The Patella continues to Perplex!!!

Few topics in knee replacement have generated as much controversy as the topic of patella resurfacing. Every surgeon literally has his own view. The world has three types of surgeons.Those that resurface always, those that never resurface and the 'selective resurfacers'. The last group think they are the smartest (I wish that were true!!) The literature obviously has articles in favour of all three groups. 


Resurfacing theoretically reduces anterior knee pain, improves quadriceps strength and stair climbing ability. But it brings with it its own set of problems like patellar instability (subluxation and dislocation), fracture, wearing/loosening of the patellar component, patellar clunk and patellar ligament tear. 


So lets see if I can put some sense in this chaos. With controversial topics, reviews and meta analysis are the best bet. 


The most recent meta analysis is from China by He Jy et al published in KNEE in 2011. They concluded that not resurfacing the patella, increased the risk of re operation for patello femoral problems significantly. Importantly there was no difference between the two groups in terms of anterior knee pain rate, knee pain score, knee society score and knee function score. And analysis of high quality studies showed no advantage of resurfacing. 


Another review from China published in 2011 had the same conclusion. There is an increased risk of re operation. This suggests that, if the patient has post-op anterior knee pain and the surgeon finds the patella unresurfaced, he will most probably open the knee!! This remains a non evidence based practice as was proved by Burnett and Bourne in 2004. They stressed that many factors play a role in the development of anterior knee pain after surgery and it should not be assumed that the pain is from the unresurfaced patella. 


So the way I see it, both options work! However there is a slight trend in literature in favour of resurfacing. 


Surgical technique (as usual) remains the most important variable to eliminate complications after resurfacing. 

The correct patellar component size, the proper thickness of the cut, medial placement of the patellar component, rule of no thumb and lateral retinaculum release when needed, should be followed when performing patellar resurfacing during TKR.

In cases where the patella is not resurfaced, the temptation to re operate for patello femoral problems should be resisted. In all probability the re surgery will fail.


And a word of caution for the 'smart selective resurfacers' - there are no proven pre or intra op criteria to decide which patellae to resurface!


Happy Replacing !


Dr Qaed Dhariwal
MS Ortho
Specialist in Joint Replacement
qaedjohar@gmail.com

High Flex Designs - a walk in the clouds

High flex TKR has caught the common man’s imagination. And the Orthopaedic surgeon is all set to take advantage. Promises of unimaginable postoperative flexion are easily made. The medical rep gives guarantees to the doctor and the doctor to the patient. The newspapers are flooded with this miracle of modern science and technology.

Is this all true? Or is it a fairy tale we are all weaving?

Mehin et al in a recent Meta-analysis studied high flex versus conventional implants.  They included only randomised clinical trials. They found no improvement in flexion with high flex implants.

Nutton et al also studied this. They did a prospective double-blind randomised controlled trial. They studied 56 patients. They found no difference in flexion.

NgFY et al also could not find better flexion in the high flex group nor could Kim et al.

Murphy et al did a review where they included 9 studies. Again high flex implants failed to show more flexion.

I think we need to be careful with high flex implants. Tall claims are made on shaky foundations.

Don’t get me wrong. We are achieving better postoperative flexion nowadays. But are we giving the prosthetic design too much credit?

It all matters. The preoperative range of motion, the severity and type of disease, the surgical skill (meticulous ligament balancing and proper implant position) and the patients’ compliance with postoperative physiotherapy.

So let’s come down from the clouds and do our part – balance, rotate and align them well. Then the magic of flexion will happen. Happy replacing!!

VARUS BEFORE - VARUS AFTER??

Knee Replacement has always been about alignment. A recent article by Pagnano et al shook the very foundations of knee replacement by claiming that alignment is a poor predictor of the durability of the implant. Ritter et al however think otherwise. They too studied a huge no of knees (6070) and concluded that alignment is after all important.

I am worried about alignment as I don’t have the luxury of navigation yet. I came across this interesting article. The authors claim that preoperative varus deformity predisposes to varus malposition of the implants. Furthermore, they say that more the varus, more is the risk of malposition. However this is not true for valgus knees in which malposition and malalignment were rare. (I find that difficult to digest)

They used an intramedullary guide for both the femur and the tibia. With varus bowing in the tibia, intramedullary guides can go wrong. This was studied by Teter et al. However they also concluded that extramedullary instrumentation is no better.

Dennis et al recommended that the extramedullary guides should be distally positioned over the center of the talus (3 mm medial to the midpoint of the ankle) to avoid varus tibial resection.

Coming back to the article in question, the authors could not specify the reasons for the varus postop alignment. It is obviously a technical issue. It is an error of the instrumentation or an error of the surgeon’s technique.

The take home message would be to be careful about alignment. Plan properly. Check and recheck during surgery. And be more careful whilst operating varus knees. Happy Replacing!! 

Does postoperative limb alignment affect implant survival in TKR? Does better alignment achieved by Navigation TKR reallly affect implant survival?

The effect of post-operative mechanical axis alignment on the survival of primary total knee replacements after a follow-up of 15 years.

J Bone Joint Surg Br. 2011 Sep;93(9):1217-22.

Bonner TJ, Eardley WG, Patterson P, Gregg PJ

Source: Queen Elizabeth Hospital, Sheriff Hill, Gateshead, Tyne and Wear NE9 6SX, UK. t.bonner10@imperial.ac.uk

Abstract:

Background:  Correct positioning and alignment of components during primary total knee replacement (TKR) is widely accepted to be an important predictor of patient satisfaction and implant durability. The apparent benefits of achieving a neutral mechanical axis (angle of 0°) of the lower limb during TKR surgery has encouraged surgeons and manufacturers to invest time and resources into achieving this alignment target. This retrospective study reports the effect of the post-operative mechanical axis of the lower limb in the coronal plane on implant survival following primary TKR.

Materials and Methods: A total of 501 TKRs in 396 patients were divided into an aligned group with a neutral mechanical axis (± 3°) and a malaligned group where the mechanical axis deviated from neutral by > 3°.

Results: At 15 years' follow-up, 33 of 458 (7.2%) TKRs were revised for aseptic loosening. Kaplan-Meier survival analysis showed a weak tendency towards improved survival with restoration of a neutral mechanical axis, but this did not reach statistical significance (p = 0.47). The pre-operative alignment, type of fixation and primary pathology did not predict either the accuracy of alignment of the mechanical axis or the survival pattern in either group

Discussion: Interest in the accurate positioning and alignment of arthroplasty components has been the subject of controversy, particularly following the development of computer navigated surgery. Justification for using computer navigation and its cost-effectiveness is based on the implication that accurate alignment improves implant survival, thereby reducing the rate of costly revision, but the evidence supporting this is scarce. In present Study the effect of post-operative alignment of the mechanical axis, measured using long-leg radiographs, on the long-term risk of revision surgery demonstrate only a weak relationship between alignment and the risk of revision surgery. Thus, the reported cost-benefit ratio of computer navigated TKR surgery using 3° as the primary outcome measure alone may exaggerate its benefit, with the effect of computer-navigated TKR on long-term implant survival remaining unproven.

Conclusion: We found that the relationship between survival of a primary TKR and mechanical axis alignment is weaker than that described in a number of previous reports.

LEVEL OF EVIDENCE: Level -  IV

IORG Arthroplasty Update

All - Polyethylene tibial component has finally proved its metal (by avoiding metal)

Initial total knee prosthesis had an all polyethylene tibial component. They went out of favour because of fears of subsidence and early failure. Metal backed components were introduced with claims of better load distribution to the proximal tibia and consequently less subsidence and loosening.
However advantages of the all polyethylene tibia cannot be ignored. The component is monoblock thereby completely eliminating backside wear. Moreover it is cheaper making the surgery more cost effective.
So what is the current status of the all polyethylene tibial component?
A ten year randomized controlled trial comparing all poly with metal backed components found no difference in the two components. They studied 566 knees.
Blumenfeld et al in a literature review recommended all poly components in older patients and less active younger patients. The only disadvantages they mentioned were an inability to change liner thickness after final component cementing and inability to use constrained inserts. Also poly exchange is not possible.
Another study in JBJS Am published in 2010 also supports the use of all poly tibial components.

As always there is another side of the coin. So check for yourself and decide. Happy replacing!!

Two-stage Exchange Arthroplasty for Infected Total Knee Arthroplasty: Predictors of Failure.

Clin Orthop Relat Res. 2011 Nov;469(11):3049-54.
Mortazavi SM, Vegari D, Ho A, Zmistowski B, Parvizi J.

Source

The Rothman Institute of Orthopaedics at Thomas Jefferson University Hospital, 925 Chestnut Street, 5th Floor, Philadelphia, PA, 19107, USA.

Abstract

BACKGROUND:

In North America, a two-stage exchange arthroplasty remains the preferred surgical treatment for chronic periprosthetic joint infection (PJI). Currently, there are no proper indicators that can guide orthopaedic surgeons in patient selection for two-stage exchange or the appropriate conditions in which to reimplant.

QUESTIONS/PURPOSES:

To identify (1) the rate of recurrent PJI after two-stage exchange and (2) the role of 15 presurgical and 11 operative factors in influencing the outcome of two-stage revision.

PATIENTS AND METHODS:

From a prospective database we identified 117 patients who had undergone two-stage exchange arthroplasty for PJI of the knee from 1997 to 2007. Failure of two-stage revision was defined as any treated knee requiring further treatment for PJI. We identified 15 presurgical and 11 surgical factors that might be related to failure. Minimum followup was 2 years (average, 3.4 years; range, 2-9.4 years).

RESULTS:

Thirty-three of 117 reimplantations (28%) required reoperation for infection. Age, gender, body mass index, and comorbidity indices were similar in both groups. Multivariate analysis provided culture-negative (odds ratio [OR], 4.5; 95% confidence interval [CI], 1.3-15.7), methicillin-resistant organisms (OR, 2.8; 95% CI, 0.8-10.3), and increased reimplantation operative time (OR, 1.01; 95% CI, 1.0-1.03) as predictors of failure. ESR and CRP values at the time of reimplantation and time from resection to reimplantation were not predictors.

CONCLUSIONS:

Our observations suggest the failure rate after two-stage reimplantation for infected TKA is relatively high. Culture-negative or methicillin-resistant PJI increases the risk of failure over four- and twofold, respectively. We identified no variables that would guide the surgeon in identifying acceptable circumstances in which to perform the second stage.

LEVEL OF EVIDENCE:

Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

IORG Arthroplasty update

Alignment of Computer-Assisted Total Knee Arthroplasty in Patients With Altered Hip Center

J Arthroplasty. 2011 Oct;26(7):1072-7.

Mullaji AB, Lingaraju AP, Shetty GM.

This study aimed to determine limb and component alignment after computer-assisted total knee arthroplasty in 30 patients (32 limbs) with an altered hip center due to a prior hip implant or deformed femoral head. There were no outliers greater than ±3° in the postoperative coronal alignment of the limb and the femoral component in relation to the altered hip center. Two limbs
(8%) were more than ±3° for coronal alignment of the femoral component in relation to the anatomical hip center and 96% of limbs had less than 2° deviation in relation to the altered hip center. 
Computer-navigated total knee arthroplasty results in accurate restoration of lower limb and component alignment in patients with prior hip implants or deformed femoral heads where accurate restoration of alignment may be challenging due to altered hip center.

IORG Arthroplasty Update