Forgot your password ?




SICOT e-Newsletter

Issue No. 43 - April 2012  

Scientific Debate

High Tibial Osteotomy versus Unicompartmental Knee Replacement

There is no doubt that a young patient less than 45 years of age with medial OA of the knee and axial varus deformity would need an HTO, whereas an elderly patient above 65 with advanced OA would need a TKR. The debate arises in the mid zone of patients 45-65 years of age who can be offered an HTO or a UKR, according to multiple factors. We present two views from highly active centres, who will try to convince you of the procedure they perform and the benefits of each. The final decision lies in the hands of the surgeon and the patient, according to the facilities, experience and ultimate patient requirements from the procedure.

Join us also on Facebook, and vote for your decision.


High Tibial Osteotomy

by Abdel Rahman Babaqi & Hatem Said
Arthroscopy Unit, Assiut University, Egypt

High tibial osteotomy is a commonly used surgical procedure for the treatment of medial compartmental osteoarthritis (OA) of the knee and has wide appeal because of the preservation of the knee joint with this method relative to the use of TKA or UKA.

The principal advantages of opening wedge high tibial osteotomy include maintenance of the bone stock, correction of the deformity close to its origin, and no requirement for a fibular osteotomy [1,2]. Although it is a good option for young patients with isolated medial compartment OA and varus deformity, it can be done even for older active people over 65 [3].

The biomechanical principle of HTO in medial compartment OA is to redistribute the weightbearing forces from the worn medial compartment across to the lateral compartment to relieve pain and to slow disease progression [4-6]. This can be accompanied by pain relief and improvements in gait and function. A correction of axial misalignment is seldom possible in UKA [7].

Mechanical release alone or a combination of HTO with arthroscopic measures (debridement, synovectomy or microfracture), chondral resurfacing or meniscal transplantation can also improve these results [8,9]. The main benefit for the patient is the preservation of the natural joint and the main advantage for the patient is that potential physical loading (professional or sports-related) is almost entirely unaffected [7].

The surgical technique underwent many variations in the fixation technique and augmentation with bone graft or bone substitutes. Although autogenous iliac graft has been used routinely as part of the technique, recent studies showed successful results after high tibial osteotomy up to 14mm without bone graft [10] or at least similar results to osteotomy with bone graft [11].

Biopsy and second-look arthroscopic and open procedures have shown that there is regrowth of fibrocartilage in the worn medial compartment with a predilection for the ulcerated regions of wear in the weightbearing portion of the medial femoral condyle [12-15].

It has been shown that when HTO for medial compartment arthrosis is performed in an otherwise healthy knee, no degenerative changes occur in the lateral or patellofemoral compartments [16].

Some authors reported that with an early and active rehabilitation program, OA patients can walk with full weight bearing at two weeks after their OWHTO procedure [17,18].

The long-term follow-up for HTO patients has also been well documented. Billings et al. reported that 43 of 64 knees had good clinical results with an average HSS knee score of 94 points at an average of 8.5 years after HTO [19]. Koshino et al reported long-term results (15~28 years) from their analysis of 75 knees in a group of 53 patients and found that the mean KSS score improved from 37 to 87 [20]. HTO gives high patient satisfaction and affords patients unrestricted activity for many years [3].

One of the beneficial outcomes after HTO is the style of sitting, one study comparing HTO vs UKA stated that [20]: "Although none of the patients in the OWHTO group could sit in the Japanese style before surgery, 17 of these 24 patients (71%) could do so after this procedure. This is an important outcome that has only been achieved thus far using OWHTO". And finally concluded: although there were no significant differences found between OWHTO and UKA procedures in terms of the postoperative KSS score, we found that the operative function score for OWHTO was significantly better than that for UKA.

Complications of HTO include osteonecrosis of proximal fragment, non union if the proximal fragment is too thin, neurological injuries especially injury to peroneal nerve, incomplete correction, DVT and compartment syndrome.

Converting HTO to knee arthroplasty is not a problem like UKA, as previous HTO doesn’t influence the function or survival of a knee in the long term [21]. One study stated that knee arthroplasty after proximal tibial osteotomy was satisfactory in 96.5% of cases over a mean follow-up of 97 months. They compare between primary knee arthroplasty with and without previous HTO, and they found there is no significant difference in clinical and radiological results apart from a greater rate of anterior knee pain and revision for secondary resurfacing of the patella in the patients with previous HTO [22].

To conclude, OWHTO is the more appropriate treatment for active patients even those aged over 65 who demand a good range of motion of the knee.

References:

  1. Lobenhoffer P, Agneskirchner JD: Improvements in surgical technique of valgus high tibial osteotomy. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2003, 11(3):132-138.
     
  2. Staubli AE, De Simoni C, Babst R, Lobenhoffer P: TomoFix: a new LCP-concept for open wedge osteotomy of the medial proximal tibia--early results in 92 cases. Injury 2003, 34 Suppl 2:B55-62.
      
  3. Hui C, Salmon LJ, Kok A, Williams HA, Hockers N, van der Tempel WM, Chana R, Pinczewski LA: Long-term survival of high tibial osteotomy for medial compartment osteoarthritis of the knee. The American journal of sports medicine 2011, 39(1):64-70.
      
  4. Amendola A, Panarella L: High tibial osteotomy for the treatment of unicompartmental arthritis of the knee. The Orthopedic clinics of North America 2005, 36(4):497-504.
      
  5. Brinkman JM, Lobenhoffer P, Agneskirchner JD, Staubli AE, Wymenga AB, van Heerwaarden RJ: Osteotomies around the knee: patient selection, stability of fixation and bone healing in high tibial osteotomies. The Journal of bone and joint surgery British volume 2008, 90(12):1548-1557.
      
  6. Virolainen P, Aro HT: High tibial osteotomy for the treatment of osteoarthritis of the knee: a review of the literature and a meta-analysis of follow-up studies. Archives of orthopaedic and trauma surgery 2004, 124(4):258-261.
     
  7. Spahn G, Hofmann GO, von Engelhardt LV, Li M, Neubauer H, Klinger HM: The impact of a high tibial valgus osteotomy and unicondylar medial arthroplasty on the treatment for knee osteoarthritis: a meta-analysis. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2011.
     
  8. Elattar M, Dhollander A, Verdonk R, Almqvist KF, Verdonk P: Twenty-six years of meniscal allograft transplantation: is it still experimental? A meta-analysis of 44 trials. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2011, 19(2):147-157.
     
  9. Schultz W, Gobel D: Articular cartilage regeneration of the knee joint after proximal tibial valgus osteotomy: a prospective study of different intra- and extra-articular operative techniques. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA 1999, 7(1):29-36.
      
  10. El-Assal MA, Khalifa YE, Abdel-Hamid MM, Said HG, Bakr HM: Opening-wedge high tibial osteotomy without bone graft. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2010, 18(7):961-966.
     
  11. Zorzi AR, da Silva HG, Muszkat C, Marques LC, Cliquet A, Jr., de Miranda JB: Opening-wedge high tibial osteotomy with and without bone graft. Artificial organs 2011, 35(3):301-307.
     
  12. Bergenudd H, Johnell O, Redlund-Johnell I, Lohmander LS: The articular cartilage after osteotomy for medial gonarthrosis. Biopsies after 2 years in 19 cases. Acta orthopaedica Scandinavica 1992, 63(4):413-416.
     
  13. Kanamiya T, Naito M, Hara M, Yoshimura I: The influences of biomechanical factors on cartilage regeneration after high tibial osteotomy for knees with medial compartment osteoarthritis: clinical and arthroscopic observations. Arthroscopy: the journal of arthroscopic & related surgery: official publication of the Arthroscopy Association of North America and the International Arthroscopy Association 2002, 18(7):725-729.
      
  14. Koshino T, Wada S, Ara Y, Saito T: Regeneration of degenerated articular cartilage after high tibial valgus osteotomy for medial compartmental osteoarthritis of the knee. The Knee 2003, 10(3):229-236.
      
  15. Odenbring S, Egund N, Lindstrand A, Lohmander LS, Willen H: Cartilage regeneration after proximal tibial osteotomy for medial gonarthrosis. An arthroscopic, roentgenographic, and histologic study. Clinical orthopaedics and related research 1992(277):210-216.
     
  16. Majima T, Yasuda K, Katsuragi R, Kaneda K: Progression of joint arthrosis 10 to 15 years after high tibial osteotomy. Clinical orthopaedics and related research 2000(381):177-184.  
      
  17. Takeuchi R, Aratake M, Bito H, Saito I, Kumagai K, Ishikawa H, Akamatsu Y, Sasaki Y, Saito T: Simultaneous bilateral opening-wedge high tibial osteotomy with early full weight-bearing exercise. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA 2008, 16(11):1030-1037.
      
  18. Takeuchi R, Ishikawa H, Aratake M, Bito H, Saito I, Kumagai K, Akamatsu Y, Saito T: Medial opening wedge high tibial osteotomy with early full weight bearing. Arthroscopy : the journal of arthroscopic & related surgery: official publication of the Arthroscopy Association of North America and the International Arthroscopy Association 2009, 25(1):46-53.
      
  19. Billings A, Scott DF, Camargo MP, Hofmann AA: High tibial osteotomy with a calibrated osteotomy guide, rigid internal fixation, and early motion. Long-term follow-up. The Journal of bone and joint surgery American volume 2000, 82(1):70-79.
      
  20. Takeuchi R, Umemoto Y, Aratake M, Bito H, Saito I, Kumagai K, Sasaki Y, Akamatsu Y, Ishikawa H, Koshino T et al: A mid term comparison of open wedge high tibial osteotomy vs unicompartmental knee arthroplasty for medial compartment osteoarthritis of the knee. Journal of orthopaedic surgery and research 2010, 5(1):65.
      
  21. Meding JB, Wing JT, Ritter MA: Does high tibial osteotomy affect the success or survival of a total knee replacement? Clinical orthopaedics and related research 2011, 469(7):1991-1994.
       
  22. Amendola L, Fosco M, Cenni E, Tigani D: Knee joint arthroplasty after tibial osteotomy. International orthopaedics 2010, 34(2):289-295.

Unicompartmental Knee Arthroplasty

by Simon Cockshott & Nadim Aslam
Worcester, United Kingdom

Introduction

The concept of unicompartmental knee arthroplasty was introduced over 30 years ago. The theoretical advantages of this procedure include:

  • preservation of bone
  • reduced operative time
  • better range of motion
  • improved gait
  • increased patient satisfaction

With careful patient selection, surgical technique, and proper implant design, unicompartmental knee arthroplasty can now be viewed as a procedure with reliable medium to long-term success [1,2].

History

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 [3].

In the late 1980’s the popularity of unicompartmental knee replacements began to fall. This was due to high failure rates. Marmor in 1988 reported 21 treatment failures in 97 cases at 10- to 13-year follow-up [4].

Laskin reported that 35% of his knees had a fair to poor result with a high incidence of loosening of the implant and degeneration of the opposite compartment with a revision rate of 22% in a 2-year follow-up of patients using the Marmor modular knee replacement [5].

In 1980, Insall published a series in which the conversion rate to a total knee arthroplasty was 28% at 5-7 years [6].

However, after recognizing the need to avoid overcorrection of the mechanical axis, surgeons ultimately were able to reduce the risk that over tensioning in the "normal" compartment would cause early failure.

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 [7].

Interest in unicompartmental knee arthroplasty was stimulated by the introduction of the mobile-bearing implant. Goodfellow and O'Connor, along with others, published excellent long-term survivorship rates associated with this technique [8]. 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 total freedom of movement (to accommodate the preferred motion pattern of the retained natural compartment).

The past few years have again seen a renewed 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 an alternative to high tibial osteotomy (HTO) in relatively young patients with medial compartment arthritis.

Indications

Appropriate patient selection is critical for unicompartmental knee arthroplasty if reliable results are to be achieved. Criteria includes:

  • Arthritis 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.)
  • Intact anterior and posterior cruciate ligaments
  • Passively correctable malalignment - varus deformity < 15° or a valgus deformity < 20°
  • Fixed flexion < 15°
  • Knee able to flex to 120°. Key for the preparation of the femoral condyle preoperatively.

Contraindications

Contraindications to a unicompartmental knee arthroplasty include the following:

  • Inflammatory arthropathy
  • Previous HTO with overcorrection
  • Sepsis
  • Tibial or femoral shaft deformity (Malunion post fracture)

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

Procedure Comparisons

Unicompartmental Knee Arthroplasty Versus High Tibial Osteotomy

Resurfacing methods are gaining popularity. Results comparing HTO with unicompartmental knee arthroplasty favour the latter.

Broughton et al demonstrated good results in 76% of patients in a replacement group and in 43% of patients in an osteotomy group [9]. 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, after a 12- to 17-year follow-up period, also reported better function and longer survival in the unicompartmental group [10].

Other publications have similarly shown more favorable results with arthroplasty [11,12]. 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.

Unicompartmental Knee Arthroplasty Versus Total Knee Arthroplasty

Laurencin et al reported that unicompartmental knee arthroplasty results in less pain, more stability, and better stair-climbing ability than in total knee arthroplasty [13].

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

In a study, Dalury et al found little or no difference in outcome between patients who received a total knee arthroplasty and those who received a unicompartmental knee arthroplasty, except for a slightly improved range of motion with unicompartmental knee arthroplasty over the total knee procedure (123º ± 9º vs 119.8º ± 7º, respectively). In their investigation, the authors identified 23 patients with osteoarthritis who had undergone a total knee arthroplasty on one side and a unicompartmental knee arthroplasty on the other, for medial compartment disease, and measured Knee Society scores, radiographic analysis, and patient preferences. Average follow-up was 46 months for total knee arthroplasty and 42 months for unicompartmental knee arthroplasty. Of the 23 patients, 11 expressed no preference between either knee and 12 preferred the unicompartmental knee; no patient preferred the total knee [14].

A prospective, randomized, controlled trial in England compared unicompartmental knee replacement with TKA over 8, 10, 12, and 15 years follow-up. At 5 years, the numbers of failures were equal in the 2 groups. At 15 years follow-up, the survivorship rate was 89.8% for unicompartmental knee replacement and 78.7% for TKA. Four of the unicompartmental knees failed, and 6 of the TKA knees failed. Newman et al determined from their findings that the results of their study justify increased use of unicompartmental replacement [15].

Results

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.

In a prospective study, Berger et al found that in a 3-month period following knee arthroplasty, no patients in the investigation who had undergone the unicompartmental knee procedure required hospital readmission, compared with 9% of patients who received total knee arthroplasty. In the study, the authors looked at 111 patients who had undergone primary knee arthroplasty, 25 of whom had unicompartmental knee arthroplasty and 86 of whom underwent total knee arthroplasty. Of the 111 patients, 104 (24 with unicompartmental knee arthroplasty and 80 with total knee arthroplasty) met discharge criteria and were discharged directly to home [16].

Saenz et al evaluated the clinical and radiographic outcomes of the EIUS unicompartmental prosthesis and found it to be associated with higher revision rates than were metal-backed implants. The implant survival rate was 89%, with 16 knees either revised or scheduled for revision. The reasons for revision included aseptic loosening of the tibial component, progressive symptomatic patellofemoral disease, and tibial component subsidence [17].

Revision

Converting a unicompartmental knee arthroplasty to a total knee arthroplasty is 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 [12].

Complications

Early complications

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.

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.

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

Late infection may occur, usually from hematogenous seeding. In addition, 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.

Unicompartmental knee arthroplasty. When a mobile-bearing prosthesis is used, the bearing can become dislocated.

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.

Contributor Information and Disclosures
    

Author

Nanne P Kort, MD, PhD  Consulting Staff, Department of Orthopedic Surgery, Orbis Medical Park Sittard, The Netherlands

Disclosure: Nothing to disclose.

Coauthor(s)

Marcus Romanowski, MD  Chief, Department of Orthopedic Surgery, Kenmore Mercy Hospital; Director, Knee and Hip Center, Kenmore Mercy Hospital; Partner, Joint Reconstruction Orthopedics

Marcus Romanowski, MD is a member of the following medical societies:
American Academy of Orthopaedic Surgeons and Arthritis Foundation

Disclosure: Nothing to disclose.

Jos van Raay, PhD  Associate Chair, Residency Director, Department of Orthopedic Surgery, Martini Hospital Groningen, Netherlands

Disclosure: Nothing to disclose.

Specialty Editor Board

Howard A Chansky, MD  Associate Professor, Department of Orthopedics and Sports Medicine, University of Washington Medical Center

Howard A Chansky, MD is a member of the following medical societies:
American Academy of Orthopaedic Surgeons

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Senior Pharmacy Editor, eMedicine

Disclosure: eMedicine Salary Employment

Thomas M DeBerardino, MD  Associate Professor, Department of Orthopedic Surgery, Consulting Surgeon, Sports Medicine, Arthroscopy and Reconstruction of the Knee, Hip and Shoulder, Team Physician, Orthopedic Consultant to UConn Department of Athletics, University of Connecticut Health Center

Thomas M DeBerardino, MD is a member of the following medical societies:
American Academy of Orthopaedic Surgeons, American Orthopaedic Association, and American Orthopaedic Society for Sports Medicine

Disclosure: Arthrex, Inc. Grant/research funds Other; Arthrex, Inc. Consulting fee Speaking and teaching; Genzyme Biosurgery. Inc. Grant/research funds Other; Musculoskeletal Transplant Foundation Grant/research funds Other; Histogenics Grant/research funds None

References:

  

  1. Borus T, Thornhill T. Unicompartmental knee arthroplasty. J Am Acad Orthop Surg. Jan 2008;16(1):9-18.
  2. Jamali AA, Scott RD, Rubash HE, Freiberg AA. Unicompartmental knee arthroplasty: past, present, and future. Am J Orthop. Jan 2009;38(1):17-23.
  3. Gunston FH. Polycentric knee arthroplasty. Prosthetic simulation of normal knee movement. J Bone Joint Surg Br. May 1971;53(2):272-7.
  4. Marmor L. Unicompartmental knee arthroplasty. Ten- to 13-year follow-up study. Clin Orthop Relat Res. Jan 1988;(226):14-20.
  5. Laskin RS. Unicompartmental tibiofemoral resurfacing arthroplasty. J Bone Joint Surg Am. Mar 1978;60(2):182-5.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. Dalury DF, Fisher DA, Adams MJ, Gonzales RA. Unicompartmental knee arthroplasty compares favorably to total knee arthroplasty in the same patient. Orthopedics. Apr 2009;32(4):
  15. [Best Evidence] Newman J, Pydisetty RV, Ackroyd C. Unicompartmental or total knee replacement: the 15-year results of a prospective randomised controlled trial. J Bone Joint Surg Br. Jan 2009;91(1):52-7.
  16. Berger RA, Kusuma SK, Sanders SA, Thill ES, Sporer SM. The feasibility and perioperative complications of outpatient knee arthroplasty. Clin Orthop Relat Res. Jun 2009;467(6):1443-9.
  17. Saenz CL, McGrath MS, Marker DR, Seyler TM, Mont MA, Bonutti PM. Early failure of a unicompartmental knee arthroplasty design with an all-polyethylene tibial component. Knee. Jan 2010;17(1):53-6.