The anatomy of the knee joint
The knee joint is the hinge connecting the femur and tibia. This joint is extremely complex which allows not only for flexing and extending of the leg but also allows slight rotation of the tibia. The joint consists of the lower section of the femur, the upper section of the tibia, and the internal section of the kneecap, all of which are covered with a layer of cartilage.
Between the femur and tibia, there are also “cushions” which serve as shock absorbers called meniscus (or menisci, plural form). The bones in the knee are connected by elastic structures called ligaments. There are cruciate and lateral ligaments which give the knee further stability without limiting the natural movement of the knee.
The articular capsule closes the entire joint and produces synovial fluid. The synovial fluid supplies the necessary nutrition to the surrounding cartilage and helps the joint lubrication providing movement without friction. The synovial fluid, together with cartilage and menisci, also has a shock absorbing function by intercepting strong forces which are then reverberated on joint during the life span of a person. The movement of the knee joint is possible due to the surrounding muscles.
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Lateral view of the bones of knee joint Lateral X-ray view of the knee
X-ray view of patello-femoral joint
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What are the Compartments of the Knee
We divide the knee into three parts or compartments.
1. The inside of the knee between the femur and tibia (the medial part of the femoro-tibial joint)
2. The outside of the knee between the femur and tibia (the lateral part of the femoro-tibial joint)
3. Between the knee cap (patella) and the femur (the patello-femoral joint)
Each one of these compartments can be replaced separately with a partial (or unicompartmental) replacement or all three can be replaced with a total knee replacement.
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Arthritis of the Patello-Femoral Joint
On occasions, arthritis can develop under the knee cap causing severe pain in the front of the knee only.
The rest of the knee, that is the femoro-tibial joint is not affected by the degenerative process. This is thought to be due to an imbalance of the ligaments and tendons around the knee. It is called ELPS
(Excessive Lateral Pressure Syndrome).The patella therefore tracts on the knee unevenly with a greater force on the outside of the knee (red arrow) than the inside (purple arrow). This results in excessive wear of the cartilage underlying the outside of the patella.It can result in disabling symptoms due to the advanced arthritis, at a relatively early age, as young as late thirties, early forties.
In the above x-rays, there is bone on bone on the outside of the knee cap (red arrow) with preservation of the
"joint space" of the knee joint proper, between the femur and tibia.
In the arthroscopic examination is demonstrated the appearance of the cartilage under the patella, which has worn down to the underlying bone. This is associated with significant inflammation within the knee.
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incidence and aetiology
Disorders of the patellofemoral joint are a common cause of knee pain throughout adult life. For teenagers and those in early adult life the disorders present as non-specific anterior knee pain for which there can be a multitude of causes and can be a cause of troublesome disability. The exact incidence is unknown but with increasing age and progressive damage to the articular surfaces, established osteoarthritis of the patellofemoral joint develops. The condition is usually symptomatic causing moderate levels of pain and disability and particularly restrict the function of the knee. Paradoxically some patients can have well established osteoarthritic change present on radiographs without significant symptoms.
Typical isolated Patellofemoral arthritis
Increased awareness of these disorders has occurred as a result of more detailed investigation of the patellofemoral joint firstly with Merchant or Ficat’s tangential plain radiograph and secondly with the more widespread use of transverse images with CT and
MR. Isolated patellofemoral disease exists in a proportion of 10% patients with osteoarthritis of the knee, and this process can remain localised for many years before progressing to the other compartments. The disease include isolated changes in either medial or lateral facets of the patellofemoral joint, or symetrical disease (Davies) and most are fundamentally related to the mechanical stability of the extensor mechanism.
This is a complex articulation transmitting force from the large extensor musculature over a narrow pulley to the tibial tubercle. Efficient function of this mechanism is essential for effective locomotion in the upright posture. Goodfellow and Hungerford described the contact bearing areas of the seven separate articulating facets of the patella and emphasised the complex overlap that occurs with the tibio femoral joint, unique in the animal kingdom. Minor degrees of incongruity with the trochlea will lead to considerable increase in the forces at the articular surfaces. Thus the patellofemoral joint is particularly vulnerable to minor degrees of incongruity and to the effects of injury. Mismatches in the articulation can result from a range of developmental malformations of either the patella or the trochlea. Alterations in the overall alignment of the limb both in varus, valgus or rotation can lead to incongruities and overload of the surfaces.
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20° 45° 90° 135°
The stability of the patello-femoral joint is largely determined by the complex muscular and retinacular arrangements of the proximal extensor mechanism. Muscular imbalance of the quadriceps mechanism is a common cause of knee dysfunction particularly when there are underlying mal-alignments or incongruities. The factors determining muscular control are as yet ill understood and quadriceps dysfunction is sometimes difficult to correct. Once it has occurred, usually through the effects of injury, it often persists. These mechanical factors can lead on to articular cartilage damage with a progressive cycle of attrition, which is not easy to reverse. Studies of the pathology of advanced patellofemoral disease show that the lateral facet of the patella and trochlea are most commonly affected with 80% of cases demonstrating this pattern of lateral mal-alignment with subluxation. A small number of cases show medial facet and trochlea disease, (<10%). The precise aetiology of this condition is obscure but it would suggest that there may be an equivalent and opposite medial overload syndrome. The remaining cases demonstrate symmetrical patterns of wear affecting equally both the medial and lateral facets of the patella and trochlea groove.
Lateral facet OA Medial facet OA
Investigations
After a careful clinical history and examination, the investigations must include a weight bearing antero-posterior and lateral view of the tibiofemoral joint X-Rays films including the Rosenberg 30° PA view. Many cases of patellofemoral disease are missed because of the failure to take tangential views of the patellofemoral joint at 30° of flexion. This has been well described by Ficat and Merchant and is an essential radiograph to demonstrate the proximal part of the patellofemoral joint.
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A/P and lateral weight bearing x rays and t angential view at 30° flexion.
Plain radiographs alone will usually demonstrate significant arthritic disease with joint space narrowing, osteophytes and subchondral sclerosis. The joint articulates through at least 130° and significant arthritic damage may be present in part of the arc of motion.
The use of dynamic CT scanning with views at 0°, 20° and 40° of flexion together with measurement of the height of the patella and tibial tubercle displacement will give a thorough investigation of the simple mechanics and structure of the patellofemoral joint.
Quadsrelaxed Quadscontracted
Dynamic stacked CT images of the P/F joint at 0° showing subluxation.
The use of NMR scanning will demonstrate in much more detail lesions of the articular surface on both the patella and the trochlea in its entire extent.
Dynamic MR studies are being developed to show the tracking of the patella throughout its early range of movement and these may eventually help to demonstrate specific malalignment syndromes
Proximal Middle Distal
MR scans showing the upper middle and lower Patella facets in full extension.
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The next step in the investigative sequence is the use of arthroscopy . This invasive technique should only be used when non-operative conservative measures have failed to control the symptoms. Useful information can be obtained and recorded about the state of the articular surfaces and the alignment of the patella. It must be remembered, however, that the magnification effect of arthroscopy can make articular lesions look several times larger than they are by direct vision. Treatment by chondrectomy can be performed at the same time to trim any loose unstable flaps of articular cartilage. Arthroscopically controlled extra or intra-articular lateral release can be performed but the place of this procedure remains controversial. In many cases the effects are short lived and it is probably only indicated in a small number of cases, which have early subluxation and tightness of the retinaculum. It is seldom effective on its own especially when there is any significant degree of lateral overload, subluxation or tilt.
Supero-lateral Portal to view patellofemoral joint.
The arthroscopic assessment should include a thorough assessment of the tibio femoral joint with a view of the patellofemoral joint, the inter-condylar notch and the lower trochlea surfaces from the inferolateral portal. An essential part of the assessment is to view the patella from the top of the supra-patella pouch usually by the supero-lateral portal. This portal can be easily identified by viewing the supra-patella pouch from below. The joint is then emptied of fluid and careful assessment of the position of the patella throughout the range of movement can be made. Static, or video images are taken of both the lateral gutter an d the trochlea groove with the knee at 0°, 20°, 40° and 60° of flexion. Similar assessments are made after realignments procedures to ensure accurate correction of tracking.
Early Treatment
All patients should undergo a full course of non-operative conservative management prior to any invasive procedure. The use of anti-inflammatory analgesics in addition to intensive rehabilitation under physiotherapy control can solve many patients’ problems. The use of patella bracing and isokinetic rehabilitation provides a selection of options for patients with early disease.
Failure to improve constitutes the indications for further investigations and treatment.
Radiographic assessment with dynamic CT scans or MR will provide useful information to assist with planning surgical treatment. Arthroscopic assessment will help to evaluate the alignment of the patellofemoral joint and give more detailed information about the state of the articular surfaces. It is important to recognise that the magnification effect of arthroscopy will make articular cartilage lesions appear several times bigger than they are
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in reality. Description of arthroscopic assessment and treatment has been fully described in the earlier section on investigations.
Arthroscopic chondrectomy can be beneficial to remove loose flaps of articular cartilage and tidy up areas of chondral irregularity. Although this will not promote healing of the chondral lesion, if followed by intensive rehabilitation, marked improvement in symptoms can occur in some cases. The addition of abrasion arthroplasty or microfracturing may be appropriate in more extensive and deeper lesions. If there is any degree of malalignment of the patella or impingement of chondral lesions as flexion occurs then distal tibial tubercle realignment procedures can be very helpful. Careful analysis of the precise characteristics of the malalignment and details of the position and extent of the chondral lesions is essential to plan the treatment. The French group in Lyon have pioneered realignment procedures for the treatment of lateral overload and subluxation using the
Elmslie Trilat technique. This can be refined and performed under arthroscopic control.
Preliminary arthroscopic assessment is performed as described above and an extraarticular mid lateral release of the lateral retinaculum performed maintaining the integrity of the lateral synovium.
This is performed under direct vision through a small lateral lazy S incision and the inferior lateral geniculate vessels can be secured. The Elmslie procedure is performed with an osteotomy of some 5cm to 7 cm leaving an intact tongue of bone at the distal end. Medial translation of the tibial tubercle can be performed up to 75% of the osteotomy surface and slight anteriorisation can be achieved by altering the angle of the osteotomy in the transverse plane. After initial displacement temporary fixation is performed to allow arthroscopic assessment of the patella tracking and stability. Further medial displacement can be performed if necessary though it is important not to exceed 75% of the osteotomy surface. The osteotomy is then secured with two fully threaded 4.0mm lagged cancellous screws. The heads countersink into the cortical bone of the tubercle and seldom cause problems. Petalling of bone on the lateral side will fill any gaps in the osteotomy and promote union.
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Five years post operation of an Elmslie realignment for subluxation.
If there is persistent malalignment in the more severe degrees of lateral subluxation or persistent instability then a medial plication of the vastus medialis retinaculum can be performed through a small medial extra-articular incision. It is important not to over- tighten this repair for fear of producing medial overload and even medial subluxation.
In cases w ith lesser degrees of lateral malalignment and subluxation Fulkerson’s osteotomy may be preferred. The angle of the osteotomy can be varied to create more anteriorisation or medialisation depending on the nature and position of the articular cartilage lesions of the patella and the degree of malalignment. Details of this procedure are described by Fulkerson (1) but considerable judgement is required to match the osteotomy with the chondral lesion.
In cases with pure lateral facet osteoarthritis, lateral facetectomy has been advocated by some authors. There is, however, no clear evidence of the quality or longevity of results from this procedure.
Patellectomy has traditionally been used as a salvage procedure for patellofemoral disorders. It has an uncertain outcome and many reports record good or excellent results in less than 50% of cases.
Ref (2) Weakness of the extensor mechanism is an inevitable consequence and poor results can be expected if there is any degree of trochlea dysplasia or persistent malalignment of the extensor mechanism.
CT scan after patellectomy showing trochlear displasia and persistant subluxation
Treatment of Established Patellofemoral Disease with an arthroplasty.
Patellofemoral arthroplasty was first reported by McKeever in 1955 (3) . Development of the procedure led to several designs being widely used in the 1970s. Reasonable shortterm results have been reported using the
Richards’ and Guepar (4 - 9)
designs. The
Lubinus prosthesis was designed in 1974 (Ref 10) . The results have proved disappointing in the medium term with only 50% successful results at 7.5 years. Nevertheless nearly half the patients continued to experience excellent function and pain relief suggesting that
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improvements in design may eliminate some of the problems. Most series have reported difficulties with achieving satisfactory patella alignment and persistent subluxation leading on to wear has been a feature of many reports. The second major cause of failure is disease progression, which has been reported from 5% to 10% in most studies. Indeed
Kooijman et al in a recent long-term review with a fifteen year follow-up, reported disease progression in over 20% of cases.
Indications
The indications for patellofemoral arthroplasty should be as strict as those for total knee replacement. There should be significant pain and disability. The use of functional scoring tools such as the reduced Womac score, the Oxford Knee Score and the Melbourne patella score can be helpful in assessing the severity of the condition.
Strict Indications for Arthroplasty


Severe symptoms and signs
 Radiographically proven severe osteoarthritis of the PFJ
No significant deformity, especially axis mal-alignment and fixed flexion
 "Normal" tibiofemoral joint
There is a large group of patients in their middle years who have got significant damage and dysfunction of the patello-femoral joint and would be much too young for a total knee replacement. Such patients should initially be treated with conservative surgical procedures including chondrectomy, articular cartilage grafting and realignment osteotomies. These treatments can often be successful for a number of years but progressive chondral damage is usually inevitable, leading on to early osteoarthritis. In such cases when there is severe pain and disability and all other surgical options have been exhausted an isolated patellofemoral arthroplasty may be considered as appropriate treatment.
Extended indications
 Failed realignment - Fulkerson/Elmslie
 Younger patient with early disease
 Dislocation & trochlea dysplasia
 Failed patellectomy
 Post - trauma (fracture or chondral damage)
Contraindications
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The treatment of patellofemoral conditions is notoriously difficult. It is essential to make a specific diagnosis of the mechanical and pathological conditions and to plan the treatment appropriately.
There are certain conditions which are much more difficult to treat and they may constitute relative or absolute contra-indications for a patellofemoral arthroplasty.
1. Patella baja (infera)
This condition is seldom successfully treated by arthroplasty because of the abnormal loading of the patellofemoral joint. This can be a developmental condition but may also be acquired following previous surgical treatment.
2. Patella alta
This condition is often responsible for significant patellofemoral disease with either instability or arthritic damage. It may be appropriate to lower the patella with a tibial tubercle transfer prior to or at the same time as the patellofemoral arthroplasty.
These cases may have significant proximal mal-alignment and great care must be taken with tracking and with the design of the proximal trochlea.
3. Algodystrophy – Regional pain syndrome
These cases are notoriously difficult and great caution must be taken in considering an arthroplasty.
4. Arthrofibrosis
This is often a secondary effect of an algodystrophy, or an abnormal response to previous surgery. It is generally unwise to attempt to treat such cases unless extremely good rehabilitation is available.
Axismal-alignment
If there is significant varus or valgus mal-alignment an isolated patellofemoral arthroplasty is probably
5. unwise. There will be an increased risk of developing disease progression in the tibio femoral joint.
6. Fixed flexion deformity
It is seldom possible to correct a fixed flexion deformity by a patellofemoral arthroplasty. This constitutes a specific contra-indication to an isolated patellofemoral arthroplasty if the deformity is mor e than 10°.
7. Restricted flexion
Flexion may be restricted due to pain inhibition. In such a case free movement of the knee under anaesthesia will confirm an appropriate indication for an arthroplasty. If the range of flexion is less than 90 degrees due to capsular
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contracture or arthrofibrosis, excellent rehabilitation facilities will be required to obtain a satisfactory result.
8. Early chondral disease (anterior knee pain syndrome)
This should never constitute an indication for a patellofemoral arthroplasty. When there is significant chondral damage in younger patients, (at least those under fifty), they should usually be considered for minimally invasive surgery,with chondrectomy, patella realignment or cartilage autograft, before being considered for an arthroplasty. In cases of failed previous surgery for significant chondral damage careful counselling of the patient should be undertaken before performing an arthroplasty.
What are the Advantages of a PFKR?
Smaller Incision
If the patella and one tibial surface appear healthy, then an incision extending approximately 3" is used to implant the Partial knee replacement components. This is much smaller than the 8" incision required for a total knee; thereby leaving a more pleasing cosmetic appearance after surgery is completed.
Less Blood Loss
Quite often patients are required to donate blood before total knee replacement providing blood to replace the quantity lost during surgery. The Partial knee replacement technique generally eliminates the need for blood transfusion.
Lower Morbidity
Benefits of a less invasive procedure include less postoperative discomfort, a shorter hospital stay, less physical therapy, and more rapid healing.
Shorter Recovery Time
Most partial knee replacement patients walk on their resurfaced knee within a few days of surgery, and are generally released from the hospital within a few days. Within 2-4 weeks most patients are driving an automatic car if the left knee is replaced and resuming most normal daily activities be about six weeks. With a total knee replacement, recovery time can be four to five times longer. Also, with a total knee replacement, extensive physical therapy may be required.
Less Bone Removed while retaining the healthy portion of the knee Only a few millimeters of bone on one compartment of the knee is removed to properly fit Partial knee replacement implants. In total knee replacement all knee surfaces lose up to 10mms of bone on each of the three compartments. Since Partial knee replacement implants save more bone, future total knee replacement procedures can more easily be performed if necessary.
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Surgical Technique
See File N°1
Pitfalls
This Patellofemoral Arthroplasty is generally very forgiving and will tolerate minor malalignments and technical errors without adverse effect. Our experience to date, however, has shown that there are some aspects that are less well tolerated:
1. Elevation of Trochlea
Elevation of the trochlea leads to overstuffing of the patellofemoral joint and is not well tolerated. The anterior cut should be parallel to the anterior cortex of the lower quarter of the femur. The trochlear component should be inset so that it is level with both medial and lateral femoral condyles unless there is significant loss of bone on the lateral side as in severe cases. The tip of the prosthesis is inset above the intercondylar notch to allow a bridge of 2-5mm of articular cartilage depending on the size of the knee joint. If this gap is large it will indicate relative extension of the prosthesis suggesting overstuffing. In the lateral post-operative radiograph the tip of the prosthesis should be at the level of, or just above Blumenstadt`s line. a) b) a) Femoral component positioned in 15° extension leading to a tight Patellofemoral joint b) Post-operative view showing correction of femoral component after revision ( see case 1 )
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2. Femoral external rotation
Failure to externally rotate the femoral component on the femur will cause lateral overstuffing and reduce the ability of the patella to track satisfactorily. This is an important feature of the Avon patella ( see highlighted case ).
Chondral and arthritis damage of tibio-femoral joint
Patellofemoral arthritis is a very slowly progressive disease and in many cases the condition will have been present for five to ten years or more. The long-term effects of a chronic synovitis with continuing release of attrition products from both articular cartilage and bone are likely to have a deleterious effect on the articular cartilage structure of the tibio femoral joint. It is, therefore, a matter of fine judgement at the time of arthroplasty as to whether there is sufficient damage to the tibio-femoral joint to justify a total knee replacement. Such is the success of a modern total knee replacement that one can be assured of an excellent long-term result, although there will inevitably be a higher morbidity from this significantly more invasive procedure.
Experience to date suggests that if there is more generalised damage to the articular surfaces of the tibio-femoral joint, damage to the menisci or grade two or more damage in the critical weight bearing areas of the tibial plateau, it may be wiser to perform a total knee replacement. On the other hand if there are only localised areas of chondral damage less than 1cm a simple chondrectomy will be adequate and allow a successful patellofemoral arthroplasty with the expectation of a longevity of ten or more years. In the younger patients under the age of 60 it is clearly desirable to carry out a compartmental arthroplasty rather than a total joint replacement.
Postoperative Management
After careful wound closure there are a number of small points of detail which will facilitate a rapid post-operative recovery and allow accelerated rehabilitation.
1. Infiltrate the wound and the cavity of the knee joint with 10 – 20mls of Marcaine
0.5% and Adrenalin 1/200,000. This allows good pain relief and reduces postoperative bleeding.
2. There is seldom very much post-operative bleeding and, therefore, it is not necessary to use suction drains either in the knee joint itself or in the subcutaneous tissues unless they are very thick.
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3.
After release of the tourniquet, elevation of the limb by 20° or 30° has been shown to reduce post-operative bleeding by at least 50%. The elevation should be maintained for 12 to 20 hours. In other words until the next morning after the operation.
4. The use of anti-inflammatory analgesics administered by mouth or by suppository is an effective way of reducing post-operative pain and swelling and assists considerably with accelerated rehabilitation. These drugs are often required for at least two to three weeks after operation or longer if there is significant synovitis.
Gastric side-effects can be considerably reduced with the use of H2 antagonists or protein pump inhibitors.
5. Ice applied regularly in the post-operative period is very effective in reducing swelling, which will aid rehabilitation. The Cryocuff or a similar system should be applied four to six times a day. This treatment may be required for several weeks into the post-operative period.
6. The patients are generally able to get up and walk on the first post-operative day and start an active range of knee movement. 90° of knee movement is generally achieved within four to six days and the patients can be discharged within this period.
7. The use of CPM is generally unnecessary and slows recovery. The occasional patient will be slow to develop flexion in which case the use of CPM for three to four days will help to develop the range of movement. Occasionally a significant postoperative haemarthrosis develops in which case early arthroscopic wash-out is desirable. If more than 90° of movement has not been obtained within four weeks then admission for manipulation and intensive rehabilitation is essential.
Physiotherapy is usually helpful as an outpatient after discharge from hospital.
Complications
There have been a small number of early complications and to date these have numbered twentytwo (6 %). These include wound inflammation, wound haematoma, wound dehiscence, haemarthrosis, post-operative stiffness requiring manipulation and one case of septic arthritis which occurred two months after operation and resolved satisfactorily.
This total accounts for 6% to date.
There have to date been only 14 cases of recurrent subluxation, two of which have required a distal realignmentprocedure. This amounts to 4 % showing a dramatic improvement on previous designs of arthroplasty. There have been ten subsequent operations including the two distal realignments. These are one manipulation under anaesthesia at three weeks for stiffness, one resuture of wound for wound dehiscence and six arthroscopies one for haematoma and one for the septic arthritis and 4 for disease progression.
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There have so far been no cases of patella loosening, fracture or wear and no cases of trochlea loosening. There have also to date been no cases of deep infection.
The main long-term problem, is that of disease progression in the tibio femoral part of the joint. This has been recorded in 27 cases, twentytwo of which so far have required revision to a total knee replacement (6 %). This can occur in either the medial or lateral compartments and there is no indication from the pre-operative and post-operative radiographs as to why this has occurred. Although some patients may have had more advanced disease with some degree of attrition in the tibiofemoral joint there have been several cases where the tibiofemoral joint has been entirely normal.
A concern has been the fact that in deep flexion the polythene patella bears against the anterior parts of the medial and lateral femoral condyles. This has led to the development and introduction of the odd facet on the patella button. In deep flexion when the patella internally rotates into the inter-condylar notch a flat odd facet on the most medial part of the patella is presented against the condyle. Investigation of several cases with disease progression by arthroscopy has in all cases shown that the area of progression is well away from any point of contact with the patella button.
The number of cases with disease progression remains small and this may be due to natural progression of the arthritic process. There is no evidence to date to suggest that the arthroplasty itself has influenced this in any way. It is probable that some of the earlier cases in the series were performed for a more advanced arthritic process. Survivorship at
5 years is 99.7% for revision for failure of the prothesis and 94% for revision due to diseases progression.
Preoperative views of significant Patellofemoral arthritis.
Disease progression in the medial compartment 6 years later
Progress After Partial Knee Replacement
In Hospital
One Knee
4 days
Two Knees
6 days
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Weeks with Walker/Cane 2
Weeks to Drive
Weeks to Dance
3-4
4-6
Weeks to Golf/Bowls 4-6
Weeks to Doubles Tennis 6-8
Weeks to Jog Not recommended
Results
2-4
3-4
6
6
8
Not recommended
A prospective study of the results of the Avon patellofemoral arthroplasty has been undertaken since its initial implantation in September 1996. To date 370 primary arthroplasties have been performed for isolated patellofemoral arthritis and significant chondral damage, which has failed to respond to conservative surgical treatment. Detailed information has been recorded about the patients including the diagnosis, previous surgical treatment and specific pathological and radiographic findings. Pre and postoperative assessments have been carried out using a variety of outcome tools. Firstly the
Bristol Knee Score (ref. 1) , which records separately pain, overall patient function and knee specific function. In addition Melbourne Patella Score (ref. 2) has been used, which specifically records information about patellofemoral function. Patients have also been scored on the Oxford Knee Score (ref. 3) , which is a disease specific fully validated patient administered scoring system. More recently the Womac 12 score (ref. 4) has been used.
Patients have been reviewed at eight months, two years, five years and will then be followed at eight, ten and twelve years. The median scores are recorded for all patients in the follow-up, excluding those that have dropped out through death or through revision.
The graphs of these follow-ups are shown below. The median outcome scores improved by 50 % at 2 years. Fiftynine knees have now been reviewed at 5 years and the median scores have remained satisfactory with a slight improvement. It is interesting to note that the median scores for all outcome measures have remained remarkably consistent throughout the follow-up period of seven years. There has been no significant change in the median outcomes with increasing numbers of patients entered into the study. This would seem to suggest a constant performance of the arthroplasty. Initially most cases were performed by the senior author but the trial has now been widened considerably to include more than ten different surgeons some of whom are in residency training (ref. 5 -
7) .
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Post-op case at 8 years with full function and no pain
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