturityW G Kernohan, Bernadette P Trainor, Pauline E Haugh,Adrienne F Johnston, R A B MollanAccepted 21 September 1992.SUMMARYHip dislocation remains the most significant childhood orthopaedic abnormalitydespite the efforts of neonatal screening, first described in 1910. A new methodof enhancing the performance of screening, the Belfast hip screener, is a non -invasive device developed to detect and interpret the vibrations ("clicks" and"clunks") which are emitted as the hips are physically tested. A progress report ispresented covering ten years' work from early records made with tape recordersto modern methods of digital signal processing.INTRODUCTIONDevelopmental dislocation of the hip is a term covering a spectrum of childhoodhip disease ranging from instability at birth to established dislocation. In NorthernIreland the disease affects two infants per thousand live births, though theincidence varies with sex, family history and environmental factors such asposture in utero, delivery, and nursing habits.1, 2, 3 Formerly called 'congenital',this term should be dropped from common usage as it excludes the possibility oflate development.4,5 In developmental hip dislocation the head of the femur, whilereducible is unstable, or it lies outside its normal position which is within theacetabulum. Early detection and immediate treatment of the condition in anabduction splint generally result in normal development without admission tohospital.1' 6 However, almost 50% of cases present late (beyond three monthsof age), necessitating extensive treatment, including traction and repeatedsurgical intervention, which does not guarantee a successful outcome.7The distinguished French orthopaedic surgeon Dr Pierre le Damany was amongthe first to describe a physical test to achieve early diagnosis.8 He developed theclinical examination of the neonatal hip by two manoeuvres. The first was simplyDepartment of Orthopaedic Surgery, The Queen's University of Belfast, Musgrave Park Hospital,Belfast BT9 7JB.W G Kernohan, PhD, Lecturer.R A B Mollan, MD, FRCS, FRCSI, Professor of Orthopaedic Surgery.Musgrave Park Hospital, Belfast BT9 7JB.Bernadette P Trainor, SRN, Research Staff Nurse.Pauline E Haugh, SRN, Research Staff Nurse.Adrienne F Johnston, RGN, Research Staff Nurse.Correspondence to Dr Kernohan.© The Ulster Medical Society,152 The Ulster Medical Journala modification of the 'telescoping' manipulation in which the femur is movedalong its length without rotation. The second described the exact placing ofthe examining hand and the stabilisation of the pelvis, as well as the control of thegreater trochanter by the middle finger, while the femoral head was gently liftedin an out of the acetabulum (Figs 1, 2). Notice his emphasis on positioning andthe description of a "ressaut" (spring-back) when the hip reduces. In 1935Ortolani9 devised a similar test to detect dislocated hips noting audible andpalpable vibration events during testing. Barlow,10 in 1962 amended thismanoeuvre so that those hips that dislocate can be detected, though, in fact, headded little to the tests described by le Damany.Fig 1. Position des mains de l'operateur etposition de l'enfant dans la recherche de lahanche subluxable (le Damany, 1910).-~~~~Zi7)~~~~~~~~~ZFig 2. En portant la cuisse dans la position deflexion - abduction, la subluxation se reduit avecun ressaut (le Damany, 1910).PILOT STUDIESThe use of miniature accelerometers to detect neonatal hip vibration duringscreening for developmental dislocation of the hip has been carried out in Belfastsince 1980.11 The original vibration technique based on analogue amplifiers andtape recording allowed these tests to be analysed in terms of detection andinterpretation. 12 The first trial of the system was carried out on children referred toa research clinic.'3, 14 The study involved selected groups totalling 306 selectedneonates, referred for vibration arthrometry. The largest subset (N = 217), wasalready diagnosed with 'clicky' hips. On testing, a total of over 600 vibrationepisodes were captured for analysis. To be certain of the clinical outcome thechildren underwent a long follow-up with several attendances over a four yearperiod. Abnormal vibrations indicating instability had a high vibration level withlow frequency. Spurious movements of the hip produced vibration with a lowlevel and low frequency whereas a safe click had a low level of vibration and ahigher frequency. Several infants went on to require treatment. When the recordswere examined retrospectively it was clear that the unstable hips were signalled atbirth by low frequency, high amplitude vibration emissions. The study included agroup of normal, clinically silent, hips, which also produced some vibration duringtesting, though on analysis these were entirely different vibrations. Using vibrationarthrometry it was possible to predict or classify vibration detected from new hips© The Ulster Medical Society, 1992.The Belfast hip screenerwith unknown pathology. The result of testing this classification system suggesteda sensitivity of 75%, a specificity of 99%, a positive predictive value of 86% anda negative predictive value of 99% (p < 0 005). The technique of vibrationarthrometry was proposed not only to facilitate hip screening, but also to assistwith careful monitoring of clicky hips. The results of the trial permitted the Belfasthip screener to be updated, giving a preliminary diagnosis of hip disorders at thetime of testing.The analogue system of recording vibrations in developmental dislocation of thehip with its separate recording and later lab-based analysis stage, was a usefulone for basic work and provided flexibility. However, it became clear that a moreconvenient and portable system would have advantages, particularly for lesscomputer - literate users. One of the first attempts to reduce the system complexityinvolved a modified Apple microcomputer, which was programmed to record hipvibrations digitally during testing.'5'16 The computer then acted both as a vibrationdatalogger and as an analyser. There were three phases of the software: capture,display and analysis. This system has come to be known as the Belfast hipscreener and has allowed larger trials to be performed.POPULATION STUDIESA large-scale trial of vibration arthrometry for hip screening was carried out on agroup of 3000 cases during December 1984 - December 1985 with finalfollow - up from 1988 to 1990. The aim was to evaluate the potential of vibrationarthrometry in early detection of developmental dislocation of the hip on arepresentative group of neonates chosen at random from five maternity hospitalsserving counties Antrim, Down and Tyrone. Since significant hardware develop -ment took place during the trial, not all vibrations were recorded in the samefashion. The initial 500 cases were recorded on analogue reel - to - reel tape. 17 Themethod proved valuable as it was possible to elicit vibration events from approx -imately one quarter of all the hips tested; vibrations were recorded from somenormal hips, from all "clicky" hips, and from all unstable hips. The vibrations weremeasured and the differences between normal and "clicky" hips were statisticallysignificant. The remainder have been categorised and detailed analysis isunderway.After further development of the computerised system, a clinical study of 300neonates focused on the ability to detect hip vibration manually in a comparativestudy of vibration arthrometry with existing maternity screening practice. Overhalf (185) produced hip vibration during testing, including several cases who laterreceived treatment. This random study of babies showed the value of vibrationarthrometry in early detection of developmental dislocation of the hip, as veryfew hip vibrations (7%) were found by routine examination by a doctor. Anexperienced examiner, the research nurse, recorded 86% of the vibrations usingthe method of vibration arthrometry. It was concluded that objective screening byvibration arthrometry would detect a higher proportion of vibration events inneonates, during the early stages of developmental dislocation of the hip.DISCUSSIONMore widespread implementation of vibration arthrometry using this hip screenerwould warrant an economic appraisal. Twelve patients, who had recently received© The Ulster Medical Society, 1992.153The Ulster Medical Journalhip replacement surgery as a result of late diagnosis of developmental dislocationwere reviewed, and all their costs were identified, although no estimates wereincluded for the pain and suffering endured by the patients.18 We estimate thatscreening with the Belfast hip screener would be successful if it were able to raisethe detection of developmental dislocation of the hip at birth from 50%, as atpresent, to 63%, with additional screening using ten teams of nurses examiningevery neonate in Northern Ireland.Changes and improvements in treatment over the years, particularly antibiotictherapy, have reduced the hospital stay needed for corrective procedures.Therefore a study of the cost of treatment in a more recent cohort of cases ofdevelopmental dislocation of the hip was undertaken.19 The potential cost.-savingof screening, by examining the costs in 36 late cases born in 1980, was found tobe £6,674 per case. This included all the costs of treatment up to 1991. Whiletreatment costs have fallen, significant savings are still possible is cases aredetected early because the cost of treatment in a nappy splint amounts to just£150. Of course, there are less quantifiable costs for the individuals diagnosedlate; principally the lifetime pain and suffering resulting from failure to diagnose,but also loss of earnings.The use of vibration arthrometry in practice depends on the method of discrimin-ation, the ability to distinguish normal from abnormal. Decision analysis hasbeen used to provide a discriminant method based on prior studies and this hasbeen incorporated into the computer programme.20 Furthermore the techniqueFig 3. Vibration arthrometry is used in early detection of dislocated and dislocatable hips by recordingand analysing vibrations produced during testing of the hip. The nurse is seen operating the Belfasthip screener.© The Ulster Medical Society, 1992.154The Belfast hip screener 155depends on careful, reproducible expert manipulation of the neonatal hip, andcurrent work has introduced additional sensors to measure applied force, angles,and displacement of the hip during testing. In this way the execution of the hiptest can be monitored and standardised. Increased reproducibility amongst ourpopulation of responsible examiners will follow.In order that more extensive clinical trials may be performed, the Belfast hipscreener was redesigned (Fig 3) to meet British Standards (BS5724) and thiswas possible only with commercial support from the local electronics industry(Systems Solutions Ltd., 75 Belfast Road, Carrickfergus, N. Ireland). Eventuallythe benefits of this form of screening may be made widely available, and amarketing strategy devised in an attempt to achieve an early diagnosis of neonatalhip dislocation beyond the confines of Musgrave Park Hospital. Developmentaldislocation of the hip is one of the biggest problems in paediatric orthopaedics.Without doubt, vibration arthrometry is not the complete solution, but thereis evidence that important new information has become available using thetechnique. This has gained international recognition, and economic analysis hasfurther shown that it may be implemented at little or no cost to the national healthservice.REFERENCES1. Bennett JT, MacEwen GD. Congenital dislocation of the hip. Recent advances and currentproblems. Clin Orthop 1989; 247: 15-21.2. Burke SW, Macey TI, Roberts JM, Johnston Ill C. Congenital dislocation of the hip in theAmerican Black. Clin Orthop 1985; 192: 120-3.3. Crossan JF, Wynne -Davies R. Research for genetic and environmental factors in orthopaedicdiseases. Clin Orthop 1986; 210: 97-105.4. Ilfeld FW, Westin GW, Makin M. Missed or developmental dislocation of the hip. Clin Orthop1986; 203: 276-81.5. Klisic PJ. Congenital dislocation of the hip - a misleading term: brief report. J Bone Joint Surg1989; 71B: 136.6. Morrissy RT, Cowie GH. Congenital dislocation of the hip. Clin Orthop 1987; 222: 79-84.7. Catford JC, Bennet GC, Wilkinson JA. Congenital hip dislocation: an increasing and stilluncontrolled disability? Br Med J 1982; 285: 1527-30.8. le Damany P. La luxation congenitale de la hanche. Paris: Felix Alcan, 1912.9. Ortolani M. Un segno poco noto e sua importanza per la diagnosi precoce di prelussazionecongenita dell'anca. Pediatria 1937; 45: 129-36.10. Barlow TG. Early diagnosis and treatment of congenital dislocation of the hip. J Bone Joint Surg1962; 44B: 292-301.11. Cowie GH, Mollan RAB, Kernohan WG, Bogues BA. Vibration emission in detecting congenitaldislocation of the hip. Orthop Rev 1984; 13: 30.5.12. Cowie GH, Bogues BA, Kernohan WG, Mollan RAB. A new aid in the diagnosis of congenitaldislocation of the hip. J Bone Joint Surg 1983; 65B: 656.13. Kernohan WG, Cowie GH, Patterson CC, Mollan RAB. Discriminating between innocent clicksand clunks due to dislocation of the neonatal hip. In: Societe Internationale de RechercheOrthopedique et de Traumatologie, Munich, 1987.14. Kernohan WG, Cowie GH, Mollan RAB. Vibration arthrometry in congenital dislocation of thehip. Clin Orthop 1991; 272: 167-74.© The Ulster Medical Society, 1992.156 The Ulster Medical Journal15. Shaw SN, Kernohan WG, Bogues BA, Mollan RAB. An Apple - based screening aid for congenitaldislocation of the hip. Proc Med Microcomput Appl. Liverpool: University Press, 1985: 23*4.16. Shaw SN, Kernohan WG, Mollan RAB. The development of a screening aid for congenitaldislocation of the hip. In: Technology in health care. Byford GH (ed). Biological EngineeringSociety, London, 1985: 107-8.17. Kernohan WG, Trainor BP, Nugent GEM, Walker PE, Timoney M, Mollan RAB. Low frequencyvibration emitted from unstable hip in human neonate. Clin Orthop (In press).18. Kernohan WG, Trainor BP, Mollan RAB, Normand CEM. Cost - benefit appraisal of screening forcongenital dislocation of the hip. J Management in Med 1990; 4: 230 - 5.19. Kernohan WG, Trainor BP, Mollan RAB, Normand CEM. Cost of treatment of congenitaldislocation of the hip. Int J Health Plan Man 1991; 6: 229 - 33.20. Kernohan WG, Patterson CC, Mollan RAB. Discriminant analysis applied to orthopaedics.In: Applications of Statistics in Medicine, Institute of Mathematics and its Applications, Cardiff1988..©B The Ulster Medical Society, 1992.

THE BELFAST HIP SCREENER - FROM INFANCY TO MATURITY

https://pure.ulster.ac.uk/ws/files/11713052/ulstermedj00075-0030.pdf

THE BELFAST HIP SCREENER - FROM INFANCY TO MATURITY

Abstract

Similar works

Full text

Available Versions

Ulster University's Research Portal