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Comparing Treatments for Patellar Dislocation

Arthroscopic surgery isn't always better than nonoperative care. That may be especially true in the case of traumatic patellar (kneecap) dislocations. In this study, surgical treatment for primary (first time) patellar dislocation is discussed. Two treatment options were included: arthroscopic and conservative (nonoperative) care. The advantages and disadvantages of each are reviewed. The long-term results (after seven years) are reported.

Patients included were military recruits from the Finish (Finland) army. Most of the patients were young men (ages 19-22) with just a few women included. All had an acute lateral patellar dislocations. The injury occurred during a sports activity or during military training. Lateral means the kneecap moved away from the midline (toward the outside of the knee). When that happens, the structures along the medial (inside) of the knee are often torn or damaged.

In particular, the medial patellofemoral ligament (MPFL) is usually injured. Studies have shown that half the restraining force holding the kneecap in place comes from the MPFL. Successful treatment must address the condition of the MPFL. If it's torn and is not repaired, then the chances of recurrent patellar dislocation increase dramatically.

Successful outcomes may depend on the type of surgery performed. Arthroscopic repair reduces the risk of injuring blood vessels and nerves in the knee. And any loose fragments of bone, cartilage, or meniscus can be removed easily.

But complete rupture of the MPFL at its femoral attachment may not be seen and cannot be restored fully by arthroscopic surgery alone. There may be other soft tissue injures that remain unidentified with arthroscopic repair. The surgeon relies on MRIs to help identify the location and extent of soft tissue damage.

The military recruits were divided in two groups. Group 1 had an acute arthroscopic repair of the medial retinaculum. The medial retinaculum is a band of connective tissue along the inside of the knee that is holding the kneecap in place. At the same time, the lateral retinaculum was released (cut) to reduce the pull from the opposite side of the knee. This arthroscopic stabilization technique was done within seven days of the injury. Details of the surgery and post-operative care were provided.

Group 2 had nonoperative care. Any large loose fragments of bone or cartilage or hematomas (pockets of blood) were removed to relieve pain. Arthroscopy was used to remove any loose bodies but no other repairs were made. Aspiration technique (needle inserted into the joint) was used to remove swelling from bleeding inside the joint.

Nonoperative care consisted of a knee brace with limited knee flexion for three to six weeks and a rehab program supervised by a physical therapist. Range-of-motion and strengthening exercises were prescribed but these weren't any different than what the operative group performed.

With nonoperative care, there is a concern for and history of recurrent (second or third) patellar dislocations. Painful instability with partial dislocation called subluxation of the patella may be the end-result of nonoperative care. But without a study of this type, it would be difficult to tell if surgery improves the outcomes or not. In today's world of evidence-based medicine, we no longer assume surgery to repair the damage would have better results compared with conservative care.

And, in fact, the authors report that the redislocation rate was not significantly different between the two groups. This suggests that 1) surgery doesn't add value or a benefit over nonoperative care or 2) the condition of the MPFL is more important in patellar stability than was previously recognized.

They did find that patients who had arthroscopic repair were able to return to their preinjury level of physical activity more often than those who were treated conservatively. In a military setting, that may be an important finding.

The authors suggest several factors that may have affected results in this study. First, failure to find and fix MPFL abnormalities may be the real key to success after lateral patellar dislocations. Second, this type of repair may not be appropriate for all traumatic MPFL injuries. For sure, they report that an MPFL rupture where it attaches to the femur (thigh bone) cannot be repaired arthroscopically from inside the joint. A different type of surgical procedure is needed.

One of the weaknesses of this study was the fact that not all patients had X-rays or MRIs done. There were various reasons for this, but it affected the authors' ability to compare results equally between those who did have the imaging studies done and those who didn't.

The fact that there were so few women in the study makes this more of a summary of treatment for men. And the equal rate of recurrent dislocations between the groups may be linked with the high levels of activity required of a group of military recruits. So, the results may only be applicable to athletes, soldiers, or highly active young adults.

Their final conclusion was that arthroscopic patellar medial retinacular repair may not be any more successful than nonoperative care in young, active, males with traumatic patellar dislocation. The stabilizing procedure does not guarantee that another dislocation won't happen. The advantages of arthroscopic surgery in such cases (faster return to work, better cosmetic results, less damage to soft tissues) may make this a better choice than open stabilizing procedures.


Petri J. Sillanpää, MD, et al. Arthroscopic Surgery for Primary Traumatic Patellar Dislocation. In The American Journal of Sports Medicine. December 2008. Vol. 36. No. 12. Pp. 2301-2309.

12/22/2008

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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