Pullen v Basildon and Thurrock University Hospitals NHS Foundation Trust

This court is concerned with a claim by Jennifer Pullen who is now 67 years of age, for damages in relation to the injurious consequences of left total hip replacement surgery allegedly performed negligently at the Defendant's Hospital in July 2009.

The Claimant's case in outline is that the acetabular cup for her replacement femur was inadequately fixed, and after becoming loose when she was recovering very shortly after the surgery, it caused her left hip to dislocate anteriorly. Because the dislocation could not be reduced by a closed method under general anaesthetic, a further and disabling operative procedure to replace the prosthetic joint was necessary. Damages have been agreed, subject to liability, in the sum of £37,500 including interest.

The court heard evidence over two days on the liability question, from Mrs Pullen herself, (on a discrete factual issue as to symptoms immediately prior to the dislocation), her husband, the surgeon in question, Mr Hearth, and expert orthopaedic surgeons on both sides, Mr Wilson for the Claimant, and Mr Bamford for the Defendant. The issues were refined, and are now fairly narrow, and therefore it was possible to complete the evidence and submissions within two days. Judgment was reserved and is now provided.

The background to the operative procedure and the subsequent revision treatment is substantially agreed. However it requires a little scrutiny to understand how it is alleged that the Defendant may have fallen below the requisite standard in the performance of the surgery.

Mrs Pullen had a previous history of arthritis in both hips. In fact her right hip had been successfully replaced in 2007. In 2009 she was suffering from recurring problems on the left-hand side causing her significant pain and affecting mobility, and she was referred by her GP, after x-rays showed extensive arthritis, to the Defendant's Hospital, where she was seen on 20^th May 2009 for the first time by Mr Hearth. He noted her to be very overweight, with some leg length discrepancy and spinal stiffness, and in view of the ongoing symptoms and the restriction on activity and mobility, he offered total left hip replacement, putting her on the waiting list. His letter to the GP indicates that he gave advice on the general risks from such surgery, including the risk of post-operative dislocation at 1%, and noted a nickel allergy which meant that the prosthesis required a Corail Pinnacle ceramic on ceramic, in other words there was to be no metal in the artificial ball and socket.

The Claimant was eventually admitted for the hip replacement, having agreed to undergo this procedure, on 31^st July 2009 in the early morning, and she was prepared for surgery in the afternoon. She was recorded as having a BMI of 42, which was categorised as morbidly obese. The anaesthetic was spinal and not general, and thus the Claimant was awake during the procedure. The necessary consent forms were completed which included a more detailed itemisation of the risks. Two of these were dislocation and loosening.

As indicated, Mr Hearth, the surgeon, had chosen a particular type of prosthetic implant, (Corail/ Pinnacle ceramic) and intended to carry out the procedure without cementing or screwing any of the components into bone when securing the fixation. He described the procedure (although he had no individual recollection of the Claimant as a patient) as follows.

First of all, with the patient on her right side, to enable a postero-lateral approach, considered to be the most efficient way of accessing the hip, minimising the muscular section and ensuring early rehabilitation, he made a posterior incision. The sciatic nerve was protected with stay sutures, and the muscles were divided to enable access to the hip joint. It was necessary to dislocate the femur so that the femoral head could be removed with a saw. With the femoral head removed, and the acetabulum exposed, the surgeon was able to make an assessment of the size of acetabular cup to be used. He noted that the Claimant’s skeletal frame was quite small for her size, and having measured the diameter he decided that a 48mm Pinnacle shell, that is the outer shell into which the acetabular insert is fitted, would be appropriate. The outer shell is in fact made of metal, although the insert would be ceramic. This meant that a slightly smaller diameter space was necessary, and at this point the space was prepared to 47mm with the use of a tool known as a reamer. This acts as a kind of cheese grater (as it has been described) to create the shape and size by removal of excess tissue. It is intended that if the shell is marginally larger than the space into which it is to fit, this enables a sufficiently tight bonding, as there is a slight plasticity in the pelvic bones to enable a gripping of the shell when it is put in place.

The court was assisted by a demonstration of one of the surgical tools used, the introducer. It is a metal tool about 20 inches in length which has several functions. First of all, the metal outer shell is screwed on to the end to enable it to be correctly positioned in the acetabulum, now a neatly sized hemisphere, with the surgeon holding and guiding the shell at the other end of the introducer. Once the surgeon is satisfied that the shell is correctly positioned, that is in a slightly anteverted (forward facing) and slightly vertical position, it is banged into place within the acetabulum with a surgical mallet to ensure that it is properly gripped by the bony surround. The ideal angles were described by the expert for the Claimant, Mr Wilson, as 10% and 35 to 40% respectively, and this appears to have been agreed by all. The introducer assisted in determining the angle because of its long stem.

At this stage, an important test is performed. It is known as the fixation test and is intended to ensure that the hemispherical cup is securely in place in the acetabulum and will not move when subjected to the kind of forces which the hip joint would create. With the end of the introducer still screwed into the cup, and the surgeon holding the handle end, it is moved from side to side to allow the pelvic bones and the connective tissue to move in conjunction. This enables the surgeon to determine whether the cup remains in place, or is loose, because if the latter, at this point the fixing would be lost, and the cup would move around in the hemispherical socket. It is necessary to exert the correct amount of force. Too much force would test the component to destruction, as it is put by the experts, and would be unnatural, and too little would be an inadequate test, exposing the patient to a risk of dislocation or loosening of the cup when subsequent natural forces were exerted.

Although Mr Hearth has no specific recollection, he is satisfied because of the entry in the surgical record describing "excellent press fit" that this is precisely what he did. If there had been any movement of the cup, and not of the pelvic structure, his evidence is that he would have taken it out and replaced it with a larger diameter cup after carrying out further reaming if necessary. As will become apparent, my finding in this respect will be crucial to the issue of liability.

Mr Hearth then moved to the next stage of the procedure, after inserting the ceramic liner in the cup, which was to insert the femoral stem into the top of the excised femur and the attached femoral head which contains the articulating component, that is the ball which was to be inserted into the ceramic acetabulum cup. The femoral head is also ceramic. Sometimes the stem is cemented in place, but in view of the Claimant's age, and the fact that the bone material was not osteoporotic, this was unnecessary.

At this point, to complete the procedure, it was necessary to reduce the hip, that is to put it back into its appropriate position in the joint and to insert the femoral head, which was 28mm in diameter, into the acetabulum, ensuring that there was no loose material in the holes in the acetabular cup. These can be utilised as screw holes if it is intended to fix the cup to the acetabulum, although that procedure was not followed on this occasion, nor is it suggested that it should have been.

The next stage comprised what is known as the stability test. This is also important in the sequence, although perhaps less so than the fixation test. It involves moving the leg and flexing the joint by up to 90 degrees and internally and externally rotating to see whether or not the joint remains in place. Mr Hearth told the court that he had no difficulty with this test, and determined not only adequate articulation of the prosthetic components, but also provided further reassurance that the fixed acetabulum cup was secure.

The operative notes record that the hip was “reduced and stable in all directions". This completed the procedure for the surgeon, after he had satisfied himself as to the stability of the joint, and he and his team repaired the soft tissues and closed the operative wound.

The surgical note also indicates that the Claimant was back from theatre at 1800 hours. Her recovery was from a spinal anaesthetic and not a general, but clearly she had to remain immobile until the following day with the necessary post surgical drains in place. The nursing note for the following 12 hours is very difficult to read, but the next significant event was the first step at the mobilisation. Here the physiotherapy record is relevant. It reads:

"pt (patient) lying in bed. Consent . Wants to get onto commode. Hand out (indecipherable) exs (exercises) shown and given. Pt came to SOEOB (sit on the edge of the bed) and asked AX (asked) patient STS (?) to RTF (Roller frame). T/F to commode. Pt mob 15 m with RF. Pt made to sit in the chair. Pt c/o (complained of) pain ↑ (increasing) and concerned about it. N/S (nursing staff) informed about a patient's pain and her concerns. Mob well (mobilise or mobilised well).”

The importance of this note becomes clear when alternative explanations for the Claimant's subsequent hip dislocation are considered in the context of the expert evidence. However it is important to note that in her own evidence the Claimant had no recollection of being transferred onto a commode, although she accepted that it might have happened. She is adamant that she did not sit in a chair, and recalls the movement being one in which she was lifted off the bed and assisted on the zimmer frame, before being returned to the bed. Throughout this time she was conscious of her hip moving in and out as this mobilisation process was attempted, with the leg rotating as soon as she put it on the floor, experiencing significant pain. Perhaps more noteworthy (at least according to the expert Mr Wilson) is that as soon as the supporting wedge was removed when she was on the bed, the hip did not feel right, and was insecure, and on movement there was a popping sensation as the hip appeared to move in and out. She felt that she had to hold her hip in place.

The Claimant does not believe that she was taken seriously at first, but the records indicate that later that day she was taken to x-ray, having been reviewed by Mr Waheed, and a dislocation of the hip was confirmed. All the relevant x-rays have been considered by a radiologist, Dr Evans, whose report was accepted, and included in the trial bundle as an agreed document. He noted that on 1^st August 2008 there was a dislocation of the left hip prosthetic acetabular cup and an unstable hip joint. By this, I believe he is referring to the fact that both the hip and the acetabular cup were out of place, and in relation to an x-ray the following day when an attempt was made at surgical revision/reduction under general anaesthetic without reopening the wound, he described the position of the left hip as demonstrating anterior dislocation of the cusp of the superior lip of the acetabular component with a very open position, in all probability an unstable hip.

In any event, it was suggested that this was anterior dislocation of the hip, that is the femoral head was dislocating in a forward direction, and the cup into which it was placed was also antaverted, that is facing towards the centre of the body. In simple terms, the prosthesis had failed, and both cup and hip were out of place.

The unsuccessful reduction surgery was performed by Mr Singh on 2^nd August 2009, with continuing x-ray screening in all probability. Although it was possible to put the hip back in place (i.e. to reduce it), because of the position of the acetabular cup it soon dislocated again and clearly further more radical revision was necessary. Understandably Mrs Cullen was reluctant at first to involve Mr Hearth again, whom the hospital were having difficulty locating, but eventually when he was consulted and reviewed the position on 4^th August 2009, she agreed to further surgery, having been told that the ceramic cup which fits into the pelvis had moved out of alignment.

Mrs Pullen consented to a further procedure, on this occasion under general anaesthetic, performed by Mr Hearth. In his evidence to the court, Mr Hearth agreed that on opening the wound, and accessing the hip joint, the acetabular cup was found to be excessively anteverted and was so loose that it could be removed without using a special tool which would usually be inserted behind the cup.

A decision was made to use a larger acetabular cup and to ream the acetabulum to a larger diameter. The cup which was inserted on this occasion was 54mm, but to avoid recurrence two screws were inserted through the cup into the pelvis, securing it in place. As before, an "excellent press fit” was recorded in the notes for the surgery. The balance of the procedure was uneventful, with appropriate reduction of the hip joint, and recovery, and it would appear that the problem did not recur. However, the recovery process was prolonged, and had complications, which it is agreed were directly applicable to the need for the revision surgery. It is unnecessary to consider the details of those complications which are not in issue, and which form, in part, the basis of the agreed quantum.

Mr Wilson, who provided expert evidence on behalf of the Claimant, is a consultant orthopaedic and trauma surgeon, with a particular interest in knee construction. He has, however, performed over 500 hip replacement procedures, although these days his involvement arises only in the event of traumatic injury. He has a teaching role at Cardiff University. His expertise is not doubted, but the court has not been provided with a copy of his curriculum vitae in the core bundle.

He reported initially on liability and causation on 17^th November 2014, although he had previously provided a condition and prognosis report in July 2012. He accepted that the hip replacement surgery was warranted, and as described in the notes and the evidence of Mr Hearth, the surgeon, it was appropriately performed in the sense that a correct and proper method was followed. However, he was unable to accept, in the light of the movement of the acetabular cup so soon after the operation, that a secure pressfit could have been secured on the fixation test. Either the acetabular cup had been placed in an excessively open and anteverted position at the time of the surgery, (which would have been unacceptable) or the fixation and stability tests had not been adequately performed.

He noted that during the subsequent reduction surgery which he believes might have been screened under x-ray, there was no indication that the cup was moving, which might have supported a conclusion that it had been placed in an open and anteverted position (although he acknowledged in the course of his evidence before this court that such a conclusion was unlikely if it is accepted that Mr Hearth was a generally experienced and competent surgeon). In his report he did not comment on alternative explanations for hip dislocation, because none were being advanced at the time, although he appears to have been satisfied that this was an anterior dislocation of the hip which had been caused by the misplaced acetabular cup.

I shall deal with the joint report shortly, but next address the expert evidence on behalf of the Defendant, which was provided by Mr Bamford in March of this year. He is an experienced orthopaedic surgeon, and appears to have carried out a greater number of hip replacement procedures than either Mr Hearth or Mr Wilson, although he has only been involved in medico-legal work for about four years. Again, his curriculum vitae is absent. Mr Bamford placed significant reliance on the operation and the reference to a secure pressfit to satisfy himself that the procedure was carried out in an entirely appropriate manner, further supported by testing of the stability of the hip joint. He did not criticise the absence of the insertion of screws (but neither did Mr Wilson) or the position of the acetabular cup as described. A conclusion could not be drawn from the anteverted position shown subsequently on the x-ray, because the dislocation had already occurred by then.

Mr Bamford opines that movement of an uncemented cup is an uncommon but recognised complication of this kind of surgery, and if the cup had loosened during testing, particularly during the dislocation of the hip whilst on the operating table, this would have been observed. He provides a number of possible causes for subsequent dislocation, all which arise from forces placed on the hip, in other words attributing the movement of the cup to the prior dislocation of the hip. Those causes include morbid obesity, abnormal leg position when mobilising, or haematoma around the prosthesis. He did not believe that the occurrence of hip dislocation within 24 hours was an indication that the procedure had been carried out negligently.

Clearly, then, on the basis of the initial reports, an issue was emerging as to whether or not a dislocated hip had caused the acetabular cup to loosen or vice versa.

Turning to the joint report, this was prepared following a telephone exchange between the experts on 8^th September of this year. An agenda had been prepared asking specific questions on breach of duty and causation, and these were answered by the orthopaedic experts, although not strictly in accordance with the same numbered paragraphs, in a report which was typed up by Mr Bamford.

The first important question was number 4. It was asked in these terms:

“On the balance of probabilities what was the cause of the Claimant’s left hip dislocation on 1^st August 2009 ? ”

Three alternatives were postulated, either a loose acetabular component, an acetabular cup that had been placed in an excessively open and anteverted position on 31^st July, or another cause.

The reply of the experts, in the same numbered paragraph is:

"... we both agree that on the balance of probabilities that the cause was a loose acetabular component."

In other words, Mr Bamford was now accepting that the hip dislocation was preceded by the movement of the acetabular cup.

The next question at number 5 asks:

“On the balance of probabilities would the cup have moved and/or the left hip dislocated on 1^st August if the acetabular component had been placed in an acceptable position and/or a secure and competent press fit had been achieved intraoperatively on 31^st July 2009?”

The answers are provided in two separate numbered paragraphs 5 and 6, to this effect, which seem to address the balance of question 4 as well:

“We agree that it is unlikely that the cup had been placed in a position that was excessively open and anteverted on 31^st July 2009. We agree on the balance of probabilities that the cup would not have moved had a secure press fit been achieved intraoperatively as the cup would not have become loose.”

These replies are significant in two respects. First of all, Mr Wilson no longer pursues his initial alternative argument, that there had been a malposition at the time of the hip replacement surgery. Second, Mr Bamford appears to accept that a subsequent hip dislocation could not have caused a securely fixed acetabular cup to become loose. On the face of it, therefore, the issues were now becoming far narrower.

The next relevant question appears at number 6. In the light of the previous answers the only relevant sub-question was this:

“Was an acceptable and competent pressfit secured?”

The answer was seemingly unequivocal in these terms:

“We agree that on the balance of probabilities an acceptable and competent press fit was not secured intraoperatively on 31^st July 2009.”

It was this answer which encouraged counsel for the Claimant, in his skeleton argument, to confidently assert that liability was thereby conceded. However, on closer examination at the outset of the hearing, and after exchange with counsel, I was able to establish that the Defendant's case was that the words "acceptable and competent" were intended by Mr Bamford to refer to the result rather than the manner of performance. As the evidence emerged in the case, and indeed in the course of the subsequent clarifying part 35 questions and answers, this became clearer, although the wording was unfortunate.

Although there are no further relevant questions asked on the issue of liability, both experts provide further explanations for their position. Mr Wilson maintained his contention that the fixation test was not carried out adequately or within the acceptable margin of surgical error at the time of the procedure. Mr Bamford postulates that a satisfactory fixation can nevertheless prove to be subsequently wrong with loosening, either at the time of trial reduction (the stability test), or at the time of closure of the wound, or when the Claimant was applying a greater force when standing up. In none of these postulations in the joint report does Mr Bamford suggest that it was the hip dislocation itself which loosened the acetabular component.

It would seem that after a conference with counsel for the Defendant, a decision was made to put further part 35 questions to "clarify" Mr Bamford’s position, and these were drafted by Mr Piper relatively recently (a week before the trial). They were answered the following day by Mr Bamford, and although this procedure of late development of expert evidence is not normally tolerated, Mr Woolf, counsel for the Claimant, did not raise particular objection. Essentially, the questions were directed to the issue of the subsequent dislocation, and in particular whether this could have occurred even though there was an apparent pressfit achieved during the course of the operation. Whilst the questions were intended for both Mr Bamford and Mr Wilson, essentially it was Mr Bamford providing the answers in the short timescale. Clarification was sought as to whether or not he had been suggesting that Mr Hearth was acting incompetently in the performance of his surgery.

The replies justify some scrutiny because they lay at the heart of the issues which emerged in the course of the trial. Mr Bamford made the following comments:

“In the joint statement, I have considered the response that, on the balance of probabilities, the hip dislocated due to the loose acetabular component. Although this remains a possibility, it should be stated that the hip could have dislocated for other reasons such as soft tissue impingement (particularly bearing in mind the patient's BMI) a haematoma, and abnormal movement of the leg. There is no evidence to support one potential cause over another, and they should be regarded as equally possible.”

In other words he was now resiling from the position that it was more likely than not (the legal standard of proof) that a loose acetabular cup had caused the dislocation.

He provided a further comment in the second paragraph:

"As stated in my report, it is very possible that a reasonable press fit was obtained at surgery, but on dislocation of the hip the following day, the force applied to the rim of the cup as the hip came out of joint would be enough to cause loosening and hence movement of the cup."

I confess that I find it difficult to identify this precise reasoning in his early report.

Finally, when commenting on the question of the competence of Mr Hearth, Mr Bamford goes on to say this in paragraph 3:

"It is not my opinion that (earlier paragraph 7) implies that Mr Hearth was acting incompetently and there is evidence that he tested the fixation in the usual manner. As I have stated in previous reports, this is very subjective and the surgeon is not trying to test to destruction the fixation of the cup. Being an experienced surgeon I would expect Mr Hearth to have developed a feel for how hard to test the fixation. This, on rare occasions can be misleading so that cups that are felt to be solidly fixed initially subsequently become loose when an even greater force is applied across them, often when doing trial reductions particularly with large heavy legs. Even greater forces are applied by the patient when they get out of beds or chairs."

(In the course of his evidence to the court, Mr Bamford explained that he was there referring to the dislocation of the hip being the greater force.)

Mr Wilson found himself able to address them, notwithstanding the late notice. He accepted in principle that morbidly obese patients were more at risk of hip dislocation in the recovery period after surgery. Further, whilst the statistical evidence did not enable a more precise analysis, because there was no indication as to those early dislocations which occurred within 24 hours, and those within several weeks, nevertheless a hip dislocation within such an early period was an extremely rare event, and even more so in the present case, where the dislocation was anterior and not posterior.

He rejected any suggestion that the anteverted position of the cup might have given the impression that it was anterior dislocation when in fact it was a posterior dislocation. He explained that in the latter situation (posterior) it is simply not possible for the hip to "pop in and out" as occurred here, and which was consistent with the evidence of the Claimant. He was impressed by the immediate instability which she reported when the wedge was removed while still on the bed, and his conclusion was that the anterior dislocation was clearly consequential upon the anteverted position of the cup which had significantly moved. It was relevant that in the revision procedure the acetabular cup did not have to be levered out, and was found to be excessively anteverted.

Whilst acknowledging the very remote possibility that with obese patients, soft tissue impingement (if this is referring to the movement of the tissues post operatively or even on the operating table after the various tests have been carried out) could have some effect on the stability of the hip, this is likely to have led to posterior displacement, and not the anterior which was clearly present here.

Haematoma was highly unlikely in the absence of any acknowledged blood collection in the subsequent operative procedure, and in any event it was not being suggested that haematoma alone without abnormal movements or soft tissue impingement could have had such an effect.

As far as abnormal movement was concerned, he did not find any evidence of this, regarding the attempts at mobilisation as not being particularly excessive, and referring to the fact that difficulties were observed immediately after attempts were made to move the Claimant. Standing up, according to Mr Wilson, would not have created the necessary forces, as these would have been central and compressive, rather than to the rim of the acetabular cup, even if it was remotely possible that the dislocating force preceded the loosening. In such circumstances, in any event, a dislocation in an anterior fashion from standing up was highly suspicious of an anteverted cup.

As far as the x-ray was concerned, he did not agree that its opaqueness disabled a determination as to whether the hip had dislocated anteriorly or posteriorly. It was possible to observe that the femur was twisted out with the femoral head facing inwards.

In relation to the adequacy of the stability test, after the hip is reduced during the operative procedure, when the leg is flexed and extended, he made the same point that there were no excessive forces exerted on the acetabulum, and whilst this significantly loose cup might be observed to move at this point, the purpose of the test was to ensure that the joint was stable. It is a test which is still carried out with a cemented and screwed acetabular cup.

In terms of the surgical results on the first hip replacement, Mr Wilson accepted that he changed his view, and was no longer postulating an excessively anteverted cup, as opposed to a cup which was loose because it had either been over tested on fixation, or inadequately tested, in either case leading to a false belief by the surgeon that it was properly fixed. It did not have to be the case that it was spinning around in the socket, and this was simply ignored. There are acceptable parameters and margins, but in this case they were exceeded.

When asked to postulate as to how such a failure might have occurred on the part of a highly competent surgeon, he was not prepared to go so far as to say that this was a gross failure. Whilst it was possible that the component had been insufficiently hammered in the first place, it was essentially the fixation test which was inadequately performed. Because all other possibilities (as suggested by Mr Bamford) were so remote he was unable to come to any other conclusion.

Turning to Mr Bamford, he had experienced one cup displacement in the 2000 or so hip replacement procedures which he had performed. He did not elaborate on the cause of this, nor explain whether it was associated with an anterior or posterior dislocation.

He accepted that he had changed his opinion on the joint report, moving from a 51% likelihood to a 50-50 possibility in terms of the causation of the dislocation. Whilst acknowledging that he had agreed that a securely fixed cup could not move, a reference to a secure pressfit implies a spectrum of fixation from rock solid to rattling around. Allowance should be made for the fact that in some instances an impression could be given of fixation when this was not necessarily the case. A secure pressfit was one which would not move under any circumstances, but whilst the evidence of the surgeon Mr Hearth was influential, relevance of subsequent events could not be ignored. Otherwise, he maintained his position that an assumption could not be made of a failure of surgical procedure, when there were other equally likely possibilities.

Essentially, because of those possibilities, it was not unreasonable to conclude that the acetabular cup had become loose post-operatively as a result of the supervening event of a dislocation, which he accepted, by reason of the biomechanics for those events, would have to have been posterior. Mr Bamford stood by his postulated alternative causes, namely morbid obesity, with tissue impingement, sudden movement which was dramatic, or haematoma, accepting that the latter would have to be in conjunction with either of the other two.

He did not accept that the court should conclude that this was an anterior dislocation. He had seen personally two uncemented cups with what he felt to be adequate pressfit but during the stability test the cup had moved to exactly the same position as the cup seen on the x ray in this case. In other words, the impression could be given of an anterior dislocation, but this is merely because the femoral head had caused the cup to move in this fashion, and itself was lying in an abnormal position as it had nowhere else to go. It was not entirely clear to me whether he was saying that this was an anterior dislocation disguised as a posterior dislocation, or the other way round. In any event, he did not believe that it undermined his theory that these alternative possibilities were plausible explanations.

He did not accept that there was no evidence of abnormal movement. He referred to the fact that the patient would have been on strong painkillers, and there could have been a greater exertion on her part within the limits of pain. The records would not necessarily pick up such episodes.

As far as the stability test is concerned, he remained confident, thus disagreeing with Mr Wilson, that this would have picked up any loose or poorly fixed acetabular cup, because the forces are not just central, but also act on the rim of the component.

As I have indicated, these have narrowed significantly, not least because of a softening of the position of Mr Wilson. They are both factual and legal.

“Was the acetabular cup adequately fixed in the hip replacement procedure, or might it have become loose because of a subsequent event of hip displacement?

If it was not adequately fixed, does this constitute a falling below acceptable standards on the part of the operating surgeon?”

There are brief and discreet factual issues arising from the evidence of Mrs Pullen which may have a bearing on the conclusions I reach in respect of the substantive issues.

I shall deal with Mrs Pullen’s evidence first, to set the framework for my conclusions. Clearly, she was a transparent and truthful witness, doing her best to recollect this extremely unpleasant experience for her in the post-operative period. I was impressed by the way in which she distinguished between those things of which she was certain, making concessions that she might have been wrong about others. Two points are relevant: first, whether she might have engaged in a sudden or violent movement which caused the hip to dislocate in this very early part of rehabilitation, thus putting pressure on the acetabulum, and second when she first became aware of symptoms.

It is correct that the medical notes provided by the physiotherapist indicate (insofar as they can be interpreted) that Mrs Pullen was placed on both a commode and subsequently on a chair. She emphatically denies the latter, but accepts that she might have used the commode. The difficulty for me is the meaning of "made to sit in chair". “Made” could refer to "tried", or it could refer to "forced". It seems to me that the latter is unlikely, and it may be that the physiotherapist is referring to an attempt to move the Claimant after she had this onset of significant pain. Thus I prefer the evidence of the Claimant, on a balance of probabilities, on interpreting the note, even though she cannot identify the commode, that the initial movements in this period of severe pain involved being on the bed, attempting to stand up and move, and subsequently being put back on the bed again. None of this, in my judgment, is indicative of any significant movement, or abnormal movement in leg position when standing up, which is relevant to my subsequent findings.

The second point concerns the symptoms. In this regard, I am also impressed by the Claimant's evidence which was clear and unambiguous, that as the wedge was removed supporting her leg, it did not "feel right", and as soon as movement was tried, she felt a popping sensation, as if the hip was coming out of joint, and back into joint again. Thus it is a reasonable conclusion that problems with the hip, in terms of significant symptomology, were identified at the absolute beginning of the rehabilitation process with the physiotherapist. I shall consider how this relates to the principal question of identifying the timing of the acetabular loosening shortly.

Turning to the substantive questions, it seems to me appropriate to address the legal test which must be applied, and which appears to be uncontroversial.

First of all, it is axiomatic that the burden of proof rests with the Claimant to establish the causal mechanism for her injuries on a balance of probability. In this case, that is relevant not so much to the injurious consequences, which are not in dispute, but to the cause of the loosening of the acetabular cup, and in particular whether it arose intraoperatively, or in the immediate post-operative period. Whilst it may have been assumed, on the basis of a first reading of the joint report, that there was an agreement that the subsequent hip dislocation was consequential upon a loose acetabular component, on a balance of probabilities, clarification provided by the Defendant’s expert suggests that this is no longer the case, and that the loose acetabular component is but one of several possible explanations, all of which are equally likely, on the Defendant's case.

Accordingly, I must be satisfied that the Claimant has proved the most likely cause as intra-operative loosening, before I can consider any breach of duty, as it is accepted that without such an occurrence no question of any breach arises.

Second, in relation to the standard of care, a further determination as to which of the two experts I accept, (insofar as they disagree on whether or not the operation was performed in an acceptable manner), Mr Woolf, on behalf of the Claimant, urges me to consider the guidance provided by the Court of Appeal in the case of Smith v Southampton University Hospital NHS Trust [2007] EWCA Civ 387 in the judgment of Potter LJ at paragraph 44:

"….Where there is a clear conflict of medical opinion, the court's duty is not merely to say which view it prefers, but to explain why it prefers one to the other. This, in my judgment, is all the more so when the expert's view it prefers accepts a substantial element of what the less favoured expert describes as basic good practice ... it is not sufficient, in my view, simply to say that Mr Monaghan is representative of a responsible body of medical opinion and as a consequence (the Defendant surgeon) was not negligent"

In other words, it is not simply a case of the application of the Bolam test, acknowledging that two experts disagree on whether or not it was an appropriate standard, which would suggest that there was a range of responsible medical opinion within which the doctor could be judged, and accordingly there could be no attribution of negligence. Both the experts here agree that it would be inadequate and incompetent practice not to ensure that the acetabular cup was fixed, and there is no issue as to how the procedure should have been carried out. The difference appears to be that Mr Bamford places great emphasis on the statement of the surgeon, whereas Mr Wilson believes that by excluding alternative explanations, the consequences speak for themselves. It seems to me that when the primary question is answered, which essentially asks whether those alternative explanations can be excluded as unlikely or implausible, this second question will be less troubling.

Central to a determination of the first issue is the position of the dislocation. The agreed radiological evidence appears to suggest that this was anterior (paragraph 6 page 202 in bundle) and indeed until Mr Bamford postulated an alternative explanation in the course of his evidence, it was not considered that this was in dispute. On the biomechanics described, in my judgment it is unlikely that the acetabular cup which was significantly anteverted in the subsequent surgery would have allowed a posterior dislocation.

Furthermore, on this point I accept the evidence of Mr Wilson, based upon the factual account of the Claimant which in my judgment is also credible and plausible, that there was a sensation of popping in and out, which would not have been feasible had the hip dislocated anteriorly. I do not believe that Mr Bamford specifically addressed this bio mechanical problem, but preferring, instead, to explain by demonstrating with the available visual aids that even with a significantly forward facing cup, the hip could still dislocate in a posterior fashion. Unfortunately, there was no explanation provided as to how it might reduce or relocate in such circumstances, as was really happening. Thus I find that the hip had dislocated in an anterior fashion.

Mr Bamford's three alternative suggested "possibilities" should be considered in the context of what he accepted was a significant shifting of his position from the time of the joint report, and not just a case of redefining "acceptable and competent". He had originally accepted a 51% likelihood of the loose acetabular component preceding the dislocation, which is significant in the light of his opinion that a properly fixed acetabular cup would not become loose.

The court should be slow to criticise an expert who does change an opinion, and prefers a frank expression of view rather than an unswerving adherence to an original position. However, I found Mr Bamford’s reasoning on his qualified position to be disjointed, and I was left with the impression that he was so convinced by the operation note of an "excellent pressfit" and a description provided by the surgeon which was entirely appropriate, that he was endeavouring to add plausibility to what were essentially very remote possibilities.

I can address those briefly, with reference to the evidence of Mr Wilson, to demonstrate what in my judgment is implausibility. First of all the Claimant's obesity and the force is exerted on the hip when standing up. Here, I have already indicated acceptance of the Claimant's evidence that a sensation of instability was present before she even stood up. However I accept the evidence of Mr Wilson, whom I found to be an impressive and measured witness, prepared to accept a softening of his opinion as the evidence developed in the case (and at the time of the joint report as he abandoned any suggestion of an excessively anteverted acetabulum at the time of the operation). In this regard he explained how the forces operating would be compressive and central, and not lateral or at the rim of the acetabular cup. Further, if this is likely to have happened, it would be surprising that it had not occurred during the operation. This, in my judgment, determines that issue, and excludes the obesity as anything other than the most remote of possibilities.

The same considerations apply to the abnormal leg position. This is simply not supported by the nursing records. The Claimant was closely supervised in recovery, and if anything untoward had been noted, it is reasonable to assume that it would have been dealt with. Furthermore, I accept the Claimant's evidence that it did not happen.

The third possibility of haematoma, is considered in conjunction with the fourth, soft tissue impingement, because Mr Bamford accepts that the haematoma would not have acted on its own to cause any forces which might have led to the dislocation. In my judgment this is easily addressed by the fact that the dislocation occurred anteriorly and not posteriorly. Soft tissue impingement, whether in conjunction, or on its own, is likely to have caused problems at the time that the leg was rotated and extended in the stability test, and it seems to me highly unlikely when considered against other factors.

I should make this observation about Mr Bamford. I reject his evidence for the reasons set out above. He has strained to identify possibilities which in most respects are so remote as to be fanciful. However, insofar as I prefer the evidence of Mr Wilson (again for the reasons stated) I should point out that I found Mr Bamford to be lacking credibility and understanding as to the applicability of the legal test by resiling so dramatically and so recently from a position jointly adopted. I regret to say that I did not find him to be an impressive witness, although I accept that he holds his opinions genuinely and honestly.

Having found that this was a hip which had dislocated anteriorly, because of the malposition of the acetabular cup which had loosened to become anteverted, I turn to the second question.

Mr Piper, on behalf of the Defendant, like Mr Bamford, places significant store by the evidence of the operating surgeon, Mr Hearth, who, whilst having no recollection of the procedure, was extremely experienced, and quite satisfied that he would not have recorded in the notes "excellent pressfit" unless that had been achieved. It was appropriate that counsel should do so, because I found Mr Hearth to be an otherwise impressive and honest witness, who was doing his best to give a straightforward account of the procedure. Nevertheless, even the best and most competent surgeons can occasionally make mistakes. A mistake, in the context of an error of judgment, would not necessarily fall below an acceptable standard, but in this case it seems to be that any error would have been in the manner of fixation testing, whilst the subsequent stability test would not necessarily have picked up a loose acetabular cup. In this regard I accept the evidence of Mr Wilson.

Because I have excluded all other possibilities as remote, I must assess the question of the standard of care on the basis that on a balance of probabilities the acetabular cup was not properly fixed. Here, it does not matter if insufficient force had been applied by the mallet, because the use of the introducer to test the strength and fixture of the cup thereafter is entirely appropriate. (I do not believe it to be suggested, absent the other supervening causes, which I have rejected, that the cup could have loosened itself by some sort of organic displacement).

Mr Hearth would undoubtedly have been aware of the need not to over-exert the introducer tool because this would destroy the fixture. However, whilst it would be a matter of judgment based upon experience, it is just as likely that inadequate exertion would not reveal a cup which was loose and likely to move. In this case I am unable to say which of the two is the most likely, either that Mr Hearth over exerted the introducer so as to cause a loosening just before he removed the tool and applied the ceramic insert, so that he was unaware of the consequences, or alternatively applied too little force so that he was unaware of the poor fixing. In my judgment, it does not matter, because either is representative of technique falling below an acceptable standard.

This does not imply that Mr Hearth is an incompetent surgeon, or even knowingly allowed the surgery to be completed when the test had not been carried out properly. I am quite satisfied that he was unaware of any difficulty. However, the loose acetabular cup was an immediate cause of the subsequent dislocation, and on the surgery three days later appeared to be excessively anteverted requiring very little pressure to remove it. This leads to the inescapable conclusion that this was one of those rare cases in which a good and otherwise competent surgeon applied a technique other than an acceptable one. It means that there has been a breach of duty on the part of the Defendant.

Accordingly, there must be judgment for the Claimant in the agreed sum of £37,500. This judgment will be handed down in my absence, and therefore I invite the parties to agree any consequential orders. In the event that this cannot be agreed, I will receive brief written submissions in the first instance.