Removal of Well-Fixed Components during Revision Total Knee Arthroplasty

Chapter Preview

CHAPTER SYNOPSIS:

This chapter is aimed at giving the orthopedic surgeon an overview of how to approach the removal of the well-fixed components of a cemented or press-fit total knee arthroplasty. The aim is to accomplish removal of the components with the least amount of bone loss to provide as much support for the revision implants as possible. Many times these techniques involve patience on the surgeon’s part so as to optimize the situation for the revision setting.

IMPORTANT POINTS:

1

The goal in implant removal is to leave as much bone stock as possible for the revision procedure.
2

Working at the implant–cement interface is the key to achieving this goal.

CLINICAL/SURGICAL PEARLS:

1

Work at the implant–cement interface to preserve bone stock.
2

Use thin-bladed single-bevel osteotomes or thin sagittal saw blades.
3

The posterior aspects and intercondylar region of the femoral component are best approached with an offset osteotome.
4

Have a metal cutting tool available if normal techniques do not achieve the goal of removal.
5

Cemented stems may be difficult and require cortical windows or osteotomy to achieve implant removal with minimal insult to the bon integrity.
6

Stacking of osteotomes allows for broader distributed forces against the bone to prevent defects or fractures from occurring.

CLINICAL/SURGICAL PITFALLS:

1

Do not attempt to pry implants off of bone since this can cause significant bone loss or fracture.
2

Not knowing the geometry of the metaphyseal aspects of the implant can cause destruction of instruments or loss of bone when fixation around pegs and keels is not properly addressed.

VIDEO AVAILABLE:

1

Cemented femoral component removal
2

Cemented tibial component removal
3

Cemented patellar button removal
4

Cementless metal-backed patellar component removal
5

Cemented tibial stem removal

HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Total knee arthroplasty (TKA) boasts one of the highest patient satisfaction ratings of all orthopaedic procedures. Satisfaction rates have been estimated to be as high as 90% to 95% as a result of the decreased pain and improved function, which result in an improved quality of life. The number of total knee replacements performed annually in the United States continues to grow and was estimated at 400,000 in 2003. This number is expected to increase as the average age in the United States continues to rise and as the number of indications for joint replacements in younger patients continues to expand.

Despite significant improvements in biomaterials, prosthetic design, and surgical technique, prosthetic knees have a limited life span. While early failures are often attributable to infection, improper surgical technique or poor prosthetic design: late failures are more commonly caused by polyethylene wear, aseptic loosening, and osteolysis. Rand found the 15-year survivability of primary total knee replacements to be 84%. The combination of an aging population, implants with a finite life span, and presence of new indications for TKAs in younger patients results in a growing need for optimizing surgical techniques and longevity of these implants.

When compared with primary TKA, revision TKA is associated with a much wider variety of problems and potential complications. Successful implantation of a new stable and durable prosthesis requires adequate exposure, removal of components with minimal bone loss, restoration of the joint line, correct anatomic alignment, and balancing of the flexion/extension gaps. A preoperative plan that systemically evaluates each step in revision surgery is essential in attempt to foresee and hopefully prevent potential intraoperative problems. Component removal is a critical step in revision TKA. Removal of implants and cement while preserving bone stock and the extensor mechanism of the knee is time consuming and technically demanding to even the experienced surgeon. The goal of this report is to discuss the techniques of revision arthroplasty with emphasis on safe, effectual removal of implants so as to optimize the quality of the reimplantation and thereby maximize the longevity of the revision and patients’ quality of life.

INDICATIONS/CONTRAINDICATIONS

Preoperative planning is essential to a successful outcome with revision TKA. Indications for revising a TKA include unstable prosthesis after trauma, pain secondary to malalignment, and infection into the joint. Contraindications to a complete revision include inadequate bone stock, unresolved infection, and tumor requiring wide surgical resection.

A particularly deleterious cause of failure of a primary TKA is infection, which emphasizes the need for a comprehensive history and physical before revising. Excluding infection must include inquiry about wound healing problems or prolonged drainage from the knee with previous operations. Patients taking immunosuppressive medications or with a history of diabetes are also at greater risk for infection ( Table 18-1 ). Preoperative laboratories including complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein are performed in all patients to help exclude infection. Knee aspiration with synovial fluid assay, Gram stain, and culture should be performed if there is any suspicion of infection. Likewise, assessment of the patient’s nutritional status is also essential as malnutrition is associated with poor wound healing and subsequent infection. Patients with an albumin level less than 3.5 and an absolute lymphocyte count less than 1500 cells/mm are at five to seven times the risk of having wound complications.

TABLE 18-1

Risk Factors for Wound Complications

•

Rheumatoid arthritis
•

Steroid use
•

Immunosuppression
•

Malnutrition:

Preoperative lymphocyte count <1500 cells/mm ³
Preoperative albumin <3.5

•

Peripheral vascular disease
•

Multiple prior scars
•

Prolonged tourniquet times

A complete past medical history is also imperative to help identify comorbidities such as diabetes, rheumatoid arthritis, peripheral vascular disease, or immunosuppressive drugs that may predispose a patient to complications. A history of a transient, postoperative foot drop associated with a neuropraxia should alert the physician of risks for nerve injury, especially in the presence of a valgus deformity. Likewise, a patient who relays a history of postoperative difficulty with leg extension and is found to have an extensor lag or quadriceps weakness may be at risk for complications secondary to a compromised extensor mechanism of the knee. Patients with less than 90 degrees of flexion have a contracted extensor mechanism and those patients with less than 60 degrees flexion typically required an extensile exposure during revision TKA. Examining the shape and location of scars, limb alignment, and knee stability is an essential part of the preoperative evaluation. Some physicians advocate the use of a “sham incision” in patients at risk for problems with wound necrosis.

In addition to the history and physical examination, sequential, chronologic plain radiographs play an integral role in determining the mode of failure. Radiographs should be evaluated for component alignment, signs of progressive loosening, osteolysis, broken cement mantle, or heterotopic ossification. Bone scans may also be used to help diagnose infection, loosening, and occult fractures. It is also essential to obtain previous operative reports in an attempt to identify the size, model, and manufacturer of previous components such that sales representatives may be contacted to assist during implant removal and to ensure that the appropriate extraction tools are acquired preoperatively.

SURGICAL TECHNIQUE

Obtaining Optimal Exposure

The goal of exposure during revision TKA is to provide adequate visualization such that implants and cement may be removed safely while preserving the structural integrity of the knee. Every effort is made to protect ligaments and preserve bone stock. Revision surgery generally requires a larger exposure due to the presence of thick, nonresilient scar tissue and a contracted inelastic extensor mechanism. The surgeon must lower his or her threshold for performing extensile approaches as controlled damage (tibial tubercle osteotomy [TTO]) is far more favorable to repair than uncontrolled damage (patellar tendon avulsion) in already compromised tissues. It is imperative that throughout the exposure a well-vascularized epithelial and soft tissue envelope be maintained to help prevent infection. The surgical exposure is divided into three separate steps: superficial soft tissue dissection, capsular incision, and extensile exposures.

When dealing with the multioperated knee, several scars in various orientations are frequently present. Using the most lateral, vertically oriented incision best preserves the vascularity of skin flaps as the majority of the perforating arteries originate on the medial aspect of the knee from the saphenous and descending geniculate arteries. Skin flaps are kept full thickness and medial and lateral dissection is kept in the subfascial plane to minimize injury to the anastomosis of vessels lying superficial to the fascia. Proper soft tissue technique is important to minimize additional trauma to the delicate vascular supply of the skin. Sharp dissection is favored until the subfascial plane is entered. Atraumatic forceps and the avoidance of excessive skin retraction help avoid crush injuries to the soft tissues during exposure. In addition, early removal of the polyethylene spacer, as well as hyperflexing the knee and externally rotating the leg during tibial preparation, decreases tension on the soft tissues.

Following the superficial dissection and exposure of the extensor mechanism, a primary-style standard medial parapatellar arthrotomy ( Fig. 18-1 ) is typically used to enter the joint.

Pearls and Pitfalls

We do not recommend using a subvastus approach in the setting of a revision TKA unless the surgeon is prepared to perform a TTO to achieve adequate exposure. Likewise, we believe that anterolateral approaches are rarely indicated in revision TKA due to the difficulty in mobilizing the patella medially. However, in rare instances, a lateral parapatellar arthrotomy may be useful for the severely deformed, valgus knee as this exposure may dually function as a lateral release.

Following the arthrotomy, a series of soft tissue releases are performed with the purpose of increasing knee flexion. Generally, knee flexion must approach 110 degrees to evert the patella and gain adequate exposure. Adhesions from the medial and lateral gutters are released and a thorough synovectomy may be performed. The challenge for the surgeon is to protect the extensor mechanism, ligamentous structures, and osseous integrity of the knee while working on osteoporotic, stress-shielded bone in a scarred soft tissue bed. Peripatellar scar tissue is excised and patella tendon adhesions are released down to the superior border of the tibial tubercle. Quadriceps adhesions are also lysed exposing the underlying tenosynovium of the quadriceps and the distal anterior femur. Patellar mobility may be improved with release of the patellofemoral ligament from its condylar origin. The surgeon should also consider a lateral release if there continues to be significant tension on the patella tendon insertion. In the knee with a varus deformity a complete medial tibial release may be beneficial. To accomplish this, the assistant externally rotates the leg while the pes anserine and superficial MCL insertions are elevated as a flap, continuing postermedially to include the semimembranosus insertion. Once all possible releases have safely been performed, the knee should be flexed up and the patella everted without placing undue tension on the insertion of the patella tendon. The published success of individual surgeon’s ability to mobilize the extensor mechanism with soft tissue releases alone varies dramatically. Sharkey et al. recently published their results with extensor mechanism tenolysis and was noted to require only two V-Y turndowns and two patellectomies in 207 total knee revisions. In contrast, Barrack et al. and Rorabeck and Smith required extensile exposures in 49% and in 48% of their revision cases, respectively.

In the event that significant tension remains on the patella tendon, extensile exposures should aggressively be used rather than risking avulsion of the tendon. The three most classic techniques are the quadriceps snip, the V-Y patella turndown, and the TTO. Each of these techniques is associated with varying degrees of morbidity and each technique has its own benefits and potential complications.

The quadriceps snip is an extremely useful technique we use to achieve additional exposure. After making the standard medial parapatellar arthrotomy, the superior aspect of the incision is extended laterally across the quadriceps tendon ( Fig. 18-2 A ). If additional exposure is needed, the release may be extended obliquely into the vastus lateralis ( Fig. 18-2 B ). The rectus snip is a favorable procedure because it is relatively simple to perform and, compared to the standard medial parapatellar arthrotomy, there is no difference in quad strength or knee range of motion postoperatively. However, in those knees in which the extensor mechanism is particularly contracted, the traditional rectus snip may not provide sufficient exposure. A new modification of the rectus snip extends the incision both distally and laterally ( Fig. 18-2 C ) such that it may be converted to a V-Y turndown if necessary.

The V-Y patella turndown was originally described by Coonse and Adams and subsequently modified by Insall. Starting at the superior end of the medial parapatellar incision, the cut is extended distally and laterally at a 45-degree angle, creating a distally based flap. The incision extends through the lateral retinaculum, allowing both distal and lateral retraction of the patella ( Fig. 18-3 A ). Although this technique allows excellent exposure to the knee joint and typically improves postoperative range of motion in the stiff knee, the procedure does have disadvantages. Following a V-Y turndown, patients frequently lose quad strength, which manifests in an extensor lag. In addition, there is potential for the development of AVN in the patella. Scott and Siliski have since modified the procedure by extending the lateral limb through the junction of the vastus lateralis and the retinaculum, thus avoiding the superior lateral geniculate artery ( Fig. 18-3 B ). In theory, this may decrease the incidence of patella AVN and the complications associated with this.