Following total knee arthroplasty (TKA) the patella can be a common source of postoperative pain and complications. One of the complications is periprosthetic patella (PPP) fracture which has a reported incidence of 0.68% to 21% in the literature.1 The prevalence can be further subdivided into resurfaced versus unresurfaced patellas, with 0.2% to 21% of fractures occurring in resurfaced and only 0.05% occurring in unresurfaced patellas. In addition, it has been found that patella fractures after TKA are more common following revision TKA, lateral release, or with certain prosthetic designs.2 A patella fracture or any loss of the extensor mechanism in conjunction with a TKA can cause catastrophic results and lead to anteroposterior (AP) instability of the knee joint itself. Therefore, it is of vital importance for these fractures to be managed appropriately.3
To best manage PPP fractures, we must be able to decipher which fracture types will benefit from which type of management. To do this, we utilize the Ortiguera and Berry PPP fracture classification (Table 1) which breaks PPP fractures up into 3 types: type I has a stable implant and an intact extensor mechanism; type II has a disrupted extensor mechanism; and type III is where the patellar component is loose but the extensor mechanism remains intact (Table 1).1,2 Treatment for type I fractures typically consists of conservative management with immobilization. Treatment of type II fractures has historically been considered operative to restore extensor mechanism function but has had a high complication and reoperation rate with Ortiguera and Berry finding a 50% and 42% rate of complications and reoperations, respectively.1 While their classification can help decide who should be operated on, it does not provide information about the type of fixation construct. Even so, it is important to try and restore the extensor mechanism because an untreated disruption can lead to persistent extensor lag, limited range of motion (ROM) and poor quality of life.3 While the majority of type II fractures may benefit from operative management, many surgeons accept a large amount of lag in the extensor mechanism in order not to pursue operative treatment due to poor outcomes. Treatment of type III fractures involves surgery to remove the loose component with or without fixation of the fracture.
To our knowledge, there currently is no optimal technique for open reduction internal fixation (ORIF) of PPP fractures which is likely due to the infrequent nature of these injuries. In this report, we present a novel fixation method for transverse PPP fractures that was utilized in 3 knees with resurfaced patellas in 2 patients and has yielded good clinical results.
Patients who present with concern for PPP fractures should first be evaluated with a history and physical examination. Questioning should be focused on history of symptoms, mechanism of injury, and functional status. Key physical examination features are passive ROM and active ROM with particular focus on extensor lag. Radiographic evaluation should consist of AP, lateral, and merchant views of the affected knee. Comparison images from previous follow-up may be useful for determining the etiology and/or offer insight for future treatment. Radiographs, however, cannot provide definitive evidence of component stability.
Setup and Approach
The patient is placed in the supine position on a radiolucent table. A foam ramp is then placed underneath the operative leg to allow for clear lines of sight for intraoperative fluoroscopic imaging. A midline incision using the previous TKA incision is utilized for exposure but only to an extent needed for adequate fracture exposure. Dissection is performed down to the fracture site which is subsequently debrided and the stability of patellar component is determined (Fig. 1).
Reduction and Fixation
If the component is determined to be stable, an attempt at open reduction and internal fixation is begun. Reduction is accomplished using a point-to-point clamp, placed with one point on the superior aspect of the patella and the other point on the inferior aspect, ensuring that the instrument does not impede placement of the lag screw (Fig. 2). AP and lateral fluoroscopic imaging is then utilized to assess the adequacy of the reduction and changes are made until it is felt that the reduction is as anatomic as possible. A single 2.7-mm screw is then placed across the fracture in a lag by technique manner. A neutralization plate consisting of a X plate (Synthes, Warsaw, IN) from the small fragment set is then placed on the patella to ensure that there is ample bone stock available for screw placement. Once this is determined, 2 screws are placed through the plate into each fragment (Fig. 3). Following screw placement, the point-to-point clamp is removed and fracture reduction and fixation is evaluated visually and radiographically. If there has been loss of reduction or the segments are not well fixed, then the construct should be revised or augmented with another technique (ie, cerclage). Upon completion of patella ORIF, the joint is irrigated and the capsule is closed with 0 vicryl followed by quill. The subcutaneous tissue is closed with 2-0 vicryl and the skin is closed with a 3-0 running absorbable monofilament. Sterile dressings are applied along with a knee immobilizer before taking the patient off the table.
After surgery, patients are to remain in a knee immobilizer until their first postoperative follow-up at 2 weeks which is when they are switched to a total ROM brace. They are allowed to bear weight as tolerated throughout the postoperative period. ROM is introduced from 0 to 45 degrees for postoperative weeks 2 through 6. During the 6-week appointment the ROM is advanced to 90 degrees. Finally, after 9 weeks, the patient has no restrictions in motion and no longer is required to utilize the brace.
Patient A is a 70-year-old man that presented 2 years and 8 months after having staged bilateral TKA’s 6 weeks apart from one another. He sustained a fall from standing height 3 weeks before presentation to the office where he complained of acute right knee pain and chronic left knee pain. Imaging revealed bilateral displaced PPP fractures with the right side thought to be an acute injury and the left side thought to be a chronic injury (Fig. 4). ROM on the right was measured to be flexion to 120 degrees with a 10-degree extensor lag. The left side had flexion of 120 degrees with a 0-degree extensor lag. The decision was made to proceed with ORIF of the right patella to restore function of the extensor mechanism. Postoperatively the patient had no pain at 6, 12, and 24-week follow-up and active range of motion (AROM) was 0 to 85, 0 to 110, and 0 to 120 degrees, respectively at these visits.
The patient underwent ORIF of the left patella because of chronic pain 12 weeks following ORIF of the right patella and followed the same postoperative protocol. The left knee had no pain at 6 and 12 weeks postoperatively with ROM being 0 to 90 and 0 to 120 degrees, respectively.
Patient B is an 80-year-old man that stumbled and fell 6 weeks after his left TKA. He was complaining of pain, swelling, and instability. Physical examination revealed flexion ROM to 100 degrees with a 10-degree extensor lag. The patient underwent ORIF shortly after presentation and had an uncomplicated surgery. At the first postoperative appointment, the patient admitted to full weight-bearing without his immobilizer and to bending his knee. Radiographs at that time revealed failure of fixation at the distal aspect of the patella. The importance of compliance was stressed to the patient and he was placed back into a knee immobilizer for 2 additional weeks. At 4-week follow-up he displayed AROM of 0 to 90 degrees with no pain and his immobilizer was replaced with a brace set at 0 to 50 degrees. At 8 weeks postoperatively the patient reported 1/10 pain with AROM of 5 to 100 degrees.
Periprosthetic fractures of the patella, although relatively rare, do occur. Surgical treatment has been associated with a complication rate of up to 50% and reoperation rate of 42% which has challenged the indications for operative fixation.1 The search for a surgical procedure that can adequately address the pathology while minimizing complications has been a continual process with many failures. In a review that looked at different fixation methods for PPP fractures, it was determined that tension band or cerclage wiring had a failure rate with subsequent nonunion rate that was as high as 90%.4 While this is the case for PPP fractures, there have not been clinical and biomechanical studies looking solely at different fixation methods for PPP fractures. There has, however, been many clinical and biomechanical studies looking at isolated transverse patella fractures in native knees. In these studies, it was determined that a fixed-angle plate is significantly stronger biomechanically than cannulated lag screws or anterior tension wiring in regards to maximum load capacity.5 In addition, one study found that fixed-angle plates showed no fracture displacement during repetitive simulated knee-loading, whereas anterior tension wiring and lag screws with tension wiring showed significant early fracture displacement.6 As this was the case for patella fractures in native cadaver knees, similar studies need to be completed to determine whether the strength of fixed-angle plating is the same for PPP fractures.
In this report, we presented a new technique involving a lag screw with neutralization plate along with short-term follow-up in 3 knees (2 patients) for treatment of transverse PPP fractures that occurred in resurfaced patellas. It is difficult to directly compare the 2 patients involved. Patient A had bilateral PPP fractures, whereas patient B had a unilateral fracture. The time from surgery differed between case A (>2.5 y) and case B (6 wk). While there was radiographic failure in patient B, this was most likely a compliance issue and we still consider it to be clinically successful (Fig. 5). Albeit only 3 PPP fractures, this technique has yielded promising results in the treatment of transverse PPP fractures. At this time, we can only recommend this technique be used in transverse PPP fracture patterns and cannot recommend its use in fracture patterns involving significant comminution or those that involve the inferior or superior pole fractures where there may not be ample bone to allow for this fixation construct.
Preoperative assessment of the patient’s anterior soft tissue status is an important deciding factor in this treatment. The placement of hardware anteriorly on the patella can jeopardize the anterior soft tissues and incision if there is not significant coverage. In this series, we did not have concern regarding anterior soft tissue coverage; however, it certainly cannot be overlooked and should be a factor that is assessed preoperatively before utilizing this technique.
PPP fractures have altered biology and biomechanics compared with typical sport or traumatic native patella fractures. Resurfacing of the patella decreases the bone mass available for fixation. And creation of the arthrotomy disrupts the blood supply to the patella. While we know osteonecrosis does not occur with every arthrotomy, the effects of the alteration in blood flow to the patella and its effect on healing are unknown. This presents a dilemma between allowing the bone to adequately heal and preventing loss of motion which could be an area for future studies.
While the above are limitations to the cases in our report, it does not change the fact that the technique presented had 3 good clinical outcomes, including improvement in pain and extensor lag, without any significant complications. In addition, as the patients were so different, this shows that the technique can be used with success in different settings and when compliance in patients may be of question. Because of this, we would recommend this as a viable new technique to treat transverse PPP fractures.
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