Templating, calibration with THR may mitigate subsequent limb-length problems

By paying extra attention during total hip replacement to issues that may affect limb length, orthopedic surgeons may avoid the pitfalls of limb-length inequality and possibly related lawsuits, according to a total joint surgeon speaking at the Current Concepts in Joint Replacement 2010 Winter Meeting in Orlando, Fla.

During his presentation, Steven A. Stuchin, MD, of NYU Hospital for Joint Diseases in New York, discussed using such strategies for addressing limb-length inequality during total hip replacement (THR) as preoperative templating, intraoperatively measured resection, using calipers and more sophisticated measuring devices, such as computer navigation.

“The problem for us, both legally and medically, is there is no recognized absolute number for what is good and what is bad” when it comes to leg-length inequality or discrepancy in the length of the patient’s legs postoperatively, he said.

Aim for 5-mm discrepancy

In his presentation, Stuchin noted that total joint surgeons should try to keep limb-length inequality within 5 mm, although surgeons, including Sir John Charnley, have found 10-mm discrepancies acceptable.

Several strategies mentioned in his presentation document results within 5 mm, however Stuchin wrote that none of the techniques for doing that have demonstrated clear cut superiority.

Stuchin said surgeons should check arbitrary fixed points on the pelvis and the leg during the middle of the procedure and at the end to ensure the same distance is maintained throughout. Image: Stuchin SA

When reading studies on this subject, however, Stuchin encouraged his colleagues to keep in mind the investigators’ reported ± data for limb lengths, which in some published studies ranged from ± 5 mm or 6 mm to as high as –20 mm to +22 mm.

“It’s the plus/minus differential, not our average limb length, that gets us in trouble,” he said.

Surgical strategies

Fortunately, orthopedists have a variety of techniques, from simple to complex, that they can use to minimize or eliminate limb-length inequality following THR. Basic templating as first described by Mueller, and measured resection as described by Wilson are among the more straightforward, Stuchin said.

Calibration methods that account for the relationship between the center of the head and the lesser trochanter have may also be considered. According to Stuchin, that distance should be 1.035 times the diameter of the femoral head.

“If you have nothing else, that is something maybe you could work with, as well,” he said.

Check length with patient supine

Stuchin also discussed how to use manual calipers or the electronic versions used during hip navigation by creating a fixed point on the pelvis, identifying another arbitrary point and then measuring the distance between the two points. He said surgeons should check that distance in the middle of the procedure and at the end to ensure that exact distance is maintained throughout the THR, keeping in mind it can change as the leg either abducts or adducts.

Chitranjan S. Ranawat, MD, places a pin intraoperatively to indicate the specific point on the pelvis used for the measurements, Stuchin noted.

“You should always examine patients under anesthesia,” he added.

Regardless of how the patient is positioned for surgery, Stuchin recommended starting with the patient supine and studying the length of their legs in that position. He also suggested having lateral offset stems available to help with stability and leg length in THR cases. – by Susan M. Rapp

Reference:

• Stuchin SA. Limb-length inequality: Patients hate it, lawyers love it. Paper #37. Presented at the Current Concepts in Joint Replacement 2010 Winter Meeting. December 8-11, 2010. Orlando, Fla.

• Steven A. Stuchin, MD, can be reached at the NYU Hospital for Joint Diseases, 301 E. 17th St., New York, NY 10003-3804; 212-598-6708; e-mail: steven.stuchin@nyumc.org.
  Disclosure: Stuchin has no relevant financial disclosures.

Dr. Stuchin provides us with sage advice on a topic of great concern to patients and surgeons; leg-length inequality following THR. He wisely advocates a multi-pronged approach that includes both preoperative templating and intraoperative measurements as no one technique has been shown to be “fail-safe” for avoiding clinically relevant differences in leg lengths. As discussed in his presentation, there is no clear “cut-off” between acceptable and unacceptable lengthening, as patient perceptions of leg length are both unpredictable and multifactorial.

Preparing patients for the possibility of an apparent or true leg-length inequality postoperatively is also crucial. Further, educating patients that lengthening may be required to obtain adequate stability at the time of surgery is important. Finally, as Dr. Stuchin advocates, the surgeon should be prepared with a number of different options to help balance leg length and the need for prosthetic stability including higher offset stems, offset or elevated rim liners and larger femoral heads if required.

– Craig J. Della Valle, MD
Orthopedics Today Editorial Board member
Associate Professor of Orthopaedic Surgery
Rush University Medical Center, Chicago
Disclosure: He is a consultant to Biomet, Smith & Nephew and receives research support from Zimmer.