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Assessment of Surgical Difficulty
Although surgery cannot be compared with war, Sun Tzu’s philosophies, as written in The Art of War , have been used often in other fields, such as business, politics, and sports. Perhaps some of his principles can be applied when approaching surgery in general and total knee arthroplasty (TKA) specifically. None of us ever wants to be in the uncomfortable position of being “knee deep” into a TKA surgery and being faced with a surprise that we had not planned for. Even careful planning will not prevent all intraoperative surprises, but careful assessment of the patient’s physical examination, a careful review of their medical and surgical histories, and interpretation of all appropriate laboratory and imaging studies can minimize surprises. The scope of this chapter is not specifically about preoperative planning, but careful preoperative planning can help one to assess the difficulties that might occur at the time of TKA. Dr. Lavernia will go further in depth regarding preoperative planning in Chapter 5 .
I learned a critical lesson about assessing a patient in my fellowship year with Kenneth Krackow. In the first few months of my fellowship I was with a first-year orthopedic resident who was on the first day of his total joint rotation. Dr. Krackow had his usual line up of cases that day. Because it was the first day of his rotation, the resident had not seen the patients in the clinic weeks earlier when they had undergone their initial surgical consultations. The resident did not get to examine the patients, and he had not been present at the evaluation of radiographs and testing. Additionally, and most importantly, he did not get to witness the thought process and planning that Dr. Krackow had put into the case at the time the decision was made to proceed with surgery. This was in an era before electronic documentation. Dr. Krackow, as was his habit, had made index cards on every patient, whether their surgery was routine or otherwise. On those cards, he documented items such as previous surgery with scars, retained hardware, knee stability, range of motion of the knee, deformity, bone loss, and vascularity and whether or not the patient needed any further subspecialty consultation before surgery (i.e., vascular surgery or plastic surgery). A thorough plan was in place weeks before surgery. Dr. Krackow would then review this information with the residents and the fellow on his rotation before the surgery at preoperative rounds to make sure this thorough plan was indeed going to proceed with as few unknowns as possible. This review included verifying instrumentation and specialized prosthetics necessary to treat any instability/deformity or defect present, the need for intraoperative imaging or navigation (in trial at the time), having appropriate consultants available as backup if needed, verifying that bone graft was available if needed, having instrumentation available to remove any hardware that was present that might interfere with the procedure, and having available the ability for advanced soft tissue balancing (i.e., medial collateral ligament advancement; see Chapter 9 ). He then brought the index cards into the operating room and reviewed them before each case. For at least the third time, he verified that everything that he anticipated needing for that particular patient and surgery was present, whether the surgery was considered routine or not.
On that first day of the junior resident’s rotation, we had just finished a very complex valgus, flexion contracture knee arthroplasty case with severe deformity, bone loss, and medial collateral ligament laxity when the young resident and I received a lesson that became entrenched in our memories. The resident had been told before surgery that the TKA would be a difficult surgery. Not surprisingly, with Dr. Krackow’s surgical skills and his thorough preoperative planning, the surgery occurred without a hitch. Afterward, the resident, I am assuming to credit Dr. Krackow for a job well done, made the statement: “I am not sure what you guys were talking about, but that was easy!” Dr. Krackow, seeing the opportunity for a teaching moment, immediately corrected the resident: “You have no idea what exactly went into that surgery in the weeks prior to today to make it look so easy. Do not be fooled into thinking you can just show up and perform every total knee that is on the schedule.” He did not do this to admonish the resident but to teach him about the need for extensive preoperative planning.
Prolonged surgical time has been associated with increased risk of surgical infection. Therefore one can conclude that anything that makes a surgery more difficult could lead to increased complication rates. Most TKAs are straightforward and, possibly, even routine. Advances in imaging, surgical technique, technology, fixation, augmentation, instrumentation, navigation, tribology, and prosthetics now make most TKAs very manageable. However, the occasional TKA may be anything but routine. If one takes to heart Sun Tzu’s principles of planning for war and adapts them to surgery while following the example of Dr. Krackow in planning every detail on even the most apparently routine TKA, rarely will one be surprised with something unexpected during surgery. As Dr. Krackow said, “it is almost impossible to imagine that a total knee arthroplasty performed on a thin patient with good preoperative range of motion, no major deformity, and uniformly good bone quality could be anything other than straightforward from a technical standpoint, especially if one assumes no special problems with local tissues, circulation, or hemostasis” (p. 75).
This chapter will discuss items that can be considered as screening factors for difficulty in the performance of a TKA: surgical exposure and soft tissue factors excluding ligamentous instability, deformity, retained hardware, bone quality and bone loss, and ligamentous instability.
Surgical Exposure and Soft Tissue Factors Excluding Ligamentous Instability
There are data that many comorbidities can affect the outcome of TKA. This chapter only mentions comorbidities as they relate to the potential for adding difficulty to the surgical procedure and not how they might affect the ultimate outcome. Chapters 1 to 3 have covered comorbidities and their relationships to outcome. Additionally, surgical exposures and techniques are discussed in Chapter 7 . This chapter discusses how soft tissue factors can make a TKA more difficult to perform.
Morbid Obesity
Obesity in the United States is reaching epidemic proportions, and it has a major impact on lower-extremity Fig. 4.1 total joint arthroplasty, particularly TKA. Although it has been shown that patients who are morbidly obese (body mass index [BMI] >40) and undergo TKA have a higher 30-day postoperative complication rate and patients who are obese (BMI >35) have a higher risk of infection, have a higher cost of care, have longer hospital stays, have a greater odds ratio of revision from any cause, and have a higher mid- to long-term revision rate compared with patients who are not obese. Some sources conclude that patients who are obese should not be excluded from the benefit of TKA, because their overall improvement may be similar to those of patients who have a lower BMI. As the rate of obesity and morbid obesity rises in the United States, one can extrapolate that TKA in patients who are obese or morbidly obese will become more commonplace. Krackow instructs that “it is sufficient to state, for our present purposes, that obesity makes the entire total knee arthroplasty operation more difficult … one is cautioned not to disregard obesity” (p. 84). The bulky soft tissues of the calf and thigh in the patient who is obese do not allow typical flexion of the joint during surgery, thus making exposure, especially of the tibia, more challenging. The thick soft tissue envelope can also render routine instrumentation and retractors insufficient. The surgical incision must typically be longer owing to the depth of the subcutaneous fat layer. All of these factors can lead to a TKA being more difficult in patients who are obese or morbidly obese. Whiteside has described the formation of a lateral subfascial pocket to hold the patella in the everted position to aid in surgical exposure in the patient who is obese and undergoing TKA.
Previous Surgical Scars
Wound complications are obviously better avoided than treated. However, occasionally patients present with poor skin quality. Patients who have previous surgical scars, trauma, burns, and skin grafts can present for TKA. It has been shown that oxygen tension of the lateral and medial skin flaps on postoperative day one in previously unoperated knees is higher in the standard anterior midline TKA approach than in the medial parapatellar and curved medial incisions. Previous arthroscopy scars seem of little consequence. But, surgical scars from open meniscectomy, ligament reconstruction, previous osteotomy, and trauma, including surgical fixation of fractures, have the potential to be problematic. A standard anterior midline approach cannot always be used. Anything that would place a surgical incision at risk of necrosis is best avoided. Previous surgical incisions could require alteration of the standard anterior midline TKA approach. ( Fig. 4.1 ). According to Sanna et al., there are some practical rules that can be helpful in choosing the most suitable incision site for TKA when presented with previous surgical incisions:
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In the presence of a single previous incision the scar, providing it is suitable, can be used.
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If it is not possible to incorporate the scar, the distance between the old and the new incisions should be no less than two-thirds of the length of the scar, and there must be a minimum of at least a 5-cm bridge of skin between the two incisions.
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A previous horizontal incision must be crossed perpendicularly.
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In the presence of multiple previous incisions the most lateral one should be used. To avoid excessive prefascial separations, the medial one can be used, but only if the bridge of skin between the two incisions is greater than 5 cm.
The use of a sham incision technique has been described. This technique was used occasionally during my fellowship in the late 1990s. Although this technique is preferable to postoperative wound necrosis and wound complications, its use today, at least in the United States, is limited as a result of insurance requirements and the potential for other complications from a second surgical exposure.
The use of consultants, especially plastic surgery and vascular surgery, can be helpful in extreme situations. Consultation preoperatively can help in the planning of difficult surgical exposures. The benefit of this option is 2-fold. First, the best surgical approach can be planned before the actual surgery. An additional benefit comes from the fact that should a major wound complication occur, the consultant is already familiar with the patient and the situation and is ready to assist with wound care. The consultant’s availability postoperatively and possibly intraoperatively can help avoid or treat any important wound complications.
Soft Tissue Contractures and Range of Motion
TKA soft tissue balancing will be discussed in Chapter 9 . This section will therefore not go into soft tissue releases and balancing. In Chapter 5 implant selection will be discussed in detail. With extensive soft tissue balancing, occasionally specialized implants with additional constraint and stems should be available for TKA. In a case with either a fixed, severe deformity or limited preoperative range of motion specialized techniques may be required for exposure. The use of a tibial tubercle osteotomy in extension contractures can be useful in gaining intraoperative exposure and flexion ( Fig. 4.2 ). The extreme of extension contractures is seen in the case of converting a previous knee fusion to a TKA. Krackow has advocated the consideration of a tibial tubercle osteotomy for exposure in such cases. The use of additional incisions for osteophyte removal that cannot be accomplished with the standard TKA approaches may rarely, but occasionally, be required ( Fig. 4.3 ). One must be prepared to consider those techniques when indicated, and alternative approaches should be in the armamentarium of any TKA surgeon. Krackow has suggested that patients with a severely limited preoperative range of motion should also be informed before TKA that “poor preoperative range of motion correlates to some degree with poorer than average postoperative range of motion.” (p. 79)
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