Disclosure History of the Procedure: Optimal surgical management of the unicompartmental osteoarthritic knee has eluded the orthopedist for decades. McKeever is credited with recognizing that arthritis of the knee could be unicompartmental in nature. Treatment options for medial compartment arthritis have varied extensively, including valgus unloading braces; opening or closing wedge osteotomies of the proximal tibia, distal femur, or both; and unicompartmental or total knee arthroplasty (TKA). Problem: The problem facing the orthopedist in unicompartmental arthritis is addressing single compartment articular cartilage wear and biomechanical overload while preserving the integrity of the remaining knee joint. Conservative measures including bracing, weight loss, physical therapy, and injection may provide temporary relief, often delaying the need for surgical intervention. Surgical options include arthroscopy, joint debridement, microfracture, osteotomy alone, or cartilage replacement in conjunction with osteotomy. Depending upon the severity of articular cartilage damage and joint deformity, one or more of these measures may ameliorate symptoms such that no further intervention is required. In cases of recurrent pain, a unicompartmental or conventional total joint arthroplasty may be undertaken. Frequency: Osteoarthritis is a widespread joint disorder in the United States, significantly affecting more than 16 million people. Autopsy specimens have demonstrated a 90% prevalence of articular cartilage degenerative changes in weightbearing joints in individuals older than 40 years. The prevalence and severity of osteoarthritis increase with age. The international incidence of osteoarthritis is similar to that in the United States. Treatments rendered are similar to those rendered in the United States. Etiology: Osteoarthritis of the knee usually occurs secondary to mechanical factors, which include partial or complete meniscectomy, femoral osteonecrosis, lower extremity trauma, ligamentous laxity, obesity, and lower extremity malalignment. Pathophysiology: With removal of approximately one third of the meniscus, increased force is transferred directly to the tibial articular surface. The joint also becomes less congruent and is not able to disperse the force across the joint. Both of these factors increase contact stresses, which can lead to articular cartilage damage and subsequent osteoarthritis. Results from multiple laboratory studies have shown that abnormal alignment also leads to abnormal contact stress. Ogata et al, Wu et al, and Reimann performed similar studies in which a varus stress was placed across the knee. Each study documented degeneration of the articular cartilage in the medial compartment. The injury to the articular cartilage occurs in the deeper layers without any surface evidence of injury. Fractures of the tibial shaft and plateau may lead to subsequent lower extremity malalignment. Most clinicians accept less than 10° of angulation in tibial shaft fractures. For instance, residual varus angulation increases contact stresses across the medial compartment of the knee. Tibial plateau fractures also may lead to medial compartment osteoarthritis. The arthritis in this instance is due to direct articular cartilage damage caused by the intraarticular fracture. Ligamentous laxity also is a cause of medial compartment osteoarthritis. Anterior cruciate and/or lateral collateral ligamentous laxity or incompetence has been implicated as causes for medial compartment osteoarthrosis. ACL-deficient knees allow for anterior subluxation of the tibia on the femur. This leads to increased shear force upon the articular cartilage, which leads to early degeneration of the articular surface. Torsional deformities of the tibia and femur have a clinical association with the onset of medial compartment degenerative changes. The torsion may be present on the tibial or femoral side of the knee. This may lead to varus angulation and increased contact stresses across the articular cartilage of the medial joint space, which leads to accelerated medial compartment osteoarthritis. Clinical: Patients generally present with a chief symptom of pain in the knee that has worsened over time. Patients state that the knee generally feels worse in the morning when they awaken and that the knee pain generally lessens with some activity. As their activity increases during the day, so does their pain. Patients may state that anti-inflammatory drugs help alleviate the pain. Patients frequently describe pain on the inside (genu varum) or outside (genu valgum) of the knee if unicompartmental arthritis is the cause of their symptoms. History and physical examination are crucial in making the diagnosis. It is important to ascertain whether trauma to the knee has occurred, indicating an old history of fracture, articular damage, and/or ligamentous injury and malalignment. A history of pain in other joints may alert the physician to an etiology of inflammatory arthritis or bilateral lower extremity malalignment. Physical examination may reveal varus or valgus alignment of the knee. Pain over the medial joint line may indicate a meniscus tear or degenerative changes within the medial compartment. Patellar tendon tenderness also may indicate medial joint degeneration, as well as possible patellar tendon pathology. Patients may have crepitus in the knee. Range of motion (ROM) of the knee may be decreased compared to the opposite side. Fixed flexion contractures are uncommon but may occur in patients with tibiofemoral osteoarthritis. Evaluation of ligamentous stability is important. The integrity of the cruciate ligaments and collateral ligamentous stability may determine the feasible treatment options. Determining whether the patient with varus or valgus alignment of the knee can be passively corrected to neutral is of key importance. Again, this aids in determining the surgical options for treatment of medial compartment disease.
Multiple treatment options are available for isolated medial compartment osteoarthritis of the knee. Surgical intervention is indicated when conservative therapies have failed. Conservative therapies include nonsteroidal anti-inflammatory drugs (NSAIDs), joint viscosupplementation, unloading braces, and physical therapy. Arthroscopy The first operative procedure is knee arthroscopy. Arthroscopy is indicated for patients in whom conservative therapy has failed who want the most minimal surgical procedure available. Arthroscopy usually is used as a temporizing measure until definitive surgical treatment is undertaken. Knee arthroscopy sometimes is indicated as a diagnostic procedure to determine a treatment pathway or may be utilized in conjunction with a definitive procedure. Arthroscopy of the knee has not been shown to slow the course of osteoarthritis of the knee; however, it has been demonstrated to provide pain relief. The period of pain relief ranges from 6 months to a few years. Osteotomy High tibial osteotomy (HTO) is indicated in patients younger than 60 years (ideally in their sixth decade of life) who are in labor-intensive fields and experience activity-related pain with a varus alignment of the knee. The arthritis in the medial compartment must be noninflammatory, and the patient should have no patellofemoral symptoms. Certain criteria regarding ligamentous stability and presence of minimal flexion contracture must be met. If this procedure is used alone, it should be considered a temporizing measure because joint resurfacing ultimately may be required. Arthroplasty Unicompartmental knee arthroplasty (UKA) is indicated in patients who are older than 60 years who have sedentary lifestyles, noninflammatory arthritis, and pain with weightbearing. Patients may have patellofemoral disease but usually are asymptomatic in that compartment. Symptomatic patellofemoral disease is a contraindication to the procedure. Ligamentous stability, weight, and coronal deformity of less than 15° also are considered. TKA is indicated in patients older than 65 years who have somewhat sedentary lifestyles and symptomatic arthritis in 2 or 3 compartments. The arthritis may be posttraumatic, degenerative, or inflammatory.
Relevant Anatomy: See Surgical therapy. Contraindications: Contraindications to lower extremity osteotomy include inflammatory arthritis, limited ROM, advanced patellofemoral and/or lateral compartment arthritis, and varus angulation of more than 10°. Contraindications for unicompartmental arthroplasty include inflammatory arthritis, limited ROM, patellofemoral symptoms, concomitant lateral compartment disease, and anterior cruciate ligament (ACL) or symptomatic posterior cruciate ligament (PCL) deficiency. Contraindications for TKA include acute infection, extensor mechanism disruption, severe recurvatum deformity, significant neurologic deficits, and severe vascular disease. |
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Medical therapy: An attempt at conservative therapy should be undertaken before any surgical procedure is considered. Initial treatment of the patient with medial compartment osteoarthritis consists of NSAIDs, physical therapy, and valgus unloading bracing. Although sometimes underestimated by both physician and patient, physical therapy plays an especially important role in the initial management of osteoarthritis of the knee. Patients can learn early that stretching, strengthening, and ROM activities help them throughout the course of their disease. Physical therapy also may help teach the patient about pain management activities that can be performed on a daily basis to improve the patient's overall condition. Also, physical therapy may help maintain ROM of the knee and decrease the incidence of fixed flexion contractures. These contractures can have a profound effect on the patient's lifestyle and may exclude patients from meeting the surgical requirements for certain procedures. Prevention of flexion contractures makes the surgeon's job much easier at the time of surgery, regardless of the surgical procedure undertaken. NSAIDs also are an important mainstay in the treatment of medial compartment osteoarthritis. A myriad of NSAIDs is available today. The original cyclooxygenase (COX) inhibitors were nonspecific and inhibited both COX-1 and COX-2 enzymes. COX-1 is an important physiologic producer of prostaglandins. These prostaglandins fulfill many vital roles in the body. One such vital role is the production of gastric mucus. When gastric mucus production decreases, the incidence of gastritis and ulcerations greatly increases. Not all patients are able to tolerate these drugs. The increased incidence of gastrointestinal (GI) bleeding leading to hospitalization and even death led to the development of a specific COX-2 inhibitor. COX-1 also has effects on the kidney. It allows for increased renal blood flow (RBF) and glomerular filtration rate (GFR). By inhibiting this enzyme, GFR and RBF are inhibited, which leads to sodium/water retention, water intoxication, and hyperkalemia. COX-2 is essentially a pathologic enzyme. In osteoarthritis, the COX-2 enzyme is up-regulated, increasing the production of prostaglandins. These prostaglandins lead to the inflammation and pain present in arthritic knees. COX-2 inhibitors specifically target these pathologic enzymes, while allowing the physiologic enzymes to provide their needed functions. These COX-2 enzymes have greatly decreased the incidence of GI bleeding, but they are not completely void of complications. COX-2 inhibitors include celecoxib (Celebrex), valdecoxib (Bextra), and rofecoxib (Vioxx). COX-2 specific NSAIDs exhibit anti-inflammatory, analgesic, and antipyretic activities. September 30, 2004, Merck & Co, Inc, announced a voluntary withdrawal of rofecoxib (Vioxx) from the US and worldwide market because of its association with an increased rate of cardiovascular events (including heart attacks and strokes) compared to that of placebo. Alert: On April 7, 2005, valdecoxib (Bextra, by Pfizer, Inc) was voluntarily withdrawn from the US market, pending further discussion with the US Food and Drug Administration (FDA). The association of valdecoxib with potentially life-threatening risks, including myocardial infarction, stroke, and serious skin reactions, initiated an investigation to determine whether the benefits of the drug outweighed the risks. Celecoxib is indicated for relief of the symptoms of osteoarthritis and rheumatoid arthritis and to reduce the number of adenomatous colorectal polyps in familial adenomatous polyposis (FAP). The drug is indicated only in adults. The recommended dosing regimen is either 100 mg bid or 200 mg qd for osteoarthritis. The dose may be increased to 200 mg bid for rheumatoid arthritis and even higher for FAP. Absolute contraindications include hypersensitivity to celecoxib or sulfonamides. Celecoxib should not be given to patients who have had allergic reactions to other NSAIDs or aspirin. Viscosupplementation agents with hylans and hyaluronans also commonly are used. The most extensively studied viscosupplemental agent is hylan G-F 20 (Synvisc) and Hyalgan. Multiple studies have demonstrated significant statistical improvement in clinical symptoms of patients with osteoarthritis of the knee. Viscosupplementation is indicated for the treatment of pain in osteoarthritic knees that has failed to adequately respond to nonpharmacologic therapy or simple analgesics. Hylan G-F 20 is dosed at 2 mL with 3 intraarticular injections under sterile conditions once a week for a total of 3 injections. Contraindications to the use of hylan G-F 20 are known hypersensitivity to hylans and active knee joint infections or infections of the skin at the injection site. Synvisc has been associated with acute postinjection flares. These may mimic an acute septic joint but are treated with ice, rest, analgesics, and observation. The treating physician must be aware of this potential adverse effect and not mistakenly recommend surgical intervention, as would be necessary in the case of a septic knee. Viscosupplementation has not been studied in isolated medial compartment osteoarthritis. Also worth mentioning are glucosamine and chondroitin sulfates. Anecdotally, many patients and physicians report excellent results with this oral supplementation, although these drugs have been used for the last 5-10 years in Europe with reported success. Recent trials comparing glucosamine and chondroitin sulfates to ibuprofen and placebo have substantiated their effectiveness. In addition, a recent report indicated an improvement in radiographic joint space in patients using glucosamine and chondroitin sulfates. Dosages, side effects, and effects on in vivo human articular cartilage as of yet are unknown. Finally, recent studies have shown that valgus unloading braces are beneficial in the treatment of medial compartment osteoarthritis of the knee. The authors found that pain, function, and biomechanical knee loading can be altered with the valgus unloading brace. This may slow the course of the disease process by altering the biomechanics of the knee. Other studies have shown that the valgus unloading brace in association with traditional medical treatment may be even more beneficial. These braces, however, can be expensive, and patient compliance is limited at best. Patient selection is crucial for treatment with a valgus unloading brace for medial compartment osteoarthritis. Surgical therapy: Arthroscopy
Knee arthroscopy and its role in the treatment of degenerative changes of the knee are constantly changing. The treatment of degenerative arthritis of the knee by arthroscopy can be further subdivided into lavage, debridement, abrasion, and cartilage replacement. Lavage alone has been proven to provide temporary relief of symptoms in patients with degenerative arthritis. Many physicians feel that lavage alone is not enough. Debridement of loose articular cartilage or loose bodies has been proven to provide relief in up to 74% of patients at 14 months. Abrasion or subchondral drilling also may be used in the treatment of medial compartment osteoarthritis. In this technique, the subchondral bone is abraded or microfractured to bleeding bone. This allows for the formation of fibrocartilage, which functions similar to articular cartilage but is not nearly as durable. Up to 77% of patients have good results at 2-year follow-up assessments.
As of recently, authors are exploring the option of cartilage replacement with autologous osteoarticular transplant surgery (OATS) or fresh allograft OATS at the time of osteotomy. Although performed at a limited number of centers, this option enables the replacement of damaged articular cartilage at the time of biomechanical realignment.
Patients should exhaust nonoperative management regimens before arthroscopy is considered. Review the patient's history and perform a physical examination. Obtain plain radiographs as described in Workup. These radiographs help to determine the extent of the disease and the presence of any loose bodies or chondrocalcinosis.
Intraoperative findings usually consist of isolated medial compartment osteoarthritis. Chondromalacia of the medial femoral condyle and tibial plateau usually is identified. The lateral compartment is spared in the varus-aligned knee. The patellofemoral joint may show signs of chondromalacia and osteophyte formation, but the patient may have no clinical symptoms. Meniscal tears and chondral fractures or flaps may be identified and treated with an arthroscopic technique.
Postoperatively, it is important to implement early ROM exercises and isometric quadriceps strengthening as soon as possible after surgery. As swelling subsides and ROM increases, institute a strengthening program. Stationary cycle and walking programs also may be started soon following arthroscopy. In general, the recovery time from an arthroscopy ranges from 1-3 months. Patients who undergo simple debridements and lavages are on the low end of that range, while those undergoing abrasion can expect longer recovery periods.
Osteotomy
HTO for the treatment of medial compartment osteoarthritis gained acceptance for 2 reasons. First, the osteotomy can correct the varus malalignment of the limb in question, thereby reducing the stresses passed through the medial compartment of the knee. Secondly, this restoration of normal limb alignment prevents the further destruction of the medial articular cartilage and further collapse into varus. The goal of HTO in the varus-aligned knee is to correct or even overcorrect the limb into valgus, which serves to redistribute the mechanical forces from the medial compartment. Ideal candidates for HTOs are patients who are younger than 60 years and have localized activity-related knee pain, varus malalignment, and medial compartment degenerative arthritis.
Preoperative evaluation should include taking a thorough history, performing a physical examination, and taking radiographic studies of the involved limb. Physical examination should demonstrate an ROM of flexion of more than 90°, flexion contracture of less than 15°, competent medial collateral ligament (MCL), and normal or slightly increased weight. Preoperative radiographs should reveal mild-to-moderate osteoarthritis with varus alignment. No signs of arthrosis should be present in the lateral or patellofemoral compartments. Patient selection probably is the most important key to successful outcome. The patient must be appropriately counseled about the risks of the surgery, the length of the rehabilitation period, and the temporary effect of this surgery. Patients should be aware of and willing to accept the fact that they will ultimately require joint resurfacing.
In the preoperative planning period, the surgeon should choose the type of osteotomy to be performed and the method of fixation to be used. The osteotomy can be distal to the tibial tubercle as described by Jackson and Waugh or proximal as described by Coventry. Once this is determined, 3 types of osteotomies can be performed. The first is a lateral closing wedge osteotomy. In this osteotomy, a lateral wedge of bone is resected from the tibia. The angle of resection is planned from the preoperative radiographs and determined intraoperatively with fluoroscopy. The medial cortex or hinge then is left intact, and the osteotomy is fixed. This is the most stable form of osteotomy and has the highest union rate. Problems arise because the limb is shortened and the distance between the tibial tubercle and patella is decreased, thereby shortening the patellar tendon.
The second type of osteotomy described is a medial opening wedge osteotomy. Again, the wedge to be opened is determined from radiographs, and the procedure is performed under fluoroscopy. Autograft and allograft are generally used to fill the opening wedge. The osteotomy then is fixed. This osteotomy lengthens the leg and moves the tibial tubercle laterally, which may lead to patellofemoral symptoms. The risk of nonunion also is higher in this osteotomy. Fixation must be significant.
The third type is a dome osteotomy. This requires a dome cut, which can be challenging. The tibia then can be rotated into the appropriate position and fixed. This is the least stable osteotomy and requires significant fixation.
The surgeon then must choose the mode of fixation. Options include simple casting, staples and casting, plate and screw fixation, and external fixation. Each of these methods has advantages and drawbacks. Staple and cast fixation is used quite commonly. The patient and surgeon must understand that multiple cast changes may be necessary and that there may be loss of motion when the knee is removed from the cast. This type of fixation is least challenging when converting to a TKA because less hardware is used in the knee compared to the amount used in other procedures.
Recently, plate and screw fixation has become more popular. This method provides rigid fixation and allows for early motion of the knee. Issues arise because the surgical dissection is larger for this fixation. Also, the proximal fragment of the osteotomy must be large enough to accept the screw fixation without fracturing. This procedure uses a significant amount of hardware that must be removed prior to converting to a TKA.
Lastly, external fixation may be used. This provides an excellent means of fixation and allows for adjustments during the postoperative period. Early motion also is possible. Issues arise because superficial skin infections at the pin sites are common, which can lead to the dreaded complication of a septic knee. Cosmesis also may be an issue for some patients.
The fibula is tethered to the proximal tibia and must be addressed in order to afford angular correction when performing an HTO. There are 3 methods of surgical treatment of the proximal tibiofibular joint when performing an HTO. The first is division of the proximal tibiofibular joint, which allows the fibular head to slide proximally. This may risk loosening of the lateral collateral ligament (LCL). The second is resection of the fibular head, which exposes the peroneal nerve to possible iatrogenic damage. The third is a fibular osteotomy. The osteotomy may occur at any site, but use caution to avoid the peroneal nerve proximally.
Articular cartilage usually is not evaluated intraoperatively. Arthroscopy in association with HTO has not been proven to provide any additional benefit and remains quite controversial.
Postoperative management depends upon the type of fixation used. The cast and staple technique requires the patient to be immobilized for 5-8 weeks. Weightbearing is begun gradually, and by 10 weeks after surgery, the osteotomy should be healed and nontender, at which time, full weightbearing is resumed. With plate and screw fixation, early mobilization may be undertaken. Immediate ROM of the knee can be performed. Toe-touch weightbearing can be started within the first 2 weeks postoperatively. Gradual increase in weightbearing can be started at approximately 4 weeks, depending upon the stability of intraoperative fixation. Again, by 10 weeks, the osteotomy is healed and nontender, and full weightbearing is allowed. The same protocol can be followed for the use of external fixation with the knowledge that adjustments may be made to the fixator during the postoperative period (see Images 1-2).
Arthroplasty
The basic indication for UKA is isolated destruction of articular cartilage of the medial or lateral compartments. The ideal candidate is a patient older than 60 years who will place low demands on the implant. Patients who are sedentary are at less risk for mechanical failure and implant loosening than patients who are not sedentary. The patient's symptoms should occur predominantly when weightbearing. Few or no patella-related symptoms should be present. This point, however, remains controversial. The patient should have an ROM of at least 90° and less than a 5° flexion contracture. The coronal deformity of the knee should be less than 15° and correctable to an anatomically neutral position. The cruciate and collateral ligaments should be intact, and no evidence of a large lateral thrust should be present. Patients who are not obese are better candidates.
Take a thorough history, perform a complete physical examination, and obtain appropriate radiographs during the preoperative period. Radiographs should confirm that the angular deformity is at the level of the joint and is not a result of femoral or tibial bowing. The final determination of whether a patient is a candidate for UKA is made intraoperatively. Inspection of the supposed normal compartments is essential. Peripheral osteophytes on the normal condyle are insignificant, but the presence of degenerative changes is a contraindication to proceeding with UKA. The meniscus in the contralateral compartment also must be examined. It should be normal or only minimally changed.
If the possibility of inflammatory arthritis exists, TKA should be undertaken. The advantage of UKA over HTO is a lower complication rate for UKA. Most patients can be discharged from the hospital on postoperative day 1. Immediate ROM exercises with full weightbearing are started on day 1. Patients are advanced to full activity as soon as pain tolerance permits (see Images 3-4).
TKA is indicated in patients with medial compartment arthritis who are older than 65 years, have a sedentary lifestyle, and have degenerative, traumatic, or inflammatory arthritis. Take a thorough history, and perform a complete physical examination. Joint line tenderness, crepitus, and altered ROM are identified. Patients may have either a varus or a valgus alignment. Radiographs may reveal unicompartmental or tricompartmental disease. Preoperative radiographs also allow for templating, which may aide the surgical procedure. Intraoperative findings may consist of a spectrum from unicompartmental to tricompartmental changes. Meniscus tears and ACL deficiency may be encountered. Bony defects may be encountered and corrected with this procedure.
The main advantage of TKA is that it can be used to correct most mechanical problems of the knee. By eliminating most of the natural structures in the knee, TKA obviates any concern about potential deterioration of these structures over time. The technique also is very familiar to the orthopedist, and pain almost always is relieved. ROM exercises are started after surgery, and full weightbearing is started the day after surgery. Activity should progress gradually with continuous quadriceps strengthening until the wound is healed and pain has ceased. At this point, full activity is allowed (see Images 5-6).
Fresh osteochondral allografts have been used to reconstruct knee joints with defects caused by trauma, osteochondritis desiccans, osteonecrosis, osteoarthritis, and locally aggressive benign bone tumors. These procedures are highly technical and involve a large staff, including an active bone bank to procure the specimens. These allografts are performed at specialized centers. Of paramount importance in this procedure is patient selection. Grafts performed for posttraumatic changes had the best results, while those performed for primary osteoarthritis had poor results. Younger patients in the posttraumatic group had the best overall results.
The procedure is fraught with difficulty. Anatomically ligamentous stability and proper limb alignment are necessary. Very often, ACL reconstruction or corrective osteotomy must be performed prior to or at the time of allograft transplantation. Postoperatively, patients are started on passive ROM exercises. Patients' knees are braced. If an osteotomy is performed, patients are restricted to nonweightbearing. No resistive physiotherapy is performed until the brace is removed and the graft has healed, which can take up to 18 months. Follow-up care: See Surgical therapy.
For excellent patient education resources, visit eMedicine's Arthritis Center. Also, see eMedicine's patient education articles Knee Pain, Osteoarthritis, and Rheumatoid Arthritis.
Arthroscopy The main complication experienced with arthroscopy is infection. Some surgeons routinely use perioperative antibiotics, but this has not been proven efficacious. This complication is quite rare, with an incidence well below 1%. Osteotomy HTO has many possible complications. A thorough discussion should be undertaken with the patient prior to proceeding with an HTO. The discussion should address the postoperative course of immobilization and weightbearing as well as possible complications. This allows the patient to understand the time commitment necessary to provide a good result. It is generally accepted that at least 5° of valgus are necessary for adequate correction and unloading of the medial compartment. Malalignment can result from inaccurate preoperative planning, intraoperative technical errors, and failure of fixation of the osteotomy. Malalignment may be further classified as overcorrection or undercorrection. Malalignment may lead to continued symptoms or acceleration of symptoms in the contralateral compartment. Neurologic injury also has been well reported. Injury can occur to the common peroneal nerve, deep peroneal nerve, superficial peroneal nerve, or posterior tibial nerve. Injury can occur during the time of surgical exposure or postoperatively when the nerve becomes encased in scar tissue. Nerve function generally returns if the injury is a neuropraxia due to stretch unless there is an unidentified transection of the nerve at the time of surgery. Vascular injury also has been reported with HTO. The incidence of injury to the popliteal artery and vein is less than 1%; however, this complication can lead to devastating limb loss. Compartment syndrome has been reported. The syndrome occurs in the anterior compartment and can be especially difficult to identify in the immediate postoperative period. Compartment syndrome is caused by swelling in the anterior compartment that cannot be decompressed without surgery. The symptoms include pain out of proportion to the surgery and pain with passive range of motion of the muscles in the anterior compartment. In the immediate postoperative period, this determination can be quite difficult. Suspicion of this condition must be high, and surgical decompression should be swift due to the devastating complications associated with a conservatively treated compartment syndrome. Malunion, delayed union, and nonunion have been reported with HTO. Delayed union rates have been reported to be approximately 2.6%, while nonunion has been reported at 4%. Lateral closing wedge osteotomies provide the largest contact surface of cancellous bone. This, coupled with compression during fixation, leads to the highest rate of union. Deep venous thrombosis (DVT) and pulmonary embolism (PE) have been reported. DVT incidence varies from 1.2-13.5%. The incidence of PE has been reported to range from 1.2-6.1%. Appropriate DVT prophylaxis must be implemented during the postoperative period. The exact method of DVT prophylaxis is highly controversial. The incidence of infection without the use of external fixation has been reported at 3%. The use of external fixation increases the incidence of infection to 11%. Pin care, as well as prophylactic antibiotics, may be used to decrease this incidence. Postoperative stiffness can occur, especially in patients who are immobilized in a cast for an extended period. Fracture is one of the dreaded complications that can occur intraoperatively. Careful planning and caution in the operating room can prevent many of these fractures. Arthroplasty The number of reported complications with UKA has been small. Loosening has been reported, more commonly with the tibial component. However, changes in the design and surgical technique have led to a significant decrease in the incidence of this complication. Osteolysis can occur with gradual cystic changes. Progressive degeneration in the contralateral compartment occurs in approximately 5% of cases. The infection rate is about 1% with appropriate precautions. Complications for TKA include infection, neurovascular injury, extensor mechanism disruption, component failure/wear, osteolysis, and loosening. The accepted infection rate with appropriate precautions has been documented at less than 3%. Surgical technique and instrumentation have reduced the number of malpositioned components leading to early failure. Caution must be exercised when approaching the posterior aspect of the knee in making an osteotomy to avoid laceration or transection of the popliteal artery and vein. TKA performed in a valgus knee places the peroneal nerve at risk for a stretching neuropraxia. Close postoperative examinations must be performed. In general, the quoted lifespan of a TKA is approximately 10 years. Patients with increased activity, including sports, are at a higher risk of polyethylene wear and failure of the implant. Weight also can lead to increased shear stresses to the polyethylene leading to early wear and possible catastrophic failure. If a large osteochondral defect in a varus malaligned knee is present, an osteochondral allograft to correct the deformity can be considered. These are technically demanding surgical procedures. This procedure is usually only performed at centers in which a relatively high volume of this type of case. Fresh osteochondral allografts can be fraught with complications. Mechanical failure is a major concern with the fresh osteochondral allografts and can occur with malposition of the allograft or failure to realign the limb. This type of surgical error can lead to a nonunion at the junction of the host bone and allograft. Fracture of the allograft is a great concern. Failure of the fixation often can occur, especially if no healing has occurred at the junction site. Allograft bone is considered to be somewhat immunogenically privileged, especially when it is cryopreserved. Meniscal tissue and articular cartilage are believed to be immunogenically privileged in that they do not generate an immune response by the host. Fresh osteochondral allografts can be somewhat more immunogenic but are preserved and tested for a couple of weeks prior to implantation. Rejection of the allograft is theoretically possible but occurs in far less than 1% of cases. The cytokine milieu surrounding an allograft plays a role in down-regulating the initial immune response and encourages bony incorporation. The greatest fear with allograft transplantation is disease transmission. Donor selection is critical for control of this problem. All donors are screened for HIV, hepatitis, syphilis, and cytomegalovirus (CMV). Disease transmission was of the utmost concern in the 1980s when screening of the allografts and donors was suboptimal at best. Disease transmission was reported during this time period. Today, with much more stringent and thorough testing, many agencies report no incidents of disease transmission in the last 10 years. The reported risk for the recipient to become infected by a donor testing negative to HIV is less than 1 in 1 million.
Arthroscopy Up to 74% of patients undergoing arthroscopy with lavage and debridement for treatment of arthritis can achieve good-to-excellent results at 14 months. As time passes, the results begin to deteriorate. If abrasion is added, up to 77% of patients may achieve good-to-excellent results at 2 years. With time, the fibrocartilage degenerates, and patient's knee symptoms return. The main disadvantage of arthroscopy is that the procedure is only temporizing and does not address the biomechanical malalignment that coexists. Patients should be counseled that joint resurfacing eventually will be required but that some relief can be achieved with arthroscopy. Osteotomy Clinical experience has confirmed the rationale of limb realignment by HTO, but results deteriorate over the long term. Many studies show that the results of HTO are satisfactory at 5-7 years. After this time, results significantly diminish. Many factors contribute to a good result. Surgical technique and patient selection appear to be the most crucial. Younger patients with primary osteoarthritis and intact ligaments and menisci have better results than do other patients. Also, postoperative alignment with the appropriate amount of correction has a major influence on the length of time in which good results are maintained. Arthroplasty The literature currently supports the use of UKA in a carefully selected patient population. The survivorship of the prosthesis has been reported in several different studies. One study reports a 93% survivorship at minimum 10-year follow-up. Other authors site that results of UKA are not as predictable as those of TKA. However, with careful patient selection, UKA is a viable option. Zukor et al has reported a 76% success rate for 94 fresh osteochondral allografts with an average of 4.3 years follow-up. The complications experienced with meticulous surgical technique are few. The reasons given for failure are malposition of the graft or malalignment of the limb. The results of TKA are excellent, which causes some surgeons to question whether UKA is ever indicated. Reports have documented that a TKA with good cement technique and well-positioned components has more than a 90% chance of surviving more than 15 years. The results of TKA are predictable and reproducible among orthopedists.
The future of the treatment of medial compartment osteoarthritis lies in genetic engineering. Work currently is being performed to generate articular cartilage in vitro with the ultimate goal of resurfacing a femoral condyle or tibial plateau. Viscosupplementation in association with the appropriate cytokine environment is being studied to determine if articular cartilage chondrocytes can be reactivated and programmed to regenerate in order to cover defects within the knee joint. Genetic tests are being identified to determine whether patients have the gene that predisposes them to osteoarthritis, with the ultimate goal being genetic engineering to eliminate arthritis with gene therapy. Controversies abound among orthopedists regarding which osteotomy to perform and whether UKA is an acceptable alternative to TKA. Ultimately, patient selection and the surgeon's knowledge and skill level determine successful outcomes in the treatment of medial compartment osteoarthritis.
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