The vast majority of total knee arthroplasties (TKA) are performed for primary osteoarthritis, but there are numerous rheumatologic, hematologic, metabolic, and neurologic disorders that may contribute to knee dysfunction. In these “special situations,” the surgeon and supportive consultants should be cognizant of unique features that may influence clinical decision making and treatment. Preoperative optimization, postoperative care, technical aspects of the procedure, and component design should be considered. This chapter reviews several of the less common conditions with which the arthroplasty surgeon should be familiar.

Paget disease of bone is a chronic disorder of unknown etiology characterized by increased bone resorption, bone formation, and remodeling.¹ In the United States, the prevalence ranges from 1.5% to 3% in people older than 60 years and it is more common in men.¹,² Osteoclasts mediate the early stage of the disease, which is characterized by excessive bone resorption and marked elevation of serum alkaline phosphatase.³ This is followed by a mixed phase of both osteoclastic and osteoblastic activity, during which there is increased deposition of abnormal bone. Finally, a chronic sclerotic phase occurs, during which bone formation predominates, leading to osseous enlargement, trabecular thickening, sclerosis, and replacement of bone marrow with vascular and fibrous tissue.

The diagnosis of Paget disease of bone, which may be associated with localized bone pain or may be incidental, is confirmed by radiographs or laboratory studies.¹ Monoostotic and polyostotic variants exist, and the pelvis, lumbosacral spine, proximal or distal femur, and tibial plateau or diaphysis are most commonly affected.¹ When symptomatic, constant poorly localized bone pain at rest is typical.¹ Patients may also present with deformity, pathologic stress fractures, secondary arthropathy in adjacent joints, skin temperature changes, or compressive neurologic complications in the spine or skull.¹ Involvement of the hip is more common than the knee, but 10% to 12% of patients with Paget disease of bone in the knee area develop symptomatic arthritis.⁴ Radiographs parallel histologic changes and may show diffuse osteopenia, or more frequently a mixed or sclerotic picture (Fig. 47-1).¹ A bone scan, if obtained, shows increased isotope uptake in involved bone and may be used as a screening tool during evaluation of patients. However, a bone scan may be “cold” during early osteolytic stages of the disease.¹,⁵ Medical treatment of bone pain may include bisphosphonates or calcitonin to relieve symptoms and prevent potential complications and may be helpful in differentiating arthritic joint pain from pain due to the underlying disorder.¹,⁶

Total knee arthroplasty may be indicated and helpful for patients with Paget disease of bone and debilitating gonarthrosis.⁴,⁷,⁸ Most patients are in the sclerotic or relatively inactive phase of disease when presenting for arthroplasty.¹ An evaluation to exclude high-output cardiac failure should be considered, especially in patients with polyostotic disease. Two studies have reported no difference in perioperative blood loss between those patients who received preoperative bisphosphonate therapy and those who did not.⁴,⁸ Varus and anterior bowing of an enlarged distal femur are common radiographic findings (Fig. 47-2), and full-length hip-knee-ankle radiographs in both planes may assist in preoperative planning.¹,⁴ An intramedullary femoral instrument may result in a flexed or varus alignment of the distal femur resection and should be used in conjunction with preoperative planning and/or extramedullary cutting guides.⁴,⁸ When anterior tibial bowing is present, the proximal tibial resection performed with the standard extramedullary tibial guide may result in excessive anterior bone resection or compromise of the extensor mechanism.¹ When there is a severe extra-articular deformity, the choices include correcting the deformity inside the knee joint by asymmetric bone resections (often requiring a varus-valgus constrained component) or an extra-articular osteotomy prior to or in conjunction with total knee arthroplasty. Metaphyseal or diaphyseal osteotomies have been performed and usually are fixed with intramedullary rod or plate fixation.⁹,¹⁰ Medial bone loss and cysts in the proximal tibia can result in a fixed varus deformity. Arthroplasty of the knee with Paget disease of bone is usually performed with posterior-stabilized or constrained condylar components, depending on bone quality and depth of bone resection, and the ligament releases required (Fig. 47-3).¹,⁴,¹¹ Pathologic

fractures through pagetic bone are not uncommon, and the senior author recommends cement fixation of all components and use of variable length stem extensions.⁴

Lee et al.⁸ reported the results of 20 consecutive primary knees in patients with Paget disease of the bone. The mean Knee Society scores for pain improved from 41 to 97 points, and function score from 36 to 67 points postoperatively. A mismatch between the size of the femoral and tibial components was noted in 15 of 21 knees (71%), with the bone affected by Paget disease requiring the larger size component. Difficulty with exposure of the knee was common and partial detachment of the patellar tendon was required in three of four knees in which the patella could not be everted. Ligament balancing was difficult in three knees, with one requiring proximal release and reattachment of the medial collateral ligament, one had complete distal release of the medial collateral ligament, and one had a lateral ligament “reefing” to achieve balance. For these difficult arthritic knees with Paget disease of bone, the senior author prefers an elongated quadriceps tendon incision (or “quad snip” procedure) for exposure, and the use of constrained condylar components rather than collateral ligament release and reattachment or reefing.

Although the prevalence of poliomyelitis has decreased due to vaccination programs, there may occasionally be patients with the neuromuscular sequelae and severe symptomatic knee arthritis and instability. Total knee arthroplasty in these patients is technically difficult due to the combination of deformity, lower extremity weakness, and frequent multiaxial ligament instability. A recurvatum deformity may be present, as well as external rotation deformity of the tibia, excessive valgus deformity, and hindfoot abnormalities.¹² As a result of profound quadriceps weakness, patients may develop a dependence on locking the knee in hyperextension for stability.¹² This propensity to “back-knee” in the stance phase of gait alters joint mechanics, likely increasing osteoarthritic changes and progressive recurvatum.¹² Although the use of a full extremity drop-lock, hinged knee-ankle-foot brace may provide symptomatic relief, this orthosis is usually not well tolerated for prolonged use and ambulation.

If total knee arthroplasty is performed, recurvatum may be corrected by underresection of the distal femur or distal augmentation of the femoral component.¹²,¹³ This technique reduces the knee extension gap to take advantage of the cam effect of the collateral ligaments and the geometry of the femoral component. As this procedure may generate 5 to 10 degrees of flexion contracture, “buckling” or instability of the knee may occur, as patients lose the ability to stabilize their knee through hyperextension. Patients considering total knee arthroplasty should be counseled that a brace may still be required postoperatively to permit ambulation. Another option would be to perform the arthroplasty leaving the knee with 5 to 10 degrees of recurvatum, but this may increase the risk of component loosening and instability.¹⁴

Cemented posterior-stabilized or constrained condylar components with stem extensions can provide stability, can decrease the risk of early component loosening, and are recommended.¹²,¹⁵,¹⁶,¹⁷ Rarely, an extra-articular deformity may be so severe that intra-articular bone resection and soft-tissue releases may result in excessive bone loss and ligament instability. Extra-articular osteotomies have been reported for these situations¹⁸; however, it may be preferable to implant a rotating-hinge prosthesis with custom recurvatum cutting guides.¹⁶,¹⁹

Several studies report, that with careful preoperative planning and component selection, good outcomes of total knee arthroplasty in patients with poliomyelitis. Gan et al.¹⁵ reported 16 arthroplasties performed in patients with polio-affected knees with a minimum 18 months follow-up. There were eight posterior-stabilized, six cruciate-retaining, and two constrained condylar components. Modest improvements in Knee Society scores, Oxford Knee scores, and SF-36 scores were reported, with a low rate of complications. Only one patient with aseptic loosening and acquired hyperextension deformity required revision. Tigani et al.¹⁶ reported the results of 10 patients using one posterior-stabilized, two constrained condylar, and seven rotating-hinge components. Knee Society scores improved in all patients. One patient had revision for infection, and one patient, with a constrained condylar component, had a recurrent recurvatum deformity. A rotating-hinge prosthesis was recommended for these patients to permit hyperextension and compensate for loss of quadriceps strength. Jordan et al.¹⁷ reported the results of 17 primary knees in poliomyelitis patients between 1991 and 2001. The components implanted were eight posterior-stabilized, eight constrained condylar, and one rotating-hinge component. The Knee Society scores improved from 45 to 87 points, and stability was satisfactory in all patients, including four with severe quadriceps weakness. The postoperative complications included one patient with deep vein thrombosis and two knees had a manipulation for stiffness.

Parkinson disease affects approximately 4 million people worldwide and is the second most common neurodegenerative disorder following Alzheimer disease.²⁰ In this disorder, the basal ganglia (substantia nigra) undergo progressive degeneration. Patients lose motor coordination, have muscle tremors, and may have varying degrees of mental impairment. Medical treatment includes dopamine and dopaminergic agonists.

Patients with Parkinson disease who are considered for total knee arthroplasty should have some capacity for ambulation preoperatively and mental capacity to follow postoperative instructions. Relative contraindications include preoperative delirium, inability to undergo regional anesthesia, absence of a multidisciplinary team (neurologist, pain specialist, and physiatrist), a Hoehn and Yahr rating ≥ 3, a knee flexion contracture > 25 degrees, and lack of response to preoperative bupivacaine injection.²¹ Preoperative optimization and physical therapy for these patients is problematic due to the musculoskeletal rigidity, tremor, contracture, and gait instability.²¹ A multidisciplinary approach, with perioperative neurologic consultation, is helpful to decrease length of hospital stay, improve Unified Parkinson’s Disease Rating Scale scores, and improve Knee Society Pain and Function scores.²² These patients are particularly susceptible to postoperative knee flexion contractures, which may be treated with injections of botulinum toxin type A into the hamstring and gastrocnemius muscles, with static progressive extension bracing and rigorous physical therapy.²³ Intraoperatively, these patients may often require the use of constrained condylar or rotating-hinge prostheses for stability, and a postoperative femoral nerve block should be avoided as this may contribute to a flexion contracture.²¹

Several studies have reported that patients with Parkinson disease have improvements in short-term function and pain after total knee arthroplasty comparable to that in the general population.²⁴,²⁵,²⁶ Wong et al.²⁴ compared outcomes of 43 knees in patients with Parkinson disease to age-and gender-matched controls and reported no difference in range of motion (change from baseline), Oxford Knee Scores, or complications at 1 year follow-up. Tinning et al.²⁵ compared outcomes of 32 knees in patients with Parkinson disease to agematched controls and reported no difference in 1 year Knee Society scores, pain, or range of motion between the groups. However, there was a significant decrease in Knee Society Function scores at 5 years in the affected patients. Rondon et al.²⁶ reported a higher rate of revision of knees in patients with Parkinson disease, compared to control patients, in 52 total hip arthroplasties and 71 total knee arthroplasties, with 23.6% requiring revision at average follow-up of 5.3 years. There was an increased rate of infection in patients with Parkinson disease. There is progressive decline in ambulation and overall function in patients with Parkinson disease, and patients and families should be counseled preoperatively. Ashraf et al.²⁷ reported that patients with Parkinson disease have similar knee function up to 3 years postoperatively, but functional outcomes deteriorate with longer follow-up times.

Neuropathic arthritis, or Charcot arthropathy of the knee, is characterized by joint degeneration associated with a loss of sensation or impaired proprioception in the affected limb. The modern associated disorders are severe diabetes mellitus and congenital indifference to pain, with tertiary syphilis and chronic cervical disk herniation now less common.²⁸,²⁹,³⁰ The Eichenholz classification
describes the clinical and radiographic progression of the Charcot joint from the acute phase (dissolution), through the healing phase (coalescence), to the resolution phase.³⁰ Clinically, the knee joint has effusion and instability with relatively little pain considering the degree of destruction. However, approximately half of patients with neuropathic joints have moderate to severe pain with weight-bearing. The differential diagnosis includes low-grade septic arthritis, chronic crystalline arthritis, or pauci-articular rheumatoid arthritis. Radiographic joint destruction may be excessive, and progressive angular deformity is common (Fig. 47-4).²⁸ Nonoperative treatment with a long-leg brace and bisphosphonate therapy has been attempted.³⁰

Historically, neuropathic arthritis of the knee was considered an absolute contraindication for any knee arthroplasty. Knee arthrodesis, once recommended, has generally been abandoned due to poor clinical results.³¹ Over the last decade, total knee arthroplasty has been reconsidered for the neuropathic knee in the coalescence or resolution phases. Preoperatively, a complete medical and neurologic evaluation is recommended, to determine a possible treatable cause of the neuropathic knee, including testing for syphilis, diabetes mellitus, and anemias associated with vitamin B12 or thiamine deficiency. Despite extensive testing, the etiology of many cases remains unknown. There are numerous difficulties in performing total knee arthroplasty in this disorder, including fixed deformity, bone loss, poor bone quality, and collateral ligament insufficiency. Bone loss in the proximal tibia may be severe and require a metal augment, long stems, bone grafting, or highly porous cone for reconstruction (Fig. 47-5).³²,³³,³⁴ A posterior-stabilized component may be attempted, but a constrained condylar or rotating-hinge prosthesis is usually necessary for stability.³²,³³,³⁴,³⁵ A higher risk of periprosthetic fracture has also been reported.³⁴

A relatively high rate of complications has been reported after total knee arthroplasty in patients with neuropathic arthropathy. Parvizi et al.³² reported the techniques and outcomes of 40 knees at a mean of 7.9 years clinical follow-up and 6.4 years radiographic follow-up. Thirty-eight of 40 knees had bone deficiency treated by an augment in 10, autograft in 17, and allograft in 2 knees. A long stem was used in 27 knees and a rotating hinge in 5 knees. There were six reoperations for periprosthetic fracture, aseptic loosening, instability, and deep infection. Bae et al.³⁵ reported the results of 11 rotating-hinge knees at a mean of 12 years follow-up. The mean knee score increased from 45 to 95 points and mean function score increased from 45 to 94 points, and there were three major complications (two dislocations and one infection).³⁵ Tibbo et al.³⁴ reported the outcomes of 37 knees, predominantly with constrained condylar or rotating-hinge components, and 7 with a metaphyseal cone for bone loss. At 10 years, 88% of patients were free of aseptic revision and 70% were free of any revision.
Six (16%) revisions were performed: four for infection, one for tibial component loosening, and one for global instability. Three patients had an intraoperative fracture.

Hemophilia is a disorder of blood coagulation caused by inherited x-linked recessive clotting factor deficiencies.³⁶ The most common forms of hemophilia are classic hemophilia or hemophilia A, with factor VIII deficiency, and Christmas disease or hemophilia B, with factor IX deficiency.³⁶ Recurrent hemarthrosis most commonly affects the knee and there is an immune-mediated arthritis due to chronic exposure of the synovium and articular cartilage to metabolites of blood.³⁶ Chronic synovitis leads to further intra-articular bleeding and high-grade chondral loss, subchondral bone destruction, and joint contractures (Fig. 47-6).³⁶ Radiographs typically show squaring of the patella (Jordan sign), widening of the intercondylar notch, and enlarged femoral condyles, which result in femoral-tibial mismatch.³⁶ Initial management of hemarthrosis includes intravenous clotting factor replacement therapy, and occasionally aspiration and splinting.³⁶,³⁷ Synovectomy, either open, arthroscopic or with radioactive isotopes, may slow the progression of synovitis to joint destruction.³⁷,³⁸

For symptomatic end-stage arthritis, total knee arthroplasty can provide relief of pain and improvement in function. The preoperative assessment should be multidisciplinary and include measurement of Factor VIII and inhibitor levels. Preoperative transfusion should result in factor levels of 100% of normal. Each unit of factor infused per kilogram of body weight should result in a 2% increase in factor levels.³⁹ Patients with inhibitors are resistant to conventional therapy, and special techniques that overwhelm the inhibitor with high doses of factor may allow surgery to be performed safely. Historically, the prevalence of human immunodeficiency virus 1 (HIV-1) infection has ranged from 33% to 92% in patients with hemophilia A, and from 14% to 52% in patients with hemophilia B.⁴⁰ However, these rates have decreased with modern HIV awareness and treatment.⁴⁰ Screening for HIV is recommended in these patients, and antiretroviral therapy may mitigate the previously high risk of prosthetic joint infection.⁴¹,⁴² Perioperatively, surgical drains are not recommended as these result in greater blood loss and do not alter the rate of wound complications, length of stay, or functional outcomes.⁴³ A multimodal blood loss prevention protocol including use of tranexamic acid can decrease perioperative blood loss, need for transfusions, and costs of factor VIII administration.⁴⁴

Total knee arthroplasty in this disorder is very difficult, due to joint soft-tissue fibrosis, severe deformity, poor bone quality, and altered bony anatomy (Fig. 47-7). Exposure may require an extended quadriceps tendon incision or quadriceps snip procedure.⁴⁵,⁴⁶ The senior author has never had to perform a quadriceps tendon turndown or tibial tubercle osteotomy. A flexion contracture associated with valgus and external rotation deformities are most commonly seen. Posterior-stabilized components, with additional stems or metal augments, are frequently used.⁴⁷ Computer navigation was reported in one study to help restore the mechanical axis with improved accuracy of component orientation in patients with hemophilic arthropathy.⁴⁸ Robotic-assisted total knee arthroplasty has also been reported in this disorder.⁴⁹ Cement fixation of all components is generally performed (Fig. 47-8).⁵⁰,⁵¹

There are numerous reports of good functional outcomes of total knee arthroplasty in patients with hemophilic arthropathy.⁴⁵ Goddard et al.⁵² reviewed 60 knees at 9.2 years mean follow-up, and 57 (95%) had a good or excellent result. With infection and aseptic loosening as endpoints, the survival at 20 years was reported as 94%.

Although patients with severe preoperative knee flexion contractures may have improvement in motion and function after knee arthroplasty,⁴⁶ the amount of preoperative flexion contracture may predict postoperative residual flexion contracture.⁵³ One study⁵³ reported that a preoperative flexion contracture threshold of 27.5 degrees predicted a flexion contracture of more than 15 degrees at final follow-up. Some studies have reported a high rate of postoperative complications in hemophilic patients having knee arthroplasty. In a meta-analysis study of 336 knees, Moore et al.⁵⁴ reported a complication rate of 31.5%, most commonly bleeding (9%) and infection (7%). The rate of revision was 6.3%. Recurrent hemarthrosis is an infrequent late complication of knee arthroplasty, occurring in approximately 1.6% of patients. This has been previously treated by open or arthroscopic synovectomy, but embolization has been reported to be safe and effective in these patients.⁵⁵

Diabetes mellitus is a systemic disorder affecting 2% to 4% of the population in the United States.⁵⁶ The rate of total knee arthroplasty is reported to be over twice as high in diabetic patients as in the general population.⁵⁷ Although diabetes may affect almost any organ system, the effect on the vascular system, especially small vessels, is of greatest concern with regard to wound healing, the risk of infection, and the patient’s ability to tolerate the stress of surgery. The extent of impairment correlates with both the duration of disease and adequacy of control of blood glucose level. The preoperative evaluation of cardiac and renal function is important, as cardiac ischemia and impaired renal function may be present without symptoms.

Patients with diabetes mellitus have been reported to have worse functional outcome and less improvement in range of motion than patients without diabetes.⁵⁸,⁵⁹ High rates of postoperative complications are reported in diabetic patients after knee arthroplasty, and even greater with poorly controlled diabetes.⁶⁰,⁶¹ These complications include pneumonia, stroke, urinary tract infection, ileus, postoperative hemorrhage, transfusion, surgical site infection, and death.⁵⁹,⁶⁰,⁶¹,⁶²,⁶³,⁶⁴ Patients with uncontrolled diabetes have also been reported to have longer lengths of hospital stay, fewer routine discharges, and increased rates of 30-day readmission following TKA.⁶⁰,⁶¹,⁶⁵

Most importantly, patients with diabetes have an increased risk of both deep and superficial infections after total knee arthroplasty, possibly due to impaired phagocytosis.⁶⁶,⁶⁷,⁶⁸,⁶⁹,⁷⁰,⁷¹,⁷² There are conflicting reports of a higher association of elevated preoperative hemoglobin A1c with prosthetic joint infection.⁶⁸,⁶⁹,⁷⁰,⁷¹,⁷³ Two studies have recommended that total knee arthroplasty should be delayed until the Hb A1c is less than 7 to 8.⁷⁰,⁷¹

Bone strength and fracture healing are adversely affected by hyperglycemia, and one study reported an association of diabetes mellitus with an increased risk of periprosthetic fracture and aseptic loosening.⁵⁹ Maradit-Kremers et al.⁷⁴ reported that higher preoperative glucose values on the day of surgery were significantly associated with both the overall risk of revisions and revisions for aseptic loosening. Some surgeons have noted reduced complications with the use of sliding scale insulin in the perioperative period. Patients with insulin dependence should be counseled preoperatively that there is an increased risk for reoperation and decreased 10-year implant survivorship compared to nondiabetic patients.⁷⁵

Inflammatory arthropathies, including rheumatoid arthritis, juvenile rheumatoid arthritis, and spondyloarthropathy, now account for only 2.7% of lower extremity arthroplasties performed in the United States.⁷⁶ Total knee arthroplasty has been reported to decrease health care costs and improve health status in patients with these disorders.⁷⁷ Over the last several decades, the rates of total knee arthroplasty have decreased, and the average age at time of surgery has increased among these patients.⁷⁶ This is likely due to an improvement in biologic treatments.⁷⁸,⁷⁹