Orthopedics

The articles prior to January 2012 are part of the back file collection and are not available with a current paid subscription. To access the article, you may purchase it or purchase the complete back file collection here

Feature Article 

Unicompartmental Knee Arthroplasty Compares Favorably to Total Knee Arthroplasty in the Same Patient

David F. Dalury, MD; David A. Fisher, MD; Mary Jo Adams, BSN, RN; Ricardo A. Gonzales, MD

  • Orthopedics. 2009;32(4)
  • Posted April 1, 2009

Abstract

several surgical management options exist for medial knee arthritis, and it is often difficult to decide whether a unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) is appropriate. Few studies have compared UKAs and TKAs in the same patient. We identified 23 patients with osteoarthritis who had a TKA on one side and a UKA on the other. The preoperative values of the 2 knees were not statistically different. Strict criteria were used to determine whether a UKA could be performed (functional anterior cruciate ligament, minimal deformity, and minimum changes in other compartments). Preoperative radiographs were reviewed to confirm that the knee undergoing TKA had medial compartment disease only. Knee Society scores, radiographic analysis, and patient preferences were recorded for all patients. Average follow-up was 46 months (range, 7.2-148 months) and 42 months (range, 11.5-59.8 months) for TKA and UKA, respectively.

Little or no difference was found in outcomes between the 2 procedures, except for an improved range of motion with the UKA compared with the TKA (123°±9° vs 119.8°±7°, respectively). Knee Society scores improved from 45.9 to 89.7 in UKA and from 42.4 to 90.3 in TKA. Of the 23 patients, 11 expressed no preference between either knee and 12 preferred UKA; no patient preferred TKA. With appropriate patient selection, UKAs are a successful option for patients with osteoarthritis.

Options for management of medial compartment osteoarthritis of the knee include osteotomy, unicompartmental knee arthroplasty (UKA), and total knee arthroplasty (TKA). Several studies have shown that osteotomy has inferior results compared with that of either arthroplasty,1-9 and it appears that the popularity of osteotomy is declining in many centers. Long-term studies of UKAs and TKAs show successful outcomes in the 90% range at 10-year follow-up.10-12 However, to our knowledge, there are only a few studies comparing these 2 approaches in matched groups.13-15

The goal of this study was to compare the results of these 2 arthroplasties in a group of patients who had undergone both procedures, 1 on each knee.

Patient Population

Between October 1991 and October 2005, 5206 TKA procedures and 788 UKA procedures were performed by the senior authors (D.F.D., D.A.F.). Of the patients undergoing those procedures, 23 (11 women, 12 men) received a TKA on 1 side and a UKA on the contralateral side. Strict selection criteria was used in selecting patients for a UKA, including an intact anterior cruciate ligament, no deformity >10° in any plane, and only moderate degenerative changes on the surface of the patella or on the trochlea. These 23 patients formed our study group.

Six procedures (UKA and TKA) were performed concurrently, 6 were performed in a staged manner within 3 days, 5 were performed within 12 months of each other, and 6 were performed >12 months apart. Average patient age at the time of TKA was 68 years (range, 41-89 years), and at the time of UKA was 69 years (range, 47-88 years). Average body mass index (BMI) for the entire cohort was 30.5 (range, 22-49). Four patients had a BMI >35.

Preoperative and postoperative Knee Society total scores, pain scores, function scores, range of motion (ROM), and radiographic data (including alignment measurements and implant radiolucencies) were collected. In the TKA group, preoperative radiographs documented unicompartmental disease in 12, bicompartmental disease in 8, and tricompartmental disease in 3. In the UKA group, preoperative radiographs documented only unicompartmental disease.

No statistically significant differences were between the TKA and UKA groups in terms of preoperative clinical data (Knee Society total scores, pain scores, or function scores [Table 1]; ROM [Table 2]) or preoperative radiographic alignment. We considered a patient’s radiographic alignment to…

Abstract

several surgical management options exist for medial knee arthritis, and it is often difficult to decide whether a unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) is appropriate. Few studies have compared UKAs and TKAs in the same patient. We identified 23 patients with osteoarthritis who had a TKA on one side and a UKA on the other. The preoperative values of the 2 knees were not statistically different. Strict criteria were used to determine whether a UKA could be performed (functional anterior cruciate ligament, minimal deformity, and minimum changes in other compartments). Preoperative radiographs were reviewed to confirm that the knee undergoing TKA had medial compartment disease only. Knee Society scores, radiographic analysis, and patient preferences were recorded for all patients. Average follow-up was 46 months (range, 7.2-148 months) and 42 months (range, 11.5-59.8 months) for TKA and UKA, respectively.

Little or no difference was found in outcomes between the 2 procedures, except for an improved range of motion with the UKA compared with the TKA (123°±9° vs 119.8°±7°, respectively). Knee Society scores improved from 45.9 to 89.7 in UKA and from 42.4 to 90.3 in TKA. Of the 23 patients, 11 expressed no preference between either knee and 12 preferred UKA; no patient preferred TKA. With appropriate patient selection, UKAs are a successful option for patients with osteoarthritis.

Options for management of medial compartment osteoarthritis of the knee include osteotomy, unicompartmental knee arthroplasty (UKA), and total knee arthroplasty (TKA). Several studies have shown that osteotomy has inferior results compared with that of either arthroplasty,1-9 and it appears that the popularity of osteotomy is declining in many centers. Long-term studies of UKAs and TKAs show successful outcomes in the 90% range at 10-year follow-up.10-12 However, to our knowledge, there are only a few studies comparing these 2 approaches in matched groups.13-15

The goal of this study was to compare the results of these 2 arthroplasties in a group of patients who had undergone both procedures, 1 on each knee.

Materials and Methods

Patient Population

Between October 1991 and October 2005, 5206 TKA procedures and 788 UKA procedures were performed by the senior authors (D.F.D., D.A.F.). Of the patients undergoing those procedures, 23 (11 women, 12 men) received a TKA on 1 side and a UKA on the contralateral side. Strict selection criteria was used in selecting patients for a UKA, including an intact anterior cruciate ligament, no deformity >10° in any plane, and only moderate degenerative changes on the surface of the patella or on the trochlea. These 23 patients formed our study group.

Six procedures (UKA and TKA) were performed concurrently, 6 were performed in a staged manner within 3 days, 5 were performed within 12 months of each other, and 6 were performed >12 months apart. Average patient age at the time of TKA was 68 years (range, 41-89 years), and at the time of UKA was 69 years (range, 47-88 years). Average body mass index (BMI) for the entire cohort was 30.5 (range, 22-49). Four patients had a BMI >35.

Preoperative and postoperative Knee Society total scores, pain scores, function scores, range of motion (ROM), and radiographic data (including alignment measurements and implant radiolucencies) were collected. In the TKA group, preoperative radiographs documented unicompartmental disease in 12, bicompartmental disease in 8, and tricompartmental disease in 3. In the UKA group, preoperative radiographs documented only unicompartmental disease.

No statistically significant differences were between the TKA and UKA groups in terms of preoperative clinical data (Knee Society total scores, pain scores, or function scores [Table 1]; ROM [Table 2]) or preoperative radiographic alignment. We considered a patient’s radiographic alignment to be 0 at 7° of valgus on a standing anteroposterior view. Of the 23 UKA cases, preoperative alignment included 7 in valgus (average, 5°; range, 1°-9°), 13 in varus (average, 3°±1.8°; range, 2°-8°), and 3 in neutral. Of the 21 available TKA cases (2 TKA preoperative alignment data points were missing because of inadequate radiographic images), preoperative alignment included 3 in valgus (average, 7°; range, 4°-12°), 13 in varus (average, 4.8°; range, 2°-8°), and 5 in neutral. Mean absolute degrees of alignment were 3.5° (range, 0°-9°) and 4° (range, 0°-12°) for the UKA and TKA groups, respectively.

Table 1: Preoperative Knee Scores

Table 2: Preoperative Range of Motion

Postoperative complications were documented, including osteolysis and revision procedures, and patients were asked at their last postoperative visit which knee was preferred. The average follow-up was 45.9 months (range, 7.2-148 months) and 41.6 months (range, 11.5-59.8 months) for the TKA and UKA groups, respectively.

Devices and Procedures

All 23 TKA procedures involved cemented tricompartmental knee prostheses of various designs. The posterior cruciate ligament was sacrificed in 2 knees and preserved in all others. A round, all-polyethylene patella dome with 3 fixation pegs was used in all patients.

All UKA procedures (using various prosthesis designs) were performed in the medial femoral–tibial articulation replacements, and all implants were cemented. Sixteen of the tibial components were all-polyethylene and 7 were metal-backed.

All procedures were performed under tourniquet with an epidural anesthetic whenever possible. Deep venous thrombosis prophylaxis was sequential compression devices, aspirin, and early ambulation for both procedures. There were no deep infections, wound healing problems, manipulations, or recognized deep vein thromboses in any knee.

Statistical Methods

All-continuous interval and ratio data, ie, ROM and radiographic alignment, were tested for normality with the Kolmogorov-Smirnov test. Both data sets were found to be normally distributed.

Standard descriptive statistics were calculated. For normally distributed interval and ratio data, the mean, standard deviation, and range were calculated. For nominal and ordinal data, median and interquartile ranges were calculated. To determine differences between the TKA and UKA groups, a Wilcoxon test was used for ordinal data and a dependent t test was used for normally distributed continuous data. A Fisher exact chi-square analysis was used to compare the incidence of radiolucencies and postoperative complications, including osteolysis and revision. All tests were performed using an a priori level of significance of P=.05.

To determine the power achieved in the study, a post-hoc power analysis was performed using the obtained sample, ROM means, and achieved alpha level. Based on the data, the study achieved 40% power. An estimated sample size of 60 to 80 patients would be needed to achieve 80% power.

Results

We found little to no difference in outcomes between TKA and UKA knees in the same patient.

Postoperative Clinical Data

There were no statistically significant differences between the TKA and UKA knees in terms of postoperative Knee Society total scores, pain scores, and function scores. Postoperative clinical scores are presented in Table 3.

There was no statistically significant difference between TKA and UKA knees in the degree of postoperative extension. However, the degree of postoperative flexion was significantly better in UKA knees (123°±9°) than TKA knees (119.8°±7°). Similarly, the UKA knees showed a trend (P=.06) toward better total ROM (122.6°±9.3°) than the TKA knees (119.6°±7°). Postoperative ROM data are presented in Table 4.

Table 3: Postoperative Knee Scores

Table 4: Postoperative Range of Motion

In terms of knee procedure preference, 11 patients had no preference, 12 preferred the unicompartmental knee, and no patient preferred the total knee compared with the unicompartmental knee.

Postoperative Radiographic Data

There were no statistically significant differences in postoperative radiographic alignment between the UKA and TKA groups. Radiographic review consisted of standing anteroposterior, lateral, and sunrise views. Of the 23 UKA cases, 1 case was in neutral alignment and 22 cases were in valgus (4.3°±1.9°). Of the 23 TKA cases, 2 cases were in neutral alignment and 21 cases were in valgus (4.6°±1.2°). The mean absolute degrees of alignment were 4.1°±2.0° and 4.2°±1.8° for the UKA and TKA groups, respectively.

A significantly higher number of knees in the UKA group had postoperative radiolucencies: 9 compared to 3 in the TKA group. All 9 UKA radiolucencies were on the tibial undersurface, none were >1 mm, all had appeared by 1 year postoperatively, and none were progressive. No implants in either group were loose or considered radiographically at risk. Of the 3 radiolucencies in the TKA group, 1 was a complete 1-mm radiolucent line surrounding the tibial and femoral components, and the other 2 were each 1 mm in zones 11 and 14 on the tibial side.

There were no cases of osteolysis in either group.

Discussion

Interest in less invasive surgical procedures has been increasing and has led to an increased use of UKAs for the management of isolated compartment arthritis. Riddle et al16 noted an increase in UKAs done in the United States, from 10,200 in 1999 to nearly 45,000 in 2005. However, although several authors have published reports showing 10-year and even 20-year results of UKAs that are comparable to those of TKAs,17-26 to our knowledge there are few studies in the literature comparing UKAs to TKAs in matched groups,13-15 and only 1 of those compares the 2 procedures in the same patient.15

Advocates of UKAs point to studies showing superior ROM, lower incidence of stiffness, shorter recoveries, shorter hospital stays, and easier recoveries than TKAs.15,27,28 Our study showed a slightly superior ROM in the UKA group but no statistical difference between the groups in Knee Society score. There were few measurable clinical differences between the 2 groups, but it was interesting that, when asked, half of the patients stated a preference for the UKA and no patient preferred the TKA. These differences are difficult to gauge and quantify, but they were consistent across the group, and it may be that the Knee Society score is too simplistic and simply does not allow for such measurement.

Several authors have reported that UKAs can and should be left in slight undercorrection compared with traditional total knee alignment.22,26,29 In our series, overall alignment was similar in both groups, and we did not undercorrect the unicompartmental knees.

We did find a higher incidence of radiolucencies in the UKA group, all of which appeared within the first year, were not progressive, and were not associated with lower scores at final follow-up. However, additional longer-term follow-up is needed.

Most studies emphasize the importance of using strict criteria in patient selection for a UKA. Patients in our study were selected in accordance with the traditional selection criteria described by Kozinn and Scott27 and Scott and Santore.23 Patients with deformity of >10° in any plane, absent or deficient anterior cruciate ligament, or disease in >1 compartment were not offered a UKA. There is an increased interest in using these devices in young patients as a means of preserving more normal native tissue, but our patient group did not allow us to address that issue.30-34

Our study has the usual shortcomings of any retrospective investigation. This is a small series, which therefore limits our ability to make a definitive statement regarding UKA vs TKA procedures. In addition, we used various implant designs for both TKA and UKA procedures. However, because both our groups had similar preoperative knee scores, preoperative alignment, and postoperative outcomes, we found that UKAs compared favorably with TKAs in our study group.

References

  1. Berman AT, Bosacco SJ, Kirshner S, Avolio A Jr. Factors influencing long-term results in high tibial osteotomy. Clin Orthop Relat Res. 1991; (272):192-198.
  2. 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. 1986; 68(3):447-452.
  3. Insall JN, Joseph DM, Msika C. High tibial osteotomy for varus gonarthrosis. A long-term follow-up study. J Bone Joint Surg Am. 1984; 66(7):1040-1048.
  4. Karpman RR, Volz RG. Osteotomy versus unicompartmental prosthetic replacement in the treatment of unicompartmental arthritis of the knee. Orthopedics. 1982; 5(8):989-991.
  5. Matthews LS, Goldstein SA, Malvitz TA, Katz BP, Kaufer H. Proximal tibial osteotomy. Factors that influence the duration of satisfactory function. Clin Orthop Relat Res. 1988; (229):193-200.
  6. Rudan JF, Simurda MA. High tibial osteotomy. A prospective clinical and roentgenographic review. Clin Orthop Relat Res. 1990; (255):251-256.
  7. Scott RD. Three decades of experience with unicompartmental knee arthroplasty: mistakes made and lessons learned. Orthopedics. 2006; 29(9):829-831.
  8. 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. 1994; (302):134-137.
  9. Yasuda K, Majima T, Tsuchida T, Kaneda K. A ten- to 15-year follow-up observation of high tibial osteotomy in medial compartment osteoarthrosis. Clin Orthop Relat Res. 1992; (282):186-195.
  10. Font-Rodriguez DE, Scuderi GR, Insall JN. Survivorship of cemented total knee arthroplasty. Clin Orthop Relat Res. 1997; (345):79-86.
  11. Gill GS, Joshi AB. Long-term results of Kinematic Condylar knee replacement. An analysis of 404 knees. J Bone Joint Surg Br. 2001; 83(3):355-358.
  12. Malkani AL, Rand JA, Bryan RS, Wallrichs SL. Total knee arthroplasty with the kinematic condylar prosthesis. A ten-year follow-up study. J Bone Joint Surg Am. 1995; 77(3):423-431.
  13. Amin AK, Patton JT, Cook RE, Gaston M, Brenkel IJ. Unicompartmental or total knee arthroplasty?: Results from a matched study. Clin Orthop Relat Res. 2006; (451):101-106.
  14. Cameron HU, Jung YB. A comparison of unicompartmental knee replacement with total knee replacement. Orthop Rev. 1988; 17(10):983-988.
  15. Laurencin CT, Zelicof SB, Scott RD, Ewald FC. Unicompartmental versus total knee arthroplasty in the same patient. A comparative study. Clin Orthop Relat Res. 1991; (273):151-156.
  16. Riddle DL, Jiranek WA, McGlynn FJ. Yearly incidence of unicompartmental knee arthroplasty in the United States. J Arthroplasty. 2008; 23(3):408-412.
  17. Berger RA, Meneghini RM, Jacobs JJ, Sheinkop MB, Della Valle CJ, Rosenberg AG, Galante JO. Results of unicompartmental knee arthroplasty at a minimum of ten years of follow-up. J Bone Joint Surg Am. 2005; 87(5):999-1006.
  18. Berger RA, Nedeff DD, Barden RM, et al. Unicompartmental knee arthroplasty. Clinical experience at 6- to 10-year followup. Clin Orthop Relat Res. 1999; (367):50-60.
  19. Cartier P, Sanouiller JL, Grelsamer RP. Unicompartmental knee arthroplasty surgery. 10-year minimum follow-up period. J Arthroplasty. 1996; 11(7):782-788.
  20. Marmor L. Unicompartmental knee arthroplasty. Ten- to 13-year follow-up study. Clin Orthop Relat Res. 1988; (226):14-20.
  21. Marmor L. Unicompartmental arthroplasty of the knee with a minimum ten-year follow-up period. Clin Orthop Relat Res. 1988; (228):171-177.
  22. Murray DW, Goodfellow JW, O’Connor JJ. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br. 1998; 80(6):983-989.
  23. Scott RD, Santore RF. Unicondylar unicompartmental replacement for osteoarthritis of the knee. J Bone Joint Surg Am. 1981; 63(4):536-544.
  24. Squire MW, Callaghan JJ, Goetz DD, Sullivan PM, Johnston RC. Unicompartmental knee replacement. A minimum 15 year followup study. Clin Orthop Relat Res. 1999; (367):61-72.
  25. Heck DA, Marmor L, Gibson A, Rougraff BT. Unicompartmental knee arthroplasty. A multicenter investigation with long-term follow-up evaluation. Clin Orthop Relat Res. 1993; (286):154-159.
  26. Svärd UC, Price AJ. Oxford medial unicompartmental knee arthroplasty. A survival analysis of an independent series. J Bone Joint Surg Br. 2001; 83(2):191-194.
  27. Kozinn SC, Scott R. Unicondylar knee arthroplasty. J Bone Joint Surg Am. 1989; 71(1):145-150.
  28. Price AJ, Webb J, Topf H, et al. Rapid recovery after oxford unicompartmental arthroplasty through a short incision. J Arthroplasty. 2001; 16(8):970-976.
  29. Ridgeway SR, McAuley JP, Ammeen DJ, Engh GA. The effect of alignment of the knee on the outcome of unicompartmental knee replacement. J Bone Joint Surg Br. 2002; 84(3):351-355.
  30. Engh GA, McAuley JP. Unicondylar arthroplasty: an option for high-demand patients with gonarthrosis. Instr Course Lect. 1999; (48):143-148.
  31. Kort NP, van Raay JJ, van Horn JJ. The Oxford phase III unicompartmental knee replacement in patients less than 60 years of age. Knee Surg Sports Traumatol Arthrosc. 2007; 15(4):356-360.
  32. Pagnano MW, Clarke HD, Jacofsky DJ, Amendola A, Repicci JA. Surgical treatment of the middle-aged patient with arthritic knees. Instr Course Lect. 2005; (54):251-259.
  33. Pennington DW, Swienckowski JJ, Lutes WB, Drake GN. Unicompartmental knee arthroplasty in patients sixty years of age or younger. J Bone Joint Surg Am. 2003; 85(10):1968-1973.
  34. Schai PA, Suh JT, Thornhill TS, Scott RD. Unicompartmental knee arthroplasty in middle-aged patients: a 2- to 6-year follow-up evaluation. J Arthroplasty. 1998; 13(4):365-372.

Authors

Drs Dalury and Gonzales and Ms Adams are from the Department of Orthopedic Surgery, St Joseph Medical Center, Baltimore, Maryland; and Dr Fisher is from OrthoIndy, Indianapolis, Indiana.

Benefits or funds were received by the Orthopaedic Associates Research Foundation (Baltimore, Maryland) from DePuy Orthopaedics.

Correspondence should be addressed to: David F. Dalury, MD, c/o Elaine P. Henze, BJ, ELS, Medical Editor, Department of Orthopedic Surgery, Johns Hopkins Bayview Medical Center, 4940 Eastern Ave, #A672, Baltimore, MD 21224-2780.

Sign up to receive

Journal E-contents