Alignment Key To Knee Surgery Success; Even Small Degree Of Bow-Leggedness Can Lead To Degeneration Of Knee Joint After Surgery

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Source:   Duke University Medical Center (http://www.mc.duke.edu/)

Date:   Posted 7/4/2002

Alignment Key To Knee Surgery Success; Even Small Degree Of Bow-Leggedness

Can Lead To Degeneration Of Knee Joint After Surgery

ORLANDO, FLA -- Just as failing to perform an alignment on a car after

installing a new tire will lead to uneven wear and tear and ultimately tire

failure, performing knee surgery without taking into account the proper

alignment of the leg bones above and below the joint could cause future

problems including degenerative arthritis, according to a new study by Duke

University Sports Medicine researchers.

Even a small " varus knee malalignment " -- more commonly known as

bow-leggedness -- can lead to serious future problems for knee surgery

patients, the researchers said. They added that physicians should at minimum

closely monitor all young people who undergo reconstructive knee surgery to

ensure that the leg bones stay in proper alignment, and in some cases

surgically correct the bowleggedness. They see such strategy a possible

preventative measure against the future development of severe arthritis of

the knee.

" Even a relatively small malalignment in normal knees can cause dramatic

alterations in the pressures within the knee joint, and this negative effect

can be greatly magnified if the cartilage within the knee has been damaged, "

said ph Guettler, M.D., orthopedic surgeon and sports medicine fellow at

Duke. " With early recognition and intervention of the malalignment, we can

perhaps prevent the development of serious osteoarthritis from occurring in

the future. "

Guettler conducted a study whose results were prepared for presentation

today (July 3, 2002) at the 28th annual meeting of the American Orthopedic

Society for Sports Medicine (AOSSM). The study received the 2002 Herodicus

Award, given annually by Herodicus Society at the AOSSM meeting for the best

paper submitted by an orthopedic resident or sports medicine fellow.

The Duke researchers sought to characterize the effects of malalignment on

the knee joints of patients who had suffered damage to the cartilage within

the knee. Specifically, they analyzed the pressures within the knee joint

over the cartilage after the creation of a defect in the cartilage and

removal of the meniscus. The meniscus is a piece of fibrous cartilage within

the knee that acts as a cushion or " shock absorber. "

For their studies, the Duke team placed eight cadaveric human knees in an

apparatus that creates loading across the knee joint. They then used the

latest technology to measure pressures over the cartilage within the knee

joint.

The researchers found that even three degrees of malalignment, which can

only be detected by X-ray, can lead to profound deformation of the

cartilage. For example, this small deviation more than doubled pressures on

the middle of the knee joint, and peak contact pressures increased 68

percent. Over time, these uneven pressures within the joint lead to uneven

wear and tear, which leads to painful and often debilitating osteoarthritis.

" Past studies have shown that between 20 and 50 percent of patients who have

had significant knee cartilage damage developed severe arthritis, " Guettler

explained. " What hasn't been shown is why some patients do and some do not.

Our studies would suggest that a very important factor is the subtle changes

in alignment of the leg bones relative to the joint and the pressures they

place on the cartilage within the knee. "

For patients who have significant cartilage damage or have had damaged

cartilage removed, Guettler recommends that very close attention be paid to

the alignment. These patients should be followed very closely, and if any

clinical or X-ray evidence of deterioration occurs, an operation known as an

osteotomy should be considered. This surgical procedure involves taking a

wedge-shaped piece of bone out of the leg, in essence changing someone from

being bow-legged to being knock-kneed. This over-compensation relieves the

pressure on damaged parts of the knee and transfers it to undamaged areas.

" In these cases, the surgery is seen more as a preventative measure against

future osteoarthritis, as opposed to a treatment for a specific disorder, "

Guettler said. " This is an invasive procedure with known complications, yet

it should be considered for these high-risk patients. "

Timing is the key consideration for this procedure, Guettler said. The

osteotomy is usually reserved for someone in middle age who already has

developed significant osteoarthritis. Based on the results of this study, an

osteotomy would be recommended in a predominantly younger population. It

may, however, be more difficult for the parent of an injured 18-year-old to

make such a decision, since the teen-ager would not see the benefits until

decades later, Guettler said.

Guettler said that as new surgical procedures -- such as meniscus

transplants or the implantation of cartilage grown outside the body -- gain

widespread use for patients with knee injuries, physicians should pay close

attention to alignment, since it plays an important role in the ultimate

success of the procedure.

The other members of the Duke teams were Glisson, Alston Stubbs,

M.D., Jurist, M.D. and ce Higgins, M.D. The research was

supported by Duke Sports Medicine.