By Mary I. O'Connor, MD
A hinged-knee prosthesis is an appropriate implant for very select patients. Hinged-knee arthroplasty can be performed with either a standard femoral component or a modular segmental component (megaprosthesis).
Indications for the use of a hinged-knee prosthesis include massive bone loss, severe ligamentous instability, marked imbalance of the flexion-extension gap, absence of a functional extensor mechanism, revision of a previous hinged prosthesis, and complex fractures (particularly periprosthetic fractures) in elderly patients. In retrospective clinical studies, rotating hinged-knee arthroplasty with use of either a standard prosthesis or a megaprosthesis has been effective in managing complex knee problems but has been associated with a high rate of complications. Postoperative range of motion is typically satisfactory, and the average Knee Society score improved from approximately 40 to 771,2. Good-to-excellent functional outcomes were shown in only thirty-three (75%) of forty-four knees in one series3. Complication rates can be high: in one series, 32% of patients had at least one complication1; in another series, the prosthetic survival rate was 79.6% at one year and 68.2% at five years3.
Rotating hinged-knee arthroplasty can be an effective procedure for patients when complex primary and revision knee arthroplasty and fracture challenges are involved. The surgeon and patient should be aware of the high rate of complications associated with this salvage procedure. Careful patient selection and education regarding outcomes and risk are essential.
Rotating hinged-knee arthroplasty should remain in the armamentarium of the advanced knee reconstructive surgeon, but the procedure should be used with caution.
Springer BD, Hanssen AD, Sim FH, Lewallen DG. The kinematic rotating hinge prosthesis for complex knee arthroplasty. Clin Orthop Relat Res.2001;392:283-91.392283
2001
[PubMed][CrossRef]
Springer BD, Sim FH, Hanssen AD, Lewallen DG. The modular segmental kinematic rotating hinge for nonneoplastic limb salvage. Clin Orthop Relat Res.2004;421:181-7.421181
2004
[CrossRef]
Pour AE, Parvizi J, Slenker N, Purtill JJ, Sharkey PF. Rotating hinged total knee replacement: use with caution. J Bone Joint Surg Am.2007;89:1735-41.891735
2007
[CrossRef]
Patellar Fractures Following Total Knee Arthroplasty
By Kevin L. Garvin, MD
Patellar fractures are an unusual complication after total knee replacement and have been reported to occur with a prevalence of approximately 4%1. Most patellar fractures occur within three years of total knee replacement, and many may be asymptomatic or minimally symptomatic at the time of their discovery2. The specific risk factors that are associated with periprosthetic patellar fractures include those that are technical (excessive patellar resection, anterior iatrogenic patellar perforation, revision surgery, component malalignment, and lateral retinacular release), patient related (inflammatory arthritis, male sex, a high level of activity, excessive range of motion of the knee, and poor bone stock), and implant or design related (large central patellar peg, and certain types of fixation)3. Several classification systems, including those by Goldberg et al., Ortiguera and Berry, and Keating et al., have been described1,2, and these fracture classifications are similar. The authors have described longitudinal or vertical fractures with stable implants, displaced fractures, and fractures associated with a loose patellar component. Longitudinal or vertical fractures with a stable implant should be treated nonoperatively. Fractures associated with extensor mechanism disruption and a loose patellar component may be treated operatively. The decision regarding whether or not to operate on these fractures may rely on other variables, including the viability and quality of the remaining bone. Ortiguera and Berry2 reported on twelve fractures that were associated with the disruption of the extensor mechanism. Complications occurred in six of the eleven knees in which the fracture was treated operatively, and reoperation was necessary in five of those six knees. The authors also reported on twenty-eight fractures that were associated with a loose patellar component. Complications developed in nine of the twenty knees in which the fracture was treated operatively, and reoperation was necessary in four of those nine knees1. In contrast, Keating et al.1 reported on seventeen fractures that were associated with a disruption of the extensor mechanism of 1 cm or more. Only three were treated surgically, and two of those three resulted in nonunion. Keating et al.1 reported on fourteen fractures that were associated with a loose component; of the six fractures treated operatively, a deep wound infection developed in two, requiring additional surgery. In one of the six treated operatively, other complications required additional surgery.
On the basis of the results of these studies, several conclusions can be made. Periprosthetic patellar fractures are the most common fracture associated with total knee arthroplasty. The majority of the fractures can and should be treated nonoperatively (specifically, those that are vertical, minimally displaced, or in knees in which the implant is stable). Fractures associated with disruption of the extensor mechanism or a loose patellar component may require surgery if the remaining bone quality is good. Surgeons must be aware that these fractures are associated with a high risk of complications.
Keating EM, Haas G, Meding JB. Patella fracture after post total knee replacements. Clin Orthop Relat Res.2003;416:93-7.41693
2003
[PubMed][CrossRef]
Ortiguera CJ, Berry DJ. Patellar fracture after total knee arthroplasty. J Bone Joint Surg Am.2002;84:532-40.84532
2002
Sheth NP, Pedowitz DI, Lonner JH. Current concepts review. Periprosthetic patellar fractures. J Bone Joint Surg Am.2007;89:2285-96.892285
2007
[CrossRef]
Patellar Maltracking
By Paul F. Lachiewicz, MD
Maltracking of the patellar component of a total knee prosthesis usually leads to complications, such as subluxation-dislocation, fracture, excessive wear, or implant failure. Patellar maltracking is usually a sign of some other technical problem in the arthroplasty. These include incorrect rotation or alignment of the femoral or tibial components and incorrect resection or position of the patellar component. I recommend the use of posterior-stabilized components, with the femoral component aligned with the anteroposterior axis (the so-called Whiteside line1) and the epicondylar axis2, rotation of the tibial component determined with use of anatomic landmarks, and an asymmetric patellar resection. A trial reduction to test patellar tracking is performed with the aid of a towel clip. A lateral retinacular release may be required for knees that have excessive preoperative valgus alignment, severe patellofemoral arthritis, a subluxated patella on the preoperative axial radiograph, or a very stiff knee. An Insall-type proximal realignment is reserved for knees with a dislocated patella preoperatively or a history of recurrent patellar dislocation or revision for maltracking-dislocation, if the orientation of the components is correct3.
I have performed 255 consecutive primary posterior-stabilized knee arthroplasties with use of an anatomic femur and a three-peg offset-dome patella. Component alignment was performed with use of the so-called Whiteside line1 for alignment of the femoral component, the medial border of the tubercle for alignment of the tibial component, and previously reported4 techniques for alignment of the patella. The prevalence of lateral release was 6.6%, and most knees requiring this had excessive preoperative valgus (mean angle, 15°). At a follow-up time of between two and seven years (mean follow-up time, 3.5 years), there had been three patellar fractures (1.2%) and no reoperations for the patellofemoral joint. Two patellar components have radiographic loosening, but the patients are asymptomatic.
Patellar maltracking is an avoidable problem in total knee arthroplasty. When treating a patient with obvious patellar maltracking, it is necessary to evaluate the entire knee prosthesis for alignment, component rotation, and stability. At the time of reoperation for maltracking, the surgeon must be prepared to revise all components. A proximal realignment will usually be successful if component position is satisfactory.
Arima J, Whiteside LA, McCarthy DS, White SE. Femoral rotational alignment, based on the anteroposterior axis, in total knee arthroplasty in a valgus knee. A technical note. J Bone Joint Surg Am.1995;77:1331-4.771331
1995
[PubMed]
Berger RA, Rubash HE, Seel MJ, Thompson WH, Crossett LS. Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop Relat Res.1993;286:40-7.28640
1993
Larson CM, Lachiewicz PF. Patellofemoral complications with the Insall-Burstein II posterior-stabilized total knee arthroplasty. J Arthroplasty.1999;14:288-92.14288
1999
[CrossRef]
Larson CM, McDowell CM, Lachiewicz PF. One-peg versus three-peg patella component fixation in total knee arthroplasty. Clin Orthop Relat Res.2001;392:94-100.39294
2001
[CrossRef]