AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Unicompartmental knee arthroplasty has had varying degrees of acceptance since its introduction approximately 30 years ago. Frequent and early failures were cited in initial studies. By the late 1990s, however, unicompartmental knee arthroplasty for the treatment of localized knee arthritis was becoming more common, and early outcome reports were favorable. Theoretical advantages of the procedure include preservation of uninvolved tissue and bone, reduced operative time, better range of motion, improved gait, and increased patient satisfaction. With appropriate patient selection, careful surgical technique, and proper implant design, unicompartmental knee arthroplasty can now be viewed as a procedure with reliable medium- to long-term success.

For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center and Arthritis Center. Also, see eMedicine's patient education article Knee Joint Replacement.

History of the Procedure

In the late 1950s and 1960s, MacIntosh and McKeever reported on the placement of a prosthetic disk into the diseased tibial plateau. The prosthesis was inserted into the affected side of the knee joint without cement. MacIntosh first used an acrylic prosthesis but later employed a metal one with a concave surface. The McKeever prosthesis had a small, T-shaped keel on its undersurface to improve fixation.

In the early 1970s, Gunston and Marmor independently introduced the cemented unicompartmental knee arthroplasty. Gunston employed a circular runner of stainless steel and a track of high-molecular-weight polyethylene, for use as either a bicompartmental or unicompartmental replacement. In 1988, Marmor published his 10- to 13-year follow-up of 97 cases. This report included 21 treatment failures attributed to development or progression of arthritis in the other compartments or to loosening, with subsidence of a thin (6-mm), all-polyethylene tibial component.

Laskin (1978) published a 2-year follow-up of patients using the Marmor modular knee replacement; he found that 35% of the knees had a fair or poor result, with high incidence of loosening of the implant and degeneration of the opposite tibiofemoral component. The revision rate was 22%. Insall (1980) published a series in which the conversion rate to a total knee arthroplasty was 28%.

Consequently, by the late 1980s, the popularity of unicompartmental knee arthroplasty had waned. However, after recognizing the need to avoid overcorrection of the mechanical axis, surgeons ultimately were able to reduce the risk that pain in the "normal" compartment would cause early failure. With the publication of several studies in the late 1980s and 1990s reporting 10-year survivorship rates exceeding 93%, enthusiasm for unicompartmental knee arthroplasty again increased, the survivorship rates being comparable to those for total knee arthroplasty. Although in 1994, the Swedish Joint Replacement Registry reported a high percentage of poor results for unicompartmental knee arthroplasty, these outcomes mainly reflected the fact that the surgery was performed on patients with chronic inflammatory arthritis.

Interest in unicompartmental knee arthroplasty was also stimulated by the introduction of the mobile-bearing form of the procedure. Goodfellow and O'Connor (1978), along with others, published excellent long-term survivorship rates associated with this technique. Their rationale for the procedure's success was clearly stated: a mobile bearing (also called a meniscal bearing) provides the unique combination of complete congruency of the articular surface (to minimize wear and creep) and total freedom of movement (to accommodate the preferred motion pattern of the retained natural compartment).

The past few years have again seen a heightened interest in unicompartmental arthroplasty, particularly because of the introduction of the minimally invasive parapatellar technique. This form of the procedure potentially can reduce morbidity, complications, and length of hospital stay. Many now view unicompartmental knee arthroplasty as preferable to high tibial osteotomy (HTO) in relatively young patients with medial compartment arthritis.

Problem

The concept behind unicompartmental knee arthroplasty is the replacement of only the damaged part of the knee and preservation of as much normal tissue and bone as possible to allow the restoration of normal kinematics.

Because unicompartmental knee arthroplasty is typically performed for medial osteoarthritis, this condition is the focus of this article. The surgical alternatives for treating the disorder—HTO, total knee arthroplasty, and unicompartmental arthroplasty—also are discussed.

Frequency

It is estimated that approximately 5-6% of arthritic knees are suitable for unicompartmental knee arthroplasty, depending on the examining surgeon's preference.

Pathophysiology

When anteromedial tibiofemoral compartment osteoarthritis develops, the posterior parts of the medial tibial and femoral articular surface remain relatively intact, so that, in flexion, the medial collateral ligament is under normal physiologic tension. Anteromedial osteoarthritis is also referred to as an extension gap disease. In the case of a rupture of the anterior cruciate ligament (ACL), the contact point in extension moves posteriorly, causing damage to the more posterior cartilage. The resulting loss of joint space in flexion allows the medial collateral ligament to remain shortened throughout the full range of movement of the knee, consequently causing a contracture of the medial collateral ligament. Instability and the change in kinematics cause progression of the arthritis into other knee compartments.

Lateral compartment disease can be thought of as a flexion gap disorder. It usually presents with sclerosis on the posterior tibial plateau, as well as subchondral collapse and erosions on the lateral femoral condyle.

Clinical

With medial compartment involvement, the patient usually presents with progressive signs and symptoms at the medial joint line. With primary lateral compartment involvement, the pain in the early stage is frequently minimal, and the patient often presents later in the course of the disease. Although the kinematics of the knee are quite complicated, the higher frequency of medial compartment arthritis and the fact that lateral compartment disease does not typically present at an early stage of its development are related to the valgus alignment of the knee's mechanical axis.

The diagnosis of unicompartmental osteoarthritis of the knee is made on the basis of patient history, physical examination, and workup findings.

A history of trauma should alert the surgeon to the possibility of a remote fracture or articular or ligamentous damage. A history of pain in multiple joints should draw attention to the possibility of inflammatory arthritis.

The physical examination is crucial for appropriate patient selection for unicompartmental knee arthroplasty (see Indications and Contraindications). The integrity of the ACL, the mechanical alignment and range of motion of the knee, and collateral stability must be assessed.

INDICATIONS

Section 3 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Careful patient selection is critical for unicompartmental knee arthroplasty if reliable results are to be achieved. The arthritis should be predominantly confined to a single compartment. (Medial compartment osteoarthritis is usually on the anteromedial aspect of the tibial plateau, and lateral compartment osteoarthritis is typically on the femoral side.) No significant degenerative changes in the other (medial, lateral, or patellofemoral) compartments should be present, and both cruciate ligaments should be intact. Absence of the anterior cruciate is a contraindication; the ACL makes the combined rolling and sliding at the meniscal femoral and meniscal tibial interfaces possible, which may yield near-normal joint kinematics and mechanics.

The operation is also indicated in patients with osteonecrosis of the femoral condyle. Not all of the unicompartmental replacements are suitable for the lateral side, because the ligaments of the lateral compartment are more elastic than those of the medial side.

Malalignment of the limb should be passively correctable to neutral and not beyond. This usually is possible in patients with a varus deformity less than 15° or a valgus deformity less than 20°.

The deformity of the knee should be only mild; therefore, a flexion contracture should be less than 15°. Unicompartmental knee arthroplasty with excision of osteophytes in the notch cannot correct moderately severe flexion contractures.

Ideally, the knee can be flexed to 110°. This is important for the preparation of the femoral condyle during the operation.

RELEVANT ANATOMY

Section 4 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Despite a careful preoperative assessment, the ultimate determination of whether a patient is a candidate for unicompartmental knee arthroplasty may need to be made intraoperatively, keeping the indications and contraindications in mind. In some cases, it may be wise to obtain patient consent for unicompartmental or total knee replacement. Inspection of the supposedly normal compartment is essential; no significant degenerative changes should be present, and the meniscus should be normal. Peripheral osteophytes on the affected side must be identified and removed. The edges of the medial or lateral femoral condyle, the tibial plateau, and the intercondylar notch are the important surgical landmarks.

CONTRAINDICATIONS

Section 5 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Contraindications to a unicompartmental knee arthroplasty include the following:

• Inflammatory arthropathy
• Previous HTO with overcorrection
• Sepsis
• Cruciate ligament lesion
• Medial or lateral subluxation (usually associated with a torn ACL)
• Tibial or femoral shaft deformity
• Flexion contracture greater than 15°
• Varus deformity greater than 15° (medial unicompartmental knee arthroplasty)
• Valgus deformity greater than 20° (lateral unicompartmental knee arthroplasty)
• Flexion less than 110°

Unicompartmental knee arthroplasty is controversial in the presence of patellofemoral joint arthritis, youth and high activity level, obesity, chondrocalcinosis, and crystalline arthropathy.

• Patellofemoral joint arthritis - Progression of osteoarthritis in the patellofemoral joint after unicompartmental knee arthroplasty is rare, according to some studies. In the Swedish Registry, no unicompartmental knee arthroplasties have required revision for patellofemoral problems. Murray (1998, 2005), Weale (1999), and their colleagues showed that residual postoperative pain was independent of the state of the patellofemoral joint, and no knee surgery was revised because of patellofemoral problems. Unicompartmental arthroplasty improves the mechanical axis and patellar tracking and allows more normal kinematics and rapid quadriceps rehabilitation. For these reasons, osteoarthritis of the patellofemoral joint may not be considered an absolute contraindication. However, other investigators and surgeons have reached the opposite conclusion; thus, many consider patellofemoral disease to be an absolute contraindication for unicompartmental knee replacement.
• Youth and high activity level - Because younger patients tend to be more active than older individuals, they would also seem likely to have a higher revision rate for unicompartmental arthroplasty than older individuals. However, although some studies have found such differences in revision rates, others have not. Minimally invasive techniques may reduce morbidity, complications, and length of hospital stay, which may favor the use of unicompartmental knee arthroplasty in younger patients.
• Obesity - Technical difficulties and increased risk of complications are associated with obesity. However, obesity is not considered a contraindication particularly for the unicompartmental knee arthroplasty mobile-bearing design. This is because a correlation has not been found between obesity and wear.
• Chondrocalcinosis - It may be necessary to differentiate between patients with a generalized chondrocalcinosis with synovitis and, effectively, an inflammatory condition in the knee (which is a contraindication for unicompartmental knee arthroplasty) and patients with calcification in the meniscus without generalized evidence of inflammation.
• Crystalline arthropathy - Many patients with osteoarthritis have calcium pyrophosphate crystal deposition in their articular surfaces and suffer from crystalline inflammatory arthropathy. Although Bumbry and Thornhill (2001) believe that crystalline arthropathy is a contraindication to unicompartmental replacement, Murray and colleagues (1998) disagree.

WORKUP

Section 6 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Lab Studies

• An elevated erythrocyte sedimentation rate or abnormal serum calcium or phosphate levels should prompt a diagnostic workup for inflammatory or metabolic disease.

Imaging Studies

• Radiographs
• • Anteroposterior (AP, preferably in 30° of flexion) and tunnel radiographs that are made while the patient is standing can help differentiate between unicompartmental and bicompartmental or tricompartmental disease. Weight-bearing radiographs are important for evaluating narrowing of the cartilage.
  • Lateral radiographs are helpful in establishing the absence of AP tibial translation with posterior bone loss. Such bone loss is a contraindication to unicompartmental knee arthroplasty.
  • Stress AP radiographs (preferably in 20° of flexion) made with the patient supine and with valgus and then varus stress applied to the knee can unmask narrowing in the opposite compartment. Any deformity should be reducible.
• Digital radiographs
• • Digital whole-leg radiographs are obtained preoperatively while the patient is standing, to measure the alignment of the leg (tibiofemoral alignment). This may also be done postoperatively for objective measurement of the correction obtained.
  • Digital templating is possible. For some implants, the size should be chosen preoperatively.
• Technetium-99m bone scan - This scan is not routinely used, but if there is subtle evidence of diffuse disease, it can be employed to assess the other compartments for the presence of early osteoarthritis.

Diagnostic Procedures

• Arthroscopy - This procedure allows visual inspection of cartilage, both menisci and cruciate ligaments. Although not routinely used, arthroscopy can be helpful in examining patients who are not considered to be good candidates for total knee replacement but who have questionable evidence of more extensive disease than would be ideal for unicompartmental replacement.

TREATMENT

Section 7 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Surgical therapy

Unicompartmental knee arthroplasty versus HTO

Resurfacing methods are gaining popularity. Recent results comparing HTO with unicompartmental knee arthroplasty favor the latter. Broughton et al (1986) demonstrated good results in 76% of the replacement group and in 43% in the osteotomy group. Range of motion, speed of rehabilitation, and perioperative morbidity were significantly better for unicompartmental knee arthroplasty, and no signs of late deterioration were present. Weale and Newman (1994), after a 12- to 17-year follow-up period, also reported better function and longer survival in the unicompartmental group.

Recent publications similarly show more favorable results with arthroplasty (Stukenborg-Colsman, 2001; Rees, 2001). The functional benefits of unicompartmental knee arthroplasty over HTO have also been demonstrated using gait analysis, with patients displaying a more normal gait and better stair-climbing ability following unicompartmental knee arthroplasty than they did after HTO.

If a revision to a total knee arthroplasty becomes necessary, the results are now believed to be generally better if the revision occurs after a failed unicompartmental knee arthroplasty than they are following a failed HTO. (Previous HTO is a contraindication for a unicompartmental knee arthroplasty.)

Unicompartmental knee arthroplasty versus total knee arthroplasty

In the late 1980s, unicompartmental knee arthroplasty waned in popularity, largely because of problems with patient selection, operative technique, and polyethylene wear. Later, as understanding of the procedure and the associated prostheses improved, the long-term results of unicompartmental knee arthroplasty became comparable to those of total knee arthroplasty.

Functional outcome with unicompartmental knee arthroplasty is superior to that with total knee arthroplasty: the former provides better range of motion and ambulatory function. Laurencin et al (1991) found that unicompartmental knee arthroplasty also results in less pain, more stability, and better stair-climbing ability than does total knee arthroplasty.

In addition, the cost of the unicompartmental procedure is about 57% that of total knee arthroplasty.

Preoperative details

The preoperative assessment for unicompartmental knee arthroplasty largely consists of obtaining a thorough history to ensure that the patient is a good candidate for the procedure. Clinical examination and radiologic assessment are required to confirm an individual's suitability (see Indications and Contraindications).

Intraoperative details

The patient is placed in a supine position, with the draped leg set on a thigh support or in a legholder. When positioning the patient, it is necessary to ensure that the knee is free to flex to at least 120°. A sandbag or other bump is affixed to the table to help maintain flexion of the knee. A strap placed around the thigh and leg may serve the same function. The leg is draped free, and it is helpful to place a mark or ball of tape over the anterior superior iliac spine or the femoral head.

In the past, unicompartmental knee arthroplasty was performed through a standard anterior approach with dislocation of the patella, as used for total knee arthroplasty. However, in recent years, the minimally invasive form of unicompartmental arthroplasty has gained popularity; the smaller incision and arthrotomy of this technique causes less damage to the extensor mechanism because the patella is not dislocated and the suprapatellar synovial pouch remains intact.

Follow-up research has demonstrated decreased morbidity, faster rehabilitation, and reduced length of hospital stay among patients who have undergone the less invasive medial unicompartmental arthroplasty. With appropriate pain control, the surgery can safely be done as an outpatient procedure, providing substantial cost savings, and patients have reported feeling less pain postoperatively than they did preoperatively. Nevertheless, surgeons utilizing the minimally invasive approach must contend with a restricted visual field, making unicompartmental knee arthroplasty a demanding procedure.

The minimally invasive technique can also be used for lateral unicompartmental arthroplasty, although some authors prefer the standard total knee approach. With the less invasive technique, the exposure is limited, so positioning the prosthetic components is more difficult.

Recent advances in instrumentation for unicompartmental arthroplasty have increased the ability to implant the components in proper alignment and should theoretically increase the longevity of the arthroplasty. Instrumentation is crucial for proper alignment and orientation with some types of unicompartmental knee arthroplasty systems, such as the Oxford Phase III prosthetic. Other prosthetic systems, such as the Repicci II, rely more on anatomic landmarks to ensure proper component placement.

The optimal tibiofemoral alignment following unicompartmental arthroplasty has yet to be determined. Extremes of overcorrection and undercorrection are undesirable. Overcorrection may result in medial or lateral subluxation and increased loading of the unreplaced compartment (medial or lateral); undercorrection causes varus or valgus alignment of the leg and can potentially overload the implant. Most surgeons advocate undercorrection of the mechanical axis by 2-3° to avoid overloading the normal compartment.

In general, medial and lateral soft tissue releases are contraindicated because knees requiring these have too much preoperative deformity for unicompartmental knee arthroplasty. Angular correction is usually obtained with removal of peripheral osteophytes that tent the capsule and the collateral ligaments.

Computer-assisted surgery can improve the postoperative alignment of medial unicompartmental knee arthroplasty over that of conventional techniques. Real-time information about the leg axis at each step of the operation should diminish the danger of overcorrection or undercorrection. The navigation system may also be helpful in achieving a more precise component orientation. However, all investigations into the navigation system's use have comprised either bone-saw or cadaver studies. As a result of the limited exposure and restricted visual field in vivo associated with the minimally invasive procedure, it is difficult to apply the studies' results to the optimal positioning of components. Further development of the navigation technique will prove if it is more accurate than the conventional method.

Postoperative details

Mobilization of the knee and patient can start on the day after surgery. Recovery of knee function is usually rapid, with considerably less pain than that which occurs with a total knee replacement. Early mobilization is encouraged, and passive assistance by the physical therapist is advised. The patient can frequently be discharged after 2-3 days. In some centers, the procedure is now performed in day care. Mechanical prophylaxis against deep vein thrombosis is recommended for the duration of the hospitalization. Postdischarge prophylaxis is at the discretion of the surgeon.

COMPLICATIONS

Section 8 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Early complications include the following:

• Infection, superficial and deep, is possible.
• With lateral unicompartmental arthroplasty, palsy of the common peroneal nerve may occur, although this is more common with total knee arthroplasty in patients with severe flexion and valgus deformity.
• A tibial plateau fracture may result if too much stress is applied with cementation of the tibial component. The vertical tibial cut may act as a stress riser. In general, forceful impaction of the component is minimal, and this complication should be unusual.
• Ligamentous instability is rarely a problem in properly selected patients and with an intact ACL. Soft tissue releases should be minimal.
• Knee joint stiffness may occur.

Late complications include the following:

• Late infection may occur, usually from hematogenous seeding.
• Prosthesis failure or loosening is possible.
• The bearing of a mobile-bearing unicompartmental knee prosthesis may become dislocated, especially with lateral unicompartmental arthroplasty. A high, proximal, varus tibial angle along with damage to or overdistraction of the lateral soft tissue structures is thought to contribute to this problem.
• Polyethylene wear can occur, but it may be less with a mobile-bearing design.
• Undercorrection or overcorrection of the deformity and malpositioning of the components may cause late complications. In the case of overcorrection, excessive load on the opposite compartment might accelerate degenerative changes. Undercorrection places excessive load on the prosthesis, and loosening and failure may result. Improper placement of the components can cause subluxation of the tibia on the femur or impingement of the patella on the femoral component.
• Most patients develop a radiolucent line in the tibial bone-cement interface. If these lines are less than 1 mm, they usually do not progress. The appearance of a similar line under the femoral component is expected but is not easily demonstrated because of the nonplanar form of the femoral bone-cement interface.

Revision

To convert a unicompartmental knee arthroplasty to a total knee arthroplasty is somewhat more difficult than performing a primary total knee arthroplasty. The results are acceptable but debatably not as good as they are with primary total knee arthroplasty. Despite the benefit of the conservative bone cuts used for unicompartmental knee replacement, stemmed components and augments may be needed for bone loss associated with component removal or osteolysis.

Bone defects, if present, usually can be treated with a local autograft. The cumulative revision rate at 10 years is more than 3 times higher for patients in whom a failed unicompartmental knee arthroplasty has been revised to a further unicompartmental knee arthroplasty than for those in whom it has been revised to a total knee arthroplasty (Rees et al, 2001).

OUTCOME AND PROGNOSIS

Section 9 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

When nonoperative and, possibly, arthroscopic procedures fail, the surgeon may consider HTO, unicompartmental arthroplasty, or total knee arthroplasty. Unicompartmental knee arthroplasty appears to result in better function and pain relief, less morbidity, and higher patient satisfaction than do HTO and total knee arthroplasty. The long-term survival rate for unicompartmental knee arthroplasty is better than that for HTO and comparable to the long-term survival rate for a total knee arthroplasty. With strict indications, newer prostheses, and attention to surgical technique, unicompartmental knee arthroplasty has become a valuable treatment for unicompartmental knee arthritis.

FUTURE AND CONTROVERSIES

Section 10 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

As the population ages and grows, the number of people with symptoms attributable to unicompartmental knee osteoarthritis will increase. The unicompartmental knee arthroplasty offers a more physiologic alternative to HTO or total knee arthroplasty. Progress has been made in the design and implantation of unicompartmental knee arthroplasty, in particular for the medial compartment. However, complications still occur, and surgical expertise remains the most important factor in determining a successful outcome.

Whether refinement of prosthetic design and technique will make lateral compartment arthroplasty as reliable as the medial procedure remains to be seen.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

Media file 1:  Unicompartmental knee arthroplasty. The minimally invasive technique with a paramedial skin incision.
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Media file 2:  Extension of the minimally invasive skin incision for a total knee arthroplasty.
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Media file 3:  The mobile-bearing unicompartmental prosthesis.
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Media file 4:  Revision to a total knee arthroplasty; view after removal of the unicompartmental prosthesis.
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Media file 5:  Revision to a total knee arthroplasty. The earlier femoral-condylar bone cut/milling of the unicompartmental knee arthroplasty is usually less or the same as that for total knee replacement distal femoral (medial and lateral condyle) resection.
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Media type:  Photo

Media file 6:  Revision to a total knee arthroplasty. The medial or lateral proximal tibial plateau resection of the unicompartmental knee arthroplasty is usually at the same level as the proximal tibial plateau resection for total knee arthroplasty.
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Media type:  Photo

Media file 7:  Unicompartmental knee arthroplasty. A tibial plateau fracture may occur when too much stress is applied with cementation of the tibial component or after adequate trauma. The vertical tibial cut may act as a stress line.
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Media type:  X-RAY

Media file 8:  Unicompartmental knee arthroplasty. When a mobile-bearing prosthesis is used, the bearing can become dislocated.
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Media type:  X-RAY

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• Multimedia
• References

• Ahlback S. Osteoarthrosis of the knee. A radiographic investigation. Acta Radiol Diagn (Stockh). 1968;Suppl 277: 7-72. [Medline].
• Amin AK, Patton JT, Cook RE, et al. Unicompartmental or total knee arthroplasty?: Results from a matched study. Clin Orthop Relat Res. Oct 2006;451:101-6. [Medline].
• Argenson JN, Chevrol-Benkeddache Y, Aubaniac JM. Modern unicompartmental knee arthroplasty with cement: a three to ten-year follow-up study. J Bone Joint Surg Am. Dec 2002;84-A(12):2235-9. [Medline].
• Argenson JN, Parratte S. The unicompartmental knee: design and technical considerations in minimizing wear. Clin Orthop Relat Res. Nov 2006;452:137-42. [Medline].
• Baré JV, Gill HS, Beard DJ, Murray DW. A convex lateral tibial plateau for knee replacement. Knee. Mar 2006;13(2):122-6. [Medline].
• Berger RA, Jacobs JJ, Meneghini RM, et al. Rapid rehabilitation and recovery with minimally invasive total hip arthroplasty. Clin Orthop Relat Res. Dec 2004;239-47.
• Broughton NS, Newman JH, Baily RA. Unicompartmental replacement and high tibial osteotomy for osteoarthritis of the knee. A comparative study after 5-10 years' follow-up. J Bone Joint Surg Br. May 1986;68(3):447-52. [Medline].
• Brumby SA, Thornhill TS. Unicompartmental Osteoarthritis of the Knee. In: Laskin RS, ed. Controversies in Total Knee Replacement. Oxford, UK: Oxford University Press; 2001: 285-312.
• Callaghan JJ. Unicompartmental knee replacement: introduction: where have we been? Where are we now? Where are we going?. Clin Orthop Relat Res. Jan 2005;(430):272-3. [Medline].
• Cameron HU, Jung YB. A comparison of unicompartmental knee replacement with total knee replacement. Orthop Rev. Oct 1988;17(10):983-8. [Medline].
• Carr A, Keyes G, Miller R, et al. Medial unicompartmental arthroplasty. A survival study of the Oxford meniscal knee. Clin Orthop Relat Res. Oct 1993;205-13. [Medline].
• Cartier P, Sanouiller JL, Grelsamer RP. Unicompartmental knee arthroplasty surgery. 10-year minimum follow-up period. J Arthroplasty. Oct 1996;11(7):782-8. [Medline].
• Chassin EP, Mikosz RP, Andriacchi TP, Rosenberg AG. Functional analysis of cemented medial unicompartmental knee arthroplasty. J Arthroplasty. Aug 1996;11(5):553-9. [Medline].
• Cobb J, Henckel J, Gomes P, et al. Hands-on robotic unicompartmental knee replacement: a prospective, randomised controlled study of the acrobot system. J Bone Joint Surg Br. Feb 2006;88(2):188-97. [Medline].
• Cossey AJ, Spriggins AJ. The use of computer-assisted surgical navigation to prevent malalignment in unicompartmental knee arthroplasty. J Arthroplasty. Jan 2005;20(1):29-34. [Medline].
• Emerton ME, Burton D. The role of unicompartmental knee replacement. Curr Orthop. 2001;15(6):406-12.
• Engh GA, Ammeen D. Is an intact anterior cruciate ligament needed in order to have a well-functioning unicondylar knee replacement?. Clin Orthop Relat Res. Nov 2004;(428):170-3. [Medline].
• Goodfellow J, O'Connor J. The mechanics of the knee and prosthesis design. J Bone Joint Surg Br. Aug 1978;60-B(3):358-69. [Medline].
• Gunston FH. Polycentric knee arthroplasty. Prosthetic simulation of normal knee movement. J Bone Joint Surg Br. May 1971;53(2):272-7. [Medline].
• Gunther T, Murray DW, Miller R. Lateral unicompartmental arthroplasty with the Oxford meniscal knee. Knee. 1996;3:33-9.
• Heck DA, Marmor L, Gibson A, Rougraff BT. Unicompartmental knee arthroplasty. A multicenter investigation with long-term follow-up evaluation. Clin Orthop Relat Res. Jan 1993;154-9. [Medline].
• Insall J, Aglietti P. A five to seven-year follow-up of unicondylar arthroplasty. J Bone Joint Surg Am. Dec 1980;62(8):1329-37. [Medline].
• Jackson M, Sarangi PP, Newman JH. Revision total knee arthroplasty. Comparison of outcome following primary proximal tibial osteotomy or unicompartmental arthroplasty. J Arthroplasty. Oct 1994;9(5):539-42. [Medline].
• Jenny JY. Navigated unicompartmental knee replacement. Orthopedics. Oct 2005;28(10 Suppl):s1263-7. [Medline].
• Keene G, Simpson D, Kalairajah Y. Limb alignment in computer-assisted minimally-invasive unicompartmental knee replacement. J Bone Joint Surg Br. Jan 2006;88(1):44-8. [Medline].
• Keys GW. Reduced invasive approach for Oxford II medial unicompartmental knee replacement—a preliminary study. Knee. Aug 1999;6(3):193-6.
• Knutson K, Lewold S, Robertsson O, et al. The Swedish knee arthroplasty register. A nation-wide study of 30,003 knees 1976-1992. Acta Orthop Scand. Aug 1994;65(4):375-86. [Medline].
• Laskin RS. Unicompartmental knee replacement: some unanswered questions. Clin Orthop Relat Res. Nov 2001;(392):267-71. [Medline].
• Laskin RS. Unicompartmental tibiofemoral resurfacing arthroplasty. J Bone Joint Surg Am. Mar 1978;60(2):182-5. [Medline].
• Laurencin CT, Zelicof SB, Scott RD, Ewald FC. Unicompartmental versus total knee arthroplasty in the same patient. A comparative study. Clin Orthop Relat Res. Dec 1991;151-6. [Medline].
• Levine WN, Ozuna RM, Scott RD. Conversion of failed modern unicompartmental arthroplasty or high tibial osteotomy. Clin Orthop. Oct 1995;321:10-18.
• Li MG, Yao F, Joss B, et al. Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics. Knee. Oct 2006;13(5):365-70. [Medline].
• Luscombe KL, Lim J, Jones PW, White SH. Minimally invasive Oxford medial unicompartmental knee arthroplasty : A note of caution!. Int Orthop. Aug 1 2006;[Medline].
• MacIntosh DL. Hemiarthroplasty of the knee using a space occupying prosthesis for painful varus and valgus deformities. J Bone Joint Surg Am. 1958;40A:1431.
• Manzotti A, Confalonieri N, Pullen C. Unicompartmental versus computer-assisted total knee replacement for medial compartment knee arthritis: a matched paired study. Int Orthop [serial online]. Aug 2 2006;[Medline].
• Marmor L. Unicompartmental arthroplasty of the knee with a minimum ten-year follow-up period. Clin Orthop Relat Res. Mar 1988;(228):171-7. [Medline].
• Marmor L. Unicompartmental knee arthroplasty. Ten- to 13-year follow-up study. Clin Orthop Relat Res. Jan 1988;(226):14-20. [Medline].
• McAuley JP, Engh GA, Ammeen DJ. Revision of failed unicompartmental knee arthroplasty. Clin Orthop Relat Res. Nov 2001;279-82. [Medline].
• McKeever DC. Tibial plateau prosthesis. Clin Orthop. 1960;18:86-95.
• Muller PE, Pellengahr C, Witt M, et al. Influence of minimally invasive surgery on implant positioning and the functional outcome for medial unicompartmental knee arthroplasty. J Arthroplasty. Apr 2004;19(3):296-301. [Medline].
• Murray DW, Goodfellow JW, O'Connor JJ. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br. Nov 1998;80(6):983-9. [Medline].
• Murray DW. Mobile bearing unicompartmental knee replacement. Orthopedics. Sep 2005;28(9):985-7. [Medline].
• Padgett DE, Stern SH, Insall JN. Revision total knee arthroplasty for failed unicompartmental replacement. J Bone Joint Surg Am. Feb 1991;73(2):186-90. [Medline].
• Pennington DW, Swienckowski JJ, Lutes WB, Drake GN. Lateral unicompartmental knee arthroplasty: survivorship and technical considerations at an average follow-up of 12.4 years. J Arthroplasty. Jan 2006;21(1):13-7. [Medline].
• Psychoyios V, Crawford RW, O'Connor JJ, Murray DW. Wear of congruent meniscal bearings in unicompartmental knee arthroplasty: a retrieval study of 16 specimens. J Bone Joint Surg Br. Nov 1998;80(6):976-82. [Medline].
• Rees JL, Price AJ, Lynskey TG, et al. Medial unicompartmental arthroplasty after failed high tibial osteotomy. J Bone Joint Surg Br. Sep 2001;83(7):1034-6. [Medline].
• Reilly KA, Beard DJ, Barker KL, et al. Efficacy of an accelerated recovery protocol for Oxford unicompartmental knee arthroplasty--a randomised controlled trial. Knee. Oct 2005;12(5):351-7. [Medline].
• Robertsson O, Borgquist L, Knutson K, et al. Use of unicompartmental instead of tricompartmental prostheses for unicompartmental arthrosis in the knee is a cost-effective alternative. 15,437 primary tricompartmental prostheses were compared with 10,624 primary medial or lateral unicompartmental p. Acta Orthop Scand. Apr 1999;70(2):170-5. [Medline].
• Rougraff BT, Heck DA, Gibson AE. A comparison of tricompartmental and unicompartmental arthroplasty for the treatment of gonarthrosis. Clin Orthop Relat Res. Dec 1991;(273):157-64. [Medline].
• Rush J. Unicompartmental knee joint replacement. Curr Orthop. 2001;15(2):143-7.
• Sah AP, Springer BD, Scott RD. Unicompartmental knee arthroplasty in octogenarians: survival longer than the patient. Clin Orthop Relat Res. Oct 2006;(451):107-12. [Medline].
• Sculco TP. Orthopaedic crossfire--can we justify unicondylar arthroplasty as a temporizing procedure? In opposition. J Arthroplasty. Jun 2002;17(4 Suppl 1):56-8. [Medline].
• Springer BD, Scott RD, Thornhill TS. Conversion of failed unicompartmental knee arthroplasty to TKA. Clin Orthop Relat Res. May 2006;(446):214-20. [Medline].
• Squire MW, Callaghan JJ, Goetz DD, et al. Unicompartmental knee replacement. A minimum 15 year followup study. Clin Orthop Relat Res. Oct 1999;61-72. [Medline].
• Stukenborg-Colsman C, Wirth CJ, Lazovic D, Wefer A. High tibial osteotomy versus unicompartmental joint replacement in unicompartmental knee joint osteoarthritis: 7-10-year follow-up prospective randomised study. Knee. Oct 2001;8(3):187-94. [Medline].
• Tabor OB, Tabor OB. Unicompartmental arthroplasty: a long-term follow-up study. J Arthroplasty. Jun 1998;13(4):373-9. [Medline].
• Vorlat P, Verdonk R, Schauvlieghe H. The Oxford unicompartmental knee prosthesis: a 5-year follow-up. Knee Surg Sports Traumatol Arthrosc. 2000;8(3):154-8. [Medline].
• Weale AE, Murray DW, Crawford R, et al. Does arthritis progress in the retained compartments after 'Oxford' medial unicompartmental arthroplasty? A clinical and radiological study with a minimum ten-year follow-up. J Bone Joint Surg Br. Sep 1999;81(5):783-9. [Medline]. [Full Text].
• Weale AE, Newman JH. Unicompartmental arthroplasty and high tibial osteotomy for osteoarthrosis of the knee. A comparative study with a 12- to 17-year follow-up period. Clin Orthop Relat Res. May 1994;(302):134-7. [Medline].
• Weale AE, Murray DW, Crawford R, et al. Does arthritis progress in the retained compartments after 'Oxford' medial unicompartmental arthroplasty? A clinical and radiological study with a minimum ten-year follow-up. J Bone Joint Surg Br. Sep 1999;81(5):783-9. [Medline].

Article Last Updated: Jan 5, 2007