AAOS Bulletin - April, 2006

Managing litigation risk in minimally invasive total joint surgery

By B. Sonny Bal, MD, MBA

Total joint replacements performed through shorter incisions, and with improved anesthetic techniques and instruments designed to reduce soft-tissue dissection, have generated interest among surgeons, the consumer press and patients. The primary advantage of minimally invasive surgery (MIS) in total joint arthroplasty is improved patient recovery in the short term. But several reports also suggest that MIS procedures applied to total hip arthroplasty (THA) and total knee arthroplasty (TKA) may be associated with an increased incidence of complications and adverse outcomes.

This report reviews the risks that may be associated with THA and TKA, particularly when MIS techniques are used. It also discusses strategies for minimizing the risk of medical liability litigation arising from a suboptimal result.

To reduce litigation risk during minimally invasive total joint surgery, surgeons should be sure to counsel the patient preoperatively to manage patient expectations and explain potential risks, take care in the operating room, document everything and have a postopertive monitoring program in place

Leg length discrepancy

Alterations in existing leg length are sometimes necessary in THA to achieve proper tissue tension. This is a frequent source of patient dissatisfaction and medical liability litigation. The frequency of inadvertent leg lengthening may be increased with MIS THA, particularly early in the surgeon’s learning curve.

In preoperative discussions, the surgeon should always counsel the patient that the operated leg can feel longer or shorter compared to the other side after any THA. In addition to true alterations in limb length, tissue contractures, pelvic obliquity and spinal curvature can contribute to the sensation of unequal leg lengths. Patients with bilateral THAs associated with severe degenerative joint disease and tissue contractures may have persistent sensations that one leg is shorter or longer than the other. In some instances, it may not be possible to equalize leg lengths precisely during surgery, particularly in patients with a contralateral THA, and especially if that hip has had multiple revision procedures.

At our medical center, patients planning elective THA are counseled to avoid the procedure if the thought of any alteration in leg lengths is unacceptable. Leg-length problems can be anticipated by careful templating to understand existing hip offset and length relationships, anatomic variations such as dysplasia, and associated conditions such as spinal disorders. These factors all play a role in accurately performing THA, particularly when routine landmarks are obscured because of limited MIS exposures. It is safest to use a combination of methods to measure leg lengths preoperatively and postoperatively, and to document these in the operative record.

Nerve injury

The risk of injury to specific nerves during THA has been well documented. The sciatic nerve is at risk during the posterior approach. Both the femoral and the superior gluteal nerves are at risk during the direct lateral approach. The anterior approach places the femoral and the lateral femoral cutaneous nerves at risk of injury. The surgeon should document a discussion with the patient about the possibility of a nerve injury despite an otherwise uncomplicated procedure.

Having recognized and documented the risk of a nerve injury, the surgeon should take affirmative steps to minimize that risk. Careful placement of retractors, gentle traction, attention to leg lengths and palpation of the nerve, when applicable, should be routine steps. Documenting these standard procedures in the operative record shows that the surgeon recognized the risk and took steps to reduce it.

Patient-specific situations that can contribute to an increased risk of nerve injury should be recognized in advance, and the procedure modified accordingly. For example, leg lengthening is poorly tolerated in long-standing limb shortening associated with childhood diseases such as hip sepsis, dysplasia or deformity related to childhood fracture. In other cases, if judicious leg lengthening is planned as part of the procedure, proper exposure or palpation of the nerve, and somatosensory-evoked potentials may play a role in reducing the risk of nerve injury. Aggressive tissue retraction during TKA performed through a limited approach can contribute to peroneal nerve palsy. If adequate exposure is difficult during MIS TKA, the standard midline incision should be extended rather than place the patient at risk.

A dislocation or wound hematoma in the acute postoperative period can present as a nerve palsy following uncomplicated THA or TKA. The surgeon should be vigilant to this possibility so that these complications can be identified and immediately addressed. When nerve palsy occurs from injudicious leg lengthening during THA, or because of an expanding hematoma after surgery, prompt surgical correction of the underlying problem may improve the chances of nerve recovery.

Fracture

Unexpected femur fractures can occur during THA, or may become apparent after the operation, when the patient bears weight on the operated hip. The incidence of fracture may be higher with MIS THA. The surgeon can minimize the litigation risk from this complication by documenting that proper surgical techniques for the implantation of press-fit components were followed, and that the bony anatomy was checked for the possibility of an iatrogenic fracture. Recognizing and stabilizing a femur fracture can maintain the excellent outcome of a THA while reducing the risk of litigation.

Inadequate exposure during MIS THA can lead to a pelvic fracture from impaction of an uncemented cup into an underreamed acetabulum, or from inadvertent overreaming the acetabular cavity. The salvage of a grossly overreamed acetabulum is technically difficult and may require the use of allografts, metal augments, acetabular plating and other special equipment and expertise that may not be readily available. To avoid these serious complications, the surgeon should have adequate visualization of the osseous anatomy—regardless of surgical technique—and should be prepared to lengthen the incision if necessary.

Blood vessel injury

Injury to the popliteal vessels during TKA and to the iliac vessels during screw fixation of press-fit cups in THA can have devastating consequences. The fact that these injuries are foreseeable risks of the respective procedures does not necessarily absolve the surgeon of liability after a vascular injury. As is the case with protecting adjacent nerves during THA or TKA, the surgeon should routinely document the steps taken during surgery to minimize the risk of a major blood vessel injury.

Screw fixation of acetabular cups is associated with a finite risk of vascular injury. Because the outcomes of press-fit acetabular cups implanted with and without screw fixation are similar, the surgeon should document those variables—such as poor quality of press-fit, osteopenic bone—that necessitated the incremental risk of acetabular screws.

The risk of popliteal vessel injury during TKA can be reduced by protecting the posterior tissues with a retractor or other instrument that can deflect the saw blade or other cutting instrument. Routine use of these precautions lessens the chances of popliteal vessel injury. If injury does occur, and litigation follows, documentation showing that these routine precautions were in place will show that the surgeon recognized and took steps to reduce the risk. Thus, the complication occurred despite the exercise of reasonable precautions to protect the patient.

Vascular injury during THA or TKA should prompt immediate recognition and consultation with a vascular surgeon. Progressive swelling, pain or neurological changes following TKA or THA must be quickly and aggressively addressed to rule out the possibility of an expanding hematoma. Some bleeding problems can be addressed by embolization using radiographic imaging, but lacerations in major vessels require emergency surgical treatment by a vascular surgeon.

The risk of vascular injury increases in a difficult reconstruction, such as that related to congenital deformity, post-traumatic degeneration or a previously failed arthroplasty. In such instances, the surgeon should carefully consider the level of expertise and resources available before embarking on a difficult operation to avoid overwhelming available resources. Referring the patient to another facility equipped to handle complex hip or knee reconstructions may be the safer course.

Venous thrombosis and pulmonary emboli

To reduce the well-recognized risk of postoperative thrombus formation in both standard and MIS arthroplasty, some method of postoperative anticoagulation must be used in the arthroplasty patient. Preferably, the surgeon should use a multimodal deep vein thrombosis (DVT) prophylaxis program—including early ambulation, ankle and calf exercises, intermittent foot compression devices or compressive stockings—in addition to a pharmacologic agent.

Anticoagulant medications are associated with risks related to bleeding, monitoring and other adverse side effects. The surgeon should have a program of postdischarge monitoring of the patient to ensure compliance and detect any complications.

Component malpositioning

Despite improved instrumentation and computer navigation, some degree of component malpositioning can occur during THA or TKA because of suboptimal bone cuts. All modern instrumentation used to align THA and TKA components has a finite risk of error. An inadequate surgical exposure during MIS increases the risk of component malpositioning.

Suboptimal component positioning can lead to early, recurrent dislocations in THA, or to patella instability and limb malalignment following TKA. When this occurs, the surgeon should recognize the problem and its relationship to component malpositioning. Early recognition and corrective surgery can lead to a satisfactory outcome. But failure to recognize the problem, or conservative treatment when the adverse result is clearly related to less-than-optimal implant positioning, exposes the surgeon to risk.

Learning MIS surgery

MIS for THA and TKA is not for every patient, nor for every surgeon. The learning curve is steep for new operations performed using unfamiliar anatomic approaches. Training seminars, cadaver dissection and mentorship with an experienced surgeon are necessary components of training surgeons to perform MIS total joint surgery. Surgeons must clearly understand strategies for successfully managing the complications of MIS techniques and salvaging the arthroplasty by reverting to a standard, extensile approach before they embark on these procedures.

After proper training, a prudent and safe strategy for learning MIS total joint surgery is to begin shortening the incision of the familiar standard approach. Progressive shortening of the incision as the surgeon gains confidence can reduce the risk of complications. Do not commit to an incision length before the procedure. Each operation should be done with the minimum incision length that provides safe and reliable surgical exposure for that patient. Shorter incisions may be cosmetically pleasing, but incision length is not associated with improved outcomes and it should be not compromise patient safety.

Managing patient expectations

Managing patient expectations is a crucial part of the preoperative discussion with the patient, particularly with MIS procedures. Proper patient counseling will reduce the likelihood of patient disappointment and unhappiness.

Although MIS has been promoted to reduce surgical trauma and speed recovery, the patient should know about the reasonable surgical risks associated with joint replacement and should realize that these risks also apply to MIS procedures. In fact, MIS may be associated with an increased risk of adverse outcomes, especially if the surgeon is new to the procedure. The AAOS and the American Association of Hip and Knee Surgeons have developed detailed and informative position statements on MIS procedures that the patient should be encouraged to review before surgery.

Despite the attractive proposition of MIS surgery, joint replacement remains a major undertaking. For many patients, recovery is associated with a lengthy period of swelling and soreness and a gradual improvement in function. The clicking and popping of prosthetic TKA components and the lateral numbness after a TKA incision can be very disconcerting to the unprepared patient. Altered moods, decreased appetite and lengthy periods of adjustment to a prosthetic lifestyle may complicate recovery, regardless of incision length. In some instances, complete pain relief may not be possible because of associated comorbidities. Following TKA, a small number of patients remain chronically disappointed despite a successful radiographic outcome. All these considerations should be discussed with prospective total joint patients, who may have entirely different perspectives, particularly about MIS surgery.

The patient should understand that MIS may favorably affect early recovery parameters, but that any implant surgery is associated with unpredictable physical and psychosocial responses. The patient should be aware that unforeseeable variables may require that a longer incision be made, and the procedure converted to a standard THA or TKA. Enlightened patients who seek information and alternatives, and actively participate in their health care decision making, will usually have the best outcomes from joint replacement, regardless of the surgical approach.

B. Sonny Bal, MD, is vice-chair of the Legal Advisory Committee for the American Association of Hip and Knee Surgeons. He can be reached at bal@health.missouri.edu


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