Fig. 15.1
Lateral incision with a full-thickness medial flap should be utilized when multiple incisions are present. The medial parapatellar approach is performed easily despite the lateral skin incision.
Fig. 15.2
Chronic severe extensor lag after a failed primary repair of a patella tendon rupture. (a–d) The dense, adherent scar tissue with multiple anterior knee incisions required plastic surgery closure with a rotational gastrocnemius muscle flap and split thickness skin grafting after the completion of the extensor mechanism reconstruction.
After the completion of the medial parapatellar arthrotomy , the knee is kept in extension, and a 90° bent Hohmann retractor is placed along the medial and lateral joint line (deep to the patellar tendon) to expose the bone-implant interface. The deep MCL is elevated in standard fashion, and release of the medial gutter is performed. By placing limited lateral tension on the patellar tendon, adhesions and scar tissues can be identified and released within the lateral gutter allowing an improved excursion of the extensor mechanism. Avoiding over-retraction of the lateral patellar tendon is essential to avoid avulsion of the patellar tendon at its tibial tubercle attachment.
For the patient with limited preoperative range of motion, care must be taken to not avulse the patellar tendon at the tibial tubercle with knee flexion. Some advocate placement of a threaded Steinmann pin or a staple through the patellar ligament insertion at the tibial tubercle in order to disperse forces on the attachment during exposure. Another technique is to place a towel clip placed into the patellar ligament across the tibial tubercle to protect its attachment. Subluxation of the patella lateral has shown excellent results with no reported patellar tendon avulsions and a limited need for patellar eversion [14].
Removal of the polyethylene insert will also facilitate exposure. It is imperative to understand the manufacturer’s polyethylene locking system in order to execute an efficient means for its removal. Passing a quarter-inch osteotome between the polyethylene and the tibial tray is often adequate to disengage the locking mechanism. Occasionally, an Allen wrench is necessary to remove the polyethylene locking mechanism. In some constrained knee replacements, a high-speed burr and/or quarter-inch osteotomes may be needed to cut the constrained polyethylene post allowing for removal of the metal support post prior to disengaging the locking mechanism.
Once the polyethylene implant has been removed, exposure to the femoral implant is achieved with deep flexion. Using straight and offset Moreland osteotomes , the anterior, distal, and posterior cement interface of the femoral component is disrupted. Removal of the femoral implant is achieved with several mallet blows to a tamp along the anterior flange and distal surface both medially and laterally. At this point, bent Hohmann retractors are replaced medial and lateral to the tibial implant protecting the skin, medial and lateral collateral ligaments, and the patellar tendon. A PCL retractor is carefully inserted posterior to the tibial implant to accentuate facilitate exposure. Moreland osteotomes or a single-sided reciprocating saw or short oscillating saw blade is passed along the medial and lateral tibial implant to disrupt the cement-bone interface. This can be completed with Moreland osteotomes. Once the cement-bone interface is completely disrupted, a Moreland tamp is used to explant the tibia. Following tibial implant removal, the posterior capsule scar tissue and any remaining bone and/or meniscus can be carefully excised. Release of the medial and lateral gutters , as well as resection of any residual posterior scar tissue, will significantly improve the mobility of the extensor mechanism.
Options for Extensile Exposure
Even with proper medial parapatellar arthrotomy technique, adequate exposure may still not be accomplished. In this scenario, it is important to consider extensile exposure techniques. Proximal extensile techniques include quadriceps/rectus snip and V-Y incision turndown. Distal extensile techniques include tibial tubercle banana peel and the tibial tubercle osteotomy [15–21].
The quadriceps snip , discovered by chance according to Insall, creates excellent exposure while limiting the risks of the turndown procedures [18, 19]. A 45° oblique incision is performed at the proximal-lateral aspect of the quadriceps tendon and extended distal-medial across the tendon to the usual origin of a standard parapatellar arthrotomy. This technique allows significant improvement in exposure of the implants by releasing the adherent, scarred soft tissues in the lateral gutter. This release is repaired primarily at the end of the surgery with nonabsorbable suture. There have been numerous studies showing similar clinical outcomes in patients after quadriceps snip versus standard arthrotomy [19, 22, 23]. It may be necessary to include a lateral patellar retinacular release in order to provide adequate exposure and assist with patellar tracking [24].
While infrequently necessary, the V-Y turndown described by Coonse and Adams provides a very wide exposure; however, it places the extensor mechanism blood supply in jeopardy [15]. Due to these concerns, modifications of the Coonse-Adams approach have been described to limit the lateral extension of the incision, therefore minimizing disruption to the lateral superior genicular artery [16, 17]. This type of extensile exposure repair requires a delay in physical therapy to allow healing. It is the author’s opinion that the associated complications from this extensile exposure do not outweigh the potential benefit, and adequate exposure can be achieved by any of the other previously described techniques.
Often the adherent soft tissues or tight structures occur distal along the lateral tibial plateau and patellar tendon. In these scenarios, a distal-based exposure approach may be more appropriate. As described by Lahav and Hoffman, the “banana peel” technique offers improved exposure while maintaining the integrity of the proximal extensor mechanism [20]. With this technique, the patella tendon is elevated as a periosteal sleeve from the tibial tubercle. The authors describe using this technique in combination with a quadriceps snip in 102 consecutive patients, with a minimum 24-month follow-up (mean 39 months), achieving good results [20].
Other times, a more aggressive distal-based approach may be necessary in the setting of press-fit keels, cemented long stems, or porous bone in-growth cone fixation in the proximal tibia. In this scenario, a tibial tubercle osteotomy (TTO) will open the tubercle from medial to lateral, leaving a lateral periosteal hinge (Fig. 15.3) [21, 22]. Although there is a technique described using a smaller osteotomy of the tibial tubercle, it has limited support due to potential complications of failure of repair [25]. In the setting of reimplantation or revision total knee arthroplasty following two-stage treatment of infection, tibial tubercle osteotomy has been shown to be an effective, safe approach [26].
Fig. 15.3
(a–c) Tibial tubercle osteotomy provided extensile exposure for this revision total knee arthroplasty. 18-gauge wire was utilized for repairing the osteotomy.
Depending on implant selection and surgeon preference, the osteotomy fragment is repaired with an 18-gauge wire and/or 4.0 or 5.0 cortical screw/washers. Allowing early range of motion is key to obtaining good outcomes. The technique described by Whiteside and Rorabeck, utilizing wire fixation, allows the patient to undergo early range of motion [21]. According to Ries, a modification of this osteotomy attempts to decrease the distal stress riser by using a distal taper to the fragment [27].
Sun et al. recently compared quadriceps snip and tibial tubercle osteotomy for revision or reimplantation total knee arthroplasty after two-stage revision for infection [28]. Twenty-seven patients underwent TTO and 20 patients had quadriceps snip technique; there were no statistical differences in HHS score, WOMAC score, flexion contracture, and maximal flexion. The authors recommend paying specific attention to osteotomy fixation in an effort to avoid nonunion. Utilizing fresh-frozen human knee specimens, Wall et al. conducted a biomechanical comparison of “banana peel” technique and TTO [29]. Cyclical loading was used to measure mean failure strength as well as change in the distance from the inferior pole of the patella to the tibial diaphysis. There was no difference in mean failure strength on tendon distance between the two techniques. Another prospectively randomized study compared TTO with early rehabilitation protocol versus quadriceps snip for the second-stage revision for infection [30]. The TTO patients had a higher mean KSS, increased maximum knee flexion, and a lower incidence of extensor lag. There was no difference in complications or reinfection rates.
Although proximal and distal extensile exposure techniques can be combined to improve exposure, ideally the surgeon should attempt to determine which single technique provides the greatest exposure. Carefully determining the region where the soft tissue restraints are most limiting and choosing one of the appropriate techniques usually will be sufficient to ensure proper exposure.
Management of Patellar Component
In the revision scenario, it must be decided if the patella implant is to be left alone, removed, or revised. Furthermore, it can be difficult at times to assess a loose patellar component. Rosenberg described five radiographic signs to assess when determining if a patella implant is well fixed: patella fracture/fragmentation, increased bone density in the patella, trabecular collapse of the bone, bone-cement radiolucency, and lateral subluxation of the patellar bone [31]. If the implant is determined loose, proper visualization must be achieved at the implant bone interface (Fig. 15.4). This interface is often obscured by excess fibrous soft tissue that forms within months of the primary surgery; it is imperative to remove this tissue prior to assessment [32, 33]. Another potential indication for patellar implant revision is a metal-backed patella . It has been previously reported that metal-backed components may cause a high incidence of polyethylene wear [34, 35]. Although some have reported good clinical results, if metal-backed patella is identified at time of revision surgery, revision of the implant should be considered [36].
Fig. 15.4
Painful, limited flexion several years after distal femoral replacement for two-stage reimplantation for infection. The patient required an isolated patellar implant revision for the loose patellar component seen in the radiograph.
Patellar implant revision in the setting of infection can be technically challenging. In a recent study by Glynn et al., various methods of patellar revisions such as resurfacing, patelloplasty, augments with trabecular metal, impaction grafting, and patellectomy were attempted during two-stage revision for infection. KSS scores were most improved with patellar resurfacing [37]. This study highlights the importance to preserve as much patellar bone stock as possible at the total knee resection. A previous study by Pagnano et al. suggests that resection of the patellar component during revision or reimplantation total knee arthroplasty may be a reasonable approach for patients with markedly compromised patellar bone stock; however, mild or moderate anterior knee pain can be expected to persist in as much as 1/3 of these patients [38].
Technique for Removal of Patellar Component
Ease of patellar component removal is dependent on the type of implant, implant fixation, and remaining bone stock. First, stabilize the patella using two Lewin clamps perpendicular to the quadriceps tendon and patellar tendon at the superior and inferior patellar pole. The polyethylene implant on a metal-backed patellar components can usually be disengaged from the metal portion with an osteotome, thereby giving adequate exposure to the metal implant. Care must be taken to avoid patellar tendon injury when using osteotomes; it is recommended to pass the osteotomes from the proximal and lateral position only. Stacking osteotomes can be successful in the removal of the metal implant. However, in the case of the metal-backed implant, we recommend using a high-speed burr to safely and quickly remove the metal implant while preserving patellar bone stock. For removal of a cemented polyethylene implant, an oscillating saw with a short wide blade is used to cut the button from the cement mantle. A high-speed burr can be used to section cut the patellar button as well remove the polyethylene/cement from the peg holes. Care must be taken to cover the wound so debris is not spread throughout the knee.
Using Patella to Establish Joint Line
Re-establishing patellar height is a challenge in revision knee arthroplasty. Without proper restoration of the joint line, knee kinematics can be adversely affected leading to anterior knee pain, increased patellofemoral wear, patellar-polyethylene impingement, and decreased flexion [39, 40]. Ideal placement of the patellar component should be 25 mm distal to the medial epicondyle or about the width of a finger above the tibial polyethylene articular surface. Patients with significant distal femoral bone loss may need distal femoral augmentation to restore the appropriate joint line thereby avoiding patella baja and possibly improving clinical outcomes [41]. An improvement in clinical outcomes has been observed if the joint line is within ±4 mm of the unaffected side [42].
Other challenges occur due to long-standing patella baja prior to revision (Fig. 15.5). Whiteside has previously described a tibial tubercle osteotomy where the tendon is proximalized [43]. Typical risk factors and postoperative management associated with tibial tubercle osteotomy must be considered following the use of this technique.
Fig. 15.5
Patella baja reduces the excursion of the patellar tendon making exposure very difficult to during revision surgery. Placing a threaded pin at the tibial tubercle may reduce the stress on the patellar tendon insertion thereby preventing avulsion and avoiding the need for a more extensile exposure.
Addressing Patellar Remnant after Removal of Prior Patellar Component
During a primary total knee arthroplasty surgery, maintaining patellar thickness is relatively easy to achieve by adding a component with the same thickness as the amount of bone removed. In the revision scenario, the deficient patella can be a challenging issue to manage. Patella thickness should be kept greater than 12 mm to avoid fracture; this is frequently not possible during revision total arthroplasty (Fig. 15.6). Seo et al. recommend a technique using transcortical wiring for patella with less than 8 mm in thickness [44]. At a mean of 36.6 months, satisfactory results were noted with a significant improvement in KSS scores. Only 1 patient of 28 (30 knees) experienced a fracture at 1 week postoperatively.
Fig. 15.6
(a) The well -fixed metal-backed patella is a source of metallosis leading to osteolysis, chronic synovitis, and implant loosening. The extent of the metallosis is observed in the supra-synovial pouch (yellow arrows). (b) Hybrid fixation of the tibial and femoral implants with resection of the metal-backed patella. The remaining patella bone was very thin and therefore left unresurfaced.
Revising a patella with inadequate bone stock is often very difficult and may not be an option. If no implant is possible, the remaining bone may track lateral over the femoral condyle rather than within trochlear groove, contributing to further pain and quadriceps weakness. In this scenario a gull-wing patellar osteotomy is indicated [45]. This technique consists of a sagittal osteotomy on the articular surface of the patella. The medial and lateral “wings” are then displaced anteriorly into a V shape, allowing the convex surface the ability to track into the concave trochlear groove [45].
Maintaining the patella assists in preserving the moment arm of the extensor mechanism [46]. Without this mechanical advantage, hamstring and quadriceps torque production are compromised [47]. This is especially noted in early range of motion approximately 15%–30% of flexion to 30% of full extension [46]. In the setting of total knee arthroplasty, this weakness through range of motion can lead to flexion instability [48]. Furthermore, worse functional outcome has been noted in patients who underwent previous patellectomy [47, 49–51].
There have been multiple techniques described in order to reconstitute insufficient patellar bone stock [52–55]. In one study, of 100 consecutive revision total knee arthroplasties (both tibial and femoral components), only 9 had a “patellar shell” remaining [53]. A patellar pouch was created along the peripheral patellar rim using peri-patellar fibrotic tissue or a free tissue flap from the fascia lata or the supra-patellar pouch. Initial patellar thickness ranged from 7 to 9 mm; after the pouch was filled with cancellous bone graft, the average thickness was 22 mm measured on immediate postoperative Merchant radiographs. At final follow-up (mean 36.7 months), patellar thickness averaged 19.7 mm. The overall arc of range of motion improved from 82.8 to 97.8° [53]. One case series has utilized a modification of Hanssen’s technique, and the proximal portion of the patellar tendon is augmented with Achilles tendon allograft and sewn into the distal aspect of the quadriceps . The author reported improved WOMAC scores, absence of extensor lag, and 110–125° of flexion [55].
Patellar Fracture Prior to Revision or Fracture during Removal of Patellar Implant
Etiology of patella fracture is often avascular in nature. Lateral release, fat pad excision, previous surgery, or quadriceps tendon release are often seen in relation to this injury [56]. Various types of knee arthroplasty patella fractures have previously been described by Goldberg [57]. Type I fractures do not affect the implant and are usually isolated to the upper and lower poles. Type II fractures involve the extensor mechanism, with the fracture extending through the central aspect of the patella or the quadriceps. Type III fractures are divided into IIIA and IIIB. Type IIIA involves the inferior pole with disruption of the patellar tendon. Type IIIB involves the inferior pole but lacks disruption of the patellar tendon. A Type IV fracture has a loose implant disrupted from the bone interface with an associated fracture of the patella.
There may be an increased incidence of intraoperative fractures following revision of metal-backed patellas [58]. Osteolytic defects may also weaken the bone and predispose the patella to fracture. Other challenges relate to the avascular nature of the patella and predict healing problems. The surgeon may choose to treat non-displaced fractures without surgery. In one study, patients with non-displaced fractures, defined as less than 2 mm displacement, were placed into a cast in extension for 6–8 weeks and allowed to weight bear [59]. Results were noted as satisfactory for nonoperative treatment in these patients. Fracture displacement and extensor lag often require surgical treatment [57, 59, 60]. Windsor has advocated patellectomy if there is loosening of the implant or disruption of the extensor mechanism [60]. However, flexion instability and extensor lag are common complaints after patellectomy. As an alternative, patelloplasty may decrease anterior knee pain compared to patellectomy. Furthermore, a larger percentage of patients were able to climb stairs [39]. Extensor mechanism reconstruction may be another option if avascular necrosis of the patella fracture fragment exists and the patient has a significant extensor lag (Fig. 15.7).
Fig. 15.7
(a) Chronic displaced superior pole patella fracture with a 50° extensor lag. (b) Whole extensor mechanism reconstruction with screws and 18-gauge wire repair technique.
Best Management for re-Rupture of Patellar Tendon
Patellar tendon disruption following total knee arthroplasty is a devastating complication. The prevalence of patellar tendon rupture has been reported 1.4–3.2% [61]. The primary repair failure rate is greater than 90% when utilizing the following fixation methods: staples, screws, screws with washer, and nonabsorbable suture (Fig. 15.8) [62].
